Environmental Site Assessment, December 2017 · 2017-12-06 · 6.14 Data Quality Validation 81 7.0...

Environmental Site Assessment,December 2017 Army Aviation Centre Oakey Stage 2C Environmental Investigation

Department of Defence

01 December 2017 60533675 Revision 0 - Final

AECOM

Environmental Site Assessment, December 2017 – Army Aviation Centre Oakey, Stage 2C Environmental Investigation

Revision 0 – 01-Dec-2017 Prepared for – Department of Defence – ABN: 68 706 814 312

Environmental Site Assessment, December 2017

Client: Department of Defence ABN: 68 706 814 312

Prepared by AECOM Australia Pty Ltd Level 8, 540 Wickham Street, PO Box 1307, Fortitude Valley QLD 4006, Australia T +61 7 3553 2000 F +61 7 3553 2050 www.aecom.com ABN 20 093 846 925

01-Dec-2017

Job No.: 60533675

AECOM in Australia and New Zealand is certified to ISO9001, ISO14001 AS/NZS4801 and OHSAS18001.

© AECOM Australia Pty Ltd. All rights reserved.

AECOM has prepared this document for the sole use of the Client and for a specific purpose, each as expressly stated in the document. No other party should rely on this document without the prior written consent of AECOM. AECOM undertakes no duty, nor accepts any responsibility, to any third party who may rely upon or use this document. This document has been prepared based on the Client’s description of its requirements and AECOM’s experience, having regard to assumptions that AECOM can reasonably be expected to make in accordance with sound professional principles. AECOM may also have relied upon information provided by the Client and other third parties to prepare this document, some of which may not have been verified. Subject to the above conditions, this document may be transmitted, reproduced or disseminated only in its entirety. AECOM has prepared this document for the sole use of the Client and for a specific purpose, each as expressly stated in the document. No other party should rely on this document without the prior written consent of AECOM.

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Quality Information Document Environmental Site Assessment, December 2017

Ref 60533675

Date 01-Dec-2017

Prepared by James Peachey and Mark Stewart

Reviewed by Brad Eismen

Revision History

Rev Revision Date Details Authorised

Name/Position Signature

A 10 July 2017 Preliminary for Defence and Technical Advisor Review

Frances Lee / Project Manager

B 26 July 2017 Draft for Defence and Technical Advisor Review


C 7 August 2017 Draft for Queensland State Government Review


D 7 September 2017 Draft for Defence Review Frances Lee / Project Manager

E 19 October 2017 Draft for Defence Review Frances Lee / Project Manager

F 6 November 2017 Draft for Defence Review Frances Lee / Project Manager

0 1 December 2017 Final Frances Lee / Project Manager

Distribution List

Rev Revision Date Details Distribution

A 10 July 2017 Preliminary Department of Defence

B 26 July 2017 Draft Department of Defence

C 7 August 2017 Draft Department of Defence

D 7 September 2017 Draft Department of Defence

E 19 October 2017 Draft Department of Defence

F 6 November 2017 Draft Department of Defence

0 1 December 2017 Final Department of Defence

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Table of Contents Executive Summary xviii 1.0 Introduction 1

1.1 Preamble 1 1.2 Summary of Findings of Previous Investigations 1 1.3 Objectives 2

1.3.1 Site assessment 2 1.3.2 Groundwater modelling 3

1.4 Context of the 2017 Stage 2C EI 4 2.0 Scope of Work 5

2.1 Scope of Work On-Site 5 2.1.1 Source Area soil characterisation 5 2.1.2 Additional groundwater monitoring wells on-Site 6 2.1.3 Groundwater characterisation 6 2.1.4 Drainage channel characterisation 6 2.1.5 Stormwater sampling 7

2.2 Scope of Work Off-Site 7 2.2.1 Groundwater characterisation 7 2.2.2 Drainage channel soil characterisation 8 2.2.3 Surface soils 8 2.2.4 Stormwater, surface water and sediment sampling 9 2.2.5 Modelling of surface water interactions 9

2.3 Residential Sampling Program 9 2.5 Laboratory Analysis 10

2.5.1 PFAS laboratory analysis 10 2.5.2 Analysis for TOPA contaminants 10 2.5.3 Analysis for non-PFAS contaminants 10 2.5.4 Permeability testing 11

3.0 Site Identification and Environmental Setting 12 3.1 Site Location and Surrounding Land Use 12

3.1.1 Regional Oakey District 12 3.1.2 The Site 12 3.1.3 Site history 12 3.1.4 Previous environmental investigations 12

3.2 Environmental Setting 14 3.2.1 Topography 14 3.2.2 Climate 15 3.2.3 Geology 15 3.2.4 Hydrogeology 16 3.2.5 Groundwater management and use 19 3.2.6 Surface water 21 3.2.7 Wastewater management 23 3.2.8 Oakey town water supply 24 3.2.9 Historical Oakey town water supply 24 3.2.10 Sensitive local environmental receptors 24

3.3 Water Quality Objectives and Environmental Values 25 3.4 Site and Contaminant Characteristics and Limitations of Environmental

Investigation 26 3.5 PFAS properties 33

3.5.1 Key PFAS migration processes at the Site 33 3.5.2 Physical and chemical properties of PFOS and PFOA 33 3.5.3 PFAS analysis and data interpretation issues 35 3.5.4 Data variability and uncertainty 36

4.0 Approach and Methodology 41 4.1 Approach 41 4.2 Sampling Rationale 42

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4.3 Methodology 45 4.3.1 Drilling and soil sampling 45 4.3.2 Monitoring well installation and groundwater sampling 48 4.3.3 Surface water sampling 49 4.3.4 Sediment sampling 51 4.3.5 Tap and tank water sampling 51

4.4 Data Quality Objectives 51 5.0 Assessment Criteria 52

5.1 Overview 52 5.2 PFAS Assessment Criteria 52 5.3 Non-PFAS suite – Assessment Criteria 54

5.3.1 Soil 54 5.3.2 Groundwater 54 5.3.3 Surface water 55

6.0 Results 59 6.1 Rainfall during the 2017 Stage 2C EI 59 6.2 Subsurface Conditions 59

6.2.1 Stratigraphy 59 6.2.2 Oakey Creek Alluvium 60 6.2.3 Main Range Volcanics 60 6.2.4 Walloon Coal Measures 61

6.3 Hydrogeology 61 6.3.1 Groundwater elevations 61 6.3.2 Groundwater flow directions and horizontal head gradient 62 6.3.3 Vertical head gradients 62 6.3.4 Unsaturated Zone Thickness 63 6.3.5 Temporal variation in groundwater elevation 64 6.3.6 Temporal variation in surface water flow 66

6.4 Water Quality Parameter Results 67 6.4.1 Groundwater 67 6.4.2 Surface water 68

6.5 Known Hydrocarbon Impact 68 6.6 Geophysical Borehole Assessment Results 68

6.6.1 RN107812 69 6.6.2 RN87439 69 6.6.3 RN87369 69

6.7 Hydrogeological Testing 70 6.7.1 Pump tests and groundwater flow velocity 70 6.7.2 Infiltration tests 70

6.8 Soil Analytical Results 70 6.8.1 Human health and ecological screening assessment of PFAS 71 6.8.2 Leachable PFAS concentrations 72 6.8.3 TOPA soil analytical results 72 6.8.4 Particle size distribution, total organic content and total iron 72 6.8.5 Human health and ecological screening assessment of non-PFAS

COPC 72 6.9 Groundwater Analytical Results 73

6.9.1 Human health screening assessment of PFAS 74 6.9.2 Ecological screening assessment of PFAS in groundwater 74 6.9.3 TOPA groundwater analytical results 75 6.9.4 Human health and ecological screening assessment of metals and

metalloids 75 6.9.5 Human health and ecological screening assessment of petroleum

hydrocarbons: TRH, BTEX, Phenols and PAHs 76 6.9.6 Human health and ecological screening assessment of 1,4-dioxane 76 6.9.7 Human health and ecological screening assessment of OC/OP

pesticides, VOCs and SVOCs 76 6.9.8 Major ion analytical results 76

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6.10 Stormwater Analytical Results 77 6.11 Surface Water Analytical Results 78 6.12 Sediment Analytical Results 79 6.13 Residential Tank, Tap Water and Swimming Pool Sampling Results 80 6.14 Data Quality Validation 81

7.0 Discussion 82 7.1 Geology and Hydrogeology 82

7.1.1 Stratigraphy 82 7.1.2 Basal Gravel in Oakey Creek Alluvium 82 7.1.3 Groundwater hydrochemistry 83

7.2 Nature and Extent of PFAS Impacts 89 7.2.1 On-Site PFAS concentrations in soil 89 7.2.2 Evaluation of on-Site and off-Site groundwater quality and trends 98 7.2.3 Extent of PFAS in off-Site groundwater 100 7.2.4 Evaluation of groundwater PFAS trends 102 7.2.5 Extent of PFAS in deeper aquifers 105 7.2.6 PFAS in drainage channels sediments and stormwater quality 105 7.2.7 Evaluation of surface water and creek sediment quality and trends 108

7.3 Extent of non-PFAS Contaminants in Soil and Groundwater on-Site 112 7.3.1 Metals 112 7.3.2 Petroleum hydrocarbons 113 7.3.3 Other organics 113

8.0 Hydrogeological Interpretation 114 8.1 Approach 114 8.2 Waste / Sources 114

8.2.1 Primary sources 114 8.2.2 Stormwater drains 115 8.2.3 Oakey Creek 115

8.3 Storage of PFAS Water in Dams and Irrigation Return Flow 115 8.3.1 Irrigation return flow 116

8.4 Flood Inundation Areas 117 8.5 Former Landfill 118 8.6 Bores and Groundwater Extraction 118 8.7 Separation 119

8.7.1 Point sources 119 8.7.2 Surface water runoff 120 8.7.3 Farm dams 122 8.7.4 Irrigation return flow 124 8.7.5 Flood inundation 125 8.7.6 Former landfill 127 8.7.7 Groundwater extraction bores 128 8.7.8 Secondary Alteration 138

8.8 Aquifers 138 8.8.1 Oakey Creek Alluvium 138 8.8.2 Main Range Volcanics 140 8.8.3 Walloon Coal Measures 141 8.8.4 Transition zone 141

8.9 Hydrogeological (WASP) Assessment 142 8.10 Approach 142 8.11 Source Evaluation 143

8.11.1 Great Artesian Basin vulnerability comment 149 9.0 Surface Water Interactions 150

9.1 Methodology 150 9.2 Results 150

9.2.1 Regional flooding 150 9.2.2 Local flooding 151

9.3 Discussion 151 10.0 Conceptual Site Model Update 153

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10.1 Introduction 153 10.1.1 Purpose 153 10.1.2 Definition of source-pathway-receptor linkage 153

10.2 Summary of Sources of Contamination 153 10.2.1 Primary source areas 153 10.2.2 Secondary sources 154

10.3 Migration Mechanism 154 10.4 Exposure Pathways 155 10.5 Potential Receptors 155 10.6 Summary of Source-Pathway-Receptor Linkages 156

11.0 Groundwater Modelling 160 11.1 Modelling Update 160 11.2 2016 Model Limitations 160 11.3 Modelling Approach 161

11.3.1 Software change 161 11.3.2 Reset Model 161 11.3.3 Back calibration 161

11.4 Conceptualisation 161 11.4.1 Conceptual water balance 162

11.5 Model Updates 162 11.5.1 Model grid 162 11.5.2 Model boundaries 162 11.5.3 Model structure 162 11.5.4 Source locations 163 11.5.5 Model time steps 163

11.6 Model Calibration 163 11.6.1 Observation data sets 163 11.6.2 Reset model calibration 163 11.6.3 Sensitivity analysis 168

11.7 Model Projections 168 11.7.1 Base case scenario 168

11.8 Heterogeneity Calibration 169 11.9 Model Confidence Classification 169 11.10 Reset Model Comments 169

12.0 Conclusions 171 12.1 Data Gap Evaluation 171 12.2 Refinement of the Conceptual Site Model 171 12.3 Generate Input Data for the 2017 HHRA and 2017 ERA 171 12.4 Ongoing Monitoring Plan 171

13.0 References 177 14.0 Limitations 183 Appendix A Tables A Appendix B Figures B Appendix C Plates C Appendix D Bore Logs and Geological Cross-Sections D Appendix E Surveying Results E Appendix F Borehole Assessment Results F Appendix G Analytical Laboratory Reports G Appendix H Data Quality Validation, Field Sheets and Calibration Certificates H Appendix I Surface Water Modelling Results I Appendix J Groundwater Modelling Report J

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List of Tables (in text)

Table 2-1 Compounds analysed in the extended PFAS suite 10 Table 3-1 Stratigraphy (source: AECOM, 2016a) 15 Table 3-2 Environmental aspects and characteristics 27 Table 3-3 Physical and chemical properties of PFOS, PFOA and PFHxS 34 Table 3-4 Data characteristics, variability and interpretation 37 Table 4-1 Dates of sampling activities 42 Table 4-2 Sampling rationale 42 Table 4-3 Soil assessment methodology 46 Table 4-4 Monitoring well installation and groundwater sampling methodology 48 Table 4-5 Surface water sampling methodology 50 Table 4-6 Sediment sampling methodology 51 Table 5-1 PFAS criteria summary: human health and ecological 53 Table 5-2 Adopted assessment criteria – non-PFAS contaminants: soils (human health and

ecological) 56 Table 5-3 Adopted assessment criteria – non-PFAS contaminants: groundwater (human health) 57 Table 5-4 Adopted assessment criteria – non PFAS contaminants: groundwater and surface water

(ecological) 58 Table 6-1 Rainfall between January 2017 and June 2017 59 Table 6-2 Stratigraphy identified during the investigation 59 Table 6-3 Depth to Main Range Volcanics 60 Table 6-4 Summary of groundwater elevation data 61 Table 6-5 Summary of calculated vertical gradients between different hydrogeological units 63 Table 6-6 Approximate thickness of unsaturated zones in source areas 64 Table 6-7 Summary of results of continuous data loggers 65 Table 6-8 Summary of groundwater quality parameter results 67 Table 6-9 Summary of surface water quality parameter results 68 Table 6-10 Summary of PFAS concentrations in soil samples 71 Table 6-11 Summary of soil leachate analytical results 72 Table 6-12 Summary of soil analytical results: metals and metalloids 73 Table 6-13 Groundwater analytical results: assessment of PFAS concentrations in samples

collected between January and June 2017 with human health screening levels 74 Table 6-14 Groundwater analytical results: assessment of PFAS concentrations in samples

collected between January and June 2017 with ecological screening levels 75 Table 6-15 Summary of groundwater analytical results: metals and metalloids in samples collected

between January and June 2017 75 Table 6-16 Summary of major ions analytical results collected between January and June 2017 77 Table 6-17 Summary of stormwater analytical results: PFAS in samples collected between January

and June 2017 77 Table 6-18 Assessment of surface water analytical results: PFAS in samples collected between

January and June 2017 79 Table 6-19 Summary of sediment analytical results: PFAS in samples collected between January

and June 2017 80 Table 6-20 Summary of residential tank water and tap water and pool water analytical results:

PFAS in samples collected between January and June 2017 81 Table 6-21 Summary of pool water analytical results: PFAS in samples collected between January

and June 2017 81 Table 7-1 Depth where basal gravel layer was encountered 82 Table 7-2 Hydrogeochemical clusters 84 Table 7-3 Distribution of Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal

Measures groundwater samples within each HCA group, and median chemical compositions of each cluster 86

Table 7-4 Summary of PFOS sample results for all soil samples collected on-Site 90 Table 7-5 Range and mean of principal PFAS present in samples from FFTG area (results of the

highest 12 soil samples have been considered) 91 Table 7-6 Summary of off-Site soil sample results 94 Table 7-7 Summary of sample results for all samples collected off-Site 95 Table 7-8 Summary of results of surface soil samples 96

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Table 7-9 Summary of TOPA results in soil and groundwater 98 Table 7-10 Percentage range in PFAS composition in on-Site groundwater samples 99 Table 7-11 Summary of drainage channel sediment and soil results 106 Table 7-12 Summary of stormwater results 107 Table 7-13 Summary of surface water results 108 Table 7-14 Summary of distribution of PFAS in sediment in creeks from different locations across

the Investigation Area 111 Table 7-15 Summary of comparison of PFAS in sediment and surface water quality 112 Table 8-1 Summary of farm dam sample results 115 Table 8-2 Irrigation return water sample results 116 Table 8-3 Groundwater bores and samples within the flood inundation area 117 Table 8-4 Landfill groundwater summary 118 Table 8-5 Walloon Coal Measures aquifer groundwater summary 119 Table 8-6 Oakey Creek Alluvium groundwater level data 120 Table 8-7 Oakey Creek and Oakey Creek Alluvium water quality summary 121 Table 8-8 Permeability data at Dam 1 122 Table 8-9 PFAS soil results at Dam 1 123 Table 8-10 Bore logs summary 123 Table 8-11 PFAS water results at Dam 2 124 Table 8-12 Oakey Creek Alluvium bores near Dam 1 - geology 124 Table 8-13 Flood inundation bore summary 126 Table 8-14 Flood inundation bore top sediments 127 Table 8-15 Former landfill bore summary 128 Table 8-16 Registered bore assessment summary 129 Table 8-17 RN107812 bores summary 129 Table 8-18 RN107812 aquifer data 131 Table 8-19 RN87439, MWO-W-AL and MWO-W-WCM bore summary 132 Table 8-20 RN87439 aquifer data 133 Table 8-21 RN87369, MWO-V-AL and MWO-V-WCM summary 135 Table 8-22 RN87369 aquifer data 136 Table 8-23 Transition zone data 142 Table 8-24 Risk evaluation: probability and magnitude values 143 Table 8-25 Summary of source risk evaluation to groundwater resources 144 Table 10-1 Refined conceptual site model 157 Table 11-1 Estimated PFAS contaminant load in groundwater 163 Table 11-2 Reset Model calibrated aquifer parameters 164 Table 11-3 Calibrated recharge rates 164 Table 11-4 Calibrated stream bed conductance 165 Table 11-5 Transient model calibration water budget 166 Table 11-6 Source locations and calibrated PFOS loads 167 Table 11-7 Sensitivity analysis 168 Table 12-1 Data gap evaluation 172

List of Charts (in text) Chart 1 Monthly mean creek discharge (DNRM stream monitoring) (AECOM 2016a) 22 Chart 2 Monthly mean stage height (DNRM stream monitoring) (AECOM 2016a) 22 Chart 3 Hydrograph of MWA4-A and MWA5-A-UA: 10 February to 13 March 2017 66 Chart 4 Hydrograph of drainage channel 2: 10 February to 13 March 2017 67 Chart 5 Dendrogram for the hierarchical cluster analysis 85 Chart 6 Ion concentration plots for groundwater samples 88 Chart 7 Wind rose for Oakey 1973 to 2010, Bureau of Meteorology 95 Chart 8 Groundwater concentrations in selected on-Site wells: 2010 to 2017 103 Chart 9 Groundwater concentrations in residential bores within 1 km of southern site boundary:

2010 to 2017 103 Chart 10 Groundwater concentrations in selected off-Site wells within approximately 1 km of the

south-western corner of the Site: 2013 to 2017 104

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Chart 11 Groundwater concentrations in selected off-Site wells between 1 km and 2km of the south-western corner of the Site: 2014 to 2017 104

Chart 12 PFOS concentrations in Oakey Creek: 2014 to 2017 110 Chart 13 RN107812, MWO-X-AL, MWO-X-WCM Schoeller diagram 130 Chart 14 RN107812 pumping test summary 131 Chart 15 RN87439, MWO-W-AL, MWO-W-WCM Schoeller diagram 133 Chart 16 RN87439 pumping test summary 134 Chart 17 RN87369, MWO-V-AL, MWO-V-WCM Schoeller diagram 135 Chart 18 RN87369 pumping test summary 137

List of Tables (in Appendix A) Table T1 Monitoring Well Construction Details Table T2 Groundwater Elevations: November 2015 to June 2017 Table T3 Groundwater Field Quality Parameters: November 2015 to June 2017 Table T4 Surface Water Field Quality Parameters: November 2015 to June 2017 Table T5 Geotechnical Permeability Test Results Table T6 Vertical Gradient Results Table T7 Soil Analytical Results –PFAS Concentrations in On-Site Soil Bore Samples Table T8 Soil Analytical Results –PFAS Concentrations in Drainage Channel Samples Table T9 Soil Analytical Results –PFAS Concentrations in Off-Site Soil Bore Samples Table T10 Soil Analytical Results –PFAS Concentrations in Off-Site Surface Soil Samples Table T11 Soil Analytical Results – Leachate PFAS and 1,4-Dioxane Concentrations Table T12 Soil Analytical Results – TOPA Concentrations in On-Site Soil Samples Table T13 Soil Analytical Results – On-Site Metals and Metalloids Concentrations Table T14 Soil Analytical Results – On-Site Organics: TRH, BTEXN, PAH Concentrations Table T15 Soil Analytical Results – On-Site Organics: OC/OP Pesticide Concentrations Table T16 Soil Analytical Results – On-Site Organics:VOC Concentrations Table T17 Soil Analytical Results – On-Site Organics: SVOC Concentrations Table T18 Soil Analytical Results – Particle Size Distribution, Total Iron and TOC Table T19 Groundwater Analytical Results – PFAS Concentrations On-Site and Off-Site Table T20 Residential Sampling Analytical Results – PFAS Concentrations Table T21 Groundwater Analytical Results –TOPA Concentrations Table T22 Groundwater and Stormwater Analytical Results – Metal and Metalloid Concentrations Table T23 Groundwater and Stormwater Analytical Results: Organics –TRH, BTEXN, PAHs, 1,4-

Dioxane Concentrations Table T24 Groundwater and Stormwater Analytical Results: Organics – OC/OP Pesticides

Concentrations Table T25 Groundwater and Stormwater Analytical Results: Organics – VOC Concentrations Table T26 Groundwater and Stormwater Analytical Results: Organics – SVOC Concentrations Table T27 Groundwater and Stormwater Analytical Results – Major Cations and Anions Table T28 Surface Water and Stormwater Analytical Results – PFAS Concentrations Table T29 Sediment Analytical Results – PFAS Concentrations Table T30 Water QA/QC Analytical Results – Non-PFAS Concentrations Table T31 Water QA/QC Analytical Results – Rinsate PFAS Concentrations Table T32 Water QA/QC Analytical Results – Rinsate Non-PFAS Concentrations Table T33 Water QA/QC Analytical Results – Trip Blank Non-PFAS Concentrations Table T34 Historical Soil Analytical Results – On-Site and Off-Site PFAS Concentrations Table T35 Historical Groundwater Analytical Results - On-Site and Off-Site PFAS Concentrations Table T36 Historical Drainage Channel Sediment Analytical Results – On-Site PFAS

Concentrations Table T37 Historical Surface Water Analytical Results – Off-Site PFAS Concentrations Table T38 Historical Sediment Analytical Results – Off-Site PFAS Concentrations

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List of Figures (in Appendix B)

Figure F1 Site Location Figure F2 Site Layout and Asset Facilities Figure F3 Active and Depleting Sources of PFAS Figure F4 Conceptual Model of Estimated PFAS Source and History Figure F5 Regional Geology of the Oakey Area Figure F6 Location of Drainage Lines on-Site Figure F7 Groundwater Dependent Ecosystems Figure F8 Flood Inundation Areas and Predicted Queensland Floodplain Assessment Figure F9 On-Site Groundwater Monitoring Wells and Soil Bore Locations Figure F10 Locations of on-Site Wells Monitored during the Investigation Figure F11 On-Site and off-Site Drainage Channel Soil Bore Sampling Locations Figure F12 Sediment, Surface Water and Stormwater Sampling Locations Figure F13 Off-Site Groundwater Monitoring Well Locations Figure F14 Locations of Licensed Extraction Bores with Borehole Assessments and Pump Tests Figure F15 Locations of Off-Site Wells Monitored during the Investigation Figure F16 Surface Soil Sampling Locations Figure F17 Groundwater Contour Map: Oakey Creek Alluvium: March 2017 Figure F18 Groundwater Contour Map: Oakey Creek Alluvium: May 2017 Figure F19 Groundwater Contour Map: Main Range Volcanics: May 2017 Figure F20 Groundwater Contour Map: Walloon Coal Measures: May 2017 Figure F21 Approximate Extent of LNAPL in Area C1 and C2 Figure F22 PFAS Concentrations in Soil: On-Site (Eastern Half of Site) Figure F23 PFAS Concentrations in Soil: On-Site (Western Half of Site) Figure F24 PFAS Concentrations in Soil: Former Fire Training Ground Figure F25 PFAS Concentrations in Soil: Drainage Channels Figure F26 PFAS Concentrations in Soil: Off-Site (South-East) Figure F27 PFAS Concentrations in Soil: Off-Site (South-West) Figure F28 PFAS Concentrations in Soil: Surface Soil Samples Figure F29 PFAS Leachate Concentrations in Soil Figure F30 Petroleum Hydrocarbon Concentrations in Soil Figure F31 PFOS+PFHxS Concentrations in Groundwater: On-Site Figure F32 PFOA Concentrations in Groundwater: On-Site Figure F33 PFOS+PFHxS Concentrations in Groundwater: Off-Site (Oakey Creek Alluvium) Figure F34 PFOA Concentrations in Groundwater: Off-Site (Oakey Creek Alluvium) Figure F35 PFOS+PFHxS Concentrations in Groundwater: Off-Site (Main RangeVolcanics /

Walloon Coal Measures) Figure F36 PFOS+PFHxS Concentrations in Groundwater: Off-Site Residential Bore Samples Figure F37 PFOA Concentrations in Groundwater: Off-Site Residential Bore Samples Figure F38 Petroleum Hydrocarbon Concentrations in Groundwater: On-Site Figure F39 PFAS Concentrations in Stormwater in Drainage Channels Figure F40 PFOS+PFHxS Concentrations in Surface Water Figure F41 PFOA Concentrations in Surface Water Figure F42 PFOS Concentrations in Sediment Figure F43 PFOS concentrations in On-Site Soil between 0.0 and 0.5 mbgs (2010 to 2017 data) Figure F44 PFOS concentrations in On-Site Soil between 0.5 and 2.0 mbgs (2010 to 2017 data) Figure F45 PFOS concentrations in On-Site Soil >2.0 mbgs (2010 to 2017 data) Figure F46 PFOS concentrations in soil in the Former Training Ground <2.0 mbgs Figure F47 Extent of PFOS + PFHxS in Groundwater (Monitoring Wells and Residential Bores) and

Surface Water On-Site and Off-Site: February to June 2017 Figure F48 PFOS concentrations in Sediment in Drainage Channels (2010 to 2017 data) Figure F49 Conceptual Site Model Figure F50 Conceptual Site Model (in Plan) Figure F51 Conceptual Hydrogeological Model

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Acronyms Acronym Term/ Definition

AACO Army Aviation Centre Oakey

ADWG Australian Drinking Water Guideline

AECOM AECOM Australia Pty Ltd

AEP Annual Exceedance Probability

AFFF Aqueous Film Forming Foam

AGE Australasian Groundwater and Environmental Consultants Pty Ltd

AHD Australian Height Datum

ALS Australian Laboratory Services

ANZECC Australian and New Zealand and Conservation Council

ASLP Australian Standard Leaching Potential

BoM Bureau of Meteorology

BTEXN Benzene, Toluene, Ethylbenzene, Xylene, Naphthalene

COC Chain of Custody

COPC Contaminants of Potential Concern

CSM Conceptual Site Model

DA Detection Area

DAF Department of Agriculture and Fisheries (Queensland)

DCD Defence Contamination Directive

DNRM Department of Natural Resources and Mines (Queensland)

DO Dissolved Oxygen

DoEE Department of Environment and Energy [Australian Government]

DoH Department of Health (Federal)

DQO Data Quality Objectives

GDEs Groundwater Dependent Ecosystems

EC Electrical Conductivity

EHP Department of Environment and Heritage Protection (Queensland)

EI Environmental Investigation

EIL Ecological Investigation Level

EPP Environmental Protection Policy

ERA Ecological Risk Assessment

ESA Environmental Site Assessment

ESL Ecological Screening Level EtFOSA N-Ethyl perfluorooctane sulfonamide

EtFOSAA N-Ethyl perfluorooctane sulfonamidoacetic acid

EtFOSE N-Ethyl perfluorooctane sulfonamidoethanol

FFTG Former Fire Training Ground

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Acronym Term/ Definition

FOSA Perfluorooctane Sulphonamide

FSANZ Food Standards Australia and New Zealand

GAB Great Artesian Basin

GSQ Geological Survey of Queensland

HASP Health and Safety Plan

HBGV Health Based Guidance Values

HCA Hierarchical Cluster Analysis

HHRA Human Health Risk Assessment

HIL Health Investigation Level

HSL Health Screening Level

LDPE Low Density Polyethylene

LNAPL Light Non-Aqueous Phase Liquid

LOR Limit of Reporting

mAHD Metres above Australia Height Datum

mBTOC Metres Below Top of Casing

mbgs Metres Below Ground Surface

MDBA Murray-Darling Basin Authority

MRV Main Range Volcanics MeFOSA N-Methyl Perfluorooctane Sulfonamide

MeFOSAA N-Methyl Perfluorooctane Sulfonamidoacetic Acid

MeFOSE N-Methyl Perfluorooctane Sulfonamidoethanol

NATA National Association of Testing Authorities

NEPC National Environmental Protection Council

NEPM National Environment Protection Measure

NDD Non-Destructive Drilling

NHMRC National Health and Medical Research Council

OCGMA Oakey Creek Groundwater Management Area

OC / OP Pesticides Organochloride / Organophosphorus Pesticides

OMP Ongoing Monitoring Plan

ORP Oxidation Reduction Potential

PAH Poly Aromatic Hydrocarbons

PFAA Perfluoroalkyl Acids

PFAS Per- and Poly-Fluorinated Alkyl Substances

PFBS Perfluorobutane Sulfonic acid

PFCA Perfluorinated Carboxylates

PFPeS Perfluoropentane Sulfonic Acid

PFHxS Perfluorohexane Sulfonic Acid

AECOM




PFHpS Perfluoroheptane Sulfonic Acid

PFOS Perfluorooctane Sulfonic Acid

PFDS Perfluorodecane Sulfonic Acid

PFBA Perfluorobutanoic Acid

PFPeA Perfluoropentanoic Acid

PFHxA Perfluorohexanoic Acid

PFHpA Perfluoroheptanoic Acid

PFOA Perfluorooctanoic Acid

PFNA Perfluorononanoic Acid

PFDA Perfluorodecanoic Acid

PFUnDA Perfluoroundecanoic Acid

PFDoDA Perfluorododecanoic Acid

PFTrDA Perfluorotridecanoic Acid

PFTeDA Perfluorotetradecanoic Acid

PFHxS Perfluorohexanoic Acid

PFOA Perfluorooctanoic Acid

PFOS Perfluorooctane Sulfonate

PFSA Perfluorinated Sulfonates

POP Persistent Organic Pollutant

PSD Particle Size Distribution

QA/QC Quality Assurance / Quality Control

QLD Queensland

QWC Queensland Water Commission

RAAF Royal Australian Air Force

RMS Root Mean Square

RN Registered Number

RSAF Royal Singaporean Airforce

RPD Relative Percent Difference

SAQP Sampling Analysis and Quality Plan

SRMS Scaled Root Mean Square

SILO Scientific Information for Land Owners

SL Screening Level

SMP Strategic Management Plan

SOP Standard Operating Procedures

SVOC Semi-volatile Organic Compound

TDI Tolerable Daily Intake

TDS Total Dissolved Solids

AECOM




TOC Total Organic Carbon

TOPA Total Oxidisable Precursor Assay

TRC Toowoomba Regional Council

TRH Total recoverable hydrocarbons

UCL Upper Confidence Level

USCS United Soil Classification System

US EPA US Environmental Protection Agency

VOC Volatile Organic Compound

WASP Waste-Aquifer Separation Model

WCM Walloon Coal Measures

WHO World Health Organisation

WMIP Water Monitoring Information Portal

WQM Water Quality Meter

4:2 FTS 4:2 Fluorotelomer Sulfonic Acid




Units Description

GL gigalitre

km kilometre

m metre

m3/s cubic m per second

mm millimetre

mg/kg milligrams/kilogram

mg/L milligrams/litre

µg/kg micrograms/kilogram

µg/L micrograms/litre

ppm parts per million

ppb parts per billion

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Glossary of Terms Term Definition

Active source Potential PFAS source associated with current Site operations.

Aquifer Geologic formation, group of formations, or part of a formation capable of transmitting and yielding quantities of water.

Bore A cylindrical drill hole sunk into the ground from which water is pumped for use or monitoring.

Borehole A hole produced in the ground by drilling for the investigation and assessment of soil and rock profiles.

Catchment The area from which a surface watercourse or a groundwater system derives its water.

Depleting source Potential PFAS source associated with historical Site operations.

Detection Area The DA includes locations at which PFOS has been detected in groundwater samples above the LOR.

Discharge A release of water from a particular source.

Drainage Natural or artificial means for the interception and removal of surface or subsurface water.

Environment

Section 528 of the Environment Protection & Biodiversity Conservation Act 1999 Cth, defines Environment to include: (a) ecosystems and their constituent parts, including people and communities; (b) natural and physical resources; (c) the qualities and characteristics of locations, places and areas; (d) Heritage values of places; and (e) the social, economic and cultural aspects of a thing mentioned in (a), (b) or (c).

Ephemeral Existing for a short duration of time, for example, a creek with limited periods of flowing water.

Groundwater Water located within an aquifer; that is, held in the rocks and soil beneath the earth’s surface.

Groundwater monitoring well

A bore which has been specifically constructed to allow groundwater measurements to be taken and groundwater samples to be collected.

Groundwater recharge A hydrologic process by which water enters the aquifer by moving downwards from surface water to groundwater.

Hydrogeology The study of subsurface water in its geological context.

Hydrology The study of rainfall and surface water runoff processes.

Impact Influence or effect exerted by a project or other activity on the natural, built and community environment.

Investigation Area The area beyond Army Aviation Centre Oakey with identified PFAS impact that is being sampled and modelled as part of the 2017 Stage 2C EI (refer to Figure F1).

Irrigation return flow This is a process where irrigated water (e.g. stored in a dam) leaves the field via surface water flow or vertical migration to groundwater.

‘Losing’ system/creek A watercourse that contributes flow to the regional groundwater system.

Order of magnitude

This is an approximate measure of the size of a number in powers of ten. For example, if the concentration of Sample 1 is identified as being one order of magnitude higher than Sample 2, this indicates the concentration in Sample 1 is ten times higher than Sample 2. Two orders of magnitude indicates the concentration difference is ten times ten (i.e. 100 times).

Perched water Unconfined groundwater held above the water table by a layer of impermeable rock or sediment.

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Term Definition

Point source Single identifiable source of potential PFAS.

Pollutant Any matter that is not naturally present in the environment.

Runoff The portion of water that drains away as surface flow.

Saturated zone This portion of the subsurface below the groundwater table in which all pores in the soil and rock are completely filled with water.

Sensitive receiver A location where a person works or resides, including residential, hospitals, hotels, shopping centres, play grounds, recreational centres or similar.

Stormwater Water that travels through drains following precipitation events.

Surface water Water flowing or held in streams, rivers and other wetlands in the landscape.

Tributary A river or stream flowing into a larger river or lake.

Unsaturated zone The portion of the subsurface above the groundwater table. The soil and rock in this zone contains air as well as water in its pores.

Water table The surface of saturation in an unconfined aquifer at which the pressure of the water is equal to that of the atmosphere.

Waterway Any flowing stream of water, whether natural or artificially regulated (not necessarily permanent).

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Executive Summary

Introduction AECOM Australia Pty Ltd (AECOM) was commissioned by the Department of Defence (Defence) to undertake the 2017 Stage 2C Environmental Investigation (2017 Stage 2C EI) at the Army Aviation Centre Oakey (AACO) in Oakey, Queensland (the Site) and in surrounding off-Site areas (the Investigation Area).

The 2017 investigation principally targeted per- and poly-fluorinated alkyl substances (PFAS) and was designed to address data gaps identified at the completion of the Stage 2C 2016 EI studies. The 2017 Stage 2C EI built upon the results of the 2015 Stage 2B EI and the 2016 Stage 2C EI, specifically the Environmental Site Assessment. The Site and Investigation Area are presented on Figure F1 in Appendix B.

The Site was constructed in 1943, initially as a training facility and overflow aircraft maintenance depot for RAAF Base Amberley. The Site currently operates as the Army’s helicopter training school for pilots and aviation technicians and is also home to a Republic of Singapore Airforce helicopter squadron. As part of typical airbase activities, aqueous film forming foam (AFFF) was used at the Site for fire training and emergency response from the 1970s. The main AFFF product used historically by Defence was 3M Lightwater™, which contained Per- and poly-fluorinated alkyl substances (PFAS) including Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA).

From 2004, Defence commenced phasing out its use of legacy AFFF containing PFOS and PFOA as active ingredients and progressively transitioned to a product called Ansulite® for use on the Defence estate. The product currently used by Defence does not contain PFOS and PFOA as active ingredients, only in trace amounts. AECOM understands that Ansulite® is used by Defence only in emergency situations where human life is at risk, or in controlled environments to test equipment, and any Ansulite® used by Defence is captured and treated and/or disposed of at licensed waste disposal facilities in accordance with best practice regulations, and standards. Based on anecdotal evidence, for the purposes of this report, it has been assumed that Defence commenced phasing out the use of AFFF products containing PFOS and PFOA at the Site from 2005. This assumption has not been verified by Defence.

The previous investigations identified the presence of PFAS in soil, groundwater, surface water, sediment and terrestrial and aquatic biota. Investigations completed to date have identified nine key on-Site PFAS source areas, which are presented in Figure F3 in Appendix B. These PFAS source areas include three depleting and six active source areas. No new additional source areas were identified since the 2016 Stage 2C EI:

• Depleting source areas

- Former fire training ground area in Area North

- Former fire station and foam training area in Area B3

- Former fuel compound and hot refuelling point in Area F1

• Active source areas

- Hot refuel area in Area A2

- Spent AFFF recovery underground storage tank in Area A2

- Spent AFFF recovery underground storage tank in Area S1

- Spent AFFF recovery underground storage tank in Area C1

- AFFF storage and decanting areas in Area D2

- Current fire training ground in Area D2

The purpose of this 2017 Stage 2C EI Report is to provide the results of the sampling and analysis undertaken between January 2017 and June 2017 which was conducted to address the data gaps

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described in Section 1.3, and to provide additional data to support the 2017 Human Health Risk Assessment (HHRA) and 2017 Ecological Risk Assessment (ERA).

Context of the 2017 Stage 2C Environmental Investigation Tasks undertaken by AECOM between January and June 2017 have included the following:

Environmental Site Assessment (this Report): This includes investigation of on- and off-Site PFAS concentrations in soil, sediment, surface water and groundwater; hydrogeological investigations; and update of a groundwater flow model and PFAS solute transport model. Data collected from previous environmental investigations, analytical data from soil sampling undertaken during Site redevelopment projects and groundwater data from the Department of Natural Resources and Mines (DNRM) have also been incorporated into this 2017 Stage 2C EI.

Residential sampling: Sampling and analysis of bore water and soil samples (at landholder request to Defence) from residences within and near the Investigation Area. In some instances water was also sampled from rainwater tanks, taps and swimming pools. Selected data from this program have been used to inform the 2017 Stage 2C EI.

Off-Site biota sampling: Following a community survey (between February and May 2017) to investigate the consumption of edible flora and fauna within the Investigation Area, a sampling program was conducted. Samples of home-grown fruits and vegetables, chicken eggs and samples of yabbies, shrimps and mussels from local creeks were collected and analysed for PFAS. Co-located soil, sediment, surface water and groundwater were also collected and analysed for PFAS. This work was conducted to support the HHRA.

Human Health Risk Assessment (in preparation): A multiple pathway HHRA is being undertaken to evaluate the potential human health risks to identified receptors within the Oakey area. This report will update the 2016 HHRA report and include consideration of direct contact exposures to environmental media (e.g. soil, groundwater, surface water, and sediment) as well as secondary exposures via dietary intakes, including fish, invertebrates and home grown plant and animal produce. The report will also be updated to include the Human Health Based Guidance Values by the Food Standards Australia and New Zealand issued in April 2017.

Ecological Risk Assessment (in preparation): The ERA will be updated in 2017 to assess the potential risk from the identified PFAS contamination to ecological receptors which inhabit the Site and surrounding areas. The 2016 ERA assessed the potential for wider ecosystem impacts to result from the accumulation of PFAS in terrestrial and aquatic organisms exposed to PFAS contamination. The current investigation included the collection and analysis of flora and fauna samples including hares, fish, yabbies, shrimps, mussels and worms. River and bird surveys and habitat assessments were also carried out.

Community Engagement: Facilitation of community engagement as related to conduct of the 2017 Stage 2C EI and other tasks as listed above including land access, water and lifestyle surveys and community information events.

Ongoing Monitoring Plan: At the completion of the 2017 Stage 2C EI, an Ongoing Monitoring Plan (OMP) will be prepared that will cover both the environmental monitoring program and the residential sampling program. The OMP will be implemented to capture seasonal and temporal variations in groundwater and surface water PFAS concentrations and conditions (drains and creeks), provide early warning indicators for groundwater plume migration and monitor water levels and aquifer specific conditions.

Stage 2C EI Objectives and Conclusions The purpose of this Stage 2C EI Report is to provide the results of the sampling and analysis undertaken between January and June 2017 to address data gaps described in Section 1.3, and to provide additional data to support the 2017 HHRA and 2017 ERA.

The objectives and conclusions of the 2017 Stage 2C EI are summarised in Table ES1.

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Table ES1 Objectives and Conclusions of the 2017 Stage 2C EI

Data gap objective Data gap conclusion

Refinement of Groundwater Zones 1 and 2 Information has been obtained to confirm the findings of the Stage 2C 2016 EI. The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report, as they are material to the HHRA. The PFAS data set from the existing and newly installed monitoring wells is suitable to allow updating of exposure point concentrations in the 2017 HHRA. Groundwater monitoring results have refined the understanding of the current extent of contamination in the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures aquifers. Evaluation of the groundwater data trends over time suggests evidence for stable PFAS concentrations in groundwater on-Site and areas adjacent to the Site. There is limited evidence for a minor increasing trend in PFAS concentrations in down-hydraulic gradient off-Site bores which is attributed to the migration of PFAS within groundwater towards the west.

Characterisation of the full PFAS suite All soil, water and sediment samples were analysed for an extended PFAS suite of 28 compounds. The dataset shows there are 12 main PFAS present in the different media; PFOS, PFHxS, PFOA, PFHxA, PFPeS, PFBS, PFHpS, PFPeA, PFHpA, PFBA, 8:2 FTS and 6:2 FTS. The dominant contaminants present were PFHxS and PFOS. The investigation has characterised the distribution of these compounds in different media across the Investigation Area.

Acquire data to inform the OMP sampling requirements

The results of this investigation, together with the historical results, will be used to develop a suitable ongoing monitoring program for the Site. The combined dataset is adequate to allow this program to be developed.

Characterisation of non-PFAS contaminants of potential concern on-Site

The investigation has included characterisation of soil, sediment, groundwater and surface water for non-PFAS contaminants on-Site. No large areas of non-PFAS contaminants have been identified. Localised petroleum hydrocarbons impacts are present in groundwater in one area within the Site. The extent of the hydrocarbon contamination is considered to be adequately understood and does not extend beyond the Site boundary. Localised areas of elevated chromium and nickel concentrations in groundwater on-Site have been identified and do not extend beyond the Site boundary.

Potential risks to the Great Artesian Basin (GAB): • Investigate potential connections across

multiple aquifers via bores that were constructed prior to current legislated standards

Information has been obtained to characterise groundwater in underlying aquifer units and allow assessment of the potential risks to the Great Artesian Basin. The dataset is considered suitable to assess the concepts and refine the conceptual site model, which is used as the basis of the groundwater model refinement. The GAB’s vulnerability to PFAS concentration migration, from the Oakey Creek Alluvium aquifer to the Walloon Coal Measures aquifer (an aquifer of the Great Artesian Basin), is recognised to be limited, which

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• Investigate registered bores RN107812, RN87439, and RN87369

• Investigate the risk that unregistered bores pose to the GAB and any remediation or mitigation measures

• Investigate the risk to the GAB from both infiltration and via bores acting as conduits, including rectification options

is reflected in the Groundwater Model water balance. The level of risk to the Great Artesian Basin is influenced by: • a thin or permeable transition zone • the limited areas within the Investigation Area where Oakey Creek Alluvium and Walloon Coal

Measures are unconformably in contact and Main Range Volcanics is not present • groundwater extraction resulting in steeper vertical gradients • secondary alteration, such as faulting and fracturing • elevated concentrations of PFAS. Bores that could create a connection between aquifers have been assessed, based on the field evaluations of the three licensed bores (RN107812, RN87439, and RN87369) within the Investigation Area. It is considered that the potential for hydraulic connection and PFAS migration from the Oakey Creek Alluvium aquifer to the underlying Walloon Coal Measures within such bores is limited, requiring several conditions to occur, including: • perforation in casing in both units • poor cement seal • thin or no transition zone • extraction of groundwater from the bore. The vulnerability of the GAB as a result of groundwater extraction was assessed through pump tests. Aquifer testing assessments indicate that the vulnerability of the GAB is related to: • transmissivity of the units intersected and screened within the bores, where the most transmissive

unit provides the majority of groundwater into the bore (reducing mixing/blending potential) • the extraction schedule and volumes and recovery periods, which influence the extent and duration of

drawdown cones, and vertical groundwater movement potential. Investigate implications of extraction of potentially contaminated overland flow water and/or surface water by entitlement holders

An assessment of surface water storage and irrigation water has been conducted. Dams are considered to have the potential to act as localised point sources of enhanced recharge to the underlying aquifers with PFAS impacted water.

Investigate potential secondary source areas including irrigation return flow, landfill inputs and flooding along road side areas

Adequate information was collected to allow investigation of these potential secondary source areas. Evaluation of irrigation return water, the former landfill and flood inundation areas has been undertaken. It is considered that irrigation return water could be contributing to the PFAS in groundwater. However, as seepage of PFAS impacted surface water to the underlying aquifer from farm dams and drains occurs in the Investigation Area, it is not clear what contribution is as result of the more dispersed irrigation return

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water source. Based on groundwater analytical results, the former landfill is considered to be a secondary source of PFAS, based on groundwater results. The zone of impact around the former landfill is considered limited, possibly due to the lower permeability of the Oakey Creek Alluvium aquifer in this area. Available groundwater data indicate a possible correlation between the areas that have been historically flooded and the extent of PFAS within the Oakey Creek Alluvium. However, due to sediment dispersion during flooding, the coarse material is inferred to be deposited on or immediately adjacent to the Oakey Creek Alluvium and fines are transported further with the flood water. Variability in the permeability of the surficial soils may affect the rate of PFAS infiltration to underlying aquifers.

Investigate water interactions (surface water, groundwater, sediment and soil interactions)

The 2017 Stage 2C EI has investigated the migration of PFAS following interaction of surface water with sediment, surficial soils and groundwater. The results of the surface water modelling have been used to assess possible PFAS migration in surface water during flood events (sourced from PFAS in soil and sediment) to on-Site and off-Site areas. Regional and local flood modelling results suggest it is unlikely that PFAS impacted sediments will be mobilised from the Site. Under the local flood modelling scenario, PFAS has the potential to be transferred from impacted surface soils to stormwater as it passes over the soil. Surface water sources and water uses have been considered, in conjunction with sediment, to evaluate the potential for PFAS sources to alter groundwater resources.

Drainage channel characterisation • Soil sampling in drains on- and off-Site • Influence of drains on PFAS migration • Infiltration tests of drain beds • Investigate temporal variability of PFAS

in surface water and temporal variability of flow

Investigation of the main drainage channels flowing off the Site included sampling of sediment and soil and leaching tests. PFAS is present in sediment and in underlying soil along drainage channels 1, 2 and 3. Infiltration testing of drain beds has been completed and vertical permeability data have been considered in the assessment of potential for PFAS migration from the drains to the underlying Oakey Creek Alluvium aquifer. Extensive surface water sampling has been undertaken in all creeks proximal to the site. Adequate characterisation data have been collected from Oakey Creek to infer the current distribution of contamination along the creek. The highest PFAS concentrations were detected at sampling locations downstream of the outfalls of drainage channels 1, 2 and 3. Sampling of Doctor Creek located to the northwest of the Site suggests there is no current hydraulic connection with on-Site sources. Temporal variability of surface water quality in Oakey Creek was evaluated. However, no distinct trends were identified in the three years of data available.

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Source area characterisation • Ensure the nature and extent of existing

contamination on-Site is properly characterised for all relevant media

• Soil sampling on-Site where PFAS have been previously identified or in areas not yet tested

• Ensure all potential sources of PFAS on-Site are identified and prioritised in terms of PFAS mass load and potential mobility to groundwater, surface water and biota

An investigation of previously identified potential PFAS source areas was conducted. Interpretation of the new and historical dataset has improved the understanding of the distribution of PFAS contaminants in the on-Site soil profile. In particular, the 2017 Stage 2C EI has improved understanding of the extent of elevated PFAS concentrations in near-surface soil at the former fire training ground. A site-wide groundwater monitoring event was conducted and identified locally elevated PFAS groundwater concentrations close to all active and depleting source areas. Review of the PFAS composition in groundwater indicated samples from areas close to the depleting sources (former fire training ground and former fire station) to have a higher proportion of PFOS and PFHxS compared to active potential sources. An assessment of primary and secondary PFAS sources has been undertaken, to assist with the evaluation of PFAS mass loads within the groundwater transport model.

More certainty around the influence of wind as a transport mechanism

The potential for PFAS transport in wind borne dust was evaluated. The dataset is not consistent with the potential migration of PFAS from the Site in wind-borne dust. The presence of higher PFAS concentrations in surface soil in the Oakey township area is attributed to surface transport of PFAS in floodwater and sediments during inundation events and the use of groundwater containing PFAS for irrigation purposes.

Residential sampling • Continue to monitor groundwater

contamination levels where requested by the owner for agricultural enterprises within the current and future Investigation Area

This report presents the results of a sampling program of residential bores, tap water, tanks and pool water and soil across the Investigation Area. The results have been integrated with data from the dedicated groundwater monitoring network installed by Defence within the Investigation Area and residential data have only been used where the property owner has agreed for Defence to use it. Residential sample results have been provided to property owners under separate cover.

Composition of all firefighting foams should be characterised, including the identifiable PFAS suite and total oxidisable precursor assay (TOPA) analysis where foams are fluorinated

The investigation included characterisation of selected samples of soil and water for TOPA analysis from a range of locations across the Site to better characterise PFAS conditions within the Investigation Area. TOPA analysis was conducted to understand the potential for precursor compounds to be present in the Investigation Area. If present, precursor compounds have the potential to transform into PFAS end products. Statistical analysis suggests that the concentration of additional PFAS that can be generated from the transformation of unidentified precursor compounds in soil and groundwater under natural environmental conditions is expected to be low.

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Refinement of the groundwater model • Update of the model conceptualisation

based on data compiled during the site investigation works

• Refinement of the groundwater model structure, calibration and predictions

• Addressing the model limitations through the refinement of the model using new data compiled during the site investigation works

• Utilising the model to investigate data gaps and facilitate decision making and inform the OMP

Data evaluation and interrogation has allowed for the assessment of concepts and refinement of the conceptual site model, which is used as the basis of the groundwater model refinement. The key groundwater model updates, forming the Reset Model, included: • a change to MODFLOW SURFACT modelling software for consistency with similar alluvium studies

and for ease of forensic review • a reduction in model extent to simulate the plume at a local scale • the addition of three more layers to simulate the Walloon Coal Measures aquifer • an update of model layer structure using data from the most recent field investigations • an evaluation of potential source locations and source discharge rates through calibration. The Reset Model has been conducted in order to facilitate the heterogeneous calibration. The iterative calibration process minimises non-uniqueness that would arise from attempting the all-encompassing model calibration in a single step.

The calibrated reset flow model provides parameters that are consistent with the conceptual site model and comparable to other groundwater modelling studies in alluvium systems.

The updated model structure allows for further evaluation of potential plume movement within the Walloon Coal Measures aquifer, though the model projections need to be supported by further data before being assessed as reliable.

PFOS plume migration, using a conservative approach of continuous contaminant sources in uniform permeable sediments, is predicted to continue in a westerly direction within the groundwater. This modelling allowed for the assessment of contaminant sources and plume shape, which is similar to the field measurements and observations. Future modelling within heterogenic sediments will provide a more robust assessment of migration.

The groundwater assessment and model development has improved the understanding of the potential sources of PFOS and the contaminant discharge rate to groundwater. The current process of adding heterogeneity to the Oakey Creek Alluvium will further improve the matching of observed water levels and concentrations in the groundwater regime. The model results will be used to inform the OMP.

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Conclusions Refinement of the conceptual site model (CSM)

The results of the 2017 Stage 2C EI allowed for the following parameters of the CSM to be refined:

• transport mechanisms have been characterised by sampling

• exposure pathways have had data collected for use in the risk assessments

• exposed populations have had data collected for use in the risk assessments.

Generate input data for the 2017 HHRA and 2017 ERA

The following work was conducted to generate additional data for the 2017 HHRA and 2017 ERA:

• collection of soil and groundwater samples within the Investigation Area

• collection of water and sediment samples from locations in Doctor Creek, Oakey Creek and Westbrook Creek

• terrestrial and aquatic biota sampling and habitat surveys.

The additional data and refinement of the CSM will allow the development of the 2017 HHRA and 2017 ERA, which will be reported under separate cover. The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report. The groundwater zones are material to the HHRA and will be redefined in the HHRA report.

Ongoing monitoring plan

The data collected as part of 2015 Stage 2B, 2016 Stage 2C, and the 2017 Stage 2C EI will be used to develop an OMP, which will cover both the environmental monitoring program and the residential sampling program. The OMP will be implemented to:

• capture seasonal and temporal variations in groundwater and surface water PFAS concentrations and conditions (in drains and creeks)

• provide early warning indicators for migration of contaminated groundwater

• monitor water levels and aquifer specific conditions.

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1.0 Introduction

1.1 Preamble AECOM Australia Pty Ltd (AECOM) was commissioned by the Department of Defence (Defence) to undertake a 2017 Stage 2C Environmental Investigation, (2017 Stage 2C EI) at the Army Aviation Centre Oakey (AACO) in Oakey, Queensland (the Site) and in surrounding off-Site areas (the Investigation Area). The Site location and the Investigation Area are shown on Figure F1 in Appendix B.

The Site was constructed in 1943, initially as a training facility and overflow aircraft maintenance depot for RAAF Base Amberley. The Site currently operates as the Army’s helicopter training school for pilots and aviation technicians and is also home to a Republic of Singapore Airforce (RSAF) helicopter squadron. The current layout of the Site is shown in Figure F2.

As part of typical airbase activities, aqueous film forming foam (AFFF) was used at the Site for fire training and emergency response from the 1970s. The main AFFF product used historically by Defence was 3M Lightwater™, which contained Per- and poly-fluorinated alkyl substances (PFAS) including Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA).

From 2004, Defence commenced phasing out its use of legacy AFFF containing PFOS and PFOA as active ingredients and progressively transitioned to a product called Ansulite® for use on the Defence estate. The product currently used by Defence does not contain PFOS and PFOA as active ingredients, only in trace amounts. AECOM understands that Ansulite® is used by Defence only in emergency situations where human life is at risk, or in controlled environments to test equipment, and any Ansulite® used by Defence is captured and treated and/or disposed of at licensed waste disposal facilities in accordance with best practice regulations, and standards. Based on anecdotal evidence, for the purposes of this report, it has been assumed that Defence commenced phasing out the use of AFFF products containing PFOS and PFOA at the Site from 2005. This assumption has not been verified by Defence.

1.2 Summary of Findings of Previous Investigations PFAS was first identified in the groundwater at the Site during an environmental investigation in 2010. Environmental studies conducted between 2010 and 2016 have identified that soil, sediment, surface water and groundwater on- and off-Site have been impacted by PFAS. A summary of the findings of these previous investigations is provided below:

• The legacy use of PFAS-containing AFFF for fire training and emergency response activities has created a legacy of contamination. It is inferred that PFAS (including PFOS and PFOA) have leached into and accumulated in surface soils, and impregnated concrete and other pavements in the areas where they have been used. Areas affected include AFFF storage and handling areas, fire training areas, former fire stations and locations where AFFF has been used for emergency response actions, such has foaming the runway in advance of a damaged aircraft landing. The active and depleting potential sources of PFAS are presented in Figure F3, a conceptual model of estimated PFAS source and history is presented in Figure F4.

• It is likely that PFAS contamination has been mobilised in rainwater runoff and has impacted the drainage lines flowing off-Site towards the south. The drainage lines represent both an ongoing source of PFAS contamination on- and off-Site and a preferential pathway for migration of contamination from the Site. PFAS have been detected in water and sediment in the drains and in Oakey Creek.

• PFAS in groundwater has migrated off-Site from the multiple source areas on-Site towards Oakey Creek in west and south-westerly directions. The extent and orientation of the plume is more southerly than expected based on the predominantly westerly groundwater flow direction beneath the Investigation Area. The affected area extends approximately 4.5 km off-Site to the south-west.

• The PFAS concentrations in groundwater were highest in the upper zone of the Oakey Creek Alluvium aquifer (i.e. at the top of the groundwater table at approximately 14 m below ground

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surface) and contaminant movement has been potentially influenced by: groundwater pumping from bores drawing from the Oakey Creek Alluvium aquifer; migration of PFAS in surface water along southerly orientated unlined drains and Oakey Creek; and infiltration to groundwater and mobilisation of PFAS along Oakey Creek during periods of flow and recharge from the stream flow into the groundwater system at considerable distance downstream from site.

Localised petroleum hydrocarbon contamination, including light non-aqueous phase liquid (LNAPL) has been historically detected in groundwater on-Site in Area C1 (see Figure F2). The petroleum hydrocarbon contamination has been delineated down-hydraulic gradient and has not migrated to the site boundary.

This report builds on the previously issued environmental site assessment report: AECOM, 2016, Stage 2C Environmental Site Assessment, Army Aviation Centre Oakey, Department of Defence, 60438981 Final, 26 July 2016 and provides an updated understanding of the Site and the Conceptual Site Model.

1.3 Objectives The main objectives for the 2017 Stage 2C EI were:

• Conduct ‘data gap’ investigations and analysis and update the technical reports prepared as part of the 2016 Stage 2C EI (the ESA, HHRA and ERA). The purpose of the data gap analysis was to reduce uncertainty around the nature and extent of PFAS impact in relation to some of the risk exposure pathways and magnitudes and to refine assumptions used to assess risks to human health and ecological receptors.

• Develop an ongoing monitoring plan (OMP) to cover both the environmental monitoring program and the residential sampling program. The OMP will be implemented to capture seasonal and temporal variations in groundwater and surface water PFAS concentrations and conditions (drains and creeks), provide early warning indicators for migration of contaminated groundwater and monitor water levels and aquifer specific conditions.

• Continue stakeholder information and engagement to facilitate access for field works associated with the investigation and proactively inform and engage with stakeholders throughout the project.

• Capture and retain site-specific information for Defence. All site-specific data will be captured and retained for use by Defence, and the Defence Contaminated Site Register and Contamination Risk Assessment Tool records will be updated.

The data gaps addressed as part of the 2017 Stage 2C EI were identified in conjunction with relevant Queensland Government agencies and an independent Technical Advisor appointed by Defence. The data gaps relevant to this 2017 Stage 2C EI are presented in the:

• site assessment

• groundwater modelling.

1.3.1 Site assessment

The following data gaps in the site assessment were addressed:

• Refinement of data required in Groundwater Zones 1 and 2. The data collected in the 2017 Stage 2C EI will be used in the HHRA report to better define the boundaries of Groundwater Zones 1 and 2 as defined in the 2016 HHRA. The additional data collected will also be used to refine the remainder of the IA.

• Limited understanding of the presence and distribution of the extended suite of PFAS within the different sample media (soil, sediment, surface water and groundwater) (see Section 2.4) and limited understanding of the composition of all firefighting foams, including the identifiable PFAS suite and total oxidisable precursor assay (TOPA) analysis where foams are fluorinated (see Section 2.5.2).

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• An incomplete dataset to inform future environmental sampling requirements and be used as a basis for the OMP (the development of the OMP itself is considered as a separate project component).

• Limited understanding of the current groundwater conditions with respect to non-PFAS contaminants of potential concern (COPC) that may impact PFAS remediation options (see Section 2.2.3).

• Limited understanding of the potential risks to the Great Artesian Basin (GAB) (see Section 2.2.1) including:

- potential connections across multiple aquifers (e.g. Oakey Creek Alluvium to Walloon Coal Measures) via bores that were constructed prior to the current legislated standards, in particular, investigation of licensed extraction bores RN107812, RN87439 and RN87369

- the risk that unregistered bores pose to the GAB and any remediation or mitigation measures

- the groundwater resources associated with the underlying Walloon Coal Measures aquifer, which form part of the hydrogeological GAB

- the groundwater resources associated with the underlying Main Range Volcanics aquifer

• Limited understanding of the influence of potential PFAS secondary source areas, including irrigation return flow, landfill inputs and flooding along road side areas.

• Limited understanding of the implications of extraction of potentially contaminated overland flow water and/or surface water by entitlement holders.

• Limited understanding of water interactions (surface water, groundwater, sediment and soil interactions; see Section 2.2.5), the influence of flooding, surface water extraction and irrigation return on PFAS migration/extent and the correlation between concentrations in irrigation water and soil.

• Limited understanding of the influence of stormwater drainage channels on PFAS migration (see Section 2.1.4 and Section 2.2.2). In particular:

- the distribution of PFAS in sediments and near-surface soils at locations along drainage channels

- the influence of drains on PFAS migration though completion of leachate tests

- the vertical infiltration rates in drain beds

- temporal variability of PFAS in surface water

- temporal variability in flow in the drainage channels

• Limited understanding of the nature and extent of the on-Site source areas (see Section 2.1.1 and Section 2.1.2) including:

- the nature and extent of existing contamination on-Site for all relevant media (including soil, sediment, groundwater, surface water, etc.)

- identification and prioritisation of all on-Site potential sources of PFAS in terms of PFAS mass load and potential mobility to groundwater, surface water and biota

- soil sampling on-Site where PFAS have previously been identified (or areas not yet tested), but the lateral and vertical extent has not been adequately delineated

• Limited understanding of the influence of wind as a transport mechanism (see Section 2.2.3).

• Ongoing residential sampling to monitor groundwater contamination levels where requested by the owner for agricultural enterprises within the current and future Investigation Area (see Section 2.3).

1.3.2 Groundwater modelling The following groundwater modelling data gaps were addressed (see Section 2.4):

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• Refinement of the groundwater model by updating the 2016 groundwater model to include additional groundwater level and concentration data collected since development of the 2016 model. The model conceptualisation was reassessed, and included migration rates and solute transport based on additional geological, groundwater, migration mechanisms and source data and quantification of historical pumping rates from domestic and stock wells and water balance modelling for ponded areas. The refinement will support development of future monitoring programs.

• Model included limitations regarding potential sources, water interactions (mechanisms and leakage rates from sources) and solute transport. Model uncertainty was reduced by including additional calibration using the data collected as part of the 2017 Stage 2C EI, and by validation of assumptions compiled during the construction and calibration of the model.

• Limited understanding level of natural connectivity to the GAB’s formations, and the subsequent risk this poses to the aquifer and entitlement holders, and to understand the risk from both infiltration and via bores acting as conduits.

1.4 Context of the 2017 Stage 2C EI Tasks undertaken by AECOM during 2017 for the environmental investigation have included the following:

Environmental Site Assessment (ESA) (this Report): This includes investigation of on- and off-Site PFAS concentrations in soil, sediment, surface water and groundwater; hydrogeological investigations; and updates to the groundwater flow model and PFAS solute transport model. Data collected from previous environmental investigations, testing data from Site redevelopment projects and data from the Department of Natural Resources and Mines (DNRM) have also been incorporated into this 2017 Stage 2C EI Report.

Residential sampling: Sampling and analysis of bore water and soil samples (at landholder request to Defence) from residences within and near the Investigation Area. In some instances water was also sampled from rainwater tanks, taps and swimming pools. Selected data from this program have been used to inform the 2017 Stage 2C EI Report.

Off-Site biota sampling: Following a community survey (between February and May 2017) to investigate the consumption of edible flora and fauna within the Investigation Area, a sampling program was conducted. Samples of home-grown fruit and vegetables, chicken eggs and samples of yabbies, shrimps and mussels from local creeks were collected and analysed for PFAS. Co-located soil, sediment, surface water and groundwater were also collected and analysed for PFAS. This work was conducted to support the HHRA and biota results are presented in this 2017 Stage 2C EI Report.

HHRA (in preparation): Multiple pathway HHRA to evaluate the potential human health risks to identified receptors within the Oakey area. This report will update the 2016 HHRA report and included consideration of direct contact exposures to environmental media (e.g. soil, groundwater, surface water, and sediment) as well as secondary exposures via dietary intakes, including fish, invertebrates and home grown plant and animal produce. The report will also be updated to include the Human Health Based Guidance Values by the Food Standards Australia and New Zealand (FSANZ) issued in April 2017.

ERA (in preparation): The ERA has been updated in 2017 to provide assessment the potential risk from the identified PFAS contamination to ecological receptors which inhabit habitats present at the Site and surrounding area. The 2016 ERA assessed the potential for wider ecosystem impacts to result from the accumulation of PFAS in terrestrial and aquatic organisms exposed to PFAS contamination. The current investigation included the collection and analysis of flora and fauna samples including hares, fish, yabbies, shrimps, mussels and worms. River and bird surveys and habitat assessments were also carried out.

Community engagement: Facilitation of community engagement as related to conduct of the 2017 Stage 2C EI and other tasks as listed above including land access, water and lifestyle surveys and community information events.

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2.0 Scope of Work The scope of work completed to address the data gaps are presented in the following sections.

2.1 Scope of Work On-Site 2.1.1 Source Area soil characterisation

AECOM (2015a) identified that the potential depleting and active PFAS source areas at the Site included the following:

• Spent AFFF recovery tank in Area A2

• Hot refuel area in Area A2

• Spent AFFF recovery tank in Area S1

• Spent AFFF recovery tank in Area C1

• Current AFFF storage and decanting area within Area D2

• Current fire training ground within Area D2

• Former fuel compound and hot refuelling point in Area F1

• Former fire station and foam training area in Area B3

• Former fire training ground in Area North.

The location of these potential source areas are shown in Figure F3.

The scope of work activities to investigate these source areas included:

• Drilling of eight deep soil bores that were converted to groundwater monitoring wells

• Drilling of 26 shallow soil bores up to 5 mbgs that were backfilled

• Collection of soil samples from unsaturated and saturated zones

• Laboratory analysis of soil samples for COPC. Selected samples were analysed for PFAS, TOPA and a non-PFAS suite.

Due to the detection of elevated concentrations of PFAS at the former fire training ground, five additional shallow soil bores were advanced to further assess the extent of the impact.

The characterisation program was designed to:

• acquire data on the lateral and vertical distribution of PFAS in unsaturated zone soils close to all these potential source areas

• allow the residual mass of contamination in the unsaturated zone to be better estimated

• collect additional geological data to improve the understanding of the lithology and stratigraphy beneath the potential source areas to improve understanding of the migration pathways of PFAS through the unsaturated and saturated zones.

The rationale for the source area characterisation was as follows:

• For discrete sources (i.e. the underground storage tanks (USTs)), soil bores were located close to the source and advanced to at least 1 m below the level of the base of tank, to assess potential impacts from leaks or spills. For the source areas with larger footprints (such as the fire training grounds), a larger number of soil bores were advanced to provide spatial coverage of the area. As a site investigation was recently conducted in 2016 at the former fire station and fire training area in Area B3, no additional soil characterisation work was included for this area. Due to the high number of existing sampling points proximal to the spent AFFF recovery tank in Area C1, no additional soil characterisation work was included for this potential source area.

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• One new deep groundwater monitoring well was constructed at each of the source areas with the exception of the former fire training ground, where two deep bores were constructed, and the former fire station and fire training area, which had existing multiple bores. The location of the bores was designed to complement the existing monitoring network. The new groundwater monitoring wells were typically located to the south-west of the source area to allow the collection of groundwater samples down-hydraulic gradient of the source area. Two new groundwater monitoring wells were installed at the former fire training area as there was only a single existing groundwater monitoring well close to this source area.

• Three shallow soil bores (to 3 mbgs) targeted an area where AFFF was potentially discharged historically. This area was located to the east of Area D2.

• The groundwater monitoring wells were designed to target the upper zone of the Oakey Creek Alluvium aquifer as this zone was previously identified as containing the highest PFAS concentrations in groundwater.

2.1.2 Additional groundwater monitoring wells on-Site

The scope of work included drilling two additional bores, which were converted to groundwater monitoring wells. These were drilled to provide additional monitoring points in the eastern portion of the Site to provide characterisation of the area of PFAS groundwater contamination up-hydraulic gradient of the main potential source areas. These wells were designed to target the upper zone of the Oakey Creek Alluvium aquifer. Soil samples were collected from unsaturated and saturated zones and selected samples analysed for PFAS, TOPA and a non-PFAS suite.

2.1.3 Groundwater characterisation

The scope of work included monitoring of the groundwater in 57 newly installed and existing groundwater monitoring wells with samples collected from 52 wells and analysed for PFAS. Selected samples were analysed for TOPA and non-PFAS contaminants. The purpose of the sampling and analysis was to ascertain the current PFAS concentrations in the upper zone of the Oakey Creek Alluvium aquifer. Monitoring wells were selected to target the potential and known source areas of contamination as well as to characterise PFAS groundwater contamination up-hydraulic gradient (to the east) of the source areas to understand the lateral extent of the groundwater contamination.

Additional Site-wide characterisation for a broad non-PFAS suite, including organic and inorganic contaminants, was conducted in all 52 wells sampled to establish the general groundwater quality and to assist with the future planning of management options. In particular, there was a known area of LNAPL present in Area C1 and an additional aim of the groundwater characterisation was to delineate the current extent of the dissolved phase petroleum hydrocarbons.

The ten new groundwater monitoring wells were sampled and this was complemented by the sampling of 42 selected existing wells to optimise the data collection. This program allowed the characterisation of previously identified impacted areas as well as potential areas of groundwater impact that have not been previously investigated.

Groundwater level measurements were made in all 57 wells to assess the groundwater flow direction.

2.1.4 Drainage channel characterisation

Residual PFAS has previously been detected in the sediment within the on-Site drainage channels. The stormwater channels are considered to be a potential preferential pathway for PFAS to migrate off-Site to surface water bodies (Oakey Creek) and also groundwater. The scope of work included drilling of 21 shallow soil bores at selected locations along each of the three drainage channels (drainage channels 1, 2 and 3) to characterise vertical soil PFAS contamination profiles. Soil bores targeted areas along the centre of the drainage lines where water potentially pools. At two locations, a transect of three soil bores was taken across a horizontal section of the drainage channel to provide a profile of the central and side portions. Selected soil samples were analysed for an extended PFAS suite, TOPA and a non-PFAS suite. Analysis for PFAS leachate by the Australian Standard Leaching Procedure (ASLP) using deionised water was conducted on selected samples to provide information on the leaching potential of soils. Deionised water was used as it is considered to be representative of rainwater mobilising PFAS from the soil. Infiltration testing was conducted at three wells within two drainage channels to understand the permeability of the near surface soils.

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These data investigated the relationship between PFAS concentration in solid media and potential release to the environment, and to assess if migration of sediments along the drainage channels and/or through the base of the drainage channels represents a preferential pathway for PFAS migration off-Site. The data were also collected to assess if there is a connection between the sediment/soil types and PFAS leachability and to allow evaluation of the potential for PFAS in sediment/soil to act as ongoing sources of surface water and infiltrate to the underlying groundwater.

2.1.5 Stormwater sampling

Stormwater sampling from drainage channels was conducted on an opportunistic basis following heavy rainfall events. Samples were collected on two occasions (with a total of 22 samples collected) to provide a larger dataset to better understand temporal variability in PFAS concentrations in surface water. The water samples were analysed for PFAS and non-PFAS suites. Surface water level measurements were collected in drainage channel 2 by the installation of a continuous data logger for a period of one-month.

2.2 Scope of Work Off-Site 2.2.1 Groundwater characterisation The off-Site groundwater characterisation included:

• installation of 21 shallow and nine deep groundwater monitoring wells

• collection of soil samples from unsaturated and saturated zones with selected samples analysed for an extended PFAS suite and for particle size distribution (PSD), total iron and total organic carbon (TOC)

• collection of groundwater samples from all new and existing Defence-owned off-Site groundwater monitoring wells (37 wells). All samples were analysed for the extended PFAS suite with a subset analysed for TOPA

• borehole assessments of three existing registered bores by wireline logging with pumping tests conducted on these bores.

The rationales for the site investigation design were as follows:

• Establish a background bore monitoring the Oakey Creek Alluvium aquifer located hydrogeologically up-gradient (to the north-east) of the Site to provide background concentrations for comparison with on-Site and down-gradient groundwater.

• Improve the conceptual understanding of the distribution of PFAS in the Oakey Creek Alluvium aquifer within Groundwater Zone 2, additional groundwater monitoring wells were required to monitor the shallow groundwater. New groundwater monitoring wells were installed in the centre of Zone 2, in the southern central area and in the north-western and south-eastern areas.

• Improve the conceptual understanding of the distribution of PFAS in the Oakey Creek Alluvium aquifer within Groundwater Zone 1, additional groundwater monitoring wells were required to monitor the shallow groundwater. This included new groundwater monitoring wells positioned:

- in the south-eastern portion of Groundwater Zone 1

- along the leading edge of the area of PFAS contamination in the south and south-west

- within the off-Site area close to, and south-west of, the Site, which has higher PFAS concentrations in groundwater

• Characterise the groundwater immediately up- and down-hydraulic gradient of a former landfill by installing three groundwater monitoring wells. These additional groundwater wells investigated whether the landfill is a separate primary source of groundwater PFAS contamination. In addition, the new groundwater monitoring wells located in the southern portion of Oakey will provide groundwater characterisation close to other potential off-Site primary sources identified in the desktop study (AECOM 2015a) including the former waste water treatment plant (which historically processed trade waste from the Site) located along the western portion of Lorrimer

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Street and an area potentially used for off-Site fire training by non-Defence personnel along the eastern portion of Lorrimer Street.

• Investigate impacts from several bores (registered and unregistered) that have been recognised by DNRM to possibly have been constructed to access multiple aquifers. Borehole assessments using wireline logging in three licensed extraction bores (RN107812, RN87369, RN87439) investigated whether the screens potentially act as preferential pathways or conduits for contaminated groundwater from the Oakey Creek Alluvium aquifer to move into the underlying Main Range Volcanics or Walloon Coal Measures (GAB) aquifers. Following the wireline logging, pairs of groundwater monitoring wells were installed adjacent to each of the three licensed bores, into the Oakey Creek Alluvium aquifer and each underlying aquifer (Main Range Volcanics or Walloon Coal Measures). The shallow well in each pair was also designed to complement the existing monitoring network and provide additional assessment of the lateral extent of the PFAS groundwater contamination in Groundwater Zone 1.

• Investigate the risk to the Oakey Creek Alluvium aquifer at irrigation return flow (existing farm dams) and flood inundation locations. Two pairs of groundwater monitoring wells were installed adjacent to each of the two dams and two pairs of wells were installed at locations known to be impacted by floodwater. The wells were installed into the Oakey Creek Alluvium aquifer and the underlying aquifer. The shallow well in each pair was also designed to complement the existing monitoring network and provide additional delineation of the lateral extent of the PFAS groundwater contamination in Groundwater Zone 1.

• Refine the groundwater model to further assess/predict risks to the Main Range Volcanics and Walloon Coal Measures aquifers through the collection of additional hydrogeological data (water level and chemistry). The collection of hydrogeological and geochemistry data in the deeper aquifer (Main Range Volcanics and Walloon Coal Measures) wells allowed assessment of the risk to the groundwater resources from the migration of the PFAS contamination within the overlying Oakey Creek Alluvium groundwater into the underlying aquifers (Main Range Volcanics and Walloon Coal Measures). The Main Range Volcanics aquifer, while not part of the GAB, is a viable groundwater resource.

2.2.2 Drainage channel soil characterisation

The purpose of the off-Site sediment and near-surface soil characterisation was to understand the vertical and lateral distribution of residual PFAS within the off-Site portion of the drainage channels. Soil bores were advanced at three locations along each of the three main drainage channels (Drainage Channels 1, 2 and 3), representing locations close to the Site, at the midpoint between the Site boundary and Oakey Creek, and close to Oakey Creek. A total of 13 soil bores were advanced. The soil bores targeted the centre of the drainage channel, which is where water was likely to pool. At two locations along Drainage Channels 1 and 2, a transect of three soil bores was installed across a horizontal section of the drainage channel to provide a profile of the central and side portions. Selected soil samples were analysed for an extended PFAS suite and TOPA with a small number of samples analysed for PFAS leachate to understand the potential for PFAS in sediment / soil to act as ongoing sources of surface water and groundwater impact.

The data collected investigated the relationship between PFAS concentration in solid media and potential release to the environment and to determine if migration of sediments along the drainage channel and/or through the drainage channel base represent preferential pathways for PFAS migration. The data also assessed if there is a connection between the soil/sediment types and PFAS leachability, and to allow evaluation of the potential for standing water to infiltrate to the underlying aquifer.

2.2.3 Surface soils

Surface soil sampling was conducted at 45 off-Site sampling locations to collect data to evaluate the potential for PFAS in soil to be transported via wind (i.e. in soil dust), or overland in surface water during flood inundation events. Sample locations were representative of locations downwind of the prevailing wind direction (from east to west) or frequent wind directions (west to east, south-west to north-east and north-east to south-west) and locations potentially affected by inundation events or irrigation using groundwater.

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2.2.4 Stormwater, surface water and sediment sampling

The following types of sampling were conducted:

• Surface water was sampled from the three drainage channels (referred to as ‘stormwater’) on an opportunistic basis following heavy precipitation events.

• Surface water samples were collected from the three local creeks: Oakey Creek, Doctor Creek and Westbrook Creek.

Samples of sediment and aquatic biota were also collected from the creek sampling locations.

The purpose of the stormwater and creek sampling was to provide a larger dataset to better understand temporal variability in PFAS concentrations in stormwater in the drainage channels and surface water in local creeks. The creek and sediment sampling data and co-located biota samples were collected for use in the HHRA and ERA.

2.2.5 Modelling of surface water interactions The scope of work included updating the existing hydraulic model for Oakey using supporting reports/datasets (such as the Toowoomba Regional Council flood inundation modelling layers) to map the stormwater network layout on-Site and interactions between the stormwater network with surrounding hydrologic features. The work aimed to improve the understanding of the current hydrologic and drainage regime for the Site and immediate surrounds and to better understand PFAS migration patterns in surface water across the Investigation Area.

2.3 Residential Sampling Program Annual resampling of 81 residential bores (including 66 properties) was conducted between January and June 2017. Five soil samples were also collected from residential properties during the 2017 Stage 2C EI. The sample results have only been used where permission to do so has been provided by the landowner. The purpose of the sampling was to:

• collect and analyse soil samples as requested by the landowner

• continue to assess the concentrations of PFAS in groundwater sourced from off-Site abstraction bores

• monitor and assess the concentrations of PFAS in household water supplies, including: tank water from tanks used for household purposes; cold water from kitchen taps where water is supplied by tank water; and hot water from kitchen taps where water is supplied by tank water via a hot water system

• monitor and assess the concentrations of PFAS in residential swimming pools.

2.4 Groundwater Modelling The scope of work for the groundwater modelling included:

• undertaking a technical review of the model conceptualisation, model construction, calibration and simulations, particularly the approach used for solute (i.e. PFAS) transport

• updating the model conceptualisation based on data compiled during the site investigation works

• refining the groundwater model’s structure, calibration and predictions

• addressing the model’s limitations relating to stream recharge (leakage rates), layer hydraulic properties, solute transport, calibration and chemistry simulations

• utilising the model to address data gaps and facilitate decision making and inform the OMP.

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2.5 Laboratory Analysis 2.5.1 PFAS laboratory analysis

To improve understanding of the range of potential PFAS present in environmental media in the Investigation Area, all primary soil, sediment, surface water and groundwater samples were analysed for the extended PFAS suite of 28 compounds. These compounds are identified in Table 2-1. Table 2-1 Compounds analysed in the extended PFAS suite

PFAS Group Compound Abbreviation CAS No. Perfluoroalkyl Sulfonic Acids

Perfluorobutane sulfonic acid PFBS 375-73-5 Perfluoropentane sulfonic acid PFPeS 2706-91-4 Perfluorohexane sulfonic acid PFHxS 355-46-4 Perfluoroheptane sulfonic acid PFHpS 375-92-8 Perfluorooctane sulfonic acid PFOS 1763-23-1 Perfluorodecane sulfonic acid PFDS 335-77-3

Perfluoroalkyl Carboxylic Acids

Perfluorobutanoic acid PFBA 375-22-4 Perfluoropentanoic acid PFPeA 2706-90-3 Perfluorohexanoic acid PFHxA 307-24-4 Perfluoroheptanoic acid PFHpA 375-85-9 Perfluorooctanoic acid PFOA 335-67-1 Perfluorononanoic acid PFNA 375-95-1 Perfluorodecanoic acid PFDA 335-76-2 Perfluoroundecanoic acid PFUnDA 2058-94-8 Perfluorododecanoic acid PFDoDA 307-55-1 Perfluorotridecanoic acid PFTrDA 72629-94-8 Perfluorotetradecanoic acid PFTeDA 376-06-7

Perfluoroalkyl Sulfonamides

Perfluorooctane sulphonamide FOSA 754-94-6 N-Methyl perfluorooctane sulfonamide MeFOSA 31506-32-8 N-Ethyl perfluorooctane sulfonamide EtFOSA 4151-50-2 N-Methyl perfluorooctane sulfonamidoethanol MeFOSE 2448-09-7 N-Ethyl perfluorooctane sulfonamidoethanol EtFOSE 1691-99-2 N-Methyl perfluorooctane sulfonamidoacetic acid MeFOSAA 2355-31-9 N-Ethyl perfluorooctane sulfonamidoacetic acid EtFOSAA 2991-50-6

Fluorotelomer Sulfonic Acids

4:2 Fluorotelomer sulfonic acid 4:2 FTS 757124-72-4 6:2 Fluorotelomer sulfonic acid 6:2 FTS 27619-97-2 8:2 Fluorotelomer sulfonic acid 8:2 FTS 39108-34-4 10:2 Fluorotelomer sulfonic acid 10:2 FTS 120226-60-0

2.5.2 Analysis for TOPA contaminants

Selected soil and groundwater samples were analysed for the TOPA analysis to better understand PFAS conditions within the Investigation Area. The samples that had the highest PFAS concentrations from the source areas and drainage channel pathways on-site were targeted. Selected sediment samples from the off-Site drainage channels and selected off-Site groundwater samples, representing higher and lower PFAS concentrations were also analysed. The purpose of the TOPA analysis was to assess for the potential presence of carboxylic acid and sulfonic acid precursors which may not be detected using the standard analysis. There were 28 soil and 12 groundwater samples analysed for TOPA.

2.5.3 Analysis for non-PFAS contaminants

Non-PFAS COPC sample analyses was conducted to improve understanding of the range of potential non-PFAS COPC present on-Site, to obtain a representative dataset and to provide information for use in remediation planning. Groundwater and stormwater samples collected from on-Site were analysed for a generic suite of non-PFAS COPC contaminants that are potentially present on Defence sites, as identified by Golder Associates (2016a). The generic suite included metals, petroleum hydrocarbons (including total recoverable hydrocarbons (C6-C40) (TRH), benzene, toluene,

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ethylbenzene, xylenes, naphthalene (BTEXN)), polycyclic aromatic hydrocarbons (PAHs), volatile and semi-volatile organic compounds (VOCs/SVOCs) and 1,4-dioxane. All groundwater samples were also analysed for major cations and anions to aid the PFAS assessment. Selected soil samples from the near surface (i.e. between 0 and 0.5 mbgs) at locations on-Site and locations along the off-Site portion of drainage channels 1, 2 and 3 were also analysed for non PFAS COPCs (including metals), petroleum hydrocarbons (including TRH, BTEXN and PAHs), VOCs, SVOCs, organochlorine and organophosphorus pesticides (OC/OP pesticides) and 1,4-dioxane.

If potential asbestos-containing material was observed in soil, samples were to be collected and tested at the laboratory. As potential asbestos-containing material was not observed during the site investigation works, no soil samples were tested for presence of asbestos fibres.

2.5.4 Permeability testing Geotechnical soil samples were collected from seven of the off-Site soil bores that were drilled into the Main Range Volcanics and Walloon Coal Measures formations. Samples were collected at 5 m intervals and tested for permeability by falling head or constant head test in accordance with AS 1289.0-2000 Methods of testing soil for engineering purposes, Methods 6.7.1 and 6.7.2. A total of 49 soil samples were collected and tested. The purpose of the data was to improve understanding of hydrogeological parameters of the different types of rock underlying the Investigation Area to refine the parameters used in the groundwater modelling.

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3.0 Site Identification and Environmental Setting

3.1 Site Location and Surrounding Land Use 3.1.1 Regional Oakey District In a regional context, the Site is located approximately 35 km north-west of Toowoomba on the western side of the Great Dividing Range, as shown on Figure F1. Oakey is located within the Darling Downs region, approximately 128 km west of Brisbane. Current land uses surrounding the Site are largely residential and rural−residential, with some agricultural land use. The major land uses in the region are agriculture, cattle grazing and horse agistment. In Oakey the land uses include low density residential, commercial premises and industrial properties. The closest urban uses to the Site are a series of industrial properties located on Orr Road, approximately 800 m to the south of the Site.

3.1.2 The Site The Site occupies an area of approximately 850 hectares and is located on alluvial floodplains approximately 2 km north-east of Oakey. The Site is currently used by the Defence Force for Army Aviation, and has maintained a role as a military facility since the Site’s inception in 1943. The Site boundary is shown on Figure F2, along with major Site features. The northern part of the Site is the airfield, while the southern part of the Site comprises support services, buildings and infrastructure. Approximately 290 hectares of the Site are leased for agriculture (in the western portion of the Site). The Site is bounded by Corfe Road, Oakey Cooyar Road, Wilthorne Kelvinhaugh Road and Oakey Kelvinhaugh Road. The main access point to the Site is via Beale Street and Orr Road. The Warrego Highway and Western Railway Line are located approximately 3 km and 1 km to the south of the Site, respectively.

3.1.3 Site history

A detailed account of the history of the Site is described in AECOM (2015a)1. Please refer to this report for further information on the site history.

3.1.4 Previous environmental investigations

Previous investigations relevant to this 2017 Stage 2C EI are listed below. A summary of key findings from the reports prepared prior to 2015 was included in AECOM (2015a).

• SKM, 2005. Stage 1 Environmental Investigation

• CERAR, 2006. Centre for Environmental Risk Assessment and Remediation, University of South Australia, Environmental Fate of New Fire Suppressing Products (Ansulite AFFF & 3M RF) compared to Light Water: A verification of manufacturer’s claims. April 2006

• SKM, 2008. Army Aviation Centre Oakey and Borneo Barracks, Improving Water Supply Service and Security

• Intelara, 2009. Oakey Base – Buildings C2 oil separator and storage – Report on probable leak and ground contamination. Intelara Pty Ltd. March 2009

• URS, 2010. Stage 1 and Stage 2 Environmental Investigation at Army Aviation Centre, Oakey, Queensland. 14 October 2010

• Coffey Geosciences, 2011. Stage 2 (Part 2) Environmental Investigation Army Aviation Centre Oakey

1 This report has been prepared by AECOM, an independent consultant engaged by Defence, based on information and sources described in the report. The findings and interpretations set out in the report are based on data gathered by AECOM within the time available, including publicly available information, data reports prepared for the Site, inspection of on-Site and off-Site areas and interviews of current and former Site personnel (where available).

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• Parsons Brinckerhoff (PB), 2012a. Environmental Investigation – Stage 3 Risk Assessment and Remediation Design, Army Aviation Centre Oakey

• PB, 2012b. Indicative Human Health Risk Assessment, PFOS/PFOA in AACO, Swimming Pool − Army Aviation Centre Oakey

• OTEK Australia Pty Ltd, 2013. Bench Testing and Water Treatment of Swimming Pool Water Combined Refrigeration Services Army Aviation Centre Oakey (AACO) Queensland

• PB, 2013a. Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey – Groundwater Monitoring Event. December 2012

• PB, 2013b. Off-site Risk Assessment, PFOS and PFOA in Groundwater − Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey

• PB, 2013c. Human Health Risk Assessment, Petroleum Hydrocarbons in Areas C1 and C2 − Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey

• PB, 2013d. February 2013 Addendum to Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey. Groundwater Monitoring Event

• PB, 2013e. Onsite Risk Assessment, PFOS and PFOA in Groundwater: Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey. 24 May 2013

• PB, 2013f. Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey (AACO), Remedial Options Feasibility Study. 30 May 2013

• PB, 2013g. Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey (AACO), Remediation Action Plan – Petroleum Hydrocarbons in Areas SQ0335 and SQ0117. 07 June 2013

• PB, 2013h. Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey (AACO), Remediation Action Plan – Perfluorocarbons in Groundwater. 12 June 2013

Investigations undertaken following the AECOM (2015a) report included:

• AECOM, 2015b. PFAS Conceptual Site Model − Army Aviation Centre Oakey. 28 July 2015

• AECOM, 2015c. Stage 1 and Stage 2 Environmental Investigation, Army Aviation Centre Oakey − Offsite Assessment – Addendum (Aug-Nov 2014 Sampling Report)

• AECOM, 2015d. Stage 1 and Stage 2 Environmental Investigation, Army Aviation Centre Oakey – Off-site Assessment – Addendum II. (December 2014 to May 2015 sampling)

• AECOM, 2015e. Stage 1 and Stage 2 Environmental Investigation, Army Aviation Centre Oakey – Drain sediment sampling. 23 July 2015

• AECOM 2016a Stage 2C Environmental Site Assessment, Army Aviation Centre, Oakey, 60438981 Final. 26 July 2016

• AECOM 2016b Stage 2C Environmental Investigation- Human Health Risk Assessment, Army, Aviation Centre, Oakey, 60438981 Final. 01 September 2016

• AECOM 2016c Stage 2C Environmental Investigation- Preliminary Ecological Risk Assessment, Army, Aviation Centre, Oakey, 60438981 Final. 01 November 2016.

The 2016 ESA report (AECOM, 2016a) presented interpretation of the results of an environmental investigation which included: installation of 21 new groundwater monitoring wells and collection of soil, sediment, surface water and groundwater samples from across the Investigation Area. The results provided an improved understanding of the nature, extent and potential migration of PFAS contamination within the Investigation Area based on data collected between 2014 and early 2016.

The 2016 HHRA report (AECOM, 2016b) assessed 47 potential human health exposure pathways. To facilitate assessment, toxicological profiles for selected PFAS were developed. Following the release of a hazard assessment report for PFOS, PFOA and PFHxS by Food Standards Australia New Zealand (FSANZ, 2017), a sensitivity assessment (as an addendum to the 2016 HHRA (AECOM, 2017e)) was completed to provide additional precautionary recommendations for the IA.

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The current precautionary recommendations are:

• continue not drinking groundwater in the IA

• minimise home grown egg consumption in Zone 1 and 2

• avoid or minimise using groundwater for bathing, showering, home swimming, paddling pools and/or sprinkler play in Zone 1 and Zone 2

• minimise consumption of the following until additional data can be collected to refine the HHRA:

- locally caught fish (in the IA)

- home grown vegetables (Zones 1 and 2)

- home grown red meat (Zones 1 and 2).

Additional environmental investigations conducted since the issue of the 2016 Stage 2C EI reports are listed below. Data from these investigations are incorporated into the data interpretation presented in Section 7.0:

• Soil Characterisation in Area S1 (Golder Associates 2016b, Remediation Action Plan, RSAF CH-47 Chinook, Super Puma Helicopter and Support Logistics (Project N. A9032). In support of redevelopment work, 53 soil samples were collected and analysed. Soil Contamination and Characterisation Report.

• Soil Characterisation for Alder Construction (AECOM 2016d). In support of redevelopment work for the carpark and gatehouse rehabilitation, 16 soil samples were collected and analysed.

• Oakey Remediation Feasibility Study (AECOM 2016e). This was an investigation at one of the main potential PFAS source areas at the Site (Former Fire Station and Foam Training Area in Area B3). The scope of the feasibility study included the analysis of 53 soil samples.

• Soil Characterisation for Civil Terminal Extension (AECOM, 2016f). In support of redevelopment work, four soil samples were collected and analysed.

• Soil Environmental Assessment: Joint Health Command Garrison Health Facilities Upgrade (AECOM 2017a), In support of redevelopment work, four soil samples were collected and analysed.

• Residential sampling in Q2 to Q4 2016. At landholders’ request, sampling and analysis of bore, tank, tap and pool water. These data were not included in the 2016 Stage 2C EI due to timing.

3.2 Environmental Setting 3.2.1 Topography The Site is located on a relatively flat alluvial plain. The regional topography slopes to the west and south-west in the direction of the Oakey and Condamine Floodplains. The locations of the Site, Oakey Creek and Doctor Creek are shown on Figure F1. The elevation of the Site is approximately 400 mAHD. Locally, inclines have been constructed to grade the drainage system away from the runways. The Site drains to the south via a series of unlined drains discharging into Oakey Creek. Cooby Creek Reservoir is located in the headwaters of the Oakey Creek catchment that partially regulates flow in Oakey Creek.

The physiography and drainage patterns of the Oakey Creek catchment have been outlined by Murphy (1990) and categorised as follows:

• The dissected basaltic uplands in the upper part of the catchment are composed of the Main Range Volcanics and Marburg Formation that are still undergoing down cutting and erosion.

• Basaltic plateau, also located in the uplands, with more subdued relief that is undergoing limited erosion and weathering due to the low relief.

• Mature landscapes lower in the catchment with undulating relief, where the bedrock has been modified by erosion.

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• The alluvial plains flanking Oakey Creek and terraces and colluvial slopes composed of the weathered bedrock.

3.2.2 Climate The average annual rainfall, from 1970 to 2015, based on the Bureau of Meteorology Oakey Aero station #41359 dataset and the Oakey scientific information for land owners (SILO) rainfall dataset, is 633 mm/year. The wettest months occur during summer with relatively dry winter months.

Long term Oakey SILO datasets (1970 to 2015) shows average evaporation peaks at 216 mm/month in December and January and is lowest at 69.2 mm/month in June.

Potential evapotranspiration peaks at 170 mm/month in December and is lowest at 56.3 mm/month in June.

The higher evaporation compared to rainfall indicates a negative climate balance across the Oakey area.

3.2.3 Geology

The regional geology of Oakey is presented in Figure F5.

Tectonically, the Site and surrounds are situated within the central eastern part of the Clarence-Moreton Basin, which contains sediments of the Late Triassic to Later Jurassic age. The sediments comprise sandstone, siltstone, mudstone, and coal. The Walloon Coal Measures is the uppermost formation of the Clarence-Moreton Basin, which underlies the IA. Unconformably overlying the Clarence-Moreton Basin are extensive areas of unconsolidated younger alluvial sediments such as the Oakey Creek Alluvium and Main Range Volcanics.

Table 3-1 indicates the geological stratigraphy in the IA. Table 3-1 Stratigraphy (source: AECOM, 2016a)

Period Unit Lithology Geological basin

Hydrogeological basin

Cenozoic (Quaternary)

Oakey Creek Alluvium

Gravel, sand, silt and clay

Cenozoic (Tertiary)

Main Range Volcanics

Alkali-olivine basalt, minor tuff, sandstone and mudstone

Mesozoic (Jurassic)

Walloon Coal Measures

Thin-bedded, claystone, shale, siltstone, lithic and sublithic to feldspathic arenites, coal seams and partings, and minor limestone

Clarence-Moreton Basin

Great Artesian Basin

The Oakey Creek Alluvium is deposited in valleys formed on weathered Palaeozoic, Mesozoic and Cenozoic bedrock (Barnett and Muller, 2008). The alluvium and alluvial deposits are heterogeneous floodplain and sheet wash deposits. Floodplain deposits are coarse grained sands and gravels located towards the centre of the river channel. Sheet wash deposits are finer grained and surround the floodplain deposit and extend out towards the alluvial valley margins.

The Oakey Creek Alluvium consists of a mixture of sands, clays and gravels containing a basal clay transitional layer characterised by clay material that represents the uppermost part of the underlying bedrock. The alluvium increases in thickness down catchment, with a maximum thickness of approximately 100 mbgs. This sequence thickening is to be expected, with increased alluvium developed where upstream catchments are larger, and where periodic flooding under lower gradient (and more sluggish velocity) can result in significant sediment displacement and settlement.

The Oakey Creek Alluvium is flanked by Cenozoic-aged colluvium and basalt (GSQ, 1980). The colluvium consists of cemented scree deposits and rock debris that overlie the Cenozoic-aged Main Range Volcanics (basalt), which crop out approximately 1.9 km south-east of the Site.

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The Jurassic-aged Walloon Coal Measures also crop out in the area and are composed of shale, siltstone, sandstone, coal, mudstone and limestone. North-west of Oakey, the Walloon Coal Measures and the Main Range Volcanics crop out in the upper reaches of Oakey Creek. The Marburg Formation is part of the underlying GAB and is composed of Jurassic sediments that contain coal measures, sandstone, siltstone, conglomerate and oolitic limestone and outcrop to the north and upstream of the Site.

The Main Range Volcanics and Walloon Coal Measures are underlain by sandstone of the Marburg Subgroup, which consists of the Hutton and Marburg Sandstone of Jurassic age, and are part of the GAB. Raiber and Cox (2012) consider the Walloon Coal Measures and Marburg sediments to be part of the GAB stratigraphy.

3.2.4 Hydrogeology The hydrostratigraphy of the region is dependent upon the major geological units described above.

3.2.4.1 Oakey Creek Alluvium

Hydrogeological setting The unconfined Oakey Creek Alluvium aquifer is part of the Murray Darling Basin system. Groundwater within the Quaternary-aged alluvium is managed by the Department of Natural Resources and Mines (DNRM) under the Oakey Creek Groundwater Management Unit (OCGMU). The DNRM groundwater database indicated that the aquifer is used for irrigation, domestic purposes, livestock watering and edible gardens, and historically, for intermittent potable water via town water supply bores during extreme dry periods.

The hydrogeology of the Oakey Creek Alluvium is complex and has been interpreted differently in some of the work undertaken to date by consultants and government agencies. Overlying the Oakey Creek Alluvium in most areas are unconsolidated unsaturated sediments consisting of sand and clay. Colluvium consisting of heterogeneous material including sand, silt, clay and rock fragments crops out around the flanks of hills towards the edges of the Oakey Creek catchment, onlapping the Oakey Creek Alluvium.

The alluvium consists of fluvial stream overbank deposits interbedded with discontinuous sequences of sand, silt, gravel and clay. Overall, the aquifer grainsize tends to coarsen with depth. The base of the aquifer consists of a coarse grained continuous basal gravel (i.e. lower alluvium) that is underlain by a clayey horizon (known as the transition zone), which partially confines the lower basal sands and gravels from the underlying Main Range Volcanics or Walloon Coal Measures (Murphy, 1990). This layer is a combination of low permeability basal alluvial clays of the Oakey Creek Alluvium and the Main Range Volcanics or the weathered upper part of the Walloon Coal Measures.

The maximum extent of the alluvium is downstream of Oakey Creek, where the width approaches 7 km and thicknesses of 40 m. Stratigraphic data indicates that higher productivity aquifer zones (palaeochannels) have formed within former channels that are composed of clean sands and gravels. These high yielding aquifer zones are up to 500 m wide, which is significantly wider that the modern bed width of less than 30 m (Murphy, 1990).

Although the transition zone is not always present beneath the alluvium, the transition zone (together with the upper mudstones and siltstones of the Walloon Coal Measures) provides resistance to vertical groundwater flow.

Groundwater quality

On a regional scale, natural groundwater quality within the Oakey Creek Alluvium is typically of low salinity in upstream areas, where the groundwater quality is influenced by discharge from the Main Range Volcanics that crop out at the top of the catchment. As the groundwater flows down-gradient towards the Site, the salinity increases as the water chemically evolves from magnesium, calcium and bicarbonate dominated water to being dominated by sodium and chloride (Merrick and Kelly, 2007). There appears to be little difference in the water quality between the upper and lower zones in the Oakey Creek Alluvium aquifer.

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Groundwater levels

Groundwater level fluctuations within the Oakey Creek Alluvium have been monitored by DNRM in a network of nested monitoring wells. Groundwater level variation over time is presented and discussed for key monitoring wells in the 2016 ESA report (AECOM 2016a) to assess interactions between rainfall and groundwater elevation. A hydrograph study area (a circle with a 10 km radius from the centre of the Site) was selected, and publicly available groundwater level monitoring data were extracted from DNRM monitoring well data located in the hydrograph IA. The hydrographs present groundwater elevation and rainfall data available between 1991 and 2015. Overall, groundwater elevations remained relatively stable at any given location, with periodic increases in elevation resulting from significant rainfall events (e.g. January 2011).

Groundwater flow Groundwater flow within the Investigation Area typically follows topography, with flow in the alluvium generally occurring in a south-westerly direction towards Oakey Creek and the Condamine River.

Recharge and discharge Recharge to the Oakey Creek Alluvium is by natural and anthropogenic sources.

Natural sources of recharge to the catchment include:

• rainfall

• losses from rivers

• inflow from other aquifers.

Anthropogenic sources may include:

• irrigation

• unlined stormwater drains

• controlled surface water flows

• point sources such as dams or ring tanks.

Discharge from the Oakey Creek Alluvium is via five main mechanisms:

• leakage to regional (bedrock) aquifers

• evapotranspiration

• baseflow to surface drainages

• flow through the alluvial aquifer down catchment

• groundwater extraction.

Most groundwater discharge occurs via groundwater extraction for irrigation, which has been occurring on a large scale since the 1970s.

Hydraulic parameters

The transmissivity of the Oakey Creek Alluvium, based on 18 pumping tests recorded on the DNRM groundwater database, ranges from 2 to 1,100 m2/day, with an average of approximately 180 m2/day. This high average transmissivity indicates the permeable nature of the alluvium.

Elevated transmissivity has been recorded from high yielding aquifer zones, where transmissivity of up to 3,000 m2/day has been estimated.

Based on the typical saturated thickness of the alluvium, 15 m, the hydraulic conductivity (permeability) of the Oakey Creek Alluvium is estimated between 0.1 and 75 m/day using pumping test data reported in AECOM (2016a), which is based on a number of sources including Murphy (1990) and QWC (2012).

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No direct assessment of the clay-rich transition zone is available for the Oakey Creek Alluvium, however, tests in similar sediments in the Condamine River alluvium (OGIA, 2016) estimated vertical hydraulic conductivity of 1 x 10-6 m/day (an effective aquitard).

No records of aquifer storage (specific yield and specific storage) are provided by DNRM in the groundwater database for the Oakey Creek Alluvium. Estimates of specific yield for the unconfined Oakey Creek Alluvium, using groundwater level response to discharge, are about 11%. A specific yield of 8% is used in the Oakey Creek Groundwater Management Area as part of the water sharing rules (DNRM, 2015).

3.2.4.2 Main Range Volcanics

Main Range Volcanics are comprised mostly of basalt and overlie the eroded surface of the Walloon Coal Measures. Most of the volcanics are extensively eroded and covered in part with Oakey Creek Alluvium. Regionally, the average thickness of the basalt is around 70 m.

The Main Range Volcanics crop out to the north and west of the Oakey Creek catchment and are discontinuous, possibly due to dissection caused by erosion, or local deposition caused by the basalt infilling the palaeo-topography. The basalts of the Main Range Volcanics form an aquifer that provides significant quantities of good quality groundwater (Merrick and Kelly, 2007). The aquifer is a dual porosity aquifer with groundwater in the rock matrix and vesicles connected by fractures. The degree of connectivity determines the available groundwater yield, and if the fractures are not continuous, pumping the aquifer for an extended period may not be sustainable.

The majority of runoff into Oakey Creek is derived from basalts of the dissected volcanic plateau from the south and east of the Site. The Main Range Volcanics are recharged by rainfall through fractures within the basalt. The Main Range Volcanics contain significant aquifers that are used for irrigation, stock, and domestic and (historically) town water supplies. Other Tertiary basalts in the area do not tend to be as high yielding as the Main Range Volcanics (Queensland Water Commission (QWC), 2012).

The suggested bulk hydraulic conductivity of the basalt ranges from 0.004 to 4.6 m/day. This is dependent on fractures, joints, and vesicles within the basalt (QWC, 2012).

3.2.4.3 Walloon Coal Measures

The Walloon Coal Measures are composed of a mixture of sedimentary and volcanoclastic rocks including sandstone, siltstone, shale, mudstone, coal and volcanolithic sandstone. The Walloon Coal Measures are approximately 200 m thick beneath the AACO and are considered to form an effective aquitard between the Oakey Creek Alluvium and the underlying GAB Hutton and Marburg Sandstone aquifers. As such, these aquifers are not considered further. The Walloon Coal Measures are thus considered the basement unit beneath the Oakey Creek Alluvium. The Oakey Creek Alluvium is incised into the Walloon Coal Measures in places within palaeochannels or where the Main Range Volcanics are absent.

Although the Walloon Coal Measures are considered to be an aquitard, in places they function as an aquifer (QWC, 2012). The coal seams are generally the more permeable units within a sequence of dominantly low permeability mudstones, siltstones or fine-grained sandstones. Most of the coal seams comprise numerous thin, non-continuous stringers or lenses (up to 45 individual coal seams can be recognised in places) separated by bands of low permeability sediments. The coal thickness makes up less than 10% of the total thickness of the Walloon Coal Measures (QWC, 2012).

Permeability reduces with depth in the Walloon Coal Measures, especially vertical permeability, which is low at depths greater than 800 m (QWC, 2012). In general, the porosity and permeability of sandstones within the formation are limited, but there are some sandstones with high porosity and permeability, particularly within the Clarence-Moreton Basin (QWC, 2012).

The unit forms a fractured rock aquifer with generally poor quality water. The aquifer typically has a low hydraulic conductivity and consequently the groundwater yields are typically low, suitable only for stock supplies. The majority of groundwater is contained within the Walloon Coal Measures; however, the water quality is typically brackish (Hillier, 2010).

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The various units that form the Walloon Coal Measures appear to be hydraulically connected with one piezometric surface with a general westerly flow direction (Hillier, 2010). There is little groundwater quality information available for the Walloon Coal Measures. Groundwater from the Walloon Coal Measures is likely to recharge the Oakey Creek Alluvium high in the catchment, and groundwater from the Oakey Creek Alluvium is likely to discharge to the Walloon Coal Measures low in the catchment − much the same as the Main Range Volcanics. However, due to the low hydraulic conductivity of the Walloon Coal Measures, the magnitude of groundwater interaction with the Oakey Creek Alluvium is expected to be significantly less than the Main Range Volcanics.

The hydraulic conductivity of the coal seams of the Walloon Coal Measures has a range between 0.0006 and 0.9 m/day, with a median of 0.08 m/day (QWC, 2012).

The specific yield of the Walloon Coal Measures is 0.005% (QWC, 2012). Literature values for the specific yield for basalt (weathered, fractured, and vesicular basalt) are about 1 to 5%.

3.2.4.4 Great Artesian Basin The Oakey township is located within the GAB. This water is often the only reliable supply available for urban use and to properties for their domestic and stock watering requirements. However, groundwater use from the GAB in the Oakey region is limited due to the availability of shallower groundwater, predominantly from the Oakey Creek Alluvium and to a lesser extent from the Main Range Volcanics, which do not form part of the GAB. However, groundwater from the deeper aquifer that forms part of the GAB is known to be used as a supplementary source of water for industry at one location (AECOM, 2015a).

3.2.5 Groundwater management and use

3.2.5.1 Oakey Creek Groundwater Management Area Groundwater use in the area is administered by DNRM under the water sharing rules outlined in the Oakey Creek Groundwater Management Area (DNRM, 2015). The catchment includes Oakey Creek and some of its tributaries, and is bounded by Tertiary basalts and colluvium. The water sharing rules are designed to account for water use under a water licencing system and only applies to groundwater from the Oakey Creek Alluvium. The management area is divided into four sub-areas. The Site is located where the alluvium within the Oakey Creek floodplain is at its widest. The domain of the groundwater model developed for the 2017 Stage 2C EI includes two of the four Oakey Creek groundwater management sub-areas. The 2017 groundwater model domain has been reduced to include two of the four sub-areas to focus on the key areas down-hydraulic gradient of the Site.

Groundwater abstraction rates are difficult to collate, as many private bores are unregistered. Abstraction rates have been estimated by collating existing DNRM abstraction records, license entitlements, discussions with bore users during stakeholder meetings and consideration of water sharing plan rules.

The primary use for groundwater in the Oakey Creek catchment is for crop irrigation and livestock. Over-extraction and depletion of the groundwater resource within the alluvial aquifers of the Darling Downs has been recognised since the 1960s, when irrigation extraction rates increased at a rapid rate (Lane, 1979). As a result of increasing groundwater use and declining groundwater levels, unrestricted groundwater use was discontinued and licensing introduced to regulate groundwater extraction.

In 1989, the groundwater allocation for the Oakey Creek catchment was 7,500 ML/year, which was composed of irrigation (6,700 ML/year), industrial (500 ML/year), and town water supply (300 ML/year) (Murphy, 1990).

Groundwater use continued to increase and in 1996/97 compulsory water metering was introduced to assist in regulating groundwater allocations (MBDA, 2014). By 2013 the groundwater allocation for the Oakey Groundwater Management Area had increased to over 10,000 ML/year (MBDA, 2014). The algorithm to allocate annual entitlement for the catchment is complex and based on a number of factors, including abstraction from the previous year and the response of regional hydrogeological conditions. Groundwater abstraction rates from the Oakey Creek Alluvium aquifer vary from 0.1 L/s to 50.4 L/s based on information available from the DNRM groundwater database.

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3.2.5.2 Management of non-alluvial aquifers

The groundwater resources of the basalts around Oakey are managed under the Condamine Balonne Water Resource Plan2, which must meet the Murray Darling Basin Authority (MDBA) Basin Plan Sustainable Diversion Limits. The groundwater resources of the Walloon Coal Measures and other Great Artesian Basin aquifers within the Oakey Creek catchment are managed under the Water Resource (Great Artesian Basin) Plan 2006, and are administered by DNRM (QWC, 2012).

3.2.5.3 On-Site groundwater use

Historically, groundwater at the Site was extracted from the lower zone of the Oakey Creek Alluvium aquifer for:

• municipal water supply for drinking water and domestic uses (historically supplied from Toowoomba Regional Council (TRC) wells on-Site between 1960s and 1997)

• aircraft cleaning

• dust suppression

• fire-fighting training

• domestic use

• irrigation

• filling the Site’s swimming pool.

Groundwater abstraction at the Site was halted in January 2013.

The Site has been supplied with reticulated water from the Mt Kynoch Water Treatment Plant via the Oakey/Toowoomba pipeline since the construction of the pipeline in 1997. Prior to 1997, groundwater was used for all purposes on the Site, including drinking water (AECOM, 2015a), although anecdotal evidence suggests that the groundwater was not widely used for drinking because it was unpalatable. In 1997 the Site switched to town water supply for all water uses except irrigation, aircraft washing (only demineralised water), fire training and filling of the swimming pool. Use of groundwater to fill the Site’s swimming pool ceased in 2012.

The average monthly water use on-Site between July 1998 and February 2006 was between 3.5 ML and 7.9 ML (SKM, 2008). Historically, there were six bores on the Site that extracted groundwater. Defence holds four water licences (issued by DNRM), allowing a total of 474 ML to be extracted from the Oakey Creek Alluvium aquifer per year, of which 300 ML/year was licensed for the purpose of irrigation only (RN35453R – 174 ML/year, RN35983R – 275 ML/year, RN17963R – 20 ML/year and RN87138R – 5 ML/year). The bores are between 22 and 38 mbgs and yield between 0.4 L/s and 26.5 L/s. In addition, one Oakey Town Water Bore was located on-Site (RN52998) and one off-Site, near the gate house of the Site (RN36603). Bore RN36603 was decommissioned by TRC in 1997, but was recommissioned in 2008 following construction of the Oakey reverse osmosis (RO) water treatment plant. The RO plant was constructed by TRC as part of drought response measures to supplement dwindling reserves in the Toowoomba supply storage. The RO plant and supply bores were taken out of commission in November 2012. Since that time Oakey has been supplied with town water from the Mt Kynoch Water Treatment Plant via the Oakey/Toowoomba pipeline (TRC, 2016).

3.2.5.4 Off-Site groundwater use The desktop study (AECOM 2015a) identified that groundwater is or has historically been extracted from private and public bores for:

• municipal supply (historically between 1960s and 2012)

• domestic purposes (cooking, showering, laundry, filling swimming pools)

• irrigation of crops

• watering of livestock and domestic pets 2 Queensland Government, 2004, Water Resource (Condamine and Balonne) Plan 2004

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• recreational purposes (swimming pools and irrigation of community and school sporting fields and parks)

• commercial purposes (industry, hospital, mines, etc.).

As a precaution, Defence has recommended that residents do not drink water sourced from any underground water bores within the Investigation Area until further notice.

3.2.6 Surface water

3.2.6.1 Regional drainage system

The Site is located on a relatively flat alluvial plain, with Oakey Creek forming the major natural surface drainage feature. The tributaries of Cooby Creek and Westbrook Creek flow into Oakey Creek. Further downstream of Oakey township, the tributaries of Doctor Creek and Lagoon Creek flow into Oakey Creek from the north. The flood inundation areas and predicted Queensland floodplain assessment are presented in Figure F8.

Cooby Creek Reservoir is located in the headwaters of the Oakey Creek catchment. The dam is a source of water supply to Toowoomba City. The Cooby Creek Reservoir is a rock fill embankment dam with an ungated spillway across the Cooby Creek. The dam was constructed during the period 1938 to 1941. Cooby Reservoir's lowest useable storage volume was recorded at 8% in January 2010. Following the rains of January 2011, Cooby Reservoir's storage volume reached 100% (TRC, 2016).

Oakey Creek is a deeply incised, well defined, meandering watercourse and is generally considered to be a ‘losing’ system that contributes surface water flow to the regional groundwater system (AECOM, 2015a). Oakey Creek is approximately 10–15 m wide near the Oakey township. The creek is ephemeral, and during flooding events flood waters will flow over the river banks. The interaction of groundwater and surface water between the headwaters of Oakey Creek and the town of Oakey is likely to be one of surface water leaking through the bed of the creek to the underlying groundwater. This is because groundwater levels are generally below the bed of the creek and there is no opportunity to provide baseflow. Oakey Creek flows into the Condamine River located towards the west.

The Wetalla Water Reclamation Facility, operated by TRC, is located on the outskirts of Toowoomba and discharges treated effluent into Gowrie Creek, which flows into Westbrook Creek. Baseflow within Oakey Creek (downstream of the confluence with Westbrook Creek) is primarily attributed to the release of treated water into Gowrie Creek (AECOM, 2016a). Doctor Creek is a shallow, grassed floodway. The creek is not well defined upstream of the Site, but becomes more incised and defined downstream near the confluence with Oakey Creek. Doctor Creek is an intermittent stream that loses water to the alluvial aquifer when surface water is present (AECOM, 2015a). Hydrographs of creek flow (discharge) and stage height (creek water level) for the stream monitoring stations are shown in Chart 1 and Chart 2.

Surface water data were sourced from the DNRM Water Monitoring Information Portal (WMIP) for all water monitoring stations located within the Investigation Area (and immediately upstream/downstream). The WMIP data include stream level/height, stream flow/discharge and some water quality values. Nine DNRM surface water monitoring stations were identified and are located on Gowrie Creek, Oakey Creek, Cooby Creek Reservoir and Westbrook Creek. Plots of mean monthly discharge and flow duration curves were presented in AECOM (2016a).

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Chart 1 Monthly mean creek discharge (DNRM stream monitoring) (AECOM 2016a)

Chart 2 Monthly mean stage height (DNRM stream monitoring) (AECOM 2016a)

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

1967 1972 1977 1982 1987 1992 1997 2002 2007 2012

Cree

k w

ater

dis

char

ge (M

L/da

y)

Year422326A - Gowrie Ck at Cranley (1969 - present) 422330A - Oakey Ck at Oakey (1967 - 1976)422330B - Oakey Ck at Oakey (1976 - 1981) 422331A - Westbrook Ck at Arcadia (1967 - 1981)422332A - Gowrie Ck at Oakey (1967 - 1980) 422332B - Gowrie Ck at Oakey (1992 - present)422350A - Oakey Ck at Fairview (1980 - present) 422359A - Oakey Ck at Jondaryan (2011 - present)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

1967 1972 1977 1982 1987 1992 1997 2002 2007 2012

Cree

k w

ater

leve

l abo

ve b

ase

of c

reek

bed

(m)

Year422326A - Gowrie Ck at Cranley (1969 - present) 422330A - Oakey Ck at Oakey (1967 - 1976)422330B - Oakey Ck at Oakey (1976 - 1981) 422331A - Westbrook Ck at Arcadia (1967 - 1981)422332A - Gowrie Ck at Oakey (1967 - 1980) 422332B - Gowrie Ck at Oakey (1992 - present)422350A - Oakey Ck at Fairview (1980 - present) 422359A - Oakey Ck at Jondaryan (2011 - present)

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3.2.6.2 On-Site stormwater

Site stormwater flow is principally from kerb and channel, piped systems, overland flow and open drains. All of the Site drainage lines are ephemeral. The Site stormwater drainage network consists of approximately 23 km of pipe typically ranging in diameter between 300 mm and 1,200 mm, and approximately 33 km of unlined open drainage lines. Infrastructure at the Site dates back to the 1970s (AECOM, 2013).

The hydrology of the Site is split between two major catchments:

• Doctor Creek catchment – stormwater runoff in the northern part of the airfield is captured and diverted to Doctor Creek, which is a tributary of Oakey Creek and discharges into Oakey Creek, approximately 14 km downstream from the Site

• Oakey Creek catchment – all operational areas of the Site are located within the Oakey Creek catchment; therefore, all flows entering the stormwater drainage system are directed via the four main drains towards Oakey Creek, located approximately 1 km to the south of the Site.

The four main drainage channels are:

• West Drain (drainage channel 1): extends from the south-west corner of the airfield, running in a southerly direction, merging with the central drain before discharging to Oakey Creek

• Central Drain (drainage channel 2): aligned parallel to Orr Road, running in a south-westerly direction from the airfield across the Site and merging with the west drain before discharging to Oakey Creek

• East Drain (drainage channel 3): aligned parallel to Swartz Road, running south from the south-east corner of the airfield across the Site and discharging to Oakey Creek. A portion of stormwater flows from East Drain into a private farm dam, located about 800 m south of the Site. Overflow from the dam returns into the East Drain and discharges into Oakey Creek (AECOM, 2015a)

• Eastern Boundary Drain (drainage channel 4): aligned parallel with the eastern Site boundary, running in a southerly direction from the airfield and discharging to Oakey Creek.

The location of these drains and other drainage at the Site is presented on Figure F6.

A weir on Oakey Creek creates a semi-permanent water body that receives and retains runoff from the surface water drains discharging from the Site. The location of the weir is shown on Figure F6.

3.2.7 Wastewater management Until early 2014, the wastewater generated at the Site was pumped from the on-Site pumping station to the Oakey Wastewater Treatment Plant, which was located to the south of Oakey on the banks of Oakey Creek (near Lorrimer Street). Due to damage incurred during the 2011 floods the Oakey Wastewater Treatment Plant was decommissioned and demolished. Wastewater is now pumped via pumping stations to the Wetalla Wastewater Treatment Facility in Toowoomba.

The wastewater systems at the Site include:

• sewer mains

• sewage pumping stations and rising mains

• trade waste.

The majority of the Site’s wastewater flows under gravity to a low point pit and pump facility. From there it discharges into the TRC wastewater system upstream from the Council sewerage pump station in Fitzpatrick Street.

There are seven other smaller pumping stations across the Site which pump wastewater to the sewer system. The desktop study (AECOM 2015a) indicated that liquid trade waste is treated on-Site prior to discharging to the TRC wastewater or stormwater network. The Base Engineering Assessment Program undertaken by AECOM in 2013 identified no significant trade waste reticulation on Site.

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3.2.8 Oakey town water supply

TRC’s water supply consists of two water supply schemes. The first scheme, ‘central’, supplies communities including Oakey, Jondaryan and Gowrie Mountain. The second scheme, ‘eastern’, services Cotswold Hills, Torrington, Glenvale and Westbrook.

TRC provides water services to a population of around 10,000 people through almost 4,000 connections. Since 15 December 1997, Oakey has been supplied reticulated water from the Mt Kynoch Water Treatment Plant via the Oakey/Toowoomba pipeline (TRC, 2016).

3.2.9 Historical Oakey town water supply Based on anecdotal information, the regional groundwater supply was periodically (in times of drought) supplemented by groundwater extracted from five bores located within the Oakey Creek Alluvium aquifer: RN83202, RN83203, RN88380, RN147447 and RN36603 (the locations of these bores are shown on Figure F2).

Groundwater was a supplementary source only extracted during extreme dry periods. Historically, when in operation, the bores could supply up to 70% of the town’s water supply (AECOM, 2015a). For a period of two years between 2008 (when commissioned) and 2010, this water was treated at the RO plant at Ramsay Street. TRC has not abstracted groundwater for the town water supply since 2012 (TRC, 2016).

Between 2009 and 2012, the average annual extraction rate from the municipal supply bores was 386 ML/year (MBDA, 2014), compared to an estimated annual recharge from the Oakey Creek Alluvium aquifer between Jondaryan and Fairview of 2,750 ML/year (AECOM, 2015a).

3.2.10 Sensitive local environmental receptors

Oakey Creek is the primary down-gradient surface water environmental receptor from the Site. Groundwater dependent ecosystems are communities of plants, animals and other organisms whose extent and life processes are dependent on groundwater, such as wetlands and vegetation on coastal sand dunes. A search of the National Atlas of Groundwater Dependent Ecosystems (Australian Bureau of Meteorology, http://www.bom.gov.au/water/groundwater/gde/, accessed on 20 July 2017) is presented on Figure F7. The map indicates the nearest receptors with moderate potential for groundwater interaction are Oakey Creek and an unnamed dam located approximately 2.5 km south-west of the Site, between Speed Road and Warrego Highway.

With the exception of an area in the south-eastern portion of the Site, which contains remnant vegetation, the Site is not mapped as supporting terrestrial groundwater dependent ecosystems, nor does it support remnant vegetation (Queensland Globe database search). The Site is located within an area mapped as supporting potential groundwater dependent ecosystem aquifers, comprising unconsolidated sedimentary aquifers. Site investigations have identified that the water table is located around 13 m below the surface and is associated with the Oakey Creek Alluvium.

In principle, the greater the depth to groundwater the less the dependence there will be on groundwater. Available data suggest that where water levels are at depths greater than 10 m the groundwater dependency decreases and/or is minimal (Eamus et al., 2006).

The dominant structural elements of these ecosystems on Site are the Eucalypts and Corymbias. The root systems of these genera are generally located in the top 0.5–1 m of the soil profile (Jacobs, 1955), but can extend to shallow water tables of around 3 m (Flakiner et. al. 2006). Given the depth of the Site water table (13 m) and the normal shallow nature of Eucalypt and Corymbia root systems, the trees within the identified remnant vegetation area are unlikely to be dependent on groundwater. It is further considered that groundwater is not necessary to ‘maintain their communities of plants and animals, ecological processes and ecosystem services’3.

The Oakey Creek and other surface water drainages are recognised to be losing systems (as noted in Section 3.2.6.1), such that surface water – groundwater interaction is limited. Surface water is recognised to recharge groundwater resources, reducing the potential for groundwater at the surface as springs, seeps, or wetlands. The aquatic ecosystems are, therefore, not recognised to depend on groundwater ingress to meet all or some of their water requirements. 3 https://wetlandinfo.ehp.qld.gov.au/wetlands/ecology/aquatic-ecosystems-natural/groundwater-dependent/

http://www.bom.gov.au/water/groundwater/gde/

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Groundwater is also a sensitive environmental receptor that is extracted for a variety of purposes, as discussed in Section 3.2.5.

A desktop review of sensitive ecological receptors was conducted by AECOM (2015a). The Oakey area is heavily modified and largely denuded of remnant vegetation, with the majority of the landscape cleared and the Oakey Creek corridor largely consisting of landscaped parkland. Remnant vegetation identified was limited to disturbed poplar box (Eucalyptus populnea) woodland located at the Site and scattered within paddocks and road reserves. A number of ecological receptors in the form of potential terrestrial, avian and aquatic food chains were identified based on available habitat, including:

• modified pasture and grazing land which could be consumed by domestic livestock

• livestock

• riparian and terrestrial vegetation associated with ephemeral waterways, drainage lines and wetlands, which have the potential to support a diversity of food chains with significant interactions between terrestrial and aquatic systems

• remnant woodland, parkland, roadside vegetation and residential gardens, which have the potential to support a range of flora and fauna

• fish species and other aquatic biota.

In addition, higher order piscivorous (fish eating) birds and raptors are also considered to be potential receptors.

Oakey Creek is ephemeral and at the time of the 2017 Stage 2C EI was made up of a number of discrete pools with no obvious flow. No records of threatened aquatic organisms were identified during the desktop assessment. The Murray cod (Maccullochella peelii peelii) and silver perch (Bidyanus bidyanus) were, however, considered to be present due to anecdotal evidence including past stocking events. Queensland Department of Agriculture and Fisheries (DAF) has confirmed that both Murray cod and silver perch occur within Oakey Creek. These species are listed as threatened species under the Environment Protection and Biodiversity Conservation Act 1999. Sections of Oakey Creek have reportedly been stocked regularly with Murray cod, golden perch and silver perch since the late 1980s to enhance local recreational fishing opportunities.

3.3 Water Quality Objectives and Environmental Values The principal legislative basis for water quality management in Queensland is the Environmental Protection (Water) Policy (EPP), 2009, which identifies a process for identifying environmental values of waterways and establishing corresponding water quality objectives to protect identified environmental values. The Upper Oakey Creek is within the Condamine catchment and the following draft environmental values for the Upper Oakey Creek have been identified by Condamine Alliance (2017):

• Aquatic ecosystems

• Irrigation

• Farm supply

• Stock watering

• Human consumption of wild biota

• Visual appreciation (no contact with water)

• Drinking water

• Cultural and spiritual.

Condamine Alliance (2017) has not scheduled environmental values/water quality objectives for the Upper Oakey Creek and it is noted that the main COPCs identified on-Site (PFAS) are not prescribed within the water quality objectives. In the absence of specific objectives, Condamine Alliance (2017) identifies technical water quality guidelines such as the Queensland Water Quality Guidelines (DERM 2009) and Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC and

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ARMCANZ 2000) as providing default water quality objectives for the protection of ecological receptors. The guideline screening values for drinking water and recreational activities published in the Department of Health (2017) guidance and Australian Drinking Water Guidelines (NHRMC 2016), are considered to provide suitable water quality objectives for the protection of human health. The adopted screening criteria selected for assessment of soil and water samples collected during this report are presented in Section 5.0.

3.4 Site and Contaminant Characteristics and Limitations of Environmental Investigation

This section describes the aspects and interactions of the Site environment that are relevant to the investigation of the nature and extent of PFAS contamination.

An overview of the characteristics of the physical environment and PFAS that have been considered in developing the approach to the 2017 Stage 2C EI (including refinement of the CSM and understanding of potential exposure scenarios) are discussed in Table 3-2, and following sections.

The data presented in this report are considered to be appropriate to meet the objectives of the 2017 2017 Stage 2C EI, but must be interpreted with reference to:

• environmental aspects and characteristics

• PFAS migration

• PFAS properties

• PFAS analysis and data interpretation issues

• data characteristics and uncertainties (refer to Section 3.5.4).

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Table 3-2 Environmental aspects and characteristics

Aspect Characteristics and considerations for environmental investigation

Investigation strategy

Scale of Investigation Area and inherent complexity of PFAS and the evolution of knowledge

The 2017 Stage 2C EI covers a large area of more than 1,800 hectares of terrestrial environment and considers multiple media, including soil, sediment, groundwater, fresh surface water. The 2017 Stage 2C EI also considers data from waterways and floodplains in and around Oakey Creek that are extensive and dynamically complex systems where the subsurface geology and aquifer conditions are not understood in detail.

Legacy forms of AFFF contains a broad range of PFAS in different forms (cationic, anionic and zwitterionic), only some of which are known. At the current time 28 PFAS are able to be identified and quantified by analytical laboratories, and this list is being progressively expanded and lower limits of detection reduced.

The behaviour of the different PFAS vary in the environment. For instance, they are transported at different rates and by different mechanisms within the different media and sorption to soil minerals and organic carbon is variable. Research into these differences is ongoing.

Partly because of reliance on the sampling of privately owned existing groundwater bores, some off-Site areas (such as directly south of the Site) contain relatively few existing wells and data are relatively sparse over large areas. However, this is not considered to adversely affect the understanding of the IA.

As with any contamination, investigation, interpolation and interpretation between widely spread and sometimes sparse data points has been undertaken in order to better understand the nature and extent of PFAS in the Investigation Area and inform the subsequent HHRA and ERA.

The 2017 Stage 2C EI was designed to provide an improved understanding of the overall extent of PFAS in the media selected and to facilitate a better understanding of the general processes that result in transfer between media and migration of PFAS. The objective of the data set was not to calculate future remediation areas and volumes of impact in each type of media investigated.

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Source distribution, environmental complexity and interactions

PFAS sources PFAS contamination arising from the Site is inferred to be associated with multiple primary and secondary source areas within the large (850 ha) Site. The timing, exact location and mass of PFAS that was historically discharged at these source areas were not accurately recorded and therefore are not well known and not all potential sources may have been identified. As a result, there has been a reliance on anecdotal information to estimate the quantum of potential discharges responsible for the primary source areas. It is recognised that these estimates are limited in nature and are beneficial for illustrating the difference in potential volumes of AFFF deployed over different time periods during which Defence employed different management actions. Notwithstanding these uncertainties, it has been assumed by AECOM for the purposes of this report that these sources have generated groundwater impacts, and in some instances surface water impacts, which extend off the Site across its southern and western Site boundaries.

Groundwater movement

Groundwater in the Investigation Area in the Oakey Creek Alluvium aquifer is inferred to migrate in a generally westerly to south-westerly direction. The movement of water and associated PFAS in this aquifer is dynamic and is influenced by varying permeability at different depths, as well as by the depths of underlying bedrock and interactions with infiltration of rainwater, flood water and water from Oakey Creek (a losing stream) and surface water drains.

Further, the extraction of groundwater on- and off-Site may have also influenced the distribution/migration of groundwater and PFAS.

Groundwater in the Oakey Creek Alluvium aquifer is inferred to have limited connection to the underlying Walloon Coal Measures and the Great Artesian Basin, and with the Main Range Basalts adjoining the alluvium to the south. This is discussed further in Section 3.2.3.

AECOM (2015a) included a review of available historical information on environmental conditions and AFFF usage. Interviews were conducted with personnel with historical knowledge of AFFF use to better understand the extent and relative importance of potential source areas. Source infrastructure and AFFF characterisation sampling was undertaken to understand the potential for PFAS contribution from active and depleting sources of AFFF.

Soil and groundwater sampling was undertaken as part of the 2016 Stage 2C EI and 2017 Stage 2C EI, to better characterise soils, geology, hydrogeological conditions and the (preliminary) extent and depth of PFAS source areas.

Monitoring wells were installed on- and off-Site across the IA. Groundwater elevations were measured in monitoring wells and private bores to understand the groundwater flow regime within the Oakey Creek Alluvium aquifer and provide more insight into the importance of interactions between groundwater in the alluvium and the underlying and adjoining geological formations and with surface water.

The 2017 Stage 2C EI also included targeted hydrogeological investigations through the channel characterisation such as downhole assessments and aquifer testing.

A numerical groundwater flow and PFAS fate and transport model was developed to support the interpretation of data and assist development of the CSM.

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Surface water movement Surface water runoff from the Site discharges generally to the south via four major drainage channels which in turn are connected to a network of natural and manmade drainage channels and ponds which ultimately link to Oakey Creek. Flow within Oakey Creek is ephemeral and a manmade weir creates a semi-permanent water body that receives runoff from the Site (refer to Section 3.2.4).

Groundwater – surface water interactions

Throughout the IA, it is inferred that groundwater is too deep to discharge to surface water bodies or give rise to groundwater dependent ecosystems.

Information is included in the report to assist in evaluating influences of rainfall on PFAS concentrations reported in surface water and groundwater samples (see Section 3.2.2).

PFAS migration between media

The behaviour of PFAS within a dynamic environment, in terms of transport within and between media, is complex and subject to the influence of a number of climatic drivers and hydrologic responses and the nature of the PFAS. Such factors include: fluctuations in groundwater levels, and surface water flows in response to rainfall and evapotranspiration; and man-made influences, such as groundwater pumping and surface flow modification through installation of flow control structures.

Wherever possible, these characteristics have been considered in planning the investigation and in interpretation of the results. Additionally on a micro scale the geochemical and geophysical nature of the media is significantly variable across such a large Investigation Area and at present plays a relatively insignificant part in the understanding and immediate management of risk.

The 2017 Stage 2C EI included targeted hydrogeological investigations including drainage channel characterisation (soil sampling, leachate analysis, infiltration testing) and investigation of irrigation return flow pathways.

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Understanding these factors may carry greater importance at a later date when management and/or remediation actions are being designed (if required).

Time period of PFAS contamination and the 2017 Stage 2C EI

Time period of PFAS Discharges It is inferred that PFAS contamination has been occurring and migrating via surface water and groundwater potentially over a period of decades. The extent of PFAS identified in the IA reflects the cumulative impact of PFAS discharges influenced by natural and manmade processes over that time. It should be noted that the chemical constituents of AFFF have changed over the period of AFFF use and include potentially hundreds of individual compounds, only some of which can be identified and quantified. Therefore, retrospectively understanding the composition and amount of each PFAS over time is not practical.

Time period of the 2017 Stage 2C EI The 2017 Stage 2C EI has been undertaken over a relatively compressed time period (approximately January 2017 to June 2017) to achieve a reporting deadline of early July 2017. This phase of works builds on data from the previous phases and the temporal and spatial dataset is growing but limitations remain for some media more than others.

It is stressed that the data presented in the 2017 Stage 2C EI represents a ‘snapshot’ of the conditions at that point in time and may be subject to variation over time. The implications of this are discussed further in Section 3.3.

As previously stated, the focus of the 2017 Stage 2C EI was to better understand the current extent of PFAS within the Investigation Area, to further develop the CSM, to inform an assessment of risk to human health and the environment and to inform future management decisions (as appropriate).

Where comparative data are available, such as repeat sampling of installed groundwater monitoring wells between 2015 and 2017, or resampling of residential bores from 2014 to 2016, an assessment of trends has been made.

Longer term trends in PFAS movement or concentrations can be assessed following the development and implementation of the OMP, as additional data are collected and compared to data from the historical and current investigations. The existing dataset (2014 to 2017) covers a relatively short period compared to the time span of some of the potential on-Site source areas (approximately 40 years).

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PFAS concentrations and extents as shown in this report are likely to vary over time, with more rapid changes in PFAS concentration and mass flux in surface water compared to groundwater.

Non-PFAS COPC Activities at the Site have involved a potentially wide range of potential contaminants. There is the potential for these compounds to migrate in groundwater.

There is a known area of hydrocarbon contamination in groundwater in Area C1.

The 2017 Stage 2C EI included sampling and analysis of groundwater for non-PFAS COPC to provide representative data across the Site. Soil sampling for non-PFAS COPC targeted the surface and near surface soil (i.e. 0 to 0.5 mbgs) to identify the potential for surface spills.

PFAS behaviours

Some of the environmental processes and interactions that are potentially significant to the understanding of PFAS fate and transport are affected by the chemical properties of PFAS themselves. These include: moderate to high solubility in fresh water; sorption and desorption to aquifer solids and sediments within surface water drains; resistance to degradation; and accumulation within ecosystems. Some longer-chain PFAS are considered to be precursors to PFOS and PFOA and could potentially degrade and add to the concentration of PFOS and PFOA identified within the environment.

Important characteristics of PFAS, compared to most other forms of chemical contamination are: resistance to breakdown; solubility; high environmental mobility; and propensity to occur in, and migrate, in a wide range of environmental media including soil, sediment, concrete, surface water, ground water and biota; including vegetation, fish and birds.

Based on findings in the literature, it has been assumed that PFAS do not biodegrade significantly and have the potential to bioaccumulate.

A wide range of environmental media have been tested including soil, sediment, surface water, groundwater

Biota sampling has also been conducted to inform the HHRA and the ERA (to be reported separately).

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Interpretation of data variability

The characteristics of the natural and man-made systems discussed above means that environmental data collected during this 2017 Stage 2C EI is subject to potentially significant and sometimes frequent changes in concentration. As such, it is important that data presented on tables and figures in this 2017 Stage 2C EI report are reviewed in the context of the data characteristics and uncertainties discussed further in Section 3.3. The 2017 Stage 2C EI was intended to further assess the current extent of PFAS, to address specific data gaps and provide data for human health and environmental risk assessment (the HHRA and the ERA are currently in preparation). The data reported is by necessity a ‘snapshot’ in time and should not be regarded as an indication of static or long term conditions. It is anticipated that the conditions described at individual sampling points may change with time in response to environmental processes and man-made influences.

The potential for variability in PFAS concentrations and distribution has been considered conservatively when assessing the extent of impact described by this 2017 Stage 2C EI Report.

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3.5 PFAS properties As part of typical airbase activities, aqueous film forming foam (AFFF) was used at the Site for fire training and emergency response from the 1970s. The main AFFF product used historically by Defence was 3M Lightwater™, which contained Per- and poly-fluorinated alkyl substances (PFAS) including Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA). From 2004, Defence commenced phasing out its use of legacy AFFF containing PFOS and PFOA as active ingredients and progressively transitioned to a product called Ansulite® for use on the Defence estate. The product currently used by Defence does not contain PFOS and PFOA as active ingredients, only in trace amounts. AECOM understands that Ansulite® is used by Defence only in emergency situations where human life is at risk, or in controlled environments to test equipment, and any Ansulite® used by Defence is captured and treated and/or disposed of at licensed waste disposal facilities in accordance with best practice regulations, and standards. Based on anecdotal evidence, for the purposes of this report, it has been assumed that Defence commenced phasing out the use of AFFF products containing PFOS and PFOA at the Site from 2005. This assumption has not been verified by Defence.

3.5.1 Key PFAS migration processes at the Site PFAS are moderately to highly soluble, depending upon the individual PFAS chemical structure and can be readily dissolved/leached by infiltrating rainwater or groundwater or surface water.

Identified key migration processes for PFAS in water were summarised in AECOM (2015a) and include:

• surface water unlined drainage lines (on- and off-Site)

• the groundwater system (vertically and laterally, primarily via the Oakey Creek Alluvium aquifer, on- and off-Site)

• trade waste (influent on- and off-Site).

Some PFAS leach from soils and pavements under neutral water conditions. Consequently, the infiltration of water through the soil profile may mobilise some PFAS adsorbed onto and situated within the pore spaces of soil particles (although the rate of mobilisation can be impacted by the soil chemistry and the PFAS chain length and ionic composition). PFAS precursors may also degrade to generate PFOS and PFOA and other shorter chained PFAS in certain physiochemical environments down hydraulic gradient of identified sources.

3.5.2 Physical and chemical properties of PFOS and PFOA

The five general processes used to describe the fate and transport of contaminants in groundwater (Domenico and Schwartz, 1990) are:

1. Advection – transport in groundwater flow

2. Diffusion – molecular diffusion in an aquifer, independent of flow

3. Dispersion – hydrodynamic spreading of a contaminant

4. Adsorption and desorption – retardation of transport

5. Degradation – biodegradation of long-chain fluorocarbons.

Some PFAS (such as PFOS and PFOA) appear to have little contaminant transport retardation (i.e. adsorption or degradation) based on the extent of the observed contaminant plume and properties of identified PFAS. This is likely the result of the hydrophilic properties of the functional end groups of some PFAS. These and other physiochemical properties will, in some instances, prevent PFAS from adsorbing to most soil particles. An exception to this is adsorption to some metal oxyhydroxides, which are not known to be present at the site (Wang et al., 2012) and organic materials.

PFOS and PFOA are understood to be transported at nearly the same rate as groundwater or surface water Food Standards Australia (FSANZ, 2017)

Biodegradation of PFOS and PFOA has not been observed, although breakdown of longer chain ‘precursor’ PFAS (including perfluorinated carboxylates and sulfonates) can lead to PFOS, PFOA and PFHxS formation.

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As PFAS are transported with water, the concentrations will generally decrease with distance due to the processes of advection, diffusion and dispersion. The environmental fate of the PFAS contaminant mass is expected to be significantly influenced by groundwater movement, extraction and surface water drainage away from a source.

While data are limited, based on a literature review, it is generally considered that PFOS, PFOA and PFHxS are persistent contaminants in the environment, and PFOS has been listed as a persistent organic pollutant (POP) under Annex B of the Stockholm Convention since 2009.

A fact sheet, developed by the US Environmental Protection Agency’s Federal Facilities Restoration and Reuse Office (FFRRO, 2014), provides a brief summary of the physical and chemical properties of PFOS and PFOA. The summary is reproduced in Table 3-3. AECOM has also included physical and chemical properties for PFHxS, derived from publically available publications. The summary is reproduced below in Table 3-3. Table 3-3 Physical and chemical properties of PFOS, PFOA and PFHxS

Property PFOS PFOA PFHxS

CAS Number 2795-39-3 335-67-1 355-46-4

Physical description (physical state at room temperature and atmospheric pressure)

White powder White powder/waxy white solid

White crystalline powder

Molecular weight (g/mol) 538 (potassium salt) 414 400.12

Water solubility (mg/L at 25 °C)

570 (purified), 370 (freshwater), 25 (filtered seawater)

9.5 x 103 (purified) 2.3 x 103

Melting point (°C) > 400 45 to 50 272-274

Boiling point (°C) Not measurable 188 114.7

Vapour pressure at 20 °C (mm Hg) 2.48 x 10-6 0.017 0.0024*

Air water partition coefficient (Pa.m3/mol) < 2 x 10-9 Not available -2.38

Octanol-water partition coefficient (log Kow) Not measurable Not measurable 5.17

Organic-carbon partition coefficient (log Koc) 2.57 2.06 1.78

Henry’s law constant (atm m3/mol) 3.05 x 10-9 Not measurable Not measurable

Half-life

Atmospheric: 114 days Water: > 41 years (at 25º C) Photolytic: > 3.7 years Sonolysis: 20 to 63 minutes

Atmospheric: 90 days Water: > 92 years (at 25º C) Photolytic: > 349 days Sonolysis: 20 to 63 minutes

Atmospheric: 76.4 days Water: no data Photolytic: negligibly degraded via photolysis Sonolysis: no data

Notes: g/mol – grams per mole; mg/L – milligrams per litre; °C – degree Celsius; mm Hg – millimetres of mercury; Pa m3/mol – pascal-cubic metres per mole; atm m3/mol – atmosphere-cubic metres per mole. * Vapour pressure estimated based on modified grain method using US EPA (2017)

Sources: ATSDR 2009; Brooke et al. 2004; Cheng et al. 2008; EFSA 2008; US EPA 2002; UNEP 2006, FSANZ 2017; Wang et al. 2011; European Chemicals Agency, 2015

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Literature values for solubility (in purified water) for PFOS and PFOA are 570 mg/L and 9,500 mg/L, respectively (US EPA, 2014). However, the solubility of PFOS decreases in natural waters that contain high amounts of dissolved solids such that the solubility of PFOS in salt water is approximately 25 mg/L. The solubility of PFOA in water is higher than PFOS.

Literature values for the soil organic-carbon water partition coefficient (Log KOC) for PFOS and PFOA are approximately 2.57 and 2.06, respectively (US EPA, 2014). The soil organic carbon-water partitioning coefficient is the ratio of the mass of a chemical that is adsorbed in the soil per unit mass of organic carbon in the soil per the equilibrium chemical concentration in solution. KOC values are useful in predicting the mobility of organic soil contaminants; higher KOC values correlate to less mobile organic chemicals, while lower KOC values correlate to more mobile organic chemicals. In this regard, the literature values of KOC suggest that PFOS is less mobile than PFOA (although it is recognised that use of literature KOC values can be lead to under or over estimation in the natural environment).

3.5.3 PFAS analysis and data interpretation issues

The following points provide an overview of some of the issues that have been considered in validating analytical results and interpreting the results of environmental testing.

• Accurate analytical techniques – for identifying and quantifying PFAS are relatively new. The USEPA standard method was published in 2009 and Australian NATA certified commercial analysis services also became available in 2009.

• Analytical proficiency – in Australia is continuing to improve, with limits of detection improving (lowering), and the range of PFAS that can be analysed is increasing. The use of laboratory standard reference materials has also been improved to better address issues including the quantitation of linear and branched PFAS. As a consequence, some differences in analysis results can be expected when sample locations are retested using more recent analytical techniques or where samples are split (for quality control purposes) between different laboratories. These issues are considered in the data quality assurance and data validation processes that have been used in the investigation (refer to Table 3-2).

• Differences in sampling methods – over the course of several stages of investigation at the Site, groundwater has been variously sampled by methods including: HydraSleeve, bailer, low flow pumping techniques, grab samples from fruit tree locations or directly from the ‘first flush’ of residential groundwater bores and taps. These different methods can introduce additional PFAS concentration variability between locations or from the same locations over time.

• Differences in sampling purposes – some data has been collected for purposes such as classifying stockpiled soil or water that has accumulated in open excavations for the purpose of management or disposal. Such data may not be directly comparable to sampling and analysis undertaken as part of the 2017 Stage 2C EI.

• Low screening concentrations – at sub part-per-billion (ppb) and part-per-million (ppm) concentrations, very minor changes on environmental conditions can lead to seemingly large relative differences in PFAS results between adjoining sample locations or in repeat sampling events. However, the actual concentration differences may only be very small in terms of absolute concentrations.

• Fluctuation of results and long term trends at individual testing locations – it will take repeated sampling of individual monitoring wells or surface water sampling locations over time (potentially years) to develop an understanding of the range of typical variations in concentration and longer term trends (if any).

• Different analytical methods for different media – PFAS have been detected as being present in almost all media tested at the Site including soil, sediment, surface water, groundwater, irrigation water, concrete, and in biota including mammals, some vegetation, invertebrates, shellfish and fish. It is noted that different media (soil/sediments, waters, vegetation, fish etc.) all have different sample preparation and analysis processes. Laboratories are accredited (with National Association of Testing Authorities (NATA)) for PFAS analyses for soil/sediment and waters, however there are no NATA-accredited laboratories for PFAS analyses of biota. The 2017 Stage 2C EI used NATA accredited laboratories for analysis of soil/sediment and water samples.

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• Background concentrations and cross contamination – the widespread use of PFAS in industrial processes and products (including manufacture of water and grease resistant coatings, metal plating, paints, cement additives, food packaging and numerous other applications (US EPA, 2017)) over decades and its resistance to breakdown in the environment, means PFAS is being detected throughout the environment and in human blood serum from sources other than AFFF usage. Consequently there is a potential for PFAS cross contamination of samples (e.g. from the Teflon liners in sample container lids, Teflon tubing often used in groundwater sampling – it is noted that these items were not used during 2017 Stage 2C EI) that must be controlled to reduce the potential for false positive results.

3.5.4 Data variability and uncertainty

The effects and significance of the sources of uncertainty in some of the data sets collected are discussed below. The 2017 Stage 2C EI and subsequent risk assessment processes involve a range of interpretation and assumptions regarding human activity, site conditions, contaminant behaviour and natural processes. These assumptions are based on site-specific information (where available). However, it is not always possible to fully characterise or predict site conditions and human activities at a site for the exposure period considered.

The data that have been collected provides a basis for improved understanding of the nature and extent of PFAS contamination when interpreted with reference to the natural processes that are occurring at the time and the types of variability that can be expected. This is summarised in the conceptual site model in Section 10.1.

Conservative (i.e. likely to over-estimate actual conditions) assumptions have been made in the presentation of data (on figures, tables and as part of the CSM) based on the available information to reduce the potential for underestimation of the extent or concentration of impacts. In some locations, this results in locations characterised by ‘clean’ wells being indicated to be within PFAS affected areas. It is stressed that the nature and extent of contamination described in this report is not intended to be a definitive description. Rather, it is ‘snapshot’ of conditions as encountered when the samples were collected (late 2013 to mid-2017). Understanding of the nature and extent of contamination will continue to evolve as additional data are collected that expands the spatial coverage and provides an improved understanding of the temporal variability of concentrations.

Table 3-4 summarises some of the characteristics of the data that have been presented in this report, how temporal and other forms of variability may affect interpretation of the data, and the steps taken to minimise the impacts of this variability on the resultant conclusions. These factors have also been considered in presenting data (on figures, tables, CSM) within this report.

It is also noted that data used for specific purposes, such as in the HHRA or in the numerical groundwater model, are also subject to a task-specific data uncertainty evaluation (not included in this report) with conservative assumptions adopted to address the identified uncertainties.

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Table 3-4 Data characteristics, variability and interpretation

Dataset Natural and other variability, local

environmental processes Potential for change in values

Investigation strategy Interpretation strategy and significance to objectives

Groundwater elevations and potentiometric contours in Table T2 and Figures F17 to F21

• Rainfall and infiltration, flooding and standing water

• Pumping of groundwater (e.g. from irrigation bores) can locally reduce groundwater levels

• Groundwater levels have the potential to vary according to environmental conditions. Such changes would normally be evident over days to weeks but could occur faster in response to rainfall events

• Measurement of water levels at selected wells in the different aquifers (Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures) in the Investigation Area within a defined time period so the data reflects water levels across the Investigation Area at a point in time

• Installation of water level loggers in selected wells in the Oakey Creek Alluvium aquifer

• Collection of short and medium term weather data (rainfall etc.)

• While groundwater levels are subject to fluctuation, the overall gradients and flow directions established from the data are considered to be sufficient for the purpose of the 2017 Stage 2C EI

• Bore pumping has been considered in the groundwater model

Soil and sediment analysis results in Tables T6 to T18 and Figures F22 to F30, F42 to F46

• Lateral distribution of AFFF at time of use gives rise to poorly defined impact areas

• Leaching of PFAS by rainwater, surface water, flooding, erosion and deposition, excavation and filling etc.

• The lateral and vertical distribution of PFAS in soil and sediment samples is potentially extensive, occurs at widely varying concentrations and is subject to variation over relatively short distances and depths but is expected to be relatively stable over time

• Re-sampling of surface water and sediment samples at locations consistent with Stage 2C 2016 EI investigation as well as additional locations

• Collection of soil samples based on historical data to characterise and to provide information on the lateral and vertical extent

• Sediment samples collected from sediment/water interface in drains to assess potentially mobile materials

• Utilisation of co-located sediment samples collected as part of numerous tasks completed for the

• The data collected have provided the necessary understanding of source areas to support the CSM

• The data collected are considered to be sufficient for the purpose of the 2017 Stage 2C EI

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2017 Stage 2C EI, including sampling of aquatic biota for 2017 HHRA and 2017 ERA.

Groundwater analytical results in Tables T19 to T30 and Figures F31 to F41

• PFAS migration • Infiltration of rainwater/seasonal

conditions • Low precipitation conditions • Irrigation and other

pumping/abstraction • Well construction/screened

interval depths • Sampling methods (e.g. low

flow, no-purge), different sampling techniques for groundwater wells and residential bores

• Groundwater PFAS concentrations have the potential to change significantly although less rapidly than surface water. In particular, it is possible that dilution may occur following rainfall events, (potentially within hours), particularly during high surface water runoff events

• Sampling of 2017 Stage 2C EI groundwater wells followed industry standards including well development and purging

• Sampling of residential water supply bores utilised a “first flush” technique to better reflect potential human exposure conditions at point of water use

• It is possible that different sampling protocols between groundwater monitoring wells and residential bores may have resulted in slightly different results

• It is considered unlikely that these differences would have had a significant impact on the evaluation of the nature and extent of PFAS in groundwater

• The groundwater data collected are considered to be sufficient for the purpose of the 2017 Stage 2C EI

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Surface water analytical results in Tables T22 to T30 and Figures F40 and F41

• Rainfall – seasonal trends (e.g. drought) and short-term events (e.g. flooding)

• Losing stream conditions (i.e. surface water infiltration to groundwater)

• Pumping, diversion, construction dewatering

• Surface water conditions change over hours

• Surface water PFAS concentrations have the potential to change rapidly (potentially in hours), particularly during runoff events

• Collection of samples from the potentially impacted on- and off-Site drainage networks

• Collection and reporting of climate data throughout the investigation period

• Collection of field water quality parameters to facilitate characterising water type

• Continuous monitoring of surface water levels in a drainage channel using a data logger

• Clarify that data represent conditions at time of monitoring

• Interpret results in context of local processes and recent rainfall or flow events.

• Continue to collect data over time • It is considered unlikely that these

differences would have had a significant impact on the evaluation of the nature and extent of PFAS in surface water

• The surface water data collected are considered to be sufficient for the purpose of the 2017 Stage 2C EI

Illustrated groundwater extent of PFAS in Figure F47

• The interaction of natural processes and analytical variability are discussed in Section 3.4 and characteristics of the data collected are described above

• Any illustrations of extent of PFAS in groundwater are by necessity a simplification of complex environmental interactions and can only be a snapshot in time that is subject to review as additional data becomes available

• The data was used to refine Groundwater Zones 1 and 2

• Review available historical data collected during the 2017 Stage 2C EI at each sampling point and typically adopt maxima in plume interpretation to avoid false negatives

• Conservatively interpret plume extent where an impacted well is surrounded by clean wells (i.e. outliers are not ignored)

• Interpretation of extent of impact will involve available data but is not intended to be definitive

• It is noted that the current groundwater conditions are the result of previous PFAS migration and interaction with natural systems. While short-term variability is likely, it is inferred that the overall extent of impact is unlikely to significantly change in the short term

• The contoured PFAS concentration data are conservatively illustrated based on the maximum concentrations detected at any of the relevant data points

• Contouring of the data may illustrate areas as being affected with PFAS when some borehole data suggests

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concentrations below the laboratory LOR, or lower concentrations

• Trend data are available in groundwater PFAS concentrations and the dataset will be expanded as more data are acquired.

• A numerical groundwater flow model and solute transport model has been developed to assist with interpreting available data and predicting the area of impact and long-term trends

• The maps should not be interpreted on a property by property basis

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4.0 Approach and Methodology

4.1 Approach Experienced AECOM representatives carried out the necessary fieldwork in accordance with the Sampling Analysis and Quality Plan (AECOM, 2017b). An overview of the investigation locations and sampling activities are described below.

• On-Site sampling

- The locations of the 31 soil bores advanced and 10 groundwater monitoring wells installed on-site are shown on Figure F9. A total of 153 soil samples collected were analysed for PFAS, 15 soil samples for TOPA. A total of 153 samples were analysed for metals and 36 selected soil samples analysed for other non-PFAS contaminants as per Section 2.5.

- The 52 groundwater sampling locations (made up of 10 newly installed and 42 existing on-Site monitoring wells) are shown on Figure F10. Samples from all locations were analysed for a PFAS and non-PFAS contaminants as per Section 2.5. Nine samples were analysed for TOPA. Data loggers were installed in two wells to understand groundwater level changes in the Oakey Creek Alluvium aquifer.

- The locations of the 21 soil bores advanced along the drainage channels are shown on Figure F11. A total of 42 soil samples were analysed for PFAS. All 42 samples were also analysed for metals with 10 of these samples analysed for other non-PFAS contaminants as per Section 2.5. Ten samples were analysed for leachate, seven samples for TOPA. Three infiltration tests were conducted, two tests at soil bores along drainage channel 3 and one test at a location along drainage channel 2.

- The 12 stormwater (in drainage channel) sampling locations are shown on Figure F12. All stormwater samples were analysed for PFAS. A data logger was installed at drainage channel 2 to measure water levels in the drain (see Figure F10).

• Off-Site sampling - The locations of the 30 groundwater monitoring wells installed off-Site are shown on Figure

F13. A total of 102 primary soil samples collected during the installation of these wells were analysed for PFAS. The locations of three licensed extraction wells investigated during the program are shown in Figure F14. A total of 49 soil samples were laboratory tested for permeability parameters.

- The 37 groundwater sampling locations are shown on Figure F15. Samples from all locations were analysed for PFAS. Three water samples were analysed for TOPA.

- The locations of the 13 soil bores advanced along the off-Site sections of the drainage channels are shown on Figure F11. A total of 27 soil samples were analysed for PFAS with nine samples analysed for non-PFAS COPC. Eight samples were analysed for leachate and one sample for TOPA.

- The locations of the 45 samples collected of loose soil from the ground surface are shown in Figure F16. All soil samples were analysed for PFAS.

- The 11 stormwater (from along the off-Site sections of the drainage channels) sampling locations are shown on Figure F12. All stormwater samples were analysed for PFAS.

- The locations of 34 surface water and 33 sediment samples collected from Oakey Creek, Doctor Creek and Westbrook Creek are shown in Figure F12. All surface water and creek sediment samples were analysed for PFAS and three sediment samples were analysed for non-PFAS contaminants.

- The residential sampling conducted between January and June 2017 included five soil samples, 81 groundwater bores, 45 tap, 19 tank and three swimming pool water samples. All soil and water samples were analysed for PFAS.

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The fieldwork was completed between January 2017 and June 2017 as shown in Table 4-1. Table 4-1 Dates of sampling activities

Sampling activity Dates of sampling On-Site drainage channel sampling 27-28 January 2017 Off-Site drainage channel sampling 2–3 February 2017 On-Site soil bore investigation and monitoring well investigation 8–10, 21–24 February, 24 March 2017

On-Site groundwater sampling 7–16 March, 13, 28 April, 5 May 2017 On-Site stormwater sampling 28 January, 20 February, 22–24 March 2017 Off-Site groundwater monitoring well installation

27–28 February, 8 March – 1 April, 6–7 April, 18–20 April, 3, 18–19 May, 5–19 June 2017

Off-Site sediment and surface water sampling 1,6,7, 20 February, 29 March, 11–13 April, 3–4 May 2017

Off-Site borehole assessment 18–19 March, 18 April 2017

Off-Site groundwater sampling 21–24, 28 March, 12–13, 26–28 April 2017, 3, 15 May, 1 June 2017

Off-Site stormwater sampling 1–3 February, 24 March, 11 April 2017 Off-Site surface soil sampling 5, 12, 20, 26–28 April 2017

Residential sampling 10, 17, 21–24, 29 March, 4–8, 26–28 April, 3, 18, 25–26 May 2017

Biota (yabby sampling) 6–9 February, 21–24 March, 12 April 2017 Biota (hare sampling) 27 January, 21 April 2017 Fish sampling (Oakey Creek) 21–24 March 2017 Biota sampling (fruit and vegetables) 4–7, 26–28 April, 25–26 May 2017 Biota sampling (earthworms, grass) 11 April, 3–9 May 2017

4.2 Sampling Rationale The sampling rationale for the various elements of the 2017 Stage 2C EI program is summarised in Table 4-2. Table 4-2 Sampling rationale

Task Field activities Approach and rationale Monitoring well installation

Monitoring well locations

The majority of monitoring well locations targeted specific areas of interest on- and off-Site. Other locations were selected to provide information on the extent of the area of groundwater impact on- and off-Site. The new wells were positioned to complement existing Defence-owned monitoring wells.

Install wells to target the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures aquifers

The majority of groundwater monitoring wells targeted the upper zone of the Oakey Creek Alluvium aquifer as this zone contained the highest concentrations of PFAS. Paired wells consisting of wells monitoring the Oakey Creek Alluvium and underlying aquifer, either the Main Range Volcanics or Walloon Coal Measures, were installed to allow evaluation of the vertical migration of PFAS.

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Task Field activities Approach and rationale Hydro-geological investigation

Gauging event Water gauging was conducted on pre-existing and newly installed monitoring wells to assess groundwater elevation in the Investigation Area. The groundwater elevation data were used to interpret groundwater flow direction.

Groundwater level measurements

Data loggers were installed in two on-Site groundwater monitoring wells for a period of approximately one month to record changes in groundwater level to investigate if there was response in groundwater to precipitation events.

Pumping tests Pumping tests were conducted as part of the investigation on the three licensed extraction bores. The tests required pumping groundwater for an extended duration and monitoring the response in the adjacent monitoring wells that monitor the Oakey Creek Alluvium or Main Range Volcanics and underlying Walloon Coal Measures aquifer using data loggers to automatically record the changes in groundwater level. The tests were conducted to understand connectivity between these aquifer zones and provided key information for the assessment of the vulnerability of groundwater PFAS contamination to the GAB.

Infiltration testing

Falling head tests were conducted at three locations in the on-Site drainage channels to improve understanding of the infiltration potential of the drainage channels sediments and near surface soil. Locations with high potential for water pooling were targeted.

Soil sampling Surface soil samples

Loose particles of soil were collected manually at the sample location to form a sample. The sampling was conducted to understand the distribution of PFAS that may have migrated by wind resuspension or by flood inundation.

Ground surface to 1.5 mbgs

Soil samples were directly collected using a hand auger. Soil samples were collected at the required intervals such as 0.0–0.2, 0.5, 1.0 and 1.5 mbgs to provide information on near-surface quality to investigate the potential for spills. During non-destructive drilling (NDD), the soil samples were collected with hand auger at 0.5 and 1.0 mbgs. NDD terminated approximately 0.1 m above each sample interval to minimise the potential for soil samples to come into contact with water.

1.5 mbgs to target depth

For bores drilled using the sonic rig, samples deeper than 1.5 mbgs were collected from core that was recovered in plastic sleeves. For bores drilled using Geoprobe or geotechnical rigs, samples were collected from the material recovered from the push tube, auger or air hammer. Samples were collected from various depths where saturated soils were observed in both the upper and lower zones of the Oakey Creek Alluvium aquifer. Samples were also collected to target the approximate level of the base of underground infrastructure such as USTs to investigate the potential for leaks.

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Task Field activities Approach and rationale Selection of samples for analysis

AECOM selected soil samples for laboratory analysis based on whether: • soil at or near ground surface where shallow soil may have

been impacted by contaminated surface water or direct exposure to contamination

• soil at varying depths where unsaturated soil was encountered during drilling in the Oakey Creek Alluvium aquifer

• soil was in the Main Range Volcanics or Walloon Coal Measures below the Oakey Creek Alluvium

• soil characterisation was required for landfill disposal. Up to six samples per borehole were selected for submission for laboratory analysis for extended PFAS suite. Selected near surface samples from on-Site were analysed for a broad suite of non-PFAS contaminants that may be present on Defence estates. A representative selection of soil and groundwater samples from across the Investigation Area were analysed for TOPA. The soil samples analysed represented different types of soil.

Soil analysis and testing

Soil – extended PFAS suite analyses

All on-Site and off-Site soil samples were analysed for PFAS (refer to Section 2.4). The results provide characterisation of the PFAS conditions in soil on- and off-Site.

Soil – non-PFAS suite analyses

A proportion of on-Site soil samples were analysed for a wider suite of non-PFAS chemicals (e.g. metals, hydrocarbons and other organic compounds), in accordance with the rationale described in Section 2.4. These analyses were undertaken to assess if historical and/or current activities at the Site have resulted in soil impacts. All the soil samples analysed for non-PFAS COPC were from the near surface soil zone to target localised spills of non-PFAS.

Soil – geotechnical testing

Geotechnical testing was carried out to assess horizontal and vertical hydraulic conductivity (permeability) data across the site, particularly adjacent to the stormwater drains. These laboratory results, in conjunction with infiltration test data compiled in shallow soil sample holes, aids in assessing possible surface water – groundwater interactions and recharge mechanisms.

Groundwater sampling

Sampling Technique

The preferred approach to groundwater sampling was to use low flow bladder sampling technique. As this technique was limited to groundwater levels above 55 mbgs, deeper wells were sampled using the HydraSleeve sampling technique*.

Groundwater –extended PFAS suite analyses

All on-Site and off-Site samples were analysed for PFAS (refer to Section 2.4). The results provide characterisation of the PFAS conditions in groundwater on and off-Site.

Groundwater – non-PFAS suite analyses

All on-Site groundwater samples were analysed for a wider suite of non-PFAS chemicals, in accordance with the rationale described in Section 2.4. These analyses were undertaken to assess if historical and/or current activities at the Site have resulted in groundwater impacts in the vicinity of the Site boundary from compounds other than PFAS. Due to the infrequent detection of non-PFAS COPC in groundwater on-Site, groundwater samples collected from off-Site were not analysed for non-PFAS COPC. This is further discussed in Section 7.3.

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Task Field activities Approach and rationale Groundwater − major cations and anions

Groundwater samples collected from new on- and off-Site groundwater monitoring wells were analysed for major anions and cations to assist with interpretation of groundwater flow direction and to further understand connectivity between aquifer zones.

Stormwater, surface water and sediment investigation

Sampling locations

Sampling locations were selected to provide good spatial coverage along the length of the drainage channels (both on- and off-Site and along each of the three creeks, Oakey Creek, Doctor Creek and Westbrook Creek). The samples locations also included locations where biota samples were collected from to provide co-located data for use in the HHRA and ERA. Samples were collected either from the middle of the creek, or where access was restricted, from the sides of the creek.

Stormwater, surface water and sediment extended PFAS suite analysis

All samples were analysed for PFAS (refer to Section 2.4). The results provide characterisation of the current stormwater, surface water and sediment PFAS conditions on- and off-Site.

Surface water level measurements

A data logger was installed in drainage channel 2 to provide surface water level changes over a period of approximately one month

Residential sampling

Bore water, tank water, swimming pool water, surface water, soil

Residential water sampling was undertaken to further assess the water quality at the potential point of use. Samples were collected from the ‘first flush’ of water from a tap connected to a bore pump or rainwater tank.

Borehole assessment

Wireline logging A geophysical investigation was conducted at three existing licensed extraction bores to understand their construction details and the potential for the bore to connect aquifers. Following removal of the pump, the following geophysical sondes were run within all three bores: • Borehole geometry sonic (multi-finger calliper) • Optical casing investigation • Ultrasonic casing investigation (acoustic) • Cement bond log / variable density log.

Note: * An attempt was made to use low flow sampling to collect groundwater samples from deep wells with groundwater ingress deeper than 55 mbgs using a gas lifting technique, however this approach was unsuccessful due to the difficulty in maintaining sufficient pressure. Consequently the sampling was changed to the use of HydraSleeves.

4.3 Methodology Due to the ubiquity of PFAS used in a variety of everyday products and the potential for cross contamination during sampling activities, the recommended mitigation practices identified in the interim guidance document on the assessment and management of PFAS, published by Western Australia’s Department of Environmental Regulation (January 2017) were implemented during the sampling program.

4.3.1 Drilling and soil sampling Sampling methodologies and details relating to laboratory analysis of samples are described in the SAQP (AECOM, 2017a). Summaries are provided in Table 4-3.

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Table 4-3 Soil assessment methodology

Activity Details

Service clearance

AECOM obtained utility plans through the Oakey Geographical Facilities Information System and Dial-Before-You-Dig service before the start of the works. AECOM engaged a Telstra accredited service locator to use radio-detection, ground penetrating radar and reference utility plans to identify underground utilities at the proposed well locations. The locations were advanced by NDD methods to 1.5 mbgs to confirm the absence/presence of underground utilities. NDD involved the use of high pressure water and a vacuum to remove soil while minimising potential damage to any existing utilities.

Hand augering

Shallow soil bores were advanced using a hand auger to the target depths.

Drilling AECOM used three types of drilling rig to drill the soil bores, collect soil samples and install groundwater monitoring wells: • Truck-mounted sonic drill rig • Geoprobe drilling rig (push tube, solid stem auger and air hammer). Shallow wells (less than 50 mbgs): the depths of the shallow wells were based on observations of the moisture in shallow soil during drilling. The wells targeted the depth where groundwater was first encountered and were completed with a 1 m bentonite plug above the filter pack and bentonite grout to the ground surface. All shallow wells were completed in accordance with the Minimum Construction Requirements for Water Bores in Australia (National Water Commission, 2012). Deep wells (greater than 50 mbgs): the depths of the deeper wells were based on geological observations. The first wells targeted observed basalt (representing Main Range Volcanics) or coal bands/sandstone (representative of Walloon Coal Measures) which were present beneath alluvial material. The wells also targeted the depth where groundwater was first encountered following the change of geology and were completed with a 1 m bentonite plug above the filter pack and bentonite grout to the ground surface to eliminate any pathway for groundwater between the two aquifers. All deeper wells were completed in accordance with the Minimum standards for the construction and reconditioning of water bores that intersect the sediments of artesian basins in Queensland (DNRM, June 2014). This document has the following additional requirements for drilling into the GAB: • Notify DNRM prior to activities occurring • Use an appropriate licenced driller • Only screen a single formation • Only start drilling when all equipment is on site • Cement all zones except the screened zone. Minimum curing period is 24 hours • Case the entire hole – screen at the bottom and plain casing to surface. All GAB wells were completed in accordance with these requirements. Screen lengths in shallow groundwater monitoring wells were typically 6 m in length and targeted the first groundwater strike. Screens in the deeper wells (i.e. in the Main Range Volcanics or Walloon Coal Measures) were typically 3 m in length and targeted the first permeable stratum identified. For example, the screens in Walloon Coal Measures wells were typically positioned across the first coal seam encountered.

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Activity Details

Soil logging Soil logging was in general accordance with the Unified Soil Classification System (USCS) and the AECOM documented standard field procedures. Bore logs are provided in Appendix D.

Soil sampling The soil sampling methodology is described in the Sampling, Analysis and Quality Plan (AECOM, 2017a). AECOM used two methodologies to collect soil samples: 1. Ground surface to 1.5 mbgs: during NDD, the soil samples were collected

using a hand auger at ground surface, 0.5 and 1.0 mbgs. NDD terminated approximately 100 mm above each sample interval to minimise the potential for soil samples to come into contact with NDD water.

2. Depths greater than 1.5 mbgs: samples collected from depths greater than 1.5 mbgs were collected from plastic sleeves (which were PFAS free) recovered from the sonic drill rig. Samples were collected from various depths where saturated soils were observed at both the upper and lower Oakey Creek Alluvium aquifers and layers between these aquifers.

AECOM selected soil samples for laboratory analysis based on the following: • Soil at or near ground surface where shallow soil may have been impacted by

contaminated surface water or direct exposure to fire-fighting foam. • Soil at varying depths where saturated soil was encountered during drilling in the

Oakey Creek Alluvium aquifer. Up to six samples per borehole were selected for submission for laboratory analysis for extended PFAS suite. Selected near surface samples from on-Site were analysed for a broad suite of contaminants that may be present on Defence estates. A representative selection of soil and groundwater samples from across the Investigation Area were analysed for TOPA. The soil samples analysed represented different types of soil. The laboratory results were also used to characterise the soil for landfill disposal to ensure it was managed appropriately. To reduce the likelihood of cross-contamination, new disposable nitrile gloves were donned before the collection of each soil sample. Soil samples were immediately placed into 150 mL unpreserved, laboratory supplied containers. AECOM ensured non-Teflon containing sampling equipment was used to maintain sample integrity, given that the samples were to be analysed for PFAS. Sample vessels were labelled in accordance with the nomenclature identified in the SAQP. The samples were then placed into an insulated container containing crushed ice and transported to the laboratory under chain of custody (COC) documentation to the nominated laboratories. Geotechnical samples were collected from the bores and provided to the geotechnical laboratory for triaxial permeability and particle size distribution.

Field QA/QC samples

The field quality assurance / quality control (QA/QC) samples comprised intra-laboratory duplicate samples, inter-laboratory duplicate samples and rinsate blanks. Where samples were collected for volatile organics analyses, laboratory supplied trip blanks were used to inform on potential cross contamination. The results for QA/QC samples and the data validation summary are included in Appendix H.

Waste soil management

Excess soil cuttings generated during the environmental investigation were transferred to the Site for storage.

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4.3.2 Monitoring well installation and groundwater sampling

The groundwater monitoring well installation and groundwater sampling methodology is summarised in Table 4-4. Table 4-4 Monitoring well installation and groundwater sampling methodology

Activity Details Groundwater monitoring well installation

Monitoring wells were constructed from Class 18 uPVC 50 mm outside diameter machine threaded riser and slotted (0.5 mm) casing. Prior to installation, the total depth of the borehole was measured with a weighted tape. The well casing was lowered into the borehole. Graded filter sand was added to fill the annulus and extend to 1.0 m above the top of the screen. A hydrated bentonite seal 1.0 m thick was added above the filter sand and grout was put on top of the bentonite seal. Wells located on the Site were either completed with flush mounted gatic covers or steel monuments. Well construction details are provided in Appendix C.

Well development The newly constructed groundwater wells were developed using a compressor to airlift groundwater and entrained sediment in the screen and filter pack. The development reduces sample turbidity by removing fine particulate matter from the filter pack and the geologic formation near the well.

Well gauging Groundwater elevation gauging data were collected at each monitoring well during each groundwater monitoring events. Groundwater gauging data was collected on two occasions, in March 2017 and in May 2017. The field sheets are provided in Appendix H. The standing water level in each of the monitoring wells was measured in metres below top of casing (mbtoc) using an interface probe.

Field water quality parameters

Groundwater quality parameters (temperature, pH, electrical conductivity (EC), dissolved oxygen (DO) and redox potential (ORP)) were measured in the field prior to sample collection to demonstrate conditions of the groundwater in the well, which was either representative of the groundwater conditions in the targeted aquifer (low-flow sampling in monitoring wells); or representative of the groundwater being used by the landholders (groundwater abstraction bores). A calibrated water quality meter (WQM – YSI Quatro Pro Plus) was used. Groundwater used for the measurement of water quality parameters were collected in a new unpreserved lab-supplied plastic bottle at each location. The field sheets are provided in Appendix H.

Sampling The groundwater sampling procedure is described in detail in the Sampling, Analysis and Quality Plan (SAQP) (AECOM, 2017a). Groundwater samples were collected from each monitoring well using either a low flow pump or HydraSleeve sampling in accordance with Australian Standard AS5667.11 (1998) and the AECOM Standard Operating Procedure (SOP) presented in AECOM (2017a). AECOM SOPs are derived from recommendations made in ASC NEPM (2013), which states:

An appropriate method of groundwater sampling should be selected in relation to the nature of the target analytes (PFOS/PFOA) and the hydraulic characteristics of the monitoring well. In general, the use of low-flow submersible pumps minimise purging requirements are the preferred methods of groundwater sampling for site characterisation purposes. No-purge sampling techniques may also be appropriate, particularly for long-term monitoring applications.

Groundwater monitoring wells were gauged prior to sampling with an oil/water interface probe to measure depth to groundwater, total depth of the wells, and to detect the presence of NAPL.

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Activity Details Each well was sampled using a low flow pump or HydraSleeve. Before and between sampling each well, the interface probe and all other equipment which will be placed down well will be decontaminated using deionised (DI) water to reduce the risks of cross contamination. The low flow sampling used new sample tubing at each well. The AECOM SOP states that the sample tubing may contain Teflon. For this investigation, AECOM ensured non-Teflon containing tubing is used (made from low density polyethylene) to maintain sample integrity. Sample vessels were labelled in accordance with the nomenclature identified in the SAQP.

Field QA/QC samples

The field QA/QC samples comprised intra-laboratory duplicate samples, inter-laboratory duplicate samples, rinsate blanks and trip blanks. The results for QA/QC samples and a data validation summary are included in Appendix H.

Well survey All the newly installed monitoring wells were surveyed by an accredited surveyor for MGA horizontal coordinates and Australian Height Datum (AHD) levels for ground level and top of casing (TOC). The top of well casing and ground levels were surveyed on 16 March, 4 May and 23 June 2017. The survey report is presented in Appendix E.

Purge water disposal

Purged water from groundwater developing and sampling activities was placed into an intermediate bulk container or bucket and disposed of in drums stored on-Site.

4.3.3 Surface water sampling

The surface water sampling methodology is summarised in Table 4-5.

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Table 4-5 Surface water sampling methodology

Activity Details

Surface water sampling

The surface water sampling procedure is described in detail in the SAQP. The sampling was conducted in accordance with Australian Standard for Water Quality Sampling (AS 5567:1998). Samples were collected from locations along existing drains, open channels and creeks. Samples were collected from immediately below the water surface to minimise disturbance of the water column and to minimise collection of sediment in the samples. At each location a new and laboratory-supplied 125 mL non-Teflon lined bottle was attached to a telescopic sampling pole and lowered into the surface water. The sample bottle was filled to the top to ensure no headspace and the cap was immediately applied. Sample vessels were labelled in accordance with the nomenclature identified in the SAQP. The samples were then placed into an insulated container with crushed ice and transported to the laboratory under COC documentation.

Field water quality parameters

A calibrated WQM (YSI Quatro Pro Plus) was used to measure geochemical parameters by lowering the probes into the surface water and allowing them to equilibrate. General observations of the surface water quality and flow were recorded.

Decontamination A new pair of disposable nitrile gloves was used to collect each surface water sample. Decontamination of the sampling pole was undertaken using a double rinse with laboratory-supplied deionised water.

Field QA/QC samples

The field QA/QC samples comprised intra-laboratory duplicate samples, inter-laboratory duplicate samples, rinsate blanks and trip blanks. The results for QA/QC samples are included in Appendix H.

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4.3.4 Sediment sampling

The sediment sampling methodology is summarised in Table 4-6. Table 4-6 Sediment sampling methodology

Activity Details

Sediment sampling The surface water sampling procedure is described in detail in the Sampling, Analysis and Quality Plan (AECOM 2017a). Samples were collected from locations along existing drains, open channels and creeks. Samples were collected using a hand trowel or via gloved hand placing samples directly into laboratory sample jars. Before and between sampling events to reduce the risks of cross-contamination, the hand trowel used at a location was decontaminated using demineralised water and a scrubbing brush. At each location the sample jar was filled to the top to ensure no headspace and the cap was immediately applied. AECOM ensured non-Teflon containing sampling equipment was used to maintain sample integrity. Sample vessels were labelled in accordance with the nomenclature identified in the SAQP. The samples were then placed into an insulated container with crushed ice and transported to the laboratory under COC documentation.

Sediment logging Sediment logging was generally in accordance with Unified Soil Classification System (USCS).

Decontamination A new pair of disposable nitrile gloves was used to collect each sediment sample. The hand trowel was double rinsed between locations and a rinsate sample was taken from the hand trowel at the end of the sampling day.

Field QA/QC samples

The field QA/QC samples comprised intra-laboratory duplicate samples, inter-laboratory duplicate samples and rinsate blanks. The results for QA/QC samples are included in Appendix H.

4.3.5 Tap and tank water sampling Water samples collected from landholder rainwater tanks and kitchen taps were collected directly from the outlet point with samples collected from the first flush. The objective was to collect a water sample that is representative of the water used by the landholder, and therefore purging before sampling was not conducted.

4.4 Data Quality Objectives The National Environment Protection (Assessment of Site Contamination) Measure (as amended 2013) (ASC NEPM) Schedule B 2 Guideline on-Site Characterisation specifies that the nature and quality of the data produced in an investigation will be determined by the data quality objectives (DQO). As referenced by the ASC NEPM, the DQO process is detailed in the United States Environmental Protection Agency (US EPA, 2006) Guidance on Systematic Planning Using the Data Quality Objectives Process (EPA QA/G-4 : EPA/240/B-06/001), February 2006. The DQOs were specified within the SAQP. Further information is provided in Appendix H.

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5.0 Assessment Criteria

5.1 Overview The COPC investigated can be broadly split into two groups: PFAS and non-PFAS. PFAS was analysed in all media and non-PFAS was analysed in selected samples. Identifying and selecting appropriate scientifically robust assessment criteria for the Site considered the context of the CSM to ensure appropriate evaluation of potential human health and ecosystem risks. The adopted PFAS assessment criteria are intended to be conservative, for the initial assessment of human health and ecological risk (i.e. Tier 1). The assessment criteria in Table 5-1 below are sourced from the Defence Contamination Directive #8 (DCD8) (amended 2 May 2017). This document was published by Defence to provide an interim benchmark to support the progression of relevant activities on the Defence estate in a nationally consistent manner.

In the absence of formal Australian human health or ecological assessment criteria for these emerging contaminants, the DCD8 (Amendment 2) values were adopted from Department of Health (February 2017) – Final Health Based Guidelines Values (HBGV) for PFAS for use in site investigations in Australia, developed by FSANZ and the current enHealth Statement: Interim national guideline on human health reference values for per- and poly-fluoroalkyl substances for use in site investigations in Australia (June 2016).

It is noted that overall risks to human health or the environment from PFAS cannot be evaluated simply by comparison of reported PFAS concentrations with the DCD8 criteria and that the DCD8 criteria do not address PFAS other than PFOA, PFOS and PFHxS. Updated assessments of the risk to human health and the environment from PFAS are presented in AECOM (2017c) and AECOM (2017d), respectively.

5.2 PFAS Assessment Criteria At the time of preparing this report, there were two nationally adopted guidance documents on the assessment of potential health effects from PFAS.

• Department of Health (DoH), 2017. Health Based Guidance Values for PFAS for use in site investigations in Australia. April 2017 (DoH, 2017)

• FSANZ, 2017. Perfluorinated chemicals in food. Food Standards Australia New Zealand and associated supporting documents.

The screening criteria adopted in this document are sourced from the DoH document. The DoH 2017 has calculated revised drinking water quality and recreational water quality values based on the Food Safety Australia and New Zealand (FSANZ) recommended HBGV which are a tolerable daily intake (FSANZ, 2017). The use of these criteria is further supported by the values presented in the Defence Contamination Directive #8 (DCD8) (Amendment 2) on Screening Criteria dated May 2017 (DCD8, 2017). A summary of the PFAS criteria considered in this Report is presented in Table 5-1. It is noted that there are a number of national or state based technical documents that have been published in Australia. While these documents do contain criteria for PFAS these have not been considered because they are either superseded by the FSANZ (2017) HBGV, or have not been formally adopted on a national basis or within QLD. These documents include:

• NSW EPA, 2016. Incoming water standards for aquatic ecosystem protection: PFOS and PFOA

• NSW Office of Environment and Heritage (OEH), 2017. PFAS Screening Criteria (May 2017) Draft

• WA Department of Environment and Regulation (DoER), 2017. Interim Guideline on the Assessment and Management of Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) Contaminated Sites. Government of Western Australia

The HBGV nominated by FSANZ (2017) will be used in the risk assessment process to take into account ingestion and dermal contact for these exposure pathways.

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The ecological criteria adopted for this assessment is sourced from the Australian Government Department of the Environment and Energy draft guidance for the management of PFOS and PFOA (DoEE, 2016). The guidance provides screening levels for the 99% protection of freshwater species. Table 5-1 PFAS criteria summary: human health and ecological

Media Pathway Chemical Criteria Comment/reference Human receptors

Water Drinking water − groundwater

PFOS and PFHxS

0.07 µg/L

The values are from DoH (2017), which published final health based guidance values for PFAS for use in site investigations in Australia. DoH utilised the tolerable daily intake (TDI) for PFOS and PFOA from FSANZ, 2017 and the methodology described in Chapter 6.3.3 of the National Health and Medical Research Council’s (NHMRC) of the Australian Drinking Water Guidelines (ADWG) 2016 to determine drinking water values. For PFHxS, DoH 2017 noted that ‘FSANZ concluded that there was not enough toxicological and epidemiological information to justify establishing a tolerable daily intake. However, as a precaution, and for the purposes of site investigations, the PFOS tolerable daily intake should apply to PFHxS. In practice, this means that the level of PFHxS exposure should be added to the level of PFOS exposure; and this combined level be compared to the tolerable daily intake for PFOS’. The values are also presented in DCD8 (May 2017). All groundwater results were compared to these criteria.

PFOA 0.56 µg/L

Recreational water – surface water

PFOS and PFHxS

0.7 µg/L The values are from DoH (2017), which published final health based guidance values for PFAS for use in site investigations in Australia. As with the drinking water values, the DoH utilised the TDI for PFOS and PFOA from FSANZ, 2017 and ‘the methodology described in Chapter 6.3.3 of the NHMRC of the ADWG 2016 to determine recreational water quality values’ (DoH 2017). AECOM notes that Chapter 6.3.3 specifically refers to the calculation of a drinking water value. It is assumed that DoH 2017, applied the approach presented in Chapter 9.3 of NHMRC 2008 and considered a concentration 10 times that of the drinking water criterion for each compound. The values are also presented in DCD8 (May 2017). All surface water results were compared to these criteria.

PFOA 5.6 µg/L

Ecological

Water Freshwater PFOS 0.00023 µg/L DoEE, 2016 for 99% species protection

PFOA 19 µg/L DoEE, 2016 for 99% species protection

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5.3 Non-PFAS suite – Assessment Criteria Selected soil, groundwater and surface water samples were analysed for a wider suite of non-PFAS analytes, including BTEXN, TRH, metals, PAH, VOC, SVOC, OC/OP pesticides, 1,4-dioxane.

5.3.1 Soil

Soil analytical results were assessed against the guidelines developed by the National Environment Protection Council (NEPC) and documented by National Environment Protection (Assessment of Site Contamination) Measure (NEPM) 2013 and published in “Schedule B1, Guideline on Investigation Levels for Soil and Groundwater”.

The following assessment criteria were used for the assessment of risk to human health:

• Health Investigation Levels (HILs)

• Health Screening Levels (HSLs).

The following assessment criteria were used for the assessment of risk to potential ecological receptors:

• Ecological Investigation Levels (EILs)

• Ecological Screening Levels (ESLs).

The appropriate assessment criteria were selected based on land use, soil type and the depth of the soil sample. The adopted assessment criteria (as shown on tables of results) for non-PFAS contaminants in soil are listed in Table 5-2.

5.3.2 Groundwater

Environmental values and water quality objectives for groundwater are prescribed under the Environmental Protection (Water) Policy 2009 (see Section 3.3).

For both human health and environmental exposure scenarios, in the absence of applicable screening criteria, the laboratory limits of reporting (LORs) were used as an initial screen for non-PFAS to assess the contaminant concentrations in the groundwater.

5.3.2.1 Human health screening guidelines

Adopted non-PFAS screening criteria are consistent with those adopted in the Stage 2C 2016 EI (AECOM, 2016a). To assess the presence of potentially complete human exposure pathways including consideration of the proximity of residential land use to the Site, published drinking water guidelines were selected as conservative groundwater assessment criteria. The following hierarchy of screening criteria was adopted (in accordance with the approach recommended in enHealth, 2012) for human health:

• NHMRC, 2016. Australian Drinking Water Guidelines 2011, National Water Quality Management Strategy. National Resource Management Ministerial Council (NRMMC), Commonwealth of Australia, Canberra. Version 3.1, November 2016

• World Health Organization (WHO), 2011. Drinking Water Guidelines

• US EPA, 2015. Regional Screening Levels – for Tap Water Quality, last updated May 2016

• enHealth 2012. Environmental Health Risk Assessment: Guidelines for assessing human health risks from environmental hazards, Department of Health and Ageing and enHealth Council, Commonwealth of Australia (2012).

The adopted human health assessment criteria (as shown on tables of results in Appendix A) for non-PFAS contaminants in groundwater are listed in Table 5-3.

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5.3.2.2 Ecological screening guidelines

The ANZECC (2000) freshwater trigger values presented in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Volume 1 (October 2000) were adopted for ecological screening criteria, given that the receiving surface water environments immediately adjacent to the Site boundary wells sampled for non-PFAS are considered to be freshwater (i.e. drains and creeks). A 95% species protection level was selected. A 99% species protection level has been selected for PFAS due to the potential for these chemicals to bioaccumulate. As non-PFAS chemicals are generally not bioaccumulative, a species protection level appropriate for the condition of the local ecosystem (slightly to moderately disturbed condition) has been selected. The adopted assessment criteria (as shown on tables of results in Appendix A) for non-PFAS contaminants in surface water are listed in Table 5-4.

5.3.3 Surface water

Environmental values and water quality objectives for surface water are prescribed under the Environmental Protection (Water) Policy 2009 (see Section 3.3).

Analytical results were compared against the 95% protection levels for fresh water taken from the ANZECC & NHMRC Australian Water Quality Guidelines for Fresh and Marine Waters. The 95% protection level is most commonly applied to ecosystems that could be classified as slightly to moderately disturbed. Trigger values for 95% protection of species were therefore selected for the applicable analytes, with the exception of mercury, where 99% was selected. Only high reliability values were utilised in this screening assessment.

The adopted assessment criteria (as shown on tables of results in Appendix A) for non-PFAS contaminants in surface water are listed in Table 5-4.

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Table 5-2 Adopted assessment criteria – non-PFAS contaminants: soils (human health and ecological)

Compound group Analyte

Human health Ecological No applicable guideline

NEPM HIL-C/D

NEPM HSL-D

NEPM EIL-D

NEPM ESL

Metals

Arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc

Arsenic, chromium, copper, nickel, lead, zinc

Petroleum Hydrocarbons

TRH (C16-C40)

BTEX, TRH F1 and F2

PAHs

Total PAHs (based on 8)

Naphthalene

Benzo(a)pyrene

OC/OP Pesticides

DDT+DDE+DDD, aldrin and dieldrin, chlordane, endosulfan, endrin, heptachlor, HCB, methoxychlor, mirex, toxaphene

DDT

All other OC/OP pesticides

VOC

TCE, 1,1,1-TCA, PCE, cis-1,2,-dichloroethene, vinyl chloride

All other VOCs

SVOCs Phenol, cresols, pentachlorophenol

1,4-dioxane

Note: ‘-C’ indicates recreational landuse, ‘-D’ indicates commercial/industrial landuse

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Table 5-3 Adopted assessment criteria – non-PFAS contaminants: groundwater (human health)

Compound Group Analyte NHMRC

2016 WHO 2011

EPA 2015

No applicable guideline

Metals

Arsenic, cadmium, copper, mercury, nickel, lead, selenium

Chromium

Aluminium, zinc, iron

PAHs Benzo(a)pyrene

Other PAHs

Anions / Cations

Fluoride

Alkalinity, chloride, calcium, sodium, magnesium, potassium, sulphate

Petroleum Hydrocarbons

TRH (non-speciation)

Benzene, toluene, ethylbenzene, xylenes

VOC / SVOCs

Aldrin and dieldrin, atrazine, carbon tetrachloride, styrene, chlorphenvinphos, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, chlorpyrifos, DDT, diazinon, dichlorobenzenes, 1,2-dichloroethane, dichloroethenes, dichlorvos, dimethoate, EDB, endosulfan, ethion, fenthion, heptachlor, hexachlorobutadiene, malathion, pentachlorophenol, pirimphos-ethyl, tetrachloroethene, trichlorobenzenes, trichlomethanes, vinyl chloride

Bromodichloromethane, bromoform, chloroform, 1,2-dibromo-3-chloropropane, endrin

Hexachlorocyclopentadiene

All other VOCs / SVOCs

1,4-dioxane

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Table 5-4 Adopted assessment criteria – non PFAS contaminants: groundwater and surface water (ecological)

Compound Group Analyte ANZECC

2000 No applicable

guideline

Metals Arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc, selenium

Aluminium, iron

Anions / cations

Fluoride

Alkalinity, chloride, calcium, sodium, magnesium, potassium, sulphate

Petroleum hydrocarbons

Benzene, toluene, ethylbenzene, xylenes

TRH (C6-C40)

PAHs / phenols

Naphthalene, phenol

All other PAHs and phenols

OC/OP pesticides

Chlordane, DDT, endosulfan, endrin, heptachlor, azinphos methyl, chlorprifos, diazinon, dimethoate, fenitrothion, malathion, parathion

All other OC/OP pesticides

VOC / SVOCs

1,1,2-trichloroethane, aniline, nitrobenzene, 1,2-dichlorbenzene, 1,3-dichlorbenzene, 1,4-dichlorbenzene, 1,2,3-trichlorobenzene, phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, dimethylphthalate, diethylphthalate, dibutylphthalate

All other VOC/SVOCs

1,4-dioxane

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6.0 Results

6.1 Rainfall during the 2017 Stage 2C EI Rainfall data for the period between January 2017 and June 2017 was obtained from the Bureau of Meteorology’s Oakey Aero station (station number 041359) and is summarised in Table 6-1. Table 6-1 Rainfall between January 2017 and June 2017

Month Monthly rainfall total (mm)

Highest daily rainfall total (mm)

Average monthly rainfall

(mm) (1970 to 2015*)

2017 rainfall compared to long-

term average January 2017 48.6 17.0 80.6 Lower

February 2017 31.6 17.4 81.2 Lower

March 2017 160.4 52.0 48.7 Higher

April 2017 12.4 12.0 31.2 Lower

May 2017 8.4 7.2 41.5 Lower

June 2017 17.6 5.6 29.9 Lower Note: * Average monthly data based on Bureau of Meteorology’s Oakey Aero station (station number 041359) data between 1970 and 2015.

The main precipitation event that was recorded in March 2017 was associated with Ex-Cyclone Debbie. Between 30 and 31 March 2017, the total rainfall was 94.6 mm. Over the six month period there was rainfall on 27 separate days. During the investigation period, all months received lower rainfall amounts with the exception of March which had approximately three times the long-term average.

6.2 Subsurface Conditions 6.2.1 Stratigraphy

The deep drilling conducted as part of the 2017 Stage 2C EI has established the stratigraphy beneath the Investigation Area to consist of Oakey Creek Alluvium of variable thickness, which is directly underlain by either Main Range Volcanics or by Walloon Coal Measures. At two of nine locations investigated, Main Range Volcanics was underlain by Walloon Coal Measures. Transition layer soil was encountered in the lower part of the Oakey Creek Alluvium in all deep bores except where Main Range Volcanics was present at shallow depth. The geological logging indicates the subsurface is complex with variable depth to Walloon Coal Measures. Main Range Volcanics is inconsistently present and was encountered at shallow depth (3.0 mbgs) and deeper depth (greater than 57.5 mbgs). A summary of the thickness and depths of these geological units are shown in Table 6-2. Table 6-2 Stratigraphy identified during the investigation

Geological Unit Minimum depth where unit is first encountered (mbgs)

Range in depth (m) to base of unit, where proven

Oakey Creek Alluvium Surface 5.5–75.5 m

Main Range Volcanics* 3.0–57.5

6.0–33.5 m where proven. At several locations depth to base not proven (thickness of Main Range Volcanics

can be up to 70 m)

Walloon Coal Measures 39.0–75.5 Not proven (expected to be at least 200 mbgs)

Note: *Not present consistently

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6.2.2 Oakey Creek Alluvium The results of this investigation indicate that the Investigation Area is immediately underlain by the Oakey Creek Alluvium. The lithology of the alluvium is predominantly silty sandy clay with relatively thin intervals of sand or gravel. This is consistent with materials in alluvial depositional environments. The soil in the unsaturated zone generally comprises dry to slightly moist brown silty sandy clay. The sand and gravel content increases with increasing depth with saturated zones present in gravel bands. The lateral extent of the thin coarse horizons is likely to be limited and localised.

A transition zone is present in the lower part of the Oakey Creek Alluvium. This was characterised by the presence of mottled white and orange clays. The transition zone can represent either highly weathered portions of the Oakey Creek Alluvium or the underlying formation.

6.2.3 Main Range Volcanics

The Main Range Volcanics encountered was variable and ranged from competent fractured basalt to heavily weathered basalt. The weathered basalt consisted of gravel sized fragments in a clay matrix, which has potentially been weathered in situ. The redeposition of the weathered basalt during fluvial events forms part of the Oakey Creek Alluvium in the IA. During drilling, seven bores encountered the Main Range Volcanics beneath the Oakey Creek Alluvium; a summary of the depth to the top of the Main Range Volcanics and lithological description is presented in Table 6-3. Table 6-3 Depth to Main Range Volcanics

Bore Location Depth to top of the MRV / base (if present (mbgs) Lithological Description

MWO-I-MRV 57 mbgs. The depth of bore was 63 mbgs

Weathered basalt. Basalt gravel and cobbles within a basalt clay matrix.

MWO-J-WCM 57.5 mbgs. The base was proven at 63.5 mbgs

Weathered/fractured basalt from 57.5 to 63.5 mbgs

MWO-K-MRV 46.5 mbgs. The depth of bore was 55 mbgs

Weathered basalt gravel and cobbles within a basalt clay matrix.

MWO-N-AL 3 mbgs. The depth of bore was 20 mbgs

3–17 mbgs Weathered basalt gravel/cobbles in clay matrix. Unweathered rock below 17 mbgs

MWO-U-MRV 5.5 mbgs. The total bore depth of 24 mbgs Unweathered basalt below 5.5 mbgs

MWO-V-WCM 5.5 mbgs. Walloon Coal Measures present at 39.0 mbgs

Weathered basalt between 5.5 and 14 mbgs becoming a sandy clay between 14 and 39 mbgs

MWO-W-AL 6 mbgs. Walloon Coal Measures present at 20.8 mbgs

Basalt gravel and cobbles within weathered basalt clay.

Note: * See Figure F13 for bore locations

The Main Range Volcanics is present at shallow depth (less 6.0 mbgs) in the southern and south-eastern portion of the Investigation Area, as indicated by the logs at MWO-N-AL, MWO-W-WCM, MWO-V-WCM.

The Main Range Volcanics was encountered at 5.5 mbgs at MWO-U-MRV, which is located 5 km south from the Site and approximately 1 km to the south of Oakey Creek. The small thickness of Oakey Creek Alluvium at this location indicates it thins out in this area as the topography rises to the south. This demonstrates that the Oakey Creek Alluvium does not extend as far south as MWO-U-MRV.

Bores MWO-J-WCM and MWO-K-MRV are located within 1 km of each other, approximately 1.2 km to the west of the Site. At least an 8.5 m thick section of weathered basalt gravel was present at MWO-K-MRV, while only a thin layer of basalt was present at MWO-J-WCM between 57.5 and 63.5 mbgs.

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6.2.4 Walloon Coal Measures

Eight bores (MWO-H-WCM, MWO-J-WCM, MWO-V-WCM, MWO-W-AL, MWO-W-WCM, MWO-X-WCM, MWO-Y-WCM and MWO-Z-WCM) encountered WCM below the Oakey Creek Alluvium or below the Main Range Volcanics between 20.8 and 75.5 mbgs. The Walloon Coal Measures generally consisted of horizons of sandy or silty clay, silt, sandstone, siltstone and bands of coal. As the lithology of the transition zone did not contain a distinct horizon identifiable as Walloon Coal Measures, the top of the Walloon Coal Measures was assumed to be the depth where the first coal band or sandstone horizon was encountered. The screens were generally targeted to monitor across coal seams as these are considered to be the more permeable units within the Walloon Coal Measures. Based on the available literature, the base of the Walloon Coal Measures is likely to be at least 200 mbgs.

6.3 Hydrogeology 6.3.1 Groundwater elevations A summary of the range in groundwater elevations recorded during gauging events in March and May 2017 are presented in Table T2 and summarised in Table 6-4 below. Table 6-4 Summary of groundwater elevation data

Aquifer 7 to 28 March 2017 16 – 18 May 2017**

Range in hydraulic head (mAHD) No of wells Range in hydraulic head

(mAHD) No of wells

Oakey Creek Alluvium 385.437 to 398.007 63 385.844 to 395.388 15

Main Range Volcanics* 386.347 to 398.168 4

Walloon Coal Measures 379.906 to 394.226* 3

Note: * Main Range Volcanics and Walloon Coal Measures were not monitored in March 2017.

** This table excludes data for one of the Walloon Coal Measures monitoring wells (MWO-X-WCM) as during the gauging visits the pump in a nearby extraction bore was operating, which affected the groundwater level measurement in the well. As the measurements were representative of dynamic rather than a static levels, this well has been excluded from this summary.

Perched groundwater was present in two wells at the Site (MWC1-H and MWC1-J) in February 2017, with depths to groundwater 7.50 mbgs and 5.45 mbgs respectively. Depth to groundwater in other wells at the C1 and C2 locations (see Figure F2) was approximately 14.3 mbgs. Review of the bore logs indicates the perched groundwater is present within a localised sandy lens within a clay unit at these locations. Perched groundwater was not encountered in the off-Site Oakey Creek Alluvium.

Interpolated groundwater contours maps have been produced for groundwater elevation data collected from gauging events as follows:

• Gauging in Oakey Creek Alluvium in March 2017, results are presented in Figure F17

• Gauging in the Oakey Creek Alluvium in May 2017, results are presented in Figure F18

• Gauging in the Main Range Volcanics wells in May 2017, results are presented in Figure F19

• Gauging in the Walloon Coal Measures wells in May 2017, results are presented in Figure F20.

It should be noted that monitoring wells and residential bores have only been included on the figures if the landholder gave permission. As a result, not all monitoring wells and residential bores are depicted on the figures.

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6.3.2 Groundwater flow directions and horizontal head gradient

Based on the results presented in the groundwater contour maps, the overall groundwater flow direction in all three aquifers across the Investigation Area is from the east to the west. The maps for the Oakey Creek Alluvium aquifer indicate flow is towards the west, the contour map for the Main Range Volcanics aquifer indicates flow to the north-west, and the contour map for Walloon Coal Measures indicates flow to the west. It should be noted that for the Main Range Volcanics and Walloon Coal Measures aquifers, the groundwater contours are based on only a small number of monitoring wells so there is some uncertainty associated with these interpolated flow directions, as well as the hydraulic gradients. The groundwater flow directions are consistent with the understanding of regional flow. Areas of groundwater recharge are present in the east with groundwater discharge areas located to the west.

These groundwater flow directions are consistent with the regional understanding of the groundwater systems with recharge within the higher ground in the Upper Oakey Creek catchment to the east of the site and groundwater discharge to the west into Oakey Creek.

Hydraulic gradients change with depth through the groundwater profile and across the Investigation Area. As a consequence, a ‘representative’ gradient cannot be readily assigned for the entire Investigation Area. However, approximate hydraulic gradients have been defined below in the different groundwater systems. Note that the Main Range Volcanics and Walloon Coal Measures gradients are based on a small number of data points:

• Oakey Creek Alluvium – the approximate hydraulic gradient in March 2017 was 0.0014 m/m (1:700)

• Main Range Volcanics – the approximate hydraulic gradient in May 2017 was 0.0034 m/m (1:300)

• Walloon Coal Measures – the approximate hydraulic gradient in May 2017 was 0.0044 m/m (1:230).

The calculated horizontal hydraulic gradient in the Oakey Creek Alluvium is similar to the gradient calculated in May 2016 (AECOM 2016a), which was between 0.0014 and 0.0016 m/m. These results show the hydraulic gradient in the Oakey Creek Alluvium is a two times larger than the hydraulic gradient in the Main Range Volcanics and Walloon Coal Measures.

6.3.3 Vertical head gradients

The 2016 and 2017 Stage 2C EIs have installed 16 pairs of shallow and deep groundwater monitoring wells in upper and lower aquifer units (e.g. within Oakey Creek Alluvium or between Oakey Creek Alluvium and Main Range Volcanics or Walloon Coal Measures) which allows calculation of the vertical gradients using Equation 1.

𝒊 = 𝒅𝒅𝒅𝒅

(1)

Where: i = is the hydraulic gradient 𝑑ℎ = change in hydraulic head between selected wells (m) 𝑑𝑑 = change in screening distance between selected wells (m)

Vertical gradients have been calculated for paired bores within the Oakey Creek Alluvium, between the Oakey Creek Alluvium and Main Range Volcanics, between the Oakey Creek Alluvium and Walloon Coal Measures and between the Main Range Volcanics and Walloon Coal Measures. The results are presented in Table T6 and are summarised below.

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Table 6-5 Summary of calculated vertical gradients between different hydrogeological units

Location No. of datasets evaluation

Range in vertical gradient (m/m)

Interpreted vertical flow direction

Lower and Upper Oakey Creek Alluvium 8 -0.08 to 0.02 Potential hydraulic

connection

Alluvium and Main Range Volcanics 6 -0.002 to 0.003 Potential hydraulic

connection

Main Range Volcanics and Walloon Coal Measures 3 0.156 to 0.218 Downward

Alluvium and Walloon Coal Measures 7 0.004 to 0.564 Downward

6.3.3.1 Oakey Creek Alluvium (lower and upper) Vertical gradients in the eight pairs of wells that monitor lower and upper horizons within the Oakey Creek Alluvium were between -0.08 and 0.02 m/m indicating that there is hydraulic connection with potential for minor upwards or minor downwards vertical flow.

6.3.3.2 Oakey Creek Alluvium and Main Range Volcanics

Six datasets for three pairs of wells installed in the Oakey Creek Alluvium and Main Range Volcanics have been evaluated. The vertical gradients were calculated to be between -0.002 and 0.003 m/m indicating there is potential hydraulic connection (minor upwards or minor downwards) between these aquifer units.

The monitoring wells installed into the Main Range Volcanics, targeted the uppermost section of the Main Range Volcanics (<6 m), which was typically weathered and likely to be heavily fractured and therefore a hydraulic connection with the overlying Oakey Creek Alluvium is not unexpected. The wells were screened within the different formations and the wells in the Main Range Volcanics (and Walloon Coal Measures) were sealed from the Oakey Creek Alluvium. As none of the Main Range Volcanics monitoring wells were installed into deeper fractures, the vertical gradient at greater depth in the unit cannot be assessed, and it is possible that the apparent hydraulic connection indicated by these results may not be representative of the full thickness of the geological unit.

6.3.3.3 Main Range Volcanics and Walloon Coal Measures

Datasets for two pairs of wells installed in the Main Range Volcanics and Walloon Coal Measures have been evaluated. The vertical gradients were calculated to be between 0.156 and 0.218 m/m indicating there is potential for downward flow from the Main Range Volcanics into the Walloon Coal Measures.

6.3.3.4 Oakey Creek Alluvium and Walloon Coal Measures

Datasets for five pairs of wells installed in the Oakey Creek Alluvium and Walloon Coal Measures have been evaluated. The vertical gradient for the MWO-Y pair was between 0.004 and 0.023 m/m indicating potential hydraulic connection or slight downward flow (note the monitoring screens in these wells have a vertical difference of 50 m). The vertical gradient in the other four pairs of wells were calculated to be between 0.133 and 0.564 m/m indicating the potential for downward flow at these locations from the Oakey Creek Alluvium to the Walloon Coal Measures.

6.3.4 Unsaturated Zone Thickness

The range in depth to groundwater and likely depth of the unsaturated zone at the location of the PFAS source areas (shown in Figure F3) is summarised in Table 6-6.

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Table 6-6 Approximate thickness of unsaturated zones in source areas

Location Approximate thickness of

unsaturated zone (m) (based on 2017 depth to water levels)

Area A2: Spent AFFF recovery tank and hot refuel area 13.2–14.3 Area S1: Spent AFFF recovery tank 12.2–13.4

Area C1: Spent AFFF recovery tank Localised perched water at 7.5 mbgs. Regional groundwater at 14.4–14.7 mbgs

Area D2: Current AFFF storage and decanting area 10.9 Area D2: Current fire training ground 13.7 Area F1: Former fuel compound / hot refuelling point 14.7–15.0 Area B3: Former fire station and foam training area 14.1–14.7 Area North: Former fire training ground 13.2–14.2

These thicknesses show the average thickness of the unsaturated zone below the Site is between 12.2 and 15.0 m. The unsaturated zone thickness at two locations is smaller, at the current AFFF storage and decanting area in Area D2 where the unsaturated zone is 10.9 m thick, and close to the spent AFFF tank in Area C1 where there is a localised area of perched water present at 7.5 mbgs.

6.3.5 Temporal variation in groundwater elevation

Pressure transducers and data loggers were installed in two groundwater monitoring wells on-Site to understand temporal variations in groundwater elevation during a one-month period (31 days) during the wet season. Table 6-7 presents a summary of the logger details, the range of groundwater levels measured and responses identified. Hydrographs of these data are shown in Chart 3. The results indicate that there was very small variation in groundwater elevation in well MWA5-A-UA (0.15 m) with no response detected following rainfall events. The dataset in MWA4-A may be impacted by a fault within the logger as diurnal (daily) changes are present. Notwithstanding this, there was no response detected in groundwater level in this well following rainfall events.

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Table 6-7 Summary of results of continuous data loggers

Bore ID MWA4-A MWA5-A-UA

Location South-western corner of Site Along southern Site boundary

Aquifer Oakey Creek Alluvium Oakey Creek Alluvium

Lithology of screened section

Clay and gravel Sandy clay / clayey sand

Screen details 25.0–29.0 mbgs 11.5–14.5 mbgs

Depth of logger 15.0 mbgs 14.0 mbgs

Dates installed 10/02/2017 to 13/03/2017 10/02/2017 to 13/03/2017

Groundwater elevation 390.28–391.93 mAHD 389.73–389.88 mAHD

Amplitude 1.65 m 0.15 m

Responses

• Response to rainfall event on 19–20 February 2017 observed with the surface water level rising by ~0.8 m during the following three days. This was a longer duration rain event compared to later events and allowed for more effective rainfall recharge.

• No response to rainfall observed following rainfall events on 3 and 5 March 2017.

• Diurnal (daily) changes in dataset – these are likely to indicate a fault within the logger.

• Changes between 10 and 13 February 2017 potentially relate to disturbance to the water following installation of the logger.

• No response observed during monitoring period.

• No response to rainfall events apparent.

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Chart 3 Hydrograph of MWA4-A and MWA5-A-UA: 10 February to 13 March 2017

6.3.6 Temporal variation in surface water flow

Chart 4 shows the surface water elevations for a 31 day period at a location along drainage channel 2, at the point where the drain crosses the southern Site boundary (see Plates in Appendix C and Figure F6). The drainage channel drains stormwater from a large on-Site network. Four rainfall events occurred during the monitored period, with precipitation totals between 12.0 mm and 24.6 mm. The results show the following:

• Rainfall event 1 on 19 February 2017: Following the first rainfall event (14.2 mm) on 19 February 2017, there was a lag time of approximately 60 hours before water levels rose in the drainage channel. At the end of the lag time, the water level rose very quickly with the rising limb showing an increase of 0.4 m in a 25 minute period. The water level decreased slowly with the falling limb showing a drop of 0.24 m in a 9.5 hour period. The falling limb was interrupted by the effect of the second rainfall event.

• Rainfall event 2 on 20 February 2017: The second rainfall event (17.4 mm) occurred on 20 February 2017 with a similar lag time to the first rainfall event. The water level again rose over a six hour period, showing an increase of 0.5 m. The water level took approximately seven days to return to a similar level to prior the first rainfall event.

• Rainfall event 3 on 3 March 2017: Following the third rainfall event (24.6 mm), there was again a lag time of approximately 60 hours before the water level increased over a very short period (10 minutes), showing an increase of approximately 0.58 m. The hydrograph shows the falling limb of this event decreased over the next 48 hours before being affected by the fourth rainfall event.

• Rainfall event 4 on 5 March 2017: Following the fourth rainfall event (12.0 mm), there was again a lag time of approximately 60 hours before the water level increased over a very short period (25 minutes), peaking at approximately 0.50 m. The hydrograph shows the falling limb of this event decreasing over the next five days.

It is not known why the water level rises up over such a short duration following a long lag time. This indicates it takes a prolonged period for the stormwater within the Site’s catchment basin to flow into the main drain and reach the data logger location.

388.0

388.5

389.0

389.5

390.0

390.5

391.0

391.5

392.0

392.5

393.0

393.5

394.0

9/02

10/0

211

/02

12/0

213

/02

14/0

215

/02

16/0

217

/02

18/0

219

/02

20/0

221

/02

22/0

223

/02

24/0

225

/02

26/0

227

/02

28/0

21/

032/

033/

034/

035/

036/

037/

038/

039/

0310

/03

11/0

312

/03

13/0

314

/03

15/0

316

/03

Gro

undw

ater

Ele

vatio

n (m

AHD)

Date

Groundwater Elevation Changes between 10 February and 13 March 2017

MWA4-A MWA5-A-UA

Rainfall24.6mm on 3/3


Rainfall31.6mm on 19-20/2

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This is likely to reflect:

• the stormwater infrastructure on-Site

• the shape of the drainage channels

• the piezometer installation design. Chart 4 Hydrograph of drainage channel 2: 10 February to 13 March 2017

6.4 Water Quality Parameter Results 6.4.1 Groundwater A summary of the water quality parameters in the different aquifer units is presented in Table T3 and summarised in Table 6-8. Table 6-8 Summary of groundwater quality parameter results

Parameter Units Oakey Creek

Alluvium (n = 79) Main Range

Volcanics (n = 5) Walloon Coal

Measures (n = 7) Range Mean Range Mean Range Mean

pH - 6.6 – 8.9 7.3 6.9 – 7.9 7.4 7.7 – 10.0 9.0

Temperature ºC 15.9 – 29.7 23.6 22.5 – 23.6 23.0 18.3 – 25.0 21.7

Dissolved Oxygen mg/L 0.1 – 7.5 2.8 1.1 – 8.0 4.9 0.63 – 5.4 2.9

Redox Potential mV 66 – 463 279 157 – 223 185 82 – 294 182

Electrical Conductivity µS/cm 253 – 7325 2683 1255 – 3569 1986 41 – 2329 1101

Total Dissolved Solids mg/L 170 – 4908 1797 841 – 2391 1331 27 – 1560 738

0.000.100.200.300.400.500.600.700.800.901.001.101.201.301.401.501.601.701.801.902.00

9/02

11/0

2

13/0

2

15/0

2

17/0

2

19/0

2

21/0

2

23/0

2

25/0

2

27/0

2

1/03

3/03

5/03

7/03

9/03

11/0

3

13/0

3

15/0

3

17/0

3

Dept

h to

Wat

er (b

elow

rela

tive

leve

l)

Date

Surface Water Elevation in Drainage Channel 2: February to March 2017

Rainfall14.2mm on 19/217.4 mm on 20/2



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Based on the averaged results the aquifer units can be characterised as follows:

• Oakey Creek Alluvium is near neutral, moderately oxygenated, mildly reducing and brackish

• Main Range Volcanics is near-neutral, well oxygenated, moderately reducing and brackish

• Walloon Coal Measures is alkaline, moderately oxygenated, moderately reducing and fresh to brackish.

6.4.2 Surface water

A summary of the water quality parameters in the different creeks are presented in Table T4 and summarised in Table 6-9. Table 6-9 Summary of surface water quality parameter results

Parameter Units Oakey Creek

(n = 19) Doctor Creek

(n = 2) Westbrook

Creek (n = 1) Range Mean Range Mean Result

pH - 5.2 – 8.8 7.5 7.3 – 8.3 7.8 8.3

Temperature ºC 21.9 – 34.1 28.0 25.1 – 36.9 31.0 18.7

Dissolved Oxygen mg/L 1.0 – 8.9 4.4 1. 6 – 5.8 3.7 6.9

Redox Potential mV 223 – 394 271 244 – 302 273 301

Electrical Conductivity µS/cm 151 – 1116 488 388 – 496 442 762

Total Dissolved Solids mg/L 101 – 748 327 260 – 332 296 511

Based on the averaged results the creek water can be characterised as follows:

• Oakey Creek water quality is slightly alkaline, well oxygenated, mildly reducing and fresh

• Doctor Creek water quality is slightly alkaline, moderately oxygenated, mildly reducing and fresh

• Westbrook Creek water quality is slightly alkaline, well oxygenated, mildly reducing and fresh.

6.5 Known Hydrocarbon Impact A gauging event was conducted on 6 February 2017 to identify the spatial extent of the known presence of LNAPL in Area C1. The gauging event measured LNAPL in five groundwater monitoring wells (MWC1-B, -D to -G) using an interface probe4 with measured thicknesses between 1.502 and 3.72 m. The maximum thickness was measured in MWC1-E. The area impacted with LNAPL is shown in Figure F21. As shown in this figure, the gauging event has characterised the local extent of LNAPL to the southeast, south and southwest. The local extent to the north has not been characterised, however, this direction is noted to be cross-hydraulic gradient to the groundwater flow direction. The area impacted by LNAPL is contained within the Site.

6.6 Geophysical Borehole Assessment Results Wireline logging was conducted on three existing registered bores (RN107812, RN87469 and RN87369) that have previously been identified by DNRM as having the potential to cause cross flow between aquifer units (see Section 2.2.1). The locations of these wells are shown on Figure F14. The results of the borehole assessments on bores are presented in Appendix F. The main findings are presented below.

4 An interface probe allows measurement of the depth to the top of the non-aqueous phase liquid and depth to the top of the groundwater. The difference between the measurements indicates the thickness of the non-aqueous phase liquid.

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6.6.1 RN107812

The bore, according to the DNRM bore report, was drilled to 134 m through Walloon Coal Measures sediments. The down-hole geophysical survey revealed the following:

• Total bore depth was 74.0 m with PVC casing (140 mm diameter) from surface to 62.2 m. There was an uncased section between 62.2 and 74.0 mbgs. The current depth of the bore indicates it was backfilled to 74.0 mbgs.

• Slotted casing was installed in four joints between 47.13 and 62.2 mbgs. The slot length was approximately 140 mm with a 3.3 mm aperture.

The presence of a seal/gravel pack between casing and the hole could not be verified. The data indicated the hole was not cased all the way to the bottom, which indicated it is unlikely to have been sealed. The potential for a hydraulic connection between the Oakey Creek Alluvium and the Walloon Coal Measures could not be discounted. Consequently, two groundwater monitoring bores (MWO-X-AL and MWO-X-WCM) were installed adjacent to RN107812, to assess hydraulic connection, vertical hydraulic gradients, transition zone and groundwater quality. A pump test was also completed to evaluate the effects of induced pumping on groundwater levels in the aquifer units, see Section 6.7.1.

6.6.2 RN87439

The bore, according to the DNRM bore report, was drilled to 60 m through Walloon Coal Measures. The down-hole geophysical survey revealed the following:

• Total bore depth was 59.40 m with steel casing (137 mm diameter) from surface to 59.40 m. The casing was welded with external and internal flush joints.

• There were two joints of slotted casing from 44.65 to 57.66 mbgs. The slot length was approximately 310 mm and 15 mm aperture. Some slots were broken and other appeared clogged. Bore completion was slotted casing to final depth.

The presence of a seal / gravel pack between casing and the hole could not be verified. The geology cannot be verified from the bore assessment and the geological descriptions recorded in the bore card are inconclusive as they cannot be definitively identified as either Alluvium or Main Range Volcanics strata. The potential for a hydraulic connection between the Alluvium or Main Range Volcanics and the Walloon Coal Measures could not be discounted. Consequently, two groundwater monitoring bores (MWO-W-AL and MWO-W-WCM) were installed adjacent to RN87439, to assess hydraulic connection, vertical hydraulic gradients, transition zone and groundwater quality. A pump test was also completed, see Section 6.7.1.

6.6.3 RN87369 The bore, according to the DNRM bore report, was drilled to 86 m through basalt and Walloon Coal Measure sediments. The down-hole geophysical survey revealed the following:

• Total bore depth was 80.86 m with casing (165 mm diameter) from surface to 80.86 m.

• Slotted casing was installed at three separate intervals – 21.73 to 27.62 mbgs, 61.03 to 66.80 mbgs, and 74.05 to 78.49 mbgs. The slots appeared open.

• Groundwater level at 20.87 m below top of casing.

• Gamma readings indicate geological change at around 27 m from Main Range Volcanics to transitional zone clay. No clear gamma change from clay to Walloon Coal Measures coal (logged at 56 m).

• A cement bond log was conducted for the casing from 20.90 to 80.86 mbgs to assess the status of the seal separating the basalt and the coal units. Interpretation of the log indicated:

- A fair to poor bond was recorded adjacent to the slotted casing intervals, either due to fines or slumping within the annulus

- The interval from 27.60 to 33.99 m showed good to fair cement bond, however this is unlikely to provide isolation

- The remainder of the casing shows poor bond to no bond.

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Overall, the results indicated that there was a lack of zonal isolation across the entire cased interval with the potential for hydraulic connection between the upper Main Range Volcanics aquifer and the lower coal seam aquifers within this bore. Consequently, two groundwater monitoring bores (MWO-V-AL and MWO-V-WCM) were installed adjacent to RN87369, to assess hydraulic connection, vertical hydraulic gradients, transition zone and groundwater quality. A pump test was also completed, see Section 6.7.1.

6.7 Hydrogeological Testing 6.7.1 Pump tests and groundwater flow velocity

The groundwater flow velocity can be estimated based on Darcy’s law given in Equation 2, below:

𝒗 = 𝑲 ∙ 𝒅𝒅𝒅𝒅∙ 𝟏𝒏𝒆

(2)

Where: 𝑣 = is the average linear groundwater velocity or the velocity of a water molecule (m/year) 𝑑ℎ = change in hydraulic head between selected wells (m) 𝑑𝑑 = horizontal distance between selected wells (m) 𝑑ℎ𝑑𝑑

= is the horizontal hydraulic gradient (m/m) ne = is the effective porosity which is sometimes referred to as mobile porosity.

6.7.2 Infiltration tests

The information from the three infiltration tests was analysed and an estimate of vertical hydraulic conductivity has been made. Two of the tests were conducted in soil bores located along drainage channel 3 (BH-DC-01 and BH-DC-16) and the third test was conducted in a soil bore (BH-DC-12) at drainage channel 2. The locations of these soil bores are shown in Figure F11.

The first test, on drainage channel 3 within Area D, has a zone of high permeability gravel-rich clay (< 0.5 m within the drain floor) where the auger hole could not be filled to surface.

This high K zone is also recorded in bore MWD2-E, up to 1.5 m from surface (outside the drain).

This indicates zones of increased permeability occur at surface, which allows for the movement of PFAS water (runoff or drain flow) to enter the subsurface.

The other tests, within the silty or sandy clay, indicate lower vertical permeability ranging between 0.1 and 0.2 m/day.

Assuming a (thickness) depth to water of 15 m (based on the maximum thickness of the unsaturated zone (see Section 6.3.4) and a porosity of 40% for clay, the travel time through 15 m of silty or sandy clay is shown in Equation 3, below:

𝑻𝑻 = 𝒅𝒊𝑲∙ 𝟏𝒏

(3)

Where

Tt = travel time (in days) D = thickness (15 m) I = gradient = 1 for vertical K = 0.1 to 0.2 m/day n = 40% (Driscoll, 1986)

The results indicated that vertical (downward) travel time is between 3,000 and 6,000 days (8 and 16.5 years).

6.8 Soil Analytical Results The following subsections present human health and ecological screening assessments for soil samples collected during the environmental investigation.

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The soil laboratory analytical results are presented in Table T6 to Table T10 and graphically in Figure F22 to Figure F29. The laboratory analytical reports are presented in Appendix G.

6.8.1 Human health and ecological screening assessment of PFAS

The following tables present the PFAS analytical results in on-Site and off-Site soil samples:

• On-Site PFAS soil analytical results from the drilling investigation are presented in Table T7 and Figure F22, Figure F23 and Figure F24

• PFAS soil analytical results for the drainage channel investigation are presented in Table T8 and Figure F25

• Off-Site PFAS soil analytical results from the drilling investigation are presented in Table T9 and Figure F26 and Figure F27

• Off-Site PFAS surface soil analytical results are presented in Table T10 and Figure F28.

A summary of the results is presented in Table 6-10. There are currently no nationally endorsed human health or ecological screening guideline levels for PFAS in soil; therefore a screening assessment has not been undertaken. A detailed quantitative risk assessment was performed in 2016 to assess the risk of PFAS contamination to human health and the environment (AECOM, 2016b and AECOM 2016c) and these are currently being updated in 2017 (AECOM 2017c and AECOM 2017d). Table 6-10 Summary of PFAS concentrations in soil samples

Area Source area No. of

samples analysed

Max. PFOS (mg/kg)

Max. PFOA (mg/kg)

Max. PFHxS (mg/kg)

Max. Sum of PFAS

(mg/kg)

On-Site source areas

Spent AFFF recovery tank in A2 11 0.96 0.04 0.18 1.11

Hot refuel area in A2 11 0.87 0.03 0.04 1.01

Spent AFFF recovery tank in Area S1 9 0.08 0.002 0.004 0.09

Current AFFF storage area in Area D2 13 9.67 0.10 1.02 11.45

Current fire training ground in Area D2 15 0.03 0.007 0.03 0.13

Former fuel compound / refuelling point in F1 11 0.78 0.01 0.04 0.87

Former fire training ground in Area North 65 33.4 5.49 36.6 76.2

East: former area where AFFF used 9 1.14 0.04 0.14 1.43

Other On-Site bores 9 0.21 0.004 0.008 0.24

Drains On-Site 42 1.62 0.15 0.38 1.92

Off-Site 27 1.38 0.08 0.56 2.36

Off-Site bores 103 0.12 0.007 0.06 0.23

Off-Site surface soil 45 0.27 0.003 0.03 0.39

As shown in Table 6-10, higher PFAS concentrations in soil were detected in samples from the former fire training ground area and the current AFFF storage and decanting areas compared to the other potential source areas characterised.

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6.8.2 Leachable PFAS concentrations

Ten soil samples from the drainage channels and four soil samples from on-Site locations (three from the former fire training ground area and one from the current AFFF storage and decanting area within Area D2) were analysed for leachate concentrations using deionised water (ASLP). The results are presented in Table T11 and on Figure F29 and are summarised in Table 6-11. There are no human health or ecological screening values for leachates. The purpose of the leachate analysis was to understand the potential mobility of PFAS in soil in different areas of the Site. Leachate concentrations in the samples from the former fire training ground and current AFFF storage area were higher compared to the drainage channels. The samples from the former fire training ground area were mainly PFHxS (65%), and the sample from the AFFF storage and decanting area was mainly PFOS (84%). The leachate results are discussed further in Section 7.2. Table 6-11 Summary of soil leachate analytical results

Location No. of samples analysed

Range in sum of PFOS + PFHxS (µg/L)

Drainage channel 1 7 1.2–24.2 Drainage channel 2 6 0.2–2.9 Drainage channel 3 4 0.6–4.3 Former fire training ground 2 194–1684 Current AFFF storage and decanting area in D2 1 782 Area where AFFF was used east of D2 1 76.3

6.8.3 TOPA soil analytical results

A total of 28 soil samples were analysed for TOPA. The analytical results are presented in Table T12, together with the PFAS results. There are no nationally recognised human health or ecological screening guideline levels for TOPA. The TOPA results are discussed further in Section 7.2.

6.8.4 Particle size distribution, total organic content and total iron A total of 20 soil samples were tested for PSD by hydrometer at the analytical laboratory to understand the particle size distribution of the soil sample. A total of 21 soil samples were also tested for TOC and total iron. These parameters were collected to provide characterisation data for the groundwater modelling (see Appendix J). There are no relevant human health or ecological screening criteria for these parameters.

6.8.5 Human health and ecological screening assessment of non-PFAS COPC

6.8.5.1 Metals and metalloids

A total of 176 soil samples were analysed for eight metals/metalloids5. The results are presented in Table T13 and summarised in Table 6-12 below. As the maximum metal concentrations in soil are all significantly lower than the adopted human health screening levels, further statistical analysis of the data, such as calculating the 95th percentile upper confidence level, has not been undertaken.

Site-specific EILs have been calculated for chromium, copper, nickel and zinc using the NEPM tool box EIL calculation spreadsheet (NEPM, 2013) and are presented in Table T13 with the results of the assessment summarised in Table 6-12 below. Soil results for arsenic and lead have been assessed against generic EILs for commercial landuse. All soil samples were below the EILs with the exception of seven soil samples that exceeded the copper EIL and one soil sample that exceeded the zinc EIL. Due to the rare exceedance of the EILs, the results of the investigation indicate the soil metal concentrations are unlikely to present an unacceptable risk to the environment.

5 For convenience, these summaries for non-PFAS contaminants also includes the soil samples collected from on-Site and off-Site drainage channels, off-Site bores and sediment samples.

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Table 6-12 Summary of soil analytical results: metals and metalloids

Metal Max. soil

concentration (mg/kg)

No of samples where

concentration >LOR

No. of exceedances of NEPM 2013 HILs

(Recreational / Commercial)

No. of exceedances of NEPM 2013 EILs

Commercial (NEPM 2013)

Arsenic <5 0 0 0 Cadmium 2 4 0 No screening level Chromium 270 176 0 7

Copper 106 176 0 0 Lead 87 169 0 0

Mercury <0.1 0 0 No screening level Nickel 359 176 0 0 Zinc 2230 176 0 1

6.8.5.2 TRH, BTEXN, phenols and PAHs

A total of 55 soil samples were analysed for TRH, BTEXN, phenols and PAHs5. The results are presented in Table T14 and on Figure F30. With the exception of five samples, all results were below the limit of reporting. TRH was detected in these five samples of which three were from the drainage channels (BH-DC13, BH-DC16, BH-DC26B all from 0.0–0.2 mbgs) and two samples were from the former fire training ground area (BH-N-J and BH-N-O, both at 0.5 mbgs). Trace concentrations (i.e. concentrations close to the limit of reporting) of PAHs were detected in samples from BH-DC-13 and 26B (2.5 mg/kg and 3.6 mg/kg, respectively) and a trace concentration of 3- and 4-methylphenol (0.7 mg/kg) was also detected in the sample from BH-DC-13.

The highest TRH concentrations were detected in the sample from BH-DC13, which contained 24 mg/kg TRH F16 and 1460 mg/kg of TRH F2 to F47. The TRH F2 fraction (330 mg/kg) exceeded the NEPM ESL by approximately a factor of two in this sample. There were no exceedances of the NEPM HSL in these samples.

There were no other exceedances of the adopted human health and ecological screening levels.

6.8.5.3 OC/OP pesticides, volatile and semi-volatile organic compounds

A total of 55 soil samples were analysed for OC/OP pesticides, VOCs and SVOCs, these results are presented in Table T15, Table T16 and Table T17 respectively. All results were close to, or below, the limits of reporting. There were no exceedances of adopted human health or ecological screening guideline levels.

6.8.5.4 1,4-dioxane A total of 55 soil samples were analysed for 1,4-dioxane. The results are presented in Table T11. All results were below the limit of reporting. There are no relevant human health or ecological guideline screening levels for 1,4-dioxane in soil.

6.8.5.5 Asbestos

Asbestos cement fragments were not visually identified during the fieldwork. No samples were collected and tested.

6.9 Groundwater Analytical Results The following subsections present human health and ecological screening assessments for groundwater samples collected during the environmental investigation.

The groundwater laboratory analytical results are presented in Table T19 – Table T30 and on Figure F31 to Figure F38. The laboratory analytical reports are presented in Appendix G.

6 TRH F1 is TRH C6-C10 minus BTEX 7 TRH F2 is TRH C10 to C16 minus naphthalene, TRH F3 is TRH C16-C34 and TRH F4 is C34-C40

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6.9.1 Human health screening assessment of PFAS

The on-Site PFAS groundwater analytical results from the groundwater monitoring event are presented in Table T19 and on Figure F32. A summary of the results for different potential source areas on-Site is presented in Table 6-13. A total of 49 (out of 52) groundwater samples collected from on-Site groundwater monitoring wells exceeded the adopted human health screening level for PFOS + PFHxS. The maximum concentration was detected in MWB3-A (853 µg/L), which is located close to the former fire station and foam training area. A total of 22 groundwater samples collected from on-Site groundwater monitoring wells exceeded the adopted human health screening level for PFOA. The maximum concentration was detected in MWB3-A (42.5 µg/L).

The off-Site PFAS groundwater analytical results from the groundwater monitoring event are also presented in Table T19 and summarised in Table 6-13 and shown on Figure F33 – Figure F35. Out of 37 groundwater samples collected from the off-Site groundwater monitoring wells, the adopted human health screening guideline level for PFOS + PFHxS was exceeded in 17 samples. The maximum concentration was detected in MWO-L-AL at 16.9 µg/L located along Racecourse Road, approximately 700 m south-west of the Site. There was no exceedance of the PFOA screening level in any of the off-Site groundwater samples.

The off-Site residential bore analytical results for PFAS are presented in Table T19 and on Figure F36 (for PFOS+PFHxS) and Figure F37 (PFOA) and indicated 45 of the 81 samples exceeded the drinking water guideline level for PFOS + PFHxS. The highest concentration detected was 26.3 µg/L in the sample from GW34, which is located approximately 1 km to the south of the western portion of the southern Site boundary. Four bore samples exceeded the PFOA human health screening level with a maximum of 1.3 µg/L at RN147352. Table 6-13 Groundwater analytical results: assessment of PFAS concentrations in samples collected between January

and June 2017 with human health screening levels

Area No. of

samples analysed

Maximum PFOS+PFHxS concentration

(µg/L)

No. of samples that

exceeded PFOS+PFHxS

screening level (SL) (0.07 µg/L)

Maximum PFOA

concentration (µg/L)

No. of samples

that exceeded PFOA SL

(0.56 µg/L)

All on-Site bores 52 853 49 42.5 22

Off-Site monitoring bores (excluding residential bores)

37 16.9 17 0.5 0

Residential bores 81 26.3 46 1.3 5

6.9.2 Ecological screening assessment of PFAS in groundwater Table 6-14 shows the results of an ecological screening assessment on the groundwater samples. The 99% level for the protection of freshwater species has been selected for PFOS and PFOA due to the potential for these contaminants to bioaccumulate. The PFOS screening level is very low and below the limit of reporting resulting in exceedance of the screening level by all on-Site and off-Site samples (total of 118) where PFOS was detected. As the screening level is above the limit of reporting, it is not possible to ascertain if the other 52 samples also exceed the screening level. Two on-Site groundwater samples exceeded the PFOA ecological screening level. These were from the two wells located close to the former fire station (MW202 and MWB3-A).

The 2017 Stage 2C EI included the collection and analysis of off-Site aquatic biota samples. The results of the biota sampling have been used in the HHRA and ERA reports to assess the risk to human health and ecological receptors. The results of the biota sampling are reported in the HHRA report (AECOM, 2017c in preparation).

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Table 6-14 Groundwater analytical results: assessment of PFAS concentrations in samples collected between January and June 2017 with ecological screening levels

Area No. of

samples analysed

Max PFOS concentration

(µg/L)

No. of samples that exceeded

PFOS SL (0.00023 µg/L)

Max. PFOA concentration

(µg/L)

No. of samples that

exceeded PFOA SL (19 µg/L)

On-Site bores 52 249 49 42.5 2

Off-Site bores (excluding residential bores)

37 9.0 20 0.5 0

Residential bores 81 21.4 49 1.3 0

6.9.3 TOPA groundwater analytical results A total of 12 groundwater samples were analysed for TOPA. The analytical results are presented in Table T21, together with the PFAS results. There are no nationally recognised human health or ecological screening guideline levels for TOPA. Further discussion of the TOPA results is presented in Section 7.2.1.11.

6.9.4 Human health and ecological screening assessment of metals and metalloids

A total of 52 groundwater samples collected from on-Site groundwater monitoring wells and one sample from the off-Site background bore (MWO-F-AL) were analysed for metals and metalloids. The results are presented in Table T22 with a summary presented in Table 6-15. Table 6-15 Summary of groundwater analytical results: metals and metalloids in samples collected between January

and June 2017

Dissolved Metal

Maximum groundwater concentration

(mg/L)

Human health guideline-

drinking water (ADWG, 2016)

No. of samples exceeding

human health screening level

Ecological water guideline

(ANZECC 2000 Freshwater

95%)*

No. of samples exceeding ecological

screening level

Aluminium 0.58 None 0 0.055 0 Arsenic 0.002 0.01 0 0.024 0

Cadmium <0.0001 0.002 0 0.002 0 Chromium 0.01 None 0 0.008 6

Copper 0.014 2.0 0 0.012 1 Iron 1.27 None 0 None 0 Lead <0.001 0.01 0 0.083 0

Mercury <0.0001 0.001 0 0.0006 0 Nickel 0.11 0.02 5 0.093 1

Selenium 0.01 0.01 0 0.011 0 Zinc 0.02 None 0 0.067 0

Note: * Screening levels for cadmium, chromium, copper, lead, nickel and zinc have been adjusted for hardness in accordance with the guidance in ANZECC (2000).

As shown in the table above, the concentrations of nickel in samples from five monitoring wells exceeded the drinking water guideline screening level. The maximum concentration detected (0.11 mg/L) was a factor of 5.5 times higher the screening level.

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The concentrations of three metals in groundwater samples exceeded the ecological screening level for 95% protection of freshwater ecosystems. These were for chromium in six samples and copper and nickel in one sample each. The maximum concentrations of these metals were up to 25% higher than the screening level. The screening level for copper was only exceeded in the off-Site background bore. The metal concentrations are further discussed in Section 7.3.

6.9.5 Human health and ecological screening assessment of petroleum hydrocarbons: TRH, BTEX, Phenols and PAHs

A total of 52 groundwater samples collected from on-Site groundwater monitoring wells were analysed for TRH, BTEX, phenols and PAHs. The results are presented in Table T23 and shown on Figure F38.

PAHs were not detected above the limit of reporting in any of the groundwater samples analysed. TRH fractions were detected in seven of the 52 samples analysed (MWA2-E, MWA4-B-BB, MWA4-B-UA, MWC1-C, MWC2-L, MWN-I and MWN-K). The TRH C6-C40 concentration in MWC1-C was 3120 µg/L, all other sample concentrations were an order of magnitude lower.

With the exception of one sample (MWC1-C), BTEX compounds and phenols were not detected above the limit of reporting. The groundwater sample from MWC1-C contained 4 µg/L benzene, 5 µg/L ethylbenzene and 5 µg/L total xylenes. Groundwater monitoring well MWC1-C is located proximal to the known area of hydrocarbon contamination in Area C1. The concentration of benzene exceeded the NHRMC drinking water screening level by a factor of four.

There were no other exceedances of the human health screening guideline level. There were no exceedances of the ecological screening guideline levels. The petroleum hydrocarbon concentrations are further discussed in Section 7.3.

6.9.6 Human health and ecological screening assessment of 1,4-dioxane A total of 14 groundwater samples collected from on-Site groundwater monitoring wells were analysed for 1,4-dioxane. The results are presented in Table T23. 1,4-dioxane was not detected above the limit of reporting in any sample. There was no exceedance of the adopted human health screening guideline levels. There is no ecological screening guideline level available for 1,4-dioxane.

6.9.7 Human health and ecological screening assessment of OC/OP pesticides, VOCs and SVOCs

A total of 52 groundwater samples from on-Site groundwater monitoring wells were analysed for OC/OP pesticides, VOCs and SVOCs, the results are presented in Table T24, Table T25 and Table T26 respectively. With six exceptions, these organic compounds were not detected above the limit of reporting in any the samples. The exceptions were 44 µg/L 1,2,4-trimethylbenzene in MWC1-C, 10 µg/L cis-1,2-dichloroethene in MWC2-E, 6 µg/L chloroform in MWC2-K and between 4 and 7 µg/L di-n-butyl phthalate in MWC2-L, MWC2-M, MWD2-A.

There were no exceedances of the adopted human health or ecological screening guideline levels.

6.9.8 Major ion analytical results

A total of 89 groundwater samples collected from on-Site and off-Site groundwater monitoring wells and residential bores were analysed for major anions and cations. The results are presented in Table T27 with a summary presented in Table 6-16. With the exception of fluoride, there are no relevant human health or ecological screening levels available for these analytes. Fluoride did not exceed the human health screening guideline levels.

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Table 6-16 Summary of major ions analytical results collected between January and June 2017

Ion Units No. of results No. > LOR Minimum Maximum

Hardness as CaCO3 mg/L 89 89 21 2210 Alkalinity (hydroxide) as CaCO3 mg/L 89 0 0 0 Alkalinity (bicarbonate as CaCO3) mg/L 89 89 12 2410 Alkalinity (carbonate as CaCO3) mg/L 89 16 <1 355 Calcium mg/L 89 89 2 564 Magnesium mg/L 89 86 2 390 Potassium mg/L 89 86 <1 45 Sulfate as SO4 mg/L 89 87 <1 620 Sodium mg/L 89 89 25 1980 Chloride mg/L 89 89 7 3240 Fluoride mg/L 66 61 0.1 0.8

6.10 Stormwater Analytical Results A total of 23 water samples were collected from the three drainage channels including locations on- and off-Site and analysed for PFAS and non-PFAS COPC. The PFAS analytical results are presented in Table T28 and on Figure F39. A summary is presented in Table 6-17. Table 6-17 Summary of stormwater analytical results: PFAS in samples collected between January and June 2017

Drainage channel 1 Drainage channel 2 Drainage channel 3

On-Site Off-Site On-Site Off-Site On-Site Off-Site

No. of samples analysed 3 5 4 4 5 2

Maximum PFOS +PFHxS (µg/L) 4.5 3.9 1.2 1.0 1.4 6.9

No. of samples exceeding PFOS+PFHxS human health recreational SL

3 5 2 4 4 2

No. of samples exceeding PFOS+PFHxS human health drinking water SL

3 5 4 4 5 2

Maximum PFOA concentration (µg/L)

0.2 0.1 0.04 0.03 11.7 0.9

No. of samples exceeding PFOA human health recreational SL

0 0 0 0 1 0

No. of samples exceeding PFOA human health drinking water SL

0 0 0 0 2 1

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The results indicate nine of the 12 water samples collected from on-Site locations exceeded the adopted human health screening level for recreational water for PFOS+PFHxS and one of the 12 samples exceeded the adopted screening guideline level for PFOA. The maximum PFOS+PFHxS concentration of 4.5 µg/L was detected in a sample (SW66) collected from drainage channel 1 at the Site boundary. The maximum PFOA concentration of 11.7 µg/L was detected in a sample (SW21) collected from the drainage channel 3 adjacent to the current AFFF storage and decanting area.

Ten of the 11 water samples collected from off-Site drainage channels exceeded the adopted human health screening guideline level for recreational water for PFOS+PFHxS. None of the samples exceeded the PFOA human health screening guideline level. The maximum PFOS+PFHxS concentration of 6.9 µg/L was detected in a sample (SW57) collected from the drainage channel 3 approximately midway between the Site boundary and Oakey Creek.

Due to the potential for stormwater to be used to top up dams or used for irrigation, or to migrate to groundwater, stormwater results have also been compared to adopted screening guideline levels for drinking water. Assessment of the results indicates that water samples from all three drainage channels exceeded the PFOS+PFHxS screening level. The screening level for PFOA was exceeded in three of the seven water samples from drainage channel 3, with no exceedances in the water samples collected from drainage channels 1 and 2.

The stormwater results are further discussed in Section 7.2.6.

Five stormwater samples collected from the on-Site portion of the drainage channels were analysed for a non-PFAS suite. The results of metals, petroleum hydrocarbons, OC/OP pesticides, VOCs and SVOCs are presented in Table T22 to Table T27, respectively. These tables show the following:

• Metals: Two samples (SW24 and SW25) exceeded the ecological screening level for zinc. All other samples were below the human health and ecological screening guideline levels.

• Petroleum hydrocarbons: TRH C10-C40 was detected in all three samples between 100 and 1020 µg/L. BTEX, PAHs and phenols were not detected above the limit of reporting. There was no exceedance of the human health or ecological screening guideline levels.

• OC/OP pesticides, VOCs or SVOCs: No compound was detected above the limit of reporting and there was no exceedance of human health or ecological screening guideline levels.

6.11 Surface Water Analytical Results A total of 34 surface water samples were collected from Oakey Creek, Doctor Creek and Westbrook Creek and analysed for PFAS. The results are presented in Table T28, shown on Figure F40 and Figure F41 and summarised in Table 6-19.

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Table 6-18 Assessment of surface water analytical results: PFAS in samples collected between January and June 2017

Creek Doctor Creek Oakey Creek Westbrook Creek

No. of samples analysed 12 21 1

Maximum PFOS +PFHxS (µg/L) (No. of samples >LOR) <LOR (0) 0.82 (18) 0.01 (1)

No. of samples exceeding PFOS +PFHxS human health (recreational) guideline 0 3 0

Maximum PFOS (µg/L) (No. of samples >LOR) <LOR (0) 0.60 (18) 0.01 (1)

No. of samples exceeding PFOS ecological (99% protection) guideline 0 18 1

Maximum PFOA (µg/L) (No. of samples >LOR) <LOR (0) 0.19 (14) <LOR (0)

No. of samples exceeding PFOA human health recreational guideline 0 0 0

No. of samples exceeding PFOA ecological (99% protection) guidelines 0 0 0

Surface water samples from three locations in Oakey Creek exceeded the PFOS +PFHxS adopted screening guideline level for human health (recreational activities) as follows:

• SW18 (0.82 µg/L) – located <100 m downstream of the discharge point of drainage channels 1 and 2

• SW13 (0.82 µg/L) – located at the discharge point of drainage channels 1 and 2

• SW11 (0.77 µg/L) – located approximately 1 km downstream of the discharge point of drainage channels 1 and 2.

The surface water results are further discussed in Section 7.2.6.

Surface water samples from 18 sampling locations exceeded the adopted ecological screening guideline level for the protection of freshwater species (99% species protection – high conservation) for PFOS. It is noted that the limit of reporting for PFOS was 43 times higher than the screening level so samples with PFOS concentrations reported to be below the limit of reporting cannot be assessed. No PFOS impact was detected above the limit of reporting for samples from Doctor Creek; in contrast, a large proportion of samples from Oakey Creek (17 out of 21) and Westbrook Creek (one out of one sample) exceeded the screening level. The maximum PFOS concentration, located at SW84 (0.6 µg/L) was located approximately 300 m downstream of the confluence of drainage channels 1 and 2.

The 2017 Stage 2C EI included the collection and analysis of off-Site aquatic biota samples from the creeks. The results of the biota sampling have been used in the HHRA and ERA reports to assess the risk to human health and ecological receptors. The results of the biota sampling are reported in the HHRA report (AECOM, 2017c in preparation) and ERA report (AECOM, 2017d in preparation).

6.12 Sediment Analytical Results A total of 33 sediment samples were collected from Oakey Creek, Doctor Creek and Westbrook Creek and analysed for PFAS. The results are presented in Table T29, shown on Figure F42 and summarised in Table 6-19.

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Table 6-19 Summary of sediment analytical results: PFAS in samples collected between January and June 2017

Creek location No. of

samples analysed

Maximum PFOS (mg/kg) (No. of samples >LOR)

Maximum PFOA (mg/kg) (No. of samples >LOR)

Maximum PFHxS (mg/kg) (No. of samples >LOR)

Doctor Creek 13 0.0072 (3) <LOR (0) 0.0013 (1)

Oakey Creek 19 0.0308 (17) 0.0013 (5) 0.0008 (10)

Westbrook Creek 1 0.0007 (1) <LOR (0) <LOR (0)

The maximum concentration of PFOS in the sediment samples was 0.03 mg/kg at two locations along Oakey Creek. One of the locations was close to and downstream of the discharge point of drainage channels 1 and 2 (SED62), the other location was upstream of the discharge point of drainage channels 1 and 2 (SED65). PFOA and PFHxS were close to, or below the limit of reporting in all sediment samples. The sediment PFAS results will be assessed within the HHRA and ERA to understand risk to potential receptors. The sediment results have been used in the HHRA and ERA reports (AECOM [2017c], and AECOM [2017d], respectively) to quantitatively assess the risk to human health and ecological receptors. Consequently, a screening assessment is not included in this report.

Three sediment samples collected from Oakey Creek and Westbrook Creek were analysed for a non-PFAS suite. The results of metals, petroleum hydrocarbons, OC/OP pesticides, VOCs and SVOCS are presented in Table T13 to Table T17, respectively. These tables show the following:

• Metals: One sediment sample (SED38) slightly exceeded the adopted screening level for copper.

• Petroleum hydrocarbons: TRH C10-C40 was detected in all samples between 110 and 200 µg/L. BTEX, PAHs and phenols were not detected above the limit of reporting. There was no exceedance of the adopted screening levels.

• OC/OP pesticides, VOCs or SVOCs: No compound was detected above the limit of reporting and there was no exceedance of the adopted screening levels.

6.13 Residential Tank, Tap Water and Swimming Pool Sampling Results The residential tank, tap water and swimming pool water analytical results are presented in Table T20. A summary is presented in Table 6-20 and Table 6-21.

• Tap and tank water samples: PFAS was rarely detected in tank and tap water samples with four samples out of a total of 64 analysed containing PFOS+PFHxS concentrations greater than the limit of reporting. PFOA was not detected in any of the 64 samples.

• Pool samples: PFAS (PFOS+PFHxS and PFOA) was detected above the limit of reporting in two of the three pool water samples analysed. None of these water samples exceeded the human health screening guideline level for recreational activities.

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Table 6-20 Summary of residential tank water and tap water and pool water analytical results: PFAS in samples collected between January and June 2017

Sampling type

No. of samples analysed

Maximum PFOS +

PFHxS (µg/L) (No. of

samples >LOR)


PFOS drinking water

screening level

Maximum PFOA (mg/kg)

(No. of samples >LOR)

No. of samples exceeding PFOA

drinking water screening level

Tank water 19 0.03 (2) 0 <LOR (0) 0

Tap water 45 0.03 (2) 0 <LOR (0) 0

Table 6-21 Summary of pool water analytical results: PFAS in samples collected between January and June 2017

Sampling type

No. of samples analysed

Maximum PFOS +

PFHxS (µg/L) (No. of

samples >LOR)


PFOS recreational

screening level

Maximum PFOA (mg/kg)

(No. of samples >LOR)

No. of samples exceeding PFOA

recreational screening level

Pool water 3 0.28 (2) 0 0.04 (2) 0

6.14 Data Quality Validation The soil and sediment quality assurance analytical results are presented in with the soil results in Table T7 to Table T18, the water quality assurance analytical results are presented in Table T30 to Table T33. The data quality validation for this environmental investigation is presented in Appendix H.

In summary, while some non-conformances have been identified, these are considered of minor importance and it is concluded that the dataset presented in this report is suitable for use in the assessment.

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7.0 Discussion

7.1 Geology and Hydrogeology 7.1.1 Stratigraphy This 2017 Stage 2C EI has established that there is a variable depth to the bedrock underneath the Oakey Creek Alluvium. The top of the Walloon Coal Measures was encountered between 20.8 and 75.5 mbgs with Main Range Volcanics variably encountered with variable thickness, where present. At two locations (MWO-H-WCM and MWO-Z-WCM), the Oakey Creek Alluvium was found to be more than 70 m in thickness, indicating the potential presence of infilled paleochannels (i.e. former river valleys in the Jurassic era that were infilled during later geological periods). A transition zone has been encountered at the base of the Oakey Creek Alluvium in all deep bores (except where Main Range Volcanics was present at shallow depth in the southern and south-eastern portions of the IA), which potentially represents a more weathered section of the Oakey Creek Alluvium or underlying basement rocks. The investigation results indicate the transition zone is present in the lower portion of the Oakey Creek Alluvium across the Investigation Area.

Geological cross-sections of the Investigation Area are presented in Figure D-2 (east–west) and Figure D-3 (north–south) in Appendix D.

7.1.2 Basal Gravel in Oakey Creek Alluvium

Previous investigations have identified that one of the main hydrogeological features of the Oakey Creek Alluvium aquifer is the presence of a coarse grained basal gravel that is underlain by the transition zone. This was observed in five of the nine deep off-Site wells as identified in Table 7-1. The five bores (see Figure F13) where the basal gravel layer was detected are all located within 1 km of the southern boundary of the Site. The depth to the top of the basal gravel layer is relatively consistent, between 46.5 and 50.0 mbgs. Due to the limited data available, the lateral distribution of the basal gravel layer is uncertain. Table 7-1 Depth where basal gravel layer was encountered

Bore ID* Estimated depth where basal gravel was encountered (mbgs)

Estimated thickness of transition zone (m) to underlying unit

MWO-H-AL 48.0 to 50.0 mbgs 15.5 (50.0 to 75.5 mbgs)

MWO-I-MRV 50.0 to 50.9 mbgs 6.1 (50.9 to 57.0 mbgs)

MWO-J-WCM 48.6 to 49.5 mbgs 8.0 (49.5 to 57.5 mbgs)

MWO-Y-WCM 46.5 to 47.4 mbgs 5.3 (55.6 to 60.9 mbgs)

MWO-Z-WCM 49.5 to 52.5 mbgs 20.0 (52.5 to 72.5 mbgs)

Below the basal gravel layer were clays, which reflect the parent material, either the Main Range Volcanics or the weathered upper part of the Walloon Coal Measures. This represents the transition zone between the alluvium and the underlying strata. As indicated in Table 7-1, the estimated thickness of the transition zone is variable, between 5.3 and 20.0 m. The transition to Main Range Volcanics was characterised by colour changes such as the presence of red brown, green, black or purple clays, while the transition to Walloon Coal Measures was characterised by the presence of mottled white, purple or orange brown clays.

The large range in Oakey Creek Alluvium thickness across the Investigation Area demonstrates that it lies unconformably on the underlying strata, with the deeper thicknesses providing evidence for the presence of infilled paleochannel structures, such as at MWO-H-AL, where the base of the Oakey Creek Alluvium was encountered at 75.5 mbgs.

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The hydrogeological interpretation in the context of the project objectives is presented in Section 8.0. Although the results in this investigation indicate the upper zone of the Main Range Volcanics aquifer is hydraulically connected to the overlying Oakey Creek Alluvium aquifer, based on the available literature (see Section 3.2.4.2), on a regional scale the Main Range Volcanics is interpreted to be a separate aquifer.

7.1.3 Groundwater hydrochemistry

To support hydrogeological interpretation and assist in the development of the conceptual site model for the Site, the groundwater hydrochemistry within the Quaternary-aged Oakey Creek Alluvium, Tertiary-aged Main Range Volcanics and Jurassic-aged Walloon Coal Measures were evaluated and are discussed below.

The existing hydrochemical character of the different aquifers and their potential connectivity or linkage has been assessed based on multivariate statistical analysis of major ions in addition to individual parameters such as EC and pH for the identification of patterns in groundwaters of the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures.

7.1.3.1 Data source

The hydrochemical data were based on groundwater quality data collected between February 2017 and May 2017. Samples were collected using standard sampling protocols. A total of 89 groundwater analyses results were initially screened for nine parameters (HCO3

-, Cl-, SO42-, pH (field), EC (field),

Ca, Na, K and Mg). EC readings were used as a measure of salinity. It was observed that not all parameters were measured in each groundwater sample. As such, groundwater samples with incomplete analysis were omitted from the data set.

Further data reduction was applied by recognising that analyses should be charge neutral so that the total charge of cations and anions reported in the analysis (i.e. ionic balance) should be equal. The ionic balance provides a test of groundwater sample quality and consistency in laboratory analysis. All chemical analyses used in the hydrochemistry assessment had an ionic balance of less than 10%, The ionic balance of 10% was selected (Güler et al., 2002; Guggenmos et al., 2011) instead of the commonly used standard of 5% (Freeze and Cherry, 1979) so that only analyses with significant charge imbalances were omitted.

The hydrochemistry assessment is therefore based on 70 groundwater analyses, consisting of 49 water samples from on-Site groundwater monitoring wells, 15 groundwater samples from off-Site wells and six groundwater samples from residential bores. Where values were reported as less than the laboratory limit of reporting, the limit of reporting value was used for calculation purposes as a conservative estimate. The results show that 89% of the data have an ionic balance of less than 5%.

7.1.3.2 Multivariate statistical analysis method

The existing hydrochemical character of groundwater within the different aquifers and their potential connectivity was assessed using multivariate statistical analysis. Connectivity can be defined as the ease with which groundwater can flow within or between geological formations.

Multivariate statistical analysis provides a way to use more parameters to assess hydrochemistry (Güler et al., 2002). For example, traditional graphical techniques such as Piper, Schoeller or Stiff diagrams often lack clarity where large datasets are displayed and normally only include the major ions and no option to directly include EC or pH in the interpretation. In contrast, provided that there are at least five observations for every parameter included in the analysis (Hair et al. 2006), there is no limit to the number of parameters that can be used in a multivariate statistical analysis.

Hierarchical cluster analysis (HCA) is a commonly used multivariate statistical analysis technique, which categorises samples into hydrochemical facies or groupings according to their statistical similarities, and these clusters can then be used to identify hydrological and geological processes or controls on water chemistry. Hydrochemical facies produced by multivariate statistical analysis are supported by statistical robustness (Güler et al. 2002) compared to traditional graphical methods, which produce groupings or trends that can often incorporate a degree of subjective assessment.

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Hierarchical cluster analysis was performed using NCSS Data Analysis (Version 11) statistical software package (NCSS, LLC, Kaysville, Utah). Ion ratios (K/Na, SO42-/Cl- and HCO3-/Cl-) were used in conjunction with hierarchical cluster analysis to further explore the hydrochemistry of the hierarchical cluster analysis groups and to assist with the assessment of hydrogeochemical processes within each of the aquifers.

7.1.3.3 Hydrochemistry

The ability of HCA to classify groundwater chemistry into coherent groups that may be distinguished in terms of aquifer type, subsurface residence time and degree of human impact on water chemistry provides a good opportunity to conduct hydrogeochemical modelling and understand groundwater geochemical evolution among the different groups or subgroups.

The 70 water samples, included 60 groundwater samples from the Oakey Creek Alluvium aquifer, two groundwater samples from the Main Range Volcanics aquifer, two groundwater samples from the Walloon Coal Measures and six residential bore water samples (for which the aquifer source is unknown), were assessed using HCA. Following an iterative process, five clusters and six sub-clusters were identified from the resultant dendrogram (Chart 5). A summary of the clusters is shown in Table 7-2. Table 7-2 Hydrogeochemical clusters

Cluster Groundwater monitoring wells Aquifer unit

A GW93 (68) Unknown

B MWO-J-WCM (53) Walloon Coal Measures

C MWO-C1-H (19) Perched water in Oakey Creek Alluvium

D1 GW90 (65) Unknown

D2 MWB3-A (14), MWC1-C (18), MWC1-I (20), MWC2-E (25), MWC2-N (30), MWC2-O (31), MWS1-B (47), MWS1-D (48)

Oakey Creek Alluvium

E1 MWO-W-WCM (62) Walloon Coal Measures

E2 GW92 (67) Unknown

E3 MWO-X-AL (63) Oakey Creek Alluvium

E4

MW201 (1), MW202 (2), MWA1-B (3), MWA2-A (4), MWA2-B (5), MWA2-C (6), MWA2-D (7), MWA2-E (8), MWA4-B-BB (9), MWA4-B-LA (10), MWA4-B-UA (11), MWA5-A-LA (12), MWA5-A-UA (13), MWB5-A (15), MWB5-B (16), MWB5-C (17), MWC2-A (21), MWC2-B (22), MWC2-C (23), MWC2-D (24), MWC2-I (26), MWC2-K (27), MWC2-L (28), MWC2-M (29), MWC2-Q (32), MWC3-A (33), MWD2-A (34), MWD2-E (35), MWE-J (36), MWF1-B (37), MWF1-C (38), MWF1-G (39), MWF1-H (40), MWG1-A-LA (41), MWG1-C-LA (42), MWN-B (43), MWN-D (44), MWN-J (45), MWS1-A (46), MWB3-B (49), MWO-F-AL (50), MWO-G-AL (51), MWO-J-AL (52), MWO-K-AL (54), MWO-K-MRV (55), MWO-L-AL (56), MWO-N-AL (57), MWO-O-AL (58), MWO-P-AL (59), MWO-Q-AL (60), MWO-R-AL (61), MWO-Y-AL (64), GW91 (66), GW94 (69),GW95 (70)

Oakey Creek Alluvium and Main Range Volcanics (GW91, GW94, GW95 unknown aquifer)

Note: Corresponding row number, as shown in Chart 3, is identified in parenthesis.

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Chart 5 Dendrogram for the hierarchical cluster analysis

Note: The horizontal axis of the dendrogram represents the distance or dissimilarity between clusters. The vertical axis represents objects or clusters. Each joining of two clusters is represented on the graph by the splitting of a horizontal line into two horizontal lines. The horizontal position of the split, depicted by the short vertical bar, gives the distance (dissimilarity) between the two clusters. Lines that join at a particular distance or cut-off value are considered to be clustered. The fill or line colours correspond to each different cluster and each set of contiguous non-cluster.

Cluster A contains one groundwater sample with the highest salinity and sodium concentration (Table 7-3). This sample was collected from a residential bore. Cluster B consisted of one groundwater sample from the Walloon Coal Measures with characteristically high pH (pH >9) and proportion of potassium. Cluster C is composed of one groundwater sample from the alluvial aquifer with high bicarbonate and sulfate concentrations. Cluster D groundwater samples from the alluvial aquifer contained relatively high chloride and low sulfate concentrations. Conversely, Cluster E alluvial groundwater samples were characterised by low chloride, magnesium and calcium concentrations and salinity levels.

Chart 5 shows that groundwater samples (MWO-J-WCM and MWO-W-WCM) from the WCM (cluster row 53 and row 62, respectively) are quite different from any of the other groundwater samples analysed (due to a high pH and/or potassium), suggesting limited connectivity between the coal measures and overlying MRV aquifer.

Median values were calculated for each of the nine hydrochemical parameters for each cluster and sub-cluster, as shown in Table 7-3, which includes results from all of the nine variables that were used in the hierarchical cluster analysis. Also shown in Table 7-3 are the ion ratios (K/Na, SO42-/Cl- and HCO3-/Cl-). The hydrochemistry of each cluster and sub-cluster is compared using the median values of the hydrochemical parameters of the hierarchical cluster analysis.

Distance

0 1 2 3 414

29111216151322515659

356

3742

760263349325239443843451070614128345766

83654

9695535584050

246212324271764636762142518203031474865195368

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Table 7-3 Distribution of Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures groundwater samples within each HCA group, and median chemical compositions of each cluster

Clu

ster

/ Su

b-cl

uste

r

Oak

ey C

reek

A

lluvi

um

Mai

n R

ange

Vo

lcan

ics

Wal

loon

Coa

l M

easu

res

Unk

now

n

Bic

arbo

nate

A

lkal

inity

( as

mg

CaC

O3/L

)

Car

bona

te

Alk

alin

ity (a

s m

g C

aCO

3/L)

Chl

orid

e (m

g/L)

Sulfa

te (a

s SO

42-)

(mg/

L)

SO42-

/Cl-

HC

O3- /C

l-

Cal

cium

(mg/

L)

Mag

nesi

um

(mg/

L)

Pota

ssiu

m (m

g/L)

Sodi

um (m

g/L)

K/N

a

Fiel

d pH

Fiel

d EC

(µS/

cm)

A 0 0 0 1 803 1 3200 620 0.0715 0.1779 361 317 2 1980 0.0006 6.74 10749

B 0 0 1 0 133 151 345 21 0.0225 0.2732 8 25 25 290 0.0507 9.39 1590

C 1 0 0 0 1100 1 581 592 0.3760 1.3419 104 128 2 798 0.0015 6.97 4324

D 8 0 0 1 716 1 1740 31 0.0057 0.2732 217 219 4 908 0.0030 6.80 6066

D1 0 0 0 1 664 1 3240 61 0.0069 0.1453 243 390 3 1360 0.0013 6.44 4846

D2 8 0 0 0 721 1 1670 31 0.0054 0.2977 217 209 4 842 0.0031 6.82 6316

E 51 2 1 4 376 1 441 23 0.0163 0.5534 82 66 2.5 239 0.0059 7.22 1900

E1 0 0 1 0 487 23 438 64 0.0539 0.7881 52 36 15 411 0.0215 7.68 2329

E2 0 0 0 1 129 1 55 5 0.0335 1.6624 7 2 1 93 0.0063 8.63 421.9

E3 1 0 0 0 439 1 885 27 0.0113 0.3516 111 135 3 435 0.0041 8.24 4161

E4 50 2 0 3 368 1 444 23 0.0160 0.5461 82 66 2 239 0.0058 7.20 1843

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7.1.3.4 Cluster A

The aquifer in the single bore assigned to Cluster A, where this bore is screened, is unknown; however, the groundwater quality is characterised by high chloride and sodium concentrations and salinity (>10 mS/cm), with low K/Na ratio (Table 7-3 and Chart 6). Potassium and sodium are two monovalent ions that behave very differently in natural water systems. Although potassium is highly soluble, it is readily incorporated into clay minerals and, thus, rarely occurs in high concentrations in natural waters. Contrastingly, sodium is a more conservative ion (Hem, 1985). Furthermore, biological factors such as the leaching of organic material in surface runoff often influence potassium concentrations. On these basis, it is appears that the groundwater from Cluster A has had longer residence times compared to the other groundwater samples or there has been considerable evapotranspiration during recharge.

7.1.3.5 Cluster B

Although groundwater samples from the Walloon Coal Measures (Cluster B and sub-cluster E1) aquifer are brackish, there is a clear hydrochemical distinction between groundwater dominated by high pH and relatively higher HCO3-/Cl- ratio (MWO-J-WCM) and groundwater with circum-neutral pH and low HCO3-/Cl- ratio (MWO-W-WCM), suggesting different evolutionary pathways. The groundwater samples from the coal measures are characterised by higher potassium concentrations compared to those derived from the alluvium and tertiary aquifers due to the leaching of potassium from organic material within the coal bed. Table 7-3 and Chart 6 shows that the groundwater samples from the Walloon Coal Measures are distinctly different to those from the Main Range Volcanics and Oakey Creek Alluvium. This suggests that there is limited connectivity between the Walloon Coal Measures and the overlying aquifers.

7.1.3.6 Cluster C Cluster C is composed of one groundwater sample from the Oakey Creek Alluvium aquifer characterised by high bicarbonate and HCO3-/Cl- ratio. This groundwater sample (MWC1-H) is notably high in sulfate concentrations compared to other alluvial groundwater samples. In the sedimentary setting, the three main sources of SO_4^(2-) are seawater, evaporite minerals (primarily anhydrite (CaSO₄) and gypsum (CaSO₄•2H₂O)) and pyrite (which must be oxidised to form 〖SO〗_4^(2-)) (Dworkin and Land 1996; Hounslow 1995).

To assess if the dissolution of evaporite (gypsum and/or anhydrite) and carbonate (calcite and/or dolomite) is a plausible water-rock process in the system, (Ca+Mg) versus 〖(SO〗_4^(2-)+HCO_3^-) graphs were constructed (Chart 6). Data plotting close to the 1:1 line is indicative of these dissolution reactions occurring. If ion exchange is the process, it will shift the points to the right due to an excess of SO_4^(2-)+HCO_3^- (Cerling et al, 1989; Fisher and Mullican, 1997) as shown in Equation 4:

Na_2≡Clay + Ca^(2+) (Mg^(2+)) → 〖2Na〗^++Ca(Mg)≡Clay [4]

Reverse ion exchange processes tends to shift the points to the left due to a large excess of Ca+Mg, which can be explained by the following reaction shown in Equation 5:

2Na^++Ca(Mg)≡Clay → Na_2≡Clay+ Ca^(2+) (Mg^(2+) ) [5]

Chart 6 shows that dissolution of evaporite and carbonate minerals as well as ion exchange processes are plausible water-rock processes occurring within the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures aquifers. It is recognised that the groundwater sample collected from MWC1-H plot well to the right of the 1:1 line possibly due to excess sulfate concentrations derived from on-site anthropogenic sources including fertilisers, insecticides, fungicides and wastewater.

7.1.3.7 Cluster D

Cluster D groundwater samples are from the Oakey Creek Alluvium aquifer and are saline and contain relatively high chloride and sodium concentrations (Chart 6 and Table 7-3). Sub-cluster D1, consisting of one residential groundwater sample, contains comparatively higher chloride and sodium concentrations then sub-cluster D2, which largely contains eight alluvial groundwater samples. The presence of higher calcium and magnesium concentrations, due to the potential dissolution of carbonate minerals, are characteristics of Cluster D groundwater samples compared to other alluvial groundwater samples (Cluster E).

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7.1.3.8 Cluster E

Samples assigned to Cluster E are characterised by low chloride, magnesium and calcium concentrations and salinity levels (Chart 6 and Table 7-3). Samples assigned to sub-clusters E1 (Walloon Coal Measures) and E2 (residential bore) are distinctly different to sub-clusters E3 and E4. Sub-cluster E1 contains relatively higher potassium concentrations as well as detectable bicarbonate alkalinity. Sub-cluster E2 groundwater is characterised as fresh, with high HCO3

-/Cl- ratio (1.6624), very low ion concentrations and alkaline (pH 8.63).

Although sub-cluster E2 (AACO-GW92) and sub-cluster E3 (AACO-MWO-X-AL) groundwater samples were similar in pH, the latter was brackish/saline and contained higher proportions of chloride, sodium, calcium and magnesium concentrations. Samples assigned to sub-cluster E4 include 50 alluvial groundwaters, three residential bore water samples and interestingly, two groundwater samples from the Main Range Volcanics, suggesting that alluvial groundwater samples from this group may be interacting with the Main Range Volcanics.

The groundwater samples of sub-cluster E2, E3 and E4 contained much less potassium than sub-cluster E1, indicating minimal recent contact with vegetation and topsoil. Chart 6 Ion concentration plots for groundwater samples

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7.1.3.9 Summary

Multivariate statistical analysis (HCA) approach was used to characterise the hydrochemical nature of groundwater within the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures, and their potential connectivity. Ion ratios were used in conjunction with hierarchical cluster analysis to further explore the hydrochemistry of the hierarchical cluster analysis groups and to assist with the assessment of hydrogeochemical processes within each of the aquifers.

Hierarchical cluster analysis revealed 11 groups (five clusters and six sub-clusters) characterised by distinct hydrochemical patterns. Groundwater samples from the Walloon Coal Measures aquifer was found to be quite different from any of the other groundwater samples analysed, suggesting limited connectivity with the overlying Main Range Volcanics and Oakey Creek Alluvium aquifers. However, there is possible connectivity between the Oakey Creek Alluvium and Main Range Volcanics aquifers.

The dissolution of evaporite and carbonate minerals as well as ion exchange processes are plausible water-rock processes occurring within the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures to explain the geochemical profile, in particular, the dominance of sodium and chloride ions.

7.2 Nature and Extent of PFAS Impacts 7.2.1 On-Site PFAS concentrations in soil

Historical soil quality data from the period 2010 to 2016 have been combined with the results of the 2017 investigation to show the distribution of PFOS across the Site. PFOS is shown as this chemical has been consistently analysed during the current and historical investigations and this contaminant is generally present at higher concentrations compared to other PFAS. Figure F43 shows all results in the depth interval 0.0 to 0.5 mbgs, Figure F44 shows all results in the 0.5 to 2.0 mbgs depth interval and Figure F45 shows all results greater than 2.0 mbgs. Where multiple sample results are available for the depth intervals, only the highest sample result is shown.

The figures show that PFOS is consistently detected in near-surface soil (<0.5 mbgs) at all locations sampled across the Site. High PFOS concentrations are also present in the 0.5–2.0 mbgs depth interval, with very high concentrations present in the vicinity of several potential source areas including the former fire training ground and former fire station and foam training area in B3. Below 2.0 mbgs, PFOS concentrations in soil are much lower (at the locations sampled).

A statistical summary of 2017 and historical on-Site soil analytical results for PFOS in different depth intervals are presented in Table 7-4. The depth intervals have been selected to represent shallow soil (0.0–0.5 mbgs and 0.5–2.0 mbgs), deeper soil in the unsaturated zone (2.0–13.0 mbgs) and soil likely to be in the vadose or saturated zones (greater than 13.0 mbgs). Results are shown both including and excluding the samples from the former fire training ground (FFTG), which are considered to represent a separate sample population as many of the results from the soil in this source area are higher compared to PFAS concentrations in soil samples from other areas of the Site.

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Table 7-4 Summary of PFOS sample results for all soil samples collected on-Site

Contaminant PFOS

Depth <0.5 mbgs 0.5-2.0 mbgs 2.0-13.0 mbgs

>13.0 mbgs

Location All data Excluding FFTG** All data Excluding

FFTG** All data All data

No of samples 188 155 120 98 127 37 No of samples >LOR 173 140 91 69 51 18

Maximum (mg/kg) 33.4 9.7 30.0 6.80 0.80 0.034 Mean (mg/kg) 1.25 0.38 0.68 0.29 0.03 0.003

Standard Deviation (mg/kg) 3.93 1.22 3.07 1.02 0.11 0.006

95%UCL* (mg/kg) 12.8 2.03 1.90 0.74 0.07 0.008

Note: * 95% UCL shows the 95th percentile upper confidence level (UCL) of the arithmetic mean. These have been calculated using US EPA ProUCL v5.1.002. Samples below LOR were assumed to be equal to half the LOR.

** Excluding samples from the former fire training ground which represent a different sample population.

These results show PFOS is frequently present in soil in the 0.0 to 2.0 mbgs depth interval on-Site with PFOS detected in 86% of samples, with a mean concentration of between 0.29 and 0.38 mg/kg and a 95% UCL of at least 0.74 mg/kg. In the unsaturated zone below 2.0 mbgs, PFOS concentrations are less frequently detected (in 42% of samples), with the 95% UCL at least two orders of magnitude lower.

These results are further discussed in the following subsections in the context of the main potential source areas.

7.2.1.1 Former fire training ground in Area North

The soil dataset for the FFTG includes 76 samples including 11 historical and 65 new soil results. The analytical soil results indicate high concentrations of PFAS in and around the estimated footprint of the former fire training ground8, which were the highest soil concentrations detected during the 2017 Stage 2C EI. The ground is unsealed in this area with vegetation present at surface. The desktop study (AECOM, 2015a) indicates that the FFTG was concreted for approximately six of the 20 years that the facility operated.

The highest soil concentrations at the FFTG were detected in the 0.5–2.0 mbgs depth interval (see Figure F24). Due to the presence of high concentrations of a range of PFAS in the soil at this location, the results are considered in terms of the sum of 28 PFAS. A figure showing the lateral distribution of maximum sum of PFAS concentrations in the 0.0–2.0 mbgs depth interval is shown in Figure F46. This figure shows the highest concentrations (i.e. >20 mg/kg PFAS) are at BH-N-J, BH-N-K, BH-N-N, BH-N-O, BH-N-P, BH-O-T, BH-N-U and BH-N-W indicating there is a source of residual PFAS soil contamination associated with the former operation of the FFTG.

The sample with the highest concentration was BH-N-O at 2.0 mbgs which recorded a concentration of 76.2 mg/kg for the sum of PFAS. PFAS concentrations in the soil at the FFTG peaked between 0.5 and 2 mbgs with samples from 0.1 mbgs generally having lower concentrations than the 0.5–2.0 mbgs depth interval. The lower concentrations in the shallower zone may be due to leaching of PFAS from the surface soils.

Fourteen soil samples recorded sum of PFAS concentrations of greater than 10 mg/kg. Evaluation of the composition of these samples indicates that there were nine main PFASs present. The range in the percentage distribution (as a function of the sum of 28 compounds) and average composition of these samples is shown in Table 7-5.

8 The former footprint of the former fire training ground is not known.

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Table 7-5 Range and mean of principal PFAS present in samples from FFTG area (results of the highest 12 soil samples have been considered)

Compound Range (%) Mean (%) PFOS 4.1 to 96.5 40.0 PFOA 0.2 to 18.7 5.2 PFHxS 2.0 to 65.6 34.4 PFHxA 0.5 to 19.0 8.5 PFPeS 0.1 to 11.0 3.8 PFBS 0.1 to 7.0 3.4

PFHpS 0.2 to 6.7 1.8 PFPeA 0.04 to 3.7 1.5 PFHpA 0.03 to 1.5 0.6 PFBA 0.0 to 1.1 0.5

Evaluation of the PFAS composition in these 12 samples shows large variabilities in the concentration of the compounds, for example, PFOS comprised between 4.1 and 96.5% of the total PFAS concentration. The main compounds present are PFOS and PFHxS. The relatively elevated concentrations of other perfluorinated carboxylates (PFCAs) and perfluorinated sulfonates (PFSAs) besides PFOS and PFOA indicate the potential for future transformation into these end products in the presence of an oxidising environment. TOPA analyses were conducted on samples from the FFTG to investigate the potential for additional precursors to be present (see Section 7.2.1.11).

The area at the former fire training ground with PFAS soil impact covers an area at least 60 m (east–west) by 30 m (north–south). The area with the highest concentrations is centred around bore BH-N-O with lower concentrations present in all other directions. All ‘sum of PFAS’ concentrations at the locations sampled were less than 0.62 mg/kg by 3.0 mbgs, which indicates the residual mass of the contamination lies in the shallower depth interval, less than 3.0 mbgs.

Leachate results were conducted on the two soil samples with the highest concentrations, with the results ranging from 0.2 to 1.7 mg/L PFOS+PFHxS. PFHxS had the highest leachate concentration, comprising 65% of the leachate. Due to the unsealed nature of the ground surface, the subsurface PFAS identified in this area is considered to have the potential to migrate to the groundwater table following infiltration due to precipitation events or inundation events.

Some of the PFAS other than PFOS are present at high concentrations in soil samples from the FFTG. For example the sample from BH-N-O at 2.0 mbgs reported the sum of 28 PFAS to be 76.2 mg/kg, which included 8.0 mg/kg PFOS, 35.0 mg/kg PFHxS, 14.5 mg/kg PFHxA, 8.3 mg/kg, PFPeS, 3.4 mg/kg PFBS and 3.7 mg/kg PFOA.

A stormwater drainage channel is present in the southern portion of the FFTG area, running in an east–west direction and connecting with drainage channel 1. It is possible that this stormwater channel has provided a preferential pathway for the migration of PFAS contamination from surface soils in the FFTG area.

Groundwater analytical results from three groundwater monitoring wells sampled in the area of the former fire training ground in March 2017 indicated that PFOS + PFHxS concentrations were up to 40.4 µg/L (see Figure F31). The concentration of PFOS + PFHxS in groundwater in the FFTG is lower compared to the concentrations in groundwater close to other source areas such as the former fire station and foam training area in B3 and around the spent AFFF tank in C1.

Overall, the soil data indicate the FFTG to be a source area with high PFAS concentrations present in soil and groundwater. There is potential for ongoing migration from the soil flux to groundwater.

7.2.1.2 Spent AFFF recovery tank and hot refuel area in Area A2

Current and historical soil data have been reviewed for 27 soil samples from eight locations. The soil sample results indicate higher concentrations of PFAS were present in the near surface (i.e. at 0.5 mbgs, which are likely to be associated with surface transport mechanisms (maximum PFOS was 0.95 mg/kg). All soil concentrations in deeper samples from this area of the Site were at least two

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orders of magnitude lower. The soil data did not indicate evidence for unsaturated zone impact in the vicinity of the tank or in the hot refuel concrete pad areas.

Groundwater monitoring of wells close to the hot refuel area in March 2017 indicated concentrations of PFOS +PFHxS between 0.6 and 20.5 µg/L and PFOS+PFHxS concentrations close to the spent AFFF tank were between 5.7 and 7.1 µg/L (see Figure F31). One of the new wells (MWA2-D) contained concentrations of fluorotelemer sulfonic acids of 5.8 µg/L 6:2 FTS and 4.0 µg/L 8:2 FTS. This indicates the potential for future transformation (i.e. partial degradation) to a more persistent end point product such as PFOA at this location in the presence of an oxidising environment. The higher concentrations and presence of higher concentrations of fluorotelemers may indicate a local source, however as this location is noted to be down hydraulic gradient of the former fire training ground, it is not possible to identify the source of PFAS groundwater contamination in this part of the Site.

7.2.1.3 Spent AFFF recovery tank in Area S1

Current and historical soil data have been reviewed for 19 soil samples from five locations. This surface area of the spent AFFF tank was sealed with concrete. All PFAS concentrations in soil close to this potential source area at all depths were low (the maximum PFOS concentration in the soil samples analysed was 0.07 mg/kg at 12.0 mbgs). The near-surface soil concentrations were lower compared to other areas on-Site, which is attributed to the sealed nature of the surface at this location. The soil data did not indicate evidence for unsaturated zone soil impact in the vicinity of the tank.

The groundwater analytical results from March 2017 indicated high concentrations (greater than 100 µg/L PFOS+PFHxS) in samples from two (MWS1-B and MWO-S1-D) of the three monitoring wells that were sampled in Area S1 (see Figure F31). The results suggest the presence of a source close to these monitoring wells. The two wells that are more affected are located to the north-east and south-west of the tank, with the well with lower concentrations present to the south-east. As the highest PFAS concentrations are present in the well down hydraulic gradient (south-west) of the Area S1 AFFF tank (MWO-S1-D), this suggests this tank (or something else at this location) may be a source of groundwater contamination.

7.2.1.4 Spent AFFF recovery tank in Area C1

Due to the high number of existing groundwater monitoring wells, additional soil bores were not advanced in this area of the Site. Historical soil data have been reviewed for 28 soil samples from eight locations. Seven of these samples contained detectable concentrations of PFOS with maximum concentration of 0.42 mg/kg present at 0.5 mbgs at BH-C2-C.

The five monitoring wells closest to the tank all contain LNAPL between 1.50 and 3.72 m thick and consequently were not sampled. The closest down hydraulic gradient well that was sampled was MWC1-H, which is located 40 m to the west. This well contained the highest PFAS concentration in this area (62.5 µg/L PFOS+PFHxS) in March 2017 (see Figure F31). High PFAS concentrations were also detected in a second well (MWC1-C) close to the tank (42.7 µg/L PFOS+PFHxS). The samples from ten other wells located to the south and west of the tank contained lower concentrations, between 1.1 and 15.0 µg/L PFOS+PFHxS, indicating the lateral extent is characterised in these directions.

Depth to groundwater in MWC1-H was 7.49 mbgs, which is shallower than other wells in the area (e.g. depth to groundwater at MWC1-C was 14.62 mbgs) indicating perched water at this location. Review of the bore log for MWC1-H indicates the presence of a thin sandy clay layer between 6.9 and 7.6 mbgs within a clay unit. As the base of screen is at 14.0 mbgs, the well is unlikely to intercept regional groundwater. This suggests that PFAS in perched water is present within a localised sandy lens. The presence of PFAS concentrations in the regional groundwater at MWC1-C indicates both perched groundwater and deeper groundwater are impacted with the tank considered a possible source of the groundwater impact.

7.2.1.5 Current AFFF storage and decanting area within Area D2 There were no historical soil data available close to this potential source area. The highest PFAS concentrations in soil samples collected in this area during the current investigation were detected in the near-surface from 0.5 mbgs. One of the samples contained higher concentrations relative to the other samples (BH-D2-H 9.7 mg/kg PFOS at 0.5 mbgs), located in the north-eastern portion of the potential source area, which suggests the discharge of AFFF to ground at the location of this soil bore. The results for deeper samples at this location indicate PFAS is concentrated in the near-surface soil.

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The PFOS concentrations in the samples collected from this bore at 2.0 mbgs and 3.0 mbgs were two and four orders of magnitude lower, respectively, compared to the sample from 0.5 mbgs. This suggests the extent of PFAS in soil at this location to be localised.

Other near-surface samples contained lower PFAS concentrations. The next highest concentration was 0.57 mg/kg PFOS at BH-D2-F at 0.5 mbgs. The highest subsurface sample PFAS concentration was at BH-D2-E at 3.0 mbgs which contained 0.07 mg/kg PFOS.

The groundwater sample collected from the single well (MWD2-E) located down hydraulic gradient of the storage area contained 16.1 µg/L PFOS+PFHxS in March 2017 (see Figure F31), which is possibly associated with this source area. Although the local lateral extent is not fully characterised, the Site-wide groundwater monitoring data collected in February 2017, including a number of monitoring wells along the hydraulic gradient, provide understanding of the spatial distribution of PFAS in groundwater across the Site.

Overall the results indicate the presence of localised surface-derived soil PFAS at a location to the north-east of the storage area. The soil results combined with the presence of PFAS in groundwater down-hydraulic gradient of this area suggests the AFFF storage area to be a potential source of soil and groundwater contamination.

7.2.1.6 Current fire training ground within Area D2 There were no historical soil data available close to this potential source area. With the exception of one near-surface soil sample, all results from soil bores were at relatively low concentrations, below 0.004 mg/kg PFOS. The exception was from BH-D2-C at 0.5 mbgs which recorded a concentration of 0.03 mg/kg PFOS. The results do not indicate significant PFAS contamination in the near-surface or subsurface soils at the locations investigated around the current fire training ground.

Five groundwater monitoring wells located down hydraulic gradient (to west and south-west) of the current fire training ground were sampled in March 2017. The three wells (MWD2-A, MWC2-K and MWC2-L) closest to the training ground (<50 m distance) contained higher PFAS concentrations at 19.7–31.8 µg/L PFOS+PFHxS, compared to the more distant wells (see Figure F31). MWC3-A, located 150 m to the south-west, contained 0.5 µg/L PFOS+PFHxS.

Although the soil results do not indicate high PFAS concentrations at the locations tested, the presence of higher PFAS concentrations in groundwater close to the current fire training ground may indicate this area to be a potential source of groundwater contamination.

7.2.1.7 Former fuel compound and hot refuelling point in Area F1

Historical and current soil data have been reviewed including 17 sample results from five locations in this area of the Site. Near-surface soil results from 0.5 mbgs indicate the presence of PFAS contaminants at shallow depths at all five locations tested (maximum of 0.78 mg/kg PFOS). Subsurface samples were at least one order of magnitude lower. The soil dataset does not indicate large areas of PFAS contaminated soil in this area.

Groundwater analytical results from March 2017 indicate PFOS+PFHxS concentrations in this area to be between 2.8 and 28.6 µg/L (see Figure F31). The highest concentrations were located in the north-eastern portion of F1 with lower concentration down hydraulic gradient (to the south-west). This suggests there is a local source impacting the groundwater close to the position of MWF1-C.

7.2.1.8 Former fire station and foam training area in Area B3 Due to the existence of a large historical soil dataset for this area which includes 70 samples from 20 soil bores, no new soil bores were advanced as part of the current investigation. The highest soil concentrations detected was at BH218 at 1.0 mbgs, which contained 6.8 mg/kg PFOS. Twelve other bores contained soil concentrations greater than 1.0 mg/kg PFOS. All samples with higher concentrations were present in the 0.5–2.0 mbgs depth interval.

Groundwater concentrations in wells in this area are the highest on-Site and indicate this area may be a source of groundwater contamination. The concentrations of PFOS+PFHxS in MWB3-A and MW202 in March 2017 were 853 µg/L and 505 µg/L respectively (see Figure F31). It is noted that PFHxS was the dominant chemical present at MWB3-A (604 µg/L), while PFOS was the dominant chemical present at MW202 (211 mg/kg).

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This demonstrates the variability in individual compound concentrations. Although the local lateral extent is not fully characterised, the Site-wide groundwater monitoring data collected in February 2017, including a number of monitoring wells along the hydraulic gradient, provides understanding of the spatial distribution of PFAS in groundwater across the Site.

The higher PFAS concentrations detected in groundwater suggests that there is potentially an area of undetected soil impacts close to the former fire station and foam training area. The built-up nature of this area and presence of infrastructure restricts access to underlying soils in this area.

7.2.1.9 Area of AFFF discharge in Area East PFAS was detected in all three of the near surface soil samples from 0.5 mbgs with PFOS concentrations up to 1.14 mg/kg. There was no PFAS detected in the subsurface soils (i.e. >0.5 mbgs). The results suggest that near-surface soil may be impacted in localised areas by the historical discharge of AFFF.

7.2.1.10 Off-Site PFAS concentrations in soil

Soil samples from 2017 investigation A summary of the soil results for 2017 dataset is shown in Table 7-6. The table shows the maximum concentrations reduce with increased depth. Table 7-6 Summary of off-Site soil sample results

Area No. >LOR (total

No. of samples)

Max. PFOS concentration

(mg/kg) PFAS present

Near surface samples (<0.5 mbgs) 8 (22) 0.120 1 (PFOS)

Unsaturated zone samples (0.5–2.0 mbgs) 2 (3) 0.006 1 (PFOS)

Unsaturated zone samples (2.0–13.0 mbgs) 19 (59) 0.015

6 (PFOS, PFBA, PFHpS, PFOA, PFHxA

and PFHxS)

Saturated zone samples (>13.0 mbgs) 4 (17) 0.009 3 (PFHxA, PFHxS,

PFOS)

The samples with detectable PFAS concentrations in the near-surface zone are noted to be within areas previously flooded or are close to surface water features (creek, drainage channels / dams) or areas irrigated with groundwater. The presence of PFAS at these locations may be associated with the presence of impacted surface water. For example, the maximum concentration was detected at MWO-X-WCM at 0.5 mbgs at 0.12 mg/kg. This location is within the floodplain of Oakey Creek.

With four exceptions, the samples with detectable PFAS concentrations in the unsaturated zone were from the same bores where PFAS was detected in the near-surface. The detection impact is likely to be associated with vertical migration from the near surface zone. The four exceptions had concentrations of PFOS approximately one order of magnitude less than the 0.0–0.5 mbgs depth interval.

The four samples with PFAS concentrations detected in the saturated zone were all from bores where PFAS has been detected at higher concentrations in the groundwater. The detections are considered to represent adsorption of the contaminants in groundwater to soil/rock in the saturated zone.

Soil samples from 2010–2017 investigations

A statistical summary of 2017 and historical off-Site soil analytical results for PFOS in different depth intervals are presented in Table 7-7. Statistics for PFOS have been calculated as this contaminant is generally present at higher concentrations compared to other PFAS. The depth intervals have been selected to represent shallow soil (0.0–2.0 mbgs), deeper soil in the unsaturated zone (2.0–13.0 mbgs) and soil likely to be in the vadose or saturated zones (>13.0 mbgs).

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Table 7-7 Summary of sample results for all samples collected off-Site

Contaminant PFOS Depth <0.5 mbgs 0.5-2.0 mbgs 2.0-13.0 mbgs >13.0 mbgs

No of samples 196 3 67 29 No of samples >LOR 172 2 18 4

Maximum (mg/kg) 0.1900 0.0006 0.0150 0.0092 Mean (mg/kg) 0.0165 0.0006 0.0008 0.0005

Standard deviation (mg/kg) 0.0292 0.0002 0.0022 0.0017

95% UCL (mg/kg) 0.0256

Too few samples to

calculate 95% UCL

0.00196 0.0019

Note: * 95% UCL shows the 95th percentile upper confidence level (UCL) of the arithmetic mean. These have been calculated using US EPA ProUCL v5.1.002. Samples below LOR were assumed to be equal to half the LOR.

These results show PFOS is frequently present in soil in the 0.0–0.5 mbgs depth interval off-Site with PFOS detected in 88% of samples with a 95% UCL of 0.026 mg/kg. In the unsaturated and saturated zones below 2.0 mbgs, PFOS concentrations are less frequently detected (in 23% of samples), with the 95% UCL more than one order of magnitude lower compared to the 0.0 to 0.5 mbgs depth interval.

The presence of PFAS in the near-surface soils off-Site is attributed to migration of contaminants during historical events including flood inundation events and use of impacted borewater for irrigation purposes.

Surface soil samples The results of the 45 surface soil samples collected from off-Site areas are summarised in Table 7-8. The purpose of the sampling was to investigate wind as a transport mechanism for PFAS in soil as dust. The sampling design was based on the wind rose for the Site which is based on 11,719 observations made between 1973 and 2010, which was obtained from the Bureau of Meteorology. The wind rose is presented as Chart 7. Loose particles of soil at ground surface were collected to form a sample from each sampling position. Chart 7 Wind rose for Oakey 1973 to 2010, Bureau of Meteorology

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The wind rose shows that the prevailing wind direction was from the east, approximately 32% of the time. The next most common wind directions were from the west (15%), south-west (14%), north-east (9%), south-east (8%) and north-west (7%). Based on this, a sampling program was designed to target areas downwind of the main directions and areas around Oakey. It is known that areas in Oakey have been impacted by flood inundation and by irrigation using groundwater sourced from the Oakey Creek Alluvium aquifer. The areas sampled included the following:

• Area not impacted by flooding, down prevailing wind direction to west of Site.

• Area not impacted by flooding to south-west of Site and Oakey and downwind of a frequent wind direction.

• Area not impacted by flooding to north-east and east of Site and downwind of a frequent wind direction.

• Area potentially impacted by flooding or irrigated bore water to south of Site and downwind of an infrequent wind direction. Samples were selected to provide spatial coverage across Oakey.

A comparison of the results for these different areas is presented in Table 7-8. Due to the higher concentrations of PFAS in one of the background samples (SSL18), this sample is presented separately. Review of the exact sample location of SSL18 indicates that it was collected from sediment deposits close to a surface water feature may have been impacted due the presence of abstracted groundwater. Table 7-8 Summary of results of surface soil samples

Area No. >LOR

(Total no. of samples)

Max. PFOS Concentration

(mg/kg) PFAS present

Down prevailing wind direction to west (SSL11-14) 2 (4) 0.0003 1 (PFOS)

Frequent downwind location not impacted by flooding to

south-west of Site (SSL1-10) 2 (10) 0.0008 1 (PFOS)

Frequent downwind location, not impacted by flooding to

north-east of Site (SSL15-20) 4 (5) 0.0004 1 (PFOS)

Frequent downwind location, not impacted by flooding to

east of Site (SSL41-45) 3 (4) 0.0023 1 (PFOS)

Areas to south of Site in Oakey potentially impacted by flooding or irrigation by bore

water (SSL21-40)

21 (21) 0.080 9 (PFDS, PFHpS, PFOA, PFBS, PFHxA, PFHxS, PFNA, PFOS,

PFUnDA)

Sample to north-east, adjacent to dam (SSL18) 1 (1) 0.27

13 (PFBA, PFDS, PFHpS, PFPeA, PFPeS, PFOA, PFBS,

PFHpA, PFHxA, PFHxS, PFOS)

These results show that samples from areas that have not been impacted by floodwater and are along the prevailing wind direction or other frequent wind directions, either did not have detectable PFAS (in at least 50% of samples), or contained trace concentrations of PFOS (up to 0.0023 mg/kg). In contrast, all samples from the Oakey township area contained detectable concentrations of PFAS, with maximum PFOS at 0.08 mg/kg, which is approximately one order of magnitude higher compared to the maximum PFOS concentration in areas downwind of the frequent wind directions.

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The presence of higher PFAS concentrations in the Oakey township area is attributed to surface transport of PFAS in floodwater and sediments during inundation events and the use of groundwater containing PFAS for irrigation purposes rather than from transport of PFAS in wind-borne dust and subsequent re-deposition as surface soils. The dataset is not consistent with the potential migration of PFAS from the site in wind-borne dust.

7.2.1.11 Evaluation of TOPA soil and groundwater datasets

It is recognised that the PFCAs and PFSAs, collectively referred to as perfluoroalkyl acids (PFAAs), account for only a percentage of the mass of fluorochemical compounds in AFFF manufactured in the last few years (Houtz, 2013 published AFFF concentrate chemical composition data and references therein). Many other fluorochemicals that contain per- and poly-fluorinated portions have the potential under certain inducing conditions to undergo biotic and/or abiotic transformation processes that converts them into intermediate or terminal PFAAs. The rate of transformation varies depending on the in-situ environmental conditions. For example, Houtz (2013) found that an anaerobic environment may result in less production of PFAAs based on live culture soil/sediment laboratory microcosm studies, but were relatively more susceptible to transformation under aerobic conditions.

Because of this potential to produce PFAAs, these compounds in the environment and their intermediate transformation products, referred to as ‘PFAA precursors’ or simply ‘precursors’, are potential ongoing sources of PFAAs. The two main categories of PFAA precursors are:

• sulfonamide containing precursors, which contain a –SO2N group bound to the perfluorinated chain

• fluorotelomer precursors, which contain an ethyl group bound to the perfluorinated chain.

TOPA was conducted on a range of soil and groundwater samples from different portions of the site, and included samples with both elevated and low PFAS concentrations. The TOPA method can be used as a qualitative/semi-quantitative analytical method to demonstrate that there are PFAA precursors. These are currently not identifiable by commercial laboratories but may be converted into measurable PFCAs and PFSAs under extreme laboratory conditions via hot sodium hydroxide (NaOH) and potassium persulfate (K2S2O8) digestion under a pH of 12. There are a number of limitations associated with the generation of TOPA data, which should be considered during data interpretation. For instance, it is recognised that although microbial and biological processes can transform some PFAA precursors (e.g. perfluorinated sulfonamides), reaction conditions used in the laboratory method result in formation of PFCAs only (Houtz and Sedlak, 2012). Existing end-point compounds (e.g. PFOA and PFOS) are stable under the conditions used to oxidise the PFAA precursors in samples (Houtz and Sedlak, 2012).

Although the TOPA assay reveals the presence of precursors that may, under environmentally inducing conditions, breakdown to PFAAs, it is not intended to be an indicator or predictor of long-term endpoint of abiotic and biotic transformation processes in the field because conditions of the TOPA is more aggressive than those realised under natural environmental processes.

The range in total PFAS concentrations measured before (defined as the sum of the 28 PFAS analysed (∑PFAS28)), and after oxidation (sum TOPA C4-C14 plus sulfonates) for water (n=12) and soil (n=28) samples are shown in Table 7-9. It is noted that in some instances, the concentrations prior to oxidation were lower than those obtained post-TOPA. These differences may be due to natural variability in the samples and/or possible exhaustion of NaOH/ K2S2O8 added to samples during the oxidation assay.

Statistical analysis based on the Student’s t-test (ProUCL version 5.1) at the 95% confidence level (α = 0.05) showed that there are no significant differences (p >0.05) in the mean ∑PFAS28 and sum TOPA C4-C14 plus sulfonate concentrations. This suggests that the concentrations of additional PFAAs that can be generated from the transformation of unidentified precursor compounds in soil and groundwater under natural environmental conditions is expected to be low.

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Table 7-9 Summary of TOPA results in soil and groundwater

Media No. of samples (n)

Sum 28 PFAS (Pre-oxidation)

Sum of TOPA C4–C14 carboxylates + sulfonates

Water (µg/L) 12 9.24–1265 (30.4) 7.64–1100 (31.5)

Soil (mg/kg) 28 0.002–76.2 (0.45) 0.01–51.6 (0.48)

Note: median value in parenthesis

7.2.2 Evaluation of on-Site and off-Site groundwater quality and trends

7.2.2.1 On-Site groundwater quality Based on interpretation of the available data, AECOM conclude that there is widespread PFAS contamination in groundwater within the Oakey Creek Alluvium aquifer principally across the built up areas on-Site with locally high concentrations close to potential source areas. There are no clear ‘plumes’ of PFAS contaminated groundwater on-Site, with monitoring well samples containing high PFAS concentrations adjacent to wells containing relatively low concentrations. The uneven contaminant distribution is considered to be controlled by a combination of different processes including the transport of PFAS in surface water off-Site, the geological and hydrogeological properties of the heterogeneous stratum and the effects of groundwater extraction, on- and off-Site.

On-site groundwater is no longer extracted. The main lithology present is silty clay with localised sandy lenses that vary in their lateral and vertical extent. Areas of elevated PFAS concentration are likely to be mainly present in lower permeable soil due to sorption (see Section 8.7.3.1). The low permeable alluvium will generally retard the migration of the contaminants in groundwater across the Site. The connectivity of the coarser horizons is variable. Areas with higher connectivity would provide preferential flow pathways for the migration of contaminants.

As discussed in Section 7.2.1, groundwater PFAS concentrations are locally high close to the potential source areas. Highest concentrations have been consistently detected at the former fire station and foam training area in B3, indicating this area to be a significant source area of contaminants at the Site. Higher PFAS concentrations have also been detected in Areas S1 and C1, which may be associated with the AFFF recovery tanks in these areas. Table 7-5 shows the range in composition of PFAS in the main source areas. This table shows that 12 main compounds are present in groundwater on-Site with PFHxS and PFOS being the main compounds present.

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Table 7-10 Percentage range in PFAS composition in on-Site groundwater samples

Compound

Source areas operational between 1977 and 2003 Source areas operational since 1994 Source areas operational

since 2004 All on-Site 2017 data

(%)

Off-Site groundwater monitoring wells (%)

Former fire station (%)

Former fire training

ground (%)

Spent AFFF tank in

Area C1 (%)

Spent AFFF tank in

Area S1 (%)

Spent AFFF tank / hot

refuel area in Area A2 (%)

Former fuel compound / hot refuel in Area F1 (%)

Current fire training

ground in Area D2 (%)

Current storage area in Area D2

(%) PFOS 19.7–58.2 20.2–35.2 10.9–56.7 9.2–25.2 8.9–32.4 18.4–34.8 14.9–44.7 30.6 1.1–70.5 15.8– 80.0

PFHxS 25.7–55.9 64.9–79.8 6.7–41.8 30.8–37.1 9.4–38.5 29.4–39.2 6.3–19.2 17.6 6.3–73.6 20.0–100.0 PFHxA 7.8–13.6 11.6–46.0 1.8–11.0 14.6–18.6 6.4–13.5 6.9–18.4 6.8–12.7 9.8 0.0–34.6 3.8–12.5

PFPeS 4.9–10.1 9.0–18.4 1.0–7.6 7.6–13.2 1.3–7.1 5.2–11.1 1.0–3.9 2.7 0.4–13.4 2.1–8.5

PFBS 4.0–8.3 9.2–30.5 1.3–10.9 8.2–12.0 1.2–6.3 5.6–15.5 1.1–3.9 2.8 1.01–16.2 2.3–8.5

PFOA 3.4–6.9 3.0–9.5 1.1–8.6 2.8–5.7 3.1–6.9 0.7–2.9 6.4–13.4 8.9 0.7–13.4 0.6–5.5

PFHpS 2.4–2.9 1.9–3.7 0.5–3.3 0.9–1.9 0.7–1.9 0.7–2.1 0.7–1.6 0.8 0.6–6.1 1.0–2.3

PFPeA 1.5–2.3 1.8–9.5 0.5–5.9 2.3–4.1 1.7–8.2 2.0–3.3 4.9–18.6 6.2 0.4–18.6 0.6–15.8

PFHpA 0.5–2.7 1.4–3.5 0.6–4.9 1.5–2.1 0.0 0.9–1.4 4.3–9.3 6.8 0.0–9.3 0.6–1.7

PFBA 0.5–2.3 0.7–3.2 0.0–10.9 1.1–1.3 0.0 0.0–1.8 2.4–7.0 1.8 0.0–10.9 0.0–13.7

8:2 FTS 0.0 0.0 0.0 0.0 0.0–17.0 0.0 0.5–1.8 6.6 0.0–17.0 0.0

6:2 FTS 0.0 0.0 0.0–3.55 0.0 0.0–24.9 0.0 2.8–12.1 2.9 0.0–24.9 0.0

Note: All other PFAS were less than 1%

Bold indicates the main compound present

Composition calculations used all samples where ‘sum of PFAS’ was greater than 5 µg/L

The dates and time periods shown in the table are approximate only.

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The table above shows the PFAS composition to be variable across the Site. It is observed that groundwater samples collected from the former fire training area and former fire station area contain a relatively higher proportion of PFOS and PFHxS compared to samples from wells near the spent AFFF tanks and the current fire training ground and storage and decanting area. This may reflect different periods of AFFF in use at these facilities; the desk study (AECOM, 2015a) indicated that the former fire training ground and fire stations were operational between approximately 1977 and 2003 and used 3M Lightwater and the spent AFFF tanks have been in use since approximately 1994, which used a mix of 3M Lightwater and Ansulite®.

PFAS has also been detected in areas of the Site away from the potential source areas. For example, 16.1 µg/L PFOS+PFHxS was detected in groundwater in MWN-I, which is located near the runway in the north-eastern portion of Site. As there are no known potential sources and as it is up hydraulic gradient of these areas, the contamination is potentially related to the historical discharge of AFFF along the runway.

PFAS in groundwater has migrated off-Site beyond the down hydraulic gradient western boundary, as evidenced by the presence of PFAS in seven bores within 1 km of the western Site boundary with PFOS+PFHxS between 0.3 and 14.5 µg/L. PFAS was not detected in groundwater further down hydraulic gradient in a bore, located approximately 1.7 km from the Site boundary. PFAS is likely to migrate across the western portion of the southern Site boundary as evidenced by the detection of up to 10.5 µ/L PFOS+PFHxS at MWA5-A, which is located along the western portion of the southern boundary.

Comparison of PFAS concentrations in paired wells at MWA5-A, which are screened into different depth intervals in the Oakey Creek Alluvium, indicates that the highest PFAS concentrations are present in the upper (shallowest) portion of the aquifer, with lower concentrations as depth increases. With one exception, this trend is consistent in pairs of monitoring wells that are screened in the upper and lower portions of the Oakey Creek Alluvium aquifer (including pairs at MWO-B-UA/LA, MWO-D-UA/LA and MWO-H-UA/AL). The exception was MWO-A-UA/LA, which had higher PFAS concentrations in the well screened deeper in the aquifer.

The extent of PFOS+PFHxS in the Oakey Creek Alluvium aquifer is shown in Figure F47. This figure includes all monitoring wells and residential bores and surface water concentrations based on samples collected between January and June 2017.

7.2.3 Extent of PFAS in off-Site groundwater

Concentrations of PFAS are highest on-Site near potential source areas, with impacted groundwater extending off-Site to the south, south-west and west. As the local groundwater table is below creek level, Oakey Creek does not form a hydraulic boundary to contaminant movement. Both the creek and the drains are losing systems with water lost to underlying groundwater. PFAS in groundwater adjacent to the southern boundary of the Site is likely to be related to the surface water transport of PFAS through the unlined drains to Oakey Creek during periods of run-off and flooding with diluted PFAS concentrations vertically migrating through the drain and creek beds, infiltrating to groundwater, then migrating in groundwater flowing to the west.

In addition to the dedicated groundwater monitoring wells installed, a large number of groundwater samples have been collected from privately owned groundwater abstraction bores off-Site. In many cases the bore construction details are unknown and consequently it is unknown from which aquifer the groundwater at that location is drawn. As the Oakey Creek Alluvium aquifer is higher yielding compared to the Main Range Volcanics and Walloon Coal Measures aquifers and is also the shallowest aquifer, it is assumed that groundwater from the residential bores are representative of the Oakey Creek Alluvium aquifer.

The interpreted 2017 groundwater results for the extent of PFAS off-Site in the Oakey Creek Alluvium is presented below based on geographical area. The extent of PFOS+PFHxS in the Oakey Creek Alluvium aquifer is shown in Figure F47. This map also shows PFAS data for surface water and stormwater samples. This figure should be reviewed in conjunction with the discussion on data characteristics and uncertainties in Section 3.5.4.

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Adjacent area within 1 km to the south and south-west of the Site

This area includes areas adjacent to the drains and Oakey Creek. The 2017 dataset, which includes new and existing monitoring wells and existing bores, has improved the understanding of the extent of PFAS contaminants in this area. The highest PFAS concentrations recorded during groundwater sampling in 2017 were at GW34 and RN147352 (26.3 µg/L PFOS+PFHxS), which are located approximately 250 m and 350 m to the west (i.e. down hydraulic gradient) of drainage channel 1. Similar PFAS concentrations were also present in groundwater in a new monitoring well, MWO-L-AL (16.9 µg/L PFOS+PFHxS) and in groundwater from an existing bore, GW27 (with 24.4 µg/L PFOS+PFHxS), both located approximately 1 km south-west of the south-western corner of the Site boundary.

The detection of PFAS concentrations in groundwater in these wells indicates the off-Site area with PFAS extends approximately 500 m further to the west than assessed in the Stage 2C 2016 EI. The increased extent is due to better monitoring well coverage and the inclusion of PFHxS results. The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report (AECOM, 2017c, in preparation). The groundwater zones are material to the HHRA and will be redefined in the HHRA report.

West PFAS was detected in groundwater in a number of monitoring wells and residential bores to the west and south-west beyond MWO-L-AL (i.e. further down hydraulic gradient of the Site and Groundwater Zone 2). The most down-hydraulic gradient well with PFAS in 2017 was BORE5, which recorded 0.41 µg/L PFOS +PFHxS, and is located approximately 2 km to the west of the south-western corner of the Site. The leading edge of the area of PFAS in groundwater is likely to be close to this well.

South-east Additional groundwater monitoring wells were installed to the south-east of the Site to improve the groundwater monitoring coverage in this area. The results show PFAS was present in the groundwater between the Site and Oakey Creek at MWO-Y-AL (1.6 µg/L PFOS +PFHxS) and MWO-I-AL (0.06 µg/L PFOS+PFHxS). Groundwater results from new groundwater monitoring wells and existing residential bores on the southern side of Oakey Creek, to the south-east of MWO-M-AL did not record PFAS above the limit of reporting, indicating PFAS groundwater contamination does not extend to the south-east (based on the current dataset).

South (greater than 1 km from Site)

The 2017 results indicate that PFAS concentrations in groundwater to the south of the railway line, and east of Oakey Creek were, with three exceptions, all below the limit of reporting. The three exceptions recorded concentrations of PFOS+PFHxS in groundwater of 0.04 µg/L in GW93, 0.5 µg/L in GW57 and 0.07 µg/L in RN87439.

The 2016 residential bore results indicated an area containing PFAS in groundwater south-east of the intersection of Campbell and Lorrimer Street, which is approximately 2.5 km south of the Site with 0.92 µg/L PFOS+PFHxS recorded at GW84 in September 2016. In March 2017, groundwater in two bores in this area recorded 0.5 µg/L and 0.07 µg/L PFOS+PFHxS at GW57 and RN87439 respectively. Due to the non-detection of PFAS in groundwater in bores between the Site and these bores, the presence of PFAS in this area potentially relates to the presence of other historical off-Site local sources along Lorrimer Street, as identified in AECOM (2015a). For example, an area potentially used for off-Site firefighting training by non-Defence personnel is located immediately to the east (and up-hydraulic gradient) of this local area of impact.

South-west (greater than 1 km from Site)

Residential bores in the south-western portion of Oakey close to the former landfill have consistently contained PFAS concentrations. In 2017, three new groundwater monitoring wells were installed around the former landfill to further assess if it is a potential secondary source of contamination. PFAS concentrations were present in the down-hydraulic gradient monitoring well (PFOS+PFHxS was 6.9 µg/L in MWO-P-AL) compared to the up-hydraulic gradient monitoring well which had a maximum of 1.7 µg/L PFOS in MWO-Q-AL.

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The data provide a line of evidence that the former landfill is a secondary source of PFAS contamination and may affect groundwater quality down-hydraulic gradient of this area.

PFAS was not detected in groundwater in the new groundwater monitoring well (MWO-T-AL) located approximately 4.5 km to the south of the Site.

PFAS was detected in groundwater to the west of the former landfill with 0.3 µg/L PFOS+PFHxS detected at MWO-D-UA, located approximately 2.2 km south-west of the south-western corner of the Site. The PFAS concentrations in these wells indicate the extent of the groundwater impacts to the south-west.

No PFAS was detected in groundwater in the most distant wells to the south-west (4.5 km to the south-west of the south-western corner of the Site) indicating that PFAS contaminated groundwater does not extend to this part of the Investigation Area (based on the current dataset).

North-east

As the groundwater flow direction beneath the Site is from the east to the west, the area to the north-east of the Site is up hydraulic gradient. One new groundwater monitoring well was installed in this area to provide background groundwater conditions. No PFAS was detected in this monitoring well in March 2017.

7.2.4 Evaluation of groundwater PFAS trends Groundwater trends for PFOS have been analysed for selected wells close to potential source areas on-Site (Chart 8) and for three off-Site areas which increased in distance from the Site:

1. Off-Site bores to the south of the Site, within 1 km of the southern Site boundary (Chart 9)

2. Off-Site wells south-west of the Site, within 1 km of the south-western corner of the Site (Chart 10)

3. Off-Site wells south-west of the Site, from 1 to 2 km of the south-western corner of the Site (Chart 11).

The wells shown in Chart 8 contained the highest concentration on-Site and the data show some variability. PFOS concentrations in groundwater from three wells increased in concentration between 2010 and 2012, before decreasing. The 2017 results are similar to the 2010 results indicating stable concentrations.

There is a mixture of individual trends present (i.e. increasing, decreasing and stable) in PFOS concentration in groundwater samples from bores to the south of the Site (Chart 10).

Within 1 km of the south-western Site boundary, there is generally a stable trend (Chart 10), although one bore, GW27, showed a factor of three increase in PFOS concentrations between April 2016 and April 2017 results. Bore GW28, located very close to GW27, shows a stable trend.

Groundwater in bores within 1–2 km of the south-western Site boundary show stable trends or evidence for a minor increasing trend (Chart 11). It should be noted that PFOS concentrations in this portion of the Investigation Area are all below 1 µg/L.

Evaluation of the groundwater trends provides evidence for stable PFAS concentrations in groundwater on- and off-Site. There appears to be a minor increasing trend in PFAS concentrations in down-hydraulic gradient bores (i.e. to the south-west of the Site), which is attributed to the migration of PFAS within groundwater.

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Chart 8 Groundwater concentrations in selected on-Site wells: 2010 to 2017

Chart 9 Groundwater concentrations in residential bores within 1 km of southern site boundary: 2010 to 2017

0.01

0.1

1

10

100

1000

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Dec

-14

Jun-

15

Dec

-15

Jun-

16

Dec

-16

Jun-

17

Dec

-17

PFO

S C

once

ntra

tion

(µg/

L)

AACO-MWA2-CAACO-MWB3-AAACO-MWC1-CAACO-MWS1-BAACO-MWN-H-LA

0.01

0.1

1

10

100

1000

Jun-14 Dec-14 Jul-15 Jan-16 Aug-16 Mar-17 Sep-17

PFO

S C

once

ntra

tion

(µg/

L)

AACO-GW47 AACO-GW31AACO-GW32 AACO-GW33AACO-GW34 AACO-GW37AACO-GW49 AACO-GW43

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Chart 10 Groundwater concentrations in selected off-Site wells within approximately 1 km of the south-western corner of the Site: 2013 to 2017

Chart 11 Groundwater concentrations in selected off-Site wells between 1 km and 2km of the south-western corner of

the Site: 2014 to 2017

0.01

0.1

1

10

100

1000

Jun-13 Dec-13 Jun-14 Dec-14 Jun-15 Dec-15 Jun-16 Dec-16 Jun-17 Dec-17

PFO

S C

once

ntra

tion

(µg/

L)

AACO-BORE7 AACO-BORE8AACO-GW15 AACO-GW16AACO-GW17 AACO-GW21AACO-GW27 AACO-GW36AACO-GW28 AACO-GW30AACO-GW36 AACO-MWO-B-UA

0.01

0.10

1.00

10.00

100.00

1000.00

Nov-13 Jun-14 Dec-14 Jul-15 Jan-16 Aug-16 Mar-17 Sep-17

PFO

S C

once

ntra

tion

(µg/

L)

AACO-GW06AACO-MWO-D-LAAACO-MWO-D-UAAACO-BORE5

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7.2.4.1 Summary of off-Site PFAS groundwater impacts in Oakey Creek Alluvium

The collated data indicate the following:

• PFAS in groundwater extends from the multiple source areas on-Site in a westerly and south-westerly direction. The migration of PFAS is influenced by:

- groundwater pumping by bores drawing from the Oakey Creek Alluvium aquifer

- surface water flow along southerly orientated unlined drains and Oakey Creek with infiltration to groundwater

- mobilisation of PFAS along Oakey Creek during periods of flow and recharge from stream flow into the groundwater system.

The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report (AECOM, 2017c, in preparation). The groundwater zones are material to the HHRA and will be redefined in the HHRA report.

7.2.5 Extent of PFAS in deeper aquifers

7.2.5.1 Main Range Volcanics aquifer

Five of the newly installed groundwater monitoring wells were screened in Main Range Volcanics. The Main Range Volcanics aquifer was present at shallower depth (less than 20 mbgs) at three locations (MWO-N-AL, MWO-W-AL, MWO-U- MRV) in the south-eastern and southern portion of the Investigation Area. The sample from MWO-W-AL recorded 0.07 µg/L PFOS+PFHxS. PFAS was not recorded in MWO-N-AL, and MWO-U-AL was dry. It is noted that MWO-W-AL is located within an area that may be affected by local off-Site sources, along Lorrimer Street, see AECOM (2015a).

There was no PFAS identified in the other two wells which monitor groundwater in the Main Range Volcanics at deeper depth (greater than 50 mbgs) (MWO-I-MRV and MWO-K-MRV), which were both located closer to the Site (less than 1.2 km distance).

Further discussion on the connectivity between aquifers is discussed in Section 8.7.8.

7.2.5.2 Walloon Coal Measures aquifer

Seven new monitoring wells were screened in the Walloon Coal Measures aquifer across the Investigation Area. PFAS was detected in groundwater at two of these seven locations, at MWO-X-WCM (0.03 µg/L PFOS+PFHxS), and at MWO-H-WCM, which was at the limit of reporting (0.01 µg/L PFOS+PFHxS). Future sampling will further assess MWO-H-WCM.

The data show the Walloon Coal Measures aquifer has trace concentrations in an area to the south of the Site. PFAS migration to the Walloon Coal Measures aquifer at MWO-X-WCM may be via natural leakage from the Oakey Creek Alluvium aquifer or related to the bore construction of nearby bore RN107812, which is likely to connect both aquifers at this location. This is further discussed in Section 6.6 and Section 8.7.7.1.

7.2.6 PFAS in drainage channels sediments and stormwater quality

7.2.6.1 Drainage channel sediment and soil quality The network of drainage channels on-Site and off-Site covers many kilometres and there is a large surface area covered by these shallow drains that has been in contact with surface water runoff following rainfall events.

Table 7-11 presents a summary of the results for the different drainage channels for two different depth intervals: 0.0–0.2 mbgs (sediment) and greater than 0.2 mbgs (soil), as well as the leachate results (see also Figure F29). This includes data from the 2015 to 2016 investigation (AECOM 2016a), which are presented in Table T36. The geological logging results indicate the soil beneath the drainage channel to consist of either silty clay or clay.

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Table 7-11 Summary of drainage channel sediment and soil results

Location Maximum PFOS concentrations

(mg/kg) No. of PFAS present in

soil samples Leachate (ASLP) results

‘PFOS+PFHxS’ (µg/L) 0.0–0.2 mbgs 0.2–1.5 mbgs

On-Site drainage channel 1 0.15 0.17 19 2.0–24.2

Off-Site drainage channel 1 0.06 0.08 18 1.2–4.4





These results indicate the following:

• PFAS was detected in all 81 soil and sediment samples collected between 0.0 and 1.8 mbgs from locations representative of the full length of the drainage channels, indicating PFAS impacts are widespread. The magnitude of the on- and off-Site PFAS concentrations in sediment and soil samples was approximately similar in all three drains, although one sample from drainage channel 3 (collected in 2016) recorded a higher PFAS concentration compared to other samples. This sample, SED25, was collected from the outlet draining from current fire training ground and recorded 49.2 mg/kg 8:2 FTS, 2.8 mg/kg 6:2 FTS, 3.7 mg/kg PFOS and 1.0 mg/kg PFOA.

• Overall, the results indicate that residual PFAS are generally similarly distributed across the drainage channel network, with occasional areas with higher PFAS concentrations present.

• Concentration of PFAS in sediment is higher in samples from on-Site compared to off-Site indicating a decrease in concentrations with increased distance from the Site.

• Higher PFAS concentrations have been detected in the deeper soil samples in drainage channels 1 and 2 compared to the equivalent sediment samples at 0.0–0.2 mbgs indicating that the vertical extent of the soil contamination extends to at least 1.5 mbgs at some locations.

• A similar number of sulfonic acid and carboxylic acid compounds are present across all three drainage channels, both on-Site and off-Site. With the exception of SED25, PFOS is consistently present at the highest concentrations.

• At one location each in drainage channels 2 and 3, a transect profile of the soil across the drains was obtained by the advancement of three soil bores, one in the centre and two at the sides of the drain (DC-14A-C at drainage channel 2 and DC17A-C at drainage channel 3). The results show similar PFAS concentrations in the sample from the centre of the channel compared to the samples from along the sides. These limited results show PFAS is potentially present in the sediment and underlying soil across the width of the channels.

• The higher PFAS leachate results were from the soil/sediments with the lowest total PFAS results.

• The leachate results for soil samples indicated that the PFAS in the soil would be readily extracted into infiltrating rainwater. Soil PFAS concentrations were up to 2 mg/kg (sum of PFAS), with ASLP results for sum of PFAS in the range of 0.3–28.2 µg/L. This shows the contaminant mass in the sediment and underlying soil has the potential to leach into infiltrating liquid.

Overall, the results indicate PFAS is consistently present across all three main drainage channels, both on- and off-Site. Due to the large surface area covered by the drains, there is the potential for a large contaminant flux to be present within the sediment and underlying soil along the length and width of the drainage channels. The detection of higher concentrations in the subsurface (to at least

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1.5 mbgs) suggests that the contamination has vertically migrated, due to infiltration, into the soils beneath the drains.

The vertical extent of PFAS in soil below 1.5 mbgs is uncertain. Characterisation of the former fire training ground area indicated PFAS to be present in soil to approximately 2.0 mbgs, however, it is noted that the drainage channel environment is subject to different, more dynamic conditions with periodic surface water flows and potential for the presence of stagnant water for periods of time. The maximum depth of the bores was 1.5 mbgs, and at some locations, higher concentrations were detected at 1.5 mbgs relative to the equivalent concentrations in the 0.0– 0.2 mbgs depth interval.

The leachate results indicate potential for PFAS to leach due to infiltrating rainwater. The results provide evidence for the drainage channels to act as a secondary source of contamination to the underlying groundwater, as well as a preferential pathway for the migration of contamination from the Site into surface water.

7.2.6.2 2017 stormwater quality

A summary of water quality and PFAS present in the drainage channels, on- and off-Site is presented in Table 7-12. The historical dataset is presented in Table T37. The results show the highest PFAS concentrations, and largest number of PFAS (total of 18) present, were detected in water samples from drainage channel 3. Table 7-12 Summary of stormwater results

Location No. of

sampling points


(µg/L)

No. of PFAS

present PFAS present

On-Site drainage channel 1

3 4.5 17

8:2 FTS, PFDS, PFHpS, PFPeA, PFPeS, PFOA, PFBS, PFDA, PFDoDA, PFHpA, PFHxA, PFHxS, PFNA, PFOS, FOSA, PFTeDA, PFUnDA

Off-Site drainage channel 1

5 3.9 10 6:2 FTS, PFHpS, PFPeA, PFPeS, PFOA, PFBS, PFHpA, PFHxA, PFHxS, PFOS


4 1.2 7 PFBS, PFHpA, PFHxA, PFHxS, PFOS, PFOA, PFPeS


4 1.0 7 PFPeA, PFPeS, PFOA, PFBS, PFHxA, PFHxS, PFOS


5 1.4 18

PFOS, PFHxS, PFOA, PFHxA, 10:2 FTS, 8:2 FTS, 6:2 FTS, PFBA, PFHpS, PFPeA, PFPeS, PFBS, PFDA, PFDoDA, PFHpA, PFNA, PFTrDA, PFUnA


2 6.9 16

8:2 FTS, 6:2 FTS, PFHpS, PFPeA, PFPeS, PFOA, PFBS, PFDA, PFDoDA, PFHpA, PFHpS, PFHxA, PFHxS, PFNA, PFOS, PFUnDA

The highest concentrations in the two rounds monitored in February and March 2017 were present in samples from SW21, located on-Site in drainage channel 3. These concentrations were an order of magnitude higher than the maximum concentration detected in the other drainage channels. The high concentrations at this sampling point are due to the presence of some other PFAS including 8:2 FTS (5.9–10.7 µg/L), 6:2 FTS (3.3–10.7 µg/L), PFOA (4.1–11.7 µg/L), PFNA (3.7–9.5 µg/L), PFDA (3.2–7.6 µg/L), PFHpA (1.6–6.0 µg/L) and PFHxA (1.4– 5.3 µg/L). Sampling point SW21 is the discharge point from the current fire training ground and the high concentrations detected at this location indicates a source of contamination is present close to this position.

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Overall, the results indicate that after precipitation events, elevated concentrations of PFAS are transported along all three drainage channels, in particular along drainage channel 3. There were a larger number of PFAS detected in drainage channels 1 and 3 compared to drainage channel 2, reflecting the higher PFAS concentrations detected in drainage channels 1 and 3. These results show that the drainage channels are preferential pathways for the migration of PFAS off-Site.

7.2.7 Evaluation of surface water and creek sediment quality and trends

7.2.7.1 2017 surface water quality

Table 7-13 summarises the distribution of PFAS concentrations in surface water at different sections of creeks across the Investigation Area. Table 7-13 Summary of surface water results

Location No. of sampling points (No. of samples with PFAS >LOR)


(µg/L)

No. of PFAS

present PFAS present

Doctor Creek 12 (0) All <LOR 0 None

Oakey Creek: upstream of drainage channel 3 2 (0) All <LOR 0 None

Oakey Creek: upstream of drainage channels 1 and 2

and downstream of outflow of drainage

channel 3

3 (3) 0.43 7 6:2 FTS, PFPeA,

PFOA, PFBS, PFHxA, PFHxS, PFOS

Oakey Creek: downstream of drainage channels 1

and 2 9 (9) 0.82 13

6:2 FTS, PFHpS, PFPeA, PFPeS, PFOA, PFBS, PFDA, PFDoDA, PFHxA, PFHxS, PFNA,

PFOS, PFUnDA Upstream Westbrook

Creek prior to confluence of with Oakey Creek

1 (1) 0.01 1 PFOS

Downstream of confluence of Oakey Creek and

Westbrook Creek 6 (6) 0.03 5 PFPeA, PFOA, PFHxA,

PFHxS, PFOS

The main findings are as follows:

• Doctor Creek: No PFAS concentrations were detected above the limit of reporting in any of the 12 samples collected. There is no evidence for a pathway (e.g. via overland flow or groundwater) to be present from the on-Site sources of PFAS contamination to the Doctor Creek.

• Oakey Creek upstream of outflow of drainage channel 3: PFAS was not detected in the two surface water samples collected from upstream of the point where drainage channel 3 outflows into Oakey Creek.

• Oakey Creek upstream of outflow of drainage channels 1 and 2 and downstream of outflow of drainage channel 3: Seven PFAS were present in the three samples indicating this portion of the creek has been impacted by contaminated water discharged from drainage channel 3, sourced from AFFF released during site operations. The PFOS+PFHxS concentrations detected were all below the adopted human health screening level for recreational activities.

• Oakey Creek downstream of drainage channels 1 and 2: All nine samples collected contained PFAS with the samples closest to the outflow of drainage channels 1 and 2 recording the highest concentrations, with 13 compounds detected. PFOS+PFHxS concentrations for all nine samples are in excess of the adopted human health screening level for recreational activities.

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• Westbrook Creek upstream of confluence with Oakey Creek: The single sample analysed contained PFOS at a concentration equal to the limit of reporting. No other PFAS was detected.

• Surface water downstream of confluence of Westbrook Creek and Oakey Creek: All six samples analysed contained detectable PFAS concentrations with five compounds detected. The maximum concentration (sum of 28 PFAS) was a factor of seven lower than the maximum concentration detected close to the outflow of drainage channels 1 and 2 in Oakey Creek. The PFOS+PFHxS concentrations detected were all below the adopted human health screening level for recreational activities.

Overall the results show the highest PFAS concentrations in surface water are present immediately downstream of the outflows of the three drainage channels. The concentrations decrease with increased distance from the Site, with a corresponding decrease in the number of PFAS detected. The furthest downstream sample collected (SW05), approximately 6.5 km downstream from Site, did not exceed the adopted human health screening level for recreational activities but exceeded the ecological screening level (99% protection of freshwater species).

PFAS was not detected in the Doctor Creek located to the north-west of the Site or in Oakey Creek upstream of the drainage channels. These results indicate that there is no ongoing hydraulic or hydrogeological connection between the Site and Doctor Creek.

7.2.7.2 Evaluation of surface water trends Chart 12 shows the change in PFOS concentration in different parts of Oakey Creek between 2014 and 2017. PFOS has been selected as this compound has been consistently been analysed for PFOS since 2014. The concentrations of PFOS have been higher compared to other PFAS. The sampling locations have been selected based on the historical data available and based the suitability of sampling locations to represent the following areas:

• Upstream of outflow point of drainage channels 1 and 2 and downstream of drainage channel 3 (SW14)

• Downstream of outflow of drainage channels 1 and 2 (SW13)

• A location approximately 2 km downstream prior to confluence with Westbrook Creek (SW11)

• A location approximately 3 km downstream prior to confluence with Westbrook Creek (SW10).

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Chart 12 PFOS concentrations in Oakey Creek: 2014 to 2017

The main findings are as follows:

• Oakey Creek upstream of outflow of drainage channels 1 and 2: PFOS concentrations are similar in 2014–2017 indicating no increase or decrease in concentrations. The PFOS concentrations are only slightly higher relative to the limit of reporting.

• Oakey Creek immediately downstream of outflow of drainage channels 1 and 2: PFOS concentrations in this part of the creek have consistently been the highest concentrations detected in the creek. PFOS concentrations decreased between 2014 and 2017 by more than 50%.

• Oakey Creek approximately 2 km downstream of outflow of drainage channels 1 and 2: PFOS concentrations have been variable during the monitored period, decreasing slightly between 2014 and 2016 and increasing by a factor of five between 2016 and 2017.

• Oakey Creek approximately 2 km downstream of outflow of drainage channels 1 and 2: PFOS concentrations decreased between 2014 and 2017 by more than 50%.

It should be noted that the above interpretation is based on limited data; the data set is limited to three years of monitoring versus approximately 40 years since PFAS was introduced to the system. Although the PFOS concentrations along Oakey Creek show a general decrease over the monitored period, the longer term trend cannot be evaluated.

7.2.7.3 2017 creek sediment quality

Table 7-14 summarises the distribution of PFAS in sediment in creeks from different locations across the Investigation Area. The historical dataset is presented in Table T38.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

2/06/2014 2/12/2014 2/06/2015 2/12/2015 1/06/2016 1/12/2016 1/06/2017

PFO

S C

once

ntra

tion

(ug/

L)

PFOS Concentrations in Oakey Creek: 2014 to 2017

Oakey Creek: Upstream of Drainage Channels1&2 (SW14)Oakey Creek: Downstream of, and close to,outflow of drainage channels 1 and 2 (SW13)Oakey Creek: Approximately 2 km downstreamof confluence with Westbrook Creek (SW11)Oakey Creek: Approximately 3km downstreamof confluence with Westbrook Creek (SW10)

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Table 7-14 Summary of distribution of PFAS in sediment in creeks from different locations across the Investigation Area

Location No. of sampling points (No. of

sampling points with PFAS >LOR)

Max. PFOS concentration

(mg/kg) No. of PFAS PFAS present

Doctor Creek 13 (3) 0.007 2 PFOS, PFOA

Oakey Creek: upstream of drainage channel 3 2 (1) 0.004 1 PFOS

Oakey Creek: upstream of drainage channels 1 and 2 and downstream of outflow

of drainage channel 3

4 (4) 0.030 7

PFOA, PFHxS, PFHxA, PFDS, PFDA, PFHpA,

PFOS

Oakey Creek: downstream of drainage channels 1 and 2 7 (7) 0.030 11

PFOS, PFHxS, PFOA, PFDS, PFDA, PFHpA,

PFDoDA, PFHxA, PFNA, PFUnDA,

FOSA Upstream Westbrook Creek prior to confluence of with

Oakey Creek 1 (1) 0.0007 1 PFOS

Downstream of confluence of Oakey Creek and

Westbrook Creek 6 (5) 0.0012 3 PFDA, PFOA,

PFOS

The table above shows PFAS has been detected in all three creeks near the site including Doctor Creek (in 25% of samples) and Westbrook Creek (in 80% of samples). The highest concentrations are in Oakey Creek, with similarities in the magnitude of the maximum concentrations and range in number of PFAS detected for locations downstream of the outflow of drainage channel 3 and locations downstream of the outflow of drainage channels 1 and 2.

7.2.7.4 Comparison of stormwater, sediment and surface water quality

The detection of PFAS in a larger range of sediment sampling locations compared to the equivalent surface water locations is likely to reflect the historical migration of PFAS into the creeks. The presence of a range of PFAS in the sediment samples, particularly in Oakey Creek, reflects the different adsorption properties of different compounds. For example, fluorotelemers were detected in surface water but not reported in creek sediment samples. The impacted sediment has the potential to be transported a significant distance from Site within the creek, in particular, during periods of higher flow such as during storm events, when scouring of the creek bed may occur. A summary of a comparison between sediment and surface water quality is presented in Table 7-15.

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Table 7-15 Summary of comparison of PFAS in sediment and surface water quality

Location Surface water Sediment Comment

Doctor Creek PFAS not detected

PFAS detected in 25% of samples • PFOS, PFOA and PFHxS

Oakey Creek: upstream of drainage

channel 3

PFAS not detected

PFAS detected in one of the two

samples analysed • PFOS

Oakey Creek: upstream of drainage channels 1 and 2 and downstream of outflow of drainage channel 3

PFAS detected in 100% of samples


• PFOA, PFOS, PFHxA, PFHxS in both sediment and water

• Surface water has 6:2 FTS, PFPeA, PFBS

• Sediment has PFDS, PFDA, PFHpA

Oakey Creek: downstream of

drainage channels 1 and 2



• PFOA, PFHxA, PFHxS, PFOS, PFNA, PFUnDA PFDoDA in both sediment and water

• Surface water has 6:2 FTS, PFHpS, PFPeA, PFPeS, PFBS, PFDA

• Sediment has PFDS, PFDA, PFHpA, FOSA

Upstream Westbrook Creek prior to

confluence of with Oakey Creek

PFAS detected in the single

sample analysed

PFAS detected in the single sample

analysed • PFOS

Downstream of confluence of Oakey

Creek and Westbrook Creek



• PFOA, PFOS in both sediment and surface water

• Surface water has PFPeA, PFHxA, PFHxS

• Sediment has PFDA

7.3 Extent of non-PFAS Contaminants in Soil and Groundwater on-Site As noted previously, the focus of the 2017 Stage 2C EI was to target potential areas of PFAS contamination; so potential source areas of non-PFAS contaminants were not specifically targeted. A proportion of on-Site near-surface soil samples and all on-Site groundwater samples were analysed for a broad suite of generic inorganic and organic contaminants to provide information on the presence of these contaminants across the site.

7.3.1 Metals

Review of the soil dataset does not indicate the presence of areas of metal contamination. The concentrations detected relative to human health and ecological screening criteria for commercial land use indicate the metal concentrations in soil are suitable for the current land use.

With the exception of nickel, all metal concentrations in groundwater were below human health screening levels. Although groundwater concentrations of nickel exceeded the drinking water screening level in five wells on-Site, the on-Site water is not used for drinking purposes. Three of the groundwater samples were from wells in S1, indicating this area to contain a localised area of higher nickel concentrations. The area to the east of, and up-hydraulic gradient of, these wells is occupied by a maintenance hangar. The detected concentrations of nickel in groundwater are potentially associated with maintenance activities in this building. Nickel concentrations did not exceed human health at site boundary locations.

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With the exception of chromium in six groundwater samples and nickel in one groundwater sample, all metal concentrations in groundwater beneath the Site were below ecological screening levels. As the chromium and nickel concentrations only slightly exceeded the screening level (by up to 25%), the results are not considered to indicate an adverse risk to the environment. It is noted that copper and zinc concentrations are highest in the off-Site background bore (MWO-F-AL) indicating elevated concentrations of these metals are attributable to natural background concentrations rather than indicative of sources of metal contamination on-Site.

7.3.2 Petroleum hydrocarbons The majority of soil samples did not contain detectable concentrations of petroleum hydrocarbons. Five soil samples had hydrocarbons including two samples from drainage channel 1, one sample from drainage channel 3 and two shallow soil samples from the former fire training ground area. The detection is likely to be associated with minor surface spills of fuel.

The majority of groundwater samples collected from across the site did not contain detectable concentrations of petroleum hydrocarbons. An area of groundwater in the vicinity of the C59 AFFF tank is impacted with LNAPL with thicknesses between 1.5 and 3.72 m. A dissolved phase hydrocarbon impact has been detected in a single well to the east of the LNAPL (MWC1-C). This well contained a low concentration of benzene (4 µg/L), which exceeded the drinking water screening guideline level. The extent of the LNAPL and dissolved phase impact (including the well with the benzene detection) is delineated to the west, south, south-east and north-east by the non-presence of impacts in MWC1-H, MWC1-I, MWC2-A and MWC2-C, MWC2-K and MWD2-E. Due to the presence of buildings to the north, there is a large distance to the nearest wells to the north (>300 m to MWF1-H), and these do not contain hydrocarbons.

The area impacted by LNAPL potentially extends over an area approximately 50 m by 20 m. The observed and significant apparent thicknesses of LNAPL suggests that there has been a historical leak of hydrocarbon fuel. As no large area of dissolved phase hydrocarbon impact has been detected, the area of the LNAPL appears to be stable.

Low concentrations of diesel range hydrocarbons (TRH C16-C34 was up to 290 µg/L) were detected in groundwater samples from two wells in the former fire training ground area, one well in the hot refuel area and two wells located along the southern Site boundary. As hydrocarbons were not detected in down hydraulic gradient wells to the west, the impact in these areas appears localised.

It should be noted that silica gel clean-up was not conducted on any of the samples analysed for petroleum hydrocarbons prior to analysis, therefore the low level detections are potentially representative of polar non-petroleum hydrocarbons present from natural organic sources within the subsurface matrix and from biological and chemical oxidations, rather than indicative of localised petroleum hydrocarbon sources on-Site.

7.3.3 Other organics

The soil and groundwater results do not indicate the presence of other organic contaminants (including VOCs, SVOCs, pesticides and 1,4-dioxane) at the locations investigated.

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8.0 Hydrogeological Interpretation

8.1 Approach In order to address the groundwater related data gaps and provide an assessment of potential risks to the GAB, AECOM has adopted an assessment approach following the Waste-Aquifer Separation Model (WASP) methodology. This approach allows for the evaluation of:

• waste – which for this project relates to the evaluation of PFAS contaminant sources

• aquifer – the groundwater resources and aquifer parameters within the underlying geological units

• separation – the consideration of underlying vadose zone, geology, and migration mechanisms (such as bore construction, pumping, etc.).

The WASP approach, considering PFAS sources, migration, and groundwater resources, then allows for the consideration of:

• potential risks of PFAS contamination of the GAB aquifers

• secondary PFAS sources (landfill, irrigation water, surface water drains, bores that were constructed prior to the current legislated standards)

• water interactions (dam storage, losing creeks, inundation areas)

• contaminant movement (induced flow, localised / region scale, refining groundwater zones).

The section focuses on the following tasks:

• Assessing potential risks to the GAB

• Investigating water interactions (surface water, groundwater, sediment, and soil interactions)

• Investigating the influence of drains on PFAS migration though completion of leachate tests and infiltration tests

• Implications of extraction of potentially contaminated overland flow water and/or surface water by entitlement holders

• Ensuring all potential sources of PFAS onsite are identified and prioritised in terms of PFAS mass load and potential mobility to groundwater, surface water and biota

• Investigating of potential connections across multiple aquifers via bores that were constructed prior to the current legislated standards

• Investigating the risk that unregistered bores pose to the GAB

• Further quantifying potential secondary source areas including irrigation return flow, landfill inputs and flooding along road side areas

• Investigating registered bores RN107812, RN87439, and RN87369

• Investigating the risk to the GAB from both infiltration and via bores acting as conduits.

The WASP approach allowed for the assessment of groundwater data to respond to these information needs, assess risks, and provide comment on the groundwater related aspects identified above.

Potential PFAS source areas, both primary and secondary, are detailed in Section 3.0. These sources are considered in more detail, using the WASP approach, below.

8.2 Waste / Sources 8.2.1 Primary sources

As detailed in Section 2.1.1, potential primary PFAS source areas have been identified across the Site based on the use and storage of PFAS.

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8.2.2 Stormwater drains

It is conceptualised that the PFAS soaks into soil and accumulates as sediment within the stormwater channels, acting as a PFAS source. The PFAS in sediment can act as a source to groundwater, as follows:

• Particularly where the drain intersects more coarse grained alluvium and also in stormwater ponds within the drains (i.e. enhanced recharge potential below the ponded water).

• The PFAS in sediment can be mobilised within the (higher flow velocities) stormwater and deposited off-Site further along the stormwater channels and into Oakey Creek.

• The PFAS can dissolve in surface water runoff and migrate into surface water bodies, such as Oakey Creek.

The distribution of PFAS within the stormwater sediment and stormwater, which validates these source conceptualisations, is included in Section 6.10.

8.2.3 Oakey Creek PFAS in sediment and runoff water, draining from the Site, is recognised to have entered Oakey Creek (Section 6.11).

Oakey Creek, a meandering watercourse, is a losing system that contributes surface water to the regional groundwater system. This flow from the surface water body to groundwater allows for the potential for PFAS migration from Oakey Creek into the underlying alluvium groundwater resources.

8.3 Storage of PFAS Water in Dams and Irrigation Return Flow Two surface water storage dams, Dam 1 and Dam 2 (see Figure F14), were assessed to determine the potential for stored water to act as sources of PFAS recharge to the underlying groundwater resources. These dams were selected as:

• Dam 1 receives stormwater runoff water from drainage channel 3, interpreted to contain PFAS runoff from the Site.

• Dam 2 is filled with groundwater from residential bore GW55. This bore was sampled in January 2015 and contained 3.2 µg/L PFOS+PFHxS.

Two pairs of groundwater monitoring wells were installed adjacent to each of each of the two dams. These wells were installed into the Oakey Creek Alluvium and underlying Walloon Coal Measures bedrock aquifer.

A summary of the water sampling, dam and groundwater, is included in Table 8-1. It is noted that no recent sample data are available for Dam 1, however, the surface water sample SW57, within drainage channel 3, provides an indication of water quality entering the dam. Table 8-1 Summary of farm dam sample results

Sample location PFOS + PFHxS (µg/L) PFOA (µg/L)

Dam 1 (SW57) 6.89 0.94

MWO-Y-AL 1.58 0.16

MWO-Y-WCM <LOR <LOR

Dam 2 north (SW34A) 9.05 0.16

Dam 2 south (SW34B) 1.04 (PFOS only) 0.11

MWO-Z-AL 2.03 0.05

MWO-Z-WCM <LOR <LOR

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The summary indicates that the storage of PFAS in water in the farm dams are potential secondary sources of PFAS contaminants to the alluvium within the investigation area. Section 8.7.3 provides a more detailed assessment of migration potential from the farm dams to the underlying groundwater resources.

8.3.1 Irrigation return flow Irrigation within the Investigation Area was considered as a possible secondary source of PFAS to the underlying groundwater resources, where irrigation return flow is defined as the part of artificially applied water that is not consumed by evapotranspiration and can either drain vertically to the groundwater table or run off into a surface-water body and infiltrate to groundwater.

From a groundwater perspective, irrigation return flow (or deep drainage) is considered a possible point source of PFAS within the irrigated lands within the Investigation Area.

As Dam 1 is used for irrigation purposes and there are available monitoring bores on and adjacent to the irrigated lands on this property, the bores were used to consider irrigation return flow impacts as a potential source of PFAS contaminant to underlying aquifers.

Other areas where irrigation return flow is likely, and where AECOM have constructed groundwater monitoring bores, are the:

• RN107812 – see Figure F14

• RN87369.

A summary of bores, geology, and PFAS concentrations for these areas is included in Table 8-2. Table 8-2 Irrigation return water sample results

Sample location PFOS + PFHxS (µg/L)

PFOA (µg/L) Geology

Dam 1 (SW57) 6.89 0.94 -

MWO-Y-AL 1.58 0.16 Oakey Creek Alluvium 2 m clay over silty sandy clay to 15 mbgs

MWO-Y-WCM <LOR <LOR Oakey Creek Alluvium and weathered basalt to 60 mbgs underlain by Walloon Coal Measures

MWO-I-AL 0.12 <LOR Oakey Creek Alluvium silty sandy clay and sand, to 20 m

MWO-I-MRV <LOR <LOR Main Range Volcanics: Weathered basalt

RN107812 1.34 0.02 Oakey Creek Alluvium and Walloon Coal Measures

MWO-X-AL 0.29 <LOR Oakey Creek Alluvium silty sandy clay and coarse sand, to 20 mbgs

MWO-X-WCM 0.03 <LOR Oakey Creek Alluvium to 57.5 mbgs underlain by coal seam of Walloon Coal Measures

RN87369 <LOR <LOR Main Range Volcanics to 39 mbgs, underlain by WCM

MWO-V-AL 0.01 <LOR Oakey Creek Alluvium of silty clay to 5 mbgs, weathered basalt

MWO-V-WCM <LOR <LOR Oakey Creek Alluvium underlain by basalt then Walloon Coal Measures with a coal band at 61.5 m

Deep drainage of irrigation return water may have resulted in the migration of PFAS into the Oakey Creek Alluvium in the Dam 1 area as indicated by the presence of PFAS in groundwater in the monitoring wells monitoring the Oakey Creek Alluvium in this area.

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No PFAS concentrations were measured in supply bore, RN87369. It is noted that traces of PFAS were reported in the shallow monitoring bore MWO-V-AL, which may be as a result of PFAS migration within the groundwater (within the more permeable sediments) in the Investigation Area.

Bore, RN107812, is a bore which extracts from the coal seams within the Walloon Coal Measures. The construction, as discussed in Section 6.5 and Appendix F, may have contributed to the migration of PFAS measured in the Oakey Creek Alluvium to the monitoring well screened within the Walloon Coal Measures near RN107812. It is not immediately evident that the PFAS measured in these bores is a direct result of irrigation return water.

Based on the WASP approach the possibility of PFAS migration as a result of irrigation is considered further through the evaluation of migration through the unsaturated zone (Section 8.7.4), infiltration rates (in vertical travel time) (Section 6.7.2), and consideration of site-specific data at each of the three areas containing Dam 1, RN87369, and RN107812.

8.4 Flood Inundation Areas Floodwater spilling over drains and Oakey Creek across the Investigation Area has the potential to deposit PFAS affected runoff onto adjacent soil and vegetation and potentially infiltrating to groundwater. The ponded flood water has the potential to increase groundwater recharge potential, albeit temporarily, after flooding events. Flood mapping (Figure F8) was considered and two pairs of groundwater monitoring well were installed within these historical inundation areas. The pair included one well monitoring the Oakey Creek Alluvium, the other monitoring the bedrock (either Main Range Volcanics or Walloon Coal Measures). A summary of these bores is included in Table 8-3.

In order to further assess the possible influence of flood water/inundation on PFAS concentrations, the existing groundwater monitoring bores and the flood maps were reviewed to determine where bores were installed in the Oakey Creek Alluvium within inundation areas. These bores are included in Table 8-3. Table 8-3 Groundwater bores and samples within the flood inundation area



MWO-K-AL <LOR <LOR Oakey Creek Alluvium at 30 mbgs

MWO-K-MRV <LOR <LOR Main Range Volcanics – decomposed basalt at 55 mbgs

MWO-J-AL 0.34 <LOR Oakey Creek Alluvium – gravels at 14–20 mbgs

MWO-J-WCM <LOR <LOR Walloon Coal Measures – coal seam at 63 mbgs

MWO-L-AL 16.9 0.5 Oakey Creek Alluvium – silty sandy clay at 20 mbgs

MWO-G-AL 7.0 0.3 Oakey Creek Alluvium – gravel at 21.5 mbgs

MWO-H-AL 0.15 <LOR Oakey Creek Alluvium Transition zone – gravel at 50 mbgs

MWO-H-UA 1.82 0.06 Oakey Creek Alluvium – 20 mbgs

MWO-H-WCM 0.01 <LOR Walloon Coal Measures – coal seam at 84 mbgs

Wells MWO-K-AL and MWO-K-MRV, were constructed between the Bridge Street and the railway line, as this area is known to contain ponded water after high rainfall events (see Figure F8). Groundwater sampling of these wells does not indicate any PFAS concentrations as a result of inundation, which typically occurs in this area.

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Two wells, MWO-J-AL and MWO-J-WCM, were drilled along Williams Road. The shallower well contained 0.34 µg/L PFOS + PFHxS. No PFAS was reported within the deeper bedrock (Walloon Coal Measures) well. It is noted that MWO-J-AL is located down hydraulic gradient of the Site (groundwater flow is east to west), such that this PFAS concentration may be as a result of recognised PFAS movement within the groundwater.

All the additional Oakey Creek Alluvium wells, identified in the mapped flooded areas, have reported PFAS concentrations within the groundwater. This indicates a possible correlation between the flooded areas and PFAS within the Oakey Creek Alluvium, however, the presence at these locations are potentially due to the migration of PFAS in groundwater.

Further evaluation of the possible migration potential of PFAS into groundwater resources through flood inundation is included in Section 8.7.4.3.

8.5 Former Landfill A former landfill (Oakey waste landfill facility, see Figure F14) is located off-Site along Lorimer Street and was used for the disposal of domestic and commercial waste including waste from Defence (AECOM 2015a). The former landfill was investigated to determine if the former landfill is a secondary source of PFAS.

The characterisation of groundwater immediately up-hydraulic gradient and down-hydraulic gradient of a former facility was conducted through the installation of three groundwater monitoring wells.

The three groundwater monitoring wells were sampled in March 2017. The groundwater results are shown in Table T19 and indicate:

• Elevated PFAS concentrations were present in the down-hydraulic gradient monitoring well (MWO-P-AL contained 6.9 µg/L PFOS+PFHxS).

• The up-hydraulic gradient monitoring well (MWO-Q-AL) recorded a concentration of PFOS+PFHxS of 1.6 µg/L.

A summary of the PFAS laboratory data are included in Table 8-4. Table 8-4 Landfill groundwater summary



MWO-O-AL 0.08 <LOR Oakey Creek Alluvium – silty clay and fine sand and gravel to 30 mbgs

MWO-P-AL 6.91 0.34 Oakey Creek Alluvium – silty sandy clay with gravel to 18.5 mbgs

MWO-Q-AL 1.64 0.01 Oakey Creek Alluvium – silty sandy clay with some gravel to 17 mbgs

The groundwater quality data suggest that there is an increase in PFAS from east (MWO-Q-AL) to west (MWO-P-AL) within the groundwater as a result of groundwater flow through the former landfill footprint (where groundwater flow is from east to west). This former landfill is considered a secondary source of PFAS contamination, and groundwater quality down-hydraulic gradient of this area is potentially attributable to materials containing AFFF being disposed of to this facility when it was operational. MWO-O-AL, northwest and further down-hydraulic gradient of the landfill, is not reported to be impacted by PFAS from this secondary source.

8.6 Bores and Groundwater Extraction An indirect source of PFAS contamination is considered where groundwater extraction has resulted in local alteration of groundwater levels. The resultant drawdown cone around the extraction bore can act as a temporary groundwater ‘low’ which can facilitate the migration of PFAS compounds (within groundwater) towards the bore.

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A drawdown cone can, particularly in the lower permeable deeper bedrock aquifers (Main Range Volcanics or Walloon Coal Measures), result (i.e. the drawdown cone extends further and rebounds slower within low permeable units). The resultant drawdown cone(s) can facilitate the migration of PFAS towards the pumping bore(s) where:

• there are multi source bores, facilitating migration of PFAS into the underlying units

• extraction results in depressurised aquifers (particularly the coals seams) such that induced flow from the alluvium to the underlying depressurised aquifers can occur.

This is considered to occur at RN107812, where groundwater levels within the existing production bore and the adjacent Walloon Coal Measures monitoring bore (MWO-X-WCM) are greater than 40 mbgs. The other groundwater monitoring bores within the Walloon Coal Measures aquifer, as included in Table 8-5, have recorded groundwater levels typically at 10–20 mbgs, indicating the influence of pumping on the RN107812 bore water level. Table 8-5 Walloon Coal Measures aquifer groundwater summary

Sample location

PFOS + PFHxS (µg/L)

PFOA (µg/L)

Water level in mbgs (mAHD) Geology

MWO-J-WCM <LOR <LOR 18.14 (379.924) Walloon Coal Measures at 59 mbgs

MWO-Y-WCM <LOR <LOR 8.61 (394.226) Walloon Coal Measures at 60 mbgs

MWO-W-WCM <LOR <LOR 17.67 (386.038) Walloon Coal Measures at 37 mbgs

MWO-X-WCM 0.03 <LOR 51.75 (350.274) Walloon Coal Measures at 57 mbgs

RN107812 1.34 0.02 41.74 (361.018)* Walloon Coal Measures at 56 mbgs

Note: * Composite water level as groundwater from Oakey Creek Alluvium and Walloon Coal Measures is extracted from this bore (see Section 6.3.1)

8.7 Separation To assess the potential risks posed by the possible primary and secondary sources of PFAS contamination, the underlying geology (unsaturated and saturated zones), was examined. This helps address the separation aspect of the WASP approach and allows for the evaluation of possible migration mechanisms. The consideration of migration mechanisms is then used to evaluate risks to the groundwater resources (the aquifer component of WASP).

8.7.1 Point sources

The potential PFAS source areas across the Site, as detailed in Section 2.1.1, are considered point sources for possible groundwater contamination, such that AFFF spills, leaks, or storage/placement on unlined ground can potentially lead to build-up of PFAS in the underlying soils, which can then migrate vertically into the groundwater.

A review of available data from infiltration tests conducted in the stormwater drains provide an indication of vertical infiltration rates (refer to Section 6.7.2).

Sandy and silty clay in the unsaturated zone have estimated vertical horizontal conductivity between 0.1 and 0.2 m/day (based on the infiltration tests). Using a travel time calculation (see Section 6.7.2) it was estimated that PFAS, moving in rainfall recharge, would take between eight and 16.5 years to reach groundwater level at 15 mbgs. It is noted that this estimate is based on infiltration rate tests to 1.5 mbgs and assumes uniform sandy silty clay to the water table at 15 mbgs.

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Results from the infiltration tests (and logged in the bores) indicate that there are gravel-rich zones in the unsaturated zone, which have higher vertical permeability (infiltration tests could not be conducted as the introduced water drained rapidly within the gravel-rich zones at markedly higher rates than the 0.1–0.2 m/day estimated for the sandy silty clay). This indicates that spills, seeps, or ponding water on-Site within these discrete high permeable zones will reach the groundwater more readily (i.e. much shorter travel times than within the silty sandy clay such that PFAS compounds can reach groundwater in less than eight years).

The primary introduction of PFAS into the groundwater on-Site is considered to occur within discrete coarse-grained alluvium. The high risk areas across the site (see Figure F3) are therefore recognised where historical PFAS source areas are located on or adjacent to high permeable Oakey Creek Alluvium.

8.7.2 Surface water runoff

PFAS in sediment within the on-Site drainage channels are considered to act as sources of PFAS, either as directly migrating off-Site and into Oakey Creek of through vertical migration into the groundwater resources.

The infiltration test data, as included in Section 6.7.2 and discussed above, indicate the higher potential of vertical infiltration in the stormwater drains where water ponds and where the drains intersect high permeable gravel-rich alluvium.

The ponding water, which adds a constant head (albeit temporary), increases the vertical migration rates through the unsaturated zone compared to the point source spills or leaks onto open ground.

8.7.2.1 Oakey Creek

Groundwater level data, compiled from groundwater monitoring bores in the Oakey Creek Alluvium aquifer, indicate the potential for surface water in Oakey Creek (where the creek water level ranges from 700 mAHD at the Great Dividing Range to 340 mAHD at the confluence of the Condamine River) to recharge groundwater. The surface water elevation within the Oakey Creek, within the Investigation Area is estimated to be 398 mAHD. The groundwater level data are included in Table 8-6 and shown on Figure F13. Table 8-6 Oakey Creek Alluvium groundwater level data

Groundwater sample location

Groundwater level (mbgs / mAHD) Date

MWO-M-AL 8.86 / 395.30 17/05/2017

MWO-X-AL 7.34 / 394.48 01/06/2017

MWO-W-AL 10.19 / 393.49 01/06/2017

MWO-Q-AL 6.20 / 391.13 17/05/2017

MWO-T-AL 6.51 / 391.83 17/05/2017

MWO-R-AL 9.53 / 385.84 17/05/2017

Surface water samples were collected from Oakey Creek, the main receiving water body for the runoff from the Site (Figure F12). The PFAS data compiled from the surface water sampling are included in Table 8-7, these data are compared to groundwater PFAS concentration data collected from alluvium bores located immediately adjacent to the Oakey Creek (as evident on Figure F12 and Figure F13).

A comparison of these data was conducted to allow for the assessment of the conceptualisation that Oakey Creek, acting as a losing system, can provide a conduit for PFAS migration into the Oakey Creek Alluvium along the creek.

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Table 8-7 Oakey Creek and Oakey Creek Alluvium water quality summary

Groundwater sample location

PFOS + PFHxS (µg/L) PFOA (µg/L)

Surface water sample location

PFOS + PFHxS PFOA

MWO-M-AL <LOR <LOR Upstream / SW14 0.43 0.02

MWO-X-AL 0.19 <LOR SW13 0.82 0.02

MWO-Q-AL 1.64 0.01 SW70 0.07 <LOR

MWO-T-AL <LOR <LOR On Westbrook Creek / SW87 0.01 <LOR

MWO-R-AL <LOR <LOR Downstream / SW61 <LOR <LOR

Sample locations and Oakey Creek Alluvium bores are included in Figure F12 and Figure F13.

Upstream The upstream Oakey Creek sample (SW14) indicates PFAS concentrations have been reported downstream of the drainage channel 3 confluence with Oakey Creek. No PFAS concentration is reported in the closest Oakey Creek Alluvium bore, MWO-M-AL, which was drilled to aid in the evaluation of Groundwater Zone 2. PFAS in Oakey Creek is not identified to alter the groundwater in the alluvium at MWO-M-AL. The bore log for MWO-M-AL does not indicate marked gravel content, indicating lower permeability within this portion of the Oakey Creek Alluvium, which reduces the potential for vertical migration from the Oakey Creek to the Oakey Creek Alluvium.

Mid-stream

Monitoring bores MWO-X-AL and MWO-Q-AL both indicate PFAS concentrations within the groundwater samples:

• MWO-X-AL is constructed within high permeable coarse-grained sand, where bore collapse was recorded indicating unstable unconsolidated alluvium. This bore is located adjacent to Dam 1 and as such may be artificially recharged by dam seepage, irrigation return water, and surface water flow.

• Monitoring bore MWO-Q-AL is an up-gradient monitoring bore to the east of the former landfill. Elevated PFAS concentrations within this bore may be as a result of historical landfill activities and from surface water loss. The bore log indicates the bore was constructed within silty clay. The PFAS concentrations in the groundwater sample are markedly higher than the possible source surface water sample at MWO-Q-AL.

The available information within the mid-stream area does not clearly indicate surface water loss to groundwater resulting in PFAS migration to groundwater.

Downstream

No PFAS concentrations were reported in the groundwater, while traces of PFAS (i.e. at or close to, the limit of reporting) were detected in downstream surface water. PFAS in Oakey Creek is not identified to alter the groundwater in the alluvium at MWO-R-AL.

It is not immediately evident that Oakey Creek is acting as a continuous or effective source of PFAS to the groundwater. The continuous flow and absence of high permeable sediments/bedrock immediately below the creek (assumed to be clay-rich sediments as evident in the bore logs) reduces the seepage potential even though the surface water is a losing system (minor seepage loss as evident in the surface water flow comparisons upstream and downstream – Groundwater Model Report (AGE, 2016)).

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Westbrook Creek

Trace PFAS concentrations (i.e. at or close to, the limit of reporting) were reported in the surface water. As MWO-T-AL did not detect impacts, it is considered that Westbrook Creek does not act as a source of PFAS in groundwater. It is noted that water within the Westbrook Creek is mainly sourced from a catchment outside of the Investigation Area.

Summary

The available data do not support the interpretation that Oakey Creek is acting as a continuous or effective source of PFAS to the groundwater. The continuous flow and absence of high permeable sediments/bedrock immediately below the creek (assumed to be clay-rich sediments as evident in the bore logs) reduces the seepage potential even though the surface water is a losing system (minor seepage loss as evident in the surface water flow comparisons upstream and downstream (AGE, 2016).

8.7.3 Farm dams

The two farm dams identified to contain PFAS in water were assessed through the completion of paired monitoring wells adjacent to the dams. Based on the bore logs and geotechnical permeability test data, the underlying geology was reviewed to assess leakage/dam seepage risks or impacts.

8.7.3.1 Dam 1 The large farm dam receives excess stormwater runoff water from drainage channel 3, which transports runoff from the Site. The drain water (sample SW57) contained elevated PFAS concentrations (Table 8-1).

Groundwater measured in the two monitoring wells, MWO-Y-AL and MWO-Y-WCM; indicate PFAS within the groundwater sampled from the shallow Oakey Creek Alluvium bore only. It is conceptualised that this PFAS is as result of dam seepage, irrigation return water, or stormwater drain water loss (to groundwater).

Drill returns, collected during the bore drilling, were submitted to a geotechnical laboratory for permeability testing. The laboratory results, as included in Table 8-8, provided an estimate of permeability with depth adjacent to the dam. Table 8-8 Permeability data at Dam 1

Bore Sample depth (mbgs) Description Permeability (m/day)

MWO-Y-AL 5 Silty clay 5.53E-06 MWO-Y-WCM 10 Silty clay 1.38E-05 MWO-Y-WCM 15 Silty clay 1.12E-05 MWO-Y-WCM 25 Silty clay 1.38E-05 MWO-Y-WCM 65 Clay 1.30E-04

The available data indicate low permeable clay in this area, which reduces the potential for vertical seepage from the farm dam into the saturated zone and deeper aquifers.

An assessment of available PFAS concentrations, within the sediments with depth, was considered to further assess possible vertical migration. The soil sample results are summarised in Table 8-9.

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Table 8-9 PFAS soil results at Dam 1

Bore Sample depth (mbgs) Description Soil PFOS +

PFHxS (µg/L) Soil PFOA (µg/L)

MWO-Y-AL 0.5 Silty clay 0.0043 <LOR

MWO-Y-WCM 0.5 Silty sandy clay 0.06 0.0008

MWO-Y-AL 3 Silty clay with minor fine sand <LOR <LOR

MWO-Y-WCM 3 Clay with fine sand 0.0065 <LOR

MWO-Y-AL 8 Silty sand clay with gravel 0.0033 <LOR

MWO-Y-WCM 8 Clay 0.0087 <LOR

MWO-Y-AL 12 Silty sandy clay 0.0002 <LOR

MWO-Y-WCM 12 Silty sandy clay 0.0055 <LOR

MWO-Y-WCM 18 Siltstone 0.0108 <LOR

The available soil data indicates the highest PFAS concentrations in the near surface samples (0.5 mbgs) and the vertical distribution of PFAS shows a possible correlation with permeability, such that lower PFAS concentrations are associated with higher permeable sediments. This indicates possible accumulation of PFAS, as it migrates vertically (albeit slowly) through the unsaturated and saturated zones, within sediments of lower permeability.

8.7.3.2 Dam 2

Dam 2 is filled with groundwater, from residential bore GW55, which had 3.2 µg/L PFOS+PFHxS in January 2015. It is considered that refilling of the dam, due to evaporation losses, has resulted in the elevated PFAS concentrations reported within the dam (see Section 8.3). The two monitoring wells (MWO-Z-AL and MWO-Z-WCM) are installed as close to the dam as possible and are located immediately north of the Dam 2 (Figure F15). The bore logs (Appendix D) are summarised in Table 8-10. Table 8-10 Bore logs summary

Depth Lithology

0–13 m Dry sandy silty clay

13–26 m Wet silty sandy clay and gravel

26–36 m Wet silty clay

36–43.5 m Silty sand

43.5–49.5 m Silty clay and gravel

49.5–72.5 m Basalt gravel in a silty clay matrix (transition zone)

72.5–80 m Silt and coal to end of hole

The geology adjacent to the Dam 2 indicates sediments with higher permeability (gravel content) which would facilitate the migration of PFAS seepage from this dam.

A comparison of water quality data from the Dam 2 and the groundwater monitoring bores is included in Table 8-11.

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Table 8-11 PFAS water results at Dam 2

Bore PFOS + PFHxS (µg/L) PFOA (µg/L) Groundwater depth

(mbgs) MWO-Z-AL 2.03 0.05 12.80

MWO-Z-WCM <LOR <LOR 22.23

Dam 2 (SW34A) 9.05 0.16 -

Dam 2 is estimated to be ~2 m in depth, which indicates a thin unsaturated zone (separation) between the bottom of the dam and the alluvium groundwater, measured at 12.80 mbgs. The separation to the Walloon Coal Measures groundwater is markedly larger, some 20 m.

PFAS in the alluvium, thin separation, and the higher permeable sediments indicate that Dam 2 has the potential to act as a continuous secondary source of PFAS to the Oakey Creek Alluvium. The seepage from the dam is considered to be captured in the extraction from GW55.

8.7.4 Irrigation return flow The irrigation areas assessed in the Investigation Area, as detailed in Section 8.3, indicate possible PFAS impacted recharge to the Oakey Creek Alluvium groundwater due to irrigation return flow. The areas where this can potentially occur are around Dam 1 and the area around bore RN107812.

8.7.4.1 Dam 1 area

Irrigation return water may have resulted in the migration of PFAS into the Oakey Creek Alluvium aquifer in the Dam 1 area as it is noted that PFAS is reported in both Oakey Creek Alluvium wells on the property, adjacent to the irrigated lands. The PFAS data includes:

• MWO-Y-AL: PFOS + PFHxS 1.58 µg/L, PFOA 0.16 µg/L

• MWO-I-AL: PFOS + PFHxS 0.12 µg/L, PFOA <LOR µg/L.

Oakey Creek Alluvium monitoring wells, MWO-Y-AL and MWO-I-AL, are both installed to 20 m within the alluvial gravels. Their geological logs are summarised in Table 8-12. Table 8-12 Oakey Creek Alluvium bores near Dam 1 - geology

Depth (mbgs) MWO-Y-AL Permeability (m/day) MWO-I-AL Permeability

(m/day)

5.0 Silty clay 5.53E-06 Clayey silty sandy gravel 6.31E-03

10.0 Silty clay 1.38E-05 Clayey gravelly sand 9.50E-02

15.0 Silty clay 1.12E-05 Sandy clay 4.75E-05

The geological and permeability data indicates a marked variation across the area. The heterogeneity of the alluvium results in varying permeability, both spatially and with depth.

It is noted that MWO-I-AL intersects higher permeability sediments compared to MWO-Y-AL, and also (correspondingly) lower PFAS concentrations in the groundwater. It is therefore considered that the accumulation of PFAS occurs in the lower permeable (clay-rich) sediments.

It is noted that the two Oakey Creek Alluvium wells are located adjacent to other possible PFAS contaminant sources, including:

• MWO-Y-AL is located adjacent to the Dam 1, which is filled with PFAS impacted runoff water

• MWO-I-AL is located adjacent to stormwater drain, drainage channel 3, which contains runoff from the Site.

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8.7.4.2 Groundwater levels

Groundwater flow direction across the Investigation Area is from east to west, as detailed in Section 6.3.2, i.e. from MWO-I-AL to MWO-Y-AL. The groundwater levels, 395.3 mAHD (MWO-Y-AL) and 391.5 mAHD (MWO-I-AL) indicate a reversal of this regional flow direction near Dam 1. This is considered more likely to have occurred as groundwater seepage from the farm dam, resulting in a localised groundwater ‘mound’ beneath the dam.

Irrigation return water could be contributing to the PFAS in groundwater, however, as there are additional potential sources, it is not clear from the available information what contribution is as result of the more disperse contaminant source (irrigation).

It is noted, however, that irrigation (or seepage from the dam or stormwater drain) on clay-rich sediments would result in groundwater samples with more elevated concentrations than from areas with higher permeability.

8.7.4.3 RN107812 irrigation area

The groundwater extracted from registered bore, RN107812, is used for gardening/lawn water supply. PFAS concentrations have been reported in this bore, as well as two monitoring bores, MWO-X-AL and MWO-X-WCM, installed near RN107812.

It is considered that irrigation return water could be contributing to the PFAS in groundwater, however, as RN107812 is a multi source and utilised bore (as detailed in Section 8.7.7) the PFAS in the groundwater may not solely be attributed to irrigation return flow in this area.

8.7.5 Flood inundation Flood mapping (Figure F8) and an assessment of groundwater monitoring bores (within the Oakey Creek Alluvium) within these mapped inundation areas indicate a possible correlation between the flooded areas and PFAS within the Oakey Creek Alluvium aquifer.

A summary of geology, permeability (where available) and groundwater levels was compiled for consideration of the potential for flood inundation to recharge to groundwater, Table 8-13.

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Table 8-13 Flood inundation bore summary

Bore / PFAS in groundwater* Depth (mbgs) Geology Permeability

(m/day) Water level (mbgs / mAHD)

MWO-K-AL PFOS + PFHxS = <LOR PFOA = <LOR

5.0 Silty clay 1.04E-04 13.5 / 386.4

10.5 Clay 1.81E-05

15.0 Silty clay 3.63E-04

25.0 Silty clay 1.12E-05 MWO-J-AL PFOS + PFHxS = 0.34 PFOA = <LOR

5.0 Sandy clay 7.78E-06 11.8 / 386.2

10.0 Clay 9.50E-06

25.0 Silty clay 6.13E-06 MWO-L-AL PFOS + PFHxS = 16.9 PFOA = 0.47

- Silty sandy clay - 13.7 / 386.7

MWO-G-AL PFOS + PFHxS = 6.99 PFOA = 0.30

- Silty sandy clay with gravel

- 13.5 / 387.8

MWO-H-AL PFOS + PFHxS = 0.15 PFOA = <LOR

5.0 Sandy clay 5.01E-06 12.8 / 388.6

10.0 Clayey sand 7.00E-04

15.0 Clay 2.42E-05

20.0 Gravelly clay 1.38E-05

30.0 Silty clay 2.76E-06

40.0 Clay 2.33E-06

50.0 Clay 3.20E-05 Note: * It should be noted that monitoring wells and residential bores have only been included on the figures if the landholder gave permission. As a result, not all monitoring wells and residential bores are depicted on the figures.

Groundwater PFAS concentrations and permeability within the alluvium indicates lower PFAS concentrations within the higher permeable sediments, as recorded in MWO-K-AL and MWO-H-AL. Elevated PFAS concentrations are recorded in MWO-L-Al and MWO-G-AL, within silty sandy clay but no geotechnical laboratory permeability tests are available for these two bores to assess actual permeability.

Groundwater flow patterns and contours, compiled from Table 8-13, indicate the recognised (within this local area) flow direction of east to west. The groundwater contours are closer spaced between MWO-H-AL and MWO-L-AL than between MWO-L-AL and MWO-J-AL indicating lower permeability (i.e. wider spaced flatter groundwater gradients are representative of higher permeability and transmissivity within an aquifer). The estimated groundwater gradients are:

• Groundwater gradients between MWO-H-AL and MWO-L-AL is 1:500 (2 m change in head over 1,000 m)

• Groundwater gradients between MWO-L-AL and MWO-J-AL is 1:2550 (0.5 m change in head over 1,275 m).

The absence of PFAS in flood inundation areas and the PFAS concentration distribution corresponding to groundwater flow and lower permeable alluvium (accumulation of PFAS within low permeable alluvium) is considered to indicate that the contribution of flood inundation (as an artificial groundwater (PFAS impacted) recharge) as a PFAS source is limited. It is further considered that based on the nature of flooding, from a sediment dispersion perspective, the larger more coarse material would be deposited on or immediately adjacent to the creek levee as flow velocities decrease.

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The fine sediments will be transported further with the flood water, which are considered to reduce permeability in the topsoil. An assessment of topsoil sediments logged in the flood inundation bores is included in Table 8-14.

This contaminant transport mechanism is further considered in the soil and surface water sections, Section 7.2 and Section 9.0. Table 8-14 Flood inundation bore top sediments

Bore Depth (mbgs) Geology Comment

MWO-K-AL 0–3.5 Silty sandy clay Hard moist clay

MWO-J-AL 0–1 Silty sandy clay Wet plastic top soil

MWO-L-AL 0–1.9 Silty clay Moist hard clay

MWO-G-AL 0–2 Silty clay Moist clay-rich cover

MWO-H-AL 0–0.3 Silty sand, minor gravels Dry crumbling non-plastic sand

The bores located away from the creeks and surface drainages indicate low permeable clay cover, which retains moisture. Bore MWO-H-AL, located at the confluence of stormwater drains 1 and 2, has coarse grained top soil possibly as a result of overbank deposits associated with stormwater drain flooding.

8.7.6 Former landfill Based on the regional groundwater flow direction and PFAS concentration results in nearby monitoring bores, the former landfill is considered a secondary source of PFAS contamination. This has been investigated further by an evaluation of groundwater levels, geology, and groundwater quality.

8.7.6.1 Groundwater levels

The groundwater level data for the three new groundwater monitoring wells (MWO-Q-AL, MWO-P-AL, and MWO-O-AL) installed adjacent to the former landfill indicate that groundwater flow is from MWO-Q-AL (south-east) to MWO-O-AL (north-west) across the former landfill site. The groundwater gradient is relatively steep (in the investigation area, 1:700 (Section 6.3.2)), 1:180 indicating lower permeable alluvium in the area.

8.7.6.2 Geology

A summary of the available geology for the three bores is included in Table 8-15.

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Table 8-15 Former landfill bore summary

Bore / PFAS in (µg/L) Depth (mbgs) Geology Water level (mbgs / mAHD)

MWO-Q-AL PFOS + PFHxS = 1.64 PFOA = 0.01

2.0 Silty sandy clay 6.2 / 391.1

7.0 Silty sand and gravel

14.0 Silty sand

16.0 Silty clay and weathered basalt

17.0 Silty sandy clay MWO-P-AL PFOS + PFHxS = 6.91 PFOA = 0.34

2.0 Fine sand 9.4 / 387.4

6.0 Silty sandy clay

14.0 Silty clay


18.0 Silty sandy clay and gravel

20.0 Silty clay MWO-O-AL PFOS + PFHxS = 0.08 PFOA = <LOR

1.5 Silty sandy clay 11.8 / 386.7

19.0 Silty clay

20.0 Fine sand

24.0 Silty sandy clay with minor gravel

28.0 Silty clay and gravel


Groundwater monitoring well MWO-P-AL intersects silty clay with only a thin section of more permeable gravels intersected in the three bores. This well, located immediately down hydraulic gradient of the former landfill, is considered to intersect lower permeable alluvium which facilitates the accumulation of PFAS. The PFAS is considered to be migrating from the former landfill, within this portion of the Investigation Area.

8.7.7 Groundwater extraction bores As detailed in Section 8.6, it is considered that groundwater extraction can result in the development of localised changes (depressions) to the groundwater which can facilitate PFAS migration and accumulation, which can potentially act as an indirect source of PFAS contamination.

To investigate if the possible accumulation of PFAS due to groundwater extraction can act as a secondary source, the following assessment was conducted:

• Examine bore construction, as bores that were constructed prior to the current legislated standards can potentially facilitate the migration of PFAS into the underlying units.

• Examine the potential for induced flow from the alluvium to the underlying depressurised aquifers that could potentially facilitate the migration of PFAS into the underlying units.

8.7.7.1 Bore construction DNRM had identified three registered bores with licensed extraction, which they consider to have the potential to hydraulically connect aquifers based on bore construction. These three bores were assessed, as detailed in Section 6.5.

The evaluation of typical existing landholder bores, constructed through the Oakey Creek Alluvium aquifer and into the bedrock units (either Main Range Volcanics or Walloon Coal Measures) allowed for the assessment of PFAS migration. A summary of findings is included in Table 8-16.

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Table 8-16 Registered bore assessment summary

Bore Depth (actual / logged)

Registered Bore Bore Card Geology Description Down-Hole Geophysical Comments

RN107812 74 m (134 m)

Oakey Creek Alluvium to 37 mbgs Collapsed to 74 mbgs Transition zone (Oakey Creek Alluvium and Walloon Coal Measures) to 53 mbgs

Open hole from 62 to 74 mbgs

Walloon Coal Measures to end of hole at 134 mbgs

No evidence of cement grout or gravel pack

Large fracture present below the casing

Possible hydraulic connection between Oakey Creek Alluvium and Walloon Coal Measures

RN87439 59.4 m (60 m)

No alluvium logged Steel cased to 59.4 mbgs

Basalt to 6 mbgs Large slots (15 mm thick) no gravel pack

Sandstone to 48 mbgs Possible hydraulic connection between Main Range Volcanics and Walloon Coal Measures Coal and shale to 60 mbgs

RN87369 80.86 m (86 m)

Clay to 18 mbgs Cased to 80.86 mbgs

Basalt to 26 mbgs Slotted across basalt and Walloon Coal Measures

Transition zone (26–29 m) Poor cement bond

Walloon Coal Measures to end of hole

Possible hydraulic connection between Main Range Volcanics and Walloon Coal Measures

The bore construction assessments, using down-hole geophysics, indicated the potential for hydraulic connection between multiple aquifers. This can result in the possibility of

• mixing of groundwater types

• vertical migration of PFAS contaminants within the Oakey Creek Alluvium to underlying aquifers

• composite water levels and quality.

Paired monitoring bores, comprising a shallow (~20 m) and a deeper bedrock bore, were constructed adjacent to each of the three DNRM licensed bores. Groundwater levels, groundwater quality, and PFAS concentration data were compiled to provide an assessment of hydraulic connectivity and PFAS migration.

RN107812 Bores MWO-X-AL and MWO-X-WCM were constructed adjacent to RN107812. A summary of data for these bores is included in Table 8-17. Table 8-17 RN107812 bores summary

Bore Depth (m)

Groundwater Level (mbgs / mAHD)


PFOA (µg/L) Comment

RN107812 74 41.7 / 361.0 1.34 0.02 Blended groundwater, composite water level, vertical downward gradient

MWO-X-AL 20 7.3 / 394.4 0.29 0.00

MWO-X-WCM 68 51.7 / 350.2 0.03 0.00

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Major anion and cation concentrations from each of the bores was compiled in a Schoeller Diagram (Chart 13) to allow for an assessment of the source of groundwater extracted from RN107812. Chart 13 RN107812, MWO-X-AL, MWO-X-WCM Schoeller diagram

The available chemistry data indicate groundwater extracted from RN107812 is a mixture of groundwater from both the Oakey Creek Alluvium and the Walloon Coal Measures aquifers. The major anion and cation and PFAS concentration data indicates migration from the Oakey Creek Alluvium to the Walloon Coal Measures.

Aquifer test

To further assess the hydraulic connection between units, a short duration constant discharge aquifer test was conducted on RN107812. During pumping, the groundwater levels in all three bores were recorded to allow for an assessment of aquifer parameters and hydraulic connection.

Chart 14 provides the data compiled during the pumping test. It is noted that no water level response was measured in monitoring bore MWO-X-AL. This may be as a result of the minor groundwater extraction rate (0.46 L/s) and the high storage capacity of the alluvium.

The response to pumping (i.e. groundwater level decline and recovery as a result of extraction) in both RN107812 and MWO-X-WCM allowed for an assessment of Walloon Coal Measures aquifer hydraulic parameters, as summarised in Table 8-18.

0

5

10

15

20

25

30

Ca Mg Na+K Cl HCO3+CO3 SO4

meq

/L

RN107812-141029RN107812-170601MW-0-X-AL-170518MW-O-X-WCM-170428

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Chart 14 RN107812 pumping test summary

Table 8-18 RN107812 aquifer data

Bore Delta (s) Time (to) minutes Radius (m) Transmissivity

(m2/day) Storativity

RN107812 5.49 - - 1.3 -

MWO-X-WCM 5.95 34 27.95 1.2 0.00008

Recovery 11.07 - - 0.66 -

The aquifer test results indicate low yielding groundwater potential in the Walloon Coal Measures at RN107812, with limited aquifer storage (typical of fractured rock). The low aquifer parameters are considered to result in large drawdown cones within the Walloon Coal Measures due to extraction, which can facilitate induced flow from the overlying alluvium to the Walloon Coal Measures.

Summary

It is considered that vertical PFAS migration at RN107812 occurs as recognised in the groundwater quality. This is as a result of:

• the construction of the bore (RN107812) prior to the current legislated standards

• steeper natural vertical gradient, downwards from Oakey Creek Alluvium to the Walloon Coal Measures, due to extraction (as detailed in Section 8.6)

• thin or no competent basalt (Main Range Volcanics) between the Oakey Creek Alluvium and the Walloon Coal Measures

0

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RN107812 - Constant Rate Test

Pumping Bore Datalogger

Pumping Bore-Manual Gauging

MW-O-X-WCM Datalogger

MW-O-X-WCM Manual Gauging

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RN107812 - Constant Rate Test: pH and EC pH EC (uS/cm)

00.10.20.30.40.50.60.70.80.91-200

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RN107812 - Constant Rate Test: pH and EC ORP (mV) DO (ppm)

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• thin transition zone

• fractured rock providing preferential flow path(s)

• close proximity to Oakey Creek, which can act as a PFAS source that is captured within the RN107812 drawdown cone (capture zone).

RN87439

Bores MWO-W-AL and MWO-W-WCM were constructed adjacent to RN87439. A summary of data for the RN87439 and monitoring wells is included in Table 8-19. Table 8-19 RN87439, MWO-W-AL and MWO-W-WCM bore summary

Bore Depth (mbgs)

Groundwater level (mbgs / mAHD)


PFOA (µg/L) Comment

RN87439 59.4 11.4 / 392.2 <LOR <LOR Basalt groundwater, composite water level, vertical downward gradient

MWO-W-AL* 21 10.1 / 393.5 0.07 <LOR MWO-W-WCM

56 17.5 / 386.1 <LOR <LOR

Note: * This bore is denoted AL but is screened across the Main Range Volcanics basalt

No PFAS contaminants are reported in the production bore, RN87439. Traces of PFOS + PFHxS have been reported in the shallow monitoring well, constructed within the weathered Main Range Volcanics basalt.

An assessment of major anion and cation data from the three bores, compiled in a Schoeller diagram (Chart 15), indicate that the groundwater extracted from RN87439 is sourced from the basalt (Main Range Volcanics). This is due to the correlation between the profiles for groundwater samples from RN87439 and the shallow monitoring well that is screened across the basalt. Groundwater is extracted from the Main Range Volcanics aquifer even though the bore casing is slotted (44.65–57.66 mbgs) across the Main Range Volcanics and Walloon Coal Measures.

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Chart 15 RN87439, MWO-W-AL, MWO-W-WCM Schoeller diagram

Aquifer Test

A short duration constant discharge aquifer test was conducted on RN87439 to assess possible hydraulic connection between aquifers due to the bore construction. During pumping the groundwater levels in all three bores (RN87439, MWO-W-WCM, and MWO-W-AL) were recorded, to allow for an assessment of aquifer parameters and hydraulic connection.

Chart 16 provides the data compiled during the pumping test. It is noted that no groundwater level response was measured in monitoring bore MWO-W-AL. The pumping test was conducted at a relatively high (compared to the other pumping tests) rate of 1.5 L/s for over seven hours, the lack of response indicates high storage capacity of the Main Range Volcanics aquifer in this area.

The response to pumping in the bores allowed for an assessment of Main Range Volcanics and Walloon Coal Measures aquifer hydraulic parameters, as included in Table 8-20. Table 8-20 RN87439 aquifer data



RN87439 0.432 - - 55 -

MWO-W-WCM 0.870 10 19.23 27 0.0012

Recovery 0.63 - - 38 -

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The pumping test of RN87439 indicates good groundwater yield based on the transmissivity within the Main Range Volcanics intersected in this bore. The higher transmissivity in the Main Range Volcanics reduces the development of large drawdown cones and minimises the potential for induced flow from the overlying alluvium (albeit thin in this area). The Main Range Volcanics is recognised as the major contributor of groundwater into bore RN87439 such that there is little or no contribution from the Walloon Coal Measures (as indicated by the groundwater PFAS results).

Summary

It is considered that the higher aquifer transmissivity within the weathered and fractured basalt compared to the Walloon Coal Measures sediments, even though there is the possibility of hydraulic connection (due to the construction of the bore prior to the current legislated standards), reduces the extraction from the Walloon Coal Measures in this bore, which in turn reduces the potential for induced flow into the Walloon Coal Measures.

It is noted that the groundwater extracted from RN87439 is the same as that from MWO-W-AL but no PFAS was present in the sample from RN87439 in May 2017. This may reflect permeability differences in the basalt. It may be possible that MWO-W-AL is installed in lower permeable basalt, which has resulted in PFAS accumulation which is more readily mobilised/removed during pumping in the higher transmissive basalt at RN87439.

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RN87369

RN87369 is a production bore, located within an irrigated paddock. Monitoring bores MWO-V-AL and MWO-V-WCM were constructed within the paddock, some 10 m from RN87369. A summary of data for the bores is included in Table 8-21. Table 8-21 RN87369, MWO-V-AL and MWO-V-WCM summary

Bore Depth (m)

Groundwater level (mbgs /

mAHD) PFOS +

PFHxS (µg/L) PFOA (µg/L) Comment

RN87369 80.86 19.6 <LOR <LOR Basalt groundwater, composite water level, vertical downward gradient

MWO-V-AL* 22.5 17.4 / 384.7 0.01 <LOR

MWO-V-WCM 65 24.0 / 378.0 <LOR <LOR Note: * This bore is denoted AL but is screened across the Main Range Volcanics basalt

No PFAS was reported in the production bore, RN87369. A trace concentration of PFOS was detected in the Oakey Creek Alluvium monitoring well (MWO-V-AL). PFAS was not detected above the LOR in the Walloon Coal Measures monitoring well (MWO-V-WCM).

An assessment of major anion and cation data from the three bores, compiled in a Schoeller diagram (Chart 17), indicate that the groundwater extracted from RN87369 is sourced predominantly from the Walloon Coal Measures aquifer. This occurs even though the bore casing is slotted at three separate sections (21.7–27.6 m, 61–67 m, and 74–78 m) across the Main Range Volcanics and Walloon Coal Measures aquifers.

The groundwater sampled from the RN87369 is considered to be from the Walloon Coal Measures aquifer based on major anion concentrations, it is noted however that this may be as a result of the pumping infrastructure on this bore (only pumps for under five minutes each hour). This extraction setup may result in only groundwater immediately adjacent to the pump inlet being extracted. Chart 17 RN87369, MWO-V-AL, MWO-V-WCM Schoeller diagram

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A short duration constant discharge aquifer test (7.5 hours) was conducted on RN87369 to assess possible hydraulic connection between aquifers due to the bore construction, where this bore has three separate screened sections across the Main Range Volcanics and Walloon Coal Measures.

The groundwater level responses in RN87369, MWO-V-WCM, and MWO-V-AL indicated:

• no response in the overlying Main Range Volcanics (MWO-V-AL)

• variable water level response in the pumping well due to bore RN87369 being connected to an irrigation system on a timer, which turned off and on remotely during the test.

Chart 18 provides the pumping test data, which includes the erratic water level responses due to the irrigation system. The response to pumping in the three bores guided an estimate of aquifer hydraulic parameters, as included in Table 8-22. Table 8-22 RN87369 aquifer data



RN87369 1.960 - - 6 -

MWO-V-WCM 1.607 60 7.84 7 0.011

Recovery 2.75 - - 4 -

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The aquifer test results indicate that the Walloon Coal Measures, intersected in RN87369, has slightly higher transmissivity than the overlying basalt (Main Range Volcanics logged within the bores). Note that there are three zones of slotted casing, facilitating groundwater ingress from the overlying basalt and underlying Walloon Coal Measures. The cement bond log in Appendix F also indicates poor isolation between units, such that groundwater from the two aquifers could potentially be in hydraulic connection through this bore. The pumping test results and groundwater PFAS concentrations indicate that the main source of groundwater into the bore is from the Walloon Coal Measures aquifer.

The low yield, approximately 0.75 L/s, employed during the pump test resulted in groundwater drawdown of ~25 m below static water level (some 55 mbgs). This large drawdown within the bore recovered within four hours, even with the influence of automated irrigation extraction, indicating good recovery within the Walloon Coal Measures.

The low extraction (pump only switching on for less than five minutes every hour) and the quick groundwater level recovery indicate that the potential for induced flow from the overlying Main Range Volcanics to the Walloon Coal Measures is limited.

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8.7.8 Secondary Alteration

The fault mapping in the area, as included in the Hydrogeological Conceptualisation report for the Surat Cumulative Management Area (OGIA, 2016), indicate near vertical faults within the basement Bowen Basin, below the Clarence-Moreton Basin geological units, which include the Walloon Coal Measures in the IA. Detailed geological studies with the Surat Basin, which has similar geology (age and units) to the Clarence-Moreton Basin, indicate that the faults do not typically extend up into the Surat Basin Formations. This restricts the potential for secondary alteration within the Clarence-Moreton Basin geological units as well as the overlying Main Range Volcanics and Oakey Creek Alluvium.

The clay-rich alluvium, as recognised in the bore drilling and construction (were swelling clays resulted in difficult casing installation across the IA), is considered to drape or fold in response to faulting. This occurs due to the higher plasticity of the semi-consolidated alluvium compared to competent rock, which fractures as a result of faulting.

The nature of the alluvium (plasticity and self-sealing swelling clays) and limited occurrence of faulting is considered to reduce the potential preferential pathways to form (between the Oakey Creek Alluvium and Walloon Coal Measures) as a result of secondary alteration, which in turn reduces the potential for PFAS migration in groundwater from the Oakey Creek Alluvium to the Walloon Coal Measures.

8.8 Aquifers An updated understanding of the hydrogeological properties of the aquifers, based on the results of the 2015 to 2017 investigations, is presented in the following subsections.

The groundwater resources and aquifer parameters within the underlying geological units are considered, as part of the WASP approach, to assist in consideration of vulnerability and groundwater resource potential (current and future use).

8.8.1 Oakey Creek Alluvium

The Oakey Creek Alluvium, derived from fluvial stream over-bank deposits, comprises interbedded with discontinuous sequences of sand, silt, gravel, and clay. Infiltration test and geotechnical laboratory testing, plus geological logs, indicate the heterogeneity within the alluvium.

The transmissivity (T) of the Oakey Creek Alluvium, based on 18 pumping tests recorded on the DNRM groundwater database, ranges from 2–1,100 m2/day, with an average transmissivity of approximately 180 m2/day. This high average transmissivity indicates the permeable nature of the coarse grained sediments within the alluvium.

Based on the typical saturated thickness (b) of the Oakey Creek Alluvium, 15 m, the hydraulic conductivity (K) of the Oakey Creek Alluvium is estimated between 0.1 and 75 m/day using pumping test data (i.e. T=Kb) reported in AECOM (2016a), which is based on a number of sources including Murphy (1990) and QWC (2012).

Aquifer testing indicated a wide variation in hydraulic conductivity values. The hydraulic conductivity is considered to depend on the amount or thickness of coarse-grained sediments within the test bore(s).

No records of aquifer storage (specific yield and specific storage) are provided by DNRM in the groundwater database for the Oakey Creek Alluvium. Estimates of specific yield for the unconfined Oakey Creek Alluvium, using groundwater level response to discharge, are about 11%. A specific yield of 8% is used in the Oakey Creek Groundwater Management Area as part of the water sharing rules (DNRM, 2015).

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Pumping tests conducted on three registered bores, as detailed in Section 8.7.7, indicate high storage capacity within the alluvium, such that groundwater extraction in the underlying bedrock units does not readily result in measureable induce flow impacts (i.e. drawdown in the Oakey Creek Alluvium is not measureable when bedrock bores are pumped9 even in areas where hydraulic connection is evident in the groundwater chemistry).

These storage data are considered to be representative of the composite Oakey Creek Alluvium sediments, comprising clay, sand, and gravel. The representative specific yield ranges for these sediments are (Driscoll, 1989):

• clay 1–10%

• sand 10–30%

• gravel 15–30%.

8.8.1.1 Heterogeneity

The heterogeneity within the Oakey Creek Alluvium is as a result of the complex depositional processes that have occurred since the creek formed. The Oakey Creek Alluvium is self-formed, which means the creek channel(s) are shaped by the magnitude and frequency of flood events, such that these floods erode, deposit, and transport sediments.

Oakey Creek is recognised as a meandering channel within a flood plain, which has altered over time by erosion, avulsion and deposition of sediments. This results in multi-story coalescing fining upward sediments, based on location of the channel during overbank deposition events (Plate 1).

9 It is considered that the short duration aquifer tests are similar to groundwater extraction within the area, where pumping occurs for several hours and then allowed to recover rather than long term continuous extraction.

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Plate 1 Alluvial deposits (source: https://www.slideshare.net/MTaherHamdani/lecture-5-fluvial)

The Oakey Creek Alluvium is, and as recognised from the groundwater level data from bores screened at different depths (Section 3.4.3.2 in the Groundwater Model Report, AGE, 2016 and Table T610), a single aquifer unit where lower (clay-rich) and higher (gravel-rich) permeability sediments are in hydraulic connection.

Groundwater aquifer parameters are markedly different, both spatially and with depth, as a result of the alluvium geomorphology. This heterogeneity is recognised to influence PFAS migration (or retardation) within the Oakey Creek Alluvium, such that it influences PFAS migration within the groundwater resources associated with the alluvium.

8.8.2 Main Range Volcanics The Main Range Volcanics are comprised mostly of basalt and overlie the eroded surface of the Walloon Coal Measures. Most of the volcanics are extensively eroded and covered in part with Oakey Creek Alluvium. The average thickness of the basalt is around 70 m.

The Main Range Volcanics are recharged by rainfall, within the outcrop (volcanic plateau located south and east of the Site), through fractures and joints within the basalt, allowing for Main Range Volcanics sustainable aquifers.

10 Groundwater level in pairs within the Oakey Creek Alluvium have minor differences of centimetres as a result of sample / survey error or recharge / discharge influences.

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The suggested bulk hydraulic conductivity of the basalt ranges from 0.004 to 4.6 m/day. This is dependent on fractures, joints, and vesicles within the basalt (QWC, 2012). Site-specific hydraulic conductivity data indicates the competent basalt has low hydraulic conductivity, ranging from 0.001 to 0.018 m/day (average 0.01 m/day).

Literature values for specific yield for basalt (e.g. weathered, fractured, and vesicular basalt) are about 1–5%.

The aquifer tests conducted on two registered bores (see Section 8.7.7) indicate a high degree of heterogeneity in the Main Range Volcanics basalt. The groundwater potential of the basalt is variable as recognised by the estimated transmissivity, which ranged from 2 to 16 m2/day. It is considered that the groundwater potential of the basalt is related to its texture (vesiculated, jointing) and secondary alteration, including depth of weathering.

8.8.3 Walloon Coal Measures

The Jurassic-aged Walloon Coal Measures comprise thin discontinuous layers of siltstone, mudstone, lithic sandstone, and coal. The coal seams are generally the more permeable units (due to cleats) within these layers.

The Walloon Coal Measures are approximately 200 m thick beneath the Site and are considered to form an effective aquitard between the Oakey Creek Alluvium and the underlying GAB Hutton Sandstone. The hydraulic conductivity of the coal seams of the Walloon Coal Measures has a range between 0.0006 and 0.9 m/day, with a median of 0.08 m/day (QWC, 2012). The specific yield of the Walloon Coal Measures is 0.005% (QWC, 2012).

Aquifer tests conducted on bore RN107812 provided an indication of site-specific Walloon Coal Measures aquifer parameters (as included in Section 8.7.7.2). The Walloon Coal Measures is considered to provide low sustainable yields, as recognised from the low aquifer transmissivity (~1 m2/day) and limited storativity (0.0001).

8.8.4 Transition zone

Across much of the Oakey area, the contact between underlying geological formations is dominated by undifferentiated clay, comprising basal Oakey Creek Alluvial clays and/or weathered upper part of the bedrock, either Walloon Coal Measures or Main Range Volcanics. This clay-rich horizon is termed the transition zone. Although the transition zone is not always present beneath the alluvium, the transition zone (together with the upper mudstones and siltstones of the Walloon Coal Measures) provides resistance to vertical groundwater flow.

The transition zone generally occurs below the basal sands and gravel of the Oakey Creek Alluvium and above the basement rock (Walloon Coal Measures or Main Range Volcanics). This layer is a combination of low permeable basal alluvial clays and the weathered upper part of the Walloon Coal Measures or the Main Range Volcanics (where they exist).

The transition zone, between the Oakey Creek Alluvium and the Walloon Coal Measures or Main Range Volcanics, has been logged in several deeper monitoring bores across the investigation zone. These bores, the transition zone depth, thickness, geology and available geotechnical permeability data are included in Table 8-23.

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Table 8-23 Transition zone data

Bore Depth Geology Permeability

MWO-H-WCM 50 to 76 mbgs Sandy silty clay over Walloon Coal Measures

-

MWO-I-MRV 51 to 57 mbgs Gravelly clay over weathered basalt

1.30E-05 m/day

MWO-J-WCM 50 to 57 mbgs Silty clay over basalt 8.55E-05 m/day

MWO-K-MRV 40 to 46 mbgs Clay over basalt 1.65E-05 m/day

MWO-Y-WCM 56 to 61 mbgs Silty clay over Walloon Coal Measures

8.29E-06 m/day

MWO-W-WCM 36 to 41 mbgs Silty clay over Walloon Coal Measures

1.30E-05 m/day

MWO-X-WCM 43 to 57 mbgs Clay over Walloon Coal Measures

3.11E-06 m/day

The low permeable nature of the transition zone is recorded in all the deeper bores in Table 8-23, where permeability ranges from 8.55E-05 to 3.11E-06 m/day. This range of permeability is compared to typical liners included in waste storage facilities, including:

• geosynthetic clay liners ranges from 8.64E-05 to 8.64E-07 m/day

• compacted clay liners ranges from 8.64E-04 to 8.64E-05 m/day.

This comparison indicates the effective aquitard nature of the transition zone above the underlying bedrock units, either the Main Range Volcanics or Walloon Coal Measures.

8.9 Hydrogeological (WASP) Assessment

8.10 Approach Based on the available data compiled within the Investigation Area and the WASP evaluation, a risk evaluation of sources, in terms of likelihood and significance, was conducted. These evaluations allowed for consideration of potential environmental impacts.

The threat and associated impact specific to the groundwater resources was compiled using the methodology proposed by Skivington (1997) and the Risk Management Guidelines (AS/NZS 4360, 2004), where:

• the risk evaluation (R) of sources was conducted by considering the product of the probability (P) and the magnitude (M), i.e. R = P x M.

The risk ratings, based on scores, are then considered to evaluate potential threat to the groundwater resources, i.e. the higher the rating the more likely the source is contributing PFAS to the underlying groundwater resources. The probabilities and magnitudes values are shown in Table 8-25.

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Table 8-24 Risk evaluation: probability and magnitude values

PROBABILITY SCORE MAGNITUDE

Almost Certain 5 Catastrophic

Likely 4 Major

Possible 3 Moderate

Unlikely 2 Minor

Rare 1 Insignificant

The definitions of the terms used in Table 8-25 are as follows (AS/NZS 4360, 2004):

Probability/likelihood

Rare Will only occur in exceptional circumstances

Unlikely Could occur but not expected

Possible Could occur at some time

Likely Will probably occur in most circumstances

Almost certain Expected to occur in most circumstances

Magnitude/consequences

Insignificant Trivial environmental impact

Minor Unreasonable interference with the environment

Moderate Clearly visible impact to ecosystem, requires localised remediation

Major Damage to the environment that requires significant remediation

Catastrophic Environmental damage is irreversible, of high impact or widespread

8.11 Source Evaluation A summary of the risk evaluation of the possible on-Site PFAS sources, as detailed in Section 8.2 above, is included in Table 8-25.

The highest impacts to the groundwater resources, based on risk ratings, are considered to be:

• the point sources on Site which are located on higher permeable alluvium

• at bores that were constructed prior to the current legislated standards which can facilitate PFAS migration into underlying GAB aquifers.

Consideration of the groundwater vulnerability with regards to the GAB units is included based on the evaluation.

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Table 8-25 Summary of source risk evaluation to groundwater resources

Source Potential impact Probability Magnitude Extent Risk rating

Site source areas Primary point source contaminant sources associated with leaks, spills, and ponding of AFFF, which can migrate vertically into the groundwater

Almost certain (5) – based on reported groundwater monitoring data

Moderate (3) – soil data indicates PFAS within the top 2 m

At localised locations on Site, not evident at all potential source areas as included in Section 2.1.1

R = 5 x 3 = 15

Stormwater drains PFAS adsorbs into soil which is moved in runoff water and accumulates as sediment within the stormwater channels, acting as a PFAS source. The source can: Act a source of PFAS from the stormwater drain to groundwater

Possible (3) – areas of more coarse grained alluvium has been reported close to surface / drain floor in the investigation area

Minor (2) – trace PFAS concentrations are measured within the more permeable alluvium in these areas

Can mobilise readily within the more permeable gravel-rich alluvium, allowing for PFAS migration

R = 3 x 2 = 6

PFAS in sediment which has mobilised within the stormwater and deposited off-Site further along the stormwater channels

Possible (3) – PFAS in sediment can be deposited in areas of lower permeable (more clay-rich) alluvium where ponding (of stormwater) can occur allowing for possible enhanced groundwater recharge

Insignificant (1) – low permeability and the temporary ponding restricts the potential for increased PFAS recharge

Local within the stormwater drains

R = 3 x 1 = 3

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Oakey Creek Dissolved PFAS in surface water runoff and migrate into Oakey Creek

Almost certain (5) – PFAS have been measured within Oakey Creek

Minor (2) – PFAS are reported within the surface water, however, it is not immediately evident that Oakey Creek is acting as a continuous or effective source of PFAS to the groundwater Continuous surface water flow and low permeable sediments reduce seepage potential

PFAS has been detected in groundwater up and downstream (Table 8-7), with traces of PFAS in surface water downstream

R = 5 x 2 = 10

Farm dams Dam 1 receives stormwater runoff water from the drainage channel 3, and can act as a source of recharge to the groundwater below the dam.

Almost certain (5) – PFAS reported in the Oakey Creek Alluvium monitoring bore (MWO-Y-AL) and groundwater level data indicate groundwater mounding within the dam area

Minor (2) – possible accumulation of PFAS, as it migrates vertically through the unsaturated and saturated zones, within sediments of lower permeability

Localised impact due to limited head within the dam and low permeability of the underlying sediments, resulting in a limited contaminant extent (localised zone of equilibration)

R = 5 x 2 = 10

Dam 2 is filled with groundwater from bore GW55, which contains PFAS. The dam water contains PFAS which could act as an artificial recharge source to groundwater below the dam

Likely (4) – PFAS reported in the Oakey Creek Alluvium monitoring bore (MWO-Z-AL), the dam has been constructed below surface, and bore logs indicate coarse permeable alluvium sediments within the dam area

Minor (2) – Dam 2 is reported to contain elevated PFAS due to accumulation through refill with PFAS groundwater, this extraction reduces migration potential

Localised impact is considered due to extraction occurring immediately adjacent to Dam 2 (bore GW55)

R = 4 x 2 = 8

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Irrigation return water

Irrigation return flow is considered a possible diffuse source of PFAS within the irrigated lands, where deep drainage of irrigation water can have resulted in the migration of PFAS into the Oakey Creek Alluvium

Possible (3) – Irrigation at Dam 1 property and at RN107812 is conducted using groundwater containing PFAS

Minor (2) – The deep drainage can occur in higher permeable alluvium, which is moved readily into the groundwater and down gradient Accumulation of PFAS can occur in clay-rich low permeable irrigated lands

It is considered that irrigation return water could be contributing to the PFAS in groundwater, however, as there are additional sources (farm dams and surface water drainages) it is not clear, from available information, what contribution is as result of the more disperse contaminant source

R = 3 x 2 = 6

Flood inundation areas

Floodwater spilling over drains across the investigation area has the potential to deposit PFAS affected runoff onto adjacent soil and vegetation and potentially infiltrating to groundwater

Possible (3) – Oakey Creek Alluvium bores, within the mapped flooded areas, have reported PFAS concentrations within the groundwater. This indicates a possible correlation between the flooded areas and PFAS within the alluvium.

Insignificant (1) – The absence of PFAS in soil and groundwater in flood inundation areas, PFAS concentration distribution corresponding to groundwater flow, and recognised lower permeable alluvium (PFAS within low permeable alluvium) is considered to indicate that the contribution of flood inundation (as an artificial groundwater (PFAS impacted) recharge) PFAS source is limited

Based on flooding sediment dispersion, the coarse material is deposited on or immediately adjacent to the creek. Fines are transported further with the flood water, which due to self-sealing reduce permeability in the top soil and have smaller surface area (less PFAS concentration potential). Flood impact would be limited to immediate overbank flood areas

R = 3 x 1 = 3

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Landfill A former landfill is located off-Site, which may contain PFAS, was assessed to determine if the former landfill is a secondary source of PFAS

Likely (4) – A down-hydraulic gradient bore is reported to contain higher PFAS concentrations than the up-gradient bore relative to the former landfill

Minor (2) – The landfill has resulted in elevated PFAS concentrations in the closest downgradient bore but is not reported to have impacted on the other downgradient monitoring bore (MWO-O-AL), This indicates a limited zone of influence

The zone of impact around the former landfill is considered limited, possibly due to low permeable alluvium (resulting in accumulation in MWO-P-AL)

R = 4 x 2 = 8

Groundwater extraction

Drawdown cones resulting from groundwater extraction can facilitate PFAS migration and possible accumulation of PFAS, which can act as a secondary source

Likely (4) – Groundwater is currently used in the investigation area, groundwater levels at the RN107812 are identified to be depressurised indicating possible impacts of pumping and slow recharge

Minor (2) – PFAS contaminant migration can occur as a result of local altered groundwater flow patterns, including drawdown cones, the migration potential is (considering PFAS accumulates more readily in low permeable alluvium) restricted due to low permeable alluvium

The extent of the drawdown cone(s) is dependent on the aquifer hydraulic parameters, where higher permeability, recharge, and storage results in groundwater rebound which minimises the influence of extraction on PFAS migration potential Areas of low permeability, recharge, and storage will result in longer term drawdown cones, although of local extent (due to low permeability)

R = 4 x 2 = 8

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Bore construction Bores that were constructed prior to the current legislated standards can potentially facilitate the migration of PFAS into the underlying units

Likely (4) – Three existing bores assessed in the investigation areas, all had historical bore construction and can result in potential hydraulic connection of two different aquifers

Moderate (3) – PFAS migration can occur within man-made preferential flow pathways resulting in vertical migration which would typically not occur due to natural transition zone aquitards

It is considered that the potential for hydraulic connection and PFAS migration is limited, requiring several conditions to occur within a bore for this to occur, including: • perforation in casing in

both units • poor cement seal • limited (swelling) clay • thin or no transition

zone • extraction

R = 4 x 3 = 12

Induced flow Extraction results in depressurised aquifers (particularly the coal seams) such that induced flow from the alluvium to the underlying depressurised aquifers can occur

Possible (3) – This may have occurred at bore RN107812

Minor (2) – Groundwater extraction resulting in dewatering / depressurising of the underlying aquifers is required to produce steeper natural vertical gradients sufficient to facilitate migration through natural low permeable sediments / transition zone

It is considered that the potential for hydraulic connection and PFAS migration is limited unless: • high groundwater

extraction (above licensed / water balance volumes)

• thin or no transition zone

• fractures facilitating hydraulic connection

R = 3 x 2 = 6

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8.11.1 Great Artesian Basin vulnerability comment

The GAB groundwater resources vulnerability has been considered based on the consideration of the cumulative impacts of:

• groundwater extraction drawdown cones

• historical / multi-source bore construction

• induced flow.

It is considered that the risk of PFAS concentration migration from the Oakey Creek Alluvium to the Walloon Coal Measures is limited. An increase in vulnerability is reliant on a number of factors, which can include:

• a thin or more permeable transition zone between the Oakey Creek Alluvium and the Walloon Coal Measures

• the absence of Main Range Volcanics between the Oakey Creek Alluvium and the Walloon Coal Measures

• groundwater extraction resulting in steeper vertical gradients

• secondary alteration, such as faulting and fracturing, which can result in hydraulic connection between the Oakey Creek Alluvium and the Walloon Coal Measures

• elevated concentrations of PFAS which can readily migrate from source to the Walloon Coal Measures.

Consideration of these factors indicates that the GAB vulnerability is limited, as: • based on geological cross-sections (Appendix D) compiled from bore logs across the study area,

it is recognised that there are no areas within the IA where the Oakey Creek Alluvium and the Walloon Coal Measures are in direct (unconformable) contact. The cross-sections indicate the presence of the low permeable transition zone and/or Main Range Volcanics between the Oakey Creek Alluvium and Walloon Coal Measures over the IA

• Table 7.1 indicates transition zone thickness of 5–20 m

• limited high groundwater extraction, particularly in the low permeable (compared to the alluvium) Walloon Coal Measures

• even in bores that were constructed prior to the current legislated standards, the groundwater extracted from the bore is predominantly from the aquifer with the highest yield potential, which is Oakey Creek Alluvium, then the Main Range Volcanics, and then the Walloon Coal Measures, such that the extraction results in drawdown within the overlying units rather than the low permeable Walloon Coal Measures, reducing the downward vertical gradients

• little or no faulting or fracturing has been mapped or logged within the geology within the investigation area and the response of the clay-rich (more plastic) alluvium to faulting (see Section 8.7.8)

• the only traces of PFAS in groundwater were reported in two of the six Walloon Coal Measures bores

• higher PFAS concentration ‘hotspots’ are recognised to occur, due to accumulation, within zones of lower permeability alluvium. This reduces the potential for migration.

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9.0 Surface Water Interactions

9.1 Methodology The 2016 Stage 2C EI identified a data gap around the potential for the off-site transport of PFAS via stormwater flows. There is potential for surface water contamination where stormwater is in contact with contaminated areas on the Site. Hydrologic and hydraulic models were used to:

• inform the understanding of local hydrology and surface water runoff behaviour both on- and off-Site

• assess potential for interactions between surface water runoff and contaminated areas to determine how surface water runoff will contribute to contamination movement and transport.

The aim of the modelling was to identify surface water flow pathways and how surface water will contribute to contaminant movement. Existing hydrologic and hydraulic surface water models for the Site and Oakey region were reviewed to identify the key hydrologic and hydraulic features of the area, such as weirs, culverts, bridges etc. The models as used were:

• An XP-Rafts (XP-Solutions) hydrologic model of Oakey Creek prepared in 2014 as part of the Oakey Creek Flood study that was done in 2014

• A regional hydraulic model, developed as part of updating Toowoomba Regional Planning Scheme (TRC, 2014), was developed using a dynamically coupled 1D/2D MIKE FLOOD (MIKE Software, DHI)

• A hydraulic model specific to the Site and its surrounds was developed (AECOM, 2013) using the MIKE by DHI software package using a dynamically coupled 1D/2D MIKE FLOOD model.

The models were used to simulate flood flows, levels and extent of inundation for a range of storm events, including a 20% annual exceedance probability (AEP) (i.e. 1 in 5 year) event and 1% AEP (i.e. 1 in 100 year) event. These were used as design flood events to represent both small and large event scenarios under which local and regional flooding respectively, might be expected. The findings of the review are presented in Appendix I.

9.2 Results The surface water modelling results are presented in the following figures in Appendix I.

Figure I-1 Regional topography

Figure I-2 Regional 20% AEP

Figure I-3 Regional 1% AEP

Figure I-4 Local 20% AEP

Figure I-5 Local 1% AEP

Interpretation of the modelling results is presented in the subsections below.

9.2.1 Regional flooding In the context of this assessment, regional flooding has been considered as flooding arising from rainfall in largely upstream catchments (i.e. sunny day flooding). The Oakey Creek catchment upstream of the Site is seen (Figure I-1) to be larger in area than that of the Site catchment itself. The upper reaches of the Oakey Creek catchment display far steeper slopes than the catchment immediately surrounding the Site, with these steep areas representing the western slopes of the Great Dividing Range.

The assessment indicates that the Site is largely not affected by regional flood events associated with the 20% AEP event (Figure I-2). For areas closer to the Oakey Creek watercourse, the 20% AEP flood is not expected to result in inundation of the Oakey Creek floodplain along much of length of the creek, with the exception of some billabong/oxbow areas immediately south of the Site (Figure I-2).

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In contrast, Doctor Creek floodwaters are predicted to spill over onto the floodplain immediately north of the Site.

Predictions for the regional flooding arising from the 1% AEP event indicate that the lower reaches of Drain 1 (Western Drain) would expected to be inundated due to backwater effects arising from Oakey Creek, but the rest of the Site would not be impacted (refer to Figure I-3). Floodwaters in Doctor Creek are not predicted to extend as far as the Site. Regional flooding predictions for a 1% AEP flood would create overbank flooding in both Oakey Creek and Doctor Creek along the length of the creeks shown in Figure I-3.

9.2.2 Local flooding

Local flooding (flooding resulting from rainfall directly on the Site and its immediate surrounds), as predicted by hydraulic modelling, indicates that for a 20% AEP event, large areas of the site would be inundated to some extent (refer to Figure I-4). Extensive on-Site ponding indicates that the conveyance capacity of the Site’s formal drainage network is exceeded by the volume of runoff in this size event. Water depths up to 0.5 m are expected to occur in some locations. The arrows presented on Figure I-4 indicate the predicted direction of surface runoff, and the length of the arrow tails reflect predicted flow velocities.

As might be expected, local flooding for the 1% AEP event is predicted to be broader in areal extent and greater in depth than the 20% AEP event (refer to Figure 1-5). Flow arrows indicate that the flow patterns predicted for the 20% AEP event are broadly consistent with the flows predicted for the 1% AEP event.

9.3 Discussion PFAS transport mechanisms during a stormwater flow events can be considered as comprising:

• Potential transfer of PFAS from impacted soils or sediments into the stormwater. Under this mechanism, PFAS is transferred from the adsorbed phase on soils and into the aqueous phase (i.e. the stormwater itself). The PFAS containing water might then move off-Site flowing into the Oakey Creek or may be ponded, increasing the likelihood of the water infiltrating and allowing the PFAS to move toward the underlying groundwater systems.

• Potential transfer of PFAS from impacted soils or sediments into water infiltrating into the soil profile. Under this mechanism, PFAS is transferred from the adsorbed phase on soils and into the aqueous phase of water moving through the vadose (unsaturated) zone of soil overlying the groundwater systems. Over time, this mechanism would result in the downward and lateral movement of PFAS through the soil profile.

• Potential mobilisation and deposition of PFAS in soils or sediments as a consequence of stormwater flows. Under this mechanism, PFAS in sediments would be scoured or eroded by high velocity stormwater flows and would then be deposited in areas with slower flow velocities.

These mechanisms are not mutually exclusive and in a given storm event would be expected to contribute to varying degrees to the overall movement of PFAS contaminants.

The regional flood modelling predicts that virtually no inundation of areas away from the Oakey Creek alignment would occur during the 20% AEP event and therefore this event is considered unlikely to further contribute to the movement of PFAS contaminants. A greater extent of inundation is predicted by the regional flood modelling of the 1% AEP event, with significant areas predicted to be inundated to depths of less than 0.5 m apparently as a consequence of backwater effects arising from hydraulic structures associated with the railway line to the south of the Site. Backwater effects can be seen to extend to a limited degree onto the Site via the stormwater drainage network. In both of the modelled scenarios, it is considered unlikely that mobilisation of impacted sediments or transfer of PFAS from impacted soils to stormwater will occur to any meaningful degree.

The local flood modelling predicts that significant portions of the Site would be inundated during the 20% AEP event, as would large areas to the south-east, south and south-west of the Site. In addition to the formal drainage network on base, stormwater flows are predicted to flow off-Site to the south-west as overland flow across the agricultural field comprising the western portion of the Site and into neighbouring properties. Inundation depths of less than 0.5 m are predicted with relatively low flow

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velocities, consistent with backwater effects arising from the railway line and oxbow reaches associated with Oakey Creek.

Under this scenario, the gross export of sediment containing PFAS from the Site appears unlikely given the relatively low flow velocities. If PFAS containing soils were present at surface, there is potential for PFAS to be transferred into stormwater as it passes over the soil. Similarly, there is potential for stormwater infiltrating through PFAS containing soils to take up the PFAS but the degree of infiltration is expected to be low due to the relatively short duration of inundation. Similar observations can be drawn from the local flood modelling for the 1% AEP event where a broader extent of the site is expected to be inundated.

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10.0 Conceptual Site Model Update

10.1 Introduction 10.1.1 Purpose The purpose of the conceptual site model (CSM) is to provide an understanding of the nature and extent of PFAS impacts and the migration mechanisms, and the exposure pathways by which identified receptors may be exposed to PFAS from the Site, and to serve as a framework to assess risks to human health and ecological receptors. The CSM for the Investigation Area considered information available from reports listed in Section 3.1.4 and is based on the information presented in the PFC Conceptual Site Model, Army Aviation Centre Oakey (AECOM 2015b) and was refined during the 2016 Stage 2C EI.

In accordance with national environmental guidance (NEPM, 2013), the CSM has been further updated and refined based on data gathered during the 2017 Stage 2C EI, and reflects an improved understanding of the current extent of PFAS impacts and migration mechanisms and rates. The CSM provides a description of the current understanding of the status of PFAS source-pathway-receptor linkages.

The CSM refers to the detection area, which includes locations at which PFAS has been detected in soil/sediment, groundwater, surface water and biota samples above the limit of reporting.

Key additional information which has been drawn from this 2017 Stage 2C EI is summarised in Section 10.2, 10.3 and 10.4.

10.1.2 Definition of source-pathway-receptor linkage

In accordance with national guidance on assessment of contamination (NEPM, 2013), potential risks to receptors are evaluated based on three components:

• Source: A potentially hazardous substance that has been released into the environment

• Receptors: A person, ecosystem or ecological member potentially at risk of experiencing an adverse response following exposure to the source or derivatives of the source

• Pathway: A mechanism by which receptors can become exposed to the source or derivatives of the source.

If all three components are present at an exposure scenario, the source-pathway-receptor linkage is considered complete and a receptor is exposed to risk. However, if one of these three is missing there is no risk. These linkages will be examined in detail in the 2017 HHRA.

10.2 Summary of Sources of Contamination The main source areas of PFAS contamination on the Site are summarised below.

10.2.1 Primary source areas The following activities on or near the Site are considered to have resulted in PFAS impacts to soil, sediment, surface water and/or groundwater:

• Historical firefighting training at the former fire training ground

• Historical firefighting training at the former fire station and foam training area

• Firefighting training at the current AFFF storage and decanting area

• AFFF use associated with fuel spills at the former fuel compound and refuelling point in F1

• AFFF use associated with fuel spills at the hot fuel area concrete pads in A2

• Discharge of spent AFFF into recovery tanks at C1, S1 and A2

• AFFF was released during dispersed sporadic AFFF discharge events or responses to incidents.

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There is the potential for precursor compounds to be present in some areas in addition to the known PFAS. Some of these precursor compounds have the potential to transform into end products such as PFOS and PFOA.

The desktop study (AECOM 2015a) also identified three key time periods of PFAS potentially being released to the environment:

• Between 1977 and 2002/3 – point and diffuse depleting sources associated with the former fire training ground and former fire station and foam training area

• Between 1994 to the present – active sources associated with spent recovery AFFF recovery tanks

• Between 2004 to the present – active sources associated with the current fire training ground and AFFF storage area.

As reported in AECOM (2015a), based on anecdotal information relating to firefighting operations and training regimes, it was estimated that since approximately 1970 up to 1,273,400 L of AFFF concentrate (a mixture of 3M Lightwater and Ansulite – 3% and 6%) may have been discharged at the Site.

10.2.2 Secondary sources The following features on or near the Site are considered to potentially lead to PFAS impacts:

• Concrete infrastructure that has been in contact with AFFF

• Surface soil where AFFF was discharged to surface

• Unsaturated zone soil beneath potential source zones

• Sediment and soil along the drainage channel network

• Former trade waste system (including the former waste water treatment plant location to the south of the former landfill along Lorrimer Street)

• Sediment within Oakey Creek downstream of the discharge points of the drainage channels

• Farm dams

• Former landfill in Oakey

• An off-Site area potentially used for firefighting training by non-Defence personnel along the eastern portion of Lorrimer Street.

10.3 Migration Mechanism The following mechanisms are considered to have resulted in the migration of PFAS from the Site:

• Discharge or spilling of AFFF at the ground surface or leakage from infrastructure.

• Sorption of PFAS to soil in areas where AFFF were historically used.

• Localised dispersion of AFFF with the wind during historical application.

• Surface water runoff containing PFAS flowing into surface water drains and subsequent off-Site migration via drainage channels 1, 2 and 3, as well as sorbing into soils and sediments in the drains.

• PFAS in surface water in the drainage channels discharge in Oakey Creek, where PFAS migrates downstream. The confluence of Westbrook and Oakey Creeks has the potential to dilute PFAS impacts.

• Infiltration of PFAS in surface water from drains under ‘losing’ conditions, i.e. when water elevations in surface drains are higher than groundwater table.

• Infiltration of creek water to groundwater. Oakey Creek is a losing system with water migrating to underlying groundwater.

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• Infiltration of water from farm dams to groundwater and irrigation return flow.

• Vertical migration through bores that were constructed prior to the current legislated standards.

• Trade waste (influent on- and off-Site). Note that it has not yet been demonstrated that current wastewater treatment systems can effectively treat wastewater containing PFAS.

• Floodwater spilling over drains in some areas when capacity is exceeded and depositing PFAS affected runoff onto adjacent soil and vegetation and potentially infiltrating to groundwater as water levels fall.

• Leaching of PFAS from soil and sediments in drains and infiltration to groundwater in areas were AFFF were historically used.

• Leaching of PFAS from concrete structures and infiltration to groundwater.

• Leaching of PFAS in buried waste at the former landfill.

• Lateral and vertical migration of PFAS impacted groundwater under the influence of groundwater flow and PFAS dispersion. It is noted that historically, on- and off-Site groundwater pumping has potentially influenced contaminant migration in the aquifer as well as potentially creating secondary contamination of soil, sediment, surface water and groundwater where it is discharged and via irrigation return flow.

• Sorption of PFAS to soil below the groundwater table during migration with groundwater. Sorption to soil slows down the migration of PFAS but sorbed PFAS may continue to diffuse back into groundwater and act as a secondary source, if conditions are suitable.

• Transport of sediment containing PFAS in drainage channels and in Oakey Creek.

10.4 Exposure Pathways The following exposure pathways have been identified and will be discussed in detail in the 2017 HHRA and 2017 ERA:

• Human consumers of food grown using PFAS impacted surface water or groundwater for irrigation and/or consumption of aquatic biota from PFAS impacted surface water.

• Persons incidentally ingesting PFAS impacted soil.

• Persons in direct contact with PFAS impacted surface water during recreational activities.

• Persons drinking or using PFAS impacted abstracted groundwater from residential bores.

• Ecological receptors in direct contact with PFAS impacted soil, sediment and surface water.

10.5 Potential Receptors The following potential receptors have been identified and will be discussed in detail in the 2017 HHRA (AECOM 2017c) and 2017 ERA (AECOM 2017d):

• Residents within the detection area surrounding the Site who use abstracted groundwater. Consumers of aquatic biota and terrestrial biota (fruit and vegetables) exposed to PFAS impacted media (including soil, sediment and water).

• Recreational users of the land and waterways, within the detection area surrounding the Site.

• Commercial workers at the properties within the detection area surrounding the Site (considered to consist mostly of agricultural workers who may use groundwater during their work day, and potentially Council workers where groundwater is used by Council for irrigation).

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• Site receptors including:

- personnel who work at the Site. This is considered to encompass all personnel who undertake training or other operational works at the Site. However, for the purposes of the risk assessment, it will be assumed that relevant Site personnel use personal protective equipment during the application of foams and fire training exercises

- intrusive (i.e. involved in soil excavation) maintenance workers who may conduct infrequent maintenance activities at the Site (i.e. personnel who maintain the gardens and grassed areas at the Site)

- visitors to the Site who stay for a short period and are not frequently present at the Site (e.g. people who attend training or short-term contractors).

• The terrestrial ecosystem.

• The aquatic ecosystem.

It is noted that residents within the detection area may also be exposed via the activity specific pathways identified for other receptor groups (e.g. a resident in the detection area may also work at the Site or elsewhere in the detection area and/or undertake recreational activities in Oakey Creek). Pathways specific to recreational, commercial and Site receptors have been described separately because these receptors may reside outside the detection area.

10.6 Summary of Source-Pathway-Receptor Linkages A summary of linkages between sources, exposure pathways and receptors is presented in Table 10-1, below, and will be updated and discussed in detail in the 2017 HHRA and 2017 ERA (both in preparation).

Figure F49, Figure F50 and Figure F51 present graphical representations of the conceptual site model.

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Table 10-1 Refined conceptual site model

Primary source Secondary sources Transport mechanisms Exposure pathways

Exposed population characterisation /

receptor Linkages

On-Site areas where firefighting retardants / suppression foams (primarily AFFF) have been discharged or spilt to the environment. Off-Site areas where AFFF material has been discharged or spilt to the environment (e.g. the former landfill, the waste water treatment plant and areas used for firefighting training by non-Defence personnel). PFAS soaks into soil and / or infrastructure from where it can be eroded as sediment or leached by rainwater or flood water and migrate to groundwater, or dissolved in surface water runoff and potentially transported to affect other media.

PFAS in shallow soil (<2.0 m)

Water erosion Excavation and re-location of soil during construction activities

Human health: Incidental ingestion of soil on-Site

Commercial/industrial Complete*

Human health: Direct contact with soil on-Site

Commercial/industrial Complete*

Ecological On-Site ecosystem Complete

PFAS in groundwater

Groundwater transport in aquifer followed by extraction and use for recreational and domestic uses and irrigation

Human health: Direct ingestion of groundwater (on- and off-Site)

Commercial/industrial, residential

Incomplete

Human health: Incidental ingestion of groundwater (on- and off-Site)


Complete

Human health: Direct contact of groundwater (on- and off-Site)


Complete

PFAS in surface water

Surface water transport; in drains and on ground surface on and off-Site. Transport into Oakey Creek

Human health: Incidental ingestion of surface water (on- and off-Site)

Recreational Complete

Human health: Direct contact with surface water (on- and off-Site)

Recreational, ecosystem

Complete

Ecological (on- and off-Site) Ecosystem (on- and off-Site)

Complete

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receptor Linkages

Infiltration to groundwater followed by extraction and use for drinking water, recreational uses and irrigation.

Human health: Direct contact with groundwater (on- and off-Site).


Complete

PFAS in sediment Dispersion via surface water or via drain maintenance activities.

Human health: Incidental ingestion of sediment on-Site.

Commercial/industrial Complete

Human health: Direct contact of sediment on-Site.

Commercial/industrial Complete

Ecological (on- and off-Site). Ecosystem (on- and off-Site)

Complete

Human health: Incidental ingestion of sediment off-Site, impacted by surface water or groundwater (extracted via bore).

Residential Complete

Human health: Direct contact of sediment on- and off-Site impacted by groundwater (extracted via bore) or surface water


Complete

On-Site areas where firefighting retardants / suppression foams (primarily AFFF) have been discharged or spilt to the environment.

PFAS in pore water in creek sediments

Surface water transport off-Site into Oakey Creek.

Human health: Incidental ingestion of surface water (on- and off-Site).


Complete

Human health: Direct contact with surface water (on- and off-Site)

Recreational, ecosystem

Complete

Ecological (on- and off-Site) Ecosystem (on- and off-Site)

Complete

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receptor Linkages

Terrestrial biota Harvesting Human health: Ingestion of terrestrial organisms (including fruit and vegetables, chicken eggs)

Residential Complete


Complete

Aquatic biota Harvesting Human health: Ingestion of aquatic organisms (including fish and yabbies, shrimps and mussels)

Residential, recreational

Complete


Complete

Note: * There are no screening guidelines available for ingestion/direct contact for PFAS in soil pathways. These potential exposure pathways have been assessed in the HHRA (AECOM 2017c in preparation).

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11.0 Groundwater Modelling AGE conducted an update of the previous modelling (AGE, 2016) in line with feedback from internal and external stakeholders to simulate the PFOS plume development, and to predict future potential fate of the plume. PFOS was modelled as this chemical typically has the highest reported concentrations in the Investigation Area.

A model plan was compiled and agreed with the project’s Technical Advisor and the DNRM.

A technical groundwater modelling report, documenting the groundwater model objectives, available data sources, hydrogeological conceptual model, numerical model design, model assumptions, calibration process, and predictive results, is included in Appendix J.

11.1 Modelling Update The update of the groundwater flow and solute transport model, constructed in 2016, was conducted to better understand and simulate the movement of PFOS through the groundwater system.

The update of the model addressed suggestions from the internal project review process and from external feedback from State Government agencies, and included the following scope of works:

• A technical review of the 2016 Stage 2C model conceptualisation, model construction, calibration and simulations, and the approach used for solute transport.

• An update of 2016 Stage 2C groundwater model conceptualisation using new data compiled during the 2017 Stage 2C EI.

• The refinement of the groundwater model structure, calibration, and predictions.

• Addressing previous model limitations relating to:

- stream recharge (leakage rates)

- layer hydraulic properties

- solute transport

- calibration

- chemistry simulations.

11.2 2016 Model Limitations All models have limitations imposed by the fact that they simplify the complex real world. The previous 2016 modelling identified the following modelling limitations:

• The heterogeneity in the Oakey Creek Alluvium could provide, due to variability in the hydraulic parameters, more representative plume extent and migration.

• Potential PFAS migration through flooding and then infiltration was not simulated.

• The potential for irrigation return flow to provide a diffuse PFAS source was not simulated.

• Potential PFAS contaminant migration from the former landfill was not simulated.

• The source locations and distribution of contaminant from the total contaminant load were not fully understood.

• The basement layer of the model (representing both Walloon Coal Measures and Main Range Volcanics) was recognised to modify the concentration of the contaminants entering this model layer.

The update of the 2016 model, using the adopted approach, aimed at addressing these limitations.

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11.3 Modelling Approach The following approach to the modelling update was undertaken:

• Change the software from MODFLOW-USG to MODFLOW-SURFACT

• Update the model structure and extent

• Recalibrate this ‘reset’ model to uniform parameter distribution for the flow model

• Back calibrate the source inputs and potential locations using the ‘reset’ model.

This approach to calibrate the model in a stepwise manner and introduce detail as the calibration process progressed ensured the potential non-uniqueness was adequately addressed.

11.3.1 Software change MODFLOW-SURFACT was chosen to undertake the 2017 modelling to replace MODFLOW-USG for the following reasons:

• Ease for forensic review by the Technical Advisor and third parties

• Consistency with software used for corresponding studies at other alluvium systems

• It is industry standard MODFLOW software

• The smaller model extent allows for a manageable amount of model cells in the model, while still achieving cell sizes that meet stability criteria for the transport model.

Version 4 of MODFLOW-SURFACT was used in the model development and calibration.

11.3.2 Reset Model

The Reset Model includes for the recalibration of uniform aquifer parameters (homogeneous within each geological unit) including porosity for the transport model.

Historic and the latest observations of groundwater level and PFAS concentrations in the groundwater compiled by AECOM, were used during the calibration. The contaminant source locations included in the Reset Model are consistent with the locations employed in the 2016 model. The rate of PFOS concentration entering the groundwater has, however, been reduced to reflect the PFAS likely to be retained within the unsaturated zone/soils.

The results of the Reset Model were used as a starting point given the updates to the 2017 model.

11.3.3 Back calibration

Back calibration was conducted to address uncertainty with PFAS source locations and contaminant loads, which have migrated into the groundwater resources.

Calibration of inflow rates and manual changes to the source locations were undertaken to improve the match between the recorded PFAS concentrations in groundwater and the model predicted concentrations.

In order to address non-unique solutions, the approach was simplified. The simplification included that once a location becomes ‘active’ within the model then the source rates are considered constant throughout the simulation. This assumption is based on the observation that a high percentage of PFAS is held up within the soil profile and available to continue to feed down into the groundwater system.

11.4 Conceptualisation The groundwater conceptual model, presented in the 2016 model (AGE, 2016), remains largely unchanged for the 2017 model development. Some aspects of the conceptualisation (and its representation in the 2017 groundwater model) have been refined in response to the Technical Advisor and State Government agency feedback.

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Additional field data from drilling of bores during the 2017 Stage 2C EI have been added to the conceptualisation of groundwater resources and has been used to modify the model layer structure. This ensures the best match to the available data.

Additional data included in the refinement of the groundwater conceptual model include site-specific aquifer parameters, additional sampling locations and groundwater chemistry.

The main conceptual aspects that were updated included:

• more detail in the representation of the bedrock in the model (Walloons Coal Measures and Main Range Volcanics), specifically adding more model layers to provide practical unit thickness for the transport simulations

• secondary contaminant source locations

• ongoing PFAS source contribution (rate of contaminants into groundwater)

• recharge and discharge mechanisms.

11.4.1 Conceptual water balance

The potential in and outflows, considered for the groundwater conceptualisation, are compiled as components of the water balance. These components were used to compile an overall water balance. Focusing on the Oakey Creek Alluvium, Figure 3.2 in Appendix J provides a graphical representation of the in and outflows and the interaction with the underlying Main Range Volcanics and Walloon Coal Measures.

11.5 Model Updates 11.5.1 Model grid

With the change of software to MODFLOW-SURFACT, the model grid was changed to an orthogonal grid. The model extent was also reduced to an area more relevant to the expected contaminant movement.

The model extent includes 234 rows and 241 columns with a variable cell size to allow for the simulation of possible PFAS migration. The cell size varies from 30 x 30 m to 300 x 300 m, with some cells having dimensions of 30 x 300 m.

The model cell sizes and grid were developed considering solute transport simulation requirements, including longitudinal dispersivities, advection, and diffusion.

11.5.2 Model boundaries

As the refined model extent does not include the natural groundwater divides offered by the topographical catchment extents, the model extent boundaries were considered as continuing aquifer(s). Thus in order for the model domain to interact with these boundaries, these boundaries were simulated as general head boundaries, which was used to simulated the cross boundary flows. The reference water level assigned to the general head boundaries was determined through either groundwater levels in the alluvium, or based on the topography water level relationship in the Main Range Volcanics and Walloon Coal Measures.

Both the river (RIV) boundary condition and stream (STR) boundary conditions are used to represent the surface water interaction. Groundwater interaction with Oakey Creek, Westbrook Creek, and Gowrie Creek was modelled using information on the level of the stream bed, the depth of water in the stream, and the stream flow. The stream bed conductance was calculated from stream width, length, riverbed thickness, and the vertical hydraulic conductivity of the riverbed material.

Recharge was distributed to the model domain based on the surface geology.

11.5.3 Model structure

The update in the model structure (layers) was conducted due to:

• a change of modelling code (MODFLOW-USG to MODFLOW-SURFACT) and the associated change of the model mesh from Voronoi to orthogonal

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• additional data from drilling providing additional information regarding thicknesses of modelled units

• the requirement for more detailed modelling of the hydraulic connection between Oakey Creek Alluvium and underlying bedrock units (Main Range Volcanics and Walloon Coal Measures).

11.5.4 Source locations

The model represents the addition of PFAS to the groundwater regime by injecting a volume of water containing a concentration of the contaminant.

These source locations, as discussed in Section 8.2, were used in the back calibration and to address the issues identified in the 2016 model regarding secondary sources of contaminants. These are shown in Figure 4.7 in Appendix J.

11.5.5 Model time steps

The stress period length of the numerical model was set to three months. This interval was used to capture the seasonal variability in rainfall recharge, surface water stream flow and heads, and metered pumping.

Adaptive time stepping was used for the groundwater flow and solute transport modelling. The minimum time step was 0.003 days and the maximum time step was 24.4 days.

11.6 Model Calibration The change of modelling code to MODFLOW-SURFACT and the split of the basement geologies into more layers necessitated the need to recalibrate the Reset Model. The Reset Model was calibrated for both flow and transport using the previously assumed (AGE, 2016) source locations and contributions.

11.6.1 Observation data sets

The observation datasets of water level elevations and PFOS concentrations were updated with the most recent data available.

11.6.2 Reset model calibration

The Reset Model calibration involved changes to both aquifer hydraulic parameters and porosity to provide a new baseline for the calibration of contaminant source(s) loads and locations as shown in Table 11-1. Table 11-1 Estimated PFAS contaminant load in groundwater

Contaminant Estimated total load (kg) Estimated total in groundwater (kg)

PFOS 3,700 378

The contaminant load at each source was reduced to better represent the load in the groundwater aquifers.

11.6.2.1 Aquifer parameters The calibrated hydraulic properties for the revised model layers within the Reset Model are included in Table 11-2.

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Table 11-2 Reset Model calibrated aquifer parameters

Model layer Lithology

Horizontal hydraulic

cond. (m/day)

Vertical hydraulic

cond. (m/day)

Specific yield (%)

Specific storage

(m-1)

1 Surficial sediments of the Oakey Creek Alluvium (topsoil and clays within alluvium)

1.500 1.09037 1.00 0.00006

1, 2, 3, 4 Colluvium zone along the foothills of the Main Range Volcanics

0.750 0.00748 15.00 0.00012

1 Weathered topsoil and clayey regolith covering the Walloon Coal Measures

1.000 0.00992 2.00 0.00011

2 Upper Oakey Creek Alluvium (silty/clayey sands) 3.753 0.28701 3.33 0.00004

2, 3 Lower Oakey Creek alluvium (silty/clayey/sandy gravels) 14.544 1.02050 15.00 0.00003

3, 4 Transition zone (clay zone between Oakey Creek Alluvium and bedrock)

0.142 0.00492 1.00 0.00008

2, 3, 4, 5 Main Range Volcanics (basalt) 1.589 0.10943 10.00 0.00007

2, 3, 4, 5, 6

Walloon Coal Measures (sandstone/siltstone) 0.005 0.00011 2.50 0.00009

7 Walloon Coal Measures (coal and interburden) 0.010 0.00073 0.93 0.00004

8 Walloon Coal Measures (sandstone/siltstone) 0.005 0.00018 0.50 0.00006

The range of calibrated specific storage values are consistent for semi-confined to confined aquifers, and are comparable to literature values for similar environments.

11.6.2.2 Recharge

The recharge zones were based on outcropping geology. Table 11-3 summarises the average recharge rates in the transient calibration model. Table 11-3 Calibrated recharge rates

Recharge zone Transient model (1970 to 2017)

mm/year (on average) % annual rainfall*

Oakey Creek Alluvium 7.90 1.25

Colluvium zone along the foothills of the Main Range Volcanics 7.02 1.11

Outcrop areas of the Main Range Volcanics 7.02 1.11

Weathered topsoil and clayey regolith covering the Walloon Coal Measures 7.02 1.11

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For the alluvium, the rate of recharge was equivalent to an average of 1.25% of annual rainfall (i.e. 7.9 mm/year), which reflects the low level of rainfall recharge experienced through the surficial clay-rich sediments.

11.6.2.3 Stream bed conductance

The parameters used to calculate the conductance of the stream bed for individual streams are presented in Table 11-4. Table 11-4 Calibrated stream bed conductance

Stream/river Stream width (m)

Stream bed thickness (m)

Stream bed vertical hydraulic

conductivity (m/day) Oakey Creek – upstream 12 10 0.0031

Oakey Creek – downstream 15 10 0.0011

Gowrie Creek - upstream 12 5 0.00052

Gowrie Creek – downstream 12 5 0.0005

Westbrook Creek 10 5 0.0011

The calibrated stream bed vertical hydraulic conductivity value varied between 0.0005 m/day to 0.0011 m/day for the various streams. This rate of stream bed vertical hydraulic conductivity is low but is consistent with the conceptualisation that recharge from the streams into the groundwater system is low because of silty beds and ephemeral nature of the Oakey Creek.

11.6.2.4 Groundwater heads The modelled groundwater levels (also referred to as groundwater heads) were compared to observed groundwater heads and gradients.

The model reported a root mean square (RMS) error for the transient model of 1.6 m and a scaled root mean square (SRMS) error of 5.5%. The SRMS error is well within the recommended target of 10 % and is close to achieving the desired criterion of 5.0% SRMS.

Overall, the model simulates the dynamics of the alluvial system and the recharge events such that the transient model replicates:

• the gradual decline in groundwater water levels during the 2000s in response to below average rainfall and subsequent increases in groundwater pumping

• the response to large groundwater recharge events in 2010/2011

• the response to variable metered and unmetered groundwater pumping throughout the Oakey Creek Alluvium.

11.6.2.5 Transient water balance

The largest input components of the water budget are rainfall recharge and cross-boundary flow through the general head boundary condition. The largest output component of the budget is groundwater pumping followed by down valley flow through the general head boundary.

Table 11-5 shows individual components of the transient model water budget averaged over the calibration period (1970–2017).

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Table 11-5 Transient model calibration water budget

Parameter Input (ML/year) Output (ML/year) In – Out (ML/year)

Rainfall recharge 1170.64 - 1170.64

Stream leakage 13.11 - 13.11

Stream baseflow - 0.37 -0.37

Shallow surface drainage - 4.09 -4.09

General head boundary 578.81 681.88 -106.08

Pumping bores 0.001 1915.94 -1915.94

Total 1759.56 2602.28 -842.73

The mass balance error for each time step throughout the transient calibration period averaged 0.025% and cumulatively the error was 0.002%, indicating good accuracy of the numerical solution and overall stability of the model.

11.6.2.6 Parameter sensitivities The relative sensitivities for the parameters involved in the reset calibration process were assessed. The hydraulic conductivity, recharge, and porosity of the Oakey Creek Alluvium indicate the highest sensitivities. There are a number of parameters that do not show a significant sensitivity to the observations data sets, and these include the vertical hydraulic conductivity, and the stream bed conductivity.

11.6.2.7 Back calibration regarding contaminant sources The back calibration involved the calibration of the source input locations and rates to help define what historically has occurred.

To minimise non-uniqueness regarding the current distribution of contaminants, several assumptions were applied during the calibration design, including:

• assigning a constant rate of influx for when a source location is active within the simulation

• using broad zones for linear features (such as rivers) and not dissecting these in response to observations, even though the contribution along such a feature would be expected to be quite variable.

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The source locations with the calibrated total load entering the model for the calibration period (1970–2017) are summarised in Table 11-6. Table 11-6 Source locations and calibrated PFOS loads

Description

Approximate Introduction

Date for Modelling Purposes

Injection rate (m3/day)

Concentration (kg/m3)

PFOS load (kg)

Current fire training facility 1/01/2002 8.77269E-06 4.060 0.202

Former fire station and foam training area

31/12/1976 8.17521E-04 4.060 49.091

Former fire training ground 31/12/1976 9.24363E-05 4.060 5.551

Spent AFFF recovery UST 1/01/1994 4.86355E-05 4.060 1.694



Hot refuel area 1/01/1994 9.80158E-05 4.060 3.415

Former fuel compound, hot refuelling point

31/12/1976 1.67374E-04 4.060 10.051

Current AFFF storage, decanting areas

1/01/2002 6.39042E-05 4.060 1.468

Potential off-Site area historically used by non-Defence personnel for firefighting training

1/01/1994 9.98591E-06 4.060 0.348

Wastewater treatment plant 1/01/1994 6.59540E-05 4.060 2.298

AACO water collection tanks 1/01/1994 5.32964E-05 4.060 1.857

Drain 01 – north – above DRN01-DRN02 junction

31/12/1976 1.89348E-05 4.060 1.137

Drain 01 – south – below DRN01-DRN02 junction

31/12/1976 8.00000E-05 4.060 4.804

Drain 02 31/12/1976 3.98476E-05 4.060 2.393

Drain 03 31/12/1976 2.96922E-04 4.060 17.830

Drain 04 31/12/1976 5.30000E-04 0.001 0.008

Oakey Creek – upstream 31/12/1976 8.30000E-04 4.060 49.840

Oakey Creek – downstream 31/12/1976 1.69026E-04 0.100 0.250

Farm Dam 2 1/01/1994 7.63224E-05 0.000004 0.000

Former landfill 1/01/1994 1.72373E-04 4.060 6.005

Farm Dam 1 31/12/1976 5.48819E-04 4.060 32.956

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The calibrated total load of input of PFOS to the model during the calibration period (1970–2017) is 205 kg. During the calibration period it is predicted that approximately 6 kg are removed through pumping. This calibrated load differs from the initial estimate of around 378 kg (Table 11-1), mostly because it used the 2016 detection area as a basis, and this has since been modified in 2017.

The model reported an RMS error for the transient model of 17.2 µg/L and a SRMS of 5.85 %. The SRMS error is within the recommended target of 10 % and is close to achieving the desired criterion of 5.0% SRMS.

11.6.2.8 Model simulations Appendix J presents the modelled plume extent at the end of the calibration period for model layers 1, 3, 5 and 7. The majority of the observed PFOS concentrations are assigned to the model Lower Oakey Creek Alluvium (Layer 3) and shown on the calibrated plume extents.

It is noted that:

• Uncertainty around groundwater pumping rates may be impacting on the replication of the plume migration, where it could be driven by pumping. The variability in the spatial distribution and pumping rates is largely unknown.

• Detections immediately west of the former landfill are matched through the inclusion of this source in the model.

• The Walloon Coal Measures (Layer 7) does not indicate any PFOS contaminant migration during the calibration period. The upper weathered layer of the Walloon Coal Measures does show contaminant entering from the overlying model layers, though it remains in the layers overlying the coal. It is noted that there is limited contaminant detection data available for the Walloon Coal Measures, and this sparse distribution (mainly non-detections) influences the calibration software (PEST).

• The influence of flooding events on the spread of contaminants is considered possible with out of bank flows and runoff occurring in different directions. This was not included in the Reset Model calibration and will be included in the heterogeneity model calibration (Section 11.8), which is more suited to address this diffuse loading. This additional modelling will be compiled for input into the OMP.

11.6.3 Sensitivity analysis Sensitivity analysis was carried out on the source rates to examine the influence of these for the calibration results. The rates were increased and decreased by 5 times to see if the change resulted in significant variation in the plume extents.

Statistically the increase and decrease in the rates does impact on the level of calibration. Table 11-7 summarises the RMS and SRMS for the simulations. Table 11-7 Sensitivity analysis

Measure Baseline Increased rate (5x) Decreased rate (5x)

RMS 17.2 85.968 19.324

SRMS 5.85 29.241 6.573

11.7 Model Projections The ‘base case’ scenario is undertaken using the similar assumptions and inputs to the 2016 model, with the exception of removing seasonality in the input data. This was necessary because the stress periods assigned to the future predictive phase of the model simulation uses a period of five years, therefore seasonality could not be included. This was done to improve the model’s run times.

11.7.1 Base case scenario

The base case scenario was set up to simulate a period from 2017 to 2115 (approximately 100 years into the future).

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The transient seasonal data, used in the 2016 model, were adopted (using averages) for this scenario. The model prediction figures are included in Appendix J.

The plume extent after 100 years, assuming no remediation (do nothing), shows migration approximately 6 km to the west with the groundwater flow. This is considered conservative as it assumes continued PFAS sources for the 100 year period (i.e. no source diminishment over time).

It should be noted that these predictions are preliminary as the heterogeneity calibration can change the shape and extent of the plume. The results do, however, provide an indication of future plume movement.

11.8 Heterogeneity Calibration Calibration to simulate the heterogeneity within the Oakey Creek Alluvium is ongoing at the date of this report. This calibration process utilises the results of the back calibration of source locations and loads.

The heterogeneity calibrated model will allow for a more accurate simulation and prediction of PFAS migration. These predictions will be included in the OMP, allowing for the identification of the optimum groundwater monitoring points.

11.9 Model Confidence Classification The model simulates complex interactions between groundwater flow, streamflow, groundwater pumping, rainfall recharge, and solute transport in high detail, such that could be considered a Class 3 predictive model.

However, the model must be classified as Class 2 (in its current state) for a range of reasons, including:

• uncertainty regarding PFAS concentrations and sources

• uncertainty regarding groundwater extraction

• calibration verification

• heterogeneity is missing.

The Class 2 confidence level is suitable for predicting groundwater responses and the evaluation and management of potentially high-risk impacts. It is envisaged that with further model refinement through heterogeneity calibration, the model will address these uncertainties and move towards a confidence level of Class 3 overall.

11.10 Reset Model Comments The Reset Model has:

• adopted homogeneous distributions of parameters

• numerous assumptions around pumping, contaminant sources and timing

• attempted to determine the load of PFOS in the groundwater regime.

Despite this simplification of the complex real world, the model in its current form sufficiently meets industry standard model calibration criteria.

The modelling is an integral part of the heterogeneous calibration, thus it is likely that several aquifer parameters, corresponding water budgets, and calibration statistics will be subject to change in a subsequent update of the model. Numerical groundwater modelling is an iterative process, and the outputs of the Reset Model is subject to change as the heterogeneous calibration is completed and additional outputs are generated from the model.

The Reset Model does not simulate the recharge and potential contaminant movement that can be associated with significant flood events. This means that predicted water levels post 2011 are not well matched.

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Uncertainty analysis has not been undertaken on the Reset Model or the back calibration to sources model, rather a parameter sensitivity analysis was conducted to evaluate the effects of changes to individual model parameters. The results of an uncertainty analysis will be more pertinent for the heterogeneous model, as the results will allow for more robust model predictions.

The back calibration to sources was conducted to understand the potential source locations and contaminant supply rates, however, the results of this calibration are by no means definite. There remains uncertainty regarding the source locations and there is some detection of PFAS that have not been well matched in the Reset Model. It is considered that the heterogeneous calibration can assist in better simulating spatial PFOS concentrations; however, it is considered that it may not be possible to address all the detections observed in the groundwater. This is largely because the source of several PFAS detections is not immediately identifiable.

Irrigation return flow was a potential mechanism for contaminant spread identified in the 2016 assessment. After further assessment, it was considered that this mechanism is unlikely to be a significant contributor to the plume movement in comparison to more orthodox migration (i.e. through advective transport with groundwater flow).

In simulating the source contaminant entering the groundwater system it has been assumed that the source entering the groundwater occurs at a constant rate. In reality this would not be the case, however, there is insufficient data currently to support changing this assumption.

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12.0 Conclusions

12.1 Data Gap Evaluation The 2017 Stage 2C EI has acquired an extensive dataset for soil, groundwater, sediment and surface water quality and included the laboratory analysis of 870 samples. The key conclusions of the report, in the context of the data gap objectives, are presented in Table 12-1 below. The table also comments on the adequacy of the information obtained to address each data gap.

12.2 Refinement of the Conceptual Site Model The results of the 2017 Stage 2C EI allowed for the following parameters of the CSM to be refined:

• Transport mechanisms have been characterised by sampling

• Exposure pathways have had data collected for use in the risk assessments

• Exposed populations have had data collected for use in the risk assessments.

12.3 Generate Input Data for the 2017 HHRA and 2017 ERA The following work was conducted to generate additional data for the 2017 HHRA and 2017 ERA:

• Collection of soil and groundwater samples within the Investigation Area

• Collection of water and sediment samples from locations in Doctor Creek, Oakey Creek and Westbrook Creek

• Terrestrial and aquatic biota sampling and habitat surveys.

The additional data and refinement of the CSM will allow the development of the 2017 HHRA and 2017 ERA, which will be reported under separate cover. The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report. The groundwater zones are material to the HHRA and will be redefined in the HHRA report.

12.4 Ongoing Monitoring Plan The data collected as part of 2015 Stage 2B, 2016 Stage 2C, and the 2017 Stage 2C EI will be used to develop an OMP, which will cover both the environmental monitoring program and the residential sampling program. The OMP will be implemented to:

• capture seasonal and temporal variations in groundwater and surface water PFAS concentrations and conditions (drains and creeks)

• provide early warning indicators for migration of contaminated groundwater

• monitor water levels and aquifer specific conditions.

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Table 12-1 Data gap evaluation


Refinement of Groundwater Zones 1 and 2 Information has been obtained to confirm the findings of the Stage 2C 2016 EI. The data collected in this 2017 Stage 2C EI will be used to refine the groundwater zones in the HHRA report, as they are material to the HHRA. The PFAS data set from the existing and newly installed monitoring wells is suitable to allow updating of exposure point concentrations in the 2017 HHRA. Groundwater monitoring results have refined the understanding of the current extent of contamination in the Oakey Creek Alluvium, Main Range Volcanics and Walloon Coal Measures aquifers. Evaluation of the groundwater data trends over time suggests evidence for stable PFAS concentrations in groundwater on-Site and areas adjacent to the Site. There is limited evidence for a minor increasing trend in PFAS concentrations in down-hydraulic gradient off-Site bores which is attributed to the migration of PFAS within groundwater towards the west.

Characterisation of the full PFAS suite All soil, water and sediment samples were analysed for an extended PFAS suite of 28 compounds. The dataset shows there are 12 main PFAS present in the different media; PFOS, PFHxS, PFOA, PFHxA, PFPeS, PFBS, PFHpS, PFPeA, PFHpA, PFBA, 8:2 FTS and 6:2 FTS. The dominant contaminants present were PFHxS and PFOS. The investigation has characterised the distribution of these compounds in different media across the Investigation Area.

Acquire data to inform the OMP sampling requirements

The results of this investigation, together with the historical results, will be used to develop a suitable ongoing monitoring program for the Site. The combined dataset is adequate to allow this program to be developed.

Characterisation of non-PFAS contaminants of potential concern on-Site

The investigation has included characterisation of soil, sediment, groundwater and surface water for non-PFAS contaminants on-Site. No large areas of non-PFAS contaminants have been identified. Localised petroleum hydrocarbons impacts are present in groundwater in one area within the Site. The extent of the hydrocarbon contamination is considered to be adequately understood and does not extend beyond the Site boundary. Localised areas of elevated chromium and nickel concentrations in groundwater on-Site have been identified and do not extend beyond the Site boundary.

Potential risks to the Great Artesian Basin (GAB): • Investigate potential connections across

multiple aquifers via bores that were constructed prior to current legislated standards

Information has been obtained to characterise groundwater in underlying aquifer units and allow assessment of the potential risks to the Great Artesian Basin. The dataset is considered suitable to assess the concepts and refine the conceptual site model, which is used as the basis of the groundwater model refinement. The GAB’s vulnerability to PFAS concentration migration, from the Oakey Creek Alluvium aquifer to the Walloon Coal Measures aquifer (an aquifer of the Great Artesian Basin), is recognised to be limited, which

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• Investigate registered bores RN107812, RN87439, and RN87369

• Investigate the risk that unregistered bores pose to the GAB and any remediation or mitigation measures

• Investigate the risk to the GAB from both infiltration and via bores acting as conduits, including rectification options

is reflected in the Groundwater Model water balance. The level of risk to the Great Artesian Basin is influenced by: • a thin or permeable transition zone • the limited areas within the Investigation Area where Oakey Creek Alluvium and Walloon Coal

Measures are unconformably in contact and Main Range Volcanics is not present • groundwater extraction resulting in steeper vertical gradients • secondary alteration, such as faulting and fracturing • elevated concentrations of PFAS. Bores that could create a connection between aquifers have been assessed, based on the field evaluations of the three licensed bores (RN107812, RN87439, and RN87369) within the Investigation Area. It is considered that the potential for hydraulic connection and PFAS migration from the Oakey Creek Alluvium aquifer to the underlying Walloon Coal Measures within such bores is limited, requiring several conditions to occur, including: • perforation in casing in both units • poor cement seal • thin or no transition zone • extraction of groundwater from the bore. The vulnerability of the GAB as a result of groundwater extraction was assessed through pump tests. Aquifer testing assessments indicate that the vulnerability of the GAB is related to: • transmissivity of the units intersected and screened within the bores, where the most transmissive

unit provides the majority of groundwater into the bore (reducing mixing/blending potential) • the extraction schedule and volumes and recovery periods, which influence the extent and duration of

drawdown cones, and vertical groundwater movement potential. Investigate implications of extraction of potentially contaminated overland flow water and/or surface water by entitlement holders

An assessment of surface water storage and irrigation water has been conducted. Dams are considered to have the potential to act as localised point sources of enhanced recharge to the underlying aquifers with PFAS impacted water.

Investigate potential secondary source areas including irrigation return flow, landfill inputs and flooding along road side areas

Adequate information was collected to allow investigation of these potential secondary source areas. Evaluation of irrigation return water, the former landfill and flood inundation areas has been undertaken. It is considered that irrigation return water could be contributing to the PFAS in groundwater. However, as seepage of PFAS impacted surface water to the underlying aquifer from farm dams and drains occurs in the Investigation Area, it is not clear what contribution is as result of the more dispersed irrigation return

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water source. Based on groundwater analytical results, the former landfill is considered to be a secondary source of PFAS, based on groundwater results. The zone of impact around the former landfill is considered limited, possibly due to the lower permeability of the Oakey Creek Alluvium aquifer in this area. Available groundwater data indicate a possible correlation between the areas that have been historically flooded and the extent of PFAS within the Oakey Creek Alluvium. However, due to sediment dispersion during flooding, the coarse material is inferred to be deposited on or immediately adjacent to the Oakey Creek Alluvium and fines are transported further with the flood water. Variability in the permeability of the surficial soils may affect the rate of PFAS infiltration to underlying aquifers.

Investigate water interactions (surface water, groundwater, sediment and soil interactions)

The 2017 Stage 2C EI has investigated the migration of PFAS following interaction of surface water with sediment, surficial soils and groundwater. The results of the surface water modelling have been used to assess possible PFAS migration in surface water during flood events (sourced from PFAS in soil and sediment) to on-Site and off-Site areas. Regional and local flood modelling results suggest it is unlikely that PFAS impacted sediments will be mobilised from the Site. Under the local flood modelling scenario, PFAS has the potential to be transferred from impacted surface soils to stormwater as it passes over the soil. Surface water sources and water uses have been considered, in conjunction with sediment, to evaluate the potential for PFAS sources to alter groundwater resources.

Drainage channel characterisation • Soil sampling in drains on- and off-Site • Influence of drains on PFAS migration • Infiltration tests of drain beds • Investigate temporal variability of PFAS

in surface water and temporal variability of flow

Investigation of the main drainage channels flowing off the Site included sampling of sediment and soil and leaching tests. PFAS is present in sediment and in underlying soil along drainage channels 1, 2 and 3. Infiltration testing of drain beds has been completed and vertical permeability data have been considered in the assessment of potential for PFAS migration from the drains to the underlying Oakey Creek Alluvium aquifer. Extensive surface water sampling has been undertaken in all creeks proximal to the site. Adequate characterisation data have been collected from Oakey Creek to infer the current distribution of contamination along the creek. The highest PFAS concentrations were detected at sampling locations downstream of the outfalls of drainage channels 1, 2 and 3. Sampling of Doctor Creek located to the northwest of the Site suggests there is no current hydraulic connection with on-Site sources. Temporal variability of surface water quality in Oakey Creek was evaluated. However, no distinct trends were identified in the three years of data available.

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Source area characterisation • Ensure the nature and extent of existing

contamination on-Site is properly characterised for all relevant media

• Soil sampling on-Site where PFAS have been previously identified or in areas not yet tested

• Ensure all potential sources of PFAS on-Site are identified and prioritised in terms of PFAS mass load and potential mobility to groundwater, surface water and biota

An investigation of previously identified potential PFAS source areas was conducted. Interpretation of the new and historical dataset has improved the understanding of the distribution of PFAS contaminants in the on-Site soil profile. In particular, the 2017 Stage 2C EI has improved understanding of the extent of elevated PFAS concentrations in near-surface soil at the former fire training ground. A site-wide groundwater monitoring event was conducted and identified locally elevated PFAS groundwater concentrations close to all active and depleting source areas. Review of the PFAS composition in groundwater indicated samples from areas close to the depleting sources (former fire training ground and former fire station) to have a higher proportion of PFOS and PFHxS compared to active potential sources. An assessment of primary and secondary PFAS sources has been undertaken, to assist with the evaluation of PFAS mass loads within the groundwater transport model.

More certainty around the influence of wind as a transport mechanism

The potential for PFAS transport in wind borne dust was evaluated. The dataset is not consistent with the potential migration of PFAS from the Site in wind-borne dust. The presence of higher PFAS concentrations in surface soil in the Oakey township area is attributed to surface transport of PFAS in floodwater and sediments during inundation events and the use of groundwater containing PFAS for irrigation purposes.

Residential sampling • Continue to monitor groundwater

contamination levels where requested by the owner for agricultural enterprises within the current and future Investigation Area

This report presents the results of a sampling program of residential bores, tap water, tanks and pool water and soil across the Investigation Area. The results have been integrated with data from the dedicated groundwater monitoring network installed by Defence within the Investigation Area and residential data have only been used where the property owner has agreed for Defence to use it. Residential sample results have been provided to property owners under separate cover.

Composition of all firefighting foams should be characterised, including the identifiable PFAS suite and total oxidisable precursor assay (TOPA) analysis where foams are fluorinated

The investigation included characterisation of selected samples of soil and water for TOPA analysis from a range of locations across the Site to better characterise PFAS conditions within the Investigation Area. TOPA analysis was conducted to understand the potential for precursor compounds to be present in the Investigation Area. If present, precursor compounds have the potential to transform into PFAS end products. Statistical analysis suggests that the concentration of additional PFAS that can be generated from the transformation of unidentified precursor compounds in soil and groundwater under natural environmental conditions is expected to be low.

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Refinement of the groundwater model • Update of the model conceptualisation

based on data compiled during the site investigation works

• Refinement of the groundwater model structure, calibration and predictions

• Addressing the model limitations through the refinement of the model using new data compiled during the site investigation works

• Utilising the model to investigate data gaps and facilitate decision making and inform the OMP

Data evaluation and interrogation has allowed for the assessment of concepts and refinement of the conceptual site model, which is used as the basis of the groundwater model refinement. The key groundwater model updates, forming the Reset Model, included: • a change to MODFLOW SURFACT modelling software for consistency with similar alluvium studies

and for ease of forensic review • a reduction in model extent to simulate the plume at a local scale • the addition of three more layers to simulate the Walloon Coal Measures aquifer • an update of model layer structure using data from the most recent field investigations • an evaluation of potential source locations and source discharge rates through calibration. The Reset Model has been conducted in order to facilitate the heterogeneous calibration. The iterative calibration process minimises non-uniqueness that would arise from attempting the all-encompassing model calibration in a single step.

The calibrated reset flow model provides parameters that are consistent with the conceptual site model and comparable to other groundwater modelling studies in alluvium systems.

The updated model structure allows for further evaluation of potential plume movement within the Walloon Coal Measures aquifer, though the model projections need to be supported by further data before being assessed as reliable.

PFOS plume migration, using a conservative approach of continuous contaminant sources in uniform permeable sediments, is predicted to continue in a westerly direction within the groundwater. This modelling allowed for the assessment of contaminant sources and plume shape, which is similar to the field measurements and observations. Future modelling within heterogenic sediments will provide a more robust assessment of migration.

The groundwater assessment and model development has improved the understanding of the potential sources of PFOS and the contaminant discharge rate to groundwater. The current process of adding heterogeneity to the Oakey Creek Alluvium will further improve the matching of observed water levels and concentrations in the groundwater regime. The model results will be used to inform the OMP.

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13.0 References AECOM, 2013. Base Engineering Assessment Program, Swartz Barracks, Army Aviation Centre Oakey (Rev 1)

AECOM, 2015a. Background Review and PFC Source Study – Army Aviation Centre Oakey (Rev 1)

AECOM, 2015b. PFC Conceptual Site Model – Army Aviation Centre Oakey

AECOM, 2015c. Stage 1 and Stage 2 Environmental Investigation, Army Aviation Centre Oakey – Offsite Assessment 2013-2014 (Rev 1)

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14.0 LimitationsAECOM Australia Pty Ltd (AECOM) has prepared this report in accordance with the usual care andthoroughness of the consulting profession for the use of Department of Defence and only those thirdparties who have been authorised in writing by AECOM to rely on the report.

The report is based on generally accepted practices and standards at the time it was prepared. Noother warranty, expressed or implied, is made as to the professional advice included in this report.

The report is prepared in accordance with the scope of work and for the purpose outlined in theProposal dated 17 November 2016.

This report should be read in full. No responsibility is accepted for use of any part of this report in anyother context or for any other purpose or by third parties.

The methodology adopted and sources of information used by AECOM are outlined in the report.

Where this report indicates that information has been provided to AECOM by third parties, AECOMhas made no independent verification of this information unless required as part of the agreed scopeof work. AECOM assumes no liability for any inaccuracies in or omissions to that information.

This report was prepared between 1 May 2017 and 1 December 2017. The information in this report isconsidered to be accurate at the date of issue and is in accordance with conditions at the Site and sur-

rounding areas at the dates sampled. Opinions and recommendations presented herein apply tothe Site and surrounding areas existing at the time of our investigation and cannot necessarily apply tochanges to Site and surrounding areas of which AECOM is not aware and has not had the opportunityto evaluate. This document and the information contained herein should only be regarded as validlyrepresenting the Site and surrounding area conditions at the time of the investigation unless otherwiseexplicitly stated in a preceding section of this report. AECOM disclaims responsibility for any changesthat may have occurred after this time.

Except as required by law, no third party may use or rely on this report, unless otherwise agreed byAECOM in writing. Where such agreement is provided, AECOM will provide a letter of reliance to theagreed third party in the form required by AECOM.

To the extent permitted by law, AECOM expressly disclaims and excludes liability for any loss,damage, cost or expenses suffered by any third party relating to or resulting from the use of, orreliance on, any information contained in this report. AECOM does not admit that any action, liability orclaim may exist or be available to any third party.

AECOM does not represent that this report is suitable for use by any third party.

Except as specifically stated in this section, AECOM does not authorise the use of this report by anythird party.

It is the responsibility of third parties to independently make inquiries or seek advice in relation to theirparticular requirements.

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List of Appendices

Appendix A Tables

Appendix B Figures

Appendix C Plates

Appendix D Bore Logs and Geological Cross-sections

Appendix E Surveying Results

Appendix F Borehole Assessment Results

Appendix G Analytical Laboratory Reports

Appendix H Data Quality Validation, Field Sheets and Calibration Certificates

Appendix I Surface Water Modelling Results

Appendix J Groundwater Modelling Report

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