Department of Defence RAAF Base Tindal€¦ · v2 draft Revised document 22/01/2018 IN SR SR v3...

Department of Defence

RAAF Base Tindal

Detailed Site Investigation Report

12 February 2018

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RAAF Base Tindal Detailed Site Investigation Report

Coffey Environments Australia Pty Ltd ABN: 65 140 765 902

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RAAF Base Tindal

Prepared for Department of Defence

Prepared by Coffey Environments Australia Pty Ltd Level 1, 436 Johnston Street Abbotsford VIC 3067 Australia t: +61 3 9290 7000 f: +61 3 9290 7499 ABN: 65 140 765 902

12 February 2018

754-MELEN199420_R05

Quality information

Revision history

Revision Description Date Originator Reviewer Approver

v1 draft Original document 01/12/2017 IN SR SR

v2 draft Revised document 22/01/2018 IN SR SR

v3 draft Revised document 07/02/2018 IN SR SR

v4 Final Final 12/02/2018 IN SR SR

Distribution

Report Status No. of copies Format Distributed to Date

v1 draft 1 PDF Department of Defence 01/12/2017



Final 1 PDF Department of Defence 12/02/2018



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Table of contents

1. Introduction .................................................................................................................................. 1

1.1. Investigation Area ............................................................................................................. 1

1.2. Background ....................................................................................................................... 2

1.3. Objectives .......................................................................................................................... 3

1.4. Scope of Works ................................................................................................................. 3

1.4.1. Preliminary Site Investigation ............................................................................... 3

1.4.2. Detailed Site Investigation .................................................................................... 3

2. Base Identification ....................................................................................................................... 6

2.1. Base Details ...................................................................................................................... 6

2.2. Base Features ................................................................................................................... 6

3. Issue Identification ....................................................................................................................... 7

3.1. General Base History ........................................................................................................ 7

3.2. Previous PFAS Investigations – On-Base ........................................................................ 7

3.2.1. Historical Reports ................................................................................................. 7

3.2.2. Personnel Interviews ............................................................................................ 8

3.3. Previous PFAS Investigations – Off-Base ........................................................................ 9

3.4. AFFF Fire Suppression System Inspections ................................................................... 10

3.4.1. Fuel Farms ......................................................................................................... 10

3.4.2. Ordinance Loading Area .................................................................................... 10

3.4.3. Engine Run-up ................................................................................................... 11

3.4.4. Corrosion control facility ..................................................................................... 11

3.5. Preliminary Conceptual Site Model ................................................................................. 11

3.5.1. Elements of a Conceptual Site Model ................................................................ 11

3.5.2. Potential and Identified On-Base PFAS Source Areas ...................................... 12

3.5.3. Receptors ........................................................................................................... 14

3.5.4. Pathways – Exposure Route .............................................................................. 15

3.5.5. Potential Beneficial Uses of Water ..................................................................... 15

4. Areas of Environmental Concern .............................................................................................. 17

4.1. Fire Training Area ........................................................................................................... 17

4.1.1. Background ........................................................................................................ 17

4.2. Fire Station ...................................................................................................................... 19

4.2.1. Background ........................................................................................................ 19

4.3. Mechanical Equipment Operations Maintenance Section .............................................. 20



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4.3.1. Background ........................................................................................................ 20

4.4. Fuel Farm 1 ..................................................................................................................... 21

4.4.1. Background ........................................................................................................ 21

4.5. Fuel Farm 2 ..................................................................................................................... 22

4.5.1. Background ........................................................................................................ 22

4.6. Katherine Airport ............................................................................................................. 22

4.7. Other Identified Potential Impacted Areas On-Base ....................................................... 23

5. Environmental Setting ............................................................................................................... 24

5.1. Climate ............................................................................................................................ 24

5.2. Topography ..................................................................................................................... 24

5.3. Surface Water ................................................................................................................. 24

5.3.1. Base Open Surface Drainage Network .............................................................. 25

5.3.2. Off-Base Surface Water Bodies ......................................................................... 25

5.3.3. Flood Potential ................................................................................................... 25

5.4. Geology Overview ........................................................................................................... 26

5.4.1. Daly Basin Geology ............................................................................................ 26

5.4.2. Local Geology .................................................................................................... 27

5.5. Regional Hydrogeology ................................................................................................... 27

5.5.1. Hydrogeological Units ........................................................................................ 27

5.5.2. Limestone fractures and caverns ....................................................................... 29

5.5.3. Confined vs Unconfined Tindall Limestone aquifer ............................................ 29

5.5.4. Aquifer hydraulic properties................................................................................ 30

5.6. Conceptual Hydrogeological Model ................................................................................ 30

5.6.1. Groundwater flow mechanisms .......................................................................... 31

5.6.2. Seasonal dynamics ............................................................................................ 32

5.6.3. Rainfall and groundwater levels ......................................................................... 32

5.6.4. Aquifer recharge ................................................................................................. 33

5.6.5. Discharge ........................................................................................................... 35

5.7. Regional groundwater levels and flow ............................................................................ 36

5.7.1. Groundwater levels ............................................................................................ 36

5.7.2. Groundwater level trends ................................................................................... 37

5.7.3. Hydraulic gradients and groundwater seepage velocity .................................... 39

5.8. Groundwater Quality ....................................................................................................... 40

5.8.1. Local Area Water Use ........................................................................................ 40

5.9. Flora and Fauna .............................................................................................................. 41

5.9.1. Vegetation .......................................................................................................... 41

5.9.2. Aquatic Biota ...................................................................................................... 41



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5.9.3. Terrestrial Animals ............................................................................................. 42

6. Investigation Scope ................................................................................................................... 43

6.1. Data Quality Objectives ................................................................................................... 43

6.2. Summary of Sampling ..................................................................................................... 45

6.3. Fieldwork Methodology ................................................................................................... 47

6.3.1. Sub-surface Service Clearance ......................................................................... 48

6.3.2. Decontamination Procedures ............................................................................. 48

6.3.3. Sample Preservation and Documentation .......................................................... 48

6.3.4. Borehole Drilling and Monitoring Well Installation .............................................. 48

6.3.5. Soil Sampling ..................................................................................................... 51

6.3.6. Sediment Sampling ............................................................................................ 52

6.3.7. Groundwater Sampling ....................................................................................... 53

6.3.8. Surface Water Sampling .................................................................................... 54

6.3.9. Private Bore Sampling ........................................................................................ 55

6.4. Laboratory Analysis ......................................................................................................... 56

6.5. Quality Assurance and Quality Control ........................................................................... 56

7. Assessment Criteria .................................................................................................................. 57

7.1. Assessment Framework .................................................................................................. 57

7.2. Commonwealth ............................................................................................................... 57

7.3. Northern Territory Legislation.......................................................................................... 57

7.4. Beneficial Uses................................................................................................................ 57

7.5. Screening Criteria ........................................................................................................... 58

7.5.1. Soil ...................................................................................................................... 58

7.5.2. Groundwater ....................................................................................................... 61

7.5.3. Surface Water .................................................................................................... 63

7.5.4. Sediment ............................................................................................................ 64

7.5.5. Concrete ............................................................................................................. 65

8. Investigation Results ................................................................................................................. 66

8.1. Soil Investigation ............................................................................................................. 66

8.1.1. Soil Conditions ................................................................................................... 66

8.1.2. Soil Laboratory Results ...................................................................................... 67

8.1.3. PFAS Leachability .............................................................................................. 69

8.2. Groundwater Investigation .............................................................................................. 70

8.2.1. Existing Monitoring Wells ................................................................................... 70

8.2.2. Groundwater Monitoring Events ......................................................................... 73

8.2.3. Field Observations ............................................................................................. 73

8.2.4. Groundwater Levels and Flow ........................................................................... 74



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8.2.5. Groundwater Level Trends ................................................................................. 75

8.2.6. Groundwater/Surface Water Interaction ............................................................. 76

8.2.7. Hydraulic Gradients ............................................................................................ 78

8.2.8. Groundwater Seepage Velocity ......................................................................... 78

8.3. Groundwater Chemistry .................................................................................................. 78

8.3.1. Field Measured Groundwater Chemistry Parameters ........................................ 79

8.3.2. Groundwater Analytical Results ......................................................................... 80

8.3.3. Vertical Profiling ................................................................................................. 83

8.3.4. Concentration Trends ......................................................................................... 86

8.4. Sediment and Surface Water Investigation ..................................................................... 92

8.4.1. Rainfall Conditions ............................................................................................. 92

8.4.2. Surface Water/Sediment Conditions and Field Observations ............................ 93

8.4.3. Surface Water Field Measured Parameters ....................................................... 94

8.4.4. Surface Water Analytical Results ....................................................................... 95

8.4.5. Sediment Analytical Results ............................................................................... 96

8.4.6. Open Drains ....................................................................................................... 97

8.5. Base Infrastructure Investigation..................................................................................... 99

8.5.1. Drainage Pits ...................................................................................................... 99

8.5.2. Concrete ........................................................................................................... 101

8.6. Private Bore Investigations ........................................................................................... 102

8.6.1. Sampling Conditions ........................................................................................ 102

8.6.2. Laboratory Results ........................................................................................... 103

8.7. Non-PFAS Contamination ............................................................................................. 103

8.7.1. Soils and Sediments ......................................................................................... 103

8.7.2. Groundwater ..................................................................................................... 104

8.8. Quality Assurance and Quality Control ......................................................................... 105

8.8.1. Fulfilment of DQO Steps .................................................................................. 107

9. Discussion ............................................................................................................................... 109

9.1. Nature and Extent of Contamination - Soil .................................................................... 109

9.1.1. Fire Station ....................................................................................................... 109

9.1.2. Fire Training Area ............................................................................................. 110

9.1.3. Irrigation Paddock ............................................................................................ 111

9.1.4. Base Services and Married Quarters ............................................................... 111

9.1.5. Fuel Farm 1 ...................................................................................................... 111

9.1.6. Mechanical Equipment Operations Maintenance Section ............................... 112

9.1.7. Katherine Airport .............................................................................................. 112

9.1.8. Potential former informal fire training area ....................................................... 112



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9.2. Nature and Extent of Contamination - Groundwater ..................................................... 113

9.2.1. Fire Training Area ............................................................................................. 113

9.2.2. Fire Station ....................................................................................................... 114

9.2.3. Other On-Base Areas ....................................................................................... 115

9.2.4. Off-Base ........................................................................................................... 116

9.3. Nature and Extent of Contamination - Surface Water, Sediment and Infrastructure .... 117

9.3.1. On-Base Surface Drainage .............................................................................. 117

9.3.2. Tindal Creek – On-Base ................................................................................... 118

9.3.3. Tindal Creek – Off-Base ................................................................................... 118

9.3.4. Katherine River ................................................................................................. 119

9.4. Receptors and Exposure Pathways .............................................................................. 119

9.4.1. On-Base Human Receptors and Potential Exposure Pathways ...................... 119

9.4.2. Off-Base Human Receptors and Potential Exposure Pathways ...................... 120

9.4.3. On-Base Ecological Receptors and Potential Exposure Pathways ................. 121

9.4.4. Off-Base Ecological Receptors and Potential Exposure Pathways ................. 122

9.5. Preliminary Assessment of Risk to Identified Receptors via Exposure Pathways ........ 122

10. Conclusions ............................................................................................................................. 129

10.1. Base Setting .................................................................................................................. 129

10.2. Summary of DSI Findings ............................................................................................. 129

10.3. Refined Conceptual Site Model..................................................................................... 132

11. Further Work ............................................................................................................................ 136

12. Limitations ............................................................................................................................... 138

13. References .............................................................................................................................. 139



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Tables – In Text

Table 1.1: Rationale for nomination of Investigation Area

Table 1.2: Scope of works undertaken during the PSI

Table 1.3: Environmental sampling works summary

Table 2.1: Base identification

Table 2.2: Current Base infrastructure

Table 3.1: RAAF Base Tindal reports reviewed by Coffey

Table 3.2: Personnel interviewed by Coffey

Table 3.3: Potential AFFF affected Base locations

Table 3.4: Potential sources of PFAS contamination

Table 3.5: Summary of beneficial uses

Table 4.1: Fire Training Area summary

Table 4.2: Fire Station summary

Table 4.3: Mechanical Equipment Operations Maintenance Section summary

Table 4.4: Fuel Farm 1 summary


Table 4.6: Areas of potential impacts

Table 5.1: Tindal weather station rainfall

Table 5.2: Hydrogeological units

Table 5.3: Aquifer properties

Table 5.4: DENR monitored groundwater bore sites

Table 6.1: DSI data quality objectives

Table 6.2: Summary of investigation sampling activities

Table 6.3: Decontamination procedures

Table 6.4: Borehole drilling and monitoring well installation methodology

Table 6.5: Groundwater monitoring well locations

Table 6.6: Soil assessment methodology

Table 6.7: Groundwater sampling methodology

Table 6.8: Surface water sampling methodology

Table 6.9: Private bore sampling methodology

Table 6.10: Summary of analytical methods


Table 7.2: Proposed soil assessment criteria (mg/kg)

Table 7.3: Proposed groundwater assessment criteria (g/L)

Table 7.4: Proposed surface water assessment criteria (g/L)

Table 7.5: Proposed off-Base sediment screening values (mg/kg)

Table 8.1: Lithology summary

Table 8.2: Summary of soil analytical results



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Table 8.3: Existing monitoring wells sampled

Table 8.4: Groundwater monitoring event summary

Table 8.5: Summary of damaged/lost monitoring wells

Table 8.6: Coffey monitored groundwater bores

Table 8.7: Groundwater gradient in April 2017 and August/September 2017

Table 8.8: Groundwater seepage velocity estimates

Table 8.9: Groundwater quality summary

Table 8.10: Summary of GME groundwater analytical results (µg/L)

Table 8.11: Summary of private bore groundwater analytical results

Table 8.12 Summary of groundwater PFOS results where multiple historic events occurred

Table 8.13: Relative PFOS concentrations between April and September 2017 events

Table 8.14: Surface water quality summary

Table 8.15: Surface water analytical summary (µg/L)

Table 8.16: Summary of sediment analytical results

Table 8.17: Summary of analytical results collected from open drains

Table 8.18: Summary of analytical results collected from drainage pits

Table 8.19: Summary of analytical results collected from evaporation ponds

Table 8.20: Summary of concrete analytical results

Table 8.21: Summary of non-PFAS groundwater analytical results (µg/L)

Table 8.22: PFAS quality control sample overview

Table 8.23: DQO steps

Table 9.1: On-Base human receptors and potential exposure pathways

Table 9.2: Off-Base human receptors and potential exposure pathways

Table 9.3: On-Base ecological receptors and potential exposure pathways

Table 9.4: Off-Base ecological receptors and potential exposure pathways

Table 9.5: Human receptors and exposure pathways

Table 9.6: Potential risks to ecological receptors

Table 10.1: Summary of conceptual site model pollutant linkages

Table 11.1: Proposed additional DSI works



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Charts – In Text

Chart 5.1: Hydrograph of RN37410 and rainfall




Chart 8.1: PFOS ASLP results against total concentrations

Chart 8.2: PFHxS ASLP results against total concentrations

Chart 8.3: PFOA ASLP results against total concentrations

Chart 8.4: Hydrograph of RN029429

Chart 8.5. Vertical profiling – Fire Training Area

Chart 8.6. Vertical profiling – Fire Station

Chart 8.7. Vertical profiling – On-Base wells

Chart 8.8. Vertical profiling – Off-Base wells

Chart 8.9. PFOS concentration over time – Mechanical Operations Maintenance Section area

Chart 8.10. PFOS concentration over time – Fire Training Area

Chart 8.11. PFOS concentration over time – Fire Station

Chart 8.12: Rainfall at Tindal RAAF between October 2016 and September 2017 (BOM, 2017)

Chart 8.13: PFOS concrete ASLP results against total concentrations

Chart 9.1: PFAS composition in groundwater in the vicinity of the Fire Training Area

Chart 9.2: PFAS composition in groundwater in the vicinity of the Fire Station

Chart 9.3: PFAS composition in groundwater in the vicinity of Fuel Farm 1


Chart 9.5: PFAS composition in groundwater in the vicinity of Mechanical Operations Maintenance Section

Chart 9.6: PFAS composition in groundwater at the Katherine Tip bore compared to MW142

Figures – In Text

Figure 3.1: Source - Pathway - Receptor linkage process

Figure 4.1: Fire Training Area

Figure 5.1a: Regional geology and cross-section locations

Figure 5.1b: Cross-section across the Venn agricultural area (Section 3)

Figure 5.2: Conceptual Groundwater Model for the Katherine Region

Figure 5.3: Recharge mechanisms

Figure 5.4: Discharge zones into the Katherine River

Figure 5.5: Tindall Limestone potentiometric surface for November 2003

Figure 8.1: Cross-section across the Katherine River at the Railway Bridge gauging station

Figure 8.2: Katherine Railway Bridge stage height data (G8140001)

Figure 8.3: Uralla North and Uralla South extents



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Figure 10.1: Inferred PFAS concentrations in groundwater

Tables – Appended

Table 1: New and Existing Bore Details

Table 2: Sediment Sampling Summary

Table 3a: PFAS Soil and Sediment Results – Fire Station

Table 3b: PFAS Soil and Sediment Results – Runway

Table 3c: PFAS Soil and Sediment Results – Fire Training Area

Table 3d: PFAS Soil and Sediment Results – Base Services

Table 3e: PFAS Soil and Sediment Results – Fuel Farm 1

Table 3f: PFAS Soil and Sediment Results – Fuel Farm 2

Table 3g: PFAS Soil and Sediment Results – Irrigation Paddock

Table 3h: PFAS Soil and Sediment Results – Mechanical Equipment Operations Maintenance Section

Table 3i: PFAS Soil and Sediment Results – Katherine Airport

Table 3j: PFAS Soil and Sediment Results – On-Base Other

Table 3k: PFAS Soil and Sediment Results – Tindal Creek

Table 3l: PFAS Soil and Sediment Results – Katherine River

Table 3m: PFAS Soil and Sediment Results – Off-Base Other

Table 3n: PFAS Results – Base Infrastructure

Table 4: Historical PFOS and PFOA Soil Results

Table 5: Metals Soil and Sediment Results

Table 6: Inorganics Soil and Sediment Analytical Results

Table 7: Non-PFAS Soil and Sediment Analytical Results

Table 8a: PFAS Soil vs Leachability Results

Table 8b: PFAS Leachability Results

Table 9: Groundwater Gauging Data

Table 10a: Groundwater Field Quality Parameters

Table 10b: Surface Water Field Quality Parameters

Table 11a: PFAS Groundwater Results – End of Wet Season

Table 11b: PFAS Groundwater Results – Dry Season (July – August)

Table 11c: PFAS Groundwater Results – Baseline GME (September – October)

Table 11d: PFAS Groundwater Results – Private Bores

Table 11e: PFAS Groundwater Results – Vertical Profiling

Table 12: Historical PFOS and PFOA Groundwater Results

Table 13: Metals Groundwater Results

Table 14: Inorganics Groundwater Results

Table 15: Non-PFAS Groundwater Results

Table 16a: PFAS Surface Water Results – End of Wet Season



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Table 16b: PFAS Surface Water Results – Dry Season (July)

Table 16c: PFAS Surface Water Results – Dry Season (August)

Table 16d: PFAS Surface Water Results – Dry Season (September)

Table 16e: PFAS Surface Water Results – Base Infrastructure

Table 17: Metals Surface Water Results

Table 18: Inorganics Surface Water Results

Table 19: Non-PFAS Surface Water Results

Table 20a: Quality Control Results – Soil RPDs

Table 20b: Quality Control Results – Water RPDs

Table 20c: Quality Control Results – Blanks

Figures – Appended

Figure 1a: Overview

Figure 1b: Base location

Figure 2: Investigation Area and site features

Figure 3: On-Base sources of PFAS contamination

Figure 4: Geology and sinkholes

Figure 5: Registered groundwater well locations and well yield

Figure 6: Daly Basin aquifers

Figure 7: DENR monitored groundwater well sites

Figure 8: Topography and surface drainage

Figure 8a: Topography and surface drainage - Mechanical Equipment Operations Maintenance Section

Figure 8b: Topography and surface drainage - Fire Station

Figure 8c: Topography and surface drainage - Fuel Farm 1

Figure 8d: Topography and surface drainage - Fuel Farm 2

Figure 9: Surface water catchments and flood extents

Figure 10: On-Base Soil Investigation Overview

Figure 11a: Fire Station - Soil Analytical Results (0-0.4mBGL) - PFOS

Figure 11b: Fire Station - Soil Analytical Results (0.5-1.4mBGL) - PFOS

Figure 11c: Fire Station - Soil Analytical Results (1.5+mBGL) - PFOS

Figure 11d: Fire Station - Soil Analytical Results - PFOA

Figure 12a: Fire Training Area - Soil Analytical Results (0-0.4mBGL) - PFOS

Figure 12b: Fire Training Area - Soil Analytical Results (0.5-1.4mBGL) - PFOS

Figure 12c: Fire Training Area - Soil Analytical Results (1.5+mBGL) - PFOS

Figure 12d: Fire Training Area - Soil Analytical Results – PFOA

Figure 13a: South of Sewerage Ponds - Soil Analytical Results - PFOS

Figure 13b: South of Sewerage Ponds - Soil Analytical Results - PFOA

Figure 14a: Fuel Farm 1 - Soil Analytical Results - PFOS



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Figure 14b: Fuel Farm 1 - Soil Analytical Results - PFOA

Figure 15a: North-east Base - Soil Analytical Results - PFOS

Figure 15b: North-east Base - Soil Analytical Results - PFOA

Figure 16a: North-west Base - Soil Analytical Results - PFOS

Figure 16b: North-west Base - Soil Analytical Results - PFOA

Figure 17a: Tindal Creek - Soil Analytical Results - PFOS

Figure 17b: Tindal Creek - Soil Analytical Results - PFOA

Figure 18a: Vehicle Maintenance - Soil Analytical Results - PFOS

Figure 18b: Vehicle Maintenance - Soil Analytical Results - PFOA

Figure 19a: Test Area 1 - Soil Analytical Results - PFOS

Figure 19b: Test Area 1 - Soil Analytical Results - PFOA

Figure 20a: Southern End of Runway - Soil Analytical Results - PFOS

Figure 20b: Southern End of Runway - Soil Analytical Results - PFOA

Figure 21a: On-Base - Soil and Sediment Analytical Results - PFOS

Figure 21b: On-Base - Soil and Sediment Analytical Results - PFOA

Figure 22a: Off-Base - Soil and Sediment Analytical Results - PFOS

Figure 22b: Off-Base - Soil and Sediment Analytical Results - PFOA

Figure 23a: On-Base - Surface Sediment Analytical Results - PFOS

Figure 23b: On-Base - Surface Sediment Analytical Results - PFOA

Figure 24a: Surface Water Analytical Results - On-Base - PFOS (Infrastructure Samples)

Figure 24b: Surface Water Analytical Results - On-Base - Sum of PFOS and PFHxS (Infrastructure Samples)

Figure 24c: Surface Water Analytical Results - On-Base - PFOA (Infrastructure Samples)

Figure 25a: Surface Water Analytical Results - On-Base - PFOS (April/May 2017 Monitoring Event)

Figure 25b: Surface Water Analytical Results - On-Base - PFOS (July/August 2017 Monitoring Event)

Figure 26a: Surface Water Analytical Results - On-Base - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 26b: Surface Water Analytical Results - On-Base - Sum of PFOS and PFHxS (July/August 2017 Monitoring Event)

Figure 27a: Surface Water Analytical Results - On-Base - PFOA (April/May 2017 Monitoring Event)

Figure 27b: Surface Water Analytical Results - On-Base - PFOA (July/August 2017 Monitoring Event)

Figure 28a: Surface Water Analytical Results - Off-Base - PFOS (April/May 2017 Monitoring Event)

Figure 28b: Surface Water Analytical Results - Off-Base - PFOS (July/August 2017 Monitoring Event)

Figure 28c: Surface Water Analytical Results - Off-Base - PFOS (September 2017 Monitoring Event)

Figure 29a: Surface Water Analytical Results - Off-Base - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 29b: Surface Water Analytical Results - Off-Base - Sum of PFOS and PFHxS (July/August 2017 Monitoring Event)

Figure 29c: Surface Water Analytical Results - Off-Base - Sum of PFOS and PFHxS (September 2017 Monitoring Event)

Figure 30a: Surface Water Analytical Results - Off-Base - PFOA (April/May 2017 Monitoring Event)



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Figure 30b: Surface Water Analytical Results - Off-Base - PFOA (July/August 2017 Monitoring Event)

Figure 30c: Surface Water Analytical Results - Off-Base - PFOA (September 2017 Monitoring Event)

Figure 31: Groundwater Investigation Overview

Figure 32a: Groundwater Analytical Results - Fire Training Area - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 32b: Groundwater Analytical Results - Fire Training Area - Sum of PFOS and PFHxS (July/August 2017 Monitoring Event)

Figure 32c: Groundwater Analytical Results - Fire Training Area - Sum of PFOS and PFHxS (September 2017 Monitoring Event)

Figure 33a: Groundwater Analytical Results - Fire Training Area - PFOA (April/May 2017 Monitoring Event)

Figure 33b: Groundwater Analytical Results - Fire Training Area - PFOA (July/August 2017 Monitoring Event)

Figure 33c: Groundwater Analytical Results - Fire Training Area - PFOA (September 2017 Monitoring Event)

Figure 34a: Groundwater Analytical Results - Fire Station - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 34b: Groundwater Analytical Results - Fire Station - Sum of PFOS and PFHxS (September 2017 Monitoring Event)

Figure 35a: Groundwater Analytical Results - Fire Station - PFOA (April/May 2017 Monitoring Event)

Figure 35b: Groundwater Analytical Results - Fire Station - PFOA (September 2017 Monitoring Event)

Figure 36a: Groundwater Analytical Results - On-Base - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 36b: Groundwater Analytical Results - On-Base - Sum of PFOS and PFHxS (July/August 2017 Monitoring Event)

Figure 36c: Groundwater Analytical Results - On-Base - Sum of PFOS and PFHxS (September 2017 Monitoring Event)

Figure 37a: Groundwater Analytical Results - On-Base - PFOA (April/May 2017 Monitoring Event)

Figure 37b: Groundwater Analytical Results - On-Base - PFOA (July/August 2017 Monitoring Event)

Figure 37c: Groundwater Analytical Results - On-Base - PFOA (September 2017 Monitoring Event)

Figure 38a: Groundwater Analytical Results - Off-Base - Sum of PFOS and PFHxS (April/May 2017 Monitoring Event)

Figure 38b: Groundwater Analytical Results - Off-Base - Sum of PFOS and PFHxS (July/August 2017 Monitoring Event)

Figure 38c: Groundwater Analytical Results - Off-Base - Sum of PFOS and PFHxS (September 2017 Monitoring Event)

Figure 39a: Groundwater Analytical Results - Off-Base - PFOA (April/May 2017 Monitoring Event)

Figure 39b: Groundwater Analytical Results - Off-Base - PFOA (July/August 2017 Monitoring Event)

Figure 39c: Groundwater Analytical Results - Off-Base - PFOA (September 2017 Monitoring Event)

Figure 40a: Groundwater Analytical Results - On-Base - Sum of PFOS and PFHxS (April - September 2017)

Figure 40b: Groundwater Analytical Results - On-Base - PFOA (April - September 2017)

Figure 41a: Groundwater Analytical Results - Off-Base - Sum of PFOS and PFHxS (April - September 2017)



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Figure 41b: Groundwater Analytical Results - Off-Base - PFOA (April - September 2017)

Figure 42a: Groundwater Elevation Contours (April 2017)

Figure 42b: Groundwater Elevation Contours (July 2017)

Figure 42c: Groundwater Elevation Contours (September 2017)

Figure 43: Sum of PFOS and PFHxS concentration contours (September 2017)

Figure 44a: Cross section profile - Fire Training Area

Figure 44b: Cross section profile - Traversing Katherine River

Appendices

Appendix A: Summary of historical reports

Appendix B: Photograph Log

Appendix C: Hydrographs of DENR monitored groundwater bores

Appendix D: Borelogs and well construction details

Appendix E: Soil - Laboratory Test Certificates and CoC Documentation

Appendix F: Groundwater - Laboratory Test Certificates and CoC Documentation

Appendix G: Surface water - Laboratory Test Certificates and CoC Documentation

Appendix H: Sediment - Laboratory Test Certificates and CoC Documentation

Appendix I: Leachability - Laboratory Test Certificates and CoC Documentation

Appendix J: Residential Bores - Laboratory Test Certificates and CoC Documentation

Appendix K: Data Validation (QA/QC)

Appendix L: Hydrographs of Coffey monitored groundwater bores

Appendix M: Equipment Calibration Records

Appendix N: Surveying Data

Appendix O: Vertical Delineation Groundwater Purging Data

Appendix P: Comparison of Sampling by Low Flow and HydraSleeve

Appendix Q: Important Information about your Coffey Environmental Report



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Glossary

Aquifer A saturated permeable geological layer or formation that is permeable

enough to yield economic quantities of water.

Ansulite Current AFFF product used by RAAF.

Bore A drilled hole in the ground to intersect groundwater for extractive use, for

monitoring, or for investigation. Can also be referred to as a well.

Catchment An area which discharges to a common point.

Confined Aquifer An aquifer in which groundwater is confined under pressure.

Confining Layer

Geological material through which significant quantities of water cannot

move; located below unconfined aquifers above and below confined

aquifers.

Contamination The introduction of any undesirable component or substance into a water

source or supply.

Dissolved Solids Soluble compounds such as salts which are in solution.

Ecosystem

A system made up of the community of living things (animals, plants, and

microorganisms) which are interrelated to each other and the physical and

chemical environment in which they live.

Formation A geological structure such as a rock mass or layer.

Groundwater The water contained in an aquifer.

Groundwater Flow The movement of water in an aquifer.

Heterogeneous Having different properties or composition at different locations.

Hydraulic Conductivity A measure of the permeability of a material to groundwater flow.

Hydraulic Gradient The slope of the groundwater surface in an unconfined aquifer, or the

potentiometric surface in a confined aquifer.

Hydraulic Head Elevation to which water will rise in a bore or well, constructed in an aquifer.

Hydrogeology The study of the inter-relationships of geologic materials and processes with

water, especially groundwater.

Infiltration Rainfall penetration into the soil profile or sub-surface.

Lithology The physical composition of a rock or rock formation.

Permeability The ability to transmit fluids readily.



xvi

pH A measure of the acidity or alkalinity of a solution.

Porosity The void spaces in a rock formation.

Potentiometric Level

The level to which the water column in a well or bore installed in an aquifer

rises. A measure of the pressure head of water in the aquifer. Also known as

piezometric level.

Recharge A process through which water enters an aquifer.

Runoff Rain water that flows across the land surface, and may enter a drainage or

stream system.

Saturated Zone

The zone in which the voids in the rock are filled with water at a pressure

greater than atmospheric. The watertable represents the top of the saturated

zone in an unconfined aquifer.

Sediment Unconsolidated material deposited through the action of water.

Semi-Confined Aquifer A confined aquifer having a leaky confining layer.

Specific Yield The ratio of the volume of water a rock will yield by gravity drainage to the

volume of the rock.

Standing Water Level The depth below natural ground surface to the water level in a well or bore.

Storativity A measure of the ability of an aquifer to store water.

Total Dissolved Solids Concentration of dissolved salts (TDS).

Transmissivity The rate at which an aquifer can transmit water. It is a function of properties

of the aquifer material and the thickness of the porous media.

Unconfined Aquifer An aquifer with no confining layer between the watertable and the ground

surface where the watertable is free to rise and fall.

Unsaturated Zone The part of the geological stratum above the saturated zone. Also called the

vadose zone.

Watertable The top of the saturated zone in an unconfined aquifer.

Well

A hole drilled into a groundwater resource (aquifer) or gas resource and

commonly constructed with a casing and screen or similar. Can also be

referred to as a bore.

Well Yield The flow rate obtainable from an extraction well or bore.

3M Lightwater™ AFFF product developed by 3M in the 1960s and used at RAAF Base

Tindal.



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Abbreviations

ACM Asbestos Containing Material

AEC Area of Environmental Concern

AFFF Aqueous Film Forming Foam

AHD Australian Height Datum

ANZECC Australian and New Zealand Environment and Conservation Council

AST Aboveground Storage Tank

C6-C36 Hydrocarbon chainlength fraction

CRAT Contamination Risk Assessment Tool

CSR Contaminated Sites Register

bgs below ground surface

BH Borehole

BTEX Benzene, Toluene, Ethylbenzene and Xylenes

COC Chain of Custody

Coffey Coffey Services Australia

COPC Chemical of potential concern

CSR Contaminated Sites Register

DEM Digital elevation model

DENR Department of Environment and Natural Resources

DIPL Northern Territory Department of Infrastructure, Planning and Logistics

DNR Department of Natural Resources and Mines (now Department of Environment and Natural Resources)

DO Dissolved Oxygen

DQO Data Quality Objective

DSI Detailed Site Investigation

EC Electrical Conductivity

eH Oxidation/Reduction Potential

EILs Ecological Investigation Levels

ESA Environmental Site Assessment



xviii

Eurofins Eurofins Environment Testing Australia Pty Ltd, trading as Eurofins MGT

FTA Fire Training Area

FOSA Perfluorooctane sulfonamide

FSANZ Food Standards Australia New Zealand

FTS Fluorotelemer Sulphonate

GDE Groundwater dependent ecosystems

HILs Health Investigation Levels

HSL Health Screening Level

ID Identification

IP Interface Probe

LNAPL Light Non-aqueous Phase Liquid

LOR Limit of Reporting

µg/L micrograms per litre

mg/kg milligrams per kilogram

mg/L milligrams per litre

MW Monitoring Well

NATA National Association of Testing Authorities

N-etFOSA N-Ethyl perfluorooctane sulfonamide

N-etFOSAA N-Ethyl perfluorooctane sulfonamidoacetic acid

N-etFOSE N-ethyl perfluorooctane sulfonamidoethanol

NEPM National Environment Protection (Assessment of Site Contamination) Measure

NEPC National Environment Protection Council

N-meFOSA N-Methyl perfluorooctane sulfonamide

N-meFOSAA N-Methyl perfluorooctane sulfonamidoacetic acid

n-MeFOSE N-methyl perfluorooctane sulfonamidoethanol

NT EPA Northern Territory Environment Protection Agency

OLA Ordnance Loading Area

PAH Polycyclic Aromatic Hydrocarbon

PCBs Polychlorinated Biphenyls



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PFAS Per- and polyfluoroalkyl substances

PFBA Perfluorobutanoic acid

PFBS Perfluorobutane sulfonic acid

PFDA Perfluorodecanoic acid

PFDoA Perfluorododecanoic acid

PFDS Perfluorodecane sulfonic acid

PFOA Perfluorooctanoic Acid

PFOS Perfluorooctane Sulfonate (alternative name Perfluorooctane sulfonic acid)

PFHpA Perfluoroheptanoic acid

PFHpS Perfluoroheptane sulfonic acid

PFHxA Perfluorohexanoic acid

PFHxS Perfluorohexane sulfonic acid

PFNA Perfluorononanoic acid

PFPeA Perfluoropentanoic acid

PFPeS Perfluoropentane sulfonic acid

PFTeDA Perfluorotetradecanoic acid

PFTrDA Perfluorotridecanoic acid

PFUnA Perfluoroundecanoic acid

ppm parts per million

ppmv parts per million by volume

PSI Preliminary Site Investigation

QA Quality Assurance

QC Quality Control

RAAF Royal Australian Air Force

RL Reduced Level

RPD Relative Percent Difference

SAQP Sampling and Analysis Quality Plan

SOP Standard Operating Procedures

SW Surface water



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SWL Standing Water Level

TDS Total Dissolved Solid

TOC Top of Casing

TPH Total Petroleum Hydrocarbon

USCS Unified Soil Classification System

VOC Volatile Organic Compound

WAP Water Allocation Plan

WTP Water Treatment Plant


Coffey 754-MELEN199420_R05 12 February 2018

1

1. Introduction

Department of Defence has engaged Coffey Environments Australia Pty Ltd (Coffey) to undertake a

Detailed Site Investigation (DSI) of per- and polyfluoroalkyl substance (PFAS) at the Royal Australian

Air Force (RAAF) Base Tindal (the Base). A locality plan of the Base is presented as Figure 1a and 1b

(appended) and site features and the greater Investigation Area plan is presented as Figure 2

(appended).

The Base is located approximately 13 km south-east of the township of Katherine in the Northern

Territory (approximately 320 km south-east of Darwin). The Base covers an area of approximately

122 square kilometres. The formal Base facility forms a small portion of the overall land area, the

remainder of which is composed of Eucalypt bushland and open forest.

1.1. Investigation Area

The Investigation Area includes the Base (based on the primary source locations) and the known

extent of PFAS impact detected off-Base. The Investigation Area is generally defined by the locations

where PFOS, PFHxS and PFOA have been detected above the laboratory limit of reporting (LOR) or

may be reasonably anticipated to be present based on contaminant transport mechanisms. The

boundaries of the Investigation Area may change as more information becomes available. The

Investigation Area is depicted on Figure 2 (appended). The extent of the Investigation Area has been

based on the rationale described in Table 1.1.

Table 1.1: Rationale for nomination of Investigation Area

Boundary Description Rationale

East Base boundary

PFAS impacts in soil and groundwater have been practically delineated to the east of the identified source areas. Regional groundwater and surface water flow direction is westerly. Limited residential bore sampling to the east of the Base reported PFAS concentrations below the laboratory limit of reporting, and therefore receptor populations beyond the east of the Base boundary are not considered further.

North Base boundary and northern extent of Tindall Aquifer

The edge of the Tindall aquifer (as identified by NT Government mapping) has been adopted as the northern extent of the relevant investigation. Off-Base sampling has confirmed concentrations do not exceed limits of reporting beyond this northern boundary.

West

Approx. 200 m west/north-west of the western banks of Katherine River

Impact has been reported in the Katherine River, with groundwater discharging to the River. Contamination is unlikely to migrate far west beyond the River. This boundary is being validated with further testing and may be refined.

South

Base boundary, running west to the south of the southern-most property along Uralla Road. Deviating slightly to the south to include Tindal Creek and the discharge point to the Katherine River

Groundwater analytical results from bores at the southern end of Uralla Road have been reported below the laboratory Limit of Reporting.

As Tindal Creek is the primary migratory pathway for surface water from the Base, all of Tindal Creek has been included in the Investigation Area.



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Boundary Description Rationale

Down-stream in Katherine River

Katherine River from Jaensch Road to the Junction with the Daly River

Impact has not been identified up-stream from Knott’s Crossing, however the up-stream boundary of the Investigation Area has been defined as the boundary of the Tindall Aquifer to align with the boundary on land.

Impacts have been reported in all accessed locations down-stream of the high level bridge. Available data from Daly River indicated concentrations below drinking water health based levels at the end of the dry season, and therefore the boundary has been extended to the junction of Katherine River and the Daly River.

1.2. Background

As part of firefighting activities, Aqueous Film-Forming Foam (AFFF) was historically used and stored on RAAF Base Tindal. The activities at the Base included active suppression of fires, training and storage for emergency use, maintenance of related equipment, and other historical incidental uses or emissions. The Department of Defence recognised that the former use of these chemicals may have impacted on the environment, and are seeking to better understand the nature and extent of PFAS impacts on the base (and within the greater Defence estate).

AFFF concentrate is a clear, amber liquid and was introduced into fire extinguishing media in the late 1960’s. AFFF fire extinguishing media has been used extensively worldwide, and within Australia, from about the 1970’s by both civilian and military authorities. In legacy AFFF fire extinguishing media, as those historically used on-base, a class of manufactured chemicals known as PFAS can be present. There are hundreds of compounds within the PFAS class, but analytical methods do not exist for all of them, and some are more prevalent than others. The active ingredient in the manufactured products used by RAAF (i.e. 3% and 6% 3M Lightwater™) were typically per-fluorooctane sulfonate (PFOS), per-fluorohexane sulfonate (PFHxS) and to a lesser extent perfluorooctanoic acid (PFOA). Newer AFFF products contain shorter chain PFAS compounds (less than six carbons) and poly-fluorinated precursor compounds (i.e. PFBS, 8:2 FTS and compounds not quantified by PFAS analysis).

PFAS are a group of manufactured chemicals that are used in products that are resistant to heat, water and oil. Due to their heat resistant properties, and ability to form aqueous film forming foams, they have been used extensively in fire-fighting foam applications in Australia for decades. A significant amount of research has been conducted into the health and ecological effects of these substances, and they are understood to be highly persistent within the environment, readily leachable from soils, and bio-accumulate up the food-chain. The potential health and ecological effects of these substances are not well defined, however given their environmental persistence, enHealth has issued a precautionary warning to limit exposure to humans from these compounds.

The fully fluorinated compounds (per) are water soluble and mobile, and will tend to migrate with water. Different compounds in the PFAS group adsorb at different rates to organic carbon in soil and long chain compounds (six or more carbons) bio-accumulate in animals. Due to the mobility, PFAS compounds can be present in very large plumes associated with groundwater migration and surface waters. Organic rich sediments may act as ongoing or seasonal secondary sources of PFAS contamination to surface waters through leaching. The fully fluorinated compounds (per) found in the AFFF fire extinguishing agent does not readily degrade in the environment and are known to be highly persistent, remaining for many years following release.



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1.3. Objectives

Defence’s primary project objective is to understand potential contamination risks both on the Defence property and to the surrounding areas, resulting from historical AFFF usage.

The purpose of this DSI is to provide sufficient information on the sources of contamination, the extent and magnitude of the contaminant plume(s), the contaminant transport conditions, the migration pathways and the current extent of contamination to enable development of a robust conceptual site model. The conceptual site model will then inform a human health and/or ecological risk assessment, and guide effective management strategies.

Although the focus of the DSI investigation is on PFAS contamination, a further objective is to collect sufficient data for non-PFAS contaminants to provide an initial understanding and characterisation of potential contamination at source areas on the base.

1.4. Scope of Works

A summary of the sequence of investigations that were conducted in order to achieve the DSI objectives is discussed below.

1.4.1. Preliminary Site Investigation

A Preliminary Site Investigation (PSI) was initially undertaken to collate Base information and describe conditions and features relevant to contaminant distribution and migration. A summary of the activities undertaken as part of the PSI are presented in Table 1.2.

Table 1.2: Scope of works undertaken during the PSI

Scope item Description

Data analysis A review of previous environmental reports relating to AFFF storage and use on-Base, and reports where PFAS analysis was conducted.

Site walkover Completion of a site inspection, identifying source areas for investigation and conducting interviews with current and former (where available) on-Base personnel.

Preliminary analysis Development of a preliminary conceptual site model to describe surface water catchments and groundwater flows.

Data findings Undertaking a data gap analysis, assess uncertainties in the preliminary conceptual site model.

1.4.2. Detailed Site Investigation

A DSI was undertaken with the purpose of delineating and characterising PFAS contamination in potential source areas on the Base, with the objective of informing preliminary risk assessment and contaminant transport models.

The DSI has used the seven step Data Quality Objective (DQO) process to provide a systematic planning approach towards defining the purpose of the investigation and the type, quantity and quality of data required to make risk based decisions. The seven step DQOs are detailed in the DSI Sampling and Analysis Quality Plan (SAQP). In order to meet the purpose of the DSI and project objectives, a comprehensive field program involving soil, water and biota sampling and analysis was



4

developed. The proposed sampling works are described in detail in the DSI SAQP and summarised in Table 1.3. Most of the fieldwork has been completed, with wet season investigations to be undertaken in February 2018.

Additional monitoring of contaminant concentrations in surface water and groundwater will continue across March 2018 to monitor seasonal fluctuations and inform development and refinement of contaminant transport models. These models will provide input to the sensitivity review of risk assessments and may guide appropriate risk management approaches. Further biota assessment is also likely to occur to inform the assessment of risk to human health and ecosystems as a result of bioaccumulation of PFAS compounds in the environment.

Table 1.3: Environmental sampling works summary


End of wet season surface water and groundwater testing

April 2017

Assessment of surface water contaminant levels at 52 locations in Katherine River, Tindal Creek and on-base drains.

Assessment of water levels and PFAS concentrations in 46 existing wells on and off-Base.

End of wet season freshwater biota testing

April 2017

Collection and analysis of finfish and crustaceans from Tindal Creek and Katherine River, with paired assessment of surface water and sediment contamination.

Soil testing, sediment testing and groundwater well installation

May to September 2017

Installation of 45 new groundwater monitoring wells to supplement the existing well network.

To characterise nature and extent of contamination from known or suspected source areas, collection and analysis of:

Over 300 soil and sediment samples from drains, waterways and potential source areas;

Over 150 groundwater samples on and off-Base over three events;

Surface water samples in Katherine River approximately monthly.

Assessment of exposure point concentrations (residential bores, produce, etc.)

Ongoing

Collection and analysis of water supply and home-grown produce from private properties and institutions.

Collection of on-Base specific data to inform contaminant migration modelling, and preliminary human health or ecological risk assessments (i.e. aquifer tests, receptor behaviour surveys, off-Base surface water and sediment testing)

April to October 2017

Deployment of data loggers to monitor fluctuations in groundwater levels across seasons (to be compiled in supplementary DSI report).

Vertical profiling of contaminant concentrations in 21 target wells (see Section 8.3.3).

Analysis of soil properties relevant to PFAS adsorption.



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Collection of additional on-Base specific data to inform contaminant migration modelling, and human health or ecological risk assessments (i.e. aquifer tests, receptor behaviour surveys, ecological studies)

Ongoing

Monitor seasonal fluctuations and inform development and refinement of contaminant transport models. These models will provide input to the sensitivity review of risk assessments and may guide appropriate risk management approaches. Biota assessment to inform the assessment of risk to human health and ecosystems as a result of bioaccumulation of PFAS compounds in the environment.

Regular testing to inform assessment of seasonal fluctuations (groundwater, surface water, residential bores and biota)

Ongoing

Monitor seasonal fluctuations and inform development and refinement of contaminant transport models. These models will provide input to the sensitivity review of risk assessments and may guide appropriate risk management approaches. Biota assessment to inform the assessment of risk to human health and ecosystems as a result of bioaccumulation of PFAS compounds in the environment.



6

2. Base Identification

2.1. Base Details

For general Base information refer to Table 2.1.

Table 2.1: Base identification

Base Name RAAF Base Tindal

Base Address Tindal, NT 0853

Approximate Total Base Area 122 km2

Title Identification Details including Folio and Volume Numbers

Commonwealth freehold title, comprising Sections 5060 and 3437

(Hundred of Bagot)

Current Land Use Zoning Commonwealth Land

Adjoining Base Uses

North – Stuart Highway, followed by rural/residential land, farmland and

bushland.

East –Rural/residential, farmland and bushland

South – Rural/residential land, farmland and bushland.

West – Bushland, followed by rural/residential land (Uralla). The township

of Katherine in located approximately 13 km west, north-west of the Base.

2.2. Base Features

In order to operate and maintain both daily military and civilian flight activities, the Base has a multitude of infrastructure. In general, the current site infrastructure can be divided into three areas. Table 2.2 summarises the three areas.

Table 2.2: Current Base infrastructure

Military force projection-related facilities

Defence personnel support infrastructure

Air-Base maintenance and support facilities

Air-force runways and taxiways (RAAF aircraft movement), explosive ordnance facilities (storage and preparation), aircraft storage and combat preparation facilities, squadron workshops, laboratories and command and control facilities.

Married quarters, messes and football oval, frontline canteen and service station, golf course, Sewage Treatment Plant and horse paddock.

Aviation and vehicle fuel farms, waste disposal and landfill areas, civilian airport shared facilities, firefighting and search and rescue section and fire training areas, air movement navigation facilities and ground vehicle maintenance facilities.

While the primary AFFF usage and storage on-Base was generally associated with the Fire Training Area and Fire Station, other facilities that had the potential to be associated with primary or secondary sources were also identified on the Base for direct investigation.

Infrastructure with a recognised potential to cause environmental contamination is assessed by the Department of Defence and ranked according to an environmental risk profile and placed in a Contaminated Sites Register (CSR). A CSR list for the site was reported in ERM (2005). Coffey has reviewed the CSR and incorporated the relevant information into the DSI.



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3. Issue Identification

3.1. General Base History

RAAF Base Tindal was re-constructed and extended in the late 1950’s and early 1960’s by the

RAAF’s No. 5 Airfield Construction Squadron to provide a backup airfield for Darwin. Further

upgrades were made to RAAF Base Tindal from 1963 to 1970 for military related exercises and

civilian use and was known as a ‘bare base’. Significant upgrading and expansion of the Base

facilities were conducted during the 1980’s, forming its current configuration.

In 1987 the RAAF Base Tindal was formally established, with the Base functioning at its current

military capacity since 1988. The RAAF Base Tindal’s primary role is to provide a home for the No. 75

Squadron, which forms part of the Air Force’s Tactical Fighter Force.

The site also shares part of its air facilities (runways, taxiways and aircraft maintenance facilities) with the Katherine Tindal Civilian airport (established in the early 1990’s with the local Council).

3.2. Previous PFAS Investigations – On-Base

In order to identify potential sources of PFAS contamination, an understanding of the Base history and Base condition was developed based on review of a range of information. The information obtained was used to inform and develop the scope of this DSI.

Interviews were conducted with current and former personnel from the Base.

Coffey reviewed over 17 available reports provided by the Department of Defence, and a total of 19 reports issued by the Power and Water Corporation and DENR (or historically equivalent regulatory agency).

Groundwater hydrographs, groundwater quality data and surface water flow information was also reviewed.

3.2.1. Historical Reports

The reports selected for review were considered the most relevant to the PFAS investigation. A list of the reports reviewed is provided in Table 3.1 and a summary of the report content is provided in Appendix A.

Table 3.1: RAAF Base Tindal reports reviewed by Coffey

Report Report title

AECOM (2009a) Human Health and Screening Ecological Risk Assessment, Fire Training Area, RAAF Base Tindal, Northern Territory/Kimberley. D11029. AECOM, Gordon.

AECOM (2009b) Stage 2 (III) Environmental Investigation RAAF Base Tindal. D11029. AECOM, Darwin.

AECOM (2009c) Water Quality Investigations FY 08/09 RAAF Base Tindal. D1112501. AECOM, Darwin.

AECOM (2009d) Groundwater and Surface Water Monitoring Plan RAAF Base Tindal Northern Territory/Kimberley Region. D11029. AECOM, Darwin.

DoD (2003) Environmental Issues Associated with Defence Use of Aqueous Film Forming Foams (AFFF)



8

Report Report title

DoD (2007) Environmental Guidelines for Management of Fire Fighting Aqueous Film Forming Foam (AFFF) Products

EES (2016) Targeted Environmental Assessment for PFAS in Soil and Groundwater at RAAF Tindal. 716030. Environmental Earth Sciences, Newstead.

ERM (2005) Stage 1 Environmental Investigation RAAF Base Tindal, Northern Territory. 0028812. ERM, Spring Hill.

ERM (2007a) Landfill/Burial Sites Stage 1 Investigation NT/K RAAF Base Tindal. 0042239 RAAF Tindal Stage 1. ERM, Spring Hill.

ERM (2007b) Stage 1 and 2 Environmental Investigations NT/K RAAF Base Tindal. 0042239. ERM, Spring Hill.

GHD (2008) RAAF Base Tindal Stage 2 (Part II) Environmental Investigation. 31/21887/146637. GHD, Darwin.

GHD (2011) Report for AZ4561 Environmental Investigation of Fire Training Areas RAAF Base Tindal. GHD, Brisbane.

GHD (2012) Report for RAAF Base Tindal, Remediation Action Plan – Fire Training Area and Fire Station. 21/21200/210577. GHD.

GHD (2016a) NT Defence Environmental Monitoring Program - RAAF Base Tindal Annual Report 2016. 43/22491. GHD, Darwin.

GHD (2016b) Defence PFAS Environmental Management Preliminary Sampling Program. GHD, Darwin.

GHD (2017) RAAF Base Tindal Drainage Line Soil Sampling Summary of Results. 4322576-97135. GHD, Darwin.

Golder (2015) Stage 2 Contamination Assessment RAAF Base Tindal – New Air Combat Facilities. 1416824-011-R-RevA. Golder Associates, Milton.

Jacobs (2015) RAAF Base Tindal – New Air Combat Capability, Investigation of potential contamination in Buildings 521, 530 and 540, 75 Squadron. IH065600-2904-NP-RPT-0001. Jacobs, Melbourne.

URS (2002) Fire Station Contamination Investigation RAAF Base Tindal. As described in ERM (2005).

3.2.2. Personnel Interviews

Coffey conducted interviews with current and former Base personnel in order to identify or validate information about potential PFAS source areas. Discussions were focussed on historical and current usage of PFAS containing products across the Base. Table 3.2 lists personnel who provided anecdotal information on AFFF use at the Base.

Table 3.2: Personnel interviewed by Coffey

Personnel status Title

Current employee RAAF Base Tindal Fire Section Manager (FSGT)

Former employee (1988 – 2008) RAAF Base Tindal Fire Section Firefighter (FSGT)

Current employee RAAF Base Tindal Senior ADF Officer (SADFO)

Current employee RAAF Base Tindal Base Support Ops Officer (BSOO)

Current employee RAAF Base Tindal Base Support Ops Manager (BSOM)



9

Discussions with past and present Base personnel was undertaken to fill data gaps and indicate past use of PFAS containing products at the Base. Other interviews were conducted by ERM and are documented in ERM (2005). The anecdotal information has been used by Coffey to guide the DSI scope. Coffey has considered anecdotal information as a single line of evidence and has attempted to corroborate information with documented data or direct sampling, where available.

Additional information provided by the Department of Defence regarding potential on-Base sources is summarised in Table 3.3 and shown on Figure 3 (appended).

Table 3.3: Potential AFFF affected Base locations

Potential AFFF application Description

Foam spraying Foam would have been sprayed at the Fire Training Area, Fire Station and occasionally on the runway

Incidents/crashes with potential for AFFF application

Civilian plane crash at north-west end of runway

Crashed F/A-18 buried at “Hornet burial area”

US Marines unmanned aerial vehicle (UAV) buried at “Hornet burial area”

Plane crash at Manbulloo (anecdotal evidence is that only water was used at this crash)

Fuel tanker and car crash on Stuart highway near north-west corner of Base (off-Base)

Any time there was a fuel spill on the runway, AFFF would be applied

AFFF was used for “White Christmas” celebrations on the Base. Exact locations or volumes have not been identified

3.3. Previous PFAS Investigations – Off-Base

Surface water and groundwater sampling and testing reported by several sources in 2016 and 2017 has identified PFAS compounds at detectable concentrations in groundwater in bores between the Base and the Katherine River.

In 2016, Defence commissioned a Preliminary Sampling Program across various sites nationally, which included RAAF Base Tindal. The investigation at RAAF Base Tindal involved seven groundwater wells and two surface water samples (GHD, 2016b). PFOS was detected in two of the wells (0.05 and 0.21 µg/L) and both surface water samples (0.11 and 0.38 µg/L). One surface water sample was collected from Tindal Creek down-gradient of the Base boundary, and the other approximately 3 km further down-stream on Tindal Creek.

In November 2016 the NT Government collected water samples for PFAS analysis from six groundwater wells and three surface water locations on the Katherine River. The assessment was reported on the NT Government website (https://nt.gov.au/environment/environment-data-maps/water-testing-in-the-katherine-region) and identified detectable PFOS+PFHxS concentrations in three wells (maximum concentration of 0.45 µg/L in a well on Bicentennial Parade) and two of the surface water samples (0.02 and 0.04 µg/L) at Katherine Hot Springs and the railway bridge.

In October 2016, Power and Water Corporation conducted sampling of two production wells adjacent to their water treatment and distribution site, at the northern end of Katherine. The results were reported on the Power and Water website (http://www.powerwater.com.au/networks_and_infrastructure/water_services/pfas). The results indicated a maximum concentration of 0.33 µg/L PFOS+PFHxS.

https://nt.gov.au/environment/environment-data-maps/water-testing-in-the-katherine-region

https://nt.gov.au/environment/environment-data-maps/water-testing-in-the-katherine-region

http://www.powerwater.com.au/networks_and_infrastructure/water_services/pfas



10

In November 2016 Defence commenced approaching residents within the vicinity of the Base who were dependant on bore water. Testing has since been conducted at 183 properties and alternative drinking water has been provided to many of these properties where alternative drinking water was not available. Privacy is being considered when managing test data from residential properties, and individual results of identifiable properties are only being provided to the landowner. Where the landowner provides approval, results will be incorporated into the DSI report. Testing to date has indicated detectable concentrations of PFAS compounds (predominantly PFOS and PFHxS) in

groundwater in the northern portion of Uralla (typically between 0.1 and 4 g/L). Wells on the southern

edge of Uralla have been below the detection limit (<0.01 g/L PFOS). Groundwater bore samples

from north and east of the Base have all been reported below the detection limit (<0.01 g/L PFOS).

Collectively, these various assessments indicated PFAS contamination in groundwater across an area from the north-west edge of the Base, west and north-west to Katherine River. Available results indicated delineation of impact to the west along Katherine River, and to the east, north-east and south-east along the base boundary. The lateral extent of off-Base groundwater contamination to the north and south of Katherine had not been delineated and the vertical extent of contamination had not been investigated prior to this DSI.

3.4. AFFF Fire Suppression System Inspections

During the DSI fieldwork program, site walkover inspections were carried out at Base areas suspected of containing fire suppression systems with the potential for containing or having contained AFFF. These are described in the sections below.

3.4.1. Fuel Farms

Fuel Farm 1 and Fuel Farm 2 have fire suppression systems that are inbuilt as part of the facilities. The facility manual for each fuel farm was reviewed and indicated that the farms included AFFF foam tanks or drum stores when built, which likely contained PFAS. Inspection of the current infrastructure did not identify foam tanks connected to the suppression systems, and therefore it appears that the infrastructure was modified after construction. The current inbuilt system is supplied via an inlet booster connection located near the entry to the tank bunker. The fire suppression system in the fuel farm bunkers is operated via pumps on the attending fire truck, which then adds the AFFF to the water which is pumped through the system. Fuel Farm 1 was constructed in 1987 and Fuel Farm 2 in the mid-1990s, and therefore, based on the timeframe, both farms would likely have stored 3M Lightwater™ for application prior to it being removed from use or the systems being modified.

As part of fire management, mobile 50L 6% Ansulite AFFF trolley extinguishers are distributed across the Base. Photographs of on-Base fire suppression systems are provided in the Photograph Log in Appendix B.

3.4.2. Ordinance Loading Area

The fire suppression systems were investigated around the Ordinance Loading Areas to determine if the former or current suppression system used built-in AFFF. The current system for fire suppression at the Ordinance Loading Areas is via water hose reels, mobile trolley extinguishers, which contain 6% Ansulite foam, and hand held units. Built-in systems are water only. Based on anecdotal evidence, there have been no incidents where AFFF has been applied at the Ordinance Loading Areas. These are not considered to be potential source areas.



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3.4.3. Engine Run-up

The jet engine run up area on the south-eastern corner of the runway was inspected for evidence of current or previous fire suppression systems. Inspection of the buildings and shelter did not identify any sprinkler systems. A current 50L trolley mounted foam extinguisher was present in the shelter (6% Ansulite AFFF) and signs were on the walls of the testing shelter where hand held foam extinguishers were previously stored. This is not considered to be a potential source area.

3.4.4. Corrosion control facility

The corrosion control facility, located in 75 Squadron, was inspected for fire suppression systems and the senior officer at the facility was interviewed. The facility does not currently include any in-built fire suppression systems involving AFFF, and has not had such systems in the past.

Analytical results for samples (i.e. waste waters, sediment and concrete) collected from Base infrastructure are presented in Section 8.5.

3.5. Preliminary Conceptual Site Model

3.5.1. Elements of a Conceptual Site Model

A conceptual site model (CSM) was formulated at the start of the DSI works, utilising available

historical information and newly collated data to determine the presence of plausible exposure

pathways and hence the presence of significant risk to susceptible receptors such as humans,

ecosystems or the built environment. For a significant or identifiable risk to exist an exposure

pathway must be present. Exposure pathway identification is a three step process involving the

identification of contaminant sources, how contaminants are transported to other media and locations,

and which receptors may be exposed as a result. The process is presented in Figure 3.1.

Figure 3.1: Source - Pathway - Receptor linkage process

In the absence of a plausible exposure pathway there is no risk. Therefore, the presence of measurable concentrations of contaminants does not automatically imply that the site will cause harm. In order for this to be the case a plausible exposure pathway must be present allowing a source to adversely affect a receptor. The nature and importance of both receptors and exposure routes, which are relevant to any particular site, will vary according to its characteristics, intended end-use and its environmental setting.

SOURCE PATHWAY RECEPTOR



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3.5.2. Potential and Identified On-Base PFAS Source Areas

Source areas have been identified across the Base with respect to the potential to have used, stored or discharged PFAS-based substances. These areas are shown on Figure 3 (appended) and summarised in Table 3.4.

Table 3.4: Potential sources of PFAS contamination

PFAS source area (CSR ID)

Location Description

Fire Training Area (NT0064)

South of RAAF Base Tindal security fence approximately 280 m north-east of the Sewage Treatment Plant (NT0061) and 800 m north of Tindal Creek.

Confirmed PFAS use

This Fire Training Area is utilised for fire suppression training exercises. The Fire Training Area incorporates a central lined fire pit, three evaporation ponds, cleared area, practice equipment and combustion areas outside the lined fire pit.

AFFF has historically been used at the FTA. 3M LightwaterTM was used potentially twice a week between 1993 and approximately 2004, when it was replaced with Ansulite 3%.

Former informal Fire Training Area

South of the sewerage ponds.

Potential PFAS use

A former Base employee has indicated that foam testing was undertaken between 1988 and 1993 at an area south of the sewerage ponds, prior to construction of the current fire training area. The information was not verified by other sources and direct sampling was undertaken in the area to investigate residual impact.

Fire Station (NT0065) Airside, in the vicinity of the air traffic control tower and the Search and Rescue (SAR) helicopter hangar

Confirmed PFAS use

The Base’s firefighting operations are centralised within this location. The Fire Station has been in its current location for more than 20 years and is primarily used for vehicle storage (including fire trucks) equipment testing and equipment cleaning (including line tests).

AFFF was historically stored at the fire station and used during the filling, testing and cleaning of fire trucks.

Mechanical Equipment Operations Maintenance Section (NT0072), comprising Vehicle and Equipment maintenance areas (NT0053 and NT0072)

Within the security fence in the north-eastern portion of the Base.

Confirmed PFAS presence

Vehicle and equipment maintenance activities occur in this area, which would have historically included some vehicles and equipment that contained or had been in contact with PFAS materials (i.e. fire trucks and AFFF pumps).



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Fuel Farm 1 (NT0076) Near 75 Squadron.

Likely PFAS presence

Bunded above ground and underground fuel facility. Fuel Farm 1 has a fire suppression system that is inbuilt as part of the facility. The original facility manual for the fuel farm was reviewed and indicated that the farm included AFFF drum stores when built, which likely contained PFAS based on the facility age (1987). Inspection of the current infrastructure did not identify foam tanks connected to the suppression systems, and therefore it appears that the infrastructure was modified after construction.

Fuel Farm 2 (NT0077) Within the security fence in the northern portion of the Base.


Bunded above ground and underground fuel facility. Fuel Farm 2 has a fire suppression system that is inbuilt as part of the facility. The original facility manual for the fuel farm was reviewed and indicated that the farm included an AFFF foam tank when built, which likely contained PFAS, based on the facility age (mid-1990s). Inspection of the current infrastructure did not identify foam tanks connected to the suppression systems, and therefore it appears that the infrastructure was modified after construction.

Katherine Airport (including aircraft crash site)

At the western end of the runway.

Potential occasional PFAS use

A crash was reported to have occurred on the north-west of the northern portion of the runway. It is possible that AFFF was utilised to extinguish fires associated with the crash. Other minor AFFF use may have occurred in hangars, apron and the former fuel farm. Use of AFFF was not confirmed by any documented sources of information and direct sampling was undertaken to investigate residual impact.

Sewage Treatment Plant (NT0061), sludge drying area (NT0062), and irrigation paddock (NT0063)

Located approximately 280 m south-west of the Fire Training Area.


RAAF Base Tindal’s Sewage Treatment Plant consists of two settlement ponds (Pond 1 and Pond 2), each with a capacity of approximately 8.6 ML.

Treatment occurs through primary sedimentation. When the ponds are at capacity, the effluent water is diverted on to the nearby paddock, east of the Sewage Treatment Plant.



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Hornet Aircraft and Tactical Unmanned Aerial Vehicle Burial Site (NT0051)

Located in bushland on the north eastern portion of the Base east of the quarry (NT0052)


Burial site of crashed FA/18 aircraft and a tactical UAV in the early 1990s.

Due to the remoteness of this location and limited access for exposure to site personnel and ecology, direct sampling of this area was not undertaken. Potential impact migrating from this area was indirectly assessed based on down-gradient concentrations in groundwater.

Other diffuse or unidentified sources may also be present, such as incident response or testing along the runway, application of AFFF to fuel spills, use of foam for recreational purposes or equipment washing, discharge of handheld foam extinguishers. These areas have not been specifically identified for targeted assessment. The cumulative effect of these potential sources has been captured through investigation of the main Base drains (surface water and sediment) and site-wide groundwater investigation.

Secondary sources of PFAS include, but are not limited to:

PFAS adhered/adsorbed to soils in the vadose zone (unsaturated soils above the groundwater table), migrating to groundwater or surface water with seasonal fluctuations in groundwater levels;

PFAS in sediments along Tindal Creek, drainage lines and surface soils across the Base mobilising during the wet season; and

Movement of contaminated soils during historic construction activities and potential generation of dust containing PFAS.

Available reports and interviews have not indicated any potential disposal or activities that indicate landfills would be a potentially significant source of PFAS contamination (i.e. sewerage sludge was not disposed on-Base and waste was not burned (and extinguished)).

Based on the distribution of the potential areas of concern across the Base, and surface water and groundwater flow conceptualisation (known or inferred), the Investigation Area includes:

Land adjacent to the Fire Training Area, the Fire Station, vehicle maintenance areas and fuel farms;

Sediments and surface waters in waterways across the Base;

The receiving water bodies, namely Tindal Creek and Katherine River to the west and north-west; and

Groundwater in the area hydraulically down-gradient to the west and north-west of the Base, between the Base and Katherine River.

3.5.3. Receptors

Potential receptors where plausible pathways are present include:



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Users of extracted impacted groundwater (i.e. bore water used for drinking water, swimming, irrigation, stock watering).

Ecological receptors including flora and fauna in and around Tindal Creek and Katherine River.

Users of Tindal Creek and Katherine River (i.e. drinking water, swimming, consumption of aquatic biota).

Base personnel in impacted areas across the Base.

3.5.4. Pathways – Exposure Route

Potential pathways for the migration of PFAS associated with application and use at the Base include:

Vertical migration of PFAS through soil to the groundwater system.

Lateral migration of PFAS in groundwater towards Uralla, Katherine and the Katherine River. Pumping from large production bores, such as those present at the Research Farm and the PWC facility, is likely to influence the groundwater flow direction and may be drawing groundwater from the base further north than anticipated based on natural groundwater flow regimes. This is based on the assumption that large volumes of groundwater are being extracted from production bores at the Farm and the PWC facility, which are likely to be influencing the local hydrogeology.

Leaching of PFAS from Base soils or sediments into groundwater or surface water.

Surface water runoff of PFAS to Base drains, depressions, open pits and Tindal Creek.

Migration of PFAS in surface water (Base drains and Tindal Creek). The inferred surface water flow direction is to the north-west, towards Uralla, and then west and south-west to Katherine and the Katherine River.

Infiltration of PFAS in surface water to soil and groundwater.

Extraction of groundwater for domestic and stock watering use.

Migration of PFAS through the Base sewage system and potential application of wastewater to land.

3.5.5. Potential Beneficial Uses of Water

Review of the Natural Resources database of registered bores and uses, indicates groundwater quality and yield is suitable to support potable domestic use and irrigation extractive uses.

The beneficial uses declared under the Water Act are shown in Table 3.5.


Media Potential beneficial use Source

Groundwater Raw water for drinking water Raw water for agriculture Raw water for industrial purposes

Government Gazette No G22, 9 June 1999



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Katherine River

Aquatic ecosystem protection, Recreational Water Quality and Aesthetics Agriculture Water Use Raw Water for Drinking Water Supply (at Donkey Camp Pool)

Government Gazette No. G9, March 1997

Tindal Creek Aquatic ecosystem protection, Recreational Water Quality and Aesthetics (Not specifically listed. Selected consistent with Maud Creek.)

Government Gazette No G40, 14 October 1998

These protected beneficial uses have been used to guide selection of screening investigation levels described in Section 7.



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4. Areas of Environmental Concern

This section describes the potential sources of PFAS contamination at the Base and the existing environmental data with respect to PFAS, shown on Figure 3 (appended). Data gaps and associated proposed investigation works are further summarised in Section 6.

The soil and water quality data presented in the following section are from historical environmental investigations and the end of wet season field program undertaken by Coffey in April 2017. Both historical data and data collected by Coffey at the end of the 2017 wet season was used to develop the DSI SAQP, which was finalised in June 2017. Data collected as part of this DSI has been included in the results sections in Chapters 8 and 9.

4.1. Fire Training Area

4.1.1. Background

The Fire Training Area (NT0064) is located to the south of the runway and comprises a bunded and lined fire pit, three evaporation ponds and an open exercise ground. The infrastructure was constructed in 1993 and prior to that, fire training activities were conducted in an unlined pit south of the sewerage farm, according to anecdotal information obtained from current and former Fire Section personnel. The layout of the Fire Training Area is shown on Figure 4.1.

Figure 4.1: Fire Training Area



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Based on interviews with past and present Base employees, AFFF, containing PFOS (3M Lightwater 3% or 6%) was used for fire training exercises in the area on an average of twice a week for the period 1993 to 2004, when its use was phased out. At that time AFFF was transitioned to Ansulite, which contains significantly lower concentrations of PFOS and PFOA, but does include short-chain PFAS compounds that are precursors for PFOS, PFHxS and PFOA (among other long-chain PFAS compounds). Since 2017, all fire training exercises have been carried out using only water, with no AFFF products added.

The fire pit collects fluids and discharges into three staged evaporation ponds to the west, which discharge excess fluids into an open earth drain (if valve is opened). Anecdotal evidence from current and former fire fighters, indicated that during training and testing exercises, AFFF spray was not confined to the fire pit and was also sprayed and flowed onto the surrounding exercise ground.

There have been no reports from personnel or previous investigations of sediment/sludge in the evaporation ponds having been removed or tested for PFAS.

Table 4.1 summarises the available data (from previous investigations and data collected by Coffey in April 2017) and inferred contaminant migration pathways at the Fire Training Area.

Table 4.1: Fire Training Area summary

Identified impacts Pathways

Elevated PFAS concentrations in soils have been identified within the Fire Training Area, adjacent to the bunded fire pit

(maximum 210,000 µg/kg PFOS) and the open earthen drain

to the south-west (max. 93,000 µg/kg) (ERM, 2007, GHD, 2008 and Golder 2012) and in the surrounding area.

The observed surface soil impacts appear to have been practically delineated laterally within an area of approximately 200 m x 200 m (PFAS at detection levels are present within most soil samples collected prior to DSI).

Soil profile testing has been conducted and confirmed maximum concentrations were present in surface soils. PFOS concentrations were not delineated vertically, potentially due to the presence of rock.

Direct run-off of PFAS laden fire suppression water during active training exercises or migration of PFAS laden sediments during high rainfall events may migrate through surface drains or sheet flow to Tindal Creek.

Residual impact in soil may be acting as an on-going source of contamination to groundwater.

Direct exposure may occur to site personnel or ecology in the vicinity of the training ground.

PFAS concentrations in groundwater have been reported in previous investigations at elevated concentrations in twelve events since 2006 (a summary of historical reports is provided in Appendix A and in Tables 4 and 12, appended). Maximum

concentration 7,800 g/L PFOS in 064MW02. PFOS concentrations in groundwater were not delineated in any direction.

Groundwater impacts are likely to be migrating from the source area (the bunded fire pit, evaporation ponds and earthen drain) in an overall north-westerly direction, although variability is likely due to seasonal influences and preferential pathways in the limestone aquifer.

PFAS impacted sediments have been reported in previous investigations in the earthen drain adjacent to the training ground but were not delineated towards Tindal Creek.

Residual impact in sediments may be acting as an on-going (seasonal) source of contamination to surface water and groundwater.

Evaporation pond water concentrations were not investigated prior to this DSI. Sludge was reported to have been observed in the ponds when water levels were low (ERM 2005).

Pond water and sediment/sludge may discharge to surface water during overtopping during high rainfall events, or seepage to groundwater may occur.



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4.2. Fire Station

4.2.1. Background

The fire station (NT0065) is located on the northern side of the runway and is understood to have been in this location since the Base was established in the 1980s. AFFF, containing PFOS (3M Lightwater 3% or 6%) was used for the period 1993 to 2004, when its use was phased out. At that time, AFFF was transitioned to Ansulite, which contains significantly lower concentrations of PFOS and PFOA.

Discussions with former and current Base personnel at the Fire Station have confirmed that wet testing of fire hoses on vehicles was conducted daily at crew changeover and weekly foam testing was conducted. Tests involved opening of valves to confirm correct operation of concentrate mixing, valves and hoses. Initially foam discharge would not have been captured or minimised, but as the environmental effects and persistence became a concern, the volumes produced during testing were minimised and isolated. Testing of foam systems is no longer undertaken. Historically, there were additional foam tests each time a vehicle came back from servicing or repair. Tests were conducted at the Fire Training Area or outside the fire station building.

Table 4.2 summarises the available data (from previous investigations and data collected by Coffey in April 2017) and inferred contaminant migration pathways.

Table 4.2: Fire Station summary


PFAS concentrations in soils (surface soils to depths of 1.5 mBGS) have been identified at concentrations exceeding human health and ecological screening levels. The highest

concentrations (maximum 360,000 µg/kg PFOS at 0.2-0.3 m) have been reported in the low lying area to the south-west of the station building where wash water and surface run-off accumulated. Impact has not be delineated vertically or laterally.

Impacted soil may be presenting an on-going source of contamination to groundwater and migrating in surface water and sediments during storm events.

Detectable concentrations of PFAS have been identified in surface water and sediments in the area of the Fire Station (maximum 4.9 µg/L PFOS in 0990_SW64_17/04/30 (Coffey,

2017) and 10 µg/kg PFOS (GHD, 2017).

Surface water discharges through Base drains into Tindal Creek at the western boundary of the Base. Impacted surface water is also likely to infiltrate to groundwater. Impacted sediment may be presenting an on-going source of contamination to groundwater and surface water through leaching in wet seasons.

Elevated concentrations of PFAS compounds (maximum 260 µg/L PFOS in 065MW02) have been reported over several years. Monitoring well locations are limited to the south-western area of the fire station. Groundwater impact has not been delineated to the north, west or south.

Migration of PFAS in groundwater to down-gradient receptors.



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4.3. Mechanical Equipment Operations Maintenance Section

4.3.1. Background

Mechanical Equipment Operations Maintenance Section is the maintenance and vehicle repair area, comprising the following sub-areas:

Underground storage tank at Motor Transport Facility.

Stormwater discharge at Ground Support Equipment.

Battery Storage Area.

Waste Oil Tank at Mechanical Equipment Maintenance.

Tanker Maintenance Area.

Mechanical Equipment Operations Maintenance Section is located at 17 Squadron in the north-west of the Base. Vehicle and equipment maintenance activities occur in this area, which is likely to have historically included some equipment containing PFAS materials, i.e. fire trucks and associated pumps. Maintenance of fire trucks is now undertaken at a new facility north east of Fuel farm 1, which was constructed between 2007 and 2011.


Table 4.3: Mechanical Equipment Operations Maintenance Section summary

Identified impacts Pathway

PFAS concentrations in soils (at a depth of 0.0-0.1mBGS) have been identified at low, but detectable, concentrations in samples collected to the west and south of Mechanical Equipment Operations Maintenance Section, where a maximum PFOS

concentration of 32 g/kg was reported in sample HVT63, to the south-west of the Mechanical Operations Maintenance Section in an earthen drain that collects stormwater from the precinct (EES, 2016).

Based on the previous assessment data for this area, PFAS contaminated soil was likely presenting an on-going source of contamination to groundwater and migrating in surface water and sediments during storm events.

Limited assessment for PFAS in surface water and sediments has been undertaken in the Mechanical Equipment Operations Maintenance Section prior to the submission of the DSI SAQP in June 2017. Drain sediment sample TDL_ DRAIN 3, located to the south-west of MEOMS reported a PFOS concentration of

15.9 g/kg (GHD, 2017).


At least 15 monitoring wells have been installed in the area by previous investigations addressing other contaminants (predominantly hydrocarbons). PFAS concentrations in groundwater have been identified at Mechanical Equipment Operations Maintenance Section. Monitoring well 053MW04 (northern boundary of MEOMS) has reported PFOS concentrations of 0.87 µg/L (GHD, 2016). Monitoring well 053MW01




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Identified impacts Pathway

(southern boundary of Mechanical Equipment Operations Maintenance Section) has reported PFOS concentrations of 0.15 µg/L (GHD, 2008)

4.4. Fuel Farm 1

4.4.1. Background

Fuel Farm 1 is a bunded above ground and underground fuel facility located near to 75 Squadron, in the east of the Base. Based on a site walkover of the Fuel Farm, the fire suppression system in place consists of a ring main of water around Fuel Farm 1, which is connected to the base fire water supply. This is then connected to the Base sprinkler system via a fire truck to the boost value and the system is then operational. The fire truck supplies AFFF which is connected to the ring main to mix with water.

The original operations manual indicated four AFFF drum cabinets were part of the fire suppression system when the facility was built in 1987. However, inspection of the facility by Coffey and discussions with current facility personnel did not find any evidence of the drum cabinets or AFFF connections. The facility has therefore been assumed to have been modified sometime post construction.

No historical fires have been recorded at Fuel Farm 1, however AFFF may have been used during testing of the suppression system.

The facility is a probable PFAS source area, based on previous detection of elevated concentrations in groundwater down-gradient of the fuel farm.




Historically there has not been any soil analysis for PFAS conducted in close proximity to Fuel Farm 1.

PFAS concentrations in soils (at a depth of 0.0-0.1 mBGS) have been identified at low but detectable concentrations in soil samples collected approximately south of Fuel Farm 1 (samples HVT08 and HVT09), where a maximum PFOS

concentration of 2.6 g/kg was reported (EES, 2016).

Impacted soil may be presenting an ongoing source of contamination to groundwater and migrating in surface water and sediments during storm events.

PFAS concentrations in groundwater have been identified at Fuel Farm 1. Monitoring well 076MW02 (western boundary of the forecourt) has reported the maximum PFOS concentrations of 15 µg/L (Coffey, 2017, with a similar concentration reported by GHD (2016). A significantly lower concentration was reported up-gradient of the fuel farm 1 at 076MW01 (0.21 µg/L PFOS).


Sediment and/or surface water samples were not collected from Base drains immediately down-gradient of the Fuel Farm 1 (to the south-west), however surface water samples were

Surface water discharges through site drains into Tindal Creek at the western boundary of the Base. Impacted surface



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collected from Base drains further down-gradient, near to the south-eastern corner of the runway. A PFOS concentration of 0.06 µg/L was reported in surface water sample 0990_SW39_17/04/30 (Coffey April 2017).

water is also likely to infiltrate to groundwater. Impacted sediment may be presenting an on-going source of contamination to groundwater and surface water through leaching in wet seasons.

4.5. Fuel Farm 2

4.5.1. Background

Fuel Farm 2 is a bunded above ground and underground fuel facility located to the north of the runway and to the west of the OLAs on Link Dispersal Road. Fuel Farm 2 is understood to have a similar fire suppression system to Fuel Farm 1 and is a possible PFAS source area, based on detection of slightly elevated concentrations in groundwater down-gradient of the facility.




PFAS concentrations in soils are not known. Based on the presence of PFAS in groundwater at Fuel Farm 2 and the likelihood of an AFFF-based fire suppression system having originally been present at Fuel Farm 2, there is potential for PFAS impacts to be present in soils in the area.

Impacted soil may be presenting an on-going source of contamination to groundwater and migrating in surface water and sediments during storm events.

PFAS concentrations in groundwater were identified at Fuel Farm 2. Monitoring well 077MW01 (up-gradient of the south-eastern corner of the fuel farm 2) has reported the maximum PFOS concentration of 0.77 µg/L (Coffey, April 2017). Similar concentrations (approximately 0.3 µg/L PFOS) have been reported in groundwater wells around the fuel farm in monitoring during April by Coffey and in other events.


Surface water samples have been collected from Base drains to the south and west of Fuel Farm 2. Sample 0990_SW59_17/04/30 (closest surface water sample down-gradient of the Fuel Farm) reported at PFOS concentration of 0.29 µg/L.


4.6. Katherine Airport

Katherine (Tindal) Domestic Airport is located to the west of the north-west corner of the runway. The airport comprises a small, single building and is staffed part time as required. Air traffic is mostly charter flights and Air North flights to Darwin and Alice Springs. Domestic flights use the same runway as the RAAF Base. A crash was reported to have occurred on the north-west of the northern portion



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of the Katherine Airport runway. It is possible that AFFF were utilised to extinguish fires associated with the crash. Other minor AFFF use may have occurred in hangars, apron and the former fuel farm.

As there was no soil, groundwater, surface water or sediment sampling undertaken in the vicinity of Katherine Airport prior to this DSI, there are no known impacts associated with the area.

4.7. Other Identified Potential Impacted Areas On-Base

Through the PSI documents review of past environmental reports and interviews with current and former Base personnel other potential source/secondary source areas have been identified. These are not considered by Coffey to be primary source areas and contribution (if any) to the regional PFAS plume is considered likely to be minimal.

Table 4.6 summarises other identified areas of potential impacts.

Table 4.6: Areas of potential impacts

Area Potential impacts

Sewage treatment facility, including the Sewage Treatment Plant, Sludge Drying Area and irrigation paddock (horse paddock)

The sewage treatment facility, located to the south and south-east of the Fire Training Area, has been reported to contain PFAS within the waste water stream. The PFAS has been detected within Pond 1, Pond 2 and the effluent tap within the Sewage Treatment Plant. Sludge from the Sewage Treatment Plant collects within the unlined sludge drying area and the effluent is discharged directly into the “horse paddock”.

Sampling of the ponds and effluent tap by AECOM (2009a) identified PFOS concentrations of 0.2 µg/L and 0.1 µg/L respectively. Based on the low concentrations reported, the facility has not been considered to be a primary source area. Accumulation may have occurred in soils in the “horse paddock” due to prolonged irrigation.

Hornet Aircraft and Tactical Unmanned Aerial Vehicle Burial Site

Located in the eastern portion of the Base, the burial area contains a crashed FA18 Hornet (likely extinguished with AFFF) and an unmanned aerial vehicle. There is a potential that AFFF impacted material on the FA18 Hornet has migrated through infiltration into the underlying aquifer. The exact location of the burial site was not identified in documents reviewed by Coffey.

Recreational use of foam

It is understood that AFFF may have been used in the past for recreational activities, such as imitation snow during celebrations for “Christmas in July” on the Base and in some school sports grounds in the Katherine area (off-Base but within the Investigation Area).

Stuart Highway crash (off-Base)

There is anecdotal evidence of a vehicle collision between a fuel tanker and a car somewhere along the Stuart Highway, near to the north-western boundary of the Base, where the highway deviates around the Base. This incident was attended by RAAF Firefighters, who used AFFF on the fire. The exact location of the crash is unknown.



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5. Environmental Setting

5.1. Climate

The Katherine and Tindal area has a sub-tropical climate with distinct wet and dry seasons. RAAF Base Tindal is influenced by both tropical monsoon and inland arid climatic conditions (BoM, 2018).

The dry season generally occurs between September and May, where rainfall events are very rare during this time of year. The wet monsoon season occurs during the warmer months, in particular January to March (AECOM, 2009a) with the wet season generally begins in December after months of build-up conditions. The majority of rain falls between the December and March period and is associated with the inflow of moist west to north-westerly winds into the monsoon trough, producing convective cloud and heavy rainfall over northern Australia. Low pressure troughs can form into tropical cyclones over the wet season months. The Katherine region has been identified as potentially impacted by these tropical cyclones and the Katherine River is prone to flooding (SKM, 2001b).

The climatic data is recorded by the Bureau of Metrology (www.bom.gov.au) at the Base weather station (014932). Over the period from 1981 to 2017, the Base weather station recorded the average rainfall results presented in Table 5.1.

Table 5.1: Tindal weather station rainfall

Statistics Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

Mean rainfall (mm) 1969 to 2017

265.3 233.4 166.0 39.6 2.2 0.7 2.6 1.2 8.8 32.7 93.2 218.7 1074.4

5.2. Topography

The Base is relatively flat, sloping gently towards Tindal Creek (south-west orientation) with some small hills and limestone outcropping (ERM, 2005). Base elevations range from approximately 130 mAHD to 140 mAHD, although it is noted that the Mechanical Equipment Operations Maintenance Section area has an elevation approximately 10 m higher than the Fire Training Area. Topography and drainage figures for the Investigation area are provided in Figure 8 to Figure 8d (appended).

5.3. Surface Water

Most of the Base is within the Tindal Creek catchment area, within which the main surface water body is the Tindal Creek (AECOM, 2009a). Tindal Creek has a catchment area of 173 km2, however it is ephemeral, and does not typically flow between May and November (SKM, 2001b). Tindal Creek is a tributary of Katherine River (Figure 9, appended), and is fed by surface water from bushland and scrubland in the upper portions, but becomes groundwater fed in the wet season from Uralla through to the southern edge of Katherine.

The Tindal Creek enters the Base from the south, veers north-west, south of the sewage irrigation paddock, and continues south of the main runway before leaving the Base under the Stuart Highway to later join the Katherine River down-stream (south) of the Katherine Township (Figure 8, appended).



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5.3.1. Base Open Surface Drainage Network

Surface water run-off across the Base is collected via a series of concrete and earthen drains and is directed to two major formalised drainage channels (Figure 8, appended). The bulk of the surface run-off from the base is discharged to Tindal Creek at a location up-stream near the sewage irrigation paddock (the ‘horse paddock’), and a location down-stream of the north-western end of the airstrip (AECOM, 2009a).

5.3.2. Off-Base Surface Water Bodies

Tindal Creek enters the Base at the south-eastern boundary and flows in a west and north-westerly direction through the Base. Tindal Creek runs to the south of the Base infrastructure, collecting surface water runoff from open drains to the north of Tindal Creek. Tindal Creek exits the Base at the north-western boundary, next to the Stuart Highway. The Creek then flows to the north of Uralla and the Stuart Highway, crossing to the south of the highway at the western end of Uralla, then flowing to the south-west (south of Katherine East and Katherine). Tindal Creek joins Katherine River to the north of Katherine Tip (Figure 2, appended). There appears to be interaction with groundwater via sinkholes, with Tindal Creek flowing underground at certain points between the Base boundary and Katherine River.

A number of springs are located within the Investigation Area (shown as sinkholes on Figure 4, appended). Some springs, located south of the old Stuart Highway, flow for several months after the end of the wet season, discharging directly into the northern reach of Tindal Creek and also discharging into concrete channels that are ultimately flow into Tindal Creek (GHD, 2008).

The Katherine River consist of an incised channel, generally between 200 m and 300 m wide and 20 m deep. It has a wide, flat flood plain and the main channel is heavily vegetated (NRETAS, 2000). Where the Katherine River crosses the unconfined Tindall Limestone aquifer, groundwater feeds into it through springs on both sides of the river, the largest being the Katherine Hot Springs.

Katherine River flows through Katherine from the north-east to the south-west. Approximately 40 km down-stream of Katherine, the King River joins the Katherine River. Approximately 75 km down-stream of Katherine, the Katherine River joins the Daly River.

5.3.3. Flood Potential

The Base is generally flat, sloping gently toward Tindal Creek (the Mechanical Equipment Operations Maintenance Section area is approximately 10 m higher in elevation than the Fire Training Area). Surface water run-off is collected via a series of concrete and earthen drains and is directed to two formalised channels.

The Base stormwater is ultimately discharged to Tindal Creek at a location up-stream of the sewage irrigation site, and a location down-stream of the north-west end of the airstrip. Low lying parts of the Base have been recorded to flood during the wet season (GHD, 2008).

The main drainage feature within the Base is Tindal Creek, which eventually discharges into the Katherine River, south of the Katherine Township. The Katherine River is prone to flooding during the wet season. Figure 9 (appended) displays the modelled annual exceedance probabilities and flooding extents.



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5.4. Geology Overview

5.4.1. Daly Basin Geology

The RAAF Base Tindall lies within the Daly Basin, a broad basin structure elongated in a north-west/south-east direction. The basin is approximately 70 km wide by 350 km long (Tickell, 2005). Katherine lies on the north-eastern side of the basin and the geological formations dip at a low angle, typically less than 1 degree towards the axis of the basin in the south-west. The underlying structure of the basin has a strong influence on the orientation of major streams such as the Katherine River.

The Daly River Group is a sedimentary sequence of Lower Palaeozoic age rocks (approximately 500 million years old) that comprise the Daly Basin. The basal unit of the Daly River Group is the Tindall Limestone. This is overlain by the siltstone dominated Jinduckin Formation, which in turn is overlain by the Oolloo Dolostone (Tickell, 2009). The Daly River Group sits unconformably on a variety of Pre-Cambrian and Early Cambrian rocks. The geology is presented on Figure 4 (appended) and summarised below.

Pre-Daly River Group Rocks

In the Investigation Area two formations underlie the Tindall Limestone, the Jindare Formation and the Antrim Plateau Volcanics. The Jindare Formation is sandstone which is exposed on the north-eastern margin of the basin. It mostly overlies the Antrim Plateau Volcanics but is also interbedded with it in places (Tickell, 2005). The Antrim Plateau Volcanics are more widespread than the Jindare Formation. The Antrim Plateau Volcanics are mainly basalt with minor sandstone interbeds.

Tindall Limestone

The Tindall Limestone is Cambrian in age and present throughout the basin. Limestone and dolomitised limestone are the main rock types in the Tindall Limestone, with minor grey, maroon and green siltstone interbeds. The limestones are light grey to grey-brown in colour, hard and mostly medium to coarsely crystalline. Styolites are common and most fine-scale sedimentary structures and fossils have been obscured by re-crystallisation. In outcrop the limestone is coarsely bedded to massive (Tickell, 2005).

Jinduckin Formation

The Jinduckin Formation is the middle formation of the Daly River Group and conformably overlies the Tindall Limestone across the basin. It is dominantly a dolomitic siltstone with interbeds of dolostone and sandstone (Kruse et al., 1990). The formation generally has a higher gamma count than the Tindall Limestone and shows rapid changes reflecting alternating beds of siltstone and limestone. Individual beds are typically 2 m or less in thickness and rarely exceed 5 m.

Oolloo Dolostone

The Oolloo Dolostone is the uppermost formation in the basin, a largely undeformed sequence of shallow water carbonate rocks. Outcrop is generally poor due to the extensive cover of Cretaceous rocks. The main exposures occur at the north-western and south-eastern ends of the Daly Basin (Tickell, 2002). The Oolloo Dolostone is outside of the Investigation Area.

Cretaceous Sediments

The present day landscape is largely erosional and has resulted from the weathering and erosion of Cretaceous rocks that formerly covered the area, leaving remnant mesas and lateritic plateaus (Tickell, 2005).



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Cretaceous aged sediment and rocks overlie the Tindall Limestone in the south-eastern half of the Daly Basin. The beds predominantly consist of clay, claystone and sandy clay with lesser sandstone, sand and clayey sand. Thicknesses are generally less than 50 m. The maximum recorded thickness directly overlying the Tindall Limestone is 97 m in the Venn agricultural area, 30 km south-east of Katherine (Tickell, 2005).

5.4.2. Local Geology

Localised on-base geology generally comprised of localised cretaceous sediments overlying Tindall Limestone. During drilling works, localised cavernous areas where identified throughout the Tindall Limestone. This is generally consistent with the regional geology described above. A detailed summary of field observed geology is provided in Section 8.1.1 and bore logs are provided in Appendix D.

5.5. Regional Hydrogeology

5.5.1. Hydrogeological Units

Hydrogeological units in the Investigation Area comprise the:

Antrim Plateau Volcanics (basalts forming the base of the Tindall Limestone aquifer).

Tindall Limestone aquifer.

Jinduckin Formation.

Cretaceous sediments.

These units are displayed on Figure 4 (appended). A summary of each unit and the hydrogeological characteristics are presented in Table 5.2.

Table 5.2: Hydrogeological units

Hydrogeological unit

Lithology and hydrogeological characteristics

Basement/Bedrock

The Daly River Group unconformably rests on older Early Cambrian and Pre-Cambrian rocks. In the Investigation Area, this is the Antrim Plateau Volcanics, part of the Early to Middle Cambrian Kalkarindji continental flood basalt province. The Antrim Plateau Volcanics comprise tholeiitic basalt and basalt breccia, with minor sandstone and chert interbeds. The Antrim Plateau Volcanics are exposed to the north of Katherine and this exposure forms the northern extent of the Tindall Limestone and the Daly River Group.

Tindall Limestone

Exposed around the basin margins, this formation is comprised predominantly of medium to coarsely crystalline, styolitic limestone, and dolomitised limestone with minor siltstone interbeds (Tickell, 2005). Individual beds in the formation are effective markers and persistent across large areas. Outcrops of the formation include pinnacles, sinkholes, fissures, potholes and dissolution features, typical of karstic limestone. Cave systems are extensive in the Katherine area (Tickell, 2005).

In the Katherine area the formation is up to 160 m thick. Based on gamma logs, the unit comprises three main packages that are separated by intervals of interbedded shale, siltstone and limestone up to 10 m thick (Tickell, 2012; Figure 5.1, below). The massive limestones range in thickness from 10 m to 75 m but average about 30 m. Folding of the Tindall Limestone is reported near the Katherine River, which creates preferential groundwater pathways.



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Hydrogeological unit

Lithology and hydrogeological characteristics

The aquifer is unconfined near Katherine but is confined by the Jinduckin Formation to the south‐west. Drilling depths of production bores range from 30 to 150 m and yields are typically

2‐20 L/s, with maximum yields >100 L/s (Figure 5, appended). The limestone immediately

below the Jinduckin Formation/Tindall Limestone aquifer contact appears to be of karst origin and forms a highly productive aquifer. Generally bore yields are lower in the confined portion of the aquifer than in the unconfined.

Jinduckin Formation

The Middle Cambrian Jinduckin Formation conformably overlies the Tindall Limestone south-west of the Investigation Area, and comprises dolomitic siltstone with interbeds of dolomite and sandstone. Karst formation does not occur in the Jinduckin due to the absence of large thicknesses of carbonate rock (Karp, 2002).

The Jinduckin Formation acts as a confining layer and restricts recharge to the Tindall Limestone aquifer to negligible levels. However the Jindickin Formation also acts as an unconfined aquifer with yields of typically 0‐5 L/s from bores drilled up to 50 m deep with

occasional higher yielding bores (up to 10 L/s). Bores in this aquifer often yield supplies with excessive salinity.

Cretaceous Sediments

Typically clays, claystone, sands and sandstone, these units overly the older formations across many areas of the Daly Basin, typically as remnant outcropping mesas and plateaux where present. However in the Katherine area, thicknesses are generally less than 10 m (Karp, 2012). These units have been mapped in isolated areas in the RAAF Base Tindal (Figure 4, appended), north of the former Stuart Highway and along the western boundary. Larger areas are present north of the base.

The Daly Basin aquifers are shown on Figure 6 (appended). A cross-section through the Venn agricultural area, located on the eastern margin of the Base is presented on Figure 5.1b, below. The Tindall Limestone aquifer is the focus for this DSI.

Figure 5.1a: Regional geology and cross-section locations

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Figure 5.1b: Cross-section across the Venn agricultural area (Section 3)

Source: Figure 2 & 10 from Tickell (2005)

5.5.2. Limestone fractures and caverns

Most aquifers in the Daly Basin occur in limestone and dolostone and are formed from networks of interconnected fractures and solution cavities, which is called secondary porosity. Fractures are cracks in the rock caused by tectonic forces or from stress relief as overlying rocks are stripped away by erosion. Over geological time scales these rocks are soluble in water. The fractures gradually enlarge as water moves through them and as the rock slowly dissolves. This process can produce openings up to the size of caverns but they are more commonly sub-millimetre to centimetre scale.

Cave systems, if present provide localised pathways for the rapid movement of water. The network of fine cracks and small solution cavities form what is often a more pervasive aquifer that water can move through, generally at a much slower rate. The cave systems dominantly trend north-west to south-east. They have developed on fractures parallel to the strike of the beds. As a consequence, groundwater flow towards the Katherine River is enhanced. The major springs on the Katherine River are the discharge points for the cave systems (Tickell, 2005).

The karstic nature of the aquifers mean that on a local scale groundwater flow is via preferential pathways, however, on a basin wide scale the aquifers are considered to behave as an equivalent porous media with very high transmissivities.

5.5.3. Confined vs Unconfined Tindall Limestone aquifer

The Tindall Limestone aquifer is a fractured carbonate aquifer system that is largely overlain by the Oolloo and Jinduckin geological formations. Groundwater that is separated from atmospheric pressure by relatively impermeable material, or a reasonable thickness of overlying strata is termed confined. The Tindall aquifer is said to be confined by the Oolloo and Jinduckin geological formations to the south of Katherine (Figure 4, appended). The aquifer does not receive recharge from rainfall infiltrating through these shallower geological formations, but rather from rainfall that has entered the



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aquifer system where it outcrops from areas high up in the catchment. Therefore groundwater in confined aquifers is usually old as it has travelled a long distance from the recharge zone. Groundwater pressures in the confined Tindall aquifer in the area of Katherine are higher than that of the unconfined Tindall Limestone aquifer and sometimes above the ground surface. Where the water pressure is above the ground level water flows from the well without pumping and these wells are referred to as artesian. As the pressure is higher in the confined Tindall aquifer than the unconfined areas in the Katherine area, groundwater will not flow from the unconfined to the confined aquifer locally.

Within the Investigation Area, the Tindall Limestone aquifer is unconfined, as it is not confined by overlying material and groundwater is in direct contact with the atmosphere. The groundwater surface is called the watertable and the depth to the watertable varies according to factors such as the topography, geology, seasonal effects, and the quantity of water being pumped from the aquifer. Unconfined aquifers are usually recharged by rain or stream water infiltrating directly through the aquifer material where it is in direct contact with the ground surface.

5.5.4. Aquifer hydraulic properties

Tickell (2005) reports that over 150 domestic and irrigation bores within the Tindall Limestone aquifer have been pump tested, however only a limited number of these tests included observation bore data. Transmissivities were determined to be high, up to several thousand or tens of thousands of m2/day. However this dataset is noted as being biased as most tests are done on bores with high yields. A review of available documentation also failed to provide a reasonably quantitative description of the variation in horizontal (Kh) and vertical (Kv) hydraulic conductivity for the Tindall Limestone aquifer.

Constant rate aquifer pumping tests have been carried out at the Venn airstrip (located to the south-east of the Base) and indicate a transmissivity between 1,100 and 1,600 m2/day and a specific yield value of 0.04 (AGT, 2007). The Tindall Limestone aquifer is unconfined at this location and is approximately 14 km to the east of the Investigation Area. Pumping tests have also been undertaken on the two new Power and Water Corporation (PWC) production bores RN039059 and RN38490 and indicate a transmissivity of around 8,000 m2/day. Puhalovich (2005) noted a tendency for higher transmissivities in the area close to the Katherine River and near the Tindall Limestone aquifer unconfined/confined contact (Springvale Spring). AGT (2007) adopted a transmissivity value of 5,000 m²/day and a specific yield of 0.04 for numerical simulations of the PWC Katherine borefield. The transmissivity value of 5,000 m²/day adopted by Knapton (2006) was based on modelling results from Water Studies (2001).

A summary of aquifer properties is provided in Table 5.3.

Table 5.3: Aquifer properties

Formation Type Transmissivity range (m2/day)

Storage coefficient

Tindall Limestone Karstic limestone aquifer 2,000 – 10,000 0.04

Jinduckin Formation Confining unit <100 0.001

Oolloo Dolostone Karstic limestone aquifer 1,000-10,000 0.04

5.6. Conceptual Hydrogeological Model

Figure 5.2 provides a conceptual model of the Tindall Limestone Aquifer around the Katherine area. The model shows the interaction of the surface water and groundwater systems and accounts for ‘basin wide’ water usage in terms of impact on river flows, spring discharges and water availability to groundwater dependent ecosystems (NRETAS, 2009).



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Figure 5.2: Conceptual Groundwater Model for the Katherine Region

Source: Figure 2 from NRETAS (2009)

5.6.1. Groundwater flow mechanisms

Groundwater divides, coincident with topographic divides, are located approximately midway between the Edith and Katherine Rivers, and the Roper and Katherine Rivers (Figure 1a, appended). Groundwater recharge occurs by way of drainage via discrete pathways through streambeds, caves and sinkholes, with the limestones often exposed at the surface or covered by a thin layer of soil that may provide some degree of attenuation.

Groundwater flow in the unconfined Tindall Limestone aquifer is dominantly parallel to the basin margins, towards the major rivers where discharge occurs. Where the Tindall Limestone aquifer is confined beneath the Jinduckin Formation, the potentiometric gradient is generally shallower than that in unconfined areas indicating groundwater flow is slower. The flux of water moving through the confined aquifer is considered to be minor in comparison to that in the unconfined aquifer (Tickell, 2005). The only likely source of water for the aquifer in the confined area is via minor lateral movement from the unconfined area. Groundwater levels in the confined aquifer indicate a low gradient to the south-west and west confirming that ages increasing in that direction are related to flow. As an example between the bores RN25126 and RN7838 the age difference is 8000 years which gives an apparent velocity of groundwater of only 0.008 m/day.

In the Katherine area, groundwater flow in the unconfined Tindall Limestone aquifer proceeds towards

the Katherine River. Most groundwater levels from registered bores do not show long‐term rising or falling trends, indicative of hydraulic response in a very transmissive aquifer. The major springs on the river are the discharge points for these systems. A dye tracing test conducted just north of the Katherine River showed that water movement through cave systems can be rapid (Karp 2005). Dye released into a sinkhole took two and seven days respectively to reach springs on the river, located at distances of 2.5 km and 4 km from the sinkhole. Groundwater moves relatively slowly through the regional fracture network but when it reaches a cave system it is rapidly transported to the river.

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The minor shale beds that are interbedded with the limestone do not appear to restrict vertical groundwater flow, at least not on a regional scale. Solution cavities have probably resulted in abundant collapses through the shale beds, creating pathways for water to move between limestone layers.

5.6.2. Seasonal dynamics

Water in aquifers is generally not static; the flow is driven by gravity. It is constantly moving from areas where it enters the ground (recharge areas), through the aquifer and then eventually discharging back to the surface at lower points in the landscape (discharge areas). The seasonal cycle of wet season / dry season is one of the major influences on the movement of groundwater. Recharge and discharge zones drive the direction of groundwater flow and help to understand the likely distribution of contamination and the locations of potentially affected receptors.

As the dry season begins, the Katherine River flow is dominated by surface runoff. This source becomes rapidly depleted and groundwater then becomes the main component. Typically by July nearly all of the river flow is sourced from groundwater. This is reflected in both the recession curves of the river flow and by the chemical composition of the water. An inflection in the recession curve often marks the time at which the runoff component ceases. Analysis of Katherine rainfall records and dry season baseflows in the Katherine River has allowed the synthesis of the groundwater component of flows fed by spring discharge into the Katherine River from the Tindall Limestone aquifer (George, 2001). This analysis indicated that groundwater fed flows range between 0.65 m3/s (1930 and 1966), and about 2.5 m3/s (1900 and 1980) (George, 2001).

In order to maintain flows in the creek systems (i.e. Tindall Creek) in the dry season, the watertable must be higher than the stream bed. As it drops to stream bed level, inflow of groundwater will cease. Once it drops below the stream bed the flow can be reversed and the stream will lose water to the aquifer.

5.6.3. Rainfall and groundwater levels

Groundwater levels, recharge and discharge vary depending on rainfall. The four main time intervals over a wet/dry season cycle are shown in Chart 5.1 and discussed below.



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Source: NRETAS (2009)

The chart above shows the water levels recorded in a typical bore (RN037410) as well as the daily rainfall over a one year period.

Interval A - The early rains are lost either to evaporation or are used up in wetting the soil. No recharge takes place and water levels continue to fall as groundwater drains from the aquifer.

Interval B - Increasing rain saturates the sub-soil, allowing the first recharge to occur. Groundwater levels stop falling as recharge and discharge are in balance.

Interval C - This is the peak of the Wet season and recharge now exceeds discharge. This results in the water level rising. High groundwater levels result in greater discharge. Jolly (2002) estimated average recharge in the Katherine area through Cretaceous sediments to be 50 mm/year, half that in the unconfined areas. He noted that the annual groundwater level rises in the unconfined aquifer during average rainfall years is about 7 m compared to 3 m in areas with Cretaceous cover.

Interval D - The major rains stop and recharge ceases. The rate of discharge progressively falls as groundwater levels drop.

5.6.4. Aquifer recharge

Recharge to the Tindall Limestone aquifer occurs primarily by:

Diffuse and direct rainfall recharge (point source) from rainfall events of suitable intensity.

Recharge from the Katherine River (and other surface water systems) during the wet season.

The predominate recharge mechanisms are shown on Figure 5.3.



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Figure 5.3: Recharge mechanisms

Source: NRETAS (2009)

Point source recharge

Groundwater recharge to the unconfined Tindall Limestone aquifer occurs through both distributed (broad surface infiltration) and focussed processes (direct recharge through sinkholes or concentrated linear infiltration along creeks and drains).

A proportion of rainfall recharge occurs rapidly via caves, sinkholes and macro-pores in the unconfined Tindall Limestone aquifer (Tickell, 2005). Sinkholes are prevalent across the Investigation Area. Also most of the Base has Tindall Limestone exposed at the surface, or only a thin layer of cretaceous or Jinduckin formation at the surface, therefore some level of infiltration and recharge is expected across the Base.

The carbon dating indicates that the groundwater in the unconfined areas are relatively young, with uncorrected ages ranging up to 1950 years before present (Tickell, 2016). Some of the samples from the unconfined aquifer contained bomb-fallout carbon 14 (14C) making them less than about 50 years old. There was an influx of artificial radiocarbon (modern carbon) into the atmosphere as a result of nuclear bomb testing in the 1960’s and the percent modern carbon of groundwater recharged since that date are substantially higher than in preceding times.

Also the lack of any clear spatial pattern of the ages implies that recharge occurs throughout the unconfined area and that much of the water cycles through the aquifer rapidly to the discharge points in and along the river.

Contrasting with that, groundwater in the confined areas are considerably older and appear to increase in age towards the basin axis to the south-west. Vertical recharge through the overlying Jinduckin Formation is considered to be very unlikely. The stable isotope signatures in the confined and unconfined parts of the aquifer are essentially similar, suggesting that both are ultimately recharged from the same source. The only likely source of water for the aquifer in the confined area is via minor lateral movement from the unconfined area.



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Stream bed recharge (Katherine River and Tindall Creek)

Stream bed recharge occurs where the material beneath a stream is permeable enough to allow leakage down to an aquifer. The watertable must be lower than the riverbed otherwise leakage cannot occur.

Focussed recharge occurs in areas where surface water channels or other features exist, resulting in higher localised recharge rates during the wet season. Substantially higher recharge is expected where such features intersect karst terrain and sinkholes. Under these circumstances, large volumes of water can recharge the aquifer (Tickell, 2005) and estimates have suggested that focussed recharge may account for ~70% of recharge across the Daly Basin.

5.6.5. Discharge

Discharge from the unconfined Tindall Limestone aquifer occurs primarily:

Through discrete karstic springs.

Drainage to the Katherine River during the dry season.

Groundwater pumping for water supply and private purposes.

Discharge from the unconfined Tindall Limestone aquifer is primarily through seepage and spring discharge to the Katherine River, and discharge zones expand and contract according to fluctuations in the height of the watertable (Tickell, 2005). Groundwater/surface water connectivity is strongly controlled by the prevailing geological conditions. Regions where the carbonate sediments outcrop exhibit high connectivity with the rivers. The connectivity between the rivers and the aquifer are reduced in areas where Cretaceous aged sediments are present (Tickell, 2005).

The springs along the Katherine River act as drains for groundwater predominantly in the unconfined aquifer. Groundwater also returns to the surface at low points in the landscape. Discharge is controlled by the two types of openings that make up the aquifers. Water in the large conduits emerges from discrete springs such as Katherine Hot Spring and Rainbow Spring (Tickell, 2005). These are both cave-like openings and can have discharges up to 500 L/sec.

A more common type of discharge is less visible and originates from the widespread network of fractures rather than from caves. It consists of seepage into the river beds, often over stretches that are kilometres in length. Such discharge zones are best detected by measuring stream flows during the dry season at successive points along the rivers and noting any down-stream increases in flow. The discharge zones shown on Figure 5.4 include both stream bed seepage zones and discrete springs.



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Figure 5.4: Discharge zones into the Katherine River

Source: Figure 4 from NRETAS (2009)

5.7. Regional groundwater levels and flow

5.7.1. Groundwater levels

On a basin-wide scale, the groundwater flow within the Tindall Limestone aquifer is from the south to the north where it discharges to the Katherine River, Flora River, Douglas River and Daly River along the bed of rivers and via discrete springs. Major discharges occur along the Flora River as it intercepts the much larger groundwater flows from the Wiso Basin. Of relevance to the Investigation Area, a smaller scale sub-basin is evident in the Katherine River area where a groundwater divide occurs



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roughly coincident with surface water catchment divide of the King River. Groundwater flow is north-west towards the Katherine River from the divide to the south-east, and south-east towards the Katherine River from the area to the south-east of the Edith River. Similar small scale sub-basins discharge into the Douglas River and Daly River.

The potentiometric surface for the Tindall Limestone aquifer within the Daly Basin in November 2003 is illustrated in Tickell (2005). It shows that groundwater flow in the Investigation Area is towards the Katherine River at elevations ranging between 90 mAHD and 100 mAHD (Figure 5.5). Groundwater converges and discharges to the major surface water systems.

Figure 5.5: Tindall Limestone potentiometric surface for November 2003

Source: Figure 14 from Tickell (2005)

5.7.2. Groundwater level trends

Department of Natural Resources and Environment (DENR) have deployed pressure transducers with in-built dataloggers in a group of groundwater monitoring wells across the Katherine area to record groundwater level fluctuations over time. These monitoring wells form part of the Katherine Tindall Water Allocation Plan program and are displayed on Figure 7 (appended), and summarised in Table 5.4.

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Table 5.4: DENR monitored groundwater bore sites

Bore ID Type Aquifer screened Completion depth (mBGS)

Screen (mBGS)

Yield (L/s)

RN037412 Unconfined Tindall Limestone 42.8 42.8 - 48.8 3.0


RN037410 Unconfined Tindall Limestone 85.6 Open 2.0

RN029429 Unconfined Tindall Limestone 118.0 18.0 - 24.0 54.0 - 60.0 94.0 - 100.0

3.0 2.0 5.0



RN022397 Confined Tindall Limestone 90.0 Open 10.0


The hydrograph for RN37412 is illustrated in Chart 5.2. The well is located 1 km north-east of the existing PWC production bores on the western side of the Katherine River. Minimal influence from groundwater pumping is observed in the hydrograph. Groundwater levels are instead strongly correlated with rainfall. The groundwater level response in RN037412 is also very similar to that in RN037410 and RN037411, which are both located 6 km to the south. The hydrographs of all monitored wells listed in Table 5.4 are presented in Appendix C.


The hydrograph for RN029429 is illustrated in Chart 5.3. The well is located approximately 2 km to the west of the fire training facility adjacent to Tindall Creek. Groundwater levels are recorded close to ground surface during the wet season, suggesting that recharge is rapid, the aquifer is responsive and the aquifer may be receiving direct recharge from Tindall Creek.



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The hydrograph for RN022397 is illustrated in Chart 5.4. The well is located near the Katherine River, with the groundwater level response showing a strong influence from the seasonal levels in the river.


5.7.3. Hydraulic gradients and groundwater seepage velocity

Based on the modelling conducted by AGT (2007) the inferred horizontal hydraulic gradient across the Katherine area is approximately 0.01. Vertical hydraulic head gradients were investigated as part of the 2011 water resources investigation indicated that a slight upward vertical hydraulic gradient



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during the dry season may exist (Tickell, 2012). This analysis was undertaken on bore RN037411, located on the western side of the Katherine River. During the wet season groundwater levels were noted as being similar, indicating that the vertical hydraulic gradient is low.

The Tindall Limestone aquifer has an estimated flow rate of 90 to 180 ML/day and provides baseflow to the Katherine River (ERM, 2005). The modelled groundwater velocity in the unconfined Tindall Limestone aquifer, based on particle tracking modelling is approximately 30 m/day (AGT, 2007).

5.8. Groundwater Quality

Groundwater in the Tindall Limestone aquifer is slightly alkaline on average, but pH can range from slightly acidic (pH 6.4) to slightly alkaline (pH 8). Calcium, magnesium and bicarbonate are the dominant ions and salinity ranges between 300 and 1,500 μS/cm (CSIRO, 2009). Calcium, magnesium and bicarbonate ions dissolve relatively easily from the limestone and dolomite and once saturation is reached their concentrations do not increase any further.

Groundwater in the Jinduckin Formation contains evaporite minerals such as halite (sodium chloride) and anhydrite (calcium sulfate). Calcium and sulfate are the dominant ions in this formation, which have a salinity ranging between 300 and 3,000 μS/cm (Jolly et al. 2004).

Also encountered locally is an excess amount of radium, a naturally occurring radioactive element. This is mainly restricted to an area just west of Katherine and has only been detected in the Tindall Limestone, immediately below the contact with the overlying Jinduckin Formation. Mineralisation in the latter formation is thought to be the source of the radium.

5.8.1. Local Area Water Use

A review of registered bores within the Investigation Area was conducted from the NR Maps site (http://nrmaps.nt.gov.au/) and identified 349 registered bores within the Investigation Area (Figure 5, appended), with:

126 listed as production, farming or irrigation bores.

62 listed as investigation, observation and monitoring.

159 had no recorded purpose.

The main users of groundwater within the Investigation Area and greater Katherine region include:

Power and Water Corporation Town Water supply:

Power and Water Corporation extract and average of approximately 1.5 ML of groundwater per day from a borefield located at the southern end of Morris Road. Lansdowne, which is within the Investigation Area.

Bore water is mixed with water from the Katherine River for the town water supply.

Katherine Research Station:

Groundwater is used for five residences, offices, stock watering, lawn irrigation, a swimming pool and crop research irrigation through centre pivot, lateral move, micro-sprinklers or temporary sprinklers.

Katherine Research Station was established in 1948 by CSIRO. It was acquired by the NT Government in 1990. Throughout this time there have been irrigated crop research and cattle grazing research activities.

Since 2003, annual extraction volumes have ranged from 133.7 ML to 590 ML.

http://nrmaps.nt.gov.au/



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There are four operational extraction bores on the research station, which is within the Investigation Area.

Venn agricultural area and various other agricultural and agricultural industries, predominantly outside the Investigation Area.

Quintis sandalwood plantation, west of Katherine River, outside of the Investigation Area.

Rural stock and domestic across the region.

The Tindall Limestone aquifer is the main source of water for urban and agricultural development in the Katherine region where groundwater is used extensively for the irrigation of crops and gardens and watering of livestock, and also provides part of the drinking water supply for the town of Katherine. The Katherine Tindall Water Allocation Plan (Connor et. al, 2009) regulates the use of the resource to ensure that a balance is maintained between environmental and human demands for groundwater.

5.9. Flora and Fauna

5.9.1. Vegetation

The Investigation Area falls within the Australian tropical savanna region which covers a large portion of northern Australia. The savanna is characterised by a wet season that begins in October and lasts through March (with the heaviest rainfall from December through March) and a dry season from about April through September. Wildfires are a significant feature of the dry season and have a significant influence on the landscape and the types of plants and animals that occupy the area. The terrestrial environment at Tindal consists of large areas of bushland and open forest, that is characterised by Darwin box (Eucalyptus tectifica) and/or bloodwoods (Corbymbia) woodland with sorghum (Sorghum spp.), white grass (Sehima nervosum), and tussock grasses (ELA 2014). The eastern portion of the Base is characterised by Georgetown box (E. microneura) and/or knotted box (E. persistens) woodland, which may or may not include a shrub layer consisting of false sandalwood (Eremophila mitchellii) and sparse tussock grasses. Many of the savanna grasses are shallow rooted annuals that grow in response to rainfall. A report by SKM (2006, reported in ELA 2014) indicated that the lower lying woodland communities at Tindal are comprised primarily of E. latifolia and E. foelscheana, with Themeda spp. comprising the understory, and the higher woodland areas consist primarily of E. tetradonata and E. tectifica, with Sorghum spp. comprising the understory. Fruiting and flowering trees and plants in the riparian areas include Acacia, Eucalyptus, Ficus, Melaleuca, Nauclea, Syzygium, and Terminalia.

Patches of irrigated grass lawns are found in the landscaped areas at Tindal. The surrounding land is predominantly undeveloped or rural. Grazing is the primary use of the rural lands to the north and east of the Base, whereas rural land to the south is used for agricultural crops. To the west of the Base are small scale mango farms, rural residential properties and a quarry.

5.9.2. Aquatic Biota

The primary aquatic environments within the Investigation Area are Tindal Creek and the Katherine River. For both of these water bodies, “aquatic ecosystem protection” is a potential beneficial use declared under the Water Act (Coffey 2017b). The following fish species were identified and collected in Tindal Creek during sampling activities conducted in April 2017: bony bream (Nematalosa erebi), mouth almighty (Glossamia aprion), spangled perch (aka spangled grunter) (Leiopotherapon unicolor), and western rainbowfish (Melanotaenia australis). Inland freshwater crab were also collected from Tindal Creek. The Katherine River lies within a wide, flat floodplain, is about 20 – 30 m wide, and from the dry to wet season varies from 2 - 19 m deep, respectively. The main channel is heavily vegetated. Both saltwater crocodiles (Crocodylus porosus) and freshwater crocodiles (C.



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johnstoni) inhabit the Katherine River, however the saltwater crocodiles are removed during the dry season to protect tourists that are using the river. In the Katherine River the following fish species were identified and collected during the April 2017 sampling activities: archerfish (Toxotes chatareus), barred grunter (Amniataba percoides), bony bream, freshwater longtom (Strongylura krefftii), giant gudgeon (Oxyeleotris selheimi), mouth almighty, and spangled perch. Cherabin (freshwater prawn, Macrobrachium spinipes) were also collected from the Katherine River. Some of the other fish species known to occur in the Katherine River include western rainbowfish and Butler’s grunter fish (Syncomistes butleri) (Douglas and Kennard 2007 in AECOM 2009), barramundi (Lates calcarifer) and sooty grunter (Hephaestus fuligninosus).

5.9.3. Terrestrial Animals

Mammals within the EIA include dingo (Canis lupus dingo), northern brown bandicoot (Isoodon macrourus), wallabies (Macropus agilis), flying fox (aka fruit bats) (Pteropus spp.), microbats (such as the common sheath-tailed bat Taphozous georgianus), and other small mammals such as rodents, gliders, and possums. Northern quoll (Dasyurus hallucatus) also inhabit the area but are rare due to the impact of the cane toad. Bird species occurring in the EIA include birds of prey such as eagles and kites, forest birds such as fruit dove and fig bird, woodland birds, and aquatic birds such as cormorants, darters, egrets, jacana, and jabiru. In addition to the saltwater and freshwater crocodiles discussed above, there are a variety of other reptiles and amphibians within the EIA, including goanna, skinks, geckos, water snakes, turtles, and frogs. The cane toad (Rhinella marina) is a

problematic introduced species as it is toxic to important native species including quolls and goannas.



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6. Investigation Scope

Areas of Environmental Concern (AECs) have been identified based on existing reports or anecdotal

evidence that suggest a potential source of PFAS in the area. Down-gradient environmental

receptors have also been described as areas of environmental concern as these areas may be

impacted by multiple source areas, and require a holistic approach to investigate the impact to

beneficial values.

6.1. Data Quality Objectives

The DSI has followed the DQOs summarised in Table 6.1.

Table 6.1: DSI data quality objectives

Quality objectives

1. State the Problem

PFAS contamination sources have been identified at RAAF Base Tindal. Previous investigations have identified contaminated soil and groundwater in the vicinity of known source areas. Other potential source areas have had limited (if any) assessment for PFAS contaminant nature and extent. A comprehensive investigation of soils, waters and sediments is proposed through 2017.

The extent of PFAS contamination in groundwater and associated impact in surface water off-Base is not previously well understood. Given the tropical climate of the Tindal/Katherine area, surface water flows and groundwater recharge rates will have a strong seasonal variation.

In order to forecast the future impact of residual contamination, and inform contaminant management strategies, some modelling of contaminant transport behaviour will be required. The modelling will be undertaken following the analysis of data collected during the 2018 wet season.

2. Identify the goal of the study

The purpose of the broader investigation is to understand the nature and extent of PFAS contamination as a result of Defence activities.

The purpose of the DSI is to provide sufficient information on the sources of contamination, the contaminant transport conditions, the migration pathways and the current extent of contamination to enable a robust site model to be developed.

The conceptual site model will inform human health and/or ecological risk assessment, and guide effective management strategies.

3. Identify information inputs

Site history relating use of PFAS contaminant materials, to identify product types and locations where contamination may be emanating from (source areas).

Existing data relevant to PFAS in soil, waters and sediment, to confirm the presence of source areas, indicate the potential extent of contamination, and identify gaps in reliable data.

Surface water and groundwater flow regimes, to develop the conceptual site model about the potential migration pathways of contamination from source areas towards human and ecological receptors.

Location and types of human and environmental receptors, to guide selection of relevant screening criteria to reflect plausible exposure routes.

4. Define the boundary of the study

Based on the potential for contaminated surface water or shallow groundwater to migrate west north-west towards Katherine River, the broad study area includes land and waterways on RAAF Base Tindal and the



44

Quality objectives

area between the Base and Katherine River (Figure 2, appended). An approximate buffer of 200 m across the western side of Katherine River has been included.

5. Develop a decision rule

Primary environmental samples will be collected and analysed by the laboratories for the full suite of PFAS compounds.

Soil samples

Relative concentrations and leaching analysis provides information about potential ongoing sources of contamination to surface water and groundwater.

Absolute concentrations describe direct exposure potential where people, plants or animals may be in contact with soil and allow an assessment of risk.

Sediment samples

Relative concentrations and leaching analysis provides information about potential ongoing sources of contamination to surface water through leaching, and indications of historic migration of contamination to drains and waterways.

Relative concentrations and leaching analysis allows for correlation of PFAS concentrations in sediments with biota uptake of PFAS.

Absolute concentrations describe direct exposure potential where people, plants or animals may be in contact with sediments and allow an assessment of risk.

Groundwater samples

Relative concentrations identify sources of contamination and preferential pathways of migration to other areas of the Base, or off-Base. Relative concentrations are also used to calibrate contaminant transport models which can be used to predict future behaviour.

Comparison of groundwater concentrations and surface water concentration informs the understanding of interaction between surface water and groundwater.

Absolute concentrations (and model predictions) at the point of use, or groundwater discharge zoned, describe the exposure where direct contact between water and people, plants or animals may occur, which allows an assessment of risk.

Surface water samples

Relative concentrations identify where residual sources are creating an impact and describe preferential pathways of migration to other areas of the Base, or off-Base.

Absolute concentrations describe the exposure where direct contact between water and people, plants or animals may occur, which allows an assessment of risk.

Absolute concentrations can also be related to biota test results to inform an understanding of bioaccumulation, which then relates to assessment of associated human health or ecological risk.

PFOS, PFHxS and PFOA concentrations will be compared against screening levels relevant to the potential beneficial uses of land or water to identify potential complete pathways and potentially unacceptable risks.

The relative concentrations of all (analysed) PFAS compounds in soil and groundwater samples will be used to characterise the source areas, define the lateral and vertical extent and identify complete exposure pathways.

Residual source mass, leachability of the source and measurements of contaminant mass flux will be used to assess the contribution that each identified source area is making to adverse impact on beneficial uses.



45

Quality objectives

6. Specify performance of acceptance criteria

The assessment as a whole (including consideration of previous assessments) must reliably characterise the sources of contamination from the Base and described the risk that the contamination may pose to human or ecological receptors. In order to achieve that, there must be multiple lines of evidence to support location of source areas; the characterisation of the nature and extent of the residual source and associated surface water or ground water impact; the significance of the risk that that contamination currently poses to relevant receptors; and predictions of future impacts.

Analytical data quality indicators are described in Section 8.

7. Develop a plan for obtaining the data

The methodology and rationale for obtaining relevant data for the DSI is described in the DSI SAQP.

6.2. Summary of Sampling

To meet the objectives of the DSI and address data gaps, the sampling and assessment works described in Table 6.2 were conducted.

Table 6.2: Summary of investigation sampling activities

Location Investigation activities

Fire Training Area

Soil and sediment sampling from 45 soil bore locations (including soil samples collected during the drilling of groundwater monitoring wells) to investigate surface and sub-surface PFAS concentrations across the Fire Training Area and fill data gaps from previous soil investigations of the Fire Training Area.

Surface sediment sampling from 11 locations to investigate surface PFAS concentration in the drainage network.

Installation of five new monitoring wells in the vicinity of the Fire Training Area to assess impacts to groundwater and fill data gaps in the existing groundwater monitoring network.

Installation of four new monitoring wells approximately 200 m down-gradient (north-west) of the Fire Training Area (MW102 to MW105) to assess PFAS impact in groundwater leaving the Fire Training Area.

Vertical contaminant profiling of two existing wells (064MW02 and 064MW12) and one new monitoring well (MW103).

Sampling and analysis of groundwater from all new and existing wells.

Collection of concrete samples from three locations.

Fire Station

Soil sampling from 38 soil bore locations (including soil samples collected during the drilling of groundwater monitoring wells) to investigate surface and sub-surface PFAS concentrations.

Sediment sampling from seven surface drains directly down-gradient (north-west) of the Fire Station.

Installation of one groundwater monitoring well next to the Fire Station (MW129) to supplement existing wells and assess for impacts in the vicinity of the AFFF above-ground storage tank (AST).

Installation of five monitoring wells approximately 250 m down-gradient (north-west) of the Fire Station to assess PFAS impact leaving the area (MW124 to MW128).

Vertical contaminant profiling in two existing wells (065MW02 and 065MW03).



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Mechanical Operations Maintenance Section

Soil and sediment sampling from 20 shallow soil bores across the Mechanical Equipment Operations Maintenance Section area to investigate surface and sub-surface PFAS concentrations and fill data gaps from previous soil investigations of Mechanical Equipment Operations Maintenance Section.

Groundwater sampling from existing monitoring wells to assess for PFAS impact in groundwater from sources in the Mechanical Equipment Operations Maintenance Section area.

Collection of concrete samples from three locations.

Fuel Farm 1

Installation of two new groundwater monitoring wells (MW114 and MW115) next to the down-gradient (north-western) boundary of Fuel Farm1 to assess PFAS in groundwater leaving the Fuel Farm1 area.

Groundwater sampling of new and existing monitoring wells.

Collection of seven sediment samples from low-lying areas and open drains to assess for PFAS impacts in the Base drainage network.

Fuel Farm 2

Groundwater sampling of existing monitoring wells to assess for potential PFAS impacts in groundwater.

Collection of five sediment samples from low-lying areas and open drains to assess for PFAS impacts in the Base drainage network.

Katherine Airport (including crash site)

Soil and sediment sampling from 18 shallow soil bores across the Katherine Airport area to investigate surface and sub-surface PFAS concentrations and verify if PFAS impact has occurred in the area.

Sewage Treatment Plant, sludge drying area, and irrigation paddock

Shallow soil sampling from ten soil bores across the irrigation paddock to assess potential for PFAS impacts to soil from on-Base sewage (BH136 to BH145).

Collection of sediment and surface water samples from open drains and Tindal Creek in the vicinity of the sewage treatment plant and irrigation paddock.

Groundwater monitoring of existing bores in the area (Bore 10, Bore 11 and Bore 20) to assess the extent of PFAS impacts in groundwater.

Potential former informal Fire Training Area

Soil sampling from 12 soil bores to the south of the Fire Training Area and Sewage Treatment Plant to assess for the potential for PFAS impact in soil from potential former informal Fire Training Area (based on anecdotal evidence).

Married Quarters and Base Services

Shallow soil sampling from six soil bores across irrigated sports grounds to assess potential for PFAS impacts to soil from irrigation (BH196 to BH201).

Shallow soil sampling from three soil bores across the Married Quarters area irrigated sports grounds to assess potential for PFAS impacts to soil from irrigation (BH203 to BH205).

Groundwater sampling of one existing monitoring well (054MW02).

On and off-Base

Installation of groundwater monitoring wells to supplement existing investigation bores and private bores to assess the extent of PFAS in groundwater across the Investigation Area.

Vertical contaminant profiling of alternate monitoring wells.




47


Tindal Creek and Katherine River

Multiple rounds of surface water sampling in Katherine River. Sampling conducted at multiple locations between Donkey Camp (approximately 11 km up-stream of Stuart Highway Bridge) to 500 m after King River meets Katherine River (approximately 40 km down-stream of Stuart Highway Bridge).

Multiple surface water sampling events from three locations at Katherine Hot Springs (SW152 to SW154).

Collection of surface water samples from Tindal Creek from up-stream of Fire Training Area to where Tindal Creek joins Katherine River. Samples were collected from approximately 16 locations along Tindal Creek. Additional surface water sampling will be undertaken in Tindal Creek during the 2017/2018 wet season.

Collection of sediment samples from Katherine River and Tindal Creek at locations where surface water samples were collected.

Private bore testing

Sampling of private bores (including residential and Katherine Town Council) within the Investigation Area in order to assess and delineate PFAS impacts off-Base as well as to provide data to assess potential risks relating to groundwater use within the Investigation Area (such as drinking, irrigation, recreational and stock watering uses).

Other works

Collection of groundwater samples from additional existing on-Base monitoring wells in locations outside of the main source areas described above. Locations include, but are not limited to the following:

75 Squadron.

No. 3 Control and Reporting Unit (3CRU).

Base Power Station Unit.

Radar Station (Ross Road, Venn).

Several investigation and RN bores across the Base, away from Base infrastructure (Figure 5, appended).

Collection of surface water and/or sediment samples from on-Base drains, pits and Base infrastructure.

Works not undertaken

Hornet Aircraft and Tactical Unmanned Aerial Vehicle Burial Site:

There is restricted access to this area based on the potential presence of unexploded ordnance (UXO). As there is limited exposure to complete a pathway for direct contact with any PFAS in this area, targeted soil sampling in the area was not conducted.

Any potential source of PFAS impacts in groundwater from the Hornet burial area can be assessed through the sampling of other proposed and existing groundwater monitoring wells located down-gradient of this area.

Stuart Highway crash:

As the exact location of the potential PFAS use is unknown, no targeted soil or groundwater assessment works have been undertaken as part of this DSI. It is believed that any significant surface water or groundwater impacts caused by the use of AFFF after this incident would be captured by the regional surface water and groundwater investigation.

6.3. Fieldwork Methodology

All Coffey fieldworks were undertaken in general accordance with Coffey’s standard operating procedures (SOPs) and industry best practices. All calibration certificates are provided in Appendix M.



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6.3.1. Sub-surface Service Clearance

To avoid encountering underground services during sub-surface excavation (drilling, hand auguring or sediments sampling) works, service clearance was carried out. Service clearance was carried out by an independent contractor using electronic detection equipment and ground penetrating radar (GPR).

To assist identifying underground services dial before you dig (DBYD) plans were obtained prior to fieldworks. The DBYD plans were reviewed on-Base during service clearance activities. In addition to DBYD plans, underground service plans for the RAAF Base Tindal were obtained from the Department of Defence prior to fieldwork and were also reviewed during the service clearance activities.

All works were carried out under the supervision of an experienced Coffey site supervisor.

6.3.2. Decontamination Procedures

Where applicable, the procedures within Table 6.3 were used for decontamination of sampling equipment to be reused between soil and groundwater locations.

Table 6.3: Decontamination procedures

6.3.3. Sample Preservation and Documentation

Samples were all collected in new laboratory prepared containers suitable for PFAS and non-PFAS analysis. Once the sample was collected into the appropriate container, the sample was then immediately placed into a zip lock plastic bag and put directly into an insulated clean ice chest. The ice chest contained either ice or frozen bottles for storage whilst on-Base and then for transportation to the NATA accredited analytical laboratories Eurofins or ALS. To ensure sample integrity, all samples were transported under Chain of Custody procedures.

6.3.4. Borehole Drilling and Monitoring Well Installation

Coffey installed 45 groundwater monitoring wells into the unconfined Tindall Limestone aquifer. The Borehole and Monitoring Well Installation methodology was in general accordance with the Coffey SOP is summarised in Table 6.4. Specific installation details are provided in Table 6.5, and the bore logs provided in Appendix D. A summary of new and existing bore installation details is also presented in Table 1 (appended).

Activity Comment

Adhered Soil / Vegetation Materials

For equipment used to sample solids, all adhered material (e.g. soils or vegetation) was removed prior to use by gloved hand, paper towel or scrubbing brush.

Wash / Rinse Following removal of solids, equipment was washed in a bucket of potable water and the rinsed thoroughly with deionised/distilled water meeting Grade 3 as defined in ISO 3696.

Drying Decontaminated equipment was dried with disposable paper towel or air dried on a surface that would not result in the re-contamination of the equipment.

Storage of cleaned equipment

Where equipment was being temporarily stored between sample locations, the equipment was stored in a location to prevent re-contamination prior to its next use or was rinsed again prior to use.



49

Table 6.4: Borehole drilling and monitoring well installation methodology

Activity Comment

Borehole drilling

All sub-surface drilling holes were cleared using hand tools (hand auger, shovels etc.) to a depth of 1.0 meters below ground surface (mBGS), or into natural soils or refusal was encountered, to visually clear for services that maybe present.

Following clearance, progression of the borehole was made to the target depth using a mechanical drill rig via solid flight auger, percussion air hammer, mud rotary, diamond core and tubex. Boreholes were drilled to a minimum of 125 mm diameter for monitoring well installations. Drilling methods for each well installed are provided on bore logs in Appendix D.

Monitoring wells were initially drilled using percussion air hammer. In order to limit the potential for introduction of chemicals into the groundwater, foam was not added during air hammer drilling. This meant that on several occasions, bores collapsed before the monitoring well could be installed. Due to the high yield of the aquifers encountered during drilling, percussion air hammering also produced large amounts of waste water generation. For these reasons, it was decided that other drilling methods should be attempted to enable deeper drilling with a lower risk of bore collapse.

During rotary mud drilling works, the mud product used was predominantly AMC Bio-Vis, which is a natural polymer-based, non-toxic and biodegradable product. Bentonite powder was also used in some bores. Due to the cavernous nature of the geology being drilled in, rotary mud drilling and diamond core drilling did not generate excess waste mud/water and water used during drilling was lost into the bore. Due to the addition of water into these bores, large volumes or water were removed during well development.

Soil / Rock logging All soil and rock returns were logged in accordance with the Unified Soil Classification System (USCS) and observations of any potential contamination was recorded.

Soil sampling procedure

Soil samples were collected in general accordance with the Coffey standard operating procedure (SOP), which is based on current industry best practice and relevant guidelines and standards.

Soil samples were collected from the surface (0 to 0.1 m), sub-surface (0.2 to 0.3 m, 0.4 to 0.6 m and 0.9 to 1.0 m) and at one meter intervals (if possible or applicable) from in-situ soil returns or rock chip returns.

Soil sample collection Soil samples were collected in new laboratory supplied (LDPE) jars from Eurofins for samples requiring PFAS analysis and new laboratory supplied glass jars for other analytical suites.

Well installation

Monitoring wells were installed at target depths between 15 mBGS and 20 mBGS, using 50 mm machine slotted PVC and 50 mm riser PVC.

Once the well was installed into the borehole, the annulus was backfilled with 3 mm sand/gravel pack to approximately 0.5 m above the machine slotted PVC (screen). Above the sand/gravel was backfilled with an approximately 0.5 to 1.0 m thick layer of bentonite (water was added to the bentonite to create a seal or ‘plug’ so surface runoff could not enter the screened section of the well). Grout was then backfilled above the bentonite. To finish the monitoring well a steel flush mounted cover or a steel stand pipe monument was concreted in over the well.

All wells were installed by, or under the supervision of, an appropriately licenced driller. All wells were permitted and registered with DENR.

Well development Prior to development, the newly installed monitoring well was gauged for depth to light non-aqueous phase liquid (LNAPL) (if present), water and total depth. All wells



50

Activity Comment

were gauged from a clearly marked and designated point at the top of each well casing using an air/oil/water interface probe (IP).

All newly installed monitoring wells were developed to remove disturbed sediments and introduced drilling fluids/muds, to establish connection with the target aquifer, improve near well permeability, reduce entry of suspended solids and increase well efficiency.

Development of newly installed monitoring wells was carried out with the use of a downhole pump or air lifting. Development was continued until the volume of water added during the drilling process was removed (when the bore was drilled using rotary mud or diamond core drilling methods) or three well volumes were removed (when the bore was drilled using air hammer drilling methods), and the produced water showed significant reduction in suspended sediments and stable water quality measurements (Temperature (Temp), dissolved oxygen (DO), electrical conductivity (EC), pH, Redox). Particular attention was payed to EC, pH and DO to indicate stabilisation.

Surveying A registered surveyor was engaged to survey the newly installed monitoring well location (MGA coordinates), and elevation (Australian Height Datum). Surveying data is provided in Appendix N.

Table 6.5: Groundwater monitoring well locations

Monitoring well ID

Total well depth (mBGS)

Screen (mBGS)

Area

0990_MW100 15.0 1.0 - 15.0 West of Katherine Airport

0990_MW102 20.5 2.5 - 20.5 Fire Training

0990_MW103 17.5 2.5 - 17.5 Fire Training

0990_MW104 20.2 2.5 - 20.2 Fire Training

0990_MW105 15.2 2.7 - 15.2 Fire Training

0990_MW106 18.0 2.7 - 18.0 West of Fire Training Area

0990_MW107 22.5 1.0 – 15.0 West of Fire Training Area

0990_MW108 14.0 1.0 - 12.3 West of runway

0990_MW109 13.5 1.5 - 13.5 West of runway

0990_MW109D 20.2 15.7 - 20.2 West of runway





0990_MW114 21.5 1.0 - 21.5 Fuel Farm 1

0990_MW115 15.8 2.8 - 15.8 Fuel Farm 1

0990_MW116 20.0 2.5 – 20.0 Fire Training Area

0990_MW117 14.5 0.5 - 14.5 Western boundary of Base





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Monitoring well ID

Total well depth (mBGS)

Screen (mBGS)

Area

0990_MW120 20.5 2.5 - 20.5 Fire Training Area




0990_MW124 19.9 1.5 - 19.9 Fire Station

0990_MW125 20.0 1.5 - 20.0 Fire Station

0990_MW126 20.0 2.0 - 20.0 Fire Station

0990_MW127 20.0 1.5 – 20.0 Fire Station

0990_MW128 18.5 1.5 - 18.5 Fire Station

0990_MW129 20.1 2.1 - 20.1 Fire Station


0990_MW131 15.1 1.1 - 15.1 North-west of Base



0990_MW134 20.5 2.5 - 20.5 Katherine Research Station (south)

0990_MW135 19.1 2.5 - 19.1 Katherine Research Station (north)

0990_MW136 24.4 16.9 - 24.4 Gorge Road

0990_MW137 20.0 2.0 - 20.0 Katherine East

0990_MW138 19.5 5.5 - 19.5 Katherine East

0990_MW139 13.5 2.5 - 13.5 Bicentennial Road




0990_MW143 19.4 2.4 - 19.4 Victoria Highway

0990_MW144 20.0 3.0 - 20.0 Victoria Highway

Groundwater monitoring wells were installed to address data gaps across the Investigation Area. The gauging and sampling results from these new wells will assist with:

Characterising source area concentrations.

Delineate contaminant plumes where possible.

Mass flux measurements.

Depth profiling to characterise vertical distribution of contaminants.

Understanding groundwater surface water interaction.

6.3.5. Soil Sampling

The soil assessment was completed with reference to the guidance within following documents:



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Standards Australia 2005, AS4482.1 – 2005 Guide to the investigation and sampling of sites with potentially contaminated soil Part 1: Non-volatile and semi-volatile compounds (Standards Australia AS4482.1-2005).

Standards Australia 1999, 4482.2-1999 Guide to the Sampling and Investigation of Potentially Contaminated Soil. Part 2: Volatile Substances (Standards Australia AS4482.2-1999).

The relevant schedules of the NEPC (2013) National Environmental Protection (Assessment of Site Contamination) Measure 1999, as amended in 2013, (National Environment Protection Council).

The soil assessment completed at the Base was undertaken in accordance with the methodology detailed in Table 6.6.

Table 6.6: Soil assessment methodology

Activity Detail

Date of Field Activities First borehole sample collect: 14/06/2017. Last borehole sample collected: 24/08/2017.

Underground service clearance Upon commencement of work each location was cleared for underground services by a professional underground service location contractor utilising the appropriate detection equipment.

Strata logging Soil and rock logging was generally in accordance with AS 4482.1 and the Unified soil classification system.

Soil assessment

Soil bores were extended to a depth range of 0.5 mBGS – 4.8 mBGS using a combination of NDD methods, hand auger and crow bar. Soil samples were collected at regular intervals from hand augers or air cuttings.

Field screening Soils were inspected for visual and olfactory signs of contamination. Visual inspection of the soils was completed to assess the potential for ACM to be present.

Decontamination procedure

Decontamination of sampling equipment was completed using PFAS Free deionised water. Reusable sampling equipment (such as a trowel) was decontaminated scrubbing with a brush and a multi-wash procedure with deionised water. Fresh disposable nitrile gloves were worn for each sample collection.

Disposal of soil cuttings Soil cuttings from each location were backfilled into the borehole upon completion of the soil sampling. Soils were re-compacted to the extent practicable using the hand auger and a crowbar.

Sample preservation Samples were placed in laboratory supplied LDPE jars. Samples were stored on ice, in an esky, and transported under chain-of-custody documentation while on-Base and in transit to the laboratory.

6.3.6. Sediment Sampling

The sediment sampling was undertaken in accordance with guidance provided in the following documents:

Standards Australia 2005, AS4482.1 – 2005 Guide to the investigation and sampling of sites with potentially contaminated soil Part 1: Non-volatile and semi-volatile compounds (Standards Australia AS4482.1-2005);



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Standards Australia 1999, 4482.2-1999 Guide to the Sampling and Investigation of Potentially Contaminated Soil. Part 2: Volatile Substances (Standards Australia AS4482.2-1999);

The relevant schedules of the NEPC (2013) National Environmental Protection (Assessment of Site Contamination) Measure 1999, as amended in 2013, (National Environment Protection Council).

Sediment sampling were collected using two methods depending on the presence or absence of surface water at the sampling locations.

Where water was present, sediment samples were collected using a stainless steel dredge sampler lowered to the bottom of the water body, and dragged along the bottom to collect a sediment sample. The sampler was then removed from the water body and the sample placed into a laboratory supplied sampling container.

Where water was not present in drains or water bodies, a sample was collected directly from the base of the drain/stream bed using the sample jar or a decontaminated stainless steel trowel, and placed directly into laboratory supplied containers.

The samples were placed into eskies on ice and transported to the laboratory under chain-of-custody protocols. Primary samples were analysed by Eurofins MGT and secondary sample by ALS. The samples were received by the laboratory with sufficient time to be analysed within the recommended holding times. All equipment was decontaminated with deionised water between sampling locations.

6.3.7. Groundwater Sampling

Groundwater sampling was conducted using HDPE HydraSleeves and low flow micropurge techniques. The groundwater sampling methodology is summarised in Table 6.7.

Table 6.7: Groundwater sampling methodology

Activity Comment

Well gauging

Monitoring wells were gauged using a decontaminated oil/water IP. Wells were gauged for the depth to LNAPL (if present), water and total depth.

All gauging was from a clearly marked and designated point at the top of the well casing.

Groundwater sampling

Groundwater samples were collected using two methods (HydraSleeves and micropurge sampling. The sampling rounds conducted were as follows:

April 2017 – Hydrasleeve.

July 2017 – Hydrasleeve.

Early September 2017 – Micropurge at multiple depths.

Late September 2017 – Hydrasleeve.

A description of the sampling methods used is provided below:

Method 1: Vertical profiling of aquifer was undertaken using micropurge technique

The Micropurge technique used a stainless steel submergible housing bladder pump, with a new disposable internal bladder cartridge for each well and disposable PE tubing. The flow rate and standing water level (SWL) draw down was controlled using a microprocessor control unit and measured with the air/oil/water IP.



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Activity Comment

The pump unit was lowered to the required depths within the water column requiring sampling. After stable water quality parameter requirements were achieved, as per the Coffey SOP, a sample was collected from the disposable tubing into the laboratory supplied sample bottles.

Method 2: GME - Samples were collected using HydraSleeves

The HydraSleeves were lowered into the well and positioned at depths determined from the results of the initial vertical profiling (Method 1). As the HydraSleeve is lifted, the collapsed sampler opens and captures a discrete volume of water from the water column within the well. The collected HydraSleeve sample was decanted directly into the laboratory prepared sample bottles.

Note that HydraSleeve samplers are considered to be a passive sampling method that does not disturb the water column and as such are a preferred sampling method as outlined in the NEPM 2013 guidelines.

Sample collection

Groundwater samples were collected in new laboratory supplied bottles from Eurofins for samples requiring PFAS analysis and new laboratory supplied glass and plastic bottles for other analytical suites.

All samples were collected into bottles with appropriate preservatives and zero head space for samples requiring volatile analysis.

In-situ water quality parameters

After the sample was collected, the following in-situ water quality parameters were measured using a calibrated down-hole water quality meter:

Dissolved oxygen (DO);

Electronic conductivity (EC);

Oxidation-reduction potential (ORP);

Temperature; and

pH.

The water quality meter used was calibrated in accordance with the manufactures specifications at the beginning of each day and decontaminated with PFAS free deionised water between each location.

6.3.8. Surface Water Sampling

Surface water sampling was undertaken in accordance with guidance provided in the following documents:

AS/NZS 5667.4:1998 ‘Water Quality – Sampling Part 4: Guidance on Sampling from Lakes, natural and man-made’.

AS/NZS 5667.6:1998 ‘Water Quality – Sampling, Part 6: Guidance on sampling of rivers and streams’.

AS/NZS 5667.9: 1998 ‘Water Quality – Sampling, Part 9: Guidance on sampling from marine waters’.

Surface water samples were collected from flowing sections of water bodies (where relevant), and samples collected from the Katherine River were collected from off the eastern bank.

The surface water sampling methodology was generally consistent with industry best practice and is summarised in Table 6.8.



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Table 6.8: Surface water sampling methodology

Activity Comment

Surface water sampling

Surface water samples were collected directly into laboratory provided 500 mL PET bottles suitable for trace analysis of PFAS.

Once filled, the sampling bottle was removed from the sampler, sealed and placed into an esky on ice and transported to the laboratory under standard chain-of-custody procedures. Primary samples were analysed by Eurofins MGT and secondary sample by ALS.

Once the sample was collected a water quality meter was placed in the water body and field parameters such as pH, DO, EC, ORP and water temperature were recorded. General field observations were also recorded including anything of note about the water, colour, sheen, odour etc.

Sample collection

Where access allowed (i.e. swimming pool), a closed sample bottle was slowly lowered into the water by hand and, with the cap gradually opened allowed water to enter the container and then closed again beneath the water surface without capturing any surface film. Where access was not possible to safely reach the water by hand, an aluminium sampling pole was used to reach out approximately 1.5 m to 1.8 m into the water body (creek, river or pool) and push the sampling bottle or intermediate sampling container, open end first, into the water approximately 300 mm below the water surface, being careful not to stir up sediments (where only shallow) and minimising the amount of surface film collected.

Where the sample was not able to be collected directly into the sampling bottle, an intermediate container was used. To check that the intermediate sample container was not cross contaminating samples, equipment rinsate samples were collected.

Decontamination All equipment was decontaminated with PFAS free deionised water between sampling locations using a scrubbing brush and a multi-wash procedure with laboratory-supplied water.

In-situ water quality parameters

To capture the water quality conditions at the time of sample collection, the following water quality parameters were measured:

Dissolved oxygen (DO);

Electronic conductivity (EC);

Oxidation-reduction potential (ORP);

Turbidity;

Temperature; and

pH.

The water quality meter used was calibrated in accordance with the manufactures specifications at the beginning of each day and decontaminated between each location.

6.3.9. Private Bore Sampling

The private bore sampling methodology undertaken is summarised below in Table 6.9.



56

Table 6.9: Private bore sampling methodology

6.4. Laboratory Analysis

Primary, intra-laboratory duplicate, inter-laboratory duplicate, rinsate blank and trip blank samples were submitted to Eurofins Environmental Consultancy Pty Ltd (Eurofins) for primary analysis or ALS Environmental laboratory for secondary analysis. The selected laboratories are National Association of Testing Authorities (NATA) certified for the analysis required.

Laboratory analysis were conducted in accordance with the requirements of NEPM and are referenced to USEPA, NEPM and APHA methods. The analytical suites, laboratory methods and laboratory limits of reporting (LORs) applied for the investigation are detailed in Table 6.10.

Table 6.10: Summary of analytical methods

Analysis Analyte Waters LOR Soils LOR Method

Eurofins PFAS, primary samples 28 individual PFAS compounds

0.01 – 0.05 g/L (for individual compounds)

5 µg/kg (each compound)

In-House Method based on US EPA Method 537 Version 1.1 (LC/MS-MS) (NATA certified)

ALS PFAS, secondary samples 28 individual PFAS compounds

0.01 – 0.1g/L 1 – 0.2 µg/kg (each compound)

In-house (EP231PFC) LC/MS-MS (NATA certified)

Chain of Custody and analysis request documentation and certified laboratory reports and QC acceptance targets are included in Appendix E to Appendix J.

6.5. Quality Assurance and Quality Control

The full quality assessment is presented in the Data Validation in Appendix K. Coffey considers the laboratory quality control (QC) results are acceptable for the purposes of interpreting and verifying the primary analytical results for the soil, surface water and groundwater samples. The results of the quality assurance/quality control (QA/QC) program are further discussed in Section 8.8.

Activity Comment

Private bore sampling

Private bore samples were collected directly from the bore into laboratory supplied 500 mL polyethylene terephthalate (PET) bottles suitable for trace analysis of PFAS. The property occupant was contacted prior to arrival and then escorted Coffey staff to the location of the most direct access of water arising from the bore.

Sample collection

After liaising with the property contact and locating a sampling point closest to the bore outlet, the water was allowed to run for a minimum of one minute, dependant on the access type and distance travelled from bore to access point, to purge stagnant water within the system. The sample bottle was then placed within the flow of water and allowed to fill.

Sample preservation and analysis

Once filled, the sampling bottle was sealed and placed into an esky on ice and transported to the laboratory under standard chain-of-custody procedures. Primary samples were analysed by Eurofins MGT and secondary sample by ALS.



57

7. Assessment Criteria

7.1. Assessment Framework

This subsection describes the environmental legislation and investigation guidelines relevant to conducting contamination assessment on the Base and surrounds. Specific proposed investigation values for soil, sediment, waters and biota are presented.

7.2. Commonwealth

The National Environment Protection (Assessment of Site Contamination) Measure 1999 (NEPM), as amended in 2013, provides a nationally consistent framework for identification and investigation of contaminated sites and is given effect by individual legislation and guidelines in each state and territory.

The NEPM sets out the approach to assessment of a site from desktop review, through to quantitative risk assessment. Guidance schedules cover standard sampling and analysis technique, data interpretation and quality review, and exposure settings for assessment of risk to human health or ecology. Health and ecological investigation levels are provided for some contaminants, under specific land-use scenarios. A framework is described to support derivation of risk based levels, where default investigation levels are not provided, or exposure settings is not relevant.

7.3. Northern Territory Legislation

The Northern Territory (NT) Environmental Protection Authority (EPA) requires contaminated site that pose or threaten to pose serious or material environmental harm as defines in the Waste Management and Pollution Control Act (“the Act”) to be assessed in accordance with the requirements for environmental audits in the Act. The NT EPA requires assessment of site contamination to be conducted in accordance with the NEPM.

The Water Act is the primary piece of legislation that governs water resource regulation and management in the NT. The objective of the Water Act is “to provide for the investigation, allocation, use, control, protection, management, and administration of water resources”. Under the Water Act, beneficial uses can be declared for specific water bodies and water quality objectives are established to describe the water quality targeted to protect the relevant beneficial uses.

7.4. Beneficial Uses

Screening investigation levels have been selected for groundwater, surface water, soils and sediment based on the current and potential future land uses and identified off-Base potential receptors.

The groundwater and surface water beneficial uses declared under the Water Act 1992 are shown in Table 7.1.



58



Groundwater

Raw water for drinking water

Raw water for agriculture

Raw water for industrial purposes

Government Gazette

No G22, 9 June 1999

Katherine River

Aquatic ecosystem protection,

Recreational Water Quality and Aesthetics

Agriculture Water Use

Raw Water for Drinking Water Supply (Power and

Water extraction point at Donkey Camp Pool)

Government Gazette

No. G9, March 1997

Tindal Creek

Aquatic ecosystem protection,

Recreational Water Quality and Aesthetics

(Not specifically listed. Selected consistent with Maud

Creek.)

Government Gazette

No G40, 14 October

1998

Surface water (on-Base) Aquatic ecosystem protection,

Human health (commercial)

Professional

judgement based on

likely land use.

Sediment (on-Base) Aquatic ecosystem protection,

Human health (commercial)

Sediment (off-Base) Aquatic ecosystem protection,

Human health (open space)

Soil (on-Base) Human health (residential, open space, commercial

setting)

7.5. Screening Criteria

7.5.1. Soil

The relevant current land uses across most of the Base is considered to be open space and commercial/industrial. Other sensitive uses may also occur in specific areas, including child care or residential, and therefore a conservative health based screening value associated with residential use has been adopted, but without consideration of home-grown produce, to identify where future land use controls may be appropriate. The ecological setting of the Base is predominantly consistent with open space environment, although some areas adjacent to Tindal Creek may be considered areas of ecological significance. Due to the high volumes or rainfall run-off and infiltration during the wet season, interaction between soils and aquatic ecosystems is also recognised across the Base.

Contaminants can also present risks to soil invertebrates and upper-trophic level receptors through direct contact and incidental ingestion of soil. Potential exposure mechanisms include adverse impact on survival, growth, and reproduction. In this instance, terrestrial soil screening values will be applied at the Tier 1 screening evaluation to conservatively consider soil invertebrate exposure.

Human health screening values have been primarily sourced from:

HEPA (2017) PFAS National Environmental Management Plan (draft NEMP). Values presented in the draft NEMP related to residential setting with home-grown produce, high density residential and commercial industrial use. Values applied in this DSI were derived using the same principles as the draft NEMP, but for residential with no home-grown produce to reflect that intake from



59

produce would be assessed separately. Values for open space/recreation setting were also derived and applied for general base use rather than the NEMP commercial /industrial setting, as the site layout allows for greater exposure to soil than represented by NEPM HIL-D assumptions.

NEPC (2013) National Environment Protection (Assessment of site contamination) Measure 1999, as amended in 2013.

Ecological screening values have been primarily sourced from:

Department of the Environment and Energy (DoEE). 2016. Draft Commonwealth Environmental Management Guidance on Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic acid (PFOA). Screening values have been nominated to identify soils which may be contributing to contamination of water bodies (“Areas of ecological significance”) and to identify soils which may have direct toxicity to terrestrial ecology in different settings (“Residential/open space” and “Commercial/Industrial”). Note that the soil screening level for direct contact with terrestrial ecology has since been updated and is now based on the CRC CARE 2017 document Assessment, management and remediation guidance for perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) – Part 3: ecological screening levels (CRC CARE 2017). (The CRC CARE screening values are presented in Table 5-2 in Appendix D of CRC CARE 2017).

NEPC (2013) National Environment Protection (Assessment of site contamination) Measure 1999, as amended in 2013.

Where criteria for specific analytes are not listed in Australian guidelines, alternative criteria have

been adopted.

Where leachability is assessed, the results will be screened against the relevant water screening

levels, as an indicator of the potential for soils or sediments to contaminate surface water or

groundwater.

The proposed Soil Assessment Criteria are summarised in Table 7.2.

Table 7.2: Proposed soil assessment criteria (mg/kg)

Contaminant

Maintenance of Ecosystems1 Human Health2

Areas of Ecological

Significance

Residential / Public Open Space

Residential Recreational / Open space

PFOS 0.0111 32 9 - -

PFOS + PFHxS - - 0.6 10 1.210

PFOA 0.659 17 9 4.8 10 1010

Arsenic (III) 40 100 100 300

Cadmium NE 10 3 20 90

Copper 40 70 100 300

Chromium (III) 70 200 12,000 4 12,000 4

Iron NE NE 5,500 4 5,500 4

Lead 540 1,170 300 600



60

Contaminant

Maintenance of Ecosystems1 Human Health2

Areas of Ecological

Significance

Residential / Public Open Space

Residential Recreational / Open space

Manganese NE 220 5 3,800 19,000

Nickel 15 40 400 1,200

Zinc 70 125 7,400 30,000

Benzo(a)pyrene 0.7 0.7 NE NE

Total PAHs NE NE 300 300

Benzene 10 50 0.5 7 NL 7

Toluene 10 65 160 7 NL 7

Ethylbenzene 1.5 70 55 7 NL 7

Xylenes 10 105 40 7 NL 7

Naphthalene 10 170 3 7 NL 7

TPH >C6 – C10

less BTEX

125 180 45 7 NL 7

TPH >C10 - C16

less naphthalene

25 120 110 7 NL 7

TPH >C16 – C34 NE 300 4,500 6 5,300 6

TPH >C34 – C40 NE 2,800 6,300 6 7,400 6

* Low reliability value; NE = Not Established; NL = Not Limiting

1. NEPC (2013), Ecological Investigation Levels

2. NEPC (2013) Health Investigation Levels

3. CCME (2013) Canadian Soil Quality Guidelines for the Protection of Environmental and Human Health

4. US EPA (2016) Regional Screening Levels for Soil (Threshold Hazard Quotient 0.1)

5. US EPA (2005) Ecological Soil Screening Levels (ECO-SSLs)

6. Friebel and Nadebaum (2011), Health screening levels of petroleum hydrocarbons, HSLs direct soil contact

7. NEPM (2013) Health Screen Level for Vapour Intrusion, sand, 0m to <1m soil depth

8. Upper ranges necessary for satisfactory plant growth (Charman and Murphy, 2010)

9. CRC CARE 2017 document Assessment, management and remediation guidance for perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) – Part 3: ecological screening levels

10. Values derived using HIL-A and HIL-C setting parameters (NEPC, 2013), FSANZ 2017 tolerable daily intake (TDI) and 20% allocation of TDI.

11. Soil with the potential to impact water ways (residential and parkland) DoEE (2016) – Draft Commonwealth environmental management guidance on Perfluorooctane sulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA), October 2016.

DoEE 2016 indicates that the screening value for potential impact to waterways need only be applied where direct measurement of PFAS in water has not been conducted. Although direct measurement in drains, creeks and rivers has been conducted in this assessment, the soil screening value has still



61

been includes as it provides some indication of the areas of soil impact that may be contributing to the identified contamination in waters.

7.5.2. Groundwater

The declared beneficial use and water quality standards of the groundwater of Katherine area is raw

water for drinking water, raw water for agriculture and raw water for industrial purposes (Government

Gazette No G22, 9 June 1999).

Potable domestic

Screening values have been sourced from:

Department of the Environment and Energy (2016) – Commonwealth environmental management guidance on Perfluorooctane sulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA), October 2016.

NHMRC (2011) – Australian Drinking Water Guidelines 6, updated November 2016.

Department of Health (2017) Health Based Guidance Values for PFAS, based on FSANZ recommended TDI – Drinking water.

WHO (2011) Guidelines for Drinking-Water Quality, 4th Edition, World Health Organization.

Recreation/Irrigation

Contaminants can present risks through irrigation use by different mechanisms, including adverse

impact on plant growth, incidental human exposure during irrigation and human intake due to

accumulation in edible produce. Primary contact recreation values have been applied to

conservatively screen for elevated intake through incidental human exposure. Where groundwater is

being used for irrigation of edible produce, specific testing of irrigated soils and produce is being

conducted for PFAS to assess uptake.


Department of Health (2017) Health Based Guidance Values for PFAS, based on FSANZ recommended TDI – Primary contact recreation.

NHMRC (2008) - Guidelines for Managing Risks in Recreational Waters.

Ecosystem protection (Habitat for plants and animals)

The declared beneficial uses of Katherine River, which is the ultimate environmental receptor of

groundwater discharged from the Base, (Government Gazette No. G9, March 1997) does not specify

a level of protection, so a default protection of level of 95% of species has been nominated as a

screening value. However, where a contaminant is bio-accumulative a higher level of protection

should be considered (ANZECC & ARMCANZ 2000).


Draft Commonwealth Environmental Management Guidance on PFOS and PFOA (DoEE 2016).

ANZECC&ARMCANZ (2000) Australian Water Quality Guidelines for Fresh and Marine Waters.

Draft PFAS National Environmental Management Plan, Heads of EPAs Australia and New Zealand (HEPA, 2017). .

Groundwater criteria have been adopted from the appropriate guidelines to assess if the site

precludes any of the beneficial uses requiring protection. Primary reference has been made to the

listed guidelines, however, where no specific criteria are available, alternative criteria have been

adopted. A selection of the proposed Groundwater Assessment Criteria are summarised in Table 7.3.



62

Table 7.3: Proposed groundwater assessment criteria (g/L)

Contaminant

Ecological Human Health

Maintenance of Ecosystems Freshwater (Modified Ecosystems)1

Recreation / Irrigation2,4

Drinking water

PFOS 0.00023 (99%)3

0.13 (95%) 0.72 0.072

PFHxS NE

PFOA 19 (99%)3 220 (95%)

5.62 0.562

Arsenic (III) 24 100 10

Cadmium 0.2 10 2

Copper 1.4 200 1,000 *

Chromium (III) 3,300 10011 5012

Iron 300,000 200 300 *

Mercury 0.06 2 1

Lead 3.4 2,000 100

Manganese 1900 200 100 *

Nickel 11 200 20

Zinc 8.0 2,000 3,000 *

Benzene 950 104 1

Toluene 1805 25*4 25*

Ethylbenzene 55 3*4 3*

o-Xylene 3505

20*4 20* m-Xylene 755

p-Xylene 2005

Naphthalene 16 NE 176

TPH C6 – C10 less BTEX 9410 NE 3007

TPH >C10 - C16 less naphthalene 16010 NE 1007

TPH >C16 – C34 60010 NE 907



63

Contaminant

Ecological Human Health

Maintenance of Ecosystems Freshwater (Modified Ecosystems)1

Recreation / Irrigation2,4

Drinking water

TPH >C34 – C40 NE NE 907

1,4-Dioxane NE 5009 509

* Aesthetics value; NE = Not Established

1. ANZECC (2000) Australian Water Quality Guidelines for Fresh and Marine Waters (Freshwater – slightly to moderately modified ecosystems)

2. DoH (2017) Health Based Guidance Values for PFAS, Department of Health

3. ANZECC, Draft Australian Water Quality Guidelines for Fresh and Marine Waters (as presented in Draft Commonwealth environmental management guidance on Perfluorooctane sulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA)

4. NHMRC (2008) Guidelines for Managing Risks in Recreational. Adopted value is 10 times the Australian Drinking Water Guidelines (NHRMC, 2011), unless specified otherwise

5. Low reliability trigger value

6. US EPA (2016) Regional Screening Levels for Tap Water (Threshold Hazard Quotient 0.1)

7. WHO (2005) Guidelines for Petroleum Products in Drinking Water

8. NHMRC (2011) Australian Drinking Water Guidelines

9. WHO (2017) Guidelines for Drinking Water Quality, 4th Edition

10. RIVM (2004) Screening risk concentration (ecological). Environmental risk limits for Mineral oil (Total Petroleum Hydrocarbons)

11. Reflects total chromium

12. As chromium (VI)

7.5.3. Surface Water

Surface water criteria have been adopted from the appropriate guidelines to assess if the site precludes any of declared beneficial uses. Primary reference has been made to the guidelines listed in Section 7.5.2, however, where no specific criteria are available, alternative criteria have been adopted. The proposed Surface Water Assessment Criteria are summarised in Table 7.4.

Table 7.4: Proposed surface water assessment criteria (g/L)

Contaminant Maintenance of Ecosystems

(Modified Ecosystems) Freshwater1 Recreation3 Drinking water

PFOS 0.00023 (99%)2

0.13 (95%) 0.77 0.077

PFHxS NE

PFOA 19 (99%)2 220 (95%)

5.67 0.567

Arsenic (III) 24 100 10

Cadmium 370 20 2



64


(Modified Ecosystems) Freshwater1 Recreation3 Drinking water

Copper 1.4 1,000* 1,000 *

Chromium (III) 3,300 508 508

Iron 300,000 300* 300 *

Mercury 0.06 10 1

Lead 3.4 1,000 100

Manganese 1900 100* 100 *

Nickel 11 200 20

Zinc 8.0 3,000* 3,000 *

Benzene 950 10 1

Toluene 1804 25* 25*

Ethylbenzene 54 3* 3*

o-Xylene 3504

20* 20* m-Xylene 754

p-Xylene 2004

Naphthalene 16 NE 176

1,4-Dioxane NE 5006 506

* Aesthetics value; NE = Not Established

1. ANZECC (2000) Australian Water Quality Guidelines for Fresh and Marine Waters (Freshwater – 95% protection level)

2. ANZECC, Draft Australian Water Quality Guidelines for Fresh and Marine Waters (as referenced in Commonwealth Environmental Management Guidance on PFOS and PFOA (DoEE 2016)).

3. NHMRC (2008) Guidelines for Managing Risks in Recreational Waters. Adopted value is 10 times the Australian Drinking Water Guidelines (NHRMC, 2011), unless specified otherwise

4. Low reliability trigger value


6. WHO (2017) Guidelines for Drinking Water Quality, 4th Edition

7. DoH (2017) Health Based Guidance Values for PFAS, Department of Health

8. As chromium (VI)

7.5.4. Sediment

Contaminants in sediment may represent a potential on-going source of contamination to surface

water, and present direct exposure to benthic invertebrates, plants and indirect exposure to other

aquatic biota (i.e., amphibians, fish, etc.).



65

For off-Base sediments in surface waters such as the Katherine River and Tindal Creek, screening

values have been selected for freshwater ecosystems. The proposed soil screening values presented

in Table 7.2 will be used to assess the sediments also. CRC CARE (2017) requires that surface

water, groundwater, or pore water be also measured. Under the proposed sampling plan, surface

waters within Tindal Creek and the Katherine River will also be sampled thus meeting this

requirement.

Sediment screening values have been applied that are intended to reflect protection of the beneficial

uses of Base drain and off-Base waterbodies. However, these screening values do not reflect the

interconnections of media within the ecosystem, and where either sediment or surface water

concentrations exceed a screening value, a site specific ecological risk assessment would be required

to consider the exposure from all media, bioaccumulation and secondary exposure.

Investigation of potential for leaching has also been conducted for a range of sediments to quantify

the potential for contamination of surface waters. Where leachability was assessed, the results were

screened against the relevant water screening levels, as an indicator of the potential for soils or

sediments to contaminate surface water or groundwater.

Off-Base sediment screening values are provided in Table 7.5.

Table 7.5: Proposed off-Base sediment screening values (mg/kg)


(Modified Ecosystems) Freshwater Recreation

PFOS 0.011 1.22

PFOA 0.653 102

1. Soil with the potential to impact water ways (residential and parkland) Department of the Environment and Energy (2016) – Draft Commonwealth environmental management guidance on Perfluorooctane sulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA), October 2016.

2. Values derived using HIL-A and HIL-C setting parameters (NEPC, 2013), FSANZ 2017 tolerable daily intake (TDI) and 20% allocation of TDI.

3. CRC CARE 2017 document Assessment, management and remediation guidance for perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) – Part 3: ecological screening levels

7.5.5. Concrete

Specific screening criteria for concrete have not been nominated. Soil screening values have been applied to conservatively consider human health and ecological impacts, although the exposure potential to concrete is noted as being less than for soil (i.e. less opportunity for ingestion or duct generation.

Potential impacts from PFAS contaminated concrete have been evaluated by comparing the leachability results against surface water and groundwater screening values.



66

8. Investigation Results

8.1. Soil Investigation

8.1.1. Soil Conditions

The soil conditions encountered during drilling and well installation at the Base largely correlated to

the soil conditions expected to be encountered (as described in Section 5). Soils within the

Investigation Area typically comprised shallow fill soils (sandy clays) over various areas of the Base

underlain by limestone.

Sub-surface profiles are described in the bore logs presented in Appendix D. A summary of the

observed lithology across the Base is summarised in Table 8.1.

Table 8.1: Lithology summary

Depth interval (mBGS)

Lithology description

Fire Training Area

0 - 0.2 Sandy Clay with some Silty Clay: low to medium plasticity, brown to orange, sands are fine grained

0.2 - 3.0 Sandy Clay and Clay: medium plasticity, brown, with some gravels

3.0 - 17.0 Limestone: pale yellow to white and grey, with brown – orange clay

17.0 - 20.0 Gravelly Clay: Brown – orange, fine to coarse gravels of limestone

Fire Station

0 - 1.5 Some fill as Sand – Mostly Silty Clay with some Sandy Clay: low to medium plasticity, brown to orange, sands are fine grained

1.5 - 2.0 Silty Clay: medium to high plasticity, brown to orange

2.0 - 4.0 Clay with some Silty Clay: high plasticity, red- brown with some mottling, grey in places

4.0 - 9.0 Limestone: fine to coarse, white to pale grey, dense

9.5 -14.0 Clay: medium to high plasticity, brown to orange, with some limestone gravels

14.0 - 17.0 Limestone: fine to coarse, white to pale grey, dense

17.0 - 20.0 Gravelly Clay: medium to high plasticity with fine to coarse grains of limestone

North-west of Base

0 - 0.25 Mostly Silty Clay with some Sandy Clay: low to medium plasticity, grey to brown, sands are fine grained

0.25 - 1.0 Silty Clay: medium to high plasticity, grey to brown, traces of fine sands

1.0 - 3.5 Mostly Clay with some Silty Clay: medium to high plasticity, brown, some gravels with depth

3.5 - 20.0 Limestone: fine to coarse, grey mostly with clay yellow–brown, some variation in density

North of Base

0 - 0.3 Sandy Clay with some silt: low plasticity with fine to coarse grains, brown

0.3 -1.5 Clay: low to medium plasticity, brown, with some sand at some locations

1.5 - 3.5 Sandy Clay: low to medium plasticity, brown



67

Depth interval (mBGS)

Lithology description

3.5 - 20.0 Limestone: fine to coarse, grey mostly with clay brown to red

Research Farm

0 - 0.3 Sandy Gravels: fine to coarse, red/brown with some orange, grains sub angular

0.3 - 2.0 Clayey Sand: fine grained, dark orange-red

2.0 - 4.0 Sandy Clay: medium plasticity, orange to dark red, with increasing clay at depth

4.0 - 20.0 Limestone: fine to coarse, grey mostly with clay changing from red/orange to yellow brown

East of Katherine

0 - 0.2 Gravelly Sand, fine to coarse, red-brown, grains sub angular

0.2 - 0.4 Clayey Sand: fine grained, red-brown

0.4 - 2.0 Silty Clay: medium to high plasticity, grey

2.0 - 4.0 Clay and Silty Clay: medium plasticity, orange and pink in other locations

4.0 - 20.0 Lime/Mud stone: fine to coarse, pale grey to brown, with some gravel bands

8.1.2. Soil Laboratory Results

Soil analytical results have been summarised in Tables 3a to 3m (appended) and compared against nominated screening criteria for potential beneficial uses. Historical PFOS and PFOA soil results are presented in Table 4 (appended). Relative concentrations of PFOS + PFHxS are shown on Figure 10 to Figure 22 (appended). Laboratory certificates of analysis are presented in Appendix E. A summary of the results of soil sampling against screening criteria is presented in Table 8.2.

Table 8.2: Summary of soil analytical results

Contaminant Concentration

range (µg/kg)

No. of samples

exceeding

screening levels

Screening levels exceeded

Mechanical Equipment Operations Maintenance Section

PFOS <LOR – 120 14 Maintenance of Ecosystems - Areas of Ecological

Significance

PFHxS <LOR – 100 NA NA

PFOA <LOR NIL NIL

Fire Training Area

PFOS <LOR – 3,900 37

Human Health - Recreational, Human Health -

Residential, Maintenance of Ecosystems - Areas of

Ecological Significance

PFHxS <LOR – 7,700 NA NA

PFOA <LOR - 1,100 1 Maintenance of Ecosystems - Areas of Ecological

Significance

Area south of Waste Treatment Ponds (Former Fire Training Area)

PFOS <LOR - 7.3 NIL NIL



68


range (µg/kg)

No. of samples

exceeding

screening levels

Screening levels exceeded

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

Irrigation Paddock

PFOS <LOR – 18 6

Maintenance of Ecosystems - Areas of Ecological

Significance

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

Fire Station

PFOS

<LOR – 17,000 45

Human Health - Recreational, Human Health -

Residential, Maintenance of Ecosystems - Areas of

Ecological Significance

PFHxS <LOR – 1,800 NA NA

PFOA <LOR – 350 NIL NIL

Area between Fire Training Area and Tindal Creek to the North-west

PFOS <LOR – 49 7


Significance

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

Katherine Airport

PFOS <LOR NIL NIL

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

On-Base Residential Area and Sports Fields

PFOS <LOR NIL NIL

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

Fuel Farm 1

PFOS <LOR - 29 1


Significance

PFHxS <LOR NA NA

PFOA <LOR NIL NIL

NA – No applicable screening values nominated NIL – no exceedances of nominated screening values



69

8.1.3. PFAS Leachability

Fifty seven soil samples from across different areas of the Base were analysed for PFAS leachability

using a neutral ASLP method. Analytical results are presented in Table 8a and 8b (appended).

Laboratory certificates of analysis are presented in Appendix I.

The total and leachate concentrations of PFOS, PFHxS and PFOA are shown in Charts 8.1 to 8.3 with

the fitted linear trend line and regression coefficient. Other PFAS compounds were not detectable in

sufficient samples to develop a meaningful chart. Concrete and Fire Training Area evaporation pond

sediment samples were plotted separately (refer Section 8.5.2), as the total concentrations were

significantly higher than soils and sediments.

Chart 8.1: PFOS ASLP results against total concentrations

Chart 8.2: PFHxS ASLP results against total concentrations

Fire Training Area

Fire Station



70

Chart 8.3: PFOA ASLP results against total concentrations

The observed total to leachable concentrations showed poor correlation for soils (i.e. <95%),

particularly for PFOS. The observed leaching represented approximately 50%, taking into account

the 20 times dilution in the leaching method. There appeared to be two distinct PFOS leaching

behaviours in soils (Chart 8.1). A strong positive correlation of increasing leachability with increasing

total PFOS concentration in soil was identified at the Fire Training Area. A low leachability potential

was indicated at the Fire Station, irrespective of the total PFOS concentration identified in soil. Based

on the soil properties tested, the soil characteristic creating the difference was not apparent (i.e. no

correlation to TOC, pH, or iron).

Total organic carbon (TOC) and pH was analysed on selected soil samples to gain an understanding of the factors that may influence contaminant mobility. The full results are presented in Table 6 (appended). TOC results ranged from <0.1% to 4.3%, and typically less than 1% (99 samples).

pH ranged between 5.4 and 9.4, and was typically neutral (6.5 to 7.5) in soil and slightly alkaline (8.0 to 8.5) in sediment.

8.2. Groundwater Investigation

8.2.1. Existing Monitoring Wells

There are 349 registered bores within the Investigation Area, 112 within the Base and 237 off-Base. There are also several unregistered investigation bores on the Base.

The previously installed monitoring wells on the Base have been used for contamination assessments

and for other purposes. Of this network, only selected wells were sampled based on the potential

value they could add to the greater understanding of PFAS impacts in groundwater.

Table 8.3 provides a list of the existing wells located within the Investigation Area gauged or sampled

as a part of this project. Further detail about bore construction, where known, is presented in Table 1

(appended). The location of wells are shown on Figure 40 (appended).



71

Table 8.3: Existing monitoring wells sampled

Monitoring well ID Total well depth

(mBGS) Area Gauged Sampled

0990_046MW01 10.2 South of Runway

0990_046MW03 6.6 South of Runway

0990_048MW01 13.4 Airside

0990_049MW02 12.6 Airside

0990_050MW01 12.7 South-east of Runway

0990_050MW02 6.5 South-east of Runway

0990_053MWA NK Mechanical Equipment

Operations Maintenance Section

-

0990_053MW01 12.8 Mechanical Equipment




0990_053MW04 21 Mechanical Equipment






-

0990_054MW01 NK Base Services -

0990_054MW02 18 Base Services

0990_064MW01 13 Fire Training Area




0990_064MW05 8.7 Fire Training Area



0990_064MW10 NK Fire Training Area





0990_065MW02 12 Fire Station



72



0990_065MW03 NK Fire Station


0990_070MW01 20 Mechanical Equipment


0990_073MW02 10.9 75 Squadron

0990_076MW01 15.2 Fuel Farm 1 -

0990_076MW01 6.9 Fuel Farm 1

0990_076MW02 22.9 Fuel Farm 1

0990_076MW03 4.4 Fuel Farm 1 -

0990_077MW01 18 Fuel Farm 2

0990_077MW01 19.1 Fuel Farm 2

0990_077MW03 15.4 Fuel Farm 2


0990_269MW02 17.5 Fire Station

0990_367MW01 20 Power Station

0990_Bore 06 NK 75 Squadron

0990_Bore 07 NK 75 Squadron -

0990_Bore 10 NK Sewage Treatment Plant

0990_Bore 11 NK Irrigation Paddock

0990_Bore 20 NK Sewage Treatment Plant -

0990_Bore 24 NK Fire Station

0990_GW101 12.3 Runway

0990_NTT05236 NK NACC Construction

Workers Camp -

0990_BCPMW01 18 BCP

0990_3CRUMW01 20.9 3CRU

0990_RN022475 30 Katherine East

0990_RN002522 46.9 Katherine Research Station

0990_RN022392 80.9 Western boundary of Base

0990_RN029429 18 West of Fire Training Area

0990_RN033757 33 Katherine East -

0990_RN004881 50 Katherine South -

0990_RN007437 35 Katherine -


0990_RN020118 18.5 Katherine East -

0990_RN021099 30 Katherine -



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0990_RN022025 32 Katherine -

0990_RN022027 30 Katherine -

0990_RN022130 42 Katherine -

0990_RN022836 30 Katherine -


0990_RN029243 37 Uralla Road -



0990_RN033342 42.2 Katherine Research Station -

0990_RN028900 45 Katherine Research Station -

0990_RN026705 29 South-east Base Boundary -

0990_RN029430 127.3 South-west of Fire Training

Area

0990_RN025450 122.7 Radar Station -

NK – Not known

Where groundwater wells have been gauged but not sampled, this was usually due to the well being blocked, dry or damaged.

8.2.2. Groundwater Monitoring Events

A summary of groundwater monitoring events (including gauging and/or sampling) conducted is presented in Table 8.4, with further detail of sampling methodology and observations shown in Section 8.2.3.

Table 8.4: Groundwater monitoring event summary

Sampling event April 2017 June – August 2017 September 2017

Existing on-Base wells 45 21 33

Existing off-Base wells 5 16 25

New on-Base wells NA NA 36

New off-Base wells NA NA 11

Private off-Base wells - 34 23

Total 50 71 128

8.2.3. Field Observations

Over the period of April to September 2017, Coffey observed that some of the previously installed monitoring wells on Base to be damaged, lost or blocked. Due to the damage to the monitoring well standpipe and monument, monitoring these locations could not be undertaken. The damaged monitoring wells are summarised in Table 8.5.



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Table 8.5: Summary of damaged/lost monitoring wells

Damaged well Investigation Area Description

Bore 07 NACC Destroyed/removed during construction works

073MW01 75 Squadron Unable to locate, assumed removed

073MW02 NACC Destroyed/removed during construction works

BCPMW01 (RN025999)

West of Mechanical Equipment Operations Maintenance Section

Destroyed/removed during construction works

065MW01 Fire Station Monument knocked over, casing bent

049MW01 East of Fire Station Missing, assumed removed

RN005771 North of Fire Station

Unable to locate in historically labelled position, assume removed. Note that EES 2016 labelled Bore_24 as RN05771, and the headworks matches previous descriptions of RN05771.

054MW01 Base Services Blocked at 7 m

076MW01 Fuel Farm 1 Dry, possibly blocked well

064MW03 Fire Training Area Bent casing at surface

GW102 South-east end of runway Unable to locate well

Bore 25 East of 3CRU Unable to locate well

8.2.4. Groundwater Levels and Flow

Depth to groundwater was measured in 76 monitoring wells for the baseline GME conducted between the 20 and 28 September 2017, and surveyed top of casing levels were used to calculate the standing water level in metres Australian Height Datum (SWL mAHD).

Groundwater gauging data is presented in Table 9 (appended). Groundwater elevation contours, based on the gauging data, are presented on Figures 42a to 42c (appended) for April, July and September respectively.

RAAF Base Tindal (On-Base)

The regional groundwater flow direction across RAAF Base Tindal is to the west-north-west towards the Katherine River. An anomalously high groundwater level was recorded at 0990_MW130 located at the western boundary of the Base in September 2017. Groundwater flow also appears to have a south-westerly component onto the Base from the north east (i.e. from Tindal residential area and Base Support towards the runway).

Many local watercourses across the Base terminate in sinkholes. Surface contamination will more readily lead to groundwater contamination in these recharge areas, or where surface run-off from the contaminated area enters a recharge area.

Fire Training Area

The groundwater flow direction at the Fire Training Area is to the west-north-west towards Tindal Creek (Figure 44a, appended). PFOS concentrations measured in groundwater at the Fire Training Area provides further evidence that the dominant groundwater flow is to the north-west. PFOS concentrations in well 0990_Bore10, located to the south of the former Fire Training Area was

recorded at 0.04 g/L in July and September 2017, whereas PFOS and PFHxS concentrations in



75

wells located to the west of the Fire Training Area (0990_064MW06, 0990_MW105, 0990_MW104)

have been recorded at greater than 1.35 g/L. Therefore the former Fire Training Area is not

considered to be a potential source.

Groundwater mounding (higher localised groundwater level) was evident at 0990_064MW12 during the April, July and September 2017 gauging rounds. This well is located in the vicinity of the evaporation ponds, which may be influencing groundwater levels locally.

West of the Fire Training Area

Registered groundwater well RN029429 is located adjacent to Tindal Creek due west of the Fire Training Area. The groundwater levels recorded by DENR at RN029429 show that groundwater levels are close to the ground surface by the end of the wet season and likely controlled by recharge from the Tindal Creek, when flowing.

Groundwater levels subside during the dry season when the Tindal Creek stops flowing. Approximately 1 km to the north-west of RN029429 appears to be a localised groundwater discharge feature where the ground remains saturated all year round. Hydrographs for RN029429 are shown in Chart 8.4.

Chart 8.4: Hydrograph of RN029429

Fire Station

The interpreted groundwater surface (or piezometric head) contours indicate that groundwater flows to the north-west and this inferred gradient was consistent across the April, July and September 2017 sampling events.

Off-Base (Katherine River)

The interpreted groundwater surface (or piezometric head) contours indicate that the Katherine River is the discharge point for the unconfined Tindall aquifer and act as a hydraulic barrier to local flow systems, where groundwater migrates and discharges directly to the Katherine River from both sides. This is consistent with the regional hydrogeology model reported by DENR (Tickell, 2005 and NRETAS, 2009). The intermediate and regional groundwater flow systems (i.e. >150 mBGS) are still expected to be controlled by the strong vertical hydraulic gradients and discharge to the Katherine River where the Tindall aquifer is unconfined.

8.2.5. Groundwater Level Trends

Coffey deployed pressure transducers with in-built dataloggers in twelve groundwater monitoring wells across the Investigation Area to record groundwater level fluctuations over time. The dataloggers



76

were installed in two monitoring wells (0990_064MW13 and 0990_065MW02) in April 2017, and in the remaining ten wells in September 2017.

The transducers were deployed in both existing registered groundwater bores and newly installed groundwater wells. The wells were selected to provide a suitable spatial distribution within the shallow (<50 m) unconfined Tindall Limestone aquifer. The monitoring sites are displayed on Figure 31 (appended), and well details summarised in Table 8.6. The hydrographs are presented in Appendix L.

A groundwater level decrease of approximately 1.6 m was recorded at the Fire Station (0990_065MW02 and 0990_065MW03) and approximately 2.1 m at the Fire Training Area (0990_064MW06, 0990_064MW12 and 0990_064MW13) from April to September 2017. Since 1 April 2017 only 29.4 mm of rainfall has been recorded at RAAF Base Tindal BoM station 14932. Groundwater level monitoring conducted by DENR, as published on the Water Data Portal, indicates that groundwater levels typically continue to drop until the end of December, when rainfall and recharge becomes sufficient to cause increases.

Table 8.6: Coffey monitored groundwater bores

Bore ID Water depth at time of

logger installation (mBGS)

Aquifer screened Drilled depth

(mBGS)

Screen (mBGS)

RN38490* 37.41 Unconfined Tindall Limestone 49 37 - 49

RN39059* 37.37 Unconfined Tindall Limestone 52 40 - 52

0990_MW134* 7.05 Unconfined Tindall Limestone 20.5 2.5 – 20.5

0990_MW105 5.55 Unconfined Tindall Limestone 15.2 2.7-15.2




Bore 06 6.58 Unconfined Tindall Limestone 38.1 NK

0990_065MW02 2.98 Unconfined Tindall Limestone 12.0 3.0-12.0


RN025452 8.05 Unconfined Tindall Limestone 17.0 11.0-17.0

0990_273MW01 Dry Unconfined Tindall Limestone 20 NK

NK: Not known

8.2.6. Groundwater/Surface Water Interaction

A river gauge is monitored by DENR at the Katherine Railway Bridge (G8140001). A cross-section showing the river bathymetry, river stage height in comparison to the bridge deck level is shown on Figure 8.1 (below) and Figure 44b (appended). The gauge datum is 86.36 mAHD at 0 m.



77

Figure 8.1: Cross-section across the Katherine River at the Railway Bridge gauging station

River stage height data is available from 01/01/1970 to 22/09/2017. There are some gaps in the early portion of the record as can be seen from Figure 8.2. The lowest levels of 86.54 mAHD occurred in late 1962. The flow measured at this time was 0.69 cumecs (m3/s). The highest levels of 106.75 mAHD occurred in late January 1998, which corresponded to a flow of 7,100 cumecs.

Figure 8.2: Katherine Railway Bridge stage height data (G8140001)

The recorded groundwater level at monitoring well 0990_MW138 on the 22 September 2017 was 100.33 mAHD (Figure 42c, appended). This well is located approximately 2 km to the east of the Katherine railway bridge surface water gauging station G8140001.The stage of the river at this time was significantly lower at 86.59 mAHD. The measured groundwater gradient confirms that the overall

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0102030405060708090

100110

Flo

w (

cum

ecs)

Stag

e h

eigh

t (m

AH

D)

Katherine Railway Bridge (G8140001)

Stage height Flow

W E



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groundwater flow direction in the Investigation Area is toward the Katherine River, where it discharges. The reported water elevation in several monitored wells through a long section spanning the Katherine River are shown in Figure 44b (appended).

8.2.7. Hydraulic Gradients

Groundwater gradients have been calculated for the end of the wet season (April 2017) and end of dry season (September 2017) for relevant areas of importance where data was available (Table 8.7).

The groundwater gradient across the Investigation Area was similar in the wet and dry, with the inferred gradient towards the Katherine River. The gradient beneath the Fire Station area is an order of magnitude higher than the Fire Training Area.

Table 8.7: Groundwater gradient in April 2017 and August/September 2017

RAAF Base Tindal (On-Base)

Fire Training Area Fire Station Off-Base (Katherine River)

Wells used 0990_MW110 to 0990_MW118

0990_64MW12 to 0990_64MW06

0990_065MW03 to 0990_065MW04

0990_MW139 and G8140001

End of wet season (April 2017)

0.004 0.002 0.01 0.006

End of dry season (September 2017)

0.005 0.002 0.01 0.007

8.2.8. Groundwater Seepage Velocity

The seepage velocity at the Base is greatly influenced by both the groundwater gradient, ranging from 0.01 at the fire station to effectively flat (0.002) depending on the season, and the hydraulic conductivity. Groundwater seepage velocity estimates are shown in Table 8.8.

Table 8.8: Groundwater seepage velocity estimates

End of Wet season (April 2017) Dry season (September 2017)

Hydraulic conductivity (m/day) 50 50

Hydraulic gradient 0.004 0.005

Effective porosity 30% 30%

Seepage velocity 243 m/year 304 m/year

The range in possible seepage velocities highlights the need for PFAS concentrations in groundwater to be assessed using data specific to the hydrogeological setting within each source plume so that mass discharging from each source area can be characterised in a meaningful way to guide effective management effort. Mass flux modelling will be undertaken following the wet season field program.

8.3. Groundwater Chemistry

Water geochemistry can assist in understanding the connectivity between different parts of an aquifer system and indicate likely contaminant migration pathways. Geochemistry can also influence contaminant mobility and degradation. In the case of PFAS compounds, mobility may be reduced by high pH and organic carbon.



79

8.3.1. Field Measured Groundwater Chemistry Parameters

Groundwater was sampled with HydraSleeves deployed at 1 - 2 m below standing water level for at

least 24 hours. Water collected in the HydraSleeves had varying levels of turbidity. Some

HydraSleeves had suspended red/brown sediment in the sampled water. The standing water level

across the Base reduced during the dry season. Consequently the standing water level was lower in

September compared to sampling undertaken in April. This impacted the ability to sample all intended

wells during the GME as some wells in Mechanical Operations Maintenance Section and Fuel Farms

were dry.

Field water quality parameters were recorded during each groundwater monitoring event.

Groundwater quality parameters measured at 11 wells during the May 2017 sampling event, 22 wells

during the July 2017 sampling event and 86 monitoring wells during the September 2017 (baseline

sampling event) groundwater sampling event (22 August 2017 to 19 September 2017) are presented

in Table 10a (appended) and summarised in Table 8.9.

Table 8.9: Groundwater quality summary

Parameter Range Comment

Dissolved oxygen

0.15 mg/L to 4.31 mg/L

(Mean = 1.83 mg/L)

Indicates groundwater with typically low to moderate dissolved content across the Base. Low DO was recorded in locations with hydrocarbon impact.

As an indicative measure, it is considered that dissolved oxygen concentrations <2 mg/L are low, concentrations between 2 mg/L and 5 mg/L are moderate, and concentrations >5 mg/L are high.

Redox potential

-132.4 mV to 206.5 mV

(Mean = 81.0 mV)

Variable redox conditions exist across the Investigation Area, with reducing conditions corresponding to samples with low levels of DO. Reducing conditions were recorded at a number of locations with hydrocarbon impact and hydrocarbon odours, or down-gradient of suspected hydrocarbon impact (around Fuel Farm 1).

Electrical conductivity

169 µS/cm to 1,676 µS/cm

(Mean = 1,203 µS/cm)

EC is variable across the Investigation Area. Areas of low EC during the wet season indicate potential for mixing of surface water and groundwater and seasonal fresh water recharge of the aquifer.

EC is generally consistent with this type of aquifer.

pH

5.7 to 7.63

(Mean = 7.01)

Groundwater ranges from acidic to slightly alkaline, however most groundwater is pH neutral. This is generally consistent with a karst limestone aquifer.

Temperature

28.1°C – 36.3°C

(Mean = 31.2°C)

Groundwater temperatures are higher than the typical groundwater range (a range of 14°C – 22°C is considered normal), which is attributed to the tropical conditions and higher ambient temperature. This may also be attributable to some water quality readings being collected ex situ.



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8.3.2. Groundwater Analytical Results

Groundwater analytical results have been summarised in Tables 11a to 11e (appended) and compared against nominated screening criteria for potential beneficial uses. Historical PFOS and PFOA groundwater results are presented in Table 12 (appended). Laboratory certificates of analysis are presented in Appendix F. A summary of the results of the groundwater monitoring events against screening criteria for the three sampling events are presented in Table 8.10. Concentrations of PFOS, PFHxS and PFOA are presented graphically in Figures 24 to 27 (appended) for various areas.

Table 8.10: Summary of GME groundwater analytical results (µg/L)

Contaminant Baseline

(September 2017) End of Wet season

(April 2017) Dry season

(July/August 2017)

Fire Training Area

PFOS 0.03 – 2,800 0.06 – 3,600 0.25 – 5,000

PFOS + PFHxS 0.07 – 5,300 1.1 – 4,250 0.06 – 7,000

PFOA <LOR - 390 <LOR - 160 <LOR - 310

2000 m down-gradient of Fire Training Area

PFOS <LOR – 6.9 - -

PFOS + PFHxS <LOR – 9 - -

PFOA <LOR – 0.2 - -

5000m down-gradient of Fire Training Area

PFOS 0.03 – 1.5 - -

PFOS + PFHxS 0.06 – 2.04 - -

PFOA 0.02 – 0.03 - -

Fire Station

PFOS 0.2 - 140 0.18 - 170 -

PFOS + PFHxS 0.33 - 250 1.28 - 220 -

PFOA 0.01 - 23 0.04 – 8.2 -

Fuel Farm 1

PFOS <LOR – 5.9 0.03 - 15 0.06 – 9.3

PFOS + PFHxS <LOR – 11.6 0.035 – 26.1 0.1 – 13.5

PFOA <LOR – 0.2 0.02 - 0.35 <LOR – 0.2

Fuel Farm 2

PFOS 0.22 – 0.85 0.22 – 0.77 0.38 – 0.53

PFOS + PFHxS 0.54 – 1.22 0.53 – 1.03 0.61 – 0.78

PFOA 0.1 – 0.2 0.01 – 0.02 0.01

South of Runway



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Contaminant Baseline

(September 2017) End of Wet season

(April 2017) Dry season

(July/August 2017)

PFOS 0.01 – 5.9 0.07 - 0.93 -

PFOS + PFHxS 0.01 – 8.5 0.015 - 1.88 -

PFOA <LOR – 0.19 <LOR - 0.05 -


PFOS 0.06 – 0.43 0.03 – 0.29 0.13 - 11

PFOS + PFHxS 0.2 – 0.96 0.09 – 0.65 0.32 – 14.6

PFOA <LOR – 0.04 <LOR – 0.03 <LOR – 0.42

Married Quarters and Base Services

PFOS 0.01 0.05 0.02

PFOS + PFHxS 0.09 0.1 0.19

PFOA <LOR <LOR <LOR

South of Wastewater Treatment Plant

PFOS <LOR – 0.04 0.1 – 0.12 0.04

PFOS + PFHxS <LOR – 0.06 0.12 – 0.15 0.05 – 0.06

PFOA <LOR <LOR <LOR

Katherine Research Station

PFOS 0.01 - 1 0.61 – 1.1 <LOR – 0.98

PFOS + PFHxS 0.01 – 1.87 1.02 – 1.57 <LOR – 1.5

PFOA <LOR – 0.027 0.02 <LOR

Katherine (approximately 2000 m from Katherine River)

PFOS 0.004 – 1.1 <LOR – 0.38 -

PFOS + PFHxS 0.02 – 1.63 <LOR – 0.72 -

PFOA <LOR - 0.06 <LOR – 0.02 -

Eastern Base Boundary

PFOS <LOR - -

PFOS + PFHxS <LOR - -

PFOA <LOR - -

Bold indicates reported concentrations exceed nominated screening values for groundwater. PFOS concentrations have been compared to criteria for ecosystem protection, and PFOS+PFHxS has been compared to human health values, as presented in Tables 11a to 11c (appended). PFOA has been compared against both ecological and human health screening values.

Groundwater analytical results for private groundwater bores are summarised in Table 8.11.



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Table 8.11: Summary of private bore groundwater analytical results


range (µg/L)

No. of results exceeding

screening levels Screening Levels Exceeded

Uralla - North (15 samples)*

PFOS 0.04 – 2.8 15 Maintenance of Ecosystems - Freshwater 99% & 95%

PFOS + PFHxS 0.07 – 4.2 14 Potable Domestic, Recreation/Irrigation

PFOA <LOR – 0.07 NIL -

Uralla – South (11 samples)**

PFOS <LOR – 0.09 7 Maintenance of Ecosystems - Freshwater 99%

PFOS + PFHxS <LOR – 0.13 5 Potable Domestic, Recreation/Irrigation


North of Base (7 samples)

PFOS <LOR NIL -

PFOS + PFHxS <LOR NIL -

PFOA <LOR NIL -

Katherine (16 samples)




Gorge Road (8 samples)

PFOS <LOR NIL -


PFOA <LOR NIL -

West of Katherine River (8 samples)

PFOS <LOR – 0.14 1 Maintenance of Ecosystems - Freshwater 99% & 95%

PFOS + PFHxS <LOR – 0.24 1 Potable Domestic, Recreation/Irrigation

PFOA <LOR NIL -

Katherine Research Station Bores (5 samples)




East of Base (1 sample)

PFOS <LOR NIL -


PFOA <LOR NIL -

*Uralla North and Uralla South are approximately defined in the Figure 8.3 below. Uralla is separated into two sections for discussion purposes only.



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Figure 8.3: Uralla North and Uralla South extents

8.3.3. Vertical Profiling

In order to investigate the vertical distribution of PFAS within the water column, micropurge sampling at discrete intervals throughout the water column was undertaken. Twenty two groundwater wells around the Base were selected for vertical PFAS profiling based on their proximity (or association) with various AECs. Each groundwater well was gauged and the micropurge pump intake set at depths of 1m, 4m, 7m and 10m below the groundwater surface to evaluate the vertical PFAS distribution. The number and depths of intake were varied to reflect the available water column. Field measurements and purge details are presented in Appendix O and results are tabulated in Table 11 (appended). Vertical profiling was undertaken in September 2017 prior to the September groundwater monitoring event.

The majority of the wells show similar PFOS concentrations across the sampled depths. Highly impacted wells in the main source areas (064MW02 at the Fire Training Area and 065MW03 at the Fire station) indicated maximum concentrations at 5m and 7 m respectively below the water surface. This may indicate that infiltration and leaching has reduced the source concentrations in the very shallow parts of the aquifer. Concentrations appeared to decrease with depth in wells MW100, MW110, MW139 and MW119. These wells are generally along the centreline of the contaminant plume.

The vertical PFOS profiling undertaken across the Base, indicated that sampling (by pump or HydraSleeve) from approximately 4 m below the water surface should generally obtain a conservative representation of the PFOS contamination in the groundwater.

N



84

Graphical representations of the PFOS concentrations varying with depth are presented in the charts below, with key Base areas grouped together.

Chart 8.5: Vertical profiling - Fire Training Area

Chart 8.6: Vertical profiling - Fire Station



85

Chart 8.7: Vertical profiling - On-Base Wells

Chart 8.8: Vertical profiling - Off-Base Wells

In addition to providing information about vertical distribution of PFAS in selected wells, the low-flow sampling allowed a comparison between outcomes of sampling by HydraSleeve samples, which were used for the main groundwater monitoring events, and low-flow sampling, which has been the most commonly applied method by previous consultants. Comparison of vertical profile low-flow sample results and HydraSleeve sample results are presented in Appendix P. The review indicated:

No difference in interpretation of results collected by the different methods against screening levels.

Good repeatability. Approximately 95% of RPDs between the 1 m below water level low-flow sample and HydraSleeve result was <50%.

Testing (using the Wilcoxon-Mann-Whitney test) of the hypothesis that the data set produced by low-flow and HydraSleeve sampling were the same for the most commonly detected PFAS compounds, indicated that the two data sets can be considered the same, with 95% confidence.



86

8.3.4. Concentration Trends

Groundwater monitoring events including sampling and analysis for PFAS compounds have been conducted since 2007 as part of AFFF targeted investigations and annual environmental monitoring programs. Investigations prior to 2016 were typically limited to analysis for PFOS and PFOA, with post 2012 assessments often including 6:2FTS.

A review was conducted of the sampling methods, analytical methods and analysis results of historic events.

Most previous events (2007-2016) were completed using micro-purge sampling techniques. The depth of pump intake was not always reported, but where recorded was often near the bottom of the screened section. Sampling conducted by EES in 2016 was completed using Waterra pumps and involved purging of three well volumes.

The analysis method was by LC-MSMS in each event. Analysis for PFAS compounds was not third party certified (i.e. NATA) prior to 2012. Quantification included branched and linear isomers post 2016, which increases the accuracy of the results compared to quantification against linear isomer standards only. Analysis conducted in 2017 included internal surrogate standards for all target compounds, which improves accuracy by allowing adjustment of equipment response to each compound, rather than a single calibration across the whole compound range.

Transcription errors were noted in some historic reports between the laboratory certificates and entries in data tables or figures in reports. This typically involved reporting PFOS as PFOA concentrations, and vice versa. Where the original laboratory reports were available for review this has been corrected in Table 12 (appended).

Groundwater analysis post 2016 is considered to have higher reliability than data from prior to 2016, however results are still considered useful for consideration of trends or historic peaks.

The results of historic assessments are presented with this investigation data in Table 12 (appended).

Wells that have had multiple historic sampling events and have been included in the DSI sampling are described in Table 8.12. The range or reported PFOS concentrations and comments on the variability across sampling events is described. Other PFAS compounds have not been discussed, as other compounds were not analysed in every round (except PFOA) and PFOS was the dominant compound where other compounds were analysed.

Table 8.12: Summary of groundwater PFOS results where multiple historic events occurred

Well ID Sampling period

PFOS concentration

(g/L)

Comments

053MW01

25/09/2017 22/07/2017 28/04/2017 8/06/2016 21/04/2008 11/01/2007

0.09 0.19 0.13 0.05 0.15 <0.05

Historic and current DSI results were consistent.

053MW04

25/09/2017 20/07/2017 2/05/2017 8/06/2016 1/04/2014 2/05/2013 16/04/2012

0.08 0.13 0.29 0.04 <0.1 <0.5 0.048

Reported results over ten years vary across approximately one order of magnitude. No pattern or trend was evident.



87


PFOS concentration

(g/L)

Comments

9/05/2011 20/04/2010 20/05/2007

0.87 0.14 <2

064MW01

25/09/2017 23/07/2017 29/04/2017 10/03/2012 20/11/2007 11/05/2006

16 42 660 620 6.6 10

Results from dry season in 2017 were generally consistent with results from 2006 and 2007 dry season. Higher concentrations were reported at the end of wet season in 2012 and 2017.

064MW02

25/09/2017 23/07/2017 29/04/2017 7/06/2016 2/04/2014 2/05/2013 17/04/2012 10/03/2012 9/05/2011 22/04/2010 28/04/2009 11/11/2008 20/11/2007 11/04/2007 11/05/2006

2800 5000 3600 4010 2.5

7140 1000 1700 7800 1700 120 2700 85 <0.05 5200

Reported results over ten years vary across approximately one order of magnitude. No pattern or trend was evident. Low concentrations were reported in April 2014 and April 2007. The original reports were not available for verification of lab reports. In the absence of validation, these results are considered to be transcription errors, or anomalies. Vertical profiling in this well (Section 8.3.3) showed that sampling depth would have a significant impact on the sample concentration reported. Sampling depth was not able to be established for all of the historic events, but those that were documented were not consistent across events, and may have contributed to the variability of concentrations.

064MW03

23/07/2017 11/11/2008 20/11/2007 11/05/2006

3200 150 5.3 3.7

Higher concentrations reported in 2017, potentially due to shallow sampling depth employed in 2017, compared to total well depth.

064MW04

24/09/2017 29/04/2017 8/06/2016 1/04/2014 2/05/2013 16/04/2012 20/03/2012 9/05/2011 20/04/2010

0.49 0.28 0.04 0.8 0.55 0.26 68 1.1 0.31

Results reported over ten years vary across approximately one order of magnitude. No pattern or trend was evident. An elevated concentration was reported in March 2012, but does not appear to be characteristic of this well.

064MW05

25/09/2017 23/07/2017 29/04/2017 8/06/2016 1/04/2014 2/05/2013 16/04/2012 9/05/2011 20/04/2010 11/11/2008 20/11/2007

0.21 0.25 0.06 0.14 1.5 0.776 1 0.22 0.12 0.5 3.2

Reported results over ten years vary across approximately one order of magnitude. No pattern or trend was evident. No data from during the wet season (Dec-March) was available.

064MW06

25/09/2017 23/07/2017 29/04/2017 21/05/2007

0.17 0.35 0.22 <2

Generally consistent, although elevated reporting limit in 2007 makes comparison qualitative only.



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PFOS concentration

(g/L)

Comments

064MW08 22/09/2017 14/05/2008 20/11/2007

<0.01 <0.05 <2

All events below reporting limit

064MW10 29/04/2017 19/03/2012

3.8 1.7

Generally consistent

064MW11 24/09/2017 29/04/2017 19/03/2012

13 12 0.92

Higher concentrations reported in 2017, potentially due to shallow sampling depth employed in 2017, compared to total well depth.

064MW12

24/09/2017 20/07/2017 29/04/2017 19/03/2012

110 400 270 360

Generally consistent

064MW13

24/09/2017 20/07/2017 29/04/2017 19/03/2012

720 750 1200 620

2017 results generally consistent with 2012 results, although higher concentration reported in the end of wet season event.

064MW14

24/09/2017 29/04/2017 9/8/2016 19/03/2012

48 3.7 6.5 3.1

Highest concentration reported in September 2017, which may reflect that the sampling depth in that event was selected to obtain maximum concentration from the water column.

065MW02

26/09/2017 28/04/2017 16/9/2016 9/8/2016

120 170 61.2 36.5

Generally consistent. Due to proximity to source, the observed difference between September 2016 and 2017 events may reflect concentration profiles in the water column and different sampling depths.

065MW03 26/09/2017 28/04/2017 16/9/2016

58 110 17


065MW04 26/09/2017 28/04/2017 16/9/2016

10 35 37.9


076MW02

28/09/2017 20/07/2017 2/05/2017 7/06/2016

5.9 9.3 15 8.51

Generally consistent. Potentially higher concentrations reported during end of wet season.

Bore 10

25/09/2017 23/07/2017 29/04/2017 11/11/2008 12/05/2008 11/11/2007

0.04 0.04 0.12 0.1 <0.05 <0.05

Potentially higher concentrations reported during end of wet season.

Bore 11

25/09/2017 23/07/2017 29/04/2017 11/11/2008

<0.01 0.04 0.1 <0.1

Lowest concentration reported at the end of dry season

GW101 26/09/2017 16/9/2016

4.5 4.46

Results consistent despite different sampling method (3 bore volume purge and HydraSleeve) and different laboratories (ALS and Eurofins)



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PFOS concentration

(g/L)

Comments

077MW01 28/09/2017 28/04/2017 9/8/2016

0.85 0.77 0.4

Generally consistent. Due to proximity to source, the observed difference between August 2016 and 2017 events may reflect concentration profiles in the water column and different sampling depths.

RN005771 / Bore 24

26/09/2017 28/04/2017 16/9/2016 8/06/2016 3/04/2014 2/05/2013 18/04/2012 12/05/2008 11/11/2007

0.92 0.99 0.86 0.72 0.7 0.5 0.38 0.7 0.7

Reported results over ten years were generally consistent regardless of season or sampling method.

Concentrations of PFOS reported in various sampling events since 2007 are presented in Chart 8.9 to 8.11 below for a selection of wells.

Chart 8.9: PFOS concentrations over time – Mechanical Equipment Operations Maintenance Section area wells



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Chart 8.10: PFOS concentrations over time – Fire Training Area

Chart 8.11: PFOS concentrations over time – Fire Station

Coffey conducted a groundwater monitoring event involving available monitoring wells at the end of the wet season in April 2017 and broader groundwater monitoring events in July/August and September 2017, at the end of the dry season. Further groundwater monitoring events are planned in November 2017 and January 2018 to investigate seasonal variability.

Twenty nine were sampled by Coffey using the same method in April and September 2017. Of the 25 wells, concentrations increased between April and September in 8 of the wells. Four showed a significant increase (more than 100% increase). Table 8.13 shows PFOS concentrations and the relative change between events. Other PFAS compounds showed similar relative changes.



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Table 8.13: Relative PFOS concentrations between April and September 2017 events

Well ID

PFOS concentration (g/L) Change

between

April and

September

2017

April 2017 July/August

2017 September 2017 ^

0990_053MW01 0.13 0.19 0.09

0990_053MW04 0.29 0.13 0.08

0990_053MW06 0.14 0.19 - -

0990_054MW02 0.05 0.02 0.01

0990_064MW01 660 42 16

0990_064MW02 3600 5000 2800

0990_064MW04 0.28 - 0.49

0990_064MW05 0.06 0.25 0.21

0990_064MW06 0.22 0.35 0.17

0990_064MW11 12 - 13

0990_064MW12 270 400 110

0990_064MW13 1200 750 720

0990_064MW14 3.7 - 48

0990_065MW02 170 - 120

0990_065MW03 110 - 58

0990_065MW04 35 - 10

0990_070MW01 0.07 - 0.43

0990_076MW02 15 9.3 5.9

0990_077MW01 0.22 - 0.22 -

0990_077MW01 0.77 - 0.85

0990_269MW01 * 9.5 - 0.2

0990_269MW02 * 0.18 - 7.5

0990_367MW01 0.12 - 0.05

0990_Bore 06 0.20 - 0.27

0990_Bore 10 0.12 0.04 0.04



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Well ID

PFOS concentration (g/L) Change

between

April and

September

2017

April 2017 July/August

2017 September 2017 ^

0990_Bore 11 0.10 0.04 <0.01

0990_Bore 24 0.99 - 0.92

0990_3CRUMW01 0.18 0.06 -

0990_RN022392 <0.01 <0.01 <0.01 -

* The significant changes in concentrations in these two wells between April and September will be investigated further through seasonal sampling and vertical profiling.

^ Some of the apparent changes in concentrations between sampling events close to source areas may be due to a change in sampling depth. Sampling in September 2017 was targeted deeper than April and August events based on vertical profiling results.

There was no apparent pattern to where significant increases were observed compared to decreases, based on the April and September data alone. Further review of temporal trends will be conducted in the supplementary report, following wet season sampling events.

8.4. Sediment and Surface Water Investigation

8.4.1. Rainfall Conditions

The Katherine and Tindal area has a tropical climate with distinct wet and dry seasons. The dry season occurs between September and May. Rainfall events are very rare during this time of year, as can be seen in Chart 8.12. The wet season generally begins in December after months of build-up conditions. The majority of rain falls between December and March and is associated with the inflow of moist west to north-westerly winds into the monsoon trough, producing convective cloud and heavy rainfall over northern Australia. Low pressure troughs can form into tropical cyclones over the wet season months.

The 2017 wet season was one of the largest in recent years. As shown on Chart 8.12, the rainfall between December 2016 and March 2017 was significantly higher than the median rainfall for Tindal. The last rainfall event of the 2016/2017 wet season occurred on 14 April 2017, which received 13.6 mm. After this there were no significant rain events until October 2017.



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Chart 8.12: Rainfall at Tindal RAAF between October 2016 and September 2017 (BOM, 2017)

8.4.2. Surface Water/Sediment Conditions and Field Observations

Surface water and/or sediment samples were collected from the following features within the Base:

Low lying areas.

Tindal Creek, from approximately 900 m up-stream (south-east) of the Fire Training Area, to the point at which the creek leaves the Base.

Additional samples of surface water and sediment were collected from Base infrastructure, including:

Drainage lines and surface drainage features.

Services, including pits and drains.

Results for these samples are discussed in Section 8.5.

Surface water and/or sediment samples were collected from the following features off-Base:

Tindal Creek.

Katherine River.

Surface drainage feature between Lindsay Street and Chambers Drive, Katherine.

On-Base sediments were predominantly sampled from soils at the Base of constructed drainage lines and from the base of Tindal Creek, while off-Base sediments were predominantly sampled from Tindal Creek and Katherine River. Where sediments were collected from a location which has had surface water present during the investigation period, a corresponding surface water sample was also collected.

Sediments collected from Base drains and Tindal Creek comprised clays, silts, sands and gravels and contained varying amounts of organic matter. Sediments collected from Katherine River comprised predominantly of silty sands with organic matter. A summary of sediment and surface soil samples



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collected, including lithology and other field observations as well as details of corresponding surface water samples is provided as Table 2 (appended).

Surface water samples were collected from Tindal Creek during the end of wet season field works between March and April 2017. Samples were collected at 1 km intervals (depending on accessibility). Tindal Creek is ephemeral and was observed to be dry in most areas during field works between July and October. There were some exceptions, with surface water being observed (and sampled) in Tindal Creek approximately 1.5 km west south-west to the west of the north-western end of the runway (0990_SW137, 0990_SW162 and 0990_SW163 on Figure 25b, appended). Although surface water was observed in this part of Tindal Creek during the dry season, it appeared to be localised and was not flowing.

Surface water samples were collected from Katherine River between April and September 2017. Samples were collected as far up-stream as 1 km up-stream of Donkey Camp (SW169) and as far down-stream as 500 m beyond where King River joins Katherine River (SW171).

8.4.3. Surface Water Field Measured Parameters

Field water quality measurements were taken at each location after surface water samples were recovered. Water quality parameters measured in each water body during the water sampling events are presented in Table 10b (Appended) and summarised in Table 8.14.

Table 8.14: Surface water quality summary

Location Sampling Event

Dissolved oxygen (mg/L)

Electrical conductivity

(µS/cm)

Redox potential

(mV) pH Temperature

Katherine River – Donkey Camp to Stuart Hwy

July 2017 5.1 – 5.9 130 – 207 -20.6 – 18.7 7.9 – 8.7 26.8 – 30.8

Aug 2017 4.9 – 8.5 115 – 298 55.1 – 154.4 7.2 – 8.3 25.1 – 25.6

Katherine River –Stuart Hwy to Zimin Drive

July 2017 5.0 – 5.5 227 – 277 20.1 – 21.1 7.8 – 7.9 30.4 – 30.6

Katherine River – Zimin Drive to Tindal Creek

July 2017 3.9 – 4.5 370 – 513 22.1 – 60.9 7.1 – 7.7 27.5 – 29.3

Aug 2017 3.2 – 5.9 473 – 476 44.5 – 54.8 7.9 – 8.0 25.7 – 26.4

Sept 2017 3.8 611 127.7 7.3 27.4

Katherine River – Tindal Creek to Cossack Rd

July 2017 6.8 – 7.8 412 – 423 48.6 – 53.7 7.2 – 7.9 27.5 – 27.6

Aug 2017 3.8 – 5.7 427 - 620 126.4 – 159 7.1 – 8.0 24.6 – 26.7

Sept 2017 3.2 – 6.0 506 – 510 20.7 – 49.5 8.2 – 8.4 23.5 – 25.9

Tindal Creek, off-Base

July 2017 4.9 – 6.2 616 - 682 -48.5 – 16.9 8.3 – 8.8 26.8 – 29.1

Tindal Creek, on-Base

July 2017 5.7 – 7.7 572 - 951 2.6 - 49 8.4 – 8.9 23.6 – 26.6

Aug 2017 2.5 – 4.1 638 - 657 103.8 – 126.4 7.6 – 8.0 16.7 – 18.4

On-Base drain July 2017 5.4 – 8.8 196 - 706 -42.7 – 39.4 8.4 – 10.9 28.4 – 30.1



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8.4.4. Surface Water Analytical Results

Surface water analytical results have been summarised in Table 16 to 19 (appended) and compared against nominated screening criteria for potential beneficial uses. Relative concentrations of PFOS + PFHxS are shown on Figures 24 to 30 (appended). Laboratory certificates of analysis are presented in Appendix G. A summary of the results of the surface water sampling events against screening criteria is presented in Table 8.15.

Table 8.15: Surface water analytical summary (µg/L)

Contaminant End of Wet

season (April 2017)

Dry season (July 2017)

Dry season (August 2017)

Dry season (September 2017)

Katherine Hot Springs

PFOS - - 0.03 – 0.04 0.02 – 0.03

PFOS + PFHxS - - 0.04 – 0.05 0.03 – 0.04

PFOA - - <LOR <LOR

Katherine River

PFOS <LOR – 0.062 0.002 – 0.11 0.0096 – 0.13 0.0065 – 0.16

PFOS + PFHxS <LOR – 0.202 <LOR – 0.92 0.0096 – 0.19 <LOR – 0.013

PFOA <LOR <LOR – 0.002 0.42 <LOR – 0.003

Tindal Creek West of Base

PFOS <LOR – 2.2 0.39 – 0.76 1.4 – 1.9 -

PFOS + PFHxS <LOR – 3.5 0.92 – 1.27 1.88 – 2.53 -

PFOA <LOR – 0.082 0.04 0.04 – 0.05 -

Fuel Farm 2

PFOS 0.25 – 0.29 0.33 - -

PFOS + PFHxS 0.44 – 0.47 0.55 - -

PFOA 0.01 0.02 - -

Drainage South-east End of Runway

PFOS 0.03 – 0.06 0.04 – 0.05 - -

PFOS + PFHxS 0.04 – 0.09 0.06 – 0.08 - -

PFOA <LOR <LOR - -

Drainage North-west End of Runway

PFOS 0.27 – 1.5 - - -

PFOS + PFHxS 0.47 – 2.01 - - -

PFOA 0.01 – 0.09 - - -

Tindal Creek on Base



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Contaminant End of Wet

season (April 2017)

Dry season (July 2017)

Dry season (August 2017)

Dry season (September 2017)

PFOS 0.02 – 2.0 0.04 – 2.1 - -

PFOS + PFHxS 0.03 – 2.7 0.07 – 3.1 - -

PFOA <LOR – 0.07 <LOR – 0.06 - -

Fuel Farm 1

PFOS - 0.52 -

PFOS + PFHxS - 0.64 -

PFOA - 0.01 -

Fire Station

PFOS 0.09 – 4.9 3.7 – 3.8 - -

PFOS + PFHxS 0.11 – 7.3 4.6 – 4.71 - -

PFOA <LOR – 0.22 0.78 – 0.82 - -

8.4.5. Sediment Analytical Results

Sediment analytical results have been summarised in Table 8.16 and compared against nominated screening criteria for potential beneficial uses. Relative concentrations of PFOS + PFHxS are shown on Figures 21 to 23 (appended). Laboratory certificates of analysis are presented in Appendix H.

Table 8.16: Summary of sediment analytical results

Contaminant Concentration range (µg/kg)

No. of samples exceeding

screening criteria Screening levels exceeded


PFOS <LOR – 98 2 Maintenance of Ecosystems - Areas of Ecological Significance

PFHxS <LOR – 11 NA NA

PFOA <LOR - -

Fire Training Area

PFOS 6.4 – 3,800 10 Maintenance of Ecosystems - Areas of Ecological Significance, Human Health - Residential, Human Health - Recreational

PFHxS <LOR - 65 NA NA

PFOA <LOR - 17 - -

Katherine River

PFOS <LOR – 12 2 Maintenance of Ecosystems - Areas of Ecological Significance

PFHxS <LOR NA NA



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Contaminant Concentration range (µg/kg)

No. of samples exceeding

screening criteria Screening levels exceeded

PFOA <LOR - -

Tindal Creek on Base

PFOS <LOR - 45 4 Maintenance of Ecosystems - Areas of Ecological Significance

PFHxS <LOR NA NA

PFOA <LOR - -

Tindal Creek off Base


PFHxS <LOR NA NA

PFOA <LOR - -

Fuel Farm 1


PFHxS <LOR NA NA

PFOA <LOR - -

Fuel Farm 2

PFOS <LOR - -

PFHxS <LOR NA NA

PFOA <LOR - -

Drainage Line South-east End of Runway

PFOS <LOR – 7.6 - -

PFHxS <LOR NA NA

PFOA <LOR - -

Adjacent to Runway North and South Airside


PFHxS <LOR - 17 NA NA

PFOA <LOR - -

8.4.6. Open Drains

The Base has an extensive open and closed drainage network, with surface water runoff generally flows from the north-east and south-east of the Base and then drains towards each end of the runway. From here each main drain flows into Tindal Creek.

Surface water around Base infrastructure flows into closed drains, which eventually lead into open drains. The open drains comprise of some concrete lined sections, in other areas the open drains are unlined. Open drains are found across the airfield, along each side of the runway.

Samples of sediment were collected from open drains across the Base. A summary of sediment samples is provided in Table 3j (appended) and a summary of analytical results is presented in the table below.



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Table 8.17: Summary of analytical results collected from open drains

Sample ID Location Depth

(mBGS)

PFOS PFOA

µg/kg µg/kg

0990_BH203 Tindal Housing Area 0 <5 <5

0990_BH204 Tindal Housing Area 0 <5 <5

0990_SS100 North-west of Runway 0-0.1 8.7 <5

0990_SS100 North-west of Runway 0.2-0.3 <5 <5

0990_SS101 North-west of Runway 0-0.1 26 <5

0990_SS101 North-west of Runway 0.2-0.3 <5 <5

0990_SS102 North of Runway 0 8.1 <5

0990_SS103 North of Runway 0 <5 <5




0990_SS107 Southern Runway Drain 0 <5 <5


0990_SS145 North-west Runway Grass Area 0 7.2 <5

0990_SS146 North-west Runway Grass Area 0 <5 <5


0990_SS147 North-west Runway Grass Area 0 5.9 <5




0990_SS151 North-west Runway Grass Area 0 23 <5

0990_SS152 North-west Runway Grass Area 0 15 <5

0990_SS153 Southern Runway Drain 0 14 <5

0990_SS154 Southern Runway Drain 0 83 <5





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Sample ID Location Depth

(mBGS)

PFOS PFOA

µg/kg µg/kg

0990_SS157 Taxiway Alpha Drain 0 8.6 <5

0990_SS158 Taxiway Alpha Drain 0 490 <5

0990_SS159 Taxi ay Alpha Drain 0 17 <5







0990_SS225 MFOMS shallow drain at outlet 0 9.3 <5

0990_SS226 MFOMS shallow drain 0 <5 <5

The PFAS concentrations of sediments sampled form the open drains is considered to be relatively low except within the drain along the Alpha taxiway.

8.5. Base Infrastructure Investigation

Base infrastructure associated with the storage, use or drainage of PFAS containing products may hold PFAS contaminated sediments and/or water, providing an ongoing source to the surrounding soils or waters.

Limited infrastructure inspections were undertaken, targeting:

Waste waters and sediments in the evaporation ponds at the Fire Training Area.

Sediment and waters in open and closed base drains and pits in areas including the Fire Station/Airfield, Mechanical Equipment Operations Maintenance Section, Fuel Farm 1 and Fuel Farm 2.

Concrete in the Fire Training Area and Mechanical Operations Maintenance Section.

A detailed summary of Base infrastructure investigation works is provided in the following sections. Analytical results for Base infrastructure sampling are presented in Table 3n (appended).

8.5.1. Drainage Pits

Closed drains and pits in the vicinity of Mechanical Equipment Operations Maintenance Section, Fuel Farms and the Fire Station were visually inspected during underground service location works prior to drilling. Pits were inspected by removing cover hatches providing access to the bottom of the pit. Accessible pits observed to contain sediment and or water were sampled.



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Two pits were identified at Mechanical Equipment Operations Maintenance Section, which were from the vehicle wash down area and sediment trap interceptor from the workshop wash down area. A water sample was also collected from the retention pond at Fuel Farm 1. A summary of soil and water samples associated with these drainage pit samples is provided in Table 8.18.

Table 8.18: Summary of analytical results collected from drainage pits

Sample ID Location Sample

Type PFOS PFOA Comments

0990_SS123 Mechanical Equipment Operations Maintenance Section separation trap

Water 16 µg/L 0.42 µg/L High turbidity/sediment

0990_BH1940.0 Drilled adjacent separation trap Soil 25 µg/kg <5 µg/kg -

0990_BH194 0.5 Drilled adjacent separation trap Soil 120 µg/kg <5 µg/kg -

0990_BH194 1.0 Drilled adjacent separation trap Soil 55 µg/kg <5 µg/kg -

0990_BH194 2.0 Drilled adjacent separation trap Soil <5 µg/kg <5 µg/kg -

0990_SS122 Mechanical Operations Maintenance Section Vehicle wash down pit

Water <5 µg/kg 98 µg/kg -

0990_SW139 Fuel Farm 1 Retention Pond Surface water

0.52 µg/L 0.01 µg/L Slightly cloudy with suspended solids

0990_SW164 Fuel Farm1 fire main Water <0.01 µg/L

<0.01 µg/L

Clear

0990_SW165 Fuel Farm1 fire main Water <0.01 µg/L

<0.01 µg/L

Clear

0990_SW166 Waste separator MFOMS* Water 0.16 µg/L 1.6 µg/L Clear

* Maintenance facility north east of Fuel Farm 1 that services fire section equipment. (Built between 2007 and 2011).Fire Training Area - Infrastructure

Samples of surface water and sediment were collected from the evaporation ponds and fire training pit at the Fire Training Area. One sediment sample was collected from each of the concrete-lined ponds and from the fire training pit and surface water was collected from two of the three ponds. The pond furthest from the Fire Training Area (to the north-west) and the fire training pit were dry at the time of sampling.

A summary of sediment and surface water analytical results from the Fire Training Area infrastructure is provided in Table 8.19.



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Table 8.19: Summary of analytical results collected from evaporation ponds

Location Sample ID Sample Type PFOS PFOA

Pond closest to Fire Training Area

0990_SS113 Sediment 780,000 g/kg 74,000 g/kg

0990_SW133 Surface water 260 g/L 150 g/L

Middle pond

0990_SS114 Sediment 2,660,000 g/kg 9,700 g/kg

0990_SW132 Surface water 840 g/L 200 g/L

Pond farthest from Fire Training Area

0990_SS116 Sediment 13,000 g/kg 420 g/kg

Fire training pit 0990_SS115 Sediment 590,000 g/kg 3100 g/kg

8.5.2. Concrete

Concrete from Base areas with the potential for contact with AFFF from leaks, spills and testing was sampled. Concrete samples were collected from the Fire Training Area and Mechanical Operations Maintenance Section using a jackhammer. A summary of analytical results from concrete testing is provided in the Table 8.20.

Table 8.20: Summary of concrete analytical results

Sample ID Location

PFOA PFOS

µg/kg µg/kg

0990_CONC01 Tile from Fire Training Area pit 94 35,000

0990_CONC02 Concrete from sump in burning pit (middle of pad)

720 27,000

0990_CONC03 Concrete from evaporation pond #3 (sample location as SS116)

420 43,000

0990_CONC04 Concrete from interceptor pit at the back of Mechanical Operations Maintenance Section (same location as SS123)

9.2 24

0990_CONC05

Concrete from spoon drain at the back of the Mechanical Operations Maintenance Section workshop (same location as SS122)

4,400 110,000

0990_CONC06 Concrete from kerb at the front of Mechanical Operations Maintenance Section (near location SS121)

32 1000



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The leaching potential from concrete was assessed using the ASLP test, which involves crushing samples prior to batch leaching. The process of crushing increases contact area and is likely to overestimate the concentrations that would leach from in-situ concrete.

Chart 8.13: PFOS Concrete ASLP results against total concentrations

The results indicated some correlation between leachability in samples at different concentrations and indicated between 10 and 50% of PFOS present leached out of the solid, under the 20:1 water to solid ratio. This suggests that concrete may be a secondary source of PFAS contamination in selected areas.

8.6. Private Bore Investigations

Existing off-Base private bores were identified for sampling to investigate the resident’s potential exposure, or to provide additional information about contaminant distribution in the off-Base area. Private bore sampling was also undertaken on behalf of Defence as part of works relating to provision of alternate drinking water supply. These works also involved testing of water tanks, swimming pools and other water samples from residential properties within the Investigation Area. For the purpose of this DSI, only bore samples will be presented and discussed, and only where appropriate approval has been obtained from landowners.

Approval was sought from land owners for access to the bores for sampling and use of the data in the investigation. Analytical results for many bores sampled as part of the alternate drinking water supply testing are not able to be included in this DSI report for privacy reasons. Data from a total of 62 private bores is able to be used in this DSI report. Private bore locations are shown in Figure 30 (appended). For privacy reasons, several bores are not shown.

8.6.1. Sampling Conditions

A total of 62 private bores (where data is able to be included in this report) used for potable and non-potable domestic use were sampled and analysed for PFAS. All bores visited contained a pump and



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pipework to enable extraction for domestic use. For this reason, samples were generally collected from the closest tap or point to the bore head, without disrupting or altering the plumbing of the well.

Bores were not developed or altered during sampling. Samples were collected between April and September 2017.

8.6.2. Laboratory Results

Analytical results from private bores are provided in Table 11d (appended) and are summarised in Table 8.11.

Further sampling of private bores will be undertaken over 2017/2018 wet season and findings will be presented in the human health risk assessment and supplementary DSI report.

8.7. Non-PFAS Contamination

In addition to the investigation of PFAS at the Base, analysis for various other inorganic analytes and other potential contaminants was also undertaken in soils, sediment, groundwater and surface water.

8.7.1. Soils and Sediments

Soils and sediments were analysed for various nominated non-PFAS analytes including:

Total recoverable hydrocarbons, benzene, toluene, ethyl benzene, xylenes,

Polycyclic aromatic hydrocarbons,

Organochlorine pesticides, organophosphorus pesticides, herbicides,

Volatile and semi-volatile organic compounds and

Metals (aluminium, arsenic, cadmium, total chromium, copper, iron, lead, manganese mercury, nickel and zinc).

Results from the soil and sediment sampling for non-PFAS analytes have been collated into Tables 5, 6, and 7 (appended). The location of sediment samples are summarised in Table 2 (appended).

The majority of results for other contaminants were either below the laboratory reporting limits, or below adopted screening criteria for protection or human health or ecosystems. Where the results exceeded the adopted screening criteria, they have been discussed below.

Inorganics

Total organic carbon (TOC) and pH were analysed for selected soil samples. The results are summarised below.

TOC results ranged from <0.1% to 4.3% (105 samples), and averages around 1%. TOC concentrations were variable with depth.

Soil pH ranged from 5.4 to 9.4, and was variable with depth.

Hydrocarbons

Two locations reported concentrations of Naphthalene that exceeded the adopted screening criteria for protection of ecosystems (both areas of ecological significance and residential/open space) and exceeded the adopted human health screening criteria (residential). One sample 0990_SS114 was



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taken from the sludge in the evaporation ponds at the Fire Training Area and the other was taken at 0.4 mBGS from Fuel Farm 1 (NT00076) (0990_MW114_0.4).

Metals

Concentration of metals in both soils and sediments (including copper, iron, manganese, nickel and zinc) exceeded the adopted screening criteria for protection of ecosystems (both areas of ecological significance and residential/open space) at various locations across the Base. The concentration of manganese exceeded the adopted human health screening criteria at one location, and the concentration of iron in 98% of samples exceeded the adopted human health screening criteria. The

highest concentration of iron was 140,000,000 g/kg at 0990_BH165_1.0. Concentrations of iron is naturally high in the ferruginous soils.

The concentration of aluminium in soils and sediments was considered to be high, however screening criteria are not available. Cadmium and mercury were not identified in soils or sediments.

8.7.2. Groundwater

Groundwater samples from various bores across the Base (and off-Base) were analysed for various nominated non-PFAS analytes as defined in the project brief and Technical memo 1652034-060-M-Rev2 including:

In-situ groundwater quality parameters (including cations and anions, nitrogen compounds, pH, sulfate and total organic carbon);

Total recoverable hydrocarbons, benzene, toluene, ethyl benzene, xylenes;

Polycyclic aromatic hydrocarbons;

Organochlorine pesticides;

Volatile and semi-volatile organic compounds; and

Metals (aluminium, arsenic, cadmium, total chromium, copper, iron, lead, manganese mercury, nickel and zinc).

Results of the groundwater sampling for non-PFAS analytes have been collated into Tables 10, 13, 14 and 15 (appended).

The analytical results have been compared against screening criteria protective of the relevant environmental values for groundwater uses at the Base including irrigation, potable domestic and ecosystem protection. The majority of the groundwater results for potential contaminants are below the adopted screening criteria or below the laboratory reporting limits.

The distribution of metals concentrations in groundwater that exceeded the adopted screening criteria did not suggest any pattern or direct source of metals impact to groundwater at the Base. Concentrations of metals, except for iron, appear to be spread across the Base at similar concentrations suggesting the measured concentrations in groundwater are reflective of regional groundwater conditions, rather than an indication of anthropogenic impacts to groundwater.



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Table 8.21: Summary of non-PFAS groundwater analytical results (g/L)

Contaminant Concentration range (µg/L)

Comparison Criteria

Irrigation2 Potable

Domestic3

Maintenance of Ecosystems

(95% freshwater)1

C16 – C34 <0.1 – 0.2 NCA 0.09 0.6

C34 – C40 <0.1 – 0.5 NCA 0.09 NCA

Aluminium <50 – 80 NCA 200 55

Arsenic <1 – 29 100 10 24

Copper <1 – 4.5 200 1,000 1.4

Iron 50 – 7,200 300 300 300,000

Nickel <1 – 40 200 20 11

Zinc <5 – 48 3,000 3,000 8

1. ANZECC (2000) Australian Water Quality Guidelines for Fresh and Marine Waters (Freshwater – slightly to moderately modified ecosystems)

2. ANZECC (2000) Australian Water Quality Guidelines for Fresh and Marine Waters (Long-term irrigation value)


NCA – No Criteria Available

Bold – indicates screening criteria exceeded

Other Inorganics

Concentrations of ammonia in groundwater were generally below the LOR, however 1,800 ug/L was recorded at 0990_Bore24, located 50 m west of the Fire Station. This is likely attributed to a leaking utility pipe.

8.8. Quality Assurance and Quality Control

Coffey implemented a comprehensive quality assurance/quality control (QA/QC) program as part of our field soil, surface sediment, surface water and groundwater sampling procedures, based on relevant Australian Standards, EPA Guidelines and industry practice.

The implemented QA/QC program included the following:

The use of appropriately qualified/trained environmental scientists to conduct the assessment.

The use of standardised field records to document the findings of the assessment.

Appropriate preservation of samples during transport from the field to the laboratory.

The use of chain of custody documentation to ensure the traceability of sample transport and handling.

The use of laboratories accredited by the National Association of Testing Authorities Australia (NATA) for the analysis of samples.

The collection and analysis of field quality control samples.



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Review of internal analysis of laboratory quality control samples.

The use of appropriate laboratory reporting limits.

Compliance with sample holding times.

Comparison of field and analytical data to check for the occurrence of apparently unusual or anomalous results.

The approach is generally based on guidance from the following sources:

NEPM [the National Environment Protection (Assessment of Site Contamination) Measure 1999] as amended in 2013.

AS4482.1 Guide to the sampling and investigation of potentially contaminated soil, Part 1: Non Volatile and Semi-volatile Substances.

AS4482.2 Guide to the sampling and investigation of potentially contaminated soil, Part 2: Volatile Substances.

AS/NZ 5667.1 Water Quality Sampling – Guidance on the design of sampling programs, sampling techniques and the preservation and handling of samples.

ANZECC&ARMCANZ (2000). Australian guidelines for water quality monitoring and reporting.

ANZECC&ARMCANZ (2000). Australian and New Zealand guidelines for fresh and marine water quality.

WA DER (2017). Interim Guideline on the Assessment and Management of Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS).

Table 8.22: PFAS quality control sample overview

Sample type Primary

samples

Primary

Laboratory

duplicate

samples

Secondary

Laboratory

Triplicate

samples

Rate

Blanks

Rinsate Trip

Soil and sediment 370 30 23 14% 44 6

Groundwater 306 23 16 13% 43 24

Surface water 100 14 8 22% 9 4

The results of the data validation undertaken are presented in Appendix K.

Data quality indicators indicated poor repeatability of soil sample analysis as indicated by high relative percentage difference in the results from field duplicates (primary and secondary laboratory check samples, respectively). More elevated RPDs were recorded for soil and sediment samples, than water samples indicating the greater potential for variability of concentrations within the media sampled, which was primarily considered to be due to the heterogeneity of PFAS distribution in these media. There was not a consistent pattern of bias to one laboratory reporting higher results, which suggests sample variability, rather than a difference in extraction or quantification accuracy.

Detectable concentrations of PFAS were reported in some rinsate and trip blank samples. A total of nine rinsate blanks and four trip blanks reported detectable concentrations of PFAS throughout the sampling program.

Three of the detectable concentrations in rinsate samples were taken from the surface water sampling pole. Although the outside of the pole was decontaminated between samples, due to the pole being



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hollow it is possible that a small amount of cross contamination may have occurred from water containing PFAS inside the sampling pole when collecting the rinsate sample. When collecting a sample from a large water body, such as a river, it is unlikely that the small volume of water inside the sampling pole would attribute to cross contamination between surface water samples.

Two detectable PFAS results in rinsate blanks collected during groundwater sampling events were associated with the interface probe (IP). This was generally the only piece of reusable equipment used during HydraSleeve sampling rounds. During most rounds, the IP was only used to measure the depth to water and not the total well depth. This means that only a small part of the IP entered the water column in each well, reducing the risk of potential for cross contamination.

Four rinsate blanks collected during soil sampling works reported detectable concentrations of PFAS. Although efforts were made to decontaminate reusable equipment, such as the hand auger or trowel, it was not always possible to ensure decontamination had been completed appropriately when collecting soil samples during drilling works. Where practicable, soil samples were taken from soil not in direct contact with the surface of the hand auger or trowel, in order to limit the potential for cross contamination.

A total of four trip blank samples reported PFAS concentrations marginally above the laboratory LOR. This does not indicate a significant potential for cross contamination to have occurred. The overall likelihood of soils or liquids migrating between plastic sampling vessels during transit, or non-volatile PFAS compounds entering sampling bottles during transit was considered to be low. This was further supported by the retention of all frozen water in sealed plastic bags or bottles to limit the potential for free water to be present in the esky during transit. No PFAS sample bottles or jars were reported by the laboratory to have leaked or been affected by melted ice in transit.

The total number of duplicate and blank samples analysed was generally in accordance with the rates set out in the SAQP.

All laboratories used for soil and water analysis were NATA accredited for the methods applied. Review of method blanks, laboratory control samples and laboratory spikes indicated that suitable laboratory quality control had been applied. The primary laboratory applied internal surrogate standards to analysis of all samples for 23 of 28 compounds. Review of surrogate recovery indicated low potential for relative analyte recovery to result in inaccuracy for the target PFAS compounds (PFOS, PFHxS and PFOA).

8.8.1. Fulfilment of DQO Steps

Table 8.23: DQO steps

DQO steps DQO fulfilment DQO step fulfilled successfully?

Step 1: Problem Statement

Problem statement set out the need to further characterise PFAS sources, sensitive receptors and pathways.

Yes

Step 2: Identify the goal of the study

To understand the nature and extent of PFAS contamination as a result

of Defence activities related to RAAF Base Tindal. Yes

Step 3: Identify information inputs

Assessment of the data in the context of the adopted investigation criteria.

Yes



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DQO steps DQO fulfilment DQO step fulfilled successfully?

Step 4: Study Boundaries

Study boundaries encompassed the Base, off-Base receptors, and groundwater and surface-water pathways connecting identified on-Base sources with on- and off-Base receptors.

Yes

Step 5: Decision Rule

PFOS, PFHxS and PFOA concentrations were compared against relevant screening levels to identify complete exposure pathways, and were used to characterise the source areas and delineation of contamination

Yes

Step 6: Decision Error Limits

More than 95% of all DQIs were considered acceptable and therefore the results of the assessment are considered suitable to rely on for the purposes of characterising the nature and extent of PFAS within source areas, surface waters and groundwater.

Yes

Step 7: Design Optimisation

The sampling program presented in the SAQP was designed to obtain the necessary data to allow the identified decisions in Step 2 to be made.

Yes



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9. Discussion

9.1. Nature and Extent of Contamination - Soil

The concentrations of PFAS in soils in source areas or associated drains at the Base exceeded conservative Tier 1 screening values for the protection of human health and ecological receptors under various exposure scenarios. The primary beneficial uses of land (soils) that may be impacted on the Base include protection of local terrestrial ecosystems, protection of adjacent aquatic ecosystems and protection of human health in direct contact with source area soils or indirectly through contact with waters contaminated by leaching from soils.

Potential impact to human health was evaluated against two separate exposure scenarios including residential (outside of the secure Base area) and recreational/open space (across the remainder of the Base). Although the Base may be classed as a commercial use, the exposure potential for most users is more consistent with open space, where access to soil is possible. The open space exposure parameters are conservative for the Base, as children are also considered as receptors in derivation of the investigation level, but are unlikely to frequently be on Base.

Ecosystem protection was also evaluated against two separate exposure scenarios including areas of ecological significance (the south-western and north-eastern portion of the Base), and open space (the remainder of the Base). However, as several of the assessment locations were considered to be within areas of ecological significance, as a conservative measure this has been adopted as a default to evaluate potential risks to ecosystems.

9.1.1. Fire Station

PFOS was measured in soils during this (and previous) environmental assessments at concentrations that exceeded conservative Tier 1 screening values for the protection of human health and ecological receptors under various exposure scenarios within the vicinity of the Fire Station.

Concentrations of PFOS in soils ranged from <0.5 µg/kg to 17,000 µg/kg. Similar concentrations were observed in each location at surface, 0.5 m depth and >1 m depth. This indicates distribution of PFOS through the soil profile, consistent with a source of impact to groundwater. PFOA and PFHxS were also measured in soils ranging from <0.5 to 350 µg/kg and <5 to 1,800 µg/kg (respectively).

The areas with the highest concentrations were closest to the Fire Station, where AFFF was stored, and in the areas to the south and south-west of the Fire Station, in the low lying area that receives runoff from the hardstand outside of the Fire Station, where equipment may have been tested and washed out on a regular basis. Delineation of PFAS (to 10 µg/kg) at this site was achieved to the north, north-west and north-east. The area of highest impact is approximately 250 m x 180 m, located to the south and south-west of the Fire Station.

Human health-based screening values adopted for this AEC (Recreational – 1.2 mg/kg) were exceeded in 10 locations in this and historic assessments in the low lying area and beneath the hardstand (across an area of approximately 150 x 80m). In the most impacted areas PFOS was not vertically delineated (below the human health screening criteria) within the soil profile.

The measured concentrations of PFOS exceeded the sensitive ecological criteria in most samples with the exception of some sample locations to the north of the Fire Station, which indicates that soils in the area have the potential to leach to surface waters at concentrations that may impact aquatic ecology.

Measured concentrations of PFOA were below human health and ecological Tier 1 screening values.



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It is considered that the beneficial uses of land of human health and ecosystem protection are potentially precluded by the PFOS contamination in soils in this AEC, where contact with soil occurs in the impacted area. Leaching potential from soil is also likely to be presenting an ongoing source of impact to surface water and groundwater in the area.

Figures 11a to 11d (appended) show the extent of PFOS and PFOA in soils at the Fire Station.

9.1.2. Fire Training Area

PFOS was measured in soils during this (and previous) environmental assessments that exceeded conservative Tier 1 screening values for the protection of human health and ecological receptors under various exposure scenarios in the vicinity of the Fire Training Area.

Concentrations of PFOS in soils ranged from <0.5 µg/kg to 3,900 µg/kg (historical maximum 7,200 µg/kg), with shallow (upper 0.5 m) impacts centred around the fire training pad and surface water drains. Concentrations in these areas decreased with depth, whereas concentrations were observed to increase with depth further from the training pad, which is consistent with lateral spreading in the layered Jinduckin unit. PFOA and PFHxS were also measured in soils ranging from <0.5 to 1,100 µg/kg and <5 to 7,700 µg/kg (respectively).

Human health-based screening values adopted for this AEC (Recreational – 1.2 mg/kg) were exceeded in several locations in this and historic assessments on the fire training pad and in associated drains (across an area of approximately 150 x 100 m and at least 350 m along the surface drain). The maximum concentrations were not typically at the surface, and therefore exposure is limited unless soil disturbance occurs. In the most impacted areas PFOS was vertically delineated (below the human health screening criteria) within the top 1.0 m of the soil profile.

The measured concentrations of PFOS exceeded the ecological criteria in most samples. Delineation of PFAS (to 10 µg/kg) at this site was generally achieved to the north and south of the Fire Training Area and west of the AEC and the known impacted area is approximately 280 m x 300 m.

Concentrations of PFOA exceeded the adopted ecological assessment criteria in samples taken from the Fire Training Area. Results from all samples taken from outside the Fire Training Area were reported below the adopted assessment criteria or below the laboratory LOR in all directions. PFOA impacts are considered to be limited to the 100 m x 100 m Fire Training pad area.

Samples of sediment, water and concrete were collected from the training pad and associated

evaporation ponds. Analysis indicated PFOS concentrations up to 2,660,000 g/kg in sediment,

43,000 g/kg in concrete and 840 g/L in water. Comparison against screening values is not directly relevant, as the exposure potential is low, however the results indicate that infrastructure and associated sediments and collected water presents a potential source of PFAS impact.

It is considered that the beneficial uses of land of human health and ecosystem protection are potentially precluded by the PFOS contamination in soils in this AEC, although exposure to soils above human health screening values is limited. Leaching from residual soil and drain sediment is potentially presenting an ongoing source of impact to surface water and groundwater in the area.

Figures 12a to 12d (appended) show the extent of PFOS and PFOA in soils within this AEC.

A series of soil bore transects were completed north-west of the Fire Training Area, between the Fire Training Area and Tindal Creek, in order to assess for the potential for migration of PFAS through surface water runoff towards Tindal Creek. Seven out of 16 samples reported PFOS concentrations above the adopted sensitive ecological assessment criteria, indicating that PFAS has migrated across the surface from the Fire Training Area to Tindal Creek along this alignment.



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Figures 17a and 17b (appended) present the PFOS and PFOA results from samples collected in this area.

9.1.3. Irrigation Paddock

Ten shallow soil samples were analysed from the irrigation paddock, to the east of the waste water treatment plant. PFOS concentrations were reported between <5 µg/kg and 18 µg/kg.

Six of the ten samples reported concentrations marginally above the Tier 1 screening criteria adopted for sensitive ecological assessment. On the basis that there are no aquatic ecosystems in connection with these soils (the closest point of Tindal Creek is 100 m from the edge of the paddock), the reported impact is not considered to pose a risk to ecosystems. No results exceeded Tier 1 human health screening values.

PFOA concentrations in this area were reported below the laboratory LOR.

It is considered that the beneficial use of land of ecosystem protection is not precluded in this AEC. Leaching potential from residual soil is unlikely to be presenting a significant ongoing source of impact to surface water and groundwater in the area.


9.1.4. Base Services and Married Quarters

A total of six soil samples were analysed from irrigated sports grounds in the Base Services area and four soil samples were analysed from the Married Quarters area where bore water is used for irrigation. Concentrations of PFOS and PFOA in all samples were reported below the laboratory LOR and below the adopted Tier 1 screening values for the protection of human health and ecological receptors. This indicates that irrigation or other transport mechanisms (i.e. dust) has not resulted in accumulation of PFAS.


9.1.5. Fuel Farm 1

PFOS was measured in soils during this environmental assessment at concentrations that exceeded conservative Tier 1 screening values for the protection of ecological receptors under various exposure scenarios in the vicinity of Fuel Farm 1.

Concentrations of PFOS in soils ranged from <0.5 µg/kg to 29 µg/kg between 0 m and 0.5 m. PFOA and PFHxS were reported below the laboratory LOR in all soil samples from Fuel Farm 1.

Soil samples were also collected from a stockpile to the south-west of the farm, thought to contain waste AFFF containers. PFOS concentrations in these samples ranged from <5 µg/kg to 62 µg/kg. PFOA and PFHxS were reported below the laboratory LOR.

A sample of water from the retention pond at Fuel Farm 1 contained 0.52 µg/L of PFOS, which does not indicate a significant ongoing source of PFAS contamination in the infrastructure, but does confirm that AFFF has previously been used at the facility.

Due to the presence of operating infrastructure, concentrations in soil below the fuel farm have not been investigated and may represent ongoing source of impact to groundwater in the area.



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9.1.6. Mechanical Equipment Operations Maintenance Section

PFOS was measured in soils during this (and previous) environmental assessments at concentrations that exceeded conservative Tier 1 screening values for the protection of ecological receptors under various exposure scenarios within the Mechanical Operations Maintenance Section area. No results have exceeded Tier 1 human health based Tier 1 screening values.

Concentrations of PFOS in soils ranged from <0.5 µg/kg to 440 µg/kg. PFHxS was also measured in soils ranging from <0.5 to 100 µg/kg. PFOA was reported below the laboratory LOR in all soil samples from Mechanical Equipment Operations Maintenance Section.

PFOS impacts in soil have been delineated laterally to the west and south of Mechanical Equipment Operations Maintenance Section. Impacts have not been fully delineated vertically or laterally to the north and east of Mechanical Equipment Operations Maintenance Section. The impact appears to be related to drainage lines and infrastructure. The maximum concentration was reported at 1.0 m adjacent to a waste separation pit associated with the workshop.

Samples of water and concrete were also collected from the separation pit and indicated concentrations of 16 µg/L and 24 µg/kg respectively. Samples of concrete were also collect from the spoon drain behind the workshop and on the road side kerb, to assess impact from historic discharges from the workshop. PFOS concentrations in these locations in concrete were 110,000 and 1,000 µg/kg respectively. These concentrations in infrastructure indicate moderate potential for leaching of PFAS to surface runoff in the area.

Concentrations of PFOS in soil did not exceed human health screening values, but did exceed sensitive ecological screening values which indicate a potential to impact aquatic ecosystems via leaching or runoff. Leaching potential from infrastructure is also likely to be presenting an ongoing source of impact to surface water and groundwater in the area.


9.1.7. Katherine Airport

Shallow soil samples were collected from Katherine Airport from the north-western end of the runway and from a former fuel farm to the south-west of the airport. Concentrations of PFOS and PFOA in all samples were reported below the laboratory LOR and below the adopted assessment criteria. This indicates that there has not been a significant source of PFAS contamination in this area of the base.


9.1.8. Potential former informal fire training area

A total of 12 samples were collected from an area south of the wastewater treatment ponds, thought to have been used as a fire training area in the past. All samples were reported below the adopted assessment criteria or below the laboratory LOR for PFOS and PFOA. This indicates that there is not a residual source of PFAS in soils in this area of the Base.




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9.2. Nature and Extent of Contamination - Groundwater

The concentrations of PFOS, PFHxS and PFOA in groundwater across the Investigation Area are summarised on Figures 32 to 39 (appended) for individual monitoring events, with groundwater concentrations associated with individual known or suspected source areas discussed below. The results below relate to the September 2017 baseline sampling event.

PFAS impacts in groundwater are highest at the two primary source area (Fire Station and Fire Training Area). Other minor sources of PFAS impacted groundwater are in the vicinity of Fuel Farm 1 and Mechanical Equipment Operations Maintenance Section.

The PFAS plume extends across most of the Base and is considered to be delineated to the extent practicable on-Base. The plume extends off-Base, migrating in a north-westerly direction towards the town ship of Katherine, under the northern portion of Uralla, approximately along the line of the Stuart Highway.

The southern edge of the PFAS plume (defined by groundwater concentrations of 0.1 to 1 µg/L PFOS+PFHxS) extends across most of the southern portion of Uralla. Groundwater concentrations recorded in wells at the southern end of Uralla Road have consistently reported PFAS concentrations below the laboratory LOR, indicating that the extent of the plume has been delineated in this area.

The southern edge of the plume at Katherine East is considered delineated at the confluence of Tindal Creek and the Katherine River. It is noted however that PFAS concentrations above LOR have been detected at Katherine Tip to the south, however this is considered to be associated with another source, such as fabrics and used chemicals that have been disposed of at the Tip.

The northern edge of the plume (defined by groundwater concentrations of 0.1 to 1 µg/L PFOS+PFHxS) extends slightly to the north of the Stuart Highway, migrating towards the greater Katherine Township. The north-western edge of the PFAS plume is controlled by activities undertaken at the Katherine Research Station and at the end of Morris Road. PFOS+PFHxS concentrations are ~ 1.5 µg/L. The shape of the plume is likely due to high volumes of groundwater extraction for irrigation (at the Katherine Research Station) and for town water supply (at the south-eastern end of Morris Road).

As the PFAS plume migrates towards Katherine, it discharges into the Katherine River. The likely discharge points are associated with springs and seepages (i.e. Katherine Hot Springs). These seeps have been mapped between Morris Road to the north of Katherine town ship and the low-level crossing (Zimin Drive) to the south.

All PFOS+PFHxS groundwater monitoring results from 2017, collected by Coffey, are shown in Figures 40a and 40b (appended) and have been used to develop the concentration contours shown in Figure 43 (appended).

9.2.1. Fire Training Area

PFAS concentrations in groundwater in the vicinity of the Fire Training Area are the highest reported on-Base, with a maximum of 2,800 µg/L of PFOS reported in 0990_064MW02 (historical maximum 7,800 µg/L in 2011). PFOA and fluorotelemers are present in the source area and down-gradient. The reported PFOS, PFHxS and PFOA concentrations in the vicinity of the Fire Training Area are shown on Figures 32a to 33c (appended). The extent of impact from the Fire Training Area has not been delineated within the Base and extends off-Base to the north-west, as shown in Figures 38a to 39b (appended).

Based on relative groundwater elevations and relative PFAS concentrations, this source area appears to be contributing to impact detected down-gradient, flowing toward Tindal Creek. The composition of



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PFAS in groundwater to the south and west is dominated by PFOS and PFHxS, and has a similar compositional signature to groundwater within the suspected source zone.

Chart 9.1: PFAS composition in groundwater in the vicinity of the Fire Training Area

The composition of PFAS at the fire training facility, and along the track 50 m to the west of the Fire Training Area (wells 0990_MW102 to 0990_MW102) are the same. PFOS and PFHxS concentrations in groundwater are almost equivalent to PFOS concentrations. (Charts 9.1).

The composition of PFAS in the source area was very similar to down-gradient. The flow direction, in combination with the PFAS concentrations and composition, indicate that the PFAS detected in groundwater in this area is predominantly due to release of 3M Lightwater AFFF.

9.2.2. Fire Station

Wet testing of fire hoses on vehicles was conducted daily at crew changeover and weekly foam testing was conducted. Tests involved opening of valves to confirm correct operation of concentrate mixing, valves and hoses. Initially foam discharge would not have been captured or minimised, but as the environmental effects and persistence became understood, the volumes were minimised and isolated. Testing of foam systems is no longer undertaken. Historically, there were additional foam tests each time a vehicle came back from the mechanics. Tests were conducted at the Fire Training Area or outside the Fire Station building.

The highest PFAS concentration in the Fire Station area was reported in 0990_065MW02 (120 µg/L of PFOS) which is in the low lying area that receives drainage from the hardstand outside the Fire Station. PFOA and fluorotelemers are present in the source area and down-gradient. PFOS, PFHxS and PFOA concentrations from each monitoring event in the vicinity of the Fire Station is shown on Figures 34a to 35b (appended). The impact from the fire station has not been delineated down-gradient to the north-west. The maximum PFOS concentration reported 250m down-gradient of the inferred source area was 5.6 µg/L in 0990_MW127, confirming a west north-westerly groundwater flow direction. The impact from the Fire Station appears to connect to the plume from the Fire Training Area near GW101 (4.5 µg/L PFOS) and 046MW01 (5.9 µg/L).



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Elevated concentrations of 8:2FTS and 6:2FTS were also detected, indicating that Ansulite has also contributed to impact in this area.

Chart 9.2: PFAS composition in groundwater in the vicinity of the Fire Station

9.2.3. Other On-Base Areas

Fuel Farm 1

PFAS concentrations in groundwater indicate that historical releases have occurred. The maximum concentration reported in September 2017 was in 0990_076MW02 (5.9 µg/L PFOS and 5.7 µg/L PFHxS). The historical maximum was 15 µg/L PFOS in May 2017. PFOA and fluorotelemers are present, suggesting that some releases may have involved Ansulite. PFAS composition in groundwater in the vicinity of Fuel Farm 1 is presented in Chart 9.3. Recent groundwater wells installed less than 100 m down gradient of 0990_076MW02, reported a maximum PFOS concentration of 1.2 µg/L.


Fuel Farm 2

PFAS concentrations in groundwater indicate that a release has occurred historically. The maximum concentration in September 2017 reported in 0990_077MW01 (0.85 µg/L PFOS and 0.37 µg/L PFHxS). This well is a UPSS monitoring well installed in the area identified as containing the AFFF tank when the facility was constructed. Other wells around the facility, and directly down-gradient of 0990_077MW01, have consistently reported PFOS concentrations in the range of 0.22 to 0.53 µg/L. Fluorotelemers are present, suggesting that some releases may have involved Ansulite.

The PFAS composition at Fuel Farm 1 and 2 are similar, as shown in Chart 9.4.



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Mechanical Equipment Operations Maintenance Section is located at 17 SQN in the north-west of the secured Base. Vehicle and equipment maintenance activities occur in this area, which is likely to have historically included cleaning and maintaining equipment containing PFAS materials.

PFAS composition in groundwater in the vicinity of Mechanical Equipment Operations Maintenance Section is shown in Chart 9.5.

Chart 9.5: PFAS composition in groundwater in the vicinity of Mechanical Equipment Operations Maintenance Section

PFAS concentrations indicate that historical releases have occurred in the area. The maximum concentration in September 2017 was reported in 0990_070MW01 (0.43 µg/L PFOS and 0.53 µg/L PFHxS). Several targeted wells were dry in September 2017 and results from monitoring of additional wells through the area in the wet season will assist in defining the main sources of release in the area. The maximum PFOS concentration historically reported in the broader Mechanical Operations Maintenance Section area was 11 µg/L in 053MW02 in July 2017. This well is immediately down-gradient of the tanker refuelling bowsers. The down-gradient extent has not been delineated.

9.2.4. Off-Base

The distribution of PFOS, PFHxS and PFOA concentrations off-Base, are shown in Figures 27a to 27f (appended) for April, July and September monitoring events. Results of PFOS+PFHxS analysis for all groundwater sampling conducted as part of this DSI are presented in Figure 41a (appended) and represented by the contour plan presented in Figure 43 (appended). Specific areas are discussed below where the distribution or composition is not consistent with the overall plume extent and aquifer behaviour.



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Katherine Research Station

Concentrations of PFOS reported in monitoring wells at the research station (PB032 to PB035) were in the range of 0.58 to 0.83 µg/L and were higher than expected based on the groundwater flow direction and concentrations reported in other wells north of Stuart Highway. The concentration in MW134 at the southern boundary of the research station was 1.0 µg/L and has a PFAS composition consistent with the impact at the western Base boundary and that reported on the research station. The plume distribution in this area is considered to be influenced by pumping from the production bores at the station site drawing the plume further north.

Katherine Tip (July 2017)

The concentration of total PFAS in well RN031131 at the Katherine municipal tip was higher than expected based on the very low concentrations reported further north.

The composition of PFAS in groundwater at the Katherine Tip bore is different to anywhere else across the Investigation Area. PFHxA constitute the main PFAS concentrations at the site, with 0.06 µg/L recorded in September 2017 at 0990_RN31131. This indicates that PFAS reported in the Katherine Tip bore is associated with a source other than RAAF Base Tindal.

The composition of PFAS in 0990_RN031131 is shown in Chart 9.6 alongside the composition reported in 0990_MW142, which is on the southern edge of the plume from RAAF Base Tindal, approximately 3 km north of the tip.

Chart 9.6: PFAS composition in groundwater at the Katherine Tip bore compared to MW142

9.3. Nature and Extent of Contamination - Surface Water, Sediment and Infrastructure

This discussion of the nature and extent of PFAS impacts in surface water and sediments has been

divided into the primary water-sheds (and contributing surface drainage networks across the

Investigation Area) including Tindal Creek and Katherine River.

9.3.1. On-Base Surface Drainage

Surface water run-off across the site is collected via a series of concrete and earthen drains and is directed to two major formalised drainage channels. The bulk of the surface run-off from the base is discharged to Tindal Creek at locations:

Up-stream near the sewage irrigation paddock (the ‘horse paddock’), and

Down-stream of the north-western end of the airstrip.



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Surface water sampling was undertaken from on-site surface drainage networks during April 2017 at the end of the wet season. These drainage networks were dry during subsequent sampling events, and will be sampled again during the wet season.

Results of on-Base surface water assessment results are presented in Table 16a (appended) and shown for PFOS, PFOS+PFHxS and PFOA on Figures 25a, 26a and 27a (appended) respectively.

Concentrations were generally highest within the two open drains running parallel with the runway along the north-eastern side adjacent to the Fire Station. PFOS concentrations ranged from 0.01 to 4.9 µg/L in drains. The maximum concentration of PFOS was within a surface drain near the southern end of the fire station.

Surface water sampling in April 2017 identified concentrations of PFOS in the drainage network north-west of the airside access road on-site, exceeding the adopted screening criteria for maintenance of ecosystems (Freshwater 95%). This area of the Base receives runoff from the runway and fire station. Concentration of PFOS+PFHxS also exceeded health based screening values for recreational use (primary contact) adjacent to the Fire Station and between the runway and Taxiway A. PFOA was detected in surface water north-west of the airside access road, but did not exceed screening levels for protection of human health or ecology.

9.3.2. Tindal Creek – On-Base

Surface water assessment results are shown for PFOS, PFOS+PFHxS and PFOA on Figures 25a,

26a and 27a (appended) respectively.

Surface water sampling undertaken in Tindal Creek identified concentrations of PFOS exceeding the

adopted screening criteria for maintenance of ecosystems (Freshwater 95%) down-stream of the

spring that feeds the creek south-west of Katherine Airport. This area is also known to be saturated

throughout the dry season and is considered to be a localised groundwater discharge feature. It is

likely that PFOS concentrations in this part of Tindal Creek can be attributed to groundwater rather

than surface water runoff. PFOS concentrations measured at this location in April, July and August

2017 are similar. PFOS concentrations between the spring and the western Base boundary were

reported in the range 0.39 to 2.2 µg/L between April and September, but was typically 2 µg/L.

Concentrations of PFOS+PFHxS exceeded health based screening values for recreational use in

surface water samples collected in Tindal Creek down-stream of the spring.

PFOA concentrations were detectable down-stream of the spring, but did not exceed human health or

ecological screening values.

Concentrations of PFOS were lower in up-stream sections of the Tindal Creek, to the east and south of the Fire Training Area. Concentrations of PFOS measured in April 2017 in this section of the Creek ranged from 0.02 µg/L at 0990_SW037 to 0.06 µg/L at 0990_SW039 (Figure 25a, appended).

Sediment samples were collected adjacent to the Tindal Creek surface water sampling location

0990_SW009. Concentrations of PFOS exceeded the adopted screening criteria for maintenance of

sensitive ecosystems (Freshwater) and ranged from 46 to 65 µg/kg.

9.3.3. Tindal Creek – Off-Base

Surface water assessment results are shown for PFOS, PFOS+PFHxS and PFOA on Figures 28, 29

and 30 (appended) respectively.

Surface water sampling was undertaken in Tindal Creek off-Base in April 2017, concluding at the

discharge point to the Katherine River. The results identified concentrations of PFOS exceeding the



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Tier 1 screening values adopted for maintenance of ecosystems (Freshwater 95%) at points between

the Base boundary and adjacent to Zimin Drive. Concentrations of PFOS were below detection at

0990_SW029, 0990_SW031 and 0990_SW32 in May 2017 compared to an elevated concentration of

0.47 µg/L in April at a similar location. The change in concentration potentially indicates that flow in

the lower reach of Tindal Creek in the wet season is dominated by stream flow from further up the

creek, whereas flow in early dry season is dominated by local groundwater seepage, which does not

contain PFAS.

Concentrations of PFOS+PFHxS in Tindal Creek down-stream of the Base also exceeded human

health screening values for recreational use.

9.3.4. Katherine River

Surface water samples from the Katherine River were collected as far north as Lansdowne, and

approximately 8 km down-stream of Cossack.

April 2017 Sampling Event

In April 2017 the surface water sample collected at the Katherine Bridge and another sample

collected approximately 7 km down-stream recorded PFOS concentrations of 0.02 µg/L.

Concentrations of PFOS up-stream of the Katherine Bridge were below the laboratory detection limit.

July, August and September 2017 Sampling Events

In July 2017 concentrations of PFOS along the Katherine River (down-stream of the Stuart Hwy

Bridge) ranged from 0.02 to 0.11 µg/L. Similar results were also recorded in August and September

2017. PFAS contaminated groundwater discharges to the Katherine River all year, which is likely

attributing to the constant PFOS concentrations measured in the River. The maximum concentration

reported up-stream of the Stuart Hwy Bridge was 0.01 µg/L in two events in August 2017.

Concentrations of PFOS+PFHxS in the Katherine River did not exceed the Tier 1 screening values for

the protection of human health for a recreational use scenario.

Concentrations of PFOA were above standard detection limits in some samples collected from

different locations along the Katherine River at different periods. Concentrations did not exceed the

Tier 1 screening values for the protection of human health and ecological receptors under various

exposure scenarios.

9.4. Receptors and Exposure Pathways

The above sections outline the nature and extent of PFAS impacts at the Base and in off-Base areas

and also discuss the beneficial uses of various media (soil, groundwater and surface water) that are

potentially impacted by contamination. However, in some cases there is not a complete exposure

pathway. In order to better evaluate the risks posed by PFAS contamination to human health and the

environment, this section describes the potential receptors of PFAS contamination and the pathways

by which they may be exposed to PFAS.

9.4.1. On-Base Human Receptors and Potential Exposure Pathways

The following on-Base human receptors and potential exposure pathways have been identified. The identified potential exposure pathways are plausible but not necessarily complete.



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Table 9.1: On-Base human receptors and potential exposure pathways

Receptor Potential exposure pathway

On-Base workers and/or visitors (Defence personnel) whose activities and exposure durations are similar to a commercial/industrial scenario

Dermal contact with soil

Incidental ingestion of soil

Inhalation of soil/sediment derived dusts

Dermal contact and/or incidental ingestion of surface water and

sediments (from surface water drainage networks)

Construction or maintenance workers who may be exposed to contamination via dermal contact, ingestion or inhalation

Dermal contact with surface and excavated soil

Incidental ingestion of surface and excavated soil




Dermal contact and/or incidental ingestion of groundwater

On-Base residents (within accommodation areas)






9.4.2. Off-Base Human Receptors and Potential Exposure Pathways

The following off-Base human receptors and potential exposure pathways have been identified. The identified potential exposure pathways are plausible, but not necessarily complete.

Table 9.2: Off-Base human receptors and potential exposure pathways


Off-site residents (including children attending childcare or primary school)






Dermal contact with shallow groundwater

Ingestion of shallow groundwater

Ingestion of eggs produced from poultry watered with groundwater

Ingestion of locally grown fruit and vegetables irrigated with

groundwater

Ingestion of home-grown meat watered with groundwater

Off-site workers (including visitors to the airport and workers in areas surrounding the site) whose





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activities and exposure durations are similar to a commercial/industrial scenario





Off-Base construction or maintenance workers

Dermal contact with surface and excavated soil

Incidental ingestion of surface and excavated soil





Recreational users of Katherine River and Tindal Creek


sediment

Consumers of aquatic animals from within Katherine River and Tindal Creek

Ingestion of fish

Ingestion of crustaceans

9.4.3. On-Base Ecological Receptors and Potential Exposure Pathways

The following on-Base ecological receptors and potential exposure pathways have been identified. The identified potential exposure pathways are plausible, but not necessarily complete.

Table 9.3: On-Base ecological receptors and potential exposure pathways


Terrestrial flora and fauna (including plants, trees, birds, reptiles, mammals, insects)

Direct contact and uptake of contamination from soils

Direct contact and uptake of contamination in surface water

and/or sediments

Direct contact with and uptake of contamination from

groundwater (deep rooted trees or riparian plants)

Ingestion of contamination which may bio-accumulate and bi-

magnify through the food chain.

Aquatic flora and fauna which may be present in small on-site ponds, surface water drains and Tindal Creek


and/or sediments





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9.4.4. Off-Base Ecological Receptors and Potential Exposure Pathways

The following off-Base ecological receptors and exposure pathways have been identified. The identified potential exposure pathways are plausible but are not necessarily complete.

Table 9.4: Off-Base ecological receptors and potential exposure pathways


Terrestrial flora and fauna (including plants, trees, birds, reptiles, mammals, insects)

Direct contact and uptake of contamination from soils


and/or sediments

Direct contact with and uptake of contamination from

groundwater (deep rooted trees or riparian plants)



Aquatic flora and fauna


and/or sediments



9.5. Preliminary Assessment of Risk to Identified Receptors via Exposure Pathways

An evaluation of the potential risks posed to the various key receptors has been completed by comparison of PFAS concentrations within various media to the adopted screening levels (which has been adopted or calculated to be protective of the specific receptor group). The following tables describe the outcome of the comparison for human and ecological receptors for a variety of environmental media.

PFAS uptake through dermal adsorption is considered to be an insignificant pathway, where other exposure routes are present (i.e. ingestion or dust inhalation). Therefore, dermal contact has been nominated as an incomplete pathway for PFAS contamination.



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Table 9.5: Human receptors and exposure pathways

Source Transport Exposure point Exposure route Potential receptors Potential complete pathway

Soil in source

area Direct contact

Surficial soils

Incidental ingestion Base residents X

Base workers

Particulate inhalation Base residents X

Base residents

Dermal contact Base workers X

Sub-surface works

Incidental ingestion Maintenance workers

Particulate inhalation Maintenance workers

Dermal contact Maintenance workers O

Sediment in

impacted

creeks and

drains

Direct contact Surficial soils

Incidental ingestion

Base residents

Base workers

Urban residents

Rural residents

Particulate inhalation Base residents

Base workers



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Urban residents

Rural residents

Dermal contact

Base residents O

Base workers O

Urban residents O

Rural residents O

Groundwater Groundwater

extraction2 Domestic purposes1

Direct ingestion

Base workers/residents X

Urban residents X

Rural residents

Aerosol inhalation/ingestion


Urban residents X

Rural residents

Dermal contact


Urban residents* X

Rural residents O



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Irrigation


Base workers/residents

Urban residents

Rural residents

Aerosol inhalation/ingestion


Urban residents*

Rural residents

Dermal contact

Base workers/residents O

Urban residents O

Rural residents O

Indirect ingestion through plant or

animal uptake


Urban residents

Rural residents

Subsurface works Direct contact Maintenance worker

Surface water Groundwater

discharge, Domestic purposes1

Direct ingestion Rural residents

Aerosol inhalation/ingestion Rural residents



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surface water and

particle runoff Dermal contact Rural residents O

Recreational use



Urban residents

Rural residents

Dermal contact

Base workers/residents O

Urban residents O

Rural residents O

Irrigation

Incidental ingestion Rural residents

Aerosol inhalation/ingestion Rural residents

Dermal contact Rural residents O

Indirect ingestion through plant or

animal uptake Rural residents

Food source Ingestion of aquatic biota


Urban residents

Rural residents



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Ingestion of aquatic plants


Urban residents X

Rural residents

Pathway potentially complete; Pathway insignificant or incomplete; NA Pathway not applicable

* Actual uses groundwater made by urban residents is to be confirmed through water use surveys

O Potentially complete pathway but insignificant due to limited uptake through dermal adsorption

1. Includes drinking water

2. Only the more sensitive receptors and pathways presented for this preliminary evaluation



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A summary of potential risks to ecological receptors is provided in Table 9.6.

Table 9.6: Potential risks to ecological receptors

Media / Location Comparison to Investigation levels Implication

On-Base surface water

Numerous samples have reported perfluorooctane sulfonate (PFOS) concentrations above the draft ANZECC guidelines for protection of freshwater ecosystems (99% and 95% species protection levels)

There is the potential for PFOS to pose an unacceptable risk to aquatic species in on-Base waterways.

Off-Base surface water – Tindal Creek

Numerous samples have reported perfluorooctane sulfonate (PFOS) concentrations above the draft ANZECC guidelines for protection of freshwater ecosystems (99% and 95% species protection levels)

There is the potential for PFOS to pose an unacceptable risk to aquatic species in Tindal Creek.

Off-Base surface water – Katherine River

Numerous samples have reported perfluorooctane sulfonate (PFOS) concentrations above the draft ANZECC guidelines for protection of freshwater ecosystems (99% species protection levels)

There is the potential for PFOS to pose an unacceptable risk to sensitive aquatic species in Katherine River.

On-Base soils

Maximum PFOS concentrations reported in known source areas and adjacent drains exceed the soil assessment criteria for maintenance of ecosystems in a residential or public open space setting.

Numerous near surface soil and site drain samples across the base have reported PFOS concentrations that exceed the more sensitive assessment criteria relevant to protection of ecosystems in areas of ecological significance.

There is the potential for PFOS to pose an unacceptable risk to terrestrial ecology in specific areas on-Base.

There is the potential for PFOS to pose an unacceptable risk to sensitive terrestrial species on base, or for soil contamination to lead to concentrations in waterways that may pose an unacceptable risk to aquatic species.

On-Base sediments

Some samples collected from on-Base drains and Tindal Creek have reported PFOS concentrations above the nominal sediment screening value for protection of fresh water ecosystems.

There is the potential for PFOS in sediments to pose an unacceptable risk to aquatic species either directly or indirectly via leaching to surface water.

Off-Base sediments

Some samples collected from Tindal Creek have reported PFOS concentrations above the nominal sediment screening value for protection of modified fresh water ecosystems.

As detailed in the above tables, there are several primary and secondary sources of contamination, with sensitive receptors and complete pathways for exposure that exceed the adopted human health or ecological screening criteria. These scenarios will be assessed further in the Human Health and Ecological Risk Assessments (HHRA and ERA) that are being prepared for the Investigation Area.



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10. Conclusions

The activities undertaken as a part of this DSI were performed to assist Defence in developing an understanding of the nature and extent of any per- and poly-fluoroalkylated substances (PFAS) contamination from the historic use, storage and disposal of aqueous film forming foams at the Base. The principal objectives of the investigation were to identify known and potential sources of PFAS contamination at the Base, to characterise the Base setting in sufficient details so as to describe likely contaminant behaviours, and to identify receptors of the contamination and associated exposure concentrations.

10.1. Base Setting

RAAF Base Tindal is set within a sub-tropical area of Australia and subject to high-rain fall during the wet season (nominally December to March), and significantly lower rain during the dry season. The Base itself sits approximately 130 to 140 m above sea level (AHD). The Base is located on the unconfined Tindall Limestone aquifer, which is a high yielding, karst limestone aquifer.

The Base also contains a civilian airport (Katherine Airport) and the Base is bounded by rural residential properties, farmland and bushland. The Township of Katherine is located approximately 13 km west, north-west of the Base.

Surface water from the Base infiltrates to groundwater or flows overland or through drainage networks to Tindal Creek, which is located to the south of the Base infrastructure. Tindal Creek is ephemeral and in is connection with groundwater in some zones all year. The creek starts on the eastern edge of the Base, runs to the south of the runway and generally follows the alignment of Stuart Highway after leaving the Base. The creek ultimately discharges to Katherine River south of the town wastewater treatment plant.

The groundwater flow at the Base is also consistent with the Base’s topography with groundwater flowing to the west-north-west, towards Katherine River. Reduced infiltration through the dry season results in groundwater levels falling by up to approximately 6 metres from the end of the wet season to the end of the dry season. The water level drop does not change the overall groundwater flow direction, but may affect the rate of contaminant migration by changing hydraulic gradients.

10.2. Summary of DSI Findings

This DSI has identified PFAS present both on-Base and off-Base within the Investigation Area in a variety of environmental media, including soil, sediment, surface water and groundwater.

The following areas were confirmed through soil, surface water, groundwater or sediment assessment as being PFAS source areas as a result of historic use of legacy AFFF.

Fire Station and the drainage area to the west.

Fire Training Area.

Fuel Farm 1.

Mechanical Equipment Operations Maintenance Section.

Fuel Farm 2.



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Soil

The measured concentrations of PFOS within soils were generally below the adopted screening criteria for the protection of human health on Base based on a largely open space land use exposure potential for human receptors.

Residential areas are present on the broader base and off-Base areas, and the results reported in this DSI did not identify PFAS concentrations outside of the source areas above screening criteria for protection of human health in sensitive settings. Off-Base residential soil assessment is currently being undertaken to characterise impact where irrigation using contaminated bore water may have resulted in accumulation of PFAS in soils.

Concentrations of PFOS above the nominated health based recreational screening value were identified in vicinity of the Fire Station and the Fire Training Area.

Areas where concentrations of PFOS were above the adopted screening criteria, protective of human health under a residential or recreational scenario, were within restricted site areas and are therefore not considered to represent a high exposure potential to the public or on-Base residents. Environmental controls could be applied to guide soil management and minimise risk to users, construction or maintenance workers and the broader environment.

The leachability of PFAS from soils indicated that residual soil impact in all source areas is likely to be contributing to detectable concentration of PFAS in surface water and groundwater.

Groundwater

The maximum concentrations of PFAS measured within groundwater were found at the Fire Station and the Fire Training Area. Other areas on Base where PFAS was identified in groundwater, indicating a minor source of PFAS present included the following:

Fuel Farm 1.


Fuel Farm 2.

The PFAS concentrations measured in groundwater (predominantly PFOS and PFHxS) around the areas described above, as well as down-gradient of these areas, exceeded the adopted screening criteria for the protection of beneficial use of groundwater for irrigation, potable and non-domestic water use and maintenance of ecosystems.

Figure 10.1 below shows the approximate extent of PFAS contamination in groundwater in the Investigation Area. A detailed figure showing concentration contours for PFAS in groundwater is presented as Figure 43 (appended). PFAS impacts in groundwater are present in the source areas on Base, migrating with the groundwater flow through Uralla and Katherine, discharging to the Katherine River.



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Figure 10.1: Inferred PFAS concentrations in groundwater

Based on data collected since April 2017, Groundwater impacts are considered to have been delineated. Repeat monitoring of locations will continue through the wet season to assess seasonal effects. Sampling of private extraction bores will also continue to assess exposure point concentrations through the wet season. The additional data obtained will be reported and interpreted in the poste wet season supplementary DSI report.

Concentrations in groundwater were observed to increase in certain areas on and off-Base and decrease in other areas over the course of the 2017 dry season. There was no apparent pattern to where significant increases were observed compared to decreases. Further review of seasonal trends in concentrations and contaminant flux will be conducted in the supplementary report, following wet season sampling events.

Off-Base private groundwater bores tested reported concentrations of PFOS+PFHxS above the health based guidance value for drinking water, indicating a complete pathway and potentially elevated risk to users of groundwater between the Base and Katherine River.

Surface Water

Sampling and analysis of surface waters in drains, Tindal Creek and Katherine River within the Investigation Area has identified PFOS concentrations above the adopted screening values for protection of aquatic ecosystems.

Concentrations in several locations in on-Base drains and in Tindal Creek were above the health based screening values for recreational use. It is considered unlikely that human exposure to PFOS



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via drinking water or recreational use of water from on-Base drains or the on-Base portion of Tindal Creek are being realised. Recreational use of some off-Base sections of Tindal Creek is likely to occur, particularly through Uralla and where Tindal Creek discharges to Katherine River.

Concentrations of PFOS+PFHxS in Katherine River down-stream of the Stuart Highway Bridge were reported in several locations above the health based screening value for drinking water. This indicates that potable use of water from Katherine River (down-stream of the Stuart Highway) represents a potential elevated risk to human health.

The concentrations of PFAS within Katherine River generally increased from the end of the wet season until the early part of the dry season, and then remained relatively stable throughout the remainder of the dry season. Katherine River is primarily fed by springs from the Tindall Limestone aquifer in the vicinity of Katherine. PFAS concentrations in Katherine River are expected to decrease over the course of the wet season due to dilution from rainwater runoff.

At the time of reporting, this investigation had been limited to sampling at the end of the wet season and through the dry season, which limited the number of available sampling sites in Tindal Creek and in on-Base drains. Tindal Creek and open on-Base drains are ephemeral and therefore temporal trends have not been assessed.

Ongoing monitoring of surface waters in the on-Base drainage network, Tindal Creek and Katherine River will take place until the end of the wet season and will be reported in the supplementary report.

Sediment

PFAS impacts in sediments were largely consistent with locations that reported elevated PFAS in surface water. The measured PFAS concentrations in sediments in Tindal Creek and Katherine River were below health based screening values relevant to direct contact, but above the sensitive ecosystem screening criteria in several locations.

PFAS in sediments present in on-Base infrastructure were reported above human health screening criteria.

The leachability of PFAS within sediments was evaluated and although the relationship between total and leachable concentrations was not consistent, the results confirmed that impacted sediments are likely to act as a contributing source of PFAS contamination to surface water and groundwater.

Biota

Biota sampling has been undertaken during the DSI, including sampling of freshwater fin-fish and crustaceans, and home-grown produce, including eggs, fruits and vegetables. Further aquatic and terrestrial flora and fauna sampling is being conducted to inform the human health and ecological risk assessments.

The results of the biota sampling carried out to date are discussed in the Interim Human Health Risk Assessment (Coffey, 2017). Further biota sampling will be carried out and reported in the Comprehensive Human Health Risk Assessment and Ecological Risk Assessment (to be provided mid-2018).

10.3. Refined Conceptual Site Model

Based on the information gathered over the course of the DSI, the key sources, pathways and receptors for PFAS contamination are summarised in the following sections.



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Sources

A number of known and potential sources of PFAS contamination were identified during the investigation and included areas where fire training occurred, the fire station, fuel farms (which had fire-suppressions systems) and vehicle storage and maintenance areas. These key areas of environmental concern were investigated in more detail to further characterise the magnitude of PFAS within soil, sediment and groundwater at these locations.

Primary source areas of environmental concern that contained significant concentrations of PFAS included:

Fire Training Area.

Fire Station.

Other areas of environmental concern also contained PFAS concentrations within soil, sediment and groundwater, however the concentrations measured and distributions indicate lesser contributions to surface water or groundwater impact leaving the Base or potentially impacting human or ecological receptors. These included:

Fuel Farm 1.


Fuel Farm 2.

Secondary source areas, where PFAS impacts from primary source areas have migrated to, creating a residual source of PFAS contamination, include the following:

Sediments in open Base drains and Tindal Creek.

Sediments and waters in Base infrastructure in source areas (pits, drains and sewerage).

Based on the outcomes of this DSI, additional source areas identified in the preliminary CSM, including Katherine Airport, former informal Fire Training Area and the Hornet burial site in the east of the Base, are unlikely to be acting as source of PFAS contamination.

Pathways

The confirmed pathways for migration of PFAS which exist within the Investigation Area are consistent with those described in the preliminary CSM in Section 3.4. These pathways include the following.

Vertical migration of PFAS through soil to the groundwater system.

Lateral migration of PFAS in groundwater towards Uralla, Katherine and the Katherine River. Pumping from large production bores, such as those present at the Research Farm and the PWC facility, is likely to influence the groundwater flow direction and may be drawing the plume in groundwater further north than anticipated based on natural groundwater flow regimes.

Leaching of PFAS from on-Base soils or sediments into groundwater or surface water.

Surface water runoff of PFAS to on-Base drains, depressions, open pits and Tindal Creek.

Migration of PFAS in surface water (on-Base drains and Tindal Creek). The inferred surface water flow direction is to the north-west, towards Uralla, and then west and south-west to Katherine and the Katherine River.

Infiltration of PFAS in surface water to soil and groundwater.

Abstraction of groundwater for domestic and stock watering use.



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Migration of PFAS through the site sewage system and potential application of wastewater to land.

Receptors

The receptors identified during the DSI works where plausible pathways are present are:

Users of extracted impacted groundwater.

Ecological receptors including aquatic and terrestrial flora and fauna in and around Tindal Creek and Katherine River.

Users of Tindal Creek and Katherine River (including consumption of aquatic biota).

Site personnel in impacted areas of the Base.

As a result of PFAS impacts exceed the adopted tier 1 human health based screening criteria in specific scenarios, further assessment of potential impacts to the above receptors has been commenced with an Interim HHRA and will be further refined in a subsequent broader human health risk assessment. An ecological risk assessment (ERA) has also been commenced to evaluate the distribution of PFAS through the food web and identify ecological groups at risk. Where levels of uncertainty exist, these will be further investigated by additional testing to better characterise the nature and extent of PFAS impacts, and will be combined with the data from this DSI report to inform the HHRA and the ERA.

A summary of the source-pathway-receptor pollutant linkages identified from this DSI are provided in the table below. A detailed assessment of the potential exposures and risks to human health are described further in the Interim Human Health Risk Assessment and will be further expanded in the broader Human Health Risk Assessment.



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Table 10.1: Summary of conceptual site model pollutant linkages

Sources Pathways Receptors

Primary source areas:

Fire Training Area

Fire Station

Vertical migration of PFAS in shallow soils around source areas into groundwater

Migration of PFAS in groundwater through the Tindall Limestone aquifer, flowing to the west-north-west, towards Katherine River

Transfer of PFAS between groundwater and surface water via sinkholes and shallow groundwater (during the wet season).

Discharge of PFAS in groundwater into Katherine River through springs

Migration of PFAS down-stream in Katherine River

Extraction of groundwater from the Tindall Limestone aquifer via groundwater bores for potable (drinking water) and non-potable (irrigation and recreational) uses

Human Health:

Drinking PFAS impacted bore water

Ingestion of PFAS impacted bore water used to fill swimming pools

Ingestion of home-grown produce irrigated using PFAS impacted bore water

Users (including consumption of aquatic biota) Tindal of Creek and Katherine River.

Site personnel in impacted areas across the Base.

Ecological:

Uptake of PFAS by plants and animals connected to Tindal Creek and Katherine River

Additional minor source areas:

Fuel Farm 1 and Fuel Farm 2


Secondary source areas:

Sediments in open Base drains and Tindal Creek

Sediments and waters in Base closed drainage infrastructure (pits, drains and sewerage)

PFAS impacts in sediments mobilised through influx of surface water runoff in the wet season. PFAS migration through the on-Base drainage network into Tindal Creek

Migration of PFAS in surface water along Tindal Creek, into Katherine River



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11. Further Work

Several areas of uncertainty and data gaps were noted during the course of the DSI works. The following table describe these areas of uncertainty for each environmental media and proposed further works to provide additional information. These ongoing DSI works will be reported in the supplementary DSI report (scheduled for mid-2018).

Table 11.1: Proposed additional DSI works

Environmental media

Data gap / area of uncertainty Further works

Groundwater

Temporal and seasonal trends of PFAS concentrations in groundwater have not been characterised over the wet season.

Quarterly surface water and groundwater sampling at selected locations through the 2017/2018 wet season.

Ongoing sampling of private residential bores to further inform the DSI as well as the Comprehensive HHRA.

Temporal and seasonal trends of groundwater elevation and flow rate have not been characterised over the wet season.

Gauging of depth to water during quarterly groundwater monitoring events.

Collection of data from groundwater loggers installed across the Investigation Area (including three telemetered units).

Several previously existing wells across the Base that were proposed to be sampled were found to be damaged during DSI works and samples could not be collected from them.

Repair/replace and sample damaged monitoring wells, where practicable.

The vertical extent of PFAS in groundwater has not been characterised off-Base.

Installation of new (or seek access to existing) deep bores in Uralla and Katherine. Collection of additional groundwater samples from these bores.

Surface water

Temporal and seasonal trends of PFAS concentrations in surface water have not been characterised over the wet season.

Quarterly surface water and sampling at existing locations in on-Base drainage channels, Tindal Creek and Katherine River through the 2017/2018 wet season.

The first flush of surface water through Tindal Creek after heavy rain events at the start of the wet season may contain higher concentrations of PFAS than the remainder of the wet season.

Installation of auto-samplers in Tindal Creek to collect regular surface water samples over a 24 to 72 hour period after a high rainfall event at the start of the wet season. At least two auto-sampling events will be carried out over the wet season at two locations.

PFAS impacts in Katherine River have not been delineated down-stream.

Collection of additional down-stream surface water samples from Katherine River and the lower Daly River.

Soil Potential for PFAS impacts to be present in soils in the IA in areas where

Collection of shallow soil samples at school sports grounds within the IA. This will also provide an



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Environmental media

Data gap / area of uncertainty Further works

bore water is used for irrigation of sports grounds (such as in schools).

indication of whether anecdotal evidence of recreational use of AFFF has occurred at schools.

Sediment

PFAS has been identified in sediments within the Base drainage infrastructure (pits and drains). Further inspections and sampling of sediments is required to refine a future remediation approach.

Additional inspections of stormwater drains and pits across the Base to define the management requirements.



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12. Limitations

This report must be read in the context of the limitations and qualifications described in “Important information about your Coffey environmental report”, which is attached as Appendix Q.



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