Sportsmans Creek Review of Environmental Factors Appendix b

Appendix B Geotechnical Investigation Report

24 March 2014

SPORTSMANS CREEK NEW BRIDGE

GEOTECHNICAL INVESTIGATION REPORT

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Report Number. 137622029-005-R-Rev1 Distribution:1 Copy - Kellogg Brown & Root Pty Ltd 1 Copy - Golder Associates

Submitted to:dam Gaffney ellogg Brown & Root Pty Ltd 01 Kent Street SW 2000

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RTSMANS CREEK NEW BRIDGE GEOTECHNICAL STIGATION REPORT

24 March 2014 Report No. 137622029-005-R-Rev1 i

Table of Contents

1.0 INTRODUCTION ........................................................................................................................................................ 3

1.1 Terms of Reference and Objectives ............................................................................................................. 3

1.2 Project Background ...................................................................................................................................... 3

1.3 Previous Investigations and Reports ............................................................................................................ 3

2.0 OBJECTIVE AND SCOPE OF SITE INVESTIGATIONS........................................................................................... 4

3.0 REGIONAL GEOLOGY AND HYDROGEOLOGY .................................................................................................... 4

3.1 Rock and Soil Geology ................................................................................................................................. 4

3.1.1 Topography ............................................................................................................................................. 4

3.1.2 Groundwater and Hydrology ................................................................................................................... 4

3.1.3 Climatic Conditions ................................................................................................................................. 4

4.0 GEOTECHNICAL FIELD INVESTIGATIONS ............................................................................................................ 6

4.1 Scope of Work .............................................................................................................................................. 6

4.2 Boreholes ..................................................................................................................................................... 6

4.3 Test Pits ........................................................................................................................................................ 7

4.4 Cone Penetration (CPT) Testing .................................................................................................................. 7

4.4.1 Piezocone Tests ..................................................................................................................................... 7

4.4.2 Dissipation Tests ..................................................................................................................................... 7

4.4.3 Vane Shear Tests ................................................................................................................................... 8

4.5 Seismic Profiling ........................................................................................................................................... 8

4.6 Laboratory Testing ........................................................................................................................................ 8

4.6.1 Geotechnical Laboratory Testing ............................................................................................................ 8

4.6.2 Contamination and Acid Sulfate Soils Testing ........................................................................................ 9

5.0 RESULTS OF INVESTIGATIONS ........................................................................................................................... 10

5.1 Previous Investigations ............................................................................................................................... 10

5.2 2013 Golder Investigation ........................................................................................................................... 10

5.3 Geotechnical Units ...................................................................................................................................... 11

5.3.1 Seismic Profiling ................................................................................................................................... 11

5.4 Undrained Shear Strength .......................................................................................................................... 12

5.5 Soil Compressibility .................................................................................................................................... 13

5.6 Soil Plasticity .............................................................................................................................................. 14

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5.7 Subgrade Strength California Bearing Ratio ............................................................................................ 15

5.8 Results of Contamination Testing ............................................................................................................... 17

5.9 Results of Acid Sulfate Soils Testing .......................................................................................................... 18

5.9.1 Groundwater Observations ................................................................................................................... 19

6.0 DISCUSSION & RECOMMENDATIONS ................................................................................................................. 20

6.1 Embankment Concept Design .................................................................................................................... 20

6.1.1 Roads and Maritime Embankment Design Criteria ............................................................................... 20

6.2 Geotechnical Design Parameters ............................................................................................................... 22

6.2.1 Embankment Settlement (no ground treatment) ................................................................................... 22

6.2.2 Ground Treatment Options ................................................................................................................... 23

6.3 Bridge Foundation Options ......................................................................................................................... 25

6.3.1 Pile Foundation Options ........................................................................................................................ 25

6.3.2 Pile Design Parameters ........................................................................................................................ 27

6.4 Pavements .................................................................................................................................................. 28

6.5 Durability and Aggressivity ......................................................................................................................... 29

6.6 Potentially Contaminated Soils ................................................................................................................... 29

6.6.1 Discussion of Results ............................................................................................................................ 29

6.6.2 Management of Potentially Contaminated Soils .................................................................................... 30

6.7 Acid Sulfate Soils ........................................................................................................................................ 30

7.0 ADDITIONAL CONSTRUCTION CONSIDERATIONS ............................................................................................ 30

7.1 Existing Filling ............................................................................................................................................. 30

7.2 Salinity ........................................................................................................................................................ 31

7.3 Earthquake Rating ...................................................................................................................................... 31

7.4 Groundwater Management ......................................................................................................................... 31

7.5 Temporary Works ....................................................................................................................................... 31

8.0 RECOMMENDED INVESTIGATION FOR DETAILED DESIGN ............................................................................. 32

TABLES Table 1: Scope of Geotechnical Laboratory Testing ........................................................................................................... 9

Table 2: Scope of Contamination Laboratory Testing ......................................................................................................... 9

Table 3: Sportsmans Creek - Geotechnical Units ............................................................................................................. 11

Table 4: Summary geological conditions inferred from Seismic Profile ............................................................................. 12

Table 5: Laboratory CBR Results for Unit 1 South Bank ................................................................................................ 15

Table 6: Laboratory CBR Results for Unit 1 North Bank ................................................................................................ 16

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Table 7: Results of Field pH and Field Peroxide Testing .................................................................................................. 18

Table 8: Results of SPOCAS / CRS Testing ..................................................................................................................... 18

Table 9: Geotechnical Design Parameters Strength ...................................................................................................... 22

Table 10: Geotechnical Design Parameters Compressibility .......................................................................................... 22

Table 12: Predicted Settlement of Southern Embankment 1.5m surcharge and wick drains ......................................... 24

Table 13: Predicted Settlement of Southern Embankment 3m surcharge and wick drains ............................................ 24

Table 14: Alternative Pile Solutions ................................................................................................................................... 25

Table 15: Recommended Geotechnical Design Parameters for Bored Piles .................................................................... 28

FIGURES Figure 1: Site Locality Plan (attached)

Figure 2: Site Investigation Location Plan (attached)

Figure 3: Subsurface Section (attached)

Figure 4 : Lawrence Rainfall Data (www.bom.gov.au) ........................................................................................................ 5

Figure 5 : Maclean Annual Rainfall Data ............................................................................................................................. 5

Figure 6: Shear Strength Profile of Unit 1 materials .......................................................................................................... 13

Figure 7: Compressibility Parameters for Unit 1 Materials ................................................................................................ 14

Figure 8: Plasticity Index of Laboratory Samples .............................................................................................................. 15

Figure 9 : DCP to CBR Correlation - South Bank of Sportsmans Creek ........................................................................... 16

Figure 10 : DCP to CBR Correlation - North Bank of Sportsmans Creek .......................................................................... 17

Figure 11 : Adopted Soft Soil Treatment Zones ................................................................................................................ 21

APPENDICES APPENDIX ABorehole Log, Core Photography and Explanatory Notes

APPENDIX BTest Pit Logs, DCP Results and Explanatory Notes

APPENDIX CCPT, Vane Shear and Dissipation Test Results

APPENDIX DSeismic Refraction Investigation Report

APPENDIX EGeotechnical Laboratory Test Certificates and Summary Table

APPENDIX FContamination and Acid Sulfate Laboratory Test Results and Summary Tables

APPENDIX GRelevant Extracts from Previous Investigations and Reports

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ANS CREEK NEW BRIDGE GEOTECHNICAL ATION REPORT

24 March 2014 Report No. 137622029-005-R-Rev1 1

EXECUTIVE SUMMARY Roads and Maritime Services (Roads and Maritime) is planning to replace the existing Sportsmans Creek bridge by the end of 2015. Studies in mid-2013 led by Kellogg Brown & Root (KBR) identified a preferred option for the replacement bridge and road approaches. Golder Associates (Golder) carried out geotechnical studies to assess alternative alignment options and in late 2013 carried out geotechnical investigations focused on the preferred option. The study area is typical of low lying floodplain environments in the coastal areas of northern New South Wales.

To the north of the creek, the alignment of the road approaches is underlain by low strength alluvial soils to about 5 m depth, over weathered rock. Beneath the creek the rock surface slopes to the south, so that the depth to rock under the proposed position of the southern bridge abutment is about 30 m. The soils on the south side of the creek are low strength alluvial deposits, comprising mainly soft to firm normally to slightly overconsolidated clay, with loose sands at about 5 to 9 m depth. The soils are desiccated and firm to stiff in an up to 1 m thick layer at the surface. The alluvial deposits are potential acid sulfate soils with a high potential for releasing acid into the environment if they are disturbed.

The rock observed in cores taken from boreholes was sandstone and siltstone, slightly weathered and of medium to high strength. Noticeable was the abrupt transition from alluvial soils to competent rock and the absence of a transitionary residual soil layer or deep weathering profile in the rock.

Groundwater is present below about 2 m depth, corresponding to the water level in Sportsmans Creek and the nearby Clarence River.

Given the significant thickness of low strength soils, the proposed new bridge will need to be supported on piles extending to rock. On the northern side, where the depth to rock is about 5 m, bored piles installed using casing are an option that could be considered. The piles would need to be drilled into rock to form a socket deep enough to resist lateral and axial loads. Other pile types, such as precast driven piles may also be feasible, but may not provide adequate lateral load carrying capacity if they are unable to penetrate far enough into rock.

On the southern abutment, and for piers within the river channel, driven open steel tubes are an option. Steel tubes can be driven to significant depths through the water laden alluvial sediments from a barge. Other pile types, such as precast piles and bored piles, whilst feasible, may be more challenging to install from a floating platform.

The construction of approach embankments to the new bridge could involve the placement of up to 5 m of new fill above the existing ground surface. The placement of fill will induce settlements in the low strength alluvial deposits. Some of this settlement will occur during construction and could be about 600 to 2200 mm for a 5 m high embankment, depending on the construction duration and adopted ground treatment. However, significant settlement comprising ongoing primary consolidation and creep (secondary consolidation) will occur after construction is completed. This ongoing settlement has the potential to damage the pavement.

A typical ground treatment option aimed at reducing the amount of post-construction settlement is preloading and surcharging with the installation of wick drains to accelerate the rate of primary consolidation. A surcharge is an additional height of fill placed above the proposed finished pavement level. Our calculations indicate that even after preloading (with a 3 m high surcharge and wick drains) for a period of 6 to 12 months, the post-construction settlement would be of the order 500 mm over the next 20 years and the design settlement criteria stipulated by Roads and Maritime would not be achieved. A 5 m high embankment could be built without the need for treatment; however application of an additional surcharge would require the use of staged construction, geogrid or stability berms. The impact of the ongoing settlement on the pavement performance would need to be managed by periodically topping up the road level.

The impact of flood events on the on the feasibility of this ground treatment option should also be considered.



An alternative approach to ground treatment would be piled embankment approaches. A piled embankment could be designed to meet the settlement criteria, with the aim of limiting ongoing pavement maintenance. A piled embankment also avoids the need for additional quantities of fill that would be brought to site for surcharging. The feasibility of piled embankments will need to be addressed at the design development stage.

The new at-grade road approaches should be designed using a California Bearing Ratio (CBR) of 4%. Roads constructed on new engineered fill in accordance with Roads and Maritime Specification R44 can be designed using a CBR of 12%, provided the CBR of the fill is verified during construction.

Other issues that will need to be considered include:

Sources and availability of fill for embankment construction as fill will need to be imported;

Managing the potential disturbance of acid sulfate soils during construction activities;

Managing construction during wet weather when trafficability across the low-lying alluvial floodplains is likely to be poor; and

The design and construction of temporary works, such as working platforms for piling, which could extend into the river and may be prone to flood events during the construction period.



1.0 INTRODUCTION 1.1 Terms of Reference and Objectives Golder Associates Pty Ltd (Golder) was appointed by Kellogg Brown & Root Pty Ltd (KBR) to provide geotechnical services for the Sportsmans Creek new bridge project. This bridge project is part of the state-wide Bridges for the Bush Program that involves the replacement of selected timber road bridges around NSW. KBR has been appointed by NSW Roads and Maritime Services (Roads and Maritime) to carry out concept option assessment for the Sportsmans Creek new bridge project. The project also includes the demolition of the existing timber bridge at Sportsmans Creek. The NSW Government has undertaken to construct the new bridge by 2015.

Services to be provided by Golder are set out in our proposal (Ref. P37622022_001_P_Rev0, dated 20 February 2013) and variation document 137622029-004-L-Rev1, which outlines the change in investigationmethodology after completion of the desktop study. This report presents the results of a geotechnical investigation focused along the preferred alignment option of the new bridge including approach roads.

The proposed new bridge and approach roads are on the southern outskirts of Lawrence in northern New South Wales (shown in Figure 1, attached to this report).

a

1.2 Project Background The Sportsmans Creek new bridge project involves the design and construction of the new bridge (and road approaches) over Sportsmans Creek, and the demolition of the existing timber dare truss bridge. KBR developed alternative route options, from which a preferred option has been chosen.

A Concept Design Team workshop was held on 25th and 26th June 2013, involving representatives from KBR, Roads and Maritime, and appointed sub-consultants. At the workshop a preliminary evaluation of study area constraints was carried out and the initial assessment of 6 potential routes was undertaken. As part of the development of the route options Golder carried out a desktop study to assess geotechnical and environmental constraints and opportunities. The results of the desk study were presented in Golder Associates report (137622029_001_R_Rev2) Geotechnical and Environmental Desktop Study, Sportsmans Creek new bridge, 4 September 2013.

During December 2013, Golder undertook geotechnical investigations along the preferred alignment. The investigation consisted of borehole drilling, excavation of test pits, Cone Penetrometer Tests (CPTs), a seismic refraction profile across the creek bed and laboratory testing. This report presents the results of the geotechnical investigations completed by Golder and provides geotechnical input for the design development of the new bridge and approaches.

1.3 Previous Investigations and Reports Several documents and relevant previous reports were provided to Golder by KBR and Roads and Maritime for review as part of this project. Reports of specific relevance to this project included:

Coffey Geosciences Report (NR1103/1-P) on Geotechnical Investigations, Proposed New Bridge across Sportsmans Creek, 5 July 2002.

Maclean Shire Council/ RTA, Environmental Impact Statement, Demolition of existing bridge and construction of new bridge over Sportsmans Creek, Lawrence, May 2002.

RTA, Pavement Investigation Report Sportsmans Creek Bridge and Temporary Ferry Loading Areas, March 2004, Report H/42330-B

The preferred option (Option 2), differs to the alignment investigated in 2002, previously referred to as the Grafton Street alignment. The main difference between the preferred option and the previous Grafton Street alignment is the position and orientation of the southern approach to Sportsmans Creek. The position of the southern abutment of the current alignment is approximately 50m to the west of the previously investigated option.



2.0 OBJECTIVE AND SCOPE OF SITE INVESTIGATIONS The objective of the geotechnical investigations and laboratory testing was to provide information for use by Roads and Maritime and KBR during the design and development of the new bridge. This information will also enable construction tenderers to make an assessment of the impacts and implications of the geological, geotechnical, hydrogeological characteristics, potentially contaminated soils and Acid Sulfate Soils that may be disturbed during construction of the new bridge and approach embankments.

3.0 REGIONAL GEOLOGY AND HYDROGEOLOGY 3.1 Rock and Soil Geology The 1:250 000 scale NSW Department of Mineral Resources 1970 Geological Map Maclean (series sheet SH56-7) indicates that the study area is underlain, at depth, by geological rock units of the Bundamba Group. The majority of the area is underlain by rocks belonging to the Late Jurassic Grafton Formation, consisting of interbedded sandstone, clayey siltstone, claystone, and minor coal seams. Bedding is thin to thick, and commonly with a ferruginous lateritic weathering profile.

The 1:100,000 Grafton Area Coastal Quaternary Geology Map indicates that the rock units in the majority of the Lawrence area are overlain by Holocene Alluvial Deposits, which include levee and floodplain deposits of sands, silts, clays, organic mud, and minor gravels. There is also potential for Pleistocene Beach sand deposits under the alluvial deposits, which may be indurated (cemented).

There is a small area of in-channel bar deposits near the mouth of Sportsmans Creek, consisting of fluvial sand, gravel, silt and clay. There is also indication of alluvial paleochannel (buried / in-filled river channel) and inter-levee swale deposits in the vicinity of the study area, consisting of organic mud, peat, clay, silt, and fluvial sands. The Quaternary geology of the study area is presented on Figure 2, attached to this report.

3.1.1 Topography The topography within the study area is characterised by typically low elevation flood plain terrain associated with the Clarence River and Sportsmans Creek systems. The typical site elevation within the study area south of Sportsmans Creek ranges between RL 3 m to RL 5 m AHD. Elevations north of Sportsmans Creek within the study area vary laterally and range from RL 1 m to RL 5 m AHD.

3.1.2 Groundwater and Hydrology The dominant surface water feature is east-west running Sportsmans Creek, which connects to the Clarence River, within the study area. Sportsmans Creek is about 100 m in width and drains in a south-east direction under the existing bridge toward the Clarence River. Under low flow conditions, Sportsmans Creek may experience an afflux of water from the Clarence River, where water from the Clarence River flows upstream into Sportsmans Creek. There is a weir installed upstream in Sportsmans Creek, to prevent incursion of saltwater into the wetlands.1

The inferred direction of surface and ground water flow is to the east along the surface, constrained by the natural flood levies along the banks of Sportsmans Creek and through the sandy alluvium layers (charged by flow from land at higher elevations north and east of the study area).

Wet ground conditions are likely to occur behind the natural flood levies for Sportsmans Creek.

3.1.3 Climatic Conditions The geotechnical investigations (Golder 2013, Coffey 2002) and pavement investigations (RTA 2004) have been conducted during different seasonal climatic conditions. Variation in climatic conditions (particularly rainfall) will have an influence on the conditions encountered at the time of the investigations.

Historical rainfall records for the Lawrence Post Office, Bureau of Meteorology (BoM) Station Reference 058 033 and Brushgrove (Clarence Street), BoM Station Reference 580 006 were obtained from the Bureau 1 M. Tulau 1999, http://test.dnr.nsw.gov.au/care/soil/as_soils/pdfs/ass_clarence.pdf



of Meteorology website (www.bom.gov.au). Average monthly rainfall for the Lawrence station is summarised in Figure 4. Due to several data gaps in the Lawrence data, Brushgrove (10 km South of Lawrence) rainfall data has been summarised in Figure 5 to show the annual rainfall for the region over the past century. The historical mean annual rainfall for the Lawrence area is 1070 mm per year (recorded at the Lawrence Post Office), which is below the average annual rainfall limits for Roads and Maritime Climatic Zone 7, which covers the NSW North Coast and South West Rocks.

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Figure 4 : Lawrence Rainfall Data (www.bom.gov.au)

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Figure 5 : Maclean Annual Rainfall Data

The historical rainfall records indicate that:



The current investigations (Golder 2013) were carried out during drier than average December climatic conditions, with only 24 mm recorded in Dec. 2013, however 310 mm of rainfall was recorded in Nov. 2013, well in excess of the historical monthly average;

The investigations by Coffey in 2001/2002 were preceded by an extended period of several years of lower annual rainfall, with the investigations being undertaken in August, a generally dry month; and

The pavement investigations by RTA in 2004 were carried out during March and the wetter part of the annual cycle, however the annual rainfall was close to the average.

4.0 GEOTECHNICAL FIELD INVESTIGATIONS 4.1 Scope of Work The scope of the 2013 investigation was previously outlined in Section 2 of this report and consisted of:

1 borehole which was drilled using a truck mounted drilling rig;

4 test pits excavated using an excavator;

Dynamic Cone Penetrometer testing was undertaken adjacent to test pit excavations to assess in-situ material consistency and/or density;

2 Cone Penetration Tests (CPT), including in-situ dissipation and vane shear testing, using a truck mounted rig;

105 m length of overwater seismic profiling;

Coordinate survey, by registered NSW surveyors, of completed investigation locations;

Geotechnical and environmental laboratory testing of recovered samples from the borehole and test pits to determine design parameters, potential for contamination and prevalence of potential acid sulfate soils (PASS).

The location of the completed geotechnical investigations, the concept alignment and previous investigation locations that are relevant to the new bridge alignment are shown on Figure 1, attached to this report.

4.2 Boreholes Borehole BH101 was drilled using a truck mounted drilling rig, supplied by North Coast Drilling Pty Ltd. The technical objective of this borehole was to assess the nature and thickness of alluvial soils present and to determine the bedrock level on the southern bank at the approximate location of the southern abutment. The target depth of the borehole was governed by the requirement to obtain and recover a minimum of 6 m of medium strength (or better) rock.

This hole was drilled vertically (90 from horizontal). Drilling through soils was carried out using auger and rotary drilling techniques. Standard Penetration Tests (SPTs) were conducted at nominal 1.5 m intervals in non-cohesive soils or undisturbed U50 (50 mm diameter) tube samples were obtained in soft and firm alluvium soils.

On completion of the borehole, the hole was grouted to the ground surface.

The borehole drilling was carried out under the full time supervision of an experienced geotechnical engineer from Golder Associates, who instructed the drillers on in-situ testing and sampling requirements, described and logged the soil and rock encountered. Rock core obtained during the drilling was logged, boxed and photographed on site. Point Load Index (Is50) strength tests were also conducted with the results of point load strength tests included on the borehole log.

The borehole log, including results of point load index strength tests, core photography and explanatory notes is presented in Appendix A.



No additional drilling was carried out on the northern abutment as the current position of the northern abutment is similar to the previously investigation Grafton Street alignment which was previously investigated by Coffey (2001/2002) which included cored borehole information that would be suitable for the purposes of this investigation and report.

4.3 Test Pits Test Pits were excavated using a 7 t tracked excavator supplied by Shipman Construction Pty Ltd to obtain information on sub grade conditions along the alignment, to refine knowledge on the boundaries between local, near surface geological units, and to obtain bulk samples for earthworks testing. Three of the pits (TP101, TP102 and TP103) were excavated to depths of up to 3.0 m, or prior collapse of the test pit sidewalls. TP104 was only excavated to a depth of 0.8 m due to the presence of a redundant buried service at this location.

The test pits were excavated under the full time supervision of a geotechnical engineer from Golder Associates, who logged the soils encountered, photographed the completed test pit and carried out in-situ testing.

All the pits were backfilled with the excavated material, with the backfill material compacted using the bucket of the machine. Completed Test Pits were mounded to allow for some settlement of the backfill material.

Dynamic Cone Penetration (DCP) tests were conducted adjacent to the Test Pits for the purposes of assessing the in-situ density or consistency of material. DCPs were conducted from the ground surface, adjacent to each test pit to depths of up to 1.5 m or prior practical refusal.

The test pit logs, including test pit photography and results of DCP testing and explanatory notes are presented in Appendix B.

4.4 Cone Penetration (CPT) Testing 4.4.1 Piezocone Tests Two CPTs on the southern bank of Sportsmans Creek were carried out by NewSyd Geotechnical Testing, using a truck mounted CPT rig.

The cone was pushed into the ground at a rate of about 2 cm/sec. During the test the following parameters were recorded:

Cone tip resistance, qc;

Sleeve friction;

Pore pressure;

Cone inclination; and

Rate of penetration. The data was transmitted electronically to a logger and computer aboard the rig, allowing real-time observation of data plots, which are presented in Appendix C. These plots are uncorrected for the effects of the cross sectional area behind the cone tip. The plots include the parameter, Friction Ratio, which is the ratio of the sleeve to cone tip resistance. This is a useful parameter for aiding interpretation of soil types. In general, a low friction ratio indicates a coarse grained soil (sands, gravel) whereas relatively high friction ratios are indicative of fine-grained soils (clays and silts). This generalisation becomes less reliable at very low cone resistance values.

4.4.2 Dissipation Tests Two pore pressure dissipation tests were completed during the CPT testing at depths of 11.0 m and 14.5 m in CPT-1. Generally these tests were targeted in soils in which excess pore pressures were generated



during cone testing. The objective of the tests was to assess the rate of dissipation of the excess pore pressures generated by pushing the cone. This is useful for assessing the soil type, behaviour and rate of consolidation of the compressible layers. The results of the dissipation tests are plotted graphically in Appendix C.

4.4.3 Vane Shear Tests Vane shear testing is an established method of assessing the in-situ undrained peak and residual shear strengths of cohesive soils. Vane shear tests were carried out in cohesive soils because other types of in-situ tests (such as SPT tests) involve significant amounts of sample disturbance and reliance on generalised correlations.

Six Vane shear tests were undertaken using computer controlled vane shear testing apparatus from the CPT rig using the procedure described in AS 1289.6.2.1 (1997). Summary plots of the Vane Shear Results are provided in Appendix C. The vane shear tests were

4.5 Seismic Profiling Seismic refraction profiling was carried out along th

carried out in a new hole proximal to CPT101.

e overwater section of the alignment of the new bridge and approaches. A single refraction line of approximately 105m in length was carried out from the northern bank at Grafton Street to the southern bank, to the west of the boatramp. The start and end points of the refraction line were selected to correspond to the anticipated positions of the northern and southern bridge abutments. The seismic refraction profiling was undertaken by Earth Technology Solutions Pty Ltd.

The objective of carrying out seismic refraction profiling across Sportsmans Creek was to determine the bedrock profile across the creek, noting that results from previous investigations (Coffey 2001/2002) indicated significant variability in the bedrock topography. The seismic refraction profiling was selected to provide a continuous profile along the new bridge alignment.

The interpretation of seismic velocities of the insitu soils and underlying bedrock provide an efficient and continuous profile of rock head levels across the creek in advance of detailed investigations involving overwater borehole drilling.

A separate refraction report and interpreted geological long section are available in Appendix D and have been included in the inferred geological model.

4.6.1 Geotechnical Laboratory Testing A p

4.6 Laboratory Testing

rogramme of geotechnical laboratory testing was carried out by SGS Australia Pty Ltd, on samplobtained during the investigations from boreholes and test pits to classify and assess the engineerincharacteristics of the soil and rock samples collected. The scope of laboratory testing carried out is presented in Table 1.

Summary tables of test results and laboratory test certificates are included in Appendix E.

es g



Table 1: Scope of Geotechnical Laboratory Testing

Laboratory Test Number of Tests Results Standard or

Procedure

Soil index and behavior RMS T108 Atterberg Limits (PL, LL, plus linear shrinkage) 4 AS 1289.3.1.2,

3.2.1, 3.3.1, 3.4.1 Soil index and behavior RMS T107 and

Particle Size Distribution with Hydrometer 5 T190 AS1289.3.6.1/3

Moisture Content 8 Soil index and behavior RMS T120 AS 1289.2.1.1

Consolidation Tests 4 Settlement parameters AS 1289.6.6.1-1998 Consolidated Un-drained Triaxial with pore water measurements 1

Soil strength parameters

AS 1289.6.4.2

Standard Compaction and CBR 10 day soak (100% SMDD) 4.5kg surcharge. (RMS T111) 3

Pavement design parameters

RMS T111

Unconsolidated Undrained Triaxial 1 Undrained shear strength AS 1289.6.1.1-

1998

4.6.2 Contamination and Acid Sulfate Soils Testing Contamination Testing A limited suite of contamination sampling and laboratory testing was undertaken. Laboratory testing was undertaken at Envirolab Laboratories, a NATA accredited analytical laboratory in Sydney. Samples were collected using standard Quality Assurance/ Quality Control protocols for collection, preservation and transportation of environmental samples. The scope of contamination testing undertaken is presented in Table 2.

Table 2: Scope of Contamination Laboratory Testing Contaminant / Analyte Number of Tests Aggressivity- (Ph Cl SO4 EC) 3

8x metals, TRH, BTEX, PAH, OCP/OPP/PCB, Asbestos 5

Acid Sulfate Field pH Test 10

SPOCAS/CRS 6

pH, Cation Exchange Capacity, Clay Content (%) 3 Herbicides (phenoxy acid herbicides, triazine herbicides) 3



Acid Sulfate Soils Testing Soil samples were collected for the purpose of assessing for Potential Acid Sulfate Soils (PASS). A total of ten samples were collected from the borehole and test pits and were tested for field pH (pHF) and field peroxide (pHFOX).

The field pH test method is a qualitative method for assessing the potential for actual and potential acid sulfate soils. The field peroxide test is used to test for the presence of unoxidised sulphides and therefore potential acid sulfate soils.

The results of the field pH and field peroxide tests were used to determine which samples would be tested for Suspension Peroxide Oxidation Combined Acidity and Sulfate (SPOCAS) and Chromium Reducable Sulfur (CRS) tests. The following guidelines were adopted for selecting the most suitable samples for SPOCAS/CRS tests:

A pHFOX < 3

A reduction in pH of at least 1 Unit from pHF to pHFOX

The strength of reaction during oxidation Three samples were scheduled for SPOCAS / CRS testing based on the above criteria.

The results of the contaminant and acid sulfate soils testing are presented in Appendix F and discussed in more detail in Section 6.6 and 6.7.

5.0 RESULTS OF INVESTIGATIONS 5.1 Previous Investigations The previous Coffey investigation focussed on a new bridge following the Grafton Street alignment to the east of the 2013 Golder Investigation of the preferred alignment. The Coffey investigation indicates that on the southern bank of Sportsmans Creek the subsurface soils comprise an upper layer of stiff desiccated clay, overlying soft to firm clays to RL 30 m AHD . Coffey reported that the conditions at the northern approach to Sportsmans Creek consist of stiff to very stiff silty clays, and loose to medium dense clayey silty sand, to a depth of 4 m, underlain by weathered sandstone and minor siltstone. The depth to weathered rock is relatively shallow (4 m depth) at the northern approach to the bridge, and hence falls sharply to the south (34 m depth).

The Coffey investigation also consisted of six test pits, five on the southern bank and one on the northern, which investigated the shallow ground conditions. Two samples, one from each bank, were scheduled for laboratory CBR testing, no DCP results were provided to determine correlations.

In 2004 Roads and Maritime also undertook six test pits in the vicinity of the existing bridge and also to the west along Grafton St and around the boat ramp area on the southern bank. RMS-TP4 and RMS-TP5 on the southern bank and RMS-TP6 on the northern bank were considered as part of the review of the concept alignment. The test pits all encountered silty clays and clays to the depth of investigation which are inferred to be alluvial deposits associated with Sportsmans Creek. Laboratory CBR values from these pits and also DCP to CBR correlations were provided by Roads and Maritime.

Extracts (relevant borehole, test pit logs and laboratory test certificates) are attached in Appendix G.

5.2 2013 Golder Investigation The results of the most recent investigations indicate that on the southern side of Sportsmans Creek the soils above rock head are mainly soft to firm, with little increase in strength with depth as shown in the SPT results and CPT logs. It is inferred that the low shear strength soils have been deposited directly onto medium to high strength rock, with no transition through residual soil or a weathered rock profile. This suggests that scouring of the weathered rock profile occurred prior to placement of the existing soft soils.



The additional borehole (BH101) and CPTs (CPT-1 and CPT-2) to the west of the previous investigation locations (refer to Figure 2) generally encountered similar conditions to those described above and in the previous investigations. Borehole BH101 encountered thin topsoil layer, overlaying a firm desiccated clay layer; beneath this firm layer, the borehole intersected loose sands and interbedded layers of soft to very soft alluvial clays and silts. Rock head was at 32 m below the surface, from which coring commenced to recover 7.32 m of medium to high strength sandstone and siltstone.

The very low strength alluvial conditions at the southern abutment and approach to Sportsmans Creek were confirmed in CPT-101 and CPT-102, which encountered soils with generally low Cone Resistance values (qc < 1 MPa). Both CPTs and BH101 recorded a layer up to 4 m thick off loose sand between ~5 and 9 m below the ground surface.

Test pits TP-102, TP-103 and TP-104 to the north of the proposed bridge location encountered a thin, ~1.5 m, thick layer of soft to firm alluvial clay overlying alluvial sands.

5.3 Geotechnical Units For the purpose of characterisation of the subsurface conditions, the soil and rock types along the preferred route alignment have been generalised into geotechnical units, which are summarised in Table 3. This geotechnical model was developed to provide a geological overview for both soil and rock profiles and to provide engineering characteristics for this material along the alignment. The geotechnical units have been developed based on regional geological and topographical information and findings and characterisation of data from recent and historical site investigations.

Table 3: Sportsmans Creek - Geotechnical Units Unit Approx. Depth Description

(m)1

FILL/ Topsoil 0.0 0.3 Variable Clayey SAND to Silty CLAY Silty to Sandy CLAY, medium to high plasticity, soft to firm

0.3 5.0 along the south bank, soft to stiff on the northern bank 9.0 - 31

(south bank) Slightly overconsolidated to approximately 20 m depth (south Unit 1 Cohesive Alluvium bank), then normally consolidated below this depth. This unit is

0.0 4.0 interbedded with Unit 2 adjacent to the creek banks. (north bank)

The upper 300-1000mm of this unit comprises a desiccated firm to very stiff crust SAND, medium grained, very loose to loose, saturated.

Unit 2 Granular Alluvium 5.0 - 9.0 This unit is interbedded with Unit 1.

Unit 3 Residual Soil 32 - 34 (CPT-1 only) Sandy or Silty CLAY, very stiff to hard

Unit 4 Rock

>30 (southern bank)

>4.0

(northern bank)

Interbedded fine grained SANDSTONE, slightly weathered to fresh, low strength becoming high strength at approximately 1m depth into unit and SILTSTONE, slightly weathered to fresh, low strength

1) Depth below ground surface level

5.3.1 Seismic Profiling Interpretation of the seismic profiling (Appendix D) generally indicated two layers beneath the water channel, summarised in Table 4 and appended to this report.



Table 4: Summary geological conditions inferred from Seismic Profile Seismic Layer Velocity Range (m/s) Interpreted Geological Units

1 1500 1600 Alluvial sediments consistent with very loose to loose sand

(Unit 2), overlying silt and silty sand and very soft to soft clay (Unit 1)

2 2050 2250 Medium to high strength sandstone (Unit 4)

An inferred geological long section along the preferred alignment is attached to this report as Figure 3. The long section includes the recent and historical investigation information and also includes inferred boundaries between the geotechnical units.

5.4 Undrained Shear Strength The undrained shear strength of Unit 1 cohesive alluvium was assessed using the following methods for the purposes of assigning preliminary geotechnical design parameters:

Disturbed sampling and testing methods during borehole drilling, including SPT tests insitu and penetrometer tests on undisturbed tube (U50) samples;

Using results from the CPT tests and adopting standard correlations, including correction factors, for assessing undrained shear strength from cone tip resistance. The relationship between cone tip resistance, overburden stress and shear strength is shown in Figure 6. An Nkt factor of 14 was used;

Insitu vane shear tests;

Laboratory testing comprising unconsolidated undrained triaxial (UU) and consolidated undrained traixial (CU) testing.

A plot of the undrained shear strength of soils, as assessed using the above techniques, at the southern abutment is presented in Figure 6.



Figure 6: Shear Strength Profile of Unit 1 materials

5.5 Soil Compressibility The compressibility of Unit 1 cohesive alluvium was assessed using the following:

Laboratory oedemeter tests;

Correlations to Atterberg Limit laboratory test results;

Dissipation tests carried out during CPT testing.

SPIN

ORTSMANS CREEK NEW BRIDGE GEOTECHNICAL VESTIGATION REPORT


Plots of Unit 1 compressibility parameters are presented in Figure 7.

Figure 7: Compressibility Parameters for Unit 1 Materials

5.6 Soil Plasticity Figure 8 shows the plot of the soils plasticity index from laboratory samples. Results from BH01, BH101, TP101 and TP103 are plotted and generally indicate that the Unit 1 clays are medium to high plasticity. The low to medium plasticity result is from a near surface (0.5 m) sample from TP101 on the southern embankment.



Figure 8: Plasticity Index of Laboratory Samples 5.7 Subgrade Strength California Bearing Ratio The strength of subgrade materials along the approach alignments (southern and northern) has been assessed using laboratory California Bearing Ratio (CBR) tests and insitu Dynamic Cone Penetrometer (DCP) test results. Reference to relevant historical laboratory and field test results has also been made in this assessment (Coffey 2002 and RTA 2004).

Southern Approach A total of three laboratory CBR test results have been reviewed and are considered relevant to the current alignment. All CBR testing was carried out to RTA/RMS standards at the time of testing.

Laboratory results for Unit 1 indicate that in the desiccated crust, down to around 0.5 m, CBR values ranges from 5 to 7 (Table 5), however lower values are expected below this crust based on the correlation of DCP results to CBR (after applying RMS Specification T161 Penetration resistance of a soil) as shown in Figure 9.

Table 5: Laboratory CBR Results for Unit 1 South Bank Test Location Depth Laboratory CBR (at 5.0mm) TP3 0.4 to 0.8 m 7RMS-TP5 0.8 to 1.7 m 5TP101 0.5 to 1.0 m 7

SI

PORTSMANS CREEK NEW BRIDGE GEOTECHNICAL NVESTIGATION REPORT


Figure 9 : DCP to CBR Correlation - South Bank of Sportsmans Creek

0

500

1000

1500

2000

2500

3000

3500

0 2 4 6 8 10 12 14 16 18

Depthbe

lowsu

rface(m

m)

CorrelatedCBRValue

DCPtoCBRCorrelation(RMST161) SouthBank

TP101 RMSTP4 RMSTP5

Northern Approach A total of four laboratory CBR test results have been reviewed and are considered relevant to the current alignment and for Unit 1 on the northern bank of Sportsmans Creek. All CBR testing was carried out to RTA/Roads and Maritime standards at the time of testing.

Reported laboratory CBR results for subgrade materials recovered from Unit 1 ranges from 2 (measured at 2.5 mm) to 7 (Table 6). Estimated CBR values from DCP testing are between 2 and 15 below 2 m (Figure 10). Similar to Unit 1 on the southern bank, the inrange between 2 and 4 below 0.5 m depth.

ferred CBR values, correlated from DCP results, fall into a

Table 6: Laboratory CBR Results for Unit 1 North Bank Test Location Depth Laboratory CBR (at 5.0mm) TP4 0.5 to 0.8 m 7RMS-TP6 0.2 to 0.5 m 2 (2.5 mm)TP102 0.5 to 1.0 m 6TP103 0.5 to 1.0 m 4.5



Figure 10 : DCP to CBR Correlation - North Bank of Sportsmans Creek

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10 12 14 16 18

Depthbe

lowsu

rface(m

m)

CorrelatedCBRValue

DCPtoCBRCorrelation(RMST161) NorthBank

TP103 TP102 RMSTP6 TP104

It should be noted that insitu CBR values derived from DCP testing are dependent on the moisture condition of the soil at the time of testing. Extended periods of dry weather may result in higher CBR values derived from DCP testing compared to values derived during or following periods of wet weather.

5.8 Results of Contamination Testing A Geotechnical and Environmental Desk Study (Golder doc ref. 137622029-001-R-Rev2) was carried out during the options development phase for the project. The environmental assessment component of the desk study comprised of:

Review of selected publicly available historical information, including historical aerial photography.

Regulatory databases and notices, including EPA Registers of Contaminated Sites.

Publicly available hydrological, geological and soils information relevant to the study area. A site walkover was also conducted as part of the study to visually assess for potential contaminants within the study area.

Based on the results of the desk study relevant to the current bridge and approach alignment, a Phase 2 Environmental Investigation was not required. However, a limited suite of contamination testing was undertaken.

The results of laboratory tests undertaken were compared to the following criteria:

Contaminant threshold values for General Solid Waste (GSW) and Restricted Solid Waste (RSW) presented in the Waste Classification Guidelines Part 1: Classifying Waste published by the then Department of Environment, Climate Change and Water (DECCW 2009).

Investigation and screening levels for public open space land use documented in Schedule B1 of the amended National Environment Protection (Assessment of Site Contamination) Measure 1999 (NEPC 2013) (the NEPM) including:

Health Investigation Levels (HILs);



Ecological Investigation Levels (EILs);

Ecological Screening Levels (ESLs) for coarse soils; and

Health Screening Levels (HSLs).

Many of the laboratory results for analytes testing recorded non-detect for the particular analyte. For those analytes that were detected in samples, results were generally below the maximum allowable levels described in the above regulatory guidelines. One sample (identified as 137622029_tp03-004), contained benzo(a)pyrene at a concentration of 0.92 mg/kg, which exceeded the DECCW 2009 threshold value for disposal as GSW of 0.8mg/kg and the NEPC 2013 ESL of 0.7 mg/kg. The exceedance is likely attributable to shallow fill material observed at this location.

Laboratory test certificates and summary tables are presented in Appendix F.

5.9 Results of Acid Sulfate Soils Testing A total of ten samples were collected and tested for field pH and field peroxide units for purposes of assessing for the presence of actual or potential acid sulfate soils. The results of the field pH and field peroxide tests are summarised below. Table 7: Results of Field pH and Field Peroxide Testing Sample IdentificationDepth

/ pHF (field pH test)pHFOX

(field peroxide test)

pH Units (pHF - pHFOX) Reaction Rate

BH101 (0.5m) 5.3 2.9 2.4 High BH101 (2.5-2.9m) 6.3 2.9 3.4 High BH101 (5.5-5.95m) 6.7 2.1 4.6 High BH101 (16.0-16.45m) 7.8 2.3 5.5 ModerateTP101 (0.5m) 5.4 3.3 2.1 High TP102 (0.3m) 5.6 2.9 2.7 High TP102 (0.5m) 5.6 2.7 2.9 High TP103 (0.3m) 5.8 3.0 2.8 High TP103 (0.5m) 5.9 3.0 2.9 High TP104 (0.3m) 6.4 6.3 0.1 Vigorous

Results are highlighted for pHFOX1.0 and Reaction Rate > High. Bold-Italic samples were subsequently tested for SPOCAS/CRS.

Based on the results of field peroxide testing, all samples exhibit some or all of the characteristics of Potential Acid Sulfate Soils (PASS) (ASSMAC 1998).

Three samples were tested for SPOCAS/CRS testing. The results of this supplementary testing are presented below.

Table 8: Results of SPOCAS / CRS Testing Sample Identification / Depth

TPA pH 6.5 (moles H+/t) SPOS (% w/w) CRS (% w/w) a-CRS (% w/w)

Liming Rate (kg CaCO3/t)

BH101 (2.5-2.9m) 260 0.21 0.11 66 14

BH101 (5.5-5.95m) 400 0.78 0.43 270 37

TP102 (0.3m) 90 0.03



Shaded cells indicate exceedance of trigger limits presented in Table 4.4 of the ASSMAC Guidelines (ASSMAC 1998) requiring the need to prepare an acid sulfate soils management plan which would require approval by the consent authority.

5.9.1 Groundwater Observations Groundwater seepage was observed in BH101 (RL 2.43 m AHD) at a depth of 2.0 m, 1.8 m in TP101 (RL 2.86 m AHD), 2.5 m in TP102 (RL 2.54 m AHD) and 2.0 m in TP103 (RL 2.88 m AHD) indicating the local groundwater level was at approximately RL 0 m AHD at the time of the investigations; however there is some local variation on the northern embankment, possibly associated with perched water tables or water charged sand layers, with the local water level expected to fluctuate with tidal changes.



6.0 DISCUSSION & RECOMMENDATIONS The key geotechnical constraints for the new bridge and road approaches are:

the presence of more than 30 m thickness of highly compressible alluvial soils along the alignment on the south side of Sportsmans Creek that may be subject to consolidation under proposed embankment dead and live loads;

significant deepening of the rock head level from north to south along the proposed bridge alignment;

the absence of a weathering profile in the sandstone bedrock and an abrupt transition from low strength soils to relatively high strength rock;

shallow groundwater within 2 to 3 m of the ground surface; and

the potential for wet ground surface conditions. The effects of these features on the proposed new bridge design are discussed in the sections below.

6.1 Embankment Concept Design Embankment fills are required to achieve design levels on the northern and southern bridge approaches. At this preliminary stage, double sided embankments are proposed based on the current concept design and the relative flatness of the approach plains. Embankments heights (above adjacent ground level) are expected to generally be between about 1 m on the flood-plains and 5 m adjacent to the bridge abutments.

Southern Embankment The depth to rock beneath the southern embankment is up to 30 m and is largely overlain by 25 m of very soft to soft, normally consolidated cohesive alluvial sediments. A layer of loose sands 4 to 5 m thick overlies these soft sediments and is overlain by a firm layer of clay close to the ground surface.

The rock contour drops steeply from the northern to southern embankment (inferred from borehole logs, CPT refusal depths and seismic profiling) though the location of the southern extent of the Sportsmans Creek channel is unknown at this stage.

Northern Embankment Medium to high strength sandstone was encountered within 5 m of the surface in Coffey BH04, however was not confirmed in any of the recent test pits excavated in this area. The test pits on the northern side of Sportsmans Creek intersected firm to stiff alluvial clays and loose to medium dense sand layers.

6.1.1 Roads and Maritime Embankment Design Criteria Design and construction of embankments for Roads and Maritime Services (Roads and Maritime) projects are typically guided by project specific Scope of Work and Technical Criteria (SWTC) documents and Roads and Maritime Earthworks Specifications (Roads and Maritime R44). The SWTC documents typically outline the design criteria to which embankment and pavement performance is expected to comply, and Roads and Maritime Specification R44 provides the minimum requirements for earthworks including foundation preparation and fill compaction.

As outlined above the southern embankment is located over soft compressible soils and will require additional measures to manage settlement. Embankment settlements can be considered in two parts, namely construction stage settlements and post-construction settlements (PCS).

Construction stage settlements include the primary consolidation settlements and secondary consolidation (creep) settlements that have occurred up until the end of construction;



Post-construction settlements include remaining primary consolidation and secondary consolidation settlements after the completion of construction.

Embankments have the potential for large total, differential and creep settlements, and are often categorized into three zones reflecting the different behavioural requirements placed on each. A diagram of these zones is Figure 11.

Structural Zone A this is the embankment zone approximately 20 m behind the bridge abutment and includes the 6 m approach zone. Post-construction settlements and differential settlements need to be limited due to the proximity to the rigid abutment structure. The design may also require limiting the lateral displacement induced on abutment piles.

Transition Zone B this is the transition zone between the Structural Zone and the general embankment zone to provide a gradual increase in post-construction settlements. The length of the Transition Zone is expected to be about 50 m.

General embankment Zone C this is the zone beyond the Transition Zone B.

Figure 11 : Adopted Soft Soil Treatment Zones

The design of these embankments and pavements should include a strategy to optimise the pavement types and maintenance strategy with the embankment foundation improvement techniques proposed and the residual settlement predicted.

The settlement criteria selected for the approach embankments will depend on the design traffic speed, safety and other operational considerations, and Roads and Maritime strategy for pavement maintenance and whether correctional top-up courses can be used to rectify excessive settlement. Assuming a local road designation and a design speed of 50 km/hr, settlement tolerances may be in the order of:

Maximum residual settlement of 200 mm in 20 years (outside Structural Zone); and

Maximum change of grade, in any direction, of 1% over 20 years.



6.2 Geotechnical Design Parameters The material properties adopted for geotechnical analysis were derived from typical values, laboratory test results and in-situ testing carried out in 2002 and 2013. The adopted design parameters are shown in Table 9 and Table 10.

Table 9: Geotechnical Design Parameters Strength

Unit

(kN/m3) Undrained Drained

Su (kPa) c (kPa) () Embankment FILL 20 NA 2 35

0 1m: 40kPa Unit 1 Cohesive Alluvium 17 >1m: 15 + 1.2z 2 25

(to max 50kPa)1

Unit 2 Granular Alluvium 17 NA 0 27 Notes: 1. Our adopted shear strength profile for Unit 1 is shown in Figure 6

z = Depth below ground surface = Bulk unit weight Su = Undrained shear strength c = Drained cohesion = Drained Friction angle

Table 10: Geotechnical Design Parameters Compressibility

Unit E

MPa v Cc Cr

C Cv Ch eo OCR (%) (m2/yr)

Unit 1 Cohesive Alluvium NA 0.30 0.50 0.05 2.0 1.5 2.0 1.1 above 1m = 3 below 1m = 1.2

Unit 2 Granular Alluvium 10 0.20 NA NA NA NA NA NA NA Notes: E = Drained Youngs Modulus

v = Poissons Ratio Cc= Primary Compressibility Index Cr = Unloading/Reloading Index C = Secondary Compression Index Cv / Ch = coefficient of consolidation (vertical/ horizontal) eo = void ratio OCR = Over Consolidation Ratio

6.2.1 Embankment Settlement (no ground treatment) We have carried out preliminary analyses to assess the performance and long-term serviceability of the proposed bridge embankments, based on the longitudinal section provided for the preferred alignment concept design.

Southern Bank For Concept Design we have assessed the indicative settlement under embankment loading at the southern bank using the ground profile encountered in CPT-1. The preliminary embankment design drawing provided indicates that the proposed embankment height is up to 5 m above the adjacent ground level at the bridge abutment.

We have carried out analyses for six and twelve month construction (preload) durations, and for different embankment heights. We have not assessed a preload duration longer than 12 months, as this would not likely comply with project time restrictions.



The results or our assessment are shown in Table 11. Table 11: Predicted Settlement of Southern Embankment - no ground treatment

Embankment Height (m)

Predicted Construction Settlement (mm)

(Preload duration)

Predicted PCS (mm) @ 20 yrs post construction

(Preload duration)

1 200 (6 months) 300 (6 months) 2 400 (6 months) 450 (6 months) 3 500 (6 months), 600 (12 months) 600 (6 months), 550 (12 months) 4 600 (6 months), 700 (12 months) 700 (6 months), 650 (12 months) 5 700 (6 months), 800 (12 months) 800 (6 months), 750 (12 months)

Due to the significant thickness of soft ground at the southern bank, it takes approximately 60 years to reach 90% of primary consolidation. For a six or twelve month preload duration, ongoing creep settlements are expected to occur at a rate of about 100 to 150 mm per year for the first 5 years post-construction, reducing to about 50 mm per year within 5 years.

This assessment considers foundation settlement as well as internal creep of the embankment fill. We have used an embankment fill creep rate of 0.2% per log cycle of time. We have assumed that topsoil and shallow unsuitable materials will be removed prior to embankment construction.

These indicative settlement values do not meet the Roads and Maritime criteria specified above (regardless of design speed or pavement type), indicating that ground treatment will be required to reduce maintenance requirements.

Settlement magnitude and rates may vary as a result of natural soil variability and the estimates given in this report are based on the parameters we have used, which are likely to vary.

Northern Bank We have assessed the settlements under embankment loading at the northern bank using the ground profile encountered in BH4.

The results indicate that for an embankment height of 5 m and a six month preload duration, construction settlements are in the order of 600 mm, and PCS are less than 200 mm over 20 years. Ongoing creep settlements are expected to occur at a rate of about 10 to 15 mm per year.

These predicted settlement values indicate that Roads and Maritime total settlement criteria should be met, but that a transition design will be required to meet differential settlement criteria.

6.2.2 Ground Treatment Options A low embankment strategy, which consists of limiting embankment height to 1 to 2 m with occasional asphalt correctional courses, is recommended for locations away from abutments where possible.

To apply this strategy, additional excavation may be required to meet the minimum earthworks thickness requirements indicated by Roads and Maritime Specification R44 (typically about 1.2 m). If appropriate, lime stabilisation may be considered as an option to reduce the depth of excavation required.

For higher embankments, the extent and depth of soft soils underlying the southern bank is likely to render uneconomic or impractical options such as excavate and replace, stone columns or dynamic replacement. Concrete injected columns or other pile options should be suitable to support the embankment in the Structure Zone and partially in the Transition Zone.

An option to reduce PCS would be to apply a surcharge load during construction with the addition of wick drains at nominal 1.5 m spacing to accelerate settlements during the preload period. To satisfy the project time restrictions, the maximum allowable preload and surcharge duration is expected to be about 12 months.



The results of our preliminary assessment for 1.5 m and 3 m surcharge height options with wick drains are rovided in Table 12 and Table 13. p

Table 12: Predicted Settlement of Southern Embankment 1.5m surcharge and wick drains


Predicted Construction Settlement (mm)(Preload & surcharge duration)

Predicted PCS (mm) @ 20 yrs post construction

(Preload & surcharge duration)

3 1150 (6 months), 1350 (12 months) 500 (6 months), 300 (12 months)



Table 13: Predicted Settlement of Southern Embankment 3m surcharge and wick drains


Construction Settlement (mm)(Preload & surcharge duration)

PCS (mm) @ 20 yrs post construction

(Preload & surcharge duration)




For a six or twelve month preload duration, ongoing post construction settlements are expected to occur at a rate of about 100 to 150 mm per year for the first 5 years, reducing to about 50 mm per year within 5 years.

Note that to achieve 200 mm PCS, the preload and 3 m surcharge would need to be left in place for 5 years.

As the settlement shown above for the surcharge and wick drain ground treatment option does not comply with typical Roads and Maritime criteria, the impact of the ongoing settlement on the pavement performance could be assisted by periodically placing correctional top-up asphalt courses, but the Transition Zone is likely to require concrete injected columns or other pile options to provide a reasonable transition from the Structure Zone to the general embankments.

Additionally, a surcharge treatment option may not be a practical solution for Sportmans Creek due to the impact of frequent flooding events on surcharge fill placement.

Embankment Stability We have carried out limit-equilibrium slope stability analysis for short term (undrained) and long term (drained) conditions at the southern embankment using the ground profile encountered in CPT-1. The purpose of the short-term analyses was to check that the embankment would remain stable during construction. We have modelled embankment batter slopes at 2(H):1(V), and southern bank slopes at approximately 8(H):1(V) (as indicated by survey results). You advised that the embankment is to be set back approximately 20 m from the creek.

We have assessed both the cross-section embankment stability and the longitudinal stability through the abutment for a range of embankment heights. We have conservatively ignored the effect of reinforcement provided by abutment piles.

We adopted target FoS values of 1.5 for long term conditions and 1.2 for short term conditions.

The results indicate that the cross-sectional stability of the embankment is achieved for both short and long-term conditions for embankment heights of up to 5 m, without the requirement for staged construction,



stability berms or basal reinforcement. The longitudinal stability assessment indicates that for a 5 m embankment height, an embankment offset from the creek of 20 m would meet design stability requirements. Staged construction, stability berms or geogrid reinforcement are required where embankments are higher than 5 m.

At this stage we have not assessed earthquake or flooding (rapid draw-down) conditions.

6.3 Bridge Foundation Options 6.3.1 Pile Foundation Options Due to the variation in depth to rock along the length of the bridge, a practicable foundation solution will consist of one or several of the piled solutions provided in Table 14. Discussion of the geotechnical and construction challenges for each of the southern and northern abutments and piers across Sportsmans Creek is included below with recommended pile options discussed thereafter.

Table 14: Alternative Pile Solutions Pile Type (typical ultimate load capacity)

Advantages Disadvantage Limiting Depth

Precast prestressed Reasonable Cost concrete Difficult to handle overwater Large displacement Good load capacity (18T each) (fluctuating tides, 28-30m max. 550mm Dia. Octagonal Self proving waves etc) (5000kN+)

Driven Precast Segmental Concrete Piles 275mm sq (800kN) 300mmsq (1200kN) 350mm sq (1750kN) 400mm sq (2500kN)

Can be lowest cost

Self proving

Piles are slender and difficult to handle overwater

Lower capacity than bored piles

More susceptible to bending limitations due to lateral soil movement.

Numerous piles / large pile caps required

Sections: 14m Mechanical or cast-in-situ joints (expensive)

Timber (800kN) Relatively low cost

Limited depth, difficult to splice

May not be approved by Roads and Maritime

Sections: 18m

Bored piles

Relatively low cost

Higher capacity than precast piles. Can increase capacity with larger diameter

Can verify ground profile through cuttings

Extensive casing required for deep rock profile

Heavy equipment requirements

None

Continous Flight Auger (CFA) piles 600mm dia. (1400kN) 700 mm dia. (1900kN) 800 mm dia.(2500kN) 1200 mm dia. (6000kN)

Relatively low cost

Rock socketing feasible using special cutting heads

Casing not required

May not be approved by Roads and Maritime

Slenderness / Reinforcement problematic at depth



Pile Type (typical ultimate load capacity)

Advantages Disadvantage Limiting Depth

improve bending moment capacity and offset corrosion

For the driven pile solutions in Table 14, consideration should be made for high pile driving stresses that may be generated to adequately socket the piles into the sandstone bedrock.

Southern Abutment Geotechnical and construction related issues associated with the southern abutment include:

Thickness of soft, compressible soils will result in additional down-drag forces and bending on piles. Lateral capacity of piles in these soils is likely to be limited. Temporary works / foundation improvement may be required depending on piling rig loads during construction.

Depth to rock (32m) is greater than availability of pre-cast concrete pile segments.

If driven concrete piles are adopted as the preferred foundation then these would likely need to be spliced.

If bored or CFA piles are adopted as the preferred foundation option then large piling equipment would be required.

Open driven piles (eg. Tubular steel) would likely plug during driving.

Bored and CFA piles would generate a significant amount of spoil which has been classified as PASS. Spoil would need to be treated with lime prior to disposal or reuse.

Weak and compressible soils necessitate piles founding on rock as insufficient end bearing is likely within the alluvial sediments. Further, Roads and Maritime bridge specifications stipulate that piles found in sound and un-yielding rock.

Potential pile foundation options for the southern abutment include:

Large diameter bored piles socketed into rock.

CFA piles socketed into rock (subject to Roads and Maritime specifications).

Pre-cast concrete octagonal piles driven to rock.

Open steel tubular piles driven to rock with a concrete plug. Sportsmans Creek Geotechnical and construction related issues associated with central (overwater) piers include:

Construction access limitations, due to navigational clearances under the existing bridge.

Variable thickness of soft compressible sediments that would generate down-drag forces and limited lateral capacity.

be custom The variation in pile length required would require pre-cast piles (either concrete or steel) to designed and manufactured to avoid the need for cutting and splicing piles.



Bored and CFA piles would not be suitable due to the size of the piling rig required and restricted access for a jack up barge. Piles would need to be constructed from a floating barge or a temporary access bund constructed into the creek. Due to the torsional forces generated when socketing bored or CFA piles into rock these may be difficult to construct from a floating barge and require spoil handling and disposal facilities, therefore this may eliminate bored and CFA piling options for the overwater pier locations.

Corrosion and durability of all pile types (concrete or steel) would need to be considered in the detail design phase.

Management of construction related purge water / drilling spoil during piling works would need to be taken into account during planning and construction work.

Additional lateral loads on the piles / piers from flooding and vessel impact would need to be taken into account during the detail design phase.

The selection of either a pile group (eg. driven concrete piles) with a pile cap or large diameter piles constructed with either a pile to column or blade pier configuration would largely be dependent on urban design, waterway opening and cost criteria. A pile to column arrangement is likely to be the most cost effective and practical solution.

Potential pile foundation options for the central (overwater) piers include:

Pre-cast concrete octagonal piles driven to rock.

Open steel tubular piles driven to rock with a concrete plug. Northern Abutment Geotechnical and construction related issues associated with the northern abutment include:

The relatively shallow cover of soils overlying competent bedrock may limit the practicality of using pre-cast driven (steel or concrete) piles due to the low lateral capacity of the soils.

Pre-cast concrete piles may need to be specifically manufactured / customised for this project due to the relatively short length of the overall pile.

Potential foundation options for the northern abutment include:

Bored piles socketed into rock

Pre-cast driven concrete piles

Pad foundation Construction of a pad foundation would require extensive excavation and dewatering over a relatively large area. Temporary excavation support would be required.

At this stage of the concept design, the recommended piled option consists of driven open ended steel piles at the southern and mid-stream locations, and shallow bored piles on the northern embankment. Additional input will be required when structural loading is known to better refine the foundation options.

6.3.2 Pile Design Parameters provides recommended pile design parameters, which may be used for the design of bored pile foundations. Piles designed using these parameters are expected to have settlements less than 5% of the pile diameter. Additional analysis may be required to confirm pile settlements satisfy design tolerances once configurations and design loads are finalised.



filling associated with river bank remediation and the construction and excavation of the boat ramp on the southern bank of Sportsmans Creek may also exist within the study area.

Existing fill, if it is encountered beneath the footprint of the proposed alignment, should be removed prior to placing new fill.

7.2 Salinity Sportsmans Creek, particularly at the confluence with the Clarence River, has the potential to be highly saline. A review of publicly available information suggests that under low flow conditions, an afflux of saltwater can occur up the Clarence River and into Sportsmans Creek3.

7.3 Earthquake Rating The methods of assessing the earthquake risk classification are outlined in the Australian Standard AS1170.4 (2007) Structural Design Actions, Part 4: Earthquake Actions in Australia.

For the Grafton area, AS 1170.4 indicates a hazard factor of 0.05.

The governing condition for the site subsoil class is the thickness and consistency of the subsurface materials beneath the foundations. Based on the depth to rock on the southern embankment and the thickness of soft soils, a Soil Class E is assigned in accordance with Section 4.2 of AS1170.4 (2007).

For structures sited on sub-soil Class E, the design shall consider the effects of subsidence or differential settlement of the foundation material under the earthquake actions determined for the structure.

7.4 Groundwater Management Key issues to consider for the management of groundwater during construction include:

The high groundwater table, which will likely result in the requirement for dewatering of excavations. The depth of excavations for structures such as pavements should be limited where possible;

Acid sulfate soil leachate from dewatering of excavations or wick drain discharge. Where potentially acidic groundwater is encountered in excavations or produced from wick drain discharge, appropriate measures and water treatment and dosing systems will be needed manage discharge water quality;

Groundwater fluctuations related to tidal influences and flooding events. Temporary sheet piling may be required during construction to protect worksites from water inflow; and

Aquifer cross-contamination and flow due to penetrating works such as piling. The use of temporary casing for bored piles or the use of driven piles would effectively mitigate piling related cross-aquifer contamination impacts.

7.5 Temporary Works Temporary works that may be required for bridge construction include:

Working platforms for piling rigs. The stability and bearing capacity of these platforms will need to be assessed;

Installation of temporary sheet piling for dewatering activities and protection of work areas from flood events;

Placement of bridging layers to address poor site trafficability during wet weather across the low-lying floodplains.

3 M. Tulau 1999, http://test.dnr.nsw.gov.au/care/soil/as_soils/pdfs/ass_clarence.pdf



8.0 RECOMMENDED INVESTIGATION FOR DETAILED DESIGN To obtain adequate site information to proceed to detailed design, we recommend the following additional site investigation is carried out:

Boreholes and Laboratory Testing

1 x borehole to be drilled at every pier and abutment location (in order to meet Roads and Maritime requirements for bridge design), to obtain a minimum 3 m of competent rock core. This additional drilling could be completed during the detail design or prior to construction, to confirm the assumptions on pile toe elevations adopted in the detail design.

Drilling of boreholes at central (mid span) piers would require the use of rig mounted on a floating barge with the total number of additional overwater boreholes determined by the number of overwater piers.

Undisturbed samples obtained from the above boreholes to enable further laboratory testing such as UU and oedometer testing to confirm the strength and compressibility of Unit 1 materials across the site.

Additional laboratory testing on potential acid sulfate soils may be required to refine predicted liming rates of excavated spoil, should the selected / final piling option generate significant quantities of PASS materials during construction.

Underground Storage Tanks near General Store Additional assessment of the position and depth of the USTs may be required depending on the final pavement and road design in the vicinity of the General Store. Non-destructive investigative techniques could be utilised to define the extent of the USTs.

Instrumentation and Monitoring During detail design, an instrumentation and monitoring plan (IMP) should be developed for the construction and monitoring of the southern embankment. The objective of the IMP would be to measure actual movements (vertical and lateral) as well as insitu soil behaviour during and post construction in order to verify design assumptions and predictions.

The IMP may consist of installation of vibrating wire piezometers (to monitor dissipation of pore water pressures), extensometers (to monitor settlements within the alluvial material), settlement plates (to monitor settlements of the alluvial ground beneath the embankment) and inclinometers (to monitor for lateral movements). Survey monitoring of survey targets should also be included in the IMP.


24 March 2014 Report No. 137622029-005-R-Rev1

Report Signature Page

GOLDER ASSOCIATES PTY LTD

Nick Poriters Graham Scholey Senior Geotechnical Engineer Principal Geotechnical Engineer

A.B.N. 64 006 107 857

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Sportsmans Creek Review of Environmental Factors Appendix b

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