Ethelton Stage 1 ESA South Australian Environment Protection Authority 19 -Mar -2021 Doc No. R002

Ethelton Assessment Area

Stage 1 Environmental Site Assessment

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Ethelton Assessment Area Stage 1 Environmental Site Assessment

Client: South Australian Environment Protection Authority

ABN: 85 393 411 003

Prepared by

AECOM Australia Pty Ltd Level 28, 91 King William Street, Adelaide SA 5000, Australia T +61 8 7223 5400 F +61 8 7223 5499 www.aecom.com ABN 20 093 846 925

19-Mar-2021

Job No.: 60647266

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

© AECOM Australia Pty Ltd (AECOM). All rights reserved.

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

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Quality Information

Document Ethelton Assessment Area - Stage 1 Environmental Site Assessment

Ref 60647266

Date 19-Mar-2021

Prepared by Jody Elsworth / Mark Chapman

Reviewed by David Steele / Mark Chapman / Paul Carstairs

Revision History

Authorised Rev Revision Date Details Name/Position Signature

R001 3 March 2021 Draft Mark McFarlane Environment Team Lead – Geosciences and Remediation Services R002 19-Mar-2021 Final Mark McFarlane Environment Team Lead – Geosciences and Remediation Services

9

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Table of contents Executive summary i Acronyms vii 1.0 Introduction 8 1.1 Background 8 1.2 Objectives 9 1.3 Scope of works 9 1.3.1 Modifications to proposed scope 10 2.0 Background information 11 2.1 Site setting 11 2.1.1 Site location 11 2.1.2 Zoning information 11 2.1.3 Topography 11 2.1.4 Surface water 11 2.2 Regional geology and hydrogeology 12 2.2.1 Geology 12 2.2.2 Shallow soil profile 12 2.2.3 Hydrogeology 12 2.2.4 Groundwater bore data 13 2.3 Previous investigations 15 2.4 Site history summary – former dry cleaners site 15 2.5 Observations – former dry cleaners site 16 3.0 Intrusive investigations 17 3.1 Data quality objectives 17 3.2 Overview and chronology of works 18 3.3 Preparatory works 19 3.3.1 Stakeholder engagement 19 3.3.2 Well permits 19 3.3.3 Health Safety and Environment Plan 19 3.4 Selection of investigation locations 20 3.5 Service location 20 3.6 Groundwater investigation 20 3.6.1 Groundwater well drilling and logging 20 3.6.2 Soil sampling 21 3.6.3 Groundwater well construction 21 3.6.4 Groundwater well and river gauging 21 3.6.5 Groundwater well sampling 22 3.6.6 Sample handling and laboratory analysis 22 3.6.7 Waste water disposal 23 3.7 Soil vapour investigation 23 3.7.1 Soil vapour bore installation 23 3.7.2 Soil vapour bore sampling 24 3.7.3 Waste soil disposal 24 3.8 Groundwater well and soil vapour well survey 25 4.0 Quality Assurance and Data Validation 26 4.1 Groundwater well installation and development 26 4.2 Groundwater monitoring well survey data 26 4.3 Soil vapour bore integrity 26 4.3.1 Helium leak test 26 4.3.2 Isopropanol leak test 26 4.4 Soil vapour sampling – canister pressure 26 4.5 Analytical data validation 27 5.0 Results 29 5.1 Introduction 29 5.2 Soil conditions 29 5.2.1 Observed soil profile 29

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5.2.2 Geotechnical laboratory testing 29 5.3 Groundwater field results 30 5.3.1 Groundwater gauging 30 5.3.2 Port River Gauging 31 5.3.3 Field indications of groundwater impact 32 5.3.4 Groundwater field parameters 32 5.4 Groundwater laboratory results 33 5.4.1 Screening criteria 33 5.4.2 Groundwater analytical results 35 5.5 Soil vapour field screening 37 5.6 Soil vapour laboratory results 37 5.6.1 Screening criteria 37 5.6.2 Soil vapour analytical results 37 5.6.3 Comparison of analytical data to field screening results 38 6.0 Discussion 40 6.1 The Presence of Site Contamination 40 6.2 Detailed assessment of volatile halogenated compound impacts 40 6.2.1 Generalised conceptual behaviour of chlorinated ethenes 40 6.2.2 Extent and magnitude of CHC groundwater contamination 43 6.2.3 Extent and magnitude of soil vapour impacts 43 6.2.4 Critical review of soil vapour and CHC groundwater data 44 6.3 Other contaminants 44 6.3.1 Petroleum hydrocarbons 44 6.3.2 Metals 45 6.4 Groundwater chemistry 45 Groundwater salinity 46 6.5 Conceptual Site Model 47 6.6 Data gaps and uncertainties 51 7.0 Vapour intrusion risk 53 7.1 Introduction 53 7.2 Toxicity Assessment 53 7.3 Quantitative Exposure Assessment 54 7.3.1 Introduction 54 7.3.2 Scope of Modelling 54 7.3.3 Estimating Exposure Concentrations 54 7.3.4 Vapour Modelling 56 7.3.5 Geological Assumptions 56 7.4 Risk Characterisation 59 7.4.1 Methods for Quantifying Risks to Human Health 59 7.4.2 Hazard Index for Threshold Effects 59 7.4.3 Acceptable Risk 60 7.4.4 Modelling Conclusions - Residential 61 7.4.5 Modelling Conclusions – Intrusive Workers 62 7.5 Sensitivity Analysis of Key Risk Modelling Inputs 63 7.5.1 Introduction 63 7.5.2 Crawl-Space Residential Dwellings 63 7.5.3 Volumetric Air Content, Moisture Content and Soil Bulk Density 64 8.0 Conclusions 66 9.0 References 68 10.0 Report limitations 70 Appendix A Figures A Appendix B Tables B Appendix C Registered bore search C

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Appendix D Plates D Appendix E Safework SA Dangerous Goods E Appendix F Well permits F Appendix G Groundwater well and soil vapour bore logs G Appendix H Calibration certificates H Appendix I Soil vapour sampling records I Appendix J Soil vapour laboratory certificates and chain of custody J Appendix K Waste disposal certificates K Appendix L Soil geotechnical analysis L Appendix M Groundwater sampling records M Appendix N Groundwater laboratory certificates and chain of custody N Appendix O Groundwater well, river stake and soil vapour bore survey results O Appendix P Analytical data validation P Appendix Q Assessment criteria Q Appendix R Vapour Modelling R

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Executive summary AECOM Australia Pty Ltd (AECOM) was commissioned by the South Australian Environment Protection Authority (SA EPA) to conduct Stage 1 Environmental Site Assessment (ESA) works associated with the SA EPA’s Ethelton Assessment Area. The location of the Ethelton Assessment Area is shown below.

□ Elhelton EPAAssessmeot Area. Stage 1 0 Former Dry Cleaning Facility

The recently established Ethelton Assessment Area encompasses a predominantly residential area surrounding the former Bronsons Dry Cleaners site at 10-12 Marion Street, Ethelton. A Section 83A notification for 12 Marion Street was submitted to the SA EPA on 25 August 2020 by Environmental Projects Pty Ltd, who were undertaking environmental assessment work at the property. The notification reported chlorinated hydrocarbon compounds (CHCs) in shallow soil and groundwater at the 10-12 Marion Street site (EPA, 2021). The SA EPA commissioned this Stage 1 investigation with the following specific objectives: • Investigate the nature and extent of chlorinated hydrocarbon compounds in soil vapour external to the 10-12 Marion Street site.

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• Investigate the nature and extent of chlorinated hydrocarbon compounds and other key contaminants in groundwater external to the 10-12 Marion Street site. • Investigate groundwater flow direction, including potential influence from the nearby Port River, to inform potential migration of groundwater contamination. • Provide a vapour intrusion risk assessment with respect to volatile contaminants and nearby land use. Scope of work The investigations conducted by AECOM as part of the Stage 1 Assessment included: • Preparatory works including identifying existing wells to the south-east of the Assessment Area by conducting a walkover, and gaining council approval for works and groundwater well permits. • Preliminary groundwater level and salinity gauging of existing wells to the south-west of the Assessment Area, inclusive of well head survey of selected wells, to confirm the local groundwater flow direction and to inform decisions in relation to further investigation locations. • Installation and sampling of a soil vapour bore network comprising ten (10) new shallow soil vapour monitoring bores, external to the 10-12 Marion Street site and within the EPA Assessment Area. Samples were submitted for analysis for a suite including petroleum hydrocarbons and chlorinated hydrocarbon compounds (CHCs) and associated degradation indicators (ethane, ethene and methane). • Installation of eight (8) new groundwater well monitoring wells, external to the 10-12 Marion Street site and within the EPA Assessment Area, including collection and testing of geotechnical samples at selected location to inform vapour intrusion modelling. • Installation of a graduated surface water gauge on edge of Port River and recording of water elevation. • Gauging of the eight (8) new wells and eight (8) of the existing wells, inclusive of salinity profiling of the water column in five new and five existing wells. Photoionisation detector (PID) head-space screening of each newly installed well prior to sampling. • Sampling of the eight (8) new groundwater monitoring wells, inclusive of collection of additional shallow grab samples from two wells closest to the former dry cleaners site. All groundwater samples were analysed for petroleum hydrocarbons and CHCs, metals, and associated degradation indicators (ethane, ethene and methane). • Development of a conceptual site model and conduct of a vapour risk assessment. Observations Fieldworks were undertaken between 8 November 2020 and 3 February 2021. It was noted in November 2020 that the former dry cleaner site at 10 – 12 Marion Street, Ethelton had been demolished. In December 2020, three open excavations of approximately 1 m depth were observed in the north-western, central and eastern portions of the site. The excavations had been backfilled by early January, and sprinklers were observed in operation at the site of site visits from early January to early February 2021, creating areas of ponded water across the bare earth site surface. Results – Groundwater Shallow groundwater is present within the Assessment Area at depths ranging between approximately 1.2 m and 1.9 m below ground level (bgl). To the south-east, due to the relatively elevated topography, the depth to groundwater was observed to increase to as much as 4 m bgl. Groundwater flow across the broader area was assessed to be generally to the north-west, consistent with previous findings reported in the Golder Associates Groundwater Monitoring and Management Plan (GMMP) for the Precinct 1 Port Adelaide Waterfront Development which indicated north-westerly flow even at low tide (Golder Associates, 2007). Gauging results for January 2021 were indicative of localised groundwater mounding in the vicinity of the former dry cleaners site, likely associated with the observed watering of the site, and potentially resulting in a localised radial groundwater flow pattern.

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Salinity profiling typically showed an increase in salinity with depth within the wells, suggesting the presence of a less saline water lens potentially attributable to rainfall infiltration and/or leaking services. This was more pronounced in two groundwater wells (GW01 and GW02) in the immediate vicinity of the former dry cleaners site, which exhibited a low salinity lens of water from the groundwater surface to approximately 2.5 m bgl. Concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) exceeding adopted investigation levels were reported in one groundwater monitoring well installed adjacent the northern boundary of the former dry cleaners site. Concentrations of 1,2-dichloroethane (DCE) (cis- and trans- 1,2-DCE) exceeding adopted investigation levels were found in groundwater monitoring wells adjacent the northern boundary of the former dry cleaners site, cross/down gradient to the west, and down gradient to the north-west. The extent of measurable concentrations of DCE has not been delineated within the Assessment Area to the west or north-west. A number of samples reported concentrations of short chain total petroleum hydrocarbons (TPH) / total recoverable hydrocarbons (TRH) above the laboratory limits of reporting (LOR). A comparison of total CHC concentrations to TRH C6-C10 concentrations provides strong evidence that the reported short chain TPH/TRH fraction concentrations are indicative of the presence of CHCs rather than petroleum hydrocarbons, noting also that no benzene, toluene, ethylbenzene, xylenes and naphthalene (BTEXN) compounds were reported above laboratory LOR for any wells. No non-aqueous phase liquid (NAPL) was detected during the gauging of the wells. A range of dissolved metals were present in groundwater at concentrations exceeding adopted screening levels. In most cases impacts are present broadly across the Assessment Area. The distribution of copper and molybdenum impacts reported indicates a possible source in the vicinity of the former dry cleaners site, although no potentially contaminating activities likely to have given rise to these impacts have been identified. The presence of various metals concentrations renders the shallow groundwater chemically unsuitable for uses such as aquaculture, and based on results for some wells, for potable supply or irrigation use. Results – Soil vapour Soil vapour bores were installed to depths of between 0.9 m and 1.2 m in consideration of the typically shallow depth to water. Five soil vapour bores were installed paired with targeted groundwater wells to enable comparison of soil vapour and groundwater concentration data. The highest soil vapour concentrations of PCE, exceeding adopted screening levels, were reported for a soil vapour bore installed adjacent the northern boundary of the former dry cleaners site. PCE concentrations were also reported above the LOR but below the adopted screening levels in soil vapour bores to the north-west of the former dry cleaners site. Similarly, the highest soil vapour concentrations of TCE and 1,2-DCE, above the adopted screening levels, were reported adjacent the northern boundary of the former dry cleaners site; TCE concentrations above screening levels were not delineated within the Assessment Area to the north and west north-west, while 1,2-DCE impacts have not been delineated below the adopted screening levels to the west and below the laboratory LOR to the west north-west or north-west. Elevated concentrations of chloroform were reported in soil vapour immediately adjacent the former dry cleaners site to the north, with minor concentrations reported immediately up-gradient to the east and down-gradient to the north-west. Concentrations of 2-Propanone (acetone) were also reported highest immediately adjacent the former dry cleaners site and immediately cross-gradient to the north- east. Lower concentrations of acetone were reported in vapour to the south, west and north-west of the Assessment Area. Minor concentrations of BTEXN, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene were reported in a number of soil vapour bores located within the assessment Area above the laboratory LOR but well below the adopted residential guidelines. No concentrations were reported in soil vapour immediately adjacent the former dry cleaners site. Discussion and Conclusions Four objectives were identified for the investigation, and discussion and conclusions are provided in relation to these objectives below.

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1. To investigate the nature and extent of chlorinated hydrocarbon compounds and other key contaminants in groundwater external to the 10-12 Marion Street site CHC compounds were identified in groundwater in the immediate vicinity of the former dry cleaners site and extending down-gradient to the north-west. The presence of PCE and breakdown products TCE and DCE is indicative of the occurrence of breakdown via reductive dechlorination. The absence of CHC in up-gradient wells to the south-east indicates the former dry cleaning operations at 10- 12 Marion Street are likely to be the source of the observed impacts. Notably, breakdown product DCE was observed to extend down-gradient of the site to the north-west in the direction of groundwater flow to the western boundary of the Assessment Area. No NAPL was detected during the gauging of the wells and no concentrations of CHCs were reported of magnitude indicating DNAPL presence. A comparison of total CHC concentrations to reported short chain TRH concentrations provided strong evidence that the reported short chain TPH/TRH fraction concentrations are indicative of the presence of CHCs rather than petroleum hydrocarbons. 2. To investigate groundwater flow direction, including potential influence from the nearby Port River, to inform potential migration of groundwater contamination Both the groundwater level gauging to the south-east of the Assessment Area in November 2020, and within the Assessment Area and south-east of the Assessment Area in January 2021, indicated an overall north-west groundwater flow direction. This apparent north-westerly groundwater flow is consistent with the observed distribution of groundwater and soil vapour impacts. Localised groundwater mounding in the vicinity of the former dry cleaners site was apparent in January 2021, and suggests localised radial groundwater flow. Given the observed distribution of CHC impacts solely in wells to the north-west of the former dry cleaners site, the apparent radial groundwater flow is likely to be only recent or not significant in terms of historical migration of impacts. Based on the Port River gauging, it is apparent that the minimum low tide may extend below current groundwater levels in the vicinity of the Assessment Area, suggesting the potential for an easterly flow toward the Port Adelaide River during low tide. There is no evidence to indicate easterly groundwater flow from the Assessment Area towards the river, either from inferred groundwater contours, previous studies, or the observed distribution of groundwater and soil vapour impacts. 3. To investigate the nature and extent of chlorinated hydrocarbon compounds in soil vapour external to the 10-12 Marion Street site Maximum concentrations of CHCs in soil vapour were reported for bores in the vicinity of the former dry cleaners site, with lesser concentrations extending to the north-west. It is noted that the extent of soil vapour impacts (TCE and DCE) has not been delineated to below NEPM interim Health Investigation Level (HIL) screening levels within the boundary of the Assessment Area, with the potential for impacts to extend across the western boundary. The apparent soil vapour impacts, inclusive of PCE, TCE and 1,2-DCE, are assessed to be attributable to volatilisation from the identified groundwater concentrations. The absence of impacts up-gradient (to the south-east) of the former dry cleaners site, supports inference from groundwater results that former dry cleaners site is a likely source of groundwater impacts. 4. To provide a vapour intrusion risk assessment with respect to volatile contaminants and nearby land uses The assessment of potential vapour intrusion risk gave consideration to the identified magnitude and extent of CHCs in groundwater and soil vapour in the context of the primarily residential development across the Assessment Area and the potential for receptors to also include maintenance workers involved in subsurface excavations, and utilised the US EPA Johnson and Ettinger-based model to calculate vapour concentrations at the point of exposure. With respect to vapour inhalation risk in a residential occupancy scenario, reference was made to the TCE-specific Indoor Air Level Response ranges developed by the SA EPA and SA Health. While a similar PCE framework has previously been referenced for the EPA Brighton Assessment Area, this

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remains an interim guideline only. Accordingly, AECOM adopted and extended the approach of the TCE-specific framework in consideration of the combined results for the CHCs. Based on the outcome of the modelling, AECOM concluded that vapour intrusion risks fall within the “Safe” range, other than in the vicinity of a hot-spot in the “Investigation” range, centred around the elevated groundwater and vapour impacts identified at the paired groundwater well and soil vapour bore on Marion St, immediately adjacent to the former dry cleaning site, as shown on the Figure below. Reported concentrations in vapour wells SV04 and SV05 to the north of Marion St and the former dry- cleaner site, and at SV02, up-gradient on the eastern side of Warrawee Rd, do not imply unacceptable vapour intrusion risks in these neighbouring properties. While soil vapour concentrations of TCE and DCE were identified marginally above HIL screening levels at some perimeter soil vapour wells, the magnitude of the observed concentrations were such that the vapour intrusion risk is considered to have been delineated to below “Investigation” risk level level within the Assessment Area.

Vapour intrusion interpolated hazard indices (PCE, TCE and DCE)

□-°"'- O ~·r,...Qrc.no; r.,,,,..... • ...,s.,]la,• ..,e:,.

The predicted concentrations in a 1m deep trench (i.e. above the water table) in the area of highest measured vapour concentrations were well below commercial industrial guidelines, indicating no unacceptable risk to intrusive workers from vapour intrusion into excavations.

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Data gaps and uncertainties The following data gaps and uncertainties relevant to the assessment are noted: • Concentrations of CHCs in groundwater have been delineated to below adopted screening criteria in all directions within the Assessment Area with the exception of DCE impacts in groundwater to the west of GW05 and GW06 along the western boundary, where there are marginal exceedances of drinking water guidelines. • There is no temporal data with which to consider contaminant concentration changes over time and no assessment as to whether the CHC plume is shrinking, stable or expanding can be made. • Groundwater contours across the Assessment Area have been inferred only from water levels gauged during a period of irrigation of the former dry cleaners site, which is also currently bare earth and subject to infiltration not previously possible. Further gauging events in the absence of site irrigation may enable understanding of the more typical groundwater flow in the area. It is noted also that it is unclear to what extent the operation of the Hart Street stormwater pumping station may be impacting local groundwater flow, although the overall flow direction has been noted to be consistent with previous findings. • Limited discrete sampling of groundwater identified vertical heterogeneity in chlorinated ethene concentrations, with materially higher concentrations present in shallow grab samples, compared to traditionally purged samples. This infers solvent impacts are located preferentially in the observed fresh-water lens, close to the former dry-cleaner site; however, vertically-discrete sampling was limited to shallow (relatively fresh water) grab samples in two wells and therefore limited data exists regarding the spatial extent, temporal changes or relative magnitudes of this apparent vertical heterogeneity. Additional temporal data and discrete sampling above and below the freshwater-saline water interface would aid in clarifying the significance of the apparent influence of preferential irrigation of the former dry cleaners site on vapour intrusion risks. • While site-specific geological testing was undertaken to inform vapour modelling at the site, the obtained data (particularly moisture content, a key parameter) was highly variable in otherwise similarly logged materials, with the measured results lying at both the high and low extremes of physically possible data. This inconsistency in results was addressed via adoption of more moderate literature values for key input parameters, considered to provide realistic, but appropriately conservative values, as well as by sensitivity analysis. Avoiding the use of water lancing when using non-destructive digging in sands would reduce the risk of artificially wetting soils. While there are always practical constraints with bore locations, targeting samples from beneath sealed ground would also be of value in better mimicking expected moisture profiles beneath buildings. • Soil vapour analysis is limited to one round of monitoring, such that temporal and seasonal variability has not been assessed. It is noted also that the soil vapour samples were collected approximately one month prior to the groundwater samples in this investigation. If the environment is relatively dynamic, potentially due to preferential recharge in some areas of the Assessment Area (such as surface watering observed at 10-12 Marion Street between January and February 2021), this may materially affect measured concentrations and associated risk estimates. • It is noted that there was no data collected on private properties as part of this investigation, including at the former dry cleaners site. As such, the spatial boundaries of the interpolated risk contours (in the figure above) are subject to some uncertainty, particularly towards the residential properties to the west and south-west of the former dry cleaners. If materially higher COPC concentrations were identified at the 10-12 Marion Street property, this could alter the risk assessment conclusions for these surrounding properties. These conclusions should be read in conjunction with the limitations presented in Section 10.0 of this report.

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Acronyms ADWG Australian Drinking Water Guideline ANZECC Australia and New Zealand Environment and Conservation Council ASC NEPM National Environment Protection (Assessment of Site Contamination) Measure ASTM ASTM International, formerly American Society for Testing and Materials BTEX benzene, toluene, ethylbenzene and xylenes CoPC Chemical of Potential Concern CRC CARE Cooperative Research Centre for Contamination Assessment and Remediation of the Environment CSM Conceptual Site Model DCE dichloroethene DEW Department for Environment and Water DNAPL dense non-aqueous phase liquid EC Electrical Conductivity EPA Environment Protection Authority ESA Environmental Site Assessment HIL Health Investigation Level HI Hazard Index HQ Hazard Quotient HSL Health Screening Level LNAPL light non-aqueous phase liquid LOR Limit of Reporting m bgl metres below ground level m bTOC metres below Top of Casing m AHD metres above Australian Height Datum NAPL non-aqueous phase liquid NEPC National Environment Protection Council NEPM National Environment Protection Measure NHMRC National Health and Medical Research Council. PCA Potentially Contaminating Activity PCE tetrachloroethene (also known as perchloroethene or perchloroethylene) PID Photoionisation detector ppb parts per billion ppm parts per million SWL Standing Water Level TCE trichloroethene (also known as trichloroethylene) TDS Total Dissolved Solids VC vinyl chloride VHC volatile halogenated compound WHO World Health Organisation

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1.0 Introduction

1.1 Background AECOM Australia Pty Ltd (AECOM) was commissioned by the South Australian Environment Protection Authority (SA EPA) in November 2020 to conduct Stage 1 Environmental Assessment works associated with the SA EPA’s Ethelton Assessment Area. The location of the Ethelton Assessment Area is shown on Figure 1-1. Figure 1-1 Location of the SA EPA Ethelton Assessment Area

□ Ethelton EPAAssessmeflt Area. Stage 1 Former Ory Cleaning Facility D

A Section 83A notification for the 10-12 Marion Street site was submitted to the SA EPA on 25 August 2020 by Environmental Projects Pty Ltd, who were undertaking environmental assessment work at the property on behalf of the prospective purchaser (current owner) of the property, Nawras Pty Ltd. The notification reported chlorinated hydrocarbon compounds (CHCs) in shallow soil and groundwater at the 10-12 Marion Street site (EPA, 2021). The site was formerly a large-scale dry cleaner that operated from the 1920s and was understood to include several underground storage tanks.

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Information reviewed by EPA had indicated the following: • Tetrachloroethene (PCE), trichloroethene (TCE) and cis-1,2-dichloroethene (cis-DCE) had been identified in groundwater grab samples and soil vapour passive samples collected at 10-12 Marion Street, Ethelton (sampled July/August 2020). • The concentrations of PCE (up to 110,000 µg/m3), TCE (up to 5,000 µg/m3) and cis-DCE (15,000 µg/m3) measured in soil vapour at the source site were well above the ASC NEPM 1999 interim health investigation levels (2,000 µg/m3, 20 µg/m3, and 80 µg/m3, respectively) for consideration of vapour intrusion risk in a residential land use setting. Other volatile compounds were also detected in soil vapour samples. • Concentrations of contaminants in shallow groundwater (observed at 1.6 m below surface) at the source site also suggested a potential risk to nearby users of groundwater. Salinity records suggest groundwater may be of potable quality.

1.2 Objectives The objectives of the Stage 1 assessment works were: • Investigate the nature and extent of chlorinated hydrocarbon compounds and other key contaminants in groundwater external to the 10-12 Marion Street site. • Investigate groundwater flow direction, including potential influence from the nearby Port River, to inform potential migration of groundwater contamination. • Investigate the nature and extent of chlorinated hydrocarbon compounds in soil vapour external to the 10-12 Marion Street site. • Provide a vapour intrusion risk assessment with respect to volatile contaminants and nearby land use.

1.3 Scope of works The scope of works conducted as part of the Stage 1 investigations included the following key elements: • Preparatory works including identifying existing wells to the south-east of the Assessment Area by conducting a walkover, and gaining council approval for works and groundwater well permits. • Preliminary groundwater level and salinity gauging of existing wells to the south-west of the Assessment Area, inclusive of well head survey of selected wells, to confirm the local groundwater flow direction and to inform decisions in relation to further investigation locations. • Installation and sampling of a soil vapour bore network comprising ten (10) new shallow soil vapour monitoring bores, external to the 10-12 Marion Street site and within the EPA Assessment Area. Samples were submitted for analysis for a suite including petroleum hydrocarbons and chlorinated hydrocarbon compounds (CHCs) and associated degradation indicators (ethane, ethene and methane). • Installation of eight (8) new groundwater well monitoring wells, external to the 10-12 Marion Street site and within the EPA Assessment Area, including collection and testing of geotechnical samples at selected location to inform vapour intrusion modelling. • Installation of a graduated surface water gauge on edge of Port River and recording of water elevation. • Gauging of the eight (8) new wells and eight (8) of the existing wells, inclusive of salinity profiling of the water column in five new and five existing wells. Photoionisation detector (PID) head-space screening of each newly installed well prior to sampling. • Sampling of the eight (8) new groundwater monitoring wells using the low flow technique in general accordance with Schedule B2 of the National Environment Protection (Assessment of Site Contamination) Measure 1999 (ASC NEPM) (National Environment Protection Council

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(NEPC), 1999, as amended). Two additional shallow grab samples were also collected from two wells closest to the former dry cleaners site. All groundwater samples were analysed for petroleum hydrocarbons and CHCs, metals, and associated degradation indicators (ethane, ethene and methane). • Development of a conceptual site model and conduct of a vapour risk assessment. • Preparation of this assessment report. 1.3.1 Modifications to proposed scope The results of the salinity profiling conducted on 21 January 2021 showed markedly lower salinity in the upper portion of the water column at groundwater well GW01 located adjacent the northern property boundary of the former dry cleaners site at 10 – 12 Marion Street, Ethelton; by a depth of 1.5m to 2.0 m into the water column. There was also slightly reduced salinity at GW02 located adjacent the former dry cleaners site to the east. The SA EPA and AECOM agreed to additional sampling of upper portion of the water column at GW01 and GW02 which was successfully carried out on 22 January 2021. Formal approval of this modification was provided by the SA EPA on 29 January 2021. A detailed description of the actual scope of work conducted is presented in Section 3 of this report.

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2.0 Background information

2.1 Site setting 2.1.1 Site location The Ethelton Assessment Area is located in the north-western portion of the Adelaide metropolitan area at the southern end of the LeFevre Peninsula, a spit of land typically 2 km wide bordered by the Gulf St Vincent to the west and the Port Adelaide River to the east. The Assessment Area covers approximately 2.8 hectares and currently consists primarily of residential properties with a stormwater pumping station in the north-east portion of the Assessment Area. The location of the Stage 1 Assessment Area is shown on the attached Site Locality Plan (Figure 1, Appendix A). The boundary of the Ethelton Assessment Area (as delineated in Figure 1-1) includes the following roadways: • North: Hart Street. • South: Mary Street. • East: Causeway Road. • West: Deslandes Street. 2.1.2 Zoning information The whole of the assessment area is zoned and described as Residential in the Port Adelaide Enfield Council Development Plan as Consolidated 25 October 2020 and detailed on Zone Map PAdE/16. Lotsearch prepared a site summary report for the former dry cleaners site at 10 – 12 Marion Street, Ethelton and a copy was provided to AECOM by the SA EPA. The Lotsearch information collected in May 2020 and provided in the May 2020 Preliminary Site Investigation – Site History report (Environmental Projects, 2020), showed two additional land uses including Commercial land use, which encompasses the 10-12 Marion Street site and Utilities or Industry land use, which encompasses the water pumping station at 4-6 Hart Street, Ethelton. The desired characteristics and objectives of the development zone correspond closely to the current generalised land use information as shown on Figure 2 in Appendix A. 2.1.3 Topography Based on the Department for Environment and Water (DEW) Nature Maps website, the topography of the Assessment Area is described as follows: • The Assessment Area is generally flat lying at approximately 0 m to 2 m Australian Height Datum (mAHD); • The Assessment Area slopes in a north north-westerly direction; and • Land rises at Hart Street to the vehicle overpass to approximately 6 m AHD. 2.1.4 Surface water The nearest surface water body is the Port Adelaide River located approximately 150 m east of the Assessment Area (Figure 1). West Lakes is located approximately 500 m south-east of the Assessment Area. The Gulf St Vincent is located is located approximately 1.5 km west of the Assessment Area. The Hart Street pump station is located in the north-east portion of the Assessment Area and is designed to collect stormwater from the low lying area west of the Port River via the gravity stormwater network, and discharge it to the river by pumping. The SA EPA provided AECOM with correspondence with the City of Port Adelaide Enfield, which did not include information on how often the pump runs, other than that it is triggered by the water levels in sumps, so theoretically by large rainfall or accumulation of smaller flows. While it predominantly pumps stormwater, council acknowledge in a recent email to the SA EPA (dated 5 March 2021), that as a result of pipe joins, some groundwater

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might be collected and pumped out. There is a potential then that operation of the pump station and the deeper stormwater network may have an influence on the direction of groundwater flow in the vicinity of the Assessment Area.

2.2 Regional geology and hydrogeology 2.2.1 Geology The 1:100,000 geological map of Adelaide1 shows that the Assessment Area is predominately underlain by the St Kilda Formation, consisting of coastal marine sediments, calcareous, fossiliferous sand and mud originating from intertidal sand flats, beaches and tidal marshes and organic, gypsiferous clay of supratidal flats. The dominant overlying soil strata consists of layered sediments of mixed marine and river origin-sands, silts, clays and organic deposits2. 2.2.2 Shallow soil profile Reference to the Soils Association Map of the Adelaide Region (Taylor et al, 1972), as shown in the extract presented as Figure 2-1 below, reflects the information presented in the geological map (Section 2.2.1) and indicates the majority of the Assessment Area to be underlain by Dunes Sand type DS1 sands, which are described as layered old dune sands, generally compact and normally brown colours along with integrated soils and Red Brown Earths type RB5a (Brown clay or sandy clay soils with granular structure over sandy clay with some lime) and RB9 (Mottled silty clay over brown silty clay with granular structure, slight lime, becoming sandy with depth). Figure 2-1 Extract from Taylor et al “Soils Association Map of the Adelaide Region”

2.2.3 Hydrogeology According to Gerges (2006)3 the Assessment Area is located within hydrogeological zone 3C. This zone is stated to contain five to six Quaternary aquifers and also three to four, almost flat lying,

1 South Australian Department of Mines and Energy, 1980. 2 Taylor, J.K., South Australian Department of Mines and Energy, 1972 3 DWLBC Report 2006/10 ‘Overview of the hydrogeology of the Adelaide metropolitan area’, Department of Water, Land and Biodiversity Conservation, 2006

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Tertiary aquifers. The first and second Tertiary aquifers are the thickest and the most productive, with relatively low salinity. The greatest proportion of abstracted groundwater for industrial and recreational use comes from the first Tertiary aquifer. Based on maps presented in the Gerges report, the salinities of groundwater in the Quaternary aquifers and in the underlying first Tertiary aquifer (T1) in this area are likely to be in the following ranges: • Q1 to Q3: less than 1,000 to 2,500 mg/L total dissolved solids (TDS) • Q4 and Q5: less than 1,000 to 1,500 mg/L TDS • Q6: 1,000 to 1,500 mg/L TDS • T1: 500 to 1,000 mg/L TDS It is generally understood that a groundwater divide lies beneath the LeFevre peninsula, such that shallow groundwater on the western side flows west towards Gulf St Vincent and groundwater on the eastern side (i.e. the site location) flows east towards the river. While this easterly flow is a regional expectation this close to the Port River, it is noted that localised flow regimes can differ. We note that the Golder Associates Groundwater Monitoring and Management Plan (GMMP) for the Precinct 1 Port Adelaide Waterfront Development (provided on 9 November 2020 by the EPA to assist with preparation of this submission) includes a groundwater contour plan for the area to the east of the subject site, which indicates north-westerly flow even at low tide (Golder Associates, 2007). The GMMP also discusses that this assessment is inconsistent with historical findings by URS (2001), and that the observed north-westerly flow may have been attributable to historical dewatering in the vicinity of the north-western portion of the Precinct 1 site between 2004 and 2005. The GMMP also notes that SA Government publications indicate a likely groundwater flow to the east. It was on the basis of this conflicting information that AECOM conducted a gauging event of existing wells in advance of further intrusive works. As discussed in detail in Section 5.3.1, existing wells located to the east and south-east of the source site were re-surveyed and gauged. The results confirmed local groundwater flow direction between the Port River and the site was to the north-west. 2.2.4 Groundwater bore data A search for registered groundwater bores located within 2 km of the former dry cleaners site (as indicated in Figure 1-1) was undertaken by reviewing the Department for Environment and Water WaterConnect online groundwater database on 29 January 2021 (DEW, 2021). A total of 1078 registered bores were identified within an approximate 2 km radius of the former dry cleaners site and are listed in Appendix C. Of these, approximately 700 are shallow bores located within the peninsula. Of the 1078 bores identified, 927 are potentially operational4. The purposes of the 927 potentially operational bores is summarised in Table 2-1. Table 2-1: Summary of potentially operational bores within 2 km radius of Assessment Area

Purpose # of wells Domestic 418 Investigation / Monitoring / Observation 185 Irrigation 63 Environment 22 Drainage 5 Industrial 1 Recreational 1

4 Bores listed as abandoned, backfilled or not in use are deemed to not be in operation.

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Purpose # of wells Stock 1 Not Listed 382

Table 2-2 provides a summary of the average parameters (where listed) for the 927 identified bores. The average values of salinity in all aquifer suggests that groundwater is potentially suitable for potable use, irrigation, general water uses, livestock watering and aquaculture as per the Environment Protection (Water Quality) Policy (EPA, 2015). Table 2-2: Recorded aquifer parameters # of Average Installation Average Average Average Aquifer Wells Depth SWL Salinity Yield # m bgl m bgl mg/L L/s Qhcks 803 6.3 3.2 1528 0.7 Qpah 80 15.1 2.4 7507 0.3 Qhe 1 10.0 - - - T1 4 128 6.4 2120 11.9 Unknown 40 6.6 2.0 8025 0.5 Notes: Shading indicates information not recorded in database bgl = below ground level; SWL = standing water level; TDS = total dissolved solids Qhck Saint Kilda Formation Qpah Hindmarsh Clay Qhe Holocene Aeolian Sediments T1 Port Willunga Formation

It should be noted that not all bores within the vicinity of the Assessment Area are listed with a specified purpose(s); the specified purpose does not infer other uses are not possible and further, it is possible that other unknown, unregistered bores are present in the vicinity of the Assessment Area. No additional actions have been undertaken by AECOM to identify if unregistered bores may exist or are in use.

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2.3 Previous investigations The SA EPA provided three reports associated with the Assessment Area or environs: • Environmental Projects, 2020. Preliminary Site History Investigation – Site History, 10-12 Marion Street, Ethelton, South Australia, 20 May 2020. • Golder Associates, 2007, Port Adelaide Waterfront Redevelopment, Groundwater Monitoring and Management Plan, Precinct 1, Port Adelaide, South Australia, 2 February 2007. • SA EPA, 2021, EPA Report, 10-12 Marion Street, Ethelton, March 2021. The SA EPA also provided a copy of the Section 83A notification for 12 Marion Street (25 August 2020), provided by Environmental Projects Pty Ltd.

2.4 Site history summary – former dry cleaners site A site history summary based on the Preliminary Site History Investigation – Site History report (Environmental Projects, 2020) and information provided by the SA EPA is listed below for the former dry cleaners site located at 10 – 12 Marion Street, Ethelton. As early as 1900s the former dry cleaners site was a brewery (Glanville Brewery). The operations at the site changed to large-scale dry cleaning (Bronsons dry cleaners) from as early as the 1920s. In 1996, the site ownership was transferred to Environ Man Pty Ltd; based on information supplied by the SA EPA (SA EPA, 2021), the site was used as a linen laundry but no longer for dry cleaning activities. Bronsons dry cleaners also owned adjacent land at 5-9 Marion Street and 6 Warrawee Road. The historical site activities likely incorporated a broad range of chemical use. Table 2-3 below summarises the CoPC associated with the Potentially Contaminating Activities (PCAs) identified for the site. Table 2-3 PCA and CoPC associated with site operations

PCA Comments CoPC Dry Cleaning The site was listed as a dry cleaners since as Chlorinated solvents. early as the 1920s. Fuel and oil Underground storage tanks were removed for Benzene, toluene, storage the north-western, central and eastern portions ethylbenzene, xylenes of the site. Specific tank contents unknown. (BTEX), phenolic, poly aromatic hydrocarbons (PAH), petroleum hydrocarbons. Brewery The site was listed as brewery as early as 1900s Ethanol, methanol, esters and prior to 1920s Chemical storage Presumably various storage of chemicals across See above. the site.

A figure extracted from the Lotsearch report in the PSI (Environmental Projects, 2020) is shown below (Figure 2-2) and shows the historical businesses identified in the Universal Business Directory (UBD) and Sands and McDougall directory. Bronsons dry cleaners operated at 10 – 12 Marion Street and also at 5 Marion Street Ethelton (1 and 2 in Figure 2-2), located approximately 19 m north of this site and four other dry cleaners (4, 5, 7 and 8 in Figure 2-2) were in operation from 1955 within 143 m north-west, 184 m south-east, 261 m south-west and 296 m north-west of the former dry cleaners site. Nine motor garages and service stations were also listed within 500 m of the former dry cleaners site, with the closest at 42 Deslandes Street which was in operations in 1965 (3 in Figure 2-2).

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Figure 2-2 Historical Business Directories - Dry Cleaners, Motor Garages & Service Stations 1930-1991

2.5 Observations – former dry cleaners site The below observations in relation to site were made by the SA EPA and AECOM during works program. Photos of the former dry cleaners site provided in the SA EPA report (SA EPA, 2021) and taken by AECOM during the investigation are presented in Appendix D. • July to August 2020: Soil, soil vapour and groundwater sampling was conducted by Environmental Projects (as per Section 83A notification). • October 2020: Buildings at the site were demolished. At least five underground storage tanks were removed from the north-western, central and eastern portions of the site. Specific tank contents were unknown although the Safework SA Dangerous Substance Licence search provided by the SA EPA indicated a 0.2 KL class 3 tank. The tank pits were backfilled after removal of the tanks. The Safework SA Dangerous Substance Licence Search is presented in Appendix E. • December 2020: Excavations observed to approximately 1 m deep in the north-western, central and eastern portions of the site. • Early January 2021: Excavations were backfilled. • 10 to 14 January, 21 to 23 January and 3 Feb: Sprinklers were observed in operation at the site, with water pooling apparent at surface.

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3.0 Intrusive investigations

3.1 Data quality objectives As stated in Appendix B of Schedule B2 Guidelines on Site Characterisation, of the National Environment Protection (Assessment of Site Contamination) Measure 1999 (ASC NEPM), the Data Quality Objectives (DQO) process is used to “define the type, quantity, and quality of data needed to support decisions relating to the environmental condition of a site”. The seven DQOs steps for these works are described in Table 3-1 below. Table 3-1 Data Quality Objectives

DQO Step Details of DQO process State the problem Uncertainties exist in relation to the extent CHC impacts in groundwater and soil vapour, and possible offsite risks associated with the impacts. Key issues: • Elevated CHC impact in soil and groundwater has been identified on-site and has not been delineated. Identify goals of the • Characterise nature and extent of groundwater and soil vapour data investigation to contribute to assessment of dissolved phase plume stability and further confirm groundwater flow direction; • Assess potential risks associated with identified impacts. Identify information • Review historical reports, including field and analytical data; inputs • Preliminary groundwater level and salinity gauging of existing wells to the south-west of the Assessment Area, inclusive of well head survey of selected wells, to confirm the local groundwater flow direction. • Installation and sampling of a soil vapour bore network comprising ten new shallow soil vapour monitoring bores, external to the 10-12 Marion Street site and within the EPA Assessment Area. • Installation and sampling of eight new groundwater well monitoring wells, external to the 10-12 Marion Street site and within the EPA Assessment Area, including collection and testing of geotechnical samples at selected location to inform vapour intrusion modelling. • Installation of a graduated surface water gauge on edge of Port River and recording of water elevation. • Gauging of the eight new wells and eight of the existing wells, inclusive of salinity profiling of the water column in five new and five existing wells. Photoionisation detector (PID) head-space screening of each newly installed well prior to sampling. Refer to Figure 2, Appendix A for locations of groundwater wells and soil vapour bores and exiting well network. Define study On-site and off-site groundwater well and soil vapour bore network as boundaries illustrated in Figure 2, Appendix A. The vertical study boundaries are defined as the ground surface to a maximum depth of 10 m bgl. Develop an analytical The primary reference for site contamination assessment in Australia is approach the ASC NEPM (2013). The SA Environment Protection (EP) Act provides a regulatory framework for the investigation and management of contaminated land and waters in SA, with the EP (Water Quality) Policy 2015 (WQEPP (2105)) providing details to support the EP Act and for regulation and management of water quality in SA inland surface waters, marine waters and groundwater. The SA EPA Guidelines for the Assessment and Remediation of Site Contamination (GAR) (revised 2019) details published criteria deemed as appropriate by the SA EPA for assessment of chemical impacts to groundwater. These referenced

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DQO Step Details of DQO process criteria are consistent with the approach outlined in the ASC NEPM and WQEPP. An assessment has been conducted in accordance with the GAR to determine the environmental values for the site groundwater (refer to Appendix J). Analysis of groundwater and soil vapour samples for CoPC. Specify limits on • The potential for significant decision errors is minimised by decision errors completing a robust QA/QC program in accordance with NEPM guideline requirements; and • As advocated by the US EPA and NEPM, professional judgement is used in assessing the suitability/limitations of collected data for interpretive use in determining the contamination status of the site. This includes consideration of data quality control/ assurance measures undertaken to provide information of the accuracy and precision of the laboratory analytical data and also consideration of the analytical data with regard to field/site observations. Refer to Section 4.5 for quality assurance / quality control measures to be implemented in this DSI investigation. Optimise the design Based on the previous Steps 1 to 6 of the DQO process, the design for obtaining the required data (i.e. proposed field and laboratory programs) is presented in Section 3.6 (groundwater assessment) and Section 3.7 (soil vapour assessment).

3.2 Overview and chronology of works The scope and timing of field investigations is summarised in Table 3-2 below. Table 3-2 Overview of field works Investigation Works conducted Date of works element Preliminary Site visit to identify existing wells to 8 November 2020 Investigations south-east of Assessment Area. Groundwater gauging and salinity testing 26 November 2020 of existing well network. Survey of 10 selected existing wells 3 December 2020 (GW121 to GW123, GW125, GW126, GW131, GW137, GW143, GW144 and PGW141A) to enable calculation of groundwater levels and assessment of groundwater flow direction. Soil Vapour Underground service clearance for new 17 December 2020 Investigations soil vapour bores (SV01 to SV10). Installation of 10 new shallow soil vapour 18 December 2020 bores (SV01 to SV10). Based on observed shallow groundwater levels, soil vapour bores were installed to depths of between 0.9 m and 1.2 m bgl. Sampling of the 10 soil vapour bores 22 December 2020 (SV01 to SV10). Survey of location of the 10 new soil 15 January 2021 vapour bores (SV01 to SV10). Collection and disposal of soil (drill 2 January 2021 spoil).

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Investigation Works conducted Date of works element Groundwater Underground service clearance and non- 11 January 2021 Investigations destructive drilling at locations of proposed groundwater wells. Installation and development of 8 new Well Installation groundwater monitoring wells (GW01 to 11 to 14 January 2021 GW08). 6 geotechnical samples were collected from 3 bores GW02, GW05 Well Development: and GW08. 12 to 15 January 2021 Survey of well head elevation and 15 January 2021 location of the 8 new groundwater wells (GW01 to GW08), and installation of a surveyed gauging point in the Port River (RS01) to enable river level gauging concurrent with gauging events. Gauging of all 8 new groundwater 21 January 2021 monitoring wells, 8 selected existing wells (GW121, GW122, GW123, GW125, GW126, GW131, GW137 and GW143), inclusive of salinity measurements with depth in 5 of the newly installed wells (GW01, GW02, GW03, GW05 and GW08) and 5 selected existing wells (GW122, GW125, GW126, GW131 and GW143). PID screening of vapours using an EX- 22 January 2021 CAP fitted to the 8 new groundwater wells (GW01 to GW08). Groundwater sampling (GW01 to GW08) 22 January 2021 using low flow. Two additional grab samples were collected from shallow water in two wells (GW01 and GW02). Gauging of the river gauge (RG01). Collection and disposal of soil (drill spoil) Soil: 2 January 2021 and purge water. Groundwater: 3 February 2021

3.3 Preparatory works 3.3.1 Stakeholder engagement Prior to commencement of works, AECOM liaised with the City of Port Adelaide Enfield for permission for groundwater well and soil vapour bore installations on behalf of the SA EPA. An initial application for “Permit for temporary investigation/ geotechnical/ fencing on council land” issued pursuant to Section 221 and 222 of the Local Government Act 1999 was completed by AECOM and approved by council on 15 December 2021. 3.3.2 Well permits South Australian legislation requires a well permit to be issued for the installation of each individual groundwater monitoring well. Well permits for each of the installed wells were obtained from Department for Environment and Water (DEW) in advance of the intrusive works, and are presented in Appendix F. 3.3.3 Health Safety and Environment Plan A site-specific Safety, Health and Environment Management Plan (SHEMP) was developed for the site to manage risks to the investigation team, subcontractors, site personnel and the broader population,

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as well as risks to the environment, that might arise from the performance of AECOM’s site assessment works.

3.4 Selection of investigation locations AECOM conducted a preliminary groundwater level gauging and salinity gauging of existing wells to the south-west of the Assessment Area, to confirm the local groundwater flow direction to inform selection of investigation locations. This assessment was considered warranted on the basis of conflicting information on groundwater flow as discussed in the Golder Associates GMMP (Golder Associates, 2007). Review of well head elevation data provided in the GMMP against site observations identified the need for an updated well survey, as a number of wells had evidently been modified from standpipe to Gatic in the course of redevelopment of this area. The groundwater gauging results which were salinity corrected (Table 1 and Table 2, Appendix B), showed groundwater flow direction was generally north-west between the Port River and the Assessment Area, consistent with the interpretation presented in the GMMP (Golder Associates, 2007). On this basis, AECOM proceeded with the locations as initially nominated by EPA, subject to minor adjustments based on service location.

3.5 Service location Sure Search was engaged to mark out identifiable underground and aboveground services at all soil vapour bore locations using Dial Before You Dig (DBYD) plans and radio frequency detection. Underground service location works for the soil vapour bore locations were undertaken on 17 December 2020. Due to services restricting access to investigation locations, groundwater well GW04 was moved to the north-west across Deslandes Street and GW08 was moved to the south across Mary Street. Soil vapour bore SV02 was also moved north east across Warrawee Street to avoid services. Pipeline Technology Services (Pipeline) was engaged to mark out identifiable underground and aboveground services at all groundwater well locations using Dial Before You Dig (DBYD) plans and radio frequency detection. Underground service location works for the groundwater well locations were undertaken on 11 January 2021.

3.6 Groundwater investigation 3.6.1 Groundwater well drilling and logging Eight new groundwater wells were installed in January 2021 on public land as part of this investigation. The wells, denoted GW01 to GW08, were distributed with the aim of characterising and delineating groundwater impacts within the SA EPA Assessment Area. The new groundwater well locations are shown on Figure 2, Appendix A. At all locations, boreholes were initially advanced using an air knife and vacuum truck to a nominal depth of 1.5 m (or shallower where natural soil was confirmed) and a diameter greater than the proposed auger hole before proceeding with mechanical drilling, in order to mitigate risk to underground services. The air knife holes were backfilled with sand prior to subsequent drilling. Following the non-destructive drilling, groundwater wells were drilled to target depth and constructed by WB Drilling using truck-mounted drill rigs equipped with push tube and hollow auger facilities. Drilling and well installation was completed in the full-time presence of AECOM field investigators. The encountered stratigraphy was logged by an experienced AECOM field investigator on the basis of recovered core and hollow auger cuttings, with reference to the Unified Soil Classification System (USCS). Soil descriptions for the lithology encountered at each location during drilling are presented in the bore logs in Appendix G. Photographs of core and hollow auger cuttings are presented in Appendix D.

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Soil samples from the surface and changes in lithology and/or regular depth intervals within each soil bore were screened for VOCs using a PID that was calibrated to a known concentration of isobutylene calibration gas. Calibration certificates are provided in Appendix H. PID readings are presented on the borehole logs in Appendix G. Drilling equipment which had contact with soils was decontaminated between groundwater wells with either high-pressure potable water (large equipment) or by hand washing with Decon 90 solution and potable water rinse, at the end of each day at the drillers yard. Soil cuttings were contained in labelled 205 L drums and disposed of by an independent waste disposal contractor (Cleanaway) to a waste disposal facility (Cleanaway Wingfield) in accordance with SA regulations. The waste disposal certificates are presented in Appendix K. 3.6.2 Soil sampling At three locations (GW02, GW05 and GW08) during groundwater monitoring well installation, two undisturbed core samples were obtained using 50 mm diameter thin walled sampling tubes (U50s) to enable geotechnical property testing. The samples were retrieved from the following locations and depths: • Well GW02 at depths of 0.65 m to 1.05 m and 1.05 m to 1.45 m. • Well GW05 at depths of 0.5 m to 0.9 m and 0.9 m to 1.4 m. • Well GW08 at depths of 0.65 m to 1.05 m and 1.05 m to 1.45 m. The samples were sent to the Coffey geotechnical laboratory for analysis for the determination and calculation of bulk density, moisture content, dry density, void ratio, degree of saturation, air and water-filled porosity and specific gravity. The chain of custody (COC) and laboratory certificate of analysis is provided in Appendix L. 3.6.3 Groundwater well construction Groundwater monitoring wells were drilled and installed to 4.0 m bgl. All groundwater wells were constructed using 3 m of 50 mm diameter, Class 18 uPVC threaded screen and blank casing, enclosed in a filter sock to protect against silting, with the water level intersecting the screen for all wells. The wells were completed with sand filter packs to approximately 0.5 m above the screen and sealed with bentonite to the surface. Gatic covers were installed and sealed with concrete flush with the surrounding surface. All well caps were fitted with a well identification labels. Construction details for the groundwater monitoring wells are presented in Appendix G. Photos of the finished wells with well labels are presented in Appendix D. Following installation of the monitoring wells, each well was developed using dedicated disposable bailers, typically by removing a minimum of five bore volumes. Further detail on well development is presented in Section 4.1. Ex-situ measurements of groundwater pH, dissolved oxygen (DO), reduction potential (redox), temperature, and electrical conductivity (EC) were taken following the removal of each bore volume, using a water quality meter. Calibration certificates are provided in Appendix H. Well development sheets are included in Appendix M. 3.6.4 Groundwater well and river gauging Groundwater level gauging of 8 new and 8 existing wells, inclusive of salinity profiling of the water column in 5 new and 5 existing wells was conducted six days after the final well was developed and one day prior to the groundwater sampling. The depth to groundwater at each well was measured from the top of casing using an oil/water interface probe. Salinity was gauged as EC with depth from the top of casing using a Temperature, Level and Conductivity (TLC) meter. The salinity profile of the water column in 5 new and 5 existing wells was recorded by measuring EC just below the surface of the water level, then at 0.5 m increments to the total depth of each well. Well gauging results are provided in Table 1, salinity correction calculations are provided in Table 2, and well salinity profile results are provided in Table 3 (Appendix B).

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To reduce the potential for cross-contamination between bores during gauging and sampling, the interface probe was rinsed with Decon90 and fresh water prior to the commencement of field work and between sampling locations. A graduated surface water gauge was installed on the edge of the Port River by Linkup Construction Surveys on 21 January 2021, to enable recording of the river water elevation. It was gauged by AECOM one the day after the well gauging on the 22 January 2021 at 9:30 am (approximately 15 minutes after high tide) and at 4:20 pm (approximately 1 hour after low tide). The low and high tide times are based on the Outer Harbour tide times predicted in the Bureau of Meteorology (BOM), South Australian tide tables (BOM, 2021). 3.6.5 Groundwater well sampling The new groundwater monitoring wells were sampled on 22 January 2021. Prior to sampling, each well was fitted with an EX-CAP and screened for 10 mins using a PID with 10.6eV lamp. The highest PID reading was recorded. All wells were sampled using the low flow technique in general accordance with the ASC NEPM (1999). Low flow sampling was carried out by pumping each monitoring well at a low flow rate using a peristaltic pump with its intake placed within the screened section of the monitoring well. Each well was purged prior to sampling, and the standing water level in each well was monitored at regular intervals during the purging process to allow the pumping rate to be adjusted with the aim of achieving a stable water level with minimal drawdown, thereby minimising both introduction of air to the groundwater and mobilization of particulate matter from the water table formation. Ex-situ measurements of groundwater pH, Dissolved Oxygen (DO), redox potential, temperature, and Electrical Conductivity (EC) were conducted during the purging process. Sampling was undertaken once field parameters had stabilised. Visual and olfactory evidence of the presence of petroleum hydrocarbons or CHC compounds (where present) were recorded during sampling of all wells. At wells GW01 and GW02, initial grab samples were collected from the uppermost portion of the water column using the peristaltic pump at a low pump rate, prior to conduct of the low flow sampling as described above. These samples were collected due to the salinity profiles in these wells, closest to the former dry cleaners site, appearing to be affected by the observed watering activities. Field parameters of temperature, pH, EC, DO and redox were recorded for these grab samples. Field records are summarised in Table 4 (Appendix B). Copies of the groundwater purge and sampling sheets are provided in Appendix M. To reduce the potential for cross-contamination between bores during gauging and sampling, the interface probe was rinsed with Decon90 and fresh water prior to the commencement of field work and between sampling locations. During low-flow sampling, dedicated water hoses were used at each monitoring well, and the pump was decontaminated with Decon90 prior to use at each monitoring well. 3.6.6 Sample handling and laboratory analysis Groundwater samples were placed in laboratory-supplied bottles and held in chilled conditions pending and during transport. Samples were sent under standard AECOM chain of custody (COC) protocols to Envirolab as the primary laboratory for analysis. A blind coded intra-laboratory duplicate was also sent to Envirolab while and inter-laboratory field duplicate sample was sent to Eurofins-mgt. Samples collected from the groundwater monitoring wells were analysed for the chemical suites detailed in Table 3-2.

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Table 3-3 Groundwater analytical schedule

Well IDs Samples Analyses conducted GW01 to All VOCs, inclusive of volatile halogenated compounds PCE, TCE, GW08 TCA, 1,1-DCE, cis- and trans-1,2-DCE, 1,1-DCA, vinyl chloride, chloroform and carbon tetrachloride. Degradation indicators (ethane, ethene and methane) Total Recoverable Hydrocarbons (TRH)/Total Petroleum Hydrocarbons (TPH) and benzene, toluene, ethylbenzene, xylenes and naphthalene (BTEXN) Metals (As, Ba, Be, B, Cd, Co, Cr, CrVI, Cu, Hg, Pb, Ni, Mo, Mn, Sn, Ag, Zn) Major cations and anions (Na, K, Ca, Mg, Cl, SO4, CO3, HCO3, OH-, Total Alkalinity, F) Nutrients: NO3, NO2, NOx, Reactive P, NH3 TDS

GW01 and Additional VOCs inclusive of volatile halogenated compounds PCE, TCE, GW02 shallow grab TCA, 1,1-DCE, cis- and trans-1,2-DCE, 1,1-DCA, vinyl samples chloride, chloroform and carbon tetrachloride) TRH/TPH and BTEXN Major cations and anions (Na, K, Ca, Mg, Cl, SO4, CO3, HCO3, OH-, Total Alkalinity, F) TDS

Quality assurance/quality control (QA/QC) samples (duplicate, triplicate, field blank, rinsate blank and trip blank) were collected and analysed in accordance with the ASC NEPM. The COC documents and laboratory certificates of analysis are provided in Appendix N. 3.6.7 Waste water disposal Waste groundwater was collected into sealed labelled drums which were disposed of by an independent waste disposal contractor to a waste disposal facility in accordance with SA regulations. Waste disposal certificates are provided in Appendix K.

3.7 Soil vapour investigation 3.7.1 Soil vapour bore installation Ten soil vapour bores were installed in December 2020 at locations denoted SV01 to SV10 by WB Drilling in the full-time presence of an AECOM field scientist. Vapour bores were installed to depths of between 0.9 m and 1.2 m in consideration of the typically shallow depth to water. The locations of the vapour bores are shown on Figure 2 (Appendix A). Selected vapour bores were installed in proximity to planned groundwater monitoring well locations to enable comparison of soil vapour and groundwater concentrations. The paired bores included, SV01 with GW01, SV02 with GW02, SV07 with GW05 and SV09 with GW06. Following service clearance, the vapour bores were advanced to depth using a hand auger. The soil profile encountered during drilling was photographed and logged using visual-tactile methods in accordance with AS1726 (2017) . Borehole logs are presented in Appendix G; core photographs are also included in Appendix D.

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The vapour bores were constructed by setting a piece of ¼” OD Teflon tubing with a stainless steel screen of approximately 200 mm length at the base of the hole, packing with sand to approximately 100 mm above the screen and isolating from the surface using a bentonite seal and cement/bentonite grout to the surface. Each bore was finished at the surface with a concreted flush Gatic cover protecting the upper end of the tubing, which was terminated with a Swagelok fitting. All vapour bores were fitted with a bore identification labels. Soil vapour bore construction details are provided in Appendix G. Photos of the finished wells with well labels are presented in Appendix D. 3.7.2 Soil vapour bore sampling The 10 new soil vapour bores were sampled on 22 December 2020 in accordance with the following procedures: • Each well was screened in the field using a PID and a landfill gas meter for measuring carbon dioxide (CO2), methane (CH4) and oxygen (O2). Field screening was conducted for sufficient time to allow for purging of the well. Calibration certificates for the PID and landfill gas meter are provided in Appendix H. • Leak testing of bores and sample trains was undertaken using a combination of vacuum, helium and isopropanol: - Vacuum line test. With all Teflon lines securely fitted using Swagelok nuts and ferrules, and the valves to the well and to the canister closed, a hand pump was used to evacuate the lines, producing a vacuum of at least -20 inHg. Upon cessation of pumping, the vacuum was monitored for one minute. If unacceptable leaks were detected, fittings were checked, tightened, or replaced and the vacuum test repeated. - Helium gas leak test. The sampling train was passed through a shroud (bucket), which was placed over the well, ensuring an adequate seal with the ground to prevent substantial leakage of the tracer gas. The shroud was filled with the helium tracer gas and the concentration of helium in the sampling train recorded using a helium detector for five minutes. The concentration of helium within the shroud was then recorded. If the concentration in the sampling train was greater than 10% of the shroud concentration then fittings were checked, tightened, or replaced, then re-tested. - Isopropanol leak test. Consistent with the methodology outlined in CRC CARE Technical Report No.23 (CRC CARE, 2013), an isopropanol-soaked cloth was placed under a shroud housing the well head, canister and sampling train. The sample canisters were then laboratory analysed additionally for isopropanol to check for leakage into the sampling train. • Samples were collected into laboratory-certified, evacuated (summa) canisters, equipped with 1- hour flow regulators. Canister valves were closed while the canisters remained under partial vacuum, to enable checking for leaks following transport to the laboratories. Soil vapour purge records are provided in Appendix I. • Samples were sent under standard AECOM COC protocols to Eurofins-mgt as the primary laboratory for analysis. A blind coded intra-laboratory duplicate was also sent to Eurofins-mgt, while inter-laboratory field duplicate samples were sent to Envirolab. • All samples were analysed for CHC compounds (PCE, TCE, TCA, 1,1-DCE, cis- and trans-1,2- DCE, 1,1-DCA, VC, chloroform and carbon tetrachloride), TRH >C6-C10, TRH >C6-C10 minus BTEXN (F1), TRH >C10-C12, BTEXN, hexane, heptane, cyclohexane, trimethylbenzenes) and aliphatic and aromatic volatile petroleum hydrocarbons (VPH). Samples were also analysed for isopropanol for sampling integrity verification. The COCs and laboratory certificates of analysis are provided in Appendix J. 3.7.3 Waste soil disposal Waste soil was collected into sealed labelled drums which were disposed of by an independent waste disposal contractor to a waste disposal facility in accordance with SA regulations. Waste disposal certificates are provided in Appendix K.

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3.8 Groundwater well and soil vapour well survey Selected existing wells to the east and south-east of the Assessment Area were resurveyed by a subcontracted surveyor (LinkUp) on 15 December 2020. New groundwater monitoring wells (GW01 to GW08) and soil vapour bores (SV01 to SV10) were surveyed and the graduated surface water marker on edge of Port River by LinkUp on 21 January 2021. The surface water marker was then gauged at low tide and high tide on the 22 January 2021. The survey results are provided in Appendix O. Groundwater monitoring well construction details and survey information are summarised in Table 1, Appendix B.

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4.0 Quality Assurance and Data Validation This section presents the findings of QA/QC assessments undertaken with respect to both the groundwater and soil vapour monitoring works undertaken. Validation summary reports and tables of field duplicates, laboratory duplicates and matrix spike/matrix spike duplicates are provided in Appendix P.

4.1 Groundwater well installation and development Details of the 8 groundwater monitoring wells (GW01 to GW08) installed as part of this Stage 1 investigation are summarised in Table 1 (Appendix B). All wells were installed to 4.0 m bgl, and all were constructed with a 3 m screened interval at the base of the well. The measured standing water level for all new wells has been recorded within the screened interval. At least five bore volumes were removed from all new wells at least one week prior to sampling. Sufficient inflow was observed to permit sampling using low flow techniques. In all cases, the well construction and development was considered appropriate for the acquired samples to be submitted for analysis.

4.2 Groundwater monitoring well survey data Survey data received for the soil vapour bores and wells was checked and apparent anomalies resolved before use in well location plans and generation of groundwater level contours.

4.3 Soil vapour bore integrity Comprehensive details of vapour sampling integrity checks are presented in the data validation report (Appendix P) attached, with selected details discussed below. 4.3.1 Helium leak test Field records for helium vapour leak testing conducted in December 2020 are summarised in the Soil Vapour Leak Testing table (Appendix P) attached. In accordance with the ITRC5 guidance, a maximum relative helium concentration of 10% within the sampling train compared to the shroud is considered acceptable for sampling (i.e. small leaks are not considered to invalidate the results). The results from the helium leak testing showed no helium was detected in the sampling train, indicating that the integrity of the wells and sampling trains was acceptable. 4.3.2 Isopropanol leak test An assessment of the isopropanol test data from December 2020 vapour bore sampling is made on the basis of the relative concentrations in the sample and the shroud. Consistent with the ITRC (2007) guidance and CRC CARE TR23 (Wright, 2013), a leak of up to 10% (well/ shroud relative) is considered acceptable, and as such a minor leak is not considered to invalidate the data. As can be seen from Soil Vapour Leak Testing table (Appendix P), no leaks of significance were noted (maximum reported well/shroud ratio of 0.002%), and the data is considered suitable for interpretation.

4.4 Soil vapour sampling – canister pressure Laboratory receiving pressures for canister samples were within acceptable ranges, noting that: • All canisters were received by the laboratories with residual vacuums. • All canister vacuums on receipt by the laboratory were sufficiently close to the canister vacuum of completion of sampling for sample integrity to be considered satisfactory. The sample canister for

5 ITRC (2007), Vapor Intrusion Pathway: A Practical Guideline, Interstate Technology and Regulatory Council Vapor Intrusion Team, Jan 2007.

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SV09 was recorded to have a final canister pressure post sampling of -5“Hg, and the laboratory receipt pressure was -2.3“Hg). While this indicates a potential for the SV09 results to be biased low by approximately 11% due to observed vacuum reductions during transit, such differences in reading are not uncommon and considered more likely to be associated with the field gauge accuracy. In any event, this low bias would not have a material influence on the project outcomes.

4.5 Analytical data validation Chain of custody details and laboratory certificates are provided in Appendix J (soil vapour samples) and Appendix N (Groundwater samples). A summary of the laboratory batches is provided in Table 4-1 below. Table 4-1 Sampling and laboratory analysis summary Lab certificate Sample Laboratory Sample date Sample type batch ID technique 765575 Eurofins 22 December 2020 Primary Summa Canisters Soil Vapour 258822 Envirolab 22 December 2020 Secondary Soil Vapour 24174 Envirolab 22 January 2021 Primary Low Flow (GW01 Groundwater to GW08) and grab sample (GW01 and GW02)

769514 Eurofins 22 January 2021 Secondary Low flow Groundwater

The data validation guidelines adopted by AECOM provide a consistent approach for the evaluation of analytical data. These guidelines are based upon data validation guidance published in the ASC NEPM (NEPC, 1999). The process involves the checking of analytical procedure compliance and an assessment of the accuracy and precision of analytical data from a range of QA/QC measures, generated from both the sampling and analytical programs. Specific elements that have been checked and assessed by this project are: • preservation and storage of samples upon collection and during transport to the laboratory; • sample holding times; • use of appropriate analytical and field sampling procedures; • required limits of reporting; • frequency of conducting quality control measurements; • rinsate, field and trip blank results; • laboratory blank results; • field duplicate and triplicate results; • laboratory duplicate results; • matrix spike results; • surrogates spike results; • laboratory control spike and laboratory control spike duplicate results; • continuing calibration verifications; • leak testing (soil vapour);

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• canister pressure (soil vapour); and • the occurrence of apparently unusual or anomalous results, e.g., laboratory results that appear to be inconsistent with field observations or measurements. Validation summary reports and tables of field duplicates, laboratory duplicates and matrix spike/matrix spike duplicates are provided in Appendix P. From this information together with the detailed data validation analysis, it is concluded that the quality of the analytical data is such that it can be used as a basis for interpretation with reference to the comments included in Appendix P.

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5.0 Results

5.1 Introduction This section presents the results of field and laboratory testing of soil, groundwater and soil vapour.

5.2 Soil conditions 5.2.1 Observed soil profile Based on published data (refer Section 2.2.2), soil types across the Assessment Area were anticipated to be Dunes Sand type DS1 sands, which are described as layered old dune sands, generally compact and normally brown colours along with integrated soils and Red Brown Earths type RB5a (Brown clay or sandy clay soils with granular structure over sandy clay with some lime) and RB9 (Mottled silty clay over brown silty clay with granular structure, slight lime, becoming sandy with depth). Based on the borehole logs for groundwater wells and soil vapour bores drilled during the Stage 1 investigation, the soil profile across the Assessment Area was as follows: • Fill: typically gravel to sandy clayey gravel, brown, fine to coarse grained from surface to a maximum depth of 0.8 m depth. • Silty clay to sandy clay; medium plasticity, brown mottled orange, fine to medium grained was observed (as a maximum) between 0.2 m depth and 0.8 m depth. This clay layer was not observed at all locations. • Sand; fine to medium grained, orange brown mottled cream, with trace shell fragments to 1.4 m to 2.6 m depth becoming dark grey with some wood fragments, organic material and hydrogen sulphide odour at to the maximum depth of the bore holes at 4.0 m depth. Bitumen was observed within the fill layer at GW04 from 0.15 m to 0.3 m and a concrete layer was observed within the fill layer at 0.2 m to 0.3 m depth at SV09. 5.2.2 Geotechnical laboratory testing Soil physical property testing results from U50 tubes collected from wells GW02, GW05 and GW08 are presented in Appendix L and summarised in Table 5-1 below. Table 5-1 Summary of Geotechnical Soil Laboratory Results

Sample Sample Soil Soil Bulk Dry Total Water Air Filled % ID Depth (m) Classification Moisture Density Density Porosity Filled Porosity Saturation and (%) (t/m3) (t/m3) Porosity Description 0.65-1.05 Sand 24.8 1.76 1.41 46.333 34.915 11.418 75.36 GW02 1.05-1.45 Sand 27.7 1.93 1.51 41.950 41.905 0.045 99.89

0.50-0.90 Sand 5.3 1.67 1.59 39.870 8.336 31.534 20.91 GW05 0.90-1.40 Sand 3.4 1.54 1.49 43.447 5.094 38.353 11.73

0.50-0.90 Clay 34.4 1.85 1.38 47.431 47.330 0.101 99.79 GW08 0.90-1.40 Sand 45.4 1.68 1.15 55.456 52.348 3.109 94.40

It is noted that although the sampled materials were logged as varying from sand to sandy clay in the field, the testing laboratory summarised the materials as sand and clay. A detailed material classification was outside the testing laboratory’s scope. While the bore logs (Figure 5-1 below and Appendix G) infer very similar geology across these three locations, with sand logged from at most 0.5 m to the depth of the vapour wells, the reported results of the geotechnical testing vary widely. GW05 was reported to have very low moisture contents of 3.4

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and 5.3 wt%; this is well below the conservative moisture contents adopted for sand by CRC CARE Technical Report 10 in conducting vapour modelling to support the NEPM HSLs. In contrast GW02 and GW08 contained samples that were almost fully saturated with water, with moisture contents reported at up to 45% by weight, despite being logged as dry in the field. In the case of the GW08 samples, the shallow sample spanned a thin silty clay section from 0.5-0.7 m bgl, with sand beneath. Discussion with the geotechnical laboratory resulted in them prioritising the clay section of this undisturbed sample. It is noted that both the shallow clay and the underlying sand were reported as almost fully saturated with water. The remaining five samples analysed were similarly logged as sand. Figure 5-1 Geotechnical Testing Bore Logs

A:COM MONITORING WELL GW02 .4;"(0"'4 MONITORING WEL L OWOS 4=CnM MONITORING WELL GWOI F~•-~=~--::~r~.::..,,_•:"1-:-.. =:'' 1=- =. .. -·-- ---·~-- = 1:- =- -- ~·- f! ---~ JI J l_ 1I ~?.i. l If h-· -~~,: J11.!.d ~~ 1bi1-· ~ r-- I~ ='-•-=--= - --='i.':=.i=.... - -- - i I ~=~ .1,<... - - 1.._ hto-::: ~-.::

u -~-= _.. _,._ ., ~::. '" i-::"-.c 1-.::...... ~:.:.- iii.= :.:=-~=- - -I - - I ~ • I 11-< I

5.3 Groundwater field results 5.3.1 Groundwater gauging Description of the site-specific hydrogeology is based on observations made during the site groundwater monitoring and sampling. Findings and observations with respect to the site-specific hydrogeology are summarised in Table 5-2 below. Table 5-2 Hydrogeological summary

Aspect Results Depth to December 2020 groundwater Prior to the installation of the new wells, the SWL of the existing wells located to the east and south-east of the Assessment Area ranged from approximately 2.18 m below ground level (m bgl) (GW123, located immediately east of the Assessment Area) to approximately 4.0 m bgl (GW131, located further east of the Assessment Area). January 2021 The SWL within the Assessment Area ranged from approximately 1.18 m bgl (GW08, located along the southern boundary of the Assessment Area) to approximately 1.90 m bgl (GW03, located in the north-east portion of the Assessment Area). The SWL to the south-east of the Assessment Area ranged from 2.08 m bgl (GW123, located approximately 60m east south-east of the Assessment Area) and 4.05 m bgl (GW131, located approximately 90 m east south-east of the Assessment Area).

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Aspect Results A summary of SWLs in presented in Table 1 (Appendix B).

Groundwater Salinity data was collected for all wells within the assessment area and selected inferred flow wells to the east and south-east of the Assessment Area toward the Port River. direction Groundwater elevations along with salinity corrected groundwater elevations calculated for monitoring wells in the vicinity of the Assessment Area are calculated in Table 2 (Appendix B) and presented on tabulated in Table 1 (Appendix B). Salinity corrected groundwater elevations varied between -0.814 m AHD (GW04, in the north-western portion of the Assessment Area, January 2021) and 0.359 m AHD (GW126, to the south-east of the Assessment Area, November 2020). Inferred groundwater piezometric contours based on salinity corrected groundwater elevations from November 2020 and January 2021 are presented graphically on Figures 3a and 3b, and indicate groundwater flow predominantly north-westerly between the Port River and the Assessment Area. The groundwater flow was consistent across each gauging event. Within the Assessment Area, an elevated SWL was noted for GW01 located immediately to the north of the former dry cleaners site. It is inferred, based on this and the observation of relatively fresh groundwater salinity, that groundwater mounding is present as a result of the apparently substantial watering of the site with sprinkler hoses (which was observed to be in effect several times during the investigation between 10 January and 3 February). This groundwater mounding is likely to be creating radial flow in the vicinity of the former dry cleaners site. It is noted that there is no earlier SWL data for the Assessment Area available to assess the groundwater contours prior to commencement of watering.

Groundwater Based on the inferred groundwater contours for the complete monitoring well hydraulic network presented in Figure 3b (Appendix A), the hydraulic gradient appears gradient to be marginally flatter in the far northern portion of the Assessment Area. An average hydraulic gradient is estimated of the order of 0.005 between the Port River and the Assessment Area. Within the Assessment Area the hydraulic gradient is estimated of the order of 0.01. NAPL presence No NAPL was detected during the gauging of the wells.

5.3.2 Port River Gauging The GMMP suggested groundwater level to the east of the Assessment Area varies as a result of tides in the Port Adelaide River, up to 0.5 m at approximately 20 m distance from the river to 0.05 m at approximately 100 m distance from the river (Golder Associates, 2007). Therefore a river gauge was installed to assess the range of water levels in the river and whether there is a gradient in groundwater levels and the likelihood for migration of impacts of to the river. The Port River gauge was gauged on 22 January 2021 at approximately low tide (-0.7 m AHD) and at approximately high tide (0.52 m AHD) showing an approximate 1.22 m AHD difference in tide height. The tide heights provided on the BOM tide tables for Outer Harbour are based on lowest astronomical tide datum (mLAT) and were 1.95 mLAT at high tide (9:13 am) and 0.57 mLAT at low tide (3:24 pm). Comparison of river gauging data to tidal predications suggests an approximate correction factor of 1.35 m which can be applied to predicted Outer Harbour tide heights in mLAT to estimate corresponding river height to the east of the Assessment Area, noting however that there is uncertainty in the time lag and relative amplitude of tide movements at Outer Harbor and within the Port River. Taking into account these uncertainties, it is apparent that at low tides, the Port Adelaide River level may be lower than the standing water levels measured in the Assessment Area. Despite this, no

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evidence of easterly groundwater flow towards the river from the Assessment Area is apparent, from either gauged groundwater elevations or distribution of impacts, consistent with previous findings reported in the GMMP for the Precinct 1 Port Adelaide Waterfront Development which indicated north- westerly flow even at low tide (Golder Associates, 2007). 5.3.3 Field indications of groundwater impact At each of the newly installed wells (GW01 to GW08), PID headspace screening was conducted by fitting an EXCAP to the wells and monitoring for 10 minutes using a PID. The highest PID reading was recorded at GW01 with a PID reading of 15.2 ppm. All other PID readings were below 1.0 ppm and are noted on the groundwater sampling and purging records presented in Appendix M. No other observations suggesting potential groundwater impacts were noted. Hydrogen sulphide odours were noted at GW02, GW04 and GW06, but are not uncommon for wells installed in the marine St Kilda Formation. 5.3.4 Groundwater field parameters Field parameters measured during well development and groundwater sampling were recorded on the groundwater purge records presented in Appendix M. Field parameters measured during well groundwater sampling are presented in Table 4 (Appendix B) and summarised in Table 5-3 below. Table 5-3 Groundwater field parameters and observations

Parameter Results and comments pH Groundwater pH values generally ranged from approximately 6.11 to 7.08, indicative of generally neutral conditions. Measured pH values were generally consistent for development and sampling. The groundwater well development and sampling records presented in Appendix M. Oxidation/ Redox potential ranged from -94.5 to -31.3 mV indicating typically slightly Reduction reducing conditions. This is with the exception of the shallow water sampled at Potential (ORP) GW01 which was 71.4 mV compared with -79.2 mV sampled deeper in the water column at this location. While these results indicate an anaerobic environment, these redox values may not be low enough to infer ongoing reductive dechlorination of PCE and TCE, with redox potentials generally needing to be closer to those of sulphate reduction (-200 mV) for reductive dechlorination. It is noted however, that the micro-scale redox environment can vary in the subsurface, such that localised conditions may be conducive to degradation. Dissolved DO readings ranged between 0.01 mg/L and 0.69 mg/L and were consistent Oxygen (DO) with expectations – typically higher readings obtained during development of new wells consistent with agitation of the water column, and generally low readings obtained from low flow sampling. This is with the exception of the shallow water sampled at GW01 (on the verge adjacent the site north) which had a DO of 4.46 mg/L compared with a DO of 0.04 mg/L in water sampled deeper in the water column at this location. The high DO for the shallow sample is not considered to be attributable to the sampling method, which was used also for the shallow sample at GW02 which did not indicate elevated DO.

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Parameter Results and comments Electrical Initial SWL and salinity gauging of existing wells east and south-east of the conductivity Assessment Area in November 2020 showed salinity levels generally decreased with distance from the Port River, with EC in the range of 26,900 µS/cm and 75,700 µS/cm. This is with the exception of GW121 which reported a lower TDS of 14,400 µS/cm, potentially due to this well not having a well cap or Gatic plate to protect from surface water infiltration. Salinity profiling was conducted on five newly installed wells and five existing wells and results showed salinity increased with depth in all wells with the exception of wells GW125 and GW126 which were located along the Port River shoreline. GW125 installed to approximately 8.0 m depth was the deeper well of the paired wells and did not vary significantly with depth. GW126 was only installed to approximately 4.3 m depth and slightly decreased in salinity with depth. Salinity levels at GW01 were considerably lower than the other wells that were profiled with EC at approximately 1,200 µS/cm to a depth of approximately 2.5 m depth, then increasing to an EC of 49,500 µS/cm to the depth of the well at 4.0 m bgl. Salinity profiling results are presented in Table 3 (Appendix B). Salinity EC values collected during sampling of the deeper water column ranged from approximately 23,530 µS/cm to 40,970 µS/cm, with an average of approximately 35,000 µS/cm. This is with the exception of the shallow water sampled at GW01 and GW02 which was 1,797 µS/cm and 7,501 µS/cm respectively. The lowest salinity values reported during sampling for the deeper water column were reported for GW01 (28,730 µS/cm) and GW02 (23,529 µS/cm), all other ECs were reported above 32,000 µS/cm. It is noted that laboratory-measured salinity values during sampling of the deeper water column were in close agreement with salinity values estimated from field EC measurements during sampling for the samples tested as presented Table 2 (field measured salinity) and Table 5 (laboratory measured salinity) (Appendix B). The field measured EC with the EC probe during gauging were generally higher than the laboratory and field EC measurements taken during sampling. The widespread presence of a low salinity lens appears currently exaggerated at GW01. This may be due to both direct percolation of rainfall and watering observed at formerly sealed 10-12 Marion Street (now unsealed post demolition) between January and February 2021. The underlying groundwater is more saline, with generally higher salinity values closer to the Port Adelaide River. Temperature Recorded water temperatures ranged from 21.6 to 26.6 degrees Celsius.

5.4 Groundwater laboratory results Groundwater analytical laboratory reports and COC documentation are presented in Appendix J. Graphical presentations for the targeted contaminants of potential concern and tabulated summary results and are presented in Appendix A and Appendix B, respectively. 5.4.1 Screening criteria The following discussion should be read in conjunction with the discussion presented in Appendix P. Determination of groundwater environmental values from WQEPP An assessment of background groundwater salinity was conducted utilising information from the WaterConnect database (Section 2.2.4), field measured salinity, and laboratory results for salinity (Section 5.3.3). Total dissolved solids measurements (excluding the TDS measured at GW01 which is likely affected by the watering of the former dry cleaners site) ranged from approximately 16,645 mg/L (GW02) to 24,600 mg/L (GW03). Salinity profiling showed the average TDS across a variety of depth measurements within the screened section of selected groundwater wells within the Assessment Area and up-gradient to the south-east, indicated that native TDS is better approximated as 16,645 mg/L

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(GW02) to 37,592 mg/L (GW125). However, the potential for beneficial groundwater use cannot be precluded as the WaterConnect data base search returned an average for all registered bores of 1,528 mg/L which suggests potable water. On the basis of this assessment, applicable groundwater environmental values for the site are required to include the following: • drinking water for human consumption; • primary industries (irrigation and general use); • primary industries (livestock); and • primary industries (aquaculture). Determination of environmental values for surface water interaction The following relevant surface water bodies were identified within a 2 km buffer zone of the site as required by the SA EPA publication Guidelines for the assessment and remediation of site contamination (the “GAR”) (SA EPA, 2018): • Port River – marine receptor approximately 150 m east; • Gulf St Vincent – marine receptor approximately 1.5 km west; and • West lakes – marine receptor approximately 530 m south. Accordingly, environmental values for the site are required to include the following: • Aquatic ecosystems (marine); and • Recreational (non-domestic). Assessment of local groundwater use Based on recorded groundwater uses for all registered bores in the vicinity of the Assessment Area, as detailed in Section 2.2.4, environmental values for the site are required to include the following: • drinking water for human consumption – based on 418 bores recording domestic use (DOM) with 144 records reporting operational use; • primary industries (irrigation and general use) – based on 63 bores recording irrigation (IRR) with operational or unknown status (and one bore with equipped status i.e. pump, windmill etc.) and one bore reporting stock use with unknown status; and • recreational – based on one bore recording operational recreational use. The same environmental values would be inferred for consideration of Quaternary bores only. Selection of groundwater assessment criteria Based on the assessment conducted in accordance with the GAR as presented above, the assessment of groundwater is required consider the following environmental values: • Potable use; • Aquatic ecosystem protection (marine); • Recreation and aesthetics (primary and aesthetic); • Agriculture (irrigation); • Agriculture (livestock watering); and • Agriculture (aquaculture). Groundwater assessment criteria appropriate to these environmental values and recognised by the SA EPA have been selected in accordance with the hierarchy presented in Table 2 of Appendix Q, and are shown on the groundwater analytical results tables presented in Appendix B. The World Health Organisation (WHO) Guidelines for Drinking-water Quality are referred to for TCE only, in the absence of other applicable criteria.

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Health Screening Levels (HSLs) for vapour intrusion Reference is also made to the groundwater health screening levels (HSLs) presented in the ASC NEPM (NEPC, 1999). The HSLs adopted for this investigation are based on the presence of industrial/commercial, recreational and residential land uses within the vicinity of the site, with sand soil (for a conservative screening) and with groundwater present at a depth in the range 2-4 m bgl, however groundwater has been gauged shallower within the Assessment Area, between approximately 1.2 m bgl and 1.9 m bgl. The HSLs are shown on the groundwater analytical results tables presented in Appendix B. 5.4.2 Groundwater analytical results 5.4.2.1 Petroleum hydrocarbons and BTEX Groundwater analytical results are assessed against criteria in Table 5, Appendix B. A number of samples reported concentrations of TPH C6-C9 or TRH C6-C10 above the laboratory limits of reporting (LOR). A comparison of total CHC concentrations to TRH C6-C10 concentrations (as plotted in Figure 5.2 below) provides strong evidence that the reported short chain fraction TPH/TRH concentrations are indicative of the presence of CHCs rather than petroleum hydrocarbons, noting also that no BTEX compounds were reported above laboratory LOR for any wells. Figure 5-2 Comparison of total CHCs to TRH C6-C10 in groundwater

Total CHCs vs TRH C6-C10 in Groundwater 1000 r 800 • 600

400

Sum PCE, TCE, DCE, DCA, DCA, DCE, TCE, PCE, Sum

- •

200 VC and chloroform (µg/L) (µg/L) and chloroform VC

0 • 0 200 400 600 800 1000 Total CHCs CHCs Total TRH C6-C10 (less BTEX) (µg/L)

Minor concentrations of longer chain petroleum hydrocarbons (TPH C16-C34/TRH C10-C40) were reported in well GW01 (QC201 only; inter-laboratory duplicate). No TRH concentrations exceeded the commercial/industrial or residential HSLs.

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5.4.2.2 Volatile halogenated compounds CHC results are summarised in Table 5-4 below. Table 5-4 Summary of CHC groundwater analytical results Wells > LOR but below Wells exceeding Analyte Units Min result Max result investigation investigation levels levels Tetrachloroethene µg/L

Wells exceeding Analyte Units Min result Max result investigation levels Arsenic mg/L

Chromium mg/L

Hexavalent mg/L

Lead mg/L

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Wells exceeding Analyte Units Min result Max result investigation levels Manganese mg/L 0.32 7.9 All tested

Molybdenum mg/L 0.004 (GW08) 0.35 (GW01 (QC01)) All tested except GW08

Nickel mg/L

Zinc mg/L

5.4.2.4 Major cations and anions Results for the major cation and anion analysis are presented in Section 6.3.

5.5 Soil vapour field screening Both prior to and following soil vapour sampling from each of the new soil vapour wells, AECOM screened for VOCs using a PID connected to the sampling train. The recorded PID measurements pre- and post-purging are presented in Table 6 (Appendix B), together with measurements of methane, oxygen and carbon dioxide. The PID was equipped with a 10.6 eV lamp, which is suitable for detection of CHCs TCE, PCE, 1,1- and 1,2-DCE and VC. There was observed to be generally reasonable agreement between pre- and post-sampling PID readings.

5.6 Soil vapour laboratory results 5.6.1 Screening criteria The ASC NEPM includes interim soil vapour health investigation levels (HILs) for some chlorinated solvents, including TCE, as well as HSLs for petroleum hydrocarbon and BTEXN compounds. Residential and Commercial/Industrial interim HILs and HSLs have been referenced for this assessment. It is noted that the ASC NEPM does not include a screening criterion for trans-1,2-DCE, however the ASC NEPM introduction to cis-1,2-DCE includes the following assessment of the trans-isomer toxicity: “cis-1,2-DCE is considered to be more toxic than trans-1,2-DCE and hence the HILs derived for the cis-isomer are adequately protective of exposures associated with the trans-isomer”. There are no NEPM soil vapour guidelines for 1,1-DCE, however the US EPA provide an ambient air guideline for residential exposure for 1,1-DCE of 210 µg/m3. Based on application of a conservative, 10-fold soil vapour to indoor air attenuation factor (consistent with the ASC NEPM interim HIL derivation), a soil vapour screening level of 2100 µg/m3 can be derived for 1,1-DCE; similar to the PCE soil vapour interim HIL in the NEPM. 5.6.2 Soil vapour analytical results Laboratory certificates for the analysis of CHCs from summa canister samples are attached as Appendix J. Soil vapour analytical results are assessed against criteria in Table 7, Appendix B. A summary of the results for petroleum hydrocarbon compounds and CHCs for sampling conducted in December 2020 is presented in Table 5-6.

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Table 5-6 Summary of soil vapour analytical results – petroleum hydrocarbons and CHCs Residential Min Bores exceeding CHC Units Max result criteria result residential criteria value TRH C6-C10 (minus µg/m3 < LOR 120,000 180,000 - BTEX)* (SV01) TRH >C10-C16 (minus µg/m3 < LOR 260 (SV07) 130,000 - naphthalene)* Benzene µg/m3 < LOR 48 (SV04) 1,000 - Toluene µg/m3 < LOR 110 (SV04) 1,300,000 - Ethylbenzene µg/m3 < LOR 22 (SV04) 330,000 - Total xylenes µg/m3 < LOR 140 (SV07) 220,000 - Naphthalene µg/m3 < LOR

5.6.3 Comparison of analytical data to field screening results A comparison of AECOM’s reported total CHC concentrations (Sum PCE, TCE, DCE, vinyl chloride and chloroform) to the pre- and post-sampling PID readings is presented in Table 6 (Appendix B). Comparison of PID data (post-sampling) with laboratory measured total CHC concentrations indicates a reasonable correlation, as shown in Figure 5-3 below. PID detects post sampling were reported for SV01 (10.9 ppm) which reported a total CHC concentration of 94,709 µg/m3and SV05 (0.2 ppm) which reported a total CHC concentration of 1,997 µg/m3. While PID screening of soil vapour bores is expected to provide a reasonably reliable semi-quantitative indicator of laboratory CHC results, there is insufficient site data for a confident assessment in this regard.

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Figure 5-3 Comparison of total CHCs in soil vapour samples to post- sampling PID reading

CHCs in Soil Vapour vs Post-Sampling PIO ~ 100000 0 • uf~ 10000 UE I- O> w-2: 1000 • a..UE .... E-2 :::, 0 100 C/) a ' :c (/) 0 10 u - G~ 1 (ii 0.1 10 100 0 I- Pl D Reading Post Sampling (ppm)

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6.0 Discussion

6.1 The Presence of Site Contamination The SA Environment Protection Act (1993) is the primary legislation dealing with Site Contamination in the state. For the purposes of the Act, site contamination exists at a site if — a. chemical substances are present on or below the surface of the site in concentrations above the background concentrations (if any); and b. the chemical substances have, at least in part, come to be present there as a result of an activity at the site or elsewhere; and c. the presence of the chemical substances in those concentrations has resulted in — i. actual or potential harm to the health or safety of human beings that is not trivial, taking into account current or proposed land uses; or ii. actual or potential harm to water that is not trivial; or iii. other actual or potential environmental harm that is not trivial, taking into account current or proposed land uses. The SA EPA[1] considers that actual harm to groundwater that is not trivial has occurred if chemical substances are present • in excess of background concentrations and: - above the water quality criteria for the appropriate protected environmental value; or, where there is no value, - above the laboratory limit of reporting using a laboratory method approved by the SA EPA. Based on the measured concentrations of PCE, TCE and DCE in the water table aquifer adjacent to, and down-gradient of, the 10-12 Marion Rd site, it is assessed that site contamination of groundwater exists in the Assessment Area.

6.2 Detailed assessment of volatile halogenated compound impacts 6.2.1 Generalised conceptual behaviour of chlorinated ethenes Chlorinated ethenes in groundwater If PCE and/or TCE are released into groundwater as dense non-aqueous phase liquid (DNAPL) they tend to sink until they reach a low permeability layer that they cannot penetrate, or until the NAPL mass is reduced (by leaving a ‘trail’ of residual NAPL along the path), such that there is insufficient mass for continued movement of the liquid. However, as the NAPL migrates downward it may also migrate laterally, spreading out in response to localised heterogeneities in the aquifer permeability, as illustrated in Figure 6-1 below. DNAPL may be mobile or present only as residual DNAPL in disconnected pore spaces, or as smearing on soil particles. When DNAPL is in contact with groundwater the contaminants gradually dissolve into the water, creating a dissolved phase ‘plume’ that can then migrate down-gradient with the groundwater as well as, to a lesser extent, diffuse (driven by concentration gradients) in all directions. A ‘rule of thumb’ for assessing whether residual DNAPL may be present near a groundwater monitoring well, based on observed concentrations in the groundwater, is that dissolved concentrations above approximately 1% of the aqueous pure-phase solubility may be indicative of the local presence of DNAPL.6 On this basis, PCE concentrations above approximately 2 mg/L could indicate the presence of DNAPL, while this is approximately 10 mg/L for TCE and 35 mg/L for DCE.

[1] SA EPA (2019) – Guidelines for the assessment and remediation of site contamination, SA Environment Protection Authority 6 US EPA. 1992. Estimating Potential for Occurrence of DNAPL at Superfund Sites. OSWER Publication 9355.4-07FS. National Technical Information Service (NTIS) Order Number PB92-963338CDH.

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In the case of the Ethelton Assessment Area, none of the reported groundwater CHC concentrations are indicative of the potential local presence of DNAPL, with the largest recorded PCE concentration 0.5 mg/L. Figure 6-1 Schematic illustration of DNAPL distribution in unconsolidated deposits7

release

GWflo.,1 pool

dissolved plume residual

DNAPl pool In fractures DNAPL residual In fractures

The more highly chlorinated ethenes (PCE, TCE) are relatively biodegradation resistant (stable) in aerobic (oxygenated) environments. However, under anaerobic (reducing) conditions PCE and TCE can degrade into less-chlorinated ethenes by a process of successive dechlorination, producing daughter products as shown in Figure 6-2. Figure 6-2 Abiotic and biological transformation pathways

PCE CC12=CC1Z 1,1,1-TCA ,,/1 CC13=CH3 TCE / 1'------...------~ ✓✓ I _.,,,.,...,. CC12=CHC1 ~ MMi·,nn oorr M inor .,,,,.,,,.-- ..______~ ~ / I ✓/ I / ,, / I 1,1-DCA ~------, r----=------, /// / CHC12=CH3 trans-1,2-DCE ci s-1,2-DCE * 1,1-DCE ✓ I I CC12=C HC1 CC12=CHCl CC12=CH2 I I I Chloroethane I I CH2Cl=CH3 I vc I / CH2=CHC1 / I / I I I I I I / / ~ Biotic: reactioos Ethene Acetate <- -- Abiotic reactions CH2=C H2 CH2=CH2 * Primary reaction

Ethane CH2=CH2 Ca rbon dioxide, water, chloride Abiotic .and blologi~I trinsformaUon pathwiy5 for seree1ed chlorinined solvents. C02+H20+d- Adilpted from Weldemeier et;.al.1999, Naturo/A rte,rua rlon of Fuels ond Chlorinated Sofvents In the ~ubsurfot.~ John Wiley & son~ roe, USA. 1'3'39.

7 UK Environment Agency (2003) ‘An illustrated handbook of DNAPL transport and fate in the subsurface’, Environment Agency R&D Publication 133

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Therefore, when PCE or TCE are identified as chemicals of concern in environmental investigations, their chlorinated daughter products (DCE and VC) are also of potential concern. Commonly PCE and or TCE are likely to be the principal source chemicals where the chlorinated ethenes have originated from use as degreasing solvents. DCE and VC may then be generated via this reductive dechlorination process. Although there are three forms (isomers) of DCE (1,1-DCE, cis-1,2-DCE and trans-1,2-DCE), the main one to be formed from degradation of TCE is typically cis-1,2-DCE. The measured groundwater conditions across the monitoring network are potentially conducive to ongoing biodegradation of the higher chlorinated ethenes. Excluding the field redox of the shallow water sample collected at GW01, which is considered likely to have been affected by the watering of the source site, the field measured redox potentials were all mildly reducing, averaging approximately - 71 mV. Localised biodegradation is also clearly evident with concentrations of DCE reported in GW01 located immediately adjacent the site to the north and also at GW05 and GW06 which are down gradient of the site to the north-west and west respectively. However, whether the reductive dechlorination is ongoing due to the natural anaerobic environment or whether the presence of petroleum hydrocarbons induced localised and temporary strongly reducing conditions is uncertain. It is noted no vinyl chloride was identified in groundwater or vapour, and this does not suggest ongoing, active reductive dechlorination of DCE. Additional temporal data will likely aid in clarifying this situation. Chlorinated ethenes in vapour US EPA (2012)8 and ITRC (2007)9 provide recent technical guidance summarising expected behaviour of volatile CoPC for the vapour intrusion pathway. For chlorinated ethenes such as PCE, TCE and cis-1,2-DCE, the following summarises the expected generalised behaviour and aids in supporting the adopted investigation approach and consequent assessment. • Chemicals volatilise from impacted soil and/or groundwater and diffuse towards regions of lower chemical concentration (Diffusion). • Soil gas can be drawn into a building due to a number of factors, including barometric pressure changes, wind load, thermal currents, or depressurization from building exhaust fans (Advection). • The rate of movement of vapours into buildings is a difficult value to quantify and depends on the geology, chemical properties, building design, operation and condition, and the pressure differential. • Advective transport is likely to be most significant in the region very close to a basement or a foundation, and soil gas velocities decrease rapidly with increasing distance from the structure. The reach of the building “zone of influence” on soil gas flow is usually less than a few feet (around 1 m), vertically and horizontally.

It is noted that advection may not have a net effect on chronic exposure (i.e. long term), as buildings may also be over-pressurised (as opposed to under-pressurised), thereby reducing the potential for vapour intrusion part of the time. The UK Environment Agency does not recommend generic inclusion of advective flow in its CLEA model10 due to absence of evidence of a sustained driving force for advective flow. • PCE, TCE and, to a lesser extent, cis-1,2-DCE vapours are unlikely to biodegrade to any significant degree while migrating through the vadose zone. The same is not true for VC which can be susceptible to aerobic, vadose zone biodegradation, in a similar manner to that routinely observed for petroleum hydrocarbons. • Soil vapour concentrations can be higher beneath sealed surfaces (such as roads, building slabs) compared to similar depths beneath open surfaces due to build-up beneath the slab.

8 US EPA (2012) Conceptual Model Scenarios for the Vapor Intrusion Pathway, US EPA Office of Solid Waste and Emergency Response (EPA 530-R-10-003), February 2012 9 ITRC (2007) Vapor Intrusion Pathway: A Practical Guideline, Technical and Regulatory Guidance, Interstate Technology and Regulatory Council Vapor Intrusion Team, January 2007 10 UK Environment Agency (2009), Updated Technical Background to the CLEA model, http://www.environment- agency.gov.uk/static/documents/Research/CLEA_Report_-_final.pdf

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• All else being equal, soil vapour concentrations are proportional to source concentrations and soil vapour concentrations will be higher closer to the source. • In general, temporal variability in soil vapour concentrations (at 4 feet/ 1.2 m depth) is relatively minor, having been found to vary by up to only a factor of 2, and seasonal variations are less than a factor of 5. Effects would be expected to be greater closer to the ground surface and greater variation may be apparent during heavy periods of precipitation (ITRC; 2007)11. • Infiltration from rainfall can potentially affect soil vapour concentrations by displacing soil gas, dissolving CHCs and restricting vertical migration. Generally, such soil moisture is unlikely to penetrate to any great depth and samples collected at depths greater than about 3 feet/ 0.9 m (or beneath surface cover) are unlikely to be significantly affected. 6.2.2 Extent and magnitude of CHC groundwater contamination The results of groundwater analyses for CHCs reporting concentrations above laboratory LOR are presented in Figure 5 (Appendix A). PCE and TCE impacts to groundwater were only reported adjacent the site to the north at GW01 in the shallow and deeper water samples and exceeded adopted guidelines. The shallow water sample collected reported the highest concentration of PCE and TCE, suggesting the watering of the former dry cleaners site may be causing enhanced leaching of residual soil impacts from the vadose zone soils and into the water table and off site. Concentrations cis 1,2-DCE in excess of the adopted guidelines were reported at GW01, along with concentrations being reported at GW05 and GW06 down gradient of the site to the north-west and west respectively. DCE concentrations were reported at relatively similar concentration in all three wells where it was detected, between 60 µg/L (GW05) and 220 µg/L (QC201; inter-laboratory duplicate of GW01). The presence of the cis 1,2 DCE isomer as the dominant DCE species is consistent with biodegradation from PCE and/or TCE (Figure 6-2). The PCE and TCE impacts are delineated to less than the laboratory LOR in all directions within the Assessment Area. The DCE impacts to groundwater have not been delineated to below the LOR to the west and north-west of the Assessment Area (Figure 5, Appendix A). 6.2.3 Extent and magnitude of soil vapour impacts Figures 6A and 6B show the distribution of PCE, TCE, DCE and TRH/ BTEXN in soil vapour across the network of soil vapour bores. The following observations are made: • The highest concentrations of CHCs in soil vapour were reported for soil vapour bore (SV01) immediately adjacent the former dry cleaners site at 10-12 Marion Street, with the next highest in soil vapour bore SV06 located to the west. The presence of the highest CHC concentrations in soil vapour at SV01 corresponded to the presence of the highest groundwater concentrations in paired well GW01. • Concentrations of PCE in soil vapour exceeded residential screening levels at soil vapour bore SV01. The PCE impacts have been delineated to below the residential screening levels. • The highest concentration of TCE in soil vapour, exceeding residential screening levels, was reported for vapour well SV01, located adjacent the former dry cleaners site. TCE in soil vapour was also reported exceeding adopted residential screening levels at SV04 to the north-east, SV05 to the north-west and SV06 and SV08 to the west in the vicinity of residential properties, and is not delineated in these directions. No TCE was measured in vapour bore SV07 to the north, down-gradient of the other potential source sites. • The highest concentrations of DCE, exceeding the adopted residential screening levels, were also recorded at SV01. DCE impacts in soil vapour were also reported exceeding the residential screening levels at SV06 and SV09 to the west of Assessment Area in the vicinity of residential properties, and DCE in soil vapour is not delineated below adopted guidelines in this direction. DCE was also reported above the LOR but below the adopted guidelines at SV07 and SV08 to the north-east of the former dry cleaners site. The impacts at SV08 are down-gradient of the

11 ITRC (2001) – Vapor Intrusion Pathway: A Practical Guideline, Interstate Technology & Regulatory Council, January 2007.

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impacts at SV06, however there was no impact at SV05 which lies between SV07 and the former dry cleaners site at 10-12 Marion Street. It is noted that trace levels of volatile petroleum hydrocarbons were identified (albeit at concentrations well below guidelines) in the wells to the north and northwest of the former dry cleaners site at 10-12 Marion Street. The presence of TCE and DCE are consistent with biodegradation of PCE and the presence of some petroleum products would likely facilitate this chlorinated dehalogenation. • Concentrations of chloroform were reported exceeding adopted residential screening levels in soil vapour bore SV01.Concentrations of chloroform were also reported above the LOR but below adopted guidelines at SV02 to the east of the former dry cleaners site and SV05 the north-west of the former dry cleaners site. Concentrations of chloroform in groundwater across the Assessment Area were reported below the laboratory LOR. The concentrations of CHCs in soil vapour are characterised by of maximum concentrations in the vicinity of the former dry cleaners site at 10-12 Marion Street, with lesser concentrations extending to the north-west. There is some potential also for contribution from other source sites to the north-west. It is expected that the soil vapour impacts originate from the groundwater CHC plume, noting that although PCE and TCE groundwater impacts were not observed to be as laterally extensive as the vapour impacts, the low vapour concentrations reported downgradient might be attributable to groundwater concentrations less than the laboratory LOR. 6.2.4 Critical review of soil vapour and CHC groundwater data Comparison of vapour and groundwater data As noted above, at a broad scale, the distribution of groundwater and soil vapour impacts are consistent, and the soil vapour impacts may be generally attributed to volatile emissions from impacted groundwater. Comparison of soil vapour data to theoretical values based on groundwater concentrations A number of the soil vapour bores were installed paired with targeted groundwater wells to assess the relationship between soil vapour and groundwater CHC concentrations. Table 8 (Appendix B) presents a comparison, for paired vapour bores and groundwater wells (SV01/GW01, SV07/GW05 and SV09/GW06), of measured PCE, TCE and DCE soil vapour concentrations to the theoretical maximum soil vapour concentration based on application of Henry’s Law Constant. For the paired samples SV07/GW05 and SV09/GW06, the vapour concentrations were less than 1% of the theoretical maximum. For the similarly purged SV01/GW01 samples, the % is materially higher at 40- 60 % of the theoretical maximum for PCE and TCE. The higher vapour concentrations imply relatively greater impact and higher concentrations in the saturated zone near the top of the water table. Comparison of the shallow and the deep groundwater samples collected at GW01 found higher concentrations of CHC in the fresh, shallow water, compared to the deeper, higher salinity water. This is consistent with the higher vapour concentrations evident at SV01 (both relative and absolute magnitude) and potentially attributable to the substantial irrigation between January and February 2021 of the former dry cleaners site causing leaching CHC from the site into the shallow water table (Plate No 4; Appendix D).

6.3 Other contaminants 6.3.1 Petroleum hydrocarbons Short chain hydrocarbon fractions were reported for groundwater in well GW01 located adjacent the site to the north and groundwater in GW05 and GW06 located immediately down-gradient of site. These concentrations were representative of the CHC impacts. Minor concentrations of BTEXN were reported in soil vapour above the laboratory LOR but below the adopted screening levels in all soil vapour bores with the exception of SV01 located immediately adjacent the former dry cleaners site to the north, SV06 located down-gradient to the north-west and SV10 to the south-wet of the Assessment Area. Due to the absence of BTEXN immediately adjacent the former dry cleaners site it is not expected these impacts are associate with this site.

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Concentrations of 1,2,4-trimethylbenzene were reported above the laboratory LOR at SV05 and SV07 and, 1,3,5-trimethylbenzene was reported at SV07. The impacts at SV07 could potentially be associated with the former motor garage and service station which was in operation at 42 Deslandes Street (adjacent SV07 to the east) in 1965. Minor concentrations of acetone were also reported above the LOR varied concentrations across the Assessment area, with the highest concentrations report at SV01 immediately adjacent the former dry cleaners and SV03 south of the Assessment Area. 6.3.2 Metals A number of the tested metals were present at concentrations above the adopted investigation levels in groundwater. Boron, cobalt and manganese were present widely across the Assessment Area at concentrations above investigation levels. Nickel and zinc were also present across the Assessment Area and were reported above investigation levels at GW05. There was no clear indication of a relationship between the former dry cleaners site or distribution of CHC impacts and the distribution of these metals and they are considered likely to represent background concentrations. Elevated copper and molybdenum concentrations were reported in groundwater adjacent the site at GW01. Molybdenum concentrations in groundwater were reported in all wells across the Assessment Area, however the concentrations were at least 5-fold lower than those at GW01. The distribution of copper and molybdenum impacts reported indicates a possible source in the vicinity of the former dry cleaners site, although no potentially contaminating activities likely to have given rise to these impacts have been identified. The presence of these and other background metals concentrations renders the shallow groundwater chemically unsuitable for potable supply or irrigation use.

6.4 Groundwater chemistry Samples from all wells were analysed for major anions and major cations to provide information on groundwater chemistry across the Assessment Area. The results of the anion/cation analysis are presented graphically on a Piper diagram (Figure 6-3 below). This plots the relative proportions of major ions to enable identification of samples that appear to have different water chemistry. As can be seen from Figure 6-3, the GW01 and GW02 shallow samples appear materially different to the other groundwater wells in the network, with a materially lower proportion of chloride. This is consistent with the much lower salinity observed in these shallow samples, close to the former dry-cleaner.

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Figure 6-3 Comparison of groundwater ionic comparison

W01 ,;:- • GW01_S ~ ,a•.::! ~ ,!i • GW02 If!' .,, '#,,--?·"' ~ er, • GW02_S ...... "~" e GW03 F ", • GW04 ~ ~ ~ \ s," t::, GWOS /1? • GW06 s • GW07 •

GW03

0

100 80 60 40 20 0 0 20 40 60 80 100 Calcium(Ca) Chloride(CI) • Auonde(F)

Fluoride was also analysed for all groundwater samples and only minor variations in concentrations across the site ranging between 0.5 mg/L at GW01 (shallow sample) to 1.6 mg/L at GW02 (deeper sample) were noted. There was no evidence of a relationship with the irrigation of the site and the fluoride concentrations.

Groundwater salinity The TDS plot is shown in Figure 4 (Appendix A) for wells within the vicinity of the Assessment Area. The reduced salinity at GW121 south-east of the Assessment Area is likely due to water infiltration from the surface as there was no well cap or Gatic plate on this well. Reduced TDS immediately adjacent the former dry cleaners site at GW01, is potentially due to the watering of the site, however the reduced salinity at GW06 relative to the remainder of the network, suggests there is a relationship with the CHC impacts in groundwater also extending in this direction (Figure 4). Salinity profiling of groundwater at GW01 and GW02 also showed a less saline lens of water at the surface to approximately 2.5m depth. This is consistent with the TDS plots and the anion/cation analysis for wells within the Assessment Area, suggesting the watering of the site could be affecting the distribution of CHC impacts.

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6.5 Conceptual Site Model A CSM based on investigation data is summarised in Table 6-1 below and presented on Figure 7 (Appendix A). Table 6-1 Conceptual Site Model Site characterisation Assessment The Assessment Area, as defined by the SA EPA, covers approximately 2.8 Area hectares. History of A dry cleaner has operated at the potential source site (10-12 Marion Street, land use Ethelton) which included at least five underground storage tanks. The dry cleaner also owned the nearby 5-9 Marion Street (19 m north of the site) and 6 Warrawee Road (13 m west of the site) that are both now residential, however the specific activities undertaken on these properties is not known. A motor garage and service station was historically present 67 m north-west of the site. Local geology The soil profile across the Assessment Area consists of a gravel to sandy clayey gravel fill layer typically from surface to up to 0.8 m depth. At some locations this was underlain by a silty clay to sandy clay layer to a maximum depth of 0.8 m. The surficial fill (and clay, where present) are underlain by sands of the St Kilda formation, comprising sand, fine to medium grained with trace shell fragments to 1.4 m to 2.6 m depth becoming dark grey with some wood fragments, organic material and hydrogen sulphide odour at to the maximum depth of the bore holes at 4.0 m depth.

Hydrogeology Shallow groundwater is present beneath the Assessment Area at depths ranging from approximately 1.2 m bgl (immediately adjacent the site to the north) to 1.9 m bgl (north-north east of the site). Groundwater typically flows in a north-westerly direction. The average hydraulic gradient is estimated of the order of 0.01 within the Assessment Area. Groundwater mounding was evident around GW01 creating radial flow in the vicinity of this location and is likely associated with the watering of the site which was observed between January. There was no evidence of groundwater flow to the east of the Assessment Area, towards the Port River.

Hydrology The nearest surface water body is the Port River located east across Causeway Road, approximately 150 m from the edge of the Assessment Area. West Lakes is located approximately 550 km south-east of the Assessment Area. The Gulf of St Vincent is located approximately 1.5 km west of the Assessment Area. Preferential There was variable fill across the surface of Assessment Area with a discontinuous pathways silty clay to sandy clay layer beneath. Groundwater lies within a relatively uniform sand aquifer, although potential exists for zones of granular service trench backfill offering higher hydraulic conductivity, although no evidence of such preferential migration has been established.

Identified chemical impacts

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Groundwater CHCs: impacts • Groundwater contaminants include PCE, TCE and 1,2-DCE (cis- and trans-). • PCE reported the highest concentrations and is above adopted guidelines immediately adjacent the site to the north at one location (GW01) and TCE is has also been reported above adopted guidelines at this location. DCE has a broader distribution at measurable concentrations and is above adopted investigation levels immediately adjacent the site and down-hydraulic gradient at two locations (GW05 and GW06) to the north-west. • Groundwater CHC impacts appear to have migrated in a north-westerly direction from the dry cleaners site in accordance with the predominant flow direction associated with the shallow aquifer. • There is potential for contribution from other sites to the north-west of the former dry cleaners at 10-12 Marion Street. Petroleum Hydrocarbons: • No long chain petroleum hydrocarbons or BTEX compounds have been observed in groundwater. Metals: • Dissolved metals including boron, cobalt, copper, manganese and molybdenum are present in groundwater at concentrations exceeding adopted screening levels; in many cases impacts are broadly across the Assessment Area. • The presence of these metals renders the shallow groundwater chemically unsuitable for uses such as aquaculture, and based on results for some wells, for potable supply or irrigation use. Soil vapour CHCs: impacts • Soil vapour CHCs include TCE, PCE, 1,2-DCE (cis- and trans-) and chloroform. Maximum soil vapour concentrations were reported in SV01 corresponding to the groundwater well exhibiting the highest CHC concentrations in groundwater (GW01). • PCE in soil vapour exceeded residential screening levels at one soil vapour bore (SV01) immediately adjacent the former dry cleaners site. The PCE impacts have not been delineated to below the residential screening levels to the north, north-west and north-east. • Concentrations of TCE and DCE in soil vapour exceeding residential screening levels were reported for vapour well SV01, located adjacent the former dry cleaners site. These impacts in soil vapour extend north-west of the former dry cleaners site consistent with in the direction of groundwater flow and are not delineated within the Assessment Area. PID screening of SV01 and SV06 was consistent with the CHC impacts and TCE concentrations in soil vapour at SV01 corresponded to the groundwater well exhibiting the highest concentrations of TCE in groundwater (GW01). • The soil vapour results for CHCs adjacent the site are generally reflective of groundwater impacts and indicative that the groundwater impacts are the likely source of the observed vapour concentrations. Petroleum hydrocarbons: • Reported TRH C6-C10 fractions are reflective of the presence of CHCs. Reported concentrations of TRH C10-C16 and BTEXN fall at least 1.5 orders of magnitude below the Residential criteria. • BTEXN, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and acetone concentrations in soil vapour were all reported above the laboratory LOR but well below the adopted residential guidelines within the Assessment Area. Based on the variable spatial distribution of these impacts, there is no evidence to suggest they are associated with the former dry cleaners site.

Potential exposure pathways

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Contaminants For the purpose of this report, the primary chemicals of potential concern comprise of Potential CHCs, and specifically, the following chlorinated ethenes which have been Concern identified in groundwater and/or soil vapour at concentrations exceeding screening criteria: • PCE • TCE • cis- and trans- 1,2- DCE • chloroform Concentrations of boron, cobalt, copper, manganese and molybdenum exceeded the adopted screening criteria, and are thus included as CoPC.

Suspected The former dry cleaning activities at the site at 10-12 Marion Street are considered source and a likely source of the observed CHC impacts to groundwater and soil vapour affected adjacent the site and in wells and soil vapour bores to the west to north-west. It is media possible that there are contributions from other source sites, including associated with potential former dry cleaning activities at 5 Marion Street and 6 Warrawee Road. Based on the distribution of groundwater and soil vapour impacts immediately to the north-west of 10-12 Marion Street, it is unlikely these other sites are significant sources. Known affected media include shallow groundwater at a depth of between 1.2 m (upper surface) and 4.0 m bgl (maximum well depth), and soil vapour in the vadose zone. Groundwater analytical results provide no indication of the presence of DNAPL at locations investigated. Exposure An “exposure pathway” is a means by which a population or individual (“receptor”) pathways may be exposed to site-derived contaminants. Receptors may be either human (e.g. building occupants) or environmental (e.g. discharge to a river or lake). Potential exposure pathways are evaluated for completeness based on the existence of: • a source of chemical contamination; • a mechanism for release of contaminants from identified sources; • a contaminant retention or transport medium (e.g. soil, air, groundwater etc.); • potential receptors of contamination; and • a mechanism for chemical intake by receptors at the point of exposure (i.e. ingestion, dermal contact or inhalation). Whenever one or more of the exposure pathway elements is missing, the exposure pathway is incomplete that is, if there is contamination present, but no exposure route to receptors, then there no risk to human health and/or the environment.

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Sensitive The following potential receptors are identified. receptors Human: • Current and future occupants of and visitors to residential properties; • Current and future underground trench/maintenance/utility workers; and • Down-gradient groundwater bore users. Ecological: • Groundwater ecosystems within the Assessment Area; and • The aquatic ecosystems of the Port Adelaide River, West Lakes, and the Gulf St Vincent. In general, the potential for exposure to sub-surface derived volatile chemicals in outdoor air is materially less than in indoor air, due to lower concentrations and lower assumed duration of exposure (less time outdoors). Additionally, exposure to receptors other than residents (e.g. occupational workers) is likely to be less than for residents due to reduced exposure time and duration. As such, occupants of residential properties are considered the most sensitive receptor with respect to evaluation of risk through vapour intrusion pathways. Based on the inferred groundwater flow to the north-west, the Port River and West Lakes do not appear to be likely receptors of groundwater from beneath the Assessment Area.

Contaminant The following contaminant transport mechanisms are identified in relation to transport impacts in the shallow groundwater body: mechanisms • Flow within the aquifer to hydraulically down-gradient groundwater wells and potentially to surface water bodies; • Vapour generation and/or flow via subsurface preferential pathways; and Within the broader area of impacted groundwater: • Direct contact with impacted groundwater (use of bores within area of plume); • Incidental ingestion of extracted groundwater; and • Inhalation of vapours (either during extraction/use or through vapour intrusion into buildings or outdoor airspaces).

Assessment of risk Groundwater Measured concentrations of CHCs and selected metals exceed the adopted risks assessment criteria for potable and/or primary contact recreation (assuming 10 x potable criteria) in a number of wells within the Assessment Area. Salinity profiling showed the average TDS across a variety of depth measurements within the screened section of selected groundwater wells within the Assessment Area and up-gradient to the south-east, indicated that native TDS is better approximated as 16,645 mg/L (GW02) to 37,592 mg/L (GW125). However, the potential for beneficial groundwater use cannot be precluded on the basis of one groundwater monitoring event as the WaterConnect data base search returned an average of 1,528 mg/L which suggests potable water. The generally elevated salinity, and the presence of CHC impacts and various metals concentrations across the Assessment Area render the shallow groundwater chemically unsuitable for uses such as aquaculture, potable supply or irrigation use.

Vapour Vapour intrusion risks are considered quantitatively in Section 7. intrusion risks

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Complete exposure pathways: Identified Based on the results of this investigation, and taking into account available pathways and historical information and DEW (2021) WaterConnect bore information, the areas of following complete exposure pathways, and associated risks, are possible for the potential risk Ethelton Assessment Area: • exposure (direct contact, incidental ingestion and/or inhalation of vapours) during use of groundwater for domestic (e.g. drinking water, plumbing, garden irrigation) and/or recreational (e.g. filling of swimming pools/spas) purposes; • vapour intrusion into indoor air within a number of residential properties; • vapour intrusion into residential cellars/basements (if present; assumed unlikely based on shallow depth to groundwater); and • vapour intrusion risk to trench/maintenance/utility workers.

6.6 Data gaps and uncertainties The following data gaps relevant to the assessment are noted: • Concentrations of CHCs in groundwater have been delineated to below adopted screening criteria in all directions within the Assessment Area with the exception of DCE impacts in groundwater to the west of GW05 and GW06 along the western boundary, where there are marginal exceedances of drinking water guidelines. • There is no temporal data with which to consider contaminant concentration changes over time and no assessment as to whether the CHC plume is shrinking, stable or expanding can be made. • Groundwater contours across the Assessment Area have been inferred only from water levels gauged during a period of irrigation of the former dry cleaners site, which is also currently bare earth and subject to infiltration not previously possible. Further gauging events in the absence of site irrigation may enable understanding of the more typical groundwater flow in the area. It is noted also that it is unclear to what extent the operation of the Hart Street stormwater pumping station may be impacting local groundwater flow, although the overall flow direction has been noted to be consistent with previous findings. • Limited discrete sampling of groundwater identified vertical heterogeneity in chlorinated ethene concentrations, with materially higher concentrations present in shallow grab samples, compared to traditionally purged samples. This infers solvent impacts are located preferentially in the observed fresh-water lens, close to the former dry-cleaner site; however, vertically-discrete sampling was limited to shallow (relatively fresh water) grab samples in two wells and therefore limited data exists regarding the spatial extent, temporal changes or relative magnitudes of this apparent vertical heterogeneity. Additional temporal data and discrete sampling above and below the freshwater-saline water interface would aid in clarifying the significance of the apparent influence of preferential irrigation of the former dry cleaners site on vapour intrusion risks. • While site-specific geological testing was undertaken to inform vapour modelling at the site, the obtained data (particularly moisture content, a key parameter) was highly variable in otherwise similarly logged materials, with the measured results lying at both the high and low extremes of physically possible data. This inconsistency in results was addressed via adoption of more moderate literature values for key input parameters, considered to provide realistic, but appropriately conservative values, as well as by sensitivity analysis. Avoiding the use of water lancing when using non-destructive digging in sands would reduce the risk of artificially wetting soils. While there are always practical constraints with bore locations, targeting samples from beneath sealed ground would also be of value in better mimicking expected moisture profiles beneath buildings. • Soil vapour analysis is limited to one round of monitoring, such that temporal and seasonal variability has not been assessed. It is noted also that the soil vapour samples were collected approximately one month prior to the groundwater samples in this investigation. If the environment is relatively dynamic, potentially due to preferential recharge in some areas of the Assessment Area , such that direct percolation of both rainfall and applied irrigation water observed at formerly sealed 10-12 Marion Street (now unsealed post demolition) between

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January and February 2021, this may materially affect measured concentrations and associated risk estimates. • It is noted that there was no data collected on private properties as part of this investigation, including at the former dry cleaners site. As such, the spatial boundaries of the interpolated risk contours (in the figure above) are subject to some uncertainty, particularly towards the residential properties to the west and south-west of the former dry cleaners. If materially higher COPC concentrations were identified at the 10-12 Marion Street property, this could alter the risk assessment conclusions for these surrounding properties.

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7.0 Vapour intrusion risk

7.1 Introduction This section builds on the qualitative conceptual site model (Table 6-1) to quantitatively consider the potentially complete and significant exposure pathway of vapour intrusion. It uses vapour modelling from measured sub-surface concentrations to establish whether identified soil vapour concentrations may represent unacceptable vapour risks to building occupants and other identified receptors comprising: • Current and future occupants of residential properties • Current and future underground trench/maintenance/utility workers. While the source of the measured vapour impacts is noted to be groundwater concentrations, modelling has not been undertaken from groundwater. As discussed in Section 6.1.4, there is a vertical concentration gradient apparent, with higher groundwater concentrations evident in the fresh- water lens in GW01. Equilibrium vapour concentrations are also very low compared to the theoretical maximum based on groundwater concentrations and Henry’s Law at wells away from the former dry- cleaner site (Section 6.1.4). This may infer the observed fresh-water lens is less impacted with CHCs compared to the bulk, away from the former dry-cleaner site. As such, it was not considered appropriate to model vapour intrusion risks from groundwater, given that the observed vapour concentrations were so far below equilibrium levels and modelling based on groundwater would therefore overestimate apparent vapour risks over the majority of the plume. Soil vapour concentrations have been used in preference as the assumed vapour source, and this approach is consistent with NEPM guidance.

7.2 Toxicity Assessment The ASC NEPM adopts inhalation toxicity data based on several sources for TCE, and cis-1,2-DCE. A detailed toxicity review and assessment for these chlorinated hydrocarbons is included in the ASC NEPM Schedule B7, Appendix 6, available from the Australian Government Website12. The adopted toxicity data, as advocated in the NEPM, is summarised in Table 7-1 below. Table 7-1 Chlorinated COPC Toxicity Data Summary (NEPC 2013)

Threshold Risk Chemical of Potential Critical Effect Summary Value or Ref Concern Guideline Perchloroethene Tolerable concentration in air derived on the basis of 0.2 mg/m3 WHO the most sensitive endpoint, namely neurotoxicological 2006 effects. LOAEC of 20 mg/m3 from an occupational inhalation study and an uncertainty factor of 100.

It is noted that the slightly more conservative US EPA (2012) RfC of 0.04 mg/m3 was considered in the NEPM. The NEPM concluded that the WHO and US EPA studies considered the same key studies and the main difference between the derived guidelines related to the adoption of uncertainty factors. The WHO derivation was assessed as consistent with Australian approaches and appropriate for derivation of soil vapour HILs. Trichloroethene Inhalation Unit Risk based on non-Hodgkin’s Unit Risk = US EPA (carcinogenic affects – lymphoma, renal cell carcinoma and liver tumours in 0.004 (mg/m3)-1 2011 non-threshold) humans (epidemiological), with a 4-fold adjustment for multiple tumour sites.

12 http://www.comlaw.gov.au/Details/F2013C00288/Html/Volume_15

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Threshold Risk Chemical of Potential Critical Effect Summary Value or Ref Concern Guideline Trichloroethene (non- RfC based on route-extrapolation from, and oral studies 0.002 mg/m3 US EPA carcinogenic affects – for, the critical effects of heart malformations in rats and 2011 threshold) immunotoxicity in mice, and incorporation of uncertainty factors ranging from 10 to 100. cis-1,2-Dichloroethene Inhalation value obtained from extrapolation from oral 0.007 mg/m3 US EPA US EPA value. A review of genotoxicity by WHO (2011) 2010 provided unclear results. A review conducted by the US EPA (2010) suggested that overall, 1,2-DCE is not genotoxic or mutagenic. On this basis, the NEPC considers the adoption of a threshold dose-response appropriate.

7.3 Quantitative Exposure Assessment 7.3.1 Introduction This section outlines quantitative vapour intrusion modelling and sensitivity analysis undertaken to assess the potential for human health risk associated with the presence of CHC impacts in the subsurface. Modelling has been undertaken using an inhouse model “RiskE” for slab on ground properties and the US EPA (2017) Excel-spreadsheet-based model for crawl-space homes. Both spreadsheets use the Johnson and Ettinger (J&E) algorithms and spreadsheets incorporating the assumptions and calculations are also included in Appendix R. 7.3.2 Scope of Modelling Two generic, residential building construction types are contemplated in modelling of vapour intrusion for this assessment: • Slab-on-ground (typically a concrete “stiffened raft” footing or strip footings and concrete floor slab poured on the ground surface) • Timber floor with crawlspace (where the timber floor is supported typically from concrete strip footings or stumps, such that a shallow (generally ventilated) crawlspace is present between the ground surface and the timber floor structure) Due to the shallow depth to groundwater observed at the site (1.1-1.9 m bgl; Section 5.3.1), the presence of basements has not been modelled. The standard assumption for a basement is 2.4 m deep, and this would mean basement floors would likely be well below the water table in the vicinity of the site and therefore unlikely to be practical. It is noted however, that no site specific information has been sought on the presence of basements. In addition, the following Commercial vapour intrusion exposure scenarios are considered: • Excavation workers. As noted above, modelling has been undertaken based on measured concentrations in soil vapour. 7.3.3 Estimating Exposure Concentrations 7.3.3.1 Introduction In order to evaluate the risks to human health via inhalation of vapours it is necessary to estimate an exposure point concentration for each COPC. The exposure point concentration is calculated as a concentration (expressed as µg/m3) in air within the breathing zone of the receptor. For different exposure pathways the exposure point breathing zone may be indoor air (ground floor or basement), outdoor air or within an excavation or utility pit. The exposure point concentration in the case of indoor

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air may be estimated via a number of different methods depending on the data available. These methods are discussed below. 7.3.3.2 Groundwater Source Concentrations This method involves modelling indoor air concentrations using measured groundwater concentrations and information on overlying soils and relevant buildings. This modelling is typically conducted using the J&E vapour transport model (USEPA, 2017)13 and also as documented in ASTM 1739-95 (2010)14 and comprises the following four distinct steps (listed here in relation to a concrete slab-on-ground scenario): • Modelling the partitioning of the volatile contaminant between the aqueous phase in groundwater and the vapour phase immediately above the water table using Henry’s Law. • Modelling the migration of contaminant vapours upwards through the unsaturated zone soils to beneath the concrete slab underlying the building. • Modelling the migration of contaminant vapours through the concrete slab into the building, or via a subfloor crawl-space with underlying dirt floor. • Modelling the dilution of the contaminant vapours within indoor air on the basis of the air exchange (ventilation) rates within the building. This process involves the use of a series of assumptions and conservative simplifications of complex process at each stage of the modelling process, and consequently typically provides an overestimate of actual indoor air concentrations. Measured groundwater concentrations have not been used as modelling inputs for this investigation, as outlined in Section 7.1, above. 7.3.3.3 Soil Vapour Source Concentrations The use of measured soil vapour concentrations from within the unsaturated zone in conjunction with the J&E model reduces the uncertainty to some extent by removing the need to model the partitioning process (Step 1 above). While the uncertainty inherent in Step 2 (migration through the unsaturated zone) can also be reduced by using soil vapour data obtained from relatively shallow depths close to the depth of the building foundation (including sub-slab data), it should be noted however, that concentrations at shallower depth are likely to be more variable over time than deeper soil vapour samples. In addition, the inherent assumption implicit in using soil vapour data as a source term, is that the source of the impacts is present at the depth of the vapour sample and this can overemphasise the role of advection (over diffusion), particularly where the vapour data is shallow, as advection is a near surface phenomenon. The J&E model is used to model migration from the point of measurement through the soil profile to the slab (or crawl-space), through the building foundations, and dilution within the building. Measured soil vapour concentrations of TCE from 1 m (Table 7) have been used as modelling inputs. 7.3.3.4 Direct Measurement of Indoor Air Concentrations The final method for assessing concentrations of COPC in indoor air is via direct measurement. This can be conducted using a number of methods including adsorbent tubes and evacuated canisters. Direct measurement of indoor air concentrations has the great advantage of removing the need for mathematical modelling of partitioning, migration and dilution processes; however, there are a number of factors which make the process of obtaining a truly representative sample of indoor air problematic. These factors include: • Temporal variations in indoor air concentrations due to variations in ventilation regimes within the building and variations in atmospheric conditions.

13 USEPA, 2017. Documentation for EPA’s Implementation of the Johnson and Ettinger Model to Evaluate Site Specific Vapor Intrusion in Buildings, V6.0, September. 14 ASTM (2010), Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites E1739-95, ASTM International, Reapproved 2010

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• Spatial variations within a given building due to the influence of preferential migration pathways such as drains and service lines. • Non-site related sources of COPC. The principal COPC for this investigation (PCE and TCE) are used in a range of consumer products and processes such as dry-cleaning, aerosol paints, degreasers, automotive chemicals, furniture polish and cleaners that may be present in homes and workplaces. Consequently, there is scope for indoor air sampling to be affected by sources present in the home, such that reported concentrations of COPC in indoor air may be unrelated to site-derived contamination. No direct measurement of COPC concentrations in indoor air was undertaken for this investigation. 7.3.4 Vapour Modelling 7.3.4.1 Introduction The J&E vapour transport model (USEPA, 2017) has been used to estimate the potential concentrations of volatile COPC within residential buildings above impacts identified in groundwater. 7.3.4.2 Residential Buildings As noted above, parameters in the model were adjusted to characterise emissions into two types of buildings: • Buildings constructed on a concrete slab at ground level • Buildings constructed with a raised (uninhabited) crawl space. The model incorporates pressure-driven (advective) flows into the building, such as those associated with wind effects on the structure, stack effects due to heating or unbalanced mechanical ventilation. Advection is noted by US EPA to be a near surface phenomenon. The model also identifies, based on the geology, depth to source and building parameters, whether advection or diffusion provides the rate limiting step for vapour intrusion. For crawl space homes, the model does not assume a pressure differential to drive advective flows. Based on the available data set, the modelling has been undertaken using the 1-1.2 m deep vapour concentrations Given that a soil vapour source term has been used rather than a groundwater source, the model has been adjusted so that the measured soil vapour concentration at the relevant vapour well depth is entered as the source term, rather than using a soil vapour concentration calculated via partitioning from the groundwater source via Henry’s Law. It is noted that shallow vapour concentrations are potentially more prone to temporal variability than groundwater impacts or deep soil vapour and the assumption of a shallow vapour source ignores the potentially rate limiting step of contaminants having to diffuse more slowly up to this depth from a deeper source. 7.3.4.3 Intrusive Workers in excavations Potential vapour intrusion risks to excavation workers were assessed via modelling from the measured soil vapour concentrations. The approach used mirrored that used by CRC CARE in deriving an effective trench exchange rate based on conservative assumptions for wind speed (one-tenth of default outdoor air) and assuming a 1 m deep trench, above groundwater impacts. 7.3.5 Geological Assumptions The generalised soil profile logged during drilling works across the Assessment Area is summarised in Section 5.2.1. Based on the borehole logs for groundwater wells and soil vapour bores drilled during the Stage 1 investigation, the soil profile across the Assessment Area was as follows: • Fill: typically gravel to sandy clayey gravel, brown, fine to coarse grained from surface to a maximum depth of 0.8 m depth. • Silty clay to sandy clay; medium plasticity, brown mottled orange, fine to medium grained was observed (as a maximum) between 0.2 m depth and 0.8 m depth. This clay layer was not observed at all locations.

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• Sand; fine to medium grained, orange brown mottled cream, with trace shell fragments to 1.4 m to 2.6 m depth becoming dark grey with some wood fragments, organic material and hydrogen sulphide odour at to the maximum depth of the bore holes at 4.0 m depth. The depth to groundwater across the investigation area ranged from 1.18 m in GW08 to 1.90 m in GW03, however it is noted that these two wells lie outside the identified contamination plume (to the northeast and south of the former dry-cleaner, respectively. The average groundwater level across the CHC-impacted portion of the assessment area was approximately 1.5 m bgl, with the shallowest depth to water (1.28 m) being at GW01, immediately adjacent to the former dry-cleaner. This relatively shallow depth appears to have been influenced by preferential freshwater recharge from irrigation of the former dry-cleaner. Table 7-2 provides the generalise soil profile used for vapour modelling at the site. While fill was identified to a depth of up to 0.8 m, this fill was generally sand and gravelly sand. It is unlikely to be materially different in terms of porosity and vapour migration than natural sands and no site-specific geotechnical data exists for the fill. A conservative assumption of greater pore space and lower moisture content has been attributed to a shallow fill layer to represent potential backfill gravels beneath a slab. A single Stratum B geology, with a depth of 1.1. m was adopted for crawl-space properties (refer Section 7.5.2). Table 7-2: Generalised soil profile observed across Assessment Area for Vapour Modelling

Stratum Depth Range Soil type A 0 – 0.1 Sand, Gravelly Sand B 0.1 – 1.1 (vapour well depth) Sand, Sandy Clay

As discussed in Section 5.2.2, the reported geotechnical data from three vapour wells at the site was highly variable with regard to moisture content; ranging from essentially fully saturated to extremely dry, in soils that were logged as essentially identical sands. As the vapour transport models are highly sensitive to soil moisture, this site-specific data is not considered sufficiently reliable for interpretive use and, as such, the modelling has instead been based on default geological parameters consistent with the derivation of the HSLs in the NEPM in CRC CARE Technical Report 10 (2011). The adopted geological parameters based on the calibration process are presented in Table 7-3. Section 7.5.3 considers the site-specific data further as part of a sensitivity analysis. Table 7-3: Adopted geological parameters – slab on ground residential properties

Parameter Adopted Value Unit Source Strata A – Fill Thickness 0.1 m As per Table 7.2 Total Porosity 0.396 - Water Filled Porosity 0.032 - Air Filled Porosity 0.364 - CRC CARE (2011) Bulk Density 1.6 g/cm3 Saturation 8 % Strata B – Sand Thickness 1 m As per Table 7.2 Total Porosity 0.387 - Water Filled Porosity 0.130 - CRC CARE (2011) Air Filled Porosity 0.257 - Bulk Density 1.625 g/cm3

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Parameter Adopted Value Unit Source Saturation 34 % Capillary Fringe Height 0.2 m Capillary Fringe Water Filled Porosity 0.348 - Capillary Fringe Air Filled Porosity 0.039 - Capillary Fringe Saturation 90 %

7.3.5.1 Building Assumptions Table 7-4 presents the building assumptions made for each modelling scenario. Generic values have largely been adopted from CRC CARE (TR10).

One variation from the CRC CARE generic values is the adoption of the US EPA generic Qsoil/Qbuilding ratio of 0.003 (as recommended in US EPA, 2017) for crawl-space buildings, compared to the CRC th CARE value of 0.005. The US EPA value the 50 percentile (median) sub slab attenuation value as calculated from the US EPAs Vapour Intrusion Database.

The effect of variation of Qsoil/Qbuilding is assessed as part of the sensitivity analysis in Section 7.5. Table 7-4: Building Assumptions – residential slab on ground properties Adapted Parameter Symbol Source Value Residential Slab on Ground Depth below grade to base of Lb foundation 0.1 m

Foundation thickness Lf 0.1 m

Fraction of foundation area with cracks eta 0.001 - CRC CARE (2011) Enclosed space floor area Abf 150 m2

Enclosed space mixing height Hb 2.4 m

Indoor air exchange rate ach 0.6 1/hr

Qsoil/Qbuilding (Generic Ratio) Qsoil_Qb 0.005 - Calculated as:

3 Building Ventilation Rate Qb 216 m /hr 퐴푏푓 ∗ 퐻푏 ∗ 푎푐ℎ

Calculated as: Average vapour flow rate into building Qsoil 0.65 m3/hr Qsoil_Qb * Qb

Residential Crawl Space / Dirt Floor Depth below grade to base of Assumed based on typical Lb foundation 0.0 m South Australian home construction. Foundation thickness Lf 0.0 m

Fraction of foundation area with cracks eta 1 - US EPA (2017)

Qsoil/Qbuilding (Generic Ratio) Qsoil_Qb 0.003 - US EPA (2017)

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Adapted Parameter Symbol Source Value Enclosed space floor area Abf 150 m2 CRC CARE (2011) Adopted based on CRC CARE (2011) living space for slab on ground homes. Enclosed space mixing height Hb 2.4 m This assumption assumes no ventilation within the crawl space area. Indoor air exchange rate ach 0.6 1/hr CRC CARE (2011)

Building Ventilation Rate Calculated as: Qb 216 m3/hr 퐴푏푓 ∗ 퐻푏 ∗ 푎푐ℎ

Commercial Trench Worker Depth below grade to base of Lb foundation 1.0 m

Foundation thickness Lf 0.0 m Fraction of foundation area with cracks eta 1 - CRC CARE (2011) Enclosed space floor area Abf 10 m2

Enclosed space mixing height Hb 1 m

Indoor air exchange rate ach 87.5 1/hr

Ventilation Rate Calculated as: Qb 875 m3/hr 퐴푏푓 ∗ 퐻푏 ∗ 푎푐ℎ

7.4 Risk Characterisation 7.4.1 Methods for Quantifying Risks to Human Health Risk characterisation is the final step in a quantitative risk assessment. It involves the incorporation of the exposure assessment and toxicity assessment to provide a quantitative assessment of potential health risks. In the assessment presented, evaluation of exposures to the COPC generally involves an assessment of threshold (non-carcinogenic) and non-threshold (carcinogenic) risks. The calculation of risks has been undertaken using an in-house spreadsheet model. The equations utilised within RiskE apply risk assessment methodology as outlined in Appendix R, following protocols established by enHealth and USEPA. The output from this model has been incorporated into the tables presented in the text of the report and into the calculation sheets contained in Appendix R. 7.4.2 Hazard Index for Threshold Effects The potential for adverse threshold effects resulting from inhalation exposure to an individual COPC, is evaluated by comparing an exposure concentration with the adopted guideline, Threshold Risk Value

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(TRV) or Reference Concentration (RfC). The resulting ratio is referred to by the USEPA as the hazard quotient (USEPA, 1989)15 and is derived in the following manner for inhalation exposures: Hazard Quotient (HQ) = Exposure Concentration in Air / (RfC – Background) If the exposure concentration in air for the individual COPC exceeds the RfC with consideration of background intakes, (i.e., if the hazard quotient exceeds one), this indicates potentially unacceptable exposures. The hazard quotient does not represent a statistical probability of an effect occurring. To assess the overall potential for adverse health effects posed by simultaneous exposure to multiple chemicals, the hazard quotients for each chemical and exposure pathway are summed. The resulting sum is referred to by the USEPA as the hazard index (HI). The HI approach assumes that multiple sub-threshold exposures to several chemicals could result in a cumulative adverse health effect, and exposures are summed over all intake routes. 7.4.3 Acceptable Risk For TCE-specific vapour intrusion assessment, the SA EPA and SA Health collaborated in development of Indoor Air Level Response Ranges. These indoor air concentration ranges are presented in Figure 7-1, below. The TRV or RfC for TCE of 2 µg/m3 (Section 7.2) was adopted as the upper end of the “Validation” range, where concentrations are deemed safe, but ongoing monitoring may be appropriate. TCE results up to one order of magnitude above this concentration (20 µg/m3) fell into the “Investigation” range, wherein although no immediate health concerns were considered to be associated with such levels, further assessment was required. These concentrations (2 and 20 µg/m3 TCE) are equivalent to Hazard Indices of 1 and 10. An “acceptable” risk in this assessment has been defined as a Hazard Index no greater than 1.0 (as per risk assessment industry practice, supported by protocols outlined in enHealth (2012) and USEPA guidance). TCE concentrations above 20 µg/m3 (HQ = 10) fall into the intervention range, warranting follow up action. It is noted that there is currently no equivalent SA Health/EPA Response Range guidance for the related chlorinated ethenes PCE16 and DCE, identified along with TCE at this site (nor for vinyl chloride), however an equivalent framework to Figure 7-1 has been adopted here, based on the Hazard Index. A Hazard Quotient of <1 indicates the exposure point concentration falls below the reference concentration for that chemical. For each exposure scenario, Hazard Quotients for each of the three chemicals of potential concern (PCE, TCE, cis-1,2-DCE) are summed to provide a Hazard Index. This approach (additivity) is consistent with a screening level approach recommended in enHealth (2012). Accordingly: • Where the Hazard Index for the CoPC for any modelled scenario is <1, this is considered to be equivalent to results within the “Validation” range of the SA EPA/SA Health Indoor Air Level Response Range. • Where the Hazard Index for the CoPC for any modelled scenario is >1 but <10, this is considered to be equivalent to results within the “Investigation” range of the SA EPA/SA Health Indoor Air Level Response Range. • Where the sum of Hazard Index for the CoPC for any modelled scenario is >10 but <100, this might be considered to be equivalent to results within the “Intervention” range of the SA EPA/SA

15 United States Environment Protection Agency (US EPA) 1989. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual. Interim Final, Office of Emergency and Remedial Response, US EPA, Washington DC. OSWER Directive 9285.7-0/a.

16 An Interim PCE Response Range has been adopted by the SA EPA in the case of the Brighton Assessment Area but is not yet widely endorsed (https://www.epa.sa.gov.au/files/14159_brighton_pce_interim_indoor_air_range.pdf)

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Health Indoor Air Level Response Range, indicative of a potential health risk and warranting further action. All hazard quotient and hazard index calculations are presented in Appendix R. Figure 7-1 SA EPA TCE Response Ranges

Indoor Air Lose!, Nothing det£.,.>.<,:t-cd

Indoor Air Level: Above de!E-Chon - less U-,n 2 (pgi m 'I

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Indoor Air Levet 2 - less rr.an 20 (pg/111 ')

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Indoor Air L1tvet 20 - less lhiln 200 (µgin, i

Intervention

.Accelerated ' 1\IOJ9i!-D ,~llllo. .. ,Intervention . -"""'°""'~~ ....~~ ·

7.4.4 Modelling Conclusions - Residential As discussed above, the potential vapour intrusion risk is a function of the predicted (modelled) indoor air concentrations of PCE, TCE and DCE, relative to their respective guidelines. A hazard index between 1 and 10 represents modelled equivalent concentrations in the “Investigation Range”, based on the EPAs assessment framework for TCE. Vapour intrusion modelling has been used to calculate attenuation factors for each of the COPC. The attenuation factor is the reduction in concentration from the measured soil vapour into indoor air. This attenuation factor has then been applied to the measured soil vapour concentrations to estimate indoor air concentrations and associated risks. Where duplicate samples have been collected (SV01), the highest reported concentrations have been used. This data is summarised in Table 7-5.

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Table 7-5 Soil Vapour - Indoor Air Attenuation Factors, Concentrations and Risk Estimates

Soil Vapour (ug/m3) Indoor Air (ug/m3) Indoor Air Vapour PCE TCE DCE PCE TCE DCE Hazard Well Index soil gas : indoor air atten factor 7.5E- 04 9.7E- 04 1.0E- 03 52,000 7,100 800 SV01 49,000 7,100 790 60.59 11.59 1.15 5.75 81,000 12,000 1,100 SV02 <8 <6 <5 0.006 0.005 0.005 0.003 SV03 21 <6 <5 0.016 0.005 0.005 0.003 SV04 560 31 <5 0.419 0.03 0.005 0.016 SV05 830 130 <5 0.621 0.126 0.005 0.061 SV06 1600 310 66 1.197 0.299 0.069 0.152 SV07 12 <7 6.7 0.009 0.007 0.007 0.004 SV08 <8 28 55 0.006 0.027 0.058 0.019 SV09 <7 15 170 0.005 0.014 0.178 0.028 SV10 <8 <7 <5 0.006 0.007 0.005 0.004

Figure 9 shows the interpolated spatial areas for predicted hazard indices of 0.1, 1 and 10, based on the modelling assumptions detailed above for slab-on-ground homes. Vapour intrusion risks are assessed to be in the “Safe” range (HI<1), other than in the vicinity of a hot- spot in the “Investigation” range, centred around the elevated groundwater and vapour impacts identified at GW01/SV01, on Marion St, immediately adjacent to the form dry-cleaner site. It is noted that despite that measured concentrations in SV01 being dominated by PCE, the relative toxicity of TCE (100 times higher than PCE) means that the risk profile is still dominated by TCE, contributing to approx. 90% of the risk. In the case of the SA Health interim assessment framework for PCE16, it is noted that PCE, along with TCE, would fall into the “Investigation” range based on SV01. It is also noted that there was no data collected on private properties, including the former dry-cleaner site. As such, the spatial boundaries of the interpolated risk contours on Figure 9 are subject to some uncertainty towards the residential properties to the west and southwest of the former dry cleaners. Concentrations in vapour wells (SV04 and SV05) to the north of Marion St and the former dry-cleaner site, and at SV02, upgradient on Warrawee Rd, do not imply unacceptable vapour intrusion risks in these neighbouring properties. Soil vapour impacts have been delineated to below “Investigation” risk level equivalents, down- gradient of the site. 7.4.5 Modelling Conclusions – Intrusive Workers The predicted concentrations in a 1m deep trench (i.e. above the water table) in the area of highest measured vapour concentrations were well below commercial industrial guidelines, indicating no unacceptable risk to intrusive workers from vapour intrusion into excavations. The input and output modelling assumptions are included in the spreadsheets in Appendix R.

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7.5 Sensitivity Analysis of Key Risk Modelling Inputs 7.5.1 Introduction CRC CARE TR10 derived HSLs for petroleum hydrocarbons using the J&E model. As part of the sensitivity analysis document (Part 3), a summary of the key input parameters was included (refer to Figure 7-3). This CRC CARE assessment found the key parameters that the modelling was sensitive to were: • Moisture content • The advection (pressure driven flow) rate • Vapour biodegradation (not considered applicable to PCE or TCE) • Source life for soils (finite/infinite source) – not considered applicable for groundwater sources • Organic carbon content (relevant for modelling from a soil source only) • The indoor air exchange rate. Other parameters were found by CRC CARE to be relatively insensitive. Figure 7-2 CRC CARE Technical Report 10, Part 3 Sensitivity Analysis Summary (Figure 4)

ratio cra cks in co

air ex

oncrete sla

0.001 0.01 0. 1 10 100 1000 10000

7.5.2 Crawl-Space Residential Dwellings The US EPA (2017) vapour intrusion model was used to model vapour intrusion from measured soil vapour impacts into homes with crawl-space construction. It is noted that no detailed building survey has been undertaken to assess the specific construction details for homes in the area. As for the slab on ground modelling, the crawl space model was used to calculate attenuation factors from soil vapour to indoor air. These attenuation factors are then applied to the measured soil vapour concentrations in the investigation area to enable mapping of risk levels across the plume (as per Figure 9 for slab on ground construction). The attenuation factors derived with the US EPA model were between 10 and 32% higher (Table 19) for the crawl-space model, compared to the slab on ground scenario, with this reflected in proportionally higher indoor air concentrations (Table 20) for crawl-space homes.

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It is noted that the US EPA model does not incorporate ventilation within the crawl-space itself, so this is likely to result in over-estimation of indoor air concentrations. The difference between the two modelled scenarios are not considered significantly different, given the uncertainties associated with modelling and spatial and temporal data limitations. Table 7-6 Soil Vapour - Indoor Air Attenuation Factors, Comparison of Slab vs Crawl-Space Homes

Attenuation Factor PCE TCE DCE Slab on Ground 7.5E-04 9.7E-04 1.0E-03 Crawl Space 8.3E-04 1.1E-03 1.5E-03 RPD 10% 13% 32%

Table 7-7 Soil Vapour - Indoor Air Attenuation Factors, Concentrations and Risk Estimates – Crawl-Space Homes

Soil Vapour (ug/m3) Indoor Air (ug/m3) Vapour PCE TCE DCE PCE TCE DCE Well soil gas : indoor air atten factor 8.3E- 04 1.1E- 03 1.5E- 03 52,000 7,100 800 SV01 49,000 7,100 790 67.2 13.2 1.6 81,000 12,000 1,100 SV02 <8 <6 <5 <0.01 <0.01 <0.01 SV03 21 <6 <5 0.02 <0.01 <0.01 SV04 560 31 <5 0.46 0.03 <0.01 SV05 830 130 <5 0.69 0.14 <0.01 SV06 1600 310 66 1.33 0.34 0.10 SV07 12 <7 6.7 0.01 <0.01 0.01 SV08 <8 28 55 <0.01 0.03 0.08 SV09 <7 15 170 <0.01 0.02 0.25 SV10 <8 <7 <5 <0.01 <0.01 <0.01

7.5.3 Volumetric Air Content, Moisture Content and Soil Bulk Density The volumetric air content, moisture content and soil bulk density are related parameters as far as the J&E model are concerned, in that they affect the air-filled pore space, through which the model assumes the majority of vapour transport occurs. As can be seen from Figure 7-2 above, moisture content is potentially the most significant variable considered in the J&E model. Increasing the soil bulk density decreases the available soil pore space and thereby reduces vapour transport (all else being equal). Increases in moisture content similarly reduce the available air-filled porosity as the moisture takes up more of the available pore space, thereby reducing vapour migration. As noted in Section 7.3.5, the site-specific geological data was highly variable, with moisture contents in similarly logged sands ranging from 3.4% to 45.4 % and the associated degree of moisture saturation of the pore space ranging from 11% to 99.9%. Both these high and low degrees of saturation were considered questionable and hence modelling was predicated on generic geological data adopted from CRC CARE TR 11.

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Using the driest (lowest % saturation) sample taken from sand in GW05 results in an approximate doubling of predicted indoor air concentrations. The concentrations are based on the highest soil vapour impacts, measured at SV01. In this case, it is noted that the TCE would move into the intervention range in the area surrounding SV01. In contrast, adopting the highest % pore saturation sample from GW02 (also a sand), results in a decrease in predicted indoor air concentrations by two to three orders of magnitude to essentially trivial levels. Adopting the generic CRC CARE parameters is considered a sensible approach given the significant level of variability and associated uncertainty inherent in use of the site-specific geological data. Table 7-8 Predicted Indoor Air Concentrations as a Function of Pore Saturation Low High Vadose Zone Layer 2 Adopted Moisture Moisture Characteristics (CRC CARE) (GW05) (GW02) Depth of Layer [m] 1 1 1 Moisture Content [cm3/g] 0.034 0.08 0.277 Organic Carbon Fraction - 0.003 0.003 0.003 Soil Bulk Density [g/cm3] 1.49 1.625 1.51 Density of Solids [g/cm3] 2.65 2.65 2.65 Total Soil Porosity [cm3/cm3] 0.44 0.39 0.43 Volumetric Water Content [cm3/cm3] 0.05 0.13 0.42 Volumetric Air Content [cm3/cm3] 0.39 0.26 0.01 Tetrachloroethene (µg/m3) 136.11 60.59 0.08 Trichloroethene (µg/m3) 24.47 11.59 0.02 cis-1,2-dichloroethene (µg/m3) 2.38 1.15 0.01

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8.0 Conclusions The investigations conducted by AECOM between November 2020 and February 2021 within the SA EPA Ethelton Assessment Area included the following key elements: • Groundwater level and salinity gauging of existing wells to the south-west of the Assessment Area, inclusive of well head survey of selected wells, to confirm the local groundwater flow direction and to inform decisions in relation to further investigation locations. • Installation and sampling of a groundwater well monitoring network comprising eight (8) new wells, external to the 10-12 Marion Street site and within the EPA Assessment Area, • Installation and sampling of a soil vapour bore network comprising ten (10) new soil vapour monitoring bores, external to the 10-12 Marion Street site within the EPA Assessment Area. • Collection and testing of geotechnical samples at selected well locations to inform vapour intrusion modelling. • Development of a conceptual site model and conduct of a vapour risk assessment. Four objectives were identified for the investigation, and conclusions are provided in relation to these objectives below. 1. To investigate the nature and extent of chlorinated hydrocarbon compounds and other key contaminants in groundwater external to the 10-12 Marion Street site CHC compounds were identified in groundwater in the immediate vicinity of the former dry cleaners site and extending downgradient to the north-west. The presence of PCE and breakdown products TCE and DCE is indicative of the occurrence of breakdown via reductive dechlorination. The absence of CHC in up-gradient wells to the south-east indicates the former dry cleaning operations at 10- 12 Marion Street are likely to be the source of the observed impacts. Notably, breakdown product DCE was observed to extend down-gradient of the site to the north-west in the direction of groundwater flow to the western boundary of the Assessment Area. No NAPL was detected during the gauging of the wells and no concentrations of CHCs were reported of magnitude indicating DNAPL presence. A comparison of total CHC concentrations to reported short chain TRH concentrations provided strong evidence that the reported short chain TPH/TRH fraction concentrations are indicative of the presence of CHCs rather than petroleum hydrocarbons. Based on the measured concentration of PCE, TCE and DCE in the water table aquifer adjacent to and down-gradient of the 10-12 Marion Street site, it is assessed that the site contamination of groundwater exists in the Assessment Area. 2. To investigate groundwater flow direction, including potential influence from the nearby Port River, to inform potential migration of groundwater contamination Both the groundwater level gauging to the south-east of the Assessment Area in November 2020, and within the Assessment Area and south-east of the Assessment Area in January 2021, indicated an overall north-west groundwater flow direction. This apparent north-westerly groundwater flow is consistent with the observed distribution of groundwater and soil vapour impacts. Localised groundwater mounding in the vicinity of the former dry cleaners site was apparent in January 2021, and suggests localised radial groundwater flow. Given the observed distribution of CHC impacts solely in wells to the north-west of the former dry cleaners site, the apparent radial groundwater flow is likely to be only recent or not significant in terms of historical migration of impacts. Based on the Port River gauging, it is apparent that the minimum low tide may extend below current groundwater levels in the vicinity of the Assessment Area, suggesting the potential for an easterly flow toward the Port Adelaide River during low tide. There is no evidence to indicate easterly groundwater flow from the Assessment Area towards the river, either from inferred groundwater contours, previous studies, or the observed distribution of groundwater and soil vapour impacts.

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3. To investigate the nature and extent of chlorinated hydrocarbon compounds in soil vapour external to the 10-12 Marion Street site Maximum concentrations of CHCs in soil vapour were reported for bores in the vicinity of the former dry cleaners site, with lesser concentrations extending to the north-west. It is noted that the extent of soil vapour impacts (TCE and DCE) has not been delineated to below NEPM interim Health Investigation Level (HIL) screening levels within the boundary of the Assessment Area, with the potential for impacts to extend across the western boundary. The apparent soil vapour impacts, inclusive of PCE, TCE and 1,2-DCE, are assessed to be attributable to volatilisation from the identified groundwater concentrations. The absence of impacts up-gradient (to the south-east) of the former dry cleaners site, supports inference from groundwater results that former dry cleaners site is a likely source of groundwater impacts. 4. To provide a vapour intrusion risk assessment with respect to volatile contaminants and nearby land uses The assessment of potential vapour intrusion risk gave consideration to the identified magnitude and extent of CHCs in groundwater and soil vapour in the context of the primarily residential development across the Assessment Area and the potential for receptors to also include maintenance workers involved in subsurface excavations, and utilised the US EPA Johnson and Ettinger-based model to calculate vapour concentrations at the point of exposure. With respect to vapour inhalation risk in a residential occupancy scenario, reference was made to the TCE-specific Indoor Air Level Response ranges developed by the SA EPA and SA Health. While a similar PCE framework has previously been referenced for the EPA Brighton Assessment Area, this remains an interim guideline only. Accordingly, AECOM adopted and extended the approach of the TCE-specific framework in consideration of the combined results for the CHCs. Based on the outcome of the modelling, AECOM concluded that vapour intrusion risks fall within the “Safe” range, other than in the vicinity of a hot-spot in the “Investigation” range, centred around the elevated groundwater and vapour impacts identified at the paired groundwater well and soil vapour bore on Marion St, immediately adjacent to the former dry cleaning site, as shown on the Figure below. Reported concentrations in vapour wells SV04 and SV05 to the north of Marion St and the former dry- cleaner site, and at SV02, up-gradient on the eastern side of Warrawee Rd, do not imply unacceptable vapour intrusion risks in these neighbouring properties. While soil vapour concentrations of TCE and DCE were identified marginally above HIL screening levels at some perimeter soil vapour wells, the magnitude of the observed concentrations were such that the vapour intrusion risk is considered to have been delineated to below “Investigation” risk level level within the Assessment Area. These conclusions should be read in conjunction with the limitations presented in Section 10.0 of this report.

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9.0 References ANZECC, 1992, Australian Water Quality Guidelines for Fresh and Marine Waters, National Water Quality Management Strategy, Australian and New Zealand Environment and Conservation Council, November 1992. ANZECC/ARMCANZ, 2000, Australian and New Zealand guidelines for fresh and marine water quality, national water quality management strategy October 2000. AS1726 1993, Australian Standard, Geotechnical Site Investigations, council of Australian Standards, 13 April 1993. ASC NEPM, 1999, National Environment Protection (Assessment of Site Contamination) Measure 1999 (as amended 2013). BOM, 2021, Australian Government Bureau of Meteorology, South Australian Tide Tables http://www.bom.gov.au/oceanography/projects/ntc/sa_tide_tables.shtml CCME, 2007, Canadian Soil Quality Guidelines, Trichloroethylene, Environmental and Human Health Effects, Scientific Supporting Document. Canadian Council of Ministers of the Environment (CCME), 2007. CRC CARE, 2013, CRC CARE Technical Report no. 23 – Petroleum Hydrocarbon Vapour Intrusion Assessment: Australian Guidance, CRC CARE Pty Ltd, June 2013. DEW, 2021, Groundwater Data Online Database, WaterConnect, Department of Environment and Water, Government of South Australia, accessed 19 January 2021. https://www.waterconnect.sa.gov.au/GD. DME, 1980, 1:50,000 Geological Map of Adelaide, Department of Mines and Energy DWLBC, 2004, Aquifer Storage Capacities of the Adelaide Region, Report 2004/47, Department of Water, Land and Biodiversity Conservation, 2004. enHealth, 2012a. Environmental Health Risk Assessment, Guidelines for Assessing Human Health Risks from Environmental Hazards Update, June 2012 enHealth, 2012b. Australian Exposure Assessment Handbook, June 2012. Environmental Projects, 2020. Preliminary Site Investigation – Site History report Gerges N, 2006, Overview of the hydrogeology of the Adelaide metropolitan area, Report DWLBC 2006/10, Government of South Australia, through Department of Water, Land and Biodiversity Conservation, Adelaide. Golder Associates, 2007, Port Adelaide Waterfront Redevelopment, Groundwater Monitoring and Management Plan, Precinct 1, Port Adelaide, South Australia, 2 February 2007. Government of South Australia, 2021, NatureMaps website, accessed 19 January 2021, https://data.environment.sa.gov.au/NatureMaps/Pages/default.aspx. ITRC, 2007, Vapor Intrusion Pathway: A Practical Guideline, Technical and Regulatory Guidance, Interstate Technology and Regulatory Council Vapor Intrusion Team, January 2007 NHMRC/NRMMC, 2011, Australian Drinking Water Guidelines 6, National Health and Medical Research Council, updated March 2015. NHMRC and ARMCANZ, 2011 Australian Drinking Water Guidelines - 6. National Water Quality Management Strategy, National Health and Medical Research Council and the Agriculture and Resource Management Council of Australia and New Zealand), updated Feb 2016 NHMRC, 2008, Guidelines for Managing Risks in Recreational Waters, National Health and Medical Research Council, Australian Government, 2008. SA EPA 2007, Regulatory Monitoring and Testing – Groundwater Sampling, South Australian Environmental Protection Authority, June 2007

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SA EPA, 2009, Site Contamination – Guidelines for the Assessment and Remediation of Groundwater Contamination, South Australian Environment Protection Authority, February 2009. SA EPA, 2021, EPA Report, 10-12 Marion Street, Ethelton. March 2021. SA EPP (Water Quality), 2015, South Australian Environment Protection (Water Quality) Policy 2015 under the Environment Protection Act 1993, Government of South Australia. Status gazetted Sheard & Bowman, 1996 “Soils, stratigraphy and engineering geology of near surface materials of the Adelaide Plains” M.J. Sheard and G.M. Bowman, Report 94/9. Taylor, J.K., 1972, Soil Association Map of Adelaide, South Australian Department of Mines and Energy, 1972. UK Environment Agency, 2003, An illustrated handbook of DNAPL transport and fate in the subsurface, Environment Agency R&D Publication 133 US EPA. 1992, Estimating Potential for Occurrence of DNAPL at Superfund Sites. OSWER Publication 9355.4-07FS. National Technical Information Service (NTIS) Order Number PB92- 963338CDH. US EPA, 2012, Conceptual Model Scenarios for the Vapor Intrusion Pathway, US EPA Office of Solid Waste and Emergency Response (EPA 530-R-10-003), February 2012 US EPA 2017, Documentation for EPA’s Implementation of the Johnson and Ettinger Model to Evaluate Site Specific Vapour Intrusion into Buildings, Version 6, September 2017. WHO, 2011, Guidelines for Drinking Water, Fourth Edition, World Health Organisation, 2011.

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10.0 Report limitations The conclusions and all information in this Report is provided strictly in accordance with and subject to the following limitations and recommendations: a. This Report has been prepared for the benefit of the South Australian Environment Protection Authority (SA EPA). b. Except as required by law, no third party may use or rely on, this Report unless otherwise agreed by AECOM in writing. Where such agreement is provided, AECOM will provide a letter of reliance to the agreed third party in the form required by AECOM. c. This Report should be read in full and no excerpts are to be taken as representative of the findings. No responsibility is accepted by AECOM for use of any part of this Report in any other context. d. This conclusion is based solely on the information and findings contained in this Report. e. This conclusion is based solely on the scope of work agreed between AECOM and SA EPA and described in Section 1.3 ("Scope of Works") of this Report. f. This Report is dated 19 March 2021 and is based on the conditions encountered during the site investigations conducted, and information reviewed, from November 2020 to March 2021. AECOM accepts no responsibility for any events arising from any changes in site conditions or in the information reviewed that have occurred after the completion of the site investigations. g. The investigations carried out for the purposes of the Report have been undertaken, and the Report has been prepared, in accordance with normal prudent practice and by reference to applicable environmental regulatory authority and industry standards, guidelines and assessment criteria in existence at the date of this Report. h. Where this Report indicates that information has been provided to AECOM by third parties, AECOM has made no independent verification of this information except as expressly stated in the Report. AECOM assumes no liability for any inaccuracies in or omissions to that information. i. AECOM has tested only for those chemicals specifically referred to in this Report. AECOM makes no statement or representation as to the existence (or otherwise) of any other chemicals. j. Except as otherwise specifically stated in this Report, AECOM makes no warranty or representation as to the presence or otherwise of asbestos and/or asbestos containing materials (“ACM”) on the site. If fill has been imported on to the site at any time, or if any buildings constructed prior to 1970 have been demolished on the site or materials from such buildings disposed of on the site, the site may contain asbestos or ACM. Without limiting the generality of sub-clauses (h) and (m), even if asbestos was tested for and those test results did not reveal the presence of asbestos at specific points of sampling, asbestos may still be present at the site if fill has been imported at any time, or if any buildings constructed prior to 1970 have been demolished on the site or materials from such buildings disposed of on the site. k. No investigations have been undertaken into any off-site conditions, or whether any adjoining sites may have been impacted by contamination or other conditions originating from this site. l. Investigations undertaken in respect of this Report are constrained by the particular site conditions, such as the location of buildings, services and vegetation. As a result, not all relevant site features and contamination may have been identified in this Report. m. Subsurface conditions can vary across a particular site and cannot be exhaustively defined by the investigations described in this Report. It is unlikely therefore that the results and estimations expressed in this Report will represent conditions at any location removed from the specific points of sampling. n. A site which appears to be unaffected by contamination at the time the Report was prepared may later, due to natural phenomena or human intervention, become contaminated.

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o. Except as specifically stated above, AECOM makes no warranty, statement or representation of any kind concerning the suitability of the site for any purpose or the permissibility of any use, development or re-development of the site. p. Use, development or re-development of the site for any purpose may require planning and other approvals and, in some cases, environmental regulatory authority approval. AECOM offers no opinion as to whether the current use has any or all approvals required, is operating in accordance with any approvals, the likelihood of obtaining any approvals for development or redevelopment of the site, or the conditions and obligations which such approvals may impose, which may include the requirement for additional environmental works. q. AECOM makes no determination or recommendation regarding a decision to provide or not to provide financing with respect to the site. r. The ongoing use of the site and/or the use of the site for any different purpose may require the owner/user to manage and/or remediate site conditions, such as contamination and other conditions, including but not limited to conditions referred to in this Report. s. To the extent permitted by law, AECOM expressly disclaims and excludes liability for any loss, damage, cost or expenses suffered by any third party relating to or resulting from the use of, or reliance on, any information contained in this Report. AECOM does not admit that any action, liability or claim may exist or be available to any third party. t. Except as specifically stated in this section, AECOM does not authorise the use of this Report by any third party. u. It is the responsibility of third parties to independently make inquiries or seek advice in relation to their particular requirements and proposed use of the site.

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