Former ChlorAlkali Plant, Human Health and Environmental Risk Assessment - 2013 Prepared for : Orica Limited

20 June 2013

Document History and Status

Report Reference O/13/CAPR001 Revision A - Final Date 20 June 2013

Previous Revisions

Limitations

Environmental Risk Sciences (enRiskS) has prepared this report for the use of Orica Limited (Orica) in accordance with the usual care and thoroughness of the consulting profession. It is based on generally accepted practices and standards at the time it was prepared. No other warranty, expressed or implied, is made as to the professional advice included in this report.

It is prepared in accordance with the scope of work and for the purpose outlined in the Section 1 of this report.

The methodology adopted and sources of information used are outlined in this report. Environmental Risk Sciences has made no independent verification of this information beyond the agreed scope of works and assumes no responsibility for any inaccuracies or omissions. No indications were found that information contained in the reports or data provided by Orica for use in this assessment was false.

This report was prepared from January to June 2013 and is based on the information provided and reviewed at that time. Environmental Risk Sciences disclaims responsibility for any changes that may have occurred after this time.

This report should be read in full. No responsibility is accepted for use of any part of this report in any other context or for any other purpose or by third parties. This report does not purport to give legal advice. Legal advice can only be given by qualified legal practitioners.

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Table of Contents

Section 1. Introduction ...... 1 1.1 Background ...... 1 1.2 Objectives and Scope of Works ...... 2 1.3 Approach to the Assessment of Environmental Risk ...... 3 1.4 Approach to the Assessment of Human Health Risk ...... 3 1.4.1 General...... 3 1.4.2 Issue Identification...... 5 1.4.3 Exposure Assessment ...... 5 1.4.6 Risk Characterisation and Acceptability of Risk ...... 9 1.5 Features of the Risk Assessment ...... 11

Section 2. Mercury in the Environment ...... 12 2.1 Introduction ...... 12 2.2 Mercury in the Environment ...... 12 2.2.1 General...... 12 2.2.2 Atmosphere ...... 13 2.2.3 Soil ...... 14 2.2.4 Groundwater...... 14 2.2.5 Environment ...... 15 2.3 Toxicity of Mercury – Human Health ...... 16 2.4 Toxicity of Mercury - Environment ...... 19 2.4.1 Bioavailability, Bioaccumulation and Biomagnification ...... 19 2.4.2 General Toxicity to Ecological Receptors ...... 20

Section 3. Environmental Setting ...... 21 3.1 Introduction ...... 21 3.2 Geology ...... 21 3.2.1 Regional Geology ...... 21 3.2.2 FCAP Site Geology ...... 23 3.3 Hydrogeology ...... 25 3.3.1 Regional Hydrogeology ...... 25 3.3.2 Site Hydrogeology ...... 26

Section 4. Identification of Risk Issues ...... 29 4.1 Introduction ...... 29 4.2 Guidelines...... 29 4.2.1 General...... 29 4.2.2 Soil Guidelines ...... 29 4.2.3 Sediment Guidelines ...... 31 4.2.4 Groundwater and Surface Water Guidelines ...... 32 4.3 Review of Soil Data from FCAP ...... 33 4.4 Review of Groundwater Data and Identification of Issues ...... 35 4.4.1 Summary of Previous Investigations ...... 35 4.4.2 Summary of Mercury in Groundwater ...... 38

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4.4.3 Conceptual Model for Mercury Source, Fate and Transport in Groundwater ...... 39 4.4.4 Identification of Issues – Mercury in Groundwater ...... 42 4.5 Mercury Vapour Conceptual Site Model ...... 44 4.6 Presence of Mercury in Other Off-Site Areas ...... 45 4.6.1 Summary of Previous Investigations ...... 45 4.6.2 Mechanisms of Off-site Discharges of Mercury to Surface Water ...... 47 4.7 Summary of Issues Identified ...... 49

Section 5. Quantification of Exposure and Risk – Human Health ...... 51 5.1 General ...... 51 5.2 Identification of Complete Exposure Pathways ...... 51 5.3 Assessment of Exposure and Risk - FCAP Site ...... 55 5.3.1 General...... 55 5.3.2 Mercury Soil and Dust Concentrations ...... 56 5.3.3 Mercury Vapour Concentrations ...... 57 5.3.4 Risk Calculations ...... 61 5.4 Assessment of Exposure and Risk Off-Site ...... 65 5.4.1 General...... 65 5.4.2 Mercury Concentrations in Groundwater ...... 67 5.4.3 Mercury Vapour Concentrations ...... 67 5.4.4 Risk Calculations ...... 67

Section 6. Assessment of Risk – Environmental ...... 72 6.1 General ...... 72 6.2 Potential for Off-Site Impacts to the Environment ...... 72 6.2.1 Off-Site Migration of Groundwater ...... 72 6.2.2 Surface Water Discharges ...... 74

Section 7. Risk Management ...... 76 7.1 General ...... 76 7.2 Risk Management Measures to Address Risks to Human Health ...... 76 7.2.1 General...... 76 7.2.2 Risk Based Concentration (RBC) – Blocks M and A ...... 77 Consideration of ...... 78 7.2.3 Other Exposures Associated with RBC ...... 78 7.3 Risk Management Measures to Address Ongoing Source to Surface Water and Groundwater ...... 80

Section 8. Uncertainty...... 85 8.1 General ...... 85 8.2 Uncertainty ...... 85 8.2.1 Sampling and Analysis ...... 85 8.2.2 Exposure Assessment ...... 86 8.2.3 Toxicological Assessment ...... 87 8.3 Variability ...... 88

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Section 9. Conclusions ...... 91

Section 10. References ...... 93

Tables

Table 2.1 Summary of Human Toxicological Reference Values for Mercury Table 3.1 Summary of Stratigraphic Layers in Botany Sands Table 3.2 Soil Profile for FCAP and Downgradient Areas Table 3.3 Regional Hydraulic Parameters – Botany Aquifer Table 4.1 Summary of Key Issues – FCAP Soil Table 4.2 Summary of Risk Issues - FCAP Table 5.1 Summary of Exposure Pathways – Human Health Table 5.2 Calculated Vapour Concentrations – FCAP Table 5.3 Summary of Exposure Assumptions and Risk Calculations – Commercial/Industrial Workers on FCAP Table 5.4 Summary of Exposure Assumptions and Risk Calculations – Intrusive Workers on FCAP Table 5.5 Summary of On-Site Risk – Future Use of FCAP Table 5.6 Maximum Concentration of Mercury Species in Off-Site Shallow Groundwater – Main Plumes (all concentrations reported as mg/L) Table 5.7 Summary of Exposure Assumptions and Risk Calculations – Off-Site Commercial/Industrial Workers Table 5.8 Summary of Exposure Assumptions – General Public in Off-Site Areas Table 5.9 Summary of Exposure Assumptions and Risk Calculations – Off-Site Intrusive Workers Table 5.10 Summary of Off-Site Risk – Future Use of FCAP Table 7.1 Derived RBC (protection of on-site risks) – Total Mercury in Soil (mg/kg) Table 7.2 Derived RBC (protection of risk on and off-site) – Total Mercury in Soil (mg/kg) Table 8.1 Sensitivity of Key Variable Considered in the HHERA Table 9.1 Derived RBC – Total Mercury in Soil (mg/kg)

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Figures

Figure 1 Site Location Plan and Surface Topography (from URS 2008d) Figure 2 Extent of GEEA (from NSW Department of Water) Figure 3 Chemical Monitoring Well Locations (from Golder 2013) Figure 4a Dissolved Mercury, Total Mercury and Methyl Mercury Concentrations, Shallow Aquifer (from Golder 2013) Figure 4b Mercury Concentrations, Shallow Aquifer (from Golder 2011) Figure 5a Dissolved Mercury, Total Mercury and Methyl Mercury Concentrations, Intermediate Aquifer (from Golder 2013) Figure 5b Mercury Concentrations, Intermediate Aquifer (from Golder 2011) Figure 6a Dissolved Mercury, Total Mercury and Methyl Mercury Concentrations, Deep Aquifer (from Golder 2013) Figure 6b Mercury Concentrations, Deep Aquifer (from Golder 2011) Figure 7 Plan View of Conceptual Model of Mercury Fate and Transport in Groundwater (from URS 2008d) Figure 8 Exposure Conceptual Site Model (from URS 2008d)

Appendices

Appendix A Equations Appendix B Toxicity of Mercury Appendix C Review of Soil Data Appendix D Summary of Groundwater Data Appendix E Emissions Sampling Report Appendix F Emission Calculations for Vapour Model Calibration Appendix G Risk Calculations On-Site Appendix H Risk Calculations Off-Site

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Glossary of Terms Acute Exposure Contact with a substance that occurs once or for only a short time (up to 14 days). Adsorption The process of taking in. For a person or an animal, absorption is the process of a substance getting into the body through the eyes, skin, stomach, intestines, or lungs. ADI Acceptable Daily Intake – The amount of a chemical a person can be exposed to on a daily basis over an extended period of time (usually a lifetime) without suffering deleterious effects. Additive Effect A biologic response to exposure to multiple substances that equals the sum of responses of all the individual substances added together [compare with antagonistic effect and synergistic effect] Adverse Health Effect A change in body function or cell structure that might lead to disease or health problems Antagonistic Effect A biologic response to exposure to multiple substances that is less than would be expected if the known effects of the individual substances were added together [compare with additive effect and synergistic effect]. ANZECC Australia and New Zealand Environment and Conservation Council AT Averaging Time Background Level An average or expected amount of a substance or material in a specific environment, or typical amounts of substances that occur naturally in an environment.

BGL Below ground level Biodegradation Decomposition or breakdown of a substance through the action of micro-organisms (such as bacteria or fungi) or other natural physical processes (such as sunlight). BIP Botany Industrial Park Biota Plants and animals in an environment. Some of these plants and animals might be sources of food, clothing, or medicines for people. Body Burden The total amount of a substance in the body. Some substances build up in the body because they are stored in fat or bone or because they leave the body very slowly. BTEX Benzene, toluene, ethylbenzene and total xylenes BW Body weight Carcinogen A substance that causes cancer. CF Unit Conversion Factor CHC Chlorinated Hydrocarbon Chronic Exposure Contact with a substance that occurs over a long time (more than 1 year) [compare with acute exposure and intermediate duration exposure] COPC Chemical of Potential Concern – chemicals identified within relevant media (groundwater, air, biota, sediment and surface water) that are considered to be of potential significance and warrant further quantification as part of the health risk assessment. CPWE Car-Park Waste Encapsulation CTC Carbon tetrachloride DCE Dichloroethene DCM Dichloromethane, or methylene chloride DECCW Department of Environment, Climate Change and Water Dermal Contact Contact with (touching) the skin [see route of exposure]. Detection Limit The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.

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Glossary of Terms Dose The amount of a substance to which a person is exposed over some time period. Dose is a measurement of exposure. Dose is often expressed as milligram (amount) per kilogram (a measure of body weight) per day (a measure of time) when people eat or drink contaminated water, food, or soil. In general, the greater the dose, the greater the likelihood of an effect. An “exposure dose” is how much of a substance is encountered in the environment. An “absorbed dose” is the amount of a substance that actually got into the body through the eyes, skin, stomach, intestines, or lungs. ED Exposure Duration EDC Ethylene dichloride of 1,2-dichloroethane EF Exposure Frequency EPA Environment Protection Authority ET Exposure time Exposure Contact with a substance by swallowing, breathing, or touching the skin or eyes. Exposure may be short-term [acute exposure], of intermediate duration, or long-term [chronic exposure]. Exposure The process of finding out how people come into contact with a hazardous substance, how Assessment often and for how long they are in contact with the substance, and how much of the substance they are in contact with. Exposure Pathway The route a substance takes from its source (where it began) to its end point (where it ends), and how people can come into contact with (or get exposed to) it. An exposure pathway has five parts: a source of contamination (such as chemical leakage into the subsurface); an environmental media and transport mechanism (such as movement through groundwater); a point of exposure (such as a private well); a route of exposure (eating, drinking, breathing, or touching), and a receptor population (people potentially or actually exposed). When all five parts are present, the exposure pathway is termed a completed exposure pathway. Groundwater Water beneath the earth's surface in the spaces between soil particles and between rock surfaces [compare with surface water]. Guideline Value Guideline value is a concentration in soil, sediment, water, biota or air (established by relevant regulatory authorities such as the NSW Department of Environment and Conservation (DEC) or institutions such as the National Health and Medical Research Council (NHMRC), Australia and New Zealand Environment and Conservation Council (ANZECC) and World Health Organisation (WHO)), that is used to identify conditions below which no adverse effects, nuisance or indirect health effects are expected. The derivation of a guideline value utilises relevant studies on animals or humans and relevant factors to account for inter- and intra- species variations and uncertainty factors. Separate guidelines may be identified for protection of human health and the environment. Dependent on the source, guidelines will have different names, such as investigation level, trigger value, ambient guideline etc. Hazard Quotient/ Hazard quotient is the ratio of daily chemical calculated for a specific receptor and exposure Hazard Index (HQ/HI) pathway, to the acceptable or safe dose (ADI, TDI, RfD etc.) for that chemical. A value less than 1 indicates that the intake is less than the safe intake. A hazard index is the sum of the hazard quotients for all chemicals exposure pathways for a receptor. HIL Health Investigation Level HHRA Human Health Risk Assessment Ingestion The act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way [see route of exposure]. Inhalation The act of breathing. A hazardous substance can enter the body this way [see route of exposure].

Intermediate Contact with a substance that occurs for more than 14 days and less than a year [compare Exposure Duration with acute exposure and chronic exposure]. LOAEL Lowest-observed-adverse-effect-level - The lowest tested dose of a substance that has been reported to cause harmful (adverse) health effects in people or animals

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Glossary of Terms LOR Limit of Reporting

Mercury Species: Hg0 Elemental mercury, quicksilver, metallic mercury Hg2+ Mercuric mercury (mercury (II)) 2+ Hg2 Mercurous mercury (mercury (I)) + HgCH3 Mono-methylmercury (mercury (II))

Hg(CH3)2 Di-methylmercury (mercury (II))

HgCl2 Mercuric chloride - HgCl3 Mercuric chloride complex 2- HgCl4 Mercuric chloride complex

Hg2Cl2 Mercurous chloride, Calomel (solid) HgO Mercury oxide (solid)

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Executive Summary

Introduction

URS Australia Pty Ltd (URS) completed a human health and environmental risk assessment (HHERA) associated with mercury contamination identified at and in the vicinity of the former ChlorAlkali Plant (FCAP) located within the Botany Industrial Park (BIP) in 2008. The 2008 HHERA (URS 2008d) was conducted to assess potential risks to human health and the environment associated with the presence of mercury contamination in soil and groundwater at and in the vicinity of the FCAP. The HHERA addressed potential current risks associated with the FCAP.

Following completion of the HHERA comments on the report have been provided to Orica Limited (Orica) via the New South Wales Environment Protection Authority (NSW EPA).

Environmental Risk Sciences Pty Ltd (enRiskS) has been commissioned by Orica to update the FCAP HHERA to address the comment received, additional data collected since completion of the 2008 HHERA (URS 2008d) and update the assessment based on the revised National Environment Protection (Assessment of Site Contamination) Measure (NEPM) (NEPC 1999 amended 2013) and the current understanding of mercury toxicity. The proposed remediation and subsequent end uses of the FCAP area has also been changed since 2008. Hence the assessment presented in this report is an update of the 2008 HHERA.

The FCAP operated using the ChlorAlkali Process and mercury cells from 1944 until 2001 when it was replaced with a membrane cell process. There were four key areas associated with the FCAP that have been considered in this assessment. These include:

 Block G – Cell Block;  Block L – Chlorine Liquefaction and Chlorine Storage Area;  Block M – Hydrogen and Brine Treatment Area; and  Block A – Caustic Soda Filtration and Storage.

Areas located outside of the FCAP site (both within and outside of the boundaries of the BIP) are referred to as “off-site” areas.

The HHERA has been undertaken in general accordance with guidelines provided by enHealth (2012a), NEPM (1999 amended 2013) and ANZECC (2000). The HHERA has also considered the long-term beneficial use of groundwater as requested by the NSW EPA.

Risk Issues Identified

Mercury is a pervasive and persistent chemical in the environment. Once released into the environment, mercury undergoes a series of complex chemical and physical transformations as it cycles among the atmosphere, land, and water. These processes are complex and the characteristics of mercury that have the potential to be of concern with respect to human health and the environment include its form (or species, such as elemental [Hg0], inorganic mercury species or methylmercury), mobility in the environment, toxicity and persistence in the environment, and its ability to accumulate and bioconcentrate as methylmercury. The potential for the presence of

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mercury in the environment to be of concern with respect to human health or the environment also depends on the potential for exposure.

The characteristics of mercury, the history of the FCAP site and information on the use of the site and off-site areas have been reviewed in conjunction with all the available data collected and groundwater modelling completed on and off the site with the aim of identifying key issues that require detailed consideration in the HHERA, as follows:

 Soil: Hg0 and total mercury impacts have been identified in a number of locations (primarily beneath Block G, however some areas of Blocks M and A have also been identified). The presence of mercury in soil at the FCAP site is considered to be an issue as there is the potential for direct contact (should impacts be near the surface, or excavated), inhalation of Hg0 vapours (indoors and outdoors) and potentially providing an ongoing source to groundwater.  Groundwater beneath the FCAP: Mercury has been reported (present as dissolved inorganic species, sorbed mercury, Hg0 and methylmercury) in shallow, intermediate and deep aquifers. No risk issues have been identified as groundwater is not used on the former CAP and the BIP for any purpose (or reasonably foreseeable future purpose). While considered negligible, the potential for vapour migration and intrusion issues from the presence of Hg0 reported in the groundwater have been considered.  Groundwater beneath down-gradient areas: Mercury has been reported (present as dissolved inorganic species, sorbed mercury, Hg0 and methylmercury) in shallow, intermediate and deep aquifers with concentrations decreasing downgradient of the FCAP - source area. Mercuric chloride complex (HgCl3 ) has been identified as the dominant modelled mercury species in downgradient areas. Some Hg0 is also present; however concentrations are less than in the source area. Mercury-impacted groundwater derived from the FCAP has not migrated to nor has discharged to any receiving body. Potential for further - migration downgradient is considered likely based on mobility of HgCl3 species that dominate the plume. Hence future migration and discharge to Springvale Drain (and subsequent discharge to Penrhyn Estuary) need to be considered.

Potential for vapour migration and intrusion issues from the presence of Hg0 in the groundwater are considered to be negligible, however potential exposures have been assessed. While no groundwater is currently extracted for any purpose in the industrial area off site, and the area is within the Groundwater Extraction Exclusion Area (GEEA), industrial water extraction and use is permissible under licence from the NSW Office of Water and hence relevant beneficial uses (industrial use) of groundwater in this area has been assessed.

Presence of mercury in soil and groundwater at the source area remains an ongoing source to the off-site groundwater.

The assessment of the above risk issues has considered the nature and extent of mercury contamination (associated with the FCAP), the proposed future use of Blocks G, M and A as well as remediation measures outlined in the remediation action plans (RAP) prepared for Block G (Golder 2012a) and Blocks M and A (Golder 2012b).

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Conclusions

Environment

The assessment undertaken has focused on the available data and studies undertaken to assess the potential for mercury-impacted groundwater identified beneath and down-gradient of the FCAP to migrate to and discharge into downgradient receiving bodies, such as Springvale Drain and Penrhyn Estuary. Based on the available information, mercury-impacted groundwater has not discharged to any receiving environment, however the presence of mercury in soil and groundwater beneath the FCAP provides an ongoing source to groundwater (and potentially surface water) that requires consideration with respect to future environmental risks.

It is noted that mercury concentrations in surface water of Springvale Drain or Penrhyn Estuary are not reported during routine surface water monitoring program. As surface water runoff from the FCAP and the further migration of the groundwater plume could result in the discharge of mercury to Springvale Drain or Penrhyn Estuary, the inclusion of mercury in the analysis of samples collected in these areas would provide additional data for the assessment of off-site risks to human health and the environment associated with the FCAP.

The risk management measures proposed to be implemented within the RAPs (Golder 2012a and 2012b) are aimed at mitigating the potential for Blocks G, M and A to remain an ongoing source to groundwater and/or surface water.

Human Health

In relation to the proposed future industrial use of Blocks G (open space only) and Blocks M and A (outdoor space and/or future industrial buildings), potentially unacceptable risks have been identified in relation to potential exposures in Block G (from the inhalation of Hg0 vapours outdoors and direct contact with mercury impacted soil) and Blocks M and A (from the inhalation of Hg0 vapours indoors and potentially outdoors). In relation to the risks identified the following can be noted:

 Block G: The proposed construction of a vapour barrier and cut-off wall will prevent direct contact by workers with mercury impacted soil. In addition the proposed barrier and cut-off wall with mitigate the vertical and lateral migration of Hg0 vapours from this area mitigating future inhalation risks to workers (as well as in all off-site areas). The proposed barrier and cut-off wall will also prevent rain infiltration and lateral migration of groundwater mitigating the potential for mercury impacted soil to remain an ongoing source to groundwater. These measures effectively mitigate all risks associated with the mercury impacted materials identified within Block G.

 Blocks M and A: The proposed remediation involves excavation of Hg0 impacted soil and placement of these materials in Block G where they will be contained and effectively managed. Other mercury impacted soil will be excavated and transported off-site for appropriate disposal. These measures are intended to effectively remediate mercury impacted materials identified in Blocks M and A. To assist in the remediation of these areas risk-based criteria (RBC) have been derived to ensure that the remediation adequately addresses the long-term risks issues on the site (as well as ensuring potential off-site risk

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issues associated with off-site inhalation of vapours and ongoing source to groundwater are effectively managed).

The derived RBC for Blocks M and A that are protective of long-term exposures on and off the site (including consideration of ongoing source to groundwater contamination) are summarised in the following:

Derived RBC – Total Mercury in Soil (mg/kg)

Location RBC – Outdoor/Open Space Use RBC – Construction of Industrial Buildings* Block M 240 100 Block A 460 180 * RBC relevant where no vapour mitigation system is implemented within the future building.

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Section 1. Introduction 1.1 Background URS Australia Pty Ltd (URS) completed a human health and environmental risk assessment (HHERA) associated with mercury contamination identified at and in the vicinity of the former ChlorAlkali Plant (FCAP) located within the Botany Industrial Park (BIP) in 2008. The 2008 HHERA was conducted to assess potential risks to human health and the environment associated with the presence of mercury contamination in soil and groundwater at and in the vicinity of the FCAP. The HHERA addressed potential current risks associated with the FCAP.

Following completion of the HHERA comments on the report have been provided to Orica Limited (Orica) via the New South Wales Environment Protection Authority (NSW EPA).

Environmental Risk Sciences Pty Ltd (enRiskS) has been commissioned by Orica Limited (Orica) to update the FCAP HHERA to address the comments received, additional data collected since completion of the 2008 HHERA and update the assessment based on the current understanding of mercury toxicity. Hence the assessment presented in this report is an update of the 2008 HHERA.

It is noted that overall the comments provided on the FCAP HHERA to the NSW EPA are written in an unprofessional and unhelpful tone/manner which hinders the ability to address or partially address many of the comments provided as it is not entirely clear exactly what is concerning the reviewer. Hence this report has not been able to specifically address every comment provided. Where the comments can be addressed this has been included in this report.

There are three main types of electrolytic processes used in the production of chlorine: (1) the diaphragm cell process; (2) the mercury cell process; and (3) the membrane cell process (Austin 1984). The mercury cell process was the method used at the FCAP located within the BIP (refer to Figure 1) for the manufacture of chlorine, hydrogen, and sodium hydroxide (caustic soda) solution. The FCAP operated using the ChlorAlkali Process and mercury cells from 1944 until 2001 when it was replaced with a membrane cell process.

The FCAP has been the subject of intrusive investigations, which have focused on the following key process areas:

 Block G – Cell Block;

 Block L – Chlorine Liquefaction and Chlorine Storage Area;

 Block M – Hydrogen and Brine Treatment Area; and

 Block A – Caustic Soda Filtration and Storage.

Blocks A, M and L have infrastructure present and are currently operational areas. Block G (Cell Block), however, has been decommissioned and demolished. Within the Cell Block there were three cell rooms, namely H, Mk1 and B1 cell rooms, and the brine purification section.

These areas (Blocks G, L, M and A) located within the BIP are hereinafter referred to as the “FCAP site” or “the site”. Areas located outside of these areas (both within and outside of the boundaries of the BIP) are hereafter referred to as “off-site” areas.

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Investigations conducted on and off the FCAP site (refer to Section 4) to characterise the nature and extent of current level of contamination have identified the presence of elemental and inorganic mercury in soil within the area of the FCAP located on the BIP and mercury in groundwater beneath and downgradient of the FCAP (on BIP) and extending off site to the south west.

In addition more detailed hydrogeochemical modelling and conceptual model associated with the potential fate and transport of mercury in the groundwater developed by URS (2008a and 2008b) and Laase (2010) has been incorporated into this report.

The assessment presented in this report addresses potential risks to human health and the environment associated with the nature and extent of current mercury contamination identified at the FCAP site, and in down-gradient off-site areas. The assessment has not addressed historical exposures associated with the operation of the FCAP.

1.2 Objectives and Scope of Works Overall the objectives of the HHERA are to:

 Provide a quantitative assessment of potential risks to human health associated with the presence of mercury in soil at the FCAP and groundwater beneath and downgradient of the FCAP based on the potential for the FCAP area to be used for other industrial purposes;

 Provide a quantitative assessment of potential risks to human health associated with the presence of mercury identified in groundwater in areas located off site and downgradient of the BIP. The assessment is undertaken based on the existing zoning of the areas impacted and includes consideration of long-term beneficial use of groundwater;

 Provide a qualitative assessment of potential risks to the environment associated with the presence of mercury in soil and groundwater, particularly within off-site (outside of the BIP) areas; and

 Where required, develop risk-based remediation goals (soil and/or groundwater) that can be considered as part of the remediation of the FCAP area or used as screening or trigger levels for further investigation.

The assessment presented in this report is an update of the previous HHERA conducted by URS (URS 2008d).

The focus of this HHERA is associated with the presence of the varying forms of mercury in soil and groundwater derived from the FCAP. While the assessment draws on data available with respect to mercury on and in the vicinity of the BIP, the HHERA does not consider risks to human health associated with the presence of any other chemicals on the BIP (or associated with historical operations at the BIP) which have been subject to separate assessments. The 2010 Consolidated Human Health Risk Assessment (CHHRA, enRiskS 2011) has been completed to address risk to human health in areas located off the BIP associated with all the chemicals of potential concern associated with operations on the BIP.

It is also noted that the HHERA presented in this report (or the CHHRA) does not consider any chemicals (including mercury) that may be present in soils and groundwater that relate to the

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operation of other industries in areas surrounding the BIP (including historical operations and discharges from the BIP or other industries).

It is not the purpose of the HHERA to present and discuss risk management activities; rather the HHERA aims to provide technical information and assessments to enable appropriate risk management decisions to be made. It is also noted that the HHERA presented is a site-specific assessment that has been undertaken on the basis of data and toxicological information available to January 2013.

1.3 Approach to the Assessment of Environmental Risk The assessment of environmental risk has been conducted in accordance with the following guidelines:

 National Environment Protection Council (Austin 1984; NEPC 1999 amended 2013a) - Guideline on Ecological Risk Assessment” (Schedule B(5)). This guideline addresses only risks to terrestrial environments and has not been prepared to cover aquatic environments. The FCAP is located within the BIP which is used for a range of industrial purposes. It is expected that the BIP will continue to be used for industrial purposes consistent with the current BIP operations. Hence the focus of the environmental risk assessment should be on the off-site (outside of the BIP) environment, namely Springvale Drain, Floodvale Drain, Penrhyn Estuary, Botany Bay and Long Dam located to the south, south west and west of the FCAP and associated ecosystems.

 ANZECC and ARMCANZ (2000) National Water Quality Management Strategy, Australian and New Zealand Guidelines for Fresh and Marine Water Quality. These guidelines more specifically relate to the aquatic environment (water quality and sediment quality) of Springvale Drain, Floodvale Drain, Penrhyn Estuary, Botany Bay and Long Dam.

Based on the above guidelines the environmental risk assessment (presented in Section 6) has been conducted as a qualitative assessment according to the following steps:

 Assessment of the potential for contaminant migration beyond the BIP boundary and potential for discharge into Springvale Drain, Floodvale Drain, Penrhyn Estuary, Botany Bay and Long Dam; and

 Evaluation of the potential for contaminant migration to adversely affect the quality of the surrounding water and ecological systems.

1.4 Approach to the Assessment of Human Health Risk 1.4.1 General The approach taken to the quantitative assessment of human health risks is in accordance with guidelines/protocols endorsed by Australian regulators, as outlined in the following:

 enHealth: Environmental Health Risk Assessment, Guidelines for Assessing Human Health Risks from Environmental Hazards (enHealth 2012a, 2012b);

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 The NEPC1 guidelines including:

o NEPM Schedule B(4) Guideline on Health Risk Assessment Methodology (NEPC 1999 amended 2013b);

o NEPM Schedule B(6) Guideline on Risk Based Assessment of Groundwater Contamination (NEPC 1999 amended 2013c); and

o NEPM Schedule (7a) Guideline on Health-Based Investigation Levels (NEPC 1999 amended 2013d)

 “The Health Risk Assessment and Management of Contaminated Sites” (EPHC 2003; SAHC 1991, 1993, 1996, 1998); and

 ANZECC/NHMRC2 (ANZECC 1992).

The above documents currently provide only general guidance for the completion of these tasks and, as such, the more detailed protocols and guidelines developed by international agencies (USEPA 1989, 1991, 1996, 2002, 2004b, 2004a, 2009a; WHO 2008) have been used to provide supplementary guidance. The guidelines specifically relate to accepted methodologies associated with the quantification of exposure and risks to human health.

The overall approach is outlined in the following figure (modified from enHealth 2012a).

1 The NEPC guidelines have been under revision and are proposed to be released in 2013. The underlying principles within the 2013 NEPC revisions have not changed from those presented in the current guidance, however there are some aspects that provide more specific guidance and the revision has considered more current information. Where relevant, more specific and current information (consistent with that being adopted in the NEPC revision) has been adopted in this report. 2 Guidance is noted to have been rescinded by NHMRC, however there are a number of aspects associated with the assessment of risks to human health that are addressed in this document that have not been taken up into more recent and more general guidance provided by NEPC and enHealth.

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Engage the Stakeholders, Risk Communication and Community Consultation

ISSUE IDENTIFICATION - Identification of key issues relevant to the quantification of risks to human health - Identify data gaps relevant to the assessment of exposure and risk

HAZARD ASSESSMENT EXPOSURE ASSESSMENT

Hazard Identification Dose-response - Analysis of hazard locations - Review available data Assessment - Identification of exposed populations that define potential - Collection and analysis - Identification of potential exposure pathways hazard of relevant data - Quantification of relevant exposure parameters - Define acceptable risk - Uncertainty analysis for - Uncertainty analysis for exposure assessment step relevant for defining a dose-response hazard assessment step

Review and RISK CHARACTERISATION Review and reality check - Based on the quantification of exposure and reality check dose-response, risks to human health are quantified. - Evaluate uncertainty - Provide conclusions

RISK MANAGEMENT - Define the options and evaluate the environmental health, economic, social and political aspects of the options - Make informed decisions - Take actions to implement the decisions - Monitor and evaluate the effectiveness of the action taken

The following presents a summary of the methodology adopted in the quantification of human health risks. Further detail on the approach adopted for each of the key stages are summarised in the following sections, with all equations used presented in Appendix A.

1.4.2 Issue Identification This involves a review of the available mercury data relevant to the FCAP site and off-site areas with respect to the form in which it occurs in soil and groundwater in these areas. The aim of this review is to identify key issues that warrant more detailed assessment within the HHERA to address current or potential exposures on the FCAP, downgradient of the FCAP and in off-site areas.

1.4.3 Exposure Assessment This task draws on the evaluation undertaken as part of the “Issue Identification” stage, and involves a detailed evaluation, identification and quantification (where required) of the potential exposure pathways and all significant population groups.

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The exposure assessment is undertaken to be representative of a particular population, and does not calculate the exposure for a given individual. Populations are grouped so as to reflect common activities undertaken by that group (such as workers or children) or by the location of the population in relation to the contaminant distribution. For this reason it is important that the exposure assessment be undertaken in such a way that the most sensitive individuals within the potentially exposed population are adequately protected. The exposure assessment has been structured in the following way:

 Identification of the population(s) that might be exposed to mercury at the FCAP site and downgradient of the site;

 Identification of the activities by which exposure might take place for each population;

 Identification of parameters which define activity (such as time spent indoors) and physiological exposure parameters (such as body weight and inhalation rate); and

 Identification of the chemical concentration and its form at the point of exposure. This may include the identification and use of models to estimate chemical concentrations for receptors and exposure pathways that cannot be measured directly.

Key Pathways and Receptors Receptor populations are similar groups of people who live or work in the study area and who might be exposed to mercury in the areas on the FCAP, downgradient of the FCAP (on BIP) or areas further downgradient (off the BIP).

An exposure pathway describes a unique mechanism by which an individual or population might be exposed to chemicals or physical agents at or originating from a source. Each exposure pathway includes:

 a source or release from a source;

 a transport/exposure medium or exposure route; and

 an exposure point.

If any one of these mechanisms is missing (such as transport mechanism or exposure point), then the pathway is considered to be incomplete. An exposure pathway can be considered to be less significant if the potential for a receptor or population to be exposed to the key contaminants identified is considered to be low. This might be due to a number of factors, which might include dilution, chemical transformation, or partitioning onto solids or into vapour during the transport from the source to the point of exposure or limited time for exposure.

Quantification of Chemical Intake When quantifying chemical intake or exposure to environmental contaminants, the risk assessment process focuses on exposure occurring over a prolonged period of years, and, possibly, a lifetime, i.e., a chronic exposure. Whilst an activity might occur infrequently (i.e., several days a year), it might occur regularly over a long period, and, therefore, have the potential to increase long term or chronic intake of the chemical.

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The assessment presented has addressed potential worst-case exposures in areas off the BIP, and exposure has been calculated for a Reasonable Maximum Exposure (RME) scenario estimated by using intake variables and chemical concentrations that define the highest exposure that is reasonably likely to occur in the area assessed. The RME is likely to provide a conservative, or over-, estimate of total exposure, and, therefore, health risk.

The following steps have been followed to estimate chemical intake:

 Identification of exposure parameters for each of the identified exposure pathways and receptors. These are values that describe the physical and behavioural parameters relevant to the potentially exposed population and the pathway of exposure. Some examples include ingestion rate (e.g. amount of soil or dust ingested at work each day), inhalation rate (volume of air inhaled during different activities), exposure frequency (i.e., hours per day or days per year), exposure duration (e.g. number of years at work) and body weight. Where available, exposure parameters have been obtained from Australian sources (enHealth 2012a, 2012b; NEPC 1999 amended 2013b; SAHC 1991, 1993, 1996, 1998);

 Estimation of the chemical concentration in each medium relevant to the receptor groups and exposure pathways. This involves the estimation of potential concentrations in air 0 (mercury vapour Hg (vap)) and in other media such as soil and groundwater (including various inorganic mercury species and methylmercury) where relevant to the assessment of a complete exposure pathway; and

 Calculation of the daily chemical intake or exposure concentration using the relevant exposure parameters and chemical concentration.

Assumptions and calculations relevant to the quantification of chemical intake are presented within this assessment.

Hazard/Toxicity Assessment The objective of the toxicity assessment is to identify toxicity values for COPCs that can be used to quantify potential risks to human health associated with calculated intake. Toxicity can be defined as “the quality or degree of being poisonous or harmful to plant, animal or human life” (NEPC 1999 amended 2013b).

The objective of the toxicity review is to identify appropriate quantitative toxicity values for each chemical and pathway of exposure (oral, dermal or inhalation) that can be used to quantify risk. This has involved the following key steps:

1. Identify the relevant health end-points, and, where carcinogenicity is identified, the mechanism of action. This has enabled the identification of whether a threshold or non- threshold dose-response approach is appropriate; and 2. Identify the most appropriate quantitative value for the assessment of threshold or non- threshold effects. This includes consideration of susceptible populations, where relevant.

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Step 1: Identify Health End-Points and Dose-Response

The quantitative assessment of potential risks to human health for any chemical requires the consideration of the relevant (and most sensitive) health end-points, and, where carcinogenicity is identified, the mechanism of action needs to be reviewed and considered.

For chemicals that are not carcinogenic, a threshold exists below which there are no adverse effects (for all relevant end-points). The threshold typically adopted in risk calculations (using a toxicity reference value [TRV] such as acceptable/tolerable daily intake [ADI/TDI] or tolerable concentration [TC]) is based on the lowest no observed adverse effect level (NOAEL), typically from animal or human (e.g. occupational) studies, and the application of a number of safety or uncertainty factors. Intakes/exposures lower than the TRVs are considered “safe”, or not associated with an adverse health risk (NHMRC 1999).

Where the chemical has the potential for carcinogenic effects, the mechanism of action needs to be understood as this defines the most appropriate dose-response approach to be considered. Carcinogenic effects are associated with multi-step and multi-mechanism processes that may include genetic damage, altering gene expression and stimulating proliferation of transformed cells. Some carcinogens have the potential to result in genetic (DNA) damage (gene mutation, gene amplification, chromosomal rearrangement), and are termed genotoxic carcinogens. For these carcinogens it is assumed that any exposure may result in one mutation or one DNA damage event that is considered sufficient to initiate the process for the development of cancer sometime during a lifetime (NHMRC, 1999). Hence, no safe-dose or threshold is assumed (hence any exposure is associated with some level of incremental lifetime risk), and assessment of exposure is based on a linear or non-threshold approach using TRVs termed as slope factors or unit risk values.

For other (non-genotoxic) carcinogens, while some form of genetic damage (or altered cell growth) is still necessary for cancer to develop, it is not the primary mode of action for these chemicals. For these chemicals, carcinogenic effects are associated with indirect mechanisms (that do not directly interact with genetic material) where a threshold is believed to exist, and are characterised using threshold TRVs such as an ADI/TDI or a TC.

The USEPA (USEPA 2005b) requires the mode of action for carcinogenicity to be clearly understood before accepting a threshold approach for assessing exposures to non-genotoxic carcinogens. Where data are lacking and the mechanism is poorly understood, the default is to adopt a non-threshold approach.

Current industry practice in Australia is to not simply default to a non-threshold approach where understanding (or data) is lacking (as in the US); rather, the approach is to provide an adequate review of available information to enable a decision to be made based on the weight of evidence (enHealth 2012a; NEPC 1999 amended 2013b). This approach has been adopted in this assessment.

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Step 2: Identify Appropriate Quantitative Toxicity Reference Values

Once the most appropriate dose-response approach has been reviewed, quantitative TRVs can be selected for use in a risk assessment. Current Australian guidance is available (enHealth 2012a; NEPC 1999 amended 2013b) on the selection of quantitative values from Levels 1, 2 or 3 sources.

Data should be obtained from Level 1 sources where possible, with preference for published Australian ADIs. However, it is noted that the agencies (Australian and International) listed as Level 1 sources do not always update their reviews and assessment in a timely manner. This can result in different assessments being provided by different agencies based on different databases of information. As this is the case, the selection of appropriate TRVs has been based on an evaluation of currency and suitability for use. The list of appropriate Level 1,2 and 3 sources of TRVs are presented in enHealth guidance (enHealth 2012a).

Consideration of Sensitive Populations

This refers to the assessment of sensitive populations, such as young children, who may be more susceptible than addressed on the basis of published TRVs (discussed above) to adverse health effects. The issue of assessing childhood sensitivity is complex (Hines et al. 2010), and involves a wide range of factors that may not be addressed in the current approaches to the quantification of risk. The USEPA (USEPA 2005b, 2005a) has provided additional guidance on assessment of early- lifetime exposures associated with carcinogens that have a mutagenic mode of action. Children are assumed to be at increased risk for tumour development following exposure to mutagens due to their rapid growth, fuelled by rapid cell replication. It is thought that a child’s DNA repair mechanisms may not be able to keep up with the rapid cell replication. The WHO (WHO 2006) provides a more detailed review of susceptibility associated with more general exposure to environmental agents where consideration of risk assessment approaches that address childhood developmental life stages is recommended.

In relation to this assessment, mercury (all forms of mercury considered in this assessment) has not be demonstrated to be genotoxic or mutagenic (refer to Appendix B) and hence no additional consideration of these early lifetime exposures is relevant. It is noted that the assessment of mercury has considered all identified health endpoints that include reproductive and developmental effects, and developed quantitative TRVs that are based on the most sensitive of these endpoints. In addition safety/uncertainty factors are included to further address the range of sensitivities that may be present in a population. Hence the TRVs adopted in this assessment are considered suitable for the assessment of potential exposures by all members of a population, including more sensitive groups such as infants, young children and the elderly.

1.4.6 Risk Characterisation and Acceptability of Risk Risk characterisation is the final step in a quantitative risk assessment. It involves the incorporation of the exposure and toxicity assessment to provide a quantitative evaluation of risk. Risk is characterised separately for threshold and non-threshold carcinogenic effects as outlined below. For threshold and non-threshold effects, the discussion presented outlines a technically acceptable level of risk. However, it should be noted that the acceptability of risk also needs to consider the community.

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As noted in Section 2, the assessment of risks to human health associated with different forms of mercury involves the calculation of a threshold dose response only. Hence no non-threshold risk is calculated in this HHERA.

Risks can be defined to be “acceptable” or tolerable if the exposed public could be expected to bear them without undue concern. Risks may be considered to be unacceptable if they exceed a specified regulatory limit, or if the circumstances are such that the risks cannot be accepted. Negligible risks are those that are so small that there is no cause for concern about them, or so unlikely that there is no reason to take action to reduce them.

Perceptions of risk are also important in determining whether risks from contamination in particular locations can be considered tolerable. The risks that tend to be of greatest concern are those that are involuntary (such as groundwater contamination), man-made and perceived as potentially catastrophic in their consequences.

While risk assessments can help to quantify levels of risk, and identify a “technically acceptable level of risk”, risk is usually an emotive issue and the level of perceived risk acceptable to the community may differ depending on the knowledge and lifestyle expectations of the community involved.

In the case of human health risk assessments associated with contamination in the environment, the potential health effects are not necessarily well defined or measurable, and, hence, some degree of debate arises as to the level of acceptable risk. There is a common expectation that risks should be reduced to as low as reasonably practicable or achievable. The process of evaluating risk to human health associated with exposures in areas surrounding the BIP has followed accepted methodology, as agreed with NSW EPA and NSW Health, and accepted methods of defining a technically acceptable risk, which are considered to be conservative and protective of all individuals.

The process of risk assessment aims to assist risk managers in addressing the potential impact of a proposed development or an existing or possibly foreseeable future situation on the surrounding community and the communication of the potential risks.

Assessment of Threshold Effects The quantification of potential exposure and risks to human health associated with the presence of chemicals where a threshold dose-response approach is appropriate has been undertaken by comparing the estimated intake (or exposure concentration) with the threshold values adopted that represent a tolerable intake (or concentration), with consideration for background intakes3. The calculated ratio is termed a Hazard or Risk Index (HI/RI), which is the sum of all ratios (termed Hazard or Risk Quotients [HQ/RQ]) over all relevant pathways of exposure. These are calculated using the following equations:

Daily Chemical Intake Hazard/ Risk Quotient[HQ / RQ](oralor dermal)  (TRV Background)

3 Background intakes are intakes of a chemical that are derived from sources other than the contamination being assessed. This may include dietary intakes and intakes from drinking water or urban air.

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ExposureConcentrationin Air Hazard/Risk Quotient[HQ /RQ](inhalation)  TRV  Background

Hazard/Risk Index (HI/RI)  HQ /RQ All pathways

The interpretation of an acceptable HI/RI needs to recognise an inherent degree of conservatism that is built into the establishment of appropriate TRVs adopted (using many uncertainty factors) and the exposure assessment. Hence, in reviewing and interpreting the calculated HI/RI the following is noted:

 A HI/RI less than or equal to a value of 1 (where intake or exposure is less than or equal to the threshold) represents no cause for concern (as per risk assessment industry practice, supported by published guidance (NEPC 1999 amended 2013b; USEPA 1989)); and

 A HI/RI greater than 1 requires further consideration within the context of the assessment undertaken, particularly with respect to the level of conservatism in the assumptions adopted for the quantification of exposure and the level of uncertainty within the toxicity (threshold) values adopted.

1.5 Features of the Risk Assessment The risk assessment has been carried out in accordance with international best practice and general principles and methodology accepted in Australia by groups such as ANZECC, NHMRC, NEPC and enHealth. However, there are certain features of risk assessment methodology that are fundamental to the assessment of the outputs and to drawing conclusions on the significance of the results. These are summarised below:

 The risk assessment is a mathematical procedure that addresses potential exposure pathways based on an understanding of the nature and contamination status of the area, current zoning and uses of the area by the general public. The risk assessment is based on estimation of worst-case concentrations identified in relevant exposure media and hence is expected to overestimate the actual risks;

 Conclusions can only be drawn with respect to the environmental media currently contaminated with mercury at and downgradient of the FCAP. This report does not present a review of historical workplace practices or exposures on the BIP;

 The risk assessment does not present an evaluation of the health status of the existing community in the area. Rather, it is a logical process of calculating the potential daily intake of chemicals associated with exposure to contamination at and downgradient of the FCAP. This estimate is then compared to regulatory and published estimates of daily intakes that a person may be exposed to over a lifetime without unacceptable risks to their health;

 The risk assessment reflects the current state of knowledge regarding the potential adverse human and ecological effects of various forms of mercury identified. This knowledge base may change as more insight into biological processes is gained, further studies are undertaken and more detailed and critical review of information is conducted.

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Section 2. Mercury in the Environment 2.1 Introduction Mercury is a pervasive and persistent chemical in the environment. It is a naturally occurring element that is released from a variety of sources including human activities. Once released into the environment, mercury undergoes a series of complex chemical and physical transformations as it cycles among the atmosphere, land, and water. Humans, plants, and animals are routinely exposed to mercury and accumulate it during this cycle, potentially resulting in a variety of ecological and human health impacts.

The characteristics of mercury that make it a health and environmental problem are its toxicity and persistence in the environment, and its ability to accumulate and bioconcentrate as methylmercury in aquatic species. The following sections present additional detail on the general behaviour of mercury in the environment, and the toxicity of different forms of mercury in humans and the environment. There are a range of documents published that address the presence of mercury in the environment and potential for exposure. The following discussion presents a summary of information available presented in peer-reviewed reports and publications (ATSDR 1999, 2009; JECFA 2011; USEPA, 1997a, 1997b, 2009b; WHO 2003).

2.2 Mercury in the Environment 2.2.1 General Mercury is a naturally occurring element that is mobilised from natural sources (such as volcanoes) as well as human sources (including mining and combustion sources). Mercury (Hg) in the environment, including groundwater, exhibits complex behaviour that affects both its mobility and potential toxicity. Mercury has a low solubility in water; however, it also has the potential to form multiple species in the environment, which can lead to increased total mercury concentrations in aqueous systems. The relative toxicity of mercury is also dependent on the form in which it occurs, which, in groundwater, is dependent on: biogeochemical processes; partitioning between solids, groundwater, and vapour; and complexation with dissolved organic and inorganic ligands. Redox, pH conditions, and groundwater composition are, consequently, all important components of determining the likely form, and therefore, potential fate of mercury in the environment.

0 2+ Mercury can exist in three oxidation states: Hg (metallic – elemental), Hg2 (mercurous or Hg(I)), and Hg2+ (mercuric or Hg(II)). The properties and behaviour of mercury depend on the oxidation state. Mercurous and mercuric mercury can form numerous inorganic and organic chemical compounds; however, mercurous mercury is rarely stable under ordinary environmental conditions. Most of the mercury encountered in water/soil/sediments/biota (all environmental media except the atmosphere) is in the form of inorganic mercury salts and organomercurics.

With respect to the assessment of chemical properties, fate and transport and toxicity mercury is most commonly assessed in three key forms: elemental, inorganic and organic.

 Elemental (Hg0) or metallic mercury is a silvery, shiny liquid at room temperature that produces a colourless, odourless vapour at room temperature. The unique properties of Hg0, such as its ability to conduct electricity and its coefficient of expansion, make it useful for a variety of specialised uses, (e.g. temperature measurement in thermometers). Where

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metallic mercury is present, it partitions strongly to air. Most of the mercury encountered in the atmosphere is Hg0 vapour.

 Inorganic compounds can be formed when Hg0 combines with elements such as sulphur, chlorine or oxygen. These compounds are usually known as mercury salts.

 Organic mercury compounds occur when Hg0 combines with carbon and hydrogen.

In the environment, microorganisms (bacteria and fungi) and natural processes can change mercury from one form to another.

2.2.2 Atmosphere Mercury is emitted to the atmosphere through both naturally occurring and anthropogenic processes. Natural processes include volatilisation of mercury in marine and aquatic environments, volatilisation from vegetation, degassing of geologic materials (e.g., soils) and volcanic emissions. The natural emissions are thought to be primarily in the Hg0 form.

Anthropogenic mercury releases are thought to be dominated on the national scale by industrial processes and combustion sources that release mercury into the atmosphere. Fossil fuels like coal contain small amounts of mercury so when these fuels are burnt (cars, power stations etc.) mercury is released. Mercury has been used in a variety of industrial processes like gold mining and chlorine production but these uses are being phased out. When mercury is released to the atmosphere from a stack it can be either gaseous or particulate forms of mercury. Gaseous mercury emissions are thought to include both elemental (Hg0) and oxidised chemical forms (mostly Hg(II)), while particulate mercury emissions are thought to be composed primarily of oxidised compounds due to the relatively high vapour pressure of Hg0.

Pollutants released to the atmosphere can be removed from the atmosphere and returned to the surface in three ways. If the compound is water soluble then it dissolves in the water vapour in the air and is rained out. If the compound is in particulate form then it can be washed out by the rain (wet deposition) or it can fall due to the effects of gravity as the particles get big enough (dry deposition).

Mercury released into the atmosphere from natural and anthropogenic sources in particulate form deposits via wet (rain) or dry (particulate/dust) processes. The particles contain mercury mainly in the form of oxidised mercury or (Hg(II)). This oxidised mercury can be from either direct deposition 0 of emitted Hg(II) or from conversion of emitted elemental Hg to Hg(II) through ozone-mediated reduction. The former process may result in elevated deposition rates of Hg(II) around atmospheric emission sources.

Hg0 vapour is not susceptible to these major deposition processes due to its high vapour pressure and low water solubility. It cannot dissolve in the water vapour in the atmosphere and is not in particulate form unless it reaches high levels in the atmosphere where ozone-mediated reduction can occur. Consequently, Hg0 remains in the atmosphere for a long period of time with an average residence time in the atmosphere of about one year. This process results in regional/global transport followed by deposition when it eventually is converted into particles. Hence deposition from Hg0 sources does not occur in the area located close to the source, rather these emissions contribute to more regional/global distribution of mercury.

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2.2.3 Soil In soil, mercury mainly occurs as metallic/elemental mercury and inorganic mercury(II) compounds. Elemental mercury in soil may undergo several transformations depending on the soil characteristics. Conditions (e.g., pH, temperature and soil humic content) are typically favourable for the formation of inorganic mercury compounds. Mercuric complexes tend to dominate, forming - - 2- complexes and solids with the most common ionic species (Cl , OH , CO3 and sulphide). Although inorganic Hg(II) compounds can be quite soluble (and, potentially mobile) they form complexes with soil organic matter (mainly fulvic and humic acids) and mineral colloids; the former is the dominating process. This is due largely to the affinity of Hg(II) and its inorganic compounds for sulfur-containing functional groups.

This complexing behaviour greatly limits the mobility of mercury in soil. In general, much of the mercury in soil is bound to bulk organic matter and is susceptible to elution in runoff only by being attached to suspended soil. Some Hg(II), however, will be adsorbed onto dissolvable organic ligands and other forms of dissolved organic carbon (DOC) and might then partition to runoff in the dissolved phase. In addition where the organic carbon content of soil is low the potential for inorganic mercury compounds to be bound and not mobile (and present in the dissolved phase), is lower.

Methylmercury can be formed by various microbial processes acting on Hg(II) species. In general, approximately 1-3% of the total mercury in surface soil is methylmercury (with higher percentages in soil with higher organic content and under slightly acidic conditions), and as is the case for Hg(II) species, it will be bound largely to organic matter.

2.2.4 Groundwater The presence and mobility of mercury in groundwater is complex and will depend on a wide range of factors that include the nature of mercury in the source area and the characteristics of the soil and groundwater environments.

Two solid forms of mercury, mercury oxide (HgO) and Hg0, are not very soluble in water in these forms are not considered to be mobile and impact on groundwater quality. HgS species have limited solubility in water and limited mobility in soils and tend to be unstable, precipitating as insoluble HgS in most environments. Hence where these largely insoluble forms of mercury are present in soil they are not likely to be present (in these forms) in runoff or water that may infiltrate the surface and migrate to groundwater.

The presence of more soluble inorganic mercury compounds in soil may result in these compounds migrating to and impacting on groundwater. The mercury species, however can undergo a number of chemical transformations depending on conditions in the subsurface, that may change the behaviour of mercury once in the groundwater system. More specifically, in groundwater, the dominant form of dissolved mercury species will vary with pH, redox conditions and salinity.

+ In oxidised freshwater with circum-neutral pH, Hg(OH)2 dominates. HgCO3 and HgOH are minor

species in the Hg(II) system, as their formation is typically suppressed by the presence of Hg(OH)2. - As salinity increases, Cl complexes tend to dominate. At low pH (~pH 2), HgCl2 is the dominant dissolved chloride complex; however it is relatively unstable, and therefore it does not tend to be - significant in the environmental behaviour of mercury. As chloride activity increases, HgCl3 begins

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2- to dominate, especially in very saline waters. HgCl4 dominates in oxidising seawater. As conditions become more reducing or as mercury activity increases, Hg0 will dominate and can potentially form fine droplets of Hg0; however in groundwater environments where inorganic or organic ligands are present, it will tend to reform complexes with ligands, or will sorb onto the solid phase.

Different aqueous mercury species have different potentials to partition into either the solid mineral phase of the aquifer, or into dissolved or solid organic carbon in groundwater or the aquifer sediments. These processes will depend on a range of factors that include pH, the presence of dissolved organic matter, such as humic acids, and presence of chloride. In general, however an increase in humic acid may increase the solubility of the less mobile species (HgS and HgO), mercury mobility increases within increases in the ratio of chloride to total, sorption of mercury species to soils decreases with increasing groundwater pH and sorption of mercury will generally increase with increased solid organic matter.

The results of geochemical modelling at the FCAP site and downgradient (URS, 2008b) indicate 2+ that, in the FCAP source zone, dissolved mercury forms mercurous mercury (Hg2 ) preferentially - over mercuric chloride complex (HgCl3 ). This has implications for the transport of mercury away 2+ from the source zone since Hg2 is a cation and, therefore, is more likely to sorb to clays and other - aquifer particles than HgCl3 , which dominates in the downgradient areas of the groundwater plume. Higher concentrations of total mercury relative to the sum of laboratory-speciated mercury further indicate that sorption might be an important process in the FCAP source area.

The biotransformation of inorganic mercury species to methylated organic species in water bodies can occur in the sediment/soil and the water. Sulfur-reducing bacteria are responsible for most of the mercury methylation in the environment, with these processes occurring more favourably under anaerobic conditions.

Increased dissolved organic carbon levels reduce methylation of mercury in the water column, possibly as a result of the binding of free mercury ions to the dissolved organic carbon at low pH, thus reducing their availability for methylation, or the dissolved organic carbon may inhibit the methylating bacteria.

Once formed, methylmercury tends to be metastable in the environment, and can be bioaccumulated by organisms. Additionally, microbial activity can enhance demethylation of methylmercury, forming Hg0 or Hg2+ and other inorganic mercury complexes.

2.2.5 Environment There are a number of pathways by which mercury can enter the fresh or marine water environments: Hg(II) and methylmercury from atmospheric deposition (wet and dry) can enter water bodies directly; Hg(II) and methylmercury can be transported to water bodies in runoff (bound to suspended soil/humus or attached to dissolved organic carbon); or Hg(II) and methylmercury can leach into the water body from groundwater flow in the upper soil layers.

Once in the water system, complexation and transformation processes will occur. Once entering a water body, mercury can remain in the water column (further partitioned as dissolved or attached to suspended material), be lost from the water body through drainage water, undergo transformation to

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more volatile Hg0 or dimethylmercury and revolatilise into the atmosphere, settle into the sediment or be taken up by aquatic biota.

Methylation is a key step in the entrance of mercury into the food chain. The biotransformation of inorganic mercury species to methylated organic species in water bodies can occur in the sediment and the water column. Methylmercury is very bioavailable and accumulates in fish through the aquatic food web; nearly 100% of the mercury found in fish muscle tissue is methylated.

2.3 Toxicity of Mercury – Human Health The three forms of mercury noted in Section 2.2.1, namely elemental mercury, inorganic mercury and methymercury, are the most commonly evaluated with respect to behaviour in the environment and toxicity. Hence the further assessment of mercury toxicity is based on these three groups.

The review of potential risk issues presented in Section 4 has identified the need to consider risks to human health associated with the presence of mercury in soil and groundwater primarily in the form of Hg0 and inorganic mercury, with a lower potential for the presence of methylmercury. This evaluation, however has considered the toxicity relevant for all three mercury groups.

A detailed toxicity summary for mercury is presented in Appendix B of this report. This summary has considered the most current information available in relation to the toxicity of the three forms of mercury evaluated in accordance with current, endorsed, Australian guidance (enHealth 2012a; NEPC 1999 amended 2013b).

Review of toxicological studies and risk assessments for all forms of mercury by several countries and international organisations have established levels of daily or weekly intakes of mercury that are estimated to be “safe” (UNEP 2008). That is, there is a threshold or reference level below which exposures/intakes are not associated with adverse effects. The WHO makes it clear in their assessment that these reference levels are not a clear dividing line between safe and unsafe. This is because they have incorporated a number of safety/uncertainty factors into their calculation of the reference level for mercury which means a slight exceedance of this value does not immediately result in adverse effects.

The quantitative toxicity reference values (TRVs) identified for the assessment of potential exposure to mercury (all forms) are based on these safe levels (that incorporate a range of safety factors). The safe levels are associated with the amount of mercury a member of the general population may be exposed to every day for a lifetime. Hence these values are relevant to the assessment of chronic (long-term) exposures. The quantification of risk, also requires the assessment of exposures that may occur infrequently or over a short period of time (less than 1 year, such as exposures that may occur during the maintenance of services). These exposures are termed sub-chronic. Hence both chronic and sub-chronic TRVs have been identified and considered in this assessment.

The following table presents a summary of the key human health aspects in relation to exposure and adverse effects associated with elemental, inorganic and methylmercury (refer to Appendix B for further detail).

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Table 2.1 Summary of Human Toxicological Reference Values for Mercury

Elemental Mercury Potential for Mercury is a heavy metal that occurs naturally as a mineral and is widely distributed by natural Exposure and anthropogenic processes. The most significant natural source of atmospheric mercury is the degassing of the Earth’s crust and oceans and emissions from volcanoes. Hg0 is a dense, silvery white metal which is liquid at room temperature, readily volatilises and is considered to be the predominant form of mercury in the atmosphere (i.e. as a vapour). As discussed in Section 2.2.2, elemental mercury has a long residence time in the atmosphere and hence can be widely transported before it is transformed and redeposited as Hg(II) via wet or dry deposition processes. Exposure to Hg0 is predominantly associated with the inhalation of mercury vapour. Approximately 80% of inhaled Hg0 is absorbed through the lungs by rapid diffusion. In contrast, only 0.01% of Hg0 is absorbed through the gastrointestinal tract. Dermal and oral exposures are not considered to be of significance or result in adverse health effects (WHO 2003). Health Effects The key health effects relevant for the assessment of exposure to Hg0 are impaired lung function (acute exposures) and central nervous system (CNS)/ kidney damage (chronic exposures). Identified TRVs for Quantitative Risk Assessment* Inhalation TRV: 0.0002 mg/m3 (WHO 2003) or 0.2 µg/m3 – relevant to the inhalation pathway only (other pathways not of significance for this form of mercury) for chronic and sub-chronic exposures. This value has also been adopted as a screening level chronic air guideline in the review of ambient air data collected on the site boundary. Background 10% of inhalation TRV intakes:

Inorganic Mercury** Potential for The fate and transport properties of inorganic mercury compounds differ. In particular the Exposure solubility and sorption properties differ; however with respect to the potential for exposure the most significant route of exposure is absorption by the oral route. Inorganic mercury compounds are not volatile and therefore the inhalation of inorganic mercury compounds bound to particulates is the only inhalation exposure that might be relevant. Inhalation intakes of inorganic mercury are dependent on the size and solubility of particles. Dermal absorption of inorganic mercury in soil is considered to be low, with 0.1% absorption considered in this assessment. Health Effects The key health effects relevant for the assessment of exposure to inorganic mercury compounds include gastrointestinal, cardiovascular and kidney effects (acute exposures) and kidney damage (chronic exposures). Inorganic mercury, particularly mercuric chloride can cause CNS effects. Mercuric chloride has been classified by the USEPA as a possible human carcinogen, however the mechanism of carcinogenicity has not been shown to be genotoxic, and carcinogenic effects have only been observed at exposures higher than those that cause other adverse effects. Hence a threshold (safe) level can be adopted for the assessment of all these adverse effects. Identified TRVs for Quantitative Risk Assessment* Chronic Oral: 0.0006 mg/kg/day (WHO 2011) for oral and inhalation routes of exposure Oral/Dermal Dermal: 0.000042 mg/kg/day following application of a GAF of 7%# TRV: Subchronic Oral: 0.002 mg/kg/day (ATSDR 1999) for oral and inhalation routes of exposure Oral/Dermal Dermal: 0.00014 mg/kg/day following application of a GAF of 7%# TRV:

Background 40% for oral and dermal intakes (as % of TRV) intakes: 10% for inhalation intakes

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Table 2.1 (continued)

Methylmercury Potential for Methylmercury is an organic form of mercury. Biological processes, such as bacterial activity in Exposure plants and sediments can transform mercury to methylmercury. The mercury methylation process depends on mercury loadings, microbial activity, nutrient content, pH and redox condition, suspended sediment load, sedimentation rates, and other variables; anaerobic conditions favour methylmercury formation more than aerobic conditions. Methylmercury is somewhat soluble in water and is the most bioaccumulative and toxic form of mercury. While most of the mercury in aquatic systems is expected to be in the inorganic form, more than 95% of the mercury accumulated by biota is in the form of methylmercury. The most significant route of exposure is absorption by the oral route (where methylmercury in the diet is almost completely absorbed). Inhalation of methylmercury vapour and particulates also occurs. Absorption via the dermal route is considered low, with absorption from soil assumed to be the same as for inorganic mercury (0.1%). Methyl mercury is distributed via the blood to all tissues. It can cross into the brain and foetus. The major site of systemic deposition of methyl mercury is the kidney. Hair levels are typically used as an index of exposure to mercury and there is a proportional relationship between mercury intake, blood mercury and hair mercury. Health Effects The key health effects relevant for the assessment of exposure to methylmercury are the central nervous system (CNS). There is also evidence to suggest that the embryo and foetus are more sensitive to methylmercury exposures. Other effects associated with methyl mercury include damage to other tissues and organs including the lung, cardiovascular system, liver and kidney. Methylmercury has been classified as a possible human carcinogen by the USEPA and IARC, however the mechanism of carcinogenicity has not been shown to be genotoxic and a threshold (safe) level can be adopted for the assessment of all these adverse effects. Identified TRVs for Quantitative Risk Assessment* Oral TRV: 0.00023 mg/kg/day (EA 2009; WHO 2011) adopted for all routes of exposure, relevant to the assessment of chronic and sub-chronic exposures. Background 20% for all intakes (as % of TRV) intakes: Notes: # The USEPA (USEPA 2004b) has recommended the use of a gastrointestinal absorption factor (GAF) of 7% for inorganic mercury based on mercuric chloride and other soluble mercury salt studies used in the derivation of the oral RfD. The GAF is used to modify the oral TRV to a dermal value in accordance with the USEPA (2004) guidance. * The toxicity reference values identified for the assessment of chronic and subchronic is in accordance with Australian guidance (enHealth 2012a; NEPC 1999 amended 2013b) and are based on the protection of the most sensitive adverse effects identified. ** The term inorganic mercury refers to a wide group of mercury compounds. These include mercuric and mercurous mercury as well as inorganic mercury salts formed when Hg0 combines with elements such as chlorine, oxygen or sulphur. In general, mercuric chloride is expected to be the most common inorganic form in the soil and water environment. However it is noted that the results of geochemical modelling (URS, 2008b) indicate that, in the source 2+ - zone, dissolved mercury forms mercurous mercury (Hg2 ) preferentially over mercuric chloride complex (HgCl3 ). As the water solubility and bioavailability of many other inorganic compounds, notably mercurous compounds, are much less than those of mercuric chloride, such compounds are likely to be less toxic, and hence the tolerable intake adopted above is likely to err on the conservative side.

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2.4 Toxicity of Mercury - Environment 2.4.1 Bioavailability, Bioaccumulation and Biomagnification Bioaccumulation of mercury has been shown to occur in aquatic plants, invertebrates, insects, scavengers, fish and mammals. Benthic organisms are particularly susceptible to bioaccumulation of mercury (especially methylmercury) due to their close ties to the geochemistry of the sediments that they live on and in. Uptake occurs primarily via dissolved-phase mercury in interstitial pore waters, with the mass of mercury bound in the sediment serving as a source. Studies have shown that bioaccumulation of mercury in invertebrate benthic organisms is relatively low in comparison to higher trophic level organisms such as mussels, shrimp, crabs and fish. This is due in part to the ability of the different organisms to eliminate mercury from their systems following initial uptake.

Methylmercury is preferentially bioaccumulated in organisms, although bioaccumulation of mercury in the inorganic forms (neutral and charged aqueous complexes, e.g., Hg(OH)2, HgCl2) has also been documented. Preferential uptake of methylmercury is due in part to its greater solubility in biological fluids and its lower rate of elimination in comparison to other organic and inorganic mercury complexes.

In particular, methylmercury has a very high affinity for sulfhydryl groups in proteins and is absorbed much more efficiently by organisms than inorganic mercury forms. Uptake and accumulation of mercury in the water column takes place primarily via food. Mercury is later redistributed throughout other tissues in the organism and retained for long periods of time. Inorganic mercury complexes can be initially taken up within the digestive tract of fish but the majority of mercury is soon excreted.

Biomagnification of mercury through the food chain as methylmercury has been demonstrated in high trophic-level piscivorous fish and can be especially significant in marine mammals that feed on these fish, although this varies widely between species.

The bioavailability of mercury to an organism is dependent both on the physical and chemical nature of the impacted media (e.g., sediment) and the ecological habits (e.g., feeding) and physiological characteristics of the organism (e.g., physiological aspects that promote bioaccumulation). The same geochemical factors that govern the fate and transport of mercury in the environment affect bioavailability to organisms. Characteristics of soil, sediment or water that promote the bioavailability of mercury in organisms include high concentrations of methylmercury, low concentration of organic carbon (both dissolved and particulate) available for binding, low capacity to form charged inorganic complexes, and moderate redox conditions. Hg0 vapour is readily absorbed through plant shoots, and can also readily cross root membranes with transpiration water.

Bioavailability for birds and mammals is highly variable, depending in part on feeding habits. Primary uptake in earthworms plays an important role in bioaccumulation of mercury in terrestrial food chains. Absorption of methylmercury and HgCl2 in the gastro-intestinal tract of birds and mammals is greater than for inorganic forms. Bioaccumulation is generally higher in predators in comparison to herbivores.

Bioavailability of mercury in sediments has been demonstrated to decrease with increasing organic carbon content. Other agents that can reduce the bioavailability of mercury include chloride, carbonates and hydroxides.

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2.4.2 General Toxicity to Ecological Receptors The toxicity of mercury is dependent on the form of mercury present, geochemical factors such as temperature, salinity and pH, the sensitivity of individual species at different growth stages and the tolerance of individual organism.

Toxicological effects of mercury on aquatic organisms can include neurological damage, reproductive impairment, growth inhibition, developmental abnormalities, and altered behavioural responses. Reproductive endpoints have generally been shown to be more susceptible to mercury toxicity than growth or survival endpoints.

Methylmercury has been shown to be significantly more toxic to aquatic life than inorganic forms of mercury. Toxicity has also been shown to increase with increasing temperature and decreasing oxygen content. The complexity of mercury toxicity in the environment with respect to these and other factors often necessitates the collection of site-specific data to accurately assess biological effects, rather than reliance on chemical data and the use of generic screening levels or model results.

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Section 3. Environmental Setting 3.1 Introduction This section presents a summary of the environmental setting of the FCAP and surrounding areas. The information presented has been drawn from previous investigations undertaken by URS in 2006 and 2007.

Regionally, the BIP is located on an area of former sand dunes and coastal swamps within the Botany Basin. The elevation of the site drops from around 20 m above sea level on the eastern side of the site (Denison Street) to less than 5 m above sea level on the western side. An extensive low lying (less than 5 m above sea level) area which was formerly swampy, occurs to the west of the site (this was formerly referred to as Veterans Swamp). Natural drainage from the site is towards Springvale Drain, which drains the low lying area southwards to Botany Bay. Springvale Drain runs south via open sections of drain as well as a piped underground section. The drain enters the bay via Penrhyn Estuary, which was formed by the reclamation of the Port Botany Container Terminal area. The FCAP area of the BIP lies between 12 and 16 m Australian Height Datum (AHD) and is generally flat (Figure 1).

3.2 Geology 3.2.1 Regional Geology The following description of regional geology is extracted from the Stage 1 and Stage 2 Investigation report (URS, 2006a) and the Conceptual Site Model (CSM) Report (Golder 2011).

The Botany Basin occupies an area of approximately 80 km2 and lies to the south of the City of Sydney. The areal extent of the basin is bounded by Centennial Park in the north, Randwick and Matraville in the east, Alexandria and Rockdale to the west, the Kurnell Peninsula and the northern part of the Sutherland Shire to the south.

The Quaternary sediments in the Botany basin are up to 80 m thick (APM test bore 37 drilled in 1955) and overlie the bedrock surface of the Hawkesbury Sandstone, into which old river channels (palaeochannels) have been incised (AGEE & Woodward Clyde, 1990). The Quaternary sediments are comprised of predominantly unconsolidated to semi-consolidated permeable sands. These are interspersed with lenses and layers of peat, peaty sands, silts and clay (low permeability) which become more common in the lower part of the sequence (AGEE & Woodward Clyde, 1990).

Hard, iron cemented, sand layers locally referred to as “Waterloo Rock” are common in the upper portion of the aquifer and are postulated by Roy (1980) to be due to sub-areal weathering. The sediments thicken towards the south and southeast and form a discontinuous sequence that ranges from fluvial, estuarine, terrestrial swamp and aeolian depositional environments (Roy, 1980).

The conceptual geological model of the site was refined as part of the groundwater investigations at the site (Woodward Clyde, 1996) including information gained from the 95 cone penetration test (CPT) holes advanced to bedrock.

Griffin (1963) and Smart (1974) recognised three main stratigraphic divisions in the Botany Sands, which are:

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 Zone 1 – a basal zone of clayey sand and sandy clay with discontinuous layers of gravel, peat and peaty clay;

 Zone 2 – a middle zone of predominantly sand with intercalated peat, sandy peat and peaty sand; and

 Zone 3 – an upper zone of sand with few thin discontinuous peat or silt layers.

Later work conducted by Albani et al (1978) and Roy (1980) identified a deeper fourth unit of interbedded sands of marine origin and clays deposited with estuarine shells. Within the bedrock channels (palaeochannels) the sand and clays are underlain with a basal sand with some gravel of fluvial origin.

From a review of the data collected as part of the site investigations and other available data collated by Woodward-Clyde (1996), a three layer model consistent with Smart’s (1974) has been developed as follows:

Table 3.1 Summary of Stratigraphic Layers in Botany Sands

Woodward-Clyde Smart (1974) Description Typical (1996) Thickness Layer 1 Zone 3 Upper Sand Zone 0 to 6 m Layer 2 Zone 2 Middle Sand Zone 10 to 20 m Layer 3 Zone 1 Basal Zone 2 to 10m

Although four major stratigraphic units have been recognised in the Botany Basin, from a groundwater flow perspective the lowermost unit (Unit 1 as defined by Albani et al, 1978; Roy, 1980) is restricted to the deep palaeochannels and Botany Bay and may be lumped with Smart’s Zone 1, and is herein termed Layer 3. The three layer system is discussed below.

Layer 1 The uppermost layer is generally fill that overlies medium to high density sand, with few thin discontinuous layers of peat or silt. The sand is typically loose, fine to medium grained, sub-angular to sub-rounded, moderately sorted quartz sand, with minor fine heavy minerals.

The thickness of Layer 1 ranges from approximately 4 m to over 10 m, with the thickest sections developed on the north trending dune ridges that occur along Stephen Road to the west of Southlands and further to the north adjacent to the Eastlake Golf Course.

This layer lies between the ground surface and the top of the groundwater table beneath the FCAP site and downgradient areas.

Layer 2 Layer 2 is typically characterised by sand. The sand is generally fine grained, sub-angular to sub- rounded, poorly sorted, with minor fine grained heavy minerals. The sand is generally finer grained and more poorly sorted than the sand encountered in Layer 1. Layer 2 contains various thin (approximately 0.5 m thick) discontinuous low permeability layers that are comprised of peat, peaty

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clay, peaty sand, clayey sand and silty sand, depending on the localised depositional environment. The lateral extent of the various low permeability layers can range from less than 50 m up to 500 m. The Botany Sands are commonly tightly packed at depth.

The unit is approximately 20 m thick, but ranges from less than 10 m thick over bedrock near the southern end of the BIP, to over 30 m near the northern end of the BIP and in the lower reaches of the Lakes Valley Palaeochannel.

Layer 3 Layer 3 is a basal zone of clayey sand and sandy clay with discontinuous layers of gravel, peat and peaty clay. The lithology of this layer is quite variable and reflects the various depositional environments. The top of Layer 3 is commonly characterised by the presence of organic rich layers which are commonly clayey and appear to be relatively continuous across the Botany area.

The distribution of Layer 3 is restricted to the deep parts of the Basin (reflecting its estuarine and restricted lagoonal depositional environments) and is absent from the eastern part of the basin, where the FCAP is situated.

Hawkesbury Sandstone In general the top surface of the Hawkesbury Sandstone bedrock deepens to the north and west away from the BIP and shows a variety of erosional features in the Hawkesbury Sandstone Basement from north to south:

 A broad basement valley at the northern end of the BIP that extends from Denison Street in a westerly direction beneath the former Polypropylene Plant and Olefines II Plant and merges into the Lakes Valley Palaeochannel which extends in a southerly direction into Botany Bay; and

 A westerly trending basement ridge extending beneath the southern portion of the BIP.

3.2.2 FCAP Site Geology A detailed description of the site geology is contained in the previous BIP investigations (AGEE & Woodward Clyde, 1990; Woodward Clyde, 1996). Investigations undertaken by URS in 2007 provide information relevant for Blocks A, L, G and M.

Based on the available information (URS 2007a; URS 2008b, 2008d) the following table presents a summary of the general soil profile beneath each key area on the FCAP site and downgradient areas (refer to Figure 1 for locations).

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Table 3.2 Soil Profile for FCAP and Downgradient Areas

Depth (m below Soil Type/Description ground level) FCAP Site Block L (Chlorine Liquefaction and Chlorine Storage Area) 0.0 – 0.2 Concrete slab (one location sampled in 2007) 0.0 – 1.0 FILL: sand, grey/brown, medium to coarse grain, boulders 20-50 mm, loose. 0.2 – 17 (depth of SAND: (natural) grey/brown to white, medium to coarse grain, loose. investigations) Block M (Hydrogen and Brine Treatment Area) 0.0 – 0.4 FILL: sand with blue metal (angular gravel), brown, coarse grain. 0.0 – 19 SAND: (natural) grey/orange/brown, medium to coarse grain, loose. 19 – 20 (depth of Sandy CLAY: weathered sandstone, yellow, light brown, orange, red, fine grained sand investigations) Block G (Cell Block) 0.0 – 0.1 Bitumen slab 0.0 – 1.0 FILL: topsoil and reworked natural sands with occasional gravels, roadbase, brown/grey, dry. 0.2 – 19.5 SAND: (natural) medium to coarse grained grey/brown sands, loose. Sand noted to becoming white and yellow/brown below 6.0m. Dense (well compacted) later noted at 12-12.5m depth. 19.5 – 20 (depth of CLAY and PEAT: Dense layer identified investigations) Block A (Caustic Soda Filtration and Storage) 0.0 – 0.25 Asphalt 0.0 – 0.8 FILL: roadbase, brown/black compacted sandstone 0.45 – 21 (depth of SAND: (natural) grey/brown, medium to coarse grain, loose, some sandstone rock. investigations) Downgradient of FCAP 0.0 – 0.2 Asphalt/concrete 0.1 – 3.5 FILL: Sand, grey/brown, fine grained (some bricks and gravels noted in MWC17) 0.6 – 3.0 SAND: light brown to grey, fine grained 3.0 – 3.2 PEAT identified in MWC11 and WC32 4.2 – 4.7 PEAT identified in WC30 3.2 – 21 SAND: light brown/grey, fine grained 11 - 12 PEAT identified in MW12 16.5 - 21 (depth of CLAY: soft, white/grey, weathered sandstone investigations)

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3.3 Hydrogeology 3.3.1 Regional Hydrogeology The following is obtained from the CSM Report (Golder 2011).

The Botany Sands contain a system of unconfined and semi-confined aquifers that are referred to as the Botany aquifer. The Botany aquifer was one of the early sources of water for Sydney and an important source of industrial water in the Botany area where up to 44 ML/day has been used on average. Previous work (Griffin, 1963; Smart, 1974; AGEE and Woodward Clyde, 1990) indicates that there is considerable variation in the groundwater yield of the sand, suggesting that there are discrete high yielding layers, or aquifers, within the sequence. These layers are interconnected vertically via leakage through the confining peat and clay layers and laterally by the discontinuous geometry of most of the confining units. Review of data obtained from the operation of the GTP provides additional evidence of the variable and discontinuous nature of confining layers.

The water table elevations range from 35 m AHD at Centennial Park at the northern end of the basin to 0 m AHD at Botany Bay. Groundwater generally flows in a south-westerly direction, with an average hydraulic gradient of 1:120 (~0.008 m/m) (AGEE and Woodward Clyde, 1990). The groundwater flow direction for both the shallow and deep aquifers is in a south-westerly direction and discharges into Botany Bay. This is consistent with the regional groundwater flow patterns in the Botany Sands Aquifer.

Hydraulic parameters of the regional Botany Aquifer are summarised in the following table (refer to Golder 2011).

Table 3.3 Regional Hydraulic Parameters – Botany Aquifer

Stratigraphic Layer Average Measured Median Hydraulic Porosity Specific Yield (aquifer) Hydraulic Conductivity (based Conductivity on Hydraulic Model (m/day) Calibration) (m/day) Layer 1 18 10 0.37 0.20 Layer 2 23 13-15 0.30 0.28 Layer 3 1.2 12 0.35 0.21 Low permeability layers - 1.3 - - (e.g. peat)

The vertical hydraulic conductivity (Kv) of the sequence is likely to be variable depending on the local presence of clay and peat confining units, with a value of 0.010 to 0.1 m/day likely to be representative of the sequence as a whole.

Smart (1974) estimated the porosity of the Botany Sands from laboratory measurements of compacted disturbed samples, with values ranging from 0.33 to 0.44 with a mean of 0.42. CTP testing conducted under the Stage 2 program identified porosities of 0.37 for Layer 1, 0.30 for Layer 2 (reported to be more dense than Layer 1) with variable values reported for Layer 3.

Precipitation in the Botany Basin averages 1100 mm/year which equates to 2.7-16.8 ML/d of recharge (based on assuming 6%-37% of rainfall recharges the aquifer). Higher rates of recharge

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have been inferred at the Botany Golf Course. The main recharge area from rainfall infiltration is Centennial Park at the northern end of the catchment. Other significant recharges occur in green spaces. Parks and golf courses. In the vicinity of Southlands, groundwater levels are controlled by Springvale and Floodvale Drains.

Groundwater from the Botany Sands aquifer has historically been extracted for a range of domestic, industrial and irrigation purposes. Currently groundwater is extracted from local industrial production bores as well as the Groundwater Treatment Plant (GTP) wells. The operation of the GTP has resulted in a lowering of shallow groundwater levels, and, hence, a reduction in the interaction of shallow groundwater with Springvale Drain.

Groundwater use in areas surrounding the BIP is subject to restrictions put in place by the NSW Office of Water (formerly the Department of Water and Energy [DWE] and before that the Department of Natural Resources [DNR]). The Groundwater Extraction Exclusion Area (GEEA) comprises areas down-gradient of the BIP as well as a larger area associated with other sources of groundwater contamination. The extent of the current GEEA, known as Zone 1, is shown in Figure 2.

The groundwater velocities in the vicinity of BIP were calculated from hydraulic gradients and estimates of the hydraulic conductivity. The groundwater velocities in the shallow and intermediate aquifers were estimated to be in the range 80 to 260 m/year generally in a west to south-westerly direction.

Groundwater velocities alone do not accurately reflect the movement of dissolved chemical species in an aquifer, which can be affected by hydrodynamic dispersion due to heterogeneity, anisotropy, and molecular diffusion in the aquifer, and by absorption and, in the case of reactive chemical species, abiotic and biotic transformations.

3.3.2 Site Hydrogeology The following hydrogeological details relevant to the FCAP and the area downgradient have been reported following more recent groundwater investigations undertaken by URS (2007b, 2008a). These reports note variable hydrogeological conditions beneath the FCAP site (source area) and downgradient areas. A more detailed review of the hydrogeological and hydrochemical model in the area is presented by URS in the report “Mercury Fate and Transport Chlor-Alkali Groundwater and Soil Investigation” (2008b). The following presents a summary of the conceptual model developed (URS, 2008b) for the FCAP site and off-site areas. Refer to Figure 3 for groundwater well locations referred to in the following discussion.

Groundwater flow directions in the shallow, intermediate, and deep sections of the unconfined aquifer are to the southwest of the FCAP, predominantly consistent with the groundwater flow directions that were estimated for this region. Recent groundwater elevation data indicate that extraction from the Primary Containment Area (PCA) and other containment lines associated with the operation of the GTP might have led to groundwater flow lines in the intermediate and deep aquifer being pulled slightly further to the west.

Groundwater elevations vary across the site and in downgradient areas. On the BIP beneath the FCAP, the depth to groundwater (shallow aquifer) ranges from 3.8 to 6.9 m below ground level (m

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bgl). Downgradient from the FCAP and BIP the depth to groundwater (shallow aquifer) varies from 0.74 mbgl at MWB12_S (corner of Sourthlands) to 1.7 mbgl at WG30, 4.2 mbgl at MCW16_S and 3.8 mbgl at MWC15_S.

The assessment of mercury fate and transport in groundwater depends on a range of factors, one of which is the presence of brine water or fresh water. The following provides a summary of inputs into the groundwater system at, and in the vicinity of the FCAP.

Brine Input The presence of brines in the groundwater system has the potential to affect the vertical flow/mixing of groundwater aquifers,groundwater salinity and total dissolved solids (TDS).

Vertical hydraulic gradients to the southwest of the FCAP vary. In the FCAP source area, density- corrected vertical hydraulic gradients are downwards from the intermediate to the deep aquifer across the FCAP area; however, they are upwards from the intermediate to the shallow aquifer at several locations. Groundwater in the intermediate aquifer in the source area is saline, probably as a result of downward flow of brines from the former Brine Treatment Area and FCAP. These brines are producing a density effect that appears to limit downward recharge of fresh water into the intermediate aquifer in the source area. The downward gradients from the intermediate to deep aquifer in the source area, and the elevated salinity in the deep and intermediate aquifers, further indicate previous downward migration of brine.

Groundwater salinity and major and minor ion ratios provide an indication of the potential extent of the brine plume derived from the former Brine Treatment Area and FCAP. Elevated electrical conductivity (EC) values extend in the intermediate aquifer to MWC16 and MWC17, and Cl/Br ratios remain elevated in groundwater from these locations, indicating that brine from the source area has probably migrated at least to these locations. EC values from previous monitoring of the deep aquifer at MWC16 and MWC17 also indicate that brines might have migrated into these areas from the source area. However, MWC16 and MWC17 are sufficiently near the coast that some of the elevated salinity might be related to sea water intrusion into the deep aquifer.

Review of TDS content and dissolved mercury and methylmercury concentrations clearly show the penetration of brine into the intermediate and deep aquifers and the subsequent downgradient migration of that brine within these aquifers (refer to URS, 2008b for relevant figures) in the vicinity of the FCAP.

Clear differences in groundwater elevations, TDS and mercury concentrations indicate that, especially away from the FCAP source area, vertical migration of groundwater between the shallow, intermediate, and deep aquifers is limited. Consequently, away from the FCAP source zone, the plume distribution is more likely to be controlled by lateral than vertical transport.

Fresh water input Assessment of the migration of salinity associated with brines from the former Brine Treatment Area and the FCAP is complicated by the influx of fresh (low salinity) groundwater in some locations.

In the FCAP source area, the shallow aquifer in some areas is characterised by groundwater with low chloride concentrations and Cl/Br ratios, consistent with fresh groundwater. This fresh groundwater is likely to have resulted from a combination of recharge and flow from upgradient into

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the shallow aquifer in the vicinity of the FCAP. This recharge has not penetrated significantly into the underlying intermediate aquifer, probably because of the density effect associated with brines in the intermediate aquifer as discussed above. This zone of fresh water extends at least to MWC08, and potentially to MWC11 (see below).

A second zone of fresh water inflow is apparent in the shallow and intermediate aquifers at MWC11. At this location, fresh water appears to cross the primary groundwater flow direction, resulting in influx of fresh water, probably from the east, into these aquifers. The deep aquifer is not affected. Previous EC data indicate that the fresh water in the shallow aquifer has persisted since 2006, when monitoring began; however, EC in the intermediate aquifer has declined, from saline to fresh, since late 2006. The fresh water in the shallow aquifer might be related to the recharge near MWC11, or associated with the recharge of fresh water upgradient. However, the change in EC in the intermediate aquifer at both MWC10 and MWC11 indicates a change in conditions and it is considered possible that pumping at the PCA has induced the flow of fresh water from the east in the intermediate aquifer.

The upgradient groundwater quality (characterised by low EC values) is apparent in samples from WG35 and WG212, located upgradient of the FCAP source zone. Declining EC values in groundwater in the deep aquifer at MWC01 indicate that fresh water might be displacing previously brine-impacted groundwater in this area.

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Section 4. Identification of Risk Issues

4.1 Introduction The following presents a review of the available data with the key objective of identifying key issues that warrant detailed assessment with respect to risks to human health or the environment. The former operations at the FCAP have been identified as potential sources of mercury impacts to soil and groundwater. Based on review of the potential for exposure presented in Section 5, this review focuses on issues that might be relevant in mercury impacted soil in the four Blocks associated with the FCAP (Blocks L, M, G and A) and groundwater beneath and off-site downgradient of the FCAP site.

As the focus of this HHERA is the assessment of mercury, review of the data and information requires consideration of the likely form of mercury contamination at the FCAP and guidelines that are relevant to the identification of potential issues that warrant more detailed evaluation.

4.2 Guidelines 4.2.1 General Data collected from the FCAP and off-site areas have been reviewed against published guidelines that are protective of human health and the environment. This review is undertaken to identify where contamination (and in which media) are sufficiently elevated that they require more detailed evaluation in this assessment.

It is noted that the guidelines presented below are screening level guidelines that are based on the protection of human health or the environment (relevant to a wide range of situations) and as such draw on the available information on the nature and toxicity of the different forms of mercury as presented in Section 2. The guidelines adopted in this assessment are those that are currently endorsed for use (in such evaluations) in NSW. They have been derived to be protective of human health and environmental risks for a wide range of exposure scenarios (i.e. widely applicable) and are used to identify contaminants and potential situations where further, more site-specific investigations or assessments are required. The guidelines are not a clear dividing line between exposures or situations that do not result in any adverse effects and those that do (as is outlined in the supporting documentations for the guidelines referenced below).

Guidelines are only generally available for the three key groups of mercury (as outlined in Section 2) that include Hg0, inorganic mercury and methylmercury. It is noted that guidelines are not available for all these forms of mercury in all the media assessed.

4.2.2 Soil Guidelines The FCAP is located within an industrial area (within the BIP) and hence it is appropriate that soil data collected from the FCAP are compared with criteria that relate to the proposed ongoing use of the site for industrial purposes. It is noted that the BIP does not allow uses such as childcare centres, education or health care facilities to be constructed on the site, hence soil criteria that are protective of these more sensitive uses, have not been used.

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The Health Investigations Levels (HILs) relevant to the assessment of contaminated land have been revised in 2013 (NEPC 1999 amended 2013d). The revision has only been endorsed at the time of writing this assessment and hence the revised HILs are in a transition period of application in NSW. This means that the revised HILs should be used for all new assessments, however for existing projects the former HILs also remain valid. For the purpose of this assessment, the revised HILs have been adopted.

For the assessment of soil in the FCAP area, industrial soil HILs (Level D) have been adopted, which for mercury are:

 Mercury as inorganic mercury: HIL D = 730 mg/kg

 Methylmercury: HIL D = 180 mg/kg

No HILs have been established for elemental mercury in soil, hence the presence of elemental mercury requires a site specific assessment.

In relation to the update of the HILs (NEPC 1999 amended 2013d), the revision undertaken (and released in 2013) considered the most up-to-date toxicological evaluations in line with good scientific practice and protocols established in Australia (enHealth 2012a; NEPC 1999 amended 2013b). These protocols provide the basis for ensuring that published peer-reviewed data/information are considered and the quantitative dose-response approach adopted follows accepted, peer-reviewed processes to ensure that all adverse health effects are adequately and appropriately addressed. The revision to the HIL for mercury has considered the following:

 The HILs for inorganic mercury and methyl mercury have been revised. The NEPM revision has made it clear that the HILs do not address elemental mercury and that where elemental mercury is present a site-specific assessment is required.

 Specific exposure factors directly relevant to each of the landuse scenarios have been revised. This includes the use of exposure factors relevant to commercial/industrial use (such as working 8 hours per day for 240 days per year by adults only). This approach is different from that adopted in the derivation of the former HILs as these were derived for only a low-density residential use (where a young child was most exposed) and an exposure adjustment factor was applied for other landuses. For the commercial/industrial HIL the exposure adjustment factor is 0.2 (i.e. the commercial/industrial HIL is 5 times higher than the residential HIL). This exposure adjustment factor previously adopted is highly conservative. Hence the revised commercial/industrial HILs for mercury (and most other compounds considered in the HILs) are higher than the former commercial/industrial HILs.

 Current data on mercury intakes by the general population from sources other than soil contamination (such as food, dental amalgam, water and air) have been reviewed and included in the revised calculations.

 The current published peer-reviewed evaluations of health effects and quantitative dose response (toxicity) information for inorganic and methyl mercury (relevant to oral, dermal and inhalation exposures) have been reviewed in line with guidance provided by enHealth (2012a).

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As a consequence of the above reviews, the revised commercial/industrial HILs for both inorganic mercury and methylmercury are higher than the former HILs considered in the previous HHERA (URS 2008d).

4.2.3 Sediment Guidelines There are no human health risk based quality guidelines available for sediments in Australia or the US. The available sediment quality guidelines have been derived to be protective of ecological end- points, not human health. The Netherlands have published sediment quality values for both soil and sediment with the intention of enabling the return of contaminated land to any potential use, rather than tailoring the level of remediation to the intended use of the land (e.g., residential or commercial). The values that have been derived include general targets and intervention values as well as indicators of severe contamination. The serious risk concentration (SRC) (based on the protection of human health for sediments), considered to be an intervention value, for mercury (inorganic) is 6700 mg/kg.

Soil HILs can also be utilised to screen sediment concentrations, and given the lack of sediment specific health based criteria, the HILs have been considered in this assessment. Depending on the nature of the exposure, soil HILs available for residential (Level A) or recreational (Level C) scenarios may be appropriate. The residential soil HIL is based on the assumption that young children come into direct contact with contaminated soil and dust (indoors) all day every day. The recreational soil HIL is based on the assumption that young children come into direct contact with outdoor soil only (i.e. no exposure to dust indoors) every day. In relation to sediments that are not located in areas where children frequent, as is the situation identified in this assessment (refer to Section 5 for further discussion), use of recreational HILs is considered appropriate and conservative.

The recreational soil HILs for mercury are (NEPC 1999 amended 2013d):

 Mercury as inorganic mercury: HIL C = 80 mg/kg

 Methylmercury: HIL C = 13 mg/kg

No HILs have been established for elemental mercury in soil and hence where elemental mercury is present in this situation a site specific assessment will be required.

It is noted that the discussion presented in Section 4.2.2 in relation to the revision of the HILs remains relevant to the recreational HILs.

With respect to the protection of the environment ANZECC/ARMCANZ (2000) interim sediment quality guidelines of 0.15 mg/kg (low effects range, trigger value) and 1 mg/kg (high effects range) are currently available. This guideline is based on total mercury reported in sediments.

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4.2.4 Groundwater and Surface Water Guidelines Groundwater directly beneath the FCAP is not extracted and used for any purpose on the BIP. In addition it is noted that the BIP and all areas downgradient, extending to Botany Bay, are within the Groundwater Extraction Exclusion Area (GEEA) (refer to Section 3.3.2). Non-industrial use of groundwater in this area remains banned. However it is noted that industrial use of groundwater within the GEEA is allowed under licence from DWE provided it can be demonstrated that use of the water is “fit for purpose” and “not causing environmental harm”. A survey undertaken by Orica in 2005 did not identify industrial premises to the southwest of the FCAP that utilised groundwater for any purpose.

While considered unlikely that such a licence would be granted within the GEEA, the potential for industrial areas downgradient of the FCAP to obtain a licence to use groundwater for industrial purposes warrants consideration. Consideration of beneficial uses of groundwater in these downgradient areas in the HHERA was also requested by the DECC (now the NSW EPA).

In relation to the assessment of potential beneficial uses of groundwater, the guidance document “Guidelines for the Assessment and Management of Groundwater Contamination” (DEC 2007) notes that an assessment of all relevant environmental values should relate to those associated with current and realistic future beneficial uses of groundwater. The document also notes that “water quality objectives should always protect the groundwater quality to a level that meets the most sensitive end user’s requirements” and “restricting access to groundwater will not be considered an appropriate management strategy in isolation unless there are no other remediation options available”. In accordance with NEPC (NEPC 1999 amended 2013c) the environmental values/beneficial uses that can be considered include:

 Protection of ecosystems;

 Aquaculture and human consumers of food;

 Agricultural water (irrigation and stock water);

 Recreation and aesthetics;

 Drinking water; and

 Industrial water.

Following this approach Groundwater Investigation Levels (GILs) have been defined (NEPC 1999 amended 2013c) for some of the above beneficial uses. For mercury the available GILs are:

 Mercury in drinking water should not exceed 0.001 mg/L (NHMRC 2011). This guideline value was established based on the toxicity of methylmercury which is the more toxic form of mercury. Hence the value is considered conservative for the assessment of inorganic mercury in groundwater;

 A recreational water quality guideline of 0.01 mg/L can be determined on the basis of the drinking water guideline and application of an exposure adjustment factor of 10 (NHMRC 2008);

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 Mercury in water used for agricultural use (irrigation and livestock) should not exceed 0.002 mg/L (ANZECC/ARMCANZ 2000).

With respect to the protection of the environment, the National Water Quality Guidelines (ANZECC/ARMCANZ 2000) provide water criteria that are based on protection of aquatic ecosystems. While this guideline applies to concentrations in water at the point of discharge into an aquatic environment, it can be used for the purpose of reviewing the groundwater data for issues that might be relevant should contaminated groundwater discharge to any such environment. The following water quality criteria are available for mercury and have been used for an evaluation of groundwater and surface water quality:

 A high reliability trigger value of 0.0004 mg/L is calculated for inorganic mercury based on a 95% protection level. This trigger value has been used to assess groundwater concentrations, however, as it does not address bioaccumulation, it is not suitable for the assessment of any mercury concentrations reported in surface water.

 For slightly to moderately disturbed systems a trigger level for inorganic mercury in marine water of 0.0001 mg/L is recommended. This is based on a 99% protection level where there are no site-specific data available to adjust for bioaccumulation. This value is the same as that recommended by Canada to protect consumers of fish and is relevant to use when evaluating surface water data.

 No water quality guidelines or trigger values are available for methylmercury in ANZECC/ARMCANZ (2000). In the absence of Australian guidance values, screening levels based on toxicological benchmarks (Suter II & Tsao 1996) have been adopted. Suter II and Tsao (1996) present water quality screening guidelines for fresh water ecosystems. These are based on the United States Environmental Protection Agency (USEPA) Tier II method, and the Secondary Acute Value (SAV) and Secondary Chronic Value (SCV) are equivalent to the Final Acute Value (FAV) and Final Chronic Value (FCV). Although the methodology used to derive these guidelines is different to the methodology used to derive the ANZECC/ARMCANZ (2000) water quality guidelines and trigger values, they nonetheless provide a useful basis for screening concentrations of methylmercury in aquatic environments. The Tier II SAV for methylmercury is 0.099 µg/L, whilst the SCV is 0.0028 µg/L.

4.3 Review of Soil Data from FCAP Soil investigations have been undertaken on, and adjacent to the FCAP from 1990 to 2009. Appendix C presents a summary of the soil investigations undertaken, focusing on the four key areas of the FCAP: Block G, Block L, Block M and Block A. It is noted that the assessment of mercury in soil at the FCAP is based on laboratory analysis of total mercury and visual identification (in the field and in samples collected) of Hg0. Laboratory analysis of individual mercury species (various inorganic species, Hg0 and methylmercury) is complex with specific methods not well established. Review of the soil data is limited to the more generalised analytical data available. Where these data have then been used in this assessment they have been assumed to representative of 100% inorganic mercury species (where the species present is the most toxic, refer to Section 2) and/or 100% Hg0.

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Based on the review presented in Appendix C, the following table presents a summary of the key issues identified in soil each of the areas on the FCAP. It is noted that while investigations have been undertaken to assist in the delineation of the lateral extent of the contamination, the vertical extent of mercury contaminated soil in these areas has not been delineated.

Table 4.1 Summary of Key Issues – FCAP Soil

Summary of Potential Sources of Mercury Potential Exposure Issues Range of Mercury in Each Key Area Concentrations Reported Industrial Soil Guideline (HIL D for inorganic mercury): 730 mg/kg Block L - Chlorine Liquefaction and Chlorine Storage Area Mercury was not handled in this area, however potential sources include: Mercury contaminated process wastes and Concentrations reported in the former 1.45 to 4300 mg/kg demolition wastes placed in former pit (materials waste materials may be representative of removed in 2007) mercury levels in other areas of the FCAP Materials were removed in 2007 and the 13 to 430 mg/kg pit pressure cleaned. Residual mercury (arithmetic average 207 levels remain in the concrete of the pit. mg/kg) Pit is not accessible and mercury contamination considered to be bound to concrete and a negligible source of Hg0 vapours. Mercury impacted soil beneath area Presence of hot-spots of mercury 0.2 to 272 mg/kg impacted soil, most likely to be associated within inorganic mercury species. Block M – Hydrogen and Brine Sludge Treatment Area Based on historical use of this area mercury There is the potential for mercury to be 0.47 to 2190 mg/kg contamination may be present in the following present as inorganic species as well as areas: Hg0. Visible Hg0 identified in  former hydrogen compression area 4 of the samples (mercury vapour was present as an collected. impurity and was removed during compression and also in the purification process);  brine sludge filtration (mercury suspended or dissolved in the recirculating brine solution was precipitated in the sludge from the brine purification process in Block G); and  mercury retort (including the lay-down area in its vicinity for equipment and other materials to be treated). Block G – Cell Block The Cell Rooms are identified as the primary Mercury in soil beneath Block G has 0.2 to 14500 mg/kg potential source of mercury (elemental) been identified as inorganic species as contamination at the FCAP. The largest volume of well as Hg0. Visible Hg0 identified in mercury was used on this Block. The ground floor many areas of Block G. of this cell room was not sealed for the first 8 Visible Hg0 appears to years (or more) of operation. Anecdotal evidence be confined to the brick suggests there were former spills of Hg0 in this footings, concrete slab, area. and underlying soils associated with the former cell rooms and related infrastructure. As part of the brine purification process in Block Mercury may have been present as Up to 1000 mg/kg in G, brine sludge was produced and collected in inorganic species or fine droplets of Hg0. brine sludge. There is Clariflocculator Settling Tanks 1 and 2. The no longer brine sludge

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Summary of Potential Sources of Mercury Potential Exposure Issues Range of Mercury in Each Key Area Concentrations Reported mercury in the brine sludge was derived from the storage at FCAP. recirculating brine solution. As the brine passed through the electrolytic mercury cells mercury became suspended or dissolved in the brine. Block A – Caustic Soda Filtration This area was used for the removal of mercury Mercury may also have been lost to the 0.4 to 1110 mg/kg from the caustic soda. Activated carbon filtration environment during filter cleaning. and, later, microfiltration was used to remove the Anecdotal information suggests that there Small specks and mercury. It is understood that the mercury was could have been some loss of mercury- droplets have been predominantly suspended in the unfiltered caustic contaminated caustic soda. identified in soil in this soda from the FCAP as colloidal microdroplets There is the potential for the presence of area. (possibly stabilised with an oxide or hydroxide inorganic mercury species as well as coating). Some mercury may also have been Hg0, which may have been present as present as dissolved oxy-hydroxide complexes. fine micro-droplets. Caustic soda may have affected the local pH of Soil pH ranged from 8.2 the groundwater and as such the speciation of the to 10.2 suggesting mercury. Both mercury and alkali are considered alkaline conditions. to be contaminants of potential concern in Block A.

Based on the above, the FCAP remains a source of inorganic mercury and Hg0 in soil, with the presence of Hg0 also considered to be a source of Hg0 vapours to air (on the FCAP site, on the BIP and off the BIP).

It is noted that these areas are currently contained within the remediation building, where entry into the building is controlled under an occupational health and safety plan, and indoor air is only vented following treatment through an activated carbon filtration system to remove Hg0 vapours.

4.4 Review of Groundwater Data and Identification of Issues 4.4.1 Summary of Previous Investigations Groundwater data, relevant to the assessment of mercury, have been collected during monitoring rounds undertaken in 1996, 2005, 2006, 2007, 2008, 2011 and 2012. These data have been collected beneath the FCAP as well as off-site downgradient areas. The key outcomes of previous environmental investigations relevant to this assessment are summarised below.

 Sampling during the Stage 2 Botany Groundwater Survey (Woodward Clyde, 1996) noted that sulphide appears to be ubiquitous in the groundwater and the inferred distribution of sulphide throughout the shallow and deep groundwater is irregular with the highest concentrations occurring throughout Southlands. Concentrations of sulphide up to 78.5 mg/L were reported downgradient of the FCAP.

 Groundwater was sampled and analysed in December 2005 and May 2006 (URS, 2006c). In the shallow aquifer elevated (exceeding the ANZECC 95% Trigger Level) concentrations of mercury were reported near and extending downgradient to the southwest of the cell block (Block G) and Block A. In the intermediate aquifer elevated (exceeding the ANZECC Trigger Level) concentrations of mercury were reported near and extending downgradient to the south and south west of the cell block (Block G). Lower concentrations were reported in the deep aquifer with concentrations in off-site wells being less than the ANZECC Trigger Level.

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The pH impact observed in groundwater beneath the site was centred on Block A (likely due to historical caustic soda filtration and storage in this area). This block could represent a source area for both mercury and alkaline pH (caustic) contamination (pH>10). A plume of alkaline groundwater extends off-site in both the shallow and intermediate aquifers. In contrast an alkaline groundwater plume is not apparent in the deeper aquifer. Acidic pH values (pH < 3) were measured in groundwater from the shallow and intermediate aquifers beneath Block M, and in the shallow aquifer to the southwest (Block L).

 Given the relatively high concentrations of mercury encountered in the groundwater (up to 5 mg/L), it was considered likely that the majority of mercury measured in groundwater is present as dissolved mercury salts, probably mostly as mercuric chloride. This could be derived from either transformation of Hg0 beneath the cell block (Block G) or, more likely, from direct percolation and dissolution of inorganic mercury in solution from the brine circuit (Block G) and/or caustic soda storage and filtration area (Block A). This observation is consistent with the conceptual site model, presented in Section 4.4.3.

 Groundwater investigations were undertaken by URS in 2006 and 2007 (October 2006, January, February and May 2007). These included the sampling of 18 on-site groundwater well locations (48 samples from shallow, intermediate and deep wells) and 9 off-site groundwater well locations (26 samples). Dissolved phase mercury concentrations ranged from less than the limit of reporting (LOR) (<0.0001 mg/L) to 22.9 mg/L (WG32) with 31% of the samples containing dissolved mercury exceeding the ANZECC Trigger level. A selected number of groundwater samples (across a range of pH values) were analysed for the presence of methylmercury. In May 2007, methylmercury concentrations reported ranged from <0.0001 µg/L to 0.112 µg/L. The proportion of methylmercury in on-site areas comprised 0.005% to 0.3% of the dissolved mercury reported. The proportion of methylmercury in off-site areas comprised 0.05% to 4% of the dissolved mercury.

 Further groundwater investigations were undertaken by URS in February 2008 (URS, 2008a). These investigations were completed to specifically collect groundwater data to provide further information on the geochemical nature of the impacts for use in geochemical modelling. The work included sampling groundwater from 21 wells on and off the site with analysis for mercury (dissolved with limited analysis for total, methyl, and elemental mercury), major ions, minor ions, bi-carbonate / carbonate alkalinity, dissolved organic carbon (DOC), iron, nitrate, ammonia, and methane. In addition soil samples from two on- site locations (depths of 7, 11 and 18 m bgl) were collected and sent to CSIRO to establish site-specific partition coefficients. Dissolved phase concentrations in groundwater ranged from less than the LOR (<0.0001 mg/L) to 7.69 mg/L (WG32) with 60% of the samples containing dissolved mercury exceeding the ANZECC Trigger level. Exceedances of the guideline were noted in the shallow, intermediate and deep aquifers. A selected number of groundwater samples were analysed for the presence of methylmercury. In February 2008, methylmercury concentrations reported ranged from <0.0001 µg/L to 6.44 µg/L (WG32). Elemental and total mercury was analysed in samples collected from six locations (three from shallow aquifer and three from intermediate aquifer). Hg0 was detected above the LOR in all samples analysed.

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 URS installed 2 additional groundwater monitoring wells (MWC18 and MWC19) and sampled all new and existing FCAP monitoring wells located off the BIP, in 2009. All groundwater samples collected were analysed for dissolved and total mercury, major and minor ions, bromide, iron, TDS and DOC. Dissolved mercury concentrations ranged from less than the LOR (<0.0001 mg/L) to 0.0042 mg/L with higher concentrations reported in the shallow aquifer.

 Groundwater monitoring rounds were conducted by Golder in November 2011 and December 2012. These involved the sampling of groundwater from 19 (in November 2011) to 22 (December 2012) wells located on and off the site (targeting the shallow, intermediate and deep aquifers where accessible). Samples collected were evaluated for key groundwater parameters (pH, EC, redox potential, DO and temperature) and analysed for mercury (dissolved and total), major ions, bi-carbonate / carbonate alkalinity, bromide (November 2011 only) and dissolved organic carbon (DOC in December 2012 only).

o 2011: Dissolved phase concentrations in groundwater ranged from less than the LOR (<0.0001 mg/L) to 9 mg/L (WG32) with the maximum concentrations reported in shallow wells located immediately downgradient of the FCAP (MWC04, MWC05, MWC06 and MWC08). Concentrations decreased sharply with distance downgradient of the FCAP. The concentrations reported were consistent with previous sampling rounds and the modelled concentrations as presented by Laase (2010). 44% of the samples collected reported concentrations in excess of the ANZECC Trigger level. The analytical program did not include analysis of methylmercury.

o 2012: Dissolved phase concentrations in groundwater ranged from less than the LOR (<0.0001 mg/L) to 1.32 mg/L (MWC08I) with 65% of the samples containing dissolved mercury exceeding the ANZECC Trigger level. Exceedances of the guideline were noted in the shallow, intermediate and deep aquifers. Methylmercury concentrations were reported in a number of wells in 2012. Concentrations reported ranged from <0.001 µg/L to 0.64 µg/L (maximum reported at MWC14 in intermediate depth well). The methylmercury concentrations are general consistent with those reported in previous sampling rounds (in particular data collected in 2008).

 The sampling conducted from 2008 to 2012 consistently reported concentrations of total mercury higher than dissolved mercury in all wells, suggesting some of the mercury is present in the solid phase via sorption or precipitation of solids such as mercury sulphides.

The locations of the monitoring wells and bundle piezometers sampled are shown in Figure 3. Appendix D presents a summary of mercury concentrations reported in groundwater during this period.

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4.4.2 Summary of Mercury in Groundwater The following presents a summary of review of all groundwater data collected to 2008 (URS, 2008b) and in 2011 and 2012 (Golder 2011, 2013), refer to Figure 3 for well locations:

Summary of Mercury Distributions The distribution of mercury species and total mercury in groundwater from the shallow, intermediate, and deep aquifers in the vicinity and downgradient of the FCAP is, as expected, complex, varying with aquifer, position relative to the source, and potentially with major ion composition and concentration. The highest dissolved, elemental, and total mercury concentrations are associated with the aquifers in the FCAP source zone, and dissolved and elemental mercury concentrations are relatively well correlated.

Dissolved, elemental, and total mercury concentrations indicate that mercury has penetrated to the deep aquifer in the FCAP source zone and that vertical transport of mercury in this zone was an important mechanism. Hg0 has been identified in soil within the FCAP area (as outlined in Section 4.3). Vertical migration is likely to have occurred if the capillary pressure of Hg0 in these source areas exceeded the entry pressure (Pankow & Cherry 1996).

In low permeability peaty/clayey layers and capillary barriers may have restricted vertical migration before reaching sandstone bedrock and caused lateral migration as controlled by layer topography. There is the potential for Hg0 to be present in the groundwater aquifer at peat or clay lenses through the profile and at the bedrock interface. The presence of Hg0 in the shallow aquifer downgradient of the FCAP site (at concentrations significantly lower than beneath the FCAP area), at MWC15, indicates that these processes are likely to have occurred along lower hydraulic conductivity layers. Other processes that be occurring in groundwater include the formation of Hg0 associated with processes such as mercury desorption and demethylation during groundwater flow.

Although Hg0 was not analysed for in groundwater samples from the deep aquifer, the low (<200 µg/L) dissolved mercury concentrations indicate that Hg0 is not likely to be present at elevated concentrations.

Although mercury has a strong affinity for organic matter and clay fines, the lithology beneath the FCAP consists of sand with occasional (thin and discontinuous) peaty/clayey lenses, and it is considered unlikely that there has been significant sorption of mercury. Given the relatively high concentrations of mercury encountered in the groundwater beneath the FCAP, it is considered likely that the majority of mercury measured in groundwater is present as dissolved inorganic mercury complexes.

Methylmercury concentrations in groundwater have been observed to occur in samples with elevated dissolved mercury concentrations with the ratio of methylmercury to dissolved mercury ranging from <0.08% to 0.78%.

The concentrations of mercury (dissolved, methyl and total mercury) in the shallow, intermediate and deep groundwater monitoring networks based on the most recent monitoring data (Golder 2013) are presented in Figures 4a, 5a and 6a. Figures 4b, 5b and 6b present concentrations of mercury in the shallow, intermediate and deep groundwater monitoring wells based on data

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reported in 2011 (Golder 2011) where further speciation of mercury was undertaken (i.e. concentrations of dissolved, methyl, elemental and total mercury are presented)

Summary of Mercury Concentrations through Time The changes in dissolved mercury concentrations through time provide an indication of the status of the mercury plume in the shallow, intermediate, and deep aquifers. In and near the FCAP, consistently elevated dissolved mercury concentrations, together with the measured speciated mercury data (including Hg0), indicate that this area is behaving as an ongoing source of dissolved mercury to all aquifers. This area extends to MWC08 and WG32 in the shallow and intermediate aquifers.

Downgradient, at and beyond MWC11, the dissolved mercury plume is defined in the deep aquifer by values that have been consistently below the detection limit. In the intermediate aquifer, the boundary of the plume is defined to the south by consistent non-detect values at MWC17_I; however the leading edge of the plume is not defined to the southwest. Increasing mercury concentrations in groundwater from MWC16_I indicate that the plume might be gradually expanding in this area and the dissolved mercury plume in the shallow aquifer remains undelineated at MWC16. Mercury in the shallow aquifer has not been delineated to the southwest with detections of dissolved mercury in MWC17_S, MWC16_S, MWC18_S and MWC19_S.

4.4.3 Conceptual Model for Mercury Source, Fate and Transport in Groundwater The Stage 1 and Stage 2 Investigation (URS 2006a) and Mercury Fate and Transport Chlor-Alkali Groundwater and Soil Investigation (URS 2008b) provide a detailed review of the potential nature of mercury contamination at the FCAP and relevant fate and transport issues. Knowledge of speciation is essential to establishing the key pathways and factors affecting the mobility and retention of mercury in soil. In assessing these factors the following discussion has focused on two key areas:

 The source zone (or source area) which is defined as the media (soils and groundwater) beneath the FCAP site where former operations at the site might have been identified as sources and where the nature of the mercury identified in these areas could also be considered as an ongoing source to groundwater beneath the FCAP and areas downgradient; and

 Downgradient of the source zone (or source area) which is defined as the groundwater aquifer that extends downgradient of the area identified as the source zone. Some of this area is located within the boundaries of the BIP, however much of the area, and focus of this assessment, relates to the downgradient plume that extends off-site (i.e. downgradient of the BIP boundary).

Based on the review presented in the above documents, in particular the available data on dissolved and speciated mercury, groundwater composition, aquifer geology, and longer-term head and water quality data, the following outlines the predicted geochemistry of mercury at the FCAP.

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Source Zone Anecdotal evidence suggests that significant quantities of Hg0 might have been lost to the subsurface at the FCAP. There are no reliable estimates of such losses, but it has been reported that Hg0 is a common contaminant under the cell building footprints of former mercury cell ChlorAlkali plants. If this has occurred, Hg0 could have pooled at the base of the concrete floor slabs. A proportion could have migrated vertically if the capillary pressure at the base of the pool of mercury could overcome the entry pressure (Pankow & Cherry 1996). The very high interfacial tension would be expected to significantly restrict the potential for vertical migration. If this has occurred (as may have occurred if micro-droplets were present), it is likely that it would have proceeded through groundwater Layers 1 and 2 and might have been restricted by the presence of peat or clay layers in the profile or the sandstone bedrock. At the peat layers or bedrock it is likely that the migration of mercury would be influenced by subsurface topography. Hg0 is sparingly soluble and without transformation to mercury salts, it is considered unlikely that significant quantities would have dissolved.

Some of the Hg0 might have undergone transformation to more soluble mercury salts. Many mercury salts are significantly more soluble than Hg0. The main sources of soluble mercury salts, however, would have been from the brine circuit in Block G and, to a lesser extent, the caustic soda storage and filtration areas in Block A. Some colloidal droplets of Hg0 (which were historically present in unfiltered caustic soda from the FCAP) might also be present in groundwater in the vicinity of Block A.

Dissolved, elemental, and total mercury concentrations indicate that mercury has penetrated to the deep aquifer in the source zone and that vertical transport of mercury in this zone was an important mechanism. Chloride concentrations and chloride to bromide ratios indicate that the mercury is, in many locations, also associated with the migration of brines. However, the locations that indicate the highest brine impacts (intermediate and deep aquifers) are not always associated with the highest mercury concentrations (shallow and intermediate aquifers). Mercury and chloride concentrations indicate that downward migration has probably occurred in the source zone to at least the intermediate zone and, in some locations, to the deeper aquifer. In the source area, the high density of Hg0 and brines that were present when the FCAP was active might have resulted in the preferential downward migration of these components before significant lateral migration, associated with groundwater flow, could occur.

The persistence of elevated mercury concentrations in the shallow aquifer, even where low salinity groundwater has entered the aquifer, indicate that part of this dissolved mercury might be derived either from dissolution of disseminated Hg0, from desorption and demethylation of mercury, or from long-term release of mercury-impacted groundwater from more clay-rich zones of the aquifer.

The results of geochemical modelling (URS 2008b) indicate that, in the source zone, dissolved 2+ - mercury forms mercurous mercury (Hg2 ) preferentially over mercuric chloride complex (HgCl3 ). 2+ This has implications for the transport of mercury away from the source zone since Hg2 is a cation - and, therefore, is more likely to sorb to clays and other aquifer particles than HgCl3 , which dominates in the downgradient areas of the plume. Higher concentrations of total mercury relative to the sum of laboratory-speciated mercury, further indicate that sorption might be an important process in the source.

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Methylmercury is the dominant species formed when mercury is desorbed from surfaces (URS 2008b). Consequently, the higher methylmercury concentrations and methylmercury to dissolved mercury ratios that occur in some areas of the source zone are consistent with increased sorption. Inverse relationships between methylmercury and DOC or methane indicate that, in highly reducing or organic rich groundwater zones, methylmercury could be degrading.

Persistent elevated concentrations of dissolved mercury, even as groundwater salinity decreases, combined with the elevated concentrations of methylmercury, elemental and total mercury all indicate that parts of the shallow and intermediate aquifers in the vicinity and immediately downgradient of the FCAP should be considered to behave as an ongoing source zone, providing dissolved mercury for subsequent transport downgradient.

Mercury Downgradient of the Source Zone A brine plume appears to extend from the source towards the south and southwest, indicating transport of brines from the vicinity of the FCAP. However, the occurrence of the brine plume is not entirely consistent with that of the mercury. Brine that is not directly associated with mercury might have been derived from the former Brine Treatment Area, and the source of mercury appears to be more limited to the area of the FCAP and zones immediately downgradient to the south and southwest.

With the mercury concentrations, the zone of fresh water that extends beyond the source area might indicate an important groundwater flow path in the shallow aquifer away from the source area to the south. Elevated dissolved and elemental mercury concentrations in the intermediate and deep aquifers to the south of the FCAP also indicate that this is an important flow and transport direction away from the FCAP in these aquifers. This flow direction is not entirely consistent with the overall southwesterly groundwater flow direction; however, it could represent: a preferential pathway associated with local aquifer heterogeneity; historical pumping from groundwater production bores ICI1 (near Gate 1: shut down in the 1960s) and ICI3 (near the tennis courts: shut down in 1958) and associated sorption/desorption processes (AGEE & Woodward-Clyde 1990); or variations in locations and concentrations of mercury and brine in the source zone.

As the plume extends away from the source zone, the dominant migration pathway appears to shift more towards the southwest, as indicated by major ion and mercury concentrations in groundwater from the shallow and intermediate aquifers at MWC16. This shift in migration pathway is more consistent with the current groundwater flow direction as indicated by groundwater elevations.

- Once away from the source zone, HgCl3 becomes the dominant modelled mercury species, which has implications for the potential for sorption onto aquifer sediments and the subsequent formation - of methylmercury during desorption. Since HgCl3 is an anion it is less likely to sorb onto clays and 2+ other aquifer materials than Hg2 , which dominated in the source zone.

Mercury concentration and speciation data also indicate that ongoing sources of mercury are likely to become less important downgradient of the source zone. Based on field observations and laboratory analyses, the migration of Hg0 downgradient from the FCAP during its operation is likely to have been limited. Additionally, as there is currently little evidence of significant sorption of mercury species downgradient, it is unlikely that this area will act as a significant ongoing source of mercury to groundwater.

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The influx of fresh water into the intermediate aquifer in the vicinity of MWC11 is also likely to affect ongoing plume migration. It could potentially cut off the downgradient portion of the plume in the intermediate aquifer (e.g., MWC15 and south). Additionally, if this fresh groundwater is a result of pumping at the PCA, the PCA could ultimately capture this part of the plume. The portion of the plume that is cut off from the source area is likely to continue to migrate downgradient; however, the rate at which it migrates could change depending on the effects of pumping. It is noted that the mercury source is old and the historical rate of migration has been slow as the mercury plume has not migrated a significant distance off site (particularly when compared to the extent of off-site migration of more mobile chlorinated hydrocarbons in groundwater).

Based on data collected to December 2012, dissolved mercury identified in groundwater beneath the FCAP is unlikely to have migrated to Long Dam since this location does not appear to be directly down hydraulic gradient of the plume. Springvale Drain and Penrhyn Estuary (and Botany Bay) are downgradient of the current location of the plume and, as such, there is the potential for dissolved mercury from the plume to migrate into these features.

Existing data do not indicate that the groundwater plume is currently discharging to these environments. Further modelling of mercury groundwater migration (Laase, 2010) indicated that, while the GTP is operating (and lowering the shallow water table), the mercury impacted plumes will continue to migrate down-gradient, beneath Springvale Drain, and then be captured by Foreshore Road and Southlands extraction wells. Hence, mercury impacted groundwater is not expected to migrate to and discharge into these surface water bodies (or Botany Bay) while the GTP is operational (which is expected to be for a significant period of time).

Further discussion on the potential for off-site migration and discharge to environmentally sensitive areas is presented in Sections 6 and 7.

Conceptual Model Figures 7 and 8 present diagrammatic and cross-sectional conceptual models of mercury fate and transport in groundwater at the source and downgradient of the site (taken from the HHERA (URS 2008d).

4.4.4 Identification of Issues – Mercury in Groundwater On the basis of the above, key issues relevant to the assessment of mercury in groundwater relate to the presence of elemental and dissolved phase mercury in groundwater beneath the FCAP (which has the potential to also remain as an ongoing source) and downgradient off-site as well as the presence of mercury (elemental and mercury salts) in Blocks G, A, L and M that remain as ongoing sources to groundwater. More specifically the following can be summarised:

 Key processes occurring in the source area are: the downward vertical migration of brines into the intermediate and deep aquifers; more limited downward vertical migration of elemental and dissolved mercury into these aquifers; sorption and desorption of mercury (in 2+ particular associated with the presence of Hg2 which will more likely sorb to particles); and 2+ input and lateral movement of fresh water in the shallow aquifer. The presence of Hg2 in the source zone (with the potential to sorb to soils) and some Hg0 suggests this area is likely to remain a source of mercury to the plume area.

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-  Once away from the source zone, HgCl3 becomes the dominant modelled mercury species, which has implications for the potential for sorption onto aquifer sediments and the - subsequent formation of methylmercury during desorption. Since HgCl3 is an anion it is less 2+ likely to sorb onto clays and other aquifer materials than Hg2 , which dominates in the source zone. Hence, downgradient of the source area mercury in groundwater may be relatively mobile, however the available data do not support this outcome as the mercury plume has not migrated a significant distance down-gradient.

 Key processes occurring in the plume area are: lateral vertical migration of diluted brines into the intermediate and deep aquifers; lateral migration of dissolved mercury in shallow and, to a lesser extent, intermediate aquifers; sorption and desorption of mercury along groundwater flow paths; recharge of fresh water to the shallow aquifer; lateral input of fresh water from the east in the shallow and intermediate aquifers; and change to the flow regime due to pumping at the PCA and Secondary Containment Area (SCA). Mercury concentrations do not indicate that significant mercury sources (sorbed mercury or Hg0) persist in the plume area; rather, mercury is likely to cycle through different species, sorbing and desorbing from aquifer solids.

With respect to the potential issues that might be of significance with respect to the assessment of risks to human health and the environment the following can be noted:

 Mercury in groundwater beneath the source area can be considered a source to the migration of mercury in groundwater off-site;

 While Hg0 has been identified in groundwater in the source area, the potential for vapour migration issues to be of significance is considered to be negligible for the following reasons:

o Hg0 is essentially insoluble and the very high interfacial tension of Hg0 would be expected to significantly restrict the potential for vertical migration. If Hg0 were present as micro-droplets these droplets may be sufficiently small to overcome the higher interfacial tension and result in vertical migration to groundwater. If this occurred then the vertical migration of these micro-droplets will continue until a less permeable clay (or peat) layer is encountered in the aquifer. Hence the Hg0 micro droplets will not be expected to be sitting in groundwater at the top of the water table, where phase partitioning to gas/vapour phase can occur. Phase partitioning to the gas/vapour phase cannot occur within the saturated zone. It can only occur at the top of the water table where there is an interface between the saturated and unsaturated zones.

o The recharge of fresh water at the top of the water table within the source area is expected to significantly impede the potential for any Hg0 that might be present at the top of the aquifer to partition to a gaseous phase.

 Mercuric chloride complexes dominate mercury in the downgradient areas of the plume. While there is no evidence at present that indicates that this plume has migrated to or discharged into any off-site receiving body, the nature of the plume suggests that it will continue to migrate downgradient and could discharge into a receiving body in the future.

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 The concentration of Hg0 measured in groundwater at one location in the shallow aquifer in the downgradient plume is over one order of magnitude lower than that in the source area. As discussed above for the source area, the potential for vapour migration from Hg0 in groundwater to be of significance is considered to be negligible.

It is noted that while the potential for Hg0 vapour migration from groundwater is considered to be negligible, it has not been confirmed. Therefore the quantification of risk has considered this as a potential exposure pathway to address this uncertainty (refer to Sections 5.3 and 5.4).

4.5 Mercury Vapour Conceptual Site Model The presence of Hg0 in soil and groundwater provides a source by which Hg0 vapours can be present in the air directly above the source areas as well as down-wind of these areas. Hg0 in soil at the FCAP is consider to be the most significant ongoing source of Hg0 vapours that may be released to air, and affect the air quality on the FCAP (if these impacts are not remediated), the BIP or in off-site residential areas.

The potential for Hg0 vapours to be present in air (outdoors or within future buildings) on the FCAP site have been evaluated in detail in Section 5.3.

Further evaluation of the potential for Hg0 vapours to be of concern in areas located off the BIP has been undertaken. These evaluations have considered the potential migration of Hg0 vapours via dispersion in the atmosphere as well as the lateral migration of Hg0 vapours in soil gas. In relation to the potential for these pathways to be of concern, the following can be noted:

 Prior to the construction of the current remediation enclosure at the FCAP site, URS (2009) undertook ambient air sampling of mercury in areas located between the FCAP site and the closest boundary to off-site residential areas, located along the BIP/Denison Street boundary. Air samples were collected using real-time monitors so that peak Hg0 (logged on a 5 second basis) and 24 hour average Hg0 concentrations were able to be reported. The sampling was undertaken when the prevailing wind direction was from the FCAP to the monitoring locations. The conditions during which sampling occurred included periods of stable weather conditions which are likely to be associated with poorer mixing and dilution down-wind of any Hg0 emissions from the FCAP. The monitoring showed a good correlation between wind direction and the measured Hg0 vapours down-wind of the FCAP, confirming the source of the measured Hg0 vapours was the FCAP. Concentrations of Hg0 vapour over a 24 hour period range from 0.033 to 0.046 µg/m3, well below the adopted chronic air guideline of 0.2 µg/m3 (WHO 2003) (refer to Table 2.1 and Appendix B). The peak concentrations reported were mostly below the chronic air guideline and all were well below the California OEHHA acute guideline (OEHHA 2008) (relevant for the assessment of short- duration peak exposures). On the basis of the range of concentrations of Hg0 vapour in air at the boundary locations sampled, no adverse health effects (acute or chronic) would be expected by any member of the population (workers or residents).

 The potential for Hg0 vapour in the subsurface (present in the soil pores as soil gas) to migrate laterally (beneath the sealed surface areas) from the FCAP and impact on areas located off the BIP, in particular residential areas, was evaluated by URS (2010). Soil gas samples were collected (from a depth of 1 m below ground level) on the eastern boundary of

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the BIP (closest to the FCAP) and on the BIP close to the FCAP on 2 separate sampling events. Higher concentrations of Hg0 in soil gas were reported closer to the FCAP site compared with the boundary locations (consistent with the lateral diffusion of Hg0 vapours from the FCAP source). Soil gas concentrations reported on the site boundary ranged from 0.011 to 0.081 µg/m3. If these vapours migrated further laterally and into a residential home (with no further diffusion or dilution, which is unlikely to occur) then the concentrations would not be considered to be of concern as they are all well below the adopted chronic air guideline of 0.2 µg/m3 (WHO 2003) (refer to Table 2.1 and Appendix B).

Based on the above, potential exposures in residential areas located down-wind of the FCAP (prior to the construction of the remediation enclosure) were below chronic air guidelines established to be protective of adverse health effects in all members of the population (associated with exposures that may occur all day every day for a lifetime). In addition, the data collected has shown that some lateral vapour migration is occurring from the FCAP (beneath sealed areas of the BIP) to the boundary, the concentrations of Hg0 in soil gas on the site boundary are below the chronic air guidelines.

The FCAP area is currently enclosed by the remediation building/enclosure with all Hg0 vapours present within the enclosure released to air via carbon beds to capture and mitigate atmospheric emissions of Hg0 from the building. While this system is operating off-site concentrations of Hg0 vapours will be lower than when the FCAP was not enclosed.

Hence these exposure pathways are not considered to be of significance and have not been further evaluated in the forward calculation of risk, however they have been further evaluated in Section 7.

It is noted that the nature of the emission from the FCAP, namely vapour phase Hg0, results in mercury being present in the atmosphere in a form that does not readily deposit to surface soil. As discussed in Section 2.2.2, Hg0 needs to undergo transformation within the atmosphere to a form that can be deposited via wet (rain) and dry (dust) processes. This occurs slowly and does not result in mercury deposition close to the FCAP source. Hence the potential for depositional mercury to be present in areas surrounding the FCAP is considered to be negligible.

4.6 Presence of Mercury in Other Off-Site Areas 4.6.1 Summary of Previous Investigations In addition to data on the concentration of mercury in groundwater beneath off-site areas and downgradient of the FCAP, data is also available for sediments in Springvale Drain and Penrhyn Estuary, as well as biota in Penrhyn Estuary and surface water in Penrhyn Estuary, Springvale Drain and Floodvale Drain. The key outcomes of previous environmental investigations relevant to off-site areas are summarised below.

 In Springvale Drain, the concentrations of mercury in surface sediment ranged from 15 to 220 mg/kg (Woodward Clyde, 1996), exceeding the HIL “A” and “C” values of 40 and 80 mg/kg respectively and the ANZECC/ARMCANZ (2000) interim sediment quality value of 1 mg/kg. The concentrations were higher in surficial sediment than in deeper sediment. The source of this mercury was not identified, however, it was concluded that the concentrations of mercury present in sediment were unlikely to have arisen from groundwater

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contamination, rather they are most likely to have derived from historical discharges from the BIP into Springvale Drain via former drains. Springvale Drain sediments within the open drain located on Southlands were excavated and removed in 2001.

 Concentrations of mercury reported in sediment and biota in Penrhyn Estuary (likely to be associated with historical discharges via Springvale Drain) were assessed in the CHHRA (enRiskS 2011). Risks to human health associated with mercury in this environment were considered low and acceptable with respect to exposure to mercury in sediment. Concentrations of mercury in biota (representative of recreationally caught fish) were all below the relevant maximum residue levels (MRLs) available from Food Standards Australia New Zealand (FSANZ 2011). It is noted that a ban on the collection of all fish and shellfish (including oysters) in Penrhyn Estuary was gazetted by the NSW Government in November 2004. This was due to the presence of other compounds, namely hexachlorobenzene and hexachlorobutadiene levels reported in biota from the estuary. As part of the Port Botany Expansion works, the dredging works undertaken will have redistributed sediments within Penrhyn Estuary. In addition as a result of these works, Penrhyn Estuary is no longer accessible to the public (including via boat) and hence there is no longer any potential for exposure to mercury impacted sediments in the estuary. While the fishing ban remains in place, access restrictions limit the potential for the catching of fish species from the estuary.

 Additional surface water samples were collected from eight locations – two from Springvale Drain, two from Floodvale Drain and four from Penrhyn Estuary – and analysed for dissolved and total mercury in October 2006 (URS 2006c). Dissolved mercury was not detected above the limit of reporting (LOR) of 0.0001 mg/L in any surface water samples or the field duplicates. Total mercury concentrations however, ranged from less than the LOR (0.0001 mg/L) to 0.0007 mg/L. Total mercury was detected in surface water sampled at Penrhyn Estuary at the outlet of Floodvale Drain (SW029) and Springvale Drain (SW031). Total mercury was also detected in Springvale Drain at Southlands (SW046 and SW049). Total mercury concentrations reported in SW046 and SW029 exceeded the ANZECC (2000) Trigger Value for mercury, however the concentrations reported were less than the recreational water quality guideline for mercury. The absence of dissolved mercury and presence of total mercury indicate that the mercury present is likely to be sorbed to suspended solids within the water column. These detections are associated with the presence of mercury impacts in Springvale Drain derived from historical discharges via drains.

Mercury has also been reported in soil at Southlands (associated with historical placement of fill and waste materials from various industries), however this is not part of the scope of this assessment and is being addressed within the work currently being undertaken for the proposed development of Southlands.

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4.6.2 Mechanisms of Off-site Discharges of Mercury to Surface Water The mechanism by which mercury has accumulated in the sediment, suspended particulates in surface water and biota of Springvale Drain and Penrhyn Estuary has been reviewed (Woodward Clyde 1997) and the following conceptual mechanisms identified for mercury:

Primary: 1. Trade waste discharges prior to connection to sewer in 1958 2. Historical leaks and spills on the BIP and off-site migration via surface water 3. Boiler ash migration (via erosion) to the drain Secondary: 1. Ongoing migration of small quantities of mercury in sediment via stormwater drains from residual mercury contained in interceptor pits and potential source areas at the BIP 2. Shallow groundwater infiltration to the stormwater system at the FCAP and migration of soluble mercury salts via surface water to Springvale Drain

The primary mechanisms by which mercury contamination was discharged to Springvale Drain, and subsequently to Penrhyn Estuary is via historical discharges (prior to the connection of trade waste to sewer) and leaks and spills that were discharged directly off-site via drains. The presence of mercury in sediments and surface water (primarily associated with resuspension of solids) in these areas are not associated with the presence of mercury in groundwater.

Following demolition of the FCAP, a number of these pathways no longer exist as the plant is no longer operational and many of the stormwater drains on the FCAP have been removed or blocked. However, based on information provided by Orica, during heavier rainfall events where surface water exceeds infiltration, runoff flows off the FCAP area to the street gutters (on BIP) and mixes with other BIP stormwater. Water from the FCAP area flows into Stormwater Interceptor Pit No 1 (IP1). In drier weather, pumps divert flows from IP1 to the effluent system on the BIP. During high rainfall events the quantity of water in the stormwater system can exceed pumping capacity resulting in discharge to Springvale Drain and subsequently Penrhyn Estuary. Data collected by Orica from the effluent system indicate some correlation between mercury concentrations in effluent water and rain events indicating the FCAP remains a potential source for off-site migration of mercury in stormwater.

Orica has indicated that measurable concentrations of mercury have been reported in effluent water during operation of the FCAP and since the closure and demolition of the FCAP. The concentration of mercury in effluent water has reduced since the demolition of the FCAP. Current data suggest concentrations of mercury in effluent water from IP1 less than 1 µg/L (and typically < LOR) during normal flows and peaking at less than 5 µg/L following a significant rainfall event. It is considered likely that concentrations reported in effluent water is associated with the suspension of particulates from site runoff or resuspension of particulates in sludge or sediment in the interceptor pits (hence very low concentrations detected during low-flow – quiescent – conditions). The concentrations reported are not considered likely to be associated with dissolved mercury. These concentrations do not discharge directly off-site unless there is a significant rainfall event that results in overflow of the interceptor pit. Under these conditions, such high rainfall events will result in significant dilution prior to entry into any off-site area such as Springvale Drain or Penrhyn Estuary. On this basis, current discharges are expected to be low and do not warrant detailed consideration in the HHERA.

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It is noted that information on the potential for discharge and concentrations of mercury in effluent has been provided to the NSW EPA.

No additional data have been collected with respect to sediment and biota concentrations in the off- site areas since 2004 (when the last round of sediment samples were collected and considered in the CHHRA). Since mercury concentrations in stormwater runoff from the FCAP are expected to be lower than in the past, it is not expected that the concentrations considered for the assessment of potential exposures in Penrhyn Estuary in the CHHRA are likely to have increased. Hence the assessment presented within the CHHRA remains conservative and appropriate with respect to exposure to mercury. It is noted that the assessment presented with the CHHRA considered exposures to mercury as well as a range of other chemicals derived from historical operations at the BIP.

Total mercury concentrations reported in surface water samples collected from Springvale Drain, Floodvale Drain and Penrhyn Estuary in 2006 are below the recreational water quality guideline (which is equal to the drinking water guideline). This is consistent with surface water data considered in the CHHRA where total mercury concentrations were detected on occasion, but were lower than the drinking water guideline. As noted previously, it is expected that the detection of mercury in surface water is associated with the resuspension of particulates as no dissolved phase mercury has been reported above the LOR.

The potential for mercury to discharge into Long Dam has not been assessed within the CHHRA as no data were available from the dam with respect to mercury in sediments and surface water. No further data are available, however the following can be noted:

 Long Dam is a concrete lined conduit on Perry Street Canal created by a concrete weir. The dam (approximately 585 m2) serves as water storage for industrial use. The water in Long Dam comprises stormwater, urban runoff, industrial discharges and groundwater (pumped into the canal to supply water to Amcor). There is no or very limited access to the dam by the general public and it is not used for any recreational purpose.

 The ecological value of Long Dam (Orica 2005 and URS 2007d) was considered to be negligible. This is particularly relevant following the filling in of the western half of the dam in January 2007 to construct an access road. This resulted in the loss of all aquatic habitats in this area. The remaining half of the dam is lined with concrete-filled geofabric with no aquatic vegetation present.

 Review of the groundwater data does not indicate that mercury impacted groundwater derived from the FCAP has migrated to and is discharging to Long Dam.

 Information presented in previous investigations suggests that the most significant pathway for off-site migration of mercury from the FCAP involved historical discharges to Springvale Drain and Penrhyn Estuary. No information is available that specifically identifies current or historical discharges from the FCAP to Long Dam.

 Hence, while the environment of Long Dam might be affected by contaminants derived from a range of industries in the area, it is not considered to currently be a receiving environment for mercury that could be derived from the FCAP.

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Based on available information, mercury impacted groundwater beneath FCAP and associated downgradient off-site areas have not discharged to any environmental receiving body. However the presence of mercury in groundwater needs to be considered with respect to beneficial uses relating to potential industrial use of the water.

4.7 Summary of Issues Identified The following table presents a summary of the issues considered with respect to the presence of mercury at, beneath and downgradient of the FCAP. The table highlights the key issues that require further consideration within this assessment.

Table 4.2 Summary of Risk Issues - FCAP

Area and Review Undertaken Key Issue Identified Media Evaluated FCAP site and within the BIP (used for industrial purposes) Soil Block L Review of site history and soil No Hg0 identified and all soil concentrations reported total concentrations reported. mercury concentrations less than the industrial soil HIL (NEPC 1999 amended 2013d). Block M Review of site history and soil Hg0 identified in 4 samples. concentrations reported. Concentrations of total mercury reported in soil in a number of locations that exceed the industrial soil HIL (NEPC 1999 amended 2013d). The vertical extent of soil contamination is not delineated. Block G Review of site history, visual Hg0 identified in an area estimated to cover assessment and soil concentrations approximately 5,652 m2 beneath former cell rooms, slab reported. and footings. Concentrations of total mercury reported in soil in a number of locations that exceed the industrial soil HIL (NEPC 1999 amended 2013d). The vertical extent of soil contamination is not delineated. Block A Review of site history, visual Hg0 identified in an area estimated to cover assessment and soil concentrations approximately 31.6 m2. Based on site history, elevated reported. concentrations of total mercury could be present within Block A (not currently accessible) and should be adequately characterised and assessed (update HHERA as required) if existing structures and slabs are removed. BIP Review of soil data from areas Mercury concentrations in soil in areas outside of the located outside of the FCAP, within FCAP has not reported levels that exceed the industrial the BIP. soil HIL (NEPC 1999 amended 2013d). The concentrations reported are well below all health based investigation levels (for all landuses) suggesting that limited off-site atmospheric deposition of mercury has occurred. Groundwater Beneath FCAP Concentrations of mercury (present No issues identified as groundwater is not used on the 2+ - (source area) and as Hg2 (dominant), HgCl3 , sorbed FCAP and the BIP for any purpose (or reasonably downgradient Hg, Hg0 and methylmercury) that foreseeable future purpose). Potential for vapour (within BIP) exceed the GILs (NEPC 1999 migration and intrusion issues from the presence of Hg0 amended 2013c) reported in shallow, in the groundwater considered negligible, however intermediate and deep aquifers. potential exposures will be quantified to address uncertainty in relation to this pathway.

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Area and Review Undertaken Key Issue Identified Media Evaluated Off-site and downgradient of the BIP Off-site migration Ambient air data collected between Based on the available data the off-site migration of Hg0 of Hg0 vapours FCAP site and closest boundary with vapours from the FCAP site is not considered to be from FCAP residential areas (BIP/Denison Street) significant. The FCAP area is now enclosed within the prior to construction of FCAP remediation building/enclosure where emissions to air are remediation building/enclosure. Soil treated via carbon beds. gas data have been collected close to Presence of Hg0 vapours from the FCAP is not the FCAP site and on the closest associated with local deposition issues. boundary with residential areas (BIP/Denison Street). All concentrations reported in these sampling programs are lower than health based guidelines (WHO 2003). Off-site Concentrations of mercury that Based on current data, mercury impacted groundwater groundwater exceed the GILs (NEPC 1999 that could be derived from the FCAP is not discharging to (downgradient of amended 2013c) reported in shallow, any environmental receiving body. BIP) intermediate and deep aquifers. Potential for further migration downgradient likely based - - HgCl3 becomes the dominant on mobility of HgCl3 species that dominates the plume. modelled mercury species in Hence future migration and discharge to Springvale Drain downgradient areas. Concentrations (and subsequent discharge to Penrhyn Estuary) need to 0 decrease downgradient. Some Hg is be considered. also present; however concentrations Potential for vapour migration and intrusion issues from are less than in source area. Some the presence of Hg0 in the groundwater considered methylmercury present (depending on negligible, however potential exposures will be quantified local conditions), some sorption to address uncertainty. occurring (especially where less Cl present). However the potential for While no groundwater is currently extracted for any sorption is lower than in source zone. purpose in the industrial area off-site, and the area is Mercury impacted groundwater has within the GEEA, industrial water extraction and use is not migrated to or discharged into any permissible under licence from the DWE and hence receiving body. relevant beneficial uses (industrial use) of groundwater in this area needs to be considered. Presence of mercury in soil and groundwater at the source area remains an ongoing source to the off-site groundwater. Historical Accumulation of mercury in sediments Conclusions presented within the CHHRA with respect to discharges (via (and resuspension of particulates in mercury in Springvale Drain and Penrhyn Estuary drains) to surface water) in Springvale Drain remain. Springvale Drain and Penrhyn Estuary and biota within and Penrhyn Penrhyn Estuary has been assessed Estuary within the CHHRA. No additional data are available to suggest increased concentrations in these areas or the need to revise the CHHRA. Current Discharge to Springvale Drain and No significant issues identified that warrant detailed discharges from Penrhyn Estuary of mercury in assessment. However it is noted that surface water runoff the BIP via surface water runoff during high from the area is managed by Orica. surface water rainfall events only when dilution will runoff occur. Actual concentrations discharged into receiving environments during these events are unknown however discharge is expected to be infrequent and well diluted.

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Section 5. Quantification of Exposure and Risk – Human Health 5.1 General This section identifies the human populations (receptors) who could be exposed to mercury from the FCAP, outlines the mechanisms (pathways) by which these populations could be exposed and provides a quantitative estimate of exposure, chemical intake and risk.

5.2 Identification of Complete Exposure Pathways In reviewing the available information on the FCAP presented in Section 4, key issues in relation to the presence of mercury in the environment have been identified (refer to Table 4.2) that warrant further detailed assessment within the HHERA. With respect to the identification of complete and significant exposure pathways, the following can be noted:

 The BIP is zoned for industrial use and it is expected that the area of the FCAP will continue to be used for industrial purposes. Operations within the BIP do not allow for more sensitive uses (such as childcare or healthcare facilities) hence the potential uses of the FCAP area are limited to industrial uses only (i.e. no children will be directly exposed within the BIP).

 Mercury has been identified in soil within the FCAP with both elemental and inorganic mercury reported in a number of areas (consistent with the site history). Workers on the FCAP site may come into direct contact with mercury contaminated soil during future uses of the site. In addition to the assessment of direct contact exposures, the presence of Hg0 in soil is considered to be of significance in relation to vapour emissions and inhalation exposures4. Inorganic mercury is not volatile and would only be released to air via the emission of dust. As the site is currently predominantly sealed and is expected to remain sealed (or grassed) following development, the long-term generation of dust is not considered significant. However, for the purpose of this assessment, the potential exposure to mercury in dust has been included to ensure that all possible future uses of the site are addressed. These could include leaving the site open following remediation. Therefore there might be no buildings or paved areas on the site. In this case there is the potential for dusts to be generated via wind erosion and other activities, such as maintaining gardens (if any are present). It is noted that the generation of dusts during remediation and/or development should be managed to minimise dust emissions from the area.

 Mercury in groundwater is present predominantly as inorganic mercury (dominant forms are 2+ - most likely Hg2 (source zone) and HgCl3 (downgradient)), with some methylmercury (reported to comprise up to 4% of the total mercury). Inorganic and organic forms of mercury are not volatile and hence the only potentially complete pathways of exposure relate to direct contact with groundwater.

4 Exposure to elemental mercury is predominantly associated with the inhalation of mercury vapour. Approximately 80% of inhaled elemental mercury is absorbed through the lungs by rapid diffusion. In contrast, only 0.01% of elemental mercury is absorbed through the gastrointestinal tract. Dermal and oral exposures are unlikely to be of significance or result in adverse health effects (WHO 2003)

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 Hg0 has been measured in groundwater from the shallow and intermediate aquifers in this area and from the shallow aquifer at the one downgradient location that was sampled and tested for Hg0. The concentration of Hg0 in groundwater downgradient of the site is an order of magnitude lower than the maximum concentrations measured in groundwater from the source zone. In addition, the Hg0 that is present is not expected to be present at the top of the water table where partitioning to the gaseous phase occurs (as Hg0 is more dense than water and where possible, will sink to a level of lower permeability, refer to Section 4.4.4). Hence potential emissions to air from Hg0 identified in groundwater in the FCAP source zone or downgradient of the site are considered to be incomplete. However there is some degree of uncertainty associated with the assumptions made with respect to the likely behaviour of Hg0 in groundwater and the available data are limited. Hence the potential for Hg0 vapour migration from groundwater has been considered a possible exposure pathway for this assessment to determine whether it has the potential to be of significance with respect to the assessment of exposure and risk on and off the site.

 Groundwater is not extracted for any purpose on the FCAP site or other areas downgradient within the BIP, nor is it expected to be extracted under the current management plan for the BIP. Areas located off site (off the BIP) and downgradient of the FCAP where mercury contaminated groundwater has migrated are zoned for railway and commercial/industrial use. As noted in Section 4.2, while the area is located within the GEEA, the assessment presented has considered the potential for commercial/industrial premises in the off-site area to apply for a licence to extract groundwater. If such a scenario, beneficial use, is considered then there is the potential for groundwater in the off-site areas to be used for industrial purposes. This could include irrigation of gardens in the commercial/industrial area, use as industrial process water (not as potable water) or in cooling towers. On this basis there is the potential (not currently relevant) for future industrial use of groundwater beneath the off-site plume area. This could result in exposures to workers and the general public via direct contact (including the ingestion of water droplets that could be sprayed during irrigation or industrial use). These pathways have been evaluated in detail in the CHHRA.

 As discussed in Sections 4.4.3 and 6, mercury impacted groundwater has not been shown to have migrated to and discharge into environmental receptors such as Springvale Drain, Penrhyn Estuary, Long Dam or Botany Bay and hence exposures that might be associated with the discharge of groundwater are currently considered to be incomplete. However there is the potential for the plume to migrate further towards Springvale Drain. Given the uncertainties in plume behaviour in the middle and downgradient parts of the plume in response to changing hydraulic and salinity conditions, its future migration and potential interaction with Springvale Drain or Penryhn Estuary cannot yet be assessed. Further monitoring and investigation at the leading edge and in the interior of the plume will assist with this assessment.

 Groundwater is at least 2.7 m bgl beneath the FCAP and 1.7 m bgl beneath off-site (outside of the BIP) areas where mercury contamination has been identified. In the south-eastern corner of Southlands, in the vicinity of MWB12 and MWB18, groundwater is more shallow (0.7 m bgl). Direct contact with groundwater during normal day-to-day work within the FCAP and off-site areas would not be expected to occur. There would also be limited potential for direct contact with mercury-impacted groundwater during intrusive works associated with the

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maintenance of underground utilities (where the depth to such services is unlikely to be greater than 1-2 m bgl as per ANZECC 1992). Irrespective, should contact occur, it would be of an incidental and infrequent nature and is considered of less significance. However, given the potential for shallow groundwater (less than 1.7 m depth) in the off-site areas, potential exposures to mercury in shallow groundwater by workers involved in intrusive works in off-site areas has been assessed.

 It should be noted that contact with groundwater during intrusive works in off-site areas could include exposure to chlorinated hydrocarbons present in the shallow aquifer (depending on the area where such works occurred). Intrusive works undertaken in the area are expected to be conducted in accordance with regulatory and industry-specific occupational health and safety requirements (including requirements for confined spaces). These workers might not be aware of the potential presence of mercury impacts in shallow groundwater and therefore potential exposures by these workers have been assessed further as noted above.

 The assessment of exposures to mercury-impacted soils on the FCAP during intrusive works is considered relevant.

 While mercury-impacted groundwater has not been shown to have migrated to and discharged into the receiving environments, the presence of various forms of mercury in soil and groundwater at the FCAP remains a potential source to ongoing contamination to groundwater (beneath the site and the off-site plume) and potential for further migration and discharge of groundwater to the off-site environment. These issues have been considered in the derivation of risk-based criteria for the remediation of the source area (refer to Section 7).

Based on the use of the site and surrounding area and the nature and extent of impacts identified in soils and groundwater, the following exposure pathways are considered to be complete and to warrant further assessment for the key receptor groups identified.

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Table 5.1 Summary of Exposure Pathways – Human Health

Receptor/Exposure Pathway Activity Workers on FCAP Potentially Significant Pathways of Exposure - Inhalation of Hg0 vapour associated with the presence of Hg0 in soil Work on the site following development for industrial use. (and concrete slabs) remaining in Block G, portions of Block A and Use includes the construction of a building or leaving the Block M. area open with no buildings or other significant ground cover. - Incidental ingestion of inorganic mercury in soil Note current work activities and exposures are managed - Dermal contact with inorganic mercury in soil under a management plan for the area. Less significant Pathways of Exposure – included in this assessment to address uncertainty - Inhalation of Hg0 vapour associated with the presence of Hg0 in Work on the site following development for industrial use. groundwater (unlikely, but possible exposure pathway). Use includes the construction of a building or leaving the - Inhalation of inorganic mercury in dust that could be generated through area open with no buildings or other significant ground cover. wind erosion and on-site activities. Note current work activities and exposures are managed under a management plan for the area. Intrusive workers on FCAP Potentially Significant Pathways of Exposure - Inhalation of Hg0 vapour within excavations on site. Undertaking intrusive activities in areas on the site. - Incidental ingestion of inorganic mercury in soils on the FCAP area Activities include the construction of new buildings or the - Dermal contact with inorganic mercury in soils on the FCAP area maintenance of services. It is noted that any intrusive works would be expected to follow requirements outlined in the management plan for the BIP including relevant occupational health and safety plans and information relating to the presence of chlorinated hydrocarbons in shallow groundwater. Less significant Pathways of Exposure – included in this assessment to address uncertainty - Inhalation of inorganic mercury in dust that could be generated through Undertaking intrusive activities in areas on the site. wind erosion and on-site activities. Off-site intrusive maintenance workers Potentially Significant Pathways of Exposure - Incidental ingestion of inorganic and methylmercury in the event that Undertaking intrusive activities in off-site areas above the shallow groundwater is intersected during excavation works*. mercury plume. Activities include the construction of new - Dermal contact with inorganic and methylmercury in the event that buildings or the maintenance of services. shallow groundwater is intersected during excavation works*. Less significant Pathways of Exposure – included in this assessment to address uncertainty - Inhalation of Hg0 vapour (derived from groundwater) outdoors and Undertaking intrusive activities in off-site areas above the within excavations. mercury plume. Activities include the construction of new buildings or the maintenance of services. Off-site workers and the general public in downgradient areas Potentially Significant Pathways of Exposure - Incidental ingestion of inorganic mercury in groundwater following At present, all exposure pathways relevant to the presence of extraction and use for irrigation or industrial purposes*1. This includes mercury in groundwater are assessed as incomplete or of ingestion of mercury droplets generated when water is sprayed. less significance. - Dermal contact with inorganic mercury in groundwater following However, future use of groundwater has been evaluated. The extraction and use for irrigation or industrial purposes*1. only likely uses include irrigation of gardens and grassed - Inhalation of Hg0 vapour following extraction and use for irrigation of areas, industrial process water (not as part of food and industrial purposes that involve spraying*1. beverage production) and cooling towers. With respect to exposure, use for regular watering of gardens and grassed areas is considered the most significant. As these activities could be undertaken in areas where the general public visits, exposures by the general public to the use of groundwater for irrigation in the area have been considered. Less significant Pathways of Exposure – included in this assessment to address uncertainty - Inhalation of Hg0 vapour that could be associated with the presence of Hg0 in off-site groundwater2; Notes: * Exposure pathways only relevant for areas off-site that are located off the BIP. 1 It is noted that the area is located within the GEEA and therefore any extraction and use of the water is currently not permitted unless a licence is obtained from DWE where the use is supported by an assessment that the water is “fit for purpose” and “not causing environmental harm”. While not occurring at present, the potential for use in the industrial area has been included in this assessment. Beneficial uses of groundwater in the downgradient area are considered to be industrial use only. 2 The potential for Hg0 in groundwater to result in vapour phase concentrations in the subsurface and subsequent migration and intrusion into buildings is considered negligible (refer to Section 4.4.4 and discussion above), however, to address any uncertainty, the exposure pathway has been included in the assessment.

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Exposures by visitors would be lower than long-term workers due to the short duration spent on site. Hence quantification of risks to visitors is not proposed to be undertaken.

Conceptual Site Model Figure 8 presents a diagrammatic conceptual site model associated with the key exposure pathways and mechanisms summarised above.

5.3 Assessment of Exposure and Risk - FCAP Site 5.3.1 General The quantification of risk associated with exposures relevant to the presence of mercury contamination identified in soil and groundwater beneath the FCAP site has been undertaken in accordance with methodology presented in Section 1, equations presented in Appendix A and toxicity reference values presented in Section 2.3 (and Appendix B).

The quantification of exposure involved the identification of parameters and exposure concentrations that are considered representative of reasonable maximum exposures by all receptors and significant exposure pathways identified and considered in this assessment. Sections 5.3.2 and 5.3.3 present a summary of the concentrations used in this assessment to quantify exposure. Section 5.3.4 presents a summary of the exposure assumptions and the calculated risks for each of the pathways considered relevant to future uses of the FCAP site.

In relation to the FCAP the following should be noted:

 There are no risk issues (concentrations of inorganic mercury in soil that exceed the commercial/industrial HIL and no Hg0 present) identified in soil within Block L. Hence no detailed risk calculations (or risk-based criteria) have been undertaken for Block L;  A Remediation Action Plan (RAP) has been prepared for Block G (Golder 2012a). The RAP outlines the following: o Construction of a capping system to restrict vapour emissions, rainwater infiltration, direct contact with soil within Block G and accommodate potential future use as working salt stockpile; o Construction of a containment wall to restrict lateral subsurface vapour migration and restrict groundwater ingress and egress. The wall will extend through the unsaturated zone (where it will function as a vapour barrier) and into the saturated zone (extending to a nominal key-in depth of 1 m into the underlying clayey soil or sandstone layers); o Replacement of the salt stockpile to the east of Block G; and o Future use of Block G will not include the construction or any future buildings;

Based on the above the potential source of vapours and groundwater contamination will be effectively managed. This management system, along with the proposed use of the site (open space) has been considered in the assessment undertaken.

 A RAP has also been prepared for Blocks M and A (Golder 2012b) that involves the remediation of soil within these areas (with Hg0 contaminated soil placed beneath the proposed capping and containment system in Block G and the remaining mercury contaminated materials remediated via excavation, transportation and disposal off-site).

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Future use of these areas may include open space and the construction of an industrial building.

5.3.2 Mercury Soil and Dust Concentrations Soil Mercury is present in soil as Hg0 and inorganic mercury. In relation to the quantification of direct contact exposures (i.e. ingestion and dermal contact) and the inhalation of mercury sorbed to particulates that may be released to air as dust during intrusive works, exposure to inorganic mercury is relevant. Exposures associated with the presence of Hg0 are related to vapour inhalation only and the vapour phase concentrations in the workplace are further discussed in Section 5.3.3.

The concentration of inorganic mercury adopted in soil within Blocks G, M and A has been taken to be equal to the arithmetic average concentration reported in all soil samples (based on the maximum reported at each location/depth where Hg0 was identified) where Hg0 was visibly identified in the sample. For each of the areas evaluated in this assessment the soil concentration adopted is as follows:

 Block M = 773 mg/kg  Block A = 1110 mg/kg (maximum as Hg0 only identified in one location)  Block G = 4099 mg/kg

These soil concentrations are expected to be a conservative estimation of mercury in soil in these areas as they are biased to only include the highest concentrations of total mercury reported (which also coincided with the identification of Hg0).

Dust The potential for the inhalation of inorganic mercury on dust is relevant where the site is left open with no or very little surface cover (such as concrete, grass or gardens) or intrusive works (such as construction or trenching) occur. The potential concentration of inorganic mercury dust that might be generated during these situations has been estimated using a Particulate Emission Factor (PEF). A PEF is a ratio of the concentration in soil (mg/kg) to the concentration in air (mg/m3). Therefore the concentration of mercury particulates in air can be estimated using the soil concentration adopted for Blocks M, A and G, as outlined above. The PEF has been estimated using equations for outdoor workers (USEPA 1996, 2002) and has been calculated to be 1x109 mg/kg per mg/m3 This approach is considered suitable for the assessment of dust exposures by workers in outdoor areas who could also be involved in moderate digging, other landscaping activities and mowing.

Dust emissions that may occur during remediation have been evaluated separately (PAEHolmes 2010) and are expected to be managed (and mitigated) as part of the proposed remediation to ensure that exposures by workers and on the site boundary are acceptable.

The indoor air concentration has been estimated as 50% of the outdoor air concentration (enHealth 2012b).

Calculation of the PEF and inorganic concentrations in air is presented in Appendix G.

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5.3.3 Mercury Vapour Concentrations In the quantification of Hg0 vapour inhalation on the FCAP, exposures that may be derived from the presence of Hg0 in both soil and groundwater have been estimated, as outlined in the following.

Volatilisation from Soil This relates to Hg0 vapours derived from impacts identified in soil within Block G and portions of Block A and Block M. The partitioning of Hg0 from soil to a vapour phase is complex and while models are available to assist in the estimation of volatilisation of volatile organic compounds from soil or water, these models have not been well established for Hg0. Hence surface emissions data were obtained to assist in the calibration of a vapour model for Hg0.

For the purpose of calibrating the emissions model (in particular the identification of the most appropriate value to adopt for Koc), emissions data were collected from a range of areas on the FCAP where visible Hg0 was, and was not, identified. Appendix E presents the methodology and results of the sampling program undertaken for this purpose5. The measured emission rates of Hg0 from the areas assessed have been reviewed in conjunction with a vapour model utilised to estimate phase partitioning from elemental Hg0 in soil (assuming the total mercury concentration reported comprises 100% Hg0) and emission from a source at or close to the surface (where the Hg0 was visible).

Equations adopted for the modelling of potential emissions of Hg0 from the surface of the ground are derived from ASTM (2002), and are presented in Appendix A. For Block G, where most of the data have been collected, and where more significant areas are impacted by Hg0, a comparison of modelled and measured emission rates has been undertaken (refer to Appendix F for calculations) where data collected at each sample location as well as the data set as a whole have been reviewed. Based on the review undertaken the following can be noted:

 The modelling of emissions to air from any volatile source typically includes consideration of a saturated vapour phase concentration. This is a concentration in the vapour phase directly above the soil/source where an equilibrium upper limit is achieved and will not be exceeded with increased soil concentrations. This is the case particularly for volatile organic chemicals. Observation of the measured emission rates suggests that this is not the case with Hg0 in soil at the FCAP as a number of the measured emission rates exceed the modelled emission rates if saturated vapour phase is considered. If the saturated vapour phase concentration is not considered in the calculations (as an upper limit) then the modelled emission rates approach and in some cases exceed the measured emission rates.

5 It is noted that the sampling program outlined in Appendix E was not designed to quantify vapour emissions at every location sampled for the purpose of characterising exposure (as there are limitations with any sampling program). Rather the sampling program was designed to enable data to be collected to determine a relationship between measured Hg0 vapours and the modelling of vapours based on the measured concentration of total mercury in soil. Hence only data that enable that relationship to be determined were used from Appendix E. There was no other use for the data collected and reported in Appendix E.

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 On an individual sample location basis, there does not appear to be a significant correlation between the modelled emission rate (based on total mercury reported in soil using a whole digestion analytical method) and measured emission rates. It is noted that the flux emissions sample was collected within 2 m of the location where the soil sample was collected. In addition, the collection of the soil sample (while still being a composite sample) provides a discrete sample of soil from the general location that might or might not include visible Hg0. The results of the analysis of the soil sample will only reflect what was in the sample collected and is expected to include both inorganic mercury and Hg0. The collection of flux emissions is an in situ measure of an emission rate overlying soil from all depths at the location (not just surface soil). As the presence of visible Hg0 is variable, the comparison of an emission rate based on a discrete soil sample and an in situ measurement is expected to reflect these differences. This is expected to have affected the likelihood of obtaining any significant correlation on an individual location basis.

 If the data collected from the FCAP are assessed as a whole, a correlation can be observed. In particular:

o The average modelled emission rate (using both the subsurface source equation [assuming the source is 0.1 m from the surface or building foundation] and the surface source equation) from all locations in Block G sampled (68 mg/day/m2 and 72 mg/day/m2 respectively) is slightly lower than, but essentially equivalent to, the average measured emission rate from the same locations (74 mg/day/m2); and

o The average modelled emission rate (using both the subsurface and surface source equations) from all locations sampled where visible Hg0 was reported in the soil sample (130 mg/day/m2 and 137 mg/day/m2 respectively) is slightly higher, but essentially equivalent to the average measured emission rate from locations where visible Hg0 was reported in surface soil at the same locations (105 mg/day/m2).

On the basis of the above, the use of modelling to estimate emissions from the ground surface from a concentration of total mercury in soil (conservatively assumed to be 100% Hg0 in the modelling) is considered appropriate to provide an average from the area assessed or a reasonable maximum average from only the areas assessed where visible mercury was reported. For the assessment of Hg0 emissions the average concentration where Hg0 was reported has been adopted in this assessment.

With respect to the quantification of exposure (where the assessment has focused on chronic and subchronic exposures), the calculation of an average emission rate where visible Hg0 was identified is considered relevant for quantifying exposures in areas directly above the source (indoor or outdoor air where emissions from the area considered are mixed prior to inhalation) as well as in areas located down-wind of the source (where the emissions from the area will be an average over the area which will be subsequently mixed/dispersed down-wind prior to exposure).

On the basis of the above, the further modelling of emissions of Hg0 from the surface to indoor and outdoor air has been based on the average soil concentration from samples where visible mercury was identified (considered a reasonable maximum exposure) as presented for Blocks M, A and G in Section 5.3.2. As noted above, this provides an emission rate that is equivalent to an average measured emission rate from areas where visible mercury is reported.

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Volatilisation from Groundwater Potential emissions to air from Hg0 identified in groundwater has been modelled based on the maximum reported Hg0 concentration from beneath the FCAP area of 0.0428 mg/L. This concentration is assumed to be present beneath the whole FCAP site. While it is considered unlikely that the Hg0 will be present at the top of the water table, and available to partition to a vapour phase, it has been assumed that it does partition to a vapour phase and diffuse though the overlying soil (sand/fill). The methodology associated with the modelling undertaken is presented in Appendix A, with calculations presented in Appendix G.

Estimation of Indoor and Outdoor Air Concentrations The concentration of Hg0 in air at the point where exposure occurs, indoors or outdoors, has been modelled assuming the following:

 Development of Block G will involve the construction of an appropriate vapour capping and cut-off wall with the area proposed to be used for open space (likely storage) following completion of these areas. Following remediation, Blocks M and A may be used for open space, with the potential construction of an industrial building requiring consideration. Any buildings constructed on Blocks M and A will be expected to be constructed as slab-on- grade with no subsurface basement, consistent with other industrial buildings on the BIP.

 Vapour phase concentrations within a potential building on Blocks M and A have been estimated using a vapour model (USEPA 2004a) adopting parameters relevant for the assessment of a sound concrete slab with Hg0 impacted soils directly beneath the slab (with the model set up as for soils at or near the ground surface) or groundwater. Review of the available soil data (and the lateral extent of Hg0 impacts) indicates that Hg0 in soil may be present beneath 100% of a future building that is 10 m x 10 m in size if constructed on Block M, but only beneath 50% of a future building that is 10 m x 10 m in size if constructed on Block A. It is assumed that Hg0 impacted groundwater may be present beneath 100% of these areas. While the dimensions and ventilation of such a building are unknown, it has been assumed that the building is located above all or part of Blocks M or A and complies with the Australian Building Code including minimum air exchange rates (currently as stipulated in AS1668.2 1991). Details on the model adopted are presented in Appendix A and calculations are presented for on-site areas in Appendix G.

 Vapour phase concentrations within outdoor areas (not covered with buildings) have been estimated for Blocks M, A and G assuming the presence of Hg0 contamination in soil at the surface. Potential concentrations in an excavation have also been modelled using this approach (assuming an excavation to 1 m depth). The outdoor air concentration has then been estimated using published vapour migration equations (ASTM 2002). Details on the model adopted and calculations are presented in Appendices A and G.

 Modelling of concentrations in air has utilised parameters relevant to Hg0 (RAIS) with the

value of Kd adopted from USEPA (Allison & Allison 2005).

Following this approach, indoor and outdoor concentrations of Hg0 have been estimated based on potential emissions that may be derived from soil and groundwater. The calculated air concentrations are summarised in the following table.

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Table 5.2 Calculated Vapour Concentrations – FCAP

Source of Hg0 Source Estimated Vapour Concentrations at Concentration Location of Potential Future Exposure (mg/m3) Indoors Outdoors Excavations Groundwater – Assumed beneath whole FCAP site Vapours derived from groundwater source 0.042 mg/L 0.000063 0.00000029 0.0000041 Soil Sources Block G 4099 mg/kg NA 0.0039 0.28 Block M 773 mg/kg 0.0055 0.00073 0.054 Block A 1110 mg/kg 0.0040 0.00026 0.026

The estimated contribution of Hg0 vapours derived from the groundwater source are essentially negligible in comparison with Hg0 vapours derived from the soil source.

It is noted that the monitoring undertaken during soil investigation works has indicated that the movement of soils containing Hg0 impacts has the potential to result in higher concentrations than estimated/modelled in the breathing zone (within excavations and outdoors). Hence appropriate monitoring and management must be undertaken during such works on the FCAP.

The calculated vapour phase concentration indoors and outdoors has been compared with breathing zone concentrations of mercury detected for health and safety purposes during soil investigations undertaken by URS in 2007 where the Hg0 vapour concentrations ranged from

The calculated concentrations have also been compared with modelling of emissions from the FCAP (Block G) presented in the CPWE Remediation Environmental Assessment, Air Quality Impact Assessment (PAE, 2007). The modelling considered a total estimated emission from the FCAP area of 30 kg/year of mercury and dimensions of Block G to provide a maximum ground level concentration outdoors (close to, but not directly over impacts) on the FCAP of 0.00056 mg/m3. The modelling presented in this assessment has estimated an outdoor air concentration of 0.0039 mg/m3 (directly above impacts) which is slightly higher, but similar to (when uncertainties in measurements and models are considered) that estimated by PAE.

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5.3.4 Risk Calculations Tables 5.3 and 5.4 present a summary of the exposure pathways, exposure parameters and concentrations adopted and the calculated threshold risks relevant to potential exposures on the FCAP. Table 5.5 presents a summary of the calculated risks for future use of the FCAP assuming that no remediation or management measures are undertaken (such as vapour barriers, cut-off walls and/or removal of accessible soil).

Detailed calculations of risk are presented in Appendix G.

It is noted that in all risk calculations presented, totals have been rounded to one or two significant figures, consistent with the level of variability and uncertainty in the assessment conducted.

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Table 5.3 Summary of Exposure Assumptions and Risk Calculations – Commercial/Industrial Workers on FCAP

Scenario/ Exposure Chemical Concentrations Exposure Parameters Calculated Threshold Risk (HI) Pathways Block M Block A Block G Parameters relevant for all pathways Body weight of 78 kg for adult workers as per enHealth (2012b). Exposures may occur each workday, i.e. 240 days per year for a working life of 30 years. All exposures are assumed to occur in the area assessed Exposures associated with Exposed Soil (where impacted surface soil remains accessible)

Workers assumed to ingest 25 mg soil and dust derived from the FCAP Ingestion of mercury in every day while working, where 100% of the mercury ingested is assumed 0.45 0.65 2.4 soil and dust at FCAP Average soil concentration for all samples where visible Hg0 was identified as per to be bioavailable. Section 5.3.2. The concentration has It is assumed that workers get all of their hands dirty with soil and dust been assumed to be representative of Dermal absorption of from the FCAP area every day. It is assumed that this soil remains on the 100% inorganic mercury species in these mercury in soil and dust hands for 12 hours of the day where 0.51 mg of soil sticks to each cm2 of 0.074 0.11 0.39 calculations. at FCAP skin. Once on the skin 0.1% of the mercury reported in soil is assumed to penetrate the skin and enter the body. Calculated based on the soil Inhalation of mercury concentration and a particulate emission It is assumed that workers on the site are present in outdoor work areas or inside buildings (adjacent to the sorbed to dust particles factor relevant to wind erosion of open Indoors 0.000055 0.000079 NA that may be present in surfaces (as per Section 5.3.2). The dust open surface areas) for 10 hours per day, for every day 0.00011 0.00016 0.00058 air due to wind erosion is assumed to be 100% respirable (i.e. they are at work. Outdoors from unsealed surfaces 100% of the dust is small enough to penetrate into the lungs) Vapour Inhalation Exposures (occur regardless of whether impacted soil is accessible as evaluated above) Soil Source: It is assumed that workers on the site are Vapours are modelled to indoor and present in outdoor work areas or inside buildings (directly Indoors 8.4 6.0 NA 0 Inhalation of Hg0 outdoor air based on soil and above the Hg impacted soil at the FCAP) for 10 hours per Outdoors 1.1 0.4 5.9 vapours that may migate groundwater concentrations as outlined in day, for every day they are at work. from soil or groundwater Section 5.3.3. Groundwater Source: It is assumed that workers on the beneath the FCAP area site are present in outdoor work areas or inside buildings Indoors 0.096 0.096 NA 0 (directly above the Hg impacted soil at the FCAP) for 10 Outdoors 0.00045 0.00045 0.00045 hours per day, for every day they are at work. Target Risk ≤1 ≤1 ≤1

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Table 5.4 Summary of Exposure Assumptions and Risk Calculations – Intrusive Workers on FCAP

Scenario/ Exposure Chemical Concentrations Exposure Parameters Calculated Threshold Risk (HI) Pathways Block M Block A Block G Parameters relevant for all pathways Body weight of 78 kg for adult workers as per enHealth (2012b). Intrusive works may occur on 10 days each year over 5 separate years. Exposures associated with Exposed Soil

Workers assumed to ingest 330 mg soil and dust every day during Ingestion of mercury in intrusive works, where 100% of the mercury ingested is assumed to be 0.075 0.11 0.4 soil and dust at FCAP Average soil concentration for all bioavailable. samples where visible Hg0 was identified as per Section 5.3.2. The It is assumed that workers get all of their hands, forearms and lower legs concentration has been assumed to be dirty with soil and dust from the FCAP area every day during intrusive Dermal absorption of representative of 100% inorganic works. It is assumed that this soil remains on the hands for 12 hours of the mercury in soil and dust at 2 0.0027 0.0039 0.014 mercury species in these calculations. day where 0.51 mg of soil sticks to each cm of skin. Once on the skin FCAP 0.1% of the mercury reported in soil is assumed to penetrate the skin and enter the body. Calculated based on the soil concentration and a particulate emission Inhalation of mercury factor relevant to wind erosion of open sorbed to dust particles It is assumed that workers on the site are present in or adjacent to surfaces (as per Section 5.3.2). The 0.0000046 0.0000066 0.000024 that may be present in air excavations for 10 hours each day. dust is assumed to be 100% respirable during intrusive activities (i.e. 100% of the dust is small enough to penetrate into the lungs) Vapour Inhalation Exposures

Soil Source: It is assumed that workers on the site are present in Vapours are modelled into excavation 4.5 1.6 24 Inhalation of Hg0 vapours excavations for 10 hours each day. air based on soil (assuming 100% total that may migate from soil 0 Hg is present as Hg ) and groundwater or groundwater beneath concentrations as outlined in Section the FCAP area 5.3.3. Groundwater Source: It is assumed that workers on the site are present in 0.00026 0.00026 0.00026 excavations for 10 hours each day.

Target Risk ≤1 ≤1 ≤1

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Table 5.5 Summary of On-Site Risk – Future Use of FCAP

Exposure Form of Mercury Calculated Threshold Risk Calculated Threshold Risk Pathway Assessed/Assumed* (HI) – Chronic Exposures by (HI) – Subchronic Exposures for Exposure Workers by Intrusive Workers Block M Block M Block A Block G Block M Block M Block A Block G No Buildings Permitted (exposures outdoors all day) Inhalation of Hg0 vapour derived from 1.1 0.4 5.9 4.5 1.6 24 vapour outdoors soil impacts Hg0 vapour derived from 0.00045 0.00045 0.00045 0.00026 0.00026 0.00026 groundwater impacts Inhalation of dust Inorganic Hg 0.00011 0.00016 0.00058 0.000005 0.000007 0.000024 outdoors Ingestion of soil Inorganic Hg 0.45 0.65 2.4 0.075 0.11 0.4 Dermal contact Inorganic Hg 0.074 0.11 0.39 0.0027 0.0039 0.014 with soil Total Risk 1.6 1.2 8.7 4.6 1.7 24 New Industrial Buildings Permitted (exposures indoors all day) Inhalation of Hg0 vapour derived from 8.4 6.0 NA NA NA NA vapour indoors soil impacts Hg0 vapour derived from 0.096 0.096 NA NA NA NA groundwater impacts Inhalation of dust Inorganic Hg 0.000055 0.000079 NA NA NA NA indoors Ingestion of soil Inorganic Hg 0.45 0.65 NA NA NA NA Dermal contact Inorganic Hg 0.074 0.11 NA NA NA NA with soil Total Risk 9.0 6.9 NA NA NA NA

Target Risk ≤1 ≤1 ≤1 ≤1 ≤1 ≤1 * As no speciated soil data are available it has been assumed that 100% of the soil concentration comprises either inorganic mercury species or Hg0 (whichever is the most conservative assumption for each scenario). This has resulted in double counting of potential exposures associated with the presence of mercury at the FCAP.

On the basis of the above calculations the following can be noted:

 For use of FCAP (Blocks M, A and G) as outdoor areas only:

o Risks to long-term workers on the site (assuming no risk management or remediation is undertaken) associated with the inhalation of Hg0 is considered unacceptable within Blocks M and G. Risks within Block A are lower (primarily due to the lower portion of the Block that is impacted by Hg0) and are considered to be unacceptable. It is noted that at some locations and in some conditions higher emissions of Hg0 might occur resulting in short duration peaks (acute exposures). These peak exposures are not expected to affect the conclusions presented in relation to the vapour inhalation pathway.

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o Risks to long-term workers who may come into regular direct contact with mercury impacted surface soil (where the site is unsealed with pavers, concrete, asphalt or grass) are considered to be unacceptable within Block G only. Risks on Block M and Block A are lower and are considered to be acceptable.

o Workers involved in intrusive works in Blocks M, A and G have the potential for exposures (and risks) to be elevated and unacceptable. These risks are associated with the inhalation of Hg0 vapours within and close to excavations. It is noted that workers undertaking such activities on the FCAP will be required to meet all requirements under the BIP occupational health and safety plan. This will require the monitoring and management of mercury vapours and exposures within the workplace during such activities. Hence the potential for these exposures to occur should be clear within the plan and appropriate measures available to manage exposures to an acceptable level.

 For use of FCAP Blocks M and A with new industrial buildings:

o Risks to long-term workers on the site (assuming no risk management or remediation is undertaken) associated with the inhalation of Hg0 within future buildings constructed on Blocks M and A above Hg0 impacted soil is considered unacceptable.

o Risks to long-term workers who may come into regular direct contact with mercury impacted surface soil (where the site is unsealed with pavers, concrete, asphalt or grass) are considered to be acceptable within Blocks M and A.

The assessment presented indicates risk management measures would be required to address exposures identified on the FCAP area prior to further use for industrial purposes. This is further discussed in Section 7.

5.4 Assessment of Exposure and Risk Off-Site 5.4.1 General There are currently no significant complete exposure pathways relevant for the off-site areas located above the mercury impacted groundwater plume. However a number of exposure scenarios have been considered in this assessment as outlined in Table 5.1. In particular consideration of potential future beneficial use of groundwater in the off-site area (outside of the BIP) has been included. Beneficial use in this area is considered to be associated with potential irrigation or industrial use only. These uses could include the following:

 Cooling tower water;

 Spray irrigation of garden areas and lawns, including areas that could be accessed by the general public such as public gardens; and

 Chemical process water (not considered to include potable water supply, use in food and beverage manufacturing or use on crops for human consumption).

The most significant scenario that could be associated with the use of groundwater is considered to be spray irrigation. This has the potential to result in exposures by workers and the general public.

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A scenario is considered to be of less significance where a lower potential for exposure by workers and/or the general public is identified. This could be associated with shorter or less frequent exposure time or duration or factors that limit the potential for exposure to occur such as the location of the use or use within an essentially closed industrial process. The rationale for assessment of the level of significance of the other groundwater use scenarios identified is summarised below:

 Exposures associated with the use of water within cooling towers are considered to be of less significance. This is due to the location of cooling towers on industrial or commercial buildings (typically in areas not accessible by the general public) limiting direct access to the cooling tower water to workers. With respect to the potential exposure by the general public to volatile chemicals (should they be present) or water droplets from the operation of the cooling towers, these exposures are expected to be lower than for spray irrigation where the general public could be in close proximity to the irrigation area (such as a public park or open accessible landscaped area) and exposure by inhalation and ingestion could readily occur during and after (e.g. wet grass) irrigation. It has also been assumed that the cooling towers are operated and maintained in accordance with all relevant standards and codes of practice as it is not relevant in this assessment to consider risks to human health associated with poor maintenance of cooling towers (such as the risk of legionella).

 It is also possible that the extracted water could be used for a range of chemical and industrial processes. These processes could involve closed systems with minimal mechanisms by which workers and the general public could be exposed to the water on an infrequent let alone a regular basis. In the event that the water was mixed with other chemicals as part of a chemical or industrial process or application the resultant chemical product would be required to meet relevant quality control standards irrespective of whether or not extracted groundwater has been used. Hence the health issues associated with handling, storage or processing of the products should not differ regardless of the use of extracted groundwater.

Hence the above scenarios are not considered to be of significance within this assessment.

The quantification of potential exposures during use of groundwater for the purpose of irrigation has been assessed in detail in the CHHRA (enRiskS 2011) where risks posed by the presence of mercury and other chlorinated hydrocarbons were considered. Based on the conservative assessment of these uses within the CHHRA, potential risks to human health (workers and the general public) were identified to be unacceptable. The calculated risks were dominated by the presence of chlorinated hydrocarbons in the shallow groundwater, not mercury. This assessment however has only focused on the presence of mercury in groundwater. The approach and assumptions adopted for the quantification of exposures during irrigation use is consistent with that adopted in the CHHRA.

The quantification of risk associated with exposures relevant to the presence of mercury contamination identified in groundwater beneath off-site areas located downgradient of the FCAP site has been undertaken in accordance with methodology presented in Section 1, equations presented in Appendix A and toxicity reference values presented in Section 2.3 (and Appendix B).

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The quantification of exposure involved the identification of parameters and exposure concentrations that are considered representative of reasonable maximum exposures by all receptors and significant exposure pathways identified and considered in this assessment. Sections 5.4.2 and 5.4.3 present a summary of the concentrations used in this assessment to quantify exposure. Section 5.4.4 presents a summary of the exposure assumptions and the calculated risks for each of the pathways considered relevant to potential exposures in these areas.

5.4.2 Mercury Concentrations in Groundwater Groundwater concentrations in areas downgradient of the FCAP have been evaluated on a number of occasions. Based on the available data to the end of 2012, the maximum concentrations of elemental, inorganic and methyl mercury reported in shallow groundwater in areas located off the BIP have been considered in this assessment. These concentrations are summarised in Table 5.6.

Table 5.6 Maximum Concentration of Mercury Species in Off-Site Shallow Groundwater – Main Plumes (all concentrations reported as mg/L) CHC Detected Maximum Concentration in shallow groundwater (location and date when reported) Inorganic mercury 0.254 (MWC15S, Feb ’08) Methyl mercury 0.000052 (MWC17S, May ’07) Elemental mercury 0.00012 (MW15S, Feb ’08)

In this assessment it has been conservatively assumed that these maximum concentrations will be present in shallow groundwater that is intersected during intrusive works, and will be extracted and used for irrigation (every time groundwater is used for this purpose).

5.4.3 Mercury Vapour Concentrations Mercury vapours may be present in air due to volatilisation from Hg0 that may be present in groundwater and during the use of groundwater for the purpose of irrigation. The modelling of Hg0 from groundwater has been undertaken using the vapour model as described in Section 5.3.3, based on the concentration of Hg0 in off-site groundwater as summarised in Table 5.6.

Estimation of potential concentrations of Hg0 in air during the use of groundwater in excavations where groundwater seepage occurs and during irrigation has used a volatilisation model. This model has estimated vapour phase concentrations of Hg0 based on the concentration of Hg0 reported in groundwater as summarised in Table 5.6. Equations relevant to this model are outlined in Appendix A.

5.4.4 Risk Calculations Tables 5.7 to 5.9 present a summary of the exposure pathways, exposure parameters and concentrations adopted and the calculated threshold risks relevant to potential exposures in areas located down-gradient of the FCAP. These calculated risks are summarised in Table 5.10.

Detailed calculations of risk are presented in Appendix H.

It is noted that in all risk calculations presented, totals have been rounded to one or two significant figures, consistent with the level of variability and uncertainty in the assessment conducted.

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Table 5.7 Summary of Exposure Assumptions and Risk Calculations – Off-Site Commercial/Industrial Workers

Scenario/ Exposure Pathways Chemical Concentrations Exposure Parameters Calculated Threshold Risk (HI) Parameters relevant for all pathways Body weight of 78 kg for adult workers as per enHealth (2012b). Exposures may occur each workday, i.e. 240 days per year for a working life of 30 years. All exposures are assumed to occur in the one area above the most significantly impacted area of the FCAP Exposures associated with Direct Contact with Groundwater During Use for Irrigation or Industrial Water Workers assumed to ingest 50 mL water, 2 days every work week (where Ingestion of mercury in groundwater Maximum concentration of inorganic irrigation occurs or process water accessed) where 100% of the mercury ingested 0.12 and methylmercury reported in is assumed to be bioavailable. groundwater as per Section 5.4.2. It is assumed that workers get all of their hands wet, for 8 hours on 2 days per Dermal absorption of mercury in work week. When wet mercury penetrates the skin and enters the body at a rate of 0.30 groundwater 0.001 cm/hr.

0 Modelled on the basis of the maximum Inhalation of Hg vapours released 0 concentration of Hg as per Section It is assumed that workers are exposed to vapours during these activities for 8 during spray irrigation of 0.0025 5.4.2 and a volatilisation model relevant hours per day on 2 days every work week. groundwater to spray irrigation. Total Risk 0.42 Vapour Inhalation Exposures (occur regardless of the extraction and use of groundwater)

0 Vapours are modelled to indoor and 0 Inhalation of Hg vapours that may It is assumed that workers are inside buildings (directly above the Hg impacted outdoor air based on soil and migate from groundwater beneath groundwater) for 10 hours per day, for every day they are at work. Exposures 0.00033 groundwater concentrations as outlined the off-site areas indorrs are higher than outdoors, hence only indoor risks are presented. in Section 5.4.3. Target Risk ≤1

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Table 5.8 Summary of Exposure Assumptions – General Public in Off-Site Areas

Scenario/ Exposure Pathways Chemical Concentrations Exposure Parameters Calculated Threshold Risk (HI) Parameters relevant for all pathways Body weight of 13.2 kg for children aged 0 to 5 years, 34.5 kg for children aged 6 to 15 years and 78 kg for adults. Exposures may occur for a lifetime, assessed as 6 years from 0 to 5 years of age, 10 years from 6 to 15 years of age and 35 years as an adult 16 years and over. All exposures are assumed to occur above mercury impacted groundwater.

0 Vapours are modelled to indoor and General Public - Inhalation of Hg The general public visits commercial businesses in the area for 1 hour each day outdoor air based on soil and vapours derived from shallow on 20 days each year on 10 separate years. The calculation presented is relevant 0.0000028 groundwater concentrations as outlined groundwater for all members of the general public (adults and children). in Section 5.4.3. Exposures associated with Potential Extraction and Use of Groundwater for Irrigation Ingestion and dermal contact with Maximum concentration of inorganic Assumes the general public comes into contact with irrigation water on 90 days groundwater used for irrigation of and methylmercury reported in per year where 5 mL (1 teaspoon) water is ingested each time. It is assumed that public areas groundwater as per Section 5.4.2. exposed skin (hands, forearms and lower legs and feet) get wet every time. When wet mercury penetrates the skin and enters the body at a rate of 0.001 cm/hr. Young children 0.50 Older Children 0.38 Adults 0.20

0 Modelled on the basis of the maximum Inhalation of Hg vapours released 0 It is assumed to the general public may be in the vicinity of irrigation activities on concentration of Hg as per Section during spray irrigation of 90 days each year for 1 hour each day. The calculation presented is relevant for 0.00029 5.4.2 and a volatilisation model relevant groundwater all members of the general public (adults and children). to spray irrigation.

Total Risk (including irrigation) 0.5 Target Risk ≤1

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Table 5.9 Summary of Exposure Assumptions and Risk Calculations – Off-Site Intrusive Workers

Scenario/ Exposure Pathways Chemical Concentrations Exposure Parameters Calculated Threshold Risk (HI) Parameters relevant for all pathways Body weight of 78 kg for adult workers as per enHealth (2012b). Intrusive works may occur on 10 days each year over 5 separate years. Exposures associated with Direct Contact with Shallow Groundwater in Excavations Workers assumed to ingest 5 mL water (equal to 1 teaspoon) every day during Ingestion of mercury in shallow intrusive works, where 100% of the mercury ingested is assumed to be 0.0012 groundwater seepage Maximum concentration of inorganic and methylmercury reported in bioavailable. groundwater as per Section 5.4.2. It is assumed that workers get all of their hands, forearms and lower legs wet with Dermal absorption of mercury in groundwater seepage for 3.3 hours (1/3rd time spent in an excavation) every day 0.039 shallow groundwater seepage during intrusive works. It is assumed that dissolved mercury in groundwater penetrates the skin and enters the body at a rate of 0.001 cm/hr.

Inhalation of Hg0 vapours that may Modelled on the basis of the maximum 0 be present in excavations where concentration of Hg as per Section It is assumed that workers are in excavations for 10 hours each day. 0.0010 seepage occurs 5.4.2 and a volatilisation model.

Total Risk 0.04 Target Risk ≤1

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Table 5.10 Summary of Off-Site Risk – Future Use of FCAP

Exposure Form of Mercury Calculated Calculated Threshold Calculated Pathway Assessed for Threshold Risk (HI) – Chronic Threshold Risk Exposure Risk (HI) – Exposures by the (HI) – Subchronic Chronic General Public* Exposures by Exposures by Intrusive Workers Workers Inhalation of Hg0 vapour derived 0.00033 0.0000028 na volatiles indoors from groundwater impacts Inhalation of Hg0 vapour derived na (most significant exposures indoors) 0.0010 volatiles outdoors from groundwater impacts Hg0 vapour released 0.0025 0.00029 na during irrigation use of groundwater Ingestion of Inorganic and 0.12 Adult = 0.011 0.0012 groundwater* methylmercury Older child = 0.025 Young child = 0.066 Dermal contact Inorganic and 0.30 Adult = 0.20 0.039 with groundwater* methylmercury Older child = 0.35 Young child = 0.43 Total Risk 0.4 Adult = 0.2 0.04 Older child = 0.4 Young child (lifetime) = 0.5 Target Risk ≤1 ≤1 ≤1 * Exposure pathways and receptors only relevant for areas off-site that are located off the BIP.

The calculated HI for all exposures assessed in the off-site downgradient areas are less than the target HI of 1. Hence risks to human health in the downgradient off-site areas associated with the presence of mercury in groundwater are considered to be acceptable.

This assessment includes consideration of exposures associated with beneficial use of the groundwater in areas located off the BIP (should such use be allowed in the area), namely industrial water. It is noted, however that the presence of chlorinated hydrocarbons in groundwater in this area results in risks that are considered potentially unacceptable (refer to the CHHRA, enRiskS 2011), and hence the extraction and use of groundwater should be banned, consistent with the current GEEA.

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Section 6. Assessment of Risk – Environmental 6.1 General This section presents an evaluation of the potential for mercury impacts derived from the FCAP to discharge to an environmental receiving body. In particular the assessment has reviewed information summarised in Section 4 with respect to potential discharges via groundwater and surface water. Based on review of the downgradient area, the most significant and potential environmental receiving body identified is Penrhyn Estuary. The ecological value of Penrhyn Estuary has been subject to extensive study, most recently as part of the EIS for the expansion of Port Botany by Sydney Ports and for the GTP EIS (URS, 2004b).

Penrhyn Estuary is a relatively small manmade estuary that was constructed in the 1970s during development of Port Botany. The estuary comprises intertidal sand and mud flats predominantly within the upper estuary, surrounded by low lying vegetated sand dunes.

6.2 Potential for Off-Site Impacts to the Environment 6.2.1 Off-Site Migration of Groundwater The potential for mercury contaminated groundwater to migrate to and discharge into downgradient surface water features is not just dependent on the groundwater flow (velocity). The distribution of mercury species and total mercury in groundwater from the shallow, intermediate, and deep aquifers in the vicinity and downgradient of the FCAP is complex, varying with aquifer, position relative to the source, and potentially with major ion composition and concentration.

Review of the FCAP and downgradient areas within the Conceptual Site Model (CSM) report (Golder 2011) has identified the following key processes:

Within the FCAP Source Zone:

 The downward vertical migration of brines into the intermediate and deep aquifers, with more limited downward vertical migration of elemental and dissolved mercury into these aquifers;

 The results of geochemical modelling indicate that, in the source zone, dissolved mercury 2+ - forms Hg2 preferentially over HgCl3 .

2+  Sorption and desorption of mercury (in particular associated with the presence of Hg2 , which will more likely sorb to particles); and

 Influx and lateral movement of fresh groundwater in the shallow aquifer.

Downgradient of Source Zone:

-  Away from the source zone, HgCl3 becomes the dominant species which is more soluble, is less likely to sorb to solids and is relatively mobile;

 Lateral and vertical migration of diluted brines into the intermediate and deep aquifers;

 Lateral migration of dissolved mercury in the shallow and intermediate aquifers has been identified;

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 Sorption and desorption of mercury along groundwater flow paths. The partitioning and mobility of mercury in aquifer sands are significantly affected by both pH and chloride concentrations and the combined interactions of these changes are complex; and

 Recharge of fresh water into the shallow aquifer, lateral input of fresh water from the east in the shallow and intermediate aquifers and change in flow regime due to pumping at the PCA and SCA.

Mercury concentrations do not indicate that significant mercury sources (sorbed mercury or Hg0) persist in the groundwater plume area, rather, mercury is likely to cycle through different species, sorbing and desorbing from aquifer solids.

Review of potential interactions between groundwater and surface water bodies, including Springvale Drain and Penrhyn Estuary, as well as the potential for mercury contaminated groundwater to discharge into these water features has been evaluated in the groundwater modelling report (Laase 2010) and the CSM Report (Golder 2011). Based on the evaluations presented in these reports the following can be noted:

 Based on data collected to December 2012, dissolved mercury identified in groundwater beneath the FCAP is unlikely to have migrated to Long Dam or directly from groundwater to Botany Bay since these locations do not appear to be directly down hydraulic gradient of the plume.

 Springvale Drain and Penrhyn Estuary are downgradient of the current location of the plume and, as such, there is the potential for dissolved mercury from the plume to migrate into these features. In relation to these feature, the following is noted:

o The water table of the shallow aquifer is significantly influenced by Springvale and Floodvale Drains, with groundwater discharge into the drains historically occurring through Southlands and towards Botany Bay. In general, when shallow groundwater levels are higher than the invert of Springvale Drain (or Floodvale Drain), shallow groundwater discharges to the drain (base flow). GTP operation and periods of below-average rainfall cause the shallow groundwater table to drop below the base of Springvale Drain at Southlands.

o Prior to the operation of the GTP, shallow groundwater seepage discharged into Springvale Drain. Operation of the GTP, and in particular the BIP containment line, lowers shallow groundwater adjacent to Springvale Drain and results in decreased discharge of groundwater to the drain. However, the increase in shallow groundwater levels following rainfall is more rapid than the decrease in levels caused by hydraulic containment and as a result there is ongoing potential for groundwater discharge to the drain after rainfall events

o Surface water enters the inner estuary via Springvale Drain that discharges into the eastern upper reaches of the estuary, respectively. Surface water flow from Springvale Drain is inferred to be a key contributor to contaminant concentrations within Penrhyn Estuary. Downgradient, at and beyond MWC11, the dissolved mercury plume is defined in the deep aquifer by values that have been consistently

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below the detection limit. In the shallow and intermediate aquifer, the boundary of the plume is defined to the south by consistent very low or non-detect values at MWC17. Increasing mercury concentrations in groundwater at MWC16 and detection of mercury at MWC18 and MWC19 indicate that the plume might be gradually expanding to the southwest.

o Surface water data collected from Springvale Drain has not detected concentrations of dissolved phase mercury.

o More detailed modelling of mercury groundwater migration (Laase, 2010) indicated that, while the GTP is operating (and lowering the shallow water table), the mercury impacted plumes will continue to migrate down-gradient, beneath Springvale Drain, and then be captured by Foreshore Road and Southlands containment extraction wells. Modelling has estimated that the time required for the mercury plume to reach the containment lines is salinity dependent and ranges from 5 to more than 100 years. If the FCAP source is removed the mercury has been estimated to remain in groundwater for 60 to more than 100 years.

Based on the available data, and the detailed modelling undertaken (where the operation of the GTP has also been considered) (Laase 2010) the mercury impacted groundwater plume is not currently discharging to these environments. While the GTP is operational (which is expected to continue for a significant period of time), mercury impacted groundwater is not expected to reach and discharge into any surface water body located downgradient of the site.

6.2.2 Surface Water Discharges In addition to the above, there is the potential for mercury to be present in stormwater runoff under high rainfall events from the FCAP area that could discharge to Springvale Drain and then Penrhyn Estuary. These events are expected to be infrequent and, as they only occur during high rainfall events, any discharges will be significantly diluted by the high rainfall runoff in the area (particularly from large paved areas of the site and surrounding industrial areas). Mercury concentrations in surface water under these events is not available, however concentrations would be expected to be well diluted with rainwater and significantly lower than during historical operations of the FCAP that led to the concentrations previously identified and assessed in Penrhyn Estuary.

Due to historical discharges of mercury (via drains), mercury has been reported in sediments and biota sampled within Penrhyn Estuary. These concentrations have been assessed from the perspective of risks to humans who might catch and consume fish and oysters in the area. No specific studies have been undertaken that relate mercury concentrations reported in biota and sediment with ecological effects, however the studies undertaken for the Port Botany EIS (URS, 2003) indicated that Penrhyn Estuary was a functioning ecological unit with abundant and diverse benthos providing a foraging habitat for a variety of shorebird species. The foraging habitat has been identified as the prime ecological value of the estuary within the wider ecology of Botany Bay. This value is to be protected and enhanced as part of the development of Port Botany.

Other than the bioaccumulation of mercury in biota, no specific environmental issues have been identified with respect to mercury reported in Penrhyn Estuary.

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It is also noted that risk management measures undertaken at the FCAP site (refer to Section 7) should also include consideration of mercury in the area remaining as a source to groundwater and surface water runoff.

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Section 7. Risk Management 7.1 General The assessment of risk to human health and the environment has identified a number of issues that, in the absence of additional data, warrant management measures to be undertaken to reduce the level of risk. The issues identified include the following:

 Presence of Hg0 in a number of areas within Blocks G, M and A that has the potential to result in elevated concentrations of mercury vapour in outdoor air (Blocks G and M) and indoor air (Blocks M and A);

 Presence of inorganic mercury in soil in Block G that has the potential to result in elevated exposures should soil be available for direct contact on a regular basis; and

 Presence of Hg0 and inorganic mercury in soil that remain a source to groundwater.

These issues have been further reviewed with the aim of identifying measures that could be undertaken to reduce the level of risk to human health or the environment. The following has incorporated proposed risk management and mitigation measures outlined in the RAPs (Golder 2012a and 2012b).

7.2 Risk Management Measures to Address Risks to Human Health 7.2.1 General Within Block G the following risk mitigation measures are proposed (Golder 2012a):

 Construction of a capping system to restrict vapour emissions, rainwater infiltration, direct contact with soil within Block G and accommodate potential future use as working salt stockpile;  Construction of a containment wall to restrict lateral subsurface vapour migration and restrict groundwater ingress and egress. The wall will extend through the unsaturated zone (where it will function as a vapour barrier) and into the saturated zone (extending to a nominal key-in depth of 1 m into the underlying clayey soil or sandstone layers);  Replacement of the salt stockpile to the east of Block G (which is contributing to the mobilisation of mercury impacts in groundwater); and  No future construction of buildings on Block G.

Based on the above direct contact with mercury impacted soil will be eliminated and the potential source of mercury vapour emissions and groundwater contamination will be effectively managed. The implementation of these measures (provided the design of the vapour barrier adequately addresses the Hg0 risk issues identified on the site as well as ensuring off-site migration of these vapours is negligible) will adequately address the risk issues identified within Block G. There is no requirement to identify any other mitigation measures or derive remediation criteria.

Within Blocks M and A the proposed remediation (Golder 2012b) involves the following:

 Hg0 contaminated soil from these areas will be excavated and placed beneath the proposed capping and containment system in Block G; and

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 the remaining mercury contaminated materials remediated via excavation, transportation and disposal off-site.

Future use of Blocks M and A may include open space or construction of industrial buildings (as has been considered in the quantification of potential risks). In these areas the only risk that requires mitigation relates to potential inhalation exposures to Hg0 that remain in soil and the potential for these impacts to remain an ongoing source to groundwater. The RAP proposes to excavate and remove Hg0 impacted soil and move it to Block G where these risks will be effectively managed through the implementation of the vapour barrier and cut-off wall system. If Hg0 materials are effectively removed from Blocks M and A, then no further unacceptable risks remain within these areas. However if the remediation works cannot remove all of the Hg0 from Blocks M and A it is appropriate to derive risk-based criteria that can be used to validate the effective removal of mercury impacted soil from these areas (and their subsequent suitability for use as open space or for the construction of industrial buildings).

7.2.2 Risk Based Concentration (RBC) – Blocks M and A Risk-based concentrations (RBC) have been derived for mercury in soil that is protective of long- term risks to workers on the site. The calculation has not considered exposures by workers undertaking intrusive works as these would need to be undertaken (and exposure managed) in accordance with the site occupational management plan.

The derivation of a RBC has been undertaken based on a total mercury concentration that can be reported by laboratory analysis of soil samples collected. Review of analytical methods by URS (2008c) suggests that all samples need to be analysed using a whole sample digestion methodology to ensure the analysis provides a representative analysis of total mercury (inorganic and Hg0) in the soils sampled.

To address the proposed future uses of Blocks M and A as open space and/or construction of future industrial buildings, two RBC for total mercury in soil have been derived. As the calculated risk (HI) is directly proportional to the total mercury concentration considered in the risk calculations, a ratio approach has been adopted to calculate RBC that are associated with a total HI of 1 (where exposure to all forms of mercury in soil is considered acceptable). The derived RBC have been rounded to two significant figures (to reflect the level of uncertainty in the derivation and measurement of total mercury in soil). On this basis the following RBC have been derived:

Table 7.1 Derived RBC (protection of on-site risks) – Total Mercury in Soil (mg/kg)

Location RBC – Outdoor/Open Space Use RBC – Construction of Industrial Buildings Block M 480 100 Block A 920 180

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7.2.3 Consideration of Other Exposures Associated with RBC Exposures on BIP In relation to other areas on the BIP, potential concentrations of Hg0 vapour will be lower than directly above the FCAP site due to dispersion of the vapours downwind. Hence if the vapour concentrations on the FCAP are acceptable for workers, undertaking a 10 hour work shift every day, then it will also be acceptable for workers in other areas of the BIP downwind of the FCAP. Review of Hg0 vapour in soil gas data collected by URS (2010) did not identify any unacceptable risk issues for workers in other areas of the BIP.

Off-Site Exposures The RBC for mercury have been derived on the basis of the protection of worker health within Blocks M and A on the FCAP, based on reasonable scenarios for future use. The RBCs and the proposed vapour barrier and cut-off wall in Block G, however, are still associated with some level of Hg0 vapour emissions from these areas. These emissions may be blown off site to adjacent residential areas. Hence the potential contribution Hg0 vapour released to air from the FCAP to exposures in off-site residential areas assuming soil is remediated to meet the RBC has been calculated. It is expected that the design of the vapour barrier and cut-off wall system will include consideration of future exposures both on and off the site and hence the potential for future off-site exposures to Hg0 from Block G has not been further considered in this section.

Prior to the construction of the remediation building/enclosure, review of off-site dispersion of Hg0 vapour emissions from the FCAP (all Blocks) was conducted by PAE Holmes (2010). The modelling undertaken adopted the same phase partitioning as considered in the vapour modelling presented in Section 5.3.36, however the model was used by PAE Holmes to estimate an hourly emission rate that varied with changing soil temperatures (which were conservatively assumed to equal the ambient air temperature). The emission rate calculated was based on a weighted average soil concentration from the FCAP area, assuming that 100% of the total mercury concentrations reported were Hg0, with a calibration factor incorporated to address the presence of a concrete slab over most of the FCAP site. The downwind modelling of emissions was undertaken in accordance with the NSW EPA Approved Methods (DEC 2005) utilising local meteorological data. Based on the situation considered in the modelling, off-site concentrations of Hg0 vapour were all well below the chronic air criteria of 0.2 µg/m3 (WHO 2003), with the maximum annual-average concentration predicted at the closest off-site residential premises equal to 0.027 µg/m3. On this basis there were no unacceptable off-site risks associated with Hg0 vapour emissions form the FCAP at the time modelled. It is noted that the PAE Holmes modelling only considered emissions from Blocks G. No assessment was included for Blocks M or A. As the future emissions from Block G will be effectively mitigated through the installation of the proposed vapour barrier and cut-off wall, the calculations undertaken are not directly relevant to the proposed future use of Block G (following remediation).

6 The assumptions adopted for the soil at the FCAP were generally consistent, however it is noted that PAE Holmes (2010) adopted a soil moisture content of 12% whereas the modelling presented in this report has adopted 8%. Review of these values indicates that emissions would increase by <1% if the lower soil moisture content of 8% were adopted in the PAE Holmes (2010) evaluation. Hence this difference is not considered significant.

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Regardless, the following can be noted in relation to potential emissions from Blocks M and A:

 In relation to the future use scenarios considered in this report within Blocks M and A, the construction of a building will result in capping of much of the mercury impacted soil with concrete which is expected to be more sound than the concrete considered in the PAE Holmes (2010) modelling. The off-site concentrations of Hg0 are expected to be lower now than was predicted in the PAE Holmes report because of the construction of the remediation building/enclosure, as would be the case if a new industrial building were constructed on the site.  Where there are no buildings or concrete surface cover potential Hg0 vapour impacts that may occur off-site can be estimated. The dispersion modelling presented by PAE Holmes (2010) for Block G shows that ground level concentrations of Hg0 are approximately 10 times lower in the closest off-site residential properties when compared with those close to Block G. While a smaller surface area is impacted with Hg0 in Blocks M and A, it can be conservatively assumed that at worst a 10-fold reduction in Hg0 concentrations in air may occur between Blocks M and A and the closest off-site residential area. If this is assumed then the following is noted: o Block M: Based on the outdoor RBC of 480 mg/kg, the Hg0 vapour concentration on Block M is calculated to be 0.00045 mg/m3. If a 10 -fold dispersion factor is applied the worst-case off-site Hg0 concentration is estimated to be 0.000045 mg/m3 or 0.05 µg/m3, which is lower than the long-term (annual-average) air criterion of 0.2 µg/m3 (WHO 2003) relevant to the off-site areas. On this basis the RBC for mercury in soil in Block M does not require any further refinement. o Block A: Based on the outdoor RBC of 920 mg/kg, the Hg0 vapour concentration on Block A is calculated to be 0.00022 mg/m3. If a 10-fold dispersion factor is applied the worst-case off-site Hg0 concentration is estimated to be 0.000022 mg/m3 or 0.02 µg/m3, which is lower than the long-term (annual-average) air criterion of 0.2 µg/m3 (WHO 2003) relevant to the off-site areas. On this basis the RBC for mercury in soil in Block A does not require any further refinement. o If Hg0 impacts from both Blocks M and A were assumed to be additive, the total predicted concentration of Hg0 in off-site areas would be 0.07 µg/m3, which is lower than the long-term (annual-average) air criterion of 0.2 µg/m3 (WHO 2003) relevant to the off-site areas.

The above calculation assumes that 100% of the permissible level of Hg0 vapour in the off-site areas could be derived from emissions to air from the FCAP site.

There are some issues that contribute to uncertainties in these calculations, specifically the form of mercury and background exposures. Because mercury is naturally occurring in our diet everyone is exposed to small quantities. The mercury in our diets is in the form of inorganic mercury or methylmercury. Soil and water criteria take into account these forms of mercury. In air, the WHO (2003) annual-average criterion is based solely on exposure to Hg0 vapour and does not specifically address these background concentrations.

The form of mercury affects how easily mercury can enter the body. Inhalation of Hg0 vapour allows mercury to be absorbed into the body much more easily than the inorganic forms which are normally present in soil and diet. However once mercury is absorbed into the body, regardless of the origin in

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the environment, it is the total amount of mercury that is relevant to determining the potential for adverse effects. Hence when setting the RBC that is relevant to the off-site residential areas, some allowance for intakes of mercury from other sources should be considered (i.e. not all of their intake should be derived from the FCAP source alone)7. When this aspect is considered, an uncertainty factor of 2 fold should be considered in the outdoor soil RBC for Blocks M and A.

Based on the discussion presented above the following RBC are recommended for Blocks M and A:

Table 7.2 Derived RBC (protection of risk on and off-site) – Total Mercury in Soil (mg/kg)

Location RBC – Outdoor/Open Space Use RBC – Construction of Industrial Buildings Block M 240 100 Block A 460 180

It is noted that the RBC derived for the scenario where buildings may be constructed does not take into account the design and implementation of vapour mitigation barriers/systems in these buildings. Should such vapour mitigation measure be considered in future building designs (and these are shown to be effective in mitigating vapour intrusion into the buildings) then the RBC for buildings are no longer relevant.

7.3 Risk Management Measures to Address Ongoing Source to Surface Water and Groundwater The presence of mercury impacts in soil at the FCAP remains an ongoing source to groundwater and, to a limited extent, surface water during high rainfall events (infrequent). In addition, mercury in groundwater beneath the FCAP is also considered a source to the off-site groundwater plume.

There are currently no unacceptable risks to human health or the environment identified on or off the site associated with mercury-impacted groundwater beneath the FCAP and off-site areas identified based on data collected to December 2012. However increased concentrations in the plume area and the potential for further migration downgradient have been identified. Therefore the adoption of any risk management measures and/or RBC for mercury in soil will also need to consider the potential for the area to remain a source to groundwater.

As identified in the risk calculations (refer to Sections 5.3.4 and 5.4.4) the potential risks to human health associated with the presence of Hg0 in groundwater beneath the FCAP and off-site areas are considered negligible. It is considered that removal of Hg0 to a level protective of inhalation

7 It is noted that such a consideration has not been applied for workers on the FCAP site. The ambient air guideline derived by the WHO (2003) is based on occupational exposure studies. These studies involved workers exposed to Hg0 vapour in the workplace. The workers will also have been exposed to other forms of mercury via the diet and dental amalgams. These other intakes were not measured or accounted for in the development of the chronic air guideline. Only uncertainty factors that relate the occupational data to the general community have been considered. For setting a health based soil guideline for workers on the FCAP site, the inclusion of these other intakes within the underlying studies used to derive the chronic air guideline are considered sufficiently protective of potential intakes from all sources (not just the FCAP).

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exposures on the site (presented above) should also be protective of any limited potential for further contribution to surface water and groundwater given the low water solubility of Hg0.

On this basis the calculation of a soil concentration that is protective of surface water and groundwater has focused on the more soluble inorganic species, in particular the potential presence of chloride complexes (which are more mobile) in the plume downgradient of the FCAP source area. Generally, the behaviour of inorganic mercury in soils has been studied and the following can be noted (EA 2009):

 Complexation of mercury with OH- or Cl- and organic matter play an important role in its mobility. Complexation with OH- or Cl- increases the aqueous concentrations and mobility of mercury.

 Mercury can form complexes with both dissolved and solid organic matter. The partitioning of organic matter between aqueous and solid phases is pH dependent with a greater proportion dissolved at higher pH.

 The presence of Cl- in groundwater decreases the sorption of mercury to organic matter and mineral matrices due to the formation of stable chloride complexes (von Canstein et al. 1999), significantly increasing the concentration and potential mobility of mercury in groundwater.

 Sorption in high pH soils is dominated by the presence of clay minerals and iron oxides. Strong binding of mercury to organic matter results in low availability and mobility of mercury in soils.

The above general behaviours were also observed in the work undertaken by the CSIRO with respect to soil in the groundwater source zone (reported by URS, 2008b). More specifically in relation to the determination of a mercury soil/water partition coefficient (Kd) the following is noted:

 Under the conditions tested, the maximum Kd values occurred at pH 6-8, with significantly

lower Kd values occurring at pH 9, and under more acidic conditions;

-  Where Cl concentrations were low, the formation of Hg(OH)2 would occur at higher pH, potentially decreasing the amount of Hg sorbed to particles. Therefore pH could play an important role in adsorption in areas with fresh water inflow and low salinity;

 However, for most of the site, with higher salinity and Cl- concentrations, the formation of Hg- 8 Cl complexes would be an important control on Kd at the site ;

-  Increasing Cl concentrations result in a decrease in Kd supporting modelling completed by URS (2008b) that concludes that the Hg-Cl species dominate at higher chloride concentrations and in these conditions, the formation of these species will lead to desorption, increasing mobility;

8 It is noted that the highest Kd value of CSIRO work is at SB01 “black” material – this could be organic rich, and the significantly higher Kd at this location may be as a result of organic matter.

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 The results on the study suggest that ionic mercury can be mobilised from contaminated aquifer sands by addition of sodium chloride.

On the basis of the above, the mercury impacted groundwater identified beneath the FCAP is expected to remain a source to off-site groundwater as conditions in the area (in particular pH and chloride) are resulting in the mobilisation of mercury in the aquifer.

The removal (or appropriate sealing, bunding and covering) of the salt stockpile upgradient of the FCAP should be considered an important risk management measure to reduce the potential for ongoing mobilisation from the groundwater source. This is proposed to be addressed in the remediation options outlined in the RAP for Block G (Golder 2012a).

For soil (above the aquifer) in the general area of the FCAP, organic content is low (<0.4%) and soil pH is high (on average 9.3), hence there is the potential for mercury to desorb and leach to water and migrate to groundwater and potentially to surface water runoff.

It is noted that the proposed remediation measures in Block G (barrier and cut-off wall) are intended to prevent the infiltration of rainwater (and hence leaching of mercury in soil to groundwater) and the lateral migration of mercury impacted groundwater. These measures are intended to mitigate the potential for mercury impacts in Block G to remain an ongoing source of contamination to groundwater.

Such measures have not been considered in Blocks M and A. Hence a soil RBC for inorganic mercury protective of leaching to groundwater has been calculated using the soil/water partitioning equations presented in the document “Soil Screening Guidance: Technical Background Document, EPS540/R-95/128” (USEPA 1996). The equation used is as follows:

E C  C  (K  W )  DAF S W d P b ...Equation 7.1

Where:

CS = Leach-Based Soil Value (mg/kg)

CW = Groundwater Quality Standard (mg/L)

Kd = Soil/water partitioning coefficient (L/kg)

EW = Water filled soil porosity, taken to be 0.06 (Lwater/Lsoil)

Pb = Dry soil bulk density, taken to be 1.6 (kg/L) DAF = Dilution Attenuation Factor (unitless)

Soil/Water Partition Coefficient

The value Kd indicates the proportion of contaminant absorbed onto soil and, for metals, can be affected by a range of soil and chemical conditions including pH, speciation of elements, Eh, salinity, clay and organic matter in the soil. Hence there is a high degree of variability in Kd values

reported in literature for inorganics, including mercury. For inorganic mercury Kd values in literature range from <100 to >50000 L/kg reflecting varying analyses undertaken, forms and concentrations of mercury and differing soil and groundwater conditions. For total mercury relevant to inorganic forms Kd values range from 19 to 5800 L/kg (OEPA 2005).

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While the site-specific work on Kd values completed by the CSIRO (where values ranging from 35 to 4280 L/kg were reported, refer to URS, 2008b) was for soil in the aquifer source area, the data are considered relevant to the unsaturated soil as the soil type (excluding peat layers) and key properties are consistent. The key issues affecting mobility of mercury in soil were identified as pH and the presence of chloride. Soil pH is high (>9) and while the concentration of chloride in soil was reported to be low (URS, 2008c), elevated concentrations of chloride are of concern in the aquifer. It is expected that different areas of the FCAP will have conditions that result in varying Kd values. Similarly in downgradient areas of the groundwater aquifer conditions will also differ (in particular pH which is closer to 6, lower at the FCAP source area). For the purpose of this assessment a conservative approach has been adopted in the selection of a value of Kd. The value relevant for the most conservative conditions that might be present (high chloride), of 35 L/kg, has been selected for use in this calculation.

Groundwater Quality Standard The level of protection require for the off-site groundwater aquifer also needs to be determined. In considering this issue the following is of note:

 The FCAP and off-site areas are located with the GEEA and hence the installation and use of groundwater bores is not permitted.

 Groundwater (shallow, intermediate and deep) in the off-site areas considered are impacted with concentrations of chlorinated hydrocarbons that would preclude the extraction and use of the water for any purpose (as risks to human health have been determined to be unacceptable, as per the CHHRA (enRiskS 2011)).

 The assessment presented in this report has not identified any unacceptable risks to human health (Section 5) and the environment (Section 6) associated with the mercury identified in off-site groundwater.

Groundwater is not discharging to receiving environments and is not expected to discharge to off- site environments while the GTP remains operational. Irrespective of the GEEA or presence of chlorinated hydrocarbons in the groundwater, target concentrations of mercury in groundwater have been established based on the protection of a reasonable beneficial use.

A target total mercury concentration has been derived to be protective of exposures by all off-site receptors based on the potential for groundwater to be extracted and used for industrial use (as considered in the calculations and assumptions presented in Section 5.4). As the calculated risks presented in Table 5.10 are directly proportional to the inorganic mercury concentration9 considered (where a maximum HI of 0.5 is calculated based on a groundwater concentration of 0.25 mg/L inorganic mercury), a target criterion of 0.5 mg/L in groundwater can be calculated that is associated with a total HI of 1 (for the most significant receptor – young children [general public exposures]). This concentration is assumed to be 100% inorganic mercury, most likely present as Hg-Cl complex.

9 Based on the risk calculations undertaken and presented in Section 5.4, the contribution to risk associated with the presence of Hg0 and methylmercury in groundwater is low and essentially negligible

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Dilution Attenuation Factor (DAF) As mercury in soil leachate moves through soil and groundwater, it is subject to physical, chemical and biological processes that tend to reduce the concentration at any receptor point (in this case assumed to be off the BIP). The DAF is the ratio of the concentration in soil leachate to the concentration in groundwater at the receptor point. There is a range of issues that could be considered in the calculation of a DAF, however the approach adopted for this assessment is the simple approach (USEPA 1996) that only considers dilution in groundwater. Given the location of the FCAP to the boundary of the BIP, and if the groundwater quality standard above is considered to apply at the boundary, this simple approach is considered conservative. The approach adopted assumes the aquifer is unconfined and unconsolidated, and has homogeneous and isotropic properties. Using the ASTM model approach (USEPA 1996) and groundwater parameters relevant to the groundwater aquifer in the vicinity of the FCAP, the DAF is calculated as follows:

d DAF  (1 U  ) ...Equation 7.2 gw IL

Where:

Ugw = Darcy groundwater velocity = 110 m/year d = mixing zone depth = 3 m (based on where most of the mercury contamination is reported in groundwater) I = infiltration rate = 0.15 x annual rainfall of 1.1 m = 0.165 m/year L = length of source parallel to flow = 40 m based on Block M impacts as most significant

Based on these values a DAF of 51 has been calculated.

Calculated RBC Protective of Groundwater Following the above approach, the RBC for mercury in soil (that is protective of groundwater) is 893 mg/kg. This value is greater than the RBC derived to be protective of risks to human health on and off the site (as presented in Table 7.2) and therefore the RBC for Blocks M and A are considered to be adequately protective of issues associated with an ongoing source to groundwater (for soil above water table).

In relation to surface water, the prime issue to consider is the potential for surface erosion and management should be focused on the stability of the soil surface rather than relying on an RBC.

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Section 8. Uncertainty 8.1 General This section presents a discussion on uncertainty and variability with respect to the HHERA presented. The conduct of a HHERA requires the consideration of available data and the selection and use of numerous parameters to define exposure and toxicity, all of which are associated with some degree of uncertainty and variability.

8.2 Uncertainty Uncertainty in any assessment refers to a lack of knowledge and is an important aspect of the risk assessment process. An assessment of uncertainty is a qualitative process relating to the selection and rejection of specific data, estimates or scenarios within the HHERA. In general, to compensate for uncertainty, conservative assumptions are often made that result in an overestimate rather than an underestimate of risk.

In general, the uncertainties and limitations of the HHERA can be classified into the following categories:

 Sampling and analysis;

 Receptor exposure assessment; and

 Toxicological assessment.

The risk assessment process following Australian (enHealth 2012a; NEPC 1999 amended 2013b) and international (USEPA 1989, 1991, 2009a; WHO 2008) guidance provides a systematic means for organising, analysing and presenting information on the nature and magnitude of risks to public health posed by chemical exposures.

Despite the advanced state of the current risk assessment methodology, uncertainties and limitations are inherent in the risk assessment process. This section discusses the uncertainties and limitations associated with this risk assessment

8.2.1 Sampling and Analysis The assessment of soil and groundwater conditions has been based on an evaluation of the site history and on the results of prior soil and groundwater investigations with the HHERA undertaken on the basis of soil and groundwater data available to the end of 2012.

With respect to the available data used in this assessment, the following outlines the uncertainties identified and how they have been addressed within the HHERA:

 Characterisation of soil on the FCAP using different analytical methods. An assessment of different analytical methods was undertaken by URS (2008c) to identify the most appropriate method to ensure that the analysis for total mercury reflected both inorganic and elemental mercury. Samples analysed using a whole digestion method were identified as the most representative. Samples collected prior to 2008 did not utilise this method and could have underestimated the total mercury concentration as elemental mercury was routinely observed to settle at the bottom of the sample container (and not included in the analysis

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undertaken). To address this uncertainty, soil data collected prior to 2008 have not been used in the quantification of exposures on the site.

 The vertical extent of mercury impacts in soils has not been delineated on the FCAP site. The HHERA has considered that the concentrations reported in soil are present at all points of exposure (surface and subsurface during intrusive works). In addition, an RBC for the remediation of soil on the site has been established based on the protection of human health and the environment in Blocks M and A. Therefore any further data collected from depth during remediation or other subsequent works can be reviewed/considered with respect to human health and environmental risks.

 Comparison of measured flux emission rates with modelled emission rates (based on reported total mercury concentrations in soil at the same location) suggests that while the average emission rates across the whole site show consistency, significant variability is noted at individual locations. It is likely that the variability reflects the use of a discrete soil sample in the modelled emission rate whereas the measured emission rate was collected from the surface of a larger area, overlying the mercury-impacted soil (full vertical extent).

 The collection of Hg0 emission rates from the site has been undertaken on one occasion only. While the sampling conditions were considered suitable (dry soils), observations in the field reported significant variability in Hg0 emissions in warmer conditions. Hence there is the potential for higher emissions to occur during warmer months. This variability has been addressed in the modelling of off-site Hg0 vapour emissions which was further used to refine the outdoor air RBC (refer to Section 7.2.3).

 The available groundwater data for off-site areas are limited. To address potential uncertainties associated with the off-site areas, the maximum reported total, methyl- and elemental mercury concentrations have been used to assess exposures in all off-site areas overlying the plume. This is expected to overestimate risk.

Inferences about the nature and continuity of soils and groundwater contamination away from the sampling points are made but cannot be guaranteed.

8.2.2 Exposure Assessment Risk assessments require the adoption of several assumptions in order to assess potential human exposure. This risk assessment includes assumptions about general characteristics and patterns of human exposure relevant to the on- and off-site groups. These assumptions are conservative and have been developed to provide an estimate of maximum possible exposures rather than the actual exposures. For example the assessment of off-site inhalation exposures has assumed that residents remain at home for 24 hours per day, 7 days per week for a lifetime. Workers on the FCAP site are assumed to spend their working lifetime in the one location, spending up to 10 hours per day at the same location (either inside or outside), every work day. This approach is expected to overestimate the risks.

A vapour migration model has been used to estimate the concentration of volatile chemicals in outdoor and indoor air. The vapour migration models used to estimate air concentrations are typically conservative and utilise simplistic assumptions. The approach adopted in this assessment

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has been to utilise the vapour model only where it has been shown to correlate with measured data. This has minimised the potential to overestimate or underestimate long term (i.e. lifetime) exposures. It is expected that vapour emissions will vary over short periods of time (due to temperature and rainfall conditions) however the assessment presented in this assessment specifically relates to exposures that occur over a lifetime and this short duration variability does not affect these conclusions.

8.2.3 Toxicological Assessment In general, the available scientific information is insufficient to provide a thorough understanding of all of the potential toxic properties of chemicals to which humans could be exposed. In some cases data obtained from occupational exposure studies are used. Where these studies are used the data are typically obtained from situations where there are higher levels of exposure (compared with environmental exposures) and the studies incorporate exposures from the occupational environment (which is where the level of exposure is measured) as well as other exposures that occur outside of the workplace. When using these data for evaluating potential effects in the wide community, uncertainty/safety factors are applied to extrapolate the data from an occupational environment (where the duration of exposure is less than a lifetime) and to address the range of sensitivities more likely to be present in the general community.

More commonly there are less data available from occupational or other human studies and hence data are obtained from animal studies. It is necessary, therefore, to extrapolate data obtained under other conditions of exposure and involving experimental laboratory animals to those relevant to exposures that may occur in the general community. This can introduce two types of uncertainties into the risk assessment, as follows:

 Those related to extrapolating from one species to another; and

 Those related to extrapolating from the high exposure doses, usually used in experimental animal studies, to lower doses usually estimated for human exposure situations.

The majority of the toxicological knowledge of chemicals comes from experiments with laboratory animals, although there can be interspecies differences in chemical absorption, metabolism, excretion and toxic response. There can also be uncertainties concerning the relevance of animal studies using exposure routes that differ from human exposure routes. In addition, the frequent necessity to extrapolate results of short-term or sub-chronic animal studies to humans exposed over a lifetime has inherent uncertainty.

In order to adjust for these uncertainties, the quantitative toxicity reference values incorporate safety factors that can typically vary from 10 to 1000.

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8.3 Variability Variability is uncertainty due to unresolved variation in physical, chemical and biological processes, human behavioural patterns, seasonal changes, and data for site characterisation.

Table 8.1 presents a list of the major input variables used in the risk assessment. The table presents the range of practical values for each variable, the value used in the risk assessment, the likely variability, relative sensitivity and the uncertainty associated with the variable.

Table 8.1 Sensitivity of Key Variable Considered in the HHERA

Input Variable Practical Value Used in Effect on Relative Relative Range of Risk Risk if Model Uncertainty Values Assessment Variable Sensitivity increased Soil dry bulk Dependent on 1.6 g/cm3 for fill/ Decrease Low Low as sufficient density soil type, sands, based on data are available to however for data from Botany support the selected sands and fill, area, consistent value. value can range with the default from 1.3 to 2 recommended in the derivation of HSLs (Friebel & Nadebaum 2011) Moisture Content Values for 4% for fill/sands, Decrease Negligible Low as this value is sand/fill range the lower end of based on the lower from 4% to 12%, the available data (more conservative) with data from the site as end of available collected from this best allows for site-specific data Botany Sands (in correlation more coastal between modelled Matraville area) and measure ranging from 5% emissions to 16% Enclosed air 0.18 to 4 per 2 per hour for Decrease Low Low. Note that exchange rate hour commercial current building buildings based on codes uses old current Building Australian Standard. Code of Australia New standard has not been adopted in the BCA due to concerns regarding the low values recommended and workplace health. Fraction of 0.0001 to 0.01 0.0038, the default No change Negligible Negligible as the cracks in floor recommended in within range migration of vapours and walls available guidance is more significant (USEPA 2004a) via advection (pressure) driven mechanisms, rather than diffusion through the gaps and cracks. Ratio of Qsoil 0.05 – 0.0001 0.0001 Increase Moderate Value selected (parameter based on lower end relevant to the of range, considered pressure driven relevant for migration of industrial premises.

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Input Variable Practical Value Used in Effect on Relative Relative Range of Risk Risk if Model Uncertainty Values Assessment Variable Sensitivity increased vapours form subsurface to indoor air) to Qbuilding (air flow rate inside building) Soil/water For elemental 6310 L/kg for Hg0 Decrease Moderate to Low as published partition mercury in soil, in soil high value used in this coefficient Kd for no specific Kd assessment. The 0 Hg values are use of this value has available, shown good however a value agreement between for total mercury modelled and has been measured vapour adopted. emissions.

Soil/water Kd for inorganic 35 L/kg for Decrease Moderate Low to moderate. partition forms in inorganic forms of Site-specific coefficient Kd for groundwater Hg in soils above (conservative) data inorganic Hg zone and below water used, however table relevance to soils above water table assumed. Groundwater and Range of Maximum Increase Moderate Groundwater - low Soil concentrations groundwater (as conservative Concentration reported on and concentrations values used) off the FCAP used. Average soil Soil – moderate as site. concentration some uncertainty reported from remains about the samples where data available. visible Hg0 was identified in Blocks G, M and A has been used in assessment. It has also been assumed that 100% of the total mercury reported is present as both elemental and inorganic species. Body weight Body weights of 78 kg for adults, Decrease Low Moderate as the adults, older 34.5 kg for older values used are children and children and 13.2 considered relevant young children kg for young based on a large vary widely children database of body weights that shows a significant distribution in the population. Exposure Wide range of Lifetime (or Increase Low to Low as conservative frequency and values could be working lifetime) moderate values adopted duration relevant exposures assumed for most scenarios considered.

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It is recognised that most of the exposure values as well as parameters selected for the purpose of modelling vapour migration and intrusion are based on variable physiological, behavioural or physical parameters. All of these values, therefore, can be considered to be variables with most of the parameters considered better represented as a distribution rather than a single point value. However it should be highlighted that in the assessment presented the quantification of risks to human health has provided an estimate of reasonable maximum exposure where an upper limit or reasonable upper limit of most key variables has been adopted. The compounding effect of utilising reasonable upper limits for all these key variables is expected to give rise to an overestimation of actual risk.

Overall, while a number of parameters used within the HHERA have a moderate degree of uncertainty and variability associated with them and the outcome of the assessment is sensitive (to varying degrees) to changes in these parameters, values used to define these parameters have been selected to be conservative. This has resulted in the calculation of risk, which is expected to be conservative, and an overestimation of actual risk.

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Section 9. Conclusions An assessment of risks to human health and the environment associated with the presence of mercury in soil and groundwater beneath the FCAP site and off-site areas has been undertaken. The assessment has provided a review of existing data, including consideration of more detailed assessment of mercury hydro-geochemistry beneath the FCAP and off-site areas to identify key issues that warrant detailed assessment within the HHERA.

The key issues identified include the visual identification of free Hg0 beneath Block G (most impacted area), Block A and Block M. Elevated concentrations of total mercury (associated with Hg0 and inorganic mercury) have also been reported in soil beneath Block G and Block M.

Mercury impacted groundwater has been reported beneath the FCAP, extending off-site beneath adjacent commercial industrial premises. Mercury impacted groundwater, derived from the FCAP, has not discharged to any receiving environment and groundwater modelling has shown that while the GTP is operating the mercury impacted groundwater will not discharge to any off-site receiving environment. However the presence of mercury in soils and groundwater beneath the FCAP provides an ongoing source to groundwater (and potentially surface water runoff discharged from the FCAP site via drains on the BIP) that requires consideration in the long-term management of risks on the site.

The assessment conducted has considered the nature and extent of mercury contamination (associated with the FCAP), the proposed future use of Blocks G, M and A as well as remediation measures outlined in the remediation action plans (RAP) prepared for Block G (Golder 2012a) and Blocks M and A (Golder 2012b).

In relation to the proposed future industrial use of Blocks G (open space only) and Blocks M and A (outdoor space and/or future industrial buildings), potentially unacceptable risks have been identified in relation to potential exposures in Block G (from the inhalation of Hg0 vapours outdoors and direct contact with mercury impacted soil) and Blocks M and A (from the inhalation of Hg0 vapours indoors and potentially outdoors). In relation to the risks identified the following can be noted:

 Block G: The proposed construction of a barrier and cut-off wall (Golder 2012a) will prevent direct contact by workers with mercury impacted soil. In addition the proposed barrier and cut-off wall will mitigate the vertical and lateral migration of Hg0 vapours from this area mitigating future inhalation risks to workers (as well as in all off-site areas). The proposed barrier and cut-off wall will also prevent rain infiltration and lateral migration of groundwater mitigating the potential for mercury impacted soil to remain an ongoing source to groundwater. These measures effectively mitigate all risks associated with the mercury impacted materials identified within Block G.

 Blocks M and A: The proposed remediation (Golder 2012b) involves excavation of Hg0 impacted soil and placement of these materials in Block G where they will be contained and effectively managed. Other mercury impacted soil will be excavated and transported off-site for appropriate disposal. These measures are intended to effectively remediate mercury impacted materials identified in Blocks M and A. To assist in the remediation of these areas risk-based criteria (RBC) have been derived to ensure that the remediation adequately

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addresses the long-term risks issues on the site (as well as ensuring potential off-site risk issues associated with off-site inhalation of vapours and ongoing source to groundwater are effectively managed).

The derived RBC for Blocks M and A that are protective of long-term exposures on and off the site (including consideration of ongoing source to groundwater contamination) are summarised in the following:

Table 9.1 Derived RBC – Total Mercury in Soil (mg/kg)

Location RBC – Outdoor/Open Space Use RBC – Construction of Industrial Buildings* Block M 240 100 Block A 460 180 * RBC relevant where no vapour mitigation system is implemented within the future building.

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Section 10. References

Site Investigations and Evaluation Reports: AGEE and Woodward Clyde, 1990. Stage 1 Preliminary Investigation, ICI Botany Environmental Survey, AG Environmental Engineers & Woodward Clyde Consultants Inc, May 1990.

Dames and Moore, (1998). Environmental Impact Statement (EIS). Replacement Chlor Alkali Plant for Orica Australia Pty Ltd, Dames & Moore, 28 June 1998 (Ref 39408-001-070).

enRiskS 2011, Consolidated Human Health Risk Assessment – 2010. Report prepared for Orica Australia Pty Ltd, 24 August 2011.

Golder 2011, Groundwater Monitoring 2011 – Former Chlor Alkali Plant, Botany Industrial Park. Letter report prepared by Golder Associates, 9 November 2012.

Golder 2012a, Block G, Former Chlor Alkali Plant, Botany Industrial Park, Remediation Action Plan. Report prepared by Golder Associates 12 July 2012.

Golder 2012b, Block A and M, Former Chlor Alkali Plant, Botany Industrial Park, Remediation Action Plan. Report prepared by Golder Associates 11 July 2012.

Golder 2013, Former Chloralkali Plant, Groundwater monitoring Program, Baseline Monitoring Event: December 2012, Botany Industrial Park. Report dated 26 April 2013.

Laase, A. D., 2010. Evaluation of Potential Mercury Migration from the Former Chloralkali Plant. Draft February 2010.

Orica, 2005. Review of Environmental Factors for an Excess Treated Water Discharge Pipeline to Sydney Water’s Bunnerong Stormwater Channel SC11 to be conducted for the Botany Groundwater Remediation Project. 2 June 2005, EN.1591.69.PR006, Rev O. Prepared by Orica Australia Pty Ltd.

PAE, 2007. Air Quality Impact Assessment for Remediation of the Car Park Waste Encapsulation at the Botany Industrial Park. Prepared by Pacific Air and Environment for Orica.

PAE Holmes, 2010. Amended Report - Mercury Investigations, Boundary Ambient Air Modelling Former ChlorAlkali Plant, Botany Industrial Park, Banksmeadow. Letter report prepared by PAE Holmes, 24 June 2010.

URS, 2003. Port Botany Environmental Impact Statement (EIS). Prepared for Sydney Ports Corporation.

URS, 2004a. Geotechnical and Environmental Assessment for Proposed Groundwater Treatment Plant at Orica Botany, URS Australia Pty Ltd., 18 June 2004 (Ref 46160-005-4101).

URS, 2004b. Botany Groundwater Cleanup Project, Environmental Impact Statement, URS November 2004.

URS, 2005. Consolidated Human Health Risk Assessment. Orica Botany. August 2005.

URS, 2006a. Stage 1 and 2 Investigations, Former Chlor Alkali Plant, Orica Botany, Botany Industrial Park, Consolidated Investigation Report. 31 August 2006, R001b Final.

URS, 2006b. Orica Botany Environmental Survey, Stage 4 – Remediation. Groundwater Treatment Plant (GTP) Quarterly Groundwater and Surface Water Monitoring Report- March 2006. Document Number R02, 30 June 2006.

URS, 2006c. Results of Additional Groundwater and Surface Water Investigation, Former Chlor Alkali Plant, Orica Botany, Botany Industrial Park, Orica Botany. October 2006 Final.

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URS, 2007a. Results of Additional Soil Sampling, Former Chlor Alkali Plant, Orica Botany. Final Letter Report, 31 July 2007.

URS, 2007b. Results of Additional Groundwater Investigation, May 2007. Former Chlor Alkali Plant, Orica Botany, 31 July 2007.

URS, 2007c. Results of Offsite Groundwater Investigation, Former Chlor Alkali Plant, Orica Botany, Botany Industrial Park, Orica Botany. January & February 2007 Final.

URS, 2007d. Assessment of Chlorine Compounds in Discharge from the Orica Botany Groundwater Treatment Plant and Downstream Surface Waters. Letter Report dated 26 February 2007, Project number 43217458.

URS, 2008a. Mercury Fate and Mobility Assessment. Data Report for February 2008 On-Site and Offsite Investigations, ChlorAlkali Plant, Orica Botany, NSW. Letter Report issued June 2008.

URS, 2008b. Mercury Fate and Transport ChlorAlkali Groundwater and Soil Investigation, ChlorAlkali Plant, Orica Botany, NSW, August 2008.

URS, 2008c. Stage 1 – Soil Characterisation of the ChlorAlkali Soil Washing Trials Project. August 2008.

URS, 2008d. Human Health and Environmental Risk Assessment, Former ChlorAlkali Plant, Botany Industrial Park. Prepared for Orica Australia Pty Ltd, 21 Aug 2008.

URS, 2009. Boundary Mercury Ambient Air Sampling. Letter Report prepared by URS Australia dated 7 July 2009.

URS, 2010. Soil Mercury Vapour at Former ChlorAlkali Plant, Botany. Prepared for Orica Australia Pty Limited, August 2010.

Woodward Clyde, 1996. ICI Botany, Groundwater Stage 2 Survey, Contract S2/C3 Water/Soil Phase 2, Woodward Clyde, August 1996. Doc 3390R1-D.

Woodward Clyde, 1997. Stage 3 Groundwater Survey, ICI Botany Springvale Drain Investigation – HCB and Mercury Study in Sediments, Surface Water and Groundwater, Woodward Clyde, March 1997, Document R004D5.

Hydrology References Albani, A.D., Rickwood, P.C., Johnson, B.D., McGrath, C.A. and Taylor, J.W., 1978. A Geological Investigation of the Seabed Area of the Sutherland Shire. Unisearch Ltd – A Report for Sutherland Shire Council (unpublished).

Griffin, R.J., 1963. The Botany Basin. Bull. Geol. Surv., NSW,18.

Pankow, J.F. and Cherry, J.A., 1996. Dense Chlorinated Solvents and other DNAPLs in groundwater: History, Behaviour, and Remediation. Waterloo Press, Oregan

Roy, P.S., 1980. Quarternary Geology. In Geology of the Sydney Basin, 1:100,000 Sheets 9130, C.Herbert (Ed). Geological Survey of New South Wales. Department of Mineral Resources.

Smart, J.V., 1974. The Geology, Hydrogeology and Groundwater Chemistry of Part of the Botany Basin, New South Wales. M Sc. Thesis, University of Sydney (unpublished).

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Other References: Allison, JD & Allison, TL 2005, Partition Coefficients for Metals in Surface Water, Soil and Waste, USEPA.

ANZECC 1992, Australian and New Zealand Guidelines for the Assessment and Management of Contaminated Sites, Australian and New Zealand Environment and Conservation Council and National Health and Medical Research Council,

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ASTM 2002, Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum release Sites, American Society for Testing and Materials,

ATSDR 1999, Toxicological Profile for Mercury, Agency for Toxic Substances and Disease Registry. .

ATSDR 2009, Children’s Exposure to Elemental Mercury: A National Review of Exposure Events, The Agency for Toxic Substances and Disease Registry and Centers for Disease Control and Prevention, Mercury Workgroup.

Austin, GT 1984, Shreve’s, Chemical Process Industries, 5th Edition edn, McGraw-Hill International Editions,

DEC 2005, Approved Methods for the Modelling and Assessment of Air Pollutants in New South Wales, Department of Environment and Conservation NSW (DEC),

DEC 2007, Contaminated Sites, Guidelines for the Assessment and Management of Groundwater Contamination.,

EA 2009, Supplementary information for the derivation of SGV for mercury, Environment Agency, Bristol, UK.

enHealth 2012a, Environmental Health Risk Assessment, Guidelines for assessing human health risks from environmental hazards, Commonwealth of Australia, Canberra.

enHealth 2012b, Australian Exposure Factors Guide, Commonwealth of Australia.

EPHC 2003, Health and Environmental Assessment of Site Contamination, Proceedings of the Fifth National Workshop on the Assessment of Site Contamination, Environment Protection & Heritage Council, Adelaide.

Friebel, E & Nadebaum, P 2011, Health screening levels for petroleum hydrocarbons in soil and groundwater. Part 1: Technical development document, CRC for Contamination Assessment and Remediation of the Environment, CRC CARE Technical Report no. 10, Adelaide.

FSANZ 2011, The 23rd Australian Total Diet Study. .

Hines, RN, Sargent, D, Autrup, H, Birnbaum, LS, Brent, RL, Doerrer, NG, Cohen Hubal, EA, Juberg, DR, Laurent, C, Luebke, R, Olejniczak, K, Portier, CJ & Slikker, W 2010, 'Approaches for assessing risks to sensitive populations: lessons learned from evaluating risks in the pediatric population', Toxicological sciences : an official journal of the Society of Toxicology, vol. 113, no. 1, Jan, pp. 4-26.

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NEPC 1999 amended 2013a, Schedule B(5) Guideline of Ecological Risk Assessment, National Environment Protection (Assessment of Site Contamination) Measure,

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NEPC 1999 amended 2013c, Schedule B(6) Guideline on Risk Based Assessment of Groundwater Contamination, National Environment Protection Council,

NEPC 1999 amended 2013d, Schedule B(7), Gudieline on Health-Based Investigation Levels, National Environment Protection Council,

NHMRC 1999, Toxicity Assessment for Carcinogenic Soil Contaminants, National Health and Medical Research Council,

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NHMRC 2011, Australian Drinking Water Guidelines, National Water Quality Management Strategy, National Health and Medical Research Council and Natural Resource Management Ministerial Council, Commonwealth of Australia, Canberra.

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SAHC 1991, The Health Risk Assessment and Management of Contaminated Sites, Proceedings of the First National Workshop on the Assessment of Site Contamination, Adelaide.

SAHC 1993, The Health Risk Assessment and Management of Contaminated Sites, Proceedings of the Second National Workshop on the Assessment of Site Contamination, Adelaide.

SAHC 1996, The Health Risk Assessment and Management of Contaminated Sites, Proceedings of the Third National Workshop on the Assessment of Site Contamination, Adelaide.

SAHC 1998, The Health Risk Assessment and Management of Contaminated Sites, Proceedings of the Fourth National Workshop on the Assessment of Site Contamination.

Suter II, GW & Tsao, CL 1996, Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects on Aquatic Biota: 1996 Revision, U.S. Department of Energy, Office of Environmental Management.

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USEPA Integrated Risk Information System (IRIS), United States Environmental Protection Agency, 2012.

USEPA 1989, Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A), Office of Emergency and Remedial Response, United States Environmental Protection Agency, Washington.

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USEPA 1997a, Mercury Study Report to Congress, Volume III: Fate and Transport of Mercury in the Environment, United States Environmental Protection Agency, Office of Air Quality Planning & Standards and Office of Research and Development.

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USEPA 1997b, Mercury Study Report to Congress, Volume V: Health Effects of Mercury and Mercury Compounds, United States Environmental Protection Agency, Office of Air Quality Planning & Standards and Office of Research and Development.

USEPA 2002, Supplemental Guidance for Developing Soil Screning Levels for Superfund Sites, Office of Emergency and Remedial Response, United States Environmental Protection Agency.

USEPA 2004a, User's Guide for Evaluating Subsurface Vapor Intrusion into Buildings, United States Environmental Protection Agency, Washington.

USEPA 2004b, Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual, (Part E, Supplemental Guidance for Dermal Risk Assessment), United States Environmental Protection Agency, Washington, D.C.

USEPA 2005a, Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens, Risk Assessment Forum, United States Environmental Protection Agency, Washington.

USEPA 2005b, Guidelines for Carcinogen Risk Assessment, Risk Assessment Forum, United States Environmental Protection Agency, Washington.

USEPA 2009a, Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual, (Part F, Supplemental Guidance for Inhalation Risk Assessment), United States Environmental Protection Agency, Washington, D.C.

USEPA 2009b, Report to Congress: Potential Export of Mercury Compounds from the United States for Conversion to Elemental Mercury, United States Environmental Protection Agency, Office of Pollution Prevention and Toxic Substances. von Canstein, H, Li, Y, Timmis, KN, Deckwer, WD & Wagner-Dobler, I 1999, 'Removal of mercury from chloralkali electrolysis wastewater by a mercury-resistant Pseudomonas putida strain', Applied and environmental microbiology, vol. 65, no. 12, Dec, pp. 5279-5284.

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