human health and screening ecological risk assessment fire

Prepared for:

Department of Defence

Environmental Impact Management National Contamination Management Unit Canberra Act 2600

Human Health and Screening Ecological Risk Assessment Fire Training Area, RAAF Base Tindal, Northern Territory/Kimberley Final

AECOM

25 September 2009

Document No.: D11029_RPTFinal_25Sep09.doc

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Human Health and Screening Ecological

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Distribution

Human Health and Screening Ecological Risk Assessment Fire Training Area, RAAF Base Tindal, Northern Territory/Kimberley

25 September 2009

Copies Recipient Copies Recipient

1 Melissa Woltmann Defence Project Manager Department of Defence BP3-2-B036 Brindabella Park Canberra ACT 2600

1 Project File AECOM Suite 3, 17-19 Lindsay Street Darwin NT 0800

1 Technical Advisor ERM PO Box 266 South Melbourne Vic 3205

1 Library AECOM Level 5, 828 Pacific Highway Gordon NSW 2072

© AECOM * ENSR Australia Pty Ltd (trading as AECOM and hereafter referred to as AECOM) has prepared this document for the purpose

which is described in the Scope of Works section, and was based on information provided by the client, AECOM's understanding of the site conditions, and AECOM's experience, having regard to the assumptions that AECOM can reasonably be expected to make in accordance with sound professional principles.

* This document was prepared for the sole use of the party identified on the cover sheet, and that party is the only intended beneficiary of AECOM's work.

* No other party should rely on the document without the prior written consent of AECOM, and AECOM undertakes no duty to, nor accepts any responsibility to, any third party who may rely upon this document.

* All rights reserved. No section or element of this document may be removed from this document, extracted, reproduced, electronically stored or transmitted in any form without the prior written permission of AECOM.

By ENSR Australia Pty Ltd (trading as AECOM) ABN: 34 060 204 702 Level 5, 828 Pacific Highway Gordon NSW 2072 PO Box 726 Pymble NSW 2073 Ph: +61 2 8484 8999 Fax: +61 2 8484 8989 ____________________________________

Principal, Risk Assessment

____________________________________

Senior Environmental Scientist

____________________________________

Principal Remediation Engineer

____________________________________

National Service Line Leader - Contaminated Site Services

Technical Peer Reviewer: Date:

Associate Environmental Engineer

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Contents

GLOSSARY OF TERMS............................................................................................................................V EXECUTIVE SUMMARY....................................................................................................................... ES1 1.0 INTRODUCTION.........................................................................................................................1

1.1 Objectives and Scope of Work ....................................................................................1 1.2 Existing Data................................................................................................................3 1.3 Methodology ................................................................................................................3

2.0 SITE DESCRIPTION...................................................................................................................5 2.1 Site Location and Layout .............................................................................................5 2.2 Current and Proposed Land Use.................................................................................5 2.3 Current Surrounding Land Use....................................................................................6 2.4 Surface Water..............................................................................................................6 2.5 Geology .......................................................................................................................6 2.6 Hydrogeology...............................................................................................................7 2.7 Hydrology.....................................................................................................................8

3.0 SUMMARY OF PREVIOUS INVESTIGATIONS ........................................................................9 3.1 ERM (2005) – Stage 1 Investigation............................................................................9 3.2 ERM (2007) - Landfill/Burial Sites Stage 1 Investigation...........................................10 3.3 ERM (2007) - Stage 1 and 2 Investigations ..............................................................11 3.4 GHD (2008) - Stage 2, Part II Investigation...............................................................11 3.5 AECOM (2009a) - Stage 2 Part III Groundwater Investigation .................................13 3.6 AECOM (2009b) - Water Quality Investigations FY08/09, RAAF Base

Tindal .........................................................................................................................14 4.0 DATA EVALUATION................................................................................................................15

4.1 Nature and Extent of Contamination .........................................................................15 4.2 Quality Assurance and Quality Control (QA/QC) ......................................................17 4.3 Chemicals of Potential Concern ................................................................................17

4.3.1 Adopted Soil Investigation Levels ..............................................................18 4.3.2 Chemicals of Potential Concern – Soil and Sediment ...............................18 4.3.3 Adopted Groundwater Investigation Levels ...............................................20 4.3.4 Chemicals of Potential Concern - Groundwater.........................................20

5.0 TOXICITY (DOSE-RESPONSE) ASSESSMENT.....................................................................23 5.1 Non-Threshold Dose Response Factors ...................................................................23 5.2 Acceptable Daily Intakes ...........................................................................................24

5.2.1 Background Intakes....................................................................................24 6.0 EXPOSURE ASSESSMENT ....................................................................................................27

6.1 Potential Receptors ...................................................................................................27 6.2 Potential Exposure Pathways....................................................................................28 6.3 Exposure Parameters ................................................................................................29 6.4 Representative Chemical Exposure Point Concentrations........................................31 6.5 Estimation of Chemical Intakes .................................................................................32

7.0 HUMAN HEALTH RISK CHARACTERISATION.....................................................................33 7.1 Non-Threshold Risk Estimates ..................................................................................33

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7.2 Threshold Risk Estimates..........................................................................................33 7.3 Summary of Estimated Human Health Risks ............................................................34

8.0 PRELIMINARY ECOLOGICAL RISK ASSESSMENT.............................................................37 8.1 Background................................................................................................................37 8.2 Receptors ..................................................................................................................37 8.3 Exposure Assessment ...............................................................................................38 8.4 Toxicity Assessment ..................................................................................................38 8.5 Risk Characterisation.................................................................................................40

9.0 UNCERTAINTIES.....................................................................................................................41 9.1 Sampling and Analysis ..............................................................................................41 9.2 Exposure Assessment ...............................................................................................41 9.3 Toxicological Assessment .........................................................................................42 9.4 Ecological Risk Uncertainty Considerations..............................................................42

10.0 CONCLUSIONS AND RECOMMENDATIONS........................................................................45 10.1 Human Health............................................................................................................45 10.2 Ecological Effects ......................................................................................................46

11.0 REFERENCES..........................................................................................................................47

List of Tables

Body Report

Table 1: FTA (NT0064) Monitoring Well Standing Water Levels (measured November 2008).................8 Table 2: PFOS Historical Comparison at NT0064 FTA............................................................................14 Table 3: RAAF Tindal Extraction Bores PFOS Analytical Results (based on GHD, 2008)......................16 Table 4: Reasonable Maximum Human Exposure Parameters Used in the Risk Assessments .............30 Table 5: PFOS and PFOA Exposure Point Concentrations .....................................................................31 Table 6: Human Health Risk Calculation Summary .................................................................................34 Tables Section

Table T1: Data Summary and CoPC Selection Process - Soil Table T2: Data Summary and CoPC Selection Process - Groundwater

List of Figures

Figures Section

Figure F1: Site Location Figure F2: Conceptual Site Model

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List of Appendices

Appendix A Site Layout Figure 13 (GHD, 2008) Site Layout including CSR Locations Figure 15 (GHD, 2008) Site Layout including BH and 064MW Location Figure 2 (ERM, 2007) Site Layout including BH and 064MW Locations Appendix B Dose Response Derivation Appendix C Staff/Trainee Fire fighter Modelling Results Appendix D Maintenance/Construction Worker Modelling Results Appendix E On-site and Off-site Residential Modelling Results Appendix F Tindal Ecological Species List

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Glossary of Terms

Acronym Description

ADI Acceptable Daily Intake

AECOM ENSR Australia Pty Ltd (trading as AECOM)

AFFF Aqueous Fire Fighting Foam

AHD Australian Height Datum

BTEX Benzene, Toluene, Ethylbenzene and Xylenes

CDI Chronic Daily Intake

COPC Chemical of Potential Concern

CSM Conceptual Site Model

CSR Contaminated Sites Register

DGBE Diethylene Glycol Butyl Ether

ED Exposure Duration

EF Exposure Frequency

EIL Environmental Investigation Level

EPC Exposure Point Concentrations

ERM Environmental Resources Management Australia

ET Exposure Time

GHD GHD Pty Ltd

HHERA Human Health and Screening Ecological Risk Assessment

HI Hazard Index

HIL Health Investigation Level

HQ Hazard Quotient

LOR Limit of Reporting

mBGL Metres Below Ground Level

MDH Minnesota Department of Health

MEOMS Mechanical Equipment Operations Maintenance Section

MPCA Minnesota Pollution Central Agency

064MW Monitoring Well

NEPC National Environment Protection Council

NHMRC National Health And Medical Research Council

NOEC No Observable Effect Concentrations

PAH Polycyclic Aromatic Hydrocarbon

PFOA Per Fluoro Octanoic Acid

PFOS Per Fluoro Octane Sulphonate

PPB Part Per Billion

PPE Personal Protective Equipment

PQL Practical Quantitation Limit

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Acronym Description

PSH Phase Separated Hydrocarbon

RAAF Royal Australian Air Force

RAIS Risk Assessment Information System

RfC Reference Concentration

RfD Reference Dose

RME Reasonable Maximum Exposure

RSL Regional Screening Level (USEPA September 2008)

SF Slope Factor

SWL Standing Water Level

TC Tolerable Concentration

TDI Tolerable Daily Intake

TPH Total Petroleum Hydrocarbons

USEPA United States Environmental Protection Agency

UST Underground Storage Tank

VOC Volatile Organic Compound

WHO World Health Organization

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Executive Summary

ENSR Australia Pty Ltd (trading as AECOM and hereafter referred to as AECOM) has undertaken on behalf of the Department of Defence (Defence) a Human Health and Screening Ecological Risk Assessment (HHERA) of soil and groundwater contamination identified in the vicinity of the Fire Training Area of Royal Australian Air Force (RAAF) Base Tindal (the Site), Katherine, Northern Territory.

The objectives of the HHERA were:

• To quantify potential risks to human health and the environment as a result of the fire-fighting chemical contamination present at the Site.

• To inform Defence regarding specific remediation goals which are considered protective of human health and the environment at the Site.

A Conceptual Site Model (CSM) for risk assessment purposes has been developed based on earlier Site reports and on the exposure pathway analysis undertaken in the present report.

The HHERA of soil and groundwater contamination in the vicinity of the Fire Training Area of RAAF Base Tindal (the Site) has reached the following conclusions with respect to human health and ecological risks.

Human Health:

• Per Fluoro Octane Sulphonate (PFOS) and Per Fluoro Octanoic Acid (PFOA) are the key monitored Chemicals of Potential Concern (COPC) with respect to potential effects on human health.

With respect to potential human receptors:

• The estimated hazard index for Site staff and trainees under a Reasonable Maximum Exposure (RME) scenario does not exceed a nationally-acceptable risk criterion.

• The estimated risk to maintenance workers undertaking sub-surface soil work for a Reasonable Maximum Exposure (RME) scenario on the Site slightly exceeds the recommended acceptable risk criterion. However the following are relevant to interpreting the risk estimates for that scenario:

- The estimated (30 days per year) duration of subsoil work at the Site used in the risk estimation for future work is considered a conservative exposure duration (i.e. the risk is considered no higher than the estimate and is almost certainly lower).

- The estimates are for RME, not average exposure scenario.

- The modelled concentrations of PFOS and PFOA have been overestimated by using the highest measured level of PFOS /PFOA in surface soil rather than the average concentration which will be encountered.

- PFOS and PFOA contamination in soil are expected to reduce over time because these chemicals are no longer used at the traditional concentrations in current and future Aqueous Film Fighting Foam (AFFF).

Interpretation of the risk estimates for that scenario therefore suggests that the risk to Defence would be considered acceptable.

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• The estimated risk for children (assumed age 0-6 years old for the risk calculations) and adult residents of the Katherine area and of the Base drinking from the Katherine town water supply does not exceed a nationally-acceptable risk criterion.

• The estimated risk for children and adult residents fishing or swimming in the area of Tindal Creek does not exceed a nationally-acceptable risk criterion.

• The estimated risk for children of the Katherine area and of the Base, combined activities of drinking from the Katherine town water supply, fishing and swimming in the area of Tindal Creek slightly exceeds a nationally-acceptable risk criterion. However the following are relevant to interpreting the risk estimates for that scenario:

- The likelihood that some 5 g of fish derived from the Tindal Creek would be consumed by adults and children over a 64 and 6 year period, respectively, is considered low.

- The Tindal Creek is likely flowing in a manner which might support fish habitation and swimming only in the monsoon season and therefore for a period of only several months of the year.

- PFOS concentrations in Tindal Creek would be expected to be significantly diluted in the creek water compared with groundwater (064MW07) in a scenario where fish habitation is occurring.

- The estimate of PFOS concentration used for the fish bioconcentration calculations is a PQL lower limit of reporting at 064MW07 and may overestimate the actual concentration of PFOS entering Tindal Creek from groundwater.


Overall, the above risk estimates indicate that no unacceptable risk is posed to Site staff or trainees from routine training activities, and to residents of Tindal Creek, the Base, and Katherine with respect to fish ingestion and recreational activities.

Ecological Effects:

Due to the nature of Site fire-training activities, including use of the Site for foot-traffic, vehicle access, pit-burning, and AFFF use, and given its likely future continuation for this purpose, the terrestrial environment in the immediate vicinity of the Site is highly disturbed, and the terrestrial ecological value of the Site is considered to be low.

Terrestrial pathways by which wildlife receptors at the Site and adjacent areas may be exposed to soil and surface water contamination nevertheless are considered to be complete. Such pathways would involve PFOS migration from surface soil through wind or rain erosion, depositing PFOS in undergrowth adjacent the Site, and the emergence of groundwater into local creeks.

In light of the approach used in Australian trigger value guidance for ecological protection, the reported observation that a lowest PFOS concentration NOEC for fish in an early life stage test is only three orders of magnitude above PFOS concentrations reported in a bore water sample taken at the Base (bore RN005771- Table 2) groundwater entering local watercourses at similar PFOS concentrations potentially represents a risk to the local aquatic food web and to species reproduction. Continued monitoring of groundwater concentrations at 064MW07, 064MW06, and 064MW05, including across seasonal extremes of weather, is advisable in order to ensure that groundwater concentrations do not significantly increase PFOS concentrations in Tindal Creek.

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Tindal Creek is an ephemeral creek (generally flows only between December and April) and is the main surface water body that enters RAAF Tindal from the south and veers northwest before leaving under the Stuart Highway. The numerous depressions and sinks located across the Base significantly increase the risk of surface water directly entering the groundwater (SKM, 2001). In addition, groundwater and surface water sensitivity are considered to be high because:

• Surface water runoff is directed to the ephemeral Tindal Creek which subsequently flows into Katherine River, which is the source of potable water in the region.

• The karst conditions of the Tindall Limestone Formation provide direct conduit connectivity from the Base to both onsite groundwater extraction wells and down gradient springs and the Katherine River.

Summary:

In summary, the risk assessment results indicate that the current concentrations of PFOS and PFOA contamination in soil and groundwater at the Site do not represent an unacceptable risk provided that:

• appropriate Personal Protective Equipment (PPE) is provided for extended duration (weeks) maintenance work at the FTA site (i.e. standard Level D PPE)

• ongoing monitoring of PFOS concentrations in soil adjacent the Site and in groundwater entering Tindal Creek (064MW07), and in surface water of Tindal Creek as near as possible to the FTA site is warranted until the environmental situation is more fully characterised, noting that the prevention of potential bioaccumulation of PFOS in fish and bioaccumulation in wildlife are relevant considerations in local environment protection.

With respect to remediation goals for FTA redevelopment, based on the current HHERA, PFOS and PFOA concentrations reported in the validation program which are no greater than the maximum reported to date on the Site are considered acceptable for human health and environment protection.

It is recommended that the Department of Defence continue to monitor groundwater concentrations in order to demonstrate that concentrations are not increasing.

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1.0 Introduction

ENSR Australia Pty Ltd (trading as AECOM and hereafter referred to as AECOM) was engaged by the Department of Defence (Defence) to undertake a Human Health and Screening Ecological Risk Assessment (HHERA) of soil and groundwater contamination identified in the vicinity of the Fire Training Area (FTA) of RAAF Base Tindal (the Site), Katherine, Northern Territory.

1.1 Objectives and Scope of Work

The objectives of the HHERA were:

• To quantify potential risks to human health and the environment as a result of the fire-fighting chemical contamination present at the Site.

• To inform Defence regarding specific remediation goals which are considered protective of human health and the environment at the Site.

Four key components of a HHERA process are:

- data evaluation

- pathway and exposure assessment

- toxicological evaluation

- risk characterization and uncertainty analysis.

The scope of work to achieve the above objective comprised the following:

• Review of previous environmental assessment reports for the Site, notably:

- ERM Australia, Stage 1 Environmental Investigation, RAAF Base Tindal, Northern Territory, June 2005 (ERM, 2005)

- ERM Australia, Landfill / Burial Sites, Stage 1 Environmental Investigations, June 2007 (ERM, 2007a)

- ERM Australia, Stage 1 & 2 Environmental Investigations, NT/K RAAF Base Tindal, June 2007 (ERM, 2007b)

- GHD Department of Defence, RAAF Base Tindal Stage 2 (Part II) Environmental Investigation, Northern Territory, July 2008 (GHD, 2008).

• Review of existing laboratory analytical data relevant to the Site supplied to AECOM in Excel-compatible electronic format, where available, or extracted from AECOM, 2009, Stage 2 (III) Environmental Investigations.

• Review of data generated by the AECOM, 2009, Stage 2 (Part III) Environmental Investigation.

• Identification of significant data gaps, if any.

• Conduct a screening Health Risk Assessment, based on calculated chemical intake factors and exposure-adjusted soil, groundwater and air concentrations (where applicable) for on-site receptors, based on previous Site investigations and monitoring.

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• Confirmation of the chemicals of potential concern (CoPC) present in soil and groundwater. Previous investigations indicated that CoPC were likely to include the following:

- Per Fluoro Octane Sulphonate (PFOS) and its salts

- Diethylene Glycol Butyl Ether

- Aqueous Fire Fighting Foam (AFFF) dye

- synthetic detergents

- other fluoro alkyl surfactants

- other organic fluorochemicals

- petroleum hydrocarbons

- polycyclic aromatic hydrocarbons (PAH)

- metals.

• Review of toxicological data for each CoPC and identification of appropriate toxicity values for use in risk calculations.

• Review of chemical and physical properties of each CoPC and classification of volatile verses non-volatile chemicals for vapour transport modelling purposes, if required.

• Establishment of representative exposure point concentrations (EPCs) in soil and groundwater for evaluation of direct contact risks, and derivation of reasonable upper bound (95% upper confidence limit or maximum) concentrations for each source area requiring assessment.

• Use of the United States Environmental Protection Agency (USEPA) BioScreen model, as required, to assess petroleum hydrocarbon basic fate and transformation processes relevant to groundwater.

• Identification of potentially significant receptors, such as:

- current or future base occupants living and working on the Site

- fire fighters undergoing training

- construction workers, as required

- off-site neighbours, including adjacent properties and the Katherine township

- farm and native species which inhabit local properties or creeks/habitats adjacent the Site (screening review).

• Identification of potentially significant exposure pathways.

• Confirmation of a Conceptual Site Model (CSM) for risk assessment purposes.

• Establishment of relevant exposure parameters for identified receptors and exposure pathways.

• Establishment of relevant Site geological and hydrogeologic parameters to be used in groundwater modelling, as required. Groundwater fate and transport modelling was not required following confirmation in the Risk Assessment that soil vapour exposure was not a relevant exposure pathway and confirmation that use of down gradient monitoring results were suitable for off-site chemical exposure point calculations.

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• Preparation of a detailed report (this report), which includes the above components, and attendance at telephone conferences to discuss the results with the client or associated stakeholders.

1.2 Existing Data

In preparing this report, AECOM has referred to analytical data and information presented in the following documents and reports:

• ERM Australia, Stage 1 Environmental Investigation, RAAF Base Tindal, Northern Territory, June 2005 (ERM, 2005)

• ERM Australia, Stage 1 & 2 Environmental Investigations, NT/K RAAF Base Tindal, June 2007 (ERM, 2007b)

• GHD Department of Defence, RAAF Base Tindal Stage 2 (Part II) Environmental Investigation, Northern Territory, July 2008 (GHD, 2008)

• AECOM, Stage 2 (Part III) Environmental Investigation (Draft), RAAF Base Tindal, Northern Territory (AECOM, 2009).

1.3 Methodology

The HHERA was undertaken in accordance with the following nationally adopted guidelines and policy:

• National Environmental Protection Council (NEPC), 1999. National Environment Protection (Assessment of Land Contamination) Measure:

- Schedule B(4) Guideline on Health Risk Assessment Methodology (NEPC, 1999a)

- Schedule B(5) Guideline on Ecological Risk Assessment (NEPC, 1999b)

- Schedule B(7a) Guideline on the Investigation Levels for Soil and Groundwater (NEPC, 1999c)

- Schedule B(7b) Guidelines on Exposure Scenarios and Exposure Settings (NEPC, 1999d).

• Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia & New Zealand (ARMCANZ), 2000. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality.

• enHealth guidance documents:

- Health Impact Assessment Guidelines (2001)

- Environmental Health Risk Assessment, Guidelines for Assessing Human Health Risks from Environmental Hazards (2002).

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2.0 Site Description

2.1 Site Location and Layout

RAAF Tindal is located approximately 320 km south-east of Darwin, and approximately 13 km south-east of the township of Katherine, in the Northern Territory (Refer to Figure 1). The developed grounds cover a small portion of the 122 km2 area, the majority being open Eucalypt bushland (GHD, 2008).

RAAF Tindal lies within the coastal wet season region of northern Australia. The area experiences a wet-dry tropical climate pattern, with a distinct, extended rainy season between November and April and a dry season between May and October.

The Fire Training Area (FTA NT0064, the Site) is located in the south-west corner of the Base, accessed by Fall River Road, in proximity to an old landfill area and the Base Sewage Treatment Plant (NT0061) (refer to Appendix A, Figure 15).

The Site covers a cleared area of approximately 150 m2, with a bunded fire pit for liquid fuel fire exercises centrally located and surrounded by paving. Containers also used for fire fighting training are located to the south-west of the fire pit and ponds for evaporation of fire pit effluents (draining underground), are located to the north-west of the fire pit (ERM, 2007) (refer to Appendix A, Figure 13).

2.2 Current and Proposed Land Use

RAAF Base Tindal, operating as a joint civil-military airfield, employs some 600 military and civilian personnel. There are married quarters, messes and a football oval, a canteen and service station, a golf course, sewage-treatment plant and horse paddock on the Base (See Appendix A for Site Layout, as shown in Figure 15 of GHD, 2008).

Military service personnel and contractors are considered to be the most predominant occupiers of the Base facilities, based on stakeholder interviews. However, family members may intermittently be expected to frequent the associated open space areas. The turnover rate of military personnel is relatively frequent, estimated as some two to three years at interview (ERM, 2005).

Activities undertaken at the Site include liquid fuel fire fighting with Ansulite AFFF (since 2002) at the central fire pit. In the western area of the Site, shipping containers with partially burnt materials including furniture has been observed, along with car bodies (AECOM, 2009a).

AECOM understands that the Base is likely to continue to be redeveloped and expanded as a priority Defence establishment, and current Base activities are therefore likely to continue for the foreseeable future.

During the Stage 2 (III) Investigations (AECOM, 2009), it was reported that the existing FTA at RAAF Tindal would be decommissioned and replaced by a new facility (constructed in the same location) designed to accommodate the new larger fire trucks, known as the Panthers. It is understood that a key design requirement of the new FTA would be to provide more space to manoeuvre the larger and heavier fire trucks as well as providing a more suitable target size. It has subsequently been reported that re-development of the FTA has been placed on hold for the foreseeable future. Notwithstanding, Defence has commissioned a review of FTAs across the Defence estate under its Pollution Prevention Program.

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2.3 Current Surrounding Land Use

The land surrounding the Base is occupied primarily by grazing and rural/residential land. The Katherine township is located approximately 13 km to the north-west.

The key surrounding land uses at the Base comprise the following (AECOM, 2008a):

• North: the Stuart Highway and grazing and rural/residential land (including Jarrahdale Station).

• East: partially disturbed bushland, rural land and mango farms, and the township of Katherine approximately 13 km to the east-north-east.

• South: the Cutta Cutta Caves National Park.

• West: grazing land and a quarry, from which blue metal road base is mined.

The Fire Training Area (NT0046) is bounded by:

• RAAF Tindal’s Sewerage Treatment Plant, Irrigated Horse Paddock and Tindal Creek to the south

• native bushland and Tindal Creek to the west

• RAAF Tindal security fence and operational area to the north

• native bushland to the east (AECOM, 2009).

2.4 Surface Water

Most of RAAF Tindal lies within the Tindal Creek catchment area, within which the main surface water body is Tindal Creek. The source of Tindal Creek, which is an ephemeral southern tributary of the Katherine River (SKM, 2007), is approximately 20 km south of the Base (GHD, 2008). The creek enters the Base from the south, veers northwest, south of the main runway before leaving the Base under the Stuart Highway to later join the Katherine River downstream of the Katherine Township (see detailed description of hydrology in Section 2.7). Tindal Creek passes by the FTA approximately 800 m south.

2.5 Geology

The Tindal area is part of the Daly Basin which is described within the 1:250,000 Geological Map Series for Katherine SD 53-9, (1994) as being dominated by lowland plains consisting of limestone, mudstone, dolostone and minor sandstone deposited in peri tidal to open shelf marine environments. Most of the limestone in the Tindal area is overlain by Quaternary laterite, ferricrete and residual loamy sands (ENSR, 2008b in AECOM, 2009).

Geology and lithology information reported in previous assessments (SKM, 2001 reviewed by AECOM, 2009) describes the Tindal area as belonging to the Cambrian land system, which is an area of extensive stony erosional plains. These erosional karst plains are characterised by loamy red earths, with the occasional limestone outcrops, scattered sinkholes, shallow depressions and stream channels incised in bedrock.

A number of soil groups have been identified in the Tindal area, and include the following broad groups (in order of occurrence) (SKM, 2001):

• Red earths - sandy and loamy red earths derived from silicified sandstone and limestone.

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• Earthy sands - dark-reddish brown, loose, clayey sand profile and are generally well-drained.

• Yellow earths - similar to red earths, but tend to become water logged during the wet season.

• Lateritic podzols (used extensively as borrow pits during the construction of RAAF Tindal) – sandy to mottled yellow-brown to red clay with ironstone present.

• Lithosols - containing high amounts of rock fragments and confined to areas where rock outcrops are common.

• Grey-brown clays - clay textured soils that crack widely and are very dry.

The Site-specific lithology within the FTA is described as a mixture of sandy clay, limestone and gravelly clay. The limestone lithology identified from the monitoring well borelogs (ERM, 2007; GHD, 2008) within the FTA ranged between 4.0 mBGL at 064MW01 to 7.5 mBGL at 064MW04.

2.6 Hydrogeology

The Tindal and Katherine region is underlain by the Daly River Catchment Aquifer Formation, which is thought to be over 100 km wide and over 300 km long. This aquifer, also known as ‘Tindall Limestone’, is generally a deep, unconfined aquifer ranging from the surface (approximately 130 m Australian Height Datum (AHD)) in the Katherine River area to depth (approximately 650 m AHD) located 50 km south-west of Katherine. The Jinduckin Formation overlies a portion of the subsurface area of the Tindall Limestone. The Tindall Limestone Aquifer has an estimated flow rate of 90 to 180 mega litres/day and provides base flow to the Katherine River (ERM, 2005).

The Katherine Water Control District is largely made up the unconfined section of the Tindall Limestone Aquifer and is clearly demarcated within the Daly River Catchment Aquifer Formation. The township obtains its drinking water from the Katherine River and supplements its supply with groundwater from the extraction bore fields within the Katherine Water Control District. RAAF Tindal potable water is supplied by the Katherine township. In addition to this supply, on-site extraction bores, which obtain groundwater resources directly from the Tindall Limestone, are primarily used for irrigation purposes (ENSR, 2008a).

Potential groundwater sensitivity is considered to be high due to the karst conditions of the Tindall Limestone Formation likely providing direct conduit connectivity from the Base to both on-site groundwater extraction bores (located within the Base, but outside the FTA), down gradient springs and bores, Tindal Creek, and subsequently the Katherine River (ENSR, 2008a reviewed in AECOM, 2009).

Groundwater bore information reported in a previous Stage 2 Investigation (ERM, 2007) identified 92 registered bores within a 2 km radius of the Base. Approximately 80% of these were registered for stock and domestic use, and 20% were registered for irrigation/industrial use (GHD, 2008). Of these, five bores were reported to be actively used for groundwater extraction (ENSR, 2008b in AECOM, 2009):

• RN005771 (between the ordnance loading areas)

• RN25650 (ordinance preparation area)

• RN25999 (golf course bore)

• 248 (sports field bore)

• RN26704 (sewage treatment plant bore 845).

GHD (2008) reported groundwater at relatively shallow depths of between 4.455 metres below ground level (mBGL) and 4.81 mBGL.

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In the most recent groundwater investigation at the Site undertaken on 11 and 12 November (the start of the Wet season) 2008 (AECOM, 2009), groundwater samples were collected from the pre-existing monitoring wells 064MW02, 064MW03 and 064MW05. The groundwater wells selected for monitoring where chosen because they represented the most significantly impacted groundwater monitoring wells identified by the preceding investigations, and also provided a good distribution across and down-hydraulic gradient of the FTA.

During the November 2008 monitoring event (AECOM, 2009), standing water levels (SWL) were measured at all monitoring wells located around the FTA, as summarised in Table 1 below and shown in Appendix A (Figure 13). No phase separated hydrocarbons (PSH) were detected in any of the wells.

Table 1: FTA (NT0064) Monitoring Well Standing Water Levels (measured November 2008)

Monitoring Well Location Description SWL (mBGS)

Reduced SWL (m AHD)

064MW01 ~26 m east of Central Training Pit 7.22 126.85

064MW02 ~15 m west of Central Training Pit 7.67 126.75

064MW03 ~16 m north of Central Training Pit 7.46 126.83

064MW04 ~100 m south-east of Central Training Pit in nearby bushland

7.30 126.10

064MW05 ~120m south-west of Central Training Pit in nearby bushland

7.53 125.74

064MW06 ~240 m west of Central Training Pit in nearby bushland

6.75 125.95

Refer to previous investigations for bore log and screen setting information.

GHD (2008) reported groundwater standing water levels measured between March (the end of the Wet season) and June (the Dry season) 2006. However, the AECOM (2009) groundwater levels were measured on 11 and 12 November (the start of the wet season) 2008. The difference in SWL between these investigations is inferred to be due to seasonal variation.

Based on the SWLs measured in the groundwater monitoring wells associated with the FTA (NT0064), groundwater was inferred to be flowing to the south-west and west towards Tindal Creek (refer to Table 1), as indicated in ERM (2007) and AECOM (2009a).

2.7 Hydrology

Liquid from training activities in the fire pit drains underground into three concrete lined evaporation ponds located in the north west of the Site. Overflow from these ponds decants to an open drainage channel which runs from the southeast to the northwest of the site (ERM, 2005), away from Tindal Creek. Liquid from the central fire pit can also be drained directly to the open drainage channel via a series of gate valves located between the fire pit and the evaporation ponds.

Tindal Creek is located approximately 800 m south of the FTA. The creek is ephemeral, and dry outside of the wet season (approximately November to March). During the wet season high rainfall and surface flooding occurs at the site (ERM 2005, 2007). Stormwater runoff and drainage from the Site flow in a general west to southwest direction and also charge the creek. When flowing, the creek flows to the northwest, meeting the Katherine River downstream of the Katherine Township (ERM, 2005).

The Katherine River is located approximately 13 km north west of the Site and is the primary source of potable drinking water for the Katherine Township and the RAAF Base. During the dry season it is understood that groundwater supplements the water flow (ERM, 2005).

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3.0 Summary of Previous Investigations

3.1 ERM (2005) – Stage 1 Investigation

ERM conducted an initial risk assessment of the potential hazards posed to human health and the environment from possible contamination present at the “high risk” sites within the Base, including the FTA. Also included in the report was a proposed Stage 2 Sampling and Analysis Plan for further investigations, based on the Risk Assessment outcomes.

ERM reviewed previous reports (URS, 2002 Fire Station Contamination Investigation) and provided background information on fire-fighting activities. Results of the review relevant to this risk assessment include:

• It was estimated that approximately 104,000L per year of waste water containing residual AFFF was released into the storm water drain and the evaporation pond.

• It was assessed that contamination was also likely to have resulted from vehicle/ equipment wash down.

• Potential for off-site contamination exists, which would be in contravention of the Waste Management and Pollution Control Act, 1998.

• Recommendations were made to reduce the production of waste-water and to install interceptor traps (at the Fire Station).

In addition, a review of AFFF Material Safety Data Sheet (MSDS) and toxicological information was given, as follows:

The AFFF used at Tindal up until 2003, was classed as either 3% or 6% 3M. The MSDS describes 3M as containing the following ingredients:

• water (70<80%)

• Diethylene Glycol Butyl Ether (10<30%)

• dye (<5%)

• synthetic Detergents (<5%)

• fluoruoalkyl surfactants, (<5%) and

• residual organic fluorochemicals (not determined)

Toxicological information indicates that the organic fluorochemicals have the potential to be absorbed and remain in the human body for long periods of time and may accumulate with repeated exposures. Although adverse health effects were not reported when used ‘in accordance with the specifications’ toxicological studies elsewhere have suggested that a number of potentially adverse health affects may result following prolonged exposure to significant quantities of organic fluorochemicals or in particular PFOS (OECD, 2002; US EPA, 2005). Toxicological data suggests that PFOS and its salts has the potential to disrupt reproductive and developmental processes in humans, (OECD, 2002).

From discussions with personnel on-Site, ERM identified that AFFF had not been used in training exercises since 2002/2003, however it was used up to twice per week between 1988 and 2002 at the FTA. It is understood that the FTA experiences surface flooding at different times of the year and has experienced extensive flooding previously.

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CoPC identified by ERM included heavy metals (arsenic, copper, cadmium, chromium, lead, mercury, nickel and zinc), total petroleum hydrocarbons (TPH), benzene, toluene, ethylbenzene and xylenes (BTEX), fuel additives, polycyclic aromatic hydrocarbons (PAH), PFOS and fluorochemicals.

Receptors identified by ERM included:

• Human Health: Site workers, recreational water use, and drinking water (people in the Katherine region)

• Environment: groundwater, and the Tindal Creek ecosystem.

As a result of the risk assessment, area NT0064 (the FTA) was designated as “high risk” due to the potential leaching of CoPC from unsaturated soils entering groundwater and Tindal Creek.

Recommendations were made for a Stage 2 assessment at the Site, including targeted soil and groundwater sampling. With respect to ecological risk, ERM considered sediments to be indicative of the harmful contaminants in the environment as a storage area, and proposed a sediment sampling and screening assessment to be conducted.

3.2 ERM (2007) - Landfill/Burial Sites Stage 1 Investigation

ERM conducted a Stage 1 investigation for identified landfill/burial sites at the Tindal Base. The FTA was not explicitly investigated, however areas with proximity to the Site were discussed.

The following areas were identified in proximity to the FTA Site:

• Sewage treatment ponds, located 200 m to the south of the Site (CSR NT0061 Current Sewage Treatment Plant)

- Groundwater flow was inferred to be towards the west.

- Surface run-off at the Site flows into Tindal Creek, approximately 500 m to the south-west. (Due to the flow patterns and location of the site, the contaminants related to the sewage treatment plant should not affect the FTA).

- Ecological Consideration: Birds, including ducks and local water birds swimming on and drinking from the ponds were noted as having previously died from botulism, indicating that the treatment processes undertaken in the ponds may not be sufficiently destroying pathogens and microbiological activity in the waste water. The site is highly disturbed, characterised by colonising grasses and surrounded by scrubby eucalypt bushland.

• Landfill at the Old Sewage Plant, located 150 m to the north-west of the Site (CSR NT0267 Landfill).

- Groundwater flow was identified to the west and surface water flow to the south in constructed drainage channels which then flow west into Tindal Creek. (Due to the flow patterns and location of the site, the contaminants related to the landfill area should not affect the FTA).

- Ecological Consideration: Surface water quality was assumed to be good, as there were numerous frogs and toads living in the water. The area is disturbed, but has naturally regenerated with native eucalypts and wattle. Colonising grasses ('Gamba Grass' Andropogon gayanus) up to 3 m in height were noted surrounding the lagoon area.

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3.3 ERM (2007) - Stage 1 and 2 Investigations

ERM conducted Stage 1 and 2 investigations of nine target sites, including the NT0064 FTA. The works also identified improvements that could be made to site activities to minimise the potential for future impacts.

The Stage 1 Investigation of the FTA, undertaken in February 2006, included site inspections and interviews with key stakeholders.

On completion of the Stage 1 Investigations, Sampling and Analytical Plans for Stage 2 Investigations were developed and works were undertaken between March and June 2006. The scope of works included drilling soil bores and installation of monitoring wells at selected locations within the target sites. Soil, groundwater and surface water samples were collected and submitted for analysis for a range of CoPC.

A Stage 2 Risk Assessment was developed by refining Conceptual Site Models for each site and using the Defence Risk Assessment Tool. The constitution of AFFF, its use on the site and CoPC identified are as outlined above in Section 3.1. The receptors identified were also consistent with those identified in ERM (2005), along with the addition of stock potentially ingesting groundwater used for stock watering or irrigation. An interim Health Investigation Level (HIL) for PFOS was calculated at 0.85mg/kg for soil. Discussion of the derivation, including calculations, was provided in Section 7.3.4 of the ERM (2007) report.

ERM (2007) noted that:

The Stage 2 Risk Assessment identified a High Risk for CSR NT0064, as a source of impact to soil and groundwater has been confirmed (NT0064 - High Risk Band, 133 Risk Rating).

It should be appreciated that the risk levels attributed to most of the risk dimensions are low to moderate for all pollutant linkages identified in the CSM. The risk dimensions that generate the highest risk level are legislative compliance and environment and heritage with respect to potential impacts on freshwater aquatic ecosystems and flora/fauna of ecological significance.

With respect to ecological considerations, ERM inferred that the presence of threatened plant and animal species, including sixteen (16) plant, seven (7) reptile and fish species, seven (7) bird and four (4) mammal species within the Tindal and Katherine area, further suggests that the Tindal Base occurs in an ecologically significant area. (Reported in the National Land & Water Resources Audit Report, Monitoring and Evaluation Trials, Northern Territory Region, Phase 1 Report, November 2004, Natural Heritage Trust, Canberra ACT.)

Due to the high rainfall and intermittent flooding that occurs at the Site, ERM considered that surface water and local ecosystems may also be considered moderately vulnerable.

3.4 GHD (2008) - Stage 2, Part II Investigation

Based on the conclusions of ERM (2007), Defence requested further investigation into two of the CSR sites at RAAF Tindal:

• Fire Training Area (NT0064)

• Mechanical Equipment Operations Maintenance Section (MEOMS): Underground Storage Tank (UST) Motor Transport Operational Facility (NT0053).

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The objectives of the Stage 2 investigation were to refine the risk rating, and identify and manage the environmental risks so that the on-going operation and capability of the base can be maintained. The following summary discusses Part II of the investigation, which provided details regarding soil, sediment and groundwater contamination detected and recommendations based on the findings.

CoPC identified for the FTA included metals (As, Ba, Be, Cd, Cr, Co, Cu, Mn, Ni, Pb, V, Zn, Hg), PFOS, PAHs, TPH, and volatile organic compounds (VOC).

Additional groundwater sampling analytes included halogenated aliphatics and aromatics, fumigants, trichloromethanes, sodium, calcium, magnesium, potassium, bicarbonate, carbonate, chloride, sulphate and nitrate, nutrients, TPH, TDS and pH.

GHD reported the following:

Soil/Sediments

• PFOS was detected in all soil and sediment samples from the site.

• Concentrations in soil generally decreased with depth.

• Elevated concentrations of some CoPC were reported in the sediments present in natural and man made drainage lines connected to the FTA.

• PFOS concentrations in sediment samples down gradient, near Tindal Creek were below the Limit of Reporting (LOR).

• TPH was detected at concentrations above the nominated guidelines for soil (NSW EPA, 1994) (found at NT0064/1). This was considered by GHD to have likely resulted from jet and diesel fuel used in burning or extinguishing practice, or from the mobile diesel tank north of the central burn pit. However, GHD also noted that the lack of similar previous results indicated a seasonal fluctuation.

• Hydrocarbon impact was detected in shallow sediment collected from the surface water drainage channel adjacent to the concrete pad and burn pit.

Groundwater

• PFOS was also detected in groundwater samples at the Site, with concentrations at least one order of magnitude greater than the Minnesota Department of Health (MDH) 2007 drinking water guidelines (maximum concentrations down gradient). Historical reporting showed fluctuations in the levels of PFOS detected. GHD noted that the extent of downgradient PFOS impact is unknown due to access constraints.

• Selected metals (arsenic, barium, copper, iron, lead, manganese, nickel and zinc) were identified at concentrations exceeding the relevant criteria. Noting:

- After applying correction factors to compensate for the local water hardness, nickel and zinc no longer exceeded the guidelines.

- Manganese does not have a published correction factor, however it is reported to also decrease in toxicity with increased water hardness (ANZECC, 2000).

- Iron concentrations were reported to be associated with regional hydrogeology, and barium concentrations with local mineralogy.

- Arsenic concentrations were reported to be likely due to historic pesticide and herbicide use.

Additional background information on the Site from a risk workshop attended by GHD included:

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• Liquid wastes from the MEOMS sullage pit, together with other products such as paint stripper, have been used as a fuel source during training activities.

• Training activities and fuel burning have occurred outside of the burning containers, central concrete pad and burn pit.

• The 3M AFFF has been observed as corrosive to metals.

• Vegetation die back in the area between the three evaporation ponds in the northwest corner of the Site has been noted. This observation was also reported during fieldwork by GHD in November 2007 and May 2008.

Potential human and/or ecological exposure pathways considered by GHD were:

• Ingestion and dermal contact with PFOS in soil/sediment.

• Dermal contact with or ingestion of contaminated groundwater used for irrigation.

• Dermal exposure to surface water.

• Soil and sediment drying to form an inhalable dust to human and ecological receptors.

• Minimal risk of PFOS impact to Tindal Creek, due to distance and decreasing concentrations.

GHD adopted the then current Minnesota Department of Health (MDH, 2007) guidelines for PFOS and PFOA for the investigation. It was considered and concluded that the ERM (2007) derived interim HIL value was overly conservative due to a safety factor of 100 being applied (in addition to a safety factor of 500).

Data gaps identified by GHD included:

• Surface water samples were not collected as part of the Stage 2 (Part II) environmental investigation.

3.5 AECOM (2009a) - Stage 2 Part III Groundwater Investigation

The objective of the Stage 2 (Part III) investigations at the Base was to provide additional delineation and characterisation of groundwater contamination identified by previous investigations, through completion of a single groundwater monitoring event. The investigations were carried out in parallel with investigations at over a dozen other CSR sites on the Base.

At the FTA Site, groundwater samples were collected and analysed from three pre-existing groundwater monitoring wells generally located down-hydraulic gradient of the FTA, during November 2008. The inclusion of the FTA in the Stage 2 (III) groundwater investigation was to provide further information for development of a Stage 3 Remedial Action Plan (RAP) for RAAF Tindal.

The results of the investigation indicated:

• concentrations of PFOS above the adopted MDH (2009) guideline for potable water

• concentrations of arsenic, cadmium, cobalt, nickel and vanadium above the ANZECC (2000) Ecosystems Fresh Water (95%) and NHMRC (2004) Australian Drinking Water – Health and outside the background concentrations established for the Base

• concentrations of barium, copper and zinc above the ANZECC (2000) Ecosystems Fresh Water (95%) and NHMRC (2004) Australian Drinking Water – Health but within the background concentrations established for the Base

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• PFOS and heavy metal concentrations were consistent with previous investigations (ERM, 2007 and ERM, 2008).

3.6 AECOM (2009b) - Water Quality Investigations FY08/09, RAAF Base Tindal

AECOM was contracted by Spotless Managed and Support Services (Spotless) to conduct the 2009 “post wet’ season macroinvertebrate, surface water and groundwater monitoring event at RAAF Tindal. The monitoring event was undertaken on 27 to 29 April 2009 and included collecting samples from groundwater monitoring well 064MW02. The results of the monitoring program identified:

• Concentrations of copper, uranium and zinc above the ANZECC 2000 (freshwater 95% protection level) guidelines, which were consistent with the GHD, 2008 results.

• Nutrient concentrations, particularly total nitrogen, total phosphorous and reactive phosphorous were elevated and exceeded the ANZECC 2000 (Upland River - Freshwater) but were generally consistent with historical data.

• TPH, BTEX and PAHs concentrations were reported as below the laboratory LOR during 2009 and 2008. A strong ambient hydrocarbon odour was detected at the FTA during sampling which was believed to be coming from the three open-air retention ponds.

• PFOS and PFOA concentrations reported at 064MW02 in April 2009 were above the adopted MDH (2009) guideline for potable water of 0.3 μg/L (AECOM 2009b).

A comparison of the PFOS analysis results with those of previous monitoring programs is presented in Table 2.

Table 2: PFOS Historical Comparison at NT0064 FTA

Location ERM 2007

May 06

GHD WQMP Jan 07

GHD WQMP Apr 07

GHD Nov 07

GHD May 08

AECOM Nov 08

AECOM Apr 09

MDH Potable water(μg/L)

064MW02 5200 - <0.05 85 - 2700 120

064MW03 3.7 - - 5.3 - 150 -

064MW05 - - - 3.2 - 0.5 -

0.3

Highlighted cells represent exceedence of the adopted guideline

All concentrations in μg/L/

Table 2 shows that elevated PFOS concentrations have persisted since monitoring commenced at the Fire Training Area in May 2006 (ERM, 2007). In particular PFOS concentrations in:

• 064MW02, located west of the central fire pit within the FTA, have consistently been several orders of magnitude above the site assessment criteria

• 064MW3, located north of the central fire pit within the FTA, have apparently increased recently with the November 2008 concentration an order of magnitude greater than the previous reported concentrations

• 064MW5, located approximately 120 m down-hydraulic gradient of the FTA, have possibly reduced by an order of magnitude, but remain above the site assessment criteria (AECOM, 2009).

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4.0 Data Evaluation

The following sections provide a summary of: the nature and extent of contamination identified at the Site; an evaluation of the usability of the analytical data available for risk assessment purposes; and, identification of the chemicals of potential concern (CoPC) considered relevant to the risk assessment.

4.1 Nature and Extent of Contamination

Following Stage 1 and 2 Environmental Investigations, ERM (2007) reported the following:

• PFOS concentrations in soil at 0.5 mBGL and 3.0 mBGL were above the derived HIL of 0.85 mg/L.

• PFOS concentrations in all sediment samples were above the derived HIL, with a maximum concentration (at location SS03) of 93 mg/kg, adjacent the settlement ponds (Refer to Appendix A-Figure 13 for SS locations).

• PFOS concentrations in groundwater at 064MW01, 064MW02 and 064MW03 were above then adopted MDH (2007) guideline of 0.001 mg/L.

• The highest PFOS concentration (210 mg/kg at 0.5 mBGL) was recorded on the northern side of the fire pit hardstand.

• TPH concentrations in one sediment sample (SS05) were above NSW EPA (1994) guidelines (see Appendix A – Figure 2 ERM 2007 for SS locations).

• BH01-BH04 was sampled at depths of 0.5 mBGS and 2-3 mBGS. No TPH and BTEX soil sample concentrations were reported as exceeding adopted criteria. All samples were below the LOR or Non-Detect, except BH02 where TPH C15-28 was reported at 350 mg/kg.

• Surface water concentrations of TPH were reported at 29.1 mg/L in SSD01 a sample taken from the drainage channel on the south western boundary of the site which receives runoff from the settlement ponds(see Appendix A – Figure 2 ERM 2007 for SSD011 location). From this result, ERM inferred that attenuation of TPH in the evaporation ponds was not occurring and that:

TPH compounds are being discharged to the environment in the surface water discharge.

GHD (2008) summarised the results of six monthly groundwater quality monitoring conducted within the FTA (NT0064) in May 2006 and November 2007 and additional soil investigations with the following findings:

• Groundwater in the FTA area experienced large fluctuations in depth between the wet and dry seasons.

• 0.5 mm of phase separated hydrocarbons (PSH) in 064MW01 adjacent to and west of the burn pit.

• PFOS and PFOA impacted soil was identified and delineated at investigation locations adjacent to the central pit and in the surface water drainage lines.

PFOS and PFOA soil concentrations:

- decreased with depth in 70% of soil sampling locations

- decreased with distance from the central burn pit

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- no soil samples exceeded the PFOS or PFOA MDH (2007) guideline for commercial/ industrial land use, however five samples exceeded the MDH (2007) PFOS guideline for residential land use.

• The maximum concentration of PFOS reported in sediments (54 mg/kg at SS1, located in the surface water drain to the south-west of the FTA) exceeded the MDH (2007) commercial/industrial soil guideline.

• Concentrations of PFOS in groundwater exceeded the adopted MDH (2007) guideline for potable water of 0.3μg/L at 064MW01, 064MW02, 064MW03 and 064MW05, but were generally less than those reported by the Stage 2 EI. This was attributed to the possible migration of the plume.

• Concentrations of COPC in soil at all sampling locations were below the NEPM (1999) HILs, where available.

Groundwater Base bores (Table 2) are located hydraulically up-gradient of the Site. Details of groundwater extraction bores present within the Tindal site are provided in Table 2 below.

Table 3: RAAF Tindal Extraction Bores PFOS Analytical Results (based on GHD, 2008)

Bore ID Location Approx. Distance and Direction

from FTA

Potential Use(s) PFOS Concentration

(μg/L)

RN25650 Ordnance Preparation Area

3 km – east Ablution/grey water for Squadron 75 (ammunition preparation)

< 0.05

RN005771 Between Ordnance Loading Areas

2 km – north Not in use, former production bore

0.7

RN25999 Golf Course 3 km – north Irrigation of golf course

< 0.05

Sports Field Bore Sports Fields 2.5 km – north Irrigation of sports fields

< 0.05

STP 845 Sewage Treatment Plant (STP)

0.2 km – south Ablution water, paddock irrigation and livestock water

< 0.05

In an emergency, the golf course production bore RN 25999 may be used as an emergency potable water supply for the Site. For

routine use, the Base potable water supply is derived from the Power and Water Corporation water treatment facility in Katherine

Township (a mixture of river water and groundwater), which is approximately 13 km to the northwest of the Base.

The groundwater monitoring data therefore indicates that PFOS/PFOA is not currently impacting on the extraction well down gradient of the Site.

In summary, the key contamination issues identified during previous investigations were:

• Elevated concentrations of PFOS and PFOA were identified in soil, with concentrations generally decreasing with depth below the surface, and decreasing with distance from the burn pit.

• Elevated concentrations of PFOS and TPH were also identified in sediments in drains and ponds in the vicinity of the FTA site.

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• PFOS and TPH (including PSH at one location) have been identified in groundwater. TPH has also been detected in surface water in nearby drains.

4.2 Quality Assurance and Quality Control (QA/QC)

The data set is considered to be of sufficient quality to form a basis for the present risk assessment, based on the following observations:

• The ERM (2005) report provided the following information with respect to the proposed sampling plan and QA/QC methodologies:

- The proposed soil sampling plan for the Site included 7 soil sampling locations at a range of depths, 42 samples collected, 25 samples selected for analysis (based on photoionisation detector (PID) readings and field observations), plus 2 duplicates, 1 spike and a blank.

- The proposed groundwater sampling plan included 1 groundwater monitoring well, sampled twice a year.

- A list of QA/QC procedures was provided, and it was noted that only NATA accredited laboratories were to be used.

• ERM (2007) conducted a Full Data Quality Assessment (Annex E) and reported that :

All analytical results and associated quality assurance/quality control evaluation measures are considered acceptable for use in environmental assessment.

• GHD (2008) conducted a QA/QC Data Validation Assessment (Appendix G) and concluded that:

Although there were some minor non-conformances the majority of the GHD QAQC parameters were within the specified requirements and therefore, overall, the data is considered to be valid and of sufficient quality to meet the objectives of the RAAF Base Tindal Stage 2(Part II) Investigation.

• AECOM (2009a) conducted a QA/QC Data Validation Assessment (Appendix G) and concluded that:

Based upon a review of the field and laboratory QA/QC program results, the indicators either all complied with the required standards, or showed variations that are not considered to present a significant effect on the quality of the data obtained.

It is therefore concluded that, for the purposes of this Stage 2 (III) Investigation, the laboratory analytical results are suitable for interpretation and acceptable for use in this contamination assessment.

4.3 Chemicals of Potential Concern

Chemicals of potential concern (CoPCs) were selected as chemicals that have consistently exceeded adopted health and/or environment-based investigation concentrations.

The CoPC selection process has been based on data obtained during the more recent soil and groundwater investigations, i.e. those conducted in November 2007 and May 2008 (reported by GHD, 2008) and in November 2008 (AECOM, 2009a).

Selection of CoPCs was undertaken by comparison of reported concentrations of chemicals in soil, sediment and groundwater at the FTA site to adopted investigation levels for protection of human health and the environment.

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4.3.1 Adopted Soil Investigation Levels

The following specific human health-based investigation levels were adopted for soil/sediments at the Site:

• Australian NEPMs Health Investigation Level (HIL) F commercial/industrial (NEPC, 1999c).

• USEPA Regional Screening Levels for Industrial Soil (USEPA, April 2009).

• USEPA Provisional Health Advisories for PFOA and PFOS (USEPA 2009b).

• Minnesota Department of Health Soil Criteria (MDH 2008, MPCA 2009).

The following specific environmental investigation levels for soil/sediments at the Site were adopted:

• NEPC (1999c) Ecological Investigation Levels (EILs) for current or potential future land use scenarios.

• NSWEPA (1994) Contaminated Sites: Guidelines for Assessing Service Station Sites.

The investigation levels published by the above sources are summarised in Tables T1 and T2 and the adopted guideline values, based on the above hierarchy, have been compared to chemical concentrations reported at the Site.

4.3.2 Chemicals of Potential Concern – Soil and Sediment

Protection of Human Health

The soil and sediment concentrations reported by ERM (2007) and GHD (2008) have been compared to human-health based soil investigation levels (HIL-F) and NSW EPA and MDH guidelines, as shown in Table T1. Based on this comparison, the following potential human health soil CoPCs have been considered for the FTA (Refer to Appendix A-Figure 13 for sampling locations):

• PFOS / PFOA associated with the historical use of AFFF.

- The maximum concentration of PFOS in soil (210 mg/kg) was reported for borehole 064BH01 (0.5 mBGL), which was located directly adjacent the training pad.

- The maximum concentration of PFOA in soil (2.3 mg/kg) was reported for borehole SB4 (0.3 mBGL), which was located in the northwest corner outside the fire pit.

- The maximum concentration of PFOS in sediment (54 mg/kg) was reported for surface sample SS01, located adjacent storage containers and some distance from the training pad.

- The maximum concentration of PFOA in sediment (1.1 mg/kg) was reported for surface sample SS01, located adjacent storage containers and some distance from the training pad.

• Petroleum hydrocarbons (TPH C10-C36), which are used for fuel or as accelerants for fires set in the FTA. TPH C6-C9 was not detected in any sample.

- The maximum concentration of TPH (C10-C36) in soil (2 630 mg/kg) was reported for borehole SB12 (0.0 mBGL), which was located to the south west of the Site past the drainage channel.

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- The maximum concentration of TPH (C10-C36) in sediment (520 mg/kg) was reported for sample 0064SS05, which was located to the south west of the Site just before the drainage channel.

TPH was detected above the investigation criteria in several soil samples near the settling pond in a recent investigation (AECOM, 2009a). Due to their isolated incidence on the site, and the proposed use of personal protective equipment for training and for site maintenance purposes, TPH are not considered to be a significant chemical of concern.

Diethylene glycol butyl ether (DGBE), a primary constituent of most AFFF mixtures, was not analysed in previous Site investigations. From a risk assessment perspective, in light of DGBE’s higher oral reference dose (some three orders of magnitude above that derived in the present report for PFOS/PFOA (OECD, 2002), and given DGBEs reported rapid degradation potential (AECOM, 2009), it is considered the DGBE does not represent a significant risk at the Site and has therefore not been further evaluated.

Based on this comparison, and on the CoPC selection methodology outlined above, the following human health soil CoPCs have been selected for the FTA:

• PFOS

• PFOA.

Ecological Protection

The adopted investigation levels for 95% ecological protection are presented along with maximum reported soil concentrations based on the ERM (2007) and GHD (2008) investigations in Table T1.

Based on this comparison, and on the CoPC selection methodology outlined above, the following ecosystem soil CoPCs have been selected for the FTA:

• PFOS

• PFOA.

Based on the available historical information, the potential chemicals of interest at NT0064 from an ecological risk perspective include:

• PFOS / PFOA associated with the historical use of AFFF.

• Hydrocarbons which are used for fuel or as accelerants for fires set in the FTA.

• Selected metals (Arsenic, Barium, Chromium, Copper, Manganese, Nickel, Vanadium, and Zinc).

Based on this comparison, and on the CoPC selection methodology outlined above, the following ecosystem soil CoPCs have been selected for the FTA:

• PFOS

• PFOA.

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4.3.3 Adopted Groundwater Investigation Levels

Selection of CoPCs in groundwater was based on comparison of reported concentrations of chemicals in groundwater monitoring wells within and around the FTA area to adopted investigation levels for protection of human health and the environment, based on the NEPM (1999) hierarchy of toxicity criteria selection.

The following groundwater investigation levels were adopted (where available):

• Australian Drinking Water Guidelines (NHMRC, 2004).

• ANZECC (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality 95% protection guidelines.

• USEPA Regional Screening Levels for Tap Water (USEPA, 2009).

The 95% Ecosystem protection level of the ANZECC/ARMCANZ Guidelines were adopted consistent with the NEPM-based interpretation of the level of disturbance to the ecology adjacent the FTA, and consistent with the previous investigation reports.

4.3.4 Chemicals of Potential Concern - Groundwater

Protection of Human Health

The adopted investigation levels for human health protection are presented, together with maximum reported groundwater concentrations based on the ERM (2007), GHD (2008) and AECOM (2009) monitoring events in Table T2.

The results shown in Table T2 indicated that the following analytes exceeded the health-based assessment guidelines:

• Selected metals (arsenic, barium, manganese and nickel)

• PFOS

• PFOA.

In addition, phase-separated hydrocarbons (PSH) were observed at monitoring well 064MW01 (GHD, 2008), however this was not detected in the most recent groundwater investigation (AECOM, 2009).

While arsenic, barium, manganese, nickel and vanadium exceeded the screening criteria (Table T2), they are not considered a significant human health risk due to the following:

• The depth to groundwater for industrial use of the site precludes direct contact by staff or maintenance workers.

• The exceedences (other than for manganese) are relatively minor.

• In humans, manganese is an essential nutrient with roles including bone mineralization, metabolism, and metabolic regulation. Adverse health impacts in humans have been associated with prolonged drinking water or food intakes only (WHO CICAD document 12, 1999).

• AECOM (2009a) considered that the naturally occurring heavy metal concentrations observed at the Site and other areas of the Base, notably manganese, are a result of groundwater conditions mobilising naturally occurring heavy metals.

Petroleum hydrocarbons are not considered as a significant risk due to the following:

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• The screening criteria have been exceeded only in isolated areas of the Site and only by one fraction of TPH (C10-C36).

• Groundwater is at depth. The minimum reported depth is 4.455 mBGL (sampled at the end of wet and beginning of dry season by GHD, 2008) and maximum 7.67mAHD (sampled at the start of the wet season by AECOM, 2009).

• Failure to detect TPH in groundwater across the FTA site in May 2008 (GHD, 2008) and November 2008 GME (AECOM, 2009).

AECOM (2009) noted that elevated PFOS concentrations have persisted in groundwater at the FTA site since monitoring commenced in May 2006, particularly at the following locations:

• 064MW02, located west of the central pit within the FTA. PFOS concentrations have been consistently several orders of magnitude above the Site assessment criteria.

• 064MW03, located north of the central pit within the FTA. PFOS concentrations increased by an order of magnitude in November 2008 compared to previously reported concentrations.

• 064MW05 located approximately 120 m hydraulically down gradient of the FTA. Concentrations of PFOS have reduced approximately by an order of magnitude, but remain above the Site assessment criteria.

Based on this comparison, and on the CoPC selection methodology outlined above, the following groundwater human health CoPCs have been selected for the FTA:

• PFOS

• PFOA.

Ecological Protection

The adopted investigation levels for 95% ecological protection are presented along with maximum reported groundwater concentrations (based on ERM 2007, GHD 2008, and AECOM 2009 groundwater monitoring events) in Table T2. The CoPC selection processes, and the risk assessment, have relied on these recent groundwater analytical results (i.e. data collected between November 2007 and November 2008).

Based on the comparison shown in Table T2, the following groundwater ecological CoPCs have been selected:

• PFOS

• PFOA.

Petroleum hydrocarbons are not considered as a significant risk due to the following:

• The screening criteria have been exceeded only in isolated areas of the Site and only by one fraction of TPH (C10-C36).

• The groundwater is at depth. The minimum reported depth is 4.455 mBGL (sampled at the end of wet and beginning of dry season by GHD, 2008) and maximum 7.67 mBGL (sampled at the start of the wet season by AECOM, 2009).

• Failure to detect TPH in groundwater across the FTA site in May 2008 (GHD, 2008) and November 2008 GME (AECOM, 2009).

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Concentrations of arsenic, barium, manganese, nickel and vanadium exceeded the ecological groundwater screening criteria, however they are not considered as a significant ecological risk specifically on the FTA Site due to the following:

• The high level of ecological disturbance on the training area.

• The exceedences (other than for manganese and nickel) are relatively small. Ecologically, manganese is an essential nutrient for microorganisms, plants, and animals.

• Vanadium and nickel are reported to be relatively ubiquitous in soil, however the Site concentrations are within the NEPM background soil concentrations for Australia (AECOM 2009). Groundwater is considered to be associated with these soil concentration levels in this region of the Northern Territory (AECOM, 2009). Consequently, vanadium and nickel have not been further evaluated in this risk assessment.

It should be noted that the ecological risk from the presence of groundwater contaminants and potential transport to Base land directly adjacent the FTA, where ecological habitat is less disturbed, warrants consideration and is discussed further in Section 8 of this report.

Based on the comparison shown in Table T2, the following groundwater ecological CoPCs have been selected:

• PFOS

• PFOA.

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5.0 Toxicity (Dose-Response) Assessment

The objective of the toxicity assessment component is to identify the toxicity values for each CoPC to be used for the quantification of potential human health risks.

The toxicity values adopted are based on two different approaches to the characterisation of dose-response (NHMRC, 1999 and USEPA, 1989):

• For chemicals that have the potential to result in carcinogenic effects that are associated with a genotoxic mechanism, any level of exposure is assumed to result in some incremental lifetime risk. These chemicals are there assessed on the basis of a non-threshold dose-response relationship.

• For other chemicals that may be associated with non-carcinogenic effects, or other carcinogenic effects that are not genotoxic, a threshold is considered relevant.

The threshold level is considered a level of exposure below which no adverse effects would occur. However, exceedence of the threshold level does not imply that adverse effects will occur, as there are a number of uncertainties and safety factors incorporated into the threshold value adopted. Rather, exceedence of the threshold level indicates that further evaluation of potential exposure is required.

The toxicity values adopted for the CoPCs in this risk assessment are presented in Appendices C to E and have been obtained (where available) from the following information sources (in order of preference):

• National Environment Protection Council (NEPC) reports and documents

• National Health & Medical Research Council publications

• World Health Organisation (WHO) - Air Quality Guidelines for Europe; Drinking Water Guidelines

• enHealth Council documents

• National Environmental Health Forum documents

• US Environmental Protection Agency (USEPA) reports and documents

• Peer reviewed journals (Level 2 source, as described in enHealth).

Toxicity values for PFOS and PFOA are not yet available in the listed guidance documents. Therefore, a tolerable daily dose equivalent has been derived using:

• USEPA Provisional Health Advisories for PFOA and PFOS (USEPA 2009b).

Consideration was also given to guidance information in:

• Minnesota Department of Health Soil and Groundwater Criteria (MDH 2008).

5.1 Non-Threshold Dose Response Factors

Non-threshold dose-response factors are only applied to genotoxic carcinogens. A genotoxic carcinogen is a substance or agent (in this case a chemical) that has the potential to produce cancer in humans by damaging genetic material. For these types of substances, there is no theoretical safe threshold of exposure. In other words, exposure to these substances, no matter how low, is considered to have the

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potential to cause cancer. However, the probability that cancer may in fact be produced (or cancer potency) varies from chemical to chemical.

PFOS and PFOA have been assessed on the basis that they are not considered to exhibit non-threshold toxicity. This approach is based on the following:

• WHO guidance that PFOS is non-mutagenic.

• USEPA guidance that the evidence for carcinogenic characteristics for PFOA and its salts is not sufficient.

• USEPA and MDH guidance which has established provisional health advisory concentrations for tolerable exposures to PFOS and PFOA (USEPA 2005, MDH 2008).

A review of published toxicity data indicated that cancer slope factors have not been assigned for any of the identified CoPCs. Consequently, potential carcinogenic risks have not been further evaluated for the FTA Site.

5.2 Acceptable Daily Intakes

Potential health effects that are assessed on the basis of a threshold typically utilise a threshold value termed an acceptable or tolerable daily intake (ADI or TDI) or reference dose (RfD). For the purpose of this assessment, the threshold value adopted has been termed a TDI. A TDI can be defined as a chemical intake below which it is considered unlikely that adverse effects would occur in human populations, including sensitive sub-groups (e.g. the very young or elderly). Hence, the TDI relates to intakes from all sources, including both Site-related exposure and background intakes (where relevant).

Where relevant to exposures, the threshold value is typically termed a tolerable concentration (TC), which is an estimate of a concentration below which it is considered that continuous exposure to people (including sensitive subgroups) is considered likely to be without risk of deleterious effects during a lifetime.

The derivation in the present report of a tolerable daily dose equivalent for ingestion of PFOS and PFOA and for application to adults and children (where applicable) was performed as described in Appendix B.

The tolerable daily doses derived for PFOS and PFOA are more conservative (i.e. lower) than the tolerable dose derived by MDH (2008). This more conservative dose is used for the current risk assessment based on the NEPM (1999) information source hierarchy.

5.2.1 Background Intakes

NEPC (1999a) and enHealth (2002) guidance indicate that background intakes of CoPC assessed on the basis of a threshold approach (i.e. using a TDI) should be considered in the assessment of overall risks associated with exposure to these chemicals. Given the remote nature of the Site, background intakes of man-made contaminants are therefore considered likely to be lower than those for receptors in urban areas.

With respect to potential background exposures to PFOS/PFOA relevant to the Katherine area, there is little specific information available from Australian sources, however there is comparative information from international studies. PERFORCE (2006) review reported PFOS and PFOA concentrations of up to 50 mg/L in large European rivers. The concentration was expected to include sources such as local PFOS/PFOA manufacturing. River sediment concentrations of PFOS were reported as not generally observed above some 0.5 x 10-6 mg/kg in the same review. Furthermore, the reference doses derived for PFOS and PFOA in this report are based on a USEPA health advisory which takes into account

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potential population background exposures, and which applied a safety factor for those potential exposures (Appendix B).

It is considered that the population around Katherine and the Tindal Base are not likely to be routinely exposed to significant concentrations of PFOS or PFOA in the absence of local manufacturing of these agents. Therefore, the primary exposure source is likely to be from the AFFF used in the region. No further inputs due to potential additional (i.e. background) exposure sources have been applied in the current risk assessment.

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6.0 Exposure Assessment

The purpose of the exposure assessment is to identify potentially exposed populations and significant exposure pathways, and to estimate chemical intakes for each of these pathways.

6.1 Potential Receptors

Potential human and ecological receptors which may be exposed to Site-related CoPCs under the current and future land use scenarios are considered to be:

• fire fighters undergoing training

• site construction/maintenance workers undertaking intrusive activities

• on- and off-Site residents/occasional recreational users (adults and children) of the Katherine area/Tindal Creek (into which groundwater from the Site may discharge) or the Katherine River (into which Tindal Creek discharges)

• farm and native species which inhabit local properties or creeks/habitats adjacent to the Site.

Other potential receptors which may contact groundwater from the Site have also been identified, however further evaluation was not considered warranted, as described below:

• Aboriginal communities:

It was considered unlikely that indigenous persons frequenting local land areas would access the Base on a regular basis other than for business or visitation purposes. The Base is fenced off from the surrounding land. However there is no fence specifically around the FTA area.

Consequently, potential risks to these receptors from impacted soil or groundwater are considered to be minimal, and have therefore not been further evaluated.

• Adjacent agricultural properties:

The adjacent agricultural (grazing) properties are either hydraulically up-gradient, or are separated from the Base area by Tindal Creek. Furthermore, a Japanese study of PFOS concentrations in beef cattle in Japan reported concentrations in locally grown beef to be an order of magnitude below levels observed in fish, and concluded that the concentrations did not pose a risk to cattle or to human health (Guruge et al. 2004).

Consequently, potential risks to these receptors from Site-impacted groundwater are considered to be minimal, and have therefore not been further evaluated.

• Potential on-site and down gradient extractive use(s) of groundwater:

- The nearest down gradient extraction bore to the FTA is reported to be the Sewerage Treatment Plant bore 845. This bore is located 0.5km SW of the Site and is reportedly used for irrigation purposes, but not for drinking purposes. Potential risks associated with incidental contact with groundwater during irrigation are considered to be minimal.

- As PFOS/PFOA is not currently impacting on the extraction well down gradient of the site (See Section 4.1) receptors that utilise town drinking water or bore extraction of groundwater for irrigation are therefore not considered current receptors of concern with respect to the Site.

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- Nevertheless, the Tindal Creek is potentially connected with Katherine River in the wet season. Therefore consideration of potential drinking water and swimming exposures is provided in this report for conservative screening purposes, together with fish consumption pathway consideration.

6.2 Potential Exposure Pathways

An exposure pathway is a mechanism by which an individual or population may be exposed to chemicals at or originating from the Site. For a complete exposure pathway to exist, the following four key elements are required:

• a source and mechanism of chemical release

• a transport medium (e.g. vapour, groundwater)

• a point of potential contact with the contaminated medium (i.e. the exposure point)

• An exposure route (e.g. inhalation, ingestion, dermal contact).

If one or more of these elements are missing, the exposure pathway is described as being incomplete, i.e., there is no exposure and therefore no risk.

Based on earlier investigations of the nature and extent of contamination, significant exposure pathways by which potential receptors (identified in Section 4.1 above) may be exposed to Site-derived CoPCs are considered to be the following:

• FTA Site staff and/or trainee fire fighters at the Site:

- Ingestion of surface soil/sediments (0.0mBGL-0.2mBGL).

Sediment results used are from surface samples (SS01 and SS02) taken near the southwest and southeast boundary of the site (See Appendix A, Figure 13). It is assumed the sediments would be soil outside of flooding events.

• Maintenance workers digging in trenches:

- Ingestion of subsurface soil (>0.2 mBGL).

Significant direct contact with soil at or below 1 mBGL is not considered likely, unless significant deeper excavation works are proposed.

• Off-Site neighbours/occasional recreational users of Tindal Creek/Katherine River.

- Ingestion of potable drinking water.

- Ingestion of surface water while swimming.

- Ingestion of fish and shellfish.

With respect to fish consumption as a potential human exposure pathway for groundwater discharging into Tindal Creek, the following considerations are relevant:

• Tindal Creek is ephemeral in behaviour, however it is possible that edible fish may inhabit the creek adjacent the Base for several months of the year during the wet season.

• International research (OECD 2002) and regulatory guidance (MDH 2008) have identified that PFOS (but not PFOA) may bioaccumulate in fish, and that fish consumption is a potential exposure pathway for humans.

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• Groundwater monitoring at 064MW07 is considered to be the most relevant site information for consideration of potential PFOS concentrations in groundwater which may enter Tindal Creek.

• PFOS contamination in 064MW05 and 064MW06 reported lower PFOS concentrations in comparison to monitoring wells closer to the FTA pit and training areas.

• Bore water monitoring results at the STP bore (Table 2) did not detect PFOS contamination of bore water.

• It should be noted that groundwater travelling from the FTA in the direction of Tindal Creek may potentially be affected by contaminants which may be sourced further up gradient of the FTA.

A Conceptual Site Model illustrating the relevant environmental media and potential exposure pathways for each of the identified potential receptors is provided in Figure 2.

Potential human exposure pathways considered to be incomplete include the following.

• Direct contact with groundwater during training, maintenance or construction activities at the FTA Site is not considered to be significant due to the depth to groundwater (reported as varying seasonally between 4 and 7 mBGL (ERM, 2007).The extraction bore outside the FTA area and down gradient is not reported to be impacted by FTA Site-related CoPC, as summarised in Table 2 above.

• Dust inhalation is considered to be an insignificant exposure pathway for Site staff, trainees and maintenance workers based on the intermittent durations of exposure and the wet training protocols employed on the Site.

• Dermal exposure is considered to be an insignificant exposure pathway for Site staff, trainees and maintenance workers based on the required levels of OH&S protective uniform for training, the commitment to prepare a site EMP for training and maintenance work and considering the low dermal toxicity characteristics of fluoro-octanoates reported in animal studies (OECD 2002).

• Direct contact with surface water at the FTA Site is not considered to be significant due to the absence of Site standing-water natural features.

• PFOS/PFOA are not volatile (OECD, 2002), and therefore inhalation of volatile components is not considered to be a complete exposure pathway.

6.3 Exposure Parameters

Human exposure parameters adopted in this risk assessment were obtained from the following recognised Australian sources:

• enHealth Council. 2002. Environmental Health Risk Assessment, Guidelines for Assessing Human Health Risks from Environmental Hazards.

• National Environment Protection Council (NEPC). 1999a. Guideline on Health Risk Assessment Methodology (Schedule B(4)) In: National Environment Protection (Assessment of Site Contamination) Measure.

• US Environmental Protection Agency (USEPA). 1989. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (and associated updates to this document, as referenced below).

• USEPA (2008) Child Exposure Factors Handbook, EPA/600/R-06/096F.

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Where specific guidance was not available from the literature, conservative estimates for exposure parameters have been adopted. Parameters adopted in this assessment are summarised in Table 4 below.

The exposure parameters used in the calculations, sourced from Australian guidance (enHealth 2002) and, where required, from the Risk Assessment Information System (RAIS, 2009), and are presented in Appendices C to E.

Table 4: Reasonable Maximum Human Exposure Parameters Used in the Risk Assessments

Parameter Adopted RME Value

Adult

Source

Common Parameters

Body Weight (kg) 70 (adult male) NEPC (1999a); enHealth (2002)

Averaging Time – noncarcinogens (years)

30 USEPA (1989) (equal to exposure duration)

On-Site Staff and Trainees

Exposure Duration (years) 30 NEPC (1999a); enHealth (2002)

Exposure Frequency (days/year)

80 1 day/week for 50 weeks/year plus one month of daily exercises

Soil/Sediment Ingestion Rate (mg/day)

25 NEPC (1999a)

On-Site Maintenance/Construction Workers

Exposure Duration (years) 1 NEPC (1999a); enHealth (2002)


30 1 month/year

Soil/Sediment Ingestion Rate (mg/day)

100 NEPC (1999a)

Off-Site Neighbours (Adult)

Exposure Duration (years) 64 AECOM estimate


365 Assume at home every day

Exposure Time – Swimming (hours/day)

1 AECOM estimate average

Surface Water Ingestion Rate – Swimming (L/hr)

0.05 AECOM estimate average

Ingestion Rate – Fish (kg/day) 0.005 USEPA (2008)

Off-Site Neighbours (Child 0-6 years old)

Exposure Duration (years) 6 AECOM estimate


365 Assume at home every day

Exposure Time – Swimming (hours/day)

1 AECOM estimate average

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Parameter Adopted RME Value

Adult

Source

Surface Water Ingestion Rate – Swimming (L/hr)

0.1 AECOM estimate average

Ingestion Rate – Fish (kg/day) 0.003 USEPA (2008)

6.4 Representative Chemical Exposure Point Concentrations

The evaluation of potential risks requires the selection and/or estimation of exposure point concentrations of CoPCs for identified receptors.

The maximum reported CoPC concentrations in surface soil, subsurface soil and groundwater have conservatively been used as input parameters to the vapour and emission models. These concentrations are summarised in Table 5.

Exposure point concentrations of CoPCs in the direct soil exposure, drinking water, swimming (ingestion), and fish consumption scenarios have been calculated, as detailed in Appendices C to E.

Table 5: PFOS and PFOA Exposure Point Concentrations

Adopted Exposure Point Concentrations Receptor

Soil PFOS (mg/kg)

Soil PFOA (mg/kg)

Groundwater

PFOS (μg/L)

Groundwater

PFOA (μg/L)

Staff and Trainees

93 (maximum surface concentration)

(ERM, 2007)

1.3 (maximum surface concentration) (GHD, 2008)

N/A N/A

Site Maintenance 210 (0.5MBGL - Sub-Surface)

ERM, 2007

2.3 (0.3MBGL Sub-Surface) GHD, 2008

N/A N/A

Off-Site Neighbours

- Potable drinking water

N/A N/A 0.07 (Tindal potable water) (GHD 2008)

0.05 (Tindal potable water) (GHD 2008)

- Tindal Creek: fish consumption1

N/A N/A 0.05 (064MW07)

[bio-concentrated tissue concentration = 80 ng/g fish] (Appendix B)

No bio-concentration

(MDH 2006)

- Tindal Creek: swimming

N/A N/A 0.05 (064MW07)

(GHD 2008)

0.05 (064MW07)

(GHD 2008)

1 PFOS bioaccumulates in fish whereas PFOA does not (MDH 2008b). Adopted PFOS Bioconcentration Factor = 1500

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For potable water exposure estimates, the (single) GHD (2008) concentration of PFOS in drinking water which was above the laboratory Practical Quantitation Limit (PQL) has been.

With respect to risk from PFOS exposure through contamination of edible fish, a short literature review of the widely reported bioconcentration behaviour of PFOS in fish has been undertaken. In order to identify a bioaccumulation factor for edible fish tissue, consideration was given to data and conclusions provided in the reviews OECD (2002) and Environment Canada (2006), particularly reported PFOS bioconcentrated in the tissues of carp when test concentrations of 2 and 20 μg/L were considered (OECD 2002). That review reported that fish were exposed for 58 days with allowances for excessive mortality effects. Bioconcentration factors were calculated to be 720 for 20 μg/L, and 200 to 1500 for 2 μg/L (OECD 2002). Environment Canada has reported that in laboratory studies bioconcentration factors for PFOS in fish ranged from 690 to 2796 (Environment Canada (2006).

Based on these references, a bioconcentration factor of 1500 mg/kg fish per mg/L water is considered to represent a reasonable estimate factor for application to PFOS bioconcentration in fish in Tindal Creek.

The most recent PFOS concentration in groundwater measured at 064MW07 (i.e. the PQL) has been used, together with published indications of potential bioconcentration of PFOS in fish, to estimate potential PFOS concentrations in fish resulting from FTA-derived groundwater which may discharge Tindal Creek.

There is a possibility that the karst conditions through which groundwater flows at the Site may preferentially direct contaminated groundwater to Tindal Creek. Therefore surface water monitoring of Tindal Creek water at a point as close as possible to the FTA should be considered as recommended in AECOM (2009b).

6.5 Estimation of Chemical Intakes

Intake factors and resultant risk calculations for the potential receptors and exposure pathways identified in this report are detailed in Appendices C to E, and discussed in Section 7.0.

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7.0 Human Health Risk Characterisation

Risk characterisation is the final step in the quantitative risk assessment process. In this step, data gathered and derived from the toxicity and exposure assessments are used to derive quantitative estimates of both cancer (non-threshold) and non-cancer (threshold) risks.

Calculations have been undertaken using in-house risk based models using excel spreadsheets. The calculations undertaken in the risk assessment for the identified receptors and exposure pathways are presented in Appendix C to E.

7.1 Non-Threshold Risk Estimates

As cancer slope factors have not been identified for any of the CoPC for the Site (as discussed in Section 5.0), potential non-threshold/carcinogenic risks have not been further evaluated.

7.2 Threshold Risk Estimates

Threshold risks associated with the potential inhalation of chemicals assessed on the basis of a threshold approach have been evaluated by comparing the daily chemical intake with its respective TDI allowable from the Site (TDI minus background intakes). The resulting ratio, referred to as the hazard quotient, is derived in the following manner:

HQ = CDI ÷ TDI

where:

HQ = Hazard Quotient (unitless)

CDI = Chronic Daily Intake (mg/kg/day)

TDI = Acceptable Daily Intake (mg/kg/day).

Where the exposure level for a given chemical exceeds the TDI (i.e. if the hazard quotient is greater than 1), a potentially unacceptable chemical intake is indicated.

To assess the overall potential for adverse health effects posed by simultaneous exposure to a number of chemicals, the hazard quotients for each chemical and exposure pathway are summed. The resulting sum is referred to as the hazard index (HI), and is calculated using the following equation.

HI = HQ chemical (i) + HQ chemical (i) + …. + HQ Chemical (n)

where:

HI = Hazard Index (unitless)

HQ = Hazard Quotient (unitless)

Chemical (i) = Chemical number ‘(i)’ of ‘(n)’ chemicals in a mixture.

The hazard index approach assumes that multiple sub-threshold exposures to several chemicals could result in an adverse health effect (assuming the target organs and effects are the same), and therefore the exposures are summed over all intake routes. If the sum is less than one, then cumulative exposure to the chemicals is unlikely to result in an adverse effect. If the sum is greater than one, a more detailed

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and critical evaluation of the hazards may be required, or appropriate risk management measures at the Site may need to be implemented.

7.3 Summary of Estimated Human Health Risks

A summary of the calculated threshold risk estimates is presented in Table 6 below. Detailed risk calculations are included in Appendices C to E.

Table 6: Human Health Risk Calculation Summary

Estimated Hazard Index Scenario

Adult (Average

Exposure)

Adult (Reasonable

Maximum Exposure)

Child (Average

Exposure)

Child (Reasonable

Maximum Exposure)

Staff and Trainees 0.23 0.37 N/A N/A

Site Maintenance/Construction Workers

0.83 1.2 N/A N/A

Base and Off-site Neighbours

- Potable water 0.14 0.4

- Fish consumption 0.29 0.91

- Swimming 0.0027 0.028

Total off-site combined 0.42 1.3

Note:

Grey shaded values are those that exceed adopted acceptable risk criteria.

Reasonable maximum exposure estimate risks have been calculated , as compared to average exposure risk estimates, in order to conservatively bound possible uncertainties in average exposure assumptions.

The following points are noted with respect to the risk estimates summarised above:

• The estimated hazard index for FTA site maintenance (trench) workers under the Reasonable Maximum Exposure scenario slightly exceeds the adopted acceptable risk criteria (1.0). However, interpretation of the risk estimates for that scenario should consider the following:

- The modelled one month per year of trench maintenance work at FTA is considered conservative for a site which has limited infrastructure on the ground.

- The adopted concentrations of PFOS and PFOA in soil are considered conservative as the highest reported concentrations, rather than the average concentrations, have been used.

- PFOS and PFOA impact in soil is not expected to increase over time as these chemicals are no longer used at the traditional concentrations in AFFF (Department of Defence, personal Communication May 2009).

• The estimated hazard index for children fishing and swimming in Tindal Creek, together with drinking town water, slightly exceeded the adopted acceptable risk

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criteria (1.0). The most significant contributions to the total risk were the consumption of potable water from the town supply and fish from Tindal Creek.

However, interpretation of the risk estimates for that scenario should consider the following:

- The likelihood that an average of 3 to 5 g/day of fish caught from Tindal Creek would be consumed over a long period by adults and children (a 64 and 6 year period, respectively) is considered low.

- The Tindal Creek is likely flowing in a manner which might support fish habitation only in the wet season for a period of several months of the year, rather than for the entire year (as assumed in the risk calculations).

- PFOS concentrations in Tindal Creek would be expected to be significantly diluted in creek water compared with groundwater (064MW07) in a scenario where fish habitation is occurring.

- The estimate of PFOS concentration used for the fish bioconcentration calculations is a PQL lower limit of reporting at 064MW07 and may overestimate the concentration of PFOS in groundwater discharging into Tindal Creek.

- Potable water intakes are based on a single laboratory result (GHD 2008). All other drinking water supply results have reported PFOS at concentrations below the LOR (AECOM 2009).

Considering the above, the potential risks calculated and summarised in Table 5 above are considered to be conservative and likely to be an over-estimate.

Australian regulatory guidance includes the NSW DECC (2005) position on Criteria for Risk and Hazard Index which states that threshold risks with Hazard Index (HI2) less than 0.2 are considered acceptable, risks with HI between 0.2 and 10 require best practice reduction and risks with HI greater than 10 are considered as not acceptable. The DECC guidance is framed for toxic air pollutant regulation, but is indicative with respect to toxicological effects. An HI of equal to or less than 1.0 is considered to confirm no adverse health impacts to receptors for potential exposures over (in this case) a thirty year period for workers or a lifetime exposure for residents.

Overall, the above risk estimates indicate that no unacceptable risk is posed to FTA Site staff or trainees from routine training activities, nor to residents of Tindal Creek, the Base, and Katherine with respect to drinking, fish ingestion and recreational activities.

However, the risk assessment results indicate that appropriate personal protection equipment (PPE - gloves, long sleeves and pants, good OH&S hygiene) and procedures should be implemented for intrusive maintenance work below ground conducted at the FTA. Furthermore, potential down gradient impacts on surface water quality is a relevant consideration in local environment protection, and ongoing monitoring of PFOS concentrations in groundwater and in Tindal Creek surface water as near as possible to the FTA Site is considered to be warranted.

2 HI is the sum of individual chemical non-cancer hazard quotients. The hazard quotient is a comparison of the experienced air concentration of a chemical to an exposure level published as acceptable by certain regulatory agencies.

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8.0 Preliminary Ecological Risk Assessment

8.1 Background

Preliminary advice on potential ecological risks relevant to the Site has been requested by Defence, consistent with Australian NEPM guidance (NEPC, 1999b) that ecological risk be considered when:

• Previous studies identify contaminant concentrations above background levels.

• The site history indicates a potential for harmful environmental effects.

• Significant data gaps exist for contaminant toxicity or information about potential receptors.

• Rare and endangered species or habitats are known to be present in proximity to the site.

As noted in Section 2.9, identified CoPC were screened against Australian ecological guidelines using the following hierarchy:

• ANZECC (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality 95% protection guidelines.

• NEPC (1999c) Ecological Investigation Levels (EILs) for current or potential future land use scenarios.

• NSWEPA (1994) Contaminated Sites: Guidelines for Assessing Service Station Sites.

The investigation levels published by the above sources are summarised in Tables T1 and T2 and the adopted value based on the above hierarchy are compared to chemical concentrations detected at the Site.

8.2 Receptors

Limited information is available on ecological species and communities on a local or regional basis in the Northern Territory. Research on state and local government Internet sites sourced a list of species from the trial Land and Water Resources Audit (LWRA, 2005) for the Daly region, which includes the Tindal area. A university study on the river flows and fish in the Daly region (Douglas and Kennard, 2007) provided local information on some of the species present in the waterways of the area, such as Katherine River.

AECOM has compiled a table of the species identified as likely to occur in proximity to the Site using information from these studies, as well as tables and observation notes from previous consultant reports (ERM, 2007) (refer to Appendix F).

Receptors considered likely to be present at the site include:

• transitory birds - which feed on insects/small vertebrates

• insects

• small vertebrates - such as mice, and during flooding frogs have been observed at the Sewage Treatment Plant 150 m northwest of the Site (ERM, 2007a)

• large vertebrates – such as kangaroos, feral pigs, feral cattle

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• plants - from eucalypt scrub communities.

In proximity to the Site, Tindal Creek provides additional habitat however as it is ephemeral, the habitat provided to aquatic species such as fish and turtles is likely to be short term.

The societal and ecological significance of the Site is considered low, as there is restricted access for the public and the Site has a history of being utilised for Defence training.

The habitat is highly disturbed and it is considered unlikely that any of the identified threatened or vulnerable species are present at the Site. The economic significance of the Site is also considered low as there is no commercial fishing or similar activities related to the ecological condition of the Site.


The Site has previously been cleared of bushland and currently has native grasses, shrubs and sparse eucalypt tree growth. The RAAF base is fenced which restricts access to larger mammals such as livestock from nearby agricultural land. In addition, the FTA has human presence and vehicle movement at the Site and from the nearby road. The habitat at the Site is therefore considered suitable for highly mobile (e.g. birds) and small terrestrial species.

Potential exposure pathways are considered as follows:

• Contact with impacted surface soil through digging or when moving around the Site.

• Ingestion of impacted surface soil by insects.

• Ingestion of prey (insects/small vertebrates) which has had contact with impacted surface soil.

• Contact with (including ingestion) groundwater discharging into nearby Tindal Creek.

• Contact with (including ingestion) surface water during flooding at the Site, contaminated by surface soil and fuel pit waste.

As PFOS and PFOA are not volatile, inhalation is not considered a potential exposure pathway.

8.4 Toxicity Assessment

A preliminary review of existing information regarding potential ecological toxicity of PFOS indicated the following:

• Animal studies show that PFOS is well absorbed orally and distributes mainly in the serum and the liver. Elimination from the body is slow and occurs via the urine and faeces. There are species differences in the elimination half-life of PFOS.

• PFOS is bioaccumulative (OECD, 2002), and exhibits a half life of 100 days for rats, 200 days for monkeys (versus years for humans).

• PFOS is toxic to mammalian species and of low to moderate toxicity to aquatic organisms (OECD, 2002). There is currently no information on the effects of PFOS on soil/sediment dwelling organisms.

• Adverse signs of toxicity were observed in 90-day rat studies including increases in liver enzymes, hepatic vacuolization and hepatocellular hypertrophy, gastrointestinal effects, haematological abnormalities, weight loss, convulsions, and death. These effects were reported at doses of 2 mg/kg/day and higher in the diet. Postnatal deaths and other developmental effects were reported at low doses in offspring in a 2-generation reproductive toxicity study in rats. PFOS concentrations were higher in

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the liver than in the serum, and males had greatly increased PFOS concentrations in serum and liver when compared with females of the same dose group. The data appear to indicate that reduced pup survival may be a result of in utero exposure to PFOS and that post-natal exposure via milk in conjunction with in utero exposure may also contribute to reduced pup survival. In contrast, exposure during lactation alone, through milk from exposed dams, does not appear to have any adverse effect on pup viability (OECD 2002).

• In birds, PFOS effects have been reported on two species, the Mallard duck (Anas platyrhynchos), and the Northern Bobwhite quail (Colinus virginianus). The lowest acute dietary LC50 value of 220 mg/kg of food was determined in the test with the quail. The lowest NOEC of 37 mg/kg of food for effects on body weight was, in contrast, obtained in the test with the duck.

• PFOS showed moderate acute toxicity to aquatic organisms, the lowest available LC50 for fish is a 96-hour LC50 of 4.7 mg/l to the fathead minnow (Pimephales promelas) for the lithium salt (OECD 2002) and in Pimephales promelas (static) 96-hour tests an LC50 of 9.5mg/l, and a 96-hour NOEC of 3.3mg/l for the PFOS potassium salt (OECD 2002).

• For aquatic invertebrates, the lowest available EC50 for freshwater species is a 48-hour EC50 of 27 mg/l for Daphnia magna and for saltwater species, a 96-hour LC50

value of 3.6 mg/L for the mysid shrimp (Mysidopsis_bahia). Both tests were conducted on the potassium salt.

• Long-term toxicity data is available for fish and aquatic invertebrates. The lowest NOEC for fish is a 42 day NOEC (survival) of 0.3 mg/L in an early life stage test with Pimephales promelas using the potassium salt . The lowest NOEC for aquatic invertebrates is a 35-day NOECreproduction of 0.25 mg/L for Mysidopsis bahia using the potassium salt. For freshwater species, there is a 28-day NOECreproduction of 7 mg/L for Daphnia magna, also using the potassium salt.

• Two tests carried out on PFOS potassium salt with one species of freshwater invertebrate – the ‘water flea’ (Daphnia magna) reported end points of survival, growth and reproduction measured over exposure periods of up to 28 days. NOECs of 12 and 7 mg/L have been determined for D. magna reproduction in 21 and 28-day tests respectively. In the 21-day test, the NOECs for survival and growth were also 12 mg/L, indicating that reproduction was no more sensitive than the two other end points.

• In algae, a growth inhibition test has been carried out on PFOS potassium salt with Lemna gibba (Duckweed). The test gave a 7-day LC50 of 108 mg/L for inhibition of frond production, and a 7-day NOEC of 15.1 mg/L based on the inhibition of frond production and evidence of sub-lethal effects.

• In amphibians, the results of a teratogenesis study carried out with Xenopus laevis (African clawed frog) showed PFOS potassium salt to be acutely toxic to (96-hour LC50 of 13.8 mg/L), and malformations in (96-hour EC50 of 12.1 mg/L), frog embryos. The minimum concentration that inhibited growth of the embryos was determined to be 7.97 mg/L. A teratogenic index of 1.1 was determined from the ratio of the 96-hour LC50 to the 96-hour EC50, indicating a low potential for PFOS to be a developmental hazard in this species.

• In bees, data available from acute oral and contact toxicity tests on the honey bee (Apis mellifera) using PFOS potassium salt. These studies indicated moderate and high orders of toxicity of PFOS to bees. The acute oral test yielded a 72-hour LD50 for ingestion of PFOS of 0.40 g/bee, and a 72-hour NOEL of 0.21 g/bee. The contact test yielded a 96-hour LD50 of 4.78 μg/bee and a 96-hour NOEL of 1.93 g/bee.

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Sampling of several wildlife species from a variety of sites across the United States has shown widespread distribution of PFOS and it was detected in the parts per billion (ppb) range in the plasma of several species of eagles, wild birds, and fish. PFOS has been detected in marine mammals at a number of locations across the world (OECD 2002).

Toxicity information relating to aquatic plants was not used from the OECD (2002) report as the results had been considered by OECD to be questionable due to methodologies used in the studies compared.

8.5 Risk Characterisation

Due to the nature of Site fire-training activities, including use of the Site for foot-traffic, vehicle access (including trucks), pit-burning, and AFFF use, and given its likely future continuation for this purpose, the terrestrial environment in the immediate vicinity of the Site is highly disturbed, and the terrestrial ecological value of the Site is considered to be low. It is also noted that the majority of PFOS, petroleum hydrocarbon, and metal impacts at the Site have been identified in subsurface soil and in groundwater (ERM 2007, GHD 2008, AECOM 2009). Adverse impacts to terrestrial and to ephemeral aquatic ecological receptors are therefore not considered likely in the immediate FTA area, particularly given the localised nature of residual reported surface soil impacts.

However, terrestrial pathways by which wildlife receptors may be exposed to Site-related surface equipment and impacted soil are considered to be complete. Such pathways would involve PFOS migration from surface soil through wind or rainwater-induced erosion, and deposition of PFOS in undergrowth adjacent the FTA site. The variety of toxicity endpoints described in Section 8.4 indicates that, should wildlife be exposed to significant concentrations of PFOS, this may affect survival potential of small mammals and birds, and invertebrates including bees, and reproductive and developmental potential of vertebrates.

With respect to aquatic fauna and flora, the range of reported LC and NOEL data described in Section 8.4 is higher than the concentrations of PFOS reported in groundwater for 064MW07, 064MW05 and 064MW06 (GHD 2008). Both monitoring points are located down gradient from the Site to Tindal Creek (the nearest watercourse).

However, Australian regulatory guidance (ANZECC 2000) routinely incorporates safety factors of 10 to 1000-fold depending upon the reliability of available scientific information, reducing LOEC and NOEC data in order to identify appropriately conservative ecological exposure trigger point concentrations of concern. Therefore, the observation that a lowest NOEC for fish in a 42 day NOEC (survival) was 0.3 mg/L in an early life stage test with Pimephales promelas indicates that groundwater entering the local watercourses in flood conditions and exhibiting concentrations of PFOS similar to those found in groundwater at bore RN005771 (Table 2) potentially represents a risk to the local aquatic food web and to species reproduction.

Continued monitoring of PFOS concentrations in groundwater down gradient of the Site at 064MW07, 064MW06 and 064MW05, including across seasonal variations of weather, is recommended due to the potential for groundwater discharge to impact on water quality in Tindal Creek.

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9.0 Uncertainties

In general, the uncertainties and limitations of human health and ecological risk assessment can be classified into the following categories:

• sampling and analysis

• exposure assessment

• toxicological assessment.

The risk assessment process following available guidance documents presented in Section 1.4 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.

9.1 Sampling and Analysis

The soil and groundwater data used in the risk assessment has been collected by AECOM and other consultants based on the knowledge of the Site history and hydrogeological conditions. The analytical suite has also been selected based on a knowledge of former Site activities, and hence has focussed on chemicals which were known to have previously been used at the Site. There is the potential for chemicals to be present on the Site which have not been characterised based on omission from Site history records.

Overall, the soil and groundwater data utilised in this risk assessment are considered to be representative of environmental conditions at the Site at the time of sampling. The HRA has used maximum concentrations for the characterisation of most exposures in order to provide an upper bound estimate of potential exposures and risks at the Site. It is noted that the maximum reported soil and representative groundwater concentrations (estimates of fish bioconcentration) are considered likely to represent unrealistically high exposure point concentrations, as it is considered highly unlikely that a receptor would be exposed to these concentrations for the entire exposure duration. However, risks associated with continued exposure to these concentrations have been estimated to be conservative and to ensure that any uncertainties that exist in the data set are accounted for.

The identification of CoPC in groundwater has considered use of current guidelines that are based on the more conservative endpoint of drinking water, and identification of CoPC in soil have been based on soil guidelines designed primarily for industrial land use. The approach adopted is therefore considered appropriate for the identification of key chemicals that warrant more detailed 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 Site and surrounding areas. The assumptions used are conservative and developed to provide an estimate of reasonable maximum exposures rather than the actual exposures. This approach tends to overestimate the risks.

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9.3 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 may be exposed. It is necessary, therefore, to extrapolate these properties from data obtained under other conditions of exposure and involving experimental laboratory animals.

This may introduce two types of uncertainties into the risk assessment, as follows:

• Those related to extrapolating from one species to another.

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

The majority of the toxicological knowledge of chemicals comes from experiments with laboratory animals, although there may be interspecies differences in chemical absorption, metabolism, excretion and toxic response. There may 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 subchronic animal studies to humans exposed over a lifetime has inherent uncertainty.

In order to adjust for these uncertainties, ADIs and RfDs incorporate safety factors that may vary from 10 to 1000.

The approach to evaluating risks for mixtures of chemicals assesses dose additively and does not account for potential synergism, antagonism or differences in target organ specificity and mechanism of action. In general, it is considered likely that the additive approach has the effect of overestimating risks. This is because chemicals that have no additive effects are included together as well as chemicals that may have additive effects.

9.4 Ecological Risk Uncertainty Considerations

Evaluation of ecological risks is constrained by uncertainty (lack of knowledge) regarding data, exposure, toxicity, and risk issues. Although risk assessment follows a formal scientific approach, making assumptions or estimates based on limited data or by incorporating professional judgment is an inherent part of the process. Uncertainties built into the estimation of exposures and risks may act either to increase or decrease the identified risks, depending on the source of uncertainty. Common sources of uncertainty include those related to the development of the CSM, the factors used to develop the risk estimate (e.g., exposure assumptions and toxicity assumptions), and uncertainty in the parameters used to evaluate risk (e.g., data gaps, exposure point estimates).

The common uncertainties associated with data quality, exposure assessment, toxicity assessment, and risk characterization include the following general categories:

• data quality

• toxicity assessment;

• exposure assessment;

• Exposure Point Concentrations

• nature and extent of CoPCs

• risk characterization.

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In general, risk assessments are designed to include conservative assumptions to avoid overlooking potential ecological risk. Because of these assumptions and estimates, the results of the risk calculations are themselves subject to a certain degree of uncertainty, and it is important to keep this in mind when interpreting the results of a risk assessment. These uncertainties, based on NEPC (1999b) guidance, may be used for appropriate decision-making, or to move on to a more detailed level of ecological risk assessment.

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10.0 Conclusions and Recommendations

The Human Health and Screening Ecological Risk Assessment (HHERA) of soil and groundwater contamination in the vicinity of the Fire Training Area of the RAAF Base Tindal (the Site) undertaken by AECOM has reached the following conclusions with respect to human health and ecological risks.

10.1 Human Health

• PFOS and PFOA are the key monitored CoPC with respect to potential effects on human health.

With respect to potential human receptors:

• The estimated hazard index for FTA staff and trainees under the Reasonable Maximum Exposure scenario did not exceed the relevant adopted acceptable risk criterion (1.0).

• The estimated risks to maintenance workers undertaking sub-surface soil work on the FTA Site marginally exceeded the nominated acceptable risk level (1.0). The following further points should be taken into account when interpreting the risk estimates for that scenario:

- the estimated 30 days per year duration of subsoil work at the FTA site is considered a conservative exposure duration parameter

- the estimates are for a reasonable maximum exposure, not the average exposures

- the modelled concentrations of PFOS and PFOA have been overestimated by using the highest measured level of PFOS /PFOA in surface soil rather than the average concentration which will be encountered

- PFOS and PFOA contamination in soil are expected to reduce over time because these chemicals are no longer used at the traditional concentrations in current and future AFFF.

Considering the above, the estimated risks to maintenance/construction workers are considered to be conservative and likely to represent and over-estimate. Interpretation of the risk estimates for that scenario therefore suggests that the risk to Defence would be considered acceptable.

• The estimated hazard index for children and adult residents of the Katherine area, and of the Base, drinking from the Katherine town water supply did not exceed the relevant adopted acceptable risk criterion (1.0).

• The estimated hazard index for children and adult residents fishing or swimming in the area of Tindal Creek did not exceed the relevant adopted acceptable risk criteria.

• However, when the activities of drinking from the Katherine town water supply, fishing and swimming in the area of Tindal Creek were combined, the estimated risks for neighbouring children slightly exceeded the adopted risk criterion. However the following are relevant to interpreting the risk estimates for that scenario:

- The likelihood that some 3 to 5 g/day of fish derived from the Tindal Creek would be consumed by adults and children over a 64 and 6 year period, respectively, is considered low.

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- The Tindal Creek is likely flowing in a manner which might support fish habitation and swimming only in the wet season, not for the entire year as assumed in the risk calculations.

- PFOS concentrations in Tindal Creek would be expected to be significantly diluted in creek water compared with groundwater (064MW07) in a scenario where fish habitation is occurring. As a conservative measure, potential dilution affects were not incorporated into the risk calculations.

- The estimate of PFOS concentration used for the fish bioconcentration calculations was the laboratory PQL, which may overestimate the concentration of PFOS in groundwater discharging into Tindal Creek.


Overall, the above risk estimates indicate that no unacceptable risk is posed to FTA Site staff or trainees from routine training activities, or to neighbouring residents.

The risk assessment results also indicate that:

• Appropriate Personal Protective Equipment (PPE) and procedures should be implemented for maintenance work conducted at the FTA site.

• Prevention of potential bioaccumulation of PFOS in fish and bioaccumulation in wildlife are relevant considerations in local environment protection.

• Ongoing monitoring of PFOS concentrations in groundwater which may discharge into Tindal Creek (064MW07) and in Tindal Creek surface water near the FTA site is considered warranted.

The results and conclusions of the report are considered to be suitable to assist Defence in making informed decisions about remediation requirements.

With respect to remediation goals for FTA redevelopment, based on the current HHERA, PFOS and PFOA concentrations reported in the validation program which are no greater than the maximum reported to date on the Site are considered acceptable for human health and environment protection.

10.2 Ecological Effects

Due to the nature of Site fire-training activities, including use of the Site for foot-traffic, vehicle access (including trucks), pit-burning, and AFFF use, and given its likely future continuation for this purpose, the terrestrial environment in the immediate vicinity of the FTA Site is highly disturbed, and the terrestrial ecological value of the Site is considered to be low.

However, terrestrial pathways by which wildlife receptors may be exposed to Site-related surface equipment and impacted soil are considered to be complete. Such pathways would involve PFOS migration from surface soil through wind or rainwater-induced erosion, and deposition of PFOS in undergrowth adjacent the FTA site.

Continued monitoring of PFOS concentrations in groundwater down gradient of the Site at 064MW07, 064MW06 and 064MW05, including across seasonal variations of weather, and in Tindal Creek surface water as near as possible to the FTA site is recommended due to the potential for groundwater discharge to impact on water quality in Tindal Creek.

It is recommended that the Department of Defence continue to monitor groundwater concentrations in order to demonstrate that concentrations are not increasing.

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11.0 References

AECOM. 2009a. Stage 2 (III) Environmental Investigation, RAAF Base Tindal, Northern Territory. Unpublished report prepared for the Department of Defence. Canberra.

AECOM. 2009b. Water Quality Investigations FY08/09, RAAF Base Tindal. Unpublished report prepared for Spotless Managed and Support Services. Darwin.

Department of Environment and Climate Change (DECC). 2005. Approved Methods for the Modelling and Assessment of Air Pollutants in New South Wales 2005. New South Wales Government. Sydney.

Douglas, M. and Kennard, M. 2007. Daly River Fish and Flows Project: An Environmental Flows Study, September 2007 Newsletter. http://www.track.gov.au/sites/track.boab.info/files/uploads/Daly%20River%20fish%20and%20flows%20project%20-%20an%20environmental%20study,%20Sept%202007.pdf. Accessed 21 May 2009.

European Food Safety Authority (EFSA). 2008. Opinion of the Scientific Panel on Contaminants in the Food Chain on Perfluorooctane sulphonate (PFOS) and Perfluorooctanoic acid (PFOA) and their Salts. EFSA Journal. 2008. Journal number 653. 1-131.

enHealth. 2002. Environmental Health Risk Assessment, Guidelines for Assessing Human Health Risks from Environmental Hazards. June 2002.

Environment Canada. 2006. Ecological Screening Assessment on PFOS, Its salts and Its Precursors www.ec.gc.ca/CEPAregistry.documents/subs_list/PFOS_SAR/PFOS_P1.cfm.

ENSR Australia Pty Ltd (ENSR). 2008a. Sampling and Analysis Plan – Stage 2(III) Environmental Investigation – RAAF Base Tindal Northern Territory/Kimberley. Unpublished report prepared for Department of Defence.

ENSR Australia Pty Ltd (ENSR). 2008b. Groundwater and Surface Water Monitoring Plan – RAAF Base Tindal Northern Territory/Kimberley Region. Unpublished report prepared for the Department of Defence.

Environmental Resources Management Australia (ERM). 2005. Stage 1 Environmental Investigation, RAAF Base Tindal, Northern Territory. Unpublished report for the Department of Defence (Reference 002881 June 2005).

Environmental Resources Management Australia (ERM). 2007a. Stage 1 Environmental Investigations NT/K, RAAF Base Tindal. Unpublished report for the Department of Defence (Reference 0042239 RAAF Tindal Stage 1. June 2007).

Environmental Resources Management Australia (ERM). 2007b. Stage 1 and 2 Environmental Investigations NT/K, RAAF Base Tindal. Unpublished report for the Department of Defence (Reference 0042239 RP1. June 2007).

GHD. 2008. RAAF Base Tindal, Stage 2 (Part II) Environmental Investigation. Unpublished report for the Department of Defence (Ref. 31/21887/146637. July 2008).

Goeden. H, and Kelley. J. 2006. Perfluorochemicals in Minnesota. Submission to Senate Environment and Natural resources Committee. Minnesota Department of Health. 27 February 2006.

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Guruge. K. S., Taniyasu, S., Miyazaki, S., Yamanaka, N. and Yamashita, N. 2004. Age Dependent Accumulation of Perfluoronated Chemicals in Beef Cattle. Organohalogen Compounds. 66. 4029-4034.

IRIS. 2009. Integrated Risk Information System. On-line resource: www.epa.gov/iris. Accessed February 2009.

Lau, C., Anitole, K., Hodes, C., et al. 2007. Perfluoroalkyl acids: A review of monitoring and toxicological findings. Toxicol. Sci. 99 (2) 366-394.

Minnesota Pollution Central Agency (MPCA). 2009. Draft Guidelines, Risk Based Guidance of the Soil Human Health Pathway. Minnesota Pollution Central Agency. June 2009.

Minnesota Department of Health (MDH). 2006. Presentation on Perfluorochemicals in Minnesota. Minnesota Department of Health, Division of Environmental Health, Site Assessment and Consultation Unit, February 2006.

Minnesota Department of Health (MDH). 2008. Issues and Needs for PFAA Exposure and Health Research: A State Perspective. Minnesota Department of Health, Division of Environmental Health, Site Assessment and Consultation Unit, June 2008.

National Environment Protection Council (NEPC). 1999a. Schedule B(4) Guideline on Health Risk Assessment Methodology. In: National Environment Protection (Assessment of Site Contamination) Measure.

National Environment Protection Council (NEPC). 1999b. Schedule B(5) Guideline on Ecological Risk Assessment. In: National Environment Protection (Assessment of Site Contamination) Measure.

National Environment Protection Council (NEPC). 1999c. Schedule B(7a) Guideline on the Investigation Levels for Soil and Groundwater. In: National Environment Protection (Assessment of Site Contamination) Measure.

National Environment Protection Council (NEPC). 1999d. Schedule B(7b) Guidelines on Exposure Scenarios and Exposure Settings. In: National Environment Protection (Assessment of Site Contamination) Measure.

National Health and Medical Research Council (NHMRC). 1999. Toxicity Assessment for Carcinogenic Soil Contaminants. National Health and Medical Research Council, endorsed 6 September 1999.

National Health and Medical Research Council (NHMRC). 2004. Australian Drinking Water Guidelines. National Health and Medical Research Council.

National Land and Water Resources Audit (NLWRA). 2005. Monitoring and Evaluation Trials, Northern Territory Region, Phase 1 Report. National Land and Water Resources Audit. November 2004.

Organisation for Economic Co-operation and Development (OECD). 2002. Hazard Assessment of Perfluorooctane Sulfonate (PFOS) and its Salts. Organisation for Economic Co-operation and Development. ENV/JM/RD(2002)17/FINAL.

RAIS. 2009. Risk Assessment Information System. http://rais.ornl.gov. U.S. Department of Energy Office of Environmental Management, Oak Ridge Operations Office. Accessed February 2009.

SKM. 2001. Environmental Management Plan for RAAF Base Tindal. Unpublished report for the Department of Defence (Ref. DNR04674. 19 July 2001).

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United States Environmental Protection Agency (USEPA). 1989. Risk Assessment Guidance for Superfund Volume 1. Human Health Evaluation Manual (Part A). Office of Emergency and Remedial Response. USEPA. Washington DC. EPA/540/1-89/002. December 1989.

United States Environmental Protection Agency (USEPA). 1991. Guidelines for Developmental Toxicity Risk Assessment, Published on December 5, 1991, Federal Register 56(234):63798-63826.

United States Environmental Protection Agency (USEPA). 1996. Guidelines for Reproductive Toxicity Risk Assessment. Published on October 31, 1996, Federal Register 61(212):56274-56322.

United States Environmental Protection Agency (USEPA). 2005. Draft Risk Assessment of the Potential Human Health Effects Associated with Exposure to PFOA and its salts. USEPA. Science Advisory Board Review Draft, January 2005.

United States Environmental Protection Agency (USEPA). 2008. Child Exposure Factors Handbook, USEPA. National Centre for Environmental Assessment. Office of Research and Development, Washington. Ref EPA/600/R-06/096F. September, 2008.

United States Environmental Protection Agency (USEPA). 2009b. Provisional Health Advisories for Perfluorooctanoic acid (PFOA) and Perfluorooctane Sulfonate (PFOS). USEPA. Office of Water, January 8, 2009.

United States Environmental Protection Agency (USEPA). 2009a. Regional Screening Levels for Chemical Contaminants at Superfund Sites. Available from: http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/Generic_Tables/index.htm. Accessed June 2009.

World Health Organisation (WHO). 2004. Manganese And Its Compounds: Environmental Aspects. Concise International Chemical Assessment Document (CICAD) 63.

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Tables

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Tindal RAAF - Fire Training AreaTable T1 - Soil/Sediment Concentrations for CoPC Screening

NEPM B7a (1999)

MDH (2008)

NEPM B1 (1999)

GHD max Location GHD max Location ERM max Location ERM max Location

HIL F Soil Soil - Ind EIL Soil Soil Soil Sediment Soil Sediment

mg/kg mg/kg mg/kg mg/Kg mg/Kg mg/Kg mg/kg mg/Kg

Arsenic 500 NV 20 NV <LOR (5) all - - 6BH03 (0.5m),

BH04 (3m)2 0064SS04 (0.0m)

Barium NV NV 300 NV 120 SB11 (0.0m) - - - - - -

Berrylium 100 NV NV NV - - - - - - - -

Cadmium 100 NV 3 NV <LOR (1) all - - 0.1 BH03 (0.5m) <LOR (0.1) all

Chromium 500 NV 50b NV 53 SB4 (0.0m) - - 38 BH04 (3m) 24 0064SS03 (0.0m)

Cobalt 500 NV NV NV - - - - - - - -

Copper 5000 NV 100 NV - - - - 52 BH03 (0.5m) 9 0064SS06 (0.0m)

Lead 1500 NV 600 300 - - - - 15 BH03 (0.5m) 10 0064SS06 (0.0m)

Magnesium NV NV NV NV - - - - - - - -

Manganese 7500 NV 500 NV 522 SB12 (0.0m) - - - - - -

Mercury 75 NV 1 NV <LOR (5) all - - <LOR (0.05) all 0.050064SS05, 0064SS06

(0.0m)

Nickel 3000 NV 60 NV 12 SB8 (0.0m) - - 15 BH04 (3m) 6 0064SS06 (0.0m)

Vanadium NV NV 50 NV 170 SB2 (0.0m) - - - - - -

Zinc 35000 NV 200 NV - - - - 65 BH02 (0.5m) 16 0064SS03 (0.0m)

PFOA (PerFluoroOctanoicAcid) NV 0.013 NV NV 2.3 SB4 (0.3m) 1.1 SS1 - - - -

PFOS (PerFluoro-Octane Sulphonate) NV 0.014 NV NV 18 SB4 (0.3m) 54 SS1 210 BH01 (0.5m) - -

Benzene NV NV NV 1 <LOR (0.2) all - - <LOR (0.2) all <LOR (0.2) all

Toluene NV NV NV 1.4/130 <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Ethylbenzene NV NV NV 3.1/50 <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Xylene o NV NV NV NV <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Xylene p NV NV NV NV <LOR (0.5) all - - <LOR (1) all <LOR (1) all

Total Xylenes NV NV NV 14/25 <1 all - - - - - -

Anthracene NV NV NV NV <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Benzo(a)pyrene 5 NV NV 1 <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Fluoranthrene NV NV NV NV <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Napthalene NV NV NV NV <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Phenanthrene NV NV NV NV <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

Total 20 NV NV 20 <LOR (0.5) all - - <LOR (0.5) all <LOR (0.5) all

C06-C09 NV NV NV 65 <LOR (10) all - - <10 all <10 all

C10-C14 NV NV NV NV 780 SB12 (0.0m) - - <50 all 520 0064SS05 (0.0m)

C15-28 NV NV NV NV 1670 SB12 (0.0m) - - 350 BH02 (0.5m) <100 all

C29-36 NV NV NV NV 180 SB12 (0.0m) - - <100 all <100 all

C10-C36 NV NV NV 1000 2630 SB12 (0.0m) - - 350 BH02 (0.5m) 520 0064SS05 (0.0m)

Notes:

Exceeded criteriaSoil resultsGroundwater resultsHuman HealthEcological HealthCriteria compared and exceedences shaded according to NEPM hierarchy

a = aestheticb = ANZECC (1992) Australian and New Zealand Guidelines for Assessment and Management of Contaminated Sitesc = other guideline value (Netherlands Ministry of Housing)d = SSD01 surface sample taken from drainage channel

DGBE disregarded as a COPC as per Section 4.3.2nv = no value- = not analysed

BTEX

Previous Reports - GHD (2008) Stage 2 Part II

PAH

TPH

Previous Reports - ERM (2007) Stage 1 & 2 Final

NSW EPA (1994)

Chemicals

Metals

Guidelines

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Tindal RAAF - Fire Training AreaTable T2 - Groundwater Concentrations for CoPC Screening

NHMRC (2004)

WHO (2004)

USEPA RSLs (2008)

USEPA provisional

(2009)

MDH (2008)

Anzecc (2000) 95%

GHD max Location ERM max LocationMaximum Reported

ConcentrationLocation

Drinking Drinking Drinking Drinking Drinking Eco GW Drinking/GW GW GW GW

mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

Arsenic 0.007 0.01 0.000045 NV NV0.0000024iii 0.0000013v

NV 0.018 MW04-MW08 0.011 MW02 0.01 064MW02

Barium 0.7 0.7 7.3 NV NV NV NV 1.9 MW05,MW07,MW08 - - 2.28 064MW05

Berrylium NV NV 0.073 NV NV NV NV <LOR (0.001) all - - - -

Cadmium 0.002 NV NV NV NV NV NV <LOR (0.0001) all <LOR (0.0001) all 0.0019 064MW02

Chromium 0.05 NV NV NV NV 0.001 NV 0.002 MW03 <LOR 0.001) all - -

Cobalt NV NV NV NV NV NV NV 0.037 MW07 - - 0.014 064MW05

Copper 2 NV NV NV NV 0.0014 NV 0.002 MW05, MW06 0.007 SSD01d 0.003 064MW02

Lead 0.01 NV NV NV NV 0.00340.01/ 0.001-

0.0050.014 MW06 <LOR (0.001) all - -

Magnesium NV NV NV NV NV NV NV - - - - - -

Manganese 0.5 0.4 0.88 NV NV 1.9 NV 7.16 MW04-MW08 - - - -

Mercury 0.001 NV NV NV NV NV NV <LOR (0.0001) all <LOR (0.0001) all - -

Nickel 0.02 0.02 0.73 NV NV 0.011 NV 0.075 MW01 - MW05 0.017 MW01 0.036 064MW03

Vanadium NV NV 0.18 NV NV NV NV 0.018 MW06 - - 0.11 064MW02

Zinc 3a NV NV NV NV 0.008 NV 0.01 MW01-MW09 0.026 MW03 0.018 064MW05

PFOA (PerFluoroOctanoicAcid) NV NV NV 0.0002 0.0003 NV NV 0.063 MW02 - - - -

PFOS (PerFluoro-Octane Sulphonate) NV NV NV 0.0004 0.0003 NV NV 0.085 MW02 5.2 MW02 - -

Benzene 0.001 NV NV NV NV 0.95 0.01/0.3 <LOR (0.001) all <5 (LOR 1)EP01, MW01, MW03, Q201,

SSD01- -

Toluene 0.8 NV NV NV NV NV 0.8/0.3 <LOR (0.002) all <5 (LOR 1) all - -

Ethylbenzene 0.3 NV NV NV NV NV 0.3/0.14 <LOR (0.002) all <5 (LOR 1) all - -

Xylene o NV NV NV NV NV 0.35 NV <LOR (0.002) all <5 (LOR 1) all - -

Xylene p NV NV NV NV NV 0.2 NV <LOR (0.002) all <5 (LOR 1) all - -

Total Xylenes 0.6 NV NV NV NV NV 0.6/0.38 <4 all - - - -

Anthracene NV NV NV NV NV NV NV <LOR (0.001) all <LOR (1) all - -

Benzo(a)pyrene 0.00001 NV NV NV NV NV 0.0001 <LOR (0.5) all <LOR (1) all - -

Fluoranthrene NV NV NV NV NV NV NV <LOR (0.001) all <LOR (1) all - -

Napthalene NV NV NV NV NV 0.016 NV <LOR (0.001) all <LOR (1) all - -

Phenanthrene NV NV NV NV NV NV NV <LOR (0.001) all <LOR (1) all - -

Total NV NV NV NV NV NV 0.001 <LOR (0.001) all <LOR (1) all - -

C06-C09 NV NV NV NV NV NV NV <LOR (0.02) all - - - -

C10-C14 NV NV NV NV NV NV NV 5.49 MW07 17.6 SSD01 - -

C15-28 NV NV NV NV NV NV NV 1.6 MW07 10.4 SSD01 - -

C29-36 NV NV NV NV NV NV NV 0.18 MW07 1.1 SSD01 - -

C10-C36 NV NV NV NV NV NV NV 7.27c MW07 29.1 SSD01 - -

Notes:

Exceeded criteriaSoil resultsGroundwater resultsHuman HealthEcological HealthCriteria compared and exceedences shaded according to NEPM hierarchy

a = aestheticb = ANZECC (1992) Australian and New Zealand Guidelines for Assessment and Management of Contaminated Sitesc = other guideline value (Netherlands Ministry of Housing)d = SSD01 surface sample taken from drainage channel

DGBE disregarded as a COPC as per Section 4.3.2nv = no value- = not analysed

PAH

Chemicals

TPH

BTEX

NSW EPA (1994)

GuidelinesPrevious Reports - GHD

(2008) Stage 2 Part IIENSR (2009)

Metals

Previous Reports - ERM (2007) Stage 1 & 2 Final

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Figures

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KATHERINE

DARWIN

PROJECT SITE

PROJECT SITE

Van Diemen Gulf

Kath

eri

ne

Riv

er

Kat

her

ine

Riv

er

VIC

TO

RIA

HIG

HW

AY

STUART HIGHWAY

STUART HIGHWAY

Uralla

Katherine EastKatherine East

Katherine SouthKatherine South

BIC

EN

TEN

NIA

LRO

AD

Cossack

Tindal Creek

Tindal Creek

G:\Projects\D\D11000_D11099\D11029 Tindal HHERA\D1102901 F1

F1

Figure

PROJECT ID

LAST MODIFIED

CREATED BY

D11029

TO

TO 17 06 2009

AECOM does not warrant the accuracy or completeness ofinformation displayed in this map and any person using it does soat their own risk. AECOM shall bear no responsibility or liability forany errors, faults, defects, or omissions in the information.

ENVIRONMENT

www.aecom.comDepartment of Defence

Human Health and Screening Ecological Risk

Assessment

Fire Training Area, RAAF Base, Tindal,

Northern Territory/Kimberley

Site Location

0 1500m

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Tindal FTA HHERAConceptual Site Model

Source Media Media Route

Staff/Trainee Fire Fighter

Maintenance/ Construction

Worker

Off-Site neighbour

Ecosystem

Ingestion x (runoff)Dermal x (runoff)

Inhalation (spray) x x x x

Ingestion x x

(fish/drinking/swimming)

Dermal x x xInhalation (vapour) x x x x

Ingestion x (dust)Dermal x (dust)

Inhalation (dust) x x

Ingestion x (trench) x xDermal x (trench) x x

Inhalation x (trench) x x

Ingestion x x x xDermal x x x x

Inhalation x x x x

Ingestion x x x xDermal x x x x

Inhalation x x x x

x = Non - Applicable Pathway = Potential Complete Pathway = Complete Exposure Pathway

Outdoor Air

Water

Soil

Air

Surface Water

Groundwater

Site surficial soil/sediment

Site suburface soil

Fire Training Area - Aqueous Fire Fighting Foam Dispersal Activities

Receptor

Indoor Air

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Appendix A

Site Layout

Figure 13 (GHD, 2008) Site Layout including CSR Locations

Figure 15 (GHD, 2008) Site Layout including BH and 064MW Location

Figure 2 (ERM, 2007) Site Layout including BH and 064MW Locations

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Appendix B

Dose Response Derivation

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Derivation of an Oral and Inhalation Reference Dose for PFOS and PFOA

The USEPA considers that epidemiological studies of exposure to PFOS and potential related adverse health outcomes in humans are inconclusive at present. The Office of Water (USEPA 2009) therefore has developed Provisional Health Advisory values for PFOA and PFOS to assess potential risk from exposure to these chemicals through drinking water.

The general equation used by the USEPA for the derivation of the Provisional Health Advisory is:

([NOAEL or BMDL10) x BW x RSC]) ÷ (UF x Extrapolation Factor x Water intake)

Where:

NOAEL = No Observed Adverse Effect Level in animal study selected

BW = body weight (child - 10kg);

RSC = relative source contribution (20% = 0.2 - to allow for background intake);

UF = uncertainty factor- interspecies extrapolation

EF = Extrapolation factor- adjusting for species internal half-life and elimination time

Water intake = (child - 1 litre per day)

The benchmark dose was identified by USEPA for PFOS following an evaluation of selected animal studies (USEPA 2009) and an NOAEL of 0.03 mg/kg/day was identified.

The extrapolation factor was based on consideration given by the USEPA to convert half-life data to clearance data in deriving the advisory.

The exposure scenario of a 10-kg child consuming 1 L/day of drinking water was identified as the most sensitive human receptor relationship to calculate the Provisional Health Advisories for PFOA and PFOS. This population subgroup was used because children, who consume more drinking water on a body weight basis than adults, have a higher exposure on a body weight basis than adults.

A default relative source contribution of 20% was used to allow for exposure from other sources such as food, dust and soil.

Using these methods, the USEPA derived a provisional health advisory for PFOA of 0.4 g/L and for PFOS of 0.2 g/L.

The advisory is identified by the USEPA to be for subchronic exposure.

The value is considered by the USEPA as protective of all population subgroup and life stages.

AECOM has used these advisories to develop an allowable oral ingestion dose for the purposes of screening potential exposures to PFOS and PFOA at the FTA site as follows:

[Provisional Health Advisory ( g/L) x consumption (L/d)] ÷ Body Weight (Kg)

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Hence for PFOA:

Allowable dose = [0.04 x 1] ÷ 10 = 0.04 g per kg per day

X 10-3 conversion factor micrograms to milligrams

Allowable dose = 0.04 x 10-3 mg per kg per day [4 x 10-5 mg per kg per day]

Hence for PFOS:

Allowable dose = [0.02 x 1] ÷ 10 = 0.02 g per kg per day

X 10-3 conversion factor micrograms to milligrams

Allowable dose = 0.02 x 10-3 mg per kg per day [2 x 10-5 mg per kg per day]

These allowable dose derivations have been applied for screening the risks to oral exposure to PFOS and PFOA in the absence of other available guidance from Australian sources, consistent with approaches used in Australia to apply national drinking water dose guidance to oral exposures of chemicals (NHMRC 2004).

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Appendix C

Staff/Trainee Fire fighter Modelling Results

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APPENDIX C

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Maintenance/Construction Worker Modelling Results

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On-site and Off-site Residential Modelling Results

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APPENDIX E

RISK SUMMARY

Off Site Neighbour - Fishing/Drinking/Swimming

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Tindal Ecological Species List

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Table of Species or Species Habitat likely to occur at or near the Site

Threatened Status Scientific name Common name

National NT Other notes Source

AMPHIBIANS/REPTILES

Carettochelys insculpta Pig-nosed Turtle Recently nominated as VU

Near Threatened

significance attached because of iconic status on the Daly River NLWRA (2005)

Crocodylus johnstoni Freshwater Crocodile Listed NLWRA (2005)

Crocodylus porosus Crocodile significance attached because of exploitation and public safety issues NLWRA (2005)

Natator depressus Flatback Turtle VU DD NLWRA (2005)

Frogs/Toads observed at Landfill site (NT0267) RAAF Base

ERM 2007 – Landfill Investigation

BIRDS

Amytornis woodwardi White-throated Grasswren VU (Nitmiluk) NLWRA (2005)

Anseranas semipalmata Magpie Goose significance attached because it is a major food resource, and focus for recreational hunting

NLWRA (2005)

Apus pacificus Fork-tailed Swift Migratory NLWRA (2005)

Ardea alba Great Egret, White Egret Migratory NLWRA (2005)

Ardea ibis Cattle Egret Migratory NLWRA (2005)

Charadrius veredus Oriental Plover, Oriental Dotterel Migratory NLWRA (2005)

Coracina tenuirostris melvillensis Melville Cicadabird Migratory NLWRA (2005)

Erythrotriorchis radiatus Red Goshawk VU VU NLWRA (2005)

Erythrura gouldiae Gouldian Finch EN EN Migratory NLWRA (2005)

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Falcunculus (frontatus) whitei

Northern (crested) shrike-tit

(VU) DD Migratory NLWRA (2005)

Geophaps smithii Partridge Pigeon VU NT NLWRA (2005)

Glareola maldivarum Oriental Pratincole Migratory NLWRA (2005)

Haliaeetus leucogaster White-bellied Sea-Eagle Migratory NLWRA (2005)

Merops ornatus Rainbow Bee-eater Migratory NLWRA (2005)

Numenius minutus Little Curlew, Little Whimbrel Migratory NLWRA (2005)

Poecilodryas superciliosa cerviniventris

Derby White-browed Robin Migratory NLWRA (2005)

Tyto novaehollandiae kimberli

Masked Owl (north Australian mainland subspecies)

VU NLWRA (2005)

FISH

Glyphis sp. River shark CE EN NLWRA (2005)

Lates calcarifer Barramundi significance attached because of its focus for recreational fishing industry NLWRA (2005)

Melanotaenia australi Western rainbowfish found in Katherine River Douglas, M., and Kennard, M.(2007)

Pristis microdon Freshwater Sawfish VU VU NLWRA (2005)

Syncomistes butleri Butlers grunter fish found in Katherine River Douglas, M., and Kennard, M.(2007)

INSECTS

Petasida ephippigera Leichhardt’s grasshopper VU (Nitmiluk) NLWRA (2005)

Setobaudinia victoriana land-snail VU NLWRA (2005)

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MAMMALS

Conilurus penicillatus Brush-tailed Rabbit-rat VU NLWRA (2005)

Dasyurus hallucatus Northern Quoll Nominated as VU VU NLWRA (2005)

Phascogale (tapoatafa) pirata

(Northern) brush-tailed phascogale VU NLWRA (2005)

Xeromys myoides False water-rat (Watermouse) VU DD NLWRA (2005)

PLANTS

Acacia praetermissa VU A Wattle-like shrub NLWRA (2005)

Andropogon gayanus Gamba Grass observed at Landfill site (NT0267) RAAF Base

ERM 2007 – Landfill Investigation

Boronia tolerans VU VU Small flowering shrub NLWRA (2005)

Boronia verecunda VU Small flowering shrub NLWRA (2005)

Clausena D39161 Tipperary

NLWRA (2005)

Cycas armstrongii VU Cycad NLWRA (2005)

Heliotropium amnis-edith A wildflower NLWRA (2005)

Hibiscus vitifolius tropical rose mallow VU NLWRA (2005)

Lithomyrtus linariifolia VU A wildflower NLWRA (2005)

Nervilia plicata EN An orchid NLWRA (2005)

Schoutenia ovata VU NLWRA (2005)

Sphaerostephanos unitus A fern NLWRA (2005)

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Spirogyra spp. benthic macroalgae Considered significant by Erskine et al. as a significant baseline resource for aquatic food webs.

NLWRA (2005)

Utricularia singeriana EN A carnivorous bladderwort NLWRA (2005)

Vacoparis macrospermum NLWRA (2005)

Vallisneria nana Ribbon weed significance attached because it is the principal food resource for pig-nosed turtles, and a possible indicator of water quality

NLWRA (2005)

Zeuxine oblonga VU An orchid NLWRA (2005)

Note:

Acronyms for conservation status: CE=critically endangered; EN=endangered; VU=vulnerable, NT=near threatened, DD=data deficient

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human health and screening ecological risk assessment fire

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