REPORT - der.wa.gov.au · The DER has a role in implementing the Environmental Protection Act 1986...

July 2016

THEVENARD ISLAND RETIREMENT PROJECT

Remedial Action Plan

Chevron Document Number: ABU140900084

REPO

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Report Number. 127643109-119-R-Rev5 Distribution: 1 Electronic Copy – Chevron Australia Pty Ltd 1 Electronic Copy – Golder Associates Pty Ltd

Submitted to: Jennifer Brauhart Chevron Australia Pty Ltd Level 14/34F, QV1 Building 250 St Georges Terrace PERTH WA 6000

THEVENARD ISLAND – REMEDIAL ACTION PLAN

Table of Contents

1.0 INTRODUCTION ........................................................................................................................................................ 1

1.1 General ......................................................................................................................................................... 1

1.2 Purpose ........................................................................................................................................................ 1

1.3 Interaction with Supporting Project Documentation ...................................................................................... 1

1.4 Objective of the Remedial Action Plan .......................................................................................................... 2

1.5 Scope of Remedial Action Plan .................................................................................................................... 2

1.6 Structure of Remedial Action Plan ................................................................................................................ 3

2.0 ROLES AND RESPONSIBILITIES FOR REMEDIATION ......................................................................................... 4

2.1 Chevron ........................................................................................................................................................ 4

2.2 Environmental and Civil Consultant .............................................................................................................. 4

2.2.1 Environmental Construction Quality Assurance (ECQA)......................................................................... 5

2.2.2 Civil Construction Quality Assurance (CCQA) ........................................................................................ 5

2.2.3 Environmental Auditor ............................................................................................................................. 5

2.2.4 Remediation Contractor .......................................................................................................................... 6

3.0 OVERVIEW OF SITE SETTING ................................................................................................................................ 7

3.1 Site Description and Operations ................................................................................................................... 7

3.2 Geology and Hydrogeology .......................................................................................................................... 7

4.0 FRAMEWORK FOR REMEDIATION WORKS ........................................................................................................ 10

4.1 Legislative Framework ................................................................................................................................ 10

4.2 Remediation Contaminants of Interest ........................................................................................................ 10

5.0 END USE OF SITE AND REMEDIATION APPROACH .......................................................................................... 11

5.1 End Use of Site ........................................................................................................................................... 11

5.2 Summary of Risk Assessment .................................................................................................................... 11

5.3 Remediation of TRH impacted Soil & Reintegration of Cement Containing Materials ................................ 12

5.3.1 Approach ............................................................................................................................................... 12

5.3.2 Soil Assessment Criteria ....................................................................................................................... 14

5.4 Groundwater Remediation and Management ............................................................................................. 15

5.4.1 Remediation and Management Approach ............................................................................................. 15

5.4.2 Groundwater Assessment Criteria ........................................................................................................ 15

6.0 REMEDIATION EXECUTION STEPS...................................................................................................................... 16

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6.1 Overview ..................................................................................................................................................... 16

6.2 Preliminary Works ....................................................................................................................................... 16

6.2.1 Site Establishment and Management Plans .......................................................................................... 16

6.2.2 Set Out the Excavations ........................................................................................................................ 16

6.2.3 Materials Tracking System .................................................................................................................... 17

6.3 Excavate, Segregate and Transfer Materials .............................................................................................. 17

6.3.1 Excavate materials ................................................................................................................................ 17

6.3.2 Validation .............................................................................................................................................. 18

6.3.3 Surveys and Quantities ......................................................................................................................... 18

6.3.4 Crushing of CCM................................................................................................................................... 18

6.3.5 Transfer Material to the Amendment Facility ......................................................................................... 18

6.4 Amendment of TRH Impacted Soil ............................................................................................................. 18

6.5 Generation of Final Landform ..................................................................................................................... 20

6.5.1 Placement ............................................................................................................................................. 20

6.5.2 Surveys ................................................................................................................................................. 21

6.6 Reporting .................................................................................................................................................... 22

7.0 VALIDATION OF SOIL REMEDIATION .................................................................................................................. 23

7.1 Validation of Excavation Extent .................................................................................................................. 23

7.1.1 Validation Approach .............................................................................................................................. 23

7.1.2 Validation Sampling Density Guidelines ................................................................................................ 24

7.1.3 Application of the Assessment Criteria to Validation ............................................................................. 24

7.2 Soil Remediation and CCM Reintegration End Point Criteria ..................................................................... 25

7.3 Contingency Plan ........................................................................................................................................ 25

7.4 Reporting .................................................................................................................................................... 25

8.0 GROUNDWATER REMEDIATION AND MANAGEMENT VALIDATION ................................................................ 26

8.1 Validation Approach .................................................................................................................................... 26

8.1.1 Site Management Plan .......................................................................................................................... 26

8.2 Groundwater End Point Criteria .................................................................................................................. 26

8.2.1 Contingency Plan .................................................................................................................................. 27

8.2.2 Reporting .............................................................................................................................................. 28

8.3 Quality Assurance and Quality Control Requirements ................................................................................ 28

9.0 ENVIRONMENTAL AUDIT ...................................................................................................................................... 29

9.1 Auditor Liaison ............................................................................................................................................ 29

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9.2 Expected Audit Outcome ............................................................................................................................ 29

10.0 REFERENCES ......................................................................................................................................................... 30

TABLES Table 1: Soil Assessment Criteria ..................................................................................................................................... 14

Table 2: Groundwater Assessment Criteria ....................................................................................................................... 15

Table 3: Minimum recommended validation samples and spacing (from AS 4482.1 2005) .............................................. 24

Table 4: Soil Remediation and CCM Reintegration End Point Criteria .............................................................................. 25

Table 5: Groundwater MNA Validation End Point Criteria ................................................................................................. 27

Table 6: Groundwater Risk to Receptors End Point Criteria ............................................................................................. 27

FIGURES Figure 1: Thevenard Retirement Project – Site Deliverables Flow Chart ............................................................................ 2

Figure 2: Thevenard Island and Approximate Site Boundary .............................................................................................. 8

Figure 3: Current Onshore Processing Facility (including APEC boundaries) ..................................................................... 9

Figure 4: Indicative Profiles of Final Landform .................................................................................................................. 14

Figure 5: Remediation Flow Chart ..................................................................................................................................... 16

Figure 6: Profile 1 of Final Landform ................................................................................................................................. 20



APPENDICES APPENDIX A Key Soil Remediation Information

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List of Acronyms Acronym Definition

APEC Area of Potential Environmental Concern API Separator Refers to the Oil/Water Separator in APEC A that uses the American Petroleum Institute design bgl Below Ground Level BTEXN Benzene, Toluene, Ethylbenzene, Xylenes, Naphthalene CALM Department of Conservation and Land Management CCQA Civil Construction Quality Assurance CCM Cement Containing Materials COI Chemical of Interest CSM Conceptual Site Model CSS Cement Stabilised Sand DEC Department of Environment and Conservation (now DER) DEP Department of Environmental Protection (now DER) DER Department of Environment Regulation DoE Department of Environment (now DER) DSI Detailed Site Investigation DQO Data Quality Objective ECQA Environmental Construction Quality Assurance EIL Environmental Investigation Level ESA Environmental Site Assessment ESL Environmental Screening Level GMP Groundwater Monitoring Plan HIL Health Investigation Level HSL Health Screening Level LEL Lower Explosive Limit LOR Limits of Reporting MIPL Mackerel Islands Pty Ltd MNA Monitored Natural Attenuation MSDS Material Safety Data Sheet NEPM National Environmental Protection Measure PAHs Polycyclic Aromatic Hydrocarbons PID Photoionisation Detector RAP Remedial Action Plan RCE Remedial Cost Estimate SMP Site Management Plan SVOC Semi-volatile Organic Compounds TDS Total Dissolved Solids TOC Total Organic Carbon TPH Total Petroleum Hydrocarbon TVI Thevenard Island VOC Volatile Organic Compounds QA/QC Quality Control/Quality Assurance

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Key Terms Term Definition

COI

The chemicals of interest (COI) are those chemicals for which remediation or management actions are planned to mitigate risk. These COIs are specifically hydrocarbon constituents (TRH for soil and TRH, Naphthalene and BTEX for groundwater).

Soil Assessment Criteria

COI concentrations for soil that are applicable to the remediation project based on the proposed end use for the site. The Soil Assessment Criteria are used to select the TRH impacted soil for remediation.

TRH Impacted Soil Soil on the site where TRH concentrations exceed the Soil Assessment Criteria.

Groundwater Assessment Criteria

Groundwater Assessment Criteria are applied to groundwater monitoring results to evaluate the potential risk to receptors during the remediation and management approach.

Impacted Groundwater Groundwater on the site where contaminant concentrations exceed the Groundwater Assessment Criteria.

End Point Criteria

End Point Criteria are used to validate that the soil and groundwater remediation outcomes have been achieved in accordance the outlined approach. These End Point Criteria include metrics such as chemical properties, e.g., MNA parameters such as the extent of PSH, DPH plume stability and geochemistry, and spatial factors, e.g., depth and location for placement of amended soil and CSS, depth and location for placement of CCM, final landform profile.

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1.0 INTRODUCTION 1.1 General Chevron Australia Pty Ltd (Chevron) engaged Golder Associates Pty Ltd (Golder) to provide environmental site investigation services for Thevenard Island (TVI) and Tubridgi Gas Metering Station (Tubridgi) in Western Australia.

While TVI and Tubridgi are collectively referred to as the TVI Asset, Tubridgi is geographically separate from TVI. The focus of this document is the remedial action plan (RAP) for Thevenard Island, and as such the Tubridgi site is not discussed further in this document. Assessments conducted at the Tubridgi site are covered under a separate Detailed Site Investigation report.

Since 1988, Chevron has operated an oil and gas production facility (‘the site’) within an area on the eastern end of TVI. TVI is a Nature Conservation Reserve and is Part of Crown Reserve No. 33174. The WA Department of Parks and Wildlife (DPaW) has stewardship and management responsibilities for the island. The DER has a role in implementing the Environmental Protection Act 1986 (EPA, 1986) and Contaminated Sites Act 2003 (DER, 2007).

Chevron is currently undergoing decommissioning and retirement of its facilities on TVI, with the view towards undertaking site remediation and obtaining relinquishment of its lease. The overall TVI Retirement Project will entail plug and abandonment of production wells, decommissioning of onshore infrastructure and facilities, decommissioning of offshore pipelines and platforms and rehabilitation and remediation of the environment.

Chevron has defined an End State Vision for the remediation of the site. The End State Vision is Chevron’s goal for the final condition of the site and forms the basis for Chevron’s remediation approach as presented in Chevron’s Decommissioning and Rehabilitation Plan (Chevron 2014) as presented to the Department of Mines and Petroleum, the Office of the Environmental Protection Authority, the Department of Parks and Wildlife, the Department of Environmental Regulation, Department of Transport, Pilbara Ports Authority and the Shire of Ashburton.. The End State Vision is to:

Restore to a condition similar and compatible with the adjacent environment

The site is currently classified as “Contaminated – Remediation Required” by the Department of Environment Regulation (DER). For Chevron to relinquish the site lease back to DPaW, the site is required to be reclassified through remediation and/or a risk assessment to a classification of “Remediated – Restricted Use”. This will be achieved through the completion of a contaminated sites Audit, conducted by a Department of Environment Regulation (DER) Accredited Contaminated Sites Auditor, and through the submission of a Mandatory Auditor Report (MAR) to the DER. The DER accredited Environmental Auditor engaged to complete the MAR is Mr Jeremy Hogben of Environmental Resources Management (Australia) Pty Ltd (ERM).

1.2 Purpose The purpose of the RAP is to outline the remediation approach for soil and groundwater at TVI for auditor and regulatory approval. The RAP is to outline how to remediate, and how to validate remediation is complete in order to support site reclassification under the Contaminated Sites Act (2003).

Once approved, the remediation approach within the RAP is to be adhered to by the remediation contractor, notwithstanding that detailed plans and work instructions are to be developed to manage the job within the bounds of the approved RAP.

1.3 Interaction with Supporting Project Documentation The RAP draws upon on analysis and interpretation from supporting project documentation, including the Remediation Framework Document (Golder, 2015a), Detailed Site Investigations (Golder, 2013a, 2013b 2014f) and Conceptual Site Models (Golder, 2012a; 2015b). A flowchart showing the relationship between key supporting project documentation is shown in Figure 1.

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Set out the requirements for the application of the Soil Assessment Criteria and undertaking the validation of the works either through the use of existing data, additional pre-excavation detailed site investigation (DSI), or sampling during excavation works.

Establish validation protocols for managing the remediation works, including material tracking. Establish validation protocols to confirm that remediation is complete, and that the remediation

approach has been achieved.

1.6 Structure of Remedial Action Plan The structure of the RAP is as follows:

Section 2.0: The roles and responsibilities of the remediation project stakeholders. Section 3.0: An overview of the site setting. Section 4.0: Legislative context and contaminants of interest (COIs). Section 5.0: Remediation Approach. Provides an overview of the remediation approach for soil and

groundwater and reintegration approach for cement containing materials from the Remediation Framework Document. It includes a summary of relevant risks to human and ecological receptors posed by contaminated soil, contaminated groundwater and cement containing materials. It also includes Assessment Criteria for soil and groundwater COIs that are applicable to the RAP.

Section 6.0: Remediation Methodology. Provides the execution steps that are to be followed to implement the remediation approach for TRH impacted soil and reintegration of CCM in to the final landform.

Section 7.0: Validation of Soil Remediation. Defines the validation activities that will be undertaken prior to, during and post remediation. Defines the End Point Criteria that validate the completion of the remediation of soil and reintegration of CCM into the final landform.

Section 8.0: Validation of Groundwater Remediation. Defines the validation activities that will be undertaken prior to, during and post remediation for groundwater as well as the End Point Criteria that will be used to validate completion of groundwater remediation.

Section 9.0: Environmental Audit and site reclassification, which includes the expected Auditor liaison and Environmental Audit outcome of the remediation works.

Appendix A provides a list of the key steps of the remediation works, the key soil amendment parameters and the Soil Assessment Criteria.



2.0 ROLES AND RESPONSIBILITIES FOR REMEDIATION 2.1 Chevron Chevron is the current lease holder of the site and as part of relinquishing its lease there are legal and regulatory obligations for the remediation and rehabilitation of the site. Chevron has also defined an End State Vision that defines the overall objective with respect to the remediation of the lease area.

Chevron is responsible for remediating and rehabilitating the site in accordance with the relevant regulatory requirements by:

Engagement of an Environmental and Civil Consultant to conduct the necessary assessment works, and provide advice on the remediation approach. Within this role is this provision of on-site personnel for environmental or civil construction quality assurance (ECQA or CCQA) who will conduct verification and validation of the remediation works and generation of the final landform.

Engagement of an Environmental Auditor to audit the assessment, remediation, validation and verification processes.

Engagement of a Remediation Contractor, based on the results of a tender evaluation process, to execute the remediation.

2.2 Environmental and Civil Consultant The Environmental and Civil Consultant is responsible for providing advice on site management and civil construction aspects of the remediation works. The Environmental and Civil Consultant also provides support to Chevron in the form of on-site personnel, termed the Environmental Construction Quality Assurance (ECQA) and Civil Construction Quality Assurance (CCQA). These sub-roles are discussed in the following sub-sections.

The Environmental Consultant also provides support to Chevron in relation to the following:

Integrating remediation with future land use considerations Managing the Environmental Auditor requirements Managing the site data through a GIS and associated database system Developing an integrated cost plan to support remediation planning. Whilst the Auditor is engaged by Chevron, the Environmental Consultant (and ECQA) is to be responsible for assisting Chevron with managing the technical process, negotiation and outcomes with the Auditor that are required to be achieved through the audit process.

The Environmental Consultant (and ECQA) role during the site remediation is to assist in resolving environmental issues as they arise, to undertake verification of compliance with Commonwealth and Western Australia regulations and legislation, and validate remediation completion.



2.2.1 Environmental Construction Quality Assurance (ECQA) During the remediation works, on-site environmental personnel are to be present to oversee environmental aspects of the works, and provide independent oversight that the remediation approach is being implemented in accordance with the remediation contract. Therefore, the ECQA is likely to be responsible for:

Monitoring of the works conducted by the Remediation Contractor to confirm adherence to the remediation contract. It is not the ECQA’s role to direct the Remediation Contractor, however, the ECQA may, when required, provide advice to the Remediation Contractor based on the results of verification or validation sampling conducted by the ECQA.

Assessment of the presence of, and/or the concentration of, contaminants during excavation or amendment of TRH impacted material (validation sampling).

Validation of amendment of TRH impacted material. This is likely to be conducted through systematic sampling of remediated material to verify the material has reached the remedial target.

Coordination of laboratory testing and reporting of analytical results for samples obtained during validation sampling.

Conduct air monitoring to ensure that excessive levels of dust are not generated during the demolition/remediation works, including in administration areas, and to assess levels of VOCs and potentially fibrous materials in proximity to works where these contaminants may be present.

2.2.2 Civil Construction Quality Assurance (CCQA) During the earthworks, on-site civil personnel are to oversee activities during excavations and generation of the final landform. The CCQA is likely to be responsible for:

Recording of compaction control testing (as required) undertaken by Remediation Contractor. Inspection and approval of anchor trenches (as required). Inspection and approval of earthworks items as instructed by Chevron as part of the remediation

works.

Collation and reporting of tests conducted to be reported to Chevron to ensure the Remediation Contractor adheres to the remediation works.

2.2.3 Environmental Auditor The site is currently subject to an Environmental Audit in accordance with the Contaminated Sites Act 2003. The Environmental Auditor’s responsibilities include, but are not limited to, the following:

Ensuring the methods used in the assessment of TRH impacted material and remediation are to a standard commensurate with the final proposed land use.

Review and endorsement of the Remediation Framework Document, RAP, and the associated objectives, strategies, processes and outcomes to be achieved during the remediation.

Liaison with DER as required. Review and endorsement of other key deliverables for the project. Provide guidance and recommendations to DER for the reclassification of the site from “Contaminated –

Remediation Required” to “Remediated – Restricted Use” as appropriate confirming the adequacy of the assessment and remediation.



2.2.4 Remediation Contractor The Remediation Contractor’s responsibilities include but are not limited to the following:

Adherence to the tender specification and remediation contract. Preparation of and implementation and compliance with the project deliverables. These include the

following key documents: a logistics programme, health, safety and environment plan, excavation method statement, soil blending method statement, material placement plan and material stockpile inventory. However, other documents may also be required.

Compliance with all relevant Commonwealth and Western Australia legislation. Undertaking and completing the remedial works in accordance with the requirements of this RAP and

the Remediation Contract.

Identify features, such as roads or vegetation, to be retained throughout the remediation works and protecting these features during works.

Liaison with the ECQA and CCQA to ensure validation of excavations, remediated material and other relevant testing is undertaken throughout the remedial works.

Regular liaison with Chevron regarding progression of the remediation works. Collation and provision of all documentation related to the remedial works to verify works occur in

accordance with the remediation approach, and to validate completion of remediation per the approach.

Further details of the responsibilities of the Remediation Contractor are contained in Section 6.0.



3.0 OVERVIEW OF SITE SETTING The Section provides an overview of the Site. Further details of the Site setting can be found in relevant supporting documentation (refer to Section 10.0).

3.1 Site Description and Operations TVI is located approximately 25 km north north-west of Onslow and 65 km south-west of Barrow Island in Western Australia (Figure 2). TVI is a low and relatively flat, vegetated, mid-shelf cay approximately 5 km long by 1 km wide. The island surface primarily consists of dune ridges to approximately 5 m in height. Three geomorphic units are present: a fore dune; an island ridge system, comprising linear ridges and swales; and a coastal Aeolian platform.

The Chevron lease covers an area of approximately 33.4 hectares. It has been predominantly cleared and levelled to accommodate the onshore facilities (Figure 3). The majority of the process plant was constructed on an excavated area lower than original ground level. Further details of the Site setting are contained in the Preliminary Site Investigation (Golder, 2012b).

The southern part of the lease area includes the extreme eastern end of TVI’s airstrip (which is shared with Mackerel Island Pty Ltd (MIPL)), plus the chemical storage area, oil and gas wells, and the jetty.

Exploration and production operations have been conducted on TVI and surrounding areas since the early 1960s. The first oil was produced on TVI in 1989. Oilfield operations are conducted under petroleum production leases TL/4 and TL/7 and a pipeline licence (TL/15), which are administered by the Department of Mines and Petroleum (DMP). At the time the approvals were granted for the site, the operating company was West Australian Petroleum Pty Ltd (WAPET).

Chevron production facilities included oil and gas production wells, processing, storage and distribution facilities which are primarily concentrated in the north-eastern portion of TVI (Figure 3).

Roads within the lease area are constructed using either a cement stabilised sand (CSS) base with a (cement based) paver top layer, or from CSS (typically not thoroughfares), or they are sandy tracks.

Much of the process plant site (approximately 40% of the lease area) is covered by hardstand or impermeable bunding. Other buildings at the site, e.g. accommodation and administration facilities, the warehouse, the chemical store, and the production office, are constructed with either concrete slab or are anchored demountable structures.

3.2 Geology and Hydrogeology TVI formed as an accumulation of sediment over coral. Geology at the Site is generally described as upper layers of sand and gravelly sand underlain by calcarenite containing an interbedded layer of limestone and lenses of gravelly sand/gravelly clay calcarenite (Golder, 2012a).

Unconfined superficial groundwater predominantly flows within the gravelly sand and upper calcarenite. Although there is some degree of stratification in the geology, groundwater level results from across the site indicate the aquifer displays the properties of an isotropic, porous medium (Golder, 2012a).

Groundwater occurs beneath the site between 1 to 7 m bgs, varying according to topography and proximity to the coast. Groundwater consists of a thin lens (approximately 7 m thick) of fresh to brackish water (as a result of recharge and infiltration) overlying more saline waters.



Figure 2: Thevenard Island and Approximate Site Boundary



4.0 FRAMEWORK FOR REMEDIATION WORKS 4.1 Legislative Framework The principal legislative framework for the identification and management of contaminated sites in Western Australia (WA) is the Contaminated Sites Act 2003 (GoWA, 2003). The principal legislative framework for environment protection and pollution control in Western Australia is the Environment Protection Act 1986 (GoWA, 1986)

As per guidance from the DER, the Contaminated Sites Act (2003) should be used in conjunction with the National Environment Protection (Assessment of Site Contamination) Measure 1999 (NEPM) amended 2013 (NEPM, 2013).

4.2 Remediation Contaminants of Interest Based on the results of investigations undertaken at the site, remediation contaminants of interest (COIs) for soil are:

TRH fractions >C10-C16 (F2) and >C16-C34 (F3). With regard to groundwater, the following contaminants are remediation COIs:

TRH fractions >C10-C16 (F2) and >C16-C34 (F3) Benzene, Toluene, Ethylbenzene and Xylenes Naphthalene.



5.0 END USE OF SITE AND REMEDIATION APPROACH 5.1 End Use of Site The End State Vision states that the remediation project is to restore the lease area to a condition similar and compatible with the adjacent environment. Therefore, the TVI Retirement Project aims to generate a landform that is compatible with the adjacent TVI environment, which is, as stated in the CSM (Golder, 2012): a relatively flat and vegetated cay with a fore dune, island ridge system and a coastal aeolian platform.

To guide the development of the remediation approach, risk assessments for soil, groundwater, and cement containing materials were undertaken. The following section provides an overview of the findings from those risk assessments. This is followed by the remediation approach for soil and groundwater, which satisfy the proposed end use. The soil remediation approach also includes the approach for reintegration of cement containing materials.

5.2 Summary of Risk Assessment A risk assessment was undertaken using the results from assessments of soil, groundwater and cement containing materials. This incorporated the anticipated future site use to establish the potential risk to future receptors based on complete source-pathway-receptor linkages. The results of this assessment are as follows:

Groundwater: Dissolved phase petroleum hydrocarbons are present within Area of Potential Environmental Concern A (APEC A – process plant, Oil/Water separator1 (known as the API Separator) and wash-down drain areas), and APEC L – Saladin C pipeline leak location (refer to Figure 3 for the location of these APECs). Investigations indicate that these impacts are inferred to be degrading through natural attenuation, with the spatial extent of impacts decreasing with time. Further, investigations to date show that the impacts are not discharging into the marine environment. Therefore, the potential risk to the marine environment is considered negligible.

Groundwater contamination exists on the site in localised areas above criteria that are protective of drinking water. It is assumed that any future use of groundwater on site as a potable water source (post-lease relinquishment) would be sourced through groundwater extraction with treatment. Given that groundwater at TVI is generally brackish to saline due the proximity to the ocean, the use of untreated shallow drinking water as a potable water source would not be expected. As such, the use of potentially-impacted groundwater as a drinking water is not considered an operable exposure pathway for human receptors without treatment.

Monitoring indicates that contamination is not currently present at the MIPL lease boundary. The results of conservative numerical groundwater modelling of Saladin C impacts indicates that groundwater from the Saladin C leak area has the potential to migrate off ssite, and as such identified areas where it is suggested that groundwater should not be extracted. Chevron has provided a map to MIPL containing exclusion zones where it has recommended no bores be drilled, so that MIPL does not cause or contribute to contamination on its own lease. MIPL has installed three groundwater extraction wells on the MIPL lease which are not located within this exclusion zone.

Groundwater, Vapour: Within the Chevron lease area, exposure from soil vapour generated from TRH impacted groundwater to outdoor and indoor air was considered a potentially complete pathway, however, concentrations measured in groundwater for the majority of the site will not likely pose a risk.

Further details of the groundwater assessment work undertaken are contained in the Remediation Framework Document (Golder, 2014c).

1 The oil/water separator is also commonly referred to as the API Separator (e.g. American Petroleum Institute design Oil/Water Separator)).



Soil: There are concentrations of TRH that exceed the Soil Assessment Criteria that may indicate a potential risk from direct contact to terrestrial flora and fauna. Therefore, remediation is proposed for these areas of soil impacts. An overview of the proposed remedial approach for soil is contained in Section 5.3.1. Criteria protective of human health for TRH in shallow soils are greater than those proposed for protection of ecological receptors and hence the remedial approach will be protective of these receptors for a future recreational/open space use.

Soil, Vapour: Soil results were also assessed for their potential risk of exposure via the outdoor or indoor air vapour intrusion pathway to commercial or recreation human receptors based on the anticipated future land use scenario. However, the concentrations measured in soil for the majority of the site are not likely to pose a risk via the vapour intrusion to commercial or recreation human receptors.

Further details of the soil assessment work undertaken are contained in the Remediation Framework Document (Golder, 2014c).

CCM: Cement containing materials, which include cement stabilised sand (CSS), pavers and other concrete materials, were assessed for their potential re-use in site rehabilitation. The results from CCM assessments reported elevated pH in leachability testing, however, it was assessed during the material characterisation study that the elevated pH would be sufficiently buffered by groundwater (Golder 2014e).

With respect to CSS, results reported that the metal median concentrations were below the relevant ecological criteria and/or relatively similar to background concentrations.

With respect to concrete/pavers, the majority of metals were either below relevant ecological criteria and/or relatively similar to background with the exception of aluminium and hexavalent chromium. However, leachability tests undertaken during the materials characterisation study, indicated that aluminium did not leach in any significant concentrations compared to background, and that due to the hydraulic conditions at the site, concentrations of hexavalent chromium were not likely to exceed relevant criteria in the groundwater (Golder 2014e).

Therefore, results from the assessment of CCM do not indicate a significant risk is posed to the terrestrial flora or fauna, and that there is no apparent impediment to CCM being re-used on site.

Although the results indicate no risk from a contaminated sites perspective, growing conditions within 100% crushed CSS may be sub-optimal for plant establishment due to other aspects (e.g. physical properties such as soil structure). These potentially sub-optimal conditions have been considered in developing the scope of works required to establish the final landform for the site and re-integration of CCM.

5.3 Remediation of TRH impacted Soil & Reintegration of Cement Containing Materials

5.3.1 Approach The remedial approach for TRH impacted soil, and the reintegration approach for CCM, is to reinstate the final landform using on-site materials such that it is similar and compatible with the adjacent environment. Material balances have been assessed and final landform elevation mapped to confirm that the final landform can accommodate the proposed material types and layering presented. TRH impacted soil and CCM are to be prepared for reinstatement in the final landform by implementing the following approach:

1) Excavate all CCM (cement stabilised sand, concrete/pavers) and crush. For details of crush size and crushing procedure, see Section 6.3.4.

2) Where it is assessed (prior to or during remediation) that soil impacts exceed the Soil Assessment Criteria (Table 1), these impacts are to be excavated to 1.5 m below the proposed final ground surface. This will include unexpected finds of TRH impacted soil encountered during decommissioning and/or remediation.



3) Soil below 1.5 m below the proposed final ground surface is to remain in situ as it is considered that there are minimal exposure pathways to ecological receptors, and the risk of ongoing impacts to groundwater is low. This forms Component A of Profile 1 of the proposed final landform (Figure 4).

4) The excavated TRH impacted soil (from item 1 above) is to be transferred to the on-site amendment area and amended with a portion of the excavated CSS at a ratio of 1:1, before reintegration into the final landform at 1.5 m below the proposed final ground surface within the footprint or up hydraulic gradient of areas of known historical groundwater impacts. Amended soil forms Component B of Profile 2 (Figure 4). For details on the amendment procedure see Section 6.4.

5) Remaining CCM (cement stabilised sand, concrete/pavers) are to form Component C of Profile 3 and be reintegrated into the landform at 1.5 m bgs (Figure 4).

6) All reinstated amended soil (Component B of Profile 2) and CCM (Component C of Profile 3) are to be placed within the inland portion of the island, inland of the erosion setback (i.e. back from the dunal areas).

7) The top 1.5 m of the final landform is to be shaped using endemic “clean” soil.

Notes:

a) TRH impacted CSS is to be amended as per TRH impacted soil, then reinstated per Component B of Profile 2.

b) TRH impacted concrete/pavers are to be reinstated directly without amendment, however only in areas within the footprint or up hydraulic gradient of areas of known historical hydrocarbon impact, i.e. reinstated as per Component B of Profile 2.

c) There is the potential that CSS may be reincorporated within 0 – 1.5 m of final landform surface if amended with endemic “clean” soil (50%:50%) based on the results of the plant trials. This is to be confirmed through further trials. An addendum to the RAP may be created at a later date to incorporate specific requirements for this portion of the profile including the specific depth range in which this material can be used.

d) Unexpected finds of TRH will be assessed based on field screening, subjective visual and olfactory observations of heavily stained soils, strong hydrocarbon odours or the presence of phase separated/residual hydrocarbons. Where encountered during the decommissioning and/or remediation these soils will be managed in accordance with the remediation process outlined above.

For further details of the landform configuration see Section 6.5.



5.4 Groundwater Remediation and Management 5.4.1 Remediation and Management Approach Groundwater investigations undertaken at the site have assessed that degradation of impacts is occurring, and that groundwater contamination poses a low potential risk to receptors. The groundwater remediation approach involves monitored natural attenuation (MNA) of groundwater impacts. The management actions involve the use of administrative controls to reduce the risk of extraction of shallow impacted groundwater on the site post relinquishment. This approach is considered protective of potential human and ecological receptors and the marine environment.

To achieve this:

Groundwater monitoring will be conducted for 2 years post completion of soil remediation works to confirm that soil remediation, CCM reintegration and/or generation of the final landform works do not adversely alter:

contaminant distribution in groundwater, or

MNA processes to a point where risk to receptors becomes unacceptable.

This will be validated through comparison to the End Point Criteria. Once these criteria are met, this will enable reclassification of the site to “Remediated – Restricted Use”, with the restriction related to extraction and use of shallow groundwater. End Point Criteria for groundwater remediation and monitoring are outlined in Section 8.2.

Following relinquishment of the site, administrative controls which will remain are proposed as follows: A ‘for interest only deposited plan’ (FIODP) to be retained on the site after relinquishment to control

the extraction and use of groundwater without treatment.

5.4.2 Groundwater Assessment Criteria Groundwater receptors to be protected as part of the ongoing management of risk are:

People that might extract and use the groundwater (following treatment) on MIPL. Marine ecosystems. Therefore, for this purpose, the Groundwater Assessment Criteria listed in Table 2 are to be applied to groundwater monitoring results to evaluate the potential risk to receptors during the remediation and management approach.

Table 2: Groundwater Assessment Criteria

Analyte DER Marine Water (mg/L) DER Drinking Water

(Health) (mg/L) DER Domestic Non-Potable Water

(mg/L)

Benzene 0.7 0.001 0.01 Toluene 0.18 0.8 0.025 Ethylbenzene 0.005 0.3 0.003 Xylenes (sum of) 0.625 0.6 0.02 Naphthalene 0.05 - -

Notes: “-” DER criteria are not available



6.0 REMEDIATION EXECUTION STEPS 6.1 Overview The soil remediation works on the site essentially require TRH impacted soil to be excavated and amended prior to being reintegrated into the landform, as detailed in Figure 5. However, in conjunction with the soil remediation works, CCM will be excavated and reintegrated into the Final Landform.

Figure 5: Remediation Flow Chart

The following sections outline the key activities that will occur as part of the execution of the remediation works and that are relevant to this RAP.

6.2 Preliminary Works 6.2.1 Site Establishment and Management Plans The Contractor site establishment actions will include:

Preparation of all necessary management plans to execute the remediation works; Mobilisation to site and set up the equipment necessary to carry out the remediation works; and Establishing the soil amendment area. 6.2.2 Set Out the Excavations The following preliminary works are to be conducted based on the results of the soil investigations, including any additional pre-excavation sampling (if conducted):

The Environmental Consultant will provide a set of drawings specifying the location and extent of excavations for provision to the Remediation Contractor.

The Remediation Contractor will set out the excavations using survey markers which will be verified by the Environmental Consultant (or ECQA) prior to commencement of excavating activities.

Preliminary Works

• Site Establishment• Management

plans• Materials Tracking

system• Set out works

Excavate, Segregate and Transfer

Materials

Amendment of TRH Impacted Soil

Generate Final Landform

Validate Performance of Works

• Excavate Contaminated Soil and CCM

• Segregate/crush CSS and concrete/pavers

• Survey excavation extents

• Validate completion of excavation

• Amend TRH impacted soil and CSS

• Mix and condition TRH impacted soil during amendment period

• Monitor amendment process

• Place amended soil and CCMs at specified excavation locations and depths

• Survey placement of amended soil and CCM

• Survey final landform

• Validate completion of soil remediation and CCM reintegration works to End Point Criteria

Soil Remediation

Complete

CCM Reintegrated

into Final Landform

End Point



6.2.3 Materials Tracking System The Remediation Contractor will develop a materials tracking system for the movement of solid materials during the remediation works. The materials tracking system is to be applied to all TRH impacted materials, amended materials and CCM generated by the remediation works.

The materials tracking system should adopt a logical and consistent nomenclature (e.g. a grid based system may be appropriate) to enable identification of the origin or destination of materials on site, detailing:

Identification of APECs (including sub-APEC identifier) for TRH impacted soil. Unique material type identifiers (including type of CCM) and amendment batches. Positional information on the origin and destination of the materials. The Remediation Contractor should:

Provide a copy of each Record of Soil Movement to the ECQA within 48 hours of the completion of the soil movement.

Provide a summary of all soil movement in EXCEL spreadsheet (or equivalent) format to the ECQA format and include as a minimum:

The unique identification code from the nomenclature system.

The location or area from which the TRH impacted material, amended material or CCM was removed.

The indicative volume of the material and its current status, e.g. stockpile number, amendment etc.

Its final destination both laterally and vertically with respect to the final landform surface.

Any non-compliance with the materials tracking system during the remediation works as identified by the Remediation Contractor, ECQA or Chevron is to be rectified by the Remediation Contractor. This may include sampling or testing by the ECQA in order to re-establish or confirm the presence of contamination or that the material meets the remediation amendment or blending ratio.

6.3 Excavate, Segregate and Transfer Materials 6.3.1 Excavate materials The Remediation Contractor will excavate and segregate the following different material types:

TRH impacted soil CCM

Non-TRH impacted CCM

− CSS

− Concrete/pavers

TRH impacted CCM

− TRH impacted CSS

− TRH impacted Concrete/pavers.



6.3.2 Validation Validation of the excavations is to occur as described in Section 7.1.

6.3.3 Surveys and Quantities The Remediation Contractor will conduct pre and post surveys of the excavations with reference to set out points, maintained control points and benchmarks to verify the quantities and for documentation in the materials tracking system. The survey will be carried out using a licensed or approved surveyor.

6.3.4 Crushing of CCM The Remediation Contractor will prepare the CCM as follows:

Cement stabilised sand (CSS) is to be crushed to a grainsize of less than 20 mm. This grainsize is required for reuse on the site as well as blending CSS with TRH impacted soil as part of the amendment process.

Concrete, bricks and pavers is to be broken down, steel removed, and crushed to a grainsize of less than 20 mm for direct reuse on site.

Noting that following crushing TRH impacted CSS is to be amended as per the method proposed for TRH impacted soils (Section 6.4). Following crushing, TRH impacted concrete/pavers are to be reinstated directly without amendment, however only in areas within the footprint or up hydraulic gradient of areas of known historical hydrocarbon impact in groundwater (refer Section 5.3.1).

6.3.5 Transfer Material to the Amendment Facility The Remediation Contractor is to transport each material type to the soil amendment facility or stockpile area.

6.4 Amendment of TRH Impacted Soil The Remediation Contractor should amend excavated TRH impacted soil using the following general work flow:

TRH impacted soil and crushed CSS are to be amended in a 1:1 ratio in the designated amendment area and wetted to attain 90% field capacity, or approximately 0.08 m3 water per 1 m3 of soil. The Remediation Contractor is to apply fresh water only and record the water chemistry (salinity) as well as confirm the moisture content of the soil mix via measurement.

The amended material is to be moved to the amendment area within the facility, where it is to be shaped into windrows in accordance with the following requirements:

Each windrow is to be assigned a number in a sequential manner to aid record-keeping.

The windrows must be contained within the amendment area.

The lengths of windrows is to be established based on the quantity of material requiring amendment, the aeration requirements and the available space within the amendment area.

The base width should be established such that the amendment material is not required to be trafficked by heavy machinery, unless otherwise agreed with Chevron.

The height of the windrows is to be at the discretion of the Remediation Contractor, however, based on the design used during the pilot trials the height is recommended to be 0.5 m to 1.0 m.

The number of operational windrows may vary with time, based on the rate of TRH impacted soil excavation and the efficiency of the stockpiling and blending process.



The windrows should be aerated periodically as follows: Aeration is to be achieved through tilling, using a backhoe or similar equipment.

Tilling is to occur at least once per month to promote oxygenation of the soil. The tilling frequency may be adjusted based on the observed rate of biodegradation. One complete turn-over of the material is to be undertaken as a minimum per windrow per tilling event.

The date of tilling for each windrow is to be recorded.

The underlying clean sand should not be mixed into the windrow during tilling.

The Remediation Contractor should: Sample the windrow at time-zero, i.e., at placement of the windrow.

Periodically (nominally monthly after time-zero) sample the soil to assess the level of contamination, and monitor amendment variables at a rate of 1 sample per 50 m3 of the windrow. Each sample is to be taken at a depth equivalent to half the height of the windrow.

The maximum amendment time is 3 months. Shorter timeframes may be approved by Chevron or the ECQA where the results of sampling undertaken by the Remediation Contractor throughout the amendment period have demonstrated that TRH concentrations are at or below the Soil Assessment Criteria (see Section 5.3.2).

The ECQA is to: Collect samples and despatch to a NATA accredited laboratory to independently validate soil

amendment data.

Review material tracking and testing records from the Remediation Contractor to validate that soil amendment has been performed in accordance with the RAP.

Upon completion of soil amendment, the ECQA will authorise reuse of the material within the designated re-use area (See Section 6.5), noting:

The windrow should not be moved until reuse is formally authorised by the ECQA.

If the ECQA deems that soil treatment has not been performed in accordance with the RAP, additional treatment time may be prescribed by the ECQA.



6.6 Reporting The Remediation Contractor will prepare a remediation report that will document the soil remediation and CCM reintegration works and to validate the final condition of the site with respect to soil and CCM. The report is to provide the following:

Summary of soil remediation works undertaken, such as total volume of soil amended and placed, and the total volume of CCM crushed and placed.

Summary of the extent of excavations of TRH impacted material (where applicable) based on results of validation sampling.

Summary of the material movements from the Materials Tracking System. Description of the source of any material placed on the site. Surveyed levels and as-built drawings generated as a result of excavations and placement of materials. This report will be required after completion of the soil remediation and CCM reintegration works.

The Environmental and Civil Consultant will be required to prepare two reports:

A soil validation report to summarise the assessments undertaken by the ECQA and CCQA during the soil remediation and CCM reintegration works. This will document the assessments conducted during the remediation and reintegration works, and is likely to include the following:

Summary of results from the validation assessment (i.e. validation of excavation extent)

Summary of results from validation assessments undertaken on windrow amendment

Summary of CCQA assessments (where undertaken)

A Section outlining how the End Point Criteria for soil remediation and CCM reintegration have been met.

A Section outlining recommendations on potential restrictions on use of the land (if required).

A groundwater report that summaries: The status of groundwater pre- and post- completion of the remediation and reintegration works.

The status of groundwater for the nominal 2 year monitoring period post- completion of remediation and reintegration works.

Demonstration that the groundwater status meets the groundwater End Point Criteria (Section 8.2) so the site can be considered suitable for reclassification to “Remediated – Restricted Use”.

A Section outlining recommendations on potential restrictions on use of groundwater (if required). The reports are to be provided to the Environmental Auditor to assist with endorsement of reclassification of the Site’s status.



7.0 VALIDATION OF SOIL REMEDIATION 7.1 Validation of Excavation Extent A detailed site investigation has been conducted to evaluate the lateral and vertical extent of contamination on site, and the site conceptual model is considered well developed and appropriate to understand distribution of soil and groundwater impacts.

The objective of validation is to confirm for soils within 1.5 m of final grade:

the lateral extent of excavations in order to segregate materials above the Soil Assessment Criteria that contaminant concentrations for soils remaining in situ are acceptable based on the intended land

use.

7.1.1 Validation Approach There is already considerable data developed through the historic investigations carried out to date that are intended to form the basis for the validation data set.

Validation is to be undertaken by one, or a combination of:

Evaluation of the historical data set, including DSI; Additional pre-excavation sampling may be undertaken where insufficient historical data are available;

and

Sampling and/or field observations during (and post) remediation excavations to confirm lateral remediation extents.

Notwithstanding the validation approach, the final data set is to be obtained at a sampling frequency commensurate with the Australian Standard sampling requirements for validating an excavation or stockpile (see Section 7.1.2).

Consistent with the remediation approach for TRH impacted soil (Section 5.3.1, Profile 2 of Figure 4), the base, and portions of excavation walls that extend deeper than 1.5 m below the final landform surface do not need to be validated and the Australian Standard will not apply. The validation sample density is therefore to be based on the area of walls that are within 1.5 m of the final landform surface to determine the lateral extent of excavations.

In the event that additional sampling is planned, a sampling and analysis plan (SAP) is to be developed with the quantity and position of soil samples based on both the Australian Standard requirements and consideration of residual hydrocarbon impacts with respect to the final landform surface. Historical soil sampling data are to be considered in development of the SAP, and included as part of the validation data set.

The remote location of the site means that there may be difficulties in obtaining laboratory data in an appropriate timeframe to make decisions on final excavation extents and backfilling. Hence, the final validation data set may be supplemented by the use of field screening methods or aesthetics. Any such field decision making is to be agreed in consultation with the Auditor prior to works. It is the intention that field screening samples may comprise part of the validation data set and hence be included in the frequency of sampling outlined in Section 7.1.2.



7.1.2 Validation Sampling Density Guidelines DER guidance outlines that validation samples are to be obtained from the walls and base of excavation using an evenly spaced grid-based sampling pattern (relative to the final landform surface), with the spacing and number of samples obtained dependent on the size of the excavation. The recommended minimum spacing and number of validation samples to be obtained from an excavation are listed in Table 3.

Unexpected finds of TRH impacted soil may be encountered during decommissioning/remediation. These will be assessed in accordance with the remedial approach (Section 5.3.1) and, where required, validated in accordance with the validation approach.

Table 3: Minimum recommended validation samples and spacing (from AS 4482.1 2005) Area of Excavation

(m2) Minimum Number of Sampling Points

Recommended Resulting Grid Size

(m)

4000 Consult Australian Standard AS 4482.1 2005 for appropriate density

7.1.3 Application of the Assessment Criteria to Validation Soil Assessment Criteria for TRH (Section 5.3.2) are intended to be applied to an area, or “domain” of the site rather than to a single data point. Variation in concentration above and below the criterion can occur without the overall conditions adversely affecting the ecological system. Hence, the criteria should generally be compared to “average” soil conditions and hence it is conservative to compare the soil TRH results to individual or maximum measured result at any one location. It is therefore recommended that the following rules are adopted in evaluating the final condition of soil at the site following remediation:

Up to nine samples. Where up to nine samples have been collected for a “domain” the characterisation of the soil should be based on the average (mean) of the results as long as the maximum result is less than 2.5 times the applicable criterion. This is considered to be a reasonably conservative approach that is consistent with guidance for comparison of soil investigation results to soil screening level criteria in the NEPM. This limits the variability allowed in the sampling results and provides for a conservative decision where the conditions are not met.

Greater than 10 samples. For a sample set of 10 or more samples, the 95% upper confidence limit on the mean (UCL) should be considered.

Determination of average (mean) concentrations and calculation of the 95% UCL must also evaluate whether there are outliers in the data set which may indicate the presence of a “hot spot”. An outlier may be defined for this purpose as an individual result that is more than 2.5 times the Soil Assessment Criteria. Where this is the case, the spatial distribution of the data used for the statistical analysis should be examined to establish whether the outlier is indicative of a ‘hot spot’. For example, the spatial analysis should examine:

in the case of multiple outliers, whether they are grouped or randomly distributed; or

in the case of one outlier, whether nearby concentrations are elevated. The evaluation of outliers will be undertaken by the ECQA in consultation Chevron.



7.2 Soil Remediation and CCM Reintegration End Point Criteria Soil remediation and CCM reintegration works will be deemed complete once End Point Criteria have been met. Table 4 lists End Point Criteria objectives and demonstrable criteria to be used to validate that these have been met.

Table 4: Soil Remediation and CCM Reintegration End Point Criteria Objective Approach Demonstrable Criterion

TRH concentrations in the top 1.5 m of the final landform surface are less than or equal to the Soil Assessment Criteria.

Implemented through the approach outlined in Section 5.3.1.

Material tracking records, validation of excavation extent and surveys demonstrate that the final landform requirements have been met. Refer to Sections 6.2.3, 6.3, 6.5 and 7.1.

TRH impacted Soil and CSS (i.e. with TRH concentration greater than the Soil Assessment Criteria) that is excavated due to being within 1.5 m of the final landform surface has been amended.

Implemented through the approach outlined in Section 5.3.1

Material tracking records, records of amendment and associated sampling data demonstrate that amendment has occurred in accordance with the methodology nominated in the RAP. Refer to Sections 6.2.3 and 6.4.

Amended soil and CSS have been placed in the TRH impacted groundwater location of the final landform.

Implemented through the approach outlined in Section 5.3.1

Material tracking records and surveys demonstrate that the final landform requirements have been met. Refer to Sections 6.2.3 and 6.5.

Amended soil, amended CSS and other CCM have been placed as per the vertical profile.

Implemented through the approach outlined in Section 5.3.1.

Material tracking records and surveys demonstrate that the final landform requirements have been met. Refer to Sections 6.2.3 and 6.5.

7.3 Contingency Plan The contingency plan will be triggered if the validation process identifies that the End Point Criteria have not been met. The contingency plan will involve the following steps:

ECQA to check and confirm the information through actions such as: Review and inspection of field material tracking records, survey data, sampling data, or report

content (refer Table 4 and Section 6.6).

If appropriate, conduct soil sampling and/or exploratory test pits to confirm the results.

If the ECQA confirms non-compliance with the End Point Criteria then the ECQA is to evaluate whether there is an unacceptable risk to human or ecological receptors.

If ECQA assesses that there is an unacceptable risk, then the ECQA and/or Remediation Contractor will be required perform rectification works (Remediation Contractor) or implement an appropriate management action (ECQA) to control the risk.

7.4 Reporting Soil remediation validation is to be documented in final reports from the Remediation Contractor and Environmental and Civil Consultant (Section 6.6). These reports are to be used by the Auditor to complete the Environmental Audit (Section 9.0).



8.0 GROUNDWATER REMEDIATION AND MANAGEMENT VALIDATION

8.1 Validation Approach The groundwater monitoring data is to be evaluated to validate that:

There is evidence of ongoing attenuation of the impacted groundwater post remediation and parameters indicating monitored natural attenuation are not affected by the generation of the final landform.

The generation of the final landform has not adversely altered concentrations of contaminants in groundwater and hence the risks to human health and marine ecosystem remain acceptable.

This validation approach forms the basis for the groundwater End Point Criteria (Section 8.2).

8.1.1 Site Management Plan A Site Management Plan is to be developed for use following soil remediation to assist in the collection of data to validate the groundwater management and remediation approach. The SMP will outline groundwater monitoring activities, such as well locations, monitoring frequency, groundwater sampling method, QAQC procedures, analytical schedule, and reporting requirements which will be conducted to validate that the MNA End Point Criteria and Risk to Receptors End Point Criteria (Section 8.2) have been met.

It is anticipated that groundwater monitoring is to be undertaken for 2 years post soil remediation to validate the conceptual site model, and confirm an understanding of the risk profile. This is considered sufficient time to evaluate effects from changes to the soil profile and to consider seasonal effects based on the observed rates of MNA for TRH plumes on the site as outlined in the Remediation Framework document.

As per the current groundwater management plans for the site, the monitoring will be conducted on two main types of wells:

Coastal Wells – Monitoring wells that are close to the marine ecosystem down gradient of TRH impacted groundwater.

Sentinel Wells – Monitoring wells that are in the proximity of groundwater impacts from TRH and are targeted to monitor risk to other sensitive receptors such as MIPL and/or assist in understanding the natural attenuation of the TRH impacts over time.

Groundwater monitoring, as outlined within the SMP, is planned to confirm that natural attenuation processes continue to the satisfaction of the Auditor and risk to receptors is acceptable. At this point:

Groundwater monitoring will cease and remediation will be considered complete for the purposes of the audit.

Site reclassification to “Remediated – Restricted Use” will be sought. 8.2 Groundwater End Point Criteria Following soil remediation, groundwater monitoring will be undertaken to confirm that natural attenuation is still ongoing, and that soil remediation activities have not adversely altered groundwater dynamics or contaminant distribution.

Monitoring will be undertaken to confirm the risk to marine ecosystems and off-site receptors (MIPL) receptors remains acceptable.

Groundwater remediation and management will be deemed complete once ‘MNA’ and ‘Risk to Receptor’ End Point Criteria have been met.

Table 5 and Table 6 list End Point Criteria objectives, and demonstrable criteria to be used to validate that these have been met.



Table 5: Groundwater MNA Validation End Point Criteria Objective Approach Demonstrable Criteria

PSH apparent in-well thickness is stable or reducing over time

Collection of groundwater gauging data during and post-soil remediation.

Gauging results demonstrate that thicknesses are stable or reducing over time.

PSH extent is stable or diminishing

Collection of groundwater gauging data during and post-soil remediation.

Gauging results demonstrate that the spatial extent of PSH is stable or diminishing.

DPH extent of COIs is stable or diminishing (no adverse change in extent caused by extraction of water by MIPL)

Collection during and post-soil remediation of groundwater samples during routine groundwater monitoring events.

Groundwater monitoring reports including areal or cross-sectional plume maps show stable or diminishing COI DPH extent with time.

Groundwater flow and geochemical characteristics in impacted areas are not altered by remediation.

Collection during and post-soil remediation of groundwater gauging data and groundwater samples during routine groundwater monitoring events.

Unaltered flow and geochemical conditions are demonstrated by the following datasets:

Groundwater COI data show MNA processes are unaffected

Geochemical parameters indicate ongoing MNA (likely including sulfate, iron species, alkalinity, nitrate, organic carbon, dissolved oxygen, redox potential).

Groundwater gauging data shows no significant change in groundwater flow as a result of site activities.

Table 6: Groundwater Risk to Receptors End Point Criteria Objective Approach Demonstrable Criteria

COI concentrations in coastal wells are below Groundwater Assessment Criteria for marine ecosystems.

Collection during and post-soil remediation of groundwater samples during routine groundwater monitoring events from coastal wells.

Groundwater monitoring reports show analytical data below Groundwater Assessment Criteria at coastal wells (Section 5.4.2).

COI concentrations in site boundary sentinel wells are below Groundwater Assessment Criteria for drinking water and non-potable water.

Collection during and post-soil remediation of groundwater samples during routine groundwater monitoring events from sentinel wells.

Groundwater monitoring reports show analytical data below Groundwater Assessment Criteria at sentinel wells (Section 5.4.2).

8.2.1 Contingency Plan The following factors will trigger the implementation of the contingency plan within the 2 year validation period:

Concentrations of COIs above Groundwater Assessment Criteria within the marine coastal wells. No TRH Groundwater Assessment Criteria exist and hence a detection of TRH above the LOR in a coastal well will trigger further assessment of the risk.

Concentrations of COIs above Groundwater Assessment Criteria within the site boundary sentinel wells. No TRH Groundwater Assessment Criteria exist and hence a detection of TRH above the LOR in a sentinel on the boundary of the MIPL lease area will trigger further assessment of the risk



Sustained cessation of natural attenuation processes as measured in sentinel wells that target TRH impacted groundwater.

The contingency plan will involve the following steps;

Verify the reproducibility of the results, i.e., resample groundwater monitoring wells to verify the result. Assess whether there is a change in risk, i.e., assess whether the change in result alters the assessed

risk.

Triggering of a risk management action. 8.2.2 Reporting Reporting of groundwater monitoring, validation of MNA performance and risk to receptors will be in accordance with the frequency and requirements of the SMP.

8.3 Quality Assurance and Quality Control Requirements The QA/QC program for soil and groundwater samples obtained during the remediation works is to be in accordance with the DER Contaminated Sites Management Series and National Environment Protection (Assessment of Site Contamination) Measures guidelines:

the analytical laboratory will be accredited by the National Association of Testing Authorities (NATA) for the methods used;

provision of sample chain of custody; comparison of field and laboratory analytical data; compliance with sample holding times and sample receipt temperatures; sample collection methods to prevent cross contamination:

decontamination drilling and sampling equipment (where dedicated equipment not used) between each location; and

nitrile gloves changed between collection of each sample.

one blind duplicate sample and one split duplicate is to be collected and analysed per 20 samples per media;

one trip blank (prepared by the laboratory) is to be analysed per day of sample collection; one decontamination rinsate sample is to be collected during each day of drilling or groundwater

sampling; and

review of laboratory internal analysis of matrix spike/matrix spike duplicates, duplicates, blanks and spike recoveries.

As part of internal laboratory QA/QC, the analytical laboratory is to perform internal duplicate analyses and also report the results from the analysis of method blanks and spiked samples as a recovery percentage.

Relative percentage differences (RPDs) are to be calculated for each blind duplicate pair as a measure of the precision (repeatability) of sample recovery and analysis. RPD calculations are unable to be performed where one or both of the results are reported below the laboratory limit of reporting (LOR). Where both results for a duplicate pair are below the LOR, the correlation is to be considered acceptable and the results, therefore, validated. When one of the two results in a duplicate pair is reported below the LOR, the USEPA criteria for results less than five times the LOR are to be adopted. This guideline accepts results as validated where the difference between the duplicate pair is less than ±2 × LOR for soil and ±1 × LOR for groundwater.



9.0 ENVIRONMENTAL AUDIT 9.1 Auditor Liaison The ECQA is to assist Chevron in keeping the Auditor informed of progress, changes and decisions being made during the site assessment and remediation. It is expected that the opportunities for Auditor communication on the remediation works will be based on the following lines of communication:

Workshops on particular issues Auditor review of reports Provision of updated maps, figures and associated databases (anticipated to be supplied for the

Auditor’s information only)

Telephone and email communication as issues arise Update meetings with Chevron and DER. Regular updating of new data generated during the remediation is critical to confirm remaining assessment and remediation actions prior to completion and to minimise the time between completion of soil remediation activities and completion of the Environmental Audit.

Auditor liaison needs to be driven both ways with the ECQA providing site information and setting out the project direction and associated program information and the Auditor responding with requirements and questions as to the progress and direction as well as raising emerging issues.

9.2 Expected Audit Outcome The expected minimum Environmental Audit outcome is reclassification of the site to “Remediated – Restricted Use”. In line with the End State Vision, the Site is envisaged to be remediated to a level consistent with a parks and recreational land use. Therefore, the restrictions placed on the Site as a result of completing the Environmental Audit need to be commensurate with this future land use. At this stage, the expected outcomes may include:

An update to the Contaminated Sites database, to revise the contamination status of the site to “Remediated – Restricted Use”

A memorial on the Certificate of Title for a ‘for interest only deposited plan’ (FIODP) on part of the current lease area which restricts:

future extraction of groundwater from impacted areas of the lease.

major earthworks (in impacted areas) that are greater than 1.5m in depth and that materially alter the landform, unless a risk assessment has been carried out to demonstrate that there is no change to the risk profile.

Restrictions likely to be required for reclassification of the site to “Remediation – Restricted Use” will be further defined during the implementation of the RAP and in consultation with the Auditor. Recommendations for restriction would be detailed in the final soil validation and groundwater reports for endorsement by the Auditor. It is anticipated that these restrictions would be placed within a memorial on the Certificate of Title for the site at the prerogative of the DER.

An interim report will be requested from the Auditor to confirm that the remediation of soil and reintegration of CCM has been completed in accordance with RAP.



10.0 REFERENCES Golder Associates Pty Ltd, 2012a, Thevenard Island – Conceptual Site Model. Golder document 087643491-061-R-Rev3. September 2012.

Golder Associates Pty Ltd, 2012b, Thevenard Island, Preliminary Site Investigation, Golder document: 127643041-003-R-Rev0, issued December 2012

Golder Associates Pty Ltd, 2012c, Thevenard Island Groundwater Management Plan. Golder document 127643013-016-R-Rev0. Issued September 2012.

Golder Associates Pty Ltd, 2013a, Detailed Site Investigation, Thevenard Island, Golder document 127613109-019-R-Rev0, issued August 2013

Golder Associates Pty Ltd, 2013b, Additional and Confirmatory Groundwater Monitoring (DSI), Thevenard Island, Golder document 127643109-052-R-Rev0, issued May 2015.

Golder Associates Pty Ltd, 2014a, TRH Criterion Review – Thevenard Island Ecological Risk Assessment, Golder document: 127643109-081-M-Rev0, date issued 21 March 2014

Golder Associates Pty Ltd, 2014b, Results from Further Delineation of Soil Impacts at the APECS on Thevenard Island. Ref 127643109-073-L-RevA DRAFT. Issued February 2014.

Golder Associates Pty Ltd, 2014d, TPH F3 Fraction (C16-C34) Criterion Review – Thevenard Island, Golder document 127643109-031-TM-Rev2, issued 31 October 2014.

Golder Associates Pty Ltd, 2014e, 2014 Materials Characterisation, Thevenard Island, Golder Document 127643109-050-R-Rev3, issued February 2014.

Golder Associates Pty Ltd, 2014f, 2014 Supplementary Detailed Site Investigation. Thevenard Island Retirement, Golder document 127643109-128R-M-Rev2, issued April 2015.

Golder Associates Pty Ltd, 2015a, Remediation Framework Document, Thevenard Island, Golder document 127643109-098-R-Rev2, date issued June 2015.

Golder Associates Pty Ltd, 2015b, Saladin C Pipeline Leak Area- Conceptual Site Model, Thevenard Island, Golder Document 127643109-133-R-Rev0, issued June 2015.

Government of Western Australia (GoWA, 2003), Contaminated Sites Act 2003, Version 01-d0-02, Issued 1 December 2010

Government of Western Australia (GoWA, 1986), Environment Protection Act 1986, Version 08-b0-02, Issued 18 November 2013National Environment Protection Amendment (NEPM), 2013. National Environment Protection (Assessment of Site Contamination) Amendment Measure 2013 (No. 1). Issued by the NEPC, 11 April 2013.



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July 2016 Report No. 127643109-119-R-Rev5


APPENDIX A Key Soil Remediation Information

July 2016 Report No. 127643109-119-R-Rev5

APPENDIX A TVI RAP - Key Soil Remediation Information

July 2016 Reference No. 127643109-119-R-Rev4 1/2

KEY REMEDIATION STEPS

Activity Definition RAP

Section

Soil Validation Assessment of areas of contamination to verify final extent of excavations.

Section 7.0

Setting Out and Generation of As-Built Drawings

Usage of results from previous investigation works and/or the Pre-Validation DSI to set-out survey markers for excavations and generation of drawings indicating extent of excavations.

Section 6.2

Excavation of Impacted Material

Excavation of TRH impacted soil and transport to amendment and stockpile area.

Section 6.3

Excavation of Cement Containing Material (CSS, concrete, pavers)

Excavation of CSS, pavers and concrete and transport to the amendment and stockpile area.

Section 6.3

Crushing/Stockpiling/Blending Crushing of CCMs to the required grainsize Blending of CSS and TRH impacted material.

Section 6.3.4 Section 6.4

Amendment of TRH Impacted Soil

Creation of windrows for amendment of TRH impacted soil. Section 6.4

Placement of Materials within Final Landform and Generation of Final Landform

Movement of amended soil or crushed CCM to specified areas within the final landform.

Section 6.5

KEY BIOREMEDIATION INFORMATION

Activity Definition RAP

Section

Crush Size Less than 20 mm Section 6.3.4

Blending Ratio Impacted soil and crushed CSS are blended in a 1:1 ratio. Section 6.4

Aeration Requirements At least once per month and at least complete turn-over per windrow.

Section 6.4

Amendment Time Maximum 3 months Section 6.4

Suggested Windrow Dimensions

At the discretion of the Remediation Contractor, however, based on the pilot trials the height is recommended to be 0.5 m to 1.0 m and the base width established such that the amendment material is not requ

REPORT - der.wa.gov.au · The DER has a role in implementing the Environmental Protection Act 1986...

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