Kinmore Green OSMP

DOCUMENT STATUS

FIGURES

FIGURE 1: Extent of Stages 1B and 2

FIGURE 2: Extent of Kinmore Green Residential Estate

APPENDICES

APPENDIX A: DEPOSITED PLANS

APPENDIX B: STRUCTURE PLAN

APPENDIX C: PREVIOUS REPORTS

APPENDIX D: AS CONSTRUCTED DRAWINGS – LIMESTONE RAFT AND GRMS

APPENDIX E: RESTRICTIVE COVENANTS

APPENDIX F: LOT PLANS

APPENDIX G: GROUNDWATER AND LANDFILL GAS SAMPLING ANALYSIS AND QUALITY PLAN

APPENDIX H: PARCEL DARCH PTY LTD LETTERS OF COMMITMENT

APPENDIX I: INFORMATION BROCHURE FOR RESIDENTS AND STAKEHOLDERS

APPENDIX J: UNDERSTANDING YOUR REPORT

1. INTRODUCTION

This report presents Galt Environmental Pty Ltd’s (Galt’s) ongoing site management plan (OSMP) for Stages 1B & 2 of Kinmore Green Residential Estate located at 46 Driver Road, Darch (the site). Additionally, this OSMP includes ongoing management measures for the overall Kinmore Green Residential Estate.

The overall proposed development comprises construction of residential lots, associated road reserves, public open space (POS) and a commercial precinct.

This plan has been developed to facilitate ongoing management of the site (post construction) in context of the risks associated with historical landfill material at the site. Furthermore, the OSMP has been developed to protect human health by establishing conditions or guidelines for ongoing use of the site in order to protect the gas risk mitigation system (GRMS) which underlies the remediated (‘made ground’) from damage/breaches. The OSMP will be used to guide the ongoing use of the broader site and provide guidance to:

individual lot owners to manage residential/commercial lots; the local government authority (LGA) to manage land parcels including public open spaces (POS)and roads/reserves; and utilities/services and other future workers at the site.

This document must be provided to all (current and future) individual lot owners, responsible parties and body corporates within the Kinmore Green Residential Estate. Furthermore, a Form 6 – Landowner’s Disclosure Before Completion of Land Transaction under Section 68 of the Contaminated Sites Act 2003 must be required to facilitate the change of land ownership.

The structure of the OSMP is in accordance with the Department of Water and Environment Regulation (DWER) (2021) Assessment and Management of Contaminated Sites, under the Contaminated Sites Act 2003 and has been designed for implementation in perpetuity.

This OSMP has been developed specifically for landowners in Stages 1B and 2 and focuses on the responsibility of induvial residential landowners within these stages. Additionally, this OSMP includes management measures to be implemented by the developer, Parcel Darch Pty Ltd. for the overall

Kinmore Green Residential Estate

It should be noted that a separate OSMP is being prepared for the POS. This OSMP will be prepared by Parcel Darch Pty Ltd for City of Wanneroo to sign-off prior to acceptance of the land.

The extent the Stages 1B and 2 with boundary coordinate are shown on Figure 1. Deposited plans for Stages 1B and 2 indicating proposed lot numbers are provided in Appendix A. The extent of the Kinmore Green Residential Estate is shown on Figure 2. The overall Structure Plan for the Estate is provided in Appendix B.

2. SITE DESCRIPTION AND HISTORY

The Kinmore Green Residential Estate forms part of the previous Lot 8000, which incorporated the current Lot 2 (subject site) and the adjacent Lot 1, which is located to the northwest of the subject site.

Lot 2 was originally mined for sand supplies for the building and construction industry. Upon completion of quarrying activities, the site operated as a non-organic waste disposal facility (mainly building rubble). The site has now been entirely filled apart from the adjacent Lot 1 (note: Lot 1 is not considered part of this study).

Progressive filling of Lot 2 began in about 1989, initially in the northeast corner, then along the eastern boundary. The filling process to the west and along the eastern boundary (south of the northeast corner of fill) was inspected on an

ongoing basis by Soil and Rock Engineering Pty Ltd (SRE). A section in the southwest corner of the site adjacent Driver Road was also filled under the direction of SRE personnel.

It is understood that the majority of the initial fill was placed in accordance with City of Wanneroo requirements, initially under the guidance of City of Wanneroo personnel, then by SRE for a number of years. We also understand that records for this phase of the work have been lost.

We further understand that the remaining area (southern section) was: progressively filled with non-organic waste processed through a crushing plant; and filled in an engineered manner which involved placing in loose layers up to about 0.5 m thick and compacting using multiple passes of rubber tired and tracked earthmoving equipment inclusive of a rubbish compactor.

The site, with the exception of Stage 1A, is currently classified as Contaminated – remediation required under the Contaminated Sites Act 2003 (the Act). The site was classified under Section 13 of the Act to reflect additional technical information supplied to the Department of Water and Environmental Regulation (DWER) by July 2021. The technical information was outlined in a mandatory auditor’s report (MAR) based on the findings of the 3-part DSI (see Appenidx B for references).

Stage 1A has recently be reclassified as ‘Remediated for restricted use’ with a restriction on abstraction of groundwater for any purpose other than analytical testing.

The site was first classified under Section 13 of the Contaminated Sites Act, 2003 based on information supplied to the Department of Environment and Conservation (DEC) by September 2008.

The aim of the development is to make the site suitable for the proposed use (in context of the existing gas, soil and groundwater conditions) and facilitate reclassification under the CS Act as Remediated for restricted use (RRU) for Stages 1B and 2. It is anticipated that reclassification of future stages to RRU will be achieved following further remedial works and implementation of OSMPs.

3. PREVIOUS REPORTS AND SUPPLIED INFORMATION

A number of previous reports and supplied information have been provided and used during the course of the site investigation and remediation works. The reports are listed in Appendix B.

A copy of the reports above may be obtained by any landowner upon request to Parcel Darch Pty Ltd or by submitting a detailed summary of records (DSR) request through DWER1

4. OBJECTIVES

The objectives of the OSMP are as follows:

provide an appropriate methodology for soil disturbing works across the site i.e. during construction (installation of buried services beneath individual residential/commercial lots) and/or future maintenance/repair works; provide restrictions on excavation depth across the site based on the subsurface conditions; ensure protection of the gas risk mitigation system (GRMS) in order to protect human health by establishing guidelines for ongoing site use; provide recommendations on the use of groundwater beneath the site; and

1 Fees are associated with submitting a DSR search request.

to detail the management responsibilities for both Stages 1B and 2 and the Kinmore Green Residential Estate as a whole.

5. SITE IDENTIFICATION

The site location and boundary coordinates of Kinmore Green are shown in Figure 1 and summarised in Table 1

Table 1: Site Identification – Kinmore Green

Site Identification

Street Address 46 Driver Road

Locality Darch, 6065

Legal Identification (Parent Lot) Lot 9000

Local Government City of Wanneroo Boundary Coordinates (MGA 94) See Figure 1

Area (Parent Lot) 24.7 ha

Current Zoning Zoned as ‘Urban Development’ under the City of Wanneroo District Planning Scheme No. 2 (DPS2)

Current Landowner Parcel Darch 2019 Pty Ltd

Proposed Land Use Mixed use residential and public open space (POS)

Stage 1A Lots Lots 186-189, 204-207, 267-276, and 291

Stage 1B Lots Lots 277-288, 254-266

Stage 2A Lots Lots 181-193, 200-203, 208-211

Stage 2B Lots Lot 226-253

Current Site Classification (Stage 1A) Remediated for restricted use

Current Site Classification (balance of the site) Contaminated – remediation required

Proposed Site Classification (Stages 1B and 2) Remediated for restricted use

Deposited plans for Stages 1B and 2 are provided in Appendix A

6. STAGING PLAN

The following lot release for Stages 1 & 2 are as follows:

Stage 1: 43 lots total

o Stage 1A2: 18 Lots (no GRMS required)

o Stage 1B: 23 Lots (GRMS installed)

Stage 2: 45 Lots (GRMS installed)

2 This OSMP is not applicable to Stage 1A of the Kinmore Green development.

Lots in Stages 1B and 2 that are underlain by a GRMS are shown on Figure 2 with as-constructed drawings provided in Appendix D

Approximate timing for construction of the various Stages is provided below.

Stage 3, 4 and part of 7 – Q3/Q4 2023

Group housing site – Q4 2023

Stage 3 civil works – Q1/Q2 2024

Stage 4 civil works – Q3/Q4 2024

Stage 5, 6, and part of 7 – Q2 2024

Commercial precinct – Q3/Q4 2024

Stage 5 civil works – Q1 2025

Stage 6 civil works – Q3 2025

Stage 8 and 9 – timing unknown as reliant on interface with Lot 1 Driver

Road works

Future lot releases will be outlined at the time of the stage release by the developer and updated in a separate OSMP for prepare for each area accordingly.

7. SITE CLASSIFICATION

The DWER contaminated sites database indicates that the majority of the Kinmore Green Residential Estate is classified as ‘Contaminated – remediation required’ as of November 2022 Stage 1A has recently be reclassified as ‘Remediated for restricted use’ with a restriction on abstraction of groundwater for any purpose other than analytical testing.

Galt Environmental (2022b) has been developed to facilitate construction at the site to a level which will result in the Stages 1B and 2 being classified as ‘Remediated for restricted use’ under the CS Act 2003 A copy of the revised DSR will be provided once the site has been reclassified.

It is anticipated that the following memorials on title (MoT) will be applicable to each lot within Stages 1B and 2

Groundwater Abstraction

Ground water abstraction of the underlying aquifer is prohibited on each of the development Lots. This includes and not limited to ground water bores used for reticulation or irrigation within a Lot and/or groundwater abstraction for human consumption.

Excavations

Excavations or intrusive works are limited to the top 2.0 m of the soil profile. Excavations below this level are not permitted due to the presence of the GRMS and the risk of potential damage to the membrane (thus presenting a hazard to human health via vertical gas migration) Excavation to a maximum depth of 2.0 m will ensure there is a minimum of 0.2 m of in situ material over the upper level of the GRMS at all times. All ground disturbing activities are limited to the excavation restrictions, including the following commonly undertaken on residential sites:

gardening; underground installations (e.g. water connections, swimming pools, additional soak wells footings for patios/pergolas or similar); and repairs and maintenance (typically services)

No Build Zone

All lots within Stages 1B and 2 have a 1 m wide ‘no build zone’ at the rear of the property (or in a few instances, a side boundary). This area is to be keep free of all habitable structures and sealed surfaces. This area is to remain as a passive venting zone in perpetuity.

8. SITE CONDITIONS

8.1 Overview

A summary of site soil, groundwater and landfill gas conditions relevant to this OSMP are presented in the following sections.

8.2 Soil

All residential lots within Stages 1B and 2 are underlain by a minimum of 2.2 m of sand capping material to create an effective barrier between uncontrolled fill and sensitive receptors.

A limestone raft co-located with a gas risk mitigation system (GRMS) has been constructed at a depth not less than 2.2 m below finished lot levels. The limestone raft has been constructed to ensure the site is geotechnically suitable in context of the proposed development

Previous studies indicate that uncontrolled fill has been shown to be present across large portions of the site. However, the pathway between onsite sources and receptors has been removed through construction of the limestone raft, installation of GRMS, and placement of a 2.2 m thick sand capping layer. As such, the presence of potential contaminants within the uncontrolled fill is not considered to present a risk to onsite receptors.

The as-constructed drawings showing the location of the limestone raft are shown in Appendix D.

8.3 Groundwater

Galt Environmental (2021b) indicates:

the groundwater flow direction is south southwest; dissolved metals (arsenic, boron, copper, iron, mercury, nickel, zinc) exceeded the freshwater (FW) criteria at the majority of monitoring wells;

sulfate, dissolved metals (arsenic and nickel), and PFHxS plus PFOS exceeded the relevant drinking water (DW) criteria at a number of locations across the site; dissolved iron exceeded the short-term irrigation (STI) criterion of 10 mg/L at MW04; concentrations of dissolved arsenic and nickel exceeded the STI criteria during the first groundwater monitoring event (GME) but were either below the laboratory LOR or conformed to the adopted criteria during the second GME;

groundwater at the site is not considered to present a risk to the environment in the context of the proposed land use;

groundwater at the site is not considered suitable for use as a drinking water source or for domestic irrigation; and

groundwater at the site is considered suitable for irrigation of POS.

The classification of the site under the Contaminated Sites Act 2003 restricts the use of groundwater within residential and commercial lots for any purpose other than for analytical testing

8.4 Landfill Gas

Galt Environmental (2021a) indicates there are elevated concentrations of methane and carbon dioxide in the ground primarily attributed to the green waste (grass) contained within the construction and demolition waste and sand fill, but there is no evidence of large-scale pressure driven (advective) flow (evidenced by the extensive gas monitoring data). Importantly, there is no evidence of material that could drive gas out of the ground in large volumes. This conclusion is consistent with the nature of the material, the gas generation assessment (reported separately) and lack of significant lateral migration.

The assessment indicates the on-site future landfill gas risks across the entirety of the Kinmore Green Residential Estate fall within a Very Low and Low risk regime. Despite the gas generation assessment suggesting slightly higher vertical gas emissions, the quantitative gas modelling showed equilibrium indoor methane concentrations are unlikely to exceed the adopted action level (5,000ppm) even without any building gas protection measures.

Other key risk considerations identified in the conceptual site model (namely, potentially higher landfill gas regimes via barometric pumping and sensitivity of the proposed development) indicates the potential for unacceptable gas intrusion risks only where the proposed buildings are constructed directly above the landfill waste materials. It was therefore recommended that gas protection measures be installed beneath future residential buildings only where the buildings are located above landfill waste materials. The gas protection measures included one level of protection (i.e., a geomembrane) in addition to the sand cap, which will, in practice, behave as a biocover. To minimise opportunity for future tampering, a single deep geomembrane barrier has been installed rather than protection measures in each building.

The Structure Plan for the Kinmore Green Residential Estate has been endorsed by the Western Australian Planning Commission (WAPC) and administered City of Wanneroo. No amendments to this scheme, such as changing the area dedicated to public open space, can be considered without review and endorsement of WAPC on advice from key regulatory agencies such as DWER. Therefore, it is not envisaged that the built form of the Estate will in any way change from the approved plan. As such, the main venting zone through the POS will always remain in place ensuring that the overall gas regime does not adversely impact surrounding residents.

9. ONGOING SITE MANAGEMENT STRATEGY

9.1 Stages 1B & 2

9.1.1 Soil

Stages 1B and 2 will be suitable for residential purposes following completion of the remediation works. The ongoing site management measures required are as follows:

Excavation for development of individual residential lots is limited to the upper 2.0 m of the soil profile (providing a separation of 0.2 m to the GRMS at all times). This includes excavation for services and any accessory development features such as swimming pools, spas, soakwells etc. We note that basement garages or similar would likely be not achievable based on the permissible excavation depth.

No penetration of the GRMS is permitted for any purpose.

All municipal services for Stages 1B and 2 will be installed within the upper 2 m of the soil profile eliminating the need for maintenance or repair works close to or below the GRMS.

Registration of a Restrictive Covenant on all Lots within Stages 1B and 2 by Landgate relating to ground disturbing works on each certificate of title of lots. This is to ensure the current and future landowners (if any) are aware of the restrictions relating to planning/development at their sites. Furthermore, the restrictive covenant will be incorporated into LGA planning systems, thereby restricting approval of unsuitable

development features that may interfere with the GRMS. The restrictive covenant will also ensure that the there are no significant changes to finished lot levels across the site and thereby preserve the separation of buildings from the GRMS.

As demonstrated in the development specific landfill gas risk assessment (DSLFGRA), the on-site future landfill gas risks across the entirety of the Kinmore Green Residential Estate fall within a Very Low and Low risk regime. As such, minor excavations for features such as swimming pools, spas, soakwells within the sand cap are acceptable. We also note that the Restrictive Covenant will remain on title information in perpetuity and cannot be lifted.

It is noted that soakwell construction will be undertaken in accordance with the Urban Water Management Plan (UWMP) (Urbaqua, 2021) prepared for the site and endorsed by the City of Wanneroo on advice from DWER. The UWMP shows soakwells installed directly into the sand cap with separation from the GRMS. The soakwells are only backfilled with lot-derived sand.

Given the soakwells are:

i. installed above the GRMS;

ii. backfilled with lot-derived sand; and

iii. outside the building footprint on each lot;

it is not considered possible for preferential LFG pathways to exist.

Further noted in the UWMP, the limestone rafts between lots are graded at 1:100 slope towards the road reserve to prevent any ponding of infiltrated water on top of the GRMS.

9.1.2 Groundwater

Given that groundwater beneath the Stages 1B and 2 is not considered suitable for drinking water or residential irrigation purposes, registration of a memorial with Landgate restricting groundwater abstraction will be place on each certificate of title of lots sold within the residential portion of the site. This is to ensure the current and future landowners (if any) are aware of the restrictions relating to using groundwater from the superficial aquifer for domestic purposes at their sites. Furthermore, the memorial will be incorporated into regulatory databases and water extraction licencing systems preventing approval of extraction bores across the site.

A groundwater monitoring program will be implemented to ensure:

concentrations of COPC in groundwater remain, at a minimum, consistent 3with the current understanding of groundwater quality beneath the site; and short- and long-term protection of identified receptors from COPC in groundwater.

Ongoing groundwater monitoring will also provide additional information relating to the suitability of groundwater for beneficial uses

The methodology for groundwater monitoring is presented in a sampling analysis and quality plan (SAQP) provided in Appenidx G.

3 Fluctuations of field parameters and laboratory results are highly likely due to the heterogeneous nature of the superficial aquifer and interaction of groundwater with the overlying landfill waste mass

9.1.3 Landfill Gas

As demonstrated in DSLFGRA, the on-site future landfill gas risks across Stages 1B and 2 fall within a Very Low and Low risk regime.

The DSLFGRA identified that there are elevated concentrations of methane and carbon dioxide in the ground primarily attributed to the green waste (grass) contained within the construction and demolition waste and sand fill, but there is no evidence of large-scale pressure driven (advective) flow (evidenced by the extensive gas monitoring data). Importantly, there is no evidence of material that could drive gas out of the ground in large volumes. This conclusion is consistent with the nature of the material, the gas generation assessment (reported separately) and lack of significant lateral migration.

The risk assessment gas generation model indicated that slightly higher vertical gas emissions were possible. However, the quantitative gas modelling showed equilibrium indoor methane concentrations are unlikely to exceed the adopted action level (5,000ppm) even without any building gas protection measures.

In Stages 1B and 2, a GRMS has been locally (to alter the vertical migration of landfill gas such that it is directed away from building footprints within each lot. The GRMS has been designed such that there is a passive venting zone at the rear of each lot(s) over which the main building is not permitted to be constructed under a Restrictive Covenant that has been placed on the lots. This will ensure that the site-wide gas regime is not materially changed.

Information provided to landowners in Stages 1B and 2 includes the following:

Lot plan indicating the location of the GRMS beneath the lot ;

A 1 m wide ‘No build zone’ required for passive venting typically at the rear of each lot

Maintaining the broad soil type within the setback and road reserves i.e. ensuring that sand (as described by AS 1726) is the primary fill material.

Maintaining the 2.2 m separation from the underlying GRMS.

This information is provided in a brochure that will be provided to all residents within Stages 1B and 2 and on lot plans provided to each purchaser at the time of signing a sales contract

A copy of the restrictive covenant is provided in Appendix E. Lot plans showing the geomembrane and passive venting zones for all lots covered by this OSMP are provided in Appendix F

GRMS Location

A drawing showing the general cross section of the GRMS is shown in Inline Image 1 below. As-constructed survey drawings showing the location and extent of the GRMS including the passive venting zones (i.e. portions of the lots not underlain by a GRMS) are shown in Appendix D The GRMS QA validation report is separately provided as part of the remediation and validation report (RVR) (available from Parcel Darch Pty Ltd upon request or from DWER via a detailed summary of records search).

Inline Image 1: Site Remediation and GRMS Installation

GRMS Breach

For the purposes of this OSMP, breaches of the GRMS will be categorised as follows:

Type 1 Breach: a small partial or full penetration of the cushion geotextile, geomembrane and separation geotextile layers (as shown in Inline Image 1 above) outside the building envelope.

Type 2 Breach: a small partial or full penetration of the cushion geotextile, geomembrane and separation geotextile layers within the building footprint.

If a Type 1 breach to the GRMS does occur (in contravention of this OSMP, restrictive covenant, and CoT memorial), it is not anticipated that repair of the membrane will be required due to the following:

very low and low gas risk shown to be present at the site; and the breach will have occurred outside any habitable areas during excavation for a swimming pool and/or installation of an irrigation bore.

In the event of a Type 2 breach of the GRMS, Parcel Darch Pty Ltd, in consultation with the landowner, will be responsible for assessment, management, and remediation (if required) of the GRMS. If required, a targeted risk assessment will be undertaken to characterise whether the breach represents a risk to human health prior to repairs and/or remediation being undertaken. The outcomes of this risk assessment and/or repairs/remediation will be provided to DWER, and the Auditor as required.

Any breach of the GRMS (Type 1 or Type 2) must be reported to Parcel Darch Pty Ltd, the Auditor, and DWER. DWER must be contacted within 24 hours via their 24-hour hotline (1300 762 982) or via email at info@dwer.wa.gov.au

Landfill Gas Verification Monitoring

Following installation of the GRMS, temporary landfill gas monitoring wells will be installed at selected locations targeting the following:

immediately above the GRMS typically within a lot; passive venting zones typically at lot boundaries; and in selected utility boxes (e.g. Telstra pit).

A SAQP addressing LFG verification monitoring is presented in Appendix G and the purpose discussed briefly below.

The purpose of the LFG verification monitoring is to:

1. Provide additional verification that the GRMS has been correctly installed whereby negligible concentrations of CH4 or CO2 are detected.

2. Verify that the passive venting zones are functioning as intended whereby CH4 and CO2 should be detected at concentrations consistent with the pre-development LFG regime.

3. Demonstrate that LFG is not accumulating in utility boxes/trenches that may be accessed by maintenance workers.

Once it has been established that the GRMS has been installed correctly and functioning as intended (demonstrated by the verification monitoring outlined above) the Stage-specific monitoring will cease.

9.1.4 Roles and Responsibilities

The roles and responsibilities for implementation of the OSMP for Stages 1B and 2 are detailed in Table 2 below.

Table 2: Roles and Responsibilities – Stages 1B and 2

Landowner Provision of OSMP to contractors

Landowner Maintaining rear setbacks and soil types remaining consistent with aspurchased lots to ensure passive venting.

No excavation below 2 m

No installation of domestic irrigation bores

All contractors engaged to undertake works at the site involving ground distrubance

Prior to undertaking any ground disturbing works

Landowner Reporting of damage to the GRMS Parcel Darch Pty Ltd, DWER, and Auditor Within 24 hours of identifying damage to the GRMS

Parcel Darch Pty Ltd

Advice and repairs to the GRMS (where breach occurs)

Regulatory Authorities Advice to site owners in the event of damage to the GRMS

Parcel Darch Pty Ltd

Verification LFG monitoring following installation of GRMS

Parcel Darch Pty Ltd

DWER

and Auditor

Within 3 months of completion of GRMS

9.2 Kinmore Green Residential Estate

9.2.1 Soil

A separate OSMP will be developed for the POS and subsequent stages of Kinmore Green Residential Estate. The key mitigation and management measures relating to soil (primarily ACM) in the POS and road reserves are as follows:

ensuring the 1 m sand cap is maintained and regularly inspected across the entirety of the POS; excavations below 1 m which may encounter uncontrolled fill being undertaken in accordance with a taskspecific risk assessment; and reinstatement of the 1 m sand cap following excavations below 1 m is undertaken in a controlled manner such that uncontrolled fill is not inadvertently entrained shallower in the soil profile; road reserves will not be widened beyond that shown in the structure plan; and excavation below 2 m in the road reserves will be undertaken in accordance with a task-specific management plan to ensure uncontrolled fill (if encountered) is appropriately managed.

9.2.2 Groundwater

Given that groundwater beneath the Kinmore Green Residential Estate is not considered suitable for drinking water or residential irrigation purposes, registration of a memorial with Landgate restricting groundwater abstraction will be place on each certificate of title of lots sold within the residential portion of the site. This is to ensure the current and future landowners (if any) are aware of the restrictions relating to using groundwater from the superficial aquifer for domestic purposes at their sites. Furthermore, the memorial will be incorporated into regulatory databases and water extraction licencing systems preventing approval of extraction bores across the site.

It should be noted that an irrigation bore is proposed for the POS.

Implementation of a groundwater monitoring program across the Kinmore Green Residential Estate is required to ensure:

concentrations of COPC in groundwater remain, at a minimum, consistent 5with the current understanding of groundwater quality beneath the site; and short- and long-term protection of identified receptors from COPC in groundwater.

Ongoing groundwater monitoring will also provide additional information relating to the suitability of groundwater for beneficial uses (i.e. irrigation of POS).

The methodology for groundwater monitoring is presented in a sampling analysis and quality plan (SAQP) provided in Appenidx G

5 Fluctuations of field parameters and laboratory results are highly likely due to the heterogeneous nature of the superficial aquifer and interaction of groundwater with the overlying landfill waste mass

9.2.3 Landfill Gas

A separate OSMP will be developed for the POS and subsequent stages of Kinmore Green Residential Estate. The key mitigation and management measures relating to LFG across Kinmore Green Residential Estate are as follows:

maintaining the area designated as public open space to remain open including no paving or enclosed structures;

maintaining the broad soil type within road reserves and the public open space i.e. ensuring that sand (as described by AS 1726) is the primary fill material to facilitate passive venting of the landfill mass; and no widening of road reserves that may impact on passive venting zones.

The Structure Plan for the Kinmore Green Residential Estate has been endorsed by the Western Australian Planning Commission (WAPC) and administered City of Wanneroo. No amendments to this scheme, such as changing the area dedicated to public open space, can be considered without review and endorsement of WAPC on advice from key regulatory agencies such as DWER. Therefore, it is not envisaged that the built form of the Estate will in any way change from the approved plan.

Long-Term Landfill Gas Monitoring

We note that ongoing LFG monitoring across the Kinmore Green Residential Estate will be ongoing until completion of the development and ceased upon agreement with the Auditor and relevant stakeholders. The ongoing LFG monitoring program has been designed to ensure that the overall gas regime is not significantly altered by remedial works in the residential and commercial precincts, specifically the installation of the GRMS.

The key design elements that aim to ensure the site-wide gas regime is not altered are:

1. Ensuring the overall design of Kinmore Green Residential Estate is not significantly changed; and

2. Ensure the GRMS is installed in designated areas (i.e. beneath residential lots) with sufficient passive venting capabilities.

As noted in Section 9.2.4, the Structure Plan cannot be amended without endorsement from WAPC on advice from regularly agencies such as DWER. As such, the main venting zone through the POS will always remain in place ensuring that the overall gas regime does not adversely impact surrounding residents. The long-term LFG monitoring program detailed in the SAQP has been designed such that any changes to the LFG regime will be identified in a timely manner and remedial measures, as committed to by Parch Darch Pty Ltd (see Section 12), will be put in place if required.

Additional Landfill Gas Mitigation Measures (if required)

In the event that long-term LFG monitoring results indicate that one or more of the following are occurring:

the gas regime in the sand cap is trending towards higher methane or carbon dioxide concentrations with values exceeding:

o 1% v/v methane6; or

o 5% v/v carbon dioxide6; there are indications of lateral gas migration towards surrounding residential properties as evidenced by any borehole flow greater than 1 L/hr

Parcel Darch Pty will immediately undertake a risk assessment to quantify the health risk posed to onsite and offsite residents. If the assessment determines that additional gas risk mitigation is required beyond the existing geomembrane

and sand cap, Parcel Darch Pty Ltd will be responsible for designing and implementing these mitigation measures. When determining additional gas risk mitigation systems, the following factors would need be considered:

a large number of lots are likely to have completed homes on them or are in the process of being built on; access to private lots is likely to be limited; and the additional mitigation measures may need ongoing management and/or maintenance.

Based on these factors, it is considered that the following measures are considered potentially feasible for additional gas risk mitigation:

installation of gas collection trenches within road verges, and passive or active venting in safe locations; installation of additional geomembrane layers within future stages yet to be built; and injection of low permeability grout into designated areas to prevent lateral gas migration.

It should be noted that the options listed above are not exhaustive and additional mitigation measures may be considered based on the outcomes of the health risk assessment.

Workplace Health and Safety Requirements for Maintenance Workers

It is not anticipated that there will be any unacceptable risk to onsite maintenance workers within the Kinmore Green Residential Estate. Notwithstanding, workplace health and safety (WHS) controls for maintenance workers conducting works on underground services will be managed as per the approved Code of Practice – Confined Spaces authorised under Section 274 of the Work Health Safety Act 2020.

Under the Code of Practice, confined space entry controls must be implemented by the persons conducting a business or undertaking (PCBU). The controls include the issuing of a permit for confined space entry. It is noted that that a determination of whether works comprise confined space entry is the responsibility of the PCBU. However, entry to any excavation greater 1.5 m deep (which is the most likely scenario at the site) would likely be classified as confined space and as such, appropriate controls must be in place. In this instance, the PCBU would need to have their own confined space entry procedures which would be compliant with the Code of Practice.

9.2.4 Roles and Responsibilities

The roles and responsibilities for implementation of this management plan for the Kinmore Green Residential Estate are outlined in Table 3

Implementation of additional remediation measures should post development monitoring indicate an unacceptable risk to human health on or off-site with the intent of ensuring that buildings within and adjacent to the development are suitable for occupation.

Table 3: Roles and Responsibilities – Kinmore Green Residential Estate

Parcel Darch Pty Ltd

Ensuring the overall design of the development (i.e. location of residential precincts, POS, commercial, etc.) does not materially change.

Parcel Darch Pty Ltd

Implementation of a groundwater monitoring program across the Kinmore Green Residential Estate

10. FINAL CONCEPTUAL SITE MODEL

Following successful implementation and validation of remedial works across the site, a final conceptual site model (CSM) has been developed to demonstrate that risks to onsite and offsite residents, public open space users, and maintenance works are appropriately managed.

The final CSM is presented in Inline Image 1 below.

11. DEVELOPER COMMITMENTS

Parcel Darch Pty Ltd has committed to the following:

ongoing monitoring until a characteristic situation (CS) 1 rating is achieved for a 12-month period within each stage; and

additional remediation measures should post-development monitoring demonstrate an unacceptable risk to human health on or off-site with the intent of ensuring that buildings within and adjacent to the development are suitable for occupation.

These commitments have been made to DWER and are considered binding for the duration of the project. The letters outlining specific developer commitments from Parcel Darch Pty Ltd are provided in Appendix H.

Inline Image 1: Final Conceptual Site Model

12. COMMUNITY CONSULTATION

In order to ensure that the obligations of the OSMP are understood by future landowners, a simple information brochure has been prepared by the developer. A copy of this brochure will be provided to all landowners, the City of Wanneroo and other relevant stakeholders. Additionally, a copy of the brochure will be available on the Kinmore Green website. A copy of the brochure is provided in Appendix I.

In addition, Parcel Darch Pty Ltd will provide a Form 6 to the purchasers of each lot with copies lodged with DWER. This is a requirement under Section 68 of the Contaminated Sites Act 2003.

13. CLOSURE

We draw your attention to Appendix I of this report, “Understanding Your Report”. The information provided within is intended to inform you as to what your realistic expectations of this report should be. This information is provided not to reduce the level of responsibility accepted by Galt, but to ensure that all parties who rely on this report are aware of the responsibilities each assumes in so doing.

GALT ENVIRONMENTAL PTY LTD

Brad Palmer

Environmental Scientist

https://galtgeo.sharepoint.com/sites/WAG180113/Shared

Appendix A: Deposited Plans

Appendix B: Structure Plan

Appendix C: Previous Reports

PREVIOUS REPORTS

Soil & Rock Engineering Pty Ltd, Quality Plan for Filling Operations, Landsdale Non-Organic Waste Facility (Soil Rock 2000)

Soil & Rock Engineering Pty Ltd, Audit Report No.1 Landsdale Non-Organic Landfill Development (Soil Rock 2001)

RPS Bowman Bishaw Gorman (RPS), Preliminary Site Investigation – Lot 1441 Driver Road (RPS 2005)

WSP Environmental Pty Ltd, Preliminary Site Investigation, 50 Driver Road, Darch (WSP 2008a).

WSP Environmental Pty Ltd, 50 Driver Road – Summary of Landfill Gas Data from Perimeter Monitoring Wells (WSP 2008b)

WSP Environmental Pty Ltd, Tier 1 Risk Assessment - 50 Driver Road, Darch (WSP 2009a)

WSP Environmental Pty Ltd, Sampling, Analysis and Quality Plan - 50 Driver Road, Darch (WSP 2009b).

WSP Environmental Pty Ltd, Landfill Gas Monitoring Report 1 - 50 Driver Road, Darch (WSP 2009c)

WSP Environmental Pty Ltd, Landfill Gas Monitoring Report 2 - 50 Driver Road, Darch (WSP 2009d)

WSP Environmental Pty Ltd, Landfill Gas Monitoring Report 3 - 50 Driver Road, Darch (WSP 2009e).

WSP Environmental Pty Ltd, Groundwater Monitoring Report - 50 Driver Road, Darch (WSP 2009f)

WSP Environmental Pty Ltd, 50 Driver Road – Strategy for Monitoring Landfill Gas (WSP 2010)

WSP, 2011 Annual Landfill Gas Monitoring Report (WSP 2012a).

WSP, Groundwater Monitoring Report – 50 Driver Road, Darch (WSP 2012b)

Environmental Strategies (ES), 2013 Landfill Gas Monitoring – 50 Driver Road, Darch (ES 2013)

Golder Associates, Furniss Road Landfill, Darch – Data Gaps Analysis and Preliminary Conceptual Site Model (Golder 2014). Strategen, 2018, Environmental Due Diligence Report – 26 Driver Road, Darch WA (Strategen 2018)

Galt Geotechnics, 2019, Geotechnical Assessment – Stage 1, Proposed Mixed-use Development, 26 Driver Road, Darch. (Galt Geotechnics, 2019).

Galt Environmental, 2019, Preliminary Site Investigation and Data Gap Analysis, Lot 2 Driver Road, Darch. (Galt Environmental, 2019a)

Galt Environmental, 2019, Sampling Analysis and Quality Plan, Lot 2 Driver Road, Darch. (Galt Environmental, 2019b).

Galt Environmental, 2021, Detailed Site Investigation – Part I – Landfill Gas, Lot 2 Driver Road, Darch. (Galt Environmental, 2021a)

Galt Environmental, 2021, Detailed Site Investigation – Part II – Groundwater Assessment, Lot 2 Driver Road, Darch. (Galt Environmental, 2021b)

Galt Environmental, 2021, Detailed Site Investigation – Part III – Soil Assessment, Lot 2 Driver Road, Darch. (Galt Environmental, 2021c).

Galt Environmental, 2021, Remediation Options Appraisal, Lot 2 Driver Road, Darch. (Galt Environmental, 2021d)

The Environmental Protection Group (Aust) Pty Ltd, 2022, Technical Specification for Gas Risk Mitigation System. (EPG, 2022a)

The Environmental Protection Group (Aust) Pty Ltd, 2022, Construction Quality Assurance Plan for Gas Mitigation System. (EPG, 2022b).

The Environmental Protection Group (Aust) Pty Ltd, 2022, Conceptual Design of Building Gas Protection Measures – Lot 2, 26 Driver Road Darch. (EPG, 2022c).

The Environmental Protection Group (Aust) Pty Ltd, 2022, Development Specific Landfill Gas Risk Assessment, Former Landfill, Lot 2, 26 Driver Road, Darch. (EPG, 2022d).

The Environmental Protection Group (Aust) Pty Ltd, 2022, Landfill Gas Generation Assessment, Former Landfill, Lot 2, 26 Driver Road, Darch. (EPG, 2022e).

Galt Environmental, 2022, Addendum Study, Former Underground Storage Tanks, Workshops, Sheds, Equipment Storage Areas and House, Proposed Mixed-Use Development, Lot 2 Driver Road, Darch. (Galt Environmental, 2022a).

Galt Environmental, 2022, Remediation Action Plan, Proposed Mixed-Use Development. Lot 2 Driver Road, Darch. (Galt Environmental, 2023a);

Galt Environmental, 2022, Remediation and Validation Report – Stages 1B & 2 Kinmore Green Residential Estate (Galt Environmental, 2023b).

www.galtenv.com.au

50 Edward Street OSBORNE PARK WA 6017

T: +61 (8) 6272-0200 ABN:

Appendix D: As Constructed Drawings –Limestone Raft and GRMS

Stage2A

Earthworks-HDPEGeomembrane

AsConExtents-Stage2A

2407-SK-023C

Appendix E: Restrictive Covenants

Appendix F: Lot Plans

Appendix G: Groundwater and Landfill Gas Sampling Analysis and Quality Plan

TECHNICAL MEMORANDUM

J1801113 028 TM Rev6

To: Steve Claudio e-mail: steve@parcelproperty.com

Cc: Vanessa Bryant

10 August 2023

Cc email: : vanessa.bryant@senversa.com.au

From: Brad Palmer Sender’s email: brad.palmer@galtenv.com.au

SAMPLING, ANALYSIS AND QUALITY PLAN

KINMORE GREEN RESIDENTIAL ESTATE 46 DRIVER ROAD, DARCH

Dear Steve,

1. INTRODUCTION

This report presents Galt Environmental Pty Ltd’s (Galt’s) sampling, analysis, and quality plan (SAQP) for groundwater (GW) and landfill gas (LFG) monitoring at the mixed-use development located at 46 Driver Road, Darch (the site). The site relative to the surrounding area is shown on Figure 1.

This SAQP should be read in conjunction with the remediation action plan (RAP) and ongoing site management plan (OSMP) for the site.

2. OBJECTIVES

The objectives of the SAQP are as follows:

to ensure that the GRMS is not significantly altering the existing ground gas regime; to ensure that the remediation measures are protective of environmental and human health; provide a methodology to assess the impacts of the gas membrane and fill soils on the distribution of ground gasses on a stage -by-stage basis;

to ensure the remediation objectives with respects to LFG and GW as outlined in the remediation action plan (RAP) are met; and ensure concentrations of contaminants of potential concern (COPC) in groundwater remain, at a minimum, consistent with the current understanding of groundwater quality beneath the site; and ensure short- and long-term protection of identified receptors from COPC in groundwater.

3. OVERVIEW

This SAQP forms part of the overall RAP and OSMP for the site. As part of the RAP and OSMP, GW and LFG will require ongoing assessment in the following scenarios:

1. Stage specific monitoring post installation of the gas risk mitigation system (GRMS) to verify that efficacy of the system.

2. Long-term monitoring of the LFG over the entirety of the site

3. Long term monitoring of the GW across the site.

www.galtenv.com.au

50 Edward Street OSBORNE PARK WA 6017

T: +61 (8) 6272-0200

ABN: 96 520 810 622

Stage-Specific LFG Monitoring

LFG monitoring is required to confirm prevailing site-wide gas regime and identify any changes to these conditions (and the overall site risk) after the construction of the GRMS as the stages are developed.

CIRIA C665 (2007) Assessing risks posed by hazardous ground gases to buildings indicates the following monitoring requirements are applicable to developments on LFG sites:

monitoring is carried out and reported in a completion report for all sites; aims to confirm that the soil gas regime remains within the design parameters of the protective measures (in this case the GRMS); and

ground gas monitoring program should have a defined date of cessation.

Long-term LFG Monitoring

Elevated methane and carbon dioxide concentrations are present at the site (as a result of historical landfilling) and may pose risk to receptors if left unmanaged. As part of commitments of Parcel Darch Pty Ltd, ongoing LFG monitoring is required until CS1 rating is achieved for a 12-month period across all wells within a stage area

Additionally, long-term monitoring is required to assess changes to the LFG regime (if any) as each stage of the development is completed. The long-term monitoring program will continue to evaluate the LFG regime at the site boundaries, particularly the southern and eastern boundaries adjacent to existing residents to ensure that offsite receptors are not adversely impacted in the event the gas regime changes.

Long-term Groundwater

Given that groundwater beneath the site is not considered suitable for drinking water of residential irrigation purposes, registration of a memorial with Landgate restricting groundwater abstraction will be place on each certificate of title of lots sold within the residential portion of the site.

Implementation of a groundwater monitoring program is required to ensure: concentrations of COPC in groundwater remain, at a minimum, consistent with the current understanding of groundwater quality beneath the site; and short- and long-term protection of identified receptors from COPC in groundwater.

Ongoing groundwater monitoring will also provide additional information relating to the suitability of groundwater for beneficial uses (i.e. irrigation of POS).

4. DATA QUALITY OBJECTIVES

4.1 Overview

The following data quality objectives (DQOs) are considered appropriate for the project and are consistent with the processes set out in Australian Standard (AS) 4482.1 and NEPM (2013). The DQOs have been incorporated into the OSMP as discussed throughout the remainder of this document.

4.2 Step 1 – State the Problem

The key problems to be addressed are as follows:

What is the ongoing groundwater contamination status at the site?

Is the soil gas regime remaining within the design parameters of the protective measures post installation of the GRMS?

Is LFG present at concentrations, flow rates and composition that present a risk or require further assessment and control measures after development of the site?

What is the long-term LFG trend across the site?

4.3 Step 2 – Identify the Decision

The key decisions for the SAQP are as follows:

Completeness of contaminant source-pathway-receptor linkages.

Determination on whether the quantity and quality of field and laboratory data is considered appropriate to address the requirements of the assessment.

The requirement for additional work (i.e. investigations, remediation or management) to ensure the site is suitable for the purposes of the development an doesn’t pose human or ecological health risks above acceptable. Management of potential off-site migration of contaminants.

The presence of off-site sources/impacts that may be migrating on to the site (i.e. groundwater and/or LFG).

4.4 Step 3 – Identify Inputs to the Decision

There are a number of parameters that are considered to be likely to influence the outcomes of the GW and LFG monitoring

These parameters are considered to be as follows:

type and distribution of COPC within the groundwater at the site; toxicity of the COPC and their persistence; sufficient quantity and distribution of sampling locations; robust field and laboratory QA/QC data to assess data suitability; national association of testing authorities (NATA) accredited laboratory methods used for analytical testing; assessment of analytical data against appropriate assessment criteria (for the proposed land use) as stipulated by regulatory authorities and guidance documents.

The media identified as requiring assessment at the site are summarised in Table 1.

Table 1: Media Requiring Assessment

Media Yes No

Justification

Air x Assessment of ground gas above the GRMS post-installation and across the site in the long-term.

Surface Water x No surface water bodies are present on site. Adjacent water bodies such as drainage swamps are not considered to be hydraulically connected to the superficial aquifer.

Groundwater x Assessment of the ongoing groundwater conditions at the site is required.

4.5 Step 4 – Define the Study Boundary

The study boundary for the groundwater and long-term LFG monitoring (including eastings/northings) are shown on Figure 1 of the RAP The stages that will be monitored as part of the stage-specific LFG verification monitoring are also presented on Figure 2 of the RAP

The lateral and vertical extent of the long-term investigation is limited to the location and maximum depth of LFG/groundwater monitoring wells. The location and extent of the verification wells are limited to the depth of the GRMS, which is designed at 2.2 m below ground level (BGL).

The temporal boundary of the groundwater and long-term LFG monitoring is at least until completion of all stages of the Kinmore Green Estate (currently estimated at 2025 but likely subject to change). The temporal boundary of the stage-specific LFG verification monitoring is from completion of the relevant stage until approximately 3 months thereafter.

4.6 Step 5 – Develop a Decision Rule

The decision rules for the project will be based on an analysis of the land use and potential receptors.

The decision rules in addressing the objective of the investigation are as follows:

the applicable groundwater and LFG assessment criteria will be adopted based on the site use; groundwater analytical results along with LFG field data and calculated GSVs will be assessed against the adopted assessment criteria; exceedances of assessment criteria will trigger a review of the potential risks to human health and the environment, and possible implementations of mitigation procedures; the QA/QC data will be evaluated with respect to the acceptable ranges outlined in the RAP; and the accuracy and precision of the field and laboratory data will be scrutinised for possible errors or anomalies.

4.7 Step 6 – Specify Limits on Decision Errors

The DQOs define how the quality of data collected through the phases of investigation is to be assessed. The evaluation criteria are summarised in Table 2 below.

Table 2: Evaluation Criteria of Each Aspect of the Investigation Data Quality Indicators Evaluation Criteria

Documentation and data completeness

Site conditions accurately described. Sampling locations accurately described. Completion of field notes, calibration certificates, chain-of-custody documentation and laboratory test certificates. Samples collected from all areas of potential environmental concern. Samples are scheduled for analysis of all COPC.

Use of appropriate techniques for sampling, storage and transport of samples.

Data comparability

Data representativeness

Precision for sampling and analysis

Use of National Association of Testing Authorities (NATA) accredited primary and secondary laboratories

Collection of quality control samples for comparative purposes.

Collection of representative samples from each sampling location and across the site.

Use of appropriate techniques for sampling, storage and transport of samples.

Use of properly trained and qualified personnel. Use of duplicate samples collected at a minimum rate of 1 in 20 (i.e. 5%). Assessment of the relative percentage difference (RPD) between primary, and duplicate samples.

Acceptable recovery of laboratory matrix spikes. Acceptable quality of rinsate blanks.

Data Quality Indicators

Accuracy

4.8 Step 7 – Optimise the Design

Evaluation Criteria

Correct application of assessment criteria for the proposed land use providing an accurate benchmark for data comparison. Statistical analysis (where required) to understand whether results conform to the assessment criteria/standards and the presence of any data set outliers that may affect interpretation of results. Undertaking the assessment in accordance with correct regulations, guidelines and procedures as outlined above to provide an accurate site condition/contamination status.

The GW and LFG sampling locations are typically grid-based aimed to characterise the nature and extent of COPC at the site and identify any potential “hot spots”. As the development proceeds, additional monitoring location will be required to replace wells damaged or destroyed during construction. The location of replacement wells will be evaluated to ensure approximately the same distribution and density of locations will be maintained.

5. SAMPLING, ANALYSIS & QUALITY PLAN

5.1 Landfill Gas

5.1.1. LFG Verification Monitoring

Temporary LFG monitoring wells will be installed at selected locations targeting the following: immediately above the GRMS typically within a lot (and in the lower lot in Situation B on Inline Image 2); and passive venting zones (Situation A, B and C as shown on Inline Images 1-3)

In addition, selected utility boxes within each new stage will be sampled to ensure LFG are not accumulating within these spaces.

The purpose of these monitoring locations is to:

1) Provide verification that the GRMS has been correctly installed whereby negligible concentrations of CH4 or CO2 are detected.

2) Verify that the passive venting zones are functioning as intended whereby CH4 and CO2 should be detected at concentrations consistent with the pre-development LFG regime.

3) Demonstrate that LFG is not accumulating in utility boxes/trenches that may be accessed by maintenance workers.

Inline Image

Verification Monitoring (Situation A) – passive venting zone with low retaining wall

LFG well (lower) Gas consistent with existing regime

LFG well (upper) Gas consistent with existing regime

Inline

Verification Monitoring (Situation B) – passive venting with high retaining wall

1:

Image 2:

Inline Image 3: Verification Monitoring (Situation C) – passive venting along southern boundary Assessment Criteria

In accordance with DWER (2021) Assessment and Management of Contaminated Sites, adopted assessment criteria for LFG and vapour management have been derived from the following guideline documents:

CIRIA C665 (2007); and

New South Wales Environmental Protection Authority (2020). Assessment and management of hazardous ground gases. Contaminated Land Guidelines.

Additionally, assessment criteria have also been derived from the following standards and guidance:

Safe Work Australia (2019). Workplace exposure standards for airborne contaminants. DoH (2022) Hydrogen sulfide and public health https://ww2.health.wa.gov.au/Articles/F_I/Hydrogen-sulfide-and-publichealth.

Adopted LFG assessment criteria are presented in Table 3

Verification wells (above GRMS)

Verification wells (passive venting zones)

Values consistent with ambient background

Values equal to or less than predevelopment gas regime

Notes: 1. LEL – lower explosive limit

Table 3: LFG Assessment Criteria

Assessment Criteria

Values consistent with ambient background

Values equal to or less than predevelopment gas regime

Values consistent with ambient background

Values consistent with predevelopment gas regime

Values consistent with ambient background

Values consistent with predevelopment gas regime

Values consistent with predevelopment gas regime

Nil

Values equal to or less than predevelopment gas regime

Ambient background concentrations will be recorded using a GA5000 in open air during each monitoring event. These values will then be adopted as suitable criteria for assessment of data collected from verification wells located directly above the GRMS.

Pre-development gas values for each verification well were derived from LFG well previously located in the areas of the same stage of those wells which are being monitored and for which historical data is available.

The adopted assessment criteria have been derived to ensure protection of onsite and offsite receptors following construction works and into the future. In the event an exceedance of assessment criteria is noted, comparison of the results with historical monitoring data will be undertaken. This will ensure that the implementation of management controls/contingencies has been done so appropriately.

Spacing

Based on CIRIA guidance documentation (Table 4.2), the site is considered to be a moderate gas hazard, given its use as a landfill site with limited putrescible wastes and historical sand quarrying activities. While this table applies to the investigation of landfill sites where the gas regime is unknown, it is considered that this is also suitable to provide the same assessment after the installation of the GRMS. As the site is proposed to be developed for residential, with and underlaying GRMS the end sensitivity of the site is considered to be moderate Based on this initial spacing of LFG monitoring wells should be 25-50 m within residential areas and 50-75 m in commercial and POS areas

The spatial distribution of LFG verification well locations will be chosen to ensure ‘Situation’ scenarios were evaluated within each Stage. Additionally, verification wells will be located directly above the GRMS in each Stage area to evaluate LFG conditions directly within the anticipated building footprint of further houses. For the majority of residential stages (Stage 3-10) where the land overlays uncontrolled fill this will consist of:

3 passive venting wells (minimum) which represent either situation A, B, & C depending on the nature of the installation of retaining wall and GRMS installation in a stage-by stage basis. It is noted that in some stages, certain ‘Situation’

scenarios will not be present due to the civil design. Therefore, a formation of three verification wells reflecting the civil design or another similar methodology which allows for assessment of passive venting must be conducted.

3 wells above the GRMS

At least one utility box within the new stage area.

Indicative LFG verification monitoring locations are shown on Figure 2.

Duration and Frequency

Wells should be installed within 1 month of the completion of the GRMS, with at least monitoring occurring on a weekly basis until completion of construction in the stage. The weekly monitoring events will include selected bores located on adjacent stages Should any exceedances be noted, additional monitoring events will be undertaken. Due to the very low risk nature on the site and as suggested in section 10.6 of the CIRIA guidelines, post construction monitoring should take place before the sale of the occupation of the site. A minimum of 5 monitoring events will be conducted for the verification monitoring.

Installation

The LFG monitoring wells will be installed in accordance with the following specifications:

50 mm polyvinyl chloride (PVC) Class 18 blank and screened casings; screened casing slots 0.4 mm in width located across the thickness of uncontrolled fill material; blank and screened PVC casing connected by flush mounted factory-threaded joints; chemically inert primary filter pack material with a high coefficient of uniformity, extending at least 0.5 m above the screened PVC casing; bentonite pellets as an annular sealant, extending 0.5 m above the filter pack; wells cement-grouted at the surface; fitted with quick connect single gas taps; and wells finished at approximately 20 cm above ground level

LFG monitoring wells will be installed in boreholes advanced with a drilling rig to exactly 2 m, 0.2 m above the GRMS.

Monitoring

LFG monitoring was undertaken with reference to the procedures outlined in CIRIA C665 (CIRIA, 2007) and NSW EPA (2012) Guidelines for the Assessment and Management of Site Impacted by Hazardous Ground Gases guideline documents

LFG monitoring was undertaken using intrinsically safe handheld monitoring equipment. The designation of intrinsically safe monitoring equipment ensures the equipment was appropriate to be used in potentially hazardous atmospheres.

Landfill gas and vapour monitoring was undertaken using a Geotech (QED) GA5000.

All monitoring equipment used for LFG monitoring was externally calibrated prior to use on site.

Monitoring data was stored electronically on the device and downloaded at the completion of each monitoring event.

Monitoring in the field recorded the following parameters:

methane; carbon dioxide; oxygen; carbon monoxide; hydrogen sulphide;

atmospheric pressure; and gas flow

The following general meteorological conditions will also be recorded for each field event: date; barometric pressure range; barometric pressure change (ie falling, rising, steady); rainfall; temperature range; and general weather conditions.

5.1.2. Long-Term LFG Monitoring

Long-term monitoring of a selection of wells in non-earth worked sections across the entire site adjacent which have historical monitoring data must be completed with regularity and after the construction if each stage. Additionally, monitoring long-term monitoring wells in completed stages immediately adjacent to the latest stage completed will be included in the monitoring program. This is required to show that the GRMS and earthworks are not affecting the site-wide gas regime nor adjacent stages that have been completed. Where long-term wells are destroyed by construction works, suitable replacement locations will be selected for new wells.

It should be noted that selected ‘Situation B’ verification wells will be included in the monitoring program. Additionally, selected utility boxes will be monitored as part of the long-term program to verify that LFG is not accumulating in these areas.

The locations for LFG monitoring wells have been selected based on the following factors:

must provide adequate coverage across the site; wherever possible are located in publicly accessible locations; and not interfere with buried services.

Indicative locations for long-term LFG monitoring wells once construction is complete at the estate are shown on Figure 3.

Assessment Criteria

LFG monitoring assessment criteria have been adopted from the following documents (as specified in Department of Water and Environment Regulation (2014) Contaminated Sites Guidelines:

CIRIA C665 (CIRIA, 2007); and NSW EPA (2012) Guidelines for the Assessment and Management of Site Impacted by Hazardous Ground Gases.

Ground gases concentrations and gas screening values (GSV) will be compared again criteria as outlined Table 8.5 of CIRIA (2007). GSV use both gas concentrations and borehole flow rates to define a characteristic situation for a site based on the limiting borehole gas volume for flow for methane and carbon dioxide. The ‘worst case’ is adopted and therefore, the GSV calculations presented will be based upon maximum (peak) concentrations of methane and carbon dioxide recorded.

CIRIA C665 does not present screening values for other gases such as hydrogen sulfide and carbon monoxide. Where required, hydrogen sulfide and carbon monoxide gas concentrations will be compared to the following guidelines:

DoH (2009) Environmental Health Guide: Hydrogen Sulfide and Public Health; and National Occupational Health and Safety Commission (NOHSC) (1995) Adopted National Exposure Standards for Atmospheric Contaminants in the Occupational Environment.

Spacing - Residential

Based on CIRIA guidance documentation (Table 4.2), the site is considered to be a moderate gas hazard, given its use as a landfill site with limited putrescible wastes and historical sand quarrying activities As the site is proposed to be developed for residential, with and underlaying GRMS the end sensitivity of the site is considered to be moderate. Based on this factor, initial spacing of LFG monitoring wells should be 25 to 50 m Wells from adjacent stages can be considered when making this assessment, provided the spacing is less than 50 m. Indicative locations for monitoring wells throughout the Estate are shown on Figure 3. These locations include selected ‘Situation B’ wells for each completed stage from the verification monitoring program.

Spacing – Commercial and POS

Based on CIRIA guidance documentation (Table 4.2), the site is considered to be a moderate gas hazard, given its use as a landfill site with limited putrescible wastes and historical sand quarrying activities As the site is proposed to be developed for commercial use, the end sensitivity of the site is considered to be low Based on this initial spacing of LFG monitoring wells should be 50 to 75 m Indicative locations for monitoring wells throughout the Estate are shown on Figure 3.

Duration and Frequency

LFG monitoring will be undertaken on a monthly basis following the completion of site works. Where possible monitoring will be undertaken during ‘worst case’ atmospheric conditions as defined by NSW EPA (2010). LFG monitoring will be ongoing until a CS1 rating achieved for 12-month period on a stage-by-stage basis.

Where construction works on a new stage are ongoing, long-term monitoring wells in adjacent completed stages will be included monitored on a weekly basis as part of the verification monitoring protocol outlined in Section 5.1.1.

Installation

The LFG monitoring wells will be installed in accordance with the following specifications:

50 mm polyvinyl chloride (PVC) Class 18 blank and screened casings; screened casing slots 0.4 mm in width located across the thickness of uncontrolled fill material; blank and screened PVC casing connected by flush mounted factory-threaded joints; chemically inert primary filter pack material with a high coefficient of uniformity, extending at least 0.5 m above the screened PVC casing;

bentonite pellets as an annular sealant, extending 0.5 m above the filter pack; wells cement-grouted at the surface; fitted with quick connect single gas taps; and wells finished at ground level with lockable steel risers.

LFG monitoring wells will be installed in boreholes advanced with a drilling rig through the entire thickness of the landfill body. Boreholes will be advanced until natural sands are encountered to ensure full penetration of the landfill material.

Monitoring

LFG monitoring will be undertaken with reference to the procedures outlined in CIRIA C665 (CIRIA, 2007) and NSW EPA (2012) Guidelines for the Assessment and Management of Site Impacted by Hazardous Ground Gases guideline documents

Monitoring in the field will be undertaken using a Geotech GA5000 portable infra-red gas analyser with internal flow pod and PID for the following:

methane; carbon dioxide;

oxygen; carbon monoxide; hydrogen sulphide; atmospheric pressure; and gas flow

Ambient background concentrations will be recorded during each monitoring event with measurements to be taken from an offsite location and away from any ongoing works that may affect the readings.

The NSW EPA (20120) advises that monitoring should:

Include measurements undertaken during falling atmospheric pressure but that requirements are otherwise site specific depending on sensitivity of site use, ground gases of concern and generation potential of the source (i.e. not prescriptive - professional judgement based on a sound conceptual site model). The key requirement should be to capture the worst-case meteorological scenario. For infrequent slow-moving weather systems, a longer period of monitoring is likely to be required to capture worst case conditions (the guidance states a 5th percentile 3-hour pressure decrease rate based on a 2-year dataset from the nearest Bureau of Meteorology (BoM) site with continuous pressure recording can be used to estimate a worst case).

Monitoring Well Replacement

Monitoring wells will be replaced at a rate broadly consistent with pre-development density. The wells will be replaced at a minimum within 6 months of civil earthworks completion and all services installed, and before homes are built and inhabited.

5.2 Groundwater Location

At a minimum the groundwater bores must be stablished for each Stage area including the POS and the commercial precinct, upon completion such that there is:

one upgradient bore to establish the quality of groundwater entering the site (one for each aquifer or geological unit of interest); and

two or three bores to monitor groundwater quality immediately downgradient and also lateral to each contaminant source (for each aquifer or geological unit of interest).

COPC

The following COPCs should be tested in the soil bores across the entirety of the site:

heavy metals

TRH

BTEXN

PAH

VOCs

PFAS/PFOA

dissolved methane (groundwater)

C1 to C4 gases

major anions and cations

total organic carbon

Assessment Criteria

We understand a restriction on groundwater use at the site will likely be applicable as part of the final site contamination classification. However, beneficial off-site uses of groundwater are likely to be for irrigation and non-potable purposes.

Assessment criteria for groundwater contamination have been adopted from the following documents:

NEPM (2013); DER (2014); Australian and New Zealand Environment and Conservation Council (ANZECC) (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality; Department of Health (DoH) (2014) Contaminated Sites ground and surface water chemical screening guidelines; and Department of Water and Environment Regulation (DWER) (2017) Interim Guideline on the Assessment and Management of Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS).

Specific groundwater assessment criteria adopted for the commercial precinct are as follows:

groundwater investigation levels - fresh waters (FW); non-potable use of groundwater (NPUG); long term irrigation (LTI); and non-potable and recreational uses.

Installation

One groundwater monitoring well is proposed to be installed in the proposed commercial precinct (in addition to the existing monitoring wells).

Groundwater monitoring wells are proposed to be dual purpose and also serve as LFG monitoring locations. The depth and screened interval of each well will be dependent upon onsite conditions including depth to groundwater and the thickness of the landfill body.

Wells will be constructed using 50 mm, class 18 flush-threaded PVC. The screened interval will be installed so that a minimum of 2 m of screen is below the water table, however the screened interval will continue through the entire thickness of the landfill body (until the sand cap layer). Gravel pack will be placed in the annulus around the screened portion of the standpipe with a minimum 0.5 m (thickness) bentonite plug placed above the gravel pack. The wells will be fitted with a lockable gas monitoring cap and the well head will be protected by a lockable steel riser. Each groundwater monitoring well will be developed to remove fine sediment from the well and gravel pack. Wells will be sampled no sooner than 7 days after installation and development to allow equilibration of the well with the surrounding aquifer.

Monitoring

Groundwater samples will be collected from the groundwater wells in accordance with the following Australian Standards:

AS 5667.1:1998 Water Quality Sampling. Part I – Guidance on the Design of Sampling Programs, Sampling Techniques and the Preservation and Handling of Samples;

AS 5667.11:1998 Water Quality Sampling. Part II – Guidance on the Sampling of Groundwater; and Heads of Environmental Protection Agencies (HEPA) Australia and New Zealand (2018) PFAS National Environmental Management Plan.

Recovery of groundwater samples will be undertaken utilising low flow techniques

Spacing

It is anticipated that monitoring wells previously used during the DSI will be progressively removed as construction works commence. As such, additional wells will be installed across the estate to facilitate monitoring during the construction works. Well spacing must be broadly consistent with pre-development levels, and must accommodate the locations presented above to allow for upstream and downstream sampling of the various stages and the POS.

Indicative groundwater monitoring locations are shown on Figure 4.

Frequency and Duration

Groundwater monitoring will be undertaken bi-annually in order to capture post summer and post winter aquifer conditions. Once the seasonal variation is considered to be understood and reasonably classified, annual monitoring can be considered.

Monitoring Well Replacement

Monitoring wells will be replaced at a rate broadly consistent with pre-development density. The wells will be replaced at a minimum within 6 months of civil earthworks completion and all services installed, and before homes are built and inhabited.

6. REPORTING

LFG

GRMS Verification

An LFG GRMS verification monitoring report (GRMS VMR) must be produced post-monitoring period prior on a stage-by stage basis. This is to ensure that the GRMS has been installed correctly prior to any outlay of costs on the next stage of development, reducing any economic impact on the Lot owners, and health impact on site workers. The GRMS VMR will be prepared by Galt or a suitably experienced environmental consultant for review by the principal, CSA and DWER.

The remediation validation management report will include the following:

scope of works performed, including verification well installation methodology; evidence of compliance of methodology with this SAQP; monitoring records (air, gas); relevant testing plans; verification well monitoring data; historical versus post GRMS monitoring data; data of existing wells to show that the site-wide gas regime hasn’t changed significantly as a result of site-works.

Annual

On an annual basis an ongoing validation report (VR) will be produced confirming that the groundwater sampling and LFG works were undertaken in accordance with this SAQP. The VR will be prepared by Galt or a suitably experienced environmental consultant for review by the principal, CSA and DWER.

The remediation validation management report will be prepared in accordance with DWER guidelines and will include the following:

scope of works performed; site records; evidence of compliance with this RAP during development/remedial works; monitoring records (air, groundwater, gas); relevant sampling plans;

validation results; and chain of custody laboratory analysis documentation; tabulated analytical results and detailed review of QA/QC results.

7. CLOSURE

We draw your attention to Attachment B of this report, “Understanding your Report”. The information provided within is intended to inform you as to what your realistic expectations of this report should be. This information is provided not to reduce the level of responsibility accepted by Galt, but to ensure that all parties who rely on this report are aware of the responsibilities each assumes in so doing.

Yours Faithfully,

GALT ENVIRONMENTAL PTY LTD

Brad Palmer

Environmental Scientist

Attachments:

A – Figures

B – Understanding Your Report

https://galtgeo.sharepoint.com/sites/WAG180113/Shared

Appendix H: Parcel Darch Pty Ltd Letters of Commitment

7 March 2023

Andrew Miller

Senior Manager | Contaminated Sites

Prime House, 8 Davidson Terrace

JOONDALUP WA 6027

Dear Andrew,

RE: LOT 2 DRIVER ROAD, DARCH

Further to my letter dated 17 February 2023, we have received feedback from Department of Health in relation to Parcel Darch Pty Ltd ongoing commitment to the monitoring and post development mitigation (if required).

Based on this feedback from the Department of Health, Parcel Darch Pty Ltd commits to ongoing monitoring until a CS1 level is achieved for a 12 month period within each stage. The monitoring locations were specified in Figure 6 of the Remediation Action Plan and will be incorporated in future Site Management Plans. These may likely be amended following review to align with open space and accessibility as provided in the Kinmore Green Sales Plan. The nominated monitoring locations are within road reserves and rear of lots to be retained by Parcel Darch Pty Ltd until CS1 levels are observed for 12 months of each stage

This monitoring plan, included in the RAP, addresses the Estate as a whole. Further monitoring bores will be installed in consultation with the project consultant team and Auditor. These final locations will be placed in future Site Management Plans. Any bores that may be damaged will be reinstated immediately to ensure continuity of the data. The monitoring commitment will continue for the balance of the site.

Yours sincerely,

JEREMY CORDINA

General Manager Land

– Parcel Property

POA: O127582 Parcel Darch Pty Ltd

Cc: Penny Woodberry | Penny.Woodberry@dwer.wa.gov.au David Jackson | David.Jackson@health.wa.gov.au

Encl: Ongoing monitoring bore plan provided within Site Management Plan

Updated monitoring bore plan to align with retained lots, car parks and road reserves

Letter from Parcel Darch Pty Ltd dated 17th February 2023

Friday, 17 February 2023

Andrew Miller

Senior Manager | Contaminated

Sites

Prime House, 8 Davidson Terrace, Joondalup WA 6027

Dear Andrew,

Thank you for the letter to DWER’s contaminated sites auditor Servensa in relation to Lot 2 Driver Road, Darch dated 17 February 2023 enclosed to this letter.

Within this letter, DWER have requested additional information and confirmation of the developer's commitment to the site following the issue of title. Whilst Servensa will respond to the request for additional information, Parcel Darch Pty Ltd (the Developer) would like to provide the following commitment to DWER and our customers beyond the issue of title for stages currently complete.

Lot 2, 2 Driver Road Development is a 321 lot development of which the first 70 lots are complete. The forecast development timeframe for the balance of the development is 5 years and Parcel Darch Pty Ltd commits to the ongoing monitoring of the completed lots to ensure mitigation measures are performing as intended. The first stage of the development was completed in April 2022 and since this time, post-development monitoring has demonstrated the effectiveness of the mitigation measures.

Parcel Darch Pty Ltd also commits to additional remediation measures should post-development monitoring demonstrate an unacceptable risk to human health on or off-site with the intent of ensuring that buildings within and adjacent to the development are suitable for occupation.

Based on the exhaustive information and validation provided over the past 18 months Parcel Darch Pty Ltd is hopeful that this letter along with the information requested in your letter, to be provided by Servensa will allow DWER to release the required clearances for the site.

If you have any concerns or questions with the information outlined above do not hesitate to contact the undersign on 0437 399 994.

Yours sincerely

JEREMY CORDINA

General Manager Land – Parcel Property

POA: O127582 Parcel Darch Pty Ltd

Cc: Penny Woodberry | penny.woodberry@dwer.wa.gov.au

Our ref: DMO2765, DEC7644/5

Enquiries: Penny Woodberry, Ph 6364 7197

Email: penny.woodberry@dwer.wa.gov.au

Vanessa Bryant Contaminated Sites Auditor Senversa

Email: vanessa.bryant@senversa.com.au

Dear Vanessa

MANDATORY AUDITOR’S REPORT – LOT 2 DRIVER ROAD, DARCH

Thank you for submitting the report ‘Mandatory Auditor’s Report 26 Driver Road, Darch, Western Australia’ (Senversa, 16 December 2022) (the MAR) and supporting consultants’ reports to the Department of Water and Environmental Regulation (the department). The MAR and reports were received on 19 December 2022. The addendum to the MAR providing supplementary information was received on 18 January 2023.

It is understood that the MAR and addendum were prepared to satisfy Condition 1 of the Western Australian Planning Commission (WAPC) subdivision approval no. 159221 set for Lot 2 Driver Road, Darch on 6 April 2021. The MAR and addendum follow the submission of previous milestone MARs in June 2021, April 2022 and June 2022.

Following a preliminary review of the MAR, the department and the Department of Health (DoH) agreed that further review of the GasSim modelling supporting the landfill gas risk assessment was warranted. This is because of the complexity and sensitivity of the proposed development, and the significant reliance of the risk assessment on this modelling work. As such, the department requested additional details of the experience of the auditor’s supporting expert and the level of review of the GasSim model carried out by the supporting expert. The requested details were provided by the auditor as part of the addendum to the MAR.

In addition, internal advice was sought from the department’s Industry Regulation, Waste Industries branch (Industry Regulation) with experience in the use and review of GasSim modelling in landfill gas risk assessment. The response to the internal advice request indicated that GasSim is broadly used, and is the most common model for applications assessed by Industry Regulation for existing and proposed landfill cells. The model is commonly referenced in extra jurisdictional landfill guidelines and standards. In addition, Industry Regulation indicated that the inputs applied in the model are in accordance with the GasSim requirements.

Industry Regulation highlighted the following aspects which have the potential to influence the accuracy and appropriateness of the outputs and resultant measures:

• Material characterisation:

The Landfill Gas Generation Assessment1 states that deposited uncontrolled materials are representative of a relatively inert landfill that is not significantly biochemically active. Industry Regulation notes that the Geotechnical Reports2,3 used to develop inputs into GasSim do not provide detailed and comprehensive characterisation of the waste types within the uncontrolled fill areas. Given the sensitivity of the proposed land use, a Detailed Geological Assessment for the full extent of the historical waste body would provide a higher level of certainty for the model input values and estimates.

The level of conservativeness and relevant rationale built into the inputs and resulting mitigation methods is noted, however, Industry Regulation is unable to provide specific advice on whether this conservativeness is sufficient to account for the uncertainties in the material properties of the waste body.

• Settlement / stability:

The Geotechnical Reports characterise the lots as ‘locally loose, deep (up to 25m) uncontrolled fill containing putrescible material’. Noting that overall and differential settlement due to the heterogeneity in waste composition and degradation represent a risk to liner integrity in the gas mitigation membrane, the Geotechnical Reports include recommendations for manual compaction of the exposed waste via a vibratory roller prior to placement of remedial layers and the membrane. This recommendation does not appear to have been proposed in the Conceptual Design4 or Technical Specification5 .

Where the auditor queries the expected settlement and associated membrane resilience (in the MAR Appendix A), the quoted values of 0 to 20 millimetres appear to represent the lower end of the suggested range within the geotechnical reports for well compacted fill. The consultant states that the reinforced limestone raft underlying the membrane is designed to mitigate differential settlement and associated strains on the membrane. There does not appear to be robust demonstration of the ability of the limestone raft layer to fulfil this function.

1 Landfill Gas Generation Assessment, Former Landfill Lot 2, 26 Driver Road Darch WA (Core Environmental Projects, 17 November 2022)

2 Geotechnical Assessment – Stage 1 Proposed Mixed-Use Development 26 Driver Road, Darch (Galt Geotechnics, 17 September 2019)

3 Geotechnical Assessment Proposed Mixed-Use Development 26 Driver Road, Darch. (Galt Geotechnics, 21 October 2019)

4 Conceptual Design of Building Gas Protection Measures, Lot 2, 26 Driver Road Darch (Core Environmental Projects, 17 November 2022)

5 Technical Specification for Gas Risk Mitigation System, Stage 1 & 2, 26 Driver Road Darch WA (Core Environmental Projects, 23 May 2022)

Assurance:

The Construction Quality Assurance Plan6 includes only manufacturer’s quality assurance, on-site visual inspection and non-destructive weld tests for installation. This may be sufficient for separation geotextiles but for an HDPE membrane as part of a critical containment landfill cap proposal, Industry Regulation generally require the CQA plan to include on-site post-delivery CQA conformance testing (including destructive tests for materials and welds) with the requirement for submission of a detailed validation report assessing compliance with values and tolerances within the plan, including laboratory results. Sub-grade and interface stability assessments may be required depending on the siting and geometry of the waste body.

The department requests that further discussion is provided for each of the above aspects responding to the points raised by Industry Regulation.

The department recognises that it is likely not possible to remove all uncertainty in the landfill gas risk assessment carried out. Therefore, the department requests confirmation of the proponent’s commitment to implement necessary contingency actions to address potential unacceptable risks to human health post-development on or off-site, and to ensure that residences and buildings within or adjacent to the development are suitable for occupation. This includes the Stage 1A development where the department understands that civil works are now complete.

The department looks forward to the receipt of additional information addressing the above. The MAR, addendum to the MAR and the technical advice received from Industry Regulation has been referred to the DoH for review, who may have additional questions or points for clarification.

In closing, the department reiterates the previous recommendation for communication and data sharing between the different parties progressing development of Lot 1 Furniss Rd and Lot 2 Driver Rd to ensure consistency in approach to risk assessment and remedial planning in the context of the proposed development as a whole. Given the potential for the separate development plans of Lot 1 and Lot 2 to impact the other, alignment between the different parties is likely to ensure the best outcome for future site users and adjacent receptors in relation to effective long-term management of the potential risks to human health associated with ground gas.

If you have any queries in the interim, please contact Manager Contaminated Sites, Penny Woodberry, on 6364 7197

Yours sincerely

Andrew Miller SENIOR MANAGER CONTAMINATED SITES

17 February 2023

6 Construction Quality Assurance Plan for Gas Risk Mitigation System, Stage 1 & 2, 26 Driver Road Darch (Core Environmental Projects, 23 May 2022)

Friday, 17 February 2023

Andrew Miller

Senior Manager | Contaminated

Sites

Prime House, 8 Davidson Terrace, Joondalup WA 6027

Dear Andrew,

Thank you for the letter to DWER’s contaminated sites auditor Servensa in relation to Lot 2 Driver Road, Darch dated 17 February 2023 enclosed to this letter.

Within this letter, DWER have requested additional information and confirmation of the developer's commitment to the site following the issue of title. Whilst Servensa will respond to the request for additional information, Parcel Darch Pty Ltd (the Developer) would like to provide the following commitment to DWER and our customers beyond the issue of title for stages currently complete.

Lot 2, 2 Driver Road Development is a 321 lot development of which the first 70 lots are complete. The forecast development timeframe for the balance of the development is 5 years and Parcel Darch Pty Ltd commits to the ongoing monitoring of the completed lots to ensure mitigation measures are performing as intended. The first stage of the development was completed in April 2022 and since this time, post-development monitoring has demonstrated the effectiveness of the mitigation measures.

Parcel Darch Pty Ltd also commits to additional remediation measures should post-development monitoring demonstrate an unacceptable risk to human health on or off-site with the intent of ensuring that buildings within and adjacent to the development are suitable for occupation.

Based on the exhaustive information and validation provided over the past 18 months Parcel Darch Pty Ltd is hopeful that this letter along with the information requested in your letter, to be provided by Servensa will allow DWER to release the required clearances for the site.

If you have any concerns or questions with the information outlined above do not hesitate to contact the undersign on 0437 399 994.

Yours sincerely

JEREMY CORDINA

General Manager Land – Parcel Property

POA: O127582 Parcel Darch Pty Ltd

Cc: Penny Woodberry | penny.woodberry@dwer.wa.gov.au

Our ref: DMO2765, DEC7644/5

Enquiries: Penny Woodberry, Ph 6364 7197

Email: penny.woodberry@dwer.wa.gov.au

Vanessa Bryant Contaminated Sites Auditor Senversa

Email: vanessa.bryant@senversa.com.au

Dear Vanessa

MANDATORY AUDITOR’S REPORT – LOT 2 DRIVER ROAD, DARCH

Thank you for submitting the report ‘Mandatory Auditor’s Report 26 Driver Road, Darch, Western Australia’ (Senversa, 16 December 2022) (the MAR) and supporting consultants’ reports to the Department of Water and Environmental Regulation (the department). The MAR and reports were received on 19 December 2022. The addendum to the MAR providing supplementary information was received on 18 January 2023.

It is understood that the MAR and addendum were prepared to satisfy Condition 1 of the Western Australian Planning Commission (WAPC) subdivision approval no. 159221 set for Lot 2 Driver Road, Darch on 6 April 2021. The MAR and addendum follow the submission of previous milestone MARs in June 2021, April 2022 and June 2022.

Following a preliminary review of the MAR, the department and the Department of Health (DoH) agreed that further review of the GasSim modelling supporting the landfill gas risk assessment was warranted. This is because of the complexity and sensitivity of the proposed development, and the significant reliance of the risk assessment on this modelling work. As such, the department requested additional details of the experience of the auditor’s supporting expert and the level of review of the GasSim model carried out by the supporting expert. The requested details were provided by the auditor as part of the addendum to the MAR.

In addition, internal advice was sought from the department’s Industry Regulation, Waste Industries branch (Industry Regulation) with experience in the use and review of GasSim modelling in landfill gas risk assessment. The response to the internal advice request indicated that GasSim is broadly used, and is the most common model for applications assessed by Industry Regulation for existing and proposed landfill cells. The model is commonly referenced in extra jurisdictional landfill guidelines and standards. In addition, Industry Regulation indicated that the inputs applied in the model are in accordance with the GasSim requirements.

Industry Regulation highlighted the following aspects which have the potential to influence the accuracy and appropriateness of the outputs and resultant measures:

• Material characterisation:

The Landfill Gas Generation Assessment1 states that deposited uncontrolled materials are representative of a relatively inert landfill that is not significantly biochemically active. Industry Regulation notes that the Geotechnical Reports2,3 used to develop inputs into GasSim do not provide detailed and comprehensive characterisation of the waste types within the uncontrolled fill areas. Given the sensitivity of the proposed land use, a Detailed Geological Assessment for the full extent of the historical waste body would provide a higher level of certainty for the model input values and estimates.

The level of conservativeness and relevant rationale built into the inputs and resulting mitigation methods is noted, however, Industry Regulation is unable to provide specific advice on whether this conservativeness is sufficient to account for the uncertainties in the material properties of the waste body.

• Settlement / stability:

The Geotechnical Reports characterise the lots as ‘locally loose, deep (up to 25m) uncontrolled fill containing putrescible material’. Noting that overall and differential settlement due to the heterogeneity in waste composition and degradation represent a risk to liner integrity in the gas mitigation membrane, the Geotechnical Reports include recommendations for manual compaction of the exposed waste via a vibratory roller prior to placement of remedial layers and the membrane. This recommendation does not appear to have been proposed in the Conceptual Design4 or Technical Specification5 .

Where the auditor queries the expected settlement and associated membrane resilience (in the MAR Appendix A), the quoted values of 0 to 20 millimetres appear to represent the lower end of the suggested range within the geotechnical reports for well compacted fill. The consultant states that the reinforced limestone raft underlying the membrane is designed to mitigate differential settlement and associated strains on the membrane. There does not appear to be robust demonstration of the ability of the limestone raft layer to fulfil this function.

1 Landfill Gas Generation Assessment, Former Landfill Lot 2, 26 Driver Road Darch WA (Core Environmental Projects, 17 November 2022)

2 Geotechnical Assessment – Stage 1 Proposed Mixed-Use Development 26 Driver Road, Darch (Galt Geotechnics, 17 September 2019)

3 Geotechnical Assessment Proposed Mixed-Use Development 26 Driver Road, Darch. (Galt Geotechnics, 21 October 2019)

4 Conceptual Design of Building Gas Protection Measures, Lot 2, 26 Driver Road Darch (Core Environmental Projects, 17 November 2022)

5 Technical Specification for Gas Risk Mitigation System, Stage 1 & 2, 26 Driver Road Darch WA (Core Environmental Projects, 23 May 2022)

Assurance:

The Construction Quality Assurance Plan6 includes only manufacturer’s quality assurance, on-site visual inspection and non-destructive weld tests for installation. This may be sufficient for separation geotextiles but for an HDPE membrane as part of a critical containment landfill cap proposal, Industry Regulation generally require the CQA plan to include on-site post-delivery CQA conformance testing (including destructive tests for materials and welds) with the requirement for submission of a detailed validation report assessing compliance with values and tolerances within the plan, including laboratory results. Sub-grade and interface stability assessments may be required depending on the siting and geometry of the waste body.

The department requests that further discussion is provided for each of the above aspects responding to the points raised by Industry Regulation.

The department recognises that it is likely not possible to remove all uncertainty in the landfill gas risk assessment carried out. Therefore, the department requests confirmation of the proponent’s commitment to implement necessary contingency actions to address potential unacceptable risks to human health post-development on or off-site, and to ensure that residences and buildings within or adjacent to the development are suitable for occupation. This includes the Stage 1A development where the department understands that civil works are now complete.

The department looks forward to the receipt of additional information addressing the above. The MAR, addendum to the MAR and the technical advice received from Industry Regulation has been referred to the DoH for review, who may have additional questions or points for clarification.

In closing, the department reiterates the previous recommendation for communication and data sharing between the different parties progressing development of Lot 1 Furniss Rd and Lot 2 Driver Rd to ensure consistency in approach to risk assessment and remedial planning in the context of the proposed development as a whole. Given the potential for the separate development plans of Lot 1 and Lot 2 to impact the other, alignment between the different parties is likely to ensure the best outcome for future site users and adjacent receptors in relation to effective long-term management of the potential risks to human health associated with ground gas.

If you have any queries in the interim, please contact Manager Contaminated Sites, Penny Woodberry, on 6364 7197

Yours sincerely

Andrew Miller SENIOR MANAGER CONTAMINATED SITES

17 February 2023

6 Construction Quality Assurance Plan for Gas Risk Mitigation System, Stage 1 & 2, 26 Driver Road Darch (Core Environmental Projects, 23 May 2022)

Appendix I: Information Brochure For Residents and Stakeholders

SITE MANAGEMENT PLAN

Congratulations on your recent purchase!

This leaflet has been created to help you understand siteworks and building on your block and any future endeavours you might undertake.

Welcome to Kinmore Green, an estate surrounded by everything you need. Life here feels just right.

The site is classified as ‘Remediated for restricted use’ under the Contaminated Sites Act 2003.

The site is COMPLETELY SAFE FOR YOU AND YOUR FAMILY based on extensive remediation done by the developer.

The Developer has lodged a Restrictive Covenant on each title within Kinmore Green which outlines all of the restrictions contained in this brochure.

SITE RISKS ARE MITIGATED BY INSTALLATION OF A GAS-PROOF MEMBRANE DEEP BELOW THE GROUND.

This membrane has been engineered to provide a factor of safety many times higher than required to provide piece of mind for residents.

The membrane is located more than 2m below each lot. Therefore you can safely excavate up to 2m for a swimming pool or spa (subject to council approval).

This classification is very common for residential estates and ensures that all health risks appropriately mitigated through certain restrictions on what you can do at your property. Remediated for Restricted use.

More information can be sourced from Parcel, DWER (Department of Water and Environmental Regulation) or the Kinmore Green website, www.kinmoregreen.com.au

YOU CANNOT BUILD ON THE PASSIVE VENTING ZONE

YOU MAY NOT DIG DEEPER THAN 2M

The location of the membrane and passive venting zone is shown on each owner’s lot plan. The passive venting zone can not have habitable structures or sealed surfaces on it. kinmoregreen.com.au

YOU CAN NOT INSTALL AN IRRIGATION BORE

UNDERSTANDING YOUR REPORT

1. EXPECTATIONS OF THE REPORT

This document has been prepared to clarify what is and is not provided in your report. It is intended to inform you of what your realistic expectations of this report should be and how to manage your risks associated with the conditions on site.

Geotechnical engineering and environmental science are less exact than other engineering and scientific disciplines. We include this information to help you understand where our responsibilities begin and end. You should read and understand this information. Please contact us if you do not understand the report or this explanation. We have extensive experience in a wide variety of projects and we can help you to manage your risk.

2. THIS REPORT RELATES TO PROJECT-SPECIFIC CONDITIONS

This report was developed for a unique set of project-specific conditions to meet the needs of the nominated client. It took into account the following:

the project objectives as we understood them and as described in this report; the specific site mentioned in this report; and the current and proposed development at the site.

It should not be used for any purpose other than that indicated in the report. You should not rely on this report if any of the following conditions apply:

the report was not written for you;

the report was not written for the site specific to your development; the report was not written for your project (including a development at the correct site but other than that listed in the report); or

the report was written before significant changes occurred at the site (such as a development or a change in ground conditions).

You should always inform us of changes in the proposed project (including minor changes) and request an assessment of their impact.

Where we are not informed of developments relevant to your report, we cannot be held responsible or liable for problems that may arise as a consequence.

Where design is to be carried out by others using information provided by us, we recommend that we be involved in the design process by being engaged for consultation with other members of the project team. Furthermore, we recommend that we be able to review work produced by other members of the project team that relies on information provided in our report.

3. DATA PROVIDED BY THIRD PARTIES

Where data is provided by third parties, it will be identified as such in our reports. We necessarily rely on the completeness and accuracy of data provided by third parties in order to draw conclusions presented in our reports. We are not responsible for omissions, incomplete or inaccurate data associated with third party data, including where we have been requested to provide advice in relation to field investigation data provided by third parties.

4. SOIL LOGS

Our reports often include logs of intrusive and non-intrusive investigation techniques. These logs are based on our interpretation of field data and laboratory results. The logs should only be read in conjunction with the report they were issued with and should not be re-drawn for inclusion in other documents not prepared by us.

5. THIRD PARTY RELIANCE

We have prepared this report for use by the client. This report must be regarded as confidential to the client and the client’s professional advisors. We do not accept any responsibility for contents of this document from any party other than the nominated client. We take no responsibility for any damages suffered by a third party because of any decisions or actions they may make based on this report. Any reliance or decisions made by a third party based on this report are the responsibility of the third party and not of us.

6. CHANGE IN SUBSURFACE CONDITIONS

The recommendations in this report are based on the ground conditions that existed at the time when the study was undertaken. Changes in ground conditions can occur in numerous ways including anthropogenic events (such as construction or contaminating activities on or adjacent to the site) or natural events (such as floods, groundwater fluctuations or earthquakes). We should be consulted prior to use of this report so that we can comment on its reliability. It is important to note that where ground conditions have changed, additional sampling, testing or analysis may be required to fully assess the changed conditions.

7. SUBSURFACE CONDITIONS DURING CONSTRUCTION

Practical constraints mean that we cannot know every minute detail about the subsurface conditions at a particular site. We use professional judgement to form an opinion about the subsurface conditions at the site. Some variation to our evaluated conditions is likely and significant variation is possible. Accordingly, our report should not be considered as final as it is developed from professional judgement and opinion.

The most effective means of dealing with unanticipated ground conditions is to engage us for construction support. We can only finalise our recommendations by observing actual subsurface conditions encountered during construction. We cannot accept liability for a report’s recommendations if we cannot observe construction.

8. ENVIRONMENTAL AND GEOTECHNICAL ISSUES

Unless specifically mentioned otherwise in our report, environmental considerations are not addressed in geotechnical reports Similarly, geotechnical issues are not addressed in environmental reports. The investigation techniques used for geotechnical investigations can differ from those used for environmental investigations. It is the client’s responsibility to satisfy themselves that geotechnical and environmental considerations have been taken into account for the site.

Geotechnical advice presented in a Galt Environmental report has been provided by Galt Geotechnics under a sub-contract agreement. Similarly, environmental advice presented in a Galt Geotechnics report has been provided by Galt Environmental under a sub-contract agreement.

Unless specifically noted otherwise, no parties shall draw any inferences about the applicability of the Western Australian state government landfill levy from the contents of this document. O:\Administration\Standard