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Maddingley Brown Coal Landfill, Annual Environmental Audit Report 2013 East Maddingley Road, Bacchus Marsh, Victoria
Prepared for: The Maddingley Mining Trust Pty Ltd PO Box 276, Bacchus Marsh Vic 3340
16 January 2014
Distribution
Distribution
Maddingley Brown Coal Landfill, Annual Environmental Audit Report 2013, East Maddingley Road, Bacchus Marsh, Victoria
16 January 2014
Copies Recipient Copies Recipient
1 PDF Mr Tim Tillig 1 PDF Mr Nick Simmons Environmental, Quality & Safety Officer 1 hard copy Senior Environment Protection The Maddingley Mining Trust Pty Ltd Officer - Landfill PO Box 376 Specialist Regulatory Services Bacchus Marsh Vic 3340 EPA Victoria GPO Box 4395, Melbourne Vic 3001
1 PDF Manager Environmental Audit 1 PDF Mr Peter J Ramsay 1 hardcopy Environmental Performance Unit Peter J Ramsay & Associates Pty EPA Victoria Ltd GPO Box 4395, Melbourne Vic 3001 By email to [email protected]
Senversa Project File
1 Reliance - This document has been prepared solely for the use of The Maddingley Mining Trust Pty Ltd. No responsibility or liability to any third party is accepted for any damages arising out of the use of this document by any third party.
2 Copyright and Intellectual Property – No portion of this document may be removed, extracted, copied, electronically stored or disseminated in any form without the prior written permission of Senversa. Intellectual property in relation to the methodology undertaken during the creation of this document remains the property of Senversa.
3 Principles and Limitations of Investigation - This document is issued subject to the technical principles, limitations and assumptions provided in Section 11.0.
4 Confidentiality – This report was prepared for The Maddingley Mining Trust Pty Ltd and may contain confidential information. If you receive this report in error, please contact Senversa and we will arrange collection of this document.
Senversa Pty Ltd ABN: 89 132 231 380 Ground Floor, 51 Clarke Street, Southbank Vic 3006 tel: + 61 3 9606 0070; fax: + 61 3 9606 0074 www.senversa.com.au
Patrick Clarke Environmental Auditor Appointed Pursuant to the Environment Protection Act 1970
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Executive Summary
Executive Summary
Introduction Patrick Clarke, an employee of Senversa Pty Ltd (Senversa) and a person appointed as an Environmental Auditor (Contaminated Land) under Section 53S of the Environment Protection Act 1970 (the Act), conducted this audit. Maddingley currently manages and administers the landfill operations at the Maddingley Brown Coal Landfill (MBC Landfill) located at East Maddingley Road, Bacchus Marsh (refer to Figure 1 in the 2012-2013 Annual Review – URS, 2013b presented in Appendix C). The environmental audit (and subsequent audit report) is required under Conditions 3.22 to 3.23 of the EPA Victoria Waste Discharge Licence ES90, issued on 6 October 1978 and last amended on 26 August 2009. A copy of Waste Discharge Licence ES90 is included in Appendix A. Patrick Clarke conducted the preceding environmental audits on the site in 2005, 2007, 2008, 2009, 2010, 2011 and 2012. Previous audit reports have included recommendations to address management issues and data gaps regarding groundwater monitoring and leachate monitoring and management. Summary Information Information relating to the site and environmental audit process is summarised as follows:
Summary of Audit Information
EPA file reference no. 64662-10
Auditor Mr Patrick Clarke
Auditor Term of Appointment 19 January 2012 to 18 January 2017
Name of person requesting audit Mr Tim Tillig
Relationship to premises/location Environmental, Quality & Safety Officer
Date of request 6 September 2013
Date EPA notified of audit 10 September 2013
Completion date of the audit 16 January 2014
Reason for audit Requirement of Waste Discharge Licence ES90, issued by EPA on 6 October 1978 and last amended 26 August 2009.
Description of activity Waste deposition, leachate generation and m anagement associated at a licensed landfill.
EPA region Metropolitan
EPA Officer Nick Simmons
Dominant — Lot on plan (Prior to subdivision) Crown Allotment 59
Additional — Lot on plan(s) Crown Allotments 59, 59A, 59B & 59C
Site/premises name Maddingley Brown Coal Landfill
Building/complex sub-unit No. n/a
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Executive Summary
Summary of Audit Information
Street/Lot — Lower No. n/a
Street/Lot — Upper No. n/a
Street Name East Maddingley
Street type (road, court, etc) Road
Street suffix (North, South etc) n/a
Suburb Bacchus Marsh
Postcode 3340
GIS coordinate of site centroid 37o 42’ 30.8’’S Latitude (GDA94)
Longitude (GDA94) 104o 26’ 35.2’’
Site Area Audit covers landfill areas A, B, C, D and E and associated leachate and water ponds only, approximately 215,000m2.
Members and categories of support team utilised None
Outcome of the audit Environmental A udit R eport with r ecommendations for on -going groundwater and leachate management and monitoring at the site.
• Confirm requirements for Leachate Management Plan, February 2014. Further work or requirements • Install pressure transducers, data loggers and remote telemetry to allow continuous monitoring of leachate levels in the landfill and collect reliable leachate level data. • If leachate levels are above elevations which ensure groundwater flow into Area A, prepare a plan to increase leachate extraction rates from Area A. • Install monitoring four wells in Fyansford Formation between Areas A and E and Parwan Creek. • Include monitoring for volatile fatty acids in Fyansford Formation wells around leachate ponds (BH11, BH17 and BH23). • Review groundwater sampling methodology. • Investigate the extent of waste and side-lining of the western side of Area A. • Develop final cap designs and tie-ins with side-liners. • Complete biannual surveys of waste levels to confirm final filling levels and identify areas ready for capping. • Implement rehabilitation plan for final capping. • Install additional groundwater monitoring well in Lower Werribee Formation hydraulically down-gradient of BH21 and 23.
Groundwater segment Lower Werribee Aquifer - Segment B
Based on bac kground c oncentrations o f a mmonia, and pendi ng a determination by the Authority, the beneficial uses of the Lower Werribee Aquifer may be limited to the following: • Maintenance of ecosystems. • Irrigation. • Industrial water use.
Fyansford Aquifer - Segment B
Surrounding land use North – Agricultural South – Agricultural East – Agricultural West – Agricultural
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Executive Summary
Groundwater and Leachate Monitoring Leachate level monitoring results show a significant reduction of leachate levels in Area A. Current leachate levels indicate an up-ward hydraulic gradient exists between the Lower Werribee Aquifer and the landfill which should be protective of water quality in the aquifer. However, there are significant concerns regarding the reliability of leachate level data within the landfill and it is recommended that leachate level monitoring is improved to collect continuous data and have it available, through remote telemetry, to MBC’s management team at their desks. It is recommended that leachate monitoring wells LB01A and LB02A are maintained as monitoring wells only and they are not used to extract leachate. Due to waste placement starting to extend above the top of the coal seam, it is recommended that four new leachate monitoring wells are installed in the Fyansford Formation to the east and south of Areas A and E, between the landfill and Parwan Creek. Nitrate in groundwater in a perched water table in the Fyansford Formation adjacent to the Leachate Ponds suggests that seepage from the ponds is occurring. It is recommended that groundwater from bores around the Leachate Ponds are also analysed for volatile fatty acids (VFAs). In general, the quality of groundwater extracted from the Groundwater Dewatering Sump is consistent with water quality in the Lower Werribee Aquifer and there is no strong evidence of leachate impacts. However, a slight rising trend in ammonia concentrations will need to be assessed based on the results of future rounds of monitoring. There is no clear evidence of impacts on water quality in the Lower Werribee Aquifer associated with leachate in Areas A and E. Concentrations of metals, ammonia and sulphate in monitoring bores BH21 and BH22 suggest potential impacts on groundwater associated with Areas B, C and D. An additional groundwater monitoring well installed in the Lower Werribee Aquifer hydraulically down-gradient of BH21 and BH22 is recommended. It is recommended that sufficient data is collected to allow a numerical hydrogeological and solute transport model to be reliably calibrated. Leachate Management A Leachate Management Plan (LMP) is currently being prepared for the site which will document leachate extraction, storage, treatment and monitoring requirements to comply with the requirements of Pollution Abatement Notice No. 10800 (the PAN), issued by EPA in July 2012. It is understood that the requirements of the PAN will be finalised in February 2014. If reliable leachate level data indicates that leachate levels in Area A and E1 to E3 are above recommended elevations which will maintain an upward hydraulic gradient from the Lower Werribee Aquifer, prepare a plan to increase leachate extraction rates from Area A and E1 to E3. Once the LMP has been implemented and leachate levels can be effectively controlled. It is recommended that leachate pumping shut-down trials are conducted to provide data to calibrate a numerical hydrogeological and solute transport model to that it can be used to assess post-closure management requirements and potential future disposal of retentate into the landfill. Landfill Construction The extent of waste to the west of Area A has not been clearly defined at the site and whether a clay side-wall liner is present between the waste and the Maddingley Coal Seam. An investigation is recommended to confirm the extent of waste and presence of the side-liner to allow integration of the final cap design. It is understood that designs for the final capping layer will be prepared for the site during the first half of 2014. If reliable leachate level data indicates that leachate levels in Area A are significantly above
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Executive Summary
the toe of the western slope of Area A, leachate drains and collection features should be incorporated into the lower sections of final cap design. It is noted that the side-wall liner above the Firewall which will act as a barrier between solid inert waste and the Fyansford Formation is currently being designed. I have provided comments for consideration by the designer, auditor assessing the design and EPA in relation to the design of the side-wall liner (refer to Section 6.5).
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Contents
Contents
Executive Summary ...... ii
List of Acronyms ...... ix
1.0 Introduction...... 1
1.1 Background...... 1
1.2 Site Description ...... 1
1.3 Firewall ...... 2
1.4 Works Approval: Landfill Extension ...... 3
1.5 PAN Conditions 3.2 and 3.4 ...... 4
2.0 Audit Process ...... 6
2.1 Audit Objective ...... 6
2.2 Activity Undertaken ...... 6
2.3 Segments Considered ...... 7
2.4 Elements Considered ...... 7
2.5 Audit Criteria ...... 7
2.6 Beneficial Uses – Groundwater ...... 8 2.6.1 Fyansford Aquifer ...... 8 2.6.2 Lower Werribee Aquifer ...... 8
2.7 Audit Methodology ...... 9
2.8 Audit Team ...... 10
2.9 Risk Assessment ...... 10
2.10 Audit Timeframe ...... 10
2.11 Exclusions ...... 10
3.0 Compliance Assessment ...... 11
3.1 Compliance with Licence Conditions ...... 11
3.2 Compliance with 2012 Audit Recommendations ...... 12
4.0 Geology and Hydrogeology ...... 18
4.1 Geology ...... 18
4.2 Hydrogeology ...... 19
4.3 Groundwater Levels and Flow Direction ...... 20 4.3.1 Fyansford Aquifer ...... 20 4.3.2 Lower Werribee Aquifer ...... 20
4.4 Bore Construction and Monitored Aquifers ...... 21
5.0 Leachate, Groundwater and Surface Water Monitoring ...... 23
5.1 Analytical Data Quality ...... 23
5.2 Leachate Monitoring ...... 24 5.2.1 Standing Leachate Levels ...... 24 5.2.2 Leachate Analytical Results ...... 26
5.3 Groundwater Monitoring ...... 27
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Contents
5.3.1 Fyansford Aquifer ...... 27 5.3.2 Lower Werribee Aquifer ...... 28 5.3.3 Extracted Groundwater ...... 30
6.0 Landfill Design and Construction ...... 31
6.1 Area A ...... 31
6.2 Area E ...... 32 6.2.1 Areas E to E3 ...... 32 6.2.2 Areas E4 & E5 ...... 32
6.3 Areas B and C ...... 34
6.4 Firewall ...... 34
6.5 Area A and E Side Liner Extension ...... 36
6.6 Leachate Ponds ...... 37
6.7 Area D ...... 38
7.0 Leachate Generation and Management ...... 39
7.1 Current Leachate and Groundwater Extraction Rates ...... 39
7.2 Future Leachate and Groundwater Extraction Rates ...... 40
7.3 Reduction of Leachate Generation Rates ...... 41
7.4 Current and Proposed Leachate Treatment and Disposal ...... 41
8.0 Conceptual Site Model ...... 43
8.1 Leachate Ponds ...... 43
8.2 Landfill Areas A and E ...... 44 8.2.1 Lower Werribee Formation ...... 44 8.2.2 Landfill Side Liner Extension Adjacent to the Fyansford Formation ...... 45
8.3 Areas B, C & D ...... 47
8.4 Firewall ...... 48
8.5 Parwan Creek ...... 49
8.6 Dam D4 & Irrigation Dam ...... 49
9.0 Risk Assessment ...... 50
9.1 Risk Communication ...... 50
9.2 Risk Context...... 50
9.3 Risk Identification ...... 52
9.4 Risk Analysis and Evaluation ...... 53
10.0 Recommendations ...... 60
10.1 Immediate Actions ...... 60
11.0 Principles and Limitations of Investigation ...... 64
12.0 References ...... 65
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Contents
Figures Figure 1: Parwan Creek Survey Data Figure 2: Maddinley Coal Seam Survey Data Figure 3: West-East Hydrogeological Cross-section
Appendix A: EPA Waste Discharge Licence ES90, 26 August 2009
Appendix B: Pollution Abatement Notice NO10800, 4 July 2012
Appendix C: Annual Report 2012-2013, 30 October 2013
Appendix D: Audit Issues Register 15 November 2013 (review of Annual Report 2012-2013, 30 October 2013)
Appendix E: Notice of Exemption 19 March 2008
Appendix F: Works Approval WA70655 & Revised Final Contours
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List of Acronyms
List of Acronyms
Acronym Definition
AHD Australian Height Datum
AMG Australian Map Grid
AS Australian Standard
ANZECC Australian and New Zealand Environment and Conservation Council
BH Borehole
EPA V ictoria P ublication 788. 1 – Best P ractice E nvironmental Management – Siting, BPEM Design, Operation and Rehabilitation of Landfills, September 2010.
COC Chain of custody
COD Chemical Oxygen Demand
CoPC Contaminants of potential concern
CQAP Construction quality assurance plan
CSM Conceptual site model
DO Dissolved oxygen
EC Electrical conductivity
EPA Environment Protection Authority Victoria
GME Groundwater monitoring event
HA Hydrogeological Assessment
Best Practice Environmental Management Siting, Design, Operation and R ehabilitation of Landfill BPEM Landfills, EPA Publication 788.1, September 2010
LMP Leachate Management Plan
LOR Limit of reporting m metres
MBC Maddingley Brown Coal m bgl Metres below ground level mg/L Milligrams per litre
MW Monitoring well
m1079503_051_rpt_16jan14 ix
List of Acronyms
Acronym Definition
NATA National Association of Testing Authorities
NEPM National Environmental Protection Measure
PAN Pollution Abatement Notice
PCR Primary contact recreation
PID Photoionisation detector
QC Quality control
PIW Prescribed industrial waste
RPD Relative percentage difference
SEPP State Environment Protection Policy
SO4 Sulphate
SWL Standing water level
TDS Total dissolved solids
TKN Total Kjeldahl Nitrogen
TOC Total Organic Carbon
µg/L Micrograms per litre
VFAs Volatile Fatty Acids
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Introduction
1.0 Introduction
1.1 Background
This environmental audit of groundwater and leachate impacts was conducted in response to a request from Mr Tim Tillig (Environmental, Quality & Safety Officer), on behalf of The Maddingley Mining Trust Pty Ltd (Maddingley). Maddingley currently manages and administers the landfill operations at the Maddingley Brown Coal Landfill (MBC Landfill) located at East Maddingley Road, Bacchus Marsh (refer to Figure 1 in the 2012-2013 Annual Review – URS, 2013b presented in Appendix C). The environmental audit (and subsequent audit report) is required under Conditions 3.22 to 3.23 of the EPA Victoria Waste Discharge Licence ES90, issued on 6 October 1978 and last amended on 26 August 2009. A copy of Waste Discharge Licence ES90 is included in Appendix A. Patrick Clarke, an employee of Senversa Pty Ltd (Senversa) and a person appointed as an Environmental Auditor (Contaminated Land) under Section 53S of the Environment Protection Act 1970 (the Act), conducted this audit. The audit was conducted in accordance with Section 53V, Part IXD, of the Act and in a manner consistent with relevant guidelines issued by the Environment Protection Authority Victoria (EPA), in particular, the “Environmental Auditor Guidelines for the Preparation of Environmental Audit Reports on Risk to the Environment” (Publication 952.4, April 2013) and “Environmental Auditor Guidelines for Conducting Environmental Audits” (EPA Publication 953.2, October 2007). Patrick Clarke conducted the preceding environmental audits on the site in 2005, 2007, 2008, 2009, 2010, 2011 and 2012. Previous audit reports have included recommendations to address management issues and data gaps regarding groundwater monitoring and leachate monitoring and management. A current Pollution Abatement Notice (PAN), No. 10800, issued by EPA in July 2012 includes requirements based on recommendations from the 2011 environmental audit. A copy of the PAN is included in Appendix B. Further information relating to the PAN requirements is provided in Section 1.5.
1.2 Site Description
The MBC Landfill is located approximately three kilometres south-southeast of the Bacchus Marsh town centre (refer to Appendix C of this report and Figure 1 in URS, 2013b). The EPA licenced boundary is defined by the licence premises boundary provided within the Waste Discharge Licence (refer to Appendix A of this report). The licenced premise boundary does not include the entire site and specifically only includes landfill areas A, B, C, D and E and associated leachate and water ponds, approximately 215,000m2 in area. As illustrated in Figure 2 of URS 2013b, the landfill is defined by the following areas:
• Area A – Landfilling began in the western portion of Area A and extended to the east with the progressive construction of Areas, E, E1, E2, E3, E4 and most recently E5. Due to the poor isolation of those cells from each other, i.e. the eastern portion of Area A and the western edge of Area E cells, the tipping areas have merged into each other. The current EPA Waste Discharge Licence still refers to Areas A and E as separate areas. Area A is subject to landfilling with solid inert waste from industrial and commercial services, shredded tyres and paper pulp. • Area B - Area B is used for composting (including biosolids, green waste, non-prescribed foundry sands, paper pulp, fowl manure and saw dust) and is not used for landfilling.
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Introduction
• Area C - Area C was subject to landfilling with Low-Level Contaminated Soil (LLCS) (as described in superseded EPA Publication 448, Classification of Wastes) until 30 June 2007. From 1 July 2007, this area was licensed to accept Category C contaminated soils as specified in Industrial Waste Resource Guideline, Soil Hazard Categorization and Management, EPA Publication IWRG621, June 2009. Area C only occasionally receives small amounts of Category C contaminated soils. • Area D - Area D has landfilled potential acid sulfate soils which were deposited in water. It is understood this area has now reached capacity. • Area E – Area E is currently subject to landfilling with solid inert waste from industrial and commercial services, shredded tyres, waste acid sulfate soils, metal recycling shredder residue (floc) and paper pulp. Area E includes cells E, E1, E2, E3, E4 and the recently constructed Cell E5, which began accepting waste in 2011. Areas A and E and the area around the existing leachate ponds to the west of the landfill form the primary focus of historical and current groundwater monitoring at the site. Areas A and E are referred to as “the landfilling areas” herein. Recently installed groundwater bores provide data on groundwater quality in the vicinity of Areas B, C and D. Monitoring data from those bores was provided for the first time in the 2010-2011 Annual Monitoring Review – URS, 2011a. The Leachate Treatment Area for the site is located to the west of the open cut mine/landfilling area, on a topographical highpoint. The leachate treatment area comprises two older clay lined leachate ponds and riffle systems. An up-graded leachate treatment system has been designed and constructed, as observed at a site inspection on the 12 November 2013, including a membrane filtration system and since September 2013, has been in the commissioning stage and operated intermittently. The leachate treatment system is currently through an approvals process with EPA as part of PAN conditions (see Section 1.5). Refer to Section 6.0 for further detail on landfill design and construction.
1.3 Firewall
The Firewall is located to the south of Area A and east of Area E and is intended to act as a fire protection barrier between the landfill and the coal face to mitigate the risk of landfill fires propagating into the surrounding coal seam. It is understood that the original intent of the EPA license was that the Firewall consisted of compacted earth not less than 13.5m thick (refer condition 2.21 of EPA licence ES90 located in Appendix A). MBC advised it applied to EPA to reuse Category C contaminated soil (previously known as low level contaminated soil) in the Firewall in 2000 and the application was granted in 2002. EPA approval was provided in the form of a Notice of Exemption (refer Appendix E), referencing the following legislation:
• Exemption from complying with sections 19A and 20 of the Environment Protection Act 1970 (only relevant parts of each section are listed below):
19A Scheduled premises (1) The occupier of a scheduled premises must not do any act or thing, including the commencement of any construction, installation or modification of plant, equipment or process or any subsequent step in relation thereto, which is likely to cause— (a)an increase or alteration in the waste discharged or emitted from, deposited to, or produced at, the premises; or (3) The occupier of any premises must not do any act or thing in relation to those premises that would make those premises a scheduled premises except in accordance with a works approval, a research, development and demonstration approval or a notice issued by the Authority.
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Introduction
20 Licensing of certain premises (1) The occupier of a scheduled premise must not undertake at those premises— (a)the discharge, emission or deposit of waste to the environment; or (b)the reprocessing, treatment, storage, containment, disposal or handling of waste; or (c)the reprocessing, treatment, storage, containment, disposal or handling of substances which are a danger or potential danger to the quality of the environment or any segment of the environment; or (d)an activity which creates a state of potential danger to the quality of the environment or any segment of the environment— unless licensed to do so under this Act.
• Exemption from complying with regulation 16(1)(a) of the Environment Protection (Prescribed Waste) Regulations 1998: 16. Exemption to certain persons
(1) The Authority may—
(a) exempt a waste reuser, a waste recycler or a recoverer of energy from complying with section 19A(3A) or 20(3A) of the Act; The exemption provided was reviewed every 3 years since its issue in 2002. In 2011, EPA revised the notice as the 1998 PIW regulations were superseded by the Environment Protection (Industrial Waste Resource) Regulations 2009. The equivalent exemption under the current regulations relates to Part 5, Section 38, Exemption for Secondary Beneficial Reuse. The revised notice was advertised by EPA and objections by third parties relating to the reuse of Category C soil in the Firewall were lodged. At this time, placement of Category C contaminated soil in the Firewall area may not be legally defined as part of the EPA licensed landfilling activities on the basis of it being granted an exemption. Senversa understands that whether the firewall is part of the landfill is a legal issue currently being considered as part of matters between EPA and MBC before the Supreme Court. Although it is not clear whether the firewall and potential risk to the groundwater and surface water environments is part of the audit scope, the Auditor has included an assessment of risk to the environment and the appropriateness of the current monitoring requirements and systems for both MBC and EPA to consider. Refer to Section 6.4 for a description of the construction of the Firewall.
1.4 Works Approval: Landfill Extension
MBC was issued with a Works Approval to extend the landfill to the north into the Stage 2 area of the current landfill, which is known as Stage 1. Works Approval WA70655 (refer Appendix F) was issued on 7 March 2013 and points of interest are noted below:
• It is valid for 2 years unless the works have started. • Works covered in the Stage 2 area include: . Design and construction of cells 6 and 7. . Design and construction of remaining cells 8 to 10. . Design and construction of a new firewall cell (with clean fill or clay and Category C contaminated soil). • Works covered in the Stage 1 area include: • Installation of a permanent cap on the Stage 1 landfill. • A new leachate collection system, approved by EPA, must be installed and operational before the deposit of any waste into any landfill cell (in Stage 2) approved in the works approval.
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Introduction
• Any cell, pond or firewall must be designed and approved as per EPA publication 1323 and constructed under audit. • The new firewall will extend along the eastern, northern and western boundaries of the Stage 2 landfill along exposed coal faces, as well as the southern boundary, which abuts solid inert waste placed in the Stage 1 landfill area. A revised final contour plan for Stage 1 of the landfill formed part of the works approval application and, according to MBC, is considered part of the works approved in the works approval. A copy of the revised final contours is found in Appendix F. It is important to note that the change in contour levels over Stage 1 has increased the peak elevation of waste in Area A by 15 m, and has likely delayed the final capping of Areas A and E.
1.5 PAN Conditions 3.2 and 3.4
MBC was issued with a Pollution Abatement Notice (PAN), NO10800 on 4 July 2012 of which two conditions relate to the groundwater protection and leachate management at the landfill, specifically conditions 3.2 and 3.4 as outlined below:
3.2 By 31 August 2012, you must undertake a hydrogeological assessment (HA) in accordance with EPA Publication 668 to determine the maximum level of leachate to be maintained in Areas A and E (excluding Cell E5) which allows the groundwater quality objectives in the State Environment Protection Policy (Groundwaters of Victoria) to be met below the landfill in the Lower Werribee Formation Aquifer.
3.4 By 31 December 2012, you must develop a leachate management plan (LMP) for drawing down leachate levels in Areas A and E sufficient to prevent pollution of groundwater. This plan must provide a disposal solution for ”retentate” from the leachate treatment process that does not include disposal back into the landfill. This plan must be verified by an EPA appointed Environmental Auditor. It is understood that MBC wish to dispose of retentate from the proposed leachate treatment process into Areas E4 and E5 of the landfill. MBC indicated that in recent mediation with EPA in relation to the PAN conditions EPA may be willing to allow the retentate to be disposed back to the landfill provided there is no impact on the surrounding groundwater. MBC has requested Patrick Clarke review the Draft HA&LMP and provide preliminary comment on the adequacy of the documents in assessing potential impacts on groundwater quality at the site associated with disposal of retentate back into Areas E4 and E5. It was confirmed that the EPA’s expectation of the Auditor’s role in relation to MBC’s compliance with the PAN included:
• A review of the draft HA, and • A review of the draft LMP, specifically addressing retentate re-injection into Cells E4 and E5 and the potential impact on groundwater. • Provide an opinion on the maximum level of leachate to be maintained to protect groundwater quality in the Lower Werribee Aquifer (PAN requirement 3.2). • Provide an opinion on leachate disposal options that do not require retentate to be disposed to the landfill (PAN requirement 3.4). • Provide an opinion on aspects of the HA and LMP relating to disposal of retentate in the landfill and whether groundwater quality in the Lower Werribee Aquifer would be protected. The HA and LMP documents are being prepared by URS as a separate exercise, to assess the potential impacts of disposal of retentate back into Areas E4 and E5 and to document leachate management procedures associated with the leachate treatment plant. Some aspects of the HA will also address progress toward development of a tool to evaluate long-term and post closure options for leachate management and assessment of groundwater impacts (i.e. recommendations from previous annual audit reports).
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Introduction
However, preparation of the HA and LMP is in progress and it is anticipated a more detailed assessment of both documents, as they relate to long-term management, would be incorporated into the following annual audit. The Auditor has completed a preliminary review of Revision 1 of both documents and will complete a final review of both documents in the coming weeks.
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Audit Process
2.0 Audit Process
2.1 Audit Objective
The objective of this Environmental Audit is for the Auditor to form an opinion as to whether or not the protected beneficial uses of groundwater have been affected by operation of the landfill, and to define what measures are required to further assess the risks of pollution and/or what measures are required to undertake works to reduce risks to an acceptable level.
2.2 Activity Undertaken
The licence issued by the EPA on 6 October 1978 and most recently amended 26 August 2009 (refer Appendix A), includes the following auditing requirements: Condition 3.22: By no later than 30 September each year, the licence holder must submit to the Authority an environmental audit report prepared by an environmental Auditor appointed under the Environment Protection Act 1970 in relation to the risk of any possible harm or detriment to groundwaters caused by the activities of the licence holder on the premises as determined by: a. the review of relevant management records and practises as the Auditor sees fit; b. an inspection of any relevant activity on the site as the Auditor sees fit; and c. the taking of any sample, measurement, reading or test that are relevant to the impact of the landfill’s operations on the quality of local groundwater, as the Auditor sees fit. Condition 3.23: Specifically, the environmental audit report referred to in Condition 3.22 shall: a. assess the adequacy of groundwater and leachate monitoring program (including bore network) to assess the risk to the beneficial uses of groundwater, having regard to, amongst other things: i. the location, depth, screen interval and other construction details in relation to the site hydrogeology; ii. groundwater sampling practices and field records; and iii. the analytical program and procedures, and results; b. subject to the adequacy of the groundwater and leachate monitoring program, assess the risk to the beneficial uses of groundwater surrounding the premises having regard to; i. whether groundwater quality objectives are being met at the site boundary; and ii. the likelihood of beneficial uses being realised; and c. depending on the level of risk to beneficial uses of groundwater surrounding the premises determined in 3.23 b) either: i. identify measures necessary to ensure the risk to beneficial uses is minimised and maintained at an acceptable level; or ii. where the level of risk to beneficial uses of groundwater is determined to be unacceptable, conduct an assessment of the operation and design of the landfill against best practice requirements and recommend measures and an implementation timetable to reduce and subsequently maintain the risk at an acceptable level.
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Audit Process
d. If the groundwater monitoring program assessed at 3.23 a) is deemed to be inadequate, recommend measures including an implementation timetable, to ensure the risks to the beneficial uses of groundwater surrounding the site to be determined.
2.3 Segments Considered
The geographical extent of the activity undertaken for this audit comprises the licensed premises covered by Waste Discharge Licence number ES90 and elements of the surrounding environment potentially impacted by activities in the licensed area. The licensed area has an overall footprint of approximately 215,000 m2, and includes Areas A, E, B, C, D and associated leachate ponds and surface water dams. It is unclear to the Auditor as to whether the Firewall separating solid inert waste from the surrounding coal seam extending along the eastern boundary of Areas A and E and the southern boundary of Area E forms part of the licenced landfill or in fact sits outside the licenced landfill area on the basis of an exemption from the Environment Protection (Industrial Waste Resource) Regulations 2009 (see Section 1.3). However, the Auditor will continue to assess the risk to groundwater and the need for monitoring around the Firewall and will include this information for consideration by MBC and EPA.
2.4 Elements Considered
The element of the surrounding environment that was considered by the audit is groundwater. Specific groundwater elements are as follows:
• Fyansford Formation Aquifer (Fyansford Aquifer), which is an unconfined aquifer that occurs above the Maddingley Coal Seam. • Lower Werribee Aquifer (Lower Werribee Aquifer), which is a confined aquifer that occurs beneath the Maddingley Coal Seam.
2.5 Audit Criteria
The selected criteria for this audit have been identified by the following sources:
• Australian and New Zealand Environment and Conservation Council (ANZECC) - Australian Water Quality Guidelines for Fresh and Marine Waters, 2000. • Environment Protection Act 1970. • EPA Publication 668 – Hydrogeological Assessment (Groundwater Quality) Guidelines, 2006. • EPA Publication 788.1, Best Practice Environmental Management (BPEM) – Siting, Design, Operation and Rehabilitation of Landfills, September 2010. • National Environmental Protection Council - National Environment Protection (Assessment of Site Contamination) Measure, 1999 (as amended in 2013). • State Environmental Protection Policy (SEPP) – Groundwater of Victoria, 1997 and related groundwater quality guidelines. • State Environmental Protection Policy (SEPP) – Prevention and Management of Contamination of Land, 2002 (as amended in September 2013) and related land contamination guidelines. • State Environmental Protection Policy (SEPP) – Waters of Victoria, 2003 and related surface water quality guidelines. • EPA Victoria – Waste Discharge Licence No. ES90, last amended 26 August 2009. • Waste Management Policy – Siting, Design and Management of Landfills, 2004 and related landfill management guidelines.
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Audit Process
• Water Act 1989.
2.6 Beneficial Uses – Groundwater
2.6.1 Fyansford Aquifer Based on monitoring data from Boreholes BH7, BH11, BH15 and BH 17 from July 2006 to July 2013, total dissolved solids (TDS) concentrations have ranged from 4,200 mg/L to 17,000 mg/L in the Fyansford Aquifer. The relatively high salinities in the Fyansford Aquifer were considered to be associated with potential impacts from the adjacent water bodies (BH7 and BH15 – irrigation dam, BH11 and BH17 – leachate ponds). Therefore, they were not considered to be a true representation of background groundwater quality. The beneficial use map series for aquifers in south western Victoria indicates that groundwater within the Fyansford Formation in the vicinity of the site is classified as Segment B. On this basis, groundwater in the Fyansford Aquifer was previously classified as Segment B (1,001 – 3,500 mg/L TDS) in accordance with State Environment Protection Policy (Groundwaters of Victoria) (the SEPP GoV). Monitoring bore (BH23) was installed to the west of the leachate ponds (refer to Figure 2 of URS 2013b for its location), screened within the Fyansford Aquifer, in October 2012 and its location is considered to be representative of background groundwater quality of the Fyansford Aquifer, i.e. the bore is not impacted or influenced by nearby water ways or ponds or other sources of potential impact. BH23 was monitored in January and July 2013 and TDS concentrations were 12,000 and 13,000 mg/L respectively. On this basis, the Auditor is of the opinion that groundwater in the Fyansford Aquifer can be classified as Segment C (3,501 – 13,000 mg/L TDS). The protected beneficial uses for Segment C groundwater are:
• Maintenance of ecosystems - Groundwater within the Fyansford Aquifer is likely to discharge to the Parwan Creek and/or surface water bodies on- and off-site. • Stock watering - Given that the site is located in a rural area, there is the potential that groundwater could be extracted for stock watering purposes. • Industrial water use - Although there is no significant industrial development currently located in the vicinity, groundwater may be extracted for industrial water use purposes at some time in the future. • Primary contact recreation - Given that groundwater is likely to discharge to the Parwan Creek there is the potential that the groundwater and surface water could be used for primary contact. • Buildings and structures - Given the depth of groundwater, it is unlikely that groundwater will affect off-site buildings and structures.
2.6.2 Lower Werribee Aquifer TDS has ranged from 1,200 mg/L to 8,400 mg/L in the Lower Werribee Aquifer based on monitoring data from Boreholes BH1, BH2, BH3, BH4, BH5, BH6, BH8, BH10, BH12, BH16, BH18, BH19, BH20, BH21 and BH22 from August 1999 to July 2013. Historically, groundwater monitoring bore BH12 has been considered the most indicative of background conditions in the Lower Werribee Aquifer. TDS concentrations in BH12 have ranged from 2,000 mg/L to 5,300 mg/L with a mean, from fifteen monitoring events, of approximately 3,920 mg/L. Monitoring data is now available for bores BH18, BH19 and BH20 which were installed outside the boundaries of the site in early 2010. Over the four rounds of monitoring reported to date, mean TDS concentrations from each of the newer monitoring bores are as follows:
• BH18 – 2,514 mg/L.
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Audit Process
• BH19 – 5,657 mg/L. • BH20 – 2,300 mg/L. Background concentrations of TDS in the Lower Werribee Aquifer vary from the upper end of the range for Segment B to the lower end of the range for Segment C groundwater, as defined in the SEPP GoV. Consistent with EPA’s approach to identifying groundwater segments, the Auditor has adopted the conservative assumption that groundwater in the Lower Werribee Aquifer are consistent with Segment B. The protected beneficial uses for Segment B groundwater are:
• Maintenance of ecosystems - Groundwater in the Lower Werribee Aquifer may ultimately discharge to Werribee River. However, the Werribee River is approximately 2 klm north and northeast of the site. • Agriculture, parks and gardens – Given the site is located in a rural area and hydraulically up- gradient of a market gardening area, there is potential that groundwater could be extracted for irrigation. • Stock watering - Given that the site is located in a rural area, there is the potential that groundwater could be extracted for stock watering purposes. • Industrial water use - Although there is no significant industrial development currently located in the vicinity, groundwater may be extracted for industrial water use purposes at some time in the future. • Primary contact recreation - Given that groundwater is likely to discharge to the Parwan Creek and Werribee River there is the potential that the groundwater and surface water could be used for primary contact. • Buildings and structures - Given the depth of groundwater, it is unlikely that groundwater will affect off-site buildings and structures.
2.7 Audit Methodology
The methodology used to conduct the MBC annual groundwater audit consisted of the following:
• Notification to EPA in accordance with Appendix 1 of EPA Publication 952.3 of the request to prepare an environmental audit report. Notification was sent on 10 September 2013. • Review of the information the assessment consultant provided: . URS Australia Pty Ltd (URS, 2013b), Preliminary Final Report 2012-2013 Annual Review, Maddingley Brown Coal Landfill, 30 October 2013 . Auditor comments on the above document dated 15 November 2013 and URS response dated 21 November 2013 (refer Appendix C). . URS Australia Pty Ltd (URS, 2013c), Final Report 2012-2013 Annual Review, Maddingley Brown Coal Landfill, 26 November 2013 (refer Appendix C) – limited review by the Auditor. • A site inspection with Tim Tilling, Environmental, Quality & Safety Officer, for The Maddingley Mining Trust on 12 November 2013 (to inspect landfill operations and discuss the progress of groundwater monitoring, leachate extraction and implementation of the previous audit recommendations). • Discussions with Tim Tilling relating to the following: . Leachate management and progress of the construction and implementation of the upgraded leachate treatment plant. . General site management and development of the landfill cells.
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Audit Process
. The revised solid inert waste side liner extension design prepared by Meinhardt. . The works approval issued by EPA in early 2013 extending the landfill into the Stage 2 area. • A compliance assessment against relevant Licence Conditions and the recommendations of the 2012 audit report. • Review of PAN No. 10800 issued by EPA in July 2012 and its requirements (refer Appendix B). • Review of Works Approval WA70655 issued on 7 March 2013 (refer Appendix F). • Review of a draft hydrogeological risk assessment and leachate management plan (URS, 2013a). • Review of a revised technical specification design for the Landfill Side Wall Liner Extension Stage 1 and 2 (Meinhardt, 2013) – design currently being reviewed by the appointed Construction Environmental Auditor, Peter J Ramsay of Peter J Ramsay & Associates. • Review of survey data collated by BGL Surveying: . Parwan Creek elevations taken in August 2011, and . Elevations of the Maddingley Coal Seam and Fyansford Formation Interface taken in September 2013. • Review of aerial survey data of the landfill working contours as at 28 June 2013. • Conducted a risk assessment of potential impacts to groundwater. • Provide a list of draft recommendations to MBC for comment. MBC provided comments and additional information relating to key recommendations. • Completion of this audit report.
2.8 Audit Team
In conducting this audit, assistance has been provided by Nadia Verga (Auditor Representative) from Senversa. Patrick Clarke relied on his own expertise in completing this audit (i.e. expert support team members were not consulted).
2.9 Risk Assessment
A qualitative assessment of risk to groundwater quality has been completed in general accordance with the requirements of AS/NZS ISO 31000:2009, Risk management – Principles and guidelines (Standard Australia/Standards New Zealand, 2009).
2.10 Audit Timeframe
The audit was conducted over a period from 10 September 2013 to 29 November 2013 and considered information and monitoring data available for the site from July 2012 to September 2013.
2.11 Exclusions
Specific exclusions from the scope of the audit relate to air emissions and surface water quality. No direct measurement of air quality or landfill gas accumulation within the landfill or surrounding formations was undertaken. Landfill gas monitoring has not previously been a requirement of the EPA licence. The requirement in the current licence conditions is limited to groundwater so consideration of air and surface waters has not been included in the scope of this audit. However, risk to surface water has been considered in the context of potential groundwater discharge to surface water bodies.
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Compliance Assessment
3.0 Compliance Assessment
3.1 Compliance with Licence Conditions
EPA licence conditions relating only to leachate management, leachate monitoring, groundwater monitoring and reporting have been assessed for compliance. The conditions and comments on compliance are summarised in the following table.
Licence Condition Compliance Auditor’s Comment Status
Table 1 Metal recycling Non-compliant Shredder floc was placed in Areas A and E during the Auditor’s site inspection shredder floc acceptable for on the 12 November 2013. The Auditor has been informed verbally by MBC landfilling in Area E only that previous licence amendments referred to the acceptance of floc material over Area A. MBC may consider updating references to Areas A and E with EPA in a future licence amendment.
2.11 Leachate reuse/disposal Compliant A Research Development and Demonstration (RD&D) application on a leachate R,D&D treatment approach was submitted and approved by EPA (11 January 2008). PAN No. 10800 issued by EPA in July 2012 requires the submission of a leachate management plan by 31 December 2012 and operation in accordance with the plan by 1 June 2013. MBC is currently in mediation with EPA in relation to the conditions in the PAN.
2.12 Works approval This licence condition may be superseded by the recent PAN issued by EPA in application for upgrade of July 2012 which requires the submission of a leachate management plan by 31 Non-compliant leachate reuse/disposal December 2012 and operation in accordance with the plan by 1 June 2013, thus system the construction of a leachate collection and treatment system is now required as part of works to satisfy the PAN conditions and may be considered exempt from the works approval process. Non-compliance is noted as a Works Approval Application was not submitted by the required date, being 29 July 2008. MBC is currently in mediation with EPA in relation to the conditions in the PAN.
2.13 Leachate extraction Non-compliant Measurement of standing leachate levels in sumps (see Section 5.2.1 and (depth of leachate not to Table 4.4 in URS 2013b) indicated that leachate levels in Areas A and E were exceed 300 mm) not being maintained at less than 300 mm above the lowest point of the drainage layer. This licence condition may not be suitable for an unlined landfill cell such as Area A as it does not contain a leachate drainage layer or base liner and may also be difficult to comply with in the newly lined Area E cells due to the poor isolation of the waste within each of these areas i.e. no side liner exists to physically and hydraulically separate accumulated leachate within the waste. It is also noted that groundwater inflow to the older unlined cells (Cell A) will result in leachate levels rising in the waste unless continuous leachate extraction is followed.
2.14 Management of water on Compliant Based on the Auditor’s inspection of the site, there was no evidence of surface landfill surface (leachate or water pooling on the landfill surface. water must not be allowed to pool on landfill surface)
2.15 Surface water drainage Unclear The auditor is satisfied that adequate surface water drainage features are in (diversion from waste disposal place to divert surface water run-off away from waste disposal areas in Areas A areas) and E such that they do not contribute to leachate generation. While there may have previously been potential for leachate runoff from Areas A and E to enter unlicensed and unlined parts of the site, it was noted at the site inspection conducted on the 12 November 2013, the western batter of Area A and southern batters of Areas A and E were almost completely covered with compacted clay (i.e. an intermediate clay cap), and so this issue should now be resolved. However, the potential for leachate bursts through the intermediate clay cap associated with leachate heads needs to be effectively managed. Low pH levels in Dam D4 during the July 2013 monitoring round suggest that impacted surface water runoff in Landfill Areas B, C and/or D may be entering the dam, however, further monitoring is required to confirm this.
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Compliance Assessment
Licence Condition Compliance Auditor’s Comment Status
2.16 Leachate must not be Compliant Discussions with the landfill operator indicate that leachate is no longer used for sprayed onto cells dust suppression. However, it continues to be disposed back onto Cell E5. A letter from EPA to the operator dated 14 November 2011 (refer Appendix B URS 2012b) indicates the EPA has allowed irrigation of leachate in Cell E4 and E5 only as a temporary leachate management measure.
3.1 Maintain Compliant The groundwater monitoring bores specified in the licence, as well as others groundwater bores more recently installed, are being maintained.
3.3 and 3.4 Groundwater Compliant The groundwater monitoring has been carried out as specified. monitoring
3.6 Maintain Compliant Based on the Auditor’s inspection of the site, the groundwater collection sump is groundwater collection sump being maintained.
3.7 Maintain leachate sumps Non-Compliant Sump A1 was constructed as a replacement sump in Area A in August 2012. However, leachate extraction and recovery from the well has been unsuccessful. MBC is yet to develop a new leachate extraction plan for Area A. The leachate sumps in Area E (E4 and E5 sumps) are being maintained as leachate extraction and sampling has occurred throughout 2012-2013. Sump C in Area C is being maintained as it was sampled in July 2013, however it is currently not being used for leachate extraction. Refer to Sections 5.2.1 and 7.0 for more detail.
3.8 Measurement of standing Compliant Standing leachate levels were obtained in July 2012, January 2013 and July leachate levels 2013 from all sumps at the landfill including Sump A1, Sump E4, Sump E5, Sump C and the Firewall Sump.
3.9 Analysis of leachate Compliant Leachate analysis has been carried out as specified in the licence. Most issues from the previous reporting period were resolved after Auditor enquiries in September 2012, resulting in URS providing the laboratory with updated sample and analyte lists in October 2012 for their future reference.
3.14 Sampling and analysis Compliant Sampling and analysis of groundwater has been carried out as specified.
3.18 e) Site water balance In progress Completion of a site water balance is not possible given current data gaps. In particular, it appears likely that groundwater beneath Areas A and E is contributing to leachate generation (i.e. there is a hydraulic head that has the potential to cause a net upward flow of groundwater into the landfill cells). The groundwater contribution to leachate generation is not known and will require adequate leachate and groundwater elevation data, leachate pumping trials and a comprehensive groundwater model (HA preparation in progress). Leachate pumping trials are unlikely to be practicable until a new leachate treatment and management system is implemented.
3.22 Environmental Audit Non-Compliant The Annual Monitoring Review report prepared by URS was submitted to the Report submitted by 30 Auditor on 30 October 2013 making submission of the audit report by 30 September 2013 September 2013 impractical. Additional information and clarifications of information were requested by the Auditor and reponses provided in December 2013.
3.2 Compliance with 2012 Audit Recommendations
The Auditor made a number of recommendations relating to management of leachate and risks to groundwater and surface water in the 2012 audit. The status of compliance with the recommendations of the 2012 audit report is summarised in the table below. It is noted that several of the recommendations have not, at the time of this report, been complied with. Where that is the case and the recommendations are still relevant they are repeated in this report (see Section 10.0).
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Compliance Assessment
Short Term Actions
Recommendation Implementation Auditor’s Comments Timetable
The stability of the lower section of the western batter of June 2013 Geotechnical investigation completed in July Area A should be investigated as a priority by a 2013 by NSP Geotechnics indicated that the geotechnical engineer or similar. Further short term lower section of the western batter of Area A is actions will be dependent on the conclusions of the potentially unstable. investigation. Depending on the results of further MBC have indicated that waste extends further investigation, reducing leachate heads on the western to the west of the current toe of the lower side of Area A may be required to stabilise the slope and western batter and the slope can be completed maintain lower leachate levels across Area A. at a lower angle. It is recommended that MBC conduct an investigation to confirm the extent of waste, commission a design for the lower western slope and construct that design with a final cap over the lower slope. Refer to Section 6.1 for more detail.
Continue to apply and maintain interim clay capping over On-going This will be an ongoing requirement. Landfill Areas A and E. The batters around west and north of Area A have been covered with interim clay. Part of Cells E4 and E5 are covered with interim cap. The peak of the landfill remains the active tipping area. The Auditor notes that some of the capped areas, particularly on the eastern side of the landfill, will become active tipping areas again due to the revised final contours approved as part of Works Approval WA70655. Stripping and re-application of interim clay cover will be required. The Auditor recommends the degree of erosion over the interim cap be monitored closely and repaired where required, particularly along the western batter of Area A.
Identify sections of Landfill Areas A and E which may be June 2013 Incomplete. covered with final capping immediately and prepare a Revised final contours for the landfill were Rehabilitation Plan, including a cap design specification, a approved as part of Works Approval WA70655 construction quality assurance (CQA) plan, and an in March 2013 (refer to Appendix I of URS estimated capping start date. It is assumed that the cap 2013b). design and CQA plan would be submitted for EPA approval. The current working contours at the landfill as at June 2013 (refer to Appendix H of URS 2013b) indicate the western batter of Area A and the northern batter of Area A and Cell E5 are at or close to the revised final contours in these areas. Further grading works are likely to be required, then final capping could be placed over the western and northern batters of Area A.
Investigate options for increasing leachate pumping rates June 2013 In progress. from Area A to maintain an up-ward hydraulic gradient Extraction from Sump A1 has been from the underlying Lower Werribee Aquifer and, if unsuccessful as it has failed to recover and required, to ensure stability of the western batter of Area produce large volumes of leachate. A. Develop a plan for increased leachate pumping from Area A. HA and LMP currently being prepared by URS – the Auditor has completed a preliminary review of both documents. The Auditor will conduct a final review of both documents in the coming weeks. It is expected that further leachate level data will be required to assess whether further lowering of leachate in Area A is required and, if so, how it will be lowered. Refer to Section 7.0 for further detail.
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Compliance Assessment
Recommendation Implementation Auditor’s Comments Timetable
Confirm whether a side liner exists along the western side June 2013 – Incomplete. of landfill Area A, filled by previous owners, in order to information to be MBC advises some sections of the western design final cap tie ins. included in boundary of Area A were exposed using on-site Rehabilitation machinery; however, evidence of the work and Plan above. its findings has not been made available to the Auditor. The Auditor is of the opinion that confirmation of the presence of this side liner must occur as soon as possible in order to progress design of final capping of the western batter of Area A and key-in with any side liner between the waste and coal. Refer to Section 6.1 for more detail.
Commission new leachate treatment system so that Was due to be Incomplete. leachate levels in landfill areas A and E are maintained completed by Commissioning of the new leachate treatment below the inferred groundwater levels in the Lower June 2013 to plant commenced in September 2013 and is Werribee Formation. comply with the now operated intermittently. Management of PAN. Still in the by-product of retentate remains an ongoing progress. issue requiring resolution that continues to be investigated as part of PAN mediation between MBC and EPA. Timing will be dependent on finalisation of an HA and LMP and subsequent EPA approval.
Re-lining of the existing leachate ponds or construction of Condition 3.6 of Incomplete. new lined leachate ponds. PAN No. 10800 HA and LMP currently being prepared by URS If the new leachate treatment system has yet to be requires – the Auditor has completed a preliminary commissioned, alternative means of leachate storage or completion by 1 review of Revision 1 of both documents and will disposal may be required to allow re-lining of the leachate June 2013. complete a final review of both documents in ponds or construction of new leachate ponds. the coming weeks. Based on preliminary review of the draft HA, the Auditor understands that MBC will need to expand current leachate storage at the site and will need to construct new leachate ponds. WA70655 requires any new pond must be designed and approved as per EPA publication 1323 and constructed under audit. The Auditor is of the opinion that design of additional pond storage should commence as soon as possible to progress construction during the current warmer, drier weather. Re-lining of the existing ponds should be placed on hold until the following summer period so that further monitoring of volatile fatty acids (VFAs) in the groundwater can occur in 2014 (to confirm whether they are leaking or not).
Ensure leachate levels in the Firewall Sump are monitored January 2014 Partially complete. and included in the 2012-2013 annual monitoring review. Leachate levels were monitored in the sump Re-survey the top of the sump. during the July 2013 monitoring round. The sump was re-surveyed in July 2013, however, the elevation of the top of the sump noted in Table 1 of URS 2013b indicates the sump is sitting below the elevation of the waste, taken from the June 2013 aerial survey in Appendix H of URS 2013b, therefore there is some uncertainty in relation to the measured leachate levels from this sump.
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Compliance Assessment
Recommendation Implementation Auditor’s Comments Timetable
Record leachate extraction volumes from the Firewall January 2014 Completed. Sump with a flow meter or similar. Include in the 2012- A flow meter was installed and operating in the 2013 annual monitoring review. Firewall sump in June 2013. The measured extraction volume for the month of June was 631m3. MBC has indicated that the extraction volumes from the sump since then have reduced significantly.
Maintain LB01A and LB02A as leachate monitoring wells, June 2013 Incomplete. rather than leachate sumps. It is recommended that Leachate was extracted from LB02A over a leachate levels in LB01A and LB02A are continuously period of two weeks (approximately 17,000L). monitored using pressure transducers and data loggers. Leachate levels in LB01A and LB02A should be used to MBC have purchased two data loggers for assess risk to the underlying Lower Werribee Aquifer installation in both wells, however, they have associated with potential vertical down-ward hydraulic not been installed. Given the unexplained gradients. Continuous leachate level data will assist in the decrease in leachate levels in Area A from HA in understanding leachate responses to rainfall and August 2012 to July 2013 i.e. leachate levels may be used as part of leachate pumping trials. Leachate dropped over 12 m in LB02A over 12 months level monitoring data should be included in the annual without active leachate extraction from the area, monitoring report. the Auditor is of the opinion that installation of data loggers in the wells is critical to understanding the relationship between leachate levels and rainfall and the upward hydraulic gradient from the Lower Werribee Aquifer.
Provide access to the Groundwater Dewatering Sump with June 2013 Incomplete. an elevated work platform or similar during each The Auditor notes that MGT obtain leachate monitoring round so water levels in the sump can be samples from the sump when the dewatering accurately measured. pump is operational (from a sample tap from the discharge line). Therefore it is difficult for MGT to measure the groundwater levels in the sump while the pump infrastructure remains down the well. It is also difficult to drop the water level meter down the sump as it lies on an angle. A new method of groundwater level monitoring should be devised by MBC in conjunction with MGT and URS as soon as possible.
Survey the contact between the base of the Fyansford May 2013 Completed. Formation and the upper surface of the coal seam in the The interface between the Maddingley Coal western, eastern, southern and northern walls of the mine Seam and the Fyansford Formation was pit. Survey of an inferior coal seam, should it exist, should surveyed by BGL Surveying in September also be conducted. Detail should be included in the 2012- 2013, however, was not completed along the 2013 annual monitoring review and the hydrogeological southern boundary of the landfill as the Auditor cross-section. due to the elevation of the firewall has exceeding the base of the Fyansford formation. Refer to Section 8.4 for further detail.
Survey the final elevation of the top of the Firewall (Areas Southern part of Incomplete. 1 to 4) for comparison with the Fyansford Formation and the firewall – as Coal Seam interface. Detail should be included in the soon as possible, 2012-2013 annual monitoring review and the and then as soon hydrogeological cross-section. as each part of the Firewall reaches the extent of the inferior coal seam
Survey elevations of the base of Parwan Creek. Detail May 2013 Completed. should be included in the 2012-2013 annual monitoring The creek was surveyed by BGL Surveying in review and the hydrogeological cross-section. August 2011. The information was provided to the Auditor in October 2013.
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Compliance Assessment
Recommendation Implementation Auditor’s Comments Timetable
Install four groundwater monitoring bores in the Fyansford January 2014 Incomplete. Aquifer between the Fire Wall and Parwan Creek on the The Auditor notes that these groundwater bores southern and eastern side of Areas A and E. should be installed before waste is placed adjacent to the Fyansford Formation, which the Auditor understands has already occurred along the southern boundary of the landfill. Refer to Section 8.4 for further detail.
Secondary Actions
Recommendation Implementation Auditor’s Comments Timetable
Ensure all leachate sumps and bores are accessible for leachate June 2013 All leachate sumps were available level monitoring and sampling. This includes removal of pumps for leachate level monitoring and prior to the commencement of monitoring rounds and providing safe sampling in January and July 2013, access to the edge of the sump/bore if it protrudes greater than apart from Sump E4 and the 1.5m from the surface. Firewall Sump in January 2013. However, leachate levels were not taken.
Ensure leachate levels in Sump C are monitored and included in the January 2014 Completed. 2012-2013 annual monitoring review (currently not included in table Leachate levels in Sump C were 5-4 of URS 2012b). taken in January and July 2013.
Continue to prepare a reliable hydrogeological assessment (HA) for August 2014 In progress. the site to assess the following: HA and LMP currently being • Long-term leachate seepage rates from the landfill post prepared by URS – the Auditor has closure. completed a preliminary review of of • Drawdown on the peizometric surface in the Lower Werribee both documents and will complete a Aquifer associated with extraction from the Groundwater final review of both documents in Sump. the coming weeks. Given this part of the landfill is nearing closure; determine the EPA must be engaged to obtain leachate levels to be maintained to protect groundwater. agreement with timing which differs from condition 3.2 of PAN No. 10800, “…by 31 August 2012, or subsequent EPA approved variations.”
Complete leachate pumping trials on all sumps in order to calibrate Once capacity to Incomplete. and refine a hydrogeological conceptual model for the site, which extract, treat and A leachate pumping test on Sump would form part of the HA above. dispose of A1 was conducted on 22 October leachate has been 2012 and failed to maintain a established. constant pumping rate and did not Timing to be achieve steady-state conditions. As agreed with EPA. an alternative, recovery data was analysed rather than drawdown. The transmissivity of the waste was estimated to be 0.21m/d, and the hydraulic conductivity 0.01 m/d. The Auditor expects further detail to be provided in the revised HA and LMP in the coming weeks, in relation to pumping trials and calibration of the numerical model.
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Compliance Assessment
Recommendation Implementation Auditor’s Comments Timetable
The rate of collection and analysis of quality control samples must Continue for future Completed. be increased to meet the requirements of relevant guidelines. The monitoring rounds. Refer to Section 5.1 for further Auditor was advised by URS in October 2012 that the sampling detail and Section 4.5 of URS technicians have been informed to collect additional QA/QC 2013b. samples and that this commenced in July 2012.
The annual groundwater monitoring report for FY12/13 should September 2013 Partially complete. include July 2013 monitoring results and should be submitted to the The 2012-2013 annual review auditor as soon as possible and no later than 12 weeks prior to the included July 2013 monitoring due date. MBC to seek an extension on the submission of the next results, however, was provided to groundwater audit report until the end of December 2013. the Auditor on 30 October 2013.
Ensure all parameters are tested in leachate samples (sumps and Continue for future Partially complete. ponds). Auditor enquiries in September 2012 resulted in URS monitoring rounds. TOC and Tin were missing from providing the laboratory with updated sample and analyte lists in leachate sumps and ponds in October 2012 for their future reference. January 2013. Refer to URS 2013b.
Include the bore log of BH23 and new monitoring wells in the August 2013 Completed. Fyansford Formation in the 2012-2013 annual monitoring review Borelog of BH23 found in Appendix and in the hydrogeological cross-section. D of URS 2013b.
Ensure newly constructed groundwater monitoring wells are August 2013 Completed. surveyed and included in the July 2013 monitoring round. BH23 was surveyed and included in the January and July 2013 monitoring rounds. Refer to URS, 2013b.
Pursue further historical information about the construction of the August 2013 Completed. current and former dewatering sumps and how they are connected. URS indicate a DPI search for such Investigate former extractive work plans that may be held by the documents was completed as part Department of Primary Industries. of the preparation of the HA and information in relation to this was not identified.
Add phenols analysis to groundwater testing in BH21 and BH22 in July 2013 Completed. future monitoring rounds. monitoring round Phenols analysis completed for these bores in July 2013. Refer to URS 2013b.
Analyse a larger suite of metals in Lower Werribee Formation July 2013 Completed. groundwater bores hydraulically down gradient of Area C and the monitoring round Refer to URS 2013b. Firewall. Cadmium, Chromium, Copper, Mercury, Lead, Selenium, Tin and Zinc to be included in future monitoring rounds for groundwater bores BH6, BH16, BH2, BH21 and BH22
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Geology and Hydrogeology
4.0 Geology and Hydrogeology
4.1 Geology
Golder conducted a review of the geological setting as part of its hydrogeological assessment (Golder, 2008). In general, the Auditor agrees with the findings of the Golder report relating to the geological setting. The geology of the site and surrounds is presented in the following section of the Bacchus March 1:50,000 Geological Map.
The geological units (from oldest to youngest) at the site consist of the following:
• Ordovician Basement Sediments - This formation consists of mainly marine slate, shale, sandstone and siltstone sediments. • Tertiary Werribee Formation – Two members of the Werribee Formation exist at the site. These are the Maddingley Coal Seam and the Lower Werribee Formation, as described below: . Undifferentiated Werribee Formation – This formation is encountered below the Maddingley Coal Seam in the site vicinity and is referred to as the Lower Werribee Formation. It consists of fluvial clays, sands and minor gravels. It is noted that it was previously referred to as the Lerderderg Gravel Member but more a more recent interpretation did not support the occurrence of a distinguishable gravel and coarse sand unit beneath the Maddingley Coal Seam (Golder, 2008). . Maddingley Coal Seam – This formation surrounds the base and walls of the MBC landfill and has/is continued to be mined at the site. It comprises of brown coal with minor clay and silts.
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Geology and Hydrogeology
• Tertiary Fyansford Formation - This formation is encountered above the Maddingley Coal Seam and consists of marine silts, sands and marls. The Fyansford Formation in the vicinity of the site was previously interpreted as Upper Werribee Formation (Douglas and Ferguson, 1988). The current interpretation of regional geology (Birch, 2003) reclassified the Upper Werribee Formation as Fyansford formation. • Quaternary Newer Volcanic Basalt - This formation consists of olivine or labradorite olivine basalts, dark to light grey in colour, coarsely vesicular and interbedded with minor silty sands and baked soils. It is understood that the Newer Volcanics is not found to the north of the site around the Werribee River. The Newer Volcanics Basalt outcrops on the slopes on the eastern side of Parwan Creek opposite the site but does not appear to be present beneath the site. • Quaternary Alluvial Deposits – This formation consists of various clay, sand, silt and gravels associated with high level river terraces. Quaternary Alluvial deposits outcrop across the area west and northwest of the open cut pit and over the Newer Volcanics on the eastern side of Parwan Creek.
4.2 Hydrogeology
Golder conducted a review of site hydrogeology as part of its hydrogeological assessment (Golder, 2008). In general, the Auditor agrees with the findings of the Golder report relating to site hydrogeology. A conceptual cross section, running from west to east, through the site is presented in Figure 3 of this report. The main hydrostatic features relating to the landfill are shown in Figure 3. The main hydrostratigraphic units at the site and in the surrounding area (from shallowest to deepest) include:
• Alluvial sediments (Unconfined aquifer). • Newer Volcanics (Unconfined aquifer). • Fyansford Formation (Unconfined aquifer). • Maddingley Coal Seam (Confining layer or Aquitard). • Lower Werribee Formation (Confined aquifer). • Ordovician Basement Sediments (Confined aquifer). As illustrated in the Conceptual Geological Cross Section, the open cut pit and landfilling areas are within the Maddingley Coal Seam. The Fyansford Aquifer overlies the Maddingley Coal Seam and was presumably removed as overburden as part of the excavation of the open cut pit. As a consequence, the Fyansford Aquifer is not present beneath the landfill areas. However, the Fyansford Formation Quaternary Alluvial Deposits and Newer Volcanics are present beneath the leachate ponds (L1 and L2), Fire Dam (D5) and the irrigation dam. The Fyansford and New Volcanics Aquifer appear to be part of the same hydraulic system. The Maddingley Coal Seam is a formation, reported to be up to 59 metres thick, of low hydraulic conductivity material that confines groundwater within the underlying Lower Werribee Aquifer and provides a base to perch groundwater in the overlying Fyansford Formation. Surface drains have been constructed in benches cut into the Maddingley Coal Seam in the walls of the open cut pit, immediately beneath the lower surface of the Fyansford Formation, to intercept groundwater seepage from the formations overlying the coal seam and direct it to stormwater dams. As a consequence, groundwater in the Fyansford and other formations overlying the Maddingly Coal Seam drain into the open cut pit.
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Geology and Hydrogeology
A clay barrier was reportedly placed above the Maddingley Coal Seam at the landfill base in Area A for fire protection purposes. More recently, an engineered landfill liner system has been installed beneath Area E. Although the extent, thickness and permeability of the clay barrier in Area A is not clearly understood, the drilling of leachate bores LB01, LB02, LB01A and LB02A has provided some elevation data. The landfill design and construction is discussed in further detail in Section 6.0. Leachate is present in the waste and appears to be perched over the landfill liner (Area E) and clay barrier (Area A) at the base of the landfill. However, due to an apparent upward vertical hydraulic gradient, it is possible that groundwater from the Lower Werribee Aquifer is contributing to leachate generation. Although no engineering details of its construction exist, groundwater is thought to be extracted from the Lower Werribee Aquifer (or possibly partly from the Maddingley Coal Seam) via a groundwater interception system believed to consist of a series of trenches excavated into the Maddingley Coal Seam and extending beneath Area E. Groundwater is extracted from the interception system via the Groundwater Dewatering Sump. The geochemistry, in terms of major cations and anions, of water extracted from the Groundwater Dewatering Sump is consistent with the geochemistry of groundwater in monitoring wells screened in the Lower Werribee Aquifer, but may also show signs of groundwater quality within the Maddingley Coal Seam i.e. elevated ammonia levels. However, the degree of hydraulic connection between the groundwater interception system and the Lower Werribee Aquifer has yet to be confirmed. The Auditor recommends further historical information is pursued in relation to the construction of the current and former groundwater dewatering sumps and how they are connected. Former extractive licence work plans including site surveys and water management strategies may be held by the Department of Primary Industries.
4.3 Groundwater Levels and Flow Direction
4.3.1 Fyansford Aquifer Groundwater flow in the Fyansford and other shallow aquifers at the site is predominantly toward the open cut pit (see Figure 3 of URS 2013b), which is consistent with the complete sequence of these formations being exposed in the walls of the open cut pit. Monitoring of newly installed groundwater bore BH23 in 2013, located to the west of the leachate treatment ponds, further confirms this. After showing a steady decrease between 2008 and 2010, the measured groundwater levels in the Fyansford Formation Aquifer rose by up to 2 m, as reported during the 2010-2011 monitoring period. The rise in water levels in the Fyansford Aquifer is most likely attributable to increased recharge associated with higher rainfall over this period, compared to the preceding nine years of below average rainfall. Groundwater levels reported during the 2012-13 monitoring period have remained relatively stable in BH11 and BH17 to the west of the landfill and in the vicinity of leachate ponds L1 and L2. However, groundwater levels in BH7 and BH15 to the north of the landfill and adjacent to the Parwan Creek and the Irrigation Dam, dropped nearly 3 m between July 2012 and January 2013, and then rose again between 0.5 m to 1.5 m in July 2013. Groundwater elevations in BH23, since it was installed in October 2012, are similar to those seen in BH17, located adjacent to leachate pond L1, refer to inferred groundwater levels in Figure 3. Groundwater elevations in BH11 located adjacent to leachate pond L2 remain approximately 27m higher than the nearest Fyansford formation groundwater bores (BH17 and BH23) and is considered to represent perched water over a shallower low permeability layer in the Fyansford Formation. Groundwater elevations in BH11 have continued to range between 130.74 to 132.2 mAHD since July 2006.
4.3.2 Lower Werribee Aquifer Contours of groundwater elevation in the Lower Werribee Aquifer, presented in Figure 4 of URS 2013b indicate that regionally groundwater flows from south west to north east across the site. Groundwater levels measured in BH18 indicate groundwater flow in the Lower Werribee Aquifer from
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Geology and Hydrogeology
the area east of the site has a westerly component back toward the landfill. Groundwater levels in the Lower Werribee Aquifer have fluctuated up to around 1 m to 2 m over recent years. However, the largest change is seen in groundwater levels monitored in BH16, approximately 50 m to the east of the Groundwater Dewatering Sump, which has seen an unexplained increase of 5.4 m from January 2010 to January 2012, and has steadily been decreasing since then to 75.27 mAHD in July 2013. There is currently uncertainty as to whether the lowest area in the piezometric surface in the Lower Werribee Aquifer is located northeast of the landfill, between BH2 and BH18, or is a cone of depression, centred on the Groundwater Dewatering Sump, associated with continuous extraction from the Lower Werribee Aquifer. The actual elevation of groundwater in and adjacent to the Groundwater Dewatering Sump is estimated at approximately 64 mAHD (last measured in July 2008), which would suggest a significant cone of depression is being caused in the piezometric surface of the Lower Werribee Aquifer. Standing water levels in the Groundwater Dewatering Sump have not been collected since 2008 due to access issues. More current data on the standing water levels within the Groundwater Dewatering Sump are required to better assess the likely extent of the cone of depression. In 2011, URS conducted preliminary groundwater modelling which suggested that the rate of groundwater extraction from the Groundwater Dewatering Sump, 10,594 m3/year, is insufficient to cause a significant cone of depression in the piezometric surface of the Lower Werribee Aquifer. Golder had previously been commissioned to establish a more detailed groundwater model for the site to provide a more accurate basis to model potential drawdown around the Groundwater Dewatering Sump. URS is currently completing numerical modelling of the site as part of the HA (as required by condition 3.2 of PAN No. 10800). Groundwater levels in the Groundwater Dewatering Sump should be monitored in order to calibrate any groundwater modelling completed in future revisions of the document. Groundwater elevations have consistently indicated a marked downward hydraulic gradient from the Fyansford Aquifer to the Lower Werribee Aquifer in the site vicinity. The difference in hydraulic head between the two varies across the site but was at least 20 m during the most recent reporting period. For the nested bores BH7 (Fyansford Aquifer) and BH8 (Lower Werribee Aquifer) the depth to water was approximately 24.22 m higher in the Fyansford Formation Aquifer compared to the Lower Werribee Aquifer in July 2013. Based on currently available data, it is difficult to assess the vertical hydraulic gradient between the Lower Werribee Aquifer and leachate in the landfill. Based on water levels in the Groundwater Dewatering Sump (2008) representing the Lower Werribee Aquifer and leachate levels in bores LB01A and LB02A (in July 2013), it would appear there is an upward hydraulic gradient from the Lower Werribee Aquifer to the landfill. As such, groundwater from the Lower Werribee Aquifer may be contributing to leachate generation. If leachate were seeping down through the landfill liner, chemical impacts should be evident in groundwater extracted from the Groundwater Dewatering Sump. Refer to Section 5.3.2 for a description of groundwater monitoring data obtained from the Lower Werribee Formation.
4.4 Bore Construction and Monitored Aquifers
The monitoring bore and sump locations are shown in Figure 2 of the 2012-2013 Annual Review (URS, 2013b). Details of the monitoring network are as follows:
Bore/Sump ID Aquifer/Medium Activity
BH7, BH11, BH13, BH15, Fyansford Aquifer Monitoring bore BH17 and BH231
BH2, BH4, BH6, BH8, BH10, BH12, BH16, Lower Werribee Aquifer Monitoring bore
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Geology and Hydrogeology
Bore/Sump ID Aquifer/Medium Activity
BH18, BH19, BH20, BH21 and BH22
Groundwater Dewatering Sump Lower Werribee Aquifer / Dewatering and monitoring Maddingley Coal Seam
Landfill Area A sumps: Leachate Leachate collection and monitoring Sump A12
Landfill Area A monitoring wells: Leachate Primarily leachate monitoring, but may LB02A2,3 also be used for leachate collection
Landfill Area E sumps: Leachate Leachate collection and monitoring E4 and E5
Landfill Area E monitoring wells: Leachate Primarily leachate monitoring, but may LB01A2,3 also be used for leachate collection
Landfill Area C sumps: Leachate (from Category C Leachate collection and monitoring C contaminated soil)
Firewall Leachate Sump Leachate (from Category C Leachate collection and monitoring contaminated soil)
1 Recently installed in October 2012 and included in monitoring rounds since January 2013.
2 Recently installed in August 2012 as replacements and included in monitoring rounds since August 2012.
3 Constructed so they can also be used for leachate extraction if required.
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Leachate, Groundwater and Surface Water Monitoring
5.0 Leachate, Groundwater and Surface Water Monitoring
5.1 Analytical Data Quality
This section presents a review of the quality assurance procedures and quality control results for groundwater monitoring. URS included an assessment of analytical data quality in section 4.5.1 of URS 2013b. The Auditor reviewed that section of the report and conducted spot checks of the quality assurance data provided. Most issues surrounding leachate analytical parameters tested in various leachate sump and dam samples have been resolved since the 2011-2012 annual review. Auditor enquiries in September 2012 resulted in URS providing the laboratory with updated sample and analyte lists in October 2012 for their future reference. This should continue for future monitoring rounds. Overall, the Auditor agrees with the assessment of data quality conducted by URS. The data set for the 2011-2012 period is sufficient, with respect to data quality, for interpretive use. Where issues were identified with quality controls results, URS used the data in an appropriate manner which did not affect the overall assessment of risk to groundwater. The Auditor makes the following recommendations in relation to the integrity of monitoring data used in the annual review:
• The Auditor agrees with URS that leachate samples from the leachate dams should not be filtered prior to analysis, as per the leachate well and sump samples. • Low flow sampling of groundwater bores is not required at the landfill as volatile contaminants are not chemicals of interest at the site. It may also not be appropriate in collecting representative samples of the aquifer, and BH20 is an example where this may be the case as groundwater was noted to froth and had an elevated pH during sampling. The sampling methodology for groundwater monitoring bores must be conducted by removing 3 borehole casing volumes first, rather than using low flow sampling. This should be implemented by sampling personnel at the next monitoring round. • Low flow sampling methodology used for groundwater monitoring bores must ensure that sampling occurs from the screened interval of the groundwater bore. This information should be provided to sampling personnel each monitoring round. If this information is not available, sampling personnel should be instructed to confirm the base of the monitoring bore at the time of sampling and then place the sample pump inlet 1 to 2 m above the base of the bore. • Ensure that nitrate, nitrite, total nitrogen and TKN are monitored in all dams on site in future monitoring rounds. The Auditor notes that these parameters are required in the EPA licence to be analysed in leachate ponds L1 and L2, but not in Dams D4, D5, D6, Irrigation Dam and Surface Water Dam. However, nitrate, nitrite, total nitrogen and TKN have been analysed in these dams since January 2009 but were not included in the January and July 2013 monitoring rounds. In section 4.5.1 of URS 2013b, URS note that the laboratory did not provide ionic balance calculations for leachate samples. The Auditor does not think these calculations are appropriate for leachate samples.
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Leachate, Groundwater and Surface Water Monitoring
5.2 Leachate Monitoring
5.2.1 Standing Leachate Levels Standing leachate levels varied between the leachate sumps. The levels reported are discussed below:
• Sump A1 (Area A) was drilled as a replacement sump in August 2012 and recorded a depth to leachate of 44.6 m in July 2013. The measured depth to leachate equated to a relative leachate elevation of 76.06 mAHD and a saturated thickness of approximately 15.76 m of leachate within the sump. The leachate elevation in the sump dropped 13.74 m since the January 2013 monitoring round, without active leachate extraction from the sump or surrounding area. For this reason, the leachate levels from this sump are considered unreliable until leachate levels are confirmed by further monitoring. • LB01A (Area E) was drilled as a replacement monitoring bore in August 2012 and recorded a depth to leachate of 39.2 m in July 2013. The measured depth to leachate equated to a relative leachate elevation of 71.91 mAHD and a saturated thickness of approximately 7.21 m of leachate within the well. • LB02A (Area A) was drilled as a replacement monitoring bore in August 2012 and recorded a depth to leachate of 36.73 m in July 2013. The measured depth to leachate equated to a relative leachate elevation of 80.03 mAHD and a thickness of approximately 22.55 m of leachate within the well. The leachate elevation in the sump dropped 12.35 m since the January 2013 monitoring round, without active leachate extraction from the sump or surrounding area. For this reason, the leachate levels from this sump are considered unreliable until leachate levels are confirmed by further monitoring. • Sump E4 (Area E) recorded a depth to leachate of 24.73 m during the July 2013 sampling round. The measured depth to leachate equated to a relative leachate elevation of 60.6 mAHD and a thickness of approximately -0.4 m of leachate within the sump. It is assumed the sump was raised at some point between it being surveyed and monitored, as such, the leachate thickness is expected to be around 2 m (as concrete collar extensions are normally 2.4 m high). This would be consistent with leachate thicknesses seen in the sump in 2011-2012. Leachate levels in the sump may not be representative as leachate extraction occurred within the sump and it may not have recovered fully at the time of monitoring. • Sump E5 (Area E5) recorded a depth to leachate of 3.6 m in July 2013. The measured depth to leachate equated to a relative leachate level of 69.87 mAHD and a saturated thickness of approximately 1.17 m of leachate within the sump. Leachate levels in the sump may not be representative as leachate extraction occurred within the sump and it may not have recovered fully at the time of monitoring. • Firewall Sump recorded a depth to leachate of 21.96 m in July 2013. The measured depth to leachate equated to a relative leachate level of 63.7 mAHD and a thickness of approximately 2.1 m of leachate within the sump. The last leachate level taken in the sump was in January 2011 and indicated approximately 11.5 m depth of leachate. Therefore leachate levels have decreased by 9.4 m in approximately 2.5 years. A flow meter was installed within this sump in June 2013, which indicated extraction rates in June 2013 were relatively high but have dropped since. Leachate levels in the sump may not be representative as leachate extraction occurred within the sump and it may not have recovered fully at the time of monitoring. • Sump C recorded a depth to leachate of 12.48 m in July 2013. The measured depth to leachate equated to a relative leachate level of 76.52 mAHD and a thickness of approximately 1.42 m of leachate within the sump. Leachate was not extracted from this sump in 2012/13. It is unclear if
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Leachate, Groundwater and Surface Water Monitoring
leachate levels within the sump are representative of leachate levels within Area C as construction data in relation to the base of Area C and the sump is unavailable (refer Section 6.3 for further detail). Overall, due to the unexplained reduction in leachate levels measured within Area A and cells E to E3, leachate elevations monitored throughout 2012-2013 are considered unreliable and as such, there remains a large degree of uncertainty as to what the true leachate levels within these areas may be. Installation of continuous leachate level monitoring infrastructure will provide the Auditor with more reliable data in order to assess the risk posed to groundwater by varying leachate thicknesses. There also continues to be uncertainty in the surveyed top of casing for the leachate wells and sumps, particularly along the eastern boundary of the site (Sump E4, Firewall Sump and the Groundwater Dewatering Sump). While Table 1 of URS 2013b indicates the sumps were re-surveyed in the month of July 2013, it appears some of them were raised after they were surveyed and before the July 2013 monitoring round took place i.e. current top of casing is below the working contours of the landfill shown in the June 2013 aerial survey (Appendix H of URS 2013b).
Refer to the inferred leachate levels across the landfill in Figure 3. With respect to leachate elevations relative to groundwater elevations the following is noted:
• The leachate level of 76.06 m AHD in Sump A1, when compared to inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 4 m below inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 71.91 m AHD in bore LB01A (Area E), when compared to inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 5 m below inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 80.03 m AHD in bore LB02A (Area A), when compared to inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 2.5 m below the inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 60.6 m AHD in Sump E4, when compared to inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 14 m below the inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 69.87 m in Sump E5, when compared to inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 7 m below the inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 76.52 m AHD in Sump C, when compared with inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 5.5 m below the inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. • The leachate level of 63.7 m AHD in the Firewall Sump, when compared with inferred groundwater contours in the Lower Werribee Aquifer (refer Figure 4, URS, 2013b), is approximately 11 m below the inferred groundwater elevation in the vicinity. This suggests potential for an upward hydraulic gradient from groundwater to leachate. Based on the leachate level elevations discussed above, measured leachate levels suggest they are below inferred groundwater levels. However, the Auditor is of the opinion that the leachate levels throughout 2012 to 2013 are potentially unreliable and therefore it is uncertain whether there is an
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Leachate, Groundwater and Surface Water Monitoring
upward vertical hydraulic gradient from groundwater to leachate or a downward vertical hydraulic gradient from leachate to groundwater. Further leachate levels monitoring using data loggers and remote telemetry is recommended to provide more dependable leachate level data. Depth of leachate at distances away from leachate sumps raises potential concerns in relation to build up of leachate head beneath the interim cover on the western side of Area A. This raises the risk of slope failure or leachate bursts along this batter, resulting in leachate or waste discharge outside the licenced area and/or safety issues for staff working in the western coal pit area. Refer to Section 6.1 for further detail.
5.2.2 Leachate Analytical Results Leachate samples were able to be taken and analysed from all leachate sumps and wells duringthe January and July 2013 monitoring rounds. Leachate quality is summarised as follows:
• Neutral to slightly alkaline. • Moderately reducing to moderately oxidising. • Low dissolved oxygen. • Temperature similar to that of groundwater (leachate samples are expected to be warmer than recorded but are thought to cool once the sample reaches the surface). • Moderate to high salinity with TDS concentrations normally ranging from 5,500 mg/L to 16,000 mg/L, while leachate from Sump A taken in January 2012 recorded a TDS reading of 23,000 mg/L. • Relatively high ammonia, ranging from 350 mg/L to 1,500 mg/L, with occasional results reaching 2,300 mg/L, much higher compared to groundwater. • Generally dark coloured water, slight to moderate turbidity and slight to very strong leachate odours. Leachate from the Firewall Sump and Sump C, areas which both receive Category C contaminated soil, shows slightly different characteristics to leachate from Landfill Areas A and E (Type 3 landfill leachate) as ammonia levels are much lower and have ranged from 0.22 mg/L to 22 mg/L and TDS concentrations also seem lower and hover around 4,900 mg/L to 7000 mg/L. Sulphate as S and SO4 is also much higher in the Firewall Sump and Sump C compared to Type 3 landfill leachate. Monitoring results from the Firewall Sump in July 2013 indicate a jump in Ammonia and Volatile Fatty Acid Concentrations (VFAs) in comparison to historical levels. Ammonia was recorded as 22 mg/L and VFAs were recorded at 690 mg/L. Other parameters which increased in concentration in the Firewall Sump in July 2013 include Chemical Oxygen Demand, Total Organic Carbon and TKN. It is unclear whether this may be an ongoing trend, as such, further monitoring results are required throughout 2014 to confirm whether this may be the case. Increased iron and manganese concentrations in the Firewall Sump in July 2011 appear to be a laboratory reporting error and concentrations detected in January and July 2013 have returned to previous levels. Other metal concentrations seem to be increasing based on monitoring results obtained in January and July 2013, including cadmium, copper, mercury, selenium, tin and zinc, and most noticeably selenium rising from <0.005 mg/L in July 2011 to 19 mg/L in July 2013. Further monitoring of the sump in 2014 should confirm whether the increased concentrations are increasing over time. In last year’s audit report, it was identified that groundwater monitoring for metals was limited to Iron and Manganese whereas leachate monitoring included a larger suite of metals. The Auditor concluded there was a data gap where groundwater bores screened within the Lower Werribee Formation and located hydraulically down gradient from the Firewall and Area C were not monitored for the full metal suite monitored in leachate sumps. Therefore the auditor recommended that
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Cadmium, Chromium, Copper, Mercury, Lead, Selenium, Tin and Zinc be included in future monitoring rounds for groundwater bores BH6, BH16, BH2, BH21 and BH22. This was completed during the January and July 2013 monitoring rounds, refer to Section 5.3.2 for further detail.
5.3 Groundwater Monitoring
Groundwater bores were sampled in the months of July 2012, January and July 2013 and analysed for parameters required in Licence ES90. Standing water levels were unable to be measured in the Groundwater Dewatering Sump due to access issues. Groundwater levels were able to be taken in artesian groundwater bores BH10, BH21 and BH22 with the installation of pressure valves and taps in 2012. BH13 was dry as per previous monitoring rounds. The monitoring results are discussed for each aquifer in the sections below. Licence condition 3.6 part a) requires the licence holder to maintain a groundwater collection sump as shown on the plan of premises. Sampling or monitoring of standing water levels in the groundwater collection sump, otherwise known as the Groundwater Dewatering Sump is not a licence requirement but has been a recommendation of the Auditor over recent years as it will assist in development and calibration of the HA. The Groundwater Dewatering Sump was sampled in July 2012, January 2013 and July 2013. Samples are obtained from a tap in the extraction pump discharge line. Standing water levels have not been measured since July 2008 due to the following reasons:
• Pump infrastructure restricts access down the sump with a water level meter, however, pump infrastructure is used to obtain a groundwater sample; and • It is difficult to slide a water level meter down a sloping sump. The Auditor recommends a method to obtain water levels in the sump be devised between MBC, sampling personnel and URS as soon as possible. The Groundwater Dewatering Sump is being maintained as a groundwater collection sump and is being used for groundwater extraction. Refer to Section 5.3.3 for dewatering volumes.
5.3.1 Fyansford Aquifer Assessment of background concentrations in the Fyansford Aquifer has been difficult because of uncertainty regarding groundwater flow direction and because there are so few bores (see Section 4.3.1). The recent installation of groundwater bore BH23 has provided certainty in relation to the Segment of groundwater applicable to the Fyansford Aquifer at the site, being Segment C. In general, due to the depressurisation of mining activities, groundwater flow in the Fyansford Aquifer is expected to be radial towards the coal pit and landfilling areas as discussed in URS 2013b). As such, monitoring bores BH11, BH13 and BH17 are expected to be hydraulically down-gradient of the Leachate Storage Ponds. Monitoring bores BH7 and BH15 still have the potential to be impacted by the adjacent irrigation dam and recharge from Parwan Creek, which may explain the lower TDS concentrations in these bores compared to the bores on the western side of the pit. As outlined in Table 4-6 of URS, 2013b, the following parameters exceed adopted ANZECC, 2000 acceptance criteria: TDS stock watering all bores in all monitoring rounds
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Leachate, Groundwater and Surface Water Monitoring
Sulphate stock watering BH11, BH17 and BH23 in all monitoring rounds (except for BH23 in January 2013) Ammonia fresh water ecosystems BH7 in all monitoring rounds Nitrate freshwater ecosystems BH 11 (all monitoring rounds) and BH7 (July 2013 only) Manganese freshwater ecosystems BH7 (all monitoring rounds) and BH15 (July 2012) Selenium stock watering BH11 & BH17 (all monitoring rounds) TDS concentration in BH11 has been trending downwards since July 2006 from 17,000 to 9,800 mg/L in January 2013. However, TDS in BH11 spiked again to 14,000 mg/L in July 2013. TDS concentrations in this bore exceed TDS concentrations in other Fyansford Formation bores apart from the new background bore, BH23, which registered TDS concentrations of 12,000 and 13,000 mg/L in January and July 2013 monitoring rounds respectively. Bicarbonate concentrations in BH11 and BH23 also look similar. Nitrate concentrations in BH11 continue to be well above other bores ranging from 9.3 to 36 mg/L since July 2006. BH11 is considered to be located down-hydraulic gradient from leachate pond L1. Nitrate and TDS concentrations in BH11 appear to indicate that leachate pond L1 is leaking. TDS and nitrate levels in BH17, adjacent to leachate pond L2, do not exhibit the same characteristics as BH11. Continued elevated groundwater levels in BH11 in comparison to other Fyansford Formation bores indicate perched water levels around pond L1 as shown in Figure 3. Refer to Section 8.1 for more information.
5.3.2 Lower Werribee Aquifer Groundwater Dewatering Sump Historical information indicates that the Groundwater Dewatering Sump extracts groundwater from the Maddingley Coal Seam i.e. its base sits within the coal seam rather than in the Lower Werribee Formation. During the most recent reporting period water quality from the Groundwater Dewatering Sump continues to appear similar in characteristics to groundwater from within the Lower Werribee Formation. Concentrations of ammonia, bicarbonate, TOC and TDS reported from the January 2008 monitoring round were either anomalous or representative of a short-term impact from leachate. However, it is noted that ammonia (as N) and TKN concentrations from the Groundwater Dewatering Sump continue to be an order of magnitude higher than from other bores monitoring the Lower Werribee Aquifer. Ammonia and TKN concentrations decreased in the sump from July 2008 until July 2011 but have been slowly increasing since July 2012. The lowest Ammonia level detected in the Groundwater Dewatering Sump was 3.7 mg/L in August 2006. Current ammonia and TKN values from the July 2013 monitoring round are 29 and 31 mg/L respectively and may either be indicators of leachate impact or may be reflective of groundwater being extracted from the Maddingley Coal Seam, rather than the Lower Werribee Formation as the same increase in concentrations is not seen in TDS. Groundwater Monitoring Bore Network
As discussed in Section 4.3.2, groundwater contours presented in Figure 4 of URS, 2013b indicate groundwater flows generally from south west to north east across the site. Groundwater elevation data from BH18, recently installed to the east of the site, provides evidence of a cone of depression that is
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Leachate, Groundwater and Surface Water Monitoring
likely to have been created by extraction from the Groundwater Dewatering Sump. Groundwater flow in the Lower Werribee Aquifer in the vicinity of Area E is likely to be toward the Groundwater Dewatering Sump rather than off-site to the east. As outlined in Table 4-7 of URS, 2013b, the following parameters exceed adopted ANZECC, 2000 acceptance criteria: TDS stock watering BH2, BH4, BH10, BH19, BH21 and BH22 (all rounds) and BH12 (July 2012 only) Sulphate as SO4 stock watering Artesian bores BH10, BH21 and BH22 (all rounds) Ammonia freshwater ecosystems BH2, BH8, BH10, BH12, BH18, BH19, BH21, BH22 (all rounds), BH4 and BH6 (July 2012 and January 2013), BH16 (July 2012) Manganese freshwater ecosystems BH21 (all rounds) Copper freshwater ecosystems BH16, BH21, BH22 (both rounds since parameter introduced in January 2013) Zinc freshwater ecosystems BH16, BH21, BH22 (both rounds since parameter introduced in January 2013) Comments on the monitoring results for bores screened within the Lower Werribee Aquifer are as follows:
• Trilinear plots presented in Figure 4-8 of URS 2013b indicate that the groundwater from all bores screened within the Lower Werribee Aquifer indicate similar cation and anion ratios. The major ion composition is dominated by sodium and chloride. Water quality from the Groundwater Dewatering Sump also has similar ratios of cations and anions to the Lower Werribee Aquifer bores. • The recently installed bores (BH21 and BH22) adjacent to Areas B, C and D report similar TDS and sulphate concentrations to leachate in Sump C. Manganese in BH21 continues to be reported at concentrations higher than most other bores within the monitoring network. Additional metals, copper and zinc, were both detected in BH21 and BH22. Phenols analyses were included in the July 2013 monitoring as per last year’s audit recommendation and were reported below the limit of reporting. Both BH21 and BH22 appear to show impact to groundwater from landfilling in the area. Refer to Section 8.3 for further detail. In the Auditor’s opinion, whilst there are potential indicators of slight leachate impacts on groundwater in the Groundwater Dewatering Sump, which is thought to draw groundwater, at least in part, from the Maddingley Coal Seam, there is no clear evidence of leachate impact in the Lower Werribee Aquifer. Concentrations of potential indicators of leachate impact in groundwater monitoring bores screened in the Lower Werribee Aquifer i.e. Ammonia and TDS, are similar to concentrations reported in background bore BH19. That is, there is no clear trend of concentrations elevated with respect to what may be considered regional groundwater quality. Chemical concentrations present in groundwater monitoring bores are not considered to represent groundwater pollution under the SEPP GoV.
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Leachate, Groundwater and Surface Water Monitoring
It is worth noting that groundwater from the Groundwater Dewatering Sump is discharged to the Irrigation Dam (URS, 2013b) whereas it was previously discharged to Dam D4. The ammonia concentration in the Irrigation dam was reported at 0.27 mg/L in July 2013 (compared with 29 mg/L reported in the Groundwater Dewatering Sump during the same monitoring round). However, water from Dam D4, which is also transferred to the Irrigation Dam, may have the potential to dilute ammonia concentrations.
5.3.3 Extracted Groundwater A total of 12,828 m3 of groundwater was extracted from beneath Areas A and E via the Groundwater Dewatering Sump during the 2012-2013 reporting period. The riser was re-surveyed in July 2011 but a water level has not been measured since July 2008 due to unresolved access issues.
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Landfill Design and Construction
6.0 Landfill Design and Construction
6.1 Area A
Documentation of the design and construction of the older cells (Area A) within the landfill is very limited. It is understood that the intent of the original liner placed over Maddingley Coal Seam at the base of the landfill in the late 1970’s was primarily to stop potential fires in the landfill propagating into the underlying Maddingley Coal Seam. The permeability of the basal liner over much of Area A may be higher than that required under best practice guidelines (i.e. <1 x 10-9 m/sec). The Maddingley Coal Seam acts as an aquitard to the underlying Lower Werribee Aquifer. However, the permeability of the Maddingley Coal Seam beneath Areas A and E has not been accurately quantified. Bore logs for the leachate sumps and monitoring bores installed in August 2012 indicate the base of Area A and the base of the older section of Area E (Cells E to E3) both consist of up to 2.5 m of clay, as outlined below:
• Monitoring well LB01A (bordering between Area A and the older Area E): the bentonite and cement grout base of the well went through approximately 2m of clay with traces of waste through it, and then approximately 2m of clay with a trace of coal at the base. The base of waste in this area was encountered around 61 mAHD; • Monitoring well LB02A (centre of Area A): the bentonite and cement grout base of the well went through approximately 1m of clay mixed with waste and then approximately 2.5m of clay. Waste was encountered up to 55 mAHD; • Sump A1: the bentonite and cement grout base of the sump went through approximately 3m of clay before reaching coal at the base. Waste was encountered up to 58 mAHD. The base of the waste in Area A seems to range between 55 and 58 mAHD. Leachate Sump A was replaced by Sump A1 in mid-2012 which was installed down to an elevation of 60 mAHD, with a 6 m stainless steel screen at the base. Unfortunately, leachate extraction from this well has been unsuccessful as there has been minimal leachate recovery within the well. The bore log indicates the well is screened within waste containing residues of paper pulp, which may have affected its performance. Refer to Figure 3 for a cross-section of the area. Leachate levels in Area A in July 2013 were reported at 76.06 and 80.03 mAHD in Sump A1 and LB02A respectively, the leachate thickness varying from 15 to 23 m. Significant depths of leachate are not unexpected given the absence of a drainage layer and basal leachate drains across much of the area, periods when leachate sumps were not functioning effectively and the limited available capacity in the Leachate Ponds. In addition, groundwater and leachate elevation data indicates that groundwater from underlying the Lower Werribee Aquifer may be a significant contributor to leachate within Areas A and E (see Section 5.2.1). It is unknown whether a barrier was placed on the western side of Area A between waste and coal as no records exist. Recent geotechnical investigations completed in July 2013 to assess the stability of the western batter of Area A (NSP Geotechnics, 2013) included drilling of six boreholes along the access road in this area, which encountered waste to 15 m depth. The road elevation currently sits at around 84 mAHD, therefore it is likely that drilling in this area reached an elevation of approximately 69 mAHD. Engineering bore logs indicate approximately 0.5 m of silty clay was encountered in each borehole at the road level, and then waste was encountered up to 15 m depth. The bore logs did not identify clay or other natural materials indicating that waste was likely placed up against coal in this area. An intrusive investigation to expose material in this area would determine whether a barrier exists or not. MBC advised that some intrusive work took place in 2013; however, documented evidence of the findings has not been presented to the Auditor. Side slope stability of the western side of Area A still remains a potential concern if leachate levels rise significantly above the base of the slope. Although leachate levels in the nearest well, LB02A,
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Landfill Design and Construction
seemed to have dropped considerably since mid-2012, the reliability of the monitored leachate levels in Area A is questionable (refer Section 5.2.1). The Auditor raised this concern in the 2012 audit report, where the potential leachate heads could build up beneath the interim cover on the western side of Area A. The risk of slope failure or leachate bursts along this batter could result in leachate or waste discharge outside the licenced area and/or safety issues for staff working in the western coal pit area. In July 2013, the leachate levels in LB02A were recorded at 80.03 mAHD (were 92.8 mAHD in August 2012) while the access road along the western batter of Area A sits at around 84 mAHD as per the aerial taken in June 2013 (refer Appendix H of URS 2013b) and the working surface of the western coal pit sat at around 81.3 mAHD to 82.2 m AHD. Leachate levels within Area A in July 2013 now sit below the working surface of the western coal pit, whereas in comparison to mid-2012, they were 8 to 10 m higher than the open coal pit. There is no clear explanation as to how leachate levels within Area A decreased so dramatically within the space of 12 months without active extraction of leachate within the area, therefore, the stability of the lower section of the western batter of Area A still remains a concern and the recommendations of the geotechnical investigation should be implemented as soon as possible. Recommendations include:
• Obtain reliable leachate level data in Area A to confirm if leachate levels are below the level of the base of the western batter. • Conduct and investigation to confirm the western extent of waste in Area A and whether a clay side-liner exists against the coal seam. • Prepare designs for a final slope, final capping layers and tie-in with the side liner and/or coal. • If leachate levels extend above the base of the western batter in Area A, to lower leachate levels.
6.2 Area E
6.2.1 Areas E to E3 Areas E, E1, E2 and E3 are believed to have compacted clay basal liners. However, as built design drawings and documentation were either not prepared at the time or are unavailable for review by the Auditor. The clay base of the Areas E to E3 is understood to have been constructed 1 m thick, with a permeability of 1 x 10-9 m/s, including a drainage layer over the clay, with all 4 cells sloping in a north westerly direction toward a leachate sump on the edge of Area A. The leachate sump (Sump A) is no functional, (URS, 2013a). The construction audit report prepared for Cell E4 by Golder Associates in 2007 indicates a clay liner was present beneath Areas E1 and E3 for connection with Area E4. No documentation exists to indicate these areas were hydraulically separated from Area A. The area underneath these cells is said to have been filled with overburden and some solid inert waste and it is unknown whether the solid inert waste was removed before the cell basal liners were constructed.
6.2.2 Areas E4 & E5 As built construction audit reports were retained for both Cells E4 and E5 (E4 prepared by Golder Associates in 2007 and E5 prepared by Peter J Ramsay & Associates in 2010 or 2011). Cell E4 has an engineered liner system of a 1 m thick compacted clay liner with a leachate aggregate drainage layer varying in thickness from 0.3 to 0.8 m (URS, 2013a). The surveyed top of liner sits between 62 and 63 mAHD, approximately 4 to 7 m higher than the base of Area A. MBC has advised that Cell E5 was a piggyback cell, sitting above previously deposited paper pulp and small amounts of inert waste approximately 12 m to 14m in depth, followed by the original clay liner placed over the base of the original quarry floor. A settlement protection layer was placed and consists of 300mm of non-descriptive crushed rock and a Tensar Geogrid layer. The basal liner of Cell E5 consists of geosynthetic clay liner (GCL) and a minimum 150 mm compacted clay which acts to protect the GCL and was used to form the floor grades. A 300mm leachate drainage layer
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Landfill Design and Construction
comprising 40mm diameter aggregate (washed pebbles sourced from local pits) and geotextile separation layer were then placed over this. This cell was designed by AECOM, construction was supervised by Meindhardt and audited by Peter Ramsay & Associates. This description is confirmed in URS, 2013a. The surveyed top of clay liner sits between 68 and 71 mAHD, approximately 13 to 16 m shallower than the base of Area A. No documentation exists to indicate these areas were hydraulically separated from Area A or E to E3. Leachate sumps are located in Areas E4 and E5 and MBC advise that Sump E4 drains Cell E4 and approximately half of Area E5 (the eastern side) due to the orientation of the floor grades. Sump E5 drains the other half of Area E5. This is supported by URS, 2013a. Leachate levels taken from active leachate extraction sumps E4 and E5 were 60.60 and 69.87 mAHD respectively, with a leachate thickness of around 2m in Sump E4 and 1.17 m in Sump E5. The leachate thickness in Sump E4 is an estimate as its thickness was reported in URS, 2013b as -0.4 m, therefore it’s assumed the sump was raised an additional concrete collar length after it was last surveyed. Leachate levels measured from active sumps may not be representative of fully recovered leachate conditions. Based on reported leachate levels, the licence requirement to maintain a saturated depth of leachate of no more than 300 mm (0.3 m) is not being achieved. The licence condition that a maximum depth of leachate of 300mm may not be suitable for an unlined landfill cell such as Area A as it does not contain a leachate drainage layer or an engineered base liner. Maintaining a leachate depth of 300mm may also be difficult to comply with in the newly lined Area E cells due to the poor isolation of the waste between Areas A and E, i.e. no side liner exists to physically and hydraulically separate accumulated leachate between the cells. Incident rainfall over active (i.e. uncapped) areas of the landfill is likely to be a significant contributor to leachate generation. The Auditor did note at the site inspection conducted on the 12 November 2013, the western batter of Area A and southern batters of Areas A and E were almost completely covered with compacted clay (i.e. an intermediate clay cap) and this should help reduce infiltration in future, however, some erosion of the interim cap was evident along the steeper western slope of Area A (see photograph below).
Interim clay cap over the western batter of Area A – evidence of erosion
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Landfill Design and Construction
6.3 Areas B and C
No documentation of the design and construction of the liner systems beneath Areas B and C have been presented to the Auditor. MBC understand that a compacted clay basal liner was installed beneath Area C which is licenced to accept Category C PIW soil for landfilling. MBC have indicated that the clay basal liner has been exposed at the toe of the eastern side of Area C during works to tie in a bund wall at the base of the slope. Prior to acceptance of these types of soils, previous versions of the EPA licence allowed landfilling of shredded tyres in this area (URS, 2013a). It is understood that this area was capped with clay material around 2002. In 1999, Areas B and C were noted to have accepted low level contaminated soils in an unlined area (previously known as Area A) (URS, 2013a). It is not clear if a basal liner was installed beneath Area B. Area B is used for composting and has the potential to generate and store leachate. Historically, previous versions of the EPA licence permitted this area to receive solid inert waste and then shredded tyres over a compacted earth base of varying thickness (URS,2013a). There is no documentation or evidence that a basal drainage layer was installed over the basal clay liner in Areas B or C. A single vertical leachate sump (Sump C) is installed in Area C, however, leachate is not currently extracted from the sump. The leachate thickness in the sump has not exceeded 2 m since January 2012 (without active extraction). Given the lack of construction data surrounding the base of Area C and its sump, and the possible leachate impact seen in groundwater bores BH21 and BH22 down hydraulic gradient of the area, it is possible that leachate impact may be originating from Area C, however, given waste deposition occurred in unlined areas underneath the cell, it may be possible that impact seen in BH21 and BH22 may have originated from the older, deeper deposited waste.
6.4 Firewall
It is unclear to the Auditor as to whether the Firewall separating solid inert waste from the surrounding coal seam extending along the eastern boundary of Areas A and E and the southern boundary of Area E forms part of the licenced landfill or in fact sits outside the licenced landfill area. On the assumption that placement of contaminated soil in the Firewall area may be considered part of the licenced activities, the Auditor has assessed the risks to groundwater posed by the construction and installation of the Firewall and has included this information for consideration by MBC and EPA.
The Auditor’s understanding of the construction of the Firewall is described below, as advised by MBC. The Auditor also reviewed EPA approved technical specification designs provided by MBC for Areas 3 and 4 of the Firewall (Golder, 2008a and Golder, 2008b respectively). Firewall Areas 1 and 2 The Firewall consists of Areas 1 to 4. Areas 1 and 2 were not constructed under Environmental Audit and construction records are not available for these areas. Area 1 and 2 of the Firewall are located along the southern boundary of landfill Area A and the south eastern corner of Area E. MBC advises a compacted clay liner approximately 1m thick exists along the base and either side of the Firewall in these areas (against the waste and coal interfaces). It is understood that the clay base liner is graded toward the centre of the floor, where a leachate collection pipe and aggregate layer are located. Areas 3 and 4 were constructed under Environmental Audit, and were both designed by Golder Associates in 2008. A description of their construction based upon the EPA approved design (not the construction audit) is provided below. Firewall Area 3
• Area 3 is located along the eastern boundary of Cell E4. • The technical specification was prepared in August 2008 and outlined the design of the sideliner of the Firewall in Area 3.
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Landfill Design and Construction
• The technical specification of Area 3’s base liner was not included (as it was constructed in August 2007 under audit with Golder Associates). • The Firewall side liner consisted of minimum 1m thick compacted clay on either side of the Category C contaminated soil interface with coal and waste. The compacted clay properties were generally consistent with those required for Type 3 landfill liners. Material properties are outlined in the technical specification. • Drawing D0003 of the technical specification indicates the base of Area 3 Firewall consisted of existing clay, i.e. the base clay liner of Cell E4 (constructed under separate audit), a drainage aggregate layer, then geomembrane and geotextile. Further detail on the base liner is not provided. • A drainage layer was not constructed along the side liner elevation. • The design included detail on how the extension of the Firewall sump and the Groundwater Dewatering Sump should occur while the Firewall and its side liner were both extended. The design required placement of crushed rock around the riser pipes for protection. • Drawings that formed part of the technical specification indicate the design was meant for the full elevation of the Firewall side liner until it reached the top of the coal face, however, the elevation of the top of the coal face is not specified in the drawings. Firewall Area 4
• Area 4 is located along the eastern boundary of Cell E4 and E5. • The technical specification was prepared in September 2008 and outlined the design of the base and sideliner of the Firewall in Area 4. • The base liner of the Firewall included a minimum 1m thick compacted clay liner, 1.5mm smooth HDPE, cushion geotextile (>400g/m2), 300mm thick leachate drainage layer, 160mm diameter leachate collection pipe and separation geotextile on top of the drainage aggregate. Material properties are outlined in the technical specification. • The geomembrane and geotextile were both anchored into the outer coal wall and then anchored into the inner compacted clay bund which formed the edge of Cell E4’s basal liner. • The compacted clay of Area 4’s base liner was joined with the base of Area 3 and the base of Cell E4. MBC advises the clay basal liner of Area 4 of the Firewall also joined with the GCL basal liner of Cell E5 when it was constructed at a later date. Connection detail between the clay basal liner of the Firewall and the GCL basal liner of Cell E5 was not provided. • The Firewall side liner consisted of minimum 1m thick compacted clay on either side of the Category C contaminated soil interface with coal and waste. The compacted clay properties were consistent with those required for Type 3 landfill liners. Material properties are outlined in the technical specification. • A drainage layer was not constructed along the side liner elevation. • Drawings that formed part of the technical specification indicate the design was meant for the full elevation of the Firewall side liner until it reached the top of the coal face, however, the elevation of the top of the coal face is not specified in the drawings. The Firewall Sump is located within Area 3 of the firewall and is connected to the drainage layers installed beneath the firewall in Areas 1 to 4. The leachate level in the sump in July 2013 was 63.7 mAHD, the leachate thickness was 2.10 m, which has decreased significantly since the last time it was monitored in January 2011 (leachate thickness was 11.50 m). Active leachate extraction occurs from this sump.
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Landfill Design and Construction
6.5 Area A and E Side Liner Extension
It is understood that designs are currently being prepared by Meinhardt Pty Ltd (Meinhardt) for the side-wall liner above the fire wall along the southern and eastern perimeter of Areas A and E. It is also understood that Peter J Ramsay of Peter J Ramsay & Associates will be completing an assessment of the design in accordance with EPA Publication 1323.2. Once Mr Ramsay has completed his assessment of the design, the design documents and Mr Ramsay’s assessment report will be submitted for approval by EPA. Based on my understanding of the hydrogeological setting and likely leachate management requirements at the site, the Auditor has prepared some comments for consideration by the Meinhardt, Peter Ramsay and EPA in preparing and reviewing the design of the side-wall liner above the Firewall. The comments should be considered with reference to the west-east cross section of the site included as Figure 3 of this report. Comments on the requirements for the side-wall liner design are as follows:
• It is likely that leachate levels in Areas A and E of the landfill will need to be maintained at elevations between 65 m AHD and 72 m AHD to protect water quality in the Lower Werribee Aquifer by maintaining an upward hydraulic gradient. The base of the Fyansford Formation on the eastern and southern sides of Areas A and E is significantly higher than the likely leachate levels (88.6 m AHD to 92.4 m AHD). As such, groundwater seepage from the Fyansford Formation into the landfill is likely to contribute to leachate generation in the landfill on an on-going basis, including post-closure. To minimise post-closure leachate management requirements at the site, the performance of the side-wall liner in minimising seepage into the landfill is critical. • A robust, low permeability side-wall liner is strongly recommended for the side-wall liner. It should be noted that the side-wall liner will, in part, extend below water table in the Fyansford Aquifer. A composite of 1 m of compacted clay and a GCL or high-density polyethylene (HDPE) liner should be considered. • Consideration should be given to incorporation of a permanent groundwater drain at the base of the Fyansford Formation on the exterior of the side-wall liner. A permanent drain for the Fyansford Formation Aquifer adjacent to the landfill would allow leachate generation to be minimised by pumping groundwater from the Fyansford Aquifer. It is likely that groundwater from the Fyansford Aquifer could be readily discharged to Parwan Creek, whereas leachate extraction is likely to involve treatment and a much higher level of management. • Preparation of a sub-grade layer on a steep side wall will need to be carefully considered. A groundwater drain at the base of the Fyansford Aquifer, as mentioned in the preceeding comment, would also allow more effective dewatering of the formation and preparation of an adequate sub- grade for the side-wall liner. • If the design is to incorporate GCL as the internal layer, or only low permeability layer, in the side- wall liner, it will be exposed to weather and rain for extended periods while placement of waste extends upward to the full height of the side-wall. Protection of an exposed GCL should be specified in the side-wall design. • It is understood that along the southern section of the Firewall, Category C prescribed waste have been placed above the upper level of the Maddingley Coal Seam. Survey data is now available on the upper surface of the Maddingley Coal Seam in the wall of the pit. It is recommended that Category C waste does not extend within 1 m of the elevation of the upper surface of high-grade Maddingley Coal Seam and clay is placed from the top of the waste to the level of the base of the Fyansford Formation (i.e. opposite the lower grade coal seam). If Category C waste extends above the base of the Fyansford Formation, consideration would need to be given to up-grading the side-wall liner design to be consistent with a Type 2 landfill liner in the Landfill BPEM. It is
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Landfill Design and Construction
recommended that the levels of the top of waste are specified in the design drawings for the Firewall and side-wall liner above the Firewall. • Based on observations at the site, the Firewall and Groundwater Dewatering Sumps will extend through solid inert waste once the side liner extension is completed and solid inert waste will be placed against it (see photograph in Section 8.2.2). Draft side liner designs provided to Patrick Clarke for review did not include detail as to how both sumps will be extended and protected in future, and how the current material sitting around the sumps will be sealed off to prevent Type 3 leachate from seeping vertically down around the outer edge of the sumps into the firewall and external geological formations. Alternatively, the sumps should be realigned outside the side-wall liner. It may be appropriate to recess the sump extensions into the Fyansford Formation external to the side wall liner to protect them during construction of the side liner. Details of the Firewall and Groundwater Dewatering Sump extensions should be included within the side liner design specification. • Construction of the side-wall liner may require the Fyansford Formation sub-grade to be battered back to an angle which would allow efficient construction. It is understood that the boundary within which waste can be placed consistent with the original Works Approval is not well defined with respect to distance from Parwan Creek. If the sub-grade slope is battered back significantly, waste may be placed within 50 m of Parwan Creek, which would not be consistent with the current Landfill BPEM. Consideration should be given to how close to Parwan Creek waste will be placed.
6.6 Leachate Ponds
Two leachate ponds, L1 and L2, exist to the west of the landfill in an elevated area. They have been constructed with compacted clay and are connected by a riffle system used to aerate the leachate transferred from L1 to L2. The area occupied by the ponds is approximately 16,600 m2 and their total holding capacity is approximately 16,600 m3, assuming 0.5 m freeboard is maintained and approximately 1 m depth of leachate is stored (URS, 2013a). Construction records of the ponds are not available.
Leachate pond L1 and riffle system
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Landfill Design and Construction
6.7 Area D
Area D is understood to include the Area to the north of Dam D4, but does not include Dam D4 itself (as per licence boundaries outlined in EPA Waste Discharge Licence ES90). It is licenced to receive potential acid sulphate soils and was known to deposit them within the water body that used to be present in the area. The area looks to have reached capacity as the former water body is no longer visible (refer to Section 8.3 for a photo of the area). The June 2013 aerial found in Appendix H of URS, 2013b indicates waste deposition in Area D may have occurred outside the licence boundary and extended into Dam D4. It is unknown whether potential acid sulphate soils have been accepted at the landfill in 2012-2013 as this information has not been included in the annual review (URS, 2013b). The Auditor recommends that MBC confirm with EPA the boundary of Area D and whether it includes Dam D4 or not as waste deposition appears to have encroached into the Dam D4 area. The Auditor also recommends that MBC confirm how stormwater management practices will be amended when construction of the landfill extension commences in the area currently occupied by Dam D4 as it appears to be fed by stormwater runoff from Areas B, C, D and the western coal pit. This information should be included in the annual monitoring review report for FY13/14.
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Leachate Generation and Management
7.0 Leachate Generation and Management
To more effectively manage leachate at the site, the following objectives should be achieved:
• Reduce leachate generation rates. • Obtain reliable leachate level data in Areas A and E. • Increase rates of leachate extraction from Area A. • Increase leachate storage capacity outside landfill cells. • Select the appropriate mix of proposed leachate treatment and disposal options that will be implemented. • Increase the rate of leachate treatment or disposal while the landfill remains uncapped. In the coming weeks, the Auditor will review the HA and parts of the LMP relating to disposal of retentate in Areas A and E and provide comments and recommendations. It was confirmed that the EPA’s expectation of the Auditor’s role in relation to MBC’s compliance with the PAN No. 10800 (refer Appendix B): • A review of the HA. • A review of the LMP, specifically addressing retentate re-injection into Cells E4 and E5 and the potential impact on groundwater. • Provide an opinion on the maximum level of leachate to be maintained to protect groundwater quality in the Lower Werribee Aquifer (PAN requirement 3.2). • Provide an opinion on leachate disposal options that do not require retentate to be disposed to the landfill (PAN requirement 3.4). • Provide an opinion on aspects of the HA and LMP relating to disposal of retentate in the landfill and whether groundwater quality in the Lower Werribee Aquifer would be protected. The assessment of the proposed leachate treatment plant is considered outside the scope of the Auditor’s review of the LMP, and it is assumed this will be completed by Environmental Auditor, Mr Paul Fridell, of ERM Consulting. The following sections summarise current and proposed leachate management measures at the landfill.
7.1 Current Leachate and Groundwater Extraction Rates
Leachate extracted from the landfill, as measured by cumulative flow meters, was recorded daily. Monthly totals are presented in Table 3-2 of the Annual Monitoring Review (URS, 2013b). Details of the volumes extracted during the 2012-2013 monitoring period are as follows:
• Leachate was unable to be extracted from Area A via replacement Sump A1. • 20,422 m3 was extracted from Area E4 via Sump E4. • 7,123 m3 was extracted from Area E5 via Sump E5. • No records were available regarding the amount of leachate pumped from the Firewall Sump prior to June 2013. MBC advises that leachate from the Firewall Sump is pumped to Sump E5 before it is pumped to the leachate ponds. A flow meter was installed in the Firewall Sump in June 2013. The total leachate extracted in the month of June 2013 was 631m3. MBC advises that leachate extraction rates from this sump have reduced significantly since June.
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Leachate Generation and Management
• Leachate is not extracted from Sump C. • A total of 12,828 m3 of groundwater was extracted from under the landfill from the Groundwater Dewatering sump and is reported to be diverted to the Irrigation Dam – no discharge occurred into Parwan Creek in 2012-2013 (URS, 2013b). Leachate extraction rates from Sumps E4 and E5 are similar to that of recent years. A leachate pumping test on Sump A1 was conducted on 22 October 2012 and failed to maintain a constant pumping rate and did not achieve steady-state conditions. As an alternative, recovery data was analysed rather than drawdown. The transmissivity of the waste was estimated to be 0.21m/d, and the hydraulic conductivity 0.01 m/d (URS, 2013a). The Auditor expects further detail to be provided in the revised HA and LMP in the coming weeks, in relation to pumping trials and calibration of the HA. Since the trial, leachate has not been extracted from this sump. Leachate monitoring wells LB01A and LB02A were installed to monitor leachate levels in Area A and Cells E to E3. MBC advises that leachate was extracted from LB02A for two weeks in July 2013 and approximately 17,000 L was removed. Leachate extraction has since ceased. Sump A1, LB01A and LB02A are constructed in the same manner. Given leachate extraction from Sump A1 has been unsuccessful; the design of future leachate extraction wells should be reconsidered to include the following aspects:
• Longer screened intervals to allow leachate to enter the well from a larger waste depth. • Installation of shallower wells i.e. the depth of a new well does not need to reach the base of the landfill, it should only intersect the elevation of the inferred groundwater levels in the Lower Werribee Aquifer by 2 to 5 m. • Consideration of the material used in the construction of the well i.e. HDPE versus stainless steel. Leachate levels in Sump C were monitored in July 2013 (refer Table 4a in URS, 2013b). Leachate thickness in the sump was approximately 1.42 m and has not been greater than 2 m since January 2012. Information in relation to the construction of the base liner and Sump C is not available (URS, 2013b). It is unclear if leachate levels in Sump C are representative of leachate levels in Area C. Some groundwater impact is evident in BH21 and BH22 hydraulically down-gradient of the area, however, given that landfilling took place beneath Areas B and C, current groundwater impact in the area may be attributable to waste deposition above and/or below the base liner of Area C. Leachate levels in the Firewall Sump were not checked since January 2011 and the depth of leachate was approximately 11.5m at the time. Reasons for not gauging the levels during each monitoring round were not provided. Leachate levels in the Firewall Sump were checked in again in July 2013, and the leachate thickness was measured as 2.1 m, a reduction of 9.4 m in approximately 2.5 years. Leachate extracted from the Firewall Sump is pumped to Sump E5 first before it is pumped to the leachate storage ponds, as the pump in Sump E5 is unable to pump the full distance to the ponds. Given EPA’s recent advice on separate storage of Type 3 leachate from the landfill and leachate from the firewall (containing Category C contaminated soil), this practice should cease immediately, and a relay storage tank installed in the vicinity of Sump E5 in order to allow extraction from the Firewall Sump to continue.
7.2 Future Leachate and Groundwater Extraction Rates
The leachate extraction system in Area A and E to E3 will need to be expanded in order to maintain leachate levels below the predicted groundwater levels in the Lower Werribee Formation, which in turn will protect both the Lower Werribee Formation and Fyansford Formation from leachate impact by maintaining an inward groundwater flow (lateral and vertical) into these landfill areas.
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Leachate Generation and Management
Leachate extraction recommendations for the entire landfill area rely on the Auditor’s review of Revision 2 of the HA and LMP, however, leachate extraction recommendations specific to Area A include (in order of implementation):
• Installation of leachate drainage drains beneath the interim or final cap along the western batter of Area A, connected to a central drainage point and sump along the western boundary of this area, in order to alleviate potential leachate build up along this batter and minimise the risk of slope stability failure. • Extraction of leachate from the five existing landfill gas extraction wells in the western portion of Area A. • A revised design of new leachate extraction wells retrospectively installed in Area A. • Additional vertical leachate extraction wells in Area A.
7.3 Reduction of Leachate Generation Rates
The most practicable means of reducing leachate generation are as follows:
• Reduce infiltration of incident rainfall into active landfill cells by applying interim and finally capping layers of as much of the landfill surface as practical. • Reduce contributions to leachate generation from groundwater in the Lower Werribee Aquifer by maintaining groundwater extraction for the Groundwater Sump. • Reduce contributions to leachate generation from groundwater in the Fyansford Formation Aquifer by establishing a robust, low permeability side-wall liner above the Firewall and, potentially, draining the Fyansford Aquifer immediately outside the side-wall liner (refer to Section 6.5 for details). Interim cap has been placed over much of the western and northern batters of Area A, which is likely to have contributed significantly to reducing leachate generation rates. The current working contours at the landfill as at June 2013 (refer to Appendix H of URS 2013b) indicate the western batter of Area A and the northern batter of Area A and Cell E5 are at or close to the revised final contours in these areas. The Auditor is of the opinion that final capping may commence along the western batter of Area A without delay (approximately a 60 to 80 m wide area) as it will not tie into the new side liner extension. It is unclear what works may be required along the northern boundary of the current landfill in order to comply with WA70655. Regular surveying of the working contours of the landfill e.g. six monthly aerial surveys, which are then compared with the final contours of the landfill, will assist in identifying other areas that may become available for final capping.
7.4 Current and Proposed Leachate Treatment and Disposal
As stated in previous Audit Reports, the storage capacity of the leachate treatment ponds are likely to be insufficient to lower leachate levels to less than 300 mm above the basal liner without some alternative means of treatment or disposal. However, the appropriateness of the license condition requiring maintenance of such low levels of leachate in the landfill should be reconsidered in the context of the existing and future leachate controls and management. The volume of leachate being removed is currently being managed by temporary storage in the Leachate Ponds (which hold approximately 16,600 m3 of leachate with 0.5 m of freeboard) and by storage in Cell E5. Approximately 85% (23,916 m3) of the total recorded amount of leachate extracted was applied back over Area E5 for dust suppression. The remaining 4,260 m3 of leachate either evaporated from the ponds or seeped into the subsurface beneath the Leachate Ponds.
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Leachate Generation and Management
It is understood that the new leachate treatment system has been designed to treat a larger volume of extracted leachate than the current system. However, the auditor has completed a preliminary review of the HA, and it indicates the current treatment capacity of the treatment plant, being 80KL/day, is less than the predicted leachate volumes to be extracted from the landfill to maintain leachate levels below the inferred groundwater levels in the Lower Werribee Formation (while the landfill remains uncapped). An assessment of acceptable leachate levels in Areas A and E will depend on a more thorough understanding of vertical hydraulic gradients between leachate in the landfill and the underlying Lower Werribee Aquifer and assessment of the long-term stability of the western slope of Area A. Further development of the HA should provide an improved understanding of these relationships. The mix of treatment and disposal options should be confirmed so design input parameters of the treatment plant can be finalised during its commissioning phase. Current options considered include the treatment plant, irrigation, sand washing, evaporation (increased pond storage) and dust suppression over cells E4 and E5. The draft version of the HA (URS, 2013a) indicates that current leachate storage capacity will need to be expanded, design and construction of new leachate storage ponds should be pursued as soon as possible so that construction may occur over this summer period. Design and construction should be in accordance with EPA Publication 1323, Landfill Licensing Guidelines, as required by WA70655.
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Conceptual Site Model
8.0 Conceptual Site Model
A conceptual site model (CSM) has been developed for the site as a basis for assessment of risk to segments of the environment. The CSM is based on identification of sources, pathways and receptors. The conceptual site model for the landfill is presented graphically in Figure 3. The principal sources-pathways-receptors for contamination of groundwater and surface water are summarised in the following table:
Source Pathway Receptor(s)
Leachate in Leachate Ponds Seepage through the basal liner Fyansford Aquifer
Leachate in landfill Areas A and E Seepage through the basal liner and Lower Werribee Aquifer Maddingley Coal Seam
Leachate in landfill Areas A and E Seepage through the side-wall liner Fyansford Aquifer extension above the Firewall Parwan Creek
Leachate in the Firewall Seepage through the basal liner and Lower Werribee Aquifer (Category C contaminated soil) Maddingley Coal Seam
Seepage through the side liner above the Fyansford Aquifer Maddingley Coal Seam (southern section of Parwan Creek the Firewall)
Leachate in Areas B, C and D Seepage through the basal liner and Lower Werribee Aquifer Maddingley Coal Seam
Leachate in Areas B, C and D Surface water runoff Dam D4 Irrigation Dam Parwan Creek Southern & eastern irrigation areas
1 This is considered a future potential source for contamination of groundwater and surface water, when waste tipping reaches this height in the landfill. Assessment of potential impacts for each source is discussed below.
8.1 Leachate Ponds
Groundwater elevations in BH11 located adjacent to leachate pond L2 remain approximately 27m higher than the nearest Fyansford formation groundwater bores (BH17 and BH23) and is considered to represent perched water over a shallower low permeability layer in the Fyansford Formation (refer to Figure 3). Groundwater elevations in BH11 have continued to range between 130.74 to 132.2 mAHD since July 2006. There is evidence of leachate impacts on groundwater perched in the Fyansford Aquifer east of the leachate ponds (i.e. borehole BH11). Elevated concentrations of nitrate in BH11 may be an indicator
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Conceptual Site Model
that leachate pond L1 is leaking. The presence of a perched water table well above the regionally extensive aquifer in the base of the Fyansford Formation in the vicinity of BH11 may, at least in part, be attributable to seepage from the adjacent ponds. It is assumed that leachate has seeped through the base of the leachate ponds and impacted the underlying water table. Groundwater elevation contours and the elevation of the top of the clay in the open cut pit indicate that groundwater in the Fyansford Aquifer beneath the leachate ponds will ultimately discharge to the pit as seepage is occurring at the contact with the underlying Maddingley Coal Seam. There is clear visual evidence of groundwater seepage occurring from the Fyansford Formation immediately overlying the Maddingley Coal Seam in the western wall of the open cut pit. Groundwater seepage from the western face of the open cut pit would ultimately discharge to Dam D4 at the site. As such, the area of groundwater pollution of the Fyansford Aquifer is likely to be limited to between the leachate ponds and the open cut pit. TDS concentrations in BH23 are similar to concentrations found in BH11 and BH17. Elevated groundwater levels in BH11 support the theory that leachate pond L1 is leaking, however, given the similarities of groundwater characteristics between the three bores, the Auditor recommends that volatile fatty acids (VFAs) are monitored in all three bores throughout 2014 to confirm if the ponds are leaking.
8.2 Landfill Areas A and E
8.2.1 Lower Werribee Formation Vertical hydraulic gradients between leachate in the landfill and the underlying Lower Werribee Aquifer have yet to be accurately determined. The most recent water level data suggest an up-ward vertical hydraulic gradient may exist in Areas A and E, despite a leachate depth in the landfill of up to 22 m over the landfill base in Area A. If an up-ward gradient exists, the risk to water quality in the underlying Lower Werribee Aquifer is likely to be minimal. However, groundwater could be contributing to leachate generation. As described in Section 5.2.1, due to the explained dramatic reduction in leachate levels in Area A since August 2012, measured leachate depths and elevations are not considered reliable. If a vertical down-ward gradient were to exist between leachate in the landfill and the underlying Lower Werribee Aquifer, some form of water quality impact should be evident in groundwater extracted from the Groundwater Dewatering Sump. One round of monitoring in January 2008 indicated strong evidence of leachate impacts in water extracted from the Groundwater Sump (TDS at 12,000 mg/L and ammonia at 480 mg/L). Continuous monitoring for electrical conductivity (EC) for some months after January 2008 and biannual monitoring since indicated lower concentrations generally consistent with background water quality in the Lower Werribee Formation. The only on-going evidence of leachate contamination in the Groundwater Dewatering Sump is ammonia concentrations (29 mg/L in July 2013) approximately one order of magnitude higher than in background monitoring bore, BH19 (1.5 mg/L). However, the dewatering system is thought to extract groundwater, at least in part, from the Maddingley Coal Seam rather than directly from the Lower Werribee Aquifer (see Figure 3). As such, ammonia levels may be expected to be somewhat higher in the Groundwater Sump than in monitoring bores screened directly in the Lower Werribee Aquifer. Based on the understanding that the dewatering system partially extract groundwater which has been in contact with the coal and the fact that there is no evidence of leachate impacts on groundwater samples from monitoring wells installed in the Lower Werribee Aquifer hydraulically down-gradient of the landfill, beneficial uses of groundwater in the aquifer are not considered to have been impacted by leachate from the landfill. However, due to the large degree of uncertainty as to what the true leachate levels within these areas, further assessment is required of the long-term risk to groundwater quality in the Lower Werribee Aquifer, post closure. It is likely that effective long-term management of leachate impacts on the Lower Werribee Aquifer, particularly in Area A where the basal liner quality is questionable, will involve maintaining an upward hydraulic gradient from the Lower Werribee Aquifer. Long-term management may involve continued
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Conceptual Site Model
pumping of leachate from the landfill or continued extraction of groundwater from the Groundwater Sump. It is worth noting that URS have modelled impacts on groundwater quality in the Lower Werribee Aquifer under conditions where an upward hydraulic gradient is maintained. The modelling conducted by URS has the significant limitation that it cannot be effectively calibrated due to the lack of reliable leachate level data and lack of field trials to assess the permeability of the layers beneath the landfill and contributions of groundwater to leachate generation. Impacts on groundwater quality in the Lower Werribee Aquifer modelled by URS are attributable to diffusion processes working against upward groundwater advection. URS’s modelling does indicate that groundwater quality in the Lower Werribee Aquifer will be impacted. However, the impacts will be limited to within the site boundaries. It is recommended that the numerical model of the site is calibrated against field trials on the landfill involving lowering leachate levels in Areas A and E, then temporarily ceasing leachate extraction during a period of low rainfall to allow leachate levels to rebound. Conducting appropriate field trials will require reliable leachate level data, the ability to lower leachate levels in Area A and capacity within leachate storage and treatment systems to handle additional leachate pumping rates.
8.2.2 Landfill Side Liner Extension Adjacent to the Fyansford Formation Leachate in the landfill is currently hydraulically separated from the Fyansford Aquifer and Parwan Creek by air space within the open cut pit, aside from sections of the Firewall along the southern boundary which have exceeded the elevation of the base of the Fyansford Formation. As such, it is currently considered unlikely that leachate in the landfill can currently impact water quality in the Fyansford Aquifer or Parwan Creek while the majority of airspace remains unfilled and groundwater extraction continues from the Groundwater Dewatering Sump (see Figure 3). However, once the side liner extension is filled above the contact between the Maddingley Coal Seam and the Fyansford Formation, there is potential for leachate to impact groundwater in the Fyansford Aquifer. Recent data from the June 2013 aerial survey (refer Appendix H of URS, 2013b) indicates that the construction of the firewall along the southern boundary of the landfill has already exceeded the interface between the Maddingley Coal Seam and the Fyansford Formation (see Figure 2). Refer to Section 8.4 below. Over the extended period of below average rainfall from the early 2000s until 2010 there was very little evidence of groundwater being present in the base of the Fyansford Formation in the eastern and southern walls of the coal mine, opposite Areas A and E. Significant groundwater seepage from the Fyansford Aquifer over the upper surface of the Maddingley Coal Seam was observed during the Auditor’s site inspection last year in 2012 and this year on 12 November 2013. It is worth noting that as part of the development of the open cut coal mine, a bench and surface drain was constructed in the coal immediately beneath the contact with the Fyansford Formation to drain groundwater seepage around the wall of the pit to a dam in the northeast corner of the pit. The existing drain strongly supports the presence of an aquifer in the lower part of the Fyansford Formation on the eastern side of the pit. The Fyansford Aquifer may be ephemeral due to discharge into the open cut pit. However, the Fyansford Aquifer is likely to be a permanent groundwater resource once the open cut pit has been filled and groundwater is no longer discharged.
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Conceptual Site Model
Seepage evident from the Fyansford Formation above the coal seam along the north-eastern side of the landfill
As discussed in Section 6.5, consideration should be given to limiting the maximum elevation that Category C contaminated soil can be placed in the Firewall to a level at least 1 m below the base of the Fyansford Formation. If Category C contaminated soil extends above the base of the Fyansford Formation, a side liner consistent with Type 2 landfills in the Landfill BPEM may need to be considered. Based on observations at the site, the Firewall and Groundwater Dewatering Sumps will extend through solid inert waste once the side liner extension is completed and solid inert waste is placed against it. The revised side liner design does not include detail as to how both sumps will be extended and protected in future, and how the current material sitting around the sumps will be sealed off to prevent Type 3 leachate from seeping vertically down around the outer edge of the sumps into the firewall and external geological formations. This detail should be included within the side liner design specification.
Firewall Sump (in front of firewall clay liner and within Category C contaminated soil) and Groundwater Dewatering Sump (behind the firewall clay liner) – the elevation of the Firewall seems to have reached the base of the Fyansford Formation (inferior coal seam not evident)
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Conceptual Site Model
8.3 Areas B, C & D
As discussed in Section 5.3.2, the recently installed bores (BH21 and BH22) adjacent to Areas B, C and D report similar TDS and sulphate concentrations to leachate in Sump C. Manganese in BH21 continues to be reported at concentrations higher than most other bores within the monitoring network. Additional metals, copper and zinc, were both detected in BH21 and BH22 (BH21 exceeded freshwater ecosystem criteria for copper in July 2013, zinc in January and July 2013 and manganese in all rounds and BH22 exceeded freshwater ecosystem criteria for copper and zinc in January and July 2013). The pH in both bores continues to decrease since they were installed in 2011 (apart from the last monitoring round for BH22 in July 2013). Phenols analyses were included in the July 2013 monitoring as per last year’s audit recommendation and were reported below the limit of reporting. Both BH21 and BH22 have chemical concentrations consistent with impact to groundwater from landfilling in the area. However, as the locations of the two bores are between Areas C and D, impact may be attributable to one or all of the sources listed below, including:
• Waste deposition in Area C (Category C contaminated soils). • Waste deposition in water bodies found in Area D (potential acid sulphate soils). • Composting activities in Area B i.e. compost leachate and/or surface water runoff. • Historical landfilling in unlined areas beneath Areas B and C which included deposition of Category C contaminated soils (formerly known as low level contaminated soils), solid inert waste and shredded tyres. Reliable leachate level data is not currently available for Area C. Water levels in Dam D4 are likely to be below the peizometric levels in BH21 and BH22 suggesting and upward hydraulic gradient from the Lower Werribee Aquifer. If an upward hydraulic gradient exists, impacts on water quality may be due to diffusion processes. It is recommended that more reliable leachate level data is obtained in Areas C and D.
Landfill Areas B, C and D and Dam D4 to the north of Areas A and E (future Stage 2 landfill area) – facing north – note exposed coal seam along the northern and eastern sides of the pit which can no longer be seen around landfill Areas A and E
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Conceptual Site Model
8.4 Firewall
Based on groundwater monitoring results from bores screened in the Lower Werribee Aquifer and from the Groundwater Dewatering Sump, there is no clear evidence to date that leachate from the Firewall has impacted groundwater quality in that aquifer. However, an extended suite of metals have been monitored in bores screened in the Lower Werribee Aquifer between the firewall and Parwan Creek since January 2013 (previous audit recommendation), and BH16 has exceeded freshwater ecosystem criteria (ANZECC, 2000) for copper and zinc in July 2013. As there has only been one exceedance from two monitoring rounds, further monitoring is required to determine whether this is an ongoing trend. As part of previous audits, the level of waste within the landfill and Category C contaminated soil placed in the Firewall has been below the upper level of the Maddingley Coal Seam. As such, there has been no risk to groundwater quality in the Fyansford Aquifer associated with the waste. However, waste levels in the landfill and the extent of the Firewall are approaching an elevation where they will be level with the Fyansford Formation. As such, leachate associated with solid inert waste in the upper part of landfill Areas A and E represents a future risk to groundwater quality in the Fyansford Aquifer.
Exposed coal seam to the north of Area E
Eastern side of Area E facing north – firewall has reached the base of Fyansford Formation (coal seam not evident except for the area to the north of the landfill in the background). Vegetation along the Fyansford Formation may be evidence of groundwater seepage Based upon the working contours at the landfill taken from an aerial survey in June 2013 (Appendix H, URS, 2013b), the current elevation of the southern portion of the firewall currently sits between approximately 95 to 96.5 mAHD. Figure 2 provides the elevation of the base of the Fyansford Formation, as it changes to the inferior coal seam, along the eastern and western boundaries of the landfill, but does not include the southern boundary. This survey data was collected by ground survey on 16 September 2013 (BGL Surveying). Elevations along the red line represent the top of the coal seam and elevations along the blue line represent the base of the Fyansford Formation. The difference between them is the thickness of the inferior coal seam. Survey data was not obtained for the southern boundary – it is assumed it could not be obtained because the elevation of the firewall has exceeded it. Extrapolation of the surveyed locations from the eastern side of the landfill and the western side indicates the base of the Fyansford Formation is likely to range between 92.4 mAHD to 94.3 mAHD respectively. This indicates that the top of the firewall is likely to have exceeded the base of the Fyansford Formation between 2 and 2.5 m and that prescribed industrial waste (PIW), i.e. Category C contaminated soils, have been deposited adjacent to a geological formation other than coal with minimal liner protection i.e. 1 m of compacted clay.
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Conceptual Site Model
8.5 Parwan Creek
Parwan Creek is in essence a man-made drainage line used to divert the creek to allow excavation of the coal mine, it was diverted to the eastern side of the site in the 1940s. It is not clear from information provided to the Auditor to date whether there is potential for groundwater in the Fyansford Aquifer to discharge to Parwan Creek where it passes the unfilled landfill area extending above the top of the Firewall. No groundwater monitoring bores are currently installed in the Fyansford Aquifer between the landfill area extending above the top of the Firewall and Parwan Creek. If groundwater in the Fyansford Aquifer were to be contaminated by leachate in the landfill once the side liner is extended, there is potential for contaminated groundwater to discharge to the creek. Sections of the creek have been lined with clay (URS, 2013a). In 1994, cracks in the southern wall of the mine were repaired to prevent water flow from the Parwan Creek entering the pit. Parts of the creek were also lined with clay to reduce leakage. Surveyed elevations of the base of the Parwan Creek were recently provided by MBC, which were measured in August 2011 by BGL Surveying. The information provided is presented in Figure 1. The lowest point of the creek surveyed along the eastern boundary of the current landfill ranged from 95.37 mAHD near BH2 (just north of Cell E5) to 95.75 mAHD near BH16 and the Groundwater Sump (adjacent to Cell E4). The lowest point of the creek surveyed along the southern boundary of the landfill ranged from 96.85 mAHD south of BH6 to 98.38 mAHD south of the western open coal pit. The revised design of the side liner extension described in Section 6.5 indicates that the upper eastern side of the landfill will extend much closer to Parwan Creek than the lower part of the landfill currently does, and is likely to come within 40m of the creek in some sections. While the surveyed elevations of the Parwan Creek are useful in understanding the relationship between the creek and the Fyansford Formation, groundwater monitoring bores in the Fyansford Aquifer in the vicinity of the Firewall between the landfill and Parwan Creek would allow risk to groundwater and surface water quality to be assessed.
8.6 Dam D4 & Irrigation Dam
The measured pH of water in Dam D4 in July 2013 was much lower, pH 4.0, than previous monitoring rounds which have been close to neutral. Section 3.4 of URS 2013b indicates water from Dam D4 originates from seepage of groundwater from the Lower Werribee Formation and surface water runoff from the surrounding area. It also indicates water from Dam D4 is transferred to the Irrigation Dam. Water quality in the Irrigation Dam in July 2013 is similar to Dam D4, with an unusually low pH of 3.9, as opposed to a pH between 7 and 8.5 in previous years. The low pH in Dam D4 may be an indication that surface water runoff from Area D may be acidic. Area D is licenced to and has accepted potential acid sulphate soils. It is unknown if this waste type was accepted recently in 2012-2013. Working contours shown in Appendix H of URS 2013b indicate that surface water runoff from Areas B, C and D is likely to discharge into Dam D4. In response to the Auditor raising the issue of low pH in Dam D4, MBC commissioned additional pH testing of water in Dam D4 and soils around the dam which may have affected the pH of run-off. Additional sampling indicated that the pH of water in Dam D4 was consistent with historical results and generally neutral to slightly alkaline.
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Risk Assessment
9.0 Risk Assessment
The risk of harm or detriment to human health and the groundwater environment has been assessed using a qualitative method consistent with AS/NZS ISO 31000:2009, Risk management – Principles and guidelines (Standard Australia/Standards New Zealand, 2009).
9.1 Risk Communication
Risk communication is the process of consulting with internal and external stakeholders in the risk assessment process concerning the process as a whole. The communication process involved the following:
• The auditor worked with MBC and its consultant, URS, through meetings, site inspections and reports to provide input on the risk assessment. • Provision of the audit scope to EPA. • Receipt of feedback from EPA on audits of risk to groundwater conducted previously for the site. Consultation with owners and occupiers of surrounding properties and the general public was not undertaken as part of the audit.
9.2 Risk Context
As discussed in Section 2.0, the scope of the audit was to assess the risk of any possible harm or detriment to groundwaters and surface water caused by the activities of the licence holder on the premises. Risk is defined as a function of the likelihood of a hazard occurring and the consequences of that hazard. As a mathematical formula, risk is represented by the following equation: Risk = Consequence x Likelihood Qualitative levels of consequence associated with impact to groundwater caused by activities of the licence holder are presented in the table below.
Table 1: Consequence Levels
Level Descriptor Definition
6 Extreme Beneficial uses which have been realised have been impacted by contamination such that those uses can no longer be sustained. Impacts have caused impacts to human health or caused measurable impacts to surrounding ecosystems including significant species mortality.
5 Severe Relevant beneficial uses have been impacted off-site such that those uses can no longer be sustained without significant additional engineering or management measures. There is potential for contaminated groundwater to discharge directly to a surface water body and cause impacts to ecosystems.
4 Major Groundwater pollution has been detected in off-site groundwater bores. However, relevant (existing) groundwater uses have not been impacted. There is potential for contaminated groundwater to be discharged from the site via the groundwater dewatering system at the site.
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Risk Assessment
Level Descriptor Definition
3 Significant Groundwater pollution, with respect to one or more protected beneficial uses, has been detected in on-site bores. Contamination has been detected in off-site groundwater bores at concentrations less than screening criteria for protected beneficial uses.
2 Minor Contamination has been detected in on-site groundwater bores at concentrations less than investigation criteria for protected beneficial uses. As such, groundwater pollution has not occurred however contaminants have been released to the environment.
1 Insignificant Some evidence of leachate interaction with groundwater or leachate interaction cannot be ruled out.
Qualitative levels of likelihood associated with contamination resulting in the potential for beneficial uses to be precluded are presented in the table below. Table 2: Likelihood Levels
Level Descriptor Definition Indicative Frequency
5 Certain Event has occurred and is likely occur on an annual basis Once a year or more frequently
4 Likely Event has occurred and is likely to occur again Once in every three years
3 Possible Event has occurred and may re-occur within the next few years. Once in ten years There is a realistic potential for the event to occur.
2 Unlikely Event has not occurred and is unlikely to occur at the site Once in 30 years
1 Highly unlikely It is conceivable that the event may occur but only if circumstances Once in 50 years affecting the hazard change significantly
Using a qualitative methodology, the risk associated with each hazard has been evaluated into descriptive risk ranges as follows:
Table 3: Risk Level Matrix
Consequence Likelihood
1 2 3 4 5
6 Medium High Very High Extreme Extreme (6) (12) (18) (24) (30)
5 Medium High High Very High Extreme (5) (10) (15) (20) (25)
4 Low Medium High Very High Very High (4) (8) (12) (16) (20)
3 Low Medium Medium High High (3) (6) (9) (12) (15)
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Risk Assessment
Consequence Likelihood
2 Low Low Medium Medium High (2) (4) (6) (8) (10)
1 Low Low Low Low Medium (1) (2) (3) (4) (5)
The risk ranges were developed to reflect the Auditor’s understanding of EPA requirements regarding the management of groundwater at an operational landfill. The risk ranges and management responses are presented in the table below:
Table 4: Risk Ranges
Risk Risk Management Response Range Descriptor
0 - 5 Low No management response required.
6 – 10 Medium Further monitoring or assessment of groundwater contamination required. Monitoring network or methodology needs up-grading. Current onsite management procedures to be continued. Contingency measures may need to be developed to address potential issues indicated by assessment or monitoring results.
11 – 15 High Additional onsite management procedures need to be implemented. Existing leachate and groundwater pumping systems may need to be enhanced or operational procedures changed to reduce risks to groundwater or surface water quality. Monitoring network or methodology needs up-grading. Uncertainty associated with potential risks need to be resolved as a priority.
16 – 20 Very High Remedial measures need to be developed and implemented to restore beneficial uses of groundwater or where practicable, obtain a determination of Clean Up to the Extent Practicable (CUTEP) from EPA, consistent with EPA Publication 840. Consider potential application of a Groundwater Attenuation Zone as per requirements of SEPP GoV. Remedial works or additional infrastructure need to be implemented to mitigate risks to human health or the environment. Any uncertainty associated with potential risks identified need to be addressed as a priority to ensure an unacceptable hazard does not exist.
21 + Extreme Immediately implement engineering and management measures to cease risks to human health and surrounding ecosystems. Remedial measures need to be developed and implemented to restore beneficial uses of groundwater or obtain a determination of Clean Up to the Extent Practicable (CUTEP) from EPA, consistent with EPA Publication 840. Apply a Groundwater Attenuation Zone as per requirements of SEPP GoV.
9.3 Risk Identification
The principal risks associated with impacts to beneficial uses of groundwater caused by activities of the licence holder are as follows:
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Risk Assessment
• Pollution of groundwater on-site only. • Pollution of groundwater both on-site and off-site. • Pollution of groundwater for which beneficial uses are being realised (e.g. extraction for use or discharge to surface water ecosystems). Impacts to either the Fyansford Aquifer or Lower Werribee Aquifer were considered separately.
9.4 Risk Analysis and Evaluation
The analysis and evaluation of the risks identified in Section 9.3 and based on the source-pathway- receptors presented in the CSM (refer Section 8.0) is documented in the table below. Risks identified have been split into Short and Long Term Risks.
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
SHORT TERM RISKS
1 Seepage of Fyansford 3 Significant 5 Certain 15 High leachate from Aquifer Leachate Evidence of nitrate impact of On-site pollution of Unless clear evidence can be provided that leakage Ponds groundwater, which may be due groundwater has been from the ponds is not on-going, the basal liner of the through the to seepage through the base of confirmed over a number of Leachate Ponds should be up-graded to reduce basal liner the leachate ponds, has been monitoring rounds. seepage to groundwater. Condition 3.6 of the PAN detected onsite in BH11 in a issued by EPA in July 2012 requires the ponds to be perched water table in the upper relined to the same standards as Cell E5 by 1 June layers of the Fyansford 2013. The Auditor understands that re-lining of the Formation between the ponds existing leachate ponds is yet to commence. and the Maddingley Coal Mine to the west of the landfill. As the recently constructed background Fyansford Formation bore BH23 displays similar TDS values to Groundwater impacts appear to BH11 and BH17, VFAs should be including in be limited to within the site monitoring of bores BH11, BH17 and BH23 in January boundary and ultimately is likely and July 2014 to confirm whether leachate ponds L1 to discharge into the coal mining and L2 are leaking. area to the east of the Leachate Ponds and west of landfilling Storage capacity requirements for the leachate ponds Area A (as confirmed by recent need to be considered as part of the development and monitoring in newly constructed implementation of a Leachate Management Plan for the bore BH23, to the west of the site. treatment plant area).
2 Seepage of Lower Werribee 3 Significant 3 Possible 9 Medium leachate from Aquifer the Fire Wall There is no clear evidence to As there has only been one Contaminated soil should not be placed in contact with through the date that leachate from the exceedance of copper and the Fyansford Formation. Placement should not exceed basal liner Firewall has impacted zinc in one bore from two the coal seam/Fyansford Formation interface along the groundwater quality in that monitoring rounds, further southern and eastern boundaries of landfill areas A and aquifer. However, an extended monitoring is required to E. suite of metals have been determine whether this is an monitored in bores screened in ongoing trend. Maintain separate leachate collection system operation. the Lower Werribee Aquifer Continue current monitoring requirements. between the firewall and Documentation of earlier Parwan Creek since January stages of the Firewall basal 2013 (previous audit liner construction is limited. recommendation), and BH16 The Firewall liner is has exceeded freshwater understood to include a basal
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
ecosystem criteria (ANZECC, liner and leachate collection 2000) for copper and zinc in system and a 1m thick July 2013. compacted clay side wall liner which abuts waste and the coal wall. Leachate head in the Firewall Sump was 2.1m in July 2013.
3 Seepage of Fyansford 3 Significant 3 Possible 9 Medium leachate from Formation the Fire Wall Potential for impact cannot be Construction of the firewall Install 4 Fyansford Formation groundwater monitoring through the measured. There is a data gap has exceeded the base of the bores between the firewall and Parwan Creek as soon side liner as no Fyansford Formation Fyansford Formation along as possible. groundwater monitoring bores the southern boundary of the exist between the firewall and landfill by 2 to 2.5 m. Parwan Creek.
4 Seepage of Lower Werribee 4 Major 3 Possible 12 High leachate from Aquifer Areas A and E An upward hydraulic gradient is Indicators of groundwater Improve leachate level monitoring in Areas A and E. believed to exist beneath Areas pollution were detected in through the Maintain LB01A and LB02A as leachate monitoring basal liner A and E, which should be January 2008 in the protective of groundwater in the Groundwater Sump. wells, rather than extraction wells.Install additional and MCS leachate monitoring wells in Areas A and E. (under current Lower Werribee Aquifer. Monitoring before and since conditions However, leachate level data is has indicated that the data It is recommended that leachate levels are continuously with considered unreliable. was either anomalous or an monitored using pressure transducers and data. It is indicator of leachate impact groundwater Slightly elevated ammonia also recommended that remote telemetry is installed to dewatering that was short-term only and allow daily access to leachate level data by MBC’s levels have been detected in has dissipated. and leachate samples from the Groundwater management team at their desks. Continuous leachate extraction) Sump in 2008. Since 2008, There is evidence of elevated level data will also assist in the HA in understanding water quality in the ammonia concentrations in leachate responses to rainfall and groundwater inflows Groundwater Sump does not the Groundwater Dewatering and may be used as part of leachate pumping trials. indicate groundwater pollution Sump approximately one On-going monitoring of groundwater quality consistent has occurred. However, on- order of magnitude above with the Licence requirements should continue. going evidence of leachate background conditions. contamination in the However, background A leachate treatment/disposal system must be Groundwater Dewatering Sump conditions are likely to implemented to allow leachate levels in the landfill to be is ammonia concentrations (29 preclude a number of the lowered and maintained below potentiometric levels in mg/L in July 2013) protected beneficial uses. the Lower Werribee Aquifer, particularly in unlined areas approximately one order of of the landfill and more so in Area A. It is understood
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
magnitude higher than in that an up-graded leachate treatment system has been background monitoring bore, constructed and will be commissioned upon resolution BH19 (1.5 mg/L). of the management of the retentate (currently under mediation between EPA and the Operator). If significant leachate contamination of water Operation of the groundwater dewatering systems extracted from the Groundwater should continue. It is recommended that a means of Sump occurs, it may need to be more accurately monitoring groundwater elevations in treated as leachate. the Groundwater Sump is established and conducted on a regular basis with groundwater monitoring requirements in the EPA Licence.
5 Seepage of Lower Werribee 3 Significant 4 Likely 12 High leachate from Aquifer Areas B, C Both BH21 and BH22 appear to Based on monitoring results Continue monitoring leachate sumps and groundwater and D and show impact to groundwater event appears to have monitoring bores in Areas B and C. historical quality from landfilling in the occurred and is likely to waste beneath area. continue to occur. Continue to analyse groundwater samples for a larger Areas B and C suite of metals in Lower Werribee Formation Manganese in BH21 continues Impacts appear more likely to groundwater bores hydraulically down gradient of Area to be reported at concentrations be due to diffusion processes C and the Firewall i.e. Cadmium, Chromium, Copper, higher than most other bores or associated with historical Mercury, Lead, Selenium, Tin and Zinc for groundwater within the monitoring network. waste beneath current bores BH6, BH16, BH2, BH21 and BH22. Additional metals, copper and operations. More reliable zinc, were both detected in leachate level data is required Install leachate monitoring wells in Area C. BH21 and BH22 (BH21 to assess mechanisms exceeded freshwater ecosystem causing groundwater impacts. Install an additional groundwater monitoring well east of criteria for copper in July 2013, BH21 and BH22 to assess impacts on the Lower zinc in January and July 2013 Werribee Aquifer hydraulically down-gradient of Areas and manganese in all rounds B, C and D. and BH22 exceeded freshwater ecosystem criteria for copper and zinc in January and July 2013). The pH in both bores continues to decrease since they were installed in 2011 (apart from the last monitoring round for BH22 in July 2013).
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
6 Run-Off and Dam D4 2 Minor 4 Likely 8 Medium seepage from Areas B, C Evidence of low pH (4.0) in on- July 2013 round of monitoring Continue monitoring of dams to confirm pH and metals and D site water body (Dam D4). indicated acidic water found in after a rainfall event. Dam D4 on site. Water is Potential for metals to leach understood to be transferred Cover Area D with interim clay cap. directly into Lower Werribee to Irrigation Dam adjacent to Aquifer. Parwan Creek. Subsequent monitoring to indicated pH levels in Dam D4 were closer to neutral.
7 Leachate and Western coal 6 Extreme 3 Possible 18 Very High waste extraction area / outburst from Workers Slope failure could lead to Slope has been stable for a Collect more reliable leachate level data in Area A. leachate and waste discharge considerable period and Area A Implement recommendations made by NSP western batter into the western coal pit. current leachate level data Environmental impact remains suggests leachate levels are Geotechnics (geotechnical investigation report July on site. below the base of the slope. 2013) as soon as possible. Given the large degree of Workers may be present in the Investigate and document the extent of waste and uncertainty as to what the true whether a side wall liner is present against the coal. western coal pit during slope leachate levels within Area A failure event, leading to injury or are, it is considered this event Develop final cap designs for the western batter death. is possible. including, if necessary, a leachate collection system along the lower sections of western batter.
LONG TERM RISKS
8 Seepage of Fyansford 5 Severe 3 Possible 15 High leachate from Aquifer Areas A and E Leachate from the side wall The EPA-approved Side Liner Install groundwater monitoring wells in the Fyansford and the extension above the Firewall, or Extension is being revised Aquifer between the Fire Wall and Parwan Creek. It is Firewall leachate from Areas A and E due to the revised landfill final recommended that four monitoring wells are installed, Extension migrating through the extension, contours approved under two east and two south of Areas A and E. may impact groundwater quality WA70655. An appropriate in the Fyansford Aquifer. side liner should be protective Assess aquifer parameters for the Fyansford Aquifer in Groundwater seepage from the of the Fyansford Aquifer. the recommended monitoring wells. Fyansford Formation was Survey the elevation of the top of the firewall, observed during the site The base of the side liner extension appears to be particularly in the south.
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
inspection. above the base of the Confirm with EPA where elevation of the construction of Fyansford Formation and the the firewall should cease. If groundwater in the Fyansford elevation of the top of the Aquifer is impacted by leachate, firewall is unknown. Share the Auditor’s comments relating to the proposed the potential for groundwater to design of the side liner extension with the designer discharge into Parwan Creek The risk to groundwater will (Meinhardt) and assessor (Peter Ramsay). needs to be assessed. manifest when solid inert waste is placed against the Amend the proposed side liner extension design Side Liner Extension in future, specification to include detail as to how the firewall although it is likely that post sump and groundwater dewatering sump will be closure management will extended through solid inert waste placed above the require leachate levels to be firewall. maintained below the inferred Consider amending the proposed side liner extension groundwater levels in the design specification to include a composite liner Lower Werribee Formation. between the top of the firewall and the base of the side No groundwater data is liner extension. available for the Fyansford Manage the risk of groundwater from the Fyansford Aquifer east and south of Formation seeping into the landfill, through the side liner Area A and E to assess side- extension and an external groundwater drain. See liner performance and Section 6.5. potential contributions to leachate generation.
9 Seepage of Lower Werribee 3 If leachate levels in Areas A and 3 Based on potential hydraulic 9 Medium leachate from Aquifer E are not maintained below the conditions post closure, it is Areas A and E piezometric surface in the considered possible, that Continue to prepare a reliable hydrogeological (long-term Lower Werribee Aquifer and significant impacts to assessment (HA) for the site which is calibrated against post closure groundwater extraction ceases, groundwater quality in the data collected during field trials as a basis for conditions) there is potential for Lower Werribee Aquifer may demonstrating how groundwater quality in the Lower groundwater quality to be occur if groundwater Werribee Aquifer will be protected post-closure. The HA significantly impacted. extraction were to cease and should assess the following: leachate levels were allowed • Contributions of rainfall and groundwater to
to rise significantly above leachate generation. potentiometric levels in the • Drawdown on the piezometric surface in the underlying aquifer. In Lower Werribee Aquifer associated with extraction particular, the effectiveness of from the Groundwater Sump. the basal liner and the depth • Given this part of the landfill is nearing closure; and permeability of the determine the leachate levels to be maintained to underlying coal seam beneath protect groundwater. Area A has yet to be • Long-term leachate seepage rates from the landfill
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Risk Assessment
Hazard Source / Receptor Consequence Likelihood Risk Pathway Level Description Level Description Level Management Measure
adequately assessed. post closure. • Leachate pumping rates to maintain vertical hydraulic gradients that are protective of groundwater quality. • Permeability of layers underlying the landfill.
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Recommendations
10.0 Recommendations
Based on the findings throughout the report, particularly the items discussed in the conceptual site model in Section 8.0 and the risk assessment completed in Section 9.4, the following works and activities relating to management of leachate and risks to groundwater and surface water are recommended along with a proposed timetable.
10.1 Immediate Actions
Number Recommendation Implementation Timetable
Leachate Management
1 A Continue to collect data will allow a numerical hydrogeological and solute transport January 2014 - model to be reliably calibrated (refer to Monitoring recommendatons). ongoing
1 B Once the LMP has been implemented and reliable leachate level data confirms December 2015 that leachate levels have been adequately drawn down to levels which are protective of the Lower Werribee and Fyansord Aquifers, conduct leachate pumping shut down trials to provided data to calibrate the numerical model. Leachate pumping shut down trials should be conducted during periods of low rainfall to assess groundwater contributions to leachate generation and the permeability of the liners and Maddingley Coal Seam underlying the landfill.
1 C Once appropriate data has been collected (refer to Items 1A and B), the numerical December 2015 model should be calibrated against site data and used to assess the following: • Long-term leachate seepage rates from the landfill post closure. • Drawdown on the peizometric surface in the Lower Werribee Aquifer associated with extraction from the Groundwater Sump. • The maximum level of leachate to be maintained to protect groundwater quality in the Lower Werribee Aquifer and Fyansford Formation post closure. • Post-closure leachate pumping rates. • Potential benefits of continuing groundwater extraction from the Groundwater Sump and a drain to dewater the Fyansford Formation Aquifer external to the side-wall liner. • Appropriateness of retentate disposal to the landfill following completion of Stage 1 (Areas A and E) of the landfill.
1 D If reliable leachate level data indicates that leachate levels in Areas A and E1 to May 2014 - decide E3 are above the recommended elevation which will maintain and upward whether a leachate hydraulic gradient, prepare a plan increase leachate extraction rates. Measures to extraction plan is increase leachate extraction from Area A may include the following measures: required based on leachate levels. 1. Install drainage strips underneath the interim or final cap along the lower sections of the western batter of Area A to alleviate potential leachate build up underneath the cap and reduce the risk of slope failure. The strip drains should tie into a drain at the toe of the batter, and drain to a collection sump and allow leachate extraction from the western and northern batters of Area A. 2. Install leachate extraction infrastructure in the existing 5 landfill gas extraction wells along the western side of Area A and commence pumping as soon as possible. 3. Install a cumulative flow meter in the collection sump at the base of the leachate strip drains as well as at each landfill gas extraction well described above. and monitor leachate levels in LB01A, LB02A and Sump A1 (not to be used for extraction).
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Recommendations
Number Recommendation Implementation Timetable
1 E Given leachate extraction from Sump A1 has been unsuccessful in yielding May 2014 significant quantities of groundwater, the design of future leachate extraction wells should be reconsidered to include the following aspects: • Longer screened intervals to allow leachate to enter the well from a larger waste depth. • Installation of shallower wells i.e. the depth of a new well does not need to reach the base of the landfill, it should only intersect the elevation of the inferred groundwater levels in the Lower Werribee Aquifer by 2 to 5 m. • Consideration of the material used in the construction of the well i.e. HDPE versus stainless steel.
1 F Confirm the mix of leachate treatment, storage and management options that will February 2014 be used to dispose of leachate and include these commitments in the LMP.
Landfill Rehabilitation
2 A Continue to apply and maintain interim clay capping over Landfill Areas A and E. Ongoing Closely monitor for erosion and repair as required, particularly along the western batter of Area A.
2 B Prepare a landfill rehabilitation plan and, as a minimum, include the first stage June 2014 over the western batter of Area A (60 to 80 m wide area) and (if possible) the northern batter of Area A and Cell E5. The plan should include the following approach: 1. Fill the outer edges of the landfill to final profile, particularly the western batter of Area A and northern batter of Area A and Cell E5 which are close to or at final profile. Confirm whether the northern batter of Area A and Cell E5 are able to be capped or if other works associated with WA70655 must be completed first. 2. Prepare cap subgrade in the above areas, or as a minimum, over the western batter of Area A. 3. Confirm whether a side liner exists along the western side of landfill Area A, filled by previous owners, in order to design final cap tie-ins. (see recommendation 3B). 4. Confirm revised final contours with EPA. 5. Prepare cap design specification and construction quality assurance plan as well as a design assessment as per EPA Publication 1323. Include a design of a bund along the toe of the western batter of Area A (if it is confirmed that a liner along this boundary does not exist). 6. Obtain EPA approval of cap design. 7. Build bund along the toe of the western batter of Area A (if required). 8. Commence capping of the western side of Area A.
2 C Regular surveying of the working contours of the landfill e.g. six monthly aerial Ongoing - surveys, which are then compared with the final contours of the landfill, will assist commence in in identifying other areas that may become available for final capping. January 2014 Provide the surveyor with the latest endorsed final contours.
Landfill Construction
3 A Complete an intrusive investigation along the entire western side of Area A to April 2014 confirm the following: • Map the western extent of waste placement in Area A. • Whether a clay side-wall liner was placed between waste and the coal seam beneath the current level of filling. The results of the investigation should be documented in a report with photographs, test pit logs and surveyed test pit locations.
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Recommendations
Number Recommendation Implementation Timetable
3 B Use the results of the investigation along the western side of Area A to complete June 2014 final capping designs including tie-in with the side-wall liner and final batter slopes.
Design of the lower sections of the western and northern slopes of Area A should
consider incorporation of leachate collection drains to assist in lowering leachate levels in that part of the landfill (see Item 1D-1).
Monitoring
4 A Maintain LB01A and LB02A as leachate monitoring wells, rather than leachate Complete by end of sumps. It is recommended that leachate levels in the following wells and sumps March 2014 are continuously monitored using pressure transducers and data loggers: • LB01A. • LB02A. It is recommended that remote telemetry is installed with data loggers to allow leachate level data to be monitored daily by MBC’s management team from their desks. Alarms should be set up to warn MBC’s management team when leachate levels are approaching target elevations determined from the HA and LMP review. Similar monitoring arrangements should be established in proposed new leachate monitoring wells in Areas E4 and E5.
4 B Install four groundwater monitoring bores in the Fyansford Aquifer between the March 2014 Side Liner Extension and Parwan Creek on the southern and eastern side of Areas A and E before waste is placed adjacent to the Fyansford Formation.
4 C Monitor Fyansford Formation groundwater monitoring bores BH11, BH17 & BH23 January 2014 for VFAs during the January and July 2014 monitoring rounds to confirm whether leachate ponds L1 and L2 are leaking.
4 D Review groundwater sampling methodology to ensure a consistent and repeatable January 2014 procedure is documented and completed. Ensure that a robust sampling methodology is implemented. Sampling methodology for groundwater monitoring bores must be conducted by either: • Purging bores until field chemical parameters have stabilised prior to sampling using bailers or some other approved sampling pump or device. • Low flow sampling where the rationale for the sampling method and depth interval has been clearly articulated. The purging method is considered preferable at this site given the data quality requirements and for comparison to historical monitoring data.
4 E If low flow sampling is used: January 2014 • Sampling methodology for groundwater monitoring bores must ensure that sampling occurs from the screened interval of the groundwater bore. • The target depth interval for low flow sampling in each well should be documented. This information should be provided to sampling personnel each monitoring round.
4 F The Auditor agrees with URS (URS, 2013b) that leachate samples from the January 2014 leachate dams should not be filtered prior to analysis, as per the leachate well and sump samples. This should be communicated to sampling personnel prior to the next monitoring round.
4 G Ensure that nitrate, nitrite, total nitrogen and TKN are monitored in all dams on site January 2014 in future monitoring rounds. Nitrate, nitrite, total nitrogen and TKN have been analysed in these dams since January 2009 but were not included in the January and July 2013 monitoring rounds.
4 H The date the leachate sumps and monitoring wells are extended should be January 2014 recorded and the length of the extension noted. Alternatively, the sumps and
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Recommendations
Number Recommendation Implementation Timetable
wells should be re-surveyed prior to each monitoring round.
4 I MBC should devise a new method with sampling personnel and URS to monitor June 2014 (prior to groundwater levels in the Groundwater Dewatering Sump, while pump July 2014 monitoring infrastructure is in place. This is required to provide a more accurate basis to round) model potential drawdown around the Groundwater Dewatering Sump. As for leachate monitoring bores, it is recommended that continuous leachate level data is collected and remote telemetry installed to allow leachate level data to be monitored daily by MBC’s management team from their desks.
4 J Electrical conductivity of leachate extracted from sumps E4 and E5 should be June 2014 monitored continuously.
Surface Water Management
5 A Confirm with EPA the boundary of Area D and whether it includes Dam D4 or not December 2013 as waste deposition appears to have encroached into the Dam D4 area.
5 B Confirm how stormwater management practices will be amended when August 2014 construction of the landfill extension commences in the area currently occupied by Dam D4 as it appears to be fed by stormwater runoff from Areas B, C, D and the western coal pit. This information should be included in the annual monitoring review report for FY13/14.
Reporting
6 A The annual monitoring review for FY13/14 should include January and July 2014 August 2014 monitoring results and should be submitted to the auditor as soon as possible. MBC to seek an extension on the submission of the next groundwater audit report until the end of December 2014.
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Principles and Limitations of Investigation
11.0 Principles and Limitations of Investigation
The conclusions and recommendations presented in this report have been based on the information provided and the Auditor’s professional judgement. Key limitations and areas of uncertainty associated with the report include the following:
• Groundwater and leachate elevation data in Landfill Area A and E and in the vicinity of the groundwater extraction system is limited and the vertical hydraulic gradient between the Lower Werribee Aquifer and possible leachate beneath the landfill is not clearly defined. • It is unclear to the Auditor whether the Firewall surrounding the eastern side of Area A and E and the southern side of Area A forms part of the licenced area i.e. whether the risk of impact from the Firewall forms part of the groundwater audit for the landfill. • The Auditor has completed a preliminary review of Revision 1 of a HA and LMP, however, incorporation of this review into this audit report is limited, and will be included in the next audit reporting period, once the Auditor has completed a review of Revision 2 of both documents. A fundamental assumption to the conduct of the audit is that the information provided to the Auditor is accurate and complete. In particular, that no information relating to waste management, leachate management and potential groundwater impacts has been withheld from the Auditor.
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References
12.0 References
AECOM (AECOM, 2009), Technical Specification Maddingley Brown Coal Landfill Side Wall Liner Extension, 5 June 2009 Australian and New Zealand Environment and Conservation Council, (ANZECC, 2000). Australian and New Zealand Guidelines for Fresh and Marine Water Quality Australian and New Zealand Environment and Conservation Council, (ANZECC, 1992). Australian Water Quality Guidelines For Fresh and Marine Waters BGL Surveying, Interface Between Maddingley Coal Seam & Fyansford Formation (AutoCAD file), 16 September 2013 BGL Surveying, Base of Parwan Creek (AutoCAD file), 29 August 2011 Birch, W.D. (Editor) 2003. Geology of Victoria. Geological Society of Australia Special Publication 23. Geological Society of Australia (Victoria Division) Douglas, J.G. and Ferguson, J.A., 1988. Geology of Victoria, Victorian Division, Geological Society of Australia Incorporated, August 1988. Edited by Douglas, J.G. and Ferguson, J.A. Environment Protection Act 1970 Environment Protection (Prescribed Waste) Regulations 1998 EPA Publication 952.4 - Environmental Auditor Guidelines for the Preparation of Environmental Audit Reports on Risk to the Environment, April 2013 EPA Publication 788.1, Best Practice Environmental Management (BPEM) – Siting, Design, Operation and Rehabilitation of Landfills, September 2010 EPA Publication IWRG701, Sampling and Analysis of Waters, Wastewaters, Soils and Wastes, June 2009 EPA Publication 953.2 – Environmental Auditor Guidelines for Conducting Environmental Audits, October 2007 EPA Publication 668, Hydrogeological Assessment (Groundwater Quality) Guidelines, September 2006 EPA Publication 669, Groundwater Sampling Guidelines, April 2000 Golder Associates Pty Ltd, Well Installation Maddingley Brown Coal (May – June 2010), 4 August 2010 Golder Associates Pty Ltd, Hydrogeological Assessment, Maddingley Brown Coal, Bacchus Marsh, Victoria, 15 September 2008 Golder Associates, Environmental Audit Report for Construction of Cell E4, March 2007
Golder Associates Pty Ltd (Golder, 2018a), Technical Specification for Stage 3 Firewall Extension (Sideliner), August 2008 Golder Associates Pty Ltd (Golder, 2018b), Technical Specification for Stage 4 Firewall Base Liner and Extension (Sideliner), September 2008 Landair Surveys, Site Aerial Survey (AutoCAD file), 28 June 2013 Meinhardt Infrastructure & Environment Pty Ltd (Meinhardt 2013), Technical Specification and Construction Quality Assurance (CQA) Plan Construction of Sidewall Liner Extension Stage 1 & 2 (Area E & A), Revision A, September 2013
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References
National Environmental Protection Council, National Environmental Protection (Assessment of Site Contamination) Measure, 1999 (as amended in 2013) NSP Geotechnics Pty Ltd (NSP Geotechnics, 2013), Geotechnical Investigation for MBC Landfill Project – Area A West, July 2013 State Environment Protection Policy (Groundwaters of Victoria), 1997 State Environmental Protection Policy (Prevention and Management of Contamination of Land), 2002 (as amended in September 2013) State Environment Protection Policy (Waters of Victoria), 2003 Standards Australia/Standards New Zealand, AS/NZS ISO 31000:2009, Risk management – Principles and guidelines, 2009 URS Australia Pty Ltd (URS, 2013a), Draft Report Maddingley Brown Coal Landfill Hydrogeological Risk Assessment & Leachate Management Plan, 15 October 2013 URS Australia Pty Ltd (URS, 2013b), Preliminary Final Report 2012-2013 Annual Review, Maddingley Brown Coal Landfill, 30 October 2013 URS Australia Pty Ltd (URS, 2013c), Final Report 2012-2013 Annual Review, Maddingley Brown Coal Landfill, 26 November 2013 URS Australia Pty Ltd (URS, 2012a), 2011-2012 Annual Report, Maddingley Brown Coal Landfill, Tilleys Road Bacchus Marsh, Victoria, 11 September 2012 URS Australia Pty Ltd (URS, 2012b), 2011-2012 Annual Report, Maddingley Brown Coal Landfill, Tilleys Road Bacchus Marsh, Victoria, 22 October 2012 URS Australia Pty Ltd (URS, 2011a), 2010-2011 Annual Monitoring Review, Maddingley Brown Coal Landfill, East Maddingley Road Bacchus Marsh, Victoria, 28 September 2011 URS Australia Pty Ltd (URS, 2011b), Addendum to 2010-2011 Annual Monitoring Review, Maddingley Brown Coal Landfill, East Maddingley Road Bacchus Marsh, Victoria, 12 December 2011 URS Australia Pty Ltd (URS, 2010), 2009-2010 Annual Monitoring Review, Maddingley Brown Coal Landfill, East Maddingley Road Bacchus Marsh, Victoria Waste Management Policy - Siting, Design and Management of Landfills, 2004 Water Act 1989
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Figures
Figures
Figure 1: Parwan Creek Survey Data
Figure 2: Maddinley Coal Seam Survey Data
Figure 3: West-East Hydrogeological Cross-section
m1079503_051_rpt_16jan14
115
9 5
1 0 0
9 5 93.818 9 5 94.262 ± 0 0 1 130
135 105
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9 5 9 5
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95 95 90 90 94.542
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95 95.251 115
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110 90 A@ BH2 140 140 Photo 5 Photo1 100 100 95.371 95.135
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BH10 120 120 A@ 85
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75 75
115 115
95 95 75 75 500 85
85 85 95.415
80 80 95.211
135 130 95 100
1 0 0 80 80
90 105
100 85 85
95 95
110 110 100
90 90 90 90
0 0 1
750 1 0 0 95 95
125 95.493 95.570
100 85
110
0 0 1
115 1000 115
95 1 0 0 105 105
1 0 5 97.716 Photo1 95.635 100 1 0 0
100
90 105 105 115 115
1 0 0 90 90
85
110 110 1250 Groundwater Sump 110 115 95 95 A@ 120 BH16 A@ 100 1 0 5 105
115
90
105 100 95.746 1 0 0
110 95.763 95 95 1500
1 0 0
90
90 90 95 95
105 100 85 95
105 1 0 5
100 115 90 90
1 0 5 120 120
1 0 0
Photo7
95
110 110 90 96.165
100 100 95.843 125 125
1 0 5
1 0 0
1 0 5
105 105
100 85 115 115 105
5 0 1
105 1 0 5
1 0 5
105 105 1 0 5 105 105
1 0 5
Photo8 1 0 0
95 95 BH6 A@ 90 90 5 0 1 95.829
1 0 0 Photo10 98.826 1 0 0 96.076
97.018
1 0 5 95 95 97.188 1 0 0 BH12 90 100 A@ 97.281 1 0 0 A@ 97.170 1 0 5 97.128 100 BH5 97.140 98.131
1 0 5 110
1 05 105 1 0 97.600 1 0 5
97.615
100 100 100
1 0 0 105 105 97.175
97.242 1 0 0 120 120 1 0 5 1 0 0 98.332
0 0 1
1 0 5 96.140
125 125 99.638 97.556 110 110 100
95 105 501
1 0 0 105 105 96.985 1 0 5 98.766 1 0 0 96.417
105 100 96.9441 0 0 96.0761 0 0 1 0 0 97.955
1 0 0 97.962 1 0 5 1 0 5 98.984 96.848 96.970 100
98.706 1 0 0 95 97.905 1 0 0 95.868 1 0 0 96.405
1 0 5 96.932
130 130 98.381
1 0 0 100 100 97.071 96.061
1 0 0 98.400
96.304 1 0 5 115
Path:Y:\16_GIS\Jobs\M1079502 - MBC\MXDs\M1079502 Fig1_ Parwan Creek.mxd 100
Legend Designed: E. Vella Scale: 1:4,000 Figure No: 1 A@ Groundwater Bore Location Watercourse - Parwan Creek Cross Section Alignment Surface Contours Drawn: S. Koroblitsas Date: 26/11/2013 Title: Parwan Creek Chainage Checked: Revision: A S S Project: 53V Annual Landfill Groundwater Audit Address: e nv Grounder Floor 51a Clarke Street File: M1079502 Fig1_ Parwan Creek Notes: Southbank Victoria 3006 Location: East Maddingley Road Bacchus Marsh Phone: (03) 9606 0070 Parwan Creek Survey Contours sourced from BGL Surveying - Aug 2011 0 25 50 100 150 200 Fax: (03) 9606 0074 Contours sourced from Landair Aerial - June 2013 Metres Website: www.senversa.com.au Aerial sourced from Google Earth Pro Datum AGD1966, Projection MGA Zone 55 Client: The Maddingley Mining Trust Pty Ltd ± 115 130
135 105
125
120 105
115 110 100
105 A@ BH15 110 110
100
120
BH7 A@A@BH8 125 135
100 130 100 105
130
115
95 135 135
95
86.295 100 100
110 110 85.87995
120 100
125 120 95
95 95 90 #0#090 90 #0 84.342
125 125 #0 #0 #0 87.448 #0 #0 84.926
75 80 90 90 90 85
105 87.094 86.195 70 85 A@ 86.06885.470 BH21 65
70 130 130
90 #0
95 87.508
A@ 80
BH22 95 125 135 135
65 80 80
100 60 75 85 89.229 130 #0
#0 90 90 86.986
75 #0#0
INF EROIR COAL SE AM 86.584 85 #0#088.988 86.908
90 88.950 115 65 65 #0 110 #0
60 87.176
90 90 88.467 100 100 87.373 70 #0#0
135 120
130 70 87.340 #0#0 88.848 70 89.029 87.546 #0#0
90 80 75
60
80 80 88.693 105 80 87.615 #0#0 95
130 130 125
125 125 120 65 87.646 #0 88.350 85 #0
95 115 87.751 #0#0 89.032
BH4 A@ 60 70
75
65 65 87.867 #0#0 88.181 85 85 70 70
110 90 A@ BH2 140 140 87.809 #0#0 100 88.212
100
BH10 88.756 #0 88.493 120 120 A@ #0#0 85
105 87.945 90
#0#0INF EROIR COAL SE AM
90 90
88.432 75
115 115
75 75 95 95 85 85 #0 89.195 500 #0
88.504 85 85
80 80 88.649
135 100
130 95 #0#0 88.335 80
90 105 105 100
85 85 #0#0 89.407
95 95
110 110 88.367 100 100
90 90 90 90
750 #0#0 95 95 88.403
125 88.743 #0 90.946
100 85 #0 110 88.542
#0#0 91.047 115 1000 115 90.555 95
91.477 #0 88.536 91.187 #0#0 105 92.804 #0#0 88.540 #0#0 91.464
93.425 100 88.429 90.056 100 90 #0#0 105 #0 92.073
115 115 #0 90 90
85
110 110 1250 Groundwater Sump 110 115 95 90.295 95 A@#0#0 120 93.867 #0#0 BH16 A@ 100 105 88.661
115 INF EROIR COAL SE AM 90 88.933 #0 90.544
93.151105 #0 89.420 89.197 #0 100 90.776
#0 110 #0 95 95 1500
90 89.689
90 90 #0
INFEROIR COAL SEAM 89.597 93.820 95 #0#0 90.918
#0 105 100 85 89.779 #0 95 105
93.158 100 115 #0 90.430 89.903 #0 91.868 #0 90 #0
90.101 #0 92.234 120 93.156 90.708 #0 #0#0 90.026 #0
95 110 110 #0
94.337 90 #0 100 90.017 #0 92.366
#0 91.420 125
105 105
100 85 115 115 105
105 94.623 105 #0 91.189 105
#0 95 BH6 A@
90.950 90 #0INF EROIR COAL SE AM 90.409
95 95 100 A@ BH12 #0 90 A@ 100 BH5 #0 #0 92.310 #0 #0 110 105
94.699 94.267
100 100 100
105 105 94.192
120 120 125 125
110 110 100 95 105 105 105
105 100 100 100
95
130 130
100 100 115 115 100 115 Path:Y:\16_GIS\Jobs\M1079502 - MBC\MXDs\M1079502 Fig2_ MCS.mxd
Legend Designed: N. Verga Scale: 1:4,000 Figure No: 2 A@ Groundwater Bore Location Top of Maddingley Coal Seam Cross Section Alignment Surface Contours Drawn: S. Koroblitsas Date: 26/11/2013 Title: Maddingley Coal Seam and Chainage Fyansford Formation Interface Base Fyansford Formation Checked: Revision: A S S Project: 53V Annual Landfill Groundwater Audit Address: e nv Grounder Floor 51a Clarke Street File: M1079502 Fig2_ MCS Southbank Victoria 3006 Notes: Maddingley Coal Seam and Fyansford Formation Interface sourced from BGL Surveying -Sept 2013 Location: East Maddingley Road Bacchus Marsh Phone: (03) 9606 0070 0 25 50 100 150 200 Contours sourced from Landair Aerial - June 2013 Fax: (03) 9606 0074 Metres Website: www.senversa.com.au Aerial sourced from Google Earth Pro Datum AGD1966, Projection MGA Zone 55 Client: The Maddingley Mining Trust Pty Ltd LEACHATE DAM (L1) EXISTING SURFACE 150.0 SURVEY BH19 BH13 (28 June 2013) . . BH17
. BH11 Landair Aerial
140.0 . #
130.0 g 8 g Perched Water
120.0 Fyansford Formation Approximate Location of LB02A BH4 CURRENT COAL . Geotech Investigation Bores
110.0 DRY EXTRACTION AREA
# g # 101.87 g g g g g g 102.91 8 g g 8g g g
100.0 g g g g
g g # g # g 93.63 g g 8 g g 8 90.0 Inferior Coal Seam
8# 80.03 80.0 ? Maddingley Coal Seam 70.0 Elevation (mAHD) Elevation ? 60.0 ? Clay Barrier (Fire Protection) 50.0
40.0
30.0 Lower Werribee Formation EXISTING SURFACE
LEVELS (mAHD) 95.372 87.933 81.678 88.114 95.826 97.984 20.0 141.114 142.423 142.537 142.537 142.537 142.537 140.423 139.556 141.162 141.897 142.000 141.996 142.443 142.630 142.311 141.863 137.501 132.488 128.939 125.499 119.122 118.582 118.001 114.502 111.476 106.705 102.627 101.662 100.561 100.824 104.870 110.006 114.995 116.044 116.020 0 20 40 60 80
CHAINAGE 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700 720 740 760 780 800 820 840 860 880 900 920 940 960 980 Distance (m)
140.0 140.0
130.0 130.0 Potential gap exists between the base of the Fyansford PARWAN CREEK V SumpA1 Formation and the base of the side liner extension - 120.0 extent of firewall construction unknown 120.0 Approximate Location of VLB02A BH4 CURRENT COAL V Geotech Investigation Bores V LB01A 110.0 EXTRACTION AREA BH16 110.0 V Fyansford Formation g g g g g g g g g g g g g g 100.0
g g g 100.0
g g # g # 93.63 g g g ~95 mAHD 8 g 8 92.80 g g Firewall Sump ~90.7 mAHD Inferior Coal Seam V V V 90.0 90.0 Waste Inferior Coal Seam
E4 Sump Groundwater Sump
# # 80.03 # 79.70 79.80
8 8 8 80.0
80.0 g # ? g 76.06 #
8 8 75.27 71.91# 8 Maddingley Coal Seam
70.0 Cell E5 Base 70.0
# Firewall
# ? # 63.70 8 ? (mAHD) Elevation 63.50 8 8 60.0 60.0 Elevation (mAHD) Elevation ? Clay Barrier (Fire Protection) Cell E4 - Engineered Clay Liner 50.0 50.0
40.0 40.0 Lower Werribee Formation 30.0 30.0 EXISTING SURFACE LEVELS (mAHD) 95.372 87.933 81.678 88.114 95.826 97.984 99.828 91.420 90.525 87.979 87.638 97.057 99.132 99.957 119.122 20.0 111.476 106.705 102.627 101.662 100.561 100.824 104.870 110.006 114.995 116.044 116.020 116.187 114.484 116.734 117.852 117.929 117.998 117.968 117.657 115.529 105.187 103.251 103.583 103.310 105.673 108.624 113.292 119.059 123.296 124.989 125.671 20.0 580 600 640 660 680 700 720 740 760 780 800 820 840 860 880 900 920 940 960 980 1000 1020 1040 1060 1080 1100 1120 1140 1160 1180 1200 1220 1240 1260 1280 1300 1320 1340 1360 1380 1400 1420 1440 1460 1480 1500 1520 1540
Path: Y:\16_GIS\Jobs\M1079502 Path: MBC\MXDs\M1079502- Fig3_CSM.mxd Source: Land and Waste Contours: - Landair Aerial Survey June 2013 Distance (m) Legend# 8 Designed: N. Verga Date: 29/11/2013 Figure No: 3 Standing Water Level (mAHD) Cell E5 base Clay Liner . Bore Location Propsed Sideliner Extension Firewall Drawn: S. Koroblitsas Revision: A Inferred SWL - Lower Werribee Formation (mAHD) Monitoring Bore Fyansford Formation Title: West - East Cross Section Background SWL Lower Werribee Formation (mAHD) Monitoring Bore - Screened Interval Inferior Coal Seam Checked: P. Clarke Scale: See Axis on figure (A3) S S g Inferred SWL - Fyansford Formation(mAHD) Extraction Bore Landfill Waste Project: 53V Annual Landfill Groundwater Audit nv r a g g Extraction Bore - Screened Interval Lower Werribee Formation Address: e Grounde Floor 51 Clarke Street Perched Water Aquifer (mAHD) File: M1079502 Fig3_CSM Southbank Victoria 3006 2013 Leachate Level (mAHD) Surface Existing Maddingley Coal Seam Location: East Maddingley Road Bacchus Marsh Phone: (03) 9606 0070 2012 Leachate Level (mAHD) Clay Barrier (Fire Protection) Water/Dam Fax: (03) 9606 0074 Website: www.senversa.com.au Geology Symbol Client: The Maddingley Mining Trust Pty Ltd