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Environmental Assessment Report Burnie City Council – Stage 1 Landfill Leachate Treatment, BWMC

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ENVIRONMENTAL ASSESSMENT REPORT

Stage 1 Landfill Leachate Treatment

Burnie Waste Management Centre

Burnie City Council Board of the Environment Protection Authority

February 2016


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Environmental Assessment Report

Proponent Burnie City Council

Proposal Stage 1 Landfill Leachate Treatment

Location Burnie Waste Management Centre

NELMS no. 9421/1

Doc1 folder 242878

Doc1 no. H503051

Class of Assessment 2B

Assessment process milestones

7 September 2015 Notice of Intent received by Board

30 September 2015 DPEMP Guidelines issued

28 November 2015 Start of public consultation period

11 January 2016 End of public consultation period


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Acronyms

ARI Average return interval

Board Board of the Environment Protection Authority

BWMC Burnie Waste Management Centre

DPEMP Development Proposal and Environmental Management Plan

DPIPWE Department of Primary Industries, Parks, Water and Environment

EIA Environmental impact assessment

EMPC Act Environmental Management and Pollution Control Act 1994

EMPCS Environmental management and pollution control system

EPBC Act Environment Protection and Biodiversity Conservation Act 1999 (Cth)

ET Evapotranspiration

GCL Geosynthetic Clay Liner

LLDPE Linear Low Density Polyethylene

LUPA Act Land Use Planning and Approvals Act 1993

MH1 Manhole 1

PCAB Policy and Conservation Advice Branch

RMPS Resource management and planning system

SD Sustainable development

SIDP Stormwater Infrastructure Development Project

WQO Water Quality Objective


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Report summary

This report provides an environmental assessment of Burnie City Council’s proposed Stage 1 landfill leachate treatment system. The proposal is for the development of a wetland treatment system and associated hydraulic infrastructure to manage and treat up to 600 kL/day of leachate from the Burnie Waste Management Centre (BWMC) landfill, 289 Mooreville Road, Burnie It involves the decommissioning of the current leachate discharge system to TasWater’s sewage network, and the construction of a series of wetland treatment ponds on top of the stage 1 landfill. Treated leachate from the ponds will be discharged to a constructed infiltration wet forest, with point discharge during high flows to an unnamed tributary of Cooee Creek. This report has been prepared based on information provided by the proponent in the Development Proposal and Environmental Management Plan (DPEMP). Relevant government agencies and the public have been consulted and their submissions and comments considered as part of this assessment. Further details of the assessment process are presented in section 1 of this report. Section 2 describes the statutory objectives and principles underpinning the assessment. Details of the proposal are provided in section 3. Section 4 reviews the need for the proposal and considers the proposal, site and design alternatives. Section 5 summarises the public and agency consultation process. The detailed evaluation of key issues is in section 6, and other issues are evaluated in section 7 and Appendix 1. The report conclusions are contained in section 8. Appendix 2 contains an environment protection notice for the proposal. Attachment 5 of the environment protection notice contains the table of commitments from the DPEMP.


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Table of Contents

1 Approvals process .................................................................................... 1

2 SD objectives and EIA principles .............................................................. 2

3 The proposal ............................................................................................ 3

4 Need for proposal and alternatives ......................................................... 11

5 Public and agency consultation .............................................................. 13

6 Evaluation of key issues ......................................................................... 14

6.1 Effluent quality and surface water impacts ...................................................................... 14 6.2 Groundwater impacts and geotechnical risks .................................................................. 24

7 Other issues ........................................................................................... 30

8 Report conclusions ................................................................................. 31

9 References ............................................................................................. 33

10 Appendices ......................................................................................... 34

Appendix 1 Assessment of other issues .............................................................................. 35 Appendix 2 Environment Protection Notice .......................................................................... 42


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1 Approvals process

A Notice of Intent in relation to the proposal was received by the Board of the Environment Protection Authority (the Board) on 7 September 2015. As required by section 27(1) of the Environmental Management and Pollution Control Act 1994 (EMPC Act), Burnie City Council referred the proposal to the Board of the Environment Protection Authority (the Board) on 7 September 2015. The proposal is defined as a ‘level 2 activity’ under clause 3(a), Schedule 2 of the Environmental Management and Pollution Control Act 1994 (EMPC Act), being a wastewater treatment works. The Board required that information to support the proposal be provided in the form of a Development Proposal and Environmental Management Plan (DPEMP) prepared in accordance with guidelines issued by the Board on 30 September 2015. Several drafts of the DPEMP were submitted to the EPA for comment prior to its finalisation and acceptance on behalf of the Board. The DPEMP was released for public inspection for a 28-day period commencing on 28 November 2015. Advertisements were placed in The Advocate and on the EPA website. The DPEMP was also referred at that time to relevant government agencies for comment. One public submission was received.


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2 SD objectives and EIA principles

The proposal must be considered by the Board in the context of the objectives of the Resource Management and Planning System of Tasmania (RMPS), and in the context of the objectives of the Environmental Management and Pollution Control System (EMPCS) (both sets of objectives are specified in Schedule 1 the EMPC Act). The functions of the Board are to administer and enforce the provisions of the Act, and in particular to use its best endeavours to further the RMPS and EMPCS objectives.

The Board must undertake the assessment of the proposal in accordance with the Environmental Impact Assessment Principles defined in Section 74 of the EMPC Act.


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3 The proposal

The proposal is for the development of a wetland treatment system and associated hydraulic infrastructure to manage and treat up to 600 kL/day of leachate from the Burnie Waste Management Centre (BWMC) landfill, on-site, located at 289 Mooreville Road, Burnie (Figures 1 and 2). It involves the decommissioning of the current leachate discharge system to TasWater’s sewage network, and construction of a series of wetland treatment ponds on top of the stage 1 landfill to remove contaminants (Figure 3). Treated leachate from the ponds will be discharged to a constructed infiltration wet forest, with point discharge to an unnamed tributary of Cooee Creek during above average flows. The wetland will consist of the following elements (Figures 3 and 4):

Pre-filter sedimentation/precipitation pond – for removal of iron, manganese and other metals. Limestone or limesand will be incorporated in the pond to elevate pH;

Surface flow wetland ponds – 2 in parallel to allow draining, maintenance and operation of one or both cells depending on flows;

Subsurface flow biofilters to promote denitrification;

Polishing pond with adsorption media to allow further treatment;

A recirculation system to return leachate to the head of the system if non‐compliant;

Infiltration wet forest to allow further attenuation of residual nutrients/contaminants, with diffuse subsurface release to the unnamed tributary of Cooee Creek; and

Phytoremediation swale to intercept, divert and treat seepage flows that emanate from the northern embankment during extreme rain events.

Design contingencies have been built into the system to deal with power failure, maintenance outages and storm events, including provision of an emergency storage tank and sufficient capacity within the wetland and pump system to deliver and contain a 24 hour, 80 year event. A new connection to the TasWater sewer network will be established and maintained as a contingency against discharge non‐compliance and pump failure. The proposed wetland treatment system is a component of the federally funded Stormwater Infrastructure Development Project (SIDP) to deliver stormwater improvement across the Burnie municipality. Stormwater and creek enhancement works at the BWMC site are being undertaken as a parallel project within the SIDP framework. These works will occur concurrently with the proposed leachate wetland treatment project. The main characteristics of the proposal are summarised in Table 1. A detailed description of the proposal is provided in Section 2 of the DPEMP. Table 1: Summary of the proposal’s main characteristics

Activity

Wetland leachate treatment works treating up to 600 kL per day of leachate.

Location and planning context

Location Burnie Waste Management Centre (BWMC), 289 Mooreville Road, Burnie (Figure 1).

Land zoning Utilities zone (Burnie Interim Planning Scheme 2013)

Land tenure Local Government (freehold owned by Burnie City Council)


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Existing site

Land Use Municipal waste management centre. The BWMC site includes a landfill site (Stage 1 and Stage 2), waste transfer, resource recovery facility, recycle/recovery loops and associated infrastructure (Figure 3). The site has been used for waste management since 1987. Prior to this the land was used for livestock grazing.

Topography The BWMC site comprises approximately 28 ha of moderate sloping ground within a broad valley at the head of a tributary to Cooee Creek. The natural ground elevation is approximately 165 m AHD at the southern end and 139 m AHD at the outlet to the Cooee Creek tributary at the northern end. The Stage 1 landfill lies within a valley tract constructed over two spring-fed gullies and a swamp, and is largely contained within the natural topography.

Geology The geology of the site is characterised by highly weathered Tertiary volcanic basalts underlain by Precambrian dolerites. Creek lines and valleys also contain Quaternary quartz sediments and river silts and gravels.

Soils Tertiary basalt ferrosols, characterised as mainly brown to orange clays and silts of low to medium plasticity, associated with weathered basalt.

Hydrology The BWMC is located within the catchment of Cooee Creek. A tributary of Cooee Creek originates approximately 100 m upstream of the landfill, and rises as springs mostly within the landfill site itself. The tributary connects to Cooee Creek approximately 3.0 km north-west of the site. The catchment area of the tributary (herein referred to as the ‘unnamed tributary’) is 5.2 km

2, or approximately 5%

of the total Cooee Creek catchment, and constitutes less than 1.5% of flow in Cooee Creek. The unnamed tributary receives all on-site stormwater plus groundwater flows that bypass the leachate collection system to TasWater. Stormwater at the BWMC site is managed by a network of open channels, cut-off swale drains and pipe conveyance infrastructures (see Figure 30 of the DPEMP).

Groundwater According to the DPEMP, the site acts as a groundwater discharge zone with spring expressions along the valley slopes and floor. During development of the Stage 1 landfill the spring-fed gullies and majority of the tributary on site were infilled, diverted and/or modified for landfill activities. The pipe system installed in the base of the landfill cell to collect the spring flow and surrounding groundwater seepage was compromised during construction. The leachate collection stream is subsequently dominated by groundwater, representing approximately 80-90% of flow.

Fauna There is suitable habitat for the Burnie burrowing crayfish in the unnamed tributary at the southern extent of BWMC. The spotted tailed quoll, Green and gold frog and Eastern barred bandicoot could also potentially inhabit this area, although no evidence was found.

Flora No threatened flora has been recorded on site.

Local region

Climate The average annual rainfall at Burnie (Round Hill) is 946 mm. Mean monthly maximum temperature ranges from 13 C

o (July) to 21 C

o (January and

February). Mean monthly minimum temperature ranges from 6 C

o (July and August) to 13 C

o

(February). Wind is predominantly westerly or south-westerly.


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Surrounding land zoning, tenure and uses

The land surrounding the BWMC is Private Freehold. The land to the west and south is mainly agricultural, zoned Rural Resource. The area to the north and east is zoned as General Residential. The nearest residential subdivision is on Three Mile Lane Road, approximately 200m from the site. According to the DPEMP, there are fifteen known water licence holders along Cooee Creek and the unnamed tributary. Abstracted water is primarily used for the irrigation of vegetable crops and pasture during summer months.

Species of conservation significance

The following threatened species, listed under the Environment Protection and Biodiversity Conservation Act (1999, EPBC Act) and/or the Tasmanian Threatened Species Protection Act (1999, TSP Act), have been recorded within 1 km of the unnamed tributary (Appendix 2 of the DPEMP):

Giant freshwater crayfish (Astacopsis gouldi);

Burnie burrowing crayfish (Engaeus yabbimunna);

Swift parrot (Lathamus discolour);

Eastern Barred bandicoot (Perameles gunii);

Tasmanian devil (Sarcophilus harrisii); and

Masked owl (Tyto novaehollandiae).

Proposed infrastructure

Key infrastructure (Figure 4)

150 kL emergency leachate storage tank;

Existing pump station (refurbished);

New connection to the existing TasWater sewer network;

Existing leachate collection underground pipes;

Rising main to the head of the treatment wetland;

Wetland; o Pre-treatment pond; o Surface flow ponds; o Sub-surface flow ponds; and o Polishing pond.

Infiltration wet forest;

Seepage phytoremediation swale; and

Overflow swale to connect to the unnamed tributary Other infrastructure

Site stormwater infrastructure (see Figures 7, 8 and 30 of the DPEMP).

Inputs

Water Leachate/water required for maintenance of wetland communities.

Energy Fuel for back up pump.

Other raw materials

The following materials will be required for construction:

Topsoil (part recovered from site, part imported);

Limestone gravel for the pre-filter;

Scoria;

Clay recovered from the site;

LLDPE liner;

Zeolite; and

Plants.

Wastes and emissions

Liquid Treated leachate, landfill seepage.

Atmospheric Dust from internal and external traffic and materials handling during construction.

Potential for odour from wetlands.

Solid Sediment sludge generated during maintenance activities.


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Controlled wastes

Sediment from pre-filter and leachate chamber, which is likely to contain metals.

Noise Generated during construction from use of heavy machinery.

Greenhouse gases

Generated from use of heavy machinery during construction.

Construction, commissioning and operations

Proposal timetable

Construction: February 2016 to end of July 2016.

Commissioning will commence after the establishment of the wetland plants, and when the wetland is sufficiently ‘full’ and discharging. Commissioning will be considered to be completed after six months of validation monitoring has demonstrated the acceptable performance of the system.

Operating hours

The system will operate 24 hrs a day, every day for the forecast life of the leachate treatment system (minimum 20-30 years). The pumps will operate between 8-24 hrs per day.


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Figure 1: Location of the stage 1 landfill, Burnie Waste Management Centre (Figure 1 of the DPEMP)


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Figure 2: Land Boundary shown in blue (altered from Figure 2 of the DPEMP) (Dividing red line indicates two separate titles, Title reference 145841/1 & 27996/2)

Title ref: 145841/1

Title ref: 27996/2


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Figure 3: General site layout (altered from Figure 6 of the DPEMP).

Discharge point to unnamed tributary

Stage 1 Landfill

Unnamed tributary of Cooee Creek


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Figure 4: Wetland treatment system layout (Appendix 7 of the DPEMP).


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4 Need for proposal and alternatives

Need for the proposal The proposal is an important component of the federally funded Stormwater Infrastructure Development Project (SIDP). The goal of the SIDP is to deliver stormwater improvement across the Burnie municipality that will reduce discharge and infiltration to TasWater’s waste water network by at least 1.9ML per day, releasing significant capacity in the network for forecasted increases in waste water flows from the municipality. The SIDP is therefore a critical investment in ‘infrastructure-readiness’ to help realise the region’s economic expansion opportunities. The proposed leachate treatment project will reduce discharge by up to 600kL/day, accounting for almost a third of the SIDP stormwater diversion target. According to the DPEMP, the proposal is critical to achieving the objectives of the SIDP. The DPEMP has indicated that the leachate treatment project will have to be substantially delivered by the end June 2016, otherwise SIDP funding will need to be returned or re-appropriated, and the project will not proceed. The DPEMP also outlined the following concerns with regard to continual discharge to TasWater’s sewer network:

The highly dilute leachate stream periodically causes biological performance issues for the receiving Waste Water Treatment Plant (WWTP);

The WWTP and sewer network currently operates near capacity;

Removing trade waste flows from the sewer would reduce the number of non-compliant discharge events;

The objectives of the SIDP would not be met;

Occasional leachate overflows to the unnamed tributary would continue in high rainfall events; and

Likely increase in disposal charges. A representation was received suggesting that the key motive for the proposal was the change in management of the sewer network from Council to TasWater, and subsequent charges of $190,000 per annum for disposal to sewer. Project alternatives The following project alternatives were evaluated:

On‐site treatment system vs full decommissioning and remediation of the Stage 1 landfill vs continuing with discharge to sewer;

On-site and off-site reuse and disposal options;

On-site treatment approaches and technologies; and

Alternative wetland locations. The relevant reports are contained in the following DPEMP appendices;

Appendix 1 - Burnie Waste Management Centre (BWMC) Stage 1 Landfill Leachate Treatment Study - Options Development & Evaluation, July 2014;

Appendix 5 - Assessment of Alternate Leachate Management Options, May 2015; and

Appendix 4 - Addendum to Stage 1 Landfill Leachate Treatment Study – Design changes & Alternative Wetland Option Assessment, May 2015.

A summary is contained in Section 3 of the DPEMP, and provided below.


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On‐site treatment was assessed as the best economic, environmental and social option against the removal of Stage 1 waste to a new waste cell on site, or removal off-site, and decommissioning and remediation of the Stage 1 landfill. Ten on-site treatment approaches were initially screened (see Table 7 of the DPEMP), with the following options assessed in detail:

Membrane bioreactor;

Reverse osmosis plant; and

Constructed wetlands. A wetland system was considered the best option for the following reasons:

Passive and sustainable treatment;

Low reliance on energy/no chemical requirements;

Able to deal with changes in flow and leachate quality;

Simplicity of operation and lower operating cost; and

Potential for value add-ons, e.g. biodiversity enhancement. A wetland system constructed on top of the Stage 1 landfill was considered the best location when assessed against project risk, cost and community impact and sustainability (Table 8 of the DPEMP). The DPEMP considered the reuse of treated leachate, including on-site irrigation of the capped landfill and surrounding grass buffers and off-site irrigation of pasture. Both options however were considered unfeasible due to the high rainfall in the area and absence of high volume users within a feasible proximity. Department of State Growth, Growth Strategy & Coordination Branch, provided the following comments:

Liquid trade waste in the Burnie area has been a constraint to industry development. TasWater’s current lack of capacity in the Burnie region could constrain the Lion cheese factory development and any future development, particularly in food related industries.

This project will enable current industry development to be maximised, and help alleviate a potential constraint to future development.


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5 Public and agency consultation

One representation was received. The main issue of concern in the representation was that the proposal will result in leachate from the landfill being discharged into the Cooee Creek, instead of into the sewer system. The DPEMP was referred to a number of government agencies/bodies with an interest in the proposal. Responses were received from the following:

Department of State Growth, Growth Strategy & Coordination Branch; and

TasWater.

The following Divisions/areas of the Department of Primary Industries, Parks, Water and Environment also provided submissions on the DPEMP:

Water Specialist, EPA Division; and

Policy and Conservation Advice Branch (PCAB), Natural & Cultural Heritage Division.

The proponent has also undertaken its own public consultation process, as outlined in Section 4 of the DPEMP. According to the DPEMP, the consultation process was undertaken in accordance with the aims, principles and approaches outlined in, “A Tasmanian Government Framework for Community Engagement”, Department of Premier and Cabinet, December 2013. Key stakeholders consulted included TasWater, adjacent landowners, downstream landowners (residents along the unnamed tributary and Cooee Creek) and downstream water users. Early consultation determined initial concerns from several downstream landowners, including water users. These concerns related to the potential impact of leachate discharge on creek water quality, crop/vegetable irrigation and livestock drinking. According to the DPEMP, the landholders concerns were allayed through follow up consultation. Additional consultation with the key stakeholders is planned, as outlined in Section 4 of the DPEMP.


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6 Evaluation of key issues

The key environmental issues relevant to the proposal that were identified for detailed evaluation in this report were:

Effluent quality and surface water impacts; and

Groundwater impacts and geo-technical risks.

These issues are discussed in the following subsections.

6.1 Effluent quality and surface water impacts

Description

Existing environment Protected Environmental Values (PEVs) have not been formally identified for the Cooee Creek catchment, including the unnamed tributary. The following PEVs were therefore adopted:

Protection of aquatic ecosystems (modified)

Recreational water use (secondary contact); and

Agricultural water use (irrigation and stock watering). The DPEMP considers both the unnamed tributary of Cooee Creek (herein referred to as the unnamed tributary) and Cooee Creek to be impacted, and classify the systems as slightly or moderately disturbed (condition 2 ecosystems) based on ANZECC (2000) guidelines. This classification is used for the setting of water quality trigger values in the DPEMP (and as referred to in this report). Water quality sampling of Cooee Creek and the unnamed tributary was undertaken in April 2014 at 4 locations on each creek system (see Appendix 1 of the DPEMP, Section 11). Results for the unnamed tributary are summarised in Table 2 (see Table 20 of the DPEMP for a complete summary of the water quality results). The key parameters of concern are nutrients (total nitrogen (TN), nitrate and total phosphorus (TP)) and total metals (aluminium, copper, lead), with values above the ANZECC trigger values at most sites (Table 20). Cooee Creek contained elevated levels of total nitrogen and total aluminium and copper. The unnamed tributary currently receives all stormwater flows from the BWMC site, median discharge of 252 Kl/day (average of 286 Kl/day), in addition to groundwater flows that bypass the leachate collection system to TasWater. Stormwater discharged from the site to the unnamed tributary contains elevated nutrient levels, as well as Al, Fe, Mn, and Zn. According to the DPEMP, elevated levels of Al and Zn compared with the leachate suggest contamination origins other than the Stage 1 landfill. Median values for TN, nitrate and Al all exceed the ANZECC trigger values (Table 18 of the DPEMP). Annual mass stormwater loads discharged to the tributary include the following; TN 178 kg/annum, TP 2.3 kg/annum, Fe 181 kg/annum, Mn 44 kg/annum, and Al 18.1 kg/annum. Note, stormwater entering the site also contains elevated nutrients levels (TN and TP). According to the DPEMP, this is most likely as a result of fertiliser use on upstream farm properties.


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Leachate from the landfill is currently discharged to TasWater’s sewer network, and therefore does not impact upon the receiving environment. The exception is during high flows events (e.g. 1:20 year ARI) or storm events which exceed the pump capacity, and leachate breaches the separation weir in the MH1 chamber to access the stormwater system. The leachate is dominated by groundwater and has the following characteristics:

High levels of nitrogen (TN, average 8.1 mg/L) and ammonia (average 7.8 mg/L), with exceedance of ANZECC (2000) trigger values on all but one sampling occasion. The results from 33 samples collected between January 2005 and November 2013 were used in the analysis of leachate chemistry.

High concentrations of total Fe and Mn, with Mn found to exceed the ANZECC (2000) trigger value in the majority of samples.

Slightly elevated concentrations of total Al, Cr, Cu, Ni and Zn, with exceedance of the ANZECC (2000) trigger values on at least one sampling occasion.

Average and median flow of 350 kL/day and 311 kL/day respectively; and

90th percentile flow is approximately 600 kL/day. Potential impacts Contamination of the unnamed tributary and Cooee creek via untreated or poorly treated leachate could impact on livestock, irrigation for crops and pasture, threatened species (Burnie burrowing crayfish, Giant freshwater crayfish), and degrade the ecological values of the creek systems. The proposal will result in:

The discharge of treated leachate from the wetland polishing pond (Figure 4) to the on-site infiltration wetland forest during low and average flows, with indirect discharge to the unnamed creek via subsurface flow.

Direct discharge of treated leachate to the unnamed tributary in high seasonal flows, prolonged rainfall events which generate above average leachate flows, and peak flows.

Daily rainfall and leachate data for the period 2010 to 2014 (including peak rainfall events) was used to generate a daily water balance, with the following assumptions:

Area of the infiltration wet forest is 4,000 m2, with a 100 mm operating water depth and additional 100 mm freeboard activated in large flow periods.

All water in excess of evapotranspiration (ET) and soil storages within the infiltration wetland forest is assumed to discharge via surface flows to the unnamed tributary; and

Infiltration rate is 1*10 -̂6 m/s. Tables 26 and 28 of the DPEMP show the estimated average daily volumes to be discharged to the infiltration wet forest post treatment, and that subsequently discharged directly to the unnamed tributary via surface flows. According to the DPEMP, direct discharge will occur when leachate flows are greater than approximately 360 m3/day. Volumes discharged direct to the creek range from an average of 15.9 m3/day for the driest month to an average of 187 m3/day for the wettest month. Accounting for the total pump capacity (duty and standby duty, combine 43 L/s or 3,542 m3/day), pipe network and capacity within the wetland system (3,600 m3 - 5,500 m3 of freeboard, dependant on season), the facility will be able to effectively deliver and detain leachate flows generated in a 24 hour, 80 year event. The DPEMP acknowledges however that the wetland may not effectively treat the leachate flows during such an event. Under such a scenario, recirculation of the leachate and slow release


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discharge can be undertaken to ensure appropriate detention time within the system, and compliance with water quality targets (see below). According to the DPEMP, the wetland has the ability to treat (i.e. to water quality targets) the 90th percentile flow (600 m3/day). Figure 37 of the DPEMP illustrates the water balance of the wetland system and routing paths for median and high flows. Leachate flows in excess of approximately 3600 m3/day or 43 L/s will be directed to the unnamed creek via the emergency storage chamber. These excess flows will constitute release of untreated leachate once the emergency storage is at capacity. Treatment of leachate, proposed water quality targets and mass loadings Pollutant concentrations in the leachate (pre-treatment) and modelled wetland effluent concentrations (discharge of treated leachate to the infiltration wet forest) are shown in Table 2 below. Table 2 Leachate pollutant concentrations, modelled pollutant concentrations in the wetland effluent (treated leachate discharged to the infiltration wet forest), and water quality of the receiving environment (unnamed tributary) (altered from Tables 11, 12, 20 and 25 of the DPEMP).

Pollutant Average pollutant concentrations (mg/l) in the leachate (From Tables 11 & 12 of the DPEMP)

Modelled# pollutant

concentrations (mg/l) in wetland effluent (Averaged across 12 months, Table 25 of the DPEMP)

Modelled# pollutant

concentrations (mg/l) in wetland effluent (wettest month), Table 25 of the DPEMP)

Unnamed creek – Median pollutant concentrations (mg/l) (Table 20 of DPEMP)

TN 8.1 (0.5) 0.47 1.00 1.8

Ammonium N

7.8 (1.61) 0.40 0.89 0.05

Nitrate N 0.48 0.03 0.07 0.625

TP 0.036 0.01 0.015 0.045

Fe 12.9 0.04 0.10 0.55

Mn 2.1 (1.9) 0.15 0.34 0.135

Zn 0.007 0.00 (0.0002) 0.00 (0.0006) 0.00(0.005)

Al 0.045 0.055* 0.105

Cu 0.0007 0.0014* 0.00 (0.004)

Cr 0.0007 0.001* N/A

Ni 0.01 0.011* 0.00(0.001)

# - For nutrients, iron, manganese and zinc - concentrations were modelled based on an approach outlined in Kadlec & Wallace 2008, and using mean monthly concentrations, temperature adjustments and pollutant specific removal rate coefficients (Table 25 of the DPEMP). * - These values were not modelled. They represent the proposed concentration targets, as outlined in Table 3 below. Red values indicate exceedance of ANZECC trigger values (trigger values are shown in brackets).

Note, for clarification Table 25 of the DPEMP is titled “Pollutant concentrations in the infiltration wetland effluent”. Interrogation of the data in Tables 25, 26 and 27 however indicates that the


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modelled concentrations in Table 25 (as used in Table 2 above) represent the treated leachate discharged to the infiltration wet forest. It is understood that the effect of the infiltration wet forest on pollutant concentrations was not modelled. The proposed water quality targets for discharge to the unnamed tributary after treatment are shown in Table 3. Note, these only refer to direct surface flow discharge to the tributary from the infiltration wet forest. Table 3 Proposed water quality targets for discharge to the unnamed tributary (altered from Table 23 of the DPEMP). Stressors Target Basis

Turbidity (NTU) 7.8 EPA target

Conductivity (us/cm) 205

Temperature (0C) 16.7

pH 7.5 Interim target

Dissolved oxygen (mg/l) 10

Total nitrogen 1.45

Total phosphorous 0.03

Toxicants

Ammonia (mg/l) 1.61 ANZECC (2000) Aquatic Ecosystem – 95% level of protection. Note, According to the DPEMP, the Fe target was based on advice on soluble Fe from the EPA.

Nitrate (mg/l) 0.7

Al (µg/l) 55

Fe (µg/l) 300

Cr (µg/l) 1

Cu (µg/l) 1.4

Mn (µg/l) 1900

Ni (µg/l) 11

Sn (µg/l) 5

Zn (µg/l) 8

Default triggers

Enterococci (organisms/100ml)

230 ANZECC (2000) Recreational – secondary contact 95% level of protection

Iron 10 ANZECC (2000) Primary industry – short term irrigation & livestock drinking E.coli (CFU/100mL) <100 cfu / 100 ml

Note, draft Water Quality Objectives (WQOs) for Cooee Creek have been developed as part of the Water Quality Guidelines (WQGs) for the Cam Catchment. These draft WQOs were used to establish the proposed turbidity, conductivity and temperature water quality targets. The interim targets are those derived using the site specific monitoring data set from the April 2014 water quality surveys, and are intended to be adopted immediately. According to the DPEMP, these targets will be revised at a later date, based on the inclusion of creek-specific data into the EPA Cooee Creek dataset and finalisation of the Cooee Creek WQOs. The DPEMP notes however that this will only be undertaken upon validation of the performance of the treatment system, which is suggested may take several years. Predicted annual discharge to the unnamed tributary from infiltration wet forest surface flows, and mass loadings of key pollutants, are shown in Table 4. Table 29 of the DPEMP shows average monthly mass loads.


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Table 4 Annual discharge and predicted mass loadings (based on modelled concentrations, except Al, which was based on the proposed water quality target, Table 23 of the DPEMP) to the unnamed tributary for the years 2011 to 2014 (Table 20 of the DPEMP).

According to the DPEMP, daily mass loading of key pollutants for 90th percentile flows (peak loading) are approximately 4 times higher compared to average daily flows. Such peak loading occurs on average 2-3 times per month. Mass balance calculations are only based on surface flow to the unnamed tributary via the infiltration wet forest. According to the DPEMP, due to attenuation within the vertical soil profile (~2.5 – 4.5 m depth) and the long flow path (>100 m), the concentration of pollutants in the subsurface flow is expected to be attenuated by greater than 90% (typical of riparian buffers). The proponent therefore anticipates that mass load contributions from subsurface discharge will be minor. The proponent considers the proposal is unlikely to impact the unnamed tributary and Cooee Creek water quality, key biota (see Section 7, Issue 4), and downstream users.

Management measures

Undertake works to separate the stormwater from the MH1 leachate chamber (commitment 1), to avoid untreated leachate discharge via the stormwater system. Construction of an emergency storage tank and recirculation system and operate for non-compliant water (commitment 6). Leachate overflows from the MH1 chamber which may occur from flow in excess of the pump capacity, or dual pump failure (i.e. both duty and duty standby pump) will be managed via a 150 kL emergency storage tank. The tank will provide 6 hours storage for the 90 percentile flow and approximately 10 hours storage for average daily flow. A recirculation pipe and pump will be installed from the polishing pond to enable return of flows to the treatment network if they are non-compliant. Recirculation will occur when the infiltration wet forest is at capacity and no attenuation of additional flow is possible (i.e. there is surface flow to the tributary), and either:

Flow into the wetland exceeds the maximum treatable design flow (1500 m3/day); or

One or more on-line parameters at the polishing pond (ammonia, pH, conductivity) exceed a specified maximum trigger value (initial value to be used is that as shown in Table 3). Note, these values will be refined during the commissioning phase once system performance is proved.


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The recirculation pump to return non-compliant flows will be solar operated, and hence not prone to power outages. According to Figure 37, the recirculation of non-compliant flows will occur at a maximum rate of 4L/s or 350 m3/day. Construct a new connection to sewer maintained in case of non-compliance, as a final contingency (commitment 7). According to the DPEMP, flows to sewer are only envisaged when raw leachate cannot be delivered to the wetland system due to pump failure and the capacity in the manhole chamber and emergency storage tank is not reinstated within 24 hours (low flow events) or 6 hours (high flow events). Retain wetland designer during construction / contract management phases to ensure quality control of all system components (e.g. liner, hydraulics, planting, etc.) and safeguard management elements are constructed as per design (commitment 8).

Monitoring

Establish a new compliance monitoring point at the creek discharge point and monitor flows (continuous, on-line) and pollutants as shown in Table 33, when discharge events occur (commitment 10). Establish a performance monitoring point at the polishing wetland outlet and install on-line flow and monitoring sufficient to determine recirculation requirements (commitment 11). Undertake sampling in accordance with the proposed monitoring schedule shown in Table 33 (commitment 12).

The current and proposed sampling locations are shown in Figure 41 of the DPEMP, and include influent leachate at MH1, the outlet of the polishing pond, and outlet of the infiltration wetland forest (when discharging to the unnamed tributary).

The following additional monitoring is proposed for the first year:

Outlet of the pre-treatment cell to gauge metal removal (Fe/Mn) performance;

Surface flow wetland effluent to gauge the performance of the surface flow wetland cells; and

Sub-surface flow wetland effluent to gauge the performance of the subsurface wetland cells.

The analytical parameters and monitoring frequency are detailed in Table 33 of the DPEMP, and include continuous online (telemetry) monitoring of flow, pH, electrical conductivity (EC) and ammonia at the outlet of the polishing pond to permit monitoring for re-circulation, and continuous flow monitoring of leachate influent at MH1. Nutrients and the majority of metals will be monitored quarterly, with increased frequency during the first year of operation (Table 33).

Public and agency comment and responses

A representor indicated that they were opposed to the proposal on the grounds that it will result in leachate from the landfill being discharged into Cooee Creek rather than sewer.


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The representor’s concerns, with regard to the potential impact of leachate on the receiving environment, are addressed in the Evaluation Section below. The representor also makes reference to the existing regulatory instrument and previous EMP, suggesting adherence to the current strategy to collect and discharge leachate to sewer. See Section 4 for a summary of the key drivers for the proposal. TasWater provided the following comment:

Any discharge to sewer can only be undertaken under a Trade Waste Agreement, which outlines limits for discharge quality and quantities;

It is unlikely that discharges to the sewer during storm events will be allowed; and

Potential scenarios which are also of concern include pump failure, disposal of non-compliant leachate and significant storm events. These issues will be dealt with through the Trade Waste Agreement.

Evaluation

The proposal will divert relatively minor (predominantly nutrient) loads to the unnamed tributary which would otherwise have reported to the sewer network. These loads are predicted to be an order of magnitude less than what is currently discharged via the stormwater system. The unnamed tributary is in relatively poor condition, due to historic and current impacts not only from the landfill, but also adjacent land use and residential developments. Indeed, the data and modelling suggests that the treated effluent will likely be of better quality than the tributary’s current surface water quality (Table 2). Further, the proponent considers the increased flow to the environment, which would otherwise be directed to TasWater’s network, may improve instream habitat (see Section 7, Issue 4), although current stormwater input is significantly greater than the predicted treated effluent discharged via surface flow (e.g. 130 m3/day compared with 15.9 m3/day during dry months, see Figure 31 of the DPEMP for stormwater discharge). It is nevertheless agreed that the proposal will unlikely have a significant impact on the water quality of the unnamed tributary. Indeed, the proposal is predicted to treat to specific water quality targets at the polishing pond, providing an inherent level of conservatism when considering the buffering effects of the infiltration wetland forest. While specific modelling was not undertaken, it is agreed that vegetated buffers can remove a significant proportion of pollutants. Given the small hydrological contribution of the unnamed tributary to Cooee Creek, Cooee Creek is unlikely to be impacted by the proposed release of treated leachate. To confirm that the proposal will not impact upon the receiving environment’s water quality, an ambient water quality monitoring program is required (condition M1). In considering section 15 of the State Policy on Water Quality Management (1997)(SWP 1997), the DPEMP presents a satisfactory argument for an unavoidable discharge, in that re-use, re-cycle and land application schemes would not be practical. Further, the reasoning for the removal of the leachate from the TasWater wastewater treatment network is well founded. The proposed water quality targets for discharge to the unnamed tributary are considered to be appropriate. The argument presented to consider ammonia and nitrate as both stressors and toxicants appears sound, and in the absence of significant site specific data sets or toxicant specific draft WQOs, adopting the ANZECC (2000) default trigger values for 95% species level of protection is appropriate. The adoption of these trigger values is equally appropriate for metals.


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With regard to the key stressors, TN and TP, the DPEMP adequately argues that the draft WQOs for Cooee Creek are not appropriate, given the low sample size (2 to 4) and comparatively degraded nature of the unnamed tributary (as supported by the 2014 survey data). It is noted that the proposed target for TN (1.45 mg/l) is below the measured median value for the unnamed tributary (1.8 mg/l, Table 22 of the DPEMP), and well below the recommended target for sewage treatment works discharge to the environment (Emission Limit Guidelines for Sewage Treatment Plants, DPIWE, 2001). The proposed water quality targets are considered to be consistent with section 15.1(c) of the SWP 1997, and would unlikely prejudice the achievement of water quality objectives for the receiving environment (unnamed tributary), or those for Cooee Creek. The targets are higher than the predicted effluent pollutant concentrations, and are considered achievable. To ensure protection of the receiving environment it is considered necessary to impose an emission limit on the main toxicant of concern, ammonia (condition EF1). The limit is the same as the proposed water quality target (Table 3) and ANZECC (2000) default trigger value for 95% species level protection. The emission limit will apply at the outlet of the infiltration forest (monitoring point EFF2, Figure 41 of the DPEMP). According to the DPEMP, the concentrations of heavy metals in the Stage 1 leachate are characteristic of a mature leachate that has undergone fermentation, and are generally low. Condition EF2 nevertheless applies an investigation trigger limit to apply from the commencement of operations (condition G6) at the polishing pond, for Zn, Ni, Cu and Cr, toxic metals found to have exceeded the ANZECC (2000) default trigger value on at least one occasion. With the proper functioning of the wetland, these metals are not expected to be a concern. If elevated concentrations in the polishing pond are found however, an investigation is required to determine the reason. The buffering effect of the infiltration wet forest will reduce the risk of elevated levels being temporarily discharged to the environment. Other metals of potential concern that may be expected within the leachate from municipal landfills, such as As, Cd, Hg, and Pb, were predominantly found below the level of detection. The commitment (6) to recirculate non-compliant flow from the polishing pond back into the treatment system is supported. Condition EF2 will ensure that recirculation is undertaken if ammonia levels exceed 1.61 mg/L, the trigger value proposed in the DPEMP, and when the infiltration wet forest is at capacity with no further attenuation of flow. The condition permits a case to be submitted to the Director to change the trigger value should it be demonstrated that it won’t increase the risk of environmental harm occurring. Note, the proponent has subsequently indicated that the ‘maximum treatable design flow’ of 1500 m3/day, proposed as a recirculation trigger, is incorrect in terms of system capacity to treat to the proposed water quality targets. Condition OP1 requires the conditions for recirculation be contained within the Operation and Maintenance Plan, also mitigating for any loss of knowledge from the site. The proposed monitoring schedule is comprehensive and required at the outlet of the infiltration wet forest (commitment 10), the polishing pond (commitment 11), and at MH1 for influent leachate (condition M2). Condition M2 requires monthly monitoring for ammonia (lab tested) at the polishing pond to provide an ongoing check against the results of the on-line instruments.


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The proposal to include additional monitoring locations during the first year of operation (commitment 12), allowing fine tuning of the operating parameters (e.g. flow and operating depths), optimisation of the performance of the wetland system and detection of any issues at an early stage, is supported. The proposed higher frequency of sampling during the first year of operation is regarded as important (commitment 12). This is required to be maintained (condition M2). Condition M2 nevertheless allows a case to be submitted to the Director to reduce the monitoring frequency, or indeed remove unnecessary parameters, should data indicate the consistent and acceptable performance of the facility and evidenced irrelevance of parameters. Monitoring for enterococci organisms, excluded from monitoring table 33, is also required (condition M2). Condition M3 requires all samples be taken and processed according to acceptable standards. A report of all water quality monitoring results will be submitted to the EPA on a quarterly basis (condition M4). Note, condition M4 allows a case to be submitted to the Director to reduce the reporting frequency, again should the monitoring demonstrate the consistent and acceptable performance of the facility. The commitment (7) to construct and maintain a new connection to sewer is considered important and required by condition EF3. Note, according to the DPEMP, flows to sewer are only envisaged when raw leachate cannot be delivered to the wetland system due to pump failure (both duty and duty standby) and capacity in the manhole chamber and emergency storage tank is not reinstated. It is agreed that the recirculation system and inherent storage capacity within the wetland (see below, condition CN1) should negate the requirement to discharge non-compliant flows to sewer, provided that higher flows can be managed within the wetland system to ensure the recirculation pump capacity (4 L/s, 350 m3/day) is not exceeded. TasWater have indicated that it is unlikely discharges to sewer will be permitted during rainfall events, and a Trade Wastewater Agreement may contain limits for discharge quality and quantity. A discharge plan to sewer, in accordance with a Trade Waste Agreement (TWA), is required (condition EF3). In considering the rare event that both duty and duty standby pumps fail, and discharge to sewer is temporarily prohibited due to rainfall, the DPEMP contends that the emergency storage tank (commitment 6) would provide sufficient time to repair the pumps. The proponent further indicated that they would have access to a portable submersible pump, if required. A release of leachate to the environment as a result of a temporary prohibition on discharge to sewer is considered a low risk. Note, the Director is required to be notified in the event of dual pump failure (condition G10). Condition EF1 (limits) will apply from the commencement of commissioning (condition G5 requires notification of commissioning). Discharge to TasWater is proposed to be maintained during this phase, thereby ensuring compliance with condition EF1 during the testing of the wetland. The commitment (commitment 1) to undertake works to separate the stormwater from the MH1 leachate chamber (see Figure 5 of the DPEMP), to avoid untreated leachate discharge via the stormwater system in a 1 in 20 year event, is considered important (condition CN1). This will effectively decrease the frequency of leachate release to the environment from approximately a 20 year event to greater than an 80 year event.


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During extreme events involving a release, the leachate will be diluted with large stormwater input and flood flows. Any impact to the environment would likely be negligible. To ensure adequate built-in storage capacity of the wetland system, condition CN1 requires that the wetland ponds be constructed as described in the DPEMP, with 3,600 m3 to 5,500 m3 of freeboard capacity. Commitment 8 will also assist in this matter, and is supported. According to Appendix 1, stage 2 leachate is currently disposed into TasWater’s sewer system. It is suggested that the stage 2 leachate stream may eventually be incorporated into the on-site treatment strategy. Condition G9 however restricts the wetland facility to treating only leachate from the stage 1 landfill, as an assessment of the potential impact of the stage 2 stream on treatment efficiency was not undertaken or presented in the DPEMP. An annual environmental report is required (condition G8). Monitoring of leachate chemistry since 2005 suggests polycyclic aromatic hydrocarbons are unlikely to be an issue, with only 4 having been occasionally detected, and only then at very low levels. Organic pollutants, including pesticides, are generally not detected in the leachate. Finally, the proposed micro-biological targets (E.coli and Enterococci) are appropriate for the protection of irrigation waters for livestock, pasture and cropping. The targets however are above the ANZECC (2000) trigger values for the irrigation of vegetable crops that are eaten raw (e.g. lettuce)(<10 cfu/100 ml). According to the DPEMP, annual monitoring has shown E.coli levels in the leachate to be always below the detection level. Appendix 1 referenced an E.coli mean of 5 cfu/100 ml. The proponent has indicated, to their knowledge, that the TAFE farm is the only downstream irrigator of vegetables with water drawn from a dam feed by both Cooee Creek and the unnamed tributary. According to the proponent, they are only grown for research purposes and are not directly consumed or on sold. In considering the above, and, as according to the proponent, with further pathogen reduction via the treatment process and higher levels of contamination already within the catchment from downstream users, it is agreed that a stringent pathogen protection level of <10 cfu/100 ml is impracticable and not warranted. Note, Conditions M1 and M2 nevertheless will ensure pathogen levels are monitored within the treated effluent and ambient environment. Stormwater management project On-site stormwater is being managed as a parallel project to the current proposal. Part of the proposed stormwater improvement works is the construction of a stormwater swale between MH1 and the unnamed tributary (Figure 13 of the DPEMP). The proponent expects the stormwater swale will remove at least 30% of the stormwater total nitrogen and phosphorus loads and more than 80% of the stormwater metal load. In considering the relatively large stormwater mass loads (as outlined above), a large net reduction in annual loads to the receiving environment is anticipated with both projects on line.

Conclusions

The proponent has a general environmental duty to conduct the activity in accordance with the commitments (OI2).


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The proponent will be required to comply with the following conditions:

G8 Annual Environmental Review

G9 No Stage 2 landfill leachate

CN1 Construction of the wetland leachate treatment facility

EF1 Ammonia discharge limit to the unnamed tributary

EF2 Polishing pond recirculation and investigation trigger limits

M1 Ambient monitoring of receiving waters

M2 Monitoring requirements

M3 Dealing with samples obtained for monitoring

M4 Monitoring reporting and record keeping

6.2 Groundwater impacts and geotechnical risks

Description

Groundwater The regional, subregional (Cooee Creek), and local site catchment hydrogeology has been well characterised (e.g. Martin and Currie 2008, Entura 2011), including the installation and monitoring of a large number of bores (Sloane 2000, Coffey 2004, 2007, 2008, SKM 2007, Tasman Geotechnics 2015). Groundwater quality monitoring has been undertaken across the site since 1991. According to the DPEMP, these studies and investigations indicate that the landfill site is confined within a natural tertiary basalt valley and is a groundwater discharge zone, with an upward flow into the landfill effectively preventing leachate from leaking into the natural aquifers. The DPEMP concludes that the potential for groundwater contamination is remote, with all site runoff reporting to the unnamed tributary as surface or subsurface discharge. Monitoring bores on-site show that the groundwater is slightly acidic to neutral pH, with elevated nutrients (mainly nitrogen) and some metals (Table 17 of DPEMP). Landfill seepage Two seepage events have occurred from the landfill northern containment bund after extreme (>80 year ARI) or extended rainfall periods, in 2007 and 2013. In both cases the seepages expressed as localised ponding which eventually infiltrated, with no discharge to the creek. Samples taken during the 2013 event indicated very high Al concentrations (4,210 ug/L), and elevated concentrations of Cr, Cu, Mn, Ni, Pb and Zn, exceeding ANZECC (2000) trigger values. The proposal includes the establishment of a phytoremediation swale (Figure 4) to intercept and treat seepage flows from the landfill containment bund. The swale will be pervious and part filled with limestone to provide an alkalinity buffer and prevent acidification of soils. Plant species with metal tolerant and uptake capabilities will be used. Flows in excess of the infiltration treatment capacity will be discharged to the MH1 chamber.


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Geotechnical risks The following potential hazards were identified:

Wetland leakage – potential to saturate the landfill cell and impact on the integrity of the containment bund via saturation and weakening, increased lateral seepage through the containment bund; and

Wetland mass load – potential for landfill cap settlement, loss of structural integrity of the containment bund, and risk to overall stability. Differential settlement of the landfill cap may impact liner integrity, promoting wetland leakage, and also lead to localised subsidence of wetland cell bunds and potential overtopping of leachate.

The proponent identified the following relevant key aspects of the stage 1 landfill:

It is relatively shallow (10 m) and has been closed for over 10 years (ceased receiving waste in 2004 and was capped in 2005);

It is constructed on natural clay that forms the base of the landfill;

The containment bund comprises the northern face of the Stage 1 landfill, and includes both an excavated portion and constructed embankment;

The landfill is capped with 1 to 2 m of compacted clay and a growing medium (at least 0.5 m thick). The cap in the southern section of the landfill contains a GCL layer, while the cap in the northern section of the landfill contains an aggregate rock layer for lateral drainage;

The cap effectively prevents seepage of runoff into the landfill cell; and

A section of the cap was recently surcharged by a mass of stockpiled soil 3.5 m to 6 m high with a footprint of approximately 6000 m2.

A geotechnical model and quantitative geotechnical risk assessment was undertaken by Tasman Geotechnics (Appendix 6 of the DPEMP). The key findings of the risk assessment are as follows:

The landfill has already completed primary consolidation;

The landfill cap is currently experiencing less than 2 mm/yr settlement (long term settlement as a result of biodegradation);

The estimated weight of the proposed wetland system is approximately 17 kPa (24 kPa accounting for the wetland bunds), which is considered to be a minor load;

Consolidation settlement of the landfill cap under the wetland mass load is predicted to be approximately 230 mm, completed within 2 years;

The risk of wetland leakage is considered to be minor, due to construction with a LLDPE liner over an existing clay cap, and in part over a GCL liner;

Any leakages to the landfill will be collected by the leachate collection system;

The stockpile of clay materials placed on top of the landfill had an estimated pressure of 52 kPa. Settlement at the base of the stockpile was measured to be 50 to 600 mm over a 7 year period;

The wetland bund height will be less than 2 m to avoid the potential for excessive settlement (1.2 to 1.5 m to accommodate the liner, substrate, water and freeboard for extreme storm events with an additional to 0.1 m incorporated to accommodate long‐term settlement);

The proposed wetland may result in tensile strains in the capping clay (and in the wetland structure itself). The probability of either the wetland or the landfill cap being compromised is considered to be very low; and

Placement of the wetlands at least 10m from the landfill crest will not adversely impact on the stability of the containment bund wall.

The DPEMP concludes that the proposed wetland system poses a low to very low geotechnical risk.


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According to the DPEMP, the location of the proposed wetland was assessed as being at minimal risk of inundation from catchments to the east of the site or flooding from the existing stormwater infrastructure on-site during an extreme 1000 year ARI event. The DPEMP indicates that direct rainfall volumes generated in a 1000 year rainfall event will be accommodated within the wetland system with a freeboard of 182 mm. The minimum freeboard will be 200 mm.

Management measures

Groundwater Ensure interception and treatment of extreme storm event leachate seepages that may occur along the northern embankment within a phytoremediation swale (commitment 9). Undertake sampling in accordance with the proposed monitoring schedule shown in Table 33 (commitment 33). The proposed monitoring schedule is summarised as follows:

The existing groundwater monitoring location at the proposed infiltration wetland forest (GW1, see Figure 41 of the DPEMP for monitoring locations) will be maintained. During the first year of operation, the monitoring of physical parameters and nutrients will be increased to monthly and metals increased to every two months;

Should no appreciable change in levels or quality occur in the first year, monitoring frequency of physical parameters, nutrients and metals may be reduced to quarterly; and

Groundwater monitoring at locations up-gradient of the proposed wetland system (i.e. locations GW2 and GW3) will remain unchanged.

Management for geotechnical risks Ensure appropriate freeboard to accommodate the 1000 year rainfall event (182 mm) (commitment 3). Limit the placement of the wetland system to at least 10 m from the landfill crest (commitment 2). Limit the height of bunds to <2 m to prevent excessive settlement (commitment 4). Use a LLDPE liner to reduce wetland seepage risks (commitment 5). With regard to wetland leakage, the following management measures were also outlined in the DPEMP:

Contiguous flow monitoring at the wetland influent and wetland effluent locations to allow for a water balance to be carried out to determine water losses (beyond evapo-transpiration).

The existing piezometers installed along the landfill cap for monitoring of leachate standing levels will also be retained where possible and will continue to be monitored.

After heavy rainfall events, visual checks of flows in the infiltration swale will be undertaken.

If leakages arise, the relevant section of the wetland will be taken off-line and repaired. Install 4 survey markers and undertake fortnightly monitoring of settlement levels across the landfill pre, during and post construction for several months (commitment 18). Undertake annual monitoring of settlement levels across the landfill (commitment 26).


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With regard to settlement, the following management measures were also outlined in the DPEMP:

Quarterly checks of wetland perimeter bunds to ensure the minimum freeboard depth is maintained.

Any localised areas that may have settled below the minimum 200 mm level will be repaired by adding fill material and potentially extending the liner.

Retain wetland designer during construction / contract management phases to ensure quality control of all system components (e.g. liner, hydraulics, planting, etc.) and safeguard management elements are constructed as per design (commitment 8)

Public and agency comment and responses

No public or agency comment was received.

Evaluation

Groundwater Sufficient studies have been undertaken of the area to indicate that the BWMC site is a confined groundwater discharge zone, with an upward flow into the landfill preventing leachate leakage into the natural aquifers. It is agreed that the potential for groundwater contamination is remote, with low flow treated effluent to discharge to the unnamed tributary via subsurface flows through the infiltration forest. The quality of the effluent discharged to the infiltration forest is discussed in section 6.1. The proposed monitoring program (Table 33 of the DPEMP, commitment 33) to assess the potential for change in groundwater level and quality at the infiltration forest is considered appropriate, and required by condition M2. The proposed increased sampling frequency during the first year of operation is considered important (condition M2). Condition M2 allows a case to be to be submitted for altering the sampling frequency should no appreciable change in groundwater parameters occur. The commitment (9) to intercept and treat any leachate seepages that may occur in extreme events (e.g. > 80 year ARI) with the construction of a phytoremediation swale and alkaline buffering, is supported. According to the DPEMP, flows in excess of the infiltration treatment capacity of the swale will be discharged to the MH1 chamber, preventing direct discharge to the unnamed tributary. Significant seepages are not expected, unless there is a compromise in the integrity of the cap and or wetland leakage. These issues are addressed below. Geotechnical risks The geotechnical risk assessment undertaken by Tasman Geotechnics (Appendix 6 of the DPEMP) concludes that the proposed wetland system poses a low to very low risk of wetland mass load failure, settlement and compromises in structural integrity, and wetland leakage. This conclusion was supported by a peer review of the BWMC Stage 1 landfill leachate treatment hydro-geotechnical risk assessment (Appendix 6 of the DPEMP) undertaken by Golder Associates Pty Ltd. In their review, they did not identify any fatal flaws in the proposal.


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The review noted however that the measured settlement of the landfill site is not based on accurate measurements at survey beacons, and therefore due to different point density between survey times and associated inherent error, a settlement rate of 2 mm/year cannot regarded as accurate. Tasman Geotechnics indicates that ‘typical’ settlement of the landfill between the survey times (May 2006 and April 2013) was less than 2mm/yr, with a maximum settlement of approximately 50mm, equating to about 7mm/year. Both the peer review and Tasman Geotechnics nevertheless conclude that the expected settlement is not considered significant enough to impact upon the performance of the wetland. The peer review recommends however the use of a Linear Low Density Polyethylene (LLDPE) liner (commitment 5), to allow for differential settlement (required by condition CN1). The review also highlighted the need for it to be installed with sufficient protective layers to protect it from damage. Condition CN1 will ensure that it is installed according to relevant standards.

To ensure the wetland is constructed to limit the degree of landfill settlement and reduce the potential for impact on structural integrity, commitments 2 and 4 are considered important and also required by condition CN1. The commitment (18) to install 4 survey markers and undertake fortnightly monitoring of settlement levels across the landfill pre-during and post construction is considered important. Note, the proponent has indicated that the exact coordinates of the survey points will be determined during the detailed design stage. Further, it is unclear in the DPEMP the exact number of markers to be installed, with at least 8 suggested for construction monitoring. Condition M5 therefore requires a settlement monitoring plan be submitted to the Director for approval. Annual monitoring of settlement (commitment 26) would be appropriate once consolidation settlement has taken place, and previous monitoring has demonstrated negligible settlement. It is noted an additional 100 mm of wetland freeboard has been factored into the design to accommodate long term settlement. Given the predicted settlement rates, this should be sufficient for the anticipated life of the facility. It is agreed that the wetland will have only a minor leakage risk given it will be underlain with a LLDPE liner (condition CN1) over an existing clay cap, and in part a GCL liner. The proposed measures are considered adequate to be able to detect a significant leakage in the wetland. The proponent has indicated that at least some of the existing piezometers will be retained, and that additional ones can be reinstated after construction works. This is considered an important monitoring tool for leakage, and required by condition M6. The commitment (3) to retain adequate freeboard for a 1000 year event is supported (condition CN1), and will ensure erosion of the landfill cap from wetland overflow does not occur. The potential for inundation of the wetlands from flood waters is not considered a realistic possibility.

Conclusions



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M5 Settlement Monitoring Plan

M6 Installation and monitoring of piezometers


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7 Other issues

In addition to the key issues, the following environmental issues are considered relevant to the proposal and have been evaluated in Appendix 1.

1. Solid waste management

2. Air emissions

3. Noise emissions

4. Flora and fauna

5. Weed and disease management

6. Dangerous goods and environmentally hazardous materials

7. Heritage (European and Aboriginal)

8. Decommissioning and rehabilitation


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8 Report conclusions

This assessment has been based upon the information provided by the proponent in the DPEMP, and in correspondence and discussion between the EPA Division and the proponent and the proponent’s representatives. This assessment has incorporated specialist advice provided by EPA Division scientific specialists and regulatory staff, other Divisions of DPIPWE and other government agencies. This assessment has taken into account issues raised in public submissions. It is concluded that:

1. the RMPS and EMPCS objectives have been duly and properly pursued in the assessment of the proposal; and

2. the assessment of the proposal has been undertaken in accordance with the Environmental Impact Assessment Principles.

It is concluded that the proposal is capable of being managed in an environmentally acceptable manner such that it is unlikely that the RMPS and EMPCS objectives would be compromised, provided that the environment protection notice appended to this report is issued and served and its requirements are duly complied with, including commitments made by the proponent in the DPEMP.


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9 References

DPIWE (2001); Emission Limit Guidelines for Sewage Treatment Plants.

Syrinx Environmental Pty Ltd (2015); Burnie Waste Management Centre, Stage 1 Landfill Leachate Treatment Wetland Development Proposal & Environmental Management Plan (dated November 2015); Syrinx Environmental Pty Ltd, Perth, WA; prepared for Burnie City Council.


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10 Appendices

Appendix 1 Assessment of other issues Appendix 2 Environment protection notice, includes Attachment 5 - DPEMP commitments

Appendix 2


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Appendix 1 Assessment of other issues

Issue 1: Solid waste management

Description of potential impacts

Solid waste will be generated via periodic removal of sediment sludge from the leachate sediment chambers and the wetland pre-filter pond (Figure 4). According to the DPEMP, the leachate contains low levels of TSS and organics, with no requirement for chemical dosing for precipitation/coagulation. The wetland is therefore expected to generate very low levels of sediment/sludge, estimated at < 1 tonne per annum. The pre-filter is designed to promote the precipitation of metals. The sediment is therefore likely to contain high concentrations of metals and will require to be managed as a controlled waste.

Management measures proposed in DPEMP

Accumulated sediment will be removed from the pre-filter pond and leachate sediment chambers using a vacuum truck, with material disposed to an appropriate landfill facility. Sediment removal from the leachate sediment chambers will be undertaken annually, and from the pre-filter pond as required.

Develop Operation and Maintenance Plans which detail the required maintenance activities and frequencies and ensure their appropriate implementation (commitment 14); and

Undertake appropriate training of staff responsible for system monitoring & maintenance, including preparation of user friendly management and maintenance plans (commitment 27).

Public and agency comment

No comment was received.

Evaluation

The proposal to handle the accumulated sediment via a vacuum truck for disposal off-site is considered appropriate. Transport and disposal of any controlled waste must be undertaken by authorised persons (condition WM1). Note, the handling (including dispatch) of a controlled waste under the Environmental Management and Pollution (Waste Management) Regulations 2010, (the Regulations) requires approval. To ensure appropriate maintenance is undertaken to facilitate the proper functioning of the wetland system and removal and management of sediment sludge, commitments 14 and 27 are required (condition OP1, see Issue 2). General litter management on-site will continue to be regulated through Permit No 6224.

Conclusion


WM1 Controlled waste transport

OP1 Operation and maintenance plan

Issue 2: Air emissions


The nearest sensitive receptors to the site are the neighbouring farm properties, approximately 50 metres from the site boundary to the north west (235 metres to the wetland ponds) and 150 metres to the north (224 metres to the wetland ponds). A residential subdivision on Three Mile Lane Road is located approximately 200 metres to the north from the site boundary. There is potential for air quality (odour) impacts if the wetland treatment system is allowed to become anoxic, resulting in the build-up and release of H2S and/or methane gases. According to the DPEMP, this

Appendix 2


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is considered unlikely as the system is designed to be shallow and aerobic, with an operational regime that incorporates routine drawdown of wetland cells to maintain oxygenation of the sediments and to ensure aerobic degradation of organics. The pond systems will have inlet/outlet flow control valves for variation of flow, reducing the potential for stagnation and excessive flow detention, and siphon drainage pipes to allow for full draining.

The surface flow wetland is also configured so as to distribute flows into four pairs of cells in series. During very low flow periods (150 kL/day or less), only some cells will operate to prevent stagnation and generation of organics, that may otherwise lead to excessive odour. The DPEMP notes that there is also a potential for localised odours if/when leachate seepages occur along the northern embankment. Dust may be generated during construction works.


Develop Operation and Maintenance Plans which detail the required maintenance activities and frequencies and ensure their appropriate implementation (commitment 14); and

Undertake appropriate training of staff responsible for system monitoring & maintenance, including preparation of user friendly management and maintenance plans (commitment 27).

Dust control will be implemented during construction in order to minimise export off site. Water tankers will be utilised to prevent dust emissions if soil moisture is low and wind velocity is high.



Evaluation

Two odour complaints relating to the disposal of waste water treatment sludge at the site have been previously recorded (2007 & 2008). According to the DPEMP, no complaints have been received since cessation of sludge disposal, mid-2007. Given the proximity of residents to the site, odour may become an issue if appropriate management and maintenance practices, such as oxygenation of sediments and removal and disposal of sludge (Issue 1), are not implemented (condition OP1). Odour from the seepages is unlikely to cause a nuisance given the likely low volumes involved and the interception and treatment within the phytoremediation swale. If odour does occur however from a result of mis-management of the wetland system or excessive seepage, condition A1 will ensure appropriate odour management measures are undertaken to prevent an odour nuisance occurring beyond the boundary of the site. The proposed dust control measures to be implemented during construction are considered important given the proximity of residences, and hence required by condition A1.

Conclusion


A1 Odour management

A2 Control of dust emissions during construction

Issue 3: Noise emissions


Noise emissions during operation will be limited to the raw leachate submersible pump. Noise emissions will occur during construction from the use of heavy machinery (as detailed in Table 1).

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Noise will be managed by restricting construction activities to daylight hours in accordance with the Hours of Use specified in the Environmental Management and Pollution Control (Miscellaneous Noise) Regulations 2004 - Schedule 7:

Monday to Friday 7 am to 6 pm inclusive;

Saturday 8 am to 6 pm inclusive; and

Sundays and Public Holidays 10 am to 6 pm inclusive.



Evaluation

Noise emissions during operation will be limited to the pump system. According to the DPEMP, the pumps will be operating anywhere between 8 hrs and 24 hrs per day. This is equivalent to the current pump operation cycle. Both pumps will be submersible and housed within the manhole (MH1) with a 200 mm concrete lid. While the pumps will operate overnight, noise issues from their operation are not anticipated. It is noted that a diesel generator will also be installed at the manhole (MH1) as a back-up for power outages. The generator will only be tested during the daytime as part of maintenance activities. It will only be called upon very infrequently to operate at other times if there is a power outage. Restrictions on the operation of the facility to mitigate the potential for noise nuisance is not considered necessary, however the proponent should nevertheless be directed to section 53 of EMPCA (legal obligation LO4), which will ensure noise emissions do not unreasonably interfere with a person’s enjoyment of the environment. The nearest residence to the construction/earthworks site is approximately 80 metres to the west of the infiltration forest, and 220 metres to the north of the wetland ponds. Limiting the proposed construction hours to those outlined in the Environmental Management and Pollution Control (Miscellaneous Noise) Regulations 2014 - Schedule 7, will mitigate the potential for noise nuisance during night time and early morning hours. This is considered important and reinforced by condition N1. Given the temporary nature of the earthworks, approximately 4 months in length, noise generated from the movement and operation of heavy equipment during daytime hours should not be an issue. Nevertheless, section 53 of EMPCA (legal obligation LO4) and still applies.

Conclusion


N1 Operating hours - Construction

Noise emissions must not unreasonably interfere with a person’s enjoyment of the environment (refer Legal Obligations LO4).

Issue 4: Flora and fauna


The proposal will not result in the clearing or indirect disturbance of native vegetation within or outside of the project site. Indeed, according to the DPEMP it will result in an approximately 2 ha of native vegetation and wetland habitat being established. The nearest threatened ecological community is a wetland community, hydrologically connected to the unnamed tributary, approximately 2 kms downstream. According to the DPEMP, the wetland is degraded (due to siltation and weed invasion) and is likely to be either unaffected by the proposal or will slightly benefit from the enhanced environmental flows. No threatened flora was identified on site.

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The Burnie burrowing crayfish (Engaeus yabbimunna) and Giant freshwater crayfish (Astacopsis gouldi) are known to occur downstream of the BWMC site, with suitable habitat for both species occurring on the unnamed tributary (Natural Values Report). Entrained sediment into the creek system, and or reduced water quality, may impact Giant freshwater crayfish (Astacopsis gouldi) and Burnie burrowing crayfish (Engaeus yabbimunna) habitat.


Use of sediment controls (traps, sediment curtains) during creek enhancement works, and reuse of sediment within landfill area (commitment 20);

No clearing of native vegetation (commitment 19);

Undertake restoration works in the immediate unnamed creek discharge area to reduce weeds, enhance riparian vegetation, improve habitat and reduce erosion (commitment 22); and

Undertake an annual condition assessment of the unnamed tributary to Three Mile Rd (commitment 23).

Sediment traps and temporary lined stormwater bunds up to 400 mm high will be constructed to manage surface water flows during the construction period.

Silt curtains will be installed within the creek during construction of the infiltration wet forest, stormwater swale, manhole refurbishment works and creek enhancement works.



Evaluation

The use sediment control measures such as traps, stormwater bunds and silt curtains to reduce the potential for sediment loss downstream during construction is considered important, and required by condition EF4. This is supported by PCAB. PCAB also supports the undertaking to treat leachate flows to ANZECC Water Quality Guidelines (2000), with contingencies in place to recycle if not compliant, store and treat increased flows and maintain back-up power supplies (see Section 6.1). If the conditions contained in this report are implemented, it is unlikely the proposal will have a significant impact on the Burnie burrowing crayfish (Engaeus yabbimunna), Giant freshwater crayfish (Astacopsis gouldi), or indeed the threatened wetland community. Creek restoration and enhancement works are not a part of the proposal. Commitments 20 and 22 are nevertheless supported. Indeed, PCAB noted that many areas of the unnamed creek are infested with the weed Glyceria maxima, which is a potential threat to the Burnie burrowing crayfish (Engaeus yabbimunna) and Giant freshwater crayfish (Astacopsis gouldi). The intention of commitment 23, to assess the anticipated positive creek benefits associated with improved environmental flows and biodiversity improvement works, is supported. It is noted however that this will likely require the consent of the neighbouring property owner. The commitment (19) to not clear native vegetation is also supported. PCAB does not consider the proposal however will have a significant impact on Tasmanian devil (Sarcophilus harrisii), Spotted-tailed quoll (Dasyurus maculatus maculatus), Green and gold frog (litoria raniformis) and the Eastern barred bandicoot (Perameles gunnii gunnii). PCAB supports the maintenance of trees with suitable hollows for threatened bird species (e.g. Swift Parrots (Lathamus discolour) and Masked owl (Tyto novaehollandiae castanops) during creek restoration works.

Conclusion

No conditions are necessary.

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Issue 5: Weed and disease management


According to the DPEMP, seventeen weed/exotic species were identified along the survey area, from the BWMC site to the confluence of the unnamed tributary and Cooee creek. Of these, four species (Gorse, Blackberry, Pampas grass and Elisha's tears) are listed as Declared Weeds under the Weed Management Act 1999. A heavy weed infestation of Glyceria maxima, a non-declared weed, was identified along the section of the unnamed tributary that flows through the BWMC.


Management practices to prevent the spread of pests, weeds and diseases into uninfected areas will include measures such as:

Dieback free construction materials will be used;

All imported soils will be certified and purchased from accredited suppliers only;

Equipment, machinery and vehicle inspection, washdown and disinfection procedures will be implemented and enforced prior to site entry and departure;

Weed control will be undertaken prior to clear and grub works; and

Ongoing weed control and disease management will be undertaken in accordance with an Operational and Maintenance Plan to be developed.



Evaluation

According to the DPEMP, during construction works the site will be managed so as to limit the introduction and spread of introduced plant species, weeds, pests and diseases (Phytophthora cinnamomi). The exampled measures outlined above appear to be appropriate. Given the occurrence of declared weeds within the near vicinity however and the fact that Glyceria maxima is a potential threat to the Burnie burrowing crayfish and Giant freshwater crayfish, all weed and disease management control must be undertaken in accordance with the DPIPWE (2015) Weed and Disease Planning and Hygiene Guidelines – Preventing the spread of weeds and diseases in Tasmania, (Condition OP1).

Conclusion


OP1 Operation and Maintenance Plan

Issue 6: Dangerous goods and environmentally hazardous materials


A diesel back-up generator will be installed at the leachate manhole chamber (MH1). The generator will be checked and refuelled as part of weekly scheduled maintenance activities. Diesel will not be stored on site.

Fuel will be required for heavy equipment during construction of the wetland. Contractors will be required to address the management of dangerous substances within a Construction Management Plan.


No management measures were proposed.

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Evaluation

To ensure that refuelling of the back-up generator, and the handling and temporary storage of fuels during construction does not cause any environmental harm, the proponent is required to adhere to conditions H1 and H2. The proponents have noted their legal obligations with respect to the Dangerous Substances (Safe Handling) Act 2005 and Dangerous Substances (Safe Handling) Regulations 2009 (Legal Obligation LO1).

Conclusion

The proponent will be required to comply with the following standard conditions:

H1 Storage and handling of hazardous materials

H2 Spill Kits

The storage, handling and transport of dangerous goods, explosives and dangerous substances must comply with the requirements of relevant State Acts and any regulations thereunder (refer Legal Obligations LO1).

Issue 7: Heritage (European and Aboriginal)


It is highly unlikely that Aboriginal artefacts will be encountered during construction of the treatment system as the majority of works will occur on the landfill. There will be no impact on heritage buildings and/or associated historical structures as a result of the proposal.


In the unlikely event that any artefacts or sites are discovered during construction /operation, all activities will cease immediately until a proper assessment is undertaken. The appropriate personnel at the Aboriginal Heritage Tasmania (division of the Department of Primary Industries, Parks, Water and Environment) will be contacted to assess the situation and agree upon the appropriate management measures.



Evaluation

Aboriginal Heritage Tasmania have advised that there are unlikely to be any Aboriginal heritage issues associated with the proposal due to the high level of ground disturbance in the past. The management measure proposed is nevertheless supported (Legal obligation LO4).

Conclusion

Any relics discovered should be managed in accordance with the Aboriginal Relics Act 1975 (refer Information Schedule LO4).

Issue 8: Decommissioning and rehabilitation


The Burnie Waste Management Centre is expected to have a minimum life span of between 20 and 30 years. The wetland will continue to be managed during this period. According to the DPEMP, it is expected that at some point in time the data on water quality discharge from

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the landfill may indicate that the leachate is acceptable for direct infiltration on-site, and treatment by the wetland is no longer required. At site closure, the DPEMP suggested that the wetland could be repurposed as a stormwater treatment system, and / or opened to the public as a recreational biodiversity reserve.


No management measures were proposed.



Evaluation

Standard conditions DC1 (Notification of cessation), DC2 (Temporary suspension of activity), DC3 (Decommissioning and Rehabilitation Plan) and DC4 (Implementation of the DRP) are required to ensure appropriate decommissioning and rehabilitation of the site.

Conclusion


DC1 Notification of cessation

DC2 Temporary suspension of activity

DC3 Decommissioning and Rehabilitation Plan

DC4 Implementation of the DRP

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Appendix 2 Environment Protection Notice

stage 1 landfill leachate treatment - epa tasmania city council...landfill leachate treatment...

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