Westside Mine Final Void Management Plan EMP-WO-ECP-012 · Westside Mine Environmental Management Plan Revision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management

Westside Mine Final VoidManagement Plan

EMP-WO-ECP-012

August 2010

Westside Mine Environmental Management PlanRevision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management PlanDocument ID: EMP-WO-ECP-012 Authorised: Neil Rae i of 47

TABLE OF CONTENTS

1.0 Introduction................................................................................... 11.1 Purpose and Scope ..............................................................................11.2 Objectives .............................................................................................11.3 Roles and Responsibilities..................................................................3

2.0 Legislative Requirements............................................................ 42.1 Development Consent..........................................................................42.2 Department of Environment, Climate Change and Water (DECCW) 4

2.2.1 NSW Office of Water ......................................................................................4

2.3 Xstrata Coal...........................................................................................4

3.0 Existing Environment................................................................... 53.1 Surrounding Features and Land Use..................................................53.2 Geology .................................................................................................53.3 Hydrology and Hydrogeology .............................................................5

4.0 Land Use Options – Final Void ................................................... 94.1 Water Storage .......................................................................................9

4.1.1 Rainfall and Evaporation Analysis...................................................................9

4.1.2 Calculation of Water Inflows..........................................................................10

4.2 Partial Backfilling ...............................................................................164.3 Long-Term Land Use..........................................................................17

5.0 Control Measures ....................................................................... 185.1 Employee, Contractor, Visitor and Public Safety ............................185.2 Final Void Slope Stability...................................................................18

5.2.1 Low Wall Slope Stability ...............................................................................18

5.2.2 High Wall Slope Stability...............................................................................19

5.3 Water Quality ......................................................................................195.3.1 Surface Water ..............................................................................................19

5.3.2 Groundwater ................................................................................................20

5.3.3 Predicted Quality of Water Discharge ...........................................................20

5.4 CWR Leachate ....................................................................................215.5 Spontaneous Combustion.................................................................22

6.0 Monitoring and Communication ............................................... 23

Westside Mine Environmental Management PlanRevision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management PlanDocument ID: EMP-WO-ECP-012 Authorised: Neil Rae ii of 47

6.1 Consultation Regarding this Plan .....................................................236.2 Monitoring and Maintenance of the Water Management System...236.3 Reporting.............................................................................................236.4 Corrective Action................................................................................246.5 Complaints Resolution.......................................................................24

7.0 Auditing and Review .................................................................. 25

8.0 References .................................................................................. 26

FIGURES

Figure 1 Site Location........................................................................................ 2Figure 2 Site Features........................................................................................ 6Figure 3 Watercourses....................................................................................... 7Figure 4 Void Catchment Area ........................................................................ 12Figure 5 Final Void Water Cycle...................................................................... 13Figure 6 Relationship Between Groundwater Inflow and Water Level ........ 13Figure 7 Estimated Rise in Water Storage Volume within the Final Void.... 15Figure 8 Estimated Change in Void Water Level ........................................... 15Figure 9 Comparison Between Site Rainfall Data and BOM Data ................ 35Figure 10 Monthly Rainfall Statistics................................................................ 36Figure 11 Number of Rain Days of Various Magnitudes................................. 36Figure 12 Daily Rainfall Magnitudes ................................................................. 37Figure 13 Average Daily Evaporation Rates .................................................... 38

APPENDICES

A Development Consent DA 125-5-2002B Correspondence with the NSW Department of PlanningC Final Void Cross Sections (3V:1H)D Rainfall and Evaporation Data AnalysisE CWR Leachate ResultsF Spontaneous Combustion Control MeasuresG Government Agency Consultation

Westside Mine Environmental Management PlanRevision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management PlanDocument ID: EMP-WO-ECP-012 Authorised: Neil Rae iii of 47

Westside Mine Environmental Management PlanRevision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management PlanDocument ID: EMP-WO-ECP-012 Authorised: Neil Rae 1 of 47

1.0 Introduction

Westside Mine is an open cut coal mine located approximately 20 kilometres southwest ofNewcastle NSW, in the Lake Macquarie Local Government Area (LGA). The site location isshown in Figure 1. The mine has been operating since 1992, and is currently managed byOceanic Coal Australia Limited (OCAL) on behalf of the Macquarie Coal Joint Venture(MCJV). Hunter Valley Earthmoving Company Pty Ltd (HVE) is the nominated operator ofWestside Mine.

OCAL was granted development consent (DA 125-5-2002) on 23 January 2003 by the NSWMinister for Planning to construct and operate the Westside Mine Southern Extension. This21 year development consent allowed open cut mining operations to continue for a further 7to 12 years. It is currently envisaged that mining operations at Westside Mine will cease in2012.

A Condition of Consent for the development approval is the preparation of a Final VoidManagement Plan (FVMP) at least two years prior to completion of mining from the SouthernExtension. The specific requirements of the FVMP are outlined in Condition 4.4 of theDevelopment Consent (Appendix A).

This plan is part of the Westside Mine Environmental Management Plan (EMP), which isgenerally in accordance with the OCAL Environmental Management System (EMS) and theXstrata Coal NSW (XCN) Environmental Management Framework.

1.1 Purpose and Scope

The purpose of this FVMP is to identify the options for final use(s) of the void followingcompletion of open cut mining at Westside Mine, identify environmental impacts associatedwith the proposed use(s) of the final void, outline strategies to minimise potential impacts andidentify monitoring requirements.

1.2 Objectives

The primary objective of the FVMP is to manage and minimise the environmental impacts ofthe final void as outlined above. The plan also seeks to satisfy the following objectives:

Comply with appropriate statutory and corporate requirements, including the Conditionsof Consent (Appendix A) and Environment Protection Licence (EPL) 4033.Correspondence with the NSW Department of Planning (DoP) is included in Appendix B.

Propose measures to be incorporated in the final landform which aim to minimisepotential safety hazards to the employees, contractors, visitors and general public.

Describe geotechnical aspects of the final void design to management slope stability.

Identify future water licensing requirements.

Propose ongoing environmental monitoring requirements for management of the finalvoid.

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© 2010. While GHD has taken care to ensure the accuracy of this product, GHD and GEOSCIENCES AUSTRALIA, WESTSIDE MINE, GHD make no representations or warranties about its accuracy, completeness or suitabilityfor any particular purpose. GHD and GEOSCIENCES AUSTRALIA, WESTSIDE MINE, GHD cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequentialdamage) which are or may be incurred as a result of the product being inaccurate, incomplete or unsuitable in any way and for any reason.

Job NumberRevision A

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Date 25 JUN 2010oOceanic Coal Australia LimitedFinal Void Management Plan

Westside MineLocality Plan

Data Source: Geosciences Australia: Topography - 2007; Westside Mine: Elevation Data - 2010; GHD: Catchment Data - 2010. Created by: tmorton, pcgmcdiarmid

Level 3, GHD Tower, 24 Honeysuckle Drive, Newcastle NSW 2300 T 61 2 4979 9999 F 61 2 4979 9988 E [email protected] W www.ghd.com.au

Map Projection: Transverse MercatorHorizontal Datum: Geocentric Datum of Australia (GDA)

Grid: Map Grid of Australia 1994, Zone 56

1:150,000(at A4)

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1.3 Roles and Responsibilities

The roles and responsibilities of OCAL employees in regards to this FVMP are outlined inTable 1.

Table 1 Roles and Responsibilities

Role Responsibilities

Westside Mine Operations Manager Ensuring that adequate resources are availablefor the implementation of this plan.

Assisting in the review of this document asrequired.

OCAL Environment and Community Manager Undertaking regular environmental inspectionsand inspections after high rainfall events.

Coordinating the monitoring program outlined inthis plan.

Coordinating the review of this document asrequired.

Westside Mine Operations Engineer / SiteEnvironmental Supervisor

Ensuring earthmoving works are built to adesign which will deliver a suitable finallandform.

Inspection of dams and relevant drains.

Supervising rehabilitation activities.

All employees and contractors Undertaking all activities in accordance with thisplan.


2.0 Legislative Requirements

2.1 Development Consent

This FVMP has been developed in accordance with the relevant Conditions of Consent of theWestside Mine Southern Extension Development. The conditions relating to this plan areincluded in Appendix A.

2.2 Department of Environment, Climate Change and Water(DECCW)

Mining and associated activities at Westside Mine are undertaken in accordance with theEPL 4033, which is held by HVE. The EPL specifies general monitoring, recording andreporting requirements for Westside Mine. The FVMP has been developed with reference tothe current EPL.

2.2.1 NSW Office of Water

Westside Mine currently holds a licence to extract groundwater from the open cut pit for minedewatering. This licence was re-issued by the Department of Water and Energy (DWE), nowthe Office of Water, on 2 May 2008 and is valid to 1 May 2013.

Westside Mine also holds a licence for monitoring bores N2175, N2176 and N2178. Thislicence was issued on 17 March 2003 for perpetuity.

2.3 Xstrata Coal

This plan is part of the Westside Mine Environmental Management Plan (EMP), which isgenerally in accordance with the OCAL Environmental Management System (EMS) and theXstrata Coal NSW (XCN) Environmental Management Framework.


3.0 Existing Environment

The final void is located within the Southern Extension area in the south-eastern portion ofthe Westside Mine lease boundary, as shown in Figure 2.

3.1 Surrounding Features and Land Use

The topography steepens to the south of the final void to form an east-west trendingridgeline. This ridgeline separates the lease boundary from rural residential town ofWakefield. Further to the south is Newstan Colliery (owned by Centennial Coal). The surfacefacilities of West Wallsend Colliery adjoin the northern boundary of the Westside Mine leaseboundary, while the Teralba Quarry and Macquarie Coal Preparation Plant (MCPP) arelocated to the southeast and east respectively.

The urban areas of Killingworth and Barnsley are located in close proximity to the west andnortheast of the lease boundary respectively. Otherwise, the site is predominantlysurrounded by remnant bushland.

3.2 Geology

Both the Great Northern and Fassifern seams are mined at Westside Mine. These strataform part of the upper Permian Age Newcastle Coal Measures and regionally dip atapproximately three degrees to the south. The seams outcrop in the vicinity of WestsideMine forming a shallow, localised basin structure. Awaba Tuff typically separates the GreatNorthern Seam from the underlying Fassifern Seam, while the Great Northern Seam istypically overlain by Teralba Conglomerate at this location.

Old bord and pillar workings are present within the Great Northern Seam in the vicinity of theSouthern Extension area.

3.3 Hydrology and Hydrogeology

Westside Mine is located in the Cockle Creek catchment, approximately 9 km upstream fromLake Macquarie and 2.5 km upstream from the tidal limit (controlled by the James Streetweir). The lease area is located upstream from the confluence of Diega Creek with CockleCreek. Cockle Creek generally flows in an easterly direction to the north of the final void,while Diega Creek generally flows in a northerly direction to the east of the final void (Figure2). The location of the Westside Mine site within the Cockle Creek catchment is shown inFigure 3.

Based on available water quality data collected by OCAL, surface water within Cockle Creekis generally fresh and slightly acidic upstream of Westside Mine and brackish to saline andslightly alkaline downstream. Based on available data, an average of approximately 1600 MLof mine water and surface water runoff is currently discharged to Cockle Creek each year viacombined discharge point 16. Surface water monitoring and discharge locations are shown inFigure 2. Although the quality and quantity of the discharge consistently meets limits set inEPL 4033, the discharge has changed the reach of the creek downstream of the site from afresh and slightly acidic system to a brackish to saline and slightly alkaline system. It is likelythat the aquatic environment in this reach has adapted to these changed conditions over theyears.

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LEGEND

© 2010. While GHD has taken care to ensure the accuracy of this product, GHD and GEOSCIENCES AUSTRALIA, GHD, WESTSIDE MINE make no representations or warranties about its accuracy, completeness or suitabilityfor any particular purpose. GHD and GEOSCIENCES AUSTRALIA, GHD, WESTSIDE MINE cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequentialdamage) which are or may be incurred as a result of the product being inaccurate, incomplete or unsuitable in any way and for any reason.


22-15145

Date 25 JUN 2010oOceanic Coal Australia LimitedFinal Void Management Plan

Westside MineSurface Features

Data Source: Geosciences Australia: Topography - 2007; GHD: Catchment Data - 2010; Westside Mine: Elevation Data and Aerial Imagery - 2010. Created by: tmorton, pcgmcdiarmid




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LEGEND

o© 2010. While GHD has taken care to ensure the accuracy of this product, GHD and GEOSCIENCES AUSTRALIA, GHD make no representations or warranties about its accuracy, completeness or suitability for any particular purpose. GHD and GEOSCIENCES AUSTRALIA, GHD cannot accept liability of any kind(whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred as a result of the product being inaccurate, incomplete or unsuitable in any way and for any reason.

Date 25 JUN 2010

Oceanic Coal Australia LimitedFinal Void Management Plan

Watercourses withinWestside Mine Lease Area

Data Source: Geosciences Australia: Topography - 2007; GHD: Catchment Data - 2010. Created by: tmorton, pcgmcdiarmid


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The main groundwater aquifers at Westside Mine are:

Alluvium associated with Cockle Creek and Diega Creek.

Great Northern and Fassifern seams.

Alluvial groundwater flow is typically governed by creek flow and discharges into theassociated creek. Coal seam groundwater flow typically follows the dip and orientation of theseam.

Based on available groundwater quality data for OCAL monitoring well N2178, groundwaterin Diega Creek alluvium is generally slightly acidic to slightly alkaline and fresh to slightlybrackish. Over the period 2002 to 2010, groundwater levels in the Diega Creek alluvium haveincreased slightly (as indicated by water levels in well N2178). OCAL monitoring welllocations are shown in Figure 2.

Groundwater in the Permian rock aquifers, based on available groundwater quality data forOCAL monitoring wells N2175 and N2176, is slightly to moderately acidic and saline. Basedon available groundwater level data, piezometric head within the Permian rock aquifersadjacent to the final void dropped substantially since June 2007. Note that a 1 in 100 yearstorm event (for 24 hour duration) occurred early in this month.

A search of the NSW Groundwater Bore Database indicates that local beneficial usage ofthese aquifers for domestic or agricultural purposes is minimal. In addition to the threegroundwater monitoring wells owned by OCAL, only four registered groundwater bores werefound within an area extending 3 km from the Westside Mine lease boundary. All registeredbores are located to the south of the lease boundary and are upstream of the Westside Minefinal void. Available information is limited, although it appears that only one of theseregistered bores draw groundwater from an alluvial aquifer.


4.0 Land Use Options – Final Void

Open cut mining at the Southern Extension area will leave an open pit void (final void) atmine closure. The approximate dimensions of the void are 450 m wide × 750 m long. It isestimated that the total air space of this void is approximately 3.6 million m3 up to the level ofthe east levee. The options available for post mining land uses are generally determined bythe location and nature of the void. Two options are considered appropriate at this point intime:

Utilising the void as a water storage facility.

Partially backfilling the void with overburden and coarse coal washery reject (CWR).

Although the options presented at this time are considered appropriate, there may be moreappropriate options at mine closure. Any such additional options would need to be assessedat that time. The two options identified are discussed in more detail below. Cross sections foreach option are shown in Appendix C.

4.1 Water Storage

In the event that MCPP or another adjacent mine do not require the final void for overburdenand/or reject disposal, the void will be allowed to fill with water (both runoff and groundwater)to create a water storage dam. As such, the void will form part of the ongoing watermanagement of the site.

Analysis of likely surface water and groundwater inflows into the void has been undertaken topredict the rate at which the void will fill. The following data were used in the analysis:

Site topography and final void landform.

Floor contours for the Great Northern and Fassifern seams.

Rainfall and evaporation data.

4.1.1 Rainfall and Evaporation Analysis

Available site rainfall data extends from June 1993 to April 2010. This data has beencollected in accordance with the EPL 4033. The current license requirement is the collectionof daily rainfall using a rainfall gauge. Valid data must be reported for at least 80% of theannual return period.

For the purposes of assessing the operation of the void as water storage, it was considerednecessary to use a dataset that included at least 20 years of continuous daily rainfall data.Therefore, rainfall data from the Bureau of Meteorology (BOM) Toronto WWTP Station(located approximately 5.9 km to the south east of Westside Mine) was obtained andreviewed. The period of data obtained extended from 1972 through to 2010. Over this period,there were 12 months with no rainfall data (mostly during 2002). Therefore, daily rainfall datafrom the BOM Edgeworth WWTP station (located approximately 4.4 km to the north east ofWestside Mine) were used to fill the data gaps. Average monthly evaporation data wassourced from the BOM Williamtown RAAF Station (located approximately 25 kilometres tothe northeast of Westside Mine).


A comparison between the site rainfall data and BOM data, and statistical analysis of BOMdata, are included in Appendix D. It was considered that the adoption of BOM data for thepurposes of assessing the final void is appropriate. The rainfall reported between 1972 and2010 was applied over a 37 year period from 2012 to estimate inflows into the final voidstorage upon completion of mining.

It should be noted that the adoption of historical rainfall data for further projections does nottake into consideration potential variations in rainfall and evaporation patterns as a result ofclimate change.

4.1.2 Calculation of Water Inflows

The model used to represent the water balance for the final void was Goldsim Version 9.6(Goldsim Technology, 2007). This software is a graphical object orientated system simulationsoftware for completing either static or dynamic systems. It is like a “visual spreadsheet” thatallows one to visually create and manipulate data and equations.

Simulation, in this context, is defined as a process of creating a model of a system (such as amine water management system) in order to identify and understand the factors that controlthe system performance or predict (forecast) the future behaviour of the system.

The water balance modelling was completed using:

Daily time steps (the shortest period of data available).

Runoff from the void catchment was represented by an initial loss/runoff factor – this wasused to convert daily rainfalls into surface runoff values when the daily rainfall hasexceeded the initial loss of rainfall (infiltration which is subsequently transpired byvegetation). The void catchment area is shown in Figure 4.

Groundwater inflows were calculated externally to the Goldsim model using the Darcyanalytical equation.

4.1.2.1 Model Structure

The model was configured to represent the water cycles of the final void as series ofelements, each containing preset rules and data linked to represent the water transferaround the water cycles. The overall structure of the model is shown in Figure 5.

With the completion of open cut mining, it is believed that the void will be left as a capturepoint for catchment and groundwater inflows. A water cycle was modelled that consisted ofthree components: catchment runoff, groundwater inflow and evaporation.

Based on the final void landform and seam contours, a number of assumptions andapproximations were made in regards to the physical dimensions of the final void and itsrepresentation in the final surface:

Bottom of the void: approximately -14.7 m AHD.

Level at which void will spill to Diega Creek: approximately 12 m AHD. The spillway willbe located in the north east part of the void. To reduce potential for flows over thespillway it is proposed to install a low flow pipe approximately 0.8 m below the level of thespillway.


Void catchment area: 80 ha.

Total void storage: approximately 3470 ML (before discharge to Diega Creek).

Pasture/grassed/revegetated area initial loss: 10 mm.

Impervious area initial loss: 2.5 mm.

4.1.2.2 Groundwater Inflows

The final void walls will be battered with Awaba tuff at a slope of no more than 18 degrees toimprove wall stability and safety. The batter will form a barrier between the exposed coalseams and void space, reducing the inflow of coal seam groundwater into the void. TheGreat Northern seam is currently exposed along the southern and south-eastern walls of thevoid, while the Fassifern seam is currently exposed along the southern, eastern and northernwalls.

The Darcy equation in the following form was used to estimate groundwater inflows:

Q = KibL

where:

Q = inflow (m3/day) into the final void, assumed to be primarily from coal seams.K = hydraulic conductivity of the Awaba tuff (assumed to be 0.009 m/day).I = hydraulic gradient across the Awaba tuff.b = thickness of the seepage face (m).L = length of seepage face (m).

Hydraulic conductivities are based on data reported in Pacific Power (1997) CooranbongColliery Life Extension Project: Overburden Strata Groundwater Study, and AustralasianGroundwater & Environmental Consultants Pty Ltd (AGE) (2007) Statement of EnvironmentalEffects – Groundwater for Newstan Colliery. The hydraulic conductivity adopted for Awabatuff is at the higher end of the range reported in these documents for non coal seam stratawithin the upper Newcastle Coal Measures.

The hydraulic gradient was assumed to be the difference between the groundwater head atthe seam face behind the batter and the elevation of the seepage face along the batter,divided by the thickness of the batter between the seam face and seepage face. The head atthe seam face was assumed to be 20 m for both seams, which is the anecdotal level ofunderground water within the old Rhondda Colliery workings to the southeast of the void.The thickness of the seepage face along the batter was assumed to be half the thickness ofthe coal seam, which was assumed to be 5.5 m for the Great Northern seam and 8.5 m forthe Fassifern seam. The length of the effective seepage face was assumed to be 250 m forthe Great Northern seam and 855 m for the Fassifern seam. For a void with no water, thehydraulic gradient across the Awaba tuff was calculated to be approximately 0.5 for seepagefrom the Great Northern seam and 0.3 for seepage from the Fassifern seam. The hydraulicgradient and groundwater inflow into the void reduces as the water level in the void rises.

Based on these assumptions, future groundwater inflows into the final void were calculatedto range from 2.1 to 4.7 ML/year (depending on the level of water in the void). Therelationship between groundwater inflow and void water level is shown in Figure 6.

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LEGEND

o© 2010. While GHD has taken care to ensure the accuracy of this product, GHD and GEOSCIENCES AUSTRALIA, WESTSIDE MINE, GHD, DEPARTMENT OF LANDS make no representations or warranties about its accuracy, completeness or suitability for any particular purpose. GHD and GEOSCIENCES AUSTRALIA, WESTSIDEMINE, GHD, DEPARTMENT OF LANDS cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred as a result of the product being inaccurate, incomplete or unsuitable in any way andfor any reason.

Date 25 JUN 2010

Oceanic Coal Australia LimitedFinal Void Management Plan

Westside MineLocal Catchment to Mine Void

Data Source: Geosciences Australia: Topography - 2007; Westside Mine: Elevation Data - 2010; GHD: Catchment Boundaries - 2010; Department of Lands: Cadastre - 2007. Created by: tmorton, pcgmcdiarmid


1:11,157 (at A4)

HEATONSTATE

FOREST

SLATE

YCREEK

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CKLEC

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EEK

MINMI CREEK

TORO

NTO

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AWABA ROAD

SYDNEY

NEW

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GEORG

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O OTHDRIVE

KILLINGWORTH

SEAHAMPTON

MINMI

AWABA Locality Map

RailwayWatercourseContour (2m)

Final SurfaceContour (0.5m)Cadastre

Westside Lease BoundaryProposed Final VoidMine Void Catchment


Figure 5 Final Void Water Cycle

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Figure 6 Relationship Between Groundwater Inflow and Water Level

It is not considered that there will be outflow of water from the void to the coal seams. Sincegroundwater continues to be intercepted following completion of mining, a groundwaterinterception licence will need to be maintained.

4.1.2.3 Total Inflows

The mean predicted values for each of the elements over the simulated period (37 yearsfrom completion of mining) are provided in Table 2. Also provided are the respectiveminimum and maximum values in brackets to give an indication of the range of likely values.


Table 2 Annual Water Transfers – Final Void

Element Average Annual Transfer Rate (ML/yr)

Evaporation 394.6 (470.95-73.58)

Catchment Runoff 474.6 (1001.49-208.14)

Groundwater Inflow 2.89 (4.7-2.16)

Void Spill / Discharge 7.27 (261.73-0)

Based on available data and assumptions, the model indicates that the final void would filland discharge to Diega Creek after approximately 17 years. In year 18, total discharge isestimated to be about 260 ML, occurring over 20 days. Therefore the rate of discharge overthis period is estimated to be 13 ML/day. The discharge coincides with a high rainfall year, inparticular a 1 in 20 to 1 in 100 rainfall event (based on 24 hours duration) recorded forToronto WWTP in February 1990. Therefore flow in Diega and Cockle Creeks would begreater during this period and would provide additional dilution to the overflow. Thediscussion in Section 5.3 outlines how the likely impacts of the final void storage on theenvironment are not considered significant, regardless of whether the void fills or not.Preliminary weir calculations have shown that a typical spillway 18 m wide and 0.5 m highwould adequately control this overflow.

Figure 7 shows the estimated change in water storage volume within the final void over the37 years following the completion of mining in 2012. The associated change in void waterlevel is shown in Figure 8. The estimated total void storage of 3470 ML is predicted to bereached after 17 years (in year 2029). Between years 2030 and 2049, the void is estimatedto remain at between 60 to 70% capacity and no further discharges are predicted. The fall instorage volume following discharge in 2029 is the result of the greater influence ofevaporation (based on BOM rainfall and evaporation data). Note that the predicted storagevolumes are based on actual rainfall and evaporation recorded over a 37 year period, asdiscussed in Section 4.1.1. If these patterns of rainfall and evaporation vary in the future, thedischarge pattern may be different.

Note that predicted water transfers are based upon a mix of data as follows:

Relatively reliable data:

BOM rainfall and evaporation data.

Monitored rainfall data at Westside Mine.

Surface catchment areas based on topographic maps.

Seam floor elevations.

Less reliable data:

Site infiltration rates for normal and revegetated catchment areas.

Estimates of storage capacities.

Triangulation of surface information provided.


Hydraulic conductivity of Awaba tuff batters.

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18/11/2010 10/05/2016 31/10/2021 23/04/2027 13/10/2032 5/04/2038 26/09/2043 18/03/2049

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Figure 7 Estimated Rise in Water Storage Volume within the Final Void

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Figure 8 Estimated Change in Void Water Level


As a result of the items listed within the “less reliable data” category there is likely to be a riskthat the provided estimates may be inaccurate. It is suggested that the individual predictionsgiven above should be considered reliable to +/- 30% until more data is gathered.

It should be noted however, that a low flow discharge pipe approximately 0.8 m below anappropriately engineered spillway is proposed to be constructed to reduce the potential forsignificant spikes in discharge volumes following rainfall events and allow for variation in thereliability of water transfer data.

4.2 Partial Backfilling

Part of the final void may be used as a long term storage facility for coarse CWR. Any futureproposals to use the voids or part thereof for such a purpose would require approval from theNSW DoP, as well as a Section 100 approval under the Coal Mine Health and Safety Act2002 from the Department of Industry and Investment (DII). Consultation with DII hasindicated that they have no objection to the emplacement of coarse CWR material atWestside Mine.

The transport of coarse CWR from OCAL’s MCPP to Westside Mine was assessed inSection 4.17 of the Westside Mine Southern Extension Environmental Impact Statement(Umwelt, 2002). Details regarding the transport of the CWR material will also be outlined inthe revised Westside Mine Materials Management Plan. The transport of CWR material fromMCPP to Westside Mine would use the OCAL private haul road and therefore not require theuse of public roads.

The maximum volume of coarse CWR to be supplied to Westside Mine by the MCPP isdependent on the reject emplacement opportunities at MCPP including the results of a trial toemplace tailings in the Teralba Colliery underground workings and a trial to emplace coarsereject on the existing tailings dam. Dewatering of the void may be necessary prior toemplacement of coarse CWR. It is likely that the more water stored in the void prior toemplacement the greater the dewatering rate required. It is considered that the rate ofdewatering would be limited by the volumetric discharge limits in EPL 4033. The total volumeof the void to the maximum expected emplacement height for the partial backfill option isapproximately 6 Mbcm (million bulk cubic metres).

Coarse CWR from the Newcastle Coalfields is typically low in pyritic material and composedprimarily of clay minerals, quartz and carbonates. It therefore tends to produce a slightlyalkaline leachate. An analysis of leachate from CWR sourced from the MCPP has beencarried out to identify any surface water or groundwater impacts that may occur as a result ofthe long term emplacement of CWR at Westside Mine. Results are included in Appendix E.The coarse CWR from the MCPP was found to be moderately alkaline (pH 9.8), which isindicative of the presence of carbonate minerals.

Upon completion of backfilling, as required, the area will be capped so that there is nopotential for spontaneous combustion. The area would then be revegetated with speciesnative to the area.

As shown in Appendix C, a free draining landscape would be created under the partialbackfilling option. Water management would involve the construction of a sedimentationbasin downstream of the backfilled void, designed to cater for the five day 95th percentileevent in accordance with Managing Urban Stormwater: Soils and Construction Volume 2EMines and Quarries. The embankment and spillway associated with the sediment basin willbe designed and constructed to be structurally sound to cope with a 100 year AverageRecurrence Interval (ARI) design storm event. This nominated design criterion has beenselected based on the sedimentation basin being a structure that provides for control of


sediment while revegetation is occurring with the expected duration of disturbance beinggreater than three years and the receiving environment being sensitive. It is currently notintended to remove the sediment basin in the longer term as there is no justification of thisadditional disturbance of the area.

This sedimentation basin would cater for 95% of the average annual rainfall applied to thetotal catchment area. The captured runoff would then need to be treated, as required, prior tobeing discharged. From experience with discharge water from Westside Mine and MCPP thewater that would be discharged would not have any significant adverse impact on DiegaCreek (Sections 5.3 and 5.4). The quantity of the discharged water will be variabledepending upon the total rainfall and the intensity of the rainfall.

If the selected final void option requires a sedimentation basin to be built, the Westside MineSoil and Water Management Plan will be reviewed to incorporate required changes for themanagement of the sedimentation basin and also nominate any other additional measuresthat could be incorporated to further improve the management of sediment and erosioncontrol.

4.3 Long-Term Land Use

The long-term land use with both options (either using the void as a water storage or partialbackfilling of the void) is for the area that is not part of the water storage to be revegetatedback to natural bushland which is in harmony with the surroundings. The rehabilitation wouldbe carried out so that the area is self sustaining with a water management arrangement thatrequires minimal maintenance.

After OCAL has completed mining operations in the surrounding area, the Westside Minearea including the final void could be identified for development. This development will onlyproceed after development consent is obtained following appropriate environmental studies.Possible uses of the site could include a recycling facility that is able to store materials thatare unable to be recycled. Other uses may include a recreation area or aquaculture whichuses the water storage.

It is planned to carry out rehabilitation of the area as far as practicable in a way that does notcompromise the potential future uses of the site.

Any environmental assessment for future use of the site following mining operations wouldinclude assessment of measures required to maintain public safety.


5.0 Control Measures

The aim of this FVMP is to address the risks identified by OCAL as being associated with thefinal void. Consultation has been undertaken with relevant government departments andcommunity members to assist in identifying risks to be addressed. The principal areas ofincreased potential hazards were identified as being:

Safety hazards to employees, contractors and general public.

Contamination into adjacent waterways and groundwater.

Leachate from the coarse CWR contaminating surface water and groundwater.

Final void slope instability (low wall and high wall).

Spontaneous combustion event.

5.1 Employee, Contractor, Visitor and Public Safety

At mine closure, one of the main priorities for the final void will be to render it safe forhumans, livestock and wildlife. In order to achieve this, the following key activities have or willbe considered:

Instability of the low wall can induce failures or mass movement. To ensure the stability ofthe low walls they will be battered back to a long term stable design.

Instability of the high wall can also induce failures and mass movement. All high walls onsite will be remediated and material built against them so that the hazard of failure andhumans/fauna falling from these structures is eliminated.

Where possible fill against the exposed coal seams will be covered with inert material toprevent ignition either from spontaneous combustion, bushfires or human interference.

Maintain access tracks on site for adequate bushfire management and inspection.

Danger signs showing the risk to public safety and prohibiting public access have beenerected at intervals along the fence adjacent to Wakefield Road.

5.2 Final Void Slope Stability

5.2.1 Low Wall Slope Stability

Stability of the low wall will be achieved in the following manner:

The low walls will be battered back from the angle of repose (~37°) to a maximum of 18°with the design of 14° to ensure long term slope stability.

Conventionally, permanent rehabilitated coal mine slopes are designed to a factor ofSafety (FoS) of between 1.3 to 1.5. The slope stability of the final void slopes have beenanalysed by OCAL using appropriate material strengths, slope geometries and


groundwater levels. Throughout the modelled slope stability analyses the lowest slopestability factor of safety achieved was greater than 1.5.

Within the Northern Rehabilitation area of Westside Mine these similar slope angles haveproved to be conducive to successful rehabilitation and in keeping with the surroundingtopography.

Surface water drainage on and over the low wall will be minimised through theconstruction of drainage control structures.

Erosion of the low wall will be controlled by limiting the length of slope through the use ofcontour and graded drains, minimising the slope, and by the establishment of suitablevegetation.

All low wall areas will be revegetated in accordance with the Mining Operation Plan(MOP).

5.2.2 High Wall Slope Stability

For the purposes of this document the high wall is comprised of undisturbed, solid materialoccurring at the mining perimeter adjacent to Diega Creek and Wakefield Road to the eastand southern sides of the final void. The high wall material comprises of a range of naturallyoccurring soil or rock materials of varying strengths or states of weathering.

To ensure the safety of the final void, the surrounding final high wall slopes will be left in acondition where the risk of slope failure is minimised. They will be treated in the samemanner as the low walls, whereby they are backfilled against and battered to a maximum of18° with a goal of 14° being optimal. By providing this significant volume of backfill with arelatively low slope angle against the high walls it will give a high factor of safety.

5.3 Water Quality

5.3.1 Surface Water

Once mining at Westside Mine is complete and the final void is used as water storage, it islikely that there will be a substantial drop in the volume of water discharged to Cockle Creekvia discharge point 16. This could result in a reduction in the electrical conductivity in thedownstream water and is likely to result in a reduction in the load of suspended solidsdischarged to the creek. Although there will likely be a water quality improvement in thevicinity of the discharge point, the reduction in flows downstream of the site may impact thelocal aquatic environment.

Once the final void has filled to its maximum capacity there will be a period of discharge toDiega Creek, although water transfer modelling reported in Section 4.1 indicates that this willnot be a continuous long term discharge. It is likely that the quality of this discharge water willbe similar to the current water quality at discharge point 16, resulting in a temporary changein water quality and flow in Diega Creek. Further, the likely higher flows within Diega andCockle Creeks during the discharge (since it is likely to occur during a high rainfall event) willminimise any water quality or flow impacts. Hence, any impacts to the environment resultingfrom discharge from the final void water storage are not considered to be significant or longterm.


The water quality in Diega and Cockle Creeks will be monitored in accordance with thelegislative requirements at the time. It may be necessary to apply for a new licence dischargepoint for Diega Creek if discharge is to occur in the future.

If the emplacement of CWR was to occur within the final void, water would be extracted, asrequired, prior to emplacement and discharged at a licensed discharge point in accordancewith license conditions and limits. It is not considered that the discharge of this extractedwater would have any additional impacts to the current approved discharge at dischargepoint 16.

5.3.2 Groundwater

As identified in Section 3.3, there does not appear to be any beneficial use of alluvialgroundwater for domestic or agricultural use in the area down gradient of Westside Mine.Therefore, any changes to alluvial groundwater levels or quality may result in impacts to theenvironment only i.e. surface water and Groundwater Dependent Ecosystems (GDEs) if theyexist in this area.

A review of groundwater levels in Diega Creek alluvium (based on data from monitoring wellN2178) suggests a slight increase over the period 2002 to 2010. There is no evidence tosuggest that there has been a loss of groundwater from the Diega Creek alluvium as a resultof mining of the Southern Extension. Further, there is no evidence to suggest thatgroundwater quality in Diega Creek alluvium has been impacted by mine water. It is unlikelythat filling of the final void will impact Diega Creek alluvium, particularly due to the batteringof the void walls with low permeability Awaba tuff. This barrier will minimise seepage of waterout of the void. Temporary overflow of water from the final void to Diega Creek maytemporarily increase the electrical conductivity of groundwater within Diega Creek alluvium.

5.3.3 Predicted Quality of Water Discharge

Westside Mine has collected a large amount of data on mine water quality discharges fromoperations in the East pit. Typical water quality results are shown in Table 3. The mine wateris typically suitable to be discharged directly to Cockle Creek in accordance with the EPL.

Table 3 Typical Water Quality of Current Westside Mine Discharge

Parameter Unit Reported Result

Electrical Conductivity S/cm 6700

pH pH units 7.6

Total Suspended Solids mg/L 2

5.3.3.1 Electrical Conductivity

The predicted water quality of any discharge from the final void is expected to have a lowerconductivity than the current mine water discharge since the more saline water would bedeeper within the void and lower saline water would tend to be at the surface near thedischarge point. In addition, discharges will generally coincide with high rainfall events whichwill likely reduce the overall salinity of the water and also reduce the pH of the water to moreneutral levels.


5.3.3.2 pH / Acidity

The pH data collected as part of historical water quality monitoring indicates that acid minedrainage is not an issue at Westside Mine. If the void is to be left as it is post mining, themajority of material on the northern, southern and eastern slopes will be comprised of theFassifern seam interburden material which is the Awaba Tuff/Claystone. The Western slopesof the void will comprise of a mixture of Great Northern seam overburden and Fassifernseam interburden with soil partially covering the western slope. These overburden and soiltypes have been analysed for a suite of soil tests by the Department of Lands Sconeresearch laboratory. The Awaba Tuff material has a pH in the alkaline range of approximately8.2 to 8.4. The Great Northern seam overburden and associated soils are slightly acidic inthe range of 5.1 to 5.5, although these pH levels are not indicative of oxidised sulfideminerals and associated clay minerals that would form acid mine drainage.

5.3.3.3 Total Suspended Solids

The saline groundwater inflow that occurs provides a natural flocculent which can settle outsuspended solids in the mine water. In regard to discharges from the final void, it isconsidered that the water in the final void will have sufficient salinity to provide someflocculation of suspended solids and hence the TSS of any discharges will likely remain low.

5.3.3.4 Heavy Metals

Heavy metal analysis that has been undertaken on current Westside Mine discharge waterhas generally not reported elevated concentrations with respect to ANZECC/ARMCANZ(2000) default trigger values and concentrations reported for Cockle Creek (both upstreamand downstream of Westside Mine). Therefore, it is not expected that heavy metalconcentrations in final void discharges will result in environmental impacts.

As discussed in Section 5.3.1, the likely higher flows within Diega and Cockle Creeks duringthe discharge (since it is likely to occur during a high rainfall event) will minimise any waterquality impacts.

5.4 CWR Leachate

As discussed in Section 4.2, an analysis of local CWR leachate has been carried out toidentify any surface water or groundwater impacts that may occur as a result of the long termemplacement of CWR at Westside Mine. Results are included in Appendix E.

The coarse CWR material is moderately alkaline (pH 9.8), which is indicative of the presenceof carbonate minerals. Metal concentrations are relatively low and reflective of the naturalmineralogy of the interburden materials. Minor detections of polynuclear aromatichydrocarbons (PAHs) are likely attributable to the natural organic/coal content of the CWR.

A distilled water leach (ASLP) was undertaken to determine the properties of CWR leachateunder natural rainfall conditions. The pH of the leach water rose from 7.8 to 9.1 as a result ofinteraction with CWR. It is considered that mobilisation of metals would be limited at this pH.Concentrations of metals in the leachate were consistently below the ANZECC/ARMCANZ(2000) freshwater trigger values for the protection of 95% aquatic ecosystems with theexception of aluminium and zinc. These metals are typically abundant in natural aquaticsystems and are likely to pose minimal impacts to Diega and Cockle Creeks. Heavy metal


monitoring in Cockle Creek (at the upstream and downstream monitoring locations) iscurrently being undertaken on a monthly basis in accordance with the EPL.

There were also minor detections of PAHs in the CWR leachate. There were noexceedances of ANZECC/ARMCANZ (2000) trigger values where they are available(naphthalene). It is considered that baseline concentrations of PAHs in Diega and CockleCreek should be established prior to the emplacement of CWR at Westside Mine.

5.5 Spontaneous Combustion

While spontaneous combustion has not occurred at Westside Mine, it has been included inthis FVMP for reference as it is can be an issue associated with final voids, particularly wherecoal seams (and other carbonaceous materials) are left exposed (i.e. not capped orcovered). There is also the possibility that a bushfire post closure could ignite the seams ifthey were in close proximity to the fire.

Should any outbreaks of spontaneous combustion occur during the final years of miningoperations, details of the materials involved, presence of pyrites, location, date, time andclimatic conditions will be recorded on surveyed plans. These areas will be assessed atclosure to ensure appropriate mitigation measures are in place to minimise the likelihood ofspontaneous combustion occurring post mine closure. These areas would also be includedas part of the ongoing inspection and monitoring that will be required following closure of themine and before final lease relinquishment.

In the case of the emplacement of CWR at Westside Mine, the control of spontaneouscombustion of coarse reject material will be undertaken in accordance with the processesadopted at the MCPP. These are included in Appendix F.


6.0 Monitoring and Communication

6.1 Consultation Regarding this Plan

The draft version of this FVMP was provided to the DoP, DII, NSW Office of Water (NOW)and Lake Macquarie City Council (LMCC) for comment. Comments received from theagencies were used to prepare the final version of the plan. The comments are provided inAppendix G as well as where they are addressed in this FVMP.

6.2 Monitoring and Maintenance of the Water ManagementSystem

Post mining inspections of the site will include the monitoring of:

Water quality as per the EPL requirements.

Monitoring of pH, electrical conductivity, suspended solids and water levels in the finalvoids and dams.

Ongoing monitoring of groundwater levels and groundwater quality.

Revegetation progress of disturbed areas.

Scour or sedimentation of drains or basin outlets.

From the inspections, if the type and/or location of sediment and erosion control strategiesprove to be ineffective, modification of the control structures will be undertaken. Additionalinspections will be undertaken during and after high rainfall events to ensure theeffectiveness of the controls. Regular inspections will involve completion of inspection reportsto alert the requirements of modification and/or desilting. Desilting of the structures will becarried out before the efficiency of the structure is impeded; this can be assessed mainlythrough visual assessment. Inspections of the structural integrity of the structures will also beassessed to ensure their on-going effectiveness.

6.3 Reporting

The results of final void control measures adopted will be reported in a monthlyenvironmental checklist. Requirements for corrective actions identified during monthlyinspections will be reported to the Westside Mine Operations Manager for approval andactioning.

Discharges from the current licensed discharge points will continue to be monitored andreported on in accordance with EPL conditions. An annual return will be submitted on anannual basis for the Westside Mine EPL.

Reporting of final void management will be undertaken in the Annual EnvironmentalManagement Reports provided to DII, DoP, NSW Office of Water, LMCC and the WestsideMine Community Consultative Committee.


6.4 Corrective Action

Work practices and activities are analysed for potential risk to the environment in accordancewith the OCAL procedure EMS-P-001 Ongoing Identification of Aspects and Impacts.

On receipt of an incident/complaint reporting form, site inspection non-conformance ormonitoring result that indicates a non-conformance with the EPL. The OCAL Environmentand Community Coordinator is to undertake an investigation and recommend corrective orpreventative action. Any non-conformances will be investigated to determine the source orevent(s) that led to the non-conformance and if possible, measures taken to minimise thepossibility of a re-occurrence. The OCAL Environment and Community Coordinator is toreport all non-conformances to the Westside Mine Operations Manager.

6.5 Complaints Resolution

A procedure for handling complaints has been implemented as part of the OCAL EMS. Theprocedure EMS-P-005 Community Complaint and Environmental Incident ManagementProcedure ensures a consistent approach to managing any complaints. All legitimatecomplaints are thoroughly investigated to determine the cause. Initial contact will be made,where possible, with the complainant within 24 hours of receiving the complaint.

A 24-hour complaint response line has been established via the Westside Mine normaltelephone number to facilitate the procedure. The mine telephone number appears on allcorrespondence and information leaflets to neighbours and is prominently displayed at themain entrance to the mine site. All complaints will be documented and filed in the WestsideMine EMM. Documentation will include the date and time of the complaint, the complainant'sname and contact phone number, who received the complaint, the initial response to thecomplaint, any necessary further response actions, and feedback from the complainant.

The complaints register is reported to the Community Consultative Committee (CCC)showing complaint details and responses. The number and nature of complaints is also to bereported in the AEMR.


7.0 Auditing and Review

This FVMP is to be reviewed as directed by the Director-General of DoP, or prior to theimplementation of significant changes to the management of the final void at Westside Mine.The review process is to be conducted in consultation with the relevant government agenciesand should reflect changes in environmental requirements and changes in technology oroperational procedures. Auditing of the FVMP will also occur in accordance with theWestside Mine EMS.


8.0 References

ANZECC/ARMCANZ (2000). Australian and New Zealand Guidelines for Fresh and MarineWater Quality.

Australasian Groundwater & Environmental Consultants Pty Ltd (AGE) (2007) Statement ofEnvironmental Effects – Groundwater for Newstan Colliery.

Department of Environment and Climate Change (2008). Waste Classification Guidelines.Department of Environment and Climate Change NSW, Sydney.

EMS-P-001 Ongoing Identification of Aspects and Impacts.

EMS-P-005 Community Complaint and Environmental Incident Management Procedure.

Pacific Power (1997) Cooranbong Colliery Life Extension Project: Overburden StrataGroundwater Study.

Umwelt (Australia) Pty Ltd (2002). Westside Mine Southern Extension Environmental ImpactAssessment. Prepared for Oceanic Coal Australia Limited.


Appendix A

Development Consent DA 125-5-2002


Condition 4.4 Void Management

(a) The Applicant shall, at least two years prior to completion of mining from the Southern Extensionof Westside Mine, prepare a Final Void Management Plan to the satisfaction of the Director-General, in consultation with the DMR, DLWC, and LMCC. The Plan shall include, but not belimited to, the following:

(i) details of a strategy for the long term management of the final voids and the watercontained in them;

(ii) strategies that shall be implemented to minimise any adverse impacts where theassessment indicates the potential for degradation to surrounding water resources;and

(iii) any further requirements as set out at that time through consultation with the Director-General, DMR, DLWC, and LMCC.


Appendix B

Correspondence with the NSW Department of Planning



Appendix C

Final Void Cross Sections (3V:1H)




Appendix D

Rainfall and Evaporation Data Analysis


A comparison between the site and BOM data was undertaken for the period between 1972and 2010 and the outcomes are provided in Figure 9. It was determined that the two sets ofrainfall data are comparable and therefore adoption of the Toronto and Edgeworth WWTPstation rainfall data will provide a reasonable representation of the rainfall at Westside Mine.

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Figure 9 Comparison Between Site Rainfall Data and BOM Data

The statistics for the BOM rainfall data set are as follows:

Minimum annual rainfall – 676 mm in 1980.

Average annual rainfall – 1171 mm.

Median annual rainfall – 1083 mm.

Maximum annual rainfall – 1856 mm in 1990.

Monthly rainfall statistics were also determined for the period of record and selected statisticsare provided in Figure 10. The average monthly rainfalls were observed to vary from a low ofapproximately 58 mm in October to a high of approximately 149 mm in February. Figure 10shows a considerable variation in the maximum recorded monthly rainfalls, with themaximum monthly value being approximately 564 mm in February to a lowest maximummonthly value of approximately 145 mm in July.


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Figure 10 Monthly Rainfall Statistics

An analysis of the rainfall data was undertaken to enable an understanding of the likelyrainfall patterns at the site. For various intervals of daily rainfall, the average number of daysper year which fall within each interval are presented in Figure 11. The graph also presentsthe cumulative days per year as a percentage against the same rainfall intervals.

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Figure 11 Number of Rain Days of Various Magnitudes


As presented in Figure 11, the average number of non rainfall days per year is approximately239, which is greater than 65% of days in a year, while the number of rain days receivingless than 5 mm of rainfall is approximately 19%.

The data presented within Figure 11 was amended to exclude days without recorded rainfallto enable a more detailed view of the data. As presented in Figure 12, the amount of rainfalling on any one day decreases for rainfall greater than 5 mm. On average, approximately15% of days in the year receive greater than 5 mm of rain with approximately 3% of days inthe year receiving greater than 25 mm of rain.

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Figure 12 Daily Rainfall Magnitudes

Average monthly evaporation data was sourced from the BOM for Williamtown RAAF Station(located approximately 25 kilometres from Westside Mine). This information was reviewedand the average monthly evaporation rates were input to the Goldsim model. The averagedaily evaporation estimated for Westside Mine is presented in Figure 13. The average annualevaporation rate for the Williamtown RAAF Station was approximately 1731 mm, comparedto the annual average rainfall of 1092 mm. This gives an annual deficit (difference betweenannual rainfall and annual evaporation) of approximately 639 mm.


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12

34

5

67

8

Janu

ary

Februa

ryMarc

hApri

lMay

June Ju

ly

Augus

t

Septem

ber

Octobe

r

Novem

ber

Decem

ber

Month

Ave

rage

Eva

pora

tion

(mm

/day

)

Figure 13 Average Daily Evaporation Rates


Appendix E

CWR Leachate Results

Table E1 CWR Leachate Analysis ResultsFi

eld

ID

Sam

ple

Dat

e

Initi

al p

H

Fina

l pH

Alu

min

ium

Ars

enic

Bar

ium

Ber

ylliu

m

Bor

on

Cad

miu

m

Chr

omiu

m (V

I)

Cop

per

Lead

Man

gane

se

Mer

cury

Mol

ybde

num

Nic

kel

Sele

nium

Silv

er

Zinc

Fluo

ride

Ace

naph

then

e

Ace

naph

thyl

ene

Ant

hrac

ene

Ben

z(a)

anth

race

ne

Ben

zo(a

)pyr

ene

Ben

zo(b

)fluo

rant

hene

Ben

zo(g

.h.i)

pery

lene

Ben

zo(k

)fluo

rant

hene

Chr

ysen

e

Dib

enz(

a.h)

anth

race

ne

Fluo

rant

hene

Fluo

rene

Inde

no(1

.2.3

.cd)

pyre

ne

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htha

lene

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anth

rene

Pyre

ne

Tota

l PA

H

mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/L mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg0.1 0.1 50 5 10 1 50 1 2 5 5 5 0.1 2 2 5 2 5 0.1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 -

CWR 28-May-08 9.8 - 5640 9 250 <1 <50 <1 2 15 22 334 0.2 <2 2 <5 <2 40 <0.5 <0.5 <0.5 0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 0.6 <0.5 <0.5 0.8 2.5 0.7 5.1

mg/L mg/kg mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L

0.055 0.013a - - 0.37b 0.0002 0.001b 0.0014 0.0034 1.9b 0.0006 - 0.0011 0.0011 0.00005 0.008b 16ASLP 12-Jun-08 7.8 9.1 4.18 <0.01 1 <0.01 0.3 <0.05 <0.01 <0.01 <0.01 <0.01 <0.0001 0.01 <0.01 <0.01 <0.01 0.08 0.3 <1.0 <1.0 2.2 <1.0 <0.5 <1.0 <1.0 <1.0 <1.0 <1.0 3 1.3 <1.0 3.8 10.8 2 23.1

Exceeds ANZECC 95% Protection for Freshwatera As(V) for 95% as it is the more conservative valueb 99% values recommended for chemicals that bioaccumulate.

ANZECC 95% Protection forFreshwater

PAHMetals

Units

UnitsLOR


Appendix F

Spontaneous Combustion Control Measures


Extraction from S126 Application at MCPP


Appendix G

Government Agency Consultation


The following table provides the comments received from Government Agency Consultationand where they are addressed in the FVMP.

Government Agency Comments OCALResponse /Location

Department of Planning1. Understanding of the FVMP would be improved by the inclusion ofcross-sections (probably 2 would be enough) through the plannedvoid and the relative levels and locations of Cockle and Diega Creeksand the flooded workings in the coal seams.

Figure 4 added

2. The FVMP is required to consider "the creation of a free-draininglandscape". The only version of the landscape that has been presented isa "fill and spill" landform for the void.

Section 4.2

3. There does not seem to have been any consideration of "the long-termland use of the reshaped landform and the surrounding areas and ensurethat these are compatible".

Section 4.3

4. There does not appear to be any detail provided on how the successof the FVMP would be monitored.

Sections 6.2,6.3, 6.4, 7.0

5. No details of the size and volume of the final void or how muchmaterial (CWR) would be able to be emplaced in the void.

Sections 4.0,4.2

6. Why do values of predicted annual groundwater inflow differbetween the base of page 11 (2.1 to 4.7 ML) and Table 2 (2.16 to 2.98)?

Table 2revised

7. I find the outcome for predicted discharges from the void to be highlyunusual as presented in Figure 7. Is it a realistic expectation that therewould be no discharge from the void for 17 years, then have a dischargeof 260 ML for a single year; and then to revert to no further discharge forthe modelled period. I find it very hard to believe that this prediction isrealistic.

Modellingbased onactual rainfalland evap data.Section 4.1

8. The section on water quality (section 5.3) should be supported by dataon existing water quality and predicted quality of water discharge and ananalysis of the potential impacts of this water on Diega Creek. Shouldthese impacts be other than benign, then the option of piping dischargesto tidal areas for discharge should be explored.

Table 3 andSection 5.3.3

D I & I1. Consist of plan(s) and supporting text to document a process ofdesign, planning and management procedures for final rehabilitation ofthe area (as identified in the MOP).

To be done aspart of MineClosure MOP

2. Identify final rehabilitation procedures and completion criteria whichsatisfy the MOP condition.


3. Provide documentation text in accordance with the Department's MOPGuidelines.


4. State the preferred option and potential alternative post-mining landuse for the final void.

Section 4.3and to be doneas part of MineClosure MOP

5. Provide safe access to the pit void floor and security against publicaccess to steep slopes, ramps endwalls and highwalls.

Section 5.1

6. Predict both the Standing Water Levels (SWL) in the final void and thewater quality.

Figure 9,Section 5.3.3



7. Outline the drainage arrangements of the surrounding rehabilitatedlandform. Note: Is drainage to be preferentially directed into or away fromthe final void? Illustrate the interceptor drain around the perimeter of finalslopes to redirect runoff from over low wall crest.

Figure 4

8. Discuss the occurrence of any residual carbonaceous material or coalseams which may cause spontaneous combustion and/or acid leachateand outline any control procedures.

Sections 5.3.3,5.4, 5.5

9. Provide a time frame of final mine sequence to establish the final voidconfiguration after coaling is completed.

Section 4.1.2.3

10. Outline the rehabilitation procedures for final void configuration:shaping method and equipment used, erosion control structures,topdressing and revegetation, geotechnical slope stability analysis of finaldesign slopes.Note: General reference guidelines for final landforms may be found inSection 5.2 Landscaping from Mine Rehabilitation Handbook – AustralianMining Industry Council.

Sections 4.2,4.3, 5.2.1,5.2.2

11. Outline the Maintenance and Monitoring arrangements andresponsibilities.

Sect 6.0

LMCC – Comments from the Sustainability Department1. Whilst the potential land use of the final void is for water storage, thereport does not identify any end use for this storage. For example, minelakes may be used for wildlife conservation, irrigation, as a potable watersource, for recreation or aquaculture. Without a clear end use, it is verydifficult to ascertain whether the proposed storage method is adequate interms of water quality, safe access, and impact on the surroundingenvironment for this prescribed end-use.

Section 4.3

2. The expected increase and decrease in flow volumes, whilstdescribed as short term, are significant. To ensure adequate protection tothe downstream environment, suitable discharge levels should beestablished in response to actual rainfall and water storage volumes.This would ensure that environmental flows could be produced whenneeded and likewise discharge events to avoid overspill of the proposedweir. Such measures would significantly reduce the impact ondownstream eco-systems, channel stability, and water quality. Channelstabilisation would be required with any new discharge points using scourprotection techniques such as quarry rock and geotextile.

Section 4.1.2

3. The proponent should be encouraged to consider a beneficial end-use for the final void that has an environmental benefit, either throughrehabilitation of the site or converting the site to a usage that negates theneed for additional clearing. For instance, there are examples of suchsites being used for waste disposal in order to avoid clearing a bushlandsite for the same purpose.

Section 4.3

LMCC – Comments from the Development Assessment and Compliance Department1. Provide detailed cross sections within the Management Plan toillustrate the final treatment of the void for both land-use options identifiedin part 4.0 of the report.

Figure 4

2. Include specific Geotechnical advice for the treatment of the voidbatters including the long-term impact for slope stability, given the extentand location of the coal seams and taking into consideration the

Sections 5.2.1,5.2.2



groundwater inflow. Include a Geotechnical Assessment as part of theManagement Plan.3. The statement in Part 4.1.2.3 of the Management Plan under “lessreliable data,” suggests that the individual predictions for total inflows intothe void should only be considered reliable to +/- 30% accuracy untilmore data is gathered. This should be further examined with the aim ofhaving more accurate predictions for the total water inflows.

Section 4.1.2.3

4. The option of partial backfilling of the void with coarse coal washeryreject (CWR), should be further expanded to outline the volumes of CWRexpected, the impacts on Council’s roads in respect to haulage routesand the ongoing management and maintenance of the void area. If thepartial filling option was to occur it is likely to take a considerable time topartially fill the void, which should be quantified in the Management Plan.Note this option does not seem to satisfy the requirements of theDepartment of Planning in its letter dated 4/5/10, which states:“emplacement of coal rejects in the final void in terms of: -volumes ofrejects likely to be emplaced; and –effect of rejects on both surface andgroundwater quality.”

Sections 4.2,5.3.3, 5.4

5. Provide additional comments in the Management Plan to identify thePublic Safety issues in respect to the long-term management of the voidincluding details of the future ownership of the site.

Sections 4.3,5.1

6. Provide an Acid Sulfate Soil assessment report for both options forthe treatment of the void, with particular emphasis on the partial fillingoption for imported CWR.

Assessmentincluded inSections 5.3.3,5.4

LMCC – Environmental ManagementThe mine leachate and run off waters presently flow into Diega Creek,which feeds into the headwaters of Cockle Creek.Following decommissioning of the open cut activities, there will be anoverall reduction of flow to the creeks, which will lower the creek waterlevels. This may have some impact on the aquatic environment, more soDiega Creek and the upper reaches of Cockle Creek.The consultant has identified a reduction of electrical conductivity inthose waters, but a lowering of suspended solids.Whilst my area of expertise is not aquatic ecosystems, I think that therewill be a corresponding reduction in dissolved oxygen levels which maycause aquatic die off and eutrophication of the upper areas of both Diegaand Cockle Creek. The flow reduction rate to Diega Creek will be immediate, and the voidcould take up to 17 years to fill. Following this period, overflow from thevoid will occur, and be directed once again to the creek system.The resulting water quality may be highly alkaline due to the coal rejectwaste, but mobilisation of metals, according to the consultant will beminimised because of this high pH. The resulting flow to the creeks afterthe void has filled will be related to rainfall surface water run off. The information provided is not definitive in terms of final water quality,any treatment needed to it and end result.

Section 5.3



LMCC - Integrated Planning

In relation to the management plan note that the zoning of the land isproposed to change from the current Zone 9 Natural Resources to acombination of SP1 Special Activities (Mine) and E2 EnvironmentalConservation, as shown on the attached draft zone map.

It is suggested that you review the proposed zoning and land use table(extract attached) to determine if you wish to make a submission on thedraft Lake Macquarie LEP 2011 once it goes on public exhibition laterthis year.

OCAL proposeto make asubmission onthe LMCC LEP2011

Documents

Westside Mine Final Void Management Plan EMP-WO-ECP-012 · Westside Mine Environmental Management Plan Revision No. 1 Date: August 2010 Review Due: June 2013 File: Final Void Management