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Microsoft Word - eps bull edit final for EPA with pics.docArgyle Diamond Mine - Underground Project 110 km south of Kununurra, East Kimberley
Argyle Diamond Mines Pty Limited
Report and Recommendations of the Environmental Protection Authority
Environmental Protection Authority Perth, Western Australia
Bulletin 1205 November 2005
03/06/2004 Referral received
28/06/2004 Intention to set EPS Level of Assessment advertised (no appeals) 3
- EPA accepts scoping document (if one provided) -
Proponent’s Final EPS document received by EPA 28/10/05
EPA report to the Minister for the Environment; Science 14/11/05
ISBN. 0 7307 6846 5 ISSN. 1030 - 0120 Assessment No. 1606
Contents Page
4-1 Impacts to Hydrology................................................................................................... 8
4-2 Biodiversity –Terrestrial flora and fauna and subterranean fauna ............................. 12
4-3 Rehabilitation, Decommissioning, Closure and Rehabilitation ................................. 16
5. Conclusions ................................................................................................................... 19
6. Recommendations ........................................................................................................ 21 Tables Table 1 Summary of key proposal characteristics ..................................................................... 2 Figures Figure 1. Regional Location of Argyle Diamond Mine Operations .......................................... 4 Figure 2. Argyle Diamond Mine Lease Areas and Surrounding Stations.................................. 5 Figure 3. Location of the Proposed Works for the Underground Mine ..................................... 6 Appendices 1. References 2. Recommended Environmental Conditions and Proponent’s Consolidated Commitments
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1. Introduction This report provides the advice and recommendations of the Environmental Protection Authority (EPA) to the Minister for the Environment on the environmental factors relevant to a proposal by Argyle Diamond Mines Pty Limited (Argyle) to develop an underground mine and associated infrastructure, which will be located at their current open cut diamond mine site. The EPA was advised of the underground proposal in June 2004. Based on the information provided, the EPA considered that while the proposal had the potential to have an effect on the environment, the proposal could be readily managed to meet the EPA’s environmental objectives. Consequently it was notified in The West Australian newspaper on 28 June 2004 that, subject to preparation of a suitable Environmental Protection Statement (EPS) document, the EPA intended to set the level of assessment at EPS. The proponent has prepared the EPS that accompanies this report (Argyle, 2005). The EPA considers that the proposal described can be managed in an acceptable manner subject to the commitments to the proposal being legally binding. The EPA therefore has determined under Section 40 (1) that the level of assessment for the proposal is EPS, and this report provides the EPA advice and recommendations in accordance with Section 44 (1). 2. The proposal
Argyle proposes to further extend the life of the current open pit mine by developing an underground mine and associated infrastructure at the same site. The proposal is described in detail in Section 2 of the proponent’s “Argyle Diamond Mines – Underground Project, Environmental Protection Statement,” EPS document (Argyle, 2005). The Argyle Diamond Mine is located approximately 110 kilometres (km) south of Kununurra in the East Kimberley region of Western Australia (Figure 1). Mining commenced in the main Argyle ore body (referred to as AK1) in 1985. Open pit mining is currently scheduled to cease in 2008 with the processing of ore to be completed by the end of 2009. An additional resource in the northern section of the open pit, referred to as the Northern Bowl, is currently being investigated and if mined may extend the open pit processing operation until 2012. In order to extend the life of mine to around 2024, a feasibility study was undertaken to assess the development of an underground mine and associated infrastructure at the site. The underground proposal will be next to and under the existing open cut mine accessing the AK1 ore body (Figure 3). The Exploratory Decline was subject of a proposal under the Diamond (Argyle Diamond Mines Joint Venture) Agreement Act 19981-1983 which was submitted to the Minister for State Development in June 2003 and approved in August 2003. The development of the underground Exploratory Decline commenced in December 2003. The lamproite pipe that contains the diamondiferous ore is approximately 1.5km long and ranges between 150-500m wide, and extends to approximately 600m below the planned final base of the AK1 pit (Figures 2 and 3). It is proposed that the ore body will be mined in two stages using both block cave mining and sub level cave mining from 2008. Stage 1 involves mining the Upper Block and Southern Tail Block. The proposed completion date for Stage 1
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is 2017. Stage 2 involves mining the Lower Block and it is proposed to commence in approximately 2017 and be completed by 2024. The underground proposal will also include the construction of a new Tailings Storage Facility (TSF2) and a new Reclaim Pond (RCP3). The proposal is described in detail in Section 4 of the proponent’s EPS. The key components of the proposal are detailed in Table 1 below. Table 1: Key Proposal Characteristics of the Argyle Underground Mine Proposal
Element Underground Project
Life of Mine Around 20 years Mining depth Maximum of 675m Mining Methods Stage 1 Upper Level Block Cave mining
Stage 2 Sub Level Cave mining Major Project Components
Underground Declines Underground Mining Levels Underground and surface conveyors Box cut portal Surge bin Secondary crusher Extension to some existing surface infrastructure Temporary ore and waste stockpiles Laydown areas Refrigeration plant Bulk Air Cooler and fans Exhaust shafts Services corridor Dewatering system New Tailings Storage Facility New Reclaim Pond
Refer to Figures in the EPS especially 3-6, 4-1 and 4-2
Total Ore Production Stage 1 - 60 Mt Stage 2 – 37 Mt
Ore Processing Through existing Processing Plant at around 8 Mtpa for Stage 1 and 4.5 Mtpa for Stage 2
Key materials Ground support construction materials Fibrecrete Explosives Electric cables, pipes and ventilation ducting Diesel fuel Concrete Steel
4, 700 t 330,000 t 15,000 t 6,000 t 26 ML 24,000 m3 5,000 t
Total Waste Rock Over Project Life 4.3 Mt Dewatering Requirements 19 – 83 ML/day Crater Area Mostly within the existing open pit and
waste rock dump area Tailings 100 Mt TSF2 Area of Disturbance 126 ha
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RCP3 Area of Disturbance 133 ha Underground mine water requirements 700 kL/day Processing water requirements 12, 000 - 22,000 kL/day Water Supply From dewatering operations, Gap Dam,
Upper Limestone Creek Waste Rock Dump Seepage Retention Dam, Reclaim Ponds, and if necessary, Lake Argyle.
Power Requirements Additional 4 - 12 MW Power Supply Ord Hydroelectric Scheme, with the deficit
to be provided for an initial 2-3 years by the on site diesel power station until alternative power supply established
Heavy Vehicle Movements Offsite – reduce from 12 per day to 1-2 per day On site – Reduce from 670 hours/day to 36 hours/day
Construction Workforce Maximum of around 500 Total Workforce Around 450
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Figure 1: Regional Location of Argyle Diamond Mine Operations (Argyle, 2005)
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Figure 2: Argyle Diamond Mine Lease Areas and Surrounding Stations (Argyle, 2005)
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Figure 3: Location of the Proposed Works for the Underground Mine (Argyle, 2005)
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3. Consultation During the preparation of the EPS, the proponent has undertaken consultation with key stakeholders including government agencies, the Traditional Owners, the Kimberley Land Council, Environs Kimberley and local communities. In addition to the Traditional Owner groups that were involved in Indigenous Land Use Agreements (ILUA), the proponent also consulted with an additional 30 Aboriginal communities and 24 community organisations in the East Kimberley. Argyle has applied the stakeholder input obtained from the 2002-2003 consultation programme activities to identify issues and to assist in the scoping of the studies to be undertaken for the exploratory decline, the underground project and during the preparation of the EPS. Argyle has been working with the Kimberley Land Council (KLC) and Traditional Owners since 2001 to establish an ILUA. This ILUA was signed in September 20004 and was registered with the National Native Title tribunal in April 2005. In the ILUA the Traditional Owners provided their consent for past, present and future mining operations including the proposed underground mine (Argyle, 2005). The traditional owners also agreed that the current mining area is acceptable in relation to Aboriginal heritage. Further information on Aboriginal sites is addressed in Section 3.17 of the EPS (Argyle, 2005). In addition to the ILUA, a management plan agreement has been established to address the day-to-day relationship between Argyle and Traditional Owners. This additional agreement contains management plans that address issues including Aboriginal site protection, land access and land management. Argyle will continue to liaise with the key stakeholders and government agencies during the operational and closure stages of the proposal and has provided a summary of consultation in Appendix E of the EPS document. The main issues raised by stakeholders during meetings held with the proponent during preparation of the EPS were:
• Indigenous Land Use Agreements (ILUA) and heritage protection; • dewatering and impact on springs, flora and fauna, acid rock drainage and tailings
management; and • rehabilitation, closure and decommissioning.
The EPA considers that hydrological impacts, biodiversity, and mine rehabilitation and closure to be the most important issues and these are addressed in Section 4.
4 Relevant environmental factors The summary of all of the environmental factors and their management is outlined in Table ES2 of the EPS, pages xx-xxvii, (Argyle, 2005). It is the EPA’s opinion that the following are the environmental factors relevant to the proposal which require assessment in this report: a) Impacts to Hydrology; b) Biodiversity –Terrestrial flora and fauna, subterranean fauna; and c) Decommissioning, Closure and Rehabilitation
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The EPA considers that the remaining factors can be adequately managed through the proponent’s environmental management plans (EMPs), which have been presented with the EPS document, Appendix G. The proponent has made a commitment to implement the EMPs.
4-1 Impacts to Hydrology
Description The project area is within the Ord River catchment, upstream of Lake Argyle and is drained by four creeks (Flying Fox, Smoke, Limestone and Wesley Spring Creek). The depth to groundwater beneath the plains is generally within 15 m of the ground surface. There are also a number of springs in the area, the closest being Devil Devil Spring and Tjamindum/Nanbum (Wesley Spring). It is thought the dewatering may have the greatest potential impact on these two springs. Dewatering will occur as part of this underground project. Dewatering, as well as the construction and operation of the underground mine, will cause changes to the local hydrological conditions. Potential impacts could include:
• change in local and regional aquifer pressures; • leakage of groundwater from the shallow alluvial zone; • change of runoff in surface drainages; • loss of yield at the Springs; • change in groundwater quality; and • those relating to post mining recovery of groundwater levels.
Dewatering for the underground mine was computer modeled to determine impacts on local and regional groundwater systems. Groundwater level declines were identified as having the potential to impact on spring hydrology and biodiversity. Drawdown caused by dewatering is predicted to expand outward along the east and west ridges for distances of around 4km and 7km respectively (Argyle, 2005). The total predicted drawdown at the proposed completion date in 2024 is shown in figure 6.1 of the EPS. Hydrological studies indicate that groundwater will need to be removed from the underground mine at an average rate of 4ML/day at the completion of open cut mining to around 10ML/day towards the completion of the underground mine in 2024. Groundwater modeling has indicated that although groundwater pressures will be affected in the area, no significant changes to surface runoff in local drainages, shallow aquifer hydrology, and groundwater quality will result. In the event that any adverse impacts are detected near the springs, the proponent has developed plans to manage the impacts. Dewatering for the open pit mine has already dewatered the rock strata near Devil Devil Spring and therefore the spring no longer flows during the dry season. Wesley Spring is located to the southwest of the mine and to date has not been affected by dewatering operations for the open pit. Wesley Spring is located approximately 1km from the predicted area of drawdown and it may have a number of source areas. It is possible that these source areas will be impacted from dewatering, therefore indirectly impacting on Wesley Springs. Given seepage to Wesley Spring Creek is likely to be sourced through elevated groundwater storage that is depleted during the dry season, this spring may naturally cease to flow during extreme dry spells.
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Leakage of groundwater may affect the recharge process within the predicted depressurisation zone (see figure 3-7 of EPS) extending beneath the south of the southern water rock dump (Argyle, 2005). The rate of leakage is estimated at 3.3% of the average annual rainfall. However, since the rate of leakage is low, and the potential impact location is near the mine pit and southward of the southern waste rock dumps (WRDs), predicted impacts on vegetation are low and are discussed further in section 4.2. As part of total site operations Argyle currently monitors groundwater for both water quality and level in order to identify any potential impacts from mining operations. Argyle will expand the monitoring program with the proposed underground operations. Argyle (2005) has predicted that, following the completion of mining operations, groundwater levels will recover, due to the contribution from groundwater seepage and annual runoff during the wet season over a period of 150 years. Acid Rock Drainage (ARD) has also been identified as a potential issue for the project. An ARD Management Plan has been prepared that allows for characterisation, selective placement, and minimisation of rainfall infiltration into potentially ARD forming materials. Collection of seepage from waste rock dumps and monitoring of dewatering discharge, groundwater and surface water will also occur to identify if ARD products are entering the environment. Acid rock drainage (ARD) will cause an impact when runoff and seepage containing sulphides and magnesium sulphate (MgSO4) enters the environment resulting in adverse impacts. On the Argyle lease area deposits of MgSO4 have been recognised as a symptom of ARD from WRDs (Argyle, 2005), although nothing has been directly identified in the underground proposal area. Studies are also to be carried out to determine the ecological impacts of ARD products such as MgSO4 in the environment. To be able to control the ARD material in the WRDs, Argyle will control the flow of oxygen and water flow through the material. Argyle is investigating control methods to do this. Potential acid forming materials will be placed in ‘cells’ within the WRDs, in areas that are not susceptible to erosion. The cells would be effectively sealed from air and water by the use of low permeable covers and barriers or inert waste rock material (Argyle, 2005). The other method will be to control surface water flow over the WRDs by designing them for water shedding or by constructing ‘a store and release cover system’ which will lower the rainfall infiltration into any potentially acid forming materials. The controls will minimise the formation and movement of primary and secondary ARD products with the seepage from the site (Argyle, 2005). Assessment The area considered for assessment is the lease area where the underground project infrastructure will be constructed and surrounding areas that may become affected by dewatering. The EPA’s environmental objectives for this factor are:
• to ensure that lowering of groundwater due to dewatering operations does not cause adverse impacts on local hydrology and the environment; and
• to ensure that ARD does not cause adverse impacts on the environment. The EPA notes that dewatering activities in the AK1 open pit have already lowered local groundwater levels around the pit and surrounds and will continue to do so until the end of mine life. Development of the underground mine will further expand the dewatered zone around the mine until Stage 2 mining is completed. Cessation of dewatering at the end of
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mining will result in groundwater levels recovering over many decades to form a partially water-filled crater-lake. To date, Wesley Spring has not been affected by dewatering operations for the open pit and hydrogeological modelling has indicated that impacts on the spring due to dewatering for the proposed underground operations are unlikely. However, on advice from the Department of Environment (DoE) the proponent developed a Wesley Springs Management Plan (WSMP) (Appendix G - B17, Argyle, 2005) as a contingency measure in case dewatering activities do affect the spring. The EPA notes that the WSMP outlines monitoring and reporting protocols that will be followed in the event of changes to the typical groundwater and surface water conditions. Argyle has committed to minimising adverse impacts to Wesley Spring in all its forms. In addition to existing hydrological data for the spring, a variety of methods will be used to collect further baseline conditions within 3 months of the start of underground development. The proponent has consulted with the DoE in order to explore potential management options should impacts on Wesley Spring occur in the future. The intent of this early consultation was to reduce time lag associated with development of triggers and management actions at a later stage. Potential management actions in the event of adverse impacts on Wesley Spring include:
• determining baseline flow rates, pond dimensions, groundwater elevations and creek vegetation;
• monitoring of the above parameters; • identifying and evaluating any changes, including the cause of the change, to the
above parameters; • consulting with Traditional Owners on proposed management measures; and • implementation of agreed management actions.
The management measures that may be implemented should impacts be identified will include:
• replenishment of the surface water using either redirected surface water runoff or groundwater;
• replenishment of the groundwater aquifer zones. Any replenishment that may be considered and the various sources or replenishment water will firstly be discussed with the Traditional Owners and then the regulatory authorities prior to any actions being implemented (Argyle, 2005). Artificial Recharge is not an option due to the beliefs of the Traditional Owners. The EPA notes that Argyle has produced the WSMP. However, advice from the DoE to the EPA raised concerns regarding the WSMP, which commits to consultation, but to date has no prescriptive actions. The EPA recommends that Argyle set up a ‘site team’ to develop a Wesley Spring response strategy. On advice from DoE the ‘site team’ should include Argyle environmental personnel, a groundwater specialist, and staff from the Water and Rivers Commission in an overview capacity (draft recommended condition 8). The response strategy would develop probabilities of environmental impacts on the spring, mathematically model the impacts and then devise sound response actions. Once this strategy is in place, then the company would have a modelled response prepared in advance of any impact triggers, and
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could immediately engage in discussions with traditional owners on the management actions available. Traditional Owners and Argyle have also prepared and agreed upon a Management Plan for Devil Devil Spring. Presently, groundwater levels for Devil Devil Spring are approximately 120mAHD, well below the surface elevation of the spring, and are expected to drawdown a further 70m to approximately 50mAHD by the end of mine life in 2024. No further impacts on Devil Devil Spring are anticipated to occur as a result of this proposal as there is no hydraulic connection between the spring and the dewatered groundwater system. Baseline groundwater elevations, groundwater and surface water quality information, and spring vegetation health will be determined prior to the start of underground mine development. The EPA considers that these measures will provide adequate baseline data in order to assess any future impacts. Groundwater and surface water conditions will continue to be monitored following the characterisation of baseline conditions. The hydrological model will be recalibrated if predicted and actual groundwater responses differ. This will assist…

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