Referral of proposed action

Project title: TSF4 wall raise

1 Summary of proposed action 1.1 Short description An increase in tailings storage capacity of the existing tailings cell, Tailings Storage Facility number 4 (TSF4), is proposed to extend the life of TSF4 for an additional five years. TSF4 is expected to reach its current design height of 30m by December 2017. The proposed action is to increase the wall height to 40m for the continued storage of tailings produced from the existing process plant. Raising the wall height of TSF4 delays the need to construct an additional tailings cell. Activities to raise the TSF4 wall height will be wholly located within the boundaries of the existing site. Existing environmental management and mitigation measures already successfully employed at Olympic Dam will be used. The likelihood of any significant impact from increasing the height of the wall on the environment is expected to be very low to negligible. 1.2 Latitude and longitude Latitude Longitude location degrees minutes seconds degrees minutes seconds point

NW corner -30 26 26.16 136 49 11.17 NE corner -30 26 7.55 136 49 58.87 SE corner -30 26 56.12 136 50 12.25 SW corner -30 27 7.40 136 49 23.54

1.3 Locality and property description The wall raise will be carried out on the existing TSF4 tailings cell, located on the Olympic Dam special mining lease (SML) and within the boundaries of the Olympic Dam mine site. The nearest communities include the township of Roxby Downs approximately 16km to the south, established in 1988 to service the Olympic Dam operation and house the majority of the workforce. Current population of Roxby Downs is around 4,000. Other nearby communities include Andamooka, approximately 30km to the east, and Woomera, approximately 90km to the south. 1.4 Size of the development 200 ha footprint or work area (hectares) 1.5 Street address of the site Not applicable

1.6 Lot description Volume 5140 Folio 575 (Sections 1475 and 1516 Out of Hundreds (Andamooka)) 1.7 Local Government Area and Council contact (if known) Not applicable. 1.8 Time frame Wall raising occurs on a continuous basis at a rate between approximately 1 and 1.5 m per year (maximum 2 m per year). Wall height is expected to reach 30m by December 2017 and will continue to 40m after that date, with completion expected around September 2023.  Commence: December 2017  Completion: September 2023

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1.9 Alternatives to proposed No action

X Yes, you must also complete section 2.2

1.10 Alternative time frames etc X No

Yes, you must also complete Section 2.3. For each alternative, location, time frame, or activity identified, you must also complete details in Sections 1.2-1.9, 2.4-2.7 and 3.3 (where relevant). 1.11 State assessment No

X Yes, you must also complete Section 2.5

1.12 Component of larger action No X Yes, you must also complete Section 2.7 1.13 Related actions/proposals X No Yes, provide details: 1.14 Australian Government X No funding Yes, provide details: 1.15 Great Barrier Reef Marine X No Park Yes, you must also complete Section 3.1 (h), 3.2 (e)

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2 Detailed description of proposed action 2.1 Description of proposed action The existing operations at Olympic Dam comprise an underground mine, mineral processing plant and associated infrastructure located within the Special Mining Lease. The waste streams resulting from the processing of are managed in separate facilities, which include the Tailings Retention System (TRS) with two active Tailings Storage Facilities (TSFs) for tailings solids and Evaporation Ponds (EPs) for tailings liquor. An aerial view of the existing TRS, showing the location of the proposed activity is shown in Figure 1.

Figure 1: Layout of Olympic Dam operations showing TSFs Tailings disposal flowsheet The tailings from the minerals extraction process are produced as underflow from the counter-current decantation (CCD) thickeners at the process plant. Part of the underflow stream can be split off and directed to the tailings deslimes plant, where the coarse fraction is extracted by hydrocycloning for use in cemented aggregate fill (CAF), which is used for mine backfill. The cyclone overflow (slimes) is thickened in the slimes thickener and the underflow from this thickener is recombined with the remainder of the CCD underflow in the tailings surge tank. The tailings are then pumped from the surge tank to the tailings storage facility. The existing pipelines carrying the slurry to the storage cells comprise four 400 mm diameter high density polyethylene lined steel pipelines, which are laid above ground on concrete supports. The pipelines lie within bunded corridors for their entire length. A typical schematic diagram of the tailings flow sheet is presented as Figure 2. Supernatant liquor and storm water runoff from the tailings storage cells is decanted into the evaporation ponds. A flow stream from the evaporation ponds is pumped back to the process to reduce liquor inventory and gain some benefit from contained product metals. Only small volumes can be taken back to the circuit due to the high chloride content affecting the recovery of .

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Figure 2: Schematic of the tailings disposal circuit Current cell operating configuration TSF4 and TSF5 are operated by cycling the tailings flow approximately 40% to TSF4 and 60% to TSF5. The rate of rise for TSF4 is currently 1.5 m/year and 1.3 m/year for TSF5 which is well below the design maximum of 2 m/year. Construction methodology The perimeter embankments are raised by the upstream technique (see cross-section Figure 3), constructed using a compacted 50:50 mixture of tailings and suitable embankment fill. The raise height is typically 1 to 1.5 m constructed in one raise per year. The thin layer deposition of the tailings and long drying times (controlled by the rate of rise) promote the over- consolidation of the tailings (through desiccation) to ensure that the strength of the tailings exceeds the minimum strength used in the design analysis. To restrict the egress of radon, a 0.5 m clay barrier layer covers the external face, protected by 0.5 m rock armouring.

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Figure 3: Typical TSF4 wall raise detail Timing of proposed activity At current production rates, TSF4 will reach its current design height of 30m (131 AHD) in December 2017 (Figure 4).

Figure 4: TSF4 crest level Proposed action The proposed action is to increase the current design height of TSF4 to a maximum crest elevation of RL141 m (total wall height of 40m above ground level). In doing so the tailings storage capacity of TSF4 will be

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increased and the life extended by an additional five years. TSF4 will continue to be operated and raised as per existing operational procedures. The corresponding area, storage capacity and predicted operating rate of rise are shown in Table 1 for the proposed design height, compared with the current approved height and an intermediate elevation (RL136 m). The geometry of the embankment remains unchanged with a downstream slope of 2.75H:1V (approximately 20°). The rate of rise will be less than the maximum design rate of rise 2.0 m/y. Table 1: TSF4 proposed design

Units Approved Design Intermediate Proposed Final Height Design Height RL (AHD) m 131 136 141 Area ha 168 162 154 Storage capacity M m3 48.4 55.5 64.8 Slopes H:V 2.75:1 2.75:1 2.75:1 Rate of rise m/y <2.0 1.60 1.70 Forecast date to Dec-17 Sep-20 Sep-23 reach height By raising the embankment height of the existing TSF4 to 40m, it will:  Reduce total land disturbance (over the life of mine)  Maximise the use of the current facility footprint  Delay the land disturbance and costs associated with constructing a new TSF  Not increase current seepage rates experienced  Not increase avifauna interactions (by delaying construction of a subsequent TSF, and the corresponding increase in TSF area.)  Maintain embankment factors of safety as recommended by ANCOLD  Not increase worker or public radiation exposure from Olympic Dam (which are currently well within compliance limits.) 2.2 Alternatives to taking the proposed action Due to the requirement for ongoing tailings storage capacity, as a result of the continued operation of the mine and processing plant, taking no action is not a feasible alternative. As noted in section 2.1 above (see current cell operating configuration) TSF4 is operated in conjunction with TSF5 by cycling tailings deposition between the two cells. An alternative that was considered was the use of TSF5 only. However, this option causes the rate of rise of tailings in the cell to exceed the safe design maximum of 2 m/year, as well as causing additional production issues at the process plant. A feasible alternative, and one that remains the option in the event that the design height of TSF4 is not increased, is to construct and commission a new tailings cell. This option is not preferred primarily because of the associated increased environmental impacts of additional land clearing (approximately 200 ha) and the heightened risk to avifauna from increased TSF surface area. Construction of a new TSF also has a high capital cost. Increasing the design height of TSF4 delays the requirement for an additional tailings cell by approximately five years. 2.3 Alternative locations, time frames or activities that form part of the referred action Not applicable 2.4 Context, planning framework and state/local government requirements Western Mining Corporation Limited (WMC) discovered the Olympic Dam deposit in 1975, and formed a joint venture with BP Group in 1979 to develop the project. In April 1993, WMC (Olympic Dam Corporation) Pty Ltd purchased BP Group’s share. Following the BHP Billiton Group takeover of WMC Resources Ltd in June 2005, WMC (Olympic Dam Corporation) Pty Ltd became a member of the BHP Billiton Group and changed its name to BHP Billiton Olympic Dam Corporation Pty Ltd. The Olympic Dam operation has government approval following three previous environmental impact assessments (EIS; Kinhill-Stearns Roger 1982; Kinhill 1997; BHP Billiton 2009, 2011). Following the initial approval underground mining and production commenced in 1988. Conditional approval to produce up to 350,000 tonnes per annum (tpa) of plus associated products was obtained following the 1997 EIS.

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Approval was obtained from the South Australian and Commonwealth governments in October 2011 to further expand the mine to up to 750,000 tpa copper (contained in products) through the construction of an open pit mine, additional processing facilities and associated infrastructure. In 2012 BHP Billiton took the decision to defer the open pit expansion and investigate alternative mining and processing technologies. Olympic Dam operates subject to a number of other acts, licenses and approval conditions including: • The Roxby Downs (Indenture Ratification) Act 1982 (Ratification Act) – The Act provides statutory authority for an agreement (Indenture) between BHP Billiton and the State of . The Indenture establishes the legal framework for existing and future operations at Olympic Dam and defines the roles and responsibilities of the South Australian Government and BHP Billiton • Environmental Protection and Management Program (EPMP) – The EPMP is a requirement of both the Indenture and the South Australian and Commonwealth government approvals of October 2011. It defines ODC’s commitments and obligations relating to protection, management and rehabilitation of the environment. • SA Environment Protection Authority (EPA) License 1301 – authorisation to undertake activities of environmental significance under the Environment Protection Act 1993 subject to certain conditions. • License LM1 – issued under the Radiation Protection and Control Act 1982 for standards relating to the Code of Practice and Safety Guide for Radiation Protection and Radioactive Waste Management in Mining and Mineral Processing (ARPANSA) • Special Water Licenses (SWLs) – ODC has two SWLs, issued under the Indenture, which provide conditional authorisation to extract water from the Great Artesian Basin for supply to the operation. 2.5 Environmental impact assessments under Commonwealth, state or territory legislation Under the Code of Practice and Safety Guide for Radiation Protection and Radioactive Waste Management in Mining and Mineral Processing (ARPANSA) (enforced through ODC’s licence LM1 under the Radiation Protection and Control Act 1982) ODC is required to inform the EPA of the proposal to change the design height of TSF4 and the EPA may direct that a new Radiation Management Plan or Radioactive Waste Management Plan be submitted for authorisation. 2.6 Public consultation (including with Indigenous stakeholders) In July 2010, ODC received conditional approval from the Minister for Aboriginal Affairs and Reconciliation, in accordance with the Indenture and the Aboriginal Heritage Act 1979 to;  excavate land within the Special Mining Lease (SML) (the Application Area)  explore for any items of Aboriginal Heritage; and  remove or otherwise interfere with any items of Aboriginal Heritage that may be within the Application area, whether or not those items have been identified, are known or recorded The TSF4 wall raise will be located within the Application Area referred to in the approval. As TSF4 is a currently operating facility, further public consultation is not considered to be warranted. 2.7 A staged development or component of a larger project TSF4, and the proposed action, are a part of the ongoing operations of Olympic Dam which received approval under the Environment Protection (Impact of Proposals) Act 1974 on 30 June 1998. See section 2.1 for further details.

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3 Description of environment & likely impacts

3.1 Matters of national environmental significance 3.1 (a) World Heritage Properties

Description There are no World Heritage properties within 500km of the site of the proposed action. Nature and extent of likely impact Significant impacts are considered extremely unlikely.

3.1 (b) National Heritage Places

Description The nearest National Heritage place is the Witjira-Dalhousie Springs, several hundred kilometres to the north. Nature and extent of likely impact Significant impacts are considered extremely unlikely.

3.1 (c) Wetlands of International Importance (declared Ramsar wetlands)

Description The nearest Ramsar wetland is the Coongie Lakes, several hundred kilometres to the north-east. Nature and extent of likely impact Significant impacts are considered extremely unlikely.

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3.1 (d) Listed threatened species and ecological communities

Description Baseline flora and fauna surveys were conducted for the Olympic Dam operation for the 1982, 1997 and 2009/2011 EISs. Extensive monitoring and reporting of fauna and flora and the impacts of the operation has also been carried out since commencement of the operation, resulting in extensive datasets of fauna and flora species known to occur in different habitats within the area. The environmental features of the Olympic Dam area, including an assessment of listed threatened species and ecological communities within the broader impact footprint of the potential expansion, were comprehensively described and assessed in the 2009 Olympic Dam Expansion Draft Environmental Impact Statement (BHP Billiton 2009), and the 2011 Supplementary Environmental Impact Statement (BHP Billiton, 2011). Both documents are available for download at: http://www.bhpbilliton.com/home/aboutus/regulatory/Pages/default.aspx#013_Copper (accessed 06/01/2014) A localised search of the TSF4 area using the EPBC search tool reported four listed threatened species. There are no threatened ecological communities. Birds  Acanthiza iredalei iredalei (Slender Billed Thornbilll) – Vulnerable, species or species habitat known to occur within area.  Amytornus modestus (Thick-billed Grasswren) – Vulnerable, species or species habitat known to occur within area. Mammals  Macrotis lagotis (Greater Bilby) – Vulnerable, species or species habitat known to occur within area. Previously locally extinct, this species was reintroduced to Arid Recovery in 2000 and has been recorded breeding outside Arid Recovery on the SML and surrounding pastoral properties.  Pseudomys australis (Plains Rat) – Vulnerable, species or species habitat known to occur within area.

Nature and extent of likely impact TSF4, as described in section 2, is a currently operating facility, with the height of the walls currently being raised to the current design height of 30m as part of normal operating procedure. The proposed action intends to continue this process as normal, with the only difference being a change in the final design height from 30m to 40m. Neither the surface area of the TSF nor any of the operating procedures will change as a result of the proposed action. A small amount of additional monitoring will be undertaken. No additional environmental impact will occur.

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3.1 (e) Listed migratory species

Description See 3.1 (d) above. A localised search of the TSF4 area using the EPBC search tool reported five listed migratory species, and six listed marine species (five common to both lists). Migratory marine birds (including listed marine species)  Apus pacificus (Fork-tailed Swift) – Species or species habitat likely to occur within area Migratory terrestrial species (including listed marine species)  Merops ornatus (Rainbow Bee-eater) – Species or species habitat likely to occur within area Migratory wetland species (including listed marine species)  Ardea alba (Great Egret, White Egret) – Species or species habitat likely to occur within area  Ardea ibis (Cattle Egret) – Species or species habitat likely to occur within area  Charadrius veredus (Oriental Plover, Oriental Dotterel) – Species or species habitat likely to occur within area Other listed marine species Pandion haliaetus (Osprey) – Species or species habitat likely to occur within area. Not recorded within the OD SML area. Nature and extent of likely impact As noted at 3.1(d) above, neither the surface area of the TSF nor any of the operating procedures will change as a result of the proposed action. As such no additional environmental impact will occur.

3.1 (f) Commonwealth marine area (If the action is in the Commonwealth marine area, complete 3.2(c) instead. This section is for actions taken outside the Commonwealth marine area that may have impacts on that area.) Description The proposal is over 500 kilometres from the Commonwealth marine area. Nature and extent of likely impact Significant impacts are considered extremely unlikely.

3.1 (g) Commonwealth land (If the action is on Commonwealth land, complete 3.2(d) instead. This section is for actions taken outside Commonwealth land that may have impacts on that land.) Description There is no Commonwealth land in the vicinity of the proposal. Nature and extent of likely impact Significant impacts are considered extremely unlikely.

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3.1 (h) The Great Barrier Reef Marine Park

Description The proposal is in South Australia and will not affect the Great Barrier Reef Marine Park. Nature and extent of likely impact None.

3.1 (i) A water resource, in relation to coal seam gas development and large coal mining development

Description Not applicable. Nature and extent of likely impact

3.2 Nuclear actions, actions taken by the Commonwealth (or Commonwealth agency), actions taken in a Commonwealth marine area, actions taken on Commonwealth land, or actions taken in the Great Barrier Reef Marine Park

3.2 (a) Is the proposed action a nuclear action? X No Yes (provide details below) The action is not considered to be a nuclear action. Olympic Dam, and the associated tailings storage facilities, is an approved operation. None of the method or volume of tailings disposal, the operation of the TSF or the method of TSF wall construction change as a result of this proposal.

3.2 (b) Is the proposed action to be taken by the X No Commonwealth or a Commonwealth agency? Yes (provide details below) If yes, nature & extent of likely impact on the whole environment

3.2 (c) Is the proposed action to be taken in a X No Commonwealth marine area? Yes (provide details below) If yes, nature & extent of likely impact on the whole environment (in addition to 3.1(f))

3.2 (d) Is the proposed action to be taken on X No Commonwealth land? Yes (provide details below) If yes, nature & extent of likely impact on the whole environment (in addition to 3.1(g))

3.2 (e) Is the proposed action to be taken in the X No Great Barrier Reef Marine Park? Yes (provide details below) If yes, nature & extent of likely impact on the whole environment (in addition to 3.1(h))

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3.3 Other important features of the environment The project area is wholly contained within the bounds of the SML at the existing Olympic Dam site. The environmental features of the site, including the aspects listed below, were comprehensively described and assessed in the 2009 Olympic Dam Expansion Draft Environmental Impact Statement (BHP Billiton 2009), and the 2011 Supplementary Environmental Impact Statement (BHP Billiton, 2011). Both documents are available for download at: http://www.bhpbilliton.com/home/aboutus/regulatory/Pages/default.aspx#013_Copper (accessed 06/01/2014) and cover the information requested under subsections 3.3 (a) to 3.3 (m) below. The following descriptions describe important features in the general region of Olympic Dam. The area is arid to semi-arid with high summer temperatures and low rainfall. TSF4 itself was approved for construction and commissioning in January 1999 and has been in continuous use since that time. The area is therefore highly disturbed. 3.3 (a) Flora and fauna Surveys of the immediate area of the SML and Roxby Downs have identified 242 native flora species and 45 introduced species, 14 of which are declared weeds. Fauna species include 184 birds, 29 mammals, 47 reptiles and one amphibian. 3.3 (b) Hydrology, including water flows The area around Olympic Dam receives very little rainfall (the annual average is 167 mm) and has a high evaporation rate (the annual average is around 3,000 mm). However, when it does rain it is often in high intensity events, which can lead to localised flooding given the flat terrain of the area. Stormwater is held temporarily in swales or clay pans before it evaporates or infiltrates. The region is characterised by many small, enclosed catchments, individually bound by east–west trending dunes, generally up to eight metres high. Typically, each catchment contains a boundary formed by the crest of sand dunes, an upper interdunal corridor (swale) and a lower depression, often a clay pan. The sand ridges are highly permeable. Rainfall infiltrates quickly through the sandy profile, draining into the swale and clay pan after being redirected by a thick layer of clayey soil under the sand dunes. The clayey soils of the swales and clay pans are less permeable and, in periods of significant rainfall, collect water in low depressions. These dune-swale and clay pan catchments vary in size from 10–300 ha and are typically 1–3 km long. Stormwater within the swales and clay pans infiltrates the surface cracks of the clay soils, causing them to swell. In most instances the swelling of the clay soils reduces infiltration significantly, leading to surface water ponding. Depending on the rainfall event, surface water may stay in the swales and clay pans from a few days to a few weeks, but only rainfall events of a significant intensity and duration result in ponding for more than one month. The ponded water in this land system is generally fresh and of high quality. There are no defined watercourses in the area, and surface waters from the small catchments very rarely flow into the neighbouring catchments. No stormwater from the area of the existing operation (including the heap leach trial area) flows off the SML. 3.3 (c) Soil and Vegetation characteristics The soil landscape of the area consists of sand dunes with interdunal clay pans and swales, with sand dunes consisting of red to reddish-brown sands. Interdunal areas consist of clayey soils with gibber surface rock and little vegetation, whilst clay pans generally have no surface rock or vegetation. The region is dominated by three vegetation communities (dunefields, swales and gibber plains) that occur repeatedly and are associated with the two major landform types: dunefields and stony tablelands. The dunefields are generally dominated by Acacia woodland and tall shrubland vegetation on the dune ridges, merging into low chenopod shrubland vegetation in the dune swales. 3.3 (d) Outstanding natural features There are no outstanding natural features in the immediate area. 3.3 (e) Remnant native vegetation Native vegetation in the region is relatively intact, although some areas are highly disturbed. The region contains relatively large areas of northern cypress pine (Callitris glaucophylla) and western myall (Acacia papyrocarpa) communities that are biologically important and poorly preserved elsewhere in formal conservation areas.

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3.3 (f) Gradient (or depth range if action is to be taken in a marine area) The topography is of generally low relief, the area being dominated by a landform of low undulating dunes, swales and clay pans. 3.3 (g) Current state of the environment Native vegetation in the region is relatively intact, although some areas are highly disturbed. The area is too arid for agriculture but sheep and cattle grazing of the rangelands is extensive. Grazing by livestock and rabbits has degraded vegetation to varying degrees. 3.3 (h) Commonwealth Heritage Places or other places recognised as having heritage values None. 3.3 (i) Indigenous heritage values Comprehensive and ongoing Aboriginal cultural heritage investigations have been undertaken over several decades in the Olympic Dam area, in conjunction with Aboriginal groups. Historically the region was subject to nomadic occupation only, and no Aboriginal communities lived there permanently. However, many sites and artefacts remain as evidence of historical nomadic occupation and use, and the area is rich in surface scatters of stone artefacts and quarries. Most of the sites are considered to be of low scientific significance, with no salvage potential. At the same time, however, cultural heritage is important to contemporary Aboriginal people. 3.3 (j) Other important or unique values of the environment None. 3.3 (k) Tenure of the action area (eg freehold, leasehold) The SML, containing TSF4, is freehold. 3.3 (l) Existing land/marine uses of area The Olympic Dam mining and metallurgical facilities are located on the SML and include the following land uses:  Underground mining  Metallurgical processing  Quarry  Storage of solid and liquid wastes (TSF)  Storage of solid wastes (landfill)  Sewage treatment  Water treatment and storage  Supply of electricity (substation)  Buffer areas (vegetation/habitat)  Conservation (Arid Recovery – part). 3.3 (m) Any proposed land/marine uses of area None.

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4 Measures to avoid or reduce impacts As the TSF4 wall raise is a continuation of existing operational procedures and wholly contained within the existing Olympic Dam site, measures to avoid or reduce impacts are based on those successfully implemented and managed at Olympic Dam since 1988. 4.1 Environmental risk The environmental aspects of the TRS are discussed and assessed in detail the 1997 and 2009 Environmental Impact Statements and are reviewed annually through the Aspects and Impacts register and EPMP processes. The TRS environmental risks identified in the EPMP are:  Embankment stability  Seepage  Fauna Interaction  Radioactive Waste  Closure and Rehabilitation The design and management controls that control the risks are defined in a Tailings Retention System Management Plan and a Tailings Retention System Operation, maintenance and surveillance manual. Independent annual auditing ensures that the required controls are being implemented correctly and regular monitoring will track any changes in the embankments. 4.2 Embankment stability 4.2.1 During operation The embankment stability for the proposed height increase has been assessed in accordance with the methodology recommended in ANCOLD (2012) ‘Guidelines on Tailings Dams – Planning, Design, Construction, Operation and Closure’. The stability of the embankment at the proposed design height of RL 141m is considered adequate under all loading conditions. While the factors of safety give some indication of the probability of failure, ODC recognises that other factors may lead to an embankment failure, and is therefore committed to ensuring the ongoing stability of the TSF embankments by continuing the rigorous inspection, surveillance and monitoring program currently in place. The current stability risk controls are described in the TRS Management Plan, which will be revised to incorporate the new design height and the associated changes in strength monitoring frequency. Regular monitoring and independent annual auditing will ensure the required controls are being implemented correctly and monitoring will track any changes in the embankments. The ongoing strength monitoring will be supported by the local measurement of tailings strengths prior to the construction of upstream raises using simple methods e.g. hand held drop weight CPT equipment, together with electric CPT at embankment cross sections at which pore pressure monitoring is currently carried out approximately every four to five years. Once an embankment reaches a height of 25 m, geotechnical testing will be carried out every 3 years or 5 m raise in height, whichever occurs first. This will facilitate performance monitoring to confirm that the undrained shear strength is developing as predicted, and that the stability factors of safety are greater than the design criterion of 1.5. Should observations and/or monitoring indicate a trend towards a stability factor that may decrease to below 1.5, the cause of the measured reduction will be investigated e.g. lower tailings strength or higher phreatic surface than predicted, and a suitable control developed and implemented to regain the desired trend. An example of such a control would be the use of an internal drain at an intermediate raise height, to control the position of the phreatic surface. Alternatively, the embankment could be stepped in to reduce the overall slope. The operational procedures as outlined in the Tailings Management Plan and the Tailings Retention System Operation, maintenance and surveillance manual will remain unchanged with the exception of the frequency of CPT to measure the in-situ strengths. The frequency of testing for embankments higher than 25 m will be increased from approximately every four to five years to approximately every 3 years or at a maximum of a 5 m increase in height, whichever occurs first. 4.2.2 Impact of pond size on stability There may be occasions where the surface pond size increases in response to a major rainfall event. Under this temporary, short term loading condition, there will be little change in the position of the phreatic surface from the conservative line assumed in the analysis. The factor of safety for the lower bound typical case is calculated at 1.70 for a high pond condition, a negligible reduction from the normal operating condition (1.72).

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4.2.3Embankment Stability at Closure Once TSF4 has been decommissioned and is being allowed to drain down prior to construction of the closure cover, the phreatic surface will decline gradually, with an associated increase in the tailings strength as pore pressures dissipate further. The factor of safety for this case is calculated at 1.95, i.e. a significant increase from the lower bound operating factor of safety of 1.72 just prior to the cessation of tailings deposition. The stability of the embankment is expected to increase further as the phreatic surface recedes and the tailings strength increases. 4.2.4 Post-Seismic Stability Recent laboratory testing on the Olympic Dam Tailings based on seismic loading parameters associated with the maximum credible earthquake has confirmed that the OD tailings is not potentially liquefiable and also that there is negligible loss of undrained strength in the tailings during cyclic shearing. All the stability analyses conducted therefore include full consideration of the maximum credible earthquake as recommended in ANCOLD 2012. 4.3 Seepage The TSF area and the geochemistry of the tailings liquor remain unchanged. Geochemical modelling of seepage carried out for the 2009 EIS (BHP Billiton 2009, Appendix K4), assessed for design heights of 65m, provided the following conclusions:  During the operational phase most of the acid present will be neutralised within the immediate underlying sediment layer, consistent with observations for the existing TSF.  Post closure, percolation rates decrease but remain elevated at levels slightly below predicted operational seepage rates for an estimated 150-250 years.  After drawdown is complete, percolation rates would then be expected to decrease to a rate equal to net infiltration from rainfall, with acidity release decreasing to correspondingly low levels. Current commitments to maintaining as small a pond as possible and to ensuring the ground water table level does not exceed 80 m AHD remain unchanged. 4.4 Fauna Interaction During operation of TSF4 up to the proposed new design height, neither the TRS water balance nor the habitat area attractive to avifauna will change compared to the current position. On the other hand, the increased capacity of TSF4 will delay the construction of additional TSF cells thereby reducing the surface water area available to avifauna. 4.5 Radiological impacts Increasing the wall height of TSF4 is not expected to result in any change to the level of environmental radiological emissions or to individual occupational exposure. 4.6 Closure ODC has a comprehensive Rehabilitation and Closure Plan for the Olympic Dam Operation. The plan will be updated to reflect the changes (if any) required by an increase in the height of TSF4. Long-term erosion assessments conducted for the approved Rehabilitation and Closure Plan remain valid for the TSF4 embankment raise. The simulation was modelled for a rock armoured TSF outer batter slope with a linear slope profile height of 65m and a 50% gradient. The current gradient of TSF4 is approximately 20%, suggesting that erosion from TSF4 at 40m would be less than or similar to that presented in the closure plan.

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5 Conclusion on the likelihood of significant impacts 5.1 Do you THINK your proposed action is a controlled action?

X No, complete section 5.2 Yes, complete section 5.3

5.2 Proposed action IS NOT a controlled action. As the TSF4 wall raise is a continuation of existing operational procedures and wholly contained within the existing Olympic Dam site, the likelihood of any significant impact on the environment is expected to be very low to negligible. The proposed action is not a nuclear action, as noted in section 3.2 (a) of this referral. Additionally, increasing the design height of TSF4 has a net environmental benefit by delaying the need to construct an additional tailings cell. Existing environmental management and mitigation measures successfully employed at Olympic Dam will be used. 5.3 Proposed action IS a controlled action Matters likely to be impacted World Heritage values (sections 12 and 15A) National Heritage places (sections 15B and 15C) Wetlands of international importance (sections 16 and 17B) Listed threatened species and communities (sections 18 and 18A) Listed migratory species (sections 20 and 20A) Protection of the environment from nuclear actions (sections 21 and 22A) Commonwealth marine environment (sections 23 and 24A) Great Barrier Reef Marine Park (sections 24B and 24C) A water resource, in relation to coal seam gas development and large coal mining development (sections 24D and 24E) Protection of the environment from actions involving Commonwealth land (sections 26 and 27A) Protection of the environment from Commonwealth actions (section 28) Commonwealth Heritage places overseas (sections 27B and 27C)

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6 Environmental record of the responsible party Yes No 6.1 Does the party taking the action have a satisfactory record of responsible environmental X management?

Provide details ODC has operated the Olympic Dam mine since the commencement of underground mining in 1988. Extensive monitoring, regulation, reporting and review of the operation has occurred over that time and the operation has had no significant adverse impacts on the environment. Environmental performance is reported annually to the State Government. Past copies of the annual environmental management and monitoring report are available on the website of the SA Government Department of State Development. (http://www.minerals.dmitre.sa.gov.au/mines__and__developing_projects/approved_mines/o lympic_dam, accessed 23/12/2014)

6.2 Has either (a) the party proposing to take the action, or (b) if a permit has been applied for X in relation to the action, the person making the application - ever been subject to any proceedings under a Commonwealth, State or Territory law for the protection of the environment or the conservation and sustainable use of natural resources?

If yes, provide details

6.3 If the party taking the action is a corporation, will the action be taken in accordance with X the corporation’s environmental policy and planning framework?

If yes, provide details of environmental policy and planning framework Environmental issues are managed at Olympic Dam in accordance with the operation’s AS/NZS ISO 14001/2004 certified environmental management system (EMS), a principle component of which is the EPMP. The EPMP is approved by both the State and Commonwealth Governments. The overall structure of the ODC EMS and hierarchy of documents is illustrated in Figure 5. The scope of the EPMP is defined within the central, orange portion of the diagram. Within BHP Billiton, the management of environment and community is guided by the BHP Billiton Charter and Group Level Documents (GLDs). The GLDs cover the entire lifecycle of operations, from exploration and planning through to operation and closure (decommissioning, remediation and rehabilitation). The relevant objectives of the GLDs are to:  support the implementation of the Charter and the Guide to Business Conduct across BHP Billiton;  provide a risk-based environment and community (EC) management system framework, consistent with: o BHP Billiton Risk Management Policy; o international policies, standards and management practices to which BHP Billiton has committed, including the:  United Nations Global Compact;  United Nations Universal Declaration of Human Rights;  International Council on Mining and Metals (ICMM) Sustainable Development Framework;  World Bank Operational Directive on Involuntary Resettlement;  US-UK Voluntary Principles on Security and Human Rights;  recommendations of the International Commission on Radiological Protection (specifically the system of dose limitation);  negotiated agreements with local communities;  other regional commitments;  set out and formalise the expectations for progressive development and implementation of more specific and detailed EC management systems at all levels of BHP Billiton;

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 provide auditable criteria, against which EC management systems across BHP Billiton can be measured;  drive continual improvement towards leading industry practice. Guided by the Charter and GLDs, the EMS (and EPMP) at Olympic Dam are implemented through a four-tiered approach. These consist of an overarching policy (in the form of the sustainable development commitment), followed by the standards and procedures (the Environmental Management Manual (EMM), Environmental Management Program (EMP) and Monitoring Programs (MPs)) that together make up the EPMP.

Figure 5: EMS and hierarchy of documents The approved EPMP incorporates an environmental management program (EMP) that addresses the potentially significant environmental aspects and impacts that have been identified through an analysis and prioritisation of the environmental risks, legal obligations and community concerns relevant to ODC. It documents the processes, systems, criteria and other requirements designed to manage the prioritised aspects and impacts, including (as appropriate):  environmental values, and the key risks to those values;  environmental outcomes that ODC is required to achieve relating to potential environmental impacts;  clear, specific and measurable compliance criteria that demonstrate achievement of the outcome(s);  leading indicator(s) criteria, providing early warning of trends that indicate a compliance criterion may not be met;  management and operational controls designed to deal with the environmental risk (of the impact), including any regulatory conditions (where specified);  contingency options to be used in the event that identified risks are realised; The EMP is divided into five distinct categories or ‘IDs’, each related to an area of the operation for which specific environmental management measures are required. Each ID is further subdivided into the specific EMP focused on one specific aspect and impact. The five top level IDs are:  use and disturbance of natural resources; o Measures for dealing with environmental impacts associated with land clearing and disturbance, spread of weeds and other pest species, and groundwater level drawdown.  storage, transport and handling of hazardous materials; o Prevention and mitigation of environmental impacts as a result of spills involving chemicals, hydrocarbons or radioactive process materials.  operation of industrial systems; o Control and prevention measures for emissions associated with the operation of the Olympic Dam mine and processing facility. These include particulate (dust) and radioactive emissions, sulphur dioxide and greenhouse gases.  generation of industrial wastes;

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o Measures for dealing with environmental impacts resulting from waste generation and storage. This includes issues associated with the storage of tailings, such as seepage to groundwater, embankment wall stability, and impacts to native fauna (birds) arising from contact with the tailings storage facilities. Also included are controls for waste rock storage, and the disposal and storage of radioactive and solid wastes.  interaction with communities; o Covers the employment and accommodation of people and measures for social cohesion. The EMP also refers to a number of monitoring programs (MPs) describing how data is collected to support the outcomes and criteria of each ID in the EMP. Further details of the Olympic Dam environmental policy and planning framework, and the EPMP itself, can be found in the 2013 Environmental Protection and Management Program (BHP Billiton, 2013; http://www.bhpbilliton.com/home/society/regulatory/Pages/default.aspx#013_Copper, accessed 23/12/2014)

Yes No 6.4 Has the party taking the action previously referred an action under the EPBC Act, or been X responsible for undertaking an action referred under the EPBC Act?

Provide name of proposal and EPBC reference number (if known) Olympic Dam Heap Leach Trial (EPBC 2014/7280) Expansion of the Olympic Dam copper, uranium, gold and silver mine, processing plant and associated infrastructure (EPBC 2005/2270) pilot desalination plant, Olympic Dam expansion project (EPBC 2007/3391)

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7 Information sources and attachments (For the information provided above)

7.1 References

Available to Public Y BHP Billiton, 2009, ‘Olympic Dam Expansion Draft Environmental Impact Statement’, http://www.bhpbilliton.com/home/aboutus/regulatory/Pages/default.aspx#013_Copper, accessed 06/01/2014 Y BHP Billiton, 2011, ‘Olympic Dam Expansion Supplementary Environmental Impact Statement’, http://www.bhpbilliton.com/home/aboutus/regulatory/Pages/default.aspx#013_Copper, accessed 06/01/2014 Y BHP Billiton, 2013, ‘Olympic Dam 2013 Environmental Protection and Management Programme’, http://www.bhpbilliton.com/home/aboutus/regulatory/Pages/default.aspx#013_Copper, accessed 06/01/2014 Y Kinhill Engineers Pty Ltd, 1997, ‘Olympic Dam Expansion Project: Environmental Impact Statement’, May 1997 Y Kinhill-Stearns Roger Joint Venture, 1982, ‘Olympic Dam Project: Draft Environmental Impact Statement’

7.2 Reliability and date of information The source and date of information used is as shown in the reference list at section 7.1 above. The data and information contained in the EIS documents and summarised (where appropriate) in section 3 was relied upon for approvals related to the Olympic Dam operation. 7.3 Attachments  attached Title of attachment(s) You must attach figures, maps or aerial photographs Contained within referral showing the project locality (section 1) GIS file delineating the boundary of the  TSF4WallRaise.zip referral area (section 1) figures, maps or aerial photographs showing the location of the project in respect to any matters of national environmental significance or important features of the environments (section 3) If relevant, attach copies of any state or local government approvals and consent conditions (section 2.5) copies of any completed assessments to meet state or local government approvals and outcomes of public consultations, if available (section 2.6) copies of any flora and fauna investigations and surveys (section 3) technical reports relevant to the

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assessment of impacts on protected matters that support the arguments and conclusions in the referral (section 3 and 4) report(s) on any public consultations undertaken, including with Indigenous stakeholders (section 3)

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8 Contacts, signatures and declarations

Project title: TSF4 wall raise

8.1 Person proposing to take action

1. Name and Title: Darryl Cuzzubbo Asset President Olympic Dam

2. Organisation BHP Billiton Olympic Dam Corporation Pty Ltd 3. EPBC Referral Number 4: ACN / ABN 99 007 835 761 5. Postal address GPO Box 1777, , SA, 5001 6. Telephone: (08) 8671 8888 7. Email: [email protected]

8. Name of designated

proponent (if not the same person at item 1 above 9. ACN/ABN of

designated proponent (if not the same person named at item 1 above): Declaration I declare that to the best of my knowledge the information I have given on, or attached to this form is complete, current and correct. I understand that giving false or misleading information is a serious offence. I agree to be the proponent for this action. I declare that I am not taking the action on behalf of or for the benefit of any other person or entity.

Signature Date 29/12/2014

8.2 Person preparing the referral information (if different from 8.1) Name As per section 8.1

Title Organisation name should match entity identified in ABN/ACN search Organisation

ACN / ABN (if applicable)

Postal address

Telephone

Email

Declaration I declare that to the best of my knowledge the information I have given on, or attached to this form is complete, current and correct. I understand that giving false or misleading information is a serious offence.

Signature Date

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