Phone: (08) 9093 0024 Mobile: 0435 249 583 Email: [email protected] 52 to 56 Oroya St, Boulder PO Box 2027 Boulder WA 6432 ABN 47141175297 21st November 2018 MEMORANDUM: DEWATERING DISHCARGE FROM THE PENNY FIND PROJECT TO LAKE PENNY 1 INTRODUCTION ................................................................................................... 1 2 RECEIVING ENVIRONMENT ................................................................................ 4 2.1 Regional Setting ........................................................................................................... 4 2.2 Climate .......................................................................................................................... 5 2.3 Topography and Land systems .................................................................................. 5 2.4 Geology ......................................................................................................................... 8 2.5 Hydrology .................................................................................................................... 10 2.5.1 Water Quality ........................................................................................................ 12 2.5.2 Sediment Quality .................................................................................................. 13 2.6 Vegetation ................................................................................................................... 14 2.7 Aquatic Biota .............................................................................................................. 15 3 BIBLIOGRAPHY ................................................................................................. 17 TABLES Table 1-1: Water Balance/ Dewatering Rates for underground mining 2 Table 2-1: Soil Landscape Systems within the Penny’s Find Project 6 Table 2-2: Groundwater Quality Analytical Results 12 Table 2-3: Storage Dam Sediment Analytical Results 13 Table 2-4: Species list for Heath of Melaleuca lateriflora and low heath of Tecticornia indica subsp. bidens on salt lake edge 14 Table 2-5: Cyanobacteria and algal taxa identified from Lake Yindarlgooda, Swan 15 Table 2-6: Aquatic invertebrate taxa recorded from Lake Yindarlgooda, Swan 16 FIGURES Figure 1-1: Location of Penny’s Find Project 1 Figure 1-2: Penny’s Find Site Layout 2 Figure 1-3: Prescribed Premise Boundary and dewatering map 3 Figure 2-1: Map of IBRA subregions in the vicinity of Penny’s Find 4 Figure 2-2: Mean rainfall and maximum temperature Kalgoorlie-Boulder Airport (#12038) (Bureau of Meteorology, 2018) 5 Figure 2-3: Map of Soil Landscape Systems within the Penny’s Find Project 7 Figure 2-4: Geomorpholgy of the Penny’s Find Project 9 Figure 2-6: Regional Hydrology (Geoscience Australia, 2000) 10 Figure 2-5: Surface water flow and drainage (MWES, 2015) 11 PLATES Plate 1: Heath of Melaleuca lateriflora and low heath of Tecticornia indica subsp. bidens on salt lake edge (September 2015) 14 1 INTRODUCTION The Penny’s Find gold deposit is held jointly by Empire Resources Ltd (Empire) which holds 60% and private company Brimstone Resources Ltd (Brimstone) which holds 40%. Collectively the parties are referred to as the Penny’s Find Joint Venture (PFJV). The Penny’s Find deposit is located within the Hampton Hill Pastoral Lease in the Shire of Kalgoorlie-Boulder, approximately 45km north-east of Kalgoorlie-Boulder (Figure 1-1). Figure 1-1: Location of Penny’s Find Project The Penny’s Find Project (Figure 1-2) includes the following mine features: • Open pit mining of a single pit (5m below groundwater table) • One Waste Rock Landform (Class 1) • Abandonment Bund • ROM Pad • Office • Laydown/Hardstand areas • Road and pipelines (Transport and Infrastructure Corridors) • Magazine • Storage Dam-Saline Water • Diversion Channel • Topsoil Stockpiles 1 Figure 1-2: Penny’s Find Site Layout Open pit mining commenced in the first week of May 2017 and was completed in April 2018 with the site currently on care and maintenance. A total of 4,102,458 tonnes of rock was mined (146,670 tonnes of ore, 5000 tonnes of low grade and 3,950,783 tonnes of waste rock). High grade ore has been hauled offsite for processing however 5000 tonnes of low grade ore remains stockpiled on the ROM Pad. Waste Rock has been used to construct bunding on site and used in the construction of the Waste Rock Landform (WRL). Empire now propose to conduct underground mining within the open pit (pending Mining Proposal approval). Underground mining is planned for depth of 100m below the open pit base, by constructing an underground portal in the eastern face of the open pit. No other changes to the mining project/ infrastructure are proposed. As dewatering rates will increase for the underground operation (increase to approximately 25L/sec) an estimated 821,250 kL per annum (Table 1-1) of dewatering is estimated which requires DWER licencing (applications pending approvals). Table 1-1: Water Balance/ Dewatering Rates for underground mining Quarter Dewatering (KL) Jan-Mar 2019 202,500 Apr-June 2019 204,750 Jul-Sept 2019 207,000 Oct-Dec 2019 207,000 Total Annual 2019 821,250 Jan-Mar 2020 204,750 Apr-June 2020 204,750 Total Annual 2020 409,500 2 Dewatering previously conducted for the open pit operation was transmitted via above ground pipelines (contained within 2m wide v-drain with 0.5m high earth bunds) for storage of water in one storage dam (clay-lined) and any excess water discharged into Lake Penny. Location of pipelines and storage dam are shown in Figure 1-3. No changes to the dewatering infrastructure previously approved and in place are proposed. The storage dam and dewatering pipelines will be operated in accordance with previous mining approvals and the pending DWER licences. The current turkey nest storage dam is constructed to give a free board volume of ~2,000 m3 or 1.0 days at the proposed underground mine pumping rates. Figure 1-3: Prescribed Premise Boundary and dewatering map 3 2 RECEIVING ENVIRONMENT 2.1 Regional Setting The Penny’s Find Project lies within the Murchison Region of the Eremaean Province of WA in a region known as the Austin Botanical District. The area consists of predominantly mulga low woodland on plains and reduces to scrub on hills (Beard, 1990). The Murchison Region is further divided into subregions, based on the IBRA, with the project area located within the Eastern Murchison (MUR1) subregion (Figure 2-1). The area is characterised by internal drainage and extensive areas of elevated red desert sand plains with minimal dune development. Salt lake systems are present in the area and are associated with ancient paleodrainage channels. Broad plains of red-brown soils and breakaways exist, adjacent to red sandplains. Vegetation is dominated by mulga woodlands, with hummock grasslands, salt bush shrublands and Tecticornia shrublands. Land uses include Unallocated Crown Land, Crown reserves, pastoral grazing, freehold, conservation and mining (Cowan, 2001). Figure 2-1: Map of IBRA subregions in the vicinity of Penny’s Find Botanica Consulting 4 2.2 Climate The climate of the Eastern Murchison subregion is classified as arid to semi-arid, characterised by cool winters and hot summers. Rainfall is highly variable, with an annual average of 255 mm (Figure 2-2). High intensity, short duration rainfall events linked to tropical lows in the north of Western Australia often occur in late summer (Clarke, 1994). However, majority of the rainfall occurs in winter as a result of cold fronts moving in from the Southern Ocean. Climate data for the Kalgoorlie-Boulder Airport weather station (#12038), located approximately 45km south-west of the Project is provided in Figure 2-2 (Bureau of Meteorology, 2018). Figure 2-2: Mean rainfall and maximum temperature Kalgoorlie-Boulder Airport (#12038) (Bureau of Meteorology, 2018) 2.3 Topography and Land systems The Eastern Murchison subregion is dominated by Archaean granite-greenstone terrain, with the landscape comprising low hills, mesas of duricrust separated by flat colluvium and alluvial plains. The western half of the bioregion comprises the Murchison Catchment (Australian Natural Resources Atlas, 2009) and drainage occurs westwards towards the Murchison River and south into Lake Austin. This subregion is characterized by its internal drainage and extensive area of elevated red desert sandplains (Cowan, 2001). Another important feature of the system is the salt lake systems associated with the occluded Paleo within drainage system. Beard (1990) describes the topography of the region as undulating with occasional ranges of low hills and extensive sandplains located in the East. The dominant soil type is a shallow earthy loam, overlying red-brown hardpan. Red earthy sands can be found on the sandplains. The Penny’s Find Project is located at 350m elevation. Botanica Consulting 5 The Penny’s Find Project occurs within the Kambalda Zone (265) of the Kalgoorlie Province (26). The Kambalda Zone is characterised by flat to undulating plains (with hills, ranges and some salt lakes and stony plains) on greenstone and granitic rocks of the Yilgarn Craton. Soils are comprised of calcareous loamy earths and red loamy earths with Salt lakes soils and some red-brown hardpan shallow loams and red sandy duplexes. Vegetation is predominately red mallee blackbutt- salmon gum-gimlet woodlands with mulga and halophytic shrublands (and some spinifex grasslands). This zone is located in the south-eastern Goldfields between Menzies,