The Yeelirrie uranium deposit is the largest known uranium deposit in Western Australia. It occurs in calcrete hosted material in the central drainage channel of a wide, flat and long valley which is flanked by granitic breakaways of low topographic relief with elevations between 490 m AHD and 610 m AHD.

The mineralisation extends from the surface to an approximate depth of 10 m, with the main concentration centred about 4 m below the surface, with a thickness ranging from 1 to 7 m. The surface extent of the identified resource is 9 km long and an average of 1 km wide, with a maximum width of about 1.5 km.

Lithological and mineralogical studies conducted in the Yeelirrie valley (WMC 1975, and studies conducted for this PER) show that there are four principal lithological units at the proposed development site:

1. Overburden: consisting of a combination of sandy loam, siliceous and ferruginous cemented hard- pan and carbonated loam, which is probably a weathered calcrete.
2. Calcrete: a calcite and/or dolomite replacement of the clay-quartz, although relics of partially replaced clay-quartz are common throughout the calcrete. The upper portion of the calcrete comprises friable ‘earthy calcrete’, a continuous layer grading upwards into the overlying soils. Nodular porcellanous calcrete represents the lower layer of the calcrete and consists of up to 70% carbonate (McKay and Miezitis 2001).
3. Clay-quartz: a kaolinitic clay-quartz allu ........

Mining of the pit would use standard surface mining equipment, such as excavators and front-end-loaders in conjunction with haul trucks and scrapers, to remove the ore and overburden. Due to the typically high friability of the ore and overburden material, minimal drilling and blasting would be required, although this technique may be needed in areas of the open pit if hard rock was encountered. For the purpose of the impact assessment presented in this document, a realistic worst-case scenario has been adopted, whereby 16 blasts are undertaken each year, using a total of about 70 tonnes of explosives and emulsion product.

Given the shallow nature and relatively small footprint of the area being mined at any time, the total mining fleet would consist of 3 to 6 excavators, or similar surface mining equipment, feeding about 12 haul trucks. Standard surface mining support fleet would include water trucks, graders, drill rigs and bulldozers. From the open pit, ore will be trucked to various stockpile areas based on grade and other geochemical characteristics.

The open pit mine will be about 9km long, up to 1.5km wide and about 10m deep. Up to 14 million tonnes (Mt) of overburden and ore would be mined annually during the mining preproduction pre-strip phase, with an average extraction rate of around 8 Mtpa.

The major features of the open pit:
Length of ore body - 9 km;
Average/maximum width of the ore body - 1 to 1.5 km;
Average pit depth - 10 m.

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The Project requires water of various qualities and quantities for different uses during the construction and operation phases. The biggest single demand is for raw process water in the grinding and leaching circuits. The second biggest use of water is for dust suppression. Both uses can accommodate poor water quality from saline sources. The total annualised average operational water demand is estimated at around 8.7 ML/d, with about 4.8 ML/d required for metallurgical processing and the remainder used as required for dust suppression and the reverse osmosis plant within the mining operation.

A much smaller demand for water during construction and operation is for feed water to a reverse osmosis (RO) desalination plant to produce low-salinity water (about 500 mg/L). This water will be used for steam generation and other parts of the process circuit (2.2 ML/d), as well as for producing potable water for the accommodation village and on-site workforce. This feed water supply would preferably be lower-salinity water than the expected pit dewatering discharge and therefore would be provided from higher-quality groundwater sources.

Pit dewatering will provide a valuable water supply for the first four years of the Project. To meet the need for increasing make-up water supplies, a series of wellfields surrounding the Project has been identified and assessed to be the best option. Water supply infrastructure would be constructed to link the Project to these wellfields situated within the State Agreement area, hereafter referred to as the Yeelirrie Wellfield and bores.