The proposed McPhillamys Gold Mine (the project) is located within the eastern Lachlan Fold Belt of Central New South Wales. The local geology is predominantly fractured rock with limited potential for groundwater development due primarily to low hydraulic conductivity and porosity. Although the low productivity of the groundwater sources limits potential impacts on groundwater receptors, this also adds additional pressure on securing a suitable water supply to meet mining and ore processing requirements.
The project water demand is expected to range from 13-16 ML/day for around a decade. Securing a reliable water supply is therefore a critical aspect of the project. Water captured on site (mine water inflows, rainfall and runoff in disturbed areas) will be the priority source of the project water requirements, including reuse of that water wherever possible.
EMM Consulting Pty Ltd (EMM) is assisting Regis Resources Ltd (Regis) with approvals for the project. To support the project, an options assessment was conducted to identify potential water supply sources which included diversion of wastewater from a wastewater treatment plant, diversion of surplus water from collieries within 100 km of the proposed mine, surface water extraction (unregulated rivers and regulated rivers) and the development of a groundwater borefield within an adjacent higher productivity aquifer. The assessment suggested the most favourable option is the diversion of surplus water from a colliery operation, where there are currently water quality and stream disposal constraints. In comparison to the other options assessed, this scenario has environmental benefits as it limits additional groundwater abstraction and surface water take within the region.
The collieries near Lithgow are currently discharging excess mine dewatering volumes to watercourses within the Sydney Basin. In addition, there are flooded workings at collieries currently under care and maintenance. Diverting this brackish water will enable reuse of surplus water that would otherwise require treatment before being discharged to the environment.