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Hope Downs Groundwater Dependant Ecosystem Modelling and Dewatering, Pilbara, WA

Hope Downs Groundwater Dependant Ecosystem Modelling and Dewatering, Pilbara, WA

RPS was engaged by Hope Downs Management Services to assist with groundwater investigations (drilling and testing) and to conduct groundwater modelling of the proposed development of the Hope 1 Deposit within the Weeli Wolli Catchment.

RPS adapted an existing groundwater model and re-calibrated it using new longterm and short-term test pumping data derived from extensive hydrogeological and ecological research and test work in the Hope Downs area. The revised groundwater model was used to simulate various dewatering and decommissioning scenarios to assess the effects on the hydro geological system.

One of the key objectives of the modelling was to design water management methods that would maintain or improve the integrity and beneficial use of the groundwater system that supports Weeli Wolli Spring. The spring is a well vegetated, groundwater-fed, surface water feature located 6.5km downstream of the Hope 1 (North) Deposit. State-of-the-art features for stream-aquifer interaction were applied to develop an accurate calibration to groundwater-dependent flow at the spring, as well as to nearby monitoring bore data. The model has been independently reviewed.

The aim for the decommissioning of the Hope Downs Deposits was to achieve aquifer recovery whereby Weeli Wolli Spring would return to within 10% of premining flow rates, unsupported by any intervention such as re-injection or piped water discharge. A reasonable timeframe to achieve sustainable recovery was identified as within twenty years of the completion of mining. Various options were trailed using the model, including aquifer storage and recovery (ASR) methods, to develop a suitable water management strategy to support the project approvals process.

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