THE PROJECT

The Southdown Joint Venture is planning to mine the Southdown magnetite deposit, located nearby to Wellstead, about 90 km north-east of Albany. The total mineral resource at Southdown is currently 1.25 Bt at 33.7 % Davis Tube Recovery.

At a mining rate of 5 Mtpa, it is estimated that up to 120 L/s of saline water will be required during the mine construction phase, and that up 110 L/s of fresh water will be required for ore processing and the operation of a slurry pipeline to Albany during the mine operation phase.

The main options for obtaining the water are a desalination plant at Cape Riche and/or sedimentary aquifers within sub-basins of the Bremer Basin between Albany and Wellstead.

The results of exploration drilling conducted by Rockwater revealed the presence of a large sub-basin (of the Bremer Basin) centred on Wellstead.  Two deep, saline, confined aquifers were identified within the Werillup Formation at the base of the Wellstead sun-basin, which were subsequently evaluated by the drilling and testing of several production bores.

A five-layer MODFLOW model was developed based on the results the exploration, and production bore drilling and testing programmes.  Calibration of the model was performed in  steady-state, mostly using water levels in the overlying Pallinup Formation, which is widely used for stock-water supply.

Transient runs of the model indicated that the confined Werillup aquifers should be able to supply the 120 L/s of saline water needed for the mine construction phase, without significantly affecting water levels in the Pallinup Formation (water table aquifer).

Rockwater became involved with the Southdown project in 2006.  Since then, we have also delineated sub-basins at Sunday Swamp and Redmond-King River, and established a fresh-water borefield at Redmond-King River.

• Flow modelling in MODFLOW
• Drilling, testing and modelling reports

• Gravity surveys
• Air-core exploration drilling
• Mud-rotary production bores
• Down-hole geophysical logging
• Pumping tests
• Water quality sampling