Dewatering Optimization at a Proposed Iron Mine Site in Western Australia


HGL provided an optimal design for a dewatering program at an open-pit mine in the Pilbara region of Western Australia. HGL deployed its Physics-Based Management Optimization (PBMOTM) system to optimize the mine dewatering program for a lens in the middle of the mining area and compared the results to the subjective engineering judgment developed solution. Locations for candidate extraction wells and exclusion zones were provided to HGL. In total, 113 wells, comprising 100 ex-pit wells and 13 in-pit wells, were supplied as candidate wells for PBMOTM to optimize. The ex-pit wells were scheduled to begin operating before mining operations extended below the water table, and the in-pit wells were scheduled to be activated after 4 years of mining, when those well locations would be available and accessible. The dewatering strategy developed using subjective engineering judgment would have required using 26 extraction wells to meet the mining schedule. However, the PBMOTM optimal design required use of only 17 individual wells, with no more than 11 extraction wells operating at any one time.

Project Highlights
Used a MODFLOW-SURFACTTM variably saturated, mass conserving calibrated flow model combined with the PBMOTM global optimal search strategy to determine an optimal dewatering program.
Realized the following benefits by using the PBMOTM design rather than the subjective engineering design:

  • A significant reduction in peak flow rates and total volume of water extracted, resulting in an estimated savings of $4.6 million.
  • Compliance of all extraction well locations with restrictions on well placement.
  • Compliance of all groundwater levels with mine schedule requirements.