Dewatering is underway at the Koolan Island mine, in Western Australia's Kimberley, following the building of a concrete seepage barrier at the seawall in mid-July.
Forced to wait on the sidelines in a necessary waiting period while the final seepage barrier panels were cured, Mount Gibson is now using large capacity submersible pumps to remove seawater from the pit at a rate of 1500 litres per second.
At this rate the pit should be empty by the end of the year.
While the first 40m of water in the pit will effectively be ambient seawater that is not expected to have any environmental impacts, the quality of the deeper water will be lower, and could contain sediments and elevated metals levels. However, testing over the depth of the pit shows water quality to b...