Water is required for many functions on a mine site, including dust control, mineral processing, transporting tailings and site amenities. The majority of water used at KCGM is saline groundwater and recycled water, although some potable water is also required for operations.
KCGM uses around 12.5 gigalitres of water each year: approximately 14% potable water from the Goldfields water supply scheme, 6% recycled or treated effluent and 80% saline groundwater or water recovered and recycled from operations. KCGM’s Water Efficiency Management Plan is aligned with the Water Corporation’s Waterwise Business Programme aimed at minimising potable water use.
Groundwater in the Goldfields is saline, ranging from sea water quality to hypersaline water, which is up to five times saltier than sea water. The groundwater – which has no beneficial use other than for mining or mineral processing – is regularly monitored for depth and quality change.
Most of the water is used in the processing plants and ends in KCGM’s four tailings storage facilities (TSFs), designed by specialist engineers to withstand floods, earthquakes and erosion, and regularly inspected in accordance with government regulations.
“Tailings” are the waste products from the Fimiston and Gidji Processing Plants, a slurry mixture of finely ground solids, residual reagents and process water, and are about 45% solids and 55% water. The tailings are pumped to the TSF, the solids settle and the water is recycled for reuse in the Plants. In unlined TSFs approximately 30% passes to ground and is termed seepage. KCGM has Seepage and Groundwater Management Plans which include monitoring, and a combination of production bores and seepage interception trenches to minimise the impact on vegetation. KCGM has both lined and unlined TSFs. More than 50% of the water discharged to the tailings storage facilities is recovered and reused.
To prevent seepage and spills of saline water and to protect soil and vegetation, KCGM’s 150 kilometres of water and tailings pipelines have leak detectors and are regularly inspected. Monitoring assesses whether vegetation is affected by changing groundwater levels, each TSF is fully fenced to prevent animals accessing the sites and bird netting has also been installed at the Gidji TSFs.