Both the Fimiston Mill and the Gidji Roaster generate tailings waste. The Fimiston Mill processes ore from the Super Pit and the Mt Charlotte Underground Mine and the Gidji Roaster processes the refractory sulphide ores that cannot be fully processed at the Fimiston Mill. KCGM operates three tailings storage facilities (TSFs), one at the Gidji Roaster and two serving the Fimiston Mill.
Tailings are discharged on to the storage facilities from smaller pipe outlets "spigots" which are evenly spaced on the main pipe, which encircles the upper perimeter of the TSF. The tailings flow toward the centre of the storage facility. The TSFs are layed out into cells or paddocks. Tailings discharge from a run of spigots is frequently relocated around all sides of the paddock to deposit the tailings evenly and to allow the tailings to dry and consolidate. Once the paddock is filled, the tailings is discharged to an alternative paddock on the facility. This allows the former paddock to dry out and for the height of the embankment on the non-operational paddock to be raised and the cycle is repeated.
KCGM undertakes detailed inspections and checks of operational tailings storage facilities and related pipeline infrastructure including, three hourly checks by operators, daily checks by supervisors, weekly inspections by supervisors and monthly system inspections by engineers.
Groundwater monitoring is undertaken in accordance with the monitoring schedule in the environmental licence for each of the facilities. The monitoring schedule includes both water level measurement and groundwater sampling and analysis.
Analysis is done in both the field and a National Association of Testing Authorities (NATA) accredited laboratory. Field analysis is for pH and electrical conductivity. Laboratory analysis is for WAD, total and free cyanide, pH, TDS and electrical conductivity.
Monitoring of the health of vegetation around the Fimiston and Gidji TSFs has been conducted to assess if vegetation has been affected by changing groundwater levels. Monitoring involves the assessment of tree health at specific locations.
Formal recording of bird use of the tailings storage facilities was initiated in August 1997 through incorporation into the three hourly tailings inspection sheets and fauna awareness sessions. Usage or presence of any other fauna is reported internally and records are maintained in a database.
To deter birds from accessing the facility, netting has been installed over the supernatant pond on both paddocks of the Gidji TSF and two propane gas (noise disturbance) cannons are in place. Additional flagging tape and a strobe light have also been installed to deter birds from landing on the bird netting at night. Perimeter fencing of the Gidji tailings storage facility was also upgraded in January 1998 to prevent access by larger fauna.