Published in March 2006 Australian Longwall Magazine

The company identified the fire as a problem in early 2004 as it continued to burn further towards the west, jeopardising the stability of the Doherty Creek escarpment.

Solid Energy initially trialled a number of grout materials and methods, including Rocsil Foam, Strataseal, Bentonite, foaming cement, and bulk grout mixing plant with different blends of clay, sand, cement kiln dust and ash from coal combustion.

Solid Energy decided upon the grout plant, owned and operated by a local contractor, to produce a grouting slurry made from clay, sand and cement kiln dust for pumping into the ground. The plant is now in full production and produces 20 tonnes per hour of slurry.

Thermocouples in the ground give localised temperature information on a weekly basis and are being used to assess the effectiveness of the grouting operation. Thermal imagery photography is flown annually to assess the overall state of fire.

Solid Energy said the grouting program was already showing good results. Ground movement around the Doherty Creek escarpment is regularly monitored to assess stability.

The company said overburden stripping, as part of the project to mine coal in the north block of XY Ridge, had improved the long-term stability of the slopes above Doherty Creek. Taking coal from the area also removes the risk of the fire spreading further east along the escarpment.

The fire is now currently burning over an area of about 25 hectares.