Coal Mining continued
Throughout the 1960s and 1970s improved techniques increased the productivity of miners and the volume of coal they were able to extract, resulting in a steady decrease
in numbers employed. From 1960 underground mining used new techniques, employing scraper loaders and a "grunching" system which shot coal off the coal face for loading onto scraper chain conveyors.
By the late 1990s underground mining occurred at depths of between 150 and 500 metres. The coal seam is reached by vertical shafts or sloping tunnels. Coal was
extracted using machines called continuous miners or longwall equipment. Continuous miners cut out blocks of coal leaving behind pillars to support the roof. Longwall
mining used hydraulic rams to support the roof while a cutting head removed coal from the length of the wall.
In 1950 Western Collieries opened its first open cut mine near Collie Burn. During open cut mining, soil and rock is removed by excavators, front end
loaders and trucks. Once the coal seam is exposed, it is drilled, blasted and mined in strips. Then the coal is transported by truck or rail. By 2000
approximately 80 per cent of the coal mined at Collie was extracted from four open cut mines.
From the early 1960s to the end of the twentieth century there were just two coal mining companies operating in
Western Australia - Western Collieries Pty Ltd and Griffin Coal Mining Co Ltd. The coal industry was worth $250 million a year, generating approximately 75 per cent of the State's electricity through the SECWA Muja Power
Station.Although small by world standards, the coal industry in Western Australia at the start of the twenty first century is significant - directly employing 1200 people. In
addition, a further 1000 people are employed in power generation and supply industries.