Collie Coal History: Early Mining
The coal seams in the Collie coalfield are in most places overlain by barren clays and sands, frequently over 20 metres thick. Where the coal seams are closest to the surface is not necessarily where the sands and clays are thinnest, consequently the early miners faced a considerable task exposing the coal, which was developed by following the seam underground from this point.
The soft, saturated sediments did not make shaft construction appropriate, although shallow timbered shafts were used for trial mines and mine ventilation purposes. Underground mining had the advantage that all of the subsequent effort was in “paydirt.”
Because the coal is not very transmissive to water (permeable) they could mine at some depth without undue worry about the saturated sediments around them. There were disadvantages for example only a minor percentage of the coal could be recovered and there were occasional problems with roof support.
The coal seam was undercut with a slot at the base of the face, initially by hand pick and later using mechanised cutters. This allowed the overhanging coal to be drilled and shot down with explosives, making a fairly coarse product which was in demand for the railways of the day. Coal produced was taken to the surface in horse-drawn skips and later, on conveyor belts. By 1943 the coalfield had produced 22 million tonnes of coal, all from underground mines.
The war brought a sense of greater urgency to coal production and a simultaneous shortage of labour. The development of larger equipment meant that open cut mining was recognised as a viable alternative to underground methods, because open cut mining was less labour intensive.
The Stockton open cut mine commenced in 1943 using mechanical shovels and trucks, both of which were very small by today’s standards.
A single dragline was used on the coalfield for some years, but did not have the reach to cope with the deeper excavations dictated by the thick, unproductive overburdens. This machine now sits at Griffin’s Muja Mine entrance, as a reminder of the company’s past. In the history of the Collie coalfield there have been 12 underground mines and 18 open cuts. The last underground mines were closed in 1994.
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