The New South Wales based company, a member of the 4Logik Alliance, prides itself on taking on difficult jobs so when the Gibson salvage presented itself, Alterrain was not about to shy away from the challenge.
Gibson, located near Wollongong, was mined briefly as a bord and pillar operation. Thin Seam Mining was contracted by Allied Coal to extract hard coking coal from the 1.2m thick Balgownie seam, using United States designed equipment. However, in the wake of the closure of Allied’s Bellambi West mine, operations at Gibson were also stopped twelve months ago.
What was left deep underground was a set of unique low profile production equipment consisting of a continuous miner, three shuttle cars, a Fletcher roof bolter, breaker feeder, one kilometre of conveyor belt and structure, and various electrical equipment and ancillary items.
To get the salvage underway, the 4Logik Alliance had to jump through a number of bureaucracy hoops. Equipment owner Bounty negotiated the complex path between mine owner, the NSW department of mineral resources (DMR) and unions. Alterrain said often the finite legalities seemed insurmountable.
In the end, a sub-lease was established within the existing mine so the area which held the equipment could be defined as a separate mine under the NSW Coal Mining Act, for a period of six weeks.
Alterrain, with mine manager Paul Coxhead and project manager Luke Franklin, immediately set to work re-establishing the mine as a working operation, including the establishment of management, safety and environmental management plans to the satisfaction of the DMR.
The main challenge facing the recovery team was the low seam height which presented operating difficulties such as maintaining and mobilising equipment with limited room.
Franklin said due to the mine being inactive for a period of twelve months there was significant floor heave present, therefore restricting access to the mine. This created unusual hazards not usually associated with mining operations. Strata conditions had also deteriorated over a period of time.
“The Alterrain team overcame these challenges by performing a geotechnical audit identifying the route and controls to put in place to ensure a safe and efficient access for the men and equipment. Techniques were based on traditional support models for roof support and floor brushing,” said Franklin.
Safety was a prime concern as the thin seam workings had a history of falls and collapses. The establishment of a route at acceptable working height with safe strata support in excess of 250m of floor had to be brushed and ripped to achieve a working height of 1.3m. The entire travelling road of 2500m required rehabilitation so that the equipment could be extracted hassle free. More than 120 x 10" special props were placed in areas of deteriorated roof to ensure the stability of the transport corridor.
Alterrain also had to re-establish the entire underground electrical reticulation from the surface back to the working face, a distance of 2.5kms. The fire hydrant system also had to be bought back up to compliance before power was restored underground.
“This type of work is difficult enough in a two metre plus seam but the levels of difficulty are accentuated in a 1-1.2m high seam,” said Franklin. “With the equipment being somewhere near to three kilometres from the surface there was no easy way, just hard grunt. I had a great crew of men, everybody pitched in and toiled very hard to make this happen.”
Once power had been restored and roadways secured, the traditional thin seam mining equipment, including the low profile battery operated haulage units, could be recovered. These units (DBT 488 UN-A-TRAC scoops), which stood approximately 1.2m high, were used to start recovering the equipment that could not be powered.
The roof bolter, continuous miner and breaker feeder were propelled with power to the surface, and the fixed assets including transformers, conveyor belt drive heads and structure as well as normal mine services were removed. On completion of the equipment extraction all of the electrical reticulation had to be re-salvaged.
“Our team was aware up front and confident that we could deliver on our promise in a six week time frame. Alterrain achieved their deadline without injuries,” he said.
The recovered equipment is now with Bounty Industries who are confident it will be redeployed in low profile seams nationally.
Alterrain are a relatively new venture, but boast a team experienced in many major underground coal sites in Australia and internationally. Team members had previously performed similar tasks in the hard rock and mining construction sectors. Alterrain offers a broad scope of services, including drill and blast, fall recovery, roadway rehabilitation, shaft works and underground concrete works.