Published in the June 2008 Australian Longwall Magazine

The North Wambo Underground longwall in New South Wales’ Upper Hunter Valley is significant on many fronts. It is the first time the Wambo seam has ever been longwall mined. It is also one of three greenfield mines Peabody completed last year, being the only longwall operation.

Peabody Energy acquired North Wambo Underground from Tony Haggarty’s Excel Coal in 2006. Excel had committed to the mine in August 2005, awarded equipment contracts predominantly to Joy Mining Machinery and began development. After all, North Wambo Underground made good sense. With 26 million tonnes of reserves, its high yielding, low ash coal could be blended with the neighbouring open cut, as well as the company’s other mines.

As with most new mines in these skill-short days, North Wambo recruited a workforce with 80% of employees new to longwall mining. Peabody was lucky enough to time its opening with the closure of Anglo Coal’s Dartbrook mine, and picked up several experienced personnel. The producer was also careful to get people in place well before the start-up of the longwall for comprehensive training. Part of that training was hands-on, with the longwall mini-build on the surface from April to August 2007.

During September the longwall was installed underground. The longwall included a Joy 7LS2a shearer with 375kW cutter motors; 146 Joy two-leg 1050t supports at 1.75m wide with RS20S control system; Joy AFC with 42mm chain; and two 850kW TTT transmissions, including a 1000EP/BP gearbox and 562TTT Voith drive.

The mine also installed a Macquarie Manufacturing monorail, three SES pump stations and electrics from Ampcontrol.

North Wambo has done some tweaking to its face since installation. At the time of Australian Longwall Magazine’s visit, the mine was expecting the delivery of a new set of bigger drums (from 1524mm by 980mm to 1600mm by 1150mm).

“In October 2007 we started the longwall at a crawl as the surface belt was yet to be up and working. The longwall had to stop two months later in December for the surface conveyors to be commissioned,” said North Wambo Underground production superintendent Wouter Niehaus.

With tonnages slowly building from 50,000 tonnes in December to 100,000t in January, real improvement started to show in February at 161,000t. In April the mine produced 205,000t – putting it on track to produce at least 2.6 million ROM tonnes in 2008 and 3Mt plus from 2009 onwards.

At the time of the visit, North Wambo Underground was 670m into its first panel. The longwall face was straight and standing up well, and a “coal river” – as Niehaus coined it – was flowing.

The 2m Wambo seam has previously been extracted, in the 1970s, by the Wambo bord and pillar operation. Whilst this is the first time the Wambo seam will be longwall mined, the seam is far from being isolated. Below the mine is the active United longwall and above it are the old Ridge, Homestead and Wollemi mines.

The United mine, however, poses some challenges. United works in a gassy seam and undertakes goaf gas drainage. What this means for North Wambo Underground is that in its first block it will encounter three fully cased and grouted boreholes – varying from 300mm to 400mm in diameter.

Besides the boreholes, the block also has a thrust fault zone, about 150m long, showing fractured ground. “We don’t anticipate major problems with these faults. Our plan is to stop before the faulted zone and give the wall a birthday – make sure everything is fully maintained and is all working – and then go as fast as possible through the fault,” Niehaus said.

The mine has been laid out to take best advantage of the highwall left over from the Wambo open cut. A portal entry for the first four blocks comes off the highwall, and the last four blocks will take advantage of having their gate roads straight off the highwall.

Throughout its mines in the US and Australia, Peabody Energy runs a Centre of Excellence program which strives for continuous improvement to achieve world best practice. Under the program, North Wambo Underground is bringing together US-based Peabody personnel, consultants, and all levels of employees at the mine to pitch ideas to improve the operation. The COE process will cover the longwall, development, engineering, conveyors and the preparation plant.

Part of achieving best practice has already been identified with the mine reviewing the option to go from seven days development and five days longwall, to seven days on both.

On the development panel the two Joy 12CM32 continuous miners will be split instead of operating in the same panel and by doing this North Wambo Underground anticipates a considerable increase in development productivity. Whilst development currently boasts a 130-day float for the second longwall, by longwall three the float is expected to shrink to 50 days, necessitating the continuous miner split.

Besides the continuous miners, North Wambo Underground also operates three Waracars and two Stamler feeder breakers. Transport and other work are undertaken by a fleet of nine personnel carriers and six load haul dump vehicles (LHDs).

In another innovation, North Wambo Underground is taking delivery of NLT Messenger Cap Lamps – an integrated communications device which enables real-time, two-way text messaging.

North Wambo Underground is also assessing options to reduce dust exposure to its operators on the face. The project will assess where the dust is being generated, look at best location of water sprays and make operators aware of the hazard to reduce exposure through positioning and operation.

Even though the mine is still in the first of eight 3Mt blocks, the operation has plenty of options for extending its life. Conceptual studies are currently in place assessing the Arrowfield and Whybrow seams.