Mini-wall option at Chain Valley

LD Operations aims to extend mining in two key areas of the Chain Valley mine in New South Wales by another five years using continuous miners, along with a possible mini-wall.

Blair Price

Well-known as a contractor, LDO became the mine operator after acquiring Peabody Energy’s 80% stake in Chain Valley in December 2009.

Consultancy AECOM submitted the preliminary environmental assessment to the state government last month and work is underway on the environmental assessment.

Under the No 1 Domain and No 2 Domain Continuation project, LDO is seeking approval to produce up to 1.2 million tonnes per annum of run-of-mine coal.

Mining will target the two domains in tenements ML 1051 and ML 1052, plus an area of first workings in Parcel A within the Fassifern seam about 190-230m underneath the Lake Macquarie seabed.

While there are another seven mining permits in the Chain Valley area, LDO is not seeking approval to extract more coal in these areas under this application.

But there are more plans underway to put forward another application to give the operation a 21-year mine life.

The project targeting the two domains will make use of existing infrastructure.

But the construction of an alternative mine ventilation shaft and fan will take place before LDO starts decommissioning the existing infrastructure.

The alternative mine shaft will make use of an existing shaft within the pit top area of the colliery.

Possible mining methods

Chain Valley traditionally uses bord and pillar mining techniques but AECOM noted that the secondary extraction of removing most of the pillars would be required to make the mine a commercial success.

The full or secondary extraction will involve either place change mining using CMs or the establishment of a mini-wall block.

The subsidence from place change mining is expected to reach 510 millimetres, while cutting a mini-wall block is estimated to keep subsidence down to just 175mm.

AECOM said the mini-wall block at Chain Valley would have a 60m face width, while longwall mining typically starts with block widths of more than 200m.

The length of the block was not mentioned.

An in-place miner – a wide-head CM with attached bolting rigs – would take care of first workings and drive the roadways for the mini-wall under this option.

No coal reject is produced at the colliery and the mine aims to produce up to 1.2Mtpa of low-sulfur, high ash thermal coal for export and domestic markets.

The mine employs about 120 full time personnel and was first established in 1960.

Sojitz Resources owns the other 20% of Chain Valley under the Wallarah Coal Joint Venture, while previous owners of the mine have also included Coal & Allied, BHP Billiton and Excel Coal.

AECOM said WCJV’s Moonee and Wallarah mines were closed or about to be closed around the time LDO acquired Chain Valley.

Mine closure and rehabilitation activities are underway at the Moonee mine and associated Catherine Hill Bay coal preparation plant.

Bounty Mining wound up its last contract at Chain Valley at the end of July.