One of the previously approved miniwalls was for mining directly underneath Bowmans Creek.

Apart from the technical and economic difficulties faced in the previous plan, Department of Planning major project assessments executive director Chris Wilson said there was uncertainty about how much cracking of the creek bed this layout would cause.

By diverting the creek, no mining will take place underneath the waterway.

The 955-metre eastern diversion of the creek along an alluvial floodplain will replace about 1480m of the existing creek through the excavation of 140,000 cubic metres of soil.

The 780m western diversion of the creek will replace about 838m of the waterway through excavation of 180,000cm.

Under the modification, miniwall panels 5-9 are removed and four full-width longwall panels are introduced into the multi-seam mine plan.

The smaller-width longwall panel 8 in the northwest corner was also approved.

While there was opposition from activist groups Rivers SOS and the Hunter Valley Water Users Association, Xstrata Coal also raised concerns.

One concern was over groundwater impacts and potential seepage into its nearby Ravensworth Underground mine, which recently received environmental approval to extend the length of four longwall panels.

In gaining approval, Ashton committed to various water management controls.

The mine will provide a 40m setback between the longwall panels and the creek alignment.

Ashton must also return high-quality water to Bowmans Creek during dry times when water allocations cannot be used, plus purchase water licences from other water users to compensate for any loss of groundwater into the mine.

“The approved modification will allow the diverted Bowmans Creek and the longwall panels to be kept separate,” Wilson said.

“This compares to the current approval, which would have seen Bowmans Creek sitting across the mining panel layout. This is a positive outcome for both Bowmans

Creek and Ashton’s coal production.

“The creek diversions are designed to mimic the natural river environment, to create a variety of aquatic habitats.”

The creek diversion project and associated modified mining plan are expected to allow access to another 5.3 million tonnes of coal.

Mining is expected to continue until 2024 at the 195-strong operation because of the approval.

Subsidence is expected to reach a cumulative maximum of up to 8 metres above five panels and up to 6m above longwall panel 8.

The Ashton longwall operation, 14 kilometres northwest of Singleton, is owned by Yancoal Australia, which completed its acquisition of Felix Resources a year ago.