It said it was concerned at the level of subsidence management at the Hunter Valley mine.

Glencore Xstrata requested the modification after identifying an opportunity to improve mine progression and maximise resource recovery by refining the approved underground mine plan for extraction within the Liddell Seam.

The proposed modification involves changes to the width, orientation and location of longwall panels in the Upper and Middle Liddell seams.

It also entails extending mine life by about six years, to July 2024, to allow extraction of the Liddell Seam and install gas drainage infrastructure.

“Given the potential coal resource recovery from the modified mine plan, and the absence of significant residual environmental impacts, the department is satisfied that the proposed modification is in the public interest and should be approved, subject to conditions,” the department’s director-general states.

“The department is concerned at the absence of a strong, contemporary subsidence impact management regime under the existing consent, and proposes to include conditions requiring the preparation of an extraction plan for all longwalls which are not covered by an SMP [subsidence management plan] approval granted prior to January 1, 2014.

“The potential impacts of the additional goaf gas drainage and ventilation infrastructure, and other minor surface facility upgrades, all have limited environmental impacts.”

Ravensworth Underground Mine (RUM) holds SMP approvals to extract Longwalls 1-9, with approval for Longwalls 8 and 9 being granted on April 18.

RUM recently lodged an SMP application to develop and extract Longwalls 10-15, which would complete extraction in the Pikes Gully Seam.

In December, limited SMP approval was granted to allow the company to develop first workings for Longwalls 10 and 11.

The director-general said he was satisfied that the proposed re-orientation of RUM's Liddell Seam mine plan was materially the same in scope and potential impacts as the approved mine plan.

“However, DA 104/96 was first granted in November 1996 and has since been modified a total of eight times,” he said.

“While elements of the development consent are reasonably contemporary in nature, others reflect the standard conditions applied to underground coal mines more than a decade ago.

“The department consequently considers it appropriate to completely replace and contemporise the RUM consent, as it has done over recent years with many mines in the Hunter Valley and other parts of the state. Xstrata has agreed to this approach, and has since reviewed and accepted the proposed conditions of consent.”