The department says it is not aware of any breaches of the mine’s conditions of approval, noting that the company always reported surface impacts in an “extremely timely manner” to all relevant government agencies.

“The department remains committed to ensuring the mine operates in line with its existing planning approvals,” it said.

“Any future applications will be subject to rigorous merit assessment processes and appropriate conditions of approval.”

In relation to the most recent approval for Area 3B of the mine plan, the department noted that the director-general’s approval of the subsidence management plan in February this year represented a “significant strengthening of the mine’s regulatory regime”

“In particular, approval was only given for mining to occur in five out of 10 proposed longwalls, with approval for the remaining five longwalls dependent on satisfactory environmental outcomes for the first five,” it said.

The department said the surface impacts noticed by environmental groups and nearby residents appeared to be related to Area 3A of the mine plan, which received approval to begin mining in 2009.

The impacts appeared to be unrelated to Area 3B, for which the department gave approval for mining to commence in February this year, it said.

“The department’s assessments in relation to the Dendrobium mine have made it clear that, should mining be approved, some surface impacts were to be expected,” the department said.

“As a result, the department’s consideration of mining in this area has always involved a careful balancing of potential economic benefits against expected environmental and other impacts.

“Our assessments have indicated throughout that no significant impacts are expected on the quantity or quality of Sydney’s drinking water supplies. This remains the department’s position.”

During the department’s 2009 planning assessment, it became clear that the most significant natural feature potentially affected within Area 3A was a very large waterfall on Sandy Creek.

Conditions of approval required the company to avoid all impacts on the waterfall and consequently the company pulled back its proposed mine plan in this area.

As a result, mining stopped some 400m short of the waterfall, sterilising a large amount of coal.

The mining has been completed with no impacts on the natural feature.