Voluntary redundancies have been offered to a workforce already reduced to a shadow of its former size by years of financial troubles and uncertainty over the miner's future.

The Russell Vale colliery will shut down production over Easter, with the majority of the workforce having to take leave, and workers have until April 10 to decide if they will take redundancy.

Chief operating officer David Stone told the Mercury late on Friday the company was restructuring its workforce as it tried to find a way to get through the period until it could obtain the necessary state and federal approvals to expand its longwall operations.

He was unable to say how many jobs would go, as multiple proposals had been put to the workforce in negotiations over the past three days.

But the Mercury understands the numbers could be significant.

"Wollongong Coal is in an ongoing discussion with employees about ways it can restructure the workforce as it seeks state and federal approvals," he said.

"We've put some options to limit the effect on people."

The company is awaiting a verdict from the Planning Assessment Commission on whether it can expand into more longwall panels, which are needed to keep the Russell Vale mine running.

The decision was due last Friday but has been put back to April 10 as the PAC seeks more information from the Dams Safety Committee.

The April 10 deadline for redundancies was not related to the PAC, as the "restructure" was going ahead regardless of the PAC decision, Mr Stone said.

At last count, which was in December, the mine employed 219 workers.

Wollongong Coal's financial difficulties again came to the fore this month when it downgraded its longstanding sponsorship of the Wollongong Hawks basketball club. The Hawks then went into voluntary administration.

The Dams Safety Committee is a statutory body tasked with ensuring the safety of dams in NSW, including the Cataract, Cordeaux and Woronora dams above the Illawarra escarpment - dams which provide drinking water to Sydney and Wollongong.

The Wollongong Coal proposal includes longwall mining under some of the swampland that flows into the Cataract Dam.

Environmentalists predict the mining could cause subsidence which causes creek beds to crack, resulting in the loss of water.

But the Planning Department has expressed its confidence that Wollongong Coal can adequately mitigate the environmental impacts of its actions.