The IPC will hold hearings on the proposal on October 18 and 19, with residents invited to write submissions or register to speak before commission's hearing.

The NSW Department of Planning, Industry and Environment has recommended the mine expansion be approved, saying the revised plan for bord and pillar mining, rather than longwall, would be safer for the environment above.

Environmentalists were furious at this call, saying the company could not be trusted with mining beneath the Sydney-Wollongong drinking water catchment.

Read more: Developer sidesteps questions over escarpment plans

The Protect Our Water Alliance (POWA), a relatively new environmental group which focuses on the catchment, urged people to make their voices heard.

"The mining expansion will drain both surface and ground water from the Cataract Reservoir catchment, part of the catchment's Special Areas that forbid public access because of their sensitivity and strategic importance," POWA spokeswoman Kaye Osborn said.

"Our communities won't see any benefits of this project, only a trashed water catchment and warmed climate for generations into the future.

"POWA will continue to oppose the Russell Vale mine expansion, and all mining in our water catchment. The upcoming Independent Planning Commission is an opportunity for Wollongong to be heard, and for our communities to collectively demand a safe, secure drinking water supply into the future."

POWA and the Lock the Gate Alliance are hosting a webinar on the IPC on Tuesday, October 6, at 6.30pm.

People can register to participate in the hearing by video conferencing or by telephone, via the IPC website.

The deadline for written submissions to the IPC is Tuesday, October 27.

We depend on subscription revenue to support our journalism. If you are able, please subscribe here. If you are already a subscriber, thank you for your support.