Wollondilly MP Nathaniel Smith has slammed the NSW Department of Planning's approval of the Tahmoor mine expansion.
The department's report recommending the approval of the SIMEC Tahmoor Coking Coal plan to expand its operations was released late last year.
Mr Smith condemned the timing of the report.
He said the project would mine directly beneath the northern and north-eastern outskirts of the township of Bargo including homes, rural properties, and public utilities such as the Main Southern Railway and the Moomba to Sydney Gas Pipeline.
"The 166-page report was dropped in the middle of the night just days before Christmas and without warning to me or my office", Mr Smith said.
"The original DA (development application) gives clear insight to the intent of this project - to eventually mine directly under the entire township of Bargo.
"Whether it is 751 or 143 homes affected, that is the lives of those families changed forever - numbers that are unconscionable."
The Department of Planning's report predicts homes in the area may experience a maximum conventional subsidence of up to 1,450mm.
However, the report also found that the mine site is susceptible to non-conventional subsidence that may increase those predicted maximums.
This is due to geological anomalies such as the mine site's close proximity to the Nepean Fault zone.
Mr Smith cautioned against viewing the issue through the usual coal mine culture wars.
"Even at conventional levels of subsidence, NSW Planning predicts that at least 22 homes will be affected to such a degree that offers of acquisition may need to be made", Mr Smith said.
"Mining has served this country very well throughout our history and plays a vital role in our future.
"But it must work for the community and we should never allow people's homes in established townships to be destroyed by mining.
"I have personally seen the devastation to homes and heard the heart-breaking experiences of mine subsidence from my constituents.
"These cases can take many years to resolve."
SIMEC head of coal mines Peter Vale said the company welcomed the department's recommendation for the project to be approved, 'citing a reasonable balance between maximising the recovery of a coal resource of State significance and minimising the potential environmental and amenity impacts'.
"If approved, the project will secure the futures of more than 400 staff and has been independently forecast to inject over $130m into local businesses such as cafes, restaurants, fuel stations and our suppliers," he said.
"It will also play a critical role in the future of Australian steelmaking, supplying high quality metallurgical coal to a number of steelworks around the country, including GFG's own Whyalla Steelworks.
"As part of our revised mine plan, we reduced the homes directly mined under in Bargo by 80 percent, while 90 percent of the homes at risk of potential subsidence fall in the nil to minor repairs category.
"In its report, the DPIE states it 'is satisfied that a well-established regulatory and compensatory framework exists, which has been successfully implemented at other underground mines in the region to ensure houses are appropriately maintained and restored to a condition equal or better than their pre-mining state at no financial cost to the owners.'
"We've met with Mr Smith on a number of occasions to update him on the project.
"We'd still like the opportunity to discuss his concerns and the Subsidence Advisory NSW process, which will be the independent body residents deal with should they have concerns."
If the mine's extension is approved approximately 400 jobs will be secured and mining operations will continue until 2032.
University of Western Sydney Professor Ian Wright has spent a decade researching the effects of waste water from the Tahmoor Coal mine on the Nepean and Bargo river system.
He told the Advertiser last year the level of pollutants in some sections of the river was "unnaturally high".
"The Environmental Impact Statement (EIS) for the mine shows that waste from the mine makes up two thirds of the flow of the Bargo River - which is really high," he said.
"How I distill it down is that for the past 10 years we have been trying to find out how this waste affects the ecology of river life and it shows that the growth of algae has choked the river.
"The Nepean River is actually in really good shape but mine waste changes the river in a negative way where it meets the Bargo River."
The expansion proposal will now proceed to the next phase which will include online public hearings conducted by the NSW Independent Planning Commission.
Speaker registrations are now open through the NSW Planning website and will close on February 5, 2021 with hearings scheduled later in the month.
"I'll be registering to have my say and I encourage anyone potentially impacted by this proposal to also register and have their say", Mr Smith said.
"Bargo residents should have confidence that I will be their voice on this issue and stand with them to stop this mine expansion."
Electronic Public Hearings will be held on Monday, February 15 and Tuesday, February 16 2021 from 10am at: www.ipcn.nsw.gov.au/livestream.
Written submissions will be accepted up to 5pm on February 24 via email, post or the online portal: www.ipcn.nsw.gov.au/have-your-say.