LAKE Macquarie councillors have objected to new mining activity at West Wallsend Colliery.
Owner Glencore applied to extend longwall panels 51 and 52 between Ryhope and Wakefield.
With the company's major grout spill at Mount Sugarloaf Conservation Area in mind, councillors were reserved when Glencore's Wade Covey spoke at a meeting.
"We acknowledge and regret the unpredicted subsidence impacts that occurred during 2012 in the Sugarloaf State Conservation Area," Mr Covey said.
"This project is in a different area with different topography and has different geological conditions and the same subsidence risks do not exist."
Council staff recommended a submission be made to the Department of Planning and Environment highlighting concerns about subsidence, connective cracking and negative impacts on Ryhope's biodiversity.
These concerns have only surfaced recently, as the council approved the colliery's application to continue mining operations in 2012.
But Glencore's request to extend the longwalls has raised alarms.
Mr Covey and Mr Ostermann urged the council to reconsider its position.
However, director city strategy Tony Farrell said the council had concluded the subsidence risk was too great to retract its submission.
He said it was an area of concern that warranted further consultation.
The NSW Department of Planning and Environment will determine the application's outcome.
If given the green light, the longwall extensions are expected to take place in November.