The proposal, which is now on public exhibition after being lodged with the state government, would increase the capacity of the open pit to take 177 million more tonnes of tailings.

That is equivalent to seven extra years' use.

The planning application, named Modification 13, has also revealed Cadia plans to create a lake on top of the open pit once its use expires.

Other features of the application include decommissioning of a ventilation shaft in the pit which would be covered over by the additional tailings and the installation of a new shaft away from the open pit.

The modification also reveals plans for constructing additional "buttressing" of the southern tailings dam.

A collapse in the northern tailings dam wall last year forced Cadia to stop using the dams for depositing tailings and instead pump it into the open pit.

A Cadia spokeswoman said the company was still looking at options about how it would repair the northern dam wall.

The application said the modification would not alter the amount of mining, ore processing or tailings creation at the mine. "Nor would it alter the project operational workforce," it said.

The application said Cadia had consulted with nearby residents, the Environmentally Concerned Citizens of Orange group plus the Orange City, Blayney Shire and Cabonne councils.

All three councils have supported the mine's modification plans.

It is available for public viewing online and at the councils' offices until Thursday October 10.