Peabody Energy is seeking to expand its Wilpinjong coal mine north-east of Mudgee in order to extract a further three millions tonnes of coal from the open-cut project.
The company has requested the state Planning Department for a modification on its original 2006 approval, with the planned changes on public display until September 9.
As well as planning a ramp up in production, changes include expanding the project by 70 hectares, the upgrade of its coal handling and preparation plant, and permission to begin operating a light vehicle servicing workshop.
The expansion is set to create a further 80 jobs at the coal mine.
Wilpinjong's project development manager Jamie Lees said the $18 million expansion would not extend the mine's life beyond its 2027 authorisation, ABC reported.
Lees says the proposal comes after a resources review last year.
"The capital improvement is not significant, it's only about $18m, but with the increase in coal we get access to, we see an increase of employment of 80 people over 12 months and I suppose if you flow those jobs on, you have an indirect benefit of 157 jobs," he said.
"And from a regional output, or business turnover, that can equate out to $234m."
Peabody purchased Wilpinjong in 2006. The mine has a workforce of around 550 people, including contractors, after recently transitioning to Peabody owned and operated in April this year.
Wilpinjong produced 12.5 million tons of saleable coal in 2012.