The Lock the Gate Alliance (LTGA) has come off a long run up to deliver a scathing review of the proposition, criticising the company's motives and decision-making as well as calling into question their care towards the community.

Located 20 kilometres north of Muswellbrook, the site is aiming to extend its mining area to allow an extra 52 million tonnes of coal to be extracted, on top of pushing back the winding down of operations by a further five years (from 2025 to 2030).

LTGA spokesperson Georgina Woods claims that would cause additional damage to an area than has already fallen victim the consequences of nearby mining.

"This mine expansion will widen the area affected by the noise and air pollution from Mangoola coal mine, which is already considerable, and has depopulated the once thriving Wybong district," she said.

"The company has a responsibility to help this region adjust to that decline, and digging another big hole will only make the Hunter more economically vulnerable because it means putting off the tough decisions on diversification that will take years to work through."

Ms Woods believes Glencore, who owns Mangoola which currently employs 400 people, needs to think harder about how it can benefit the community moving forward.

She said the proposal would be detrimental to the company's restructuring efforts if it were to be approved.

"Expanding this mine will also put off the tough job Glencore has in providing its workforce and the community in Muswellbrook with the resources and plans they need to start planning for the long-term," she stated.

Issues with air quality were also raised by LTGA, with their concerns about the Upper Hunter in particular well noted.

People from both sides of the divide are sure to have strong opinions on the topic and are encouraged to make submissions to DPIE.

Visit the website for more information and have your say on the project by Wednesday, August 28.