Supervisors at the Appin mine will today vote on whether to authorise rare industrial action in their pay dispute with Illawarra Coal.
About 50 mine deputies are pushing for pay increases including an 18 per cent "market adjustment" plus 4 per cent rises each year as part of a new enterprise agreement.
The supervisors' union says the seemingly large increase would bring pay in line with market rates and would recognise the deputies' key role in the company's enormous earnings.
Results from the protected action ballot are expected tomorrow.
The supervisors are voting on a range of possible actions which include brief stop-work meetings through to potentially damaging week-long stoppages.
Association of Professional Engineers, Scientists and Managers of Australia collieries staff division director Catherine Bolger said no progress was made with Illawarra Coal in the past week.
"Deputies are the front-line supervisors in a coal mine and they are responsible for front-line safety, and, in a mine that's a very gassy mine with a lot of issues like Appin, it's really important that experienced deputies are working there," she said.
"When you look at the rates of pay for deputies in the industry they've significantly increased over the last four years and Appin deputies are simply seeking that they be adjusted according to the market.
"It's not an unrealistic claim. It's quite a modest claim when you compare Illawarra Coal's earnings over the last four years, which was $2.258 billion."
She declined to provide details of the company's offer because of good faith bargaining rules.
However, the minimum rate at the beginning of the 2008 agreement was $110,500, she said.
Deputies were asking for annual percentage pay increases to be included in the new award, rather than individual increases.
"The deputies don't want that same format because they feel that the individual annual increase process isn't transparent," Ms Bolger said.
She expected workers to strongly endorse industrial action as a "last resort".
An Illawarra Coal spokeswoman said the company hoped supervisors voted not to take action.
"What is needed now is for us all to focus on our safety and production performance in order to remain a strong and viable business during these economically challenging times," she said.
"Illawarra Coal is interested in continuing to work with employees and their representatives to reach a reasonable agreement.
"However, at the moment the union is seeking an increase of 27 per cent in salaried wages which is out of step with market standards."
She said Illawarra Coal's "exceptionally low turnover" for mine supervisors showed it offered "competitive arrangements".
Other sticking points for workers include arbitration and the redundancy process.