Supervisors at Illawarra Coal's Appin mine will enter the second day of an unprecedented two-week strike today.
Fifty-two frontline supervisors - called deputies - walked off the job early yesterday morning in an effort to bring months of failed negotiations over base rates of pay at the mine to a head.
Yesterday, the company declined to say exactly what impact the strike would have on its Appin operations.
"Illawarra Coal is implementing plans to ensure the safe and efficient operation of the mine during the period of industrial action," a spokeswoman said.
The union representing the supervisors said their pay claim was "very reasonable" and would bring base rates into line with NSW standards, understood to be about $150,000 a year.
However, the company - a subsidiary of BHP Billiton - has previously said supervisors were "competitively remunerated" and their claims were "unreasonable".
Association of Professional Engineers, Scientists and Managers of Australia Collieries director Catherine Bolger yesterday said deputies played a key role in safety and production at the mine.
"They think it's unfair that the mining supervisors in the Illawarra are not paid the industry average, and they think that Illawarra mining workers should be valued in the same way as workers throughout the rest of NSW," she said.
"Throughout the last four years, these workers have been on an enterprise agreement and they've been locked out of any market adjustments through that time, when there's been a period of great growth within the mining industry."
Ms Bolger said the supervisors felt BHP's corporate management was interfering in negotiations.
She said, despite its $2.3 billion in earnings in the past four years, Illawarra Coal had argued there was no additional money.
"Even when we try to work within their budget, they still say there's nothing that can be done," she said.
"They're just not negotiating properly."
Illawarra Coal president Troy McDonald previously said the industrial action would not result in agreement.
"Such action will only cause uncertainty for the mine, all its employees and the broader Illawarra community," he said.
He said the supervisors' base salaries had increased by more than 18 per cent in the past four years, including an average increase of 5 per cent in September.
South Coast Labour Council secretary Arthur Rorris backed the Appin supervisors yesterday, saying they deserved the same pay as others in the industry.