In short:
Workers at Premier Coal have voted to take protected industrial action after talks between unions and the Chinese-owned miner broke down.
The parties are trying to negotiate their final enterprise agreement before coal-fired power is phased out in WA in 2030.
What's next?
The WA government says the industrial action will not impact electricity supplies to the grid, with Synergy stockpiling coal.
Industrial action is set to hit the heart of Western Australia's power grid after talks between unionised staff and management at one of the state's struggling coal mines broke down.
Premier Coal is the main supplier to state-owned power provider Synergy's Muja and Collie power plants, 200km south of Perth.
The mine is owned by Yancoal Australia, which is controlled by Chinese state-backed miner Yankuang Energy Group.
Workers are pushing for better pay and clarity on their redundancies as part of their final enterprise agreement, with WA's state-owned coal power plants set to be shuttered by 2030.
Final talks on Wednesday morning failed to reach a resolution, setting the scene for strike action, according to Australian Manufacturing Workers' Union (AMWU) state secretary Steve McCartney.
"The arrogance of that company — they just treat [the workers] with contempt,"he said.
"They weren't listening to anything."
Mr McCartney said WA energy consumers should brace for grid disruption if the dispute leads to protracted industrial action.
The ABC has contacted Yancoal Australia for comment.
Strike at the heart of energy grid
The state government said any strike action would not affect power supplies, as Synergy had already stockpiled coal.
The industrial unrest follows confirmation taxpayers would help cover costs of the rehabilitation at the mine, with the government pushing Premier Coal to merge with Indian-owned competitor Griffin Coal.
"What Premier Coal is doing is acting like a hedge fund and trying to work out how much money they can milk out of the government without spending their own; that's a disgrace," Mr McCartney said.
He said workers will meet over the next two days to discuss potential dates and lengths for the stop-work action, with support for stoppages longer than 12 hours.
"[Workers] need to make a solid decision so that the company understand we aren't going to tolerate getting pushed around,"he said.
More than 90 per cent of the workforce at Premier Coal are unionised.
The vast majority of Mining and Energy Union (MEU) and AMWU workers backed a strike in a recent ballot.
Clarity on the end of coal
The protection against future reductions to workers' redundancy payments are a central sticking point in the negotiations.
MEU state secretary Greg Busson said workers were growing increasingly anxious about the 2030 deadline, and wanted clarity as the company winds down operations.
"[Workers] just want certainty about what their last couple of years at Premier Coal are going to look like," he said.
In April, Premier Coal announced the loss of between 70 and 100 jobs at its mine site near Collie, citing slowing demand for coal-fired power.
Shadow Energy Minister Steve Thomas said workers at the state-owned power stations were receiving better support than the mine workers.
"There is a quiet desperation creeping into the coalfields at Collie as the Labor government closes their industry down, and this industrial action is just the next step," he said.
"There is no certainty for these workers, and it is no wonder that they are pushing for a better deal in the final three years of their job tenure."
"The government doesn't need to end coal by the end of 2029, and it shouldn't shaft non-Synergy workers in the process."
A Cook government spokesperson said workers had a right to bargain for wages, and it had supported the Collie transition with more than $700 million in funding.
The spokesperson said the funds included $3.2 million to support Premier Coal workers and contractors impacted by the recent shutdown.