A RIO TINTO-run mine underpaid 20 workers for more than two years, a court has found.
In September 2015 Rio Tinto's Hail Creek mine reduced shift lengths from 12.5 hours to 12 hours for 20 operators and maintainers.
This meant the worker's weekly rostered shift dropped below 47.75 hours per week, which the company said reduced the "roster allowance" payments they were entitled under their contracts.
Roster allowance payments were designed to make up for working over the mine's 24-hour, seven day a week operation.
But the CFMEU took the mine to court and claimed the reduction in pay breached their worker's contracts. The union argued the agreement stated rostered hours were "indicative" and employees were expected to work for as long as needed.
The CMFEU said this meant some workers had been underpaid $4500 and others $4200 every year since late 2015.
Federal Court Justice Darryl Rangiah on Friday found the mine's argument the 20 workers no longer worked the prescribed 45.75 hours per week was correct, but this did not mean the roster allowance could be reduced.
"The reduction of the shift lengths by 30 minutes must have resulted in a reduction in the indicative number of hours per week to something below 45.75. That is the premise of the employer's case," he said.
But Justice Rangiah said as the contract said employees were expected to work "hours that are reasonably necessary to perform their role".
"While the roster allowance has been reduced by $4500 per annum for one group of affected employees and by $4200 per annum for another, they may still be required to work the same hours as before.
"In my opinion, a reduction of the rostered hours to 42.5 hours per week is not substantial enough to conclude that the rosters do not meet the description of an 'indicative 45.75-hour week'."
Justice Rangiah said the workers could end up doing the same amount of work and be paid thousands less for it. But he said there was "no suggestion" Hail Creek had orchestrated a "deliberate strategy" to have workers do the same work for less money.
He said the underpayment breached the Fair Work Act.
Hail Creek and the union will submit to the court what penalty, compensation and relief should be paid. -NewsRegional
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