Rio Tinto's Mt Thorley Warkworth coal mine has been fined by the NSW Department of Planning and Infrastructure after failing to minimise dust emissions.
A $3000 fine was issued after an investigation into "significant dust emissions from the Mt Thorley Warkworth mine on Sunday 13 May," the Department says.
The miner has been warned that "further breaches for dust emissions are likely to attract stronger enforcement action by the Department, including the potential for criminal proceedings in the Land and Environment Court".
In January the mine came under fire for the placement of its water fill points, which reduced the effectiveness of the water cart fleet and its dust reduction activities.
Rio stated that this issue had been identified in 2010, and it had since secured funding to solve the problem, with the initial two fill points commissioned in December 2011, and the remaining three in February.
These new fill points are predicted to cut fill times by up to 15 minutes, while the storage capacity of each point has also been increased to enable continuous refills.
Rio stated that an early warning system for faults had been installed as well as automatic cut off.
It also received a number of noise complaints in January, accounting for 85% of submitted complaints.
According to the Department, breezes and low cloud cover contributed to noise transfer from the mines.
The Department's executive director for major development assessment, Chris Wilson, said the mine has now failed to minimise offsite dust emissions and had not suspended or modified operations.
"Both the Upper Hunter Air Quality Network and the mine's own real-time air quality monitor showed a spike in dust levels above the permitted 24 hour average," Wilson said.
"Our investigations have indicated that the mine's air quality and dust mitigation measures required under the mine's planning approval, were not adequate on that day."
While the complaints occurred over a weekend, an officer from the nearby Singleton compliance unit was able to immediately attend the mine; Wilson adding that "the compliance officer observed that the mine was continuing to operate a dragline and excavator, despite dust being generated.
"These activities should have been suspended by the mine in the windy conditions."
Under its existing operating approvals, the mine has to 'implement best management practice to minimise odour, fume, and dust emissions'.
"This includes commitments by the mine to minimise wind-blown and traffic generated dust from coal handling and coal stockpiles, using water sprays on coal stockpiles to reduce airborne dust and using water trucks to minimise dust on roads.
"The inspection found these commitments were not being complied with on 13 May," Wilson said.
"Consequently large volumes of dust from mining operations flowed across the Putty road and the dust was also visible from the Golden Highway," he added.
"The decision to issue a penalty notice to the mine follows two previous warning letters last year in relation to dust."