Coal miner Peabody has been threatened with suspension of its pollution licence after yet another incident of runoff into a creek running into the Royal National Park.
Officers from the Environment Protection Authority (EPA) were on site inspecting Camp Gully Creek on Thursday when they saw the water had turned grey and turbid.
The Metropolitan Colliery has been given three clean-up notices already this year regarding runoff of fine coal material from the mine upstream.
The latest incident has proved too much for the EPA, which announced a wide-ranging review of the mine's Environment Protection Licence would be brought forward two years.
This would include the EPA "considering all available options to protect the environment and community, including suspending the licence", it said.
EPA CEO Tony Chappel said the escalation of its response followed a series of "unacceptable" events.
"This review will commence immediately as the repeated discharges of coal material into our pristine environment is unacceptable," he said.
"Yesterday, we saw another incident when EPA officers were conducting routine monitoring at Camp Gully Creek and observed grey, turbid water with possible coal material present.
"It is disappointing that we have now seen multiple incidents in a matter of months - we expect far better from our industry neighbours who have a responsibility to operate in accordance with their licence for the health of the environment and community.
"Yesterday, our officers collected further water samples for analysis which will form part of our ongoing investigation.
"Understandably, the community is rightly distressed by the impact these events are having on our environment and as part of this licence review we encourage them to have their say which we will take into consideration when assessing all of our regulatory options."
A Peabody spokeswoman said the company was "100 per cent" committed to protecting the environment.
"Peabody is already working closely with the Environment Protection Agency on a comprehensive plan to improve surface water management and satisfy the requirements for next year's review," she said.
"[On Thursday] equipment being used to maintain our clean water drainage systems inadvertently disturbed sediment.
"Metropolitan Collieries remains 100 per cent committed to protecting the local environment and meeting community expectations of our operations."
There have been multiple instances of coal fines washing into Camp Gully Creek, which feeds the Hacking River, which flows through the length of the Royal National Park.
Witnesses in September described how coal pollution had penetrated almost the the entire length of the river to the Audley Weir.
The EPA last week gave Peabody another clean-up notice, the third this year, directing the US-owned miner to clean large amounts of built-up coal fines out of its retention dams so they can properly contain large amounts of water.
But Dr Ian Wright, senior lecturer at Western Sydney University, said proper monitoring was needed downstream because the EPA licence did not capture the reality of the sensitive area.
"It's not so much what's coming out of that waste pipe, it's the overall impact on Camp Creek and the Hacking," he said.
"The runoff in storms isn't captured by the licence."
The EPA has indicated improved water quality monitoring downstream could be included in its licence review.
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