Environmental groups are calling for tough action from the state government following another pollution incident at the Peabody Metropolitan Colliery at Helensburgh.

A landslip, which occurred in early August following 80mm of rain, caused sediment to be washed into Camp Gully Creek, which flows into the Hacking River.

The Environment Protection Authority (EPA) issued a clean-up notice the next day for the 600 square metre area, which was not part of the mine's active operations and was not being disturbed at the time of incident.

James McCormack, editor of Wild magazine, posted, "What I found was shocking. Thick black sludge was smeared over the rocks and banks of the Hacking River and of its beautiful rainforest tributary Camp Gully Creek".

President of National Parks Association of NSW Southern Sydney Branch, Brian Everingham, said there had been many such incidents at the mine.

"The EPA is only too willing to do nothing more than a slap on the wrist," he said. "The waters of the Hacking River downstream are therefore at risk," he said.

"We call upon the Minister for the Environment to act aggressively to ensure that the EPA is fit for purpose, that Peabody is called to account and that given that this is but one of a series of breaches by Peabody, that its licence to operate and its terms of operations are withdrawn forthwith."

Sutherland Shire Environment Centre spokeswoman Catherine Reynolds said, "Prevention Notices that were issued to the company in September 2022, and subsequent conditions imposed by the EPA have not been sufficient to ensure that pollution events such as this cease occurring," she said.

"We maintain our position that this is not an appropriate location for a coal mine. The continued operation of the colliery at this site represents an ongoing risk to the Royal National Park."

Peabody advised the media of the incident and the preliminary works that were being undertaken to minimise impacts to water quality.

"Our company is committed to working as quickly and carefully as possible to remove the material from the affected area in cooperation with the EPA," Peabody Australia president Jamie Frankcombe said.

EPA director of operations Adam Gilligan said initial reports were of significantly increased turbidity in the creek, with discoloured water and sediment extending downstream to the Hacking River.

"EPA officers observed a significant amount of slumped material in the creek and collected water samples for analysis," he said.

"We have issued a clean-up notice to Metropolitan Collieries to ensure they urgently develop a plan to remove this material from the creek."

Scientists engaged in the program, which was launched in May 2023, to restore platypuses to Royal National Park were concerned the thick, black sediment could contaminate their food supply.

UNSW researcher and project lead, Gilad Bino told ABC Illawarra he had received some assurances from the EPA it was a localised event, "so, we do not think that, at the moment, [the landslip] poses a threat to the platypus."

However, Dr Bino said the research team had recorded a visible increase in system turbidity through devices placed in the Hacking River.

James McCormack, editor of Wild magazine, who inspected the site, wrote, "What I found was shocking. Thick black sludge was smeared over the rocks and banks of the Hacking River and of its beautiful rainforest tributary Camp Gully Creek".

Sutherland Shire Environment Centre spokeswoman Catherine Reynolds said "We've seen so many pollution events from this mine over the last year it's hard to see how the 'environmental protection' part of the license applies".

"Prevention Notices that were issued to the company in September 2022, and subsequent conditions imposed by the EPA have not been sufficient to ensure that pollution events such as this cease occurring," she said.

"We maintain our position that this is not an appropriate location for a coal mine. The continued operation of the colliery at this site represents an ongoing risk to the Royal National Park.

"Earlier this year, Environment Minister Penny Sharpe promised an EPA with teeth. The fines applied to date are insignificant to a company this size."

In January 2023, Ms Sharpe, who was at that time the shadow minister, visited Camp Gully Creek with Heathcote MP Maryanne Stuart, who later wrote on social media, "We are all fed up with the NSW Government's approach, giving them a gentle slap on the wrist".

Following the latest incident, Ms Stuart thanked all those who had contacted her, and provided an update on the clean-up.

Ms Stuart said the EPA's clean-up notice required Peabody to urgently develop a plan and to remove the material from the creek and to provide weekly progress updates.

"Works must continue until the EPA is satisfied that the creek has been restored," she said.

"The clean-up and stabilisation of the bank is anticipated to take several weeks. EPA officers are conducting frequent inspections of the clean-up activities to ensure the work is being done appropriately and promptly."