A July 2 incident saw the overflow of material from a holding cell in the reject emplacement area. As a result, all relevant agencies and authorities were notified and Centennial has continued to work with these bodies, it said.

“The site has been stabilised and the spill contained and sediment fences have been erected between the mine site and the Wollangambe River to prevent further impact,” the company said.

“Last week Clarence was on a scheduled one week shutdown. The area where the incident occurred remains shutdown.

“The cause of the incident is still being investigated.”

The New South Wales Environmental Protection Agency revealed that the incident at the mine resulted in water and coal fines entering the nearby Wollangambe River with at least 150m of the river showing signs of impact.

“The EPA is obviously very concerned about any impacts on the Wollangambe River, which runs into the Greater Blue Mountains World Heritage Area about 2km downstream of the mine,” EPA south director Gary Whytcross said.

“This is a very sensitive environment. A full assessment of environmental impacts is continuing and the EPA is collecting evidence on to determine potential breaches of the environmental legislation.”