Last week the EPA said it was investigating a dam collapse at Peabody Energy’s Wambo coal mine in the Hunter Valley which resulted in a portion of the dam wall collapsing and discharging sediment- laden rainwater to the environment.

In latest developments, Warkworth personnel contacted the EPA regarding the partial collapse of the wall on 6 January. At that time, the company indicated that the event had not caused or threatened material harm to the environment. Nonetheless, the EPA requested an incident report.

The company also advised the EPA that it had undertaken work to contain the sediment laden water. However, photographs provided to the EPA on 15 January suggest that sediment laden water – made up of soil and sand is continuing to leave the site, and a quantity of sediment from the original incident is yet to be cleaned up.

The EPA has requested additional information from Warkworth and will be conducting a site inspection to assess the impact. Depending on the outcome of the investigation, the EPA will consider further regulatory action.

The EPA has also directed the company to clean-up the site to prevent further mobilisation of sediment, both on and off the site, and clean up the accumulated sediment that has already left the site.

A Rio Tinto spokesperson told in a statement: “A partial failure occurred in a sediment dam at the Mount Thorley Warkworth site during the heavy rainfall experienced across the Hunter Valley last week, with falls in excess of 100 millimetres recorded in the Singleton area.

“We voluntarily reported the incident on the same day to the Environmental Protection Authority as well as the Singleton Council, which sent an engineer to inspect the site and confirm there was no risk to motorists.

“The dam contained runoff water from pre-mining activities, and flowed through culverts under Wallaby Scrub Road on to Coal & Allied owned farm land. The dam was drained and deepened to prevent further flow of water.

“As part of ongoing and regular monitoring of the area, we inspected the dam on Friday following rainfall to confirm that no water is leaving the dam.

“The incident is being fully investigated in cooperation with the Environmental Protection Authority.”