The EPA is also concerned that it took nearly a week for mine personnel to discover the problem and report it. An assessment of the monitoring systems currently in place at the mine will form part of the EPA’s investigation.

The EPA was informed of the incident on Monday evening after Peabody reported it to the Environment Line.

The company said the dam wall may have collapsed last week but says it only came to the attention of mine staff on Monday.

EPA officers were onsite on Tuesday to carry out an inspection and to interview mine personnel. Samples were also taken for testing.

EPA North Director, Gary Davey said the amount of material that might have left the site from the dam is unknown at this stage.

“Communities across the Hunter and Mid-North Coast regions have just experienced record rainfall over the last seven days,” he said.

“While this is a factor to consider, the EPA’s investigation will also examine how the dam, which was used as a sediment control measure, is managed, maintained and monitored.

“Wambo Coal, like all environment protection licence holders, has a responsibility to comply with the conditions set out in its licence and to ensure its activities do not cause harm to the environment.

“It is important that the company has appropriate procedures in place to ensure that its systems and safeguards do not fail. However, in the event of a failure, it is vital that there is an early warning process so that action can be taken quickly and the EPA notified.

“Failure to meet these requirements can be a breach of environmental legislation and may result in regulatory action from the EPA.

“The Hunter River catchment is a sensitive environmental area, relied upon by industry, farmers and the wider community for its freshness and good water quality.”

The EPA will be carrying out a thorough investigation of the incident and has also requested a full incident report from Wambo Coal.

ICN contacted Peabody Energy for comment.