Centennial Coal's plan to divert water has raised pollution concerns.

A water scientist has expressed concerns over a proposal by Centennial Coal to divert a significant amount of untreated groundwater from its Angus Place Colliery into Sydney's Wangcol Creek, potentially exacerbating pollution in the catchment area.

Centennial Coal has applied to the NSW Department of Planning and Environment to discharge 10 megalitres daily into Wangcol Creek, an estimated five-fold increase. 

The coal company cites the need to bypass its water treatment plant, which is operating at capacity, as the reason for the additional discharge.

The company's modification report allegedly highlights the need to manage the risk of flooding as a key factor, stating that the mine may not be viable in the future if flooding occurs.

The Angus Place Colliery, dormant since 2015, is planned to reopen under the name Angus Place West to secure coal supply to the nearby Mount Piper Power Station until its closure in 2040.

According to planning documents, the water currently released into Wangcol Creek contains elevated levels of heavy metals such as cobalt, iron, nickel, and zinc and is mainly untreated groundwater. 

Centennial Coal argues that diluting these contaminants with water from Angus Place would improve water quality by reducing contaminant concentrations.

However, environmental expert Ian Wright of Western Sydney University disagrees, suggesting that the discharge could increase pollution levels. 

He has told the ABC that the salt, nickel, and zinc pollutants in the mine water are toxic to aquatic life.

While the concentrations of these pollutants may decrease, the increased volume of water could spread them further downstream, having a more significant environmental impact.

Wright says that the current environmental licence from the Environment Protection Authority (EPA) is ineffective, as it sets low benchmarks for pollution and does not include salt, nickel, and zinc in its limits. 

The EPA issued a statement to reporters saying it “looks forward to seeing improvements in the quality of discharge water into the catchment”.

Concerns have also been raised by local food growers who rely on water from the area for their crops and are worried about potential contamination. They emphasise the importance of expanding the water treatment plant's capacity.

WaterNSW says it is closely monitoring the situation and ensuring treated water from Warragamba Dam remains safe to drink. The proposal is pending approval and expected to run until August 2024.