Toxic discharge from an underground Blue Mountains coal mine is causing major damage to protected local waterways, raising concerns about the regulation of mining in local heritage areas. 

A Western Sydney University study published in the Journal of Water, Air, Soil Pollution examined the active Clarence Colliery mine near Lithgow, where mine waste discharge and contaminated surface runoff flows into the protected World Heritage Conservation Area.

Dr Ian Wright, from the School of Science and Health, says underground coal mining has been a major industry in the Blue Mountains region, east of Sydney, for more than a century.

"Mining has supported the development of towns and power stations in the Blue Mountains, but the subsequent environmental impacts are ongoing," Wright says.

"When the Federal Government nominated for the Blue Mountains area to be listed as a World Heritage Area, it highlighted the important role of the NSW Government's Environment Protection Authority in regulating coal mines.

"However, the ongoing toxicity uncovered by this study highlights the failure of statutory process across two levels of government, and the lack of appropriate planning approvals and ongoing environmental pollution licensing."

The operators of the underground coal mine, Centennial Coal, have been allowed to discharge mine waste into the river under its environmental licence since the 1980s. 

The study analysed heavy metal concentrations and macroinvertebrate health to determine the water quality of the Wollangambe River and its tributaries near the point of the wastewater discharge. Beyond the boundaries of the mine, the majority of the study area falls within Blue Mountains National Park and Wollemi National Park.

The study found macroinvertebrates diversity dropped by more than 63% – such a reduction of 'family richness' is larger than many coal mines regionally and internationally.

In addition, the concentrations of nickel and zinc that this study detected in the Wollangambe River below the mine discharge were at levels that are known to be hazardous for aquatic species.

Wright says the difference between the wastewater discharge and the otherwise near-pristine condition of the local river system is stark.

"The pollution from the mine extends at least 22 kilometres downstream, and includes thermal pollution, increased salinity and increased concentrations of zinc and nickel," he explains. 

"The mine's waste discharge has strongly modified the river's ionic composition, and is causing major impairment of the aquatic ecosystem."

The ABC reported that the study prompted swift action from the Environment Protection Authority (EPA), who changed the operating licence, reducing the amount of metals and salt that could be in the discharge waters

A spokeswoman for Centennial Coal, Katie Brassil, told the ABC the EPA was currently finalising the five-year review of its Environmental Protection Licence (EPL).

"This process included extensive aquatic ecology, ecotoxicology and macroinvertebrate investigations and monitoring in consultation with the EPA, Office of Environment and Heritage, and community stakeholders including Dr Ian Wright," she said.  

"As a result of this review Clarence will operate under a new EPL, which will include agreed reductions in metal concentration limits for all water discharged to the Wollangambe.

"Clarence will also be required to comply with a Pollution Reduction Programme (PRP), also to be issued by the EPA, which will result in Centennial formalising options to address all water quality issues and to meet specific water quality milestones.