Environmentalists say a coal mine in NSW is threatening Sydney’s drinking water. 

A new report has uncovered the discharge of contaminated metals from Peabody Energy’s Metropolitan Coal Mine in the Royal National Park near Helensburgh, into Worona Reservoir, which supplies drinking water to Sydney and the Illawarra. 

Analysis by former WaterNSW hydrologist Peter Dupen has found that the rock beneath the Reservoir is cracking in unrecognised and unpredictable ways which is drying out catchments, diverting underground streams and spewing iron, manganese and other contaminants into the water supply. 

Mr Dupen says coal extraction is causing large scale fractures to develop beneath ridges and valleys around the Reservoir. 

“What we are now seeing is unexpectedly extensive fractures opening beneath the streams, stored waters and pristine catchments of the Woronora Special Area,” he said. 

“This has led to several hundred metres of a perennial stream called the Eastern Tributary going dry since early 2017, as well as drainage of the neighbouring ridge groundwater which feeds the stream.  

“If we continue to allow longwalls of coal to be extracted from the Metropolitan Mine, we will continue to see potentially catastrophic drying of the protected catchments and streams currently collecting Sydney’s high quality drinking water. It’s not that the water is leaving the catchment, it’s that the pathways it is now taking to reach the reservoir is different to the natural filtering pathways and is much worse from a water quality perspective. 

“Groundwater in the ridges is now draining out more quickly into the local streams. When the water emerges, it is saturated with iron, magnesia, aluminium and a range of other metals and salts,” said Dupen. 

The analysis of publicly available information was commissioned by the Nature Conservation Council with the support of the Sutherland Shire Environment Centre. 

“This mine has long plagued the Royal National Park with sludge and damaged precious ecosystems, " says NCC Chief Executive Jacqui Mumford. 

“Now it looks like the mine is also drying surrounding creeks and pumping even more pollutants into the water supply. Not only is our drinking water being threatened, but so is the health of one of Sydney’s last koala habitats.” 

The subsidence effect is also causing upland swamps, streamlines and pristine forests - which naturally filter and cleanse the weather supply - to further dry out. 

“I recommend that further mining beneath the Reservoir be immediately halted until the implications of this new type of impact are reviewed. If confirmed, the NSW Government should withdraw approval and leave this environmentally costly coal in the ground,” said Dupen. 

The NCC says mining under drinking water catchments must stop and is demanding that the NSW Environment Minister must immediately: 

  • Halt extraction and fully investigate the hydrological and ecological impacts of the Metropolitan Mine on the Woronora catchment, including its tributaries 

  • Rule out any expansion of mining under any water catchment 

  • Survey koalas in the Woronora Special Area to gain a full understanding of, and protect, the population 

The study is accessible in PDF form, here.