New South Wales has allowed a coal mining extension under Sydney's Woronora water reservoir.

The NSW Department of Planning, Industry and Environment has granted approval to Peabody Energy to extend its coal mining activities under one of Greater Sydney’s reservoirs.

According to the Sydney Morning Herald, the decision was made earlier this month. The plan is for two longwalls to go beneath the Woronora reservoir, which supplies parts of southern Sydney and the northern Illawarra.

It is the first time in two decades that coal mining has been approved directly beneath one of Greater Sydney’s reservoirs.

The decision was reportedly made before a petition against the plan could be debated in the NSW parliament, which has now been suspended due to the COVID-19 crisis.

“We don’t have enough detailed information of the extent of impact of mining on the primary function and purpose of the special areas which is to supply drinking water into Greater Sydney and the Illawarra,” said Peter Turner, mining projects science officer at the National Parks Association.

Experts say that previously, subsidence as a result of mining has caused issues with water quality, which later required the water to be treated.

The NSW Department of Planning, Industry and Environment says the Metropolitan mine was “carefully designed to limit subsidence and surface impacts, including the depth of mining, the narrow width of the longwall panels and larger pillars between longwalls”.

“All the experts have advised that the proposed mining would not compromise the reservoir – but have recommended a range of precautionary adaptive measures to ensure the mining is carefully monitored,” a spokesperson said.