Longwall coal mining approval threatens Sydney water catchment

Campaigners survey the Cataract Dam in February. Photo: Protect Our Water Alliance / Facebook

As the COVID-19 emergency ramps up, the New South Wales government has quietly given United States coal giant Peabody Energy the go-ahead to extend three longwall coal mines, two of which are underneath Wollongong’s Woronora Reservoir.

On March 16, NSW planning minister Rob Stokes told Metropolitan coal, a Peabody subsidiary, that the extraction plan needs to be “sufficiently robust” to limit the impact of subsidence, including the loss of water — a problem impacting Cataract Reservoir.

Community opposition to longwall mining under water catchments has been a feature of politics in this state for many years. Parliament was due to debate a 10,000-strong petition, organised by the Sutherland Shire Environment Centre, against Peabody Energy’s expansion plans. However, parliament was shut down before that could happen, quietly giving approval instead.

Protect Our Water Alliance (POWA) spokesperson Kaye Osborn told Green Left that the community is “very angry” because “the mines have an impact on all our water”.

“Stokes has given approval for mining to progress from beneath the streams and swamps that feed the Woronora Reservoir to beneath the reservoir itself,” she said.

The Greater Sydney Drinking Water Catchment supplies 5 million people across Sydney, the Illawarra, Blue Mountains, Shoalhaven, Goulburn and the Southern Highlands. The Upper Nepean and Woronora catchments on the Illawarra plateau (between Wollongong, the Royal National Park and the Southern Highlands) provide drinking water. Five reservoirs — Woronora, Cataract, Cordeaux, Nepean and Avon — are on the Illawarra Plateau and are connected via rivers, tunnels and weirs.

The gross hypocrisy of the government’s decision, Osborn said, is that the off-limits “special areas” only apply to surface water in the catchments. Mining leases and underground coal mines are exempt.

“Of the five reservoirs on the Illawarra Plateau, only the Nepean is free from being mined either alongside, or underneath it,” she said.

“These reservoirs supply 20–30% of the Greater Sydney water supply system. They are the sole supplier for the Illawarra and Macarthur regions, as well as the Sutherland Shire. They are also crucial in times of drought, because they are located in an area of high rainfall. Greater Sydney’s largest reservoir — Warragamba — is further west and the area has less rainfall.

“The Illawarra Plateau area has more reliable rainfall so, when the Warragamba Dam is low or compromised such as in the cryptosporidium water crisis of 1998, all of Greater Sydney could rely on our catchments.

“By comparison, Sydney’s expensive desalination plant only supplies 15% of our drinking water.”

Governments have been allowing longwall mining here since the 1960s.

“The Cataract Reservoir was undermined between 1972 and 2000, resulting in significant subsidence and surface cracking,” Osborn said.

“Peabody has been mining coal around the Woronora Reservoir for more than 10 years. But now, the new longwalls have been approved directly under the reservoir. It is shocking because it will undermine the water supply for Sutherland Shire.”

The Office of the NSW Chief Scientist commissioned an independent panel to assess coal mining at the Metropolitan and Dendrobium coal mines in the Greater Sydney Water Catchment Special Areas. Its 2019 report found that mining could go ahead provided that strict conditions were adhered to, even though it found “evidence that mining … has resulted and continues to result in losses of water from the Greater Sydney water supply system”.

Osborn explained that longwall mining results in cracking that can extend from the coal seam to the surface as the area above the mine collapses.

“Water that would have found its way into the reservoirs is diverted into these cracks and then flows out or is pumped out of the mines. The mining also damages groundwater systems and changes the hydrology of the catchment,” she said.

A 2016 report from the NSW Chief Scientist found that up to 42 million litres of water a day, the equivalent of 13% of the daily water supply from the Woronora, Cataract, Cordeaux and Avon reservoirs, can be lost in this way.

“It is disturbing that the impacts of longwall mining on the water catchments are poorly documented, difficult to predict and can escalate over time.

Studies have found that subsidence has occurred 25 years after longwall mining has ended," Osborn said. "There are no successful examples of remediation after longwall mining has finished.

“Sydney is the only city in the world that allows longwall mining under a public water catchment. There is no good reason for this."

POWA recently organised a convoy to witness the longwall mining damage at the Cataract Reservoir, and is looking at how to keep the pressure up under COVID-19 physical distancing requirements.

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