Environment

‘No place for mining’: coal mines drain water from dams

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Two coal mines in Greater Sydney's catchment area are likely to be diverting millions of litres of water daily from reservoirs, an independent panel has found, prompting calls for a halt to further mining.

The panel's "initial report", released before Christmas, found it "plausible" the Dendrobium underground mine between the Avon and Cordeaux dams was diverting 3 million litres a day into its workings. The nearby Metropolitan mine's inflows were put at half a million litres, diverted from Woronora Reservoir that supplies Wollongong.

Sydney Water's Cordeaux Dam near Wollongong , is losing water flows to a nearby underground coal mine.

Sydney Water's Cordeaux Dam near Wollongong , is losing water flows to a nearby underground coal mine.Credit:Nick Moir

The panel endorsed the Berejiklian government's approach of approving expansion – in the form of longwall mining – on an "incremental basis" that allowed for adjustments according to emerging "knowledge gaps".

The experts conceded that while understanding of impacts of mining in the Special Areas had "progressed substantially" over the past decade, remaining limits on monitoring and modelling means it remained "difficult" to confirm the mines had only "negligible consequences on surface water supplies" as claimed by miners.

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WaterNSW welcomed the "frank" report, saying it had long highlighted "the unacceptable risk posed by longwall mining" in the catchment.

The government agency singled out the Dendrobium mine, saying no expansion should be approved unless officials were confident there would be no further water losses.

Water losses are caused by subsidence after the coal is extracted. Fissures reaching the surface drain creeks and swamps, and could – if they extend horizontally – affect the reservoirs too.

"WaterNSW holds the firm view that no further longwall mining should be approved within the Special Areas with dimensions of the size currently undertaken at the Dendrobium mine," a spokesman said.

'Trial and error'

Peter Turner, mining projects science officer for the National Parks Association, said the experts acknowledged many of the limits in understanding how mining was affecting Sydney's water supplies.

“Subsidence-induced leakage from the Avon and Cordeaux Reservoirs caused by the exceptionally aggressive and damaging Dendrobium mine may soon pass – without detection by current monitoring and modelling systems – the million litres a day limit set by the Dams Safety Committee," Dr Turner said.

"There would appear to be little basis for confidence that this limit has not already been passed.”

How subsidence under the catchment can lead to water loss from reservoirs and surface creeks.

How subsidence under the catchment can lead to water loss from reservoirs and surface creeks.Credit:Kiran Charles/NPA

"There should be no such further mining approvals until the extent and significance of water losses can be assessed and predictively estimated with a high degree of scientific confidence,'" he said. "The Special Areas are no place for mining development by trial and error.”

'Strict' controls

A spokesman for South32, owner of Dendrobium, said the mine operated under a "strict performance criteria and comprehensive monitoring requirements".

"We take our environmental responsibilities seriously and work with the relevant government authorities to manage and report our compliance activities, including environmental performance," he said.

Don Harwin, the minister for utilities, said water was "a precious resource and any loss is an issue". However, losses from mining were dwarfed by evaporation or environmental flows of as much as 820 million litres per day.

A spokesman for the Department of Planning and Environment said Denderobium was "one of the most strictly regulated mines in NSW".

"The Department is already implementing many of the recommendations in the Independent Panels interim report, including requiring the mining company to strengthen monitoring and modelling of surface and ground water impacts, and to review the design of future longwall panels," he said.

A dried-out creek above the Dendrobium mine in the Special Areas of Sydney's water catchment.

A dried-out creek above the Dendrobium mine in the Special Areas of Sydney's water catchment.Credit:Julie Sheppard

'No licence'

Georgina Woods, a spokeswoman for Lock the Gate, noted the mines were effectively taking surface water without a water licence.

"This is a breach of the Water Management Act, which clearly requires mining companies to hold Water Access Licences for any water taken in the course of mining," she said.

Labor's mining spokesman Adam Searle said his party would reinstate the original “neutral or beneficial effect” test for all developments in the drinking water catchment, weakened by the Berejiklian government in 2017, if elected in March.

“To maintain public confidence, we believe there should be no further regulatory approvals given for mining in the water catchment until the [expert panel's study] is complete," he said.

Cate Faehrmann, Greens environment spokeswoman, said the study confirmed that coal mining in the water catchment was "stupid and reckless”.

“There simply is no safe way to mine through water tables and under major dams without causing cracking, subsidence and significant water loss," she said.

“It's time for all parties to put water before coal and ban new coal mining in our drinking water catchments.”

Peter Hannam is Environment Editor at The Sydney Morning Herald. He covers broad environmental issues ranging from climate change to renewable energy for Fairfax Media.

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