'Shocking': Mining damage in Sydney's catchment prompts calls for halt

Flows from a "significant" water source for one of Sydney's dams are turning orange and disappearing beneath the surface because of an underground coal mine that is slated to expand to beneath the reservoir itself.

The Eastern Tributary, which supplies the Woronora Reservoir in Sydney's south-west, goes from pristine conditions to stagnant, highly discoloured pools within only a few hundred metres, a visit guided by WaterNSW this week revealed.

Water all but completely disappears into cracks in the sandstone bedrock above the mine.

The Planning Department says its compliance team in 2018 found "some of the performance measures" of the Metropolitan mine had exceeded approval conditions.

The government has agreed to let the miner test remediation efforts. These involve using a type of resin to fill the cracks caused by subsidence after coal is removed.

The department says "based on the latest advice, on a catchment-wide basis, the impact on water is minimal", while Peabody says its data shows "changes to water quality and quantity have been negligible" since it won approval for the project in 2009.

Peter Turner, mining projects science officer for the National Parks Association, said: “A lack of pre-mining data, limited monitoring, and inadequate catchment and reservoir water-balance modelling make it essentially impossible to reliably determine how much water was actually being lost.”

"The debate is whether all [the water] makes it back to the reservoir. If it does - which seems

is unlikely - it’ll carry material just like this," Dr Turner said, pointing to pea-green water
and orange deposits caused by water passing over subsidence cracks,
leaching out iron and manganese among other minerals.”

'Paramount importance'

In a 2014 report on mining in the catchment, the NSW Chief Scientist found Sydney was alone among major cities to permit such activities.

Sydney's dam levels have fallen more sharply in the past year or so than even during the Millennium Drought, and will likely dive below 50 per cent by mid-August without decent rains.

Orange is the new pristine? Visitors to one of the Special Areas of Sydney's catchment area this week, (left to right), Georgina Woods from Lock the Gate, Peter Turner of the National Parks Association, Western Sydney University's Ian Wright and Kaye Osborn from the Protect Our Water Alliance.Credit: Janie Barrett

South 32's Dendrobium mine is also planning a big expansion and, on Thursday, the miner opened its environmental impact statement for public comment. WaterNSW estimates its cracking costs the catchments 1.28 billion litres of water yearly.

Next month, the Independent Expert Panel for Mining in the Catchment is scheduled to finalise its report.

Discolouration at the spot in the Eastern Tributary where the water vanishes, in the Woronora catchment area, south-west of Sydney.Credit: Janie Barrett

"Sydney’s drinking water catchment is of paramount importance to the future of our city and state," Planning Minister Rob Stokes said.

"We will take any action needed to ensure the pristine condition of the catchment is maintained and will consider the panel’s recommendations in detail once their final report is delivered."

A Peabody spokeswoman said, "Our company takes its environmental responsibilities seriously and we honestly and transparently abide by the strict environmental performance criteria and comprehensive monitoring requirements set down in our government approvals."

Kaye Osburn, a spokeswoman for the Protect Our Water Alliance, said her newly formed group wants mining in Special Areas to cease.

"We’ve seen the shocking damage," she said, after visiting the area.

"Households, industries and businesses are making efforts to reduce their water use, while the miners are ploughing through our catchment and even beneath our reservoirs."

Professor Ian Wright of Western Sydney University stands beside a stagnant pool near where the Eastern Tributary disappears below the surface.Credit: Janie Barrett

In 2009, Metropolitan gained in-principle approval for 25 longwall extractions, at least 10 of which are currently expected to pass below Woronora Reservoir. It is expected the miner will seek the nod in September for the first of those sub-reservoir seams to be mined.

"It's troubling that monitoring and modelling inadequacies will make it difficult or impossible to detect slow but nonetheless significant leakage from the reservoir - into groundwater flows that leave the catchment - once mining under Woronora Reservoir starts," Dr Turner said.

Ian Wright, a freshwater ecologist at Western Sydney University, said water emerging from fresh cracks "mobilises so many elements in the periodic table".

Cordeaux Reservoir, part of Sydney's water catchment, was just 41 per cent full this week. The city's water storages in total are on track to drop below half full in August.Credit: Janie Barrett

While iron and manganese brought out colour, just trace elements of zinc and nickel "are very toxic to aquatic life", he said.

Nearby areas he has studied are "pulsating with life [and] highly diverse", unlike what he found this week.

Georgina Woods, a spokeswoman for Lock The Gate, said the government should be planning for an exit of coal extraction from the Special Areas.

“There’s a lot of short-term thinking in the way coal mining is managed in NSW, and the mining in the catchment is the starkest example of this," she said.

A spokesman for WaterNSW said the impacts on the Eastern Tributary "underscore WaterNSW’s long-standing advice about the risks to water quality and quantity posed by longwall mining activity in the Special Areas of Sydney’s declared catchment".

"WaterNSW considers it important to carefully reassess the predicted impacts of future mining beneath the base of Woronora Reservoir," he said.