WaterNSW says South32’s proposal to extend Dendrobium mine could cause cracking in the walls of two dams

This article is more than 11 months old

This article is more than 11 months old

WaterNSW has objected to the expansion of a coalmine under Sydney’s drinking water catchment because the project would cause unacceptable impacts, including the loss of 3.3bn litres of water a year.

The government-owned water corporation has also warned that mining company South32’s proposal to extend the mining operations at its Dendrobium coking coalmine could cause cracking in the walls of two dams that supply water to the Illawarra and Macarthur regions, and may harm 26 endangered coastal swamps.

In a submission to the New South Wales Department of Planning, Industry and Environment, WaterNSW says the extension of the mine in the Illawarra region should not proceed in its current form.

“WaterNSW strongly objects to the project (as currently proposed),” the submission says.

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The South32 proposal is the first to be lodged for coalmining in the NSW special areas in more than a decade.

It is also the first in the special areas to be subject to a test that requires developments in the Sydney drinking water catchment to have either a neutral or beneficial effect on water quality.

Sydney’s dam storage levels are currently sitting below 50% after they dropped to that level in August, the first time in more than a decade.

WaterNSW’s submission says the predicted impacts on both water and ecology are “unacceptable” because they would affect the corporation’s ability to deliver on its core function to “protect and enhance the quality and quantity of water” in the Sydney drinking water catchment.

The submission raises concerns about several environmental impacts, including potential subsidence that would be “higher than recorded figures at any other mine in the Southern Coalfield”.

It warns that the project would cause an “unprecedented level of surface-to-seam fracturing and groundwater depressurisation, which would result in a range of significant predicted impacts”.

As examples, WaterNSW said the project would cause 3.3bn litres of catchment water loss a year, would increase the volume of metals in streams above the mining area, and affect 26 endangered coastal upland swamps.

It said South32’s environmental impact statement predicted that, in a dry year, there would be a 100% reduction in stream flow to the Avon Reservoir within the catchments over the proposed mining area.

“WaterNSW has calculated this may reduce the catchment yield of the Avon Reservoir by up to 3.9%,” the submission says.

WaterNSW said there was also the potential for mining activity to cause cracking in the walls of the Avon and Cordeaux dams. A spokesman said WaterNSW had concerns about this and more information was required from South32.

“WaterNSW has expressed strong concerns about the impacts of the proposal on water quantity and quality, swamps and dam infrastructure,” a spokesman said.

“In particular, the mine design (as currently proposed) is predicted to cause surface-to-seam fracturing across the entire mining area, which would result in substantial groundwater depressurisation.”

The corporation has asked for the proposal to be referred to an independent expert panel that is reviewing mining projects in the greater Sydney water catchment. The panel’s report is expected sometime this month.

It’s submission asks for alternative designs from the company that “avoid or reduce” environmental impacts, including reducing the mining dimensions.

A spokeswoman for South32 said the company takes its “environmental responsibilities seriously and understand(s) the sensitivities of working within the Metropolitan Special Area”.

“The EIS reflects that we will not mine under water supply reservoirs, named watercourses and key stream features,” she said.

“Approval of the project will sustain the employment of around 400 people, create an additional 100 jobs and ensure the supply of metallurgical coal to local and overseas customers until 2048.”

But Carmel Flint, the national coordinator of Lock the Gate, said the advice from WaterNSW should be treated seriously by the state government.

“Our view is this is quite an extraordinary and scathing analysis by WaterNSW,” she said.

“I’ve rarely seen an agency or department put in such a strongly-worded objection to a mining proposal.

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“3.3 billion litres per year of surface water take is incredibly significant, particularly given the time we’re in now during such a serious drought.”

The NSW planning minister, Rob Stokes, said “Sydney’s drinking water catchment is of paramount importance to the future of our city and state”.

“That’s why we’ve established an independent panel with world leading experts to provide advice on mining in Sydney’s drinking water catchment,” he said.

“The panel’s report will inform the future of mining in the catchment.”

A spokesman for the NSW planning, industry and environment department said it had requested a “detailed response” from South32 to all public submissions on the development, including WaterNSW’s submission.

“The department will then rigorously assess the merits of the proposal taking into consideration advice from water experts, government agencies and the community before making its recommendation,” he said.