Mining in the water catchment above the Illawarra escarpment is likely to be causing more environmental damage than planning approvals forecast, a new report from the NSW Chief Scientist says.
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And the modelling and monitoring of drinking catchment water had been inadequate at the Dendrobium mine – not providing enough data on groundwater or surface water, or how much of this water is drained into mined areas.
This means claims by mining companies that water damage has been “negligible” may be meaningless, as they can not be properly verified.
Ensuring a “negligible” impact on certain environments is often a condition of mining approvals in sensitive areas.
The Independent Expert Panel for Mining in the Catchment (IEPMC) had been examining the impact of the Dendrobium and Metropolitan mines on the Special Areas within the drinking water catchment.
Among the more alarming findings of its initial report were that South32’s Dendrobium mine could be draining 3 million litres of water (more than an Olympic pool) each day from reservoirs and groundwater into the mine workings.
The report also found it was likely this was caused by a large connected “fracturing” or cracking, of the bedrock because of mining subsidence at Dendrobium.
It said the Metropolitan colliery appeared to be draining about half a million litres into its mine working each day, but there did not appear to be a “connected fracture regime”.
The panel said a different system should be used for calculating the seriousness of rock fracturing, when assessing likely damage.
The report said it still needed to consider the cumulative effects of water loss caused by multiple mining areas, as well as the significance of these for the drinking water supply.
It said longwall mining at Dendrobium and Metropolitan should only be approved “on an incremental basis” because there were “knowledge gaps that have the potential to jeopardise compliance with performance measures”.
The IEPMC initial report was completed on November 12 but made public by the Department of Planning and Environment at 4.45pm on Thursday, December 20.
It will now be open for public submissions until February 28.
The Metropolitan Special Area was created to protect the waters of the Avon, Cataract, Cordeaux and Nepean reservoirs.
