04 October 2012

Alex Schaap On The Dumping Of Toxic Waste Under Beaconsfield

Hi Alex,
After reading this report from the Sydney Morning Herald and attending an information session by Beaconsfield Gold, I'm concerned the EPA is allowing the dumping of toxic waste tailings directly into the water table under Beaconsfield. After talking with people in the industry in WA, I would like to suggest the mixing of cement with the residues before pumping underground. http://www.tailings.info/storage/backfill.htm
Obviously this would make the tailings less susceptible to movement beyond the mine voids into areas where they could pose a public health risk.
I hope you give this suggestion some consideration. I don't think it would greatly increase the cost of disposing of the mine residues.

Mr Stevens
  The EPA has considered the environmental aspects of tailings deposition within the underground workings at Beaconsfield. When compared to a surface tailings dam there are environmental benefits of underground deposition, for example subaqueous disposal will ensure that any residual sulphides do not oxidise to form acidic and metalliferous drainage. Furthermore, the long term risks associated with surface tailings dams are avoided, such as liner failure, dam wall failure and ongoing seepage. The surface tailings dam can subsequently be decommissioned and rehabilitated.
The tailings will have low levels of contaminants, hence environmental risks are considered to be low whether the tailings are deposited above or below ground.
Tailings will be deposited deep underground, submerged below a salt water cover. No tailings will be deposited above the 375m level and consequently there is no interaction expected with the overlying groundwater.
Please note there is no net environmental benefit in storing the tailings in a cement matrix in this particular case. If the mine is reopened in future, some of the tailings may need to be moved into stope areas where mining would not be scheduled to occur. At that point in time cement may be mixed with the tailings to permanently backfill such stopes and to provide additional support to the mine workings.
If you are concerned about the potential sterilisation of gold resources remaining underground at Beaconsfield, I can advise that such matters were considered by Mineral Resources Tasmania who advise that the placement of tailings within the mine will not significantly increase the already substantial cost of re-opening the mine in the future. If you have any further queries about this matter you may wish to contact MRT.
Alex Schaap
Director, Environment Protection Authority

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