Gippsland Environment Group Inc
Lobbying against environmental threats on the unceded lands of the GunaiKurnai, Yaitmathang, Ngarigo and Bidwell Peoples
Stockman Mine
Overview
Stockman Project Pty Ltd is a wholly owned subsidiary of Independence Group NL. The company plans to mine two copper and zinc deposits in the headwaters of the Tambo River, 16km east of Benambra in Victoria's High Country.
The company intends to re-open the old Benambra 'Wilga' mine and develop the 'Currawong' mine and re-use and expand the existing tailings dam. Approximately one million tonnes of ore will be processed each year, producing 850,000 tonnes of tailings annually to obtain approximately 150,000 tonnes of copper and zinc concentrates per year.
On 30th October 2014 the previous Victorian Planning Minister Matthew Guy approved the Stockman Base Metals Project Environmental Effects Statement (EES). On 19th December 2014 Federal Minister for Environment Greg Hunt approved the EES regarding matters of national significance.
Risks to the environment
The company plans to recommission and expand the old tailings storage dam in order to store up to seven million tonnes of additional toxic tailings. This would be ten times the volume currently stored in the dam. The earthen and rock dam wall will be raised another 25 meters in a series of staged lifts to a total height of 45m above the valley floor, and expand the surface area from 8ha to approximately 32ha. The tailings dam is constructed across the headwaters of Straight Creek, a tributary of the Tambo river which flows into the Ramsar listed Gippsland Lakes.
The Stockman EES states that the tailings will have to remain covered with two meters of water forever to prevent an acid reaction from occurring if the mine tailings, containing the mineral pyrite, are exposed to air. The dam wall plastic liner on the original tailings dam has an estimated lifespan of possibly 30 years. The concrete grout curtain at the inside base of the dam wall has a life span of 80-100 years. The new plastic liners of the proposed dam may have a lifespan of 100-200 years. There is no way that the grout curtain or plastic liners could be repaired or replaced when they inevitably fail. If the dam wall fails at any time in the next thousands of years, the ecosystem of the Tambo River and Gippsland Lakes will be destroyed.
Risks to the environment
The company plans to recommission and expand the old tailings storage dam in order to store up to seven million tonnes of additional toxic tailings. This would be ten times the volume currently stored in the dam. The earthen and rock dam wall will be raised another 25 meters in a series of staged lifts to a total height of 45m above the valley floor, and expand the surface area from 8ha to approximately 32ha. The tailings dam is constructed across the headwaters of Straight Creek, a tributary of the Tambo river which flows into the Ramsar listed Gippsland Lakes.
The Stockman EES states that the tailings will have to remain covered with two meters of water forever to prevent an acid reaction from occurring if the mine tailings, containing the mineral pyrite, are exposed to air. The dam wall plastic liner on the original tailings dam has an estimated lifespan of possibly 30 years. The concrete grout curtain at the inside base of the dam wall has a life span of 80-100 years. The new plastic liners of the proposed dam may have a lifespan of 100-200 years. There is no way that the grout curtain or plastic liners could be repaired or replaced when they inevitably fail. If the dam wall fails at any time in the next thousands of years, the ecosystem of the Tambo River and Gippsland Lakes will be destroyed.
Above: Tailings dam during remediation. Source: ATC Williams. It cost Victorian taxpayers $6.9m for Department of Primary Industries to remediate the site in 2006.
Background
The original Benambra mine was operated by Denehurst from 1992 to 1996. Denehurst went bust and ceased operations, abandoning the site and forfeiting their environmental bond of only $350,000; leaving behind a tailings dam leaking acid and heavy metals into the Tambo River. DPI had to make emergency discharges from the tailings dam a number of times between 1999 and 2005 to prevent the tailings dam overtopping (the tailings dam had been built without a spillway) and potentially failing.
These discharges contained heavy metals many times in excess of the Australian and New Zealand Environment and Conservation Council (ANZECC) freshwater limits. Another mining company, Austminex, had the option to take over the operation in 2001 but plunging metal prices made the proposal uneconomic, leaving the environmental disaster the responsibility of DPI.
Prior to remediation EPA authorised further discharges in order to lower the water level of the tailings dam before work could begin on repairing the tailings dam. Water quality objectives for heavy metals were set much higher than ANZECC freshwater limits e.g: zinc was 20 times higher. See report here (19MB pdf).
It cost Victorian taxpayers $6.9m for DPI to remediate the site in 2006.
However, the tailings dam is still leaking contaminated water with elevated levels of cadmium, copper and zinc above ANZEEC freshwater limits at a rate of approx. 86,000L per day through the northern abutment and operates as a 'flow through' system down the spillway into Straight Creek and the Tambo River.
Take Action
Independence Group holds a mining licence over the majority of the area of the proposed Stockman Project, however the company does not have a licence over the tailings dam, which was exempt from any mining operations after rehabilitation in 2006. (0.2MB PDF)The Victorian Minister for Energy and Resources Lily D'Ambrosio will have to lift that exemption and issue a mining license over the tailings dam area before work can proceed as proposed in the Stockman Base Metals Project EES. Contact the relevant Ministers and your local MP to express your concern about the Stockman Project. Request that no mining licence is issued over the tailings dam or works approvals granted to expand the tailings dam, as the risks the development poses to the health of the Tambo River and the communities along its length all the way to the Gippsland Lakes are simply unacceptable.
GEG Media Release
Stockman Project: Work Plan – Mining Regulator Ignores Risks to Tambo River and Gippsland Lakes.
July, 2019
Stockman Project
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