The key remaining aspect of the Draft Mine Rehabilitation and Closure Plan is an approved strategy to fill and maintain the mine pit with water. While we have investigated a range of potential options to support filling the mine pit in a timely manner, an approved strategy remains outstanding.
We acknowledge the importance of this matter to the community and will continue to engage as we undertake investigations to deliver the best possible outcome for the future of the site, the community and the environment.
About the Strategy
Approximately 18 gigalitres of water is needed to fill the mine pit. As at July 2023 there is approximately three gigalitres of water present.
Our preferred option is for a ‘fast’ fill strategy to fill the mine pit over five to 10 years by supplementing the natural filling of the mine with a combination of Upper Eastern View Formation groundwater and peak flows from Salt Creek.
This will support a critical fire break to minimise the fire risk to the Anglesea township and potential benefits to the environment, the regional economy and the community from the future land use of the rehabilitated landscape.
The alternative is to continue with a natural fill, which may take 50 to 100 years and will not support the broader outcomes expected by the community and government in a timely manner.
Groundwater Pumping Test
In 2021 we completed a groundwater pumping test to provide Alcoa, regulators and the community with science-based information to determine whether groundwater can be used to fill the mine pit without adverse impact on groundwater dependent ecosystems, including the Anglesea River.
The rigorous process is overseen by Victorian government agencies and departments and to date has involved more than three years of work and engagement. Importantly, the data gathered during the pumping test did not identify any adverse impacts on groundwater dependent ecosystems, including the Anglesea River.
During the test regular updates were provided to the community and key stakeholders. Those published updates can be seen here.
The test was undertaken by expert hydrogeologists, with oversight by a co-regulator technical working group comprising representatives from Southern Rural Water, Department of Energy, Environment and Climate Action (DEECA), Corangamite Catchment Management Authority, EPA Victoria, Earth Resources Regulation and Barwon Water.
- The pumping test data is being used to update the Anglesea Groundwater Model, in conjunction with Barwon Water and independently reviewed by a Technical Review Panel established by DEECA; and
- The test data and Anglesea Groundwater Model will also inform a groundwater impact and environmental risk assessment to be undertaken by Alcoa.
These steps will determine if a sustainable pumping rate can be achieved, that is, one that does not adversely impact groundwater dependent ecosystems, including the Anglesea River.
The outcome of these steps will also determine if we apply to Southern Rural Water for a licence amendment to support the filling of the mine pit with groundwater. To date, no decision has been made.
The aquifers and bores continue to be closely monitored and information shared with community and regulators via regular updates emailed to our community database and published on our website. You can read the full collection of those updates here.