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 of November 2024 there is approximately three and a half gigalitres of water present.
Our preferred option is for a fast fill strategy to fill the mine pit over seven to ten years by supplementing the natural filling of the mine with a combination of Upper Eastern View Formation groundwater and peak flows from Salt Creek.
The fast fill strategy is currently subject to a groundwater licence amendment application (details below), however no active work is being undertaken on the option to use peak flows from Salt Creek as this will be determined as part of the final Mine Rehabilitation and Closure Plan.
This strategy 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 up to 50 years and will not support the broader outcomes expected by the community and government in a timely manner.
The strategy is independent of whether the Eden Project Anglesea concept or other future land use concepts are realised.
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 was overseen by Victorian government agencies and departments. 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 data retrieved was used to update the Anglesea Groundwater Model in conjunction with Barwon Water and was independently reviewed by a Technical Review Panel established by DEECA.
Together with the Anglesea Groundwater Model, the data was also used to inform a groundwater impact and environmental risk assessment undertaken by Alcoa. This revealed a sustainable pumping rate that does not adversely impact groundwater dependent ecosystems, including the Anglesea River, can be achieved.
Groundwater Licence Amendment Application
Alcoa submitted a formal groundwater licence amendment application with Southern Rural Water in July 2024 requesting approval to pump groundwater from the Upper Eastern View Formation (UEVF) to fill the mine pit in seven to ten years.
The amended application seeks 1.5 gigalitres per year for up to 10 years - a volume that represents less than 0.1 per cent of the aquifer’s total groundwater content and 60 per cent less than the company’s historical extraction rate.
If approved, the licence will enable Alcoa to accelerate the return of the former mine and power station site to the community while providing long-term environmental benefits sooner - in contrast to a natural fill approach which may take up to 50 years.
The decision to submit the licence application was made following consideration of feedback received during three well-attended community open house sessions and is backed by more than four years’ technical work.
This rigorous process included analysis of hydrogeological models, actual historical data, independent technical studies, groundwater pumping tests, as well as the development of a groundwater model in conjunction with Barwon Water - all of which have indicated the proposed extraction would have no adverse impact on groundwater dependent ecosystems, including the Anglesea River.
The application forms part of Alcoa’s ongoing efforts to finalise an approved mine water filling strategy to fill the mine pit in a timely manner and subsequently accelerate the return of the site to the community.