Mine Water Filling Strategy

Anglesea mine pit aerial

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.

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 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.

Next Steps

  • 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.

Discussion Board

We’ve listed the top questions asked about the Mine Water Filling Strategy below. If you have a question about the strategy or any other aspect of our rehabilitation activities, please email angleseaps@alcoa.com.au.

We have a regulatory obligation to develop the final Anglesea Mine Rehabilitation and Closure Plan to deliver a safe, stable and sustainable landform in a timely manner.

Creating a waterbody supports:

  • A critical fire break to minimise fire risk to the Anglesea township (in line with the Hazelwood Mine Fire Inquiry 15/16 Report) and a source of water for firefighting accessible to aerial appliances;
  • Assists the geotechnical stability through the weight of water at the base of the mine; and
  • Potential benefits to the environment, the regional economy and the community from the future land use of the rehabilitated landscape.

In addition, filling the waterbody in a shorter timeframe is of strategic importance to the region and will:

  • Facilitate earlier community access to the rehabilitated mine site;
  • Have the potential to support the long-term management options for the Anglesea River;
  • Assist in stabilising the aquifer systems intersected by the mine pit; and
  • Be a potential catalyst to accelerate the development of recycled water infrastructure and the regulatory framework to enable recycled water use in the mine and the broader region.

We have investigated and conducted technical analysis on a range of filling options including:

  • Restoration of Salt Creek into its original path to the mine pit;
  • Use of groundwater from the Upper Eastern View Formation (UEVF) aquifer;
  • Use of groundwater from the Lower Eastern View (LEVF) aquifer;
  • Use of recycled water from Barwon Water’s Black Rock water reclamation plant in Breamlea; and
  • The natural fill option (groundwater infiltration and rain) which is estimated to take more than 50 years.

Of these, our preference is to use a combination of surface water, including peak flows from Salt Creek, and groundwater from the UEVF aquifer which will see the waterbody filled in seven to ten years.

We have a regulatory obligation to develop the final Anglesea Mine Rehabilitation and Closure Plan to deliver a safe, stable and sustainable landform in a timely manner.

The Mine Water Filling Strategy is independent of whether the Eden Project Anglesea concept or other future land use concepts are realised.

Results of the recent groundwater pumping test, overseen by multiple government departments, indicate the pumping resulted in no impact to groundwater dependent ecosystems, including the Anglesea River.

Similarly, historical studies commissioned by Victorian government agencies provide no evidence that our operations have negatively contributed to the health of the Anglesea River.

The use of groundwater requires approval from Southern Rural Water.

While we are encouraged by the positive results from the groundwater pumping test, we will not make a decision to seek a licence amendment for the use of groundwater longer term until the current technical process is complete.

Part of this ongoing work is updating the Anglesea Groundwater Model, which is underway. The model will also be independently peer-reviewed by a government-appointed Technical Review Panel. We also plan to undertake a further groundwater impact and environmental risk assessment. We expect this work to be completed in Q1 2024.

Importantly, we will run community engagement activities when these steps are complete to share the analysis, seek community feedback and further understand any concerns.

Recycled water may present a future opportunity to assist in filling and maintaining the waterbody, pending resolution of key issues including:

  • The EPA framework for the use of recycled water in a mine;
  • The broader social acceptance of recycled water;
  • The infrastructure and timeline to deliver recycled water; and
  • A business plan incorporating multiple users and applications to make it viable.

To deliver the above benefits, we need to start supplementing the natural filling of the mine now while these issues are being addressed as part of a regional recycled water plan.