Environmental groups fear toxic coal ash will be released into the environment if the former Hazelwood coal mine in eastern Victoria is flooded and turned into a lake.
Coal ash is a by-product of burning coal for power generation and contains contaminants that include heavy metals such as mercury and arsenic.
At 640 gigalitres, the Hazelwood coal mine is bigger than Sydney Harbour and sits directly south of Morwell in the Latrobe Valley.
The mine's owner, French energy giant Engie, is preparing an Environmental Effects Statement (EES) for the Victorian government on its plans to fill it with water from the Latrobe River system.
The EES is not expected to be assessed by the planning minister until 2024.
But groups such as Environmental Justice Australia (EJA) want the Victorian government to consider alternative options for rehabilitating the site.
EJA environmental lawyer Chloe Badcock said the organisation had commissioned two reports that found coal ash would likely be released into the lake if the mine was flooded without a prior clean-up.
"The reports found that removing the coal ash from the mine pit before flooding it would be more proactive, more protective, and more expensive for Engie," Ms Badcock said.
EJA wanted other options considered, such as partially filling it with solid material.
Engie has previously said it wanted to turn the mine into a lake because it was the safest and most stable solution.
Environmental concerns
In 2020, Victoria's Environment Protection Authority issued Engie a clean-up notice after a coal ash dam at Hazelwood that was not properly lined leached into groundwater.
Coal ash at Hazelwood is stored in an on-site dam known as the Hazelwood Ash Retention Area (HARA), which is designed to prevent it from being released into the atmosphere.
EJA report author Steven Campbell has raised concerns about the stability of the HARA if it was submerged in water.
He has recommended removing coal ash prior to filling the mine with water.
Tracey Anton from the local environment group, Friends of Latrobe Water, said all parties needed to acknowledge that a mine lake could be potentially toxic.
"If they have a full pit lake, that toxic material, the coal ash, will merge with the water and then either seep into the groundwater or flow through into the Morwell River," she said.
Engie said it was working with the Victorian Government and local communities in order to prepare an EES that would lead to a "safe, stable, sustainable rehabilitation" of the mine.
"The EES for the Hazelwood Rehabilitation Project is in the early stages. Stakeholders will have the opportunity to comment on draft Scoping Requirements for the EES when they are released by the Department of Environment, Land, Water and Planning," a company spokesperson said.
