Environmental groups are concerned about a plan to turn the Hazelwood coal mine into a lake. 

French energy giant Engie - owner of the Hazelwood coal mine - is reportedly working on an Environmental Effects Statement (EES) on its plans to fill the 640 gigalitre mine with water from the Latrobe River system.

But Environmental Justice Australia (EJA) is concerned that toxic coal ash could be released into the environment if the mine becomes a lake.

EJA environmental lawyer Chloe Badcock says two reports have found coal ash is likely to be released into the lake if the mine is 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 told reporters this week.

EJA says other options should be considered, such as partially filling the mine with solid material. 

Engie says turning the mine into a lake would be the safest and most stable solution. 

The company says it is working with the Victorian Government and local communities for the “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.

Victoria's Environment Protection Authority issued Engie a clean-up notice in 2020 after a coal ash from an improperly lined dam leached into groundwater.

The EES is unlikely to be ready for the planning minister until 2024.