Environmental groups say newly released documents which raise concerns about water availability and groundwater pollution cast fresh doubt over a plan to turn Victoria’s three brown coal mines into lakes when they close.

A Victorian Government ecological effects statement has revealed using water from the Latrobe River system to fill the mines would exacerbate a decline in environmental values and loss of biodiversity in a future drying climate.

The Latrobe River runs through the Latrobe Valley and central Gippsland and is used for drinking water, irrigating farmland and flows into the Ramsar-listed Gippsland Lakes wetlands.

Ramsar wetlands are rare or unique and of international importance.

The ecological effects statement found decreasing water availability from filling the mines would have a range of impacts on the river, its estuary and the Gippsland Lakes.

These include the loss of vegetation and a decrease in the numbers and breeding of native fish, waterbirds, frogs and turtles.

The study builds on the Government’s mine rehabilitation strategy released earlier this year, which found if drying continued the river’s inflows would be half their historic average when the last mine, at the Loy Yang power station, was due to close in 2048.

Look at other options

Environment Victoria campaigns manager Nick Aberle said the Government’s reports showed there was not enough of the Latrobe River system to fill “three mines or potentially even any mines” with river water.

“If you were to take that water out of the Latrobe river system, it is going to have a major environmental impact on the river system all the way down to the to the Gippsland Lakes,” Dr Aberle said.

Filling the mines with river water would take decades, with the Hazelwood mine, which closed in 2017, requiring 638 gigalitres.

The Yallourn mine, due to close in 2032, would need 725 and Loy Yang, which is scheduled to shut down in 2048, has a capacity of 1,420GL.

Average in-flows into the Latrobe have fallen from 800GL a year to 600GL a year since 1997 .

Government modelling in the rehabilitation strategy found under a dry climate scenario, the river’s average in-flows could drop to 334 gigalitres a year by 2080.

He said it was time for the mines’ owners to begin considering rehabilitation options which did not involve water or to investigate alternate sources of water.

“What those alternative water sources probably include are things like the desalination plant, recycled water from treatment plants and using that water to put that in the mine if a non-water solution isn’t going to work,” Dr Aberle said.

Owners told to clean up

Documents released to environmental groups under Freedom of Information and obtained by the ABC show in October, the Environment Protection Authority (EPA) issued the Hazelwood’s owner, Engie, with clean-up notices.

The notices were issued after groundwater contamination was found inside the mine at the Hazelwood Ash Retention Area (HARA) and at its eastern overburden dump.

Groundwater bores at both sites at the mine found leaching from Hazelwood’s ash waste, with the notices saying the water tested exceeded the guidelines for “Water Dependent Ecosystems, Water Based Recreation, Potable Water Supply, Agriculture and Irrigation (stock watering) and Agriculture and Irrigation (irrigation)”.

The EPA found increased levels of cobalt, iron, manganese, nickel, sodium and magnesium detected may have occurred because of leaching from the HARA.

The notices reveal the EPA became aware in 2005 that the HARA was not adequately constructed and had the potential “to result in contamination of underlying groundwater”.

In a statement, the EPA said it was addressing pollution issues with the Hazelwood mine and ash landfills and the “EPA has issued regulatory notices which will guide clean up and ongoing management of the site”.

Mine audit underway

The EPA clean-up notice says the risk to a future lake at Hazelwood is beyond the scope of its audit, but it requires Engie to assess the extent of any contamination within and beyond the mine site and to analyse any potential risks to future uses of the area.

An Engie spokesperson said the audit was underway and would be completed next year.

“It is common for a site-wide clean-up notice to be issued by EPA Victoria upon the closure of a large industrial site such as Hazelwood,” the spokesperson said.

He said the company remained committed to filling the mine and making sure there was no risk to the environment or the community.

Environmental groups concerned

But environmental groups say the contents of the EPA’s clean-up notice are “disturbing” and raise questions about the Hazelwood lake plan.

“[The HARA] sits actually in the middle of the area that they want to flood. So it’s 35 hectares,” said Tracey Anton, a member of Gippsland group Friends of Latrobe Water.

Dr Aberle said while he believed a mine lake was not viable, Engie needed to clean up the area to avoid creating a “toxic lake”.

“The water quality in any lake would be quite problematic just because of that coal ash,” he said.

“So really, the first step before Hazelwood starts putting any water anywhere would need to be to clean up that coal ash dump at the bottom of the pit.”