A river reduced to channels and mudflats will greet tourists at Anglesea if authorities stop discharging water from Alcoa’s abandoned mine without supplementary action, a report reveals.
Adverse impacts on the community and environment would also emerge as acid sulphate soils upstream increasingly affected the Anglesea River’s alkalinity, the GHD report said.
But it ruled out the “no action” option, instead recommending alternatives including continued discharge from the mine, alternative freshwater sources or pumping in seawater.
State Government posted the report online before hosting a “community open house” on Thursday to discuss options for the river
The river’s future came under doubt after Alcoa closed its upstream mine and power station last year. The mine had pumped around four million litres of ground and pit water into the river daily.
The river suffered from acid inflows in recent years, with several mass fish-kill incidents and complaints of damage to tourism trade as visitors were warned to stay away from the water.
The State Government continued discharging the mine water to keep the river high last summer but commissioned the GHD study to identify long-term options.
GHD found that ceasing the mine discharge could reduce the river level around a metre in summer.
Consequently exposed mudflats could then leach acid into the river with various adverse impacts, the report said.
“Activation of acid sulphate soils under low water levels over the summer period presents a significant risk to ecological, social and economic assets.”
The mine water was mostly ineffective as a buffer against acid inflows but helped prevent “stratification”, or layers of salty and freshwater, during inflows from the sea, the report said.
There are five recommended mitigation options “for further assessment”:
· Discharging from the mine at a reduced rate, possibly around one million litres daily.
· Discharging treated mine pit water.
· Freshwater alternatives, such as drain, recycled or potable water.
· Pumping in seawater.
· And, using a mix of sources including the sea and the mine pit.
The government said it would use feedback from Thursday’s open house in choosing a strategy.
“We are working closely with the local Anglesea community to ensure we get the best outcomes for the Anglesea River,” Water Minister Lisa Neville said.
“This is also about ensuring the river continues to service the community as well as provide a suitable habitat for native plants and animals.
“The community’s input into the future management of the Anglesea River is critical.”
