The New South Wales government will fast-track a proposal to raise the wall of Sydney's Warragamba Dam by declaring it critical state infrastructure.
Premier Dominic Perrottet said the plan to raise the dam wall by 14 metres would help "future proof" Western Sydney from major flood events.
"This infrastructure project will save lives and protect property," Mr Perrottet said.
"If there was a major flooding event in the Hawkesbury-Nepean, by raising the dam wall we would reduce those properties that would be affected from 15,000 to 5,000.
"Currently we would have to evacuate around 90,000 people — that would be reduced to 14,000 people."
The declaration means the New South Wales Planning Minister will have final approval for the project.
Mr Perrottet said the proposal would still be subject to a "rigorous" assessment process, which includes assessment by the New South Wales Environment Protection Authority and the federal government.
But he said the declaration of critical state significant infrastructure would "streamline" the assessment process.
"The minister will ensure, through being the final decision-maker, that it's not caught up in red tape, in court cases, in government bureaucracy," he said.
"This is about getting this project done, protecting lives and saving properties across our state."
Former Planning Minister Rob Stokes declined to make raising the dam wall a critical state significant infrastructure project in 2021.
But current Planning Minister Anthony Roberts said the urgency to raise the dam wall had changed following four major flood events in the Hawkesbury-Nepean catchment within 18 months and an independent inquiry into the state's flood disaster earlier this year.
"This is critical infrastructure," he said.
"It needs to be fast-tracked, it's got to go through all the processes, and we'll deal with those issues as they come up.
"But that's the difference between the previous decision and the decision we've made today."
There have already been about 2,000 submissions to WaterNSW regarding the proposal to raise the dam wall.
The state government said WaterNSW would respond to the feedback and issues raised in the submissions before a comprehensive assessment is undertaken in accordance with the New South Wales Environmental Planning and Assessment Act.
The project is controversial with some opponents who argue raising the dam wall will destroy environmental and Indigenous cultural sites in the Blue Mountains.
Some critics also believe the project is designed to allow more development in flood prone areas of Western Sydney.
New South Wales opposition leader Chris Minns said he was "very skeptical" about the government's plan and pledged not to raise the wall if elected next year.
"The costs associated with this plan are astronomical and that doesn't include any of the environmental offsets that will have to be paid by NSW taxpayers," he said.
"[And] 45 per cent of floodwaters do not come over the top of Warragamba, they come down the Grose, Colo and Nepean Rivers."
Mr Minns said Labor were consulting with experts about all possible strategies for flood mitigation, one of which includes lowering the dam level by 12 metres, but no commitments had been made.
He said it was important not to increase the population living on the floodplains and said that was the Coalition government's "ultimate agenda".
Minister for Lands and Water Kevin Anderson said any plan to lower Warragamba’s water supply level would have "severe consequences" such as putting Sydney into severe water restrictions and increasing people's water bills.
