The environmental impact statement for the proposed raising of the Warragamba Dam wall was released this week, attracting criticism from many quarters.
Stuart Ayres, minister for western Sydney, said of the document: "This is a significant milestone in the delivery of raising Warragamba Dam wall. It's an extensive, even exhaustive, environmental impact statement."
But Blue Mountains MP, Trish Doyle, said it fell "far short" in its assessment of the true impacts on the environment and Indigenous cultural heritage.
"I am outraged that this proposal to raise the Warragamba Dam wall is still being considered," said Ms Doyle. "I vividly recall when ... Stuart Ayres stood on the flood plains and proudly declared that there would be development as far as the eye could see, which raises serious doubts about the real motivation for this project."
The mayor, Mark Greenhill, said it could spell the end of the World Heritage listing for the Mountains.
"The raising of the Warragamba Dam will destroy World Heritage listed wilderness on Sydney's doorstep and desecrate Indigenous heritage and threatened biodiversity. Why? To satisfy the NSW Government's unrelenting quest to reach housing targets in western Sydney."
Blue Mountains council formally opposed the proposal in January 2019, noting that it posed the risk of serious and irreparable damage to Gundungurra Country.
The Colong Foundation's Harry Burkitt said the EIS was "littered with mistruths and undercooked figures" which attempted to justify "the destruction of priceless Indigenous heritage and some of Australia's most threatened species".
He said the document was "fundamentally flawed" in key areas.
He cited several examples, including the fact that just three hours was spent surveying for koalas and one day spent surveying for platypus across 65 kilometres of watercourse that would be intermittently inundated by the raised wall.
Mr Burkitt said the EIS "seriously understated" the extent of inundation in the pristine Kowmung and Kedumba rivers. And he said no experts were engaged to study the impact of the project on the "outstanding universal values" for which the Mountains' national parks were originally placed on the World Heritage list.
The EIS was backed by the Property Council of Australia, which said a raised wall would protect people in the Hawkesbury Nepean catchment from floods.
The council's western Sydney director, Ross Grove, said: "The government will need to be swift and decisive in delivering the wall and supporting infrastructure if we are to protect homes, communities and lives."