"These sites are all that we have left - and once they are gone, that's it - they're gone."
Warragamba resident Kazan Brown said the state government's recent report on indigenous heritage sites in the Blue Mountains Heritage Area was inadequate.
The report details what impact raising the Warragamba Dam wall would have on the sacred sites.
"I can't go into all of the details in the report as it's confidential at the moment but it's got to do with what's not in the report," the Gundungurra woman said.
"If you are going to make a report you have to make sure everything is included so that it is a proper report."
Ms Brown told the AAP the report was"insulting" and "culturally insensitive".
"This report completely disregards Aboriginal culture," she said.
"It's a kick in the guts. It's been written in favour of the government and not us."
Gundungurra people, along with Wollondilly Council and Blue Mountains Council, will hold a protest meeting to extend the feedback time for the report.
"We were only given 41 days and we would like an extra month ideally," she said.
"It's a 2000 page document and there are a lot of things missing or that need changing.
"We will still be making submissions but more time to provide adequate feedback would be better.
"It's probably wishful thinking that the timeline would change as they seem hellbent on this timeline but we hope [the government] will listen to us."
Gundungurra people used the caves throughout the Blue Mountains Heritage area, including Burragorang Valley, as shelter and a place to protect their art.
Two of the four caves were submerged in the first flooding of the valley and now the other two would be lost if the government's plan to raise the dam wall is approved.
The NSW Government plan to raise the wall to mitigate the risk of flooding in the Hawkesbury region.
"There was no Environmental Impact Statement process the first time around and it is estimated that we lost about 80 per cent of our sites," Ms Brown said.
"Now we are about to lose what is left."
Wollondilly mayor Matthew Deeth said both councils (Wollondilly and Blue Mountains) were fully supportive of the Gundungurra people.
"I think a time extension is a reasonable request given the serious nature of the 2000-page document," he said.
"We are talking about the complete destruction of what is left of significant cultural sites.
"We need to consider the huge impact of what could be lost not just for indigenous people but the whole community."