Archaeologists have labelled a draft report for the controversial raising of NSW's Warragamba Dam wall as partly flawed and inadequate.
Scarp Archaeology director Michael Slack and University of Queensland Associate Professor Annie Ross criticised the draft Aboriginal cultural heritage assessment for the wall raising, saying it doesn't meet best practice.
The Berejiklian government's proposal to raise the wall at least 14 metres will flood parts of the heritage-listed Blue Mountains which includes Aboriginal cultural sites.
In a submission to a NSW parliamentary inquiry examining the plan, Dr Slack and Dr Ross argue the assessment pays little attention to Aboriginal cultural values.
"The survey strategy is flawed," the submission, requested by Traditional Owner Kazan Brown, said.
"The assessment of impact focuses almost entirely on archaeological sites and ignores Aboriginal connections to place and country."
The archaeologists also argue the report includes no recommendations on how to mitigate impacts to places of Aboriginal significance that will be destroyed by the wall raising.
"We find the draft report to be inadequate, and in places flawed," they said in the submission.
In another submission to the upper house inquiry, ecologist Steven Douglas describes the assessment process for the wall raising as "flawed from a very early stage".
Dr Douglas, who was paid by environmental charity the Colong Foundation for Wilderness to produce the submission, said the assessment has not considered the cost of environmental and world heritage impacts.
He claims if a cost analysis of the environmental effects of the dam raising would have been completed, it would be in the "many millions of dollars".
This could mean that raising the dam wall is economically unfeasible, he added.
"The biodiversity costs are very high to the extent that this option becomes uncompetitive or much less competitive compared with others," Dr Douglas said.
His submission argues the government has left consideration of these costs to "very late" in the process.
"This failure is inconsistent with economic due diligence, as it exposes the state to potentially enormous costs that were not considered in critical cost/benefit analyses," Dr Douglas said.
Former NSW environment minister Bob Debus also made a submission to the public inquiry and warned the Berejiklian government's "casual lack of concern" for world heritage obligations threatens Australia's international reputation.
The NSW government in its submission said the flood risk in the Hawkesbury-Nepean Valley has been described by insurers as "the most significant and unmitigated community flood exposure in Australia".
Raising Warragamba Dam wall will temporarily capture floodwaters to reduce and delay floods to allow more time for evacuation, the state government said.
The project came under scrutiny earlier this year after AAP revealed the coalition was actually planning to raise the dam abutments at each end of the wall by 17 metres to allow for future modifications to hold back additional water.
The NSW government revealed in its inquiry submission that the project design includes raising the dam abutments up to 17 metres to allow the dam to "safely pass" the most extreme possible flood.
The joint-party inquiry will be chaired by Independent MP Justin Field with hearings to start in Sydney on November 22.
The project's environmental impact statement will be released for public comment in early 2020. It will then be subject to federal government approval.