The Blue Mountains Conservation Society has added its voice to the calls for an environmental impact statement for the whole upgrade of the Great Western Highway from Katoomba.
Society senior vice-president, Madi Maclean, said an EIS should take into consideration the entire section of works across the Upper Mountains, from Katoomba to Little Hartley.
"There are currently several sections of highway designated for upgrade from Katoomba to Medlow Bath and Blackheath to Mount Victoria and Little Hartley yet it's not being assessed at a whole," she said.
"These upgrades and duplications will each impact the surrounding environment, whether at a surface level or the aquifers deep below and there needs to be a comprehensive environmental assessment that addresses the cumulative impact of these works."
A Review of Environmental Factors (REF) has been used to assess the Little Hartley section and a small section of the Katoomba to Blackheath upgrade but Ms Maclean said it wan't comprehensive enough nor binding, for the significance of this development.
"The REF is grossly inadequate for such major works as it doesn't meet legislative requirements or take into consideration the fragility of the surrounding environment, much of it being World Heritage National Park," she said.
Transport for NSW Director West Alistair Lunn said the body takes its responsibilities towards protecting the environment "very seriously".
"We have worked closely with the community and Blue Mountains City Council with regards to the environmental assessment between Katoomba and Medlow Bath and we have listened to the feedback that they have provided," said Mr Lunn.
"We will continue to work with the community and with council as the project progresses, and to be open and transparent about the environmental assessment process.
"It is important to note that an REF process requires the same investigations, impact identification, assessment, and mitigation measures as an EIS.
"Carrying out the environmental assessment in this manner does not alter Transport for NSW's requirement to assess environmental impacts."
The Conservation Society joins Blue Mountains City Council and the Medlow Bath Residents Association in seeking an EIS rather than a number of REFs.
An EIS is bound by legislation and details the environmental impacts of the development and how they'll be managed, Ms Maclean said. As well as addressing key features of the surrounding environment that may be affected, including the World Heritage-listed Blue Mountains National Park, other conservation and culturally significant areas, she said the report should also explore ecologically sustainable development.
