A group protesting against the construction of a new water treatment plant on Auckland's west coast says new reports show it could destroy endangered native bush.
Auckland Council's water provider Watercare has proposed building the plant in Titirangi after community protesters defeated plans to build in Oratia.
The Huia water treatment plant is Auckland's third-largest plant and comprises almost 20 percent of Auckland's water supply, but it is considered to be at the end of its life.
A rebuild to allow for more efficient treatment of water from four supply dams has been proposed at the site, which is on the corner of Woodlands Park Road and Mānuka Road.
The site sits within the Waitākere Ecological District, which is part of the Waitākere Ranges Heritage area.
The Titirangi Protection Group, protesting the plant, said 70 percent of the proposed four hectare treatment site was an endangered forest ecosystem.
Spokesperson Belynda Groot said two reports - one commissioned by Watercare and another by independent ecologist Shona Myers - highlighted the area's high ecological value.
The reports showed the area was home to regenerating kauri, broad-leaved forest, kahikatea-swamp maire forest, and forms wildlife corridors to adjoining forest.
"In a recent interview Mayor Goff described the site as mostly scrub and gorse, so we hope that in light of evidence from experts he will reconsider his position," Ms Groot said.
"From the beginning [Watercare] has been fairly dismissive of what we have been saying, so it is great to have back up from the scientists."
Ms Groot wanted Watercare to consider another area to build that did not destroy native forest such as regenerating kauri.
"We want some creative, innovative thinking to come from Watercare to come up with a better solution.
"We understand that a new water treatment plant is required, we just don't think it needs to be at the expense of our environment."
Watercare has declined to comment while other reports are being collated.