The closely knit community of Oratia is hugely relieved after Watercare ditched plans for a $400 million-plus water treatment plant that would have destroyed the lives and houses of many residents.

"For the last four months the community has been living on a knife edge, not sure if they were going to have a home to live in or if the beautiful valley of Oratia was going to be torn apart," said Oratia Heritage Society spokesman Paul Goldsmith.

He was commenting after the Watercare board dropped plans at two different sites on Parker Rd in Oratia and chose a 50ha site alongside the existing Huia water treatment plant at Titirangi.

Simply put, those affected residents in Parker Rd could not be relocated locally

Board chairwoman Margaret Devlin said the assessment process found the Parker Rd North and Manuka Rd sites emerged about the same on technical, environmental and economic grounds.

The decision boiled down to loss of native bush at the Manuka Rd site in Titirangi versus the loss of 12 or 18 houses at Parker Rd.

Watercare, Devlin said, could make up for cutting down native trees through a planting programme on a forestry block in the Hunua Ranges, but could not easily mitigate for the loss of homes.

"Simply put, those affected residents in Parker Rd could not be relocated locally," she said.

The decision followed fierce opposition from Oratia residents, who turned out in their hundreds at two public meetings. Deputy Prime Minister Paula Bennett, who has lived in Oratia for eight years, offered her backing.

Goldsmith felt a huge sense of relief and "pride at being part of a community where everyone has got each other's back and people came out in support".

"We are an integrated community, we are connected to the land, to each other with our heritage," said Goldsmith, whose feijoa orchard was one of 18 or 12 properties needed for one of the two options.

"If they had built a water treatment plant at Parker Rd there would be significant social impact, 104 people being forcibly removed is significant. All credit to Watercare, they have listened and heard," he said.

Now the attention will shift to Titirangi, where Watercare will seek consent to build the new water treatment plant on a site next door to the 90-year-old Huia plant, where four houses once used for plant staff have disappeared and the land reverted to native bush.

Watercare estimates it will take three years to gain consent, plan and design the new plant, and three years to build. It is hoped the $396 million plant, will be operational by 2023.

The two options at Parker Rd were costed at $417 million and $425 million.

The Titirangi Protection Group is angry and promised to fight the decision, saying the Manuka Rd development site is located at the "Gateway to the Waitakere Ranges" and led to large scale clearance of protected heritage bush, including significant kauri trees, with more than 60 species of native flora and fauna.

Titirangi Residents and Ratepayers Association chairwoman Dr Mels Barton said the community, Watercare and Auckland Council needed to work together on the design to have the minimum impact on the environment and local residents.

This point was reiterated by Waitakere councillor Penny Hulse, who said while Oratia celebrates, and rightly so, there needed to be a genuine opportunity to talk with the Titirangi community.

The Watercare board has instructed management to minimise adverse effects on significant trees within the construction area and establish a community liaison group.