It's called the "Kaituna Cut" and for local Māori it was a wound which never healed.
Te Rūnanga o Ngāti Whakaue ki Maketū manager Maria Horne represents the original Maketū action group which has been advocating for remediation since the 1970s.
"It's been a long-term grievance... and I'm going back to the 1920s for our Ngāti Whakaue ki Tai people," she said.
The cut was created in 1956 at Maketū, diverting the flow of water away from the river mouth so the surrounding areas could be farmed.
The new land for farmers came at a price, with the loss of kaimoana stocks as the health of the estuary suffered.
"[The Maketū Action Group] knew that any re-diversion would take away their pātaka kai," Horne said.
"I'm one of a long line before me that actually put a lot of effort into trying to sway the councils to return the Kaituna river to the Maketū estuary and it only got recognised in the 1970s.
Coastal catchments manager for the Bay of Plenty Regional Council Pim De Monchy said there was no better time to put the area right.
"Maketū estuary has been declining for 60 years and the time is right now to spend a bit of money, do some significant works to try and put right what we can."
"The project aims to bring back 20 per cent of the Kaituna River and recreate 20 hectares of wetlands. In 1956, the river was diverted out to sea with benefits for land drainage. But over the last 60 years, the estuary has suffered as a result."
The river is now half full of sand, has lost 90 percent of its wetlands and populations of both finfish and shellfish have crashed.
"What we're trying to do in response, is act on the requests from Te Arawa people who've been asking for the return of the Kaituna River since 1979. They've been quite patient about that," De Monchy said.
"We're about half way through a two-year construction programme and well ahead of schedule. We were hoping to open the project in June 2020 but the project is now looking like we can get to stage one commissioning before Christmas this year."
The $16 million project is being funded by the Bay of Plenty Regional Council, with local councils and iwi working together to ensure its success.
"The co-governance is made up of four councils, with the regional council, Tauranga City Council, Western Bay Council and the Rotorua Lakes Council," said Dean Flavell, Chairman of Te Maru o Kaituna River Authority.
"Also associated to that entity are the various iwi on the river. We have the Pumautanga up at the top who represents Ngāti Pikiao and Tūhourangi. And we have Tapuika, Ngāti Whakaue, Rangiwewehi and Waitaha.
"By working together, we're hoping that the decisions we made are more to do with the protection of the river. It's our generation's contribution towards that end goal of well-being for the river and its waterways."
It's a large-scale project, including the creation of a 650m channel and stop bank. There'll also be a realigned road, a new public boat ramp and more than 20 hectares of new wetlands.
"What this means for the public is that, over time, the health of the estuary and lower river will improve," De Monchy said.
"What's also more available now is public access. Some of the land that was previously private is now public and there are plans afoot with the district council to create some additional walkways and cycleways."
And with the project well ahead of schedule, there's finally some light at the end of the very long tunnel.
"I can't wait until the land is actually removed so that the river can flow in its natural form back through the estuary," Horne said.
"We're very happy. We have supported the regional council in any aspect, even going as far as to the Environmental Court to get this re-diversion. We ourselves have gone and advocated through our treaty negotiations for land for new wetlands.
"Going forward, I'd like to see us all make a concerted effort in creating more wetlands and appreciating the environment and it's not just tangata whēnua that has to do it – it has to be a concerted effort by everyone."