The council announced yesterday plans for the long-awaited new headquarters were signed off in a closed-door meeting.
Interim chief executive Pim Borren said the council’s more than 300 staff were now spread across three sites in the city.
"The building is an important step together with the decisions made three years ago in increasing the investment in our regional council to ensure we’re fit for purpose and can achieve the ambitious work programme in front of us."
The new building - at the former central Dunedin Warehouse site in Maclaggan St - will be known as the Whare Rūnaka (council house).
It was bought and will be built by the council-owned Port Otago, and leased back long term to the council.
Port Otago chief executive Kevin Winders said the port company bought the building for about $10 million with an arrangement with the council to underwrite it as a tenant.
The company would put another $35 million into the site and the council would complete the fit-out at its own cost for about $11 million.
About a third of the present ground-floor car park would be filled in and turned into a "wet room" area where council staff could process samples collected in the field.
The High St facade would be entirely new and had input from iwi.
A "high-tech" roof would be installed to create a "good, modern work environment".
The consenting process would begin immediately and hopefully take about three months, and the construction site was expected to be established in about six.
The company would use the same team - Calder Stewart, GHD Woodhead and Octa Associates Ltd - as it had for Port Otago’s new $19.5 million office at Port Chalmers, Mr Winders said.
"In a perfect world that team will end up coming off our project in late June and then move into site here."
If things went well, the construction would be complete by next December.
In 2021, the Otago Daily Times reported councillors were told a completion date for the project of last December was an "aspirational target".
The council has spent more than a decade searching for a new Dunedin base.
Mr Winders said the company and council had a five-year fixed rental agreement for $2.59 million a year, which would be subject to a market review.
It had already increased by $339,000 a year because of inflationary pressures.
The council had a 20-year lease and two 10-year rights of renewal.
Yesterday, two councillors, Crs Michael Laws and Gary Kelliher, independently contacted the ODT to say they opposed the new council building.
In its statement yesterday, the council also said Port Otago would reacquire a Birch St-Kitchener St site, planned as the site for the new headquarters more than a decade ago, for $7.9 million.
Mr Winders said the port company would look to develop the site over time.
