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However, despite discussions starting between its chief executive and the owner of the site, the council insists it is just "one of many" options.
The council voted last month in private session to direct council chief executive Sarah Gardner to negotiate with owners of a site straddling Anzac Ave and Harrow St, southeast of Emerson's Brewery.
The information came from a public-excluded agenda obtained by the Otago Daily Times.
The site includes the 2100sqm building of design-and-build firm Miller Creative, leased to 2020.
It also includes a light industrial-use premises leased to the Otago Polytechnic as a workshop, three student flats, a four-bedroom house, 30 storage units and a 250sqm warehouse.
When asked about the site, council chief executive Sarah Gardner said there were still a "range of options" for a headquarters site.
She would not discuss whether discussions on any of the other options were as advanced as for the Anzac Ave site.
"All of those motions are made in public excluded so I can't really comment."
Council chairman Stephen Woodhead said all site options were within the Dunedin "city boundaries".
He would not comment on negotiations.
"What I can say is we've said to Mrs Gardner to move as quickly on this as she can."
A further $600,000 has been approved from the council's building reserve for planning and design of a new headquarters.
Council executive officer Ian McCabe said these funds were available as the council underspent on design for the project in the last year because its Dowling St site bid fell through.
"We've got about 25 sites which were presented to us when we did registrations of interest and we're currently shortlisting those at present."
The Anzac Ave site includes five different titles, all owned by Miller Studios Property Limited.
Company director Tony Johnston, of Dunedin, said he was told by the regional council his was one of 13 sites being investigated for the project.
The group of sites was advertised for sale mid-last year.
Port Otago-owned Chalmers Property has provided a "formal indicative proposal" to design and build the headquarters.
In its meeting last month the council asked for "due diligence" on the site in regard to climate change and adaptation.
Council science, hazards and engineering director Gavin Palmer was to action this request.
The council previously spent $9,715,000 on land purchases, site assessments and temporary office space relating to the search for a new headquarters, which has lasted more than a decade.
It was announced in July that the council's most recent site bid, a Dunedin City Council-owned car park in Dowling St, was abandoned.