The Wellington City Council has released further details on its proposal to strengthen the city's Town Hall and create a music hub there.
The strengthening will cost $90 million, and will bring the building up to 100 percent of the building code.
On Thursday, councillors will debate the proposal, which outlines three possible options for the building. The agenda for the meeting can be seen here.
The first would simply strengthen the Town Hall, and the second would add the New Zealand Symphony Orchestra and School of Music as the main tenants.
The third would establish a Civic Music Hub, with the School of Music expanding into adjacent buildings, including the Municipal Office Buildings and "building additional spaces under the eaves of the Michael Fowler Centre".
Although rents were yet to be agreed, the documents indicated the council's annual income from the strengthened building would start at about $500,000 and the tenancies would span 25 years.
It said the musicians would share 60 percent of the building, "in return for a rental stream at market-derived rental levels".
"The rental stream will more than cover the operating costs of the Town Hall building," the documents said.
As part of the proposal, councillors would be asked to delegate authority to the council's chief executive and mayor to finalise and execute the music hub deal.
If councillors accept the proposal, the next step would be to develop detailed designs for the strengthening, which is due to begin in August next year.
The documents also revealed more details about the strengthening work.
It said it would include base-isolation technology in the foundations, because it would be more expensive to strengthen the building to 67 percent of the code without them.
"In the case of the Town Hall, base isolation reduces the horizontal load at the base of the structure to about half of what it would be without base isolation... [It] significantly reduces seismic loads to the building structure and therefore reduces work to the building above ground level."
Other changes included demolishing and rebuilding the West Hall, with "an exciting new architectural insertion".
The Ilott Theatre would have a flat floor, new screw piles would be installed and the basement would be bigger.
Even though the report's authors said the proposal "has been carefully considered and is at a more advanced stage than at any other time of the Town Hall project", they said it was a "complex project and ... is still not without risk".
If it goes according to plan, the work would be finished in June 2021.