A way to save and earthquake- strengthen the council administration building and clock tower, built in 1957, has been found - and within touch of the original budget.
But there's a price: the three- storey west wing extension (1967) and the supper room/cafeteria at the back (1980s) would be demolished.
At a meeting tonight city councillors will also debate a more radical alternative.
For about the same money, the buildings could be demolished and a new, single-storey modern block erected on the eastern part of the precinct.
Earthquake-strengthening and modernising the interior of the original 1957 building is estimated to cost $22.1 million. The new building would cost $21.1m.
Both estimates include the cost of temporarily leasing space for council staff elsewhere in the city for a 15-month construction phase, and a 20 per cent contingency allowance.
Deputy Mayor David Bassett chairs a Project Steering Group of senior officers and councillors which has been investigating the issues for 18 months.
He says the two options have been shortlisted from a list of 14. The decision appears to be a no- brainer.
The council can save, and modernise the interior, of a much- beloved heritage building in the city's civic heart versus demolition and building something new that could look out of place across from the heritage library and St James' Church. But Cr Bassett insists they are putting up two options for serious debate.
Modernising the 1957 building to open plan for much better workplace efficiency, using space wasted by lots of corridors, will mean extra room for staff.
But losing the west wing means up to 60 of the 230 staff housed at Laings Rd would have to be permanently accommodated off site.
There was much to weigh up, he says. The council's own policy requires the buildings to be 67 per cent of the New Building Standard by 2018, or demolished.
But given the key importance of the council operation in an earthquake - the Christchurch events showed us that - councillors in this case opted for a higher, 100 per cent compliance.
Other weighted criteria included: meets future service requirements; heritage preservation; value for money; future flexibility; and contribution to the CBD Making Places strategy.
City infrastructure manager Bruce Sherlock says though it was built 10 years after the main building, the west wing was the most "seismically compromised".
Consultants say the site is prone to liquefaction and extensive ground remediation is required, whatever is on the site.
But trying to shore up the west wing would be particularly expensive, adding about $12m to the bill.
Building a multistorey building on the same site would cost $26m, or $34m on a new site.
Why not lease a building elsewhere - say, the Serepisos tower on Petone foreshore, or a (strengthened) Levene/Contact Energy building at VIC?
Mr Sherlock says renting sufficient space would cost more than $1m a year.
"That's cheaper in today's market but the market can't always stay like that.
"Over the long term, leasing has got to be more expensive."
Anyway, says Cr Bassett, that doesn't solve the problem of the earthquake-prone council building.
Should it just be demolished or left as a "boarded-up eyesore", he asks.
"What sort of a message does that send out, especially to other building owners also facing [earthquake strengthening] costs?".
Mr Sherlock says feelers were put out: Would anyone take on the council building, with its earthquake issues, for $1?
"There were no takers," he says.
Cr Bassett says the possibility of council amalgamations is another complicating factor.
If we join Upper Hutt, a smaller council building could be a good fit and there would be no need for offices for 60 staff off site.
If we later joined a super-city, the heritage council building, with a modern "future-proofed" open plan office interior, would be a realistic sale prospect if no longer needed for civic purposes.
Mayor Ray Wallace says the council has gone to great lengths to ensure every aspect of this project was examined thoroughly. Whichever of the two options councillors adopt tonight, design work will start immediately, and the 15-month construction period will begin in early 2014.
- Hutt News