Wellington Library. Photo: CC BY 2.0
Wellington ratepayers can breathe a sigh of relief that the central library rebuild is not going the way of the Town Hall upgrade.
"We have not identified any significant project difficulties or risks that are causing an overall concern," the city council told RNZ on Thursday.
While it is not quite sure what the existing piles sit on - according to a newly released geotech report - the new piles are down and done, and the ground is looking solid compared to the squidgy Town Hall just 100 metres away.
"The project is currently on programme and is within the approved budget," it said.
In the Capital's ever-more rickety Te Ngākau Civic Square, that is rare music. Close by, the Michael Fowler Centre got slapped in August with an earthquake-prone notice - the worst category - and the structurally questionable City to Sea bridge is edging closer to a demolition talked about since 2019.
Actual demolition of another of the square's buildings, its young (1990s) and flawed administration block, moved closer this week with the city council voting to pull forward about a quarter of the $8 million funding set aside to pull it down.
In 2015, council budgeted $100m for the entire Te Ngākau makeover, including earthquake strengthening and public space improvements. That has now been sunk in the Town Hall foundations alone.
It is bedevilled by what engineers have called "aggressive soils and brackish water", coupled with a high water table.
But the $189m Te Matapihi library job just across the pavers, and sitting on similarly reclaimed land, has escaped those perils.
"The rock layer at Te Matapihi is at between 3m and 8m, which is much shallower than the Town Hall," the council said.
The only major work below the water table is the lift pits. "There are no concerns."
The Town Hall job has been subject to review after review. Not Te Matapihi.
File image. Photo: RNZ / Samuel Rillstone
"No specific project reviews have been completed ... as the project is progressing to programme and budget"; no legal review had been needed either.
Consent reviews of the structure, fire and facade had been done.
The project is not without a wildcard or two.
Engineers' reports say there is probably an underground alluvial stream under the library which, like the fill in the reclaimed sections, would move around more in an earthquake than the rock does.
The existing piles sunk in the 1990s raise a question in the geotech report.
"All the piles are likely to have been embedded into the greywacke rock, but there is no information to confirm the pile depths," it said.
All the new piling was finished a few weeks ago.
Some low-level contamination detected in the soil was not a concern either.
Usefully, the site has "very low or no liquefaction potential" in a one-in-25-year level earthquake.
The existing building could not stay as-is: The concrete floors between levels did not have wide enough lips to sit on, a weakness exposed by research after the 2016 Kaikōura earthquake.
The smooth sailing so far makes the controversial decision to save the 1991 building - belatedly categorised as the city's youngest Category 1 historic site - look better.
Next door, at the blighted orange admin block, deserted for five years, it has taken till now to warm up $2.4m for a start on demolition before next July, instead of waiting even longer.
This does not sort out the future of the 1950s municipal office building - moved out of in 2018 - in between the admin block and the Town Hall.
Council is still talking about "redeveloping or strengthening" this building.
Councillor Tim Brown said sorting out both was critical for the successful completion of the Town Hall.
"This project is a key part of bringing the life back to Te Ngākau Civic Square," said the acting chair of the environment and infrastructure committee in a statement.
A tender to redevelop this area would open before Christmas and run till March.
A redevelopment plan for the whole square agreed in 2021 sets a height limit at about that of the library, lower than the municipal block.