'Precautionary approach' after seismic test on Spring St parking building

Spring St parking garage. Photo / File

Seismic issues have been found in the Spring St parking building, but Tauranga City Council and engineers say it can continue to be used.

In a meeting today the council received a report from a preliminary seismic assessment of the building.

It came just a month after the council abandoned construction of a new parking building in Harington St due to the prohibitive cost of fixing the structure's seismic resistance design deficiencies.

The meeting heard the Spring St assessment was ordered proactively due to learnings from the Christchurch and Kaikoura earthquakes.

Those events exposed seismic vulnerabilities in some buildings that had long-span precast concrete floors, a construction method used in the Spring St building.

It was built in 1994 and has not previously had a seismic assessment as one was not required under the Building Act, according to a report by engineer Dave Brunsdon, director of Kestral Group.

The preliminary assessment evaluated the floors and other aspects of the building against modern seismic resistance standards for existing buildings.

It found that a more detailed seismic assessment was needed to evaluate the potential risks associated with the main structural walls, seating of the precast concrete floor units and ramps in the building.

This assessment would include a geotechnical examination to find out more about the potential for liquefaction in the area.

He recommended the council add extra supports to the seating of the long span floor slabs at an estimated cost of $581,000.

This will involve work on every suspended floor unit in the building, requiring an estimated 1028 bracket in total. The additional assessment might find the need for more floor fixes, so the work has not yet been scheduled.

Strengthening of a block wall on the northeastern side of the building, however, will take place after the detailed assessments are finished, the meeting heard. It had an estimated cost of $141,000.

Brunsdon's report said the risks found so far did not mean the building should be regarded as dangerous, or that the way it was used should change.

In a statement after the meeting, council corporate services manager Paul Davidson said the council was taking a "proactive approach to ensure the structure is safe for community use if a major earthquake did occur".

He said planning was underway for the work on the north-eastern side of the building, which could cause minor disruptions for car park users.

The detailed assessment and geotechnical investigation was expected to be done in around three months.

The Western Bay of Plenty area sits within the medium seismic risk area defined by the Ministry of Business, Innovation and Employment. The statutory timeframe for completing any required strengthening was relatively long at 25 years.

"We, therefore, have time to assess and implement any remedial works which are considered appropriate, in a manner which will ensure the long-term safety of the building and minimise any impacts on CBD parking availability," Davidson said.