Earthquake strengthening planned for Tauranga City Council parking buildings

Earthquake strengthening will start on the Elizabeth St car park building, as well as Spring St. Photo / File

Tauranga's car park buildings are at risk of damage should a significant earthquake happen, the city council has discovered.

It comes as the Ministry of Business, Innovation and Employment released the details of all earthquake-prone buildings (EPBs) in New Zealand's high seismic risk areas have now been identified by local territorial authorities.

Priority buildings are certain types of earthquake-prone buildings in high and medium seismic risk areas that are considered to present a higher risk because of their construction type, use or location.

While Tauranga and Rotorua sit in the medium risk area, and do not need to report back and identify earthquake-prone buildings until 2022, 82 buildings in the region have been identified as a risk.

Precautionary seismic assessments of Tauranga City Council's Spring and Elizabeth St car park buildings have highlighted areas where strengthening and remediation work should be carried out to reduce the risk to users and the extent of the damage.

Council corporate services general manager Paul Davidson said although there was no regulatory requirement to carry out the assessments, expert engineering advice suggested it would be prudent to do so.

"A learning from the Canterbury and Kaikoura earthquakes was that buildings with long-span precast concrete flooring systems can have vulnerabilities and as both buildings utilise that system, we wanted to ensure that any works needed to surpass the required earthquake resistance standard were identified."

Parts of both buildings do not meet the minimum 34 per cent "new building standard" (NBS) rating, which technically means they could be classified as earthquake-prone, Davidson said, requiring strengthening or demolition to be carried out within 25 years.

"Advice provided by Chartered Professional Engineers, Kestrel Group, stresses the NBS ratings for the buildings do not mean they are dangerous, or that there is any need to change the current use," Davidson said.

"We are now working with engineering consultancy Beca to finalise strengthening options and costs and develop a timeline for the structural work to bring both buildings up to at least a 55 per cent NBS rating."

Work would be scheduled to minimise inconvenience for regular users, but it was likely each building would need to be closed to the public for a period of time.

"We'll be working hard to make sure the closure periods don't overlap and keep them as short as possible. Council staff will also provide advice on alternative all-day parking options for car park users."

Work to be undertaken on the Spring St car park includes the installation of additional steel bracing components and provision of independent support for the bridge linking to the roof of the adjacent building at 29 Grey St.

An earlier component of work to apply seismic restraints to non-structural block walls on the northeastern side of the building is expected to start this month.

Ramp transitions will be the focus of remediation work at the Elizabeth St car park for the first four levels of the building plus connections between the eastern stair tower and the building.

The council is working with the co-owners of the Elizabeth St building to minimise any effects of the work programme on their commercial tenants.

A report on the buildings' seismic status was received by commissioners in a public excluded session of the council meeting held on March 8.

That report is now publicly available on the council website.