Council gave all-clear to quake-prone Hutt Hospital block last year

The DHB used a 10-year-old seismic assessment to persuade the Hutt City Council to go easy on it in May 2021.
The DHB used a 10-year-old seismic assessment to persuade the Hutt City Council to go easy on it in May 2021. Photo credit: Image - RNZ; Don Thomas

By Phil Pennington for RNZ

Documents show the major hospital block about to be shut in Lower Hutt due to earthquake weakness was ruled not earthquake-prone just one year ago.

The DHB used a 10-year-old seismic assessment to persuade the Hutt City Council to go easy on it in May 2021.

But a year later, this week, an updated assessment has reversed that: The Heretaunga Block with several wards is newly rated at just 15 percent of New Building Standard (NBS) and might have to start being evacuated within weeks.

Even back in 2011, the engineers Aurecon were worried about its weaknesses and outlined to the DHB a way to strengthen it.

"While the level of the building strength is relatively low, it is not considered to be 'earthquake prone'," the DSA (a tool for measuring the intrinsic strength of a building) said. It rated the block at 43 percent NBS.

Then Aurecon wrote in bold: "However, the nature of the failure mechanisms should be considered as we believe they could lead to sudden loss of capacity and possible collapse of parts of the structure."

Read the full report (PDF 11MB)

The DHB has known this since 2011. It used this DSA last year to argue to council the block was not quake-prone.

The 2011 assessment it relied on had not undergone a range of updates arising from lessons learned in the 2016 Kaikōura quake.

The Heretaunga block survived that 7.8-Richter quake, when a collection of other buildings in Wellington did not and had to be demolished in the months and years after it.

The Hutt City Council came looking at the Heretaunga block in 2019, correspondence provided to RNZ by the council shows.

It was required to, under earthquake-prone building rules adopted in 2017 that set an early 2020 deadline.

"The 2020 deadline was for councils in areas of high seismic risk (such as Hutt City) to identify priority buildings (including hospitals) which were in the council's view potentially earthquake-prone," MBIE said in a statement.

"Once the council requests an engineering assessment, the building owner has one year to produce it. The council will then consider that information and if it is accepted as earthquake prone, will put the building on the register as an earthquake-prone building, although there is no set timeframe for doing this."

That then starts the clock ticking on a seven and a half year deadline to fix or demolish.

A quake-prone building is under 34 percent of the New Building Standard (Heretaunga's new interim rating of 15 percent - peer reviewers are still assessing it - puts it in a zone where it is 25 times more likely to fail than if it were at 100 percent NBS).

Council gave all-clear to quake-prone Hutt Hospital block last year
Photo credit: Image - RNZ; Don Thomas

One-year deadline to assess

The records show Hutt City wrote to the DHB in December 2019, saying the Heretaunga Block looked like it might be earthquake-prone. It was definitely a "priority" building, which cuts the time in half to tackle any risks.

The council gave the DHB a year to do an assessment.

Had it done so, the DHB would have known 18 months ago the Heretaunga Block was quake-prone.

The DHB could have got a year's extension on an assessment, if it had asked by October 2020, but the council did not produce a record of it asking for that either.

The health board did not meet the deadlines, tightened up under earthquake regulations changed to increase safety in response to the Kaikōura quake.

Instead, a year ago, six months after the December 2020 assessment deadline, the DHB met the council to discuss the seismic status of the Heretaunga. The council wanted to know how critical it was - either an IL3 or IL4 building. The Importance Level can revolve around if a building is needed to offer surgical or emergency services - which the Heretaunga is not, so it's an IL3.

The council had not suggested it was on the basis of it being an IL4 that it might be quake-prone.

One week later, on 13 May, the council wrote back that it had received and accepted Aurecon's 2011 seismic assessment "and using this information has determined the building not earthquake prone".

Read the council's letter

The council told RNZ last night it had "determined that the Heretaunga Block was not earthquake-prone in May 2021 based on the information provided to it [by Hutt Valley DHB] and in accordance with the EPB methodology".

It said it got the new draft DSA on Tuesday this week and was reviewing it according to the Building Act, and expected to get more information about the peer-reviewed DSA next week.

'Undesirable failure mechanism'

RNZ has asked the DHB if any of the strengthening recommended in 2011 was done between then and now.

That 2011 assessment came 10 months after the Christchurch quake which pancaked several buildings, killing scores of people.

In it, Aurecon told the DHB that "two significant issues are immediately apparent" - that the Heretaunga Block's structural system "abruptly changes from a stiff wall system to a flexible frame system above level".

"This is likely to put significant stress on the frame's columns."

Secondly, the beams were significantly larger than the columns, so the columns were likely to yield before the beams.

"This is an extremely undesirable failure mechanism ... which can lead to collapse of the floors," the report said.

It is not known if this has been fixed.

The Hutt is far from alone in having earthquake-prone hospital buildings still serving patients.

That's also the case in high-quake-risk Hawke's Bay and Canterbury, and less-risk Taranaki, as well as many other DHBs.

The approach to dealing with quake-prone buildings - to strengthen or replace, and in what timeframe - varies hugely.

Taranaki said it was ahead of its 12-year timeframe to replace its clinical services block that at just 10 percent NBS, has the lowest seismic rating of any public building providing key medical services to patients.

The DHB said it was on track to open a six-storey building by the end of 2025 to house many acute clinical services including: ED, ICU, maternity, primary birthing, neonatal, radiology, laboratory and a roof-top helipad.

Hawke's Bay is further behind, while Canterbury is further ahead, at least at its quake-prone Parkside block, where work finally began this year to strengthen it by the end of the year.

In low-risk Auckland, the quake-prone Galbraith building that houses many key services at Middlemore Hospital, is not expected to be replaced till 2035-40.

RNZ yesterday morning asked Health New Zealand how it would manage the major infrastructure problems facing hospitals, and whether it would set up an infrastructure taskforce, after it takes over from DHBs in July.

It did not respond.

Health Minister Andrew Little said he is not aware of any other buildings in the health sector that are in the same state as the Hutt Hospital.

Little told Morning Report he understands the widespread concern about the Heretaunga Block, however, the new rating doesn't mean the building is going to fall down immediately.