Seismic Policy, Wellington City Council Style (part 1)

Part  one: Compliance with the law

As we head towards the Appeal of the Determination on the test case, our thoughts have turned anew to the way the Wellington City Council developed their seismic strengthening  policy. When we prepared our Determination submissions we reviewed the material  received under an Official Information Act request for the Wellington City Council’s seismic policy formulation documents.  This update tells part of the story that emerges from those documents.

To put this story in context, under the Building Act 2004, the Council was required to establish earthquake prone building policies.  However, the legisation did not prescribe any particular policy. It was left to the Council and the Wellington community to develop a policy approach appropriate for Wellington.

The policy formulation story a lengthy one, so we have divided it into three updates.

The first, and most significant for the test case, is the way the Council  ensured that its policies gave effect to the definition of an earthquake building under section 122(1)the Building Act 2004. This provides that the an earthquake prone building:

  • will have its ultimate capacity exceeded in a moderate earthquake; and
  • would be likely to collapse

Section 124  describes the Council’s powers if it is satisfied that a building is earthquake prone.

The satisfied test is a strong one. It is not a matter of the Council knocking another building off the list, using the cheapest methodology possible. It must be satisfird that a building is earhquake prone and to be satisfied is a strong test. The following Oxford dictionary definition has been cited with approval by judge that considered an appeal of a MBIE Determination.

“Satisfy – to furnish with sufficient proof or information, to assure or set free from doubt or uncertainty and to convince and solve a doubt, difficulty.”

The critical issue in the test case is that the Council’s EPB building designations are void because the Council did not apply the legal test. Instead it applied the New Zealand Society for Earthquake Engineering methodology that that switched the term ultimate capacity in (a) for ultimate limit state, and ignored (b) altogether.  The effect was to apply a different, and much tougher, test than allowed under the Act.


The second issue is that even if the NZSEE EPB definition was legally robust, the use of the Initial Evaluation Procedure (IEP) methodology could not provide suffcient assurance to allow the Council to be satisfied that the %NBS rating was less than 34. The NZSEE describes the IEP as “a coarse screening involving as few resources as reasonably possible. It is expected that the IEP will be followed by a more detailed assessment for those buildings identified in the evaluation as likely to be Earthquake Prone (EPB) in terms of the provisions of the NZ Building Act 2004.”

Note that the objective of the initial evaluation is to identify, with an acceptable confidence level, all those buildings, which will be potentially Earthquake Prone. At the same time the initial evaluation process must not catch an unacceptable number of buildings, which on detailed evaluation, pass the test.”

The NZSEE was somewhat unclear here.  If the IEP is meant to capture all buildings that are potentially earthquake prone then this is more or less a meaningless statement. A large number of buildings might potentially have a %NBS of less than 34. But what matters in terms of the Act is the actual %NBS.  A local authority needed to know how accurately the IEPs assess the actual %NBS of a building, not whether it potentially fails the 34 %NBS test.

What is notably lacking in the Guidance Document are the results of a test of the IEP against actual detailed evaluation assessment results.  As the NZSEE actively promoted the use of the IEP this was an essential step.


The Council’s documents

The first sight we have of a consideration of the meaning of the provisions in 122(1) is a document  dated 12 August 2004 (sic – it must have been 2005), with notes from a meeting to discuss policy development for earthquake prone, dangerous and insantitory buildings. The meeting was attended by the WCC, Regional Council, Hutt City and Upper Hutt.

“Requirements of the Building act covered. EA, Hutt City council noted some case law which might help in the interpretation of terms. A clear definition of  terms might not be helpful as it could be constraining.”

Obviously the definition of EPB was an issue, but the WCC policy analyst who drafted the note was not too keen on being constrained by the law.


  1. E-mail from senior policy analyst to advising engineers (BECA) dated 16 Sept 2005

“We need a specific piece of work giving me the margin of error of the IEP”.

This shows that the analyst was aware of the key issue with the use of the IEP. If the Council was to be satisfied with a %NBS assessment, then it needed assurance of the IEP’s accuracy. However, what was provided in the return letter was not an accuracy assessment. There  was just a table of IEP outcomes for different types of buildings. There was no follow up action by the Council officer on this point.


  1. Power point for a discussion with engineers power point dated 10 October 2005.

EQPB defined in regulations 1/3 current code (NZS 1170.5:2004)

This was obviously incorrect. The regulations define a moderate earthquake not an earthquake prone building.

“Criteria for EQB  1/3 and collapse –  IEP to do this?   The key question is whether a building is likely to collapse in a moderate earthquake”

The key question was identified but the understanding of the Act was inaccurate.


  1. Draft doc undated but probably October 2005

The excerpts from this document show the strategy that was adopted to get around the legal ‘problem’ that the Council, not owners, was responsible for determing whether a building is earthquake prone.

Two potential problems arise from the IEP. May be performed by any structural engineer leading to the possibility of inconsistency.

Second, the Act does not provide for, and legal advice confirms, building owners to be responsible for assessing whether their buildings are earthquake prone or not.

It is therefore proposed  that the Council must be responsible for identifying buildings that are potentially earthquake prone (ie identifying buildings that are built prior to 1976 through a file search) and then the IEP.

Advice is given that the Council cannot enforce a strengthening greater than the Act requires.

So the approach taken was not to be satisfied that a building was earthquake prone as the law requires, but to be satisfied against less meaningful, and indeed legally meaningless test, that a building was potentially earthquake prone. As we shall see owners were expected to provide the expensive detailed assessment to prove that a building was not earthquake prone.


  1. 1 November 2015 e-mail to consulting engineers

The Council’s approach seemed to have crystalised in the mind of the senior policy analyst, who appeared to be primarily responsible for the development of  the WCC EPB policy, in this e-mail.

“Following on from the engineers meeting at the Council the other week there have been other opinions sought about the best way to proceed given the differing interpretations of practitioners. We are coming to the view that we are not in a position to interprete the wording in the Act and that to ensure a consistent approach council should engage consultants to help with the assessment.”

This is an extraordinary comment. The Council must be satisfied that a building is earthquake prone, but the officer’s response was to duck the issue by ‘outsourcing’ the decisions to consultants.  By this stage the Council’s officers must have known that the consultants would be using the NZSEE IEP approach, that ignored the likely to collapse test.

“As noted in previous discussions there are two approaches that could be followed. One has the IEP done simply on a visual inspection with the info you have indicated above (base information -construction dates etc.). the other would also include information gathered from a review of the drawings and other info from the Council archives. Althought the second method would provide the most robust result, the first is in my view still viable. Neither approach is fool proof.

My guess is that with the first approach the assessments could be done on an average of 30 min per building.,,, the second  I am thinking would  add 15-30 minutes per building say 60 min building. I would suggest that a trial be run to say 100 randomly chosen buildings.

A smaller proportion could be subject to a detailed assessment but this would only be required if the Council needed confidence that the method was not bringing too many non EPBs into the net.”

An assessment taking 30 minutes, that doesn’t even involve a review of the building files,  could hardly provide a basis for the Council to satisfy itself that a building is EPB.

From the documents provided there is no evidence that the Council ever compared detailed assessments with IEP results. Clearly they were not concerned that too many non EPBs would be bought into the net. When the policy was reviewed in 2008 it was found that 75 percent of IEPs were incorrectly identifying buildings as having a %NBS as less than 34%.  It did not occur to the Council officers conducting that review to reassess the use of the IEP methodology.

“Advice we have been given indicates that for a building to be earthquake prone both subsection a) and b) of section 122(1) must apply and the interpretation of ‘likely to collapse must be read in the context of the definition as a whole. So the part b) is about collapse (even if only partial collapse) in a moderate earthquake (the context). This raises some queries for me including:

  • Is this different from your understanding? You are aware I do not like the second part of the Act clause. My own view is different from what I know has been given as legal advice. I suspect that only a Court case would establish the “correct” legal interpretation. I believe that if this part of the act is to remain it will be necessary to interprete it in the broadest manner possible, as we have indicated in the guidelines.

This is telling, the Council officer did not like the legal opinion, so developed a policy that effectively ignored it.

  • “Will an IEP infer likely collapse, or is it only an assessment of part a) exceedance of ultimate capacity in a moderate earthquake. The IEP and the Society’s guidelines determine % new building standard. Collapse is not mentioned if only for the reason it is impossible to predict reliably.
  • Re the buildings your firm researched for the DHB, do they potentially meet the criteria of a) and b). If not there is little point in further investigating them because they do not meet the earthquake prone test and Council has no other mechanism to address their potential structural deficiencies. The guidelines will be supported by the DHB. On this basis they must have some status on the matter  of how collapse is to be dealt with”.


Again some telling comments. The officer was not interested in the evidence that might show that buildings are not earthquake prone buildings.  The Council officers had bought the story that there were large numbers of buildings that had potential ‘critical structural weaknesses’, and were a high risk even in a relatively weak earthquake.  They were on a mission to deal with them, earthquake prone or not.

What they were not aware of is that the NZSEE guidelines, and hence the IEP, set an unlawful test for the identification of the so-called critical structural weaknesses. The  models are calibrated to assess the impact of these weakness in a much stronger design strength earthquake, not a moderate  earthquake, as required by law.

If the Council officers had read the NZSEE Guidance document, or had been correctly advised by their engineering advisers, they would have discovered that.

The final point is also telling. We don’t know what a EPB is, the thinking goes, but don’t worry the guidelines are being supported by the DHB and they must know something. Hardly a compelling basis for being satisfied that the NZSEE Guidelines methodology is consistent with the law, when the responsibility for the policy rests squarely with the Council.

There is no record of any response to the e-mail.  We will be asking for it.


What wasn’t done

There is no evidence in the documents that the Council reviewed the critical parts of the NZSEE Guidence document. In particular:

  • No questions were asked about ‘critical structural weakness’ adjustments in the IEP or even on what critical structural weaknesses were.
  • The NZSEE ‘interpretation’ of the law was not subject to legal review.


So where did they end up

The Council EPB policy was formulated so buildings would be assessed as being ‘potentially earthquake’ prone. Owners would be informed of this and be given the IEP %NBS rating. They would then have  6 months to convince the Council that the building is not earthquake prone. If the Council was satisfied that the building is not earthquake prone then the status of the building would be changed and the owner informed.


The effect of the policy was to reverse the onus of proof of a building’s seismic status from the Council to owners,and to shift the cost of a detailed assessment on to buildings owners. In effect the IEP was used not just as a guide to whether a building was potentially earthquake prone, but as the decision metric that it was actually earthquake prone.


The key issue of whether the whether the %NBS  framework was consistent with the law was simplied ignored.


And what was the Council told

About the important stuff, nothing.

  • Not a word was said about the choice (or more accurately the evasion) on the earthquake prone building definition issue.
  • The policy was described as not significant under the Council’s significance policy. This was obviously untrue. The Officials had seen a cost benefit report that put the cost to Wellinton property owners at $260 million, (and that looked to be a significant underestimate).

We will have more to say about this in our next update.