EBSS responses on hastings Opera House closure

 The Hastings Opera House Closure

Recently Hastings City Council staff presented a paper to their council in which they made a spirited defence of the decision to close the Opera house and the Municipal buildings. The paper raises some important issues about Councils’ decision making  (and building owners more generally); how they react to engineering advice that their building has a %NBS of less than 34; and the quality and nature of the advice they are given. We thought it useful to work through and discuss the points that were made.

The key issues that arise from the Opera House Case are:

  • Should buildings be immediately closed and streets fenced off if a building has a %NBS rating of less than 34.
  • If an owner has an engineers report identifying a most likely source of failure does this mean that they should not conduct any risk assessment before considering strengthening options.

The Council staff are saying yes on both counts.

The points made in the paper are as follows.

Engineering advice

3.1.1 Council obtained engineering advice from a number of sources, all of whom were broadly in agreement regarding building closure. Strata Group carried out the initial review of the Opera House Theatre Building; EQ Struc the review of the Municipal Building.


We have seen two of the reports.  They did not mention immediately closing the buildings. The results of two of the assessments were summarised in the review of the Opera House and Municipal building decision making.  There was no mention of immediate closure in the summaries.

3.1.6  All four highly experienced engineers confirmed the earthquake prone status and risk to life.


The engineers did not assess whether the buildings were likely to collapse in a moderate earthquake, as the law requires before a building can be designated as earthquake prone.  The statement that the buildings pose a risk to life is misleading. All buildings pose some risk to life in a seismically active area. The 34% NBS trigger point does not provide a brightline separation between buildings that pose a risk to life and those that don’t.  Nor does the 75%NBS level provide that separation. What matters is how big the risk is; how much of a difference strengthening makes; and whether the risk reduction is worth the cost. These critical issues were not addressed by any of the engineers.

3.1.8  Holmes Group was consequently engaged to complete concept and preliminary design work for a repair solution. OPUS international consultants have been engaged to peer review the work of the Holmes Group. The initial concept design and detailed modelling further supports the risk and likelihood of failure. The preliminary design report is to be presented with the Independent Working Party (IWP) report to the Council meeting in December 2015.


There is no risk and likelihood of failure assessment in the Holmes report.

3.1.10  The analysis used was not solely based on the New Zealand Society for Earthquake Engineers (NZSEE) guidelines, it also used engineering first principles and international best practice.


International best practice involves life safety risk assessments and cost benefit analysis in decision making.

3.1.11  The importance level of the building is clearly defined by the loadings code (NZS 1170) which is cited by the Building Act. Importance Level 3 includes ‘buildings or facilities ….where more than 300 people can congregate in one structures must be assessed against.


The Supreme Court made it clear that Council’s cannot impose higher standards than provided for in the Act. The test is in the Act is that a building must be likely to collapse in a moderate earthquake.  A higher standard cannot be imposed because of the buildings ‘importance’.

The loadings code is not cited in the earthquake prone building section of the Building Act.

3.1.12  The concept design report and findings from Holmes was provided initially to Councillors at an interactive workshop with Holmes and Win Clark on 26 February 2015. At the workshop the particular issues with the current buildings were discussed and questions responded to. Holmes confirmed that their detailed Non Linear Time History models clearly demonstrated that the current structure would fail quickly in a design event.


The statement that the building would fail quickly in a design level earthquake (0.39g) implies that this is almost certain to happen.  This is not supported by the GNS Science modeling of building performance in earthquakes.  This modeling suggests that the probability of a sound unreinforced masonry building collapsing in a design strength earthquake is relatively low.  It is also worth noting that the building survived the Hawkes Bay earthquake, which would have been above design strength.  One of the reasons it survived was the cushioning effect of the soft ground on which it is built (see the GNS Science report ‘Estimated damage and casualties from earthquakes affecting Auckland’ appendix 1 for a discussion of this point).

In the NZSEE guidance framework soft ground is a negative factor that results in lower %NBS assessments.

This is another case where the link to the new building standard in the NZSEE guidance framework can produce a wrong outcome.  Ground conditions can affect the intensity of more moderate earthquakes and this is relevant for an assessment of building functionality in more frequent moderate earthquakes. But it is not very relevant for a consideration of life safety risk where it is the performance in stronger earthquakes that matters.

Legal issues

3.2.5  Council received advice that in the face of the information the Council had in its possession from the Detailed Seismic Assessments that these gave rise to a duty upon the Council as landowner to take reasonable active steps towards ensuring public safety is not compromised. This needed to be considered in the context of the public facility, the lease of premises by Hutchinsons, and public in adjacent footpaths. While not explicitly recommending any particular course of action, Council and Council staff in considering its duties, considered closure to be an optimal approach.


The source of obligation of the Council’s duty as a landowner ‘to take reasonable active steps towards ensuring public safety is not compromised’ is not cited. If it is the Building Act then the only obligation as landowner to comply with lawful requirements imposed by the Council under the Act. The Council, as the regulator must act in accordance with its own policy.

The Council’s policy is as follows:

4.1  Policy Statement

Council will actively seek to identify buildings that are potentially earthquake-prone and allocate them a suitable priority, in order to take appropriate action to ensure they are made safe in reasonable time frames.

There is no mention in the earthquake prone building policy of a requirement to immediately close a  building  if it is found to be earthquake prone. The following general explanation of the Council’s approach is made in the document:
There exists a need to balance the benefits to a community in upgrading a building that is dangerous, earthquake-prone or insanitary against the ability of the community to meet the cost involved. For example, the cost to address all problem premises discovered in the District in the shortest possible time frame could be prohibitive.

It is clear that the Council did not receive specific legal advice to close the building.

Regulatory Authority

3.2.6  In terms of Council’s regulatory role, Simpson Grierson provided advice on the legal definition of earthquake-prone building and the circumstances in which a Council may decide to issue an earthquake-prone building notice under s124 of the Act; and if it so were to do, the content which ought to be included in such a notice.

3.2.7  The legal advice confirmed that both parts (a) and (b) of s122 (1) of the Act have to be satisfied before a building can be deemed to be earthquake-prone. After analysis by staff it was clear that in the case of both buildings, the legal test was satisfied.


It is clear that the staff did not apply the legal test. To do that they would have to assess whether the building was likely to collapse in a moderate earthquake and that they were satisfied that it would.  It also seems that the Council’s lawyers did not assess the methodology (from the NZSEE guidance document) that the staff were applying. If they had, they should have noted that the likely to collapse test was explicitly described as not part of the framework and that there were serious issues with the legality of the Council’s approach.

The Guidance document states:

NZSEE holds the view that the collapse criterion given in subclause 122 (1) (b) of the Act does not relate back to expected performance in a moderate earthquake but rather to an overall expectation. Thus it does not in itself affect the recommendations made in these guidelines.

3.2.10  Based on the engineering reports and likelihood building collapse causing injury or death to persons, or damage to other property in a moderate earthquake, notices were served under s124. The notices set out requirements to prevent people from approaching the building’s nearer than is safe, and timeframes for strengthening/demolition of the buildings.


As the Council had no policy to prevent people from approaching buildings that are just designated as earthquake prone, the Council’s action was not consistent with its policy. The Council has a policy to prevent people using dangerous buildings but the buildings were not designated as dangerous.

The Council has designated other buildings as earthquake prone. The footpaths adjacent to these buildings have not been fenced off.  It is not clear  what is so special about the risk that the Opera House and Municipal buildings pose to pedestians.

Risk Assessments

3.3.1  There have been calls for Council to undertake some form of formal risk assessment, essentially weighing the risks and consequences of an earthquake happening against the likelihood of people being in the theatre at the time.

3.3.2  Council officers reject this approach. Staff would formally advise Council against such an approach in the strongest terms should Council be of a mind to consider it.

3.3.3 Risk Assessments of the nature proposed can be of use in some circumstances. However, in the view of staff such an approach would be unwise here. Regardless of how small the numerical probability of a fatal event occurring might be, Council now knows both the failure mode for the building, and the fact that this could cause serious harm and/or death to persons inside the building or in the streets adjacent. Council and individual Councillors would have significant difficulty in explaining their decision making should a fatal event occur. Liability could well ensue.


As noted above the Council is required in law to make an assessment of the likelihood that the buildings will collapse in a moderate earthquake. That is a risk assessment for this event.

A broader risk assessment would consider the probability that lives would be lost over the range of possible events. The argument that regardless of how small the risk, the risk is not relevant because Council now knows the failure mode of the building simply doesn’t follow. Most engineering assessment will identify the weaker structural elements of a building that are more likely to precipitate a building collapse, in the rare event that a sufficiently severe event occurs to cause a collapse.  This doesn’t mean that the probability of the earthquake events and the likelihood of collapse should be ignored and that there should be no risk assessment.

Even if the buildings are strengthened there can no guarantee that they will survive an extreme earthquake so the problem of explaining why more wasn’t done (say base isolation) can still arise.

It is not stated here how the liability could ‘well ensue’. Presumably the reference is to liability under the Workplace health and safety legislation, which is covered below.

3.3.4  It is also necessary for Councillors to consider its duties under health and safety regulations. The concept of whether an event is Foreseeable is one of the considerations entities such as WorkSafe consider. In the case of the Theatre and Municipal buildings of the HBOH complex Council as a number of reports from various engineers that confirm that in a design event that death or injury is likely to occur to people.


Worksafe New Zealand have explicitly stated in a public position statement dated December 2013 that: “We will not take health and safety enforcement action against you in relation to the structural integrity of your building to withstand an earthquake because this is covered by the Building Act and any enforcement action will come from your local Council. If a building is earthquake prone we consider this to be a Building Act issue.”

Even if a building has been designated as earthquake prone the owner or employer will not be subject to prosecution  should there be  death or injury in an earthquake.  The Council should have been advised by their lawyers of this position statement.

3.3.5  In any event the Building Act notice would make it difficult for Council to overturn previous decisions.


There is nothing in the Building Act that would make it difficult for the Council to reverse a previous decision.