Chateau Tongariro seismic report: Risk ‘very high’, Crown will need to fund strengthening or demolish, experts say

The Chateau Tongariro was closed in February. Photo / Supplied

The Chateau Tongariro has very risky and serious vulnerability to earthquakes, a Detailed Seismic Assessment of the building has found - and the scale and likely cost of remediation means there is a very considerable likelihood the Crown will need to foot the bill if eventual demolition is to be avoided.

Professionals in building engineering and architecture approached by the Herald agreed an injection of tens of millions of dollars of public money into the historic hotel is likely to be required at a minimum.

It is possible an alternative non-government operator will lease the building and share the cost of remediation with the Crown, or foot the bill itself.

The hotel is situated on Crown land in Tongariro National Park on the lower reaches of Mount Ruapehu, an active volcano, and just under 10 kilometres from the crater lake at its summit. The Chateau was built in 1929 in the style of the grand Canadian railway hotels, though in recent years parts of its interior have become quite shabby. It is considered an important draw for tourists to the region.

The Department of Conservation (DoC) declined to answer questions about the seismic report, the cost of remediation and the site’s hefty ongoing maintenance costs, outside the lengthy Official Information Act (OIA) process.

On March 9, DoC took over responsibility for the Chateau from Malaysia-based hotelier KAH NZ, following protracted and failed negotiations to renew the company’s long-term lease on the site and buildings.

KAH closed the iconic hotel in February and announced it would surrender the lease (which from 2020 was renewed month-to-month).

The company blamed the business closure on the seismic strengthening work the building needs and business uncertainty resulting from the financial troubles of local skifields, Whakapapa and Tūroa. It was also dogged by staffing difficulties and was issued three improvement notices by WorkSafe last year.

The Detailed Seismic Assessment (DSA), conducted for KAH by engineers WSP, found the Chateau meets just 15 per cent of new building standards (NBS) and it has received an “E” grade, representing a “very high risk” to occupants in the event of an earthquake. The rating is derived from the weakest elements of the building.

The report says the poor building rating is “dominated by failure of the unreinforced masonry infill and cladding elements, the governing mechanism is a soft storey failure at the ground floor due to a change in architectural plan from the storeys above.”

E is the worst life-safety performance rating on New Zealand’s grading system for earthquake risk to people. E grade buildings represent a risk to occupants more than 25 times higher than that expected in a new building.

The report was released under the OIA by Heritage NZ. The Crown entity lists the Chateau as a Category 1 Historic Place. As such, any strengthening and renovation work would need to minimise the effect on the building’s heritage value.

There is no immediate requirement to strengthen the building under New Zealand legislation; however, the cost to the Crown of maintaining the empty hotel appears to be significant.

It was estimated at $680,000 for under four months (March 9 to June 30, 2023) in a March email to DoC chief executive Penny Nelson (sent by DoC’s deputy director general national operations and regulatory services).

The correspondence was released to the Herald under the OIA. A DoC spokesperson declined to answer follow-up questions about the ongoing maintenance costs outside the OIA.

Eyeballing the cost

The WSP report recommends two options for remediation of the main Chateau building, but it does not estimate costs.

Lloyd Macomber, architect and director of Salmond Reed Architects, has wide experience in heritage building consulting and estimated the cost would run to tens of millions of dollars. He said seismic strengthening work would almost undoubtedly need to be coupled with other work to bring the building up to the standard of a modern amenity, and he would not rule out a cost above $100 million.

“We don’t even have a specific engineering design. We’d need months of back and forth with structural engineers, heritage consultants, heritage architects, Heritage New Zealand, an awful lot of time and money, just to get to a point where you can get a view of cost,” he said.

DoC, Heritage NZ, Land Information New Zealand and the Ministry of Business, Innovation and Employment, are all part of a government steering committee working to decide the Chateau’s future, documents released to the Herald suggest.

WSP recommends two strengthening options: the centrepiece of one is a system of base isolation, centred on the basement and below basement level of the Chateau; the lynchpin of the other is a reinforced concrete shear wall system to transfer loads to the foundations.

The Chateau Tongariro at Tongariro National Park.

The report notes that the building’s heritage status will also need to be considered and addressed.

Jason Ingham, a professor of structural engineering and head of department at the Department of Civil and Environmental Engineering at the University of Auckland, said the Chateau is undoubtedly a big project and while he was loath to put a cost to an upgrade, he agreed that it could top $100m.

Several building professionals said the Christchurch Cathedral rebuild may provide an indicative order of magnitude, though they cautioned that it is very early days in understanding costs for the Chateau.

In 2016, the estimated cost for the cathedral work was $104m; that estimate has now risen to $154m and completion is not expected until 2027.

Ingham said that in his personal opinion, the Chateau is such a special building, with such a particular role in the national fabric and identity, that the Government will need to bring it back to full use and capacity.

In the absence of firm cost estimates and in light of the October election, the decision is likely to fall to the next Government.

Lease without strengthening

Ingham noted it is technically possible to lease a E grade building without remediation, but he’s not sure he’s seen it done and it would be unlikely for the Crown to pursue such an option.

In October 2022 the Ruapehu District Council slapped the Chateau with an earthquake-prone building warning notice, displayed to hotel users, following a three-year process to ascertain the building’s seismic risk, required under the Building (Earthquake-prone Buildings) Amendment Act 2016.

The council advised KAH that under the legislation it then had 25 years from the date of the notice in which to undertake the strengthening, and because of the building’s heritage status, the owner could apply for an extension of up to 10 years (a maximum of 35 years in which to complete the necessary strengthening work).

At a minimum the legislation requires the building be brought to a standard of 34 per cent NBS (the WSP report recommends it is lifted to 67 per cent).

There is no legal requirement to strengthen a building above the threshold of 34 per cent NBS

DoC statement

In an emailed statement accompanying the release of documents to the Herald earlier this month, DoC’s director, operations support, Karl Beckert, said the department still has “a number of residual matters to be concluded” with KAH around the terms of the lease.

He said that once the transition is complete, the department will turn its focus to considering the various options for the Chateau Tongariro Hotel’s future.

He confirmed receipt of inquiries of interest in the Chateau. “Once we have determined what the long-term future for the property could be, we will be in a better position to respond to any suggestions or proposals for its use,” he said.