Canterbury Museum Awards Contract For Its New Base-Isolated Basement And Building

Cantabrians will see their new Museum rising out of the ground from next year.

The Museum has awarded the contract to build the new base-isolated basement and 5-level building to Leighs Construction. This will include a large floor to ceiling atrium, a new home for the 26-metre long blue whale skeleton.

Tenders for the construction contract were all well above the Museum’s anticipated budget. The projected cost of the new Museum has also increased due to an extra $3.8 million to remove asbestos from the Robert McDougall Gallery and another $5 million due to unexpected ground conditions which has slowed progress beneath the Gallery (see note).

In response to the tenders, the Museum has identified further cost savings of about $11 million.

The projected total cost of the redeveloped Museum is now $247 million, up 20.5% from $205 million in 2022. The Museum is scheduled to reopen 6 months later than previously planned, in mid-2029.

The Museum’s funding shortfall has increased from $44.6 million to $86.6 million due to the higher costs.

Museum Board Chair David Ayers says the Museum has enough committed funding secured to complete a weathertight and insurable building and base-isolated basement, and to install any plant that is integral to the building construction phase. This stage was made affordable by moving elements of the building fit out and installation of the remaining building services to the next stage of the project.

“We’re really disappointed with the increase given our strict cost control to date. But we’re not alone in facing escalating construction costs. It wasn’t unexpected against the inflationary backdrop of recent years,” David Ayers says.

“The new Museum is being developed in discrete stages to ensure that we’re not committing to any work that we can’t afford. This careful and responsible approach means we have time to raise the remaining funds. In the meantime, we need to keep building to maintain the buying power of the funds we already have.

“But if we need to pause the project in 3 years, the building structure and base-isolated basement will be complete and ready for fit-out.”

Museum Tumuaki/Director Anthony Wright says the Museum is actively working on its fundraising plan. “We’re still confident that we can raise the extra money to fit out the building and the exhibition spaces.”

“We’re really looking forward to reopening the Museum for Cantabrians. It will be a must-see attraction for visitors from across Aotearoa New Zealand and the globe, with world-class facilities to care for the treasures in the Museum collection of more than 2.3 million objects.

“Meanwhile, we’re continuing to welcome local and international visitors to our three central city attractions – Ravenscar House Museum, Quake City and the pop-up Museum at 66 Gloucester Street. Watch out for Wharenui Harikoa, the new exhibition at the Museum pop-up opening in December.

“We’re fully engaged in designing and building 6,500 sq metres of new exhibits, completing our inventory project and maintaining a strong focus on fundraising to complete the project.”

The first two stages of the project, demolishing the twentieth century buildings and the above ground strengthening of the Robert McDougall Gallery, have been completed. A Leighs March Construction Joint Venture is currently installing the 12-metre-deep outer wall for the base-isolated basement under the Gallery and new building. The ground floor of the Robert McDougall Gallery is also being strengthened and supported to prepare for the excavation of the base-isolated basement. This work is scheduled to be finished in May 2025.

A series of major infrastructure projects in Te Waipounamu/South Island have all experienced reported cost increases. Christchurch's new metro sports facility Parakiore, the ChristChurch Cathedral restoration and the new Court Theatre have all seen budgets rise by over 50%. Te Una Museum of Southland recently announced a 17% cost rise for a new building for which detailed design is yet to start.

Background

2020: Museum consults and seeks feedback on its proposal to redevelop the Museum. Budget $195 million.

2022 Developed design phase, costs higher than expected. Significant cuts to project scope including base isolation and basement storage under the heritage Mountfort buildings and a walkway across the atrium. Budget increase held to 5% at $205 million.

Decision made to proceed with redevelopment after consultation with Museum’s local authority funders.

September 2022 to April 2023, the Museum closes to the public, staff and the collection move out of Rolleston Avenue to temporary storage and office space in Hornby.

2023: July: Museum opens pop up at 66 Gloucester Street.

2024: Museum staff focus turns to developing the visitor experience for the new Museum which includes more than 60 new exhibitions and displays. Major inventory of the collection continues identifying, cataloguing and uploading objects to Collections Online.

The Build

The Museum is actively managing the project by only letting contracts for which it has committed funds in hand, currently $160.4 million. To manage that, the Museum is being redeveloped in six discrete stages:

1. Above ground strengthening of the Robert McDougall Gallery, funded by building owners Christchurch City Council (Cook Brothers, completed in 2023).
2. Stripping and demolition of the twentieth century buildings (Ceres, completed May to December 2023).
3. Strengthening the ground floor of the Robert McDougall Gallery so that the building can be separated from its basement and supported by micro piles.

Creating the 12-metre-deep outer basement wall round the new building and the Gallery. (Leighs March Joint Venture, started February 2024, underway, due for competition mid-2025).

Work on the underground level of the new Museum is funded by the Museum’s local authority funders (Christchurch City and Hurunui, Selwyn and Waimakariri District Councils), plus central government contributions from the Greater Christchurch Regeneration contingency funding and Regional Culture and Heritage Fund of the Ministry for Culture and Heritage, and a grant from the Lottery Grants Board.

4. Construction of base-isolated basement and new 5-level above ground building, installation of essential plant. (Leighs Construction, start 2025).

5. Building services and fit out including partitions, finishes, joinery etc. (Completed end 2028).

6. Installation of new visitor experience, move back from Hornby to new Museum (first six months of 2029).

7. Mid 2029: Cantabrians welcomed back to their Museum.

Unforseen Ground Conditions

Construction of the outer basement wall uses a highly specialised technique which involves excavating a narrow reinforced trench that is filled with a bentonite slurry, temporarily supporting the soil. The trench is then filled with a reinforced concrete creating an exterior protective wall (effectively a reverse swimming pool) around the structure which the base-isolated basement and 5-level above ground structure will be built on.

This work has been slowed down by a layer of river cobbles 10 metres down under the Robert McDougall Gallery which hadn’t been identified in geotechnical surveying (the Museum site is largely sand and gravels). Bentonite slurry was leaking into the voids between the cobbles. The contractors are now adding cement grout to the trench to fill the voids. The grout is excavated out before the bentonite slurry is pumped into the retaining wall trench. This is taking longer and will cost more to complete but is confined to a discrete part of the overall site.

The contractors encountered similar problems installing the more than 300 micro piles that will support the Gallery building while the old basement is excavated out for the new base-isolated basement.

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