An extraordinary piece of engineering is unfolding deep underground, hidden from the world.
Beneath the Robert McDougall Gallery on the edge of Christchurch Botanic Gardens, a team of workers and engineers are preparing to put the much-loved building on stilts.
The 1930s Robert McDougall Gallery is being revamped and strengthened as part of the redevelopment of Canterbury Museum’s Rolleston Avenue site. It will link to a new building that will wrap around the Museum’s restored heritage buildings. In the Gallery we'll display artworks from the Museum collection and other cultural institutions. Curators are poring through the Museum collection, uncovering lost gems that will go on display for the first time in many decades when the Museum reopens in 2029.
The Gallery has already been strengthened above ground and the underground engineering work will bring it up to 100% of building code, making it a safe home for Canterbury’s precious taonga (treasures). But this comes with its own challenges.
In the basement, hundreds of steel tubes about the width of a lamppost have been drilled down 11 metres into the ground. These tubes have then been filled with steel reinforcement and grout. The entire weight of the gallery will soon be carefully placed on this forest of over 300 micropiles. The old basement will then be dug away and a new base-isolated one built in its place. The weight of the gallery will then be transferred from the micropiles to this new basement. This underground strengthening work is due to be completed by the end of the year.
Holmes New Zealand Technical Director Didier Pettinga says that once the old basement has been demolished it will look like the Robert McDougall Gallery is standing on stilts. Until the new basement is completed, you will be able to see under the building from one side to the other, through the micropiles.
“To get base isolation under an existing building is a big challenge. There’s been all this work happening in the basement space, but no one has been able to see it.”
The technique was pioneered in New Zealand and is a well-established way to bring heritage buildings up to modern building standards. One of the first times the technique was used in New Zealand was to install base isolation beneath Parliament House and the Parliamentary Library in Wellington. Over 400 base isolators were installed between 1992 and 1995 using the same technique being used on the Robert McDougall Gallery. It was the biggest strengthening and modernising project ever undertaken in New Zealand at the time.
“The introduction of base isolation under heritage buildings is something that New Zealand has pioneered. It’s a slow process. It’s very detailed and very complex.”
The work on the Robert McDougall Gallery is a key part of the redevelopment of Canterbury Museum. Contractors are making good progress on the project. The tired twentieth-century Museum buildings have been demolished, the outer basement wall is now complete and part of the basement has been excavated down to about 6 metres.
Once the basement is complete, Cantabrians will start to see the new 5-level above ground Museum building emerge from behind the heritage buildings on Rolleston Avenue. The Museum has the committed funds in hand to complete the storage basement and the new building so that they are weather-tight and insurable. If we had to pause construction to raise more money, that would be in 2028 when this stage of the project is completed.
A world-class new Museum, with restored heritage buildings, a revamped Robert McDougall Gallery, a dramatic new atrium and much more exhibition space, will rise on the site. Join us on this amazing journey to a new and exciting Museum.
