Significant Town Hall foundation work begins

Christchurch City Council has reached its first major milestone in the Town Hall restoration with the beginning of foundation work that will significantly strengthen the building.

A technique known as jet grouting has begun on the site, which will see more than 1000 large concrete piles injected eight metres into the ground. Three jet grout machines have been specifically imported from Germany to carry out the work.

A total of 27,000 cubic metres of jet grout concrete – which would fill 270 average family swimming pools, 37,500 bath tubs or 200 buses – will be used during the process. A thick concrete slab will be laid over the concrete columns once the jet grout work is complete, which will help to bring the Town Hall up to 100 per cent of New Building Standard. The work is expected to be completed in June next year.

During the February 2011 earthquake, the land beneath and around the Town Hall was severely damaged. Although the building itself fared relatively well, significant strengthening of its foundations is needed. Jet grouting has been identified as the most effective repair solution to address the land issues underneath the Town Hall.

The Council appointed Hawkins in June 2015 to undertake the restoration work. For the past five months, Hawkins has been preparing the site in preparation for this first significant repair work to begin.

Council Unit Manager Anchor Projects Liam Nolan says the restoration work will ensure the Town Hall can continue to be enjoyed by Christchurch residents for the next 50 years and beyond.

"The Town Hall is one of the city's most treasured Civic and heritage buildings and this restoration work will ensure it is better and stronger than it was pre-earthquake. Starting on the Town Hall foundations marks the culmination of four years of work. This has included engineering assessments, going through a tender process and appointing a contractor to undertake the restoration work.

"By the time we've finished work on foundations, the ground underneath the building will be significantly stabilised, ensuring we can get on with the rest of the work needed to restore this building to a world-class facility that can be used for many years to come."

Hawkins Project Manager Paul Youngman says, "Hawkins is using the innovative jet-grouting method for the foundations. Grout and water is injected into the ground at high velocity to create columns of soilcrete, which is soil cemented with grout. The columns will overlap and interlock to create an earthquake-resistant underground wall of columns that will protect the building from soil movements.”

A total of $127.5 million has been budgeted for the Town Hall restoration, which will be completed in 2018. The restoration work also includes a significant upgrade and refurbishment of the facility.

ENDS

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