Watch progress on the Town Hall restoration.

It is a year since Christchurch City Council approved the $127.5 million repair and restoration of the Town Hall – a project that is expected to take three years to complete.

The main contractors, Hawkins, have spent most of that time working to strengthen the building’s foundations so the building is protected from future earthquakes.

They have installed about 1100 jet-grout concrete columns – each between six and eight metres metres long – into the ground beneath the Town Hall to create an earthquake-resistant underground wall of columns that will be protect the building from any soil movement.

It has been a logistically challenging task and has taken about 30,000 cubic metres of concrete but with the last of the jet grout columns in the ground, they are now ready to move onto the next stage of the project.

“Over the next 12 months they’ll be removing all the old concrete slabs and re-laying new concrete slabs, each of which will be about 900 millimetres thick,’’ said Patrick Cantillon, who is project managing the restoration of the Town Hall for the Council.

“They’ll also be re-levelling the Limes Room. To do that they will prop the building in the air with scaffolding, then snap and remove the 12 columns that currently hold it up so they can re-level it. Once it is level they will add in some diagonal bracing and build new columns to support it.’’

Hawkins South Island Regional Manager Steve Taw said the restoration of the Town Hall was a "technically challenging’’ project but they were proud to be helping rebuild the city's infrastructure.

“In heritage projects such as these there  will always be  challenges but we’re pleased with the progress to date and we’re right on track,’’ Mr Taw said.

Between 60 and 70 people from 10 different nationalities were currently working on the site but that number would grow to about 300 as they started to piece the building back together.

Christchurch Mayor Lianne Dalziel, who recently visited the site, said the amount of work going on was unbelievable.

“I’ve been watching it from the outside but it is even more unbelievable from the inside,’’ said Mayor Dalziel.

The completion of the project, scheduled for mid-2018, would be a huge milestone for the city and a cause for celebration.

“People have so many memories of coming to the Town Hall for graduation ceremonies, concerts and all sorts of different events. This really is the living room of our city and it is something we have truly missed,’’ Mayor Dalziel said.

Council City Services General Manager David Adamson said the heritage values of the Town Hall were being preserved as part of the restoration project but opportunities were also being taken to make improvements to some aspects of the building.

The James Hay Theatre and auditorium, for example, were being modernised to ensure they provided world-class performance spaces that could be enjoyed for many years to come, while the restaurant and function room were going to be built back better to fix problems with the original spaces.

“We’re 12 months into the project now and we’re still on budget and on time so we’re really pleased with that,’’ Mr Adamson said.