The costs for seismic and other upgrades at Duncan’s historic City Hall is estimated to be more than $10 million.
A staff report that was on the agenda at the council meeting on April 19 summarized a document on the issue that was prepared for the city by Tectonica Management Inc., at a cost of $65,000.
The report stated that there is a large variability of soils in the area that result in the risk of liquefaction, which can lead to a higher seismic load on buildings in the event of an earthquake.
As a result, the preferred option for making City Hall more seismically secure is called the base-isolation method, which would see the building separated from its foundations and non-linear bearings used to allow the foundation and building to move at different rates as the earth below City Hall moves during an earthquake.
“Not all buildings are suitable for base isolation,” said Rachel Hastings, Duncan’s manager of building and bylaw services, in the report.
“However, the level of intrusion caused by a conventional seismic retrofit and the required preservation of City Hall as a heritage asset is of sufficient historical significance to justify the comparative cost increase of installing a base-isolation system.”
Hastings said the costs of a conventional seismic retrofit at City Hall, which was constructed in 1913, would be approximately $4 million, while a base-isolation upgrade would cost about $4.95 million.
But she said it’s important to note that a conventional retrofit does not protect City Hall from a heritage perspective.
“It provides seismic safety for the occupants so the building does not collapse, but the building will not be usable after a code-level earthquake,” Hastings said.
“Whereas, with a base-isolation retrofit, the building can be used after a code-level earthquake, justifying the additional costs. This pricing represents the approximate cost to complete the seismic upgrade works and generally repair disturbed finishes to their original state. They do not capture any costs associated with other upgrades and improvements [in the building].”
Hastings said the total project cost for the proposed upgrades at City Hall is currently more than $10 million, which would also include a new roof, plumbing, HVAC, electrical and sprinkler systems in the building.
She said the costs of the construction of a new building on a different site would be between $7.2 million and $8 million, so the cost to upgrade and protect the existing City Hall is approximately $2.5 million relative to a new building on a new site.
“This construction premium of $2.5 million is essentially the cost to preserve arguably the most iconic building in Duncan and perhaps the Cowichan Valley,” Hastings said.
“With that said, the city does not currently have [more than] $7 million in funds to replace City Hall, and staff believe that there is a far greater likelihood of grant monies to fund the preservation of a heritage building than to fund a new City Hall on land that city does not as of yet own.”
Hasting said the next step is for the city to seek grant opportunities for the full seismic upgrade construction project at City Hall.
“At this time, construction will not proceed until grant monies have been secured, and council resolves to move ahead with the project,” she said.