Hadgraft Wilson Place is visible on the right side of the photo, next to the UBCO construction site.

(JESSE TOMAS / iNFOnews.ca)

The recent controversy surrounding the damage caused by UBC Okanagan’s attempt to build a deep underground parking garage could discourage developers from attempting similar projects that would enable more development in downtown Kelowna.

UBCO is building a tower in downtown Kelowna and its initial plan was to build a four-storey underground parking garage. Settlement issues created by the garage’s excavation caused significant damage to surrounding buildings.

One of the buildings that was damaged was Hadgraft Wilson Place, a subsidized housing building for people with fixed income and disabilities. The building was evacuated at the start of April and tenants have filed two class action lawsuits against the university and the city.

The university has restarted construction but modified its plan with a shallower parking garage.

UBCO civil engineering professor Dwayne Tannant said engineers and developers have wanted to build large underground parking garages in Kelowna for years and the university's failure in this case could set back those ambitions.

“Unfortunately, the first test was not a success story, and it's going to set back this concept for a decade,” Tannant said. 

READ MORE: City of Kelowna, UBCO sued over downtown building debacle

Downtown Kelowna’s proximity to Okanagan Lake means the soil composition is soft, making it expensive and time consuming to build large structures. As the city’s population grows and the skyline grows taller, parking is becoming a bigger problem.

The problems caused by UBCO’s attempt at an ambitious underground parking garage could significantly slow down development since the alternative to underground parking is above ground parking garages that would take up valuable real estate.

“In the UBC building they're having issues with their big anchors that are tying back the walls, and I'm not entirely sure what the cause is there,” Tannant said.

“That's going to chase away, or make everybody else... afraid of going underground for parking. Then it forces parking to be only one or two floors below ground, or maybe above ground,” he said. “Who wants to have parking lots on the ground floor taking away opportunities to have restaurants and art galleries?”

In the early days of Kelowna’s geological formation Mill Creek, Mission Creek and Brant Creek flowed into Okanagan Lake and carried fine sands and silts along the way, he said. Kelowna is built on fine sands and silts which is a primary reason for the lack of underground garages and the problems with skyscraper construction.

Tannant said there are clearly ways to build skyscrapers and even underground parking on soft soil like Kelowna’s, the problem is the methods can be expensive and time consuming.

Long steel piles, gravel columns and stone columns are methods for making tall, heavy structures secure on soft soil, another technique for working around ground settling problems is pre-consolidation.

READ MORE: UBCO not releasing engineering reports for downtown excavation that caused evacuation

Pre-consolidation is when a big pile of soil is put on the development site so the ground can compact over time and prevent future settling issues from occurring because the settling happens before construction even starts. The problem with pre-consolidation is it can take years for the soil to settle.

"Where the big towers at One Water Street are located, for probably a decade, there was a massive pile of soil sitting there," he said. 

A pitfall for construction projects in Kelowna is the diversity in the soil, and how difficult it is to accurately measure the soil quality. Each construction project has a geotechnical survey where an expert takes samples from the soil to determine things like how much weight it can hold.

Kelowna’s soil composition varies so much that it is difficult to measure the quality of a large site.

“You try to take a representative number of boreholes or geophysical sampling to try to understand the distribution of the soils that are going to be below your footing, but you might miss something,” he said.

Tannant said there are solutions for building on soft soil which are utilized in other parts of the world with similar soil types, but they typically require a lot of money or time.

“Shanghai, for example, has some massive tall buildings there on soils that are probably quite similar to what we have here in downtown Kelowna, but they're spending a tremendous amount of money for sinking really, really long piles,” he said.

READ MORE: Is 2024 the year Okanagan Lake floating bridge becomes a suspension bridge?

He said the floating bridge between West Kelowna and Kelowna is an example of how engineers have come up with creative solutions to construction challenges in the city.

“There’s a floating portion but both ends are supported on piles in relatively weak soils,” he said.

Tannant said while there are conflicts between the challenges presented by the ground in Kelowna and the economics of construction in the city, there will come a point in the future when it makes sense for developers to sink the money to prevent the projects from sinking.

“It's an economic limit rather than a technical limit,” he said. “As the land becomes more and more valuable as we run out of places to live, then they'll switch over to making use of these sites and justifying the higher cost of putting the foundations in because everything above the ground is going to be worth more per square meter.”

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