Sliding slope near The Home Depot a lesson in unstable earth

Thompson Rivers University geology professors take KTW on a tour of a section of Kenna Cartwright Park, with its geological characteristics like cracks in the earth and heaving paths. And, were you aware that, 55-million years ago, an active volcano sat where the park is today?

CLICK ON THE ARROWS AT THE SIDES OF THE PHOTO TO SEE MORE IMAGES

The slope to the west of the Hillside Drive location of The Home Depot will keep moving for the foreseeable future, according to a Thompson Rivers University geology professor who has for years used the area as a field-trip aide to show students what unstable ground looks like.

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Last week, the big-box hardware store was forced to evacuate and close for days after ground instability led to movement in a support column on the southwest corner of the building.

Now back up and running, the affected section of the store remains closed and support jacks have been installed beneath the impacted columns and beams.

Sliding slope near The Home Depot a lesson in unstable earth, _3
Geology faculty lecturer Dr. Steve Van Wagoner shows where half the service road in Kenna Cartwright Park slipped downward. - Allen Douglas/KTW

“In nature, naturally, hills want to be eroded,” TRU geology professor Dr. Nancy Van Wagoner told KTW.

“So, you take things from high spots and move them to low spots. That’s what is happening.”

Van Wagoner said the slope on the eastern edge of Kenna Cartwright Park was altered when The Home Depot store was built more than 15 years ago.

The outlet opened in June 2003.

A retaining wall on the western edge of the store’s parking lot was constructed to hold back the hill, but Van Wagoner said an underground fault has created problems that are evident along nearby trails in Kenna Cartwright Park.

“When you undercut the slope, you really need to do something to retain it,” she said.

Van Wagoner and her husband, Steve, who also teaches geology at TRU, have been taking students to the slope west of The Home Depot for years, pointing out geological characteristics like cracks in the earth and heaving paths — prominent features they say change on a regular basis.

Kenna slope Home Depot
Dr. Nancy Van Wagoner walks along the ridge created by the shifting hillside. - Allen Douglas/KTW

On May 12, The Home Depot’s Kamloops store was evacuated and closed. Hand-written signs posted on a barricade erected at the parking lot entrance said the cause was unstable ground.

“We have engaged structural engineers and teams to ascertain the current situation,” one sign read.

“Due to structural concerns as a result of ground movement near our store, we are temporarily closing for the near future for the health and safety of our associates and customers,” read the other.

The store reopened on May 16, but the southwest contractors’ entrance remains closed, as does the tool rental section, located near those doors.

An employee of The Home Depot, who was not authorized to speak on the record, told KTW the plan is to shutter the store for an extended period to address the issues in a fulsome manner. The worker said scheduling that work is being complicated by the ongoing COVID-19 pandemic.

Steps to ensure the safety of The Home Depot have been taken for years in Kenna Cartwright Park, but the problem is not going away.

Kenna slope Home Depot
Dr. Steve Wagoner shows how the soil becomes unstable and unable to hold weight as it gets wet. - Allen Douglas/KTW

The issue is most problematic each spring, when snowmelt and rain make the ground wet.

Van Wagoner compared it to building a sand castle. A little bit of water will help the material stay together, but too much can be catastrophic — sloppy sand will flatten out.

The problem slope adjacent to The Home Depot is glacial till, Van Wagoner said — “poorly consolidated” material left behind by prehistoric glaciers.

Fifty-five million years ago, an active volcano sat where Kenna Cartwright Park is today, Van Wagoner said, describing it as more active than eruptions in present-day Hawaii.

The glacial till rests up against the volcanic material. When it gets wet, Van Wagoner said, a fault forces material down and toward the store within the slope, buckling up underneath The Home Depot’s parking lot and, potentially, the building itself.

West of The Home Depot, red metal pipes stick out of the ground in Kenna Cartwright Park. They are used by engineers to measure the slope’s water level. On the retaining wall in the store’s parking lot, white plastic piping collects water through perforated lines drilled into the hill. It is all an expensive effort to keep the slope where it is.

The problem is not an uncommon one in Kamloops, but Van Wagoner said it usually happens in residential neighbourhoods where slopes are prevalent — Juniper Ridge, Aberdeen and Batchelor Heights, among others.

“Landslides are a major issue for us here,” she said. “It depends on the rainfall, it depends on a lot of things that are going on, but these things can change.”

According to Van Wagoner, Mother Nature is trying to claw back the slope that was altered when The Home Depot was built in 2003. But, she said, she’s confident engineers will be able to figure it out and keep the building safe for the time being.

“I’m sure the engineers are looking carefully to remediate the situation,” Van Wagoner said.

“But, if people were to go away, eventually that retaining wall would go away and this glacial till would slide and go back to what we call an angle of repose — a very stable slope.”

© Kamloops This Week

 


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