Crews drilling holes in the bank of White Rock’s hump this week shouldn’t be cause for undue alarm, according to city engineering and municipal operations director Rob Thompson.
The installation of sensor monitors, being done by Levelton Consultants Ltd., is more a case of the city doing “due diligence,” he said.
“It’s an assessment of the stability of the slope along the hump,” he said. “I’m expecting a report from the consultants in a couple of months.”
But Thompson said that while the latest study is an attempt to be “proactive” about the slope, he acknowledges that a worst-case scenario might have a serious impact on the city.
He noted the retaining-wall system along the water side of Marine Drive is “quite old.”
“A geotechnical survey of the slope in the summer of last year showed evidence of slight movement,” Thompson said, noting that while this was not cause for alarm, it was enough to flag the slope for further examination.
The geotechnical work was done when three trees that the city deemed unstable were removed along the top of the retaining wall. If those trees had fallen, Thompson said, they might, depending on soil conditions, have taken much of the bank with them – which could have led to a “catastrophic failure.”
He pointed out the city has “great investment in resources” in the area, which includes the road, storm drains and sanitary sewer system.
“That carries all the sanitary flow from the east side of the city. If that was put out of commission, the result would be unimaginable.”
Potential risk to the BNSF line at the foot of the slope has also ensured full railway co-operation with the current study, he said.
Thompson said the report from the consultants will help determine whether additional “containment systems” are needed for the slope.
Thompson said he recognizes that slope vegetation continues to be an emotional issue among residents embroiled in an ongoing debate over preserving vegetation versus preserving views, he said he has to approach it from a “wholly safety, risk-management perspective.”
“We need to have a sustainable vegetation management plan along the slope,” he said.