Claremont Access cleanup begins

This winter’s mild temperatures likely contributed to the collapse of the retaining wall along the Claremont Access, says a local geoscientist.

Wilf Ruland says that the constant temperature fluctuations over the past several months have been especially hard on infrastructure — including the retaining wall that burst and unleashed mud and debris on the roadway Wednesday.

“What repeated freeze and thaw can do is lead soils and things like road beds to break down,” Ruland said. “It could have loosened things on the cliff above the top retaining wall. One possibility is that the water coming off of that slope and cliff face, together with the freeze and thaw, just loosened things up.”

Gerry Davis, the city’s director of public works, said the downbound access lanes will remain closed until at least Friday morning. Engineers have finished investigating the portion of the retaining wall that collapsed, but were expected to continue to check on the structure of the whole wall into Friday.

Davis says the city will reopen the access as soon as possible.

“If the safety issue is addressed and we can even open one lane, we’ll do that,” he said. “We appreciate the patience of the community, understanding there is a safety issue, and we thank them for their co-operation.”

So far, the city hasn’t released any details about the cost of the damage.

Like Ruland, Davis says the weather was likely a contributing factor to the collapse. Davis said yard waste dumped over the escarpment trapped moisture against the wall, which also could have caused damage. Ruland said extra moisture could have permeated deep into the soil and gotten trapped against the wall.

In most years, the freezing ground creates a barrier against any running groundwater.

“If, for some reason, the drainage system behind the wall isn’t working properly and you have a buildup of water behind that, it becomes a dam,” Ruland said, “and the thing isn’t built to be a dam. Water is incredibly powerful and heavy.”

When the access was last inspected in November 2010, engineers recommended that minor repairs — such as removing the yard waste and replacing a damaged guide rail — be completed within five years. That wasn’t done because of scant infrastructure resources, Davis said.

The next retaining walls scheduled to be replaced are at the Sherman Cut and the Queen Street access, scheduled for 2013 and 2014. Since those walls are scheduled to be replaced, they are inspected annually.

Davis said the Claremont retaining wall was built in 1971 and so was still within its expected 40- to 50-year lifespan.

“In this case, these panels had life left in them. And they failed,” Davis said. “We did everything we could.”

ereilly@thespec.com

905-526-2452 | @EmmaatTheSpec

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Claremont Access cleanup begins