Trans-Canada reopens after B.C. mudslide

The Trans-Canada Highway east of Chilliwack, B.C., has reopened after a slide left mud and debris across the road Wednesday, forcing closure of the highway.

Two westbound lanes reopened early Thursday morning, and the eastbound lanes were reopened just after 10 a.m. PT, several hours ahead of schedule.

Police have conducted a ground search and found no buried cars, but say they won't know for sure until the slide, between Chilliwack and Hope, near the Herrling Island Road exit, has been completely cleared.

At least one driver was caught in the mudslide. The woman suffered minor injuries when her car rolled twice as tonnes of debrisroared down over four lanes of the highway and a railway line at about 10:15 a.m. PT Wednesday.

It left a mountain of mud and debris measuring 3,000 square metres and several metres deep in places.

The debris also swamped a CN Rail line, stopping a freight train, but there was no derailment and no members of the train crew were hurt.

Traffic was diverted to Highway 7 via Highway 9 through Agassiz until Thursday morning, wreaking havoc for commuters.

Common slide area

Mike Roberts, a professor emeritus of geology and earth science at Simon Fraser University, said mudslides are common in that part of the Fraser Valley.

"It is common in our mountainous region," he said. "When we have rain, as we've done in the last few weeks, [and]melting snow, the soil becomes completely saturated. The rocks are weakened because the water gets between the soil particles.

"Imaginetwo orthree cubic metres of material simply sliding from the stream bank into the stream, and that could be the start of a mud flow."

Roberts has been touring the area for several years with his students, pointing out steep cliffs loaded with debris ideal conditions for a mudslide.

Geological engineer Frank Baumann said a number of factors contributed to the slide Wednesday.

"It's very steep, it is covered with a layer of very thin soils that can't hold a lot of water, and then it gets very wet, both because of rainfall and now because of melting snow that keeps those thin soils saturated with water," he said.

"So ]it's] that combination of steepness, loose thin soils and water."

Baumann said old logging roads built before higher safety standards were implemented have been responsible for other slides in the area, but it's not clear whether these were a factor in this incident.