August 18, 2008

MINISTRY OF TRANSPORTATION

The rockslide that closed the Sea-to-Sky Highway between Whistler and Vancouver could happen again if the government doesn’t act, says a geotechnical engineer.

Engineering consultant raises concerns over Porteau Bluff

RICHARD GILBERT

staff writer

Additional rockslides are possible on the Sea-to-Sky Highway and more work needs to be done to reduce the risk of future incidents, says an international engineering consultant.

“They (Ministry of Transportation) need to do a modern reassessment of the whole of Porteau Bluff using current design standards for dealing with an unstable rock formation, which includes taking earthquake loading into account,” said Frank Baumann, a geotechnical engineer from Squamish.

“This has been talked about for years. It is sad that we have to wait for something to happen before the discussion starts.”

B.C. premier Gordon Campbell addressed the issue at a recent press conference in Beijing about the upcoming 2010 Olympic games.

He described the slide as a 200-year event and said there will be adequate contingencies in place for any problems that could arise.

In sharp contrast, Baumann inspected the site of the slide from a boat in Howe Sound on Aug. 2, same day the Sea-to-Sky Highway reopened.

He is convinced more work is needed immediately to avoid a repeat of last month’s slide.

The Ministry of Transportation disagrees with Baumann’s view.

“The immediate work that needed to be done was completed,” said Jeff Knight, a spokesperson with the ministry.

“Future inspection will determine if bolting and meshing will be necessary in the longer term. Enhanced inspection will take place next year. ”

The Sea to Sky Highway has been undergoing extensive widening and upgrading at a cost of more than $600 million in preparation for the 2010 Winter Olympics in Vancouver and Whistler.

However, the Ministry of Highways did not include this section of highway in the project.

“The bluff wasn’t part of the upgrade because the ministry felt there was enough room to add a third lane by paving the railway line,” he said.

“To do any more work beyond the extra lane could be extremely expensive. That is why this location wasn’t chosen for work in the $600 million Sea-to-Sky Highway improvement project.”

Knight said the ministry analyzed the entire highway and determined other areas had a higher priority.

Baumann disagrees with the assessment.

He argued that the recent blasting and removal of the most unstable rock did not eliminate the risk of other slabs falling.

“There are a bunch of big tilted slabs of rock hanging above the highway,” said Baumann.

“These joints dip, like a stack of books one on top of the other, tilted toward the highway.”

According to Baumann, the threat of rockslides at Porteau Bluff has been known for a while and is studied by engineering students as a textbook example of rockslide geology.

“I have led many field trips with engineers through there,” he said.

“This is a must stop for a geohazard field trip. It goes back to 1955 when Great Pacific Eastern Railway went through. They were the first to expose the slope or undermine those big slabs.”

He said that the highway includes several serious problems with the existing bolting design, including: the bolts weren’t drilled deep enough, not enough bolts were put in place, the bolts were not grouted to prevent rust and the original design did not account properly for earthquakes.

“It is now known that a magnitude 9 earthquake could happen here, but at the time it was believed to be 7,” he said.

“There is a much greater hazard from earthquakes and bolting does not take earthquake loading into account. If this portion of road shakes, a big slab could come down.”

Baumann argued that a slide could lead to a substantial loss of life if it occurred during a period of peak traffic.

He recommended that the overhanging slabs at Porteau Bluff be addressed immediately, while the province upgrades the rest of the highway.

Baumann also said that the government wasn’t prepared for the massive landslide, which closed the highway on July 29.

“Nothing happened until a private helijet and water taxis got transportation going” he said.

“The government built an emergency ferry terminal in Porteau Cove, but it should have been placed further north. They took a chance putting it on the wrong side of one of the most unstable areas in Howe Sound.”

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