November 3, 2008

B.C. MINISTRY OF TRANSPORTION

The massive fissure is clearly visible above Highway 97 in the Okanagan Valley.

Highway 97 remains closed as geotechnical experts evaluate unstable rock face

RICHARD GILBERT

staff writer

Highway 97 in B.C’s Okanagan region could be closed for weeks or even months after a huge crack appeared on a slope above a highway widening project.

Geotechnical experts have been evaluating the unstable rock face above Highway 97, which is about five kilometres north of Summerland.

The highway was closed on Oct. 24 because continuing movement of the slope threatens to send the rock face crashing down on the road.

“There were concerns that the unstable rock bluff could come down on the highway,” said Jeff Knight, spokesperson for the Ministry of Transportation and Infrastructure.

The $54-million Bentley Road project involves widening seven kms of Highway 97 from two to four lanes.

The project by Arthon Contractors Inc. of Kelowna is on the main highway connecting Kelowna and Penticton through the Okanagan Valley.

The company’s website reported that the fissure opened high on the mountain and is several feet wide and perhaps 30 feet deep. An estimated 200,000 cubic metres of material have broken away from the hillside north of Summerland.

“There was 15 millimetres of movement on Oct. 27 and the day before that there was 10 mm movement,” explained Knight.

“This is why we have the closure, because the highway is unsafe. In order to reopen the highway, we need to have a couple of days of no movement.”

A lot of blasting is required for the Bentley Road project because it goes through some rough terrain. Construction work calls for the excavation of one million metres of rock and 500,000 metres of soil.

“The geotechnical investigation said the crack was there before road construction began and the blasting exposed the fault,” said Knight.

The Ministry of Transportation flew in their top geotechnical experts from Vancouver and Victoria to evaluate the seriousness of the problem.

They are monitoring the slope.

The ministry was also working on access road construction to bring heavy equipment up to the bluff.

“Today (Oct. 29) they are planning to do drilling and some localized blasting to help assess the stability of the rock mass,” said Knight. “This will provide some more information to determine the next steps.”

The chief geotechnical engineer is planning to remove material from the crest of the bluff and add material to the toe.

This will help reduce the risk of a rock slide by adding resistance and strength, as well as balancing off the weight of the slope.

Knight said that the bluff contains about 30,000 truckloads of material, which is about 20 times more material than the rockslide that recently closed the Sea to Sky Highway.

A detour adds two hours to the trip from Penticton to Kelowna.

Some media have speculated that the sheer size of the bluff, combined with its sudden appearance and movement, suggest that the highway could remain closed for a month or longer.

The fissure could also affect the construction schedule for the Bentley Road project, which was supposed to be completed in the fall of 2009.

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