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North side of Whistler Mountain slips after heavy rains



Other areas of greater concern during storm

An area prone to small landslides on Whistler Mountain has slipped another half metre towards Fitzsimmons Creek after the recent heavy rains.

The municipality is not alarmed by the movement.

"(It) doesn’t surprise me at all," said Brian Barnett, general manager of public works and engineering at the municipality.

"I would have been a little nervous if it had moved several metres like it did years ago but (half a metre) would be what we’d expect."

The small chunk of sensitive Crown land, lying 2.5 kilometres upstream from the village, has been slipping down towards the creek for years. It raised serious concerns for Whistler when a heavy rainstorm in 1991 caused the land to drop more than three metres at once.

An independent geological engineer who has studied the area extensively was concerned when he heard about the latest movement.

"That is not good. As a matter of fact, that’s bad news," said Frank Baumann, an engineer based in Squamish.

Even small slips in the land could cause damage in Whistler he said particularly in the area near the day skiers’ parking lots and the bus loop.

"It doesn’t matter whether it’s slowly moving," he said.

"Any movement of a major failure like that is cause for major alarm."

Studies point to the area moving in small increments, about 100 millimetres a year, at a time. A major movement like the 3.3 metre drop in 1991 is likely to occur only once every 100 years.

"All the engineering studies we’ve done to date show it’s really quite stable," said Barnett.

"It’s not so sensitive that it’s considered to be a significant threat or hazard."

Ledcor, the power company proposing to build a small hydroelectric power project on Fitzsimmons Creek, has done its own independent studies, with Baumann’s help, about the risk of putting a small run-of-river project in the area.

Project Development Manager Derek Hutchinson said the company is taking into account a worst-case scenario where a big portion of the land would slide, forming a dam in the creek, with the water then filling behind the dam and eventually bursting.

"That has always been the risk," said Hutchinson.

"By doing some field measurements we’ve figured that in the absolute worst case we could get a 17 metre high dam and that could store 70,000 cubic metres of water.

"What is the real challenge in this is you’ve got this dam but you don’t know how quickly it will fail... but making certain prudent estimates we think that we would get a flood wave on the order of 750 to 1,000 cubic metres per second."