Alaska's Keystone Canyon

Highway access to the city at the end of the trans-Alaska pipeline has been cut off indefinitely by avalanches, including one that dammed a river and created a lake up to a half-mile long across the roadway in a 300-foot wide mountain canyon.

State Department of Transportation officials said Monday that the snow slide about 12 miles outside Valdez on the Richardson Highway cannot be cleared until water behind the snow drains. The water in Keystone Canyon is too deep on the upstream side for crews to approach the snow dam. Officials fear that digging from the downstream side could trigger a dangerous surge of water and harm work crews. (AP)

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