To erase avalanche danger, NDOT triggers its own

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RENO, Nev. (KOLO) Most of the people who travel the Mount Rose Highway on a regular basis keep track of the road conditions, but it's unlikely they give much thought to the slopes above the roadway and the danger lurking there.

In fact, they don't have to; the Department of Transportation is keeping an eye on things.

Avalanches can and do happen at any number of spots in the Sierra, some above highways, but just below the summit on the east side, they are just about predictable.

The causes of avalanches can be complex, but it helps to picture the layers of snow laid down in succession by each storm, subjected to thaw and freeze cycles, each with its own density, even temperature.

It can add up to an unstable layer cake. Add the heavy load left by a new storm and it's an avalanche just waiting for the right trigger.

"It could be as simple as the sonic boom from a jet, a skier, a snowboarder or all of a sudden, all on its own, it could just release," says NDOT's District Engineer Thor Dyson.

Dyson and others aren't waiting for that to happen. They watch conditions closely and before it happens they schedule an avalanche of their own.

"We want to bring that snow down on our terms, safely in a controlled environment."

In fact, along this troublesome stretch of roadway, they've installed a permanent system to trigger them.

Big tubes were installed on the ridge line above the roadway, each fed by a mixture of propane and oxygen. Then--with traffic below halted, it's ignited.

The explosion carries the same impact as 30 sticks of dynamite, a shock wave through the air and ground, bringing the unstable snowpack down the slope, often covering the roadway.

From there it's just a matter of cleaning it up and opening the road to traffic.

A Sierra avalanche, purposely caused, a threat to safety neutralized.

"Safety of the motorist is our prime concern," says Dyson. "The last thing we want to do is bury a motorist or bury an NDOT operator that's working underneath that avalanche zone."