Monday, March 16, 2015

A light winter helps WSDOT do some heavy lifting on the North Cascades Highway

By Tom Pearce

Skiers may be cursing the lack of snow, but when it comes to the spring reopening of the North Cascades Highway, it’s actually a good thing. We’ve been clearing a rock slide and loose rock since early December 2014 about eight miles east of the Diablo Gate, where we close the highway in the west each winter.

During a regular snowy winter we probably couldn’t have done much, if any, of this rock removal until the snow melted. That could have delayed the annual spring reopening of the popular scenic highway. Instead, we may be looking at a relatively early opening. More on that later.

We closed the Diablo Gate at milepost 134 on Nov. 24, when the snow started to pile up at Washington Pass and Rainy Pass. About two weeks later a large rock slide crashed down onto the highway near Granite Creek. Our crews cleared the initial slide, but since then it’s been a game of cat-and-mouse with the hillside.

Geologists evaluated the site after we removed the initial rock fall and found there was still a lot more loose rock up on the hillside that could potentially come down. In February we hired a contractor to remove the rest of that loose rock. However, shortly after they finished our geologists used laser measurements and found the hillside was still moving.  In late February we blasted the unstable part of slope and cleared the debris. 

New measurements revealed the slope stabilized. Now contractor crews are bolting the remaining rock to the hillside to keep it in place. We expect to finish that work in a week or so. Then we’ll be ready for the snow plows to clear the North Cascades Highway.

The initial slide covered more than 100 yards of the highway.

Our crews scouted the highway for plowing last week. This year we have 15 to 30 feet of snow on the highway around the Liberty Bell avalanche chutes near Washington Pass. Sounds like a lot, right? Not really; in past years we’ve seen 50 to 70 feet of snow in these locations. Our crews began clearing the highway from the east side on March 16 and will begin clearing from the west side on March 23. That’s about a week earlier than recent years. It will take about a month to clear the snow from the highway.

The contractor brought in “Rockzilla,” a long-armed
machine to remove loose rock from the hillside.

We caught a break with the lack of snow this year. Most years the Granite Creek area would be covered with snow, and we’d just be starting the rock slide clean-up, delaying the opening. Instead, we dealt with this site when the highway is closed anyway. Now we can focus on clearing snow. If we don’t have a significant snowstorm, we may see our earliest opening in 10 years. That’s good news for everyone.

Find photos of the North Cascades Highway reopening effort on Flickr.