Friday, February 9, 2018

Safety over speed during landslide repairs

By Andrea E. Petrich

It's not just 60 mph traffic on the interstates that put our maintenance crews at risk - it's everything from falling trees to inattentive drivers to avalanches and this week, it was the rain.

State Route 9 between Mt. Vernon and Arlington reopened Thursday evening following four days of a 24/7 closure as rain saturated hillsides, fields and roadways around northwest Washington.
During a weekend of heavy rain in northwestern Washington, the hillside
above SR 9 near Mt. Vernon slide across the highway.

On Sunday, Feb. 4 while many of us were enjoying the Super Bowl, crews from our Mt. Vernon maintenance shop were putting up signs where water was covering roads and cleaning out culverts, including one along SR 9 south of Lake McMurray. They'd cleaned out what debris they could but the amount of water coming down was too much for the culvert and was washing over the road. The crews left to get warning signs but when they returned they found a landslide full of mud, trees and a huge concrete chunk of old dairy equipment from high on the hillside blocking both lanes of the highway.
Trees, mud and a large concrete piece of old dairy equipment was part of
the slide that covered SR 9 when a slide happened on Sunday, Feb. 4.

We closed the road overnight until our geotechnical engineers could safely assess the stability of the slope. Once on the scene our geotechs didn't detect any movement in the slope so our crews spent Monday afternoon and all day Tuesday clearing out trees, mud and breaking up that concrete structure to haul away while dealing with continued rainfall. They were nearly done and ready to reopen the road on Tuesday afternoon when another slide came down onto the road. It brought enough debris that it came up to the top track of our excavator – about three feet off the ground - that was on the road clearing a section of culvert.

This created another safety hazard and our crews got out of the area. A geotech returned to the scene on Wednesday and found that instead of absorbing the continued rain, the hillside was quickly pushing it out. Our crews realized they needed to do something to help move that water out of the area to get the road back open.
As soon as they safely could, our maintenance crews started work to cut, break up and clear the debris across SR 9.

The geotech approved work to resume on Thursday so we got to work cutting trees that had lost their secure base in the slide, removing mud and rocks from the road and installing new drainage to help move that water.

The final step was getting the dirt and muck covering the road lifted off to make lane striping visible, which our sweeper truck handled faster than expected and the road reopened at about 5 p.m.

Preventing slides during heavy rainfall is a challenge and can't always be avoided, though we try. We monitor areas where slides are common and our maintenance teams regularly look for changes in a landscape which may indicate movement, including trees or rocks which may have shifted. If anything out of the ordinary is noticed, we call in geotechs to evaluate, which may lead to us removing hazards, adding bolts to hold rocks in place or building catch basins or barriers. But sometimes, weather simply wins out.
Nearly finished clearing the first slide, crews were close to opening the highway
when another slide knocked down trees and more mud across SR 9.

You can help too. If you see anything that looks unusual, please call 911 so that they can alert the right agency to go have a look. We try to see everything on our highways but we can't be everywhere, and any help you can provide is appreciated.

The closure of SR 9 was tough, both for those of you who typically use the highway, and for our crews working to get it back open. A big thanks to all of you for your patience, and a huge kudos to our crews who battled some very tough elements and sometimes dangerous conditions to get the slide cleared.