The Washington State Department of Transportation is wrapping up a project aimed at deterring debris flows along U.S. 2/Stevens Pass Highway from “burn scars” left behind by the 2022 Bolt Creek Fire, which burned nearly 15,000 acres in the Mount Baker-Snoqualmie National Forest.
[Above photo by WSDOT]
The agency noted in a blog post about the project that wildfires can change the landscape, turning dense trees and vegetation into large areas with ashes and dry soil – areas known as burn scars.
“If it rains a lot or snow on the ground melts really fast, these burn scars can produce fast-moving landslides called debris flows,” WSDOT said. “These can be dangerous and might harm people and property within their path.”
After the Bolt Creek wildfire, WSDOT personnel studied the area and found two areas near the burn scar – about four miles northwest of Skykomish – that posed a “higher risk” of debris flows of mud and loose rock potentially affecting U.S. 2.
“We had to close U.S. 2 east of Gold Bar several times because of the active fire and debris falling onto the highway,” WSDOT noted. “The fire also left a burn scar that will take several years to recover.”
To mitigate the impact of such debris flows on the roadway and surrounding area, the WSDOT built a series of walls, berms, and fences along certain sections of U.S. 2 to protect both the roadway and its stormwater culverts.
WSDOT built two debris fences – one 60 feet long and the other 110 feet long – above specific culverts to help stop detritus from blocking roadway culverts if debris flows occur happens.
Along another section of the roadway, WSDOT built six-foot-tall wall, called a berm, made of natural materials. This berm will guide any potential debris flows away from U.S. 2 to a lower natural “catch” area near the highway. The berm is 94 feet long and required nearly 300 tons of material to build. In spring 2024, the agency said it will add native plant seeds to further help stabilize the berm area.
“Our maintenance crews will keep an eye on the highway along the burn scar, looking for downed trees and limbs, clearing ditches and culverts and looking for any early warning signs of a potential debris flow,” WSDOT noted. “Hopefully, the berm and the fences are never tested by a debris flow, but … we have taken the necessary steps to reduce the risk and keep U.S. 2 open while the area recovers from the Bolt Creek Fire.”