A new, larger culvert that carries water and runoff under Highway 153 about 1 mile south of Black Canyon was installed last Friday (March 11) by the Washington State Department of Transportation (WSDOT). The new culvert was able to handle the large volume of water that was still cascading down the hillside this past weekend.
The work enabled WSDOT to reopen the roadway to all traffic after a mud and rockslide closed it on March 6.
There were three slides within about a 2-mile stretch of the roadway, from 5 miles north of Pateros to Black Canyon Road, where trees and vegetation burned severely in the summer of 2014, leaving few roots to anchor the steep slope east of the roadway, according to the WSDOT maintenance supervisor.
The most serious slide was about 1 mile south of Black Canyon, where a culvert became plugged and mud and water spewed across the road and over a steep embankment into the Methow River.
WSDOT said the slides appear to have been caused when heavy rain saturated the slopes above the highway.
Road crews initially reopened one lane by installing two temporary, smaller culverts.