WSDOT crews at scene; working to install temporary culvert
By Marcy Stamper
A major slide of mud and rocks about 1 mile south of Black Canyon closed state Highway 153 early Sunday (March 6) after heavy rain fell overnight. Crews from the Washington State Department of Transportation (WSDOT) were on scene Sunday morning clearing debris and water from the roadway at three sites.
The most serious slide was about 1 mile south of Black Canyon, where a culvert became plugged and mud and water were cascading across the road and spilling over a steep embankment into the Methow River. There were two smaller slides, one about a mile north of the major damage and the other a little south of it.
WSDOT got a call Sunday morning around 4:30 a.m. and a crew arrived at the scene shortly after that, according to Don Becker, Twisp maintenance supervisor for WSDOT.
The crew had to clear some trees from the roadway when they first arrived, but the major task was to clear enough debris from the road and divert the fast-flowing water and mud to be able to install a temporary culvert, said Wayne Rice, the WSDOT maintenance supervisor at the scene.
Rice had no firm prediction for when Route 153 could be reopened, since road engineers were still assessing the damage and condition of the roadway and culverts at all three slides. Half a dozen crew members were already at the scene, but they were still awaiting more equipment, which was en route as of 11 a.m. Sunday, said Rice.
Road crews will cut the pavement to install the temporary culvert and then backfill the area to reopen the road. The temporary culvert will remain in place until they can unclog the regular culvert, said Rice.
The water, mud and other debris came so fast that the flow plugged the existing culvert, causing it to overtop the road, according to Rice. Rice said they still don’t know if only the inlet was blocked, or if debris had clogged the entire culvert. Rice said they don’t know how high above the road the slide started.
The existing culvert starts about 20 feet upstream of the road on the west slope, said Rice. It angles under the road to its outlet, halfway down the steep slope above the Methow River on the east side of the highway.
Wildfires in the past two summers severely burned the steep slopes around Black Canyon, and most trees there are dead and blackened. “We’ve been very fortunate this year [in terms of mudslides], with the fires and no vegetation,” said Rice. The culvert was able to handle a heavy rain in mid-February, but faster rains deposit more material, he said. The trees that had to be cleared from the roadway were burnt trees that were no longer anchored, said Becker.
Last year a mudslide caused problems in another burned area near Black Canyon when the ground was still frozen and water streamed over the highway, said Rice. That slide was not at an existing drainage and didn’t involve a culvert, he said.
The rain also caused minor problems in Frazer Creek on Highway 20 heading east over the Loup, about 6 miles from the junction with Route 153, said Rice. Rice said he didn’t have reports of water spilling onto that roadway and that crews were “managing the flow to keep the water in where it belongs.”