Heavy rains trigger torrent of water, rocks
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 remove 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.
WSDOT road crews cut the pavement to install two temporary culverts and backfilled the area to reopen one lane with traffic controlled by a flagger on Monday. Crews will close the road again on Friday morning (March 11) to replace the temporary culverts with a larger one, and expect to reopen it that evening, according to Okanogan County Emergency Management.
The culvert at the northernmost slide was handling the water well on Tuesday (March 8), but crews are at the scene to make sure it doesn’t plug up again, said Rice on Tuesday. The culvert at the southernmost slide is still clogged. Crews will work on opening that culvert on Wednesday (March 9).
Lots of rain
Rain recorded in the area in just 24 hours was twice the average for the entire month of March for Wenatchee — the nearest location with long-term records — according to Greg Koch, a forecaster with National Weather Service (NWS) in Spokane.
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. 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 burned 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.
There were few problems elsewhere in the county. Many culverts became clogged, causing shoulder washes, according to Okanogan County Maintenance Coordinator Kenneth Stanley. Stanley said he was pleasantly surprised that damage had been minor. “It was nothing real significant — just a mess, not impassable,” he said.
Erosion was reported on some dirt roads in the county, according to Okanogan County Emergency Manager Maurice Goodall.
Stanley said they are keeping an eye on conditions because of the forecast for heavy rain and a flood watch for Wednesday and Thursday (March 9 and 10), followed by more wet weather. NWS is forecasting cooler weather, which could bring snow in the mountains, but the Methow Valley could receive as much as another inch of rain late Wednesday to early Thursday, said Koch.
Rainfall recorded last weekend at the stations closest to Black Canyon ranged from 1.04 inches in Chelan, .97 inches at Chief Joseph Dam in Bridgeport, .75 inches in Winthrop, .82 inches in Mazama, and 1.22 inches in Waterville, according to Koch. The majority of that rain fell Saturday night and early Sunday, he said.
Rain gauges installed by NWS to alert people to the potential for mudslides in the burn scar from the Carlton Complex Fire — which includes the slopes near Black Canyon — registered 1.4 inches in that vicinity, said Koch.
These amounts are significantly above average. The average precipitation for Wenatchee for the entire month of March is .61 inches, and the record there was 2.24 inches, in 1937, said Koch.
Phone service working again
The road work cut off all landline service in the Methow Valley north of Black Canyon after equipment digging to make the road repairs damaged fiber-optic lines on Sunday evening, according to Goodall.
The outage affected all long-distance calls in and out of the valley until midday Monday, but people could make local calls. It also cut off calls to 911. Cell phones worked for all local, long-distance and emergency calls.