Clearing Highway 20’s slides took manpower, equipment and planning
By Ann McCreary
After working continuously for more than a week to clear 3,000 dump truck loads of mud, boulders, trees and debris from the roadway, state transportation crews were able to reopen the North Cascades Highway on Monday morning (Aug. 19).
“We worked daylight to dark for eight days,” said Don Becker, maintenance supervisor of the Washington State Department of Transportation (WSDOT) shop in Twisp.
Highway 20 was inundated by eight landslides brought down by intense rainstorms that began Saturday evening, Aug. 10, and continued the following day. The damage closed the highway between mileposts 147, the winter closure gate, and milepost 155, two miles west of Rainy Pass.
The largest slide occurred near milepost 150, depositing mud, trees and boulders over one-fourth of a mile and piling debris up to 15 feet deep on the highway, Becker said. He said initial estimates that the slide reached depths of 25 feet were a bit high.
About 25 people from transportation shops in Twisp, Brewster and Newhalem worked throughout the week. WSDOT also contracted with Lloyd Logging of Twisp to provide a Caterpillar D8 bulldozer.
Determining where to deposit the tons of dirt, rocks and trees after they were removed from the roadway required collaboration between state transportation and U.S. Forest Service officials. Because the North Cascades Highway passes through Forest Service land, Forest Service officials needed to approve where and how crews disposed of the material.
After meeting with District Ranger Mike Liu, as well as hydrologists and fish biologists from the Methow Ranger District, transportation crews deposited most of the debris at a department stockpile site at milepost 153, near Swamp Creek, Becker said.
In areas where slides deposited mud and debris on steep slopes next to the highway, crews flattened out those areas to create more gentle slopes. “We will need to mulch and hydro seed those areas,” Becker said.
Several truckloads of large rocks were hauled to Twisp to be stored by WSDOT for future use in road construction and Forest Service projects.
A number of boulders brought down by the slides were too big to pick up, Becker said. “They are somewhat smaller than a Volkswagen. Some of them we’re going to have to pop [blow up] to clear,” Becker said.
Removing the mud was challenging “because the material was so wet,” Becker said. “It was heavy and hard to haul. It was like hauling pudding. It would just want to flow all the time.”
The intense rain, hail and winds that caused the slides appear to have been confined to a five-mile area between mileposts 150 and 155. “There was hardly any water at all that ran at milepost 148 … and at the summit of Rainy Pass there was nothing,” Becker said.
Before the highway could reopen, crews repaired damaged guardrails, completed initial drainage and ditches, and repaired damaged pavement. Becker said crews will continue working through September to create culverts and drainage systems to contain future runoff.
“We’re pretty much building a new plan for ditches alongside the roadway and catchment basins,” said Jeff Adamson, WSDOT spokesman. “After you’ve had a slide like this the hillsides behave differently. They don’t hold as much water. In the years after a slide the risk of more slides is higher.”
Motorists should expect some occasional short delays as crews work on drainage and the slopes on both sides of the highway for the next several weeks, Adamson said.
The eight-day closure of the scenic highway interrupted business in the valley during the height of the summer tourist season.
“It affected quite a few travelers,” said Bryan Alexander, assistant manager of Pearrygin Lake State Park, where all campsites are usually reserved months in advance. “In the first couple of days we had 10 or so cancellations, because of the distance people would have to drive.”
“After that it had a trickle effect. The number of day users went down significantly. Normally the day use parking lot would be full on weekends. We probably saw a 50 percent drop,” Alexander said.
“We really dropped off” after the highway closed, said Serena Lockwood, assistant manager of the Mazama Country Store, the last stop for food and gas on the valley’s far end.
Lockwood estimated business fell off by about 40 percent while the North Cascades Highway was closed, but picked up again immediately after it reopened Monday.
“A lot of our … sales are people headed over the pass or coming down from the pass. Yesterday a lot more people were stopping in for lunch,” Lockwood said Tuesday.
Alternate routes to and from the Methow Valley carried more traffic while Highway 20 was closed.
One traveler who was eastbound on Highway 2 on Sunday afternoon (Aug. 18) said that there was a solid line of slow-moving westbound vehicles from Monroe all the way to Index, about 20 miles. Eastbound traffic over Stevens Pass was not impacted, he said.