A mud slide that began during recent heavy rains will force traveler delays on State Route 18 starting tonight, when crews begin work to stabilize a slope under the westbound lane just east of the Holder Creek Bridge.

Recent storms caused Holder Creek to flood and erode the hillside supporting the roadway.

“We will stabilize the hillside to protect against further erosion and damage,” said Dave Lindberg, project engineer. “The shoulder of the roadway has already cracked and if we have additional flooding we could lose the highway.”

To keep drivers safe and create a safe working space, crews will close the westbound lane and shift all traffic onto the two eastbound lanes during construction. Starting at 7:30 p.m. on Monday and Tuesday, crews will reduce traffic to one lane while they set up the new configuration. Pilot cars will guide drivers through the area, with the lanes reopening by 4:30 a.m. the following morning. The recommended speed limit for westbound traffic will also be temporarily reduced from 55 mph to 45 mph during construction.

Drivers should expect delays during the work, which is expected to wrap up in March. An average of 20,000 vehicles use this stretch of highway each day, including about 3,000 trucks.

“Right now, trucks can use the eastbound truck climbing lane to make their way up the long, steep hill,” Lindberg said. “During construction, trucks will use the general purpose lane with all of the regular commuters. Drivers should allow some extra time for their trips.”

Crews will stabilize about 250 feet of the hillside by building a large rock and gravel wall, known as a rock buttress. They will also repair the damaged shoulder and guardrail. At night, drivers can expect both directions of SR 18 to be reduced to a single lane, with flaggers alternating traffic through the work zone.

WSDOT selected contractor Tri-State Construction for the roughly $600,000 emergency repair project.

For more information, visit the project Web site: www.wsdot.wa.gov/Projects/SR18/TigerMtnSlope/.