South Jorsted Creek slide debris and road, US 101.

Several years of heavy winter rainfall triggered two massive slides which blocked US Highway 101 along Hood Canal in late February 1999.

High groundwater levels, steep slopes, and lubricated layers of glacial till combined to create these slides. Closure of the highway appeared to be a strong possibility in the initial analyses of the slides. Repairs however, are underway and the highway is open.

The two slides occurred along Hood Canal, between Lilliwaup and Eldon on US 101. Lilliwaup Vicinity Slide: MP 326 Eldon Vicinity Slide: MP 322

Two Slides

		North Lilliwaup Slide A massive slide closed a one mile long section of US 101 north of Lilliwaup, February 1999. Mud, trees and debris clogged 1,800 feet of highway. The slide continued to move, despite attempts by Department of Transportation crews to clear debris. By April 12th, however, crews opened one lane of the highway. Drains were placed in the hillside to lower the water table and help stabilize the slide. By late June, two highway lanes were opened. Although repair plans originally included a retaining wall or rock buttress, evidence indicated that improved drainage could stabilize the slope. 85 horizontal drains and ground monitoring instruments will be installed.
		South Jorsted Creek Slide At first, this slide appeared to be smaller than the Lilliwaup slide. But this slide proved to be as large and more dangerous than the Lilliwaup slide. Debris 35 feet deep covered the roadway. Attempts by DOT crews to clear debris triggered more sliding. Horizontal drains were installed to divert excess groundwater from the slope. 300 gallons per minute flowed continuously for several weeks. Following geologist's recommendations, DOT crews constructed a one-lane gravel road over the slide debris. The 500 foot long road was opened to traffic in June and is controlled by a temporary signal. More drains will be installed in this area and further repairs will take place in the Spring and Summer of 2000.

Sliding soils and woody debris above US 101 along Hood Canal.

Slides, Patterns and causes of slides along Puget Sound.
Geology, How glaciers left a legacy of unstable bluffs.
Understanding Erosion, What to consider on land loss.