DESCRIPTION: Unusually heavy rainfall in mid-January 2012 caused a series of landslides in Lincoln County, Oregon. During that time, a section of unpaved roadway failed on Logsden Road at about MP 18.3. The failure was apparently triggered by runoff from the road surface and a partially blocked culvert. A large volume of soil, rock, trees and debris flowed down to an existing timber road. The resulting near-vertical headwall closed Logsden Road, which provides access to county residents and local timber trucks.
SERVICE: Foundation Engineering evaluated the failure and concluded a rock buttress would be the most practical, cost-efficient method to quickly repair the landslide and re‑open the road. Working with the engineering team and a contractor selected by the County, Foundation Engineering developed guidelines in the field for keyway construction, fill slopes, and drainage. The landslide was repaired within two weeks using ±8,800 tons of large riprap and jaw-run quarry rock. Additional improvements included regrading the roadway, installing additional culverts, and repairing adjacent slopes that had been damaged by erosion.