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US 26 Sunset Highway Landslide

U.S. 26 Sunset Highway Landslide
Washington County, Oregon

Heavy rains triggered a landslide that failed the edge of pavement along a narrow portion of U.S. Hwy 26 in the northern Oregon Coast Range and reduced traffic to one lane. Under an indefinite-delivery contract for geotechnical services, ODOT retained GRI to investigate the slide and develop a plan for repair. GRI subcontracted Berger/ABAM Engineers, a structural engineering firm, to provide retaining wall design services and structural engineering assistance during construction. This project was completed on an emergency basis, and minimal disruption to traffic was required. A tied-back micropile retaining wall was designed, which allowed one lane of traffic to remain open during construction of the repair. Within 3 weeks of the initial site visit, GRI completed a geotechnical investigation of the slide area, and the team presented construction plans and specifications to repair the landslide, and the project was published for bid. The entire project took just 7 weeks from the notice-to-proceed to construction completion. The highway was reopened to motorists with no traffic restrictions. ODOT attributed the success of the project to the team’s technical expertise, quick response, and overall commitment to their needs on this assignment.

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