The Crown Point Viaduct was constructed in 1915 and is an approximately 600-foot-long concrete structure located at the outside of the curved highway section surrounding the Vista House. The viaduct supports the pedestrian walkway at the edge of the highway and around Vista House. The structure consists of a flat reinforced concrete slab that spans from a foundation wall near the edge of the pavement to the walkway railing/girder, which is supported by 29 concrete columns. The roadway at the location of the viaduct is supported by rockery and concrete walls with an exposed height of up to 15 to 17 feet. GRI provided geotechnical services to develop alternatives for restoration of the viaduct, which included new foundations; repair, replacement, or improvement of retaining walls; and new roadway pavement. The foundation restoration alternatives evaluated by the design team included the use of existing spread footings, modification of existing spread footings, new spread footings, and replacement of existing spread footings with micropiles. Alternatives developed for repair and strengthening, or replacement, of the retaining walls included removal of fill and replacement with MSE walls, use of soil nails to improve the stability of the roadway fill, and construction of a reticulated micropile wall to reinforce the soil without removing the existing rockery wall. Geotechnical services included review of available information for the structure, a site reconnaissance, preparation of a work plan, and subsurface explorations in a sensitive environmental and scenic area. GRI also provided recommendations for rehabilitation of the existing asphalt pavement which is underlain by original Warrenite pavement that is approximately 100 years old. GRI provided consultation services during construction.

Location: Multnomah County, Oregon

Owner: Federal Highway Administration/Oregon Department of Transportation

Market Sector: Transportation, Federal

Services: Geotechnical Engineering, Seismic Engineering