DESCRIPTION: Portland Bureau of Transportation plans to remove the bridge on NE Glisan east of NE 90th Street in Portland Oregon. Built in 1911 as an overcrossing for the railroad, the bridge portals were buried with fill after the railway was abandoned in the 1950’s. The geotechnical objectives for the project included evaluation of settlement for up to 15 feet of structural fill required to support the replacement road and sidewalks, and impacts to project construction from sequential demolition of bridge and sequencing of earthwork construction allowing for major-arterial roadway to remain open. Project challenges included limited access for explorations below existing bridge, limited traffic closures and work hour restrictions, and existing portal fill consisting of construction rubble and railroad ballast.
SERVICES: Our scope of work included site permitting, developing work plan and traffic control plan, exploratory drilling including borings and hand-auger borings, Dynamic Cone Penetrometer testing, laboratory testing, and engineering analyses. Recommendations were developed for mitigation of settlement, development of Resilient Modulus parameters for new pavement design, and recommendations for sequencing site construction to limit impacts to earthwork construction, traffic, and public transit.