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Spencer Creek Bridge
The Spencer Creek Bridge Replacement project is one of the first design-build ground improvement contracts awarded in the State of Oregon. The project called for the replacement of the US 101 bridge over Spencer Creek requiring construction of two large bridge abutment embankments over soft liquefiable soils and installation of drilled shafts for the bridge abutment structure. Lachel served as the designer for Condon Johnson & Associates, the ground improvement subcontractor. The design of stone columns for ground improvement was developed to mitigate liquefaction potential below the approach embankments. Due to the complex geology and mixed soil conditions, detailed liquefaction analysis of over 20 soil profiles was completed as part of the stone column design for ground improvement. Massive seismic loading, as is expected during a subduction zone earthquake was applied analytically to the improved soils. Estimates of post-improvement liquefaction settlement and the soil’s composite residual shear strength were shown to be within acceptable limits allowing this coastal life-line structure to remain serviceable. Lachel also provided construction quality assurance services for installation of the stone columns and drilled shafts.
