Colbert Bridge No. 3703 over the Little Spokane River was originally constructed in 1953 and in recent years had been placed under load restrictions. Plans are in place to replace the existing structure with a single-span bridge featuring 42-inch-deep precast concrete girders and a cast-in-place concrete deck. BAI completed geotechnical exploration and analysis to assist the County in designing the proposed bridge replacement. Geotechnical recommendations provided by BAI included deep foundation design for axial and lateral loading, seismic considerations, earth pressures and lateral resistance for abutment walls, streambed soil gradations for scour analysis, and recommendations for earthwork to support replacement of the existing bridge.
