Fifteen Mile Creek Bridge, King County Road Services Division
CivilTech was responsible for seismic analysis to determine applicable retrofit alternatives to bring Fifteen Mile Creek Bridge into compliance with King County’s Level II serviceability requirements based on a 475 year earthquake. CivilTech proposed retrofit alternatives that included installation of steel brace frames, augercast piles, cast-in-place concrete piles, and steel piles. Later, King County requested additional seismic evaluations to account for a remaining bridge life of 20 years, rather than the standard bridge life of 75 to 100 years. The new analysis evaluated the bridge subjected to a 95-year earthquake. CivilTech provided an evaluation of risks, costs, and benefits associated with each seismic scenario.