Nacimiento Lake Drive Bridge Replacement at the San Antonio River, Monterey County, CA

The County of Monterey originally retained Biggs Cardosa to provide project management and structural engineering to evaluate the existing Nacimiento Lake Drive Bridge as part of the Monterey County Seismic Retrofit Program administered by the County of Monterey with Caltrans oversight and HBP funding.  The existing structure is an 89-year-old, 4-span steel pratt through-truss that carries Nacimiento Lake Drive over the San Antonio River in rural southern Monterey County. Two retrofit strategies were proposed.  The first consisted of modifying the superstructure and replacing the weak substructure.  The second strategy considered was the total replacement of the bridge.  A cost-benefit analysis of the two alternatives was done, and the total replacement option was selected. The new structure will be a two-span post-tensioned box girder structure approximately 270 feet long and will be placed approximately 140 feet to the east of the existing structure.