OPAC Consulting Engineers

Central Viaduct

San Francisco, California


California Department of Transportation


Design completed 1992

Scope of work:

Seismic Retrofit Design

Construction cost:


Services Performed:

  • Independent check of the load development
  • Retrofit design
  • Drawing production
  • Shoring design


  • Seismic analysis
  • Design and analysis of shoring support systems

Following the 7.1 magnitude Loma Prieta earthquake on October 17, 1989, Caltrans engaged Tudor Engineering Company as prime consultant to design the seismic strengthening of the Central Viaduct (U.S. 101). This double-decker viaduct structure extends from the vicinity of Mission Street to the end of the approach ramps at Fell and Oak Streets in San Francisco, California. The retrofit design guidelines intend to prevent collapse during major earthquake. Tudor selected OPAC to perform an independent check of the load development, shoring calculations and production drawings for the proposed retrofit.