Why were the Antioch and Dumbarton bridges not included in the original state Toll Bridge Seismic Retrofit Program?
Because the Antioch Bridge (built in 1978) and the Dumbarton Bridge (1982) met seismic standards established after the 1971 Sylmar earthquake in Southern California, and were relatively new when the state Toll Bridge Seismic Retrofit Program was established, neither was included in the first round of seismic safety studies. However, due to findings from subsequent quakes — including Loma Prieta in 1989, Northridge in 1994 and Kobe (Japan) in 1995 — seismic standards now are much higher. A two-year evaluation conducted by BATA and Caltrans shows both bridges need significant strengthening to protect public safety.
