Earthquake concerns for proposed high school site

October 17, 1989. Cupertino, Calif. We just sat down to watch the World Series between Oakland Athletics and San Francisco Giants when the house started to shake. The Loma Prieta earthquake was under way. The epicenter was 18 miles from the house. We had a real shaky time but suffered little damage. The house was built on good ground.

In San Francisco and Oakland, 55 miles north, it was an entirely different story. The Cypress structure of the freeway collapsed, dropping the upper level on top of the cars below. The Oakland – San Francisco bridge had a section collapse. The Marina District in San Francisco had severe damage. Sixty-one people died

The structures in San Francisco and Oakland that failed were built on alluvial soil. The proposed site of the Bonsall Unified School District High School on Gird Road is alluvial soil. As in the San Francisco Bay Area (and Northridge) there is ground water at a shallow depth. The alluvial soil with the ground water and the earthquake motion becomes liquefied and amplifies the destructive force.

So, why would you build a school on such precarious soil when a viable, essentially no risk (bed rock) location at the Sullivan site is available? Certainly the Lilac fire caused a great deal of discern but, per Cal Fire, the Sullivan site is a moderate fire hazard zone. The Gird site is very high.

BUSD officials, you have the Leighton 4-22-16 report and access to the Cal Fire data. What are you thinking??

Vic Dervin