On October 6, 2013 the California Office of Emergency Services (CalOES) published its 2013 State of California Multi-Hazard Mitigation Plan complete with a chapter from the USGS on volcano hazard mitigation.
Volcano Hazard Mitigation Included in California Multi-hazard Mitigation Plan
This document is the official statement of the State's hazard identification, vulnerability analysis, and hazard mitigation strategy. Volcanic eruptions occur in California about as frequently as the largest San Andreas Fault Zone earthquakes. Our State Geologist, John Parrish states, "California is the most geologically diverse state in the Nation. We are known for our earthquakes, landslides, and flood hazards. But our nearly forgotten hazard is our volcanoes." With as many as ten eruptions in the last 1,000 years, recognizing the potential for renewed volcanism in California is an essential first step in mitigating hazardous impacts.
You can see the full Mitigation Plan on the CalOES website.