The 2019 Sonoma County Civil Grand Jury investigated the risk of a major earthquake in Sonoma County and the effect that it could have on residents, due to impacts on water supplies. Because most people in Sonoma County rely on water supplied by Sonoma Water to nine city contractors and special districts, the Grand Jury’s report focuses on how well-prepared Sonoma Water and its contractors are to respond to a major earthquake. Among the Grand Jury’s findings was “Sonoma Water and its water contractors maintain a well-designed system and have made significant progress in mitigating earthquake risks. Ongoing efforts are needed to reduce remaining risks.”
Since a natural hazard assessment was conducted in 2008, and its first Local Hazard Mitigation Plan was prepared, Sonoma Water has completed numerous natural hazard mitigation projects, including the critical installation of 14 isolation valves that allow water to be cut off and rerouted if an aqueduct is damaged. The Grand Jury also credits Sonoma Water with twice updating the original hazard mitigation plan to identify new issues and to remove those items that have been completed.
Further improvements are planned as funding becomes available. In the event of a major earthquake, Sonoma Water has developed a triage plan for water delivery following larger quakes, which includes coordination with water contractors, maintaining system pressure, providing public notice, isolating water losses and using mutual aid and from other water agencies as needed. Sonoma Water maintains and updates a variety of emergency plans that guide response to all hazards and restoration of essential services.
The results of the Grand Jury assessment include findings and recommendations to ensure our region is ready for a large quake. Sonoma Water appreciates the diligence and thoroughness of the Grand Jury and looks forward to reviewing these recommendations with its water contractors and preparing the required responses.
The report findings included:
• In the event of a major earthquake, water supplies could be disrupted for days or weeks, but reduced water supplies may be provided through alternative means.
• Measures implemented by Sonoma Water to reduce the risk of critical water shortages following an earthquake have relied on state and federal grants, but implementation is behind schedule.
• More public outreach is needed to educate residents about the risks and individual responsibility for earthquake preparedness, including maintaining their own emergency source of water for more than three days.
The report recommendations include:
• Prepare and maintain standard operating procedures (SOPs) for restoring water after an earthquake emergency;
• Along with its water contractors, derive and publicize more realistic outage periods and provide updated information to the public;
• Maintain inventory lists with supplies and materials that could be needed to restore water supply and improve stockpiling;
• Improve coordination with water contractors, including field exercises;
• Establish options to accelerate funding of high-priority mitigation measures.
In addition to the findings and recommendations, the report also states that “Throughout this investigation, the Civil Grand Jury has been impressed with the expertise, education and dedication of the staff at Sonoma Water and its contractors.”