A lack of water—for fighting fires—did far more damage to San Francisco in 1906 than the earthquake itself. A similar problem complicated response to the Oakland Hills fire in 1991. Water agencies understand that water is often an essential part of disaster response, but a disaster can also be catastrophic for water storage and delivery systems. While water systems may be functioning at reduced efficiency, the demand for water escalates in the first few days after a disaster, because of firefighting and medical needs. According to a 2002 report from the Bay Area Economic Forum, post-earthquake water shortages could shut down many businesses and industries, sometimes permanently, which would affect daily living, disaster recovery, jobs and the region's economy.
Engineers in the region's water agencies have been working to learn the lessons of past earthquakes, including exchanging ideas with counterparts in Japan. They know that old cast iron pipe cracks easily in quakes, particularly where soil liquefaction occurs, and that other types of pipe can pull apart if not properly designed and installed. They know that sloshing in storage tanks can create twists, bulges, and leaks which flood downhill neighborhoods. They have also seen that the Alaskan oil pipeline, designed to slide sideways as much as 20 feet, did so without breaking in a recent major quake. The agencies are applying this knowledge here and now to improve quake preparedness.
In late October, the East Bay Municipal Utility District (EBMUD) announced that the water level behind San Pablo Dam had been lowered to decrease the potential for dam failure in a major quake on the Hayward Fault. Although the earthen dam has had regular inspections, the last rigorous evaluation was in the 1970s. Current structural analysis methods combined with recent USGS data on the Hayward Fault show that the risk of quake damage is greater than anticipated in the past.
Later that week, EBMUD hosted a forum on "The Earthquake Risk to Water Supplies", co-sponsored by the Northern California Chapter of the Earthquake Engineering Research Institute, EBMUD, the Federal Emergency Management Agency, San Francisco Public Utilities Commission (SFPUC), the Santa Clara Valley Water District (SCVWD), and the Bay Area Water Supply and Conservation Agency (BAWSCA).
All of the water agencies sponsoring the forum have key water distribution pipelines that cross at least one major fault. Dr. David Schwartz from USGS told the forum participants that another major quake in the Bay Area is imminent, and much more likely than other threats faced by utilities, such as terrorist acts. "We can't predict `when'", he said, "but we can forecast `where' and `how big'." Since 1927 there have been very few quakes compared to the historic pattern in the region, but much of the region's growth has happened in that period. With all the major faults in the Bay Area, the likelihood of an earthquake larger than 6.5 magnitude is 90% in the next 30 years.
In the East Bay, EBMUD is nearing the end of a 10-year seismic retrofit program which has included storage tank strengthening, building miles of additional pipelines to create alternate distribution routes, and creation of a new segment for the Claremont Tunnel (see August/September 2003, November/December 1998 issues). Marilyn Miller of EBMUD says, "Our next steps include re-running our computer model to see how the improvements will function, planning for immediate post-event response, and setting up more frequent inspections, especially for older facilities."
A recent state law requires SFPUC to develop an emergency response plan for restoring water service after an earthquake as part of rebuilding the Hetch Hetchy water system. Approximately half of the 77 projects in the SFPUC emergency response plan are regional, and most are costly. A particular concern for SFPUC has been the Irvington Tunnel, which has not been inspected in decades because there is no alternative facility which could be put into service to allow access to the tunnel. Since SFPUC supplies water via BAWSCA agencies to many residents of water districts outside San Francisco as well as within the city, the law also requires planning for equitable water distribution following a disaster. In the meantime, San Mateo county and city officials have already created a water distribution plan for emergencies.
In the South Bay, SCVWD is currently drafting a water infrastructure reliability plan to address the three most likely threats—earthquake, regional power outage, and flooding/landslide hazards. The plan sets level of service goals for service after a disaster, evaluates what is needed to reduce the time when water will not be available to retail suppliers who purchase water from SCVWD for their customers, and presents the next steps for implementation. These include stockpiling extra pipe for repairs so it will be available post-disaster, adding groundwater wells throughout the district, and securing district facilities against damage so that staff and equipment will be safe and functional. The draft plan will be available in December.
Getting assistance from outside the Bay Area after a major disaster, particularly if the need is great, may take a long time. Equipment and supplies would need to share a dysfunctional transportation network with other disaster relief. However, because the region is so large, not all agencies would be equally damaged in a disaster, making mutual aid agreements an important component of planning. Over the past few years a number of districts have built interties between their distribution systems to bypass outages. In addition, agreements to share equipment and supplies which were developed after the Oakland Hills fire have been formally incorporated into a mutual-aid framework called WARN, which now includes agencies throughout California.
The goal for all the regional water agencies is to keep water available during and after a disaster, for firefighters, hospitals, homes and businesses. When—not if—an earthquake occurs, the region's future may depend on how well the lessons from previous disasters have been learned.
Leslie Stewart
For more information: Materials from the October forum are online at http://www.quake06.org/quake06/u_and_t.html