14 ATTACHMENT 1 EXHIBIT A - Laserfiche WebLink

Chapter 8 Water Shortage Contingency Plan THE CITY OF PL£ASANTON Earthquakes are common, relatively well -tracked, and studied in California. While California experiences hundreds of earthquakes each year, most are below 3.0 on the Richter Scale (i.e., magnitude 3.0) and cause minimal damage. The United States Geological Survey (USGS) roughly defines strong earthquakes (which can cause moderate damage to structures) as measuring greater than 5.0 on the Richter Scale, while major earthquakes measure more than 7.0 on the Richter Scale. In California, strong earthquakes occur every two to three years, and major earthquakes occur once a decade. The Calaveras, Greenville, Hayward, and Mt. Diablo faults are in the vicinity of the Tri -Valley region. A 2016 report2 by the USGS estimated the probabilities for magnitude -6.7 (or larger) earthquakes on major fault lines in the San Francisco Bay Area by the year 2043. The Hayward Fault has a 33 percent chance of one or more earthquakes of magnitude -6.7 or larger by 2043, while the Calaveras Fault has a 26 percent chance of one or more such earthquakes in that timeframe. The Greenville and Mt. Diablo faults each have a 16 percent chance of one or more earthquakes of magnitude -6.7 or larger by 2043. The 2018 LHMP evaluated the impact of earthquakes on critical facilities and infrastructure using a Hazus analysis. Results for utilities infrastructure (including water system facilities) are presented in terms of level of damage and time to return to functionality. There are five damage levels (no damage, slight damage, moderate damage, extensive damage, and complete damage) and six time increments (1, 3, 7, 14, 30, and 90 days). Results are categorized by earthquake location; there are separate scenarios for earthquakes on each of the Calaveras, Greenville, Hayward, Mt. Diablo, and San Andreas faults. According to the 2018 LHMP, earthquakes on the Hayward and Calaveras faults would be most significant. In its earthquake analysis, the 2018 LHMP identified 120 critical utility facilities (i.e., providing water, electricity, and communications service) in the Tri -Valley region. Over 80 percent of utility facilities would experience at least moderate damage for an earthquake on the Hayward Fault, while approximately 44 percent would be at least moderately damaged by a Calaveras Fault earthquake. For earthquakes on the other faults analyzed (Greenville, Mt. Diablo, San Andreas), this number is below 15 percent. Seven days after an earthquake on the Hayward Fault, one of these facilities has an approximately 52 percent chance of being fully functional. This increases to approximately 84 percent for an earthquake on the Calaveras Fault and above 92 percent for earthquakes on the Greenville, Mt. Diablo, and San Andreas faults. Table 18-3 of the 2018 LHMP summarizes alternatives for mitigating the earthquake hazard on personal, corporate, and government scales. Mitigation options potentially applicable to the City include the following: • Locate critical facilities outside hazard area where possible • Harden infrastructure • Provide redundancy for critical functions • Include retrofitting and replacement of critical system elements in capital improvement plan • Warehouse critical infrastructure components such as pipe materials • Develop and adopt a continuity of operations plan z U.S. Geological Survey (USGS), 2016. Earthquake Outlook for the San Francisco Bay Region 2014-2043. https://Pubs.usgs.gov/fs/2016/3020/fs2Ol63020.odf WEST YOST N-680-60-20-04-WP-R-680-2020UWMP 8-2 City of Pleasanton 2020 Urban Water Management Plan May 2021