Depending on the cause and severity of the local plant outage or seismic event, potential damage to treatment and conveyance facilities may extend from short to long-term disruptions in imported and local water supply deliveries. Unlike drought conditions, which manifest over several years, the response measures available to respond to a catastrophic interruption are limited. During such an event, the IRWD Board, at its discretion, may choose to implement mandatory measures at earlier levels of shortages. See also Section 1.3 Seismic Risk Assessment and Mitigation Plan below for additional information. For additional information on response to severe drought events and consecutive multi-dry year analyses refer to the UWMP, Sections 6 and 7. 1.3 Seismic Risk Assessment and Mitigation Plan LAW 10632.5. (a) In addition to the requirements of paragraph (3) of subdivision (a) of Section 10632, beginning January 1, 2020, the plan shall include a seismic risk assessment and mitigation plan to assess the vulnerability of each of the various facilities of a water system and mitigate those vulnerabilities. (b) An urban water supplier shall update the seismic risk assessment and mitigation plan when updating its urban water management plan as required by Section 10621. (c) An urban water supplier may comply with this section by submitting, pursuant to Section 10644, a copy of the most recent adopted local hazard mitigation plan or multihazard mitigation plan under the federal Disaster Mitigation Act of 2000 (Public Law 106-390) if the local hazard mitigation plan or multihazard mitigation plan addresses seismic risk. As stated in the CWC Section 10632.5.(a), beginning January 1, 2020, the UWMP shall include a seismic risk assessment and mitigation plan to assess the vulnerability of each of the various facilities of a water system and mitigate those vulnerabilities. An urban water supplier may comply with this section by submitting, pursuant to Section 10644, a copy of the most recent adopted local hazard mitigation plan or multi-hazard mitigation plan under the federal Disaster Mitigation Act of 2000 (Public Law 106-390) if the local hazard mitigation plan or multi-hazard mitigation plan addresses seismic risk. In January 2025, IRWD completed and submitted the “Water System Risk and Resilience Assessment (RRA): A Comprehensive Analysis Consistent with America’s Water Infrastructure Act of 2018 (AWIA)” in coordination with the Municipal Water District of Orange County (MWDOC) and the Water Emergency Response Organization of Orange County (WEROC). This assessment updated the baseline risks created in 2020 to account for new assets and upgrades to the system and adheres to the updated ANSI/AWWA J100-21 Standard. The document was accepted and certified as complete by the Environmental Protection Agency, Exhibit B . In addition, IRWD has completed numerous seismic studies for individual projects and facilities including dam seismic hazard potentials, water system disruption potential in the case of major earthquake, and full system vulnerabilities similar to the AWIA RRA.
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IRWD – 2025 Water Shortage Contingency Plan
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