County of Orange, Orange County Fire Authority, California State Water Resource Control Board Division of Drinking Water, and other entities to ensure a holistic approach and a well- coordinated emergency response. II. Assessment Approach Following the J100-21 Standard, IRWD’s risk assessment followed a seven-step process that began with the identification and confirmation of critical assets within the potable water system. The previously selected critical assets were presented to the assessment team for review and update. Next, the assessment team identified and prioritized the set of threats, against which the assessment was to be conducted. All reference threats along with three additional threats (aging infrastructure, drought, and earthquake liquefaction) were considered, with 17 threats being used in the assessment. The final list of 117 threat-asset pairs were assessed for their consequences from the threat, vulnerability to the threat, and likelihood of threat occurrence. The final risk baseline values were presented to the assessment team for an evaluation of accuracy and completeness. III. Key System Elements IRWD’s potable water facilities include the Dyer Road Wellfield, the Baker Water Treatment Plant, the Irvine Desalter Project which treats drinking water in the Irvine sub-basin, the Deep Aquifer Treatment System that removes the tinted color from local groundwater, Wells 21 and 22 Desalter Project, that recovers and treats local impaired groundwater for potable use, and 36 drinking water reservoirs with a combined 150 MG storage capacity. Potable water is distributed through 1,767 miles of distribution pipelines. IV. Vulnerability Assessment After identifying critical assets and the threats of concern, each critical asset was paired to every identified threat. The assessment team then evaluated the plausibility of the identified threat having significant consequence to the critical asset and prioritized those threat-asset pairs of concern to their system. Out of a possible 810 pairs, a total of 117 threat-asset pairs were ultimately selected to be included in the assessment. These threat-asset pairs represent the most significant concern to the District. V. Earthquake Liquefaction Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. For example, during the 1989 Loma Prieta, California, earthquake, liquefaction of the soils and debris used to fill in a lagoon caused major subsidence, fracturing, and horizontal sliding of the ground surface in the Marina district in San Francisco. The risk assessment team identified earthquake liquefaction to be a threat of concern to water assets located in liquefaction zones. Earthquake liquefaction is a concern for the Michelson Ops Complex (which includes the Michelson Operations Center, the Chemical Storage Facility
WSCP - 10
IRWD – 2025 Water Shortage Contingency Plan
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