Santiago Creek Recharge Basin, had detectable results above the Notification Levels but below the Response Level for PFOA and PFOS. IRWD voluntarily stopped serving the water from OPA- 1 in September 2018. IRWD partnered with OCWD to construct a new treatment system that removes PFAS from the local groundwater. The treatment facility was completed in 2025 and uses ion exchange technology to remove PFAS from groundwater pumped from OPA-1. With treatment implemented, there are no detectable levels of PFAS in water produced from OPA-1. IRWD drinking water wells 21, 22, and 110 now have detectable levels of PFAS near or above regulatory thresholds of concern, and these wells are not currently served to customers while IRWD evaluates and implements treatment options. None of IRWD’s drinking water served to customers has PFOA or PFOS, or any of the other PFAS compounds above regulatory thresholds including EPA’s recently adopted PFAS Maximum Contaminant Levels (MCLs), which
become effective in 2029. Imported Water Quality
Per Metropolitan’s 2025 UWMP, Metropolitan employs a multi-barrier approach to safeguard the public’s drinking water. The first step in Metropolitan’s multi-barrier approach is protecting the quality of the source water and development of water management programs that maintain and enhance water quality (Metropolitan 2025 UWMP). Contaminants that cannot be sufficiently controlled through protection of source waters are handled through changed water treatment protocols or blending. These practices can increase the costs and/or reduce operating flexibility and safety margins. Metropolitan also implements measures to prevent water quality deterioration in its distribution system after water leaves its treatment plants and ensures distribution system integrity through a regular program of maintenance and inspection and uses chloramines to maintain a stable disinfectant residual in delivered water (Metropolitan 2025 UWMP). The final step in Metropolitan’s multi-barrier approach is routine testing of treated water to monitor the effectiveness of treatment and distribution processes. Metropolitan has reported that to date, it has not identified any water quality risks that cannot be mitigated.
7.4 Drought Risk Assessment
Law
10612. “Drought Risk Assessment” means a method that examines water shortage risks based on the driest five-year historic sequence for the agency’s water supply, as described in subdivision (b) of Section 10635. 10635 (b) Every urban water supplier shall include, as part of its urban water management plan, a drought risk assessment for its water service to its customers as part of information considered in developing the demand management measures and water supply projects and programs to be included in the urban water management plan. The urban water supplier may conduct an interim update or updates to this drought risk assessment within the five-year cycle of its urban water management plan update. The drought risk assessment shall include each of the following: (1) A description of the data, methodology, and basis for one or more supply shortage conditions that are necessary to conduct a drought risk assessment for a drought period that lasts five consecutive water years, starting from the year following when the assessment is conducted.
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IRWD – 2025 Urban Water Management Plan
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