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2025 URBAN WATER MANAGEMENT PLAN <br /> MAY 2026/FINAL DRAFT/CAROLLO <br /> drinking water standards, unmanaged infestations can degrade habitats, clog infrastructure, and reduce <br /> the aesthetic and recreational value of lakes and reservoirs. State and regional agencies continue to <br /> monitor golden mussel movement and evaluate appropriate response strategies to limit their spread <br /> (MET, 2025). <br /> 7.2.3.2 Groundwater <br /> Groundwater is a reliable component of the water supply for Orange County, and the OCWD manages the <br /> Orange County groundwater basin to provide long-term quality and sustainability. The basin supports a <br /> significant portion of the region's water demands and is monitored through an extensive network of <br /> production, monitoring, and recharge wells that provide data on water levels and water quality conditions <br /> across the aquifer system. <br /> Orange County Groundwater Basin <br /> OCWD is responsible for managing the OC Basin. To maintain groundwater quality, OCWD conducts an <br /> extensive monitoring program that serves to manage the OC Basin's groundwater production, control <br /> groundwater contamination, and comply with all required laws and regulations.A network of nearly <br /> 700 groundwater wells provides OCWD a source for samples, which are tested for a variety of purposes. <br /> OCWD collects samples each month to monitor Basin water quality. The total number of water samples <br /> analyzed varies year-to-year due to regulatory requirements, conditions in the basin, and applied research <br /> and/or special study demands.These samples are collected and tested according to approved federal and <br /> state procedures as well as industry-recognized quality assurance and control protocols (City of La Habra <br /> et al., 2017). OCWD routinely tests for hundreds of regulated constituents, but the parameters discussed, <br /> PFAS, TDS, and nitrate, are of focus because they represent the most relevant regional and regulatory <br /> considerations that influence groundwater management and long-term supply planning.These issues do <br /> not indicate that the groundwater basin is unsafe; rather, they are discussed because they are key focus <br /> areas for state agencies and water suppliers throughout Southern California. <br /> PFAS are of particular concern for groundwater quality, and since the summer of 2019, the DDW requires <br /> testing for PFAS compounds in some groundwater production wells in the OCWD area.According to the <br /> EPA, the established federal Maximum Contaminant Levels (MCLs) for certain PFAS compounds in <br /> drinking water, including 4 nanograms per liter (ng/L), or parts per trillion (ppt), for PFOA and PFOS. In <br /> addition, the California State Water Resources Control Board has established health-based Notification <br /> Levels (NLs) and Response Levels (RLs) for several PFAS compounds. The current NLs are 4 ng/L for PFOA <br /> and 4 ng/L for PFOS, while the RLs are 10 ng/L for PFOA and 40 ng/L for PFOS. If PFAS concentrations <br /> exceed the NL,water systems must notify their governing body; if concentrations exceed the RL,water <br /> systems are expected to take corrective actions such as removing the source from service or <br /> implementing treatment. <br /> PFAS have been detected in the OC Basin in very tiny amounts (parts per trillion), entering primarily via <br /> the Santa Ana River whose flows infiltrate into the basin. Despite playing no role in releasing PFAS into the <br /> environment, OCWD is working with its cities and retail water districts to remove it from local water <br /> supplies in order to comply with new state and federal regulations. More than 100 wells have been <br /> impacted due to various state and federal regulations. Fifteen impacted agencies will have to temporarily <br /> purchase more costly imported water to replace PFAS contaminated supplies.As of 2025, 53 impacted <br /> wells are back online due to close to a billion dollars being spent on state-of-the-art testing, research and <br /> CITY OF SANTA ANA <br />