SPRING VALLEY — A class of toxic compounds known as "forever chemicals" has been found in the Sweetwater Reservoir, the primary water source for Sweetwater Authority customers in southern San Diego County — including residents of Spring Valley, National City, Bonita, and parts of Chula Vista.

The chemicals, formally known as PFAS (perfluoroalkyl and polyfluoroalkyl substances), are human-made compounds that break down extremely slowly in the environment and have been linked to health risks including reproductive issues, hormonal disruption, and possible carcinogenic effects. Of the 29 PFAS that Sweetwater Authority is required to test for, five were detected — in both the Sweetwater Reservoir and at the Perdue Treatment Plant in Spring Valley.

Authority officials say the water is currently safe to drink, and recent testing conducted in January 2026 showed PFAS levels at their lowest point in more than a year. However, two of the detected chemicals remain close to state health advisory response levels — meaning further increases could require action and potentially push up customer rates.

Environmental engineers hired by the authority estimate it could cost as much as $40 million to fully address the contamination. One promising short-term approach involves blending Sweetwater Reservoir water with transfers from Loveland Reservoir near Alpine, a strategy that reduced PFAS concentrations significantly after a major transfer in December 2025. Officials said that transfer alone could save customers between $12 million and $15 million in water purchase costs over the coming year.

The authority has been proactive compared to state and federal minimums, alerting customers about PFAS in 2024 before it was required. New EPA rules setting federal limits for PFAS in drinking water are scheduled to take effect in 2029, at which point utilities will need full mitigation strategies in place. Sweetwater Authority officials say they are committed to transparency and continuing to hold community workshops as testing and engineering studies progress.