Sonoma: PFAS in city water, idled well tops federal limit

The City of Sonoma has detected PFAS — the long-lived industrial compounds known as “forever chemicals” — in its drinking water system, including one municipal well that tested above the federal limit that took effect in 2024. The amounts reaching Sonoma taps are tiny, and the city says its water still meets state and federal drinking water standards.

Key Takeaways

PFAS turned up in both Sonoma’s purchased Russian River supply and its own groundwater wells, mostly at trace levels.
One city well, Well 2, tested at 6.23 parts per trillion for PFOA — above the EPA’s 4-ppt limit — but it has not sent water into the system since 2020.
The water Sonoma actually delivers stays within state and federal standards, and the city is not recommending bottled water.
The city quietly posted a cluster of question-and-answer pages on June 30 and says it will notify customers if future tests require it.
The EPA set the first national PFAS limits in 2024, then proposed in May 2026 to roll some back and push the compliance deadline to 2031.

PFAS — per- and polyfluoroalkyl substances — are manufactured chemicals used since the 1950s in products that resist heat, oil, grease, stains and water, from nonstick cookware to firefighting foam. They do not break down easily and build up in the environment and in people over time. Federal regulators link long-term exposure to higher cholesterol, immune and liver effects, developmental harm and an increased risk of kidney and testicular cancer.

What the city found

Sonoma buys most of its water from Sonoma Water, the county agency that pipes Russian River supply to nine cities and districts, and supplements it with its own groundwater wells. The city tested both sources under the U.S. Environmental Protection Agency’s fifth Unregulated Contaminant Monitoring Rule, a nationwide sampling program that ran from 2023 through 2025 to help set future standards.

In the purchased Russian River supply, several PFAS compounds showed up at trace levels — PFOA averaging 0.191 parts per trillion, PFOS at 0.26, and a handful of others between 0.06 and 0.26 parts per trillion, with single samples ranging as high as about 1.8 parts per trillion. All of those readings sit far below the state’s notification and response levels.

The city’s own wells told a different story. All but one were non-detect for PFAS. The exception was Well 2, where PFOA measured 6.23 parts per trillion and a related compound, PFHxA, measured 6.13. The PFOA reading is above the EPA’s limit of 4 parts per trillion and above California’s notification level of 5.1, though below the state’s response level of 10.

There is an important caveat printed in the city’s own report: Well 2 “is an active source but has not distributed water into the system since 2020.” Under the EPA’s rule, compliance is judged on the treated water a system actually delivers, sampled where it enters the distribution system — not on a well that has sat idle for years.

Sonoma is not the only wine country town taking a hard look at its supply. St. Helena recently mapped where its drinking water comes from, and to the north, Cloverdale just picked a representative for talks over its water district.

A soft posture, and a flurry of FAQs

The city addressed the detections quietly, posting a cluster of question-and-answer pages to its website on the morning of June 30 — “Is my drinking water safe?” “Does finding PFAS mean my tap water is unsafe?” and “Should I stop drinking tap water or buy bottled water?”

“Based on current monitoring results, water delivered to City of Sonoma customers continues to meet applicable drinking water standards and requirements,” the city says on the first of those pages. It is not recommending bottled water or any change in how residents use their tap water, and it says it will notify customers “promptly” if future testing turns up levels that require public notification or response.

Detecting a chemical, the city notes, is not the same as exceeding a standard: it says modern testing is sensitive enough to find PFAS at extremely small concentrations, and “detecting PFAS does not automatically mean drinking water standards have been exceeded.”

A moving regulatory target

Sonoma’s results land in the middle of a shifting federal picture. In April 2024, the EPA set the first national drinking water limits for PFAS, including a maximum contaminant level of 4 parts per trillion each for PFOA and PFOS. In May 2026, the agency proposed to pull back part of that rule — rescinding limits for several other PFAS compounds and pushing the compliance deadline for PFOA and PFOS out two years, to 2031. The public comment period on those changes closes July 20, with a hearing set for July 7.

That timeline gives systems like Sonoma’s room to plan. It also leaves the 4-parts-per-trillion figure that Well 2 exceeded standing as the federal benchmark, even as Washington argues over when to enforce it.

Sonoma sells its dirt — the terroir that ends up in the glass. Now a forever chemical has turned up in one of its wells, even if that well stopped pumping years ago and the water at the tap tests clean.

Frequently Asked Questions

Is Sonoma’s tap water safe to drink?

The city says yes. It reports that the water delivered to customers continues to meet applicable drinking water standards, and it is not recommending bottled water or any change in how residents use their tap water.

Which well had the high PFAS reading?

Well 2, where PFOA measured 6.23 parts per trillion — above the EPA’s 4-ppt limit. The city’s report says Well 2 is an active source but has not distributed water into the system since 2020, so its water is not what flows to taps.