By Lance Green, Friends of Starkweather Creek

It’s been known that for many years PFAS chemicals were released into Starkweather Creek from firefighting training at Dane County Regional Airport and that Wisconsin Department of Natural Resources measurements showed high levels of these perfluoroalkyl and polyfluoroalkyl substances in the creek. You can wade in the creek and downstream lakes without much threat to your health if you avoid drinking the water and wash off afterward. But eating fish from these waters will provide a much larger dose of PFAS. The DNR also posted warning signs and established advisory limits for folks to limit their fish consumption in the creek and the Yahara River lakes downstream.

What are the levels in these waters?

Of the over 14,000 types of PFAS chemicals, health standards have only been established for a few and vary widely across the world. The Environmental Protection Agency’s standards for safe drinking water are 4 parts per trillion for two types — PFOS and PFOA. The DNR standards for surface water are 8 ppt for PFOS and 95 ppt for PFOA. You can compare those numbers with our results below.

In the fall of 2024, Friends of Starkweather Creek began measuring levels of PFAS in Starkweather Creek, the Yahara Chain, Madison Metro Sewage District outfall and other Dane County locations. We decided to sample annually to show current levels and any possible trends. We repeated sampling in the fall of 2025 for the creek, lakes and MMSD outfall. We used Cyclopure samplers that measure 55 different PFAS chemicals.

In the west branch of Starkweather Creek, we found extremely high levels (up to 1,704 ppt PFOS and 139 ppt PFOS) just below the airport, well above DNR standards, although slightly lower than in 2024. Levels got lower as we measured downstream. The west branch above the airport, as well as the east branch, tested well below the DNR standard for PFOS and PFOA, similar to last year.

Levels of PFAS in the Yahara River downstream of Starkweather Creek (lakes Monona, Waubesa and Kegonsa) were also similar to last year (8-12 ppt PFOS, 2-3 ppt PFOA), barely above the DNR standards for PFOS and well below the PFAS standards. Lake Mendota’s water tested nearly PFAS-free in both years.

The sewage district only discharges effluent into Badfish Creek these days, where we measured PFAS levels (6 ppt PFOS, 5 ppt PFOA) close to last year’s results — just above the EPA drinking water standards for PFOS and below state surface water standards.

Future thoughts

We hope future sampling will continue to show a decline of PFAS levels in Starkweather Creek and the downstream lakes. In 2025, the airport began a process to reduce PFAS in some highly contaminated areas. Its recent report showing results is very promising — showing greatly reduced PFAS levels in test wells near the remediation project. We hope this indicates their process is truly breaking down PFAS chemicals into harmless substances.

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