60-16 A Systematic Approach to Testing of Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water in Rural Eau Claire County, Wisconsin

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

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Per- and poly-fluoroalkyl substances (PFAS) are a collection of widely used contaminants, and have been coined as “forever chemicals” due to their long-lasting nature in the environment. Impacts on human health are thought to be associated with the development of cancers, thyroid issues, and reproductive issues. PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) are particularly concerning due to their hazardous health impacts at very low concentrations and their historic widespread use. PFOA was phased out in the United States beginning in 2003 and banned in 2014. PFOS was phased out of production in the United States in 2002.

In 2024, PFAS were detected in exceedance of regulatory recommendations in several private wells in rural southwest Eau Claire County, leading to county-wide systematic testing of select private wells in collaboration with the Eau Claire City-County Health Department. Private wells were selected based on history of land spreading practices, homeowner's permission, and availability of a digital well construction log. A public service announcement was also released by the Health Department to facilitate broadscale testing across the county.

Between July 2024 and April 2025, student researchers at UWEC sampled 147 private wells for metals, nitrate, coliform bacteria, hardness, and PFAS. Samples were analyzed at the Wisconsin State Laboratory of Hygiene following PFAS guidelines in the Wisconsin Expectations document (33 PFAS in 2024, 40 PFAS in 2025, including 18 PFAS compounds regulated in EPA 537.1). All other testing was conducted at the Eau Claire County Health Department. Approximately 23% of the samples collected during that time showed PFAS detection, with 5% exceeding the EPA limit of 4 ppt (parts per trillion) for PFOA and PFOS. Private wells with elevated PFOA and PFOS were mapped alongside historic industrial solids land spreading sites. Visual inspection of this map shows several wells with elevated PFOA/PFOS in close proximity to industrial solids spreading. Due to the recent reduction of materials containing PFOA and PFOS, it is suspected that the PFOA/PFOS  in private wells is from legacy contamination and not related to present day processes, including land spreading. There is not a clear indication of elevated PFAS corresponding with wastewater or septic land spreading. There is no clear relationship between elevated PFAS and exceedances in other water quality parameters, including nitrate.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10633

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