Proactive Prediction: Mapping PFAs Risk in Dane County

Abstract

This paper mapped soil and bedrock characteristics, demographic information and the locations of per- and polyfluoroalkyl substance (PFAs) point sources in Dane County, in an attempt to predict municipal wells that would likely test positive for PFAs contamination, and to assess the distribution of exposure risk across different communities. A growing body of research indicates that the ubiquitous dispersal of PFAs in the environment could pose serious harm to humans and other living things, but testing for these compounds is challenging and voluntary. A spatial analysis of PFAs exposure risk in Dane County suggests wells on Madison’s East Side are the most likely to be contaminated. We reached this conclusion after assigning contamination probability scores to municipal wells in Dane County, based on their proximity to PFAs point sources and groundwater contamination susceptibility ratings, which we mapped on ArcGIS. The findings of our study were roughly consistent with the results the City of Madison produced after they carried out actual tests on municipal wells over the course of the fall. Based on the City’s results, our study appears to have underpredicted the number of wells that tested for high levels of PFAs contamination and overpredicted the number that tested for trace amounts. Our paper offers a geographic approach to managing PFAs that could be applied to other emerging contaminants as well. The availability of city-wide test data provides a valuable opportunity to test our spatial analysis against actual conditions, and to refine our methods in the future.