Winneshiek County in NE Iowa experiences elevated rates of some waterborne diseases. The area’s karst geology, which provides rapid routes for surface contaminants to reach aquifers, springs, and streams, leads to exposure risks via well water consumption and contact with recreational surface waters, both of which are prevalent in the region. To address these risks, we will collect pathogen data needed for the exposure assessment step of a quantitative microbial risk assessment, as well as pathogen source information necessary for risk management. Samples will be collected from 20 wells during the spring and from 7 surface waters following summer rainfall events. Quantitative PCR will be used to establish the abundance of diverse water-borne pathogens. In addition, species-specific fecal markers will be quantified to establish sources.