FATE AND TRANSPORT OF PER AND POLYFLUOROALKYL SUBSTANCE CONTAMINATION IN AN UNCONSOLIDATED AQUIFER, NORTH BENNINGTON, VERMONT

Per and polyfluoroalkyl substances (PFAS), globally ubiquitous emerging groundwater contaminants, are commonly found near industrial sites, such as plastics manufacturers, and sites where aqueous fire-fighting foams were heavily used. A large PFAS groundwater plume near an industrial site in North Bennington, Vermont resulted from aerosol deposition on the land surface and subsequent transmission through the vadose zone via infiltrating precipitation. Unconsolidated and bedrock aquifers are contaminated over an area of >100 square miles with over 1,0000 impacted private wells. This study seeks to understand perfluorooctanoic acid (PFOA) fate and transport in a glacial till aquifer, transmission of PFOA contamination from the glacial aquifer to the bedrock aquifer, and partitioning of PFOA between glacial sediments and groundwater. Observations from a network of seven overburden monitoring wells on Bennington College’s campus suggest relationships between local flow patterns and contamination levels. Wells were monitored with pressure transducer/temperature data loggers across seasonal transitions and during slug tests. Local hydraulic conductivities were determined using the Hvorslev slug test method. Wells in the network display order-of-magnitude variation in PFOA concentration over lateral distances of ~50 meters. Preliminary results indicate that lower hydraulic conductivity wells, whose water levels and temperatures respond much more slowly to precipitation events and seasonal changes, have significantly (up to ten times) higher PFOA concentrations than wells with higher hydraulic conductivity wells with faster response times. These patterns suggest dilution of contamination by recent recharge along higher permeability flow paths.