Aqueous-film-forming foam (AFFF), containing per- and polyfluoroalkyl substances (PFAS), has long been used for fire-suppression and firefighter training at the Bemidji airport, as it has at many airports across the country. The PFAS have migrated into groundwater and are being captured by the city’s drinking-water-supply wells. In 2017, the Minnesota Department of Health (MDH) updated the health-based advisory values (HBVs) for two types of PFAS. The city asked Barr to identify immediate and short- and long-term response actions to keep their water supply in compliance with the new HBVs.
After developing well-pumping modifications and groundwater modeling to help predict how quickly the water quality would change due to the modified pumping scheme, we then worked with the city to help plan and implement near-term actions while long-term solutions were evaluated.
Barr helped facilitate a granular activated carbon (GAC) accelerated column test and a single-pass ion exchange pilot test to evaluate the most effective PFAS treatment technology and to identify if iron and manganese removal would be needed to facilitate effective PFAS treatment. Barr also assisted the city in forming a technical advisory committee to consult with the MDH on the long-term approach to managing PFAS-impacted drinking water.
We ultimately designed a 2.2 million-gallons-per-day drinking water treatment plant consisting of greensand filtration for iron and manganese removal, followed by GAC treatment for PFAS removal. We prepared plans and technical specifications, cost estimates, and public bidding documents. Barr also helped obtain more than $20 million in bonding and related funding for the project. Our assistance included helping present the project to the Minnesota senate finance committee for inclusion in a state bonding bill.
Construction began in July 2020, and Barr provided full-time construction observation and administration services leading up to the plant’s start-up in early 2021. Bemidji is now benefiting from water that is not only PFAS- and iron-free but also free of manganese, another contaminant of concern identified by the state.