Urban Stormwater PFAS Sources
Stormwater runoff in urban areas picks up PFAS from multiple sources including PFAS-treated surfaces (textiles, carpets, building materials), AFFF residue at fire training sites, leachate from improperly sited waste disposal areas, and atmospheric deposition of PFAS from air. Unlike industrial point sources with permit requirements, stormwater is a diffuse source that is much harder to control and monitor. Urban stormwater PFAS concentrations can range from background levels in areas distant from contamination to significantly elevated levels near PFAS source areas.
Airport and Industrial Site Runoff
Airports with AFFF-related soil contamination represent concentrated PFAS stormwater sources, as precipitation mobilizes PFAS from contaminated soil into runoff that ultimately reaches surface water bodies. Stormwater management systems at these sites — detention ponds, bioretention areas, and stormwater treatment wetlands — typically have limited effectiveness for PFAS removal, as the conventional designs were not intended for dissolved chemical removal. Some airports have implemented activated carbon stormwater treatment systems to prevent PFAS migration off-site.
Infiltration and Groundwater Recharge
Stormwater that infiltrates through soil rather than running off directly to surface water introduces PFAS into the vadose zone and ultimately into groundwater. Permeable pavement, bioswales, and infiltration basins used in low-impact development stormwater management can inadvertently create preferential pathways for PFAS infiltration in contaminated areas. Groundwater recharge from contaminated stormwater has contributed to PFAS contamination in public water supply aquifers in several documented cases.
Regulatory Framework for Stormwater PFAS
The Clean Water Act’s National Pollutant Discharge Elimination System (NPDES) program regulates point source stormwater discharges but has historically not included specific PFAS limits. EPA is developing PFAS effluent guidelines for several industrial categories and may expand stormwater PFAS requirements. States including Michigan have begun requiring PFAS sampling in stormwater discharge permits for high-risk facilities, establishing a framework that may become more broadly adopted as PFAS regulatory attention grows.