Jenny Olmsted, P.E.

Mitigation Strategies for PFAS in Stormwater: A Collection of Case Studies

Jenny Olmsted, P.E., Environmental Engineer, CDM Smith

Per- and polyfluoroalkyl substances (PFAS) present a persistent and complex challenge in urban stormwater systems, necessitating innovative management strategies to mitigate environmental and public health risks.  PFAS can enter stormwater systems through multiple pathways including industrial discharges, airport operations, urban surface runoff, and atmospheric deposition, making it challenging to pinpoint and manage sources effectively. PFAS comprise thousands of compounds with varying fate and transport properties.  Monitoring and treating such a diverse group requires specialized analytical methods and tailored treatment technologies. Conventional stormwater structures, such as detention basins and vegetated retention areas, are not equipped to remove PFAS and may inadvertently facilitate their migration into soil and groundwater. Due to their environmental persistence and unique fate and transport characteristics, PFAS that accumulate on both paved and unpaved surfaces can continue leaching into stormwater systems for decades, serving as a long-term source of contamination. Treatment technologies developed for PFAS removal in drinking water and groundwater often face challenges when applied to stormwater due to elevated levels of suspended solids, organic carbon, and other co-contaminants. Many states have yet to establish definitive standards for PFAS concentrations in stormwater, and those that have typically address only a limited subset of compounds. This regulatory void creates uncertainty in setting design goals and determining appropriate treatment targets.    Mitigating PFAS in stormwater requires a tiered approach that balances effectiveness, feasibility, and cost. The first and most proactive strategy is source control, which involves preventing stormwater from contacting PFAS-contaminated media—such as soils, pavement, or industrial materials—through isolation, containment, or diversion techniques. This method minimizes downstream contamination and is often the most cost-effective long-term solution, however successful implementation requires a robust PFAS conceptual site model. The second strategy focuses on optimizing existing stormwater infrastructure, such as retrofitting detention basins or bioretention systems with PFAS-targeted amendments like activated carbon or specialized media. This approach leverages existing assets while enhancing their ability to capture and retain PFAS. The third option is to install dedicated PFAS treatment systems such as advanced filtration units designed specifically for PFAS removal. While these systems can offer targeted performance, they are typically expensive to implement and may be less efficient when dealing with the variable water quality and flow conditions characteristic of stormwater. An integrated strategy that prioritizes source control and infrastructure optimization, with selective use of treatment systems, offers the most practical path forward.    This presentation highlights findings from four case studies on practical strategies for managing PFAS in stormwater systems. Approaches include in situ soil mixing with commercial amendments to reduce PFAS leaching from soil to stormwater and enhancements to existing stormwater control measures using passive sorptive media. It also showcases CDM Smith’s recent work on aerosol and foam enhanced PFAS capture, along with a review of PFAS dynamics in plant-based stormwater systems, all aimed at advancing treatment train implementation. These strategies contribute to a broader multi-stage treatment approach, offering scalable, site-specific solutions for PFAS mitigation.

Jenny L. Olmsted, P.E., is an environmental engineer specializing in the fate, transport, and management of per‑ and polyfluoroalkyl substances (PFAS) in soil, groundwater, concrete, and stormwater systems. Her work focuses on understanding PFAS behavior in urban environments where stormwater infrastructure acts as a primary transport and long‑term source pathway.

Ms. Olmsted has supported PFAS investigations at fire training facilities, industrial sites, and municipal systems impacted by fluorinated foams, urban runoff, and other primary PFAS sources. Her experience includes developing PFAS conceptual site models; evaluating source control strategies; and assessing PFAS migration from soils, concrete, and paved surfaces into stormwater and groundwater. She has contributed to feasibility studies evaluating stormwater‑applicable PFAS mitigation approaches, including in situ soil amendments, sorptive media, and retrofits to existing stormwater controls.

Her background also includes PFAS forensics and background analysis, including evaluation of precursor transformation, source differentiation, and interpretation of PFAS fingerprints to support site investigations. Ms. Olmsted is a licensed Professional Engineer in Florida and Georgia and holds bachelor’s and master’s degrees in environmental engineering from the University of Florida.