PFAS in Stormwater: What We Know
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Per- and polyfluoroalkyl substances (PFAS), including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are a class of man-made chemicals not naturally found in the environment.

Increasingly, studies are showing their ubiquitous occurrence in the environment as well as their potentially negative effects on human and aquatic health. Due to the strength of their carbon-fluorine bonds, PFAS are highly persistent in the environment and difficult to remediate. This presentation will begin with an overview of PFAS sources, physiochemical properties, environmental fate and transport, exposure pathways and toxicology with a specific focus on how these topics impact stormwater. A brief overview of the occurrence of PFAS in drinking water sources in the U.S. as well as a synthesis of the state of knowledge regarding the characterization and remediation of PFAS-impacted sites will also be discussed.

Next, the results of a recent literature review on emerging contaminants in stormwater will be presented including seven studies with detectable concentrations of PFAS compounds from varying landuses. Some studies showed residential stormwater runoff concentrations below EPA's health advisory level of 70 parts per trillion (ppt), while other studies showed concentrations above this level in stormwater runoff from industrial and commercial sites. These results and other implications on future regulations or downstream impacts from stormwater (e.g., risks/concerns of stormwater infiltration on groundwater quality) will be discussed.

This presentation will conclude with an overview of Geosyntec's ongoing applied research PFAS projects, PFAS and specifically, PFAS in stormwater. If available, PFAS removal effectiveness of different media blends (used in bioretention or other best management practices [BMPs]) will be presented along with leaching and sorption results for these media combinations. A recently initiated study in collaboration with Texas Tech University and the U.S. Navy National Warfare Center will also be discussed, including an overview of how this project is implementing a novel study plan to determine how structural BMPs are influencing the loading of PFAS and other pollutants of concern in stormwater and the risks of sediment recontamination. The presentation will then conclude with an overview of outstanding questions and additional research needs to fill present data gaps and further our understanding of the fate and transport of PFAS and PFAS-alternative compounds in stormwater and how to cost-effectively treat them.

The audience will be invited to participate through a Q&A session to understand existing and future PFAS concerns. This presentation is directly related to the conference's theme of "Stormwater… Why We Do What We do: Looking back and Looking forward" as the presentation addresses an emerging stormwater topic in its infancy that is gaining increased awareness due to widespread groundwater/drinking water contamination and has the potential to impact future stormwater management planning.

Publication Summary

  • Geosyntec Authors: Rula Deeb, Adam Questad, Brandon Steets, John Merrill
  • All Authors: Rula Deeb, Adam Questad, Brandon Steets, John Merrill
  • Title: 2019 CASQA Annual Conference
  • Event or Publication: Event
  • Practice Areas: Urban Stormwater Management Planning and Design
  • Citation: Geosyntec will make substantial technical contributions at the California Stormwater Quality Association (CASQA) Annual Conference at the Monterey Conference Center in Monterey, California on October 7-9, 2019.
  • Date: October 7-9, 2019
  • Location: Monterey, California
  • Publication Type: Platform Presentation