Development of a Risk-Based Assessment Tool for PFAS Contaminated Sites

Date of Award


Degree Name

M.S. in Civil Engineering


Department of Civil & Environmental Engineering & Engineering Mechanics


Advisor: Denise Taylor


The United States Environmental Protection Agency (USEPA) has a long-standing groundwater policy aimed at preventing adverse effects to human health and the environment and to protect the environmental integrity of the nation's groundwater resources (USEPA, 1991). To that end, EPA considers emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) to pose considerable risk to vital drinking water sources. Despite the concerns with PFAS, science is still determining important factors in the risk they pose to human health and the environment such as fate and transport, toxicology, and effective treatment methods. Of particular concern to Federal facilities is historic use of PFAS containing compounds such as those commonly found in fire-fighting foam. Specifically, the Air Force has used fire-fighting foam for decades because of Federal Aviation Administration requirements and because it has been the best available product to fight hydrocarbon fueled fires. A risk assessment tool was developed through this thesis work and intended for use in analyzing PFAS contaminated sites to rank them relative to the risk they each pose to human health and the environment. The risk assessment coincides with steps normally taken throughout the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) process for site evaluation. Three risk factors were utilized for the assessment: contaminant concentration, exposure pathway, and site hydrogeology. Risk parameters were developed for each factor and scores assigned to each variable. Risk factors and parameters received a weight based on the risk they posed relative to each other. The risk assessment tool was then applied to 36 potentially PFAS contaminated sites on Wright-Patterson Air Force Base (WPAFB).Results of the WPAFB site risk assessment were summarized in a site ranking that was compared to a ranking previously produced through a CERCLA site inspection (SI). The risk assessment ranking was significantly different than the SI ranking. However, the risk assessment presented in this thesis provides a more comprehensive and holistic site assessment. The WPAFB sites were divided into six different categories: test/training areas, hangars, fire stations, emergency responses, surface water outfalls, and other. The risk assessment ranking suggests sites with long term, continued use or sites with very large volumes released pose the greatest risk. These types of sites dominated the top of the ranking. All of the emergency response sites where a one-time, small volume was released all ranked at the very bottom of the ranking. None of these sites were found to have impacted environmental media. Critical to the CERCLA process, especially at Federal facilities, is funding to execute remedial actions. The site ranking provides a basis on which fiscal decisions can be made. For the purposes of this analysis it was assumed the top 5 ranked sites would be considered first for funding and carried on to the next steps in the CERCLA process. Despite the difference in approach for the two assessments evaluated, this thesis risk assessment and the CERCLA SI, the top five ranked sites from the thesis risk assessment included two of the highest ranked sites from the SI. The significance of this is that these two sites clearly pose a risk to human health and the environment and should be included in the remedial investigation regardless of the risk assessment used for site prioritization.


Civil Engineering, Environmental Management, Environmental Engineering, PFAS, PFOS, PFOA, risk assessment, CERCLA

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Copyright 2020, author