Regulatory overview of PFAS and identification of potentially impacted sites in Denver, CO using GIS analysis

Abstract

DONLON, JOSEPH D. Regulatory overview of PFAS and identifying potentially impacted sites in Denver, CO using GIS analysis. (Under the direction of Dr. Elizabeth Nichols).

Per- and polyfluoroalkyl substances (PFAS) are considered an emerging contaminant due their persistence in the environment and their ability to cause adverse health effects in humans. Once released into environmental media, they can easily infiltrate to and impact vadose zones and groundwater where they remain for very long periods of time and can be transported great distances with groundwater flow. Most releases of PFAS into the environment can be attributed to industrial discharges, spills, leachate from landfills, and the use of aqueous film-forming foam (AFFF) on class B fires. PFAS have already been identified in numerous drinking water systems and in groundwater across the United States. Given the relatively recent discovery of the adverse health and environmental effects of these chemicals and the widespread impacts already seen across the country, federal, state, and local governments have begun regulating many PFAS, such as PFOA and PFOS. This applies to the State of Colorado which has passed numerous bills and policies that set numeric standards for state waters, limit the use of AFFF, and track facilities that use the chemicals. The U.S. Environmental Protection Agency (USEPA) has set health advisory levels for PFAS in water and is planning on proposing to designate certain PFAS like PFOA and PFOS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), or Superfund. This will have serious implications for sites impacted by PFAS. If EPA identifies or suspects sites of having PFAS impacts, they would be able to order the potentially responsible parties (PRPs) to conduct investigation, remediation, and monitoring efforts until the sites are deemed clean and protective of human health and the environment. Denver, Colorado is one of many places that may be subjected to such enforcement in the future. It is highly likely that PFAS impact exist within the City and County of Denver (CCD) due to the presence of heavy industrial areas, historic urban fill (HUF) areas, and large number of fire stations and fire training facilities. The exact locations of potential impacts are currently unknown so it would be beneficial for CCD to preemptively identify potentially impacted city-owned sites and conduct site investigations, assessments, and before the federal government subjects the city to costly and time-consuming enforcement actions and potential Superfund designations. To help identify potentially impacted sites across the city, a geographic information system (GIS) was used to create a PFAS “heatmap” by running a site suitability analysis utilizing fuzzy analysis. Fuzzy analysis assigns values to cells within a map based on their proximity to certain input factors. The higher the value, the closer to that input the cell is. In this case, the input factors included proximity to fire stations, HUF areas, industrial sites that are suspected dischargers of PFAS, industrial sites that have registered quantities of PFAS, and groundwater accumulation areas. The results of this analysis showed that multiple potential hotspots existed along the South Platte River corridor along the western central portion of the city. This corridor houses many of the city’s industrial zones and HUF areas and is also where much of the local groundwater flows. These factors combined make these locations top candidates for potentially impacted sites and are therefore where preliminary site investigations should begin. CCD has property interest/ownership in some of these areas; specifically in an existing Superfund site and in various areas of right-of-way (ROW). CCD should therefore prioritize investigating these sites in in order to identify actual impacts so they can be remediated, and its future environmental and financial liabilities can be limited.