June 3, 2024
On May 29, 2024, the United States Environmental Protection Agency (EPA) issued a unilateral emergency order (Order) to the U.S. Air Force (AF) and Arizona Air National Guard (AANG) pursuant to the Safe Drinking Water Act (SDWA) Section 1431 for per- and polyfluoroalkyl substances (PFAS) contamination from the two parties impacting drinking water supplies for the City of Tucson.
The groundwater supply at issue in the Order has long been the subject of environmental enforcement and remediation due to decades of contamination from multiple nearby sites. AF’s Air Force Plant #44 and Tucson International Airport separately contributed to the contamination through plumes containing trichloroethylene (TCE) and 1,4-dioxane—used at the sites as solvents—migrating from each site into groundwater. This contamination earned the area a spot on the Comprehensive Environmental Response, Compensation, and Liability Act (CERLCA or Superfund) National Priorities List—EPA listed the site in 1983 as the Tucson International Airport Area Superfund Site (Site).
In addition to TCE, 1,4-dioxane, and other contaminants present at the site, PFAS were also later identified as contaminants of concern. PFAS detections in the groundwater at the Site have been found at concentrations as high as 53,000 parts per trillion (also expressed as nanograms per liter). The remedy, referred to as the Tucson Area Remediation Project (TARP), designed to treat the contaminated groundwater at the Site, though modified over the years to address certain later-discovered contaminants, was primarily designed only for treatment of TCE and 1,4-dioxane. The City of Tucson’s Tucson Water, which serves water to Tucson residents, operates the TARP and has taken measures to address PFAS levels in the water. However, challenges with the existing TARP remedy and persistent PFAS contamination have led to wells being deemed unsuitable for use and taken offline, resulting in decreased water supply for the City.
AF’s Plant #44 and AANG’s Morris Air National Guard have contributed to the PFAS contamination, which remains unaddressed at the Site and places a strain on the existing TARP infrastructure. EPA has designated the water source in the area as a sole-source aquifer, meaning that any contamination of or reduction in the water source could be of significant harm to public health.
To address the endangerment posed by these facts, EPA Region 9 issued the Order to AF and AANG. The Order requires the parties to develop a PFAS Water Treatment Plan outlining a long-term PFAS treatment solution, and submit the plan to EPA for approval within 60 days of the Order’s effective date. The plan must include such content as plans for sampling and for addressing high PFAS concentrations and contact information for project leads. Once effective, the parties’ failure to comply with the Order’s requirements could lead to further enforcement action, including penalties for noncompliance, from EPA.