Challenges Old and New for an Established Superfund-to-Drinking Water Program in Tucson, AZ

The Tucson International Airport Area Groundwater Remediation Project (TARP) is a Federal Superfund groundwater remediation program that has produced municipal drinking water for the City of Tucson, Arizona’s water customers since 1994. Throughout TARP’s 25-year history, Tucson Water has operated two remediation wellfields and a water treatment plant (WTP) to treat volatile organic chemicals (VOCs), primarily trichloroethene (TCE). In 2002, a second water quality challenge surfaced when 1,4‑dioxane was first detected in TARP groundwater. Tucson Water initially managed 1,4-dioxane concentrations by blending TARP treated water with other potable water sources while studying effectiveness of advanced oxidation processes (AOPs). When EPA reduced the Drinking Water Health Advisory levels for 1,4-dioxane by nearly an order of magnitude in 2011, the blending approach was no longer viable, and Tucson Water completed design and construction of a UV-hydrogen peroxide AOP facility in early 2014. Having solved the TCE and 1,4-dioxane challenges, Tucson Water is now faced with its third water quality challenge at TARP due to PFOA/PFOS levels above EPA’s Drinking Water Health Advisory published in May 2016, along with ongoing operation, maintenance, and replacement challenges for aging wells. This presentation reviews TARP’s history and details its challenges and evolving innovative solutions.