2026: An Explanation of Significant Differences to the 2023 Interim Record of Decision (ROD) Amendment for Area A North of Los Reales Road Treatment for Per- and Polyfluoroalkyl Substances (PFAS) is published in June.

The U.S. Environmental Protection Agency (EPA) and the City of Tucson entered into an agreement for a PFAS removal action in March. Treatment technology was to be installed at the existing Tucson Airport Remediation Project (TARP) facility for the removal of PFAS, which is present in groundwater extracted for the trichloroethene (TCE) plume containment.

2023: EPA issued the Third Five-Year Review Report for the Tucson International Airport Area (TIAA) Superfund Site. 

The Arizona Department of Environmental Quality (ADEQ) and the City of Tucson entered into an agreement for reimbursement of qualified expenses up to $24,900 to administer the addition of PFAS treatment to TARP. The agreement was amended and restated in April 2025.

EPA issued an Interim ROD Amendment for the treatment of 1,4-dioxane using Advanced Oxidation Process (AOP) at TARP.

2021: ADEQ funded $2 million dollars to build a temporary pipeline and permanent outfall structure to convey treated water leaving TARP to the Santa Cruz River.

2018: EPA issued the Second Five-Year Review Report for the TIAA Superfund Site.

TARP wells, sampled by Tucson Water, show detections of PFAS.

2014: An AOP water treatment system was incorporated into the existing TARP system. The AOP system removed 1,4-dioxane, as well as other volatile organic compounds, including TCE, from water. The treated water from the TARP groundwater treatment facility was delivered to the Tucson Water department distribution system.

2013: Tucson Water started sampling groundwater at TARP for PFAS.

EPA issued the First Five-Year Review Report for the TIAA Superfund Site.

2010: The Tucson Water Department conducted a pilot testing of ozone‐peroxide and UV light– peroxide advanced oxidation treatment for 1,4‐dioxane and concluded that Ultraviolet light– peroxide was the preferred technology. 

2004: EPA asked Tucson Water Department and TARP representatives to begin a Remedial Investigation/Feasibility Study to evaluate available remedial technologies to address 1,4‐dioxane contamination. 

2003: ADEQ provided funding, from EPA, for Pima Department of Environmental Quality to perform an on-going private well monitoring program (South-Side Private Well Monitoring Program) for 1,4-dioxane and other contaminants.

2002 – 2004: In 2002, ADEQ sampled and analyzed private water wells for 1,4-dioxane as part of the South-Side Private Well Monitoring Program. During the spring and summer of 2002, 1,4-Dioxane was discovered at TARP and Air Force Plant 44 (AFP44) wells ranging from 1.0 to 54 parts per billion (ppb). In 2004, 1,4-Dioxane was detected at 600 ppb from an AFP44 well.

1995: Tucson community members formed a Community Advisory Group called the Unified Community Advisory Board.

1994: The TARP treatment plant began operations.

• From September 1994 to February 2014, groundwater was treated by Packed Column Aeration;
• From February 2014 to the Present, groundwater was treated by AOP;
• In 2003, Tucson Water started blending water because of the presence of 14-Dioxane;
• In April 2020, the Packed Column Aeration Retirement Demonstration was started;
• From June 2021 to November 2021, the plant was shut down. Once restarted treated water was no longer used as drinking water. The treated water is now directed to the Santa Cruz River or the Tucson Water Recycled Water System.

1992: EPA issued a Unilateral Order (UAO; Docket No. 92‐09, July 9, 1992) to Tucson Airport Authority, City of Tucson, General Dynamics Corporation, and McDonnell Douglas Corporation, for performance of a Remedial Investigation/Feasibility Study of the TIAA Superfund Site.

1991: EPA and the Settling Parties entered into a Consent Decree for the TARP.

1988: A ROD was signed by EPA to treat the groundwater north of Los Reales Road by pump and treatment. Treated water was to be discharged to the municipal water distribution system.

The “Feasibility Study for Groundwater Remediation in the Tucson Airport Area” report was released for public review and comment.

1987: EPA sent general notice letters to the potentially responsible parties, officially notifying them of their potential liability for groundwater remedy north of Los Reales Road.

1985: The Arizona Department of Health Services completed the draft final Remedial Investigation for the area north of Los Reales Road. The Arizona Department of Water Resources conducted a feasibility study.

1983: The TIAA Superfund site was added to the National Priorities List (NPL) on September 8, 1983. Soon thereafter, the Air Force began an extensive investigation of groundwater contamination at the AFP44 site, which revealed high levels of TCE in the groundwater.

1982: The TIAA Superfund Site was listed on “Expanded Eligibility List,” a preliminary NPL.

1952: A groundwater sample from a municipal supply well indicated elevated levels of chromium. Residents complained of foul‐smelling water.