2025 – 2026: Extraction well E-08R was drilled and constructed. Replacement of recharge well R-24 was initiated in 2026.

In 2025, a final In-Situ Bioremediation and Aquitard Flushing Pilot Test Technical Report for the regional groundwater plume south of Los Reales Road (Site OT012) was issued.

The groundwater pump and treat system shut down in June 2025 when extraction well E-08 became inoperable due to a failure in the well screen. Between 2025 and 2026, replacement extraction well E-08R was installed.

2023: A per- and polyfluoroalkyl substances (PFAS) Non-Time Critical Removal Action was initiated. The planned tasks included bench scale and treatability testing, test well and extraction well installation, and installation of a short-term treatment system with a planned two-year operation. In March 2024, a temporary extraction well was installed at a PFAS hot spot (Fire Engine Wash Area), however, after evaluating the initial results, it was determined that operation of the short-term treatment system at the temporary extraction well was not viable to the concentrations of non-PFAS constituents, including bromide and 1,4-dioxane (1,4-DX). In response, a PFAS treatment system was installed at existing extraction well E-18R. 

A Remedial Investigation PFAS field investigation was initiated to develop a comprehensive understanding of the nature and extent of PFAS constituents in soil, groundwater, surface water, and sediment at identified Aqueous Film Forming Foam (AFFF) sites. The investigation targeted the following locations:

• Fire Engine Wash Area (FEWA)
• Fire Engine Wash Outfall (FEWO)
• Building 864

An indoor air monitoring and Sub-Slab Depressurization System was operated at Building 801 to mitigate vapor intrusion (VI) of trichloroethene (TCE).

2022: Based on a 2021 Site Inspection report, the Air Force conducted an Off-Installation Site Inspection. Two private wells were identified and sampled. Perfluorooctanesulfonic acid was detected at 2.6 parts per trillion (ppt) and 18.6 ppt.

2021: The Air Force issued a Final Site Inspection Report of AFFF areas at Air Force Plant 44 (APF44). The purpose was to evaluate whether AFFF-derived PFAS releases occurred at the Fire Engine Wash Area, Fire Engine Wash Outfall, and/or Building 864.

2020: The Record of Decision (ROD) for OT012 was published. The Selected Remedy consisted of:

• Continued operations and optimization of an existing groundwater pump & treat system to improve removal and containment of contaminants of concern (COCs) within the AFP44 and Los Reales Road boundaries.
• Treatment of hotspot COCs areas in groundwater within the boundary of AFP44 utilizing in-situ treatment technology and/or extraction within the hotspot areas to prevent migration of higher concentrations of COCs to the AFP44 boundary. 
• Long-Term Monitoring (LTM) of groundwater conditions of COCs to measure the progress of remediation.
• Monitored Natural Attenuation (MNA) of the off-site COCs plume looking at the physical and biochemical capabilities of the aquifer to naturally decrease the COCs.
• Institutional Control to prevent use of groundwater within the footprint of OT012.

As part of the PFAS investigation work, 11 monitor wells were installed.

2019: The groundwater treatment plant was shut down from 2019 to 2023. The system was fixed and upgraded.

2017 – 2018: A soil VI study was undertaken to evaluate the nature, extent, and potential health risk associated with Building 801.

In April 2018, a Final Preliminary Assessment Report for AFFF Areas was published. The purpose was to identify locations were use or storage of AFFF may have resulted in releases of PFAS. Of the eight locations identified three were recommended for further investigation (Fire Engine Wash Area, Fire Engine Wash Outfall, and Building 864).

2016: A Focused Feasibility Study for OT012 was published and recommended:

• Continue operation of Pump & Treat system and implementation of remedial process optimization.
• Implement In-Situ Bioremediation with bioaugmentation at “hot spot” or high-concentration source areas for five years.
• Implementing LTM for 20 years followed by MNA of groundwater for 10 years.
• Maintain existing Institutional Controls.

2014 – 2015: From April 2014 to June 2015, hydrofracturing technology was used to cut fissures into the tight formations for 15 injection wells at DP003.

In 2014, the Air Force issued a Proposed Plan for No Further Action at the 1980s Pistol Range. The original public comment period was Sept. 17 to Oct. 16, 2014. In response to community concerns, the comment period was extended to Dec. 4, 2014. The Air Force also began treatability studies to determine the effectiveness of hydraulically fracturing and in-situ treatment of groundwater contamination within fine-grained units underlying AFP44.

2013: The Air Force continued to investigate offsite 1,4-DX groundwater contamination north of Los Reales Road. Once the nature and extent of offsite 1,4‑DX contamination is defined, technologies would be evaluated to address groundwater contamination. The Air Force completed work plans to perform expedited field investigations and treatability studies for alternative remedial actions at AFP44, which were evaluated and approved by ADEQ and the Environmental Protection Agency (EPA).

2012: The Air Force entered into a Performance Based Remediation initiative to maximize the effectiveness of remedial actions at AFP44. As part of this initiative, a new contracting team was hired in late summer. The contracting team was tasked with performing expedited field investigations and treatability studies to provide the Air Force with alternative remedial actions. Revisions to the Site Management Plan of the 2011 Federal Facility Agreement (FFA) were presented.

2011: In September, the Air Force signed an FFA with EPA and ADEQ to clean up property at AFP44. Under the terms of the agreement, the Air Force would work with EPA and ADEQ to remediate areas impacted south of Los Reales Road. The agreement provided for regulatory oversight of the Air Force's Superfund work at AFP44. The agreement ensured that EPA and ADEQ would continue to have an active role in the investigation and cleanup performed. 

To help determine the mechanism by which chromium may be attenuating in the subsurface at Building 801 area, the Air Force collected soil boring and groundwater samples. The data would be validated and a geochemical evaluation of these data would be presented in a forthcoming focused Feasibility Study.

Several activities of the Phase II 1,4-DX focused Remedial Investigation were completed to further define the nature and extent of 1,4-DX in the groundwater.

2010: Several activities of the Phase II focused Remedial Investigation were completed to further define the nature and extent of 1,4-DX in the groundwater. These activities included: documenting potential sources of 1,4-DX, compiling and reviewing existing information related to 1,4-DX in groundwater, and identifying data gaps. The Air Force also further investigated an area of higher TCE contamination near monitor well EPA-03. As a result, ADEQ, EPA, and the Air Force agreed upon two locations where monitor well pairs would be installed to help assess the extent and degree of groundwater contamination.

In-situ pilot studies were continued to evaluate the use of potassium permanganate to degrade Volatile Organic Compounds (VOCs) in groundwater beneath the FACO Landfill and Inactive Drainage Channel Disposal Pits. During this time period, an evaluation was performed of aerobic biodegradation of TCE and 1,4-DX in groundwater.  Results of this evaluation and additional studies would be presented in the focused Feasibility Study for 1,4-DX.

2009: In September, an advanced oxidation groundwater treatment system became fully operational.  The high-pressure oxidation treatment system was designed to remove 1,4-DX while effectively removing VOCs. This new system replaced the air-stripping treatment system, built in 1987.

The Air Force submitted a Phase II focused Remedial Investigation work plan for 1,4-DX. They also submitted a final Shallow Groundwater Zone Remedial Process Optimization work plan that included rotosonic drilling of five boreholes and two or three wells for further characterization of the shallow groundwater zone.

The EPA drafted an FFA and requested comments from the Air Force and ADEQ. This agreement would establish a procedural framework and schedule for developing, implementing and monitoring appropriate response actions at the site. The Air Force, EPA, and ADEQ reviewed information pertaining to the status of solid waste management units as these would be covered under the FFA.

2008: The advanced oxidation treatment system upgrade was delivered to AFP44 in June. The Air Force proceeded with installation of the system.

Since 1996, the duel-phase extraction (DPE) System had pumped and treated shallow groundwater and lowered the water table to expose more of the vadose zone to soil vapor extraction (SVE) treatment. In early 2008, the DPE system was evaluated for operational efficiency and it was determined that it was no longer effective. The DPE system was shut down on Nov. 1, 2008. Together, the DPE and SVE systems removed approximately 107,514 pounds of VOCs from subsurface soils.

The Air Force completed the Phase I focused Remedial Investigation of 1,4-DX. The report included data acquisition and management, review of historical reports and models, and evaluation of 1,4-DX water quality data collected by the United States Geological Survey. In October, the Air Force submitted to the agencies a Shallow Groundwater Zone Remedial Process Optimization workplan, which included installation of new monitor wells.

2007: On July 13, the EPA issued an Administrative Order for Response Action to the Air Force and Raytheon Company to design, build, and operate an advanced oxidation treatment plant at AFP44 for the treatment of TCE and 1,4-DX. This plant would replace the existing treatment plant. EPA issued this order using provisions from the Safe Drinking Water Act. Additionally, in April, EPA issued a draft settlement agreement to the Air Force to initiate a focused Remedial Investigation/Feasibility Study of 1,4-DX.

2006: The United States Geological Survey Arizona Water Science Center and the Air Force Aeronautical Systems Command sampled several wells in July to investigate 1,4-DX contamination in groundwater west of AFP44 and to further define the extent of the 1,4-DX groundwater plume. Thirty-four wells were sampled and 1,4-DX concentrations ranged from non-detect to 11 parts per billion (ppb).

2002 – 2004: During the spring and summer of 2002, 1,4-DX was discovered at the site in concentrations ranging from 1.0 to 54 ppb. In 2004 1,4-DX was detected at 600 ppb from an AFP44 monitor well.

At FACO Landfill post-SVE monitoring was completed. Vadose zone contamination was reduced to a level that would not impact groundwater above the TCE maximum contaminant level.

2000: In September, the ranch site was closed after vadose zone contamination was reduced to a level where groundwater would not be impacted above the maximum contaminant level.

1994 – 1997: A Feasibility Study for soil remediation was completed. From 1994 to 1996, DPE systems were installed to treat VOC-contaminated soils and groundwater. In 1996, large-scale SVE systems were built to remove VOCs from soils. In 1996 and 1997, the Air Force produced a new ROD that specified SVE treatment of VOC contaminated soils at AFP44.

Starting in 1995, nearly 57,000 tons of metals-contaminated soils (cadmium, chromium, and lead) were excavated and removed from the site.

1993: A risk assessment was performed to identify sites that required soil remediation

1991 – 1992: A remedial investigation of soil contamination at AFP44 was conducted, with supplemental field work completed in 1993 and 1995.

1987: A large-scale pump, treat, and reinjection system was constructed. This system was installed to provide containment and remediation of regional aquifer groundwater contamination.

1985: The Air Force issued a ROD for the regional groundwater at AFP44.

1983: The Tucson International Airport Area Superfund site (which includes the AFP44 project area) was added to the National Priorities List on September 8. 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.

1981: The EPA and the Arizona Department of Health Services identified VOCs in the upper zone of the regional aquifer. Beginning this year, the City of Tucson closed all municipal wells that exceeded the state action level for TCE, the primary groundwater contaminant, and notified private well users of the potential risks.

1976: The State of Arizona closed a well at AFP44 due to high levels of chromium.

1950s: The site operated as a federally-owned weapons manufacturing facility under contract by the Raytheon Company (formerly Hughes Missile Systems). The facility occupied over 2 million square feet of buildings. Waste disposal practices included: industrial wastewater treatment, storage, discharge of wastes into unlined surface impoundments, and land disposal of industrial wastewater, spent solvents, dilute acids and concentrated acids and alkalines. Waste disposal practices led to widespread soil and groundwater contamination. Groundwater contamination spread northward (down gradient) beyond the site.

Groundwater contamination was noted in the early 1950s when elevated levels of chromium were detected in a municipal water supply well near AFP44 and when residents complained about water quality problems in their private wells.