1950 - 1970: Historic industrial and defense related activities resulted in the release of hazardous wastes into the groundwater leading to extensive contamination of the regional aquifer. The Airport Property is a source of groundwater contamination to the TARP plume which lies just to the northwest.

1983: The TIAA site was placed on the NPL on September 8, 1983.

1995 - 1997: In 1995, a preliminary feasibility evaluation was completed. In 1996, a remedial investigation (RI) was completed; the RI characterized the extent and concentration of contaminants in the soil and SGZ at the Airport Property project area. In 1997, a feasibility study  report was completed and EPA issued a Record of Decision (ROD) for the soils and SGZ of the Airport Property. From March to May 1997, excavation of PCB-contaminated soils in the El Vado Residential Neighborhood and at the Three Hangers area of the Airport Property was completed. The excavated soils in the residential areas were replaced with clean fill dirt and new landscaping.

1999: A CD was negotiated and signed. This CD formalized agreements between EPA and the Settling Defendants, which included General Dynamics Corporation, McDonnell Douglas Corporation, the City of Tucson, and the TAA. The CD provided for the cleanup of a highly contaminated portion of the Airport Property near the Three Hangars area.  The CD specified that the Settling Defendants will design, build and fund remediation systems in accordance with the ROD and reimburse EPA for past costs. The CD also provided for resolution of other claims between EPA and the Settling Defendants.

The CD calls for four separate remedies for the Three Hangars area: 1) an SVE system to remove TCE from the soils; 2) a groundwater pump and treat remediation system to contain (and if possible, remediate) TCE contamination in the SGZ; 3) excavation and off-site disposal of PCBs and metals-contaminated soils and sediments; and 4) capping and monitoring of an abandoned landfill. Part of the SGZ is included in an area of technical impracticability, meaning that there is no known technology that can provide complete remediation. However, this area will be hydraulically contained and closely monitored to ensure that contamination does not spread, and new technologies will be evaluated as they become available.

2002: The Settling Defendants performed a series of geophysical surveys to guide exploratory drilling in an effort to locate highly transmissive gravel subunits within the SGZ west of the Three Hangars area. Five extraction wells were installed in gravel subunits to cut off the SGZ from the TARP plume. Pumping rates for the five extraction wells were lower than expected.

In August, an SGZ remedy and SVE remedy technical memorandum was completed. This document, also known as the 30% design report, specified that a pump and treat system will be installed to capture and remediate SGZ contamination and prevent this contamination from spreading into the regional aquifer. It also called for SVE treatment of contaminated soils on the Airport Property. Low levels [approximately 3.0 parts per billion (ppb)] of 1,4-dioxane was detected in the upper zone of the regional aquifer, but it is thought to have originated from the AFP-44 site.

2004: The contaminant 1,4-dioxane was detected at up to 36 ppb.

2005: In July, the contractor for the site submitted a proposal to conduct additional investigations to more fully characterize the SGZ at the west end of Runway 3. In this area, carbon tetrachloride-contaminated groundwater was of limited aerial extent, but was not completely characterized.

2006: In March, the contractor for the site submitted the PCB Soils Field Investigation Summary report which detailed the sampling and analysis activities completed as part of the PCB Soils Field Investigation and characterization of the Canale System at the site.  In October, the contractors submitted the PCB soils design report/remedial action work plan, which presented the final design and remedial action work plan for the PCB Remedy for the Airport Property. Also, the Settling Defendants began a pilot test of in-situ oxidation using potassium permanganate to reduce 1,1-dichloroethene (1,1-DCE) concentrations in groundwater at the Samsonite Building Area.

2007: Construction was completed on the groundwater and SVE treatment plant for the Airport Property. Based on the construction inspection report, EPA determined that the treatment plant was operational and functional. On November 5th, EPA, the Arizona Department of Environmental Quality (ADEQ), and the TAA hosted a dedication ceremony for the new groundwater and SVE treatment plant.

The contractor for the Settling Defendants submitted a work plan for additional investigations to delineate the SGZ at the west end of Runway 3. The work plan included borehole drilling, depth specific groundwater sampling, and installation of one or more wells. The purpose of these investigations was to better understand the complex hydrogeology at the site and to delineate the carbon tetrachloride groundwater plume to the west of the Airport Property.

The Settling Defendants continued to monitor groundwater for the reduction of 1,1-DCE at the Samsonite Building Area, where potassium permanganate was previously injected at a series of wells, as part of an in-situ oxidation pilot study. Potassium permanganate was still present in many wells and it appeared that reduction of 1,1-DCE continued.

The Settling Defendants elected to construct a landfill cap in one area of the site that will function as a parking lot. The landfill cap was designed using a model that determines the infiltration rate through the asphalt cover.

2008: The Settling Defendants continued semi-annual water quality sampling and quarterly water level monitoring at the Samsonite Building Area. At the beginning of year, potassium permanganate (which is being used to oxidize 1,1-DCE contamination) was still present in over ten of the wells within the Samsonite Building Area. The Settling Defendants elected not to use an asphalt cover on the TAA landfill and are instead proceeding with a standard RCRA Subtitle D landfill cap design.

2009: The Settling Defendants continued negotiating property access agreements with the Tohono O’odham Nation for a monitor well installation on tribal property. The well will be used to further delineate the carbon tetrachloride groundwater plume near the west end of Runway 3 at the Tucson Airport. The Settling Defendants also submitted a final design for the TAA landfill.

2010: The Airport Property remediation systems continued to operate: The  SGZ remediation system currently includes six groundwater extraction wells pumping groundwater to a treatment facility that uses an Air Stripper to remove VOCs from the extracted groundwater.  The treated water is re-injected into the Regional Aquifer.  The Air Stripper off-gas is treated by vapor phase granular activated carbon (GAC).

The objectives of the SGZ Remedy are to contain contaminated groundwater within the SGZ, prevent contaminant migration from the SGZ to the Regional Aquifer, and to prevent the contamination of previously uncontaminated groundwater while restoring portions of the SGZ to drinking water standards.

The SVE Remedy also continued to operate.  The objectives of the SVE Remedy are to contain the VOC contamination within the Technical Impracticability Zone and to contain the VOC contamination within the area near well SVE-07.

2011: The Settling Defendants for the Tucson Airport Property completed construction work to close the TAA landfill. Final stages of hydro-seeding for the new landfill soil cap were completed in the fall.  Hydro-seeding will allow for natural vegetation to grow at the site.  The final reports for closure of the landfill were submitted in the fall.

2012: The Settling Defendants, which include General Dynamics Corporation, McDonnell Douglas Corporation, the City of Tucson, and the TAA, submitted the construction completion report for the PCB soils remedy in June.

2013: ADEQ performed a pre-certification inspection of the TAA Landfill Remedy landfill cap in Feb.. Both the SGZ remedy system and the SVE system continued to operate and remove VOCs from the groundwater and soil.

2014: The Settling Defendants continued to perform soil boring and groundwater investigations under and near the Three Hangars building in an effort to better understand the hydrogeology in the area. The SGZ remedy [groundwater remediation system] continued to operate throughout 2014. The Settling Defendants also finalized an EPA/ADEQ-approved work plan to perform Soil Vapor Intrusion investigations west of the Airport Property.