Tucson International Airport Area

Tucson International Airport Area

Superfund Site | Tucson International Airport Area: Page 2 of 2

The regional aquifer (historically targeted for groundwater resource development for public water supply purposes) is composed of three major hydrostratigraphic units: the upper zone of the regional aquifer, the lower zone of the regional aquifer, and the undivided regional aquifer. A middle aquitard divides the regional aquifer into upper and lower zones under most of the site.  In the southern and central portions of the site, groundwater contamination has been found mainly within the upper zone of the regional aquifer as the vertical extent of contamination has been limited by the presence of the middle aquitard.

Depth to groundwater in the regional aquifer varies from 80 to 240 feet below ground surface. The general groundwater flow direction is toward the north-northwest. For more detailed discussion of the site hydrogeology of each of the seven TIAA Superfund site project areas, please refer to their individual web pages.

Action Taken

Remediation systems are in operation at TARP, AANG, the Airport Property (Three Hangars), West-Cap, Texas Instruments, and AFP-44.

Status

The Air Force finalized investigation of offsite 1,4-dioxane groundwater contamination north of AFP-44 (North of Los Reales Road/TARP) and proposed technologies to address this contamination.  The existing groundwater remediation system at AFP-44 includes an advanced oxidation treatment system to treat 1,4-dioxane, which began continuous operation in 2009, and air strippers to remove TCE. In 2015, the Air Force issued a Record of Decision (ROD) for No Further Action (NFA) at the 1980s Pistol Range at AFP-44. 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 AFP-44. Currently, the Air Force is working on a Record of Decision Amendment for groundwater to incorporate the advanced oxidation treatment system  They are also working with ADEQ and U.S. EPA to update the operations and maintenance plan for the pump-and-treat system.

The Tucson Airport Authority operates a shallow groundwater zone (SGZ) remedy to treat TCE that includes pumping, treating, and reinjecting SGZ groundwater and a soil vapor extraction (SVE) system. ADEQ and U.S. EPA have engaged the Settling Defendants for the Airport Property project area in a series of technical meetings to try to better understand the local hydrogeology in this area and determine the effectiveness of the SGZ remedy.  Recently, an additional paleochannel with TCE and 1,4-dioxane contaminated groundwater was discovered and these data are being incorporated into the conceptual site model.

The Tucson Water Department constructed an advanced oxidation process (AOP) treatment system that began operating in 2014. The purpose of the AOP treatment system is to remove 1,4-dioxane and TCE from the contaminated regional aquifer groundwater.  Recently, ADEQ and U.S. EPA have agreed that the old air-stripping treatment system can be dismantled because the new AOP system treats both TCE and 1,4-dioxane.

Following issuance of the April 2012 Record of Decision (ROD) amendment for Area B [AANG, West-Cap, West Plume B, and Texas Instruments], U.S. EPA implemented an In-Situ Chemical Oxidation (ISCO) remedy to replace the pump and treat remedy at West-Cap. Texas Instruments also implemented an ISCO remedy, and the National Guard Bureau (NGB)/AANG has implanted an ISCO pilot test. Monitored natural attenuation continues for West Plume B.

For more detailed discussion of the status of each of the seven TIAA Superfund site project areas, please refer to their individual web pages.

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