Superfund Site | 162nd Fighter Wing Arizona Air National Guard
EPA #: AZD980737530
Superfund National Priority List (NPL) Status: The EPA listed this site on Sept. 9, 1983
The Arizona Air National Guard (AANG) site is located on the north-central side of the Tucson International Airport and is bounded on the north by Valencia Road, and on the west, south, and east by the Tucson International Airport.
Contaminants of Concern
The current contaminants of concern in groundwater include volatile organic compounds (VOCs); mainly trichloroethene (TCE). Currently, the concentration of TCE in groundwater ranges from less than 0.5 parts per billion (ppb) to 9.3 ppb. The federal drinking water standard for TCE is 5.0 ppb. The Contaminants of concern at the site may change as new data becomes available.
Public Health Impact
The City of Tucson is the main municipal water provider at this site. All municipal wells in the area that were contaminated with TCE have been shut down. Most of the domestic wells have either been shut down or converted to irrigation wells. If you are drinking water from a private well within the boundaries of the TIAA site, please contact the ADEQ Project Manager.
The vadose zone at the AANG project area extends from the surface to a depth of approximately 88 feet below ground surface (bgs) and is composed of silty sands, caliche deposits, and gravelly sands. The upper zone of the regional aquifer consists of two subunits and a middle aquitard. All of the known groundwater contamination at the AANG project area is found in these three hydrostratigraphic units. The upper subunit consists of well-graded, gravelly, course sand and is found at a depth of approximately 88 to 103 feet bgs. The middle aquitard separates the upper and lower subunits and is composed of tight sandy silt with scattered pebbles. The middle aquitard lies at a depth of about 103 to 128 feet bgs. The lower subunit is found at a depth of approximately 128 to 138 feet bgs and is composed primarily of course-grained sand. There is also a northwest-southeast trending sand channel in the lower subunit along the south-central portion of the AANG base.
The groundwater flow direction in the upper and lower subunits is toward the northwest, and the depth to groundwater is approximately 90 feet bgs. More detailed descriptions of the hydrogeology of the AANG project area can be found in reports and studies available at the TIAA Information Repository.
A pump and treat remediation system was installed at the AANG project area in May 1997 to capture and treat groundwater contaminated with VOCs and to prevent offsite migration by maintaining hydraulic control of the TCE groundwater plume. Between May 1997 and May 2012, a total of approximately 820 million gallons of groundwater were treated, and approximately 39 pounds of TCE were removed from the upper regional aquifer. The system was shut down in May 2012 and a quarterly groundwater monitoring rebound program began. An SVE system operated at Site 5 from April 1996 to November 1997, and an In-Situ Chemical Oxidation (ISCO) pilot test was conducted in 2008.
The pump and treat remediation system is still shut down because TCE concentration levels in groundwater are now below federal maximum contaminant levels (MCLs) in most AANG wells.
Following issuance of a Record of Decision (ROD) Amendment in April 2012, EPA and ADEQ entered into discussions with the National Guard Bureau (NGB) and the AANG to implement the ISCO remedy for the AANG site. In late 2014, the NGB/AANG began Remedial Design activities, and in the spring of 2015 the AANG conducted baseline groundwater sampling of approximately 100 monitoring wells within the AANG and West Plume B project areas. EPA and ADEQ are still negotiating with the NGB and AANG to develop a final design and implement the ISCO remedy.
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