162nd Fighter Wing Arizona Air National Guard

Fighter jet taking off at AANG

AANG | Site History

1956: The base became operational in training functions for various tactical fighter aircraft. The AANG 162nd Tactical Fighter Group Base has been used to train fighter pilots from the United States and other countries. Operations also include aircraft and vehicle maintenance and fueling. These activities resulted in the release of hazardous substances to the soil and groundwater.

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

1995 - 1997: In June 1995, a remedial investigation (RI) was completed. The RI characterized the extent of contamination in the soil and groundwater at the AANG project area. Eight sites were investigated on the AANG property, but only site 5 required active remediation of soil and groundwater. Site 5 included a wash rack area that was used for the engine shop and aircraft maintenance shops from 1959 to 1985.

1995: a feasibility study (FS) for site 5 soils was completed. In February 1996, the Remedial Design for groundwater remediation was completed. In August 1996, a ROD was completed that specified that soil vapor extraction (SVE) would be used to remediate TCE- contaminated soil at site 5.

1996 - 1997: The site 5 SVE system removed approximately 64 pounds of volatile organic compounds (VOCs) and reduced the concentration of VOCs in the soil gas to below the cleanup goal of less than 200 micrograms per liter (mg/l). At this level, groundwater would no longer be impacted. Pursuant to the EPA's 1988 regional groundwater ROD, a groundwater pump and treat system for site 5 was built in 1997. This remediation system extracts contaminated groundwater and removes contaminants using air stripping technology before re-injecting the treated water into shallow vadose zone wells.

2002: In May, EPA and ADEQ completed an RI report that identified the AANG as a source for groundwater contamination at West Plume B.

2003: The AANG completed a Five Year Review (FYR) of their groundwater remediation system to determine if any modifications or improvements were needed. One of the main conclusions of the FYR was that the AANG cannot completely clean up the groundwater at their site until EPA achieves full capture of the upgradient  West-Cap plume.

2004: An amended ROD for groundwater at West-Cap and West Plume B was completed in September.

2005: EPA began remedial design of additional extraction wells at West-Cap.

2006: The AANG installed three new monitor wells on the south end of West Plume B.  Groundwater sample results indicated that these well locations would be useful for possible monitored natural attenuation  monitoring at West Plume B.

2007: To address a data gap, between July and August, the AANG installed six new monitor wells west of the AANG property boundary. The August groundwater sample analysis results for these wells ranged from non-detect to 7.2 ppb for TCE. The U.S. Air Force conducted a Remedial Process Optimization (RPO) at the AANG project area in October. The purpose of the Air Force's RPO process is to evaluate the status and optimize remediation at sites across the United States. The last RPO for the AANG project area occurred in 2002. The RPO occurs in three phases with Phase I focusing on data collection and review, Phase II directed at intensive evaluation of system optimization and applicability of new technologies, and Phase III focused on implementation of recommendations developed from the first two phases. The Air Force conducted Phase I and most of Phase II during a site visit in October.

2008: The AANG began well drilling related to an in-situ pilot study of potassium permanganate at the base.

2009: The groundwater remediation system at the AANG site 5 continued to operate.

2010: In September , the 162nd FW-AANG submitted a report on the results of the ISCO pilot study. The ISCO pilot test evaluated the effectiveness of potassium permanganate (KMnO4) in oxidizing TCE in groundwater.  Results of the ISCO pilot test suggested that TCE was effectively oxidized by the KMnO4. The AANG reported that the TCE groundwater plume in both the upper and lower subunits at the AANG project area appeared to be steadily decreasing.  The reduction of the TCE groundwater plume may be attributed to the combination of remedial actions [ISCO and the GWETRS] in operation at the project area.

2011: EPA issued a proposed plan to amend the existing ROD for the clean-up projects associated with the Area B.  This included the AANG, West-Cap, West Plume B, and the Texas Instruments Project Areas.  In the proposed plan, EPA evaluated several remedial alternatives including ISCO using potassium permanganate.

2012: In April, EPA issued a ROD Amendment.  The ROD Amendment selected ISCO using potassium permanganate to replace the pump and treat remedy at the AANG, West-Cap, and Texas Instruments Project Areas.  The ROD Amendment also concluded that monitored natural attenuation will continue for West Plume B.  The GWETRS was shut down in May and a quarterly groundwater monitoring rebound program began. 

2013: The National Guard Bureau (NGB) and the AANG began discussions with ADEQ and EPA for implementation of the final ISCO phase at the AANG property.

2014: The NGB/AANG began Remedial Design activities to implement the requirements identified in the ROD Amendment. EPA and ADEQ continued to work closely with the NGB/AANG to ensure that the activities were implemented in accordance with the ROD Amendment.