Davis-Monthan Air Force Base

Davis-Monthan Air Force Base

Location

Eastern Tucson, Ariz. The northern boundary gradually descends to the south from Golf Links Road to Irvington Road. The eastern boundary is Harrison Road and the western boundary is Alvernon Way. The southern-most boundary is Valencia Road on the east side of the site.

Contaminants of Concern

The contaminants of concern at the ST-35 site include petroleum hydrocarbons and BTEX in soils. The contaminants of concern at the ST-52 and ST-36 sites also include petroleum hydrocarbons. Contaminants of concern at the LF-01 landfill site include methane gas, volatile organic compounds (VOCs), and metals in soil. Contaminants of concern may change as new data become available.

Public Health Concerns

The City of Tucson is the main municipal water provider at this site. All municipal wells in the area that were contaminated have been shut down. The municipal water supply in the area now comes from wells outside the site. A long-term groundwater monitoring program is in place and many of the wells are monitored quarterly.

Site Hydrogeology

DMAFB is located within the Tucson basin, a northwest trending alluvial valley. The Santa Cruz River flows northwesterly and provides the main drainage for the Tucson basin and is located approximately 4.6 miles west of the base. DMAFB is located in the Sonoran Desert which has an arid climate with a low precipitation rate of 12 inches per year and a high evaporation rate of 65 inches per year.

Groundwater occurs within the unconsolidated alluvial deposits consisting of interfingering sand, gravel, silt, and clay. The saturated thickness of these sediments is extremely variable, being thin (less than 200 feet) toward the mountains and thickening (greater than 5,000 feet) toward the center of the basin. These deposits were distributed laterally over time by a constantly changing stream course.

In the vicinity of DMAFB, the Pantano Formation, Tinaja Beds, and Fort Lowell Formation are the primary water bearing units. Groundwater is encountered at approximately 350 feet below ground surface near DMAFB, and groundwater generally flows in a northwest direction.

Action Taken

Most of the areas of contamination at DMAFB have been investigated and remediated. Sites ST-35 and ST-52 had petroleum contamination and were treated with soil-vapor extraction (SVE). ST-36 and ST-55 are also petroleum contaminated sites. ST-36 was treated with SVE and ST-55 will likely receive risk-based closure. RW-16 was a low-level radioactive waste site that has been excavated and closed. Waste from RW-16 was reprocessed in Wampum, Pennsylvania and then buried by Waste Control Specialists in Texas. There were three military munitions sites at DMAFB. Geophysical surveys and limited excavations were conducted and these sites will be closed with land use controls to prohibit residential use. The only remaining active site at DMAFB is LF-01, which was an old landfill. LF-01 had a methane control system and landfill cap installed in 1999. There were no groundwater impacts and LF-01 is now in long-term operation and maintenance of the landfill cap and methane collection system.

Status

A preliminary assessment/site investigation (PA/SI) for per and polyfluorinated alkyl substances (PFAS) was initiated at DMAFB. Completed in 2015, the preliminary assessment identified six areas that require additional investigations, which will be conducted in 2018. 

Pending the results of the PFAS site investigation, all remediation sites at DMAFB should be closed by the end of 2018 with the exception of landfill LF-01, which will continue to need operation and maintenance of the landfill cap and methane collection system.

Community Involvement Activities

There is no community involvement activity associated with this site at this time.