The Air Force began using a legacy formula of aqueous film-forming foam (AFFF) to extinguish petroleum fires such as those associated with burning aircraft. AFFF is an extremely efficient extinguishing method for widely used across commercial industries and the armed services to extinguish petroleum fires associated with aircraft emergencies. It is also known to have contained PFOS and PFOA.
The U.S. Environmental Protection Agency (EPA) issued provisional health advisories for PFOS and PFOA.
AFCEC launched a comprehensive Preliminary Assessment process to identify Department of Defense installations with fire training areas, emergency response locations, and aircraft crash sites where AFFF had likely been used.
AFCEC concluded its Preliminary Assessment at Davis-Monthan, identifying three areas of interest for investigation. These areas of interest include the DM Fire Training Area near the southeastern end of the DM flight line, a storm-water outfall canal located on the north end of the flight line and four historical crash sites along the length of the flight line where AFFF had been deployed.
The EPA established a lifetime health advisory (LHA) level of 70 parts per trillion for PFOS and/or PFOA. The LHA does not include other PFAS compounds and is only applicable to exposure to PFOS/PFOA via the consumption of drinking water. The LHA is non-regulatory and not enforceable.
Davis-Monthan transitioned from the legacy formula of AFFF to a new formula that meets both military specification requirements for firefighting and the goals of the EPA’s PFOA Stewardship Program. It contains no PFOS and only trace amounts of PFOA, and is not used in training activities. The only time the installation’s emergency responders would use this foam is in the event of a fuel fire. If used, preventive actions would be taken to limit the release of PFOA into the environment. The last time any version of AFFF was used at Davis-Monthan was in 2006, when the 355th Civil Engineer Squadron’s fire department employed it in response to an aircraft emergency on the flight line.
Nine on-base water supply well samples were collected and six tap water sources were tested, which resulted in no detection for PFOS or PFOA.
The Air Force completed enterprise-wide sampling of drinking water to ensure supplies met EPA guidelines. This initial work, coupled with the 2010 Preliminary Assessment has resulted in the Site Inspections that have taken place at installations across the country in recent years, including at DM, and the continued work that is ongoing today.
An initial Site Inspection was conducted, the results of which were released in February 2019. This inspection involved soil samples and groundwater samples collected from the areas of interest identified during the 2015 preliminary assessment. Zero of the groundwater samples taken tested above the EPA’s LHA level of 70 parts per trillion.
Two additional monitoring wells were installed within 100-Acre Wood Park near the northwest boundary of the base. This was accomplished through an agreement between the Air Force, Tucson Water, Pima Flood Control and Tucson Parks and Recreation to minimize impact to the environment while optimizing the ability to obtain accurate groundwater data.
Sample data taken from these wells was released by AFCEC as an addendum to the Site Inspection report in June 2019. PFOS and PFOA were detected at 935 parts per trillion at one well and 14,400 parts per trillion at the second for a combination of PFOS and PFOA, with the concentrations decreasing with depth.
In October, AFCEC initiated a contract for an expanded Site Inspection to test private wells located within one mile down gradient of the installation.
Davis-Monthan and AFCEC identified 14 potential private wells within one mile down gradient of the installation. Every effort was made to contact the well owners to inform them of the EPA’s LHA for PFOS/PFOA, that potential PFOS/PFOA source areas had been identified at Davis-Monthan and to request permission to collect samples from their wells. Two wells were sampled, and neither tested above the EPA’s LHA.
In June, AFCEC awarded a contract for a Remedial Investigation at Davis-Monthan to further study the nature and extent of PFOS and PFOA impact in the area. This investigation is expected to include ongoing sampling of surface water, groundwater, sediment and soil on the base through the fall of 2024. That sampling will be accomplished through the installation and development of an estimated 24 new monitoring wells, 30 to 45 surface sampling locations and 15 soil boring locations.
In July, AFCEC completed developing a Conceptual Site Modeling (CSM) that showed the hydrogeology, ground water flow and the local Tucson area geology that was presented to ADEQ, Tucson Water and City of Tucson. This information has been a very valuable tool as we continue to work together to learn more about the PFSO/FPOA in the Tucson area.
In February, representatives from AFCEC and Davis-Monthan briefed members of the Tucson City Council, Tucson Water, ADEQ, City of Tucson staff members and residents of Ward 6 on Air Force actions to date and its ongoing partnerships with city, state and national regulatory organizations to identify, respond to and prevent PFOS/PFOA impacts on Tucson’s drinking water.
In April, the first phase of Remedial Investigation fieldwork began.
In June, representatives from AFCEC, the National Guard Bureau, Davis-Monthan AFB and Morris Air National Guard Base participated in a second public forum alongside members of the Tucson City Council, Tucson Water, ADEQ, City of Tucson staff members and residents of Ward 6 to provide updates on past and planned future actions to identify, respond to and prevent PFOS/PFOA impacts on Tucson’s drinking water.
In August, AFCEC began its expanded site sampling targeting private wells within two miles down gradient of the installation. AFCEC received permission to test 11 of 19 wells identified in this area. Four were found to be connected to city water, three were not in use and one was used only for irrigation. Results found no detections of PFOS/PFOA above the EPA's LHA in any of the wells sampled.
By the end of September, four monitoring wells were installed in the vicinity of the north end of the base boundary as part of the AFCEC remedial investigation. Information gathered from these monitoring wells will guide the project team towards identifying the source and extent of impact. By the end of December, three additional monitoring wells were installed, bringing the total to seven.
Additionally, an Air Force Environmental Services Agreement (ESA) was approved with ADEQ to begin operation of the PFAS pilot demonstration/treatment facility in October that is immediately off-base to the north. This resource allocation will provide funding associated with plant construction and ongoing operations for up to one year. Data will be shared between ADEQ, City of Tucson, and Davis-Monthan in order to determine the effectiveness of the treatment process, gather aquifer data that may be useful in future cleanup efforts, as well as the immediate removal of contaminants to reduce the impact of PFAS in the local aquifer. The facility began limited operation at the end of December.
The PFAS pilot demonstration/treatment facility was unveiled in a ribbon cutting ceremony in mid-January. The plant uses a former, inactive Tucson Water supply well to clean up to 360,000 gallons per day (source). Full-time operation of the facility began in early February.
The second phase of the Remedial Investigation is expected to begin in Spring 2022 and will include the installation of additional monitoring wells and measuring devices, as well as soil sampling.