DAVIS-MONTHAN AIR FORCE BASE, Ariz.-- The Air Force Civil Engineer Center (AFCEC) is distributing this public notice to inform the community that an Engineering Evaluation/Cost Analysis (EE/CA) for a Non-Time Critical Removal Action (NTCRA) is available for public review and comment. The EE/CA, dated September 2024, documents AFCEC’s decision to undertake a NTCRA to address releases from the use of aqueous film-forming foam (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) during the U.S. Air Force (USAF) firefighting activities at Davis-Monthan Air Force Base (DMAFB).
The Preliminary Assessment and Site Inspection identified PFAS in regional groundwater through the collection of groundwater samples from monitoring wells within and surrounding DMAFB. Multiple samples had concentrations of combined perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) at or above the U.S. Department of Defense (DoD) screening level of 70 nanograms per liter (ng/L). In August 2023, DoD released new guidelines for the investigation of PFOA and PFOS to account for updated U.S. Environmental Protection Agency (EPA) Office of Water screening levels. AFCEC used the May 2023 EPA Regional Screening Levels (RSLs) of 4 ng/L for PFOS and 6 ng/L for PFOA as a basis for design in this EE/CA. The basis of design that AFCEC used is a combined breakthrough concentration of 10 ng/L based on the May 2023 RSL of 6 ng/L for PFOA and 4 ng/L for PFOS.
Drinking water wells within 4 miles of the northern portion of FT003P-Sub, formerly referred to as the Stormwater Outfall Canal, are impacted by PFAS above the DoD screening level of 70 ng/L. Additionally, drinking water wells further downgradient are at risk of being impacted by PFAS and create an unacceptable risk for human exposure to contaminants (via the ingestion pathway). This NTCRA is necessary due to (1) the exceedance of PFAS above the DoD screening level of 70 ng/L and (2) the potential human exposure to PFAS via ingestion. This EE/CA defines the removal action objectives, identifies and evaluates potential alternatives for completing the NTCRA, and presents AFCEC’s recommended alternative for the installation of a groundwater extraction treatment system using ion exchange resin to extract PFAS from the groundwater then discharging the treated water off site into the Kino Restoration Project Flood Control Basin. AFCEC will implement the NTCRA in accordance with the National Contingency Plan, as presented in 40 Code of Federal Regulations §300.415 Parts (a) and (b) and its applicable subparts, to protect water supply wells impacted from PFAS migrating outside of DMAFB.
The selected alternative satisfies the removal action objectives by preventing the exposure of off-base residents to drinking water that contains PFOS and/or PFOA, individually or combined, at concentrations that exceed the DoD screening level. The recommended removal action alternative will target PFAS from migrating outside of DMAFB and further impacting drinking water wells above the DoD screening level for combined PFOS and PFOA concentrations. It is assumed that as clean water is reintroduced through the area, and the presence of PFAS-impacted water is decreased, the drinking water wells will attenuate and be available for drinking water use once they achieve the cleanup standard. The recommended removal action alternative will also prevent additional drinking water wells located further downgradient from being impacted by the PFAS release.
Interested members of the public are encouraged to review and comment on this EE/CA. During the 30-day comment period, the public may comment in writing to the following address or by e-mail.
Mr. Shane Hansen, Remedial Project Manager
Davis-Monthan AFB
3775 N Fifth St., Bldg. 4201
Davis-Monthan AFB, AZ 85707
E-mail: shane.hansen.4@us.af.mil
Phone: 928-965-0980
A copy of the EE/CA will be available at the Joel D. Valdez Main Library at 101 North Stone Ave., Tucson, AZ, and at the Air Force Administrative Record at the following website: https://ar.cce.af.mil/. The public comment period will be open from December 20, 2024, to January 18, 2025.