Formatted Title
Remediation Case Study of Aqueous Film-Forming Foam (AFFF) Containing Per- and Polyfluoroalkyl Substances (PFAS) Deployed at an Aircraft Crash Site
Background/Objectives
Until recently, emergency responders commonly used aqueous film-forming foam (AFFF) containing per- and polyfluoroalkyl substances (PFAS) at aircraft crash sites. On 25 August 2019, a private C-130 crashed during an emergency landing at the Santa Barbara Airport. Because the crash released approximately 1,440 gallons of Jet A Fuel, emergency responders deployed AFFF as a precaution against fire. This case study, of one of the first substantially complete PFAS remediation projects in California, provides a unique perspective on remediating PFAS from the initial discharge of AFFF to a final remedy.
Approach/Activities
The project team tailored PFAS remediation techniques to the different objectives of three phases of remediation: initial emergency response, interim remedial action, and final remedial action. While designing the three phases, the team had to consider whether remediation techniques were compatible with site conditions, including airport operations, background PFAS conditions, wet-season rainfall, and evolving regulatory standards. The initial emergency response focused on containing and removing AFFF from the crash site. This initial response included AFFF recovery by vacuuming and using absorbents. After the initial response, the AFFF deployment area was delineated and an impermeable cover was deployed in advance of expected rain. The cover was designed to reduce the amount of residual AFFF that stormwater might transport to surface water and groundwater. The protective cover was designed so it did not interrupt airport operations. Installing the protective cover allowed time for the project team to perform a fingerprinting study of the deployed AFFF to differentiate it from background PFAS. The project team delineated and characterized the PFAS in soils before a final remediation strategy was designed and implemented. Pre-characterization of PFAS in soils allowed for removing impacted soil at night when the airport was closed within a 5-hour work window. Throughout the remediation process, frequent communication with the lead regulatory agency, the Central Coast Regional Water Quality Control Board, was essential because California regulatory standards were being developed during the remediation. This collaboration allowed for the remediation design to consider the standards that were in draft but that were expected to eventually influence regulatory closure of the cleanup.
Results/Lessons Learned
This case study presents a site conceptual model, design parameters of the cover installed as an interim remedial measure, soil and groundwater data related to PFAS characterization and fingerprinting, and design of the final remedial action. In addition, this article discusses how the California PFAS standards were applied in the remediation in order to support regulatory closure.