Swamp Creek PFAS

Updated August 2025

Snohomish County reported contamination at the Swamp Creek area to Ecology in October 2024. After reviewing the reported contamination, Ecology listed the Site on the Contaminated Sites List in January 2025. The Site is currently being cleaned up independently by Snohomish County under the Model Toxics Control Act (MTCA). As investigations continue at the Site, Ecology may either provide assistance through the Voluntary Cleanup Program, or manage the Site along with the Paine Field Fire Training Pit PFAS site (CSID 16912) located to the northwest in a formal agreement.

The Model Toxics Control Act (MTCA) is Washington’s environmental cleanup law. It provides requirements for contaminated site cleanup and sets standards that protect human health and the environment. Ecology enacts MTCA and oversees cleanups. The MTCA site cleanup process is completed in steps over a variable timeline.

The Swamp Creek PFAS site is located in the southeastern portion of Paine Field near South Everett. It consists of undeveloped wetlands and streams which receive stormwater from the southeastern portion of Paine Field, including Aviation Technical Services (ATS) Hangar 1. These wetlands drain to a stormwater detention pond located southeast of the Airport Road Recycling and Transfer Station between Airport Road and 112th Street Southwest, which in turn drains to a tributary of Swamp Creek.

Based in records and reports, aqueous film forming foam (AFFF), was used as a fire suppressant in the fire control system in ATS Hangar 1. AFFF is known to contain per- and polyfluoroalkyl substances (PFAS). Some types of PFAS, including those found in AFFF, don’t break down easily. Since PFAS can build up in humans and animals, they can increase the risk of negative health impacts.

Releases of AFFF were documented at Hangar 1 in the 1990s and 2000s. As part of an investigation conducted in 2022 to assess the extent of known releases of PFAS in other portions of the airport, a soil sample was collected in the wetlands in the northern portion of the Swamp Creek area. While no PFAS compounds were detected above the relevant MTCA cleanup levels, one compound was detected above laboratory reporting limits.

Soil, sediments from stormwater catch basins, and surface water samples were collected from the Swamp Creek area in February 2024 to determine if AFFF released at ATS Hangar 1 impacted these wetlands. The following contaminants were identified in each media:

• Soil: Perflourooctanoic acid (PFOA), perflourooctane sulfonic acid (PFOS), perflourononanoic acid (PFNA), and perflourohexane sulfonic acid (PFHxS)
  
  
• Surface water: PFOA, PFOS, and PFHxS