PFAS Around Brunswick Naval Air Station

Map showing the location of the PFAS spill

Map of location of PFAS spill.

On August 19, 2024, an accidental release of approximately 1,450 gallons of PFAS-based Aqueous Film Forming Foam concentrate mixed with 50,000 gallons of water occurred in Hangar 4 on the former Brunswick Naval Air Station. See below for more information about this spill.

Based on data from the Department of Environmental Protection, (DEP), perfluorooctane sulfonate (PFOS) was the primary PFAS compound of the released foam, making up 77% of the measured compounds.

Based on current information, the foam/water mixture released in Hangar 4 entered the stormwater system, which connected to a series of ponds (“Pond A,” “Pond B,” “Picnic Pond”) into Mere Brook. Mere Brook drains into upper Harpswell Cove.

Due to the historic contamination of the Air Station superfund site, this area of Harpswell Cove has been closed for shellfish harvesting since 2016.

This webpage is up to date as of July 29, 2025. Data collection is ongoing and future results will be shared periodically below.

Bigelow Laboratory’s PFAS Monitoring Program

Technician Caitlyn Olsen collectng water samples.

Bigelow Laboratory has been monitoring PFAS in areas around BNAS through a Casco Bay-wide project since 2023 in collaboration with Friends of Casco Bay (FOCB), funded by Maine Sea Grant.

Through 2025, Bigelow Laboratory and FOCB are following up with three bay-wide monitoring campaigns through an EPA/National Estuaries Program-funded project (see map below). In addition, Bigelow Laboratory started a weekly sampling at selected monitoring stations immediately after the spill to complement Maine DEP sampling.

For all monitoring activities, samples are analyzed in the institute's, state-accredited PFAS Facility using EPA Method 1633 (40 PFAS).

Map of PFAS testing stations.

Pre-Spill Concentrations around Harpswell/Brunswick

The map below shows the concentrations of PFOS across Casco Bay in 2023. The numbers show the concentration in nanograms per liter (ng/L) or parts per trillion (ppt).

  • Across Casco Bay, low levels of PFOS were detected at most sites (relative to the new EPA drinking water standards of 4 ng/L or 4 ppt). These concentrations correspond to background levels that can be found in most marine environments along Maine’s coast.
  • Slightly higher values — but still relatively low — were observed along the Kennebec Estuary and in the Androscoggin River. Rivers can be impacted by agricultural runoff from sites that have historically been treated with PFAS-containing biosolids or by discharge of storm- or wastewater.
  • Low-tide PFOS levels were approximately 5 to 10 times the EPA drinking water limits in the mouth of Mere Brook. However, these concentrations were diluted within a short distance; all other Harpswell Cove stations showed background levels of PFOS.
Map showing the concentrations of PFOS across Casco Bay in 2023

Post-Spill Monitoring

Map of the Casco Bay area showing testing sites in relationship to the spill site

Since August 2024, Bigelow Laboratory has performed regular monitoring of PFAS in Harpswell Cove and Harpswell Sound (see map at right).

The bar graphs below show the PFAS concentration as a sum of eight specific compounds (PFOS, PFOA, PFHxS, 6:2FTS, PFHxA, PFOSA, PFNA, PFHpA).

PFAS concentration increased one month after the spill at all stations, and returned to pre-spill levels within two to three months.

bar graphs showing the concentreation levels of PFAS at monitoring sites over time, indicating the decreasing level of PFAS after the spill

More Information

Learn more about the spill and response:

News coverage:

Background and remediation information about BNAS Superfund Site can be found here:

Contact us

Media inquiries: communications@bigelow.org
Project information: caeppli@bigelow.org

 Learn More about PFAS Testing

Brunswick PFAS Spill