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The Navy is requesting property owner permission to sample private drinking water wells within a sampling area near NSF Thurmont for per- and polyfluoroalkyl substances, or PFAS.

Introduction

PFAS are a family of thousands of different chemicals that have been used since the 1950s in many household and industrial products because of their stain- and water-repellent properties. PFAS are now present virtually everywhere in the world because of the large amounts that have been manufactured and used. Once these compounds are released, many of them tend to stay in the environment for a very long time. The Navy and Department of Defense (DoD) have developed policies to address past releases of PFAS at installations nationwide.

The most common activity that could have resulted in the historical release of PFAS to the environment at NSF Thurmont (Figure 1) is the use of firefighting foam (specifically, aqueous film-forming foam, or AFFF) for testing, training, firefighting, and other life-saving emergency responses. Because of this historical use, PFAS are present in the groundwater at NSF Thurmont and have been detected in nearby drinking water wells that are located in the direction that the groundwater flows away from NSF Thurmont.

On April 26, 2024, the United States Environmental Protection Agency (EPA) published a final National Primary Drinking Water Regulation (NPDWR) establishing nationwide drinking water standards for certain PFAS under the Safe Drinking Water Act. The regulation applies to public drinking water systems. Operators of public drinking water systems regulated by the NPDWR have until April 2029 to meet these standards. In September 2024, DoD published “Prioritization of Department of Defense Cleanup Actions to Implement the Federal Drinking Water Standards for Per- and Polyfluoroalkyl Substances under the Defense Environmental Restoration Program,” which describes DoD’s plans to incorporate the EPA’s drinking water regulation into DoD’s ongoing PFAS cleanups and prioritize actions to address private drinking water wells with the highest levels of PFAS from DoD activities. Table 1 shows the levels that all of DoD, including the Navy, is authorized to use to address PFAS in private drinking water wells.

Table 1 presents the DoD PFAS Interim Action Levels for Private Drinking Water Wells. The DoD’s September 2024 policy memorandum can be found here.

These levels are based on current EPA NPDWR levels. If EPA updates applicable requirements, DoD will review and update its policy as appropriate.

Private Drinking Water Well Sampling near NSF Thurmont

In 2023, the Navy sampled 5 private drinking water wells near NSF Thurmont. At that time the Navy sampled all drinking water sources within the identified sampling area, which include 1 drinking water well in Cunningham Falls State Park, 8 drinking water wells in Catoctin Mountain Park, and Hunting Creek Lake which is a source of drinking water for Cunningham Falls State Park. Perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonic acid (PFOS) were not detected above 70 parts per trillion (ppt), the DoD action level at the time. In consideration of the DoD PFAS Interim Action Levels for Private Drinking Water Wells and on-Facility groundwater concentrations, additional private drinking water sampling is being conducted.

At this time, the Navy is requesting property owner permission to sample private drinking water wells located in the sampling area (Figure 2), including those previously sampled by the Navy.

Actions Based on Private Drinking Water Sampling Results

The preliminary results from the private drinking water well sampling are expected approximately 30 days after collecting the samples. The Navy provides notification to the property owners and tenants of their drinking water results and any follow-up actions, if needed.

The Navy will address PFAS in private drinking water wells in keeping with the DoD policy:

PFAS at or above the DoD PFAS Interim Actions Levels for Private Drinking Water Wells (Table 1). The Navy will work with property owners to implement an enduring solution as soon as possible. Options for enduring solutions may include connection to public water supply or installation of a drinking water treatment system. For any drinking water wells with PFOA and PFOS, individually or combined, above 70 ppt, the Navy can provide bottled water for drinking and cooking to property owners or tenants until a more enduring solution is implemented.

PFAS below the DoD PFAS Interim Action Levels for Private Drinking Water Wells (Table 1). For final remedial actions, the Navy will address drinking water down to EPA NPDWR or background levels in accordance with Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) requirements.

2023 Off-Facility Drinking Water Sampling

In 2023, the Navy sampled water sources based on information that was available at that time about potential PFAS releases at NSF Thurmont. The 2023 sampling area was established 1 mile in the direction that groundwater flows away from the potential release areas. Table 2 provides a summary of the results of the sampling. Table 3 presents the individual well PFAS results to date. There were no detections of PFOA and/or PFOS above 70 ppt, the Navy’s action level at the time. The Navy has re-evaluated the 2023 results using the current DoD PFAS Interim Action Levels for Private Drinking Water Wells (Table 1).

*70 ppt for PFOA and PFOS, individually or combined, was the Navy’s action level at the time of this sampling.

¹For any drinking water wells with PFOA and/or PFOS individually or combined above 70 ppt, the Navy can provide bottled water for drinking and cooking until a more enduring solution is implemented.

Hazard Index. Calculated for HFPO-DA, PFBS, PFNA, and PFHxS when two or more of these compounds are detected in the sample. Calculated per EPA recommendations (Maximum Contaminant Level Goals (MCLGs) for Three Individual Per- and Polyfluoroalkyl Substances (PFAS) and a Mixture of Four PFAS, 2024) as follows:

NC = Not Calculated.

PFOA+PFOS is only calculated when both are detected.

ND = not detected

J = laboratory estimated value

ppt = parts per trillion

Identification of PFAS Releases at NSF Thurmont

In 2021, a comprehensive PFAS Preliminary Assessment was initiated, which identified the following areas where releases of PFAS-containing materials may have occurred.

• Fire Station Area

• Hangar Area

As of June 2025, a Site Inspection of groundwater and soil at these two areas has been completed. A Remedial Investigation is being planned. The Navy will continue investigating PFAS at NSF Thurmont following the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) process and will evaluate if actions are needed.

NSF Thurmont Private Drinking Water Well Sampling Documents

• Private Drinking Water Well Sampling Fact Sheet (2025)

• Open House Posters

• NSF Thurmont Drinking Water Sampling Fact Sheet (2023)

• Drinking Water Sampling FAQ

• Homeowner Questionnaire

• POC card

• Example Letter to request sampling

• Example Results Letter Packet

• On-Base Public Meeting Flyer

Links

• DoD PFAS website

• EPA PFAS website

• ATSDR PFAS website