The Navy has conducted sampling of private drinking water sources within a sampling area near NSF Thurmont for per- and polyfluoroalkyl substances, or PFAS. The Navy will continue responding to new requests for private drinking water sampling within the sampling area.
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Property owners with a drinking water source in the sampling area may call 833-222-3282 or email environmental_coordinator@jacobs.com to schedule a sampling appointment.
If you have questions about the drinking water sampling, please email NDW_PublicAffairs@us.navy.mil or leave a detailed voicemail at 833-222-3282. A Navy representative will return your email or call.
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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.
Figure 1 - FACILITY LOCATION MAP
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 memorandum can be found here.
Table 1. DoD PFAS Interim Action Levels for Private Drinking Water Wells
| PFAS |
Level |
| perfluorooctanoic acid (PFOA) |
12 parts per trillion (ppt) |
| perfluorooctane sulfonic acid (PFOS) |
12 ppt |
| perfluorononanoic acid (PFNA) |
30 ppt |
| perfluorohexane sulfonic acid (PFHxS) |
30 ppt |
| hexafluoropropylene oxide dimer acid (HFPO-DA or GenX) |
30 ppt |
| hazard index for mixture of at least two of PFHxS, PFNA, HFPO-DA, and perfluorobutane sulfonic acid (PFBS) |
3 (no units) |
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 five private drinking water wells near NSF Thurmont and all other drinking water sources within the identified sampling area. The sampled sources included one drinking water well in Cunningham Falls State Park, eight drinking water wells in Catoctin Mountain Park, and surface water in 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), which was the Navy’s action level at the time.
In consideration of the DoD PFAS Interim Action Levels for Private Drinking Water Wells (Table 1) and on-Facility groundwater concentrations, additional private drinking water sampling was conducted in September and October 2025. Sampling was offered to property owners of parcels with private drinking water sources located in the sampling area (Figure 2), including those previously sampled by the Navy. None of the samples collected in 2025 contained PFAS levels that are at or above the DoD PFAS Interim Action Levels for Private Drinking Water Wells (Table 1).
Table 2 presents a summary of the drinking water sampling results to date. Table 3 presents the individual drinking water sampling results to date.
Table 2. NSF Thurmont – Off-Facility Drinking Water Sample Results Summary as of November 2025
| Year |
Number of Drinking Water Samples |
Number of Samples with No Detections of PFAS with a DoD PFAS Interim Action Level for Private Drinking Water Wells |
Number of Samples with Detections of PFAS Below the DoD PFAS Interim Action Levels for Private Drinking Water Wells |
Number of Samples with Detections of PFAS at or Above the DoD PFAS Interim Action Levels for Private Drinking Water Wells |
Number of Samples with Detections of PFOA and/or PFOS above 70 ppt[a] |
| 2023 |
19 |
11 |
8 |
0 |
0 |
| 2025 |
25 |
9 |
16 |
0 |
0 |
[a] For any drinking water sources 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.
Table 3. NSF Thurmont – 2023 - 2025 Off-Facility Drinking Water Sample Results
NSF Thurmont – 2023 - 2025 Off-Facility Drinking Water Sample Results
Figure 2 - SAMPLING RESULTS
Actions Based on Private Drinking Water Sampling Results
The preliminary results from the private drinking water 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 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 sources 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.
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.
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Fire Station Area
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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 Sampling Documents