Naval Support Activity Mechanicsburg

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The Navy is requesting property owner permission to sample private drinking water wells within sampling areas near Naval Support Activity Mechanicsburg 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 Naval Support Activity (NSA) Mechanicsburg (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 NSA Mechanicsburg and have been detected in nearby drinking water wells that are located in the direction that the groundwater flows away from NSA Mechanicsburg.

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 regulations 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.

ppt = part(s) per trillion
If EPA updates applicable requirements, DoD will review and update its policy as appropriate.

Private Drinking Water Well Sampling near NSA Mechanicsburg

Certain PFAS have been detected in groundwater at NSA Mechanicsburg above the DoD PFAS Interim Action Levels for Private Drinking Water Wells. The Navy continues to collect additional information about groundwater flow at NSA Mechanicsburg through ongoing investigations. Based on the Navy’s current conceptual site model and understanding of groundwater flow at NSA Mechanicsburg, an expanded sampling area has been established 1 mile in the direction that groundwater flows away from on base locations with detections at or above the DoD PFAS Interim Action Levels for Private Drinking Water Wells (Figure 3).

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 that were previously sampled by the Navy in the 2019 and the 2022 Sampling Areas (Figure 2). . Records indicate that some properties within the three sampling areas receive drinking water from Veolia Water Pennsylvania or Pennsylvania American Water. If your drinking water is provided by Veolia Water Pennsylvania or Pennsylvania American Water, the Navy does not need to sample your drinking water. Property owners and tenants should contact their drinking water provider (Veolia Water Pennsylvania or Pennsylvania American Water) with any questions regarding its treatment and testing of drinking water.

Actions Based on Private Drinking Water Well Sampling Results

The preliminary results from the private drinking water well sampling are expected approximately 30 days after collecting the samples. Once the Navy receives the preliminary drinking water sample results, the Navy will call property owners (and tenants, if present) to provide the preliminary drinking water sample 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 will 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.

2019- 2022 Private Drinking Water Well Sampling

Between 2019 and 2022, the Navy sampled 68 private drinking water wells based on information that was available at that time about potential PFAS releases at NSA Mechanicsburg. The 2019 and 2022 sampling areas, shown in Figure 2, were established 1 mile in the direction that groundwater flows away from the release areas shown in Figure 3. Table 2 provides a summary of the results of the 2019-2022 sampling. There was one detection of PFOA and/or PFOS above 70 ppt, the Navy’s action level at the time; this property has been provided with bottled water for drinking and cooking since the PFOA/PFOS concentration was detected. Table 3 presents the PFAS results for individual wells in the 2019 and 2022 sampling areas. The Navy has re-evaluated the 2019-2022 off-base private drinking water well results using the current DoD PFAS Interim Action Levels for Private Drinking Water Wells (Table 1). Eight (8) private drinking water well near NSA Mechanicsburg contains PFAS at or above these levels. Once the property owner grants permission, the Navy will install an enduring solution.

¹ 70 ppt for PFOA and PFOS, individually or combined, was the Navy’s action level at the time of this sampling.
² Wells with no detections of PFOA and/or PFOS are not included in the count.
 

Hazard Index: Calculated when 2 or more of HFPO-DA, PFBS, PFNA, and PFHxS are detected (USEPA, 2024).
NC = Not Calculated
ND = Not Detected
ppt = parts per trillion
¹ Displays the highest detected result of each PFAS for each drinking water well sampled. Sample numbers do not correspond to a specific property. Table organized based on PFOA+PFOS (ppt) concentrations, least to greatest.

Identification of PFAS Releases at NSA Mechanicsburg

A PFAS Preliminary Assessment (PA) was finalized in 2020 (Tetra Tech, 2020) that identified areas where releases of PFAS may have occurred. Based on the results of the PFAS PA, a PFAS Site Inspection (SI) (Tetra Tech, 2021) was completed. Sample collection and analysis of groundwater and soil were conducted from April 2021 to June 2021. PFAS were found in groundwater and soil at NSA Mechanicsburg. The PFAS sites investigated at NSA Mechanicsburg are listed below and are depicted on Figure 3. Remedial investigations are ongoing at the following release areas:

• Former Building 0-D – Former Firefighting Training Tank

• Former Sanitary Sewage Plant and Sludge Drying Beds

• Helicopter Pad Former Firefighting Training Area

• Lawnmower Fire Area

• Site 3 – Former Ball Road Landfill and Burn Pits

• Building 206 – Fire Department Storage Facility

• Building 306A – Fire Department

• Former Southern Firefighting Training Area

The Navy will continue investigating PFAS at NSA Mechanicsburg following the CERCLA process and will evaluate if actions are needed. To find out more about all of the environmental investigations at NSA Mechanicsburg, visit NSA Mechanicsburg Administrative Record.

NSA Mechanicsburg Private Drinking Water Well Sampling Documents

Private Drinking Water Well Sampling Fact Sheet

Private Drinking Water Well Sampling Initial Notification Letter

Drinking Water Well Questionnaire

Right of Entry Agreement for Sampling of Drinking Water Well(s)

Frequently Asked Questions Drinking Water Sampling for PFAS

Within Sampling Area, but No Private Drinking Water Well Postcard

Open House Posters

Helpful Links

DoD PFAS website

EPA PFAS website

ATSDR PFAS website

To learn more about the Department of Defense’s response to PFAS in private drinking water wells, the November 19, 2024 DoD PFAS Outreach Event recording can be found here.