Allegany Ballistics Laboratory

Site 1 is situated adjacent to the North Branch Potomac River, along the northern border of the developed portion of Plant 1 at Allegany Ballistics Laboratory (ABL). The site boundary encompasses a total of 13.9 acres with the Active Burning Ground (ABG) consisting of 8.5 acres and the Outside Active Burning Ground (OABG) consisting of 5.4 acres. The ABG is a fenced area currently used for burning reactive wastes and is regulated under a Resource Conservation and Recovery Act (RCRA) permit. The burning of reactive material at the ABG began in 1959. Historical disposal of spent acids and solvents generated by plant operations during the 1970s and 1980s occurred in three former disposal pits located in the ABG. Reportedly, trichloroethene (TCE), a volatile organic compound (VOC), was the primary spent solvent that was disposed in the pits, which are known to be a source of impacts to groundwater. The OABG consists of a 5.4-acre parcel outside of the fenced area that was historically used for the disposal of various wastes (demolition debris, drums, and rocket casings), as well as for burning waste and spreading ash from the early 1960s until approximately 1981. The OABG is no longer in use and the area is not included within the boundaries of the active RCRA permit.

Site 1 has been characterized through several investigations and studies since 1983. The results of a Focused Remedial Investigation for Site 1 indicated that VOCs were the most widespread constituents detected in Site 1 media, with TCE detected most often and at the highest concentrations in soil and groundwater.

In the early to mid-1990s, management of the environmental remediation of Site 1 was separated in two Operable Units (OU) due to the size and complexity of total site cleanup. Site 1 soil (OU-4) was investigated separately from the groundwater, surface water, and sediment (OU-3). A Record of Decision (ROD) was signed in May 1997 for Site 1 groundwater, surface water, and sediment (OU-3). A ROD was signed in September 2014 for Site 1 soil (OU-4).

The selected remedy identified in the ROD for Site 1 OU-3 (groundwater and the surface water and sediment of the North Branch Potomac River adjacent to Site 1 consists of site-wide alluvial and bedrock groundwater containment (i.e., capture and removal) with subsequent onsite treatment and discharge of treated water to the river; long-term monitoring (LTM); and land use controls (LUCs) Construction of a groundwater treatment plant was completed in September 1997. Extraction and treatment of impacted groundwater began in September 1998 and continues today. The plant has treated an average volume of 150 gallons per minute of groundwater extracted from Site 1 since 1998. LTM of groundwater, surface water, and sediment were implemented in 1998 and is ongoing. LUCs are in place to prevent unacceptable exposure to groundwater.

LTM data collected for OU-3 and evaluated in the fifth ABL Five-Year Review indicated there is a potential negative influence on river receptors adjacent to Site 1 but that completion of the remedy for OU-4 is anticipated to positively impact the OU-3 remedy effectiveness. River protectiveness sampling of sediment, surface water, and biota was conducted in 2022 following completion of the OU-4 soil removal action. The evaluation of the 2022 river monitoring data concluded that the data were similar to the 2015 baseline and demonstrates that soil removal activities have not negatively impacted river sediment.

The selected remedy for the ABG identified in the ROD for OU-4 consists of excavation and offsite disposal of impacted soil, LUCs, and long-term management. The remedial action for the ABG was completed in August 2017. The selected remedy for the OABG identified in the ROD for OU-4 consists of removal of surface debris, excavation and offsite disposal of impacted soil, land-use controls, and long-term management. The excavation and soil removal activities at the OABG were conducted from June 2017 to October 2019, followed by site restoration activities, which were completed in 2021. A Remedial Action Completion Report was signed in March 2022 documenting the completion of the remedial action and demonstrating the remedial action objectives had been met and the OU had achieved Response Complete. LUCs are in place to prevent unacceptable exposure to soil.

Detailed information from previous investigations and remedial actions conducted at Site 1 is available in the Administrative Record.

The Site 5 inert landfill operated from the early1960s to 1985, accepting inert wastes generated by Allegany Ballistics Laboratory. The landfill is located on a terrace above the North Branch Potomac River southwest of Plant 1. Inert wastes were defined as wastes neither impacted by explosives nor generated at an area on the facility where explosives were managed.

Several investigations were performed to evaluate the nature and extent of impacts to environmental media at Site 5. In general, low levels of volatile organic compounds (VOCs), pesticides, and inorganics were detected in soil samples collected around the perimeter of the landfill. In addition, the VOC trichloroethene (TCE) was detected in Site 5 groundwater downgradient of the landfill.

The remediation at Site 5 is managed as two separate Operable Units (OUs). A Record of Decision (ROD) for Site 5 landfill contents and surface soil (OU-1) was signed in February 1997. A ROD for Site 5 groundwater, surface water, and sediment (OU-2) was signed in February 2006.

The selected remedy identified in the ROD for OU-1 was an impermeable landfill cap, land-use controls (LUCs), a landfill gas venting system, and post-closure requirements. Landfill cap construction was completed in September 1997, and landfill operations and maintenance and LUCs to prevent unacceptable exposure to landfill contents and associated soil are ongoing as specified in the ROD.

The selected remedy identified in the ROD for OU-2 included installation of a permeable reactive barrier wall filled with zero-valent iron to treat TCE in alluvial groundwater downgradient of the Site 5 landfill. This remedy also included monitored natural attenuation and LUCs. The permeable reactive barrier was installed in June 2006. A long-term monitoring program for groundwater was implemented in 1998 in addition to the O&M activities of the landfill cap remedy. Monitored natural attenuation and LUCs to prevent exposure to unacceptable exposure to groundwater are ongoing.

Per- and polyfluoroalkyl substances (PFAS) were detected at concentrations above United States Environmental Protection Agency Regional Screening Levels in groundwater at Site 5 during a facility-wide Site Inspection conducted for PFAS. The PFAS Site Inspection Report, finalized in December 2023, recommended a Remedial Investigation to further investigate PFAS impacts at the site.

Detailed information from previous investigations conducted at Site 5 is available in the Administrative Record.

Site 10 (formerly designated as Site Production Well A [PWA]) is an 8-acre area located in the south-central area of the developed portion of Plant 1 at ABL. The site consists of the area that includes a former trichloroethene (TCE) still adjacent to Building 157, referred to as former PWA, and former Production Well C.

Previous investigations identified impacts to groundwater attributed to historic activities at Building 157 that involved distillation of used degreasing solvents from the former TCE still that operated adjacent to the Building during 1959 and the early-1960s. Because volatile organic compounds (VOCs) were detected in the PWA well as early as 1980, the use of PWA as a water source was discontinued.

Site 10 is being managed as two separate Operable Units (OUs). An Interim Record of Decision (ROD) for Site 10 groundwater (OU-5) was signed in August 1998. A No Further Action ROD was signed for Site 10 soil (OU-6) in 2007.

The selected interim remedy for Site 10 groundwater was “hot-spot” groundwater extraction with subsequent treatment and discharge of treated water to the river. A treatment facility was designed and constructed near Site 1 to remove hazardous constituents from the extracted groundwater. The implementation of the interim remedial action at Site 10, which initially included three extraction wells connected to the Site 1 treatment plant, was completed in February 1999. Subsequent to the implementation of the interim remedial action, aquifer testing and modeling indicated the need for additional extraction wells at Site 10for the bedrock aquifer to adequately contain impacted groundwater. These changes to the extraction system were implemented in February 2003. This expanded groundwater extraction system was documented as the remedy for Site 10 groundwater in a ROD signed in September 2005. Long-term monitoring, including groundwater sampling, and land use controls (LUCs) to prevent exposure to unacceptable exposure to groundwater are ongoing.

A Vapor Intrusion (VI) investigation was initiated in 2016. Several rounds of VI sampling have been conducted at select buildings at the site to assess VI, the most recent of which occurred in 2022. The results of the investigation indicated potential future unacceptable risks associated with the VI pathway. Therefore, the Navy intends to modify the LUCs to address the VI pathway.

During the 2016 VI investigation, two basement sumps were identified in the occupied portion of one of the site buildings. These sumps were used to prevent basement flooding through redirection of groundwater seepage to a nearby surface drainage. In 2017, the sump water (groundwater) and water and sediment in the drainage ditch downstream from the building were sampled for tetrachloroethene and TCE. While the risk screening concluded these data pose no unacceptable risks to human health or the environment, the ROD specifies that groundwater will be used for environmental monitoring and extraction purposes only so an Explanation of Significant Differences was finalized in 2019 to allow an exception for the groundwater to be pumped from the sump in the basement of the building.

The fifth Five-Year Review for Allegany Ballistics Laboratory, finalized in 2018, recommended improvement to the existing groundwater remediation system effectiveness. An investigation was completed in 2019 to refine the extents of the VOC plumes at the site and a pilot study began in July 2020 to evaluate the groundwater VOC plume while the extraction system was shut down. The pilot test was completed in 2022. Based on the favorable results of the shutdown, lack of plume expansion, multiple lines of evidence supporting natural attenuation, and low residual VOC concentrations, it was determined the system would remain off and additional data would be collected to support a remedy transition to monitored natural attenuation with LUCs. Planning for the additional pilot study data collection is ongoing and data collection is expected to begin in 2026.

Per- and polyfluoroalkyl substances (PFAS) were detected at concentrations above United States Environmental Protection Agency Regional Screening Levels in groundwater at Site 10 during a facility-wide Site Inspection conducted for PFAS. The PFAS Site Inspection Report, finalized in December 2023, recommended a Remedial Investigation to further investigate PFAS impacts at the site.

Detailed information from previous investigations conducted at Site 10 is available in the Administrative Record.

Site 11 originally consisted of a boiler house (Building 215), fuel oil storage area, and a deep bedrock production well known as F-Well. The original boiler house, built in the late1950s, was approximately 1,000 square feet and housed a single boiler unit. In 1961, F-Well was installed adjacent to Building 215 to provide potable water to Plant 1 as well as to the boiler housed in Building 215. Following its installation, attempts to use F-Well were unsuccessful due to sand flowing into the well through fractures in the bedrock and as a result F-Well was never put into production. In 1962, an addition was added to the boiler house that doubled its size and the number of boilers. During this expansion, F-Well was covered by the building addition’s foundation. In the late1980s, the boiler house was decommissioned.

In 1995, an Advanced Site Inspection was conducted to characterize potential groundwater and soil impacts in and around F-Well and a former oil pit. Prior to the Advanced Site Inspection, the facility removed the former oil pit and any visibly impacted soil. The ASI identified a limited area of soil impacts and an area of alluvial and bedrock groundwater impacts. Furthermore, light aqueous phase liquid (LNAPL) and dense aqueous phase liquid (DNAPL) were detected in F-Well during a downhole video camera survey and over-drilling activity. The LNAPL and DNAPL were removed during the over-drilling activity. Several investigations were conducted following the Advanced Site Inspection, identifying volatile organic compounds and inorganic impacts to groundwater.

A Record of Decision (ROD) for Site 11 was signed in January 2012 (the ROD was combined for Sites 11 and 12 because of their close proximity to each other and similar impacts). The selected remedy for Site 11 is focused enhanced anaerobic biodegradation, monitored natural attenuation, and land use controls (LUCs). Remedial action at Site 11 took place on November 2012 and included injection of a carbon-containing material to the groundwater to treat chlorinated compounds using enhanced reductive dechlorination, in accordance with the ROD. Long-term monitoring, including groundwater sampling, and LUCs to prevent unacceptable exposure to groundwater are ongoing.

Detailed information from previous investigations conducted at Site 11 is available in the Administrative Record.

Site 12 (formerly designated as Area of Concern [AOC] N) is located in the northwestern portion of Plant 1, just north of Site 11. Five solid waste management units (SWMUs) are associated with Building 167, located within Site 12. A list of the SWMUs are provided below.

• SWMU 12 Former Alodine Treatment Tank

• SWMU 14 Current Alodine Waste Storage Area I (no longer in use)

• SWMU 24S Building 167 Satellite Accumulation Area I (outside building)

• SWMU 37N Building 167 Wastewater Sump

• SWMU 52 Current Alodine Treatment Tank (no longer in use)

Several investigations have been conducted at these SWMUs and a removal action was performed in 2000 to remove the wastewater sump located at SWMU 37N, its contents, and potentially impacted soil immediately surrounding the unit. The results of the investigations and post-confirmatory soil sampling indicated that several inorganic constituents and several organic constituents were present in soil above risk-based screening criteria and in groundwater above risk-based screening criteria. During subsequent investigations, volatile organic compounds were discovered in the alluvial aquifer and based upon these investigations it was determined AOC N be designated as a Site 12.

In 2005, a soil excavation with off-site disposal was conducted to address human and ecological risks identified in Site 12 soil. The Remedial Investigation at Site 12 was finalized in 2009. A Record of Decision (ROD) for Site 12 was signed in January 2012 (the ROD was combined for Sites 11 and 12 because of their close proximity to each other and similar impacts). The selected remedy for Site 12 is focused enhanced anaerobic biodegradation, monitored natural attenuation, and land use controls (LUCs). Remedial action at Site 12 took place on November 2012 and included injection of a carbon-containing material to the groundwater to treat chlorinated compounds using enhanced reductive dechlorination, in accordance with the ROD. Long-term monitoring, including groundwater sampling, and LUCs to prevent unacceptable exposure to groundwater are ongoing.

A Vapor Intrusion (VI) investigation was initiated in 2016. Several rounds of VI sampling have been conducted at select buildings at the site to assess VI, the most recent of which occurred in 2022. The results of the investigation indicate potential unacceptable risks associated with the VI pathway. Therefore, the Navy intends to modify the LUCs to address the VI pathway.

Detailed information from previous investigations conducted at Site 12 is available in the Administrative Record.

Site 13 (formerly designated as a portion of solid waste management unit [SWMU] 27A) consists of an area of trichloroethene (TCE) impacts to alluvial groundwater, at an area where the SWMU 27A drainage ditch crosses Range Road. The Range Road Area is in the southeastern portion of Plant 1.

The investigations for Site 13 sought to identify the source of the TCE impacts, which had sporadically been detected in various outfalls during the National Pollutant Discharge Elimination System monitoring program. Because TCE is no longer used at the facility, it was determined that impacted groundwater near the Range Road intersection was the source of the TCE impacts in the drainage ditch. Subsequent investigations identified TCE in groundwater trending to the east-northeast and roughly parallel to the Plant 1 drainage system near the Range Road and H Street intersection.

Though there are no known potential sources of TCE at Site 13, a search of historical information conducted during the Phase III Investigation revealed that there was a boiler (Building 106A) northeast of the Range Road and H Street intersection where degreasing operations dating to 1952 were conducted. No potential source of TCE southwest of the intersection was identified.

The Navy is currently developing a combined Remedial Investigation and Feasibility Study for Site 13, which is expected to be finalized in 2025.

Detailed information from previous investigations conducted at Site 13 is available in the Administrative Record.