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Site 1 - Old Incinerator Ash Disposal Area
Site 1, the Old Incinerator Ash Disposal Area, was located at the north edge of the Activity near the Facility Storage Building. Ash from the Old Incinerator had been deposited in this area. Between 1954 and 1973, about 3 tons per year of classified documents and small quantities of paint and film wastes were incinerated at this location. Metals from paint and film wastes were potential sources of contamination to soil and groundwater. A second incinerator was located on the eastern facility boundary near the Advanced Medium Range Air-to-Air Missile Development (AMRAD) Building (not shown on figure).
This site is divided into two areas: a 5,000-square-feet area at the base of the Old Incinerator, which is mostly covered by pavement; and an 8,000-square-feet area to the east of the Old Incinerator, which is covered with fill and is partially re-vegetated.
A risk assessment based on residential use did not identify potential unacceptable human health risks or risks to the environment at Site 1. Therefore, no action is necessary at Site 1 to ensure protection of human health and the environment. A No Further Action ROD was issued in September 2000.
Previous investigations, plans and documentation at this site are: IAS; RI/RA; PP; ROD.
No Further Action
Site 2 - Components Laboratory Fuel Tank
Site 2, the former Components Laboratory Fuel Tank was located at the northeast corner of the Components Laboratory Building (Building 1). It was a 20,000-gallon underground storage tank (UST), which supplied No. 6 fuel oil for boilers from 1953 to 1982. In 1982, the UST was drained, cleaned, and abandoned in-place because of a leak of approximately 200 gallons of No. 6 fuel oil to the surrounding soil. Chemicals of potential concern (COPCs) were total petroleum hydrocarbons (TPH) in soil, and TPH and metals in surface water.
An oil/water separator was installed in 1982 to collect oil and water, which had percolated through the soil as a result of the release. The UST and approximately 50 to 75 cubic yards of oil-contaminated soil were removed in 1989.
A risk assessment based on residential use did not identify potential unacceptable human health risks or risks to the environment at Site 2. Therefore, no further action is necessary at Site 2 to ensure protection of human health and the environment. A No Further Action ROD was issued in September 2000.
Previous investigations, plans and documentation at this site are: IAS; RI/RA; PP; ROD.
No Further Action
Site 3 - Chlorinated Solvent Groundwater Plume, Northern Plume
Site 3 is a dissolved-phase chlorinated volatile organic compound (VOC) plume in groundwater at the northern portion of NWIRP Bedford (north of Hartwell Road) near the Facility Storage Building (FSB) and the Components Laboratory (Building 1). The plume extends primarily northwest to a wetland area on private property. Only trace levels of chlorinated VOCs have reached groundwater beneath Elm Brook. The plume appears to be migrating primarily in the unconsolidated (overburden) deposits. Chlorinated VOCs are slow to migrate from the area because of the nature of the groundwater aquifer (low permeability of the glacial till layers). Elevated chlorinated VOC concentrations are also present in soil throughout the saturated, silty till unit, generally from 30 to 50 feet below ground surface.
The source area of the plume is located under the paved loading dock associated with Building 1. There has been one documented release of 55 gallons of Axothene, which contains 1,1,1-trichloroethane, in the loading dock area of Building 1 in 1976, but no other releases of chlorinated VOCs to the subsurface have been recorded. Potential sources which may have contributed to the Site 3 northern plume include: the Components Laboratory, the FSB print shop, a storm drain connected to the FSB, the Antenna Range Building, the former Transportation Building, the AMRAD building, the former hazardous waste storage area, and the Old Incinerator. Chlorinated solvents could have been released directly to the ground or into the storm drain system, and then released to the groundwater through cracks in the system.
In 1997, the Navy implemented a groundwater extraction and treatment system (GWETS) as an Interim Remedial Action to prevent off-migration of contaminants to the adjacent wetland area and Bedford town wells. Quarterly or semiannual groundwater monitoring has occurred since the treatment system start-up in 1997. The Navy also conducted a pilot electrical resistance heating study to reduce concentrations of chlorinated VOCs in the source area in 2003. The Site 3 ROD was signed in 2010. The remedy for Site 3 included continued operation of the GWETS, and in-situ enhanced bioremediation with injection of emulsified vegetable oil at the Site 3 source area in 2012 and 2017. The current semi-annual groundwater monitoring frequency will continue at Site 3; samples will be analyzed for chemicals of concern (COCs) and natural attenuation parameters. Because of the extent of contamination and the nature of the groundwater aquifer (situated in a tight glacial till and fractured bedrock), the ultimate cleanup of Site 3 is expected to require several decades.
Land use controls (LUCs) were implemented to restrict future use of the site to industrial/commercial scenarios, to prohibit the use of the groundwater aquifer as drinking water, to restrict building occupancy because there is the potential for vapor intrusion from soil, and to require annual inspections of the site to ensure LUCs are continuing to be implemented. An evaluation of human health risk was performed in 2020 to reassess soil human health risks related to the potential land use as residential. The evaluation determined no unacceptable risks to human health from soil exposure. The USEPA and Massachusetts Department of Environmental Protection concurred with the conclusions of the technical memorandum presenting these results.
In 2014, the first Five Year Review (FYR) for NWIRP Bedford identified 1,4-dioxane as an emergent contaminant of concern that is potentially present at the site. Groundwater at Site 3 was analyzed for 1,4 dioxane because of the presence of 1,1,1-trichloroethane, which was commonly stabilized with 1,4 dioxane. A groundwater investigation in 2014 determined that 1,4-dioxane was present at Site 3. 1,4-Dioxane was detected in groundwater samples and was also observed in both the influent and effluent streams of the GWETS. Additional groundwater sampling was performed in 2015 to further delineate the extent of 1,4-dioxane at Site 3. Based on the presence of 1,4-dioxane in groundwater, the groundwater monitoring program for Site 3 was updated to include 1,4-dioxane sampling at select monitoring wells and surface water locations. An addendum to the Sampling and Analysis Plan for Groundwater was completed in September 2019 to detail the changes to the groundwater monitoring program.
A treatability study for 1,4-dioxane in the groundwater treatment system was completed in March 2020. Development of a remedial design to modify the groundwater treatment system for 1,4-dioxane was completed in April 2020. The Navy implemented a modification to the GWETS to include treatment for 1,4-dioxane in 2021.
The Navy is currently conducting a Supplemental Response Action investigation to further improve the current delineation of the chlorinated VOCs and determine the nature and extent of the emerging chemical 1,4-dioxane as well as refine the Navy’s current understanding of the Site 3 source area. Additional monitoring wells are being installed to further characterize groundwater as part of the in-progress groundwater investigation. Based on the results of the groundwater investigation, a Supplemental Response Action Groundwater Investigation of Chlorinated Solvents and 1,4-Dioxane report will be prepared and additional modifications may be made to the remedial actions and long-term monitoring (LTM) program.
Previous investigations, plans and documentation at this site are: RI/RA; FS; PP; ROD; Treatability Study; and Remedial Designs.
Contaminated groundwater extraction and treatment, in-situ enhanced biodegradation, and LUCs have been implemented; Semi-annual Groundwater Monitoring and a Supplemental Response Action groundwater investigation are being conducted; Remedial Action is in progress.
Site 3 - Chlorinated Solvent Groundwater Plume, Southern Plume (SFTA)
Chlorinated VOCs are present in groundwater in the southern portion of NWIRP Bedford south of Hartwell Road in the area known as the Southern Flight Test Area (SFTA). The SFTA site is completely unrelated to Site 3 and is handled as a separate site even though it is referred to as Site 3. The source of groundwater contamination has not been determined; however, the source is not likely to the north because chlorinated VOCs were not detected in groundwater wells upgradient of the highest detected concentrations. The highest concentrations of chlorinated VOCs (predominantly TCE), were detected in two bedrock wells (MW-8B and MW-24R) that are 250 feet southeast of the Hanger Building 5 at depths of 26 to 37 feet below the concrete slab. No VOCs were found in surface soil just beneath the concrete slab. There are no known solvent spills or solvent storage areas in the southern parcel. Therefore, it is the Navy's belief that the original source of the groundwater VOCs in the southern plume is the adjacent Air Force Superfund site (Hanscom Site 1) where groundwater is contaminated with TCE. Groundwater flow in the SFTA is predominantly to the south and southeast in both the surficial and bedrock aquifers.
An RI/RA found no unacceptable risks associated with analytes in soil for current and likely future site use. Groundwater monitoring for monitored natural attenuation evaluation began in 1993. Semi-annual groundwater monitoring was initiated in 2002. In 2008, the Navy and the Air Force signed a Memorandum of Understanding (MOU) to ensure that groundwater monitoring and information sharing would continue for the SFTA and Air Force sites. An ESD was finalized in 2014 to incorporate SFTA into the monitored natural attenuation (MNA) program, and to implement the LUCs established in the Site 3 ROD for the SFTA. This ESD will ensure the continued monitoring, control, and oversight of the SFTA cleanup under CERCLA.
Groundwater monitoring data and TCE concentration trends indicate that the residual contamination in SFTA groundwater is attenuating at a rate such that target groundwater cleanup goals will be met within an acceptable timeframe with the 2015 ESD estimating achievement of the cleanup goals within 9 to 16 years and the April 2018 semi-annual groundwater monitoring report noting attenuation in bedrock groundwater would likely be complete in approximately 20 years. The Navy estimates that by 2030, this site will be clean and the SFTA LUCs can be eliminated. Decreases in TCE concentrations are likely attributable to natural attenuation processes occurring in SFTA groundwater, and to the operation of an Air Force groundwater extraction system located at Hanscom Site 1 to the east of the SFTA to address a separate area of groundwater contamination.
The SFTA property was sold in spring 2019. To support the sale, the Navy prepared these documents: an Operating Properly and Successfully (OPS) Demonstration, an Interim Remedial Action Completion Report (IRACR), Notice of Activity and Use Limitations (NAUL), and an Environmental Condition of Property (ECP).
The FYR required additional/supplemental sampling because of the SFTA's proximity to the nearby fire training area at Hanscom Air Force Base (AFB). There was a high probability that the emergent chemicals, perfluoroalkyl substances (PFAS) (including perfluorooctanoic acid [PFOA] and perfluorooctanesulfonic acid [PFOS]) could have migrated onto Navy property. Initially, the PFAS that were detected in the SFTA groundwater were at concentrations below the public health advisory levels; however, in 2016, EPA significantly reduced the health advisory values for PFOA and PFOS to 70 parts per trillion. Because PFAS concentrations exceeded these criteria, PFAS analysis was added to the LTM sampling events to obtain additional data, but it is not part of the LTM program for the SFTA. Once regulatory guidance is available and sufficient data have been collected, the Navy will coordinate with the U.S. Air Force to determine if additional investigations and evaluation of risk of PFAS in groundwater are warranted based on the concentrations and availability of Tier 1, 2, or 3 toxicity values.
Previous investigations, plans and documentation at this site are: RI/RA; FS; ESD; OPS; ECP; NAUL.
LUCs/NAUL have been implemented; Semi-annual Groundwater Monitoring is being conducted; Remedial Action is in progress.
Site 4 - Benzene, Toluene, Ethylbenzene, and Xylene Plume
A benzene, toluene, ethylbenzene, and xylene (BTEX) plume is associated with releases from maintenance activities at the former Transportation Building and a 7,600-gallon UST which was formerly located there. The BTEX plume in groundwater has migrated to the north of NWIRP Bedford, to an off-property wetland area. Most of the Site 4 plume is comingled with the Site 3 plume.
The UST and approximately 75 to 100 cubic yards of oil-contaminated soil were removed in 1989.
Groundwater impacts were delineated through a series of phased investigations that occurred from 1989 through 1997. BTEX were identified as the COCs in site groundwater. In 1999, the BTEX plume extended over 0.75 acres (approximately 50 feet in width and 700 feet in length) in shallow overburden groundwater.
An RI/RA identified risks if site groundwater was to be used as a drinking water supply. Three rounds of in situ chemical oxidation were conducted from 2000 to 2002, and the changes in groundwater concentrations were monitored. This treatment did not reduce BTEX concentrations sufficiently to achieve the cleanup goal, but helped to reduce contamination. Source area reduction, conducted from 2003 to 2004 with electrical resistance heating, reduced BTEX concentrations by 82.2 to 99.7 percent. Subsequent groundwater monitoring through 2008 showed a rebound in Site 4 plume groundwater BTEX concentrations because of the release of soil-bound BTEX.
The Site 4 ROD was signed in 2009. Selective excavation of the source area described in the ROD was not necessary based on pre-design investigation results. LUCs were implemented to restrict future use of the site to industrial/commercial scenarios, to prohibit the use of groundwater as drinking water, to restrict building occupancy because of the potential for vapor intrusion from soil, and to require annual inspections of the site to ensure that LUCs are continuing to be implemented.
Quarterly groundwater monitoring for the residual groundwater plume was initiated in 2012 until 2019. MNA is occurring at a rate slower than expected. In the 2009 ROD, it was estimated that that the target cleanup goal for BTEX groundwater would be achieved within 5 to 10 years. Recent monitoring shows COC results in the groundwater appear to fluctuate at concentrations near the cleanup goals and the Navy added another 10 years to the LTM program. Based on no further plume expansion and reductions in COC concentration, the groundwater monitoring program for Site 4 was optimized to reduce the frequency of sampling to annually, discontinue sampling at select monitoring wells, and analyze groundwater for benzene only. An addendum to the Sampling and Analysis Plan for Groundwater was completed in September 2019 to detail the changes to the groundwater monitoring program.
An evaluation of human health risk was performed in 2020 to reassess soil human health risks related to the potential land use as residential. The evaluation determined no unacceptable risks to human health from soil exposure. The technical memorandum presenting these results is currently being reviewed by the USEPA and Massachusetts Department of Environmental Protection.
Previous investigations, plans and documentation at this site are: IAS; RI/RA; FS; PP; ROD.
LUCs have been implemented; Annual Groundwater Monitoring is being conducted. Remedial Action is in progress.