September 1997 SD-5 South Groundwater Plume The purpose of this fact sheet is to provide background on the Storm Drain 5 (SD-5) groundwater plume emanating from the Massachusetts Military Reservation (MMR). Cleanup of the SD-5 contamination is divided into three projects: source cleanup, cleanup of the northern part of the plume, and cleanup of the southern part of the plume. The Air Force’s preferred method of treating the source area is under regulatory review. A treatment system is in operation for the northern part of the plume. Alternatives are under consideration to clean up the southern part of the plume. This fact sheet provides background information that will help people make informed decisions about the alternatives for the southern part of the plume. Project managers from the Air Force Center for Environmental Excellence (AFCEE), the U.S. Environmental Protection Agency (EPA), and the Massachusetts Department of Environmental Protection (DEP) will be evaluating alternatives to recommend the most appropriate solutions for the southern part of this plume. The alternatives currently under consideration are described in the fact sheet Storm Drain 5 South Plume Response Alternatives. Public involvement during the decision-making period is critical to selecting an alternative that not only cleans up the southern part of the plume and meets regulatory requirements, but also is most acceptable to the affected communities. This fact sheet (along with the fact sheet called Groundwater Treatment Technologies) will provide background information in an effort to help people make informed decisions. Source of the Plume The source of the Storm Drain 5 (SD-5) groundwater plume is the SD-5 site on the MMR, which historically received runoff from various military and industrial activities on the base. Other sources include several buildings on the western side of Runway No. 5, two underground fuel storage/transfer systems, the Non-Destructive Inspection Laboratory, and the Corrosion Control Shop. A Proposed Plan describing the Air Force’s preferred alternative for addressing the SD-5 source area is currently under regulatory review. AFCEE’s preferred alternative involves excavating contaminated soils and mixing them with asphalt and gravel, which hold the contaminants in place. The asphalt can then be used to pave roads on MMR. What is a Plume? A groundwater plume is a body of groundwater containing contaminants that exceed federal and state drinking water levels or other risk-based levels at multiple test well locations. Contaminated water can result when fuels, solvents, or other contaminants are spilled or released on the ground. When these materials filter through the sandy Cape Cod soil, they encounter groundwater, or the water table, where the soil is saturated with water. As the groundwater moves, the contaminants are carried with it, creating a groundwater plume. Primary Contaminants The primary contaminants in the SD-5 plume are trichloroethylene (TCE) and perchloroethylene (PCE), both of which are chlorinated solvents formerly used at the MMR. The northern part of the plume also contains 1,2 dichloroethylene (1,2-DCE), another chlorinated solvent. The southern part of the plume does not contain 1,2-DCE, but also contains ethylene dibromide (EDB) a fuel additive formerly used at the MMR. Area Affected by the Plume The map on page 4 of this fact sheet shows the groundwater plume, including the existing wells that currently are treating the northern part of the plume. The entire SD-5 groundwater plume is approximately 10,000 feet long, a maximum of 1000 feet wide, and 20 to 100 feet thick. The southern part of the plume is approximately 4,500 feet long, a maximum of 1,000 feet wide, and averages 50 feet thick. Maximum concentrations are approximately 27 micro grams per liter (m g/L) for TCE, 5 m g/L for PCE, 1 m g/L for 1,2-DCE, and 0.12 m g/L for EDB. The SD-5 South plume extends south from the base toward Ashumet and Johns Ponds and is believed to be flowing under and possibly into Johns Pond; studies are currently underway to verify this. The primary contaminants in the plume have not been detected in the surface waters of Ashumet or Johns Ponds. Plume Cleanup Activities To Date: An extraction, treatment, and reinjection (ETR) system was installed in the northern part of the SD-5 groundwater plume. The system consists of 10 extraction and 8 reinjection wells located on-base near the MMR border and an on-base treatment plant for the extracted water. The ETR system draws the water out of the ground and removes the solvent contamination by running the water through activated carbon canisters. The carbon adsorbs, or holds onto, the contaminants. Clean water is then returned to the groundwater by the reinjection wells. The carbon canisters are recycled off-site periodically. Construction began in February 1997 and the system began operation on August 4, 1997, two days ahead of the EPA-enforceable deadline. The groundwater flowing into and the treated water flowing out of the plant was sampled daily during the initial startup period, which ended August 15, 1997. Currently, the water is sampled weekly to ensure the system continues to perform properly. Next Steps: The southern part of the SD-5 plume is one of four plumes currently going through the "decision criteria" process, a public process that enables the remedial project managers and the public to compare and evaluate cleanup alternatives. In the next few months, AFCEE, with oversight by the EPA and the DEP, will determine the most appropriate method for cleaning up the southern part of the SD-5 plume. The process to select that method will use "decision criteria" which will help highlight the tradeoffs associated with different alternatives. The decision criteria focus on protection of human health and the environment, regulatory requirements, effectiveness of treatment technologies, costs, and community acceptance. Public involvement during the decision-making period is critical to selecting an alternative that not only cleans up the groundwater and meets regulatory requirements, but also is most acceptable to the affected communities. The project managers from AFCEE, EPA, and MassDEP invite you to learn about the project and participate in the decision-making process. Opportunities to participate in the decision process include:
The time and location of public meetings will be announced in neighborhood notices, news releases, and advertisements in local newspapers. For More Information Additional information about cleanup activities is available on our website: http://www.mmr.org For more information, please contact the Community Involvement Office for the Installation Restoration Program by calling (508) 968-4678 or by sending an electronic mail message to: jwhitaker@mafmh.ang.af.mil Schedule
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