Community Guide to the Installation Restoration Program at the Massachusetts Military Reservation, Summer 1998

Storm Drain 5 (SD-5) Groundwater Plume

Source of the Plume

The source of the Storm Drain 5 (SD-5) groundwater plume is the SD-5 site, which received surface runoff from various military and industrial activities on the MMR. Other sources include two underground fuel storagetransfer systems, the Non-Destructive Inspection Laboratory, the Corrosion Control Shop, and buildings on the western side of Runway No. 5.

The proposed plan for "Six Areas of Contamination" includes a description of the Air Force’s preferred alternative for addressing the SD-5 source area. This proposed plan was released for public comment in November, 1997, and has been approved by the regulatory agencies. The Record of Decision is currently under regulatory review. AFCEE’s preferred alternative consists of excavating contaminated soils and mixing them with asphalt and gravel to hold the contaminants in place. The asphalt will then be used as a base of sub-base material for roads on the MMR.

Primary Plume Contaminants

The primary contaminants in the SD-5 plume are TCE and PCE, both chlorinated solvents formerly used at the MMR. The northern part of the plume contains 1,2-dichloroethylene (1,2-DCE), another chlorinated solvent. The southern part of the plume does not contain 1,2-DCE, but the fuel additive EDB formerly used at the MMR has been detected sporadically there. Maximum concentrations that have been detected are 43 ppb for TCE, 5 ppb for PCE, 1 ppb for 1,2-DCE, and 0.12 m g/L for EDB. The safe drinking water standards, or safe drinking water standards, are 5 ppb for TCE, PCE, and 1,2-DCE, and .02 ppb for EDB.

Affected Area

The SD-5 groundwater plume is about 10,000 feet long, approximately 500 feet wide in the north and a maximum 1,000 feet wide in the south, and 20 to 100 feet thick. The southern part of the plume is about 4,500 feet long, a maximum 1,000 feet wide, and an average 50 feet thick.

The SD-5 South plume extends from the southeast base boundary toward Ashumet and Johns Ponds and extends beneath and into Johns Pond. The primary contaminants in the plume have not been detected in the surface waters of Ashumet or Johns Ponds.

Plume Cleanup

An ETR system was installed in the northern part of the groundwater plume. The system consists of 10 extraction wells and 8 reinjection wells near the MMR border and a treatment plant for the extracted water, all located on the base.

Interior of the SD-5 North ETR Treatment Plant

The ETR system draws the water out of the ground and removes the contamination by running the water through canisters of activated carbon. The carbon adsorbs, or holds onto, the contaminants. Reinjection wells return the clean water to the aquifer. The carbon canisters are recycled off-site. Construction began in February 1997, and the system began operation on August 4, 1997, 2 days ahead of the EPA deadline.

Groundwater flowing into and treated water flowing out of the plant is sampled weekly to ensure that the system continues to perform properly.

The southern part of the SD-5 plume was one of four plumes to undergo the "decision criteria" process in 1997, a public process that enabled the remedial project managers and the public to compare and evaluate cleanup alternatives.

In December 1997, after careful consideration of the advantages and disadvantages of each plume response alternative and comments received during the public comment period, the remedial project managers from AFCEE, EPA, and MassDEP decided on an alternative to treat the SD-5 South plume.

The selected alternative uses recirculating well technology to reduce the contaminant mass. Recirculating wells will be installed along Hooppole Road and within the body of the plume. The exact locations and number of wells, and other refinements of the remedial system, will be determined during engineering design. Maximum engineering flexibility will allow for good design using the most up-to-date technical information about the plume.

Next Steps

• Analysis of data gaps began in the spring of 1998. Results are available to the public. Data gap analysis included drilling on Johns Pond in June 1998 to collect samples from beneath the pond bottom.
• Engineering plans will be re-evaluated as a result of the data gap analysis. Following this evaluation, design of the selected system will begin. Plans will be made available to the public.
• Information updates will be provided to the public periodically.
• AFCEE representatives will meet with neighborhood groups and other community groups as requested.
• Coordination among AFCEE, EPA, DEP, citizen advisory teams, and the affected communities will continue.
• AFCEE, EPA, and MassDEP encourage residents to attend citizen process action team and public meetings, become involved with the SD-5 South cleanup, and sign up on the site mailing list to receive updates.
• The public will be notified before work begins and during key construction activities.
• The enforceable milestone for full-scale system startup is June 22, 1999.

SD-5 North Treatment Plant Construction