Fact Sheet # 98-13 Chemical Spill 10 (CS-10) Source and Groundwater Plume
Update The purpose of this fact sheet is to provide updated information regarding the Chemical Spill 10 (CS-10) source and groundwater plume emanating from the Massachusetts Military Reservation (MMR). 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) have carefully considered plume response alternatives, and chosen a response action as outlined in the fact sheet Chemical Spill 10 (CS-10) Plume Response Decision and announced on August 21, 1997. Words in italics are defined in the glossary at the end of this fact sheet. They are only italicized the first time they are used. Source of the CS-10 Plume The primary source of the CS-10 groundwater plume is the 38-acre area of the former Boeing Michigan Aeronautical Research Center (BOMARC) Missile Site and current Unit Training Equipment Site (UTES). The source area is located near the eastern boundary of the MMR on Camp Edwards, east of Greenway Road. The BOMARC Missile Site was operated between 1962 and 1973 and UTES has been operated from 1978 to present for maintenance and storage of armored and other wheeled vehicles. In the past, spills and releases of cleaning solvents occurred in these areas. Since December 1995, a pollution prevention program has been in place at UTES to ensure that current petroleum use and disposal do not affect the groundwater. For the BOMARC site, the remedial investigation, which defines the nature and extent of contamination, has been completed. A feasibility study, which outlines options for addressing the contamination, has also been completed. A proposed plan, which describes AFCEE’s preferred alternative for addressing the site, will be released for public comment in early fall 1998. Following public comment, a record of decision describing the final decision will be released; it is scheduled for late 1998. Once the record of decision has been signed, planning of the selected remedy will begin. A Focused Feasibility Study was performed to evaluate alternatives for controlling potential site risks. This study provides the basis for the CS-10 Proposed Plan. Source Cleanup Determination of the source of the contamination is critical to the cleanup of the groundwater plume. Removal of the source is also part of the activities undertaken by AFCEE. Activities to date include conducting a Remedial Investigation (RI), preparing a Focused Feasibility Study, and a Proposed Plan outlining alternatives for reducing site risks. The Proposed Plan will present analysis of various cleanup options and a preferred alternative which may inlcude removal of shallow soils that present the greatest risk and treatment of the soils on-site by asphalt batching. Asphalt batching allows the reuse of the materials for road paving projects. Deeper soils may be treated to reduce contaminant concentrations and prevent groundwater contamination. Sampling and monitoring will continue to be conducted to ensure that the activities are effective. Cleanup Responsibilities AFCEE is responsible for cleanup activities associated with groundwater contamination at MMR. This involves soil remediation in areas that are source areas for the CS-10 groundwater plume. The source also includes fifteen drainage structures that were removed and two drainage structures cleaned and filled with concrete. Recent samples taken at the source location did not detect any PCBs in the soil. Shallow soil samples taken in the area during a remedial investigation in 1993 did show PCB concentrations up to 4200 ug/kg. AFCEE is addressing soil contamination as part of their cleanup activities. Radioactive materials may have been used at the BOMARC site. A preliminary survey for radioactive materials was conducted by the DEP, and no materials were found. AFCEE is conducting a further survey for radioactive materials at the site. In addition to the groundwater contaminant sources, there are several other potential risks to human health and the environment at the site that were investigated by the Massachusetts Army National Guard. These include asbestos and lead paint in the buildings and possible PCBs in older transformers. No PCBs were found in the transformer oils at the source. Primary Contaminants of the Plume The primary contaminants of the CS-10 plume are trichloroethylene (TCE), perchloroethylene (PCE), and 1,2 dichloroethylene (1,2-DCE). PCE and TCE are common solvents used for equipment maintenance and degreasing. Affected Area The attached map depicts the CS-10 plume. Most of the plume affects the south-central area of the base. The plume is approximately 17,000 feet long, a maximum of 4,000 feet wide, and varies in thickness up to 140 feet thick. The eastern lobe of CS-10 has migrated in the groundwater off base near the Falmouth Gate. It has been tracked to the northwest edge of Ashumet Pond. In general, the CS-10 plume is over 120 feet below ground and 60 feet below the water table along most of its length. Additional drilling and sampling is scheduled to begin in October 1998 to determine whether the plume is flowing deep under Ashumet Pond. None of the primary contaminants contained in the CS-10 plume have been detected in the surface water or sediments of Ashumet Pond. Plume Decision Criteria Process The decision criteria process used for selecting the cleanup alternative was developed cooperatively by AFCEE, EPA, and DEP. It includes requirements of federal and state environmental regulations, but was tailored to meet the specific needs and interests of the projects and concerns of the community surrounding the MMR. 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 agreed, by consensus, on the alternative that best met the decision criteria. Remedy Selected The selected alternative uses extraction, treatment, and reinjection (ETR) technology. The selected alternative was designed with consideration of property access issues and adverse impacts to sensitive ecological areas along the shoreline of Ashumet Pond. Instead of an extraction fence along the pond, the alternative uses an extraction fence along Sandwich Road. This alternative is generally acceptable to the public. Because the fence is upgradient of the leading edge of the plume in the Ashumet Pond area, a small portion of the plume will not be captured (less than two percent by mass). Components of the selected alternative include the Sandwich Road ETR fence, the Southern ETR fence, the Southwest ETR fence, and the additional refinement of in-plume action. The Sandwich Road ETR fence will capture the mass of contaminants at and just north of Sandwich Road. The Southern ETR fence will protect existing and future water supplies south of a portion of the CS-10 plume. The Southwest ETR fence will protect an uncontaminated portion of the aquifer southwest of the plume. In-plume action will seek to reduce the mass of contaminants entering the silts, reduce higher concentrations of contaminants before they reach the ETR well fences, minimize hydrological impacts, and improve the performance of the system. The South/Southwest ETR fences are currently being reevaluated as part of the Southwest Operable Unit (SWOU) investigation. In addition, the recirculating wells in the area of higher contaminant concentration north of Sandwich Road will continue to operate and provide ongoing reduction of contaminant mass during design and construction of the Sandwich Road well fence. The Air Force will continue to monitor the progress and operation of the recirculating wells. Plume Progress Update The decision process was completed in August 1997 and a project execution plan written and approved in September 1997. A sampling and analysis plan has been implemented and monitoring wells were installed through spring 1998. On-going ecological sampling is being conducted. Thirty-four wells were sampled for data gap analysis to prepare the treatment system design. Final engineering design work will continue throughout 1998 to complete construction to meet a treatment system startup date for the Sandwich Road well fence and in-plume treatment system of June 28, 1999. EPA granted an extension for the treatment system associated with the South/Southwest well fence to reevaluate it as part of the SWOU. It is now scheduled for completion in April 2000. Public Involvement There is significant opportunity for public involvement during the start up phase. Engineering design plans will be available to the public. Information updates will be provided, and AFCEE representatives will meet with neighborhood and community groups at any time, as requested. AFCEE, EPA, and MassDEP encourage residents to attend citizen advisory team meetings, become more informed and involved with the CS-10 cleanup, and sign up for the site mailing list to receive updates.
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: dkarson@mafmh.ang.af.mil
|
