Fact Sheet #98-20 Storm Drain 5 (SD-5) Groundwater Plume and Source Update The purpose of this fact sheet is to invite the public to participate in upcoming community involvement activities related to the Storm Drain 5 South (SD-5S) groundwater plume emanating from the Massachusetts Military Reservation (MMR).
This fact sheet also provides background information on the SD-5 groundwater plume and its source. LEARN MORE ABOUT AFCEE’S RECOMMENDATIONS AFCEE will present the results of its recent analyses and recommendations at a poster session and public meeting. The informal poster session will be followed by a presentation and a question and answer period.
A public hearing to receive public comments also will be held.
WHAT DO YOU THINK? AFCEE is accepting formal public comments on its recommendations from December 29, 1998 to January 28, 1999. You don’t have to be a technical expert to comment—if you have a concern or preference, AFCEE, EPA, and MassDEP want to hear it before making a final decision on the best solution for the SD-5S groundwater plume. There are several ways to submit a public comment
PLUME CLEANUP Progress Update for SD-5 South The southern part of the SD-5 plume was one of four plumes to undergo the "decision criteria matrix" process in 1997. The decision criteria process used for selecting the cleanup alternative for SD-5S plume was developed cooperatively by AFCEE, EPA, DEP, and the public. It included requirements of federal and state environmental regulation, but was tailored to meet the specific needs, interests 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 reached consensus that the alternative described below best balanced the decision criteria for SD-5 South. Selected Alternative for SD-5 South (December 1997 Decision) The selected alternative for the southern part of the SD-5 groundwater plume, as presented in December 1997, is as follows: The selected alternative uses recirculating well technology to achieve a significant degree of contaminant mass reduction. Recirculating wells are scheduled to be installed along Hooppole Road and within the body of the plume (see Figure 1). The exact location and number of wells were to be determined by consideration of the following criteria:
AFCEE will expedite construction of recirculating wells along Hooppole Road to reduce contaminant mass in the plume before it reaches Johns Pond. Expediting the installation of these recirculating wells will help capture some of the estimated 95-98 percent of the SD-5S plume mass that flows into Johns Pond. The full-system startup date is June 22, 1999. As part of the decision, data gap analysis was to be completed. Data gap analysis is a study or series of studies to provide additional details regarding aquifer characteristics and contaminant distribution. Specifically, for SD-5S, data gap analysis included:
After the data gap investigations are completed, the agencies will determine if the selected alternative protects human and ecological health and protects and restores the aquifer.
SD-5 South Interaction with Johns Pond Investigations to ascertain what is happening to the plume as it interacts with Johns Pond are complete. The field activities performed to investigate the interaction of the SD-5S plume with Johns Pond included: [1] two geophysical surveys; [2] passive vapor-diffusion sampling; [3] the completion of twelve in-pond groundwater screening borings and [4] the completion of ten new groundwater monitoring wells. These field activities were planned to complement one another and assist in the development of an updated conceptual model for plume-pond interaction. Two geophysical surveys were conducted by the U.S. Geological Survey (USGS) between April 6 and April 8, 1998 to obtain information on shallow subbottom stratigraphy in Johns Pond. The geophysical surveys involved two techniques: ground penetrating radar (GPR) and continuous seismic reflection profiling (CSR). Fourteen track lines within the potential SD-5S plume discharge area in Johns Pond were surveyed using GPR techniques. The survey lines were located using a military-grade global positioning system. Sixteen track lines, roughly corresponding with the locations of the GPR track lines, were then surveyed using CSR methods. The seismic surveys have provided a much better view of the pond bottom topography. The USGS also performed passive vapor diffusion sampling at the pond bottom and has identified an area where the plume is upwelling into the pond (see Figure 2). Another passive sampling survey was performed in mid-November, 1998. EPA personnel, from their laboratory in Lexington, MA analyzed the samples collected. This data was shared with AFCEE and the USGS. The drilling program confirmed results of the passive sampling by finding the same contaminants at the same depth within the pond bottom. Twelve wells were installed at locations across Johns Pond from the boat ramp southeasterly to the other side of the pond. The wells were installed below the bottom of the pond to depths averaging 75 feet with one well to a depth of 170 feet. Recent drilling activities included the installation of ten additional monitoring wells to determine proper recirculating well placement. Four groundwater monitoring wells were installed in August 1998 and six more were installed in October 1998 (see Figure 2) Groundwater sampling from these new wells provided updated data on the current distribution of SD-5S plume contamination. Significant Findings to Date For SD-5S The results of the field activities provide a sound conceptual model of interaction of the SD-5S plume and Johns Pond. Results from these studies show:
PUBLIC INVOLVEMENT Because AFCEE has concluded that the SD-5S plume is discharging into Johns Pond and none of its related contamination has been detected in the pond surface water, AFCEE has determined that there is no unacceptable risk (swimming, wading, and fishing) to human health and the environment. Therefore, AFCEE has determined that no added benefit would be achieved from an active groundwater remediation system. This initial analysis has led to a proposal to reexamine the chosen remedy. AFCEE is suggesting long-term monitoring versus Alternative E (recirculating wells). AFCEE is inviting the EPA, DEP, and the community to review and comment on this proposal. Following is the planned community involvement schedule for SD-5 South:
AFCEE’s commitment to the current alternative for construction of recirculating wells is on a tight construction schedule, therefore AFCEE will continue with pre-construction activities until public comment and regulatory reviews have been received, and a revised decision agreed upon. Currently, AFCEE is proceeding on these parallel schedules to: [1] maintain enforceable milestones for design and construction of the current cleanup plan, and [2] propose possible suspension of the current design and construction plans (i.e. evaluate other alternatives utilizing the most recent data). As part of this process, AFCEE, EPA and MassDEP will continue an ongoing public involvement effort to ensure that the public is kept informed and has an opportunity to provide input on the ongoing remedial actions at SD-5. Particular efforts will be made to involve residents living near and on Johns Pond. AFCEE, EPA, and the MassDEP encourage residents to attend citizen teams (i.e. JPAT) and public meetings, become involved with the SD-5S cleanup and sign up on the site mailing list to receive updates. PLUME CLEANUP In 1997, an extraction, treatment, and reinjection (ETR) system was initiated at the base boundary to capture the northern part of the SD-5 groundwater plume. The system consists of 10 extraction and 8 reinjection wells and an on-base treatment plant. The ETR system draws the water out of the ground, sends it through underground pipes to the treatment plant where, the contamination is removed by filtering the water through activated carbon canisters. The carbon adsorbs, or holds onto, the contaminants. Clean water is then returned to the groundwater via reinjection wells. Construction of the ETR remedial system started in February 1997. System start-up began on August 4, 1997, 2 days ahead of the enforceable milestone date. The SD-5 North Treatment plant uses 4 carbon filter tanks, each containing 20,000 lbs. of activated carbon. The carbon filters are recycled periodically off-site at a licensed recycling facility. The system pumps and treats about 350 gallons per minute (over 500,000 gallons a day). The water is sampled weekly to ensure that the system continues to perform properly. As of November 1998, 243 million gallons of groundwater from the SD-5 plume have been treated. The system has removed 3.7 pounds of solvents and 26.2 pounds of fuel-related contaminants. The SD-5 North Treatment plant is being modified to accept contaminated groundwater from the Sandwich Rd. portion of the Chemical Spill 10 (CS-10) plume starting in late 1999. Goals of the SD-5N ETR System AFCEE initiated three programs to meet these goals: [1] In-plant monitoring; [2] Performance Monitoring Evaluation (PME) Program and [3] Ecological Monitoring Program. The in-plant monitoring program ensures that no contaminants are being re-introduced back into the aquifer during the reinjection phase of the treatment. It also ensures that the chemistry of the cleaned groundwater is consistent with the surrounding groundwater. To accomplish this, the influent and effluent of the treatment plant is checked monthly to ensure no carbon filter breakthrough is occurring and that groundwater chemistry, such as pH or dissolved oxygen, is not being altered. The Performance Monitoring Evaluation (PME) Program was developed to determine if the ETR system captures the plume. The PME program: [1] Monitors the groundwater chemistry and contaminant levels upgradient and downngradient of the ETR system to ensure that the contaminated groundwater is captured; [2] Ensures that the reinjected water has no significant impacts on the chemistry of the natural groundwater; and [3] monitors the movement of the groundwater through hydraulic measurements to ensure that the ETR system influences the movement of the groundwater as designed and does not significantly impact the groundwater levels (i.e. raising the water table in the vicinity of the reinjection wells). Thirty wells are measured monthly for water levels and twenty wells are sampled bi-monthly for groundwater chemistry. Starting in 1999, the frequency of monitoring will be reduced to quarterly for chemical and hydraulic monitoring. As part of the annual base-wide Ecological Monitoring Program, which began in 1997, the area around the SD-5 Treatment Plant (Ashumet and Johns Ponds) and the ETR system are sampled for chemical and biological factors such as [1] Chemical parameters; [2] Physicochemical parameters; and [3] Field parameters and [4] Biological parameters. This program also checks to see if the impacts by the ETR system affect the sensitive ecology in the immediate area. Significant Findings To Date for SD-5 North Additionally, data shows that the SD-5N plume and the SD-5S plume are now separated by a zone of clean groundwater that is expanding immediately downgradient from the SD-5 North Treatment Plant. This means that the SD-5 North Treatment system is effectively capturing and treating the northern part of the plume. As a result, clean groundwater is now moving toward the Briarwood neighborhood. The most northern portion of the SD-5S plume should reach Johns Pond within 8 to10 years. BACKGROUND INFORMATION Source of the Plume Primary Contaminants At present, the highest contaminant concentrations detected in the SD-5 plume are 56 parts per billion (ppb or ug/l, 00MW0524) for TCE, 4 ppb (00MW0564) for PCE, 82 ppb for cis-1,2 DCE and 0.15 ppb for EDB. The maximum contaminant level allowed under Massachusetts’s safe drinking water standards (MCL) is 5 ppb for TCE and PCE, 70 ppb for cis-1,2 DCE and 0.02 ppb for EDB. Area Affected by the Plume SD-5N extends from the source area south to the base boundary, where it is captured by an extraction, treatment, and reinjection (ETR) system. SD-5S extends 300 feet south of the ETR system toward the northwest side of Ashumet Pond and Johns Pond. Studies have shown that most of the SD-5S plume discharges to Johns Pond. SOURCE CLEANUP 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. AFCEE, EPA, and MassDEP signed the Record of Decision (ROD) in September 1998. AFCEE’s preferred alternative for the SD-5 source area consists of excavating the contaminated soils and mixing them with a cold asphalt emulsion - a process called asphalt batching. The new asphalt will then be used as sub-base material for roads on the MMR. For More Information Jim Murphy, Community Relations Coordinator Ellie Grillo, Community Involvement Coordinator activated carbon—a highly adsorbent form of carbon used to remove organic molecules from an air or liquid source. Carbon has the ability to attract organic molecules and hold them in pores within the carbon granule. adsorb—to attach by physical or chemical attraction biological parameters—specific types of vegetation, endangered species, species of special concern, phytoplankton, zooplankton, and benthic macroinvertebrates breakthrough—the inability of the activated carbon to filter out contaminants within the holding tank. chemical parameters—the chemical constituents (priority pollutants) of the groundwater based on laboratory analysis. These include VOCs (volatile organic compounds), EDB, (etheylene dibromide), SVOCs (semi-volatile organic compounds) and metals. cis-1,2 dichloroethene (DCE)—a chlorinated solvent, used for industrial purposes. continuous seismic reflection (CSR)—a sound beam that penetrates the pond sediments and returns a profile of the variations in sediment layers. It is used in conjunction with ground penetrating radar. data gap analysis—a study or series of studies to provide additional details regarding aquifer characteristics and contaminant distribution. The studies may consist of literature reviews and/or field work. The information is used to assist with the design of the selected alternative. downgradient—the direction toward which groundwater flows. drive point—a small monitoring well driven by hand for areas where the water table is very shallow (less than 7 feet). effluent—water leaving the treatment plant, after treatment ethylene dibromide (EDB)—an additive in aviation gas to control the build-up of lead in the engines. extraction, treatment, and reinjection (ETR)—a system that extracts groundwater, treats it to reduce or eliminate contaminants and reinjects the treated water into the aquifer field parameters—the non-chemical parameters of groundwater. These include pH, temperature, DO (dissolved oxygen), specific conductivity, ORP (oxidation-reduction potential), and turbidity penetrating radar (GPR)—a radar beam that penetrates the pond sediments and returns a profile of the variations in sediment layers. It is used in conjunction with continuous seismic reflection. groundwater plume—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 influent—water going into the treatment plant, prior to treatment Joint Process Action Team (JPAT)—a citizen team that provides input on AFCEE issues and decisions. maximum contaminant levels (MCLs)—the maximum concentration of a given contaminant allowed in drinking water under state and federal regulations. passive vapor diffusion samplers—a small bottle placed in a plastic bag and buried several inches into the pond bottom. Vapors migrate through the plastic and into the bottle where they can be analyzed for contaminants by a laboratory. physicochemical parameters—organic and inorganic parameters not normally associated with contamination. These include nutrients (phosphorus, nitrates), TOC (total organic carbon), DOC (dissolved organic carbon), alkalinity, TSS/TDS (total suspended/total dissolved solids), chlorophyll a, and hardness. plume response alternative—a specific configuration of treatment system(s) to be compared and evaluated. recirculating well—a process for capturing, treating, and releasing groundwater within the same well. The process is designed to minimize impacts on the water table. remedial project managers—the program managers appointed by the Air Force Center for Environmental Excellence (AFCEE), the U.S. Environmental Protection Agency (EPA), and the Massachusetts Department of Environmental Protection (DEP). tetrachloroethene (PCE)—also referred to as perchloroethene; a man-made solvent commonly used for metal degreasing and in dry-cleaning clothes trichloroethene (TCE)—a solvent used to dissolve or disperse another substance such as oil, and is often used in metal degreasing. zone of upwelling—an area of the water table where plume contaminants discharge to a surface body.
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