Fact sheet # 98-23 Fuel Spill 12 Source and Groundwater Plume Update The purpose of this fact sheet is to provide information on one of the groundwater plumes emanating from the Massachusetts Military Reservation (MMR) and its source area. Items in italics are defined in the glossary at the end of this fact sheet. Source of the Plume The source of the Fuel Spill 12 (FS-12) groundwater plume is a confirmed leak during the early 1970s in a now-abandoned fuel pipeline that ran approximately 12.2 miles from the Cape Cod Canal to the POL yard for the 102nd Fighter Wing. The pipeline carried aviation gasoline (AVGAS). The leak was discovered along Greenway Road, just north of Snake Pond at the MMR. The Massachusetts Department of Environmental Protection (DEP) is overseeing a project that is testing and evaluating the entire pipeline for any other leaks. Primary Contaminants The primary contaminants in the FS-12 soils and groundwater are the hydrocarbon compounds benzene and ethylene dibromide (EDB), both probable carcinogens. EDB is a compound that was added to leaded gasoline, including aviation gasoline (AVGAS), to inhibit the build-up of lead in engines. Based on the most recent groundwater sampling (August 1998), the maximum levels detected are about 160 ug/l (ug/l or parts per billion) for EDB and 1100 ug/l for benzene. The highest levels for both contaminants were detected in the center most region of the plume (see Fig. 1). The Massachusetts state safe drinking water standards, or maximum contaminant levels (MCLs), are 0.02 ug/l for EDB and 5 ug/l for benzene. Area Affected by the Plume The FS-12 pipeline leak created a groundwater plume, approximately 4,400 feet long, a maximum of 1,900 feet wide, and 40 to 100 feet thick. The FS-12 plume affects groundwater from the source area on the MMR to an area just east of Snake Pond in Sandwich. (see Fig.1) Source Cleanup The FS-12 pipeline leak released an estimated 70,000 gallons of AVGAS hydrocarbons to the environment. Soils in the unsaturated zone were contaminated as the hydrocarbons percolated downward to the underlying aquifer. As the soils became saturated with the contaminants, the remaining portion of the AVGAS was carried downward to the aquifer, where it migrated to the southeast, along the natural groundwater flow path. Since October 1995, AFCEE has removed over 44,580 pounds of contaminants (approximately 10% of the fuel spill) using a process called air sparging and vapor extraction (ASVE). This process removes hydrocarbons from both soil and shallow groundwater by injecting air bubbles into the upper groundwater near the source, where the plume is the shallowest, causing the volatile components of the release to rise to where they can be captured in the unsaturated overlying soils. The vapor is retrieved by a vacuum system and treated aboveground by passing it through a catalytic oxidizer (similar to an automobile catalytic converter) that uses heat and a metal catalyst to break down the contaminants to carbon dioxide and water. The air (in vapor phase) then passes through activated carbon filters that rid the air of any remaining fuel compounds. The carbon filters are recycled periodically off-site at a licensed recycling facility. The primary purpose of ASVE is to remove hydrocarbons from the soil, although to some extent, some beneficial effects in groundwater do occur. In February 1998, when system removal had been optimized, and no additional benefit of continued operation was obtainable, the system was turned off. Confirmation testing began in the spring of 1998, and based on the results of that testing, the system was officially decommissioned with regulatory approval. It was completely removed in May, 1998.
Plume Cleanup The remaining portion of the fuel not removed by the ASVE system was dissolved into the groundwater. In 1997, AFCEE constructed an extraction, treatment and reinjection (ETR) system to contain and clean up the FS-12 groundwater plume. The system consists of 25 extraction wells to remove contaminated groundwater, a treatment plant, and 23 reinjection wells to return clean water to the aquifer. The treatment plant was originally designed to use two systems to remove the fuel-related compounds from the groundwater - a primary "ultraviolet oxidation" (UV/OX) system, and a secondary carbon filtration unit. The UV/OX uses an ultraviolet light to degrade and remove most of the fuel compounds. This process is followed by activated carbon filters to remove any residual fuel compounds. The fuel compounds stick to, or "adsorb" to the activated carbon granules as they pass through the filter and clean water is then returned to the aquifer (see Fig.2) Construction of the ETR remedial system started in November 1996. All off-base construction and site restoration activities were completed by June 23, 1997, so that the property, a youth summer camp, was available for seasonal use. Site restoration included road and road shoulder repair (i.e., paving, grass seeding, shrub and tree planting), pond shoreline repair, and restoration of the camp athletic field (which was used to store equipment and materials during construction.) System start-up began on September 18, 1997, 6 days ahead of the enforceable milestone date. After the initial start-up, the UV/OX system was discontinued and only carbon filters are being used today. Testing determined that influent levels of contaminants were low enough so that the primary treatment, UV/OX, was not necessary. Today, only carbon filtration units are used. However, the UV/OX is still available if necessary. The FS-12 Treatment plant uses 6 carbon filter tanks, each containing 20,000 lbs. of activated carbon. The system pumps and treats about 800 gallons per minute (over 1 million gallons a day). The water is sampled weekly to ensure that the system continues to perform properly. As of September 1998, 400 million gallons of groundwater from the FS-12 plume have been treated and 72 pounds of benzene and 80 pounds of EDB have been removed. Goals of the ETR System Several goals were set for the FS-12 ETR system, including: [1] Contain the groundwater plume; [2] Treat the groundwater to non-detectable levels; [3] Avoid ecological impact to surrounding areas, namely Snake Pond; [4] Reinject cleaned water into the aquifer so the chemistry of the groundwater is not altered and [5] Prevent impact on the downgradient J.Braden Thompson (JBT) plume, which is, another nearby groundwater plume, but not related to MMR. The MassDEP is currently working to contain the JBT plume. 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 groundwater during the reinjection phase of the treatment. It also makes sure 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 is not being altered. Carbon filtration breakthrough is defined as the inability of the activated carbon to filter out contaminants within the holding tank. The Performance Monitoring Evaluation (PME) Program was developed to determine if the ETR system is capturing the plume. The PME program: [1] monitors the down-gradient portion of the plume to ensure proper groundwater chemistry, that is, the same parameters as the surrounding groundwater; [2] ensures that the contaminants are being captured by the ETR system; [3] ensures that the reinjection water does not significantly impact the groundwater (i.e. raising the water table in the vicinity of the reinjection wells). Fifty wells were selected, and are sampled monthly for water level; and bi-monthly for groundwater chemistry (see Fig.3). As part of the annual base-wide Ecological Monitoring Program, beginning in 1997, the area around Snake Pond and the ETR system are sampled for chemical and biological factors such as [1] Chemical parameters; [2] physicochemical parameters; [3] field parameters, and [4] biological parameters. This program also checks to see if the plume or any other impacts from the ETR system affect the sensitive ecological features in the immediate area.
Phase II The ETR system was designed with a second phase (Phase II) of construction that could be implemented in case any contamination was not captured by the ETR system as originally built. The second phase concept included as many as five new extraction wells downgradient (south) of the current ETR system. To determine if Phase II was needed, additional groundwater monitoring was conducted. Twenty-six new monitoring wells were installed, and sampled in June and August. Wells were again sampled in October, and are scheduled to be sampled, in December. These wells, which are located upgradient of the likely Phase II extraction well locations, will provide adequate warning for the Phase II system to be built before contaminants escape. All data was evaluated to determine the need for the Phase II ETR fence. These results were used to determine if concentrations of contaminants that may have escaped the existing ETR fence during that time were significant enough to warrant installing additional extraction wells downgradient of the current ETR fence. The data showed no significant EDB downgradient of the existing extraction well fence.. Significant Findings To Date AFCEE, EPA, and MassDEP have evaluated results of the three on-going programs. These results include: [1] The treatment plant has been operating successfully and no unanticipated breakthroughs of carbon have occurred; [2] The PME program has demonstrated that the ETR system is capturing the plume and no contaminants are by-passing the existing extraction well fence; [3] The PME program has shown that the core of the plume has moved southward towards the extraction well fence where it can be better captured; [4] As anticipated, a very small portion of the plume had migrated past the current extraction fence. This is due to the lag time between the design of the system and its construction and startup in September 1997; and [5] Based on the findings of the Ecological Monitoring Program, to date there have been no significant impacts caused by the ETR system to sensitive ecological receptors. The regulatory agencies, Environmental Protection Agency (EPA), and the Massachusetts Department of Environmental Protection (DEP) have reviewed the most recent groundwater monitoring data from both Phase I and Phase II sampling efforts. [The PME groundwater data and all other information is contained in the Draft FS-12 Phase II Technical Memorandum, dated October 1998]. Based on the available data, it was concluded that the construction of the Phase II ETR fence is not warranted at this time. Additionally, continued monitoring of the existing Phase I ETR system and the quarterly groundwater sampling results will be performed to verify that this conclusion holds true. The ETR system and all data will be reviewed as part of the 5-year review process required by CERCLA. For More Information Doug Karson, Community Involvement Specialist 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. air sparging and vapor extraction (ASVE)—two groundwater treatment technologies used together to remove contamination by introducing air bubbles deep in the ground, causing contaminants to rise as a vapor, which is then retrieved and treated. adsorb—to attach by physical or chemical attraction benzene—a common industrial chemical often found in crude oil and gasoline biological parameters—specific types of vegetation, endangered species, species of special concern, phytoplankton, zooplankton, and benthic macroinvertebrates CERCLA—Comprehensive Environmental Response, Compensation and Liability Act 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. 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. 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. field parameters—the non-chemical parameters of groundwater. These include pH, temperature, DO (dissolved oxygen), specific conductivity, ORP (oxidation-reduction potential), and turbidity influent—water going into the treatment plant, prior to treatment effluent—water leaving the treatment plant, after treatment maximum contaminant levels (MCLs)—the maximum concentration of a given contaminant allowed in drinking water under state and federal regulations. 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. residual product—fuel floating on the water table. saturated—unable to hold or contain more liquids ultraviolet oxidation—a chemical reaction using ultraviolet light to degrade organic compounds. unsaturated zone—soils that lie within the area in ground from the surface to the water table.
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