Site Name: ELMENDORF AIR FORCE BASE
EPA ID: AK8570028649 EPA Region: 10 Metro Statistical Area: 0380
N BOUNDRY OF CITY LIMITS, ANCHORAGE, AK 99506
Operable Unit: 05
ROD ID: EPA/ROD/R10-95/108 ROD Date: 12/28/94
Contaminant: TCE, PCBs
Keys: soil contamination, sediment contamination, groundwater contamination, surface water contamination, excavation, on-site treatment, natural attenuation, institutional controls, groundwater monitoring, surface water monitoring
Abstract:
Please note that the text in this document summarizes the Record of Decision purposes of facilitating searching and retrieving key text on the ROD. It is no the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.
Elmendorf AFB is located approximately two miles north of downtown Anchorage, Alaska. The base provides defense for the United States through surveillance, logistics, and communications support. Operating Unit (OU) 5 is located along the southern boundary of Elmendorf AFB, and covers an area over 7,000 feet long and 1,200 feet wide.
Operating Unit 5 is geographically diverse. In the western part of the OU, a bluff gives way to a broad flat area that ends in Ship Creek. In the eastern ar a more gently sloping bluff leads to a wetland called the beaver pond area. The beaver pond area is a wetland in the eastern part of OU 5 where there are severa shallow connected water bodies and marsh areas. The central part of the OU is a transitional area with a bluff and some surface water features, including the snowmelt pond and a fish hatchery. The snowmelt pond is an elongated shallow wa body measuring approximately 50 x 300 feet and is located in the center of the O It was formed by beavers backing up natural drainage. It is called the snowmelt pond because snow is often piled on top of the bluff, in the area near the pond.
Runoff generally flows from north to south through the OU towards Ship Creek. Drainage ditches facilitate runoff in the western area. The snowmelt pond is an drainage ditch which has backed up and formed a broad, shallow pond.
Land uses vary across OU 5. The primary land use throughout most of the OU i industrial. Diesel fuel, jet fuel, multiproduct fuel lines, and distribution li are located in OU 5 on top of the bluff (see Figure 1-2). An Army Corps of Engineers (COE) building is located near the western side of the OU, above the bluff. Some military residential units are located back from the bluff on the eastern and western sides of the OU. Ship Creek flows from east to west along t southern edge of the base.
As part of the ongoing mission at Elmendorf Air Force Base, aircraft are regu refueled and many of the fuel lines are located in OU 5. These fuel lines have, times, leaked fuel into the soil and groundwater surrounding the pipelines. Bef the leaks could be detected, fuel product and fuel constituents such as benzene migrated from the leak to the water table. This migration from source areas is primary cause of contamination at OU 5. The risk assessment considered the curr and future transport of contaminants to potential receptors.
Three of the source areas are identified based on leaks in buried tanks and pipelines. In the late 1950s at Source ST37, several thousand gallons of diesel fuel leaked from a fuel line south of the U.S. Army Corps of Engineers (COE) building. Over the years, thousands of gallons of fuel have been recovered from hydrocarbon seeps using absorbents at the face of the bluff, immediately south o this site. The ST38 leak occurred in the mid-1960s in a JP-4 jet fuel pipeline. with ST37, migration led to seepage of fuel sheens from the bluff, east of the snowmelt pond. No fuel was recovered. ST46 had a pipeline leak occur in 1978 w JP-4 jet fuel seeped into the wetlands at the base of the bluff and Ship Creek. After the leaking pipe was repaired, fuel continued to seep from the bank into t beaver pond. All leaks have been repaired and the pipelines and tanks are given annual checks and triennial detailed evaluations to locate leaks.
At a fourth site (SS42), an estimated 8,000-gallon, one-time spill of diesel occurred in March 1976. Most of the fuel was recovered off the frozen ground. final two source areas are identified as SD40, and SS53 and are directly upgradi of where the fuel seeped from the bluff. At SD40, oil was reported seeping out the bank near the railroad tracks and flowing through a marsh into Ship Creek du the late-1960s. (However, the Remedial Investigation did not find any residual contamination in Ship Creek.) The source of this oil could not be determined. SS53, another fuel seep of unknown origin, was observed during the spring thaw f an unspecified number of years. The seep flowed into a drainage ditch parallel Post Road. The potential source area, is in the middle of the OU along the rail right of way.
Solvent constituents, primarily TCE, are detected in the supper aquifer groun in OU 5. The solvent sources are located upgradient of the OU, in areas where solvent spills or disposal occurred in the past. Source areas include ship drai (OU 3) and sanitary landfills (OU 1, OU 2 [ST-20]). Solvents from these upgradi source areas have migrated toward OU 5 in the groundwater. Plumes from these so areas are well-defined geographically, and OU 5 is known to capture approximatel 90% of the groundwater flowing from Elmendorf AFB. Based on the results of environmental investigations, Elmendorf AFB was liste the National Priorities List by the U.S. Environmental Protection Agency (U.S. E in August 1990. This listing designated the facility as a federal site subject the remedial response requirements of CERCLA, as amended by the Superfund Amendm and Reauthorization Act of 1986. On 22 November 1991, the USAF, U.S. EPA, and t Alaska Department of Environmental Conservation (ADEC) signed the Federal Facili Agreement (FFA) for Elmendorf AFB. The contaminated areas of Elmendorf AFB were divided into seven OUs, each to be managed as a separate region and investigated according to varying schedules. There are six RCRA source areas along the upgradient edge of the western and central portions of OU 5. All six of these source areas are currently going through RCRA clean closure. However, if contamination has reached the groundwater, it will be addressed under CERCLA and handled as part of the action at OU 5.
Remedy:
The selected remedy for the site has many components. First, contaminated se water in the western and middle portions of the OU will be passively drained usi horizontally inserted extraction wells in the bluff. The water will flow to a constructed wetland, currently planned to be built in the snowmelt pond. A laye material such as gravel will be placed over the sediments which contain PCBs in order to isolate the contamination. Second, approximately 3,000 cubic yards of soil contaminated with fuel pro be excavated and treated at an on-base treatment facility to reduce contaminant concentrations below cleanup goals. The treated soil will be reused on base eit to fill the excavation or for general fill. Third, natural attenuation will be relied upon to attain cleanup levels in contaminated upper aquifer and surface water other than seep water, including th beaver pond wetland area. Fourth, institutional controls that prohibit use of the upper aquifer will that people will not be exposed to contaminated groundwater until cleanup goals achieved. Fifth, groundwater, seep water, and surface water will initially be sample quarterly basis. Sediment will be sampled annually. Results of the monitoring program will be assessed annually for at least the first five years to determine cleanup levels have been achieved. If cleanup levels have not been reached, aggressive actions such as air sparging with soil vapor extraction or active extraction with air stripping may be necessary. Bioventing of soil is an additi option that could treat soil contamination. If there are any significant differences between the actions being taken as part of this ROD, an explanation significant differences or a ROD amendment will be issued.
Operable Unit: 02
ROD ID: EPA/ROD/R10-95/112 ROD Date: 03/31/95
Contaminant: PCBs, fuel, solvents, fuel constituents
Keys: soil, contaminated groundwater, containment, extraction, pump and treat, ai stripping, off-site discharge, source control, groundwater remediation, underground storage tanks, groundwater monitoring, institutional controls
Abstract:
Please note that the text in this document summarizes the Record of Decision purposes of facilitating searching and retrieving key text on the ROD. It is no the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.
Elmendorf AFB is located approximately two miles north of downtown Anchorage. base provides defense for the United States through surveillance, logistics, and communications support. OU 5 is located along the southern boundary of Elmendor AFB and covers an area over 7,000 feet long and over 1,200 feet wide.
OU 5 is geographically diverse. In the western part of the OU, a steep bluff way to a broad flat area that ends in Ship Creek. In the eastern area, a more gently sloping bluff leads to wetland called the beaver pond area. The beaver p area is a wetland in the eastern part of OU 5 where there are several shallow connected water bodies and marsh areas. The central part of the OU is a transitional area with a bluff and some surface water features, including the snowmelt pond and a fish hatchery. The snowmelt pond is an elongate shallow wat body measuring approximately 50 x 300 feet and is located in the center of the O It was formed by beavers backing up natural drainages. It is called the snowmel pond because snow is often piled on top of the bluff, in the area near the pond.
Land uses vary across OU 5. The primary land use throughout most of the OU i industrial. Diesel fuel, jet fuel, multiproduct fuel lines, and distribution li are located in OU 5 on top of the bluff. An Army Corps of Engineers (COE) build is located near the western side of the OU, above the bluff. Some military residential units are located back from the bluff on the eastern and western sid of the OU. Ship Creek flows from east to west along the southern edge of the ba
As part of the ongoing mission at Elmendorf Air Force Base, aircraft are regu refueled and many of the fuel lines are located in OU 5. These fuel lines have, times, leaked fuel into the soil and groundwater surrounding the pipelines. Bef the leaks could be detected, fuel product and fuel constituents such as benzene migrated from the leak to the water table. This migration from source areas is primary cause of contamination at OU 5. Understanding transport is important bec the contaminants and risks are not always associated with the source area, but w the area where an exposure is possible. The risk assessment considered the curr and future transport of contaminants to potential receptors.
In OU 5, the discovery of hydrocarbon seeps in the early 1980s was the first indication of the leaks. From the leak, fuel migrated in a southerly direction seeping from the bluff face located along the southern end of OU 5. When leaks identified they were repaired and residual hydrocarbon was recovered to the exte possible. Hydrocarbon was recovered at the bluff face using absorbents and skim any floating product found on surface water drainages. The remaining hydrocarbo and hydrocarbon constituents are the primary cause of environmental impact at OU
Two investigations were conducted while completing the Feasibility Study (FS) one study, the extent of PCB contaminants in the snowmelt pond water and sedimen were identified. In the other study, the capacity of the beaver pond wetland ar to naturally attenuate contamination was assessed. In addition, the Elmendorf Bioenvironmental Engineering Services Group (BESG) has been collecting groundwat and surface water samples from throughout Elmendorf AFB since 1987.
Remedy:
OU2 consists of three source areas: the ST20 Underground Waste Storage Tank, ST41 Tank Spill (Four Million Gallon Hill), and the ST41 Sludge Disposal Area. Although contaminated soil and groundwater were found in the vicinity of ST20 an ST41 Sludge Disposal Area, it is attributed to upgradient source areas ST48 and Tank Spill, respectively. No actual or threatened release of hazardous substanc from ST20 or ST41 Sludge Disposal Area were found during the Remedial Investigation/Feasibility Study. The contaminated media in ST20 will be address under the State Elmendorf Environmental Restoration Agreement (SERA) program, an the contaminated media in the ST41 Sludge Disposal Area is being addressed under ST41 Tank Spill remedial action.
The selected remedies address free product, surface water seeps, source contr groundwater at the ST41 tank spill source area.
The remedy selected to address free product and surface water seeps is contin operation of the interim remedial action, previously selected and documented in Interim Action ROD which was signed in September of 1992. The major components the interim remedial action were as follows: containment of seeps us product recycling; extraction of fuel product from the groundwater surface in th shallow aquifer to minimize further migration; treatment of extracted groundwate and seep water by an air stripping process to meet federal, state, and local regulations; treatment of the emissions from the air stripping process to meet s regulations and permit requirements; and disposal of the treated groundwater in accordance with federal, state, and local regulations by discharge to the munici sewer system.
This final ROD incorporates the interim remedial action, and includes additio remedies for source control and groundwater remediation. The interim action is intended to achieve free product recovery and to control the mobilization of contaminants into the shallow groundwater or surface water. The efficiency of t interim action, specifically with respect to ensuring that wetlands are not adversely impacted, and that all technically practicable free product that is removed will be evaluated as part of the selected remedy.
The selected remedy for ST41 source control includes the following major and filling them with an inert material; excavating, removing, disposal/recycling of the piping system; removing contaminated soils that may contribute to groundwater contamination; treating in a pre- approved facility revegetating the area.
The selected remedy for ST41 groundwater includes the following major comp monitoring the groundwater beneath and adjacent to the site to evaluate contamin migration and timely reduction of contaminant concentrations by natural attenuation within 21 years. This will include five-year reviews to assess the protectivene of the remedial action as long as contamination remains above unacceptable level Maintaining institutional controls that restrict access to groundwater and groundwater development will be implemented at the site as long as hazardous substances remain on the site at levels that preclude unrestricted use. The specific institutional controls to be implemented and/or maintained at OU2 are a follows: development of a site map showing the areas current and potentially impacted by groundwater contaminants that will be included in the Base Comprehen Plan; zoning the affected area for undeveloped outdoor/recreational use only; continued enforcement of base policy prohibiting installation of groundwater wel (other than for monitoring purposes) into the shallow aquifer underlying OU2; an prohibiting unauthorized access to existing water supply and groundwater monitor
wells.
In addition, to ensure long-term integrity of the above land use controls, th Force will ensure that, to the extent that groundwater contamination remains abo unacceptable levels, deed restrictions or equivalent safeguards will be implemen in the event that property containing such contamination is transferred by the A Force.
The contingent remedy for ST41 groundwater includes the following major compone migration; treating the extracted water with an air stripping process to meet federal, state and local water quality regulations; treating the air emissions f the air stripping process to meet state and base air emission permit requirement disposing of the treated groundwater in accordance with federal, state, and loca regulations and permit requirements; five-year review to assess the protectiveness of the remedial action; and monitoring of the effectiveness of the groundwater containment and treatment process until the benzene concentrations reach the Maximum Contaminant Level (MCL) or the groundwater n longer poses an unacceptable health risk.