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Record of Decision System (RODS)

NAVAL SURFACE WARFARE CENTER - DAHLGREN

Abstract

Site Name:  NAVAL SURFACE WARFARE CENTER - DAHLGREN
Address:  2 MI E OF INTER 301 & 206 
City & State:  DAHLGREN  VA  22448
County:  KING GEORGE
 
EPA ID:  VA7170024684
EPA Region:  03
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-98/070
ROD Date:  09/30/1998
Operable Unit(s):  05
 
Media:  Groundwater, Sediment, Soil, Solid Waste, Surface Water
 
Contaminant:  Base Neutral Acids, Inorganics, Metals, Nitroaromatics, PAH, PCBs, Pesticides, VOC
 
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Naval Surface Warfare Center Dahlgren site (NSWCDL) is located in Dahlgren, Virginia.

Operable Unit 1 (OU1):
Site 12, the Chemical Burn Area, is one of several Installation Restoration (IR) sites located at the NSWCDL facility. Site 12 is situated on the Mainside of the base and is bounded on its western side by Gambo Creek. Groundwater production wells supplying potable water to NSWCDL are over 600 feet deep and located over 4,000 feet south of Site 12. These wells are unaffected by contaminants related to Site 12. The closest residences, on-base Navy housing consisting of over 150 homes, are within 6,000 feet southwest of Site 12.
Activity in the vicinity of Site 12 first began about 1952 when a 600 by 600-foot area was cleared of vegetation. Later, around 1964, two pits were observed in the cleared area. It was reported that fuel had been used to burn laboratory materials and metallic hardware and equipment at the pit. The last burn was conducted in the fall of 1982. By 1986, the pit and fence at Site 12 were no longer visible due to the amount of vegetation present in the area. By late 1986, the fence was removed and the pit was filled in by regrading the area. Known or potential wastes disposed of at Site 12 include fuel oils, spent solvents, metals, caustics, hypochlorite, polymers, glues, and decontaminated chemical warfare agent solution.

Site 12 was identified as a potential area of contamination in the initial investigation performed in the early 1980s. Confirmation of contamination at Site 12 occurred between 1983 and 1984. Results of sampling at the site were reported in 1986. One of the two Records of Decision (RODs) issued in September 1997 address Site 12.

OU2:
Site 2, the Fenced Ordnance Area, is one of several Installation Restoration (IR) sites located at the NSWCDL facility. Site 2 is situated on the Mainside of the base and is bounded on its western side by Gambo Creek. Groundwater production wells supplying potable water to NSWCDL are located over 4,000 feet south of Site 2. The closest residences, on-base Navy housing consisting of over 150 homes, are within 6,000 feet southwest of Site 2.

Evidence shows that activity at Site 2 began around 1943, when a small cleared area was observed in a photo. By 1952, the area had grown larger and a pile of dark-colored dirt was present in the northwest corner. In the early 1970s, a fenced landfill area was excavated and reportedly used for the disposal of metal ordnance materials that may have contained explosive residue. In addition, asbestos pipe wrappings, rinsed pesticide containers, ordnance hardware, and machine parts were buried in this area. Trenching operations also occurred at the site in the 1980s.

The initial assessment on the site was conducted in 1981 and concluded that radioactive monitoring should be completed. Other studies were performed and have been completed in 1991-1992. One of the two RODs issued in September 1997 address Site 2.

OU3:
The Disposal/Burn Area (Site 9) is an inactive landfill, approximately 5 acres in size, located off Caskey Road in the central portion of the Mainside, adjacent to the southwestern shore of Gambo Creek and associated marsh area. Gambo Creek and its associated marsh area border approximately two-thirds of the site to the east and north. The majority of the remaining area surrounding Site 9 is wooded. Historic information indicates that the facility used this area as a sanitary landfill from the early 1940s until 1971. However, dumping and occasional burial of construction debris and tree stumps continued until 1984. Site 58, also called the Building 1350 Landfill, is an extension of Site 9 to the southwest and is approximately 0.7 acre in size. This landfill was in use during a later period than Site 9. A ROD addressing contaminated soil, groundwater, and sediments associated with Site 9 and Site 58 was completed in September 1998.

OU5:
The 1400 Area Landfill (Site 17) is an inactive landfill located in the northwest corner of the NSWCDL. Two unnamed drainage tributaries form the western and eastern boundaries of the site. A small pond is located in the western portion of the site with a marsh on the eastern portion. The site was used as a landfill, where municipal solid waste and construction debris were deposited, compacted, and covered on a periodic basis during the early 1970s and possibly until 1978. The landfill is fully vegetated with tall grass. Soil cover exists over the majority of the landfill. The area bordering the site to the north and west is undeveloped and heavily wooded. A ROD addressing contaminated soil and groundwater at Site 17 was completed in September 1998.
 
Remedy:  The selected remedy for Site 17 is to use phytoremediation to address both soils and groundwater. Institutional controls, as well as groundwater, surface water, and sediment monitoring will also be a portion of the remedy. A landfill area would be capped to address surface soil contamination with a 2-foot-thick vegetative soil layer. Natural vegetation such as hybrid poplars and evergreens would be planted on this layer to control erosion and reduce infiltration and groundwater discharge to the tributaries via evapotranspiration and as a habitat enhancement. The alternative cap would achieve an equivalent net reduction in infiltration and provide equivalent erosion protection.

Waste/fill within 100 feet of the tributaries would be excavated. It is estimated that 17,600 cubic yards would have to be excavated and consolidated beneath the cap. The marsh sediment near GW17-13 would be remediated to address residual mercury contamination, even though the sediment criteria are not exceeded. The remedy would excavate 970 cubic yards of marsh sediment and transport to an off-site treatment and disposal facility. Groundwater discharging to surface water bodies at Site 17 would be contained by reducing infiltration and evapotranspiration using natural vegetation such as hybrid poplars and evergreens.

Institutional controls would be implemented to limit future land use. Institutional controls will include access controls, signs along the perimeter of the site, restrictions on shallow groundwater use for drinking water, description of land use controls in the base master plan, periodic monitoring and re-evaluation of land use controls, annual certification that institutional controls are in place, notification to the Environmental Protection Agency (EPA) and state regulators whenever the Navy anticipates any major changes in land use restrictions, public notice, and a deed notification.

Monitoring of sediment, surface water, and groundwater will be conducted to ensure that no adverse effects to ecological receptors are occurring due to release of Site 17 contaminants. This alternative maintains institutional controls on the media of concern until a residential land-use scenario has been evaluated in the risk assessment and a decisions is made at that time to either maintain or deleted the institutional controls on one or all of these media.

Estimated Capital Cost: $2,400,000
Estimated Annual O&M Costs: $37,000 for one year and $15,550 for five years
Estimated Present Worth Costs: $2,800,000
 
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