Record of Decision System (RODS)
NEW LONDON SUBMARINE BASE
|Site Name:||NEW LONDON SUBMARINE BASE|
|Address:||ROUTE 12 CRYSTAL LAKE RD|
|City & State:||NEW LONDON CT 06349|
|NPL Status:||Currently on the Final NPL|
|ROD Type:||Record of Decision|
|Media:||Groundwater, Sediment, Soil, Surface Water|
|Contaminant:||Base Neutral Acids, Dioxins/Dibenzofurans, Inorganics, Metals, PAH, PCBs, Pesticides, VOC|
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 United States Navy Submarine Base New London (NSB-NLON) consists of approximately 547 acres of land and associated buildings in southeastern Connecticut in the towns of Ledyard and Groton. NSB-NLON is situated on the east bank of the Thames River, approximately 6 miles north of Long Island Sound, and is bounded to the east by Connecticut Route 12, to the south by Crystal Lake Road, and to the west by the Thames River.
In 1867, the State of Connecticut donated a 122-acre parcel on the east bank of the Thames River to the Navy. The Navy began using the property in 1868 when it was officially designated as a Navy Yard. The Navy designated the site a Submarine Base in 1916. Between 1935 and 1945, the Navy built in excess of 180 buildings and expanded NSB-NLON from 112 to 497 acres through the acquisition of adjacent land.
NSB-NLON currently serves as a major support center for the U.S. Atlantic fleet. Additionally, NSB-NLON includes housing for Navy personnel and their families, submarine training facilities, military offices, medical facilities, and facilities designed for the maintenance, repair, and overhaul of submarines. Land use adjacent to the NSB-NLON is generally residential or commercial.
The Groton Water Department supplies potable water to NSB-NLON. The primary sources of the Groton water supply are reservoirs that are supplemented with wells. The water supplies are located within the Poquonock River Watershed, located east of NSB-NLON, which is not within the NSB-NLON watershed. Groundwater at NSB-NLON is not used for potable water.
In 1975, the Department of Defense developed a program, known as the Installation Restoration Program (IRP) to investigate and clean up problem areas involving contamination at federal facilities such as the NSB-NLON. The NSB-NLON was placed on the National Priority List (NPL) in August 1990.
Operable Unit 1 (OU1):
The Area A landfill is located in the northeastern and north-central section of the site. It is approximately 13 acres in size. It is a flat area bordered by a steep, wooded hillside, that rises to the south, a steep wooded ravine to the west and a wetland, referred to as the Area A Wetland, to the north. Runoff from the landfill drains as overland flow north into the Area A Wetland, which discharges to the Area A downstream and ultimately to the Thames River.
The landfill opened sometime prior to 1957. From 1963 to 1973, non-salvageable materials generated by submarines and base operations were disposed in the Area A landfill. There are no records indicating volume or type of waste disposal in the landfill. However, they may include radioactive wastes and medical wastes from the hospital; industrial wastes from the ship repair and maintenance facilities; commercial/residential wastes from housing and office facilities; and bulky wastes from construction activities. On-site landfilling operations ceased in 1973, and a bituminous concrete pad was constructed in the southwest portion of the landfill for staging of industrial materials and equipment.
A Record of Decision (ROD) was completed in September 1995 addressing the Area A Landfill.
The Defense Reutilization and Marketing Office (DRMO) is located adjacent to the Thames River in the northwestern section of NSB-NLON. The site covers approximately 3 acres of land gently sloping towards the river. From 1950 to 1969, the DRMO was used as a landfill and waste burning area. At various times, metal and wood products have been stored over most of the site. Building 491 was used to store miscellaneous items including batteries. A Phase I Remedial Investigation (RI), a Phase II RI, and a Focused Feasibility Study (FFS) were conducted over the course of several years, ending in March 1997. A time-critical removal action was completed in January 1995, wherein approximately 4,700 tons of contaminated soil were excavated and disposed of at an off-site hazardous waste landfill. One of the two RODs completed in March 1998 addressed DRMO soil and groundwater.
The Area A Downstream/Overbank Disposal Area (Area A Downstream/OBDA) drains the Area A Landfill and Area A Wetland through water bodies and streams that ultimately flow into the Thames River. The main cause of contamination at the Area A Downstream/OBDA was the application of pesticides. These pesticides were reportedly applied on the surface of water bodies to control mosquito proliferation adjacent to nearby base recreational facilities. Additional contaminants are the inorganic constituents of the river dredge spoil which have been carried over from adjacent sites. A Phase I RI, a Phase II RI, a FFS, and a Wetlands Functions and Values Assessment were conducted over the course of several years, ending in May 1997. One of the two RODs completed in March 1998 addresses the Area A Downstream/OBDA soil and sediment (and surface water to the extent necessary for the remediation of sediment).
The Spent Acid Storage and Disposal Area (SASDA) is a tank that was used for temporary storage of waste battery acid before and after World War II. The batteries were placed on a concrete pad next to the tank where some acid occasionally leaked. The SASDA is located in a paved parking lot in a well-developed portion of the NSB-NLON. The former tank and the surrounding soils encompass approximately 1000 square feet.
A removal action was completed in January 1995. The tank, 318 tons of lead contaminated soils, contaminated pavement, and the tank contents were removed. The excavated area was backfilled with clean borrow and covered with bituminous pavement. A ROD presenting the no further action decision for the soils at the SASDA was completed in September 1997.
The Rubble Fill Area at Bunker A-86 (Site 4) is located southwest of the Area A Landfill. The size of the site is approximately 25 feet in width by 60 feet in length. Assessments indicated discarded construction materials (wood and concrete) and chemical containers were present at the site. A removal action was completed in May 1997, during which approximately 300 cubic yards of contaminated soil were removed from Site 4 and placed underneath the RCRA C cap at the adjacent Area A Landfill. The wood debris was disposed off-site. A ROD for Site 4 soils was completed in June 1998.
The Navy has selected Excavation/Dredging, On-site Dewatering, and Off-site Disposal of Soil/Sediment; Restoration of Wetlands and Waterways; and Monitoring as the most appropriate remedy for soil and sediment at Area A Downstream/Overbank Disposal Area (Area A Downstream/OBDA) at Naval Submarine Base New London (NSB-NLON).
The selected remedy consists of excavation of the contaminated soil and sediment, followed by on-site dewatering and off-site disposal. The sequence of actions envisioned at a conceptual state is as follows: (1) removal, on-site treatment, and discharge of standing water from ponds and streams with appropriate stream flow diversions; (2) clearing/grubbing of contaminated soil areas; (3) dredging, on-site dewatering and off-site disposal of contaminated sediment; (4) excavation, on-site dewatering and off-site disposal of contaminated soil; (5) placement of clean soil backfill over the excavated soil areas with top soil cover and revegetation to replace altered wetland functions and values; and (6) placement of suitable borrow material over the dredged sediment areas (such as sand in ponds and gravel in streams) and restoration of aquatic habitats. All of the groundwater seepage and surface water run on into the site from adjacent Area A wetland and Area A Landfill will be diverted to bypass the areas of the proposed excavation and be discharged into downstream culverts. The residues from dewatering and wastewater treatment, 1600 tons of clogged filter, spent filter elements, and 10 tons of granular activated carbon (GAC) would be disposed of off-site. Fencing and security measures are assumed to be present and will continue to be instituted during the remedial action.
Approximately 1.0 million gallons of standing water will be treated on site by filtration and GAC adsorption at the Dewatering/Wastewater Treatment (DW/WWT) facility and discharged downstream of the site at a suitable location in a storm sewer that will ultimately discharge to Thames River. Approximately 7,000 cubic yards of contaminated sediment will be excavated. The estimated depths of excavation are expected to vary between 0.5 feet to 3.0 feet depending on the depth to clean sediment. The excavated sediment will be transported to the DW/WWT facility. This facility is expected to be constructed at or near the neighboring Area A Landfill. Furthermore, approximately 11,000 cubic yards of contaminated soil will be excavated and transported to the DW/WWT facility. The areas, depths and volumes of excavation are likely to change when the extent of contamination is clearly defined at the time of remedial design.
Monitoring of contaminated media would be conducted to assess any migration or need for future action. Moreover, in the event of future transfer of property, the deed would carry records of the contamination and restrict potential land development.
Estimated Capital Cost: $8,080,000
Estimated O&M Costs: $50,000 (wetland restoration total cost for years 0 to 5)
Estimated Net Present Worth Costs: $8,125,000
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