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The New London Submarine Base site covers 576 acres on the eastern bank of the Thames River in Groton and Ledyard, Connecticut. Wastes generated at the base contaminated soil, sediment, and groundwater. Long-term cleanup and monitoring are ongoing.

The base was established in 1868. It has served as an operation and support base for submarine activities in the Atlantic Ocean since 1916. The site contains many contaminated areas, including three landfills, chemical storage sites, tank farms, contaminated watercourses, and varying degrees of groundwater contamination. The U.S. Navy is the lead agency for site investigation and cleanup, with oversight provided by EPA and the Connecticut Department of Energy and Environmental Protection.

From 1957 to 1973, VOCs, pesticides, PCBs, spent battery acids and other wastes were buried below the water table in an 11-acre landfill situated near wetlands. A disposal area known as the Over Bank Disposal Area was created after an earthen dam was built in 1957. This Defense Reutilization and Marketing Office was used as a burning ground and landfill from 1950 to 1969 and is now used for temporary storage. Inspection reports from 1982 recorded leaking containers and evidence of spills associated with containers stored on the ground. In 1983, about 40 gallons of PCB-contaminated oil were reported to have been spilled onto the ground. In 1988, Navy sampling revealed lead, cadmium and pesticides in sediments and surface water.

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What Is Being Done to Clean Up the Site?

The site is being addressed through federal actions.

There has been substantial environmental progress at the site. All three of the landfills have been capped. Eight removal actions have been completed. Contaminated soil and sediment at the area known as the Over Bank Disposal Area has been removed. Wetland restoration and soil excavation at the weapons center has finished. Site areas are listed below. The Navy investigated almost all of these areas in 1990.

Area A Landfill: This landfill had accepted all non-salvageable materials. Leachate from the landfill drains into wetland and is ultimately carried downstream and discharged into the Thames River. In late 1995, a cleanup plan was developed that included installing a double-lined landfill cap and monitoring the site. This work was done in 1997. Before this, however, a cleanup was done at a drum storage area on top of the landfill.

Over Bank Disposal Area: The Navy removed all contaminated soils and debris as an interim cleanup measure in March 1997. The 1998 cleanup plan required excavating and dredging contaminated soil and sediment, and wetlands restoration. A follow-on cleanup addressed related compounds discovered at the new source area. The remedy was updated in 2007 to include institutional controls and five-year reviews because some waste was left in place.

Defense Realization and Marketing Office: The Navy removed soil contaminated with PCBs and lead, filled the area with clean fill, and placed asphalt over the area. Monitoring will determine if the cleanup was successful. The 1998 and 2006 remedies required restrictions to prevent digging, disturbing the cap and other areas as well as groundwater monitoring to make sure contaminants do not migrate to the Thames River. These remedies were in place by 2008.

Lower Sub Base: In 1994, the Navy removed lead-contaminated soil from the Building 31 area, disposed it off site, and filled the area with clean fill. In January 2010, the Navy dredged contaminated sediments near Pier 1 in the former marine railway. A final remedy was selected for the site in 2012 for soil, sediment, and groundwater.  The remedy is currently being constructed.

Goss Cove Landfill: Landfill capping finished in October 2001. Groundwater monitoring is ongoing.

Area A Weapons Center: Excavation of contaminated soil and sediment finished in late 2001.

Torpedo Shops: A 2004 decision by EPA requires excavation with off-site disposal. About 1,600 cubic yards of contaminated soil was excavated and disposed off site.

Basewide Groundwater: For some parts of the site, use restrictions were put in place to ban extraction and use of the groundwater.

Area A Wetland: Excavation of contaminated sediments and restoration of native wetland vegetation finished in 2013.

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What Is the Current Site Status?

There has been substantial environmental progress at the Naval Submarine Base. All three of the landfills have been capped, eight removal actions have been completed and contaminated soil and sediment at the area known as the Over Bank Disposal Area has been removed. Wetland restoration is finished at this area. And soil excavation was finished at the weapons center in December 2001.

Of the 40 sites originally identified, 38 have been cleaned up or closed out. Although only one site requires further action, all potential health risks have been controlled. In addition, while many of the contaminants detected across the site were within acceptable risk standards for industrial use, risks associated with future residential use scenarios were identified and are the focus of EPA’s former and future cleanup decisions.

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