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The Islip Municipal Sanitary Landfill site is located in Islip, New York. The 55-acre landfill is part of a 109-acre complex operated by the Islip Resource Recovery Agency. The Town of Islip operated the landfill from 1963 to 1990. Wastes disposed of at the landfill contaminated groundwater with hazardous chemicals. Following cleanup efforts to protect human health and the environment, the site’s long-term remedy is in place. Operation and maintenance activities are ongoing, including the operation of a groundwater treatment system.

Landfilling operations began in 1963 when an incinerator was built on site. Prior to construction of the incinerator, sand mining took place on the site property. In 1968, the incinerator closed down. By 1978, the landfill was the only operating public landfill in Islip. Landfill activities at the site took place in phases (cells). While the landfill property is 109 acres, only 55.4 acres were filled during Phases I and II. Phase I and Phase II reflect the unlined and lined area of the landfill, respectively. The remainder of the site property was used for temporary storage of ash fill, sand storage and borrow areas, setback/buffer zones, vehicle storage and other support uses. Most of the landfilling activities in the unlined portion of the landfill were carried out from the late 1960s through the early 1980s. In June 1978, 55-gallon drums containing dry cleaning solvent wastes were allegedly disposed of at the landfill.

In 1979, two houses on the eastern end of Woods Edge Court were purchased by the Town of Islip because high concentrations of methane suspected to have originated from the landfill were detected in the basements. In 1980, the Whiporwill School was closed due to suspected vinyl chloride contamination in the air. Subsequent air samples did not confirm this contamination, and the school reopened as a day care center. In 1983, an active gas collection system was installed to control migration of explosive gases beyond the site boundary. The gases, primarily methane and carbon dioxide, are collected in extraction wells and directed to generators, where the gas is burned to generate electricity, or to flares. In 1980, groundwater investigations near the landfill found private wells contaminated with vinyl chloride and tetrachloroethylene. The Town of Islip connected the homes to the public water supply.

Following additional site investigations, EPA placed the site on the Superfund program’s National Priorities List in March 1989.

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What Has Been Done to Clean Up the Site?

Initial Actions: Sampling in 1980 found private wells next to the landfill were contaminated with volatile organic compounds (VOCs). In response, the Town of Islip connected these residents to the public water supply in 1981.

Long-term Cleanup: After site investigations to identify the nature and extent of contamination and identify cleanup options, EPA selected the remedy in the site’s September 1992 Record of Decision (ROD). It included capping the landfill and treating the most contaminated portion of the aquifer. Cap installation started in early 1993 and finished in 1994. It uses multiple geosynthetic and soil layers. Cap maintenance activities are ongoing. Construction of the site’s groundwater pump-and-treat system finished in 1996. Since September 1996, the system has operated at a capacity of 350 gallons per minute. To date, approximately 5 billion gallons of contaminated groundwater have been treated. All scheduled site construction has been completed.

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What Is the Current Site Status?

The site is being addressed in two phases: initial actions and a long-term remedial phase focused on cleanup of the entire site.

The capping of the landfill has greatly reduced the potential for exposure to contaminants, and has also reduced both the generation of leachate and the release of contaminants into the aquifer.

Construction at the site was determined to be complete on April 8, 1998.

Operation and maintenance activities are ongoing.

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