Superfund Information Systems: Site Profile

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The 38-acre Syosset Landfill site is located in Oyster Bay, New York. The landfill operated from about 1933 to 1975. Between 1933 and 1967, no restrictions were imposed on the types of wastes accepted at the landfill. Waste types included commercial, industrial, residential, demolition, agricultural, sludge material and ash. In 1967, with the opening of another landfill east of Syosset in Old Bethpage, the town stopped using the landfill for disposal of domestically generated wastes. Some industrial wastes continued to be disposed of at the landfill until its closure in 1975. Following the site’s cleanup, EPA took it off the Superfund program’s National Priorities List in April 2005.

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What Has Been Done to Clean Up the Site?

Immediate Actions: A permanent ventilation trench prevents gas migration from the site to the school area nearby. Continuing air analysis indicates that the gas concentrations in the area north of the ventilation trench were reduced to non-detectable levels.

On-site Contamination: After an investigation to determine the extent and nature of on-site contamination. EPA selected a remedy in the site’s 1990 Record of Decision, or ROD. It called for capping the landfill, monitoring and maintaining the gas collection system, installing an additional gas venting system, monitoring air and groundwater quality, maintaining the fence around the perimeter of the landfill, and implementing institutional controls to restrict future use of the landfill. Capping of the landfill finished in November 1997. About 6.7 million tons of contaminated material were contained.

Off-site Contamination: The possible migration of contaminants from the landfill was investigated in 1992 and 1993. EPA determined that contamination was limited and did not pose a significant threat to human health or the environment. Therefore, no groundwater remediation was necessary. EPA documented this conclusion in the site’s March 1996 ROD.

EPA conducted a five-year review at the site in February 2017. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The review concluded that response actions at the site are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment. There are no exposure pathways that could result in unacceptable risks. None are expected as long as site use remains consistent with the site’s access and institutional controls, and those controls are properly monitored and maintained. The next five-year review is scheduled for February 2022.

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What Is the Current Site Status?

The site was addressed in two stages: immediate actions and a long-term remedial phase focused on cleanup of the entire site.

The threat of gas vapor migration from the landfill has been eliminated. In October 1996, the installation of the cap was completed and approximately 6,732,000 tons of waste were contained. The capping of the landfill has eliminated the potential of a direct contact threat and will control leachate generation associated with rainfall infiltration.

In 2005, EPA determined that the responsible parties and others have implemented all appropriate response actions selected in the 1990 ROD. Following the site’s cleanup, EPA took it off the Superfund program’s National Priorities List in April 2005.

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