The Islip Municipal Sanitary Landfill covers 55 acres in Islip, New York and operated from 1963 to 1990. The U.S. Environmental Protection Agency (EPA) placed it on the National Priorities List (NPL), a roster of the country's most serious hazardous waste sites, in March 1989. Physical construction of the cleanup is complete, and the site has reached "sitewide ready for anticipated use" status, meaning cleanup goals for current and foreseeable land uses have been met. Long-term operation and maintenance continue under EPA oversight.
The site contaminated groundwater with 37 identified chemicals. Groundwater contaminants include metals such as arsenic, cadmium, chromium, lead, mercury, and nickel, along with volatile organic compounds (VOCs) like trichloroethene, tetrachloroethene, benzene, toluene, and chloroform. Landfill gas also carries several of these VOCs, including benzene, toluene, vinyl chloride, chlorobenzene, and ethylbenzene. In 1980, private wells near the landfill tested positive for contaminants, and the Town of Islip connected affected homes to the public water supply.
The cleanup remedy chosen in September 1992 involved capping the landfill and treating contaminated groundwater. Workers installed the multi-layer cap between 1993 and 1994. A groundwater pump-and-treat system, completed in 1996, runs at 350 gallons per minute and has treated roughly 5 billion gallons of contaminated groundwater. The cap has greatly reduced leachate generation and contaminant release into the aquifer. All scheduled construction was finished by April 8, 1998. The cleanup also includes a landfill gas collection and treatment system, extraction wells, drainage and erosion controls, and institutional controls.
Human exposure to contamination is currently under control. Contaminated groundwater has been stabilized in its original area, and monitoring continues to confirm it stays contained. The EPA completed its sixth Five-Year Review on September 13, 2023, confirming that cleanup actions continue to protect public health and the environment. The next five-year review is estimated between September and November 2028. The Town of Islip has also installed solar panels near the top of the landfill that generate enough electricity to power site operations.
Community members with questions can contact EPA's Community Involvement Coordinator or the Remedial Project Manager. Site documents can be reviewed in person at several locations, including the Central Islip Public Library, the Islip Town Clerk's Office, and the EPA's Superfund Records Center at 290 Broadway in New York City.
