The Port Washington Landfill site is on the eastern portion of Manhasset Neck, Nassau County, Long Island, New York. The 139-acre municipally owned site consists of two landfilled areas separated by a vacant area. The Record of Decision addresses the 53-acre inactive landfill on the western portion of the site, which is the suspected source of methane gas thought to cause furnace explosions in residences neighboring the landfill during 1979 through 1981. From 1974 to 1983 the landfill operator accepted incinerator residue, residential and commercial refuse, and construction rubble for disposal. Because extensive air monitoring, performed in 1981, revealed high methane levels in several areas residences, a venting system was installed to prevent subsurface gases from migrating west of the landfill and to destroy hazardous chemicals commonly detected in sanitary landfill gas. The selected remedial action for the site includes capping the landfill; rehabilitating the existing gas collection system and installing additional vacuum extraction vents; ground water pumping and treatment.