These discharges contained heavy metals, cyanide, PCBs, oil and grease. Sediments contaminated by the outfalls were dredged in 1978 and placed in the Jamaica Island Landfill, but concentrations of several heavy metals can still be detected off-shore. The DRMO was used for temporary storage of scrap metal, motors, paper wastes, lead and nickel-cadmium batteries, and other materials that were to be recycled or disposed of. Surface water runoff and erosion resulted in direct input of water and contaminated soil to the river. Batteries were observed in the past to be littering the shoreline.
Contaminants associated with the site include heavy metals, PCBs and petroleum hydrocarbons.
Hazardous and nonhazardous wastes were disposed of at the 25-acre landfill between 1945 and 1978. The area was originally a tidal flat between Jamaica and Seavey's islands. The materials reportedly disposed of in the landfill included the dredged spoils from Site 5, solvents, sludge, asbestos, blasting grit, incinerator ash and vaults containing mercury contaminated materials. Potential contaminants include heavy metals and organic compounds. Vaults containing mercury-contaminated materials were reportedly buried at two different locations in the Jamaica Island Landfill.