Nassau County Executive Edward Mangano (March 19, 2012)

Nassau County Executive Edward Mangano (March 19, 2012) Credit: Howard Schnapp

Nassau County Executive Edward Mangano is opposing a state plan to clean up toxic groundwater flowing beneath the Bethpage Community Park, saying it doesn't do enough to protect 250,000 area residents.

The Oyster Bay Town park was donated in 1962 by what is now Northrop Grumman. For decades the aerospace company legally disposed of paint, oils, chromium-tainted sludge, arsenic, solvents and other compounds at the site. The contaminated plume has affected several water district wells and is moving toward others.

The state Department of Environmental Conservation issued a cleanup plan for the park in late May focusing on a 3.75-acre parcel that is home to ballfields. The agency closed its public comment period Monday.

"After two decades of investigations, the DEC has not found a solution to control the migration of this plume and mitigate its impacts on Nassau County water suppliers," Mangano, a Bethpage resident, wrote in a July 27 letter to the DEC.

Agency officials Monday evening did not have a tally of comments the DEC had received. A final decision on the cleanup plan is to be made in 90 to 120 days. "DEC is keenly aware of the public's concern and will consider all comments submitted," spokeswoman Lisa King said.

Contamination was discovered in water supplies in 1995. The carcinogens trichloroethylene -- known as TCE -- and polychlorinated biphenyls -- known as PCBs -- have been found in the soil and groundwater. Chromium, cadmium and volatile organic compounds also have been identified.

The $61.5 million state plan calls for the installation of at least one well to extract and treat groundwater, and the excavation of 45,000 cubic yards of shallow soil and 25,000 cubic yards of deeper soil at the site and nearby residential yards.

The plume's "migration impacts our water supply and threatens further contamination of Long Island's sole source aquifer, drinking water supplies and the Great South Bay," Nassau County Legis. David Denenberg (D-Merrick) wrote to the DEC earlier this month, saying the toxins threaten 33 public drinking supply wells in Massapequa, Bethpage and South Farmingdale, as well as those owned by Long Island American Water, a private supplier.

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