The New York State Department of Environmental Conservation (DEC) will hold a public meeting at 7:30 p.m. on Tuesday, Feb. 25 to present its plan for interim remediation of groundwater contamination emanating from the General Instrument Corporation Inactive Hazardous Waste Disposal Site. The meeting will be held in the Dutch Lane Elementary School located at 50 Stewart Avenue in Hicksville.

Vishay General Semiconductor (VGS), the corporate successor to General Instrument Corporation, has developed plans to install a groundwater recirculation system to begin remediation of groundwater contamination. Groundwater recirculation involves extracting groundwater from approximately 270 feet below the ground surface, "stripping" the volatile contaminants from the water and reinjecting the cleaned water. The water then circulates back through the ground and a portion of it is retreated. The system will be designed to intercept the entire width of the plume(s) that is presently attributed to the former General Instrument site.

The 11.5-acre General Instrument site is located on the northeast corner of the intersection of West John Street and Cantiague Rock Road in Hicksville. In 1994 General Instrument Corporation ended operations at the facility and moved all facility furnishings and equipment from the site. When it was in operation, the facility developed and manufactured electronic devices.

Processes at the site involved the use of a variety of chemicals including chlorinated and non-chlorinated solvents. Waste solvents were stored in two underground tanks at the site. General Instrument determined in 1980 that a 2,000-gallon tank may have leaked. The tank and some of the affected soils were removed in December 1980, and groundwater monitoring wells were installed to evaluate potential effects on groundwater. In 1982 a 1,000-gallon tank was removed. The chlorinated solvents trichloroethylene (TCE), perchloroethylene (PCE or perc), also known as tetrachloroethylene, and cis-1,2, dichloroethylene (DCE), a breakdown product of TCE have been found in the soil and groundwater at this site.

Investigations completed since 1986 have revealed that soils were contaminated by solvents in the vicinity of the two previously removed waste solvent tanks. In addition, three distinct plumes of contaminated groundwater were identified: one associated with the 2,000-gallon tank, one associated with the 1,000- gallon tank area and one attributed to an old sump in the floor of a tunnel beneath the building.

VGS has completed five phases of groundwater investigation under DEC oversight. However, additional investigation work is necessary to delineate the extent and fate of the offsite dissolved plumes. Other Investigations of groundwater in the area, including the former Sylvania Electric Products site north of the General Instrument site could indicate other sources of groundwater contamination exist in the area.

In addition to the planned groundwater recirculation system, VGS will evaluate the quality of the groundwater just upgradient of two Hicksville Water District public water supply wells located on Stewart Avenue. Volatile organic compounds have been detected in these wells, but the drinking water is treated to make it safe to consume. The contamination in the wells cannot be attributed to the General Instrument site or any other site at this time. VGS will install a monitoring well upgradient of the water supply wells. This well will serve as a point to measure the quality of groundwater approaching the public supply wells and to detect if any of the known plumes from any of the upgradient sites are approaching the public supply wells.

In 1997 NYSDEC issued a Record of Decision that selected soil vapor extraction as the preferred remedy for onsite soil contamination. The soil vapor extraction system had been installed in 1994 as an interim remedial measure, and continues to operate. Removal of the contamination from the soil above the water table appears to be complete at two of the three source areas. Groundwater monitoring will continue to confirm complete remediation.

At the Feb. 25 meeting, DEC and State Department of Health staff will review the history of the site and describe the results of investigations completed to date and the rationale behind the current proposal. Meeting participants will be given the opportunity to ask questions on the plan.

Copies of investigation reports and other site documents are available at the Hicksville Public Library and at the DEC's regional office in Stony Brook. Information is also available at www.dec.state.ny.us/website/reg1/hazwaste.html or may be obtained by calling Mark Lowery at (631) 444-0350.