A plume of ground water enriched by liquid metal‐plating effluent has formed downgradient from an industrial park in southeast Nassau County, New York. Discharges from the plant to the shallow aquifer began in the 1940's and continue to the present.
Core samples of aquifer material from the plume were analyzed by oxalate extraction and dithionite‐citrate‐bicarbonate (DCB) extraction methods for the presence of chromium and cadmium. Results of the extraction indicate that for 1 kilogram of soil, the median concentrations of extracted chromium and cadmium in aquifer material are 7.5 and 1.1 milligrams, respectively, and the maximum concentrations are 19 and 2.3 milligrams, respectively.
Recent geologic data indicate an extensive lacustrine clay unit within the glacial deposits in the area between the Harbor Hill and Ronkonkoma moraines in north-central Suffolk County. The unit, locally known as the "Smithtown clay unit" (informal usage), is an integral part of the glacial aquifer in this area. The clay occurs at depths varying from 90 feet above to 150 feet below National Geodetic Vertical Datum of 1929 (NGVD) and attains a maximum thickness of 170 feet in the northern part of the Town of Smithtown. Its upper surface is mostly above NGVD and reaches a maximum altitude of 90 feet in the Town of Huntington. The unit is predominantly clay but locally contains lenses of sand, silt, and gravel. The upper part of the clay is generally light to dark brown; the lower part is light gray, which is characteristic of other clays in the glacial aquifer.
The groundwater resources of the Pine Barrens, in southeastern Suffolk County, were appraised during 1982-83 for their potential for use as a supply of potable water. The study area encompasses approximately 50 square miles. The Precambrian bedrock is overlain by Cretaceous, Pleistocene, and Holocene deposits. The surficial material consists of morainal and outwash deposits overlain by recent beach and marsh deposits. The groundwater reservoir consists of three aquifers the Lloyd and the Magothy of Cretaceous age and the upper glacial of Pleistocene age. The water is generally of suitable quality for drinking and most other uses except in several localized spots where point-source contamination has been documented. Precipitation is the sole source of recharge. Average annual precipitation recorded in the area during 1943-82 was 43 inches, about half of which reaches the groundwater reservoir. Overland runoff is estimated to be 0.5 inches per year, and evapotranspiration 23 inches per year. Total public water-supply withdrawal in the area in 1982 is estimated to have been 9.09 million gallons per day (Mgal/d). The upper glacial aquifer is the major source of public water; pumpage in 1982 was 7.88 Mgal/d; pumpage from the Magothy was 1.02 Mgal/d, and pumpage from the Lloyd aquifer was 0.19 Mgal/d. Stream discharge is measured periodically at 17 streamflowmeasurement sites on the 11 streams in the Pine Barrens.
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