STUDY LOCATION AND HYDROGEOLOGY
A recent groundwater flow and mass transport study on Long Island in Nassau County, New York evaluated plume transport in the confined Lloyd aquifer. The study was initiated following the detection of organic compounds of unknown origin at a public supply well that was screened in the Lloyd aquifer. The analysis objective was to evaluate whether a groundwater plume migration pathway existed from an identified potential source area, where cooling water injection wells could have introduced contaminants into the confined aquifer and impacted the public supply well. The relative locations of the cooling wells and the public supply well are shown in Figure 1.
The cooling water injection wells were installed in the 1960s. The affected public supply well was installed in 2002 as a replacement for an older well and organic compounds were detected at the new well shortly after start up. Limited operational information is available about the cooling water injection wells. The groundwater system on Long Island consists of unconsolidated deposits of clay, sand and gravel underlain by Precambrian bedrock (Smolensky and others, 1989). Late Cretaceous deltaic clays, sand and gravel comprise the Lloyd sand, Raritan clay and Magothy formation.