Problem - The major hydrogeologic units of Long Island, New York, have been delineated as part of the islandwide mapping effort of Smolensky, Buxton, and Shernoff that was published in 1989 as U.S. Geological Survey (USGS) Hydrologic Atlas (HA) 709. Concern about local details in the hydrogeologic framework that may not be represented in HA-709 has led the USGS, in cooperation with the U.S. Environmental Protection Agency (EPA), to assess the hydrogeology of the Long Island area so ground-water-flow modeling planned by EPA can more fully reflect local hydrogeologic conditions.
Objectives - The primary objective of this project is to construct geographic information system (GIS) datasets of the altitudes of the land surface, water table, and upper surfaces of the Magothy aquifer and Raritan confining unit depicted in HA-709. Newly collected well logs provided by the EPA will be interpreted, and used to evaluate and confirm or update the upper-surface altitudes of these and any significant local hydrogeologic units, as necessary.
Approach - The EPA has installed wells and collected stratigraphic information and gamma logs from over 30 locations since HA-709 was published. These EPA records, together with stratigraphic logs at 52 wells that were available in earlier studies, are to be compiled and incorporated into a database of borehole characteristics. The development of the borehole database will be combined with use of the GIS datasets derived from HA-709 to evaluate local details in the hydrogeologic framework, with emphasis on the Magothy aquifer.
Benefits - The results of this study will provide the EPA with an electronic dataset, which can be useful in the construction and calibration of future ground-water flow models. As additional data become available and are added to the database, the extent of local clay beds within the Magothy aquifer could be delineated to support subsequent modeling efforts and other assessments.
Location by County
Nassau County, NY