From purpose and scope: This report is the first in a three-part series describing the U.S. Geological Survey's efforts in the detailed hydrologic investigation of southern Nassau and southwest Suffolk Counties, which includes a ground-water modeling study to predict the effects of an extensive sewer network scheduled to be completed in 1985. As the introduction to the series, this report has four objectives: (1) to present a detailed description of the hydrologic system in the area, including newly acquired hydrogeologic information; (2) to define the hydrogeologic factors that will be affected by the sewer network; (3) to explain the modeling strategy and describe the techniques used to develop the ground-water models of the two adjacent areas studied; and (4) to present a preliminary evaluation of the effects of sewers as predicted by a regional ground-water flow model.

Purpose and scope: This report discusses the design, theory of operation, performance characteristics, and sampling implications if the inclined gravity lysimeter. This variation of a gravity lysimeter can be constructed to maximize capture efficiency and eliminate artificial filtration and is used most successfully in coarse, moist soils where access for installation is from a trench or observation manhole.

Purpose and scope: This report depicts in detail the areal extent, altitude, thickness, and lithology of the "20-foot" clay and Gardiners Clay (the two thickest and most extensive near-surface confining layers in the area) and redefines the surface of the geologic units that directly underlie these clay units at various locations--the Matawan Group-Magothy Formation, undifferentiated, the Monmouth Group, and the Jameco Gravel.

Purpose and scope: This report presents results from an evaluation of geologic data collected and compiled as part of a continuing investigation and appraisal of hydrologic conditions in Suffolk County. The investigation is part of a cooperative program of water-resources studies made by the U.S. Geological Survey in cooperation with the Suffolk County Water Authority and the Suffolk County Department of Health Services.