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: The Meadowbrook artificial-recharge project, a cooperative effort between the U.S. Geological Survey and the Nassau County Department of Public Works (NCDPW) since 1975, is intended to demonstrate the feasibility of using reclaimed wastewater to replenish and improve the quality of Long Island's ground water. This report presents the results of geologic, hydrologic, and hydrochemical studies that were done at the Meadowbrook artificial-recharge site to define conditions prevailing before the start of recharge operations.

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.

This report presents the analysis of "data from three two-day aquifer tests of the unconfined aquifer (water-table_ aquifer in southern Nassau Count, Long Island, during the autumn of 1979.

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 describes (1) methods of computation used to obtain the daily lake inflows and outflows and river discharges; (2) sources of error and their implications for reliability of the computed values; and (3) a technique for smoothing lake-level hydrographs that minimizes the effect of random fluctuations in daily lake-levels resulting from seiche or wind action.

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.

From purpose and scope: The main purpose of this monitoring was to gather several years of data on PCB concentrations preparatory to removal of contaminated sediments by dredging, which was originally scheduled for the early 1980's. Plans for dredging and disposal of sediments are currently being reevaluated. This report examines the contribution and transport of PCB's (polychlorinated biphenyls) from various reaches of the Hudson River and the changes in PCB concentration since 1977, when discharge was terminated.

From purpose and scope: The purpose of the study was to collect detailed water level information needed for calibration of the U.S. Geological Survey's digital computer model of ground-water flow.

From purpose and scope: The purpose of this report is to develop and test steady-state method for the measurement of propane-gas desorption coefficients in a natural channel flow as the first phase of the field assessments of hydrocarbon gas tracer method for reaeration coefficients. Three field tests were conducted in a straight 5.2 km reach of the Cowaselon Creek near Canastota, New York in June, July, and October, 1981.

From purpose and scope: This study was undertaken to evaluate the reduction in PCB concentrations in Hudson River water that occurs during treatment at the Waterford plant. The concentration of PCB's in untreated Hudson River water were compared with those in treated drinking water at Waterford, and an average removal efficiency at the treatment plant was calculated.