Abstract: A facility consisting of a circular recharge basin 6.10 meters in diameter with a central observation manhole was developed on Long Island to study the role of the unsaturated zone during aquifer recharge with tertiary-treated sewage. The manhole extends through most of the 7.5-meter-thick unsaturated zone, which is composed of glacial outwash sand and gravel, and enables collection of water samples and monitoring of dynamic characteristics of the unsaturated zone during recharge experiments. The system contains instrumentation for monitoring infiltration rate, pressure-head distribution, soil-moisture content, ground-water levels, and soil gases. The 24.55-square-meter recharge basin has operated in all seasons intermittently since April 1975 and, as of April 1978, has transmitted 62 million liters of tertiary-treated effluent to the water-table aquifer. Overall performance of the facility indicates that it is suitably designed for monitoring the unsaturated zone during artificial-recharge experiments.

Abstract: Concentrations of nitrate, chloride, and total sol ids in water in the Magothy aquifer, southeast Nassau County, N.Y., show a steadily increasing trend from the early 1950's to 1973. Vertical distribution of nitrate, chloride, and total-solids concentrations as shown in sections of the study area indicate downward movement of these constituents. Maximum concentrations are in a zone underlying the areas of Westbury, Hicksvil.le, and Plainview. Nitrate (as nitrogen) concentration increased from 4-5 milligrams per liter to 7 milligrams per liter in the area of Westbury and from 3 to 10 milligrams per liter in Plainview during the period 1950-73. During this same period, a 10 milligram-per-liter line of equal-chloride concentration on a cross section in the Westbury area moved downward a distance of less than 50 feet (15 meters), and in the area of Hicksville nearly 150 feet (45 meters). Total-solids concentration doubled in the area of Plainview, where maximum downward movement of pollutants was observed.

This report presents the results of water sampling in two New York counties and concludes that the possibly cause of fluctuations of chloride, sulfate, and nitrate in the water are "precipitation, lawn fertilizer, dissolved salts from storm runoff, and effluent from septic tanks and cesspools." This report also includes a number of maps and graphs.