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.

From purpose and scope: The study was made to obtain baseline data for the island (Shelter Island) and as part of a larger study of shallow ground-water quality in Suffolk County, New York.

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.