HYDROGEOLOGIC EVALUATION OF A SHALLOW GLACIAL AQUIFER

As a means of conserving water on the Youngstown State University campus, the suitability of a shallow glacial aquifer as an alternative water source for the University lawn sprinkler system was evaluated by students in the Introduction to Ground Water course during fall semester 2010. The evaluation focused on hydraulic conductivity, transmissivity and storativity physical properties and the aquifer aerial extent. The physical properties of the aquifer were determined using soil auger samples, slug tests, and a 33 hour aquifer pumping and recovery test utilizing one pumping well and a network of nine observation wells. The aerial extent of the aquifer was determined using topographic expression, soil auger boreholes, and pre-existing borehole logs used in the design of numerous campus buildings.

The aquifer is part of a Pleistocene kame terrace along the Mahoning River. It is a fine grained and well graded sandy material (CL-ML) having an average total thickness and saturated thickness of 8.9 feet and 7.0 feet, respectively. The aquifer is overlain by approximately six feet of silty clay (ML). The aquifer is present over an area of approximately 30 acres; however, its continuity is disturbed by numerous building foundations and utility installations. Laboratory determinations of permeability on soil auger samples yielded an average hydraulic conductivity of 0.51 ft/day (1.80 x 10^-4 cm/sec). Aquifer transmissivity and storativity were determined from slug test and pump test results using Bouwer-Rice and Neuman solutions for an unconfined aquifer and the AQTESOLV (v 3.5) computer program. The average transmissivity was 5.02 ft²/day and the average storativity was 0.18.

The pump test results indicate the aquifer is capable of yielding 17,000 ft³/hour; an amount that exceeds the University lawn sprinkler system demand. This value assumes ground water flow from surrounding areas will replace the produced water as pumping proceeds. The actual sustainable production is substantially reduced as the aquifer volume and continuity is affected by building foundations and the aquifer may be bounded by non-contributing materials such as clay and other low permeable materials. In addition, maximized aquifer yield requires the installation of multiple production wells which may be economically unfeasible.