OBSERVATIONS AT THE BALL STATE UNIVERSITY GROUNDWATER GEOPHYSICS WELL FIELD SINCE 1991

Records from three groundwater monitoring wells drilled for instructional purposes in 1991 are summarized. The wells are all completed in a glacial sand and gravel sitting directly on bedrock at 8 to 12 meter depth on the north end of campus. The records include gamma logs, seasonal temperature depth profiles, and conductivity. The water level data include periods of continuous hourly record which at various times show ideal examples of drawdown due to pumping at two deeper bedrock wells more than 500 meters distance, changes due to intense rainfall, more rapid fluctuations in a shallower perched horizon, effects of changes in barometric pressure, and earth tides. The water conductivity changes are related to leachate from a nearby coal storage pile and the subsequent remedial construction of a concrete pad and improved drainage retention pond.

There have been numerous student exercises for water flow direction, slug tests, water quality sampling, and geophysics. The site has been the location of over 20 different sets of student collected combined seismic refraction, resistivity sounding, and resitivity profile lines which are related to changes in the glacial stratigraphy, bedrock depth, seasonal water level change, and a leachate plume. A second set of three wells at the university's Cooper Farm environmental field area 2.5 km to the west were constructed in 2004 and have recently been equipped with a wireless monitoring system which allows continuous correlation of water depth, temperature, barometric pressure, soil moisture, total rainfall, and rainfall intensity. The subsurface geology of this site has also been studied using several pairs of refraction seismic and electric resistivity lines which demonstrate the importance of using both geophysical methods to better interpret subsurface wet and dry clay, sand and gravel, and weathered bedrock horizons.