BASELINE HYDROGEOLOGIC CHARACTERISTICS OF THE GROUND-SOURCE GEOTHERMAL FIELD AT BALL STATE UNIVERSITY (MUNCIE, IN)

In May 2009, Ball State University (Muncie, IN) began drilling the nation’s largest ground-source geothermal project to replace aging coal-fired boilers. Its activation is projected for Summer 2011. Geothermal exchange loops were installed to add or remove heat from the ground to moderate the temperatures in campus buildings. Currently, in phase one, approximately 1800 geothermal wells have been drilled to a depth of 400 ft in a 15-ft grid pattern. These wells are divided into two fields (North and South) and are located in the northern part of campus. Cardinal Creek flows from the Duck Pond between the North and South geothermal fields. In the southwest corner of the South field, groundwater is pumped from the construction site of the new geothermal heat-exchange building and is being discharged into the Duck Pond and Cardinal Creek.

Ball State University upper-level geology students are observing and measuring the potential impact of the geothermal well field on groundwater temperature and flow direction. The class is determining baseline hydrogeologic conditions, which will be used for comparisons when the ground-source geothermal field goes online. Baseline data sets are being gathered using ten monitoring wells: two shallow wells in gravel (~30 ft) and eight deeper wells in limestone (~70 ft). Using a downhole probe, temperature, conductivity, and potentiometric surface data were collected. Based on water elevations, three-point problems for the field area were developed to show the direction of groundwater movement.

Initial studies show that the current water temperatures are more consistent at depth than at the potentiometric surface. The overall trend of groundwater flow is approximately S36°W (from northeast to southwest). In addition, the three-point problems suggest that the dewatering pump is presently creating a groundwater depression, which is diverting groundwater from the North field and drawing water from the Cardinal Creek. Upcoming investigations will further study groundwater characteristics such as flow rates and water chemistry.

Additional co-authors: MOODY, Diana; DRANSFIELD, Joe; BARNS, Clayton; POLICICCHIO, Heather; STERLING, Kara; ALEXANDER, Aaron M.; and GAFFIN, D.H., Geological Sciences, Ball State University, Muncie IN