Most of Iowa's land surface is underlain by unconsolidated materials deposited during past glacial advances. These deposits are predominantly glacial tills with a significant clay content, and have long been considered to be relatively impermeable. For decades, glacial deposits were used as societies' "container" for waste disposal, and were believed to largely eliminate the movement of contaminants from the land surface to underlying aquifers. However, these deposits contain lithologic heterogeneities that may increase their ability to transmit groundwater. In addition, weathered tills contain fractures which further enhance their permeability. It has become apparent that these materials do not provide the safeguard once presumed.
To better assess the hydrologic and hydrogeochemical properties of glacial tills, the Geological Survey Bureau initiated the Aquitard Hydrology project. Two sites were investigated; one is located on the latest Wisconsinan glacial tills of the Des Moines Lobe, at an Iowa State University experimental farm, near Ames. Studies at this site were a cooperative venture between the Geological Survey Bureau and Iowa State University -- particularly the departments of Agricultural and Biosystems Engineering, Agronomy, Civil Engineering, and Geological and Atmospheric Sciences. The second site is located on Pre-Illinoian tills, roughly half-way between Iowa City and Cedar Rapids. Studies at this site were a cooperative venture between the Geological Survey Bureau and the USGS - Water Resources Division, Iowa District office. The Aquitard Hydrology project was officially funded for the period 1988-1992, but investigations continue. Numerous external publications have resulted from this effort. For further information contact Bob Libra (Robert.Libra@dnr.iowa.gov) at (319)335-1585.