Submitted to: Ohio Journal of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2000
Publication Date: N/A
Citation: N/A Interpretive Summary: Water and contaminants obviously do move through the so-called impermeable glacial till deposits underlying most of the Midwest US. Evidences of surface and ground water contamination from sources such as leaking landfills, septic leach fields, and food processing waste lagoons indicate that glacial tills are not impermeable, and, in fact, that substantial amounts of water and contaminants can move through the tills. Recent studies indicate the presence of extensive fractures within the glacial till deposits. There is a need to increase awareness of the fractures and to understand more about their origin, their properties, and their contribution to ground water recharge and contaminant transport. This paper reports that water moves through these fractures much faster than would be estimated by conventional measurement technologies used for siting landfills and other waste disposal systems. This information will be helpful to hydrogeologists for estimating recharge rates, to consultants and others who do waste treatment facility siting for evaluating site suitability, and to the general public who will benefit from having treatment facilities that are properly sited and do not leak.
Technical Abstract: Water and contaminants obviously do move through the so-called impermeable glacial tills in Ohio. This study was conducted to illustrate the extensive presence of fractures in the till and to quantify the differences in hydraulic conductivity and physical and chemical properties between the fracture-affected zones and the surrounding till matrix. In-situ measurements of the saturated hydraulic conductivity were made in small boreholes positioned either in the natrix or intersecting the fractures. Soil from both the fracture faces and the matrix was analyzed for particle size distribution, clay mineralogy, calcite, dolomite, and iron content. Hydraulic conductivity measured in boreholes intersecting fractures was 0.045 cm/hr, one order of magnitude greater than in boreholes in the matrix. Particle size distribution was the same for the fracture faces and the matrix. The fracture faces showed no significant change in total clay content and a slight increase in expandable clay. Carbonate content was 62% greater, dolomite content was 6% lower, and iron content was 73% lower on the fracture faces as compared to the matrix. The fractures affected approximately 7% of the soil volume.