Properties of the fractured glacial till at the Madison County, Ohio, Field Workshop Pit Site

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 hydra ulic conductivity and physical and chemical properties between the fracture -affected zones and the till matrix. In situ measurements of the saturated hydraulic conductivity were made in small boreholes positioned either in th e matrix or intersecting the fractures. Soil samples from both the fracture faces and the matrix were analyzed for particle size distribution, clay mi neralogy, calcite, dolomite, and. iron content. Hydraulic conductivity meas ured in boreholes intersecting fractures was 1.25 x 10(-5) cm/sec (0.018 in /hr), one order of magnitude greater than in boreholes in the matrix. Parti cle size distribution was the same for the fracture faces and the matrix. T he fracture faces showed no significant change in total clay content and a slight increase in expandable clay. Calcite content was 62% greater, dolomi te content was 6% lower, and iron content was 73% lower on the fracture fac es as compared to the matrix. The fractures affected approximately 7% of th e soil volume.