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~_~ Subsurface conditions encountered in the 23 exploratory borings at the site vary with location and depth, with the strata typically consisting of a very thick layer of very stiff to hard, slightly moist, lean clay with gravel and scattered to numerous small to very large rock fragments (CL-GC), overlying shale or interbedded sandstone and shale or coal at depths exceeding 70 feet. Ground water was encountered in only three borings, at depots of 20 to 48 feet. The following sections describe each strata in more detail. Lean Clay with Gravel (CL-GC): The majority of the overburden materials at this site can be described as a matrix of silty lean clay supporting scattered to numerous fragments of sandstone. The sandstone fragments were distributed unpredictably with depth. As shown on the Boring Logs, some holes encountered more gravel-cobble-boulder (GCB) material titan others, in particular, Borings 2, 3, 4, 5, 12 and 13. Some of the borings encountered mostly clay, with • some discrete boulders or cobbles, such as Borings 14-23. Still other Borings (6, 8, 9 & 11) were predominantly clay and small shale and coal fmgments. The plasticity of the clay was low in samples tested from Borings 1-4 in the extreme lower part of the project, and in Borings 11, 15, l9 and 22 from the edges of the project area. These samples generally had liquid limits of 21 to 34 and plasticity indices of 4 to 17. Percent silt and clay fines content varied up to 89. Most of the rest of the samples tested had liquid limits of 34 to 47 and plasticity indices 17 to 25, indicating a moderately plastic, but still lean, clay. Resistivity testing of a sample of the sandy clay from Boring 11 at a depth of 9 feet indicates a rather low minimum resistivity of 150 oltm-cm at a moisture content of about 23 percent. The pH of that sample was found to be 8.1, or slightly basic. Two samples of clay were tested and found to have anon-detectable amount of water-soluble sulfate. • 9