DRAFT <br />observed in the borings, our experience in the project area indicates boulders are likely <br />present in the gravel and cobbles. Similarly, our experience indicates wood debris could <br />be present in the possible fill. The relative density of the gravel and cobbles generally <br />ranges from loose to very dense and is typically medium dense to dense. The results of <br />grain-size analyses on samples of the gravel and cobbles are provided on Figures 15A and <br />16A. It should be noted that the grain-size analyses were completed on disturbed samples <br />obtained from the borings, and therefore may differ from actual conditions. <br />It should be noted that significant loss of drilling fluid was observed in some locations in <br />the gravel and cobbles, indicating "open-work" zones, or material with little sand and silt <br />content. Open-work gravel and cobble deposits have a high permeability and are generally <br />capable of allowing significant groundwater flows and accepting large volumes of drilling <br />fluid or grout, which can be important considerations fortemporary excavation dewatering <br />and the installation of grouted ground anchors. <br />d. SAND, GRAVEL, SILT and CLAY (Decomposed Volcanic Mudstone) <br />Soils derived from the weathering and decomposition of volcanic mudstone were <br />encountered beneath the gravel and cobbles and extend to depths of about 20.7 feet to <br />50 feet below the ground surface. These soils are highly variable and range from sand to <br />gravel to silt and clay. The gravel portion of the decomposed volcanic mudstone is <br />generally subrounded to rounded, silty, and sandy. The sand portion of the decomposed <br />volcanic mudstone is typically silty and contains scattered gravel. The silt and clay portions <br />of the decomposed volcanic mudstone typically contain varying amounts of sand and <br />scattered gravel. In general, the decomposed volcanic mudstone unit grades from coarse <br />grained to more fine grained with depth. The relative density of the sand and gravel <br />portions of the unit generally ranges from medium dense to very dense and the relative <br />consistency of the silt and clay portions of the unit ranges from stiff to hard. The natural <br />moisture content of the sand ranges from about 22% to 54%, and the natural moisture <br />content of the silt and clay ranges from about 17% to 59%. The results of Atterberg-limits <br />determinations for a sample of the decomposed volcanic mudstone are summarized on <br />Figure 17A and indicate the soil has a moderate plasticity with a plasticity index value of <br />about 16%. The results of laboratory consolidation testing completed on a sample of the <br />decomposed volcanic mudstone are summarized on Figure 19A and indicate the soil is <br />typically moderately to heavily overconsolidated and has a low compressibility in the <br />overconsolidated range of pressures. Boring B-11 was terminated in the decomposed <br />volcanic mudstone at a depth of about 26.5 feet. <br />e. SAND, SILT, and CLAY (Decomposed Sandstone/Siltstone) <br />Soils derived from the weathering and decomposition of sedimentary rock were <br />encountered beneath the decomposed volcanic mudstone and extend to the maximum <br />GRI #6497-A - 2.MO Indoor Football Practice Facility Page 5 <br />August 26, 2021 <br />