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-4 - <br />clean sands and gravels, to clayey or silty sands and <br />gravels and silts. At the locations explored by our bor- <br />ings, bedrock consists of a gray siltstone; although a <br />geologic section of the core trench prepared by Homestake <br />Mining Company during construction of the dam indicates <br />that sandstones and shales are present beneath other por- <br />tions of the embankment. The locations of our borings <br />and tes� pits are shown on Plate 2, Plot Plan. <br />A brown, non -plastic silt (ML) is located be- <br />neath the upstream shell of the dam between stations <br />2+00 and 4'.50. This is the soil that Mr. Gellhaus ref- <br />erenced'as being a potential cause of instability in the <br />embankment.* This materia]. is apparently lenticular and <br />grades out downstream. The silt stratum was only en- <br />countered in Boring 1, Test Pit 1, and possibly in Bor- <br />ing 3. Its thickness ranges from 3 to 8 feet at these <br />locations. <br />Groundwater was encountered in all of the bor- <br />ings except Boring 1. The depth to groundwater in Bor- <br />ings 2, 3, and 4 ranged from 16 to 27 feet below the <br />* "Review of Embankment Design, Lower Homestake Tailings <br />Pond for Homestake Mining Company, Creede, Colorado," <br />October 1974, by Francis-Meador-Gellhaus, Inc. <br />GAMES C MOORE <br />