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<br />,e. <br />'f!/8J <br /> <br />Below 20 feet of outwash the demarcation be- <br />tween morainal material and underlying stream <br />gravels is not clearly marked. At 150 feet the <br />hole was still in typical stream gravel. strata <br />and nests of boulders at all depths. Some percolation at all depths <br />and a temporary water table falling as hole opened, to elevation <br />7956, 10 feet above river level, probably the permanent water table. <br /> <br />Drill Hole No.2. <br />Depth 150 ft. <br /> <br />Design of Dam. The design and details of the dam are shown <br /> <br />on Drawing 254-D-146. The compacted earth-fill dam of 180 feet maxi- <br /> <br />mum height,.. would have its crest at elevation 8,143. The crest would <br /> <br />be 1,450 feet long. The impervious upstream portion of the embankment. <br /> <br />20 feet wide at the crest, would have an upstream slope of 3 to 1 down <br /> <br />to a 10-foot berm at elevation 8,030, below which the slope would be <br /> <br />10 to 1 to stream level.. Three feet of dumped rock riprap would ex- <br /> <br />tend from the crest to the berm. <br /> <br />The downstream slope of the impervious section would have <br /> <br />.~"'" <br />~1~~J <br />",,,,",' <br /> <br />a slope of 1 to 1, behind which a fill of morainal material with <br /> <br />crest width of 5 feet would have an outer slope of 1-3/4 to 1. A <br /> <br />dumped rock section resting on the morainal material would have an <br /> <br />outer slope of 2 to 1 from a crest width of 10 feet to elevation <br /> <br />8~040, below which the slope would be 8 to 1 to elevation 7,990, and <br /> <br />2 to 1 to river bottom. The total crest width would be 35 feet. <br /> <br />The foundation would be prepared by stripping 12 inches <br /> <br />fram the whole area, and laying sewer tile drains at the downstream <br /> <br />edge of the embankment, where an inverted filter would also be in- <br /> <br />stalled under the rock fill. A cutoff trench with 20-foot bottcm <br /> <br />and 1 to 1 side slopes would be excavated 30 feet deep across the <br /> <br />valley bottom. This trench would be continuous with a trench 3 feet <br /> <br />/.J <br /> <br />52 <br />