Laserfiche WebLink
<br />wide and 2.5 feet deep through rock, where in place, which would <br /> <br />. <br /> <br />serve as a base for a concrete cutoff wall 5 to 10 feet high. Back- <br /> <br />fill of selected material would be used in the cutoff trenches. <br /> <br />Vfuerever stripping or other measures taken in preparing foundation <br /> <br />e~pose the morainal deposit or the stream gravels, as well as in <br /> <br />places where these are naturally exposed, blankets of impervious <br /> <br />earth fill 20 feet or more thick, would be placed to cover these <br /> <br />open deposits for at least 200 feet above the upstream toe of the <br /> <br />dam. A concrete parapet wall 3 feet high would be placed at the up- <br /> <br />stream edge of the crest. <br /> <br />Outlet Works. During construction, flood flows of 1,000 <br /> <br />second feet may be expected after June 10, when the regular spring <br /> <br />flood has passed. The outlet tunnel, intended to carry such floods <br /> <br />1.5:~" <br />1~1~tI <br /> <br />with inlet grade at 7,983 and outlet grade at 7,965, would be 12 <br /> <br />feet in diameter inside a l5-inch reinforced concrete lining. <br /> <br />After use as a bypass during construction this tunnel <br /> <br />would be used as an outlet by installing two 36-inch ring follower <br /> <br />gates in a chamber approximately on the a~is of the dam. These <br /> <br />gates in tandem with 30-inch needle valves also placed in the gate <br /> <br />chamber would discharge through the lower end of the tunnel into <br /> <br />the s pilhray stilling basin. <br /> <br />The total discharge capacity would be about 700 second feet <br /> <br />from a full reservoir, or 300 second feet as free flow from an empty <br /> <br />reservoir. A 24-inch air vent would run from surface to the tunnel <br /> <br />below the needle valves in the same shaft excavation as a lined <br /> <br />53 <br />