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a , <br /> EMBANKMENT DESIGN <br /> Existing Embankment <br /> The existing embankment is a zoned earth and rock-fill dam. The average upstream <br /> slope is 2.25:1 (H:V), with three 10-foot wide benches at elevations 10,645, 10,675, and <br /> 10,705 feet. Intermediate slopes between the benches are 2:1. The downstream slope <br /> is 2:1 (H:V) above elevation 10,650 feet and 2.5:1 below. The crest width is 15 feet and <br /> is located at about elevation 10,725 feet. The existing dam was constructed in two <br /> stages, the first stage (crest elevation 10,705 feet) was completed in 1966 while the <br /> second stage was completed in 1968. <br /> Seepage from the dam is collected in an open ditch along the toe of the slope and <br /> is channelized to a small collection pond located downstream of the embankment. The <br /> collected water is pumped back to the reservoir. Accurate pumping records were <br /> maintained for a period beginning in October 1985 and ending June 1991. The records <br /> show an average pumping rate of 15,340 gallons per day or 10.7 gallons per-minute. The <br /> seepage rate from the dam is somewhat less than this rate because the collection pond <br /> intercepts snowmelt originating from the downstream face of the dam during spring <br /> months. It is estimated that the historic average seepage rate through the dam is about <br /> seven gallons per minute. <br /> A 24-inch diameter corrugated metal pipe conduit is placed through the embank- <br /> ment at about elevation 10,704 feet for the purpose of conveying flows from an upstream <br /> interceptor canal through the dam and into the East Fork Eagle River drainage. Prior to <br /> construction, the conduit will be inspected for areas of corrosion or failure. The upper 50 <br /> feet of the metal conduit will be grouted solid. A concrete cutoff collar will be placed at <br /> the upper end of the conduit, and a sand filter diaphragm will be placed near the <br /> downstream end. Prior to construction, the bypass conduit will be inspected. If areas of <br /> corrosion and/or failure are discovered, the conduit will be removed in lieu of grouting and <br /> construction of the cutoff and filter. Removal of the conduit would require excavation and <br /> 5 <br />