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The quantities and costs for the spillway for the enlargement is included in Table 6, and Table 7 <br /> includes the spillway cost for the existing dam. <br /> 12.4 Embankment: The existing Red Mesa Reservoir is 1172 acre-feet in capacity, it will be <br /> enlarged to 4070 acre-feet. The normal reservoir water surface area will be increased from 56 <br /> acres to about 150 acres. The embankment will be raised 29 feet from the present 58 feet to 87 <br /> feet. Figure 4 is a 7.5 minute USGS quadrangle map showing the existing reservoir area and the <br /> enlarged area. <br /> The enlarged embankment will be placed on the downstream slope of the dam. The enlarged <br /> embankment will have an upstream slope of 3.2 to 1 (the current slope) and the downstream <br /> slope will be 2.5 to 1 (currently it is 2.4 to 1). The crest width will be 25 feet (currently 10 feet). <br /> The toe will be about 180 feet downstream of the existing toe. Figure 5 shows a cross section of <br /> the enlarged embankment. <br /> The existing embankment is about 400 feet long (stations 22+00 to 26+00 shown on Figure 2). <br /> The enlarged embankment will be about 1450 feet long (stations 12+50 to 27+00). The station <br /> numbering is from east to west so the majority of the embankment extension is on the east side <br /> of the existing dam. Figure 6 shows the front view of the enlarged dam. The volume of the <br /> enlarged embankment is determined by estimating the enlarged embankment volume in Table 4 <br /> and subtracting the existing embankment volume, Table 5. An estimated 275,000 cubic yards of <br /> material will be placed to enlarge the embankment. <br /> A cutoff trench 10 to 20 feet deep will be constructed downstream of the existing toe under the <br /> highest part of the new embankment and under the east part of the embankment from stations <br /> 12+50 to 22+00. The SCS geotechnical investigations showed that the east abutment was <br /> overlain with alluvial deposits which require a cutoff. <br /> p q <br /> The existing embankment will be stripped of all humus, rocks, and other unsuitable material; a <br /> depth of about 2 feet. Below the toe of the existing dam,native material will be stripped a depth <br /> of 10 feet. Material will be hauled and placed on the downstream slope in 8 to 12 inch layers <br /> and compacted. The height of the dam will be over built by 2 to 3 feet to allow for settling based <br /> upon the SCS Soils Mechanic Report. Based on the SCS Geology Report there is adequate <br /> borrow material north and east of the dam and upstream of the present reservoir which consists <br /> of reddish-brown eolian deposits classified as silty and sandy clay, underlain by well graded <br /> gravels and sand. <br /> 24 <br />