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<br />Chapter IV - Formulation of Alternatives <br /> <br />Several alternatives were developed to meet the project purpose of rehabilitating the Ryan <br />Gulch Dam. Alternatives were formulated to address the problems described in Chapter I of this <br />report, which included: I) spillway enlargement, 2) reservoir seepage, and 3) rehabilitation of the <br />outlet works. <br /> <br />Figure IV-I shows the general configuration of the existing dam and natural spillway with <br />respect to the reservoir. The existing spillway is located on the right abutment (east) as indicated <br />in the figure. Access to the dam is obtained from the left abutment (west) through a gate, as <br />indicated on the figure. The existing 24-inch outlet works is indicated in the drawing with dashed <br />lines. The reservoir area is to the south of the dam. Seepage areas are indicated along the toe of the <br />dam to the north. The drill holes that RMC completed in 1984 are indicated in the figure. <br /> <br />A. Spillway Alternatives <br />Spillway Alternative Sl - Roller Compacted Concrete <br />Alternative S 1 consists of widening the existing spillway crest on the right abutment from <br />approximately 40 feet to 115 feet, as shown in Figure IV-2. The widened spillway crest will be at <br />elevation 5014.4, which is the same as the existing design crest elevation, and the spillway channel <br />downstream of the crest will be sloped at one percent, as shown in Figure IV-3. A portion of the <br />widened spillway will be excavated into the sandstone/siltstone bedrock on the right abutment. A <br />new compacted earthfill berm will be constructed on the right end of the existing embankment to <br />serve as a training berm for the spillway and to protect the toe of the embankment. Figure IV-4 <br />shows the training berm has a crest width of20 feet at elevation 5018.7, which matches the existing <br />crest elevation of the embankment. <br /> <br />RCC will be used to armor the approach channel, crest, and channel downstream of the crest <br />of the widened spillway, and also along the east slope of the new training berm, as indicated in <br />Figure IV-3. RCC is a zero-slump concrete that is placed in compacted lifts with conventional earth- <br />moving equipment. On the spillway channel invert, the RCC will be 2 feet thick. On the side slopes <br /> <br />ClWORK\PROJECTSlRYAN\FE.\SREPORTlRYANRPT DOC <br /> <br />10 <br /> <br />lanu3r)'I:,I999 <br />