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<br />Spillway Alternative S4 - Right Abutment Riprap <br />Spillway Alternative S4 is similar to Alternative S2 with the exception that the spillway is <br />lined with riprap instead of ABC as indicated in Figures N-II through N-l3. <br /> <br />Spillway Alternative S5 - Left Abutment Riprap <br />Spillway Alternative S5 consists of excavating a trapezoidal 5-foot cut with a 95-foot bottom <br />and l31-foot top widths into the dam embankment, as indicated in Figures N-14 and IV-15. The <br />spillway chute w<luld transition from 95 feet to 65 feet bottom wide and from a 4: 1 to 2: I sideslope, <br />approximately 200 feet downstream from the spillway crest. The chute would convey the flood <br />flows to the natural channel downstream of the dam. The 3.43% sloped chute would require fill and <br />cut as indicated in Figure N-15. <br /> <br />B. Seepage Control Alternatives <br />Embankment Alternative El - Clay Liner <br />Embankment Alternative EI involves grading and then lining the upstream face of the dam <br />with clay, as shown in Figure N-16. The clay liner would extend 950 feet from the left to right dam <br />abutments. The clay liner would be 12-foot thick and would be protected with 2-foot thick riprap. <br />The clay liner would extend from the top of the embankment down to the dam heel. Then a <br />concrete slurry wall would extend down vertically to bedrock to cutoff subsurface seepage. The <br />seepage would be reduced by approximately 95% using a clay liner or synthetic liner, which is <br />presented in Alternative E2. <br /> <br />Embankment Alternative E2 - Synthetic Liner <br />Embankment Altemative E2 involves grading and then lining the upstream face of the dam <br />with an HDPE synthetic liner, as shown in Figure N-17. The liner would be protected with 2 feet <br />of cover soil. Riprap would then be added to protect the system from wave and wind erosion. The <br />liner system would extend from the left to right dam abutment. The liner would extend from the <br />dam crest down to the heel of the dam. The synthetic liner would be anchored into a concrete <br />foundation wall at the heel of the dam. The wall would then be extended down to bedrock for a <br />positive seepage cutoff. <br /> <br />CIWORK'PROJECTS\RY AN\FEASREPORl'.RY ANRPT,OQC <br /> <br />12 <br /> <br />JlIIluaryI2.1999 <br />