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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />1.5 Auxiliary Spillway <br /> <br />The auxil iary spillway consists of riprap-protected overflow earth dikes with <br />a crest elevation approximately one foot above the service spillway at 9088.0. <br />These di kes fl ank the concrete servi ce spill way for a di stance of about 150 <br />feet to the right and 100 feet to the left. The dikes are roughly 10 feet <br />wide at the crest with 2H to 1V upstream and downstream slopes. <br /> <br />In 1984, materials were removed from the outer eight feet of the upstream face <br />of the auxiliary spillway dikes and used as fill at the downstream toe of the <br />dam. The crest of the di kes was a1 so lowered one foot at thi s time. Thi s <br />resulted in a substantial reduction of the seepage path through the dikes and <br />along the contact wi th the concrete spill way structure. An attempt was then <br />made to rearmor the dikes with riprap. The present riprap protection on the <br />auxiliary spillway is sparse and poorly graded. Large pieces of riprap (10 to <br />36 inches) directly overly the gravelly sand earthfil1. <br /> <br />If it were required to operate, the auxiliary spillway would likely fail <br />because of: 1) inadequate protection of the relatively steep 2H to 1V <br />downstl'eam slope; 2) the lack of fil teri ng and beddi ng between the earthfil1 <br />and slope protecti on; and 3) the hi gh potenti a1 for pi pi ng of the erosi ve <br />earthfil1 beneath the riprap. The probability of the auxiliary spillway <br />operating, if full storage were allowed in the reservoir, is high because of <br />crest undulations along the dikes. Surveying performed during the site <br />inspections indicated that in many places the dike crest is less than 0.5 feet <br />above the service spillway crest, and in one location, level with it. A table <br />showing the results of that surveying is included in Figure V.2. <br /> <br />1.6 Emergency Spillway <br /> <br />An emergency spillway, approximately 180 feet wide, is notched into the <br />embankment dam adjacent to the ri ght abutment. The crest of thi s notch lias <br />designed to be 30 feet wide at elevation 9090.0, three feet above the service <br />spillway and three feet below the embankment crest. Surveying during the site <br />i nspecti on i ndi cated that the crest is in fact 30 feet wi de, but that the <br />elevation is generally higher than designed, ranging from 9089.9 to 9092.0. <br /> <br />1231H <br /> <br />-43- <br />