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end of the pipe. The hydraulic cylinders are under water which is harsh conditions for the rhydraulic <br />ra.m and seals. Regular maintenance is necessary to ensure the operators are in working condition. <br />Prospect Reservoir Dam <br />The reservoir dam embankment has a maximum vertical height of approximately 45 feet, a crest <br />length of about 5300 feet, and is a homogenous earthfill dam. The upstream slope of the dam is at <br />2H to 1 V slope with concrete facing along the slope for erosion protection. The downstream face <br />is at a slope of approximately 2H to 1 Vand is grass covered. The crest of the dam is approximately <br />18 feet in width. The dam was constructed in 1914 and failed due to piping in 1980. The maximum <br />discharge of reservoir water during the failure was 4,097 cfs. <br />Due to the problems of the past, the dam embankment has been modified several times. T'he dam <br />embankments still experience some problems due to the original construction methods and seepage <br />problems. Our geotechncial investigation of the outlet section indicates the soils in the embanktnent <br />adjacent to the outlet liave somewhat low density and low shear strength. <br />The outlet conduit was originally a cast-in-place concrete pipe and the downstream section has been <br />lined two times previously with steel pipes grouted in place. The section of the conduit from the <br />inlet to the control gate appears to be the origina148 inch reinforced concrete pipe. The pipe has <br />some cracking but otherwise is in fair condition. <br />The outlet is controlled by one hydraulicly operated slide gate installed in a gate tower near the dam <br />crest. <br />The downstream section of the outlet is in need of repair or replacement in the near future. The <br />conduit has perforations, is leaking, has reached its safe life, and needs to be repaired soon to ensure <br />the safety of the dam. <br />The upstream slope protection on the dam face is a concrete slab that covers the entire face. The <br />concrete does not have a filter layer below it and thus the dam is susceptible to loss of fines from <br />wave action. The concrete is somewhat deteriorated and some areas are relatively soft and has <br />reached its useful life. The concrete has been patched and repaired quite frequently by the Company <br />and we would expect these maintenance costs to increased with time. <br />ALTERNATIVESEVALUATED <br />During our study of two reservoirs dams, we evaluated the following alternatives: 1) No action <br />alternative, 2) Repair critical components, and 3) complete rehabilitation ofreservoir dam and outlet <br />works. Following is a summary of our assessment of each alternative for the two reservoirs. <br />Horsecreek & Prospect Reservoirs - 06.014 <br />Henrylyn Irrigation District Page 7 <br />