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<br />OLYMPUS DAM <br />EARLY WARNING SYSTEM <br /> <br />David B. Fisher <br />Bureau of Reclamation <br /> <br />Background <br /> <br />Olympus Dam is located on the Big Thompson River two and one-half <br />miles east of Estes Park, Colorado. The dam was constructed between 1947 <br />and 1949 and is a composite structure consisting of a zoned earth embank- <br />ment and a concrete gravity spillway section. The dam has a total crest length <br />of 1,951 feet, which includes a 1,631-foot-long embankment section and a <br />320-foot-long concrete section. The embankment has a structural height of 70 <br />feet, with a crest elevation of 7,481 feet. A 3-foot-high parapet wall and curb <br />were constructed on the upstream side of the 30-foot-wide crest. <br />The concrete section of the dam, which is located at the right abutment, <br />contains both a spillway and an outlet works. The spillway is an ogee crest <br />with a crest elevation of 7,460 feet. Releases are controlled by five 20-foot <br />by 17-foot radial gates with a discharge capacity of 21,200 ft3/S at a <br />maximum water surface of 7,475. <br />Lake Estes, which is formed by Olympus Dam, was designed as an <br />afterbay for the Estes Powerplant. Lake Estes must maintain an operating <br />level between elevations 7469.5 and 7475.0 for power production. At the <br />maximum water surface elevation, 7475.0, the reservoir is approximately one <br />mile long, has a surface area of 185 acres. and impounds 3,068 acre-feet of <br /> <br />~ <br />~ <br /> <br />~ <br /> <br />storage. <br />There are no irrigation releases made directly into the Big Thompson <br />River. The releases for power generation into Olympus Siphon are ultimately <br />restored in Carter and Horsetooth Reservoirs. which provide releases directly <br />to the irrigation districts <br /> <br />Deficiencies <br /> <br />The hydrologic deficiency for Olympus Dam is related to the safe passage <br />of the Probable Maximum Flood (PMF). The thunderstorm PMF is <br />characterized by a peak discharge of 83,900 ft3/s and a two-day volume of <br />