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<br />In July 1971, a Special Flood HazalCd Infonnation RepolCt was plCepalCed by the <br /> <br />COlCpS of EngineelCs folC the urban lCeaches of Sand, Toll Gate, and CherlCY Creeks. <br /> <br />In June 1975, the Omaha District published the second inspection repolCt of <br /> <br />the ChelClCY ClCeek Lake project, entitled "Embankment, Outlet WOlCks, and Spillway, <br /> <br />PelCiodic Inspection RepolCt No.2." The inspection and subsequent analysis <br /> <br />indicated that the outlet wOlCks appeared to be in good condition and the <br /> <br />embankment and its foundation were satisfactolCily stable. The inspection lCepolCt <br /> <br />also indicated that the growth of vegetation and accumulation of sediment on the <br /> <br />spillway bottom caused by elCosion of t~e sideslopes had lCaised the spillway's <br /> <br /> <br />effective crest elevation and increased the roughness, <br /> <br />With the sloughed conditions of the spillway, the PMF as the Inflow Design <br />Flood (IDF) based on HMR No. 44 developed for Chatfield would have overtopped the <br />dam by about 1 foot. Cleanout and m~nor modifications to the spillway were <br />considered to improve the situation. However, it was recommended that <br />consideration be given to modifying the operating criteria to draw down the upper <br />half of the pool faster so that the occurrence of a PMF event on top of a full <br />flood control pool would be less likely, permitting the PMF to be contained <br />within the freeboard zone. With channel implCovements on CherlCY Creek between the <br />dam and the South Platte River and with additional hydrologic control upon <br />completion of Chatfield and Bear Creek Dams, it was felt a change in operating <br />criteria was practicable. <br /> <br />In October 1976, the Omaha Distr~ct published a Flood Plain Information <br /> <br /> <br />Report for upper Cherry Creek, from Cherry Creek Lake upstream to the vicinity <br /> <br />of Franktown. <br /> <br />The Urban Drainage and Flood Control District, a regional engineering body, <br /> <br /> <br />published Phase A and Phase B of a "Cherry Creek Major Drainageway Plan" in July <br /> <br />1976 and May 1977, respectively. The reports recommended palCtial channel <br /> <br /> <br />improvements and cleanout which would contain the IOO-yealC flood within the <br /> <br />Cherry Creek channel. Channel improvements have been made from the mouth <br /> <br /> <br />upstream to about First Avenue. Maintenance and replacement of drop structures <br /> <br />in the rest of the channel is done as funds become available, <br /> <br />4 <br />