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a 56' wide trapezoidal channel had a contro l elevation of 5251.4 ft MSL in the left abutment <br />of the dam. The impoundment storage at this elevation is 146 acre feet with a depth of <br />approximately 8 -11 feet. The crest of the dam lies at 5255.4 ft MSL where the impounded <br />volume increases to nearly 400 acre feet at a depth of 13 -16 feet. <br />S G w 4 ■ #' E 884,, A..- �I <br />Bhth ANe t Upper Derby Dam <br />Lower Derby Dam <br />�. Lake Ladora Dam <br />t— -I F7$lhAue —i-'. <br />1Aen? ❑ ti <br />E 72nd Ave - -- O <br />8S - ...„ <br />. Q <br />17 Ae7trge <br />Rocky Mountain Ars rz. <br />Lake Mary Dam <br />�1 <br />• • E 64th qye -- l ,; jr E.64th R e <br />~as'�i.ngton y,�Y r CrtY .. Dick s Sporting.: J <br />Gools Park , .a voncs <br />ss i <br />-E SBth Are- -rte `L EE&11Are s <br />..' 11 �'•__. -- '� ..-..- F55rh-Ave� -•E 5 6th •Rre -z-- <br />m <br />�5 85 W Havana Street Dam <br />Ely ;wanaa - ,rthe.st .Atas.•.. <br />! " ThXhops Al t I I I I d i.E47.h Ave-.. - - LSa�teedto <br />,t, �i Narthfeld•Siapleton »° <br />, <br />Figure 1 - Vicinity map with Flow Paths (Source: Google Maps) <br />The design of the spillway consisted of a trapezoidal concrete control section with 56 foot <br />bottom width, 6H: IV side slopes at a depth of 4 feet. The longitudinal length of the concrete <br />control section was approximately 20 feet downstream of which the channel transitioned to a <br />moderately steep (5 %) riprap lined open channel cut through the left abutment of the dam. <br />The left abutment consists of an overburden of 15 - 20 feet of silty sands overlying a <br />c lays tonelsiltstone bedrock. Some riprap bedding was placed between the rip rap and <br />underlying silty sand, but it appeared to be fairly coarse (generally uniform 314" crushed <br />roc k) . <br />Since the dam is an `uncontrolled' flood control dam, there are no gates to operate or other <br />operations necessary during a storm. The service spillway i5 ungated so that as the reservoir <br />accumulates water during storm events, releases are made to the downstream channel as <br />soon as the dead storage i5 accumulated. As the reservoir storage increases to the emergency <br />spillway level, the head on the service spillway increases and releases increase. Once the <br />reservoir water level exceeds the emergency spillway crest elevation, releases from the <br />