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- 35- I I I I I I I I I I I I I I I I I I I 85. The design of this reach of channel was restricted by the improvements within Belle Creek subdivision. Tie-ins with these improvements resulted in the need for constructing a channel above grade, raising of East 104th Avenue and US-85, and under-sizing of culverts upstream along the Rolla Tributary. The proposed ROW is 160 feet wide. l-5'x6' RCBC and 7-l0'x6' RCBCs are proposed to convey flows beneath East 104th Avenue, US.85, and US-6/1-76. The Union Pacific Tributary parallels the UPRR on the east side of the tracks. An improved channel is proposed to convey the 100-year flow. The proposed ROW is 96-feet wide. Approximately 82 linear feet ofa lO'x5' and 5'x5' RCBC are proposed under East 96th Avenue. Approximately 145 linear feet of 5.1 0'x3' RCBC is proposed at the spur of the Union Pacific Railroad. This crossing is undersized due to the elevation of the existing spur and restrictions downstream (see Direct Flow Tributary section). Rolla Tributary Maul Reservoir Tributary The Rolla Tributary begins upstream of 1-76 and parallels the Union Pacific Railroad on the west side of the tracks. An improved channel is proposed to convey the 100-ycar flow. The proposed ROW 90-feet wide. 5-l0'x3' RCBC are proposed at two of the spurs of the Union Pacific Railroad. The spur at Station 61+75 is assumed to be abandoned or purchased at the timc of implementation: At 96th Avenue, 3-IO'x5' RCBCs are proposed to convey flows under the street. It is proposed that the Maul Reservoir Tributary will intercept Arsenal North flow from the RMA and take it under 96th Avenue and directly into Maul Reservoir. A low flow channel is proposed to convey the flow during normal discharge. One 1O'x4' RCBC will convey the flows under 96th Avenue. This is a change from the recommended plan nccessitated by construction of the Eagle Creek subdivision in the path of the previously recommended channel alignment. Arsenal North Tributarv Wolpert Tributary The Birch and relocated Elm Tributaries flow into the Arsenal North Drainage. An improved channel, with low flow channel, is proposed to convey the 100-year flow. The proposed ROW is 90 feet wide. Approximately 65 linear feet of2-IO'x5' and l-5'x5' RCBCs is proposed at Havana Street. A I 75-foot long inverted siphon is proposed to convey flows from the O'Brian Canal beneath Arsenal North Tributary. This inverted siphon will consist of five 96-inch diameter reinforced concrete barrels. A 175-foot long inverted siphon is proposed at the intersection of Burlington Ditch and Arsenal North Tributary, which will consist of a single 54-inch diameter reinforced concrete pipe. Approximately 82 linear feet of 3-1 0'x6' RCBC is proposed at Union Pacific Railroad. Previously, the alignment for First Creek crossed Brighton Road and turned north. This aligrunent did not match with the two. foot mapping provided by Adams County. The project sponsors agreed that the First Creek alignment should be as shown on the attached Plan & Profile sheets. This change in alignment creates an area that is not tributary to First Creek but directly flows to the South Platte River. An improved channel is proposed to convey the 100.year flow. The proposed ROW is varies from 85 to 78-feet wide along Wolpert Tributary. Maul Reservoir Preliminary Desil!n Further Described Birch Tributary Construction of an earthen dam across the span of First Creek, at a location approximately 1,900 fcct upstream of the existing SH-2, will create the reservoir by restricting and backing up the flow from the creek behind this structure. This dam will rise 22-feet above natural grade on the upstream end and has been preliminarily designed with 5 - 3' x 10' CBC's. Figure V1-l illustrates the inflow and outflow hydro graphs at the Maul Reservoir for I OO-year base model condition. Birch Tributary has been channelized from north of 96th Avenue to the Arsenal North Tributary. This channel runs parallel to Dallas Street through the Phelps Tointon Industrial Park. Others designed and constructed this channel and its accompanying detention to convey the 100.year flows through the industrial park. Elm Tributary A more detailed description of the proccdures used to dcvelop the preliminary design can be found in the TC&B Internal Memorandum entitled "Preliminary Investigation of Maul Reservoir" (Reference 25). As the memo explains, the modcling procedures used in the design consisted of: Elm Tributary has been channelized from the confluence with Arsenal North Tributary to 96th Avcnue within the Mountainview Industrial Park. The new channel does not contain the 100-year flow, therefore floodplain management is proposed. A transition (GSB drop proposed) will be needed at the confluence with Arsenal North Tributary. Improvements upstream of 96th Avenue include approximately 164 feet of 10'x5' RCBC under Burlington North Santa Fe Railroad and SH- 2. . Developing the inflow hydro graph at the dam using the UDSWM model . Determining the storage available upstrcam of the location of the dam from existing topo . Developing the storage-outflow curve for the reservoir based on the available storage and the outlet configuration using the XPSWMM computer model, see Table VIol . Routing the inflow hydro graph through the pond (the pond defined by its storage-outflow relationship) using the U.S. Army Corps of Engineers HEC-l modeling program Union Pacific Tributary