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I I I I I I \1 I I I I I I I I I I I I Direct Flow Tributary include approximately 164 feet of lO'x5' RCBC under Burlington North Santa Fe Railroad and SH- 2. An improved channel with trickle charmel is proposed for the area between SH-2 and 96th Ave. A channel is proposed to run north from the confluence of Arsenal North Tributary and Rolla at the southwest comer of I-76/Union Pacific Railroad intersection to First Creek on the west side of US 85. The design of this reach of channel was restricted by the improvements within Belle Creek subdivision. A grass. lined trapezoidal channel with embankment stabilization (without low flow channel) is proposed to allow for a shallower improved channel. The proposed ROW is 200 feet wide. 1-5'x6' RCBC and 7-l0'x6' RCBCs are proposed to convey flows beneath East 104th Avenue, US-85, and US-6/I-76. Union Pacific Tributary Rolla Tributary 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 of5-l0'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). 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-year flow. The proposed ROW 90-feet wide. 5-10'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 time of implementation. At 96th Avenue, 3-IO'x5' RCBCs are proposed to convey flows under the street. Maul Reservoir Tributary Arsenal North Tributary 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 10'x4' RCBC will convcy the flows under 96th Avenue. This is a change from the recommcnded plan necessitated by construction of the Eagle Creek subdivision in the path of the previously recommended channel alignment. 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 I 75-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 of3-l0'x6' RCBC is proposed at Union Paci fic Railroad. Wolpert Tributary Previously, the alignment for First Creek crossed Brighton Road and turned north. This alignment 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. Summary Birch Tributary The total estimated cost of construction of the recommended and selected improvements described in Chapter VI of this report is approximately $39,145,316. 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 Often, fiscal constraints do not allow for implementation and construction of all improvements in a short time span. Therefore, it is necessary to develop a list of improvement priorities based on a review of the improvements needed throughout the entire Lower First Creek Watershed. In general, improvements that may provide immediate reduction in the risk of harm to or loss of human life were given highest priority, followed by those that may provide future reduction in the risk of damage to property, and finally those improvements that may not be needed immediately, but are recommended at some time in the future. Another important consideration in the prioritization of the improvements discussed in this report is the fact that, in general, all of the improvements are part of the overall system and not independent of one-another. Therefore, proper prioritization is vital to the successful implementation of the selected drainage plan. Elm Tributary has been channelized from the confluence with Arsenal North Tributary to 96th Avenue 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 ES.5