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prepared by Michael Baker, Ir" Inc, This study utilized the cross-sections presented in the 1980 report, A . new study was prepared south of Town in the 1990 FEMA Flood Insurance Study by the United States Bureau of Reclamation (USBR) for FEMA, Our understanding from the FEMA office in Denver is that the USBR 1990 study did not change the floodplain analysis prepared by Michael Baker, Ir" Inc" in 1982 for the reach under consideration in this study (through Section No, 27), Thus, the Michael Baker, Ir., Inc" HEC-2 computer analysis was used as the baseline data for the reach upstream of the Union Pacific Railroad, IV. PROJECT DESCRIPTION The Coal Creek Flood Control Project begins at cross-section D (Section 17,2, Briggs Street) on Firm Panel No, 080181-0001D (see Figure-4), A transition of the channel will begin at the existing bridge and continue to the Lower Boulder Ditch siphon at Section E (Section 17,9), A levee will be built to protect the Town from the 1 DO-year flow and channel improvements will be made to the natural channel from Section E to Section G (Section 19,2), An existing pair of culverts will be replaced at Section G with a 3-cell precast low-flow crossing with 540 square feet of opening, Upstream of Section G, the improved channel will be transitioned to match the existing channel on . the west banle The existing trees and brush will be removed from the existing channel bottom and west bank, The channel will be widened along the east bank. These improvements will be continued to the Union Pacific Railroad Bridge at Section K (Section 22,1), The flow characteristics through the Union Pacific Bridge will be improved by adding 2 spans to the east end of the bridge, South of the Union Pacific Bridge, the natural channel will be excavated to a 110 foot bottom width with 3 to 1 sideslopes, The channel excavation will continue to the new PeD)' Street Bridge. The PeD)' Street Bridge is being replaced by Weld County, The new bridge will be a two span, 120 foot wide bridge with a 2 foot center pier and 1.5 to I sideslopes, The top of the bridge will be set at elevation 5,027.49 and the bottom of the structure will be about elevation 5,024.4, This is about 1 'h feet higher than the existing bridge, A copy of the bridge plan and profile and layout is included in Appendix G, The upstream channel will be transitioned from the new bridge to the existing channel. A levee for the 100-year flow will be constructed along the Union Pacific Railroad embankment. It will extend southwest, parallel to the railroad until it matches existing grade, . 2