Board of Adjustment Agenda and Packet 2003 04 16

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• URBAN DRAINAGE AND FLOOD CONTROL: They have no objection to the concept of a bridge in that location but they did have several "technical" comments that were addressed or will be addressed if the City issues a permit on an application that would be made to FEMA. • COLORADO WATER CONSERVATION BOARD: No comments were made from this agency on the proposal. • CITY OF LOUISVILLE LAND MANAGEMENT DEPARTMENT: No "official" comments were made on this proposal but they are aware of the project and support the development. REVIEW CRITERIA: The Board of Adjustment has authority to hear and decide, grant or deny this application for a Floodplain Development Permit pursuant to the powers granted the Board in § 17.48.110 C. of the Louisville Municipal Code. The Board may grant a permit only if it makes findings that all of the criteria, as established under § 17.56.160 A-E, have been satisfied, insofar as applicable. The following regulations shall apply in the flood regulatory district and all areas of special flood hazard: • 17.56.160 A. Flood District Encroachments: "The cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot at any point. Certification by a registered professional engineer stating that any encroachment shall not result in such an increase in flood levels during the occurrence of a 100-year flood shall be required." Information provided in the current Drainage Report for this project states that the 100- year peak water -flow (discharge) at this location (under the bridge) is 3900 cubic feet per second, (page 3 of the narrative provided). The bridge will be a 2-span concrete bridge approximately 247 feet long and 87 feet - wide. The bottom width between the abutment slopes will be about 125 feet. The angle of the bridge across the creek bed is approximately 26 degrees, it is not being constructed at a "90 degree" angle (straight across) to "fit" or allow for any flood flow that may occur. The clearance above the channel bottom varies from 16 to 23 feet, (bottom of bridge to bottom of creek). The piers proposed in the creek bed are approximately three -feet wide and are triangular in shape to assist water flow during a potential flood. The sides of the flow channel will be lined with new rip -rap rocks and the Coal Creek pedestrian/bike trail will be aligned to pass under the northerly span on the abutments just above the base flood elevation line. 3