Board of Adjustment Agenda and Packet 2003 04 16

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SUMMARY: The property is zoned A - Agricultural and is in the floodplain area for Coal Creek. If a Floodplain Development Permit were issued, it would allow for the construction of this important bridge and road section of 96th Street. The cost of is bridge is approximately $2.8 million; the total cost for the 96th Street Road extension is approximately $10 million. Coal Creek Basin The drainage basin of Coal Creek at the project site is about 30 square miles in area. Coal Creek begins as a foothills stream approximately 25 miles west of the project site. The drainage way flows northeasterly to join Boulder Creek in east -central Boulder County. Coal Creek Channel At the site location, Coal Creek is a low flow channel with wide banks. The overall stream slope in this area is approximately 1.4 percent. The inner banks are lined with wetlands vegetation; the outer banks include native grasses. The floodplain area under the bridge site consists of silt and gravel sand, and loose gravel on top of sandstone and clay bedrock. Coal Creek Flood History Flooding along coal Creek is mainly caused by snowmelt, but heavy rainfall has also caused many floods in the area. The "peak" flood times are listed as May through September. Significant floods have been recorded in 1876, 1891, 1896, 1921, 1935, 1938, 1949, 1957 and 1969, with the largest flood recorded in 1896. Floods normally peak within a few hours after heavy rainfalls. The applicant has provided sufficient information in the application packet provided to the Board for review. An important item of note in the application is the FEMA National Flood Insurance Program Floodplain Development Permit - Elevation Certificate (EC) that if approved, will need to be sent to FEMA for review and approval and kept on record with the City of Louisville. In conjunction with the city, FEMA monitors development approved in floodplains. DEVELOPMENT APPLICATION REFERRAL COMMENTS: The Floodplain Development Permit application was sent to interested and/or affected City of Louisville departments and agencies for any comments related to the issuance of said permit. The following review comments were collected: • PUBLIC WORKS: In cooperation with Wilson and Company, the City of Louisville prepared the report included in this packet. Their comments are included in that report. • FEMA: The City has been in contact with FEMA throughout the design process and development of a permit. They have no comments at this time but are aware of the proposal. 2