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<br />. <br /> <br />. <br /> <br />. <br /> <br />1. <br /> <br />INTRODUCTION <br /> <br />1.1 PURPOSE <br /> <br />The purpose of this report and supporting documentation is to request a Conditional <br />Letter of Map Revision (CLOMR) of the Flood Insurance Study and Flood Insurance <br />Rate Maps (FIRM) for the City of Sterling, Colorado and Logan County, Colorado <br />dated September 29, 1989 (both maps). On behalf of the City of Sterling (City) and <br />Logan County (County), we are requesting the Federal Emergency Management <br />Agency (FEMA) review the modifications to the flood hazard information for the <br />Pawnee Creek Overflow from County Road 22 ~ to the confluence with Sand Creek. <br /> <br />The drainage improvements for the Pawnee Creek Overflow include the installation <br />of a Flood Control Interceptor Channel along County Road 22 K The interceptor <br />channel is proposed to be constructed with capacity for the 100-year Pawnee Creek <br />Overflow discharge. Flows exceeding this discharge (i.e. 500-yearflood) are <br />expected to continue past the interceptor channel, following the historic flow path. . <br />This CLOMR will have an affect on the flood hazard information for the flood <br />having a 1 percent chance of being equaled or exceeded in any given year (base or <br />100-year flood) for both the City of Sterling and Logan County. Floodplains for the <br />flood having a 0.2 percent chance of being equaled or exceeded in any given year <br />(500-year flood) were not originally identified on the Logan County effective maps. <br />This CLOMR submittal incorporates revisions to the base flood elevations (BFEs); <br />the width of the Special Flood Hazard Area (SFHA), which is the area that would be <br />inundated by the base flood; and the width of the regulatory floodway for the <br />Pawnee Creek Overflow. The following report identifies the Flood Insurance Rate <br />Map changes in more detail. <br /> <br />1.2 BACKGROUND <br /> <br />Historically, Pawnee Creek Overflow receives water from spills in Pawnee Creek <br />during high flow events. The largest spills occur along the north bank of Pawnee <br />Creek immediately downstream of County Road 33. Additional flow spills from the <br />north bank just upstream of the crossings with US Highway 6 and Union Pacific <br />Railroad. These crossings have limited capacity through their existing bridges and <br />extra flow is diverted to the north alongside the highway. Flows from these spill <br />areas continue to the north and combine to form the Pawnee Creek Overflow. They <br />converge adjacent to the Riverside Cemetery, located to the south of the City of <br />Sterling, and continue flowing into town. Therefore, as a result, the City of Sterling <br />and Logan County have proposed to construct an interceptor channel to collect the <br />Pawnee Creek Overflows and reroute them to the South Platte River before they <br />reach the city limits. <br /> <br />The revised reaches of the Pawnee Creek Overflow included in this revision request <br />are shown on FIRM panels 080294000lC and 0802940002 C, dated September 29, <br />