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<br />. <br /> <br />floodplain that could be removed, since it clearly outlines the extent of each IOO-year <br />floodplain independently, The majority of the IOO-year floodplain eliminated as a <br />result of this project would be where the Pawnee Creek Overflow existed <br />independently of the other drainageways and was not overlapped by other <br />floodplains. Another portion of the IOO-year floodplain that would be removed is <br />where the FPIDP indicated shallow sheet flow flooding or the topography indicated <br />shallow flooding less than I-foot in depth, The following sections discus the <br />changes to the FIRM maps in more detail. <br /> <br />Lo~an County FIRM Map: <br /> <br />Pawnee Creek Overflow Interceptor Channel: <br /> <br />The Pawnee Creek Overflow Interceptor Channel is proposed to be constructed to <br />collect IOO-year flows from the Pawnee Creek Overflow before they reach the <br />Riverside Cemetery and Sterling. Base Flood Elevations (BFE's) have been <br />established in the proposed channel for the IOO-year event from 5000-feet west of <br />US Highway 6, along County Road 22Yz to the approximate IOO-year floodplain of <br />the South Platte River. <br /> <br />North of Interceptor Channel: <br /> <br />. <br /> <br />The Pawnee Creek Overflow approximate IOO-year (Zone A) floodplain north of the <br />interceptor channel will be eliminated as a result of the project. During the 500-year <br />event, it is anticipated that about 6,OOO-cfs of the 11 ,OOO-cfs will by-pass the <br />interceptor channel and continue north to Sterling, Therefore, the SFHA boundary <br />would change from Zone A, to Zone X (shaded) to reflect the potential flood hazard <br />due to the 500-year flow, <br /> <br />City of Sterlin~ FIRM Map: <br /> <br />Changes to the City of Sterling FIRM map were based primarily on the FPIDP report <br />by Charles Leaf, et al. Additional hydraulics was not completed in Sterling as part of <br />this revision request. The following information corresponds to the specific areas <br />shown on the Annotated FIRM map, <br /> <br />Area A: <br />Area A represents the area of floodplain that resulted solely from the Pawnee Creek <br />Overflow, This area was changed to a Zone X (Shaded) area since it will still be <br />subject to inundation by residual 500-year flows from the Pawnee Creek Overflow, <br />500-year overflows from Sand Creek and the South Platte River will also cover this <br />area, <br /> <br />. <br /> <br />Area B: <br />According to the FPIDP report, this area is inundated by storm water from Sand <br />Creek and local drainage, The Sand Creek BFE's indicate that this area is <br /> <br />6 <br />