|
<br />.
<br />
<br />1989, for the City of Sterling, Colorado, and FIRM panels 0801100330 B, and
<br />0801100335 B dated September 29, 1989 for Logan County, Colorado. (Appendix
<br />C). With the construction of the Interceptor Channel, Pawnee Creek Overflows will
<br />be collected at County Road 22\1" and conveyed through a 100-year design channel
<br />to the South Platte River. This project will eliminate the 100-year Pawnee Creek
<br />Overflow floodplain north of County Road 22\1" thus reducing the impact Pawnee
<br />Creek flooding has on the City of Sterling and Riverside Cemetery. A detailed
<br />study for the Pawnee Creek Overflow, through Sterling, is presented in the City of
<br />Sterling Flood Insurance Study and associated Flood Insurance Rate Map, Flood
<br />Profiles are presented on Panel 02P. The proposed Interceptor Channel is designed
<br />to have a 100-year discharge capacity and will convey all flows up to 5000-cfs
<br />directly to the South Platte River. The remaining 6000-cfs of the total 500-year
<br />discharge (ll,OOO-cfs) is expected to bypass the interceptor and continue into town,
<br />following the historic flow path. Copies of the effective FIS information for this area
<br />and a copy of the effective FIRM information have been included in Appendix B,
<br />The effective FIRM for the City of Sterling shows the Pawnee Creek Overflow as a
<br />detailed study area between Pioneer Drainage Ditch and the confluence with Sand
<br />Creek. These portions of the overflow contain Zone designations AE, AH, AO, X
<br />shaded, X unshaded. No effective floodway is shown, The effective FIRM for
<br />Logan County shows the Pawnee Creek Overflow as an area of approximate study
<br />with a Zone A designation, No LOMR revisions have occurred in this area since the
<br />completion of the original study. This request would eliminate the effective Profile
<br />Panel 02P, in the City of Sterling FIS, and replace it with a new panel for the new
<br />reach along the Interceptor Channel, in the Logan County FIS, As a result, the SFHA
<br />will be modified and designated, The Logan County FIS Floodway Data Table will
<br />be modified to reflect the construction of the Pawnee Creek Interceptor Channel
<br />Floodway. The SFHA from the Pawnee Creek Overflow will be eliminated north of
<br />the interceptor channel, including the detailed areas within the City of Sterling
<br />Corporate Limits, An area designated as Zone X shaded (500-year flood) will
<br />replace the effective SFHA areas, since flow exceeding the interceptor channel
<br />capacity will continue to follow the historic path north, A regulatory floodway is
<br />proposed along the interceptor channel.
<br />
<br />.
<br />
<br />.
<br />
<br />With the construction of the interceptor channel, changes will occur in the SFHA,
<br />BFE's, and floodway along the Pawnee Creek Overflow, The appropriate
<br />Application/Certification Forms (I, 4, 5, 6 and 7) have been filled out and are
<br />provided in Appendix A. Appendices B and C contain the effective and annotated
<br />flood hazard information, respectively. Appendix D contains the notification to the
<br />Colorado Water Conservation Board, Appendix E contains the proposed conditions
<br />floodplain and floodway models, A request was made to Michael Baker Jr., Inc, for
<br />background information on the South Platte River, Sand Creek, Pawnee Creek,
<br />Pawnee Creek Overflow, and Pioneer Ditch on June II, 200 I, Their response letter
<br />indicated that they did not have any of the technical backup data for this area
<br />Appendix B), However, since the proposed interceptor channel would reroute the
<br />100-year flows, the effective hydraulic information does not appear to be applicable,
<br />Workmaps displaying the proposed conditions are contained in Appendix F,
<br />
<br />2
<br />
|