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<br />2. PROPOSED SOLUTIONS <br /> <br />. General <br /> <br />Common to each alternative (except for Alternative No.1 the "No Action" Alternative), but not <br />discussed in detail are flood warning systems and maintenance programs. <br /> <br />. <br /> <br />. <br /> <br />Alternative Improvements <br /> <br />Based on a review of the existing reports and discussions with the project sponsors and local citizens, <br />the following improvements were selected for further study. A conceptual design of all of the <br />proposed projects was completed in sufficient detail to determine construction quantities and cost <br />estimates. <br /> <br />Alternative No.1: ''No Action" alternative. A series of seven public meetings with land owners and <br />concerned citizens were held between December 1997 and JlIDUary 1998. This alternative was <br />uniformly not acceptable given the past series of serious flood events and subsequent damages. <br /> <br />Alternative No.2: This alternative will restrict the 100-year flood flows from overflowing into the <br />left overbank floodplain near where the Pawnee Creek crosses HWY 6. Protection would be provided <br />to agricultural lands and the City of Sterling. This alternative was the recommended alternative from <br />the "City of Sterling Drainage and Flood Control Implementation Plan" dated June 1997. This <br />alternative is shown on Figure 8 lIDd consists of a system of flood control levees. In general, the levees <br />would follow along the north side of Pawnee Creek beginning upstream of CR. 29 and continuing east <br />to HWY 6. Since the levees would be designed for the 100-year storm, they would be required to have <br />3 feet of freeboard by FEMA. The existing bridges at HWY 6 would be improved to convey the 100- <br />year discharge under the bridges. For the southbound lanes, the existing concrete bridge would be <br />expllDded by adding 4 cells of20' wide X 8' tall RCBs to the south of the existing bridge. The existing <br />timber bridge along the northbound lanes would be replaced. The COOT currently has plans to replace <br />the timber bridge within the next 3 to 5 years. In the summer of 1996, the UPRRlBNRR replaced their <br />bridge located just downstream of HWY 6 for structural reasons. Design of the new railroad bridge was <br />such that the new bridge will ultimately convey the 100-year peak discharge. Since the proposed <br />bridge improvements would allow more flow downstream of HWY 6, a second system of levees and a <br />floodwall are proposed to confme stormwater downstream of the highway to the 100-year floodplain of <br />the South Platte River. The estimated project cost of the proposed improvements along Pawnee Creek <br />is $1,135,500. This cost does not include the new bridge at HWY 6 by COOT or the newly <br />constructed railroad crossing by UPRR. <br /> <br />These proposed improvements would eliminate the Pawnee Creek overflows from draining into the <br />City. The overflows are estimated to be about 5,000 cfs during the 100-year storm. Eliminating these <br />overflows removes a substantial amount of land and mllDY structures from the floodplain in both Logan <br />County and the City of Sterling.e <br />Alternative No.3. This alternative is a series of upstream flood control reservoirs as presented in the <br />report entitled "Flood Plain Management Study, Pawnee Creek and Logan Creek, Colorado" dated <br />April 1992. This alternative will store flood waters in detention structures in the upper watershed. <br />General location of the reservoirs are shown on Figure 9. <br /> <br />III-7 <br />