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expanded by adding 4 cells of20' wide X 8' tall RCBs to the south of the existing bridg"" Th", existing timbl'r bridge along the northbound lanes would be replaced. The CDOT currently has plans to replace the timhcr bridge within the next 3 to 5 years. In the summer of 1996, Ihe UPRRlBNRR replaced their bridg.: IUC<lted just downstr",am of HWY 6 for slruetural reasons. /k"ign of tht: new railroad bridge was such that the new bridge will ultimatclyconvey the lOO-yearpeakdiseharge. Since the proposed bridge improvemellts would all"w more flow downstream of HWY 6, a second system of levees and a tloodwall arc proposed to confine storm water downstream of the highway to the 100-year floodplain of the South Platte River. The estimated prujttl cust of the proposed improvements along Pawnee Creek is $1,135.500. Ibis cost does not include the new bridge at HWY 6 by CDOT or the newly constructedrailmadcrussingbyuPRR. These proposed improvements would eliminate tht: Pawnee Cn..'ek oved1ows from draining into the City. The overflows are estimated 10 be about 5,000 cfs during the I OO-year storm. Eliminating these overflows removes a substantial amount of land and many structures !Tom the floodplain in both Logan County and the City of Sterling. Altunative No. .,. This alternalive is a ~ries (If upstream flood control reservoirs as presented in the report entilled "Flood Plain Management Study, Pawnec Crcek and Logan Creek, Colorado" datcd April 1992, This alternative will storc lJo\ldwaters in detention structures in thc upper watershed. General location ofthc reservoirs is sh\lwnon Figure 10. Alternative !'io. 4: This alternative will e\lllect the Pawn~'e Creek over/low und divert these flows directly to the South Plalte River in the general vicinity of the Cemetery ju.st south of Sterling, This altern"tlve consists of construction ofa ~rm havinl:\unapproximat..,h..,i;thtoI5 feet to thc north and ,,"'st of the Riverside Cemetery. This bcnm would collect and prevent flnws from the Pawnee nvertlow fmm emering the Cit), along the HWY 6iRailroad cmb,mkments. Inclu(kd in Ihc alternative is lowering of CR. 24, construction of a channel with a concrete flondwall, a closure structure for HWY 6. construction of box culverts under the railroad, a siphon for the Sterling No. I Oitch, and C(lnslrU<.:tiull of a trapezoidal channel to the South Platte River. lbis alternative is shown on Figure II. Alternative No. S: The propos<:d alternative will provide a conveyance structure at Town of Atwood, increasing the bridge capadtics at the main,tcm of Pawnee Creek, channel cleaning, (debris removal) and stabilization mcasures upstream ofIIWY 6 to CR 29, and the project features of Alternative No.4. This alternative e(m~ist~ uf constmetior! of Alternative No.4, along with modifications and new HWY 6 bridgc~. cbanne1 and levee impmvcments down~tream ofth", llPRR at Town of Atwood. Flows in excess llf the design event on the mainstem would thus r!ecc~.~iW.t", providing the project features at the Riverside Cemetery, Alternative No, 5 would d('el"t.~se the $t'verity of the IOD-year flood event in the area wcst of H\VY 6 b<:twt--cn the Pawn"'e Creek Bridge and the Cemetery. hut wOl1ld nm eliminate 1111 ovcrlJo,,"'s. In addition, Ihis alternative would provide /1ond benefits to the community of Atwood Thisaltemative is shown on Figure 12. AllernQtin :-00. 6: This alternative provides a drainage floodway upstrcillll of the Town of Atwood thai ,Evens hwnee Creek to tile south, ai",,1/. CR 29 <iir~'Clly 10 th<.' :)outh t'bUe Klver. I he tloodway would be sized for the' 100-year storm peak flow and wpuld handle a discharge cquall<l the July 19'17 Hood evental thai location. Thisaltcmative wouid require crossings for the Pawne.: lrri~ation Ditch. and j100th HWY 6 and the \JI'RR. 'lhis alternative is shown on Figure 13. "