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utilizing existing culverts in this area. ~inor improvements are needed in the existing Dry Creek channel through the Alta Vista area. Reach C, An improved channel carrying 1,400-cfs was designed for the Valley Airpark area. The channel follows the existing Dry Creek channel utilizing the existing culvert under Highway 14. Culvert improvements were included at two local streets and a siphon designed for the Cache la poudre Reservoir Inlet Canal. Reach c: An improved grass-lined channel was designed to carry 520-cfs through the Valley Airpark development and south of Highway 14 to the poudre River. Culverts at two local streets and a siphon for the cache la poudre Reservoir Inlet Canal were also designed to convey this residual 10-year flow. Presently, no channel exists south of the Larimer and Weld County Canal for a distance of 1,000-feet and there is no means to carry waters across the canal. An improved channel upstream from the canal in Reach A will require a means of containing these flows south of the Larimer-Weld County Canal through Reach B. To lessen the impact on the developed area south of canal and as the cost- effective solution, a bypass channel diverting flood water away from the development was used in several of the alternatives as opposed to routing flows through this high-density commercial and residential area. The bypass channel intercepts flows above the canal crossing and generally flows south to its terminus with the poudre River. 1I1ternative *5 A combination of the la-year and 100-year events was the basis for design of this alternative. Channel improvements were developed within reach A for 10-year event protection. The lOO-year storm event was used to size improvements to the Larimer and Weld County Canal and the bypass ch,mnel from there to the poudre River. Reach A: Improvements to the reach for a design flow of 720-cfs consists of increasing the capacity of the culvert under Meadow Lane. Another improvement that was analyzed in detail w~s the use of a detention pond on undeveloped property immediately north of Vine Road. The roadway embankment with some increase in height would store a considerable quantity of flood water, but its shallow depth lIould require use of nearly 80 acres of 1a,,'" ':ene cost of land made this solution more expensive than channel improvements downstream. For this reason, this improvement is not a part of the alternatives presented in this report. Residual inflow for the laO-year storm below the diversion was USCG to design improvcment~ to the remaining channel downstr~am. Reach B: 11 bypass channel for the lOO-year event with improvements to the Larimer and Weld County Canal was designed to carry storm water to the Poudre RiveL. Two new culverts were required for the bypass channel. one at the Union Pacific Railroad and the other at Willox Lane. Re",idual flood ,,'ater from the lOa-year event \\'<lS -29- For all alternatives considered, drainageway improvements in undeveloped areas were assumed to be consistent with upstream and downstream facilities presented in this report. These imprnv~ments would be subject to appro~al by the City of Fort Collins or Larimer County to insure that the total drainage system is compatible. No costs were included for these improvements in undeveloped areas. Altern<ltive *6 is a non-structural flood plain management alternative and is discussed further on in this report. )0- channel",)' thnluqh the College Avenue area '~'ith dc:;ign improvements in thte culverts upstream and downstream of this street. A grass- lined ch"ll1nel bypass around the J\lta Vista area includi:1g a box culvert under LeMay Avenue is required.