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same, with onlv tht: width varying. The proposed lOO-year diversion channel will require the acquisition of35.17 acres offce title and 3.21 acres of tempo raryworkarea easements, The diversion channel alignment runs through 4 different lOnings and will affect 18 landowners. The 7.onings within the corridor and the acreages within each wne are commercial (3,16 acres of fel: tilk and 1.82 acres of easements), industrial (3.77 acres of fee title),residential (12.25 acres of fee title and 0.67 acres of easements) and agricultura1 (15.99 acres of fee title and 0.72 acres of easements). There is only one residential dwelling that will require relocation benefits under Public Law 91-646 for both the lOO-year and 30-ycar diversion channel plan. The total estimated Real Estate cost forlhe 100-year diversion channel project is $463,201. Rcal Estate cost estimate and typical fee title and temporary work area e.1scment agreements are presented in Appendix D. FLOODING IMPACTS llhasbcena,sumed that all excess excavated material from the diversion channel can be disposed of within 5 miles of the excavation on existing City, county, or private land,wilh no associated dumping fccor land acquisition cost. The cost toacquireadis- po<.al site for the excess excavation malerial, if needed, will be ,m additional east lhat will havc to be added to the real estate eOSlS as a non-Federnl cost and may ch angethe B/C ratio. Land acquisition or dump fee custs may be offset by a reduction of hauling costs if suitable disposal si te~ are found close to the excavation site. I I , , , I I I , I i , With the lOO-year plan in place, Dry Creek discharges would be significantly reduced from Larimer and Weld Canal to its confluence with the Cache La Poudre River, Table 6-1 shows a comparison of discharges for existing eonditionsand with diversion of flows. The water surface profiles for Dry Creek also reflect a reduction in stage from Larimer and Weld Canal downstream to the mouth for the with-diversion channel condi- tion. Plates 9 ancllOshow the flood profiles for existing conditions with the 100-year channel diversion and plates II and 12 show the without-channel diversion, beginning at the mouth and ending at Larimer and Weld Canal. To determine the effects of floods greater than the 100-year event on the lOO.ycar plan, the split-flow option was utilized to determine the amount of discharge that would pass over the diversion weir and into Larimer and Weld Canal during a 500-year event. Ilwasdeterminedthatapproximatelyl,550c.f.s. ofthe9,420 e.f.s.500-yeardischarge wOllld pass over the weir and into Larimer and Weld Canal, while 7,870 e.f.~. would pass down the diversion channel. It was assumed that the 1,550 c.b. overflow from the 500-year event would breach Larimer and Weld Canal and flow downstream. Thae would be little induced flooding frnm the 500.year event along the diversion channel downstream from Willox Lane becallS<: the majority of the flow would be contained within the ehannel or freeboard zonc. The profiles also show that the lOO-ycarchanncl diversion profiles would convcrge with the existing Dry Creek profiles about 1500 feet upstream from the location wllere Dry Creek flows "\'Quld enter the diversion channel. Theproposcd 30-ycar diversion channel will require theacquisilion of2 9,02 acres of fee title, and the total estimated Real Estate cost is $360,000. No acreage or value hasbcen included for a dump site for wasting exeess excavation material. With the 100-year channel diversion plan, the residual tlood damages from Dry Creek between Larimer and Weld Canal and Collcge Avenue could hc reduced or eliminated throllgh localized channcl imprOvCI1\Cllts, inc1udingchannelcleanoutand 6-5 6-6