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CHM'TER 6 _ EVAL\JATION OF WITH-PROJECT CO:-.iDITIO:-i PLA:-iS nownstream from the training levees, the channel diversion would have a diversion weir to allow evcnts greater than the 1O().ycarevent to pass into Larimer and Weld Canal for the lOO-yearchannel diversion plan and to allow events greater than the 30. yc.arevent to pass into Larimer and Weld Canal for the 30-year channel diversion plan. In addition, low flows up to the j-year event would l:>ealJowed to pass into the canal to facilitate downstream divcrsion of irrigation water for both the lOO-yearand the 30-year channel diversion plans. The diversion weir would consist of a 160-foot-long, rock-lined ovcr- flow section with a maximum heightof5 feet. The backslopc would be IV on 10H. A small, 1.5-foot-high rock sill would be placcd at the entrance to the channel diversion to fore<: flows of less than the 5-year event to pass dircctly into Larimer and Wel dCanal. The de>eriplion and analysis Oflhe with-projed condition plans (loo-year plan and 30-year plan) that were studied during the recormaissance extension, their effects on flooding, their potential impacts, plan cost estimates, and economic summaries are contained in this section. DF.8CRIPTIO;.J OF PLI\;o.lS A lOO-yearchanncl di\'ersion and a 30-)'earchannel diversion, both alongahgn- ment B. were evaluated. Tht: alignment B channel diversion would begin in the lower portion of reach A, about 500 feet upstream from Larimer and Weld Canal, and flow ,outhwest, crossing the canal about 300 feel "cst of where the existing Dry Creek channcl crosses the canaL The channel WOllld cross WiIlox Lane and the UPRR tracks. extend $(Iuth fora\J.out2,500fectthrough an open area wesl<.,fHickory Village Mol"l", Ho,ne Park, then extend SO\lthca~1 Md discharge into the Cache La P0udre Riwr Roth plans would require relocati0n of the homeslead south of Willox Lane and WCSt of the UPRR. Larimer and Weld Canal would pass un(!cr the Dr)' Creek channel diversion through a 12-foot-diametcr siphon sized to pa~~ 1,000 c.f.~. Larimer and Weld Canal has a decreed water right of approximately 600 c.f.s., but has a maximum capacity of about 1.000 c. f.s, The siphon was de~igned for this maximum capaeit],. Over tht: siphon, the channel diversion would mn,i,t ofa 70-foot.long rectangular concrete channel that would bc 100 fecI wide for the lOO-year channel divcrsion plM and 40 teet ""ide for the 30-year channel diversion plan. Upstre;lm from the Larimer and Weld C;lnal crossing. training levxs would be constrllcted to direct or transition Dry Creck flows mto the channel diversion over a distanceofahoul120fccl. The ehannel diversion foralignmenlBisshownotl pla1t:,5, 6, and 7. The act\lalla)'out shown on these plates is for the 30-yearchanncl di~crsi"n, The alignn'cnt for lhe llX).ycar channel diversion h hasicallv the same with S<'Hlle minor adiusrmer\l> mad!;' to accomnHJ,dale the wider channel. The channel diversion would be a grass-hned channel with a 120-fool bottom widlh for the lOO-year channel diversion plan, and 5Q~footbottom width for the 30-year chan- nel diversion plan. Both plans would have I vertical on 4 horiwntal side ~Iopes. The IOO-yearchannel div~rsiorl wOllld carry a loo-ycardischargeof5,020c.r.,. The30.year channeldlvcrsinn w<lLlld carry a 30-year discharge of 2,830 c.f.s. The average depth of lhechannc1 di~ersion woold be ahout 5 feet forbolh of tile plans. The averagevclocily in the channel Jivcrsion wOllld bcabollt 7.8 feet pcr second fnrthe lOO-yearflo.,xlevt:nt. Thea,'crage velocity inth<'channcl diversion would t>c abollt 7.5 fectper s.<.'cnlld forthc 30-year nood e,cn!. After a design loo-yeilf or :-O.year nood event a~ applicable to each 61 6-2