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<br />toe immediately adjacent to the southwest corner of the pond <br />is also at elevation 4,926 feet. Ups.tream from t:he pond to <br />the 5th street Bridge, the average slope of the river <br />channel is two-1:enths of one percent. <br /> <br />An alterna1:ive capable of meeting diversion flow <br />objectives over a large range of riverflow conditions would <br />be an upstream diversion structure, located in the vicinity <br />of the 5th Strent Bridge. Since the City of Delt:a currently <br />plans to replacn the bridge in the near future, a <br />combination bridge/drop structure/diversion facility could <br />be constructed. Such a structure would also aid in <br />providing additional head to an existing diversion on the <br />left bank just <iownstream from the bridge. <br /> <br />The survey showed, however, that as long as there is <br />some flow depth in the river, a pipeline extending upstream <br />to the bridge wlluld probably not be necessary for diversions <br />of 5 to 10 cfs. This scenario appears very probable, <br />especially in l.Lght of the potential upstream AB Lateral <br />Project which wiluld result in greatly increased flows during <br />much of the yea:~. If final site select,ion can be deferred <br />until the dispo:;i tion of the AB Lateral proj ect is known, a <br />simple diversio:l struct.ure near the lagoon may be feasible. <br />This means that with proper design considerations, an <br />appropriate dilmrsion facility may be able to be sited <br />adj acent to the southwest corner of the ponel. <br /> <br />There are :;everal considerations that \-lOuld be involved <br />with either of ':he diversion sites. These include the means <br />of conveyance (pipeline or open channel), screening and/or <br />filtration to p:;~event undesirable fish and sediment from <br />entering the pO:1d, seepage lining alternatives, and <br />pumping. EachLs described below. <br /> <br />Pipe Alternatives - Three types of pipe, wen! considered <br />for the diversil)n conduit: reinforced concrete, plastic, <br />and corrugated metal. Because all three were comparable in <br />cost, the reinfl)rced concrete pipe was selected because of <br />its strength, dnrability, and relat:ively low' friction loss. <br />Sizing of the p,Lpe is critical regardless of whet:her the <br />adjacent diversion site or the bridge diversion site is <br />chosen. At the adjacent site, the pipe,line was sized based <br />on maximum perm.Lssible hydraulic losses of 1 foot: or less. <br />At the bridge site, tot.al hydraulic losses cannot exceed 4 <br />feet. For a 5-<:fs design flow, 24-.inch-dia:rneter pipe could <br />be used at both the lower and upper sites. This size pipe <br />would provide a buffer for such considerations as siltation <br />of the pipe, p~le seepage losses, and hydraulic losses. For <br />a lO-cfs design, a 30-inch-diameter pipe would be preferred <br />over smaller pipe at either diversion site for the same <br />reasons. Cost nstimates of the 24-.inch reinforced concrete <br />pipe for the 5-<:fs alternative range from $18 to $20 per <br />lineal foot. For the lO-cfs alternative, 30-inch reinforced <br />concrete pipe would cost between $25 and $28. Excavation, <br />placement of thn pipe, and backfill, as well as other <br /> <br />15 <br />