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The a~ove I ist of damage. have bee" converted 1 nto dol lars and used i~ analyzing benefits for the follO"ingalternative treatment plans. (See StructlJral'1easuresandComparisonofAlternativestables). This alternathewould inclUde no improvelnents on the West Basin because there appears to be no sigriificanc flOOd damages diong this channe 1. Alternat1veNo.l This alternative considers: (1) collecting runuff from the East B~s1n drainage above lower Cactus Valley Ditch and u,ing a drop inlet spillway to pass this floodwater under the ditch to a stable outlet downstream, (2) divert1ng Sixteenth Street Basin flows to the east boundary of S1lt to ~ collection area and using a drop inlet spillway to pass this water under Grand Avenue, under the lower Cactus Valley Ditch, and under US Highway 6 to a location where the flows can be outletted to a stable grade. (3) collectiMg Seventh Street Basin flows at the mouth of the canyon north of town and using a drop inlet spillway and pipe to carry the flows to the lower Cactus Valley Ditch where it will outlet into the ditch, (4) building up First Street and County Road 231 to divert First Street Basin flows that exceed culvert and channel capacities to an overflow channel. ThiS overflo>; channel leads to an adjacent drainage to the west. The overflow would be collected at the lower Cactus Valley Ditch into a drop inlet spillway that would pass under the ditch and continue to an area below the small pond ~t City Park near Dogwood Drive, (S) lininy the lower Cactus Valley Ditch from Seventh Street to the channel west of town that leadS to the City Park referred to in Item 4 above. The lined ditch would handle floOd flows from Seventh Street Basin as well as 1rrigationflows. flitch flows greater than 50cfs would be spilled 1ntothe City Park drainage because of the limited capacity ot an inverted si phon structure a Short distance downstream. Alternative No. 2 This alternative would be the same as Alternat1ve No.1 with the following exceptions: 1. Item number 3 would inclUde a continuation of the pipe under the lower Cactus Va 11 ey Oitch and on south to the ra il rO~d. A pi pe would be jacked under the railroad to allow d1scharge at a stable outlet above 1-70. 2. It~ number 5 (d1tch lining) wauld not be 1ncluded. Alternative No. 3 ThiS alt~rOdt i v.. would inc1wi.. lining the Lower Cactus Valley D1tch from Ninth Street to a spill loc~t1on at the City Park Orainage. The capacity of the lined ditch would be sufficient to carry flOOd flows from Seventh Street Basin and normal i rr1 gation flows (50 cfs). Some dike wor~ would also be necessary at County Road 231 on First Street Basin similar to Item No .4in Alternative No. I. There would be no improvements to West Basin, Sixteenth Street Basin, or East Basin in this alternative. - 24 - -23-