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VI-6 The channel from Colfax Avenue to 3rd Avenue would be lowered up to6 feet. This would require rebuilding the Public $erviceCoo1lpany's inflatable dam at the Zuni Power Plant. The channel would be widened in several areas by cutting tile hanks and providing a lowbcnch,orbyusfngvertical c oncrete walls. Sridges in thi~ reach would be modified to acc~nmodate the deepened Channel and many would have the maintenance trail modified to be a<1jacent to an abutment and pl aced on vert ica 1 retai n i ng lOa 11 ~ to increase flow area under the bridges. REACH 6 . CHERRY CREEK TO FRANKLIN The limited stroctural improvements in this reach include erosion protec- tion. The channel betlOeen Interstate 70 and Franklin Street would be deepened and improved. In addition, the Franklin Street bridge and the adjacent railroad bridge \\Quid be rebuilt. The Franklin Street bridge would be raised 3.5 feet, and the railroad bridge rebuilt lOith a single center pier. The Chicago Rock Island railroad bridge upstream of Denve~ metro Should be rebuilt using a single center pier. REACH 5 COLFAX TO CHERRY CREEK Between Interstate 25 and Colfax Avenue the South Platte River would be lOidened in several locations by movIng the banks back about 20feetuflder the limited structural improv~ents proposed. Widening of the river is 1 im1ted by the railroads and roa"'i that are paraliel to the rive~. Thl' pedestrian bridge upstream of Interstate 25 should be relocated or rebuilt to provide a wider cross section. U~der th!' Int!'r<;tatp 25 hrirlge the roc~ armori ~g lOould be removed and repl aced wi th vert ical concrete wall s. :)olOflstream of the Interstate 25 bridge the sewer line crossIng should be removed or lowered. The alterflative cho~en wi 11 depend on pi a~s for the Central Platte Valley Development. REACH 7 - FRANKLIN TO SAND CREEK The reCOl1111ended a1ternative of limited structural alternatives for tMs reach includes erosion protection. The major reconmeflded structural im- provement i'i the add1tion of a boat chute and pond flush gates to tile Bur- 1 ington Diversion Dam. The Gardners Ditch diversion structure at Yor~ Street would be lOlOered and a boat chute added. The Gardners Diversion should be moved upstream to a point jU'it downstream of the Burlington Diversion Dam where the small structure required would also protect a sewer line crossing. The railroad bridge downstream of York Street should be rebuilt to provide a wider span lO1th no pier,; in the river itself. Ifl several areas the r1ver channel should be widened by cutting back the banks. DolOnstream of the sewer crossing the cl1anflel would be widened O~ the rigM bank by providing a 150 foot wide channel dfld a 50 foot bench at about the 10-year flood level. The left bank woll1d remain undisturb!'d. Thf'Farmers and Gardeners Dam at Conflueflce Park would be1olOered tOdbollt 3 feet and rebuilt to provide the sound of falling water. A new diversion dam wOllld bl' constructed about 1,000 feet up<;tream with a hoat chute i~corporated to provide a 820 foot crest length. ThenelOdiversiondamboatchuteafldthe rehuilt Farmers an" Gardners D~" boat chute would be connected to provide a bOdt chule almost 1.000 feet long. The ared below the confluence with Cherry Cree~ lOill remain relatively undisturbed. REACH 8 . SAND CREEK TO BASELINE ROAD The 10-year engineered stable channel a1ternativewaschosen in this reach because it is effective and least costly for 'llaflaging flood,. It al~o h cOlllpat ib 1 e lOi th t.he cont inued extract ioo of mioera 1 re~ources a long the rivf'r. The alterMtlve involves the stabilization of the river haflks with rlprap and vegetation IOhen the alignment has reached thereCOrmlpflded con- figuration. The invert of the rivpr >IOu1d be al1o"",d to degrarle until the rlesired elev~tion has been attaifled at IOhich ti~e it would be stabilized to prevent furthe~ degradat ion. Bridge toun~at1ons would be protected to eli'llinatedamage associated with dpgradatiofl. l I