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" " 2. ^dequacy of ~tural detentIon and conveyance. I , I I ! I , , i finAd ~ a narrow channel or only wndeveloped land is inundated this alter- naU"" is attracti"e. In Milliken, however, such is not the CAse. The flooding Is ~ide"pread over developed urban areae. Legislation, fLood insurance, or floodproofing will not reduce the "Ktent of flooding. ~lso, indlrecto<)sts.."sociatedwlthlegls1at1on, non_developabLe pro perty, and future flooding ..rise. Flood plain zoning is recommended in proposed deten- tion pond areas ..""oelated with structural improvements. Considering the seriousness of the drainage problems in Milliken, the most practical solution.. will be found among the structural alternatives. l!:ach of the thn'" drainage......"s ero,"...... the 'l'hClllpson and Pl..tte Oitch. Conservative design ~BB~eB the ditch is flo~ing at capacity when runoff waters reach it. ~lternatives which cross the irrigation ditch on the surfece all employ e similer ditch cr08sing<'lesign. The ""rth b4nl<.of the Tho"'pson and Pl~tt(j Pitch opposite the drainage channel would be e"cav~t..d to the nor- mal operating wat(jr surface elevation of the irrigation ditch. In this way, flow in excess of the Thompson end Pl~tte Ditch capacity would spill out to be contained by a drainage structure downstream. The ditch crossings ere all located just upstream of flow constrictions (culverts or bridge openingsl on the irrigation ditch which would improve the efficiency of the crossing. ~n essential part of all of these alternatives is regular inspection and maintenance. Theeapacity of the structures involved is hasedonhydraulics whioh ~88utrle specific gr~des ..",1 wloDsl:.ruct..d (;I1l""rI:.1I and channels. If the drainage systems are to function as intended, grades ~st be maintained, cul"ert8 and oI,,,nnels l<ept in good rep.llir =d free of debris and sediment, ~nd the assumed channel vegetation oonditions must be presur"ed. Detailed c'llculations used in de"elOpll'ent o! the alternatives ..pp..ar in theTechnicalM.dendwn. Vl. ALTERNATIVE IM~ROVEMENT PLANS Conceptual ~pro~ement plane for the drainageways were formulated to alleviate flood damages in M1111l<en. In the !o....ulation of alternati~e ~~ pro~ement plans the following factors he"e been considered. 1. Long-termre11ef of flood problems. 3. Use of streets for con~eying stor'" ",..ter. 4. Drainage capacity of pevedstreets. 5. Av..ilableright-o!-way. 6. Ease of....intenance andacceos. 7. water quality ~provements. a. Eroaioncontrol. 9. Safety. The design criteria utilized to formulate the alternative impro"e",ent plane are those contained in "Drainage Crit..ria and Street Deoign M4nua l!or the TOwn of Milliken, Colorado~ (reference 11) which hao been submitted as p~rt of this project. lmprovement Alternatives Based on the analysia presented, alternative improvenlent plans were de- veloped for e"ch of the flow ~ths inCluding both reaches of the Lola Park Tributary. All hydraulic design w"s ~s..d on the pr"dicted 100-y....r disch"rge. The "ltern"tives formUlated for each drainageway are independent of thoee developed for any of the other drainageways. ~ such, any option for a given drainage path can be ~tched with any alternati"e solution to another route'a prol>l"""'. 'rhe '>lccep<:ion is the nonstructur~l altern~ti"., (Alt..rnati"" 1l for the Ea'ltern ~low ~"th which would add to the Lola parI< Tributary problema. Nonatructural alternati~es (Alternative 1 for each drainageway) involve nonstructural mRSSUree each aA floodproo!ing individual structures, flood insurance, or establishing flood plain zoning regulationB. The nonatructural alterMti""e haw, the ..c1v..nr.ag..of low oonetructlon costa. If new is COn- w..~t"rn Flow Path The solution to the erosion and flOOding problems plaguing th.. Weatern Flow path is to provide ~ distinct flow path(sl protected to withstand eroding VQlocit.ea. groaion on Quentine, Pauline, Olive, Norma. and Marjorie ~venues can be eliminated by paving the streeta. Three structural alter- natives to eliminate flooding on Quentin.. Avenue follow.