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VI-3 Deep Tunnel. The deep tunnel alternatIve Is comprised of a system of collection ponds that control flow into a tunnel that Is considerably below grade. I t was estimated that the tunnel would be constl"ucted by "mole" methods which would seem suItable In the Denver format'lon at depths of 40 to 100 feet. Extensive shor'lng IolOuld not seem to be nec,. essary but a simultaneous boring lInIng operation would be. ApproxImately nine ponds would be neceSsa'"y to allow reasonab'IEl entrar1ce points. The present channel thalweg would be used to collect and r'oute flow to the ponds. In most locations only channel clearIng m"asures wou I d be necessa ry wh I ch wou I d be perf()rm,~d as rout I ne ma In tenance operatIons. RIght of way would be necesS<lry for the tunnel a'llgnment, with strict measures to prevent any further development near the exist- Ing channel alignment. The approxImate capital cost of a systE.m of hIgh velocity tunnE.ts ranq- Inq from 8 to 12 feet In dIameter, collectIon ponds, and other- appurten- ances would be about 10.5 mIll Ion dollars,. Land costs would llpproxlmate 0.2 mTlllon dollars for a narrow right of way and pond areas, brlnglnq the total to 10.7 mIllion dollars. The operatIons and maintenance costs would be quIte high for the tunnel llnd pond system, bes'ldes nor.. mal channel maIntenance. Surface ConduIt. Somewhat sImilar to the deep tunnel alternatIve, this alternatIve would be fundamentally a system of collection and control ponds, lInked wIth a hydraulIcally effIcient conduit system. The COn- duIt would be placed In a straIghtened alignment along the present thal- weg. The depth would be suffIcient to allow adequate hydraulic; heads and a surface swale to collect local runoff. A 75 foot rrght of ~IllY would be necessary to provIde a reasonllble surface channel and acceSS to the conduit. The cost of this system with conduit sIzes up to 1i+ feet In diameter would be 8.6 mTlllon dollars with approxImately 0.6 mIllion dollar"s addItional land costs, brIngIng the total to 9,2 mIllion dollars. The operatIons and maIntenance costs would be very nearly the same as the deep tunnel alternatives, but much hIgher than conventIonal sur-- face Improvement schemes. Grass.'Uned Channel. This alternatIve would Include a grass-lIned channel from a sedImentatIon pond located ,above the traIler courts In Reach 2, all the way to the confluence with Clear Creek. All ()f the culverts, except the two large box culverts on IJ. S. 6 and 1-70, would be replaced with multIple culverts or brIdges. The multIple uses and benefIts, Implemented under Denver RegIonal CouncIl of Governments' (DRCOG) crlter-la,would be hIgher than other alternatIves. Tne'rewould be moderate operation and maintenance costs.