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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 \<lOuld not seem to be nec,. essary but a simultaneous boring lIning operation would be. ApproxTmately nine ponds would be necessa,-y to allow reasonab'le entrar1ce points. The present channel thalweg would be used to coT lect and ,'oute flow to the ponds. In most locations only channel cTearlng m"asures wou 1 d be necessa ry wh I ch wou 1 d be perf()rm,~d as rout I ne ma In tenance operatTons. RTght of way would be necesS<lry for the tunnel a'ITgnment, with strict measures to prevent any further development near the exist- Ing channel alignment. The approximate capital cost of a systl'm of hTgh velocity tunnl,]s ran'l- In'l from 8 to 12 feet In dIameter, collection ponds, and othe,- 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, brlnglng the total to 10.7 million dollars. Thl' operatTons and maintenance costs would be quite high for the tunnl'l llnd pond system, bes'ldes nOr" mal channel maTntenance. Surface ConduIt. Somewhat slmllar to the deep tunnel alternatIve, this alternatIve would be fundamentally a syst"m of collection and control ponds, lInked wIth a hydraulIcally effIcient conduit system. The COn- duit would be placed Tn a straightened alignment along the present thal- weg. The depth would be sufficient to allow adequate hydraulic; hl'ads and a surface swale to collect local runoff. A 75 foot rrght of ~IllY would be necessary to provIde a reasonllble surface channel and aCGess to the conduit. The cost of this system with conduit sfzes up to 1i+ feet I'n 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 su,-- face Improvement schemes. Grass-'Lined Channel. This alternatIve wCould Tnclude a grass-I fned channel from a sedImentatIon pond located ,above the trsl ler courts In Reach 2, all the way to the confluence with Clear ereek. All ()f the culverts, except the two large box culverts on IJ. S. 6 and 1-70, would be replaced with multTple culverts or bridges. The multIple uses and benefIts, Implemented under Denver RegIonal CouncIl of Governments' (DRCOG) crlterTa,would be hIgher than other alternatIves, Tne'rewould b.e moderate operation and ml'lintenance costs,