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<br />. Install inverted siphons with inlet and outlet <br />structures to separat~ the flood flow from the <br />Platte Canyon Ditch and Nevada Ditch irrigation <br />water. Construct earth berms on both sides of ditch <br />crossings to confine ~lood water in the drainage <br />channel. <br /> <br />DOWNSTREAM REACH (KIEWIT AREA) OF MAIN BRANCH OF BASIN 6200 <br /> <br />This drainage area was not included in the Phase A study. <br />Also no benefit-cost ratios wer~ determined for possible <br />alternativ~s. <br /> <br />. Install 380 feet of g~ass-lined channel from Platte <br />Canyon Road to the spoil piles designed to carry the <br />lOa-year flood flow. Install two 4.5-foot drops and <br />stone rip rap on the channel bottom to reduce flow <br />velocity and eliminate channel erosion. <br /> <br />. Cut a 240-foot trapezoid channel through the spoil <br />pile with a base width of 21 feet and side slopes of <br />1 to 1 without grass lining. The channel bottom <br />would be rip rapped to reduce the erosion potential. <br /> <br />. Install an inverted siphon with inlet and outlet <br />structures to separate irrigation water from flood <br />flows at the intersection of Platte Canyon Ditch and <br />the drainage channel. <br /> <br />. Put stone rip rap 50 feet long downstream of spoil <br />pile to reduce the erosion potential in transition <br />reach from the spoil pile cut to the downstream <br />natural drainage waterway. <br /> <br />DIRECT FLOW BASIN 6100.5 <br /> <br />In this basin, initial storm drainage problems were considered <br />rather than flooding problems because there is no defined <br />existing flood drainage channel and the area is fully developed. <br />The 2-year initial flood event was used as recommended in the <br />Urban Storm Drainage criteria Manual. <br /> <br />. Construct the initial storm drainage channel by <br />routing the flows south onto Sheridan Blvd. right-of-way <br />to the rear of the hOmes facing Hinsdale Avenue and <br />then east to the existing ponding area. Install a <br />catch basin with steel grating across Hinsdale <br />Avenue at Sheridan Blvd. intersection to catch storm <br />water from the streets. <br /> <br />2-6 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />