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<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 /> <br />A 100-year concrete-lined channel which was to extend between East 112th Avenue <br />and the Upper Pond in Reach 3 had the highest benefit/cost ratio for that type of channel <br />and was part of the consultants' recommendation. The study's sponsors, however, elected <br />to lay an underground conduit with an overflow channel for aesthetical and safety con- <br />siderations. <br /> <br />Since current flood damage figures are quite low from Cherry Drive to East 112th <br />Avenue, a structural plan did not seem presently feasible. However, to assure that as <br />much of the runoff as possible is routed into the 112th Avenue pond and for purposes of <br />continuity, it was recommended that a grass channel designed to convey the 10-year storm <br />be constructed. Additionally, it was suggested that provisions be made to convey a 100- <br />year flood safely through any future development in order to prevent additional flood <br />damages from occurring in the new development. This improvement could be made a <br />condition of the development of adjacent land, reducing the project costs to the City of <br />Thornton. <br /> <br />The benefit/cost analysis for improvements in the vicinity of the East 112th Way <br />cul-de-sac disclosed that the enlargement of the existing storm sewer system to a 10 year <br />design storm would have yielded the highest return per construction dollar and, therefore, <br />incorporated into the recommended plan. However, sponsoring entities selected the 100- <br />year storm as the design storm, drawing all the homes along the cul-de-sac out of the 100- <br />year floodplain. <br /> <br />N-5 <br />