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<br />Design Frequency for Channel Improvem'"cb3:: The desi"n frE'quency <br />'Eor drainage improvement:s is-'depe'nde:c,':--niij'.nly on the cost-benef:.t <br />analysis. The agreement between the IJrban Drainage and Flood <br />Control DistI'ict and Camp Dresser s: McBe'~ for Phase A studies <br />was to invest:igate 'I:he 2-, 10-, 100-y,"ar flood events and t:he <br />Corps of Engineers' Standard Project: !Clom!. The cost and <br />benefit information of a fourth desi';rn frequency betw'"''!n 10- <br />and lOO-year flood event, in addition to the 2-, 10-, and 100- <br />year :Elood event was required. in ordc: I~ to se 1ect a design <br />frequency for channel improvements. CDM provided the Corps <br />\~ith the cost: and right:-of-way requin~ments for the 2,-, 10,-, <br />and 100-year design frequencies plus the :?5-y(~ar desiqn f"",- <br />quency. The Corps reevaluated the cost-benefit analysis and <br />suggested a design frequency for ch~~nel improvements. <br /> <br />Lowry Air Force Base: The Corps of Engiru~ers performed the pre- <br />'Limin"lry design and -cost estimate for the improvEeTnents on Lowry <br />Air Force Base, which consist: of K("lly Pond, t:he Opper Lowry <br />Detenl:ion facility, and the flood channel from the ini:ersection <br />of S. Havana Stree.t and E. Alameda Avenue to the P:Loposed Upper <br />Lowry Detention pond. CDM provided aLL hydrologic information <br />to the Corps of Engineers and maintair~d close coordination <br />~;iththe Corps of Engineers on the upstream facili.ties discharg-- <br />ing ],;1to Lowry Air Foce Base. Upon completion of .the prel :i,minary <br />design for the improvements on Lovlry Air Force Base, the Corps <br />of Engineers provided a release rate of 5G cfs from Kelly Pond. <br />CDM also performed t,he preliminary deco"cgr of the low flow pip" <br />from ,the intersection of S. Havana S1:reet and E. J,lameda Avenue <br />too th'l proposed Upper Lowry Detention Pan:', and thE' flood channel <br />along E. Alameda Avenue. <br /> <br />.~ond ~-B: Because 1:he actual storage voJume for PandA-Ii is <br />larger than indicated in the Phase A repc:~t (at the cr'est of the <br />'~rnergency spillway, the storage volUIn'" is 191 acre feet instead <br />of 148 acre feet), t:he requirements for Pond A-B were reevaluat<~d <br />accordingly. Consideration of deepening the pond ve",.sus raisinq <br />.the embankment was made. <br /> <br />The l:}cation of the flood channel leadin'l from Pond A...3 as 1'1'0-- <br />posed in the Phase A report was reeva10ated b,"cause of the zoned <br />uses ,:)f the proposed right-of-way. <br /> <br />prainage Area No.3: Drainage A:r,ea No. :\ was conside:cl"d as a <br />separate drainage problem in the Phase A report beoausE'! of the <br />high elevation of .the embankment and road.Hay surrounding l^1indsor <br />Lake. The overload runoff from Drainaqe hrea No.. 3 is trapped in <br />a low area between t:he Windsor La}.;:e roadvlilY and Mississippi Avenue. <br />::t wa" recommended in t.he Phase A report to drain ,the overland <br />runoff from Drainage Area No.3 into privately-owned windsor Lake, <br />;Ihich would require drainage righ,ts and E>i'.sernE!llts" <br /> <br />The Dayton detention pond included in 1:hi~, preliminary design <br />provides sufficient volume to handle t:he runoff from part of <br />Drainage Area No.3 without draininq into windsor Lake.. A <br />~:uggeBtion was made by the City of A\J:,:'ora, that, the location of <br /> <br />-5- <br />