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r STORM DETENTION CALCULATIONS <br /> FOR ,` <br /> EVERETT MALL PLAZA - PHASE II <br /> March 28, 1984 z'° <br /> Project No. 1198 <br /> I <br /> The original site vegetation consisted of scrub alder with unc:e:growth' of natal, <br /> etc• Since the site had apparently been cleared prior to the establishment of <br /> I „ this vegetation, an existing run-off coeffecient of "C" 0.10 is lustif '� . <br /> • sag �- � ;�,}r1 A,�. <br /> .! Total Site Area = 577,188 S.F. = 13-25 Ac- �i----. + ' <br /> I • s d = 1200'¢ S - 2'!t = <br /> ,• <br /> Exist, NC" - 0_10 V = 1.0 ft.,/sec. <br /> 'i �' 10 + 12001(60)(1 0) =.30.0 Alin. i10 = 1.05 in./hr. <br /> Q Ci,4. $.,•�0I)tt;, J(13.25) - 1.39 CFS = `Allow. Release Rate <br /> Dev ,I SC" 0 85 (see note at end of calculations) <br /> i;)O `1.39/(13.25)(0.90) = 0.12 CFS/Acre - "C" <br /> I <« T. -2S �# 27�D510.12 -25 + 150.2 = .125.2. 1in. <br /> V _ (4,�)(125•2) - (40)(0.12)(125.2) = 3,007•5 CF <br /> of (3,007.5)(13.25)f 0 85) = 33,872 CF Storage Requir l•, <br /> z <br /> ed storage. wi:1 be acco aced it an underground concrete vault an <br /> d in <br /> ...Q,► ; pig system with the overflow elevation set at 508.50..in the outlet <br /> •c cture. <br /> Vs.'it tibi @ downstream 1 - <br /> . <br /> end <br /> t <br /> - Max. Water Surf. Elev.. 508.29 <br /> ..----. ,5 508.8S`. <br /> I <br /> �; <br /> 20` EncA a 218. no sq ft. � ' <br /> ' ` _ � — ;cam, 4I ,,- „ •1. . <br /> 14 ' r'- <br /> �. ;:� •� g97.4 a <br /> ' / r`i <br /> '. �. F t. t <br /> J C <br /> I ': <br /> ..,' - /// <br />