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' �� <br />� <br />STORM DETENTION CALCULATIONS <br />FOR <br />HAGCENS, INC. <br />EVERETT MALL SHOPPING CENTER <br />October 17, 7983 <br />Project No. 1254 <br />Original site vegetation consisted of scrub alder with undergrowth of salal, etc. <br />Since the site had epparently been cleared prior to the establishment of this <br />vegetation, an existing runoff coefficient of "C" = 0.10 is justified. <br />Total Site Area = 435,465.734 S.F. = 10.0 Ac. <br />Peripheral Landscape Area = 47,200 S.F. = 1.08 Ac. <br />d= 850't s= 2at Exist. "C" = 0.10 V= 1.0 Ft./Sec. <br />Tc = 10 + 850/(60)('I.0) = 24.2 min. i�p = 7.17 in./hr. <br />Q= ciA =(0.10)(1.17)(10.0) = 1.17 C FS = Allow. Release Rate <br />Developed "C" _( 8. 92) ( 0. 90) +( 1. 08) ( 0. 20) = 0. 82 <br />10.0 <br />Qo = 1..17/(10.0)(0.82) = 0.14 <br />T = -25 + 27p6/O.14 = -25 + 139.0 = 114.0 min. <br />Vs = (4329)(114.0) - (40)(0.14)(114.0) = 2912.0 CF <br />139.0 <br />Vt =(2912.0) (10.0) (0.82) = 23, 876 CF Storage Required <br />Storage Consists Of: <br />168 LF - 90" d pipe @=F4.18 CF/LF = 7422 CF <br />190 LF - 78" � pipe @ 33.18 C F/LF = 6304 C F <br />550 LF - 54" d pipe @ 15.90 C F/LF = 8745 C F <br />344 LF - 18" � pjpe C� 1.77 CF/LF = 609 CF <br />358 LF - 12" d pipe C� 0.79 C F/LF = 283 C F <br />8.34 LF - 54" � pipe @'.5.90 C F/LF = 131. C F <br />24.4 LF - 48" � pipe @ 12.57 CF/LF = 307 CF <br />Total Storage =238D2 CF <br />Note: Volume does not represent pipes that will be partially full or volumes within <br />Type I C.B.s. This will add an additional 200 CFt bringing the total available <br />storage to approximate:ly 2R, 000 CF ) 23, 878 CF required. <br />