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Itica�ca}•"I�raci I �- Lol 5 <br /> Sinnn llrainacc Itcpnrt <br /> � 4 Water Quality Calculations <br /> Water quality will be provided per the City of Everett standards. A vegetated <br /> ' treatment cell will be locaied at the toe of the existing slope near the eastern <br /> boundary of the site. (Please see the Developed Conditions Exhibit located in <br /> � the Appendix.) The wetpond will be preceded by a 72-inch diameter tank at the <br /> top of tlie slope under the proposed pavement. The combined permanent pool , <br /> Ivolume is greater than the volume of runoff from the 6 month, 24-hour storm � <br /> Ievent. <br /> F�ermanent Pool Volume <br /> IThe volume of the developed 6 month, 24-hour storm event has been calculated <br /> using the SBUH method and thE computer modeling program StormShed. <br /> StormShed calculates the total runoff volume based on the type of ground cover <br /> and the time of concentration. The following are the parameters used in the <br /> StormShed modeling. <br /> Ground Cover <br /> I StreeUParking Lot 1 3f or,ies @ CN = 98 <br /> Landscaping 0.51 :�cres @ CN = 8G <br /> �' Time of Concentration <br /> Pervious <br /> Flow type: Description: Li�nglh: Siope: CoefL Travei Time <br /> � Sheel Off Bank 3Q00 ft 1�.00°0 0.150' 3.51 min <br /> Channel conveyance :ystem 500.00 ft 1.00% 42.0000 1.98 min <br /> i Impervious <br /> Flow lype: Description: Lenglh: Slope: CoefL' Travel Time <br /> Sheet Across streel 30.00 fl 2.00'0 0.0110 0.57 min <br /> Channel Conveyance syslem 1015.0(' ft 1.00So 42.0000 4.03 min <br /> Rainfall ' <br /> 6 month rainfall =64°�0 0(2 ycar �� <br /> = O.G4 x 1.5�' <br /> =0.99" <br /> The following is tlie StormShed output summary. Please refer to the Appendix <br /> for the complete SiormShed output. <br /> Dev WQ Event Summary: <br /> BasinlD Peak Q Peak T Peak Vol Area Melhod f2aintype Event <br /> ------ (cfs) ;h�s) (ao-tt) ac /Loss <br /> IDevlVO 0:� P.00 O.W67 1.8i SBUHISCS TYPEtA 6-monih <br /> Prhiu.n�, ,_ ,nu.� - - � - - � - - � - ----- Pagc ? <br /> I �'I'RI;�D <br />