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STOR�tAV:A7l� 2 SI"iL' PLrW <br />AUGUST:1 AVOODS CO�llOA11�9U11S <br />C3\9P RD?0 I:AT�ND1=D DG"fGNT[ON DRY V.�AUL"17TANK <br />�1:1Y ?0. 2003 <br />PACiE 2i <br />The drainage design is based on the following standards. The ctcvcloi;cd onsite runoff <br />ratcs will be detained to die City of Everett standards, '/ the 2 ycar and malching dic 10 <br />and 100 yeac The Detained Off�ite Basin runoff from the east will bc conveyed throuch <br />the stonn drain system wi8iout dctention, however the comUined releasc rates will bc <br />restricted to correct for the bypass of Basins 3& 4. The flow from the 6ypass Ofi�sitc <br />Basin �vill not b� detaincd and the flow control will be uIrsized to accommod��e thc <br />offsite tlow. A combination two ycaz orifice and notch weir for the 10 �. 100 year c� rnt <br />are proposed meet the dischargc requirements. A 3�% correction factor has becn :�pplicd <br />to the live storage portion of this vault based on the Uasin impervious co�erage of <br />�rrCo:;;�n��t�h' 60°%. See attached StormShedT" output in Appendix D. <br />Thc runoff rntes from dic applicablc ba:;ins arc as follo�vs: <br />2 Year 10 Year 100 1'c:�r <br />Existing Qayin 2 0.032 cfs 0.13 cfs 0.37 cti <br />8xisting I3asin 3 0.00�1 cfs 0.01 cfs 0.04 cf; <br />Gsisting Qasin 4 0.003 cfs 0.01 cfs 0.04 cts <br />Detained Offsite Basin 0.22 cfs 0.52 cfs I.O� cfs <br />Devcloped I3asin 3 0.09 cfs 0.13 efs 0.19 cfs <br />Devclopcd Basin 4 0.07 cfs 0.11 cts 0.16 cis <br />I he allowable relcasc rates trom the detention vault are calculated as follo�ti s: <br />Lsist Ciasin 2+ Gxist Basin 3+ 6xist Basin -3 + Dctained Offsitc Basin- Dcc [iasin �- <br />Dev Basin -1 <br />Stonn I�i��cnt Allowal'•Ic_rcicasc rtuc <br />2 Year 0.032/2 + 0.00-t/2 + 0.003/2 + 0.2Z - 0.09 - 0.07 - 0.03 cts <br />lOYcar 0.12+0.01 +0.01 +0.52-0.13-0.11 =0.42c1s <br />I00Ycar 0.37+p.0�}�-0.04+1.OS-0.19-0.I6=1.1�cts <br />The design for the detention system is :�s fullows: <br />V:�UL'I' DI�IL.NSIONS <br />Design Vault Length = 5037 icet <br />Corrected Vault Lcn�th = 50.37�`1.3�(corrcctiun fuctor) = 6S feet <br />Vault Width = 33 1'cet <br />Dcsign Vault "live" Storage Volume = 1 1,�4=i6 cubic feet <br />Co�-ected Vault "live" Storagc Volume = 15,�152 cubic fect <br />P'LO�V CONTROL IN�ORDIATION (UNADJUSTGD) <br />Outtlow Llcvation = �04.� fcet <br />2 Year Orifice Elevation = 502.� feet <br />2 Ycar Oriticc Diametcr = 1.125 incli <br />10 R 100 Year Notcl� Glevation = 509.�2 fe�t <br />l0 �C 100 Year Notch Length = 0.55 feet <br />Overtlow Elevation = 510.-33 feet <br />J 6�:nsc�:Cra;�F�.;�..cw':co.�..51eP'.an�9alrocw�T-c�s�ssac�-nncoGDWH/srm <br />