Laserfiche WebLink
� <br /> CITY Oc E�%�='T'�' 0`�-52T� nF'r�eV'f'rON REQUSRvur_,yTS • <br /> . . <br /> ' i:�e si�ing of on-site detentions ia t`�e City of E':erett is <br /> based an a 24 hour desiga stor� t:rpical o= long duration <br /> winter stor�s in �ve:et�. For sites larqer t.han 5.0 acres, <br /> on-site detentions systams will be siaed by City of Everett <br /> perscnnel with t`se use of EP3's comnuter based stor:water <br /> management model (Sw'i�) . A cony of the comnuter printout will • <br /> be provided to t'�e apol�cant at his/her request. <br /> For sites s�aller than 5.0 acres, a series of tal�les shown <br /> beloa allaw the zoplicant to dete�aine his ar her or.-site <br /> detention z'ec�aireaent. Thesa tables were develoned based upon <br /> a series of ccz�puter siaulations o= stor�water rur.oi'_ f:o� a <br /> hypothetical 20 ac=e draiaa?e basin. This 20 ac=e d:ainar,e <br /> basin included ten parcels varying in shaoe and size f=oa o.25 <br /> ac:-es to 5.0 ac�es. <br /> Fow ''a use t!:e t>_bles: <br /> The fi=st sten is to dete�ine t`�e des?.gn storm critzr_a for <br /> t�e site in a_ues�ion. Ta�le 1 shows the desi.�,n stors criteria <br /> r '- The locat_ens of <br /> Par eich= drai:zace basins/areas in �e_et... <br /> �.e crainage basins are sho•.m �Z �=�'-"'- l. <br /> ��er t'�e des_cn stara c==eria are dete�i^.ed, 't=e allco.-able <br /> zelease =zte for 't=e on-s:t= detent:cn sys�en is �'ecexiae3 by <br /> usinq tables 1 .thsou?h 4. To use t�les 3 t'srouch 4, t4e <br /> ex:stir:g slore and ground cover conditions of t5e site in <br /> cuest_on nee3 to be deter�ined. � • <br /> The slope of t^_e site aus� be deta�:se3 from a taecgranhical <br /> sur�ey of t..�e site or by usinq t�e City's 198b aerial <br /> tonoc,.,-znhical maes. The slone refers to the slooe of overland <br /> flow rather than �e slope o: the caannel or swale t�at drains <br /> t'�e site. The existing ground coves ean be classit'_ed as , <br /> Weods or forestea; as larrns, grass or landscagir-g; zs bare <br /> '► or as an +�per�ious <br /> comnacted ear`.h or gravel sur�aced; <br /> � sur�zce. • <br /> The ninimua size �rifice allowed £os cn-site detention systems <br /> is 2" . Assuminc a bo•r:da .,oriEice (contraction cnef'_ic_eat of <br /> 0.51) and a hezd of t�o feet, t`.:e ainixvs f�oW r3te 't�=augn a <br /> 2" ori•`ica is 0.1� e:s. T?ierefore, allowable rele_sa rates cf <br /> less t'�an .13 c`s should not be usa3 to. cslculate on-site <br /> detention reauire�ents (<ee e:camnle ;2 beloa) . <br /> . ' � <br /> 1 • • . <br /> i I <br />