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• <br />CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />Ucsi�n Crilcria <br />� I)esign criteria (on•.ir.on are;e filter sinps ;uc tiie sanr� as �p�°< �Ii�d jor h.�.nc Th�•r �t�v,•r. Howceer. ih_• <br />;iring of a narro�v;uca iltcr sVip is based on thc Icngth of flo�rpath draining to �he filter strip and ;hc <br />ionciwdinal slopc of the filter strip iisclf (pnrallcl to the (lo�.path). <br />�up 1 Deteimine the Iength o(the flowp,�th Gom thc upsveam to the do��nstream edge of thc impervio;:; <br />:ica draining sltcet flow to thc strip Nonrally this is thc .c,vnc as Ihc �eidth uf ihc pavcd ;uca, but i(thc sitc it <br />• �:.�ped, the flow paih may hc longer than ihe �eid�h of the intpervious area. <br />.G�p 2 Calculate thc longitudmal slupr ot thc tilicr strip (along the dircc�ion of unconccnvaccd flow), <br />aecraged oeer ihe total ��-idth of the filte- z�rip. The �r.inimum sizing slop; is 2 percent. IRhe slope is Ic,: <br />than 2 pciccnt, usc 2 perceni for sizing pu;p�xs. Thc maximum sllo�vable fi!�er strip slope is 20 perccr�t IC <br />d:c slopc cxcecds 20 percent, thc fihcr sirip must bc stepped du�vn the slopc so that tlie treatmen; are� <br />heheren drop sections do no� have a longitudinal slope �;rca�cr llidil LO j1CfCCI1L DfOP SCC(IORS R7USt I'C <br />� p;o�ided �vith crosion protection at thc ba�c vid flow sprcadcts to rc-sprcad tln��c. Vcrtical drops alr�:�r c' � <br />�lope ;nu�t ro: r.�cecd I� inches in heieln. I(lhis i� not possible, a dit7eient �reaiment facilit} mus, I�c <br />scic:tcd. <br />�7�p .3 Selcct the apprnprinte filler str,p leng�h for ih^ (lowpath Icngih and filter stnp lonettudira! �;o� c <br />� steps 1 and Z above) Irom thc ��raph in Figure 4,3. The filter sirip must be designed to provide t':�ti <br />n;ir,imum length L along the cntire stmt[h of pavemenl draining into it. <br />� T�, use thz graph � Find the Icngih oC the flowpath on one of Ihe cun�es (interpolalc bet�seen cur��es as <br />ncccssary). Mo��c along thc curvc to thc point whcrc thc design longitudinal slopc of ihc fihcr sinp � x- <br />i>.i�l is directly bclo�r. Read the filter strip Icneth on ihe t-azis �ehich corresponds to the in'.i=nt ,� . <br />��on1;. 1 �, ` <br />V\Y��"i" � � iJG..� �-��.n� f�(E� <br />� <br />� <br />Er <br />e <br />J <br />V <br />� <br />20.0 '_"_—._"_r_____.____'.__'_.____. <br />I <br />I5.0 __'_..._.__ I —_'_ _. -_.--,-_=. <br />Flowpath � ,��%�_ / <br />- 70fcc1 � ✓� i�� <br />� �� <br />�' I _ q. �� <br />� �) li - . . _ __ -- ` {/ _ _ _-. _ <br />1� k�.y / <br />� pP. /' ��1 iCII <br />�` ' / <br />!(�.� � � <br />.� <br />L� � �"� ! ��IO IL'C� <br />__'_ <br />s � �:- I,.-- <br />� �, � <br />o^i 4'la 5,�„ io°;, <br />Fillcr Ship tilu�u <br />4b1r munm�m� �t!la�c,oA(r fdlcr snrp (rnrd� �s J frrt <br />is^� zo^a <br />Figure 6.2 Filter Strip Lengths for Narrow Right-of-Way <br />Vofume lll - Fl��.�� (�pntrol and TreaLnent <br />G-a <br />� <br />� <br />J <br />� <br />