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� <br />� <br />� <br />C7 <br />7 <br />CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />Ucsigu Crilcria <br />Desien critcria fo� n:uro�v area filter strips are the samc as specr)iedj.n• ba.n� >ilrc�� srrrps Hrnaevcr, tl�.�� <br />;izing of a narrow arca filter svip is based on the len�th ot (lo��path draining to the fiher strip and thc <br />longiwdinal slopc of U�,c tiltcr strip itself (parallel io thc (lo��path). <br />��rp l Dctcrminc the length of dte flowpnth irom thc upstrevn to Uie donnsvcam e<Ige of the impcn io.:. <br />:,ea draining shect f?mv to the strip. Nonnallq this is tLe same as Ihc widlh of thc paved arca, but if Ihc snr i� <br />.I��pcA, dic Oow paih ma�� bc longcr tha�i tL•c ��iAth of the impervious �rca. <br />?�n 2 Calculate the IongituAinal tilop� of the tilter strip (aleng the diicction of unconcentrated (lo�v), <br />��eia�cA ocer the to;al �cidih o(tlu filter strip. Il�e minimum sizing slope is 2 percent. If the slope is Ic�� <br />�:n 2 perccnl, ux 2 pereeut (or si�inr purposes. The m.�.eimum �illo�a:�blc fihcr strip tlope is 20 perccnt. li <br />� c;lope exceeds :0 percent, tl;e filier sirip miist he ste�>ped do�vn the slope su th.�t ihe treatment ares <br />�:t«ern drop secuons do not ha�e a longitudinal slope gre:i,cr thar 20 perccnt. Drop sec�ions must bc <br />i�o�idcd �vith crosion protcction at thc basc and flow spreadcrs to rc-sprcad tlo��s. Vcnical drops alonr; tl:„ <br />�I��pe nuist not exceed I � inchcs in I�eiFJv. If,his is not possible, a dilfcrent treatment `acilin� must be <br />cclec�ed. <br />`���? 3 SdcU thc appropriatc filicr strip len_r,th for ihc floupath Icngth and (il�cr strip longitudinal ,:��;�, <br />� S;c��s I and 2 abo�c) fiom thc graah in Pigurc 1.4. 'fhe filtcr strip must Le desiencd to provide ;i:;. <br />n��.inimum Icngth L along ;he ec�ire s�retch of paeerrcrt draining into it. <br />I �; use !he �raph. find lhc Icng�h of the (lo�tipa[h on onc of thc currvcs (intcmol:uc bctuccn cun r< :c <br />�rcrtisary). Move along the curve to tl�,e pnim where the design longiwdinal slope of the }iiter �irp i�- <br />,e.isi i, direeth helo�v. Read the filter s!np lencih on the �-;L�is which eorresponds to th: in;� r�cc;i,�n <br />p���nt i <br />1y St�a.�ed `�w.� <br />i <br />zo 0 <br />I5.0 <br />L <br />:l <br />� <br />- iuo <br />6 <br />s <br />� <br />4 S0 <br />� <br />I -- <br />– � — -�--- - _y-�-_-- ' � � <br />f4o�vpaih � � � �r � � <br />v <br />= 7�) �CLI p' <br />'� r <br />� � �� <br />r„ <br />4_,-_ . - - - - - - - <br />f �-'" I�` zo r«� - / <br />xV- <br />, �� .� <br />a • �. <br />�_ ' _ I'_-_. <br />�R . <br />I `�O;cc� <br />rC �'�t.� lni�-utl� '�1.� <br />iyv� .n�1u�cS �low <br />c �Y��J�I <br />t6.= ���.,l�t lu: <br />���>�, �'�� se� � io';; is°.� <br />I-iltcr Sirip tilo�M <br />,A'nft oun�m:monllnunhlej�;trr1•iplo�gdi�s4f�';I <br />Figure 6,2 Filter Strip Lengths for Narrow Right-of-Way. <br />b'olunre lll - Fbiv Control and Trea(nrent <br />6-: <br />2u"� <br />