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4.2 Runoff Conveyance and Treatment BMPs <br />BMP C200: Interceptor Dike and Swale <br />Purpnse Providc a ridgc of compacted soil, or a ridgc with an upslope s�vale, at the <br />lop or base of a disturbed slope or along thc perimctcr of a disturbed <br />construction area to com•ey stormwater. Use the dike and/or s�vale to <br />intercept the nmoff from unprotectcd arcas and direct it to arcas wherc <br />crosion can bc controllcd. lhis can prcvcnt stom� runofTfrom cntcring thc <br />�eork arca or sedimcnt-laden runoff from Icaving the constn�ction sitc. <br />Conditions nJUsc \1'here the runo0' Gom an cxposed sitc or disturbed slope must be com�eycd <br />to :m crosion control facility which can safcly convcy the stormwatcr. <br />• Loca�c upslopc of � constniction sitc to prcvcnt nmofl� From cntcring <br />disturbcd arca. <br />• R'hen placed horizontally across a distunc�d slope, it reduces thc <br />amount and ��clocit}' of nmoff (lo�ving do���n thc slope. <br />• Locate do�cnslope to coliect nmoff Gom a disturhed arca anJ direct it <br />to a scdicncnt basin. <br />Design and • Dike an�Uor swalc and channc) must bc s�abilizcd with temporiry or <br />lnsmflatinn pcnnancnt vcgctation or othcr channcl protcction during construction. <br />Specificalions . Channel requires a positi��e grade for drainagr, steeper grades requirc <br />channcl protcction and check dams. <br />• Re��ie�e con�,truction for arcas ��here o�enopping may occur. <br />• Can be used at top oCne�� fill beforc vegetation is cstablished. <br />• �1ay be u�ed as a pernianent diversion chamid to carr}� Uie runofT. <br />• Sub-basin �ributary arca should bc onc acrc or Icss. <br />• Desi�n capaciry (or thc pcak flow from a 10-ycar. 24-hour stunn, <br />assuming a l'ypc I A rainf.111 distribution, for tcmporary f:uilitics. <br />Altcmati��cly, tuc LG limcs Ihr 10-ycar. I-hour Oow indicatcd by an <br />appro�cd continuous nmotTmodcl. Por f;icilitirs that «•ill also servc <br />on a pernianeni basis, cunsult thc local goeemn�ent's drainage <br />rcquircments. <br />Intcrecptor dikcs shall ntect thc fiillo�eing critcria: <br />Top \Vid�h 2 fcct minimum. <br />HcigM I.5 fcct minimwn un bcnn. <br />Sidc Slopc 2:1 or O:utcr. <br />Gr.�dc Depcnds on topogr.iphy, ho���ever. dike system minimum is <br />O.i"/o, maximum is I%. <br />Compaction Minimum of 90 perccnt ASTM DG98 standard proctor. <br />Febr�ary 2005 Volume 11- Conshucfion Sformwater Pollution Prevenlion 4-57 <br />