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An Engineering services Company <br /> BMP 12.70 Sheet Flow Dispersion <br /> Sheet flow dispersion is the simplest method of runoff control. This BMP can be used for <br /> any impervious or pervious surface that is graded so as to avoid concentrating flows. <br /> Because flows are already dispersed as they leave the surface, they need only traverse <br /> a narrow band of adjacent vegetation for effective attenuation and treatment. <br /> BMP 12.70 for dispersing roof runoff is not feasible due to the lack of sufficient flow path <br /> available to disperse the runoff. <br /> The project proposes to flow the offsite tributary area and a portion of the drive through to <br /> the bioretention swale. This will provide addition water quality and natural retention prior <br /> do discharge to the public system above what is required. Stormwater runoff generated <br /> from the proposed structure will be directed through downspout connections and routed <br /> to the new Type A catch basin before being discharged to the public system. The new <br /> catch basin will also collect runoff from the areas of the parking which cannot drain to the <br /> bioretention swale will serve to combine all of the flows. <br /> SECTION 7 — Special Requirements <br /> 7.1 Public Works Policy#2-11 <br /> An interim stormwater control policy has been put into effect in the Combined Sewer Area <br /> by the City of Everett as a result of recent localized surcharges of the City's combined <br /> sewer system. Pursuant to the policy the proposed project will provide flow control that <br /> meets or exceeds the runoff levels of the site's existing conditions. A detention tank <br /> system will be installed onsite to mitigate the runoff effects. Refer to Sections 6.1 — 6.3 <br /> for a detailed description of the flow control analysis. Public Works Policy #2-11 is <br /> described below: <br /> Public Work Policy# 2-11 Supersedes%Hoy#1-11 <br /> SUBJECT: Stommater control in tin combined sewer wee. <br /> The combined sewer area shall be that described in the attached map or as updated by <br /> City of Everett Public Works Utility Mapping, <br /> Starbucks Page 8 <br /> Broadway and 10t Store <br /> Drainage Report <br /> May 2014 <br />