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8ti13 Ei'ERGRLEN �I:�IY <br />Lve:ett, Washineton <br />S1orm Drainage Report <br />,bfarch 22, '007 <br />Analysis and Design of Detention is not required for this project since development will <br />I�equired Iiunoff Controi reduce to the overatl impervious area from 24,958f sq.fr. to 23,008= <br />BA'IPs sq.fr. <br />Miscclluncous rorms and <br />Workshcets <br />Othcr Permits <br />Maintenance and <br />Operatimi Requirements <br />Water quality treatment is required for die project since it involves <br />the "r^development of 5,000 square fcet or more:' R'ater quality <br />treatment «�ill be provided on-site using a StormFilter catch basin <br />structure containing four (4) ZPG me!��� filter cartri��es. It w:l] <br />be sized to treat developed runoff from ti�e �vater quality design <br />storm <br />Storm water runoff from the roof suriaces does not require water <br />quality treatment. Therefore, roof drainage will not be combined <br />rvitl� the parking lot drainace. The proposed Uuildi��g roof drains �vill <br />be tightlined in a separate conveyance pipe and connect do���nstream <br />of the water quality facility. <br />The Stortnfilter design is based on tre�ting on]y the �~�ater qualiq� <br />storm from the majorit�� of the on-site pavement area. City ef <br />Lverett standards require treafiient of �Vater Quality De�ign S,onn <br />defined as the 6 month 2K-hour stonn (more precisely 64% of the 2 <br />yr 24-l�our sto:m or 0.96 inches). Plo���s above the 6-month storm <br />are also passed through the StonnFilter prior to being dischargin� <br />into il�e public storm system. See Appendic B jnr calcrrinlio�rs. <br />Conveyance and Backwater calculations sliow :hat the proposed pipe <br />system has suCficicnt capacity to handle the 25 year storm event <br />without o��ertopping the catch basin rims. See AppeirdEi 6 jor <br />calculntinns. <br />AII suppoRing calculations and �vorksheets are included in the <br />nppendices. <br />NPDES Permit No/ Applicnble <br />City of Gverett Building Pennit <br />The maintenance for the erosion and sediment co�trol BMPs will be <br />as follo�vs: All erosion and sediment features will be inspected <br />regularly throughout construction and will be repaired, maintained <br />or supplemented witli further crosion control items as nceded. <br />The drainage faciliry maintenance requirements ���ere taken from the <br />Ciry of Gverett Stornnvater �lanagement Manual and are included in <br />��nn-�«��t c. Alsq the City of Everett requires the annual submittal <br />of a certi6cate of inspection/maintenance fo; eacli StormPilter. <br />\V�11P•ecific Inc Ever�reenfi�m�—Sta�utDrnina,�eRepa't <br />r. u,;,,.,,r.�,,,:.-r.:::,,�„nrn.:;uen,�,��,��ny�.,,�,n;;u,sn-,",�,,:,�;r_,.r,.�..,�. ",,.,:mr.•,..c,. =a'�nr.r..- June J� ?007/Pnge? <br />