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! <br /> � preliminary stortn drain calculations, a l`10-year storm event during proposed develaped <br /> I coodidons will generate 14.58 cfs of stonnwater runoff. This flow will be treated prior to <br /> reaching our site, th:refore this flow shall be'intercxpted witttin our property boundary <br /> and rerouted within stormwater pipes direcdy to Mertill and Ring Cneek. <br /> � OQslte Drainage DescrfpUon: <br /> IDrainage leaving the site via Merrill and Ring Crcek continues notth for approzimately <br /> 1.2 mil;s and discharges into Possession Bay, which is located in Puget Sound. A typical <br /> I cross-section of Merrill and Ring Creek is trapezoidal in shape vith a bottom wi3th of <br /> approzimately 4 to 5 feet and 1:1 side slope. The stream channel is gendy sloped nnd the <br /> riparian zone consists of small hees and dense unde�rush. Durieg the site investigation <br /> � some slight bank sloughing and erosion were apparem. However, there is no evidence of <br /> inadequate capacity or oveRopping of the stream's banks. The stream was flowing at a <br /> depth of 8 inches and had approzimately 3 feet of freeboard at the time of inspection. <br /> � <br /> Conveyance System: . <br /> (_ <br /> The conveyance system is designed in accordance with the standar,ls oudined in the <br /> ' current Everott Stormwater Management Manual. As required, th� 25-year design storm <br /> event is used to deterniine the size of the stormwater pipes. Atta�:6ed is a table indicating <br /> catch basin collection aeeas and their respecdve pervious :a�d impervious areas. From <br /> � each of the catch basin's respecdve area, weighted "C" vaiues are obtained and used in <br /> the conveyance calculations. See the attached cone�yancc table to verify the proposed <br /> stortn drain system has adequa.e capacity to convcy the dev;loped flows on the site. <br /> � <br /> � <br /> � <br /> � <br /> ' <br /> ' <br /> 1 <br /> 1 4 � <br />