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� <br />� <br />�. <br />'. <br />� <br />L� <br />� <br />� <br />� <br />1 <br />' <br />� <br />1.5 ANAYLSIS AND DESIGN O� REQiJIF.ED RUN-OFF <br />C'ONTROL: <br />a. On-site Drainage System: <br />Collection and conveyance des�n: <br />The proposed storm drainage system will collect run-off using a network of <br />catch basins and. connecting piF�es and then it will route the flow into a wet <br />vault ]ocated at the southeasten, comer of the site. This vault is sized based <br />on tfit^ analysis that was done for the Master Drainage plan for the site. <br />Furthermore, the vault will provide Oil/Water separarion and water quality <br />treatment prior to discha�•�e into the exisring wet pond on site. All the <br />conriecrior.� points iiito the existing, drainage system have been field verified <br />in accordance with City of Everett Public Works requirements. The <br />conveyance systems aze sized for the 25-year storm flow. <br />Water quantity control (detention desi�nl: <br />T'he Washington Department of Ecology's "stream bank protecrion <br />standard" was applied in the original drainage design (see attached report). <br />The detenrion facility was desi�ed to restrict the post-development <br />discharge to the following levels: <br />1 <br />2. <br />3. <br />Run-off released during the 2-yeaz storm does not exceed 50% of <br />the released during the 2-yeaz storm under existing conditiAns. <br />Run-off released during the 10-year storm does not exceed that <br />released during the 10-year storm under existing conditions. <br />Run-off released during 100-year storm does not exceed that <br />released during the 100-year storm under existing condidons. <br />Based on this analysis, it was determined that a 2I0 lineaz feet of 48-inches <br />diameter detention pipe would be adequatc to limit our site dischazge to the <br />above limits. <br />