2506 MELVIN AVE 2018-01-02 MF Import

� Willows Apamnrnu Ihainage Smdy � 09/16/2009 � DEVELOPED SITE CONDITIONS 'I'hc proposed project wil] repiace an existing single family development including a � house and a shed building with a 4,200 sf two story apartment building, a paved asphalt driveway with supporting pazking lot azea and a lazge patio surfaced with porous pavement. 'The building and surrounding facilities aze to be handicap accessible with ' sidewalk grades of 5%or less. There aze currently no stotm drains on the property frontage along Melvin Avenue. On-site impervious surfaces induding the rooftop and asphalt driveway plus parking area I will be dcained into an on-site detention system via conventional roof drains and catch basins and routed to the downstream cotridor for transport t}u'ough the I-5 drainage �� system. The only exception to the conventional drainage design will be the sidewalk and patio surfaces, which will be constructed upon an over-excavated foundation to be back- filled with pervious material. The sidewalk and patio surfaces will be porous concrete or I equal adding a "green" benefit to the project and thereby reducing the impacts to the dovmstream conditions. � The Washington DOT plans have been examined to determine the capacity of the rock filled swale (I.e. under the sound suppression wall) to caay the existing and proposed sub-basin runoff. No information was pmvided by WSDOT which would illustrate the Lsize or depth of the facility provided. Since the DOE 2005 Storm Manuel has not yet been fotmally adopted by Everett, this ( si*.e will be required to provide detention using the SBUH methodology as cuirendy appmved. L �_ 1 l. ! ! I � 3 PROJECT:o5812 1