5105 CHINOOK DR 2016-01-01 MF Import

1. PROJECT OVERVIEW This document is intended to provide engineering information necessary to support the SFR building permit application to the City of Everett for this property. The site is located at 50xx Chinook Dr, Everetl, WA 96203, refer to figure 1 for a vicinity map. The parcel area is approximately 0.30 acres. In addition, a 60'x15' driveway access easement has been provided by the property to the south to provide access to the proposed garage. The existing sile contains some large deciduous trees, blackberries and other brush along with dense ground cover. The new SFR will be located in the southwestern comer of the parcel with as much vegetation retained as possible along the north and east sides of the site. The parcel is located west of a low draw which drains to the north. This low area callects runoH from the parcels located between Ocean Ave and Chinook Drive. This project proposes to construct less than 4,000 sf of new impervious surfaces. Therefore, Minimum requiremenls 1-5 apply to all of the new impervious surfaces for this project along with all the disturbed pervious suriaces. This proposal does nol meet any of the land-use criteria that require specific source control for the final use and a SWPPP has been prepared to address the runoH from the site during construction. Refer to Sections 4 and 5 for a detailed discussion. Figures 2 8 3 are provided to show the existing and developed basins and runoff conditions for this site. The runoff in the existing condition will spread over the pervious surfaces as sheet flow and drain to the north and east. Wlth all of the site runoff being collected in the low "draw" located along the western property line. In the developed conditions all of the runoff from ihe new roof surfaces will be dispersed using two level spreaders over amended or native soil more than 25-feet from any adjacent property line. The driveway runoff will be dispersed using a transition zone with a minimum flow palh of t0-feet over amended soils The soils assessment for this project shows the on-site soils to be loamy sand. The soils professional for this project is Jamie Balterman and he stated that the water table/hard pan layer is at more than 6' below grade. Theretore, infiltration is not viable due to sile slopes. For this project dispersion is required tor the NPGIS on this project and the runoH(rom the new PGIS will be dispersed along the edge of the driveway via a transition zone as noted previously. The drainage design has been laid out per the COE 2010 Stormwater Management Manual. Due to the size of this project only Mmimum requirements 1-5 apply to the proposed drainage design as noted above. Included on the following page is a copy of ihe MR flow chart out of ihe COE Drainage Manual showing how Ihe applicable mmimum requirements were determined. Chinook Sf R - - ------ — iz-o�:s �'�� Jan 2012 Page 3 4,��