9900 19TH AVE SE 2018-01-02 MF Import

1.0 INTRODUCTION/GENERAL INFORMATION The proposed Home Base project is located in the south half of the southeast quarter of the southeast quarter of Section 18, Township 28 North, Range 5 East, Willamette Meridian, City of Everett, Snohomish County, Washington. The site is bounded by Interstate 5 to the west, 100th Street S.F. to the south, 19th Avenue S.E. to the east, and a commercial zoned site containing a public skating rink to the north. Site developtm nt will consist of construction of a 110,000-square foot Home Base, a 3,400-square foot restaurant, and related parking, utilities, and storm drainage improvements. A significant amount of fill will need to be imported to bring the western half of the site to grade for the proposed Home Base building. This fill will include the filling of an on -site wetland area, approximately 42,800 square feet in size. The project also includes complete street improvements for 100th Street S.E. west of 19th Avenue S.E. In general, the proposed storm drainage/detention and water quality treatment system for this project will consist of three independent elements. An existing off -site detention pond for the Family Tree apartment complex located south of the project will be reconstructed to improve its water quality treatment benefits and detention volume. Also, a new wet/detention pond will be constructed on the Home Base site to provide water quality and detention for site development. Each pond will also function as dead and live storage compensation for the removal of the existing wetland. In addition to these ponds, an on -site detention tank will be constructed exclusively for roof drainage detention. The basic pu=se of this narrative and the following calculations and exhibits is to demonstrate how the gmilamd combination of detention and water quality imnrovements will achieve the following three EQuirements: 1. Replacing water quality features and storage volumes currently being provided by the existing wetland. 2. Improving all off -site detention and water quality features provided by the existing off - site pond to be reconstructed. 3. Meeting or exceeding City of Everett Woods Creek Basin requirements for on -site detention and water quality treatment. ' hese items are discussed in extensive detail in Sections 5 and 6 of this report. 2.0 EXISTING SITE CONDITIONS The 9.8-acre Home Base site is currently undeveloped and contains no defined drainage courses except for the undefined channel which contains standing water within the wetlands. The east half of the site is relatively flat, generally sloping east to west, at 1 to 5 percent. Approximately half of this area is open space and half is wooded with brush and small trees. The existing wetland bisects the west half of the site, which consists of heavy brush and trees. The existing slopes east and west of the wetland are relatively steep, with grades up to 2H:1V. The existing wetland appears to have standing water of varying depths of approximately 0 to 30 inches, with some scattered deeper pockets. 5947.001 [KL/jssftl