3900 BROADWAY BASE FILE 2016-01-01 MF Import

) 1.O PROJECT OVERVIEW 1.1 Purpose and Scope This stormwater site plan report addresses the design of the stormwater system supporting the proposed administration facility improvements at Everett School District in the Ci[y of E��erett, Washington. The project site is located at approximately 2021 40`" Street, adjacent to the Memorial SWdium. A Viciniry Map is provided in Appendix A. The proposed development encompasses a single parcel, which is currently partially forested and mostly covered in grass. See the Existing Conditions Map in P.ppendix A for more informa:ion. A new, three-story administration buildi�g will be mnstructed on the parcel. New pedestrian walkways connecting the proposed building to Broadway and 41�` Street will be constructed. Pedes:rian fadlities, Iandscaping areas, parking, and supporting utilities for the proposed construction are considered part of this project. See the Developed Conditions Map in Appendix A for more information. To manage stormwater from the developed site, two separate underground detentian pipes vr�ll be constructed. All drainage systems have been designed to meet the City of Everett stormwater management requirements, including the interim policy dated August 17, 2011 which supersedes Public Works Policy #1-il for stormwater control in Corrbined Sewer Areas. This was in response to heavy ) storm events which caused localized surcharges in the City's combined sewer system, Flooding paits of North Everett. 1.2 Existing Conditions Summary 1.2.1 Land Cover As previously stated, the site is currently partially forested, and grassy. This area is approximately 5.11 acres. See the Existing Conditions Map i� Appendix A for more information. 1.2.2 Topogrephy The site generally slopes from the south to tlie r�orth. The topographic relief across the site is approximately 52 feet, with the highest elevation at 136 feet at the southwest corner oF the site along 4151 Street, and the lowest elevation at 84 feet aiong the southern edge of the existing practice field. There are no critical areas on or adjacent to either site. 1.2.3 Soil Conditfons Geotechnicai field exploretions at the site performed by Associated Earth Sciences, Inc. (AES[) describe onsite soils as varyi�g over the site. The entire site has a layer of topsoil that is not suitable for structural fill. Existing fill material was encountered in the areas around exploration _ pits EP-7 through EP-11 where the proposed building and north parking will be. This fill ranges in depth From 9 feet to more than 17.5 feet, at which point the exploratory excavation was Stormwater;ite Plan Report OQ . 0 Everett School DisViR Commumry Rewurce Cen[er 1 208387.10