3313 OAKES AVE 2020-07-14 - Laserfiche WebLink

STORMWATER SITE PLAN May 10,2017 OAKES AVENUE APARTMENTS PAGE 3 METHODOLOGY The drainage design for the project has been prepared based on the requirements of the 2017 City of Everett Stormwater Management Manual(based on DOE 2012/2014 SWMM). This site also falls within the combined sewer area, and Public Works policy 2-11 is in effect. • The project will develop less than 5,000 sf of pollution generating impervious surfaces, • The project will develop less than 5,000 sf of impervious surfaces, • The project does not convert more than % of an acre of native to lawn or 2.5 acres of native to pasture. • The project will have more than 2,000 sf of new plus replaced impervious surfaces. • The site has less than 35%existing impervious coverage and is not a redevelopment site • Minimum Requirements 1-5 are required (MR 1-5). See Figures 2.1 and 2.2, City of Everett " Flow Chart for Determining Requirements for New and Redevelopment". Additional requirements per Public Works Policy 2-11: • Policy 2-11 contains special conditions related to MR 6 and MR 7, which are not applicable to this project. • MR 5, On-site Stormwater Management recommends the use of several infiltration or dispersion BMP's, as well as amended soils. This project is constructed on Vashon Till and is infeasible for infiltration per geotech recommendation. The impermeable soil type in conjunction with a small site with proximity to other structures and property lines deems dispersion infeasible. The use of amended soils is specified for all lawn, planter and landscaped areas. City Code also requires pavers to be used in the proposed drive aisle courtyard. Pavers allow stormwater to seep through and into the ground beneath to infiltrate. Infiltration is contraindicated by this site's soils and per geotech;an underdrain is provided. • I • P:Work(Sharefile)tProiects\20'16y16-208 Rainier Building CioyCE\I)C)CS yDrain'v2017 05 I0'I6-208 Oakes Drain Rpt.doc