1004 BROADWAY EVCC STUDENT HOUSING - PUBLIC WORKS 2017-01-13

STORMWATER SITE PLAN EVERETT COMMUNITY COLLEGE HOUSING - BROADWAY PROJECT OVERVIEW SEPTEMBER 11, 2015 PAGE 1 This Stormwater Site Plan has been prepared for the Everett Community College Housing project located at the SW corner of the intersection of North Broadway and 10th Street, see Figure 1: Vicinity Map. The site consists of three tax parcels, (00385422101700, 00385422101800, 29051700204700), each currently containing a single family house, two of which have garage buildings, see Figure 2: Existing Site Map. The proposal is to remove the existing structures and redevelop the site as a multi-story building for students at Everett Community College. Nine parking stalls will be constructed along the alley to the west. See Figure 3: Developed Conditions. The project totals: New Impervious: 5,227 sf ,,�� ,,;� Replaced Impervious: 8,276 sf � � `" ( � ' L ) / •jZ� � METHODOLOGY �� ` The drainage design for the project has been prepared based on the_requirements of the 2010 City of Everett Stormwater Management Manual (CESMM�WWHM3�as provided by DOE has been used for determining basin runoff and for sizing of the stormwater facilities. Based on the Chapter 2.1.1 the site has the following parameters: • The project will result in 1,933 sf of pollution generating surface. • The project will have 5,227 sf of new impervious area. • The project does not convert 3/ 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 replaced impervious. • The site is a redevelopment site with greater than 35% existing impervious. • This is not a road project. • The project will redevelop more than 5,000 sf of impervious area. Therefore the project will need to meet Minimum Requirements 1-9. The project lies within the Combined Sewer area of the City of Everett and must meet Public Works Policy #2-11 which states that runoff treatment is not required and initial site conditions are considered the "existing site conditions" as long is CSOs and basement flooding are not increased. The site currently has no treatment or flow control requirement due to size. However, the City does request that some form of control be used to lower flows to the extent possible. For that purpose, a 40 foot long detention pipe will be installed to detain runoff and release it at rates below the current conditions. P:'\1'„rKl'n�jrrl.'21115 15-17U h��i- R�n�id�ccn'('I I)O('S F:ni Rnaid��;i� I)riin�i�c IS-171LJuc