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Proposed Site Information: <br /> 1. How will your project change the existing conditions? <br /> This project will replace the existing(864sf) house with a (3,070sf)duplex.The duplex will <br /> take vehicle access(264sf)from the existing alley. <br /> 2. Please provide the following quantities of proposed hard surfaces in square feet: <br /> Proposed Roof Area: 3,070 <br /> Proposed Other Hard Surfaces(pavement,gravel,etc.): Sidewalk 807 sf, Driveway 264 sf <br /> 3. How will you manage rooftop runoff after the project is completed? <br /> Onsite infiltration areas will not be used as the underlying infiltrative capacity of Till soils is <br /> minimal.Additionally,the deisgn criteria cannot be met to provide 250sf per 1,000sf of <br /> rooftop. Raingardens will also not be able to be used as the low permeability of Till soils will <br /> likely create stagnate water. Downspout Dispersion will not be able to be used as there is <br /> not a 25ft flow path on the site while still complying with the GMA and City of Everett Code. <br /> Downspout perforated pipe stub outs/infiltration trench will be proposed.An infiltration <br /> trench is shown to the maximum extent feasible. The trench is connected through the <br /> center with a perforated pipe to release un-infiltrated stormwater. This trench measures <br /> 26.3 sf and is maximized amongst the setbacks between homes and property lines <br /> 4. How will you manage stormwater runoff from hard surfaces(driveways,paved pathways, <br /> patios,etc.)?Evaluate each type of hard surface separately. <br /> Stormwater will sheet flow from driveways and sidewalks to the street and alley catch <br /> basins. <br /> Plan for Permanent On Site Stormwater Management: <br /> You are required to"infiltrate, retain,and disperse stormwater"on your site to the maximum extent <br /> you can without causing erosion or flooding.The goal is to get stormwater runoff in contact with <br /> vegetated surfaces as much as possible before discharging to downstream conveyance systems. <br /> See Volume III,Chapter 12 of the 2010 Stormwater Management Manual for stormwater facility <br /> requirements: https://everettwa.gov/DocumentCenter/Home/View/1214 <br /> 1. Determine which options you must use for managing stormwater from rooftops via downspout <br /> disconnect by considering the following Best Management Practices(BMPs) in order: <br /> • BMP 12.30 On-site Infiltration Areas <br /> • BMP 12.40 Raingardens <br /> • BMP 12.50 Downspout Dispersion <br /> Notes: <br /> a. If location criteria can be met, but sizing criteria cannot,you must implement the BMPs to <br /> the maximum extent you can without causing erosion or flooding. Pre-sized facilities have <br /> been designed to meet 100%mitigation. Facilities may be able to be installed to achieve <br /> some stormwater mitigation. <br /> b. Other innovative downspout control BMPs such as rain barrels,ornamental ponds, <br /> downspout cisterns,dry wells,or other downspout water storage devices may also be used <br /> Pa e3of7 <br />