615 80TH ST SW 2022-01-03 - Laserfiche WebLink

1. How will your project change the existing conditions? No change to existing conditions, except to a portion of existing paving/concrete slab, and compacted gravel surfaces will be changed to metal roofed building. 2. Please provide the following quantities of proposed hard surfaces in square feet: Proposed Roof Area: 10,980 sf of new roof area Proposed Other Hard Surfaces (pavement, gravel, etc.): Existing hard surfaces will be covered by roof area resulting in 10,980 sf less of road/parking area surfaces. (no new PGIS) 3. How will you manage rooftop runoff after the project is completed? New rooftop runoff will be routed in new tight line system to the existing drain line on the property. Stormwater will discharge to the public storm drain in Hardeson Rd. via existing 8" diameter PVC line, preserving the existing site conditions. 4. How will you manage stormwater runoff from hard surfaces (driveways, paved pathways, patios, etc.)? Evaluate each type of hard surface separately. No change anticipated to the existing system of catch basins. Plan for Permanent On.Site Stormwater Management: You are required to "infiltrate, retain, and disperse stormwater" on your site to the maximum extent you can without causing erosion or flooding. The goal is to get stormwater runoff in contact with vegetated surfaces as much as possible before discharging to downstream conveyance systems. See Volume III, Chapter 12 of the 2010 Stormwater Management Manual for stormwater facility requirements: https://everettwa.gov/DocumentCenter/Home/View/1214 1. Determine which options you must use for managing stormwater from rooftops via downspout disconnect by considering the following Best Management Practices (BMPs) in order: • BMP 12.30 On -site Infiltration Areas • BMP 12.40 Raingardens • BMP 12.50 Downspout Dispersion Notes: a. If location criteria can be met, but sizing criteria cannot, you must implement the BMPs to the maximum extent you can without causing erosion or flooding. Pre -sized facilities have been designed to meet 100% mitigation. Facilities may be able to be installed to achieve some stormwater mitigation. b. Other innovative downspout control BMPs such as rain barrels, ornamental ponds, downspout cisterns, dry wells, or other downspout water storage devices may also be used with prior approval by the City of Everett. These are options to consider after the above listed BMPs are evaluated. 2. Determine which options you must use for managing stormwater from hard surfaces (driveways, paved pathways, etc.) by considering the following for each type of hard surface proposed: • BMP 12.60 Concentrated Flow Dispersion • BMP 12.70 Sheet Flow Dispersion Note: Propose an alternative stormwater management plan if none of the above BMPs can feasibly be installed. (Examples: Shallow vegetated Swale, perforated pipe stub -out, etc.) { L4f�n�Page ♦.,. `T �� ... t4`f �_ !_ E ..1 �..�..:� .:. �_ �'tJ �..�t L� +..:�i �}l e...., ... L '.. ..J :: .:3 � levei�fTjgrj`v