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Option I. Dispersion Design Worksheet <br />*This BMP can only be used for roof runoff per the SWMMWW* <br />• Roof area requiring mitigation (ftz): 321 <br />• Minimum 50 ft flow path provided: x Yes No <br />Dispersion systems with 25-50 ft vegetated flow path must be modeled by a WA State Licensed <br />Engineer using a continuous runoff model to confirm project meets the flow control <br />requirements, attach modeling results to this worksheet. Dispersion is not allowed where less <br />than 25 ft flow path can be achieved and another BMP shall be used to meet the flow control <br />requirement. <br />Number of splashblock downspout dispersions: 1 and/or Downspout dispersion <br />trenches 1 (Minimum of two-50 ft long downspout dispersions and one per 350 sf of roof <br />area, is required to meet the flow control requirement using this worksheet) <br />✓ Downspout Dispersion areas do not overlap. <br />One of the following must be met for the dispersion area(s), check one: <br />✓ The vegetated flow path consists of well -established lawn or pasture, landscaping with <br />well -established groundcover, native vegetation with natural groundcover, or an area that meets <br />BMP T5.13: Post -Construction Soil Quality and Depth. The groundcover is dense enough to help <br />disperse and infiltrate flows and to prevent erosion. <br />BMP T5.13 Post -Construction Soil Quality and Depth is being provided for dispersion areas <br />(area to be shown on project plans) <br />The following design criteria shall be met (check each to confirm the requirement has <br />been met): <br />I. Maintain a setback of at least 5 feet between any edge of the vegetated flow path and any structure or <br />property line. ✓ <br />2. Setback requirements in Section 4-4.1 (3) of the DCSS have been met. ✓ <br />Including: <br />• 50 feet setback from slopes greater than 15 percent and greater than 10 feet in height. <br />3. Maintain a vegetated flow path of at least 50 feet between the discharge point and any property line, <br />structure, slope steeper than 15%, stream, wetland, lake, or other impervious surface. Sensitive area <br />buffers may count toward flow path lengths. ✓ <br />4. A maximum of 350 square feet of roof area may drain to each splashblock or dispersion trench. ✓ <br />5. Place a splashblock or a pad of crushed rock (2 feet wide by 3 feet long by 6 inches deep) at each <br />downspout discharge point. ✓ <br />City of Everett Public Works <br />Small Project Stormwater Site Plan Report for Projects in 12 <br />the Combined Sewer Area -September 2022 <br />