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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(ft2): 554 <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: 2 and/or Downspout dispersion <br /> trenches (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 /> f 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 /> �413MP 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. 1 <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 />