2812 BAKER AVE 2023-12-01 - Laserfiche WebLink

Option 2B Rain Garden Design Worksheet The top of the ponded surface area below the overflow shall beat lean 13.5%of the net new impervious surface area draining to the rain garden. Projects that have a greater contributing impervious area to the BMP shall use the larger of the two areas, or as an alternative may have the BHP sized by an Engineer using a continuous runoff model to meet the flow control requirements of Section 6.10 of the DCSS. The table below provides design geometry based upon contributing impervious area. Refer to the Rain Garden Handbookfor Western Washlneton:AGuide for Design, Installation, and Maintenance (Hinman all 2013) for construction guidance. Sioretention shall be designed in accordance with section 6.10 of the DCSS and the SWMMW W. Use the following criteria for design of the bioretention pond. SEE SIORETENTION EXAMPLE AT THE BACK OF THIS PACKET FOR REFERENCE The applicable Setback requirements in Section 4-4.1 (3) have been met, including: • 50 feet setback from slopes greater than 15 percent and greater than 10 feet in height. Minimum Side Slope = 3:1 Minimum Infiltration Rate = 0.3 ini Minimum depth of Biosoil = 12-inches Pending depth = 6-inches Freeboard = 6-inches Table 2B—Small Project Rain Garden Flow Control Design Sizing WWI 200 to 400 54 19 400 to 600 81 36 600 to 800 108 55 800 to 1000 135 74 1000 to 1200 162 95 1200 to 1400 189 116 1400 to 1600 216 137 1600 to 1800 243 358 1800 to 2000 270 1 180 • Net new impervious area requiring mitigation fits): • Contributing impervious area to BMP: • Total contributing area including landscaped area (Rt): Design Top of Funded Surface Area (fta) = 0.135'(contributing impervious area (ftt)) fta City ofErereb Public Works Small Project Stmmw ar See Plan Reporl for Pneects in 15 Me Caroni Sewer Ane-Sepkmber 2022