1605 SE EVERETT MALL WAY WALMART 2018-01-01 MF Import

Seattle,Washington T 2065 www.pacl22.9an570d.com TURNING VISIONS INTO REALITY Parking Flat 5.52 C, Lawn, Flat 0.91 C IMP DISP FLAT 0.04 Total 8.57 Table 4 - Proposed Flow Rates Event Flow rate(cfs) 2-year 0.904 25-year 1.964 100-year 2.704 The project site is considered one basin as all catch basins are conveyed to the flow control structure near the main signalized entrance of the site. As mentioned in the Site Assessment section above, the Bob's Burger and Brew stormwater drains through the project site, but stormwater for that property is managed on-site prior to discharge to the project site. The flow control structure information and detention pipe sizes and lengths are based on the as-built plans and topographic survey performed for the redevelopment. When calculating new impervious surfaces, the pavement repair required for utility installation and modification was not considered. This is an exemption per section 2.1.5 Volume I of the Manual. A type C soil, Alderwood, was used based on Table 5.5 in Volume I of the Manual and the Geotechnical report. Offsite drainage contributions to the basin are minimal as the surrounding areas are fully developed, or drain away from the site. Limited areas of the shared driveway drain onsite, and are identified on Figured 2 of Appendix A. D. Stormwater Flow Control Plan Modifications to the existing flow control system are not proposed. As discussed in sections above, it has been determined that Minimum Requirement #7 does not apply to the site. - However, an analysis of the existing flow control system is provided in this report for reference and to assist the owner with maintaining the system. This information is based on available as-built information received from past owners, and a current topographic survey. For additional information see Appendix C - Stormwater Flow Control - Supplemental Information. Everett Mall Plaza Parcel III Retail Expansion Stormwater Site Plan Page 20