1815 13TH ST SEATTLE CHILDRENS NORTH CLINIC 2019-07-08

MAGNUSSON KLEMENCIC ASSOCIATES ■ Minimum Requirement# Description Action Required Notes 6 Runoff Treatment N/A See VIII Permanent Stormwater Control Plan 7 Flow Control Yes See VIII Permanent Stormwater Control Plan 8 Wetlands Protection No See below 9 Operations and Maintenance Yes See VIII Permanent Stormwater Control Plan Minimum Requirement #1: Stormwater Site Plan Preparation This report has been prepared using the guidelines of the COESWMM. Drawings that provide additional information regarding the Permanent Stormwater Control Plan are provided in Appendix D. Minimum Requirement #4: Natural Drainage Systems and Outfalls Preservation The routing of stormwater conveyance on the North Site will stay within the same basin and will outfall to the same public combined sewer main as the existing discharge. By maintaining the same discharge point, this requirement is met with no action required. Minimum Requirement #5: On-Site Stormwater Management Minimum Requirement#5 states that on-site stormwater management best management practices (BMPs) should be implemented to infiltrate, retain, and disperse stormwater on-site,with the goal of reducing the hydrologic disruption of developed sites. In addition to the specific BMPs considered below, the project aims to retain existing site features that provide natural stormwater management and maintain the existing soil and vegetation to the extent feasible. Proposed site grading was designed to follow existing topography as close as possible in order to minimize earthwork impacts and disturbance footprint. ■ BMP 12.10—Vegetation Protection Areas. The COE-required landscape buffer that exists around most of the perimeter of the North Site project (as shown on Figure 2, where residencies are adjacent) will remain or be replanted where disturbed. Proposed site features have been designed to minimize impacts to this buffer along with other areas of existing vegetation to be protected. See Landscape drawings for areas of existing vegetation to remain and be protected during construction, as well as areas that will be replanted. ■ BMP 12.20— Post-Construction Soil Quantity and Depth. The landscape design proposes amended soils in disturbed areas of the North Site. For areas where full replanting is required, such as in the buffer and in the new island within the eastern parking lot, "Option 3— Import Topsoil Meeting Organic Matter Content Standards" will apply as described in Volume III, Chapter 12, of the COESWMM. Even lightly disturbed areas, requiring minor regrading and possibly hydroseeding, will also likely follow Option 3 standards. Storm Drainage Report 5 Providence Regional Medical Center Everett North Site, Everett, Washington