2514 RAINIER AVE 2022-03-01 - Laserfiche WebLink

NORTH MIDDLE SCHOOL 0 After the application of Minimum Requirement #7, the resulting stormwater flow is not anticipated to increase the Combined Sewer Overflows (CSOs) or the basement flooding in the combined sewer area. MINIMUM REQUIREMENTS The Minimum Requirements are summarized in Table 5 with further explanation of actions required provided where noted. Based on the threshold assessment above, all Minimum Requirements will apply to the project with the exception of Minimum Requirement #6. Table 4. Minimum Requirement Summary Minimum Description Action Required Notes Requirement # 1 Stormwater Site Plan Preparation Yes See below 2 Construction Stormwater Pollution Yes See IV Construction Prevention Stormwater Pollution Prevention Plan 3 Source Control of Pollution Yes See V Source Control Plan 4 Natural Drainage Systems and Outfalls No See below Preservation 5 On -Site Stormwater Management Yes See below 6 Runoff Treatment N/A See VIII Permanent Stormwater Control Plan 7 Flow Control No" See VIII Permanent Stormwater Control Plan 8 Wetlands Protection N/A See below 9 Operations and Maintenance Yes See VIII Permanent Stormwater Control Plan " Yes, if synthetic field alternate is accepted by the school district; flow control will be required. See Section VIII, "Stormwater Flow 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 B in the CSWPPP. MINIMUM REQUIREMENT #4: NATURAL DRAINAGE SYSTEMS AND OUTFALLS PRESERVATION The routing of stormwater conveyance on the 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 12.20 — Post -Construction Soil Quantity and Depth. The landscape design proposes amended • soils in disturbed area of the North Middle School site. For areas where full replanting is required, "Option 3 — Import Topsoil Meeting Organic Matter Content Standards" will apply as described in Volume COUGHLINPORTERLUNDEEN