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NORTH MIDDLE SCHOOL <br /> II. SITE DEVELOPMENT PLAN WITH ON-SITE STORMWATER <br /> MANAGEMENT <br /> PROJECT THRESHOLDS <br /> THRESHOLD DISCHARGE <br /> The project site discharges to a single threshold discharge area but is conveyed from the site at many different <br /> points. <br /> IMPERVIOUS SURFACE <br /> The existing and proposed impervious areas for the North Middle School portables site are summarized in Table <br /> 1. <br /> Table 1. Existing and Proposed Impervious Surfaces <br /> Impervious Surface Area (square feet) Area (acres) <br /> Existing 545 0.013 <br /> Proposed 10,570 0.243 <br /> INTERIM POLICY <br /> The project will discharge to the public combined sewer system (it is within the combined sewer area)and creates <br /> and/or redevelops more than 2,000 square feet of impervious area, so the"Public Works Interim Policy 2-11: <br /> Stormwater Control in the Combined Sewer Area"(Interim Policy)will apply. See Appendix A for a copy of the <br /> Interim Policy. <br /> According to the Interim Policy,the project will be required to consider all Minimum Requirements with the <br /> following exceptions: <br /> • Minimum Requirement#6 is not applicable; <br /> • Minimum Requirement#7 can now be assessed replacing the term"a forested land cover"with"the <br /> existing site conditions." <br /> After the application of Minimum Requirement#7,the resulting stormwater flow is not anticipated to increase the <br /> Combined Sewer Overflows(CSOs)or the basement flooding in the combined sewer area. However,flow control <br /> will only be provided for these temporary portables in the event that t the portables have not been removed from <br /> the site at the conclusion of September 2019. <br /> MINIMUM REQUIREMENTS <br /> The Minimum Requirements are summarized in Table 5 with further explanation of actions required provided <br /> where noted. Based on the threshold assessment above, all Minimum Requirements will apply to the project with <br /> the exception of Minimum Requirement#6. <br /> Table 4. Minimum Requirement Summary <br /> Minimum Description Action Required Notes <br /> Requirement# <br /> 1 Stormwater Site Plan Preparation Yes See below <br /> 2 Construction Stormwater Pollution Yes See III Construction <br /> Prevention Stormwater Pollution <br /> Prevention Plan <br /> 3 Source Control of Pollution Yes See IV Source Control <br /> Plan <br /> 4 Natural Drainage Systems and Outfalls No See below <br /> Preservation <br /> COUGHLINPORTERLUNDEEN 2 <br />