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• <br /> Schaffer SFR <br /> Minimum Requirement # 2: SWPPP Narrative <br /> O Refer to separate SWPPP Report. <br /> Minimal Requirement # 3: Water Pollution Source Control <br /> All proposed development is to consist of residential construction. No water pollution <br />• source control is needed. <br /> Minimum Requirement # 4: Preservation of Natural Drainage Systems and , <br /> Outfalls, and provisions of off-site mitigation <br /> O No changes to the existing drainage systems and outfalls are proposed with this <br /> development. Site runoff will continue to flow into the wetland area within the southern <br /> portion of the site, which discharges toward the existing City documented storm drainage <br /> conveyance on a property to the south <br /> Minimum Requirement#5 On-Site Storm Water Management <br /> Due to the project proposing less than 5,000 sf of new hard surfaces, Minimum <br /> Requirements 1 through 5 must be evaluated. Per 2012 (w/2014 updates) DOE <br /> SWMMWW,the following BMPs must be implemented when feasible: <br />• <br /> Lawn and landscaped areas: <br /> • Post-Construction Soil Quality and Depth in accordance with BMP T5.13 in <br /> Chapter 5 of Volume V. Feasible for all new lawn/landscaped areas. <br />• Roofs feasibility description: <br /> 1. Full Dispersion per BMP T5.30 <br /> i. Full Dispersion is infeasible due to all available dispersion flow paths <br /> being less than 100' in length to wetland and property boundaries. <br /> 2. Downspout Full Infiltration per BMP T5.10A. <br /> i. Full Infiltration is infeasible due to inadequate soil depth according to a <br />• soil log taken on the property showing approximately 12"to hardpan. <br /> 3. Rain Garden or Bioretention per BMP T5.14A. <br /> i. Due to inadequate soil depth to provide proper separation beneath any <br /> potential rain garden or bioretention,these facilities are infeasible. <br /> 4. Downspout Dispersion Systems in accordance with BMP T5.10B. <br />• i. Downspout Dispersion is feasible for the site. Splash blocks will be used <br /> for all roof runoff due to the site containing flow paths in excess of 50' <br /> Dispersion Trench Sizing Calculation: <br /> - One splash block per 700 sf of roof area <br /> -Proposed roof area to blocks= 1,345 sf. <br />• -Total blocks required=> 1,345 sf. /700 sf. = 1.92 <br /> =>Designed blocks=2 <br />• WESTERN ENGINEERS,INC. 11 PROJECT:17-1666-A <br />