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Cooley Smiles Dental Clinic 17318.20 October 18,2017 <br /> Drainage Report Section II, Page 2 <br /> Minimum Requirement#1: Preparation of Stormwater Site Plans:The stormwater site plan consists of <br /> this report and the civil drawings, and is prepared in accordance with Chapter 3 of Volume 1 of the <br /> SWMMWW. <br /> Minimum Requirement#2: Construction Stormwater Pollution Prevention Plan (SWPPP):The SWPPP <br /> shall include a narrative and drawings.The SWPPP narrative shall include documentation that addresses <br /> the 13 elements of Construction Stormwater Pollution Prevention. See Section V and the civil drawings. <br /> Minimum Requirement#3:Source Control of Pollution: Source control BMPs during construction are <br /> described in Section IV, which addresses Minimum Requirement#2. It is not anticipated that permanent <br /> source control BMPs will be required as the site does not contain any of the activities listed in Vol IV Ch. <br /> 3-5 of the 2014 SWMMWW. <br /> Minimum Requirement#4: Preservation of Natural Drainage Systems and Outfalls: Natural drainage <br /> patterns shall be maintained, and discharges from the project site shall occur at the natural location,to <br /> the maximum extent practicable.The manner by which runoff is discharged from the project site must <br /> not cause a significant adverse impact to downstream receiving waters and down-gradient properties. <br /> All projects shall submit an off-site qualitative analysis.A qualitative analysis of the upstream and <br /> downstream system entering the site is presented in Section III. <br /> Minimum Requirement#5:On-Site Stormwater Management: Per Table 1-2.5.1 of the 2014 <br /> SWMMWW, redevelopment projects on any parcel inside the Urban Growth Area that trigger Minimum <br /> Requirements#1 through#9 must demonstrate compliance with the Low Impact Development <br /> Performance Standard and BMP T5.13; or use On-Site Stormwater Management BMPs from List#2.This <br /> project will demonstrate compliance with the Low Impact Development Performance Standard. See <br /> Section IV. <br /> Minimum Requirement#6: Runoff Treatment:This requirement applies to the new plus replaced hard <br /> surfaces and the converted vegetation areas.The following projects require construction of stormwater <br /> treatment facilities: <br /> i.) Projects in which the total of pollution-generating hard surface (PGHS) is 5,000 square feet <br /> or more in a threshold discharge area of the project, or <br /> ii.) Projects in which the total of pollution-generating pervious surfaces (PGPS)—not including <br /> permeable pavements is 0.75 acres or more in a threshold discharge area, and from which <br /> there will be a surface discharge in a natural or man-made conveyance system from the site. <br /> This project's total of PGHS is less than 5,000 square feet and runoff treatment is not <br /> required. <br /> The project requires water quality treatment because the total amount of pollution-generating hard <br /> surface (PGHS) is 5,000 square feet or more in a threshold discharge area of the project. See Section IV. <br /> 250 4th Avenue South,Suite 200 <br /> Edmonds,WA 98020 <br /> ENGINEERING ph.425.778.8500 I f.425.778.5536 <br /> www.cgengineering.com <br />