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11 <br />.1 <br />5. SOURCE CONTROL <br />This project proposes to construct a new SFR and paved driveway. Volume IV of the 2014 <br />DOE Stormwater Management Manual was reviewed for specific BMPs required for this <br />type of land -use. None of the activities or land uses contained in any of the chapters in <br />Volume IV applies to this project. Therefore, no site/development specific source control <br />BMPs are required for this project. <br />6. PRESERVATION OF NATURAL DRAINAGE SYSTEM <br />The runoff from the impervious improvements will be collected and tight lined directly to the <br />toe of the bluff to the northwest within the BNSF railroad R/W. This is based on the City of <br />Everett Staff decision to prohibit infiltration of impervious surfaces on this site due to <br />concerns regarding the proximity to the bluff. This will slightly change the existing conditions <br />of the site but the outfall from the proposed system will be within 100-feet of Puget Sound. <br />7. ON -SITE STORMWATER MANAGEMENT <br />The on -site soils were found to be Alderwood-Everett gravelly sandy loam. It has been <br />determined that infiltration is not feasible .due to the presence of the existing steep <br />slopes/bluff along the northwestern side of this site. Therefore, a collection/conveyance <br />system has been designed to tightline all proposed hard surface runoff down the slope to <br />the northwest to be discharged at the toe of the slope within the BNSF railroad R/W. <br />Finally, any area of the site not proposed to be covered with impervious surfaces but graded <br />or compacted will be treated to meet the criteria for DOE BMP T.5.13. Please refer to the <br />engineering plans for the locations of the soil amendments and additional details. <br />& RUNOFFTREATMENT <br />As noted before this project proposes to install a total of 3,896 of PGIS to serve this project <br />based on the Owner/Applicants plans. <br />Per the 2014 DOE Stormwater Manual "Minimum Requirements 6: Runoff Treatment — <br />Requirements" a project is required to provide runoff treatment if: <br />(a) Projects in which the total effective, pollution -generating impervious surface (PGIS) is <br />5,000 square feet or more in a threshold discharge area of the project; or <br />' <br />(b) Projects in which the total of pollution -generating pervious surface (PGPS) is three- <br />quarters of an acre or more in a threshold discharge area, and from which there is asurface <br />discharge into a natural or man-made conveyance system from the site. <br />' <br />As shown in the area summary above this project proposes to construct less than 5,000 sf <br />of PGIS and is therefore below the threshold of requiring runoff treatment. <br />F <br />F_ <br />Mazza SFR <br />November 2019. <br />Revised: April 2020 <br />19-1014 <br />Page 9 <br />