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5. SOURCE CONTROL <br /> This project proposes to construct 2 new SFRs on this short plat with driveway <br /> additions/improvements to serve the new SFR's. Per Volume 1 of the City of Everett 2010 <br /> Stormwater Management Manual residential development does not require source control. <br /> 6. PRESERVATION OF NATURAL DRAINAGE SYSTEM <br /> The runoff from the impervious improvements will be collected and tight lined directly to <br /> the toe of the bluff to the north 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 <br /> conditions of the site but the outfall from the proposed system will be within 100-feet of <br /> Puget Sound. <br /> 7. ON-SITE STORMWATER MANAGEMENT <br /> The on-site soils were found to be Esperance sands, with the water table not encountered <br /> at a depth of 31.5 feet below grade and an infiltration rate of 4.5 in/hr. It has been <br /> determined that infiltration is not feasible due to the presence of the existing steep <br /> slopes/bluff along the north side of this site. Therefore, a collection/conveyance system <br /> has been designed to safely convey the runoff from the developed impervious surfaces to <br /> the base of the bluff on the BNSF R/W. This will be done with a series of yard drains and <br /> CBs along with 6" PVC and HDPE (fused joint) pipe along with a diffuser tee, also fused to <br /> the HDPE pipe at the toe of the bluff for energy dissipation. <br /> Finally, any area of the site not proposed to be covered with impervious surfaces but <br /> graded or compacted will be treated to meet the criteria for DOE BMP T.5.13. Please <br /> refer to the engineering plans for the locations of the soil amendments and additional <br /> details. <br /> Robinett Short Plat 15-0403 <br /> Revised:April,2016 Page 11 <br />