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5. SOURCE CONTROL <br /> This project proposes to construct 56 new townhome units on this site with new access <br /> roads. Per Volume IV of the City of Everett 2010 Stormwater Management Manual multi- <br /> family developments need to review the activity worksheet for any items that apply to the <br /> project. For this project A7.12 "Maintenance of Stormwater Drainage and Treatment • <br /> Facilities" applies. A copy of the Required BMPS are included in Appendix A and an O&M <br /> is included with this report. Please note the additional referenced BMP S.9 is not included <br /> in the drainage manual. The manual stops at BMP S.7. <br /> 6. PRESERVATION OF NATURAL DRAINAGE SYSTEM <br /> The runoff from the improvements will be mostly collected and conveyed, treated, detained <br /> and then discharged to the existing 16th Ave SE conveyance system in the southeast <br /> corner of the site. Some runoff will be allowed to flow west and into the existing wetland to <br /> maintain the hydrology. In addition, all pervious surfaces will receive amended soils to <br /> allow them to better absorb the runoff. <br /> 7. ON-SITE STORMWATER MANAGEMENT <br /> The soils for this project were found to be Alderwood - Urban Land Complex with a hard <br /> pan layer between 20 and 40-inches below grade. Subsurface infiltration is not feasible <br /> for this project. However, based on the wetlands and buffers to the west there is a 30-60' <br /> flow path available over native vegetation for the improvements within the NW and SW <br /> basins. In addition, these wetlands are ponded type wetlands which will aid in providing <br /> additional storage prior to the release to the north or south. The ponding of the runoff will <br /> aid in additional attenuation of flow and additional time/opportunity for further absorption of <br /> the runoff. In order to maximize the absorption capacity of the soil beneath the <br /> landscaping all pervious surface areas will have the soil amended to meet the criteria for <br /> DOE BMP T.5.13. Please refer to the engineering plans for the locations of the soil <br /> amendments and additional details. <br /> Northlake Court Townhomes 13-0609 <br /> May,2014 Page 11 <br />