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SAGE HOMES NORTHWEST, LLC <br />HARBORS EDGE DRAINAGE REPORT <br />AUGUST 2022 <br />3. OFFSITE ANALYSIS <br />This section of the report is intended to address Minimum Requirement #1 and #4, as outlined in the <br />SWMMWW. <br />3.1 RESOURCE REVIEW SUMMARY <br />The NRCS web soil survey identifies an Alderwood gravelly sandy loam soil unit underlying the site. <br />Alderwood gravelly sandy loam soils are typically considered to be an "outwash" soil unit. However, <br />due to the silt present the soils will be modeled as till soils. The 2019 SWMMWW in Volume III-2.2 <br />states that, "Outwash soils over high ground water or an impervious soil layer have low infiltration <br />rates and act like till soils." The project site itself is located within a single drainage basin, which <br />generally slopes to the northwest. A copy of the Web Soil Survey map is provided in Appendix A of <br />this report. <br />The Federal Emergency Management Agency (FEMA) identifies the project site on Flood Insurance <br />Rate Map (FIRM) panel #53061C1010F; it is not shown to be in a flood hazard area. A FEMA map has <br />been provided in Appendix A of this report for reference. <br />According to the City of Everett GIS map, a small portion of the project is located in a very <br />high/severe landslide hazard area. <br />A critical areas study was issued for the project and has been submitted to the City under separate <br />cover. The report identifies the existing wetland to be filled in. <br />Ecology's Water Quality Assessment map was consulted to determine if the project may contribute to <br />a 303(d) assessed waterway. There are no 303(d)-listed waterways in the quarter -mile downstream <br />flowpath evaluated for the project. A printout from the Water Quality Assessment map is provided in <br />Appendix A of this report. <br />3.2 UPSTREAM BASIN ANALYSIS <br />The project site is bounded on the north by Mukilteo Boulevard and on the south, east, and west by <br />some existing houses. On the south side of the property, there are a few existing backyards and <br />houses that will sheet flow onto the existing property. The tributary upstream basin has been <br />depicted on a map in Appendix B of this report. <br />3.3 DOWNSTREAM FLOWPATH ANALYSIS <br />The existing topography of the site slopes north towards Mukilteo Boulevard. Any runoff is conveyed <br />to an existing stormwater system in Mukilteo Boulevard that discharges into an unnamed stream that <br />flows into Edgewater Creek then goes through a 30" culvert under the railroad and discharges into <br />Puget Sound. <br />PACE / PAGE 9 <br />