2801 35TH AVE NE 2025-04-07 - Laserfiche WebLink

STORMWATER SITE PLAN 8/18/2023 SOUTHWEST STORAGE YARD 2 MR 1: PREPARATION OF STORMWATER SITE PLANS DRAINAGE PLAN DESCRIPTION This Drainage Basin Summary has been prepared for the proposed new storage yard at 28th Place NE and 35t"Avenue NE.The project involves the grading and construction of an outdoor storage facility on the site with supporting access, surfacing, and frontage improvements. Figure 1:Vicinity Map depicts the location of the project. The project site consists of vacant land covering approximately 3.84 acres (Tax ID#: 29050500401000).This tax parcel is divided by 35t"Avenue NE with the northern portion being joined in development to 29050400300400.The proposal herein consists only of the property to the south and west of 35t" and north of 28t"consisting of 35,670 sf(0.819 ac) of land. The site has been previously filled above the local floodplain elevation (12.0) and the development area is relatively flat with elevations ranging from 10-12.The edges of the fill slope down to native grade at slopes ranging from 15%to 33%. Ground cover is erosion control grasses. See Figure 2: Existing Conditions for a graphic depiction of the current site conditions.There are no existing structures on site.The right of way of SR 529 runs along the west boundary such that the property is surrounded by right of way. Access for the proposed development will be from 35th Avenue NE near the northwest corner of the site. See Figure 3: Developed Conditions for the layout. METHODOLOGY The 2019 Department of Ecology Stormwater Manual as adopted by the City of Everett was used as the basis of design. The site has the following characteristics: Approximately 0.93 acres disturbed area. Less than 35%existing impervious The project will result in approximately 31,620 sf of new impervious area. This requires the drainage system to meet Minimum Requirements 1-9. SOILS DESCRIPTION A geotechnical report has been prepared by Nelson Geotechnical Associates, Inc dated July 8, 2022, and titled Geotechnical Engineering Evaluation -SeaCon Union Slough Storage Yard.They performed borings and test pits on the site. No borings were performed on the subject property, however,the two properties were filled at the same time with the same material and are functionally alike. In general,the site is underlain by 8-10 foot of undocumented fill above native sands and gravels with trace silt. Groundwater seepage was encountered in some test pits at a depth of 9-10 feet. CRITICAL AREAS There are no critical areas in the development area. DOWNSTREAM ANALYSIS The downstream analysis is based on GIS data, Cedar River DEM 2014 LiDAR, a site visit that followed the dike from SR 529 east to the tide gate and a second site visit that followed the ditch line along the dike south to its connection point with the large conveyance channel. P.\work\Projccts\zozl\zl 162 sea con\CE\o06\ST0RMwATER SITE PLAN SMALL.docx