600 54TH ST SW I Geotech Report 2025-01-29

GEOTECHNICAL INVESTIGATION EVERETT,WASHINGTON March 2,2018 1.0 Introduction In accordance with your authorization,Cobalt Geosciences,LLC(Cobalt)has completed a geotechnical investigation for the proposed residential plat located at 600—54th Street SW in Everett,Washington (Figure 1). The purpose of the geotechnical investigation was to identify subsurface conditions and to provide geotechnical recommendations for foundation design,earthwork,soil compaction,utilities,general pavement guidelines,stormwater management,and suitability of the on-site soils for use as fill. The scope of work for the geotechnical investigation consisted of a site investigation followed by engineering analyses to prepare this report. Recommendations presented herein pertain to various geotechnical aspects of the proposed development,including foundation design,drainage,and earthwork. 2.0 Project Description The proposed development will likely include a 9 or io lot residential subdivision, access roadway construction, utility placement, and stormwater infrastructure (vault or pond). A provided site layout is included as Figure 2. We anticipate that foundation loads will be generally light and that site grading will include cuts and fills on the order of io feet or less for mass grading,foundation and detention vault placement,and roadway construction. Deeper excavations may be proposed for detention facilities. We should be provided with the final plans in order to update our recommendations,if necessary. 3.o Site Description The site is located at 600—54th Street SW in Everett,Washington(Figure i). The property consists of three parcels(No.'s o0436800003800,00436800003900,and 28o4oio0ioi400)with a total area of about 5 acres. The site area is shown on the Site Plan in Figure 2,which shows the lot layout,roadway location,and existing topography. The site is undeveloped and vegetated with blackberry vines,Scotch Broom,grasses,ferns,as well as dense areas of small diameter deciduous trees along with localized stands of Cedar,Fir,and other evergreen trees. The site consists of a portion of a ravine that was locally affected by previous grading activities(fill placement,soil removal,re-grading). In general,the south half of the site slopes inward from the east and west at magnitudes of 5 to 5o percent and topographic relief of about 4o feet. Much of the south and east sides of this area appear to have been unaffected by previous grading and vegetated with mostly native species. The north half of the site generally slopes downward toward the east. Near the north property lines, slopes extend downward toward the south and into the ravine area at magnitudes ranging from io to ioo percent. The topographic relief in this area is about 50 feet. 1 P.O Box 82243,Kenmore,WA 98028