2416 61ST ST SE 2022-03-04 - Laserfiche WebLink

2416 615t Street SE Limited Subsurface Exploration and Geotechnical Everett, Washington Assessment for Slab and Foundation Repair GEOLOGIC MAPPING Based on our review of a regional geologic map of the site and vicinity (Geologic Map of the Everett 7.5-minute Quadrangle, Snohomish County, Washington — U.S. Geological Survey [USGS], Miscellaneous Field Studies Map MF-1748, 1:24,000, by J.P. Minard, [1985)), the site is mapped as being underlain by Vashon advance outwash deposits. The subsurface conditions encountered within our explorations are in general agreement with the regional geologic map in that we encountered Vashon advance outwash sediments at all locations explored, as further discussed below. LIMITED SUBSURFACE EXPLORATION We explored subsurface conditions at the site on October 12, 2021. A total of three hand-auger borings (HB-1 through HB-3) were performed near/within the noted distressed areas to depths of about 4 to 5 feet below exterior grade. HB-1 and HB-2 were performed along the southeast and northeast exterior of the building, respectively, and HB-3 was performed beneath the kitchen floor slab after a portion of the slab was removed for plumbing repairs. The approximate locations of the hand-auger borings relative to existing site features are shown on the"Existing Site and Exploration Plan," Figure 2. The hand-auger borings were advanced with a 4-inch-diameter open-barrel steel auger and the subsurface conditions encountered were logged by a geologist from our firm. The samples obtained from the auger barrel were classified in the field, and representative portions were placed in watertight containers. The samples were then transported to our laboratory for further visual classification. Soil descriptions shown on our exploration logs (see Appendix A) are based on the effort required to advance the hand auger, probing resistance within the borehole, and field observations. The hand-auger borings were backfilled with excavated soil. A description of the soil types encountered in our borings are provided below. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by any past grading and/or filling.The nature and extent of any variations between the field explorations may not become evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this letter-report and make the appropriate changes. Fill Directly below the ground surface, all borings encountered existing fill soils consisting of very loose to loose, moist to wet, brown to dark brown, silty fine sand with some gravel and scattered organics. The fill soils below the kitchen floor slab appeared to be loose and very moist to wet, likely due to water leakage from the cracked drain pipe located below the slab. The fill soils were encountered to depths of about 2 to 3.5 feet below exterior grade. October 26,2021 ASSOCIATED EARTH SCIENCES,INC. 8o/Id-20210370E001-002 age 4//C/