1528 GRAND AVE Geotech Report 2022-10-25

GeoTest Services, Inc. Report Date 7/17/2019 Anderson Residence-Everett,Washington GTS Project No.19-0384 ds 'r adjacent unit to the east (uphill) is mapped as Vashon Till (Qvt), which typically consists of a highly consolidated mix of silt,sand, cobbles and boulders and resembles concrete. The soils encountered in our explorations appear to be more representative of a recessional deposit than a glacially consolidated deposit. Further, no till or transitional bed soils were identified in our explorations. The observed soil conditions do, however, appear to conform to previously published subsurface soil information from an unrelated City of Everett project close to the project site. Groundwater Groundwater was not encountered at the time of our subsurface explorations. The groundwater conditions reported on the exploration logs are for the specific locations and dates indicated, and therefore may not be indicative of other locations and/or times. Groundwater levels are variable and groundwater conditions will fluctuate depending on local subsurface conditions, precipitation, and changes in on-site and off site use. GEOLOGIC HAZARDS Landslide Hazard The City of Everett Municipal Code (EMC) 19.37.080.A.1 states that"very high" landslide hazards are those with"slopes greater than 15 percent in the Qtb,Qw,and Qls geologic units,"while "high" landslide hazards are those with "slopes greater than forty percent in all other geologic units." The slope in the western portion of the property exceeds forty percent.Soils encountered in our explorations consisted of Recessional Outwash, corresponding to a "high" landslide hazard per the EMC. The lower 1/3rd of the slope is mapped as Transitional Bed (Qtb) on the referenced geologic map with a slope greater than 15 percent, which would elevate the risk to a "very high" hazard area per the EMC. It is notable, however, that GTS did not observe the Transitional Bed exposure during our investigation. The City of Everett Critical Areas Map 2 (Goodwill, 2006) supports the "high" landslide hazard designation for this property. Large scale global instability, consisting of deep-seated rotational failures, can extend down into the subsurface to substantial depths. These failures typically leave geomorphic evidence of their existence on the slope. Typical indicators are recessional and sometimes nested head scarps, tension cracks, sag ponds, seepage zones, hummocky ground surface and slump blocks. Obvious visual indications of large-scale global slope instability,such as those referenced above,were not observed M�:fi ;IGF, 4. ,,.,�; aP �..ay Hi, ,,+'Y�'✓,'::`: 3