3214 BROADWAY SEPA 017 - 004 Geotech Report 2025-04-14

American Property DevelL, .ient ES-0599.05 January 16, 2015 Page 3 Updated January 22, 2015 At the boring locations, native soils consisting predominantly of medium dense to very dense silty sand with small amounts of gravel (21 to 4 percent) were encountered. These soils are classified by the Unified Soil Classification System as silty sand with gravel (SM). At both borings dense silty sand deposits were encountered the entire length of the boring. The only significant change in lithology was at boring B-1 where the upper twenty feet of samples were 21.1 percent gravel. This was the highest percentage of gravel content for the site. However, below twenty feet gravel percentage deceases significantly. The lower gravel content (3.8 to 13.3 percent) is characteristic of the subject property. Overall the soils at both borings appear to be similar in sorting and silt content. In general, test pits recently excavated confirm these conditions. The geologic map of the area identifies Quaternary Till (Qqt) deposits throughout the site and surrounding areas with is consistent with the results of the soil borings. With respect to the subject property, we interpret the upper dense to very dense deposits of silty sand with gravel to be associated with Quaternary Till. In general, the dense to very dense silty sand with gravel and sand deposits exhibit relatively good soil strength characteristics. In our opinion, the erosion potential of these soils can generally be characterized as low to moderate. Groundwater Groundwater was not encountered at the test locations. However, locally perched groundwater seepage is possible during the construction phase of the project. Groundwater seepage can generally be characterized as a perched condition at the contact between the upper deposits of fill and weathered native soils, and the underlying unweathered glacial till deposits. Due to the anticipated depth of the proposed garage level excavation, we anticipate perched groundwater seepage will be encountered in the proposed excavations. Due to the generally dense to very dense condition of the native soils, we do not anticipate groundwater seepage will adversely impact excavation stability, provided the excavations are appropriately sloped or shored. It should be noted that groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater seepage rates and levels are generally higher during the wetter, winter months. Geologcally Hazardous Areas and Environmental Sensitive Features Review As part of our report preparation, we reviewed available maps and resources to identify designated geological hazardous areas for the site. Specifically, we reviewed the city of Everett's municipal code regarding Environmental Sensitive Features (37.40) and Geological Hazardous Areas (37.080). Earth Solutions NW,LLC