3214 BROADWAY Geotech Report 2022-10-25

American Property Development ES-0599.06 June 9, 2016 Page 3 Revised October 16, 2017 Subsurface Thee borings and two test pits were completed at the site for purposes of assessing soil and groundwater conditions. Two borings (B-1 and B-2) were completed on September 7, 2006, the test pits were completed on November 19, 2014, and the third boring (B-101) was completed on May 24, 2016. Please refer to the boring and test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. The maximum explored depth was approximately 26.5 feet below existing grade. At the boring locations, native soils consisting predominantly of medium dense to very dense silty sand with small amounts of gravel were encountered. These soils are classified by the Unified Soil Classification System as silty sand with gravel (SM). At the boring locations, dense silty sand deposits were encountered the entire length of the borings. The only significant change in lithology was at boring B-101 where at 10 feet the sample was 30.5 percent gravel. This was the highest percentage of gravel content for the site. However, below ten feet the gravel percentage deceases significantly. The lower gravel content (3.8 to 13.3 percent) is characteristic of the subject property. Overall the soils at the boring locations appear to be similar in sorting and silt content. In general, the test pits 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. Earth Solutions NW,LLC