10111 9TH AVE W EMERALD COURT APARTMENTS Geotech Report 2022-10-20

s � Geotechnical Engineering Evaluation NGA File No.910814 Emerald Court Apartment Building November 21,2014 Everett,Washington Page 3 soil in Test Pit 1, we encountered dense to very dense, gray, silty fine to medium sand with gravel and varying amounts of iron-oxide staining. Below the weathered soil in Test Pit 2,we encountered stiff,gray silt. We interpreted these soils to be glacial till. Test Pits 1 and 2 were terminated at depths of 6.3 feet and 6.8 feet below the existing ground surface,respectively. At the surface of Test Pits 3 and 4, which were located within the parking lot, we encountered approximately 0.1 feet of surficial weeds/scattered grasses. Below the weeds, we encountered approximately one to two feet of medium dense, orange-brown,silty fine to medium sand with gravel and roots. We interpreted this material as weathered glacial till. Below the weathered soil, we encountered dense to very dense, gray, silty fine to medium sand with gravel and varying amounts of iron-oxide staining. We interpreted this material to be glacial till. Test Pits 3 and 4 were terminated at depths of 7.0 feet and 6.8 feet below the existing ground surface,respectively. Test Pits 5 and 6 were excavated within the area of the planned underground detention pipes. Below a surficial layer of weeds, we encountered approximately 0.5 to 0.7 feet of topsoil underlain by approximately 2.2 to 3.0 feet of loose to medium dense, silty fine to medium sand with roots. We interpreted this soil to be weathered glacial till. Below the weathered soil, we encountered very dense, silty fine to medium sand with gravel and trace cobbles. We interpreted this material to be glacial till. Test Pits 5 and 6 were terminated within the native glacial till at a depths of 8.8 feet and 9.7 feet below the existing ground surface,respectively. Hydrologic Conditions Groundwater seepage was encountered in Test Pit 1 at 0.8 feet; Test Pit 2 at 5.4 feet; Test Pit 5 at 3.5 feet; and Test Pit 6 between 3.0 and 9.0 feet. There is a high potential for a perched groundwater condition to develop within this site during the wetter periods of the year. Perched water occurs when surface water infiltrates through less dense, more permeable soils such as the weathered soil, and accumulates on top of a relatively low permeable material such as the dense to very dense glacial till soils at depth. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. NELSON GEOTECHNICAL ASSOCIATES, INC.