Thomco Construction Inc. 6/14/2021

KRAZAN&ASSOCIATES,INC. KA Project No. 092-20006 DRAFT Geotechnical Engineering Investigation 1 Everett Water Main"V" May 7,2020 Page No. 7 I Although our explorations were not obstructed, there is the potential for obstructions such as debris or boulders to be encountered in undocumented fill and native soils. For additional information about the soils encountered,please refer to the logs of the exploratory soil borings in Appendix A. Groundwater The soil borings were observed for the presence of groundwater during drilling operations. Groundwater seepage was encountered in soil boring B-4 at a depth of about 5.0 feet, and in soil boring B-7 at a depth of approximately 5.0 feet. Moist to wet conditions were encountered in soil boring B-9 from about 0.5 to 4.5 feet in depth. The groundwater seepage and wet soil conditions were interpreted as perched groundwater. There is the potential for perched groundwater conditions to develop in the site soils. Perched groundwater occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of a relatively low-permeability soil layer. Perched water tends to vary spatially and is dependent upon the amount of rainfall, and does not represent a regional groundwater "table" within the upper soil horizons. We would expect the amount of perched water to decrease during drier times of the year and increase during wetter periods. It should be recognized that groundwater elevations may fluctuate with time. The groundwater level will be dependent upon seasonal precipitation, irrigation, land use, and climatic conditions, as well as other factors. Therefore, groundwater levels at the time of the field investigation may be different from those encountered during the construction phase of the project. The evaluation of such factors is beyond the scope of this report. GEOLOGIC HAZARDS Erosion Concern/Hazard Project Area 1: The Natural Resources Conservation Services (NRCS) map for Snohomish County classifies the site area as Alderwood gravelly sandy loam (15 to 30 percent slopes) and Alderwood- Everett gravelly sandy barns (25 to 70 percent slopes). The NRCS indicates that both soil types have a severe hazard for erosion when exposed. Project Area 2: The Natural Resources Conservation Services (NRCS) map for Snohomish County classifies the site area as Alderwood-Urban land complex(2 to 8 percent slopes). The NRCS indicates that the Alderwood-Urban land complex soils (2 to 8 percent slopes)have a moderate hazard for erosion when exposed. The Urban land area was not rated for hazard of erosion. I Krazan&Associates,Inc. Offices Serving The Western United States I