10105 19TH AVE SE Geotech Report 2018-01-02 MF Import

:, _ _.... .. . T � ' ' • ' i � Geotechnical Engineering Evaluation Everett Veterinary Clinic February 21, 2002 � NGA File No.342902 Page 4 ( test pit logs should be reviewed. � We encountered a su�cial layer of topsoil 0.4- to l.2-feet thick in all of the explorations. The topsoil Iconsisted of loose, silty, fine to coarse sand with organics, rools, ar.d gravel. Underlying the topsoil, we encountered a weathered horizon up to 2.0 feet thick. The weathered horizon consisted of loose to ( medium dense, brown,silty,fine to coarse sand with gravel,interpreted to be weathered glacial till. i Underlying the weathered horizon we encountered unweathered glacial till at a depth 1.5 to 3.0 feet below the ground surface. The unweathe!eA glacial till consisted of gray, medium dense to dense, silty, fine to Icoarse sand with gravel. Hydrologic Condidons: Slight to heuvy ground water seepage was encountered in all of the explorations Iexcept Test Pit 2, near the northeast comer of the site. This seepage was encounlered imrt�ediately above the unweathered glacial till, 1.5 to 3.0 feet below the ground surFace. This water is interproted to be I perched ground water. We expect that perched ground water conditions could occur throughout the site. l I Perched ground water occurs when surface water infiltrates through more perm�able, near-surface soils, und is impeded by less permeable soils at depth. The amounts of perched ground water tend to vary depending upon the amount of recharge. We would expect that perched ground water would be more � prevalent during wetter times of the year. IErosion Hazard The erosion haznrd criteriu used for determination of affected areas includes soil type, slope gradient, Ivegztation cover, and grourd water conditions. The erosion sensitiviry is related to vegetative cover and ' the specific surface soil types, which are related to the underlying geologic soil units. The�gil 5urvev of ! Snohomish County Area. Washin�ron, by the Soil C�nservation Service was reviewed to determine the erosion hazard of the on-site soils. The site surface soils were classified using the SCS classification system as Alderwood-Urban land complex (2 ro 8 percent slopes). The erosion hazard for these soils is '� ' listed as being slight. The glacial soils we encountered in our explorations are consistent with the � Alderwoal-Urban land complex soils. ' JI { i NELSON GEOTECHNICAL ASSOCIATES, INL. � . -