902 PINE ST NORTH SOUND BEHAVIORAL HEALTH TREATMENT CENTER Geotech Report 2022-10-25

GeoTest Services, Inc. November 16,2018 North Puget Sound Behavioral Health—Treatment Center Addition Job No. 18-0770 General Geologic Conditions Geologic information for the project site was obtained from the Geologic map of Marysville quadrangle, Snohomish County, Washington (Minard, 1985) published by the U.S. Geological Survey. According to the referenced map, near surface soils in the vicinity of the project site consist of Glacial Till (Qtv). According to Minard, the till, locally called Vashon till generally consists of a nonsorted mixture of clay, silt, sand, pebbles, cobbles, and boulders. It is a compact lodgment till and if often referred to as hardpan. Native soils encountered during our subsurface exploration were generally consistent with the mapped till deposits. Groundwater At the time of our subsurface investigation in October of 2018, groundwater seepage was encountered in two of the exploration borings at depths of 20 feet BGS at B-1 and 15 feet BGS at B-4. We anticipate this seepage to be indicative of localized perched water lenses within an otherwise low permeability geologic unit. The groundwater conditions reported on the exploration logs are for the specific locations and date indicated, and therefore may not necessarily be indicative of other locations 111 and/or times. Groundwater levels are not static and groundwater conditions will vary depending on local subsurface conditions, precipitation, changes in site use, both on and off site, and other factors. It should be noted, that groundwater conditions on-site are seasonally variable. Based on our previous experience, ground water elevations seasonally vary and can raise or lower several feet. Typically, groundwater elevations are highest in the late winter and early spring months, and lowest in late summer or early fall. GEOLOGIC HZAZARDS Based on the online interactive Geologic Map of Washington State, published by the Washington State Department of Natural Resources, the subject site is rated as a very low liquefaction susceptibility area. However, this map only provides an estimate of the likelihood that soil will liquefy as a result of earthquake shaking and is meant as a general guide to delineate areas prone to liquefaction. Though no known faults are mapped in the vicinity of the site, the Pacific Northwest is prone very large regional seismic events with a mean recurrence interval of approximately 475 years. Conventional construction techniques in the area do not typically include mitigation for liquefaction hazards based on the mapped site rating or the type of anticipated construction. The gently sloped site topography does not present significant landslide or erosion I hazards. No other potential geologic hazards were observed at the site or are described in the regional geologic maps. Thus, it is our opinion that the site does not contain seismic, landslide or erosion hazards as defined by municipal code, and no specific mitigation for I these hazards is recommended. I I Page 4 of 17 I