902 PINE ST NORTH SOUND BEHAVIORAL HEALTH TREATMENT CENTER 2025-11-04

GeoTest Services, Inc. November 16,2018 North Puget Sound Behavioral Health-Treatment Center Addition Job No. 18-0770 CONCLUSIONS AND RECOMMENDATIONS Based upon evaluation of the data collected during this investigation, it is our opinion that subsurface conditions at the site are suitable for the proposed improvements, provided the recommendations contained herein are incorporated into the project design. The proposed building is intended to be placed adjacent to an existing structure and in an area of previous development, mostly consisting of asphalt parking, hardscape and landscape features. Exploration data indicates generally shallow fill in most locations with depths up to 1-foot BGS before encountering dense native glacial till soil to the maximum depths of exploration. We anticipate that building foundations can be placed directly on dense native soil. Slab areas that are stripped of asphalt or landscaping organics are likely eligible to be placed directly on existing structural fill or on native soil. We recommend verification of actual conditions by a qualified representative from our firm during construction. Site Preparation and Earthwork ' The portions of the site to be occupied by the proposed building foundations should be prepared by removing existing topsoil, fill, organic landscape material and loose/soft, upper portions of the native soil. Slab areas may be prepared by removing surficial topsoil and organic material, while existing fill compacted to "structural fill" requirements placed over firm and unyielding native soil may remain. Pavement, hardscape and walkway areas may be placed on native soil or existing fill after removal of any organic soil. GTS anticipates approximately 1 foot of surface stripping to reach suitable native soils in most locations. However, localized areas may require up to 5 feet of removal and replacement with structural fill, based on our boring exploration at B-4 in the northeast !. area of exploration. After site stripping has occurred, the exposed subgrade under all areas to be occupied by soil-supported floor slabs, spread or continuous foundations, pavement or new sidewalk areas should be evaluated to ensure a firm and unyielding condition and proof rolled with a loaded dump truck, large self-propelled vibrating roller, or similar piece of equipment applicable to the size of the excavation. Soils disturbed during excavation should be recompacted prior to placement of structural fill or foundation elements. Recompaction of the near-surface soils does not reduce or eliminate the need for overexcavation, where required, of near-surface loose soils or fill material below foundation elements. The purpose of recompacting and proof rolling near- surface soils is to identify possible loose or soft soil deposits and recompact, if feasible, the soil disturbed during site excavation activities. Proof rolling should be observed by qualified geotechnical personnel. Areas exhibiting significant deflection, pumping, rutting, yielding or are observed to have elevated moisture contents that prevent the soil from being adequately compacted should be overexcavated to firm soil. Overexcavated areas should be backfilled with structural fill as recommended elsewhere in this report. During periods of wet weather, proof rolling could damage the exposed subgrade. Under these conditions, qualified geotechnical personnel should observe subgrade conditions to determine if proof rolling is feasible. I Page 5 of 17