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Report (2) mac l .,f 2$ GeoP Engineering,Inc. Real-World Geotechnical Solutions Investigation• Design • Construction Support August 19, 2020 GeoPacific Project No. 17-4524 JT Smith Companies 5285 Meadows Road, Suite 175 Lake Oswego, Oregon 97035 Via email to: jotey@jtsmithco.com and nsmith@jtsmithco.com Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE RED CEDAR SUBDIVISION—LOT 1 7557 SW RED CEDAR WAY TIGARD, OREGON Reference: Summary Report of Geotechnical Observation and Testing. SW 74th Avenue Subdivision (AKA Red Cedar Estates), Tigard, Oregon. GeoPacific Engineering report dated October 23, 2019 GeoPacific Engineering, Inc. (GeoPacific) conducted on-call density testing and construction observation services for the Red Cedar Subdivision site. This letter addresses the building pad subgrade for Lot 1 of the development. It is our understanding that the planned structure will consist of a single-family home with a suspended garage. GeoPacific visited the site August 17, 2020 to observe the foundation conditions for Lot 1. Upon our arrival, the foundation excavation was complete and extended approximately 1 to 10 feet below the surrounding grade. The foundation bearing soils consisted of engineered fill soils and native silt soils, which were evaluated with a Humboldt hand probe. Probing efforts yielded 2 to 4 inches of penetration, indicating stiff to very stiff consistency of the foundation bearing material. The footing layout of Lot 1 is relatively flat and the surrounding properties slope downward to the north. Footing-to-wall setbacks do not appear to be an issue. Structural fill will be necessary to support tall basement walls along the deeper cuts at the south end of the home. Footing-to-slope setbacks should not be an issue once the structural fill is placed. Based on observed conditions, foundation subgrade soils as prepared are considered suitable to support the anticipated allowable bearing pressure of 1,500 psf. Estimated settlement under the allowable bearing pressure is 1 inch total, and '/2 inch differential, measured over a horizontal distance of 20 feet. Care should be taken to avoid saturation or disturbance of footing subgrade soils during and after excavation. If footing bearing soils become saturated or disturbed, any softened soil or slough should be removed and replaced with crushed aggregate or additional concrete. In general, footing excavations should be cleaned such that no more than approximately 1-inch of loose soils are present prior to pouring concrete. 14835 SW 72' Avenue Tel (503) 598-8445 'ortland, Oregon 97224 Fax (503) 941-9281 Red Cedar— Lot 1 GeoPacific Project No. 17-4524 Construction should include typical measures for controlling subsurface water beneath the homes, including positive crawlspace drainage to an adequate low-point drain exiting the foundation, visqueen covering the exposed ground in the crawlspace, and crawlspace ventilation (foundation vents). The homebuyers should be informed and educated that some slow flowing water in the crawlspaces is considered normal and not necessarily detrimental to the home given these other design elements are incorporated into its construction. Appropriate design professionals should be consulted regarding crawlspace ventilation, building material selection and mold prevention issues, which are outside GeoPacific's area of expertise. We have prepared this report for JT Smith Companies, and it should not be relied upon by third parties without consulting GeoPacific. Within the limitations of scope, schedule and budget, GeoPacific attempted to execute these services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology at the time the report was prepared. The conclusions and interpretations presented in this report should not be construed as a warranty of the subsurface conditions. No warranty, expressed or implied, is made. The scope of our work did not include flood hazard evaluations, environmental assessments, the presence or absence of wetlands; or potential hazardous substances in the soil, surface water, or groundwater at this site. We appreciate this opportunity to be of service. Sincerely, GEOPACIFIC ENGINEERING, INC. N ( vi4T,.., . / OREGO n't3D.t " EXPIRES!06/30/20ZA James D. Imbrie, G.E., C.E.G. Principal Geotechnical Engineer 2 GEOPACIFIC ENGINEERING, INC.