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Report (2) -' r2021-DOIOg GEOPACIFIC Real-World Geotechnical Solutions Investigation •Design•Construction Support April 19, 2021 GeoPacific Project No. 21-5769 Westwood Homes, LLC 12700 NW Cornell Road Portland, Oregon 97229 Phone: 503-715-2383 Via email to: Darrin Krause at darrin@westwoodhomesllc.com Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE BURT'S LANDING—LOT 6 11837 SW PENNY LANE ✓ TIGARD,OREGON GeoPacific visited the site today to observe the foundation preparation at Lot 6 of the development. It is our understanding that the planned structure will consist of a single-family residence utilizing conventional spread footings. At the time of our arrival, the excavation was complete and extended approximately 18 to 24 inches below the surrounding grade. The footing layout and adjacent properties are relatively flat, and the deeper excavation was due to removing a thick layer of organic debris across the surface of the lot. The underlying foundation bearing material consisted of native sandy silt soils, which were determined to be stiff to very stiff consistency when evaluated with a hand probe. Footing-to-wall and footing-to-slope setbacks do not appear to be an issue. 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'/2-inch of loose soils are present prior to pouring concrete. 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 14835 SW 72nd Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax(503)941-9281 Burts Landing, Westwood Homes—Lot 6 GeoPacific Project No. 21-5769 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 Westwood Homes, LLC, 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. 14 4A OREGOS l EXPIRES:06/30/2 2I_ James D. Imbrie, P.E. Principal Geotechnical Engineer 2 GEOPACIFIC ENGINEERING, INC.