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Report (16) 5T 2023 - 0022 3 GEOPI1CIF�IC) x Real-World Geotechnical Solutions Investigation• Design •Construction Support October 3, 2023 Project No. 22-6162 Ichijo USA Co., LTD Attn: Erik Gomez 1509 SW Sunset Blvd. Suite 2-D Portland, Oregon 97239 Via email to: erik.gomez(a�ichijousa.com FOUNDATION SUBGRADE REVIEW LOT 166 RIVER TERRACE CROSSING AKA CROSSING AT BULL MOUNTAIN 15632 SW EVERGLADE AVENUE TIGARD, OREGON This letter addresses the single-family home foundation subgrade on Lot 166 of the River Terrace Crossing development, also known as Crossing at Bull Mountain. We understand that the proposed building is a two-story home with a daylight basement or a tall crawlspace. As part of this evaluation, GeoPacific visited the site on September 25 and October 2, 2023 to observe the subgrade foundation preparation. At the time of our site visit, the foundation excavation was complete and generally extended approximately 6 to 36 inches below the surrounding grades. Subgrade generally appeared to consist of gravelly silt engineered fill. The foundation layout of Lot 166 is stepped down to the east in benches about 3 to 4 feet tall. The total vertical relief is approximately 10 feet. There is an existing Lock+Load retaining wall to the east of the house footprint. On September 25, 2023, the embedment depth of the rear footing was not dep enough in some places to achieve the adequate footing-to-wall setback. Also on that day, there were three areas where the upper 6 inches of the subgrade was very soft. We painted out the areas and recommended deeper embedment for the rear footing and removal of the soft soils. On October 3, 2023, we observed that our recommendations had been carried out. Footing-to-wall and footing-to- slope setbacks did appear to be adequate. Structural backfill may be necessary if footings are proposed near the vertical benches. Based on observed conditions, foundation subgrades as prepared are considered suitable to support the planned allowable bearing pressure of 1,500 psf. Estimated settlement under the allowable bearing pressure is 1-inch total, and 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, 14835 SW 72"d Avenue Tel(503)598-8445 Portland,Oregon 97224 Fax(503)941-9281 GeoPacific Engineering, Inc. Job No. 22-6162 Lot 166 River Terrace Crossing 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 incorporated into its construction. Adequate crawlspace drainage is not something that geotechnical consultants can verify; the purpose of our visit is for observations of foundation bearing conditions only. 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 Ichijo USA, 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. . III "kr y ;", ti f i • 1-712/31123 Benjamin G. Anderson, P.E. Associate Engineer