Report (4) AtageiL.-,
GEDPPCIFIC
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Real-World Geotechnical Solutions
Investigation• Design•Construction Support
August 25, 2023
Project No. 22-6162 M c 3 20 2-3 - 000 ?-3
Ichijo USA Co., LTD
Attn: Erik Gomez
1509 SW Sunset Blvd. Suite 2-D
Portland, Oregon 97239
Via email to: erik.qomez(@jchijousa.com
FOUNDATION SUBGRADE REVIEW
LOT 79 RIVER TERRACE CROSSING AKA CROSSING AT BULL MOUNTAIN
15804 SW 150th AVENUE
TIGARD, OREGON
This letter addresses the single-family home foundation subgrade on Lot 79 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 crawl space. As part of this evaluation, GeoPacific visited the site
on August 15, 2023 to observe the subgrade foundation preparation. At the time of our site visit, the
foundation excavation was complete and was generally 6 to 18 inches below surrounding grades.
A thin lift of gravel had been placed over the foundation subgrade soils as protective cover.
Subgrade generally appeared to consist of stiff native silt and bedrock. The foundation layout of Lot
79 is stepped down to the south with two benches about 6 to 18 inches tall. Footing-to-wall and
footing-to-slope setbacks did not appear to be an issue for the structure.
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,
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 cons'dered normal and not necessarily detrimental to the home given these other
design elements inc rporated into its construction. Adequate crawlspace drainage is not something
that geotechnical nsultants can verify; the purpose of our visit is for observations of foundation
bearing conditions only. Appropriate design professionals should be consulted regarding
14835 SW 72nd Avenue Tel(503)598-8445
Portland,Oregon 97224 Fax(503)941-9281
GeoPacific Engineering, Inc.
Job No. 19-5287
Lot 79 River Terrace Crossing
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.
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Benjamin G. Anderson, P.E.
Associate Engineer