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GEDPPCIFIC
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Real-World Geotechnical Solutions
Investigation • Design • Construction Support
April 15, 2021
Project No. 20-5628 i22-'
Stonebridge Job No. 3011 ivi
Stonebridge Homes NW LLC
4230 SW Galewood St., Ste. 100
Lake Oswego, OR 97035
Fax 503-387-7615
Email: Andy(a�stonebridgehomesnw.com; JimD(a�stonebridgehomesnw.com; tianar(r�stonebridge-
realty.com
FOUNDATION SUBGRADE REVIEW
LOT 15- FORAN HILLS
13114 SW FORAN HILLS
TIGARD, OREGON
This letter addresses the single-family home foundation subgrade on Lot 15. We understand that the
proposed building is a two-story home with a crawl space. As part of this evaluation, GeoPacific
visited the site today to observe the subgrade foundation preparation. At the time of our site visit,
the foundation excavation was complete and extended 12 to 24 inches below existing ground
surface. The foundation bearing soils generally consisted of stiff, native silt. Probing efforts with a
1/2-inch soil probe resulted in 1/2 to 4 inches of penetration into the subgrade fill soils, indicating stiff
consistency. The layout of Lot 15 is nearly flat. Footing-to-wall and footing-to-slope setbacks were
not an issue.
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
1 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 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
14835 SW 72"d Avenue Tel (503)598-8445
Portland,Oregon 97224 Fax(503)941-9281
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GEOPACIF'IC
Job No. 20 5628
Lot 15 Foran Hills
crawlspace ventilation, building material selection and mold prevention issues, which are outside
GeoPacific's area of expertise.
i
We have prepared this report for Stonebridge Homes, 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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EXPIRES:06/30/20 23
James D. Imbrie, G.E.
Geotechnical Engineer
1