Report . .
:.
GeoP • INc
Engineering,Inc.
Real-World Geotechnical Solutions
Investigation • Design •Construction Support
January 31, 2020
Project No. 18-4824
Stonebridge Job No. 2758
Stonebridge Homes NW LLC
Andy Thomas
4230 SW Galewood St., Ste. 100
Lake Oswego, OR 97035
Fax 503-387-7615
Email. Andyastonebridgehomesnw.corn: JimD cx stonebridgehomesnw.com; tianar@stonebridqe-
realty.com
FOUNDATION SUBGRADE REVIEW /11 ¶yz °�! 000 I '
LOT 4—BRIGHTWOOD SUBDIVISION ( .
11124 SW 114TH PLACE
TIGARD, OREGON
GeoPacific Engineering Inc. (GeoPacific) previously performed a geotechnical engineering
investigation of the site and provided recommendations for site development. We also conducted
on-call density testing and construction observations services during site development. This letter
addresses the single-family home foundation subgrade on Lot 4. We understand that the proposed
building is a two-story home with a crawl space.
As part of this evaluation, GeoPacific visited the site January 30, 2020 to observe the foundation
subgrade preparation. At the time of our site visit, the foundation excavation was complete and
extended 6 to 18 inches below the surrounding grade. A thin lift of granular fill was placed over the
subgrade soils as protective cover for wet weather work. The foundation bearing soils consisted of
engineered fill, which was evaluated with a Humboldt hand probe. Probing efforts yielded 2 to 3
inches of penetration, indicating stiff to very stiff consistency of the foundation bearing soils. The
layout of Lot 4 and the adjacent properties is relatively flat. Footing-to-wall and footing-to-slope
setbacks did not appear to be 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
excavations should be cleaned such that no more than approximately %-inch of loose soils are
present prior to pouring concrete.
14835 SW 72nd Avenue Tel(503)598-8445
Portland, Oregon 97224 Fax(503)941-9281
. -
GeoPacific Engineering, Inc.
Job No. 18-4824
Lot 4 Brightwood
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
crawispaces 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 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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Benjamin G. Anderson, P.E.
Senior Engineer