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CITY OF TIGARD, WASHINGTON COUNTY, OREGON
SURVEYED JULY 12, 2021
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PREPARED FOR: ( ( ( 7 6
DAVID WEEKLEY HOMES
1905 NW 169TH PLACE, SUITE 210 ( ,\\
BEAVERTON, OR. 97006
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NICK A. LAFOND
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CD RENEWS: 12/31/2022
°' I, NICK A. LAFOND, A REGISTERED PROFESSIONAL LAND SCALE
t SURVEYOR IN THE STATE OF OREGON, HEREBY CERTIFY THAT 30 0 15 30
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a FOUNDATION FOR LOT 12 OF "TRILLIUM HILL". 1 INCH = 30 FEET
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s� DRAWN BY: JRH DATE: 7/14/21 PACIFIC COMMUNITY DESIGN
a REVIEWED BY: T2 DATE: 7/14/21
Z 130-002 PLANNING - ENGINEERING - SURVEYING
PROJECT NO.: (503) 941-9484
GEEJPRCIFIC
Real-World Geotechnical Solutions
Investigation • Design•Construction Support
July 19, 2021
Project No. 18-5046
David Weekly Homes
1905 NW 169th Place, Suite 102
Beaverton, Oregon 97006
Phone: 503-213-4408
Email: dmillermoylanta@dwhomes.com
FOUNDATION SUBGRADE REVIEW
LOT 12—TRILLIUM HILL
TIGARD, OREGON
This letter addresses the single-family home foundation subgrade on Lot 12. We understand that the
proposed building is a two-story home with a crawl space. As part of this evaluation, GeoPacific
visited the site last week and today to observe the subgrade foundation preparation. At the time of
our site visits, the foundation excavation was complete and extended approximately 6 to 24 inches
below existing ground surface. The foundation bearing soils appeared to consist of compacted fill
soils. Probing efforts with a I/2-inch soil probe resulted in 1 to 2 inches of penetration into the
subgrade fill indicating medium stiff to very stiff consistency. The layout of Lot 12 has slope
descending toward the rear of the lot. Footing-to-wall and footing-to-slope setbacks appeared to be
adequate based on the anticipated layout.
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 3/4 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 1/2-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
crawlspace ventilation, building material selection and mold prevention issues, which are outside
GeoPacific's area of expertise.
14835 SW 72nd Avenue Tel(503)598-8445
Portland,Oregon 97224 Fax(503)941-9281
GEOPACIFIC
Job No. 18-5046
Lot 12 Trillium Hill
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.
OR°D PRO
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EXPIRES:06/30120 23
James D. Imbrie, G.E.
Geotechnical Engineer