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GeoPacific
Engineering.Inc.
Real-World Geotechnical Solutions
Investigation • Design • Construction Support
February 13, 2020
GeoPacific Project No. 15-4010
Riverside Homes, LLC
17933 NW Evergreen Parkway, Suite 370
Beaverton, OR 97006
Via email to Brett Groves (BGroves@riversidehome.com) and Amilian Avgi
(AAvgi@riversidehome.corn)
Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE
ELDERBERRY RIDGE SUBDIVISION—LOT 8
14944 S.W. BELVOIR COURT
TIGARD,OREGON
GeoPacific Engineering, Inc. (GeoPacific) conducted on-call density testing and construction
observation services for the Elderberry Ridge Subdivision site. This letter addresses the footing
subgrade conditions for Lot 8 of the development. It is our understanding that the planned
structure will consist of a single-family residence utilizing conventional spread footings.
GeoPacific personnel visited the site February 11th, 2019 to observe subgrade preparation for
the foundation excavation at Lot 8. The excavation depth was approximately 12-60 inches
below the surrounding grade. The foundation bearing soils consisted of engineered fill soils,
which were evaluated with a Humboldt hand probe. Probing efforts indicated predominantly stiff
soils throughout the footing subgrade layout. The footing layout of Lot 8 and the adjacent lots is
a relatively flat pad with a 12-foot tall, 2H:1V slope downward at the east side of the pad.
Footing-to-slope and footing-to-wall setbacks were adequate at more than 5 feet horizontal.
Some sloughing of vertical cuts is anticipated and will need to be mucked/removed. The deck
footings on the slope will require backfilling with compacted structural fill consisting of crushed
aggregate.
Based on observed conditions, the footing subgrade soils are considered suitable for foundation
support. The foundation subgrade as prepared is 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 Y2-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
14835 SW 72nO Avenue Tel (503) 598-8445
Portland,-Oregon 97224 Fax(503) 941-9281
Elderberry Ridge - Lot 8
GeoPacific Project No. 15-4010
slow flowing water in the crawlspaces is considered normal and not necessarily detrimental to
the home given these other design elements are incorporated into its construction. 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 Riverside 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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James D. lmbrie, G.E., C.E.G.
Principal Geotechnical Engineer
2 GEOPACIFIC ENGINEERING. INC.
FOUNDATION CERTIFICATION
SETBACK
TS:
FRONT:E15 FEETN LOT 8 OF "ELDERBERRY RIDGE"
FRONT GARAGE: 20 FEET WASHINGTON COUNTY, OREGON
SIDE: 5 FEET
REAR: 15 FEET DATE: FEBRUARY 13, 2020
'TRACT 6'
SO0'54'49'W 45.00'
1 -...."11.17 .411 -.1.111.-
N SCALE 1" = 20 FEET
SETBACK LINE I [1-
Aid
(TYPICAL) �`� I
I
H 0 CO CV 0 cv
$ \; $ I, CUNTON H. STUBBS JR., A REGISTERED
PROFESSIONAL LAND SURVEYOR IN THE STATE
LOT 9 ka \ LOT 8 3 LOT 7 cCURAGTOELY SURVEYED ANDY MAPPEDI THE
Q ^.' I i FOUNDATION FOR LOT 8 OF 'ELDERBERRY
\ rn co RIDGE', AS STAKED ON FEBRUARY 12, 2020.
z THE BOUNDARY ONES DEPICTED HEREON WERE
5.0' GARAGE 5 0' ESTABLISHED BY HOLDING RECORD INFORMATION
\ AND MONUMENTATION FROM THE PLAT OF SAID
a \ \ SUBDIVISION, THIS CERTIFICATION SHOULD NOT
o -- - - - -t - - --I SERVE AS A BOUNDARY SURVEY.
J
i o
N
b - REGISTERED
�_ c
`" PROFESSIONAL
_._ LAND SURVEYOR
f f NO0'54'49"E 45.00' (/f,
``1 oR GON
JANUARY 15, 200 i"
"' SW BELVIOR COURT CUNTON H. STUBBS'JR.
ui ` 55469LS
RENEWS: 06/30/20
PREPARED FOR: JOB NAME: ELDERBERRY RIDGE
RIVERSIDE HOMES, LLC. JOB NUMBER: 1884 NJORTHWEST 1815 NW 169th PLACE,
SUITE 2090
17933 NW EVERGREEN PLACE DRAWING NUMBER: 1884 STAKED BEAVERTON, OR 97006
SUITE 370 PHONE:503-848-2127
URVEYING AX:503-848-2179
BEAVERTON, OR 97006 DRAWN BY: BJA � Inc.. nwaurveyingOnwarvy.com
CHECKED BY: CHS