Report •
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9igineering Inc
Real -World Geotechnical Solutions
Investigation • Design • Construction Support
July 26, 2011
GeoPacific Project No. 04 -8996
Steve Pollard / Miriam Wilson ✓`'( -Zb r / (j G O Z/
West Hills Development
735 SW 185 Avenue
Beaverton, Oregon 97006
Via e-mail with hard copies mailed
Copies: Sandro Guerrero, Arbor Field Office (sguerrero@a,arborhomes.com)
Subject: SUMMARY REPORT OF GEOTECHNICAL OBSERVATION AND TESTING
ALPINE VIEW - LOT 14 —
SW BULL MOUNTAIN ROAD
WASHINGTON COUNTY, OREGON
References: 1. Geotechnical Engineering Report, Alpine View Development, Tigard, Oregon, GeoPacific
Engineering, Inc. report dated December 22, 2004.
2. Soil Engineers' Summary Report, Alpine View Subdivision, Tigard, Oregon, GeoPacific
Engineering, Inc. report dated January 30, 2006.
GeoPacific Engineering, Inc. (GeoPacific) conducted on -call testing and construction observation
services for the Alpine View project, located north of SW Bull Mountain Road in Washington
County, Oregon. The development consists of grading lots for residential structures, and associated
improvements that include new streets and driveways, underground utilities, and water quality
facilities.
This report addresses construction activities and building pad preparation for Lot 14, which is
located in an area of native soils. GeoPacific observed topsoil stripping, subgrade preparation and
fill placement, and performed density testing of engineered fills during mass grading of the project
site (see Reference 2).
As part of this evaluation, GeoPacific personnel visited the site on July 26, 2011 to observe the
foundation excavation. Soils were evaluated using a steel "T" probe. Excavations extended to
depths of about 2 to 4 feet to provide level terraces for foundation construction. Soils exposed
consisted predominantly of very stiff, gravelly silt, engineered fill.
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
%2 inch differential, measured over a horizontal distance of 20 feet. Where stepped foundations are
present, a 1H:1 V setback should be maintained to avoid surcharging of the lower foundation wall.
13910 SW Galbreath Drive, Suite 102 Tel (503) 625 -4455
Sherwood, Oregon 97140 Fax (503) 625 -4405
July 26, 2011
GeoPacific Project No. 04 -8996
No deck footing, patio, or other appurtenant structure subgrades were observed at the time of our
site visit.
Due to silty / clayey soils encountered throughout the site, building foundations should incorporate
appropriate drainage measures. Crawlspaces should be provided with a low -point drain and pass
through pipes should be installed through footings which would otherwise restrict water flow to the
low -point drain.
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 about 'A inch of loose soils are present prior 1
to pouring concrete.
We have prepared this report for West Hills Development / Arbor 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,
environmental assessments or evaluations regarding the presence or absence of wetlands or
hazardous or toxic substances in the soil, surface water, or groundwater at this site.
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We appreciate this opportunity to be of service.
Sincerely,
GEOPAC i ;e•• i EKING, INC.
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EXPIRES: 06- 30-20
Scott L. Hardman, P.E., G.E.
Principal Geotechnical Engineer
044996- Alpine View Lot 14.doc 2 GEOPACIFIC ENGINEERING, INC.
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