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GeoPãciffc
Engineering,Inc.
Real-World Geotechnical Solutions
Investigation •Design•Construction Support
March 8, 2019
Project No. 15-3853
Matt McBride
Windwood Construction, Inc.
12655 SW North Dakota
Tigard, Oregon 97223
SUBJECT: FOUNDATION SUBGRADE REVIEW
LOT 1 ANNAND HILL SUBDIVISION
TIGARD, OREGON
Reference: 1. GeoPacific Engineering, Inc., Geotechnical Engineering Report, Annand Hill Subdivision,
SW 109th Avenue,Tax Lots 2S110AC00200 and 25110AD0880,Washington County, Tigard,
Oregon, dated July 30, 2015.
2. GeoPacific Engineering, Inc., Summary Report Of Geotechnical Observation and Testing,
Annand Hill Subdivision, Tigard, Oregon, dated June 26, 2017.
GeoPacific Engineering Inc. visited the site today twice to review the single-family home foundation
subgrade on Lot 1. We understand that the proposed building is a two-story home. In our opinion,
the observed subgrade is adequate for support to an allowable bearing pressure of 1,500 psf.
At the time of our second site visit, the excavation was nearly complete and soils exposed in
foundation excavation consisted of predominantly stiff, compacted fill soils that could be probed
about 1 to 2 inches with moderate pressure using a steel "T" bar probe. Up to 2.5 feet of soft fill was
removed over most of the home except at the front, where stiff soils were encountered. The
expected maximum anticipated total and differential footing movements (generally from soil
expansion and/or settlement) are 1 inch and 3/4 inch, respectively, over a span of 20 feet. Footing-to-
slope setbacks were not an issue.
It should be noted that the on-site soils are very moisture sensitive and will soften significantly in wet
weather conditions if not adequately protected. Due to relatively impervious silty and clayey soils
encountered throughout the site, all foundations should incorporate appropriate drainage measures
in accordance with the International Residential Code. Adequate crawlspace drainage is not
something that geotechnical consultants can verify; the purpose of our visit is for observations of
foundation bearing conditions only.
Our work scope pertains to a geotechnical engineer's foundation excavation review only and the
conditions existing and exposed at the time of our site visit. 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. No warranty, express or implied, is made. If you have
any questions, please call.
14835 SW 72nd Avenue Tel(503)598-8445
Portland,Oregon 97224 Fax(503)941-9281
GeoPacific Engineering, Inc.
Job No. 15-3853
Lot 1 Annand Hill
Sincerely,
GeoPacific Engineering,Inc.
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EXPIRES:06/30/20t/.
James D. Imbrie, G.E.
Geotechnical Engineer