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Fngineeritig.Inc
Real-World Geotechnical Solutions
Investigation• Design• Construction Support
February 3, 2016
Project No. 15-3723
Mike Loomis
Lennar Northwest, Inc.
11807 NE 99th Street, Ste. 1170
Vancouver, WA 98682
Phone: (360) 258-7900
Via email with hard copies mailed: (chuck.mcallister@lennar.com)
SUBJECT: FOUNDATION SUBGRADE OBSERVATION FOR LOT 7
OAK STREET ESTATES SUBDIVISION
TIGARD, OREGON
Reference: GeoPacific Engineering, Inc., Summary Report of Geotechnical Observation and
Testing, Oak Street Estates, Tigard, Oregon, October 21, 2015, Job No. 13-3175.
GeoPacific Engineering Inc. visited the site today to review the single family home foundation
subgrade on Lot 7. We understand that the proposed building is a two-story daylight basement
home, on a downward sloping lot to the west and north. In our opinion, the observed subgrade is
generally adequate for support to an allowable bearing pressure of 1,500 psf; however a little
more mucking is needed on the north end of the westernmost footing/building corner. After
concrete placement a significant amount of structural backfilling is required. 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.
At the time of our site visit, the excavation was nearly complete. The excavation consisted of
predominantly stiff engineered fill soils at the front and stiff native soils on the lower portion that
probed less than 1 to 12 inches with heavy pressure using a steel "T" bar probe. These soils are
considered adequate to support the planned foundation loads. Footing-to-slope setbacks were
adequate and foundation embedment depths appeared adequate.
Due to silty soils encountered throughout the site, all 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.
14835 SW 72nd Avenue Tel(503)598-8445
Portland, Oregon 97224 Fax(503) 941-9281
Oak Street Estates Lot 7
GeoPacific Project No. 15-3723
Our work scope pertains to a geotechnical engineer's foundation excavation review only and the
of scope,
existingand exposed at the time of our site visit. Within the limitations s e
PP .
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.
Sincerely,
GEOPACIFIC ENGINEERING, INC.
. S
ct
171
OREGON
EXPIRES:06/30/20
James D. Imbrie, P.E., G.E.
Geotechnical Engineer
2 GEOPACIFIC ENGINEERING, INC.