Report �- —° Main Office Branch Office
P.O. Box 23814 4060 Hudson Ave., NE
C arlson Testing, Inc. Tigard, Oregon 97281 Salem,
Phone (503) 684 -3460 Phone e (5 (503) 3) 589 -1289-12
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FAX (503) 684-0954 FAX (503) 589 -1309
S' e
November 16, 1998 ,� (� O Z
CTI #97-G1155 q, 7 �'u� i�d2 V�
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Harper Righellis, Inc. o f •
5200 SW Macadam Ave. - Suite 580 (',\ 1N(
Portland, OR 97201
FINAL REPORT OF EARTHWORK OBSERVATION AND TESTING FILE COPY
TIGARD WOODS SUBDIVISION EtiC1 9$ – 00 %8
TIGARD, OREGON
Carlson Testing Inc. (CTI), has conducted on -call inspection services for the earthwork at the
above residential development located on SW Landau Place & SW Landau Street in Tigard,
Oregon. This letter briefly summarizes our observations and testing during construction and
the as -built soil conditions to the best of our knowledge. This letter also provides
recommendations for foundation design and soil guidelines during construction of the single -
family homes.
SITE PREPARATION AND FILL PLACEMENT
Based on our visual observations and our density test results no engineered fill was placed
on any of the lots or the streets. Density tests were conducted on the storm and sewer
trenches and the base course only.
OBSERVATIONS
From our observations and hand probing, the surface of the most lots are covered with
approximately 18 to 24 inches of newer strippings, uncompacted material, and /or water
softened soils that will require excavation prior to construction of foundations with the
following exceptions: Lot 1 contains up to 4 feet of uncompacted material on it's surface.
In addition, the utility trench along the east side of the lot appear to have been backfilled with
on -site soils with no compactive effort and has settled nearly 10 inches. Approximately 3 feet
of soft, old fill was encountered on Lot 5. A small stockpile of material was observed near
the center of Lot 8. This pile should be removed prior to the foundation excavation. Lot 2 has
an existing structure.
HOUSE EXCAVATION GUIDELINES
We anticipate foundation excavation depths to vary throughout the subdivision. The 1
foundation excavation for Lot 1 is anticipated to range between 31/2 and 4 feet. In addition,
the proposed foundation should have a minimum horizontal setback of 5 feet off the edge of
the uncompacted trench. The foundation excavation for Lot 3 and 4 is anticipated to be 18
and 24 inches, respectively. Excavation depths ranging between 2 and 3 feet are expected
on 5 through 8. We anticipate the deeper excavations (3 feet) will be necessary along the
back side of the lots near the ravine. Some groundwater seepage and /or water flow should
be anticipated. Perimeter footing drains may be required for Lots 5 through 8.
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CTI #97-G1155
Tigard Woods
Page 2
If excavated material is spread around the lot deeper than one foot and is expected to support
appurtenant structures such as deck footings and sidewalks, it should be placed, compacted,
and tested as engineered fill.
The foundation excavations for Lots 5 through 8 should be reviewed by a Geotechnical
Engineer.
FOUNDATIONS
The proposed one- to two -story residential buildings will likely be founded on shallow spread
footings bearing on competent native soils or engineered fill. Spread footing design and
construction should generally conform to UBC Chapter 1 8 and /or Chapter 4 of the CABO One
and Two Family Dwelling Code, except where we specifically recommend otherwise. •
For protection against frost heave we recommend that spread footings on nonexpansive soils
have a minimum final embedment depth of 18 inches for exterior grades on level ground. The
recommended minimum widths for continuous wall footings are tabulated below:
Minimum Width for
No. of Stories Continuous Footing
(floors supported) (in)
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1 -story 1 2
2 -story 15
As previously stated, the allowable bearing pressure can be taken as 1,500 lb/ft for footings
bearing on competent native subsoils or engineered fill. The recommended maximum load is
20 kips for column footings. For heavier column loads and masonry chimneys, a Soil Engineer
should be consulted. The coefficient of friction between on -site soil and poured -in -place
concrete may be taken as 0.35. The maximum anticipated total and differential footing
movements are 1 inch and 3 /4 inch, respectively, over a span of 20 feet.
If requested, CTI can provide inspection services to verify that suitable foundation subgrade
is exposed prior to placement of concrete.
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CTI #97-G1155
Tigard Woods
Page 3
CLOSING AND LIMITATIONS
Our reports pertain to the materials tested /inspected only. This letter should be made available
to each builder in the develo•ment• however information contained herein is not to be
re•roduced exce.t in full without odor authorization from this office. This letter should not
be construed to relieve or lessen the responsibility of the contractor or owner's site
representative for this site work, but is provided for the minimum required governmental
.assurance. Our support was given on an as- needed basis as requested. If conditions are
encountered during foundation excavation which differ from this report, then the developer
(Harper /Righellis) and CTI should be allowed to review the condition before corrective actions
are taken. Corrective work performed by the builder without notifying the above parties will
be interpreted as an acceptance of the conditions encountered.
Respectfully submitted,
CARLSON TESTING, INC. PR Ores
2 14743 '7
OREGON
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23.1'1'
Brian D. Leach, ch, E.I.
Engineering Associate James D. Imbrie, P.E.
Principal Engineer
Attachments: Summary report of in -place soil density tests
cc: City of Tigard Bldg. Dept.
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