Plans 04 -06 -2009 16:30 From-GRI 503-644 -8034 T -545 P.002/003 F -318
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July 20, 2007 4166 LOT 11 ADDITIONAL C.O. SERVICES LTR
Accent Residential Homes
12583 SW Autumnview Street
Tigard, OR 97224
Attention: Sean Foushee
SUBJECT: Additional Construction Observation Services
Lot 11, Mountain View Estates Subdivision
12492 SW St Andrews Lane
Tigard, Oregon
City of Tigard Building Permit No. MST 20074)0015
At your request, on June 7, 2007, GRI visited the above - referenced lot in the Mountain View Estates
subdivision to observe the exposed foundation subgrade of the house under construction. At the time of
the first visit, the foundation excavation was not complete. A second visit was made on July 18, 2007, to
observe the completed foundation prior to placement of concrete in the completed forms. This letter
summarizes our observations and provides our conclusions and recommendations regarding the suitability
of the work performed. As you know, GRI completed a geotechnical investigation for this project. The
findings of our studies and our conclusions and recommendations for design and construction of the
project are summarized in our November 30, 2004, report to LanPacific, Inc. entitled, "Geotechnical
Investigation, Mountain View Estates, Tigard, Oregon." Additional design recommendations regarding
foundations and retaining wall design were provided to Accent Homes in the following memoranda by
G RI:
"Retaining Wall Design, Mountain View Estates, Tigard, Oregon ;" dated December 30, 2005.
'Global Stability, Proposed Retaining Walls and Fill Slopes, Mountain View Estates,
Tigard, Oregon;" dated February 17, 2006.
"House Foundation Design, Mountain View Estates, Tigard, Oregon;" dated March 20, 2006.
"Retaining Wall #4, Mountain View Estates, Tigard, Oregon;" dated June 29, 2006.
Our construction -phase services during site development included evaluating the installation of
subdrainage systems north and south of SW Autumnview Drive and placement and compaction of
structural fill during general grading for Lots 5 through 14. Our observations during construction were
documented in daily Site Visit Reports and are summarized in our letter to you dated January 19, 2007. A
copy of each daily SVR report was also provided to you as the work was accomplished.
At the time of our site visit on July 18, 2007, the foundation excavation was complete, and the forms and
reinforcing steel were in place on Lot 11. The exposed subgrade consisted of hard, intact basalt on the
04-06 -2009 16:30 From -GRI 503- 644 -8034 T -545 P.003/003 F -318
uphill foundation line and stiff to hard, clayey silt and stiff to hard, clayey silt fill with scattered gravel -size
pieces of concrete and angular rock at other locations. The subgrade was moist on the surface from recent
light rainfall and was lightly desiccated below a depth of about 4 in. At the time of our visit on July 18,
2007, the forms for the second row of foundations from the south were on the edge of a vertical cut and
will require backfilling with relatively clean crushed rock such as 3/4 —in, -minus placed and compacted as
structural fill to 95% of the maximum dry density as determined by ASTM 0 698. The slope of the
structural backfill should be 2H :1V or flatter. You indicated that following placement and curing of the
concrete in the foundation walls, footing drains would be installed, black asphaltic waterproofing would
be applied to the embedded portions of the walls, and the walls would be backfilled with compacted
granular material to about 3 ft above the drains, and compacted native silt backfill would be placed above
that granular material to grade.
Based on our observations at the site and assuming the structural fill will be placed to support the second
row of footing from the south, it is our opinion that preparation of the footing subgrades was accomplished
in substantial conformance with the plans and specifications and our recommendations for this project,
and the subgrades are suitable for support of the proposed building loads. Please contact the undersigned
if you have any questions regarding this correspondence.
Submitted for GRI,
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David D. Driscoll, PE Matthew S. Shanahan, PE
Principal Project Engineer
cc: Eric Esparza / LanPacific Inc. (eme @lanpacific.com)
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