Report I *.
GEOTECHNICAL ENGINEERING EVALUATION
PROPOSED FOUNDATION REPAIR
HO PROPERTY
13809 SW NORTHVIEW DRIVE
TIGARD, OREGON
APPTined
Condidanally Approved....J
See Utter for Follow ( 3
I A J� o r .
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Prepared for:
Levi Huffman
TerraFirma Foundation Repair
7901 Old Hwy 99 N.
Roseburg, Or 97470
January 8, 2009
Project No. 356 -004
TERRA DOLCE CONSULTANTS, INC.
OFFICE COPY
• TERRA DOLCE CONSULTANTS, INC.
4706 NE 75 AVE
PORTLAND, OREGON 97218
503 -502 -5114
January 8, 2009
Project No. 356 -004
Levi Huffman
TerraFirma Foundation Repair
7901 Old Hwy 99 N.
Roseburg, Or 97470
GEOTECHNICAL ENGINEERING EVALUATION
PROPOSED FOUNDATION REPAIR
HO PROPERTY
13809 SW NORTHVZE'W DRIVE
TIGARD, OREGON
Dear Levi:
As requested, Terra Dolce Consultants, Inc. (TDC) is pleased to present this report
summarizing our recommendations for the proposed foundation repair at the
referenced project. The scope of our work included conducting a site visit to
observe surface conditions of the house, reviewing geologic maps of the area, and
providing soil parameters for the proposed underpinning of the foundation. TDC
understands that Artisan Engineering, LLC has prepared the Structural Engineering
Report for the property.
Site and Project Descriptions
The project site is located on Northview Drive in Tigard, Oregon. The site is
developed with a 2 -story, single family house. Exterior loads on the house are
carried on a perimeter continuous footing. Interior loads are carried on isolated pier
footings.
The property is situated on the northern flank of the Bull Mountain. The property is
relatively flat from the street to the back of the property, where there is a 6 to 8 -foot-
high slope that drops to the adjacent property to the north. The slope is supported at
the toe with a small retaining structure. The flat backyard consists of fill. The fill, as
described by the owners, consists of fine - grained soils that were a result of the
excavation that occurred around the development. The fill was placed and tracked
in with a dozer, but apparently not compacted.
TDC observed the interior and of the house. In the interior of the house, there are
cracks in the sheetrock in various locations of the house. The cracks tend to be at
the seams of the sheetrock and are more noticeable in the northern portion of the
house.
On the exterior of the house, there are several cracks in the perimeter foundation.
The largest crack is along the western foundation wall.
GEOLOGIC SETTING
Review of geologic maps indicates that the site is underlain with the Willamette Silt.
The finer sediments are predominantly quartz and feldspar and also contain white
mica. Soil development commonly introduces significant clay into the upper 5 to 10
feet of the deposits. The fine sediments are up to 150 feet thick and mantle slopes up
to an elevation of 300 feet.
To the south of the property, Bull Mountain is underlain with the Columbia River
Basalt, Troutdale Formation, and the Upland Silt.
CONCLUSIONS AND RECOMMENDATIONS
The conclusions and recommendations presented in this report are based on the
information provided by TerraFirma Foundation Repair, results of the site visit, and
professional judgment. We have observed only a small portion of the pertinent
surface conditions. No subsurface investigations were completed for this portion of
•
the project. If subsurface data is requested, then that will be in addition to the work
that has been completed.
General
In our opinion, the site is geotechnically suitable for the proposed foundation repair.
This conclusion is based on the assumptions that the recommendations presented in
this report should be followed, and that during construction site conditions change
from what is presented in this report, that we will be consulted for updated
recommendations for developing the site.
No subsurface investigation was completed for the project. As noted above,
however, the backyard appears to consist of fill. The fill was used to create a flat
yard, and is potentially up to 6 feet deep.
Allowable Bearing Capacity. The allowable bearing pressure of the soil is 1,500
psf. This allowable pressure assumes that the bearing surface is firm native soil, with
no organics, undocumented fill, or deleterious materials. The proposed foundation
underpinning should extend through the fill and into the stiffer native soils.
Seismic Risk. Earthquake hazard within the vicinity of the property is low, with a
moderate risk of earthquake amplification, but low risk of earthquake induced
liquefaction.
Lateral Design Consideration. The primary purpose for the underpinning is to
provide vertical underpinning for the existing foundation. The underpinning system
is not intended to provide lateral support. If lateral support is required, then
additional piles should be installed specifically to provide lateral support.
Soil Corrosion Potential. Review of the Soil Conservation Service soil data indicate
that the shallow soils at the site are expected to be silt overlying sand and gravel.
The data indicate that the soil has a moderate potential for soil corrosion. Corrosion
of steel should be anticipated with the proposed foundation repair.
Terra Firm Foundation Repair January 8, 2008 Page 2
Geotechnical Evaluation
13808 SW Northview Drive
Tigard, Oregon
Project No. 358-004
Groundwater Considerations. Review of the Oregon Water. Resource Department
data for the surrounding vicinity indicates that the depth to groundwater averages
100 feet in the area. Because the property is on the northern flanks of the Bull
Mountain, however, there is the potential for groundwater flow within the shallow
depths.
Drainage and Backfill. Site work will be adjacent to the existing foundation. The
existing downspouts were found to have poor connections with the drain. The
connections should be restored to working conditions. If trenching is required, then
the trenches should be backfilled and compacted into place. The drainage and
backfill should be sloped such that the water drains away from the foundation.
LIMITATIONS
Geotechnical review is of paramount importance in engineering practice. The poor
performance of many foundations has been attributed to inadequate construction
review. On -site grading and earthwork should be observed and, where necessary,
tested by a qualified engineering firm to verify the compliance with the
recommendations contained in this report. Foundation excavation should also be
observed to compare the generalized site conditions assumed in this report with
those found on the site at the time of construction. If the plans for site development
are changed, or if various or undesirable geotechnical conditions are encountered
during construction, the geotechnical engineer should be consulted for further
recommendations.
This report is issued with the understanding that it is the responsibility of the owner
to ensure that the recommendations are incorporated in the plans and the necessary
steps are taken to see that the constructor and subcontractors carry out such
recommendations in the field. Geotechnical engineering is characterized by a
certain degree of uncertainty. Professional judgments presented are based partly
on our understanding of the proposed construction and partly on our general
experience. Our engineering work and judgments rendered meet current
professional standards; no other warranties, either expressed or implied are made.
This report is subject to review and should not be relied upon after a period of 3
years.
TerraFirm Foundation Repair January 8, 2008 Page 3
Geotechnical Evaluation
13806 SW Northview Drive
Tigard, Oregon
Project No. 356 -004
It has been a pleasure providing you the geotechnical services for this project. If
you have any questions, please call at 503.502.5114.
Sincerely,
Terra Dolce Consultants, Inc. _
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Cynthia L. Hovind, P.E., G.E.
Professional Geotechnical Engineer, OR- 17857PE
Attachments
Figure 1- Vicinity Map
Figure 2 - Site Map
TerraFirm Foundation Repair January 8, 2008 Page 4
Geotechnical Evaluation
13808 SW Northview Drive
Tigard, Oregon
Project No. 388 -004
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503 - 502-5114 Tigard, OR
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Terra Dolce Consultants, Inc. TerraFirma
4706 NE 75th Avenue Ho Property
Portland, Oregon
Phone 503.502.5114 13809 SW Northview Drive
Fax 503.206.5114 Tigard, OR
Project No. 356 -004 I January 8, 2009 I Vicinity Map I Figure 1