HomeMy WebLinkAboutBuilding Miscellaneous 2014-4-25 S1v- c045
K & A Engineering, Inc.
91051 S.Willamette Street
P. 0. Box 8486, Coburg, OR 97408
(541) 684-9399 Voice
engineering (541) 684-9358 FAX
kaengineers.com
April 25,2014 Project: 14024
Town & County, LLC
6019 Graystone Loop
Springfield, OR 97478
Subject: Geotechnical Site Evaluation - Foundation Pad Construction
New Single-family Residence
5717 Peridot Way, Springfield Oregon
PURPOSE AND SCOPE
At your request, K &A Engineering, Inc. has completed a geotechnical evaluation of the existing soils on the
subject property. Our understanding is that a wood-framed single-family residence supported by a cast-in-
place concrete spread and strip footing foundation system is proposed for construction on this site.
The purpose of our evaluation was to determine the suitability of the soils for construction of the proposed
structure, and provide recommendations for construction of the foundation. The scope of our services is limited
to general suitability with respect to bearing capacity and expansive soils.
SITE OBSERVATIONS
General Site Surface Conditions
The project site is residential lot located on the south side of Peridot Way. The lot slopes gently facing the east,
at an estimated grade of 5 to 10-percent.
Vegetation at the site, prior to excavation, consisted of moderately dense grasses.
There were no visual indications of slope movement, or overly soft or unstable soils, or excessive surface
erosion.
Subsurface Soil Conditions
Based on our observations during foundation pad excavation and construction, soils at the site consisted of
approximately:
• 2 to 2.5-feet of undocumented fill consisting of brown organic silts and construction debris, over
• 1.5 to 2-feet of dark brown (original) organic silts (topsoil), over
• 1-foot of reddish-brown, moderately stiff silty-clay, over
• Reddish-tan weathered sandstone (breaks out into angular fragments of soft rock).
No groundwater was observed from the excavation which had a maximum cut depth of approximately 5-feet
along the west and northwest portion of the pad.
K& A Engineering, Inc.
Foundation Pad Construction
Foundation pad construction consisted of stripping and removing all fills and organics and excavating the
subgrade on undisturbed reddish-brown stiff sandy-clay or weathered sandstone. The subgrade was
excavated into three benches that are separated in elevation by 0.5 to 1.0-feet.
The cut depth along the west and northwest edges of the foundation pad ranged from approximately 3.5 to 6-5-
feet. Our understanding is that this is the garage area and that a low retaining wall will be constructed as part of
the perimeter foundation in this area.
Approximately 0.5 to 1.5-feet of 3"—0 crushed aggregate fill was placed on the subgrade benches and
compacted using a vibratory steel drum roller. Testing of this large aggregate for maximum dry-
density/optimum water content is not possible. Based on our observations, we believe that the aggregate fill,
as placed, has an adequate density (after compaction).
A perimeter foundation drain consisting of a 3-inch perforated pipe surrounded with separation geotextile was
placed around the perimeter of the foundation pad at or near the subgrade along the west and northwest sides
of the foundation pad. A solid pipe routes water to the east edge of the foundation pad.
SUMMARY AND RECOMMENDATIONS
General Suitability
The foundation pad, as constructed, is suitable for construction of a single-family residence supported by
conventional cast-in-place concrete spread footings.
We recommend acceptance of the foundation pad, including crushed aggregate fill, as constructed, by the
local building official.
Foundation Support
The foundation pad, as constructed, is suitable to support a conventional reinforced cast-in-place concrete
spread footing system. We recommend a design allowable bearing capacity of 2,500-pounds per square foot.
Expansive Soils
The reddish-brown stiff silty-clay and sandstone subgrade has a moderate potential for volume change with
changes in water content. However, the depth of the subgrade below finished grade around the perimeter
foundation is sufficient to keep these soils at relatively constant water content. This mitigates the hazard, and
no further mitigation is required for expansive soils.
Project: 14024 5717 Peridot Way, Springfield, Oregon Page 2 of 3
Client: Town & Country, LLC April 25, 2014
K & A Engineering, Inc.
LIMITATIONS OF THIS REPORT
This report has been prepared for the exclusive use of Town and Country, LLC and its contractors and design
consultants for the subject proposed structure.
This geotechnical evaluation, analysis, and recommendations meet the standards of care of competent
geotechnical engineers providing similar services at the time these services were provided. We do not warrant
or guarantee site surface or subsurface conditions.
Thank you for the opportunity to be of service. Please call us if you have questions or need further assistance.
Respectfully,
ccs PROF�cS
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DEWS
DmRES _ 12/31/2014
Michael Remboldt, P.E., G.E.
K &A Engineering, Inc.
Project 14024 5717 Peridot Way, Springfield, Oregon Page 3 of 3
Client: Town & Country, LLC April 25, 2014