Report MID
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REDMOND GEOTECHNICAL SERVICES
D O v Project No. 1183.002.G
1 Page No. 1
March 4, 2013
Mr. Dan MacNaughton
Daniel MacNaughton, Inc.
3802 SW Martins Lane
Portland, Oregon 97239
Dear Mr. MacNaughton:
Re: Geotechnical Consultation Services, Evaluation of Residential Home Site Subgrade Excavation,
Lot # 22, 10160 SW 70 Avenue, Tigard, Oregon
In accordance with your request, we have completed our evaluation of the residential home site
subgrade excavation at the above subject lot. The purpose of our work at this time was to offer our
opinion with regard to the suitability of the exposed subgrade soils for support of the planned new
residential foundations.
Specifically, on March 1, 2013 we were present at the site to check the condition of the exposed
subgrade soils. Observations made at this time revealed that the proposed residential lot had been
recently excavated with a tracked excavator (cat). Additionally, the site excavation work was
observed to extend to a stripping depth which removed the surficial topsoil materials. Further, hand
probing across the subject building pad found the exposed subgrade soils to be firm to very firm
native (residual) clayey silt to silty clay soils.
In this regard, based on the results of our recent site observations and hand probing, we are of the
opinion that the subject proposed residential building lot has been suitably stripped of surface
vegetation and the exposed subgrade soils are suitable for support of the planned residential
structure based on an allowable contact bearing pressure of up to 2,000 psf. However, we point out
that northwest corner of the residential foundation excavation was observed to be located directly
adjacent to an existing descending slope. As such, we are of the opinion that the first five (5) feet of
the northerly perimeter footing extending east from the northwest corner be extended an
additional twelve (12) inches below the existing footing excavation grade.
Project No. 1183.002.G
Page No. 2
Additionally, depending on when the foundations may be poured, it may be desirable to place an
approximate 2- to 4 -inch lift of compacted crushed rock over the grade to help protect the exposed
subgrade soils from wet and /or inclement weather.
We appreciate this opportunity to be of service to you at this time and trust that the above
information is suitable to your present needs. Should you have any questions regarding the above or
if you require any additional information and /or assistance, please do not hesitate to call.
HOFF
Sincerely, N /
Daniel M. Redmond, P.E., G.E. OREGON
President /Principal Geotechnical Engineer a wr is. Is 0
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