HomeMy WebLinkAboutSoils Investigation 07.14.17CTV CO Engíne ering, Inc .
Civíl Engineering ConsulTonts
P O. Box 1758
3ó5 West 50 Norfh, Suite W-l
Vernal, Utoh B4O7B
July 14,20'17
Richard Ruse
Clayton Homes
671 23 Road
Grand Junction, CO 81505
Dear Richard,
Subject: Soil lnvesligation - tllamer at TBD Odin Street, S¡lt, Golorado
I am writing this letter to report the findings of a soil investigation that was conducted at the proposed
site for the Warner residence at TBD Odin Street near Silt, Colorado. The investigatìon entailed the
analysis of one soil sample that was taken from the proposed construction site at approximately the
bearing depth of the proposed foundation. Testing of the soil sample included a sieve analysis and
Atterberg Limits testing. The test results were used to classify the soil sarnple as 'CH' according to the
Unified Soil Classification System. Copies of ihe soil data are included with this letter.
CH soils are homogeneous inorganic clays and may be silty or sandy as is the case with this soil.
Literature suggests that medium to stiff CH soils are likely to have bearing capacities in the range of:
4,000 psf. Recognizing that no specific bearing capacity testing was performed, I recommend that a
more conseryative bearing capacity of 1500 psf be used for design purposes.
Over the years, a number of studies have been conducted in an effort to correlate soil shrink-swell
potential to atterberg limii data. According to one study, liquid limiis less than 25% and plasticity
indexes less than 15%, generally suggest a soil will have a low shrinl</swell potential. The liquid limit of
the sample tested was found to be 39. The plasticity index for the sample was found to be 8. Thus,
according to the referenced study, the soil cannot be ruled out for being expansive. lt should be noted
that Atterberg limits tests do not address mineralogy and thus may be limited in their ability to reliably
predict soil shrink-swell potential.
Every effort should be taken to limit soil moisture in the vicinity of the foundation. Walkways, driveways,
and ground surfaces should be graded to flow away from the foundation. Gutter dor,rrn-spout outlets
should discharge at least five feet away from the foundation. Vegetation requiring significant watering
should not be planted near the foundation.
No testing was done to determine the collapse potential of the soil. ln my experience, soil collapse
results in a îar more catastrophic foundation failure than soil expansion. ln every instance of sorl
collapse failure ihat I have investigated, the damaged home was founded r¡¡ithin a naturally occurring
alluvial fan at the outfall of a natural drainage. The figure below is not the property in question but is
included as an example of a situation where soil collapse damage a home. Alluvial soils often derive
their shength from mineral bonds that form behveen loosely deposited soil particles. When these soils
become wet, the mineral bonds dissolve, allowing the soil to consolidate (i.e. collapse) under any load
Phone (435)789-5448 * Fax (435\789-4485
Emoil : vonceking@civcoengíneer¡ng.com
. Page2 Juty14.Z017
ln excess of that which €xisled lhe when the mineral bonds formed. To minimize the possibility of lhis
home being founded on collapsiile soils, verify trat lhe chosen location ls nowhere near the outÞll of
any naturaldralnage.
ln summary, the soll under üre foundation uas nol speciñcally tested to deþrmine expansfueness but
resulb of aüerberg limils testing suggest lhat the soll cannot be rulEd out as hlng expanslve. Llksnise
he soll was not specifically tcslcd to determine bearing capacity but r¡vas found to be of a tpe having
charaderistic bearlrp capaclties ln the range of 4(X)0 psf. For deslgn purposes, a 15(X) psf bearing
capaclty ls recommended. The home oryr¡er should make every efiort to keêp molstre fom belrg
lnþoduced to the soll near lhe foundalion. Any fuhre purcñaser of tre home should be apglsed of the
underlying soil charac'terlstlcs and the lmportance of keeplng molsh¡re auãyfom ün foundaüon.
This condudes my report. Please notc ürat ûrls lnvesügaüon was performed for the prrpose of
providing genaral informaüon regarding üre soil underl$ng tlre proposed home and mákes no
predlcdon of fmndatonal perfurmance. PlEase conhct me if you have questions regardlng lhis report.
Sincerely,
VanceV. King, PE
ErUlneer
CIVCO Enginearing, lnc.
Endosure
Cc Project File
7.1î,t
353'.15
Q. C. Testing. lnc
2944 S 1500 E
VERNAL, UTAH 84078
Phone (435)789-0220
Fax (435) 781-1876
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