HomeMy WebLinkAboutSoils Report 01.08.2020CIVCO Engineering, Inc.
Civil Engineering Consultants
P.O. Box 1758
365 West 50 North, Suite W-1
Vernal, Utah 84078
January 8, 2020
Richard Ruse
Clayton Homes
671 23 Road
Grand Junction, CO 81505
Dear Richard,
Subject 8o11 Investigation —Wafters Residence at Tract 25 CR 237,85t, CO
I am writing to report the findings of a soil investigation that was conducted at the proposed site for the
Wafters residence at Tract 25 County Road 237, Silt, Colorado. The investigation entailed the analysis
of one soil sample that was taken at approximately the location and bearing depth of the proposed
foundation. Testing of the soil sample included a sieve analysis and Atterberg Limits testing. The
results of the soil testing were used to classify the soil sample as 'CL - Sandy Lean Clay' according to
the Unified Soil Classification System. A copy of the soil data is included with this letter.
CL soils are inorganic clays of low to medium plasticity. In addition to clay particles, CL soils may
contain a fair amount of gravel-, sand-, and silt -sized particles. The sample tested contained a sizable
proportion (47.6%) of particles that are sand -sized (#200 Sieve) or larger. Literature suggests that
medium to stiff CL 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 conservative bearing
capacity of 2000 psi be used for design purposes.
Over the years, a number of studies have been conducted in an effort to correlate soil expansiveness
to atterberg limit data. According to one study, soils with Liquid Limits less than 50% and Plasticity
Indices that less than 25%, generally have a low potential for expansion (Snethen, Johnson, and
Patrick, 1977). The soil sample tested was found to have a Liquid Limit of 31% and a Plasticity Index of
119% Thus, according to the referenced study, the soil in question is anticipated to have a low
expansion potential. It should be noted that Atterberg Limits testing does not address mineralogy and
thus may have a limited ability to reliably predict soil expansion potential.
CL soils often are susceptible to frost heave. Methods should be implemented to lessen the likelihood
of frost heave. Foundations should extend to below frost depth or be frost -protected by some other
means. Water should be kept away from the foundation. Walkways, driveways, and ground surfaces
should be graded to flow away from the foundation. Gutter down -spout outlets should be kept 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 soil's collapse potential. In my experience, foundation failures
due to soil collapse are generally even more catastrophic than failures due to soil expansion, In every
instance of soil collapse failure that I have investigated, the damaged home was located at the mouth
of a pronounced drainage, such as a canyon or gully where the soil has been deposited alluvially by
intermittent runoff water flows.
Alluvialiy-deposited soils are typically not very dense and derive their strength from mineral bonds that
form between soil particles. When these soils become wet, the mineral bonds dissolve, allowing the
soil particles to consolidate (collapse) under any load that is in excess of that which existed when the
mineral bonds originally formed.
Phone (435)789-5448 * Fax (435)789-4485
Email: vancekingecivcoengineering.com
• Page 2 January 8, 2020
Verify that the project site is not at the mouth of any obvious drainage. Implementing the
aforementioned methods for lowering the risk of frost heave is also key to lessening the risk of soil
collapse failure.
In summary, the soil under the foundation was not specifically tested to determine its expansiveness
but results of atterberg limits testing suggest that the soil has a low expansion potential. Likewise, the
soil was not specifically tested to determine bearing capacity but was found to be of a type having
characteristic bearing capacities in the range of 4000 psf. For design purposes, a 2000 psf bearing
capacity Is recommended. No speck testing was performed to determine the collapse potential of the
soil. The home owner should make every effort to keep moisture from being introduced to the soil near
the foundation. Any future purchaser of the home should be apprised of the underlying soil
characteristics and the importance of keeping moisture away from the foundation.
This concludes my report. Please note that this investigation was •performed for the purpose of
providing general information regarding the soil underlying the proposed home and makes no
prediction of foundational performance. This report should not be regarded as documentation of a
geotechnical investigation as I am not a geotechnical engineer and this study was not conducted to any
generally accepted standard of geotechnical engineering practice. Please contact me If you have
questions regarding this report.
Sincerely,
Vance V. King, PE
Engineer
CIVCO Engineering, Inc.
Enclosure
Cc: Project File
Q. C. Testing. Inc
2944 S 1500 E
VERNAL, UTAH 84078
Phone (435) 789-0220
Fax (435) 781-1876
Project No. or Client:
Material Type:
Distance from CL:
SIEVE ANALYSIS AND ATTEBERG LIMITS
=CO Engineering - Walters residence, Silt, CO
Q. C. TESTING
v
native - unified soil classification Stations:
Depth:
Date Sampled
AASHTO T-27 Coarse Gradation
Sieve
Size
Weight
(Ret
% Ret.
% Ret.
% Total
Passing
Sieve
Size
Specs
3" (75mm)
87
H2O WL
34.7
3"
H20 %
2" (50mm)
Washed Dry Wt.
1
2"
80.9
1.5" (37.5mm)
71.8
1.5"
1" (25m)
1"
49.2
3/4" (1emm)
62.5
3/4"
1/2" (12.5mm)
1/2"
23.8
3/8" (9.5m)
58.0
3/8"
#4 (4.75mm)
#4
#4 (4.75mm)
WET WT.
#80 (180pm)
#4 (4.75mm)
DRY WT.
#100 (150pm)
Total
#200
30.7
MF=
Tested By TD
Fine Gradation
(Liquid Limit
Size
Weight
IRet.
% Ret.
% Pass
#4 (4.75mm)
69.3
13.0
87
H2O WL
34.7
#8 (2.36mm)
H20 %
6.1
Washed Dry Wt.
1
#10 (2.0mrn)
80.9
15.2
71.8
#16 (1.18mm)
#20 (65opm)
49.2
9.3
62.5
a30 (600pm)
;040 (425pm)
23.8
4.5
58.0
i#50 (300pm)
#60 (250pm)
#80 (180pm)
#100 (150pm)
#200
30.7
5.8
52.2
•#200 (75pm)
2.0
Total
Remarks SOIL CLASSIFICATION (unified)
Date Tested: 12/13/2019
UNIFIED Atterberg Limit
(Liquid Limit
31
Meek Limit
:20
(Plastic index
11
Claasniwlan
CL -sandy lean clay
44 Moisture Data
Wet Wt.
566.6
Dry Wt.
531,9
H2O WL
34.7
H20 %
6.1
Washed Dry Wt.
1
355.9