HomeMy WebLinkAboutSoils Report 08.18.2020CIVCO Engineering, Inc.
Civil Engineering Consultants
P.O. Box 1758
365 West 50 North, Suite W-1
Vernal, Utah 84078
August 18, 2020
Shawn Ruse
Clayton Homes
671 23 Road
Grand Junction, CO 81505
Dear Shawn,
Subject Sop investigation — Bishop Residence at TBD CR 301, Parachute, CO
I am writing to report the findings of a soil investigation that was conducted at the proposed site for the
Bishop residence at TBD County Road 301, Parachute, 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 (32.3%) 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, 1 recommend that a more conservative bearing
capacity of 2000 psf 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
10%. Thus, according to the referenced study, the soil in question is anticipated to have a low
expansion potential. It should be noted that Attertierg 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 boated 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.
Alluvially-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: vancekingeocivcoengineering,com
• Page 2 August 18, 2020
Verify that the project site is not at the mouth of any obvious drainage. The aforementioned methods
for lowering the risk of frost heave are 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 specific testing was performed to determine the collapse potential of the
soil. The homeowner 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
CIVCO Engineering - Bishop residence
Q_ C_ TESTING
7
native - unified soil classification Stations:
Depth:
Date Sampled
AASHTO T-27 Coarse Gradation
Sieve
Size
Weight T
Ret.
% Ret.
% Total
Passing
Sieve
Size
Specs
3" (75mm)
3"
2" (somm)
2"
1.5" (37.5mm)
1.5"
1"(25mm)
0
0
100
1"
3/4" (iemm)
31.5
8.9
91.7
3/4"
1/2" (125mm)
1/2"
3/8" (9.5mm)
3/8"
#4 (4.75mm)
#4
4/4 (4 75mm)
WET WT.
-#4 (4.75mm)
DRY WT.
Total
MF=
Tested By 138
Fine Gradation
Size
Weight
Ret.
% Ret.
% Pass
#4 (4 75mm)
#8 (2 38mm)
_
#10 (2 omm)
2.7
0.8
90.3
#16 (1 ism)
#20 (85opm)
9.6
2.7
87.6
#30 (s0o).n)
ft40 (425 vn)
19.1
5.4
82.2
.450 (3ooi.n)
f160 (25ojn)
.480 (isownl
I/100 (1sopm)_
I/200
51.4
14.5
67.7
4/200 (75um)
239.0
67.8
Total
Remarks SOIL CLASSIFICATION (unified)
Date Tested: 8/13/2020
UNIFIED Atterberg Limit
Uo,id Limit
31
Plastic Unw
21
Plastic Index
10
Classification
CL - sandy lean clay
4/4 Moisture Data
Wel WI.
364
Dry WI.
353.3
H2O Wt.
10.7
H2O%
3.0
Washed Dry Wt.
122.2
LIQUID AND PLASTIC LIMITS TEST REPORT
60
50
40
z
V30
- 20
10 -
Dashed line indicates the approximate
upper limit boundary for natural soils / --7
1 /
/
/
/
/
/
0
a
33.6
33.2
32.8
32.4
1-
w 32
z
chi 31.6
Q 31.2
30.8
30.4
10
20
•
0ti
ML or OL
30 40 50 60
LIQUID LIMIT
70
MH or OH
80 90 100 110
•
•
•
30
29.6
5
•
6 7 8 9
MATERIAL DESCRIPTION
native
NUMBER OF BLOWS
LL
31
PL
21
PI
10
20
•
25 30 40
%<#4o
Project No. Client: Civco
Project: Soil Classifications
Location: Bishop residence
QC TESTING, INC.
Remarks:
o%<#2oo
Figure
usCs
Tested By: TD