HomeMy WebLinkAboutSoils Report 06.03.2015CIVCO Engineering, Inc.
Civil Engineering Consultants
P.O. Box 1758
365 West 50 North, Suite W-1
Vernal, Utah 84078
June 3, 2015
Brian Quintana
Clayton Homes
671 23 Road
Grand Junction, CO 81505
Dear Brian,
Subject: Soil Investigation - Long Residence in Parachute, CO
I am writing this letter to report the findings of a soil investigation that was conducted at the proposed
site for the Long residence that is to be built in Parachute, Colorado. The investigation 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 sample as 'CL -ML' according to
the Unified Soil Classification System. Copies of the soil data are included with this letter.
CL -ML soils are inorganic clays of low to medium plasticity with silt. In addition to clay and silt particles,
CL -ML soils may contain a fair amount of gravel-, and sand -sized particles. The sample tested
contained (17.6%) of particles that were sand -sized (#200 Sieve) or larger. Thus the soil is further
characterized as "sandy silty clad'. Literature suggests that medium to stiff CL -ML soils are likely to
have bearing capacities in the range of 3,000 psf. Recognizing that no specific bearing capacity testing
was performed, I recommend that a more conservative 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 (i.e. expansiveness) to atterberg limit data. According to one study, soils having liquid limits
less than 35% and plasticity indexes less than 12%, are generally non -expansive, (Snethen, Johnson,
and Patrick, 1977). The tested soil sample had a measured liquid limit of 23% and a plasticity index of
4% and thus is anticipated to have a very low potential to be expansive. Please note that Atterberg
limits testing does not address mineralogy and thus may be limited in its ability to reliably predict soil
shrink -swell potential.
Though the Atterberg Limits testing suggests a non -expansive soil, frost heave could still cause
problems for the foundation. Foundations should extend to below frost depth or be frost -protected by
some other means. Water should be kept away from the foundations. 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.
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 (i.e. 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: vanceking@civcoengineering.com
* Page 2 June 3, 2019
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 proposed foundation was not specifically tested to determine
expansiveness but was found to have properties consistent with soils having 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 3000 psf. For design purposes, a 1500 psf
bearing capacity is recommended. 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
CIVCO Engineering - Long residence
Q. C. TESTING
native - unified soil classification
Depth:
Date Sampled
AASHTO T-27 Coarse Gradation
Sieve
Size
Weight
Ret.
% Ret.
% Ret.
% Total
Passing
Sieve
Size
Specs
3" (75mm)
44.7
H2O %
11.7
3"
0
2" (50mm)
100
2"
4.2
1.5" (37.5mm)
98.9
1.5"
1" (25mm)
1"
1.5
3/4" (19mm)
98.5
3/4"
112" (12.5mm)
1/2"
3.4
318" (9.5mm)
97.6
3/8"
#4 (4.75mm)
#d
-#4 (4.75mm)
WET WT.
#80 (180pm)
-#4 (4.75mm)
DRY WT.
#100 (150pm)
Total
#200
58.2
MF=
Tested By CN
Fine Gradation
Liquid Limit
Size
Weight
Ret.
% Ret.
% Pass
#4 (4.75mm)
Classification
CL -ML sandy silty clay
44.7
H2O %
11.7
#8 (2.36mm)
0
0.0
100
#10 (2.0mm)
4.2
1.1
98.9
#16 (1.18mm)
#20 (850pm)
1.5
0.4
98.5
#30 (600pm)
#40 (425pm)
3.4
0.9
97.6
#50 (300pm)
#60 (250pm)
#80 (180pm)
#100 (150pm)
#200
58.2
15.2
82.4
-#200 (75pm)
315.2
82.4
Total
Remarks SOIL CLASSIFICATION (unified)
Stations:
Date Tested: 5/13/2019
UNIFIED Atterberg Limit
Liquid Limit
23
Plastic Limit
19
Plastic index
4
Classification
CL -ML sandy silty clay
#4 Moisture Data
Wet Wt.
427.3
Dry Wt.
382.6
H2O Wt.
44.7
H2O %
11.7
Washed Dry Wt.
90.6