HomeMy WebLinkAboutSubsoils Study for Foundation Designrcn Hiffi[#*ffifnn:'i*"'
An Employcc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Office l,ocations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
PARCEL #217720112003
NORTH OF COUNTY ROAD 320
GARFIELD COUNTY, COLORADO
PROJECT NO.24-7-543
DECEMBER3l,,2024
PREPARED FOR:
JOSE SALAZAR
P.O. BOX 91
RIFLE, COLORADO 81650
valentinbustillos09@hotmail. com
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION
SITE CONDITIONS
FIELD EXPLORATION
SUBSURFACE CONDITIONS .....
FOUNDATION BEARING CONDITIONS
DESIGN RECOMMENDATIONS ...
FOUNDATTONS...
FLOOR SLABS.....
UNDERDRAIN SYSTEM
SURFACE DRAINAGE.....................
LIMITATIONS
FIGURE I - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 - SWELL-CONSOLIDATION TEST RESULTS
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Kumar & Associates, lnc, @ Project No, 24-7-543
PURPOSE AND SCOPE OF STUDY
This report presents the results ofa subsoil study for a proposed residence to be located on parcel
number 217720112003,off of Village Drive, Garfield County Colorado. The project site is
shown on Figure 1. The purpose of the study was to develop recommendations for the
foundation design. The study was conducted in accordance with our agreement for geotechnical
engineering services to Jose Salazar dated September 13, 2024.
An exploratory boring was drilled to obtain information on the subsurface conditions. Samples
of the subsoils obtained during the field exploration were tested in the laboratory to determine
their classification, compressibility and other engineering characteristics. The results of the field
exploration and laboratory testing were analyzed to develop recommendations for foundation
types, depths, and allowable pressures for the proposed building foundation. This report
summarizes the data obtained during this study and presents our conclusions, design
recommendations and other geotechnical engineering considerations based on the proposed
construction and the subsurface conditions encounter"dQ -I-2oZ5 nots-i
llnnPROPOSED CONSTRUCTION
The proposed residence will be a one-story wood frJRrN9[a
g'a,le fioer inthe urattached gregp. Grading for the structure is assumed to be relatively minor
with cut depths between about 3 to 5 feet. We assume relatively light foundation loadings,
typical of the proposed type of construction.
If building loadings, location or grading plans change significantly from those described above,
we should be notified to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The site is located north of County Road 320 and east of Village Drive. The site currently a
vacant lot vegetated with grasses. The lot slopes gently down to the northeast.
FIELD EXPLORATION
The field exploration for the project was conducted on October 9,2024. One exploratory boring
was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring
was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted CME-
458 drill rig. The boring was logged by a representative of Kumar & Associates, Inc.
Samples of the subsoils were taken with I% inch and 2 inch I.D. spoon samplers. The samplers
were driven into the subsoils at various depths with blows from a 140 pound hammer falling 30
inches. This test is similar to the standard penetration test described by ASTM Method D-1586
Kumar & Associates, lnc, @ Project No, 24-7-543
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The penetration resistance values are an indication of the relative density or consistency of the
subsoils. Depths at which the samples were taken and the penetration resistance values are
shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory
for review by the project engineer and testing.
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils below about Yzfootof topsoil, consist of about 5 feet of slightly sandy clay overlying
silty, sandy gravel, cobbles and boulders. Drilling in the dense granular soils with auger
equipment was difficult due to the cobbles and boulders and drilling refusal was encountered
in the deposit at 6 feet.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and gradation analyses. Results of swell-consolidation tests performed on relatively
undisturbed samples of the clay subsoils are shown on Figure 3. The sample taken at 2 feet in
the boring showed a minor expansion potential when wetted under a constant light surcharge.
The sample taken at 4 feet showed a minor collapse potential when wetted under a constant light
surcharge.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist.
FOUNDATION BEARING CONDITIONS
The natural fine-grained soils encountered at the site typically have low bearing capacity and, in
our experience, a low to moderate compressibility, mainly when wetted under loading. Lightly
loaded spread footings placed on the natural fine-grained soils can be used with a risk of
settlement. A low risk of settlement would be to place the footings on the deeper relatively
dense natural granular soils beneath the clay soils or on compacted structural fill. The suitability
of the exposed soils for bearing should be further evaluated at the time of excavation.
Recommendations for a spread footing foundation bearing on the natural soils are presented
below. If recommendations for footings placed on structural fill are desired, we should be
contacted for additional recommendations.
DESIGN RE COMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nafure of
the proposed construction, we recommend the residence be founded with spread footings bearing
on the natural undisturbed soils.
Kumar & Associates, lnc. @ Project No. 24.7-il3
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The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural clay soils should be designed for
an allowable bearing pressure ofl,ilb! Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about I inch or less. Additional post-construction differential settlement could
be around 1 to 2 inches if the bearing soils beneath the foundation become wetted.
Footings placed entirely on the deep coarse granular soils can be designed for an
allowable bearing pressure of 2,500 psf.
2) The footings should have a minimum width of l8 inches for continuous walls and
2 feet for isolated pads.
3) Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement
of foundations at least 36 inches below exterior grade is typically used in this
area. '^\
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of af least 12 feet.
Foundation walls acting as retaining structures should also be designed to resist a
lateral earth pressure corresponding to an equivalent fluid unit weight of at least
55 pcf.
5) Any existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the relatively stiff natural sandy silt
soils. The exposed soils in footing areas should then be moistened and
compacted.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade
construction. To reduce the effects of some differential movement, floor slabs should be
separated from all bearing walls and columns with expansion joints which allow unrestrained
vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. The requirements for joint spacing and slab reinforcement should be established by the
designer based on experience and the intended slab use. A minimum 4-inch layer of road base
gravel should be placed beneath slabs-on-grade to provide support. This material should consist
of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than l2olo
passing the No. 200 sieve.
Kumar & Associates, lnc. @ Project No, 24.7.543
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All fill materials for support of floor slabs should be compacted to at least 95o/o of maxlmum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site clay soils devoid of vegetation, topsoil and oversized rock.
UNDERDRAIN SYSTEM
The proposed shallow crawlspace and slab-on-grade garage should not require and underdrain
system provided that the surface grading recommendations contained in this report are followed.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at
all times after the residence and garage have been completed:
l) Inundation ofthe foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95Yo of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in paved areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area at this time. We make no warranty either express or implied.
The conclusions and recommendations submitted in this report are based upon the data obtained
from the exploratory boring drilled at the location indicated on Figure l, the proposed type of
construction and our experience in the area. Our services do not include determining the
presence, prevention or possibility of mold or other biological contaminants (MOBC) developing
in the future. If the client is concerned about MOBC, then a professional in this special field of
practice should be consulted. Our findings include interpolation and extrapolation of the
subsurface conditions identified at the exploratory boring and variations in the subsurface
conditions may not become evident until excavation is performed. If conditions encountered
during construction appear different from those described in this report, we should be notified so
that re-evaluation of the recommendations may be made.
Kumar & Associates, Inc. @ Project No. 24-7-543
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This report has been prepared for the exclusive use by our client for design purposes. We are
not responsible for technical interpretations by others of our information. As the project evolves,
we should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to veri$ that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
Respectfully Submitted,
Kumar & Assoeiates,
Robert L. Duran, P
Reviewed by:
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Daniel E. Hardin, P.E.
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APPROXIMATE LOCATION
OF PROPOSED HOUSE
APPROXIMATE SITE BOUNDARY
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24-7 -543 Kumar & Associates LOCATION OF TXPLORATORY BORING Fig. 1
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WC=7.4
DD=99
BORING 1 LEGEND
0 16/12
WC=4.5 N
TOPSOIL, ORGANIC SANDY SILTY CLAY, FIRM, SLIGHTLY MOIST,
BROWN.
DD=1 07
LL=23
Pl=10
CLAY (CL), S|LTY, SLTGHTLY SANDY, VERY ST|FF, SLTGHTLY Mo|ST,
LIGHT BROWN, SLIGHTLY CALCAREOUS.
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DENSE,
(GM), COBBLES, AND BOULDERS, SANDY, SILTY, VERY
SLIGHTLY MOIST, LIGHT BROWN, BASALT ROCKS.
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DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
10 DR|VE SAMPLE, 1 3/E-|NCH t.D. SPIT Sp00N STANDARD
PENETRATION TEST.
16712DR|VE SAMPLE BLOW C0UNT. INDICATES THAT 16 8L0WS 0F'-I'- A 14o-POUND HAMMER FALLING 30 INCHES WERE REQUIRED
TO DRIVE THE SAMPLER 12 INCHES.
i PRACTICAL AUGER REFUSAL, WHERE SHOTVN ABOVE BOTTOM OF
BORING, INDICATES THAT MULTIPLE ATTEMPTS WHERE MADE TO
ADVANCE THE HOLE.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON OCTOBER 9,2024
WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
2, THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE
SITE PLAN PROVIDED.
5. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT
MEASURED AND THE LOG OF THE EXPLORATORY BORING IS
PLOTTED TO DEPTH.
4, THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED
ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN
MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE
TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSTTV (pcr) (lSrU D 2216)t
-2OO = PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140);
LL = LIQUID LIMIT (ASTM D A518);
PI = PLASTICITY INDEX (ASTM D 4318).
Kumar & Associates LOG OF EXPLORATORY BORING Fig. 224-7 -543
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SAMPLE OF: Cloy
FROM:Borlngl@2'
WC = 4.5 %, DD = 107 pcf
LL=23,P1=10
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
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SAMPLE OF: Cloy
FROM:Boringl@4'
WC = 7.4 %, DD = 99 pcf
-2OO = 93 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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24-7 -543 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 3