HomeMy WebLinkAboutSoils Report 05.17.2019Geotechnical and Materials Engineers
and Environmental Scientists
An Empla yool Owned Company
5020 County Road 154
iilenwood Springs, CO 81601
phone: (970) 945-7988
tax: (970) 945-8454
email: kaglenwood@kumarusa.eom
,vww.kurnarusa.com
Office Locutions: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
RECEIVED
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 29, SUN MEADOW ESTATES
SOUTH MEADOW CIRCLE
GARFIELD COUNTY, COLORADO
PROJECT NO. 19-7-258
MAY 17, 2019
PREPARED FOR:
JUAN CARDENAS
27653 HIGHWAY 6, #609
RIFLE, COLORADO 81650
{Itarreoli29Agna ai i.co m)
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 2 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 2 -
FOUNDATION BEARING CONDITIONS - 3 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FLOOR SLABS - 4 -
UNDERDRAIN SYSTEM - 5 -
SURFACE DRAINAGE - 5 -
LIMITATIONS - 5 -
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURES 4 and 5 - SWELL -CONSOLIDATION TEST RESULTS
TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS
Kumar & Associates, Inc. `' Project No.19-7-258
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located on Lot
29, Sun Meadow Estates, South Meadow Circle, 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 Juan Cardenas dated April 24, 2019. Hepworth-Pawlak Geotechnical
Inc., now Kumar and Associates, previously performed a preliminary geotechnical study for Sun
Meadow Estates (formerly Mamms View Subdivision) and presented our findings in -a report
dated March 28, 2000, Job No. 100 169.
A field exploration program consisting of exploratory borings was conducted 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 or
swell 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
encountered.
PROPOSED CONSTRUCTION
The proposed residence will be a one story structure with attached garage. Ground floor will be
slab -on -grade. Grading for the structure is assumed to be relatively minor with cut depths
between about 2 to 6 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.
Kumar & Associates, Inc. '° Project No. 19.7-258
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SITE CONDITIONS
The subject site was vacant at the time of our field exploration. The ground surface is
moderately sloping down to the west. Elevation difference across the assumed building area is
about 4 feet. Vegetation consists of grass and weeds.
FIELD EXPLORATION
The field exploration for the project was conducted on May 2, 2019. Two exploratory borings
were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. The
borings were advanced with 4 inch diameter continuous flight augers powered by a truck -
mounted CME-45B drill rig. The borings were logged by a representative of Kumar &
Associates, Inc.
Samples of the subsoils were taken with a 2 inch I.D. spoon sampler. The sampler was 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. 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 Logs of Exploratory Borings, Figure 2. The samples were returned to our
laboratory for review by the project engineer and testing.
SUBSURFACE CONDITIONS
Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The
subsoils consist of about % foot of topsoil overlying very stiff, sandy clay and silt, underlain at a
depth of 7 feet by loose to medium dense, silty to very silty sand down to the maximum depth
explored, 31 feet.
Laboratory testing performed on samples obtained from the borings included natural moisture
content and density and finer than sand grain size gradation analyses. Results of swell -
consolidation testing performed on relatively undisturbed drive samples, presented on Figures 4
and 5, indicate low compressibility under light loading and a low to moderate expansion
potential when wetted. The samples were moderately compressible under increased loading after
wetting. The laboratory testing is summarized in Table 1.
Kumar & Associates, Inc. `` Project No,19-7-258
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No free water was encountered in the borings at the time of drilling and the subsoils were
slightly moist to very moist at depth.
FOUNDATION BEARING CONDITIONS
The upper clay soils at the site possess generally low bearing capacity and low to moderate
expansion potential when wetted. The clay soils were only encountered to a depth of 7 feet.
Spread footings bearing on the natural soils can be used for foundation support provided some
risk of movement and distress is acceptable. There is some risk of movement primarily if the
bearing soils were to become wetted and precautions should be taken to prevent wetting. The
swell potential of the exposed soils should be further evaluated during excavation and prior to
the placement of concrete.
Providing 3 feet of structural fill below the footings or use of a helical pier type deep foundation
would provide a lower risk of foundation movement. Provided below are recommendations for
footings bearing on the natural clay soils. If recommendations for bearing on structural fill or for
a helical pier type foundation system are desired, we should be contacted.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, the residence can be founded with spread footings bearing on the
natural soils with some risk of movement. The risk of movement is primarily if wetting of the
bearing soils were to occur and precautions should be taken to prevent wetting.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural soils should be designed for an
allowable bearing pressure of 2,000 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about 1 inch or less. There could be additional differential movement of about
'/2 inch if the bearing soils become wetted depending on the depth and extent of
the wetting.
Kumar & Associates, Inc. 0 Project No. 19-7-258
4
2) The footings should have a minimum width of 18 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 and better withstand the effects of some differential movement such as
by assuming an unsupported length of at least 14 feet. Foundation walls acting as
retaining structures (if any) should also be designed to resist a lateral earth
pressure corresponding to an equivalent fluid unit weight of at least 55 pcf.
5) Topsoil and any loose disturbed soils should be removed and the footing bearing
level extended down to the natural soils. The exposed soils in footing area 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 clay soils are expansive when wetted. We recommend at least 3 feet of
imported 3/-inch road base be placed below slabs -on -grade. The fill should be compacted to at
least 95% of the maximum standard Proctor density at a moisture content near optimum. 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.
FLOOR SLABS — VAPOR RETARDERS
We recommend vapor retarders conform to at least the minimum requirements of ASTM E1745
Class C material. Certain floor types are more sensitive to water vapor transmission than others.
For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor
transmission are utilized, we recommenda vapor barrier be utilized conforming to the minimum
Kumar & Associates, Inc. Project No.19.7-258
5
requirements of ASTM E1745 Class A material. The vapor retarder should be installed in
accordance with the manufacturers' recommendations and ASTM E1643.
UNDERDRAIN SYSTEM
It is our understanding the finished floor elevation at the lowest level. is at or above the
surrounding grade. Therefore, a foundation drain system is not required.
If the finished floor elevation of the proposed structure has a floor level below the surrounding
grade, we should be contacted to provide recommendations for an underdrain system.
All earth
retaining structures should be properly drained.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the residence has been completed:
1) Inundation of the 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 95% 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. Free -draining wall backfill (if any)
should be capped with about 2 feet of the on -site soils and covered with filter
fabric to reduce surface water infiltration.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least 10
feet from foundation walls.
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.
Kumar & Associates, Inc. ' Project No.19-7.258
6
The conclusions and recommendations submitted in this report are based upon the data obtained
from the exploratory borings drilled at the locations indicated on Figure 1, 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 borings 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.
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 verify 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 & Associates, Inc.
James H. Parsons, E.I.
Reviewed by:
c„,„,
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Daniel E. Hardin, P.E. - 24.44
JHP/kac <, �o '
cc: Luis Arreola (arreola2O i :� " •
Kumar & Associates, inc. Project No. 19-7-258
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LOT 28
SOUTH MEADOW CIR
Kumar & Associates
LOCATION OF EXPLORATORY BORINGS
Fig. 1
0
5
10
--- 15
20
25
30
- 35
BORING 1
EL. 5442'
33/12
'72] 23/12
/ WC=5.5
DD=113
15/12
WC=4.4
DD=107
-200=55
10/12
9/12
10/12
BORING 2
EL. 5440.5'
0
32/12
WC=6.6
DD=114
/
' �] 27/12
/ WC=6.1
DD=117
-200=81
2112
WC 3.8
DD=108
20/12
WC=3.5
DD=107
-200=43
5
10 -
15-
20
25
30 -
35
-40 40
19-7-258
Kumar & Associates
LOGS OF EXPLORATORY BORINGS
Fig. 2
LEGEND
iftr
TOPSOIL; SILT AND CLAY, ORGANIC, SANDY, FIRM, MOIST, BROWN.
CLAY AND SILT (CL—ML): SANDY, VERY STIFF, SLIGHTLY CALCAREOUS, SLIGHTLY MOIST,
BROWN TO LIGHT BROWN.
SAND (SM); SILTY TO VERY SILTY, SANDY SILT LAYERS, MEDIUM DENSE TO LOOSE/STIFF TO
MEDIUM STIFF, SLIGHTLY MOIST TO WET WITH DEPTH, BROWN.
DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE.
33
/ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 33 BLOWS OF A 140—POUND HAMMER
12 FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES.
DEPTH AT WHICH BORING CAVED.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON MAY 2, 2019 WITH A 4—INCH—DIAMETER
CONTINUOUS —FLIGHT POWER AUGER.
2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY TAPING
FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4, THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE
ONLY TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D2216);
DD = DRY DENSITY (pc€) (ASTM D2216);
—200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D1140).
19-7-258 L Kumar & Associates
LEGEND AND NOTES
Fig. 3
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
2
1
—1
—2
— 3
— 4
2
1
0
— 1
— 2
SAMPLE OF: Sandy Clay and Silt
FROM: Boring 1 ® 5'
WC = 5.5 %, DD = 113 pcf
1.0 APPUED PRESSURE - KSF
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Cov on:Pepcn lnter. performed In
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EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
10 100
SAMPLE OF: Sandy Clay and Silt
FROM: Boring 2 ® 2.5'
WC = 6.6 %, DD = 114 pcf
EXPANSION UNDER CONSTANT
1.0 APPLIED PRESSURE - KSF 10
PRESSURE UPON WETTING
100
19-7-258
Kumar & Associates
SWELL —CONSOLIDATION TEST RESULTS
Fig. 4
.. 0
CONSOLIDATION - SWELL
—2
—3
—4
row INt mum cp{y e.y In the
,_.I s..led. Yn. ..lino rebel
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wIw end M.xNU'. loc. 5.1
Co+.vtldvi1v* IH9iq perform. In
xCar4onC. with 115fl 0-6y16.
SAMPLE OF: Silty Sand
FROM: Boring 2 CO 10'
WC = 3.8 %, DD = 108 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
1.0 APPUEO PRESSURE — KSF 10 100
19-7-258 Kumar & Associates ] SWELL -CONSOLIDATION TEST RESULT Fig. 5
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Proiect No. 19-7-258
SAMPLE LOCATION
NATURAL
NATURAL GRADATION
ATTERBERG LIMITS
UNCONFINED
COMPRESSIVE
STRENGTH
(PO
SOIL TYPE
BORING
DEPTH
(ftl
MOISTURE
CONTENT
(%)
DRY GRAVEL
DENSITY
(%)
Oa)
SAND
(%)
PERCENT
PASSING NO.
200 SIEVE
PLASTIC
LIQUID LIMIT INDEX
(`A) (%)
1
5
5.5
113
Sandy Clay and Silt
10
4.4
107
55
Silty Sand
2
21
6.6
114
Sandy Clay and Silt
5
6.1
117
81
Sandy Clay and Silt
10
3.8 108
Silty Sand
15
3.5 107
43
Silty Sand