HomeMy WebLinkAboutSoils Report 04.02.2019K� A
Kumar & Associates, Inc.
Geotechnical and Materials Engineers
and Environmental Scientists
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
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RECEIVED30
MAY 08 2019
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 9, SUN MEADOW ESTATES
NORTH MEADOW DRIVE
GARFIELD COUNTY, COLORADO
PROJECT NO. 19-7-180
APRIL 2, 2019
PREPARED FOR:
JAMES MARTINEZ
1055 COUNTY ROAD 255
RIFLE, COLORADO 81650
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 1 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 2 -
FOUNDATION BEARING CONDITIONS - 2 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FLOOR SLABS - 4 -
SURFACE DRAINAGE - 4 -
LIMITATIONS - 5 -
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 - SWELL -CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
Kumar & Associates, Inc. Project No. 19-7-180
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located on Lot 9,
Sun Meadow Estates, North Meadow 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 proposal for geotechnical
engineering services to James Martinez dated March 7, 2019.
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 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 on a thickened slab foundation. Grading
for the structure is assumed to be relatively minor with cut depths between about 2 to 4 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 lot is vacant and the ground surface appears mostly natural. The terrain is relatively flat
with a gentle slope down to the south. Vegetation consists of grass and weeds. The surrounding
lots have one- to two-story single-family residences. North Meadow Drive is to the east and
Antonelli Lane is to the south. The center of the building site was staked where the exploratory
boring was drilled as shown on Figure 1.
Kumar & Associates, Inc. Project No. 19-7-180
2
FIELD EXPLORATION
The field exploration for the project was conducted on March 25, 2019. One exploratory boring
was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring
was advanced with 4 -inch diameter continuous flight augers powered by a truck -mounted CME -
45B drill rig. The boring was logged by a representative of Kumar & Associates.
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 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 consist of about 1 foot of topsoil overlying 9 feet of very stiff silt and clay underlain by
medium dense silty sand with scattered gravel.
Laboratory testing performed on samples obtained from the boring included natural moisture
content, density, and percent fines (passing the number 200 sieve). Results of swell -
consolidation testing performed on relatively undisturbed drive samples of the silt and clay,
presented on Figure 3, indicate low compressibility under conditions of loading and minor
expansion upon wetting under constant load. The laboratory testing is summarized in Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist.
FOUNDATION BEARING CONDITIONS
'Iiie silt and clay soils showed a slight expansion potential.
Spread footings bearing on the
natural soils appear feasible for foundation support with some risk of movement and distress.
Kumar & Associates, Inc. Project No. 19.7-180
3
The risk of movement is primarily if the bearing soils were to become wetted and precautions
should be taken to prevent wetting. Removal and replacement of a depth of the natural soils
(typically 3 to 4 feet) in a moistened and compacted condition below the footings could be done
to reduce the risk of foundation movement and building distress. The expansion potential of the
subgrade should be further evaluated for possible mitigation measures at the time of excavation.
Use of a relatively deep foundation system, such as drilled piers or helical piers, that extend
down to below anticipated wetting depth or into less compressible soils would provide a
relatively low risk of foundation movement. Provided below are recommendations for spread
footings bearing on the natural soils. If recommendations for spread footings bearing on a depth
of compacted structural fill, drilled piers or helical piers are desired, we should be contacted.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction
, the building can be founded with spread footings bearing on the
natural soils with a risk of movement and distress.
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 1,500 psf.
Based on experience, we expect initial
settlement of footings designed and constructed as discussed in this section will
be about 1 inch or less. The magnitude of the additional movement would depend
on the depth and extent of the wetting but may be on the order of 1 to 11/2 inches.
2) The footings should have a minimum width of 16 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
unless protected against frost by insulation extending down and out from the
perimeter of the heated structure.
Kumar & Associates, Inc. Project No. 19-7-180
The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab -on -grade
4
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 12 feet.
Foundation walls acting as retaining structures (if any) should also be designed to
resist lateral earth pressures of at least 55 pcf equivalent fluid unit weight.
5) The topsoil and any loose or disturbed soils should be removed and the footing
bearing level extended down to the firm 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
construction.
To reduce the effects of some differential movement, non-structural 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 relatively well graded sand and gravel such as road base should be placed beneath
interior slabs for support. This material should consist of minus 2 inch aggregate with at least
50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site soils devoid of vegetation and topsoil or imported granular soils.
SURFACE DRAINAGE
Development of proper surface grading and drainage will be critical to keeping the bearing soils
dry and limiting building movement and distress. 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.
Kumar & Associates, Inc. Project No. 19.7-180
5
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.
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. Consideration should be given to use of xeriscape to
limit potential wetting of soils below the building from landscape irrigation.
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 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 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.
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
Kumar & Associates, Inc. Project No. 19.7.180
6
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.
Shane J. Robat, P.E.
Project Manager
Reviewed by:
Steven L. Pawlak, P.
SJR/kac
Kumar & Associates, Inc. Project No. 19-7.180
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APPROXIMATE SCALE—FEET
ANTONELLI LANE
Kumar & Associates
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VICINITY MAP
NOT TO SCALE
LOCATION OF EXPLORATORY BORING
Fig. 1
DEPTH-FEET
-
-- 5
— 10
•— 15
BORING 1
30/12
WC=5.6
DD=113
/ /
.-117 12
WC=6.1
•
DD=96
/ —200=58
22/12
WC=4.6
DD=112
—200=44
50/12
WC=3.5
DD=123
• —200=17
LEGEND
7
/
TOPSOIL; ORGANIC, SILTY, CLAYEY, SAND, FIRM, MOIST,
BROWN,
SILT AND CLAY (ML—CL); SANDY, VERY STIFF, SLIGHTLY
MOIST, BROWN.
SAND (SM); SILTY TO VERY SILTY, SOME SANDSTONE GRAVEL,
MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, TAN.
DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE.
30/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 30 BLOWS OF
A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED
TO DRIVE THE SAMPLER 12 INCHES.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON MARCH 25, 2019
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.
3. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED
20 f 24/12 ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD
r USED.
] WC=5.1
:. DD=113 4. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES
BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE
— GRADUAL. G
— 25:' S. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE
____ t 16/12
6. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
— —200 = PERCENTAGE PASSING N0. 200 SIEVE (ASTM D 1140).
TIME OF DRILLING.
30
35
19-7-180
19/12
Kumar & Associates
LOG OF EXPLORATORY BORING
Fig. 2
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
2
1
— 2
1
0
— 1
— 2
— 3
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SAMPLE OF: Sandy Silty Clay
FROM: Boring 1 2.5'
WC = 5.6 %, DD = 113 pcf
• EXPANSION UNDER CONSTANT
1 PRESSURE UPON WETTING
rpm
1.0 APPLIED PRESSURE - KSF
10 100
SAMPLE OF: Very Silty Clayey Sand
FROM: Boring 1 ® 20'
WC = 5.1 %, DD = 113 pcf
•
I I 1''
r
--;_.I_I_ 1
EXPANSION UNDER CONSTANT
`I
I i PRESSURE UPON WETTING
1.0 APPLIED PRESSURE — KSF
19-7-180 Kumar & Associates
10 100
SWELL -CONSOLIDATION TEST RESULTS
Geotechnical and Materials Engineers
and Environmental Scientists
Xumarusa.com
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 19-7.180
GRADATION
SAMPLE LOCATIONNATURAL
ATTERBERG LIMITS
UNCONFINED
!
BORING
DEPTH
(ft)
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITYC1°))
_ (Pci)
GRAVEL
SAND
PERCENT
P
200 SIEVE
mimic
LIQUID LIMB INDEX
(%1 , I%)
COMPRESSIVE
STRENGTH
(Psf)
SOIL TYPE
1
2'/2
5.6
113
Sandy Silty Clay
5
6.1
96
58
Very Sandy Silt and Clay
10
4.6
112
44
Very Silty Clayey Sand
15
3.5
123
17
Silty Sand
20
5.1
113
Very Silty Clayey Sand