HomeMy WebLinkAboutSoils Report 09.22.2020Kumar & Associates, Inc.®
Geotechnical and Materials Engineers
and Environmental Scientists
An Employee Owned Company
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED STEEL BUILDING
1001 BRUCE ROAD
NEW CASTLE, COLORADO
PROJECT NO. 20-7-396
SEPTEMBER 22, 2020
PREPARED FOR:
TATE FAIRBANKS
P.O. BOX 2251
GLENWOOD SPRINGS, COLORADO 81602
(tate(a tatecivil.com)
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 1 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 2 -
FOUNDATION BEARING CONDITIONS - 3 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FLOOR SLABS - 4 -
UNDERDRAIN SYSTEM - 4 -
SURFACE DRAINAGE - 5 -
LIMITATIONS - 5 -
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOG OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURE 4 - GRADATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
Kumar & Associates, Inc. ° Project No. 20-7-396
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed steel building to be located at
1001 Bruce Road, New Castle, 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 Tate Fairbanks dated
July 16, 2020.
A field exploration program consisting of exploratory borings was conducted to obtain
information on the subsurface conditions. Samples of the subsoils and bedrock obtained during
the field exploration were tested in the laboratory to determine their classification 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 building will be a tall single story steel frame structure with a footprint of 50 by
120 feet. Ground floor will be slab -on -grade. Grading for the structure is assumed to be
relatively minor with cut depths between about 1 to 3 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 subject site was vacant at the time of our field exploration. It appeared to have been used as
a material borrow area in the past. The ground surface was graded into benches generally
sloping down to the south. Elevation difference across the proposed building areas was
estimated at 8 to 10 feet. Vegetation consisted of sagebrush, grass and weeds with scattered
deciduous trees outside of the proposed building area. The trees within the building area had
been removed prior to our exploration.
Kumar & Associates, Inc. ° Project No. 20-7-396
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FIELD EXPLORATION
The field exploration for the project was conducted on July 20, 2020. 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 1% 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.
The penetration resistance values are an indication of the relative density or consistency of the
subsoils and hardness of the bedrock. 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 in Boring 1 consisted of 61/2 feet of dense, silty gravelly sand with cobbles. Refusal to
drilling was encountered at 61/2 feet. The subsoils in Boring 2 consist of dense, clayey sand and
gravel, down to 7 feet underlain by medium dense to dense clayey sandy gravel down to
161/2 feet where hard claystone bedrock was encountered to the maximum explored depth of
21 feet.
Laboratory testing performed on samples obtained from the borings included natural moisture
content. Results of gradation analyses performed on small diameter drive samples (minus
11/2-inch fraction) of the coarse granular subsoils are shown on Figure 4. The laboratory testing
is summarized in Table 1.
Free water was encountered in Boring 2 at a depth of 13 feet, 4 inches at the time of drilling and
the subsoils were slightly moist to wet.
Kumar & Associates, Inc. ° Project No. 20-7-396
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FOUNDATION BEARING CONDITIONS
The upper sand and gravel and underlying clayey gravel soils encountered at the site possess a
moderate bearing capacity and typically low settlement potential. The claystone bedrock
encountered at the site possesses a moderate to high bearing capacity and may possibly have
variable low to moderate swell potential when wetted. Spread footings bearing on the natural
granular soils encountered at the site should be feasible for support of the proposed construction
with a low risk of movement.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, we recommend the building be founded with spread footings bearing
on the natural granular soils.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural granular soils should be designed for
an allowable bearing pressure of 3,000 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about 1 inch or less.
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.
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 10 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 45 pcf.
Kumar & Associates, Inc. ° Project No. 20-7-396
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5) All topsoil and any loose or disturbed soils should be removed and he footing
bearing level extended down to the relatively dense natural granular soils. The
exposed soils in footing area should then be moistened and compacted. If water
seepage is encountered, the footing areas should be dewatered before concrete
placement.
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 or organic root zones, 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 free -draining gravel should be placed beneath basement level slabs to facilitate drainage.
This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4
sieve and less than 2% 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 granular soils devoid of vegetation, topsoil and oversized (plus 5-inch) rock.
UNDERDRAIN SYSTEM
It is our understanding the proposed finished floor elevation will be at or above the surrounding
grade. Therefore, a foundation drain system is not required.
If the finished floor elevation of the proposed structure is revised to have 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.
Kumar & Associates, Inc. ° Project No. 20-7-396
-5
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the building 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 6 inches in the first 10 feet in unpaved areas and a minimum slope of
21/2 inches in the first 10 feet in paved areas. Free -draining wall backfill should be
capped with about 2 feet of the on -site soils to reduce surface water infiltration.
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 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.
Kumar & Associates, Inc. ® Project No. 20-7-396
6
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:
Daniel E. Hardin,
JHP/kac
Kumar & Associates, Inc. ® Project No. 20-7-396
20-7-396
Kumar & Associates
1-70
VICINITY MAP
NOT TO SCALE
LOCATION OF EXPLORATORY BORINGS
Fig. 1
BORING 1
EL. 100'
BORING 2
EL. 97'
DEPTH -FEET
0
5
10
15
20
76/12
WC=2.3
+4=20
—200=13
50/0
66/12
WC=2.4
+4=40
—200=20
56/12
13/12
WC=6.5
—200=20
50/2
50/2
0
5
10
15
20
25 25
DEPTH -FEET
20-7-396
Kumar & Associates
LOG OF EXPLORATORY BORINGS
Fig. 2
LEGEND
GRAVEL (GM); SANDY, WITH COBBLES, SILTY, DENSE, SLIGHTLY MOIST, BROWN.
GRAVEL AND SAND (GC -SC); CLAYEY WITH COBBLES, DENSE, SLIGHTLY MOIST, MIXED
BROWN.
GRAVEL (GC); SANDY, CLAYEY WITH COBBLES, DENSE TO MEDIUM DENSE, MOIST TO WET,
MIXED BROWN.
CLAYSTONE BEDROCK, HARD, SLIGHTLY MOIST, GRAY -BROWN.
DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
DRIVE SAMPLE, 1 3/8-INCH I.D. SPLIT SPOON STANDARD PENETRATION TEST.
31 /6 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 31 BLOWS OF A 140-POUND HAMMER
FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 6 INCHES.
Q DEPTH TO WATER LEVEL ENCOUNTERED AT THE TIME OF DRILLING.
DEPTH AT WHICH BORING CAVED FOLLOWING DRILLING.
t PRACTICAL AUGER REFUSAL.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON JULY 20, 2020 WITH A 4-INCH-DIAMETER
CONTINUOUS -FLIGHT POWER AUGER.
2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING
FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL AND REFER
TO THE GROUND AT BORING 1 AS ELEV. = 100.0 FEET, ASSUMED.
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 LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER
CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D6913);
-200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D1140).
20-7-396
Kumar & Associates
LEGEND AND NOTES
Fig. 3
I
PERCENT PASSING
A., W A U J 00 10 O
.00 O O O O O O O O O O
HYDROMETER ANALYSIS
SIEVE ANALYSIS
O+ 0 0 V N A W 01 00
O O O alO O O O O
O
PERCENT RETAINED
TIME READINGS
24 HRS 7 HRS
45 MIN 15 MIN 60MIN 19MIN 4MIN 1MIN #200
U.S. STANDARD SERIES
/100 #50 #40 #30 #
6 #1? #8
#4
CLEAR SQUARE OPENINGS
3/8" 3/4" 1 1 2" 3" 51"6" 8
I
I
1
I
I
1
1
I
I
I
I
1
I
I
1
I
1
I
I
1
I
I
I
1
I
I
1
1
I
I
1
I
1
I
1
I
I
1
I
1
I
I
1
I
1
I
I
I
I
I
1
I
I
1
I
I
1
.002
I I
.005
1 1 11
.009 .019
111 1 1 1
.037 .075
DIAMETER
1 1 1
.150
I
.300
OF PARTICLES
IIIIIII
1 .600
.425
1.
IN
1
8 1 2.36
2.0
MILLIMETERS
11
4.75
1 1 1 1 1
9
1
5 19
111 1 1 1
38.1 76.2
1 1 11
127
152
200
SAND
GRAVEL
CLAY TO SILT
FINE MEDIUM COARSE
FINE COARSE
COBBLES
GRAVEL 20 %
LIQUID LIMIT
SAMPLE OF: Gravelly Silty Sand
SAND 67 % SILT
PLASTICITY INDEX
FROM:
AND CLAY 13 %
Boring 1 0 2.5'
pPERCENT PASSING
O O O O O O O O O O O O
HYDROMETER ANALYSIS
SIEVE ANALYSIS
24 HRS
45 MIN
TIME READINGS
7 HRS
15 MIN 6OMIN 19MIN 4MIN 1MIN p200
U.S. STANDARD SERIES
#100 50 #40 30 16 #10
/8 p4
CLEAR SQUARE OPENINGS
3/8" 3 4" 1 1 2" 3" 5"6" 8"0
10
20
30
40
50 W
F
60
70
80
90
.002
I I
.005
1 1 1
.009
1
.019
I I
.037
1 1 1 1
.075
DIAMETER
1 1 1
.150
I
.300
OF PARTICLES
1 1 1 1 1 1 1 I 1 1 1 1 1
.600 1.18 2.36 4.75 9
425 2.0
IN MILLIMETERS
1
5 19
I I 1 1 1 1
38.1 76.2
1 1 1 1
127
152
100
200
SAND
GRAVEL
CLAY TO SILT
FINE MEDIUM COARSE
FINE COARSE
COBBLES
GRAVEL 40 % SAND 40 % SILT AND CLAY 20 %
LIQUID LIMIT PLASTICITY INDEX
These test results apply only to the
SAMPLE OF: Clayey Sand and Gravel FROM: Boring 2 0 2.5' samples which were tested. The
testing report shall not be reproduced,
except in full, without the written
approval of Kumar & Associates, Inc.
Sieve analysis testing is performed in
accordance with ASTM D6913, ASTM D7928,
ASTM C136 and/or ASTM D1140.
20-7-396
Kumar & Associates
GRADATION TEST RESULTS
Fig. 4
I(+A
Kumar & Associates, Inc®
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 20-7-396
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITY
(pcf)
GRADATION
PERCENT
PASSING 200 SIEVE
ATTERBERG LIMITS
UNCONFINED
COMPRESSIVE
STRENGTH
(psf)
SOIL TYPE
BORING
DEPTH
(ft)
GRAVEL
(%)
SAND
(%)
LIQUID LIMIT
(%)
PLASTIC
INDEX
(%)
1
2Y2
2.3
20
67
13
Gravelly Silty Sand
2
21A
2.4
40
40
20
Clayey Sand and Gravel
10
6.5
20
Clayey Sand and Gravel