HomeMy WebLinkAboutSoils Report 08.14.2020K+A
Kumar & 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: kaglenwoodgkumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
August 14, 2020
Edgar Cuc
1853 County Road 109
Glenwood Springs, Colorado 81601
valenzcuc�7agmail.com
Project No.20-7-359
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 28, Callicotte
Ranch, Missouri Heights, 1181 Callicotte Ranch Drive, Garfield County,
Colorado
Dear Edgar:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was conducted in accordance with our proposal for geotechnical
engineering services to you dated June 19, 2020. The data obtained and our recommendations
based on the proposed construction and subsurface conditions encountered are presented in this
report.
Proposed Construction: The proposed residence will be a 1 and 2 story structure with an
attached garage located in the area of the site near Pits 1 and 2 shown on Figure 1. Ground floor
will be structural over crawlspace for the living areas and slab -on -grade for the garage. Cut
depths are expected to range between about 2 to 5 feet. Foundation loadings for this type of
construction are assumed to be relatively light and typical of the proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Subsident Potential: Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the
site. These rocks are a sequence of gypsiferous shale, fine-grained sandstone and siltstone with
some massive beds of gypsum and limestone. There is a possibility that massive gypsum
deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of
the gypsum under certain conditions can cause sinkholes to develop and can produce areas of
localized subsidence. During previous work in the area, sinkholes have been observed scattered
throughout the lower Roaring Fork Valley. These sinkholes appear similar to others associated
with the Eagle Valley Evaporite in the area.
Sinkholes were not observed in the immediate area of the subject lot. No evidence of cavities
was encountered in the subsurface materials; however, the exploratory pits were relatively
shallow, for foundation design only. Based on our present knowledge of the subsurface
conditions at the site, it cannot be said for certain that sinkholes will not develop. The risk of
2
future ground subsidence on Lot 28 throughout the service life of the proposed residence, in our
opinion, is low; however, the owner should be made aware of the potential for sinkhole
development. If further investigation of possible cavities in the bedrock below the site is desired,
we should be contacted.
Site Conditions: The subject site was vacant at the time of our field investigation. The ground
surface is variably sloping generally down to the west at grades between 5 and 20 percent.
Vegetation consists of grass, weeds, sage brush and juniper and pinyon trees. Basalt cobbles and
boulders are scattered on the ground surface.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating
2 exploratory pits in the area of the residence and 2 profile pits in the septic area at the
approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The
subsoils encountered, below about 1 to 2 feet of topsoil, consist of medium dense to dense, silty
sandy gravel and basalt rocks with a caliche matrix to the maximum excavated depth of 6. The
soils were similar in both the excavated pits and the profile pits. Results of gradation analyses
performed on samples (minus 3 -inch fraction) obtained from the site are presented on Figures 3
and 4. No free water was observed in the pits at the time of excavation and the soils were
slightly moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory and profile pits and the nature of the proposed construction, we recommend spread
footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of
2,000 psf for support of the proposed residence. The matrix soils can compress after wetting and
there could be some post -construction foundation settlement. Footings should be a minimum
width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils
encountered at the foundation bearing level within the excavation should be removed and the
footing bearing level extended down to the undisturbed natural soils. Exterior footings should be
provided with adequate cover above their bearing elevations for frost protection. Placement of
footings at least 36 inches below the exterior grade is typically used in this area. 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 should be designed to resist a lateral earth pressure based on an equivalent fluid unit
weight of at least 50 pcf for the on-site soil as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly to
moderately 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
Kumar & Associates, Inc. ® Project No. 20-7.359
-3 -
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 less than
50% passing 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 soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: Although free water was not encountered during our exploration, it has
been our experience in the area that local perched groundwater can develop during times of
heavy precipitation or seasonal runoff. Frozen ground during spring runoff can also create a
perched condition. We recommend below -grade construction, such as retaining walls and
crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain
system.
The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above
the invert level with free -draining granular material. The drain should be placed at each level of
excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to
a suitable gravity outlet. Free -draining granular material used in the underdrain system should
contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a
maximum size of 2 inches. The drain gravel backfill should be at least 1'/2 feet deep.
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.
Free -draining wall backfill should be capped with about 2 feet of the on-site, finer
graded soils to reduce surface water infiltration.
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 pavement and walkway 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 the building. Consideration should be given to the use of xeriscape
to limit potential wetting of soils below the foundation caused by irrigation.
Kumar & Associates, Inc. ® Project No. 20-7-359
-4 -
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 pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2, 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 pits 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 at once so 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.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
Kumar & Associates, Inc.
James H. Parsons, E.I.
Reviewed by:
Daniel E. Hardin,
JHP/kac
attachments Figu
Figure
Figure 3 —
ploratory Pits
loratory Pits
ra ion Test Results
Figure 4 — USDA Gradation Test Results
Table 1 — Summary of Laboratory Test Results
Kumar & Associates, Inc. 8
Project No. 20-7-359
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0101.1:6
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r
PIT 2 •
PP -2 PIT 1
❑R
100 0 100 200
APPROXIMATE SCALE -FEET
20-7-359
Kumar & Associates
LOCATION OF EXPLORATORY PITS
Fig. 1
1-
w
w
I
x
1-
a
w
-
- 5
PIT 1
EL. 109.5'
LEGEND
z
PIT 2
EL. 104.5'
WC=12.6
+4=12
-200=53
LL=50
PI=17
PP -1
EL. 100'
PP -2
EL. 101.2'
(GRAVEL=58
SAND=34
SILT=7
CLAY=1
0
WC=4.2 5
TOPSOIL; SAND, SILTY, GRAVELLY, SCATTERED BASALT COBBLES AND BOULDERS, ORGANICS,
SLIGHTLY MOIST, BROWN, FIRM.
GRAVEL (GM); COBBLES, SANDY, SCATTERED BOULDERS, SILTY, CALICHE MATRIX, MEDIUM
DENSE TO DENSE, SLIGHTLY MOIST, PALE GRAY TAN.
HAND DRIVE SAMPLE.
II DISTURBED BULK SAMPLE.
4 PRACTICAL REFUSAL TO EXCAVATION.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED ON JULY 10, 2020 WITH A TRACKED
MINI -EXCAVATOR.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO
PROFILE PIT 1 AS 100', ASSUMED.
4. THE EXPLORATORY PIT 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 PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF DRILLING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140);
LL = LIQUID LIMIT (ASTM D4318);
PI = PLASTICITY INDEX (ASTM D4318);
GRAVEL = PERCENT RETAINED ON NO. 10 SIEVE;
SAND = PERCENT PASSING NO. 10 SIEVE AND RETAINED ON NO. 325 SIEVE;
SILT = PERCENT PASSING NO. 325 SIEVE TO PARTICLE SIZE .002MM;
CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002MM.
1-
w
w
x
w
20-7-359
Kumar & Associates
LOGS OF EXPLORATORY PITS
Fig. 2
HYDROMETER ANALYSIS
SIEVE ANALYSIS
TINE READINGS
24 HRS 7 HRS
46 DIN f 1141. 1iM0
U
1100
5. STANDARD SERIES
110 0
.
8 &9
!1 �4
CLEAR SQUARE OPENINGS
_Mr 3/1 1 1�"
S 6' 8"o
100
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1
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1
ILL
1
10
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60
3
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40
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60 •
40
1
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1
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1
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30
1
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1
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70
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1
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80
20
1
1
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10
1—
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3
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'1
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11J1
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—
100
o '`1-1 1-1 "1"" I
.901 ,001'. .005. .06E .019
I—L V 3=. 1 1 r 1 =u_
.037 .075 .150 .305 .4r28 .600
DIAMETER OF PARTICLES
3.1 ri TTY 1 JT1...
1. 8 2102.36 4,75 1.5 111 56.1 78,5 127152
IN MILLIMETERS
200
SAND
GRAVEL
COBBLES
CLAY TO SILT f
FINE MEDIUM COARSE
FINE COARSE
GRAVEL 12 % SAND 35 % SILT AND CLAY 53 %
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Gravelly Sandy Silt Matrix FROM: Boring 2 0 2.5'-3.5'
These test results apply only to the
samples which wilt* /Wad. Tho
tsstlnq tvport eh0fi n01 Ee repproduced,
except In full, wlih0 1 the wrlHan
opprcval of Y.unlar R *1.00101.1. Inc.
Slave anelysie fastingg 11 pertcrmed In
eocerdonce with ASTM D6913, ASTM D7928,
ASTM C136 and/or ASTM D1140.
• 20-7-359
Kumar & Associates
GRADATION TEST RESULTS
Fig. 3
HYDROMETER ANALYSIS
SIEVE ANALYSIS
24
,15
TIME READINGS
HR. 7 HR 1 MIN.
IN 1S1 N, 60MIN 19MIN. 4MIN. #325
U.S. STANDARD SERIES i CLEAR SQUARE OPENINGS
#140 #60 #35 #18 #10 #4 3/6" 3/4" 11/2"
3" 5"6' 6'
iiimmEmirmomm
3 N Ut O) 0 0 0
O O
0
0 O O O O O C
PERCENT PASSING
PERCENT RETAINED
J t0 m J 0) 01 W N
J O
CI 1 III°
IO III! 1°111 1° IO - O I 1°111
MI
M
=
.-_.!1"I_i-M
--
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.001 .002 .005 .009 .019 .045 .106 .025 .500 1.00 2.00 4.75 9 5 19.0 37.5 76.2 152 203
DIAMETER OF PARTICLES IN MILLIMETERS
•
SILT
SAND CRAWL
V. FINE 1 FINE 1 MEnIUM 1 coAVSE Iv. CORx0E SAW.1. 1 AEIMJM 1 LAME
COBBLES
GRAVEL 58 % SAND 34 % SILT 7 % CLAY 1 %
USDA SOIL TYPE: Very Gravelly Sand FROM: Profile Pit 2 @ 4' to 6'
20-7-359
Kumar & Associates
USDA GRADATION TEST RESULTS
Fig. 4
K+A
Kumar & Associates, Inc.®
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Proiect No. 20-7-359
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)
Atterberg Limits
GRADATION
USDA SOIL TEXTURE SOIL TYPE
PIT
DEPTH
(ft)
Liquid
Limit
(%)
Plastic
Index
(%)
GRAVEL
(%)
SAND
(%)
SILT&CLAY
(%)
GRAVEL
(%)
SAND
(%)
SILT
(%)
CLAY
(%)
Pit 2
23 Viz°
12.6
50
17
12
35 53
Gravelly Sandy Silt
Profile
Pit 2
4 to 6
4.2
58
34
7
1
Very Gravelly Sandy
r
I