HomeMy WebLinkAboutSoils Report 05.31.2017H-PtiKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED GARAGE
3627 COUNTY ROAD 100
GARFIELD COUNTY, COLORADO
PROJECT NO. 17-7-413
MAY 31, 2017
PREPARED FOR:
JIM FUNSTEN
3627 COUNTY ROAD 100
CARBONDALE, COLORADO 81623
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - I -
SITE CONDITIONS - 7 _
SUBSIDENCE POTENTIAL - 2 -
FIELD EXPLORATION . 2
SUBSURFACE CONDITIONS - 3 -
DESIGN RECOMMENDATIONS - 3 -
NEW FOUNDATIONS - 3 -
FLOORSLABS _4-
UNDERDRAIN SYSTEM - 5 -
SURFACE DRAINAGE - 5 -
LIMITATIONS _ 6 -
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURES 4, 5 AND 6 - SWELL -CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
H-P-KUMAR
Project No. 17-7-413
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed garage, to be located at 3627
County Road 100, 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 Jim Funsten
dated May 19, 2017.
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 garage will be a tall one story steel frame and metal sided structure with slab -on -
grade floor. Grading for the structure is assumed to be relatively minor with cut depths between
about 2 to 3 feet. It is planned to use the existing foundation of a previous shop structure (which
has been removed) for support of the new garage. A new foundation will be placed just south of
the existing foundation as the new building is somewhat larger than the previous building. We
understand the existing, continuous foundation footings are 2 feet wide. The new interior slab
will have a 12 -inch thickened edge placed on top of the concrete stem wall. The slab will
generally be 6 inches thick. We assume relatively light foundation loadings, typical of the
proposed type of construction.
H-P%KUMAR
Project No. 17-7-413
-2 -
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
There is an existing foundation at the building site. An excavation has been made for the new,
southern part of the building. The excavation was about 2 feet below the surrounding terrain and
the bottom was roughly the same elevation as the existing footings. Vegetation in the building
area consists of grass and weeds. The ground surface is relatively flat and slopes down to the
south at a grade of about 3 percent. Irrigation ditches are located north and east of the building
site.
SUBSIDENCE POTENTIAL
Bedrock of the Pennsylvanian Age Eagle Valley Evaporite underlies the lower Roaring Fork
Valley. These rocks are a sequence of gypsiferious shale, fine-grained sandstone/siltstone and
limestone with some massive beds of gypsum. There is a possibility that massive.gypsum
deposits associated with the Eagle Valley Evaoprite underlie portions of the property.
Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can
produce areas of Iocalized subsidence. During previous work in the lower Roaring Fork Valley,
several broad subsidence areas and sinkholes have been observed. These sinkholes appear
similar to others associated with the Eagle Valley Evaporite in areas of the Roaring Fork Valley.
No evidence of subsidence or sinkholes were observed on the property or encountered in the
subsurface materials, however, the exploratory borings were relatively shallow, for foundation
design only. Based on our present knowledge of the subsurface conditions at the site, it can not
be said for certain that sinkholes will not develop. The risk of future ground subsidence at the
site throughout the service life of the structure, in our opinion is low, however the owner should
be aware of the potentia! for sinkhole development. If further investigation of possible cavities
in the bedrock below the site is desired, we should be contacted.
FIELD EXPLORATION
The field exploration for the project was conducted on May 22, 2017. Three exploratory borings
were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. The
H-P4KUMAR
Project No. 17-7-413
-3 -
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 H-P/Kumar
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. 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 below up to 6 inches of topsoil consist of 8 to 12 feet of soft to medium stiff sandy silty
clay overlying silty sandy gravel with cobbles and boulders at a depth of 8 to 12 feet down to the
maximum depth explored, 20 feet.
Laboratory testing performed on samples obtained from the borings included natural moisture
content, density and gradation analyses. Results of swell -consolidation testing performed on
relatively undisturbed drive samples, presented on Figures 4 to 8, indicate moderate
compressibility undcr conditions of loading and wetting. Results of gradation analyses are
shown on Figure 9. The laboratory testing is summarized in Table 1.
Free water was encountered in the borings between 8 and 91/2 feet at the time of drilling and
when checked the next day. The upper subsoils were moist to very moist.
DESIGN RECOMMENDATIONS
NEW 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 clay soils.
H -P KUMAR
Project No, 17-7-413
-4 -
The design and construction criteria presented below should be observed for a spread footing
foundation system,
1) New Footings placed on the undisturbed natural sandy silty clay soils should be
designed for an allowable bearing pressure of 1,200 psf. Based on the laboratory
testing , we expect settlement of new footings designed and constructed as
discussed in this section could be about 1 to 2 inches under full load conditions.
2) The footings should have a minimum width of 24 inches for continuous walls and
3 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 50 pcf,
5) All existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the relatively undisturbed soils. The
exposed soils in footing area should then be moistened and compacted.
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support lightly to moderately loaded
slab -on -grade construction. We understand the slab will be heavily reinforced and extend over
the perimeter foundation walls. 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. 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.
H-P%KUMAR
Project No. 17-7-413
-5 -
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
imported granular soils such as 3/4" road base devoid of vegetation, topsoil and oversized rock.
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. It has been our
experience in the area that local perched groundwater can develop during times of heavy
precipitation, seasonal runoff or irrigation season. Frozen ground during spring runoff can create
a perched condition. We recommend below -grade construction, such as retaining walls,
crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by
an underdrain and wall drain system.
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 garage 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.
H-P%KUMAR
Project No. 17-7-413
-6 -
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 al 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 there may be variations in the
subsurface conditions. If conditions encountered during construction appear different from those
described in this report, we should he 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
Louis E. Eller
Reviewed by:
Daniel E. Hardin, P.E.
LEE/kac
H-P%KUMAR
Project No. 17-7-413
17-7-413
GARAGE
COUNTY ROAD 100
EXISTING
RESIDENCE
1RR/G T1q p DN p� 1TCH
cen a
BORING 2
A
Dy
PROPOSED
GARAGE
■
BORING 3
x
co
(STING DRIVE
w
HARD DRIVEN
/ LINER SAMP
BORIN
0
30 0 30 n[1
APPROXIMATE SCALE—FEET
H-PkKUMAR FLOCATION OF EXPLORATORY BORINGS
Fig. 1
- 0
____ 5
— 15
— 20
BORING 1
EL. 98.5'
5/12
WC=16.4
DD=107
3/12
WC=21.0
DD=100
-200=92
60/12
BORING 2
EL. 100'
5/12
WC=15.4
OD=109
5/12
WC=17.9
00=104
2/12
WC=28.2
DD=91
37/12
+4=52
-200=10
BORING 3
EL. 99.5'
6/12
WC=8.7
D0=110
-200=45
3/12
WC=19.6
DD=102
26/12
0
5-
0 —
+4=60
-200=12
72/12
15
20
17-7-413
H-Pk
LOGS OF EXPLORATORY BORINGS
Fig. 2
LEGEND
Pl.
_7
r,
L
5/12
TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM, MOIST, DARK BROWN.
CLAY (CL); SANDY, SILTY, MEDIUM STIFF AND MOIST TO SOFT AND VERY MOIST TO WET WITH
DEPTH, BROWN.
GRAVEL (GP—GM); WITH COBBLES AND SMALL BOULDERS, SANDY, SILTY, MEDIUM DENSE TO
DENSE, WET, BROWN, ROUNDED ROCK.
RELATIVELY UNDISTURBED DRIVE SAMPLE; 2—INCH I.D. CALIFORNIA LINER SAMPLE.
DRIVE SAMPLE; STANDARD PENETRATION TEST (SPT), 1 3/8 INCH I.D. SPLIT SPOON
SAMPLE, ASTM D-1586.
DRIVE SAMPLE BLOW COUNT. INDICATES THAT 5 BLOWS OF A 140—POUND HAMMER
FALLING 30 INCHES WERE REQUIRED TO DRIVE THE CALIFORNIA OR SPT SAMPLER 12 INCHES.
DEPTH TO WATER LEVEL AND NUMBER OF DAYS AFTER DRILLING MEASUREMENT WAS MADE.
DEPTH AT WHICH BORING CAVED.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON MAY 22, 2017 WITH A 4—INCH DIAMETER
CONTINUOUS FLIGHT POWER AUGER.
2, THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING
FROM THE EXCAVATION.
3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY HAND LEVEL BASED ON
THE TOP OF THE EXISTING FOUNDATION WALL ELEVATION IS 100.0 FEET.
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 D 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
—200` PERCENTAGE PASSING NO. 200 SIEVE (ASTM 0 1140).
17-7-413
H -P== KUMAR
LEGEND AND NOTES
Fig. 3
1
0
1
.. 2
▪ 3
W
— 4
z
0
—5
tn0
z
0
—6
7
— 8
17-7-413
H-P=A5KUIVIAR
SWELL -CONSOLIDATION TEST RESULT
0
Fig. 4
SAMPLE OF: Sandy Silty Clay
FROM: Boring 1 0 2.5'
WC = 16.4 %, DD = 107 pcf
NO MOVEMENT UPON
WETTING
gni
iiint ""n. wzifrOmr
Nei ...:1:61. r.p,.�upd..rt.y! u
la, Vinc.,1 dw .nu... {WW1/ a
x4r4..,d Pamela.. rre. Sw
Wn..no.um us fnra a M
'ecs mdmia .t Attu ti +Sli.
1.4 APPLIED PRESSURE - NSF 10 ie
17-7-413
H-P=A5KUIVIAR
SWELL -CONSOLIDATION TEST RESULT
0
Fig. 4
CONSOLIDATION - SWELL
- 2
-3
- 4
- 5
- 6
-7
- 8
•
SAMPLE OF: Sandy Si liy Clay
FROM: Baring 2 ® 5'
WC = 17.9 '/., DD = 104 pcf
Ir... I.H ..,w i
2
-2
� -4
w
3
i
• r
—10
-12
Ind.. lin mi✓la W51S €.&I to the
iirnni.leant. TN tnl+q nynt
Mel rot bit injnelivon Binding In
.ueut V•...rllan eommmi b
aomnn .LNn.aa m
151A
I
17-7-413
SAMPLE OF: Sandy Silly Clay
FROM: Boring 2 0 10'
WC = 28.2 %, DD = 91 pcf
I.¢ APPLIIO PJ USSl1R£ — KSF 10
H-P.45KU MAR
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
SWELL—CONSOLIDATION TEST RESULT
100
Fig. 6
1
1 —3
W
CONSOLIDATION
— 4
— 5
— 6
—7
—8 •
— 9
—10
m... 1..1 ,.nu'10 000,1'
rmf.. 1.N.& IN tnl'.y rvyxl
..d.l ml G ••4_ .eg..pl M
NI, 01KrS la. en..n axvnwl b
wen u.c A.wJa.... rne_ Seel
C00044.1,11n WWp @edam...0 N
xto•dorw .V..0.511.1 4 054
17-7-413
SAMPLE OF: Sandy Silty Clay
FROM: Boring 3 ® 5'
WC = 18.6 %, DD = 102 pct
NO MOVEMENT UPON
WETTING
i.0 APPLIED PRESSURE — KSF 10
H -P- KLIMAR
SWELL -CONSOLIDATION TEST RESULT
Fig. 7
w
3
-2
z
0
1-
-3
J
0
z
0
0 -4
Theo IHt tatolo etyy p^Y to !Fp
M0' e• tor.g.
Oct not G rtpne,W, 0a[tpt
fa. Hills n. wAnw, ppm.* of
!Doric.- and hktoaio . S.+
Cortigantw. toting pr a,,4R M
oaonlancp with WV 0•chiR
17-7-413
SAMPLE OF: Sandy Silty Clay
FROM: Hard Driven Liner 01 Footing
Grade
WC = 12.5 %, DD = 110 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1.0 APPLIED PRESSURE — 100
H-PKUMAR
SWELL -CONSOLIDATION TEST RESULT
Fig. 8
[ HYDROMETER ANALYSIS
SIEVE ANALYSIS
TNT READINGS
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MILLIMETERS
1 1. 11 ]a.1 71$ In
700
SAND
GRAVEL
CLAY TO SILT
FINE MEDIUM COARSE
FINE COARSE
COBBLES
GRAVEL 52 X
LIQUID UM1T
SAMPLE OF: Slightly Silty Sandy
SAND 36 X SILT
PLASTICITY INDEX
Gravel FROM:
AND CLAY 10 X
Boring 2 0 15'
HYDROMETER ANALYSIS
SIEVE ANALYSIS
7. 1111
42 WI
nue NEt01N0S
6 6605
15 6111 e' IN 11140 4.5 1.4.121__-1245-1129---.114.04p-V2--12_0--&+0_1126
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STANDARD
12/4.1I
CLLIa 1564611 Cr CN+N05
,T •' f4' ! a S'}�-0
100
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OF PARTICLES IN MILLIMETERS
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7e 1 677
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SA ND GRAVEL
CLAY TO SILT
FINE MEDIUMCOARSE� FINE COAR5E
1
COBBLES
GRAVEL 60 X SAND 28 X SILT AND CLAY 12 X
LIQUID LIMIT PLAST CITY INDEX
SAMPLE OF: Slightly Silly Sandy Gravel FROM: Boring 3 0 10 & 15' (Comhlned)
Thos. tut mull. oppty only lo Il.
.cmptu which wort I..I.d. Th.
I.611np r.purl %hull not b. r. rvd000d,
..C.p1 In 11+11, RIIh0u1 161. x1111.61
e 010101 of KGum01 k *1106101... Inn.
5196. 6166661(!11 I.FIInQ 110/22T 01m.d In
OCCOrdenl:. 111161 ASTM ASTM C136
Ond/ar A5TIT 01140.
17-7-413
H-PtiKUMAR
GRADATION TEST RESULTS
Fig. 9
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 17-7-413
SAMPLE LOCA i ION
GRADATION
ATTERBERG LIMITS
BORING
NATURAL
MOISTURE
DEPTH CONTENT
(f.) I%) ,
NATURAL
DRY
DENSITY
(pcf) I
GRAVEL
(%)
SAND
(%)
PERCENTCOMPRESSIVE
PASSING
NO.200
SIEVE
LIQUID
LIMIT
(%)
PLASTIC
INDEX
(%)
UNCONFINED
STRENGTH
(PSF1 j{
f
SOIL TYPE
21
16.4
107
f
Sandy Silty Clay
5
21.0
100
92
Slightly Sandy Silty Clay
2
21/2
15.4
109
Sandy Silty Clay
5
17.9
104
Sandy Silty Clay
10
28.2
91
Sandy Silty Clay
15
52
38
10
Slightly Silty Sandy Gravel
3
21
8.7
110
45
Sany
Gravel Clay with
5
18.6
102
i
Sandy Silty Clay
10 & 15
(combined)
60
38
12
Slightly Silty Sandy Gravel
HD 1*
Footing
grade
12.5
110
Sandy Silty Clay
1
*Hand Driven Liner Sample from footing grade in southern foundation excavation.