HomeMy WebLinkAboutSubsoils Study for Foundation DesignlGrt[#l;iffiffi[ir;'*"'5020 County Roadl 154
Glonwood Spni'ngs, CO 816.0:l
phone: (940)i 9:45 -798t
fax: (9.700: 945 -841541
enirairl: kagl'enwoodl@kurnarusa.com
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Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collinq. GlbnwoodlSprihgs, andlSummit Coutlty, Coloradb'
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SUBSOIL STTJDY
F'OR FOUNDATION DESIGN
PROPOSED RESIDENCE
1793 COUNTY ROAD 219
GARFTELD COUNTY, COLORADO
PROJECT NO.23-7-190
JUNE 8,2023
PREPARED FOR:
PUMA PAW, LLC
ATTN: JOHN HILDERBRANT
1793 COUNTY ROAD 219
RTFLE, COLORADO 81650
i hilderbrant42@smail.com
SITE CONDITIONS
TABLE OF'CONTENTS
PURPOSE AND SCOPE OF STUDY
FIELD EXPLORATION
SUBSURFACE CONDITIONS
FOUNDATION BEARING CONDITIONS .....
DESIGN RECOMMENDATIONS
FOTINDATIONS
FLOOR SLABS
UNDERDRAIN SYSTEM
SURFACE DRAINAGE...
LIMITATIONS
FIGURE I - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURES 4 & 5- SWELL-CONSOLIDATION TEST RESULTS
FIGURE 6 - GRADATION TEST RESULTS
TABLE I - SUMMARY OF LABORATORY TEST RESULTS
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1
I
5
1
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Kumar & Associatee,.lirc. o Pr,oject No.23-7-190
PURPOSE AI\D SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed rcsidence to be located at
1793 County Road 219, Garfield Count5r, Colorado. The project site is shown on Figure 1.
The purpose of the study was to develop recommcndations for the foundation design. The study
was conducted in accordance with our agreement for geotechnical engineering services to
Puma Paw, LLC dated Marchl5,2023.
A field exploration program consisting of exploratory borings was conducted to obtain
infcrrmation 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 werc 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 over a basement. Ground floor will be slab-
on-grade. Grading for the structure is assumed to be relatively minor with cut depths between
about 3 to 9 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 site was pasture land at the time of our site visit. The house site is located in the valley
bottom. The terrain is moderately to strongly sloping to down to the east towards Middle Rifle
Creek. Middle Rifle Creek flows towards the south approximately 100 yards to the east of the
proposed home site. Vegetation consisted of grass and weeds in the pasture area with oak brush,
pinyon and juniper in surrounding areas. The valley sides had exposed Maroon Formation
bedrock.
FIELD EXPLORATION
The field exploration for the project was conducted on April 18, 2023. Two exploratory borings
were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The
borings were advanced with 4 inch diameter continuous flight augers powered by a truck-
Kumar & Associates, Inc. o Project No.23-7-190
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mounted CME-45B drill rig. The borings were logged by a representative of Kumar &
Associates, Inc.
Samples of the subsoils were taken with l% 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-l586.
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 Yz foot of topsoil overlying medium dense, silty to very silty, slightly
clayey sand with scattered gravel in Boring 1 and medium dense to dense silty to very silty sand
and gravel in Boring 2.
Laboratory testing performed on samples obtained from the borings included natural moisture
content and gradation analyses. Results of swell-consolidation testing performed on relatively
undisturbed drive samples, presented on Figures 4 and 5, indicate low to moderate
compressibility under conditions of loading and wetting. Results of gradation analyses
performed on small diameter drive samples (minus l%-inch fraction) of the coarse granular
subsoils are shown on Figure 5. The laboratory testing is summarized in Table 1.
Free water was encountered in the Boring I at the time of drilling at 26 feet depth and the
subsoils were slightly moist to wet.
F'OUNDATION BEARING CONDITIONS
The silty sand soils, which are expected to be encountered at excavation subgrade, possess low
bearing capacity and, in general, moderate settlement potential, especially when wetted. Lightly
loaded spread footings bearing on the natural soils should be feasible for foundation support with
some risk of settlement. The risk of settlement is primarily if the bearing soils were to become
wetted and precautions should be taken to prevent wetting. A lower risk of foundation
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in a moistened and well compacted condition.
Provided below are recommendations for spread footings bearing on the natural soils. If
recommendations for structural fill below the spread footings, we should be contacted.
Kumar& Associales, lhc. @ Project No.23.7.190
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DESIGN RECOMMENDATIONS
FOI.INDATIONS
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, the building can be founded with spread footings bearing on the
natural soils with some settlement risk.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
l) Footings placed on the undisturbed natural granular soils should be designed for
an allowable bearing pressure of 1,500 psf. Based on experience, we expect
sefflement of footings designed and constructed as discussed in this section will
be about I inch. There could be some additional settlement if the bearing soils
were to become wetted. The magnitude of the additional settlement would
depend on the depth and extent of the wetting but may be on the order of Yzto
1 inch.
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 such as by assuming an unsupported length of at least 12 feet.
Foundation walls acting as retaining structures should also be designed to resist a
lateral earth pressure coffesponding 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 firm natural 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 ofthe 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, 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
Kumar & Associates, lnc. @ Project No.23-7-190
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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 than2Yo passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at leastg5Yo 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 rock.
UNDERDRAIN SYSTEM
Although free water was not encountered during our exploration at probable excavation depths, it
has been our experience in mountainous areas that local perched groundwater can develop during
times of heavy precipitation or seasonal runoff. 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 system.
The drains should consist of PVC 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 I foot below lowest adjacent finish grade and sloped at a
minimum IYoto a suitable gravity outlet. Free-draining granular material used in the underdrain
system should contain less than 2%o passing the No. 200 sieve, less than 50olo passing the No. 4
sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least l% feet
deep.
SURFACE DRAINAGE
The following drainage precautions should bc observed during construction and maintained at all
times after the residence has been completed:
l) Inundation ofthe 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 should be
covered with filter fabric and capped with about 2 feet of the on-site soils to
reduce surface watcr infiltration.
Kurnar& Associileg lnc. o Project No. 23-7.190
5
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
5 feet from fotrndation walls. Consideration should be given to use of xeriscape
to reduce the potential for wetting of soils below the building caused by inigation'
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.
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 veri$ 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, lnc.
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Kumar & Associates, lnc.6 Project No.23-7-190
O BORING 2
O BORING 1
50 o
APPROXIMATE SCALE-FEET
23-7 -190 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1
BORING 1
EL. 100'
BORING 2
EL. 1 07'
0 0
11/12
WC=17.2
DD= 1 01
-2OO=48
t1/12
tNC=7,4
*4=43
-2OO=22
5 5
12/12
WC=9.0
DD= 1 0O
1s/ 12
WC=4.4
DD=95
10
11/12
WC=8.0
DD=79
LL=17
Pl=1
'10
36/12
WC=3.5
DD=122
15 15
F
LiJ
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UJo
1o/ 12
WC=7.0
-200=35
27 /12 t-IJt!tL
I-F(L
t!o
20 20
14/12 43/ 12
25 25
--->
30 30
7 /12
35 35
23-7-190 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2
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LEGEND
N
TOPSOIL; ORGANIC CLAYEY SILT AND SAND, FIRM, MOIST, DARK BROWN.
m
SAND AND GRAVEL (SM-GM); SILTY TO VERY SILTY, MEDIUM DENSE TO DENSE, MOIST TO
SLIGHTLY MOIST, MIXED REDDISH BROWN.
DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
DRIVE SAMPLE, 1 5/8-INCH r.D. SpLtT SPOON STANDARD PENETRATTON TEST.
11712 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 11 BLOWS OF A 140-POUND HAMMER'./'- FALLING 50 INCHES WERE REQUIRED To DRIVE THE SAMPLER 12 INCHES.
4 orpru ro wATER LEVEL ENcouNTERED AT THE TIME oF DRrLLrNc.
--+ DEPTH AT WHICH BORING CAVED.
NOTEg
THE EXPLORATORY BORINGS WERE DRILLED ON APRIL 18, 2023 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.
5. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL AND REFER
TO BORING 1 AS EL. 1OO" 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. I.ABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D2216);
DD = DRY DENSITY (pcf) (ASTM D2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ISTU OOSIS);
-200 = PEROENTAGE PASSING No. 200 SIEVE (ASTM Dl140);
LL = LIQUID LIMIT (ASTM D431S);Pl = PLASTICITY INDEX (ASTM D4318).
SAND (SM); SILTY TO VERY SILTY, SCATTERED GRAVEL, SLIGHTLY CLAYEY, MEDIUM DENSE,
MOIST TO WET, BROWN TO RED.
i
23-7-190 Kumar & Associates LEGEND AND NOTES Fig. 3
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SAMPLE OF: Very Silty Cloyey Sond
FROM:Boringl@5'
WC = 9.0 %, DD = 100 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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rholl mt b Erodu€d, 6EPt in
tdl. $thd h. rritbn opDffil of(umr ond A66itu, lnc. Sl.ll
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Fig. 4SWELL-CONSOLIDATION TEST RESULTS23-7-190 Kumar & Associates
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SAMPLE OF: Sllty Sond wilh Grovel
FROM:Borlng2@5'
WC = 4.4 ?4, DD = 95 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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-10
I.() APPLIED PRESSURE - KSF 10 100
23-7-190 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 5
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30
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HYDROMETER ANALYSIS SIEVE ANALYSIS
24 HRS 7 HRS
NYE READIXCS
&rtx ttrtx alt rvt}{at s aim
U.S. STANDARD SERIES
rlo ao t9 ttG aio ll
CI.EAR SQUANE OPEflIXsS
rtt- ttc 1 tf2' t'5'a'I
SAND GRAVEL
FINE MEDIUM COARSE FINE COARSE
t0
m
lo
F
30
to
70
oo
e0
t00
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.mt ,125
OF PARTICLES IN
CLAY TO SILT COBBLES
GRAVEL 13 X SAND
LIQUID LIITIT
SAMPLE OF: Sllty Sond ond Grovcl
55X
PLASTICIW INDEX
SILT AND CLAY 22 X
FROM: Borlng 2O2.5'
Th!!r l.d ruull. opplt onlt io lh.
rdmolar vhloh ran l.tLd. Tha
hrllirg ruport rholl nol b. ruprcduo.d,
.ro.pt ln tull, wllhoul lhr rrlll.n
ooorbvol ol Kumor & Artoolobt, lnc'
Sijvr onolyrb l.tllng l! ptrtomod ln
oooordqnci ulth AST-H D6015. ASIII D7928,
ASTX Cl!6 ond,/or ASTII Dlt4O.
23-7 -190 Kumar & Associates GRADATION TEST RESULTS Fig. 6
I(t'THHfiMMF;-*
:=
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
190
SATPLE LOCATIOiI GRA]IATIOII ATTERBERG LITIIS
BORING
lfil
DEPTH
nat
I{ATURAL
totsTuRE
CONIENT
{ocl}
NATURAL
DRY
DEIISITY
GRAVEL
(%)
SAl{D
(%)
PERCEl{T
PASSNG ilO.
2m stEvE
LIQUID LITIT
{qal roil
PTASTIC
titDEx
ln.tl
ul{c0l{FNED
coilPRESSTVE
STREI{GTH SOIL TYPE
I 2Y2 17.2 101 48 Very Silty Clayey Sand
5 9.0 100 Very Silty Clayey Sand
10 8.0 79 17 I Very Silty Sand
15 7.0 33 Silty Clayey Sand
2 2%7.4 43 35 22 Silty Sand and Gravel
5 4.4 95 Silty Sand with Gravel
10 J.J 122 Silty Sand and Gravel