HomeMy WebLinkAboutSubsoils Report for Foundation DesignI(:|l'IHffiffiffi**;''*
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5020Oounty Road [54
Glonwood Springs,'CO E lt60 I
phone: (970) 945-79E8
fax (970) 945-8![5i[
ornail : k 4gil enwood@rkiurnar,usa,oorn
An Employcc Otrfrld Coilfary www.kumarusa.com
Offise tr ocations: Demv,er (fXQ), F,adcoa Color,ado Springs, Folt Collins, lGlenwood Spu{ngs, and Surnrnir Cornrty, 'Oolonado
RECEIVED
AUCI O U 2024
GARFIELD COUNTY
COMI,IUNIIY DEVELOPMENT
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED BARN/ADU
449 RAM LANE
SILT, COLORADO
PROJECT NO.24-7-162
MARCH 29,2024
PRI,PARED F'OR:
JEREMY KERANAN
449 RAM LANE
srLT, coLoRADO 81652
i eremy@voun g-services.com
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION ..
SITE CONDITIONS....
FIELD EXPLORATION
SUBSURFACE CONDITIONS ...
DESIGN RECOMMENDATIONS
FOLINDATIONS
FLOOR SLABS
SI]RFACE DRAINAGE
LIMITATIONS
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 . LEGEND AND NOTES
FIGURE 4 - SWELL-CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
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lfu nrar & Ansociates, lnc. @ tuqlec.t l{o. 24-7--i62
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed barn/ADU to be located at
449 Pam Lane, Silt, Colorado. The project site is shown on Figure l. The purpose of the
study was to develop recommendations for the foundation design. The study was conducted
in accordance with our agreement for geotechnical engineering services to Jeremy Keranen
dated February 21,2024.
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 barn/ADU will be a one and two-story structure. Ground floor will be slab-on-
grade. Grading for the structure is assumed to be relatively minor with cut depths between
about2 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 desuibed above,
we should be notified to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The property is developed with a single-story residence. The proposed barn will be located
about 30 feet northeast ofthe house. The barn area slopes down to the south at about 10 percent
grade. Vegetation consists of sage brush and juniper trees with an understory of grass and weeds.
FIELD EXPLORATION
The field exploration for the project was conducted on March 21,2024. 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 withl% inch and 2inch 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
lftrmar& Associates, lnc. @ Pmject llo.24-7-i162
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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 hy 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 Yzfoot of topsoiloverlying 10%to l3Vzfeet of sandy silt and clay.
Relatively dense, gravelly silty sand was encountered below the silt and clay at about I 1 feet
deep in Boring 1 down to the bottom of the boring at25 feet. Siltstone/claystone bedrock was
encountered below 14 feet deep in Boring 2, down to thc bottom of the boring at25 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 3 and 4, indicate light loading and
moderate compressibility under increased loading. The shallow soils exhibited variable
settlement/heave potential when wetted under light loading. The laboratory testing is
summarized in Table l.
No free water was encountered in the borings at the time of drilling and the shallow subsoils
were moist becoming less moist with depth.
DESIGN RECOMMENDATIONS
FOLINDATIONS
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, we believe the building can be founded with spread footings bearing
on the natural silt and clay soils with a low risk of post-construction movement.
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 2,000 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about I inch or less.
2) The footings should have a minimum width of 16 inches for continuous walls and
2 feet for isolated pads.
3) [xtcrior footings arrd footings bcncath unhcatcd arcas should bc 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 buttorn to span local
anomalies such as by assuming an unsupported length of at least l0 feet.
Kumar8 Associates, lnc. o Project llo.2#7-'l62
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5)
Foundation walls acting as retaining structures (if any) should also be designed
to resist a lateral earth pressure coffesponding to an equivalent fluid unit weight
ofat least 55 pcf.
All existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the relatively firm natural soils.
The exposed soils in footing area should then be moistened and compacted.
A representative ofthe geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
6)
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 controljoints 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
sandy gravel should be placed beneath slabs to act as a leveling course. 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 least95Yo 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.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the barn has been completed:
1) 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%o of the maximum standard Proctor density in pavement and slab areas
and to at least 90%o 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 l0 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
5 feet from foundation walls. Consideration should be given to use of xeriscape
to reduce the potential for wetting of soils below the building caused by irrigation.
Kumar8 Associates, lnc. @ Project No. 2+V-162
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LIDIITAIIOF{S
IAis stdyhasbm mnducfied in acoordmcewift gencnatly aqr€d geot€chnical engineuing
principles md practim in firis uea at '"is time" We make no wulant5r eitha exprress m imptiod-
The mnclusims ad rwmmddions s$mifred in lhis rqut uc basod rryon the data {btaind
fiom the explordory boriqg$ drilld at lhe localions fudicatsd m Figwe l, fte lrqmod type of
mstructim d onr erryerienre in fte uea- Or senriro do not includc doermining the
pesre,gur"entimorpossibility ofmold orof;herbiological oontuninmts (MOBC) developing
in fu frfirs- Ifth climt is mCI€mcd abou MOBC, fta a professional in fris ryccid field of
pnadire shuldbe mnsiltod- Orn fidings inchde intupoldion md extrapoluim ofthe
subsurfrceoondittions id€ntifiodatthe €xplcatorybuings mdrraidims inthes$srrhoe
onditions may not booome sr/id€ilt rntil excavdion is performod- If mnditims enormtered
during msrudion ryca ditrererrt ftom fue d€scribd in this r€port, rre shmld be notified so
ihst ro-cnaluation of fte rwmMatims may be made-
Thisrepothasboenpepaodfuftoexclusiveusebyurclicntfudesignptnpos€$. \ilfleuenot
roryutsibte for tsclmical interpetdims by ofrsrs of our infumdion l\s tre pmoject evofuee; we
shoildprovidemtinuod aonsulwion md field servis fuingmstruction torwiema md
monitor the implmmtatim ofqn rocommendationso md to vui$ that fte rmendatims
havebeenappropriatelyint€rF€ficd- Significmtdesipchmgssmayr€quireadditimalmalJflsis
ormodificdionstotlrerommmsdationspresmtedherein Werommendon-siteesenratim
of excavdions md founddion beaing ffi ryd testing of snrucfrral fiIl by arepesentdive of
fte grctofuical enginwr-
Reryffidly Submitto{
Kumar &
Daniel E. Hardin, P.E.
Reviewed bv:
Robert L. Duran, P
DElIlkac
lnc.
Kumar & Associates, lnc, @ Proiecl No. 24-7-162
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RETAINING WALLS
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APPROXIMATE SCALE-FEET
24-7 -162 Kumar & Associates LOCATION OF TXPLORATORY BORINGS Fig. 1
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BORING 1
EL. 6050.5'
BORING 2
EL. 6047.5'
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WC=13.6
DD=92 22/12
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WC= 1 6.0
DD= 1 05
-200=50
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DD= 1 02
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24-7 -162 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2
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LEGEND
TOPSOIL; ORGANIC SANDY CLAYEY SILT, FIRM, SLIGHTLY MOIST, BROWN.
SILT AND CLAY (CL-ML); SANDY, SCATTERED GRAVEL, HARD TO VERY STIFF, SLIGHTLY MOIST,
LIGHT BROWN.
SAND AND GRAVEL (SM-GM); SILTY.
CLAYSTONE BEDROCK.
DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
i DRTVE SAMPLE, 1 5/8-INCH t.D. SPLTT SPOON STANDARD PENETRATTON TEST.
2- /4i DRIVE SAMPLE BLOW COUNT. INDICATES THAT 37 BLOWS OF A 140-POUND HAMMERrr/ tz FALLTNG Jo TNCHES WERE REeUTRED To DRrvE THE SAMPLER 12 rNcHES.
NOTES
THE EXPLORATORY BORINGS WERE DRILLED ON MARCH 21, 2024 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 OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
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 WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D22'16);
DD = DRY DENSITY (pcf) (ASTM D2216):
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D1140)
24-7-162 Kumar & Associates LEGEND AND NOTES Fig. 3
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SAMPLE OF: Sondy Silty Cloy
FROM:Boringl@2'
WC = 13,6 %, DD = 92 pcf
:
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ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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SAMPLE OF: Sondy Siliy Cloy
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PRESSURE UPON WETTING
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24-7 -162 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No.24-7-162
SAMPI F I OCATION
NATURAL
I''OISTURE
CONTENT
(%l
NATURAL
DRY
DENSITY
(Dctl
GRADATION
PERCENT
PASSING NO.
200 SIEVE
UNCONFINED
COMPRESSIVE
STRENGTH
lDsfl
SOIL TYPEBORINGDEPTH
tftl
GRAVEL
("t"1
SAND
l%\
LIQUID LIMIT
Iok\
PLASTIC
INDEX
(o/ot
1 2 13.6 92 Sandy Silt and Clay
4 16.0 103 50 Sandy Silt and Clay
24 7.3 123 Claystone Bedrock
2 9 4.8 102 Sandy Silty Clay