HomeMy WebLinkAboutSubsoil Studytcn lfunw & Assoclates, lnc. @
Geotechnical and Materials Engineers
and Environmental Scientists
5020 Counry Road 154
Glenwood Springs, CO 81601
phone: (970) 945-'7988
fax: (970) 945-8454
emai I : kaglenwood@kumarusa.com
www.kumarusa.çomAn Emfloyco ot,vncd Compsny
Offrce Locations: Denver (HQ), Pa¡ker, Colorado Springs, Fort Colli¡¡s, Glenwood Springs, and Surnmit County, Colorado
RECEIVED
JAN I 3 2022
GARFIELD COUNTY
cbMUUHNV DEVELOPMENT
SUBSOIL STUDY
F'OR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 9, F'IRST EAGLES POINT
BATTLEMENT MESA
I4?EAGLE RIDGE DRTVE
GARFIELD COUNTY, COLORADO
PROJECT NO.21-7-440
JULY I2,2O2L
PREPARED tr'OR:
RUSSELL CARTWRIGHT
35 WILLO\ilVIEW WAY
PARACHUTE, COLORADO 8ró35
russecârt@smail.com
TABLE OT CONTENTS
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION
SITE CONDITIONS
FIELD EXPLORATION
SUBSURFACE CONDITIONS
FOUNDATION BEARING CONDITIONS
DE SIGN RECOMMENDATIONS
FOUNDATIONS.
FLOOR SLABS
UNDERDRAIN SYSTEM ......
SURFACE DRAINAGE......................
LMITATIONS..
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 . LOG OF EXPLORATORY BORING
FIGURE 3 . SWELL-CONSOLIDATION TEST RESULTS
FIGURE 4 . GRADATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
1
1
2-
1
a
-2-
J
3
J
4
5
5
Kumar & Associates, lnc. @ Project No.2l-7-440
PURPOSE A}[D SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located on Lot 9,
First Eagles Point, Battlement Mesa, l4}Eagle Ridge Drive, Garfield County, Colorado. The
project site is shown on Fþre l. The purpose of the study was to develop recofilmendations for
the foundation design. The study was conducted in accordance with our agreement for
geotechnical engineering services to Russell Cartwright dated lla'4;ay 12,2021.
An exploratory boring was drilled to obtain information on the subsurface conditions. Sa¡nples
of the subsoils obtained during the fietd 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 t5ryes, depths and allowable pressures for the proposed building foundation. This
report summarizes the data obtained during this study and presents our conclusions, design
recofitmendations and other geotechnical engineering considerations based on the proposbd
construction and the subsurface conditions encountered.
PROPOSED CONSTRUCTION
Plans for the proposed residence were not developed at the time of our study. The proposed
residence is expected to be a one- or two-story wood-frame structure with an attached ga'.age.
Ground floors could be a combination of slab-on-grade and structural over crawlspace. Grading
for the structure is assumed to be relatively minor with cut depths between about 2 to 5 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 recoÍlmendations contained in this report.
SITE CONDITIONS
The subject site was vacant at the time of our field exploration. The ground surface was gently
sloping down to the west at a grade of around I percent. A small drainage channel is below the
lot to the south. Vegetation consists of sparse grass and weeds with scattered bushes at the rear
of the lot and trees on the slope down to the drainage. Scattered basalt cobbles and boulders are
present on the lot.
Kumar & Associates, Inc' 6 Project No.2l-7'440
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FTELD EXPLORATION
The field exploration for the project was conducted on June 4, 2021. One exploratory boring
was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring
was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted CME-
458 drill rig. The boring was 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-1586.
The penetration resistance values are an indication of the relative density or consistency of the
subsoils. Depths at which the samples urere taken and the penetration resistance values are
shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory
for review by the project engineer and testing.
SUBSURF'ACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils consist of about lYzfeetof very stiffto hard, sandy gravelly clay overlying dense, sihy
clayey sandy gravel with cobbtes down to the maximum explored depth of 31 feet. A layer of
medium dense to dense, siþ clayey sand was encountered from 17 to 26Vz feet deep.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and density and gradation analyses. Results of swell-consolidation testing performed on
relatively undisturbed drive sample of the clay soil, presented on Figure 3, indicate low
cornpressibility under existing moisture conditions and light loading and a low expansion
potential when wetted under light surcharge. Results of gradation analyses performed on small
diameter drive samples (mirnrs 7Vz-nch fraction) of the coarse granular subsoils are shown on
Figure 4. The laboratory testing is summarizedin Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist to moist.
FOUI\DATION BEARING CONDITIONS
The upper clay soils encountered at the site possess an expansion potential when wetted. Surface
runoff, landscape irrigation and utility leakage are possible sources of water which could cause
wetting. The settlement/heave potential of the subgrade should be further evaluated at the time
of construction. Placing the foundation entirely on the gravel soils should provide a relatively
low risk of foundation movement.
Kumar & Associates, lnc. @ Project No.2l-7-440
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DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, we recommend the building be founded with spread footings bearing
on the natural gravel soils below the upper clay soils.
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 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 l8 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 lengfh of at least 10 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 for the onsite soils as backfill.
5) The topsoil, clay soils and any loose disturbed soils should be removed and the
footing bearing level extended down to the relatively dense natural granular soils.
The exposed soils in footing area should then be moistened and compacted.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FLOOR SLABS
The upper clay soils encountered possess an expansion potential and slab heave could occur if
the subgrade soils were to become wet. Slab-on-grade construction may be used for the garage
provided precautions are taken to limit potential movement and the risk of distress to the
building is understood and accepted by the owner. A positive way to reduce the risk of slab
movement is to construct sffucturally supported floors over crawlspace and is recoûlmended for
Kumar & Associates, lnc.6 Project No.2l.7-440
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the clay subgrade conditions. The settlemenVheave potential of the garage slab subgrade should
be further evaluated at the time of construction.
Slab-on-grade construction may be used in the garage area provided the risk of distress is
understood by the o\ilner. We recommend removing the clay soils from below garage floor slab
areas and reestablishing the bearing level with non-expansive structural fill such as 3/o-inchroad
base.
To reduce the effects of some differential movement, nonstructural floor slabs should be
separated from all bearing walls and columns with expansion joints which allow unrestrainsd
vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. The requirements for joint spacing and slab reinfotcement 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-irchaggregate with at least 50% retained on the No. 4 sieve
and less than2Yo passing the No. 200 siçve.
All fïllmaterials for support of floor slabs should be compacted to at least 95Vo 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.
The above recoÍrmendations will not prevent slab heave if the expansive clay soils underlying
slabs-on-grade become wet. However, the recoûtmendations will reduce the efifects if slab heave
occurs. All plumbing lines should be pressure tested before backfilling to help reduce the
potential for wetting.
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 create a perched condition. TVe
recofltmend below-grade construction, such as retaining walls, crawlspace and basement areas,
be protected from wetting and hydrostatic pressure buildup by an underdrain system. A
perimeter foundation drain around shallow crawlspace areas (less than 3 feet deep) should not be
required with adequate compaction of foundation backfill and positive drainage away from
foundation walls.
The drains, if used, should consist of 4-inch diameter PVC drainpipe placed in the bottom of the
wall backfill surrounded above the invert level with free-draining granular material. The drain
Kumar & Associates, lnc. ô Project No.21-7440
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should be placed at each level of excavation and at least 1 foot below lowest adjacent finish
grade and sloped at a minimum Yzo/o to a suitable gravity outlet or a properly construction
drywell. Free-draining granular material used in the underdrain system should contain less than
2o/o passingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maxirnum size
of 2 inches. The drain gravel backfill should be at least lVzfeet deep and be covered by filter
fabric.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the residence has been completed:
l) 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 ¿t 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 recofirmend a minimum
slope of 6 inches in the first l0 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in paved areÍN. Free-draining wall backfill should be
covered with frlter fabric and 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.
5) Landscaping which requires regular heavy inigation 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 inigation.
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area atthis time. 'We make no warranty either express or implied.
The conclusions and recoÍrmendations submitted in this report are based upon the data obtained
from the exploratory boring drilled at the location 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
Kumar & Associates, lnc. @ Project No.21-7440
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practice should be consulted. Our findings include interpolation and extrapolation of the
subsurface conditions identified at the exploratory boring and variations in the subsurface
conditions may not become evident until excavation is performed. If conditions encountered
during construction appear different from those desøibed 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 veriry that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recomme,nd 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, In
James H. Parsons,
Reviewed by:
**/.
Steven L. Pawlak, P.E.
JHP/kac
Y.
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5t66t
Kumar & Associates, lnc. ô Project No. 21-7-440
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BORING 1 LEGEND
CLAY
HARD,
(CL); VERY SANDY, GRAVELLY, vtRY STIFF T0
SLIGHTLY MOIsT, TAN.
27/6,50/7
WC=i5.2
DD=94
cRAVtL (GM-GC); SILTY, CLAYEY, SANDY, C0BBLES, SANDY
LAYERS, DENSE, SLIGHTLY MOIST, LIGHT BROWN IO TAN.
29/6, 50/1.5 SAND (SM-SC); VERY SILTY, CLAYTY, SCATTERED GRAVEL,
MEDIUM DENST TO DENSE, MOIsT, TAN.5
4e/t2
L
LJ
I
DRIVT SAMPLE, 2-INCH I.O. CALIFORNIA LINER SAMPLE.
10 21/6, s0/1
DRTVE SAMPLE, r 5/8-|NCH t.D. SPUT SP00N STANDARD
PENETRATION TEST.
.^r."DR|VE SAMPLT BLOW COUNT. INDICATES THAT 49 BLOWS 0F1r/ t¿
^
i4o-pouND HAMMER FALLTNG g0 rNcHEs rllEnt REQUTRED
TO DRIVT THE SAMPLER 12 INCHES.
15 50/3.st-l¡ll¡lu-
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NOTES
I THE EXPLORATORY BORING WAS DRILLTD ON JUNE 4, 2021
WITI] A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
20 22/12
2. THE LOCATION OF THE TXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE
SITE PLAN PROVIDED.
3. THE TLEVATION OF THE TXPLORATORY BORINC WAS NOT
MEASURED AND THE LOG OF THE EXPLORATORY BORING IS
PLOTTED TO DEPTH.
25
46/12
1. THI EXPLORATORY BORING LOCATION SHOULD BE CONSIDERËD
ACCURATE ONLY TO THE DEGREE IMPLITD BY THE MTÏHOD
USTD.
5. THE LINES BETWEEN MATTRIALS SHOWN ON THE EXPLORAÏORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES
BETWTEN MATERIAL TYPTS AND THE TRANSITIONS MAY BE
GRADUAL.
50 50/t 6. GROUNDWATER WAS NOT TNCOUNTERED IN THE BORING AT ÏHE
TIME OF DRILUNC.
35
7. LABORAÏORY TTSÏ RISULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (PCf) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIIVE (ISTU O OSI¡);
-2OO = PERCINTAGE PASSING NO. 2OO SIEVE (ASTM D 1140).
WC=4.5
+4=37
-200=51
Fig. 2LOG OF EXPLORATORY BORINGKumar & Associates21 -7-440
I
SAMPLE 0F: Sondy Cloy
FROM: Boring 1 O t'
WC = 15.2 %, DD = 94 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
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116. t-t ðùb opdy only þ h
Fmplè t€tad. tì. tadlng epôd
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fu$, Bilt@l lh! vltb opprcwl of
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.0 PRESSURE -t0I
Fig. 3Kumar & Associates SWELL-CONSOLIDATION TESÏ RESULTS21 -7 -440
HYDROMEIER ANALYSIS SISVE ANALYSIS
Ìl{E iÉAoNlros
I' HRs 7 HÊ3 tt ¡rm as16as It6 aio &¿
i-.- |
SAND GRAVEL
FINE MEDIUM COARSE FINE COARSE
a
ã
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too
go
t0
70
to
50
to
t0
20
t0
o
0
lo
20
30
10
30
a0
70
EO
90
too
I
È
r32
CLAY TO SILT COBgLES
GRAVEL 37 % SAND
UOUID UMIT
SAMPLE OF3 Sllly Cloyey Sondy Grovcl
32u
PLASTICITY INDEX
SILT AND CLÀY 31
'1
FROI¡: Bor¡ng 1 Q 7' &, 1o' (Combined)
Th.rc lcrt ræull3 oÞply only lo th.
rorìrÞlæ rhlch rart Lllcd. lho
l.rllng r¡porl ahqll nol be rcprqductd,
cxocÞl ln lull, wlthout lh. rrlll.n
opDrevol ot Kumor & A¡roclolcs, lnc.
Sldve onolyll¡ lGtlng lr p¡rformed ln
ocqoidon4 wllh ASfM D6915, ASÍ1, D7928,
ASIII Ctt6 6nd/or ASIM Dlt¡10.
21 -7 -440 Kumar & Associates GRADATION TEST RISULTS Fig. 4
l(+Âiiffififfir:ffiriiü-*TABLE 1SUIITMARY OF LABORATORY TEST RESU LTSNo.2l-7440Sandy ClaySiþ Clayey Sandy GravelSOIL TYPE(psflUNCONFINEDCOMPRESSIVESTRENGTHlololPt-ASTtCINDEXATTERBERG LIMITSl%ìTIQUID LIMIT1JPERCENTPASSING NO.200 slEvE('ôSAI{D3237GRADATION$lGRAVEL{ocf)ilATURALDRYDENSTY94{%ìNATURALMOISTURECONTENTts.24.57 andl0Combined{fr}DEPÌHI1SAIIPLE LOCATIONBORING