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Apnl 12,2021
Uriel Mellin
144 Cliffrose Way
Glenwood Springs, Colorado 81601
uri el.mellin(4tl¡qtinail. com Project No. 21-7-190
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot24, Callicotte
Ranch, Callicotte Ranch Drive, Garfield County, Colorado
Dear Uriel:
As requested, Kumar & Associates, Inc. performed a subsoil sfudy for design of foundations at
the subject site. The study was conducted in accordance with our agreement for geotechnical
engineering services to you dated February 9,2021, The data obtained and our
recommendations based on the proposed construction and subsurface co¡rditions encountered are
presented in this report.
Proposed Construction: Plans for the proposed residence were not available at the time of our
field exploration. The proposed residence will likely be a one and two story rrcsidence with
attached garage located on the site as shown on Figure l. Ground floors are assumed to be a
combination of structural over crawlspace and slab'on-grade. Cut depths are expected to range
between about 2 to 6 feet. Foundation loadings for this type of construction are assumed to be
relatively light and typical of the proposed type of construction.
Ifbuilding conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The subject site was vacant at the time of our field exploration. There was
approximately 1 to l%feet of snow cover present on the site. The ground suface is sloping
down to the north and north west at grades between 5 a¡rd 15 percent, generally steeper north of
the proposed building location. A drainage ditch runs through the center/n orth of Lot 24.
Vegetation consists of grass, sagebrush and sparse juniper in the proposed building area with
denser juniper growth north of the building area.
Subsidence Potential: Callicotte Ranch is underlain by Pennsylvania Age Eagle Valley
Evaporite bedrock. The evaporite contains gypsum deposits. Dissolution of the gypsum under
certain conditions can cause sinkholes to develop and can produce areas oflocalized subsidence.
During previous work in the area, a sinkhole was observed about % of amile to the north-
northeast of Lot 24, outside the Callicotte Ranch development. Sinkholes were not observed in
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the immediate area of the sutrject lot. Based on our present knowledge of the site, it cannot be
saicl for certain that sinkholes will not develop. In orr opininn, the risk of ground subsidence at
Lat 24 is low throughout the service life of the residence and similar to other lots in the area but
the owner should be aware of the potential for sinkhole development.
Subsurface Conditions: The subsutface conditions at the site were evaluated by excavating
2 exploratory pits and 2 profìle pits for septic design at the approximate locations shown on
Figure 1. The logs ofthe pits are presented on Figure 2. The subsoils encountered, below about
|t/z feet of topsoil, consist of dense, sandy basalt gravel and cobbles with boulders in caliche
matrix to the maximlrll excavated depth of 8 feet. Refusal to excavator digging was encountered
at 4t4 feet iri Pit 2" Results of a gradation analyses perfonnod on samples of silty sancl nncl gravel
(minus 3-inch fraction) obtained frour the site are presented on Figure 3. No free water was
observed in the pits at the time of excavation and the soils were slightly moist to moist.
Foundation Recommendafions: Considering the subsoil conditions encounteretl in the
exploratory pits and the nature of the ptoposed construction, we recommend spread footings
placed on the undisturbed natural soil designed fc¡r an allowable soil bearing pressure of
2,000 psf for support of the proposed residence. The matrix soils can be compressible after
wetting and there could be some post-construction foundation settlement. Footings should be a
minimum width of 16 inches for continuous walls antl 2 feet for coiumns. Loose and disturbed
soils and existing filI encountered at the foundation bearing level within the excavation should be
removecl 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 ûost
protection. Placemertt of frrotirtgs at least 36 inches below the cxterior grade is typically used in
this area. Continuous ioundation r.valls shoulclbe reinforced top and boftom to span local
anomalies such as by assuming an unsupporte{ length of at least 10 t-eet. Founclation walls
acting as retaining structures should be designecl to resist a lateral earth pressure based on an
equivalent fluid unit weight of at least 50 pcf for the an-site soil as backfill.
F'loor Slabs: Thç natural on-site soiis, exclusive of topsoil, are suitable to support lightly to
rnorlerately loaded slab-on-grade construction. To reduce the effects of some differential
moventent, floor slabs should be separated ûorn all bealing walls and colurl¡rs with expansion
joints which allow unrestrained vertical movement. Floor slab control joints should be used to
reduce darnage 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 rninimum 4 inch layer of free-draining gravel should be placed beuçath baseurent level
slabs to facilitate clrainage. This material should soüsist of minus 2-inch nggrcgatc with less than
50% passing the No. 4 sieve and less than?Yopassing tire No. 200 sieve.
Kum¡r & Associates, lnc. ''Project No. 21-7-190
-J-
Aii fill materiâls for support of floor slabs should be compacted to at least95o/a of maximum
standard Proctor clensiry at a moishire 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 encûuntered during our exploration, it has
been our experience in the arealhat local perched groundwater can develop during tirnes of
heavy precipitation or seasonal runoff. Frozenrgrouncl during spring runoff can cteate a perched
condition. We recommend below-grade construction. such as retaining walls, crawlspace and
basement areas (if any), be prolected from wetting and hydrostatic pressure buildup by an
underdrain syste'm.
The drains should consist of drainpipe placed in ths bottom of the wall hackfill surounded above
the invert level with free-draining granular material. The drain should be placed at each levei of
excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum l% to
a suitabie gavity outlet. Free-draining granular material used in the underdrain systern sirould
contain iess than 2% passing the No. 200 sieve, less than 507o passing the No. 4 sieve and have a
nraximum síze o{2 inches. The drain gravel backfill should be at least ïriz feet ðeep.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all tirnes after the residence has been completed:
1) Inundation ofthe foundation excavations and underslab areas shouid be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95Ya of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the rnaxirnum standard Proctor density in iandscape areas.
Free-draining wall backäil should be capped with about 2 fèet 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 reccmrnend a minimum
slope of i2 inches in the first l0 feet in unpaved areas and a minimum slope of
3 inches in the first l0 feet in pavement and walkway areas.
4) Roof downspouts and drains should discirarge well beyond the limíts of all
backfill.
5) Landscaping which requires regular hearry irrigation should be located at least
10 feet from the building. Consideration should be given io the use of xeriscape
to limit potential wetting of soils below the foundation caused by irrigation.
Limitations: This stutly has been conducted in accotdance with generally acceptecl geotechnical
engineering principles and practices in this area at this time" We make no warranty either
Kumar & Associates, lnc. I'Froject No. 21"7-190
4
express or irnplied. The oonclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure I
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. Our services do not include detemrining the presence, prevention or possibility of mold
or other biological contaminants (MOBC) developing in the fufure. If the client is concemed
about MOBC, then a professional in this special field of practice should be consulted. Our
findings ìnclude 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 perfirrnred. If conditions encouniered during construction eppear different frora
those described in this report, we should be notified at once so re-evaluation of the
recommendations mav be made.
This report has been prepated for the exclusive use by our client for design ptlryoses. We are not
responsible for technical interpretations by others of our information. As the prcrject evolves, we
should provide continued consultation and field services during construction to review and
nonitor the implemcntation af our recommendatíons, anrl to verify that the recomlnendations
have been appropriately interpreted, Significant design changes may require additional analysis
or modifications to the recomrnendations presented herein. We recomtnend on-site observation
of excavations and foundation bearing strata and testing of struch.ual fill by a representative of
the geotechnical engineer.
If you have any questions or i{'we may be of further assistance, please let us know
Respectfully Submitted,
Kurn*r' &,{sst¡cialrs, lnt.
Jatnes H. Parsons, P.E.
Reviewed by:
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attachments Figure I - Location of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
Figure 3 - Gradation Test Results
Figure 4 - USDA Gradation Test Results
Table 1 - Surnmary of Laboratory Test Results
Kum¿r & Associates, lnc. :.Projecl No. 21"7"190
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PIT 1 PIT 2 PROFILE PIT I PROFILE PIT 2
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LEGEND
TOPSOIL; SILT, SANDY, ORGANICS, FIRM/FROZEN, SLIGHTLY MOIST, BROWN
GRAVEL (cU); S¡H0V SILT, MATRIX, ANGULÀR BASALI, CoBBLES AND BOULDER
PALE TAN, SLIGHTLY MOIST.
Ir
DISTURgED BULK SAMPLE.
t PRACTICAL DIGGING REFUSAL
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH AN EXCAVATOR ON FEBRUARY 17,2021,
?., ÏHE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY TAPING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
5. THE ELEVATIONS OF THE EXPLORATORY PITS WERE OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULÐ BE CONSIDERED ACCURATE ONLY
TO THE DEGRET IMPLIED BY THE METHOD USED.
5. THE L¡NES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRÀDUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION.
7, LABORATORY TEST RESULTS:wc = wATER CONTENT (%) (ASTM O ZZ|A):i4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-2OO= PERCENTAOE PASSING NO. 2OO SIEVE (ASTM O II+O);
GRAVEL = PERCENTAGE RETAINED NO. 10 SIEVE
SAND = PERCENTAGE PASSING NO.10 SIEVE AND RETAINED ON No.325 SIEVE.
SILT = PERCENTAGE PASSING NO. 525 SIEVE TO PARTICLE SIZE .002MM
CLAY = PERCENT SMALLER THAN PARTICLE SIZE .O02MM
21 -7 -190 Kumar & Associates LOGS OF TXPLORATORY PITS Fig. 2
SAND GRAVEL
rINE MtDtuM lcoaRsE FINE COARSE
S'EVÊ ANALYSISHYONOMEIIP ANALYSIS
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SAMPLE OF; Sll?y Grovôl¡y Sond
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PLASTICITY INDEX
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21 -7-19A Kumar & Associates GRADAÏION TTST RTSULTS Fig. 5
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DIAMFTER OF PARTCLES IN MILLIMETERS
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21-7-190 Kumar & Associates USDA GRADATION TEST RESULTS lig. 4
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I (*rt ääffi ffi ffiå,Tuå,;***,uTABLE 1SUMMARY OF LABORATORY TEST RESULTSNo,21.7.f90SOILTYPESilty Gravelly SandGravelly SandyLoamCLAY('/.)6SILTr¿)23(%)sÂllo45USDA SOIL TEXTURE(%)GRÂVEL2611428I{ATURALÛRYDENSTTY{PrïSRAVIL94sÅ¡tDfi.)(Y.)Ttor{NÀTURALMO$IURECOilTEilT{%).41l14.2(ñ)DEPÏHTYz-46-8SAMPLE LOCATIONptTPir-2PrafilePit*2