HomeMy WebLinkAboutSubsoils Reportrcnf,'ffiffiffir"lsd"*
An Emdoyca Olmcd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Offrce locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
February 27,2025
Tom Lester
P.O. Box 2329
Basalt, Colorado 81621
toml@lesterdevelopment. com
Project No. 25-7-1 62.06
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 6, Whitecloud
Ridge, 500 Whitecloud Road, Garfield County, Colorado
Dear Tom:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations ;aa
at the subject site. The study was conducted in general accordance with our agreement for N. -
geotechnical engineering services to you dated February 25,2025. The data obtained and our \\
recommendations based on the proposed construction and subsurface conditions encountered
are presented inthis report. s,$
Proposed Construction: Plans for the proposed residence were conceptual at the time of our tt
field exploration. The proposed residence is assumed to be a two-story residence with an
attached garagelocated on the site in the general area of the pits shown on Figure 1. Ground S
floors are assumed to be structural over crawlspace for living areas and slab-on-grade for the \S
garage. Cut depths are expected to range between about 2to 6 feet. Foundation loadings for \
this type of construction are assumed to be relatively light and typical of the proposed type of ^Sconstruction. \
If building 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
patchy snow cover. The ground surface was gently sloping down to the southwest at a grade
estimated at about 5 percent. Vegetation consists of grass and sagebrush in the building areaand
juniper trees to the south of the building area. There were basalt boulders and cobbles exposed
on the ground surface in the juniper trees.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating
two exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about 1 foot of topsoil, consist of 5%
to 6 feet of silt and sand overlying dense, basalt gravel and cobbles in a calcareous sandy silt
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matrix. Results of swell-consolidation testing performed on relatively undisturbed samples of
sand and silt, presented on Figure 3, indicate low to moderate compressibility under conditions
of loading and wetting. No free water was observed in the pits at the time of excavation and the
soils were slightly moist to moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread footings
placed on the undisturbed natural soil designed for an allowable soil bearing pressure of
_199-psf&r support of the proposed residence. The soils tend to compress after wetting
Tnd there could be some post-construction foundation settlement. Footings should be a
minimum width of 18 inches for continuous walls and2 feet for columns. Loose disturbed
soils encountered at the foundation bearing level within the excavation should be removed
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 frost protection.
Placement of footings at least 3-6 iqghgbelow the exterior grade is typically used in this area.
Continuous foundation walls should be well 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 be designed to resist alateral earth pressure based on an equivalent
fluid unit weight of at least 50 pcf for the on-site soil as backfill.
X'loor 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 expansionjoints which allow
unrestrained vertical movement. 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 relatively well graded sand and gravel should be placed beneath slabs-on-grade for
support. This material should consist of minus 2-inch aggregate with less than 50% passing
the No. 4 sieve and less than l2Yo passing the No. 200 sieve.
A11 fill materials for support of floor slabs should be compacted to at least95%o of maximum
standard Proctor density at a moisture content near optimum. Required fillcan consist of the
on-site soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: Atthough free water was not encountered during our exploration, it has
been our experience in the areathatlocal 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 areas
deeper than about 4 feetand basement areas, be protected from wetting and hydrostatic pressure
buitdup by an underdrain system. The assumed shallow crawlspace area does not require a
foundation drain.
Kumar & Associates. lnc, @ Proiect No. 2S7-162.06
aJ
If installed, the drains should consist of rigid perforated 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 %o/oto a suitable gravrty outlet, drywell or sump and pump
system. Free-draining granular material used in the underdrain system should contain less than
2Yopassingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size
of 2 inches. The drain gravel backfill should be at least l%feet deep and covered with filter
fabric such as Mirafi 140N or 160N.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence 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 95Yo of the maximum standard Proctor density in pavement and slab areas
and to at least 90o/o of the maximum standard Proctor density in landscape areas.
Free-draining wall backfill should be covered with frlter fabric and capped with
about 2 feet 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 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 pavement and walkway 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
10 feet from the building. Consideration should be given to the use of xeriscape
to limit potential wetting of soils below the foundation caused by irrigation.
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 recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2,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. Ow
findings include 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 performed. If conditions encountered during construction appear different from
Kumar & Associates. lnc, o Proiec't No. 25-7-162.06
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those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design pu{poses. 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 verifr 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 filI by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
Kumar & Assoclales, lnc.
James H. Parsons, P.E.
Reviewedby:
Daniel E. Hardin, P.E.
JHPlkac
attachments Figure 1 - Location of Exploratory Pits
Figure 2-Logs of Exploratory Pits
Figure 3 - Swell-Consolidation Test Results
Table I - Summary of Laboratory Test Results
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Kumar & Associates, lnc, @ Proiect No. 25-7-162.06
120
APPROXIMATE SCALE_FEET
25-7-162.06 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
PIT 2
EL. 101.5'
0 0
WC=15.2
DD=1 00
5
WC=9.0
-200=85
WC=10.2
DD=88
-200=68 5
10 10
TOPSOIL; SILT, SANDY, ORGANICS, FIRM/FROZEN, MOIST, BROWN.
SAND AND S|LT (SM-ML); CLAYEY, CALCAREOUS HARD, SLIGHTLY MOIST, PALE TAN.
GRAVEL AND COBBLTS (CU); SMALL BOULDERS, BASALT ROCK, CALCAREOUS SANDY SILT
(cALtcHE) MATR|X, DENS,E SLIGHTLY MOIST, PALE TAN AND GRAY.
HAND DRIVE SAMPLE.
PIT 1
00'EL.
F
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t PRACTICAL REFUSAL TO THE BACKHOE DIGGING.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON FEBRUARY 25, 2025
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO
PIT 1 AS A 1OO FT ASSUMED BENCHMARK.
4. THE EXPLORATORY PIT 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 PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (PCt) (ASTU D 2216);
-2OO= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140).
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Fig. 225-7-162.06 Kumar & Associates LOGS OF EXPLORATORY PITS
SAMPLE OF: Sondy Cloyey Sllt
FROM:Plt16.2'
WC = 15.2 %, DD = 1O0 pcf
:
NO MOVEMENT UPON
WETTING
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F
cf
=oA-oz,-oc)
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=oA-zz.o
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1
-3
-4
1
0
-4
PRESSURE - KSF
- KSF
t0
10I
SAMPLE OF: Sondy Cloyey Silt
FROM:Pii2('^3.5'
WC = 1O.2 %, DD = E8 pcf
-2OO = 68 %
I
:i:l
il::1:1i
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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1:
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Fig. 3SWELL_CONSOLIDATION TEST RESULTSKumar & Associates25-7-162.06
rcn Kumr & Associates, lnc.@
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 25-7-162.06
SOILTYPE
Sandy Clayey Silt
Sandy Clayey Silt
Sandy Clayey Silt
UNCONFINED
COMPRESSIVE
STRENGTH
{osfl
ATTERBER
LIQUID LIMIT PLASTIC
INDEX
PERCENT
PASSING NO.
200 stEVE
83
68
[TION
SAND
tf/"|
GRAD
GRAVEL
(%)
NATURAL
DRY
DENSITY
{ocfl
100
88
NATURAL
MOISTURE
CONTENT
(%)
1 2 15.2
9.0
10.2
DEPTH
{ft}
4
3/,
PIT
2
Gurfield County
Driveway Exemption Letter
Date 4124/2O2s
To Whom it May Concern
Parcel Number 239L29 40 8006
Property Owner
Property Address
White Cloud Lot 6 LLC
500 White Cloud Road, Carbondale, CO 81623
M
rILI
The above address is exernpt from needing a Driveway Permit from Garfield County Road and
Bridge because:
The Driveway will not directly access a County maintained road
The driveway meets current County standards
Approved By: H. Shiles
Garfield County Representative:
For questions, please call:
Garfield County Road Bridge @ 970-625-8501
0298 Couniy Road 333A
Rifle, CO 81650 Phone: 970-625-8601 Fax: 970-625-8627
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