HomeMy WebLinkAboutSubsoils Study for Foundation DesignIC $¡#l[ffiffi1[iË;o*-'
An Employcc Owncd Gompony
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
June 12,2023
Eric Williams
981 County Road 245
New Castle, Colorado 81647
ecw5226@comcast.net
Project No.23-7-247
Subject: Subsoil Study for Foundation Design, Proposed New Residence,44157 Hwy 6,
East ofNew Castle, Garfield County, Colorado
Dear Eric:
As requested, Kumar & Associates performed a subsoil study for design of foundations at the
subject site. The data obtained and our recommendations based on the proposed construction
and subsurface conditions encountered are presented in this report. The study was conducted in
accordance with our agreement for geotechnical engineering services to you dated April 14,
2023.
Proposed Construction: An existing residence on the site has been removed and a new
residence will be constructed in its place. The new residence will be a one-story modular type
structure over crawlspace with attached slab-on-grade garage. The new residence will be located
at the same location as the previous residence and as shown on Figure 1. A portion of the
existing foundation which has remained in place may be used for the new building as feasible.
Cut depths for new foundation areas are expected to range between about2Yz to 3 feet.
Foundation loadings for this type of construction are assumed to be relatively light and typical of
the proposed type of consffuction.
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 occupied by the existing foundation from the previous
residence at the site. The existing foundation was partially slab-on-grade and partially shallow
crawlspace, and founded with spread footings as encountered in our exploratory pits. The terrain
is relatively flat ground surface was gently sloping down to the south. The Colorado River is
located across Highway 6 and I-70. Vegetation consists of grass lawn and fruit trees around the
existing foundation.
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 l% to 3 feet of foundation
backfill, consisted of stiff, very silty and occasionally clayey sand down to the maximum
I
explored depth of 6 feet. Results of swell-consolidation testing performed on relatively
undisturbed samples of the very sandy silt soils presented on Figures 3 and 4, indicate low
compressibility under existing moisture conditions and light loading and a nil to moderate
collapse (settlement under constant load) potential when wetted. The samples showed moderate
to relatively high compressibility when loaded after wetting. The laboratory testing is
summarized in Table 1.
No free water was observed in the pits at the time of excavation and the soils were generally
moist.
Where exposed at the exploratory pits, the existing spread footings for the existing foundation
appeared to be about 24 inches wide foundation.
X'oundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we believe spread footings placed
on the undisturbed natural soil designed for an allowable soil bearing pressure ef I,100 psf can
be used for support ofthe proposed residence. The soils tend to compress after wettffaìãÌF
could be some post-construction foundation settlement if the bearing soils were to become
wetted, and precautions should be taken to prevent wetting.
The footings should be a minimum width of 18 inches for continuous walls and 2 feet for
columns. Loose disturbed soils and existing fill 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 36 inches below the
exteriorgradeistypicallyusedinthisarea.Continuousroundutiffii¿bewell
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 a
lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site
soils as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab-on-grade construction. There could be some settlement if the subgrade were to become
wetted.
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 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 sand and gravel base
eeuree sheuld be pleeed beneath slabs fer suppert and te feeilitate drainsÊe, This materiel sheuld
Kumar & Associates, lnc. o Project No. 23-7-247
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consist of minus 2-inch aggregate with less than 50%o passing the No. 4 sieve and less than l2Yo
passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% ofmaximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site soils devoid of debris, topsoil and oversized (plus 6-inch) rocks.
Surface Drainage: A perimeter foundation drain around shallow (less than 4 feet deep)
crawlspace areas should not be needed with adequate compaction of foundation backfill and
positive surface drainage away from foundation walls. The following drainage precautions
should be observed during consffuction 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 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 pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backftll.
5) Landscaping which requires regular heavy irrigation, such as sod, and lawn
sprinkler heads 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 inigation.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this areaatthis 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 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 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 pits and variations in the subsurface conditions may not become evident until
excavation is performed . Ifconditions encountered during construction appeat different from
Kumar & Associates, lnc. @ Projecl No. 23-7-247
4
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
those described in this reporq 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 purposes. Vy'e 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 fill by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistanceo please let us know.
Respectfu lly Submitted,
Kumar & Associates,
James H. Parsons, P
Reviewed by:
David A. Y
JHPlkac
P
attachments Figure 1 - Location of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
Figures 3 and 4 - Swell-Consolidation Test Results
Table 1 * Summary of Laboratory Test Results
Cc DB Structural Design - Dustin Burner (¿ustln@¿Usd¡gry)
Kumar & Associates, lnc. @ Project No. 23-7-247
-TO HIGHWAY 6
EXISTING FOUNDATION
FROM PREVIOUS
STRUCTURE
PIT 2
PIT I
BENCHIIARK¡ TOP OF EXISTING
FOUNDATION, ASSUUED ELEVATION= 100'
5 10
APPROXIMATE SCALE_FEET
PROPOSED GARAGE
PROPOSED MODULAR
STRUCTURE
o
23-7 -247 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
PIT I
EL. gg'
PIT 2
EL. 99,
0 0
F
L¡Jf¡lt!
I-l-fL
L¡Jô
WC=17.3
DD=99
-2QO=62
WC=1 1.7
DD=1 O2 t-l¡J
L¡Jl!
I-FfLt!ô
5 5
WC=16.2
DD= 1 03
10
LEGEND
10
FILL: CLAY AND SILT, SANDY, STIFF, MOIST, BROWN
FILL; COBBLES WITH SMALL BOULDERS' SILTY SAND MATRIX, LOOSE, MOIST, MIXED
RED-BROWN.
SILT (ML); VERY SANDY, OCCASIONALLY CLAYEY, SCATTERED GRAVEL, STIFF, MOIST, RED
F
HAND DRIVE SAMPLE
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON APRIL 27,2023.
2. THE LOCATIONS OF fHE EXPLORATORY PITS WERE MEASURED APPROXIMATELY ÊY PACING FROM
FEATURES SHOWN ON THE FIGURE 1 SITE PLAN SKETCH.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO
TOP OF THE EXISTING FOUNDATION AS lOO' ASSUMED BENCHMARK.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY
TO TI{E 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.
7. LABORATORY TEST RESULTS:
wc = wÀTER CoNTENT (%) (ASTM D 2216);
DD = DRY DENSITY (pct) (lSrV D 2216);
-2OO= PERCENTAGE PASSING NO. 2oo SIEVE (ASTM D 1140)
23-7-247 Kumar & Associates LOGS OF IXPLORATORY PITS Fis. 2
E
t
I
SAMPLE OF: Very Sondy Cloyey Silt
FROM: Pit 1 Gt 6'
WC = I 6.2 %, DD = .l03 pcf
h
rithdt
ln
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ln
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NO MOVEMENT UPON
WETTING
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1
2
3
4
t.0 APPLIED 100
Fig. 3Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS23-7-247
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SAMPLE OF: Very Sondy Sill
FROM:Pit2@3.5'
WC = 11.7 %, DD = 102 pcf
rñftñtu
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1
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
-'j- ---- -Ì
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2
às
JJul
=UI
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zotr
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0
-2
-4
-6
-8
-10
-12
t.0 t0 t00
23-7-247 Kumar & Associates SWILL-CONSOLIDATION TEST RTSULTS Fig. 4
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TABLE I
SUMMARY OF LABORATORY TEST RESULTS
No.23-7-247
SOIL TYPE
Very Sandy Silt
Very Sandy Clayey Silt
Very Sandy Silt
losfl
UNCONFINED
COMPRESSIVE
STRENGTH
PLASTIC
INDEX
lolol
ATTERBERG LIMITS
f%ì
LIQUID LMT
PERCENT
PASSING NO.
200 slEvE
62
SAND
(%)t%t
GRAVEL
NATURAL
DRY
DENSfTY
(oc-fì
99
103
102
17.3
t6.2
tr.7
lo/ol
NATURAL
MOISTURE
CONTENT
3V,
{ft)
DEPTH
4
6
PIT
I
2
G Gurjietd County
Driveway Exemption Letter
Date 6/L2/2023
To Whom it May Concern:
Parcel Number 212334100199s
Property Owner
Property Address
Shanks HPW, LLC
44\57 HWY 6
u
LJ
The above adclress is exempt from needing a Driveway Permit from Garfield County Road and
Bridge because:
The Driveway will not cf irectly access a County nraintained road
Ihe driveway meets current Courrty standards
Approved By: H. Shiles
Garfield County Representative:
For questions, please call:
Garfield County Road Bridge @ 970-625-8601
0298 County Road 3:l3A
Rlfe, CO 8t660 Phon6: 070"625€001 Fex: 97t1.625-8827