HomeMy WebLinkAboutSubsoils Report for Foundation Designrcn Kumr & Assocl#,lnc.@
Geotechnical and Materials Engineers
and Environmental Scientists
An Employcc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970)945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (tIQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit Counry Colorado
SUBSOIL STT]DY
X'OR FOTINDATION DESIGN
PROPOSED RESIDENCE
LOT 46, PAi\ORAMA RANCHES
SUNLIGHT DRIVE
GARFIELD COUNTY, COLORADO
PROJECT NO.24-7-702
FEBRUARY 12,2025
PREPARED FOR:
RC SCHNEIDER CONSTRUCTION
ATTN: BOB SCHNEIDER
218 EAST VALLEY ROAD
CARBOI\DALE, COLORADO 81623
(Jcschneiderconst@ gmail. com)
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TABLE OT CONTENTS
PURPOSE AND SCOPE OF STUDY -1-
PROPOSED CONSTRUCTION..... ......... 1 .
SITE CONDITIONS .............. I .
SUBSURFACE CONDITIONS -2-
FOLINDATION BEARING CONDITIONS......-1-
UNDERDRAIN SYSTEM....
SURFACE DRAINAGE
LIMITATIONS 5
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS AND PITS
FIGURE 2 . LOGS OF DGLORATORY BORINGS AND PITS
FIGURES 3 AND 4 - SWELL.CONSOLIDATION TEST RESULTS
TABLE I _ SUMMARY OF LABORATORY TEST RESULTS
_1_
..-8-
Kumar & Associates, lnc. o Project No.24"7-702
PT]RPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for the proposed residence to be located on
Lot 46,Panorama Ranches, Sunlight Drive, Garfield County, 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 general accordance with our agreement for
geotechnical engineering services to RC Schneider Construction dated December 76,2024.
Exploratory borings were added to our scope of services due to the subsoil conditions initially
encountered at the site by the exploratory pits.
A field exploration program consisting of exploratory borings and pits 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 analyzedto develop recornmendations 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
Design plans for the proposed residence indicate a single-story structure above crawlspace with
an attached slab-on-grade garage located as shown on Figwe 1. Grading for the structure is
assumed to be relatively minor with cut depths of about 3 to 6 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 recommendations contained in this report.
SITE COI\DITIONS
Lot 46 was vacant and vegetated with grass, weeds and sagebrush at the time of ow site visit.
The ground surface was relatively flat and gently sloping down to the south with about 5 feet of
elevation difference across the proposed building footprint.
F'IELD EXPLORATION
The initial field exploration at the site consisted of observing 3 exploratory pits which were dug
on December 16, 2024. Due to the clay soils encountered in the pits, it was recommended to
dril|2 exploratory borings to evaluate the depth of clay soils which were then drilled on February
4,2025. The borings were advanced with 4-inch diameter continuous flight augers powered by a
truck-mounted CME-45B drill rig and logged by a representative of Kumar & Associates.
Kumar & Associates, lnc. o Project No.24-7-702
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Samples of the subsoils were taken with a 2-inchdiameter hand driven liner in the pits and with
a 2-inch I.D. spoon sampler in the borings driven into the subsoils at various depths with blows
from a 140 pound hammer falling 30 inches. This spoon sampler test is similar to the standard
penetration test described by ASTM Method D-l586. The penetration resistance values are an
indication of the relative density or consistency of the subsoils. Depths at which the samples
were taken and the penetration resistance values are shown on the Logs of Exploratory Borings
and Pits, Figure 2. The samples were returned to our laboratory for review by the project
engineer and testing.
SUBSTJRFACE CONDITIONS
Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The
subsoils encountered below about one foot of topsoil consist of very stiff, blocky sandy clay to
depths of about 5 to 10 feet overlying very stiff to hard, calcareous sandy silt and clay down to
variable depth and underlain by hard, sandy clay at Boring 1 to a depth of 25 feet.
Laboratory testing performed on samples obtained from the borings and pits included natural
moisture content and density, and finer than sand size gradation analyses. Results of swell-
consolidation testing performed on relatively undisturbed samples of the clay and silt soils,
presented on Figures 3 and 4, indicate the upper blocky clay soils are expansive and underlying
silt soils are compressible when wetted under relatively light loading. The laboratory testing is
summarized in Table 1.
No free water was encountered in the pits or borings at the time of excavation or drilling and the
subsoils were slightly moist to moist.
F'OUNDATION BEARING CONDITIONS
The clay and silt soils expected to be encountered at shallow cut depth have variable expansion
or compressibility potential, mainly when wetted. A shallow foundation placed on these soils
will have a risk of excessive settlemenVheave and building distress. The amount of movement
will depend on soil type and extent of subsurface wetting, and it will be critical to the long-term
performance of the structure to provide proper surface grading and drainage to keep the bearing
soils dry. Considering the variable nature of the subsoils, spread footings placed on compacted
structural fill are recommended to help limit the movement potential and risk of building
distress. If another type of foundation support is proposed, we should be contacted for additional
analysis and recommendations.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory borings and pits and the
nature of the proposed construction, the building can be founded with spread footings bearing on
Kumar & Associates, lnc. o Project No.24-7-702
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a minimum 3 feet of compacted structural fill soils with a risk of settlement mainly if the bearing
sotls become wetted and acceptaDle to tne owner.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
l) Footings placed on at least 3 feet of compacted filI soils should be designed for an
allowable bearing pressure of 1,500 psf. Based on experience, we expect initial
settlement of footings desighEdfidTorlstructed as discussed in this section will
be about 1 inch or less. Additional post-construction difFerential settlements of
about %to I inches could occur if the underlying natural soils become wetted.
2) The footings should have a minimum width of 18 inches for continuous walls and
2feetfor isolated pads.
---d3) 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 heavily reinforced top and bottom to span
local anomalies such as by assuming an unsupported length of at least 15 feet.
Foundation walls acting as retaining structures should also be designed to resist
lateral earth pressures corresponding to an equivalent fluid unit weight of at least
50 pcf for the onsite soils as backfill.
5) The topsoil and loose disturbed soils should be removed from the buildingarca
and down to at least 3 feet below design bearing level. The exposed soils in
footing areas should then be moistened and compacted. Structural fill should
consist of low permeable soil such as CDOT Class 6 road base extended at least
2 feetbeyond footing edges and compacted to at least9So/o of standard Proctor
density atnear optimum moisture content.
6) A representative of the geotechnical engineer should observe the building
excavation for bearing conditions and evaluate compaction of the structuralfill
during its placement prior to concrete placement.
FLOOR SLABS
The upper clay soils possess an expansion potential and slab heave could occur if the subgrade
soils were to become wet. Slab-on-grade construction can be used provided precautions are
taken to limit potential movement and the risk of distress to the building is accepted by the
owner. A positive way to reduce the risk of slab movement, which is commonly used in the
area, is to construct structurally supported floors over crawlspace which is recommended for
living areas of the residence. Where slab-on-grade is proposed, such as for the garage floor,
we recofirmend at least 2 feet of compacted structural fill underlie the slab.
Kumar & Associates, lnc. o Project No.2&7-702
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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 unrestrained
vertical movement. lnterior non-bearing partitions resting on floor slabs should be provided with
a slip joint at the bottom of the wall so that, if the slab moves, the movement cannot be
transmitted to the upper structure. This detail is also important for wallboards, stairways and
door frames. Slip joints which will allow at least 1%-inches of vertical movement are
recommended. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. Slab reinforcement and control joints 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 such as CDOT Class 6 base
course be placed immediately beneath slabs-on-grade for support. This material should consist
of minus Z-inchaggregate with less than5}%o passing the No. 4 sieve and less thanl?Yo passing
the No. 200 sieve.
Required fill beneath slabs should consist of imported relatively well graded granular material,
excluding topsoil and oversized rocks. The fiIl should be spread in thin horizontal lifts, adjusted
to near optimum moisture contento and compacted to at least95Yo of the maximum standard
Proctor density. All vegetation, topsoil and loose or disturbed soil should be removed prior to
fill placement.
The above recommendations will not prevent slab heave if the expansive soils underlying slabs-
on-grade become wet. However, the recommendations will reduce the effects if slab heave
occurs. All plumbing lines should be pressure tested before backfilling to help reduce the
potential for wetting.
UNDERDRAIN SYSTEM
Although groundwater was not encountered during our exploration, it has been our experience
in the area and where clay soils are present that local perched groundwater can develop during
times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a
perched condition. Therefore, we recommend below-grade construction, such as crawlspace and
basement areas (if any), be protected from wetting by an underdrain system. The drain should
also act to prevent buildup of hydrostatic pressures behind foundation walls.
The underdrain system should consist of a drainpipe surrowrded by free-draining granular
material placed at the bottom of the wall backfill. The drain lines should be placed at each level
of excavation and at least 1 foot below lowest adjacent finish grade, and sloped at a minimum
%Yo grade to a suitable gravity outlet. Free-draining granular material used in the drain system
should consist of minus Z-inchaggregate with less than 50Vo passing the No. 4 sieve and less
than2Yo passlng the No. 200 sieve. The drain gravel should be at least TYz feet deep. An
Kumar & Associates, lnc. @ Project No.24,7-702
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impervious liner such as 20 mil PVC should be placed below the drain gravel in a trough shape
and attached to the foundation wall above the void form with mastic to keep drain water from
flowing beneath the wall and to other areas of the building.
SURFACE DRAINAGE
Providing proper surface ggading and drainage around the building will be uitical to limiting
subsurface wetting and potential movement of the structure. 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
dwing 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 9oo/o of the maximum standard Proctor densify 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 paved areas. Graded swales should have a
minimum slope of 3%.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation such as sod and sprinkler
heads should be located at least 10 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.
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 borings and pits located as 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
practice should be consulted. Our findings include interpolation of the subsurface conditions
identified at the exploratory borings and 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 report, we should be notified so that re-evaluation of
the recommendations may be made.
Kumar & Associates, lnc. o Project No.2$7-702
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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 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 shata and testing of structural fill by a representative of
the geotechnical engineer.
Respectfu lly Submitted,
Kumar & Assoclates, lnc.
Steven L. Pawlak, P
Reviewed
Daniel E. Hardin, P.E.
SLP/kac
Kumar & Associates, lnc.6 Proiect No.24-7-702
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24-7-702 Kumar & Associates LOCATION OF EXPLORATORY
BORINGS AND PITS Fig. 1
21-7-742 Kurnar & Associates LOT 46 PANORAMA RANCHES LOGS OF EXPLORATORY BORINGS AND PITS F1s. 2
BORING I
EL 7261
BORING 2
EL 7265'
PIT ,I Ptt 2 PIT 3 I.ECiD
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TOFSOIIj ORGANIC SANDY SILT AND CL Y. nRY, ltOlST. BROWN. ROOTS.
cu! (cL,} slLTY, saNDy, vERy sflFF T0 HARO wlTH DEprH, SUGHTLY lroFr, BROWN,
ELOCKY TO SUGHTLY CALCAFEOUS wlTH D€PTH.
SILT AND CI.AY (UL-CL); SANDY, YERY SIIFF TO HARD, SUGITfLY T'OISI, I.JCHT BROWN TO
PALE WHTTE. HIGHLY CAICAREOUS.
DRTVE SATPIE, 2-INCTI I.D. CATIFORNIA LINER SATPIE.
HAND DRIVEN 2-INCH DIAIffEN LNER SAXPI..E.
23/12
22/12
22/12
23/12
WC=6.0
DD=85
WC=6.9
D0=101
-200=89
5 WC=l /+.7
DD=75
5
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2E/12
WC=2O.2
t5/12
WC=I1.5
DD=l02
We=12.7
DO=72
-2oO=77 to
DD=88 arzru DRIVE SAltP[.E BLOW COUNT. INDICATES THAT 23 BLOryS OF A 140-POUNO }tAtaUER--''- FAIJJNG 3(} INCHES W€RE REQUIRED TO DRIVE THE SAIIPIfR 'I2 INCHES.
t5 &/t2
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NOTEA
1. It{E EXPLORAToRY BORIM}S WERE DRIIED oN FE8RUAnY + m23 WTH A /t-tNcH-DlAyEtER
COI{IAIUOI'S-ruGHf PO}ER AI'CER. THE E(PLORATORY PITS YERE DUG ON DEC€Y8ER 16,
2U21 YIIHABC|(lloE.
2. THE EXPLORATORY EORINGS AND P]TS WERE LOCATED C' THE CUEilT.
3. ITIE EI.EYATIONS OF lHE EXPI.ORATORY P'TS WERE NOT T'EASURED AND IHE LOGS OF THE
EXPLOMTORY PNS ARE PLOTIED TO DEPITH. TI{E EI.EVATIONS OT tl{E EXPLORATORY BORINGS
WERE OBTAINI! BY II{TERPOIITK'N BETWEEN CONTOURS ON IHE $TE PI.AN PROVIOED
/t, THE EXPIORATOfiY HrRlt{G AND PIT UlClTtOttS AND EtrVAIfiTNS SHoUtIt B€ CONSTDERED
ACCURAIE OiILY TO I}IE DECREE ITruED ET THE IIEI}IOO USED.
20
25/6, s2/6 38/t2
WC=|1.3
DD=t05
-2OO=7E
20
3s/6,10/6
5. THE LINES BETWEEN UAIERIAIS S}IOWN ON
REPRESENT TTIE APPROXITIATE BOUNOARIES
TAY BE GMDUAL
THE EXPLORATORY
OENflEEN IIAIERIAL
BORING AI{O PITS LOGS
TYPES AND THE TRANSITIONS
25 25
30 30
6. GROUNDWATER VIAS NOT EN@UNTERED IN THE BOBNGS AND PITS AT I}IE IIME OF DRII,IING
oR EXCAV TTON.
7. IABORATORY TEST R6ULTS:
WC = WATER CoNIENT (!) (ASrI D2216);
DD = Dtrf DB{S|W (pcf) (ASn 02216)i
-2o0= PERCENIAG€ PASSIIIG l{o, 2oo slEvE (ASTil Dilao).
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SAMPLE OF: Colcqreous Sondy Sllt ond Cloy
FROM:BorlnglOg'
WC = 2O.2 %, DD = 88 pcf
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NO MOVEMENT UPON
WETTING
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SAMPLE OF: Sondy Cloy
FROM:Boring2Og'
WC = 11.5 %, DD = 102 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
-2
Fig. 324-7-702 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS
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SAMPLE OF: Colcoreous Sondy Sllt cnd Cloy
FROM:Pfi2e5'
WC = 14.7 ,6, DD = 75 pcf
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ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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Fig. 4Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS24-7-702
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project !{o..24-7-792
BORING
1
2
.,
L
1
NATURAL
MOISIURE
CONTENT
NATURAT
DRY
DENSITY
LrilTS
GRAVEL SAtID
("6)
PERCENT
PASSING NO.
200 stEvE
PLASNC
INDD(
PIT DEPTH LIQUID LITIIT
Pl"l
1 9
9
9
5
2
8
J
I 1.3
11 .5
20.2
14.7
6.9
t2.7
8.0
105
t02
88
75
1 0 1
72
85
78
89
77
UNCONFINED
cotrtPREsstvE
STRENGTH
{osfl
Calcareous Sandy Silt and
Clay
Sandy Clay
Calcareous Sandy Silt and
Clay
Calcareous Sandy Silt and
Clay
Blocky Sandy Clay
Calcareous Sandy silt and
Clay
Blocky Sandy Clay
SOIL TYPE