HomeMy WebLinkAboutSubsoil Studyrc||iäffi,[.ffifffi5,lnÊ;å.**
An Employcc Ownsd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumanrsa.com
OfÏice Locations: Denver (HQ), Parkeq Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
SUBSOIL STUDY
F'OR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 4, ORR-SMITH SUBDTVTSION
TBD COUNTY ROAD 312
GARFIELD COUNTY, COLORADO
PROJECT NO.21-7-688
DECEMBER 1,2021
PREPARED FOR:
DON REBOUL
P.O. BOX 994
NE\ü CASTLE, COLORADO 8L647
donreboulconstruction(D gmail.com
?31-309- 3 bb?
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION ..
SITE CONDITIONS...
FIELD EXPLORATION
SUBSURFACE CONDITIONS
DESIGN RECOMMENDATIONS
FOUNDATIONS
FLOOR SLABS
TINDERDRAIN SYSTEM
SURFACE DRAINAGE....
SEPTIC DISPOSAL AREA
LIMITATIONS
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS AND PITS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS AND PITS
FIGURE 3 - LEGEND AND NOTES
FIGURES 4 and 5 - SWELL-CONSOLIDATION TEST RESULTS
FIGURE 6 - GRADATION TEST RESULTS
TABLE 1. SUMMARY OF LABORATORY TEST RESULTS
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Kumar & Associates, lnc. @ ProJect No.21-7.688
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located onLot 4,
Orr-Smith Subdivision, TBD County Road 312, Garfield Counf, Colorado. The project site is
shown on Figure 1. The purpose of the study was to develop recommendations for the
foundation design. The sfudy was conducted in accordance with our agreement for geotechnical
engineering services to Don Reboul dated Augu st 23, 2021.
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 analyzed to develop recommendations 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
The proposed residence will be a single-story structure with attached garage. Ground floor will
be slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths
between about 2to 4 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 notifîed to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The subject site was vacant at the time of our field exploration. The driveway was under
construction and an existing well was near the west side of the lot. The ground surface was
gently to moderately sloping down to the north. Garfield Creek crosses the northern portion of
the lot' The subject site was previously an irrigated field and vegetation on the edge of the field
near the creek consists of oak brush.
Kumar & Associates, lnc. @ Project No. 21'7'688
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FIELD EXPLORATION
The f,reld exploration for the project was conducted on October 18,202L Two exploratory
borings were drilled and two profile pits were excavated at the locations shown on Figure I to
evaluate the subsurface conditions. The borings were advanced with 4-inch diameter continuous
flight augers powered by a truck-mounted CME-458 drill rig. The profile pits were excavated
with a rubber tracked excavator. The borings and pits were logged by a representative of Kumar
& Associates, Inc.
Samples of the subsoils were taken in the borings with 13Á-inch and 2-ìnch 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 and hardness of the bedrock. Samples of the subsoils were
taken in the pits with relatively undisturbed and disturbed sampling methods. 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.
Samples of the subsoils were taken with relatively undisturbed and disturbed sampling methods
Depths at which the samples were taken are shown on the Logs of Exploratory Pits, Figure 2.
The samples were returned to our laboratory for review by the project engineer and testing.
SUBSURFACE CONDITIONS
Graphic logs of the subsurface conditions encountered, atthe site are shown on Figure 2. The
subsoils encountered below about 1 to 1% feet of topsoil consist of stiff to very stiff, sandy clay
down to between 13 and l4Yz feet deep where medium dense/stiff sand and clay was encountered
down to 17 to 19 feet deep. Below the clay and sand soil, relatively dense silty sand and gravel
was encountered in both borings to depths of between 22 and22%feet deep where weathered to
hard sandstone/siltstone bedrock was encountered down to the maximum explored depth of
26 feet.
Laboratory testing performed on samples obtained from the borings included natural moisture
content and density and gradation analyses. Results of swell-consolidation testing performed on
relatively undisturbed drive samples of the clay soils, presented on Figures 4 and 5, indicate
variable low to moderate compressibility or expansion under conditions of light loading and
wetting. Our experience in the area indicates the expansion potential is likely anomalous and can
Kumar & Assoclates, lnc. o Project No. 21-7-688
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be neglected in foundation design. We should be contacted at the time of construction to observe
and test the exposed soils for an expansion potential. Results of gradation analyses performed on
a disturbed sample from Profile Pit 1 of the clay subsoils are shown on Figure 6. The laboratory
testing is summarized.in Table 1.
No free water was encountered in the borings or pits at the time of exploration and the subsoils
were slightly moist to very moist with depth.
DESIGN RECOMMENDATIONS
FOIINDATTONS
Considering the subsurface conditions encountered in the exploratory borings and pits and the
nature of the proposed construction, we recommend the building be founded with spread footings
bearing on the natural clay soils below the topsoil.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural soils should be designed for an
allowable bearing pressure of 1,500 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be up to about %to l% inches and mainly if the bearing soils are wetted.
2) The footings should have a minimum width of 18 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 heavily reinforced top and bottom to span
local anomalies such as by assuming an unsupported length of at least 14 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
55 pcf.
5) Topsoil and any loose disturbed soils should be removed and the footing bearing
level extended down to the firm natural soils. The exposed soils in footing area
should then be moistened and compacted.
6) A representative ofthe geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions-
Kumar & Associates, lnc. o Project No,21.7-688
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FLOOR SLABS
V/e should be contacted at the time of construction to observe and test the slab-on-grade bearing
material for expansion potential. The naturaT on-site soils, exclusive of topsoil and expansive
materials, 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 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 relatively well graded sand and gravel such as
road base should be placed beneath slabs for support. This material should consist of minus
2-inch aggregate with at least 50% retained on the No. 4 sieve and less than 12% passing the No.
200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site soils devoid of vegetation, topsoil and oversized rock.
UNDERDRAIN SYSTEM
It is our understanding the finished floor elevation at the lowest level is at or above the
surrounding grade. Therefore, a foundation drain system is not required. 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 dwing spring
runoff can create a perched condition. We recommend below-grade construction, such as
retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic
pressure buildup by an underdrain and wall drain system.
If the finished floor elevation of the proposed structure has a floor level below the surrounding
grade, we should be contacted to provide recoÍrmendations for an underdrain system. All earth
retaining structures should be properly drained.
SURFACE DRAINAGE
Providing andmaintaining proper surface drainage conditions will be critical to the long-term
satisfactory performance of the proposed residence. The following drainage precautions should
be observed during construction and maintained at all times after the residence has been
completed:
Kumar & Associates, lnc. @ Project No,21.7.688
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Excessive wetting or drying of the foundation excavations and underslab areas
should be avoided during construction. Drying can increase the expansion
potential of the clay soils.
Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95o/o 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.
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 fèet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in paved areas.
Roof downspouts and drains should discharge well beyond the limits of all
backfill.
Landscaping which requires regular heavy irrigation should be located at least
10 feet from foundation walls.
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SEPTIC DISPOSAL AREA
Two profile pits were dug at the locations shown on Figure 1. The subsurface profile mainly
consists of a silty clay loam with a strong blocþ structure. This is fypically a type 3 soil.
Results of a USDA gradation test performed on a sample of the fine-grained soils are shown on
Figure 6 and the test results are summarized on Table 1. Based on these fîndings, the tested area
should be suitable for an infiltration septic disposal system. A civil engineer should be engaged
to design the septic disposal system.
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this arca at this 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 drilled and pits excavated at the locations 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 and
extrapolation 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
Kumar & Assocíates, Inc.6 Project No, 21.7.688
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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.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical inteqpretations 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 v€riry 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 struchral fill by a representative of
the geotechnical engineer.
Respectfully Submitted,
K¡¡rnar & Âssociates, Ine.
James H. Parsons, P.E.
Reviewed by:
Steven L.
JHPlkac
Kumar & Associates, lnc, i¡Projeet No. 21.i.688
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21 -7 -688 Kumar & Associates LOCATION OF EXPLORATORY
BORINGS AND PITS Fig. 1
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BORING 1
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BORING 2
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PROFILE PIT_1
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PROFILE PIT-2
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WC=1 1.6
DD=94
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WC=11.9
DD= 1 02
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SILT=47
CLAY=36
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DD=112
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UC=5000
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21 -7 -688 Kumar & Associates LOGS OF TXPLORATORY BORINGS AND PITS Fig. 2É
LEGEND
TOPSOIL; CLAY, SANDY, ORGANIC, FIRM, MolST, DARK BROWN
cLAy (cL); SANDY, S|LTY, STIFF TO VERY STIFF, SLIGHTLY MOIST TO MOIST, BROWN, LOW
TO MEDIUM PLASTICITY.
sAND AND CLAY (SC-CL); SCATTERED GRAVEL, MEDIUM DENSE/STIFF, MOIST, BROWN.
GRAVEL AND SAND (GM-SM); SILTY, MEDIUM DENSE TO DENSE, VERY MO|ST, MIXED BROWN.
SANDSTONE/SILTSTONE BEDROCK; WEATHERED TO HARD, SLIGHTLY MOIST, BROWN. WASATCH
FORMATION.
DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
DRTVE SAMPLE, 1 3/1-|NCH t.D. SPLIT SPOON STANDARD PENETRATION TEST
DISTURBED BULK SAMPLE.
iR/1o DRIVE SAMPLE BLOW COUNT. INDICATES THAT 15 BLOWS OF A 14O-POUND HAMMER'"/ '' FALLTNG J0 tNcHES WERE REQUIRED To DRtvE THE SAMPLER t 2 tNcHEs.
---> DEPTH AT WHICH BORING CAVED.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON OCTOBER 18, 2021 WITH A 4-INCH DIAMETER
CONTINUOUS-FLIGHT POWER AUGER. THE EXPLORATORY PITS WERE EXCAVATED ON OCTOBER 1 8,
2021 WITH A RUBBER TRACKED EXCAVATOR.
2, THE LOCATIONS OF THE EXPLORATORY BORINGS AND PITS WERE MEASURED APPROXIMATELY BY
PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY BORINGS AND PITS WERE OBTAINED BY INTERPOLATION
BETWEEN CONTOURS ON THE SITE PLAN PROVIDED.
4, THE EXPLORATORY BORING AND PIT LOCAIIONS AND ELEVATIONS SHOULD BE CONSIDERED
ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING AND PIT LOGS
REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS
MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS OR PITS AT THE TIME OF DRILLING OR
DIGGING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D2216);
DD = DRY DENSITY (pct) (lsrv D2216):
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM Dl1AO);
Uc = UNCONFINED COMPRESSIVE STRENGTH (psi) (ASTM D 2166);
GRAVEL = PERCENT RETAINED ON NO. 10 SIEVE;
SAND = PERCENT PASSING NO. 1 0 SIEVE AND RETAINED 0N NO. 525 SIEVE;
SILT = PERCENT PASSING N0. 325 SIEVE TO PARTICLE SIZE .002MM;
CLAY = PERCENT SMALLER THAN PARTICLE SIZE '002MM.
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SAMPLE OF: Sondy Cloy
FROM:Borîng1@5'
WC = 1 1.9 %, DD = 102 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
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21 -7 -688 Kumar & Associates SWILL_CONSOLIDATION TTST RTSULTS Fig. 4
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SAMPLE OF: Sondy Silty Cloy
FROM:BorÌng2ro 2.5'
WC = 11.6 %, DD = 94 pcf
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21 -7 -688 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 5
HYDROMETER ANALYSIS SIEVE ANALYSIS
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24 HR, 7 HF 1 t\¡tN,
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+140 #60 #35 #18 #10 #4 1 1/2', 3" 5" 6" 8"
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60 40
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80 20
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100 0,001 .002 .005 .009 ,019 .045 .106 .025 .500 1.00 2.00 4.75
DIAIVETER OF PARTICLES IN IV1ILLIMETERS
9,5 19.0 37.5 76.2 152 203
CL}Y COBBLES
GRAVEL 1 %SAND 14 %SILT 49 %CLAY 36 %
USDA SOIL TYPE: Silty Clay, Loam FROM: Profile Pit 1 @ 4'- 5'
GRAVEL
SILT
21 -7 -688 Kumar & Associates USDA GRADATION TEST RTSULTS Fig. 6ê
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lcÂi,ffifim:miiü--TABLE 1SUMMARY OF I.ABORATORY TEST RESULTSNo.21-7-688Sandy ClaySandy ClaySand and ClaySandy Siþ ClaySilty Clay LoamSOILWPEfosflUNCONFINEDCOMPRESSIVESTRENGTH500036CLAY%l49sltT(%)SAND(%)t4IUSDA SOIL TEXTUREGRAVEL(%)63PERCENTPASSINGNO.200SIEVE79SANDf^tGRADATION("/"1GRAVEL94NATURALDRYDENSTTY(pcrl1,02112106.611811NATURALMOISTURECONTENT(%)11.916.319.00I51ZYz4to5DEPTH(fr)512Profile PitISAMPLE LOCATIONBORING