HomeMy WebLinkAboutSubsoil StudyI (*rt i;,'gr,*,ffiürn''13ü
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An Employac OumÇd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
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Office Locations: Denver (HQ), Parket Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 15, BLOCK 9
MONUMENT CREEK VILLAGE
49 PINYON PLACE
BATTLEMENT MESA, COLORADO
PROJECT NO.21-7-126
FEBRUARY 5,202I
PREPARED FOR:
PAIGE HADERLIE
C/O KIMBERLY KLEIN
704 MAIN STREET
SILT, COLORADO 81652
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TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY ........
PROPOSED CONSTRUCTION
SITE CONDITIONS..
FIELD EXPLORATION
SUBSURFACE CONDITIONS
DESIGN RECOMMENDATIONS
FOI.INDATIONS
FLOOR SLABS.
LINDERDRAIN SYSTEM
SURFACE DRAINAGE
LIMITATIONS
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 . SWELL-CONSOLIDATION TEST RESULTS
TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS
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Kumar & Associates, lnc. @ Project No. 21-7-'126
PURPOSE A¡ID SCOPE OF STUDY
This report presents the results ofa subsoil study for a proposed residence located on Lot 15,
Block 9, Monument Creek Village, 49 Pinyon Place, Battlement Mesa, 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 accordance with our proposal for geotechnical
engineering services to Paige Haderlie dated January 13, 2021.
An exploratory boring was drilled 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 foundations. 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 on Lot l5 will be a one story wood frame structure above a crawlspace
with an attached slab-on-grade garage. Grading for the structures is assumed to be relatively
minor with cut depths between about2 to 4 feet. We assume relatively light foundation loadings,
typical of the proposed type of construction.
If building loadings, locations, or grading plans change significantly from those described above,
we should be notified to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The property is vacant and vegetated with sparse grass and weeds. The ground surface appears
to have been graded for subdivision development and was partially covered with I to 2 inch deep
patches of snow. Lot 15 is bordered on the south by the cul-de-sac atthe end of Pinyon Place.
The ground surface is relatively flat and slopes gently down to the south.
Kumar & Associates, lnc. @ Project No. 21.7-'126
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FIELD EXPLORATION
The field exploration for the project was conducted on January 14,2021. An exploratory boring
was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring
was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted CME-
458 drill rig. The boring was logged by a representative of Kumar and Associates.
Samples of the subsoils were taken with l% and 2 inch 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. Depths at which the samples were taken and the penetration resistance values are
shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory
for review by the project engineer and testing.
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils, below about 6 inches of topsoil, consist of a hard to very stiff sandy silt and clay down
to about 7 feet, underlain by very dense silty clayey sandy gravel with basalt rocks down to the
bottom of the boring, llYz feet. Drilling in the dense coarse granular soils with auger equipment
was difficult and drilling refusal was encountered in the deposit.
Laboratory testing performed on samples obtained from the borings included natural moisture
content and density and percent finer than sand size gradation analyses. Results of swell-
consolidation testing performed on relatively undisturbed drive samples, presented on Figure 3,
indicate low compressibility under existing moisture conditions and light loading and a low to
moderate expansion potential when wetted. The laboratory testing is summarized in Table l.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist to moist.
Kumar & Associates, lnc. @ Project No. 21-7-126
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DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, we recommend the building be founded with spread footings bearing
on the natural fine grained subsoils.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural clay soils at the proposed crawlspace
and garage levels should be designed for an allowable bearing pressure of
2,000 psf. Based on experience, we expect initial settlement of footings designed
and constructed as discussed in this section will be about I inch or less. There
could be some additional movement of footings if the bearing soils become wet.
2) The footings should have a minimum width of l6 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
atea.
4) Continuous foundation walls should be 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 also be designed to resist
lateral earth pressure computed on the basis of an equivalent fluid unit weight of
at least 50 pcf for backfill consisting of the onsite soils.
5) All existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the relatively undisturbed soils.
6) A representative ofthe geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support Iightly loaded slab-on-grade
construction with a risk of movement similar to the foundation. To reduce the effects of some
Kumar & Associates, lnc. @ Project No. 21-7-126
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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 gravel should be placed beneath slabs-on-grade for
support. This material should consist of minus 2-inch aggregate with at least 50% retained on
the No. 4 sieve and less than l2Yo passing the No. 200 sieve.
Allfill 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 fill can consist of
imported gravel soils, such as'/o-inch road base, devoid of vegetation, topsoil, and oversized
rock.
LTNDERDRAIN SYSTEM
The proposed shallow crawlspace and slab-on-grade garage should not require an underdrain
system provided positive drainage away from the exterior of the house is maintained. If
installed, the drains should consist of drainpipe placed in the bottom of the wall backfill
sunounded 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 lo/o to a suitable gravity outlet or sump and pump. Due to the relatively flat
lot, it may be difficult to daylight a foundation perimeter drain. We recommend against
installing drywells for disposal of perimeter drain water due to the hard clay soil. Routing the
perimeter drains to an interior sump and pump inside the crawlspace may be feasible. Free-
draining granular material used in the underdrain system should contain less than 2% passing the
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.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the residence has been completed:
l) Inundation ofthe foundation excavations and underslab areas should be avoided
during construction. Drying could increase the expansion potential of the soils.
Kumar & Associates, lnc. @ Project No. 21-7-126
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2)Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95/o 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.
The onsite clay soils may be expansive when compacted and are not
recommended for backfîll under pavement or slab areas.
The ground surface sumounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first l0 feet in paved areas. Free-draining wall backfill should be
capped with about 2 feet of the on-site soils to reduce surface water infiltration.
Roof downspouts and drains should discharge well beyond the limits of all
backfill.
Landscaping which requires regular heavy irrigation should be located at least
5 feet from foundation walls.
3)
4)
s)
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area 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 boring drilled at the location 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 boring 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.
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 fìeld services during construction to review and
Kumar & Associates, lnc. @ Project No. 2'l-7-126
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monitor the implementation of our recommendations, and to verifu 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.
Respectfully Submitted,
Kumrr & Associates" Inc.
David A. Noteboom, Staff Engineer
Reviewed by:
Daniel E.
DEHlkac
Kumar & Associates, lnc. t)Project No.21-7"128
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APPROXIMATE SCALE_FEET
21 -7 -126 Kumar & Associates LOCATION OF EXPLORATORY BORING Fig. 1
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WC=5,1
DD=1 1 5
-200=87
TOPSO|L: CLAY AND SANDY SILT, 0RGANICS, R00TS, FIRM, MO|ST,
BROWN.
CLAY (CL): AND S|LT, SANDY, VERY STIFF T0 HARD, oRy T0
SLIGHTLY MOISÏ, TAN.
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WC=4,3
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GRAVEL (GC-GM): BASALT ROCKS, SANDY, SILTY, CLAYEY, VERY
DENSE, SLIGHTLY MOIST, BROWN.
50/3 DRIVE SAMPLE, 2-INCH I.D. CATIFORNIA LINER SAMPLE.
10 i DR|VE SAMPLE, 1 5/8-|NCH r.0. SPTLT SP00N STANDARD
PINETRATION TEST,
51 712 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 51 BLOWS 0F-'I '- A 14o-POUND HAMMER FALLING 30 INCHES \ryERE REQUIRED
15 I
TO DRIVE THE SAMPLTR 12 INCHES.
PRACTICAL AUGER DRILLING REFUSAL.
NOTES
THE EXPLORATORY BORING WAS DRILLED ON JANUARY 14, 2021
WIÏH A 4-INCH DIAMETTR CONTINUOUS FLIGHT POWER AUGIR.
2, THI LOCAÏION OF THE TXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURTS SHOWN ON THE SITE
PLAN PROVIDED.
3. THE ELEVATION OF THI EXPLORATORY BORING WAS MEASURED BY
HAND LEVEL AND RTFER TO THE BENCHMARK AT STREET LEVEL
AI CURB AS IOO" ASSUMED.
4. THE EXPLORATORY BORING LOCATION SHOULD BT CONSIDERED
ACCURAÏE ONLY TO THE DEGREE IMPLIED BY THT METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THT EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN
MATERIAL TYPES AND THE ÏRANSITIONS MAY BE GRAOUAL.
6 GROUNDWAÏER WAS NOT ENCOUNTERED IN THT BORING AT THE
TIMT OF DRILLING,
7, LABORATORY TEST RTSULÏS:
WC = WÀTER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (pcf) (ASIM D 2216);
-200 = PERCENTAGE PASSING N0, 200 SIEVE (ASTM D 1 1 a0);
21 -7 -126 Kumar & Associates LOG OF TXPLORATORY BORING Fig. 2
SAMPLE OF: Sondy Silt ond Cloy
FROM:Boringl@4'
WC = 4.3 %, ÐD = 115 pcf
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EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
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21 -7 -126 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig.5
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rc iiffil,ïffifffnr:,yå'*"TABLE 1SUMMARY OF LABORATORY TEST RESULTSNo. 21-7'126IBORING4IDEPTHSAMPLE LOCATION4.35It%tNATURALMOISTURECONTENT105115t%tGRAVEL(/ùSANDNATURALDRYDENSITY87PERCENTPASSING NO.2()O SIEVEUNCONFINEDCOMPRESSIVESTRENGTHATTERBERGLIQUID LIMITPLASTICINDEXSandy Silt and ClaySandy Silt and ClaySOIL TYPE