HomeMy WebLinkAboutSubsoil Studyrcrf i'ffififfi.Ësnt'rÍå**
An Employcc Orncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970)945-7988
fax: (970) 945-8454
email : kagl enwood@kumarusa.com
wwwkumarusa.com
Offrce Locations: Denver (HQ), Par*er, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
RECEIVED
JAN I 3 2022
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 3, BLOCK 7, SBCTION 2
BATLEMENT CREEK VILLAGE
542 MEADOW CREEK DRTVE
GART'IELD COUNTY, COLORADO
PROJECT NO.21-7-824
DECEMBER 30,2021
PREPARED FOR:
RUSSELL CART\YRIGHT
35 \ilILLOWVIEW WAY
PARACHUTE, COLORADO 81635
russecart@email.com
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION
SITE CONDITIONS..
DE SIGN RECOMMENDATIONS
FOUNDATIONS
FOLTNDATION AND RETAINING WALLS
FLOOR SLABS
UNDERDRAIN SYSTEM
SURFACE DRAINAGE
LIMITATIONS.........
FIGI'RE 1 . LOCATION OF ÐGLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGIIRE 3 - SIWELL-CONSOLIDATION TEST RESULTS
TABLE I. SUMMARY OF LABORATORY TEST RESULTS
1
1
I
FIELD Ð(PLORATION I
SUB STIRFACE CONDITIONS 2-
FOTINDATION BEARTNG CONDITIONS ,......2 -
J
J
4
5
5
5
-6-
Kumar & Associates, lnc.6 Project l{o.2l-7-824
PT]RPOSE AND SCOPE OF STT]DY
This report presents the results of a subsoil study for a proposed residence to be located on Lot 3,
Block 7, Section 2, Battlement Creek Village, 542Meadow Creek Drive, Garfield County,
Colorado. The project site is shown on Figure 1. The purpose of the study was to develop
tecoÍtmeûdations for the foundation design. The study was conducted in accordance with our
agreement for geotechnical engineering services to Russell Cartrvright dated October 19,2021.
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 werc analyzed to develop recoflrmendations for
foundation t5ryes, depths and allowable pressures for the proposed building foundation. This
report summarizes the data obtained during this study and presents our conclusions, design
recoûìmendations and other geotechnical engineering considerations based on the proposed
construction and the subsurface conditions encountered.
PROPOSED CONSTRUCTION
Plans for the proposed residence were conceptual at the time of our study. The proposed
residence will generally be a one or two-story wood-frame structure above crawlspace with an
attached slab-on-grade garage. Grading for the structure is assumed to be relatively minor with
cut depths between about 2 to 5 feet. V/e 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 CONDITIONS
The subject site was vacant at the time of our field exploration. The ground surface is
moderately to strongly sloping down to the north-northwest. A soil stocþile approximately 3 to
5 feet in height had been placed near the rear of the lot. Vegetation consists of scattered grass,
weeds and sagebrush.
FIELD EXPLORATION
The field exploration for the project was conducted on November 19, 2021 . One exploratory
boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The
Kumar & Associates, lnc. @ Project No.21-7-824
-2-
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 & Associates, Inc.
Samples of the subsoils were taken with l%-inch and 2-inchl.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-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 Log of Exploratory Boring, Figure 2. The samples were retumed to our laboratory
for review by the project engineer and testing.
ST]BST]RFACE C ONDITIONS
A graphic log of the subsurface conditions encounteted at the site is shown on Figure 2. The
subsoils encountered, below about I foot of topsoil, consist of very stiff, slightly sandy to sandy
silt that graded to very stiff, sandy siþ clay below about 5 feet. At about 13 feet, dense, clayey
to silty sandy gtavel and cobbles was encountered down to the maximum drilled depth of 26 feet.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and density and finer than sand grain size gradation analyses. Results of swell-
consolidation testing performed on a relatively undisturbed drive sample of the silt soil,
presented on Figure 3, indicate low compressibility under natural low moisture condition and
moderate to high compressibility when wetted and additionally loaded. 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.
F'OUNDATION BEARING CONDITIONS
The upper fine-grained soils encountered in the boring possess low bearing capacity and
generally moderate compressibility potential. The underþing coarse granular soils possess
moderate bearing capacity and typically low compressibility potential. The residence can be
supported on lightly loaded spread footings bearing on the upper fine-grained soils with a risk of
settlement. The risk of foundation settlement is primarily if the bearing soils become wetted and
precaution should be taken to prevent subsurface wetting. A lower risk option would be to
extend the bearing level down to the underlying granular soils with a deep foundation system
Kumar & Associates, lnc, o Project No.21-7-824
-3-
such as helical or bored piers. Provided below are recommendations for a spread footing
foundation. If recommendations for a deep foundation system are desired, we should be
contacted to provide them.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, the building can be founded with spread footings bearing on the fine-
grained soils with a risk of foundation settlement.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
l) Footings placed on the undisturbed natural soils should be designed for an
allowable bearing pressure of 1,000 psf. Based on experience, \¡ve expect initial
settlement of footings designed and constructed as discussed in this section will
be up to about 1 inch. Additional post-construction foundation settlement could
occur if the bearing soils become wetted. The magnitude of additional settlement
would depend on the depth and extent ofthe wetting but may be on the order of
I to l% inches.
2) The footings should have a minimum width of 20 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
lateral earth pressures as discussed in the "Foundation and Retaining Walls"
section of this report.
5) The topsoil and any loose disturbed soils should be removed and the footing
bearing level extended down to the relatively firm natural soils. The exposed
soils in footing area should then be moistened and compacted.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
Kumar & Associates, lnc. @ Project No.21-7-824
-4-
FOUNDATION AND RETAINING WALLS
Foundation walls and retaining structures which are laterally supported and can be expected to
undergo only a slight amount of deflection should be designed for a lateral earth pressure
computed on the basis of an equivalent fluid unit weight of at least 55 pcf for backfill consisting
of the on-site fine-grained soils. Cantilevered retaining structures (if any) which are separate
from the residence and can be expected to deflect sufficiently to mobilize the full active earth
pressure condition should be desigued for a lateral earth pressure computed on the basis of an
equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site fine-grained
soils.
All foundation and retaining structures should be designed for appropriate hydrostatic and
surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The
pressrres reòommended above assume drained conditions behind the walls and a horizontal
backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will
increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain
should be provided to prevent hydrostatic pressure buildup behind walls.
Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum
standard Proctor density at a moisture content near optimum. Backfill placed in pavement and
walkway areas should be compacted to at least 95% of the maximum standard Proctor density.
Care should be taken not to overcompact the backfill or use large equipment near the wall, since
this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall
backfrll should be expectedo even if the material is placed correctly, and could result in distress to
facilities constructed on the backfill.
The lateral resistance of foundation or retaining wall footings will be a combination of the
sliding resistance of the footing on the foundation materials and passive earth pressure against
the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated
based on a coefficient of friction of 0.35. Passive pressure of compacted backfill against the
sides of the footings can be calculated using an equivalent fluid unit weight of 350 pcf. The
coefficient of friction and passive pressure values recoûtmended above assume ultimate soil
strength. Suitable factors of safety should be included in the design to limit the strain which will
occur at the ultimate strength, particularþ in the case of passive resistance. Fill placed against
the sides of the footings to resist lateral loads should be compacted to at least 95% of the
maximum standard Proctor density at a moisture content near optimum.
Kumar & Associates, lnc. ô Project No,21-7-824
5
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade
construction. The silt soils are typically compressible when wetted and precautions should be
taken to prevent wetting of the subgrade soils. 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 l?Vopassrngthe No. 200 sieve.
A11fill materials for support of floor slabs should be compacted to at least 95o/o of møximum
standard Proctor density at a moisture çontent 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 foundæion drain system is not required. It has been our
experience in mountainous areas that local perched gtoundwater can develop during times of
heavy precipitation or seasonal runoff. Frozen gtound during spring runoff can create a perched
condition. 'We recommend below-grade construction, such as retaining walls 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 recommendations for an underdrain system. All earth
retaining structures should be properly drained.
SIIRFACE DRAINAGE
Providing and maintaining proper surface grading and drainage 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:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
Kumar & Associates, lnc. @ ProJect No.2'l-7-824
-6-
3)
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 densþ in landscape areas.
The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. V/e recommend a minimum
slope of 12 inches in the first l0 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
covered with filter fabric and 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, such as sod, and lawn
sprinkler heads should be located at least l0 feet from foundation walls.
Consideration shouldbe given to the use of xeriscape to limitpotential wetting
of soils below the foundation caused by irrigation.
4)
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 recoûlmendations submitted in this report are based upon the data obtained
from the exploratory boring drilled at the location indicated on Figure I, 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 constnrction 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 field services during construction to review and
monitor the implementation of our recommendations, and to verifr that the recommendations
2)
5)
Kumar & Associates, lnc, o Project No.21-7.824
-7 -
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recoÍlmendations 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.
Respectfirlly Submitted,
Kumar & Associates, Inc.
}r'rt rf lt Pa¿.aror
James H. Parsons, P.E.
Reviewed by:
Steven L.
JHP/kac
1622:2
slz ..,
Kumar & Associates, lnc. @ Project No.21-7-824
21088 S F ¿¿uut, ü t
F L t6'u.Ë..I 5
24543 $ F
,¿'u. €.
I 2b':J 0-¡'
_a
s
--J
MEADOW CREEK DRIVE
625ei0 s r
2849i
{t\l \l
I
a
I
.ç'ù'2 t
4
I'î-
2û11? S F
.d.
^cit'
;*=
BENCHIIARK:
WATER VALVT COVER
CREEK DRIVE.EL t00" AssuHED.
-*MEADow ,r^iò$'
Ð,?r
9v
50
f
I
a
3
25402 $ F
I
15
21183 S FL4
245?? S F
u.E.
r3
z3s?0 s F
2S'S.L
Êo'u.{.
1
24441 S F
tu'\t'g'
6
a
6
24ìI
2
21086 S F
4
?01?8 $ F
LOT 5
542 MEADOW
CR DR.
e
22?6bs F
BORING I
-\
25'B t*
5
0 73 3 $F2
APPROXIMATE SCALE-FEET
Fig. 1LOCATION OF EXPLORATORY BORINGKumar & Associates21 -7 -824
:
ò
BORING 1
EL. 93.5'
LEGEND
TOPSOIL; CLAY AND SILT, 0RGANIC, FIRM, SLIGHïLY
MOIST, TAN.
0 31 /12
WC=4.1
DD= 1 02
-2OO=90
SILT (ML); SÀNDY, SLIGHTLY CALCAREOUS, VERY
STIFF, SLIGHTLY MOIST, LIGHT BROWN, LOESS.
5
17 /12
WC=5.6
DD=91
CLAY (CL); SANDY, SILTY, VERY STIFF, SLIGHTLY M0|ST,
LIGHT BROWN, CALCAREOUS, POROUS, LOW PLASTICITY.
GRAVTL (GU-CC); S|LTY T0 CLAYEY, SANDY, C0BBLES
AND PROBABLE BOULDERS, I4EDIUM DTNST TO DENSE,
SLIGHTLY MOIST, LIGHT BROVÍN.1e/12
WC=5.9
DD=91
-2OO=87 F
¡
DRIVT SAMPLT, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
10 40/12
DR|VE SAMPLE, 1 3/8-INCH l.D. SPLIT SP00N STANDARD
PENTTRATION TEST.
t-l+lL¡Lr
IIt-o-l¡lo
'. r". DRIVE SAMPLE BLOW COUNT. INDICATES THAT 3l BLOWS 0Frt/ t¿
^
r4o-pouND HAMMTR FALLTNG J0 rNcHEs wERE REQUIRED
TO DRIVE THE SAMPLER 12 INCHES.
15
57 /6
20 20/12
WC=2.0
-2OO=25
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON
NOVEMBER 19, 2021 WITH A 4-INCH DIAMETER
CONTINUOUS FLIGHT POWER AUGER.
25
2. THE LOCATION OF THE EXPLORATORY BORING
WAS MEASURED APPROXIMATELY BY PACING
FROM FEATURES SHOWN ON THE SITE PLAN
PROVIDED.14/6,50/2.5
3. THE ELEVATION OF THE EXPLORAÏORY BORING
WAS MEASURED BY INSTRUMENT LEVEL AND
REFERS TO THE BENCHMARK ON FIG. 1.
50
4. TI{E EXPLORATORY BORING LOCAÏION AND
ELEVATION SHOULD BE CONSIDERED ACCURATE
ONLY TO THE DEGREE IMPLIED BY THE METHOD
USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE
EXPLORATORY BORING LOG REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL
TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE
BORING AT THE TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (PCT) (¡STU D 2216);
-200 = PERCENTAGE PASSING NO. 200 SIEVE
(ASTM D 1140).
Fig. 2LOG OF EXPLORATORY BORINGKumar & Associates21 -7-824
Ê
Ë
SAMPLE OF: Sondy Silt
FROM:BoringlO4'
WC = 5.6 %, DD = 91 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
(
\
\
I
\
\
'r
I
I
l
Ihd. tèt @ulb opp¡y ont to üG
FmCü tótc¿ Ût! ttliig rrPott
lllol not bc ßF!ôE.d. arept h
lun, ¡ithøt th rrltur aþrool of(unôr ond ¡øclqt€. h. SFll
Conaolidct¡d t*tìñE F.fm.d inmørdoÉ tith ¡slll D-416.
2
0
JıJ-¿
l¡J
=U'
t_4
zotr
ô
=-ooIAzoc)-B
-10
-12
-14
r001.0 APPLIED
Fig. 3SWELL-CONSOLIDATION TEST RTSULTS21 -7 -824 Kumar & Associates
lcrtiiffif;ffifËtr{*F;-."TABLE 1SUMMARY OF I.ABORATORY TEST RESULTSNo. 21-7{24Silty Sand and GravelSOIL TYPESlightly Sandy SiltSandy SiltSandy Sihy Clay{psfìUNCONFINEDCOMPRESSIVESTRENGTHftlPI-ASTICtl'tDB(ATTERBERG LIMITS(ololUQUID LIMfÍ25PERCENTPASSING NO.200 slEvE9087('/")SANDGRADANON{%}GRAVETI91I{ocflNAlIRALDRYDEI{SITYt024.t5.65.92.0(ololNATURALMOISTURECONTENT20tf$DEPTTII47SAIIIPTE LOCANONBORINGI