HomeMy WebLinkAboutSubsoils Report for Foundation DesignlGnfliffilfiffif6trni':1fil-*
An Employcc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
wwwkumarusa.com
Office Locations: Denver (HQ), Parkeq Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
STIBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
PARCEL 13, HIGH ASPEN RANCH
I4Z?IilIGId ASPEN DRIYE
GARFIELD COUNTY, COLORADO
PROJECT NO. 25-7-114
FEBRUARY 25,2025
PREPARED FOR:
TED AND KAREN MILLER
1248 RIMROCK DRIVE
RTFLE, COLORADO 81650
ted@tedmillerconsultins.com
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY ..............,......
PROPOSED CONSTRUC'I'ION
SITE CONDITIONS
FIELD EXPLORATTON .....
SUBSURFACE CONDITTONS
FOTINDATION BEARING CONDITIONS
DESIGN RECOMMENDATIONS ...
FOUNDATIONS
FOUNDATTON AND RETAINING WALLS
FLOOR SLABS
UNDERDRAIN SYSTEM
SURFACE DRAINAGE
LIMITATTONS.............
I.iUUKb i - LOCA'I'ION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF E)GLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURE 4 - GRADATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
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Kumar & Associates, lnc. o Project No.25.7.114
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located on Parcel
13, High Aspen Ranch, l422HighAspen Drive, Garfield County, Colorado. The project site is
shown on Figure 1. 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 Ted and Karen Miller dated January 9,2025.
A field exploration program consisting of exploratory borings 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 and other engineering
characteristics. The results of the field exploration and laboratory testing were analyzedto
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 single-story above a walkout lower level with a slab-on-grade
floor and located as shown on Figure l. Grading for the structure is assumed to be relatively
minor with cut depths up to about 10 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 CONDITIONS
The subject site was vacant and covered with about 2 feet of snow at the time of our field
exploration. The site terrain is variable with slopes ranging from gentle to moderate generally
down to the southeast as indicated by the contour lines shown on Figure I with about 10 feet of
elevation difference across the proposed building footprint. Vegetation consists of oak brush,
grass and weeds in the building area.
FIELD EXPLORATION
The field exploration for the project was conducted on February 19,2025. Three exploratory
borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions.
The borings were advanced with 4-inch diameter continuous flight augers powered by a track-
mounted CME-45 drill rig. The borings were logged by a representative of Kumar & Associates.
Kumar & Associates, lnc. @ Project No. 25'7-114
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Samples of the subsoils were taken with l%-inch 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-I586.
The pettetratiurt rcsishmuc values are an indication of the relative density or consistency of the
subsoils. Depths at which thu saurples were taken and the penetration fesistance values are
shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our
laboratory for review by the project engineer and testing.
SUBSTJRFACE COI{DITIONS
Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The
subsoils encountered, below about one foot oftopsoil, consist of medium dense, silty clayey sand
and gravel with scattered basalt cobbles and possible boulders down to the explored depths of
20 to 25 feet. At Boring 3, about 2 feet of very stifl/medium dense, sandy clay and gravel was
encountered below the topsoil. Caving of the soils at Boring 2 prevented sampling below l l feet.
Lahoratorv fesfino nerforrned nn sqrnnlec nhtqinprl frnm fha h^.i--o in-l,,.lo.l norrrrol *^i-+,.-^- -J "--"'O vv. rrr6u rrrvrugvs rrotur4l ttrvlJlulw
content and density, and gradation analyses. The subsoils were too rocky to obtain undisturbed
samples for compressibility potential testing. Results of gradation analyses performed on small
diameter drive samples (minus l%-inch fraction) of the coarse granular subsoils are shown on
Figure 4. The laboratory testing is summarized in Table l.
No free water was encountered in the borings at the time of drilling and the subsoils were
slightly moist to moist.
FOUNDATION BEARING CONDITIONS
The sand and gravel soils typically encountered in the borings possess moderate bearing capacity
and relatively low settlement potential. Sandy clay soils encountered in the building excavation
should be removed to place the foundation entirely on the underlying sand and gravel soils. In
areas where clay soils are sub-excavated,the foundation bearing level can be reestablished with
structural fill compacted to at least 98% of standard Proctor density at near optimum moisture
content or the foundation bearing level extended down to the underlying sand and gravel soils.
DESIGN RECOMMENDATIONS
FOLINDATIONS
T1^-oi.lo.i-- +L^ -'.L-"-f^^^ ^^^l:+:^ ^^ ) t-' Lt- - - t , r .vvr rr'uvr trrS rrrw ruuJur roue v(rllt]lllt lls Elltelrullrtjl9U llt tllg 9xpl0fatOfy DOnngS anq lng natUfe OI
the proposed construction, we recommend the building be foundgd with spread footings bearing
on the natural granular soils.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
Kumar & Associates, ln6. o Project No. 25-7-114
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1)Footings placed on the undisturbed natural granular soils should be designed for
an allowable bearing pressure of 2,000 psf. Based on experiense, we expect
settlement of footings designed and constructed as discussed in this section will
be about I inch or less.
The footings should have a minimum width of 16 inches for continuous walls and
2 feet for isolated pads.
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
afea-
Continuous foundation walls should be heavily reinforced top and bottom to span
local anomalies and resist potential differential movement such as by assuming an
unsupported length of at least 14 feet. Foundation walls acting as retaining
structures 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.
The topsoil, clay soils and loose or disturbed soils should be removed and the
footing bearing level extended down to the firm natural granular soils. The
exposed soils in footing area should then be moisture adjusted to near optimum
and compacted. If water seepage is encountered, the footing areas should be
dewatered before concrete placement.
A representative ofthe geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
4)
s)
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 50 pcf for backfill consisting
of the on-site granular soils. Cantilevered retaining structures which are separate from the
residence and can be expected to deflect sufficiently to mobilize the full active earth pressure
condition should be designed for a lateral earth pressure computed on the basis of an equivalent
fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. Backfill
should not contain organics, debris or rock larger than about 6 inches.
All foundation and retaining structures should be designed for appropriate hydrostatic and
surcharge pressures such as adjacent footings, traffic, construction materials and equipment.
The pressures recommended 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
2)
3)
6)
Kumar &Associates, lnc. @ Projec{ No.2S7-114
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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 he placed in uniform lifts and compacted to at least 90% of thc maximum
standard Proctor density at near optimrrm moisfttre content. Backfill placed in pavement and
walkway areas should be compacted to at leastg5Yo of the maximum standard Proctor density.
Care should be taken not to over-compact 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
backfill should be expected, even if the material is placed correctly, and could result in distress to
facilities constructed on the backfill. Backfill should not contain organics, debris or rock larger
than about 6 inches.
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 0.45. Passive pressure of compacted backfill against the
sides of the footings can be calculated using an equivalent fluid unit weight of 400 pcf. The
coefficient of friction and passive pressure values recommended 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, particularly in the case of passive resistance. Fill placed against
the sides of the footings to resist lateral loads should be a granular material compacted to at least
95Yo of the maximum standard Proctor density at a moisture content near optimum.
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, 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 damagc due to shrinkage
cracking. The requirements forjoint spacing and slab reinforcement should be established by
the designer based on experience and the intended slab use. A minimum 4-inch layer of free-
draining gravel should be placed beneath slabs to facilitate drainage. This material should
consist of minus Z-inch aggregate with at least 50% retained on the No. 4 sieve and less than
2Yo passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at leastgl%oof maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
onsite granular soils devoid of vegetation, topsoil and oversized rock.
We recommend vapor retarders conform to at least the minimum requirements of AST}y'rEIT4S
Class C material. Certain floor types are more sensitive to water vapor transmission than others.
Kumar & Associates, lnc. o Project No. 25.7-114
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For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor
transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum
requirements of ASTM 81745 Class A material. The vapor retarder should be installed in
accordance with the manufacturers' recommendations and ASTM E1643.
LTNDERDRAIN SYSTEM
Although free water was not encountered during our exploration, it has been our experience in
the area and where clayey 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. We recommend below-grade construction, such as retaining walls,
crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup
by an underdrain system.
The drains should consist of drainpipe placed in the boffom ofthe wall backfill surrounded 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 IYoto
a suitable gravity outlet. Free-draining granular material used in the underdrain system should
contain less than 2Yo passingthe No. 200 sieve, less than 50olo passing the No. 4 sieve and have a
maximum size of 2 inches. The drain gravel backfill should be at least lt/zfeet deep and covered
with filter fabric such as Mirafi l40N or 160N.
SURFACE DRATNAGE
The following drainage precautions should be observed during construction and maintained at
all times after the building has been completed:
l) 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 95%6 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 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
covered with filter fabric and capped with about 2 feetof the on-site finer-graded
soils to reduce surface water infiltration.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least
5 feet from foundation walls.
Kumar & Associates, Inc. @ Project No.2$7-114
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LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area at this time. We mako no worronty cithct cxpress or i*rplied.
The conclusions and recnmmeirdations submitted in this roport aro bosed upon thc data ohtairred
from the exploratory borings dritled at the locations indicated on Figure l, the proposed type of
conshrction 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 concemed about MOBC, then aprofessional in this special field of
practice should be consultd. Our findings include interpolation and exfapolation of the
subsurface conditions identified at the exploratory borings and variations in the subsurface
conditions may not become evident until excavation is perforrred. 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 exclusive use by our client for design pu{poses. 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 recomme,ndations, and to veriry 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,
Kumar & Associates,
Steven L. Pawlak,
Revie.we.d by:
b
Daniel E. Hardin, P.E.
SLPlkac
oc:Jordan Architecture - Brad Jordan (btadjordanarchitect@email.com)
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Kumar & Associates, lnc. o Project No.25-74i4
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APPROXIMATE SCALE-FEET
25-7 -1 1 4 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1
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DD= I 00
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WC=9.9
DD= 1 00
+4=51
-200-1 4
25-7 -1 1 4 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2
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LEGEND
TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM/FROZEN, DARK BROWN.
SAND (SC); VERY CLAYEY, GRAVELLY, MEDIUM DENSE, MOlsT, BROWN.
SAND AND GRAVEL (SC-GC); SILTY, CLAYEY, SCATTERED COBBLES, POSSIBLE BOULDERS,
BASALT FRAGMENTS AND CINDERS, DENSE, MOIST, BROWN TO RED_BROWN.
F
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DRIVE SAMPLE, 2_INCH I.D. CALIFORNIA LINER SAMPLE
DRTVE SAMPLE, 1 S/$-INCH l.D. SPLIT SPOON STANDARD PENETRATION TEST
^^ '.^ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 29 BLOWS OF A 'I4O-POUND HAMMERzrl tz FALLTNG 30 rNcHEs WERE REQUTRED To DRrvE THE SAMPLER 12 lNcHES.
---> DEPTH AT WHICH BORING CAVED.
NOTES
1 THE EXPLORATORY BORINGS WERE DRILLED ON FEBRUARY 19, 2025 WITH A 4-INCH-DIAMETER
CONTINUOUS_FLIGHT POWER AUGER.
2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING
FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4. THE EXPLORATORY BORING LOCATIONS 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 LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
5. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D2216);
DD = DRY DENSITY (PCt) (ASTU D2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D6915);
-200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D1140).
25-7-114 Kumar & Associates LEGEND AND NOTES Fig. 3
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FINE MEDIUM FINE COARSE
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DIAMETER OF PARTICLES IN
CLAY TO SILT COBBLES
un^rgl Jt ^ ililu
LIQUID LIIIIT
SAIIPLE OF; Silly Sondy Grovel
J57
PIASTIC]TY INDEX
S|LT AND ELAY I1 X
FROM: Borlng 2 O 2 &. 4 (Comblned)
Th.{ l.tl ntulL oppt only to lh.smpL. rhlch vso lqlcd. Thctctln9 r.porl rholl nol bo reproducod,.xo.pl ln tull, wllhoul lh. w.llLn
opprcYol ot Kumr & A!t@lql.r, lE,Sby! onolytl! lcllng lt porlomrd lnoccordo@ vllh-ASlll D69t5, ASIy D7928,ASII. Cll6 ondlor ASTI Dlla{t.
25-7 -1 1 4 Kumar & Associates GRADATION TEST RESULTS Fis. 4
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 25.7.114
SOIL TYPE
Slightly Silty Sand with
Gravel
Silty Sand and Gravel
Clayey Sand with Gravel
UNCONFINED
COMPRESSIVE
STRENGTH
(osf)
ATTERBERG LIMITS
PLASTIC
INDEX
(o/ol
LIQUID LIMIT
t%l
PERCENT
PASSING NO.
200 SIEVE
7
I4
36
SAND
(%)
35
GRAVEL
{7.)
5 I
NATURAL
DRY
DENSITY
(ocll
97
100
100
NATUML
MOISTURE
CONTENT
MI
20.3
9.9
17.9
SAMPLE LOCATION
DEPTH
ftl
9
2 and4
combined
2
BORING
1
2
3
Colleen Wirth
From:
Sent:
To:
Subject:
Attachments:
Follow Up Flag:
Flag Status:
Colleen Wirth
Thursday, April 10, 2025 7:11 AM
Colleen Wirth
Miller Lot 13 - zoning research
571758 - High Aspen Ranch Lot 13.pdf
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High Aspen Ranch Lot 13
ZR:O4.10.25
Must review white binder for f.s. provisions, RlF, any tocat subdivision concerns
May have a tive irrigation ditch or smatl creek thru property
Check SITE PLAN for water features
Hitty / slope of [ot may factor
Golteen Wirth
Buitding Plans Examiner
Garfietd County Community Development
108 8th Street, Suite 401
Glenwood Springs, CO 81601
(970)945-1377 efi161O
cwi rth@8a rf ield cou ntyco.gov
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