HomeMy WebLinkAboutSubsoils Report for Foundation Designl(t t#ffi,ffi#ffi*$sd**'5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
email: kaglenwood@kumarusa.com
www.kumarusa.com
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Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Surnmit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
PARCEL 22, IJTGIJ ASPEN RANCH
966 OVERLOOK DRIVE
GARFIELD COUNTY, COLORADO
PROJECT NO.25-7-449
AUGUST 21,2025
PREPARED FOR:
JORDAN ARCHITECTURE
ATTN: BRAD JORDAN
P.O. BOX 1031
GLENWOOD SPRINGS, COLORADO 81602
brad i ordanarch itect@gm ail.com
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TABLE OF CONTENT'S
PURPOSE AND SCOPE OF STUDY
PROPOSED CONSTRUCTION
SITE CONDITIONS....
FIELD EXPLORATION
SUBSURFACE CONDITIONS ...
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FOUNDATION tsbARtNG CONDI'TIONS
DESIGN RECOMMENDATIONS
FOUNDATIONS
FOUNDA'I'ION AND Rb'IAINING WALLS
FLOOR SLABS
UNDERDRAIN SYSTEM
SURFACE DRAINAGE
LIMITATIONS
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURE 4 - GRADATION TEST RESULTS
TABLE I- SUMMARY OF LABORATORY TEST RESULTS
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Kumar & Associates, lnc. o Project No. 25.7-449
PURPOSE AI{D SCOPE OF STUDY
This report presents the results ofa subsoil study for a proposed residence to be located on Parcel
22,HighAspen Ranch, 966 Overlook 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 proposal for geotechnical
engineering services to Jordan Architecture dated June 16, 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 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 single-story above a walkout lower level with a slab-on-grade
floor and located as shown on Figure 1. 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 with driveway access cut through the vegetation at the time of our
field exploration. The site terrain is hillside with moderate slopes ranging from about 15 to 25oh
generally down to the southeast as indicated by the contour lines shown on Figure 1 and about
15 feet of elevation difference across the proposed building footprint. Vegetation consists of oak
brush, grass and weeds with scattered aspen trees. Numerous basalt cobbles and boulders were
observed on the ground surface ofthe lot.
FIELD EXPLORATION
The field exploration for the project was conducted on July 25,2025. Three exploratory borings
were drilled 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 track-
mounted CME-45 drill rig. The borings were logged by a representative of Kumar & Associates
Kumar & Associates, lnc. @ Project No. 25-7-449
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Samples of the subsoils were taken with 1%-inch and 2-inch I.D. spoon samplers. The sampleis
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 Logs of Exploratory Borings, Figure 2. The samples were returned to our
laboratory for review hy the project engineer and testing.
SUBSURFACE 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 medium dense, silty clayey sand
and gravel (volcanic cinders) with scaftered basalt cobbles and possible boulders down to the
explored depths of 10 to 2l feet. At Boring 2, auger drilling refusal was encountered, likely on a
basalt boulder.
Laboratory testing performed on samples obtained from the borings included natural moisture
content and density, and gradation analyses. The subsoils were too rocky to obtain undisturbed
samples for compressibility potential testing. Results of gradation analysis performed on a small
diameter drive sample (minus lYz-inch fraction) of the coarse granular subsoils are shown on
Figure 4. The laboratory testing is summarizedin Table 1.
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. Loose cinders and sandy clay soils could be encountered
and should be removed to place the foundation entirely on the sand and gravel soils. In areas
where soils are sub-excavated, the foundation bearing level can be reestablished with onsite soil
structural fill compacted to at least 98%o 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
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, we recommend the building be founded 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, lnc. @ Project No. 25-7-449
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1)Footings placed on the undisturbed natural granular soils should be designed for
an allowable bearing pressure g|![9g! Based on experience, 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 l6 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
area.
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 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 of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
3)
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 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)
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6)
Kumar & Associates, lnc. @ Project No. 25-7-449
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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 be placed in uniform lifts and compacted to at least 90%o of the maximum
standard Proctor density at near optimum moisture content. Backfill placed in pavement and
walkway areas should be compacted to at least 95o/o 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 pressule on the wall. Some settlement of deep foundation wall
backfill should bc cxpcctcd, even if the rnaterial is placed correctly, and could result in dis[ress 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 matcrial compacted to at least
95o/o 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. '1'o reduce the etl'ects of some differential movement, floor slabs should be
separated from all bearing walls and columns with expansion joints rryhich 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 free-
draining gravel should be placed beneath slabs to facilitate drainage. This material should
consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than
2%o passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at leastg5Yo of 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 ASTMEl745
Class C material. Certain floor types are more sensitive to water vapor transmission than others.
Kumar & Associates, lnc. @ Project No. 25.7-449
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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 8I745 Class A material. The vapor retarder should be installed in
accordance with the manufacturers' recommendations and ASTM 81643.
UNDERDRAIN SYSTEM
Although free water was not encountered during our exploration, it has been our experience in
the area 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 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 lYoto
a suitable gravity outlet. Free-draining granular material used in the underdrain system should
contain less than 2o/o passingthe 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 |t/zfeet deep and covered
with filter fabric such as Mirafi 140N or 160N.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at
all times after the building has been completed:
1) 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 95o/o of the maximum standard Proctor density in pavement and slab areas
and to at least 90%o of the maximum standard Proctor density in landscape areas.
3) The ground surface sunounding 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 10 feet in paved areas. Free-draining wall backfill should be
covered with filter fabric and capped with about 2 feet of 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, lnc. @ Project No. 25-7-449
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LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this atea at this time. We make no warranty either express or implied.
Tho conolusions nnd rccommcndations submittcd in this repoft zue based upon Lhe data obl.ainetl
from the exploratory borings drilled 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) dcvcloping
in the frrhrre. 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 identitied at the exploratory borings and variations in the subsurface
conditions may not become evident until excavation is perfbrmed. If conditions encountered
during consffuction 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 purposes. We are not
responsible for technical interpretations by others of our infonnation. 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 verify that the recommendations
have been appropriately interpreted. Signifrcant 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 geotechnicai engineer.
Respectfuliy Submitted. ,
f,{m mean dr .t{sro** nton,
Steven L. Pawlak, P
Reviewed by:
Daniel E. Hardin, P.E.
SLPlkac
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25-7 -449 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1
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TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM, SLIGHTLY MOIST, DARK BROWN.
sAND AND GRAVEL (SU-GU); S|LTY, SLTGHTLY CLAYEY, COBBLES, MEDIUM DENSE TO DENSE,
DARK RED, MAINLY VOLCANIC CINDERS.
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DRIVE SAMPLE, z-INCH I.D. CALIFORNIA LINER SAMPLE.
DRIVE SAMPLE, 1 S/}-|NCH l.D. SPLIT SPOON STANDARD PENETRATION TEST.
,. "^ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 31 BLOWS OF A 140-POUND HAMMERrtl tz FALLTNG go TNcHES WERE REQU|RED To DRtvE THE SAMPLER t2 tNcHES.
t PRACTICAL AUGER DRILLING REFUSAL.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON JULY 25, 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.
5. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOI-ATION BETWEEN
CONTOURS ON THE SITE PI.AN 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 fiPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING.
7. I.ABORATORY TEST RESULTS:
wc = WATER CONTENT (%) (ASTM D2216);
DD = DRY DENSITY (pcf) (ASTM D2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM 06915);
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM Dl140).
25-7-449 Kumar & Associates LEGEND AND NOTES Fig. 3
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DIAMETER OF IN
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GRAVEL 25
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SAND 56 %
LIQUID LIMIT - PI.ASTICITY INDEX
SAMPLE OF: Cloyey Sond wllh Grovel
SILT AND CLAY 19 %
FROM:BorlngSOg'
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FINE MEDTUM lCOAnSe FINE COARSE
25-7-449 Kumar & Associates GRADATION TEST RESULTS Fis. 4
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 25-7-449
SOIL TYPE
Clayey Sand with Gravel
Clayey Sand with Gravel
Clayey Sand with Gravel
UNCONFINED
COMPRESSIVE
STRENGTH
ATTERBERG LIMITS
PLASTIC
INDEX
LIQUID LIMIT
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PERCENT
PASSING NO.
200 stEVE
18
30
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GRADATION
SAND
(%)
56
GRAVEL
(%)
25
NATURAL
DRY
DENSITY
88
88
NATURAL
MOISTURE
CONTENT
9.3
15.3
14.6
SAMPLE LOCATION
DEPTH
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5
2
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BORING
1
2
3
RESchecl*V{eb'"
Compliance Certificate
Project lnformation
Proiect Title!
Energy Code:
Location:
Construction Type:
Project Type:
Project Sub Type:
Orientation:
Conditioned Floor Area :
Glazing Area:
Climate Zone:
All Electric:
ls Renewable:
Has Battery:
Has Charger:
Has Heat Pump
Construction Site:
Proiect Notes:
Kistner Residence
2018 tECC
Garfield, Colorado
Single Family
New Construction
None
Bldg. faces 315 deg. from North
3675 ft2
28%
sb (8499 HDD)
true
true
true
false
true
Owner/Agent:Desig ner/contractor:
Report Title: Kistner Residence Report Date: 912125, II:38 AM Iol 2
Envelope Assemblies
Assembly Gross Area or
Perimeter
Prop.
U.
Factor/
F-Factor
Req'
U.
Factor/
F-Factor
Prop. Req.UA UA
Cavity Cont.
R-Value R-Value
Ceiling: Raised or Energy
Truss
Floor: Slab-On-Grade
(Heated)
lnsulation depth: 2.00'
lnsulation position:
Vertical lnsulation
Wall: Wood Frame, 16" o.c.
Orientation: Unspecifi ed
Window: Vinyl Frame
Orientation: Unspecified
Door: Solid Door (under
50% qlazing)
Orientation: Unspecified
Basement Wall: Solid
Concrete or Masonry
Orientation: Unspecifi ed
Wall height: 10.00
lnsulation depth; 1"0.00'
lllsulatiun positiur r:
lntegral lnsulation
3083
205
2784
775
44
1200
60.0
30.0
19.0
0.0
15.0
6.0
10.0
0.01-7
0.860
0.035
0.250
0.28t)
0.028
0.026
0.645
52 80
0 0
0.060
0.300
0.300
0.050
69
794
12
34
118
233
13
60
( omplianre: Passes Using UA trade-off
Compliance: 28.4% Better Than Code Max llAr qOA Yorrr UAi 361
The % Better or Worse Than Code lndex reflects how close to compliance the house is based on code trade-off rules, lt DOES
NOT provide an estimate of energy use or cost relative to a minimum-code home.
Slab-on-grade tradeoffs are no longer considered in the UA or performance compliance path in REscheck. Each slab-on-grade
assembly in the specified climate zone must meet the minimum energy code insulation R-value and depth requirements,
Compliance Statement
The proposed building design described here is consistent with the building plans, specifications, and other calculations
submitted with the permit application. The proposed building has been designed to meet the 2018 IECC requirements in
REScheck-Web and to comply with the mandatory requirements listed in the REscheck lnspection Checklist.
Max Moore -
Mechanical Engineer Max Moore 09t02t2025
Name - Title Signature Date
Report Title: Kistner Residence Report Date: 9/2/25, 11:38 AM 2ol 2