HomeMy WebLinkAboutSoils Report 02.23.2018H -PKU MAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 1, BLOCK 6, MONUMENT CREEK VILLAGE
47 WILLOWVIEW WAY
BATTLEMENT MESA, GARFIELD COUNTY, COLORADO
PROJECT NO. 18-7-157
FEBRUARY 23, 2018
PREPARED FOR:
CODY CHURCH
1072 24 ROAD
GRAND JUNCTION, COLORADO 81505
cmchurchAa1 heatinginc.com
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 1 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 2 -
FOUNDATION BEARING CONDITIONS - 3 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FOUNDATION AND RETAINING WALLS - 4 -
FLOOR SLABS 5 -
UNDERDRAIN SYSTEM - 6 -
SURFACE DRAINAGE - 6 -
LIMITATIONS - 7 -
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURES 3 AND 4 - SWELL -CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
H -P KUMAR
Project No. 18-7-157
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located on Lot 1,
Block 6, Monument Creek Village, 47 Willowview Way, Battlement Mesa, 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 accordance with our
agreement for geotechnical engineering services to Cody Church dated February 12, 2018.
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 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 one story wood frame structure over a walkout basement level
with an attached garage at the main level located on the lot as shown on Figure 1. Basement and
garage floors will be slab -on -grade. Grading for the structure is assumed to be relatively minor
with cut depths between about 3 to 8 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 site was previously occupied by a house which burned down and was removed. The site
was vacant and covered with about 1/2 inch of snow at the time of our field exploration. Some
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scattered debris was evident on the site. The lot appeared to have about 3 to 6 feet of fill on it
based on our site observations and boring information. The lot is relatively flat near the
Willowview cul-de-sac with a strong slope down to the northwest in the western part of the site.
Vegetation consisted of sparse grass and weeds.
FIELD EXPLORATION
The field exploration for the project was conducted on February 15, 2017. One exploratory
boring was drilled at the location shown on Figure 1 to evaluate the general subsurface
conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by
a truck -mounted CME -45B drill rig. The boring was logged by a representative of H-P/Kumar.
Samples of the subsoils were taken with 1% 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-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 consisted of about 6 feet of medium stiff, sandy clayey silt fill overlying relatively
dense, basalt gravel, cobbles and boulders in a sandy clay and silt matrix down to the bottom of
the boring at 12 feet. Drilling in the dense granular soils with auger equipment was difficult due
to the cobbles and boulders and drilling refusal was encountered in the deposit at the 12 feet
boring depth.
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-
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consolidation testing performed on relatively undisturbed drive samples of the fill soils,
presented on Figures 3 and 4, indicate low compressibility under light loading and a moderate to
high collapse potential (settlement under constant load) when wetted. The samples were highly
compressible under increased loading after wetting. The laboratory testing is summarized in
Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist.
FOUNDATION BEARING CONDITIONS
The fill soils encountered to a depth of 6 feet in the boring are settlement prone and should be
completely removed from below the building area. The deeper basalt gravel, cobble and boulder
soils are relatively dense and should provide good support for shallow spread footings with
relatively low settlement risk.
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
entirely on the natural basalt gravel, cobble and boulder soils below all existing fill and topsoil.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural basalt gravel, cobble and boulder soils
should be designed for an allowable bearing pressure of 2,500 psf. Based on
experience, we expect settlement of footings designed and constructed as
discussed in this section will be about 1 inch or less.
2) The footings should have a minimum width of 16 inches for continuous walls and
2 feet for isolated pads.
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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 reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 10 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) All existing fill, debris, topsoil and any loose or disturbed soils should be
removed and the footing bearing level extended down to the relatively dense
natural basalt gravel, cobble and boulder 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.
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 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 soils. The backfill should not contain
debris, topsoil or oversized (plus 6 -inch) rocks.
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
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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% of the maximum
standard Proctor density at a moisture content near optimum. Backfill 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
backfill should be expected, 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 0.40. Passive pressure of compacted backfill against the
sides of the footings can be calculated using an equivalent fluid unit weight of 325 pcfThe
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 compacted to at least 95% 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. The existing fill does not appear suitable to support building floor slab areas. The
fill may be suitable to support the garage floor slab with a risk of settlement and distress, and
should be further evaluated at the time of 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.
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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 basement level 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%
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 or an imported gravel soil such as 3/4 -inch road base, devoid of vegetation, topsoil and
oversized (plus 6 -inch) rocks.
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 also 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 surrounded above
the invert level with free -draining granular material. The drain should be placed at each level of
excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to
a suitable gravity outlet. 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 1'/2 feet deep and be
covered by filter fabric.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the residence has been completed:
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1) Inundation of the 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% 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 12 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
capped with about 2 feet of the on-site 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. Consideration should be given to use of xeriscape to
reduce the potential for wetting of soils below the building caused by irrigation.
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 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.
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Project No. 18-7-157
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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 verify 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,
H -P= KUMAR
Daniel E. Hardin, P.E.
Reviewed by•
t,- It
David A. Young, P. i1/4Jo '32216`
02 Z-��, 0,,�4;,
DEH/kac -wFri 94 ¢iVA',
H-P�KUMAR
Project No. 18-7-157
IM
10 0 10 20
APPROXIMATE SCALE -FEET
WILLOWVIEW WAY
18-7-157
H-PvKUMAR
LOCATION OF EXPLORATORY BORING
Fig. 1
0
5
10
15
BORING 1
11
5/12
WC=6.4
DD=90
—200=78
4/12
WC=6.9
DD=90
—200=84
50/6
LEGEND
X
X
Y•"'
FILL: SANDY CLAYEY SILT WITH GRAVEL, MEDIUM STIFF TO LOOSE,
SLIGHTLY MOIST, MIXED BROWN.
BASALT GRAVEL, COBBLES AND BOULDERS (GC); IN A SANDY CLAY AND
SILT MATRIX, DENSE, SLIGHTLY MOIST, BROWN SOILS WITH GRAY ROCKS.
DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE.
DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE.
5/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 5 BLOWS OF A
140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE
THE SAMPLER 12 INCHES.
I REFUSAL TO DRILLING.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON FEBRUARY 15, 2018 WITH
A 4—INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN
PROVIDED.
3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED
AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH.
4. THE EXPLORATORY BORING LOCATION 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. FLUCTUATIONS IN GROUNDWATER LEVEL MAY OCCUR WITH
TIME.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
—200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140).
18-7-157
H-PvKUMAR
LOG OF EXPLORATORY BORING
Fig. 2
2
0
J 2
W
rn
1 4
z
0
1-
J
6
0
N
z
0
° 8
—10
—12
100
18-7-157
H-P4.--'KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 3
SAMPLE OF: Sandy Clayey Silt (Fill)
FROM: Boring 1 0 2.5'
WC = 6.4 %, DD = 90 pcf
—200 = 78 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
\ND
Th...
tut results appy only to the
rumplest� The troths report
reproduced, e..pt in
full. without the written opprowl of
humor and A..odote., Inc. Seel:
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aeCmrdarcnIMpN D n
100
18-7-157
H-P4.--'KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 3
2
0
2
2
—4
w
3
1n
6
z
0
1-
J
8
0
N
z
O
-10
— 12
— 14
— 16
E
10
100
18-7-157
H -P- KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 4
SAMPLE OF: Sandy Clayey Silt (Fill)
FROM: Boring 1 0 5'
WC = 6.9 %, DD = 90 pcf
—200 = 84 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
lllam tut mutt. apply only to the
ample fated. The tooting report
.hal not be raprador<d, enypt in
fa0, althea thm vont. approval of
Kumar and a.00lotu, EL Sap
accordaanon th palm In
accordance .tth ASTM "0-r6M
E
10
100
18-7-157
H -P- KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 4
J
W
W
cc
}
O
cc
H
a
wCC
Jo
m m
L0Li -
0
2
Project No. 18-7-157
SOIL TYPE
Sandy Clayey Silt (Fill)
Sandy Clayey Silt (Fill)
UNCONFINED
COMPRESSIVE
STRENGTH
(psf)
ATTERBERG LIMITS
LIQUID PLASTIC
LIMIT INDEX
(%) (%)
PERCENT
PASSING
NO. 200
SIEVE
78
84
GRADATION
0
CD
GRAVEL
(%)
NATURAL
DRY
DENSITY
(pct)
O
OT
O
NATURAL
MOISTURE
CONTENT
(%)
71-
C\
II SAMPLE LOCATION
DEPTH
(ft)
N
i
Z
O
m