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SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 28, SUN MEADOWS ESTATES
SOUTH MEADOW CIRCLE
GARFIELD COUNTY, COLORADO
JOB NO. 115 112A
APRIL 21, 2015
PREPARED FOR:
TERRY DAVIS
816 WHITERIVER AVENUE
RIFLE, COLORADO 81650
(ten %d134.1d(ri.4ii :til.cr►in)
Parker 303 -8I! -71I9 • Colorodo Springy 719-633-55612 • Sikerthurnt 970-468-1989
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY • - 1 -
PROPOSED CONSTRUCTION -1
SITE CONDITIONS - 2 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS
- 2 -
FOUNDATION BEARING CONDITIONS emt+ wwwww *** * ti 3 -
DESIGN RECOMMENDATIONS.............- 4 -
FOUNDATIONS. - 4 -
FLOOR SLABS -5-.
UNDERDRAIN SYSTEM * ... ... .. ....... " . - . ..... •••• ........... 5 -
SURFACE DRAINAGE - 6 -
LIMITATIONS - 7 -
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2- LOGS OF EXPLORATORY BORINGS
FIGURE 3 - LEGEND AND NOTES
FIGURES 4 AND 5- SWELL -CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
Job No. 115 1 [2A
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located
on Lot 28, Sun Meadows Estates, South Meadow Circle, 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 Terry Davis dated March 30,
2015. Hepworth Pawlak Geotechnical Inc., previously performed a preliminary
geotechnical study for Sun Meadow Estates (formerly Mamms View Subdivision) and
presented our findings in a report dated March 28, 2000, Job No. 100 169.
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,
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 two story wood frame construction over a partial
basement level located on the lot as shown on Figure 1. Ground floors slab -on -grade in
the basement and garage portions, and structurally supported over crawlspace in the non -
basement portion. Grading for the structure is assumed to be relatively minor with cut
depths between about 3 to 10 feet. We assume relatively light foundation loadings,
typical of the proposed type of construction.
Job No. 115 112A
-2 -
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
Lot 28 is located to the north of South Meadow Court and bordered on the west by Lot 29
and County Road 216 on the north. The ground surface in the building area is somewhat
irregular but primarily gently sloping. Vegetation consisted of grass, weeds, and brush.
A natural drainage located along the eastern property line was dry at the time of our field
exploration.
FIELD EXPLORATION
The field exploration for the project was conducted on April 6, 2015. Two 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 truck -mounted CME -45B drill rig. The borings were logged by a
representative of Hepworth-Pawlak Geotechnical, Inc.
Samples of the subsoils were taken with a 2 inch I.D. spoon sampler. The sampler was
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 by 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 a minor (about % foot depth) of topsoil, consisted of
Job No. 115 1 [ 2A ech
-3 -
very stiff, very sandy clayey silt underlain at about 3% feet by very stiff, sandy silt and
clay that extended down to the drilled depths of 21 feet.
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 of the
soils, presented on Figures 4 and 5, indicate low to moderate compressibility under
conditions of loading and wetting. The samples typically showed a nil to low hydro -
compression potential. One sample (Boring 1 at 15 feet) showed a moderate swell
potential when wetted under a constant light surcharge. The laboratory testing is
summarized in Table 1.
No free water was encountered in the borings at the time of drilling and the subsoils were
slightly moist.
FOUNDATION BEARING CONDITIONS
The soils at the site possess generally low bearing capacity and are expected to mainly
settle if wetted. Spread footings bearing on the natural soils can be used for foundation
support provided some risk of movement and distress is acceptable. There is some risk of
movement primarily if the bearing soils were to become wetted and precautions should be
taken to prevent wetting. The moderate swell potential encountered in one of the samples
is considered an anomaly and can be neglected in the foundation design. However, the
settlement/heave potential of the bearing soils should be further evaluated at the time of
construction.
Providing several feet of structural fill (reworking of the on-site natural soils) below the
footings or use of a helical pier type foundation would provide a lower risk of foundation
movement. Provided below are recommendations for footings bearing on the natural
soils. If recommendations for bearing on structural fill or for a helical pier type
foundation system are desired, we should be contacted.
lob No. 115 1 I2A
4
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory borings, the nature
of the proposed construction and the soils typical of this area, we believe the building can
be founded with spread footings bearing on the natural soils with some risk of movement_
The risk of movement is mainly if wetting of the bearing soils were to occur and
precautions should be taken to prevent wetting.
The design and construction criteria presented below should be observed for a spread
footing foundation system.
1) Footings laced on the undisturbed natural soils should be designed for an
allowable beatitis 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 1 inch or less. There could be additional differential
movement of about %z inch if the bearing soils become wetted depending
on the depth and extent of the wetting depending.
2) The_.fings should have a minimum width of 18 inches for continuous
walls and 2 feet for isolatedjads.
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 and better withstand the effects of some
differential movement such as by assuming an unsupported length of at
least 12 feet. Foundation walls acting as retaining structures should also
be designed to resist a lateral earth pressure corresponding to an equivalent
fluid unit weight of at least 55 pcf for the on-site soil as backfill.
lob No. 115 1121 S-� tech
-5-
5) The topsoil and any loose or disturbed soils should be removed and the
footing bearing level extended down to the undisturbed natural soils. The
subgrade 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.
FLOOR SLABS
The natural on-site soils, excluding topsoil, should be suitable for support of lightly
loaded floor slabs on -grade. There could be some slab movement if the subgrade
becomes wetted as discussed above. Providing several feet of structural fill below the
slabs would act to reduce the risk of floor slab movement. The settlement/heave potential
of the bearing soils and need for structural fill 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. 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 Iess 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
should consist of soils devoid of vegetation and topsoil.
UNDERDRAIN 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
Job No. 115 112A
-6 -
can develop during times of heavy precipitation or seasonal runoff. Frozen ground during
spring runoff also can create a perched condition. We recommend below -grade
construction, such as basements and crawlspace areas, be protected from wetting and
hydrostatic pressure buildup by an underdrain system. An underdrain around shallow
crawlspace areas (less than 4 feet deep) may not be needed provide foundation backfill is
adequately compacted and positive surface drainage is provided away from foundation
walls.
Where drains are installed, they 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 or sump
where the water can be collected and pumped. 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 11/2 feet deep and covered by filter fabric such as Mirafi 140N
or 160N.
SURFACE DRAINAGE
Positive surface drainage is an important aspect of the project to prevent wetting of the
bearing soils. 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.
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
Job No. E15112A
Gtech
-7 -
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.
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 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) 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 borings 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 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
Job No. 115 112A Ge Meeh
-8 -
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.
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
411)jjJ 1 45-zd
Andrew Spickert
Reviewed by:
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Job No. 115 112A Gecstech
S' APPROXIMATE SCALE
1"=60'
COUNTY ROAD 216
1
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LOT 29
1
115112A
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LOT 28
BORING 2
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PROPOSED
RESIDENCE
•
BORING 1
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Hepworth-Powlek Geotechnleal
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1 BENCH MARK: WATER PIPE NEAR PR9PERTY
JICORNER; ELEV. = 100.0', ASSUMED/
Alr
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SOUTH MEADOW CIRCLE
LOCATION OF EXPLORATORY BORINGS
Figure 1
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10
15
20
25
115 112A
BORiNG 1
ELEV. = 104.8'
24/12
WC -4.0
OD= 104
20/12
23/12
WC=4.7
DD 111
-200 =80
22/12
WC=10.7
DD=1.21
32/12
BORING 2
ELEV. — 105.5'
29/12
26/12
WC=5.9
D0=104
22/12
WC=5.6
CID= 107
45/12
38/12
WC=5.0
DD= 113
Note: Explanation of symbols is shown on Figure 3.
H
HEAWORTFFPAWLAK GEOTECHNICAL
LOGS OF EXPLORATORY BORINGS
0
5
10
15
20
25
Figure 2
LEGEND:
IASILT (ML); very sandy, clayey, very stiff, slightly moist, light brown.
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24/12
SILT AND CLAY (ML -CL); sandy, very stiff to hard, slightly moist, light brown.
Relatively undisturbed drive sample; 2 -inch I.D. California liner sample.
Drive sample blow count; indicates that 24 blows of a 140 pound hammer falling 30 inches were
required to drive the California sampler 12 Inches.
NOTES:
1. Exploratory borings were drilled on April 6, 2015 with 4 -Inch diameter continuous flight power auger.
2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan
provided.
3. Elevations of exploratory borings were measured by instrument level and refer to the Bench Mark shown on Figure 1.
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 transitions may be gradual.
6. No free water was encountered in the borings at the time of drilling. Fluctuation in water level may occur with time.
7. Laboratory Testing Results:
WC = Water Content (%)
DD = Dry Density (pcf)
-200 = Percent passing No. 200 sieve
115 112A
1-I
Hepworth-Pewlek Geotechnical
LEGEND AND NOTES
Figure 3
Compression %
Compression - Expansion %
0
1
2
3
4
5
2
1
0
1
2
Moisture Content = 4.0 percent
Dry Density = 103 pcf
Sample of: Very Sandy Clayey Silt
From: Boring 1 at 2 y Feet
r
Compression
upon
wetting
0.1
1.0 10
APPLIED PRESSURE - ksf
100
Moisture Content = 10/ percent
Dry Density = 122 oaf
Sample of: Sandy Silty Clay
From: Boring 1 at 15 Feet
Expansion
upon
wetting
0.1
1.0 10
APPLIED PRESSURE - ksf
1
100
1 115 112A
I -I
Hepworth—Po/10k GeotechnT of
SWELL -CONSOLIDATION TEST RESULTS
Figure 4
Compression %
Compression - Expansion 96
0
1
2
3
4
1
0
1
2
Moisture Content = 5.9 percent
Dry Density = 104 pcf
Sample of: Sandy Silt and Clay
From: Boring 2 at 5 Feet
No movement
upon
wetting
0.1
1.0 10
APPLIED PRESSURE - ksf
Moisture Content = 5.6 percent
Dry Density = 110 pcf
Sample of: Sandy Sift and Clay
From: Boring 2 at 10 Feet
Expansion
upon
wetting
0.1
115 112A
1.0 10
APPLIED PRESSURE - ksf
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Hepworth—Pawlck Geotectintcal
SWELL -CONSOLIDATION TEST RESULTS
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100
Figure 5
Job No. 115 112A
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