HomeMy WebLinkAbout11.01 Subsoil Study Parcel CHEPWORTH-PAWLAK GEOTECHNICAL, INC. 5020 Road 154
Glenwood Springs, CO 81601
Fax 970 945-8454
Phone 970 945-7988
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED WILDE RESIDENCE
PARCEL C, MANGURIAN EXEMPTION
COUNTY ROAD 251, NORTH OF RIFLE
GARFIELD COUNTY, COLORADO
JOB NO. 197 200
APRIL 14, 1997
PREPARED FOR:
BILL WILDE
1427 DOGWOOD DRIVE
RIFLE, COLORADO 81650
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
April 14, 1997
Bill Wilde
1427 Dogwood Drive
Rifle, Colorado 81650
Job No. 197 200
Subject: Report Transmittal, Subsoil Study for Foundation Design, Proposed
Wilde Residence, Parcel C, Mangurian Exemption, County Road 251,
North of Rifle, Garfield County, Colorado.
Dear Mr. Wilde:
As requested, we have conducted a subsoil study for the proposed residence at the
subject site.
Subsurface conditions encountered in the exploratory boring drilled in the proposed
building area consist of 2 feet of topsoil overlying loose to medium dense clayey to silty
sand. Groundwater was not encountered in the boring at the time of drilling.
The proposed residence can be founded on spread footings placed on the natural
subsoils and designed for an allowable bearing pressure of 1,200 psf.
The report which follows describes our exploration, summarizes our findings, and
presents our recommendations. It is important that we provide consultation during
design, and field services during construction to review and monitor the implementation
of the geotechnical recommendations.
If you have any questions regarding this report, please contact us.
Sincerely,
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
Daniel E. Hardin, P.E.
Rev. By: SLP
DEH/ro
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY 1
PROPOSED CONSTRUCTION 1
SITE CONDITIONS 2
FIELD EXPLORATION 2
SUBSURFACE CONDITIONS 2
DESIGN RECOMMENDATIONS 3
FOUNDATIONS 3
FLOOR SLABS 4
SURFACE DRAINAGE 4
LIMITATIONS 5
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 - LEGEND AND NOTES
FIGURE 4 - SWELL -CONSOLIDATION TEST RESULTS
TABLE I - SUMMARY OF LABORATORY TEST RESULTS
H --P GEOTECH
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be
located on Parcel C, Mangurian Exemption, County Road 251, North of Rifle, Garfield
County, Colorado. The project site is shown on Fig. 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 Bill Wilde
dated March 21, 1997.
An exploratory boring was drilled to obtain information on subsurface
conditions. Samples of the subsoils obtained during the field exploration were tested in
the laboratory to determine their classification, compressibility 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 subsoil conditions encountered.
PROPOSED CONSTRUCTION
The proposed residence will be a 2,000 square foot, single story wood frame
structure with an attached two car garage. Ground floor will be slab -on -grade or
structural over crawlspace. Grading for the structure is assumed to be relatively minor
with cut depths between about 3 to 4 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 reevaluate the recommendations contained in
this report.
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2
SITE CONDITIONS
The site was vacant and vegetated with grass and weeds at the time of our field
work. The site is nearly level with a slight slope down to the west-northwest. There
were dry irrigation ditches near the east fence line and running northeast to southwest
across the middle of the site.
FIELD EXPLORATION
The field exploration for the project was conducted on March 24, 1997. An
exploratory boring was drilled at the location shown on Fig. 1 to evaluate the
subsurface conditions. The boring was advanced with 4 inch diameter continuous flight
augers powered by a truck -mounted Longyear BK-51HD drill rig. The boring was
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 Log of Exploratory Boring,
Fig. 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 are shown on
Fig. 2. The subsoils consist of about 2 feet of topsoil overlying medium dense to
loose, silty to clayey sand down to the maximum depth explored, 45 feet.
Laboratory testing performed on samples obtained from the boring included
natural moisture content, density and percent finer than sand size gradation analyses.
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Results of consolidation testing performed on relatively undisturbed drive samples,
presented on Fig. 4, indicate low to moderate compressibility under conditions of
loading and wetting. The laboratory testing is summarized in Table I.
No free water was encountered in the boring at the time of drilling but the hole
had caved at 13 feet when measured one week after drilling. The caving of the hole
may correspond to a groundwater seepage depth. The subsoils were moist to wet with
depth.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsoil conditions encountered in the exploratory boring and the
nature of the proposed construction, we recommend the building be founded with
spread footings bearing on the natural subsoils.
The design and construction criteria presented below should be observed for a
spread footing foundation system.
1) Footings placed on the undisturbed natural subsoils should be designed
for an allowable soil bearing pressure of 1,200 psf. Based on
experience, we expect settlement of footings designed and constructed as
discussed in this section will be about 1 inch or less. There could be
some additional differential settlement if the bearing soils become
wetted.
2) The footings should have a minimum width of 18 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 reinforced top and bottom to span
local anomalies such as by assuming an unsupported length of at least
H -P GEOTECH
4
12 feet. Foundation walls acting as retaining structures (if any) should
also be designed to resist a lateral earth pressure corresponding to an
equivalent fluid unit weight of 50 pcf.
5) All topsoil and any loose or disturbed soils should be removed and the
footing bearing level extended down to undisturbed natural subsoils.
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, 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 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 act as a leveling course and break capillary moisture
rise. 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 clayey sands or imported sand and gravel devoid of
vegetation, topsoil and oversized rock.
SURFACE DRAINAGE
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.
H -P GEOTECH
5
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 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.
4) Roof downspouts and drains should discharge well beyond the limits of
all backfill.
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 expressed 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 Fig. 1, the proposed type of construction and our experience
in the area. 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.
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
H -P GEOTECH
6
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.
Sincerely,
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
-. O E. •
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Daniel E. Hardin P.t
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Reviewed By: 44<SS,f'aNQ` 1.171A. ������`�6�•
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Steven L. Pawlak, P.E.
DEH/ro
cc: Lee Lindauer
H -P GEOTECH
I
0
0
re
r
1—
z
0
cl
197 200
I
APPROXIMATE SCALE
1"=120'
II
/
PROPERTY/
BOUNDARIES
Z
IRRIGATION
DITCH
PROPOSED
RESIDENCE
BORING 1
EXISTING
WELL
UTILITY EASEMENT
HEPWORTH — PAWLAK
GEOTECHNICAL, INC_
LOCATION OF EXPLORATORY BORING
Fig. 1
Depth Feet
0
5
10
15
20
25
30
35
40
45
BORING 1
11/12
WC=11.7
DD=115
-200=34
7/12
WC=18.8
DD=108
8/12
WC=19.1
DD=106
-200=47
6/12
8/12
0
5
10
15
20
25
30
35
NOTE: Explanation of symbols 40
is shown on Figure 3.
45
Depth — Feet
197 200
HEPWORTH — PAWLAK
GEOTECHNICAL, INC,
LOG OF EXPLORATORY BORING
Fig. 2
LEGEND:
77.7
t::7y
v•
TOPSOIL; sandy silty clay, organic, stiff, moist, dark brown. Heavy root zone upper 12 inches.
SAND (SC); clayey to silty, medium dense to loose, moist to wet, brown.
Relatively undisturbed drive sample; 2—inch I.D. California liner sample.
7/12 Drive sample blow count; indicates that 7 blows of a 140—pound hammer falling 30 inches were
required to drive the California sampler 12 inches.
---> Depth at which boring caved when checked on March 31, 1997.
NOTES:
1. The exploratory boring was drilled on March 24, 1997 with a 4—inch diameter continuous
flight power auger.
2. Location of the exploratory boring was measured approximately by pacing from house corners staked
in the field.
3. Elevation of the exploratory boring was not measured and the log of exploratory boring is drawn 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 an the exploratory boring log represent the approximate boundaries
between material types and transitions may be gradual.
6. Free water was not encountered in the boring 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.
197 200
HEPWORTH — PAWLAK
GEOTECHNICAL, INC.
LEGEND AND NOTES
Fig. 3
Compression
Compression
0
1
2
0
1
2
3
4
5
6
Moisture Content = 11.7 percent
Dry Density = 115 pcf
Sample of: Clayey Sand
From: Boring 1 at 2 Feet
No movement
upon
wetting
0.1
1.0 10
APPLIED PRESSURE — ksf
100
Moisture Content = 18.8 percent
Dry Density = 108 pcf
Sample of: Clayey sand
From: Boring 1 at 5 Feet
No movement
upon
wetting
0.1
1.0 10
APPLIED PRESSURE ksf
100
197 200
HEPWORTH -- PAWLAK
GEOTECHNICAL, INC.
SWELL — CONSOLIDATION RESULTS
Fig. 4
0
0
N
O
Z
0
SUMMARY OF LABORATORY TEST RESULTS
SOIL OR
BEDROCK TYPE
I f Clayey sand
1 I Clayey sand
c
13
0
c0
0
UNCONFINED
COMPRESSIVE
STRENGTH
(PSFI
PERCENT ATTERBERG LIMITS
PASSING LIQUID PLASTIC
NO. 200 LIMIT INDEX
SIEVE I%) (%)
34
NATURAL GRADATION
DRY GRAVEL SAND
DENSITY I%I (%)
(pc))
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SAMPLE LOCATION
DEPTH
(feet)
N
LC)
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m