HomeMy WebLinkAboutSoils Report 09.28.2016H-PvKUMAR
Geotechnical Eng nearing j Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwoodOkumarusa.com
Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado
SUBSURFACE STUDY
FOR FOUNDATION DESIGN
PROPOSED SHOP BUILDING
MYER PROPERTY
501 DAVIS POINT
GARFIELD COUNTY, COLORADO
PROJECT NO. 16-7-305
SEPTEMBER 28, 2016
PREPARED FOR:
RANDO CONSTRUCTION
ATTN: JOE RANDO
P. O. BOX 1443
RIFLE, COLORADO 81650
d 1r4051 'msn.com
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 _ g -
LIMITATIONS - 5 -
FIGURE 1 - LOCATION OF EXPLORATORY BORINGS
FIGURE 2 - LOGS OF EXPLORATORY BORINGS
FIGURE 3 LEGEND AND NOTES
FIGURES 4 through 6 - SWELL -CONSOLIDATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
H -P - KUMAR
Project No. 16-7-305
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed shop building to be located at
the Myer Property, 501 Davis Point Road, northeast of Silt, 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 Rando Construction dated August 8, 2016.
A field exploration program consisting of exploratory borings was conducted to obtain
information on the subsurface conditions. Samples of the subsurface materials 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 building will be a single story, steel frame and metal structure located on the site
as shown on Figure 1. The floor will be slab -on -grade at an elevation slightly above the existing
ground surface. Grading for the structure is assumed to be relatively minor with cut depths
between about 2 to 4 feet. We assume moderate foundation loadings carried by column pads and
connecting grade beam system, 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.
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Project No. 16-7-305
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SITE CONDITIONS
The proposed building site is vacant and has undergone some previous grading. The grading
included cuts up to about 10 feet high into the steep hillside to the west to level the site. The
ground surface is gently sloping down to the east with an estimated 1 to 2 feet of elevation
difference across the proposed building site. The site is currently used as a parking area. There
are sandstone boulders on the hillside areas to the west up to about 4 feet in diameter.
FIELD EXPLORATION
The field exploration for the project was conducted on August 9, 2016. 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 H-P/Kumar.
Samples of the subsoils and bedrock were taken with a 2 inch LD. California spoon sampler.
The sampler was driven into the subsoils and bedrock at various depths with blows from a 140
pound hammer falling 30 inches. This test is similar to the standard penetration lest described by
ASTM Method D-1586. The penetration resistance values are an indication of the relative
density or consistency of the subsoils and hardness of the bedrock. 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 nil to a few inches of gravel surface for the parking area, consisted
of about 1 foot of stiff, sandy clay and silt with shale fragments underlain by claystone/siltstone
bedrock that extended down to depths drilled of 21 feet. The claystone/siltstone bedrock was
weathered and medium hard becoming less weathered and hard to very hard with depth, and is of
the Wasatch Formation.
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Project No. 16.7.305
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Laboratory testing performed on samples obtained from the borings included natural moisture
content and density, and swell -consolidation testing. The results of the swell -consolidation
testing performed on relatively undisturbed drive samples of the claystone/siltstone, presented on
Figures 4 through 6, indicate low to moderate compressibility under conditions of loading and
wetting, with typically a minor hydro -compression potential. One sample (Boring 2 at 21/2 feet)
showed a minor swell potential when wetted under a constant 1,000 psf surcharge. The samples
that showed a hydro -compression potential may have been partly disturbed due to the sampling
process in the hard bedrock. The laboratory testing is summarized in Table 1.
No free water was encountered in the borings at the time of drilling or and the subsoils and
bedrock were slightly moist.
DESIGN RECOMMENDATIONS
FOUNDATIONS
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
entirely on undisturbed bedrock materials. The minor swell potential encountered in one of the
samples can be neglected in the foundation design.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1)
Footings placed on the undisturbed bedrock should be designed for an allowable
bearing pressure of 3,000 psf.
Based on experience, we expect settlement of
footings designed and constructed as discussed in this section will be up to about
1 inch depending on the foundation loading. There could be some additional
settlement if the bearing materials were to become wetted and precautions should
be taken to prevent wetting.
2) The footings should have a minimum width of 16 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
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Project No. 16-7-305
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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, if any, should also be designed to
resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at
least 50 pcf. Any retaining walls should have a drain system to prevent build-up
of hydro -static pressures behind the walls.
5) All existing fill, topsoil, clay and silt soils, and any loose disturbed materials
should be removed and the footing bearing level extended down to the
undisturbed bedrock materials. The exposed 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 and bedrock, exclusive of topsoil, are suitable to support lightly loaded
slab -on -grade construction. The bedrock could possess a low swell potential and should be
further evaluated for expansion potential at the time of construction to determine if
subexcavation of a shallow depth (possibly 1 to 2 feet) of the bedrock and replacement with
imported road base is needed.
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 sand and gravel road
base should be placed beneath the slab for support and 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 12% passing the No. 200 sieve.
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Project No. 16.7-305
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Ali 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 and well broken bedrock, excluding topsoil and oversized rocks, or a road base material
can be imported.
SURFACE DRAINAGE
A perimeter drain around the proposed building should not be needed due to the proposed floor
"slab -at -grade" construction. The following drainage precautions should be observed during
construction and maintained at all times after the building 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 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.
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 I, the proposed type of
construction and our experience in the area. Our services do not include determining the
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Project No. 16-7-305
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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 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-134- KU
Ott
David A. Young, P.E.3;
Reviewed by:
know
Steven L. Pawlak, P.E.
DAY/ksw
cc: SGM - Jeff Simonson (jeffsm-inc.com)
H -P t KUMAR
Project No. 16-7-305
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H-■ kKUMAR
LOCATION OF EXPLORATORY BORINGS
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BORING 1
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LOGS OF EXPLORATORY BORINGS
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LEGEND
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FILL: GRAVEL FOR DRIVEWAY, ABOUT 3" THICK. ENCOUNTERED ONLY AT BORING 2.
CLAY AND SILT (CL—ML); SANDY, GRAVELLY WITH SHALE FRAGMENTS, STIFF, SUGHTLY
MOIST, BROWN.
ICLAYSTONE/SILTSTONE BEDROCK; WEATHERED AND MEDIUM HARD BECOMING LESS
WEATHERED AND HARD TO VERY HARD WITH DEPTH, SLIGHTLY MOIST, MIXED BROWN AND
GRAY—BROWN. WASATCH FORMATION.
I] RELATIVELY UNDISTURBED DRIVE SAMPLE; 2—INCH I.Q. CAUFORNIA LINER SAMPLE.
75/5 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 75 BLOWS OF A 140—POUND HAMMER
FALLING 30 INCHES WERE REOUIRED TO DRIVE THE CAUFORNIA SAMPLER 5 INCHES.
NOTES
1. THE EXPLORATORY BORINGS WERE DRILLED ON AUGUST 9, 2016 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 NOT MEASURED AND THE LOGS OF THE
EXPLORATORY BORINGS ARE PLOTTED TO DEPTH.
4. THE EXPLORATORY BORING LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE
DEGREE IMPUED 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
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (X) (ASTM 0 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216).
16-7-305
H -PN KUMAR
LEGEND AND NOTES
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16-7-305
H-P-t-KUIVIAR
SWELL -CONSOLIDATION TEST RESULT Fig. 4
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ADDITIONAL COMPRESSION
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DUE TO WETTING
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1.0 API'1JED PRESSURE — KSF 10
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SWELL-CONSOLJDATION TEST RESULT
100
Fig. 5
Project No.18-7-305
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