HomeMy WebLinkAboutSYMBIOS LOGIC PUD - PRELIMINARY - 5-94E - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTAPR 22 '96 03:39PM RBD INC FORT COLLINS
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PRELIMINARY GEOTECHNICAL ENGINEERING REPORT
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PROPOSED NCR FACILITY
HARMONY ROAD
FORT COLLINS, COLORADO
ELI PROJECT NO, 20395113
JUNE 9, 1993
INTRODUCTION
This report contains the results of our preliminary geotechnical engineering exploration for the
proposed project to be located on Harmony Road in southeast Fort Collins, Colorado. The site is
located In the Southeast 1 /4 of Section 32, Township 7 North, Range 88 West of the 8th Principal
Meridian, Larimer County, Colorado.
The purpose of these services is to provide information and preliminary geotechnical engineering
recommendations relative to:
• subsurface soil and bedrock conditions
• groundwater conditions
• preliminary foundation design and construction
• basement construction
• floor slab design and construction
• earthwork
• drainage
The conclusions and recommendations contained in this report are based upon the results of field
and laboratory testing, engineering analyses, and experience with similar soil and structural
conditions.
PROPOSED CONSTRUCTION
Based on Information provided by Mr. Don Rott, Facilities Manager, the proposed facility is to
consist of a story office building with. a future manufacturing facility. Construction will
probably consist of steel frame, masonry structures with possible basement construction. Column
loads are expected to be relatively high.
Final site grading plans were not available prior to preparation of this report. Ground floor level
is anticipated at, or slightly above existing site grade.
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Other major site development will include the construction of paved areas adjacent to the
proposed building locations. Two levels of traffic are anticipated for pavements to be constructed
on the site. These include automobile parking and driveways and truck access.
SITE EXPLORATION
The scope of the services performed for this project included site reconnaissance by a engineering
geologist, a subsurface exploration program, laboratory testing and engineering analyses.
Figid Exol Jatlon: A total of 9 test borings were drilled to depths of 25 to 30 feet at the locations
shown on the Site Plan, Figure 1. The borings were drilled on a grid to obtain representative
coverage of the property for a preliminary evaluation of the site. All borings were advanced with
a truck -mounted drilling rig, utilizing 4-inch diameter solid stem auger. in addition to the borings,
nine 3'x3'x3' deep concrete blocks were constructed at the site by ABC Concrete of Fort Collins,
Colorado. These blocks are to be used for a site vibration study by Collin Gardon Associates of
San Mateo, California.
The location of borings were positioned in the field by measurements from property lines and
existing site features using conventional chaining methods. The accuracy of boring locations
should only be assumed to the level Implied by the methods used to determine each.
Continuous lithologic logs of each boring were recorded by the geotechnical engineer during the
drilling operations. At selected intervals, samples of the subsurface materials were taken by
means of pushing thin -walled Shelby tubes, or by driving split -spoon samplers.
Penetration resistance measurements were taken with each sampling with the split -spoon by
driving the sampler with a 140 pound hammer failing 30 inches. When property Interpreted, the
penetration resistance is a useful index to the consistency, relative density or hardness of the
materials encountered. In addition, photoionization detector (PID) readings were obtained in Boring
8 to survey for potential petroleum contamination from the underground storage tank at the site.
Groundwater conditions were evaluated in each boring at the time of site exploration, and 4 days
after drilling.
Laboratory Tooting: All samples retrieved during the field exploration were returned to the
laboratory for evaluation by the project geotechnical engineer, and were classified in accordance
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ELI Project No. 20935115
with the Unified Soil Classification system described in Appendix C. Samples of bedrock were
classified in accordance with the general notes for Bedrock Classification. At that time, the field
descriptions were confirmed or modified as necessary, final boring logs prepared, and an applicable
laboratory testing program was formulated to determine engineering properties of the subsurface
materials. Boring Logs for the project are presented in Appendix A.
Selected soil and bedrock samples were tested for the following engineering properties:
• Water content
• Dry density
• Unconfined compression
• Expansion
• Plasticity
The significance and purpose of each laboratory test is described in Appendix C. Laboratory test
results are presented in Appendix B, and were used for the geotechnical engineering analyses, and
the development of foundation and earthwork recommendations. All laboratory test were
performed in general accordance with applicable ASTM, local or other accepted standards.
SITE CONDITIONS
The site consists of irrigated farm land. A farmhouse with four outbuildings occupy the south-
central portion of the property. An underground tank is located at the north end of the existing
garage. The tank according to the landowner is 42 inches in diameter and has not been used for
18 years. The property is relatively flat and has minor drainage to the east. A relatively large
irrigation lateral cuts the property from north to south near the center of the property. The site
is bordered on the east by County Road 9, on the north by open farm fields, on the west by a
mobile home park and on the south by Harmony Road.
SUBSURFACE CONDITIONS
Geology: The proposed area is located within the Colorado Piedmont section of the Great Plains
physiographic province. The Colorado Piedmont, formed during Late Tertiary and Early quaternary
time (approximately sixty-five million (65,000,000) years ago), is a broad, erosional trench which
separates the Southern Rock Mountains from the High Plains. Structurally, the site lies along the
western flank of the Denver Basin. During the Late Mesozoic and Early Cenozoic Periods
(approximately seventy million (70,000,000) years ago), intense tectonic activity occurred,
causing the uplifting of the Front Range and the associated downwarping of the Denver Basin to
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the east. Relatively flat uplands and broad valleys characterize the present-day topography of the
Colorado Piedmont in this region.
The site is underlain by the Cretaceous Pierre Formation. The Pierre Shale underlies the site at
depths of 17 to 24%2 feet below the surface. The regional dip of the bedrock in this area is slight
and in an easterly direction. Seismic activity in the area is anticipated to be low; and from a
structural standpoint, the property should be relatively stable. Bedrock is overlain by alluvial and
residual clays and sands and gravels of Pleistocene and/or Recent Age. Due to the flat nature of
the site, geologic hazards due to mass movement, such as landslides, mudflows, etc., are not
anticipated. The property lies within the drainage basin of the Cache La Poudre River and is
elevated well above the flood plain of the stream and should not be subjected to flooding.
Mapping completed by the Colorado Geological Survey ('Hart, 1872), indicates the site in an area
of "Moderate Swell Potential". Potentially expansive materials mapped in this area Include
bedrock, weathered bedrock and surficial deposits.
Soil and Bedrock Conditions: As presented on Logs of Borings, the subsurface soils are as
follows:
1. Sllty Topsoil and Fill Material: The majority of the area tested is overlain by a 8-inch layer
of cultivated topsoil. The topsoil has been penetrated by root growth and organic matter.
A 1 %-foot layer of fill material was encountered at the surface of Boring 8. The fill is
located in the existing farmyard and consists of lean clay with sand and minor amounts of
gravel. It is not known whether the fill has been uniformly or properly compacted;
therefore, it should not be used as a foundation soil.
2. Lean Clay with Sand! A layer of lean clay and/or lean clay with sand underlies the topsoil
and/or fill in all borings and extends to depths of 3 to 734 feet below the surface. The lean
clay contains varying amounts of sand, is moist and exhibits generally low to moderate
bearing characteristics. When wetted, the lean clay exhibits low swell potential.
3. Sandy Lean Clay, A layer of tan to red sandy lean clay underlies the upper clays and
extends to the silty gravel with sand and/or bedrock below. The sandy lean clay is
moderately plastic, moist to wet and exhibits low to moderate bearing characteristics.
When wetted, the lower clay stratum exhibits low swell potential.
'Hart, Stephen S., 1972, PotentW Swei6ng Sor7 and Rock in the ftnt Range Urban Cenfdor, Colorado, Colorado
Qeologleal Survey, Environmental Geology No. 7.
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4. Silty Grayial yynh Sand: This stratum underlies the clays in Borings 1, 2, 4 through 7 and
9 at depths of 12 to 17%s feet below the surface and extends to the bedrock below. The
silty gravel contains varying amounts of sand, minor amounts of cobbles, is well graded,
medium dense and exhibits generally moderate bearing characteristics in its wet in situ
condition.
5. Sandstone-Siltstone-Clayst,one Bedrock: The bedrock was encountered in all borings at
depths of 17 to 24A feet below the surface and extends to greater depths. The upper 2
to 4%s feet of the bedrock is highly weathered; however, the underlying interbedded
sandstone-siltstone-claystone is very hard and exhibits very high bearing characteristics.
Laboratory Test Resutta; Laboratory test results indicate that the upper clay subsoils have low
expansive potential. The slitstone-claystone bedrock exhibits moderate to high expansive
potential.
_(3roundwater_Conditions: Groundwater was encountered at depths of 10%: to 14A feet in the
test borings at the time of field exploration. When checked 4 days after drilling, groundwater was
measured at depths of 10 A to 1336 feet, These observations represent only current groundwater
conditions, and may not be indicative of other times, or at other locations. Groundwater levels
can be expected to fluctuate with varying seasonal and weather conditions and irrigation demands
on and/or adjacent to the site.
Based upon review of U.S. Geological Survey maps (=Hillier, et al, 1979), regional groundwater
is expected to be encountered in unconsolidated alluvial deposits on the site, at depths ranging
from 10 to 20 feet below the existing ground surface at the project site.
Fluctuations in groundwater levels can best be determined by implementation of a groundwater
monitoring plan. Such a plan would include installation of groundwater monitoring wells, and
periodic measurement of groundwater levels over a sufficient period of time.
CONCLUSIONS AND RECOMMENDATIONS
Ge Qral Conaderat90BA: Present site configuration and grades indicate that fill will likely be
required to achieve final construction elevation. Final grading plans had not been completed prior
'Hillier, Donald E.,, Schneider. Paul A„ Jr.; and Hutchinson, F. Carter, I SS3, Depth to Water Table H9791 in the
you/der-Fort Collins -Greeley Area, Front Range Urban COrridQ& Cularsdo,United States Geological Survcy, Map 1-855-1
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