HomeMy WebLinkAboutPARAGON POINT PUD PHASE FIVE PRELIMINARY - 48 91K - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTi
GEOTECHNICAL ENGINEERING REPORT
i
PARAGON V
FORT COLLINS, COLORADO
I
j ELI PROJECT NO. 20945174
September 1, 1994
A Division of
The Terracon Companies, Inc.
Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
The site is underlain by the Cretaceous Pierre Formation. The Pierre shale underlies the site
at depths of 6'/2 to 14'% feet. The Pierre shale is overlain by residual and/or alluvial soils
of Pleistocene and/or Recent Age.
Mapping completed by the Colorado Geological Survey ('Hart, 1972), indicates the site in
an area of "Low to Moderate Swell Potential". Potentially expansive materials mapped in
this area include bedrock, weathered bedrock and colluvium (surficial units).
Soil and Bedrock Conditions: As presented on the Logs of Boring, the subsurface soils were
encountered in order of increasing depths as follows:
• Structural Fill Material: A '/2 to 7 foot layer of lean clay with sand and sandy lean
.clay fill was encountered at the surface of the eight borings drilled at the site. Field
density tests were performed during the placement of the fill material by Empire
Laboratories, Inc. in October 1993. The fill is moist and stiff to hard in situ.
• Lean Clay with Sand and Sandy Lean Clay: These strata were encountered below
the fill and extend to the bedrock below. The lean clay with sand and sandy lean
clay is moist to wet and medium in consistency.
• Siltstone-Claystone Bedrock: The bedrock was encountered at depths of 6% to
14'% feet and extends to greater depths. The upper 1'% to 2'% feet of the bedrock
is highly weathered; however, the underlying interbedded siltstone and claystone is
hard.
Field and Laboratory Test Results: Laboratory test results indicate the structural fill and clay
soils exhibit moderate swell potential and moderate bearing characteristics. The bedrock
exhibits moderate swell potential and high bearing characteristics.
Groundwater Conditions: Groundwater was not observed in any test boring at the time of
the field exploration. However, when checked 2 to 4 days after drilling, groundwater was
encountered at depths of 2Y2 to 9 feet below the surface, in Boririgs 1 through 7. Boring
8 was caved and wet at a depth of 4'/2 feet. These observations represent only current
groundwater conditions, and may not be indicative of other times, or at other locations.
.'Hart, Stephen S., 1972, Potentially Swelling Soil and Rock in the Front Range Urban Corridor, Colorado, Colorado
Geological Survey, Environmental Geology No. 7.
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Groundwater levels can be expected to fluctuate with varying seasonal and weather
conditions.
Based upon review of U.S. Geological Survey Maps ('Hillier, et al, 1983), regional
groundwater beneath the project area predominates in colluvial, landslide or windblown
materials, or in fractured weathered consolidated sedimentary bedrock located at a depth
near ground surface. Seasonal variations in groundwater conditions are expected since the
aquifer materials may not be perennially saturated. Groundwater is generally encountered
at depths ranging from 5 to 20.feet below ground surface; depth to seasonal groundwater
is generally 10 feet or less.
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.
The possibility of groundwater fluctuations should be considered when developing design
and construction plans for the project.
CONCLUSIONS AND RECOMMENDATIONS
Geotechnical Considerations: The site appears suitable for the proposed construction.
Potentially expansive soils and bedrock and relatively shallow depths of groundwater will
attention in the design and construction.
The following foundation systems were evaluated for use on the site:
• spread footings and/or grade beams bearing on undisturbed soils;
• spread footings and/or grade beams bearing on existing structural fill;
• spread footings and/or grade beams bearing on newly placed engineered fill.
Slab -on -grade construction is considered acceptable for use provided that design and
construction recommendations are followed. However, given the expansive nature of the
clays (especially the structural fill clays) and bedrock soils, consideration should be given
'Hillier, Donald E.; Schneider, Paul A., Jr.; and Hutchinson, E. Carter, 1983, Depth to Water Table (1979) In the Boulder -Fort
Collins -Greeley Area, Front Range Urban Corridor, Colorado, United States Geological Survey, Map 1-855-1.
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
to use of structural floor systems. In addition, all finished lower floor slabs or crawl spaces
should be placed a minimum of 3 feet above existing groundwater, or complete dewatering
systems should be provided around the slab and/or lower crawl -space areas.
Foundation Systems: Due to the presence of moderate -swelling soils on the site, spread
footing and/or grade beam foundations bearing upon undisturbed subsoils, existing
structural fill, and/or newly placed engineered fill are recommended for support for the
proposed structures. The footings may be designed for a maximum bearing pressure of
2,000 psf. In addition, the footings should be sized to maintain a minimum dead -load
pressure of 750 psf. The design bearing pressure applies to dead loads plus 1 /2 of design
live load conditions. The design bearing pressure may be increased by one-third when
considering total loads that include wind or seismic conditions.
In order to maintain the minimum dead -load pressure, it may be necessary to design and
construct a system of grade beams and isolated footing pads. To maintain the minimum
dead -load pressure on footings, a minimum 4-inch void space should be provided beneath
the grade beams between footing pads (if utilized).
The existing fill on the site may be used for support of foundations. Field density tests
were performed in the structural fill as it was placed by Empire Laboratories, Inc. in October
1993.
Exterior footings should be placed a minimum of 30 inches below finished grade for frost
protection. The bottom of all footings should be placed a minimum of 2 feet above the
bedrock stratum. Finished grade is the lowest adjacent grade for perimeter footings and
floor level for interior footings.
Footings should be proportioned to minimize differential foundation movement.
Proportioning on the basis of equal total settlement is recommended; however,
proportioning to relative constant dead -load pressure will also reduce differential settlement
between adjacent footings. Total or differential settlement resulting from the assumed
structural loads are estimated to be on the order of 3/4 inch(es) or less. Additional
foundation movements could occur if water from any source infiltrates the foundation soils;
therefore, proper drainage should be provided in the final design and during construction.
For foundations adjacent to slopes, a minimum horizontal setback of five (5) feet should be
maintained between the foundation base and slope face. In addition, the setback should
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
such that an imaginary line extending downward at 45 degrees from the nearest foundation
edge does not intersect the slope.
Crawl Space Construction: Crawl -space construction is feasible at the site providing the
finished lower crawl space is placed a minimum of 3 feet above the existing groundwater.
Where the finished crawl space is placed within 3 feet of existing groundwater, placement
of a perimeter drainage system is recommended.
The drainage system should be constructed around the exterior perimeter of the crawl -space
foundation, and sloped at a minimum 1 /8 inch per foot to a suitable outlet, such as a sump
and pump system.
The drainage system should consist of a properly sized perforated pipe, embedded in free -
draining gravel, placed in a trench at least 12-inches in width. Gravel should extend a
minimum of 3-inches beneath the bottom of the pipe, and at least 2 feet above the bottom
of the foundation wall. The gravel should be covered with drainage fabric prior to
placement of foundation backfill.
Seismic Considerations: The project site is located in Seismic Risk Zone I of the Seismic
Zone Map of the United States as indicated by the Uniform Building Code. Based upon the
nature of the subsurface materials, a seismic site coefficient, "s" of 1.0 should be used for
the design of structures for the proposed project (Uniform Building Code, Table No. 23-J).
i,
Floor Slab Design and Construction: The variability of the existing soils at approximate slab
subgrade_elev.ation_could_resultin differential movement of floor slab -on -grade should
expansive soils become elevated in moisture content. Use of structural floor systems,
structurally supported independent of the subgrade soils, is a positive means of eliminating
the potentially detrimental effects of floor movement.
If slab -on -grade is utilized, the subgrade soils should be prepared as outlined in the
earthwork section of this report.
Additional floor slab design and construction recommendations are as follows:
• Positive separations and/or isolation joints should be provided between slabs
and all foundations, columns or utility lines to allow independent movement.
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Geotechnical Engineering Exploration Terracon
Mr. Byron Collins
ELI Project No. 20945174
• Contraction joints should be provided in slabs to control the location and
extent of cracking. Maximum joint spacing of 15 to 20 feet in each direction
is recommended.
• A minimum 2-inch void space should be constructed above, or below non -
bearing partition walls placed on the floor slab. Special framing details should
be provided at door jambs and frames within partition walls to avoid potential
distortion. Partition walls should be isolated from suspended ceilings.
• Interior trench backfill placed beneath slabs should be compacted in
accordance with recommended specifications outlined below.
• In areas subjected to normal loading, a minimum 4-inch layer of clean -graded
gravel should be placed beneath interior slabs.
• A minimum 6-inch layer of free -draining gravel should be placed in crawl -
space areas in conjunction with the perimeter drainage system.
• Floor slabs should not be constructed on frozen subgrade.
• Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1 R are recommended.
Pavement Design and Construction: Design of pavements for the project have been based
on-the-procedures-outlined_in_the 1,986_Guideline_f_or Design of Pavement Structures by the
American. Association of State Highway and Transportation Officials (AASHTO). Areas
within proposed pavements on the site will be divided into two categories based upon
anticipated traffic and usage.
Traffic criteria provided for pavement thickness designs include single 18-kip equivalent axle
loads (ESAL's) of 36,500 for the proposed Finch Court.
Based upon AASHTO criteria, Colorado is located within Climatic Region VI of the United
States. This region is characterized as being dry, with hard ground freeze and spring thaw.
The spring thaw condition typically results in saturated or near -saturated subgrade soil
moisture conditions. The AASHTO criteria suggests that these moisture conditions are
prevalent for approximately 12-1/2% of the annual moisture variation cycle.
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Local drainage characteristics of proposed pavements areas are considered for vary from
fair depending upon location on the site. For purposes of this design analysis, fair drainage
characteristics are considered to control the design. These characteristics, coupled with the
approximate duration of saturated subgrade conditions, results in a design drainage.
coefficient of 1.0 when applying the AASHTO criteria for design.
For flexible pavement design, a terminal serviceability index of 2.0 was utilized along with
an inherent reliability of 70%. Using the correlated design R-value of 5, appropriate
ESALs/day, environmental criteria and other factors, the structural numbers (SN) of the
pavement sections were determined on the basis of the 1986 AASHTO design equation.
In addition to the flexible pavement design analyses, a rigid pavement design analysis was
completed, based upon AASHTO design procedures. Rigid pavement design is based on an
evaluation of the Modulus of Subgrade Reaction of the soils (K-value), the Modulus of
Rupture of the concrete, and other factors previously outlined. The design K-value of 100
for the subgrade soil was determined by correlation to the laboratory tests results. A
modulus of rupture of 650 psi (working stress 488 psi) was used for pavement concrete.
The rigid pavement thicknesses for each traffic category were determined on the basis of
the AASHTO design equation.
Recommended alternatives for flexible and rigid pavements, summarized for each traffic
area, are as follows:
Recommended Pavement Section Thickness (inches)
Traffic Area
Alternative
Asphalt
Concrete
Surface
Aggregate
Base
Course
Plant -Mixed
Bituminous
Base
Portland
Cement
Concrete
Total
Finch Court
A
3'
B
2"
4"
6"
C
6"
6"
Each alternative should be investigated with respect to current material availability and
economic conditions.
Aggregate base course (if used on the site) should consist of a blend of sand and gravel
which meets strict specifications for quality and gradation. Use of materials meeting
Colorado Department of Transportation Class 5 or 6 specifications is recommended.
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Aggregate base course should be placed in lifts not exceeding six inches and should be
compacted to a minimum of 95% Standard Proctor density (ASTM D698)..
Asphalt concrete should be obtained from an approved mix design stating the Marshall or
Hveem properties, optimum asphalt content, job mix formula, and recommended mixing and
placing temperatures. Aggregate used in asphalt concrete should meet a particular
gradation. Use of materials meeting Colorado Department of Transportation Grading C or .
CX specification is recommended. The mix design should be submitted prior to construction
to verify its adequacy. The asphalt materials should be placed in maximum 3-inch lifts, and
should be compacted to a minimum of .95% Marshall or Hveem density (ASTM D1559).
Plant -mixed bituminous base course should be composed of a mixture of aggregate, filler
and additives if ;required, and approved bituminous material. The bituminous base should
conform to an approved mix design stating the Marshall or Hveem properties, optimum
asphalt content, job mix formula, and recommended mixing and placing temperatures.
Aggregate used in plant -mixed bituminous base course should meet a particular gradation.
Use of aggregates meeting Colorado Department of Transforation Grading G or C
specifications is recommended. The mix design should be submitted prior to construction
to verify it adequacy. The asphalt material should be placed in maximum 3-inch lifts, and
should be compacted to a minimum of 95% Marshall or Hveem density (ASTM D1559).
Where rigid pavements are used, the concrete should be obtained from an approved mix
design with the following minimum properties:
•
Modulus of Rupture @ 28 days
................... 650 minimum
Strength Requirements ................ ........ .
• Minimum Cement Content ..................... 6.5 sacks/cu. yd.
• Cement Type ................................ Type I Portland
• Entrained Air Content .............................. 6 to 8%
• Concrete Aggregate ............ ASTM C33 and CDOT Section 703
• Aggregate Size ............................. 1 inch maximum
• Maximum Water Content ................... 0.49 lb/lb of cement
• Maximum Allowable Slump .......................... 4 inches
Concrete should be deposited by truck mixers or agitators and placed a maximum of 90
minutes from time the water is added to the mix. Other specifications outlined by the
Colorado Department of Transportation should be followed.
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Longitudinal and transverse joints should be provided as needed in concrete pavements for
expansion/contraction and isolation. The location and extent of joints should be based upon
the final pavement geometry and should be placed (in feet), at roughly twice the slab
thickness (in inches), on center in either direction. Sawed joints should be cut within 24-
hours of concrete placement, and should be a minimum of 25% of slab thickness plus 1/4
inch. All joints should be sealed to prevent entry of foreign material "and dowelled where
necessary for load transfer. Where dowels cannot be used at joints accessible to wheel
loads, pavement thickness should be increased by 25 percent at the joints and tapered to
regular thickness in 5 feet.
Future performance of pavements constructed on the clay soils at this site will be
dependent upon several factors, including:
• maintaining stable moisture content of the subgrade soils; and,
• providing for a planned program of preventative maintenance.
Since the clay soils on the site have shrink/swell characteristics, pavements could crack in
the future primarily because of expansion of the soils when subjected to an increase in
moisture content to the subgrade. The cracking, while not desirable, does not necessarily
constitute structural failure of the pavement.
The performance of all pavements can be enhanced by minimizing excess moisture which
can reach the subgrade soils. The following recommendations should be considered at.
minimum:
Site grading at a minimum 2% grade away from the pavements;
• Compaction of any utility trenches for lands aped areas to the same criteria
as the pavement subgrade;
• Sealing all landscaped areas in, or adjacent to pavements to minimize or
prevent moisture migration to subgrade soils;
• Placing compacted backfill against the exterior side of curb and gutter; and,
• Placing curb, gutter and/or sidewalk directly on subgrade soils .without the
use of base course materials.
Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Preventative maintenance should be planned and provided for through an on -going
pavement management program in order to enhance future pavement performance.
Preventative maintenance activities are intended to slow the rate of pavement deterioration,
and to preserve the pavement investment.
Preventative maintenance consists of both localized maintenance (e.g. crack sealing and
patching) and global maintenance (e.g. surface sealing). Preventative maintenance is
usually the first priority when implementing a planned pavement maintenance program and
provides the highest return on investment for pavements.
Recommended preventative maintenance policies for asphalt and jointed concrete
pavements, based upon type and severity of distress, are provided in Appendix D. Prior to
implementing any maintenance, additional engineering observation is recommended to
determine the type and extent of preventative maintenance.
Earthwork:
• Site Clearing:
1. Strip and remove existing vegetation, debris, and other deleterious materials
from proposed building and pavement areas. All exposed surfaces should be
free of mounds and depressions which could prevent uniform compaction.
2. If unexpected fills or underground facilities are encountered during site
clearing, such features should be removed and the excavation thoroughly
cleaned prior to backfill placement and/or construction. All excavations
should be observed by the geotechnical engineer prior to backfill placement.
3. Stripped materials consisting of vegetation and organic materials should be
wasted from the site, or used to revegetate exposed slopes after completion
of grading operations. If it is necessary to dispose of organic materials on -
site, they should be placed in non-structural areas, and in fill sections not
exceeding 5 feet in height.
4. Sloping areas steeper than 3:1 (horizontal:vertical) should be benched to
reduce the potential for slippage between existing slopes and fills. Benches
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
should be level and wide enough to accommodate compaction and earth
moving equipment.
5. The site should be initially graded to create a relatively level surface to
receive fill, and to provide for a relatively uniform thickness of fill beneath
proposed building structures.
6. All exposed areas which will receive fill, once properly cleared and benched
where necessary, should be scarified to a minimum depth of eight inches,
conditioned to near optimum moisture content, and compacted.
• Excavation:
1. It is anticipated that excavations for the proposed construction can be
accomplished with conventional earthmoving equipment.
2. If excavations need to penetrate into the bedrock, use of a large track -
mounted backhoe may be needed to advance the excavation.
3. Depending upon depth of excavation and seasonal conditions, groundwater
may be encountered in excavations on the site. Pumping from sumps may
be utilized to control water within excavations.. Well points may be required
for significant groundwater flow, or where excavations penetrate
aroundwater to a siqnificant depth.
• Slab Suborade Preparation:
1. Where existing soils will support floor slab, the soils should be scarified,
moisture conditioned and compacted to a minimum depth of 8 inches.
2. A minimum 4-inch layer of clean -graded gravel should be placed beneath
slabs.
3. A minimum 6-inch layer of clean, graded gravel should be placed in crawl -
space areas provided with a perimeter drainage system.
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GEOTECHNICAL ENGINEERING REPORT
PARAGON V
FORT COLLINS, COLORADO
ELI PROJECT NO. 20945174
September 1, 1994
Prepared for.
MR. BYRON COLLINS
1 OLD TOWN SQUARE, SUITE 301
FORT COLLINS, COLORADO 80524
Prepared by: — — -
Empire Laboratories, Inc.
A Division of The Terracon Companies, Inc.
301 North Howes
Fort Collins, Colorado 80521
Empire Laboratories, Inc.
A Division of,The Terracon Companies, Inc.
Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
11
Pavement Subgrade Preparation:
Terracon
1. The subgrade should be scarified, moistened as required, and recompacted
for a minimum depth of 8 inches prior to placement of fill and pavement
materials.
2. On -site clay soils may pump or become unstable or unworkable at high water
contents. Workability may be improved by scarifying and drying.
Overexcavation of wet zones and replacement with granular materials may
be necessary. Lightweight excavation equipment may be required to reduce
subgrade pumping.
Use of lime, fly ash, kiln dust, cement or geotextiles could also be considered
as. a stabilization technique. Laboratory evaluation is recommended to
determine the effect of chemical stabilization on subgrade soils prior to
construction.
Fill Materials:
1. Clean on -site soils or approved imported materials may be used as fill material
for the following:
• general site grading
• foundation areas
• exterior slab areas
• pavement areas
2. On -site bedrock materials are not recommended for use beneath structural
ares of the site, or as backfill. Should bedrock materials be used for general
site grading, placement in fills at non-structural locations on the site is
recommended.
3. Select granular materials should be used as backfill behind walls which retain
earth.
4. Frozen soils should not be used as fill or backfill.
5. Imported soils (if required) should conform to the following:
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
Percent finer by weight
Gradation ( (ASTM C136)
6.. ......................................... 100
3"....................................... 70-100
No. 4 Sieve ................................. 50-100
No. 200 Sieve .............................. 25 (max)
• Liquid Limit ........................... 35 (max)
• Plasticity Index ......................... 15 (max)
®
6.
Aggregate base should conform to Colorado Department of Transportation Class 5
or 6 specifications.
Ainin
• Placement and Compaction:
1.
Place and compact fill in horizontal lifts, using equipment and procedures that will
produce recommended moisture contents and densities throughout the lift. .
2.
Uncompacted fill lifts should not exceed 10 inches loose thickness.
3.
No fill should be placed over frozen ground.
4.
Materials should be compacted to the following:
Minimum Percent
Material (ASTM D698)
Subgrade soils beneath fill areas ..................... 95
On -site soils:
........ .... ....... .
Beneath foundations .,.. 98
Beneath slabs ............................. 95
Beneath pavements ......................... 95
Imported fill:
Beneath foundations ......................... 98
Beneath slabs 95
Beneath pavements ......................... 95
Ila
Miscellaneous backfill ............................. 90
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Geotechnical Engineering Exploration Terracon
Mr. Byron Collins
ELI Project No. 20945174
5. If a well defined maximum density curve cannot be generated by impact
all
compaction in the laboratory for any fill type, engineered fill should be
compacted to a minimum of 80 percent relative density by determined by
ASTM D4253.
6. On -site clay soils should be compacted within a moisture content range of
optimum moisture to 2 percent above optimum below building areas. On -site
clays below paved areas and imported soils should be compacted within a
moisture range of 2 percent below to 2 percent above optimum.
• Shrinkage: For balancing grading plans, estimated shrink or swell of soils and
bedrock when used as compacted fill following recommendations in this report are
as follows:
Material
Estimated Shrinkl-) Swell W
Based on ASTM D698
On -site soils:
Clays .................................... .15 to -20%
On -site bedrock materials:
Claystone-sandstone-siltstone ....................15 to -20%
• Slopes:
1. For permanent slopes in compacted fill areas, recommended maximum
configurations for_on_site_materials_are_as follows:
Material
Maximum Slope
Horizontal:Vertical
Cohesive soils (clays) 2'h:1
Bedrock........................................ 2:1
If steeper slopes are required for site development, stability analyses should
be completed to design the grading plan.
2. The face of all slopes should be compacted to the minimum specification for fill
embankments. Alternately, fill slopes can be over -built and trimmed to compacted
material.
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J
Geotechnical Engineering Exploration Terracon
Mr. Byron Collins
R ELI Project No. 20945174
• Compliance: Recommendations for slabs -on -grade, foundations and pavement elements
I; supported on compacted fills or prepared subgrade depend upon compliance with
"Earthwork" recommendations. To assess compliance, observation and testing should be
performed under the direction of the geotechnical engineer.
• Excavation and Trench Construction: Excavations into the on -site soils will encounter a
variety of conditions. Excavations into the clays and bedrock can be expected to stand on
relatively steep temporary slopes during construction. However, caving soils and
-� groundwater may also be encountered. The individual contractor(s) should be made
al responsible for designing and constructing stable, temporary excavations as required to
maintain stability of both the excavation sides and bottom. All excavations should be
I sloped or shored in the interest of safety following local, and federal regulations, including
current OSHA excavation and trench safety standards.
The soils to be penetrated by the proposed excavations may vary significantly across the
site. The preliminary soil classifications are based solely on the materials encountered in
widely spaced exploratory test borings. The contractor should verify that similar conditions
exist throughout the proposed area of excavation. If different subsurface conditions are
encountered at the time of construction, the actual conditions should be evaluated to
determine any excavation modifications necessary to maintain safe conditions.
As a safety measure, it is recommended that all vehicles and soil piles be kept to a
minimum lateral distance from the crest of the slope equal to no less than the slope height.
The exposed slope face should be protected against,the elements.
Drainage:
• Surface Drainage:
Positive drainage should be provided during construction and maintained throughout
the life of the proposed buildings. Infiltration of water into utility or foundation
excavations must be prevented during construction. Planters and other surface
features which could retain water in areas adjacent to the building or pavements
should be sealed or eliminated.
-� 2. In areas where sidewalks or paving do not immediately adjoin the structure, we
recommend that protective slopes be provided with a minimum grade of
MAI
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Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
approximately 10 percent for at least 10 feet from perimeter walls. Backfill against
footings, exterior walls, and in utility and sprinkler line trenches should be well
compacted and free of all construction debris to reduce the possibility of moisture
infiltration.
3. Downspouts, roof drains or scuppers should discharge into splash blocks or
extensions when the ground surface beneath such features is not protected by
exterior slabs or paving.
4. Sprinkler systems should not be installed within 5 feet of foundation walls.
Landscaped irrigation adjacent to the foundation system should be minimized or
eliminated.
Additional Design and Construction Considerations:
• Exterior Slab Design and Construction: Compacted subgrade or existing clay soils will
expand with increasing moisture content; therefore, exterior concrete grade slabs may
heave, resulting in cracking or vertical offsets. The potential for damage would be greatest
where exterior slabs are constructed adjacent to the building or other structural elements.
To reduce the potential for damage, we recommend:
•
•
exterior slabs be supported on fill with no, or very low expansion potential
strict moisture -density control during placement of subgrade fills
placement of effective control joints on relatively close centers and isolation
joints between slabs and other structural elements
provision for adequate drainage in areas adjoining the slabs
use of designs which allow vertical movement between the exterior slabs
and adjoining structural elements
In those locations where movement of exterior slabs cannot be tolerated or must be held
to an absolute minimum, consideration should be given to:
• Constructing slabs with a stem or key -edge, a minimum of 6 inches in width
and at least 12 inches below grade;
• supporting keys or stems on drilled piers; or
• providing structural exterior slabs supported on foundations similar to the
building.
4�
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!a! Geotechnical Engineering Exploration
Mr. Byron Collins
A� ELI Project No. 20945174
Terracon
• Underground Utility Systems: Piping should be adequately bedded for proper load
distribution. Where utilities are excavated below groundwater, temporary dewatering will
be required during the excavation, pipe placement and backfilling phases for proper
construction.
• Corrosion Protection: Results of soluble sulfate testing indicate that ASTM Type I Portland
cement is suitable for all concrete on and below grade. However, if there is no, or minimal
cost differential, use of ASTM Type II Portland cement is recommended for additional
sulfate resistance of construction concrete. Foundation concrete should be designed in
accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
GENERAL COMMENTS
It is recommended.that the Geotechnical Engineer be retained to provide a general review of final
design plans and specifications in order to confirm that grading and foundation recommendations
have been interpreted and implemented. In the event that any changes of the proposed project
are planned, the conclusions and recommendations contained in this report should be reviewed
and the report modified or supplemented as necessary.
M The Geotechnical Engineer should also be retained to provide services during excavation, grading,
Rua foundation and construction phases of the work. Observation of footing excavations should be
performed prior to placement of reinforcing and concrete to conform that satisfactory bearing
materials are present and is considered a necessary part of continuing geotechnical engineering
services -for -the project. Construction testing, including field and laboratory evaluation of fill,
backfill, pavement materials, concrete and steel should be performed to determine whether
applicable project requirements have been met. It would be logical for Empire Laboratories, Inc.
IN to provide these additional services for continuing from design through construction and to
determine the consistency of field conditions with those data used in our analyses.
The analyses and recommendations in this report are based in part upon data obtained from the
field exploration. The nature and extent of variations beyond the location of test borings may not
become evident until construction. If variations then appear evident, it may be necessary to re-
evaluate the recommendations of this report.
NMI
Rai Our professional services were performed using that degree of care and skill ordinarily exercised,
under similar circumstances, by reputable geotechnical engineers practicing in this or similar
localities. No warranty, express or implied, is made. We prepared the report as an aid in design
19
Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
of the proposed project. This report is not a bidding document. Any contractor reviewing this
report must draw his own conclusions regarding site conditions and specific construction
techniques to be used on this project.
d This report is for the exclusive purpose of providing geotechnical engineering and/or testing
information and recommendations. The scope of services for this project does not include, either
specifically or by implication, any environmental assessment of the site or identification of
contaminated or hazardous materials or conditions. If the owner is concerned about the potential
l
for such contamination, other studies should be undertaken.
11 20
11
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�0.5 Ira•. G .
.,
L -1. �--�T ��• 7,cFf15174 Empire Laboratories, Inc.
A Division of The Termcon Companies, Inc.
11
September 2, 1994
Mr. Byron Collins
1 Old Town Square, Suite 301
j Fort Collins, Colorado 80524
Empire Laboratories, Inc.
A Division of The Terracon Companies, Inc.
P.O. Box 503.301 No. Howes
Fort Collins, Colorado 80522
(303)484-0359
Fax (303) 484-0454
Chester C. Smith, P.E.
Larry G. O'Dell, P.E.
Neil R. Sherrod, C.P.G.
Re: Geotechnical Engineering Report, Paragon V
.i Lemay Avenue and Trilby Road
Fort Collins, Colorado
ELI Project No. 20945174
Empire Laboratories, Inc. (ELI) has completed a geotechnical engineering exploration for the
proposed apartment complex to be located on Lemay Avenue and Trilby Road in southeast
f Fort Collins, Colorado. This study was performed in general accordance with our proposal
number D2094279 dated August 8, 1994.
The results of our engineering study, including the boring location diagram, laboratory test
results, test boring records, and the geotechnical recommendations needed to aid in the
design and construction of foundations and other earth connected phases of this project are
attached.
The subsurface soils at the site consist of lean clay and sandy lean clay structural fill
underlain by lean clay with sand and sandy lean clay. The clay soils are underlain by
siltstone-claystone bedrock. The information obtained by the results of field exploration and
laboratory testing completed for this study, indicates that the clay soils and structural fill
exhibit moderate swell potential and moderate bearing characteristics, and bedrock exhibits
moderate swell potential and high bearing characteristics.
Based on the geotechnical engineering analysis, subsurface exploration and laboratory test
results, we recommend the proposed buildings be supported on spread footing and/or grade
beam foundation systems founded a minimum of 3 feet above the bedrock. Slab -on -grade
may be utilized for the interior floor system provided that care is taken in the placement and
compaction of the subgrade soil. If no movement can be tolerated, consideration may be
given to use of structural floor systems. Finished slabs and/or crawl spaces should be
placed a minimum of 3 feet above the bedrock stratum.
I Offices of The Terracon Companies, Inc. Geotechnical, Environmental and Materials Engineers
Arizona ■ Arkansas ■ Colorado ■ Idaho ■ Illinois ■ Iowa ■ Kansas ■ Minnesota
Missouri ■ Montana ■ Nebraska ■ Nevada ■ Oklahoma ■ Texas ■ Utah ■ Wyoming
nuAr 1Tv cur-rWcraime, SINCE Ims
Terracon
Geotechnical Engineering Exploration
Mr: -Byron Collins
ELI Project No. 20945174
Other design and construction details, based upon geotechnical conditions, are presented
in the report.
We appreciated being of service in the geotechnical engineering phase of this project, and
are prepared to assist during the construction phases as well. If you have any questions
concerning this report or any of our testing, inspection, design and consulting services,
please do not hesitate to contact us.
Sincerely,
EMPIRE LABORATORIES, INC.
A Division of The T raco Companies, Inc.
Ne1T . S e
Senior Engineering Geologist
Reviewed by:
Larry G. O'Dell, P.E.
Office Manager
NRS/LGO/cic
Copies to: Addressee (1)
Jim Sell Design - Ms. Kay Force (4)
Pp O R f,9
O�•.•...,,�j'A ram:
22750
O ' r
s10NA`
Geotechnical Engineering Exploration Terracon
Mr. Byron Collins
ELI Project No. 20945174
TABLE OF CONTENTS
Page No.
Letter of Transmittal ............................................... ii
INTRODUCTION ................................................ 1
PROPOSED CONSTRUCTION ...................................... 1
SITE EXPLORATION ............................................. 2
Field Exploration .......................................... 2
Laboratory Testing ......................................... 2
SITECONDITIONS .............................................. 3
SUBSURFACE CONDITIONS ....................................... 3
Geology................................................ 3
Soil and Bedrock Conditions .................................. 4
Field and Laboratory Test Results ............................... 4
Groundwater Conditions ..................................... 4
CONCLUSIONS AND RECOMMENDATIONS ..... :......................
Geotechnical Considerations ..................................
Foundation Systems ........................................
Crawl Space Construction ....................................
Seismic Considerations ......................................
Floor Slab Design and Construction .............................
Pavement Design and Construction .............................
Earthwork...............................................
Site Clearing ......... ......... --- ::-...........-.
5
5
6
7
7
7
8
12
Excavation......................................... 13
Slab Subgrade Preparation ............................... 13
Pavement Subgrade Preparation ........................... 14
Fill Materials ........................................ 14
Placement and Compaction .............................. 15
Shrinkage.......................................... 16
Slopes............................................ 16
Compliance......................................... 17
Excavation and Trench Construction ......................... 17
Drainage ................................................ 17
Surface Drainage .......... ................. ...... 17
Additional Design and Construction Considerations .................. 18
Exterior Slab Design and Construction ...................... 18
Underground Utility Systems ............................. 19
Corrosion Protection ................................... 19
Geotechnical Engineering Exploration Terracon
Mr. Byron Collins
ELI Project No. 20945174
TABLE OF CONTENTS (Cont'd)
Page No.
GENERAL COMMENTS ........................................... 19
APPENDIX A
Figure No.
SitePlan ................................................. 1
Logs of Borings ..................................... Al thru A8
APPENDIX B
Swell -Consolidation Test ................................ 81 thru UZ
Hveem Stabilometer Curves .................................. B3
Summary of Test Results ................................... B4
APPENDIX C: GENERAL NOTES
Drilling & Exploration ....................................... C1
Unified Soil Classification ................................... C2
Bedrock Classification, Sedimentary Bedrock ........................ C3
Laboratory Testing, Significance and Purpose ...................... C4
Report Terminology ........................................ C5
APPENDIX D
Recommended Preventative Maintenance -Asphalt Concrete Pavements .... D1
Recommended Preventative Maintenance -Jointed Concrete Pavements .... D2
GEOTECHNICAL ENGINEERING REPORT Terracon
PARAGON V
FORT COLLINS, COLORADO
ELI Project No. 20945174
September 2, 1994
INTRODUCTION
This report contains the results of our geotechnical engineering exploration for the proposed
apartment complex to be located at the northeast corner of Lemay Avenue and Trilby Road,
Fort Collins, Colorado. The site is located in the Southwest 1 /4 of Section 7, Township 6
North, Range 69 West of the 6th Principal Meridian.
The purpose of these services is to provide information and geotechnical engineering
recommendations relative to:
• subsurface soil and bedrock conditions
0 groundwater conditions
• foundation design and construction
• floor slab design and construction
• pavement 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
conditions, structures and our understanding of the proposed project.
PROPOSED CONSTRUCTION
Based on the information provided by Jim Sell Design, the proposed structures will be one -
and two-story frame apartment buildings having slab -on -grade construction. The structures
are anticipated to exhibit light wall and column loads. We further understand that
approximately 2 feet of additional fill is to be placed on the site. A cul-de-sac off will be
constructed through the center of the project area.
Geotechnical Engineering Exploration
Mr. Byron Collins Terracon
ELI Project No. 20945174
SITE EXPLORATION
The scope of the services performed for this project included site reconnaissance by an
engineering geologist, a subsurface exploration program, laboratory testing and engineering
analyses.
Field Exploration: A total of eight test borings were drilled on August 11, 1994 to depths
of 15 feet at the locations shown on the Site Plan, Figure 1. Nine borings were originally
proposed but access to the northeast portion of the site was not available to our drilling rig
due to existing wetlands. Seven borings were drilled within the footprint of the proposed
buildings, and one boring was drilled in the area of the"proposed street. All borings were
advanced with a truck -mounted drilling rig, utilizing 4-inch diameter solid stem auger.
The borings were located in the field by measurements from existing property corners and
site features. Elevations were taken at each boring location by measurements with an
engineer's level from a temporary bench mark (TBM) shown on the Site Plan. The accuracy
of boring locations and elevations should only be assumed to the level implied by the
methods used.
Continuous lithologic logs of each boring were recorded by the engineering geologist 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.
A representative bulk sample of subsurface materials was obtained from the pavement
boring.
Penetration resistance measurements were obtained -by driving "the split=spoon into`the
subsurface materials with a 140-pound hammer falling 30 inches. The penetration
resistance value is a useful index to the consistency, relative density or hardness of the
materials encountered.
Groundwater measurements were made in each boring at the time of site exploration, and
2 to 4 days after drilling.
i
Laboratory Testing: All samples retrieved during the field exploration were returned to the
laboratory .for observation by the project geotechnical engineer, and were classified in
accordance 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, an applicable
2
Geotechnical Engineering Exploration
Mr. Byron Collins
ELI Project No. 20945174
Terracon
laboratory testing program was formulated to determine engineering properties of the
subsurface materials. Boring logs were. prepared and are presented in Appendix A.
Selected soil and bedrock samples were tested for the following engineering properties:
• Water content • Expansion
• Dry density • Plasticity Index
• Consolidation • R-Value
• Compressive strength • Water soluble sulfate content
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 tests were performed in general. accordance with the applicable ASTM, local or
other accepted standards.
SITE CONDITIONS
The site consists of a vacant tract of land that has been partially filled. The existing
wetlands are located along the eastern edge of the site. The property is bordered on the
west by Lemay Avenue, on the south by Trilby Road, and on the north by Hawkeye Drive.
The area slopes to the east and has positive drainage in this direction to the existing
wetlands area.
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 two -million (2,000,000) years ago), is a broad,
erosional trench which separates the Southern Rocky 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
associated downwarping of the Denver Basin to the east. Relatively flat uplands and broad
valleys characterize the present-day topography of the Colorado Piedmont in this region.
3