HomeMy WebLinkAboutEAST PARK DISTRICT MAINTENANCE FACILITY - MJA200003 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT400 North Link Lane | Fort Collins, Colorado 80524
Telephone: 970-206-9455 Fax: 970-206-9441
GEOTECHNICAL INVESTIGATION
PROPOSED IMPROVEMENTS
BUCKING HORSE PARK
FORT COLLINS, COLORAD
CITY OF FORT COLLINS
300 Laporte Avenue
PO Box 580
Fort Collins, Colorado 80522
Attention: Brian Hergott
Project No. FC09343-125
May 8, 2020
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
TABLE OF CONTENTS
SCOPE 1
SUMMARY OF CONCLUSIONS 1
SITE CONDITIONS AND PROPOSED CONSTRUCTION 2
INVESTIGATION 3
SUBSURFACE CONDITIONS 3
Groundwater 3
SEISMICITY 4
SITE DEVELOPMENT 4
Fill Placement 4
Excavations 6
FOUNDATIONS 6
Footings 6
BELOW GRADE AREAS 7
FLOOR SYSTEMS 8
Exterior Flatwork 10
PAVEMENTS 10
Pavement Selection 11
Subgrade and Pavement Materials and Construction 12
Pavement Maintenance 12
WATER-SOLUBLE SULFATES 12
SURFACE DRAINAGE 13
CONSTRUCTION OBSERVATIONS 13
GEOTECHNICAL RISK 14
LIMITATIONS 14
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS
FIGURE 2 – SUMMARY LOGS OF EXPLORATORY BORINGS
FIGURES 3 THROUGH 6 – RESULTS OF LABORATORY TESTING
TABLE I – SUMMARY OF LABORATORY TESTING
APPENDIX A – SAMPLE SITE GRADING SPECIFICATIONS
APPENDIX B – PAVEMENT CONSTRUCTION RECOMMENDATIONS
APPENDIX C – PAVEMENT MAINTENANCE PROGRAM
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
1
SCOPE
This report presents the results of our Geotechnical Investigation for the
proposed Bucking Horse Park in Fort Collins, Colorado. The purpose of the
investigation was to evaluate the subsurface conditions and provide foundation
recommendations and geotechnical design criteria for the project. The scope was
described in our Service Agreement (Proposal No. FC-20-0144) dated April 2,
2020.
The report was prepared from data developed during field exploration,
laboratory testing, engineering analysis and experience with similar conditions.
The report includes a description of subsurface conditions found in our exploratory
borings and discussions of site development as influenced by geotechnical
considerations. Our opinions and recommendations regarding design criteria and
construction details for site development, foundations, floor systems, slabs-on-
grade, lateral earth loads, pavements and drainage are provided. The report was
prepared for the exclusive use of the City of Fort Collins in design and construction
of the proposed improvements. If the proposed construction differs from
descriptions herein, we should be requested to review our recommendations. Our
conclusions are summarized in the following paragraphs.
SUMMARY OF CONCLUSIONS
1. Soils encountered in our borings consisted of 8 to 9½ feet of sandy
clay over sand and gravel. The upper 2 to 3 feet of soils were
considered fill. Sandstone bedrock was encountered in one boring
at 23 feet to the maximum depth explored.
2. Groundwater was measured at 8½ to 12 feet during drilling. When
measured several days later, groundwater was encountered at
depths of 7½ to 10½ feet. Existing groundwater levels are not
expected to significantly affect site development. We recommend a
minimum 3-foot separation between foundation elements and
groundwater.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
2
3. Existing fill was encountered in two of our borings at depths of 2 to 3
feet. Existing fill should not support foundations or floor slabs. We
recommend removal and recompaction of the existing fill beneath
foundations and floor slabs.
4. The presence of expansive soils and bedrock constitutes a geologic
hazard. There is risk that slabs-on-grade and foundations will heave
or settle and be damaged. We judge the risk is low. We believe the
recommendations presented in this report will help to control risk of
damage; they will not eliminate that risk. Slabs-on-grade and, in
some instances, foundations may be damaged.
5. Footing foundations placed on natural, undisturbed soil and/or
properly compacted fill are recommended for the proposed
construction. Design and construction criteria for foundations are
presented in the report.
6. We believe a slab-on-grade floor is appropriate for this site. Some
movement of slab-on-grade floors should be anticipated. We expect
movements will be minor, on the order of 1 inch or less. If movement
cannot be tolerated, structural floors should be considered.
7. Surface drainage should be designed, constructed and maintained
to provide rapid removal of surface runoff away from the proposed
structures. Conservative irrigation practices should be followed to
avoid excessive wetting.
SITE CONDITIONS AND PROPOSED CONSTRUCTION
The site is located off of Environmental Drive in Fort Collins, Colorado
(Figure 1). The vacant +3.6 acre lot is relatively flat with a gradual slope down to
the southwest. A pond is located south of the site and a drainage is located to the
east. Ground cover consists of natural grasses and weeds. We understand the
proposed construction will consist of a restroom, picnic pavilions, and playground.
Pavements may include access drives and parking. We do not anticipate any
below-grade areas.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
3
INVESTIGATION
The field investigation included drilling three exploratory borings at the
locations presented on Figure 1. The borings were drilled to depths of
approximately 20 to 30 feet using 4-inch diameter, continuous-flight augers and a
truck-mounted drill. Drilling was observed by our field representative who logged
the soils and bedrock. Summary logs of the borings, including results of field
penetration resistance tests, are presented on Figure 2.
Soil and bedrock samples obtained during drilling were returned to our
laboratory and visually examined by our geotechnical engineer. Laboratory testing
was assigned and included moisture content, dry density, swell-consolidation,
particle-size analysis, and water-soluble sulfate tests. Swell-consolidation test
samples were wetted at a confining pressure which approximated the pressure
exerted by the overburden soils (overburden pressures). Results of the laboratory
tests are presented on Figures 3 through 6 and summarized in Table I.
SUBSURFACE CONDITIONS
Soils encountered in our borings consisted of 8 to 9½ feet of sandy clay over
sand and gravel. The upper 2 to 3 feet of soils were considered fill. Sandstone
bedrock was encountered in one boring at 23 feet to the maximum depth explored.
Samples tested exhibited 1.3 to 2.2 percent swell. Further descriptions of the
subsurface conditions are presented on our boring logs and in our laboratory test
results.
Groundwater
Groundwater was measured at 8½ to 12 feet during drilling. When
measured several days later, groundwater was encountered at depths of 7½ to
10½ feet. Groundwater levels are expected to fluctuate seasonally and with water
levels in the nearby water features. Existing groundwater levels are not expected
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
4
to significantly affect site development. We recommend a minimum 3-foot
separation between foundation elements and groundwater.
SEISMICITY
This area, like most of central Colorado, is subject to a low degree of seismic
risk. As in most areas of recognized low seismicity, the record of the past
earthquake activity in Colorado is incomplete.
According to the 2015 International Building Code and the subsurface
conditions encountered in our borings, this site probably classifies as a Site Class
D. Only minor damage to relatively new, properly designed and built buildings
would be expected. Wind loads, not seismic considerations, typically govern
dynamic structural design for the structures planned in this area.
SITE DEVELOPMENT
Fill Placement
The existing onsite soils are suitable for re-use as fill material provided
debris or deleterious organic materials are removed. If import material is used, it
should be tested and approved as acceptable fill by CTL|Thompson. In general,
import fill should meet or exceed the engineering qualities of the onsite soils. Areas
to receive fill should be scarified, moisture-conditioned and compacted to at least
95 percent of standard Proctor maximum dry density (ASTM D698, AASHTO T99).
Sand soils used as fill should be moistened to within 2 percent of optimum moisture
content. Clay soils should be moistened between optimum and 3 percent above
optimum moisture content. The fill should be moisture-conditioned, placed in thin,
loose lifts (8 inches or less) and compacted as described above. We should
observe placement and compaction of fill during construction. Fill placement and
compaction should not be conducted when the fill material is frozen.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
5
Existing fill was encountered in two borings to depths of up to 3 feet. Deeper
fill areas may be encountered during site development. The fill is of unknown origin
and age. The fill presents a risk of settlement or heave to improvements
constructed on the fill. We recommend the fill be removed and recompacted in the
building area.
The fill removal area should extend beyond the building footprint at least one
footing width. If the excavations to remove existing fill are deeper than about 10
feet in the planned building area, additional measures should be considered to
reduce the potential settlement of backfill. We should be advised if any of the
excavations are deeper than 10 feet below the proposed floor. The excavation
can be filled with on-site soils, moisture-conditioned and compacted as described
above. This procedure should remove the existing fill and provide more uniform
support for improvements.
The existing fill can also affect pavements and exterior flatwork. The lowest
risk alternative for exterior pavement and flatwork would also be complete removal
and recompaction. The cost could be significant. If the owner can accept a risk of
some movement and distress in these areas then partial depth removal is an
alternative. We suggest removal of the existing fill to a depth of 1 to 2 feet below
existing grade, proof rolling the exposed subgrade, and additional removal or
stabilization of areas where soft, yielding or organic soils or debris is encountered.
After this, fill placement can proceed to construction grades.
Site grading in areas of landscaping where no future improvements are
planned can be placed at a dry density of at least 90 percent of standard Proctor
maximum dry density (ASTM D 698, AASHTO T 99). Example site grading
specifications are presented in Appendix A.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
6
Water and sewer lines are often constructed beneath areas where
improvements are planned. Compaction of trench backfill can have a significant
effect on the life and serviceability overlying structures. We recommend trench
backfill be moisture conditioned and compacted as described above. Placement
and compaction of backfill should be observed and tested by a representative of
our firm during construction.
Excavations
We believe the materials found in our borings can be excavated using
conventional heavy-duty excavation equipment. Excavations should be sloped or
shored to meet local, State and Federal safety regulations. Excavation slopes
specified by OSHA are dependent upon types of soil and groundwater conditions
encountered. The contractor’s “competent person” should identify the soils and/or
rock encountered in the excavation and refer to OSHA standards to determine
appropriate slopes.
FOUNDATIONS
Our investigation indicates low-swelling soils are present at the anticipated
foundation levels. Footing foundations are recommended for the proposed
construction. Design criteria for footing foundations developed from analysis of
field and laboratory data and our experience are presented below.
Footings
1. Footings should be constructed on undisturbed natural soils or
properly compacted fill (see the Fill Placement section of this report).
All existing, uncontrolled fill should be removed from under footings
and within one footing width around footings and replaced with
properly compacted fill. Where soil is loosened during excavation, it
should be removed and replaced with compacted fill.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
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2. Footings should be designed for a net allowable soil pressure of
2,500 psf. The soil pressure can be increased 33 percent for
transient loads such as wind or seismic loads.
3. Footings should have a minimum width of at least 18 inches.
Foundations for isolated columns should have minimum dimensions
of 24 inches by 24 inches. Larger sizes may be required depending
on loads and the structural system used.
4. The soils beneath footing pads can be assigned an ultimate
coefficient of friction of 0.4 to resist lateral loads. The ability of grade
beam or footing backfill to resist lateral loads can be calculated using
a passive equivalent fluid pressure of 250 pcf. This assumes the
backfill is densely compacted and will not be removed. Deflection of
grade beams is necessary to mobilize passive earth pressure; we
recommend a factor of safety of 2 for this condition. Backfill should
be placed and compacted to the criteria in the Fill Placement section
of this report.
5. Exterior footings should be protected from frost action. We believe
30 inches of frost cover is appropriate for this site.
6. Foundation walls and grade beams should be well reinforced both
top and bottom. We recommend reinforcement sufficient to simply
span 10 feet. The reinforcement should be designed by a structural
engineer.
7. We should observe completed footing excavations to confirm
whether the subsurface conditions are similar to those found in our
borings.
BELOW GRADE AREAS
No below grade areas are planned for the structures. For this condition,
perimeter drains are not usually necessary. We should be contacted to provide
foundation drain recommendations if plans change to include basement areas.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
8
FLOOR SYSTEMS
In our opinion, it is reasonable to use slab-on-grade floors for the proposed
construction. Any fill placed for the floor subgrade should be built with densely
compacted, engineered fill as discussed in the Fill Placement section of this report.
The existing fill is not an acceptable subgrade for a slab-on-grade floor and should
be completely removed from the subgrade under a floor.
It is impossible to construct slab-on-grade floors with no risk of movement.
We believe movements due to swell will be less than 1 inch at this site. If
movement cannot be tolerated, structural floors should be used. Structural floors
can be considered for specific areas that are particularly sensitive to movement or
where equipment on the floor is sensitive to movement.
Where structurally supported floors are selected, we recommend a
minimum void between the ground surface and the underside of the floor system
of 4 inches. The minimum void should be constructed below beams and utilities
that penetrate the floor. The floor may be cast over void form. Void form should
be chosen to break down quickly after the slab is placed. We recommend against
the use of wax or plastic-coated void boxes.
Slabs may be subject to heavy point loads. The structural engineer should
design floor slab reinforcement. For design of slabs-on-grade, we recommend a
modulus of subgrade reaction of 100 pci for on-site soils.
If the owner elects to use slab-on-grade construction and accepts the risk
of movement and associated damage, we recommend the following precautions
for slab-on-grade construction at this site. These precautions can help reduce, but
not eliminate, damage or distress due to slab movement.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
9
1. Slabs should be separated from exterior walls and interior bearing
members with a slip joint that allows free vertical movement of the
slabs. This can reduce cracking if some movement of the slab
occurs.
2. Slabs should be placed directly on exposed soils or properly moisture
conditioned, compacted fill. The 2015 International Building Code
(IBC) requires a vapor retarder be placed between the base course
or subgrade soils and the concrete slab-on-grade floor. The merits
of installation of a vapor retarder below floor slabs depend on the
sensitivity of floor coverings and building use to moisture. A properly
installed vapor retarder (minimum 6-mil; 10-mil recommended) is
more beneficial below concrete slab-on-grade floors where floor
coverings, painted floor surfaces or products stored on the floor will
be sensitive to moisture. The vapor retarder is most effective when
concrete is placed directly on top of it, rather than placing a sand or
gravel leveling course between the vapor retarder and the floor slab.
The placement of concrete on the vapor retarder may increase the
risk of shrinkage cracking and curling. Use of concrete with reduced
shrinkage characteristics including minimized water content,
maximized coarse aggregate content, and reasonably low slump will
reduce the risk of shrinkage cracking and curling. Considerations
and recommendations for the installation of vapor retarders below
concrete slabs are outlined in Section 3.2.3 of the 2006 report of
American Concrete Institute (ACI) Committee 302, “Guide for
Concrete Floor and Slab Construction (ACI 302.R1-04)”.
3. If slab-bearing partitions are used, they should be designed and
constructed to allow for slab movement. At least a 2-inch void should
be maintained below or above the partitions. If the “float” is provided
at the top of partitions, the connection between interior, slab-
supported partitions and exterior, foundation supported walls should
be detailed to allow differential movement.
4. Underslab plumbing should be eliminated where feasible. Where
such plumbing is unavoidable it should be thoroughly pressure
tested for leaks prior to slab construction and be provided with
flexible couplings. Pressurized water supply lines should be brought
above the floors as quickly as possible.
5. Plumbing and utilities that pass through the slabs should be isolated
from the slabs and constructed with flexible couplings. Where water
and gas lines are connected to furnaces or heaters, the lines should
be constructed with sufficient flexibility to allow for movement.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
10
6. HVAC equipment supported on the slab should be provided with a
collapsible connection between the furnace and the ductwork, with
allowance for at least 2 inches of vertical movement.
7. The American Concrete Institute (ACI) recommends frequent control
joints be provided in slabs to reduce problems associated with
shrinkage cracking and curling. To reduce curling, the concrete mix
should have a high aggregate content and a low slump. If desired,
a shrinkage compensating admixture could be added to the concrete
to reduce the risk of shrinkage cracking. We can perform a mix
design or assist the design team in selecting a pre-existing mix.
Exterior Flatwork
We recommend exterior flatwork and sidewalks be isolated from
foundations to reduce the risk of transferring heave, settlement or freeze-thaw
movement to the structure. One alternative would be to construct the inner edges
of the flatwork on haunches or steel angles bolted to the foundation walls and
detailing the connections such that movement will cause less distress to the
building, rather than tying the slabs directly into the building foundation.
Construction on haunches or steel angles and reinforcing the sidewalks and
other exterior flatwork will reduce the potential for differential settlement and
better allow them to span across wall backfill. Frequent control joints should be
provided to reduce problems associated with shrinkage. Panels that are
approximately square perform better than rectangular areas.
PAVEMENTS
The project may include a paved parking lot and access drives. The
performance of pavements is dependent upon the characteristics of the subgrade
soil, traffic loading and frequency, climatic conditions, drainage and pavement
materials. The subgrade soil will likely provide fair to poor support for new
pavement. If fill is needed, we have assumed it will be soils with similar or better
characteristics.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
11
Flexible hot mix asphalt (HMA) over aggregate base course (ABC) is likely
planned for pavement areas. Rigid Portland cement concrete (PCC) pavement
should be used for trash enclosure areas and where the pavement will be
subjected to frequent turning of heavy vehicles. Our designs are based on the
AASHTO design method and our experience. Using the criteria discussed above
we recommend the minimum pavement sections provided in Table A.
TABLE A
RECOMMENDED PAVEMENT SECTIONS
Classification
Hot Mix Asphalt
(HMA) + Aggregate
Base Course (ABC)
Portland Cement
Concrete (PCC)
Parking Area 4" HMA +
6" ABC 5" PCC
Access Drives
/ Heavy Traffic
Areas
5" HMA +
6" ABC 6" PCC
Trash
Enclosures - 6" PCC
Pavement Selection
Composite HMA/ABC pavement over a stable subgrade is expected to
perform well at this site based on the recommendations provided. HMA provides
a stiff, stable pavement to withstand heavy loading and will provide a good fatigue
resistant pavement. However, HMA does not perform well when subjected to point
loads in areas where heavy trucks turn and maneuver at slow speeds. PCC
pavement is expected to perform well in this area; PCC pavement has better
performance in freeze-thaw conditions and should require less long-term
maintenance than HMA pavement. The PCC pavement for trash enclosures
should extend out to areas where trash trucks park to lift and empty dumpsters.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
12
Subgrade and Pavement Materials and Construction
The design of a pavement system is as much a function of the quality of the
paving materials and construction as the support characteristics of the subgrade.
The construction materials are assumed to possess sufficient quality as reflected
by the strength factors used in our design calculations. Moisture treatment criteria
and additional criteria for materials and construction requirements are presented
in Appendix B of this report.
Pavement Maintenance
Routine maintenance, such as sealing and repair of cracks, is necessary to
achieve the long-term life of a pavement system. We recommend a preventive
maintenance program be developed and followed for all pavement systems to
assure the design life can be realized. Choosing to defer maintenance usually
results in accelerated deterioration leading to higher future maintenance costs,
and/or repair. A recommended maintenance program is outlined in Appendix C.
Excavation of completed pavement for utility construction or repair can
destroy the integrity of the pavement and result in a severe decrease in
serviceability. To restore the pavement top original serviceability, careful backfill
compaction before repaving is necessary.
WATER-SOLUBLE SULFATES
Concrete that comes into contact with soils can be subject to sulfate attack.
We measured water-soluble sulfate concentrations in two samples from this site.
Concentrations were below measurable limits. Sulfate concentrations less than
0.1 percent indicate Class 0 exposure to sulfate attack for concrete that comes into
contact with the subsoils, according to the American Concrete Institute (ACI). For
this level of sulfate concentration, ACI indicates there are no special requirements
for sulfate resistance.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
13
Superficial damage may occur to the exposed surfaces of highly permeable
concrete, even though sulfate levels are relatively low. To control this risk and to
resist freeze-thaw deterioration, the water-to-cementitious materials ratio should
not exceed 0.50 for concrete in contact with soils that are likely to stay moist due
to surface drainage or high water tables. Concrete should have a total air content
of 6 percent ± 1.5 percent. We advocate all foundation walls and grade beams in
contact with the soil (including the inside and outside faces of garage and crawl
space grade beams) be damp-proofed.
SURFACE DRAINAGE
Performance of foundations, flatwork and pavements are influenced by
changes in subgrade moisture conditions. Carefully planned and maintained
surface grading can reduce the risk of wetting of the foundation soils and pavement
subgrade. We recommend a minimum slope of 5 percent in the first ten feet
outside foundations in landscaped areas. Backfill around foundations should be
moisture treated and compacted as described in Fill Placement. Roof drains
should be directed away from buildings. Downspout extensions and splash blocks
should be provided at discharge points, or roof drains should be connected to solid
pipe discharge systems. We do not recommend directing roof drains under
buildings.
CONSTRUCTION OBSERVATIONS
We recommend that CTL | Thompson, Inc. provide construction observation
services to allow us the opportunity to verify whether soil conditions are consistent
with those found during this investigation. Other observations are recommended
to review general conformance with design plans. If others perform these
observations, they must accept responsibility to judge whether the
recommendations in this report remain appropriate.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
14
GEOTECHNICAL RISK
The concept of risk is an important aspect with any geotechnical evaluation
primarily because the methods used to develop geotechnical recommendations do
not comprise an exact science. We never have complete knowledge of subsurface
conditions. Our analysis must be tempered with engineering judgment and
experience. Therefore, the recommendations presented in any geotechnical
evaluation should not be considered risk-free. Our recommendations represent our
judgment of those measures that are necessary to increase the chances that the
structures will perform satisfactorily. It is critical that all recommendations in this
report are followed during construction. Owners must assume responsibility for
maintaining the structures and use appropriate practices regarding drainage and
landscaping. Improvements performed by owners after construction, such as
construction of additions, retaining walls, landscaping and exterior flatwork, should
be completed in accordance with recommendations in this report.
LIMITATIONS
This report has been prepared for the exclusive use of the City of Fort
Collins for the purpose of providing geotechnical design and construction criteria
for the proposed project. The information, conclusions, and recommendations
presented herein are based upon consideration of many factors including, but not
limited to, the type of construction proposed, the geologic setting, and the
subsurface conditions encountered. The conclusions and recommendations
contained in the report are not valid for use by others. Standards of practice evolve
in the area of geotechnical engineering. The recommendations provided are
appropriate for about three years. If the proposed construction is not constructed
within about three years, we should be contacted to determine if we should update
this report.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
15
Two borings were drilled during this investigation to obtain a reasonably
accurate picture of the subsurface conditions. Variations in the subsurface
conditions not indicated by our borings are possible. A representative of our firm
should observe foundation excavations to confirm the exposed materials are as
anticipated from our borings.
We believe this investigation was conducted with that level of skill and care
ordinarily used by geotechnical engineers practicing under similar conditions. No
warranty, express or implied, is made.
If we can be of further service in discussing the contents of this report or in
the analysis of the influence of subsurface conditions on design of the structures,
please call.
CTLTHOMPSON, INC.
Spencer Schram, PE
Project Engineer
TH-1
TH-2
TH-3
DRAKE RD.
NANCY
GRAY AVE.
MILES
HOUSE AVE.
TIMBERLINE RD.
SITE
LEGEND:
INDICATES APPROXIMATE
LOCATION OF EXPLORATORY
BORING
TH-1
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL I T PROJECT NO. FC09343-125
FIGURE 1
Locations of
Exploratory
Borings
VICINITY MAP
(FORT COLLINS, COLORADO)
NOT TO SCALE
100' 200'
APPROXIMATE
SCALE: 1" = 200'
0'
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
35
40
15/12
30/12
41/12
WC=12.9
DD=112
SW=2.2
SS=<0.01
WC=5.0
-200=3
WC=12.9
DD=112
SW=2.2
SS=<0.01
WC=5.0
-200=3
TH-1
12/12
10/12
30/12
50/2
50/1
WC=17.2
DD=112
SW=1.3
WC=13.3
-200=49
WC=17.2
DD=112
SW=1.3
WC=13.3
-200=49
TH-2
23/12
19/12
28/12
WC=9.8
DD=113
SW=1.6
SS=<0.01
WC=4.9
-200=4
WC=9.8
Sample of FILL, CLAY, SANDY (CL) DRY UNIT WEIGHT= 112 PCF
From TH - 1 AT 2 FEET MOISTURE CONTENT= 12.9 %
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT= 112 PCF
From TH - 2 AT 4 FEET MOISTURE CONTENT= 17.2 %
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL | T PROJECT NO. FC09343-125
APPLIED PRESSURE - KSF
APPLIED PRESSURE - KSF
COMPRESSION % EXPANSION
Swell Consolidation
FIGURE 3
COMPRESSION % EXPANSION
-4
-3
-2
-1
0
1
2
3
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
-4
-3
-2
-1
0
1
2
3
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
0.1 1.0 10 100
0.1 1.0
10 100
Sample of FILL, CLAY, SANDY (CL) DRY UNIT WEIGHT= 113 PCF
From TH - 3 AT 2 FEET MOISTURE CONTENT= 9.8 %
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL | T PROJECT NO. FC09343-125
APPLIED PRESSURE - KSF
COMPRESSION % EXPANSION
Swell Consolidation
Test Results
FIGURE 4
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
0.1 1.0 10 100
Sample of SAND, GRAVELLY (SP) GRAVEL 39 % SAND 58
%
From TH - 1 AT 9 FEET SILT & CLAY 3 % LIQUID LIMIT %
PLASTICITY INDEX %
Sample of SAND, CLAYEY (SC) GRAVEL 8 % SAND 43
%
From TH - 2 AT 9 FEET SILT & CLAY 49 % LIQUID LIMIT %
PLASTICITY INDEX %
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL | T PROJECT NO. FC09343-125
FIGURE 5
Gradation
Test Results
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
Sample of GRAVEL, SANDY (GP) GRAVEL 52 % SAND 44
%
From TH - 3 AT 14 FEET SILT & CLAY 4 % LIQUID LIMIT %
PLASTICITY INDEX %
Sample of GRAVEL % SAND %
From SILT & CLAY % LIQUID LIMIT %
PLASTICITY INDEX %
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL | T PROJECT NO. FC09343-125
FIGURE 6
Gradation
Test Results
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
PASSING WATER-
MOISTURE DRY APPLIED SWELL NO. 200 SOLUBLE
DEPTH CONTENT DENSITY SWELL* PRESSURE PRESSURE SIEVE SULFATES
BORING (FEET) (%) (PCF) (%) (PSF) (PSF) (%) (%) DESCRIPTION
TH-1 2 12.9 112 2.2 500 <0.01 FILL, CLAY, SANDY (CL)
TH-1 9 5.0 3 SAND, GRAVELLY (SP)
TH-2 4 17.2 112 1.3 500 2,700 CLAY, SANDY (CL)
TH-2 9 13.3 49 SAND, CLAYEY (SC)
TH-3 2 9.8 113 1.6 500 2,400 <0.01 FILL, CLAY, SANDY (CL)
TH-3 14 4.9 4 GRAVEL, SANDY (GP)
SWELL TEST RESULTS*
TABLE I
SUMMARY OF LABORATORY TESTING
Page 1 of 1
* NEGATIVE VALUE INDICATES COMPRESSION.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL|T PROJECT NO. FC09343-125
APPENDIX A
SAMPLE SITE GRADING SPECIFICATIONS
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
A-1
SAMPLE SITE GRADING SPECIFICATIONS
1. DESCRIPTION
This item shall consist of the excavation, transportation, placement and
compaction of materials from locations indicated on the plans, or staked by the
Engineer, as necessary to achieve building site elevations.
2. GENERAL
The Geotechnical Engineer shall be the Owner's representative. The
Geotechnical Engineer shall approve fill materials, method of placement, moisture
contents and percent compaction, and shall give written approval of the completed
fill.
3. CLEARING JOB SITE
The Contractor shall remove all trees, brush and rubbish before excavation or fill
placement is begun. The Contractor shall dispose of the cleared material to
provide the Owner with a clean, neat appearing job site. Cleared material shall not
be placed in areas to receive fill or where the material will support structures of any
kind.
4. SCARIFYING AREA TO BE FILLED
All topsoil and vegetable matter shall be removed from the ground surface upon
which fill is to be placed. The surface shall then be plowed or scarified to a depth
of 8 inches until the surface is free from ruts, hummocks or other uneven features,
which would prevent uniform compaction by the equipment to be used.
5. COMPACTING AREA TO BE FILLED
After the foundation for the fill has been cleared and scarified, it shall be disked or
bladed until it is free from large clods, brought to the proper moisture content and
compacted to not less than 95 percent of maximum dry density as determined in
accordance with ASTM D 698 or AASHTO T 99.
6. FILL MATERIALS
On-site materials classifying as CL, SC, SM, SW, SP, GP, GC and GM are
acceptable. Fill soils shall be free from organic matter, debris, or other deleterious
substances, and shall not contain rocks or lumps having a diameter greater than
three (3) inches. Fill materials shall be obtained from the existing fill and other
approved sources.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
A-2
7. MOISTURE CONTENT
Fill materials shall be moisture treated. Clay soils placed below the building
envelope should be moisture-treated to between optimum and 3 percent above
optimum moisture content as determined from Standard Proctor compaction tests.
Clay soil placed exterior to the building should be moisture treated between
optimum and 3 percent above optimum moisture content. Sand soils can be
moistened to within 2 percent of optimum moisture content. Sufficient laboratory
compaction tests shall be performed to determine the optimum moisture content
for the various soils encountered in borrow areas.
The Contractor may be required to add moisture to the excavation materials in the
borrow area if, in the opinion of the Geotechnical Engineer, it is not possible to
obtain uniform moisture content by adding water on the fill surface. The Contractor
may be required to rake or disk the fill soils to provide uniform moisture content
through the soils.
The application of water to embankment materials shall be made with any type of
watering equipment approved by the Geotechnical Engineer, which will give the
desired results. Water jets from the spreader shall not be directed at the
embankment with such force that fill materials are washed out.
Should too much water be added to any part of the fill, such that the material is too
wet to permit the desired compaction from being obtained, rolling and all work on
that section of the fill shall be delayed until the material has been allowed to dry to
the required moisture content. The Contractor will be permitted to rework wet
material in an approved manner to hasten its drying.
8. COMPACTION OF FILL AREAS
Selected fill material shall be placed and mixed in evenly spread layers. After each
fill layer has been placed, it shall be uniformly compacted to not less than the
specified percentage of maximum dry density. Fill materials shall be placed such
that the thickness of loose material does not exceed 8 inches and the compacted
lift thickness does not exceed 6 inches. Fill placed under foundations, exterior
flatwork and pavements should be compacted to a minimum of 95 percent of
maximum standard Proctor dry density (ASTM D698).
Compaction, as specified above, shall be obtained by the use of sheepsfoot rollers,
multiple-wheel pneumatic-tired rollers, or other equipment approved by the
Engineer. Compaction shall be accomplished while the fill material is at the
specified moisture content. Compaction of each layer shall be continuous over the
entire area. Compaction equipment shall make sufficient trips to insure that the
required dry density is obtained.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
A-3
9. COMPACTION OF SLOPES
Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable
equipment. Compaction operations shall be continued until slopes are stable, but
not too dense for planting, and there is no appreciable amount of loose soil on the
slopes. Compaction of slopes may be done progressively in increments of three
to five feet (3' to 5') in height or after the fill is brought to its total height. Permanent
fill slopes shall not exceed 3:1 (horizontal to vertical).
10. DENSITY TESTS
Field density tests shall be made by the Geotechnical Engineer at locations and
depths of his choosing. Where sheepsfoot rollers are used, the soil may be
disturbed to a depth of several inches. Density tests shall be taken in compacted
material below the disturbed surface. When density tests indicate that the dry
density or moisture content of any layer of fill or portion thereof is below that
required, the particular layer or portion shall be reworked until the required dry
density or moisture content has been achieved.
11. SEASONAL LIMITS
No fill material shall be placed, spread or rolled while it is frozen, thawing, or during
unfavorable weather conditions. When work is interrupted by heavy precipitation,
fill operations shall not be resumed until the Geotechnical Engineer indicates that
the moisture content and dry density of previously placed materials are as
specified.
12. NOTICE REGARDING START OF GRADING
The contractor shall submit notification to the Geotechnical Engineer and Owner
advising them of the start of grading operations at least three (3) days in advance
of the starting date. Notification shall also be submitted at least 3 days in advance
of any resumption dates when grading operations have been stopped for any
reason other than adverse weather conditions.
13. REPORTING OF FIELD DENSITY TESTS
Density tests performed by the Geotechnical Engineer, as specified under "Density
Tests" above, shall be submitted progressively to the Owner. Dry density, moisture
content and percent compaction shall be reported for each test taken.
APPENDIX B
PAVEMENT CONSTRUCTION RECOMMENDATIONS
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
B-1
SUBGRADE PREPARATION
Moisture Treated Subgrade (MTS)
1. The subgrade should be stripped of organic matter, scarified,
moisture treated and compacted to the specifications stated below in
Item 2. The compacted subgrade should extend at least 3 feet
beyond the edge of the pavement where no edge support, such as
curb and gutter, are to be constructed.
2. Sandy and gravelly soils (A-1-a, A-1-b, A-3, A-2-4, A-2-5, A-2-6, A-
2-7) should be moisture conditioned near optimum moisture content
and compacted to at least 95 percent of standard Proctor maximum
dry density (ASTM D 698, AASHTO T 99). Clayey soils (A-6, A-7-5,
A-7-6) should be moisture conditioned between optimum and 3
percent above optimum moisture content and compacted to at least
95 percent of standard Proctor maximum dry density (ASTM D 698,
AASHTO T 99).
3. Utility trenches and all subsequently placed fill should be properly
compacted and tested prior to paving. As a minimum, fill should be
compacted to 95 percent of standard Proctor maximum dry density.
4. Final grading of the subgrade should be carefully controlled so the
design cross-slope is maintained and low spots in the subgrade that
could trap water are eliminated.
5. Once final subgrade elevation has been compacted and tested to
compliance and shaped to the required cross-section, the area
should be proof-rolled using a minimum axle load of 18 kips per axle.
The proof-roll should be performed while moisture contents of the
subgrade are still within the recommended limits. Drying of the
subgrade prior to proof-roll or paving should be avoided.
6. Areas that are observed by the Engineer that have soft spots in the
subgrade, or where deflection is not uniform of soft or wet subgrade
shall be ripped, scarified, dried or wetted as necessary and
recompacted to the requirements for the density and moisture. As
an alternative, those areas may be sub-excavated and replaced with
properly compacted structural backfill. Where extensively soft,
yielding subgrade is encountered; we recommend a representative
of our office observe the excavation.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
B-2
PAVEMENT MATERIALS AND CONSTRUCTION
Aggregate Base Course (ABC)
1. A Class 5 or 6 Colorado Department of Transportation (CDOT)
specified ABC should be used. A reclaimed concrete pavement
(RCP) alternative which meets the Class 5 or 6 designation and
design R-value/strength coefficient is also acceptable. Blending of
recycled products with ABC may be considered.
2. Bases should have a minimum Hveem stabilometer value of 72, or
greater. ABC, RAP, RCP, or blended materials must be moisture
stable. The change in R-value from 300-psi to 100-psi exudation
pressure should be 12 points or less.
3. ABC or RCP bases should be placed in thin lifts not to exceed 6
inches and moisture treated to near optimum moisture content.
Bases should be moisture treated to near optimum moisture content,
and compacted to at least 95 percent of standard Proctor maximum
dry density (ASTM D 698, AASHTO T 99).
4. Placement and compaction of ABC or RCP should be observed and
tested by a representative of our firm. Placement should not
commence until the underlying subgrade is properly prepared and
tested.
Hot Mix Asphalt (HMA)
1. HMA should be composed of a mixture of aggregate, filler, hydrated
lime, and asphalt cement. Some mixes may require polymer
modified asphalt cement, or make use of up to 20 percent reclaimed
asphalt pavement (RAP). A job mix design is recommended and
periodic checks on the job site should be made to verify compliance
with specifications.
2. HMA should be relatively impermeable to moisture and should be
designed with crushed aggregates that have a minimum of 80
percent of the aggregate retained on the No. 4 sieve with two
mechanically fractured faces.
3. Gradations that approach the maximum density line (within 5 percent
between the No. 4 and 50 sieves) should be avoided. A gradation
with a nominal maximum size of 1 or 2 inches developed on the fine
side of the maximum density line should be used.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
B-3
4. Total void content, voids in the mineral aggregate (VMA) and voids
filled should be considered in the selection of the optimum asphalt
cement content. The optimum asphalt content should be selected at
a total air void content of approximately 4 percent. The mixture
should have a minimum VMA of 14 percent and between 65 percent
and 80 percent of voids filled.
5. Asphalt cement should meet the requirements of the Superpave
Performance Graded (PG) Binders. The minimum performing
asphalt cement should conform to the requirements of the governing
agency.
6. Hydrated lime should be added at the rate of 1 percent by dry weight
of the aggregate and should be included in the amount passing the
No. 200 sieve. Hydrated lime for aggregate pretreatment should
conform to the requirements of ASTM C 207, Type N.
7. Paving should be performed on properly prepared, unfrozen
surfaces that are free of water, snow and ice. Paving should only be
performed when both air and surface temperatures equal, or exceed,
the temperatures specified in Table 401-3 of the 2006 Colorado
Department of Transportation Standard Specifications for Road and
Bridge Construction.
8. HMA should not be placed at a temperature lower than 245o
F for
mixes containing PG 64-22 asphalt, and 290o
F for mixes containing
polymer-modified asphalt. The breakdown compaction should be
completed before the HMA temperature drops 20o
F.
9. Wearing surface course shall be Grading S or SX for residential
roadway classifications and Grading S for collector, arterial,
industrial, and commercial roadway classifications.
10. The minimum/maximum lift thicknesses for Grade SX shall be 1½
inches/2½ inches. The minimum/maximum lift thicknesses for Grade
S shall be 2 inches/3½ inches. The minimum/maximum lift
thicknesses for Grade SG shall be 3 inches/5 inches.
11. Joints should be staggered. No joints should be placed within wheel
paths.
12. HMA should be compacted to between 92 and 96 percent of
Maximum Theoretical Density. The surface shall be sealed with a
finish roller prior to the mix cooling to 185o
F.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
B-4
13. Placement and compaction of HMA should be observed and tested
by a representative of our firm. Placement should not commence
until approval of the proof rolling as discussed in the Subgrade
Preparation section of this report. Subbase, base course or initial
pavement course shall be placed within 48 hours of approval of the
proof rolling. If the Contractor fails to place the subbase, base course
or initial pavement course within 48 hours or the condition of the
subgrade changes due to weather or other conditions, proof rolling
and correction shall be performed again.
Portland Cement Concrete (PCC)
1. Portland cement concrete should consist of Class P of the 2011
CDOT - Standard Specifications for Road and Bridge Construction
specifications for normal placement or Class E for fast-track projects.
PCC should have a minimum compressive strength of 4,200 psi at
28 days and a minimum modulus of rupture (flexural strength) of 650
psi. Job mix designs are recommended and periodic checks on the
job site should be made to verify compliance with specifications.
2. Portland cement should be Type II “low alkali” and should conform
to ASTM C 150.
3. Portland cement concrete should not be placed when the subgrade
or air temperature is below 40°F.
4. Concrete should not be placed during warm weather if the mixed
concrete has a temperature of 90°F, or higher.
5. Mixed concrete temperature placed during cold weather should have
a temperature between 50°F and 90°F.
6. Free water should not be finished into the concrete surface.
Atomizing nozzle pressure sprayers for applying finishing
compounds are recommended whenever the concrete surface
becomes difficult to finish.
7. Curing of the Portland cement concrete should be accomplished by
the use of a curing compound. The curing compound should be
applied in accordance with manufacturer recommendations.
8. Curing procedures should be implemented, as necessary, to protect
the pavement against moisture loss, rapid temperature change,
freezing, and mechanical injury.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
B-5
9. Construction joints, including longitudinal joints and transverse joints,
should be formed during construction or sawed after the concrete
has begun to set, but prior to uncontrolled cracking.
10. All joints should be properly sealed using a rod back-up and
approved epoxy sealant.
11. Traffic should not be allowed on the pavement until it has properly
cured and achieved at least 80 percent of the design strength, with
saw joints already cut.
12. Placement of Portland cement concrete should be observed and
tested by a representative of our firm. Placement should not
commence until the subgrade is properly prepared and tested.
APPENDIX C
PAVEMENT MAINTENANCE PROGRAM
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
C-1
MAINTENANCE RECOMMENDATIONS FOR FLEXIBLE PAVEMENTS
A primary cause for deterioration of pavements is oxidative aging resulting
in brittle pavements. Tire loads from traffic are necessary to "work" or knead the
asphalt concrete to keep it flexible and rejuvenated. Preventive maintenance
treatments will typically preserve the original or existing pavement by providing a
protective seal or rejuvenating the asphalt binder to extend pavement life.
1. Annual Preventive Maintenance
a. Visual pavement evaluations should be performed each spring or
fall.
b. Reports documenting the progress of distress should be kept
current to provide information on effective times to apply
preventive maintenance treatments.
c. Crack sealing should be performed annually as new cracks
appear.
2. 3 to 5 Year Preventive Maintenance
a. The owner should budget for a preventive treatment at
approximate intervals of 3 to 5 years to reduce oxidative
embrittlement problems.
b. Typical preventive maintenance treatments include chip seals,
fog seals, slurry seals and crack sealing.
3. 5 to 10 Year Corrective Maintenance
a. Corrective maintenance may be necessary, as dictated by the
pavement condition, to correct rutting, cracking and structurally
failed areas.
b. Corrective maintenance may include full depth patching, milling
and overlays.
c. In order for the pavement to provide a 20-year service life, at least
one major corrective overlay should be expected.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTLT PROJECT NO. FC09343-125
C-2
MAINTENANCE RECOMMENDATIONS FOR RIGID PAVEMENTS
High traffic volumes create pavement rutting and smooth polished surfaces.
Preventive maintenance treatments will typically preserve the original or existing
pavement by providing a protective seal and improving skid resistance through a
new wearing course.
1. Annual Preventive Maintenance
a. Visual pavement evaluations should be performed each spring or
fall.
b. Reports documenting the progress of distress should be kept
current to provide information of effective times to apply
preventive maintenance.
c. Crack sealing should be performed annually as new cracks
appear.
2. 4 to 8 Year Preventive Maintenance
a. The owner should budget for a preventive treatment at
approximate intervals of 4 to 8 years to reduce joint deterioration.
b. Typical preventive maintenance for rigid pavements includes
patching, crack sealing and joint cleaning and sealing.
c. Where joint sealants are missing or distressed, resealing is
mandatory.
3. 15 to 20 Year Corrective Maintenance
a. Corrective maintenance for rigid pavements includes patching
and slab replacement to correct subgrade failures, edge damage,
and material failure.
b. Asphalt concrete overlays may be required at 15 to 20 year
intervals to improve the structural capacity of the pavement.
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
0
10
20
30
50
60
70
80
90
100
PERCENT RETAINED
40
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
PERCENT RETAINED
0
10
20
30
40
50
60
70
80
90
100
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
0
10
20
30
50
60
70
80
90
100
PERCENT RETAINED
40
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
PERCENT RETAINED
0
10
20
30
40
50
60
70
80
90
100
DD=113
SW=1.6
SS=<0.01
WC=4.9
-200=4
TH-3
DEPTH - FEET
DRIVE SAMPLE. THE SYMBOL 15/12 INDICATES 15 BLOWS OF A 140-POUND HAMMER
FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES.
FILL, CLAY, SANDY WITH OCCASSIONAL GRAVEL, MOIST, VERY STIFF, DARK BROWN
1.
NOTES:
THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN
THIS REPORT.
WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING.
CLAY, SANDY WITH OCCASIONAL GRAVEL, MOIST, STIFF, BROWN, DARK BROWN (CL)
3.
LEGEND:
SAND AND GRAVEL, VERY MOIST TO WET, LOOSE TO DENSE, BROWN (SP, GP)
SANDSTONE, SILTY, MOIST TO WET, VERY HARD, DARK GRAY
DEPTH - FEET
WATER LEVEL MEASURED AT TIME OF DRILLING.
Summary Logs of
Exploratory Borings
THE BORINGS WERE DRILLED ON APRIL 23, 2020 USING 4-INCH DIAMETER
CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG.
FIGURE 2
WC
DD
SW
-200
LL
PI
UC
SS
-
-
-
-
-
-
-
-
INDICATES MOISTURE CONTENT (%).
INDICATES DRY DENSITY (PCF).
INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%).
INDICATES PASSING NO. 200 SIEVE (%).
INDICATES LIQUID LIMIT.
INDICATES PLASTICITY INDEX.
INDICATES UNCONFINED COMPRESSIVE STRENGTH (PSF).
INDICATES SOLUBLE SULFATE CONTENT (%).
2.
CITY OF FORT COLLINS
BUCKING HORSE PARK
CTL | T PROJECT NO. FC09343-125