HomeMy WebLinkAboutJFK OFFICE PUD - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -REPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
MARRIOTT AT FORT COLLINS
FORT COLLINS, COLORADO
BY
EMPIRE LABORATORIES, INC,
214 NORTH HOWES STREET
FORT COLLINS, COLORADO $0521
TABLE OF CONTENTS
Table of Contents .............................................. i
Letter of Transmittal .......................................... i
Report ................................... 0 ..................... 1
Appendix A •........................................ 0 ......... • A -1
Test Boring Location Plan .................................... A-2
Key to Borings ............................................... A-3
Log of Borings ............................................... A-4
Appendix B.................................................... B-1
Consolidation Test Data ...................................... B-2
Direct Shear Test Results ................................... B -6
Hveem Stabliometer Test Results ............................. B-8
Summary of Test Results ..................................... B -10
Appendix. C.................................................... C-1
i
Empire ® Laboratories, Inc.
MATERIALS AND FOUNDATION ENGINEERS
214 No. Howes Fort Collins, Colorado 80522
P.O. Box 429 (303) 484-0359
December 23, 1982
Simons, Li and Associates, Inc.
P. O. Box 1816
Fort Collins, Colorado 9CS22
Attention: Mr. Robert A. Mussetter
Gentlemen
Branch Offices
1242 Bramw000 Place
Longmont, Colorado 80501
P.O. Box 1135
303) 776-3921
3151 Nation Way
Cheyenne, Wyoming 82001
P.O. Box 10076
307) 632.9224
We are pleased to submit our Report of a Geotechnicai Investigation
prepared for the proposed Marriott at Fort Collins to be constructed in
Fort Collins, Colorado.
Based upon our findings in the subsurface, we feel that the site is
suitable for the proposed construction, providing the design criteria
and recommendations set forth In this report are met. The accompanying
report presents our findings in the subsurface and our recommendations
based upon these findings.""-_
Very truly yours,
EMPIRE LAB RA RIE r' A
John W. Hollings#rtK, Jr., P E.
Geotechnical Eng eer
Reviewed by:
C%
Chester C. Smith, P.E.
President
cic
cc: SLP, A Professional Corporation - Larry Stevens
MEMBER OF CONSULTING ENGINEERS COUNCIL 11
REPORT
OF A
GEOTECNNICAL INVESTIGATION
SCOPE
This report presents the results of a geotechnical evaluation
prepared for the proposed Marriott at Fort Collins to be constructed in
south Fort Collins, Colorado. The scope of the project Included test
borings and laboratory testing of samples obtained from these borings.
The objectives of this study were to (1) evaluate the subsurface
conditions at the site relative to the proposed construction, (2) make
recommendations regarding the design of the substructure, and (3)
recommend certain precautions which should be taken because of adverse
soil and/or groundwater conditions.
SITE EXPLORATION
The field exploration, carried out on December 8 and 9, 1982,
consisted of drilling, fogging, and sampling fourteen (14) test borings.
Elevations of the test borings were provided by Simons, LI and
Associates, Inc. In addition, Simons, Li and Associates, Inc. also
provided the property pins, and Empire Laboratories, Inc. located the
borings from these property pins. The locations of the test borings are
shown on the Test Boring Location Plan Included in Appendix A of this
report. Boring logs prepared from the field logs are shown In Appendix
A. These logs show soils encountered, location of sampling, and
groundwater at the time of the exploration. The location and boring log
of a test boring drilled during a previous Investigation at the site is also
Included.
The borings were advanced with a four -inch diameter, continuous -
type, power -flight auger drill. During the drilling operations,
engineering geologist from Empire Laboratories, Inc. was present and
made continuous observations of the soils encountered. Field resistivity
tests were performed in selected areas at the site.
1-
SITE LOCATION AND DESCRIPTION
The site of the proposed Marriott at Fort Collins is north of East
Horsetooth Road and south of east Monroe Drive between Stanford Road
and JFK Parkway In south Fort Collins, Colorado. More particularly,
the site may be described as a tract of land situate in the southwest 1 /4
of Section 25, Township 7 North, Range 69 West of the Sixth P.M.,
Larimer County, Colorado.
At the time of the investigation the site was a large vacant lot
sparsely vegetated with grasses and weeds. The area has been graded
and cut to the north and filled to the southwest and southeast. To the
south, long east -west pits have been dug for excavation of borrow
material. At the north -central portion of the site, a small abandoned
Irrigation lateral runs east -west just north of the proposed building. A
large pile of earth fill exists along the east side of the site. A small
modular bank lies northwest of the property. The entire site slopes
gradually to the southeast providing good positive drainage in this
direction. -
LABORATORY TESTS AND EVALUATION
Samples obtained from the test borings were subjected to testing In
the laboratory to provide a sound basis for evaluating the physical
properties of the soils encountered. Moisture contents, dry unit weights,
unconfined compressive strengths, water soluble sulfates, pH, swelling
potentials, and the Atterberg limits were determined. A summary of the
test results Is included in Appendix B. Consolidation,
swell -consolidation, direct shear, anti- Hveem stabilometer characteristics
were also determined, and curves showing this data are included in
Appendix. B. --
2-
SOIL AND GROUNDWATER CONDITIONS
The soil profile at the site consists of strata of materials arranged
In different combinations. In order of Increasing depths, they are as
follows:
1) Earth Fill: Overlying the site In the area of Borings 1, 2, 8,
and 11 through 14 is a one (1) to six (6) foot stratum of earth
fill. This material consists of a brown silty clay and/or red
sandy silty clay and was previously placed under controlled
conditions of moisture and compaction. This fill has been in
place for some time now, and prior to placement of any
footings, slabs, etc., preparation of the surface of this fill
should be accomplished. (See "Site Grading and Utilities"
section of this report.)
2) Silty Topsoil: Overlying the site in the area of Borings 7 and
10 is approximately one-half (112) to one (1) foot of a brown
silty topsoil. This material has been penetrated by root
growth and organic matter and should not be used as a
foundation soil or as a backfiil material. It should be noted
that several areas of topsoil were observed in the area of the
site and It appears that stripping of this material had not been
done during previous the site grading operations.
3) Silty Clay: The brown silty clay was encountered in Borings
3, S, 6, and 9 at the surface, below the earth fill In Borings
1, 2, 8, and 12 through 1-4 and beneath the topsoil In Borings
7 and 10. This material was not encountered in Borings a or
11. This clay is plastic depending upon the varying amounts
of slit and fine sand present and exhibits moderate bearing
characteristics in its dry to moist natural state. When wetted,
the clayier portions of this material exhibit low to moderate
swelling potential; and upon additional. loading, consolidation
occurs.
3-
4) Sandy Silty Clay: The red sandy silty clay was encountered
at the surface in Boring a and at depths one-half (1 /2) to
seven (7) feet in the remaining borings. This clay Is slightly
plastic depending upon the varying amounts of slit and sand
present and exhibits moderate bearing characteristics in Its
damp to moist natural state. This sandy silty clay exhibits
low to moderate swelling potential and consolidates readily
under load.
5) Sands tone -Clay stone-Shtstone Bedrock: The bedrock was
encountered in the test borings except Boring 3 at depths two
and one-half (2-1/2) to eighteen (18) feet below the surface
and extends to the depths beyond those explored. The upper
one (1) to four and one-half (4-1 /2) feet of the bedrock is
highly weathered; however, the underlying sandstone or
claystone-siitstone is firm, dense, and exhibits high bearing
characteristics. When wetted, the clay stone-sl Itstone exhibits
low to moderate swelling potentials.
6) Groundwater: At the time of the Investigation, free
groundwater was encountered in Borings 1 through 9, and 13
at depths six and one-half (6-1 /2) to twenty-one (21) feet
below the surface. Due to the proximity of the bedrock to the
surface, the formation of a perched water table is probable.
It should also be noted that groundwater levels in this area
will vary depending upon seasonal variations and flow in the
Irrigation ditches adjacent to the property.
RECOMMENDATIONS AND DISCUSSION
It Is our understanding that the proposed Marriott at Fort Collins is
to include a six -story tower structure to be used as a hotel and an
adjacent two-story commercial structure with a partial full -depth
basement. Approximate column and wall loads for the tower structure
are three hundred fifty (350) kips and twenty-three (23) kips per foot,
4-
respectively, while the loading for the two-story commercial portion is
estimated to be one hundred fifty (150) kip column loads with ten (10)
to fifteen (15) kip per foot wall toads. A swimming pool Is planned
between the commercial and tower structures. it is our understanding
that the hydraulic elevator is planned for the two-story structure, while
a conventional cable elevator with a pit is planned for the tower
structure. Retaining walls around the exterior of the structure are
planned.
The following are our recommendations for design of the
substructures as influenced by the subsurface conditions encountered in
the test borings.
Site Grading and Utilities
It Is our understanding that a majority of the preliminary site
grading has been accomplished and that stripping, fill placement, etc.,
has been observed by the geotechnical engineer. Additional site grading
should be done in accordance with the following recommendations.
The upper six (6) inches of the existing topsoil should be removed
from within the proposed building and paved areas. This topsoil may be
stockpiled on -site and used for final grading outside building and
pavement areas. Following stripping of the topsoil, the upper six (6)
Inches of the subgrade below filled areas and the subgrade in cut areas
should be scarified and recompacted two percent (2%) wet of optimum
moisture content to at least ninety percent (90%) of Standard Proctor
Density ASTM D 698-78. (See Appendix C.) All fill should consist of
the on -site silty clay and/or the sandy silty clay soils or an Imported
material approved by the geotechnleal engineer. Fill should be placed
two percent (2%) wet of optimum moisture in uniform six (6) to eight (8)
Inch lifts and compacted to at least ninety-five percent (95%) of Standard
Proctor Density ASTM D 698-78. For stability, all cut and fill slopes
should be designed on grades no steeper than 2:1. Flatter slopes are
suggested for ease of maintenance.
Qualified geotechnical personnel should be present to observe ail
stripping, preparation of the subgrade, and placement and compaction of
5-
fill. Field density tests should be taken at regular intervals to insure
that proper compaction of the subgrade and embankment has been
achieved.
Utility trenches dug four (4) or more feet into the upper clay soils
should be excavated on slopes no steeper than 1:1. The bedrock may
be excavated on near -vertical slopes. Excavation of the bedrock may,
however, require the use of heavy-duty construction equipment
especially where dense sandstone is encountered. Where utilities are
excavated below groundwater, dewatering may be needed during
placement of the pipe and backfilling for proper construction. To
minimize breakage during the backfilling operations, piping should be
adequately bedded for proper load distribution.
Backfill placed in utility trenches in open and planted areas should
be placed at optimum moisture in uniform lifts compacted to at least
ninety percent (90%) of Standard Proctor Density ASTM D 698-78, the
full depth of the trench. The upper four (4) feet of backfill placed in
utility trenches under roadways and paved areas should be placed in
uniform lifts at or near optimum moisture compacted to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78,
and the lower portion of these trenches should be compacted to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
The addition of moisture to and/or the drying of the subsoils may be
needed for proper compaction. Proper placement of the bedrock as
backfill may be difficult, and the ciaystone-siltstone should not be used
as a backfill material. It Is recommended that all compaction
requirements for utility trenches be verified in the field by density tests
performed under the direction of the geotechnical engineer.
Resistivity tests performed In -the field and pH and water soluble
sulfate tests performed in the laboratory indicate that the subsoils at the
site are noncorrosive to gray or Iron ductile pipe and protection of this
pipe will not be required.
Foundations
In view of the loads transmitted by the proposed construction and
the soil conditions encountered in the test borings, it is recommended
that the structures (both the tower structure and the two-story
commercial structure) be supported by a drilled pier and grade beam
type foundation system. Using this type of foundation system, the loads
from the structure are transmitted to the bedrock stratum, partially
through end bearing and partially through skin friction. Straight -shaft
piers drilled a minimum of three (3) feet into the firm bedrock stratum
may be designed for a maximum end bearing pressure of twenty-five
thousand (25,000) pounds per square foot. An estimated skin friction of
two thousand five hundred (2500) pounds per square foot will develop in
that portion of the pier that is embedded a minimum of three (3) feet
Into the firm bedrock stratum. To counteract swelling pressures which
will develop when the subsoils become wetted, all piers should be
designed for a minimum dead load pressure of seven thousand five
hundred (7500) pounds per square foot based upon pier end area.
Where this minimum dead load requirement cannot be satisfied, it is
recommended that a skin friction from additional embedment into the firm
bedrock be used to resist uplift. Straight -shaft piers drilled a minimum
of ten (10) feet Into the firm bedrock stratum may be designed for a
maximum end bearing pressure of forty thousand (40,000) pounds per
square foot. An estimated skin friction of four thousand (4000) pounds
per square foot will develop in that portion of the pier embedded at least
ten (10) feet into the firm bedrock stratum. For ease of construction,
all piers should be a minimum of twenty-four (24) Inches In diameter. It
should be noted that dense to very dense sandstone may be encountered
and advancing the drill hole through this material may require
heavy-duty drilling equipment. All piers should be designed and
reinforced for the imposed loadings. To resist lateral loadings, the
ultimate passive earth pressure of -the overburden soils may be
expressed by the equation Pp = 230Z pounds per square foot, where Z is
the depth in feet below finished grade. All piers should also be
reinforced their full length to resist tensile stresses created by swelling
pressures acting on the pier. It is recommended that a minimum four
4) Inch void be provided under all grade beams to prevent swelling of
the upper soils or bedrock from exerting any pressure on these beams.
The anticipated settlement of the piers under the above maximum loading
is negligible.
1-
Since free groundwater was encountered in the test borings at the
time of the Investigation, It is felt that using of the drill holes will be '
required to prevent sloughing of the overburden and to permit
dewatering of the drill holes.
It is recommended that qualified geotechnical personnel be peasant
during the drilling operations to (1) Identify the bedrock stratum, (2) to
ensure that proper penetration into the firm bedrock is obtained, (3)
make certain that all drill holes are thoroughly cleaned and adequately
dewatered prior to concrete piacem. nt, and (4) verify that all drill holes
are constructed In accordance with the plans and specifications for the
project including placement of the concrete and reinforcement.
Lightly loaded structures constructed independent of the main
structural system may be supported by conventional continuous and/or
Isolated spread footings founded In the natural, undisturbed soil or on
the existing structural fill at the site. All exterior footings should be
placed a minimum of thirty (30) Inches below finished grade for frost
protection. The undisturbed nature of the soil and/or the compaction of
the structural fill at footing level should be verified by the geotechnical
engineer prior to placement of any foundation concrete. Footings placed
at the above -noted level may be designed for a maximum allowable
bearing capacity of two thousand (2000) pounds per square foot (dead
load plus maximum live load). To counteract swelling pressures which
will develop when the subsoils become wetted, all footings should be
designed for a minimum dead load pressure of five hundred (500) pounds
per square foot.
The predicted settlement under the above maximum loading, as
determined by laboratory consolidation tests and analyses. Is
approximately three -fourths (3/4) Inch, generally considered to be within
In an acceptable tolerance for this type of construction.
Basements and Slabs on Grade
It is our understanding that a partial full -depth basement is
planned in the northwest corner of the complex. The elevator pit should
receive the same considerations as the basement. The elevation of the
6-
finished basement floor is approximately 4998.5. in view of the soil
conditions encountered in this area, it is our opinion that the proposed
basement construction is feasible. It should be noted that depending
upon the exact location of the basement, excavation into the sandstone
bedrock may be difficult and require heavy-duty construction equipment.
It is recommended that the basement be provided with a complete
dewatering system since the potential for a perched water table exists.
This dewatering system should Include subslab drainage media and a
perimeter foundation drain. In addition, provisions should be made to
dewater the basement excavation prior to and during construction of the
basement to insure the integrity of the foundation and subsiab soils and
for each of construction.
The drainage system should be placed around the entire perimeter
of the basement and should consist of a four -inch diameter, open -jointed
or perforated plastic pipe, running the full length of the trench. The
tile should be surrounded by clean, graded gravel from three -fourths
314) Inch to the #4 sieve in accordance with ASTM C 33-78, Size No.
67. The gravel should extend from at least two (2) inches below the
bottom pipe to at least four (4) feet above the finished floor slab or a
minimum of two (2) feet above the adjacent bedrock stratum, whichever
Is greater. The trench should be a minimum of twelve (12) inches wide.
To minimize the cost of the gravel backfiil, it is suggested that the
excavation be limited to the area necessary for the drainage system
construction. We recommend that the drainage tile be placed at least
twelve (12) inches below the finished basement floor slab and have a
minimum grade of one -eighth (1 /8) Inch per foot. The top of the gravel
medium should be covered with an untreated building paper to help
minimize clogging of the medium with earth backfiil. To minimize the
potential for surface water entering the system, it Is recommended that a
clay backfiil such as the on -site silty soil be placed over the entire
system compacted at or near optimum moisture to at least ninety-five
percent (95%) of Standard Proctor Density ASTM D 698-78. (See
Appendix C. )
The drainage system should empty into a sump provided in the
basement area or be disposed of by other suitable means. The sump
should be a minimum of eighteen (18) inches in diameter and four (4)
feet deep. A minimum of one (1) foot of clean, graded gravel meeting
the above specifications should be placed adjacent to the bottom and
sides of the sump. Water from the sump should be disposed of by
suitable means well beyond the foundation of the building. In addition,
the basement floor slab should be underlain by a minimum of twelve (12)
inches of washed, graded gravel meeting the above specifications.
Laterals should also be installed to remove water collected beneath the
basement floor slab.
The basement foundation walls backfilied as recommended above
should be designed for a lateral earth loading using a hydrostatic
pressure distribution and an equivalent fluid weight of gravel backflli of
forty (40) pounds per square foot per foot of depth and an equivalent
fluid weight of the on -site clayey backfill of fifty (50) pounds per
square foot per foot of depth. To resist lateral loading, the ultimate
passive earth pressure of the backf ll material may be expressed using
the equation Pp = 230Z pounds per square foot, where Z Is the depth
below the finished grade in feet.
In view of the swelling potential of the claystone bedrock at the
proposed basement floor slab elevation, it is felt that the only positive
solution for a floor slab is a structural floor slab with a void beneath It.
However, the cost of this type of floor system would be prohibitive. It
Is our opinion that, with certain precautions and knowing that some risk
is involved, a floating floor slab is feasible. If the owner is willing to
assume the risk of future slab movement and related structural damage,
the following recommendations may reduce slab movement and its adverse
effects.::-:
It Is recommended that the basement floor slabs be placed on a
minimum of twelve (12) Inches of washed, graded gravel as described
above. It is further recommended that all slabs on grade be structurally
Independent of bearing members. To minimize and control shrinkage
cracks which will develop In slabs on grade, it is suggested that
control joints be placed every ten (10) to fifteen (15) feet and that the
total area contained within these joints be less than two hundred
twenty-five (225) square feet. We also recommend that all nonbearing
10-
partitions placed on floor slabs be provided with a slip joint (either top
or bottom) such that the pressure applied by heaving floor stabs will not
damage the structure above the partition.
It should be noted that the soils at the site are plastic and are
susceptible to additional volume changes If they dry and then become re -
wetted. Therefore, it is strongly recommended that the proposed
building excavation not be permitted to remain open for an extended
period of time to prevent drying of the foundation and/or subsiab soils
to a moisture content appreciably lower than that naturally present at
the time of the Investigation.
It should be re-emphasized that even with these precautions. the
potential for slab movement exists. Slab -on -grade construction should
be undertaken only If the owner is willing to assume the risk of potential
slab heave and possible structural damage.
The upper levei finished slab elevation is proposed at elevation
5012.5. The existing subsoils encountered at the site are adequate to
support normal slab -an -grade loads. Subgrade preparation and fill
placement should be done in accordance with the *Site Grading and
Utilities" section of this report.
All office and lightly loaded slabs on grade should be underlain by
a minimum of four (4) inches of washed, graded gravel or crushed rock
devoid of fines. All slabs on grade supporting heavy floor loads should
be underlain by at least six (6) inches of crushed gravel base course
material placed at optimum moisture and compacted to at least ninety-five
percent (95%) of Standard Proctor Density ASTM 0 598-78. This
granular layer will help to distribute floor loads and will act as a
capillary . break. . Ail slabs on grade should be designed and reinforced
for the imposed loadings. it is further recommended that all slabs on
grade be structurally Independent of bearing members. To minimize and
control shrinkage cracks which trill develop in the slabs on grade. It is
suggested that control joints be placed every ten (10) to fifteen (15)
feet and that the total area contained within these joints be less than
two hundred twenty-five (225) square feet.
11-
Swimming Pool
The exact location and the elevations of the swimming pool are not
known to us at this time. Excavation of the overburden materials in the
area of the swimming pool should present no unusual problems.
However, excavation of the dense sandstone bedrock may require use of
heavy-duty excavation equipment for removal. It Is recommended that
the bottom of the swimming pool be at least three (3) feet above the
bedrock anal/or groundwater levels encountered in this investigation or
the pool be equipped with a pressure relief valve.
It Is suggested that the bottom of the pool be underlain by a
minimum of eight (8) inches of 314-inch washed, graded gravel meeting
the gradation requirements of ASTM C 33-78, Size No. 67. In addition,
It is recommended that a drainage system be placed around the perimeter
of the pool to collect and divert water in this area to a sump or to
another suitable area. Backfill against the pool sides should be placed
at or near optimum moisture content and compacted to a minimum of
ninety-five percent (95%) of Standard Proctor Density ASTM Q 698-78.
See Appendix C.) The pool sides should be designed using a
hydrostatic pressure distribution and an equivalent fluid pressure of
gravel backfill of forty (40) pounds per square foot per foot height of
wall. Slabs adjacent to the pool should be designed such that splash
water from the pool does not enter the backfill adjacent to the pool
sides. Footings and/or foundations adjacent to the pool should be placed
such that the effect of the loads from the footings do not create a lateral
pressures against the sides of the pool.
Retaining Structures
Short retaining wails, four (4) feet or less in height, constructed
at the site may be backfilled with the on -site brown silty clay or red
sandy silty clay soils. These relatively impervious clays will help
prevent surface water from reaching the backfill area. The clay backfill
should be placed at optimum moisture in uniform six (6) to eight (8)
Inch lifts and compacted to at least ninety-five percent (95%) of Standard
12-
Proctor Density ASTM D 698-78. ( See Appendix C.) These walls should
be designed using a hydrostatic pressure distribution with an equivalent
fluid pressure of the clay backfill of fifty (50) pounds per square foot
per foot of depth.
The retaining structures over four (4) feet in height constructed at
the site should be backfilled with an approved free -draining granular
material to within one and one-half (1-1 /2) to two (2) feet of the top. of
the structure. The granular backfill should be compacted to at least
seventy-five percent (75%) of Relative Density ASTM D 2049-69. The
properly compacted granular material may be expected to exert an
equivalent fluid pressure of forty (40) pounds per square foot on the
wall. This granular backfill should be overlain with an untreated
building paper to prevent the overlying clay backfill from clogging the
filtered material. The upper one and one-half (1-1/2) to two (2) feet of
the backfill behind retaining galls should consist of a relatively
Impervious clay material placed at optimum moisture In uniform six (6) to
eight (8) inch lifts and compacted to at least ninety-five percent (95%)
of Standard Proctor Density ASTM D 698-78.
Retaining wails should be provided with weep holes so that
hydrostatic pressure which may develop behind the walls will be
minimized. Positive drainage should also be provided away from the top
of the wall to prevent ponding of water in the area behind the wall.
Light Standards
It Is recommended that all light standards have .a drilled pier type
foundation. The upper sandy silty clay soil encountered at the site is
only slightly plastic and can be expected to have very little cohesion and
an internal angle of friction of approximately twenty degrees (20°). The
Intensity of the ultimate passive pressure of the upper soils encountered
at the site at a depth of Z in feet may be expressed by the equation Pp
a 230Z. The above passive pressure should be used as the design
criteria for resisting lateral loads and overturning moments developed on
the pier. All piers should extend a minimum of thirty (30) inches below
finished grade for frost protection and should be founded on the
13-
original, undisturbed soil or backfill that has been compacted to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
See Appendix C. )
Parking Areas
Flexible Pavement
It is our opinion that a flexible pavement is suitable for the
proposed parking area at the site. The flexible pavement should consist
of asphaltic concrete underlain by crushed aggregate base course and
subbase and/or full -depth asphaltic concrete. Using the City of Fort
Collins 0°Design Criteria and Standards for Streets,* a serviceability
Index of 2.0, a regional factor of 0.75. an 811" value of 5, a twenty (20)
year design life, an eighteen (18) kip equivalent daily load application of
5 for automobile parking areas and 20 for service lanes, and weighted
structural numbers of 2.1S for the automobile parking areas and 2.38 for
service lanes, the -following pavement thicknesses are recommended:
Automobile Parking Areas
Asphaltic Concrete 21"
Crushed Aggregate Base Course b"
Select Subbase 4"
Total Pavement Thickness 121"
Full -Depth Asphaltic Concrete S"
Service lanes
Asphaltic Concrete 3"
Crushed Aggregate Base Course 6"
Select Subbase 6"
Total Pavement Thickness 15"
14-
Full -Depth Asphaltic Concrete 6"
The select subbase and crushed aggregate base course should meet City
of Fort Collins specifications. The subgrade below the proposed asphalt
pavement should be prepared In accordance with the recommendations
discussed in the "Site Grading and Utilities" section of this report.
Upon preparation of the subgrade, the subbase and base course should
be placed at optimum moisture and compacted to at least ninety-eight
percent (98%) of Standard Proctor Density ASTM D 698-78. (See
Appendix C. )
It is recommended that asphaltic concrete be placed in two (2) to
three (3) Inch lifts. All asphaltic concrete should meet City of Fort
Collins specifications and should be placed In accordance with these
specifications. All subbase material shall have an "R" value of 69 or
greater, the crushed aggregate base course shall have an "R" value of
78 or greater, and the asphaltic concrete shall have an "Rt" value of 95
or greater. Field density tests should be taken in the aggregate base
and asphalt under the direction of the geotechnicai engineer. .
Rigid Pavement
A feasible pavement alternate at the site would be rigid pavement.
Using the eighteen (18) kip equivalent daily load application described
above, a modulus of subgrade reaction of one hundred. (100) pounds per
square inch per inch based upon an "R" value of 5, a design life of
twenty, (20) years, and concrete designed with a modulus of rupture of
five hundred fifty (550) pounds per square inch, the following pavement
thicknesses are recommended:
Automobile Parking _Areas
Nonreinforced Concrete - 4"
Service Lanes
Nonreinforced Concrete - 6"
15
Subgrade below the proposed pavement should be prepared in accordance
with the recommendations discussed in the "Site Grading and Utilities"
section of this report. Concrete pavement should be placed directly on
the subgrade that has been uniformly and property prepared In
accordance with the above recommendations. All concrete used in the
paving shall meet ASTM specifications, and all aggregate shall conform to
ASTM C 33-78 specifications. The concrete should be designed with
minimum modulus of rupture of five hundred fifty (550) pounds per
square inch In twenty-eight (28) days. It is recommended that
laboratory mix designs be done to determine the proper proportions of
aggregate, cement, and water necessary to meet these requirements. it
Is essential that the concrete have a law water -cunt ratio. an adequate
cement factor, and sufficient quantities of entrained air. Joints should
carefully be designed and constructed in accordance with the City of
Fort Collins ODesign Criteria and Standards for Streets" to ensure good
performance of the pavement. It is recommended that all concrete
pavement be placed In accordance with the City of Fort Collins
specifications.
If paving is done during cold weather, applicable cold weather
procedures outlined in the City's specifications should be utilized. The
concrete pavement should be properly cured and protected in accordance
with the above specifications. Concrete injured by frost should be
removed and replaced. It Is recommended that the pavement not be
opened to traffic until a flexural strength of five hundred fifty (550)
pounds per square inch is obtained or a minimum of fourteen (14) days
after the concrete has been placed.
GENERA!. RECOMMENDATIONS
1) Laboratory test results Indicate that water soluble sulfates in
the soil are negligible, and a Type I cement may be used In
concrete exposed to subsoils. Stabs on grade subjected to
de-icing chemicals should be composed of a more durable
concrete using a Type 11 ceirent with low water -cement ratios
and higher air contents.
16-
2) Finished grade should be sloped away from the structures on
all sides to give positive drainage. Ten percent (10%) for the
first ton (10) fact away from the structures Is the suggested
slope.
3) Backfill around the outside perimeter of the structures should
be mechanically compacted at optimum moisture to at least
ninety percent (90%) of Standard Proctor Density ASTM D
696-78. (See Appendix C.) Puddling should not be permitted
as a method of compaction.
a) Plumbing and utility trenches underlying slabs and paved
areas should be backfilied with an approved material compacted
to at least ninety-five percent (95%) of Standard Proctor
Density ASTM D 698-70. Puddling should not be permitted as
a method of compaction.
5) Gutters and downspouts should be designed to carry roof
runoff water well beyond the backflli area.
6) Underground sprinkling systems should be designed such that
piping is placed a minimum of five (5) feet outside the backfiil
of the structure. Heads should be designed so that Irrigation
water is not sprayed onto the foundation walls. These
recommendations should be taken into account in the landscape
planning.
7) Footing and/or pier sizes'should be proportioned to equalize
the unit loads applied to the soil and thus minimize differential
settlements.
8) It is recommended that compaction requirements specified
herein be verified In the field with density tests performed
under the direction of the geotechnical engineer.
17-
9) It Is recommended that a registered professional engineer
design the substructures and that he take into account the
findings and recommendations of this report.
GENERAL COIv MENTS
This report has been prepared to aid in the evaluation of the
property and to assist the architect and/or engineer In the design of
this project. in the event that any changes In the design of the
structures or their locations are planned, the conclusions and
recommendations contained In this report will not be considered valid
unless said changes are reviewed and conclusions of this report modified
or approved in writing by Empire Laboratories, Inc., the geotechnical
engineer of record.
Every effort was made to provide comprehensive site coverage
through careful locations of the test borings, while keeping the site
Investigation economically viable. Variations in soil and groundwater
conditions between test borings may be encountered during construction.
In order to permit correlation between the reported subsurface conditions
and the actual conditions encountered during construction and to aid in
carrying out the plans and specifications as originally contemplated, it
Is recommended that Empire Laboratories, Inc. be retained to perform
continuous construction review during the excavation and foundation
phases of the work. Empire Laboratories, Inc. assumes no responsibility
for compliance with the recommendations Included In this report unless
they have been retained to perform adequate on -site construction review
during the course of construction.
18-
APPENDIX A.
TEST BORING LOCATION PLAN
1Jo.6
No.14 No.l fl"
r
o.12
1
s ® o. 13
O DRiu ep_ ZTP-44. 3o, 19so
DR I LL.6fl DEG. 8-9 , 1982
SCALE V'= ZOO'
A-2
KEY TO BORING LOGS
TOPSOIL
7;
GRAVEL
FILL SAND & GRAVEL
SILT i SILTY SAND & GRAVEL
CLAYEY SILT o pe_
COBBLES
i. SANDY SILT a SAND, GRAVEL & COBBLES
CLAY
WEATHERED BEDROCK
i
SILTY CLAY SILTSTONE BEDROCK
SANDY CLAY CLAYSTONE BEDROCK
SAND SANDSTONE BEDROCK
SILTY SAND LIMESTONE
CLAYEYSAND
GRANITE
SANDY SILTY CLAYEl
SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 11 DAYS AFTER DRILLING
C -- HOLE CAVED
T
5/12 Indicates that blows of a 140 pound hammer failing,30 inches was required to penetrate 12 inches:
A=_3
EMPIRE LABORATORIES. INC.
LOG OF BORINGS
ELxyAmoN No. I No. 2 Wo.3
5015 20.12
2 16 12
14 12
2 6
5 12 2
50.10
i'
10.12
12112 5019-
5005 32 12 10 12
50/9
50 5
5000sz 4
50/4
4995
50/4
5.0 31-
50 3%
4990
5.0 / 2
A-4
EMPIRE LABORATORIES, INC.
LOG OF ••
EizvAmov4 No. s
31/12
5015
14/12
14/12
5010
7/12
16/12
11
50/11
39/12
111
50/5
50/5
1
4985
1
EMPIRE :•• •
0
i
LOG OF BORINGS
ELEVATION No. 7 No . 6 Mo . 9
50.15
5010
5005
5000
4995
4990
4985
rWs.
AM
r
MM
cmcm
A-6
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
5015
12/12
12/12 L
5010
17/12
11
27/12
33/12
4
1 •
4995 7
1
4990
m
1
4• m
1 .
1
EMPIRE LABORATORIES.
LOG OF BORINGS
I ELEVATION No . 13 iJ o. 14
50.10
5005
5000
4995
4990
EMPIRE LABORATORIES. INC
APPENDIX B.
U
65
O
c
5.60
55
50
CONSOLIDATION --SWELL TEST
BORING NO.
2
DEPTH
3.0
DRY DENSITY 97. 7#/ Ft3
MOISTURE
19.4
0.1 0.5 1.0 3 10
APPLIED PRESSURE—TONS/SO. FT.
0.1 0.5 1.0
APPLIED PRESSURE—TONS/SQ. FT.
B-2
0
Q
o .45
44
CONSOLIDATION --SWELL TEST
11111 PT
DENSITY
MOISTURE
iu Illn
11111 11111
11111 11111
NII 11111
0.1 0.5 1.0 S 10
APPLIED PRESSURE-TONS/SG1, FT.
0.1 0.5 1.0 5 10
APPLIED PRESSURE-TONS/SO. FT.
Q=3
57
0
IR
42
0
C
Z
0
u
4
CONSOLIDATION --SWELL TEST
PTBORINGNO— DE H
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IHII\11111
0.5 1.0 5 10
APPLIED PRESSURE-TONS/SQ. FT.
0.1 0.5 1.0 5 10
APPLIED PRESSURE—TONS/SQ. FT.
B-4
73
62
54
CONSOLIDATION --SWELL TEST
11111 BORINr. NO.7.0
MOISTURE - 11111
IIIII 11111
lGIIII 1111I'.
MEN IIIII
11111 11111
m ol11111m\s 11111
il11111
APPLIED PRESSURE-TONS/SQ. FT.
0.1 0.5 1.0 S 10
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APPENDIX C.
e
APPFNnTY f
Suggested Specifications for Placement of Compacted Earth Fill
and/or Backfills.
GENERAL
A soils engineer shall be on -site to provide continuous observation
during filling and grading operations and shall be the owner's repre-
sentative to inspect placement of all compacted fill and/or backfill on
the project. The soils engineer shall approve all earth materials prior
to their use, the methods of placing, and the degree of compaction
obtained.
MATERIALS
Soils used for all dompacted fill and backfill shall be approved by the
soils engineer prior to their use. The upper two (2) feet of compacted
earth backfill placed adjacent to exterior foundation walls shall be an
impervious, nonexpansive material. No material, including rock, having
a maximum dimension greater than six inches shall be placed in any fill.
Any fill containing rock should be carefully mixed to avoid nesting and
creation of voids. In no case shall frozen material be used as a fill
and/or backfill material.
PREPARATION__OF_ SUBGRADE
All topsoil, vegetation (including trees and brush), timber, debris,
rubbish, and other unsuitable material shall be removed to a depth
satisfactory to the soils engineer and disposed of by suitable means
before beginning preparation of the subgrade. The subgrade surface of
the area to be filled shall be scarified a minimum depth of six inches,
moistened as necessary, and compacted in a manner specified below for
the subsequent layers of fill. Fill shall not be placed on frozen or
muddy ground.
PLACING FILL
No sod, brush, frozen or thawing material, or other unsuitable material
shall be placed in the fill, and no fill shall be placed during unfavorable
weather conditions. All clods shall be broken into small pieces, and
distribution of material in the fill shall be such as to preclude the
formation of lenses of material differing from the surrounding material.
The materials shall be delivered to and spread on the fill surface in a
manner which will result in a uniformly compacted fill. Each layer
shall be thoroughly blade mixed during spreading to insure uniformity of
material and moisture in each layer. Prior to compacting, each layer
shall have a maximum thickness of eight inches, and its upper surface
shall be approximately horizontal. Each successive 6" to 8" lift of
fill being placed on slopes or hillsides should be benched into the
existing slopes, providing good bond between the fill and existing
ground.
MOISTURE CONTROL
While being compacted, the fill material in each layer shall as nearly
as practical contain the amount of moisture required for optimum compaction
or as specified, and the moisture shall be uniform throughout the fill.
The contractor may be required to add necessary moisture to the fill
material and to uniformly mix the water with the fill material if, in
the opinion of the soils engineer, it is not possible to obtain uniform
moisture content by adding water on the fill surface. If, in the opinion
of the soils engineer, the material proposed for use in the compacted
fill is too wet to permit adequate compaction, it shall be dried in an
acceptable manner prior to placement -and compaction.
COMPACTION
When an acceptable, uniform moisture content is obtained, each layer
shall be compacted by a method acceptable to the soils engineer and as
specified in the foregoing report as determined by applicable standards.
Compaction shall be performed by rolling with approved tamping rollers,
r_?
pneumatic -tired rollers, three -wheel power rollers, vibratory compactors,
or other approved equipment well -suited to the soil being compacted. If
a sheepfoot roller is used, it shall be provided with cleaner bars
attached in a manner which will prevent the accumulation of material
between the tamper feet. The rollers should be designed so that effective
weight can be increased.
MOISTURE -DENSITY DETERMINATION
Samples of representative fill materials to be placed shall be furnished
by the contractor to the soils engineer for determination of maximum
density and optimum moisture or percent of Relative Density for these
materials. Tests for this determination will.be made using methods
conforming to requirements of ASTM D 698, ASTM D 1557, or ASTM D 2049.
Copies of the results of these tests will be furnished to the owner, the
project engineer, and the contractor. These test results shall be the
basis of control for all compaction effort.
DENSITY TESTS
The density and moisture content of each layer of compacted fill will be
determined by the soils engineer in accordance with ASTM D 1556, ASTM D
2167, or ASTM D 2922. Any material found not to comply with the minimum
specified density shall be recompacted until the required density is
obtained. Sufficient density tests shall be made and submitted to
support the soils engineer's recommendations. The results of density
tests will also be furnished to the owner, the project engineer, and the.
contractor by the soils engineer. -