HomeMy WebLinkAboutKINGSTON WOODS PUD - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -REPOPTr
OF A
VEOTECHMICAL INVESTIGATIOIJ
FOR
KIh1GSTOV.11-1E VILLAGE 11.U.D;
FORT C 1_INS, COLORADO
WHEELER REALTY
FORT COLLIIJS, COLORADO
PI OJECT NO. 9088-91
BY
Lrfll`II`I.: LAM) PAfUI,'IL_:S, INC:
301 HOR'T H H(.,ti'JES STREET
F OrT COLLINS, COLORADO 80.521
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1
TABLE OF CONTENTS
Tableof Contents .............................................. i
Letterof Transmittal .. ..... ............ ..................
Report................................... 1
AppendixA ............................................. A -1
Test Boring Location Flan ......... A-2
Key to Borings ... .. ... ..... .... A-3
Logof Borings ............................................... A -4
AppendixB.................................................... B-1
Consolidation Test Data ...................................... B-2
Ilveem Stabilometer Data ........ .. ..... ... .. .. 13-6
Summary of Test. Results ..................................... B -8
AppendixC ................... ...........................a... C-1
1
Empire Laboratories, Inc.
GEOTECHNICAL ENGINEERING & MATERIALS TESTING
November 13, 1991
Wheeler Realty
1125 West Drake Road
Fort Collins, Colorado 80526
Attention: Mr. Ei.11 Neal
Gentlemen:
CORPORATE OFFICE
P.O. Box 503 • 301 No. Howes
Fort Collins, Colorado 80522
303) 484.0359
FAX No. (303) 484-0454
We are pleased to submit our Report of a Geotechnical Investigation
prepared for the proposed single-family residential subdivision to be
located on Horsetooth Road in sguthwest Fort Collins, Colorado.
Based upon our findings in the subsurface, it is our opinion the site is
suitable for the proposed construction, providing the design criteria and
recommendations set for 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 LABORATORIES, INC
AIPG
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IC/
Plei R. Sh rod '• .' c "
Senior Engineering GeologistHE
Reviewed Reviewed by: T ER
a P 6 y
r
Chester C. Smith, P.E. °c? Q '°
President iN rUOU jy
cIc
cc: Northern Engineering Service'ike Jones
Branch O es
P.O. Box 16859 P.O. Box 1135 P.O. Box 1744 P.O. Box 5659
Colorado Springs, CO 80935 Longmont, CO 80502 Greeley, CO 80632 Cheyenne, WY 82003
719) 597.2116 303) 776-3921 (303) 351-0460 (307) 832-9224
Member of Consulting Engineers Council
f Ir
REPORT
OF A
GEOTECHNICAL INVESTIGATION
SCOPE
This report presents the results of a geotechnical evaluation
prepared for the proposed Kingstowne Village subdivision to be located
on Horsetooth Road east of the Pleasant Valley and Lake Canal in
southwest Fort Collins, Colorado. The. investigation included test
borings and laboratory testing of samples obtained from these borings.
The objectives of this study were to (1) determine the geologic
characteristics of the site, (2) evaluate the subsurface conditions at the
site relative to the proposed construction, (3) make recommendations
regarding the design of the substructures, (4) recommend certain
precautions which should be taken because of adverse soil and/or ground
waiter conditions, quid (5) make recommendatiotis regarding pavement
types and thicknesses for the proposed streets to be constructed at the
site.
SITE EXPLORATION
The field e;<ploration, carried out on November 7 and 8, 1991,
consisted of drilling, logging, and sampling thirteen (13) test borings.
The test borings were located by Empire Laboratories, Inc. from existing
streets, property lines and topographic features using conventional
chaining methods. The locations of the test borings are shown on the
Test Boring Location Plan and Geologic Map 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 ground water at the time of the exploration.
The borings were advanced with a four -inch diameter, continuous -
type, power -flight auger drill. During the drilling operations, an
engineering geologist from Empire Laboratories, Inc. was present and
made continuous observations of the soils encountered.
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SITE LOCATION AND DESCRIPTION
The site is located north of Ilorsetooth Road and east of Pleasant
Valley and Lake Canal iri southwest Fort Collir,is, Colorado. More
particularly, the site is described as Kingstowne Village P.U.D., a
subdivision situate in the Southeast 1 /4 of Section 27, Township 7
North, Range 69 West of the Sixth P.M., City of Fort Collins, Larimer
County, Colorado.
The site consists of fallow farmland. A farm house and several large
and small outbuildings are located in the southeast corner of the site.
The Pleasant Valley and Lake Canal flows along the west and southwest
edges of the property. The canal then flows below Horsetooth Road
through a box culvert. The canal was dry at the time of our site
exploration. The area is relatively flat, slopes gently and uniformly to
the northeast and has positive drainage in this direction. Several
irrigation laterals cross the site. The property is currently vegetated
with grass and weeds. Several large trees are located in the northwest
portion of the site and adjacent to the existing farrn house and
outbuildings. The site is bordered on the north by the Wagon Wheel
Subdivision, on the west by Horsetooth Stables, on the east by vacant
land and on the south by Horsetooth Road, which is a two-lane,
asphalt -paved road with paved shoulders.
LABORATORY TESTS
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
weicilits, unconfined compressive strengths, water soluble sulfates,
swelling potentials, pH, sulfides, laboratory resistivity,
oxidation-reduction potential, and the Atterberg limits were determined.
A summary of the test results is included in Appendix B. Consolidation,
swell -consolidation and Hveem stabilometer characteristics were also
determined, and curves showing this data are included in Appendix B.
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SOIL AND GROUND WATER CONDITIONS
The soil profile at th.e site consists of strata of materials arranged
in different combinations. In order of increasing depths, they are as
follows:
1) Silty Topsoil: The majority of the site is overlain by a six (6)
inch layer of silty topsoil. The topsoil has been penetrated by
root growth and organic matter and should not be used as a
bearing soil or as a fill and/or backfill material.
2) Existing Pavement and Fill Material: A six (6) to nine (9) inch
layer of asphalt underlain by seven (7) to eight (8) inches of
gravel base course were encountered in Borings 11, 12 and 13
drilled through the existing pavement on Ilorsetooth Road. A
summary of pavement thicknesses is included in Appendix B. A
two -foot layer of fill material underlies the pavement. The fill
consists of a mixture of silty and/or sandy silty clay with
gravel which varies to a clayey sand and gravel.
3) Silty Clay: A layer of silty clay underlies the topsoil and/or
fill in all borings at depths of one-half (1 /2) to three (3) feet
below the surface and extends to depths of one and one-half
1-1/2) to six (6) feet below the surface. The silty clay
contains some sand and/or gravel, is dry to damp and exhibits
generally moderate bearing characteristics. VJhen wetted, the
clay stratum exhibits moderate swell potential; and upon
loading, minor consolidation occurs.
4) Sandy and/or Sandy Gravelly Silty Clay: The granular stratum
underlies the upper clays and extends to the sand and gravel
below and/or the depths explored. A lower layer of the sandy
silty clay was encountered in Borings 3, 4, 5, 6, 9 and 11 at
depths of ten (10) to thirteen (13) feet below the surface and
exterids beyond the depths explored. The red silty clay
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contains varying amounts of sand and/or gravel, is damp to
moist and exhibits generally moderate bearing characteristics.
hen wetted, the granular clay stratum exhibits slight swell
potential; and upon loading, consolidation occurs.
5) Silty Sand ar d Gravel: The sand and gravel was encountered
below and between layers of the sandy silty clay in Borings 3,
4, 5, 6, 9 and 11 through 13 at depths of three (3) to ten (10)
feet and extends to depths of thirteen (13) to greater than
fifteen (15) feet below the surface. The sand and gravel is
poorly graded, contains varying amounts of silt and minor
amounts of clay and exhibits moderate to high bearing
characteristics in its medium dense to dense natural condition.
6) (;round Water: At the time of the investigation, free ground
water was encountered in Borings 1 through 11 at depths of ten
10) to fourteen and one-half (14-1/2) feet below the surface
and extends to greater depths. No free ground water was
encountered in Borings 12 and 13 to the depths explored.
Water levels in this area are subject to change due to seasonal
variations, the volume of flow in the Pleasant. Valley and Lake
Canal adjacent to the site and irrigation demands on and/or
adjacent to the property. It is anticipated that water levels
may rise in areas adjacent to the Pleasant Valley and Lake
Canal when it is flowing.
rPc)i nr:v
The site is located within the Colorado Piedmont section of the Great
Plains physiographic province. The Colorado Piedmont, formed during
Late Tertiary and Early Quaternary time (approximately sixty-five million
65,000,000) years ago), is a broad, erosional trench which separates
the Southern Rocky Mountains from the High Plains. Structurally, the
property lies along the western flank of the Denver Basin. During the
Late Mesozoic and Early Cenozoic Periods (approximately seventy million.
70,000,000) years ago) , intense tectonic activity occurred, causing the
uplifting of the Front Range and the associated downwarping of the
Denver Basin to the east. Relatively flat uplands and broad valleys
characterize the present-day topography of the Colorado Piedmont in this
region. The site is underlain by the Cretaceous Pierre Shale Formation.
The Pierre formation is overlain by residual and alluvial soils of
Pleistocene and/or Recent Age.
Bedrock was not encountered to the depths explored. It is
anticipated the bedrock underlies the site at depths of twenty (20) to
thirty (30) feet below the surface. The regional dip of the hedruck in
this area is anticipated to be slight and in an easterly direction.
Seismic activity in the area is anticipated to below; therefore, from a
structural standpoint, the property should be relatively stable. Due to
the relatively flat nature of the property, geologic hazards due to mass
movement, such as landslides, mudflows, etc., are not anticipated. The
property lies within the drainage basin of an unnamed tributary of the
Cache La Poudre River. However, the site does not lie within the flood
plain of the river and should not he subject to flooding by the Cache La
Poudre River. Some erosion was noted along the banks of the Pleasant
Valley and Lake Canal, and rip rap has been placed on the outer bank
of the canal adjacent to the box culvert below Horsetooth Road. It is
recommended residential construction not be placed within twenty-five
25) feet of the canal.
RECOMMENDATIONS AND DISCUSSION
It is our understanding the site is to be developed for single-family
residential construction. Minor amounts of site grading are proposed.
Residential streets along with water and sewer and other utilities are to
be constructed throughout the site. Horsetooth Road is to be widened
on the south side of the property. The Pleasant Valley and Lake Canal
is to be realigned adjacent to the street, and a small detention pond is
planned in the northeast corner of the project area.
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Site Grading, Excavation and Utilities
Specifications pertaining to site grading are included [)(--low and in
Appendix C of this report. It is recommended the upper sir. (6) inches
of topsoil penetrated by root growth and organic matter below building,
filled and paved areas be stripped and stockpiled for reuse in planted
areas. It is recommended the excavations of existing buildings to be
razed be thoroughly cleaned of all debris, foundation concrete, and
building materials. The excavated areas should be inspected by the
geotechnical engineer prior to backfilling. The upper six (6) inches of
the subgrade below building, paved and filled areas should be scarified
and recompacted between optimum moisture and two percent (2%) wet of
uptimurn moisture to at least ninety-five percent (950) of Standard
Proctor Density ASTM D 698-78. (See Appendix C.) Fill and backfill
should consist of the on -site soils or imported granular material approved
by the geotechnical engineer. Fill should be placed in uniform six (6)
to eicilit (8) inch lifts and mechanically compacted) hetween optirnmm
ir!oisture and two percent (20) wet of optimum moisture to at least
ninety-five percent (950) of Standard Proctor Density ASTM D 698-78.
In computing earthwork quantities, an estimated shrinkage factor of 18
to 23 percent may be used for the on -site soils compacted to tire
above -recommended density.
It is recommended all cut and fill slopes for the relocated portion of
the Pleasant Valley and Lake Canal be placed on slopes of 2:1 or flatter.
It is recommended the top of the canal in fill sections have a minimum
ten (10) foot width for ease of construction and maintenance. The
wetted perimeter of the canal should be placed within or Fined with a
minimum one (1) foot layer of the on -site silty and/or sandy silty clay.
The clay should be compacted plus or minus two percent (2%) of optimum
moisture to at least ninety-five percent (95%) of Standard Proctor
Density ASTM D 696-78. The upper six (6) inches of the wetted
perimeter of the canal in cut sections should he scarified and
recompacted to nir ety-five percent (95%) of Standard Proctor Density
ASTN'; D 6.98-78. Sand and gravel lenses encountered within the wetted
perimeter of the relocated carial should be overexcavated a minimum of
MM
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one (1 ) foot. The overexcavated areas should be hackfilled with the
on -site clay soils compacted to the above density requirements. All cut
and fill slopes above the high water line of the canal should be covered
with a minimum of six (6) inches of topsoil and seeded with suitable
vegetation.
All excavations should be dug on safe and stable slopes. The slope
of the sides of the excavations should comply with local codes or OSHA
regulations. Where this is not practical, sheeting, shoring and/or
bracing of the excavation will be required. The sheeting, shoring and
bracing of the excavation should be done to prevent sliding or caving of
the excavation walls and to protect construction workers and adjacent
structures. The side slopes of the excavation or sheeting, shoring or
bracing should be maintained under safe conditions until completion of
backfilling. In addition, heavy construction equipment should be kept a
safe distance from the edge of the excavation.
Cuts and fills for the proposed detention pond should be placed on
slopes no steeper than 3:1. Cut areas in the detention pond should be
scarified a minimum of eight (8) inches and compacted plus or minus two
percent (2%) of optimum moisture to at least ninety-five percent (95%) of
Standard Proctor Density ASTM D 698-78. (See Appendix C.) Fill in
detention poiid areas should consist of the on -site clay material placed in
accordance with the above recommendations. For ease of construction
and maintenance, the top of the proposed detention pond should have a
minimum width of ten (10) feet. To minimize erosion, the slope and
bottom of the detention basin should be seeded. Pipes or apertures
through the detention basin should be surrounded by a minimum of two
2) feet of the upper clay soil compacted to ninety-eight percent (98%)
of Standard Proctor Density ASTM D 698-78.
Where utilities are excavated below ground water, dewatering will be
needed during placement of pipe and backfil.ling for proper construction.
All piping should be adequately bedded for proper load distribution.
Backfill placed in utility trenches in open and planted areas should be
compacted in uniform lifts at optimum moisture to at least ninety percent
90%) of Standard Proctor Density ASTNI D 698-78 the full depth of the
trench. Backfill placed in utility trenches under building and paved
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areas should be compacted at or near optimum moisture to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
Addition of moisture to and/or dryinq of the Subsoils may he needed for
proper compaction.
Stripping, grubbing, subgrade preparation, and fill and backfill
placement should be accomplished under continuous observation of the
geutechnical engineer. Field density tests should be taken daily in the
compacted subgrade, fill, and backfill under the direction of the
geutechnical engineer.
Laboratory resistivity tests, pH, oxidation-reduction potential and
sulfide tests performed in the laboratory indicate the subsoils at the
site are noncorrosive, and protection of metal utility pipe, in our opinion
will not be required.
Foundations
In view of the loads transmitted by the proposed residential
construction and the soil conditions encountered at the site, it is
recommended the structures be supported by conventional -type spread
footings and/or grade beams. All footings and/or grade beams should be
founded on the original, undisturbed soil or on a structural fill extended
to the undisturbed soil a minimum of thirty (30) inches below finished
grade for frost protection. The structural fill should be constructed in
accordance with the recommendations discussed in the "Site Grading,
Excavation and Utilities" section of this report. The structural integrity
of the fill as well as the identification and undisturbed nature of the soil
should be verified by the geutechnical engineer prior to placement of any
foundation concrete. Footings and/or grade beams founded at the above
levels may be designed for a maximum allowable bearing capacity of two
thousand five hundred (2500) pounds per square foot (dead load plus
liNixiiriuni live lu,d). To cQunteriJct sw(211ing pressures which will develop
if the subsoils become wetted, all footings and/or grade beams founded
on the clay soils should be designed for a minimum dead load of seven
hundred fifty (750) pounds per square foot.
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The predicted settlemciit under the above maximum loading, as
d(Aermined by laboratory consolidation tests, should be less than
three -fourths (3/4) inch, generally considered to be within acceptable
tolerances.
basements, Dewatering Systems mid Slabs on Grade
In view of the depth to ground water encountered at the site, it is
oLir opinion basement construction is feasible at the site. It is
recommended the finished basement slabs be placed a minimum of three
3) feet above the existing ground water. Since the potential exists for
possible seepage from the Pleasant Valley and Lake Canal, it is
recommended the structures placed adjacent to the canal be provided
with complete dewatering systems. Basements constructed adjacent to
the proposed detention pond should also be provided with complete
dewatering systems.
The dewatering system should contain a four (4) inch diameter
perforated pipe, underslab gravel, a sump and pump, and/or other
suitable drain outlet. The perforated pipe should be placed around the
entire perimeter of the lower basement area. All piping in the perimeter
trench should be surrounded by clean, graded gravel from three -fourths
3/4) inch to the #r4 sieve in accordance with ASTM C 3.3-86, Size Flo.
67. The gravel should extend from at least three (3) inches below the
bottom of the pipe to a minimum of two (2) feet above the pipe, the full
width of the trench. The trench should be a minirnum of twelve (12)
inches wide. The top of the gravel backfill adjacent to foundation walls
should be covered with an untreated buildincl paper to help minimize
clogging of the medium with earth backfill. To minimize the potential for
surface water to enter the system, it is recommended a clay backfill be
placed over the systein and compacted at or near optimum moisture to at
least ninety percent (90%) of Standard Proctor Density ASTM D 698-78.
See Appendix C.) We recommend the drainage pipe be placed at least
one (1) foot Ljelow the lower basement slab and have a minirnum grade of
one -eighth (1 /8) inch per foot. All lower level slabs surrounded by
perimeter drains should be underlain by a minimum of eight (8) inches of
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clean, graded gravel or crushed rock devoid of fines. The drainage
system should empty into a sewer underdrain should one adequately
sized to accept the anticipated flows exist at the site, or the water from
the drain should empty into a sump provided in the lower basement area.
The sump should be a minimum of eighteen (18) inches in diameter and
three (3) 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. The sump should be provided with a pump
designed to discharge all flow to the sump. Water from the sump should
be disposed of by suitable means well beyond the foundation of the
building.
Due to the swelling pressures exerted by the clay soils at subgrade,
it is our opinion the only positive solution for construction of the slab
where movement will not occur is a structural floor with a void beneath
it. However, the cost of this type of system may be prohibitive. It is
our opinion that, with certain precautions and knowing that some risk
is involved, a floating floor slab may be a reasonable alternative. 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.
Subgrade below slabs on grade at the upper level should be prepared
in accordance with the recommendations discussed in the "Site Grading,
Excavation and Utilities" section of this report. If the subgrade below
slabs on grade at the upper level is allowed to dry below the required
moisture, the subgrade should be rescarified and recompacted to two
percent (20) wet of optimum moisture to the required density just prior
to placement of underslab gravel and concrete. Slabs surrounded by
perimeter drains should be underlain by a minimum of eight (8) inches of
clean, graded gravel or crushed rock devoid of fines. All other slabs
on grade should be underlain by a minimum. of four (4) inches of clean,
graded gravel or crutihed rock devoid of fines. Garage slabs should be
reinforced with wire Mesh running through the control joints. Slabs on
grade should be designed and constructed structurally independent of
bearing members.
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To minimize and control shrinkage cracks which may develop in slabs
on grade, we suggest control joints be placed every fifteen (15) to
twenty (20) fe:et, oli(l the tot.,l tirea contained within theses joints sh()t1I(1
be no greater than four hundred (400) square feet. In addition, if
building construction is done during winter months, it is recommended
slabs on grade not be placed on frozen ground and that they be
protected from freezing temperatures until they are properly cured.
Vie further recommend nonbearing partitions placed on floor slabs
at the upper level be provided with a minimum one and one-half (1-1 /2)
inch slip joint (either top or bottom). Slip joints reduce pressure
applied by heaving floor slabs and thus minimize damage to the portion
of the structure above. It is emphasized that if the subsoils are kept
dry, movement of slabs on grade should be minimal. However, if
moisture is permitted to reach the subsoils below the slabs, heaving will
probably occur.
Box Culvert
It is understanding the existing box culvert carrying the Pleasant
Va ley and Lake Canal below liorsetooth Road is either to be enlarged or
that a new box culvert will be constructed at the site. It is
recommended additions to the box culvert or a new box culvert be
founded on the original, undisturbed soil. The identification and
undisturbed nature of the soil should be verified by the geotechnical
engineer prior to placement of foundation concrete. The box culvert
founded on the original, undisturbed clay soils or sands and gravels 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 may develop if the subsoils become
wetted, the box culvert, where possible, should be designed for a
mininruili deed load of five hundred (5UU) pour ds per square foot. The
predicted settlement under the above maximum loading should be less
than one (1) inch, generally considered to be within acceptable
tolerances.
Cutoff walls should be provided below the upstream and downstream
ends of the box culvert .to minimize erosion below the culvert. The box
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culvert and its wing walls should be backfilled with the on -site clay soils
or imported material approved by the geotechnical engineer. The
backfill should he placed in uniform sir. (6) to eight (8) hich lifts and
mechanically compacted plus or minus two percent (2%) of optimum
moisture to a minimum of ninety-five percent (95%) of Standard Proctor
Density ASTM D 698-78. (See Appendix, C.) Puddling of the backfill
should not be permitted. The box culvert walls backfilled with the
on -site clays may be designed using a hydrostatic pressure distribution
and equivalent fluid pressure of fifty-five (55) pounds per cubic foot
per foot depth of backfill. In addition, all hydrostatic pressures acting
on the walls should be taken into account in the design of the proposed
box culvert.
Streets
It is our opinion flexible pavement is suitable for the proposed street
construction at the site. A flexible pavement alternate should consist of
asphalt concrete underlain by crushed aggregate base course or asphalt
concrete underlain by plant mix bituminous base course. The design
criteria described below was utilized in determining the pavement
thicknesses for residential streets at the site and will be used in the
remaining street design as traffic data becomes available.
City of Fort Collins "Design Criteria and Standards for Streets"
dated July 1986 and AASHTO Guide to Pavement Design
18 kip ESAL — 36,500 for residential streets based on an EDLA of 5
Resilient Modulus NIR of 3775 psi based on an "R" value of 5
Reliability Factor - 70 for residential streets, 85 for collector
streets, and 90 for arterial streets
Overall Deviation - .44 for flexible pavement and ,34 for rigid
pavement
Initial Serviceability Index - 4.5
Terminal Serviceability Index - 2.0 for residential streets and 2.5
for arterial and collector streets
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Drainage Coefficient - 1.0
20-Year Design Life
Structural Numlje:r - 2.25 for residential streets
Strength Coefficients:
Asphalt Concrete - 0.44
Plant Mix Bituminous Base Course 0.34
Crushed Aggregate Base Course - 0.11
The following minimum pavement thicknesses are recommended:
Residential Streets
Asphalt Concrete 3"
Crushed Aggregate Lase Course 8"
Total Pavement Thickness 11"
Asphalt Concrete 2"
Plant IMix Bituminous Ease Course h"
Total Pavement Thickness 6"
The crushed aggregate base course should meet City of Fort Collins
Class 5 or 6 specifications. The subgrade below the proposed asphalt
pavement should be prepared in accordance with the recommendations
discussed in the "Site Grading, Excavation and Utilities" section of this
report. Due to the plastic nature of the upper subsoils, subgrade
stabilization below streets may be required. The need for subgrade
stabilization should be determined by the geotechnical engineer at the
time of construction by proof -rolling or by other suitable means. Where
necessary, the subgrade should be stabilized by geotextiles, granular pit
run, lisle, fly ash or other acceptable methods. Upon proper
preparation of the subgrade, the base course should be placed and
compacted at optimum moisture to at least ninety-five percent (95%) of
Standard Proctor Density ASTM D 698-78. (See Appendix C. )
It is recommended the asphalt concrete and/or plant mix bituminous
base course be placed in two (2) to three (3) inch lifts. All plant mix
bituminous base course and asphalt concrete shall meet City of Fort
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Collins specifications and shall be placed in accordance with these
specifications. The crushed aggregate base course shall have an "R"
value between 70 and 77, the plant mix bituminous base course shall
have an Rt value of 90 or greater, and the asphalt concrete shall have
an It value of 95 or greater. The "R" value of the pavement materials
used should be verified by laboratory tests. Field density tests should
be taken in the aggregate base course, bituminous base course, and
asphalt concrete under the direction of the geotechnical 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 on an "R" value of 5, a design life of twenty
20) years, and concrete designed with a modulus of rupture of six
hundred fifty (650) pounds per square inch, the following minimum
pavement thickness is recommended:
Residential Streets
Nonreinforced Concrete - 6"
Subgrade below proposed streets should be prepared in accordance with
the recommendations discussed in the "Site Grading, Excavation and
Utilities" section of this report. Concrete pavement should be placed
directly on the subgrade that has been uniformly and properly 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 specifications. The concrete should be designed with a
minimum modulus of rupture of six hundred fifty (650) pounds per
square inch in twenty=eight (2.8) days. It is recommended laboratory
mix designs be done to determine the proper proportions of aggregates,
cement, and water necessary to meet these requirements. It is essential
the concrete have a low water -cement ratio, an adequate cement factor,
and sufficient quantities of entrained. air. Joints should be carefully
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designed and constructed in accordance with the City of Fort Collins
Design Criteria and Standards for Streets" specifications to ensure good
performance of the pavement. It is recommended all concrete pavement
be placed in accordance with City of Fort Collins specifications. If
paving is done during cold weather, acceptable cold weather procedures
as outlined in the City 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 the pavement not be opened to traffic until
a flexural strength of four hundred (400) pounds per square inch is
obtained or a minimum of fourteen (14) days after the concrete has been
placed.
GENERAL RECOMMENDATIONS
1) Laboratory test results indicate water soluble sulfates in the
soil are negligible, and a Type 1-II cement may be used in
concrete exposed to subsoils. Slabs on grade subjected to
de-icing chemicals should be composed of a more durable.
concrete with low water -cement ratios and higher air
contents.
2) Finished grade should be sloped away from the structures on all
sides to give positive drainage. Ten percent (10%) for the first
ten (10) feet away from the structures is the suggested slope.
3) Gackfill around the outside perimeter of the structures should
be mechanically compacted at optimum moisture to at least ninety
percent (90o) of Standard Proctor Density ASTM D 698-78.
See Appendix C.) Puddling should not be permitted as a
method of compaction.
4) Plumbing and utility trenches underlying slabs and paved areas
should be backfilled with an approved material compacted to at
least ninety-five percent (95%) of Standard Proctor Density
15-
l
ASTM p 698-78. 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 backfill area.
G) Underground sprinkling systems should be designed such that
piping is placed a minimum of five (5) feet outside the backfill
of the structures. 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 grade beam sizes should be proportioned to
equalize the unit loads applied to the soil and thus minimize
differential settlements.
8) It is recommended compaction requirements in the project
specifications be verified in the field with density tests
performed under the direction of the geotechnical engineer.
9) It is recommended a registered professional engineer design the
substructures, and he should take into account the findings
and recommendations of this report.
GENERAL COMMENTS
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 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.
16-
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 around water
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 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 beeii retained to perform adequate on -site construction review
during the course of construction.
17-
APPENDIX A
SCALE 1' - 100'
e.
STOCKBRIDGE VILLAGE P.U.D.
WAGONWHEEL
EXISTING PAVE
ON BOX CULL
k HORSETOOTI
ELEV. = 105.
TRACT 1
D. 2
1.
CASA GRANDE P.U.D.
N
z
0
0
U
TRACT C
2
O
O
HW
En
ty-
Kp CRETACEOUS PIERRE FORMATION
17. PERCENT SLOPE
K
KEY TO BORING LOGS
TOPSOIL I. GRAVEL
FILL SAND & GRAVEL
SILT i SILTY SAND & GRAVEL
L CLAYEY SILT ep COBBLES
SANDY SILT SAND, GRAVEL & COBBLES
CLAY
WEATHERED BEDROCK
i
SILTY CLAY SILTSTONE BEDROCK
SANDY CLAY CLAYSTONE BEDROCK
P .1.1 SAND SANDSTONE BEDROCK
77 SILTY SAND LIMESTONE
CLAYEY SAND
F K
GRANITE
SANDY SILTY CLAY
SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 24 hrs. AFTER DRILLING
C HOLE CAVED
T
5/12 Indicates that.5 blows of a 140 pound hammer falling 30 inches was required to penetrate 12 inches.
A- 3
EMPIRE LABORATORIES, INC.
ELEVATION: No.
LOG OF
1 No. 2
BORINGS
No. 3 No. 4
100
22/ 12
j. 24./12
95
7/12
27/12
90
5/ 12
i
25/ 12
22 12
5/ 12
j
16/ 12 o
85
6/12 0 23 12
14/ 12 j.
d
80
5/12
75
7/12
TBM, existing pavement on box culvert centerline Horsetoot .,
Elevation 105.4'
A-4
EMPIRE LABORATORIES, INC.
ELEVATION:
LOG OF BORINGS
No. 5 No. 6 No. 7
100
20/12 19/12
95
16/
1290
15 12 Q
8/12
8/12 18 12
j..
P• d•
85
4/ 12
3/12
80
6/ 12
75
A-5
EMPIRE LABORATORIES. INC.
ELEVATION:
100
Mkl
I 90
519
LOG OF BORINGS
No. 8 No. 9 No. 10
LOG OF BORINGS
ELEVATION: No. 11 No. 12 No. 13
e
105
19/12
7 12
100
23/12
9 12- - - -
19/12 0
5
95
18/12 . %.
13/12 .%n .%.
j• 17/12 •/ .
9 12
o.
90 •
j•
o
a 22/12
23 12
85
a _
9/12 .._
80 _ _ -
A-7
EMPIRE LABORATORIES, INC.
APPENDIX B
510
500
490
480
44
430
42C
SWELL - CONSOLIDATION TEST PRO. 9088
0
BORING 140. : I
DEPTH: 6.0
DRY DE14SITY: 112.2 PCF
MOISTURE: L2.8
0.1 0.25 0.5 1.0 5 to
APPLIED PRESSURE - TSF
4.0
w
X 2.0
11
0.0
8 .0 L-
0.1
WATER ADDED
0.25 0.5 1.0 5
APPLIED PRESSURE - TSF
10
ElIPIRE LAB0F..f=lT0Ft,"IES P-1C.
B-2
f.. e
SWELL CONSOL IDRT ION TEST PRO. 9098
Agcl
44
43
42
c
H
41
L!r
40
t'3
r
39
3 r
j BORING 140. e 6
3.0
DRY DENSIT'Y:115.4 PCF
MOISTURE: 8.9
0
j
DEPTH.-
0
i
i
I
0
0
0
0.1 0.25 0.5 1.0
APPLIED PRESSURE — TSF
4 . I.
0 . 0
I
Z —2 .0
H
4.0
H
J
U
6.0
n . l
WATER RDDED
0.. 1 0.25 0.5 1.0
RPPLIED PRESSURE — TSF
5 10
5 10
EJ,IPIRE LABCIRATORIES INC.
6-3
SWELL - CONSOLIDnTION TEST pRo- gasp,
480
470
46P-
45f"•
43(
42(
4l 0
4 OC-
391-
0.1 0.25 0.5 1.0 5 10
APPLIED PRESSURE - TSF
4.0
DEPTH: 1.0
DRY DE14SITY: 112.3 PCF
MOISTUPE: 17.2
j
w
x 2.0
0.0
z 2.0
F4 4.0
0)
ry
8 .0 L-
0.1
WRTER ADDED
0.25 0.5 1.0 5
APPLIED PRESSURE - TSF
10
ElIPIRE LABORATORIES INC.
B-4
10i
570
560
550
540
530
520
510
500
4
9ei048
CONSOLIDATION TEST PRO. 9008
BOR214G. NO.: JO
DEPTH: 7.0
DRY DENSITY:107.9 PCF
MOISTURE* 18.8%
0.1 0.25 0.5 1.0 5 to
APPLIED PRESSURE — TSF
4.0
2.0
rn
0.0
2 . 0
4.0
0.1 0.25 0.5 1.0 5
APPLIED PRESSURE — TSF
10
EMPIRE LABOPATORIES INC.
B-5
RESISTANCE R-VALUE
C
AND EXPANSION PRESSURE
OF COMPACTED SOIL
RSTH — D 2844
CLIENT: WHEELER REALTY
PROJECT: ;INGSTOWNE P.U.D.
LOCATION OF SAMPLE: C011POSITE SAMPLE BORING 140. 3 @ 0.5' - 3.5'
SAMPLE DATA
TEST SPECIMEN 1 2 3
COMPACTION PRESSURE - PSI 0 0 0
DENSITY - PCF 97.0 103.9 107.6
MOISTURE - 27.2 22.7 19.2
EXPANSION PRESSURE - PSI 0.00 0.00 0.06
HORIZONTAL PRESSURE @ 160 psi 156 154 152
SAMPLE HEIGHT - in. 2.52 2.48 2.53
EXUDATION PRESSURE - PS.I 119 279 414
UNCORRECTED R-VALUE 1.2 2.0 2.9
CORRECTED R-VALUE 1.2 2.0 2.9
R-VALUE AT 300 PSI EXUDATION PRESSURE 2.1
LU_
80
20
r............. _....... ......i.............;....................... _..I.,.,..........
i
j... i.................: :..:.. a ...,...... ..... ..:.. : _ o ............. o ..... ........
6.............i.............. j..........................j.......................... ........ ...........j.............
I ..................... ; ....................... .. '
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i.............. i...- ............ .......:......,...... .:::: o...:.::: _................_.......................................;.............
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I ! i ! i
j:.:::.:::.:e:.........................._ ............ ........... ... ........
100 200 300 400 500 600 700 8G_i0
EXUDATION PRESSURE psi
EMPIRE LRBORRTORIES INC. -
B-6
RESL5THNCE R-VALUE RND EXPANSION PRESSURE
OF COMPACTED SOIL
RSTIl D 2844
CLIENT: WHEELER REALTY
PROJECT: KINGSTOWNE P.U.D.
LOCATION OF SAMPLE: COMPOSITE SAMPLE BORING NO. 11 @ 1.0' - 3.5'
SAMPLE DATA
TEST SPECIMEN 1 _ 2 3
COMPACTION PRESSURE - PSI 100 2.00 300
DENSITY - PCF 127.7 132.6 136.4
MOISTURE - % 11.0 9.4 8.1
EXPANSION PRESSURE - PSI 0.00 0.00 0.36
HORIZONTAL PRESSURE @,160 psi 142 110 78
SAMPLE HEIGHT - in. 2.56 2.56 2.50
EXUDATION PRESSURE - PSI 1.11 306 497
UNCORRECTED R-VALUE 7.6 24.3 44.9
CORRECTED R-VALUE 7.8 25.2 44.9
R-VALUE AT 300 PSI EXUDATION PRESSURE 24.6
1 V-1P1
80
w 60
1
J
W 40
20
t,
I
ij..........;......... , .......... .......... .................... ...................:a::...........
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j.............:............. ........ ........ ` 0-::...:.......t....:..::...-:.;............. i . ..t.......... ........
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or i 1
i ................. ............................. ........ ........ .........j,... ...... ..
4-:........ ........ i....................
100 200 300 400 500 600 700 800
EXUDATION PRESSURE — psi
EMPIRE LABORRTORIES INC.
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Compaction should meet the minimum percentages of maximum density
as set forth in the project specifications or the recommendations of the
report. The contract specifications supercede the recommendations given
in this report.
MOISTURE DENSITY RELATIONSHIP DETERMINATION
Samples of representative fill materials to be placed shall be
furnished by the contractor to the geotechnical engineer for determination
of maximum density and optimum moisture or relative density. Sufficient
laboratory moisture density or relative density curves will be made to
determine the optimum moisture content and maximum density for the.
various soils placed as fill. Tests for this determination will be made
using the appropriate method conforming to the requirements of ASTM D
698 (Standard Proctor), ASTM D 1557 (Modified Proctor) or ASTM D 4253,
D 4254 ( Relative Density) . The materials used for fill shall be classified
in accordance with ASTM D 2487 in order to permit correlation between
the moisture density relationship data and the material being placed and
compacted. Copies of the results of these tests will be furnished to the
client and others as directed by the client. These test results shall be
the basis of control for all compaction effort.
FIELD DENSITY AND MOISTURE TESTS
The in -place density and moisture content of compacted fill will be.
determined by the geotechnical engineer or his representative in
accordance with ASTM D 1556 (sand cone method) or ASTM D 2922, D
3017 (nuclear methods) . Material not meeting the required compaction
and/or moisture specifications shall be recompacted and/or moisture
conditioned until the required percent compaction and/or moisture content
is obtained. Sufficient compaction tests shall be made and submitted to
support the geotechnical engineer's or . his representative's
recommendations. The results of density tests will also be furnished to
the client and others as directed.
C-4
Boring
No.
Depth
ft)
SUMMARY
Moisture
OF TEST RESULTS
Resistivity Oxidation -Reduction
ohm -cm Potential mV Sulfide pH
3 0.5-3.5 26.7 2000 209 trace 6.8
13 1.0-4.0 17.5 2320 205 trace 7.9
SUMMARY OF PAVEMENT THICKNESSES
Boring No. Asphalt (In.) Base Course In.)
11 6 - 7 7
12 9 8
13 8 8
B-12
APPENDIX C
a ry
APPENDIX C.
Suggested Minimum Specifications for Placement of Compacted
Earth Fill and/or Backfills
GENERAL
The geotechnical engineer shall be the owner's, architect's,
engineer's or contractor's representative to observe placement of
compacted fill and/or backfill on the project. The geotechnical engineer
or his representative shall approve all earth materials prior to their use,
the method of placement and the degree of compaction.
MATERIALS
Soils used for all compacted fill and backfill shall be approved by
the geotechnical engineer or his representative prior to their use. Fill
material shall be free from organic matter, frozen material and other
unsuitable substance and shall not contain rocks or lumps having a
diameter greater than six (6) inches.
SUBGRADE PREPARATION
All topsoil, vegetation, trees, brush, timber, debris, rubbish and all
other unsuitable material shall be removed to a depth satisfactory to the
geotechnical engineer or his representative. The material shall be
disposed of by suitable means prior to beginning preparation of the
subgrade. The subgrade shall be scarified a minimum depth of six (6)
inches, moisture conditioned as necessary and compacted in a suitable
manner prior to placement of fi'l material. Fill shall not be placed until
approval by the geotechnical engineer or his representative; and in no
case, shall fill material be placed on frozen. or unstable ground.
Subgrade which is not stable may require the use of imported granular
material, geotextiles or other methods for stabilization as approved by the
geotechnical engineer.
FILL PLACEMENT
Fill material shall not be placed during unfavorable weather
conditions. Material proposed for use as fill shall be approved by the
geotechnical engineer or his representative prior to use. Proposed import
material shall be approved by the geotechnical engineer or his
representative prior to hauling to the project site. Fill material shall be
C-2
uniformly mixed such as to preclude the formation of lenses of material
differing from the surrounding material. All clods shall be broken into
small pieces. The contractor shall construct the fill in approximately
horizontal Lifts extending the entire length of the fill. The thickness of
the layers before compaction shall not be greater than eight (8) inches.
Fill being placed on slopes or hillsides shall be benched into the existing
slope. A minimum two (2) foot horizontal bench shall be cut into the
existing excavated slope for each four (4) feet vertical of fill, or each lift
should be benched slightly into the existing grade.
MOISTURE CONTROL
Prior to and during compaction operations, the fill material being
placed shall be maintained within the range of optimum moisture specified.
A general recommendation is to maintain the fill material within two
percent (2%) plus or minus of optimum moisture so that proper compaction
to the specified density may be obtained with a minimal effort.. In
building pad and paved areas, material exhibiting swelling potential shall
be maintained between optimum moisture and two percent (2%) wet of
optimum moisture content. The moisture content of the fill material shall
be maintained 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 geotechnical
engineer, it is not possible to obtain uniform moisture content by adding
water on the fill surface. If, in the opinion of the geotechnical 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. Uniform mixing may require discing, blading
or other methods approved by the geotechnical engineer or his
representative.
Adjustments of moisture content shall be made on the basis of
determinations of moisture content by field tests as construction
progresses.
COMPACTION
The contractor shall furnish and operate the necessary types and
kinds of equipment to perform the operations required to obtain the
specified compaction. This equipment may include approved tamping
rollers, rubber tired rollers, smooth wheeled rollers and vibratory
rollers. If a sheepsfoot roller is used, it shall be provided with cleaner
bars so attached as to prevent the accumulation of material between the
tamper feet. Fill areas which are not accessible to full-sized construction
equipment shall be placed in maximum four (4) inch lifts and compacted
with power tampers to the specified density.
C-3