HomeMy WebLinkAboutPARK SOUTH PUD, SECOND REPLAT - FINAL - 46-88E - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTPFPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
PARK SOUTH P.U.D.
FORT COLLINS, COLORADO
MIDDEL RFA.LTY
FORT COLLINS, COLORADO
PROJECT NO. 6780-86
BY
EMPIRE LABOP.ATORIFS, INC.
301 NORTH HOWFS STREET
FORT COLLINS, COLORADO 80521
TABLE OF CONTENTS
Table of Contents
Letterof Transmittal ..........................................
ii
Report.........................................................
1
Appendix A ....................................................
A-1
Test Boring Location Plan ....................................
A-2
Key to Borings ...............................................
A-3
Log of Borings ...............................................
A-4
Depth to Ground Water Contour Map ..........................
A-8
Depth to Bedrock Contour Map ...............................
A-9
Appendix B....................................................
B-1
Consolidation Test Data ......................................
B-2
Hveem Stabilometer Data .....................................
B-5
Summary of Test Results .....................................
B-6
Appendix C....................................................
C-1
4
Empire Laboratories, Inc.
GEOTECHNICAL ENGINEERING & MATERIALS TESTING
December 11 , 1986
Middel Realty
1407 South College Avenue
Fort Collins, Colorado 80525
Attention: Mr. Marc Middel
Gentlemen:
PO Box503 • (303),184-0359
301 No. Howes • Fort Collins, Colorado 80522
We are pleased to submit our Report of a Geotechnical Investigation
prepared for the proposed Park South P.U.D.., located at the southwest
corner of Horsetooth Road and Manhattan Avenue in south 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 LABORATORl S, INC.
t eif . Sherrod
Senior Engineering Geologist
Reviewed by:
Chester C. Smith, P.E.
President
cic
P.O. Box 1135
Longmont, Colorado 80502
(303) 776-3921
'R
C.
V� • �G1S7E ��
4808
tic h �.
Branch Offices
P.O. Box 1744
Greeley. Colorado 80632
(303) 351-0460
Member of Consulting Engineers Council
P.O. Box 10076
Cheyenne, Wyoming 82003
(307) 632.9224
P.EPORT
OF A
GEOTECHNICAI_ INVESTIGATION
SCOPE
This report presents the results of a geotechnical evaluation
prepared for the proposed residential and commercial development located
south of Horsetooth Road and west of Manhattan Avenue in south Fort
Collins, Colorado. The investigation included test borings and
laboratory testing of samples obtained from these horings.
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 substructures, (3)
recommend certain precautions which should be taken because of adverse
soil and/or ground water conditions, and (4) make recommendations
regarding pavement types and thicknesses for the proposed street
sections to be constructed at the site.
SITE EXPLORATION
The field exploration, carried out on December 1, 1986, consisted of
drilling, logging, and sampling thirteen (13) test borings. 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 loqs
are shown in Appendix A. These logs show soils encountered, location
of sampling, and ground water at the time of the exploration. Field
resistivity tests were performed in selected areas throuclhout the site
exploration.
The borings were advanced with a four -inch diameter, continuous -
type, power -flight auger drill. During the drilling operations, a
geotechnical engineer from Empire Laboratories, Inc. was present and
made continuous observations of the soils encountered.
-1-
A
SITE LOCATION AND DESCRIPTION
The proposed site is located south of Horsetooth Road and west of
Manhattan Avenue in south Fort Collins, Colorado. More particularly,
the site is described as Park South P.U.U. , situate in the Northeast 1 /4
of Section 35, Township 7 North, Range 69 West of the Sixth P.M.,
Larimer County, Colorado.
The site is a vacant field currently vegetated with grass and weeds.
Several irrigation laterals traverse the site in ati east -west direction.
The property is bordered on the north by Horsetooth Road and on the
east by Manhattan Avenue, both of which are paved. Piles of fill were
located along Manhattan Drive south of Boulder Street. The property is
relatively flat and has positive drainage to the east.
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, p1l,
swelling potentials, 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.
SOIL AND GROUND WATER 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) Silty Topsoil and Fill Material: 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 bearino soil or as a fill and/or backfill
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material. A four and one-half (4-1/2) foot layer of fill material
was encountered at the surface of Boring 1. The fill consists
of a mixture of brown silty clay and red sandy silty clay. It is
not known whether the fill has been uniformly or properly
compacted; therefore, it should not be used as a foundation
material.
(2) Silty Clay: A layer of brown silty clay underlies the topsoil in
Borings 2 through 13 and extends to the lower clay stratum
and/or the bedrock below. The upper silty clay contains minor
amounts of sand, is plastic and exhibits generally moderate
bearing characteristics in its dry to damp in situ condition.
When wetted, the upper clay stratum exhibits slight to moderate
swell potential; and upon loading, consolidation occurs.
(3) Sandy Silty Clay: A layer of red sandy silty clay underlies the
fill and upper clays. The silty clay was encountered in
Borings 1 through 9, 11 and 13 at depths one (1 ) to four and
one-half (4-1 /2) feet below the surface and extends to the sand
and gravel stratum, bedrock and/or the depths explored. The
red silty clay contains varying amounts of sar►d and/or gravel,
lenses of sand and gravel, and exhibits generally moderate
bearing characteristics in its damp to moist in situ condition.
When wetted, the drier clavier portion of this stratum exhibits
moderate swell potential, while the more moist, sandier portions
of the stratum exhibit slight swell potential. Upon loading,
consolidation occurs.
(4) Silty Sand and Gravel: The gravel stratum was encountered
within the clay layer in Borings 3 and 4 and below the clay
layers in Borings 6, 7 and 10 at depths one (1) to ten (10)
feet below the surface and extends to depths seven (7) to
thirteen (13) feet below the surface. The sand and gravel is
poorly graded, is medium dense, and exhibits moderate bearing
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•t
i
characteristics. The sand and gravel contains varying amounts
of silt and minor amounts of clay and exhibits moderate bearing
characteristics.
(5) Sandstone-Siltstone-Claystone Bedrock: The bedrock was
encountered below the upper subsoils in Borings 5 through 13
at depths two and one-half (2-1 /2) to thirteen (13) feet below
the surface and extends to ctreater depths. The upper two and
one-half (2-1 /2) to seven (7) feet of the bedrock is highly
weathered. However, the underlying interbedded sandstone,
siltstone and claystone is firm and exhibits very high bearing
characteristics. When wetted, the weathered siltstone-claystone
portion of the bedrock exhibits slight to moderate swell
potential. The firm siltstone and claystone exhibits moderate to
high swell potential.
(6) Ground Water: At the time of the investigation, free ground
water was encountered in all test borings at depths seven (7)
to eleven and one-half (11-1 /2) feet below the surface. Water
levels in this area are subject to change due to seasonal
variations and irrigation demands on and/or adjacent to the
site. In addition, where ground water is not already
encountered on top of the bedrock stratum, surface water may
percolate through the upper subsoils and become trapped on the
relatively impervious bedrock stratum, forming a perched
ground water condition.
RECOMMENDATIONS AND DISCUSSION
It is our understanding that the northern portion of the site in the
area of Borings 1 through 5 is to be developed for commercial use. A
preliminary investigation was prepared for this portion of the site since
building locations are not known and street locations and lot sizes may
vary. The remainder of the site is to be developed for single-family
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residential construction, and a complete geotechnical investigation has
been prepared for this portion of the project area.
Site Grading and Utilities
Specifications pertaining to site grading are included below and in
Appendix C of this report. It is recommended that all existing fill be
removed from below building and paved areas and stockpiled for reuse or
wasted from the site. All topsoil should be stripped from building, filled
and paved areas and stockpiled for reuse in planted areas. The upper
six (6) inches of the natural subgrade below building, paved and filled
areas should be scarified and recompacted two percent (2%) wet of
optimum moisture to at least ninety-five percent (95°) of Standard
Proctor Density ASTM D '698-78. (See Appendix C.) Fill should consist
of the on -site soils, existing fill devoid of debris, or imported material
approved by the geotechnical engineer. Fill should be placed in uniform
six (6) to eight (8) inch lifts and mechanically compacted two percent
(2%) wet of optimum moisture to at least ninety-five percent (95%) of
Standard Proctor Density ASTM D 698-78.
Bedrock encountered at the site may be used as fill material in
selected areas. Heavy-duty construction equipment equivalent to a D-8
tractor or a backhoe having a minimum one and one-half cubic yard
bucket may be needed to excavate the firm bedrock, and bedrock used
as fill should be broken into pieces less than six (6) inches in diameter.
Proper placement of the bedrock as fill may be difficult, and a disc or
other mixing equipment may be needed to obtain uniform moisture and
proper compaction. The bedrock should be used in open and planted
areas. The expansive firm claystone and siltstone bedrock should not be
used as backfill adjacent to proposed structures.
In computing earthwork quantities, an estimated shrinkage factor
of eighteen percent (18%) to twenty-three percent (23°) may be used for
the on -site soils compacted to the above -recommended density.
Utility trenches dug four (4) feet or more into the upper soils
should be excavated on stable and safe slopes, or the excavations
should be properly shored. The firm bedrock may be excavated on
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near -vertical slopes. Excavation of the firm bedrock may require the
use of heavy-duty construction equipment equivalent to a backhoe
having a minimum one and one-half cubic yard bucket. Where utilities
are excavated below ground water, dewatering will be needed during
placement of pipe and backfilling 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 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 compacted at
or near optimum moisture 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 percent (90%) of
Standard Proctor Density ASTM D 698-78. Addition of moisture to
and/or drying of the subsoils may be needed for proper compaction.
Proper placement of the bedrock as backfill may be difficult.
Stripping, grubbing, subgrade preparation, and fill and backfill
placement should be accomplished under continuous observation of the
geotechnical engineer. Field. density tests should he taken daily in the
compacted subgrade, fill, and backfill 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, and protection of utility pipe will not, in our
opinion, be required.
Foundations
A complete geotechnical investigation has been prepared for the
residential portion of the site. The commercial area located in the
northern portion of the site will be discussed in a preliminary manner.
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Residential Area
In view of the loads transmitted by the proposed residential
construction and the soil conditions encountered at the site, it is
recommended that 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 three (3) feet above
the firm bedrock layer and 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 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 geotechnical engineer prior to
placement of any foundation concrete. Footings and/or grade beams
founded at the above levels may be designed for 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 if the subsoils become wetted, all footings and/or grade
beams should be designed for a minimum dead load of seven hundred
fifty (750) pounds per square foot.
The predicted settlement under the above maximum loading, as
determined by laboratory consolidation tests, should be less than one (1 )
inch, generally considered to be within acceptable tolerances.
The bottom of all footings should be placed a minimum of three (3)
feet above the expansive firm bedrock stratum. Structures founded
within three (3) feet of the firm bedrock stratum should be supported
by a drilled pier foundation system. Using this type of foundation
system, the structure is supported by piers drilled into the bedrock
stratum and structural grade beams spanning the piers. Piers should be
straight -shaft and should be drilled within plumb tolerances of one and
one-half percent (1-1 /2%) relative to the length of the pier. The piers
are supported by the bedrock stratum partially through end bearing and
partially through skin friction. It is recommended that all piers have
minimum ten (10) foot lengths and that they be drilled a minimum of
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three (3) feet into the firm bedrock stratum. Piers founded at the
above level may be designed for a maximum allovrahle end bearing
pressure of fifteen thousand (15,000) pounds per square foot. It is
estimated that a skin friction of one thousand five hundred (1500)
pounds per square foot will be developed for that portion of the pier
embedded into the firm bedrock stratum. To counteract swelling
pressures which will develop if the subsoils become wetted, all piers
should be designed for a minimum dead load of five thousand (5000)
pounds per square foot. Where this minimUm dead load requirement
cannot be satisfied, it is recommended that skin friction from additional
embedment into the firm bedrock be used to resist uplift. To help
provide the required skin friction, the sides of the pier drilled into the
bedrock stratum should be roughened. All piers should be reinforced
their full length to resist tensile stresses created by swelling pressures
acting on the pier. It is recommended that all grade beams have a
minimum four (4) inch void between the bottom of the beam and the soil
below. The predicted settlement under the above maximum loading
should be negligible.
Drilled piers should be designed to resist all induced lateral forces.
Since all bedrock is below ground water, temporary casing of the drill
holes may be required. However, since the majority of the borings were
dry at the time of initial drilling, temporary casing may not be required
if piers are poured immediately after drilling. For ease of construction
and inspection, it is suggested that all piers should have minimum ten
(10) to twelve (12) inch diameters.
It is strongly recommended that the geotechnical engineer be
present during the drilling operations to (1) identify the firm bedrock
stratum, (2) assure that proper penetration is obtained into the sound
bedrock stratum, (3) ascertain that all drill holes are thoroughly
roughened, cleaned and dewatered prior to placement of any foundation
concrete, (4) check all drill holes to assure that they are plumb and of
the proper diameter, and (5) ensure proper placement of concrete and
reinforcement.
-8-
Commercial Area
In view of the anticipated loads transmitted by light . commercial
construction and the soil conditions encountered in the northern portion
of the site, it is our opinion that the structures should be supported by
conventional -type spread footings and/or grade beams. Footings and/or
grade beams should be founded on the original, undisturbed soil or
structural fill extended to the undisturbed soil a minimum of thirty (30)
inches below finished grade for frost protection. In no case should
footings be founded on the existing fill encountered in the northwest
portion of the site. Based on preliminary test results, footings and/or
grade beams founded at the above levels may be designed for a maximum
allowable bearing capacity between one thousand five hundred (1500) and
three thousand (3000) pounds per square foot (dead load plus maximum
live load) . To counteract swelling pressures which will develop if the
subsoils become wetted, all footings and/or grade beams should be
designed for a minimum dead load between five hundred (500) and one
thousand (1000) pounds per square foot.
Basements, Dewatering Systems and slabs on Grade
Residential Area
Due to the depth of bedrock and ground water encountered in the
proposed residential areas, it is our opinion that the majority of the site
is suitable for basement construction. The finished basement floor slabs
should be placed a minimum of three (3) feet above existing ground
water and/or the weathered bedrock stratum. In the extreme southeast
corner of the project area adjacent to Boring 13, ground water levels
were encountered at relatively shallow depths, extensive dewatering may
be required for basement construction in this area. It is suggested
conventional garden -level, crawl -space or slab -on -grade construction be
used in this portion of the site. All finished basement floors placed
within three (3) feet of existing ground water or the bedrock stratum
I�
should be provided with perimeter drainage systems. A depth to ground
water contour map and a depth to bedrock contour map is included in
Appendix A.
The drainage system should contain a four (4) inch diameter
perforated pipe running the full length of the trench. The pipe should
be surrounded by clean, graded gravel from three -fourths (3/4) inch to
the #4 sieve in accordance with ASTM C 33-78, Size No. 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 existing ground water and/or
the weathered bedrock stratum above the pipe, the full width of the
trench. To minimize the cost of gravel backfill, it is suggested that the
excavation be limited to the area necessary for construction; however,
the trench should be a minimum of twelve (12) inches wide. We
recommend that the drainage pipe be placed at least one (1) foot below
the finished lower level floor and have a minimum 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 clean,
graded gravel or crushed rock devoid of fines. The top of the gravel
medium should be covered with an untreated building 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 that a
clay backfill be placed over the system and compacted at or near
optimum moisture to at least ninety percent (90°) of Standard Proctor
Density ASTM D 698-78. (See Appendix C.) 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. Water from the sump should he disposed of by
suitable means well beyond the foundation of the building.
Due to the swelling pressures exerted by the materials at subgrade,
it is our opinion that the only positive solution for construction of
the slab where movement will not occur is a structural floor with a void
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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 slat) 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 Gradinq
and Utilities" section. If' the subgrade below slabs on grade 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 on grade should be underlain by a minimum of four (4)
inches of clean, graded gravel or crushed rock devoid of fine. 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. 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.
To minimize and control shrinkage cracks which may develop in slabs
on grade, we suggest that control joints be placed every fifteen (15) to
twenty (20) feet and that the total area contained within these joints
be no greater than four hundred (400) square feet. It is emphasized
that if the subsoils are kept dry, movement of slabs on grade should be
minimal. However, if moisture is permitted to react, the subsoils below
the slabs, heaving will probably occur.
Commercial Area
Basement construction is
feasible in the commercial
area of
the site,
provided finished basement floor slabs are placed a minimum
of
three (3)
feet above existing ground
water. Basements placed
within three (3)
feet of existing ground water
should be provided with
perimeter
drainage
systems. Ground water was
encoLintered at a depth
of eight
(8) feet
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below the surface in the eastern portion of the commercial area. Free
ground water was encountered at approximate depths of eleven (11) feet
below the surface in the remainder of the commercial area.
Subgrade below slabs on grade should be prepared in accordance
with the recommendations discussed in the "Site Grading and Utilities"
section of this report. In view of the expansive nature of the subsoils,
slabs on grade should be designed as floating slabs.
Paved Areas
It is our understanding that the northern portion of the site is to be
developed for commercial construction. Streets serving this area are to
be classified as local commercial streets in accordance with the City of
Fort Collins. All other streets within the residential part of the
development are to be classified as local or residential streets.
Flexible Pavement
It is our opinion that flexible pavement is suitable for the proposed
street construction at the site. A flexible pavement alternate should
consist of asphaltic concrete underlain by crushed aggregate base course
or asphaltic concrete underlain by plant mix bituminous base course.
Using the City of Fort Collins "Design Criteria and Standards for Streets"
dated July 1986, a serviceability index of 2.5 for local commercial streets
and 2.0 for residential streets, a regional factor of 0.75, an "R" value of
7 determined from laboratory test results, a twenty (20) year design life,
eighteen (18) kip equivalent daily load applications of 25 for local
commercial streets and 5 for residential streets as provided by the City of
Fort Collins, and weighted structural numbers of 2.80 for local commercial
streets and 2.10 for residential streets, the following pavement
thicknesses are recommended:
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— _ -___ -- - - - ----
Local Commercial Streets
Asphaltic Concrete 4"
Crushed Aggregate Base Course 9"
Total Pavement Thickness 13"
Asphaltic Concrete 2"
Plant Mix Bituminous Base Course 51"
Total Pavement Thickness 71"
Residential Streets
Asphaltic Concrete 3"
Crushed Aggregate Base Course 7"
Total Pavement Thickness 10"
Asphaltic Concrete 2"
Plant Mix Bituminous Base Course 31"
Total Pavement Thickness 51"
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 and Utilities" section of this report. 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 that the asphaltic 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 asphaltic concrete shall meet City of
Fort Collins specifications and should be placed in accordance with these
specifications. The crushed aggregate base course shall have an "R"
value between 78 and 83, the plant mix bituminous base course shall have
an Rt value of 90 or greater, and the asphaltic concrete shall have an Rt
value of 95 or greater. The "R" value of the pavement materials used
should be verified by laboratory tests. Field density tests should be
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taken in the aggregate base course, bituminous base course, and
asphaltic 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 applications described
above, a modulus of subgrade reaction of one hundred (100) pounds per
square inch per inch based on an "R" value of 7, a design life of twenty
(20) years, and concrete designed with a modulus of rupture of six
hundred (600) pounds per square inch , the following pavement
thicknesses are recommended:
Local Commercial Streets
Nonreinforced Concrete - 51"
Residential Streets
Nonreinforced Concrete - 5"
Subgrade below proposed streets 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 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 (600) pounds per square inch in twenty-eight
(28) days. It is recommended that laboratory mix designs be done to
determine the proper proportions of aggregates, cement, and water
necessary to meet these requirements. It is essential that the concrete
have a low water -cement ratio, an adequate cement factor, and sufficient
quantities of entrained air. Joints should be carefully designed and
constructed in accordance with the City of Fort Collins "Design Criteria
and Standards for Streets" to ensure good performance of the pavement.
It is recommended that all concrete pavement be placed in accordance with
- 114 -
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 that the pavement not be opened to traffic until a flexural
strength of four hundred (►100) 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 that water soluble sulfates in
the soil are negligible, and a Type I 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. Teri percent (10%) for the first
ten (10) feet away from the structures is the suggested slope.
(3) Backfill around the outside perimeters of the residential
structures should be mechanically compacted at optimum
moisture to at least ninety percent (90%) of Standard Proctor
Density ASTM D 698-78. (See Appendix C.) Puddling should
not be permitted as a method of compaction.
(4) Backfill placed around the interior and exterior perimeters of
the structures in the commercial area should be mechanically
compacted in uniform lifts. Puddling should not be permitted
as a method of compaction. Interior Backfill and exterior
backfill below paved areas should be compacted to a minimum of
ninety-five percent (95%) of Standard Proctor Density ASTM D
698-78. (See Appendix C.) Exterior backfill below planted
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areas should be compacted to a minimum of ninety percent (90%)
of Standard Proctor Density ASTM D 698-78.
(5) Gutters and downspouts should be designed to carry roof
runoff well beyond the backfill area.
(6) 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, grade beam and/or pier sizes should be proportioned
to equalize the unit loads applied 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.
(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 COMMENTS
This complete geotechnical investigation portion of 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.
-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 ground 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 it)
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 adea,uate on -site construction review
during the course of construction.
It should be noted that a preliminary investigation was prepared for
the commercial portion of this site. Bearing capacities recommended in
this portion of the report are based on preliminary tests. Due to the
variations in soil conditions and swelling pressures encountered in this
portion of the site, it is recommended that additional test borings be made
prior to construction. Samples obtained from the borings should be
tested in the laboratory to provide a basis for evaluating subsurface
conditions.
-17-
APPENDIX A.
TEST BORING LOCATION PLAN
'�I
A-2
KEY TO BOOZING LOGS
TOPSOIL
••`
GRAVEL
®
FILL
D
SAND & GRAVEL
SILT
El
SILTY SAND & GRAVEL
L�
CLAYEY SILT
M-7711
o as
COBBLES
i�
SANDY SILT
SAND, GRAVEL & COBBLES
®
CLAY
WEATHERED BEDROCK
/I
SILTY CLAY
P-A
SILTSTONE BEDROCK
SANDY CLAY
®
CLAYSTONE BEDROCK
aSAND
SANDSTONE BEDROCK
El
SILTY SAND
LIMESTONE
CLAYEY SAND
R x
x x
�Rx
GRANITE
SANDY SILTY CLAY
F-1
SHELBY TUBE SAMPLE
STANDARD PENETRATION
DRIVE SAMPLER
WATER TABLE 24 [JOURS
AFTER DRILLING
C
T
HOLE CAVED
5/12 Indicates that 5 blows of a 140 pound
hammer falling
30 inches was required to penetrate 12 inches.
A-3
110
105
100
95
90
LOG OF BORINGS
!w�
NA all
MAP
mom
■ s.
85 "' 1
80
TBI1, west end of radius @ flow line. Elevation = 100.0'.
n-n
LOG OF BORINGS
ELEUA,T-io0 I.1o. 4- Ur,. s uo . G
110
105
100
95
35
' I
-
®'
WE
W
PW
C
WN
_-
go•
.
MA
_
A--5
LOG OF BORINGS
110
105
100
olm
80
sa
+wry
- •
m
m
No Text
1�
aw Rio of
-V �r DUE,
=loop
\ ,1Jaz
.�
A-8
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IFIRINZ
� \ 1
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• ` (0 4
A-9
LQ&
APPENDIX B.
CY:::)
•411i
. 4 C.
.45,
.44
H
LL
H •4L
.4t
. 4 t_t
0
SWELL - CONSOLIDATION TEST FRCD. F-; 7 Bt_t
D E FT H: 4. t_t
1 1:3 .'3 F' i; F
tI ;I' 111RE: lS.P;
t_I. 1 t_1, 2 5 1, Et
HF'F'LIED F'F'E'- ;UF-'E - T'=,F
4 . Cl
iT
--
iii
I
I �
i
-
H
N -4tJRTER FID1)E0 ;
H
J
iii
(1
t_t
AF'F'LIED F'F'E'= IUF'E - T-F
Er"1F'IF'E LNFli F='FlT ,F'IE' I�'1 __--
B-2
I! CLD
.60cl
580
.560
.540
.5%
.500
480
.46C,
.440
A 0 l7i
SWELL - CONSOLIDATION TESI- FFL:, . 6 7 0 C,
BORING NO.: ?
DEPTH: 3.0
DRY DENSITY :104.0 PCF
MOISTURE: X.2
0.1 0. 25 0.5 1 . cl 5 1 cl
APPLIED PRESSURE - TSF
8 cl
4 0
iii
0.0
71
-4 Cl
WRTER ADDED
-12 .0
- 16.0
0. 1 0.25 0.5 1 . cl 5 1 cl
APPLIED PRESSURE TSF
EHFIRE LABC:1FATORIES INC.
B-3
r-I
4 L C
..:.D c
mm
4 . C,
Z —4 Cl
'=�� - 12. cl
CONSOLIUKION -I EST FPCI B 171
--1 E F
DEPTH: 7 C,
D F-.,,,D E IT-1 I T 12:3 7 F'f-- F
t I D 1':-:; T UPE
C, 171. 5 1 cl I cl
AFFLIED FRESSURE TSF
0.1 1 . cl 1
AFFLIED F,F,E,=;,=;UF-,E — T,::;F
EHPIRE L A E; *--:, F H T 1:) F I ES' I I -I C-
B-4
C-D
RE51STHNCE R-VHLUE AND EXPANSION PRESSURE
OF COMPACTED SOIL
A EST tl - D 2 8 4 4
CLIENT: MIDDEL REALTY
PROJECT: PARK SOUTH P.U.D.
LOCATION OF SAMPLE: BORING 9 AT 1.0"-3.0'
SAMPLE DATA
TEST SPECIMEN
1
2
COMPACTION PRESSURE
- PSI
0
40
80
DENSITY PCF
103.5
110.5
111.9
1-10I,:-;TURE %
20.7
17.6
15.9
EXPANSION PRESSURE
- PSI
0.00
0.00
0.00
HORIZONTAL PRESSURE
@ 160 psi
152
143
14CI
SA11PLE HEIGHT - in.
2.50
2.54
2.48
EXUDATION PRESSURE
- PSI
159
271
UNCORRECTED R-VALUE
2.2
el . 6
7.4
CORRECTED R-VALUE
2.2
6.6
7.4
R-VALUE AT :300 PSI
Ele-lUDATION
PRESSURE =
7.2
1 f-A f-11
.............. ............. . ............. ..............
... . ..... ...... ...... . ....... I . ............. . .............
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.......... .... ......... . ............. ......................................................... .............
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..
......... . ............. ............. ............. .............. ............. ............... .......... ............. .............. ............. ........... .............. .............
C-1 Lu
100
............. .......... ................ .............. ..................... ............. ............. .............. ............. . ............
.............. ............. ............ .............. ............. . .............
.............. ................ ............. ............. .............
C 300 400 500 E; 0 0
E Ll El A T 10 t-1 PRES 11 R E
EHPIRE LFIE;,:--)F,FiT(--,F,IE,-;
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APPENDIX C.
APPENDIX C.
Suggested Specifications for Placement of Compacted Earth Fill
and/or Backfills.
GENERAL
A geotechnical engineer shall be on -site to provide continuous observation
during filling and grading operations and shall be the owner's
representative to inspect placement of all compacted fill and/or backfill on
the project. The geotechnical 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 compacted fill and backfill shall be approved by the
geotechnical 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 (6) 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 geotechnical 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
(6) 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.
C-2
PLA'CING 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 ensure uniformity of
material and moisture in each layer. Prior to compacting, each layer shall
have a maximum thickness of eight (8) 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 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.
COMPACTION
When an acceptable, uniform moisture content is obtained, each layer shall
be compacted by a method acceptable to the geotechnical engineer and as
specified in the foregoing report as determined by applicable standards.
Compaction shall be performed by rolling with approved tamping rollers,
C-3
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 geotechnical 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 geotechnical 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 geotechnical engineer's recommendations. The results of
density tests will also be furnished to the owner, the project engineer,
and the contractor by the geotechnical engineer.
C-4