HomeMy WebLinkAboutREDTAIL RESIDENTIAL - PDP - 26-01 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGeotechnical Engineering Exploration
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Project No. 20015260
lrerracon
APPENDIX A
Site Plan and Boring Location Diagram
Bedrock Contour Map
Groundwater Contour Map
Logs of Borings
APPENDIX B
Laboratory Test Results
APPENDIX C
General Notes
Pavement Preventative Maintenance Notes
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Geotechnical Engineering Exploration ' ` 1rerracon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
provide testing and observation during excavation, grading, foundation and construction
phases of the project.
The analysis and recommendations presented in this report are based upon the data
1 obtained from the borings performed at the indicated locations and from other information
J discussed in this report. This report does not reflect variations, which may occur between
borings or across the site. The nature and extent of such variations may not become
evident until construction. If variations appear, it will be necessary to reevaluate the
recommendations of this report.
The scope of services for this project does not include either specifically or by implication
any environmental assessment of the site or identification of contaminated or hazardous
materials or conditions. If the owner is concerned about the potential for such
contamination, other studies should be undertaken.
This report has been prepared for the exclusive use of our client for specific application to
the project discussed and has been prepared in accordance with generally accepted
geotechnical engineering practices. No warranties, either express or implied, are intended
or made. In the event that changes in the.nature, design, or location of the project as
outlined in this report, are planned, the conclusions and recommendations contained in this
report shall not be considered valid unless Terracon reviews the changes, and either verifies
or modifies the conclusions of this report in writing.
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Geotechnical Engineering Exploration Ilerracon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
l Underground Utility Systems
�1 All piping should be adequately bedded for proper load distribution. It is suggested
that clean, graded gravel compacted to 75 percent of Relative Density ASTM D4253
1 be used as bedding. Where utilities are excavated below groundwater, temporary
"1 dewatering will be required during excavation, pipe placement and backfilling
operations for proper construction. Utility trenches should be, excavated on safe and
stable slopes in accordance with OSHA regulations as discussed above. Backfill
should consist of the on -site soils or'imported material approved by the geotechnical
engineer. The pipe backfill should be compacted to a minimum of 95 percent of
Standard Proctor Density ASTM D698.
Corrosion Protection
Results of soluble sulfate testing indicate that ASTM Type I Portland cement is
suitable for all concrete on and below grade. However, if there is no, or minimal cost
differential, use of ASTM Type II Portland cement is recommended for additional
sulfate resistance of construction concrete. Foundation concrete should be designed
in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
Surface Drainage
Positive drainage should be provided during construction and maintained throughout
the life of the proposed project. In areas where sidewalks or paving do not
immediately adjoin the structure, we recommend that protective slopes be provided
with a minimum grade of approximately 5 percent for at least 10 feet from perimeter
walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches
should be well compacted and free of all construction debris to reduce the possibility
of moisture infiltration.
Downspouts, roof drains or scuppers should discharge into splash blocks or
extensions when the ground surface^ beneath such features is not protected by
exterior slabs or paving. Sprinkler systems should not be installed within 5 feet of
foundation walls. Landscaped irrigation adjacent to the foundation system should be
minimized or eliminated.
GENERAL COMMENTS
Terracon should be retained to review the final design plans and specifications so comments
can be made regarding interpretation and implementation of our geotechnical
recommendations in the design and specifications. Terracon also should be retained ,to
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Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
On -site clay for backfill or grading purposes should be compacted within a moisture
content range of 2 percent below, to 2 percent above optimum. Imported or on -site
granular soils should be compacted within a moisture range of 3 percent below to 3
percent above optimum unless modified by the project geotechnical engineer.
Excavation and Trench Construction
Excavations into the on -site soils may encounter caving soils and groundwater,
depending upon the final depth of excavation. The individual contractor(s) should be
made responsible for designing and, constructing stable, temporary excavations as
required to .maintain stability of both the excavation sides,. and. ,.bottom. ....All
excavations should be sloped or shored in the interest of safety following local, and
ul federal regulations, including current OSHA excavation and trench safety standards.
The soils to be penetrated by the proposed excavations may vary significantly across
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the site. The preliminary soil classifications are based solely on the materials
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encountered in widely spaced exploratory test borings. The contractor should verify
that similar conditions exist throughout the proposed area of excavation. If different
subsurface conditions are encountered at the time of construction, the actual
conditions should be evaluated to determine any excavation modifications necessary
to maintain safe conditions.
As a safety measure, it is recommended that all vehicles and soil piles be kept to a
minimum lateral distance from the crest of the slope equal to no less than the slope
height. The exposed slope face should be protected against the elements.
Additional Design and Construction Considerations
Exterior Slab Design and Construction
Exterior slabs -on -grade, exterior architectural features and utilities founded on or in
backfill may experience some movement due to the volume change of the backfill.
Potential movement could be reduced by:
minimizing moisture increases in the backfill
controlling moisture -density during placement of backfill
using designs which allow vertical movement between the exterior features .
and adjoining structural elements
placing effective control joints on relatively close centers
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Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No..20015260
Subgrade Preparation
Subgrade soils beneath interior and exterior slabs, and beneath pavements should
be scarified, moisture conditioned and compacted to a minimum depth of 8 inches.
The moisture content and compaction of subgrade soils should be maintained until
slab or pavement construction.
Fill Materials and Placement
Clean on -site soils or approved imported materials may be used as fill material and
are suitable for use as compacted fill beneath interior or exterior floor slabs.
Imported soils (if required) should conform to the following:
Percent finer by weight
Gradation
(ASTM C136)
Engineered fill should be placed and compacted in horizontal lifts, using equipment
and procedures that will produce recommended moisture contents and densities
throughout the lift. Recommended compaction criteria for engineered fill materials are
as follows:
Minimum Percent
Material
(ASTM D698)
Scarified subgrade soils ...... :...°..............................................I...............95
On -site and imported fill soils'.".
Beneathfoundations..................................................................95
Beneathslabs............................................................................95
Beneathpavements...................................................................95
Aggregate base (beneath slabs)............................................................95
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Proposed Redtail Mixed Use Development
Cameron Park Second Filing
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Recommended preventative maintenance policies for asphalt and jointed concrete
pavements, based upon type and severity of distress, are provided. Prior to implementing
any maintenance, additional engineering observation is recommended to determine the type
and extent of preventative maintenance.
Earthwork
General Considerations
The following presents recommendations for site preparation, excavation, subgrade
fills on the
preparation and placement of engineered project.
All earthwork on the project should be observed and evaluated by Terracon. The
evaluation of earthwork should include observation and testing of engineered fill,
subgrade preparation, foundation bearing soils, and other geotechnical conditions
exposed during the construction of the project.
J Site Preparation
J Strip and remove debris, and other deleterious materials from proposed building and
pavement areas. All exposed surfaces should be free of mounds and depressions
that could prevent uniform compaction:.
The site should be initially graded Otreate a relatively level surface to receive fill,
and to provide for a relatively uniform thickness of fill beneath 'proposed building
structures.
All exposed areas which will receive fill, once properly cleared and benched where
necessary, should be scarified to a minimum depth of eight inches, conditioned to
near optimum moisture content, and compacted.
It is anticipated that excavations for the proposed construction can be accomplished
with conventional earthmoving equipment. However, deeper excavations penetrating
into the bedrock may require the use of heavy-duty equipment and/or drilling and
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blasting to advance the excavation.'�a''
Depending upon depth of excavation and seasonal conditions, groundwater will be
encountered in excavations on the site. Pumping from sumps may be utilized to
control water within excavations. Well points may be required for significant
groundwater flow, or where excavations penetrate groundwater to a significant depth.
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Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
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should be placed in maximum 3-inch lifts and should be compacted to a minimum of 92 to
96 % of Maximum Theoretical Density.
Where rigid pavements are used, the concrete should be obtained from an approved mix
design with the following minimum properties:
• Compressive Strength @ 28 days ........................................... 3500 psi minimum
• Strength Requirements.......................................................................ASTM C94
• Minimum Cement Content.........:............................................... 6.0 sacks/cu. yd.
• Cement Type ........................... :;;;.................................................Type I Portland
Entrained Air Content ..............:................. ::...::4 to 8%
• Concrete Aggregate......................................ASTM C33 and CDOT Section 703
Aggregate Size...........................................................................1 inch maximum
• Maximum Water Content.......................................................0.49 lb/lb of cement
Maximum Allowable Slump.....................................................................4 inches
Concrete should be deposited by truck mixers or agitators and placed a maximum of 90
minutes from the time the water is added to the mix. ' Other specifications outlined by the
Colorado Department of Transportation should be followed.
Longitudinal and transverse joints should be; provided as needed in concrete pavements for
expansion/contraction and isolation. The location and extent of joints should be based upon
the final pavement geometry and should' be placed (in feet) at roughly twice the slab
thickness (in inches) on center in either direction. Sawed joints should be cut within 24-
hours of concrete placement, and should be a minimum of 25% of slab thickness plus 1/4
inch. All joints should be sealed to prevent entry of foreign material and doweled where
necessary for load transfer.
_Preventative maintenance should be planned and provided for through an on -going
pavement management program in order to enhance future pavement performance.
Preventative maintenance activities are intended to slow the rate of pavement deterioration,
and to preserve the pavement investment.
Preventative maintenance consists of both "localized maintenance (e.g. crack sealing and
patching) and global maintenance (e.g. surface sealing). Preventative maintenance is
usually the first priority when implementing a planned pavement maintenance program and
provides the highest return on investment for pavements.
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Geotechnical Engineering Exploration
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
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Recommended Pavement Thicknesses (tncties) ' "
a
,
Traffic Ai ¢a
Alternative
P
4ggregate `
Portland
f
A
354
6
9'/2
Automobile
Parking
*B
2,F
3
5'/
C
5'/z
5'/�
A
4
7
11
Main Traffic
*B
3
3
6
Corridors
C
6
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*Due to the relatively plastic, cohesive subgrade soils, it is recommended that alternative A
and C be considered for this project. Terracon is providing a full -depth asphalt option for the
contractor's information only. The use of a granular aggregate base course enables a
stabilizing layer over a clay subgrade as well as acts as a capillary break should surface
water infiltrate beneath the pavement section and impact the clay subgrade soil$,,.
Each alternative should be investigated with respect to current material availability and
economic conditions. Rigid concrete pavement, a minimum of 6 inches in thickness, is
recommended at the location of dumpsters.,where trash trucks park and load.
Aggregate base course (if used on the site should consist of a blend of sand and gravel,
which meets strict specifications for quality and gradation. Use of materials meeting
Colorado Department of Transportation (CDOT) Class 5 or 6 specifications is recommended
for base course. Use of materials meeting Colorado Department of Transportation Class 1
specifications is recommended for select subbase.
Aggregate base course and select subbase should be placed in lifts not exceeding six
inches and should be compacted to a minimum of 95% Standard Proctor Density (ASTM
D698).
Asphalt concrete should be composed of.,a mixture of aggregate, filler and additives, if
required, and approved bituminous materl6(7'The bituminous base and/or asphalt concrete
should conform to approved mix designs stating the Hveem and/or SuperPave properties,
optimum asphalt content, job mix formula and recommended mixing and placing
temperatures. Aggregate used in plant -mixed bituminous base course and/or asphalt
concrete should meet particular gradations. Material meeting Colorado Department of
Transportation Grading S, SX or SG specification is recommended for asphalt concrete. Mix
designs should be submitted prior to construction to verify their adequacy. Asphalt material
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Geotechnical Engineering Exploration lrerracon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260 LT
The lateral earth pressures herein do not include any factor of safety and are not applicable
for submerged soils/hydrostatic loading. Additional recommendations may be necessary if
submerged conditions are to be included in the design.
Fill against grade beams and retaining walls should be compacted to densities specified in
Earthwork. High plasticity clay soils should not be used as backfill against retaining walls.
Compaction of each lift adjacent to walls should be accomplished with hand -operated
tampers or other lightweight compactors. Overcompaction may cause excessive lateral
earth pressures, which could result in wall movement.
Pavement Design and Construction
Design of pavements for the project have been based on the procedures outlined in the
J 1993 Guideline for Design of Pavement Structures by the American Association of State
Highway and Transportation Officials (AASHTO). Areas within proposed pavements on the
site will be divided into two categories based -upon anticipated traffic and usage.
7 Traffic criteria provided for pavement thickness designs are estimated by Terracon based on
similar projects and are to include single 18-kip equivalent single axle loads (ESAL's) of
51,100 for automobile parking, and 146,000 for heavy volume and/or truck access areas.
Local drainage characteristics of proposed pavement areas are considered to vary from fair
to good depending upon location on the site. For purposes of this design analysis, fair
�j drainage characteristics are considered to control the design. These characteristics,
J coupled with the approximate duration of saturated subgrade conditions, result in a design
drainage coefficient of 1.0 when applying the AASHTO criteria for design.
For flexible pavement design, a terminal serviceability index of 2.0 was utilized along with an
inherent reliability of 70%, and a design life of 20 years. Using an estimated design R-value
estimated at 10 based on the group index/soil classification values, appropriate ESAL/day,
environmental criteria and other factors, the structural numbers (SN) of the pavement
sections were determined on the basis of the 1993 AASHTO design equation.
In addition to the flexible pavement design analyses, a rigid pavement design analysis was
completed, based upon AASHTO design procedures.. Rigid pavement design is based on
an evaluation of the Modulus of Subgrade.:Reaction of the soils (K-value), the Modulus of
Rupture of the concrete, and other factors previously outlined. The design K-value of 100
for the subgrade soil was determined by : correlation to the laboratory tests results. A
modulus of rupture of 650 psi (working stress 488 psi) was used for pavement concrete.
The rigid pavement thicknesses for each traffic category were determined on the basis of
the AASHTO design equation.
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Geotechnical Engineering Exploration lferacon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
• If moisture sensitive floor coverings are used on interior slabs, consideration
should be given to the use of barriers to minimize potential vapor rise through
the slab.
• Floor slabs should not be constructed on frozen subgrade.
• Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1 R are recommended.
Lateral Earth Pressures
For soils above any free water surface,.'.. recommended equivalent fluid pressures for
unrestrained foundation elements are:
• Active:
Cohesive soil backfill (on -site or imported clays)....................45 psf/ft
Compacted granular backfill (on -site or imported sands) .......35 psf/ft
On -site bedrock materials .......................... not recommended for use
• Passive:
Cohesive soil backfill (on -site or imported clays)..................250 psf/ft
Compacted granular backfill (on -site or imported sands) ..... 350 psf/ft
Undisturbed soils or bedrock.-: .............................................. 350 psf/ft
• Coefficient of Base Friction..' .................................................. 0.35"
• Adhesion at Base of Footing ................................................... 500 psf
`The coefficient of base friction should be reduced to 0.30 when used in
conjunction with passive pressure
Where the design includes restrained elements, the following equivalent fluid pressures are
recommended:
• At rest:
Cohesive soil backfill (on-site:or imported clays) .................... 60 psf/ft
Compacted granular backfill (oh -site of imported sands) ....... 50 psf/ft
On -site bedrock materials .......................... not recommended for use
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Foundation excavations should be observed by the geotechnical engineer. If the soil
conditions encountered differ significantly from those presented in this report, supplemental
recommendations will be required.
Seismic Considerations
The project site is located in Seismic Risk Zone I of the Seismic Zone Map of the United
States as indicated by the 1997 Uniform Building Code. Based upon the nature of the
subsurface materials, a soil profile type Sc should be used for the design of structures for the
proposed project (1997 Uniform Building Code, Table No. 16-J).
Floor Slab Design and Construction
Some differential movement of a slab -on -grade floor system is possible should the subgrade
soils become elevated in moisture content. To reduce potential slab movements, the
subgrade soils should be prepared as outlined in the earthwork section of this report.
For structural design of concrete slabs -on -grade, a modulus of subgrade reaction of 100
pounds per cubic inch (pci) may be used for floors supported on existing or engineered fill
consisting of on -site soils. A modulus of 200 pci may be used for floors supported on at
least 2 feet of non -expansive structural fill meeting the.specifications outlined, below.... ,
Additional floor slab design and construction recommendations are as follows:
• Positive separations and/or isolation joints should be provided between slabs
and all foundations, columns-,,.' r,utility lines to allow independent movement.
• Control joints should be provided in slabs to control the location and extent of
cracking.
Interior trench backfill placed beneath slabs should be compacted in
accordance with recommended specifications outlined below.
In areas subjected to normal loading, a minimum 4-inch layer of sand, clean -
graded gravel or aggregate base course should be placed beneath interior
slabs. For heavy loading, reevaluation of slab and/or base course thickness
may be required.
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Geotechnical Engineering Exploration
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
• spread footings bearing on undisturbed natural
engineered fill.
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soils, sandstone bedrock and/or
Slab -on -grade construction is considered acceptable for use, provided that design and
construction recommendations are followed.
Foundation Systems
Due to the presence of low -to moderate swelling soils on the site, spread footing foundations
bearing. upon on -site . undisturbed subsoils and/or engineered fill . are recommended.., for
support for the proposed structure.
The spread footings to support the structure located in the vicinity of Test Boring No. 16
should bear on a minimum of 2-feet of engineered fill material and may be designed for a
maximum bearing pressure of 2,000 psf. T.he structure to be located in the vicinity of Test
Boring No. 19 should be supported by a spread footing foundation system designed for a
maximum bearing pressure of 1,500 psf. The remainder of the proposed structures should
be supported by spread footing foundations designed for a maximum bearing pressure of
2,000 psf. In addition, the footings for all of the structures should be sized to maintain a
minimum dead -load pressure of 500 psf. The design bearing pressure applies to dead loads
plus design live load conditions. The design bearing pressure may be increased by one-
third when considering total loads that include wind or seismic conditions.
Exterior footings should be placed a minimum of 30 inches below finished grade for frost
protection and to provide confinement for.the bearing soils. Finished grade is the lowest
adjacent grade for perimeter footings. It is afso recommended the bottom of the footings be
placed a minimum of 3-feet above maximumtanticipated groundwater levels.
Footings should be proportioned to reduce differential foundation movement. Proportioning
-on the basis of equal total movement is recommended; however, proportioning to relative
constant dead -load pressure will also reduce differential movement between adjacent
footings. Total movement resulting from the assumed structural loads is estimated to be on
the order of 1-inch or less. Differential movement should be on the order of 1/2 to 3/4 of the
estimated total settlement. Additional foundation movements could occur if water from any
source infiltrates the foundation soils; therefore, proper drainage should be provided in the
final design and during construction.
Footing foundations and masonry walls should be reinforced as necessary to reduce the
potential for distress caused by differential. foundation movement. The use of joints at
openings or other discontinuities in masonry -,,Walls is recommended.
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Geotechnical Engineering Exploration
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
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and 8. The surface layer encountered in the remaining test borings consisted of about 6-
inches of silty topsoil. Underlying the fill material and topsoil was the native, sandy lean clay
1.
and silty clayey sand with gravel extending; to the depths explored and/or bedrock below.
Sandstone bedrock was encountered at `approximate depths of 1-1/2 to 11-feet below
existing site grades in Test Boring Nos. 1 through 14 and 16 through 19, and extended to
the depths explored. Based on the surface elevation obtained at each test boring and the
estimated depth to bedrock encountered in each boring, we have included, in Appendix A, a
bedrock contour map, Figure 2, illustrating the bedrock profile.
The stratification boundaries shown on the enclosed boring logs represent the approximate
locations of changes in soil types; in -situ, the transition of materials may be gradual. The
soil profile for this portion of the site is generally consistent with the soil conditions presented
in our previous subsurface exploration report;
Field and Laboratory Test Results
Field and laboratory test results indicate the clays are soft to stiff in corisistericy, exhibit low -
to -moderate swell potential, and low to moderate load bearing characteristics. The granular
soils are medium dense in relative density, non -expansive and exhibit moderate bearing
characteristics. The sandstone bedrock is weathered to well -cemented, exhibits low swell
potential and moderate to high bearing characteristics.
Groundwater Conditions
Groundwater was encountered at approximate depths of 5 to 14-feet below existing site
grades in Test Boring Nos. 1, 2, 6 through:',.11, 13, and 15 through 19 when checked on
December 11, 2001. These observations'-
bservations represent groundwater conditions at the time of
the field exploration, and may not be indicative of other times, or at other locations.
Groundwater levels can be expected to fluctuate with varying seasonal and weather
conditions. The groundwater contour map for the site based on the piezometric data is
included with this report as Figure 3. The piezometric surface was estimated using linear
interpolations between test borings and was based upon groundwater elevations determined
on December 11, 2001. As illustrated from Figure 2, the groundwater flow was estimated to
be in the south to southeast directions.
ENGINEERING ANALYSES AND RECOMMENDATIONS
Geotechnical Considerations
The site appears suitable for the proposed construction based on a geotechnical
engineering viewpoint. The following foundation system was evaluated for use on the site:
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Geotechnical Engineering Exploration 1rerracon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
Laboratory Testing
All samples retrieved during the field exploration were returned to ,the laboratory for
observation by the project geotechnical engineer and were classified in accordance with the
Unified. Soil Classification System described in Appendix C. Samples of bedrock were.
classified in accordance with the general notes for Bedrock Classification. At that time, the
field descriptions were confirmed or modified as necessary and an applicable laboratory -
testing program was formulated to determine engineering properties of the subsurface
materials. Boring logs were prepared and are presented in Appendix A.
Laboratory tests were conducted on selected soil and bedrock samples and are presented in
Appendix B. The test results were used for the geotechnical engineering analyses, and the
development of foundation and earthwork recommendations. All laboratory tests were
performed in general accordance with the applicable ASTM, local or other accepted
standards.
Selected soil samples were tested for the following engineering properties:
• Water Content • Plasticity Index
• Dry Density • Water Soluble Sulfate Content
• Consolidation • Expansion
SITE CONDITIONS
The site for the proposed construction is presently a vacant tract of land situated in the west
and north portions within Cameron Park.. The west portion is vegetated with grasses and
weeds with occasional boulders on the surface, and exhibits positive surface drainage in the
south and east directions. Railroad tracks border the west portion to the west, detention
ponds to the northeast and north, a creek and trees to the east, and a vacant lot similar in
terrain lies to the south. The north portion of the site has gravel on the surface with sparse
grasses and weeds. The areas in the north portion generally drain in the south and east
directions. Existing commercial and residential structures lie to the north and to the east. A
pond is located to the south and east of Test Boring No. 1.
SUBSURFACE CONDITIONS
Soil Conditions
The subsurface soils at the site consisted ,of sandy lean clay fill material to depths of
approximately of 1-1/2 to 3-feet below existing site grades in Test Boring Nos.1 through 6
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Geotechnical Engineering Exploration Iferracon
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Terracon Project No. 20015260
PROPOSED CONSTRUCTION
J Based on information provided, we understand the proposed structures will be 8, 3 to 4-story
8-plex townhouse buildings, 2-carriage house buildings, and 4 detached garage structures,
.J having slab on grade construction, located on the western portion of the development and 9,
•J 2 to 3-story office buildings located on the northern portion of the development along with
associated paved drive and parking areas. The buildings are to be conventional wood -
framed structures with anticipated maximum wall and columns loads are estimated to be 1 to
4 klf and 10 to 75 kips, respectively.
SITE EXPLORATION
The scope of the services performed for this project included a site 'reconnaissance by a'
geotechnical engineer, a subsurface exploration program, laboratory testing and engineering
analyses.
Field Exploration
7 A total of 18 test borings were drilled on December 4 and 10, 2001. The test borings were
located within the proposed building footprints and drilled to approximate depths of 14 to 19
7 feet below existing site grades. One test boring was drilled per office and multi -family
building footprint. All borings were advanced with a truck -mounted drilling rig, utilizing 4-inch
diameter solid stem augers.
The borings were located in the field by pacing from property lines and/or existing site
features. Ground surface elevations at each boring location were obtained by
7 measurements with an engineer's level from a temporary bench mark (TBM) shown on the
Site Plan. The accuracy of boring locations and elevations should only be assumed to the
J level implied by the methods used.
Continuous lithologic logs of each boring were recorded by the geotechnical engineer during
the drilling operations. At selected intervals, samples of the subsurface materials were taken
by means of pushing thin -walled Shelby tubes, or by driving split -spoon samplers.
Penetration resistance measurements were obtained by driving the split -spoon into the
subsurface materials with a 140-pound hammer falling 30 inches. The penetration
resistance value is a useful index in estimating the consistency, relative density or hardness
—I of the materials encountered.
Groundwater conditions were evaluated in each boring at the time of site exploration and on
December 11, 2001.
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GEOTECHNICAL ENGINEERING REPORT
REDTAIL DEVELOPMENT
PROPOSED MIXED USE DEVELOPMENT
CAMERON PARK SECOND FILING
FORT COLLINS, COLORADO
TERRACON PROJECT NO. 20015260
DECEMBER 20, 2001
INTRODUCTION
This report contains the results of our geotechnical engineering exploration for the proposed
mixed use development to be located within the Cameron Park Development west of the
First Filing, in Fort Collins, Colorado. The site is located in the Southeast 1/4 of Section 2,
Township 6 North, Range 69 West of the 6th Principal Meridian.
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The purpose of these services is to provide information and geotechnical engineering
recommendations relative to:
• subsurface soil and bedrock conditions
• groundwater conditions
• foundation design and construction
• floor slab design and construction
• lateral earth pressures
• pavement design and construction
• earthwork
• drainage
The recommendations contained in this report are based upon the results of field and
laboratory testing, engineering analyses, and experience with similar soil conditions,
structures and our understanding of the proposed project.
PREVIOUS EXPLORATIONS
Terracon conducted a geotechnical exploration for Cameron Park First Filing in October
1995. For further information and findings thereof, please refer to our "Geotechnical
Engineering Report", dated November 13, 1995, Project No. 20955185.
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TABLE OF CONTENTS
Page No.
Letterof Transmittal ............................................................................................................. i
INTRODUCTION.................................................................................................................
1
PROPOSED CONSTRUCTION ................. .........................................................
............... 2
FieldExploration .............................. .......................................................................
2
LaboratoryTesting ... ...............................................................................................
3
SITECONDITIONS ..............................................................................................................
3
SoilConditions ........................................................................................................
Field and Laboratory Test Results ...........................................................................
3
4
GroundwaterConditions ..........................................................................................
4
ENGINEERING ANALYSES AND RECOMMENDATIONS .................................................
4
Geotechnical Considerations .....................................................................................
4
FoundationSystems ................................................................................................
5
SeismicConsiderations ...........................................................................................
6
Floor Slab Design and Construction ........................................................................
6
Lateral Earth Pressures ..................
......................... 7
Pavement Design and Construction ...................................................................
I ....... 8
Earthwork .......................................
General Considerations .....................................................................
I ......... 11
SitePreparation ...........................................................................
: ............... 11
JJ
Subgrade Preparation ...................................................................................
12
Fill Materials and Placement ........................................................................
12
Excavation and Trench Construction ...........................................................
13
Additional Design and Construction Considerations ................................................13
Exterior Slab Design and Construction ........................................................13
Underground Utility Systems ........................................................................
14
CorrosionProtection ....................................................................................
14
SurfaceDrainage .........................................................................................
14
GENERALCOMMENTS .....................................................................................................
14
II
I I
13,
Geotechnical Engineering Exploration
Proposed Redtail Mixed Use Development
Cameron Park Second Filing
Project No. 20016260
lrerracon
Based on the subsurface conditions encountered and the type on construction proposed, it
is recommended the structure be supported by conventional -type spread footings placed a
minimum of 3-feet above maximum anticipated groundwater levels. Slab -on -grade
construction is considered feasible at the site.,provided the recommendations set forth in the
report are followed.
We appreciate the opportunity to be of service to you on this phase of your project. If you
have any questions concerning this report, or if we may be of further service to you, please
do not hesitate to contact us.
Sincerely,
TERRACON
Gary L. Wilson, E.I.T.
Geotechnical Engineer
Copies to: (5) Addressee
Manager
J
December 20, 2001
Irerracon
301 N. Howes • P.O. Box 503
Fort Collins, Colorado 80521-0503
(970) 484-0359 Fax: (970) 484-0454
'j Lagunitas Companies
J 3944 JFK Parkway, Suite B200
Fort Collins, Colorado 80525
Attn: Mr. Jon Prouty
Re: Geotephinical Engineering Report
Redtail Development
Proposed Mixed Use Development
Cameron Park Second Filing
Fort Collins, Colorado
Terracon Project No. 20015260
Terracon has completed a geotechnical engineering exploration for the proposed mixed -use
development to be located within the Cameron Park Development west of the First Filing, in
Fort Collins, Colorado. This study was performed in general accordance with our Proposal
No. D2001397 dated November 13, 2001.
Terracon performed a geotechnical engineetirig exploration for the Cameron Park First Filing
in October of 1995. For further information and findings thereof, please refer to our
"Geotechnical Engineering Report" dated November 13, 1995, Project No. 20955185.
The results of our engineering study, including the boring location diagram, laboratory test
results, test boring records, and the geotechnical recommendations needed to aid in the
design and construction of foundations, pavements and other earth connected phases of
this project are attached.
The subsurface soils at the site consisted of sandy lean clay fill material to depths of
approximately 1-1/2 to 3-feet below existing site grades in Test Boring Nos.1 through 6 and
8. The surface layer in the remaining test borings consisted of about 6-inches of silty topsoil.
Underlying the fill material and/or topsoil was. the native, sandy lean clay and silty clayey.
sand with gravel extending to the depths explored and/or to the bedrock below. Sandstone
9 bedrock was encountered at approximate depths of 1-1/2 to 11-feet below existing site
grades in Test Boring Nos. 1 through 14 and 16 through 19, and extended to the depths
explored. Groundwater was encountered at approximate depths of 5 to 14-feet below
existing site grades in Test Boring Nos. 1, 2, 6 through 11, 13, and 15 through 19 when
checked on December 11, 2001.
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www.terracon.com - "'
GEOTECHNICAL ENGINEERING REPORT
REDTAIL DEVELOPMENT
PROPOSED MIXED USE DEVELOPMENT
CAMERON PARK SECOND FILING
FORT COLLINS, COLORADO
TERRACON PROJECT NO. 20015260
=R 2U, , -00
Prepared for:
LAGUNITAS :COMPANIES
3944 JFK PARKWAY, SUITE B200
FORT COLLINS, COLORADO 80525
ATTN: MR. JON PROUTY
Prepared by:
Terracon
301 North Howes Street
Fort Collins,."Colorado 80521
rerraco