HomeMy WebLinkAboutELEVATIONS CREDIT UNION - PDP - PDP160021 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGeotechnical Engineering Report
Elevations Credit Union
2025 South College Avenue
Fort Collins, Colorado
February 5, 2016
Terracon Project No. 20165011
Prepared for:
Elevations Credit Union
Boulder, Colorado
Prepared by:
Terracon Consultants, Inc.
Fort Collins, Colorado
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY ............................................................................................................ i
1.0 INTRODUCTION .............................................................................................................1
2.0 PROJECT INFORMATION .............................................................................................1
2.1 Project Description ...............................................................................................1
2.2 Site Location and Description...............................................................................2
3.0 SUBSURFACE CONDITIONS ........................................................................................2
3.1 Typical Subsurface Profile ...................................................................................2
3.2 Laboratory Testing ...............................................................................................3
3.3 Corrosion Protection (Water-Soluble Sulfates) .....................................................3
3.4 Groundwater ........................................................................................................3
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................4
4.1 Geotechnical Considerations ...............................................................................4
4.1.1 Existing, Undocumented Fill .....................................................................4
4.1.2 Shallow Groundwater ...............................................................................4
4.1.3 Expansive Soils ........................................................................................4
4.1.4 Foundation and Floor System Recommendations ....................................5
4.2 Earthwork.............................................................................................................5
4.2.1 Site Preparation ........................................................................................5
4.2.2 Demolition ................................................................................................6
4.2.3 Excavation ................................................................................................6
4.2.4 Subgrade Preparation ...............................................................................7
4.2.5 Fill Materials and Placement ......................................................................8
4.2.6 Compaction Requirements ........................................................................9
4.2.7 Utility Trench Backfill ................................................................................9
4.2.8 Grading and Drainage .............................................................................10
4.2.9 Exterior Slab Design and Construction ...................................................11
4.3 Foundations .......................................................................................................11
4.3.1 Helical Pile Foundations .........................................................................11
4.3.2 Piers Working in Group Action ................................................................12
4.3.3 Spread Footings - Design Recommendations .........................................13
4.3.4 Spread Footings - Construction Considerations ......................................14
4.4 Seismic Considerations......................................................................................14
4.5 Floor Systems ..............................................................................................15
4.5.1 Floor System - Design Recommendations ..............................................15
4.5.2 Floor Systems - Construction Considerations .........................................16
4.7 Lateral Earth Pressures .....................................................................................16
4.7 Pavements .........................................................................................................18
4.7.1 Pavements – Subgrade Preparation .......................................................18
4.7.2 Pavements – Design Recommendations ................................................18
4.7.3 Pavements – Construction Considerations .............................................20
4.7.4 Pavements – Maintenance .....................................................................21
5.0 GENERAL COMMENTS ...............................................................................................21
TABLE OF CONTENTS (continued)
Appendix A – FIELD EXPLORATION
Exhibit A-1 Site Location Map
Exhibit A-2 Exploration Plan
Exhibit A-3 Field Exploration Description
Exhibits A-4 and A-5 Boring Logs
Appendix B – LABORATORY TESTING
Exhibit B-1 Laboratory Testing Description
Exhibit B-2 Atterberg Limits Test Results
Exhibit B-3 Grain-size Distribution Test Results
Exhibit B-4 Consolidation Test Results
Exhibit B-5 Unconfined Compression Test Results
Appendix C – SUPPORTING DOCUMENTS
Exhibit C-1 General Notes
Exhibit C-2 Unified Soil Classification System
Exhibit C-3 Description of Rock Properties
Exhibit C-4 Laboratory Test Significance and Purpose
Exhibits C-5 and C-6 Report Terminology
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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EXECUTIVE SUMMARY
A geotechnical investigation has been performed for the proposed Elevations Credit Union to be
constructed at 2025 South College Avenue in Fort Collins, Colorado. Two (2) boring(s), presented
as Exhibits A-4 and A-5 and designated as Boring No. 1 and Boring No. 2, were performed to a depth
of approximately 29 feet below existing site grades. This report specifically addresses the
recommendations for the proposed structure. Borings performed in these areas are for informational
purposes and will be utilized by others.
Based on the information obtained from our subsurface exploration, the site can be developed for
the proposed project. However, the following geotechnical considerations were identified and will
need to be considered:
n Existing, undocumented fill was encountered in the borings performed on this site to depths
ranging from about 4 to 6 feet below existing site grades. The existing fill soils should be
removed and replaced with engineered fill beneath proposed foundations and floor slabs.
n Soft to medium stiff clay soils underlie the undocumented fill to depths of about 20 feet below
the existing site grade.
n Site soils (up to 14 feet) encountered in exploratory borings emitted a petroleum odor.
n We recommend constructing the proposed building on a deep foundation system using
helical piles advanced into the weathered sandstone bedrock. Helical piles offer the
added benefit of limiting site spoils and groundwater typically produced during
conventional drilled pier construction, both of which may be impacted with petroleum.
n As a higher risk foundation alternative, shallow footing foundations may be used to support
the proposed building provided the existing site soils are over-excavated to a depth of at least
2 feet below footing foundations and replaced with properly moisture conditioned,
compacted, imported, granular fill consisting of CDOT Class 1 Structure Backfill.
n A slab-on-grade floor system is recommended for the proposed building provided the soils
are over-excavated to a depth of at least 2 feet below the bottom of the proposed floor slab
and replaced with properly moisture conditioned, compacted fill. On-site soils may be reused
as over-excavation backfill below floor slabs, however, we recommend placing imported
granular fill as the upper 1 foot of over-excavation backfill below floor slabs.
n The 2012 International Building Code, Table 1613.5.2 IBC seismic site classification for this
site is D.
n Close monitoring of the construction operations discussed herein will be critical in achieving
the design subgrade support. We therefore recommend that Terracon be retained to
monitor this portion of the work.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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This summary should be used in conjunction with the entire report for design purposes. It should
be recognized that details were not included or fully developed in this section, and the report must
be read in its entirety for a comprehensive understanding of the items contained herein. The section
titled GENERAL COMMENTS should be read for an understanding of the report limitations.
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GEOTECHNICAL ENGINEERING REPORT
Elevations Credit Union
2025 South College Avenue
Fort Collins, Colorado
Terracon Project No. 20165011
February 5, 2016
1.0 INTRODUCTION
This report presents the results of our geotechnical engineering services performed for the
proposed Elevations Credit Union to be located at 2025 South College Avenue in Fort Collins,
Colorado. The purpose of these services is to provide information and geotechnical engineering
recommendations relative to:
n subsurface soil and bedrock conditions n foundation design and construction
n groundwater conditions n floor slab design and construction
n grading and drainage n pavement construction
n lateral earth pressures n earthwork
n seismic considerations
Our geotechnical engineering scope of work for this project included advancing two test borings
to depths of approximately 29 feet below existing site grades, laboratory testing for soil
engineering properties and engineering analyses to provide foundation, floor system and
pavement design and construction recommendations.
Logs of the borings along with an Exploration Plan (Exhibit A-2) are included in Appendix A. The
results of the laboratory testing performed on soil samples obtained from the site during the field
exploration are included in Appendix B.
2.0 PROJECT INFORMATION
2.1 Project Description
Item Description
Site layout Refer to the Exploration Plan (Exhibit A-2 in Appendix A)
Structures Single-story masonry building with access drives and parking areas.
Maximum loads (provided)
Building:
Interior Gravity Column Load – 120 kips
Continuous Non-Bearing Wall Loads – 1.5 klf
Continuous Load-Bearing Wall Loads – up to 3.5 klf
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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Item Description
Traffic loading
NAPA Traffic Class:
Automobile Parking Areas: <Class I>
Truck traffic and main drives <Class II>
2.2 Site Location and Description
Item Description
Location The project site is located at 2025 South College Avenue in Fort
Collins, Colorado.
Existing site features Infrastructure related to the now defunct One Stop Gas Station.
Surrounding developments
North: Dog Pawlour retail space
East: College Avenue
West: Residential neighborhood
South: Sherwood Lateral Ditch
Current ground cover Asphalt, concrete, and landscaping
Existing topography The site slopes north/northeast.
3.0 SUBSURFACE CONDITIONS
3.1 Typical Subsurface Profile
Specific conditions encountered at each boring location are indicated on the individual boring logs
included in Appendix A. Stratification boundaries on the boring logs represent the approximate
location of changes in soil types; in-situ, the transition between materials may be gradual. Based
on the results of the borings, subsurface conditions on the project site can be generalized as
follows:
Material Description Approximate Depth to
Bottom of Stratum (feet) Consistency/Density/Hardness
Fill materials consisting of lean clay,
sand, and gravel
About 6 feet below existing site
grades.
Sandy Lean Clay / Clayey Sand About 20 to 24 feet below
existing site grades.
Soft to medium stiff / very loose
Gravel About 21 to 25 feet below
existing site grades Medium dense
Weathered Sandstone/Sandstone
Bedrock
To the maximum depth of
exploration of about 29 to 30.5
feet.
Firm to very hard
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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3.2 Laboratory Testing
A representative soil sample was selected for swell-consolidation testing and exhibited 1.6
percent compression when wetted. The sandstone bedrock is also considered to have low
expansive potential or non-expansive. A sample of clay soil exhibited unconfined compressive
strength of approximately 1,180 pounds per square foot (psf). Samples of site soils selected for
plasticity testing exhibited low to moderate plasticity with liquid limits ranging from 28 to 45 and
plasticity indices ranging from 10 to 27. Laboratory test results are presented in Appendix B.
3.3 Corrosion Protection (Water-Soluble Sulfates)
At the time this report was prepared, the laboratory testing for water-soluble sulfates had not been
completed. We will submit a supplemental letter with the testing results and recommendations
once the testing has been completed.
3.4 Groundwater
The boreholes were observed while drilling and after completion for the presence and level of
groundwater. The water levels observed in the boreholes are noted on the attached boring logs,
and are summarized below:
Boring Number Depth to groundwater while
drilling, ft.
Groundwater elevation
immediately after drilling, ft.
1 19 4974.0
2 17 4977.8
These observations 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, and other factors. The possibility of
groundwater fluctuations should be considered when developing design and construction plans
for the project.
Groundwater level fluctuations occur due to seasonal variations in the water levels present in the
Spring Creek, amount of rainfall, runoff and other factors not evident at the time the borings
was/were performed. Therefore, groundwater levels during construction or at other times in the
life of the structure may be higher or lower than the levels indicated on the boring logs. The
possibility of groundwater level fluctuations should be considered when developing the design
and construction plans for the project.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION
4.1 Geotechnical Considerations
Based on subsurface conditions encountered in the borings, the site appears suitable for the
proposed construction from a geotechnical point of view provided certain precautions and design
and construction recommendations described in this report are followed. We have identified
geotechnical conditions that could impact design and construction of the proposed structures,
pavements, and other site improvements.
4.1.1 Existing, Undocumented Fill
As previously noted, existing undocumented fill was encountered to depths up to about 6 feet in
the borings drilled at the site. We do not possess any information regarding whether the fill was
placed under the observation of a geotechnical engineer.
Support of foundations, floor slabs, and pavements on or above existing fill soils is discussed in
this report. There is an inherent risk for the owner that compressible fill or unsuitable material
within or buried by the fill will not be discovered. This risk of unforeseen conditions cannot be
eliminated without completely removing the existing fill, but can be reduced by performing
additional testing and evaluation. Unless there is significant, irrefutable evidence indicating the fill
was properly placed and compacted, we recommend completely removing and replacing the fil
below the proposed building.
4.1.2 Shallow Groundwater
As previously stated, groundwater was measured at depths ranging from about 17 to 19 feet
below existing site grades. Terracon recommends maintaining a separation of at least 3 feet
between the bottom of proposed below-grade foundations and measured groundwater levels. It
is also possible and likely that groundwater levels below this site may rise as water levels in Spring
Creek rise.
4.1.3 Expansive Soils
Laboratory testing indicates the native clay soils did not exhibit expansive potential at the samples
in-situ moisture content. However, it is our opinion these materials will exhibit a higher expansive
potential if the clays undergo a significant loss of moisture.
This report provides recommendations to help mitigate the effects of soil shrinkage and
expansion. However, even if these procedures are followed, some movement and cracking in
the structures, pavements, and flatwork should be anticipated. The severity of cracking and other
damage such as uneven floor slabs will probably increase if any modification of the site results in
excessive wetting or drying of the expansive clays. Eliminating the risk of movement and distress
is generally not feasible, but it may be possible to further reduce the risk of movement if
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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significantly more expensive measures are used during construction. It is imperative the
recommendations described in section 4.2.8 Grading and Drainage of this report be followed to
reduce movement.
4.1.4 Foundation and Floor System Recommendations
The proposed building may be supported on helical pile foundations advanced into bedrock.
Helical piles offer the added benefit of limiting site spoils and groundwater typically produced
during conventional drilled pier construction, both of which may be impacted with petroleum. The
helical piles will be founded on weathered sandstone bedrock and will avoid constructing the
foundation system on clayey soils.
As a higher risk foundation alternative, shallow footing foundations may be used to support the
proposed building provided the existing site soils are over-excavated to a depth of at least 2 feet
below footing foundations and replaced with properly moisture conditioned, compacted, imported,
granular fill consisting of CDOT Class 1 Structure Backfill.
In addition, we recommend a slab-on-grade for the interior floor system of the proposed building,
provided the soils are over-excavated to a depth of at least 2 feet below the bottom of the proposed
floor slab and replaced with properly moisture conditioned, compacted fill. On-site soils may be
reused as over-excavation backfill below floor slabs, however, we recommend placing imported
granular fill as the upper 1 foot of over-excavation backfill below floor slabs. Even when bearing on
properly prepared soils, movement of the slab-on-grade floor system is possible should the
subgrade soils undergo an increase in moisture content. We estimate movement of about 1 inch
is possible. If the owner cannot accept the risk of slab movement, a structural floor should be
used.
4.2 Earthwork
The following presents recommendations for site preparation, demolition, excavation, subgrade
preparation and placement of engineered fills on the project. All earthwork on the project should
be observed and evaluated by Terracon on a full-time basis. The evaluation of earthwork should
include observation of over-excavation operations, testing of engineered fills, subgrade
preparation, subgrade stabilization, and other geotechnical conditions exposed during the
construction of the project. Terracon should also be retained to assist the earthwork contractor
with delineating the extent and location of existing fill materials during soil removal and
recompaction below the building.
4.2.1 Site Preparation
Prior to placing any fill, strip and remove existing vegetation (if any), the existing asphalt pavement,
and any other deleterious materials from the proposed construction area.
Stripped organic materials should be wasted from the site or used to re-vegetate landscaped areas
after completion of grading operations. Prior to the placement of fills, the site should be graded to
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill
beneath proposed structures.
4.2.2 Demolition
Demolition of the existing One Stop Gas Station should include complete removal of all foundation
systems, below-grade structural elements, pavements, and exterior flat work within the proposed
construction area. This should include removal of any utilities to be abandoned along with any loose
utility trench backfill or loose backfill found adjacent to existing foundations. All materials derived
from the demolition of existing structures and pavements should be removed from the site. The
types of foundation systems supporting the existing One Stop Gas Station are not known. If some
or all of the existing buildings are supported by drilled piers, the existing piers should be truncated
a minimum depth of 3 feet below areas of planned new construction.
Consideration could be given to re-using the asphalt and concrete provided the materials are
processed and uniformly blended with the on-site soils. Asphalt and/or concrete materials should
be processed to a maximum size of 2 inches and blended at a ratio of 30 percent asphalt/concrete
to 70 percent of on-site soils.
4.2.3 Excavation
It is anticipated that excavations for the proposed construction can be accomplished with
conventional earthmoving equipment. Excavations into the on-site soils may encounter weak soils
prone to caving.
The soils to be excavated can vary significantly across the site as their classifications are based
solely on the materials 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.
Based on the previous use of the site as a gas station, underground facilities such as septic tanks,
vaults, basements, and utilities could be encountered during construction. If unexpected fills or
underground facilities are encountered, such features should be removed and the excavation
thoroughly cleaned prior to backfill placement and/or construction.
Any existing building foundations that are exposed during the excavation of the existing fill or for the
new foundation excavations should be examined and evaluated by Terracon to determine the need
for any shoring or underpinning. Excavations should not extend into the stress influence zone of
the existing foundations without prior evaluation by Terracon. The stress influence zone is defined
as the area below a line projected down at a 1(h) to 1(v) slope from the bottom edge of the existing
foundation. Excavations within the influence zone of existing foundations can result in loss of
support, and can create settlement or failure of the existing foundations. While the evaluation of
existing foundations and the design of a shoring system are beyond the scope of this study, we can
perform these tasks as a separate study.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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Depending upon depth of excavation and seasonal conditions, surface water infiltration and/or
groundwater may be encountered in excavations on the site. It is anticipated that pumping from
sumps may be utilized to control water within excavations.
The subgrade soil conditions should be evaluated during the excavation process and the stability
of the soils determined at that time by the contractors’ Competent Person. Slope inclinations flatter
than the OSHA maximum values may have to be used. 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 federal regulations, including current OSHA
excavation and trench safety standards.
As a safety measure, it is recommended that all vehicles and soil piles be kept a minimum lateral
distance from the crest of the slope equal to the slope height. The exposed slope face should be
protected against the elements
4.2.4 Subgrade Preparation
After the undocumented existing fill and other deleterious materials have been removed from the
construction area, the top 8 inches of the exposed ground surface should be scarified, moisture
conditioned, and recompacted to at least 95 percent of the maximum dry unit weight as
determined by ASTM D698 before any new fill or foundation or pavement is placed.
After the bottom of the excavation has been compacted, engineered fill can be placed to bring the
building pad and pavement subgrade to the desired grade. Engineered fill should be placed in
accordance with the recommendations presented in subsequent sections of this report.
Engineered fill should extend below proposed footings a depth equal to the width of wall footings,
and a depth equal to one-half the width of column footings; however, a minimum of two feet of
engineered fill is recommended below, and adjacent to the edges of all footings. The engineered
fill should extend laterally an additional distance of 8 inches for each additional foot of excavation
beyond the 24-inch minimum depth. If engineered fill is placed beneath the entire building, it
should extend horizontally a minimum distance of 3 feet beyond the outside edge of perimeter
footings.
The stability of the subgrade may be affected by precipitation, repetitive construction traffic or
other factors. If unstable conditions develop, workability may be improved by scarifying and
drying. Alternatively, over-excavation of wet zones and replacement with granular materials may
be used, or crushed gravel and/or rock can be tracked or “crowded” into the unstable surface soil
until a stable working surface is attained. Use of fly ash or geotextiles could also be considered
as a stabilization technique. Laboratory evaluation is recommended to determine the effect of
chemical stabilization on subgrade soils prior to construction. Lightweight excavation equipment
may also be used to reduce subgrade pumping.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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4.2.5 Fill Materials and Placement
The on-site soils or approved granular and low plasticity cohesive imported materials may be used
as fill material. The following two tables list the material properties for suitable granular structure
backfill and imported fills. The soil removed from this site that is free of organic or objectionable
materials, as defined by a field technician who is qualified in soil material identification and
compaction procedures, can be re-used as fill for the building pad and pavement subgrade. It
should be noted that on-site soils will require reworking to adjust the moisture content to meet the
compaction criteria.
CDOT Class 1 structure backfill should meet the following material property requirements:
Gradation Percent finer by weight (ASTM C136)
2” 100
No. 4 Sieve 30-100
No.50 Sieve 10-60
No. 200 Sieve 5-20
Soil Properties Value
Liquid Limit 35 (max.)
Plastic Limit 6 (max.)
Imported soils (if required) should meet the following material property requirements:
Gradation Percent finer by weight (ASTM C136)
4” 100
3” 70-100
No. 4 Sieve 50-100
No. 200 Sieve 5-50
Soil Properties Value
Liquid Limit 35 (max.)
Plastic Limit 15 (max.)
Maximum Expansive Potential (%) Non-expansive1
1. Measured on a sample compacted to approximately 95 percent of the maximum dry unit weight as
determined by ASTM D698 at optimum moisture content. The sample is confined under a 100 psf
surcharge and submerged.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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4.2.6 Compaction Requirements
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.
Item Description
Fill lift thickness
9 inches or less in loose thickness when heavy, self-
propelled compaction equipment is used
4 to 6 inches in loose thickness when hand-guided
equipment (i.e. jumping jack or plate compactor) is used
Minimum compaction requirements
Fills less than 8 feet: 95 percent of the maximum dry unit
weight as determined by ASTM D698
Fills greater than 8 feet: 98 percent of the maximum dry
unit weight as determined by ASTM D698
Moisture content cohesive soil (clay) -1 to +3 % of the optimum moisture content
Moisture content cohesionless soil
(sand) -3 to +2 % of the optimum moisture content
1. We recommend engineered fill be tested for moisture content and compaction during placement.
Should the results of the in-place density tests indicate the specified moisture or compaction limits
have not been met, the area represented by the test should be reworked and retested as required
until the specified moisture and compaction requirements are achieved.
2. Specifically, moisture levels should be maintained low enough to allow for satisfactory compaction
to be achieved without the fill material pumping when proofrolled.
3. Moisture conditioned clay materials should not be allowed to dry out. A loss of moisture within these
materials could result in an increase in the material’s expansive potential. Subsequent wetting of
these materials could result in undesirable movement.
4. We recommend increasing the compactive effort for any fill placement greater than 8 feet to 98
percent of the maximum dry unit weight as determined by ASTM D698.
4.2.7 Utility Trench Backfill
All trench excavations should be made with sufficient working space to permit construction including
backfill placement and compaction.
All underground piping within or near the proposed structure should be designed with flexible
couplings, so minor deviations in alignment do not result in breakage or distress. Utility knockouts
in foundation walls (if implemented) should be oversized to accommodate differential movements.
It is imperative that utility trenches be properly backfilled with relatively clean materials. If utility
trenches are backfilled with relatively clean granular material, they should be capped with at least
18 inches of cohesive fill in non-pavement areas to reduce the infiltration and conveyance of surface
water through the trench backfill.
Utility trenches are a common source of water infiltration and migration. All utility trenches that
penetrate beneath the building should be effectively sealed to restrict water intrusion and flow
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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through the trenches that could migrate below the building. We recommend constructing an
effective clay “trench plug” that extends at least 5 feet out from the face of the building exterior. The
plug material should consist of clay compacted at a water content at or above the soil’s optimum
water content. The clay fill should be placed to completely surround the utility line and be compacted
in accordance with recommendations in this report.
It is strongly recommended that a representative of Terracon provide full-time observation and
compaction testing of trench backfill within building and pavement areas.
4.2.8 Grading and Drainage
All grades must be adjusted to provide effective drainage away from the proposed building during
construction and maintained throughout the life of the proposed project. Infiltration of water into
foundation excavations must be prevented during construction. Landscape irrigation adjacent to
foundations should be minimized or eliminated. Water permitted to pond near or adjacent to the
perimeter of the structure (either during or post-construction) can result in significantly higher soil
movements than those discussed in this report. As a result, any estimations of potential
movement described in this report cannot be relied upon if positive drainage is not obtained and
maintained, and water is allowed to infiltrate the fill and/or subgrade.
Exposed ground (if any) should be sloped at a minimum of 10 percent grade for at least 10 feet
beyond the perimeter of the proposed building, where possible. The use of swales, chases and/or
area drains may be required to facilitate drainage in unpaved areas around the perimeter of the
building. Backfill against foundations and exterior walls should be properly compacted and free of
all construction debris to reduce the possibility of moisture infiltration. After construction of the
proposed building and prior to project completion, we recommend verification of final grading be
performed to document positive drainage, as described above, has been achieved.
Flatwork and pavements will be subject to post-construction movement. Maximum grades
practical should be used for paving and flatwork to prevent areas where water can pond. In
addition, allowances in final grades should take into consideration post-construction movement
of flatwork, particularly if such movement would be critical. Where paving or flatwork abuts the
structure, care should be taken that joints are properly sealed and maintained to prevent the
infiltration of surface water.
Planters located adjacent to structure should preferably be self-contained. Sprinkler mains and
spray heads should be located a minimum of 5 feet away from the building line(s). Low-volume,
drip style landscaped irrigation should not be used near the building. Roof drains should
discharge on to pavements or be extended away from the structure a minimum of 10 feet through
the use of splash blocks or downspout extensions. A preferred alternative is to have the roof
drains discharge by solid pipe to storm sewers or to a detention pond or other appropriate outfall.
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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4.2.9 Exterior Slab Design and Construction
Exterior slabs on-grade, exterior architectural features, and utilities founded on, or in backfill or
the site soils will likely experience some movement due to the volume change of the material.
Potential movement could be reduced by:
n Minimizing moisture increases in the backfill;
n Controlling moisture-density during placement of the backfill;
n Using designs which allow vertical movement between the exterior features and
adjoining structural elements; and
n Placing control joints on relatively close centers.
4.3 Foundations
Terracon recommends constructing the Elevations Credit Union building on a deep foundation
system using helical piles. Helical piles would limit site spoils and avoid bearing on soft clay soils.
As a higher risk alternative, a conventional spread footing foundation system could be used provided
the existing site soils are over-excavated to a depth of at least 2 feet below footing foundations and
replaced with properly moisture conditioned, compacted, imported, granular fill consisting of CDOT
Class 1 Structure Backfill.. Design recommendations for foundations for the proposed structure
and related structural elements are presented in the following paragraphs. Additional deep
foundation recommendations (drilled piers, micropiles, etc.) can be provided on request.
4.3.1 Helical Pile Foundations
Terracon recommends helical piles bottomed in the weathered sandstone bedrock to be
appropriate for supporting the proposed building. Design recommendations for helical pile
foundations and related structural elements are presented in the following paragraphs.
Description Value
Bearing material Sandstone bedrock (weathered)
Anticipated pile length About 25 to 30 feet from existing grade
Net allowable end-bearing pressure 1 15,000 psf
Individual pile settlement About ½ inch
Void thickness (between piles and below pile
caps) 4 inches
1. 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.
We do not recommend using vertically installed helical piles to resist lateral loads without
approved lateral load test data, as these types of foundations are typically designed to resist axial
loads. Only the horizontal component of the allowable axial load should be considered to resist
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
Responsive ■ Resourceful ■ Reliable 12
the lateral loading and only in the direction of the batter. Terracon should be retained to observe
helical pile installation to verify that proper bearing materials have been encountered during
installation.
If a helical pile foundation system is selected by the project team, we recommend the helical pile
designer follow the recommendations presented in Chapter 18 of the 2009/2012 International
Building Code (IBC). We recommend the helical bearing plates for each helical pile bear in the
claystone bedrock encountered below the site. We do not recommend helical bearing plates
bottomed in native clay soils. The helical pile designer should select the size and number of helical
bearing plates for each helical pile based on planned loads and bearing materials described in our
exploratory boring logs. Torque measurements during installation of helical piles should be used to
verify the axial capacity of the helical piles. We recommend the helical pile installation contractor
provide confirmation that the installation equipment has been calibrated within one year of
installation at this project. The helical foundations should be installed per the manufacturer’s
recommendations.
To satisfy forces in the horizontal direction using LPILE, piers may be designed for the following
lateral load criteria:
Parameters Clay Sand and
Gravel
Sandstone
Bedrock
LPILE soil type1
Stiff clay
without free
water
Sand
(submerged)
Stiff clay
without free
water
Unit weight (pcf) 120 125 130
Average undrained shear strength (psf) 500 N/A 9,000
Average angle of internal friction, F (degrees) N/A 35 N/A
Coefficient of subgrade reaction, k (pci)*
100 - static
30 - cyclic
60
2,000- static
800 – cyclic
Strain, e50 (%) 0.010 N/A 0.004
1. For purposes of LPILE analysis, assume a groundwater depth of about 15 feet below existing
ground surface (approximately Elev. 4976 feet).
4.3.2 Piers Working in Group Action
Terracon recommends that helical piles should be considered to work in group action if the
horizontal spacing is less than three pile diameters (largest helical bearing-plate diameter) and
this minimum practical horizontal clear spacing between piles of at least three diameters should
be maintained.
Geotechnical Engineering Report
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4.3.3 Spread Footings - Design Recommendations
Description Value
Bearing material At least 2 feet of properly placed CDOT Class 1
Structure Backfill
Maximum allowable bearing pressure 1 Lean clay: 1,500 psf
Lateral earth pressure coefficients 2
Lean clay:
Active, Ka = 0.41
Passive, Kp = 2.46
At-rest, Ko = 0.58
Granular soil:
Active, Ka = 0.27
Passive, Kp = 3.69
At-rest, Ko = 0.43
Sliding coefficient 2 Granular soil:
µ = 0.56
Moist soil unit weight
Lean clay:
ɣ = 120 pcf
Granular soil:
ɣ = 130 pcf
Minimum embedment depth below finished
grade 3 30 inches
Estimated total movement 4 About 1 inch
Estimated differential movement 4 About ½ to ¾ of total movement
1. The recommended maximum allowable bearing pressure assumes any unsuitable fill or soft soils,
if encountered, will be over-excavated and replaced with properly compacted engineered fill. The
design bearing pressure applies to a dead load plus design live load condition. The design bearing
pressure may be increased by one-third when considering total loads that include wind or seismic
conditions.
2. The lateral earth pressure coefficients and sliding coefficients are ultimate values and do not
include a factor of safety. The foundation designer should include the appropriate factors of safety.
3. For frost protection and to reduce the effects of seasonal moisture variations in the subgrade soils.
The minimum embedment depth is for perimeter footings beneath unheated areas and is relative
to lowest adjacent finished grade, typically exterior grade.
4. The estimated movements presented above are based on the assumption that the maximum
footing size is 4 feet for column footings and 1.5 feet for continuous footings.
Footings should be proportioned to reduce differential foundation movement. As discussed, total
movement resulting from the assumed structural loads is estimated to be on the order of about 1
inch. 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
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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construction and throughout the life of the structure. Failure to maintain the proper drainage as
recommended in the 4.2.8 Grading and Drainage section of this report will nullify the movement
estimates provided above.
4.3.4 Spread Footings - Construction Considerations
To reduce the potential of “pumping” and softening of the soils at the base of the recommended
over-excavation and the requirement for corrective work, we suggest the excavation for the
proposed building be completed remotely with a track-hoe operating outside of the excavation
limits.
Spread footing construction should only be considered if the estimated foundation movement can
be tolerated. Subgrade soils beneath footings should be moisture conditioned and compacted as
described in the 4.2 Earthwork section of this report. The moisture content and compaction of
subgrade soils should be maintained until foundation construction.
Footings and foundation walls should be reinforced as necessary to reduce the potential for distress
caused by differential foundation movement.
Unstable subgrade conditions should be observed by Terracon to assess the subgrade and
provide suitable alternatives for stabilization. Stabilized areas should be proof-rolled prior to
continuing construction to assess the stability of the subgrade.
Foundation excavations should be observed by Terracon. If the soil conditions encountered differ
significantly from those presented in this report, supplemental recommendations will be required.
The structural fill should extend laterally an additional distance of 8 inches for each foot of over-
excavation. The soils should be replaced as engineered fill, conditioned to near optimum moisture
content and compacted.
4.4 Seismic Considerations
Code Used Site Classification
2012 International Building Code (IBC) 1 D 2
1. In general accordance with the 2012 International Building Code, Table 1613.5.2.
2. The 2012 International Building Code (IBC) requires a site soil profile determination extending a
depth of 100 feet for seismic site classification. The current scope requested does not include the
required 100 foot soil profile determination. The borings completed for this project extended to a
maximum depth of about 29 feet and this seismic site class definition considers that similar soil and
bedrock conditions exist below the maximum depth of the subsurface exploration. Additional
exploration to deeper depths could be performed to confirm the conditions below the current depth of
exploration. Alternatively, a geophysical exploration could be utilized in order to attempt to justify a
more favorable seismic site class.
Geotechnical Engineering Report
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4.5 Floor Systems
A slab-on-grade may be utilized for the interior floor system for the proposed control building
provided the native clay soils are over-excavated to a depth of at least 2 feet, moisture
conditioned, and compacted on-site soils. If the estimated movement cannot be tolerated, a
structurally-supported floor system, supported independent of the subgrade materials, is
recommended.
Subgrade soils beneath interior and exterior slabs and at the base of the over-excavation for
removal of existing fill should be scarified to a depth of at least 8 inches, moisture conditioned
and compacted. The moisture content and compaction of subgrade soils should be maintained
until slab construction.
4.5.1 Floor System - Design Recommendations
Even when bearing on properly prepared soils, movement of the slab-on-grade floor system is
possible should the subgrade soils undergo an increase in moisture content. We estimate
movement of about 1 inch is possible. If the owner cannot accept the risk of slab movement, a
structural floor should be used. If conventional slab-on-grade is utilized, the subgrade soils should
be over-excavated and prepared as presented in the 4.2 Earthwork section of this report.
For structural design of concrete slabs-on-grade subjected to point loadings, a modulus of
subgrade reaction of 150 pounds per cubic inch (pci) may be used for floors supported on the
recommended over-excavation backfill.
Additional floor slab design and construction recommendations are as follows:
n Positive separations and/or isolation joints should be provided between slabs and all
foundations, columns, or utility lines to allow independent movement.
n Control joints should be saw-cut in slabs in accordance with ACI Design Manual, Section
302.1R-37 8.3.12 (tooled control joints are not recommended) to control the location and
extent of cracking.
n Interior utility trench backfill placed beneath slabs should be compacted in accordance
with the recommendations presented in the 4.2 Earthwork section of this report.
n Floor slabs should not be constructed on frozen subgrade.
n A minimum 1½-inch void space should be constructed below non-bearing partition walls
placed on the floor slab. Special framing details should be provided at doorjambs and
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
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frames within partition walls to avoid potential distortion. Partition walls should be
isolated from suspended ceilings.
n The use of a vapor retarder should be considered beneath concrete slabs that will be
covered with wood, tile, carpet or other moisture sensitive or impervious floor coverings,
or when the slab will support equipment sensitive to moisture. When conditions warrant
the use of a vapor retarder, the slab designer and slab contractor should refer to ACI
302 for procedures and cautions regarding the use and placement of a vapor retarder.
n Other design and construction considerations, as outlined in the ACI Design Manual,
Section 302.1R are recommended.
4.5.2 Floor Systems - Construction Considerations
Movements of slabs-on-grade using the recommendations discussed in previous sections of this
report will likely be reduced and tend to be more uniform. The estimates discussed above assume
that the other recommendations in this report are followed. Additional movement could occur
should the subsurface soils become wetted to significant depths, which could result in potential
excessive movement causing uneven floor slabs and severe cracking. This could be due to over
watering of landscaping, poor drainage, improperly functioning drain systems, and/or broken utility
lines. Therefore, it is imperative that the recommendations presented in this report be followed.
4.7 Lateral Earth Pressures
Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed
for earth pressures at least equal to those indicated in the following table. Earth pressures will be
influenced by structural design of the walls, conditions of wall restraint, methods of construction
and/or compaction and the strength of the materials being restrained. Two wall restraint
conditions are shown. Active earth pressure is commonly used for design of free-standing
cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall
movement. The recommended design lateral earth pressures do not include a factor of safety
and do not provide for possible hydrostatic pressure on the walls.
Geotechnical Engineering Report
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EARTH PRESSURE COEFFICIENTS
Earth Pressure
Conditions
Coefficient for
Backfill Type
Equivalent Fluid
Density (pcf)
Surcharge
Pressure,
p1 (psf)
Earth
Pressure,
p2 (psf)
Active (Ka)
Imported Fill - 0.27
Lean Clay - 0.41
35
49
(0.27)S
(0.41)S
(35)H
(49)H
At-Rest (Ko)
Imported Fill - 0.43
Lean Clay - 0.58
56
70
(0.43)S
(0.58)S
(56)H
(70)H
Passive (Kp)
Imported Fill - 3.69
Lean Clay - 2.46
480
295
---
---
---
---
Applicable conditions to the above include:
n For active earth pressure, wall must rotate about base, with top lateral movements of about
0.002 H to 0.004 H, where H is wall height;
n For passive earth pressure to develop, wall must move horizontally to mobilize resistance;
n Uniform surcharge, where S is surcharge pressure;
n In-situ soil backfill weight a maximum of 120 pcf;
n Horizontal backfill, compacted between 95 and 98 percent of maximum dry unit weight as
determined by ASTM D698;
n Loading from heavy compaction equipment not included;
n No hydrostatic pressures acting on wall;
n No dynamic loading;
n No safety factor included in soil parameters; and
n Ignore passive pressure in frost zone.
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To control hydrostatic pressure behind the wall we recommend that a drain be installed at the
foundation wall with a collection pipe leading to a reliable discharge. If this is not possible, then
combined hydrostatic and lateral earth pressures should be calculated for lean clay backfill using
an equivalent fluid weighing 90 and 100 pcf for active and at-rest conditions, respectively. For
granular backfill, an equivalent fluid weighing 85 and 90 pcf should be used for active and at-rest,
respectively. These pressures do not include the influence of surcharge, equipment or floor
loading, which should be added. Heavy equipment should not operate within a distance closer
than the exposed height of retaining walls to prevent lateral pressures more than those provided.
4.7 Pavements
4.7.1 Pavements – Subgrade Preparation
On most project sites, the site grading is accomplished relatively early in the construction phase.
Fills are typically placed and compacted in a uniform manner. However as construction proceeds,
the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or
rainfall/snow melt. As a result, the pavement subgrade may not be suitable for pavement
construction and corrective action will be required. Additionally, existing undocumented fill was
encountered on this site that may not provide adequate support for new pavements. The
subgrade should be carefully evaluated at the time of pavement construction for signs of
disturbance or instability. We recommend the pavement subgrade be thoroughly proofrolled with
a loaded tandem-axle dump truck prior to final grading and paving. All pavement areas should
be moisture conditioned and properly compacted to the recommendations in this report
immediately prior to paving.
4.7.2 Pavements – Design Recommendations
Design of new privately-maintained pavements for the project has been based on the procedures
described by the National Asphalt Pavement Associations (NAPA) and the American Concrete
Institute (ACI).
We assumed the following design parameters for NAPA flexible pavement thickness design:
n Automobile Parking Areas
· Class I - Parking stalls and parking lots for cars and pick-up trucks, with
Equivalent Single Axle Load (ESAL) up to 7,000 over 20 years
n Main Traffic Corridors
· Class II – Parking lots with a maximum of 10 trucks per day with Equivalent
Single Axle Load (ESAL) up to 27,000 over 20 years (Including trash trucks)
n Subgrade Soil Characteristics
· USCS Classification – CL, classified by NAPA as poor
We assumed the following design parameters for ACI rigid pavement thickness design based
upon the average daily truck traffic (ADTT):
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n Automobile Parking Areas
· ACI Category A: Automobile parking with an ADTT of 1 over 20 years
n Main Traffic Corridors
· ACI Category B: Entrance and service lanes with an ADTT of up to 300 over
20 years (Including trash trucks)
n Subgrade Soil Characteristics
· USCS Classification – CL
n Concrete modulus of rupture value of 600 psi
We should be contacted to confirm and/or modify the recommendations contained herein if actual
traffic volumes differ from the assumed values shown above.
Recommended alternatives for flexible and rigid pavements are summarized for each traffic area
as follows:
Traffic Area
Alternative
Recommended Pavement Thickness (Inches)
Asphaltic
Concrete
Surface
Aggregate
Base
Course
Portland
Cement
Concrete
Total
Automobile Parking
(NAPA Class I and ACI Category A)
A 4 6 -- 10
B -- -- 5½ 5½
Main Traffic Corridors
(NAPA Class II and ACI Category B)
A 5 6 -- 11
B -- -- 6 6
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 aggregate
base course. Aggregate base course should be placed in lifts not exceeding 6 inches and
compacted to a minimum of 95 percent of the maximum dry unit weight as determined by ASTM
D698.
Asphaltic concrete should be composed of a mixture of aggregate, filler and additives (if required)
and approved bituminous material. The asphalt concrete should conform to approved mix
designs stating the Superpave properties, optimum asphalt content, job mix formula and
recommended mixing and placing temperatures. Aggregate used in asphalt concrete should
meet particular gradations. Material meeting CDOT Grading S or Sx specifications or equivalent
is recommended for asphalt concrete. Mix designs should be submitted prior to construction to
verify their adequacy. Asphalt material should be placed in maximum 3-inch lifts and compacted
within a range of 92 to 96 percent of the theoretical maximum (Rice) density (ASTM D2041).
Geotechnical Engineering Report
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Where rigid pavements are used, the concrete should be produced from an approved mix design
with the following minimum properties:
Properties Value
Compressive strength 4,000 psi
Cement type Type I or II portland cement
Entrained air content (%) 5 to 8
Concrete aggregate ASTM C33 and CDOT Section 703
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. Longitudinal and transverse joints should be provided
as needed in concrete pavements for expansion/contraction and isolation per ACI 325. The
location and extent of joints should be based upon the final pavement geometry. Joints should
be sealed to prevent entry of foreign material and doweled where necessary for load transfer.
For areas subject to concentrated and repetitive loading conditions such as dumpster pads, truck
delivery docks and ingress/egress aprons, we recommend using a portland cement concrete
pavement with a thickness of at least 6 inches underlain by at least 4 inches of granular base.
Prior to placement of the granular base, the areas should be thoroughly proofrolled. For dumpster
pads, the concrete pavement area should be large enough to support the container and tipping
axle of the refuse truck.
Pavement performance is affected by its surroundings. In addition to providing preventive
maintenance, the civil engineer should consider the following recommendations in the design and
layout of pavements:
n Site grades should slope a minimum of 2 percent away from the pavements;
n The subgrade and the pavement surface have a minimum 2 percent slope to promote
proper surface drainage;
n Consider appropriate edge drainage and pavement under drain systems;
n Install pavement drainage surrounding areas anticipated for frequent wetting;
n Install joint sealant and seal cracks immediately;
n Seal all landscaped areas in, or adjacent to pavements to reduce moisture migration to
subgrade soils; and
n Placing compacted, low permeability backfill against the exterior side of curb and gutter.
4.7.3 Pavements – Construction Considerations
Openings in pavement, such as landscape islands, are sources for water infiltration into
surrounding pavements. Water collects in the islands and migrates into the surrounding subgrade
soils thereby degrading support of the pavement. This is especially applicable for islands with
raised concrete curbs, irrigated foliage, and low permeability near-surface soils. The civil design
for the pavements with these conditions should include features to restrict or to collect and
Geotechnical Engineering Report
Elevations Credit Union ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
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discharge excess water from the islands. Examples of features are edge drains connected to the
storm water collection system or other suitable outlet and impermeable barriers preventing lateral
migration of water such as a cutoff wall installed to a depth below the pavement structure.
4.7.4 Pavements – Maintenance
Preventative maintenance should be planned and provided for an ongoing pavement
management program in order to enhance future pavement performance. Preventive
maintenance consists of both localized maintenance (e.g. crack and joint 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.
5.0 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 provide observation and testing
services during grading, excavation, foundation construction and other earth-related construction
phases of the project.
The analysis and recommendations presented in this report are based upon the data obtained
from the borings performed at the indicated locations and from other information discussed in this
report. This report does not reflect variations that may occur between borings, across the site, or
due to the modifying effects of construction or weather. The nature and extent of such variations
may not become evident until during or after construction. If variations appear, we should be
immediately notified so that further evaluation and supplemental recommendations can be
provided.
The scope of services for this project does not include either specifically or by implication any
environmental or biological (e.g., mold, fungi, and bacteria) assessment of the site or identification
or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about
the potential for such contamination or pollution, 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. Site
safety, excavation support, and dewatering requirements are the responsibility of others. In the
event that changes in the nature, design, or location of the project as described 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.
APPENDIX A
FIELD EXPLORATION
SITE LOCATION MAP
Elevations Credit Union
2025 South College Avenue
Fort Collins, CO
TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY
QUADRANGLES INCLUDE: FORT COLLINS, CO (1984).
1901 Sharp Point Dr Suite C
Ft. Collins, CO 80525
20165011
Project Manager:
Drawn by:
Checked by:
Approved by:
KFS
EDB
KFS
1”=2,000’
1/29/2016
Project No.
Scale:
File Name:
Date: A-1
EDB Exhibit
SITE
EXPLORATION PLAN
Elevations Credit Union
2025 South College Avenue
Fort Collins, CO
1901 Sharp Point Dr Suite C
Ft. Collins, CO 80525
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS
NOT INTENDED FOR CONSTRUCTION PURPOSES
20165011
AERIAL PHOTOGRAPHY PROVIDED
BY MICROSOFT BING MAPS
KFS
EDB
KFS
AS SHOWN
1/29/2016
Scale:
A-2
Exhibit
Project Manager:
Drawn by:
Checked by:
Approved by:
Project No.
File Name:
Date:
EDB
Approximate Location of Temporary Benchmark
(Rim of sanitary sewer–Elevation 4994.1’)
Approximate Boring Location
1
LEGEND
Geotechnical Engineering Report
«JobNameTitlePage» ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
Responsive ■ Resourceful ■ Reliable Exhibit A-3
Field Exploration Description
The locations of borings were based upon the proposed development shown on the provided site
plan. The borings were located in the field by measuring from property lines and existing site
features. The ground surface elevation was surveyed at each boring location referencing the
temporary benchmark shown on Exhibit A-2 using an engineer’s level.
The borings were drilled with a CME-75 truck-mounted rotary drill rig with solid-stem augers.
During the drilling operations, lithologic logs of the borings were recorded by the field engineer.
Disturbed samples were obtained at selected intervals utilizing a 2-inch outside diameter split-
spoon sampler and a 3-inch outside diameter ring-barrel sampler. Penetration resistance values
were recorded in a manner similar to the standard penetration test (SPT). This test consists of
driving the sampler into the ground with a 140-pound hammer free-falling through a distance of
30 inches. The number of blows required to advance the ring-barrel sampler 12 inches (18 inches
for standard split-spoon samplers, final 12 inches are recorded) or the interval indicated, is
recorded as a standard penetration resistance value (N-value). The blow count values are
indicated on the boring logs at the respective sample depths. Ring-barrel sample blow counts are
not considered N-values.
A CME automatic SPT hammer was used to advance the samplers in the borings performed on this
site. A greater efficiency is typically achieved with the automatic hammer compared to the
conventional safety hammer operated with a cathead and rope. Published correlations between the
SPT values and soil properties are based on the lower efficiency cathead and rope method. This
higher efficiency affects the standard penetration resistance blow count value by increasing the
penetration per hammer blow over what would be obtained using the cathead and rope method. The
effect of the automatic hammer's efficiency has been considered in the interpretation and analysis of
the subsurface information for this report.
The standard penetration test provides a reasonable indication of the in-place density of sandy
type materials, but only provides an indication of the relative stiffness of cohesive materials since
the blow count in these soils may be affected by the moisture content of the soil. In addition,
considerable care should be exercised in interpreting the N-values in gravelly soils, particularly
where the size of the gravel particle exceeds the inside diameter of the sampler.
Groundwater measurements were obtained in the borings at the time of site exploration. After
completion of drilling, the borings were backfilled with auger cuttings. Some settlement of the
backfill and/or patch may occur and should be repaired as soon as possible.
1177
15
16
24
98
30-17-13
28-18-10
45-18-27
32-22-10
4992.5
4986
4973.5
4969
4963.5
-1.5/2,000
3-4-5
N=9
3-3-4
N=7
5-7
3-4
2-2-3
N=5
5-19
12-13-16
N=29
50/4"
0.3
7.0
19.5
24.0
29.4
ASPHALT PAVEMENT- 4 inches
FILL - CLAYEY SAND (SC), brown to dark brown/black,
loose
CLAYEY SAND to SANDY LEAN CLAY, brown to
reddish-brown, soft to medium stiff, very loose to loose
SANDY LEAN CLAY (CL), yellowish-brown, medium stiff
WELL GRADED GRAVEL WITH SAND, reddish-brown,
angular to sub-angular
SEDIMENTARY BEDROCK - SANDSTONE, greenish-brown
to light gray, firm to very hard
Boring Terminated at 29.4 Feet
Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic
GRAPHIC LOG
THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165011_ELEVATIONS_CREDIT_UNION.GPJ TERRACON2015.GDT 2/5/16
2025 South College Avenue
Fort Collins, Colorado
SITE:
Page 1 of 1
Advancement Method:
4-inch diameter solid stem augers
Abandonment Method:
Borings backfilled with soil cuttings upon completion.
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
Notes:
Project No.: 20165011
Drill Rig: CME-75
Boring Started: 1/29/2016
12
21
23
30-17-13
31-16-15
4994.5
4989
4975.5
4972
4965.5
6-7
3-5
4-7-7
N=14
2-2-2
N=4
1-1-1
N=2
2-2-2
N=4
9-10-17
N=27
50/4"
0.3
6.0
19.5
23.0
29.4
ASPHALT PAVEMENT- 4 inches
FILL - CLAYEY SAND , brown to dark brown/black, loose
CLAYEY SAND to SANDY LEAN CLAY, brown to
reddish-brown, very loose to loose
WELL GRADED GRAVEL WITH SAND, reddish-brown,
angular to sub-angular
SEDIMENTARY BEDROCK - SANDSTONE,
greenish-brown, firm
Boring Terminated at 29.4 Feet
Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic
GRAPHIC LOG
THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165011_ELEVATIONS_CREDIT_UNION.GPJ TERRACON2015.GDT 2/5/16
2025 South College Avenue
Fort Collins, Colorado
SITE:
Page 1 of 1
Advancement Method:
Abandonment Method:
Borings backfilled with soil cuttings upon completion.
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
Notes:
Project No.: 20165011
Drill Rig: CME-75
Boring Started: 1/29/2016
BORING LOG NO. 2
CLIENT: Elevations Credit Union
2300 55th Street
Driller: S. Flanigan
Boring Completed: 1/29/2016
Exhibit:
Boulder, Colorado
APPENDIX B
LABORATORY TESTING
Geotechnical Engineering Report
«JobNameTitlePage» ■ Fort Collins, Colorado
February 5, 2016 ■ Terracon Project No. 20165011
Responsive ■ Resourceful ■ Reliable Exhibit B-1
Laboratory Testing Description
The soil and bedrock samples retrieved during the field exploration were returned to the laboratory
for observation by the project geotechnical engineer. At that time, the field descriptions were
reviewed and an applicable laboratory testing program was formulated to determine engineering
properties of the subsurface materials.
Laboratory tests were conducted on selected soil and bedrock samples. The results of these
tests are presented on the boring logs and in this appendix. The test results were used for the
geotechnical engineering analyses, and the development of foundation and earthwork
recommendations. The laboratory tests were performed in general accordance with applicable
locally accepted standards. Soil samples were classified in general accordance with the Unified
Soil Classification System described in Appendix C. Rock samples were visually classified in
general accordance with the description of rock properties presented in Appendix C. Procedural
standards noted in this report are for reference to methodology in general. In some cases variations
to methods are applied as a result of local practice or professional judgment.
n Water content n Plasticity index
n Grain-size distribution
n Swell Consolidation
n Dry density
n Compressive strength
n Water-soluble sulfate content
0
10
20
30
40
50
60
0 20 40 60 80 100
CL or OL CH or OH
ML or OL
MH or OH
Boring ID Depth PL PI Description
CLAYEY SAND
CLAYEY SAND
LEAN CLAY with SAND
SANDY LEAN CLAY
CLAYEY SAND
CLAYEY SAND
SC
CL
CL
SC
SC
"U" Line
"A" Line
30
28
45
32
30
31
17
18
18
22
17
16
13
10
27
10
13
15
42
73
62
44
41
LL USCS
1
1
1
1
2
2
ATTERBERG LIMITS RESULTS
ASTM D4318
2 - 3.5
9 - 10
14 - 15.5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
100 10 1 0.1 0.01 0.001
1
1
1
2
2
30
45
32
30
31
12.5 0.214
0.075
0.075
0.075
0.075
6 16
20 30
40 50
1.5 6 200
810
3.5
0.0
0.0
0.0
0.0
14
42.1
73.2
61.6
43.8
41.2
%Fines
LL PL PI
1 4
3/4 1/2
60
fine
1
-5
-4
-3
-2
-1
0
1
2
3
4
5
100 1,000 10,000
AXIAL STRAIN, %
PRESSURE, psf
SWELL CONSOLIDATION TEST
ASTM D4546
NOTES: Sample exhibited 1.5% compression upon wetting under an applied pressure of 2,000 psf.
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
PROJECT: Elevations Credit Union PROJECT NUMBER: 20165011
SITE: 2025 South College Avenue
Fort Collins, Colorado
CLIENT: Elevations Credit Union
2300 55th Street
EXHIBIT: B-4
Specimen Identification Classification , pcf
106 17
WC, %
1 9 - 10 ft CLAYEY SAND
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20165011_ELEVATIONS_CREDIT_UNION.GPJ TERRACON2012.GDT 2/5/16
0
100
200
300
400
500
600
700
800
900
1,000
1,100
1,200
0 2 4 6 8 10
2.42
4.13
1177
Assumed Specific Gravity:
32 22 10
Unconfined Compressive Strength (psf)
Undrained Shear Strength: (psf)
Calculated Void Ratio:
Height / Diameter Ratio:
SPECIMEN FAILURE MODE SPECIMEN TEST DATA
1.70
8.24
Moisture Content: %
Dry Density: pcf
COMPRESSIVE STRESS - psf
412.0000
DESCRIPTION: SANDY LEAN CLAY(CL)
588
LL PL PI Percent < #200 Sieve
62
AXIAL STRAIN - %
Remarks:
ASTM D2166
UNCONFINED COMPRESSION TEST
Failure Mode: Bulge (dashed)
Diameter: in.
Height: in.
Calculated Saturation: %
Failure Strain: %
Strain Rate: in/min
SAMPLE TYPE: D&M RING SAMPLE LOCATION: 1 @ 19 - 20 feet
PROJECT NUMBER: 20165011
PROJECT: Elevations Credit Union
SITE: 2025 South College Avenue
Fort Collins, Colorado
CLIENT: Elevations Credit Union
2300 55th Street
EXHIBIT: B-5
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. UNCONFINED 20165011_ELEVATIONS_CREDIT_UNION.GPJ TERRACON2012.GDT 2/5/16
APPENDIX C
SUPPORTING DOCUMENTS
Exhibit: C-1
Unconfined Compressive Strength
Qu, (psf)
500 to 1,000
2,000 to 4,000
4,000 to 8,000
1,000 to 2,000
less than 500
> 8,000
Non-plastic
Low
Medium
High
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
SAMPLING
WATER LEVEL
FIELD TESTS
GENERAL NOTES
Over 12 in. (300 mm)
12 in. to 3 in. (300mm to 75mm)
3 in. to #4 sieve (75mm to 4.75 mm)
#4 to #200 sieve (4.75mm to 0.075mm
Passing #200 sieve (0.075mm)
Particle Size
< 5
5 - 12
> 12
Percent of
Dry Weight
Descriptive Term(s)
of other constituents
RELATIVE PROPORTIONS OF FINES
0
1 - 10
11 - 30
> 30
Plasticity Index
Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry
weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have
less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and
silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be
added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined
on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.
LOCATION AND ELEVATION NOTES
Percent of
Dry Weight
Major Component
of Sample
Trace
With
Modifier
RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY
Trace
With
Modifier
DESCRIPTIVE SOIL CLASSIFICATION
Boulders
Cobbles
Gravel
Sand
UNIFIED SOIL CLASSIFICATION SYSTEM
Exhibit C-2
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse Grained Soils:
More than 50% retained
on No. 200 sieve
Gravels:
More than 50% of
coarse fraction retained
on No. 4 sieve
Clean Gravels:
Less than 5% fines C
Cu 4 and 1 Cc 3 E GW Well-graded gravel F
Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F
Gravels with Fines:
More than 12% fines C
Fines classify as ML or MH GM Silty gravel F,G,H
Fines classify as CL or CH GC Clayey gravel F,G,H
Sands:
50% or more of coarse
fraction passes No. 4
sieve
Clean Sands:
Less than 5% fines D
Cu 6 and 1 Cc 3 E SW Well-graded sand I
Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I
Sands with Fines:
More than 12% fines D
Fines classify as ML or MH SM Silty sand G,H,I
Fines classify as CL or CH SC Clayey sand G,H,I
Fine-Grained Soils:
50% or more passes the
No. 200 sieve
Silts and Clays:
Liquid limit less than 50
Inorganic:
PI 7 and plots on or above “A” line J CL Lean clay K,L,M
PI 4 or plots below “A” line J ML Silt K,L,M
Organic:
Liquid limit - oven dried
0.75 OL
Organic clay K,L,M,N
Liquid limit - not dried Organic silt K,L,M,O
Silts and Clays:
Liquid limit 50 or more
Inorganic:
PI plots on or above “A” line CH Fat clay K,L,M
PI plots below “A” line MH Elastic Silt K,L,M
Organic:
Liquid limit - oven dried
0.75 OH
Organic clay K,L,M,P
Liquid limit - not dried Organic silt K,L,M,Q
Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-inch (75-mm) sieve
B If field sample contained cobbles or boulders, or both, add “with cobbles
or boulders, or both” to group name.
DESCRIPTION OF ROCK PROPERTIES
Exhibit C-3
WEATHERING
Fresh Rock fresh, crystals bright, few joints may show slight staining. Rock rings under hammer if crystalline.
Very slight Rock generally fresh, joints stained, some joints may show thin clay coatings, crystals in broken face show
bright. Rock rings under hammer if crystalline.
Slight Rock generally fresh, joints stained, and discoloration extends into rock up to 1 in. Joints may contain clay. In
granitoid rocks some occasional feldspar crystals are dull and discolored. Crystalline rocks ring under hammer.
Moderate Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull
and discolored; some show clayey. Rock has dull sound under hammer and shows significant loss of strength
as compared with fresh rock.
Moderately severe All rock except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority
show kaolinization. Rock shows severe loss of strength and can be excavated with geologist’s pick.
Severe All rock except quartz discolored or stained. Rock “fabric” clear and evident, but reduced in strength to strong
soil. In granitoid rocks, all feldspars kaolinized to some extent. Some fragments of strong rock usually left.
Very severe All rock except quartz discolored or stained. Rock “fabric” discernible, but mass effectively reduced to “soil” with
only fragments of strong rock remaining.
Complete Rock reduced to ”soil”. Rock “fabric” not discernible or discernible only in small, scattered locations. Quartz may
be present as dikes or stringers.
HARDNESS (for engineering description of rock – not to be confused with Moh’s scale for minerals)
Very hard Cannot be scratched with knife or sharp pick. Breaking of hand specimens requires several hard blows of
geologist’s pick.
Hard Can be scratched with knife or pick only with difficulty. Hard blow of hammer required to detach hand specimen.
Moderately hard Can be scratched with knife or pick. Gouges or grooves to ¼ in. deep can be excavated by hard blow of point of
a geologist’s pick. Hand specimens can be detached by moderate blow.
Medium Can be grooved or gouged 1/16 in. deep by firm pressure on knife or pick point. Can be excavated in small
chips to pieces about 1-in. maximum size by hard blows of the point of a geologist’s pick.
Soft Can be gouged or grooved readily with knife or pick point. Can be excavated in chips to pieces several inches in
size by moderate blows of a pick point. Small thin pieces can be broken by finger pressure.
Very soft Can be carved with knife. Can be excavated readily with point of pick. Pieces 1-in. or more in thickness can be
broken with finger pressure. Can be scratched readily by fingernail.
Joint, Bedding, and Foliation Spacing in Rock
a
Spacing Joints Bedding/Foliation
Less than 2 in. Very close Very thin
2 in. – 1 ft. Close Thin
1 ft. – 3 ft. Moderately close Medium
3 ft. – 10 ft. Wide Thick
More than 10 ft. Very wide Very thick
a. Spacing refers to the distance normal to the planes, of the described feature, which are parallel to each other or nearly so.
Rock Quality Designator (RQD) a Joint Openness Descriptors
RQD, as a percentage Diagnostic description Openness Descriptor
Exceeding 90 Excellent No Visible Separation Tight
90 – 75 Good Less than 1/32 in. Slightly Open
75 – 50 Fair 1/32 to 1/8 in. Moderately Open
50 – 25 Poor 1/8 to 3/8 in. Open
Less than 25 Very poor 3/8 in. to 0.1 ft. Moderately Wide
a. RQD (given as a percentage) = length of core in pieces Greater than 0.1 ft. Wide
4 in. and longer/length of run.
References: American Society of Civil Engineers. Manuals and Reports on Engineering Practice - No. 56. Subsurface Investigation for
Design and Construction of Foundations of Buildings. New York: American Society of Civil Engineers, 1976. U.S.
Department of the Interior, Bureau of Reclamation, Engineering Geology Field Manual.
Exhibit C-4
LABORATORY TEST
SIGNIFICANCE AND PURPOSE
Test Significance Purpose
California Bearing
Ratio
Used to evaluate the potential strength of subgrade soil,
subbase, and base course material, including recycled
materials for use in road and airfield pavements.
Pavement Thickness
Design
Consolidation
Used to develop an estimate of both the rate and amount of
both differential and total settlement of a structure. Foundation Design
Direct Shear
Used to determine the consolidated drained shear strength
of soil or rock.
Bearing Capacity,
Foundation Design,
and Slope Stability
Dry Density
Used to determine the in-place density of natural, inorganic,
fine-grained soils.
Index Property Soil
Behavior
Expansion
Used to measure the expansive potential of fine-grained soil
and to provide a basis for swell potential classification.
Foundation and Slab
Design
Gradation
Used for the quantitative determination of the distribution of
particle sizes in soil. Soil Classification
Liquid & Plastic Limit,
Plasticity Index
Used as an integral part of engineering classification
systems to characterize the fine-grained fraction of soils, and
to specify the fine-grained fraction of construction materials.
Soil Classification
Permeability
Used to determine the capacity of soil or rock to conduct a
liquid or gas.
Groundwater Flow
Analysis
pH Used to determine the degree of acidity or alkalinity of a soil. Corrosion Potential
Resistivity
Used to indicate the relative ability of a soil medium to carry
electrical currents. Corrosion Potential
R-Value
Used to evaluate the potential strength of subgrade soil,
subbase, and base course material, including recycled
materials for use in road and airfield pavements.
Pavement Thickness
Design
Soluble Sulfate
Used to determine the quantitative amount of soluble
sulfates within a soil mass. Corrosion Potential
Unconfined
Compression
To obtain the approximate compressive strength of soils that
Exhibit C-5
REPORT TERMINOLOGY
(Based on ASTM D653)
Allowable Soil
Bearing Capacity
The recommended maximum contact stress developed at the interface of the foundation
element and the supporting material.
Alluvium
Soil, the constituents of which have been transported in suspension by flowing water and
subsequently deposited by sedimentation.
Aggregate Base
Course
A layer of specified material placed on a subgrade or subbase usually beneath slabs or
pavements.
Backfill A specified material placed and compacted in a confined area.
Bedrock
A natural aggregate of mineral grains connected by strong and permanent cohesive forces.
Usually requires drilling, wedging, blasting or other methods of extraordinary force for
excavation.
Bench A horizontal surface in a sloped deposit.
Caisson (Drilled
Pier or Shaft)
A concrete foundation element cast in a circular excavation which may have an enlarged base.
Sometimes referred to as a cast-in-place pier or drilled shaft.
Coefficient of
Friction
A constant proportionality factor relating normal stress and the corresponding shear stress at
which sliding starts between the two surfaces.
Colluvium
Soil, the constituents of which have been deposited chiefly by gravity such as at the foot of a
slope or cliff.
Compaction The densification of a soil by means of mechanical manipulation
Concrete Slab-on-
Grade
A concrete surface layer cast directly upon a base, subbase or subgrade, and typically used
as a floor system.
Differential
Movement Unequal settlement or heave between, or within foundation elements of structure.
Earth Pressure The pressure exerted by soil on any boundary such as a foundation wall.
ESAL
Equivalent Single Axle Load, a criteria used to convert traffic to a uniform standard, (18,000
pound axle loads).
Engineered Fill
Specified material placed and compacted to specified density and/or moisture conditions
under observations of a representative of a geotechnical engineer.
Equivalent Fluid
A hypothetical fluid having a unit weight such that it will produce a pressure against a lateral
support presumed to be equivalent to that produced by the actual soil. This simplified
approach is valid only when deformation conditions are such that the pressure increases
linearly with depth and the wall friction is neglected.
Existing Fill (or
Man-Made Fill) Materials deposited throughout the action of man prior to exploration of the site.
Existing Grade The ground surface at the time of field exploration.
Exhibit C-6
REPORT TERMINOLOGY
(Based on ASTM D653)
Expansive Potential The potential of a soil to expand (increase in volume) due to absorption of moisture.
Finished Grade The final grade created as a part of the project.
Footing A portion of the foundation of a structure that transmits loads directly to the soil.
Foundation The lower part of a structure that transmits the loads to the soil or bedrock.
Frost Depth The depth at which the ground becomes frozen during the winter season.
Grade Beam
A foundation element or wall, typically constructed of reinforced concrete, used to span between
other foundation elements such as drilled piers.
Groundwater Subsurface water found in the zone of saturation of soils or within fractures in bedrock.
Heave Upward movement.
Lithologic The characteristics which describe the composition and texture of soil and rock by observation.
Native Grade The naturally occurring ground surface.
Native Soil Naturally occurring on-site soil, sometimes referred to as natural soil.
Optimum Moisture
Content
The water content at which a soil can be compacted to a maximum dry unit weight by a given
compactive effort.
Perched Water
Groundwater, usually of limited area maintained above a normal water elevation by the
presence of an intervening relatively impervious continuous stratum.
Scarify To mechanically loosen soil or break down existing soil structure.
Settlement Downward movement.
Skin Friction (Side
Shear)
The frictional resistance developed between soil and an element of the structure such as a
drilled pier.
Soil (Earth)
Sediments or other unconsolidated accumulations of solid particles produced by the physical
and chemical disintegration of rocks, and which may or may not contain organic matter.
Strain The change in length per unit of length in a given direction.
Stress The force per unit area acting within a soil mass.
Strip To remove from present location.
Subbase A layer of specified material in a pavement system between the subgrade and base course.
Subgrade The soil prepared and compacted to support a structure, slab or pavement system.
possess sufficient cohesion to permit testing in the
unconfined state.
Bearing Capacity
Analysis for
Foundations
Water Content
Used to determine the quantitative amount of water in a soil
mass.
Index Property Soil
Behavior
C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded
gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly
graded gravel with silt, GP-GC poorly graded gravel with clay.
D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded
sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded
sand with silt, SP-SC poorly graded sand with clay
E Cu = D60/D10 Cc =
10 60
2
30
D x D
(D )
F If soil contains 15% sand, add “with sand” to group name.
G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
H If fines are organic, add “with organic fines” to group name.
I If soil contains 15% gravel, add “with gravel” to group name.
J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.
K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,”
whichever is predominant.
L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to
group name.
M If soil contains 30% plus No. 200, predominantly gravel, add
“gravelly” to group name.
N PI 4 and plots on or above “A” line.
O PI 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.
Silt or Clay
Descriptive Term(s)
of other constituents
N
(HP)
(T)
(DCP)
(PID)
(OVA)
< 15
15 - 29
> 30
Term
PLASTICITY DESCRIPTION
Water levels indicated on the soil boring
logs are the levels measured in the
borehole at the times indicated.
Groundwater level variations will occur
over time. In low permeability soils,
accurate determination of groundwater
levels is not possible with short term water
level observations.
Water Level After
a Specified Period of Time
Water Level After a
Specified Period of Time
Water Initially
Encountered
Modified
Dames &
Moore Ring
Sampler
Standard
Penetration
Test
Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy
of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was
conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic
maps of the area.
Standard Penetration Test
Resistance (Blows/Ft.)
Hand Penetrometer
Torvane
Dynamic Cone Penetrometer
Photo-Ionization Detector
Organic Vapor Analyzer
STRENGTH TERMS
Standard Penetration or
N-Value
Blows/Ft.
Descriptive Term
(Consistency)
Descriptive Term
(Density)
CONSISTENCY OF FINE-GRAINED SOILS
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing, field
visual-manual procedures or standard penetration resistance
Standard Penetration or
N-Value
Blows/Ft.
(More than 50% retained on No. 200 sieve.)
Density determined by Standard Penetration Resistance
RELATIVE DENSITY OF COARSE-GRAINED SOILS
Hard > 30
> 50 Very Stiff 15 - 30
Stiff
Medium Stiff
Very Soft 0 - 1
Medium Dense
Loose Soft
Very Dense
Dense 30 - 50 8 - 15
10 - 29 4 - 8
4 - 9 2 - 4
Very Loose 0 - 3
1
1
2
2
GRAIN SIZE IN MILLIMETERS
PERCENT FINER BY WEIGHT
coarse fine
U.HYDROMETERS. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
17
18
22
17
16
13
27
10
13
15
D100
Cc Cu
SILT OR CLAY
4
D30 D10 %Gravel %Sand
2 - 3.5
14 - 15.5
19 - 20
6 - 7.5
14 - 15.5
3/8 3 100
3 2 140
COBBLES
GRAVEL SAND
USCS Classification
51.6
0.0
0.0
0.0
0.0
D60
coarse medium
Boring ID Depth
Boring ID Depth
GRAIN SIZE DISTRIBUTION
ASTM D422
2 - 3.5
14 - 15.5
19 - 20
6 - 7.5
14 - 15.5
CLAYEY SAND (SC)
LEAN CLAY with SAND (CL)
SANDY LEAN CLAY (CL)
CLAYEY SAND (SC)
CLAYEY SAND (SC)
PROJECT NUMBER: 20165011
PROJECT: Elevations Credit Union
SITE: 2025 South College Avenue
Fort Collins, Colorado
CLIENT: Elevations Credit Union
2300 55th Street
EXHIBIT: B-3
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20165011_ELEVATIONS_CREDIT_UNION.GPJ 35159097 - ATTERBERG ISSUE.GPJ 2/5/16
19 - 20
6 - 7.5
14 - 15.5
Fines
P
L
A
S
T
I
C
I
T
Y
I
N
D
E
X
LIQUID LIMIT
PROJECT NUMBER: 20165011
PROJECT: Elevations Credit Union
SITE: 2025 South College Avenue
Fort Collins, Colorado
CLIENT: Elevations Credit Union
2300 55th Street
EXHIBIT: B-2
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. ATTERBERG LIMITS 20165011_ELEVATIONS_CREDIT_UNION.GPJ TERRACON2015.GDT 2/5/16
CL-ML
A-5
See Exhibit A-3 for description of field procedures.
See Appendix B for description of laboratory
procedures and additional data (if any).
See Appendix C for explanation of symbols and
abbreviations.
PROJECT: Elevations Credit Union
UNCONFINED
COMPRESSIVE
STRENGTH (psf)
WATER
CONTENT (%)
DRY UNIT
WEIGHT (pcf)
ATTERBERG
LIMITS
LL-PL-PI
Surface Elev.: 4994.8 (Ft.)
ELEVATION (Ft.)
SAMPLE TYPE
WATER LEVEL
OBSERVATIONS
DEPTH (Ft.)
5
10
15
20
25
SWELL-CONSOL /
LOAD (%/psf)
FIELD TEST
RESULTS
DEPTH
LOCATION See Exhibit A-2
Latitude: 40.561071° Longitude: -105.077261°
At completion of drilling
WATER LEVEL OBSERVATIONS
BORING LOG NO. 1
CLIENT: Elevations Credit Union
2300 55th Street
Driller: S. Flanigan
Boring Completed: 1/29/2016
Exhibit:
Boulder, Colorado
A-4
See Exhibit A-3 for description of field procedures.
See Appendix B for description of laboratory
procedures and additional data (if any).
See Appendix C for explanation of symbols and
abbreviations.
PROJECT: Elevations Credit Union
UNCONFINED
COMPRESSIVE
STRENGTH (psf)
WATER
CONTENT (%)
DRY UNIT
WEIGHT (pcf)
ATTERBERG
LIMITS
LL-PL-PI
Surface Elev.: 4993.0 (Ft.)
ELEVATION (Ft.)
SAMPLE TYPE
WATER LEVEL
OBSERVATIONS
DEPTH (Ft.)
5
10
15
20
25
SWELL-CONSOL /
LOAD (%/psf)
FIELD TEST
RESULTS
DEPTH
LOCATION See Exhibit A-2
Latitude: 40.561267° Longitude: -105.07759°
At completion of drilling
WATER LEVEL OBSERVATIONS