HomeMy WebLinkAbout2908 S TIMBERLINE RD MULTI-FAMILY DWELLINGS - PDP210011 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT
REPORT COVER PAGE
Geotechnical Engineering Report
__________________________________________________________________________
Timberline Apartments
Fort Collins, Colorado
May 5, 2021
Terracon Project No. 20215032
Prepared for:
Tetrad Property Group, LLC
Fort Collins, Colorado
Prepared by:
Terracon Consultants, Inc.
Fort Collins, Colorado
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REPORT TOPICS
INTRODUCTION ............................................................................................................. 1
SITE CONDITIONS ......................................................................................................... 1
PROJECT DESCRIPTION .............................................................................................. 2
GEOTECHNICAL CHARACT ERIZATION ...................................................................... 3
GEOTECHNICAL OVERVIEW ....................................................................................... 5
EARTHWORK................................................................................................................. 7
SHALLOW FOUNDATIONS ......................................................................................... 12
SEISMIC CONSIDERATIONS ...................................................................................... 17
FLOOR SLABS............................................................................................................. 17
BELOW-GRADE STRUCTURES ................................................................................. 19
PAVEMENTS ................................................................................................................ 22
FROST CONSIDERATIONS ......................................................................................... 25
CORROSIVITY.............................................................................................................. 26
GENERAL COMMENTS ............................................................................................... 26
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ATTACHMENTS
EXPLORATION AND TESTING PROCEDURES
SITE LOCATION AND EXPLORATION PLANS
EXPLORATION RESULTS
SUPPORTING INFORMATION
Note: Refer to each individual Attachment for a listing of contents.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Responsive ■ Resourceful ■ Reliable i
REPORT SUMMARY
Topic 1 Overview Statement 2
Project
Overview
A geotechnical exploration has been performed for the proposed Timberline
Apartments to be constructed at 2908 South Timberline Road in Fort Collins,
Colorado. Seven (7) borings were performed to depths of approximately 25 to 30 feet
below existing site grades. Detailed recommendations for the design of storm water
retention features and the pond are outside our scope of work.
Subsurface
Conditions
Subsurface conditions encountered in our exploratory borings generally consisted of
about 9 to 13 feet of silt or clay with varying amounts of sand and gravel over about 4
to 12 feet of sand and gravel. Claystone bedrock was encountered below the
overburden soils at depths of approximately 17 to 21 feet below existing site grades.
The upper approximately 6 inches to 2 feet of bedrock was weathered and
comparatively soft in some of the borings. Boring logs are presented in the
Exploration Results section of this report.
Groundwater
Conditions
Groundwater was encountered in all of our test borings at depths of about 12 to 13 feet
below existing site grades at the time of drilling. Groundwater levels can fluctuate in
response to site development and to varying seasonal and weather conditions,
irrigation on or adjacent to the site and fluctuations in nearby water features.
Geotechnical
Concerns
■ As previously stated, groundwater was measured at depths ranging from about 12
to 13 feet below existing site grades. Groundwater level fluctuations occur due to
seasonal variations in the water levels present in nearby water features, amount of
rainfall, runoff and other factors not evident at the time the borings were performed.
Therefore, groundwater levels during construction or at other times in the life of the
structure(s) may be higher or lower than the levels indicated on the boring logs.
Terracon recommends maintaining a separation of at least 3 feet between the
bottom of proposed below-grade foundations and measured groundwater levels.
Final site grading should be planned and designed to avoid cuts where shallow
groundwater is known to exist, and also in areas where such grading would create
shallow groundwater conditions. If deeper cuts are unavoidable, temporary
construction dewatering and/or installation of a subsurface drainage system may be
needed.
■ Com paratively soft lean clay and silt soils were encountered within the upper
approximately 9 to 13 feet in some of the borings completed at this site. These
materials present a risk for potential settlement of shallow foundations, floor slabs,
pavements and other surficial improvements. These materials can also be
susceptible to disturbance and loss of strength under repeated construction traffic
loads and unstable conditions could develop. Stabilization of soft soils may be
required at some locations to provide adequate support for construction equipment
and proposed structures. Terracon should be contacted if these conditions are
encountered to observe the conditions exposed and to provide guidance regarding
stabilization (if needed).
Earthwork
On-site soils typically appear suitable for use as general engineered fill and backfill on
the site provided they are placed and compacted as described in this report. Import
materials (if needed) should be evaluated and approved by Terracon prior to delivery
to the site. Earthwork recommendations are presented in the Earthwork section of
this report.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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Topic 1 Overview Statement 2
Grading and
Drainage
The amount of movement of foundations, floor slabs, pavements, etc. will be related to
the wetting of underlying supporting soils. Therefore, it is imperative the
recommendations discussed in the Grading and Drainage section of the Earthwork
section this report be followed to reduce potential movement. As discussed in the
Grading and Drainage section of this report, surface drainage should be designed,
constructed and maintained to provide rapid removal of surface water runoff away from
the proposed buildings and pavements. Water should not be allowed to pond adjacent
to foundations or on pavements and conservative irrigation practices should be followed
to avoid wetting foundation/slab soils and pavement subgrade. Excessive wetting of
foundations/slab soils and subgrade can cause movement and distress to foundations,
floor slabs, concrete flatwork and pavements.
Foundations
We understand the project team is planning to support the proposed buildings on
post-tensioned slab foundations. Based on the subsurface conditions encountered,
use of post-tensioned slabs is feasible for support of the structures provided some
foundation movement can be tolerated. As an alternative to post-tensioned slabs, or
for other structures planned on the site, shallow spread footing foundations can be
used. Design recommendations for foundations for the proposed structure and
related structural elements are presented in the Shallow Foundations section of
this report.
Floor Systems
For structures supported on a post-tensioned slab foundation system, the foundation
will also function as the floor system. If a conventional spread footing is used as a
foundation system, a slab-on-grade floor system is recommended provided the soils
are over-excavated to a depth of at least 2 feet below the proposed floor slab and
replaced with moisture conditioned, properly compacted engineered fill. On-site soils
are suitable as over-excavation backfill below floor slabs. Design recommendations for
floor systems for the proposed structure and related structural elements are presented
in the Floor Slabs section of this report.
Pavements
Recommended Pavement thicknesses for this project include 3½ inches of asphalt
over 6 inches of aggregate base course in light-duty parking areas and 6 inches of
asphalt over 6 inches of aggregate base course in heavy-duty drive lanes and loading
areas. Additional pavement section alternatives and discussion are presented in the
report.
Seismic
Considerations
As presented in the Seismic Considerations section of this report, the International
Building Code, which refers to Section 20 of ASCE 7, indicates the seismic site
classification for this site is D.
Construction
Observation
and Testing
Close monitoring of the construction operations and implementing drainage
recommendations discussed herein will be critical in achieving the intended
foundation, slab and pavement performance. We therefore recommend that Terracon
be retained to monitor this portion of the work.
General
Comments
This section contains important information about the limitations of this geotechnical
engineering report.
1. If the reader is reviewing this report as a pdf, the topics (bold orange font) above can be used to access the
appropriate section of the report by simply clicking on the topic itself.
2. This summary is for convenience only. It should be used in conjunction with the entire report for design
making and design purposes. It should be recognized that specific 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.
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INTRODUC TION
Geotechnical Engineering Report
Timberline Apartments
2908 South Timberline Road
Fort Collins, Colorado
Terracon Project No. 20215032
May 5, 2021
INTRODUCTION
This report presents the results of our subsu rface exploration and geotechnical engineering
services performed for the proposed Timberline Apartments to be located at 2908 South
Timberline Road in Fort Collins, Colorado. The purpose of these services is to provide information
and geotechnical engineering recommendations relative to:
■ Subsurface soil and rock conditions ■ Foundation design and construction
■ Groundwater conditions ■ Floor system design and construction
■ Site preparation and earthwork ■ Seismic considerations
■ Demolition considerations ■ Lateral earth pressures
■ Excavation considerations ■ Pavement design and construction
■ Dewatering considerations
The geotechnical engineering scope of services for this project include d the advancement of
seven (7) test borings to depths ranging from approximately 25 to 30 feet below existing site
grades.
Maps showing the site and boring locations are shown in the Site Location and Exploration
Plan sections, respectively. The results of the laboratory testing performed on soil and bedrock
samples obtained from the site during the field exploration are included on the boring logs and as
separate graphs in the Exploration Results section of this report.
SITE CONDITIONS
The following description of site conditions is derived from our site visit in association with the
field exploration and our review of publicly available geologic and topographic maps.
Item Description
Parcel Information
The project site is located on the south and east sides of 2908 South
Timberline Road in Fort Collins, Colorado. The approximate
Latitude/Longitude of the center of the site is 40.54676° N/105.03551°W
(Please refer to Site Location).
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May 5, 2021 ■ Terracon Project No. 20215032
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Item Description
Existing
Improvements
The site is currently occupied by parking areas associated with the existing
Timberline Church, located northwest of the site and native grasses and
weeds around the existing parking area.
Surrounding
Developments
The site is generally surrounded by residential developments and some
commercial developments. To the northwest of the site is the existing
Timberline Church and associated parking areas and landscaped areas. An
existing canal is present to the south of the site.
Current Ground
Cover
The current ground cover in the areas of exploration were primarily native
grasses and weeds and some areas of asphalt surfacing.
Existing Topography
Based on observations during our site visit and the provided site-surveyed
topographic maps, the site is relatively flat and total elevation change across
the site is about 5 to 10 feet.
PROJECT DESCRIPTION
Our final understanding of the project conditions is as follows:
Item Description
Information Provided
The following project information was provided to us through the following:
■ Conversation with the client.
■ Boundary & Topography Survey for Timberline Church and C.S.U.
Property, 2908 S Timberline Road, prepared by Olsson and dated March
26, 2021.
■ Conceptual Site Plan for Timberline Apartments, prepared by KBPHart
and dated March 14, 2021.
Project Description
We understand the project includes the construction of 180 apartment units in
seven (7) 3-story, walk-up apartment buildings. W e understand the apartment
buildings will be supported on post-tensioned slab foundations. In addition,
the project will include 288 parking spaces, drive lanes and access roads,
landscaped islands, sideways and a detention pond. We anticipate new
underground utilities will also be included in the proposed construction.
Project
Understanding
Terracon’s proposed scope of services presented in this proposal has been
provided under the belief that this site will be used as apartments. As such,
Terracon would like to inform the Client that if this apartment project is
converted at any time to another purpose such as condominiums, the Client
understands the services Terracon is proposing are not applicable for a
condominium project and that a separate consultant will need to be retained
for such services. Terracon will have no liability for any such unintended use
of our services and Client agrees to defend, indeminify, and hold harmless
Terracon for any such unintended usage.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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Item Description
Maximum Loads
(assumed)
■ Columns: 50 to 200 kips
■ Walls: 1 to 4 kips per linear foot (klf)
■ Slabs: 150 pounds per square foot (psf)
Grading/Slopes We anticipate minor cuts and fills on the order of 5 feet or less will be required
to achieve proposed grades.
Below-grade
Structures
■ We understand no below-grade areas (including basements or
swimming pools) are planned for this site.
■ We anticipate elevator pits will likely be included in the project
■ We understand a retaining wall may be included in the project.
Pavements
■ We assume both rigid (concrete) and flexible (asphalt) pavement
sections should be considered. Please confirm this assumption.
■ Traffic loads were not provided at the time of this report. We have
assumed traffic loads based on our understanding of the proposed
construction and our experience with similar projects
■ Pavements were designed using procedures outlined by the National
Asphalt Pavement Associations (NAPA) and the American Concrete
Institute (ACI).
If project information or assumptions vary from what is described above or if location of
construction changes, we sho uld be contacted as soon as possible to confirm and/or modify our
recommendations accordingly.
GEOTECHNICAL CHARACTERIZATION
Subsurface Profile
We have developed a general characterization of the subsurface conditions based upon our
review of the subsurface exploration, laboratory data, geologic setting and our understanding of
the project. This characterization, termed GeoModel, forms the basis of our geotechnical
calculations and evaluation of site preparation and foundation options. Conditions encounter ed at
each exploration point are indicated on the individual logs. The individual logs and the GeoModel
can be found in the Exploration Results section this report.
Model Layer Layer Name General Description Approximate Depth to
Bottom of Stratum
- Surface Asphalt or native grasses and weeds -
1 Silt
Sandy silt to sandy elastic silt, brown to
dark brown, light brown/orange brown
and tan, soft to very stiff
About 9½ to 12 feet below
existing site grades on the
southwest side of the site,
near the vicinity of
buildings 4, 5, 6 and 7.
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Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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Model Layer Layer Name General Description Approximate Depth to
Bottom of Stratum
2 Lean Clay
Lean clay with varying amounts of
sand and trace amounts of gravel,
brown to red brown with light gray,
medium stiff to very stiff
About 12 to 13 feet below
existing site grades on the
north side of the site, near
vicinity of buildings 1, 2 and
3.
3 Sand and
Gravel
Poorly graded gravel with sand, brown
to red brown, dense to very dense
About 17 to 21 feet below
existing site grades.
4 Bedrock
Claystone bedrock, weathered zone in
the upper 6 inches to 2 feet, light brown
with orange and gray in weathered
zone, gray to dark gray and very hard
in competent bedrock
To the maximum depths of
exploration of about 25 to
30 feet below existing site
grades.
As noted in General Comments, this characterization is based upon widely spaced exploration
points across the site and variations are likely.
Groundwater Conditions
The boreholes were observed while drilling for the presence and level of groundwater. Upon
removal of augers/samplers the boreholes caved due to the sand and gravel soil encountered
above bedrock, therefore groundwater levels after drilling were not able to be obtained. 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.
Elevation of Groundwater
While Drilling, ft.
1 12 4,919
2 12 4,919
3 12 4,916
4 13 4,917
5 13 4,915
6 12 4,917
7 13 4,917
These observations represent short-term groundwater conditions at the time of and shortly after
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.
Groundwater level fluctuations occur due to seasonal variations in the water levels present in
nearby water features, amount of rainfall, runoff and other factors not evident at the time the
borings were performed. Therefore, groundwater levels during construction or at other times in
the life of the structure(s) may be higher or lower than the levels indicated on the boring logs. The
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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possibility of groundwater level fluctuations should be considered when developing the design
and construction plans for the project.
Fluctuations in groundwater levels can best be determined by implementation of a groundwater
monitoring plan. Such a plan would include installation of groundwater piezometers, and periodic
measurement of groundwater levels over a sufficient period of time.
Laboratory Testing
Representative soil samples were selected for swell-consolidation testing and exhibited no
movement to 0.4 percent swell when wetted. Samples of site soils and bedrock exhibited
unconfined compressive strengths of approximately 942 and 8,158 pounds per square foot (psf).
Samples of site soils and bedrock selected for plasticity testing exhibited low to moderate plasticity
with liquid limits ranging from non -plastic to 50 and plasticity indices ranging from non-plastic to
29. Laboratory test results are presented in the Exploration Results section of this report.
Soil Infiltration Rate
W e understand the project is considering LID design and the impacts of an infiltration systems
near structures. Based on the soil encountered in our exploratory borings, we believe the soil
encountered in the upper 10 feet on the site will likely be hydrologic soil group C and will likely
have a slow infiltration rate when thoroughly wetted. Percolation tests or double -ring infiltrometer
tests can be used to determine actual infiltration rat e of the on-site soils. These services were
not included in our scope of work for project; however, can be completed, for an additional fee at
the request of the client.
GEOTECHNICAL OVERVIEW
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
several geotechnical conditions that could impact design, construction and performance of the
proposed structures, pavements, and other site improvements. These included shallow
groundwater and potentially soft, low strength clay and silt soils. These conditions will require
particular attention in project planning, design and during construction and are discussed in
greater detail in the following sections.
Shallow Groundwater
As previously stated, groundwater was measured at depths ranging from about 12 to 13 feet
below existing site grades. Groundwater level fluctuations occur due to seasonal variations in the
water levels present in nearby water features, amount of rainfall, runoff and other factors not
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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evident at the time the borings were performed. Therefore, groundwater levels during
construction or at other times in the life of the structure(s) may be higher or lower than the levels
indicated on the boring logs. Terracon recommends maintaining a separation of at least 3 feet
between the bottom of proposed below -grade foundations and measured groundwater levels.
Final site grading should be planned and designed to avoid cuts where shallow groundwater is
known to exist, and also in areas where such grading would create shallow groundwater
conditions. If deeper cuts are unavoidable, temporary construction dewatering and/or installation
of a subsurface drainage system may be needed.
Low Strength Soils
Comparatively soft lean clay and silt soils were encountered within the upper approximately 9 to
13 feet in some of the borings completed at this site. These materials present a risk for potential
settlement of shallow foundations, floor slabs, pavements and other surficial improvements.
These materials can also be susceptible to disturbance and loss of strength under repeated
construction traffic loads and unstable conditions could develop. Stabilization of soft soils may
be required at some locations to provide adequate support for construction equipment and
proposed structures. Terracon should be contacted if these conditions are encountered to
observe the conditions exposed and to provide guidance regarding stabilization (if needed).
Foundation and Floor System Recommendations
We understand the project team is planning to support the proposed buildings on post -tensioned
slabs. Based on the subsurface conditions encountered, use of post -tensioned slab foundations
is feasible for support of the structures provided some foundation movement can be tolerated. As
an alternative to post-tensioned slabs, or for other structures planned on the site, shallow spread
footing foundations can be used. Design recommendations for foundations for the proposed
structure and related structural elements are presented in the Shallow Foundations section of
this report.
For structures supported on a post -tensioned slab foundation system, the foundation will also
function as the floor system. If a conventional spread footing is used as a foundation system, a
slab-on-grade floor system is recommended provided the soils are over-excavated to a depth of at
least 2 feet below the proposed floor slab and replaced with moisture conditioned, properly
compacted engineered fill. On-site soils are suitable as over-excavation backfill below floor slabs.
Design recommendations for floor systems for the proposed structure and related structural
elements are presented in the Floor Slabs section of this report.
The General Comments section provides an understanding of the report limitations.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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EARTHWORK
The following presents recommendations for site preparation , demolition, excavation, subgrade
preparation, fill materials, compaction requirements, utility trench backfill, grading and drainage
and exterior slab design and construction. Earthwork on the project should be observed and
evaluated by Terracon. Evaluation of earthwork should include observation and/or testing of over -
excavation, subgrade preparation, placement of engineered fills, subgrade stabilization and other
geotechnical conditions exposed during the construction of the project.
Site Preparation
Prior to placing any fill, strip and remove existing vegetatio n, topsoil, and any other deleterious
materials from the proposed construction areas.
Stripped organic materials should be wasted from the site or used to re -vegetate landscaped areas
or exposed slopes after completion of grading operations. Prior to the placement of fills, the site
should be graded to create a relatively level surface to receive fill, and to provide for a relatively
uniform thickness of fill beneath proposed structures.
Demolition
Demolition of the existing parking lots and concrete should include complete removal of all 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.
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.
Excavation
It is anticipated that excavations for the proposed construction can be a ccomplished with
conventional earthmoving equipment. Excavations into the on-site soils will encounter weak and/or
saturated soil conditions with possible caving conditions.
The soils to be excavated can vary significantly across the site as their class ifications 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.
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Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
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Although evidence of fills or underground facilities such as grease pits, septic tanks, vaults,
basements, and utilities was not observed during the site reconnaissance, such features could be
encountered during construction. If unexpected underground facilities are encountered, such
features should be removed and the excavation thoroughly cleaned prior to backfill placement
and/or construction.
Any over-excavation that extends below the bottom of foundation elevation should extend laterally
beyond all edges of the foundations at least 8 inches per foot of over -excavation depth below the
foundation base elevation. The over-excavation should be backfilled to the foundation base
elevation in accordance with the recommendations presented in this report.
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. Well points may be required for
significant groundwater flow, or where excavations penetrate groundwater to a significant depth.
Groundwater seepage should be anticipated for excavations approaching the level of bedrock.
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.
Subgrade Preparation
After vegetative layer and/or existing asphalt has been removed from the construction area, the
top 10 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.
If pockets of soft, loose, or otherwise unsuitable materials are encountered at the bottom of the
foundation excavations and it is inconvenient to lower the foundations, the proposed foundation
elevations may be reestablished by over-excavating the unsuitable soils and backfilling with
compacted engineered fill or lean concrete.
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Timberline Apartments ■ Fort Collins, Colorado
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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.
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 lime, fly ash , cement or geosynthetics 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.
Fill Materials
The on-site soils or approved granular and low plasticity cohesive imported materials may be used
as fill material. Bedrock excavated during site development and construction can be reused as fill
provided the material is broken down and thoroughly processed to a “soil -like” consistency, with
no particles greater than 2 inches in size. The earthwork contractor should expec t significant
mechanical processing and moisture conditioning of the site soils and/or bedrock will be needed
to achieve proper compaction
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 30-100
No. 200 Sieve 80 (max.)
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Soil Properties Values
Liquid Limit 35 (max.)
Plasticity Index 15 (max.)
Other import fill materials types may be suitable for use on the site depending upon proposed
application and location on the site, and could be tested and approved for use on a case -by-case
basis.
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 95 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 +3 % 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 proof rolled.
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.
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 structures should be designed with flexible
couplings, so minor deviations in alignment do not result in breakage or distress. Utility knockouts
in foundation walls 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
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Timberline Apartments ■ Fort Collins, Colorado
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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 buildings should be effectively sealed to restrict water intrusion and flow
through the trenches that could migrate below the buildings. We recommend constructing an
effective clay “trench plug” that extends at least 5 feet out from the face of the building exteriors.
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.
Grading and Drainage
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 permitte d to pond near or adjacent to the
perimeter of the structures (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 5 feet
beyond the perimeter of the proposed buildings, where possible. Locally, flatter grades may be
necessary to transition ADA access requirements for flatwork. The use of swales, chases and/or
area drains may be required to facilitate drainage in unpaved areas around the perimeter of the
buildings. 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 buildings and prior to pro ject 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 f or 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 t he
structures, care should be taken that joints are properly sealed and maintained to prevent the
infiltration of surface water.
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Planters located adjacent to structures (if any) 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 be used sparingly near the building. Roof
drains should discharge on to pavements or be extended away from the structures 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 , a detention pond, or other
appropriate outfall.
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:
◼ Minimizing moisture increases in the backfill;
◼ Controlling moisture-density during placement of the backfill;
◼ Using designs which allow vertical movement between the exterior features and
adjoining structural elements; and
◼ Placing control joints on relatively close centers.
Construction Observation and Testing
The earthwork efforts should be monitored under the direction of Terracon. Monitoring should
include documentation of adequate removal of vegetation and topsoil, proof rolling, and mitigation
of areas delineated by the proof roll to require mitigation. Each lift of compacted fill should be
tested, evaluated, and reworked as necessary until approved by Terracon prior to placement of
additional lifts.
In areas of foundation excavations, the bearing subgrade should be evaluated under the direction
of Terracon. In the event that unanticipated conditions are encountered, Terracon should
prescribe mitigation options.
In addition to the documentation of the essential parameters necessary for construction, the
continuation of Terracon into the construction phase of the project provides the continuity to
maintain Terracon’s evaluation of subsurface conditions, including assessing variations and
associated design changes.
SHALLOW FOUNDATIONS
If the site has been prepared in accordance with the requirements noted in Earthwork, the
following design parameters are applicable for shallow foundations.
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Post-Tensioned Slabs – Design Recommendations
We understand the proposed buildings will be supported on post -tensioned slab foundations.
Based on the subsurface conditions encountered, use of post -tensioned slabs is feasible for
support of the structures provided some foundation movement can be tolerated and:
◼ The post-tensioned slab foundations are properly designed and constructed;
◼ Approved materials supporting the foundation are properly placed and compacted;
◼ Proper surface drainage is maintained throughout the life of the structures; and
◼ Prudent landscaping measures are used.
In our opinion, total foundation movements on the order of about 1 inch s hould be expected.
Provided foundations are properly designed, foundation movements could result in periodic, and
possibly seasonal, cosmetic distress to drywall, window frames, door frames and other features.
We would anticipate that the frequency of di stress and amount of movement would generally
diminish with time provided proper drainage is established and/or maintained. We believe
potential total foundation movements can be reduced to ½ to ¾ inch or less if at least 3 feet of
imported granular engineered fill is placed directly below the post -tensioned slab foundations.
The granular fill should consist of materials within the specified limits presented in the Fill
Materials section of the Earthwork section this report.
Based on the subsurface conditions, post-tensioned slabs should be designed using criteria
presented by the Post-Tensioning Institute1 based on the following:
Post-tensioned Slab Design Parameters PTI, Third Edition
2018 IBC/IRC
Edge Moisture Variation Distance, em
(feet)
Center Lift Condition 8.5
Edge Lift Condition 4.4
Differential Soil Movement, ym (inches)
Center Lift Condition -1.2
Edge Lift Condition 0.44
◼ Maximum Net Allowable Bearing Pressure ............................................................... 2,000 psf
◼ Slab-Subgrade Friction Coefficient,
◼ on polyethylene sheeting ................................................................................ 0.75
1 (2004, Third Edition, reprinted with 2008 Supplement), Design of Post-Tensioned Slabs-on-Ground, Post-
Tensioning Institute.
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◼ on cohesionless soils ...................................................................................... 1.00
◼ on cohesive soils............................................................................................. 2.00
The maximum net allowable bearing pressure may be increased by 1/3 for transient wind or
seismic loading.
It should be noted that ym is the estimated vertical movement at the edges of a uniformly loa ded
slab. These are theoretical values that are used in the design of post -tensioned slabs-on-grade
and do not represent the movements that would be expected from the actual loading conditions.
As previously discussed, the use of post -tensioned slabs assumes that some potential movement
is considered acceptable.
Post-Tensioned Slabs – Construction Considerations
Post-tensioned slabs, thickened or turndown edges and/or interior beams should be designed
and constructed in accordance with the requirements of the PTI and the American Concrete
Institute (ACI).
If traditional post-tensioned slab foundations are selected, exterior slab edges should be placed
a minimum of 30 inches below finished grade for frost protection. Finished grade is the lowest
adjacent grade for perimeter beams. Extending exterior slab edges to depths of at least 30 inches
will likely encroach upon soft to very loose and nearly saturated to wet soils requiring stabilization
of subgrade prior to construction.
If portions of the building floor slab will be unheated, such as patios and entryways, consideration
should be given to structurally separating these areas of the slab from the remaining in terior
portion of the slab. Exterior slab areas may be cantilevered portions of the slab which are subject
to uplift from frost heave and swelling of the expansive soils, sometimes beyond those used for
design, due to over watering of adjacent to landscap ed areas. Such movement in the exterior
slabs can result in change in slab grade to the point where negative grade results and water ponds
adjacent to the interior areas of the slab. Repairs of such conditions are difficult and costly,
particularly if the floor slabs are post-tensioned slabs.
Exterior slabs in unheated areas are subject to frost heave beneath the slab. Therefore, in design
of the exterior slabs, potential movement from frost heave should be considered in the design.
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It should be noted that the presences of 1 to 2-foot steps within long spans of post-tensioned
slabs could create a situation where the slabs at different elevations perform independently of
one another unless the steps are properly reinforced and designed to tie the slabs to gether to act
as one rigid structure. We strongly recommend that joints be designed within the full height of
the structure of the building over each step in order to help the structure be capable of
withstanding movements on the order of 1 inch.
The estimated movement should also be considered as the potential amount of tilting of the
structure, which could be caused by non -uniform, significant wetting of the subsurface materials
below the post-tensioned slab, resulting in potential movement. Failure to maintain soil water
content below the slab and to maintain proper drainage around the structure will nullify the
movement estimates provided above.
If the site has been prepared in accordance with the requirements noted in Earthwork, the
following design parameters are applicable for shallow foundations.
Spread Footings - Design Recommendations
As an alternative to post -tensioned slabs, or for other structures planned on the site, shallow
spread footing foundations can be used.
Description Values
Bearing material Properly prepared on-site soil, or new, properly
placed engineered fill.
Maximum net allowable bearing pressure1 2,000 psf
Minimum foundation dimensions Columns: 30 inches
Continuous: 18 inches
Lateral earth pressure coefficients2
Active, Ka = 0.33
Passive, Kp = 3.0
At-rest, Ko = 0.50
Sliding coefficient2 µ = 0.46
Moist soil unit weight ɣ = 120 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
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Description Values
1. The recommended maximum net 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 fact ors 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. Interior column pads in heated areas should bear at least
12 inches below the adjacent grade (or top of the floor slab) for confinement of the bearing materials and to
develop the recommended bearing pressure.
4. The estimated movements presented above are based on the assumption that the maximum footing size is
10 feet for column footings and 1.5 feet for continuous footings. Larger foundation footprints will likely require
reduced net allowable soil bearing pressures to reduce risk for potential settlement.
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 cou ld occur if water from any source infiltrates the
foundation soils; therefore, proper drainage should be provided in the final design and during
construction and throughout the life of the structure. Failure to maintain the proper drainage as
recommended in the Grading and Drainage section of the Earthwork section of this report will
nullify the movement estimates provided above.
Spread Footings - Construction Considerations
To reduce the potential of “pumping” and softening of the foundation soils at the foundation
bearing level and the requirement for corrective work, we suggest the foundation excavation for
the structures 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 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 are anticipated as excavations approac h the groundwater surface.
Unstable surfaces will need to be stabilized prior to backfilling excavations and/or constructing
the building foundation, floor slab and/or project pavements. The use of angular rock, recycled
concrete and/or gravel pushed or “c rowded” into the yielding subgrade is considered suitable
means of stabilizing the subgrade. The use of geogrid materials in conjunction with gravel could
also be considered and could be more cost effective.
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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 Terraco n. If the soil conditions encountered differ
significantly from those presented in this report, supplemental recommendations will be required.
SEISMIC CONSIDERATIONS
The seismic design requirements for buildings and other structures are based on Seismic Design
Category. Site Classification is required to determine the Seismic Design Category for a structure.
The Site Classification is based on the upper 100 feet of the site profile defined by a weighted
average value of either shear wave velocity, standard penetration resistance, or undrained shear
strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC).
Based on the soil/bedrock properties encountered at the site and as described on the exploration
logs and results, it is our professional opinion that the Seismic Site Classification is D.
Subsurface explorations at this site were extended to a maximum depth of 30 feet. The site
properties below the boring depth to 100 feet were estimated based on our experience and
knowledge of geologic conditions of the general area. Additional deeper borings or geophysical
testing may be performed to confirm the conditions below the current boring depth.
FLOOR SLABS
For structures supported on a post -tensioned slab foundation system, the foundation will also
function as the floor system. If a conventional spread footing is used as a foundation system, a
slab on grade floor system is recommended provided the soils are over -excavated to a depth of
at least 2 feet below the proposed floor slab and replaced with moisture conditioned, properly
compacted engineered fill. On -site soils are suitable as over-excavation backfill below floor slabs.
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 should
be scarified to a depth of at least 10 inches, moisture conditioned and compacted. The moisture
content and compaction of subgrade soils should be maintained until slab construction .
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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 i ncrease 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 Earthwork section of this report.
For structural design of concrete slabs-on-grade subjected to point loadings, a modulus of
subgrade reaction of 100 pounds per cubic inch (pci) may be used for floors supported on re -
compacted existing soils at the site. A modulus of 200 pci may be used for floors supported on
at least 1 foot of non-expansive, imported granular fill.
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, or utility lines to allow independent movement.
◼ 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.
◼ Interior utility trench backfill placed beneath slabs should be compacted in accordance
with the recommendations presented in the Earthwork section of this report.
◼ Floor slabs should not be constructed on frozen subgrade.
◼ Other design and construction considerations, as outlined in the ACI Design Manual,
Section 302.1R are recommended.
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 bro ken utility
lines. Therefore, it is imperative that the recommendations presented in this report be followed.
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BELOW -GRADE STRUCTURES
Lateral Earth Pressures
Below-grade structures or 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 stre ngth 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.
Earth Pressure Coefficients
Earth Pressure
Conditions
Coefficient for
Backfill Type
Equivalent Fluid
Density (pcf)
Surcharge
Pressure, p1 (psf)
Earth Pressure,
p2 (psf)
Active (Ka) 0.33 40 (0.33)S (40)H
At-Rest (Ko) 0.50 60 (0.50)S (60)H
Passive (Kp) 3.0 360 --- ---
Applicable conditions to the above include:
■ 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
■ For passive earth pressure to develop, wall must move horizontally to mobilize resistance
■ Uniform surcharge, where S is surcharge pressure
■ In -situ soil backfill weight a maximum of 120 pcf
■ Horizontal backfill, compacted between 95 and 98 percent of standard Proctor maximum
dry density
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■ Loading from heavy compaction equipment not included
■ No hydrostatic pressures acting on wall
■ No dynamic loading
■ No safety factor included
■ Ignore passive pressure in frost zone
Backfill placed against structures should consist of granular soils or low plasticity cohesive soils.
For the granular values to be valid, the granular backfill must extend out and up from the base of
the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases,
respectively. To calculate the resistance to sliding, a value of 0.32 should be used as the ultimate
coefficient of friction between the footing and the underlying soi l.
Subsurface Drainage for Below-Grade Walls
A perforated rigid plastic or metal drain line installed behind the base of walls that extend below
adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain
line around a below-grade building area or exterior retaining wall should be placed near
foundation bearing level. The drain line should be sloped to provide positive gravity drainage or
to a sump pit and pump. The drain line should be surrounded by clean, free -draining granular
material having less than 5 percent passing the No. 200 sieve. The free -draining aggregate
should be encapsulated in a filter fabric. The granular fill should extend to within 2 feet of final
grade, where it should be capped with compacted cohesive fill to reduce infiltration of surface
water into the drain system.
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As an alternative to free -draining granular fill, a pre -fabricated drainage structure may be used.
A pre-fabricated drainage structure is a plastic drainage core or mesh which is covered with filter
fabric to prevent soil intrusion, and is fastened to the wall prior to placing backfill.
To control hydrostatic pressure behind the wall we recommend that a drain be installed at the
foundation wall with a collection pipe leading t o 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 operat e within a distance closer
than the exposed height of retaining walls to prevent lateral pressures more than those provided.
Elevator Pit
We assume an elevator pit will be included in the interior of the building. The elevator pit will likely
consist of reinforced concrete walls with a concrete base slab. Based on our experience with this
type of structure, we anticipate the base slabs will be about 5 feet below the level of the finished
floor slab.
Elevator Pit - Design Recommendation
Subsurface conditions in elevator pit excavations are generally anticipated to consist of native clays
and/or sands/gravels. Groundwater was encountered at depths of about 11½ to 14 ½ feet below
existing site grades at the time of our field exploration. However, groundwater le vels can and
should be expected to fluctuate over time.
Depending upon final site grades and elevator pit elevations, groundwater could impact the
performance of the pit base slab. If the pit slab is constructed at or within about 4 feet of the level
of groundwater, the pit/slab should be designed and constructed to resist hydrostatic pressures
and uplift due to the effects of buoyancy or it should be protected by an underdrain system for
permanent dewatering. “Water-proofing” of the pit will also be need ed if permanent dewatering is
not used. Terracon should evaluate the groundwater level within each elevator pit area prior to or
during construction.
The elevator pit walls should be designed for the lateral earth pressures imposed by the soil
backfill. Earth pressures will primarily be influenced by structural design of the walls, conditions
of wall restraint and type, compaction and drainage of the backfill. For purposes of design, we
have assumed approximately 5 feet of fill will be retained by the pit walls and backfill will consist of
the on-site lean clays. If taller walls are planned, or if different type of backfill is used, we should
be contacted to review our data and confirm or modify the design criteria presented below.
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Active earth pressure is commonly used for design of walls (such as free -standing cantilever
retaining walls) and assumes some wall rotation and deflection. For walls that can deflect and
rotate about the base, with top lateral movements of about ¼ to ½ percent or more of the wall
height, lower “active” earth pressures could be considered for design. Use of the “active” condition
assumes deflection and thus cracking of walls could occur. For rigid walls where negligible or very
little rotation and deflection will occur, "at -rest" lateral earth pressures should be used in the
design.
Reinforced concrete pit walls should be designed for lateral earth pressures and/or combined
hydrostatic and lateral earth pressures at least equal to those indicated in the lateral earth
pressure table presented at the beginning of this section .
PAVEMENTS
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. 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 proof rolled with a loaded tandem-axle dump
truck prior to final g rading and paving. All pavement areas should be moisture conditioned and
properly compacted to the recommendations in this report immediately prior to paving.
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:
◼ 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
◼ 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)
◼ Subgrade Soil Characteristics
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• USCS Classification – CL/ML, 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):
◼ Automobile Parking Areas
• ACI Category A: Automobile parking with an ADTT of 1 over 20 years
◼ Main Traffic Corridors
• ACI Category A: Automobile parking area and service lanes with an ADTT of
up to 10 over 20 years
◼ Subgrade Soil Characteristics
• USCS Classification – CL/ML
◼ 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 Thicknesses (Inches)
Asphaltic
Concrete
Surface
Aggregate
Base Course
Portland
Cement
Concrete
Total
Automobile Parking
(NAPA Class I and
ACI Category A)
A 3½ 6 - 9½
B - - 5 5
Main Traffic
Corridors
(NAPA Class II and
ACI Category A)
A 6 6 - 12
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 inch es 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 con crete should conform to approved mix
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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).
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.
For areas subject to concentrated and repetitive loading conditions (if any) 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 inch es of granular
base. Prior to placement of the granular base, the areas should be thoroughly proof rolled. 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:
■ Site grades should slope a minimum of 2 percent away from the p avements;
■ The subgrade and the pavement surface have a minimum 2 percent slope to promote proper
surface drainage;
■ Consider appropriate edge drainage and pavement under drain systems;
■ Install pavement drainage surrounding areas anticipated for frequent wetting;
■ Install joint sealant and seal cracks immediately;
■ Seal all landscaped areas in, or adjacent to pavements to reduce moisture migration to
subgrade soils; and
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■ Placing compacted, low permeability backfill against the exterior side of curb and gutter.
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
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 d epth below the pavement structure.
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 localiz ed 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.
FROST CONSIDERATIONS
The soils on this site are frost susceptible, and small amounts of water can affect the performance
of the slabs on-grade, sidewalks, and pavements. Exterior slabs should be anticipated to heave
during winter months. If frost action needs to be eliminated in critical areas, we recommend the
use of non-frost susceptible (NFS) fill or structural slabs (for instance, structural stoops in front of
building doors). Placement of NFS material in large areas may not be feasible; however, the
following recommendations are provided to help reduce potential frost heave:
■ Provide surface drainage away from the building and slabs, and toward the site storm
drainage system.
■ Install drains around the perimeter of the building, stoops, below exterior slabs and
pavements, and connect them to the storm drainage system .
■ Grade clayey subgrades, so groundwater potentially perched in overlying more permeable
subgrades, such as sand or aggregate base, slope toward a site drainage system .
■ Place NFS fill as backfill beneath slabs and pavements critical to the project .
■ Place a 3 horizontal to 1 vertical (3H:1V) transition zone between NFS fill and other soils.
■ Place NFS materials in critical sidewalk areas.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Responsive ■ Resourceful ■ Reliable 26
As an alternative to extending NFS fill to the full frost depth, consideration can be made to placing
extruded polystyrene or cellular concrete under a buffer of at least 2 feet of NFS material.
CORROSIVITY
At the time this report was prepared, the laboratory testing for water -soluble sulfates had not been
completed. We will submit a supplemental section with the testing results and recommendations
once the testing has been completed.
GENERAL COMMENTS
Our analysis and opinions are based upon our understanding of the project, the geotechnical
conditions in the area, and the data obtained from our site exploration. Natural variations will occur
between exploration point locations or due to the modifying effec ts of construction or weather.
The nature and extent of such variations may not beco me evident until during or after construction.
Terracon should be retained as the Geotechnical Engineer, where noted in th is report, to provide
observation and testing services during pertinent construction phases. If variations appear, we
can provide further evaluation and supplemental recommendations. If variations are noted in the
absence of our observation and testing services on -site, we should be immediately notified so
that we can provide evaluation and supplemental recommendations.
Our Scope of Services does not include either specifically or by implication any environmental or
biological (e.g., mold, fungi, 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.
Our services and any correspondence or collaboration through this system are intended for the
sole benefit and exclusive use of our client for specific application to the project discussed and
are accomplished in accordance with generally accepted geotechnical engineering practices with
no third-party beneficiaries intended. Any third-party access to services or correspondence is
solely for information purposes to support the services provided by Terracon to our client.
Reliance upon the services and any work product is limited to our client, and is not intended for
third parties. Any use or reliance of the provided information by third parties is done solely at thei r
own risk. No warranties, either express or implied, are intended or made.
Site characteristics as provided are for design purposes and not to estimate excavation cost. Any
use of our report in that regard is done at the sole risk of the excavating cost estimator as there
may be variations on the site that are not apparent in the data that could significantly impact
excavation cost. Any parties charged with estimating excavation costs should seek their own site
characterization for specific purposes to obtain the specific level of detail necessary for costing.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Responsive ■ Resourceful ■ Reliable 27
Site safety, and cost estimating including, excavation support, and dewatering
requirements/design are the responsibility of others. If changes in the nature, design, or location
of the project are planned, our conclusions and recommendations shall not be considered valid
unless we review the changes and either verify or modify our conclusions in writing.
Responsive ■ Resourceful ■ Reliable
ATTACHMENTS
Contents:
EXPLORATION AND TESTING PROCEDURES
SITE LOCATION AND EXPLORATION PLANS
EXPLORATION RESULTS
SUPPORTING INFORMATION
Note: Refer to each individual Attachment for a listing of contents.
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2
EXPLORATION AND TESTING PROCEDURES
Field Exploration
The field exploration program consist ed of the following:
Number of Borings Boring Depth (feet) 1 Location
7 25 to 30 or auger refusal Planned building areas
Boring Layout and Elevations: We used handheld GPS equipment to locate borings with an
estimated horizontal accuracy of +/-20 feet. A ground surface elevation at each boring location
was obtained by interpolation from a provided site specific, surveyed topographic map.
Subsurface Exploration Procedures: We advanced soil borings with a truck-mounted drill rig
using solid-stem, continuous-flight augers. Three samples were obtained in the upper 10 feet of
each boring and at intervals of 5 feet thereafter. Soil sampling was performed using modified
California barrel and standard split -barrel sampling procedures. For the standard split -barrel
sampling procedure, a standard 2 -inch outer diameter split-barrel sampling spoon is driven into
the ground by a 140 -pound automatic hammer falling a distance of 30 inches. The number of
blows required to advance the sampling spoon the last 12 inches of a normal 18 -inch penetration
is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values,
also referred to as N-values, are indicated on the boring logs at the test depths. For the modified
California barrel sampling procedure, a 2½-inch outer diameter split-barrel sampling spoon is
used for sampling. Modified California barrel sampling procedures are similar to standard split -
barrel sampling procedures; however, blow counts are typically recorded for 6 -inch intervals for a
total of 12 inches of penetration. The samples were placed in appropriate containers, taken to our
soil laboratory for testing, and classified by a geotechnical engineer.
In addition, we observed and recorded groundwater levels during drilling observations. No
provisions were made to obtain delayed groundwater measurements.
Our exploration team prepared field boring logs as part of standard drilling operations including
sampling depths, penetration distances, and other relevant sampling information. Field logs will
include visual classifications of materials encountered during drilling, and our interpretation of
subsurface conditions between samples. Final boring logs, prepared from field logs, represent
the geotechnical engineer's interpretation, and include modifications based on observations an d
laboratory test results.
Property Disturbance: We backfilled borings with auger cuttings after completion. Borings
completed in pavement areas were backfilled with auger cuttings and patched with asphalt, as
Geotechnical Engineering Report
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2
appropriate. Our services did not include repair of the site beyond backfilling our boreholes, and
patching existing pavements. Excess auger cuttings were dispersed in the general vicinity of the
boreholes. Because backfill material often settles below the surface after a period, we recommend
checking boreholes periodically and backfilling, if necessary. We can provide this service, for
additional fees, at your request.
Laboratory Testing
The project engineer reviewed field data and assigned various laboratory tests to better
understand the engineerin g properties of various soil and bedrock strata. Laboratory testing was
conducted in general accordance with applicable or other locally recognized standards.
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 judgement.
Testing was performed under the direction of a geotechnical engineer and included the following:
■ Visual classification ■ Moisture content
■ Dry density ■ Atterberg limits
■ Grain-size analysis ■ One-dimensional swell
■ hydrometer ■ Unconfined compressive strength
■ Water-soluble sulfates
Our laboratory testing program includes examination of soil samples by an engineer. Based on
the material’s texture and plasticity, we described and classified soil samples in accordance with
the Unified Soil Classification System (USCS). Soil and bedrock samples obtained during our
field work will be disposed of after laboratory testing is complete unless a specific request is made
to temporarily store the samples for a longer period of time.
Bedrock samples obtained had rock classification conducted using locally accepted practices for
engineering purposes. Boring log rock classification is determined using the Description of Rock
Properties.
Responsive ■ Resourceful ■ Reliable
SITE LOCATION AND EXPLORATION PLANS
Contents:
Site Location Plan
Exploration Plan
Note: All attachments are one page unless noted above.
SITE LOCATION
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above and
outside the table – please leave that alone. Limit editing to inside the table.
The line at the bottom about the general location is a separate table line. You can edit
it as desired, but try to keep to a single line of text to avoid reformatting the page.
SITE LOCA TION
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
EXPLORATION PLAN
Timberline Apartments ■ Fort Collins, Colorado
May 5, 2021 ■ Terracon Project No. 20215032
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above and
outside the table – please leave that alone. Limit editing to inside the table.
The line at the bottom about the general location is a separate table line. You can edit
it as desired, but try to keep to a single line of text to avoid reformatting the page.
EXPLORATION P LAN
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
EXPLORATION RESULTS
Contents:
GeoModel
Boring Logs (7 pages)
Atterberg Limits
Grain Size Distribution (2 pages)
Consolidation/Swell (4 pages)
Unconfined Compressive Strength (4 pages)
Note: All attachments are one page unless noted above.
4,895
4,900
4,905
4,910
4,915
4,920
4,925
4,930
4,935
ELEVATION(MSL)(feet)Timberline Apartments Fort Collins, CO
Terracon Project No. 20215032
Layering shown on this figure has been developed by the
geotechnical engineer for purposes of modeling the subsurface
conditions as required for the subsequent geotechnical engineering
for this project.
Numbers adjacent to soil column indicate depth below ground
surface.
NOTES:
1 2
3
4
5 6
7
GEOMODEL
This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.
Groundwater levels are temporal. The levels shown are representative of the date
and time of our exploration. Significant changes are possible over time.
Water levels shown are as measured during and/or after drilling. In some cases,
boring advancement methods mask the presence/absence of groundwater. See
individual logs for details.
First Water Observation
Poorly graded gravel with sand, brown to red brown, dense to
very dense3
Claystone bedrock, weathered zone in the upper 6 inches to
2 feet, light brown with orange and gray in weathered zone,
gray to dark gray and very hard in competent bedrock
4
LEGEND
Asphalt
Sandy Silt
Poorly-graded Gravel with
Sand
Weathered Rock
Bedrock
Vegetative Layer
Sandy Lean Clay
Sandy Elastic Silt
Lean Clay with Sand
Aggregate Base Course
Clayey Sand
Model Layer General DescriptionLayer Name
Sandy silt to sandy elastic silt, brown to dark brown, light
brown/orange brown and tan, soft to very stiff1
Lean clay with varying amounts of sand and trace amounts of
gravel, brown to red brown with light gray, medium stiff to very
stiff
2
SAND AND GRAVEL
BEDROCK
SILT
LEAN CLAY
12
20.5
24.4
1
3
4
12
3
9.5
21
29.4
2
1
3
4
12
10
19
24.5
1
3
4
12
12
20.5
21
24.4
1
3
4
3
13
12
18
29.4
2
3
4
13
12
18
24.5
2
3
4
12 13
17
24.4
2
3
4
13
2-2-2
N=4
4-5
5-7-10
N=17
7-12
7-10-15
N=25
50/4"
no recovery -
grab of auger
cuttings
0/500 63
16.4
17.6
17.8
8.5
8.1
18.7
107
129
49-30-19
ASPHALT, approximately 4 inches
SANDY SILT (ML), soft to medium stiff, varies to
lean clay with varying amounts of sand
brown
brown to light brown
light brown to tan, very stiff
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, medium dense
WEATHERED CLAYSTONE, light brown with
orange and gray, weathered
CLAYSTONE, gray to dark gray, hard to very hard
Boring Terminated at 24.4 Feet
0.4
12.0
20.5
22.0
24.4
4930.5
4919
4910.5
4909
4906.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5458° Longitude: -105.0372°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4931 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings and patched with asphalt to
match existing surfaces
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 1
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
12' while drilling
WATER LEVEL OBSERVATIONS
1
3
4 SAMPLETYPE
10-15
7-8-10
N=18
6-9
22-38-31
N=69
12-26-20
N=46
skipped sample
to keep hole
open with
flowing sands
50/5"
-0.1/1,000
65
0
10.1
14.5
7.1
13.7
10.7
17.0
101
124
33-17-16
NP
NATIVE GRASSES AND WEEDS, approximately
6 inches
SANDY LEAN CLAY (CL), trace gravel, brown,
very stiff
SANDY SILT, brown, very stiff, varies to lean clay
with varying amounts of sand
POORLY GRADED GRAVEL WITH SAND (GP),
brown to red brown, dense to very dense
CLAYSTONE, gray to dark gray, hard to very hard
Boring Terminated at 29.4 Feet
0.5
3.0
9.5
21.0
29.4
4930.5
4928
4921.5
4910
4901.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSPROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
12' while drilling
WATER LEVEL OBSERVATIONS DEPTH(Ft.)5
10
15
20
25 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5460° Longitude: -105.0358°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4931 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 2
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
2
1
3
4 SAMPLETYPE
3-4-3
N=7
3-5
18-33-31
N=64
11-50/5"
skipped sample
to keep hole
open with
flowing sands
50/6"
3280 60
16.6
18.8
6.9
10.0
18.2
46-30-16
NATIVE GRASSES AND WEEDS, approximately
3 inches
SANDY SILT (ML), brown to dark brown, medium
stiff, varies to lean clay with varying amounts of
sand
trace organics
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, dense to very dense
CLAYSTONE, light brown with gray and orange to
gray, hard to very hard
Boring Terminated at 24.5 Feet
0.3
10.0
19.0
24.5
4927.5
4918
4909
4903.5
106
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)LOCATION See Exploration Plan
Latitude: 40.5464° Longitude: -105.0358°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4928 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 3
Tetrad Property Group LLCCLIENT:
ATTERBERG
LIMITS
LL-PL-PI
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
12' while drilling
WATER LEVEL OBSERVATIONS
1
3
4 SAMPLETYPE
7-16
6-8-8
N=16
1-2
22-30-35
N=65
no recovery
22-19-15
N=34
50/5"
940 58
14.1
21.3
18.0
15.5
11.0
114
105 50-29-21
NATIVE GRASSES AND WEEDS, approximately
3 inches
SANDY ELASTIC SILT (MH), brown, very stiff,
varies to lean clay with varying amounts of sand
light brown to orange brown, soft
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, dense to very dense
WEATHERED CLAYSTONE, light brown,
weathered
CLAYSTONE, gray to dark gray, hard to very hard
Boring Terminated at 24.4 Feet
0.3
12.0
20.5
21.0
24.4
4929.5
4918
4909.5
4909
4905.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20 FIELDTESTRESULTSSWELL/LOAD(%/psf)PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
13' while drilling
WATER LEVEL OBSERVATIONS UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5472° Longitude: -105.0348°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4930 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 4
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
1
3
4
3 SAMPLETYPE
7-13-15
N=28
10-15
3-4-5
N=9
16-50/5"
skipped sample
to keep hole
open with
flowing sands
skipped sample
to keep hole
open with
flowing sands
50/5"
+0.1/500
8160
78
100
12.4
16.1
17.9
9.3
14.4
114
106
44-15-29
42-21-21
NATIVE GRASSES AND WEEDS, approximately
3 inches
SANDY LEAN CLAY, trace gravel, brown, very stiff
LEAN CLAY WITH SAND (CL), red brown with
light gray/white, medium stiff
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, dense to very dense
CLAYSTONE (CL), gray to dark gray, hard to very
hard
Boring Terminated at 29.4 Feet
0.3
4.5
12.0
18.0
29.4
4927.5
4923.5
4916
4910
4898.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20
25 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5476° Longitude: -105.0349°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4928 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 5
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
13' while drilling
WATER LEVEL OBSERVATIONS
2
3
4 SAMPLETYPE
9-11
5-4-3
N=7
4-3
50/6"
13-17-26
N=43
50/6"
+0.4/1,000
57
11.1
12.3
21.0
9.0
28.5
17.9
93
111
111
36-18-18
NATIVE GRASSES AND WEEDS, approximately
3 inches
SANDY LEAN CLAY (CL), red brown with light
gray/white, very stiff
medium stiff
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, very dense
CLAYSTONE
gray to tan, medium hard
dark gray, hard to very hard
Boring Terminated at 24.5 Feet
0.3
12.0
18.0
24.5
4928.5
4917
4911
4904.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5482° Longitude: -105.0346°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4929 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 6
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
12' while drilling
WATER LEVEL OBSERVATIONS
2
3
4 SAMPLETYPE
4-5-5
N=10
4-6
6-9-10
N=19
20-25-35
N=60
28-50/3"
50/5"
2590 48
19.7
17.0
14.2
10.8
19.4
16.0
111
105
33-15-18
AGGREGATE BASE COURSE, approximately 5
inches
CLAYEY SAND (SC), red brown with light
gray/white, medium dense
trace gravel, light brown to tan
POORLY GRADED GRAVEL WITH SAND, brown
to red brown, very dense
CLAYSTONE, hard to very hard
gray with tan
gray to dark gray
Boring Terminated at 24.4 Feet
0.4
13.0
17.0
24.4
4929.5
4917
4913
4905.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THISBORINGLOGISNOTVALIDIFSEPARATEDFROMORIGINALREPORT.GEOSMARTLOG-NOWELL20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/21WATERLEVELOBSERVATIONSDEPTH(Ft.)5
10
15
20 FIELDTESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH(psf)PERCENTFINESWATERCONTENT(%)DRYUNITWEIGHT(pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5484° Longitude: -105.0350°GRAPHICLOGMODELLAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4930 (Ft.)
Page 1 of 1
Advancement Method:
4-inch diameter, solid-stem augers
Abandonment Method:
Backfilled with auger cuttings
Notes:
Project No.: 20215032
Drill Rig: CME-55
BORING LOG NO. 7
Tetrad Property Group LLCCLIENT:
Fort Collins, CO
Driller: Drilling Engineers, Inc.
Boring Completed: 04-23-2021
PROJECT: Timberline Apartments
Elevations were interpolated from a topographic site
plan.
See Exploration and Testing Procedures for a
description of field and laboratory procedures used
and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
2908 S Timberline Road
Fort Collins, CO
SITE:
Boring Started: 04-23-2021
1901 Sharp Point Dr Ste C
Fort Collins, CO
13' while drilling
WATER LEVEL OBSERVATIONS
2
3
4 SAMPLETYPE
0
10
20
30
40
50
60
0 20 40 60 80 100CHorOHCLorOLML or OL
MH or OH"U"Line"A "LineATTERBERG LIMITS RESULTS
ASTM D4318
P
L
A
S
T
I
C
I
T
Y
I
N
D
E
X
LIQUID LIMIT
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.ATTERBERGLIMITS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/2149
33
NP
46
50
44
42
36
33
30
17
NP
30
29
15
21
18
15
19
16
NP
16
21
29
21
18
18
PIPLLLBoring ID Depth
1
2
2
3
4
5
5
6
7
62.7
64.7
0.2
59.9
58.4
78.4
99.6
56.6
48.2
Fines
4 - 5
2 - 3
14 - 15.5
4 - 5
9 - 10
9 - 10.5
29 - 29.4
4 - 5.5
4 - 5
ML
CL
GP
ML
MH
CL
CL
CL
SC
SANDY SILT
SANDY LEAN CLAY
POORLY GRADED GRAVEL with SAND
SANDY SILT
SANDY ELASTIC SILT
LEAN CLAY with SAND
CLAYSTONE
SANDY LEAN CLAY
CLAYEY SAND
DescriptionUSCS
CL-ML
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
30 40 501.5 200681014413/4 1/2 60
GRAIN SIZE IN MILLIMETERSPERCENTFINERBYWEIGHT HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
4 3/8 3 100 14032
GRAIN SIZE DISTRIBUTION
ASTM D422 / ASTM C136
6 16 20
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.GRAINSIZE:USCS-220215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21mediumcoarsecoarsefine fineCOBBLESGRAVELSAND SILT OR CLAY
1
2
2
3
4
SANDY SILT (ML)
SANDY LEAN CLAY (CL)
POORLY GRADED GRAVEL with SAND (GP)
SANDY SILT (ML)
SANDY ELASTIC SILT (MH)
49
33
NP
46
50
0.46
19
16
NP
16
21
30
17
NP
30
29
27.74
4 - 5
2 - 3
14 - 15.5
4 - 5
9 - 10
17.6
10.1
13.7
18.8
18.0
1
2
2
3
4
64.7
0.2
59.9
58.4
45.217.54 - 5
2 - 3
14 - 15.5
4 - 5
9 - 10
1.3
1.2
54.1
10.5
2.1
36.0
34.1
45.7
29.6
39.5
9.5
9.5
37.5
25
9.5
0.017
11.964
0.076
0.083
1.536 0.431
Boring ID Depth WC (%)LL PL PI Cc Cu
%Clay%Fines%Silt%Sand%Gravel Boring ID Depth D100 D60 D30 D10
USCS Classification
%Cobbles
0.0
0.0
0.0
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
30 40 501.5 200681014413/4 1/2 60
GRAIN SIZE IN MILLIMETERSPERCENTFINERBYWEIGHT HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
4 3/8 3 100 14032
GRAIN SIZE DISTRIBUTION
ASTM D422 / ASTM C136
6 16 20
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.GRAINSIZE:USCS-220215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21mediumcoarsecoarsefine fineCOBBLESGRAVELSAND SILT OR CLAY
5
5
6
7
LEAN CLAY with SAND (CL)
CLAYSTONE (CL)
SANDY LEAN CLAY (CL)
CLAYEY SAND (SC)
44
42
36
33
29
21
18
18
15
21
18
15
9 - 10.5
29 - 29.4
4 - 5.5
4 - 5
17.9
14.4
12.3
17.0
5
5
6
7
78.4
99.6
56.6
28.719.5
9 - 10.5
29 - 29.4
4 - 5.5
4 - 5
0.1
0.0
0.0
0.7
21.6
0.4
43.4
51.2
9.5
2
4.75
9.5
0.09
0.152 0.006
Boring ID Depth WC (%)LL PL PI Cc Cu
%Clay%Fines%Silt%Sand%Gravel Boring ID Depth D100 D60 D30 D10
USCS Classification
%Cobbles
0.0
0.0
0.0
0.0
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000AXIALSTRAIN,%PRESSURE, psf
NOTES: Sample exhibited no movement upon wetting under an applied pressure of 500 psf.
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.TC_CONSOL_STRAIN-USCS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/211 SANDY SILT(ML)4 - 5 ft 108 16.4
Specimen Identification Classification , pcf WC, %
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000AXIALSTRAIN,%PRESSURE, psf
NOTES: Sample exhibited 0.1 percent compression upon wetting under an applied pressure of 1,000 psf.
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.TC_CONSOL_STRAIN-USCS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/212 SANDY SILT9 - 10 ft 124 7.1
Specimen Identification Classification , pcf WC, %
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000AXIALSTRAIN,%PRESSURE, psf
NOTES: Sample exhibited 0.1 percent swell upon wetting under an applied pressure of 500 psf.
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.TC_CONSOL_STRAIN-USCS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/215 LEAN CLAY WITH SAND4 - 5 ft 114 16.1
Specimen Identification Classification , pcf WC, %
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000AXIALSTRAIN,%PRESSURE, psf
NOTES: Sample exhibited 0.4 percent swell upon wetting under an applied pressure of 1,000 psf.
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.TC_CONSOL_STRAIN-USCS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/5/216 SANDY LEAN CLAY9 - 10 ft 111 21.0
Specimen Identification Classification , pcf WC, %
0
500
1,000
1,500
2,000
2,500
3,000
3,500
0 2 4 6 8 10
AXIAL STRAIN - %
UNCONFINED COMPRESSION TEST
ASTM D2166
COMPRESSIVESTRESS-psfPROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.UNCONFINEDWITHPHOTOS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21SAMPLE LOCATION:3 @ 4 - 5 feetSAMPLE TYPE: CARS
0.58
86.99
106
Strain Rate:in/min
Failure Strain:%
Calculated Saturation:%
Height:in.
Diameter:in.
SPECIMEN FAILURE PHOTOGRAPH
Remarks:
Percent < #200 SievePIPLLL
1642
DESCRIPTION: SANDY SILT(ML)
0.0800
Dry Density:pcf
Moisture Content:%
6.29
2.00
2.7
Height / Diameter Ratio:
Calculated Void Ratio:
Undrained Shear Strength:(psf)
Unconfined Compressive Strength (psf)
163046
Assumed Specific Gravity:
3284
3.86
1.93
SPECIMEN TEST DATA
18.8
59.9
0
100
200
300
400
500
600
700
800
900
1,000
0 4 8 12 16
AXIAL STRAIN - %
UNCONFINED COMPRESSION TEST
ASTM D2166
COMPRESSIVESTRESS-psfPROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.UNCONFINEDWITHPHOTOS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21SAMPLE LOCATION:4 @ 9 - 10 feetSAMPLE TYPE: CARS
0.60
81.20
105
Strain Rate:in/min
Failure Strain:%
Calculated Saturation:%
Height:in.
Diameter:in.
SPECIMEN FAILURE PHOTOGRAPH
Remarks:
Percent < #200 SievePIPLLL
471
DESCRIPTION: SANDY ELASTIC SILT(MH)
0.0800
Dry Density:pcf
Moisture Content:%
14.84
1.93
2.7
Height / Diameter Ratio:
Calculated Void Ratio:
Undrained Shear Strength:(psf)
Unconfined Compressive Strength (psf)
212950
Assumed Specific Gravity:
942
3.72
1.93
SPECIMEN TEST DATA
18.0
58.4
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
0 1.0 2.0 3.0 4.0 5.0 6.0
AXIAL STRAIN - %
UNCONFINED COMPRESSION TEST
ASTM D2166
COMPRESSIVESTRESS-psfPROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.UNCONFINEDWITHPHOTOS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21SAMPLE LOCATION:5 @ 29 - 29.4 feetSAMPLE TYPE: CARS
0.58
66.71
106
Strain Rate:in/min
Failure Strain:%
Calculated Saturation:%
Height:in.
Diameter:in.
SPECIMEN FAILURE PHOTOGRAPH
Remarks:
Percent < #200 SievePIPLLL
4079
DESCRIPTION: CLAYSTONE
0.0800
Dry Density:pcf
Moisture Content:%
4.92
2.02
2.7
Height / Diameter Ratio:
Calculated Void Ratio:
Undrained Shear Strength:(psf)
Unconfined Compressive Strength (psf)
212142
Assumed Specific Gravity:
8158
3.94
1.95
SPECIMEN TEST DATA
14.4
99.6
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
2,200
2,400
2,600
0 2 4 6 8
AXIAL STRAIN - %
UNCONFINED COMPRESSION TEST
ASTM D2166
COMPRESSIVESTRESS-psfPROJECT NUMBER: 20215032
SITE: 2908 S Timberline Road
Fort Collins, CO
PROJECT: Timberline Apartments
CLIENT: Tetrad Property Group LLC
Fort Collins, CO
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORYTESTSARENOTVALIDIFSEPARATEDFROMORIGINALREPORT.UNCONFINEDWITHPHOTOS20215032TIMBERLINEAPARTM.GPJTERRACON_DATATEMPLATE.GDT5/4/21SAMPLE LOCATION:7 @ 4 - 5 feetSAMPLE TYPE: CARS
0.52
87.92
111
Strain Rate:in/min
Failure Strain:%
Calculated Saturation:%
Height:in.
Diameter:in.
SPECIMEN FAILURE PHOTOGRAPH
Remarks:
Percent < #200 SievePIPLLL
1297
DESCRIPTION: CLAYEY SAND(SC)
0.0800
Dry Density:pcf
Moisture Content:%
6.05
2.10
2.7
Height / Diameter Ratio:
Calculated Void Ratio:
Undrained Shear Strength:(psf)
Unconfined Compressive Strength (psf)
181533
Assumed Specific Gravity:
2595
4.03
1.92
SPECIMEN TEST DATA
17.0
48.2
SUPPORTING INFORMATION
Contents:
General Notes
Unified Soil Classification System
Description of Rock Properties
Note: All attachments are one page unless noted above.
Timberline Apartments Fort Collins, CO
Terracon Project No. 20215032
2,000 to 4,000
Unconfined
Compressive
Strength
Qu, (psf)
less than 500
500 to 1,000
1,000 to 2,000
4,000 to 8,000
> 8,000
Modified
California
Ring
Sampler
Standard
Penetration
Test
N
(HP)
(T)
(DCP)
UC
(PID)
(OVA)
Standard Penetration Test
Resistance (Blows/Ft.)
Hand Penetrometer
Torvane
Dynamic Cone Penetrometer
Unconfined Compressive
Strength
Photo-Ionization Detector
Organic Vapor Analyzer
SAMPLING WATER LEVEL FIELD TESTS
GENERAL NOTES
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
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 Initially
Encountered
Water Level After a
Specified Period of Time
Water Level After
a Specified Period of Time
Cave In
Encountered
Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude and
Longitude are approximate. See Exploration and Testing Procedures in the report for the methods used to locate the
exploration points for this project. 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.
LOCATION AND ELEVATION NOTES
Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory data
exist to classify the soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this procedure is used.
ASTM D2488 "Description and Identification of Soils (Visual-Manual Procedure)" is also used to classify the soils, particularly
where insufficient laboratory data exist to classify the soils in accordance with ASTM D2487. In addition to USCS classification,
coarse grained soils are classified on the basis of their in-place relative density, and fine-grained soils are classified on the basis
of their consistency. See "Strength Terms" table below for details. The ASTM standards noted above are for reference to
methodology in general. In some cases, variations to methods are applied as a result of local practice or professional judgment.
DESCRIPTIVE SOIL CLASSIFICATION
The soil boring logs contained within this document are intended for application to the project as described in this document.
Use of these soil boring logs for any other purpose may not be appropriate.
RELEVANCE OF SOIL BORING LOG
STRENGTH TERMS
30 - 50
> 50
Descriptive
Term
(Consistency)
8 - 15
> 30
Ring
Sampler
Blows/Ft.
10 - 29 Medium Hard
< 3
2 - 4
BEDROCK
Standard
Penetration
or N-Value
Blows/Ft.
0 - 3Very Loose Very Soft
(More than 50% retained on No. 200
sieve.)
Density determined by Standard
Penetration Resistance
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing,
field visual-manual procedures or standard penetration
resistance
RELATIVE DENSITY OF COARSE-GRAINED SOILS
30 - 49
50 - 79
_
6 - 10
11 - 18
19 - 36
> 36
>79
Descriptive
Term
(Consistency)
Firm
< 20 Weathered
Hard
15 - 30
Standard
Penetration or
N-Value
Blows/Ft.
0 - 1
4 - 8
Very Hard
Ring
Sampler
Blows/Ft.
Ring
Sampler
Blows/Ft.
Soft
Medium Stiff
Stiff
Very Stiff
Hard
CONSISTENCY OF FINE-GRAINED SOILS
Standard
Penetration
or N-Value
Blows/Ft.
Loose
Medium Dense
Dense
Very Dense
< 24
24 - 35
36 - 60
61 - 96
> 96
Descriptive Term
(Density)
4 - 9 20 - 29
0 - 5
6 - 14
15 - 46
47 - 79
> 80
3 - 5
UNIFIED SOIL CLASSIFICATION SYSTEM
UNIFIED SOI L CLASSI FICATI ON SYSTEM
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 [Cc<1 or Cc>3.0] 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 [Cc<1 or Cc>3.0] 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 mat erial 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.
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 =
6010
2
30
DxD
)(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.
DESCRIPTION OF ROCK PROPERTIES
ROCK VERSION 1
WEATHERING
Term Description
Unweathered No visible sign of rock material weathering, perhaps slight discoloration on major discontinuity surfaces.
Slightly
weathered
Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be
discolored by weathering and may be somewhat weaker externally than in its fresh condition.
Moderately
weathered
Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is
present either as a continuous framework or as corestones.
Highly
weathered
More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored ro ck is
present either as a discontinuous framework or as corestones.
Completely
weathered All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact.
Residual soil All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large
change in volume, but the soil has not been significantly transported.
STRENGTH OR HARDNESS
Description Field Identification Uniaxial Compressive
Strength, psi (MPa)
Extremely weak Indented by thumbnail 40-150 (0.3-1)
Very weak Crumbles under firm blows with point of geological hammer, can be
peeled by a pocket knife 150-700 (1-5)
Weak rock Can be peeled by a pocket knife with difficulty, shallow indentations
made by firm blow with point of geological hammer 700-4,000 (5-30)
Medium strong Cannot be scraped or peeled with a pocket knife, specimen can be
fractured with single firm blow of geological hammer 4,000-7,000 (30-50)
Strong rock Specimen requires more than one blow of geological hammer to
fracture it 7,000-15,000 (50-100)
Very strong Specimen requires many blows of geological hammer to fracture it 15,000-36,000 (100-250)
Extremely strong Specimen can only be chipped with geological hammer >36,000 (>250)
DISCONTINUITY DESCRIPTION
Fracture Spacing (Joints, Faults, Other Fractures) Bedding Spacing (May Include Foliation or Banding)
Description Spacing Description Spacing
Extremely close < ¾ in (<19 mm) Laminated < ½ in (<12 mm)
Very close ¾ in – 2-1/2 in (19 - 60 mm) Very thin ½ in – 2 in (12 – 50 mm)
Close 2-1/2 in – 8 in (60 – 200 mm) Thin 2 in – 1 ft. (50 – 300 mm)
Moderate 8 in – 2 ft. (200 – 600 mm) Medium 1 ft. – 3 ft. (300 – 900 mm)
Wide 2 ft. – 6 ft. (600 mm – 2.0 m) Thick 3 ft. – 10 ft. (900 mm – 3 m)
Very Wide 6 ft. – 20 ft. (2.0 – 6 m) Massive > 10 ft. (3 m)
Discontinuity Orientation (Angle): Measure the angle of discontinuity relative to a plane perpendicular to the longitudinal axis of the
core. (For most cases, the core axis is vertical; therefore, the plane perpendicular to the core axis is horizontal.) For example, a
horizontal bedding plane would have a 0-degree angle.
ROCK QUALITY DESIGNATION (RQD) 1
Description RQD Value (%)
Very Poor 0 - 25
Poor 25 – 50
Fair 50 – 75
Good 75 – 90
Excellent 90 - 100
1. The combined length of all sound and intact core segments equal to or greater than 4 inches in length, expressed as a
percentage of the total core run length.
Reference: U.S. Department of Transportation, Federal Highway Administration, Publication No FHWA-NHI-10-034, December 2009
Technical Manual for Design and Construction of Road Tunnels – Civil Elements