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Report Cover Page
Prepared for:
Big D Oil Company
PO Box 1378
Rapid City, South Dakota 57702
Harmony Lakes – New
Convenience Store
Geotechnical Engineering Report
Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials i
Table of Contents
Introduction .................................................................................................... 1
Project Description .......................................................................................... 2
Site Conditions ................................................................................................ 3
Geotechnical Characterization ......................................................................... 4
Subsurface Profile ..................................................................................... 4
Groundwater Conditions ............................................................................. 5
Seismic Site Class ............................................................................................ 7
Corrosivity ...................................................................................................... 7
Geotechnical Overview .................................................................................... 8
Existing, Undocumented Fill ........................................................................ 8
Shallow Groundwater ................................................................................ 9
Expansive/Compressible Soils and Bedrock ................................................... 9
Low Strength and Low Relative Density Soils ................................................ 10
Permanent Dewatering ............................................................................. 10
Foundation and Floor System Recommendations ........................................... 11
Earthwork ..................................................................................................... 12
Demolition .............................................................................................. 13
Site Preparation ....................................................................................... 13
Existing Fill ............................................................................................. 14
Excavation .............................................................................................. 14
Subgrade Preparation ............................................................................... 15
Subgrade Stabilization .............................................................................. 16
Fill Material Types .................................................................................... 17
Fill Placement and Compaction Requirements ............................................... 18
Utility Trench Backfill ............................................................................... 19
Grading and Drainage ............................................................................... 20
Exterior Slab Design and Construction ......................................................... 21
Earthwork Construction Considerations ....................................................... 21
Construction Observation and Testing ......................................................... 22
Shallow Foundations ..................................................................................... 22
Spread Footings – Design Recommendations ................................................ 22
Spread Footings – Overturning and Uplift Loads ............................................ 24
Shallow Foundation Construction Considerations ........................................... 25
Deep Foundations .......................................................................................... 25
Helical Pile Foundations ............................................................................ 26
Floor Slabs .................................................................................................... 26
Floor Slabs - Design Recommendations ....................................................... 27
Floor Slabs - Construction Considerations .................................................... 28
Below-Grade Structures ................................................................................. 28
Underground Storage Tanks ...................................................................... 28
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials ii
Lateral Earth Pressures ................................................................................. 29
Design Parameters ................................................................................... 29
Pavements .................................................................................................... 31
General Pavement Comments .................................................................... 31
Pavements – Subgrade Preparation ............................................................ 31
Pavements – Design Reccomendations ........................................................ 31
Pavements – Construction Considerations .................................................... 34
Pavements – Maintenance ......................................................................... 35
Frost Considerations ...................................................................................... 35
General Comments ........................................................................................ 36
Figures
GeoModel
Attachments
Exploration and Testing Procedures
Site Location and Exploration Plans
Exploration and Laboratory Test Results
Supporting Information
Note: This report was originally delivered in a web -based format. Blue Bold text in the
report indicates a referenced section heading. The PDF version also includes hyperlinks
which direct the reader to that section and clicking on the logo will bring you
back to this page. For more interactive features, please view your project online at
client.terracon.com .
Refer to each individual Attachment for a listing of contents.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 1
Introduction
This report presents the results of our subsurface exploration and Geotechnical
Engineering services performed for the proposed convenience store building , fuel
dispensers, and associated parking areas and drive lanes to be constructed at the site
with an address of 4315 East Harmony Road in Fort Collins, Colorado . The purpose of
these services was to provide information and geotechnical engineering
recommendations relative to:
■ Sub surface soil conditions
■ Groundwater conditions
■ Seismic site classification per IBC
■ Site preparation and earthwork
■ Demolition considerations
■ Dewatering considerations
■ Foundation design and construction
■ Floor s ystem design and construction
■ Lateral earth pressure s
■ Pavement design and construction
■ Frost considerations
The geotechnical engineering Scope of Services for this project included the
advancement of test borings (designated as Boring Nos. B -1 through B -12), laboratory
testing, engineering analysis, and preparation of this report.
Drawings showing the site and boring locations are presented in the Site Location and
Exploration Plan section of this report . The results of the laboratory testing performed
on soil samples obtained from the site during our field exploration are included on the
boring logs and as separate graphs in the Exploration Results section.
A separate report utilizing the same project data will be issued to provide geotechnical
recommendations for the planned public roadway improvements (see Boring Nos. B -6
through B-8) and lift station (see Boring No. B-12) within the Harmony Lake s
development . Preliminary recommendations for planned future development of the
outlots at the site (see Boring Nos. B-9 through B -11) will also be presented in the
second report.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 2
Project Description
Our initial understanding of the project was provided in our proposal and was discussed
during project planning. A period of collaboration has transpired since the project was
initiated, and our final understanding of the project conditions is as follows:
Item Description
Information
Provided
The project information described below is based on the
following:
■ Communications with Kristin Turner at TB Group
■ Site plan provided by TB Group dated April 5th, 2024
■ Conceptual layout provided by Bulldog Engineering dated
March 7th, 2024
■ Communication with Andy Reese at Kimley-Horn and
Associates (KHA)
Project
Description
We understand the proposed project consists of the construction
of a new single-story, approximately 7,948 square-foot
convenience store building with associated parking areas and
drive lanes . We also understand 10 fuel dispensers are planned
to be constructed to the north of the building with a canopy.
Underground fuel storage tanks (USTs) are planned to the east
of the building .
We anticipate the planned convenience store, canopy structure ,
and fuel dispensers are planned to be supported on shallow,
spread footing foundations. The convenience store is anticipated
to have a slab-on-grade floor system.
Finished Floor
Elevation
Final grading plans were not provided at the time of this report.
Therefore, we anticipate the finished floor elevation for the
proposed building will be within about 4 feet of the existing site
grades at the time of our geotechnical study.
Maximum Loads
Anticipated structural loads were not provided at the time of this
report . In the absence of information provided by the design
team, we used the following loads in our engineering analysis
based on our experience with similar projects.
■ Columns: 50 kips or less
■ Walls: 1 to 5 kips per linear foot (klf)
■ Slabs: 150 pounds per square foot (psf)
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 3
Item Description
Grading/Slopes
Grading plans were not provided to Terracon at the time of this
proposal. We anticipate cuts and fills on the order of 4 feet or
less will be required to achieve proposed grades. We also
anticipate deeper cuts and fills could be required for utility
construction.
Below-Grade
Structures
USTs are planned east of the planned convenience store . We
have assumed maximum excavation depths of about 15 to 20
feet below existing grades will be required for installation of the
USTs.
Pavements
New pavements are planned as part of this project and will
likely consist of flexible asphalt and rigid concrete pavement.
Traffic loads were not available at the time of this report , so we
assumed traffic loads consistent with those of similar use. We
assumed the traffic classification consist ed of the following for the
pavements around the new convenience store:
■ Automobile Parking: Parking stalls for passenger vehicles
and pickup trucks (assumes less than 10 trucks per day )
■ Main Traffic Corridors: Traffic consisting of passenger
vehicles, single -unit delivery trucks , combination-unit
delivery trucks, and garbage trucks (assumes up to about
50 trucks per day)
The pavement design life is assumed to be approximately 20
years.
Building Code 2018 International Building Code (IBC)
Terracon should be notified if any of the above information is inconsistent with the
planned construction as modifications to our recommendations may be necessary.
Site Conditions
The following description of site conditions is derived from our site visit in association
with the field exploration .
Item Description
Parcel
Information
The project site is located at 4315 East Harmony Road in Fort
Collins, Colorado.
Latitude/Longitude (approximate): 40.5223 ° N, 104.9963 ° W
(see Site Location ).
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 4
Item Description
Existing
Improvements
Current improvements include greenhouse systems,
warehouses, office buildings, parking areas, and driveways. An
existing gas station is located on the north side of the property.
Based on historical aerial imagery from 2006, the eastern side
of the property appeared to consist of a pond. By 2009, the
northern portion of the pond appeared to be filled in . Sand
mining and regr ading has possibly taken place on the property.
Current Ground
Cover
Many of the western areas of the property are aggregate
surfaced or paved with asphalt. The eastern side of the property
is mainly earthen fields with some vegetation and aggregate
surfaced driveways .
Existing
Topography
Based on publicly available USGS topographic maps and a site
plan provided by TB Group, ground surface elevations at the
project site slope from the northwest down towards the
southeast with a total change in elevation of about 10 feet
across the site.
Geotechnical Characterization
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 the site. Conditions observed at each
exploration point are indicated on the individual logs. The individual l ogs can be found in
the Exploration Results and the GeoModel can be found in the Figures attachment of
this report.
Subsurface Profile
As part of our analyses, we identified the following model layers within the subsurface
profile. For a more detailed view of the model layer depths at each boring location, refer
to the GeoModel.
Model
Layer Layer Name General Description
1
Existing
Surfacing
Materials
About 3 to 19 inches of aggregate surfacing in Boring
Nos. B-1 to B-5, B-7 to B-9, B-11, and B-12. About
3.25 inches of asphalt in Boring No. B-6.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 5
Model
Layer Layer Name General Description
2 Existing Fill
Consisted primarily of clay soils with variable amounts
of sand and gravel or sand soils with variable amounts
of clay and gravel. Encountered in Boring Nos. B -1,
B-2, and B-4 to B-12.
3 Clay Soils Very soft to stiff clay soils with variable amounts of
sand and gravel.
4 Sand Soils Very loose to very dense sand soils with variable
amounts of fines and gravel.
5 Bedrock Medium hard to very hard claystone bedrock.
As noted in General Comments, this characterization is based upon widely spaced
exploration points across the site and variations are likely. Stratification boundaries on
the boring logs represent the approximate location of changes in material types; in situ,
the transition between materials may be gradual.
Based on our experience in the area and the results of the laboratory testing, the on -site
clayey soils are considered to have low expansive potential or to be slightly
compressible. The claystone bedrock is considered to have low to moderate expansive
potential. Laboratory test results are presented in Exploration Results.
Groundwater Conditions
The boreholes were observed while drilling and shortly after completion for the presence
and level of groundwater. In addition, delayed water levels were also obtained in some
borings. The water levels observed in the boreholes are noted on the attached boring
logs, and are summarized in the following table.
Boring
Number
Depth to
Groundwater
While Drilling,
ft.
Depth to
Groundwater
After Drilling,
ft.
Depth to
Groundwater
Approximately
24 Hours
After Drilling,
ft.
Approx.
Elevation of
Groundwater
After Drilling,
ft.1
B-1 14 9.9 Boring
backfilled ±4,837
B-2 14 8.6 Boring
backfilled ±4,839½
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 6
Boring
Number
Depth to
Groundwater
While Drilling,
ft.
Depth to
Groundwater
After Drilling,
ft.
Depth to
Groundwater
Approximately
24 Hours
After Drilling,
ft.
Approx.
Elevation of
Groundwater
After Drilling,
ft.1
B-3 7 4.9 Boring
backfilled ±4,841
B-4 14 6.3 Boring
backfilled ±4,842½
B-5 7 10 7.3 ±4,839½
B-6 7 Not measured Boring
backfilled --
B-7 7 7.3 Boring
backfilled ±4,839½
B-8 7 Not measured Boring
backfilled --
B-9 9 3.2 Boring
backfilled ±4,840
B-10 Not encountered while drilling 2.2 ±4,840
B-11 14 9.0 Boring
backfilled ±4,839
B-12 7 9.5 3.7 ±4,841½
1. Elevation of groundwater is based on the ground surface elevations at the boring locations
interpolated from a topographic site plan provided by TB Group.
These observations represent relatively short -term groundwater conditions at the time of
and after completion of the field exploration and may not be indicative of other times or
at other locations. Long -term groundwater monitoring was outside the scope of services
for this project.
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
con struction or at other times in the life of the structure may be higher or lower than the
levels indicated on the boring logs. The possibility of groundwater level fluctuations
should be considered when developing the design and construction plans for the p roject.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 7
Seismic Site Class
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 and bedrock
properties observed at the site as described on the exploration logs and laboratory test
results, our professional opinion is a Seismic Site Classification of D be considered for
the project. Subsurface explorations at this site were extended to a maximum depth of
about 34 ½ 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.
Corrosivity
The table below lists the results of laboratory soluble sulfate, soluble chloride , sulfides,
electrical resistivity, RedOx , and pH testing. The values may be used to estimate
potential corrosive characteristics of the on -site soils and bedrock with respect to
contact with the various underground materials which will be used for project
construction.
Corrosivity Test Results Summary
Boring
(Sample
Depth)
Soluble
Sulfate
(%)
Soluble
Chloride
(%)
Sulfides
Total
Salts
(%)
Electrical
Resistivity
(Ω-cm)1
RedOx
(mV) pH
B-1
(1-5 feet) 0.0405 - - - - - -
B-2
(1-5 feet ) 0.0102 0.0061 Nil 0.0935 1,500 234 8.47
B-4
(1-5 feet ) 0.0378 - - - - - -
B-8
(1-5 feet ) 0.0120 0.0016 Nil 0.0466 4,200 244 8.5
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 8
Corrosivity Test Results Summary
Boring
(Sample
Depth)
Soluble
Sulfate
(%)
Soluble
Chloride
(%)
Sulfides
Total
Salts
(%)
Electrical
Resistivity
(Ω-cm)1
RedOx
(mV) pH
B-10
(1-5 feet ) 0.0228 - - - - - -
Results of water-soluble sulfate testing indicate Exposure Class S0 according to ACI
(American Concrete Institute) 318. Therefore, ASTM Type I or II portland cement or
Type IL portland -limestone cement can be specified for all project concrete on and below
grade. Foundation concrete can be designed for low sulfate exposure in accordance with
the provisions of the ACI 318.
Numerous sources are available to characterize corrosion potential to buried metals
using the parameters above. ANSI/AWWA is commonly used for ductile iron, while
threshold values for evaluating the effect on steel can be specific to the buried feature
(e.g., piling, culverts, welded wire reinforcement, etc.) or agency for which the work is
performed. Imported fill materials may have significantly different properties than the
site materials noted above and should be evaluated if expected to be in contact w ith
metals used for construction. Consultation with a NACE certified corrosion professional is
recommended for buried metals on the site.
Geotechnical Overview
Based on subsurface conditions encountered in the boring s, 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 and
the owner understands the inherent risks associated with construction on sites un derlain
by expansive /compressible soils and bedrock. We have identified several geotechnical
conditions that could impact design, construction , and performance of the proposed
structures, pavements, and other site improvements. These included existing,
undocumented fill, shallow groundwater, expansive /compressible soils and bedrock, and
potentially soft, low strength clay soils and loose, low relative density sand soils . These
conditions will require particular attention in project planning, design , and during
construction and are discussed in greater detail in the following sections.
Existing, Undocumented Fill
Existing, undocumented fill was encountered to depths up to about 7 feet in all borings
drilled at the site except Boring No. B-3. Existing fill could exist at other locations on the
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 9
site and extend to greater depths. We do not possess any information regarding whether
the fill was placed under the observation of a geotechnical engineer. Therefore, we
consider the fill as undocumented. Undocumented fill can present a greater than normal
risk of post -construction movement of site improvements supported on or above these
materials. Consequently, exiting fill should not be relied upon for support of shallow
foundations, slabs, pavements, or other site improvements. A low risk alternative is
complete removal of existing fill below foundations, slabs, pavements , and other site
improvements and replacement with newly compacted engineered fill . A discussion
regarding alternatives to complete removal of existing fill are presented in the Existing
Fill section of Earthwork.
Shallow Groundwater
As previously presented, groundwater was measured at depths ranging from about 2.2
to 14 feet below existing site grades . In general, measured groundwater levels were
shallowest on the eastern portion of the site in the vicinity of Boring Nos. B-9, B-10, and
B-12. We understand below -grade fuel tanks are part of the planned construction .
Terracon recommends maintaining a separation of at least 3 feet (or less if stable
conditions at the subgrade bearing levels can be maintained duri ng construction)
between the bottom of proposed below -grade foundations and measured groundwater
levels during construction and after construction if possible . The purpose of this is to
allow for construction “in the dry”. Consideration could be given to raising grades at the
site to avoid construction near groundwater levels. It is also possible and likely that
groundwater levels below this site may rise as water levels in neighboring bodies of
water and/or the Cache la Poudre River rise. Final site grading should be plan ned and
designed to avoid cuts where shallow groundwater is known to exist, and in areas where
such grading would create shallow groundwater conditions . If deeper cuts are
unavoidable, temporary construction dewatering , installation of a subsurface drainage
system , and/or development of a sufficient dewatering plan by a dewatering contractor
may be needed.
Expansive /Compressible Soils and Bedrock
Expansive/compressible soils and bedrock are present on this site; however, our
experience in the area and the laboratory test results indicate on -site soils are generally
low swelling or slightly compressible . The claystone bedrock is generally considered low
to moderately swelling . This report provides recommendations to help mitigate the
effects of soil shrinkage and expansion. However, even if these procedures are followed,
some movement and cracking in the structures, pavements, and flatwork is possible.
The severity of cracking and other damage such as uneven floor slabs and flatwork will
probably increase if modification of the site results in excessive wetting or drying of the
expansive/compressible soils and/or claystone bedrock . Eliminating the risk of
movement and cosmetic distress is generally not feasible . It is imperative that the
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 10
recommendations described in the Grading and Drainage section of Earthwork be
followed to reduce potential movement.
Low Strength and Low Relative Density Soils
Comparatively soft, low strength clay soils were encountered at a depth of about 7 feet
in Boring Nos. B-2 , B-4, and B -9 and a depth of about 4 feet in Boring No. 10.
Comparatively loose, low relative density sand soils were encountered within the upper
approximately 4 feet of Boring No s. B-5 and B-7 and at depths of about 7 to 14 feet of
Boring Nos. B-10 and B -11 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/loose 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 o bserve the conditions exposed and to
provide guidance regarding stabilization (if needed).
Permanent Dewatering
Preliminary site concepts indicate the propo sed below-grade areas could extend below
the observed groundwater levels. Thus, permanent dewatering may be needed to lower
groundwater levels below permanent excavations. We recommend that , on a long -term
basis, groundwater levels be maintained at least 3 feet below the floor slab and any
below -grade areas. As an alternative, structures extending below groundwater (such as
the planned underground storage tanks) should be design as “water -tight” structures
and to resist uplift from buoyant forces.
If a permanent dewatering system is judged necessary by the project team, we suggest
the dewatering system consist of a combination of drains and sumps. The configuration
of the system will depend on the size of the below -grade areas. The locations of the
drains and/or sumps must consider maintenance accessibility.
A possible configuration would be a subsurface drain around the exterior of the below -
grade perimeter wall . The drain pipe should be properly-sized, perforated PVC or other
type of hard pipe embedded in properly graded drainage gravel. The invert of the drain
pipe should be at least 4 feet below the bottom of the floor slab for below -grade areas.
The drain pipe should discharge into a sump(s) accessible within the base of the below -
grade area.
The drainage gravel should extend vertically over the drain pipes to at least 2 feet above
the highest groundwater levels observed in the soil borings. Thus, the drain gravel will
extend into the below -grade area foundation wall backfill. The foundation walls for the
below -grade areas adjacent to the drain gravel should be properly water -proofed.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 11
Provision must be made to prevent migration or piping of the native soils into the
drainage gravel. Ideally this would be by a properly graded sand filter. Alternatively, a
filter fabric could be used. If a filter fabric is used, we strongly recommend completion of
the installation in “the dry ” condition. That is, the Contractor should dewater the
excavation so that it is free of standing water during installation of the drain
components.
Other issues to be considered include:
■ Outfall of the developed water , which could be to a storm water basin.
Evaluation of the amount of water likely to be discharged from a permanent
dewatering system was not included in our scope of services for this study but
should be evaluated, if a permanent dewatering system is selected.
■ Possible permitting requirements. If the dewatering system is considered to
be a well, permits would be required at a minimum from the Colorado State
Engineer’s Office and the State of Colorado Department of Public Health and
Environment. The permits, should they be needed, will require regular reporting
of discharged water quality. Adequate time should be included in the project
schedule to obtain the permits.
■ Maintenance. All permanent dewatering systems require regular maintenance to
ensure the drains and pumps are in proper operating condition. Underground
drains associated with the system should have cleanouts so that the system can
be flushed/cleaned periodically as underground dewatering systems can become
clogged with anaerobic microbial and other growth. The cleanout locations should
be readily accessible and a source of high pressure (water main pressure) water
available to flush the drains.
■ Monitoring. By their nature, permanent dewatering systems tend to be “out of
sight and out of mind”. Therefore, we recommend there be a monitoring system
to alert maintenance personnel if the pumps have failed and water levels are
rising in the sumps. A simple monitoring system would be to install a water
detector in a sump about 1 to 2 feet below the bottom of the below -grade area
floor slab that would activate a flashing warning light in the planned building.
Foundation and Floor System Recommendations
Due to the presence of existing fill and comparatively low strength clay soils and low
relative density sand soils at the project site, the proposed convenience store and fuel
canopy can be supported on shallow, spread footing foundation systems provided any
existing fill within the building area and below canopy foundations is removed full depth
and the soils are over -excavated to a depth of at least 2 feet below the bottom of
footings, if the existing fill thickness does not already extend to at least 2 feet below the
bottom of footings, and replaced with moisture conditioned, properly compacted
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 12
engineered fill . On -site soils free of deleterious materials are sui table for use as
engineered fill below foundations.
As an alternative to supporting the convenience store and fuel canopy on shallow
foundations, consideration could be given to supporting the proposed structures on a
deep foundation system consisting of helical piles bottomed in the rela tively dense sand
soils or the claystone bedrock to help reduce the potential for post -construction
movements of the structures , needing to dewater during construction, and bypass
thicker zones of existing fill .
Design recommendations for foundations for the proposed structures and related
structural elements are presented in the Shallow Foundations and Deep Foundations
section s of this report.
In our opinion, a concrete slab -on-grade floor system can be used for the proposed
convenience store building provided the existing fill within the building area is removed
full depth and soils are over -excavated to a depth of at least 3 feet below the base of
the floor slab, if the existing fill thickness does not already extend to at least this depth
below the floor slab, and replaced with moisture conditioned, properly compacted
engineered fill. On -site soils are suitable for use as engineered fill below the floor slab.
We recommend the top 6 inches of the engineered fill zone below the floor slab of th e
new building consist of Colorado Department of Transportation (CDOT) Class 1 structure
backfill. If the owner cannot accept the risk of floor slab movement associated with a
slab-on -grade floor system, the use of a structural floor system can be consider ed.
Terracon can be contacted to provide additional recommendations if a structural floor
system is desired for the building. Design recommendations for floor systems for the
proposed structures and related structural elements are presented in the Floor Slabs
section of this report.
The recommendations contained in this report are based upon the results of field and
laboratory testing (presented in the Exploration Results ), engineering analyses, and
our current understanding of the proposed project. The General Comments section
provides an understanding of the report limitations.
Earthwork
Earthwork is anticipated to include demolition, site preparation, excavations, evaluation
of existing fill, subgrade preparation, soil stabilization (if needed), and engineered fill
placement. The following sections provide recommendations for use in the preparation of
specifications for the project. Recommendations include critical quality criteria, as
necessary, to render the site in the state considered in our geotechnical engineering
evaluation for foundations, floor slabs, and pavements.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 13
Demolition
The proposed convenience store , canopy, and fuel dispensers are anticipated to be
constructed within the footprint of an existing warehouse and greenhouse system which
will need to be demolished along with exterior pavements and utilities. We recommend
existing foundations, slabs, and utilities be removed from within the proposed building
and fuel dispenser footprint areas and at least 5 feet beyond the outer edge of new
foundations.
For areas outside the proposed building /structure footprint areas and foundation bearing
zones, existing foundations, floor slabs, and utilities should be removed where they
conflict with proposed utilities and pavements. In such cases, existing foundations, floor
slabs, and utilities should be removed to a depth of at least 2 feet below the affected
utility or design pavement subgrade elevation.
All materials derived from the demolition of existing structures and pavements should be
removed from the site. The types of foundation systems supporting the existing
warehouse are not known. If some of the existing structures are supported by drilled
piers, the existing piers should be truncated a minimum depth of 3 feet below areas of
planned new construction.
Site Preparation
Prior to placing fill, existing vegetation, topsoil, root mats, aggregate surfacing, and
pavements should be removed. Complete stripping of the topsoil should be performed in
the proposed building /structure and parking/driveway areas. As previously stated, we
also recommend complete removal of existing, undocumented fill within proposed
building /structure areas. Existing fill was encountered in our borings extending to depths
of about 2 to 7 feet below existing site grades.
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 r eceive
fill, and to provide for a relatively uniform thickness of fill beneath proposed structures.
Although no evidence of underground facilities (such as septic tanks, cesspools, and
basements) was observed during the exploration and site reconnaissance, such features
could be encountered during construction. If unexpected fills or underground facilities
are encountered, such features should be removed, and the excavation thoroughly
cl eaned prior to backfill placement and/or construction.
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Existing Fill
As previously discussed, existing, undocumented fill was ecountered to depths ranging
from about 2 to 7 feet below the ground surface at the time of our field subsurface
exploration . Existing fill could exist at other locations on the site and extend to greater
depths. We do not possess any information regarding whether the fill was placed under
the observation of a geotechnical engineer. Therefore, we consider the fill
undocumented. Undocumented fill can present a greater than normal risk of post -
construction movement of site improvements supported on or above these materials.
Consequently, existing fill should not be relied upon for support of shallow foundations,
slabs, pavements, or other site improvements. A low-risk alternative is complete
removal of existing fill below foundations, slabs, pavements , and other site
improvements and replacement with newly compacted engineered fill.
In areas where new pavements/flatwork are planned , the existing fill need not be
completely removed and replaced provided the owner is willing to accept greater than
normal risk of movement below new pavements/flatwork. If the owner elects to
construct pavements on the existing fill to reduce initial construction costs , the following
protocol should be followed. At a minimum, we recommend the subgrade soils below
new pavements/flatwork be scarified as discussed in the Subgrade Preparation section
of Earthwork prior to placing new engineered fill or constructing new
pavements/flatwork. We also recommend thoroughly proof rolling the prepared subgrade
prior to placing aggregate base course and/or pavement/flatwork materials . Areas
exhibiting significant deflection and/or pumping during the proof roll will need to be
repaired prior to pavement/fla twork construction. Once the planned subgrade elevation
has been reached, the entire pavement /flatwork area should be proof rolled . Areas of
soft or otherwise unsuitable material should be undercut and replaced with either new
en gineered fill or suitable, existing on -site materials.
Excavation
We anticipate excavations for the proposed construction can be accomplished with
conventional earthmoving equipment. Excavations into the on-site soils will encounter
weak, soft/loose, and/or saturated soil conditions with possible caving conditions. The
bottom of excavations should be thoroughly cleaned of loose/disturbed materials prior to
backfill placement and/or construction.
The soils to be excavated can vary significantly across the site as their classifications are
based solely on the materials encountered in widely -spaced exploratory test borings.
The contractor should verify that similar conditions exist throughout the proposed area
of excavation. If different subsurface conditions are encountered at the time of
construction, the actual conditions should be evaluate d to determine any excavation
modifications necessary to maintain safe conditions.
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Excavation penetrating several feet into the bedrock (if any) may require the use of
specialized heavy -duty equipment, together with ripping or jack -hammering to advance
the excavation and facilitate rock break -up and removal . However, field penetration
resistance test results indicate the upper approximately 1 to 2 feet of bedrock are
moderately weathered and may be comparatively easier to excavate with conventional
equipment. Consideration should be given to obtaining a unit price for difficult
excavation in the contract documents for the project.
Any over-excavation extending 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 e levation 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. We anticipate
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.
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 as
defined by OSHA . 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 in terest
of safety following local, and federal regulations, including current OSHA excavation and
trench safety standards.
As a safety measure, we recommend 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 site preparation, removal of existing, undocumented fill, and completion of any
required undercuts and the recommended over-excavations below structures and slabs ,
the top 1 2 inches of the exposed ground surface should be scarified, moisture
conditioned, and compacted to at least 95 percent of the maximum dry unit weight as
determined by ASTM D698 before any new fill, foundations, slabs, pavements , and other
site improvements are placed or constructed .
Large areas of prepared subgrade should be proof rolled prior to new construction. Proof
rolling is not required in areas which are inaccessible to proof rolling equipment.
Subgrades should be proof rolled with an adequately loaded vehicle such as a fully -
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loaded tandem-axle dump truck. Proof rolling should be performed under the
observation of the Geotechnical Engineer or representative. Areas excessively deflecting
under the proof roll should be delineated and subsequently addressed by the
Geotechnical Engineer. Excessively wet or dry material should either be r emoved and
replaced with engineered fill or scarified, moisture conditioned , and compacted.
Our experience indicates the subgrade materials below existing pavements and flatwork
after demolition will likely have relatively high moisture content s and will tend to deflect
and deform (pump) under construction traffic wheel loads. After removal of existing
pavements and flatwork, the contractor should expect unstable subgrade materials will
need to be stabilized prior to fill placement and/or construction. Consequently, Terracon
recommends a contingency be provided in the construction budget to stabilize and
correct weak/unstable subgrade.
After the bottom of the excavation has been prepared as recommended above ,
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.
Subgrade Stabilization
Methods of subgrade stabilization/improvement, as described below, could include
scarification, moisture conditioning and compaction, removal of unstable materials and
replacement with granular fill (with or without geosynthetics), and chemical treatment.
The appropriate method of improvement, if required, would be dependent on factors
such as schedule, weather, the size of area to be stabilized, and the nature of the
instability. More detailed recommendations can be provided during construction as the
need for subgrade stabilization occurs. Performing site grading operations during warm
seasons and dry periods would help reduce the amount of subgrade stabilization
required.
If the exposed subgrade is unstable during proof rolling operations, it could be stabilized
using one of the methods described below.
■ Scarification and Compaction - It may be feasible to scarify, dry, and compact
the exposed soils. The success of this procedure would depend primarily upon
favorable weather and sufficient time to dry the soils. Stable subgrades likely
would not be achievable if the thickness of the unstable soil is greater than about
1 foot, if the unstable soil is at or near groundwater levels, or if construction is
performed during a period of wet or cool weather when drying is difficult.
■ Crushed Stone - The use of crushed stone or crushed concrete is a common
procedure to improve subgrade stability. Typical undercut depths would be
expected to range from about 6 to 18 inches below finished subgrade elevation.
Crushed stone and/or concrete can be tracked or “crowded” into the unstable
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subgrade until a stable working surface is attained. The use of high modulus
geosynthetics (i.e., geotextile or geogrid) could also be considered after
underground work such as utility construction is completed. Prior to placing the
geosynthetic, we recommend all below -grade construction, such as utility line
installation, be completed to avoid damaging the geosynthetic. Equipment should
not be operated above the geosynthetic until one full lift of crushed stone fill is
placed above it.
■ Chemical Treatment - Improvement of subgrades with portland cement , lime,
or fly ash could be considered for improving unstable soils. Chemical treatment
should be performed by a pre -qualified contractor having experience with
successfully treating subgrades in the project area on similar sized projects with
similar soil conditions. Results of chemical analysis of the chemical treatment
materials should be provided to the Geotechnical Engineer for review prior to use.
The hazards of chemicals blowing across the site or onto adjacent propert ies
should also be considered. Additional testing would be needed to develop specific
recommendations to improve subgrade stability by blending chemicals with the
site soils. Additional testing could include, but not be limited to, determining the
most suitab le chemical treating agent, the optimum amounts required, the
presence of sulfates in the soil, and freeze -thaw durability of the subgrade.
Further evaluation of the need and recommendations for subgrade stabilization can be
provided during construction as the geotechnical conditions are exposed.
Fill Material Types
Fill for this project should consist of engineered fill. Engineered fill is fill that meets the
criteria presented in this report and has been properly documented. On-site soils free of
deleterious materials or approved granular and low plasticity cohesive imported
materials may be used as fill material. The earthwork contractor should expect
significant mechanical processing and moisture conditioning of the site soils to achieve
proper compaction .
As recommended below floor slabs, CDOT Class 1 structure backfill should meet the
following material property requirements:
Gradation Percent Finer by Weight (ASTM C136)
2” 100
No. 4 Sieve 30-100
No. 50 Sieve 10-60
No. 200 Sieve 5-20
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Soil Properties Values
Liquid Limit 35 (max.)
Plasticity Index 6 (max.)
Imported fill materials (if required) should meet the following material property
requirements. Regardless of its source, compacted fill should consist of approved
materials that are free of organic matter and debris. Frozen material should not be used,
and fill should not be placed on a froz en subgrade.
Gradation Percent Finer by Weight (ASTM C136)
3 ” 100
1 ” 70-100
No. 4 Sieve 30-100
No. 200 Sieve 15-65
Soil Properties Values
Liquid Limit 35 (max.)
Plasticity Index 15 (max.)
Aggregate base course used below new pavements should meet CDOT requirements for
Class 5 or 6 aggregate base course materials.
Other import ed fill material 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.
Fill Placement and 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
Maximum 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 .
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Item Description
Minimum
Compaction
Requirements 1
Engineered Fill : At least 95% of the maximum dry unit weight
as determined by ASTM D698.
Engineered Fill 8 Feet or Greater: At least 9 8% of the maximum
dry unit weight as determined by ASTM D698 for the entire
depth of fill in areas receiving 8 feet of fill or greater.
Aggregate Base Course: At least 95% of maximum dry unit
weight as determined by ASTM D1557 (or AASHTO T180) in
pavement areas.
Water Content
Range 2 ,3
Cohesive (clay): -1% to +3% of optimum moisture content
Granular (sand): -3% to +3% of optimum moisture content
1. We recommend engineered fill be tested for moisture content and compaction during
placement. If 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. 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.
3. Specifically, moisture levels in granular soils should be maintained low enough to allow
for satisfactory compaction to be achieved without the fill material pumping when proof
rolled.
Utility Trench Backfill
Any loose, soft, or unsuitable materials encountered at the bottom of utility trench
excavations should be removed and replaced with engineered fill or bedding material in
accordance with public works specifications for the utility to be supported. This
recommendation is particularly applicable to utility work where settlement control of the
utility is critical. Utility t rench excavation should not be conducted below a downward
1H:1 V (Horizontal:Vertical) projection from existing foundations without enginee ring
review of shoring requirements and geotechnical observation during construction.
On -site materials are considered suitable for backfill of utility and pipe trenches from
about the top of pipe to subgrade provided the material is free of organic matte r and
deleterious substances.
Utility trench backfill should be placed and compacted as discussed earlier in this report.
Compaction of initial lifts should be accomplished with hand -operated tampers or other
lightweight compactors. Flooding or jetting for placement and compaction of backfill i s
not recommended. If utility trenches are backfilled with relatively clean granular
material, they should be capped with at least 18 inches of cohesive fill in non -pavement
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areas to reduce the infiltration and conveyance of surface water through the trench
backfill.
In areas of low permeability subgrades , utility trenches are a common source of water
infiltration and migration. Utility trenches penetrating beneath the building /structures
should be effectively sealed to restrict water intrusion and flow through the trenches,
which could migrate below the building. The trench should provide an effective trench
plug that extends at least 5 feet from the face of the building exterior. The plu g material
should consist of cementitious flowable fill or low permeability clay. The trench plug
material should be pla ced to surround the utility line. If used, the trench plug material
should be placed and compacted to comply with the water content and compaction
recommendations for engineered fill stated previously in this report.
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.
We recommend a representative of the Geotechnical Engineer provide full-time
observation and compaction testing of trench backfill within construction areas.
Grading and Drainage
All grades must provide effective drainage away from the build ings/structures during
and after construction and should be maintained throughout the life of the structure s.
Water retained next to the buildings/structures can result in soil movements greater
than those discussed in this report. Greater movements can result in unacceptable
differential floor slab and/or foundation movements, cracked slabs and walls, and roof
leaks. The roof should have gutters/drains with d ownspouts that discharge onto splash
blocks at a distance of at least 10 feet from the building s/structures.
Exposed ground should be sloped and maintained at a minimum of 5% away from the
building for at least 10 feet beyond the perimeter of the convenience store and fuel
dispensers. Locally, flatter grades may be necessary to transition ADA access
requirements for flatwork. After building construction and landscaping have been
completed, final grades should be verified to document effective drainage has been
achieved. Grades around t he structures should also be periodically inspected and
adjusted, as necessary, as part of the structure’s maintenance program.
Flatwork and pavements will be subject to post -construction movement. Maximum
grades practical should be used for paving and flatwork to prevent areas where water
can pond. In addition, allowances in final grades should take into consideration post -
constru ction movement of flatwork, particularly if such movement would be critical.
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Where paving or flatwork abuts the structures, care should be taken that joints are
properly sealed and maintained to prevent the infiltration of surface water.
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 s/structures .
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. Subgrade soils below exterior flatwork/slabs-on-grade or new fill should
be scarified to a depth of at least 12 inches, moisture conditioned, and compacted prior
to placement/construction of new engineered fill, aggregate base course, or
pavement/flatwork materials. Potential movement could be reduced by:
■ Minimizing moisture increases in subgrade soils and new fill;
■ Controlling moisture -density during subgrade preparation and new fill placement;
■ Using designs which allow vertical movement between the exterior features and
adjoining structural elements; and
■ Placing control joints on relatively close centers.
Earthwork Construction Considerations
Upon completion of filling and grading, care should be taken to maintain the subgrade
water content prior to construction of grade -supported improvements such as floor slabs
and pavements. Con struction traffic over the completed subgrades should be avoided.
The site should also be graded to prevent ponding of surface water on the prepared
subgrades or in excavations. Water collecting over or adjacent to construction areas
should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, th e
affected material should be removed, or the materials should be scarified, moisture
conditioned, and recompacted prior to floor slab or pavement construction.
Construction site safety is the sole responsibility of the contractor who controls the
means, methods, and sequencing of construction operations. Under no circumstances
shall the information provided herein be interpreted to mean Terracon is assuming
responsibility for construction site safety or the contractor's activities; such
responsibility shall neither be implied nor inferred.
Excavations or other activities resulting in ground disturbance have the potential to
affect adjoining properties and structures. Our scope of services does not include review
of available final grading information or consider potential temporary grading performed
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by the contractor for potential effects such as ground movement beyond the project
limits. A preconstruction/precondition survey should be conducted to document nearby
property/infrastructure prior to any site development activity. Ex cavation or ground
disturbance activit i es adjacent or near property lines should be monitored or
instrumented for potential ground movements that could negatively af fect adjoining
property and/or structures.
Construction Observation and Testing
The earthwork efforts should be observed by the Geotechnical Engineer (or others under
their direction). Observation should include documentation of adequate removal of
surficial materials (vegetation, topsoil, and existing aggregate surfacing and
pavements), evaluation and remediation of existing fill materials, subgrade stabilization,
as well as proof rolling and mitigation of unsuitable areas delineated by the proof roll.
Each lift of compacted fill should be tested, evaluated, and reworked, as necessary , as
recommended by the Geotechnical Engineer prior to placement of additional lifts.
In areas of foundation excavations, the bearing subgrade and exposed conditions at the
base of the recommended over -excavation should be evaluated by the Geotechnical
Engineer. If unanticipated conditions are observed, the Geotechnical Engineer should
prescri be mitigation options.
In addition to the documentation of the essential parameters necessary for construction,
the continuation of the Geotechnical Engineer into the construction phase of the project
provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface
conditions, including assessing variations and associated design changes.
Shallow Foundations
If the site has been prepared in accordance with the recommendations/requirements
noted in Geotechnical Overview and Earthwork, the following design parameters are
applicable for shallow , spread footing foundations for the proposed convenience store
and fuel dispenser canopy.
Spread Footings – Design Recommendations
Item Description
Maximum Net Allowable
Bearing Pressure 1 1,800 psf
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Item Description
Required Bearing Stratum 2
At least 2 feet of moisture conditioned, properly
compacted engineered fill and all existing fill has
been completely removed below foundations
Minimum Foundation
Dimensions
Columns: 30 inches
Continuous: 18 inches
Lateral Earth Pressure
Coefficients 3
On-site clay soils and engineered fill :
Active, K a = 0.49
Passive, Kp = 2.04
At-rest, K o = 0.66
On-site sand soils and engineered fill :
Active, K a = 0.35
Passive, Kp = 2.88
At-rest, K o = 0.52
Sliding Resistance 4
On-site clay soils and engineered fill :
130 psf (allowable cohesion)
On-site sand soil s and engineered fill :
μ = 0.42 (ultimate)
Moist Soil Unit Weight
On-site clay soils and engineered fill :
γ = 120 pcf
On-site sand soils and engineered fill:
γ = 115 pcf
Minimum Embedment Below
Finished Grade 5
Exterior footings in unheated areas:
30 inches
Interior footings and column pads in heated
areas: 12 inches
Estimated Total Movement 6 About 1 inch
Estimated Differential
Movement 6 About ½ to ¾ of total movement
1. The maximum net allowable bearing pressure is the pressure in excess of the minimum
surrounding overburden pressure at the footing base elevation. Values assume exterior
grades are no steeper than 20% within 10 feet of structure . The allowable bearing
pressure may be increased by one -third when considering the alternative load
combinations of Section 1605.3.2 of the 2018 International Building Code, however, it
should not be increased when loads are determined by the basic allowabl e stress design
load combinations of Section 1605.3.1.
2. Unsuitable or soft /loose soils should be over -excavated and replaced with engineered fill
per the recommendations pres ented in Earthwork.
3. Use of lateral earth pressures requires the footing forms be removed and compacted
engineered fill be placed against the vertical footing face. Assumes no hydrostatic
pressure. The lateral earth pressure coefficients are ultimate values and do not include a
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Item Description
factor of safety. The foundation designer should include the appropriate factors of
safety.
4. For fine-grained materials, lateral resistance using cohesion should not exceed ½ the
dead load.
5. Embedment necessary to minimize the effects of frost and/or seasonal water content
variations. For sloping ground, maintain depth below the lowest adjacent exterior grade
within 5 horizontal feet of the structure.
6. The estimated movements presented above assume the maximum footing dimension is
7 feet for column footings and maximum footing width is 3.5 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 could 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
Drain age section of Earthwork will nullify the movement estimates provided above.
Any over-excavation extending 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 e levation in accordance with the recommendations
presented in this report.
Spread Footings – Overturning and Uplift Loads
Shallow foundations subjected to overturning loads should be proportioned such that the
resultant eccentricity is maintained in the center -third of the foundation (e.g., e < b/6,
where b is the foundation width). This requirement is intended to keep the en tire
foundation area in compression during the extreme lateral/overturning load event.
Foundation oversizing may be required to satisfy this condition.
Uplift resistance of spread footings can be developed from the effective weight of the
footing and the overlying soils with consideration to the IBC basic load combinations .
Item Description
Soil Moist Unit Weight 110 pcf
Soil Effective Unit Weight 1 45 pcf
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Shallow Foundation Construction Considerations
Foundation excavations should be evaluated under the observation of the Geotechnical
Engineer. The base of all foundation excavations should be free of water and loose soil,
prior to placing concrete. Concrete should be placed soon after excavating to reduce
bearing soil disturbance. Care should be taken to prevent wetting or drying of the
bearing materials during construction. Excessively wet or dry material or any
loose/disturbed material in the bottom of foundation excavations should be
removed/reconditioned befor e foundation concrete is placed.
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 building and other structures be completed remotely with
a track-hoe operating outside of the excavation limits.
Foundation elements should be reinforced as necessary to reduce the potential for
distress caused by differential foundation movement.
Unstable subgrade conditions encountered in foundation excavations should be observed
by Terracon to assess the subgrade and provide suitable alternatives for stabilization.
Typical methods of stabilization/improvement are presented in the Subgrade
Stabilization section of Earthwork.
Deep Foundations
As an alternative to supporting the proposed convenience store and fuel dispenser
canopy structure on shallow foundations, consideration could be given to supporting the
structures on a deep foundation system consisting of helical pi les. We recommend the
helical piles be terminated in the dense sand soils or the claystone bedrock to help
reduce the potential risk of movement associated with supporting the structures on
shallow foundations bearing in areas above relatively shallow groundwater and
comparatively low strength clay or low relative density sand soils . An experienced
specialty contractor should be contacted for design and installation of helical piles.
Item Description
Soil Weight Included in Uplift
Resistance
Soil included within the prism extending up from
the top perimeter of the footing at an angle of 20
degrees from vertical to ground surface
1. Effective (or buoyant) unit weight should be used for soil above the foundation
level and below a water level. The high groundwater level should be used in
uplift design as applicable .
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Helical Pile Foundations
Helical piles bottomed in the dense sand soils or claystone bedrock could be considered
for support of the proposed convenience store fuel dispenser canopy structure. We
recommend an experienced specialty contractor be consulted about installing helical
piers in the subsurface conditions encountered in the borings.
We do not recommend using vertically installed helical piles to resist lateral loads
without approved lateral load test data, as these types of foundations are typically
designed to resist axial loads. Only the horizontal component of the allowable axial l oad
should be considered to resist the lateral loading and only in the direction of the batter.
The Geotechnical Engineer should be retained to observe helical pile installation to verify
that proper bearing materials have been encountered during installat ion.
In accordance with local building code requirements, a load test should be performed by
the helical pile installer to validate achieving the allowable design load. Load tests
should be performed using helical piles consistent in size and materials with tho se piles
planned for use during construction. Similarly, the same installation techniques and
equipment planned for use during installation of production piles should be used when
installing piles for load testing.
We recommend the helical pile designer follow the recommendations presented in
Chapter 18 of the applicable International Building Code (IBC). We recommend the
helical bearing plates for each helical pile bear in dense sand soils or claystone bedrock
encountered below the site. The helical pile designer should select the size and number
of helical bearing plates for each helical pile based on planned loads and bearing
materials described in the exploratory boring logs. Torque measurements during
installation of helical piles should be used to verify the axial capacity of the helical piles.
The Geotechnical Engineer should be provided with the torque -to-capacity relationships
for each type of pile used on the project for our review and comment prior to
mobilization to the site . We recommend the helical pile installation contractor provide
confirmation that the installation equipment has been calibrated within one year of
installation at this project. The helical foundations should be installed by a qualified
specialty contractor per the manufactu rer’s recommendations.
Floor Slabs
A concrete slab-on-grade floor system can be used for the proposed convenience store
provided any existing fill within the building/structure area is removed full depth and the
soils are over-excavated to a depth of at least 3 feet below the bottom of the floor slab,
if the existing fill thickness does not already extend to at least 3 feet below the bottom
of the floor slab , and replaced with moisture conditioned, properly compacted
engineered fill. On -site soils free of deleterious materials are suitable as engineered fill
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 27
below floor slabs. We recommend the top 6 inches of the engineered fill zone below the
floor slab of the new building consist of Colorado Department of Transportation (CDOT)
Class 1 structure backfill. 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 recommended
over-excavation should be scarified to a depth of at least 1 2 inches, moisture
conditioned, and compacted. The moisture content and compaction of subgrade soils
should be maintained until slab construction.
Floor Slab s - Design Recommendations
Even when bearing on properly prepared soils, movement of the slab -on-grade floor
system is possible should the subgrade soils undergo an increase in moisture content.
We estimate movement of about 1 inch is possible. If the owner cannot accept the risk
of slab movement, a structural floor should be used. If conventional slab -on-grade is
utilized, the subgrade soils should be over -excavated and prepared as recommended
above and 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 175 pci can be used for floors if the upper 6 inches of the
recommended over -excavation zone consists of CDOT class 1 structure backfill and the
floors are supported on the CDOT class 1 structure backfill.
The use of a vapor retarder should be considered beneath concrete slabs on grade
covered with wood, tile, carpet, or other moisture sensitive or impervious coverings,
when the project includes humidity -controlled areas, or when the slab will support
equipment sensitive to moisture. When conditions warrant the use of a vapor retarder,
the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions
regarding the use and placement of a vapor retarder.
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.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 28
■ Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1R are recommended.
Floor Slab s - Construction Considerations
Movements of slabs -on-grade using the recommendations discussed in previous sections
of this report will likely be reduced and tend to be more uniform. The estimates
discussed above assume that the other recommendations in this report are followed.
Additional movement could occur should the subsurface soils become wetted to
significant depths, which could result in potential excessive movement causing uneven
floor slabs and severe cracking. This could be due to over watering of landscaping, poor
drainage, improperly functioning drain systems, and/or broken utility lines. Therefore, it
is imperative that the recommendations presented in this report be followed.
Finished subgrade, within and for at least 10 feet beyond the floor slab, should be
protected from traffic, rutting, or other disturbance and maintained in a relatively moist
condition until floor slabs are constructed. If the subgrade should become damage d or
desiccated prior to construction of floor slabs, the affected material should be removed,
and engineered fill should be added to replace the resulting excavation. Final
conditioning of the finished subgrade should be performed immediately prior to
placement of the floor slab support course.
The Geotechnical Engineer should observe the condition of the floor slab subgrades
immediately prior to placement of the floor slab support course, reinforcing steel, and
concrete. Attention should be paid to high traffic areas that were rutted and disturb ed
earlier, and to areas where backfilled trenches are located.
Below-Grade Structures
We understand that underground fuel storage tanks will be constructed below grade. We
anticipate the bottom of the fuel tanks will be about 15 to 20 feet below grade.
Underground Storage Tanks
One boring was completed in the area of the planned underground storage tanks to a
depth of approximately 2 4½ feet below existing site grades. Relatively s hallow
groundwater was encountered at depth s of about 4½ to 5 feet below existing site
grades. During construction of the fuel storage tanks, depending upon depth of
excavation and seasonal conditions, surface water infiltration and/or groundwater will
likely be encountered in excavations on the site. It is anticipated that pumping from
sumps or other forms of temporary construction dewatering may be utilized to control
water within the excavation area. Excavatio ns penetrating the anticipated groundwater
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 29
depth will likely encounter caving soil conditions which may require the use of shoring in
the excavation. It is anticipated that excavations for the proposed construction can be
accomplished with conventional earthmoving equipment. Underground storage tan k
foundations should be designed to resist buoyant forces due to shallow groundwater and
seasonal fluctuation of about 2 to 3 feet. The tanks may need to be tied to deadman
anchors or anchored in place by other methods to resist the buoyant pressures for t he
observed groundwater if a permanent dewatering system is not utilized.
Lateral Earth Pressures
Design Parameters
Structures with unbalanced backfill levels on opposite sides should be designed for earth
pressures at least equal to values indicated in the following table. Earth pressures will be
influenced by structural design of the walls, conditions of wall restrain t, methods of
construction, and/or compaction and the strength of the materials being restrained. Two
wall restraint conditions are shown in the diagram below. Active earth pressure is
commonly used for design of free -standing cantilever retaining walls an d assumes wall
movement. The “at -rest” condition assumes no wall movement and is commonly used
for basement walls, loading dock walls, or other walls restrained at the top. The
recommended design lateral earth pressures do not include a factor of safety an d do not
provide for possible hydrostatic pressure on the walls (unless stated).
Lateral Earth Pressure Design Parameters
Earth
Pressure
Condition 1
Coefficient for
Backfill Type 2
Surcharge
Pressure 3
p1 (psf)
Equivalent Fluid Pressures
(psf) 2,4
Unsaturated 5 Submerged 5
Active (Ka) Granular - 0.35
Fine Grained - 0.49
(0.35)S
(0.49)S
(45)H
(60)H
(85)H
(90)H
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 30
Lateral Earth Pressure Design Parameters
Earth
Pressure
Condition 1
Coefficient for
Backfill Type 2
Surcharge
Pressure 3
p1 (psf)
Equivalent Fluid Pressures
(psf) 2,4
Unsaturated 5 Submerged 5
At-Rest (Ko) Granular - 0.52
Fine Grained - 0.66
(0.52)S
(0.66)S
(65)H
(80)H
(95)H
(100)H
Passive (Kp) Granular – 2.88
Fine Grained – 2.04
---
---
---
---
---
---
1. For active earth pressure, wall must rotate about base, with top lateral
movements 0.002 H to 0.004 H, where H is wall height. For passive earth
pressure, wall must move horizontally to mobilize resistance. Fat clay or other
expansive soils should not be used as backfill behind the wall.
2. Uniform, horizontal backfill, with a maximum unit weight of 120 pcf for cohesive
soils and 115 pcf for granular soils.
3. Uniform surcharge, where S is surcharge pressure.
4. Loading from heavy compaction equipment is not included.
5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage
for Below-Grade Walls below. “Submerged” conditions are recommended
when drainage behind walls is not incorporated into the design.
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, the
values presented in the Shallow Foundations section can be utilized between wall
foundations and the underlying soils.
Footings, floor slabs , or other loads bearing on backfill behind walls may have a
significant influence on the lateral earth pressure. Placing footings within wall backfill
and in the zone of active soil influence on the wall should be avoided unless structural
analyses indicate the wall can safely withstand the increased pressure.
The lateral earth pressure recommendations given in this section are applicable to the
design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity
type concrete walls. These recommendations are not applicable to the design of modular
block - geogrid reinforced backfill walls (also termed MSE walls). Recommendations
covering these types of wall systems are beyond the scope of services for this
assignment. However, we would be pleased to develop a proposal for evaluation and
design of such wall systems upon request.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 31
Pavements
General Pavement Comments
Pavement designs are provided for the traffic conditions and pavement life conditions as
noted in Project Description and in the following sections of this report. A critical
aspect of pavement performance is site preparation. Pavement designs noted in this
section must be applied to the site which has been prepared as recommended in the
Earthwork section.
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, c onstruction 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
constructio n 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
grading and paving. All pavement areas should be moisture conditioned and properly
compacted to the recommendations in this report immediately prior to paving.
Prior to pavement construction and after the pavement areas have been stripped, and
any required undercuts have been completed within the planned pavement areas, we
recommend the top 12 inches of the subgrade soils below new pavements be scarified,
moisture conditioned, and compacted prior to placing new engineered fill or constructing
new pavements due to the presence of existing fill at the site. After the subgrade has
been scarified and compacted and before placement of new fi ll and pavement, we
recommend the subgrade be proof rolled as described above.
Pavemen ts – Design Reccomendations
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 selected the following design parameters for NAPA flexible pavement thickness
design:
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 32
■ Automobile Parking Areas
o 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
o Class IV – Heavy truck lots and drive lanes with a maximum of 50 trucks
per day with Equivalent Single Axle Load (ESAL) up to 1,000,000 over 20
years (including trash trucks)
■ Subgrade Soil Characteristics
o USCS Classification – CL, SC classified by NAPA as poor to medium
We selected the following design parameters for ACI rigid pavement thickness design
based upon the average daily truck traffic (ADTT):
■ Automobile Parking Areas
o ACI Category A: Automobile parking with an ADTT of 1 over 20 years
■ Main Traffic Corridors
o ACI Category B: Entrance and truck service lanes with an ADTT of up to 50
over 20 years
■ Subgrade Soil Characteristics
o USCS Classification – CL, SC
■ 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.
The following table provides the recommended minimum thickness for AC (asphaltic
concrete) and PCC (portland cement concrete) sections.
Traffic Area Alternative
Recommended Pavement Thicknesses (Inches)
Asphaltic
Concrete
Portland
Cement
Concrete
Aggregate
Base
Course
Total
Automobile
Parking
(NAPA Class I
and ACI
Category A)
A 4 -- 6 10
B -- 5 4 1 9
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 33
Traffic Area Alternative
Recommended Pavement Thicknesses (Inches)
Asphaltic
Concrete
Portland
Cement
Concrete
Aggregate
Base
Course
Total
Main Traffic
Corridors
(NAPA Class IV
and ACI
Category B)
A 7 -- 8 15
B -- 6.5 4 1 10.5
1. Although not required for structural support, a minimum 4-inch thick aggregate base course
layer is suggested for the portland cement concrete (PCC) pavements to help reduce the
potential for slab curl, shrinkage cracking, and subgrade “pumping” through joints.
Aggregate base course 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 b ase
course. Aggregate base course should be placed in lifts not exceeding 6 inches and
compacted to a minimum of 95 percent of the maximum dry unit weight as determined
by ASTM D1557 (or AASHTO T180).
Asphaltic concrete should be composed of a mixture of aggregate, filler and additives (if
required) and approved bituminous material. The asphalt concrete should conform to
approved mix designs stating the Superpave properties, optimum asphalt content, job
mix formula and recommended mixing and placing temperatures. Aggregate used in
asphalt concrete should meet particular gradations. Material meeting CDOT Grading S or
SX specifications or equivalent is recommended for asphalt concrete. Mix designs should
b e 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 4,500 psi
Cement type Type I or II portland cement or
Type IL portland-limestone cement
Entrained air content (%) 5 to 8
Concrete aggregate ASTM C33 and CDOT section 703
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 34
Longitudinal and transverse joints should be provided as needed in concrete pavements
for expansion/contraction and isolation per ACI 330 and ACI 325. The location and
extent of joints should be based upon the final pavement geometry.
Proper joint spacing will also be required to prevent excessive slab curling and shrinkage
cracking. Joints should be sealed to prevent entry of foreign material and doweled where
necessary for load transfer.
Where practical, we recommend early -entry cutting of crack -control joints in PCC
pavements. Cutting of the concrete in its “green” state typically reduces the potential for
micro-cracking of the pavements prior to the crack control joints being formed,
com pared to cutting the joints after the concrete has fully set. Micro -cracking of
pavements may lead to crack formation in locations other than the sawed joints, and/or
reduction of fatigue life of the pavement.
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 7 inches underlain by at
least 4 inches of granular base. Prior to placement of the granular base, the subgrade
soils should be prepared as previously discussed. 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 pavements;
■ 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
■ Placing compacted, low permeability backfill against the exterior side of curb and
gutter.
Pavements – Construction Considerations
Openings in pavements, such as decorative landscaped areas, are sources for water
infiltration into surrounding pavement systems. Water can collect in the islands and
migrate into the surrounding subgrade soils thereby degrading support of the pavement.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 35
Islands with raised concrete curbs, irrigated foliage, and low permeability near -surface
soils are particular areas of concern. The civil design for the pavements with these
conditions should include features to restrict or collect and discharge excess wat er from
the islands. Examples of features are edge drains connected to the stormwater collection
system, longitudinal subdrains, or other suitable outlets and impermeable barriers
preventing lateral migration of water such as a cutoff wall installed to a d epth below the
pavement structure.
Pavements should be sloped to provide rapid drainage of surface water. Water allowed
to pond on or adjacent to the pavements could saturate the subgrade and contribute to
premature pavement deterioration. In addition, the pavement subgrade should be
graded to provide positive drainage within the granular base section. Appropriate sub -
drainage or connection to a suitable daylight outlet should be provided to remove water
from the granular subbase.
Pavements – Maintenance
The pavement sections represent minimum recommended thicknesses and, as such,
periodic upkeep should be anticipated. Preventive maintenance should be planned and
provided for through an on -going pavement management program. Maintenance
activities are inten ded to slow the rate of pavement deterioration and to preserve the
pavement investment. Pavement care consists of both localized (e.g., crack and joint
sealing and patching) and global maintenance (e.g., surface sealing). Additional
engineering consultation is recommended to determine the type and extent of a cost -
effective program. Even with periodic maintenance, some movements and related
cracking may still occur, and repairs may be required.
Frost Considerations
Some of 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 buildin g 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
drainage system.
■ Install drains around the perimeter of the building, stoops, below exterior slabs
and pavements, and connect them to the site drainage system .
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 36
■ Grade clayey subgrades so groundwater potentially perched in overlying fill or
aggregate base, slope toward a site drainage system.
■ Place NFS fill as backfill beneath slabs and pavements critical to the project.
■ Place a 3H:1V (Horizontal:Vertical) transition zone between NFS fill and other
soils.
■ Place NFS materials in critical sidewalk areas.
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.
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.
Variations will occur between exploration point locations or due to the modifying effects
of construction or weather. The nature and extent of such variations may not become
evident until during or after construction. Terracon should be retained as the
Geotechnical Engineer, where noted in this 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 th at 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 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 th ird-
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 a nd is not
intended for third parties. Any use or reliance of the provided information by third
parties is done solely at their 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
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials 37
could significantly affect 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. Site safety and cost estimating including
excavation supp ort and dewatering requirements/design are the responsibility of others.
Construction and site development have the potential to affect adjacent prop erties. Such
impacts can include damages due to vibration, modification of groun dwater/surface
water flow during construction, foundation movement due to undermining or subsidence
from excavation , as well as noise or air quality concerns. Evaluation of these items on
nearby properties are commonly associated with contractor means and methods and are
not addressed in this report. The owner and contractor should consider a
preconstruction/precondition survey of surrounding development. 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.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Figures
Contents:
GeoModel (2 pages)
4,810
4,815
4,820
4,825
4,830
4,835
4,840
4,845
4,850
EL
E
V
A
T
I
O
N
(
M
S
L
)
(
f
e
e
t
)
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:
Legend
This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.
GeoModel
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045
Harmony Lakes - New Convenience Store
Fort Collins, CO
Third Water Observation
Second Water Observation
First Water Observation
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.
Sandy Lean
Clay/Clayey Sand
Lean Clay Poorly-graded Sand
with Gravel
Claystone Lean Clay with Sand
Sandy Lean Clay
with Gravel
Well-graded Sand
with Gravel
Silty Sand with
Gravel
Clayey Sand with
Gravel
Poorly-graded Sand
with Silt and Gravel Asphalt
Model Layer Layer Name General Description
1
About 3 to 19 inches of aggregate surfacing in Boring Nos.
B-1 to B-5, B-7 to B-9, B-11, and B-12. About 3-1/4 inches
of asphalt in Boring No. B-6.
3 Very soft to stiff clay soils with variable amounts of sand
and gravel.
4 Very loose to very dense poorly graded and well graded
sand soils with variable amounts of fines and gravel.
2
Consisted primarily of clay soils with variable amounts of
sand and gravel or sand soils with variable amounts of clay
and gravel.
5 Medium hard to very hard claystone bedrock.
B-1 B-2
B-3
B-4
B-5
B-6
4862 Innovation Dr Ste 104
Aggregate SurfacingExisting Surfacing
Materials
Clay Soils
Sand Soils
Existing Fill
Bedrock
1
2
3
4
5
9.9
14
1
7
14
19
34.3
1
2
3
4
5
8.6
14
0.7
4
14
19
34.3
1
3
4
5
4.9
7
1.6
4
19
24.4
1
2
3
4
5
6.3
14
0.3
4
9
19.5
24.3
1
2
4
5
10
7
0.3
4
20.4
24.3
7.3
1
2
4
7
0.3
7
10.5
4,810
4,815
4,820
4,825
4,830
4,835
4,840
4,845
4,850
EL
E
V
A
T
I
O
N
(
M
S
L
)
(
f
e
e
t
)
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:
Legend
This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.
GeoModel
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045
Harmony Lakes - New Convenience Store
Fort Collins, CO
Third Water Observation
Second Water Observation
First Water Observation
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.
Clayey Sand
Lean Clay with Sand Poorly-graded Sand
with GravelPoorly-graded Sand
with Clay and
Gravel
Poorly-graded Sand
Well-graded Sand
with Gravel
Sandy Lean Clay
with Gravel
Well-graded Sand
with Silt and Gravel Claystone
Sandy Lean
Clay/Clayey Sand
Poorly-graded Sand
with Silt and Gravel
Model Layer Layer Name General Description
1
About 3 to 19 inches of aggregate surfacing in Boring Nos.
B-1 to B-5, B-7 to B-9, B-11, and B-12. About 3-1/4 inches
of asphalt in Boring No. B-6.
3 Very soft to stiff clay soils with variable amounts of sand
and gravel.
4 Very loose to very dense poorly graded and well graded
sand soils with variable amounts of fines and gravel.
2
Consisted primarily of clay soils with variable amounts of
sand and gravel or sand soils with variable amounts of clay
and gravel.
5 Medium hard to very hard claystone bedrock.
B-7
B-8
B-9 B-10
B-11
B-12
4862 Innovation Dr Ste 104
Aggregate SurfacingExisting Surfacing
Materials
Clay Soils
Sand Soils
Existing Fill
Bedrock
1
2
3
4
7.37
1
4
7
10.5
1
2
47
0.3
2
10.5
1
2
3
4
5
3.2
9
0.9
7
9
14.5
24.3
2
4
5
7
14
24.1
2.2
1
2
4
5
9
14
1
7
22
24.3
1
2
4
5
9.5
7
1
4
19
34.3
3.7
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Attachments
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Exploration and Testing Procedures
Field Exploration
Number of Borings Approximate Boring
Depth (feet) Location
2
(Boring Nos. B-1 and B-2) 34.3 Proposed convenience
store location
1
(Boring No . B-3) 24.4 Proposed fuel tank area
2
(Boring Nos. B-4 and B-5) 24.3 Proposed canopy/fuel
dispenser area
3 1
(Boring Nos. B -6
through B-8)
10.5 Proposed roadway
alignment
3 1
(Boring Nos. B -9
through B-11 )
24.1 to 24.3 In areas of future
developments
1 1
(Boring No. B-12)
34.3 Proposed lift station
location
1. A separate report utilizing the data from Boring Nos. B -6 through B-12 will be issued to
provide geotechnical recommendations for the planned public roadway improvements
and lift station within the Harmony Lake s development. Preliminary recommendations
for planned future development of the outlots at the site will also be presented in the
second report.
Boring Layout and Elevations: Terracon personnel provided the boring layout using
handheld GPS equipment (estimated horizontal accuracy of about ±15 feet) and
referencing existing site features. Approximate ground surface elevations at the boring
locations were obtained by interpolation from a topographic site plan provided by TB
group dated April 5, 2024 . If elevations and a more precise boring layout are desired,
we recommend the borings be surveyed.
Subsurface Exploration Procedures: We advanced the borings with a truck -mounted
drill rig using continuous -flight , hollow-stem and solid-stem augers. Sampling was
performed using standard split-barrel and modified California barrel sampling
procedures. Bulk samples of auger cuttings from the upper approximately 5 feet of each
borehole were also collected for laboratory testing. In the split-barrel sampling
procedure, a standard 2 -inch outer diameter split -barrel sampling spoon was driven into
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
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. In the modified California barrel sampling procedure, a 2½-inch outer
diameter split-barrel sampling spoon is used for sampling. Modified Californi a barrel
sampling procedures are similar to standard split spoon sampling procedure; however,
blow counts are typically recorded for 6 -inch intervals for a total of 12 inches of
penetration. Modified California barrel sampler blow counts are not considered N -values.
The samples were placed in appropriate containers and taken to our soil laboratory for
testing and classification by a Geotechnical Engineer.
We also observed the boreholes while drilling and at the completion of drilling for the
presence of groundwater . Additionally, we observed 3 of the boreholes approximately 24
hours after the completion of drilling for the presence of groundwater . The groundwater
levels are shown on the attached boring logs.
Our exploration team prepared field boring logs as part of the drilling operations. The
sampling depths, penetration distances, and other sampling information were recorded
on the field boring logs. These field logs included visual classifications of the materials
observed during drilling and our interpretation of the subsurface conditions between
samples. Final boring logs were prepared from the field logs. The final boring logs
represent the Geotec hnical Engineer's interpretation of the subsurface conditi ons at the
boring locations based on field data, observation of samples, and laboratory test results.
We backfilled the borings with auger cuttings or flowable backfill after completion of
drilling. The pavement at the location of Boring No. B -6 was patched with the asphalt
core and Utilibond. Our services did not include repair of the site beyond backfilling the
boreholes and patching existing pavement. 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.
Laboratory Testing
The project engineer reviewed the field data and assigned laboratory tests. The
laboratory testing program included the following types of tests:
■ Moisture Content
■ Dry Unit Weight
■ Atterberg Limits
■ Grain-size Distribution
■ One-dimensional Swell/Consolidation
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
■ R -value
■ Water-soluble Sulfates
■ Corrosivity Suite – pH, sulfates, chloride ion, sulfide ion, redox, total salts and
electrical resistivity
The laboratory testing program included examination of samples by an engineer and/or
geologist. Based on the results of our field and laboratory programs, we described and
classified the soil samples in accordance with the Unified Soil Classification System. A
brief description of this classification system as well as the General Notes can be found
in the Supporting Information section. Rock classification was conducted using locally
accepted practices for engineering purposes .
Laboratory test results are indicated on the boring logs and are presented in depth in
the Exploration Results section. Laboratory tests are performed in general accordance
with applicable local standards or other acceptable standards. In some cases, variations
to methods are applied as a result of local practice or professional judgement.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Site Location and Exploration Plans
Contents:
Site Location Plan
Exploration Plan
Note: All attachments are one page unless noted above.
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
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 Location
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
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 Plan
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Exploration and Laboratory Results
Contents:
Boring Logs (B-1 through B-12)
Atterberg Limits
Grain Size Distribution (3 pages)
Consolidation/Swell (10 pages)
R-Value
Water-Soluble Sulfates
Corrosivity Suite
4846
4840
4833
4828
4812.7
AGGREGATE SURFACING, about 12 inches thick
FILL - SANDY LEAN CLAY (CL), trace gravel, brown
LEAN CLAY, dark brown, medium stiff, iron oxide
present at about 9 feet
POORLY GRADED SAND WITH GRAVEL, fine to
medium grained, light brown with pink, medium
dense, possible cobbles
CLAYSTONE, yellow brown to gray, hard to very
hard, upper 1 to 2 feet is moderately weathered
Boring Terminated at 34.3 Feet
Boring Log No. B-1
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
25
30
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4847 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
54.312.1
12.3
26.5
29.0
13.4
19.4
14.1
16.9
15.4
28-15-13
1.0
7.0
14.0
19.0
34.3
<+0.1/
500
<-0.1/
1000
115
93
119
108
6-7-10
N=17
5-7
12/12"
2-2-3
N=5
3-3
6/12"
2-7-17
N=24
14-22-34
N=56
30-50/3"
50/5"
50/3"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
9.9 feet at completion of drilling
14 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-03-2025
Boring Completed
09-03-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
Hammer Type
Automatic; Hammer
Efficiency = 93%
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5223° Longitude: -104.9964°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
3
4
5
4847.3
4844
4839
4834
4829
4813.7
AGGREGATE SURFACING, about 8 inches thick
FILL - LEAN CLAY WITH SAND, trace gravel, dark
brown
LEAN CLAY, dark brown, stiff, organics at about 4
feet, increase in moisture at about 7 feet
soft to medium stiff at about 7 feet
SANDY LEAN CLAY WITH GRAVEL (CL), dark brown,
stiff
WELL GRADED SAND WITH GRAVEL, medium to
coarse grained, light brown with pink, medium dense,
possible cobbles
CLAYSTONE, gray, hard to very hard, upper 1 to 2
feet is moderately weathered
Boring Terminated at 34.3 Feet
Boring Log No. B-2
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
25
30
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4848 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
51.0
0.7
4.0
9.0
14.0
19.0
34.3
+0.2/
500 115
121
4-5-7
N=12
5-9
14/12"
1-2-2
N=4
3-15
18/12"
9-10-12
N=22
10-19-45
N=64
50/4"
50/5"
50/4"
15.4
14.8
27.6
21.2
6.9
16.8
11.7
13.8
14.2
31-20-11
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
8.6 feet at completion of drilling
14 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Hammer Type
Automatic; Hammer
Efficiency = 93%
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5222° Longitude: -104.9960°
4862 Innovation Dr Ste 104
1
2
3
4
5
4844.4
4842
4837
4827
4821.6
AGGREGATE SURFACING, about 19 inches thick
LEAN CLAY WITH SAND, dark brown, stiff, possible
organics at about 2 feet
SILTY SAND WITH GRAVEL (SM), medium grained,
dark brown, medium dense to dense
WELL GRADED SAND WITH GRAVEL, medium to
coarse grained, light brown with pink, medium dense
to very dense, possible cobbles
CLAYSTONE, gray, very hard
Boring Terminated at 24.4 Feet
Boring Log No. B-3
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4846 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
21.3
15.5
10.4
10.2
8.6
11.7
16.2
14.8
18-15-3
1.6
4.0
9.0
19.0
24.4
<+0.1/
150 113
115
4-7
11/12"
14-5-6
N=11
10-12-22
N=34
16-16-11
N=27
20-22-40
N=62
50/6"
50/5"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
4.9 feet at completion of drilling
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Hammer Type
Automatic; Hammer
Efficiency = 93%
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5223° Longitude: -104.9956°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
3
4
5
4848.7
4845
4840
4829.5
4824.7
AGGREGATE SURFACING, about 3 inches thick
FILL - SANDY LEAN CLAY, dark brown
SANDY LEAN CLAY (CL), dark brown, medium stiff,
possible calcium carbonate and organics at about 4
feet
no recovery of sample at 7 feet
very soft at about 7 feet
WELL GRADED SAND WITH GRAVEL, light brown
with pink, dense to very dense, possible cobbles
CLAYSTONE, gray, very hard, cementation at about
19.5 feet
Boring Terminated at 24.3 Feet
Boring Log No. B-4
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4849 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
68.6
0.3
4.0
9.0
19.5
24.3
+0.2/
500 112
113
5-7
12/12"
2-2-3
N=5
0-1
1/12"
8-19-17
N=36
16-27-35
N=62
18-30-50/4"
50/4"
16.8
24.5
4.3
8.2
17.8
13.8
43-18-25
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
6.3 feet at completion of drilling
14 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-03-2025
Boring Completed
09-03-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Hammer Type
Automatic; Hammer
Efficiency = 93%
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5225° Longitude: -104.9960°
4862 Innovation Dr Ste 104
1
2
3
4
5
4846.7
4843
4838
4826.6
4822.7
FILL - AGGREGATE SURFACING, about 3 inches thick
FILL - CLAYEY SAND WITH GRAVEL, dark brown to
tan
POORLY GRADED SAND WITH GRAVEL, fine to
coarse grained, brown to pink, medium dense to
dense, possible cobbles
POORLY GRADED SAND WITH SILT AND GRAVEL
(SP-SM), medium to coarse grained, light brown with
pink, dense to very dense, possible cobbles
CLAYSTONE, yellow brown to gray, very hard, upper
1 to 2 feet is moderately weathered
Boring Terminated at 24.3 Feet
Boring Log No. B-5
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4847 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
7.6
5.0
1.2
8.2
8.4
7.7
3.7
NP
0.3
4.0
9.0
20.4
24.3
112
107
3-4-4
N=8
8-20
28/12"
18-16-15
N=31
10-15-17
N=32
19-50/5"
25-30-14
N=44
50/4"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
7.3 feet after about 24 hours
10 feet at completion of drilling
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-03-2025
Boring Completed
09-03-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Hammer Type
Automatic; Hammer
Efficiency = 93%
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5225° Longitude: -104.9965°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
4
5
4848.7
4842
4838.5
ASPHALT, about 3-1/4 inches thick
FILL - CLAYEY SAND WITH GRAVEL (SC), angular to
subangular gravel, brown to dark brown with pink,
decrease in clay content at about 2.5 to 4 feet
WELL GRADED SAND WITH GRAVEL, brown with
pink and dark gray, medium dense
Boring Terminated at 10.5 Feet
Boring Log No. B-6
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4849 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
16.63.5
11.2
8.9
9.3
21-13-8
0.3
7.0
10.5
<+0.1/
150
-0.2/
500
126
122
13-26
39/12"
10-11
21/12"
10-13-16
N=29
8-13-7
N=20
Advancement Method
4 inch diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Hammer Type
Automatic; Hammer
Efficiency = 88%
Boring Started
09-26-2025
Boring Completed
09-26-2025
Abandonment Method
Boring backfilled with cementitious flowable fill and
capped with the asphalt core and utilibond.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5228° Longitude: -104.9974°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
4
4846
4843
4840
4836.5
AGGREGATE SURFACING, about 12 inches thick
FILL - CLAYEY SAND WITH GRAVEL (SC), brown,
loose
LEAN CLAY WITH SAND, dark brown, stiff, possible
organics at about 4 feet
POORLY GRADED SAND WITH GRAVEL, light brown
with pink, very dense, possible cobbles
Boring Terminated at 10.5 Feet
Boring Log No. B-7
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4847 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
37.043.1
16.6
7.3
29-14-15
1.0
4.0
7.0
10.5
+0.5/
150
+0.4/
500
94
114
4-7
11/12"
7-10
17/12"
20-35-47
N=82
20-23-23
N=46
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
7.3 feet at completion of drilling
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Hammer Type
Automatic; Hammer
Efficiency = 93%
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5220° Longitude: -104.9964°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
3
4
4840.7
4839
4837
4834
4830.5
AGGREGATE SURFACING, about 3 inches thick
FILL - POORLY GRADED SAND WITH CLAY AND
GRAVEL, brown
POORLY GRADED SAND, fine to medium grained,
brown with pink, dense
POORLY GRADED SAND, medium to coarse grained,
light brown with pink, medium dense
WELL GRADED SAND WITH GRAVEL, light brown
with pink, dense, possible cobbles
Boring Terminated at 10.5 Feet
Boring Log No. B-8
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4841 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
2.4
14.4
5.1
6.1
0.3
2.0
4.0
7.0
10.5
115
15-17-23
N=40
10-14
24/12"
16-20-22
N=42
21-24-35
N=59
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5212° Longitude: -104.9962°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
Hammer Type
Automatic; Hammer
Efficiency = 93%
1
2
4
4842.1
4836
4834
4828.5
4818.7
AGGREGATE BASE COURSE, about 11 inches thick
FILL - LEAN CLAY WITH SAND (CL), brown to gray
with pink
SANDY LEAN CLAY WITH GRAVEL, dark brown, soft
WELL GRADED SAND WITH SILT AND GRAVEL
(SW-SM), medium to coarse grained, yellow brown
with pink, very dense, possible cobbles
CLAYSTONE, yellow brown to gray, medium hard to
very hard, upper 1 to 2 feet is moderately weathered
Boring Terminated at 24.3 Feet
Boring Log No. B-9
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4843 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
71.9
7.9
17.6
13.1
29.3
9.3
20.2
13.6
16.6
40-19-21
NP
4-11
15/12"
3-3-4
N=7
0-5
5/12"
20-50/5"
17-11-22
N=33
50/4"
50/3"
0.9
7.0
9.0
14.5
24.3
87
117
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
3.2 feet at completion of drilling
9 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Hammer Type
Automatic; Hammer
Efficiency = 93%
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5213° Longitude: -104.9946°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
3
4
5
4835
4828
4817.9
FILL - LEAN CLAY WITH SAND, trace gravel, dark
brown, organics at about 2 feet
CLAYEY SAND (SC), trace gravel, dark brown, very
loose to loose
CLAYSTONE, gray, medium hard to very hard
Boring Terminated at 24.1 Feet
Boring Log No. B-10
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4842 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
35.1
16.1
16.6
20.8
17.5
14.1
13.0
7.7
30-18-12
7.0
14.0
24.1
+2.2/
1000 119
2-4-4
N=8
2-3
5/12"
0-0-0
N=0
1-2-2
N=4
20-32
52/12"
27-50/4"
50/1"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
2.2 feet after about 24 hours
Not encountered at completion of drilling
Not encountered while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-03-2025
Boring Completed
09-03-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Hammer Type
Automatic; Hammer
Efficiency = 93%
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5223° Longitude: -104.9946°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
2
4
5
4847
4841
4834
4826
4823.7
AGGREGATE SURFACING, about 12 inches thick
FILL - SANDY LEAN CLAY WITH GRAVEL, brown
CLAYEY SAND, dark brown, very loose
WELL GRADED SAND WITH GRAVEL, light brown
with pink, dense to very dense, possible cobbles
CLAYSTONE, gray, very hard
Boring Terminated at 24.3 Feet
Boring Log No. B-11
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4848 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
7.5
15.6
18.5
27.1
8.1
10.1
13.6
1.0
7.0
14.0
22.0
24.3
113
117
5-10
15/12"
3-6-9
N=15
2-2
4/12"
0-0-2
N=2
7-16-26
N=42
8-20-42
N=62
50/3"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
9 feet at completion of drilling
14 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Hammer Type
Automatic; Hammer
Efficiency = 93%
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-04-2025
Boring Completed
09-04-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5221° Longitude: -104.9971°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
1
2
4
5
4844
4841
4838
4826
4810.7
AGGREGATE SURFACING, about 12 inches thick
FILL - LEAN CLAY WITH SAND AND GRAVEL, dark
brown
POORLY GRADED SAND, trace gravel, medium
grained, light brown with pink, medium dense
POORLY GRADED SAND WITH SILT AND GRAVEL
(SP-SM), light brown with pink and dark brown,
dense
CLAYSTONE, gray, very hard
Boring Terminated at 34.3 Feet
Boring Log No. B-12
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
25
30
Facilities | Environmental |Geotechnical | Materials
Approximate Elevation: 4845 (Ft.)
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
6.7
10.1
9.3
8.8
8.5
11.5
16.3
13.4
15.2
18.4
NP
1.0
4.0
7.0
19.0
34.3
121
112
11-13
24/12"
5-5-8
N=13
16-19-17
N=36
13-19-29
N=48
5-20-25
N=45
22-50/4"
50/4"
50/3"
50/3"
Advancement Method
4-1/4 inch inside-diameter, continuous-flight,
hollow-stem augers
Notes
Water Level Observations
3.7 feet after about 24 hours
9.5 feet at completion of drilling
7 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory proceduresused and additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevation interpolated from a topographic site plan provided by TB Group.
Classification of rock estimated from disturbed samples. Core samples and petrographicanalysis may reveal other rock types.
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045 Fort Collins, CO
Drill Rig
CME 55
Driller
Terracon
Logged by
A. Ellis
Boring Started
09-03-2025
Boring Completed
09-03-2025
Abandonment Method
Boring backfilled with auger cuttings upon
completion.
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5214° Longitude: -104.9965°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
4862 Innovation Dr Ste 104
Hammer Type
Automatic; Hammer
Efficiency = 93%
1
2
4
5
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
"A" Line
ASTM D4318
CH or OH
CL or OL
ML or OL
MH or OH
13
11
3
25
NP
8
15
21
NP
12
NP
54.3
51.0
21.3
68.6
7.6
16.6
37.0
71.9
7.9
35.1
6.7
CL
CL
SM
CL
SP-SM
SC
SC
CL
SW-SM
SC
SP-SM
15
20
15
18
NP
13
14
19
NP
18
NP
13
11
3
25
NP
8
15
21
NP
12
NP
54.3
51.0
21.3
68.6
7.6
16.6
37.0
71.9
7.9
35.1
6.7
CL
CL
SM
CL
SP-SM
SC
SC
CL
SW-SM
SC
SP-SM
15
20
15
18
NP
13
14
19
NP
18
NP
28
31
18
43
NP
21
29
40
NP
30
NP
SANDY LEAN CLAY
SANDY LEAN CLAY with GRAVEL
SILTY SAND with GRAVEL
SANDY LEAN CLAY
POORLY GRADED SAND with SILT and GRAVEL
CLAYEY SAND with GRAVEL
CLAYEY SAND with GRAVEL
LEAN CLAY with SAND
WELL-GRADED SAND with SILT and GRAVEL
CLAYEY SAND
POORLY GRADED SAND with SILT and GRAVEL
Atterberg Limit Results
"U" Line
Liquid Limit
LL PL PI Fines USCS DescriptionFines
Pl
a
s
t
i
c
i
t
y
I
n
d
e
x
CL - ML
16
4
7
Facilities | Environmental |Geotechnical | Materials
2 - 3.5
9 - 10
4 - 5.5
4 - 5.5
14 - 14.9
1 - 5
1 - 5
2 - 3
9 - 9.9
9 - 10.5
7 - 8.5
B-1
B-2
B-3
B-4
B-5
B-6
B-7
B-9
B-9
B-10
B-12
Boring ID Depth (Ft)
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
4862 Innovation Dr Ste 104
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
140
HydrometerU.S. Sieve Opening in Inches
Grain Size Distribution
ASTM D422 / ASTM C136
SandGravel
2 10 14 506 2001.5 83/4 1/23/8 30 403 601
U.S. Sieve Numbers
16 2044 10063
Grain Size (mm)
coarse fine coarse finemedium Silt or ClayCobbles
Pe
r
c
e
n
t
C
o
a
r
s
e
r
b
y
W
e
i
g
h
t
Pe
r
c
e
n
t
F
i
n
e
r
b
y
W
e
i
g
h
t
100
90
80
70
60
50
40
30
20
10
0
AASHTOUSCSUSCS Classification
A-6 (4)
A-6 (3)
A-1-b (0)
A-7-6 (15)
A-1-a (0)
CL
CL
SM
CL
SP-SM
SANDY LEAN CLAY
SANDY LEAN CLAY with GRAVEL
SILTY SAND with GRAVEL
SANDY LEAN CLAY
POORLY GRADED SAND with SILT and
GRAVEL
Facilities | Environmental |Geotechnical | Materials
28
31
18
43
NP 0.80
13
11
3
25
NP
15
20
15
18
NP
%CobblesD60
0.093
0.103
0.761
5.277
D100
45.54
%Clay%Sand%Gravel
11.7
19.8
17.6
0.8
41.7
34.0
29.3
61.1
30.6
50.7
54.3
51.0
21.3
68.6
7.6
LL PL PI Cc Cu
0.0
0.0
0.0
0.0
0.0
D10
0.116
D30
0.15
0.701
25
37.5
19
9.5
25
%Fines %Silt
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID
2 - 3.5
9 - 10
4 - 5.5
4 - 5.5
14 - 14.9
B-1
B-2
B-3
B-4
B-5
2 - 3.5
9 - 10
4 - 5.5
4 - 5.5
14 - 14.9
Depth (Ft)Boring ID
B-1
B-2
B-3
B-4
B-5
Depth (Ft)
4862 Innovation Dr Ste 104
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
140
HydrometerU.S. Sieve Opening in Inches
Grain Size Distribution
ASTM D422 / ASTM C136
SandGravel
2 10 14 506 2001.5 83/4 1/23/8 30 403 601
U.S. Sieve Numbers
16 2044 10063
Grain Size (mm)
coarse fine coarse finemedium Silt or ClayCobbles
Pe
r
c
e
n
t
C
o
a
r
s
e
r
b
y
W
e
i
g
h
t
Pe
r
c
e
n
t
F
i
n
e
r
b
y
W
e
i
g
h
t
100
90
80
70
60
50
40
30
20
10
0
AASHTOUSCSUSCS Classification
A-2-4 (0)
A-6 (1)
A-6 (14)
A-1-a (0)
A-2-6 (0)
SC
SC
CL
SW-SM
SC
CLAYEY SAND with GRAVEL
CLAYEY SAND with GRAVEL
LEAN CLAY with SAND
WELL-GRADED SAND with SILT and
GRAVELCLAYEY SAND
Facilities | Environmental |Geotechnical | Materials
21
29
40
NP
30
1.11
8
15
21
NP
12
13
14
19
NP
18
%CobblesD60
4.255
0.55
5.233
0.427
D100
41.89
%Clay%Sand%Gravel
38.4
18.8
1.2
41.9
13.4
45.0
44.2
26.9
50.2
51.4
16.6
37.0
71.9
7.9
35.1
LL PL PI Cc Cu
0.0
0.0
0.0
0.0
0.0
D10
0.125
D30
0.395
0.854
19
37.5
9.5
37.5
25
%Fines %Silt
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID
1 - 5
1 - 5
2 - 3
9 - 9.9
9 - 10.5
B-6
B-7
B-9
B-9
B-10
1 - 5
1 - 5
2 - 3
9 - 9.9
9 - 10.5
Depth (Ft)Boring ID
B-6
B-7
B-9
B-9
B-10
Depth (Ft)
4862 Innovation Dr Ste 104
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
140
HydrometerU.S. Sieve Opening in Inches
Grain Size Distribution
ASTM D422 / ASTM C136
SandGravel
2 10 14 506 2001.5 83/4 1/23/8 30 403 601
U.S. Sieve Numbers
16 2044 10063
Grain Size (mm)
coarse fine coarse finemedium Silt or ClayCobbles
Pe
r
c
e
n
t
C
o
a
r
s
e
r
b
y
W
e
i
g
h
t
Pe
r
c
e
n
t
F
i
n
e
r
b
y
W
e
i
g
h
t
100
90
80
70
60
50
40
30
20
10
0
AASHTOUSCSUSCS Classification
A-1-a (0)SP-SMPOORLY GRADED SAND with SILT and
GRAVEL
Facilities | Environmental |Geotechnical | Materials
NP 0.97NPNP
%CobblesD60
5.74
D100
43.30
%Clay%Sand%Gravel
44.2 49.1 6.7
LL PL PI Cc Cu
0.0
D10
0.133
D30
0.86125
%Fines %Silt
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID
7 - 8.5B-12
7 - 8.5
Depth (Ft)Boring ID
B-12
Depth (Ft)
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited less than 0.1 percent swell upon wetting under an applied pressure of 500 psf.
12.3115
(pcf) WC (%)Description USCS
FILL - SANDY LEAN CLAY
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
4 - 5B-1
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited less than 0.1 percent compression upon wetting under an applied pressure of 1,000 psf.
29.093
(pcf) WC (%)Description USCS
LEAN CLAY
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
9 - 10B-1
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 0.2 percent swell upon wetting under an applied pressure of 500 psf.
14.8115
(pcf) WC (%)Description USCS
LEAN CLAY
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
4 - 5B-2
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited less than 0.1 percent swell upon wetting under an applied pressure of 150 psf.
15.5113
(pcf) WC (%)Description USCS
LEAN CLAY WITH SAND
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
2 - 3B-3
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 0.2 percent swell upon wetting under an applied pressure of 500 psf.
16.8112
(pcf) WC (%)Description USCS
FILL - SANDY LEAN CLAY
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
2 - 3B-4
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited less than 0.1 percent swell upon wetting under an applied pressure of 150 psf.
3.5126
(pcf) WC (%)Description USCS
FILL - CLAYEY SAND WITH GRAVEL
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
2 - 3B-6
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 0.2 percent compression upon wetting under an applied pressure of 500 psf.
11.2122
(pcf) WC (%)Description USCS
FILL - CLAYEY SAND WITH GRAVEL
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
4 - 5B-6
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 0.5 percent swell upon wetting under an applied pressure of 150 psf.
43.194
(pcf) WC (%)Description USCS
FILL - CLAYEY SAND WITH GRAVEL
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
2 - 3B-7
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 0.4 percent swell upon wetting under an applied pressure of 500 psf.
16.6114
(pcf) WC (%)Description USCS
LEAN CLAY WITH SAND
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
4 - 5B-7
4862 Innovation Dr Ste 104
-6
-5
-4
-3
-2
-1
0
1
2
3
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: The sample exhibited 2.2 percent swell upon wetting under an applied pressure of 1,000 psf.
14.1119
(pcf) WC (%)Description USCS
CLAYSTONE
Fort Collins, COTerracon Project No. 20255045
4315 E. Harmony Road | Fort Collins, Colorado
Harmony Lakes - New Convenience Store
Boring ID Depth (Ft)
14 - 15B-10
4862 Innovation Dr Ste 104
4862 Innovation Drive, Suite 104
Fort Collins, Colorado 80525
(970) 484-0359 FAX (970) 484-0454
CLIENT:Big D Oil Company DATE OF TEST:23-Sep-25
PROJECT:Harmony Lakes - New Convenience Store
LOCATION:B-7 at 1.0-5.0
TERRACON NO.20255045 CLASSIFICATION:Clayey Sand with Gravel (SC)
TEST SPECIMEN NO.1 2 3
COMPACTION PRESSURE (PSI)100 150 250
DENSITY (PCF)133.8 135.9 130.0
MOISTURE CONTENT (%)10.2 9.6 7.1
EXPANSION PRESSURE (PSI)0.00 0.00 0.00
HORIZONTAL PRESSURE @ 160 PSI 110 98 42
SAMPLE HEIGHT (INCHES)2.51 2.50 2.53
EXUDATION PRESSURE (PSI)160.3 212.8 500.3
CORRECTED R-VALUE 25.1 32.4 69.2
UNCORRECTED R-VALUE 25.1 32.4 69.2
R-VALUE @ 300 PSI EXUDATION PRESSURE =44
AASHTO T190
PRESSURE OF COMPACTED SOIL
RESISTANCE R-VALUE & EXPANSION
SAMPLE DATA TEST RESULTS
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
R-
V
A
L
U
E
EXUDATION PRESSURE - PSI
Client
B-1 B-4 B-10
1.0-5.0 1.0-5.0 1.0-5.0
405 378 228
Analyzed By:
Project
Big D Oil Company Harmony Lakes - New Convenience Store
Rapid City, SD 20255045
Date Received:9/9/2025
(mg/kg)
Results from Corrosion Testing
Sample Location
Sample Depth (ft.)
The tests were performed in general accordance with applicable ASTM and AASHTO test methods. This report is exclusively for the use of the client indicated above
and shall not be reproduced except in full without the written consent of our company. Test results transmitted herein are only applicable to the actual samples tested
at the location(s) referenced and are not necessarily indicative of the properties of other apparently similar or identical materials.
Chloe Lewis
Laboratory Supervisor
Client
9/22/2025
B-2 B-8
1'-5'1'-5'
AASHTO T289 8.47 8.5
ASTM C1580 121 120
AWWA 4500-S,D Nil Nil
ASTM D512 61 16
ASTM G200 234 244
AWWA 2520 B 935 466
ASTM G57 1500 4200
These tests were performed in general accordance with the applicable AASHTO, ASTM, and AWWA test methods. This report is exclusively
for the use of the client indicated above and shall not be reproduced without the full written consent of Terracon Consultants Inc.. Test results
transmitted herein are only applicable to the actual samples tested at the location(s) referenced and are not necessarily indicative of the
properties of other apparently similar materials.
Kyle Lemcke
9/25/2025
Verified By:
Acidity (pH)
Water Soluble Sulfate
Ion Content (mg/Kg)
Water Soluble Sulfide
Content (mg/Kg)
Water Soluble Chloride
Ion Content (mg/Kg)
Corrosivity Suite -Results
Sample Location
Project
Big D Oil Company Big D Oil Harmony Lakes
Rapid City, SD 20250545
Date Received:
Sample Depth (ft.)
Oxidation-Reduction
Potential (RmV)
Total Dissolved Salts
(mg/Kg)
Electrical Resistivity
(Ω·cm)
Harmony Lakes - New Convenience Store
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
October 21, 2025 | Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Supporting Information
Contents:
General Notes
Unified Soil Classification System
Note: All attachments are one page unless noted above.
Auger
Cuttings
Modified
California
Ring
Sampler
Standard
Penetration
Test
Facilities | Environmental |Geotechnical | Materials
Unconfined
Compressive
Strength
Qu (psf)
1,000 to 2,000
2,000 to 4,000
4,000 to 8,000
> 8,000
less than 500
500 to 1,000
Harmony Lakes - New Convenience Store
4315 E. Harmony Road | Fort Collins, Colorado
Terracon Project No. 20255045
4862 Innovation Dr Ste 104
Fort Collins, CO
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
Water Level After a
Specified Period of Time
Water Level After
a Specified Period of Time
Cave In
Encountered
Water Level Field Tests
Water Initially
Encountered
Sampling
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.
General Notes
Location And Elevation Notes
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.
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.
Exploration/field results and/or laboratory test data contained within this document are intended for application to the project as described in this
document. Use of such exploration/field results and/or laboratory test data should not be used independently of this document.
Relevance of Exploration and Laboratory Test Results
Descriptive Soil Classification
> 30
15 - 30
8 - 15
4 - 8
2 - 4
0 - 1
Very Stiff
Consistency of Fine-Grained Soils Bedrock
(More than 50% retained on No. 200 sieve.)
Density determined by Standard Penetration
Resistance
Relative Density of Coarse-Grained Soils
< 3
Consistency
Stiff
Medium Stiff
Soft
Very Soft
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing, field
visual-manual procedures or standard penetration resistance
Strength Terms
6- 10
11 - 18
19 - 36
> 36
Standard
Penetration
or N-Value
(Blows/Ft.)
Ring
Sampler
(Blows/Ft.)
Relative Density
Very Loose
Loose
Standard
Penetration
or N-Value
(Blows/Ft.)
> 50
30 - 50
10 - 29
4 - 9
Ring
Sampler
(Blows/Ft.)
Hard
Medium Dense
Dense
Very Dense
0 - 5
6 - 14
> 80
Firm
_
47 - 79
Medium Hard
Hard
Very Hard
Ring
Sampler
(Blows/Ft.)
< 24
24 - 35
36 - 60
61 - 96
>79
15 - 46
0 - 3
3 - 5
Consistency
Standard
Penetration or
N-Value
(Blows/Ft.)
< 20
20 - 29
30 - 49
50 - 79
> 96
Soft
Geotechnical Engineering Report
Harmony Lakes – New Convenience Store | Fort Collins, Colorado
Terracon Project No.20255045
Facilities | Environmental | Geotechnical | Materials
Unified Soil Classification System
Criteria for Assigning Group Symbols and Group Names Using
Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse-Grained Soils:
Gravels: Clean Gravels:
C
≥4 and 1≤Cc≤3 E F
E F
Gravels with Fines:
C
F, G, H
F, G, H
Sands: Clean Sands:
D
≥6 and 1≤Cc≤3 E I
E I
Sands with Fines:
D
G, H, I
G, H, I
Fine-Grained Soils:
Silts and Clays: Inorganic: 7 and plots above “A” line J K, L, M
4 or plots below “A” line J K, L, M
Organic: 𝐿𝐿 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑
𝐿𝐿 𝑛𝑜𝑡 𝑑𝑟𝑖𝑒𝑑<0.75
K, L, M, N
K, L, M, O
Silts and Clays: Inorganic: PI plots on or above “A” line K, L, M
PI plots below “A” line K, L, M
Organic: 𝐿𝐿 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑
𝐿𝐿 𝑛𝑜𝑡 𝑑𝑟𝑖𝑒𝑑<0.75
K, L, M, P
K, L, M, Q
Highly organic soils:
A Based on the material passing the 3 -inch (75-mm) sieve.
B If field sample contained cobbles or boulders, or both, add “with
cobbles or boulders, or both” to group name.
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 = D 60/D 10 Cc =
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.
6010
2
30
DxD
)(D