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Geotechnical Engineering Report
__________________________________________________________________________
MAVD Flex Office
Fort Collins, Colorado
October 22, 2020
Terracon Project No. 20205032
Prepared for:
MAV Development Company
Ann Arbor, Michigan
Prepared by:
Terracon Consultants, Inc.
Fort Collins, Colorado
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REPORT TOPICS
INTRODUCTION ............................................................................................................. 1
SITE CONDITIONS ......................................................................................................... 1
PROJECT DESCRIPTION .............................................................................................. 2
GEOTECHNICAL CHARACTERIZATION ...................................................................... 2
GEOTECHNICAL OVERVIEW ....................................................................................... 4
EARTHWORK................................................................................................................. 5
SHALLOW FOUNDATIONS ......................................................................................... 10
SEISMIC CONSIDERATIONS ...................................................................................... 12
FLOOR SLABS............................................................................................................. 12
PAVEMENTS ................................................................................................................ 14
CORROSIVITY.............................................................................................................. 17
GENERAL COMMENTS ............................................................................................... 17
ATTACHMENTS ........................................................................................................... 19
Note: This report was originally delivered in a web-based format.Orange 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
GeoReport logo will bring you back to this page. For more interactive features, please view your project online at
client.terracon.com.
ATTACHMENTS
EXPLORATION AND TESTING PROCEDURES
SITE LOCATION AND EXPLORATION PLANS
EXPLORATION RESULTS
SUPPORTING INFORMATION
Note: Refer to each individual Attachment for a listing of contents.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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REPORT SUMMARY
Topic 1 Overview Statement 2
Project
Overview
A geotechnical exploration has been performed for the proposed MAVD Flex Office to
be constructed at 5041 Technology Drive in Fort Collins, Colorado. Six (6) borings
were performed to depths of approximately 10 to 25 feet below existing site grades.
Detailed recommendations for the design of storm water retention features and the
pond are outside our scope of work.
Subsurface
Conditions
Subsurface conditions encountered in our exploratory borings generally consisted of
about 18 to 20 feet of lean clay with varying amounts of sand. Claystone bedrock was
encountered below the overburden soils at depths of approximately 18 to 25 feet below
existing site grades. Boring logs are presented in the Exploration Results section of
this report.
Groundwater
Conditions
Groundwater was encountered in the deeper test borings at depths of about 18 to 22
feet below existing site grades at the time of drilling. Groundwater levels can fluctuate
in response to site development and to varying seasonal and weather conditions,
irrigation on or adjacent to the site and fluctuations in nearby water features.
Geotechnical
Concerns
Expansive clays and bedrock are present on this site. This report provides
recommendations to help mitigate the effects of soil movement/heave associated with
these materials. The risk can be mitigated by careful design, construction and
maintenance practices; however, it should be recognized these procedures will not
eliminate risk. The owner should be aware and understand that on-grade slabs,
pavements and, in some instances foundations, may be affected to some degree by
the expansive soils and bedrock on this site.
Earthwork
On-site soils typically appear suitable for use as general engineered fill and backfill on
the site provided they are placed and compacted as described in this report. Import
materials (if needed) should be evaluated and approved by Terracon prior to delivery
to the site. Earthwork recommendations are presented in the Earthwork section of
this report.
Grading and
Drainage
The amount of movement of foundations, floor slabs, pavements, etc. will be related to
the wetting of underlying supporting soils. Therefore, it is imperative the
recommendations discussed in the Grading and Drainage section of the Earthwork
section this report be followed to reduce potential movement. As discussed in the
Grading and Drainage section of this report, surface drainage should be designed,
constructed and maintained to provide rapid removal of surface water runoff away from
the proposed buildings and pavements. Water should not be allowed to pond adjacent
to foundations or on pavements and conservative irrigation practices should be followed
to avoid wetting foundation/slab soils and pavement subgrade. Excessive wetting of
foundations/slab soils and subgrade can cause movement and distress to foundations,
floor slabs, concrete flatwork and pavements.
Foundations
Low to moderately expansive clay soils were encountered at anticipated shallow
foundation bearing depths. We recommend constructing the proposed building on
a spread footing foundation system, provided the soils are over-excavated to a depth
of at least 1 feet below the bottom of footings and replaced with moisture
conditioned, properly compacted fill.
Floor Systems
A slab-on-grade Floor System is recommended for the proposed building provided
the soils are over-excavated to a depth of at least 2 feet below the proposed floor slab
and replaced with moisture conditioned, properly compacted engineered fill. On-site
soils are suitable as over-excavation backfill below floor slabs.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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Topic 1 Overview Statement 2
Pavements
Recommended Pavement thicknesses for this project include 4 inches of asphalt over
6 inches of aggregate base course in light-duty parking areas and 5 inches of asphalt
over 7 inches of aggregate base course in heavy-duty drive lanes and loading areas.
Additional pavement section alternatives and discussion are presented in the report.
Seismic
Considerations
As presented in the Seismic Considerations section of this report, the International
Building Code, which refers to Section 20 of ASCE 7, indicates the seismic site
classification for this site is D.
Construction
Observation
and Testing
Close monitoring of the construction operations and implementing drainage
recommendations discussed herein will be critical in achieving the intended
foundation, slab and pavement performance. We therefore recommend that Terracon
be retained to monitor this portion of the work.
General
Comments
This section contains important information about the limitations of this geotechnical
engineering report.
1.If the reader is reviewing this report as a pdf, the topics (bold orange font) above can be used to access the
appropriate section of the report by simply clicking on the topic itself.
2.This summary is for convenience only. It should be used in conjunction with the entire report for design
making and design purposes. It should be recognized that specific details were not included or fully
developed in this section, and the report must be read in its entirety for a comprehensive understanding of
the items contained herein.
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INTRODUC TION
Geotechnical Engineering Report
MAVD Flex Office
5041 Technology Drive
Fort Collins, Colorado
Terracon Project No. 20205032
October 22, 2020
INTRODUCTION
This report presents the results of our subsurface exploration and geotechnical engineering
services performed for the proposed Flex Office to be located at 5041 Technology Drive in Fort
Collins, Colorado. The purpose of these services is to provide information and geotechnical
engineering recommendations relative to:
■Subsurface soil and rock conditions ■Foundation design and construction
■Groundwater conditions ■Floor system design and construction
■Site preparation and earthwork ■Seismic considerations
■Excavation considerations ■Pavement design and construction
The geotechnical engineering scope of services for this project included the advancement of six
test borings to depths ranging from approximately 10 to 25 feet below existing site grades.
Maps showing the site and boring locations are shown in the Site Location and Exploration
Plan sections, respectively. The results of the laboratory testing performed on soil and bedrock
samples obtained from the site during the field exploration are included on the boring logs and as
separate graphs in the Exploration Results section of this report.
SITE CONDITIONS
The following description of site conditions is derived from our site visit in association with the
field exploration and our review of publicly available geologic and topographic maps.
Item Description
Parcel Information
The project site is located at 5041 Technology Drive in Fort Collins,
Colorado. The approximate Latitude/Longitude of the center of the site is
40.51712° N/105.01634°W (Please refer to Exhibit D). See Site Location.
Existing
Improvements The site is vacant land.
Current Ground
Cover Current ground cover consists of vegetation with native grasses and weeds.
Existing Topography The site is relatively flat.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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PROJECT DESCRIPTION
Our final understanding of the project conditions is as follows:
Item Description
Information Provided Site layout and general project information provided by alm2s via email.
Project Description
The project includes construction of a new one-story, flex office building with
no basement. Building usage is planned to be business occupancy with the
potential for some light industrial.
Proposed
Construction
The building will be slab-on-grade (non-basement). Anticipated foundations
include conventional spread footings and isolated column pads. Associated
parking areas and drive lanes will be included. Storm water ponds are
conceptually planned along the western portion of the site
Maximum Loads
(assumed)
■Columns: 50 to 100 kips
■Walls: 2 to 3 kips per linear foot (klf)
■Slabs: 150 pounds per square foot (psf)
Grading/Slopes Grading plans were not provided at this time. We anticipate minor cuts and
fills on the order of 5 feet or less will be required to achieve proposed grades.
Below-grade
Structures We understand no below-grade are planned for this site
Pavements
We assume both rigid (concrete) and flexible (asphalt) pavement sections
should be considered. We have made reasonable assumptions for traffic
loading planned at this facility to assist with developing our recommendations
for pavement thickness. If our assumed traffic loading conditions are not
accurate, we should be contacted to provide revised pavement
recommendations.
If project information or assumptions vary from what is described above or if location of
construction changes, we should be contacted as soon as possible to confirm and/or modify our
recommendations accordingly.
GEOTECHNICAL CHARACTERIZATION
Subsurface Profile
We have developed a general characterization of the subsurface conditions based upon our
review of the subsurface exploration, laboratory data, geologic setting and our understanding of
the project. This characterization, termed GeoModel, forms the basis of our geotechnical
calculations and evaluation of site preparation and foundation options. Conditions encountered at
each exploration point are indicated on the individual logs. The individual logs can be found in the
Exploration Results section and the GeoModel can be found in the Figures section of this report.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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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 Approximate Depth to
Bottom of Stratum
1 Lean Clay with
Sand
Lean clay with sand, light brown to
brown, medium stiff to stiff
About 19 feet below
existing site grades.
2 Sandy Lean
Clay
Sandy lean clay, light brown to brown,
medium stiff to stiff
About 9 to 19 feet below
existing site grades.
3 Clayey Sand Clayey sand, light brown to brown,
loose to medium dense
About 14 to 24 feet below
existing site grades.
4 Claystone
Bedrock Claystone bedrock, brown gray, firm Encountered at the bottom
of all the deeper borings.
As noted in General Comments, this characterization is based upon widely spaced exploration
points across the site and variations are likely.
Groundwater Conditions
The boreholes were observed while drilling for the presence and level of groundwater. The water
levels observed in the boreholes are noted on the attached boring logs, and are summarized below:
Boring Number Depth to Groundwater While
Drilling, ft.
Elevation of Groundwater
While Drilling, ft.
1 18 4,901
2 22 4,896
3 18 4,900
4 Not encountered Not encountered
5 Not encountered Not encountered
6 Not encountered Not encountered
These observations represent short-term groundwater conditions at the time of and shortly after
the field exploration and may not be indicative of other times or at other locations. Groundwater
levels can be expected to fluctuate with varying seasonal and weather conditions, and other
factors.
Groundwater level fluctuations occur due to seasonal variations, amount of rainfall, runoff and
other factors not evident at the time the borings were performed. Therefore, groundwater levels
during construction or at other times in the life of the structure may be higher or lower than the
levels indicated on the boring logs. The possibility of groundwater level fluctuations should be
considered when developing the design and construction plans for the project. However we do
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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not believe groundwater will significantly impact the proposed construction unless deep utility
installation ( greater than about 16 to 18 feet) are planed as part of the proposed construction.
Laboratory Testing
Representative soil samples were selected for swell-consolidation testing and exhibited 0.3 to 4.6
percent swell when wetted. The clay is considered to have low to moderate expansive potential.
One sample of clay soil exhibited an unconfined compressive strength of approximately 5,664
pounds per square foot (psf). Samples of site soils and bedrock selected for plasticity testing
exhibited moderate to high plasticity with liquid limits ranging from 28 to 59 and plasticity indices
ranging from 12 to 41. Laboratory test results are presented in the Exploration Results section
of this report.
GEOTECHNICAL OVERVIEW
Based on subsurface conditions encountered in the borings, the site appears suitable for the
proposed construction from a geotechnical point of view provided certain precautions and design
and construction recommendations described in this report are followed and the owner
understands the inherent risks associated with construction on sites underlain by expansive 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 expansive soils and bedrock, and potentially soft, low strength
clay soils. These conditions will require particular attention in project planning, design and during
construction and are discussed in greater detail in the following sections.
Expansive Soils and Bedrock
Expansive soils and bedrock are present on this site and these conditions constitute a geologic
hazard. 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 flat work will probably increase if modification of the site results in
excessive wetting or drying of the expansive clays. Eliminating the risk of movement and cosmetic
distress is generally not feasible, but it may be possible to further reduce the risk of movement if
significantly more expensive measures are used during construction. It is imperative the
recommendations described in section Grading and Drainage section of the Earthwork section
of this report be followed to reduce potential movement.
Foundation and Floor System Recommendations
The proposed building can be supported by a shallow, spread footing foundation system provided
the soils are over-excavated to a depth of at least 1 foot below footings and replaced with moisture
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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conditioned, properly compacted fill. Design recommendations for foundations for the proposed
structure and related structural elements are presented in the following paragraphs.
We believe a concrete slab-on-grade floor system can be used for the proposed building provided
the soils are over-excavated to a depth of at least 2 feet below the proposed floor slab and replaced
with moisture conditioned, properly compacted engineered fill. On-site soils are suitable as over-
excavation backfill below floor slabs.
Design recommendations for foundations for the proposed structures and related structural
elements are presented in the following sections.
The General Comments section provides an understanding of the report limitations.
EARTHWORK
The following presents recommendations for site preparation, excavation, subgrade preparation,
fill materials, compaction requirements, utility trench backfill, grading and drainage and exterior
slab design and construction. Earthwork on the project should be observed and evaluated by
Terracon. Evaluation of earthwork should include observation and/or testing of over-excavation,
subgrade preparation, placement of engineered fills, subgrade stabilization and other
geotechnical conditions exposed during the construction of the project.
Site Preparation
Prior to placing any fill, strip and remove existing vegetation, topsoil, and any other deleterious
materials from the proposed construction area.
Stripped organic materials should be wasted from the site or used to re-vegetate landscaped areas
or exposed slopes after completion of grading operations. Prior to the placement of fills, the site
should be graded to create a relatively level surface to receive fill, and to provide for a relatively
uniform thickness of fill beneath proposed structures.
Excavation
It is anticipated that excavations for the proposed construction can be accomplished with
conventional earthmoving equipment.
The soils to be excavated can vary significantly across the site as their classifications are based
solely on the materials encountered in widely-spaced exploratory test borings. The contractor
should verify that similar conditions exist throughout the proposed area of excavation. If different
subsurface conditions are encountered at the time of construction, the actual conditions should be
evaluated to determine any excavation modifications necessary to maintain safe conditions.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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Although evidence of fills or underground facilities such as grease pits, septic tanks, vaults,
basements, and utilities was not observed during the site reconnaissance, such features could be
encountered during construction. If unexpected underground facilities are encountered, such
features should be removed and the excavation thoroughly cleaned prior to backfill placement
and/or construction.
Any over-excavation that extends below the bottom of foundation elevation should extend laterally
beyond all edges of the foundations at least 8 inches per foot of over-excavation depth below the
foundation base elevation. The over-excavation should be backfilled to the foundation base
elevation in accordance with the recommendations presented in this report.
Depending upon depth of excavation and seasonal conditions, surface water infiltration and/or
groundwater may be encountered in excavations on the site. It is anticipated that pumping from
sumps may be utilized to control water within excavations.
The subgrade soil conditions should be evaluated during the excavation process and the stability
of the soils determined at that time by the contractors’ Competent Person. Slope inclinations flatter
than the OSHA maximum values may have to be used. The individual contractor(s) should be
made responsible for designing and constructing stable, temporary excavations as required to
maintain stability of both the excavation sides and bottom. All excavations should be sloped or
shored in the interest of safety following local, and federal regulations, including current OSHA
excavation and trench safety standards.
As a safety measure, it is recommended that all vehicles and soil piles be kept a minimum lateral
distance from the crest of the slope equal to the slope height. The exposed slope face should be
protected against the elements
Subgrade Preparation
The top 10 inches of the exposed ground surface including at the base of the recommended over-
excavation should be scarified, moisture conditioned, and recompacted to at least 95 percent of
the maximum dry unit weight as determined by ASTM D698 before any new fill, foundation or
pavement is placed.
After the bottom of the excavation has been compacted, engineered fill can be placed to bring the
building pad and pavement subgrade to the desired grade. Engineered fill should be placed in
accordance with the recommendations presented in subsequent sections of this report.
The stability of the subgrade may be affected by precipitation, repetitive construction traffic or
other factors. If unstable conditions develop, workability may be improved by scarifying and
drying. Alternatively, over-excavation of wet zones and replacement with granular materials may
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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be used, or crushed gravel and/or rock can be tracked or “crowded” into the unstable surface soil
until a stable working surface is attained. Lightweight excavation equipment may also be used to
reduce subgrade pumping.
Fill Materials
The on-site soils or approved granular and low plasticity cohesive imported materials may be used
as fill material. The earthwork contractor should expect significant mechanical processing and
moisture conditioning of the site soils and/or bedrock will be needed to achieve proper compaction
Imported soils (if required) should meet the following material property requirements:
Gradation Percent finer by weight (ASTM C136)
4”100
3”70-100
No. 4 Sieve 50-100
No. 200 Sieve 80 (max.)
Soil Properties Values
Liquid Limit 35 (max.)
Plasticity Index 15 (max.)
Other import fill materials types may be suitable for use on the site depending upon proposed
application and location on the site, and could be tested and approved for use on a case-by-case
basis.
Compaction Requirements
Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures
that will produce recommended moisture contents and densities throughout the lift.
Item Description
Fill lift thickness
9 inches or less in loose thickness when heavy, self-
propelled compaction equipment is used
4 to 6 inches in loose thickness when hand-guided
equipment (i.e. jumping jack or plate compactor) is used
Minimum compaction requirements 95 percent of the maximum dry unit weight as determined by
ASTM D698
Moisture content cohesive soil (clay)-1 to +3 % of the optimum moisture content
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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Item Description
Moisture content cohesionless soil
(granular)-3 to +3 % of the optimum moisture content
1.We recommend engineered fill be tested for moisture content and compaction during placement. Should the
results of the in-place density tests indicate the specified moisture or compaction limits have not been met,
the area represented by the test should be reworked and retested as required until the specified moisture
and compaction requirements are achieved.
2.Specifically, moisture levels should be maintained low enough to allow for satisfactory compaction to be
achieved without the fill material pumping when proof rolled.
3.Moisture conditioned clay materials should not be allowed to dry out. A loss of moisture within these materials
could result in an increase in the material’s expansive potential. Subsequent wetting of these materials could
result in undesirable movement.
Utility Trench Backfill
All trench excavations should be made with sufficient working space to permit construction including
backfill placement and compaction.
All underground piping within or near the proposed structure should be designed with flexible
couplings, so minor deviations in alignment do not result in breakage or distress. Utility knockouts
in foundation walls should be oversized to accommodate differential movements. It is imperative
that utility trenches be properly backfilled with relatively clean materials. If utility trenches are
backfilled with relatively clean granular material, they should be capped with at least 18 inches of
cohesive fill in non-pavement areas to reduce the infiltration and conveyance of surface water
through the trench backfill.
Utility trenches are a common source of water infiltration and migration. All utility trenches that
penetrate beneath the building should be effectively sealed to restrict water intrusion and flow
through the trenches that could migrate below the building. We recommend constructing an
effective clay “trench plug” that extends at least 5 feet out from the face of the building exterior. The
plug material should consist of clay compacted at a water content at or above the soil’s optimum
water content. The clay fill should be placed to completely surround the utility line and be compacted
in accordance with recommendations in this report.
It is strongly recommended that a representative of Terracon provide full-time observation and
compaction testing of trench backfill within building and pavement areas.
Grading and Drainage
Grades must be adjusted to provide effective drainage away from the proposed building during
construction and maintained throughout the life of the proposed project. Infiltration of water into
foundation excavations must be prevented during construction. Landscape irrigation adjacent to
foundations should be minimized or eliminated. Water permitted to pond near or adjacent to the
perimeter of the structure (either during or post-construction) can result in significantly higher soil
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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movements than those discussed in this report. As a result, any estimations of potential
movement described in this report cannot be relied upon if positive drainage is not obtained and
maintained, and water is allowed to infiltrate the fill and/or subgrade.
Exposed ground (if any) should be sloped at a minimum of 10 percent grade for at least 10 feet
beyond the perimeter of the proposed building, where possible. Locally, flatter grades may be
necessary to transition ADA access requirements for flatwork. The use of swales, chases and/or
area drains may be required to facilitate drainage in unpaved areas around the perimeter of the
building. Backfill against foundations and exterior walls should be properly compacted and free of
all construction debris to reduce the possibility of moisture infiltration. After construction of the
proposed building and prior to project completion, we recommend verification of final grading be
performed to document positive drainage, as described above, has been achieved.
Flatwork and pavements will be subject to post-construction movement. Maximum grades
practical should be used for paving and flatwork to prevent areas where water can pond. In
addition, allowances in final grades should take into consideration post-construction movement
of flatwork, particularly if such movement would be critical. Where paving or flatwork abuts the
structure, care should be taken that joints are properly sealed and maintained to prevent the
infiltration of surface water.
Planters located adjacent to structure if any should preferably be self-contained. Sprinkler mains
and spray heads should be located a minimum of 5 feet away from the building line(s). Low-
volume, drip style landscaped irrigation should be used sparingly near the building. Roof drains
should discharge on to pavements or be extended away from the structure a minimum of 10 feet
through the use of splash blocks or downspout extensions. A preferred alternative is to have the
roof drains discharge by solid pipe to storm sewers, a detention pond, or other appropriate outfall.
Exterior Slab Design and Construction
Exterior slabs on-grade, exterior architectural features, and utilities founded on, or in backfill or
the site soils will likely experience some movement due to the volume change of the material.
Potential movement could be reduced by:
n Minimizing moisture increases in the backfill;
n Controlling moisture-density during placement of the backfill;
n Using designs which allow vertical movement between the exterior features and
adjoining structural elements; and
n Placing control joints on relatively close centers.
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October 22, 2020 ■ Terracon Project No. 20205032
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Construction Observation and Testing
The earthwork efforts should be monitored under the direction of Terracon. Monitoring should
include documentation of adequate removal of vegetation and topsoil, proof rolling, and mitigation
of areas delineated by the proof roll to require mitigation. Each lift of compacted fill should be
tested, evaluated, and reworked as necessary until approved by Terracon prior to placement of
additional lifts.
In areas of foundation excavations, the bearing subgrade and exposed conditions at the base of
the recommended over-excavation should be evaluated under the direction of Terracon. In the
event that unanticipated conditions are encountered, Terracon should prescribe mitigation
options.
In addition to the documentation of the essential parameters necessary for construction, the
continuation of Terracon into the construction phase of the project provides the continuity to
maintain Terracon’s evaluation of subsurface conditions, including assessing variations and
associated design changes.
SHALLOW FOUNDATIONS
If the site has been prepared in accordance with the requirements noted in Earthwork, the
following design parameters are applicable for shallow foundations.
Spread Footings - Design Recommendations
Description Values
Bearing material At least 1 foot of moisture conditioned, properly
compacted, over-excavation backfill.
Maximum net allowable bearing pressure1 2,750 psf
Minimum deadload pressure 500 psf (or as high as practical)
Minimum foundation dimensions Columns: 30 inches
Continuous: 18 inches
Lateral earth pressure coefficients2
Active, Ka = 0.35
Passive, Kp = 2.9
At-rest, Ko = 0.52
Sliding coefficient2 µ = 0.44
Moist soil unit weight ɣ = 120 pcf
Minimum embedment depth below finished
grade 3 30 inches
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
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Description Values
Subgrade modulus
k1 = 70 psi/in
ܭ(௫)=ܭଵ ቀ ଵ
ቁ
ܭ(௫)=
ܭ(௫)ቆ1 + 0.5 ∗ቀܤ
ܮ ቁቇ
1.5
Where:
k1 = coefficient of subgrade reaction of
foundations measuring 1 ft. x 1ft.
K(BxB) = coefficient of subgrade modulus for a
square foundation having dimensions BxB.
K(BxL) = coefficient of subgrade modulus for a
rectangular foundation having dimensions BxL.
Estimated total movement 4 About 1 inch
Estimated differential movement 4 About ½ to ¾ of total movement
1.The recommended maximum net allowable bearing pressure assumes any unsuitable fill or soft soils, if
encountered, will be over-excavated and replaced with properly compacted engineered fill. The design
bearing pressure applies to a dead load plus design live load condition. The design bearing pressure may
be increased by one-third when considering total loads that include wind or seismic conditions.
2.The lateral earth pressure coefficients and sliding coefficients are ultimate values and do not include a factor
of safety. The foundation designer should include the appropriate factors of safety.
3.For frost protection and to reduce the effects of seasonal moisture variations in the subgrade soils. The
minimum embedment depth is for perimeter footings beneath unheated areas and is relative to lowest
adjacent finished grade, typically exterior grade. Interior column pads in heated areas should bear at least
12 inches below the adjacent grade (or top of the floor slab) for confinement of the bearing materials and to
develop the recommended bearing pressure.
4.The estimated movements presented above are based on the assumption that the maximum footing size is
4 feet for column footings and 1.5 feet for continuous footings. Larger foundation footprints will likely require
reduced net allowable soil bearing pressures to reduce risk for potential settlement.
Footings should be proportioned to reduce differential foundation movement. As discussed, total
movement resulting from the assumed structural loads is estimated to be on the order of about 1
inch. Additional foundation movements 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 Drainage section of the Earthwork section of this report will
nullify the movement estimates provided above.
Spread Footings - Construction Considerations
To reduce the potential of “pumping” and softening of the foundation soils at the foundation
bearing level and the requirement for corrective work, we suggest the foundation excavation for
the building be completed remotely with a track-hoe operating outside of the excavation limits.
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Spread footing construction should only be considered if the estimated foundation movement can
be tolerated. Subgrade soils beneath footings should be moisture conditioned and compacted as
described in the Earthwork section of this report. The moisture content and compaction of
subgrade soils should be maintained until foundation construction.
Footings and foundation walls should be reinforced as necessary to reduce the potential for distress
caused by differential foundation movement.
Unstable surfaces will need to be stabilized prior to backfilling excavations and/or constructing
the building foundation, floor slab and/or project pavements. The use of angular rock, recycled
concrete and/or gravel pushed or “crowded” into the yielding subgrade is considered suitable
means of stabilizing the subgrade. The use of geogrid materials in conjunction with gravel could
also be considered and could be more cost effective.
Unstable subgrade conditions should be observed by Terracon to assess the subgrade and
provide suitable alternatives for stabilization. Stabilized areas should be proof rolled prior to
continuing construction to assess the stability of the subgrade.
Foundation excavations should be observed by Terracon. If the soil conditions encountered differ
significantly from those presented in this report, supplemental recommendations will be required.
SEISMIC CONSIDERATIONS
The seismic design requirements for buildings and other structures are based on Seismic Design
Category. Site Classification is required to determine the Seismic Design Category for a structure.
The Site Classification is based on the upper 100 feet of the site profile defined by a weighted
average value of either shear wave velocity, standard penetration resistance, or undrained shear
strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC).
Based on the soil/bedrock properties encountered at the site and as described on the exploration
logs and results, it is our professional opinion that the Seismic Site Classification is D.
Subsurface explorations at this site were extended to a maximum depth of 25 feet. The site
properties below the boring depth to 100 feet were estimated based on our experience and
knowledge of geologic conditions of the general area. Additional deeper borings or geophysical
testing may be performed to confirm the conditions below the current boring depth.
FLOOR SLABS
A slab-on-grade may be utilized for the interior floor system for the proposed building provided
the clay soils are over-excavated to a depth of at least 2 feet, and replaced with moisture
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 13
conditioned, properly compacted fill. On-site soils are suitable for use as over-excavation backfill
below proposed floor slabs. If the estimated movement cannot be tolerated, a structurally-
supported floor system, supported independent of the subgrade materials, is recommended.
Subgrade soils beneath interior and exterior slabs and at the base of the over-excavation should
be scarified to a depth of at least 10 inches, moisture conditioned and compacted. The moisture
content and compaction of subgrade soils should be maintained until slab construction.
Floor System - Design Recommendations
Even when bearing on properly prepared soils, movement of the slab-on-grade floor system is
possible should the subgrade soils undergo an increase in moisture content. We estimate
movement of about 1 inch is possible. If the owner cannot accept the risk of slab movement, a
structural floor should be used. If conventional slab-on-grade is utilized, the subgrade soils should
be over-excavated and prepared as presented in the Earthwork section of this report.
For structural design of concrete slabs-on-grade subjected to point loadings, a modulus of
subgrade reaction of 70 pounds per cubic inch (pci) may be used for floors supported on re-
compacted existing soils at the site. A modulus of 200 pci may be used for floors supported on
at least 1 foot of non-expansive, imported granular fill.
Additional floor slab design and construction recommendations are as follows:
n Positive separations and/or isolation joints should be provided between slabs and all
foundations, columns, or utility lines to allow independent movement.
n Control joints should be saw-cut in slabs in accordance with ACI Design Manual, Section
302.1R-37 8.3.12 (tooled control joints are not recommended) to control the location and
extent of cracking.
n Interior utility trench backfill placed beneath slabs should be compacted in accordance
with the recommendations presented in the Earthwork section of this report.
n Floor slabs should not be constructed on frozen subgrade.
n Other design and construction considerations, as outlined in the ACI Design Manual,
Section 302.1R are recommended.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 14
Floor Systems - Construction Considerations
Movements of slabs-on-grade using the recommendations discussed in previous sections of this
report will likely be reduced and tend to be more uniform. The estimates discussed above assume
that the other recommendations in this report are followed. Additional movement could occur
should the subsurface soils become wetted to significant depths, which could result in potential
excessive movement causing uneven floor slabs and severe cracking. This could be due to over
watering of landscaping, poor drainage, improperly functioning drain systems, and/or broken utility
lines. Therefore, it is imperative that the recommendations presented in this report be followed.
For slabs the will support traffic loading (if any), we recommend the slab be designed using the
Portland Cement Association method or similar mechanistic stress-based design for concrete
slabs. For slabs that will carry significant traffic, we also recommend doweled joists be considered
for the slab connections.
PAVEMENTS
Pavements – Subgrade Preparation
On most project sites, the site grading is accomplished relatively early in the construction phase.
Fills are typically placed and compacted in a uniform manner. However, as construction proceeds,
the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or
rainfall/snow melt. As a result, the pavement subgrade may not be suitable for pavement
construction and corrective action will be required. The subgrade should be carefully evaluated
at the time of pavement construction for signs of disturbance or instability. We recommend the
pavement subgrade be thoroughly proof rolled with a loaded tandem-axle dump truck prior to final
grading and paving. All pavement areas should be moisture conditioned and properly compacted
to the recommendations in this report immediately prior to paving.
Pavements – Design Recommendations
Design of new privately-maintained pavements for the project has been based on the procedures
described by the National Asphalt Pavement Associations (NAPA) and the American Concrete
Institute (ACI).
We assumed the following design parameters for NAPA flexible pavement thickness design:
n Automobile Parking Areas
·Class I - Parking stalls and parking lots for cars and pick-up trucks, with
Equivalent Single Axle Load (ESAL) up to 7,000 over 20 years
n Main Traffic Corridors
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 15
·Class II – Parking lots with a maximum of 10 trucks per day with Equivalent
Single Axle Load (ESAL) up to 27,000 over 20 years (Including trash trucks)
n Subgrade Soil Characteristics
·USCS Classification – CL, classified by NAPA as poor
We assumed the following design parameters for ACI rigid pavement thickness design based
upon the average daily truck traffic (ADTT):
n Automobile Parking Areas
·ACI Category A: Automobile parking with an ADTT of 1 over 20 years
n Main Traffic Corridors
·ACI Category A: Automobile parking area and service lanes with an ADTT of
up to 10 over 20 years
n Subgrade Soil Characteristics
·USCS Classification – CL
n Concrete modulus of rupture value of 600 psi
We should be contacted to confirm and/or modify the recommendations contained herein if actual
traffic volumes differ from the assumed values shown above.
Recommended alternatives for flexible and rigid pavements are summarized for each traffic area
as follows:
Traffic Area Alternative
Recommended Pavement Thicknesses (Inches)
Asphaltic
Concrete
Surface
Aggregate
Base Course
Portland
Cement
Concrete
Total
Automobile Parking
(NAPA Class I and
ACI Category A)
A 4 6 -10
B --5 5
Service Lanes
(NAPA Class II and
ACI Category A)
A 5 7 -12
B --6 6
Aggregate base course (if used on the site) should consist of a blend of sand and gravel which
meets strict specifications for quality and gradation. Use of materials meeting Colorado
Department of Transportation (CDOT) Class 5 or 6 specifications is recommended for aggregate
base course. Aggregate base course should be placed in lifts not exceeding 6 inches and
compacted to a minimum of 95 percent of the maximum dry unit weight as determined by ASTM
D698.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 16
Asphaltic concrete should be composed of a mixture of aggregate, filler and additives (if required)
and approved bituminous material. The asphalt concrete should conform to approved mix
designs stating the Superpave properties, optimum asphalt content, job mix formula and
recommended mixing and placing temperatures. Aggregate used in asphalt concrete should
meet particular gradations. Material meeting CDOT Grading S or SX specifications or equivalent
is recommended for asphalt concrete. Mix designs should be submitted prior to construction to
verify their adequacy. Asphalt material should be placed in maximum 3-inch lifts and compacted
within a range of 92 to 96 percent of the theoretical maximum (Rice) density (ASTM D2041).
Where rigid pavements are used, the concrete should be produced from an approved mix design
with the following minimum properties:
Properties Value
Compressive strength 4,000 psi
Cement type Type I or II portland cement
Entrained air content (%)5 to 8
Concrete aggregate ASTM C33 and CDOT section 703
Concrete should be deposited by truck mixers or agitators and placed a maximum of 90 minutes
from the time the water is added to the mix. Longitudinal and transverse joints should be provided
as needed in concrete pavements for expansion/contraction and isolation per ACI 325. The
location and extent of joints should be based upon the final pavement geometry.
For areas subject to concentrated and repetitive loading conditions (if any) such as dumpster
pads, truck delivery docks and ingress/egress aprons, we recommend using a portland cement
concrete pavement with a thickness of at least 6 inches underlain by at least 4 inches of granular
base. Prior to placement of the granular base, the areas should be thoroughly proof rolled. For
dumpster pads, the concrete pavement area should be large enough to support the container and
tipping axle of the refuse truck.
Pavement performance is affected by its surroundings. In addition to providing preventive
maintenance, the civil engineer should consider the following recommendations in the design and
layout of pavements:
■Site grades should slope a minimum of 2 percent away from the 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;
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 17
■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 pavement, such as landscape islands, are sources for water infiltration into
surrounding pavements. Water collects in the islands and migrates into the surrounding subgrade
soils thereby degrading support of the pavement. This is especially applicable for islands with
raised concrete curbs, irrigated foliage, and low permeability near-surface soils. The civil design
for the pavements with these conditions should include features to restrict or to collect and
discharge excess water from the islands. Examples of features are edge drains connected to the
storm water collection system or other suitable outlet and impermeable barriers preventing lateral
migration of water such as a cutoff wall installed to a depth below the pavement structure.
Pavements – Maintenance
Preventative maintenance should be planned and provided for an ongoing pavement
management program in order to enhance future pavement performance. Preventive
maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching)
and global maintenance (e.g. surface sealing). Preventative maintenance is usually the first
priority when implementing a planned pavement maintenance program and provides the highest
return on investment for pavements.
CORROSIVITY
At the time this report was prepared, the laboratory testing for water-soluble sulfates had not been
completed. We will submit a supplemental section with the testing results and recommendations
once the testing has been completed.
GENERAL COMMENTS
Our analysis and opinions are based upon our understanding of the project, the geotechnical
conditions in the area, and the data obtained from our site exploration. Natural variations will occur
between exploration point locations or due to the modifying 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
that we can provide evaluation and supplemental recommendations.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable 18
Our Scope of Services does not include either specifically or by implication any environmental or
biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of
pollutants, hazardous materials or conditions. If the owner is concerned about the potential for
such contamination or pollution, other studies should be undertaken.
Our services and any correspondence or collaboration through this system are intended for the
sole benefit and exclusive use of our client for specific application to the project discussed and
are accomplished in accordance with generally accepted geotechnical engineering practices with
no third-party beneficiaries intended. Any third-party access to services or correspondence is
solely for information purposes to support the services provided by Terracon to our client.
Reliance upon the services and any work product is limited to our client, and is not intended for
third parties. Any use or reliance of the provided information by third parties is done solely at 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 could significantly impact
excavation cost. Any parties charged with estimating excavation costs should seek their own site
characterization for specific purposes to obtain the specific level of detail necessary for costing.
Site safety, and cost estimating including, excavation support, and dewatering
requirements/design are the responsibility of others. If changes in the nature, design, or location
of the project are planned, our conclusions and recommendations shall not be considered valid
unless we review the changes and either verify or modify our conclusions in writing.
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ATTACHMENTS
Contents:
EXPLORATION AND TESTING PROCEDURES
SITE LOCATION AND EXPLORATION PLANS
EXPLORATION RESULTS
SUPPORTING INFORMATION
Note: Refer to each individual Attachment for a listing of contents.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2
EXPLORATION AND TESTING PROCEDURES
Field Exploration
The field exploration program consisted of the following:
Number of Borings Boring Depth (feet)Location
3 25 or auger refusal Planned building area
2 10 or auger refusal Planned parking/driveway areas
1 15 or auger refusal Planned storm water pond area
Boring Layout and Elevations: We used handheld GPS equipment to locate borings with an
estimated horizontal accuracy of +/-20 feet. A ground surface elevation at each boring location
was obtained by Terracon by interpolation from a site specific, surveyed topographic map.
Subsurface Exploration Procedures: We advanced soil borings with a truck-mounted drill rig
using continuous-flight, solid-stem augers. Three samples were obtained in the upper 10 feet of
each boring and at intervals of 5 feet thereafter. Soil sampling will be performed using modified
California barrel and standard split-barrel sampling procedures. For the standard split-barrel
sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon is driven into
the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of
blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration
is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values,
also referred to as N-values, are indicated on the boring logs at the test depths. For the modified
California barrel sampling procedure, a 2½-inch outer diameter split-barrel sampling spoon is
used for sampling. Modified California barrel sampling procedures are similar to standard split-
barrel sampling procedures; however, blow counts are typically recorded for 6-inch intervals for a
total of 12 inches of penetration. The samples were placed in appropriate containers, taken to our
soil laboratory for testing, and classified by a geotechnical engineer.
In addition, we observed and recorded groundwater levels during drilling observations.
Our exploration team prepared field boring logs as part of standard drilling operations including
sampling depths, penetration distances, and other relevant sampling information. Field logs
included visual classifications of materials encountered during drilling, and our interpretation of
subsurface conditions between samples. Final boring logs, prepared from field logs, represent
the geotechnical engineer's interpretation, and include modifications based on observations and
laboratory test results.
Geotechnical Engineering Report
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Responsive ■Resourceful ■Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2
Property Disturbance: We backfilled borings with auger cuttings after completion. Our services
did not include repair of the site beyond backfilling our boreholes. Excess auger cuttings were
dispersed in the general vicinity of the boreholes. Because backfill material often settles below
the surface after a period, we recommend checking boreholes periodically and backfilling, if
necessary. We can provide this service for additional fees, at your request.
Laboratory Testing
The project engineer reviewed field data and assigned various laboratory tests to better
understand the engineering properties of various soil and bedrock strata. Laboratory testing was
conducted in general accordance with applicable or other locally recognized standards.
Procedural standards noted in this report are for reference to methodology in general. In some
cases, variations to methods are applied as a result of local practice or professional judgement.
Testing was performed under the direction of a geotechnical engineer and included the following:
■Visual classification ■Moisture content
■Dry density ■Atterberg limits
■Grain-size analysis ■One-dimensional swell
■Water-soluble sulfates ■Unconfined compressive strength
Our laboratory testing program includes examination of soil samples by an engineer. Based on
the material’s texture and plasticity, we described and classified soil samples in accordance with
the Unified Soil Classification System (USCS). Soil and bedrock samples obtained during our
field work will be disposed of after laboratory testing is complete unless a specific request is made
to temporarily store the samples for a longer period of time.
Bedrock samples obtained had rock classification conducted using locally accepted practices for
engineering purposes. Boring log rock classification is determined using the Description of Rock
Properties.
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SITE LOCA TION AND EXPLORATI ON PLANS
Contents:
Site Location Plan
Exploration Plan
Note: All attachments are one page unless noted above.
SITE LOCATION
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above and
outside the table – please leave that alone. Limit editing to inside the table.
The line at the bottom about the general location is a separate table line. You can edit
it as desired, but try to keep to a single line of text to avoid reformatting the page.
SITE LOCA TION
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
EXPLORATION PLAN
MAVD Flex Office ■ Fort Collins, Colorado
October 22, 2020 ■ Terracon Project No. 20205032
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above and
outside the table – please leave that alone. Limit editing to inside the table.
The line at the bottom about the general location is a separate table line. You can edit
it as desired, but try to keep to a single line of text to avoid reformatting the page.
EXPLORATION P LAN
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
EXPLORATION RESULTS
Contents:
GeoModel
Boring Logs (B-1 through B-6)
Atterberg Limits
Grain Size Distribution (2)
Consolidation/Swell (4)
Unconfined Compressive Strength
Note: All attachments are one page unless noted above.
4,895
4,900
4,905
4,910
4,915
4,920
ELEVATION (MSL) (feet)MAVD Flex Office Fort Collins, CO
Terracon Project No. 20205032
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:
B-1
B-2B-3
B-4
B-5
B-6
GEOMODEL
This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.
Groundwater levels are temporal. The levels shown are representative of the date
and time of our exploration. Significant changes are possible over time.
Water levels shown are as measured during and/or after drilling. In some cases,
boring advancement methods mask the presence/absence of groundwater. See
individual logs for details.
First Water Observation
Clayey sand, light brown to brown, loose to medium dense3
Claystone bedrock, brown gray, firm4
LEGEND
Lean Clay with Sand
Clayey Sand
Claystone
Sandy Lean Clay
Bedrock
Model Layer General DescriptionLayer Name
Lean clay with sand, light brown to brown, medium stiff to stiff1
Sandy lean clay, light brown to brown, medium stiff to stiff2
Clayey Sand
Claystone Bedrock
Lean Clay with Sand
Sandy Lean Clay
19
25
25.5
1
3
4
18
14
19
24
25
2
1
3
4
22
18
25.5
2
4
18
10.5
2
10.5
29
14
15
2
3
2
egetative LayerV
8-6
3-4-3
N=7
6-13
2-3-6
N=9
5-6
9-11-7
N=18
+1.2/500
5660
72
8.4
9.5
10.6
20.5
21.7
19.2
112
124
105
35-12-23
VEGETATIVE LAYER, about 6 inches
LEAN CLAY WITH SAND, brown to red brown,
medium stiff to stiff
CLAYEY SAND, light brown to brown, loose to
medium dense
CLAYSTONE, gray brown
Boring Terminated at 25.5 Feet
0.5
19.0
25.0
25.5
4918.5
4900
4894
4893.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10
15
20
25 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5177° Longitude: -105.0161°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4919 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-1
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
18' While drilling
WATER LEVEL OBSERVATIONS
1
3
4 SAMPLE TYPE
4-4-4
N=8
8-8
4-3-5
N=8
5-8
4-5-9
N=14
8-16
+0.3/500
6410.0
10.1
10.9
24.5
23.5
23.6
105
101
99
37-14-23
VEGETATIVE LAYER, about 6 inches
SANDY LEAN CLAY, light brown to brown,
medium stiff to stiff
LEAN CLAY, brown gray, stiff
CLAYEY SAND, brown, medium dense
CLAYSTONE, brown gray, firm
Boring Terminated at 25 Feet
0.5
14.0
19.0
24.0
25.0
4917.5
4904
4899
4894
4893
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10
15
20
25 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5172° Longitude: -105.0162°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4918 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-2
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
22' While drilling
WATER LEVEL OBSERVATIONS
2
1
3
4 SAMPLE TYPE
4-4-3
N=7
4-5
2-3-4
N=7
5-6
8-10-16
N=26
11-13-16
N=29
97
10.0
10.2
20.7
13.9
23.8
24.4
91
118
59-18-41
VEGETATIVE LAYER, about 6 inches
SANDY LEAN CLAY, light brown to brown,
medium stiff
CLAYSTONE, brown gray, firm
Boring Terminated at 25.5 Feet
0.5
18.0
25.5
4917.5
4900
4892.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10
15
20
25 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5166° Longitude: -105.0165°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4918 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-3
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
18' While drilling
WATER LEVEL OBSERVATIONS
2
4 SAMPLE TYPE
4-7
5-7
3-5-5
N=10
+2.2/150
65
9.8
11.2
14.3
96
93
26-14-12
VEGETATIVE LAYER, about 6 inches
SANDY LEAN CLAY, light brown to brown, stiff
Boring Terminated at 10.5 Feet
0.5
10.5
4919.5
4909.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5178° Longitude: -105.0168°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4920 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-4
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
Ground water not encountered
WATER LEVEL OBSERVATIONS
2 SAMPLE TYPE
5-9
3-5
2-4-4
N=8
+4.6/150
88
10.5
14.3
17.6
100
96 39-17-22
VEGETATIVE LAYER, about 6 inches
SANDY LEAN CLAY, light brown to brown,
medium stiff
Boring Terminated at 10.5 Feet
0.5
10.5
4915.5
4905.5
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5165° Longitude: -105.0158°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4916 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-5
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
Ground water not encountered
WATER LEVEL OBSERVATIONS
2 SAMPLE TYPE
7-10-10
N=20
6-9
3-4-5
N=9
4-4
50
11.8
11.7
14.7
19.7
105
109
28-12-16
VEGETATIVE LAYER, about 6 inches
SANDY LEAN CLAY, light brown to brown, stiff
to very stiff
CLAYEY SAND, brown, loose to medium dense
SANDY LEAN CLAY, brown, medium stiff
Boring Terminated at 15 Feet
0.5
9.0
14.0
15.0
4918.5
4910
4905
4904
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20WATER LEVELOBSERVATIONSDEPTH (Ft.)5
10
15 FIELD TESTRESULTSSWELL/LOAD(%/psf)UNCONFINEDCOMPRESSIVESTRENGTH (psf)PERCENT FINESWATERCONTENT (%)DRY UNITWEIGHT (pcf)ATTERBERG
LIMITS
LL-PL-PI
LOCATION See Exploration Plan
Latitude: 40.5171° Longitude: -105.017°GRAPHIC LOGMODEL LAYERDEPTH ELEVATION (Ft.)
Surface Elev.: 4919 (Ft.)
Page 1 of 1
Advancement Method:
4.25" Solid Stem Auger
Abandonment Method:
Boring backfilled with auger cuttings upon completion.
Notes:
Project No.: 20205032
Drill Rig: CME 55
BORING LOG NO. B-6
MAV Development Co.CLIENT:
Ann Arbor, MI
Driller: Drilling Engineers, Inc.
Boring Completed: 10-06-2020
PROJECT: MAVD Flex Office
See Exploration and Testing Procedures for a
description of field and laboratory procedures
used and additional data (If any).
See Supporting Information for explanation of
symbols and abbreviations.
5041 Technology Drive
Fort Collins, CO
SITE:
Boring Started: 10-06-2020
1901 Sharp Point Dr Ste C
Fort Collins, CO
Ground water not encountered
WATER LEVEL OBSERVATIONS
2
3
2 SAMPLE TYPE
0
10
20
30
40
50
60
0 20 40 60 80 100CH or OHCL or OLML or OL
MH or OH"U" Line"A" Line
ATTERBERG LIMITS RESULTS
ASTM D4318
P
L
A
S
T
I
C
I
T
Y
I
N
D
E
X
LIQUID LIMIT
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. ATTERBERG LIMITS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/15/20
35
37
59
26
39
28
12
14
18
14
17
12
23
23
41
12
22
16
PIPLLLBoring ID Depth
B-1
B-2
B-3
B-4
B-5
B-6
71.8
64.0
97.1
65.2
88.3
49.9
Fines
14 - 15.5
2 - 3.5
19 - 20.5
9 - 10.5
4 - 5
9 - 10.5
CL
CL
CH
CL
CL
SC
LEAN CLAY with SAND
SANDY LEAN CLAY
CLAYSTONE BEDROCK
SANDY LEAN CLAY
LEAN CLAY
CLAYEY SAND
DescriptionUSCS
CL-ML
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
30 40 501.5 200681014413/4 1/2 60
GRAIN SIZE IN MILLIMETERSPERCENT FINER BY WEIGHTHYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
4 3/8 3 100 14032
GRAIN SIZE DISTRIBUTION
ASTM D422 / ASTM C136
6 16 20
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20mediumcoarse coarsefine fine
COBBLES GRAVEL SAND SILT OR CLAY
B-1
B-2
B-3
B-4
B-5
LEAN CLAY with SAND (CL)
SANDY LEAN CLAY (CL)
CLAYSTONE BEDROCK (CH)
SANDY LEAN CLAY (CL)
LEAN CLAY (CL)
35
37
59
26
39
23
23
41
12
22
12
14
18
14
17
14 - 15.5
2 - 3.5
19 - 20.5
9 - 10.5
4 - 5
20.5
10.0
23.8
14.3
14.3
B-1
B-2
B-3
B-4
B-5
71.8
64.0
97.1
65.2
88.3
14 - 15.5
2 - 3.5
19 - 20.5
9 - 10.5
4 - 5
0.2
2.1
0.0
0.1
0.0
28.0
33.9
2.9
34.7
11.7
9.5
12.5
4.75
9.5
4.75
Boring ID Depth WC (%)LL PL PI Cc Cu
%Clay%Fines%Silt%Sand%Gravel Boring ID Depth D100 D60 D30 D10
USCS Classification
%Cobbles
0.0
0.0
0.0
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
30 40 501.5 200681014413/4 1/2 60
GRAIN SIZE IN MILLIMETERSPERCENT FINER BY WEIGHTHYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
4 3/8 3 100 14032
GRAIN SIZE DISTRIBUTION
ASTM D422 / ASTM C136
6 16 20
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20mediumcoarse coarsefine fine
COBBLES GRAVEL SAND SILT OR CLAY
B-6 CLAYEY SAND (SC) 28 16129 - 10.5 14.7
B-6 49.99 - 10.5 0.1 50.19.5 0.131
Boring ID Depth WC (%)LL PL PI Cc Cu
%Clay%Fines%Silt%Sand%Gravel Boring ID Depth D100 D60 D30 D10
USCS Classification
%Cobbles
0.0
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
100 1,000 10,000AXIAL STRAIN, %PRESSURE, psf
NOTES: Sample exhibited 1.2 percent swell upon wetting under an applied pressure of 500 psf
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20 B-1 LEAN CLAY WITH SAND2 - 3 ft 112 8.4
Specimen Identification Classification , pcf WC, %
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
100 1,000 10,000AXIAL STRAIN, %PRESSURE, psf
NOTES: Sample exhibited 0.3 percent swell upon wetting under an applied pressure of 500 psf
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20 B-2 SANDY LEAN CLAY4 - 5 ft 105 10.1
Specimen Identification Classification , pcf WC, %
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
100 1,000 10,000AXIAL STRAIN, %PRESSURE, psf
NOTES: Sample exhibited 2.2 percent swell upon wetting under an applied pressure of 150 psf
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20 B-4 SANDY LEAN CLAY2 - 3 ft 96 9.8
Specimen Identification Classification , pcf WC, %
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
100 1,000 10,000AXIAL STRAIN, %PRESSURE, psf
NOTES: Sample exhibited 4.6 percent swell upon wetting under an applied pressure of 150 psf
SWELL CONSOLIDATION TEST
ASTM D4546
PROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20 B-5 SANDY LEAN CLAY2 - 3 ft 100 10.5
Specimen Identification Classification , pcf WC, %
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
5,500
6,000
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
AXIAL STRAIN - %
UNCONFINED COMPRESSION TEST
ASTM D2166
COMPRESSIVE STRESS - psfPROJECT NUMBER: 20205032
SITE: 5041 Technology Drive
Fort Collins, CO
PROJECT: MAVD Flex Office
CLIENT: MAV Development Co.
Ann Arbor, MI
1901 Sharp Point Dr Ste C
Fort Collins, CO
LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. UNCONFINED WITH PHOTOS 20205032 MAVD FLEX OFFICE.GPJ TERRACON_DATATEMPLATE.GDT 10/23/20SAMPLE LOCATION: B-1 @ 9 - 10 feetSAMPLE TYPE: CARS
0.33
84.62
124
Strain Rate: in/min
Failure Strain: %
Calculated Saturation: %
Height: in.
Diameter: in.
SPECIMEN FAILURE PHOTOGRAPH
Remarks:
Percent < #200 SievePIPLLL
2832
DESCRIPTION: LEAN CLAY WITH SAND
0.0800
Dry Density: pcf
Moisture Content: %
2.28
2.13
2.65
Height / Diameter Ratio:
Calculated Void Ratio:
Undrained Shear Strength: (psf)
Unconfined Compressive Strength (psf)
Assumed Specific Gravity:
5664
4.12
1.93
SPECIMEN TEST DATA
10.6
SUPPORTING INFORMA TION
Contents:
General Notes
Unified Soil Classification System
Description of Rock Properties (2)
Note: All attachments are one page unless noted above.
MAVD Flex Office Fort Collins, CO
Terracon Project No. 20205032
0.50 to 1.00
> 4.00
Unconfined Compressive
Strength
Qu, (tsf)
0.25 to 0.50
1.00 to 2.00
2.00 to 4.00
less than 0.25
Modified
California
Ring
Sampler
Standard
Penetration
Test
N
(HP)
(T)
(DCP)
UC
(PID)
(OVA)
Standard Penetration Test
Resistance (Blows/Ft.)
Hand Penetrometer
Torvane
Dynamic Cone Penetrometer
Unconfined Compressive
Strength
Photo-Ionization Detector
Organic Vapor Analyzer
SAMPLING WATER LEVEL FIELD TESTS
GENERAL NOTES
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
Water levels indicated on the soil boring logs are
the levels measured in the borehole at the times
indicated. Groundwater level variations will occur
over time. In low permeability soils, accurate
determination of groundwater levels is not
possible with short term water level
observations.
Water Initially
Encountered
Water Level After a
Specified Period of Time
Water Level After
a Specified Period of Time
Cave In
Encountered
Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude
and Longitude are approximate. See Exploration and Testing Procedures in the report for the methods used to locate the
exploration points for this project. Surface elevation data annotated with +/- indicates that no actual topographical survey
was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from
topographic maps of the area.
LOCATION AND ELEVATION NOTES
Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory
data exist to classify the soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this
procedure is used. ASTM D2488 "Description and Identification of Soils (Visual-Manual Procedure)" is also used to
classify the soils, particularly where insufficient laboratory data exist to classify the soils in accordance with ASTM D2487.
In addition to USCS classification, coarse grained soils are classified on the basis of their in-place relative density, and
fine-grained soils are classified on the basis of their consistency. See "Strength Terms" table below for details. The ASTM
standards noted above are for reference to methodology in general. In some cases, variations to methods are applied as a
result of local practice or professional judgment.
DESCRIPTIVE SOIL CLASSIFICATION
The soil boring logs contained within this document are intended for application to the project as described in this
document. Use of these soil boring logs for any other purpose may not be appropriate.
RELEVANCE OF SOIL BORING LOG
STRENGTH TERMS
Descriptive Term
(Density)
Standard Penetration or
N-Value
Blows/Ft.
Descriptive
Term
(Consistency)
Standard
Penetration or N-Value
Blows/Ft.
20 - 29
30 - 49
50 - 79
>79
Standard
Penetration
or N-Value
Blows/Ft.
BEDROCK
Very Loose
Loose
Very Soft
2 - 4
8 - 15
15 - 30
> 30
4 - 9
Medium Dense
Dense
Weathered
Medium Hard
Firm
Very HardVery Dense
(More than 50% retained on No. 200 sieve.)
Density determined by Standard Penetration
Resistance
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing,
field visual-manual procedures or standard penetration
resistance
RELATIVE DENSITY OF COARSE-GRAINED SOILS
Soft
Medium Stiff
Stiff
Very Stiff
Hard
CONSISTENCY OF FINE-GRAINED SOILS
< 200 - 1
4 - 8
0 - 3
10 - 29
30 - 50
> 50
Descriptive
Term
(Consistency)
Hard
UNIFIED SOIL CLASSIFICATION SYSTEM
UNIFIED SOI L CLASSI FICATI ON SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse-Grained Soils:
More than 50% retained
on No. 200 sieve
Gravels:
More than 50% of
coarse fraction
retained on No. 4 sieve
Clean Gravels:
Less than 5% fines C
Cu ³ 4 and 1 £ Cc £ 3 E GW Well-graded gravel F
Cu < 4 and/or [Cc<1 or Cc>3.0]E GP Poorly graded gravel F
Gravels with Fines:
More than 12% fines C
Fines classify as ML or MH GM Silty gravel F, G, H
Fines classify as CL or CH GC Clayey gravel F, G, H
Sands:
50% or more of coarse
fraction passes No. 4
sieve
Clean Sands:
Less than 5% fines D
Cu ³ 6 and 1 £ Cc £ 3 E SW Well-graded sand I
Cu < 6 and/or [Cc<1 or Cc>3.0]E SP Poorly graded sand I
Sands with Fines:
More than 12% fines D
Fines classify as ML or MH SM Silty sand G, H, I
Fines classify as CL or CH SC Clayey sand G, H, I
Fine-Grained Soils:
50% or more passes the
No. 200 sieve
Silts and Clays:
Liquid limit less than 50
Inorganic:PI > 7 and plots on or above “A”
line J
CL Lean clay K, L, M
PI < 4 or plots below “A” line J ML Silt K, L, M
Organic:Liquid limit - oven dried < 0.75 OL Organic clay K, L, M, N
Liquid limit - not dried Organic silt K, L, M, O
Silts and Clays:
Liquid limit 50 or more
Inorganic:PI plots on or above “A” line CH Fat clay K, L, M
PI plots below “A” line MH Elastic Silt K, L, M
Organic:Liquid limit - oven dried < 0.75 OH Organic clay K, L, M, P
Liquid limit - not dried Organic silt K, L, M, Q
Highly organic soils:Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the 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 = D60/D10 Cc =
6010
2
30
DxD
)(D
F If soil contains ³ 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 ³ 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 ³ 30% plus No. 200 predominantly sand, add
“sandy” to group name.
MIf soil contains ³ 30% plus No. 200, predominantly gravel, add
“gravelly” to group name.
N PI ³ 4 and plots on or above “A” line.
O PI < 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.
DESCRIPTION OF ROCK PROPERTIES
WEATHERING
Term Description
Unweathered No visible sign of rock material weathering, perhaps slight discoloration on major discontinuity surfaces.
Slightly
weathered
Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be
discolored by weathering and may be somewhat weaker externally than in its fresh condition.
Moderately
weathered
Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is
present either as a continuous framework or as corestones.
Highly
weathered
More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is
present either as a discontinuous framework or as corestones.
Completely
weathered All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact.
Residual soil All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large
change in volume, but the soil has not been significantly transported.
STRENGTH OR HARDNESS
Description Field Identification Uniaxial Compressive
Strength,psi (MPa)
Extremely weak Indented by thumbnail 40-150 (0.3-1)
Very weak Crumbles under firm blows with point of geological hammer, can be
peeled by a pocket knife 150-700 (1-5)
Weak rock Can be peeled by a pocket knife with difficulty, shallow indentations
made by firm blow with point of geological hammer 700-4,000 (5-30)
Medium strong Cannot be scraped or peeled with a pocket knife, specimen can be
fractured with single firm blow of geological hammer 4,000-7,000 (30-50)
Strong rock Specimen requires more than one blow of geological hammer to
fracture it 7,000-15,000 (50-100)
Very strong Specimen requires many blows of geological hammer to fracture it 15,000-36,000 (100-250)
Extremely strong Specimen can only be chipped with geological hammer >36,000 (>250)
DISCONTINUITY DESCRIPTION
Fracture Spacing (Joints, Faults, Other Fractures)Bedding Spacing (May Include Foliation or Banding)
Description Spacing Description Spacing
Extremely close < ¾ in (<19 mm)Laminated < ½ in (<12 mm)
Very close ¾ in – 2-1/2 in (19 - 60 mm)Very thin ½ in – 2 in (12 – 50 mm)
Close 2-1/2 in – 8 in (60 – 200 mm)Thin 2 in – 1 ft. (50 – 300 mm)
Moderate 8 in – 2 ft. (200 – 600 mm)Medium 1 ft. – 3 ft. (300 – 900 mm)
Wide 2 ft. – 6 ft. (600 mm – 2.0 m)Thick 3 ft. – 10 ft. (900 mm – 3 m)
Very Wide 6 ft. – 20 ft. (2.0 – 6 m)Massive > 10 ft. (3 m)
Discontinuity Orientation (Angle): Measure the angle of discontinuity relative to a plane perpendicular to the longitudinal axis of the
core. (For most cases, the core axis is vertical; therefore, the plane perpendicular to the core axis is horizontal.) For example, a
horizontal bedding plane would have a 0-degree angle.
ROCK QUALITY DESIGNATION (RQD)1
Description RQD Value (%)
Very Poor 0 - 25
Poor 25 – 50
Fair 50 – 75
Good 75 – 90
Excellent 90 - 100
1.The combined length of all sound and intact core segments equal to or greater than 4 inches in length, expressed as a
percentage of the total core run length.
Reference: U.S. Department of Transportation, Federal Highway Administration, Publication No FHWA-NHI-10-034, December 2009
Technical Manual for Design and Construction of Road Tunnels – Civil Elements
DESCRIPTION OF ROCK PROPERTIES
WEATHERING
Fresh Rock fresh, crystals bright, few joints may show slight staining. Rock rings under hammer if crystalline.
Very slight Rock generally fresh, joints stained, some joints may show thin clay coatings, crystals in broken face show bright.
Rock rings under hammer if crystalline.
Slight Rock generally fresh, joints stained, and discoloration extends into rock up to 1 in. Joints may contain clay. In
granitoid rocks some occasional feldspar crystals are dull and discolored. Crystalline rocks ring under hammer.
Moderate
Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull
and discolored; some show clayey. Rock has dull sound under hammer and shows significant loss of strength
as compared with fresh rock.
Moderately severe All rock except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority
show kaolinization. Rock shows severe loss of strength and can be excavated with geologist’s pick.
Severe All rock except quartz discolored or stained. Rock “fabric” clear and evident, but reduced in strength to strong
soil. In granitoid rocks, all feldspars kaolinized to some extent. Some fragments of strong rock usually left.
Very severe All rock except quartz discolored or stained. Rock “fabric” discernible, but mass effectively reduced to “soil” with
only fragments of strong rock remaining.
Complete Rock reduced to “soil”. Rock “fabric” no discernible or discernible only in small, scattered locations. Quartz may
be present as dikes or stringers.
HARDNESS (for engineering description of rock –not to be confused with Moh’s scale for minerals)
Very hard Cannot be scratched with knife or sharp pick. Breaking of hand specimens requires several hard blows of
geologist’s pick.
Hard Can be scratched with knife or pick only with difficulty. Hard blow of hammer required to detach hand specimen.
Moderately hard Can be scratched with knife or pick. Gouges or grooves to ¼ in. deep can be excavated by hard blow of point of
a geologist’s pick. Hand specimens can be detached by moderate blow.
Medium Can be grooved or gouged 1/16 in. deep by firm pressure on knife or pick point. Can be excavated in small chips
to pieces about 1-in. maximum size by hard blows of the point of a geologist’s pick.
Soft Can be gouged or grooved readily with knife or pick point. Can be excavated in chips to pieces several inches
in size by moderate blows of a pick point. Small thin pieces can be broken by finger pressure.
Very soft Can be carved with knife. Can be excavated readily with point of pick. Pieces 1-in. or more in thickness can be
broken with finger pressure. Can be scratched readily by fingernail.
Joint, Bedding, and Foliation Spacing in Rock 1
Spacing Joints Bedding/Foliation
Less than 2 in.Very close Very thin
2 in. – 1 ft.Close Thin
1 ft. – 3 ft.Moderately close Medium
3 ft. – 10 ft.Wide Thick
More than 10 ft.Very wide Very thick
1.Spacing refers to the distance normal to the planes, of the described feature, which are parallel to each other or nearly so.
Rock Quality Designator (RQD)1 Joint Openness Descriptors
RQD, as a percentage Diagnostic description Openness Descriptor
Exceeding 90 Excellent No Visible Separation Tight
90 – 75 Good Less than 1/32 in.Slightly Open
75 – 50 Fair 1/32 to 1/8 in.Moderately Open
50 – 25 Poor 1/8 to 3/8 in.Open
Less than 25 Very poor 3/8 in. to 0.1 ft.Moderately Wide
1.RQD (given as a percentage) = length of core in pieces 4
inches and longer / length of run
Greater than 0.1 ft.Wide
References: American Society of Civil Engineers. Manuals and Reports on Engineering Practice - No. 56. Subsurface Investigation for
Design and Construction of Foundations of Buildings. New York: American Society of Civil Engineers, 1976. U.S.
Department of the Interior, Bureau of Reclamation, Engineering Geology Field Manual.