HomeMy WebLinkAbout18 Geotech ReportMONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
JOB NO. B23-066-001 September 2023
REPORT OF GEOTECHNICAL INVESTIGATION
CLIENT ENGINEER
Fifth and Villard Apartments, LLC
111 W Lamme St, Suite 101
Bozeman, MT 59715
Kyle Scarr, PE
kyle.scarr@tdhengineering.com
REPORT OF GEOTECHNICAL INVESTIGATION
PROJECT NAME
PROJECT LOCATION 406.586.0277
tdhengineering.com
234 E Babcock St, Suite 3
Bozeman, MT 59715
321 NORTH 5TH AVENUE
BOZEMAN, MONTANA
9/16/2023
321 North 5th Avenue Table of Contents
Bozeman, Montana i
Table of Contents
1.0 EXECUTIVE SUMMARY ......................................................................................................... 3
2.0 INTRODUCTION ..................................................................................................................... 5
2.1 Purpose and Scope .......................................................................................................... 5
2.2 Project Description ........................................................................................................... 5
3.0 SITE CONDITIONS ................................................................................................................. 6
3.1 Geology and Physiography .............................................................................................. 6
3.2 Surface Conditions ........................................................................................................... 7
3.3 Subsurface Conditions ..................................................................................................... 8
3.3.1 Soils ........................................................................................................................... 8
3.3.2 Ground Water ........................................................................................................... 9
4.0 ENGINEERING ANALYSIS .................................................................................................. 11
4.1 Introduction ..................................................................................................................... 11
4.2 Site Grading and Excavations........................................................................................ 11
4.3 Conventional Shallow Foundations on EAP Improved Soils ......................................... 12
4.4 Deep Foundation Options .............................................................................................. 12
4.5 Foundation and Retaining Walls .................................................................................... 13
4.6 Interior Floor Slabs and Exterior Flatwork ..................................................................... 13
4.7 Pavements ..................................................................................................................... 14
4.8 On-Site Infiltration .......................................................................................................... 15
5.0 RECOMMENDATIONS ......................................................................................................... 17
5.1 Site Grading and Excavations........................................................................................ 17
5.2 Conventional Shallow Foundations on EAP Improved Soils ......................................... 18
5.3 Foundation and Retaining Walls .................................................................................... 19
5.4 Floor Slabs and Exterior Flatwork .................................................................................. 20
5.5 Pavements ..................................................................................................................... 21
5.6 On-Site Infiltration .......................................................................................................... 22
5.7 Continuing Services ....................................................................................................... 22
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES ....................................................... 24
6.1 Field Explorations ........................................................................................................... 24
6.2 Laboratory Testing ......................................................................................................... 24
7.0 LIMITATIONS ........................................................................................................................ 26
321 North 5th Avenue Appendix
Bozeman, Montana ii
APPENDIX
Boring Location Map (Figure 1)
Logs of Exploratory Borings (Figures 2 through 4)
Laboratory Test Data (Figures 5 through 11)
LTTPBind Online PG Asphalt Binder Analysis Summary
Soil Classification and Sampling Terminology for Engineering Purposes
Classification of Soils for Engineering Purposes
321 North 5th Avenue Introduction
Bozeman, Montana Page 3
GEOTECHNICAL REPORT
321 NORTH 5TH AVENUE
BOZEMAN, MONTANA
1.0 EXECUTIVE SUMMARY
The geotechnical investigation for the redevelopment of 321 North 5th Avenue in Bozeman,
Montana, encountered relatively consistent soil conditions. Based on the conceptual site plan, we
understand that the proposed project consists of a new five-story, residential structure utilizing
conventional shallow foundations and slab-on-grade construction. Additionally, it is our
understanding that the redevelopment will also include a variety of new surface features including
landscaping, exterior flatwork, and asphalt pavement for the parking lot and access road. The
subsurface soil conditions within the borings performed are comprised of an existing asphalt
surfacing section, fill material, or a topsoil horizon overlying native fine-grained soils. The fine-
grained soils extend to depths of 13.3 to 16.0 feet below existing site grades and are underlain by
native gravel deposits. However, a zone of sand containing limited gravel was observed in boring
B-2 beneath the overburden clay. This layer was observed as a transitional media extending to a
depth of approximately 18.0 feet before transitioning into native gravel. Similar gravel deposits
extend to depths of at least 21.5 feet, the maximum depth investigated. The seismic site class is D,
and the risk of seismically-induced liquefaction or soil settlement is considered low and does not
warrant additional evaluation.
The primary geotechnical concern regarding this project is the presence of relatively soft,
compressible clay soils and transitional sands extending to depths of 13.3 to 18.0 feet below
existing site grades. These zones are relatively weak and are typically unsuitable to support multi-
story structures due to excessive settlement risk. We recommend that the project utilize an
engineered aggregate pier (EAP) system, also called rammed aggregate piers (RAP), to improve
the subgrade conditions sufficiently to support a conventional footing system while controlling the
potential for settlement. Similar foundation improvements have been utilized on several structures
throughout Bozeman with great success. The allowable bearing pressure for EAP improved soils
will be specified by the EAP designer; however, in our experience design bearing pressures on the
order of 4,000 to 6,000 pounds per square foot (psf) is achievable with this system. Slab-on-grade
construction utilizing an increased thickness of base course gravel is acceptable for this project;
however, EAP improvements could also be utilized beneath the slab systems if it is economical for
the project. This option can be discussed with the EAP designer.
Based on our experience in the Bozeman area, the use of ground improvement options are
generally preferred over deep foundation systems. However, deep foundation systems such as
driven pile or cast-in-place concrete piers would also be viable to support the structure and control
settlements by transferring foundation loads down to the native gravel formations. While viable,
deep foundation options are generally slower and more expensive to construct than EAPs; thus,
they have not been considered in detail for this project. We are available to provide additional
321 North 5th Avenue Introduction
Bozeman, Montana Page 4
engineering analysis and recommendations for a deep foundation alternative should they be
considered for this project.
Additionally, we understand that the existing structure currently occupying the lot is subject to
demolition and removal prior to construction. The existing foundation of the structure is unknown;
however, care should be taken to completely remove all building components and any detrimental
fill materials from beneath the structure. Replacement of this zone should consist of properly
compacted structural fill.
321 North 5th Avenue Introduction
Bozeman, Montana Page 5
2.0 INTRODUCTION
2.1 Purpose and Scope
This report presents the results of our geotechnical study for the redevelopment of 321 North 5th
Avenue located in Bozeman, Montana. The purpose of the geotechnical study is to determine the
general surface and subsurface conditions at the proposed site and to develop geotechnical
engineering recommendations for support of the proposed structure and design of related facilities.
This report describes the field work and laboratory analyses conducted for this project, the surface
and subsurface conditions encountered, and presents our recommendations for the proposed
foundations and related site development.
Our field work included drilling three soil borings around the existing building to assess subsurface
conditions. Samples were obtained from the borings and returned to our Great Falls laboratory for
testing. Laboratory testing was performed on selected soil samples to determine engineering
properties of the subsurface materials. The information obtained during our field investigations and
laboratory analyses was used to develop recommendations for the design of the proposed
foundation systems.
2.2 Project Description
It is our understanding that the proposed project consists of a new five-story, residential structure,
exhibiting a first-floor building footprint of approximately 12,100 square feet. However, the
northeast portion of the first floor consists of outdoor open space and is canopied by the upper
floors resulting in an overall structural footprint of approximately 13,190 square feet for floors two
through five. The structure is proposed to be supported on conventional shallow foundations
incorporating slab-on-grade construction, which we anticipate will utilize both wood and steel
construction. We understand that the building primarily consists of one-bedroom residential units
with a lobby, indoor bike parking, and onsite laundry amenities on the first floor. Additionally, each
floor will include a tenant lounge. Structural loads had not been developed at the time of this report.
However, for the purpose of our analysis, we have assumed that wall loads will be less than 8,000
pounds per lineal foot and column loads will be less than 250 kips.
Based on the conceptual plan set, site development is anticipated to include new landscaping,
exterior concrete flatwork, and asphalt pavement for the parking lot and access road. If the
assumed design values presented above vary from the actual project parameters, the
recommendations presented in this report should be reevaluated.
321 North 5th Avenue Site Conditions
Bozeman, Montana Page 6
3.0 SITE CONDITIONS
3.1 Geology and Physiography
According to the geologic map of Montana, the site is geologically characterized as being upper
tertiary sediments or sedimentary rock (Tsu). This formation includes conglomerate, tuffaceous
sandstone and siltstone, marlstone, and equivalent sediment and ash beds. Regions west of the
project include variable deposits of gravel (Qgr). The gravel ranges from pebble to boulder in size
and includes varying amounts of sand, silt, and clay. These deposits are dominantly alluvial
terrace, abandoned channel and floodplain, remnant alluvial fan, and local glacial outwash.
Regions to the east are classified as being alluvium (Qal) typically comprised of gravel, sand, silt,
and clay deposits of stream and river channels and floodplains.
Additional data provided by the geologic map of Bozeman suggests the upper tertiary formation is
overlain by Alluvial-fan deposits (Qafo) of the Pleistocene epoch. These deposits consist of pebble
to small boulder size clasts containing light brown, gray, and locally reddish gray gravel in a coarse
sand and granule matrix. The gravels are suggested to be angular to subangular and locally
derived. According to the geology report, the alluvial-fan deposits are estimated to be 150 feet
thick.
Geologic Map of Montana, Edition 1.0 (2007)
Montana Bureau of Mines & Geology
Approximate
Site Location
321 North 5th Avenue Site Conditions
Bozeman, Montana Page 7
Geologic Map of the Bozeman, Southwestern Montana (2014)
Montana Bureau of Mines & Geology
Based on the subsurface conditions encountered, the site falls under seismic Site Class D. The
structural engineer should utilize the site classification above to determine the appropriate seismic
design data for use on this project in accordance with current applicable building codes. The
likelihood of seismically-induced soil liquefaction or settlement for this project is low and does not
warrant additional evaluation.
3.2 Surface Conditions
The proposed project site is located at 321 North 5th Avenue and is presently heavily developed
with a large multi-story structure. Outside the limits of the large building footprint, the lot primarily
consists of impervious surfacing including an asphalt pavement parking lot, a rigid concrete
pavement alley access road, and exterior concrete flatwork. Site landscaping is limited to sodded
lawn on the eastern and northern sides of the existing structure and a courtyard on the western
side. Currently, the finished floor elevation on the north side of the structure is higher than the
existing grades on West Villard Street, which produces slopes within the lawn of 10 to 20 percent
over a length of approximately 20 feet down towards the street. Similar slopes exist within the lawn
on the northeast side of the structure down towards North 5th Avenue. The remaining impervious
areas slope down to the north and east, towards West Villard Street and North 5th Avenue at slopes
of 1 to 2 percent. The topography is best described as nearly level with limited areas of moderate to
steep slopes.
Approximate
Site Location
321 North 5th Avenue Site Conditions
Bozeman, Montana Page 8
3.3 Subsurface Conditions
3.3.1 Soils
The subsurface soil conditions appear to be relatively consistent based on our exploratory
drilling, and soil sampling. In general, the subsurface soil conditions encountered within the
borings consist of an existing asphalt surface section, fill, or a topsoil horizon ranging in
thickness from 1.0 to 3.3 feet overlying native lean clay soil. The clays extend to depths of
13.3 to 18.0 feet below existing site grade and are underlain by native gravels, visually
classified as poorly-graded gravel with clay and sand, and clayey gravel with sand.
However, boring B-2 observed a 2-foot-thick transitional zone of sand containing limited
gravels at a depth of 16.0 feet. The native gravels extend to depths of at least 21.5 feet, the
maximum depth investigated.
The subsurface soils are described in detail on the enclosed boring logs and are
summarized below. The stratification lines shown on the logs represent approximate
boundaries between soil types and the actual in situ transition may be gradual vertically or
discontinuous laterally.
EXISTING SURFACING SECTION
Boring B-1 was located within the existing parking lot on the south side of the property and
observed a surfacing section consisting of asphalt pavement and a base course gravel.
Based on observations during drilling, the section appears to be comprised of six inches of
asphalt pavement overlying approximately six inches of gravel. The gravel base material
was visually classified as poorly-graded gravel with clay and sand and appeared relatively
dense based on the ease of drilling.
An additional surfacing section comprised of rigid concrete pavement was observed within
the access road from West Villard Street extending throughout the extents of the existing
courtyard. Due to limitations of the drilling equipment, this section was unable to be
investigated.
TOPSOIL / FILL
Borings B-2 and B-3 both encountered a limited thickness of either surficial topsoil or fill
within their surface before transitioning into native lean clay at depths of 3.0 and 3.3 feet,
respectively. The fill encountered in boring B-3 contained no obvious construction debris,
however, sporadic gravels and color changes were evident within various increments of the
samples obtained. The surficial materials are considered firm to stiff as indicated by two
penetration resistance values of 6 and 11 blow per foot (bpf). The natural moisture contents
varied from 10.6 to 21.7 percent and averaged 17.9 percent.
321 North 5th Avenue Site Conditions
Bozeman, Montana Page 9
LEAN CLAY
Lean clay was encountered in all three borings beneath the overlying surfacing section or
surficial soils at starting depths between 1.0 and 3.3 feet. The clays extend to depths of
13.3 to 16.2 feet, observing the greatest thickness on the northeast corner of the project
area. The stratum is considered soft to firm as indicated by penetration resistance values
which ranged between 4 and 8 bpf and averaged 5 bpf. The material is considered highly
compressible as indicated by the consolidation test results shown on Figures 10 and 11. In
addition to consolidation tests, an unconfined compression test was performed on a single
sample of the lean clay which indicates a maximum unconfined compressive strength of
2,070 psf before failure. One sample of the material contained 0.2 percent gravel, 4.6
percent sand, and 95.2 percent fines (silt and clay). Two samples of the clays exhibited
liquid limits of 32 and 37 percent and plasticity indices of 12 and 18 percent. The natural
moisture contents varied from 18.4 to 30.7 percent and average 24.4 percent.
POORLY-GRADED GRAVEL WITH CLAY AND SAND / CLAYEY GRAVEL WITH SAND
Native gravels were encountered in all borings beneath the overburden fine-grained soils at
depths of 13.3 to 18.0 feet. However, boring B-1 encountered a transitional media
containing high amounts of sand and limited gravels at a depth of 16.0 feet. This
transitional zone was visually classified as poorly-graded sand with clay and extends to a
depth of approximately 18.0 feet before transitioning into native gravel. The materials are
considered medium dense to very dense as indicated by penetration resistance values
which ranged between 25 to100 bpf and averaged 47 bpf. The natural moisture contents of
the native gravels varied from 6.5 to 11.2 percent and averaged 8.9 percent. The single
sample of the transitional sand exhibited a natural moisture content of 21.0 percent.
Multiple samples of the materials were combined into one composite sample to assess the
materials composition. The single composite sample of the gravel contained 45.6 percent
gravel, 36.8 percent sand, and 17.6 percent fines (silt and clay). Due to the sampling
methods utilized which are unable to sample rocks larger than 1.5-inch and result in
fracturing of some materials, the samples may not accurately depict the in-situ material
gradation of the native gravels. Additionally, drilling actions at various depths suggests the
presence of large cobbles or boulders within the gravels that were unable to be further
assessed. The native gravels extend to a depth of at least 21.5 feet, the maximum depth
investigated.
3.3.2 Ground Water
Ground water was encountered within all the borings to depths ranging from 15.9 to 16.4
feet below the ground surface. During our investigation, monitoring wells were installed in
each boring to monitor the ground water fluctuations. According to other ground water
measurements in this area of Bozeman, peak levels were reached in late June which
occurred prior to our investigation; thus, intensive groundwater monitoring was not
321 North 5th Avenue Site Conditions
Bozeman, Montana Page 10
conducted. To date, two readings have been collected from the borings. One following the
completion of our investigation in August and one from early September. The monitoring
data up to the completion of this report is summarized in the table below. We are available
to provide additional data following future monitoring cycles upon request.
Date of Measurement
Depth to Ground Water (ft)
B-1 B-2 B-3
08-09-2023 16.0 15.9 16.4
09-05-2023 16.2 16.0 16.5
The presence or absence of observed ground water may be directly related to the time of
the subsurface investigation. Numerous factors contribute to seasonal ground water
occurrences and fluctuations, and the evaluation of such factors is beyond the scope of this
report.
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 11
4.0 ENGINEERING ANALYSIS
4.1 Introduction
The primary geotechnical concern regarding this project is the presence of relatively soft and
compressible clay soil beneath the proposed structure. This zone is relatively weak and
compressible and may result in undesirable settlements of heavily loaded elements without
subgrade improvements. Based on the site conditions and the nature of the proposed construction,
conventional over-excavation and replacement methods are not anticipated to be conducive to the
overall cost of the project; thus, we recommend utilizing an engineered aggregate pier (EAP)
system, also called rammed aggregate piers (RAP). This system will improve the subgrade
conditions sufficiently to support a conventional footing system while controlling the potential for
settlement. While EAP improvements are the recommended approach for this project, alternative
deep foundation options are available should they be preferred. While viable, deep foundation
options are generally slower and more expensive to construct than EAPs; thus, they have not been
considered in detail for this project. We are available to provide additional engineering analysis and
recommendations upon request.
Additionally, we understand that the existing structure currently occupying the lot is subject to
demolition and removal prior to construction. The existing foundation of the structure is unknown;
however, care should be taken to completely remove all building components and any detrimental
fill materials from beneath the structure. Replacement of this zone should consist of properly
compacted structural fill. The thickness of the structural fill will be dependent on the final finished
floor elevation of the new building and the depth necessary to remove all fill materials and debris
from the existing building’s half basement.
4.2 Site Grading and Excavations
The ground surface at the proposed site is best described as nearly level. However, moderate to
steep slopes exist within a limited area of vegetation on the north side of the lot. Such slopes are
the result of the finished floor elevation on the north side of the existing structure being higher than
the existing grades on West Villard Street. Slopes range between 10 to 20 percent over a length of
approximately 20 feet down towards the street. Similar slopes exist within the lawn on the northeast
side of the structure down towards North 5th Avenue. The remaining impervious areas slope down
to the north and east, towards West Villard Street and North 5th Avenue at slopes of 1 to 2 percent.
Based on our field work, lean clay will be encountered in foundation excavations to the depths
anticipated. However, with the demolition of the existing structure and related site development, an
assortment of fill materials and construction debris associated with the existing development should
be anticipated. Ground water was encountered in all borings at depths ranging between 15.9 to
16.4 feet at the time of our investigation. The ground water elevation is anticipated to fluctuate
depending on the time of year and can also vary from year to year.
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 12
4.3 Conventional Shallow Foundations on EAP Improved Soils
The use of an engineered aggregate pier system (EAP), also known as a rammed aggregate piers
(RAPs), is in our opinion the best subgrade improvement system for this project. This system is
specialized and proprietary; thus, we recommend consulting a RAP design/build company such as
Specialty Foundation Systems, GeoTech Foundation Company (GTFC – West), Keller North
America, or Montana Helical Pier for the design and installation of such services. This system has
been recently used on several structures around Bozeman.
EAPs are installed by drilling a hole of a specified depth and diameter and constructing rock
columns comprised of very dense, highly compacted aggregate. Ramming of thin lifts takes place
with a high-energy beveled tamper that densifies the aggregate and forces it laterally into the
sidewalls of the hole. This action increases the lateral stress in the surrounding soil, thereby
providing a stabilized composite soil mass. The result of the EAP installation is a significant
strengthening and stiffening of the subsurface soils that would then support conventional footings.
This allows for improved performance of the clay soils without requiring it to be completely removed
thus potentially reducing the overall cost of the project. EAPs can be installed in a variety of ground
water conditions using varying methods and may or may not warrant some level of site dewatering
during construction. This should be discussed with the EAP designer / installer based on their
available equipment and abilities.
Based on our experience with the EAP system in similar conditions, we anticipate EAP elements to
utilize 24-inch to 30-inch diameter piers and lengths sufficient to tie the columns into the underlying
native gravel to provide adequate subgrade improvement for support of typical foundation loads.
Footings supported on EAP improved soils are generally designed to limit potential settlements to
less than ¾-inch with differential settlements being less than ½-inch; however, stricter design
criteria could be utilized and would likely result in more EAP elements extending to greater depths.
On EAP projects, the EAP designer typically works closely with the design team, and they create
their own EAP installation plans to be included as part of the overall package. They then provide
the specialized construction and quality control during the installation of this system. Their design is
prepared utilizing the data provided in this report and structural loads provided by the project
structural engineer. We anticipate this approach to be more economical and provide for a shorter
construction schedule than deep foundation options.
4.4 Deep Foundation Options
The engineered aggregate pier system combined with conventional foundation systems, as
discussed above, is our recommended system for this project. The use of this system is anticipated
to be more economical than alternative deep foundation options. For this reason, we have not
included detailed recommendations for any deep foundation systems as part of this report.
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 13
However, this information can be provided upon request if you believe a deep foundation option
would be preferred for the project.
4.5 Foundation and Retaining Walls
Currently, we are not aware of plans for the structure to utilize a crawlspace, basement, or other site
retaining walls. Should any of these components be included in the final design, we should be
consulted to provide suitable lateral pressures to be utilized in their design.
4.6 Interior Floor Slabs and Exterior Flatwork
The primary concern associated with slab-on-grade construction for this project is the potential for
settlement when supported over varying subsurface conditions. All existing pavement section
gravels, existing building components, and any other fill materials associated with the previous
development of the site should be removed from beneath the proposed building footprint. We
anticipate the replacement of these zones will consist of structural fill. All fill should be placed and
compacted in accordance with the recommendations provided in this report.
Based on the preliminary drawings of the site, the proposed building footprint appears to be located
directly over the existing building footprint. However, depending on the final size and orientation of
the structure, we anticipate portions of the interior floor system may be supported on a combination
of compacted fill and undisturbed native clays. The varying subsurface conditions pose some risk
of differential settlement between slabs; thus, an increased base course thickness and the
incorporation of a reinforcing geotextile is advised to help mitigate these movements.
At a minimum, interior building slabs should be underlain by 18 inches of properly compacted
granular fill overlying a reinforcing geotextile. This level of subsurface improvement is not intended
to prevent all settlement associated with construction over the varying subsurface conditions;
however, we do not anticipate overall slab movements to exceed ¾-inch with this option when slab
loads are limited 150 psf or less. Differential settlement within the structure should be on the order
of ½-inch. As an alternative, EAP improvements could also be utilized beneath slab-on-grade
systems and can be discussed with the EAP designer. Recommendations for suitable granular fill
materials, geotextiles, and subgrade preparation requirements are included in the recommendations
section of this report for your consideration.
Exterior flatwork is more easily repaired or replaced should displacement occur; thus, conventional
construction of exterior flatwork over selected site grading fill or native soils is permissible provided
the Owner is willing to accept the risk of movements and understands that a higher level of
maintenance and future repair / replacement may be required. Portions of the exterior flatwork
which are especially sensitive to vertical movement, or which may impact the structure’s
performance, should consider additional subsurface improvements as recommended for interior
floor systems.
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 14
4.7 Pavements
A pavement section is a layered system designed to distribute concentrated traffic loads to the
subgrade. Performance of the pavement structure is directly related to the physical properties of the
subgrade soils and the magnitude and frequency of traffic loadings. Pavement design procedures
are based on strength properties of the subgrade and pavement materials, along with the design
traffic conditions. Traffic information was not available at the time of this report. We have assumed
that traffic for the parking lots and access roads will be limited to passenger-type vehicles with
occasional mid-size truck traffic associated with deliveries, garbage collection, and other services.
The pavement section provided has been prepared using a maximum anticipated equivalent single
axle loading (ESAL) of 100,000 over a 20-year design life of the pavement.
The potential worst case subgrade material is the native lean clay which is classified as an A-6 soil,
in accordance with the American Association of State Highway and Transportation Officials
(AASHTO) classification. AASHTO considers this soil type to be an inferior subgrade material due
to its poor drainage properties and reduced strength when wetted. Typical California Bearing Ratio
(CBR) values for this type of soil range from 5 to 15 percent when the material can be properly
compacted during construction. Based on the results of our laboratory testing, in-situ moisture
contents were elevated to within the higher range of optimum levels, and depending on the time of
construction may increase further. For this reason, our pavement section recommendations have
been designed using a reduced CBR value of two percent to account for the potential reduction in
soil density and further elevated moisture contents. It will be necessary to properly compact the
native soils prior to placing gravel material associated with the pavement section; however,
excessive compaction on over-optimum soils can induce pumping which will further destabilize the
subgrade. Should compaction be unattainable, the prepared subgrade, at a minimum, should be
cleared of all loose soil and smoothed by static rolling only. After subgrade preparation, all
subsequent fill should be selected, placed, and compacted in accordance with our
recommendations.
A geotextile acting as a separator is recommended between the pavement section gravels and the
clay subgrade. The geotextile will prevent the upward migration of fines and the loss of aggregate
into the subgrade, thereby prolonging the structural integrity and performance of the pavement
section.
The pavement section presented in this report is based on an assumed CBR value of two percent,
assumed traffic loadings, recommended pavement section design information presented in the
Asphalt Institute and AASHTO Design Manuals, and our past pavement design experience in
Bozeman, Montana.
Please note that our design has not considered construction traffic or staging use as part of the
analysis. The sections provided are not intended to support this traffic and may not be suitable for
these purposes. If the contractor plans to utilize the pavement sections gravels for construction
access roads or as staging areas which will realize larger construction vehicles and deliveries, they
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 15
should have an engineer review their anticipated traffic conditions to determine if a thicker gravel
section is warranted to support the planned construction conditions.
4.8 On-Site Infiltration
Based on the borings performed, excavations for storm water features will encounter native lean
clay soil to depths of 13.3 to 16.0 feet overlying native gravels, which were classified as either
poorly-graded gravel with clay and sand or clayey gravel with sand. Based on percolation tests
conducted in this area of Bozeman, the clay soil is expected to have little or no permeability and is
not suitable for on-site infiltration. To ensure proper performance of subsurface storm water
systems they should extend to the surface of the native gravel. To obtain estimates for infiltration
rates to be used in design, we performed gradational analyses on one sample of the native gravels
to estimate the saturated hydraulic conductivity (ksat) using relationships developed by Massmann
(2003) and Massmann et al. (2003).
The approach utilized relates the particle diameter of the material at 10, 60, and 90 percent passing
along with the total fines content to estimate the saturated permeability of the soil neglecting any
reductions associated with compaction. The following table summarizes the resulting saturated
permeability values prior to applying the requisite correction factors.
Log10(Ksat) = -1.32 + 1.225*D10 – 0.376*fines (Coarse-Grained Soils)
Material
Description Ksat (cm/sec) Ksat (inch/min) Infiltration Rate
(min/inch)
Clayey GRAVEL
with Sand 0.01 0.13 7.91
** The values above represent the calculated range of infiltration rates based on the gradation data
developed through laboratory testing
These values must be corrected to account for the variability in the soil properties, the test method
utilized for the estimate, and the potential for long-term clogging. The estimated value was
determined based on a single test specimen for the native gravel. Based on the variability observed
in the borings and the number of tests performed, a corresponding correction factor of 0.80 is
considered appropriate for the native gravel. Furthermore, a correction factor of 0.75 is
recommended for the use of the grain size method and a factor of 0.90 for the potential long-term
clogging reduction. The initial estimated values are multiplied by these three correction factors to
obtain the maximum recommended design range for the materials.
321 North 5th Avenue Engineering Analysis
Bozeman, Montana Page 16
Material
Description
Ksat - Original
(inch/min) CFV CFT CFM
Ksat -
Corrected
(inch/min)
Corrected
Infiltration Rate
(min/inch)
Clayey GRAVEL
with Sand 0.17 0.80 0.75 0.90 0.07 14.66
Infiltration rates are commonly reported using inches per hour (in/hr). When converted, the
corrected infiltration rate noted above is 4 in/hr. Montana Department of Environmental Quality
(DEQ) Circular 8 requires the measured/calculated infiltration rate to be divided by a factor of safety
of two to arrive at a design infiltration rate. The design infiltration rate for the site is 2 in/hr. Based on
Table 2 of in DEQ Circular 8, this result is similar to suggested design infiltration rates for “gravel,
gravelly sand, or very coarse sand” with a value of 2.6 in/hr. The calculated infiltration rate is less
than the DEQ Circular 8 table values, which is expected due to the clay content in the subsurface
gravel.
321 North 5th Avenue Recommendations
Bozeman, Montana Page 17
5.0 RECOMMENDATIONS
5.1 Site Grading and Excavations
1. All topsoil and organic material, asphalt, concrete and related construction debris
should be removed from the proposed building and pavement areas and any areas
to receive site grading fill.
2. All fill and backfill should be non-expansive, free of organics and debris and should
be approved by the project geotechnical engineer. The on-site soils, exclusive of
topsoil and any existing fill materials containing construction debris, are suitable for
use as backfill outside of the building footprint and general site grading fill on this
project, provided they are moisture conditioned to levels which are conducive to
compaction.
All fill should be placed in uniform lifts not exceeding 8 inches in thickness for fine-
grained soils and not exceeding 12 inches for granular soils. All materials
compacted using hand compaction methods or small walk-behind units should
utilize a maximum lift thickness of 6 inches to ensure adequate compaction
throughout the lift. All fill and backfill shall be moisture conditioned to near the
optimum moisture content and compacted to the following percentages of the
maximum dry density determined by a standard proctor test which is outlined by
ASTM D698 or equivalent (e.g. ASTM D4253-D4254).
a) Below Foundations or Spread Footings (EAP Improved) ............ N/A
b) Subgrade Below Interior Slabs .................................................... 95%
c) Structural Fill Below Interior Slabs ............................................. 98%†
d) Foundation Wall Backfill or Below Exterior Flatwork .................. 95%
e) Below Streets, Parking Lots, or Other Paved Areas ................... 95%
f) General Landscaping or Nonstructural Areas .............................. 92%
g) Utility Trench Backfill, To Within 2 Feet of Surface..................... 95%
† Unless otherwise specified by EAP Designer of Record
For your consideration, verification of compaction requires laboratory proctor tests to
be performed on a representative sample of the soil prior to construction. These
tests can require up to one week to complete (depending on laboratory backlog) and
this should be considered when coordinating the construction schedule to ensure
that delays in construction or additional testing expense is not required due to
laboratory processing times or rush processing fees.
3. Imported structural fill should be non-expansive, free of organics and debris, and
conform to the material requirements outlined in Section 02234 of the Montana
321 North 5th Avenue Recommendations
Bozeman, Montana Page 18
Public Works Standard Specifications (MPWSS). All gradations outlined in this
standard are acceptable for use on this project; however, conventional proctor
methods (outlined in ASTM D698) shall not be used for any materials containing
less than 70 percent passing the ¾-inch sieve. Conventional proctor methods are
not suitable for these types of materials, and the field compaction value must be
determined using a relative density test outlined in ASTM D4253-4254.
4. Develop and maintain site grades which will rapidly drain surface and roof runoff
away from foundation and subgrade soils; both during and after construction. The
final site grading shall conform to the grading plan, prepared by others to satisfy the
minimum requirements of the applicable building codes.
5. At a minimum, downspouts from roof drains should discharge at least six feet away
from the foundation or beyond the limits of foundation backfill, whichever is greater.
All downspout discharge areas should be properly graded away from the structure to
promote drainage and prevent ponding.
Downspouts which will discharge directly onto relatively impervious surface (i.e.
asphalt or concrete) may discharge no less than 12 inches from the foundation wall
provided the impervious surfacing is properly graded away from the structure and
continuous within a minimum distance of six feet.
6. Site utilities should be installed with proper bedding in accordance with pipe
manufacturer’s requirements.
7. It is the responsibility of the Contractor to provide safe working conditions in
connection with underground excavations. Temporary construction excavations
greater than four feet in depth, which workers will enter, will be governed by OSHA
guidelines given in 29 CFR, Part 1926. The contractor is responsible to provide an
OSHA knowledgeable individual during all excavation activities to regularly assess
the soil conditions and ensure that all necessary safety precautions are
implemented and followed.
5.2 Conventional Shallow Foundations on EAP Improved Soils
The native soils are not suitable for the support of large bearing pressures associated with multi-
story construction without significant subsurface improvement. Based on the depth of soft
compressible clays, conventional over-excavation and replacement options are not anticipated to be
conducive to the overall cost of the project; thus, the use of engineered aggregate pier (EAP)
system is recommended to achieve higher design bearing pressures and improved foundation
performance. The EAP system design must be performed by a licensed design/build contractor
experienced with such construction. The recommendations below are intended to be preliminary
321 North 5th Avenue Recommendations
Bozeman, Montana Page 19
guidelines based on our experience with this system. These recommendations shall not be utilized
for final design of the foundation system without being verified by a licensed EAP designer.
8. Both interior and exterior footings should bear on EAP improved soils and be
designed using the maximum allowable bearing pressure to be issued by the EAP
designer. For preliminary planning purposes, maximum allowable soil bearing
pressures of 4,000 to 6,000 psf are typical for these systems. EAP elements are
anticipated to be up to 30 inches in diameter with depths extending to the native
gravels; however, EAP sizes will be specified by the designer of record based on
their analysis. Any compacted gravel specified by the EAP designer as a capping
substrate shall be compacted and installed per the EAP designer requirements.
9. Footings shall be sized to satisfy the minimum requirements of the applicable
building codes while not exceeding the maximum allowable bearing pressure
provided by the EAP designer.
10. Exterior footings and footings beneath unheated areas should be placed at least 48
inches below finished exterior grade for frost protection.
11. Lateral loads are resisted by sliding friction between the footing base and the
supporting soil and by lateral pressure against the footings opposing movement.
For preliminary design purposes, our experience indicates that a friction coefficient
of 0.5 is typical of EAP improved soils; however, this value shall be verified by the
EAP designer during the final design process. A lateral resistance pressure of 150
psf per foot of depth is appropriate for backfill consisting of properly moisture
conditioned and compacted native clays.
12. The EAP designer should consider the impacts of the vibration associated with EAP
installation and the additional lateral stress created on the existing structures which
surround the site. Pre-construction surveys of the existing structures should be
considered to document existing conditions.
13. The EAP designer / installer shall provide their own internal quality control system
and foundation installation certification.
5.3 Foundation and Retaining Walls
Currently, we are not aware of plans to incorporate a basement, crawlspace, or the need for exterior
site grading retaining walls. We can provide the appropriate lateral design parameters upon
request if these elements are needed. The following recommendations are intended to address
backfill components along conventional foundation walls.
321 North 5th Avenue Recommendations
Bozeman, Montana Page 20
14. Backfill should be selected, placed, and compacted per Item 2c above. Care should
be taken not to over-compact the backfill since this could cause excessive lateral
pressure on the walls. Only hand-operated compaction equipment should be used
within 5 feet of retaining and foundation walls.
15. Exterior footing drains are not required for this project based on our understanding
that conventional slab-on-grade construction is planned and that no basement,
crawlspace, or other below grade components are planned. In accordance with
applicable building codes, if the design will include a crawlspace, basement, or if
interior finished floor elevation will be lower than exterior grade at any location, a
foundation drain system will be required and we can provide a typical detail for the
recommended construction.
5.4 Floor Slabs and Exterior Flatwork
16. For normally loaded, exterior concrete flatwork, a typical cushion course consisting
of free-draining, crushed gravel should be placed beneath the concrete and
compacted to the requirements of Item 2c above. A cushion course thickness of six
inches is typically utilized but requirements may vary locally.
Conventional construction, as has been described, is not intended to mitigate
settlement concerns associated with the subsurface conditions encountered. In most
cases, the cost to repair and/or replace exterior flatwork when excessive
movements occur is far more economical than efforts to mitigate these movements.
However, any exterior flatwork which is especially sensitive to vertical movement or
those which would be a significant cost to replace or have detrimental impacts to the
facility operation should consider additional subsurface improvements as
recommended in Item 17 below.
17. For normally loaded, interior slab-on-grade construction, a minimum of 18 inches
structural fill should be placed beneath the slabs to the desired building elevation
and compacted to the requirements of Item 2b above. Prior to gravel installation,
the clay subgrade should be cleared of all loose soil and debris, compacted to the
requirements of Item 2a above, and overlain by a separation geotextile consisting of
a Mirafi RS380i, or equivalent, installed in accordance with all manufacturer
recommendations. Should compaction be deemed unattainable by a representative
of the geotechnical engineer, the prepared subgrade shall, at a minimum, be cleared
of all loose soil debris and smooth rolled (static methods only).
A thin cushion course may also be incorporated directly beneath the concrete slab
at the discretion of the designer or contractor. Such materials are easier to fine
grade and more conducive to the installation of interior plumbing and utilities.
321 North 5th Avenue Recommendations
Bozeman, Montana Page 21
18. Cushion course materials utilized beneath slab-on-grade applications should
conform to the requirements outlined in Section 02235 of the Montana Public Works
Standard Specifications (MPWSS). All gradation outlined in this specification are
acceptable for this application. Prior to placing the cushion course, the upper six
inches of subgrade should be compacted per Item 2.
19. Concrete floor slabs should be designed using a modulus of vertical subgrade
reaction no greater than 150 pci when designed and constructed as recommended
above.
20. Geotechnically, an underslab vapor barrier is not required for this project. A vapor
barrier is normally used to limit the migration of soil gas and moisture into occupied
spaces through floor slabs. The need for a vapor barrier should be determined by
the architect and/or structural engineer based on interior improvements and/or
moisture and gas control requirements.
21. Alternative subgrade improvement systems utilizing EAPs may be economical when
similar systems are utilized beneath foundation systems and can be discussed with
the EAP designer.
5.5 Pavements
22. The following pavement section or an approved equivalent section should be
selected in accordance with the discussions in the Engineering Analysis.
Pavement Component Component Thickness
Asphaltic Concrete Pavement 3”
Crushed Base Course 6”
Crushed Subbase Course 12”
Total 21”
23. Final pavement thicknesses exceeding 3 inches shall be constructed in two uniform
lifts.
24. Crushed base courses shall conform to the material properties outlined in Section
02235 of the Montana Public Works Standard Specifications (MPWSS). All
gradations outlined in this specification are acceptable for this application based on
the local availability and contractor preference.
321 North 5th Avenue Recommendations
Bozeman, Montana Page 22
Crushed subbase courses shall conform to material properties outlined in Section
02234 of the MPWSS. All gradations outlined in this specification are acceptable for
this application based on local availability and contractor preference.
25. Where the existing grades will be raised more than the thickness of the pavement
section, all fill should be placed, compacted and meet the general requirements
given in Item 2 above.
26. A geotextile is recommended between the pavement section and the prepared
subgrade to prevent the migration of fines upward into the gravel and the loss of
aggregate into the subgrade. A Mirafi HP 270 or equivalent geotextile is appropriate
for a separation geotextile only.
27. Ideally, the asphaltic cement should be a Performance Graded (PG) binder having
the following minimum high and low temperature values based on the desired
pavement reliability.
Reliability Min. High
Temp Rating
Min. Low
Temp Rating Ideal Oil Grade
50% 35.8 -30.6 PG 52-34
98% 39.8 -39.4 PG 52-40
In our experience, neither of the oil grades summarized above are available through
local suppliers and would result in additional costs associated with importing
specialized products. Thus, for this project the use of a PG 58-28 grade oil is
recommended as this product is locally available through asphalt suppliers and will
provide the highest reliability level without the added expense of importing
specialized products.
5.6 On-Site Infiltration
28. Infiltration features should be designed based on the following infiltration rate
determined through gradation analysis of the native gravel sample.
Anticipated Pond
Bottom Material
Recommended Design
Infiltration Rate
Clayey GRAVEL
with Sand 2 in/hr
5.7 Continuing Services
Three additional elements of geotechnical engineering service are important to the successful
completion of this project.
321 North 5th Avenue Recommendations
Bozeman, Montana Page 23
29. Consultation between the geotechnical engineer and the design professionals
during the design phases is highly recommended. This is important to ensure that
the intentions of our recommendations are incorporated into the design, and that
any changes in the design concept consider the geotechnical limitations dictated by
the on-site subsurface soil and ground water conditions.
30. Observation, monitoring, and testing during construction is required to document the
successful completion of all earthwork and foundation phases. A geotechnical
engineer from our firm should be retained to observe the excavation, earthwork, and
foundation phases of the work to determine that subsurface conditions are
compatible with those used in the analysis and design.
31. During site grading, placement of all fill and backfill should be observed and tested
to confirm that the specified density has been achieved. We recommend that the
Owner maintain control of the construction quality control by retaining the services of
an experienced construction materials testing laboratory. We are available to
provide construction inspection services as well as materials testing of compacted
soils and the placement of Portland cement concrete and asphalt. In the absence of
project specific testing frequencies, TD&H recommends the following minimum
testing frequencies be used:
Compaction Testing
Beneath Column Footings 1 Test per Footing per Lift
Beneath Wall Footings 1 Test per 50 LF of Wall per Lift
Beneath Slabs 1 Test per 1,500 SF per Lift
Foundation Backfill 1 Test per 100 LF of Wall per Lift
Parking Lot & Access Roads 1 Test per 2,500 SF per Lift
LF = Lineal Feet SF = Square Feet
321 North 5th Avenue Summary of Field & Laboratory Studies
Bozeman, Montana Page 24
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES
6.1 Field Explorations
The field exploration program was conducted on August 9, 2023. Three borings were drilled to
depths ranging from 21.0 to 21.5 feet at the locations shown on Figure 1 to observe subsurface soil
and ground water conditions. The borings were advanced through the subsurface soils using a
truck-mounted Mobile B60X drill rig equipped with 4.25-inch I.D. hollowstem augers. The
subsurface exploration and sampling methods used are indicated on the attached boring logs. The
borings were logged by Mr. Nic Couch, EI of TD&H Engineering.
Samples of the subsurface materials were taken using 1⅜-inch I.D. split spoon samplers. The
samplers were driven 18 inches, when possible, into the various strata using a 140-pound drop
hammer falling 30 inches onto the drill rods. For each sample, the number of blows required to
advance the sampler each successive six-inch increment was recorded, and the total number of
blows required to advance the sampler the final 12 inches is termed the penetration resistance (“N-
value”). This test is known as the Standard Penetration Test (SPT) described by ASTM D1586.
Penetration resistance values indicate the relative density of granular soils and the relative
consistency of fine-grained soils. Samples were also obtained by hydraulically pushing a 3-inch
I.D., thin-walled Shelby tube sampler into the subsoils. Logs of all soil borings which include soil
descriptions, sample depths, and penetration resistance values, are presented on the Figures 2
through 4.
Measurements to determine the presence and depth of ground water were made in the borings by
lowering an electronic water sounder through the open boring or auger shortly after the completion
of drilling. The depths or elevations of the water levels measured, if encountered, and the date of
measurement are shown on the boring logs.
6.2 Laboratory Testing
Samples obtained during the field exploration were returned to our materials laboratory where they
were observed and visually classified in general accordance with ASTM D2487, which is based on
the Unified Soil Classification System. Representative samples were selected for testing to
determine the engineering and physical properties of the soils in general accordance with ASTM or
other approved procedures.
Tests Conducted: To determine:
Natural Moisture Content Representative moisture content of soil at the time of
sampling.
Grain-Size Distribution Particle size distribution of soil constituents describing the
percentages of clay/silt, sand and gravel.
321 North 5th Avenue Summary of Field & Laboratory Studies
Bozeman, Montana Page 25
Atterberg Limits A method of describing the effect of varying water content on
the consistency and behavior of fine-grained soils.
Consolidation Measurements of the percent compression experienced
under various loading conditions. For use in settlement
analysis and foundation design.
Unconfined Compression Undrained shear strength properties of cohesive soils
determined in the laboratory by axial compression.
The laboratory testing program for this project consisted of 24 moisture-visual analyses, 2 sieve
(grain-size distribution) analyses, and 2 Atterberg Limits analyses. The results of the water content
analyses are presented on the boring logs, Figures 2 through 4. The grain-size distribution curves
and Atterberg limits are presented on Figures 5 through 8. In addition, one unconfined compression
and two consolidation tests were performed and are presented on Figures 9 through 11.
321 North 5th Avenue Limitations
Bozeman, Montana Page 26
7.0 LIMITATIONS
This report has been prepared in accordance with generally accepted geotechnical engineering
practices in this area for use by the client for design purposes. The findings, analyses, and
recommendations contained in this report reflect our professional opinion regarding potential
impacts the subsurface conditions may have on the proposed project and are based on site
conditions encountered. Our analysis assumes that the results of the exploratory borings are
representative of the subsurface conditions throughout the site, that is, that the subsurface
conditions everywhere are not significantly different from those disclosed by the subsurface study.
Unanticipated soil conditions are commonly encountered and cannot be fully determined by a
limited number of soil borings and laboratory analyses. Such unexpected conditions frequently
require that some additional expenditures be made to obtain a properly constructed project.
Therefore, some contingency fund is recommended to accommodate such potential extra costs.
The recommendations contained within this report are based on the subsurface conditions
observed in the borings and are subject to change pending observation of the actual subsurface
conditions encountered during construction. TD&H cannot assume responsibility or liability for the
recommendations provided if we are not provided the opportunity to perform limited construction
inspection and confirm the engineering assumptions made during our analysis. A representative of
TD&H should be retained to observe all construction activities associated with subgrade
preparation, foundations, and other geotechnical aspects of the project to ensure the conditions
encountered are consistent with our assumptions. Unforeseen conditions or undisclosed changes
to the project parameters or site conditions may warrant modification to the project
recommendations.
Long delays between the geotechnical investigation and the start of construction increase the
potential for changes to the site and subsurface conditions which could impact the applicability of
the recommendations provided. If site conditions have changed because of natural causes or
construction operations at or adjacent to the site, TD&H should be retained to review the contents of
this report to determine the applicability of the conclusions and recommendations provide
considering the time lapse or changed conditions.
Misinterpretation of the geotechnical information by other design team members is possible and can
result in costly issues during construction and with the final product. Our geotechnical engineers
are available upon request to review those portions of the plans and specifications which pertain to
earthwork and foundations to determine if they are consistent with our recommendations and to
suggest necessary modifications as warranted. This service was not included in the original scope
of the project and will require additional fees for the time required for specification and plan
document review and comment. In addition, TD&H should be involved throughout the construction
process to observe construction, particularly the placement and compaction of all fill, preparation of
all foundations, and all other geotechnical aspects. Retaining the geotechnical engineer who
prepared your geotechnical report to provide construction observation is the most effective method
of managing the risks associated with unanticipated conditions.
321 North 5th Avenue Limitations
Bozeman, Montana Page 27
This report was prepared for the exclusive use of the owner and architect and/or engineer in the
design of the subject facility. It should be made available to prospective contractors and/or the
contractor for information on factual data only and not as a warranty of subsurface conditions such
as those interpreted from the boring logs and presented in discussions of subsurface conditions
included in this report.
Prepared by: Reviewed by:
Nic Couch EI Kyle Scarr PE & Principal
Geotechnical Engineer Regional Manager
TD&H ENGINEERING TD&H ENGINEERING
LEGEND
APPROXIMATE BORING LOCATION
MW GROUNDWATER MONITORING WELL
NOTES:
THE LOCATIONS OF THE BORINGS ARE APPROXIMATE AND ARE
NOT SURVEYED MARKINGS. LOCATIONS ARE TO BE USED FOR
GENERAL REFERENCE ONLY. 321 NORTH 5TH AVENUE BOZEMAN, MONTANA APPROXIMATE BORING LOCATION MAP FIGURE 1
B-1 (MW)
B-2 (MW)
B-3 (MW)
NO
SCALE
NCC
KLS
09.15.2023
B23-066
B23-066 FIGURE
0
2
4
6
8
10
12
14
Asphalt PAVEMENT
Poorly-Graded GRAVEL with Clay and Sand,
relatively dense, dark brown, moist, base course
Lean CLAY, firm, light brown, moist, trace sand
- Soft and brown to light brown below 5.0 feet
- See Figures 9 and 10 for Unconfined Compression
and Consolidation Test Results
- See Figure 11 for Consolidation Test Result
Poorly-Graded GRAVEL with Clay and Sand,
medium dense, brown, moist to wet
0.5
1.0
13.3
4-4-4
PUSH
2-2-2
PUSH
2-2-15
T
T
LEGEND LOG OF SOIL BORING B-1SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.2
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Asphalt Surfacing
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
1 of 2
16
18
20
22
24
26
28
Clayey GRAVEL with Sand, very dense, brown, wet
Bottom of Boring (Groundwater Monitoring Well
Installed Following Completion)
- Screen from 20.0 to 10.0 feet
- Sand from 20.0 to 10.0 feet
- Bentonite from 10.0 to 1.5 feet
- Completed with Flush Mount Top
18.3
21.0
13-15-
12
12-50/
6"50/6"
LEGEND LOG OF SOIL BORING B-1SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.2
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Asphalt Surfacing
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
2 of 2
0
2
4
6
8
10
12
14
TOPSOIL: Lean CLAY, firm, dark brown, moist,
organics, some black
Lean CLAY, firm to soft, light brown, moist, some
sand
3.0
3-4-2
3-3-4
2-2-3
1-2-2
0-2-2
LEGEND LOG OF SOIL BORING B-2SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.3
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Sodded Lawn
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
1 of 2
16
18
20
22
24
26
28
Poorly-Graded SAND, medium dense, brown, moist
to wet, some gravel, trace clay
Clayey GRAVEL with Sand, dense, brown, wet
Bottom of Boring
- Screen from 20.0 to 10.0 feet
- Sand from 20.0 to 10.0 feet
- Bentonite from 10.0 to 1.0 feet
- Completed with Flush Mount Top
16.2
18.0
21.5
2-3-7
23-20-
24
LEGEND LOG OF SOIL BORING B-2SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.3
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Sodded Lawn
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
2 of 2
0
2
4
6
8
10
12
14
FILL: Sandy Lean CLAY, firm to stiff, dark brown,
moist, sporadic gravel mixed with topsoil
Lean CLAY, soft to firm, light brown to brown, moist,
trace sand
- Slight increase in sand below 10.0 feet
3.3
5-6-5
3-3-3
2-2-2
2-2-3
0-3-4
LEGEND LOG OF SOIL BORING B-3SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.4
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Unmaintained Sodded Lawn(Long Grass)
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
1 of 2
16
18
20
22
24
26
28
Poorly-Graded GRAVEL with Clay and Sand, dense
to medium dense, brown, moist to wet
Bottom of Boring (Groundwater Monitoring Well
Installed Following Completion)
- Screen from 20.0 to 10.0 feet
- Sand from 20.0 to 10.0 feet
- Bentonite from 10.0 to 1.5 feet
- Completed with Flush Mount Top
15.5
21.5
6-21-20
8-11-14
LEGEND LOG OF SOIL BORING B-3SPT blows per foot Atterberg Limits
Field Moisture content 321 North 5th Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
1-3/8-inch I.D. split spoon Logged by:Nic Couch, EI
2-1/2-inch I.D. split spoon Drilled by:O'Keefe Drilling
Truck-Mounted Mobile B60X with 4.25-inch I.D. HSA2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic
3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
August 9, 2023 B23-066-001
No sample recovery Figure No.4
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Unmaintained Sodded Lawn(Long Grass)
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSPT BLOWCOUNTSSAMPLEDEPTH (FT)PENETRATION RESISTANCE/MOISTURE CONTENT
0 10 20 30 40 50
= BLOWS PER FOOT
= MOISTURE CONTENT
2 of 2
Tested By: BC Checked By:
Particle Size Distribution Report
ASTM C117 & C136
PERCENT FINER0
10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.00010.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 0.0 0.2 0.1 0.7 3.8 95.26 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM C117 & C136)Material Description
Atterberg Limits
Coefficients
Classification
Test Remarks
Sample Date:Location: B-1
Sample Number: A-28381 Depth: 7.0 - 8.5 ft
Client:
Project:
Project No:Figure
Sieve Size
or
Diam. (mm.)
Finer
(%)
Spec.*
(%)
Out of
Spec.
(%)
Pct.
of
Fines
Lean CLAY
3/8"
#4
#10
#20
#40
#60
#80
#100
#200
100.0
99.8
99.7
99.5
99.0
98.6
98.2
97.9
95.2
21 35 14
CL A-6(14)
Report No. A-28381-206
Report Date: 8-24-2023
F.M.=0.05
8-9-2023
5th & Villard Apartments, LLC
321 North 5th Avenue
Bozeman, Montana
B23-066-001
PL= LL= PI=
D90= D85= D60=
D50= D30= D15=
D10= Cu= Cc=
USCS= AASHTO=
*(no specification provided)
5
Tested By: BC Checked By:
Particle Size Distribution Report
ASTM C117 & C136
PERCENT FINER0
10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.00010.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 13.2 32.4 11.4 13.1 12.3 17.66 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM C117 & C136)Material Description
Atterberg Limits
Coefficients
Classification
Test Remarks
Sample Date:Location: B-1 & B-2Sample Number: A-28386COMP Depth: 20.0 - 21.5 ft
Client:
Project:
Project No: Figure
Sieve Size
or
Diam. (mm.)
Finer
(%)
Spec.*
(%)
Out of
Spec.
(%)
Pct.
of
Fines
Clayey GRAVEL with Sand
1.5"
1"
3/4"
1/2"3/8"#4#10#20#40
#60
#80
#100
#200
100.0
95.3
86.8
74.766.054.443.035.329.9
26.1
23.7
22.3
17.6
Not Tested Not Tested Not Tested
21.0525 17.9019 6.97763.5038 0.4316
GC
Report No. A-28386COMP-206
Report Date: 8-25-2023
8-9-2023
5th & Villard Apartments, LLC
321 North 5th Avenue
Bozeman, Montana
B23-066-001
PL= LL= PI=
D90= D85= D60=D50= D30= D15=D10= Cu= Cc=
USCS= AASHTO=
*(no specification provided)
6
Tested By: WJC Checked By:
LIQUID AND PLASTIC LIMITS TEST REPORT
PLASTICITY INDEX0
10
20
30
40
50
60
LIQUID LIMIT
0 10 20 30 40 50 60 70 80 90 100 110
CL-ML
C L o r O L
C H o r O H
ML or OL MH or OH
Dashed line indicates the approximate
upper limit boundary for natural soils
47
WATER CONTENT33
33.5
34
34.5
35
35.5
36
36.5
37
37.5
38
NUMBER OF BLOWS
5 6 7 8 9 10 20 25 30 40
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
Project No. Client:Remarks:
Project:
Location: B-1
Sample Number: A-28381 Depth: 7.0 - 8.5 ft
Figure
Lean CLAY 35 21 14 99.0 95.2 CL
B23-066-001 5th & Villard Apartments, LLC
7
Report No. A-28381-207
Report Date: 8-29-2023321 North 5th Avenue
Bozeman, Montana
Tested By: WJC Checked By:
LIQUID AND PLASTIC LIMITS TEST REPORT
PLASTICITY INDEX0
10
20
30
40
50
60
LIQUID LIMIT
0 10 20 30 40 50 60 70 80 90 100 110
CL-ML
C L o r O L
C H o r O H
ML or OL MH or OH
Dashed line indicates the approximate
upper limit boundary for natural soils
47
WATER CONTENT32.2
32.6
33
33.4
33.8
34.2
34.6
35
35.4
35.8
36.2
NUMBER OF BLOWS
5 6 7 8 9 10 20 25 30 40
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
Project No. Client:Remarks:
Project:
Location: B-3
Sample Number: A-28398 Depth: 5.0 - 6.5 ft
Figure
Lean CLAY 34 22 12 Not Tested Not Tested CL
B23-066-001 5th & Villard Apartments, LLC
8
Report No. A-28398-207
Report Date: 8-29-2023321 North 5th Avenue
Bozeman, Montana
Tested By: CRN Checked By:
UNCONFINED COMPRESSION TEST
Project No.: B23-066-001
Date Sampled: 8-9-2023
Remarks:
Report No. A-2880-215
Report Date: 8-25-2023
Figure 9
Client:5th & Villard Apartments, LLC
Project:321 North 5th Avenue
Bozeman, Montana
Location: B-1
Sample Number: A-28380 Depth: 5.0 - 7.0 ft
Description: Lean CLAY
LL = Not Tested PI = Not TestedPL = Assumed GS= 2.7 Type: Shelby Tube
Sample No.
Unconfined strength, psf
Undrained shear strength, psf
Failure strain, %
Strain rate, in./min.
Water content, %
Wet density, pcf
Dry density, pcf
Saturation, %
Void ratio
Specimen diameter, in.
Specimen height, in.
Height/diameter ratio
1
2070
1035
4.3
0.039
24.4
119.4
96.0
87.3
0.7562
2.85
5.54
1.94Compressive Stress, psf0
1000
2000
3000
4000
Axial Strain, %
0 1.5 3 4.5 6
1
Tested By: CRN Checked By:
CONSOLIDATION TEST REPORT
Percent Strain9
8
7
6
5
4
3
2
1
0
-1
Applied Pressure - psf
100 1000 10000
Natural Dry Dens.LL PI
Sp. Overburden Pc Cc Cr Swell Press.Swell
%eoSat. Moist.
(pcf) Gr. (psf) (psf) (psf)
82.5 % 24.4 % 93.7 Not Not 2.7 700 3084 0.14 0.01 0.798
Lean CLAY CL
B23-066- 5th & Villard Apartments, LLC
321 North 5th Avenue
Bozeman, Montana
Report No. A-28380-219
Report Date: 8-25-2023
10
MATERIAL DESCRIPTION USCS AASHTO
Project No. Client:Remarks:
Project:
Location: B-1 Depth: 5.0 - 7.0 ft Sample Number: A-28380
Figure
Tested By: CRN Checked By:
CONSOLIDATION TEST REPORT
Percent Strain9
8
7
6
5
4
3
2
1
0
-1
Applied Pressure - psf
100 1000 10000
Natural Dry Dens.LL PI
Sp. Overburden Pc Cc Cr Swell Press.Swell
%eoSat. Moist.
(pcf) Gr. (psf) (psf) (psf)
70.4 % 22.5 % 90.5 Not Not 2.7 1250 3436 0.18 0.02 0.862
Lean CLAY CL
B23-066- 5th & Villard Apartments, LLC
321 North 5th Avenue
Bozeman, Montana
Report No. A-28382-219
Report Date: 8-25-2023
11
MATERIAL DESCRIPTION USCS AASHTO
Project No. Client:Remarks:
Project:
Location: B-1 Depth: 10.0 - 12.0 ft Sample Number: A-28382
Figure
General Project Information
Project Number: B23-066
Project Title: 321 North 5th Avenue
Project Description:
Climatic Data Source (MERRA)
Latitude, Degree: 45.68267
Longitude, Degree: -111.04442
Climatic Data
Lowest Yearly Air Temperature, ºC: -40.90
Low Air Temp Standard Deviation, ºC: 5.19
Yearly Degree-Days > 10 Deg. ºC: 1656.66
High Air Temperature of high 7 days: 28.91
Standard Dev. of the high 7 days: 2.01
Low Pavement Temperature 50%: -30.50
Low Pavement Temperature 98%: -39.30
High Avg Pavement Temperature of 7 Days 50%: 50.90
High Avg Pavement Temperature of 7 Days 98%: 55.06
Target Rut Depth
Target Rut Depth (mm): 16.5
Temperature Adjustments
Depth of Layer, mm: 0
Base HT PG: 52
Traffic Adjustments
Traffic loading Cumulative ESAL for the Design Period, Millions: 0.1
Traffic Speed (Fast: >70 km/h, Slow: 20-70 km/h, Standing: < 20 km/h): Standing
Performance Grade
AASHTO M320-10 Performance-Graded Asphalt Binder
PG Temperature High Low
Performance Grade Temperature at 50% Reliability 35.8 -30.6
Performance Grade Temperature at 98% Reliability 39.8 -39.4
Adjustment for Traffic (AASHTO M323-13)2.8
Adjustment for Depth 0.0 -0.0
Adjusted Performance Grade Temperature 42.6 -39.4
Selected PG Grade 52 -40
PG Grade M323, PG 52-40