HomeMy WebLinkAbout009 Appendix E - GEOTECH REPORTMONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
JOB NO. B25-083 February 2026
REPORT OF GEOTECHNICAL INVESTIGATION
`
CLIENT ENGINEER
Intrinsik Architecture, Inc
106. E Babcock St, Ste 1A
Bozeman, MT 59715
Craig Nadeau, PE
Craig.nadeau@tdhengineering.com
REPORT OF GEOTECHNICAL INVESTIGATION 785 BOARDWALK AVENUE - FERGUSON
FARMS DEVELOPMENT
406.586.0277
tdhengineering.com
234 East Babcock, Suite 3
Bozeman, MT 59715
785 BOARDWALK AVENUE – FERGUSON FARMS DEVELOPMENT
BOZEMAN, MONTANA
785 Boardwalk Avenue - Ferguson Farms Development Table of Contents Bozeman, Montana i
Table of Contents
1.0 EXECUTIVE SUMMARY ......................................................................................................... 1
2.0 INTRODUCTION ..................................................................................................................... 2
2.1 Purpose and Scope .......................................................................................................... 2
2.2 Project Description ........................................................................................................... 2
3.0 SITE CONDITIONS ................................................................................................................. 3
3.1 Geology and Physiography .............................................................................................. 3
3.2 Surface Conditions ........................................................................................................... 4
3.3 Subsurface Conditions ..................................................................................................... 5
3.3.1 Soils ......................................................................................................................... 5
3.3.2 Ground Water ......................................................................................................... 5
4.0 ENGINEERING ANALYSIS .................................................................................................... 6
4.1 Introduction ....................................................................................................................... 6
4.2 Site Grading and Excavations.......................................................................................... 6
4.3 Conventional Shallow Foundations ................................................................................. 6
4.4 Foundation and Retaining Walls ...................................................................................... 7
4.5 Interior Floor Slabs ........................................................................................................... 8
4.6 Exterior Flatwork .............................................................................................................. 8
5.0 RECOMMENDATIONS ........................................................................................................... 9
5.1 Site Grading and Excavations.......................................................................................... 9
5.2 Conventional Shallow Foundations ............................................................................... 10
5.3 Foundation and Retaining Walls .................................................................................... 12
5.4 Interior Floor Slabs ......................................................................................................... 13
5.5 Exterior Flatwork ............................................................................................................ 13
5.6 Continuing Services ....................................................................................................... 14
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES ....................................................... 15
6.1 Field Explorations ........................................................................................................... 15
6.2 Laboratory Testing ......................................................................................................... 15
7.0 LIMITATIONS ........................................................................................................................ 16
785 Boardwalk Avenue - Ferguson Farms Development Appendix Bozeman, Montana ii
APPENDIX
♦ Test Pit Location Map (Figure 1)
♦ Logs of Exploratory Test Pits (Figures 2 through 5)
♦ Laboratory Test Data (Figures 6 through 9)
♦ Soil Classification and Sampling Terminology for Engineering Purposes
♦ Classification of Soils for Engineering Purposes
785 Boardwalk Avenue - Ferguson Farms Development Executive Summary Bozeman, Montana Page 1
GEOTECHNICAL REPORT 785 BOARDWALK AVENUE – FERGUSON FARMS DEVELOPMENT
BOZEMAN MONTANA
1.0 EXECUTIVE SUMMARY
The proposed project is to be located at 785 Boardwalk Avenue in the Ferguson Farms
Development in Bozeman, Montana. The project includes construction of a two-story commercial
use structure with a footprint of approximately 7,300 square feet and gross floor area of
approximately 14,300 square feet combined over two floors. Additional project development is
anticipated to be limited to exterior concrete flatwork. The area surrounding the proposed building
site is largely developed including asphalt pavement parking and accessways; therefore,
geotechnical recommendations regarding road or parking sections have not been included within
the scope of work for this project.
Geotechnically, the site conditions encountered pose no substantial concern for the planned
construction. The native gravels and the overlying gravel fill encountered on site will be superior
bearing strata for foundations, except for a top zone which has been impacted by weed growth and
warrants removal. Gravel materials like those present have high allowable bearing capacities and
low settlement risk. Footings bearing on compacted structural fill extending to in-situ gravels which
are free of excessive organic material may be designed using a maximum allowable bearing
pressure of 4,000 psf and may consider a one-third increase in this design pressure for use in
dynamic load cases provided the recommendations included in this report are followed. Detailed
recommendations and preparations for shallow foundations are provided in this report.
The surface soils overlying the native gravels consist of a previously constructed gravel pad using
material of an unknown origin, likely associated with initial development of the surrounding area.
Although the material appears dense and competent, it has been impacted by significant weed
growth since its initial placement, with dense roots and organic material extending approximately 18
inches below the existing pad surface. Due to the presence of this organic material, it is anticipated
that up to 18 inches of the gravel fill will have to be stripped and replaced as part of construction.
This is intended to help minimize the potential for post-construction settlement due to the long-term
decomposition of organic material. At a minimum, the removal of this highly organic zone should be
performed within the building footprint. Existing organics can remain outside the building footprint at
the discretion of the Owner but can exacerbate potential long-term settlements of site features
resulting in inferior performance and potential increased maintenance.
785 Boardwalk Avenue - Ferguson Farms Development Introduction Bozeman, Montana Page 2
2.0 INTRODUCTION
2.1 Purpose and Scope
This report presents the results of our geotechnical study for the proposed two-story commercial
structure to be located at 785 Boardwalk Avenue in the Ferguson Farms Development. 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 excavating four test pits across the proposed site. Samples were obtained
from the test pits 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
Th proposed project is to be located at 785 Boardwalk Avenue near the corner of Boardwalk
Avenue and Huffine Lane in Bozeman, Montana. The project includes a two-story commercial office
structure with a footprint of approximately 7,300 square feet and a gross floor area of approximately
14,300 square feet. The project is anticipated to include exterior flatwork and landscaping as a part
of the overall site development.
Preliminary foundation loads have been provided to TD&H by Mr. Matt Anderson of Hyalite
Engineering. Anticipated loads include up to 4,200 pound per lineal foot for exterior wall loads, up to
2,000 pounds per lineal foot for interior wall loads, and up to 90 kips for columns. If loadings,
locations or conditions are significantly different from those described above, we should be notified
to re-evaluate the recommendations contained in this report.
785 Boardwalk Avenue - Ferguson Farms Development Site Conditions Bozeman, Montana Page 3
3.0 SITE CONDITIONS
3.1 Geology and Physiography
According to the geologic map of Montana, the site is geologically characterized as being gravels
(Qgr). This formation consists of variable deposits ranging from pebble to boulder size material,
which include variable amounts of sand, silt, and clay. They are typically alluvial terrace,
abandoned channel and floodplain, remnant alluvial fan, and local glacial outwash deposits.
Additional data provided by the geologic map of the Bozeman area suggest the formation described
above is overlain by alluvial fan deposits (Qafo) of the Pleistocene epoch. Near the project site, such
materials consist of light brown, gray, and locally reddish gray gravel in a coarse sand and granule
matrix. These gravels are known to be locally derived, angular and subangular, with clasts ranging
in size from pebbles to boulders. The thickness of these deposits is expected to be a maximum of
150 feet.
The site appears to be confined within the alluvial fan deposits; however, the surrounding geology
suggests the western portions of the site nearing braid plain alluvium (Qabo) of the Pleistocene
epoch. These deposits consist of cobble to boulder size clasts in a matrix of sand, silt, and clay.
The rounded to well-rounded clasts are most commonly composed of Archean metamorphic rock,
and dark colored volcanic rock, with subordinate Paleozoic limestone and Belt Supergroup
metasedimentary rocks. A well in this unit indicates a thickness of 30 feet of alluvium overlying
tertiary deposits. Similar conditions have been identified from nearby well logs which suggest
gravels extending to depths of at least 60 feet.
Geologic Map of Montana, Edition 1.0 (2007)
Montana Bureau of Mines & Geology
Approximate Site Location
785 Boardwalk Avenue - Ferguson Farms Development Site Conditions Bozeman, Montana Page 4
Geologic Map of the Bozeman Quadrangle, Southwestern Montana (2014)
Montana Bureau of Mines & Geology
Based on the limited depth of our subsurface investigation it is not possible to accurately define the
seismic site class or liquefaction risk of the property. Seismic site class is based on the average
soil properties within a 100-ft depth and to be determined accurately requires either deep borings or
use of alternative geophysical investigation methods. Based on the conditions observed in our
shallow test pits and those reported on the well logs available in the area, we advise that design
consider Site Class D. Further investigation using geophysical methods may allow for this site class
to be refined, and we are available to discuss this option with you if the project design may benefit
from the potential of an improved site classification. The risk of seismically induced settlement or
liquefaction within the depth of our limited investigation is low due to encountered gravel at or below
a depth of 9.5 feet and the relative density of the gravel formations; however, we have not
evaluated the presence of potentially sensitive layers at greater depth.
3.2 Surface Conditions
The proposed project site is located at 785 Boardwalk Avenue in Bozeman, Montana, and presently
consists of a gravel building pad and asphalt pavement parking lot. Based on background
information and site observations, the existing asphalt parking lot generally slopes to the north at
approximately two percent. The existing gravel pad is generally flat and sits in a depression with the
north, east, and southeast sides being approximately two to five feet below the grade of the existing
asphalt and landscaping. To the southwest and west of the pad, existing grades slope down and
away from the pad to meet drainage features and adjacent parking lots. The berms surrounding the
gravel pad, primarily to the north and east, are steep and slope down towards the gravel pad at
approximately 5 to 25 percent. The area adjacent to the prosed building site presently contains sod,
landscaping, and drainage features associated with prior development to adjacent properties.
Approximate
Site Location
785 Boardwalk Avenue - Ferguson Farms Development Site Conditions Bozeman, Montana Page 5
3.3 Subsurface Conditions
3.3.1 Soils
The subsurface soil conditions appear to be relatively consistent based on our exploratory
excavating and soil sampling. In general, the subsurface soil conditions encountered within
the test pits consist of approximately 3.3 to 3.7 feet of existing fill consisting of poorly-graded
gravel with sand underlain by native well-graded gravel with sand which extends to a depth
of at least 10 feet, the maximum depth investigated. Well logs in the area suggest these
native gravels extend to depths of at least 50 feet below the existing ground surface.
The subsurface soils are described in detail on the enclosed test pit 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.
SURFICIAL GRAVEL FILL: POORLY-GRADED GRAVEL WITH SAND
The poorly-graded gravel with sand appeared dense to very dense based on observed
excavation effort. The fill appears to have been in place and exposed to the elements for
since the original development and has developed an abundance of weed growth with roots
and other organics extending to depths of approximately 18 inches across the building pad.
A sample of this material contained 74.3 percent gravel, 21.1 percent sand, and 4.6 percent
fine (silt and clay). The fines were determined to be granular and non-plastic. The natural
moisture contents varied from 2.7 to 3.2 percent and averaged 2.9 percent.
NATIVE GRAVEL: WELL-GRADED GRAVEL WITH SAND
The well-graded gravel with sand appeared very dense based on observed excavation
effort. A sample of this material contained 73.1 percent of cobbles and gravel, 24.2 percent
sand, and 2.7 percent fines (silt and clay). The fines within the gravel exhibited a liquid limit
of 21 percent and a plasticity index of 4 percent. The natural moisture contents varied from
3.2 to 4.4 percent and averaged 3.9 percent.
3.3.2 Ground Water
Ground water was encountered within three of the four test pits at depths ranging from 9.3
to 9.4 feet below the existing ground surface. Water levels were measured at the time of
excavation with a steel tape. 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.
785 Boardwalk Avenue - Ferguson Farms Development Engineering Analysis Bozeman, Montana Page 6
4.0 ENGINEERING ANALYSIS
4.1 Introduction
Geotechnically the site conditions encountered pose no substantial concern for the planned
construction. The poorly-graded gravel with sand fill which lies atop of the native gravels will
provide an adequate bearing strata for foundations; however, the uppermost section of the gravel fill
has developed dense roots and organic material associated with uncontrolled weed growth and will
be a concern for long-term settlement for any features built overtop the fill in its current condition.
Up to 18 inches of this material will have to be removed and replaced with properly compacted
structural fill as part of construction to mitigate this settlement risk. Similar improvements are
required beneath the building footprint, but the existing organics can remain in areas to receive site
fill and site infrastructure associated with exterior development at the discretion of the Owner. Any
areas in which the existing organics are left in place beneath the planned construction may realize
an increased risk of long-term settlements, reduced performance, and increased maintenance
needs. The native gravels encountered will be superior bearing strata for foundations with high
allowable capacities and low settlement risk.
The proposed building area is currently a prepared gravel pad which lies at approximately the
planned bottom-of-footing elevation. As a result, imported fill is anticipated to be required to raise
interior and exterior subgrades to the design elevations. Imported fill which meets the material and
placement requirements outlined in Section 5, Item 2 of this report is expected to provide adequate
support for interior and exterior concrete elements.
4.2 Site Grading and Excavations
The ground surface at the proposed building site is generally considered flat. The prepared gravel
pad for the building site is in a depression which is near the proposed bottom of footing elevation.
The area surrounding the building site slopes up steeply to meet existing parking lot and roadway
grades to the north-northwest of the pad, and slopes down and away from the gravel pad to the
south-southwest of the building site. Based on our field work, gravel with sand will be encountered
in foundation excavations to the depths anticipated. Based on the test pits, ground water should be
below the anticipated depths of footing and utility excavations; however, depending on the time of
year, occasional pockets of trapped or perched ground water associated with recent precipitation
events should be anticipated.
4.3 Conventional Shallow Foundations
Considering the subsurface conditions encountered and the nature of the proposed construction,
the structure can be supported on conventional shallow foundations bearing directly on properly
compacted structural fill extending to in-situ gravels which are free of excess organic materials. At
least 18 inches of structural fill should be anticipated across the building footprint to remove the
zone exhibiting substantial root growth due to weeds established since its original installation.
785 Boardwalk Avenue - Ferguson Farms Development Engineering Analysis Bozeman, Montana Page 7
Greater replacement depths may be warranted in localized areas and should be evaluated during
construction to address the majority of the organic material present. At a minimum, this organic
containing zone must be removed and replaced within the building footprint and at least five feet
beyond the building footprint. If the bearing surface of the native gravel exhibits protruding cobbles
and cannot be rolled smooth, a thin leveling course should be placed between the native gravels
and the concrete to mitigate potential stress concentrations. The need for this cushion course can
be eliminated through the use of a finer graded structural fill for the replacement of the surficial zone
which warrants removal due to weed growth.
Based on our experience, the theory of elasticity, and using an allowable bearing pressure of 4,000
psf, we estimate the total settlement for footings will be less than ¾-inch. Differential settlement
within the limits of the structure should be on the order of one-half this magnitude. For design
purposes, consideration of a one-third increase in the allowable bearing pressure provided is
permitted for consideration of dynamic load cases.
The lateral resistance of spread footings is controlled by a combination of sliding resistance
between the footing and the foundation material at the base of the footing and the passive earth
pressure against the side of the footing in the direction of movement. Design parameters are given
in the recommendations section of this report.
4.4 Foundation and Retaining Walls
Based on our current understanding of the structure and site development for this project, we do not
anticipate the need for any foundations or site grading retaining walls which would retain differential
soil heights. However, these design parameters may be required for some structures such as
elevator pits or other features and have been included for consideration when appropriate.
Foundation walls and other soil retaining structures will be subjected to horizontal loading due to
lateral earth pressures. The lateral earth pressures are a function of the natural and backfill soil
types and acceptable wall movements, which affect soil strain to mobilize the shear strength of the
soil. More soil movement is required to develop greater internal shear strength and lower the lateral
pressure on the wall. To fully mobilize strength and reduce lateral pressures, soil strain and
allowable wall rotation must be greater for clay soils than for cohesionless, granular soils.
The lowest lateral earth pressure against walls for a given soil type is the active condition and
develops when wall movements occur. Passive earth pressures are developed when the wall is
forced into the soil, such as at the base of a wall on the side opposite the retained earth side. When
no soil strain is allowed by the wall, this is the "at-rest" condition, which creates pressures having
magnitudes between the passive and active conditions.
The distribution of the lateral earth pressures on the structure depends on soil type and wall
movements or deflections. In most cases, a triangular pressure distribution is satisfactory for
design and is usually represented as an equivalent fluid unit weight.
785 Boardwalk Avenue - Ferguson Farms Development Engineering Analysis Bozeman, Montana Page 8
4.5 Interior Floor Slabs
Based on our understanding of the site and proposed development, the building area currently
consists of a prepared gravel pad which lies near the anticipated bottom-of-footing elevation for the
planned construction. Consequently, imported fill will be required to raise site subgrades to design
elevations. It is recommended that all interior slab-on-grade construction bear on properly
compacted structural fill throughout the fill height required. Final structural fill thickness will be
dependent on the final grading plan and finished floor elevation.
Isolated column or wall loads to be placed on the slab, or thickened portions of the slab, are
acceptable for this project when fill utilized beneath the interior slab conform with structural fill
requirements, as discussed above, and may consider the same design bearing pressures outlined.
4.6 Exterior Flatwork
Based on the proposed development, a significant quantity of fill is expected to raise exterior grades
to the final design grading. The existing building pad exhibits abundant organics within the top 18
inches of the existing gravel due to uncontrolled weed growth. For optimal performance, this heavy
organic zone should be removed and replaced beneath all areas which will receive site grading fill;
however, this organic containing zone may remain outside the building footprint at the discretion of
the Owner provided a greater long-term risk of settlement to site features is acceptable. The use of
structural fill or similar gravel as site grading fill will provide the lowest risk to exterior site features;
however, alternative fill materials may be used outside the building footprint, when available. We
have provided recommended minimum material properties, discussed in Section 5 Item 2 of the
recommendations, to be considered if alternative import sources are considered. These guidelines
are intended to prevent the import of expansive materials or those which are unsuitable due to
contamination or other deleterious materials they contain and promote reasonable performance
when placed and compacted properly.
A leveling course of granular fill directly beneath exterior concrete is recommended to provide a
structural cushion, a capillary-break from the subgrade, and a drainage medium. Construction
typically utilizes six inches of compacted granular fill beneath exterior concrete; however, the
requirements may vary locally. This minimum cushion course thickness is considered sufficient
provided it and all underlying fill are properly compacted and were placed appropriately in
accordance with our recommendations as well as all applicable building code requirements. The
amount of risk will be directly related to the quality of fill and compaction utilized for this project.
Structural fill, or similar compacted gravel, will provide the lowest overall risk when properly placed;
however, alternative materials may be available and when utilized should comply with the
recommended material properties provided.
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 9
5.0 RECOMMENDATIONS
5.1 Site Grading and Excavations
1. All topsoil and organic-laden gravel fill should be removed and replaced from
beneath the building footprint (slabs or foundation elements) and at least five feet
beyond the building footprint in all directions at a minimum. The performance of site
development features would benefit from similar improvements across the building
pad in any areas to receive site grading fill; however, the existing organic zone may
remain in place at the discretion of the Owner provided an increased risk of long-
term settlement is acceptable for exterior site features.
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 those containing abundant organics, are suitable for use as backfill and
general site grading fill on this project. Imported fill materials for use in site grading
applications should conform to the requirements of structural fill (Item 4) when
utilized within the building footprint. Similar materials may be utilized across the
site, but if alternative import materials are considered for exterior site grading
applications it is advised the following minimum guidelines and properties be
followed:
• All imported fill shall be free of organic materials, construction debris,
contaminants, or other deleterious contents.
• Materials shall not contain cobbles or rocks larger than six-inch.
• The fines portion of the material shall not exhibit a liquid limit
exceeding 50 percent or a plasticity index exceeding 35 percent.
• All materials must be capable of being moisture conditioned and
compacted to the requirements outlined in Item 3 below.
3. 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 ...................................... 98%
b) Below Interior Slabs-on-Grade .................................................... 98%
c) Exterior Site Grading Fill and Exterior Foundation Backfill ......... 95%
d) General Landscaping or Nonstructural Areas (Top 1 foot) ......... 92%
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 10
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 require over 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.
4. Imported structural fill should be non-expansive, free of organics and debris, and
conform to the material requirements outlined in Section 02234 or Section 02235 of
the Montana Public Works Standard Specifications (MPWSS). All gradations
outlined in this standard are acceptable for use as structural fill on this project.
5. 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.
6. When possible, it is advised that downspouts from roof drains be collected and
conveyed directly to the disposal site (pond, dry well, etc.) However, 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 structures to
promote drainage and prevent ponding.
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
The design and construction criteria below should be observed for a spread footing foundation
system. The construction details should be considered when preparing the project documents.
8. Both interior and exterior footings should bear on properly compacted structural fill
(Item 4) extending to in-situ gravels which are free of excessive organic material.
The existing building pad should be prepared in accordance with Item 1,
replacement structural fill compacted to the requirements of Item 3a, and
compaction confirmed via field testing prior to footing construction.
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 11
Footings to be supported as described should be designed for a maximum allowable
bearing pressure of 4,000 psf and consideration of a one-third increase for dynamic
load cases is acceptable. Footings designed using these values and constructed as
described are not anticipated to experience settlements exceeding ¾-inch.
9. Construction using thickened slab sections to support interior walls or columns is
acceptable when structural fill materials is utilized beneath all interior slabs as
recommended in Item 20 below.
10. Soils disturbed below the planned depths of footing excavations should either be re-
compacted or be replaced with suitable compacted backfill approved by the
geotechnical engineer.
11. Footings shall be sized to satisfy the minimum requirements of the applicable
building codes while not exceeding the maximum allowable bearing pressure
provided in Item 8 above.
12. Exterior footings and footings beneath unheated areas, which will be exposed to
freezing temperatures, should bear at least 48 inches below finished exterior grade
for frost protection. Interior footings within heated controlled spaces for which frost
is not an issue can utilize shallower footings or thickened-slab construction
conforming to the requirements of Item 8 above.
13. The bottom of the footing excavations should be free of cobbles and boulders to
avoid stress concentrations acting on the base of the footings. Use of a finer-graded
structural fill (Item 4) will help to alleviate the potential for stress concentrations and
the need for a separate cushion layer.
14. 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 design purposes, the following tables summarize the recommended friction
coefficient and lateral resistance pressure to be utilized based on the design
conditions.
Bearing Soil Material Friction Coefficient
Structural Fill 0.45
Anticipated Backfill Material Lateral Earth Pressure
Structural Fill (Item 4) 300 psf/foot
General Exterior Fill
(Item 2) 150 psf/foot
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 12
15. A representative of the project geotechnical engineer should be retained to observe
the removal of the existing gravels which contain unsuitable levels of organics and
compaction of the replacement structural fill prior to the placement of concrete
formwork for foundations.
5.3 Foundation and Retaining Walls
Based on our current understanding of the structure and site development for this project, we do not
anticipate the need for any foundations or site grading retaining walls which would retain differential
soil heights. However, these design parameters may be required for select structures such as
elevator pits or other features and have been included for consideration when appropriate.
16. Foundation walls and other retaining walls which are laterally supported and can be
expected to undergo only a slight amount of deflection should be designed for a
lateral earth pressure computed on the basis of an equivalent fluid unit weight of 80
pcf for general exterior site backfill conforming to the minimum properties of Item 2
above. The lateral earth pressure can be reduced to 60 pcf when backfill will be
comprised of compacted structural fill (Item 4), typical of wall structures within the
footprint of the planned structure such as elevator pits or others.
17. If utilized, retaining structures which can deflect sufficiently to mobilize the full active
earth pressure condition, at least three percent of the exposed wall height, may be
designed for a lateral earth pressure computed on the basis of an active equivalent
fluid unit weight of 60 pcf for backfill consisting of general exterior site backfill
conforming to the minimum properties of Item 2. The lateral earth pressure can be
reduced to 45 pcf when backfill will be comprised of compacted structural fill within a
horizontal distance equal to the height of the wall.
18. Backfill should be selected, placed, and compacted per Item 3 above. Backfill
should be placed in approximately equal lift thicknesses which alternate between the
interior and exterior to avoid excessive lateral forces for which the walls were not
designed. 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 foundation and retaining walls.
19. Exterior footing drains are not required for this project based on the proposed use of
slab-on-grade construction with no below grade space and assumed that interior
finished floor elevation will be higher than finished exterior grade at all locations. A
drain system may be required and should be evaluated if this requirement is not met
for the project.
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 13
5.4 Interior Floor Slabs
20. For normally loaded, interior slab-on-grade construction, the site is anticipated to
require a large material import beneath interior building slabs to reach proposed
design elevations. Interior floor slabs should bear on properly compacted structural
fill (Item 4) extending down to the structural fill installed to replace organic containing
in-situ gravels per Item #1.
21. For normally loaded, interior slab-on-grade construction, a minimum 6-inch cushion
course consisting of free-draining, crushed gravel should be placed beneath the
slabs and compacted to the requirements of Item 3 above.
22. 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.
23. Concrete floor slabs should be designed using a modulus of vertical subgrade
reaction no greater than 300 pci when designed and constructed as recommended
above.
24. 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.
5.5 Exterior Flatwork
25. 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 3c above. A minimum cushion course
thickness of six inches is common and advised for this project. Conventional
construction, as has been described, is not intended to prevent concrete movements
which may be the result of secondary settlement of organic containing materials left
in place, surface water infiltration, frost, or other factors. 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.
26. Cushion course materials utilized beneath exterior slab-on-grade applications
should conform to the requirements outlined in Section 02235 of the Montana Public
Works Standard Specifications (MPWSS). All gradations outlined in this
785 Boardwalk Avenue - Ferguson Farms Development Recommendations Bozeman, Montana Page 14
specification are acceptable for this application. Prior to placing the cushion course,
the upper six inches of subgrade should be compacted per Item 3c.
5.6 Continuing Services
Three additional elements of geotechnical engineering service are important to the successful
completion of this project.
27. 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.
28. 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.
29. 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
LF = Lineal Feet SF = Square Feet
785 Boardwalk Avenue - Ferguson Farms Development Summary of Field & Laboratory Studies Bozeman, Montana Page 15
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES
6.1 Field Explorations
The field exploration program was conducted on December 15, 2025. A total of four test pits were
excavated to depths ranging from 9.5 to 10.0 feet at the approximate locations shown on Figure 1 to
observe subsurface soil and ground water conditions. The tests pits were excavated using a CAT
305 Excavator. The subsurface exploration and sampling methods used are indicated on the
attached test pit logs. The test pits were logged by Mr. Colton Shaff, EI of TD&H Engineering. The
location of the test pits were estimated by TD&H Engineering based on schematic design drawings
provided by Intrinsik Architecture.
Composite samples of the subsurface material were taken from the excavated spoils at discrete
sampling locations. Logs of all test pits, which include soil descriptions and sample depths are
presented on Figures 2 through 5.
Measurements to determine the depth of ground water in the test pits were made using a steel tape
measure shortly after the completion of excavating. The depths or elevations of the water levels
measured, if encountered, and the date of measurement are shown on the test pit 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. Atterberg Limits A method of describing the effect of varying water content on
the consistency and behavior of fine-grained soils.
The laboratory testing program for this project consisted of six moisture-visual analyses, two sieve
(grain-size distribution) analyses, and two Atterberg Limits analyses. The results of the water
content analyses are presented on the test pit logs, Figures 2 through 5. The grain-size distribution
curves and Atterberg limits are presented on Figures 6 through 9.
785 Boardwalk Avenue - Ferguson Farms Development Limitations Bozeman, Montana Page 16
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 test pits 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 test pits 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 test pits 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 provided
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.
785 Boardwalk Avenue - Ferguson Farms Development Limitations Bozeman, Montana Page 17
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 test pit logs and presented in discussions of subsurface conditions
included in this report.
Prepared by: Reviewed by: Colton Shaff EI Craig Nadeau PE & Principal Geotechnical Engineer Geotechnical Manager
TD&H ENGINEERING TD&H ENGINEERING
785 BOARDWALK AVENUE – FERGUSON FARMS DEVELOPMENT BOZEMAN, MONTANA APPROXIMATE TEST PIT LOCATION MAP FIGURE 1
0
1.5
3
4.5
6
7.5
9
10.5
Poorly-Graded GRAVEL with Sand, appears very dense,
brown, moist, some organics, boulders 16" and larger
-Granular, Non-Plastic
Well-Graded GRAVEL with Sand, appears very dense, dark
brown with black sand, moist
Bottom of Test Pit
3.3
9.5
Ground
water
not
encoun-
tered
G
G
LEGEND LOG OF TEST PIT TP-1Atterberg Limits
Field Moisture content 785 Boardwalk Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
Logged by:Colton Shaff, EI
Excavated by:Earth Surgeons Excavation
CAT 305 ExcavatorGNP = Granular and Nonplastic
Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
12-15-2025 B25-083-001
Figure No.2
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Existing Gravel Pad
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSAMPLEDEPTH (FT)MOISTURE CONTENT
0 10 20 30 40 50
= MOISTURE CONTENT
1 of 1
0
1.5
3
4.5
6
7.5
9
10.5
Poorly-Graded GRAVEL with Sand, appears very dense,
brown, moist, abundant organics, boulders up to 8"
Well-Graded GRAVEL with Sand, appears very dense, dark
brown with black sand, moist
Bottom of Test Pit
3.5
9.6
G
G
LEGEND LOG OF TEST PIT TP-2Atterberg Limits
Field Moisture content 785 Boardwalk Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
Logged by:Colton Shaff, EI
Excavated by:Earth Surgeons Excavation
CAT 305 ExcavatorGNP = Granular and Nonplastic
Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
12-15-2025 B25-083-001
Figure No.3
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Existing Gravel Pad
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSAMPLEDEPTH (FT)MOISTURE CONTENT
0 10 20 30 40 50
= MOISTURE CONTENT
1 of 1
0
1.5
3
4.5
6
7.5
9
10.5
Poorly-Graded GRAVEL with Sand, appears very dense,
brown, moist, abundant organics, boulders up to 12"
Well-Graded GRAVEL with Sand, appears very dense, dark
brown with black sand, moist
Bottom of Test Pit
3.3
9.5
G
LEGEND LOG OF TEST PIT TP-3Atterberg Limits
Field Moisture content 785 Boardwalk Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
Logged by:Colton Shaff, EI
Excavated by:Earth Surgeons Excavation
CAT 305 ExcavatorGNP = Granular and Nonplastic
Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
12-15-2025 B25-083-001
Figure No.4
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Existing Gravel Pad
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSAMPLEDEPTH (FT)MOISTURE CONTENT
0 10 20 30 40 50
= MOISTURE CONTENT
1 of 1
0
1.5
3
4.5
6
7.5
9
10.5
Poorly-Graded GRAVEL with Sand, appears very dense,
brown, moist, abundant organics, boulders up to 10"
Well-Graded GRAVEL with Sand, appears very dense, dark
brown with black sand, moist
Bottom of Test Pit
3.7
10.0
G
G
LEGEND LOG OF TEST PIT TP-4Atterberg Limits
Field Moisture content 785 Boardwalk Avenue
Bozeman, MontanaGroundwater Level
Grab/composite sample
Logged by:Colton Shaff, EI
Excavated by:Earth Surgeons Excavation
CAT 305 ExcavatorGNP = Granular and Nonplastic
Note: The stratification lines represent approximate
boundaries between soil types. Actual boundaries
may be gradual or transitional.
12-15-2025 B25-083-001
Figure No.5
SheetGRAPHICLOGSOIL DESCRIPTION
SURFACE:Existing Gravel Pad
SURFACE ELEVATION:Not Measured
DEPTH (FT)GROUNDWATERSAMPLEDEPTH (FT)MOISTURE CONTENT
0 10 20 30 40 50
= MOISTURE CONTENT
1 of 1
Tested By: CRN 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 61.3 13.0 3.6 8.4 9.1 4.66 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: TP-1
Sample Number: A-33041 Depth: 1.0 - 2.0 ft
Client:
Project:
Project No:Figure
Sieve Size
or
Diam. (mm.)
Finer
(%)
Spec.*
(%)
Out of
Spec.
(%)
Pct.
of
Fines
Poorly-Graded GRAVEL with Sand
3"
2.5
2"
1.5"
1"
3/4"
1/2"
3/8"
#4
#10
#20
#40
#60
#80
#100
#200
100.0
85.5
69.3
67.5
49.0
38.7
33.7
30.2
25.7
22.1
19.3
13.7
9.2
7.4
6.5
4.6
NP NV NP
67.2422 63.0512 31.2264
26.0119 9.3343 0.4929
0.2773 112.61 10.06
GP A-1-a
Report No. A-33041-206
Report Date: 1-17-2026
F.M.=6.61
12-15-2025
Intrinsik Architecture
785 Boardwalk Avenue
Bozeman, Montana
B25-083-001
PL=LL=PI=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
USCS=AASHTO=
*(no specification provided)
6
Tested By: BS/IR 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
10.2 42.4 20.5 7.7 12.0 4.5 2.76 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: TP-3
Sample Number: A-33045 Depth: 3.5 - 4.5 ft
Client:
Project:
Project No:Figure
Sieve Size
or
Diam. (mm.)
Finer
(%)
Spec.*
(%)
Out of
Spec.
(%)
Pct.
of
Fines
Well-Graded GRAVEL with Sand
12
6
3"
2"
1.5"
1"
3/4"
1/2"
3/8"
#4
#10
#20
#40
#60
#80
#100
#200
100.0
92.4
89.8
75.0
66.5
55.4
47.4
40.3
36.1
26.9
19.2
12.5
7.2
4.7
3.8
3.4
2.7
71.4
46.6
26.7
17.6
14.3
12.8
10.0
17 21 4
77.7794 64.4243 30.1326
21.0919 6.1125 1.1701
0.6209 48.53 2.00
GW A-1-a
Report No. A-33045-206X
Report Date: 1-17-2026
F.M.=6.87
12-15-2025
Intrinsik Architecture
785 Boardwalk Avenue
Bozeman, Montana
B25-083-001
PL=LL=PI=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
USCS=AASHTO=
*(no specification provided)
7
Tested By: CRN 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 CONTENT0
4
8
12
16
20
24
28
32
36
40
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: TP-1
Sample Number: A-33041 Depth: 1.0 - 2.0 ft
Figure
Poorly-Graded GRAVEL with Sand NV NP NP 13.7 4.6 GP
B25-083-001 Intrinsik Architecture
8
Report No. A-33041-207
Report Date: 1-17-2026785 Boardwalk Avenue
Bozeman, Montana
*
* Granular, Non-Plastic
Tested By: BC 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 CONTENT19.6
19.8
20
20.2
20.4
20.6
20.8
21
21.2
21.4
21.6
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: TP-3
Sample Number: A-33045 Depth: 3.5 - 4.5 ft
Figure
Well-Graded GRAVEL with Sand 21 17 4 7.2 2.7 GW
B25-083-001 Intrinsik Architecture
9
Report No. A-33045-207
Report Date: 1-17-2026785 Boardwalk Avenue
Bozeman, Montana
TD&H Engineering
Consultants
Great Falls, Kalispell, Bozeman, MT
Spokane, WA; Lewiston, ID, Watford City, ND
TD&H Engineering
ConsultantsGreat Falls, Kalispell, Bozeman, MT Spokane, WA; Lewiston, ID, Watford City, ND