HomeMy WebLinkAbout32 Geotechnical Report 03-12-19MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
JOB NO. B19-014 MARCH 2019
REPORT OF GEOTECHNICAL INVESTIGATION
CLIENT ENGINEER
Black Ridge Companies
PO Box 11590
Bozeman, MT 59719
Craig Nadeau, PE
Craig.nadeau@tdhengineering.com
REPORT OF GEOTECHNICAL INVESTIGATION
PROJECT NAME
PROJECT LOCATION 406.586.0277
tdhengineering.com
234 E. Babcock, Suite 3
Bozeman, MT 59715
GRAF STREET APARTMENTS
BOZEMAN, MONTANA
Graf Street Apartments 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 ........................................................................................................... 3
3.3 Subsurface Conditions ..................................................................................................... 4
3.3.1 Soils ........................................................................................................................... 4
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 Floor Slabs and Exterior Flatwork .................................................................................... 7
4.6 Pavements ........................................................................................................................ 8
5.0 RECOMMENDATIONS.......................................................................................................... 10
5.1 Site Grading and Excavations ........................................................................................ 10
5.2 Conventional Shallow Foundations ................................................................................ 11
5.3 Foundation and Retaining Walls .................................................................................... 12
5.4 Floor Slabs and Exterior Flatwork .................................................................................. 13
5.5 Flexible Asphalt Pavements ........................................................................................... 14
5.6 Continuing Services ....................................................................................................... 16
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES ........................................................ 18
6.1 Field Explorations ........................................................................................................... 18
6.2 Laboratory Testing ......................................................................................................... 18
7.0 LIMITATIONS ........................................................................................................................ 20
Graf Street Apartments Appendix Bozeman, Montana ii
APPENDIX
♦ Test Pit Location Map (Figure 1)
♦ Summary of Test Pits and Ground Water Monitoring (Figure 2)
♦ Laboratory Test Data (Figures 3 through 12)
♦ USGS Design Maps Summary Report
♦ LTTPBind Online PG Asphalt Binder Analysis Summary
♦ Soil Classification and Sampling Terminology for Engineering Purposes
♦ Classification of Soils for Engineering Purposes
Graf Street Apartments Executive Summary Bozeman, Montana Page 1
GEOTECHNICAL REPORT GRAF STREET APARTMENTS BOZEMAN, MONTANA
1.0 EXECUTIVE SUMMARY
The proposed Graf Street Apartment project is located between South 19th Road and Enterprise
Boulevard and between Graf Street and Lantern Lane in Bozeman, Montana. The geotechnical
investigation performed for this project showed 1.5 to 6.0 feet of surficial lean clay of which 0.5 to
2.0 feet are considered topsoil with high organic contents. The surficial clay is underlain by dense
native gravels classified as clayey gravel with sand near the upper contact and transitioning to
poorly-graded gravel with sand at depth. 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 concerns regarding this project are the presence of varying thicknesses
of potentially compressible clay soils on site and potential ground water impacts on construction.
The surficial clay is not suitable to support foundation loads for the planned construction and must
be removed and replaced with properly compacted structural fill. Due to the limited thickness of the
clay, significant volumes of structural fill are not anticipated but localized structures may warrant
structural fill thicknesses on the order of one to two feet depending on final site grading. Ground
water was encountered in 13 of the 53 test pits performed for this project at depths ranging from 6.7
to 9.5 feet below existing grade. We do not anticipate significant long-term impacts of ground water
with the assumed slab-on-grade construction; however, seasonal fluctuations could result in some
impact during construction and long-term buoyant forces on below grade structures like the planned
swimming pool. During our field work, four monitoring wells were installed for your use in monitoring
fluctuations in the ground water elevation during seasonally wet periods of the year to evaluate
potential fluctuations. The well locations are shown on Figure 1.
Interior slab systems which utilize conventional construction methods would be underlain by varying
thickness of the surficial lean clay and could realize some differential movement as a result. Due to
the limited thickness of the clay material, its complete removal and replacement with properly
compacted structural fill within building footprints is recommended for this project to mitigate any
potential concerns with slab displacement.
The site is suitable for the use of conventional shallow foundation systems and interior slab-on-
grade construction bearing on properly compacted native gravel or compacted structural fill
extending to native gravel. Footings constructed as recommended within this report should be
designed using an allowable bearing pressure of 3,000 pounds per square foot (psf) with an
allowable one-third increase for consideration of dynamic loads.
Graf Street Apartments Introduction Bozeman, Montana Page 2
2.0 INTRODUCTION
2.1 Purpose and Scope
This report presents the results of our geotechnical study for the planned Graf Street Apartment
development to be located at on the north side of Graf Street between South 19th Road and
Enterprise Boulevard 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 structures 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 53 test pits across the proposed site. Samples were obtained
from various 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.
This study is in accordance with the proposal submitted by Mr. Ahren Hastings, PE of our firm dated
January 21, 2019. Our work was authorized to proceed by Mr. Will Ralph, PE of Black Ridge
Companies by his signed acceptance of our proposal.
2.2 Project Description
It is our understanding that the proposed project consists of multiple three-story, wood-framed
apartment buildings and associated below grade pools, club houses, site parking, access roads,
pedestrian trails, and landscaping. All structures are anticipated to utilize conventional shallow
foundation systems and interior slab-on-grade construction. The only below grade construction
anticipated for this project will be the planned swimming pool which is assumed to be less than eight
feet deep. 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 4,500 pounds per lineal
foot and column loads, if any, will be less than 100 kips.
Site development will most likely include landscaping, potential grade separation retaining walls,
exterior concrete flatwork, and asphalt pavement for parking lots and roads. If the assumed design
values presented above vary from the actual project parameters, the recommendations presented in
this report should be reevaluated.
Graf Street Apartments Site Conditions Bozeman, Montana Page 3
3.0 SITE CONDITIONS
3.1 Geology and Physiography
The site is geologically characterized as containing gravel deposits which range from pebble to
boulder size and include sand, silt, and clay. These deposits are generally alluvial terrace,
abandoned channel and floodplain, remnant alluvial fan, and local glacial outwash. The gravel is
predominately subrounded to subangular and reportedly extend down to as much as 165 feet.
Upper tertiary sediments or sedimentary rock (Tsu) also frequent the Bozeman area according to
the Montana Bureau of Mines and Geology (MBMG), Geologic Map of Montana. These formations
consist of conglomerate, tuffaceous sandstone and siltstone, marlstone, and equivalent sediment
and ash beds.
Figure 1. Geologic Map of Bozeman Area (MBMG 2007)
Based on the subsurface conditions encountered, the site falls under seismic Site Class D. The
appropriate 2015 International Building Code (IBC) seismic design parameters for the site include
site coefficients of 1.22 and 1.98 for Fa and Fv, respectively. The recommended design spectral
response accelerations at short periods (SDs) and at 1-second period (SD1) are 0.589g and 0.279g,
respectively. These values represent two-thirds of the mapped response accelerations following
correction for the appropriate site classification and assume the proposed construction to fall into
risk category II. 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 between South 19th Road and Enterprise Boulevard and Graf
Street and Lantern Lane. It makes up approximately 26 acres of land which is classified as non-
Approximate Site Location
Graf Street Apartments Site Conditions Bozeman, Montana Page 4
qualified agricultural lands. The parcel was snow covered at the time of our investigation; however,
based on previous aerial photos it appears to be vegetated with native grasses. An existing stream
traverses the eastern side of the property roughly parallel to South 19th Road. Based on background
information and site observations, the project area is considered generally flat.
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 1.5 to 6.0 feet of surficial lean clay with sand and
topsoil materials overlying native gravels. The gravels extend to depths of at least 10.2 feet,
the maximum depth investigated.
The subsurface soils are summarized on the enclosed summary of test pits and ground
water monitoring (Figure 2) and below. The stratification lines shown on the summary
represent approximate boundaries between soil types and the actual in situ transition may
be gradual vertically or discontinuous laterally.
LEAN CLAY WITH SAND
Lean clay with sand was encountered in each of the test pits performed and extend to
depths of 1.5 to 6.0 feet below existing site grades. The lean clay with sand appears firm
based on the ease of excavation with the equipment utilized. A single sample of the material
obtained from TP-4 contained 19.3 percent gravel, 9.0 percent sand, and 71.7 percent fines
(clay and silt). Two additional samples exhibited liquid limits of 37 and 42 percent and
plasticity indices of 16 and 20 percent. The natural moisture contents varied from 8 to 14
percent and averaged 11 percent.
A single proctor test was performed on a bulk sample of the native clay obtained from TP-30
using methods outlined in ASTM D698. This test resulted in a maximum dry density of 106.2
pounds per cubic foot (pcf) when compacted at the optimum moisture content of 18.3
percent. Additionally, a California Bearing Ratio (CBR) test was performed per ASTM
D1883 on the same sample using varying levels of compaction at the optimum moisture
content. This test indicates that the lean clay subgrade will exhibit a CBR value of 8.0
percent when compacted to at least 95 percent of the maximum dry density determined
above.
TRANSITIONAL STRATA
Thin deposits of transitional materials were encountered between the lean clay with sand
and the underlying poorly-graded gravel with sand. These materials consisted of clayey
gravel with sand and clayey sand with gravel. These materials are considered relatively
dense based on the effort required during excavation. Two samples of these materials
obtained from test pits TP-30 and TP-41 contained 38.2 and 43.6 percent gravel, 40.6 and
Graf Street Apartments Site Conditions Bozeman, Montana Page 5
35.8 percent sand, and 21.2 and 20.6 percent fines (clay and silt), respectively. Two
samples of these transitional materials exhibited moisture contents of 5.0 and 7.2 percent.
POORLY-GRADED GRAVEL WITH SAND
Native poorly-graded gravel with sand was encountered in all 53 test pits at depths ranging
from 1.5 to 6.0 feet below existing grade and extending to depths of at least 10.2 feet, the
maximum depth investigated. The native gravel is considered relatively dense based on the
difficulty with excavation. A single bulk sample of the material contained 9.3 percent cobbles
(larger than 3-inch), 73.1 percent gravel, 21.0 percent sand, and 2.8 percent fines (clay and
silt). The same sample when tested in accordance with ASTM D4253 and D4254 (Relative
Density Test), resulted in a maximum dry density of 147.9 pcf at an optimum moisture
content of 6.5 percent.
3.3.2 Ground Water
Ground water was encountered in 13 of the 53 test pits at depths ranging from 6.7 to 9.5 feet
below existing site grades. Four monitoring wells were installed in TP-1, TP-6, TP-42, and
TP-51 by installed a 10-foot long stick of perforated 4-inch diameter SDR-35 pipe into the
open excavation and backfilling around it with the native gravels. These monitoring
locations are intended to be utilized to evaluate seasonal fluctuations in the ground water
levels up until the start of construction. No data has been collected from any of these
instruments at the time of this report and the ground water levels reported above and shown
on Figure 2 represent the depth of water at the time of our investigation. 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.
Graf Street Apartments Engineering Analysis Bozeman, Montana Page 6
4.0 ENGINEERING ANALYSIS
4.1 Introduction
The primary geotechnical concern regarding this project is the presence of varying thicknesses of
potentially compressible clay soils on site. Due to the variability of the clay thickness across site and
the potential for differential settlements, it is our opinion that the native clays are not suitable to
support foundation loads and that all foundations should extend down to native gravels or be
supported by compacted structural fill extending to native gravels. Similar improvements are
recommended for interior slab systems to negate settlement concerns and improve slab
performance. At the depths observed during our investigation, ground water is not anticipated to
have a significant impact on the design or construction for this project; however, seasonal
fluctuations in the water table are anticipated and warrant additional monitoring to evaluate the
magnitude of these fluctuations.
4.2 Site Grading and Excavations
The ground surface at the proposed site is considered nearly level. Based on our field work, limited
amounts of surficial lean clay with sand overlying native gravels are anticipated in footing and utility
excavations to the depths anticipated for this project. Based on the test pits, ground water was
present at depths of 6.7 to 9.5 feet and may be encountered in utility excavations extending to these
depths. However, seasonal fluctuations have not been evaluated for the site and may result in
ground water being encountered at shallower depths. The contractor should be prepared to
dewater any footing and utility excavations should they encounter ground water. Additionally, future
monitoring of ground water levels should be performed to determine the magnitude of seasonal
fluctuations and assess if buoyant forces need to be considered in the design of below grade
structures like the swimming pool.
4.3 Conventional Shallow Foundations
Considering the subsurface conditions encountered and the nature of the proposed construction,
the structures can be supported on conventional concrete footings bearing on properly compacted
native gravels or compacted structural fill extending to compacted native gravel. Significant
thicknesses of structural fill are not anticipated for this project but depending on the finished floor
elevations thicknesses of one to three feet should be anticipated in some areas.
Based on our experience, the theory of elasticity, and using an allowable bearing pressure of 3,000
psf, we estimate the total settlement for footings will be less than ¾-inch. Differential settlement
within the limits of each individual structure should be on the order of one-half this magnitude.
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
Graf Street Apartments Engineering Analysis Bozeman, Montana Page 7
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
Foundation walls which will retain differential soil heights are only anticipated for the below grade
pool structure. Additional site grading retaining walls may be required for this project. Similar
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. Design parameters are given in the
recommendations section of this report.
4.5 Floor Slabs and Exterior Flatwork
The natural on-site soils, exclusive of topsoil, are suitable to support lightly to moderately loaded,
exterior concrete flatwork. The native lean clay with sand is considered frost susceptible,
compressible, and prone to strength loss when wetted. For these reasons, some risk of vertical
movement beneath exterior concrete flatwork should be expected for this project. However, based
on our experience with similar soils and the limited thickness of this layer, vertical movements are
not anticipated to exceed ¾-inch when conventional construction consisting of a leveling course of
granular fill directly beneath the concrete is utilized.
Interior slab systems for structures are more susceptible to damages resulting from slab movements
and are extremely difficult and expensive to repair. For these reasons, we recommend that the
native clay be removed from beneath the interior slabs of each structure down to the native gravel
contact. This material should be replaced with compacted structural fill to improve performance of
the interior slab and control potential slab displacements. Depending on the finished floor elevation
for the structure, structural fill thicknesses of one to six feet are anticipated. Average structural fill
thicknesses should be between three and four feet. Slab-on-grade construction overlying
compacted structural fill extending down to the native gravel is not anticipated to realize vertical
Graf Street Apartments Engineering Analysis Bozeman, Montana Page 8
movements exceeding ½-inch and differential displacements should be on the order of one-half this
amount.
4.6 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 very
low equivalent single axle loads (ESALs). The pavement sections specified for these areas are the
minimum sections recommended for general constructability and exposure of the pavement over a
design life of 20 years.
We also understand that Lantern Lane is to be extended across to South 19th Road as part of this
project. Lantern Lane, once completed, would serve as an east / west collector roadway with one
travel lane in each direction. The posted speed limit is anticipated to be approximately 25 miles per
hour and the majority of traffic for this roadway should consist of passenger-type vehicles with
limited midsize truck traffic (single unit FHWA Class 7 or smaller) associated with the garbage
collection and deliveries. There is no known commercial development proximate to Lantern Lane
which would justify high levels of truck traffic. We have assumed that peak interval traffic conditions
along Lantern Lane could be as high as 300 vehicles per day once construction is completed.
Based on this assumed value, an estimated average daily traffic of 2,700 vehicles per day is
expected for this roadway which equates to just under 20 million vehicles within a typical 20-year
design life of a pavement system. We have assumed that less than 5 percent of the overall traffic
may consist of mid-size trucks with an ESAL value of 0.42. The remainder of this traffic is expected
to be light passenger-type traffic with an ESAL value of 0.0007. A maximum anticipated design
ESAL value for this roadway of up to 400,000 is anticipated based on these assumptions.
The potential worst-case subgrade material is native lean clay with sand which is classified as a A-6
or A-7-6 soils in accordance with the American Association of State Highway and Transportation
Officials (AASHTO) classification depending on the soil plasticity. AASHTO considers these soil
type to be a relatively poor subgrade due to its frost susceptibility, poor drainage properties, and low
strength. Typical California Bearing Ratio (CBR) values for this type of soil range from 5 to 15
percent when properly compacted. This was confirmed during laboratory testing which measured a
CBR value of 8.0 percent when compacted to at least 95 percent of the maximum dry density
obtained using methods outlined in ASTM D698. Preliminary moistures a sufficiently low to assume
that compaction of the subgrade strata will be feasible during construction. However, our
experience in the area is that spring runoff and snow melt typically results in a significant spike in
soil moisture and can preclude proper compaction. Thus, depending on the construction schedule,
compaction of the pavement subgrade may or may not be feasible. We have included
recommendations for modified pavement sections for construction times which are too wet to
facilitate subgrade compaction.
Graf Street Apartments Engineering Analysis Bozeman, Montana Page 9
A geotextile acting as a separator is recommended between the pavement section gravels and the
prepared 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 sections presented in this report is based on an assumed CBR value of eight percent
for properly compacted subgrade and two percent for subgrade which cannot be compacted due to
moisture at the time of construction. Additionally, our recommendations are based on 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.
Graf Street Apartments Recommendations Bozeman, Montana Page 10
5.0 RECOMMENDATIONS
5.1 Site Grading and Excavations
1. All topsoil and organic material should be removed from the proposed building and
pavement areas and any areas to receive site grading fill. For planning purposes, an
average stripping thickness of 12 to 14 inches is anticipated; however, stripping
depths of up to 24 inches may be required in some locations to remove all
detrimental organic materials.
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, are suitable for use as exterior foundation backfill and general site grading fill
provided they are moisture conditioned and conducive to adequate levels of
compaction.
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 optimum (within
approximately three percent) 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 Slab-on-Grade Construction ............................................. 98%
c) Foundation Wall Backfill .............................................................. 95%
d) Below Streets, Parking Lots, or Other Paved Areas ................... 95%
e) General Landscaping or Nonstructural Areas ............................. 92%
f) Utility Trench Backfill, To Within 2 Feet of Surface ...................... 95%
4. Imported structural fill should be non-expansive, free of organics and debris, and
conform to the material requirements outlined in Section 02234, Subsections 2.3 and
2.4 of the Montana Public Works Standard Specifications (MPWSS). All gradations
outlined in this standard are acceptable for use on this project based on local
availability and contractor preference. Native gravels, when available from other
excavations, are considered suitable for use as structural fill but may require
processing to remove rocks larger than 4-inch prior to use.
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
Graf Street Apartments Recommendations Bozeman, Montana Page 11
compaction value must be determined using a relative density test outlined in ASTM
D4253-4254.
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. We recommend that all roof downspouts be directed to the on-site storm water
systems, when possible. However, 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.
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. For planning purposes, subsoils
encountered in the test pits are considered Type B for the native lean clay and Type
C for the native gravels. The soil conditions on site can change due to changes in
soils moisture or disturbances to the site prior to construction. Thus, 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 native gravels
or compacted structural fill (Item 4) extending down to compacted native gravel.
Prior to the placement of structural fill or concrete forms, the surface of the native
gravels should be compacted and field verified to a minimum depth of 6 inches.
Footings supported as described above should be designed for a maximum
allowable soil bearing pressure of 3,000 psf provided settlements as outlined in the
Engineering Analysis are acceptable. A one-third increase in the allowable bearing
pressure is permitted for the consideration of dynamic load cases.
Graf Street Apartments Recommendations Bozeman, Montana Page 12
Based on the test pits performed, the need for structural fill beneath building
foundations will vary and will be partially controlled by the finished floor elevation
selected for each structure. Structural fill thicknesses on the order of three feet or
less are anticipated beneath footings. The limits of over-excavation and
replacement with compacted structural fill should extend at least 18 inches beyond
the outer face of the footings in all directions.
9. 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.
10. 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.
11. Exterior footings and footings beneath unheated areas should be placed at least 48
inches below finished exterior grade for frost protection.
12. The bottom of the footing excavations should be free of cobbles and boulders to
avoid stress concentrations acting on the base of the footings. In areas where
footings are supported directly on native gravels and the surface cannot be rolled
smooth due to cobbles and boulders, a thin layer of cushion gravel should be
installed between the native gravel and the footing. Cushion gravel materials should
consist of finer graded structural fill materials conforming to Item 4 above which is
placed and compacted per Item 3.
13. 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, a friction coefficient of 0.45 and a lateral resistance pressure of
200 psf per foot of depth are appropriate for footings bearing on compacted gravel or
structural fill and backfilled with properly compacted native soils.
14. A representative of the project geotechnical engineer should be retained to observe
all footing excavations and backfill phases prior to the placement of concrete
formwork in order to verify the removal of any clay soils and the proper compaction
of any structural fill and bearing gravel strata.
5.3 Foundation and Retaining Walls
The design and construction criteria presented below should be observed for foundation and
retaining walls. The construction details should be considered when preparing the project
documents.
Graf Street Apartments Recommendations Bozeman, Montana Page 13
15. Below grade walls for the swimming pool structure should be designed using at-rest
earth pressures to limit lateral deflection of the wall structure. An at-rest lateral earth
pressure computed on the basis of an equivalent fluid unit weight of 60 pcf is
appropriate for backfill consisting of structural fill or native gravels. We recommend
that gravel backfill be utilized for a distance behind the wall equal to its height.
16. Site grading retaining structures which can deflect sufficiently to mobilize the full
active earth pressure condition, approximately three percent of the exposed wall
height, may be designed for a lateral earth pressure computed on the basis of an
equivalent fluid unit weight of 60 pcf for backfill consisting of compacted lean clay.
When structural fill or native gravels are to be utilized as backfill, a reduced active
earth pressure of 30 pcf is appropriate.
17. Backfill should be selected, placed, and compacted per Items 2 and 3 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. Backfilled placed adjacent to
foundation walls for slab-on-grade structures should utilize lifts of equal thickness
which alternate between the interior and exterior of the structure.
18. Retaining walls over 4 feet in height should incorporate backfill drainage systems
and/or weep holes to prevent the accumulation of hydrostatic pore pressures.
Future monitoring of installed wells on site shall be performed during upcoming
spring and summer months to evaluate fluctuations in the ground water table.
Monthly readings are recommended to ensure that the peak time frame is measured.
If monitoring indicates that ground water may rise above the elevation of the planned
swimming pool, either an adequate drain system shall be designed by others to
maintain a water level below the bottom of pool elevation or the pool structure shall
be designed to resist the buoyant forces and lateral forces on pool walls associated
with the maximum anticipated ground water elevation.
19. Exterior footing drains are not required for the apartment structures on this project
based on our understanding that the structures are to utilize at-grade, slab-on-grade
construction. Alternative configurations which incorporate below grade spaces or
crawlspace construction would warrant the addition of a foundation drain system.
5.4 Floor Slabs and Exterior Flatwork
20. 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 2 above. Cushion course thicknesses generally range
from four to six inches but may vary based on local requirements. Conventional
Graf Street Apartments Recommendations Bozeman, Montana Page 14
construction, as has been described, is not intended to mitigate any expansion or
settlement concerns associated with the subsurface conditions encountered. Based
on the limited thickness of the clay soil, we do not anticipate abnormal levels of
performance for this type of construction; however, some vertical movement of up to
¾-inch may be realized.
21. Interior slab-on-grade construction is more susceptible to slab displacements which
can cause interior distress and are very expensive to repair. For these reasons, we
recommend that these slabs be underlain by structural fill extending to the native
gravels to improve long-term performance. Structural fill thicknesses should
generally be on the order of three and four feet beneath most structures; however,
structural fill thicknesses are anticipated to range from 18 to 72 inches over the
project area.
22. Concrete floor slabs should be designed using a modulus of vertical subgrade
reaction no greater than 400 pci when designed and constructed as recommended
above.
23. Geotechnically, an underslab vapor barrier is not required for the anticipated at-
grade slab systems planned 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 Flexible Asphalt Pavements
24. The following pavement sections or an approved equivalent section should be
selected in accordance with the discussions in the Engineering Analysis depending
on the subgrade conditions at the time of construction.
Pavement Sections for Properly Compacted, Stable Subgrade
Pavement Component
Component Thickness
Parking Lots &
Access Roads Lantern Lane
Asphaltic Concrete Pavement 3” 3”
Crushed Base Course 12” 6”
Crushed Subbase Course ----- 12”
Total 15” 21”
Graf Street Apartments Recommendations Bozeman, Montana Page 15
The pavement sections provided above assume that the subgrade at the time of
construction will be sufficiently dry to facilitate proper compaction to the requirements
of Item 3 without any instability or pumping. If subgrade moistures are elevated and
the subgrade cannot be compacted to the requirements of Item 3 or the subgrade is
unstable, the pavement sections should be modified as outlined below to account for
the weaker subgrade.
Pavement Section for Unstable or Non-compactable Subgrade
Pavement Component
Component Thickness
Parking Lots &
Access Roads Lantern Lane
Asphaltic Concrete Pavement 3” 3”
Crushed Base Course 6” 6”
Crushed Subbase Course 12” 18”
Total 21” 27”
25. Final pavement thicknesses exceeding 3 inches shall be constructed in two uniform
lifts.
26. Gradations for the crushed base courses shall conform to 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. The gradation for the subbase shall conform to Section
02234 of the MPWSS and incorporate a maximum particle size of 3-inch.
27. 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 Items 2 and 3 above.
28. 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 500X or equivalent geotextile is appropriate.
29. 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.
Graf Street Apartments Recommendations Bozeman, Montana Page 16
Reliability Min. High
Temp Rating
Min. Low
Temp Rating Ideal Oil Grade
50% 33.9 -30.6 PG 52-34
98% 37.6 -39.5 PG 52-40
For most low volume parking lot applications, a 50 percent reliability is considered
sufficient; however, a higher reliability level may be desired for improvements to
Lantern Lane. The table above outlines the ideal bituminous products for the local
climate conditions in Bozeman, Montana; however, in our experience neither of
these types of oil are commonly utilized or available through local contractors. While
the use of these oil types should improve performance, they will also increase
construction expenses associated with importing the specialized product and the use
of similar high-quality or modified asphalt products. Based on our experience, the
use of a PG 58-28 is recommended for this project. This material is frequently
utilized in Bozeman and has demonstrated acceptable performance levels for this
region.
5.6 Continuing Services
Three additional elements of geotechnical engineering service are important to the successful
completion of this project.
30. 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.
31. 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.
32. 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:
Graf Street Apartments Recommendations Bozeman, Montana Page 17
Compaction Testing
Beneath Column Footings 1 Test per Footing per Lift
Beneath Wall Footings 1 Test per 25 LF of Wall per Lift
Beneath Slabs 1 Test per 600 SF per Lift
Foundation Backfill 1 Test per 50 LF of Wall per Lift
Parking Lot & Access Roads 1 Test per 1,000 SF per Lift
LF = Lineal Feet SF = Square Feet
Concrete Testing
Structural Concrete† 1 Test per 50 CY per Day
Non-Structural Concrete 1 Test per 100 CY per Day (MPWSS Requirement) † Structural concrete includes all footings, stem walls, slabs, and other load bearing elements
CY = Cubic Yards
Graf Street Apartments Summary of Field & Laboratory Studies Bozeman, Montana Page 18
6.0 SUMMARY OF FIELD AND LABORATORY STUDIES
6.1 Field Explorations
The field exploration program was conducted on February 14 and 15, 2019. A total of 53 test pits
were excavated to depths ranging from 4.5 to 10.2 feet at the approximate locations shown on
Figure 1 to observe subsurface soil and ground water conditions. The tests pits were excavated by
Earth Surgeons using a Cat 305CR mini-excavator. The test pits were logged by Mr. Ahren
Hastings, PE of TD&H Engineering. The location of the test pits was determined based on the site
plan provided for our use and were staked by TD&H survey personnel prior to the field investigation.
Composite grab samples of the excavation spoils were collected periodically during excavation and
at distinct changes in soil strata. A summary of the subsurface soils and ground water conditions
encountered in each test pit is shown on Figure 2.
Ground water was encountered in 13 or the 53 test pits performed at depths ranging from 6.7 to 9.5
feet below existing site grades. The depth of the ground water shown on Figure 2 represents the
water depth at the time of our field investigation and is based on visual observation of water within
the open excavation. Four monitoring wells were constructed at the corners of the property by
installed a 10-foot long perforated SDR-35 pipe in the open test pit and backfill with native gravels.
No additional monitoring of these wells had been performed at the time of this report.
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, four sieve
(grain-size distribution) analysis, and two Atterberg Limits analysis. The results of these tests are
shown on Figures 3 through 9. In addition, a single relative density test, standard proctor test, and
Graf Street Apartments Summary of Field & Laboratory Studies Bozeman, Montana Page 19
California Bearing Ratio (CBR) were performed on representative bulk samples of the native
materials. The results of these tests are shown on Figures 10 through 12.
Graf Street Apartments Limitations Bozeman, Montana Page 20
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 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. We strongly advise that TD&H
be retained 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. 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.
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
Graf Street Apartments Limitations Bozeman, Montana Page 21
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: Craig Nadeau PE Ahren Hastings PE Geotechnical Department Manager Geotechnical Engineer
TD&H ENGINEERING TD&H ENGINEERING
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2-22-2019
4
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#20
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Report No. A-18998-206
Black Ridge Companies
Graf Street Apartments
Bozeman, Montana
B19-014-001
Material Description
Atterberg Limits
Coefficients
Classification
Remarks
Location: TP-4
Sample Number: A-18998 Depth: 2.5 - 3.0 ft Date:
Client:
Project:
Project No: Figure
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
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10
20
30
40
50
60
70
80
90
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GRAIN SIZE - mm.
0.00010.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 14.9 4.4 0.5 1.5 7.0 71.7
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Particle Size Distribution Report
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B19-014-001No:
Tested By: MS/WJC Checked By:
2-27-2019
5
(no specification provided)
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#40
#60
#80
#100
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1.0563 0.1949
SC
Report No. A-19004-206X
Black Ridge Companies
Graf Street Apartments
Bozeman, Montana
B19-014-001
Material Description
Atterberg Limits
Coefficients
Classification
Remarks
Location: TP-30
Sample Number: A-19004 Depth: 3.5 ft Date:
Client:
Project:
Project No: Figure
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
PE
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0
10
20
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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 19.7 18.5 6.4 16.2 18.0 21.2
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Particle Size Distribution Report
y:
B19-014-001No:
Tested By: MW/WJC Checked By:
2-27-2019
6
(no specification provided)
PL= LL= PI=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
USCS= AASHTO=
*
Poorly-Graded GRAVEL with Sand
6"
3"
1.5"
1"
3/4"
1/2"
3/8"
#4
#10
#20
#40
#60
#80
#100
#200
100.0
90.7
64.1
50.9
43.5
34.5
30.5
23.8
17.6
11.8
6.9
4.8
3.9
3.5
2.8
74.2626 63.8990 34.0949
24.6148 9.1385 1.3489
0.6728 50.67 3.64
GP
Report No. A-19005-206X
Black Ridge Companies
Graf Street Apartments
Bozeman, Montana
B19-014-001
Material Description
Atterberg Limits
Coefficients
Classification
Remarks
Location: TP-30
Sample Number: A-19005 Depth: 5.0 ft Date:
Client:
Project:
Project No: Figure
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
PE
R
C
E
N
T
F
I
N
E
R
0
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
9.3 47.2 19.7 6.2 10.7 4.1 2.8
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾ i
n
.
½ i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
Particle Size Distribution Report
y:
B19-014-001No:
Tested By: MS Checked By:
2-22-2019
7
(no specification provided)
PL= LL= PI=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
USCS= AASHTO=
*
Clayey GRAVEL with Sand
1.5"
1"
3/4"
1/2"
3/8"
#4
#10
#20
#40
#60
#80
#100
#200
100.0
85.9
81.1
72.5
67.0
56.4
47.6
38.4
29.6
25.4
23.5
22.6
20.6
29.3646 24.3744 6.1911
2.5905 0.4413
GC
Report No. A-19003-206
Black Ridge Companies
Graf Street Apartments
Bozeman, Montana
B19-014-001
Material Description
Atterberg Limits
Coefficients
Classification
Remarks
Location: TP-41
Sample Number: A-19003 Depth: 2.5 ft Date:
Client:
Project:
Project No: Figure
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
PE
R
C
E
N
T
F
I
N
E
R
0
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 18.9 24.7 8.8 18.0 9.0 20.6
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾ i
n
.
½ i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
Particle Size Distribution Report
y:
B19-014-001No:
Tested By: JS Checked By:
LIQUID AND PLASTIC LIMITS TEST REPORT
PL
A
S
T
I
C
I
T
Y
I
N
D
E
X
0
10
20
30
40
50
60
LIQUID LIMIT
01 02 03 04 05 06 07 08 09 0 1 0 0 1 1 0
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
WA
T
E
R
C
O
N
T
E
N
T
33
34
35
36
37
38
39
40
41
42
43
NUMBER OF BLOWS
56 7 8 9 1 0 2 0 25 30 40
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
Project No. Client: Remarks:
Project:
Location: TP-8
Sample Number: A-18999 Depth: 2.0 ft
Figure
Lean CLAY with Sand 37 21 16 CL
B19-014- Black Ridge Companies
8
Report No. A-18999-207
Date: 2-22-2019Graf Street Apartments
Bozeman, Montana
y:
Tested By: JS Checked By:
LIQUID AND PLASTIC LIMITS TEST REPORT
PL
A
S
T
I
C
I
T
Y
I
N
D
E
X
0
10
20
30
40
50
60
LIQUID LIMIT
01 02 03 04 05 06 07 08 09 0 1 0 0 1 1 0
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
WA
T
E
R
C
O
N
T
E
N
T
41.2
41.6
42
42.4
42.8
43.2
43.6
44
44.4
44.8
45.2
NUMBER OF BLOWS
56 7 8 9 1 0 2 0 25 30 40
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
Project No. Client: Remarks:
Project:
Location: TP-37
Sample Number: A-19002 Depth: 1.0 ft
Figure
Lean CLAY with Sand 42 22 20 CL
B19-014- Black Ridge Companies
9
Report No. A-19002-207
Date: 2-22-2019Graf Street Apartments
Bozeman, Montana
y:
Technician:
Test Procedure
2.90
9.3
2.8
FIGURE 10
Peter Klevberg, P.E.
Laboratory Manager
Relative Density, (ASTM D-4253, ASTM D-4254, ASTM D-4718)
% Retained on 3"
Project:Graf Street Apartments
Date Sample Received:2/19/2019
Attn:
Address:
Sample Source:TP-30 (5.0 ft)
REPORT OF RELATIVE DENSITY
1800 River Drive North
Great Falls, Montana 59401
Mr. Will Ralph, PE
Report Date:3/5/2019
Telephone: (406) 761-3010 Fax: (406) 727-2872
Bozeman, MT 59719 Sample Number:A-19005
PO Box 11890 Project Number:B19-014-001
Client:Black Ridge Companies Report Number:A-19005-209
Thomas, Dean & Hoskins, Inc.
WJC
Pessimum Moisture = 2.3 % Passing No. 200
Poorly-Graded GRAVEL with Sand
6.5
Specific Gravity
Unified Classification
Optimum Moisture =
Minimum Dry Density =
147.9
127.2
Maximum Dry Density =
120.0
125.0
130.0
135.0
140.0
145.0
150.0
0.0 2.0 4.0 6.0 8.0 10.0 12.0
Dr
y
D
e
n
s
i
t
y
(
p
c
f
)
Water Content (%)
ϭϮϬ
ϭϮϱ
ϭϯϬ
ϭϯϱ
ϭϰϬ
ϭϰϱ
ϭϱϬ
Ϭ ϭ ϬϮ Ϭϯ Ϭϰ Ϭϱ Ϭϲ Ϭϳ Ϭϴ Ϭϵ Ϭ ϭ Ϭ Ϭ
lb
s
.
/
c
u
.
f
t
.
Percent Relative Density
s ƵƌǀĞ
Peter Klevberg, P.E.
Laboratory Manager
Percent Relative Density
Tested By: WJC Checked By:
Moisture-Density Test Report
Dr
y
d
e
n
s
i
t
y
,
p
c
f
99
101
103
105
107
109
Water content, %
14 16 18 20 22 24 26
18.3%, 106.2 pcf
ZAV for
Sp.G. =
2.65
Test specification:ASTM D 698-12 Method A Standard
2.0 ft CL 2.65 1.6
Lean CLAY with Sand
B19-014- Black Ridge Companies
Report No. A-19006-204
Date: 2-22-2019
11
Elev/ Classification Nat.Sp.G. LL PI % > % <
Depth USCS AASHTO Moist. #4 No.200
TEST RESULTS MATERIAL DESCRIPTION
Project No. Client:Remarks:
Project:
Location: TP-30 Sample Number: A-19006
Figure
Maximum dry density = 106.2 pcf
Optimum moisture = 18.3 %
Graf Street Apartments
Bozeman, Montana
y:
BEARING RATIO TEST REPORT
ASTM D 1883-07
Project No: B19-014-001
Project: Graf Street Apartments Bozeman, Montana
Location: TP-30
Sample Number: A-19006 Depth: 2.0 ft
Date: February 15, 2019
Lean CLAY with Sand
Test Description/Remarks:
ASTM D698 with 6-inch mold
96-hour soak prior to testing
Report No. A-19006-210
Date: 3-5-2019
Figure 12
106.2 18.3CL
Material Description USCS
Max.
Dens.
(pcf)
Optimum
Moisture
(%)
LL PI
Molded
Density
(pcf)
Percent of
Max. Dens.
Moisture
(%)
Soaked
Density
(pcf)
Percent of
Max. Dens.
Moisture
(%)
CBR (%)
0.10 in. 0.20 in.
Linearity
Correction
(in.)
Surcharge
(lbs.)
Max.
Swell
(%)
1 90.5 85.2 17.8 89.7 84.5 27.6 2.9 2.6 0.000 10 0.9
2 106.2 100 17.9 105.2 99 20.3 10.6 10.8 0.011 10 1
3
Pe
n
e
t
r
a
t
i
o
n
R
e
s
i
s
t
a
n
c
e
(
p
s
i
)
0
70
140
210
280
350
Penetration Depth (in.)
0 0.1 0.2 0.3 0.4 0.5
Sw
e
l
l
(
%
)
0
0.4
0.8
1.2
1.6
2
Elapsed Time (hrs)
02 44 87 2 9 6
CB
R
(
%
)
2
5
8
11
14
Molded Density (pcf)
85 90 95 100 105 110
10 blows
56 blows
CBR at 95% Max. Density = 8.0%
for 0.10 in. Penetration