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PEOPLE WHO MAKE IT HAPPEN
PEOPLE WHO MAKE IT HAPPEN G e o t e c h n i c a l R e p o r t PEOPLE WHO MAKE IT HAPPEN dowl.com
BOZEMAN HEALTH EMERGENCY
DEPARTMENT EXPANSION
BOZEMAN, MT
February 2026
Prepared By:
1283 North 14th Avenue, Suite 101
Bozeman, Montana 59715
Project No. 4691.000617.01
Prepared For:
915 Highland Boulevard
Bozeman, Montana 59715
PEOPLE WHO MAKE IT HAPPEN
PEOPLE WHO MAKE IT HAPPEN
BOZEMAN HEALTH EMERGENCY DEPARTMENT
EXPANSION
Building Additions to South and North of Emergency Department
Prepared for:
915 Highland Boulevard
Bozeman, Montana 59715
Prepared by:
1283 North 14th Avenue, Suite 101
Bozeman, Montana 59715
Principal Author: David J. Barrick, P.E.
Reviewed By: Dennis A. Russell, P.E.
February 2026
4691.000617.01
\\dowl.com\j\projects\91\000617-01\91geoscience\report\bozeman health ed expansion final geo report.docx
Page I
TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................................. 1
1.1 Project Understanding ............................................................................................ 1
1.1.1 Existing Site Conditions ........................................................................... 1
1.1.2 Proposed Construction ............................................................................ 3
2.0 INVESTIGATION .................................................................................................. 5
2.1 Historic Geotechnical Field Investigation ................................................................ 5
2.2 Geophysical Field Investigation .............................................................................. 7
2.3 Geophysical Analysis and Interpretation................................................................. 8
2.3.1 Seismic Analysis ...................................................................................... 8
2.3.1.1 Seismic Refraction Method ....................................................................... 8
2.3.1.2 MASW Method .......................................................................................... 9
2.3.1.3 Seismic Interpretation ............................................................................... 9
2.3.2 Resistivity Analysis and Interpretation ................................................. 11
2.3.2.1 Resistivity Line – North Addition ............................................................. 11
3.0 SUBSURFACE CONDITIONS ........................................................................... 12
3.1 Site Geology ........................................................................................................ 12
3.2 Observed Soil Conditions ..................................................................................... 12
3.3 Groundwater ........................................................................................................ 13
3.3.1 Groundwater Information Center Research .......................................... 13
3.4 Seismicity ............................................................................................................. 14
3.4.1 Faulting ................................................................................................... 14
3.4.2 Design Accelerations ............................................................................. 14
3.4.3 Liquefaction ............................................................................................ 14
4.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS ................................ 15
4.1 Foundations ......................................................................................................... 15
4.1.1 Engineered Aggregate Piers .................................................................. 16
4.1.2 Drilled Shafts .......................................................................................... 17
4.1.3 Helical Piles ............................................................................................. 19
4.2 Lateral Earth Pressures ........................................................................................ 20
4.2.1 Seismic Earth Pressure .......................................................................... 21
4.2.2 Coefficient of Friction ............................................................................. 22
4.3 Slabs-on-Grade .................................................................................................... 22
4.3.1 Interior Slabs and Helipad ...................................................................... 22
4.4 Low Height Concrete Block Retaining Walls ......................................................... 22
4.5 Pavement Surfacing ............................................................................................. 23
4.5.1 Traffic ...................................................................................................... 23
4.5.2 Design Parameters ................................................................................. 23
4.5.3 Flexible Pavement .................................................................................. 24
4.5.4 Rigid Pavement ....................................................................................... 24
4.5.5 Pavement Construction Considerations ............................................... 25
4.6 Drainage .............................................................................................................. 25
4.6.1 Surface Drainage .................................................................................... 25
4.7 Earthwork ............................................................................................................. 26
4.7.1 Subgrade Preparation ............................................................................ 26
4.7.2 Excavation............................................................................................... 26
4.7.3 Dewatering .............................................................................................. 27
4.7.4 Structural Fill .......................................................................................... 27
Page II
4.7.5 Compaction Requirements .................................................................... 27
4.7.6 Testing and Observations ...................................................................... 28
4.7.7 Cold Weather Construction ................................................................... 28
4.7.8 Wet Weather/Soil Construction ............................................................. 29
4.7.9 Geosynthetics ......................................................................................... 29
4.8 Soil Chemistry and Corrosion ............................................................................... 29
5.0 GEOTECHNICAL DESIGN CONTINUITY ......................................................... 30
6.0 LIMITATIONS ..................................................................................................... 31
7.0 REFERENCES ................................................................................................... 32
PHOTOGRAPHS
Photograph 1: Collecting Seismic Data Near Existing Helipad – View Northeast ........................ 2
Photograph 2: Geophysical Survey of Northeast Addition – View Southeast ............................... 2
FIGURES
Figure 1: Vicinity and Project Location ....................................................................................... 4
Figure 2: Borehole and Geophysics Array Location Map ............................................................ 6
TABLES
Table 1: Geotechnical Exploration Summary ............................................................................. 5
Table 2: Geophysical Exploration Summary ............................................................................... 7
Table 3: Seismic Survey Parameters ......................................................................................... 8
Table 4: Electrical Resistivity Survey Parameters ...................................................................... 8
Table 5: Range of Seismic Velocities (feet per second) ........................................................... 10
Table 6: Depth to Gravel Deposits ........................................................................................... 13
Table 7: Groundwater Depths .................................................................................................. 13
Table 8: Documented Faults .................................................................................................... 14
Table 9: Seismic Design Parameters ....................................................................................... 14
Table 10: Substation Drilled Pier Recommendations Parameters ............................................ 18
Table 11: L-Pile Drilled Pier Recommendations Parameters .................................................... 19
Table 12: Helical Pier Capacities.............................................................................................. 20
Table 13: Lateral Earth Pressures ............................................................................................ 21
Table 14: Floor Slab Recommendations .................................................................................. 22
Table 15: Traffic Loading ......................................................................................................... 23
Table 16: Pavement Design Parameters .................................................................................. 24
Table 17: Fill Specifications...................................................................................................... 27
Table 18: Compaction Specifications ....................................................................................... 28
Table 19: Soil Chemistry Test Results ..................................................................................... 30
APPENDICES
Appendix A Exploration Logs
Appendix B Geophysics Outputs
Page III
EXECUTIVE SUMMARY
DOWL prepared this geotechnical report for Bozeman Health. This report specifically provides
recommendations for the proposed additions to the south and north sides of the existing Bozeman
Health Emergency Department (ED). Because of the sensitive nature of the area regarding an
active helipad, underground utilities, and active emergency vehicles, the geotechnical
recommendations were developed from a combination of historical geotechnical boreholes and
near-surface geophysics. Based on the information obtained from our subsurface exploration, the
site can be developed for the proposed project. We identified the following geotechnical
considerations:
• The subsurface investigation consists of a combination of historical geotechnical
boreholes and near-surface geophysics. Nine historical boreholes were drilled for the
construction of the existing emergency department or ICU structures. The existing
emergency department consists of a two-story structure that daylights at two elevations.
The surface elevations of the historical boreholes were based on multiple survey datums
and may vary when compared to the current topography survey. The surface elevations
of the 2008 historical geotechnical boreholes are approximately three to four feet lower
than Sanbell’s topography survey. South of the existing ED, the site is relatively flat with
a helipad. However, on the northeast side, the site slopes downwards towards the
hospital’s Entrance #1.
• The lithology consists of undocumented fill or medium-stiff to stiff lean clay overlying gravel
deposits. The depth of the gravel deposits ranges from approximately 19.0 to 35.4 feet
below the second floor’s finish floor elevation of 4,914.5 feet. Tertiary sediment classified
as silty sand underlies the gravel deposits and extends beyond the maximum depths
explored.
• No groundwater was observed during the geotechnical or geophysical investigations, with
the exception of two perched water tables.
• The 2009 geotechnical report for the existing ED structure provided foundation
recommendations consisting of: drilled shaft, helical piles, and overexcavation and
replacement with structural fill. This report provides all those recommendations and for
engineered aggregate piers as well.
• Close monitoring of the construction operations discussed herein will be critical in
achieving the design subgrade support. We therefore recommend that DOWL be retained
to monitor this portion of the work.
This section is only a summary. Recognize that we do not provide details in this section; read the
report in its entirety for a comprehensive understanding of the items contained herein.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 1
1.0 INTRODUCTION
DOWL completed a near-surface geophysical investigation of the proposed emergency
department (ED) additions at the Bozeman Health facility in Bozeman, Montana (see Figure 1).
The scope of geotechnical services consisted of reviewing existing geotechnical and geological
information, field observations, a seismic and electrical near-surface geophysical survey,
engineering analyses, and preparing this Geotechnical Report. The purpose of these services is
to provide geotechnical-related recommendations for project planning and design. We conducted
this referencing our proposal to Sanbell, dated December 3, 2025.
Our geotechnical engineering scope for this project included the initial site visit, a seismic and
electrical near-surface geophysical survey, and review of three historical geotechnical boreholes
with depths ranging from 26.5 to 31.5 feet below historical site grades, and engineering analyses
to provide foundation recommendations.
1.1 Project Understanding
1.1.1 Existing Site Conditions
The area proposed for ED expansion includes an ambulance drop-off garage and driveway,
helipad, a medical trailer, and parking lots with associated landscaping. Hospital Entrance #1 is
directly north and downhill of the proposed expansion area. The ED provides two access levels
with the higher helipad elevation and the lower basement entrance (same elevation as Entrance
#1).
South of the ED, the site is relatively flat with the helipad slightly elevated above the parking lot.
The elevation of Entrance #1 is approximately ten feet below the helipad elevation. A small fence
surrounds the helipad area. Vegetation consists of a maintained lawn, shrubs, and small conifer
trees.
Private waterlines (potable and irrigation) are located on-site in the vicinity of the proposed project.
Other existing underground utilities consist of electricity and communications. Since geotechnical
boreholes were not drilled, one-call was not performed.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 2
Photograph 1: Collecting Seismic Data Near Existing Helipad – View Northeast
Photograph 2: Geophysical Survey of Northeast Addition – View Southeast
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 3
1.1.2 Proposed Construction
Two additions are proposed for the Emergency Department. The south addition will be slab-on-
grade and will not include a basement. The proposed finished floor elevation of the south addition
will be 4,914.5 feet. The northeast addition will include a basement that matches the existing
structure. The basement finish floor elevation will be 4,899.2 feet to match the existing ED
elevation.
The proposed construction will be steel-framed with concrete on metal deck at elevated floors
and untopped metal deck at roof levels.
The south or driveway addition will be approximately 6,800 square feet, and the north addition
will be approximately 9,100 square feet.
Per information provided by Tom Kujawa, representative of Hicks Engineering, the approximate
structural loads for the additions are as follows:
• Point loads = 350 kips (service), and
• Exterior wall loads = 10 kips per linear foot (service).
BOZEMAN HEALTH ED ADDITION
GEOSCIENCE INVESTIGATION
VICINITY AND LOCATION MAP FIGURE 1
BOZEMAN HEALTH ED ADDITION - BOZEMAN, MONTANA
VICINITY MAP
NOT TO SCALE
LOCATION MAP
HAVRE
GLASGOW
SIDNEY
GLENDIVE
MILES CITY
HARDIN
BILLINGS
BOZEMAN
DILLON
BUTTE
HELENA
MISSOULA
KALISPELL
LEWISTOWN
GREAT FALLS
SHELBY
DEER LODGE
PROJECT LOCATION
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 5
2.0 INVESTIGATION
2.1 Historic Geotechnical Field Investigation
DOWL (formerly HKM Engineering and MSE-HKM) performed historical geotechnical fieldwork in
the years 1998, 2000, 2008, and 2017, consisting of site observations and drilling nine
geotechnical boreholes. We present the borehole locations in Figure 2. The drilling contractors
advanced the geotechnical borings to depths of 24.0 and 36.5 feet below the historical ground
surface. Table 1 organizes the borehole information.
Table 1: Geotechnical Exploration Summary
Borehole
Number
Borehole
Depth (feet)
Surface
Elevation (feet) Date Drilled Geotechnical
Report Name
BH-4-08 31.5 4,911.0 December 1, 2008
Emergency
Room & Patient
Wing Addition
BH-5-08 26.5 4,910.0 December 2, 2008
Emergency
Room & Patient
Wing Addition
BH-6-08 31.5 4,913.7 December 1, 2008
Emergency
Room & Patient
Wing Addition
HKM DH 101 36.5 4,913.4 June 1, 1998 Emergency
Room Addition
HKM DH 102 31.0 4,911.9 June 1, 1998 Emergency
Room Addition
BH-206 26.5 4,901.8 October 24, 2000
Bozeman
Deaconess
Option 1
BH-207 32.5 4,900.3 December 12, 2000
Bozeman
Deaconess
Option 1
B-8-17 26.5 4,902.0 December 21, 2017 ICU Addition
B-9-17 24.0 4,901.8 December 21, 2017 ICU Addition
The borehole surface elevations come from multiple geotechnical investigations with varying
survey methods. Treat the borehole surface elevation data as approximate. The first five
boreholes in Table 1 were drilled at an elevation similar to the finish floor elevation of the proposed
south addition. The bottom four boreholes in Table 1 were drilled at an elevation similar to the
basement of the proposed north addition.
HazTech Drilling, Hanson Drilling, or SK Geotechnical drilled the borings under the direction of a
DOWL geotechnical engineer or geologist using a BK-81, CME-75, or CME-55 truck-mounted drill
rigs. The drill rig was equipped with 4.5-inch I.D. hollow stem augers.
We provide historical exploration logs in Appendix A, which includes soil and groundwater
conditions as well as SPT information. Stratification boundaries on the exploration logs represent
the approximate location of changes in soil types; in situ, the transition between materials may be
gradual and may vary.
B-4-08
B-5-08
B-6-08
B-8-17
B-9-17
HKM DH 101
BH-206
BH-207
HKM DH 102
BOZEMAN HEALTH - ED EXPANSION
GEOSCIENCE INVESTIGATION
TRANSECT LOCATION MAP FIGURE 2
B-4-08
LEGEND
EXISTING GEOTECHNICAL BOREHOLE LOCATIONS
SOUTH (DRIVEWAY) ADDITION GEOPHYSICAL TRANSECT
NORTH ADDITION GEOPHYSICAL TRANSECT
START
START
END
END
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
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2.2 Geophysical Field Investigation
Geophysical data was collected at both addition sites. The south addition (ambulance driveway)
transect starts with the conifer trees south of the medical trailer and ends northeast of the helipad.
The north transect starts at the ED basement door and ends east of the helipad. The north
transect consisted of both seismic and electrical resistivity, while the driveway alignment
consisted of seismic only. Only seismic was performed at the driveway because of constant
ambulance traffic. The geophysical transects were “field-fit” to maximize data collection while
considering the efficiency of equipment, cable, and geophone placement.
DOWL performed two seismic transects, 225 feet in length, as shown in Figure 2. General
information for the geophysical transects is provided in Table 2. Two seismic data collection
methodologies were implemented along each transect: the Multichannel Analysis of Surface
Waves (MASW) and seismic refraction methods. The seismic refraction data were collected in
general accordance with ASTM D5777-18, Standard Guide for Using the Seismic Refraction
Method for Subsurface Investigations. Electrical resistivity was performed to supplement seismic
data. DOWL collected the electrical resistivity data in general accordance with ASTM D6431-18,
Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site
Characterization.
Table 2: Geophysical Exploration Summary
Transect
Transect
Length
(feet)
Transect Start
(Latitude &
Longitude)
Transect End
(Latitude &
Longitude)
Description
Driveway* 225 46° 10’ 45.63” N
112° 47’ 44.61” W
46° 10’ 46.56” N
112° 47’ 40.71” W
South Addition
Existing Driveway
Area
North Addition 225 46° 10’ 46.75” N
112° 47’ 43.30” W
46° 10’ 45.41” N
112° 47’ 42.50” W Northeast Addition
*Seismic only
The location and elevations used for the tomograms were taken in the field using a Bad Elf GPS.
The elevations were modified to match the topography elevations provided by Sanbell.
Seismic Data Collection
The seismic source (shot) or energy introduced into the ground was initiated by a 20-pound
sledgehammer striking a plate on the ground surface. Four hammer hits were used at each shot
location and summed to reduce background ambient noise. Sixteen shot locations were
implemented along each profile. Shot spacings were determined based on subsurface ray path
coverage suitable for seismic refraction tomography (SRT) and subsequent use in MASW
analysis. Seismic survey parameters used for all data collection transects are summarized in
Table 3.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 8
Table 3: Seismic Survey Parameters
Parameter Equipment, Method, or Software
Recording Instrument Geometrics Geode
Geophone Natural Period 4.5 Hertz
Number of Geophones 24
Sample Rate 0.125 millisecond (MASW)
Number of Samples 6,000 per channel
MAM Data Collection 30 minutes
Record Length 1.5 seconds
Geophone Spacing 7.5 feet
Seismic Source 20-pound sledgehammer
Stack Number 4
Refraction Analysis
Software Rayfract®
Surface Wave Analysis
Software
SeisImagerSW™ Geometrics, Inc. MASW 1D
SWprocess MASW 1D
Surface Wave Wizard/Geoplot Geometrics, Inc. MASW 2D
Electrical Resistivity Data Collection
Electrical Resistivity Tomography (ERT) data were collected by inserting 48 3/8-inch metal
electrodes in the ground in an array and injecting a low-voltage direct current. The electrical
method estimates the depth of variable geomaterials via an electrical resistivity inversion of the
field data when a contrast of conductivity is present. Electrical resistivity survey parameters used
for all data collection transects are summarized in Table 4.
Table 4: Electrical Resistivity Survey Parameters
Parameter Equipment, Method, or Software
Recording Instrument ABEM Terrameter LS2
Number of Electrodes 48
Array Gradient
Error Limit 1%
Acquisition Time 1.5 seconds
Maximum Stack Number 4
Data Filtering Software ABEM Toolbox®
Resistivity Analysis
Software Res2Dinv®
2.3 Geophysical Analysis and Interpretation
2.3.1 Seismic Analysis
2.3.1.1 Seismic Refraction Method
The seismic refraction method calculates subsurface compressional wave velocity (Vp). This
approach uses seismic body waves, in contrast to the MASW method, which employs seismic
surface waves.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 9
Using the same first arrival times, a tomographic solution can be calculated by discretizing the
subsurface into cells instead of layers. The tomographic approach thus lends itself to
characterizing laterally variable subsurface media.
2.3.1.2 MASW Method
The MASW method provides a shear wave velocity (Vs) result as a 1D profile located at the center
of the geophone spread. Optimal MASW data collection requires the seismic source (shots) to be
offset from the nearest geophone, ideally ranging between 10 and 30 percent of the geophone
spread length. Thus, shots taken inside the geophone spread will not give accurate results for
MASW analysis.
MASW uses the velocity dispersion characteristics of the high-amplitude surface wave (Rayleigh
wave) to calculate Vs with depth. SeisImagerSW and SWprocess software was used for the
MASW analysis. The project site’s Seismic Site Classification per the 2016 edition of the American
Society of Civil Engineers 7 (ASCE 7-16) Minimum Design Loads and Associated Criteria for
Building and Other Structures Table 20.2-1 are attached in Appendix B.
2D MASW profiles are attached. 2D MASW uses Common-Mid-Point (CMP) gathers to generate
shear wave velocities. Although the 2D s-wave velocity profiles resemble discretized velocity
models, the 2D profiles are formed from 1D s-wave velocity profiles calculated at two times the
geophone spacing. The starting model was set to 12 layers for the calculations. Thus, the
resolution of the MASW 2D model is twice the geophone spacing horizontally and 12 layers
vertically, resulting in a coarser resolution than SRTs. The figures are the gridded and contoured
results from the individual 1D s-wave depth velocity profiles.
2.3.1.3 Seismic Interpretation
Interpretations of the seismic data are attached. The seismic profiles represent the corresponding
calculated 2D SRTs of compressional wave velocity (Vp) and 2D (MASW) tomograms.
The shear wave velocities for geomaterials are typically 40 to 60 percent of the compression wave
velocities if there is no groundwater table. If there is a groundwater table, the shear wave velocities
are approximately 20 percent of the compression wave velocity. Groundwater does not impact
the shear wave velocities, as water has no shear strength. In geotechnical engineering terms,
compression waves can be regarded similar to total stress parameters as they tend to induce
volume change, and their propagation velocity in saturated soil is practically identical to that of
compression waves in water. Shear waves impose only shear deformation, and the velocity can
be considered an effective stress parameter.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 10
DOWL researched published representative p-wave velocities to interpret depths to bedrock or
dense sediment below the existing ground surface. Table 5 lists published seismic wave
velocities for various materials (Press, 1966). Shear wave velocities were calculated and
tabulated based on the following rule-of-thumb relationships (Burger, Sheehan, and Jones,
2006):
• Vs = 0.6Vp for crystalline rocks
• Vs = 0.5Vp for sedimentary rocks
• Vs = 0.4Vp for soils and unconsolidated sediment materials.
Table 5: Range of Seismic Velocities (feet per second)
Unconsolidated Materials Competent Bedrock (no groundwater)
P-wave
Velocities
S-wave
Velocities* P-wave
Velocities
S-wave
Velocities*
Alluvium 1,640-6,560 660-2,620 Granite 16,400-19,680 9,840-11,810
Clay 3,610-8,200 1,444-3,280 Basalt 17,710-20,990 10,630-12,600
Unsaturated
Sand 660-3,280 262-1,310 Metamorphic
Rocks 11,480-22,960 6,890-13,780
Saturated
Sand 2,620-7,220 262-1,310 Sandstone
and Shale 6,560-14,760 3,280-7,380
Unsaturated
Sand and
Gravel
1,310-1,640 525-660 Limestone 6,560-19,680 3,280-9,840
Saturated
Sand and
Gravel
1,640-4,920 525-660 Non-geomaterials
Unsaturated
Glacial Till 1,310-3,280 525-1,310 P-wave
Velocities
S-wave
Velocities
Saturated
Glacial Till 2,630-6,550 525-1,310 Water 4,592-5,248 N/A
Very Dense
Glacial Till 3,940-6,890 1,574-2,760 Air 1,087 N/A
*S-waves were calculated using the rule of thumb listed above.
Velocities are in feet per second and converted from published meters per second.
As shown in Table 5, saturated unconsolidated material or sediment has a higher p-wave velocity
range than unsaturated sediments. However, S-wave velocities don’t change with the presence
of groundwater.
The following two sections are the interpretation of two geophysical transects perform for each of
the two additions. DOWL interprets the compressional wave velocity (Vp) for the sound
geomaterials (gravel deposits and underlying silty sand) as 2,500 feet per second. The shear
wave velocities from MASW data are interpreted as 1,250 feet per second. Seismic
(compressional refraction and MASW) was only performed at the south addition because of
ambulance traffic. The MASW 1D for the determination of seismic site class was obtained from
the south addition array. The geophysics at the north addition consisted of compressional and
shear wave refraction, MASW, and electrical resistivity. DOWL combined the compressional and
shear wave refraction from the north addition to investigating the presence of a groundwater table.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 11
Seismic Line – South Addition – Ambulance Driveway
The seismic refraction tomography (Profile 1) and MASW 2D (Profile 2) profiles just south of the
helipad illustrates interpretative gravel deposits at approximate elevations ranging from 4,890 to
4,878 feet with the seismic refraction showing more undulations. This interpretation of the seismic
geophysics correlates well with the depth to gravel deposits shown in Table 6. The nine historical
boreholes show the elevations of the gravel deposits range from 4,895.5 to 4,879.1 feet. The 2D
seismic investigation consisted of compressional seismic refraction and MASW 2D.
Profile 3 of Appendix B illustrates the MASW 1D profile to calculate seismic site classification.
Appendix B also lists Table 20.3-1 from ASCE 7-16 for Seismic Site Classification. The 1D MASW
method estimates that the 1D shear wave profile extends at least 100 feet for Vs100 determination
and is located at the center of the seismic spread. Based on the 1D MASW profile, the Vs100 is
estimated to be 1,213.4 feet per second.
Profile 4 of Appendix B illustrates the MASW 1D profile to calculate seismic site classification from
an open-source software called SWProcess. SWProcess allows for the deeper analysis of the
site’s surface wave dispersion data and quantifying its uncertainty. The Vs100 determined from
SWProcess was estimated to be 1,168 feet per second with a standard deviation of 56 feet per
second when comparing three different shear wave profile models.
Seismic Line – North Addition
A seismic line was performed for the north addition and both compressional (Profile 5) and shear
wave (Profile 6) refraction, as well as MASW 2D (Profile 7). The data was collected on a hillside
but the interpretative depth to gravel deposits remains fairly consistent with depth. This indicates
that the depth to gravel deposits does not parallel the surface contours. As for the south addition,
the interpretative elevation of the gravel deposits range from approximately 4,890 to 4,880 feet.
Because there was no ambulance traffic while collecting data for the north addition, DOWL was
able to create a Vp/Vs ratio by combining the compressional and shear wave refraction profiles.
DOWL interprets the presence of a groundwater table if the Vp/Vs ratio is greater than 4.0. As
shown on Profile 8 in Appendix B, the highest Vp/Vs ratio is approximately 2.7. Section 3.3
expands on groundwater data from past geotechnical investigations.
2.3.2 Resistivity Analysis and Interpretation
The ERT method utilizes differences and contrasts in electrical resistivity to identify the
subsurface materials, depth to water, and subsurface structures. This method measures the
subsurface bulk (apparent) electrical resistivity, providing information about changes in
subsurface lithology and groundwater saturation. The measured apparent resistivity is a function
of different parameters, such as porosity, groundwater salinity, clay content, water saturation, and
how the subsurface conducts electricity.
2.3.2.1 Resistivity Line – North Addition
The resistivity investigation reveals two distinct geomaterials in the upper 40 feet of the
subsurface. At approximately elevation 4,890 feet and above, we recorded lower resistivity values
indicating undocumented fill and native lean clays. Higher resistivities were recorded below the
4,890-foot elevation, indicating the gravel and silty sand deposits.
Bozeman Health Emergency Department Expansion
Building Additions to South and North of Emergency Department February 2026
Page 12
The resistivity profile may also illustrate the existence of an underground utility with the underlying
bedding material at approximately station 70 feet.
All geophysics outputs are in Appendix B.
3.0 SUBSURFACE CONDITIONS
3.1 Site Geology
The Gallatin Valley is an intermountain basin within the Rocky Mountains. The Bridger and
Gallatin Mountain Ranges flank the valley on the east and south of the Horseshoe Hills from the
northern boundary, and the topographic divide between the Gallatin and Madison Rivers bounds
the valley on the west. The south and east sides of the Gallatin Valley are bordered by coalescing
alluvial fans that slope rather steeply from the Gallatin and Bridger Ranges. These
alluvial/fluviatile deposits range in age from Tertiary to Quaternary.
Geologic mapping of the Gallatin Valley indicates that the project site is located on the Sixmile
Creek Formation (Tsc). The lithology of the Sixmile Creek Formation is predominately light brown
to light gray, poorly stratified and poorly sorted, tuffaceous siltstone. The formation also includes
discontinuous, lenticular layers of fluvial channel conglomerate, unaltered white volcanic ash, and
mudstone.
3.2 Observed Soil Conditions
The nine historical boreholes were drilled at a preexisting parking lot with asphalt surfacing or
topsoil of landscaping areas. None of these boreholes were drilled within the proposed expansion
footprint and the conditions beyond these boreholes may differ.
The soil conditions were observed to be relatively consistent with undulations regarding the depth
to gravel deposits layer. Tertiary sediment underlies the gravel deposits and extends beyond the
maximum depths explored of 36.5 feet. Undocumented fill was observed in seven of the nine
boreholes with depths ranging from 2.4 to 10.0 feet from the ground surface.
Below the fill, native medium-stiff to very-stiff lean clay was observed with medium brown color.
Underlying the clay, alluvial gravel deposits were observed at depths ranging from 12.2 to 28.5
feet below the drilled ground surface, and the gravel deposits were observed at approximate
elevations ranging from 4,895.5 to 4,879.1 feet. Table 6 outlines the depths to gravel and the
elevation of the gravel deposits from four past geotechnical investigations of nearby structures.
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Table 6: Depth to Gravel Deposits
Borehole Surface Elevation
(feet)
Depth to Gravel
Deposits (feet)
Elevation of Gravel
Deposits (feet)
BH-4-08 4,911.0 19.5 4,891.5
BH-5-08 4,910.0 14.5 4,895.5
BH-6-08 4,913.7 22.5 4,891.2
HKM DH 101 4,913.4 28.5 4,884.9
HKM DH 102 4,911.9 19.6 4,892.3
BH-206 4,901.8 22.7 4,879.1
BH-207 4,900.3 20.0 4,880.3
B-8-17 4,902.0 13.8 4,888.2
B-9-17 4,901.8 12.2 4,889.6
In Appendix A we present the historic exploration logs with lithology descriptions as well as other
engineering properties. In the following paragraphs, we provide a general description of the soil
strata.
3.3 Groundwater
A perched groundwater table was encountered at two of the nine geotechnical boreholes at
depths of 3.0 and 14.0 feet, respectively. These observations represent groundwater conditions
only at the time of the observations and may not be indicative of other times or locations.
Groundwater conditions can change with varying seasonal and weather conditions and other
factors. Consider the possibility of groundwater fluctuations when developing design and
construction plans for the project. Table 7 lists the groundwater depths and the static groundwater
elevations observed during the four geotechnical investigations.
Table 7: Groundwater Depths
Boring Groundwater
Depth (feet)
Borehole Surface
Elevation (feet)
Static Groundwater
Elevation (feet)
B-4-08 Not Encountered 4,911.0 --
B-5-08 Not Encountered 4,910.0 --
B-6-08 3.0 – Perched 4,913.7 4,910.7
HKM DH 101 Not Encountered 4,913.4 --
HKM DH 102 14.0 - Perched 4,911.9 4,897.9
BH-206 Not Encountered 4,901.8 --
BH-207 Not Encountered 4,900.3 --
B-8-17 Not Encountered 4,902.0 --
B-9-17 Not Encountered 4,901.8 --
3.3.1 Groundwater Information Center Research
We researched the Montana Bureau of Mines and Geology's Groundwater Information Center
(GWIC, 2023) website to estimate static water levels from Section 17 of Township 2 South, Range
6 East. GWIC data is for informational purposes only and contains historical well logs, some of
which may not be accurate. Based on the GWIC research, static groundwater levels range from
10 to 87 feet below the existing ground surface with an average depth of 43.7 feet. This data was
calculated from 15 wells located within this section.
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Bozeman Health owns five wells in this section, with three wells having static groundwater data.
The static groundwater data range from 45.1 to 53.0 feet.
3.4 Seismicity
3.4.1 Faulting
The proposed development is located in an area of Quaternary faulting. Based on the USGS
Quaternary Fault Fold Database (USGS, 2025), four Quaternary faults exist within the project
vicinity:
Table 8: Documented Faults
Fault Name
Distance
from Project
Site (miles)
Recent
Earthquake
Published
Slip Rate
(mm/yr)
Fault
Length
(km)
Average
Strike
Bridger Fault ~5 Unknown < 0.2 48 N9°W
Gallatin Range Fault ~7.5 Unknown < 0.2 26 N63°E
Central Park Fault ~20 Unknown < 0.2 30 N77°E
Elk Creek Fault ~25 Unknown < 0.2 28 N62°W
Available publications do not include documentation that these faults have been offset during the
Holocene (last 15,000 years). However, the proposed structure is in an area of high seismic
activity.
3.4.2 Design Accelerations
DOWL utilized site soil and geologic data, our knowledge of local geology, MASW 1D methods,
the project location, the 2016 American Society of Civil Engineers 7 (ASCE 7), and the National
Earthquake Hazards Reduction Program (NEHRP) to estimate Seismic Site Classification of "D"
at the project site. We recommend seismic design based to the seismic parameters provided in
Table 9, which are based on the soil conditions and project location:
Table 9: Seismic Design Parameters
Period
(seconds)
Modified Acceleration
Coefficient for Site
Class D (g)
0.0 (peak) PGAM = 0.383
0.2 (short SDS = 0.562
1.0 (long) SD1 = 0.275
3.4.3 Liquefaction
Liquefaction is the partial or total loss of strength of soils that can occur during strong earthquake
shaking of significant duration. Liquefaction is a process where high shear deformations result in
progressive build-up of pore water pressure. Because the seismic load occurs rapidly, soil does
not have time to drain, and the effective stress may be reduced to near zero, resulting in a
temporary loss of shear strength. Earthquake-induced liquefaction generally occurs only under
particular conditions, which include saturation, strong earthquake ground shaking of long duration,
and loose granular soil. Liquefaction can also occur in silts and fine-grained soils. Typically,
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liquefaction occurs where the groundwater table is shallow (5 to 10 feet deep) and generally only
at depths less than approximately 50 feet.
Based on SPT N-values observed in each soil unit for this site and the lack of groundwater, it is
our opinion that the risk of liquefaction is very low at this site.
4.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS
4.1 Foundations
The assumed finish-floor elevation for the basement floor is assumed to be 4,899.2 feet, and the
second floor to be 4,914.5 feet. As discussed previously, soil conditions encountered during
historical investigations indicate medium-stiff to lean clay overlie dense to very dense gravel
deposits. Dense to very dense silty sand typically underlies the gravel deposits. The gravels were
observed at elevations ranging from 4,895.5 to 4,879.1 feet in the geotechnical boreholes. These
observed borehole depths to gravel match well with the geophysical transect depths of 2,500 feet
per second for compressional waves and 1,250 depths per second for shear waves. As shown in
the historical boreholes and near-surface geophysics, the gravel deposits undulate at the site.
The lean clay is not suitable to support conventional footings with high loads unless significant
over-excavation is performed. The lean clays are moderately compressible and may contain
layers that have collapse potential. Differential settlement is always a concern when placing
additions to existing structures. Up to 10 feet of undocumented fill was also observed in the
historical boreholes. Undocumented fill is also not suitable to support conventional footings.
Based on preliminary assumptions, DOWL estimates that all the lean clay soil would need to be
over-excavated to reduce the settlement potential of the point load footings. Without over-
excavation, the settlement of the spread footings has an estimated settlement potential of over
one inch.
Since the project consists of two additions, any settlement of the new footings will therefore be
considered differential to the existing structure. Expansion joints should be incorporated at the
interface areas between the new construction and the existing building. Excavation adjacent to
the existing footings should extend no closer than that defined by a line projected at a one-to-one
slope from the outside edge of the existing footings to the bottom of the excavation. For example,
the edge of an excavation 4 feet deep below an existing footing should be no closer than 4 feet
horizontally from the footing. If deemed necessary, underpinning of the existing footings should
be considered to ensure movement does not occur during excavation of the new basement
adjacent to the existing frost wall footing area. Additionally, to minimize the potential for additional
stress on existing footing foundations from the new footing loads, new footings should not be
placed closer than one- and one-half footing widths to existing footings. The structural engineer
may elect to rigidly connect new foundation elements to existing foundation in discrete locations,
provided that the combined behavior of the new and existing building are properly evaluated and
the existing building foundation is determined to be capable of supporting any additional loads or
effects thereof.
For the north addition that will have a basement, the basement’s finish floor elevation will be
4,899.2 feet. DOWL performed a overexcavation analysis and it is probably not feasible. With
maximum point loads of 350 kips, the entire clay layer must be removed to reduce settlement to
less than one inch. Because the gravel deposits undulate, the overexcavation will range from 3.7
to 20.1 feet. Because of the uncertainty in the depth to gravel depoits, DOWL recommends deep
foundation elements for both additions.
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We provide specific recommendations in the following sections.
4.1.1 Engineered Aggregate Piers
The proposed structures can be supported on conventional foundation overlying soil reinforced
by aggregate pier elements. The piers are constructed by drilling 24- to 36-inch diameter holes
extended below the base of the foundation and backfilling the holes with thin lifts of compacted
aggregate. Each lift is compacted using high-energy, low-frequency impact hammers that deliver
vertical ramming energy that densifies the aggregate and increases lateral stress in the soil
matrix. The system serves to reduce settlement by remediating the appropriate depth of loose
poorly graded sand with a denser composite soil matrix.
We have spoken to GeoTech Foundation Company–West regarding the suitability of installing
the aggregate pier system at the project site. DOWL estimates the allowable bearing capacity
using aggregate piers will be between 8,000 and 10,000 psf. It is recommended to use a
coefficient of friction of 0.5 between cast-in-place concrete and EAP improved subgrade. In
addition, the energy imparted by ramming aggregate into the native clays will densify the
surrounding soil, thereby reducing the settlement potential.
Aggregate Pier Installation Recommendations
If an aggregate pier-enhanced foundation system is selected, we recommend that the following
issues be considered prior to construction:
• Specifications for aggregate pier foundation systems should be prepared by the design-
build contractor.
• All of the aggregate pier element installations should be conducted under the observation
of the geotechnical engineer’s representative to verify proper installation procedures and
document any changes in the explored soil conditions.
After the foundation soils have been reinforced with aggregate pier elements, adequate protection
of the reinforced ground is required. This includes proper drainage to eliminate ponding water and
maintaining excavation distance from the installed piers. Prior to foundation installations, the
reinforced ground surface should be cleared and cleaned to the satisfaction of the geotechnical
engineer, and shallow foundations installed at grade. Excavations for foundations and final grade
cuts to slab subgrade elevations should be performed with smooth-bladed equipment to minimize
the disturbance of the aggregate piers and the surrounding soil.
Cobbles and boulders may exist within the gravel deposits. The granular substrates will most
likely slough during excavation of the aggregate piers. As a result, excavations that penetrate into
granular layers may need to be cased during installation.
Settlement
Based on anticipated loading information, the aggregate pier manufacturer estimates that bearing
capacities up to 10 ksf are possible while keeping settlement estimates at less than one inch. The
aggregate pier manufacturer should perform settlement calculations when loading information is
made available.
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4.1.2 Drilled Shafts
Based on the subsurface conditions encountered within the exploration borings, the results of the
laboratory testing, and the nature of the proposed construction, drilled shaft end bearing within
the sand and gravel deposits or silty sand and lean clay underlying the gravel deposits can be
utilized. Install concrete drilled shafts in accordance with ACI 336.1 – Specification for the
Construction of Drilled Piers. The following are general suggestions for the installation of concrete
drilled piers:
1. Reinforced concrete, straight-shaft, drilled piers, and grade beams/pier caps may be used
to support all loads of the proposed structures to limit potential vertical movement. Grade
beams/pier caps should be designed to span between pier locations while carrying the
imposed loads.
2. Piers should be founded with a 5-foot minimum penetration into the gravel deposits. The final
pier lengths will depend on the final structure elevations. Table 10 provides end bearing and
skin friction options depending on the substrate the drilled piers terminate.
3. We recommend a minimum diameter of 18 inches to facilitate proper cleaning and inspection
of the pier excavations.
4. We recommend a pier spacing of not less than three pier diameters measured from the
outside edge to the outside edge of the piers for vertical loads. Piers will behave as a group
for pier spacing less than three pier diameters, and individual pier capacities must be
reduced. The capacity reduction will depend upon pier spacing and the number of piers within
the group. If closer spacings are required, DOWL should be notified so that appropriate
reduction factors can be provided based on the actual pier layout. Group reductions for
laterally loaded piers will depend on the orientation of pier groups compared to the direction
of loading. Such reductions may be required for pier spacings of less than eight pier
diameters.
5. The foundation driller should be equipped with appropriate drilling equipment and be
prepared for any difficulties resulting from drilling into gravels, cobbles, or possible
boulders. We anticipate that casing will be necessary for each hole. The length of the
casing should be sufficient to extend from slightly above the ground surface to the planned
drill depth.
6. It is imperative that all loose slough is removed from the bottom of the pier excavations.
Loose material in the bottom of the hole will be compressible and may cause excessive
settlement of the pier if not removed. The contractor shall use the appropriately sized
cleaning bucket to remove all slough from the bottom of the excavation.
7. Cast-in-place concrete piers should fill the entire hole. Where casing is necessary, it
should be withdrawn as the concrete is poured while maintaining the casing bottom below
the top of the concrete. Concrete should be directed so that it does not come in contact
with the sidewall of the excavation and so that it has minimal contact with the reinforcing
steel. Volume calculations should be conducted during concrete placement to verify
placed volume relative to excavation volume. This is to confirm that caving of the
excavation sidewall did not occur.
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8. Concrete should not be poured into pier excavations with more than two inches of standing
water. If approved by a qualified geotechnical engineer, alternate construction methods,
such as pumped or tremied concrete from the pier bottom up, may be acceptable if proper
pier-bearing conditions can be verified.
9. Once drilling and cleaning are complete, DOWL must observe and approve the depth of
each pier excavation.
10. Place concrete immediately after the completion of drilling.
11. Concrete placed in pier excavations should have a slump of 4 to 6 inches while maintaining
minimum 28-day strength requirements. Concrete placed with temporary casing should
have a slump of 6 to 8 inches. Concrete placed through tremie methods (wet condition)
should have a slump of 8 to 9 inches to prevent voids from forming around reinforcing
steel.
Table 10: Substation Drilled Pier Recommendations Parameters
Minimum
Drilled Pier
Penetration
(feet)
Soil Type
Maximum Net
Allowable End
Bearing
Pressure (psf)
Allowable Skin
Friction
(in compression)
(psf)
Allowable
Skin Friction
(in tension)
(psf)
-- Lean Clay -- 200 120
5.0 Gravels 12,000 250 130
5.0 Silty Sand 14,000 275 160
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Table 11 lists are the recommended L-Pile parameters for drilled shafts for proposed south
expansion. The surface elevation is assumed to be 4,914.5 feet.
Table 11: L-Pile Drilled Pier Recommendations Parameters
Layer No. Depth (feet) LPile Soil Type Parameter Recommended
Value
1 0.0 to 2.0
Undocumented
Fill
Silty Sand
(Loose Sand)
Effective Unit Weight,
ɣ 100 pcf
Friction Angle, 28°
Top - p-y Modulus, k
(dry) 20 pci
Bottom - p-y
Modulus, k (dry) 25 pci
2 2.0 to 23.0 Lean Clay
(Soft Clay)
Effective Unit
Weight, ɣ 88 pcf
Undrained Shear
Strength, Su 500 psf
Soil Modulus 100 pci (static)
Top – Strain Factor,
ε50 0.015
Bottom – Strain
Factor, ε50 0.010
3 23.0 to 27.0 Gravels
(Dense Sand)
Effective Unit Weight,
ɣ 125 pcf
Friction Angle, 36°
Top - p-y Modulus, k
(dry) 220 pci
Bottom - p-y
Modulus, k (dry) 225 pci
4 27.0+ Silty Sand
(Dense Sand)
Effective Unit Weight,
ɣ 120 pcf
Friction Angle, 34°
Top - p-y Modulus, k
(dry) 220 pci
Bottom - p-y
Modulus, k (dry) 225 pci
Maximum settlement estimates using drilled shafts are on the order of less than one inch.
Differential settlement is estimated to be less than ½ inch.
4.1.3 Helical Piles
In our opinion, helical piers are a suitable foundation option. Helical piers are screw piles that can
be embedded directly in anew grade beam or pier cap. We provide design parameters for both
HELI-Pile and AB Chance brand piers in the following tables. Local contractors commonly use
both in the project area.
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Table 12: Helical Pier Capacities
HELI-PILE Helical Piers
Square shaft 1.5 inch 1.5 inch 1.75 inch
Allowable shaft capacity 27.5 kips 35 kips 55 kips
Minimum installation torque 5,500 ft-lbs 7,000 ft-lbs 11,000 ft-lbs
Shaft yield strength 70 ksi 90 ksi 90 ksi
Helix yield strength 80 ksi 80 ksi 80 ksi
A. B. Chance Helical Piers
Square shaft 1.5 inch 1.5 inch 1.75 inch
Allowable shaft capacity 27.5 kips 35 kips 50 kips
Minimum installation torque 5,500 ft-lbs 7,000 ft-lbs 10,000 ft-lbs
Shaft yield strength 70 ksi 95 ksi 95 ksi
Helix yield strength 50 or 80 ksi 80 ksi 80 ksi
A double-lead helix will likely be necessary to obtain the installation torque to achieve the
capacities shown in the table above. Based on the boring logs, the consistency of the gravel
varies, and so helical pier depths will likely range from 20 to 35 feet below the finish floor
elevation of 4,914.5. Test helical piles should be considered to evaluate depth of embedment
into the underlying strata and to obtain adequate or required torque.
The helical piers provide very little lateral resistance; the lateral loads will be resisted by the
passive soil pressure, or piers can be battered to provide lateral resistance.
Based on lab testing for determining soil resistivity, resulting in a pH ranging from 6.9 to 8.2 and
resistivity ranging from 1,610 to 1,680 ohm-cm, we estimate weight loss to be approximately 1.0
oz/ft2/year and the expected life (for 1/8" shaft loss) is approximately 60 years.
Maximum settlement estimates using helical piers are on the order of less than one inch.
Differential settlement is estimated to be less than ½ inch.
4.2 Lateral Earth Pressures
Design below-grade walls for building, landscape, and retaining walls and any structure retaining
soil to resist both lateral earth pressures from the retained soil adjacent to the structure, as well
as hydrostatic pressures from retaining water (if undrained, not recommended). Also, account for
lateral surcharge loads from equipment, slopes, or vehicles adjacent to the walls in the structural
wall design. We provide recommended lateral earth pressures for below-grade wall design, which
are provided in Table 13.
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Table 13: Lateral Earth Pressures
Lateral Earth Pressure Case Equivalent Fluid Pressure -
Unsaturated (pcf)
Structural Fill
At-rest (no wall movement) 60
Active (wall moves away from soil mass) 36
Passive (wall moves into soil mass) 420
Native Gravels (GP)
At-rest (no wall movement) 55
Active (wall moves away from soil mass) 35
Passive (wall moves into soil mass) 400
Native Lean Clay (CL)
At-rest (no wall movement) 60
Active (wall moves away from soil mass) 43
Passive (wall moves into soil mass) 258
Based on the moist unit weight of 135 pcf and friction angle of 35 degrees for
Structural Fill (GW), 125 pcf and friction angle of 34 degrees for native gravels, and
105 pcf and friction angle of 25 degrees for lean clays (CL).
• The above equivalent fluid pressures assume fully drained conditions and no hydrostatic
forces acting on the wall.
• Construct below-grade walls, retaining walls, or other retaining structures with adequate
drainage systems as specified by the Structural Engineer.
• The retaining walls move away from or toward the soil to develop active and passive
resistance. For walls that cannot tolerate movement, structurally design walls utilizing at-
rest equivalent earth pressures.
• We based the above equivalent fluid pressures on the assumption that the surface of the
backfill adjacent to the walls slopes down and away from the wall a minimum of 5 percent
for 10 feet to provide drainage.
• Lateral surcharge pressures due to traffic, equipment, slopes, storage loads, etc., are not
included in the above lateral earth pressure recommendations. Use the lateral earth
pressure coefficient of 0.5, acting over the below-grade wall height, to estimate the lateral
surcharge loads from equipment, adjacent foundations, and slopes behind and above
walls.
4.2.1 Seismic Earth Pressure
We recommend using the Mononobe-Okabe approach to determine the additional earth
pressures due to earthquakes. For the retained earth at this project, a unit weight of 120 pcf
should be used for the onsite soils (gravel and clay mixture) and 130 pcf should be used for
structural fill. Using the design peak horizontal ground acceleration of 0.34g, we estimate the
equivalent additional fluid (active) earth pressure acting on the walls will be: 17.6 pcf and 14.6 pcf
for the gravel and clay mixture or structural fill, respectively. We calculated this value using ½ the
peak ground acceleration in the horizonal direction.
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4.2.2 Coefficient of Friction
We recommend using a coefficient of friction of 0.45 between cast-in-place concrete and
structural fill, 0.30 between cast-in-place concrete and undocumented fill, clayey sand soil, and
0.20 between the cast-in-place concrete and native sands. The friction value may be combined
with the passive pressure to resist horizontal loads.
4.3 Slabs-on-Grade
4.3.1 Interior Slabs and Helipad
The native, silt soils can be used to support lightly loaded floor slabs; however, compacted
structural fill must be placed between the slab and the native soil. Design the floor slabs using the
recommendations in the table below.
Table 14: Floor Slab Recommendations
Description Value
Interior floor system Slab on-grade concrete.
Floor slab subgrade Scarify, moisture condition and recompact at least 8 inches
of on-site soil.
Base layer Place a minimum of 8 inches of structural fill, compacted in
accordance with Section 4.7.5 of this report.
Modulus of subgrade reaction 190 pounds per cubic inch (pci)
Some differential movement of a slab-on-grade floor system is possible if the moisture content of
the subgrade soils is increased. To reduce the effects of some differential movement, separate
floor slabs from bearing walls and columns with expansion joints, which allow vertical movement.
Use floor slab control joints to reduce damage due to shrinkage cracking.
4.4 Low Height Concrete Block Retaining Walls
At the time of this report, the location and height of proposed retaining walls are unknown. This
section provides recommendations for low-height (less than four feet tall) concrete block retaining
walls. From the historical geotechnical boreholes and near-surface geophysics, the subsurface
geology will consist of undocumented fill or native lean clays in the upper 13 feet soil horizon.
DOWL recommends the following material parameters similar to Montana Department of
Transportation’s Low Height Concrete Block Retaining Wall Special Provision:
• Construct precast concrete wall blacks capable of retaining a soil cut up to four feet in
height, via gravity resistance, without internal soil reinforcement. The soil slope above and
behind the wall is considered to be level to nearly level.
• The leveling pad and wall backfill material be constructed of granular material meeting the
requirements of Section 4.7.4 Structural Fill.
• Provide geotextile-wrapped 4-inch Corrugated ADS N-12 Drainage Pipe with perforations
for backfill drainage pipe (or approved equal). DOWL recommends Marafi 1120N filter
fabric (or approved equal) to wrap the drainage pipe.
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• Provide splices, fittings, and connectors that will not impede flow or damage the drainage
pipe and have sufficient strength to withstand construction handling and permanent
loading.
• Excavate the leveling pad area a minimum of two feet below the planned wall base
elevation and a minimum of 3.0 feet wider than the width of the bottom concrete blocks.
• Scarify the top 12 inches of the footing subgrade and compact in accordance with Section
4.7.
• Construct the wall according to the manufacturer’s recommendations, up to a maximum
height of four feet of retained soil.
4.5 Pavement Surfacing
An engineering evaluation has been conducted to assess the subgrade conditions and determine
a recommended pavement section for the parking areas and access lanes.
Subgrade soil conditions have been described under the Observed Soil Conditions in Section 3.2.
The subgrade is comprised predominantly of lean clay with sand or sand with variable clay or silt.
Occasional gravel and cobbles were observed within the proposed subgrade during the
investigation.
4.5.1 Traffic
The expected traffic will consist of ambulances, traditional car traffic, vans, and maintenance
vehicles. Traffic will consist of emergency vehicles and patients parking at adjacent parking lots.
We calculated equivalent single axle loads (ESALs) as shown in Table 15. If future projects that
impact general traffic routes are planned, contact DOWL to revise our recommendations as
necessary.
Table 15: Traffic Loading
Vehicle Description ADT (Design Lane) Axle Load (kips)*
Passenger Car 500 2S 2S
Pickup Truck/Van 250 2S 4S
Ambulance 200 4S 4S
Delivery Trucks 10 4S 14S
Front Wheel Loader 4 8S 8S
250/0 and 350/0 4 4S 4S
Calculated 18-kip ESALs 32,478 (flexible)
*S-Single
4.5.2 Design Parameters
We used the pavement design parameters shown in Table 16.
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Table 16: Pavement Design Parameters
Pavement Design
Parameter Design Value Source
Initial Serviceability 4.2 AASHTO 1993
Terminal Serviceability 2.0 AASHTO 1993
Reliability 85% AASHTO 1993
Drainage Coefficient 0.9 AASHTO 1993
Flexible Pavement
Design Life 20 years AASHTO 1993
Standard Deviation 0.45 AASHTO 1993
Asphalt Layer Coefficient 0.40 AASHTO 1993
Base Layer Coefficient 0.14 AASHTO 1993
Subbase Layer Coefficient 0.08 AASHTO 1993
Subgrade Resilient Modulus 4,500 psi Estimated CBR value
4.5.3 Flexible Pavement
Based on our design calculations, anticipated traffic, and field conditions, we recommend the
pavement sections shown below for the proposed new pavement areas for the parking lot. The
separation fabric will help prevent the migration of fines into the overlying crushed aggregate
course.
Flexible Pavement - Parking Lot Section
• 3-inches of asphalt
• 8-inches of crushed aggregate course
• Separation Fabric (Mirafi HP570 or approved equal)
• Subgrade prepared in accordance with Section 4.7.
4.5.4 Rigid Pavement
For areas subject to concentrated and repetitive loading conditions, such as dumpster pads and
ingress/egress aprons, we recommend using a reinforced concrete pad at least 6.5 inches thick
underlain by at least six inches of granular base. The granular base must overlie a geotextile
recommended in Section 4.7.9. In addition, we recommend that signage and/or curbing be used
to restrict truck traffic in car parking and drive lane areas.
Provide sawed or hand-formed joints at spacings not greater than 15 feet on center. Construct
the joints to be at least one-fourth of the slab thickness. Provide expansion joints at the end of
each construction sequence and between the concrete slab and adjacent structures.
For pedestrian sidewalks, DOWL recommends 4.0 inches of reinforced concrete underlain by at
least six inches of granular base.
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4.5.5 Pavement Construction Considerations
Compact fill in 8-inch loose lifts to at least 95 percent of maximum dry density at plus or minus
three percentage points of optimum moisture content according to ASTM D 698 (Standard
Proctor). DOWL must observe the subgrade soil prior to fill placement for fill or suspect soils.
Prior to fill placement, scarify the existing subgrade to a depth of at least eight inches and compact
to not less than 95 percent of maximum dry density near optimum moisture content according to
ASTM D 698 (Standard Proctor). If undocumented fill is observed, proof roll and obtain 95 percent
of the Standard Proctor. If compressible, replace with general fill or structural fill. Drying or
moisture conditioning of the subgrade soils may be required to achieve the specified compaction.
All subgrades should be proof rolled with a loaded dump truck or water truck prior to placing base
gravel. Areas where compaction criteria cannot be met or soft areas revealed by proof rolling
must be sub-excavated to a minimum depth of twelve inches and replaced with compacted
approved fill. Areas of loose or organic fill, if encountered, should be sub-excavated to remove all
unsuitable material and replaced with compacted granular fill.
All paving materials should meet and be installed in accordance with Montana Public Works
Standard Specifications. Compact base materials to not less than 98 percent of maximum dry
density at plus or minus two percent of optimum moisture according to ASTM D 698.
4.6 Drainage
Drainage is critical to the long-term performance of the water tower and mechanical building. In
the following sections, we provide recommendations for surface and subsurface drainage.
4.6.1 Surface Drainage
To reduce the potential for movement due to an increase in the moisture content of subgrade soil,
we strongly encourage the implementation of the following recommendations.
• Per the 2020 IBC, slope the ground surface within 10 feet of the structure downward a
minimum of 5 percent away from the structure. Slope the ground surface beyond 10 feet
of structures downward at least two percent away from the structure.
• Apron slabs and pavement may be used to further reduce infiltration adjacent to
structures. Aprons should consist of asphalt or Portland cement concrete pavement
placed directly adjacent to the foundation stem walls. An elastomeric sealant should also
be considered between aprons and foundation stem walls to further reduce the potential
for moisture to infiltrate the area directly adjacent to the foundations. Slope apron slabs
and pavement a minimum of 2 percent, downward, away from the building.
• Install eve gutters, downspouts, and extensions to dispose of water a minimum of 10 feet
away from the structure.
• Do not irrigate within five feet of the proposed or existing structures. Periodically inspect
and flush irrigation systems to detect potential leaks and avoid saturation of foundation
backfill.
• Install and maintain basement window well covers.
• Replace sidewalk or driveway pavement sections that slope toward the foundation.
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• Seal cracks in sidewalks, driveway and apron slabs, floor slabs, and foundation and
basement walls. Maintain sealant between adjacent slabs and between slabs and
adjacent walls.
• Remove or repair landscaping, curbs, or other barriers that impair drainage.
• Do not construct infiltration basins adjacent to or up gradient of the structures. If detention
is required by statute, infiltration basins should be located down gradient and at least 30
feet from the foundations.
4.7 Earthwork
4.7.1 Subgrade Preparation
• Soil containing vegetation and organics (topsoil) extended approximately two to three
inches below the existing ground surface in the locations explored. Remove soil containing
vegetation and organics below planned improvements or structures.
• Remove uncontrolled fill below planned improvements or structures. Prepare final native
subgrades with smooth blade equipment. To maintain an undisturbed, native soil
subgrade condition, the contractor must carefully plan and implement excavation to avoid
disturbance. Scarify, moisture condition, and compact subgrade soil as specified in the
table in Section 4.7.1.
• Grade the exposed subgrade surfaces to remove mounds and depressions, which could
prevent uniform compaction. If unexpected fills or obstructions are encountered during site
clearing or excavation, remove such features and clean the excavation prior to placing
backfill and construction.
• The site soil is moisture sensitive, susceptible to disturbance when moist or wet, and may
pump or rut under construction traffic. Soil disturbance negatively impacts the soil's
performance. Disturbed soil is prohibited below any structure or pavement, especially at
footing or slab subgrades.
• Moisture condition and compact disturbed soil or fill placed to achieve site grades to the
requirements in Table 18. This may require considerable moisture conditioning and soil
processing due to the clayey nature of the on-site soil.
• Remove pumping or rutting subgrade areas to depths between 12 and 18 inches or as
directed by DOWL.
• Replace over excavations with granular structural fill. Contact DOWL's geotechnical
engineer to review and approve the exposed subgrade.
• Once prepared and approved by the DOWL, it is the contractor's sole responsibility to
protect subgrades from degradation.
4.7.2 Excavation
Based on the materials encountered in the soil borings, conventional earthmoving equipment
should be capable of excavating the site soils.
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4.7.3 Dewatering
Groundwater will most likely not be encountered during construction. DOWL does not expect
dewatering to be needed.
4.7.4 Structural Fill
Consider fill placed within the water tower or mechanical building footprint as structural fill. The
on-site undocumented fill or elastic silt subgrade are not suitable for use below the foundations.
Soils to be reused on site must satisfy the Fill Specifications specified in Table 17.
Table 17: Fill Specifications
Soil/Fill Product Allowable Use Material Specifications
Non-Structural Fill
(Landscape Fill)
Any area that will not
have structures
(typically landscape
areas)
• Soil classified as GM, GW, SM, SW, SC, CL, CH, or
ML according to the USCS.
• Soil may not contain particles larger than 8 inches in
median diameter.
• Soil must have less than three percent of deleterious
substances such as wood, metal, plastic, and waste.
• Approved by Landscape Architect.
General Fill
• Site grading outside
the building footprint.
• Utility backfill areas
• Non-structural fill
• Foundation wall
backfill
• Soil classified as GP, GM, GW, GC, SP, SM, SW,
SC, CL, or ML according to the USCS.
• Site soil must have less than three percent
vegetation, organics, and debris.
• Soil may not contain particles larger than 6 inches in
diameter.
• The soil must contain less than 3% (by weight) of
organics, vegetation, wood, metal, plastic, or other
deleterious substances.
Structural Fill
• General fill
• Over-excavations
• Soil improvements
• Retaining Wall
backfill
• Soil classified as GP, GM, GW, SP, SM, or SP with
at least 30 percent retained on a number 4 sieve and
less than 15 percent passing a number 200 sieve.
• Soil may not contain particles larger than 2 inches in
diameter.
• The soil must contain less than 3% (by weight) of
organics, vegetation, wood, metal, plastic, or other
deleterious substances.
Unsatisfactory Soil NONE
• Soil classified as MH, OH, CH, OL, or PT may not be
used at the project site.
• Any soil type not maintaining moisture contents
within 5% of optimum during compaction is
unsatisfactory soil that must be moisture-conditioned
prior to disposal and replacement.
• Any soil containing more than 3% (by weight) of
organics, vegetation, wood, metal, plastic, or other
deleterious substances.
4.7.5 Compaction Requirements
Place fill material in lifts not exceeding eight inches in uncompacted thickness. Moisture condition
and compact fill according to Table 18.
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Table 18: Compaction Specifications
Application Moisture Content
(% of optimum) Minimum Compaction
Subgrade ±4 95% ASTM D698
Below Foundations ±4 98% ASTM D698
Below Slabs-On-Grade ±4 97% ASTM D698
Base and Subbase Courses ±4 95% ASTM D698
Utility Trenches ±4 95% ASTM D698
Site Grading Fill ±4 95% ASTM D698
Foundation Backfill ±4 95% ASTM D698
4.7.6 Testing and Observations
We recommend the following compaction testing frequencies:
• Structural Fill below Footing and Subgrade - One compaction test every 50 linear feet
of footing trench or 2 tests per wall line, whichever results in the greater number of tests,
per each 1-foot lift of fill.
• Foundation/Retaining Wall Backfill - One compaction test every 100 linear feet of wall
or 2 tests per wall line (interior and exterior sides), whichever results in the greater number
of tests, per each 1-foot lift of backfill.
• Interior and Exterior Slab Subgrade - One compaction test every 1,000 square feet of
slab area or 2 tests per slab area, whichever results in the greater number of tests, per 1-
foot lift of fill.
• Trenches - One compaction test every 150 linear feet or 2 per trench, whichever results
in the greater number of tests, per each 1-foot lift of backfill
To verify that construction conforms to the intent of the specifications, we recommend that DOWL
be retained to observe and record the following:
• Site preparation, including grubbing, stripping, excavating, and proof-rolling,
• Removal of topsoil and root zone beneath slabs and pavements,
• Interior and exterior slab subgrades,
• Excavations and sub-excavations prior to placing backfill/fill materials or prior to
construction of footings and slabs, and
• Approve additional excavation, replacement, or stabilization if the geotechnical engineer
identifies unsuitable soil during excavation or proof-rolling operations.
4.7.7 Cold Weather Construction
Do not place concrete, pavement, or fill on frozen soil. Do not use frozen soil as fill or backfill.
Remove frozen soil, snow, and ice from the subgrade or fill soil prior to continuing with
construction. Limit winter excavations to areas small enough to be refilled to finished grade or
higher on the same day. Contact DOWL to monitor fill placed during freezing conditions to reduce
the potential for placing frozen material.
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4.7.8 Wet Weather/Soil Construction
• Ideally, perform earthwork construction when the soil moisture content is less than two
percent above optimum.
• The site clay is susceptible to pumping or rutting from heavy loads such as rubber-tired
equipment or vehicles at any time of the year.
• If possible, do not perform earthwork after rainfall when the soil is wet. Allow the soil to
dry sufficiently to allow construction traffic without disturbing the subgrade.
• If the subgrade soil becomes wet, it may be necessary to perform earthwork with track-
mounted equipment that reduces vehicular pressure applied to the soil if construction
commences in wet areas or before the soil can dry enough to support wheeled vehicles.
• Even though the undocumented fill subgrade is firm, it may be easily disturbed when wet.
The elastic silt subgrade is very weak. If necessary, the contractor may place an initial 12-
inch lift of granular structural fill to help reduce the compaction energy on the unstable
subgrade. Thicker structural fill lifts can only be installed over sensitive subgrades at
DOWL's recommendation during construction. Initial thicker fill lifts and over-excavations
to remove soft, wet soil can only be placed after the contractor has attempted to moisture
condition and recompact the native soil and was unsuccessful.
• Depending on precipitation, runoff, and perched groundwater conditions, the site soil will
be near optimum moisture content. The contractor should expect these conditions and be
prepared to install runoff management facilities and replace wet or disturbed soil with
structural fill.
4.7.9 Geosynthetics
Geosynthetic fabrics are applicable when constructing on soft or wet soil, for foundations soil
improvement applications, and as separation fabrics between drainage aggregate, below the
construction access road, and at the base of slab over-excavations. Where required, apply
geosynthetics directly on approved subgrades, taut, without wrinkles, and over-lapped at least 12
inches. Consult DOWL to review geosynthetic applications or other subgrade improvement
alternatives. Geogrid is required to help support any area that exhibits unusually high
groundwater, soft pumping, or rutting conditions. Geotextile fabric placed at the bottom of the
footing excavation must meet the requirements for separation/stabilization geotextile in Section
716, Geotextiles, of the Montana Department of Transportation Standard Specifications for Road
and Bridge Construction.
As a separation/stabilization fabric in flexible, concrete, mechanical building foundations, and
gravel surfacing areas, DOWL recommends a Mirafi HP570 or approved equal.
4.8 Soil Chemistry and Corrosion
Based on the results in Table 19, concrete in contact with the on-site soil classifies as exposure
class S0 according to ACI 318 table 19.3.1.1 (ACI, 2014). The S0 exposure class recommends a
minimum compressive strength of 2,500 psi at 28 days and there are no exposure class
restrictions for S0. Details can be found in the above ACI reference and in the Portland Cement
Association publication "Design and Control of Concrete Mixtures."
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According to Corrosion/Degradation of Soil Reinforcement for Mechanically Stabilized Earth
Walls (FWHA, 2009), the soil at the site is "corrosive” to steel. Based on that publication and the
test results below, we estimate a corrosion rate of 0.95 to 0.97 ounces per square foot per year
for carbon steel and 0.26 to 0.27 ounces per square foot per year for galvanized steel. The data
in Table 19 was taken from February 23, 2009 Emergency Room and Patient Wing geotechnical
report.
Table 19: Soil Chemistry Test Results
Sample Location Soluble Sulfate
(mg/kg)
Resistivity
(ohm-cm) pH
B-1-08 at 5.0 to 6.5 feet – ICU Report Nondetectable 1,680 8.15
B-1-08 at 30.0 to 31.5 feet – ICU Report Undetectable 1,610 6.89
5.0 GEOTECHNICAL DESIGN CONTINUITY
Geotechnical design continuity will be an important aspect of the successful completion of this
project. In our opinion, geotechnical continuity can occur in three stages: planning, design, and
construction project aspects. Specifically, we recommend that DOWL maintain the geotechnical
design continuity in the following aspects:
• Plan and Specification Review: We recommend you retain DOWL to review final design
and construction plans and specifications to verify that our geotechnical recommendations
are incorporated into construction documents and provide additional recommendations
based on the final design concepts. These efforts can help provide document continuity
and reduce the potential for errors as the project concepts evolve.
• Geotechnical Design Confirmation: The potential soil variation may have a significant
impact on foundation construction. As such, we recommend you retain DOWL to provide
geotechnical engineering oversight during site grading and foundation excavation to
observe the potential variability in the soil conditions and provide consultation regarding
potential impacts on foundation construction.
• Construction Observation and Testing: We recommend that you retain DOWL to
provide foundation-related observation during site preparation, grading, structural fill
placement, and backfilling to verify compliance with the recommendations presented in
this report. We recommend hiring an accredited laboratory to perform construction testing.
Having DOWL provide oversight during this process will reduce the potential for an
unforeseen construction error, which may ultimately impact the project. If we are not
retained to perform the recommended services, we cannot be responsible for related
construction errors or omissions.
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6.0 LIMITATIONS
DOWL based the conclusions and recommendations presented in this report on the assumption
that site conditions are not substantially different than those exposed by the explorations. If
subsurface conditions are different during construction from those encountered in the
explorations, advise DOWL at once to review those conditions and reconsider recommendations
if necessary. The geotechnical recommendations provided herein are based on the premise that
an adequate program of tests and observations will be conducted during construction to document
compliance with DOWL's recommendations and confirm conditions exposed during subgrade
preparations. DOWL geotechnical personnel must review final designs to verify that
recommendations provided herein have been properly implemented.
If there is a substantial lapse of time between the submission of this report and the start of work
at the site, and especially if conditions have changed due to natural causes or construction
operations at or near the site, contact DOWL to review this report and to evaluate the applicability
of the conclusions and recommendations presented herein.
DOWL prepared this report for Bozeman Health and their Consultants to use on this project.
DOWL recommends making this report available to prospective contractors only for information
and factual data, but not as a warranty of subsurface conditions. DOWL prepared this report,
including engineering analyses, recommendations, figures, and design details for the above-
referenced site. These recommendations do not apply to other construction sites. Do not separate
the figures from the text for independent use.
DOWL performed these services in a manner consistent with the level of care and skill ordinarily
exercised by members of the profession currently practicing in this area under similar time and
budgetary constraints. No warranty is made or implied.
Any conclusions made by a construction contractor or bidder relating to construction means,
methods, techniques, sequences, or costs based upon the information provided in this report are
not the responsibility of Bozeman Health or DOWL.
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7.0 REFERENCES
ACI. (2014). Building Code Requirements for Structural Concrete. American Concrete Institute.
ASCE. (2021). Minimum Design Loads and Associated Criteria for Buildings and Other
Structures. American Socienty of Civil Engineers.
DOWL (2017). Bozeman Health Deaconess Hospital, Intensive Care Unit (ICU) Addition and
Renovation - Bozeman, MT.
DOWL HKM (2009). Geotechnical Investigation Report - Bozeman Deaconess Hospital
Proposed Emergency Room and Patient Wing Additions.
FWHA. (2009). Corrosion/Degradation of Soil Reinforcement for Mechanically Stabilized Earth
Walls. Publication No. FHWA-NHI-09-087. Federal Highways Administration.
GWIC. (2026). Ground Water Information Center. Retrieved from Montana Technological
Univesity: http://mbmggwic.mtech.edu
ICC. (2020). 2021 International Building Code. Country Club Hills: International Code Council.
Lacroix, Y., & Horn, H. (1973). Direct Determination and Indirect Evaluation of Relative Density
and Its Use on Earthwork Construction Projects: in Evaluation of Relative Density and Its
Role in Geotechnical Projects involving Cohesionless Soils. ASTM Special Technical
Publication 523, 251-280.
USGS. (2018). Earthquake Hazards - Quaternary Fault and Fold Database of the United States.
Retrieved January 25, 2026, from https://www.usgs.gov/natural-hazards/earthquake-
hazards/faults?qt-science_support_page_related_con=4#qt-
science_support_page_related_con
USGS. (2026). Earthquake Hazards: Quaternary Fault and Fold Database of the United States.
(United States Geotechnical Survey) Retrieved January 25, 2026 from
https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-
science_support_page_related_con=4#qt-science_support_page_related_con
Vantassel, J. P. & Cox, B. R. (2022). "SWprocess: a workflow for developing robust estimates of
surface wave dispersion uncertainty". Journal of Seismology.
Geotechnical-Engineering Report
Important Information about This
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The following information is provided to help.
The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.
Understand the Geotechnical-Engineering Services Provided for this ReportGeotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.
The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.
Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific TimesGeotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer
will not likely meet the needs of a civil-works constructor or even a
different civil engineer. Because each geotechnical-engineering study
is unique, each geotechnical-engineering report is unique, prepared solely for the client.
Likewise, geotechnical-engineering services are performed for a specific
project and purpose. For example, it is unlikely that a geotechnical-
engineering study for a refrigerated warehouse will be the same as
one prepared for a parking garage; and a few borings drilled during
a preliminary study to evaluate site feasibility will not be adequate to
develop geotechnical design recommendations for the project.
Do not rely on this report if your geotechnical engineer prepared it:
• for a different client;
• for a different project or purpose;
• for a different site (that may or may not include all or a portion of
the original site); or
• before important events occurred at the site or adjacent to it;
e.g., man-made events like construction or environmental
remediation, or natural events like floods, droughts, earthquakes,
or groundwater fluctuations.
Note, too, the reliability of a geotechnical-engineering report can
be affected by the passage of time, because of factors like changed
subsurface conditions; new or modified codes, standards, or
regulations; or new techniques or tools. If you are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying the recommendations in it. A minor amount
of additional testing or analysis after the passage of time – if any is
required at all – could prevent major problems.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical-
engineering report did not read the report in its entirety. Do not rely on
an executive summary. Do not read selective elements only. Read and refer to the report in full.
You Need to Inform Your Geotechnical Engineer About Change
Your geotechnical engineer considered unique, project-specific factors
when developing the scope of study behind this report and developing
the confirmation-dependent recommendations the report conveys.
Typical changes that could erode the reliability of this report include
those that affect:
• the site’s size or shape;
• the elevation, configuration, location, orientation,
function or weight of the proposed structure and
the desired performance criteria;
• the composition of the design team; or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
or site changes – even minor ones – and request an assessment of their
impact. The geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.
Most of the “Findings” Related in This Report Are Professional Opinions
Before construction begins, geotechnical engineers explore a site’s
subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from
that sampling and testing were reviewed by your geotechnical engineer,
who then applied professional judgement to form opinions about
subsurface conditions throughout the site. Actual sitewide-subsurface
conditions may differ – maybe significantly – from those indicated in
this report. Confront that risk by retaining your geotechnical engineer
to serve on the design team through project completion to obtain
informed guidance quickly, whenever needed.
This Report’s Recommendations Are Confirmation-Dependent
The recommendations included in this report – including any options or
alternatives – are confirmation-dependent. In other words, they are not
final, because the geotechnical engineer who developed them relied heavily
on judgement and opinion to do so. Your geotechnical engineer can finalize
the recommendations only after observing actual subsurface conditions
exposed during construction. If through observation your geotechnical
engineer confirms that the conditions assumed to exist actually do exist,
the recommendations can be relied upon, assuming no other changes have
occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation.
This Report Could Be Misinterpreted
Other design professionals’ misinterpretation of geotechnical-
engineering reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a continuing member of
the design team, to:
• confer with other design-team members;
• help develop specifications;
• review pertinent elements of other design professionals’ plans and
specifications; and
• be available whenever geotechnical-engineering guidance is needed.
You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.
Give Constructors a Complete Report and GuidanceSome owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note
conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that
“informational purposes” means constructors have no right to rely on
the interpretations, opinions, conclusions, or recommendations in the
report. Be certain that constructors know they may learn about specific
project requirements, including options selected from the report, only
from the design drawings and specifications. Remind constructors
that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in
a position to give constructors the information available to you, while
requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions. Conducting prebid and
preconstruction conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplines. This happens in part because soil and rock on
project sites are typically heterogeneous and not manufactured materials
with well-defined engineering properties like steel and concrete. That
lack of understanding has nurtured unrealistic expectations that have
resulted in disappointments, delays, cost overruns, claims, and disputes.
To confront that risk, geotechnical engineers commonly include
explanatory provisions in their reports. Sometimes labeled “limitations,”
many of these provisions indicate where geotechnical engineers’
responsibilities begin and end, to help others recognize their own
responsibilities and risks. Read these provisions closely. Ask questions.
Your geotechnical engineer should respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study – e.g., a “phase-one” or “phase-two” environmental
site assessment – differ significantly from those used to perform a
geotechnical-engineering study. For that reason, a geotechnical-engineering
report does not usually provide environmental findings, conclusions, or
recommendations; e.g., about the likelihood of encountering underground
storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not
obtained your own environmental information about the project site,
ask your geotechnical consultant for a recommendation on how to find
environmental risk-management guidance.
Obtain Professional Assistance to Deal with Moisture Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, the engineer’s
services were not designed, conducted, or intended to prevent
migration of moisture – including water vapor – from the soil
through building slabs and walls and into the building interior, where
it can cause mold growth and material-performance deficiencies.
Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by
including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists.
Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written
permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent
Telephone: 301/565-2733
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G e o t e c h n i c a l R e p o r t PEOPLE WHO MAKE IT HAPPEN dowl.com
Appendix A
Exploration Logs
SOIL CLASSIFICATION/LEGEND
Relative Density or Consistency
Utilizing Standard Penetration Test Values
Cohesionless Soils(a)Cohesive Soils(b)
Density(c)N blows/ft(c)
Relative
Density
(%)Consistency N blows/ft(c)
Undrained
Shear
Strength(d)
(psf)
Very loose 0 to 4 0 - 15 Very soft 0 to 2 <250
Loose 5 to 10 15 - 35 Soft 3 to 4 250 - 500
Med. Dense 11 to 29 35 - 65 Medium Stiff 5 to 8 500 – 1,000
Dense 30 to 49 65 - 85 Stiff 9 to 15 1,000 – 2,000
Very Dense Over 50 >85 Very Stiff 16 to 30 2,000 – 4,000
Hard Over 30 >4,000
(a) Soils consisting of gravel, sand and silt, either separately or in combination, possessing no
characteristics of plasticity and exhibiting drained behavior.
(b) Soils possessing the characteristics of plasticity, and exhibiting undrained behavior.(c) Undrained shear strength = ½ unconfined compressive strength.
(d) Qp - Denotes pocket penetrometer field measurement (tons per square foot) approximation to
unconfined compressive strength.
Component Definitions By Gradation
Component Size Range
Boulders Greater than 12-in.
Cobbles 3-in. to 12-in.
Gravel 3-in. to No. 4 (4.75 mm)
Coarse gravel 3-in. to ¾-in.
Fine gravel ¾-in. to No. 4 (4.75 mm)
Sand No. 4 (4.75 mm) to No. 200 (.075 mm)
Coarse sand No. 4 (4.75 mm) to No. 10 (2.0 mm)
Medium sand No. 10 (2.0 mm) to No. 40 (0.425 mm)
Fine sand No. 40 (0.425 mm) to No. 200 (0.074 mm)
Silt and Clay Smaller than No. 200 (0.075 mm)
Silt and Clay Descriptions
Description Typical Unified Designation
Silt ML (non-plastic)
Clayey Silt CL-ML (low plasticity)
Silty Clay, Lean Clay CL
Clay, Fat Clay CH
Plastic Silt MH
Organic Soils OL, OH, Pt
Descriptive Terminology Denoting
Components Proportions
Descriptive Terms Range of Proportion
Trace or Scattered 0 - 5%
Few 5 - 10%Some or Adjective(a)15 - 30%
And 30 - 50%
(a)Use gravelly, sandy or silty as appropriate.
Unless otherwise noted, drive samples advanced
with 140-lb. hammer and 30-in. drop.
Unified Soil Classification System
Criteria for Assigning Group Symbols and Names
Soil Classification
Generalized
Group Descriptions
COARSE-GRAINED SOILS GRAVELS CLEAN GRAVELS GW Well-graded gravels
More than 50%More than 50% of Less than 5% fines GP Poorly-graded gravels
retained on coarse fraction GRAVELS w/ FINES GM Gravel and silt
No. 200 sieve retained on No. 4 More than 12% fines mixtures
sieve GC Gravel & clay mixtures
SANDS CLEAN SANDS SW Well-graded sands
50% or more of Less than 5% fines SP Poorly-graded sands
coarse faction SANDS with FINES SM Sand and silt mixtures
passes No. 4 sieve More than 12% fines SC Sand and clay mixtures
FINE-GRAINED SOILS SILTS & CLAYS CL Low-plasticity clays
50% or more passes Liquid limit INORGANIC ML Non-plastic and low-
the No. 200 sieve less than 50 plasticity silts
Non-plastic and low
plasticity organic claysORGANICOL
Non-plastic and low-
plasticity organic silts
SILTS & CLAYS CH High-plasticity clays
Liquid limit INORGANIC MH High-plasticity silts
greater than 50
High-plasticity
organic clays
ORGANIC OH
High-plasticity
organic soils
HIGHLY ORGANIC SOILS Primarily organic matter, dark in color and
has an organic odor PT peat
Soil Moisture
Dry Absence of moisture,
dusty, dry to the touch
Slightly Moist
Minor existence of
moisture, not dusty, but
still dry to the touch
Moist Damp but no visiblewater
Very Moist
Zones of visible moisture
and usually above the
water table
Wet Visible free water, usually
soil is below water table
Groundwater Elevation
Water Elevation Noted During Drilling
Water Elevation Recorded After Drilling Complete
Samples
Split Spoon Sampler (2.0” OD)
Ring Sampler (3.0” OD)*
*Indicates increased blow counts
due to sampler size.
Shelby Tube Sampler (3.0” OD)
Bulk Sample (auger cuttings)
Core Barrel
0
5
10
15
20
25
30
35
4910
4905
4900
4895
4890
4885
4880
5-inches Asphalt pavement
0.4 4910.6Base Gravel 24" +/- (Poorly graded gravel
with sand (GP), moist, brown) (fill)2.4 4908.6Lean clay (CL), medium stiff to stiff, moist,
light brown with white mottling/mineral
deposits (native soil)
19.5 4891.5Poorly graded sand/poorly graded gravel
(SP/GP), dense to very dense, moist,
grayish brown to reddish brown (alluvium)
12" sand lense @ 22.5'
26.2 4884.8Silty sand (SM), medium dense to dense,
moist, orange brown, scattered black carbon
grains (tertiary sediment)
31.5 4879.5Boring terminated at 31.5'
No groundwater observed
234
357
335
272422
182020
252526
81420
81426
7
12
8
46
40
51
34
40
13/18
72%
12/18
67%
12/18
67%
10/18
56%
12/18
67%
15/18
83%
22/18
122%
20/18
111%
51
Project No.: 4531.10033.01 LOG OF BOREHOLE B-4-08
CLIENT
Bozeman Deaconess Hospital
PROJECT
Proposed Emergency Room Addition
BORING LOCATION
Near the southwest corner of the proposed addition
SITE
Proposed Addition
DOWL HKM
920 Technology Blvd., Suite A
Bozeman, Montana 59718
Telephone: (406) 586-8834
Fax: (406) 586-1730
STARTED 12/1/08 FINISHED 12/1/08
DRILL CO.Haz Tech DRILL RIG BK-81
DRILLER Paul Bray HAMMER Automatic
LOGGED BY N. Peterson APPROVED BY G. UnderhillDEPTH (FT.)MATERIAL DESCRIPTION
GRAPHIC LOGELEVATION (FT.)BULKSAMPLES
DRIVEN/PUSHBLOWS PER 6"N BLOWS/FTNUMBERIN. RECOVEREDIN. DRIVENPOCKET PENE-TROMETER, TSFTESTS
10 20 30 40N VALUE BLOWS/FT
PL LL ADDITIONAL
DATA/
REMARKS
Surface Elevation: 4911
M.C.
Sheet 1 of 1
0
5
10
15
20
25
30
35
4905
4900
4895
4890
4885
5-inches Asphalt pavement
0.4 4909.6Base Gravel 18" +/- (Poorly graded gravel
with sand (GP), moist, brown) (fill)1.9 4908.1Lean clay with sand (CL), medium stiff,
moist, light brown (possible fill)
Organics at 5'
6.5 4903.5Lean clay (CL), stiff to very stiff, moist,
medium brown (native soil)
14.5 4895.5Poorly graded sand/poorly graded gravel
(SP/GP), very dense, moist, grayish brown
to brown (alluvium)
Possible sand lenses 19 to 20'
21.0 4889Silty sand (SM), very dense, moist, orange
brown (tertiary sediment)
26.5 4883.5Boring terminated at 26.5'
No groundwater observed
533
6912
222822
50/
2"
152236
6
21
50
50
58
11/18
61%
24/24
100%
9/1850%
10/18
56%
0/2
0%
22/18
122%
58
Lab Sample #23495:
USCS=CL
Gravel=0%
Sand=4%
Fines=96%
Liquid Limit=43Plasticity Index=20
Nat Moisture=22.5%
Dry Unit Wt=102.1pcf
Unconfined (qu)=6.02ksf
Cohesion (qu/2)=3.01ksf
Project No.: 4531.10033.01 LOG OF BOREHOLE B-5-08
CLIENT
Bozeman Deaconess Hospital
PROJECT
Proposed Emergency Room Addition
BORING LOCATION
Near the southeast corner of the proposed addition
SITE
Proposed Addition
DOWL HKM
920 Technology Blvd., Suite A
Bozeman, Montana 59718
Telephone: (406) 586-8834
Fax: (406) 586-1730
STARTED 12/2/08 FINISHED 12/2/08
DRILL CO.Haz Tech DRILL RIG BK-81
DRILLER Paul Bray HAMMER Automatic
LOGGED BY N. Peterson APPROVED BY G. UnderhillDEPTH (FT.)MATERIAL DESCRIPTION
GRAPHIC LOGELEVATION (FT.)BULKSAMPLES
DRIVEN/PUSHBLOWS PER 6"N BLOWS/FTNUMBERIN. RECOVEREDIN. DRIVENPOCKET PENE-TROMETER, TSFTESTS
10 20 30 40N VALUE BLOWS/FT
PL LL ADDITIONAL
DATA/
REMARKS
Surface Elevation: 4910
M.C.
Sheet 1 of 1
0
5
10
15
20
25
30
35
4910
4905
4900
4895
4890
4885
4-inches Asphalt pavement
0.3 4913.4Base Gravel 30" +/- (Poorly graded gravel
with sand (GP), moist, brown) (fill)2.8 4910.9Lean clay with sand (CL), medium stiff, very
moist, light brown, scattered organics and
scattered fine gravel (fill)
10.0 4903.7Lean clay (CL), medium stiff, moist, reddish
brown with white mottling/mineral deposits
(native soil)
20.0 4893.7Lean clay with sand and gravel (CL), hard,
moist, reddish brown, subangular gravel
(native soil/colluvium)22.5 4891.2Poorly graded sand/poorly graded gravel
(SP/GP), very dense, moist, brown
(alluvium)25.0 4888.7Poorly graded sand with clay (SP-SC),
dense, moist, orange brown, scattered
angular gravel (tertiary sediment)27.5 4886.2Silty sand (SM), dense to very dense, moist,
orange brown, cemented in part (tertiary
sediment)
31.5 4882.2Boring terminated at 31.5'
Groundwater observed at 3' that appears to
be a "perched aquifer"
335
345
455
81126
182527
151427
152540
152539
8
9
10
37
52
41
65
64
18/18
100%
13/18
72%
15/18
83%
18/18
100%
13/18
72%
18/18
100%
18/18
100%
18/18
100%
52
65
64
Project No.: 4531.10033.01 LOG OF BOREHOLE B-6-08
CLIENT
Bozeman Deaconess Hospital
PROJECT
Proposed Emergency Room Addition
BORING LOCATION
North side of the proposed addition
SITE
Proposed Addition
DOWL HKM
920 Technology Blvd., Suite A
Bozeman, Montana 59718
Telephone: (406) 586-8834
Fax: (406) 586-1730
STARTED 12/1/08 FINISHED 12/1/08
DRILL CO.Haz Tech DRILL RIG BK-81
DRILLER Paul Bray HAMMER Automatic
LOGGED BY N. Peterson APPROVED BY G. UnderhillDEPTH (FT.)MATERIAL DESCRIPTION
GRAPHIC LOGELEVATION (FT.)BULKSAMPLES
DRIVEN/PUSHBLOWS PER 6"N BLOWS/FTNUMBERIN. RECOVEREDIN. DRIVENPOCKET PENE-TROMETER, TSFTESTS
10 20 30 40N VALUE BLOWS/FT
PL LL ADDITIONAL
DATA/
REMARKS
Surface Elevation: 4913.7
M.C.
Sheet 1 of 1
0
4
8
12
16
20
24
28
100
96
92
88
84
80
6" +/- Topsoil,OH/OL; frozen, black, organics
0.5 102.3
Fill, Lean Clay, CL; slightly moist, soft,
medium brown, trace roots
6.0 96.8
Fill, Gravel (GW), dry, gray, 3/4" crushed
possible utility trench
6.5 96.3
Lean Clay, CL; moist, soft, light brown,
mottled
10.0 92.8
Plastic Clay, CH: moist to wet, soft, tan
11.0 91.8
Lean Clay, CL; slightly moist, medium stiff,
light brown, mottled
13.8 89
Silty Clayey Gravel and Sand, GC-GM; moist,
dense, light brown to gray to multicolored, sub
rounded coarse to fine gravel
16.3 86.55
Lean Clay and Silt, CL-ML; moist, very stiff,
light brown
23.5 79.3
Silty Gravel, GM; slightly moist, very dense,
light brown to gray to multicolored
26.5 76.3
Boring terminated at 26.5 feet
No groundwater observed
2
4
5
3
1
1
2
2
4
5
415
17
1913
6
1114
9
1622
15
41
50/
3"
9
2
6
19
32
25
38
91
1
2
3
4
5
6
7
8
16/18
89%
13/18
72%
13/18
72%
18/18
100%
18/18
100%
18/18
100%
18/18
100%
14/18
78%
91
Elevation based on North
Entrance Door Slab
Elevation = 100.0 feet
Project No.: 4531.12105.01 LOG OF BOREHOLE B-8-17
CLIENT
Bozeman Deaconess Hospital
PROJECT
ICU Addition at Bozeman Deaconess Hospital
BORING LOCATION
South Portion of Addition
SITE
Bozeman Deaconess Hospital
DOWL
2090 Stadium Drive
Bozeman, Montana 59715
Telephone: (406) 586-8834
www.dowl.com
STARTED 12/21/17 FINISHED 12/21/17
DRILL CO.Haztech DRILL RIG BK-81
DRILLER Paul Bray HAMMER Auto
LOGGED BY J. Potts APPROVED BY G. UnderhillDEPTH (FT.)MATERIAL DESCRIPTION
GRAPHIC LOGELEVATION (FT.)BULKSAMPLES
DRIVEN/PUSHBLOWS PER 6"N BLOWS/FTNUMBERIN. RECOVEREDIN. DRIVENPOCKET PENE-TROMETER, TSFTESTS
10 20 30 40
N VALUE BLOWS/FT
PL LL ADDITIONAL
DATA/
REMARKS
Surface Elevation: 102.80
M.C.
Sheet 1 of 1
0
4
8
12
16
20
24
28
100
96
92
88
84
80
6" +/- Topsoil,OH/OL; frozen, black, organics
0.5 102.09
Fill, Lean Clay, CL; slightly moist, soft,
medium brown, trace roots.
2.5 100.09
Fill, Gravel (GW) 2.5 to 3.0
3.0 99.59
Lean clay, CL; most, medium stiff, light brown,
trace mottling
12.2 90.39
Silty Clayey Gravel and Sand, GC-GM;
slightly moist, very dense, light brown to gray
to multicolored, sub rounded coarse to fine
gravel, possible cobbles
no cobbles 18 to 22.2
22.2 80.39
Silt, ML; slightly moist, very dense, reddish
brown
24.0 78.59
Boring terminated at 24 feet
No groundwater observed
2
2
2
3
2
3
4
4
6
22
3250/
4"
15
2950/
4"
19
3144
13
2339
4
5
10
82
79
75
62
1
2
3
4
5
6
7
11/18
61%
13/18
72%
16/18
89%
14/18
78%
14/18
78%
17/18
94%
16/18
89%
82
79
75
62
Elevation based on North
Entrance Door Slab
Elevation = 100.0 feet
Project No.: 4531.12105.01 LOG OF BOREHOLE B-9-17
CLIENT
Bozeman Deaconess Hospital
PROJECT
ICU Addition at Bozeman Deaconess Hospital
BORING LOCATION
South Portion of Addition
SITE
Bozeman Deaconess Hospital
DOWL
2090 Stadium Drive
Bozeman, Montana 59715
Telephone: (406) 586-8834
www.dowl.com
STARTED 12/21/17 FINISHED 12/21/17
DRILL CO.Haztech DRILL RIG BK-81
DRILLER Paul Bray HAMMER Auto
LOGGED BY J. Potts APPROVED BY G. UnderhillDEPTH (FT.)MATERIAL DESCRIPTION
GRAPHIC LOGELEVATION (FT.)BULKSAMPLES
DRIVEN/PUSHBLOWS PER 6"N BLOWS/FTNUMBERIN. RECOVEREDIN. DRIVENPOCKET PENE-TROMETER, TSFTESTS
10 20 30 40
N VALUE BLOWS/FT
PL LL ADDITIONAL
DATA/
REMARKS
Surface Elevation: 102.59
M.C.
Sheet 1 of 1
G e o t e c h n i c a l R e p o r t PEOPLE WHO MAKE IT HAPPEN dowl.com
Appendix B
Geophysics Outputs
Seismic Refraction Tomography –Compressional Wave Velocities
Driveway Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Start
End
Legend
Interpretive Gravel Deposits
Geophysics Alignment
Crossing Geophysics Transect
PROFILE 1
North Addition Geophysics Transect
4850
4860
4870
4880
4890
4900
4910
Elevation (ft) 25 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205
Distance (ft)
S-wave velocity cross-section : Line ID=Driveway MASW 2D
(ft/s)
S-wave velocity
357
682
1007
1333
1658
1983
2308
Multichannel Analysis of Surface Waves (MASW) 2D – Shear Wave Velocities
Driveway Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Start
End
PROFILE 2
Legend
Interpretive Gravel Deposits
Geophysics Alignment
Crossing Geophysics Transect
North Addition Geophysics Transect
Multichannel Analysis of Surface Waves (MASW) 1D – Shear Wave Velocities - SeisImager
Driveway Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Start
End
PROFILE 3
Legend
Geophysics Alignment
MASW 1D Profile Location
0
10
20
30
40
50
60
70
80
90
100
110Depth (ft) 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600
S-wave velocity (ft/s)
S-wave velocity model (inverted) : 1015.dat
Average Vs to 100ft = 1213.4 ft/sec
412 3.2
454 6.7
530
10.5
600
14.7
893
19.3
1075
24.2
1294
29.5
1360
35.1
1373
41.1
1425
47.4
1505
54.0
1645
61.1
1953
68.4
2129
76.1
2226
84.2
2452
92.6
2484
101.4
2556
Multichannel Analysis of Surface Waves (MASW) 1D – Shear Wave Velocities - SWprocess
Driveway Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Start
End
PROFILE 4
Legend
Geophysics Alignment
MASW 1D Profile Location
Vs100 - Shear Wave Velocities Results
Driveway Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
End
Legend
Geophysics Alignment
MASW 1D Profile Location
Bozeman Health – Emergency Department – South Addition (Ambulance Driveway)
Center of Transect
Location Vs100 (feet per second)Site Class
MASW 1D – Center of Seismic Array - SeisImager 1,213.4 CD
MASW 1D – Center of Seismic Array - SWProcess 1,168.0 CD
ASCE 7-22 – Table 20.2-1 – Site Classification
Site Class Rock/Soil Type Sum of Vs Calculated Using 1D Shear Wave
Velocities (feet per second)
A Hard Rock >5,000
B Medium Hard Rock 3,000 to 5,000
BC Soft Rock 2,100 to 3,000
C Very Dense Sand or Hard Clay 1,450 to 2,100
CD Dense Sand or Very Stiff Clay 1,000 to 1,450
D Medium Dense Sand or Stiff Clay 700 to 1,000
DE Loose Sand or Medium Stiff Clay 500 to 700
E Very Loose Sand or Soft Clay ≤500
F Soils Requiring Site Response Analysis See Section 20.2.1 of ASCE 7
Start
End
Seismic Refraction Tomography – Compressional Wave Velocities
North Addition Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Start
End
Legend
Interpretive Gravel Deposits
Geophysics Alignment
Crossing Geophysics Transect
PROFILE 5
Driveway Geophysics Transect
Seismic Refraction Tomography – Shear Wave Velocities
North Addition Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Legend
Interpretive Gravel Deposits
Geophysics Alignment
Crossing Geophysics Transect
PROFILE 6
Driveway Geophysics Transect
Start
End
4850
4860
4870
4880
4890
4900
4910
Elevation (ft) 25 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205
Distance (ft)
S-wave velocity cross-section : Line ID=North Addition (Hill) MASW 2D
(ft/s)
S-wave velocity
434
768
1102
1436
1770
2104
2438
Seismic Refraction Tomography – Shear Wave Velocities
North Addition Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Legend
Interpretive Gravel Deposits
Geophysics Alignment
Crossing Geophysics Transect
PROFILE 7
Start
End
Seismic Refraction Tomography – Vp/Vs Ratio
North Addition Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
PROFILE 8
Driveway Geophysics Transect
Note: Vp/Vs above 4.0 indicates a free-flowing groundwater table.
Legend
Geophysics Alignment
Crossing Geophysics Transect
Start
End
Electrical Resistivity Tomography (ERT) – Ohm-meters
North Addition Transect
Analysis by: David Barrick Project: Bozeman Health Emergency Department Additions
Date: December 15, 2025 Project No.: 4691.000617.01
Legend
Undocumented Fill/Lean Clay Contact with Gravel and Silty Sand Deposits
Geophysics Alignment
Crossing Geophysics Transect
PROFILE 9
Driveway Geophysics Transect
Buried Utility with Pipe Bedding?
Start
End
PEOPLE WHO MAKE IT HAPPEN dowl.com G e o t e c h n i c a l R e p o r t Alaska
Anchorage 907.562.2000 5015 Business Park Blvd. Street, Anchorage, AK 99503
Fairbanks 907.374.0275 3535 College Road, Suite 100, Fairbanks, AK 99709
Juneau 907.780.3533 9085 Glacier Highway, Suite 102, Juneau, AK 99801
Arizona
Tempe 480.753.0800 4686 East Van Buren Street , Tempe, AZ 85008
Montana
Billings 406.656.6399 222 N. 32nd Street, Suite 700, Billings, MT 59101
Bozeman 406.586.8834 1283 North 14th Avenue, Suite 101, MT 59715
Helena 406.442.0370 1300 Cedar Street, Helena, MT 59601
Nevada
Elko 775.738.2121 421 Court Street, Elko, NV 89801
Reno 775.8514.788 5510 Longley Lane , Reno, NV 59511
Oregon
Bend 541.385.4772 963 SW Simpson Avenue, Suite 200, Bend, OR 97702
Eugene 541.683.6090 920 Country Club Road, Suite 100B, Eugene, OR 97401
Lake Oswego 503.620.6103 5 Centerpoint Drive, Suite 350, Lake Oswego, OR 97035
Medford 541.774.5590 831 O'Hare Parkway, Medford, OR 97504
Portland 971.280.8641 309 SW 6th Avenue, Suite 700, Portland, OR 97204
Salem 503.589.4100 4275 Commercial St SE, Ste 100, Salem, OR 97302
Washington
Redmond 425.869.2670 8420 154th Avenue NE, Redmond, WA 98052
Vancouver 360.314.2391 7200 NE 41st Street, Suite 204 Vancouver, WA 98660
Wyoming
Sheridan 307.672.9006 1833 South Sheridan Avenue, Sheridan, WY 82801
1283 North 14th Ave. │ Bozeman, MT 59715
(406) 586-8834
Lab 222 N. 32nd Street │ Billings, MT 59101
(406) 656-6399