Geotech_O-11_Bridge_Repair_9-1-2014.pdf

CLIENT: Malmstrom AFB

Base Contracting 7015 Goddard Drive Malmstrom AFB, MT 59402

ENGINEER: Thomas, Dean, & Hoskins, Inc.

1800 River Drive North Great Falls, MT 59401 Contact: Craig Nadeau, P.E.

Great Falls ● Bozeman ● Kalispell ● Shelby, Montana

Spokane, Washington ● Lewiston, Idaho

Watford City, North Dakota

1800 River Drive North Great Falls, MT 59401 (406) 761-3010

REPORT OF GEOTECHICAL INVESTIGATION

O-11 BRIDGE REPAIR – HORSE RANCH ROAD

NORTH OF LEWISTOWN, MONTANA

SEPTEMBER 2014

TD&H Job # 14-224-001 mmf Craig Seal mmf New Stamp

O-11 Bridge Repair Table of Contents North of Lewistown, Montana i

Table of Contents

1.0 EXECUTIVE SUMMARY

2.0 INTRODUCTION

2.1 Purpose and Scope

2.2 Project Description

3.0 SITE CONDITIONS

3.1 Geology and Physiography

3.2 Surface Conditions

3.3 Subsurface Conditions

3.3.1 Soils

3.3.2 Ground Water

4.0 ENGINEERING ANALYSIS

4.1 Introduction

4.2 Shallow Foundations

4.3 Deep Foundations

4.4 Wing Walls & Culvert Sides

4.5 Gravel Road Surface

5.0 RECOMMENDATIONS

5.1 Site Grading and Excavations

5.2 Conventional Shallow Foundations (Culvert Option Only)

5.3 Deep Foundation Recommendations (Driven Piling)

5.4 Wing Walls & Culvert Sides

5.5 Gravel Road Surface

5.6 Continuing Services

6.0 SUMMARY OF FIELD AND LABORATORY STUDIES

6.1 Field Explorations

6.2 Laboratory Testing

7.0 LIMITATIONS

O-11 Bridge Repair Appendix North of Lewistown, Montana ii

APPENDIX

Boring Map (Figure 1) Logs of Exploratory Borings (Figures 2 and 3) Laboratory Test Data (Figures 4 through 9) Soil Classification and Sampling Terminology for Engineering Purposes Classification of Soils for Engineering Purposes

O-11 Bridge Repair Executive Summary North of Lewistown, Montana Page 1

GEOTECHNICAL REPORT

O-11 BRIDGE REPAIR

NORTH OF LEWISTOWN, MONTANA

1.0 EXECUTIVE SUMMARY

The geotechnical investigation for the bridge repair to be located on Horse Ranch Road, north of Lewistown and near Roy, MT, encountered lean clay and poorly-graded sand layers overlying weathered shale bedrock. The seismic site class is C and the likelihood of seismically-induced soil liquefaction or settlement for this project is low and does not warrant additional evaluation. The primary geotechnical concern regarding this project is the magnitude of structural loads associated with a bridge structure and the potential for slope instabilities. Because of possible bank instability, the use of driven pile foundations bearing within the shale bedrock is the preferred foundation system for a repair or replacement bridge option. We understand that alternative options such as using culverts are being considered and would require the use of shallow foundations. Shallow foundations are permissible provided they are not located mid-slope as this can create an instability which could not be fully evaluated with the time permitted for this project. Pile foundations can be utilized if a culvert system must bear at a mid-slope elevation.

O-11 Bridge Repair Introduction North of Lewistown, Montana Page 2

2.0 INTRODUCTION

2.1 Purpose and Scope

This report presents the results of our geotechnical study for the repair/replacement of the O-11 bridge located on Horse Ranch Road north of Lewistown and near Roy, Montana. The purpose of the geotechnical study is to determine the general surface and subsurface conditions adjacent to the existing bridge structure and provide geotechnical recommendations for foundation systems which may be required to repair or replace the existing bridge structure. This report describes the field work and laboratory analyses conducted for this project, the surface and subsurface conditions encountered, and presents our recommendations for the proposed foundations and related site development.

Our field work included two drilled soil borings in proximity to the existing bridge structure.

Samples were obtained from the borings and returned to our Great Falls laboratory for testing.

Laboratory testing was performed on select soil samples to determine engineering properties of the subsurface materials. The information obtained during our field investigations and laboratory analyses was used to develop recommendations for the design of the proposed foundation systems.

This study is in general accordance with the proposal submitted by Mr. John Juras, P.E. of our firm.

Our work was authorized to proceed by Ms. Jennifer George with Malmstrom Air Force Base by her signed acceptance of our proposal.

2.2 Project Description

It is our understanding that the proposed project consists of the evaluation of the existing O-11 bridge structure to develop repair/replacement options. The existing structure has experienced distress associated with high creek flows during past years. This has resulted in lateral deflections of the existing wooden pile system and scour around the base of some piles. If a replacement structure is considered, we understand that the new structure would be approximately twenty-five feet wide and likely incorporate a single span on the order of sixty feet. The new bridge is proposed to be supported on deep foundations incorporating driven piles. Abutment service loads on the order of 600 kips per abutment are anticipated. Preliminary loads were provided by Ms. Mary Barfield, P.E.

of our firm.

As an alternative to a replacement bridge, a large span corrugated steel culvert option supported on a conventional shallow foundation at or near the streambed elevation is also being evaluated.

Foundation loads for this option had not be evaluated at the time of this report.

O-11 Bridge Repair Site Conditions North of Lewistown, Montana Page 3

3.0 SITE CONDITIONS

3.1 Geology and Physiography

The site is geologically characterized as overburden soils overlying dark gray shale of the Bearpaw Formation, part of the Beaverhead Group. The shale often contains several zones of calcareous concretions and numerous bentonite beds. To the north and east of the existing crossing bedrock associated with the Judith River Formation is encountered which is comprised primarily of fine- to coarse-grained sandstone with interbeds of gray to black carbonaceous shale. Frequent gravel deposits are encountered throughout the area as shown as QTgr on the geologic map below. These gravel deposits are generally variable and range from pebble to boulder size particles with varying amounts of sand, silt, clay1.

Geologic Map of Project Location1

Based on the subsurface conditions encountered, the site falls under seismic Site Class C. The appropriate 2009 International Building Code (IBC) seismic design parameters for the site include site coefficients of 1.2 and 1.7 for Fa and Fv, respectively. The recommended design spectral response accelerations at short periods (Ss) and at 1-second period (S1) are 0.084g and 0.042g, respectively. These values represent two-thirds of the mapped response accelerations following correction for the appropriate site classification.

1 Geologic Map of Montana, 2007 (Montana Bureau of Mines & Geology, Geologic Map 62)

North of Lewistown, Montana Page 4

3.2 Surface Conditions

The proposed project site is located at the existing O-11 bridge on Horse Ranch Road approximately nine miles north of US 191. The existing bridge is a wooden structure supported on driven wood piles. The terrain surrounding the existing bridge is considered gently sloping to very steep based on site observations.

3.3 Subsurface Conditions

3.3.1 Soils

The subsurface soil conditions appear to be somewhat variable based on our exploratory drilling and soil sampling. In general, the subsurface soil conditions encountered within the soil borings consist of frequent interbeds of clayey sand and sandy lean clay of varying thickness above a weathered shale bedrock extending to a depth of at least 51.5 feet, which was the maximum depth investigated.

The subsurface soils are described in detail on the enclosed boring logs and are summarized below. The stratification lines shown on the logs represent approximate boundaries between soil types and the actual in situ transition may be gradual vertically or discontinuous laterally.

Granular Soils Granular soils ranging from poorly-graded gravel to silty, clayey sand were observed in both borings performed with layer thicknesses ranging from less than one foot to five feet. These materials are considered loose to dense as indicated by penetration resistance values which ranged from 9 to 37 blows per foot (bpf) and averaged 20 bpf. Samples contained between 6 and 50 percent gravel, between 32 and 66 percent sand, and between 18 and 28 percent fines (silt and clay). One sample exhibited a liquid limit of 26 percent and a plasticity index of 5 percent. The natural moisture contents measured varied from 3 to 19 percent and averaged 10 percent.

Lean Clay Lean clays ranging from lean clay to sandy lean clay were encountered in both borings performed and are considered soft to stiff based on SPT values ranging 6 to 21 bpf and averaging 13 bpf. The lean clay encountered was primarily classified as sandy lean clay;

however, layers of lean clay and lean clay with sand were present. Based on laboratory testing, two samples tested contained less than 13 percent gravel, between 2 and 35 percent sand, and between 52 and 98 percent fines (clay and silt). These two samples also exhibited

North of Lewistown, Montana Page 5 a liquid limit of 32 percent and plasticity indices from 14 to 16 percent. The natural moisture contents measured varied from 7 to 19 percent and averaged 12 percent.

Weathered Shale The weathered shale was encountered in both borings at approximately 21 feet below ground surface. It is considered soft to medium hard in terms of bedrock and could also be considered hard fat clay. SPT values ranged from 42 to 90 bpf with an average of 65 bpf with multiple tests reaching refusal. The fat clay encountered was classified as weathered shale due to the high SPT values and the samples varved appearance. Based on laboratory testing, one sample tested exhibited a liquid limit of 62 percent and plasticity index of 44 percent. The natural moisture contents measured varied from 12 to 22 percent and averaged 18 percent.

3.3.2 Ground Water

Ground water was encountered within one of the soil borings at a depth of 12.7 feet below the ground surface. Water levels were measured at the time of drilling and upon completion of the investigation. The presence or absence of observed ground water may be directly related to the time of the subsurface investigation. Numerous factors contribute to seasonal ground water occurrences and fluctuations, and the evaluation of such factors is beyond the scope of this report.

O-11 Bridge Repair Engineering Analysis North of Lewistown, Montana Page 6

4.0 ENGINEERING ANALYSIS

4.1 Introduction

The primary geotechnical concern regarding this project is the potential for slope instabilities associated with the magnitude of the proposed bridge loads. Further detailed evaluation of the slopes are needed if conventional shallow foundation are to be considered; however, the use of a deep foundation system will provided adequate support and effectively eliminate the concerns associated with the slopes. In addition, alternative options for utilizing a culvert system are being considered which may require conventional shallow foundations. Similar foundations, if supported on the existing slopes, may create an instability which could not be fully evaluated due to the limited schedule for this project. Additionally, the presence of fine-grained soils was of concern during this investigation. Typically, these soils are considered poor subgrade for roadways and are not ideal for backfill; however, the blending of the native clay and sand soils during construction is likely to generate an acceptable fill material provided it is properly compacted per our recommendations.

4.2 Shallow Foundations

Considering the subsurface conditions encountered and the nature of the proposed construction, the culvert option, if preferred, can be supported on conventional shallow spread footings provided the footings can be designed to bear near existing streambed elevation. Conventional footings which must bear above streambed elevation should be supported on driven piling and grade beams unless additional time and budget is available to fully evaluate the potential for slope instability associated with this additional loading. Conventional footings bearing at or below existing streambed elevation on undisturbed natural soils should be designed using a maximum allowable soil bearing pressure of 1,500 psf. Based on the theory of elasticity and the subsurface conditions observed, we estimate the total settlement for footings will be less than ¾-inch. Differential settlement across the structure should be on the order of one-half this magnitude.

The lateral resistance of spread footings is controlled by a combination of sliding resistance between the footing and the foundation material at the base of the footing and the passive earth pressure against the side of the footing in the direction of movement. Design parameters are given in the recommendations section of this report. Shallow foundations which are supported near the riverbed must be protected from erosion and scour. This is commonly achieved by utilizing footings extending below the anticipated scour depth or by installing rip rap or other erosion control features adjacent the foundations. Similar features should be incorporated into the design.

North of Lewistown, Montana Page 7

4.3 Deep Foundations

Due to the magnitude of abutment loads, a replacement bridge structure should be supported on a deep foundation system extending down into the underlying weathered shale. Based on the subsurface conditions encountered, we recommend the use of driven piling for this project; however, alternative systems such as drilled piers or micropiles would also be acceptable. Similar systems would likely require some level of water control measures and localized casing of unstable layers during drilling. The recommendations provided below are intended for the design of a driven pile system utilizing displacement piles such as closed-end steel or pre-cast concrete piling.

If footings for the culvert option must bear above the existing streambed elevation and additional time/budget is not available for further investigation, a similar deep foundation system and grade beam should be used. Utilizing driven piles and a pile cap reduced the risk of slope instability by adding stiffening elements (piles) through the embankment soils and by transferring the majority of the structural loads downward to the weathered shale strata. The lateral resistance of deep foundations is controlled by a combination of pile bending capacity and the passive earth pressure against the side of the pile in the direction of movement. Design parameters are given in the recommendations section of this report.

4.4 Wing Walls & Culvert Sides

Wing walls and culvert sides will be subjected to horizontal loading due to lateral earth pressures.

The lateral earth pressures are a function of the natural and backfill soil types and acceptable wall movements, which affect soil strain to mobilize the shear strength of the soil. More soil movement is required to develop greater internal shear strength and lower the lateral pressure on the wall. To fully mobilize strength and reduce lateral pressures, soil strain and allowable wall rotation must be greater for clay soils than for cohesionless, granular soils.

The lowest lateral earth pressure against walls for a given soil type is the active condition and develops when wall movements occur. Passive earth pressures are developed when the wall is forced into the soil, such as at the base of a wall on the side opposite the retained earth side. When no soil strain is allowed by the wall, this is the "at-rest" condition, which creates pressures having magnitudes between the passive and active conditions.

The distribution of the lateral earth pressures on the structure depends on soil type and wall movements or deflections. In most cases, a triangular pressure distribution is satisfactory for design and is usually represented as an equivalent fluid unit weight. Design parameters are given in the recommendations section of this report.

North of Lewistown, Montana Page 8

4.5 Gravel Road Surface

A gravel road section will be required for a culvert option. Similar systems are designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and the magnitude and frequency of traffic loadings.

Gravel road design procedures are based on strength properties of the subgrade as well as the proposed surfacing materials under the design traffic conditions. Traffic information was not available at the time of this report. We understand that this bridge is utilized for military access and will be traveled by large transport trucks with axle loads on the order of 18-kips. In addition, use by local residents and larger farming equipment is anticipated. Traffic volumes are anticipated to peak during the summer and fall seasons; however, for the purposes of our analysis, we have assumed that up to two large trucks per day will cross the bridge during the twenty year road design life. Military transport vehicles we understand can have as many as nine axles.

The potential worst case subgrade material is lean clay with sand which is classified as an A-6 soil, in accordance with the American Association of State Highway and Transportation Officials (AASHTO) classification. AASHTO considers this soil type to be a fair to poor subgrade. Typical California Bearing Ratio (CBR) values for this type of soil range from 3 percent to 10 percent. It will be necessary to scarify and recompact the subgrade soils prior to placing fill material associated with the gravel section. The fill should be selected, placed, and compacted in accordance with our recommendations.

A geotextile acting as a separator is recommended between the gravel road base and the subgrade.

The geotextile will prevent the upward migration of fines and the loss of aggregate into the subgrade, thereby prolonging the structural integrity and performance of the gravel road section. The gravel road section presented in this report is based on the following assumed design parameters:

Subgrade CBR (%) 5.0 Axle Load (lbs) 18,000

Axle Passes 120,000 Tire Pressure (psi) 100

Allowable Rut Depth (in) 2.0

O-11 Bridge Repair Recommendations North of Lewistown, Montana Page 9

5.0 RECOMMENDATIONS

5.1 Site Grading and Excavations

1. All topsoil and organic material, asphalt, concrete and related construction debris should be removed from any areas to receive site grading fill. For planning purposes, a minimum stripping thickness of 6 inches is recommended. Thicker stripping depths may be warranted to remove all detrimental organics as determined once actual stripping operations are performed.

2. All fill and backfill should be non-expansive, free of organics and debris and should be approved by the project geotechnical engineer. If the metal culvert option is selected, all backfill material around the culvert should be non-corrosive. All fill should be placed in uniform lifts not exceeding 8 inches in thickness for fine-grained soils and not exceeding 12 inches for granular soils. All fill and backfill shall be compacted to the following percentages of the maximum dry density determined by a standard proctor test which is outlined by ASTM D698 or equivalent (e.g. ASTM D4253-D4254).

a) Foundation Wall Backfill ............................................................. 98%

b) Culvert Backfill ........................................................................... 98%

c) General Grading or Nonstructural Areas ..................................... 92%

3. Imported structural fill should be non-expansive, free of organics and debris, and selected per the following gradation requirements:

Screen or Sieve Size Percent Passing by Weight 3-inch 100

1½-inch 80 – 100 ¾-inch 60 – 100 No. 4 25 – 60

No. 200 12 maximum

4. A composite volumetric shrinkage factor will vary considerably based on the material type, in-situ density, and compacted density. At this time a source for potential borrow, if needed, has not been located. Shrinkage factors generally range from 5 to 20 percent; however, additional investigation is warranted to refine this value once a borrow source has been identified.

North of Lewistown, Montana Page 10

5. It is the responsibility of the Contractor to provide safe working conditions in connection with underground excavations. Temporary construction excavations greater than four feet in depth, which workers will enter, will be governed by OSHA guidelines given in 29 CFR, Part 1926. For planning purposes the subsoils encountered in the soil borings are considered Type C due to the high level of variability. An experienced individual who is knowledgeable of the OSHA requirements shall be on-site during all excavation activities to classify the soils and ensure that all applicable OSHA requirements are being followed.

5.2 Conventional Shallow Foundations (Culvert Option Only)

6. Conventional shallow foundations used to support a culvert structure should bear at or below the existing streambed elevation on undisturbed native soils. Footings should be designed for a maximum allowable soil bearing pressure of 1,500 psf provided settlements as outlined in the Engineering Analysis are acceptable.

7. Soils disturbed below the planned depths of footing excavations should either be replaced with flowable fill with an unconfined compressive strength between 200 and 500 psi at 28-days as tested per ASTM D4832.

8. Footings should either be extended below the anticipated maximum depth of scour or should be protected from scour by adequately designed rip rap or other flow control devices.

9. The bottom of the footing excavations should be free of cobbles and boulders to avoid stress concentrations acting on the base of the footings.

10. Lateral loads are resisted by sliding friction between the footing base and the supporting soil and by lateral pressure against the footings opposing movement. For design purposes, a friction coefficient of 0.25 and a lateral resistance pressure of 150 psf per foot of depth are appropriate for the footings bearing on and backfilled with native soils.

5.3 Deep Foundation Recommendations (Driven Piling)

The following recommendations should be followed for the design of a deep foundation system utilizing driven, displacement piles to support the abutments of a replacement bridge structure.

These recommendations should also be utilized for a culvert system in which the foundation support elevation is above the existing streambed elevation.

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11. Displacements piles consisting of either closed-end pipe piles or pre-cast concrete piles should be used to support foundation loads for the replacement bridge option.

Piles should be driven down to the underlying weathered shale and to adequate depth to obtained the required pile capacity. Based on the borings performed, pile lengths on the order of 25 to 35 feet are anticipated. However, piles lengths exceeding 40 feet are considered unlikely and should not be anticipated during design.

Piles should be designed using a maximum allowable end bearing pressure of 30 kips per square foot (ksf). Skin friction values of 150 and 600 psf per foot, respectively, should be assumed for the overburden soils and the underlying weathered shale. For the purposes of design, the following bedrock elevations should be assumed:

Location Depth Elevation

North Abutment 21 ft 3,264 ft South Abutment 21 ft 3,255 ft

Based on these parameters, a 30-ft long closed-end pipe pile with diameters of 12-inch and 18-inch would have an allowable capacity on the order of 50 and 90 kips, respectively.

12. The piles should be designed to resist lateral loads using the following L-Pile parameters:

Layer Depth (ft)

Model Layer Type Unit

Weight, p-y Modulus, k

Cohesive Strength, c

Soil Strain, (lb/in3) (lb/in3) (lb/in2) 0 - 21 Stiff Clay w/o Free Water 0.072 500 10.5 0.010 21+ Stiff Clay w/o Free Water 0.081 2000 41.5 0.005

13. If necessary, the piles can be filled with concrete to provide additional stiffness which would reduce the pipe wall thickness required under the design lateral loads. Pipe wall thicknesses should be greater than or equal to 0.25-inches to account for driving stresses. If concrete filler is used, concrete shall not be placed in more than 3 inches of standing water without using a tremie.

14. The minimum recommended spacing requirement between driven piles should be three diameters (center-to-center). Once pier locations and loads have been

North of Lewistown, Montana Page 12 determined, any piers required to be spaced closer than three diameters (center-to-center) should be analyzed on an individual basis to determine the appropriate axial and lateral reduction factors.

15. Prior to construction, TD&H shall perform a GRLWeap analysis based on the contractors proposed driving system to ensure it is adequate for the designed pile size and required structural capacity. In addition, a representative of the project geotechnical engineer should conduct full time observation and monitoring of the pile installation using a saximeter to approximate on-site pile capacity.

5.4 Wing Walls & Culvert Sides

The design and construction criteria presented below should be observed for wing walls on bridge abutments and for sides of culverts, if used.

16. Wing walls or culverts which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of 70 pcf for backfill consisting of the native soils. Alternatively, designs incorporating imported structural fill (Item 3) or other relatively clean granular soils which are approved by the geotechnical engineer as backfill should utilize an equivalent fluid unit weight of 50 pcf.

17. Retaining structures which can deflect sufficiently to mobilize the full active earth pressure condition, approximately 3.0 percent of the exposed wall height, may be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of 50 pcf for native backfill. If structural fill (Item 3) is utilized, only 0.3 percent deflection is required to achieve the active earth pressure condition and a reduced equivalent fluid unit weight of 35 pcf is appropriate.

18. Backfill placed against the sides of the footings and the base of the walls to resist lateral loads should be placed and compacted per the requirements of Item 2 above.

19. Backfill placed behind retaining structures should be selected, placed, and compacted per Item 2 above. Care should be taken not to over-compact the backfill since this could cause excessive lateral pressure on the walls. Only hand-operated compaction equipment should be used within 5 feet of soil retaining structures.

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5.5 Gravel Road Surface

20. The following gravel section should be utilized in conjunction with a culvert option in accordance with the discussions in the Engineering Analysis, if selected.

Pavement Component Component Thickness

Crushed Top Surfacing Type A Grade 2 6”

Crushed Base Course Grade 6A 12”

Total 18”

21. Gradations for the aggregate courses shall conform to Section 701 of the MDT

Standard Specifications for Road and Bridge Construction.

22. Where the existing grades will be raised more than the thickness of the pavement section, all fill should be placed, compacted and meet the general requirements given in Item 2. Native soils are considered sufficient; however, exterior borrow sources which do not satisfy the requirements of Item 3 should be approved by the geotechnical engineer prior to use.

23. A geotextile is recommended between the pavement section and the prepared subgrade to prevent the migration of fines upward into the gravel and the loss of aggregate into the subgrade. A woven Mirafi 500X (Product of TenCate Geosynthetics) or equivalent geotextile is appropriate.

5.6 Continuing Services

Three additional elements of geotechnical engineering service are important to the successful completion of this project.

24. Consultation between the geotechnical engineer and the design professionals during the design phases is highly recommended. This is important to ensure that the intentions of our recommendations are incorporated into the design, and that any changes in the design concept consider the geotechnical limitations dictated by the on-site subsurface soil and ground water conditions.

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25. Observation, monitoring, and testing during construction is required to document the successful completion of all earthwork and foundation phases. A geotechnical engineer from our firm should observe the excavation, earthwork, and foundation phases of the work to determine that subsurface conditions are compatible with those used in the analysis and design.

26. During site grading, placement of all fill and backfill should be observed and tested to confirm that the specified density has been achieved. We recommend that the Owner maintain control of the Construction Quality Control by retaining the services of an Accredited/Certified Construction Materials Testing Laboratory. We are available to provide construction inspection services as well as materials testing of compacted soils and the placement of Portland cement concrete.

O-11 Bridge Repair Summary of Field & Laboratory Studies North of Lewistown, Montana Page 15

6.0 SUMMARY OF FIELD AND LABORATORY STUDIES

6.1 Field Explorations

The field exploration program was conducted on August 20, 2014. A total of two soil borings were drilled to depths ranging from 30.0 to 51.5 feet at the locations shown on Figure 1 to observe subsurface soil and ground water conditions. The borings were advanced through the subsurface soils using a truck-mounted BK-81 drill rig equipped with 8-inch hollowstem augers. The subsurface exploration and sampling methods used are indicated on the attached boring logs. The soil borings were logged by Jeremy Miller of Thomas, Dean & Hoskins, Inc. (TD&H).

Samples of the subsurface materials were taken using 1⅜-inch I.D. split spoon sampler. The sampler was driven 18 inches, when possible, into the various strata using a 140-pound drop hammer falling 30 inches onto the drill rods. For each sample, the number of blows required to advance the sampler each successive six-inch increment was recorded, and the total number of blows required to advance the sampler the final 12 inches is termed the penetration resistance (“N-value”). This test is known as the Standard Penetration Test (SPT) described by ASTM D1586. Penetration resistance values indicate the relative density of granular soils and the relative consistency of fine-grained soils.

Samples were also obtained by hydraulically pushing a 3-inch I.D., thin-walled Shelby tube sampler into the subsoils. Logs of each soil boring which include soil descriptions, sample depths, and penetration resistance values, are presented on Figures 2 and 3.

Measurements to determine the presence and depth of ground water were made in the borings by lowering an electronic water sounder through the open boring shortly after the completion of drilling.

The depths or elevations of the water levels measured, if encountered, and the date of measurement are shown on the borings logs.

6.2 Laboratory Testing

Samples obtained during the field exploration were returned to our materials laboratory where they were observed and visually classified in general accordance with ASTM D2487, which is based on the Unified Soil Classification System. Representative samples were selected for testing to determine the engineering and physical properties of the soils in general accordance with ASTM or other approved procedures.

O-11 Bridge Repair Summary of Field & Laboratory Studies North of Lewistown, Montana Page 16

Tests Conducted: To determine:

Natural Moisture Content Representative moisture content of soil at the time of sampling.

Grain-Size Distribution Particle size distribution of soil constituents describing the percentages of clay/silt, sand and gravel.

Atterberg Limits A method of describing the effect of varying water content on the consistency and behavior of fine-grained soils.

Natural Dry Density Dry unit weight of samples, representative of in-place conditions.

Consolidation/Swell The amount that a soil sample compresses with loading and the influence of wetting on its behavior. For use in settlement analysis, determining expansive potential and foundation design.

UU Shear Strength (Field) The undrained, unconfined shear strength (su) of cohesive soils as determined in the field by either a pocket penetrometer or a hand torvane.

Unconfined Compression Undrained shear strength properties of cohesive soils determined in the laboratory by axial compression.

The laboratory testing program for this project consisted of 33 moisture-visual analyses, two sieve (grain-size distribution) analyses, and two Atterberg Limits analyses. The results of the water content analyses are presented on the boring logs, Figures 2 and 3. The grain-size distribution curves and Atterberg limits are presented on Figures 4 through 6. In addition, one unit weight, one consolidation-swell test, and one unconfined compression test were performed. The results of these tests are shown on Figures 7 through 9. Unconfined compressive strengths (qu) were determined in the field using a pocket penetrometer. The results are shown on the boring logs at the depths the samples were tested.

O-11 Bridge Repair Limitations North of Lewistown, Montana Page 17

7.0 LIMITATIONS

This report has been prepared in accordance with generally accepted geotechnical engineering practices in this area for use by the client for design purposes. The findings, analyses, and recommendations contained in this report are based on site conditions encountered and further assume that the results of the exploratory borings are representative of the subsurface conditions throughout the site, that is, that the subsurface conditions everywhere are not significantly different from those disclosed by the subsurface study. If during construction, subsurface conditions appear different from those encountered during our study, this office should be advised at once so we can review these conditions and reconsider our recommendations, when necessary.

Unanticipated soil conditions are commonly encountered and cannot be fully determined by a limited number of soil borings and laboratory analyses. Such unexpected conditions frequently require that additional expenditures be made to obtain a properly constructed project. Therefore, some contingency fund is recommended to accommodate such potential extra costs.

If substantial time has elapsed between the submission of this report and the start of work at the site, or if conditions have changed because of natural causes or construction operations at or adjacent to the site, we recommend that this report be reviewed to determine the applicability of the conclusions and recommendations considering the time lapse or changed conditions.

If you desire, we will review those portions of the plans and specifications which pertain to earthwork and foundations to determine if they are consistent with our recommendations. In addition, we are available to observe construction, particularly the placement and compaction of all fill, preparation of all foundations and quality control testing of Portland cement concrete.

This report was prepared for the exclusive use of the owner and architect and/or engineer in the design of the subject facility. It should be made available to prospective contractors and/or the contractor for information on factual data only and not as a warranty of subsurface conditions such as those interpreted from the boring logs and presented in discussions of subsurface conditions included in this report.

Prepared by: Reviewed by:

Craig R. Nadeau, P.E. Kyle Scarr, P.E.

Geotechnical Engineer Geotechnical Engineer mmf New Stamp mmf Kyle Scarr Signature

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Well-Graded GRAVEL with Sand and Clay, medium dense, slightly moist, light brown, some organics

Sandy Lean CLAY, stiff to very stiff, slightly moist, light brown

Lean CLAY with Sand, stiff, slightly moist, light brown, some gravel

Poorly-Graded SAND with clay, medium dense, slightly moist, light brown qu = 1.5 - 2.0 tsf

Clayey SAND, medium dense, brown, slightly moist to very moist, some gravel

Silty Clayey SAND, loose, moist to very moist, brown, some oxidation, trace gravel

Clayey SAND, loose, brown, some gravel

Lean CLAY with Sand, moderate plasticity, soft, moist, gray to brown, some oxidation qu = 0.5 - 1.0 tsf

0.5

2.5

5.0

7.5

10.0

12.0

16.0

9-13-8

5-6-5

6-8-7

10-7-17

5-5-4

2-2-4

LEGEND

LOG OF SOIL BORING B-1

SPT blows per foot Atterberg Limits

Field Moisture content MAFB O-11 Bridge Repair Horse Ranch Road - North of Lewistown, MTGroundwater Level

Grab/composite sample

1-3/8-inch I.D. split spoon Logged by: Jeremy Miller

2-1/2-inch I.D. split spoon Drilled by: HazTech Drilling Inc Truck-mounted BK-81 with 8-inch HSA

2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic

3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate boundaries between soil types. Actual boundaries may be gradual or transitional.

August 20, 2014 14-224 No sample recovery Figure No. 2

Sheet

G R

A P

H

IC

L O

G

SOIL DESCRIPTION

SURFACE: Road Shoulder, Gravel SURFACE ELEVATION: 3,285.5 ft

D E

P T

H

G R

O U

N D

W A

T E

R

S P

T B

L O

W

C O

U N

T S

S A

M P

L E

D E

P T

H

F T

) PENETRATION RESISTANCE/MOISTURE CONTENT

0 10 20 30 40 50

= BLOWS PER FOOT

= MOISTURE CONTENT

22.5

27.5

32.5

Lean CLAY, soft, moist, gray to brown

Weathered CLAYSTONE/SHALE, medium hard, light gray to dark gray, slightly moist to moist, some sands qu > 4.5 tsf

- Dark gray, some charcoal qu > 4.5 tsf

Bottom of Hole

20.0

21.8

30.5

Ground water not encoun-tered

PUSH

28-31-

21-40- 50/3"

50/5"

T

90/0.75'

50/0.5'

LEGEND

LOG OF SOIL BORING B-1

SPT blows per foot Atterberg Limits

Field Moisture content MAFB O-11 Bridge Repair Horse Ranch Road - North of Lewistown, MTGroundwater Level

Grab/composite sample

1-3/8-inch I.D. split spoon Logged by: Jeremy Miller

2-1/2-inch I.D. split spoon Drilled by: HazTech Drilling Inc Truck-mounted BK-81 with 8-inch HSA

2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic

3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate boundaries between soil types. Actual boundaries may be gradual or transitional.

August 20, 2014 14-224 No sample recovery Figure No. 2

Sheet

G R

A P

H

IC

L O

G

SOIL DESCRIPTION

SURFACE: Road Shoulder, Gravel SURFACE ELEVATION: 3,285.5 ft

D E

P T

H

G R

O U

N D

W A

T E

R

S P

T B

L O

W

C O

U N

T S

S A

M P

L E

D E

P T

H

F T

) PENETRATION RESISTANCE/MOISTURE CONTENT

0 10 20 30 40 50

= BLOWS PER FOOT

2.5

7.5

12.5

17.5

Well-Graded GRAVEL with Sand, dense, brown to gray, slightly moist, some clay

Sandy Lean CLAY, stiff, brown, dry to slightly moist

Poorly-Graded SAND with Clay and Gravel, tan to gray, slightly moist, medium dense to very dense

-Transition to brown

- Oxidized below 5.5 feet

Sandy Lean CLAY, stiff, moist, brown to dark brown, oxidation, some gravel, moderate plasicity qu = 2.5 - 4.0 tsf

Poorly-Graded SAND with Clay, loose to medium dense, brown, wet

Poorly-Graded GRAVEL with Clay and Sand, hard, slightly moist, white to orange, oxidation

Clayey GRAVEL with Sand, medium dense, saturated, brown, oxidation

0.5

2.5

7.5

12.0

12.5

15.0

12-11-7

13-12-

7-9-9

4-3-6

PUSH

9-12-7

6-6-9

T

LEGEND

LOG OF SOIL BORING B-2

SPT blows per foot Atterberg Limits

Field Moisture content MAFB O-11 Bridge Repair Horse Ranch Road - North of Lewistown, MTGroundwater Level

Grab/composite sample

1-3/8-inch I.D. split spoon Logged by: Jeremy Miller

2-1/2-inch I.D. split spoon Drilled by: HazTech Drilling Inc Truck-mounted BK-81 with 8-inch HSA

2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic

3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate boundaries between soil types. Actual boundaries may be gradual or transitional.

August 20, 2014 14-224 No sample recovery Figure No. 3

Sheet

G R

A P

H

IC

L O

G

SOIL DESCRIPTION

SURFACE: Road Shoulder, Gravel SURFACE ELEVATION: 3,276.4 ft

D E

P T

H

G R

O U

N D

W A

T E

R

S P

T B

L O

W

C O

U N

T S

S A

M P

L E

D E

P T

H

F T

) PENETRATION RESISTANCE/MOISTURE CONTENT

0 10 20 30 40 50

= BLOWS PER FOOT

22.5

27.5

32.5

Poorly-Graded SAND, dense, gray, wet, some clay

Weathered SHALE, soft to medium hard, dark brown, slightly moist, some sand

- Gray to dark brown, varved qu > 4.5 tsf

- Moist to very moist, charcoal

20.5

21.2

13-25-

19-31- 50/6

10-19-

28-46-

LEGEND

LOG OF SOIL BORING B-2

SPT blows per foot Atterberg Limits

Field Moisture content MAFB O-11 Bridge Repair Horse Ranch Road - North of Lewistown, MTGroundwater Level

Grab/composite sample

1-3/8-inch I.D. split spoon Logged by: Jeremy Miller

2-1/2-inch I.D. split spoon Drilled by: HazTech Drilling Inc Truck-mounted BK-81 with 8-inch HSA

2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic

3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate boundaries between soil types. Actual boundaries may be gradual or transitional.

August 20, 2014 14-224 No sample recovery Figure No. 3

Sheet

G R

A P

H

IC

L O

G

SOIL DESCRIPTION

SURFACE: Road Shoulder, Gravel SURFACE ELEVATION: 3,276.4 ft

D E

P T

H

G R

O U

N D

W A

T E

R

S P

T B

L O

W

C O

U N

T S

S A

M P

L E

D E

P T

H

F T

) PENETRATION RESISTANCE/MOISTURE CONTENT

0 10 20 30 40 50

= BLOWS PER FOOT

37.5

42.5

47.5

52.5

Bottom of Hole

51.5

42-50/ 2.5

28-21-

32-32-

50/0.2'

LEGEND

LOG OF SOIL BORING B-2

SPT blows per foot Atterberg Limits

Field Moisture content MAFB O-11 Bridge Repair Horse Ranch Road - North of Lewistown, MTGroundwater Level

Grab/composite sample

1-3/8-inch I.D. split spoon Logged by: Jeremy Miller

2-1/2-inch I.D. split spoon Drilled by: HazTech Drilling Inc Truck-mounted BK-81 with 8-inch HSA

2-1/2-inch I.D. ring sampler GNP = Granular and Nonplastic

3-inch I.D. thin-walled sampler Note: The stratification lines represent approximate boundaries between soil types. Actual boundaries may be gradual or transitional.

August 20, 2014 14-224 No sample recovery Figure No. 3

Sheet

G R

A P

H

IC

L O

G

SOIL DESCRIPTION

SURFACE: Road Shoulder, Gravel SURFACE ELEVATION: 3,276.4 ft

D E

P T

H

G R

O U

N D

W A

T E

R

S P

T B

L O

W

C O

U N

T S

S A

M P

L E

D E

P T

H

F T

) PENETRATION RESISTANCE/MOISTURE CONTENT

0 10 20 30 40 50

= BLOWS PER FOOT

Tested By: JS KR/JS Checked By:

Silty Clayey SAND

Lean CLAY

Report No. A-10054-206

Report No. A-10057-206 inches number size size

0.0 6.1 65.6 28.3 SC-SM 26 21 5

0.0 0.0 2.0 98.0 CL

3/4" 1/2" 3/8"

100.0 98.5 96.8

#4 #10 #20 #40 #60 #80 #100 #200

93.9 92.2 91.1 90.2 83.8 67.4 52.1 28.3

100.0 100.0 100.0 100.0

99.9 99.8 99.8 98.0

0.1647

0.0857

Location: B-1 Depth: 10.0 - 11.5 ft Sample Number: A-10054

Location: B-1 Depth: 20.0 - 21.8 ft Sample Number: A-10057

Malmstom AFB

MAFB O-11 Bridge Repair

Horse Ranch Road

14-224 4

PL PI+3" % GRAVEL % SAND % SILT % CLAY USCS LL

SIEVE PERCENT FINER SIEVE PERCENT FINER Material Description

GRAIN SIZE REMARKS:

D60

D30

D10

COEFFICIENTS

Cc

Cu

Client:

Project:

Project No.: Figure

P E

R C

E N

T F

IN

E

R

GRAIN SIZE - mm.

0.00010.0010.010.1110100 i n i n i n

½ i n i n

¾ i n

½ i n

/8 i n

Particle Size Distribution Report

CRN B

Tested By: JS Checked By:

Sandy Lean CLAY

Clayey GRAVEL with Sand

Report No. A-10067-206

Report No. A-10071-206 inches number size size

0.0 13.1 34.6 52.3 CL 32 16 16

0.0 50.1 32.2 17.7 GC

1.5" 1"

3/4" 1/2" 3/8"

100.0 94.6 94.6 89.0 88.3

100.0 78.4 73.8 66.6 61.1

#4 #10 #20 #40 #60 #80 #100 #200

86.9 85.6 84.9 84.3 81.8 75.6 69.5 52.3

49.9 41.4 36.3 33.3 30.5 27.5 25.1 17.7

0.1068 8.9772

0.2337

Location: B-2 Depth: 7.5 - 9.0 ft Sample Number: A-10067

Location: B-2 Depth: 15.0 - 16.5 ft Sample Number: A-10071

Malmstom AFB

MAFB O-11 Bridge Repair

Horse Ranch Road

14-224 5

PL PI+3" % GRAVEL % SAND % SILT % CLAY USCS LL

SIEVE PERCENT FINER SIEVE PERCENT FINER Material Description

GRAIN SIZE REMARKS:

D60

D30

D10

COEFFICIENTS

Cc

Cu

Client:

Project:

Project No.: Figure

P E

R C

E N

T F

IN

E

R

GRAIN SIZE - mm.

0.00010.0010.010.1110100 i n i n i n

½ i n i n

¾ i n

½ i n

/8 i n

Particle Size Distribution Report

Tested By: MS JS MS MS Checked By:

Silty Clayey SAND 26 21 5 90.2 28.3 SC-SM

Lean CLAY with Sand 32 18 14 CL

Sandy Lean CLAY 32 16 16 84.3 52.3 CL

Fat CLAY (Weathered SHALE) 62 18 44 CH

14-224 Malmstom AFB

MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS

Project No. Client: Remarks:

Project:

Figure

Location: B-1 Depth: 10.0 - 11.5 ft Sample Number: A-10054

Location: B-1 Depth: 16.0 - 16.5 ft Sample Number: A-10056

Location: B-2 Depth: 7.5 - 9.0 ft Sample Number: A-10067

Location: B-2 Depth: 25.0 - 26.5 ft Sample Number: A-10075

P L A

S T

IC

IT

Y I N

D E

X

LIQUID LIMIT

0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

C L o r O L

C H o r O H

ML or OL MH or OH

Dashed line indicates the approximate upper limit boundary for natural soils

LIQUID AND PLASTIC LIMITS TEST REPORT

Report No. A-10054-207

Report No. A-10056-207

Report No. A-10067-207

Report No. A-10075-207

MAFB O-11 Bridge Repair

Horse Ranch Road

Tested By: JM Checked By:

UNCONFINED COMPRESSION TEST

Project No.: 14-224

Date Sampled:

Remarks:

Report No. A-10057-215

Atterberg Limits from sample directly above tube

Figure 7

Client: Malmstom AFB

Project: MAFB O-11 Bridge Repair

Horse Ranch Road

Location: B-1

Sample Number: A-10057 Depth: 20.0 - 21.8 ft

Description: Lean CLAY

LL = 32 PI = 14PL = 18 Assumed GS= 2.70 Type: Shelby Tube

Sample No.

Unconfined strength, psf

Undrained shear strength, psf

Failure strain, %

Strain rate, in./min.

Water content, %

Wet density, pcf

Dry density, pcf

Saturation, %

Void ratio

Specimen diameter, in.

Specimen height, in.

Height/diameter ratio

2.9

0.03

15.0

136.0

118.3

95.0

0.4253

2.85

5.62

1.97

C o m p re s s iv e S tr e s s p s f

Axial Strain, %

0 1.5 3 4.5 6

Client: Report Number:

Address: Report Date:

Project:

Project Number:

Attn: Test Method: ASTM D-2950, D-3017

Technician:

Test Date:

Sample Interval:

Sample # Location

Diameter

(in.)

Height

(in.) Volume (ft³) Container #

Container

Weight

Wet Soil &

Container

(g)

Dry Soil &

Container

(g) % Moisture

Wet Density, lbs/ ft³

Dry Density,lbs/ ft³

A-10068 B-2 (10.0 - 12.0 ft) 2.830 5.600 0.020 T-23 32.5 1089.4 905.9 21.0 114.4 94.5

Deviations From Test Methods: Figure: 8

Remarks:

Ms. Jennifer George

Peter Klevberg, P.E.

Laboratory Manager

Malmstrom Air Force Base

Base Contracting

7015 Goddard Drive

Malmstrom AFB, MT 59402

A-10068-213

JM

14-224-001

O-11 Bridge

8/28/2014

B-2 (10.0 - 12.0 ft)

Report of Soil Unit Weight (SOP- 213) Thomas, Dean, & Hoskins

1800 River Drive North

Great Falls, Montana 59401

8/22/2014

CRN

CRN B

CRN

Typewriter

FOR

CONSTANT VOLUME SWELL TEST REPORT

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00

S w e ll

P re ss u re p sf

Time (min)

Sat. Moist

Project No. 14-224-001 Malmstrom Air Force Base Remarks:

Project: O-11 Bridge Report No. A-10057-216

North of Lewistown, Montana

Location: B-1 Sample Depth (ft): 20.0 - 21.8

Technician: JM Reviewed By:

Client:

Figure

AASHTO

USCS

CL

MATERIAL DESCRIPTION

Lean CLAY

Natural Dry Density

(pcf) LL PI Swell eo

Sp.

Gr.

Overburden

(psf)

Pc

(psf) Cc

N/A N/A

Cs Swell Pressure

(psf)

~ 70 N/A 0.59590.7 20.0 105.4 32 14 2.7 2640 N/A