GR_04-16_MT_Sweetgrass_210(1)_Main_Boulder_River_Road.pdf

Geotechnical Report No. 04-16

Main Boulder Final Geotechnical Report

MT SWEETGRASS 210(1)

Sweet Grass County, Montana

July 29, 2016

This page left intentionally blank.

GR 04-16 Page 3

Table of Contents

1 INTRODUCTION

1.1 Previous Geotechnical Work

2 PROJECT DESCRIPTION

2.1 Project Location

3 GEOLOGY

3.1 Topography

3.2 Regional Geology

3.2.1 Definition of Geologic Map Units (Berg et. al.)

3.3 Geo-hazards

3.3.1 Site Seismicity

3.3.1.a Two Mile Bridge 3.3.1.b Beaver Pond Retaining Wall 3.3.1.c Miller Creek Bridge

3.4 Climate Data

4 SITE CONDITIONS

4.1 Two Mile Bridge

4.2 Beaver Pond

4.3 Chippy Hill

4.4 Miller Creek Bridge

5 SUBSURFACE CONDITIONS

5.1 Two Mile Bridge

5.2 Beaver Pond

5.3 Chippy Hill

5.4 Miller Creek Bridge

5.5 Subgrade Borings

5.6 Miller Pit

5.7 Summary of Test Results

6 ANALYSIS

6.1 Two Mile and Miller Creek Bridges

6.2 Beaver Pond Retaining Wall

6.3 Chippy Hill Cut

7 DESIGN RECOMMENDATIONS

7.1 Bridge Foundations

7.1.1 Two Mile Bridge

7.1.2 Miller Creek Bridge

7.1.3 Pile Setup

7.1.4 Dynamic Pile Load Tests

7.1.5 Settlement

7.2 Wing Walls

7.3 Beaver Pond Retaining Wall

7.4 Chippy Hill Cut

7.5 Soil Cuts and Embankments

8 CONSTRUCTION CONSIDERATIONS

9 LIMITATIONS

10 REFERENCES

GR 04-16 Page 4

List of Figures

Figure 2.1-1. Project Location Map Figure 3.1-1. Topographical Map of Project Area Figure 3.2-1. Photograph of cobble and boulder sized material in river channel Figure 3.2-2. Geologic Map of the Project Area (Stickney et. al.)

Figure 3.3.1.a-1. Response Spectrum for Two Mile Bridge Figure 3.3.1.c-1. Response Spectrum for Miller Creek Bridge

List of Tables Table 3.4-1. Monthly Climate Summary for Big Timber, MT (240780) Table 5.1-1. Two Mile Bridge (N1)60 Ranges and Number of SPT Refusals Table 5.4-1. Miller Creek Bridge (N1)60 Ranges and Number of SPT Refusals Table 5.7-1. Summary of Direct Shear and Compressive Strength Testing Table 5.7-2. Summary of Classification Testing Table 6.1-1. Scour Elevations Table 7.1.1-1. Two Mile Bridge Loads per Abutment Table 7.1.2-1. Miller Creek Bridge Loads per Abutment Table 7.2-1 Design Parameters for Bridge Wing Walls Table 7.3-1 Design Parameters for Retaining Wall

Appendices APPENDIX A – Unified Soil Classification System Soil Descriptive Terminology Rock Descriptive Terms Boring Location Map Geotechnical Test Boring Logs

APPENDIX B – Rock Core Photography Test Pit Photography

APPENDIX C – Laboratory Test Reports

APPENDIX D – Hydraulics Recommendation

APPENDIX E – Ultimate Capacity vs Foundation Depth Two Mile and Miller Creek Bridge

GR 04-16 Page 5

1 INTRODUCTION

This report provides geotechnical investigation results, analysis, foundation recommendations, wall recommendations, and earthwork recommendations for the proposed Main Boulder River Road Improvements project. The project stationing referenced in this report is from the 70% design package dated April 5, 2016.

Subsurface investigation borings were completed by Haz-Tech Drilling Incorporated on behalf of Western Federal Lands Highway Division (WFLHD). All other geotechnical engineering and analysis in this report was performed by WFLHD.

1.1 Previous Geotechnical Work

As of the printing of this report, there have been no known previous geotechnical investigations or written reports outside of what was developed for this project by WFLHD. Four project related memorandums were written during the development of this project, they are:

• Geotechnical Memorandum GM34-15 MT Sweet Grass 210(1) Main Boulder Retaining Wall Selection and Slope Recommendation Memorandum

• Geotechnical Memorandum GM02-16 MT Sweet Grass 210(1) Main Boulder

Preliminary Bridge Foundation Memorandum

• Geotechnical Memorandum GM09-16 MT Sweet Grass 210(1) Main Boulder Beaver Pond Ecology Block Retaining Wall

• Geotechnical Memorandum GM12-16 MT Sweet Grass 210(1) Main Boulder

Final Bridge Foundation Memorandum

Please note that Geotechnical Memorandums GM34-15 and GM09-16 were developed prior to the decision to have the proposed retaining wall designed by the contractor.

GR 04-16 Page 6

2 PROJECT DESCRIPTION

The Main Boulder River Road Improvements project will rehabilitate approximately 16.7 miles of the Main Boulder River Road. This rehabilitation includes replacing the Two Mile Bridge, Miller Creek Bridge, vertical and horizontal alignment improvements, and updating existing culverts to aquatic organism passage (AOP) culverts. The alignment improvements include cuts in soil and rock, fills, and retaining walls.

The existing Two Mile Bridge is a single lane three span bridge with approximate span lengths of 10, 85, and 10-feet. The proposed replacement bridge is a two lane single span structure with an approximate span of 120-feet. The new structure will be built on a new alignment downstream with a slight skew to improve the approach geometry.

The existing Miller Creek Bridge is a single lane, single span bridge with an approximate span of 26-feet. The proposed replacement bridge is a two lane single span structure with an approximate span of 69-feet. The new structure will be built on a new alignment just downstream from the current structure.

The major changes in the vertical and horizontal alignments are set to take place in the Beaver Pond and Chippy Hill areas, approximate station limits of 1712+50 to 1729+50 and 1866+00 to 1870+00 prospectively. The proposed total road width (single lane road with turnouts) through the Beaver Pond section is increasing 1 to 3-feet to 14-feet wide, while the vertical adjustments range from 3 to 11-feet of grade raise. The vertical grade at Chippy Hill will be lowered up to 3-feet at the top of the grade and raised up to 10-feet near the bottom. The roadway width will be widened approximately 2-feet to 14-feet.

Three existing culverts will be upgraded to AOP culverts at Graham Creek, Blakely Creek, and East Chippy Creek and approximate stations 1703+26, 1792+93, and 1882+39 prospectively. The existing Graham Creek culvert is a 42-inch diameter, 32-foot long corrugated metal pipe culvert. The proposed AOP design will incorporate a 12-foot span, 8-foot rise, 96-foot long concrete box culvert. The existing Blakely Creek culvert is a 24-inch diameter, 26-foot long corrugated metal pipe culvert. The proposed AOP design will incorporate a 9.33-foot span, 6.25-foot rise, 62-foot long concrete box culvert. The existing East Chippy Creek culvert is a 48-inch diameter, 26-foot long corrugated metal pipe culvert. The proposed AOP design will incorporate a 10.67-foot span, 6.92-foot rise, 62-foot long structural plate pipe arch.

2.1 Project Location

This project is located in both Park and Sweet Grass County in Montana; however, the majority of the project lies within Sweet Grass County. The entire project limits are within the boundary of the Gallatin National Forest and is approximately 30 miles southwest of Big Timber, Montana, see figure 2.1-1 for a location map.

The Main Boulder River Road is primarily used for remote residences and recreation.

Summer months produce the most users typically accessing summer camps, cabins, and

GR 04-16 Page 7 camping. Heavy use continues in the fall with deer and elk hunters accessing the various portions of the Gallatin National Forest.

Figure 2.1-1. Project Location Map

I-90

Hwy 298

GR 04-16 Page 8

3 GEOLOGY

The following sections summarize the topography, regional geology, geo-hazards, and climate data for the project site.

3.1 Topography

The Boulder River begins in the Gallatin National Forest in the Absaroka Range and flows north to Big Timber, Montana. The proposed project follows the Boulder River within the Boulder River valley. The valley is narrow and has multiple draws with named and unnamed creeks flowing into the river. The valley walls are typical of mountainous terrain and are very steep. Figure 3.1-1 shows a topographical map of the project area.

Figure 3.1-1. Topographical Map of Project Area

GR 04-16 Page 9

3.2 Regional Geology

The project area is composed mostly of a Holocene aged alluvium overlying schist and/or hornfels bedrock (Stickney et. al. 2015). Areas at higher elevation in the Boulder River canyon and along tributary streams are mapped as glacial deposits. The valley where the project is located has an abundance of cobble and boulder sized alluvium in the river channel and surrounding areas (Figure 3.2-1.) with scattered glacial ground moraine in the flats located adjacent to the project site. These units are described in Section 3.2.1.

Figure 3.2-1. Photograph of cobble and boulder sized material in river channel.

GR 04-16 Page 10

Figure 3.2-2. Geologic Map of the Project Area (Stickney et. al.)

3.2.1 Definition of Geologic Map Units (Berg et. al.).

Qal Alluvium of modern channels and flood plains (Holocene) – Younger alluvium, generally confined to the present flood plain developed along active rivers and streams

Qg Glacial deposits, undivided (Holocene and Pleistocene) – Dominantly unsorted and unstratified sediment of Pleistocene glacial moraines and other associated glacial and glaciofluvial deposits. Also includes Holocene glacial deposits and

GR 04-16 Page 11 rock glacier deposits. May include subordinate alluvium, colluvium, talus, landslide deposits, and boulder fields.

Asw1 Peridotite zone, Stillwater Complex* (Archean).

Asw2 Bronzitite zone, Stillwater Complex* (Archean).

Asw3 Norite and lower gabbro zones, Stillwater Complex* (Archean).

Asw4 Lower anorthosite zone, Stillwater Complex* (Archean).

Ash Schist and hornfels (Archean) – Metasedimentary rocks consisting predominately of schist and hornfels with minor quartzite, amphibolite, and iron formation; contact metamorphosed to hornblende hornfels and pyroxene hornfels facies at and near the base of the Stillwater Igneous Complex.

*The Stillwater (igneous) complex is a large layered mafic intrusion located in southern Montana in Stillwater, Sweet Grass, and Park Counties.

3.3 Geo-hazards

There are 2 mapped faults near the project area that are both part of the Emigrant fault, the unnamed (north) section number 642a and the unnamed (south) section number 642b.

Fault number 642a had its last offset during the last 130,000 years and is approximately 15 miles from the project. Fault number 642b’s last offset was during the last 15,000 years and is approximately 20 miles from the project site (Stickney et al. 2015). These faults are the primary contributors to the seismic hazard at the site.

3.3.1 Site Seismicity

The site specific seismicity was investigated for three major structures within the project:

The Two Mile Bridge, Beaver Pond Retaining Wall, and The Miller Creek Bridge.

3.3.1.a Two Mile Bridge This bridge is located in Seismic Zone 2, Soil Site Class D, with scaled peak ground acceleration, As of 0.124g for a return period of 975 years (7% probability of exceedance in 75 years). Since the site falls within Seismic Zone 2 and layers of very loose saturated sands were not encountered, a liquefaction assessment is not required per AASHTO Bridge Design Specifications (2014) Section 10.5.4.2.

GR 04-16 Page 12

Figure 3.3.1.a-1. Response Spectrum for Two Mile Bridge.

3.3.1.b Beaver Pond Retaining Wall The seismicity of the project area was considered for the retaining wall design, however the scaled peak ground acceleration, As, for 7% probability of exceedance in 75 years is about 0.125g. Additional seismic design for retaining walls is not required by AASHTO (2014) where As is less than 0.4g. Therefore, seismic analysis is not required considering the low wall height, very low criticality of the structure, and the scaled peak ground acceleration being well below 0.4g.

3.3.1.c Miller Creek Bridge This bridge is located in Seismic Zone 2, Soil Site Class D, with scaled peak ground acceleration, As of 0.130g for 7% probability of exceedance in 75 years. Since the site falls within Seismic Zone 2 and layers of very loose saturated sands were not encountered, a liquefaction assessment is not required per AASHTO Bridge Design Specifications Section 10.5.4.2. Figures 2 and 3 below show the response spectra for the Two Mile Bridge and Miller Creek Bridge respectively.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

El as tic S ei sm ic C oe ffi ci en t, C sm

Period, T (sec)

5% DAMPED DESIGN RESPONSE SPECTRUM

GR 04-16 Page 13

Figure 3.3.1.c-1. Response Spectrum for Miller Creek Bridge.

3.4 Climate Data

The project is located in South-Central Montana with the closest weather station near Big Timber, Montana, approximately 30 miles north-northeast. Big Timber experiences nearly 15 inches of rain and 46 inches of snowfall per year on average. There are an average 201 sunny days and 70 precipitation days per year. The 30 year weather average shows there is likely to be snow on the ground from November to March.

Table 3.4-1. Monthly Climate Summary for Big Timber, MT (240780)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average Max.

Temperature (F) 37.1 41 48 58.8 68.3 77 87.1 85.5 74.2 62.1 47 39 60.4

Average Min.

Temperature (F) 16.6 18.9 23.4 31.8 39.8 47.4 53 51.1 42.4 34.7 25.8 19.4 33.7

Average Total Precipitation (in.) 0.61 0.49 0.96 1.64 2.69 2.5 1.27 1.13 1.42 1.3 0.78 0.56 15.36

Average Total Snow Fall (in.) 8.6 6.4 8.4 4.5 0.9 0 0 0 0.4 3.5 6.5 6.8 46

Average Snow Depth (in.) 2 1 1 0 0 0 0 0 0 0 1 1 0

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

El as tic S ei sm ic C oe ffi ci en t, C sm

Period, T (sec)

5% DAMPED DESIGN RESPONSE SPECTRUM

GR 04-16 Page 14

4 SITE CONDITIONS

The following subsections describe the physical settings for each of the major features analyzed as part of this report.

4.1 Two Mile Bridge

The Boulder River at this location is approximately 70 feet wide at an average depth of 6 feet. The bottom of the river is approximately 20 to 25 feet below the surface of the existing bridge deck. The slopes of the bank near the river and river bottom contain cobble and boulder sized material with a very large 8 foot diameter (approximate) boulder near where the East abutment will be located.

4.2 Beaver Pond

The Beaver Pond area is at the bottom of a tall talus slope consisting of angular to very angular boulders 18 inches to 4 feet (and larger) in diameter. It appears the Main Boulder River Road is built on the talus material in this section as it can be seen in the river channel and looks to be side cast on the fore slope of the roadway. The roadway surface consists of silty sandy gravel which is interpreted to have been hauled from nearby roadway cuts to provide a travel surface over the talus boulders.

4.3 Chippy Hill

The Chippy Hill area is within an existing rock and soil cut. The existing cut slope reveals highly fractured bedrock overlain with silty sand that likely contains cobble and boulder sized material.

4.4 Miller Creek Bridge

The Miller Creek Bridge spans Miller Creek and is dry most of the year. The creek contains cobble and boulder sized material up to 4 feet in diameter. The creek, when dry, is approximately 60 feet wide and 12 feet from the existing bridge deck to the bottom of the creek.

GR 04-16 Page 15

5 SUBSURFACE CONDITIONS

A subsurface investigation composed of geotechnical borings and test pits were completed July 19 to 29, 2015 and August 11 to 22, 2015 by Haz-Tech Inc. of Meridian, Idaho and the Sweet Water County Public Works Department. All the borings and test pits were logged in the field by a geotechnical engineer from WFLHD.

Borings were completed with a truck mounted BK 81 drill rig in all locations accessible by a wheeled vehicle during the July mobilization while a portable Christianson CS 1000 drill rig was used for difficult access locations completed in August. The portable drill rig was placed at the drilling location by use of a crane.

Test pits were dug with a John Deere 410G backhoe by a member of the Sweet Water County public works staff to investigate some of the proposed cut slopes and the potential for use of the Gallatin National Forest’s material pit (Miller Pit).

All of the borings were advanced using an 8-inch outside diameter hollow stem auger until refusal. Based on the subsurface conditions, borings were then advanced with either casing advancer or HQ sized triple-tube core barrel to the required depth.

Standard Penetration Tests (SPTs) were completed at 2.5-foot to 5-foot intervals in overburden material. The Standard Penetration Test (SPT) consists of using a 140 pound hammer with a 30 inch drop to drive a two inch outside diameter split-barrel sampler 18 inches below the bottom of the bore hole and recording the number of blow for each six-inch increment of penetration. The second and third numbers are added together to determine the blows per foot (bpf), which is known as the N-value.

All of the geotechnical boring logs completed for this project are attached to this report in Appendix A. The borings have various naming conventions. Borings labeled MB15-XX are typical geotechnical borings; borings labeled MBSG15-XX are shallow borings used to investigate existing subgrade; and borings labeled MBTP15-XX are test pits.

5.1 Two Mile Bridge

Borings MB15-01 and MB15-02 were located on the West abutment of the proposed bridge and completed with a BK-81 truck mounted drill rig with an automatic trip hammer while borings MB15-03 and MB15-04 were located on the East abutment and completed with a CS-1000 portable drill rig with a rope and cathead hammer. These borings were drilled to depths of 81.5, 60.5, 95.0, and 60.6 feet respectively. The subsurface materials were generally cobbles and boulders up to 20 inches in diameter in a silty gravel with sand or silty sand with gravel soil matrix. Approximately 72 to 73.5 feet into boring MB15-01, an 8 foot clean sand layer was encountered, the boring was terminated in this layer.

(N1)60 values are listed in below in Table 5.1-1. (N1)60 values are determined by applying correction factors for overburden pressure and hammer efficiency to the raw

GR 04-16 Page 16 blow counts (N-values). The boring logs showed a large percentage of cobbles and boulders, therefore the N-values are likely exaggerated. Table 5.1-1 lists the range of (N1)60 values for each boring, the total number of SPT samples taken, and the number of samples that reached refusal. Refusal is defined as reaching 50 blows during the second or third 6 inch interval of the SPT sample.

Table 5.1-1. Two Mile Bridge (N1)60 Ranges and Number of SPT Refusals

Boring Number

Range of (N1)60 Values

# of SPT Samples

# of SPT Refusals

MB15-01 37 - 77 14 2

MB15-02 23 - 89 11 1

MB15-03 18 - 83 12 2

MB15-04 63 - 103 10 7

5.2 Beaver Pond

Three geotechnical borings were planned for the Beaver Pond section (approximate station 1711+00 to 1730+00) of the project; however, two of the borings were eliminated because of the underground phone line location.

Boring MB15-07 (approximate station 1724+50) was drilled to a depth of 15 feet below the roadway surface and 4 SPT samples were taken at depths of 7, 10, 12.5, and 15 feet.

Automatic trip hammer blow counts (N-Value) ranged from 9 blows per foot to refusal (50 blows for 2 inches). Ground water was not encountered at this location; yet the County informed WFLHD that this section of the road is routinely overtopped by the pond and or river every spring between approximate stations 1724+00 and 1726+00.

Based on the driller’s observations of boring MB15-07, a boulder was encountered from 2 feet to 7 feet, causing the first sample to be taken at 7 feet.

5.3 Chippy Hill

Three geotechnical borings, one subgrade boring, and two test pits were planned for the Chippy Hill grade lowering/cut section, however, the underground phone line, roadway width, and the geometry of the existing cut, caused elimination of 2 of the geotechnical borings and 1 test pit. Because of the boring omissions in this section, the subgrade boring was changed to a combination subgrade and geotechnical boring, MBSG15-07.

Boring MB15-11 (approximate station 1868+50) was drilled to a depth of 40 feet below the ground surface at the top of the existing cut, 1 SPT sample was taken at a depth of 5.5 feet below the existing ground with a manual cathead hammer (N-Value) blow count of 19 blows per foot. Rock core samples were taken from 7 to 40 feet. The ground water table was not encountered at this location.

GR 04-16 Page 17

Boring MBSG15-07 (approximate station 1868+50) was drilled to a depth of 15 feet below the roadway surface, a bulk soil sample was collected from 0 to 4 feet below the roadway surface and SPT samples were taken at depths of 5, 8, 12,5 and 15 feet.

Automatic trip hammer blow counts (N-Value) ranged from 26 blows per foot to refusal (50 blows for 1 inch). The ground water table was not encountered at this location.

Based on the driller’s observations of boring MBSG15-07, bedrock was encountered from 9 feet to 15 feet based on the drill’s action. The SPT samples attempted in this zone had little to no soil during recovery. The recovery obtained appeared to be rock cuttings which matched the driller’s observations of the subsurface material.

Test pit MBTP15-07 (approximate station 1868+00) was excavated in the soil on the existing cut until bedrock was encountered. The ground water table was not encountered at this location.

The WFLHD Materials Section laboratory completed index testing of the SPT samples for boring MB15-07 and boring MBSG15-07, unconfined compression tests of rock core for boring MB15-11, and direct shear test of soil from a bulk sample taken at MBTP15-

07. Test results are available in Appendix C.

5.4 Miller Creek Bridge

Boring MB15-12 was located on the northeastern abutment of the proposed bridge and MB15-13 located on the southwestern abutment. Both borings were completed with a BK-81 truck mounted drill rig with an automatic trip hammer. These borings were drilled to depths of 100.0 and 61.5 feet respectively. The subsurface materials were generally cobbles and boulders up to 60 inches in diameter in a silty gravel with sand or silty sand with gravel soil matrix.

(N1)60 values are listed in Table 5.1-1. The boring logs showed a large percentage of cobbles and boulders, therefore the N-values are likely exaggerated. Table 5.1-1 lists the range of (N1)60 values for each boring, the total number of SPT samples taken, and the number of samples that reached refusal. Refusal is defined as reaching 50 blows with less than 6 inches of penetration of the SPT sample.

Table 5.4-1. Miller Creek Bridge (N1)60 Ranges and Number of SPT Refusals

Boring Number

Range of (N1)60 Values

# of SPT Samples

# of SPT Refusals

MB15-12 37 - 87 10 3

MB15-13 37 - 77 10 2

5.5 Subgrade Borings

A total of 13 subgrade borings, spaced approximately 0.5 miles apart throughout the project, were planned for this project. However, one (MBSG15-11) had to be deleted

GR 04-16 Page 18 from the contract because of its proximity to the buried phone line. MBSG15-07 incorporated other nearby planned borings (MB15-09 and MB15-10) because of the same issue; it was drilled to a depth of 15 feet.

A distinguishable layer of processed roadway aggregate was not observed in any of the subgrade borings. The roadway aggregate appears to have been bladed off during maintenance operations or has segregated over time. All the borings resulted in very similar field classification of the subsurface material, cobbles and boulders in a silty sand matrix.

5.6 Miller Pit

Six test pits were excavated within the disturbed Miller Pit area to depths of 7 to 9 feet deep. Photographs of the test pits are contained in APPENDIX B. These pits exposed rounded to sub-rounded cobbles and boulders in a silty sand matrix. At the time of the investigation, there were material stockpiles that were crushed from the subsurface material at Miller Pit. Grab samples of this material was sent back to the WFLHD Materials Lab for preliminary testing of gravel for the project. Tests included: sieve analysis, plasticity index, sand equivalent, durability, specific gravity (fine and coarse material), LA abrasion, soundness by sodium sulfate, accelerated weathering, immersion compression, lab manufactured plasticity index, and lab manufactured sand equivalent.

These results are provided in APPENDIX C.

5.7 Summary of Test Results

Table 5.7-1 summarizes the grab sample and rock core laboratory data while Table 5.7-2 summarizes the laboratory data from all of the soil borings. All of the test reports for the project are located in APPENDIX C.

Note that based on the driller’s comments the subsurface soils consisted mostly of cobbles and boulders and therefore the samples tested from the 2” O.D. split barrel sampler are likely not representative of the in situ materials.

Table 5.7-1. Summary of Direct Shear and Compressive Strength Testing

Boring Number Depth

Unit Weight (pcf)

Compressive Strength

(psi)

Friction Angle (φ)

Cohesion (psf)

MBTP15-01 - - - 36 557

MBTP15-05 - - - 37 169

MB15-11 10.5 172 15,900 - -

MB15-11 13 172 16,580 - -

GR 04-16 Page 19

Table 5.7-2. Summary of Classification Testing

Boring Number

Sample Number

Depth (feet)

Soil Classification

(DL145)

Apparent Specific Gravity (T100)

Moisture Content (T265)

Atterberg Limits 1 (T89)

From To AASHTO USCS Liquid Limit

Plasticity Index

MB15-01 S1 - S4 0.0 - 16.5 A-1-a(0) GM 2.777 2.3 NP NP MB15-01 S5 20.0 - 21.5 A-1-b(0) GM 2.759 9.3 NP NP MB15-01 S6 - S7 25.0 - 31.5 A-1-a(0) GM 2.826 9.0 NP NP MB15-01 S10 - S12 24.0 - 56.5 A-1-b(0) GM 2.792 9.1 NP NP MB15-02 S1 - S6 0.0 - 16.0 A-1-a(0) GM 2.755 2.5 NP NP MB15-02 S9 - S11 39.0 - 50.5 A-1-b(0) GM 2.793 8.8 NP NP MB15-03 S1 - S3 0.0 - 16.5 A-1-b(0) GM 2.815 8.3 NP NP MB15-03 S5 - S6 25.0 - 31.5 A-1-b(0) SM 2.823 10.5 NP NP MB15-03 S8 - S9 50.0 - 61.5 A-1-a(0) GM 2.807 8.7 NP NP MB15-04 S7 - S8 35.0 - 41.5 A-1-a(0) SM 2.827 9.6 NP NP

MBSG15-02 G1 0.0 - 4.0 A-1-a(0) GW-GM - - 21 3 MBSG15-07 S1 - S2 5.0 - 9.0 A-1-b(0) SM 2.768 6.3 NP NP

MB15-07 S2 10.0 - 11.5 A-1-b(0) SM 2.773 14.6 NP NP

MB15-07 S3 12.5 - 14.0 A-2-4(0) SM 2.767 21.3 NP NP

MB15-07 S4 15.0 - 16.5 A-2-4(0) SM 2.764 22.5 NP NP

MBSG15-08 S1 5.0 - 6.5 A-2-4(0) SM 2.752 8.6 NP NP

MBSG15-08 S2 7.5 - 9.0 A-1-a(0) GM 2.759 3.6 NP NP

MB15-12 S1 - S3 5.0 - 16.5 A-1-b(0) GM 2.788 5.2 NP NP

MB15-12 S5 25.0 - 26.5 - - 2.761 10.0 - -

MB15-12 S6 - S7 30.0 - 41.5 - - 2.800 7.2 - -

MB15-13 S2 - S4 5.0 - 16.5 A-1-b(0) GM 2.771 4.8 NP NP

MB15-13 S8 - S9 40.0 - 41.5 - - - 9.4 - -

MB15-14 S2 - S3 5.0 - 10.5 A-1-a(0) GM 2.854 5.2 NP NP MB15-14 S5 - S6 12.5 - 16.5 A-1-a(0) GW-GM 2.915 3.2 NP NP

NOTES:

1 NP = nonplastic.

GR 04-16 Page 20

6 ANALYSIS

All calculations used in preparation of this report were completed following the AASHTO LRFD Bridge Design Specifications, Seventh Edition (2014). The design software All Pile 7 by Civil Tech was used with the AASHTO LRFD Bridge Design Specifications for capacity analysis of the pile foundations for both bridges. All Pile 7 incorporates NAVFAC procedures when determining nominal resistance. AASHTO LRFD resistance factors were applied to the nominal resistance in order to determine the factored axial geotechnical resistance.

The software program Dips 6.0 by Rocscience was used to aid in the kinematic analysis of the rock cut at Chippy Hill.

6.1 Two Mile and Miller Creek Bridges

Various foundation types were considered during the development of this project for the two bridges including cast in place shallow foundation elements and GRS-IBS abutments. However, the scour depths were so great that excavations for these foundation types are not practical. The scour depth from the existing surface ranged from 19 to 30 feet deep. The 100 and 500 year scour elevations are below in Table 6.1-1 and were provided by Jim Neighorn, WFLHD Hydraulics Engineer, in September 2015.

Table 6.1-1. Scour Elevations

Structure 100 yr Scour Elevation (ft)

500 yr Scour Elevation Check

Flood (ft)

Two Mile Bridge 5224.1 5222.5 Miller Creek Bridge 5620.9 5619.6

With the abundance of the boulder and cobble sized material encountered in the boring, a pre-bored driven pile system is the most constructible and cost effective foundation alternative. H-pile was chosen as it should produce easier driving conditions thorough the cobbles and boulders over other pile configurations.

6.2 Beaver Pond Retaining Wall

Three wall options were analyzed using the 30% design plan set and cross sections and assuming a grade raise of 4 feet at the location of boring MB15-07 (approximate station 1724+50). The proposed height of the grade raise was provided by WFLHD Hydraulics Engineer Jim Neighorn on September 14, 2015 via email. The email is located in Appendix D. The three wall types analyzed were a gabion basket gravity wall, a MSE wall, and a precast concrete block gravity wall.

Project development staff from WFLHD found that a precast concrete block gravity wall was the most economical, but the quantity of blocks needed would not likely be readily

GR 04-16 Page 21 available. A contractor designed MSE wall utilizing geogrid reinforcement and a welded wire face has been incorporated into the plans. Additional survey beyond the fore slope of the road is likely needed.

6.3 Chippy Hill Cut

Stability of the proposed rock and soil cuts were assessed with both visual observations and kinematic analysis utilizing Rocscience Dips 6.0. The existing cuts range from 1V:1H to approximately 1.6V:1H. Where rock is easily seen, it does not appear to be stable at the existing 1.6V:1H cuts, the kinematic analysis also showed this was the case.

Soil cuts in this area appear unstable ranging from 1V:1.25H to 1V:1H and have raveled, depositing material on the roadway.

Rock core photography of boring MB15-11 at this location can be found in Appendix B.

GR 04-16 Page 22

7 DESIGN RECOMMENDATIONS

The following subsections describe the design recommendations made by the Geotechnical Section to the Project team.

7.1 Bridge Foundations

Both bridges were designed to utilize the same foundation type and material, HP14x102 piles. Piles should be pre-bored prior to driving to at least the scour elevation. The boring logs show that driving conditions will be difficult, encountering cobbles and boulders from 18 inches to 4 feet or larger, all piles should be fitted with a driving shoe before driving.

Dynamic pile load tests and signal matching are recommended to verify the pile capacity during construction. A minimum of one test pile is recommended at each abutment. The dynamic testing should be performed on the first pile driven at each abutment in order to establish the driving criteria for the subsequent piles at that abutment. The pile side resistance above the 100-year scour elevation needs to be subtracted from the total nominal pile geotechnical resistance determined during pile driving.

The capacities developed for this design are only valid if dynamic load testing is completed because LRFD resistance factors were selected for piles with capacity verified by dynamic testing with signal matching. Without the dynamic testing, the proposed design would likely lengthen or add addition piles to each abutment. See Appendix E for axial capacities of both bridges.

7.1.1 Two Mile Bridge

The minimum required foundation for the Two Mile Bridge, per abutment, consists of 1 row of 8 HP14x102 piles on 49.7 inch center to center spacing. Piles at this bridge should be pre-bored to elevation 5224.10 feet and driven to a minimum tip elevation of

5150.0 (abutment 1) and 5149.25 (abutment 2) feet. The side resistance above the scour elevation shall be determined during the dynamic load test with signal matching. Each pile should be driven to a nominal (ultimate) capacity of 204 kips plus the side resistance developed above the scour elevation. The estimated pile length is 91 feet per pile.

GR 04-16 Page 23

Table 7.1.1-1. Two Mile Bridge Loads per Abutment

Two Mile Bridge Service I Limit State Strength I Limit State

Load Type Unfactored Load (kips)

Load Factor

Factored Load (kips)

Load Factor

Factored Load (kips)

Dead load of superstructure and substructure (DC) 511 1.0 511 1.25 639

Dead load of future wearing surface (DW) 43 1.0 43 1.5 65

Vehicular live load (LL) 210 1.0 210 1.75 368 Total 764 - 764 - 1071

7.1.2 Miller Creek Bridge

The minimum required foundation for the Miller Creek Bridge, per abutment, consists of 1 row of 5 HP14x102 piles on 87 inch center to center spacing. Piles at this bridge should be pre-bored to elevation 5620.9 feet and driven to a minimum tip elevation of

5566.0 (abutment 1) and 5562.5 (abutment 2) feet. The side resistance above the scour elevation shall be determined during the dynamic load test with signal matching. Each pile should be driven to a nominal (ultimate) capacity of 261 kips plus the side resistance developed above the scour elevation. The estimated pile length is 70 feet per pile.

Table 7.1.2-1. Miller Creek Bridge Loads per Abutment

Miller Creek Bridge Service I Limit State Strength I Limit State

Load Type Unfactored

Load (kips)

Load Factor

Factored Load (kips)

Load Factor

Factored Load (kips)

Dead load of superstructure and substructure (DC) 417 1.0 417 1.25 521

Dead load of future wearing surface (DW) 28 1.0 28 1.5 42

Vehicular live load (LL) 169 1.0 169 1.75 296

Total 614 - 614 - 859

7.1.3 Pile Setup

Driving the pile will increase pore water pressure around the pile resulting in a reduction in the effective stress and the shear strength. This will reduce the nominal resistance of the pile during driving. As the excess pore pressures dissipate the nominal resistance will increase or “set-up”. AASHTO (2014) recommends allowing 2 days for silty sands for pile set-up. If the required nominal capacity for the piles is not attained by the minimum pile tip elevation, the piles should be allowed to set-up for a minimum period of 24 hours before performing a restrike.

GR 04-16 Page 24

7.1.4 Dynamic Pile Load Tests

Dynamic pile load tests and signal matching are recommended to verify the pile capacity during construction. One test pile is recommended at each abutment. The dynamic testing should be performed on the first pile driven at each abutment in order to establish the driving criteria for that abutment. The test should be performed during the initial pile driving and on a restrike test on the same pile. The total nominal resistance determined from the dynamic load tests minus the side resistance above the 100-year scour elevation must be greater than or equal to the specified nominal axial geotechnical capacity in the plans. For a pile reaching the ultimate capacity during initial driving, the restrike should occur a minimum of 24 hours following initial driving. For a pile not reaching ultimate capacity by the minimum pile tip elevation, the restrike should occur a minimum of 24 hours following the initial driving. No other piling should be driven in the same abutment during the set-up time period.

7.1.5 Settlement

The settlement at the bottom of the pile cap elevation due to service limit state load for both bridges is anticipated to be less than ½ inch.

7.2 Wing Walls

The design parameters in Table 7.2-1 were developed for use in the design of the wing walls for both bridges. These parameters assume a vertical wall with level ground at the top of the wall.

Table 7.2-1 Design Parameters for Bridge Wing Walls

Parameter Value* Moist Unit Weight, γm 130 pcf

Angle of Internal Friction, φf 34 degrees Active Earth Pressure Coeff., ka 0.26 Passive Earth Pressure Coeff., kp 6.07 At-Rest Earth Pressure Coeff., ko 0.44

Coeff. of Friction CIP Concrete, Tan δ 0.45

Coeff. of Friction Precast Concrete, Tan δ 0.21

*Design values determined in accordance with Chapter 3 of AASHTO LRFD (2014) based on a drained condition behind the wall.

GR 04-16 Page 25

7.3 Beaver Pond Retaining Wall

A contractor designed wire-faced mechanically stabilized earth wall with geogrid reinforcement is proposed at this location. The retaining wall should be faced with gabion rock (FP-14 Section 705.01) and backfilled with select granular backfill (FP-14 Section 704.08). Reinforcing elements and any separation fabric needed should be picked from Sections 714.04 and 714.03 respectively.

The nominal bearing resistance was calculated to be 6.3 ksf for the retaining wall. The wall design should incorporate a minimum 4-foot bench inf ront of the wall and be embedded a minimum of 2-feet. Design parameters for the internal stability of the wall are shown in Table 7.3-1 and should be used during the contractor’s design process.

Table 7.3-1 Design Parameters for Retaining Wall

Parameter Value*

Moist Unit Weight of Select Granular Backfill, γmSGB 130 pcf Moist Unit Weight of Retained Backfill, γmRB 130 pcf Moist Unit Weight of Foundation Soils, γmFS 130 pcf

Angle of Internal Friction of Select Granular Backfill, φfSGB 34 degrees Angle of Internal Friction of Retained Backfill, φfRB 34 degrees Angle of Internal Friction of Foundation Soils, φfFS 34 degrees

Active Earth Pressure Coeff., ka 0.26 Passive Earth Pressure Coeff., kp 6.07 At-Rest Earth Pressure Coeff., ko 0.44

7.4 Chippy Hill Cut

This section of the project should consist of compound broken back cuts. Cuts in rock should not exceed 1.33V:1H and cuts in soil should not exceed 1V:1.5H. Cuts in soil may be steepened to 1V:1H for heights up to 10 feet if seeded and covered with a rolled erosion control product conforming to 713.17 (k) immediately after the cut is made.

There appears to be a seep or spring at approximate station 1867+50, soil cuts in this area should incorporate a rock blanket from Station 1867+25 to Station 1867+75 to maintain stability.

7.5 Soil Cuts and Embankments

Cobble and boulder sized material was encountered in every boring and can be seen on the surface through the project limits. It may be necessary to employ boulder reducing techniques such as boulder busting, utilizing an excavator with a hydraulic hammer, or other means to reduce the size to 24-inches or less.

GR 04-16 Page 26

The subsurface conditions for this project should limit any permanent cuts in soil to not exceed 1V:1.5H. Any fill slopes built with native material should be clear of roots and vegetation and not built steeper than 1V:2H. It is expected that on site material from any excavations will be reused as common embankment after any clearing and grubbing, however, unsuitable soils may be encountered in the Beaver Pond area depending on the depth of excavation.

GR 04-16 Page 27

8 CONSTRUCTION CONSIDERATIONS

The following should be considered during bidding and planning for construction activities:

• Any excavations for this project will likely encounter cobbles and boulders; this will make excavation difficult.

• Cobbles and boulders are likely to be encountered during pile preboring and pile driving at both bridge locations. Fixed leads should be used in order to maintain proper alignment of the piles. A structural frame (template) may also be necessary in order to maintain pile alignment.

• Maintaining a fine grade in the Beaver Pond area for a retaining wall foundation will likely need to be completed by bringing in granular material after any excavations are made.

• Groundwater will likely be encountered in pile cap excavations. It will likely be encountered in the cuts at Chippy Hill where there is evidence of springs. It will likely be encountered in the retaining wall excavation. Dewatering may be necessary at pile cap and retaining wall excavations.

• Although there are no load restrictions on either Two Mile or Miller Creek Bridge (at the time of this report publication), the existing geometry of Two Mile Bridge may make it difficult to cross with wide and/or long loads.

• Soils encountered during the subsurface investigation were classified as OSHA Type C soils. Refer to 29 CFR 1926 Subpart P App B for OSHA sloping and benching requirements.

• It is likely that silty sands and gravels with an abundance of cobbles and boulders will be encountered in any cuts or excavations. Bedrock will likely be encountered in the Chippy Hill cut with overburden soils. The laboratory testing program showed that all soils encountered should be suitable for reuse, some aeration me be required to achieve acceptable moisture contents. Foundation soils near the Beaver pond may have high fines content and may need to go to waste.

GR 04-16 Page 28

9 LIMITATIONS

This report has been prepared to assist WFLHD, Sweet Grass County, and Gallatin National Forest with the engineering design and evaluating constructability of the Main Boulder River Road Improvement construction project. It should not be used, in part or in whole for other purposes without contacting the WFLHD Geotechnical Section for a review of the applicability of such reuse. These data are not to be used for other purposes.

The conclusions and recommendations contained in this report are based on WFLHD’s Geotechnical Section’s understanding of the project at the time that the report was written and on site conditions that existed at time of the field observations and subsurface exploration. If significant changes to the nature, configuration, or scope of the project occur during the construction phase of the work, the Geotechnical Section should be consulted to determine the impact of such changes on the final geotechnical design recommendations and conclusions presented in this report.

Subsurface exploration and associated laboratory testing describes subsurface conditions only at the sites of subsurface exploration and at the intervals where samples are collected. These data are interpreted by members of the WFLHD Geotechnical Section, who then render a professional geotechnical opinion regarding the general subsurface conditions. The distribution, continuity, thickness, and characteristics of identified (and unidentified) subsurface materials may vary considerably from that indicated by the subsurface data. In addition, the observed water levels and/or conditions indicated on the test boring logs are recorded at the time of the exploration. The water levels and/or conditions may vary considerably, with time, according to the climate, rainfall, and other factors and are otherwise dependent on the duration of, and methods used in, and interpretations made from the subsurface exploration program.

This report should be made available to prospective contractors for their information, or as factual data only, and not as a warranty of ground conditions.

Questions regarding this final geotechnical report should be addressed to Dustin Woods, PE, WFLHD Geotechnical Engineer, at (360) 619-7541, or electronically sent to dustin.woods@dot.gov.

GR 04-16 Page 30

10 REFERENCES

AASHTO LRFD Bridge Design Specifications, 7th Edition (2014), American Association of State Highway and Transportation Officials, Washington, D.C.

Berg, R.R., Christopher, B.R., Samtani, N.C. (2009). Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, FHWA-NHI-10-024- Volume 1 and FHWA-NHI-10-025-Volume 2, Geotechnical Engineering Circular No.

11, National Highway Institute, U.S. Department of Transportation, Federal Highway Administration, Washington, D.C.

Berg, Richard B., Locke, William W., Lonn, Jeffrey D. Geologic Map of the Gardiner 30’ x 60’ Quadrangle, South-Central Montana [map]. 1999. 1:100,000. “Montana Bureau of Mines and Geology”. <http://www.mbmg.mtech.edu/pdf_100k/gardiner-tiled.pdf> (October 13, 2015).

Stickney, Michael C., Haller, Kathleen M., Machette, Michael N. Special Publication No.

114: Quarternary Faults and Seismicity in Western Montana [map]. 2000. “Montana Bureau of Mines and Geology”. <http://www.mbmg.mtech.edu/pdf/SP114-earthquakemap.pdf > (October 14, 2015).

Western Regional Climate Center (2016), Coorperateve Climatological Data Summaries, Big Timber, Montana (240780): http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?mt0780, accessed 5/10/2016.

http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?mt0780

Main Boulder River Road Final Geotechnical Report

GR 04-16 Appendix A

APPENDIX A

Unified Soil Classification System Soil Descriptive Terminology

Rock Descriptive Terms Boring Location Map

Geotechnical Test Boring Logs

SOIL DESCRIPTIVE TERMINOLOGY

CONSISTENCY OF COHESIVE SOILS

SPT N-Value (blows/ft) Consistency Field Identification

0 - 1 Very Soft Easily penetrated several inches by first

2 - 4 Soft Easily penetrated several inches by thumb

5 - 8 Firm Moderate effort required to penetrate several inches by thumb

9 - 15 Stiff Readily indented by thumb but penetrated only with great effort

16 - 30 Very Stiff Readily indented by thumbnail

> 30 Hard Indented with difficulty by thumbnail

RELATIVE DENSITY OF

COHESIONLESS SOILS

SPT N-Value (blows/ft) Relative Density

0 - 4 Very Loose

5 - 10 Loose

11 - 30 Medium Dense

31 - 50 Dense

> 50 Very Dense

PARTICLE SIZE

Term Sieve Size Boulder > 12” (>300mm)

Cobble 3” - 12” (75mm - 300mm)

Gravel – coarse ¾” - 3” (19mm - 75mm)

Gravel – fine #4 - ¾” (4.75mm - 19mm)

Sand – coarse #10 - #4 (2.00mm - 4.75mm)

Sand – medium #40 - #10 (0.425mm - 2.00mm)

Sand – fine #200 - #40 (0.075mm - 0.425mm)

Silt & Clay < #200 (<0.075mm)

MOISTURE CONTENT

Dry Dusty, dry to the touch

Moist Damp, but no visible free water

Wet Visible free water, saturated, over optimum

ROCK DESCRIPTIVE TERMS

ROCK WEATHERING

Field Identification Term Crystals are bright. Discontinuities may show some minor surface staining.

No discoloration in rock fabric. Fresh

Rock mass is generally fresh. Discontinuities are stained and may contain clay. Some discoloration in rock fabric.

Slightly Weathered

Significant portions of rock show discoloration and weathering effects.

Crystals are dull and show visible chemical alteration. Discontinuities are stained and may contain secondary mineral deposits.

Moderately Weathered

Rock can be excavated with geologist’s pick. All discontinuities exhibit secondary mineralization. Complete discoloration of rock fabric. Surface of core is friable and usually pitted due to washing out of highly altered minerals by drilling water.

Highly Weathered

Rock mass is completely decomposed. Original rock “fabric” may be evident. May be reduced to soil with hand pressure. Decomposed

DISCONTINUITY SPACING ROCK QUALITY DESIGNATION (RQD)

Spacing (in) Spacing Term RQD % Designation < 2.5 Very Close 0 - 25 Very poor

2.5 – 8 Close 25 - 50 Poor 8 – 24 Moderately close 50 - 75 Fair 24 – 80 Wide 75 - 90 Good

> 80 Very Wide 90 - 100 Excellent (RQD is the percent of a core run with intact lengths greater than 4 inches excluding breaks caused by drilling.)

INTACT ROCK STRENGTH

Field Identification UCS (psi) Hardness Term Indented by thumbnail. 35 - 150 Extremely Weak (R0) Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife. 150 - 725 Very Weak (R1)

Can be peeled by a pocket knife with difficulty, shallow indentations made by firm blow with geological hammer.

725 – 3,500 Weak (R2)

Cannot be scraped or peeled with a pocket knife, specimen can be fractured with a single blow of geological hammer.

3,500 – 7,000 Medium Strong (R3)

Specimen requires more than one blow of geological hammer to fracture it. 7,000 – 15,000 Strong (R4)

Specimen requires many blows of geological hammer to fracture it. 15,000 – 36,000 Very Strong (R5)

Specimen can only be chipped with geological hammer. > 36,000 Extremely Strong (R6) (UCS – Unconfined Compressive Strength)

1 / 15

PAGEBORING LOCATION MAP

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division 610 East Fifth Street Vancouver, WA 98661

2 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

3 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

4 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

5 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

6 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

7 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

8 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

9 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

10 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

11 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

12 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

13 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

14 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

15 / 15

MAIN BOULDER RIVER ROAD

IMPROVEMENTS PROJECT

SWEET GRASS COUNTY, MONTANA

Project No.

Scale:

File Name:

Date:

MT Sweetgrass 210(1)

N.T.S

19JULY2016

Western Federal Lands Highway Division

8-10-8 (6" = 33%)

5-4-9 (5" = 28%)

50/2" (2" = 98%)

21-29-50/2.5" (8" = 55%)

S1

S2

S3

S4

COBBLES and BOULDERS in a silty gravel with sand (GM) matrix, dry to moist, brown to gray, medium dense to very dense, subrounded to subangular gravel, fine to coarse sand.

S…