Revised_Final_Elk_Lake_Pavement_Report__01-12-2016.pdf

REVISED FINAL

PAVEMENT DESIGN REPORT

MT BEAVERHEAD 273 (1)

ELK LAKE ROAD CONSTRUCTION

BEAVERHEAD COUNTY, MONTANA

January 12, 2016

YA Project No. 214-230

Prepared for:

Mr. Lee Kunselman, PE Project Manager

Atkins North America, Inc.

7604 Technology Way, Suite 400

Denver, CO 80237-2568

Prepared by:

Yeh and Associates, Inc.

2000 Clay Street Suite 200 Denver, Colorado 80211 i

TABLE OF CONTENTS

1. PURPOSE AND SCOPE OF STUDY

2. PROPOSED CONSTRUCTION

3. GEOLOGIC SETTING

3.1 SEISMICITY

4. SITE CONDITIONS

4.1 TERRAIN AND VEGETATION

4.2 CLIMATE

4.3 EXISTING CUTS AND FILLS

4.4 EXISTING AGGREGATE SURFACE CONDITION

5. SUBSURFACE INVESTIGATION

5.1 EXPLORATORY BORINGS

5.2 LABORATORY TESTING

6. SUBSURFACE CONDITIONS

7. GEOTECHNICAL ENGINEERING CONSIDERATIONS

7.1 FROST SUSCEPTIBLE SOILS

7.2 DIFFICULT COMPACTION

7.3 SHALLOW GROUNDWATER

8. PAVEMENT DESIGN RECOMMENDATIONS

9. GRADING

9.1 REINFORCED SLOPES

9.2 SUBEXCAVATION

10. MATERIAL SOURCE RECONNAISSANCE

11. LIMITATIONS

12. REFERENCES

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LIST OF FIGURES

FIGURE 1: PROJECT LOCATION MAP

FIGURE 2: GEOLOGIC MAP

FIGURE 3: GEOLOGIC MAP LEGEND

LIST OF TABLES

TABLE 1: SUBGRADE SOIL PROPERTIES BY LOCATION

TABLE 2: POTENTIAL SUBEXCAVATION LOCATIONS

LIST OF APPENDICES

APPENDIX A – PRELIMINARY PLANS WITH EXPLORATORY BORING LOCATIONS

APPENDIX B – BORING LOGS

APPENDIX C - RESULTS OF LABORATORY TESTING

APPENDIX D – PAVEMENT DESIGN CALCULATIONS

APPENDIX E – DRILLING PHOTOS

Revised Final Pavement Design Report Yeh Project No. 214-230 MT Beaverhead 273(1) Elk Lake Road Construction January 12, 2016

1. PURPOSE AND SCOPE OF STUDY

Yeh and Associates, Inc., as a subconsultant to Atkins North America, Denver, Colorado, was retained by the Federal Highway Administration (FHWA), Western Federal Lands Highway

Division (WFLHD) to provide geotechnical and surface treatment recommendations for preliminary and final design of improvements to Elk Lake Road, Beaverhead County, Montana.

The project limits on Elk Lake Road extend north and easterly from the intersection with South

Valley Road to the intersection with North Valley Road. Elk Lake Road is an unpaved gravel/dirt road and is maintained by Beaverhead County. The project location is shown on Figure 1.

Project participants include; FHWA (WFLHD), Red Rock Lakes National Wildlife Refuge, US

Fish and Wildlife Service, Beaverhead County, and Beaverhead-Deer Lodge National Forest.

The purpose of the geotechnical investigation is to evaluate geologic and subsurface conditions in the project area and provide recommendations for the design of subsurface and surface treatments and drainage improvements. This report presents the results the geotechnical investigation along Elk Lake Road (County Road 273L), MT 43, (US Forest Service RD 8384).

This report addresses potential geotechnical constraints for the proposed improvements, existing roadway conditions along Elk Lake Road, and includes recommendations for the roadway pavement structural section, drainage improvements and cut and fill slopes.

Geotechnical recommendations for foundation design for proposed structures are provided under separate cover.

2. PROPOSED CONSTRUCTION

The proposed project will rehabilitate and improve the existing approximately 2.7 miles of roadway. As proposed, the project includes clearing, excavation, grading, placement of aggregate base and an aggregate surface and drainage improvements. The improved road will generally follow the existing alignment except where minor alignment changes are proposed to improve the hydraulic conditions at skewed drainage crossings. The grade will be raised at the approaches to drainage crossings and at low-lying areas where existing surface drainage is poor. The subgrade becomes unstable in the spring due to freeze-thaw cycles and the proposed improvements may include geosynthetic reinforcement and subgrade replacement to mitigate these effects. Traffic volumes for this remote road are low. However, the road will be designed to support occasional heavy vehicles such as logging trucks and propane or septic system service trucks.

Figure 1: Project Location Map (no scale)

3. GEOLOGIC SETTING

The project location is in the northern Rocky Mountains Geophysical Province. Elk Lake Road lies in the Centennial Valley, the valley immediately to the north of, and adjacent to, the east/west trending Centennial Mountains. The Centennial Valley, a half graben is actively subsiding and tilting into the fault zone at the base of the Centennial Mountains. Fault offset is estimated at approximately 32 feet over the last 15,000 years. This offset has resulted in about

25 feet down faulting of the Centennial Valley. A large lake of approximately 65 feet deep occupied the valley in late Pleistocene time.

As shown on the following geologic map, Elk Lake Road lies upon 3 different mapped geologic formations. Holocene aged unconsolidated fluvial deposits of sand, silt and gravel (QaL-

Alluvium), are found in the area of both Red Rock Creek and Elk Creek. The borings at these locations confirmed the mapped geology.

The majority of the project is underlain by a Holocene aged low lobate deposit of unconsolidated moderately well sorted silt, sand, gravel, and cobbles (Qfy – Young Alluvial Fan Deposit). As

Project Location the ancient lake subsided, this material was deposited onto the former lakebed by the surrounding streams that empty into the valley. The borings conducted in this deposit encountered silt, sand and gravel. No cobbles were found.

At the very northern end of the project, Quaternary aged light brown to brown, well sorted unconsolidated silt and sand, (Qlc - Lacustrine Deposit) is mapped. These remnants of the former lake are often intermingled or overlain by dune sand. This is the case in the area north of Elk Creek, to the project end at the Elk Lake Road and North Valley Road intersection.

Boring 1 was placed in this area and encountered silty fine sand from the ground surface to the bottom of the boring at 11.5 feet.

3.1 Seismicity

The project location is adjacent to the Centennial Fault which is located at the southern boundary of the valley at the base of the Centennial Range. The Centennial Fault is grouped in the Idaho seismic zone or the Centennial tectonic belt which extends from the Yellowstone area into central Idaho. This is the most seismically active area in the state of Montana and several large magnitude events have occurred here in the past 100 years. The largest of these was the

Hebgen Lake earthquake which was recorded at a surface wave magnitude Ms 7.5 and caused several deaths. The event also dammed the Madison River, creating Earthquake Lake.

The Centennial fault is classified as a Class A Quaternary fault by the Montana Bureau of Mines and Geology. Class A is defined as, there being evidence that at least one large-magnitude earthquake has occurred on the fault during the Quaternary. The Centennial Fault is divided into four sections. The project is located adjacent to the Red Rock Lakes section of the fault.

Conflicting data exists on an estimate of most recent historic deformation of the Red Rock

Lakes section. The “Data for Quaternary Faults in Montana” shows a time of less than 1.6 million years ago (Ma.)

Figure 2: Geologic Map (No Scale)

Project Limits

Figure 3: Geologic Map Legend

Pertinent units include:

Qal - ALLUVIUM (HOLOCENE) Unconsolidated fluvial deposits of silt, sand and gravel

Qfy – YOUNG ALLUVIAL FAN DEPOSIT (HOLOCENE) – Low lobate deposit of unconsolidated moderately well sorted silt, sand, gravel, and cobbles at mouths of streams, most of which empty into Centennial Valley. Constituent rock types reflect bedrock exposed along streams.

Along north side of Centennial Valley, Precambrian crystalline and Cenozoic volcanic rocks predominate; along south side, rocks include, locally, in addition to the crystalline and volcanic, a wide variety of Paleozoic sedimentary rocks.

Qlc – LACUSTRINE DEPOSIT (QUATERNARY) – Light brown to brown well sorted unconsolidated silt and sand. Locally contains pebbles, about 3mm in diameter, washed in by small streams. Marked by multiple beaches, former shorelines of the dwindling glacial lake that once occupied Centennial Valley. Modern streams have trenched and dissected these lacustrine deposits, and in places dune sand intermingles with and overlies them.

4. SITE CONDITIONS

4.1 Terrain and Vegetation

Elk Lake Road is located in slightly sloping, ancient lakebed terrain of the Centennial Valley.

The road descends slightly from an elevation of approximately 6665 feet at the intersection with

South Valley Road to an elevation of approximately 6640 feet at the intersection with North

Valley Road. Within the project limits, approximately 1.5 miles of Elk Lake Road is a tangent section running due north/south. Curved sections of approximately 0.6 miles each are found at either end of the tangent section, connecting Elk Lake Road to South Valley Road and North

Valley Road.

Between South Valley Road and North Valley Road, Elk Lake Road crosses two major water courses, Red Rock Creek and Elk Creek. In addition to the creek crossings there are several low lying/wetland areas where both surface water and high groundwater affect the roadway.

Vegetation varies from sage brush and grasses on the high ground to willows and wetland associated plants in the low lying areas.

4.2 Climate

Climate data collected from the nearby Lima, Montana weather station is representative of the project location. The average annual rainfall at the Lima weather station is 11.17 inches. The majority of the rainfall occurs between April and October. The average annual snowfall is 59 inches, the majority of which occurs between September and May. The annual average lowest temperature, which occurs in December, is 7.1 degrees Fahrenheit. The annual average highest temperature, which occurs in July, is 80.1 degrees Fahrenheit.

4.3 Existing Cuts and Fills

The majority of the cut slopes at the project location are less than 3 feet high and are performing satisfactorily. The cuts composed of silty sand are generally vegetated and standing at approximately 1V:2H. At station 210+00 the existing cut slopes are approximately 7 feet high at their tallest point. These slopes are standing at approximately 1V:2H and are performing satisfactorily. The slopes at station 210+00 are perforated with numerous badger dwellings which do not appear to be affecting the overall performance of the slopes.

The fill embankment approaches to the existing bridge at Red Rock Creek are approximately 6 feet in height and appear to be performing satisfactorily. Minor fill embankments less than 2 feet in height are present at the Elk Creek crossing. This location is also performing satisfactorily.

4.4 Existing Aggregate Surface Condition

Presently, the aggregate surface is nearly non-existent. Elk Lake Road behaves as an unpaved, unsurfaced dirt road. The majority of the project area is rutted and potholed. These conditions are exacerbated by rainfall and seasonally high surface and groundwater conditions.

The road is reported to be frequently impassable from April to June when groundwater levels are high and subgrade soils are saturated from snowmelt. Because a large portion of the road is in a wetland area with poor draining soils, surface and subsurface drainage is very poor.

Spring thaw typically weakens the road bed making surface drainage improvements difficult to maintain.

5. SUBSURFACE INVESTIGATION

Yeh and Associates contracted with Inberg-Miller engineers of Riverton, Wyoming to drill exploratory borings for both the pavement and structure foundation investigations. The borings were drilled between November 19th and 21st of 2014.

5.1 Exploratory Borings

A total of 5 borings were drilled for the pavement design investigation. Underground utilities along the alignment controlled the location of the borings. The locations are shown on the 15%

Review plans in Appendix A. The logs of the borings are presented in Appendix B. Photos of the road surface conditions and boring locations are presented in Appendix D.

Borings TH-1, TH-3, TH-4, TH-5 and TH-7 were drilled to a maximum depth of 11.5 feet, to determine the existing gravel surface thickness and to evaluate subgrade conditions for pavement design. The borings were drilled with a truck mounted CME 85 drilling rig using 8 inch diameter hollow stem augers. Bulk samples of auger cuttings and split spoon samples using a 1.5 inch I.D. SPT sampler were obtained at selected intervals.

The split-spoon sampler was driven into the subsoils with a 140-pound hammer falling 30 inches. The number of blows needed to drive the sampler 12 inches constitutes the blow count, N, reported on the Boring Logs (Appendix B). The blow count can be used as a relative measure of the material stiffness or density. Upon completion, the borings were backfilled with auger cuttings.

5.2 Laboratory Testing

Samples retrieved during the field exploration were sent to the Western Federal Lands Highway

Division (WFLHD), Materials Testing Laboratory for testing. Laboratory tests, as specified in the

Scope of Work authored by WFLHD were performed on the samples submitted. American

Association of State Highway and Transportation Officials (AASHTO) and WFLHD test methods were followed. After the completion of the laboratory testing, the field descriptions were confirmed or modified as necessary and boring logs were prepared.

Laboratory tests performed included gradation (AASHTO T-11/T-27), Atterberg limits (AASHTO

T 89/T 90), moisture content (AASHTO T 265), R-value (WL-190) and Specific Gravity

(AASHTO T-100). Gradation and Atterberg limits test results were used to classify the soils in accordance with the AASHTO classification system and the Unified Soil Classification System

(USCS). Moisture content provides an estimate of the moisture conditions of the subgrade and underlying materials. Soil R-value is a measure of soil subgrade strength used for pavement design. The laboratory test results are presented in Appendix C and on the boring logs in

Appendix B.

6. SUBSURFACE CONDITIONS

The subgrade soils encountered in the pavement borings consist of silty sand, clayey sand and sandy lean clay. An existing gravel surface layer was not identified at any of the pavement boring locations. Laboratory test results on bulk soil samples recovered from the upper 5 feet of the borings show the subgrade moisture content ranges from 7.2 percent to 51.3 percent. The higher moisture contents are greater than the liquid limit for those soil samples. With the exception of the sample from Boring TH-7, which had 21 percent gravel, the subgrade samples had no or trace amounts coarse material larger than the No. 4 sieve. The percentage of fine

(less than No 200 Sieve) materials ranged from 26 to 65 percent. The higher fines content was encountered in the sandy clay subgrade samples. The plasticity index values ranged from non-plastic to 19, or medium plasticity. R-values of the samples ranged from 17 to 61. A summary of the subgrade soil properties and depth to groundwater (GW) by boring location is presented in Table 1.

Table 1: Subgrade Soil Properties by Location

Boring No.

Station Moisture Content

Depth to GW

(ft) R-Value

AASHTO

Classification

USCS

Classification

TH-1 242+20 11.9 6.6 57 A-2-4 (0) Silty Sand (SM)

TH-3 210+95 34.7 6.0 34 A-4 (4) Sandy Clay (CL)

TH-4 166+95 23.4 4.5 48 A-6 (1) Clayey Sand (SC)

TH-5 134+70 51.3 2.8 17 A-7-6 (10) Sandy Clay (CL)

TH-7 106+40 7.2 Dry 61 A-2-4 (0) Silty Sand (SC-SM)

Sampler blow counts (N values) indicate the granular subgrade soils are very loose to medium dense and the fine-grain soils are soft to medium stiff. Very loose or soft soils were typically encountered at or below the groundwater level.

7. GEOTECHNICAL ENGINEERING CONSIDERATIONS

Geotechnical engineering related conditions that could affect design and construction include frost susceptibility of the subgrade, difficulty compacting the native soils and shallow groundwater. These site conditions, discussed below, should be considered during design and construction of pavements, excavations and embankments.

7.1 Frost Susceptible Soils

Silty or clayey soils with low to medium plasticity and a relatively high percentage of fine sand, such as those encountered along Elk Lake Road, can be highly susceptible to frost heave and the formation of ice lenses in cold climates. Frost heave occurs when soils with high moisture content are subject to freezing temperatures. Migration of moisture by capillary action can cause saturation of the subgrade where these types of soils are present and groundwater is relatively shallow. The effects of frost susceptibility and capillary action can be mitigated by removal of the upper few feet of native silty sand subgrade and replacement with relatively free draining imported aggregate. A geotextile separator fabric should be placed below the imported fill to prevent migration of fine soils into the aggregate.

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7.2 Difficult Compaction

Soils with a high percentage of silty fines can be difficult to moisture condition and compact.

Moisture control is important when compacting these types of soils because slight variations of moisture content can increase the compactive effort necessary to achieve the required in-place density. Heavy rubber-tire equipment such as scrapers or smooth drum rollers operated in static mode have been successfully used to compact moisture sensitive silt and sand soils.

7.3 Shallow Groundwater

Groundwater is relatively shallow along Elk Lake Road, particularly near streams and in wetland areas. Groundwater levels should be expected to fluctuate seasonally due to run-off and infiltration from precipitation events. Shallow groundwater is typically present during spring and early summer. Maintaining the stability of excavations and construction of embankment fill will be difficult in areas of shallow groundwater.

8. PAVEMENT DESIGN RECOMMENDATIONS

The minimum design thickness of the new aggregate surface for Elk Lake Road was determined using the method in accordance with the Structural Design of Aggregate Surfacing provided in

Chapter 11 of the Project Development and Design Manual (PDDM) and the AASHTO Guide for

Design of Pavement Structures (AGDPS). The minimum aggregate surface thickness does not include additional aggregate subbase that may be required to mitigate for frost susceptible soils and poor surface drainage.

The design traffic volume is assumed to be low (less than 30,000 ESALs) over the 20-year pavement design life. This design ESAL value could represent 2 trips by FHWA Class 9 trucks

(logging or cattle trucks) each day for the life of the surfacing.

The relative subgrade soil quality in along Elk Lake Road ranges from Very Good to Very Poor based on the results of R-value tests performed by the WFLHD materials laboratory. The road is located in Climatic Region VI.

The minimum aggregate surface thickness of 9 inches was determined from Exhibit 11.4.2.-A of the Supplement for low traffic volume and poor quality subgrade soil. The aggregate surface course should consist of well-graded, crushed gravel with 8 to14 percent low plasticity fines, meeting the requirements of the Standard Specifications for Construction of Roads and Bridges

1 1 on Federal Highway Projects (FP-14) Section 703.05 (c). The fines will help bind the material, reduce dust and prevent loss of larger aggregate.

Additional subbase fill should be placed below the aggregate surface course to mitigate the effects of frost, reduce capillary rise and to provide drainage. The subbase fill should consist of at least 12 inches of aggregate meeting the requirements of Section 703.05 FP-14 with Grading

Designation D in accordance with Table 703-2 or Select Borrow meeting the requirements of

Section 704.07 FP-14. The contractor should be warned that if the select borrow material is too rounded or contains too much of one size aggregate, the contractor may have problems compacting the subbase.

A separator geotextile meeting the strength requirements of Class 1 and the hydraulic properties of Type A, per Section 714.01 of FP-14 should be placed on the subgrade beneath the subbase fill. The aggregate surface course thickness should be reduced to 6 inches when placed over 12 inches of subbase fill.

9. GRADING

The subgrade soils should be moisture conditioned and compacted prior to placing the geotextile, subbase fill and aggregate surface of the pavement section discussed above.

Preparation for placement of the geotextile and subbase fill should comply with Section 201.09 of FP-14. Native soils with high silt or clay content and existing moisture contents above optimum may require processing to moisture condition prior to compacting. Use of non-vibratory (static) compaction equipment or heavy rubber-tire earthmoving equipment may be an effective means of compacting the bases of embankment fills.

Unreinforced fill side slopes should be graded at 1 Vertical to 3 Horizontal (1V:3H) or flatter.

Cut slopes in the native soils should be graded at 1V:2H or flatter. Reinforced fill slopes, constructed as recommended below, can be graded at 1V:1H or flatter, however revegetating

1V:1H reinforced slopes can be problematic. Our experience is that revegetating reinforced slopes at 1V:1.25H or flatter will be more successful.

Cut and fill slopes should be protected from erosion, be re-vegetation, or other means.

Establishment of vegetation will be more successful on slopes graded flatter than 1V:2H. Good surface drainage should be provided around all permanent cuts and fills to direct surface runoff away from the slope faces.

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All site grading should conform to the applicable section of FP-14. Fill materials should not contain organic matter or other deleterious material. The use of native soils should be limited to non-critical areas of construction, such as well below the pavement subgrade zone. Some soils may have high moisture contents and require moisture conditioning prior to use as fill.

Temporary excavations should conform to OSHA requirements. See the Pavement Design

Recommendations section of this report for specific requirements for fill under aggregate surfacing.

9.1 Reinforced Slopes

Reinforcing fill slopes with geogrid or geotextile may be practical where proposed fills are greater than about 5 feet. Fill slopes reinforced with geotextile or geogrid layers can be an effective means to construct embankments with reduced footprints. The design of reinforced fill slopes should include analysis of internal and global stability. Vertical spacing or reinforcement should not exceed 2 feet. Reinforced fill slopes should be constructed using imported granular soils meeting the requirements of Section 704.03 of FP-14. Establishing vegetation may be difficult on slopes graded steeper than 1V:1.25H.

9.2 Subexcavation

The field investigation identified several locations along Elk Lake Road that may require subexcavation and replacement with imported granular materials to form a stable base for construction of the pavement section. These locations are described In Table 2.

Subexcavation should be performed in accordance with Section 204.07 of FP-14. Because of the presence of shallow groundwater and soft fine-grain soils, the depth of subexcavation should be limited to 18 inches. Placement of a geogrid reinforcing layer may be required to create a stable base for subexcavation backfill.

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Table 2: Potential Subexcavation Locations

Approximate

Station Landmark Conditions

136+00 to 236+00 Elk Springs Drainage

Fill will be required for the bridge approaches. Subexcavation, replacement and geogrid reinforcement may be necessary for fill embankment stability. Loose silty sand.

168+00 to 172+00 Drainage This is a topographically depressed section where additional fill may be required. Shallow groundwater, clayey sand soils.

135+50 to 142+00 Wetland Area Additional fill may be required in this section to sufficiently raise the road grade above the 3 existing culverts. Shallow groundwater, soft clay soils.

114+00 to 117+50 Red Rock Creek

Up to approximately 8 feet of fill will be required for the bridge approach at Red Rock Creek. This embankment design could incorporate geosynthetic reinforcement to steepen the embankment side slopes and lessen the footprint. Shallow groundwater, loose silty sand.

10. MATERIAL SOURCE RECONNAISSANCE

Beaverhead County operates a commercial borrow pit near the project area. The pit is located in alluvial material that is typical of the valley bottom terrain surrounding the project. Visual observations of this site indicate that a majority of the material is fine graded and not suitable for use as subbase fill or aggregate surfacing without screening and processing. Additional testing should be performed to determine if the County Pit is a suitable source for Backfill Material.

An abandoned borrow pit is located on Forest Service Land outside of the Refuge limits on

Road 8389 near Elk Lake. The material at this location may meet the projects needs but access to the site is limited and more investigation will be required to assess the suitability of this source for aggregates.

The following commercial material sources are nearby:

Parker's Sand & Gravel Inc.

2570 S Yellowstone Hwy, Saint Anthony, ID 83445

(208) 624-3536: 70.7 miles, Estimate 1 hour 42 minute haul

Fall River Sand and Gravel

1312 N 4525 E, Ashton, ID 83420

(208) 652-7770: 65.2 miles, Estimate 1 hour 40 minute haul

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KH Concrete

5074 US Highway 287 N, Ennis, MT 59729

(406) 682-7172: 72.1 miles, Estimate 1 hour 35 minute haul

11. LIMITATIONS

This study has been conducted in accordance with generally accepted geotechnical engineering practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from field reconnaissance and our understanding of the proposed type of construction. The nature and extent of subsurface variations across the site may not become evident until excavation is performed. If during construction, fill, soil, or water conditions appear to be different from those described herein, this office should be advised at once so re-evaluation of the recommendations can be made. We recommend on-site observation of excavations, native subgrade and foundation bearing strata, by a qualified geotechnical engineer.

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12. REFERENCES

MT Beaverhead 273(1) Preliminary Roadway Plan Sheets, 2014, Provided by Atkins North

America.

Draft MT Beaverhead 273(1) Elk Lake Road Scoping Meeting Minutes, July 15, 2014

U.S. Department of Transportation, Federal Highway Administration, Project Development and

Design Manual (PDDM), 2014

Guide for Design of Pavement Structures, AASHTO, 1993.

Federal Highway Administration, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, 2014.

APPENDIX A ‐ PRELIMINARY PLANS WITH

EXPLORATORY BORING LOCATIONS

TH-7

TH-6

TH-5

TH-4

TH-3

TH-2

TH-1

APPENDIX B ‐ BORING LOGS

Project Number: 214-230

Project: Elk Lake Road

Date:12/5/2014 2/11/15

Legend for Symbols Used on Borehole Logs

USCS Low Plasticity Clay

USCS Poorly-graded Gravel USCS Silt USCS Clayey Sand

USCS Clayey Sand USCS Silty Sand

Soil Lithology

Bedrock Lithology

Lab Test Abbreviations

Sample Types

Auger Cuttings Grab Sample Modified California Sampler

Standard Penetration Test

YEH AND ASSOCIATES, INC.

GEOTECHNICAL ENGINEERING CONSULTANTS

MC-Moisture Content DD-Dry Density #200-Percent Passing #200 Sieve + #4-Percent Retained #4 Sieve LL-Liquid Limit PL-Plastic Limit PI-Plastic Index S-Sulphate Content Cl-% Chlorides S/C-Swell/Consolidation UCCS-Unconfined Compressive Strength Re-Resistivity PtL-Point Load Test AASHTO-AASHTO Classification USCS-USCS Classification

* Indicates that gradation analysis was performed, Atterberg limits were not performed, but the USCS classification was applied assuming non plastic characteristics

23/25/20

2/3/3

6/7/8

MC= 11.9%

+ #4= 0% #200= 26%

AASHTO: A-2-4(0)

USCS: SM

PL= NP

LL= NP

R-Value= 57

0.0 - 11.5 ft.

Frozen.

Silty SAND, SM, light brown, moist, loose.

Silty SAND, SM, gray, wet, medium dense.

Bottom of Hole at 11.5 ft.

Ground Water Notes:

Depth Date Time

Boring Began: 11/21/2014

Drilling Method: Hollow-Stem Auger

Drill: CME 85

Driller: Inberg-Miller

Logged By: W.Hoon

Final By:

Inclination: Vertical

Completed: 11/21/2014 Drill Bit: N/A Casing: None Weather: Cloudy/Cold

Total Depth: 11.5 ft Ground Elevation:

Location: Sta. 242+20, 4 ft. Lt Coordinates: N: E:

6.6 ft 11/21/14

Boring: TH-1

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

SPT

Blows per 6 in

R Q

D

R ec ov er y

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

YEH AND ASSOCIATES, INC.

Sheet 1 of 1

Project: Elk Lake Road

Project Number: 214-230

Soil Samples

Field Notes and

Lab Tests

Date: 3/13/15

Material Desciption

Li th ol o gy

N

B O

R

IN

G L

O G

E

LK

L A

K E

R O

A D

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

D T

3/

/1

1/2/2

2/3/3

1/2/2

MC= 34.7%

+ #4= 0.8% #200= 65%

AASHTO: A-4(4)

USCS: CL

LL= 32

PI= 9%

R-Value= 34 wet below 6 feet

0.0 - 11.5 ft.

Sandy CLAY, CL, light brown, moist, medium stiff.

Bottom of Hole at 11.5 ft.

Ground Water Notes:

Depth Date Time

Boring Began: 11/21/2014

Drilling Method: Hollow-Stem Auger

Drill: CME 85

Driller: Inberg-Miller

Logged By: W.Hoon

Final By:

Inclination: Vertical

Completed: 11/21/2014 Drill Bit: N/A Casing: None Weather: Cloudy/Cold

Total Depth: 11.5 ft Ground Elevation:

Location: Sta. 210+95, 9 ft. Lt.

Coordinates: N: E:

6.0 ft 11/21/14

Boring: TH-3

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

SPT

Blows per 6 in

R Q

D

R ec ov er y

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

YEH AND ASSOCIATES, INC.

Sheet 1 of 1

Project: Elk Lake Road

Project Number: 214-230

Soil Samples

Field Notes and

Lab Tests

Date: 3/13/15

Material Desciption

Li th ol o gy

N

B O

R

IN

G L

O G

E

LK

L A

K E

R O

A D

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

2/3/9

2/1/1

2/0/0

MC= 23.4%

+ #4= 5% #200= 38%

AASHTO: A-6(1)

USCS: SC

LL= 34

PI= 13%

R-Value= 48

Wet below 4.5 feet, sand and clay proportions variable throughout borehole length

0.0 - 8.0 ft.

Clayey SAND with trace to few subangular fine gravels, SC, dark brown, moist, medium dense.

Very loose.

8.0 - 11.5 ft.

Silty SAND, SM, black, wet, very loose.

Bottom of Hole at 11.5 ft.

Ground Water Notes:

Depth Date Time

Boring Began: 11/21/2014

Drilling Method: Hollow-Stem Auger

Drill: CME 85

Driller: Inberg-Miller

Logged By: W.Hoon

Final By:

Inclination: Vertical

Completed: 11/21/2014 Drill Bit: N/A Casing: None Weather: Cloudy/Cold

Total Depth: 11.5 ft Ground Elevation:

Location: Sta. 166+95, 6 ft. Lt.

Coordinates: N: E:

4.5 ft 11/21/14

Boring: TH-4

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

SPT

Blows per 6 in

R Q

D

R ec ov er y

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

YEH AND ASSOCIATES, INC.

Sheet 1 of 1

Project: Elk Lake Road

Project Number: 214-230

Soil Samples

Field Notes and

Lab Tests

Date: 3/13/15

Material Desciption

Li th ol o gy

N

B O

R

IN

G L

O G

E

LK

L A

K E

R O

A D

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

2/2/2

0/1/1

5/6/8

MC= 51.3%

+ #4= 5.2% #200= 60%

AASHTO: A-7-6(10)

USCS: CL

LL= 45

PI= 19%

R-Value= 17

0.0 - 8.0 ft.

Sandy CLAY, CL, black, moist to wet, soft.

8.0 - 11.5 ft.

Silty SAND, SM, black, wet, medium dense.

Bottom of Hole at 11.5 ft.

Ground Water Notes:

Depth Date Time

Boring Began: 11/21/2014

Drilling Method: Hollow-Stem Auger

Drill: CME 85

Driller: Inberg-Miller

Logged By: W.Hoon

Final By:

Inclination: Vertical

Completed: 11/21/2014 Drill Bit: N/A Casing: None Weather: Cloudy/Cold

Total Depth: 11.5 ft Ground Elevation:

Location: Sta. 134+70, 5 ft. Lt.

Coordinates: N: E:

2.8 ft 11/21/14

Boring: TH-5

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

SPT

Blows per 6 in

R Q

D

R ec ov er y

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

YEH AND ASSOCIATES, INC.

Sheet 1 of 1

Project: Elk Lake Road

Project Number: 214-230

Soil Samples

Field Notes and

Lab Tests

Date: 3/13/15

Material Desciption

Li th ol o gy

N

B O

R

IN

G L

O G

E

LK

L A

K E

R O

A D

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

7/10/14

6/7/8

7/11/13

MC= 7.2%

+ #4= 21.5% #200= 27%

AASHTO: A-2-4(0)

USCS: SM-SC

LL= 24

PI= 5%

R-Value= 61

0.0 - 4.5 ft.

Silty SAND with clay and little fine rounded gravel, SC-SM, light brown, moist, medium dense.

4.5 - 11.5 ft.

Silty SAND, SM, light brown, moist, medium dense.

Bottom of Hole at 11.5 ft.

Ground Water Notes:

Depth Date Time

Boring Began: 11/21/2014

Drilling Method: Hollow-Stem Auger

Drill: CME 85

Driller: Inberg-Miller

Logged By: W.Hoon

Final By:

Inclination: Vertical

Completed: 11/21/2014 Drill Bit: N/A Casing: None Weather: Cloudy/Cold

Total Depth: 11.5 ft Ground Elevation:

Location: Sta. 106+40, 8 ft. Lt.

Coordinates: N: E:

DRY

Boring: TH-7

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

SPT

Blows per 6 in

R Q

D

R ec ov er y

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

YEH AND ASSOCIATES, INC.

Sheet 1 of 1

Project: Elk Lake Road

Project Number: 214-230

Soil Samples

Field Notes and

Lab Tests

Date: 3/13/15

Material Desciption

Li th ol o gy

N

B O

R

IN

G L

O G

E

LK

L A

K E

R O

A D

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

APPENDIX C ‐RESULTS OF LABORATORY TESTING

Project No: MT Beaverhead 273(1) Elk Lake Rd - Pavement Design Date: 2/27/15

Gradation Atterberg

TH-1 0-5 Bulk 11.9 2.657 0 74 26 NV NP NP 57 A-2-4 ( 0 ) SM

TH-3 0-5 Bulk 34.7 2.659 1 34 65 32 23 9 34 A-4 ( 4 ) CL

TH-4 0-5 Bulk 23.4 2.690 5 57 38 34 21 13 48 A-6 ( 1 ) SC

TH-5 0-5 Bulk 51.3 2.650 5 35 60 45 26 19 17 A-7-6 ( 10 ) CL

TH-7 0-5 Bulk 7.2 2.698 21 52 27 24 19 5 61 A-2-4 ( 0 ) SM

Fines < #200

LL

YEH & ASSOCIATES, INC

Summary of Laboratory Test Results

214-230 Project Name:

Sample Location Natural

Moisture Content

Apparent Specific Gravity

Chloride

Water Soluble Sulfate

Boring No.

Depth (ft) Sample

Type

Gravel > #4

Sand

PL PI

AASHTO USCS

pH Resistivity

(Ohms-cm) R-Value

CLASSIFICATION

APPENDIX D ‐ PAVEMENT DESIGN CALCULATIONS

Aggregate Surfacing Design Standards and Guidance November

CFLHD Supplement 11.4.2-1 2 of 5

Exhibit 11.4.2.-A Aggregate surfaced thickness design catalog:

Recommended aggregate thickness (in inches) for the six U.S. climatic regions, five relative qualities of roadbed soil and three levels of traffic.

U.S. Climatic Region

Relative Quality of Roadbed Soil

Traffic Level I II III IV V VI

Very Good High Medium

Low

8*

Good High Medium

Low

Fair High Medium

Low

Poor High Medium

Low

Very Poor High Medium

Low

* Thicknesses of aggregate required (in inches).

** Higher type pavement design recommended.

Poor

Low 9

APPENDIX E ‐ DRILLING PHOTOS

Figure 1 – Boring TH‐1 location

Figure 2 – Boring TH‐2 at Elk Creek

Figure 3 – Boring TH‐3

Figure 4 – Boring TH‐4 location

Figure 5 – Boring TH‐5

Figure 6 – Boring TH‐6

Figure 7 – Boring TH‐7