FinalGeotechReport.pdf

GEOTECHNICAL AND PAVEMENT REPORT

Old Divide & Fattig Creek Road Surfacing

IDIQ DTFH70-15-D-00007 Task Order 69056719F00008 WFLHD Geotechnical Report 09-19

MT Musselshell 192(1) Project 18-3763G

Submitted by

2511 Holman Avenue P. O. Box 80190

Billings, Montana 59108-0910

Prepared for

Robert Peccia & Associates P.O. Box 5653

Helena, Montana 59604

January 17, 2020

Table of Contents Description Page

A. Introduction

A.1. Old Divide Road Description A.2. Fattig Creek Road Description A.3. Scope of Services and Background

B. Results B.1. General Site Topography and Geology B.2. Engineering Reconnaissance B.3. Fattig Creek Road Pavement Conditions B.4. Soil Boring Results

C. Laboratory Test Results C.1. General C.2. Moisture Content Tests C.3. Subgrade Tests

D. Geotechnical Analysis and Recommendations D.1. Old Divide Road D.2. Fattig Creek Road D.3. Digout Pavement Section D.4. Deep Patch D.5. Specifications

E. Procedures E.1. Drilling and Sampling E.2. Soil Classifications E.3. Groundwater Observations

F. General Recommendations F.1. Basis of Recommendations F.2. Review of Design F.3. Groundwater Fluctuations F.4. Use of Report F.5. Level of Care

Attachments:

Figure 1 Partial Topographic Sketch Figure 2 Geologic Map Figures 3-5 Boring Location Sketches Photographs (11 pages) Log of Boring Sheets SG19-1 through SG19-18 Laboratory Test Results

• Sieve Analysis (10 sheets)

• Proctors (5 sheets)

• CBR Tests (5 sheets)

Simple ESAL Calculation Pavement Design Spreadsheet Conceptual Deep Patch Sketch

A. Introduction

A.1. Old Divide Road Description Old Divide Road is located in Musselshell County and is a 6.5-mile loop beginning and ending from US Highway 87. It begins (RP 0.0) about 30 miles north of Billings and ends (RP 6.5) about 35 miles north of Billings. The intersection of Old Divide Road and Fattig Creek Road is at RP 4.7. The roadway is the main access route to Signal Peak Coal Mine as well as federal lands beyond the mine entrance.

We were provided documents for the 1994 partial improvements to Old Divide Road. These documents were prepared by Morrison-Maierle/CSSA and indicate roadway improvements were performed from RP 0.0 to RP 4.7. The improvements consisted of reclaiming the existing materials in place and creating cement-treated base (CTB) then placing a double-shot bituminous surface treatment (DBST). In particular, the typicals indicated the following:

• DBST,

• 0.83' Cement Treated Base,

• Existing Reclaimed Asphalt/Base Material-varies.

SK Geotechnical purchased the assets of Braun Intertec's Montana operations in 1998, and therefore has access to the pavement design report prepared for Morrison-Maierle/CSSA for these improvements. Five soil borings were performed through the existing pavement along the 4.7-mile route. Prior to the above-referenced improvements, the borings encountered about 0.15-foot of bituminous surface underlain by 0.4- to 1.0-foot of base course, although no base was encountered in one of the borings. Beneath the existing pavement, the borings encountered primarily lean clay and fat clay subgrade as well as weathered shale and shale bedrock. The report provides alternative pavement sections for total reconstruction with crushed base course and cement-treated base as well as full depth recycling (FDR). None of these recommended sections, however, appeared to have been used for the1994 project.

History and pavement sections from RP 4.7 to RP 6.5 do not appear to be available at this time. This portion of Old Divide Road appears to have plant mix bituminous surface rather than the DBST.

A.2. Fattig Creek Road Description Fattig Creek Road begins at the intersection of Old Divide Road at RP 4.7 and heads northeast and east for 2.0 miles, where the existing pavement surfacing turns to gravel surfacing. SK Geotechnical was also involved in pavement improvements along Fattig Creek. In 2009, SK Geotechnical performed numerous pavement and adjacent cut area borings for the first three miles of Fattig Creek Road. Highly variable subgrade was encountered along the alignment ranging from silty sand underlain by lignite, lean clay, Robert Peccia & Associates January 17, 2020 Project 18-3763G Page 2 sandy lean clay and sandstone bedrock. The following pavement section was used for the first one mile of Fattig Creek Road (RP 0.0 to RP 1.0).

Asphalt Pavement 4 inches Aggregate Base course 4 inches Subbase Course 12 inches

Beyond RP 1.0, it is our understanding that Musselshell County placed pavement millings on top of existing gravel surfacing, then compacted these millings to provide a surfacing. Compacted millings surfacing is therefore present from RP 1.0 to 2.0.

A.3. Scope of Services and Background To evaluate the pavement preservation for the project, SK Geotechnical performed pavement and geotechnical evaluation along the project. Our scope of services is briefly described below.

• Reconnaissance by geotechnical engineers to observe pavement conditions and geotechnical features.

• Painting the proposed boring locations, and setting offset stakes. During the staking, the latitude and longitude coordinates were determined by an uncorrected hand-held Garmin GPS. These coordinates are indicated on the attached log of boring sheets and shown on the attached boring location sketches. Reference points related to mileage beginning at the south end of Old Divide Road and the west end of Fattig Creek Road are also included.

• Coordinating the location of underground utilities near the boring locations.

• Conducting a total of 15 penetration test borings along Old Divide Road; 14 borings to 5 feet and one boring in a slump to 19 feet. Three borings to 5 feet were performed in Fattig Creek Road.

As the borings were performed, our senior engineering assistant closely observed the existing pavement, base and subbase courses and recorded the pavement section to the nearest 1/4 inch.

• Collecting bag samples of the existing base, subbase, and subgrade for various laboratory tests.

• Classifying the samples and preparing boring logs.

• Selecting five subgrade samples for classification, Proctor, and California bearing ratio (CBR) tests. Four base course samples were also selected for classification tests.

• Discussing the project with Mr. Brad Thompson of Robert Peccia and Associates, and

• Preparing this geotechnical and pavement evaluation report containing log of borings, our analysis of the field and laboratory tests, and recommendations for pavement preservation.

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B. Results

B.1. General Site Topography and Geology Attached Figure 1 is a partial Topographic Sketch showing the 6.5-mile long Old Divide Road and 2.0-mile long Fattig Creek Road alignments in blue and red, respectively. As this sketch indicates, the roadways are located at the relative base of the Bull Mountains in hilly terrain crossing numerous coulees and drainages. Figure 2 is a portion of the Geologic Map of the Roundup 30 x 60 Minute Quadrangle, Central Montana, by Edith M. Wilde and Karen W. Porter, revised 2007, and is also attached. The map indicates that the first portion of Old Divide Road from about RP 0.0 to RP 1.5 is situated in the Lebo Member of the Fort Union Formation (Tfle) while the remaining portion of Old Divide Road and all of Fattig Creek Road are situated in the Tongue River Member of Fort Union Formation (Tftr). These formations typically consist of sandstone interbedded with carbonaceous shale, siltstone and coal beds.

The sandstone has been found to be fairly massive and the carbonaceous shale highly expansive.

B.2. Engineering Reconnaissance

B.2.a. Fieldwork. Robert Peccia & Associates, Inc. (RPA), was selected by FHWA to assist in the development of this project. SK Geotechnical will also assist in the development of the geotechnical and pavement features of the project. A reconnaissance of the alignment was performed by Mr. Gregory T.

Staffileno, PE, senior geotechnical engineer and Dustin P. Hutzenbiler, PE, geotechnical engineer, with our firm on November 20, 2018. The 6.5-mile Old Divide alignment and 2.0-mile Fattig Road alignments were observed, paying particular attention to the existing pavement surface defects and drainage. Numerous photographs of these roadways were taken, some of which have been included in this report. More photographs are available upon request.

B.2.b. Old Divide Road Pavement Conditions. It is our opinion that Old Divide Road from RP 0.0 to the intersection with Fattig Creek Road at RP 4.7 is in poor to fair condition, while the roadway surfacing is in fair condition from RP 4.7 to RP 6.5. Numerous pavement failures were observed along the roadway and are described below.

• Transverse cracks the full width of the roadway (24 feet) were observed throughout the 6.5-mile alignment. The majority of these cracks have been previously sealed and were wide (3/4 inches wide or wider), as indicated on the attached photographs. The transverse cracks also generally became wider near the pavement edges and the seal material was no longer present, which resulted in vegetation growing out of the cracks. Table 1 below summarizes the full-width transverse cracks observed during the reconnaissance. We wish to point out that these cracks were counted while driving approximately 5 miles per hour and therefore should be considered approximate. Site specific crack mapping was not performed. The transverse cracks were

Project 18-3763G Page 4 generally located at spacings ranging from about 10 feet to 150 feet with an average spacing of 90 feet.

Table 1. General Summary of Old Divide Road Transverse Cracks

Size(1) Condition Quantity Total Length, feet(2)

Large Unsealed 3 (1%) 72

Small Unsealed 138 (37%) 3312

Large Previously Sealed 215 (59%) 5160

Small Previously Sealed 11 (3%) 264

TOTAL 367 8808 feet = 1.7 miles

(1) Cracks 3/4" or larger were considered large, while cracks less than 3/4" were considered small.

(2) Old Divide Road width is approximately 24 feet, multiplied by quantity.

• Partial transverse cracks were also commonly observed along the roadway, typically ranging from about 3 to 10 feet long. About half of these cracks had been previously sealed. We estimate approximately 1500 feet of partial transverse cracks along the project.

• Longitudinal cracking was also observed along the roadway, mostly down the centerline but also in the driving lanes and near the pavement edges. Similarly, about half of these cracks had been previously sealed. Longitudinal cracks were more difficult to count the frequency and estimate the length, but they typically ranged from about 20 feet to 150 feet long. We roughly estimate approximately 2000 feet of longitudinal cracks.

• About two dozen failed pavement areas consisting of alligator cracking or patches were observed along the roadway. Several of these areas are also indicated in the attached photographs. Table 2 below summarizes the distressed pavement areas and their anticipated extents for digouts.

Table 2. Distressed Pavement for Old Divide Road Digouts.

Approximate Reference Point Distress Description Anticipated Digout

Dimensions, WxL

1.1 Alligator cracking and moderate rutting in NB wheel path 6' x 130'

1.5 Alligator cracking and moderate rutting in NB wheel path 6' x 10'

1.8 Existing patch in NB wheel path 6' x 12'

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Reference Point Distress Description Anticipated Digout

Dimensions, WxL

2.1* Existing patch, full width for culvert settlement 24' x 30'

2.7 Alligator cracking and severe rutting in NB wheel path 6' x 26'

2.8 Alligator cracking and severe rutting in NB wheel path 12' x 60'

2.8 Alligator cracking in NB wheel path 6' x 33'

3.6 Alligator cracking in NB wheel path 6' x 27'

3.6 Alligator cracking and severe rutting in SB wheel path 8' x 33'

4.0 Existing surfacing patch, cause unknown 12' x 165'

4.2 Alligator and block cracking, full width 24' x 20'

4.2 Alligator cracking along CL 12' x 10'

4.2 Alligator cracking and minor rutting in NB wheel path 6' x 50'

4.3 Alligator cracking in NB and SB wheel paths 24' x 15'

4.5 Rough surface, possible patch 14' x 50'

4.6 Alligator cracking and minor rutting in SB lane 12' x 48'

4.7 Isolated alligator cracking in 3 areas of SB lane 8' x 42'

4.9 Alligator cracking and minor rutting in NB lane 6' x 12'

4.9 Alligator cracking and severe rutting in NB lane 12' x 135'

5.3 Alligator cracking and moderate rutting in NB lane 12' x 85'

5.3 Alligator cracking and moderate rutting in SB lane 12' x 25'

5.5 Alligator cracking and minor rutting in NB wheel path 6' x 80'

5.7 Existing patch, and alligator cracking, full width 24' x 200' NB-Northbound, SB-Southbound, CL-Centerline, W-Width, L-Length

* Also need to repair erosion channel on shoulder.

B.2.c. Old Divide Road Geotechnical Features. Geotechnical features observed along the project are described below.

• Rock outcrops relatively close to the pavement edge were observed at RP's 0.8, 0.85, 3.4, 3.5, 3.8, and 4.2 and some are shown in the photographs. These outcrops were typically about 10 to 15 feet from the pavement edge. Some of the outcrops appeared to impair the sight distance while driving.

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• Barn-roof shaped embankments were common throughout the alignment. In general, the fill slopes across drainages and coulees ranged from about 5 to 30 feet deep. The barn-roof shape of the embankment is associated with a 1:1.5 (V:H) fill-slope in the top half of the embankment transitioning to a steeper 1:1 slope in the bottom half. These barn-roof embankments at fill slopes are a safety concern, but common along county roads.

• A fill slope slump was observed in the pavement at RP 2.3, and several photographs are attached.

The fill slope slump was located primarily in the southbound lane but did appear to transition to the full width of the pavement. We estimate that the fill slope slump is 200 feet long and has resulted in about 1 to 2 inches of abrupt differential movement across the pavement surface.

B.3. Fattig Creek Road Pavement Conditions Based on our observations, it is our opinion the existing pavement is in very good condition from RP 0.0 to 1.0, then in fair condition from RP 1.0 to RP 2.0. Our observations are described below.

• It appears that a chip seal has recently been placed across the pavement, making it more difficult to visually observe surface defects and distress. The only surface defect observed from RP 0.0 to

1.0 was some minor surface bleeding of the chip seal, and gouges from snowplows.

• Pavement millings were placed by Musselshell County as the surfacing from RP 1.0 to 2.0. Only four isolated areas of pavement distress and deterioration were observed along this extent of the project, which are summarized in Table 3 below.

Table 3. General Summary of Fattig Creek Road Distressed Areas and Repairs.

Reference Point Distress Description Anticipated Repair

1.2 Alligator cracking and severe rutting in EB lane 10' x 40' Digout

1.2 Patch in EB lane due to reported mine subsidence

Continue adding pavement as settlement occurs in the future.

1.8* Alligator cracking and moderate rutting in WB wheel path 5' x 9' Digout

1.8* Alligator cracking and moderate rutting in WB wheel path 6' x 27' Digout

* In addition to digout, shoulder needs to be graded to promote surface water runoff away from pavement, assume RP 1.6 to 2.0.

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• Washboard surface was present in isolated areas from RP 1.0 to RP 2.0. It is likely the gravel surfacing on which the millings were placed was wash-boarded prior to placement, and the millings followed the pattern.

B.4. Soil Boring Results

B.4.a. General. Subgrade borings SG19-1 through SG19-15 were performed along the 6.5-mile long Old Divide Road, at approximately 1/2-mile intervals. These borings were performed on October 23 and 24, 2019. Borings SG19-16 through SG19-18 were performed along Fattig Creek Road from reference point 1.0 to 2.0 also at 1/2-mile intervals. These borings were performed on October 25, 2019. Traffic control was provided during the drilling.

All of the borings were performed to a depth of 5 feet, except for Boring SG19-7 in the existing slump, which was performed to a depth of 19 feet. The borings were performed with a truck-mounted Diedrich D-120 core and auger drill. Prior to drilling, we decided to obtain 4-inch diameter cores of the existing surfacing in Borings SG19-1 through SG19-15 to permit better observations of the existing surfacing.

While drilling, we also measured the existing base and subbase materials to the nearest 1/4-inch. Bag samples of the existing base as well as bulk bag samples of the subgrade were obtained from select borings.

Log of Boring sheets indicating the depth and identification of the various soil and bedrock strata, penetration resistances, laboratory testing data, and water level information are attached. It should be noted, the depths shown as boundaries between the existing pavement materials and subsurface strata are only approximate. Fairly significant variations occur between these borings, the nature and extent of which can only be evaluated by additional borings.

B.4.b. Old Divide Road Pavement and Subgrade Conditions. Table 4 following this page contains a summary of the existing pavement and anticipated subgrade conditions encountered by borings performed along the majority of Old Divide Road. Surfacing core samples indicated unexpected surfacing materials.

Beneath the chip seal, the cores encountered asphalt concrete pavement (ACP) ranging in thickness from 2 to 3 3/4 inches in Borings SG19-1 through SG19-13. Beneath the ACP, these same borings typically encountered existing double shot ranging from 3/4- to 1 3/4-inch thick, underlain by existing recycled cement treated base (CTB) ranging in thickness from 1/2 to 7 1/2 inches. In some cases, the recycled CTB was loose (non-cemented). In about half of these borings, the subgrade was encountered directly beneath the recycled CTB while in the other half existing base course was encountered ranging in thickness from 1 to 5 1/2 inches. The average existing pavement section encountered by these borings is indicated below as well as summarized in Table 4.

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Existing ACP 3.0 inches Existing Double Shot/Recycled CTB 4.4 inches Existing Base 1.3 inches Total Thickness 8.7 inches

Significantly different pavement sections were encountered in the last 1/2 mile of Old Divide Road by Borings SG19-14 and SG19-15. These borings were therefore not included in the average pavement section. Boring SG19-14 encountered 4 inches of ACP underlain by wet lean clay to a depth of 10 inches underlain by asphalt millings to 33 inches. Boring SG19-15 encountered 3 1/4 inches of ACP underlain by base course to a depth of 29 inches.

Table 4. Old Divide Road Existing Pavement and Anticipated Subgrade Conditions up to RP 5.0 Boring SG19-1 SG19-2 SG19-3 SG19-4 SG19-5 SG19-6 SG19-7 Date Drilled 10/23/19 10/23/19 10/23/19 10/23/19 10/23/19 10/23/19 10/24/19 Approx.

Reference Point

0.03 0.35 0.76 1.16 1.57 1.98 2.35

Existing ACP 3¼" 3" 3" 3" 3¾" 3¾" 3" Existing Double Shot 1½" 1" 1" 1¾" 1" 1½" 1½"

Existing Recycled CTB 2¾" 3" ½" 2¼" 10¼" 2½"* 3¾"

Existing Base Course 5½" 3" 1½" 1" --- ¾" ---

Total Thickness 13" 10" 6" 8" 15" 8¼" 8"

Subgrade(1)

Description

Clayey Sand over

Sandy Lean Clay

Sandy Lean Clay Silty Sand Sandy

Lean Clay Sandy

Lean Clay Silty Sand Sandy Lean Clay

ASTM Class SC to CL CL SC-SM CL CL SM CL N-Values 24, 10 25, 7 11, 5 12, 6 13, 4 7, 8 19, 6

Consistency Medium Dense to

Loose

Very Stiff to Firm

Medium Dense to

Loose

Stiff to Firm

Stiff to Soft Loose Very Stiff to Firm

MC 6.9 10.9 6.2, 10.5 11.6 25.9 12.4 8.5, 10.3

Approx.

Optimum MC 10 11-14 10 11-14 11-14 10 11-14

Risk of Subgrade Failure During Surfacing

Low Medium Medium Medium Medium High Low

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Table 4. Old Divide Road Existing Pavement and Anticipated Subgrade Conditions up to RP 5.0 Continued Boring SG19-8 SG19-9 SG19-10 SG19-11 SG19-12 SG19-13 Average Date Drilled 10/24/19 10/24/19 10/24/19 10/24/19 10/24/19 10/24/19 Approx.

Reference Point 2.73 3.14 3.54 3.94 4.46 5.06

Existing ACP 3½" 2½" 3¼" 2" 3½" 3" 3.0" Existing Double Shot --- 1½" 1½" 1¼" ¾" 1" 1.1"

Existing Recycled CTB 4"* 6½"* 2¾" 3¾"(2) 2½" 7½" 3.3"

Existing Base Course --- --- --- 2"(2) --- --- 1.3"

Total Thickness 7½" 10½" 7½" 9" 6¾" 11½" 8.7" Subgrade(1)

Description Silty Sand Silty Sand Silty Sand over Sandstone

Sandy Lean Clay Silty Sand Sandy

Lean Clay

ASTM Class SM SM SM CL SM CL N-Values 8, 4 11, 3 8, 2 8, 3 12, 4 15, 8

Consistency Loose to

Very Loose

Medium Dense to

Very Loose

NT Firm to Soft

Medium Dense to

Very Loose

Stiff to Firm

MC 11.6 11.7 NT 13.4, 20.3 10.1 17.9, 17.5

Approx.

Optimum MC 10 10 10 11-14 10 11-14

Risk of Subgrade Failure During Surfacing

High High Low High Medium Medium

*Loose (non-cemented) CTB, see log.

(2) Layers are inverted, see log.

(3) Sometimes consisted of recycled materials.

NT = Not Tested

- Not included in Average

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Table 5. Fattig Creek Road Existing pavement and Anticipated Subgrade Conditions RP 1.0 to 2.0 Boring SG19-19 SG19-17 SG19-18 Date Drilled 10/25/19 10/25/19 10/25/19 Approx. Reference Point 1.03 1.48 2.00 Asphalt Milling Surfacing 6¼" 9" 8½" Dirty Base Course* 2½" --- --- Base Course --- 2½" 2" Total Thickness 8¾" 11½" 10½" Subgrade(1)

Description Lean Clay with Gravel Sandy Lean Clay Sandy Lean Clay

ASTM Class CL CL CL N-Values 11, 4 8, 18 13, 23 Consistency Stiff to Soft Firm to Very Stiff Stiff to Very

Stiff Moisture Content 12.7, 14.4 12.1, 15.8 13.6, 15.1 Optimum Moisture Content 11-14 11-14 11-14 Risk of Subgrade Failure During Total Reconstruction Medium Medium Low

(1) Anticipated subgrade that will be present beneath the proposed pavement section.

* Previous gravel surfacing left in place referred to as dirty loose base course.

We had been informed that only double shot was present beneath the existing chip seal. Therefore, it appears previous projects along Old Divide Road are not well documented which could result in variable conditions.

Beneath the existing pavement, the majority of the Old Divide Road borings encountered sandy lean clay and silty sand subgrade. Clayey sand was encountered in Boring SG19-1 and sandstone bedrock was encountered in Boring SG19-10.

Boring SG19-7 was performed deeper in the existing slump to assist in evaluation of a deep patch. This boring encountered very stiff to firm sandy lean clay to a depth of 6 1/2 feet where soft and wet sandy lean clay was encountered to a depth of 12 feet. Below 12 feet, the boring encountered stiff sandy lean clay to a depth of 14 1/2 feet where shale bedrock was encountered to the termination depth of 19 feet.

We judged the shale to be weak to moderately strong.

B.4.c. Fattig Creek Road Pavement and Subgrade Conditions. Table 5 above contains a summary of the existing pavement and anticipated subgrade conditions encountered along Fattig Creek Road from reference point 1.0 to 2.0. A relatively similar pavement section and subgrade conditions were encountered by these borings and consisted of 6 1/4 to 9 inches of asphalt millings underlain by 2 to 2 1/2 inches of base course. The base course in Boring SG19-16 was considered "dirty base course"

Project 18-3763G Page 11 while the base course in the other two borings was relatively clean. Beneath the base course, these borings encountered stiff to firm sandy lean clay and lean clay with gravel subgrade.

B.4.d. Groundwater Observations. Groundwater was not observed in any of the borings to their termination depth at the time of our fieldwork. As previously indicated, slump Boring SG19-7 did encounter wet clays from about 6 1/2 to 12 feet. Several weeks or months are usually necessary for groundwater to stabilize in these types of clay soils, and it would have been necessary to install a piezometer to permit long term measurements.

C. Laboratory Test Results

C.1. General After completion of the pavement borings, the samples were returned to our material testing laboratory.

Laboratory tests were performed in accordance with AASHTO standards. Most of the split-spoon samples from the borings were selected for moisture content tests, and the results are indicated on the attached Log of Boring Sheets. Four subgrade samples were selected for classification (sieve analysis and Atterberg limits), Proctor, and CBR tests. To evaluate the quality of the existing base and subbase course, samples from almost all the borings were collected and composite samples were created. Two base composite samples and two subbase composite samples were selected for sieve analysis and Atterberg limit tests and these results are attached. The test methods are outlined in Table 6 below.

Table 6. Test Methods Test Name AASHTO Standard Plasticity Index (Atterberg Limits) T89/T90 California Bearing Ratio, 300 psi Exudation T193 Sieve Analysis T11/T27 Natural Moisture Content T265 Moisture-Density, Standard Proctor T99 Corrosion Tests MDT Procedures

C.2. Moisture Content Tests Moisture content tests were performed on select penetration test samples and bag samples from the borings. The results are indicated on the attached Log of Boring sheets. In general, the subgrade became

Project 18-3763G Page 12 wetter with depth and was typically found to be moist to a depth of about 2 1/2 to 3 feet and then moist to wet.

C.3. Subgrade Tests Laboratory tests on subgrade samples included Atterberg limits, sieve analysis, sulfate, standard Proctor, and California bearing ratio (CBR). The results are summarized in Table 7 below.

Table 7. Summary of Subgrade Laboratory Tests

Boring Depth Atterberg Limits

P200% ASTM

Class

Sulfate

Proctor

CBR

LL PL PI MDD OMC

SG19-1 1½'-3' 16 15 1 30 SM --- --- --- ---

SG19-3 1½'-4' 19 15 4 47 SC-

SM --- 126.0 10.0 8.8

SG19-7 2½'-

6½' 21 14 7 78 CL-

ML 0.1690 123.8 11.5 5.8

SG19-11 1'-5' 23 15 8 67 CL 0.0089 116.8 14.4 5.1

SG19-15 2½'-

5½' 24 14 10 60 CL 0.0047 124.7 11.3 5.6

SG19-17 1½'-5' 22 13 9 69 CL 0.0471 122.2 12.2 3.0

C.4. Base Course Tests Base course samples from four borings were selected for classification tests, and the results are attached.

Two samples classified as poorly graded gravel with silt and sand (GP-GM), one sample classified as silty sand (SM), and one sample classified as well graded gravel with sand (GW).

D. Geotechnical Analysis and Recommendations

D.1. Old Divide Road The significant transverse and longitudinal cracking of the ACP over DBST surfacing is a concern for the roadway. The specific cause of the severe cracking is unknown although there appears to be numerous types of rehabitation projects previously performed along the roadway. It could be that highly absorptive aggregates were used in the DBST, or it may be associated with the rigidity of the underlying recycled CTB base. Considerable field and laboratory investigation, as well as document research and interviews would be necessary to determine the actual cause.

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In our opinion, the first step in pavement preservation is to repair the distressed areas indicated in Table 2 along Old Divide Road. These areas represented distressed pavement associated with alligator cracking and/or patches. Based on the borings, the surfacing failures are occurring due to inadequate pavement section (too thin) to support the traffic. The coal mine along this route does have significant truck traffic, which would cause inadequate pavement sections to fail. The relative extent of the failed areas is indicated in Table 2, and a digout section is described later in this letter.

We then recommend repairing the significant transverse and longitudinal cracks along the roadway.

Table 1 contained a summary of the estimated full-width transverse cracks. Partial transverse and longitudinal cracks estimated at about 3500 feet should also be included. Consideration should be given to performing crack mapping to better define the overall crack types and lengths. For the previously sealed small and large cracks, additional sealant should be placed over top of the existing sealant and at the edges to properly fill the cracks. It is our understanding that this is feasible by qualified contractors.

For unsealed small cracks, they should be crack sealed. For unsealed large cracks, they should be crack filled. Crack filling includes grinding out a portion of the crack.

In our Geotechnical Pavement Reconnaissance Report dated December 28, 2018, we provided three alternatives related to pavement preservation along the project; 1) chip seal only, 2) overlay only, and

3) isolation lift and overlay. It is our understanding that the isolation lift and overlay have been selected for Old Divide Road, which is in conformance with the pavement preservation objectives of the project.

We wish to point out that this approach will only result in surfacing improvements and a slight raise in grade. Major rehabilitation improvements including total pavement reconstruction and widening, vertical and horizontal alignment changes, and flattening of exiting cut and fill slopes was beyond the scope of this project at this time.

The following parameters were used to evaluate an isolation lift and overlay.

Design Period 20 years ADT 650 (per Musselshell County) Percent Trucks 9.5% (per Application) Truck Factor 1.2 Growth Rate 3.0% Change in Serviceability 1.7 Reliability 75% Roadbed Resilient Modulus 5400 psi

Specific traffic analysis results were not available, and we therefore performed a simple equivalent 18-kip single axle (ESAL's) calculation using the computer program DARwin® which is based on the 1993

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AASHTO Guide to Design of Pavement Structures. The results are attached and indicate daily ESAL's of 48, which is considered relatively light traffic. Consideration should be given to performing a more detailed traffic analysis for the Old Divide Road and discussing anticipated plans for the mine.

The above subgrade resilient modulus was calculated from the CBR test results indicated in Table 7. Five CBR tests were performed and ranged from 3.0 to 8.8 with a mean value of 5.7 and a standard deviation of 2.1. A design CBR one standard deviation below the mean was selected, or 3.6 in this case. Using conversions in the 1993 Pavement Design Manual, results in a resilient modulus of 5400 psi.

Pavement rehabilitation was analyzed using a spreadsheet based on the AASHTO 1993 Pavement Design Manual. This spreadsheet is attached and Typicals 1 through 3 address Old Divide Road resurfacing. As these typicals indicate, a 1-inch isolation lift followed by a 2-inch overlay will extend the pavement life 10 years, but not 15 or 20 years. In our opinion, this is a suitable approach for the project, however, reflection cracking will occur within 1 to 3 years. In about 3 years, the surfacing will look very similar to its current appearance.

D.2. Fattig Creek Road Fattig Creek Road was in much better condition than Old Divide Road and, in our opinion, will be easier to rehabilitate. From RP 0.0 to 1.0, the pavement is in very good condition and can be rehabilitated with a chip seal. From RP 1.0 to 2.0, existing millings were placed by the County and used as surfacing along the roadway. The digout areas identified in previous Table 3 should be repaired. As previously indicated, portions of this roadway from RP 1.0 to RP 2.0 have a washboard ride. Assuming the washboard ride is acceptable, it is our opinion a chip seal can also be applied to this portion of the roadway, as well. We anticipate a chip seal will extend the life of this pavement 5 to 8 years with routine maintenance.

D.3. Digout Pavement Section We recommend the following pavement section be used for digout areas along Old Divide Road and Fattig Creek Road.

Plant Mix Surfacing 3 inches Crushed base course, Type C or D 18 inches Geogrid, Stabilization Yes Separation-stabilization nonwoven geotextile, Class 1, Type C Yes

We wish to emphasize that crushed base course over geogrid is recommended for digout areas. Well graded 2-inch minus or 1-inch minus base is needed to help achieve aggregate interlock with the geogrid for bridging over soft, wet clay subgrades. Select borrow is not recommended. Digouts should be

Project 18-3763G Page 15 performed with smooth bladed bucket on a backhoe working off the existing surfacing. No rubber-tired equipment should be allowed within the digout areas and especially on the subgrade.

The extent of the digouts indicated in Tables 2 and 3 were visually determined in a pickup and is based on reference point (mileage). They were not surveyed and are not based on project stationing. We recommend the extents be field verified by the Contracting Officer (CO) during construction.

We also wish to point out that additional pavement failure may have occurred since our reconnaissance or could during construction due to heavy construction equipment traffic. As Table 2 and 3 indicate, the majority of the borings indicate a low to medium risk of construction equipment failures, but 4 of 18 borings indicated a high risk. A contingency should be provided for additional digouts.

D.4. Deep Patch We recommend a deep patch be constructed in the southbound lane of Old Divide Road for the fill slope slump observed at RP 2.3. We recommend assuming this deep patch is 200 feet long and is 5 feet deep.

A conceptual sketch of the deep patch is attached to this report.

D.5. Specifications We recommend that all earthwork, construction, recycling, and paving be performed in accordance with FP-14, Specifications for Construction of Roads and Bridges on Federal Highway Projects.

E. Procedures

E.1. Drilling and Sampling The penetration test borings were performed on October 23 through 25, 2019, with a truck-mounted core and auger drill. Prior to drilling, 4-inch diameter cores of the pavement were obtained from Borings SG19-1 through SG19-15. Sampling for the borings was conducted in accordance with ASTM D 1586, "Penetration Test and Split-Barrel Sampling of Soils." Using this method, we advanced the borehole with hollow-stem auger to the desired test depth. Then a 140-pound hammer falling 30 inches drove a standard, 2-inch OD split-barrel sampler a total penetration of 1 1/2 feet below the tip of the hollow-stem auger. The blows for the last foot of penetration were recorded, and are an index of soil strength characteristics.

E.2. Soil Classifications The existing pavement and soils encountered by the borings by drilling were visually classified and logged by a senior engineering assistant in accordance with ASTM D 2488, "Standard Practice for

Project 18-3763G Page 16

Description and Identification of Soils (Visual-Manual Procedures)." A summary of the ASTM classification system is attached.

E.3. Groundwater Observations About 10 minutes after taking the final sample in the bottom of a boring, our driller probed through the hollow-stem auger to check for the presence of groundwater. Immediately after withdrawal of the auger the driller again probed the depth to water or cave in. The boring was then backfilled and the surface was patched with cold-mix asphalt pavement.

F. General Recommendations

F.1. Basis of Recommendations The analyses and recommendations submitted in this report are based upon the data obtained from the soil borings performed at the locations indicated. Often, variations occur between these borings, the nature and extent of which do not become evident until additional exploration or construction is conducted. This is especially true for existing pavement thicknesses, and when considering the lack of information related to previous projects. A reevaluation of the recommendations in this report should be made after performing on-site observations during construction to note the characteristics of any variations. The variations may result in additional earthwork and pavement costs, and it is suggested a contingency be provided for this purpose.

F.2. Review of Design This report is based on the design of the proposed alignment as related to us for preparation of this report.

It is recommended we be retained to review the geotechnical and pavement aspects of the designs and specifications. With the review, we will evaluate whether any changes in design have affected the validity of the recommendations, and whether our recommendations have been correctly interpreted and implemented in the design and specifications.

F.3. Groundwater Fluctuations We made water level observations in the borings at the times and under the conditions stated on the boring logs. These data were interpreted in the text of this report. The period of observation was relatively short, and fluctuation in the groundwater level may occur due to rainfall, flooding, irrigation, spring thaw, drainage, and other seasonal and annual factors not evident at the time the observations were made. Design drawings and specifications and construction planning should recognize the possibility of fluctuations.

PARTIAL TOPOGRAPHIC SKETCH

Old Divide/Fattig Creek Road South of Roundup, Montana

Drawn by: SK/MBMG Date 12/7/18

Project: 18-3763G

Scale: None FIGURE

Sheet 1 of 1 1

Reference: Signal Mountain and Park Coulee 7.5 Minute Quadrangles, U.S. Geological Survey, North American Datum of 1983

(NAD83), 2017

N or t h

Begin Old Divide Road

Begin Fattig Creek Road

End Old Divide Road

End Fattig Creek Road

GEOLOGIC MAP

Old Divide/Fattig Creek Road South of Roundup, Montana

Drawn by: SK/USGS Date 12/6/18

Project: 18-3763G

Sheet 1 of 1 2

Begin Fattig Creek Road

Tftr

Geologic Map of the Roundup 30’x60’ Quadrangle, Central Montana By Edith M. Wilde & Karen W. Porter, 2000 (Revised 2007)

North `

End Fattig Creek Road

Tfle

BORING LOCATION SKETCH

MT Musselshell 195(1)

Old Divide & Fattig Creek Road Surfacing

Drawn by: Google Date 2016

Project: 18-3763G

Sheet of 3

Begin Fattig Cr. Road

End Fattig Cr. Road

Old Divide & Fattig Creek Road Surfacing

Drawn by: Google Date 2016

Project: 18-3763G

Sheet of 4

Old Divide Road

Old Divide & Fattig Creek Road Surfacing

Drawn by: Google Date 2016

Project: 18-3763G

Scale: None FIGURE 5

Sheet of

End Fattig Cr. Road

Begin Fattig Cr. Road Old Divide Road

RP 0.0 Looking North RP 0.03 Boring SG19-1 Looking South

RP 0.2 Typical Sealed Transverse Crack RP 0.35 Boring SG19-2 Looking North

RP 0.76 Boring SG19-3 Looking South RP 1.1 Transverse Crack

RP 1.16 Boring SG19-4 Looking North RP 1.57 Boring SG19-5 Looking South

RP 1.98 Boring SG19-6 Looking North RP 2.1 Culvert Erosion Hole Adjacent to Pavement

RP 2.3 Fill Slope Slump Pavement Distress RP 2.3 Fill Slope Slump, Pavement Differential Movement

RP 2.35 Boring SG19-7, Performed in Slump, Looking South RP 2.36 Fill Slope in Slump Area, Looking South

RP 2.7 Alligator Cracking and Sealed Transverse Crack RP 2.73 Boring SG19-8 Looking North

RP 2.8 Alligator Cracking and Rutting RP 3.14 Boring SG19-9 Looking North

RP 3.3 Rock Outcrop RP 3.3 Barnroof Fill Slope

RP 3.54 Boring SG19-10 Looking North RP 3.7 Alligator Cracking

RP 3.94 Boring SG19-11 Looking North RP 4.46 Boring SG19-12 Looking North at Intersection with Fattig Creek Road

RP 4.9 Alligator Cracking and Rutting RP 5.06 Boring SG19-13 Looking North

RP 5.7 Rough Patch with Pothole RP 5.72 Boring SG19-14 Note more recent patch

RP 6.40 Boring SG19-15 Looking West RP 6.50 Old Divide and Highway 87 Intersection, Looking East

RP 0.0 Begin Fattig Creek Road, Looking East RP 0.5 Looking East

RP 0.8 Looking East RP 1.03 Boring SG19-16 Looking West, Right Mine Entrance

RP 1.1 Blade-Placed Millings RP 1.2 Alligator Cracking and Rutting Transitioning into Large Patch Related to

Mine Subsidence, Looking East

RP 1.48 Boring SG19-17 Looking East RP 1.5 Shoving and Washboard PMS Surface, Looking East

RP 2.00 Boring SG19-18 End of Project at Cattleguard, Looking East

6.9

13.9

0-3¼" Asphalt Pavement

3¼"-4¾" Emulsified Asphalt Pavement (Double-Shot) 4¾"-7½" Recycled CTB 7½"-13" Base Course (1½" minus, dirty)

Medium dense to loose, moist, brown, Clayey SAND, fine- to coarse-grained, trace gravel. (Fill)

Very stiff, moist, olive brown, low to medium plasticity, Sandy Lean CLAY, trace gravel.

(Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.8' immediately after withdrawal of auger.

Boring then backfilled.

6.9

13.9

SC

CL

0.3 0.4 0.6

1.1

2.5

5.0

Base Sample 7½"-13" Nonplastic P200=7.8%

GP-GM

12/5

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-1

0.0

LOCATION:

SG19-1 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 0.03, 46° 12' 5.80" N, 108° 26' 54.93" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

10.9

0-3" Asphalt Pavement 3"-4" Emulsified Asphalt Pavement (Double-Shot) 4"-7" Recycled CTB

7"-10" Base Course (1" minus, dirty)

Very stiff to firm, moist to wet, brown, low plasticity, Sandy Lean CLAY. (Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.7' immediately after withdrawal of auger.

Boring then backfilled.

10.9

CL

0.2 0.3

0.6

0.9

5.0

18/7

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-2

0.0

LOCATION:

SG19-2 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 0.35, 46° 12' 20.16" N, 108° 26' 42.74" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

6.2

10.5

0"-3" Asphalt Pavement 3"-4" Emulsified Asphalt Pavement (Double-Shot) 4"-4½" Recycled CTB 4½"-6" Base Course (1" minus, dirty) Medium dense to loose, moist, brown, Silty Clayey SAND, fine- to coarse-grained, trace gravel.

(Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 3' immediately after withdrawal of auger.

Boring then backfilled.

6.2

10.5

SC

SM

0.2 0.3 0.4 0.5

5.0

Bulk Bag Sample 1½'-4'

LL=19, PL=15, PI=4

P200=47% MDD=126.0 pcf

OMC=10.0%

CBR=8.8

Note: Sandstone outcrop to south

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-3

0.0

LOCATION:

SG19-3 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 0.76, 46° 12' 30.94" N, 108° 26' 16.93" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

7.1

11.6

0"-3" Asphalt Pavement

3"-4¾" Emulsified Asphalt Pavement (Double-Shot) 4¾"-7" Recycled CTB 7"-8" Base Course (1" minus, dirty) Stiff to firm, moist, olive brown, low to medium plasticity, Sandy Lean CLAY, trace gravel.

(Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.5' immeditely after withdrawal of auger.

Boring then backfilled.

7.1

11.6

CL

0.3 0.4 0.6 0.7

5.0

Base Sample 7"-8"

LL=16, PL=13, PI=3

P200=15%

SM

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-4

0.0

LOCATION:

SG19-4 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 1.16, 46° 12' 37.30" N, 108° 25' 48.59" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

25.9

0"-3¾" Asphalt Pavement

3¾"-4¾" Emulsified Asphalt Pavement (Double-Shot) 4¾"-15" Recycled CTB

Stiff to soft, wet, brown, low to medium plasticity, Sandy Lean CLAY. (Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.6' immediately after withdrawal of auger.

Boring then backfilled.

25.9

CL

0.3 0.4

1.3

5.0

No Base Course

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-5

0.0

LOCATION:

SG19-5 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 1.57, 46° 12' 56.03" N, 108° 25' 34.51" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

12.4

0"-3¾" Asphalt Pavement

3¾"-5" Emulsified Asphalt Pavement (Double-Shot) 5"-6" Loose Reycled CTB (Non-cemented) 6"-7½" Recycled CTB 7½"-8¼" Base Course (1½" minus, dirty) Loose, moist, brown, Silty SAND, fine- to coarse-grained trace gravel. (Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.3'immediately after withdrawal of auger.

Boring then backfilled.

12.4

SM

0.3 0.4 0.5 0.6 0.8

5.0

SCALE:10/23/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-6

0.0

LOCATION:

SG19-6 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 1.98, 46° 13' 16.68" N, 108° 25' 28.29" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

8.5

10.3

11.6

0"-3" Asphalt Pavement

3"- 4¼" Emulsified Asphalt Pavement (Double-Shot) 4¼"- 8" Recycled CTB Very stiff to firm, moist, brown, low to medium plasticity, Sandy Lean CLAY. (Fill)

Soft, moist to wet, brown, low plasticity, Sandy Lean CLAY. (Alluvium)

8.5

10.3

11.6

CL

CL

0.3 0.4

0.7

6.5

No Base Course

Existing Fill Slope Slump Area

Bulk Bag Sample 2½'-6½'

LL=21, PL=14, PI=7

P200=78% MDD=123.8 pcf

OMC=11.5%

CBR=5.8

SCALE:10/24/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-7

0.0

LOCATION:

SG19-7 page 1 of 3

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 2.35, 46° 13' 35.18" N, 108° 25' 29.53" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

19.0

11.1

12.5

Sandy Lean CLAY continued

Stiff, moist, brown, low to medium plasticity, Sandy Lean CLAY, trace gravel and iron oxide staining.

(Alluvium)

SHALE, light gray, fissiled, moderately weathered, weak to moderately strong.

19.0

11.1

12.5

CL

CL

12.0

14.5

21/50-2"

SCALE:10/24/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-7 (cont.)

8.0

LOCATION:

SG19-7 page 2 of 3

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 2.35, 46° 13' 35.18" N, 108° 25' 29.53" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

7.2

SHALE continued

END OF BORING

Water not observed with 19' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 12' immediately after withdrawal of auger.

Boring then backfilled.

7.2 19.4

50-4½",set

SCALE:10/24/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-7 (cont.)

16.0

LOCATION:

SG19-7 page 3 of 3

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 2.35, 46° 13' 35.18" N, 108° 25' 29.53" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

11.6

0"-3½" Asphalt Pavement

3½"-7½" Loose Recycled CTB (Non-cemented)

Loose to very loose, moist, brown, Silty SAND, fine- to coarse-grained, trace gravel. (A1-)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.9' immediately after withdrawal of auger.

Boring then backfilled.

11.6

SM

0.3

0.6

5.0

No Base Course No emulsified asphalt pavement

SCALE:10/24/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-8

0.0

LOCATION:

SG19-8 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 2.73, 46° 13' 55.70" N, 108° 25' 24.91" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

11.7

0"-2½" Asphalt Pavement 2½"-4" Emulsified Asphalt Pavement (Double-Shot) 4"-10½" Loose Recycled CTB Gravel (Non-cemented)

Medium dense to very loose, moist, brown, Silty SAND, fine- to medium-grained, trace gravel.

(Alluvium)

END OF BORING

Water not observed with 3½' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 1.7' immediately after withdrawal of auger.

Boring then backfilled.

11.7

SM

0.2 0.3

0.9

5.0

No Base Course

SCALE:10/24/19 1" = 1'DRILLED BY: S. Robertson

Elev.

PROJECT: 18-3763G

GEOTECHNICAL EVALUATION

Old Divide & Fattig Cr Road Surfacing Mt Musselshell 192(1)

WL

MC

qp RemarksSymbol

BORING:

Depth

DATE:

SG19-9

0.0

LOCATION:

SG19-9 page 1 of 1

L O G O F B O R I N G

Description of Materials

18-3763G

METHOD: 3 1/4" HSA, Automatic

BPF

2511 Holman Avenue P. O. Box 80190

Billings, MT 59108-0190 Phone: 406.652.3930

Fax: 406.652.3944

Old Divide Road, RP 3.14, 46° 14' 15.98" N, 108° 25' 30.22" W

B O

R

IN

G B

P F

W L-

M C

Q P

3.

G

P J

L A

G N

N N

.G

D T

2/

6/

0"-3¼" Asphalt Pavement

3¼"-4¾" Emulsified Asphalt Pavement (Double-Shot) 4¾"-7½" Recycled CTB Moist, brown, Silty SAND, fine- to coarse-grained.

(Decomposed Sandstone)

SANDSTONE, brown, fine-grained, slightly to…