SD FTBL BCB 10(1)_Pavement Rpt_20210611.pdf

SUBMITTED TO:

HDR Engineering, Inc.

1670 Broadway, Suite 3400 Denver, Colorado 80202

BY:

Shannon & Wilson, Inc.

1321 Bannock St. Suite 200 Denver, Colorado 80204

(303) 825-3800 www.shannonwilson.com

PAVEMENT DESIGN REPORT

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

STURGIS, SOUTH DAKOTA

June 2021

Shannon & Wilson No: 102700-001

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CONTENTS

1 Introduction

2 Project and Site Description

3 Subsurface Explorations and Laboratory Testing

3.1 Field Investigation

3.2 Geotechnical Laboratory Testing

4 Regional Geology and Subsurface Conditions

4.1 Regional Geology

4.2 Ground Conditions

4.3 Groundwater

5 Roadway Design Recommendations

5.1 Pavement Recommendations

5.1.1 Design Methodology

5.1.2 Swelling Soil

5.1.3 Traffic Loading

5.1.4 Subgrade Soils

5.1.5 Recommended Pavement Section

5.2 Aggregate Surface Recommendations

5.2.1 Aggregate Surface Road Design

5.2.2 Aggregate Road Surfacing Maintenance

6 Construction and Materials Specifications

6.1 Site Preparation

6.2 Earthwork

6.2.1 General

6.2.2 Subgrade Preparation

6.2.2.1 Asphalt Pavement Subgrade

6.2.2.2 Aggregate Surface Reconditioning

6.2.3 Fill Placement, Moisture Conditioning and Compaction

6.2.4 Proof-Rolling

6.3 Paving Materials

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6.4 Corrosion

7 Closure

8 References

Exhibits Exhibit 5-1: Aggregate Surfaced Road Thicknesses Exhibit 5-2: Aggregate Roadway Dust Suppressant Selection Criteria Exhibit 5-3: Aggregate Roadway Dust Origin and Application Criteria Exhibit 6-1: Recommended Materials for Pavements

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan

Appendices Appendix A: Subsurface Explorations Appendix B: Laboratory Test Results Appendix C: Exploration Photographs Appendix D: Pavement Design Calculations Important Information

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1 INTRODUCTION

This report summarizes the results of our subsurface exploration and laboratory testing program and presents pavement design recommendations and construction considerations for the proposed Horse Soldier to Fort Meade Project (the Project) in Sturgis, South Dakota.

Our services were completed in general accordance with our Task Order Agreement No.

010/10001000039985 with HDR Engineering, Inc. (HDR) dated April 19, 2019. Our conclusions and recommendations in this report are based on:

The limitations of our approved scope, schedule, and budget described in our contract;

Our understanding of the Project and information provided by HDR;

Subsurface conditions observed in the borings at the time our explorations were completed; and

The results of testing performed on samples collected from the explorations.

The objective of our pavement studies was to provide recommendations and construction considerations, as presented herein, for the proposed roadway reconstruction. The authorized scope of services was based on this objective and this report should not be used for other purposes without Shannon & Wilson, Inc.’s (Shannon & Wilson’s) review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located east of Sturgis, South Dakota (Figure 1). The Horse Soldier to Fort Meade Backcountry Byway (BCB) also known as Horse Soldier Road and Old Stone Road is accessed from the north via Highway 34 near Fort Meade and from the south off of I-94 Exit

34. The roadway traverses through hilly terrain and is winding through the northern 3 miles of the Project alignment. The southern 1.6 miles has less curves and traverses through flatter terrain. The existing BCB is surfaced with aggregate and is owned and maintained by the Bureau of Land Management (BLM). We understand that traffic is generally light with greater usage during the summer months. Preliminary scoping documents indicate that the Project will include 0.1 miles of flexible pavement at the northern end of the project and the remainder of the alignment will consist of regrading the aggregate surfacing and incorporating dust palliatives. Based on discussions with HDR, we understand that the final length of flexible pavement will be determined during the plan-in-hand field review. Refer to Figure 2 for a project map.

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3 SUBSURFACE EXPLORATIONS AND LABORATORY

TESTING

3.1 Field Investigation

Shannon & Wilson conducted a field exploration program on May 24, 2019, to explore subsurface conditions along the Project alignment. The subsurface exploration program consisted of drilling and sampling eleven borings (designated SW-01 through SW-11) along the BCB, as shown in Figure 2. The borings were advanced to a depth of approximately 5 to 15 feet below the ground surface.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used. Photographs of the drilling locations are included in Appendix C.

3.2 Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index and engineering properties. Index tests included natural water content, grain size analysis, and Atterberg limits. Engineering properties tests included corrosion and Hveem Stabilometer (R-Value). Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content, fines content, and Atterberg limits are also shown on the individual boring logs included in Appendix A.

4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

The BCB is located on the northeastern rim of the Black Hills, an elongated dome type structure that rises out of the northern great plains. The core of the Black Hills is comprised of mostly Precambrian granite and is rimmed by younger Paleozoic to Cenozoic sedimentary rocks on its outer flanks. The site is located about a mile east of Sturgis, South Dakota within the Mesozoic section of sedimentary rocks exposed around the rim of the Black Hills. Based on our review of the Maps Showing Geology, Structure, and Geophysics of the Central Black Hills, South Dakota, the geology of the site consists of primarily

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Cretaceous aged Lakota Formation (Redden and DeWitt, 2009). The Lakota Formation consists of sandstone, mudstone and shale, which is consistent with our observations at the site.

4.2 Ground Conditions

The current roadway consists of aggregate surfacing varying in thickness from 2 to 9 inches at the boring locations. Below the aggregate surfacing, the borings encountered loose to medium dense silty and clayey sand, and soft to stiff clay with varying percentages of sand (American Association of State Highway and Transportation Officials [AASHTO] soil classification A-2-4, A-2-6, A-4, A-6, and A-7-6). Sandstone, claystone, and shale bedrock were also encountered throughout the alignment.

Our observations are specific to the locations, depths, and dates noted on the exploration logs in Appendix A and may not be applicable to all areas of the site. There is no amount of explorations or laboratory testing that can precisely predict the characteristics, quality, or distribution of subsurface conditions at every location throughout the site. Variations in the subsurface conditions may occur between and below the borings. Also, the passage of time or intervening causes (natural and manmade) may result in changes to the conditions of the site and subsurface conditions.

4.3 Groundwater

Groundwater was encountered in boring SW-08 at a depth of 14 feet; the remainder of the borings did not encounter groundwater. Fluctuations of groundwater levels at the site are likely and will depend on many factors, including seasonal variations, local precipitation, and flood events. Groundwater is not anticipated to affect the design or construction of the Project.

5 ROADWAY DESIGN RECOMMENDATIONS

5.1 Pavement Recommendations

Performance of a pavement system depends on the pavement material and thicknesses, subgrade strength, traffic loads and repetitions, design life, and subgrade drainage characteristics. The following sections discuss each of these aspects as they relate to the project. For design of the project, we divided the alignment into two segments. The northern segment starts at the intersection with Highway 34 and extends to boring SW-04, and the southern segment extends from boring SW-04 to the intersection with I-94.

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5.1.1 Design Methodology

Our pavement design and results are based on the design procedures presented in the 1993 AASHTO Guide for the Design of Pavement Structures with guidance from the U.S.

Department of Transportation and Federal Highway Administration (FHWA) Federal Lands Highway Project Development and Design Manual (PDDM), dated March 2008.

Pavement design inputs and calculations are presented in Appendix D.

5.1.2 Swelling Soil

Certain soil formations in South Dakota are susceptible to volume change by swelling/shrinking. This geologic phenomenon has the potential to cause substantial damage to lightly loaded structures, such as pavements, when exposed to water. To provide an indication of the swell potential of near surface soils at the site, we performed Atterberg limits, grain size distributions, and moisture contents on soil samples encountered in our explorations. Based on testing of cohesive subgrade samples from the project site, the Plasticity Index (PI) ranged from 13 to 46, and the Liquid Limit (LL) ranged from 27 to 61.

Section 11.3.2.1.3 of the PDDM specifies that 2 feet of moisture treatment is required for subgrades with a PI between 15 and 25 and an LL less than 50, which is applicable for the majority of the roadway. Some soils tested at the site would necessitate additional moisture treatment, with as much as 4 to 6 feet specified in the PDDM. The PDDM does note that the subexcavation requirements should account for the traffic volume and project significance when selecting a subexcavation depth.

In the northern section of the alignment where new pavement is proposed, the soils were generally sandy and thus have a low risk of swell susceptibility. Therefore, we recommend 8-inches of scarification, moisture conditioning, and proof rolling prior to placing the new pavement section. This should be completed in any areas where the native subgrades are exposed, or in widening areas.

At this time, we understand that permanent pavement sections will not be utilized in the southern section of the alignment. If a permanent asphalt pavement section is used in the southern section of the alignment, grades can be raised or the above-specified over-excavation is cost prohibitive, consideration could be given to scarifying to a depth matching the existing aggregate road surfacing (4 to 6 inches) as discussed in Section 6.2.2, proof rolling and placing the pavement on the existing prepared aggregate surface, provided Central Federal Lands Highway Division (CFLHD) is willing to accept a low risk of swell-related movement.

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5.1.3 Traffic Loading

Traffic counts and assumptions for the BCB were provided by the BLM. The traffic study consisted of an average daily traffic (ADT) of 61 vehicles per day for 2018. Truck traffic distribution were not provided in the traffic study; however, BLM staff estimate around 200 semi-trucks per year and the alignment is used by RV traffic in the summer months. For design we assumed 1 percent 5-axle single trailer trucks (semi-trucks), and 5 percent single unit trucks (RVs). Using the mean value of the flexible pavement equivalency factors provided in the PDDM for each vehicle class, a 25-year design life as indicated for a 4R project and assuming a 2 percent compounded growth rate, we estimated an 18 kip equivalent single axle loading (ESAL) of approximately 29,000 for each traffic lane. Our estimated ESAL calculations are provided in Appendix D. For design of the roadway, we assumed an ESAL of 50,000 based on the minimum recommend ESAL in the PDDM.

5.1.4 Subgrade Soils

As discussed in Section 4.0, the subsurface explorations completed along the of roadway generally consisted of silty sands and clays (A-2-4, A-2-6, A-4, A-6, and A-7-6). To estimate the strength of the subgrade materials, R-value tests were completed on three bulk samples from borings SW-01, SW-04, and SW-10 resulting in R-Values of 79, 27, and 4, respectively.

Laboratory index testing indicated the bulk samples consisted of AASHTO classification A- 2-4, A-2-6, and A-7-6. Due to the variability in subgrade strengths, we divided the alignment into two segments, as discussed in Section 5.1. For the northern segment, R-value tests were completed on samples from borings SW-01 and SW-04, resulting in R-values of 79 and 27, respectively. For this northern segment we used an R-value of 27 to account for potential soil variability. For the southern segment we used test results from boring SW-10, which had an R-value of 4. For the design subgrade strengths, we used an AASHTO correlation between R-value and resilient modulus, which calculates resilient modulus values of 30,276 pounds per square inch (psi) and 3,109 psi for the northern and southern segments, respectively.

5.1.5 Recommended Pavement Section

Using the PDDM procedures and the parameters outlined in Appendix D, we recommend the following pavement section for the northern and southern segments of the Project:

Northern Segment (north of Boring SW-04): 3.0 inches of hot asphalt concrete pavement (HACP) overlying 4 inches of untreated base course

Southern Segment (south of Boring SW-04): 4.5 inches of HACP overlying 6 inches of untreated base course

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5.2 Aggregate Surface Recommendations

5.2.1 Aggregate Surface Road Design

Our analysis is based on the design procedures presented in the 1993 AASHTO Guide for the Design of Pavement Structures, with guidance from the FHWA PDDM and the CFLHD supplement to the PDDM (2010) for aggregate surfaced roads.

For our analysis, we used the resilient modulus from the southern section of the alignment as discussed in Section 5.1.4.

Based on our experience, the aggregate surfaced roads typically require frequent maintenance and re-leveling every 5 years. Therefore, the below sections reflect the minimum recommended traffic loading used for design (an ESAL value of 10,000). For our analysis, we assumed a variable aggregate surface thicknesses ranging from 9 to 12 inches and calculated the anticipated rutting depth as the failure criteria for each thickness. Refer to Exhibit 5-1 for our recommended aggregate surface road sections and corresponding rutting depth.

Exhibit 5-1: Aggregate Surfaced Road Thicknesses

Aggregate Surface Thickness (inches)

Anticipated Rutting Depth (inches)

9 1.7

10 1.5

11 1.4

12 1.3

The aggregate roadway surfacing material should meet the requirements in Section 301 identified in the FP-14 U.S. Customary Units, (U.S. Department of Transportation [USDOT] and FHWA, 2014). An annual loss of aggregate of a 0.5-inch should be anticipated throughout the design life of the alignment.

The existing aggregate road surfacing generally ranged from 4 to 6 inches in thickness in the areas proposed to be improved with gravel surfacing (i.e., the southern portion of the alignment) with isolated areas as much as 9 inches. In areas where grades can be raised, the existing aggregate surfacing could be reused in the final section. For cost estimating purposes, we recommend assuming an existing aggregate surface thickness of 4 inches.

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5.2.2 Aggregate Road Surfacing Maintenance

In our opinion, the most efficient way to avoid excessive maintenance is to have a properly graded road with a crowned driving surface, a shoulder area that slopes directly away from the edge of the driving surface, and a ditch. Rutting occurs in areas where water collects in the roadway wheel path (after the occasional rain event) and saturates the subgrade.

Sheeting surface water away from the road reduces the potential for rutting. We understand this may not be feasible in all areas due to the roadway geometry. In these cases, frequent maintenance of infilling of ruts and regrading may be required, or a more permanent surface treatment should be considered.

Potholes (occurring in the aggregate surfacing) form from the loss of the fine particulate within the aggregate material. The fine particles within the gradation of the aggregate surfacing act as a binder that prevents the coarser sand and gravel sized particles from migrating. The loss of the fine material increases the roadway surface raveling and eventually leads to rutting. One common maintenance method (other than importing new aggregate surfacing material and regrading) is applying a dust suppressant product (or dust palliative).

Dust suppressants work by either adhering or binding the surficial aggregate, chemically changing the fines properties within the aggregate, or increasing the density of the road surface material to prevent fines migration. After reviewing the various types of dust palliatives, in our opinion there are three types that are appropriate for the Project site:

calcium chloride, magnesium chloride, and lignosulfonate (or lignin derivatives). The following exhibits present benefits and limitations of each of the dust palliatives (the table is reproduced from the U.S. Forest Service’s guide for Dust Palliative Selection and Application Guide [Bolander and Yamada, 1999]). Any of the three dust palliatives are suitable for this application.

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Exhibit 5-2: Aggregate Roadway Dust Suppressant Selection Criteria

Dust Palliative Attributes Limitations Environmental Impact

Calcium Chloride

- Ability to absorb water from the air is a function of temperature and relative humidity

- Significantly increases surface tension of water film between particles, helping to slow evaporation and further tighten compacted soil as drying progresses

- Treated road can be regraded and recompacted with less concern for losing moisture and density

- Requires minimum humidity level to absorb moisture from the air

- Doesn’t perform as well as MgCl in long dry spells

- Slightly corrosive to metal, highly to aluminum and its alloys, attracts moisture, thereby prolonging active period for corrosion

- Rainwater tends to leach out highly soluble chlorides

- If high fines content in treated material the surface may become slippery when wet

- Effectiveness when less than 20% solution has performance similar to water

- Water quality impact:

generally negligible if the proper buffer zone exists between treated area and water

- Fresh water aquatic impact:

may develop at chloride concentrations as low as 400 ppm for trout, up to 10,000 ppm for other fish species

- Plant impact: some species susceptible, such as pine, hemlock, poplar, ash, spruce, and maple

- Potential concerns with spills of liquid concentrate

Magnesium Chloride

- Starts to absorb water from the air at 32% relative humidity independent of temperature

- More effective than calcium chloride solutions for increasing surface tension, resulting in a very hard road surface when dry

- Treated road can be regraded and recompacted with less concern for losing moisture and density

- Requires minimum humidity level to absorb moisture from the air

- More suitable in drier climates

- In concentrated solutions, very corrosive to steel (note: some products may contain a corrosive-inhibiting additive); attracts moisture, thereby prolonging active period for corrosion

- Rainwater tends to leach out highly soluble chlorides

- If high fines content in treated material, the surface may become slippery when wet

- Effectiveness when less than 20% solution has performance similar to water

- Water quality impact:

generally negligible if the proper buffer zone exists between treated area and water

- Fresh water aquatic impact:

may develop at chloride concentrations as low as 400 ppm for trout, up to 10,000 ppm for other fish species

- Plant impact: some species susceptible, such as pine, hemlock, poplar, ash, spruce, and maple

- Potential concerns with spills

Organic Non-petroleum:

Lignin Derivatives

- Binds surface particles together

- Greatly increases dry strength of material under dry conditions

- Retains effectiveness during long dry periods with low humidity

- With high amounts of clay, it tends to remain slightly plastic permitting reshaping and additional traffic compaction

- May cause corrosion of aluminum and its alloys

- Surface binding action may be reduced or completely destroyed by heavy rain, due to solubility of solids in water

- Becomes slippery when wet, brittle when dry

- Difficult to maintain as a hard surface, but can be done under adequate moisture conditions

- Water quality impacts:

none

- Fresh water aquatic impacts: BOD may be high upon leaching into a small stream

- Plant impacts: none

- Potential concern with spills

NOTES:

BOD = biochemical oxygen demand; MgCl = Magnesium Chloride; ppm = parts per million

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Exhibit 5-3: Aggregate Roadway Dust Origin and Application Criteria

Dust Palliative Origin Application

Calcium Chloride

- By-product in the form of brine from manufacture of sodium carbonate by ammonia-soda process and of bromine from natural brines

- Three forms:

Flake, or Type I, @ 77 to 80% purity Pellet, or Type II, @ 94 to 97% purity Clear Liquid, @ 35 to 38% solids

- Generally 1 to 2 treatments per season

- Initial application:

Flake: @ 0.5 to 1.1 kg/m2, typical application 0.9 kg/m2 @77% purity Liquid: 35% to 38% residual @ 0.9 to 1.6 L/m2, typical application is 38% residual concentrate applied undiluted @ 1.6 L/m2

- Follow-up: apply @ 1/2 to 1/3 initial dosage

Magnesium Chloride

- Occurs naturally as brine (evaporated)

- Generally 1 to 2 treatments per season

- Initial application:

28 to 35% residual @ 1.4 to 2.3 L/m2, typical application is 30% residual concentrate applied undiluted @ 2.3 L/m2

- Follow-up: apply @ 1/2 initial dosage

Organic Non-petroleum:

Lignin Derivatives

- Water liquor product of sulfite paper making process, contains lignin in solution

- Composition depends on raw materials (mainly wood pulp) and chemicals used to extract cellulose;

active constituent is neutralized lignin sulfuric acid containing sugar

- Generally 1 to 2 treatments per season

- 10 to 25% residual @ 2.3 to 4.5 L/m2, typical application is 50% residual concentrate applied undiluted @ 2.3 L/m2 or 50% residual concentrate applied diluted 1:1 w/water @ 4.5 L/m2

- May be advantageous to apply in two applications

- Also comes in powdered form that is mixed 1 kg to 840 liters of water and then sprayed

NOTES:

kg = kilogram; kg/m2 = kilogram per square meter; L/m2 = Liter per square meter

6 CONSTRUCTION AND MATERIALS SPECIFICATIONS

The applicability of the design parameters in Section 5.0 is contingent on good construction practice. Poor construction techniques may alter conditions from those upon which our recommendations are based, and therefore result in poor performance. Our analyses assumed that this project is constructed according to FP-14 U.S. Customary Units (USDOT and FHWA, 2014) construction standards. The following sections provide additional construction considerations for this project.

6.1 Site Preparation

In widening areas, we recommend that brush and other vegetation be cleared and roots and stumps be removed from all areas to be graded in accordance with FP-14 Sections 201 and

203. All surface and subsurface structures associated with current development of the site, including pavements, utility poles, fence poles, underground utilities and other deleterious

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102700-001 June 2021 material, should also be removed. Any existing surficial topsoil and soil containing visible organics should be stripped and removed from all areas.

6.2 Earthwork

6.2.1 General

Earthwork, including placement of fill and subgrade preparation, should conform to the requirements provided in the FP-14 U.S. Customary Units, (USDOT and FHWA, 2014) and the recommendations provided in the following sections.

The soil materials can likely be excavated using conventional excavating equipment, such as a rubber-tired backhoe or tracked hydraulic excavator. In some project areas, shallow bedrock was encountered. However, we do not anticipate blasting will be required for rock excavation where this bedrock is encountered.

6.2.2 Subgrade Preparation

Proper subgrade preparation is required for adequate pavement and aggregate surfacing performance, as discussed below.

6.2.2.1 Asphalt Pavement Subgrade

The exposed subgrade for new pavements should be treated to an appropriate depth, as discussed in Section 5.1.2.

6.2.2.2 Aggregate Surface Reconditioning

We recommend that the existing aggregate surface be reconditioned in accordance with FP- 14 Section 303. The full depth of the existing aggregate surfacing should be scarified which will require adjusting the scarification depth in the field. In general, our borings encountered 4 to 6 inches of aggregate surfacing throughout the section of the alignment that will remain aggregate surfaced. After scarification the aggregate should be compacted in accordance with FP-14 Section 302.05 and as discussed in Section 6.2.3.

6.2.3 Fill Placement, Moisture Conditioning and Compaction

Fill material should be free of organics, deleterious material, contaminants, construction debris, and rock fragments larger than 3 inches. Fill material should be placed in horizontal lifts and be compacted to a dense and unyielding condition and to the compaction and moisture requirements in FP-14 Section 204.11.

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The thickness of loose lifts should not exceed 8 inches for heavy equipment compactors and 4 inches for hand-operated compactors, but may be less depending on that required to obtain the above relative compaction.

6.2.4 Proof-Rolling

In aggregate surfacing areas and asphalt pavement subgrade areas, the compacted surface should be proof-rolled with a fully-loaded, tandem-axle, 10-yard dump truck or equivalent.

Areas that are identified as being loose, soft, or yielding during proof-rolling and/or probing should be compacted in place or removed until dense and unyielding subgrade is exposed, then reconditioned or replaced with clean, coarse granular fill material. Care should be taken during proof-rolling and subgrade preparation to avoid disturbing subgrade soils and supporting soils that will remain in place, as they can rut and pump under repeated construction traffic. The final subgrade surface should be sloped to promote positive drainage and kept free of water at all times. Leaving the subgrade elevation high until final grading begins is a means to reduce the potential for disturbance to the final subgrade materials.

6.3 Paving Materials

The following exhibit summarizes our recommendations for pavement material selection.

All specification sections reference the FP-14 U.S. Customary Units, (USDOT and FHWA, 2014).

Exhibit 6-1: Recommended Materials for Pavements

Material Specification Additional Requirements/Comments

UTBC Section 301 Use Gradation C, D, or E

Aggregate Road Surfacing

Section 301 or 302 Refer to Table 703-3 for gradation requirements Fines content: 8.0 - 14.0 percent Plasticity Index: 10+/- 3 Minimum R-Value of 75 Compact according to Section 204.11

HACP Section 401 or 403 1/2-inch NMAS PG Binder: PG 64-28 Gyratory Number (N): 50 or 75

NOTES:

HACP = Hot Asphalt Concrete Pavement; NMAS = Nominal Maximum Aggregate Size; PG = performance grade; UTBC = Untreated Base Course

Regarding the asphalt binder for HACP, the PDDM requires SuperPave performance grade (PG) binders. The PG binders are chosen based on local weather and anticipated traffic level

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102700-001 June 2021 conditions. Using the PDDM guidelines, a minimum of 95 percent reliability is required in terms of binder performance. Using a binder within an appropriate temperature and traffic loading range allows for a higher strength and better durability, and improved cohesion will translate into improved long-term performance. To determine the recommended SuperPave Binder we used the LTPP Bind Version 3.1Beta. We recommend one 3-inch thick lift.

6.4 Corrosion

The subgrade materials encountered at the project site can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, samples of subgrade samples were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Table B-1 in Appendix B.

The resistivity measured in the samples ranged from 302 to 4,995 ohm-centimeters. Based on correlations developed by Roberge (2012), these values suggest an extremely corrosive to corrosive subsurface.

The concentration of water-soluble sulfates measured in the samples was 0.01 percent by weight or less (100 parts per million). Based on classifications as defined by ACI-318-14 (ACI, 2014), these test results suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0).

7 CLOSURE

This report has been prepared for the exclusive use of HDR and Central Federal Lands Highway Division for the purpose of providing pavement recommendations for the Horse Soldier to Fort Meade project. This pavement design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analyses and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule and budget, the analyses, conclusions and recommendations presented in this report were prepared in accordance with generally

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102700-001 June 2021 accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

Shannon & Wilson, Inc. has prepared “Important Information about Your Geotechnical Report,” to assist you and others in understanding the use and limitations of our reports.

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8 REFERENCES

American Concrete Institute (ACI), 2014, Building code requirements for structural concrete and commentary, Farmington Hills, Mich., ACI 318-14.

American Association of State Highway and Transportation Officials (AASHTO), 1993, AASHTO guide for design of pavement structures: Washington, D.C., AASHTO, 2 v.

Bolander and Yamada, 1999, Dust Palliative Selection and Application Guide, U.S.

Department of Agriculture, Forest Service.

Redden, J.A., and DeWitt, Ed, 2009, Maps showing geology, structure, and geophysics of the central Black Hills, South Dakota: U.S. Geological Survey, Scientific Investigations Map SIM-2777, scale 1:100,000.

Roberge, P.R., 2012, Handbook of corrosion engineering, Second Edition: McGraw-Hill, New York, New York.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2008, Federal Lands Highway project development and design manual (PDDM):

U.S. Department of Transportation and Federal Highway Administration.

Available from: http://flh.fhwa.dot.gov/resources/manuals/pddm/.

U.S. Department of Transportation (USDOT), Federal Highway Administration, 2014, Federal standard specifications for construction of roads and bridges on Federal Highway projects, FP-14 English Units: U.S. Department of Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/pse/specs/.

https://ngmdb.usgs.gov/Prodesc/proddesc_86264.htm https://ngmdb.usgs.gov/Prodesc/proddesc_86264.htm http://flh.fhwa.dot.gov/resources/manuals/pddm/ http://flh.fhwa.dot.gov/resources/pse/specs/

VICINITY MAP

FIG. 1

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

Sturgis, South Dakota

Map adapted from aerial imagery provided by Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

June 2021 102700-001

Fi le na m e:

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MT

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Approximate Scale in Miles

PROJECT

BOUNDARY

Sturgis

South Dakota

Project Location

Rapid City

Sturgis 29

Sioux Falls

Fort

Meade

Black Hills

National Cemetery

Map adapted from aerial imagery provided by Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

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Approximate Scale in Feet

SITE AND EXPLORATION PLAN

102700-001June 2021

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

Sturgis, South DakotaGeotechnical Boring Designation and Approximate Location

LEGEND

SW-01

Fort

Meade

SW-03

SW-02

SW-01

SW-04

SW-05

SW-06

SW-07

SW-08

SW-09

SW-10

SW-11

Cemetery Drive

S t o n e

R o a d

O l d

S t o n e

R o a d

FIG. 2

Sheet 1 of 4

Map adapted from aerial imagery provided by Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGrid, IGN, and the GIS User Community.

NOTE

Fi le na m e:

I:

\E F\

D

EN

\1

0s

\1

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FL

S D

H or se S o\ D ra fti ng \F ig ur es \1

0-

1_ Fi g_ 2.

1.

e:

6-

-2 in : k w h

0 300 600

Approximate Scale in Feet

SITE AND EXPLORATION PLAN

102700-001June 2021

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

Sturgis, South DakotaGeotechnical Boring Designation and Approximate Location

LEGEND

SW-01

SW-03

SW-02

SW-01

Source: Esri ArcGIS

SW-03

SW-04

SW-05

M at ch lin e

- S ee B el ow

M at ch lin e

- S ee A bo ve

N a t i o n a l

To Fort Meade

B a c k

Country

B y w a y

To Black Hills

National Cemetery

C e m e t e r y r i v e

S t o n e R o a d

Sheet 2 of 4

Fi le na m e:

I:

\E F\

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EN

\1

0s

\1

C

FL

S D

H or se S o\ D ra fti ng \F ig ur es \1

0-

1_ Fi g_ 2.

2.

e:

6-

-2 in : k w h

0 300 600

Approximate Scale in Feet

SITE AND EXPLORATION PLAN

102700-001June 2021

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

Sturgis, South DakotaGeotechnical Boring Designation and Approximate Location

LEGEND

SW-01

SW-06

SW-05

Source: ESRI ArcGIS

SW-07

SW-08

Map adapted from aerial imagery provided by Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGrid, IGN, and the GIS User Community.

NOTE

M at ch lin e

- S ee B el ow

M at ch lin e

- S ee A bo ve

To Fort Meade

To Black Hills

National Cemetery

S t o a d

O o n e

R o a d

Old Stone Road

O o a d

Sheet 3 of 4

Fi le na m e:

I:

\E F\

D

EN

\1

0s

\1

C

FL

S D

H or se S o\ D ra fti ng \F ig ur es \1

0-

1_ Fi g_ 2.

3.

e:

6-

-2 in : k w h

0 300 600

Approximate Scale in Feet

SITE AND EXPLORATION PLAN

102700-001June 2021

SD FTBL BCB 10(1)

Horse Soldier to Fort Meade

Sturgis, South DakotaGeotechnical Boring Designation and Approximate Location

LEGEND

SW-01

SW-09

SW-10

SW-11

Map adapted from aerial imagery provided by Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGrid, IGN, and the GIS User Community.

NOTE

M at ch lin e

- S ee B el ow

M at ch lin e

- S ee A bo ve

To Fort Meade

Black Hills

National Cemetery

O o a d

O ld S t o n e R o a d

O o a d

Source: Esri ArcGIS

Sheet 4 of 4

6/11/2021-102700-001_AA.docx A-i

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Appendix A: Subsurface Explorations

Appendix A

Subsurface Explorations

CONTENTS

A.1 Introduction ........................................................................................................................... A-1

A.2 Explorations ........................................................................................................................... A-1

A.2.1 Soil and Rock Classification System ...................................................................... A-1

A.2.2 Standard Penetration Test (SPT) ............................................................................ A-2

A.2.3 Modified California (MC) Test and Sampling ..................................................... A-2

A.2.4 Pocket Penetrometer ................................................................................................ A-2

A.2.5 Bulk Sampling .......................................................................................................... A-3

Figures Figure A-1: Soil Description and Log Key Figure A-2 Rock Classification and Log Key Figure A-3 through A-13: Log of Borings SW-01 through SW-11

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A.1 INTRODUCTION

Shannon & Wilson, Inc.’s (Shannon & Wilson’s) field exploration program was conducted on May 24, 2019, and consisted of drilling eleven borings designated SW-01 through SW-11 at the locations shown on Figure 2. Photographs of boring locations are provided in Appendix C. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The borings were coordinated (including subcontractor coordination, utility locates, and traffic control) and observed by Shannon & Wilson. Individual boring logs are presented in Figure A-2. These exploration logs represent our interpretation of the contents of the field logs and select results of laboratory testing. The borings were drilled by Northern Technologies, LLC of Black Hawk, South Dakota (under subcontract to Shannon & Wilson) using a truck-mounted CME 55 drill rig. The borings were advanced with 6-inch diameter hollow-stem augers to depths of approximately 5 to 15 feet. Where encountered, groundwater was measured at the time of drilling. On completion of drilling, the borings were backfilled with cuttings.

A.2.1 Soil and Rock Classification System

During exploration, our representative collected samples and prepared field logs of the explorations. Soil classification for this project was based on ASTM International (ASTM) Designation: D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), and ASTM Designation: D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). The Unified Soil Classification System is summarized in Figure A-1. In addition, samples were classified based on American Association of State Highway and Transportation Officials (AASHTO) Designation M-145, Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes.

The bedrock encountered in the borings was found to be very dense and hard when considered as a lithified soil material. However, when compared with other types of bedrock using the International Society for Rock Mechanics (ISRM) classification of rock strength, the rock resembles a very low strength rock. Therefore, for completeness, the boring logs contain dual descriptions of the bedrock using the Unified Soil Classification System (USCS) and rock classification shown in Figure A-2, where appropriate.

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A.2.2 Standard Penetration Test (SPT)

Disturbed samples were obtained in the borings in general accordance with the Standard Penetration Test (SPT) (ASTM Designation: D1586). The SPT consists of driving a 2-inch outside diameter (O.D.), 1.375-inch inside diameter split-spoon sampler a distance of 18 inches with a 140-pound hammer free-falling a distance of 30 inches. An automatic hammer system was used to advance the samplers. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6-inch increment of penetration and summed the blow counts for the last two 6-inch increments. This sum is recorded as the penetration resistance number, or N-value. If high penetration resistance prevented driving the total length of the sampler, the Shannon & Wilson field representative recorded the partial penetration depth and blow count. The N-values provide a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils (see Figure A-1). The raw N-values are shown on the individual boring logs. Representative portions of the split-spoon sample obtained in conjunction with the SPT were placed in a screw-top plastic jar and transported to our laboratory.

A.2.3 Modified California (MC) Test and Sampling

Samples were also obtained using a modified California (MC) barrel sampler. The MC test procedure is similar to the SPT, except a larger diameter barrel sampler (2½-inch O.D., lined with 2-inch-diameter brass tubing) is used and only driven 12 inches. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6-inch increment of penetration. As a result of the larger diameter, the MC sampler yields slightly higher raw blow count numbers when compared to SPT N-values for similar soils. In our opinion, the blow count numbers are similar between the two samplers. Because the difference in blow counts does not significantly impact our evaluation, we used the field MC blow counts over the 12-inch increment to define the relative density and consistency/stiffness of the subsurface materials following SPT terminology.

A.2.4 Pocket Penetrometer

Select cohesive soil samples were tested in the field using a pocket penetrometer. The penetrometer estimates the unconfined compressive strength of a clay soil by shearing the clay with a one-quarter-inch-diameter penetrometer and measuring the resistance (in units of tons per square foot) with a calibrated spring. Where taken, the field measurements from the pocket penetrometer are shown on the individual boring logs.

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A.2.5 Bulk Sampling

A bulk soil sample was obtained by collecting the drill cuttings from the upper 5 feet of select borings. Approximately 20 to 30 pounds of cuttings were placed in a 5-gallon bucket, sealed with a lid, and transported to our laboratory for further analysis and testing.

Sturgis, South Dakota

102700-001June 2021

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. A-1

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All percentages are by weight of total specimen passing a 3-inch sieve.

2The order of terms is: Modifying Major with Minor.

3Determined based on behavior.

4Determined based on which constituent comprises a larger percentage.

5Whichever is the lesser constituent.

COARSE-GRAINED

SOILS

(less than 50% fines)1

NOTE: Penetration resistances (N-values) shown on boring logs are as recorded in the field and have not been corrected for hammer efficiency, overburden, or other factors.

PARTICLE SIZE DEFINITIONS

RELATIVE DENSITY / CONSISTENCY

Sand or Gravel 4

30% or more coarse-grained:

Sandy or Gravelly 4

More than 12% fine-grained:

Silty or Clayey 3

15% to 30% coarse-grained:

with Sand or with Gravel 4

30% or more total coarse-grained and lesser coarse-grained constituent is 15% or more:

with Sand or with Gravel 5

Very soft Soft Medium stiff Stiff Very stiff Hard

Very loose Loose Medium dense Dense Very dense

RELATIVE

DENSITY

FINE-GRAINED SOILS

(50% or more fines)1

COHESIVE SOILS

< 2 2 - 4 4 - 8

8 - 15 15 - 30

> 30

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

S&W INORGANIC SOIL CONSTITUENT DEFINITIONS

CONSTITUENT2

COHESIONLESS SOILS

Silt, Lean Clay, Elastic Silt, or

Fat Clay 3

PERCENTAGES TERMS 1, 2

Trace

Few

Little

Some

Mostly

WELL AND BACKFILL SYMBOLS

Bentonite Cement Grout

Bentonite Grout

Bentonite Chips

Silica Sand

Perforated or Screened Casing

SHANNON & WILSON, INC.

SOIL DESCRIPTION

AND LOG KEY

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Horse Soldier to Fort Meade

Sturgis, South Dakota

June 2021

GC

SC

Inorganic

Organic

(more than 50% of coarse fraction retained on No. 4 sieve)

MAJOR DIVISIONS GROUP/GRAPHIC

SYMBOL

CH

OH

ML

CL

TYPICAL IDENTIFICATIONS

Gravel

Sand

Silty Sand; Silty Sand with Gravel

Clayey Sand; Clayey Sand with Gravel

Clayey Gravel; Clayey Gravel with Sand

Sheet 2 of 3

Gravels

Primarily organic matter, dark in color, and organic odor

SW

(more than 12% fines)

Silts and Clays

Silts and Clays

(more than 50% retained on No.

200 sieve)

(50% or more of coarse fraction passes the No. 4 sieve)

(liquid limit less than 50)

(liquid limit 50 or more)

Organic

Inorganic

FINE-GRAINED

SOILS

SM

Sands

Silty or Clayey Gravel

Silt; Silt with Sand or Gravel; Sandy or Gravelly Silt

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

HIGHLY-

ORGANIC

SOILS

COARSE-

GRAINED

SOILS

GW

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

(less than 5% fines)

PT

(more than 12% fines)

MH

SP

GP

GM

Silty or Clayey Sand

Silty Gravel; Silty Gravel with Sand

(50% or more passes the No.

200 sieve)

SOIL DESCRIPTION

AND LOG KEY

Elastic Silt; Elastic Silt with Sand or Gravel; Sandy or Gravelly Elastic Silt

Fat Clay; Fat Clay with Sand or Gravel;

Sandy or Gravelly Fat Clay

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

Poorly Graded Sand; Poorly Graded Sand with Gravel

Well-Graded Sand; Well-Graded Sand with Gravel

Well-Graded Gravel; Well-Graded Gravel with Sand

Poorly Graded Gravel; Poorly Graded Gravel with Sand

Lean Clay; Lean Clay with Sand or Gravel; Sandy or Gravelly Lean Clay

Peat or other highly organic soils (see

ASTM D4427)

FIG. A-1

OL

(less than 5% fines)

NOTES

1. Dual symbols (symbols separated by a hyphen, i.e., SP-SM, Sand with Silt) are used for soils with between 5% and 12% fines or when the liquid limit and plasticity index values plot in the CL-ML area of the plasticity chart. Graphics shown on the logs for these soil types are a combination of the two graphic symbols (e.g., SP and SM).

2. Borderline symbols (symbols separated by a slash, i.e., CL/ML, Lean Clay to Silt; SP-SM/SM, Sand with Silt to Silty Sand) indicate that the soil properties are close to the defining boundary between two groups.

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NOTE: No. 4 size = 4.75 mm = 0.187 in.; No. 200 size = 0.075 mm = 0.003 in.

UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)

(Modified From USACE Tech Memo 3-357, ASTM D2487, and ASTM D2488)

102700-001

Horse Soldier to Fort Meade

Sturgis, South Dakota

June 2021

Angular

Subangular

Subrounded

Rounded

Flat

Elongated

Sharp edges and unpolished planar surfaces.

Similar to angular, but with rounded edges.

Nearly planar sides with well-rounded edges.

Smoothly curved sides with no edges.

Width/thickness ratio > 3.

Length/width ratio > 3.

Narrow range of grain sizes present or, within the range of grain sizes present, one or more sizes are missing (Gap Graded). Meets criteria in ASTM D2487, if tested.

Full range and even distribution of grain sizes present. Meets criteria in ASTM D2487, if tested.

Crumbles or breaks with handling or slight finger pressure Crumbles or breaks with considerable finger pressure Will not crumble or break with finger pressure

Weak

Moderate

Strong

VISUAL-MANUAL CRITERIA

A 1/8-in. thread cannot be rolled at any water content.

A thread can barely be rolled and a lump cannot be formed when drier than the plastic limit.

A thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. A lump crumbles when drier than the plastic limit.

It take considerable time rolling and kneading to reach the plastic limit. A thread can be rerolled several times after reaching the plastic limit. A lump can be formed without crumbling when drier than the plastic limit.

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants Sheet 3 of 3

Interbedded

Laminated

Fissured

Slickensided

Blocky

Lensed

Homogeneous

Alternating layers of varying material or color with layers at least 1/4-inch thick; singular: bed.

Alternating layers of varying material or color with layers less than 1/4-inch thick; singular:

lamination.

Breaks along definite planes or fractures with little resistance.

Fracture planes appear polished or glossy;

sometimes striated.

Cohesive soil that can be broken down into small angular lumps that resist further breakdown.

Inclusion of small pockets of different soils, such as small lenses of sand scattered through a mass of clay.

Same color and appearance throughout.

At Time of Drilling…