ND FLAP SDN 7NE(1) PVMNT Report_AD.pdf

SUBMITTED TO:

HDR Engineering, Inc.

1670 Broadway, Suite 3400 Denver, CO 80202

BY:

Shannon & Wilson, Inc.

5900 W. 38th Avenue Wheat Ridge, CO 80212

(303) 825-3800 www.shannonwilson.com

PAVEMENT DESIGN REPORT

ND FLAP 7NE(1) Hoffer Lake Access Road

MCCLUSKY, NORTH DAKOTA

April 2025

Shannon & Wilson No: 111688-001

ND FLAP 7NE(1) Hoffer Lake Access Road Pavement Design Report

111688-001 April 2025

PAGE INTENTIONALLY LEFT BLANK FOR DOUBLE-SIDED PRINTING

4/2/2025-Hoffer Lake Revised DRAFT Pavement Design Report 10.25.24 i

Submitted To: HDR Engineering, Inc.

1670 Broadway, Suite 3400 Denver, CO 80202 Attn: Bryant Gonsalves

Subject: PAVEMENT DESIGN REPORT, ND FLAP 7NE(1) HOFFER LAKE ACCESS

ROAD, MCCLUSKY, NORTH DAKOTA

We are pleased to submit this report for the above-referenced project. This report presents our pavement design recommendations and was prepared by the undersigned. Our scope of services was specified in Task Order 007/1000100092729 of Master Agreement Number 1000100082214 with HDR Engineering, Inc. (HDR) dated September 18, 2023.

We appreciate the opportunity to be of service to you on this project. If you have questions concerning this report, or we may be of further service, please contact us.

Sincerely, SHANNON & WILSON, INC.

Brian P. Volmer David A. Varathungarajan, PE Senior Geotechnical Staff Vice President

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CONTENTS

1 Introduction

1.1 General

1.2 Scope of Services

2 Project and Site Description

3 Subsurface Exploration

4 Geotechnical Laboratory Testing

5 Regional Geology

6 Surface and Subsurface Conditions

6.1 Groundwater

6.2 Subsurface Variation

7 Pavement Analysis & Recommendations

7.1 Design Subgrade R-value

7.2 Traffic Loading

7.3 Recommended Pavement Sections

7.4 Frost Susceptibility

7.5 Expansive Subgrade Potential

7.6 Corrosion Testing

8 Construction and Material Specifications

8.1 Site Preparation

8.2 Earthwork

8.2.1 General

8.2.2 Subgrade Preparation and Fill Placement

8.2.3 Proof Rolling and Soft Subgrade Treatment

8.2.4 Undocumented Fill

8.3 Paving Materials

9 Document Review and Construciton Observation

10 Closure

11 References iii

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Exhibits Exhibit 2-1: View facing west along 7th Street NE from about 700 feet west of 5th Avenue NE.

Exhibit 2-2: View facing east with South Hoffer Lake to the right Exhibit 6-1: Existing aggregate surfacing on 7th Street NE Exhibit 7-1: Recommended Pavement Sections for 7th Street NE & Two Recreational Loops.9 Exhibit 7-2: PDDM “Guidance on Subexcavation Depth of Expansive Soils” Exhibit 7-3: Summary of Corrosion Test Results Exhibit 8-1: Superpave FAA Type Selection Guide Exhibit 8-2: Performance Graded (PG) Asphalt Binder Selection Guide Exhibit 8-1: 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: Pavement Design Calculations Important Information

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1 INTRODUCTION

1.1 General

This report summarizes the results of our subsurface exploration and laboratory testing program and presents pavement design recommendations and construction considerations for Federal Highway Administration, Central Federal Lands Division improvements to 7th Street NE and two recreational loop roads which provide access to the Hoffer Lake Recreational Area in McClusky, North Dakota (Project). Our scope of services was completed as part of the Central Federal Lands Highway Division (CFLHD) project ND FLAP SND 7NE(1) Hoffer Lake Access Road and our September 18, 2023 Task Order 007/1000100092729 of Master Agreement Number 1000100082214 with HDR. 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.

1.2 Scope of Services

Shannon & Wilson’s (SW’s) scope of services included:

Coordinating a subsurface exploration program consisting of drilling seven geotechnical borings and performing penetration testing in situ.

Performing geotechnical laboratory testing on selected samples retrieved from the borings.

Developing geotechnical recommendations for the proposed roadway reconstruction (pavement).

Preparing this geotechnical report.

The objective of our geotechnical study 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 SW’s review. The scope of our services did not include evaluating the presence of cultural resources or potentially contaminated soils at or around

111688-001 April 2025 the site. If a service is not specifically indicated in this report, do not assume it was performed.

2 PROJECT AND SITE DESCRIPTION

The Hoffer Lake Recreational Area is located approximately 2 miles north of McClusky, North Dakota (refer to Figure 1). The Project consists of paving about 1 mile of 7th Steet NE (Hoffer Lake access road) and two recreational loop roads, if funding is available. The existing roadways are about 24 feet wide and aggregate surfaced. We understand that the roadways are planned to be paved with hot-mix asphalt concrete pavement (HACP) to reduce the dust generated by traffic on the aggregate surfacing.

The planned paving limits for 7th Street NE begin at the intersection with 5th Avenue NE and end about 1 mile to the west as shown in blue on Figure 2. The limits of pavement for the recreational loop roads are shown in red on Figure 2. We understand the two recreational loop roads total about 0.2 miles of roadway.

The original plans for the Project included an additional about 0.5 miles of paving for 7th Street NE, to the west of paving limits shown on Figure 2. We understand the additional 0.5 miles of paving were removed from the Project scope, because that section of roadway experiences very little traffic.

In the Project area, 7th Street NE is generally constructed on embankment about 5 to 6 feet high. The embankment is taller near the narrow portion of embankment between North and South Hoffer lake (see Figure 2). The exposed height (above waterline in the lake) was about 10 feet at the time of our subsurface exploration. The elevation of the roadway for the recreational loops generally match adjacent grades.

The eastern half mile of 7th Street NE is generally bound by farmland to the north and south. A low (possibly infilled) area was observed from about 1/4 to 1/3 miles west of 5th Avenue NE (see Figure 2 and Exhibit 2-1). 7th Street NE slopes down from the east and west to this low area. The low area was filled with hydrophytic vegetation (cattails).

The western half mile of 7th Street NE is bound to the north and south by campsites and North and South Hoffer Lake (see Figure 2). Two corrugated metal pipe (CMP) conduits, about 2 feet in diameter, are located in the narrow portion of embankment between North and South Hoffer Lake (see Figure 2 and Exhibit 2-2). The top of the CMP conduits were about 2 feet below existing roadway grade. We understand, from telephone conversations with the Garrison Diversion Conservancy District (GDCD), that the CMP conduits do not directly transfer water from one lake to the other (North to South Hoffer Lake), but rather

111688-001 April 2025 hold pump lines that are used to transfer water from one lake to the other. The GDCD indicated, in telephone conversation with SW, that the water levels in the lakes do not reach or at least have not reached the CMP conduit elevations in over 20 years. The water levels in the lakes were about 10 feet below roadway elevation at the time of our onsite exploration in October 2023.

Exhibit 2-1: View facing west along 7th Street NE from about 700 feet west of 5th Avenue NE.

Low area with hydrophytic vegetation.

Exhibit 2-2: View facing east with South Hoffer Lake to the right.

3 SUBSURFACE EXPLORATION

SW performed a field exploration program on October 24, 2023, to explore subsurface conditions within the existing roadways. The subsurface exploration program consisted of drilling and sampling a total of seven borings designated as borings SW-01 through SW-07.

Refer to Figure 2 for the approximate boring locations. The borings were each advanced to a depth of approximately 6.0 feet.

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.

7th Street NE

East conduit.

West conduit.

South Hoffer Lake

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4 GEOTECHNICAL LABORATORY TESTING

We completed geotechnical laboratory tests on selected samples retrieved from the borings to estimate index and engineering properties. The index tests included natural water content, grain size analysis, and Atterberg limits testing. The engineering property tests included moisture-density (Proctor), California bearing ratio (CBR), swell-consolidation, and corrosion testing. The 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.

5 REGIONAL GEOLOGY

A geologic map of Sheridan County (Bluemle, 1981) indicates that the site is underlain by collapsed fluvial plains (sand and gravel) and glacial till deposits (sand and gravel in matrix of silt and clay) from the Coleharbor Group of the Pleistocene (less than about 1.8-million-year-old).

6 SURFACE AND SUBSURFACE CONDITIONS

The existing aggregate surfacing along the access and loop roads is relatively thin, generally 2 to 3 inches thick or less (see Exhibit 6-1). The aggregate surfacing was considered too thin to record at most boring locations.

Exhibit 6-1: Existing aggregate surfacing on 7th Street NE.

We typically encountered subgrade soils consisting of loose to medium dense, silty to clayey sand with various amounts of gravel over medium stiff to very stiff, fat clay. The silty to clayey sand encountered classified as A-2-4 to A-7-6 in accordance with the American Association of State Highway Officials (AASHTO) soil classification system. The fat clay classified as A-7-6.

We logged the upper 1 to 5½ feet (typically silty to clayey sand) as fill. The upper 5 feet of fill material in SW-04 included sandy lean clay. Because we are unaware of documentation for the material type and placement methods associated with the fill, we consider the fill undocumented. It is not uncommon for undocumented fills to contain deleterious materials including previous construction materials and other debris. Also, undocumented fills commonly include loose or soft soil as exemplified by the lower penetration test results on the boring logs.

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Fat clay was encountered about 5 to 5.5 feet below the ground surface (bgs) in borings SW- 01 through SW-04. Fat clay was encountered about 2 feet bgs in boring SW-06. Fat clay was not encountered in SW-05 or SW-07 to the maximum depth of the borings, which was 6 feet.

6.1 Groundwater

Groundwater was not encountered in our borings to the depth drilled. However, fluctuations of groundwater levels at the site are possible and will depend on many factors, including seasonal variations, local precipitation, flood events, and the water levels in North and South Hoffer Lake. It should be noted that groundwater levels measured during drilling only provide an indication of the groundwater level at the date and time of the measurement. The groundwater level may not be indicative of a stabilized groundwater level at that date and time depending on the types of soils, the drilling method used, and the length of time the hole remains open during drilling.

Due to the close proximity of the site to North and South Hoffer Lake, groundwater levels may be anticipated to be at or near the water surface elevations in the lakes. The water level in the lakes was observed to be about 10 feet below roadway elevation at the time of drilling.

6.2 Subsurface Variation

Our observations are specific to the locations, depths, and times noted on the logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions.

Potential variation includes, but is not limited to:

The conditions between explorations may be different.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

We assume that our interpretations of subsurface conditions are representative of subsurface conditions at the site. Unanticipated soil conditions are commonly encountered and cannot be fully determined by taking soil samples or drilling test borings. If subsurface conditions that differ from our observations or interpretation are encountered or appear to be present, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary.

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7 PAVEMENT ANALYSIS & RECOMMENDATIONS

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

Department of Transportation (USDOT) and Federal Highway Administration (FHWA) Federal Lands Highway (FLH) Project Development and Design Manual (PDDM) (USDOT & FHWA, 2018). We understand that due to the dust generation issues only HACP is being considered. Pavement design inputs and calculations are presented in Appendix C.

7.1 Design Subgrade R-value

The subgrade encountered along the roadway varied from A-2-4 to A-7-6 soils. Proctor and CBR testing was performed on two samples:

1. Boring SW-02, Sample Bulk-1, Silty Clayey Sand (SC-SM) [A-2-4],

2. Boring SW-07, Sample Bulk-1, Clayey Sand (SC) [A-7-6].

The sample from boring SW-02 was obtained from the low (possibly infilled) area located about 1/4 to 1/3 miles west of 5th Avenue NE. This sample was observed to be more granular (higher quality subgrade support) than the other subgrade samples. We chose the sample from boring SW-07 as more representative of subgrade conditions based on comparison of index properties to samples from other borings.

The CBR at 95% maximum dry density (standard Proctor) for the sample from boring SW-07 was 4.2%, which according to the AASHTO (1993) Guide for the Design of Pavement Structures correlates to a resilient modulus of about 6,300 pounds per square inch (psi). We assume that the 6,300 psi resilient modulus obtained from our laboratory testing is representative of onsite subgrade conditions.

7.2 Traffic Loading

We understand that site specific traffic loading/traffic counts are not available, but that the roadway has “very low” traffic volumes based on discussions with HDR. Therefore, we assumed an 18-kip equivalent single axle load (ESAL) of 50,000, which is the minimum traffic loading for paved roads according to the PDDM (USDOT & FHWA, 2018).

7.3 Recommended Pavement Sections

We assumed that the existing grade will be raised the thickness of the planned pavement section along most of the roadway, with the exception of the tie-in at 5th Avenue NE where the existing grade is presumed to be maintained.

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In accordance with the PDDM (USDOT & FHWA, 2018) we assumed:

A pavement design life of 25 years for the flexible pavement.

An initial and terminal serviceability index of 4.2 and 2.0, respectively (assuming an average daily traffic [ADT] volume of less than 500).

A design reliability of 75%, which applies to roadways with less than 2,500 ADT.

A standard deviation for design of 0.49, which applies to flexible pavement.

According to the PDDM (USDOT & FHWA, 2018), "historical performance has shown when a granular layer such as an aggregate base or subbase course contributes to at least 35 percent of the design SN [structural number] the pavement performs satisfactorily". SW agrees that HACP over a granular base course typically perform better than full depth HACP sections. Therefore, we provide pavement section alternatives that consist of HACP over crushed aggregate base course (CAB). Because it was relatively thin, the existing aggregate surface was neglected in our pavement analyses.

Our pavement design calculations are included in Appendix C. Exhibit 7-1 presents a summary of our recommended preliminary pavement section alternatives.

Exhibit 7-1: Recommended Pavement Sections for 7th Street NE & Two Recreational Loops

Design

ESALS

Paving Alternative

Preliminary Pavement Section1,2,3

Estimated Grade Raise

Alt.1 3 inches of HACP over 7 inches of CAB 10 inches

50,000

Alt.2 3.5 inches of HACP over 6 inches of CAB 9.5 inches

Alt.3 4 inches of HACP over 5 inches of CAB 9 inches

Alt.4 4.5 inches of HACP over 4 inches of CAB 8.5 inches

NOTE:

A layer coefficient of 0.39 was assumed for HACP.

A layer coefficient of 0.13 was assumed for CAB.

Assumes subgrade will be scarified, moisture conditioned, and recompacted to a minimum depth of 6 inches.

ESAL = Equivalent Single Axle Loading; HACP = Hot Mix Asphalt Concrete Pavement; MAB = Crushed Aggregate Base Course

A layer coefficient of 0.39 was used for the HACP, which (according to the PDDM) is consistent with bid item 403 in the USDOT and FHWA Federal Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (USDOT & FHWA, 2014). A layer coefficient of 0.13 was used for the CAB, which is consistent (according to the PDDM) with bid item 301 in FP-14 (USDOT & FHWA, 2014).

7.4 Frost Susceptibility

According to the “Design Pamphlet for the Determination of Design Subgrade in Support of the 1993 AASHTO Guide for the Design of Pavement Structures” by the Federal Highway

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Administration (FHWA) (1997), the silty to clayey sand and sandy clay encountered onsite ranges from slight to high potential frost action and the fat clay ranges from medium to very high potential frost action.

In accordance with the PDDM, typical treatment for frost susceptible soils consists of confirming there is an adequate pavement layer structure to account for the loss of bearing capacity during the spring thaw and removing or replacing highly frost susceptible soil for a portion of the expected frost depth. Based on our experience on past CFLHD projects and recommendations in the PDDM, we understand it is cost prohibitive to provide protection against frost heave on smaller projects. If this is not the case, we recommend removal and replacement with non-frost susceptible material to the full 4.5-foot minimum frost depth indicated by the North Dakota Department of Transportation (NDDOT) Design Manual (NDDOT, 2023a).

7.5 Expansive Subgrade Potential

Lean to fat clay was encountered onsite and the potential for soil expansion or heave may exist in these materials. The PDDM (USDOT & FHWA, 2018) provides a table for guidance on subexcavation depths as a function of Atterberg limits (see Exhibit 7-2).

Exhibit 7-2: PDDM “Guidance on Subexcavation Depth of Expansive Soils”

Plasticity Index (PI) Liquid Limit (LL) Depth of Subexcavation

15 – 25 < 50 2 feet

25 – 35 50 – 60 2 – 4 feet

> 35 > 60 4 – 6 feet

NOTE:

Table 7-2 is reproduced from the USDOT and Federal Highway Administration (FHWA) Federal Lands Highway (FLH) Project Development and Design Manual (PDDM) (USDOT & FHWA, 2018)

For the silty to clayey sand and sandy clay, our testing indicated that the liquid limit (LL) varies from about 22% to 44% and the plasticity index (PI) varies from about 6% to 25%. According to the PDDM (Exhibit 7-2) this corresponds to a subexcavation depth of about 2 feet; however, swell/consolidation testing on a sample of the sandy clay with a LL of 37% and PI of 25% indicated negligible (0.1%) collapse potential (see FigureB-3). Based on the Atterberg limits and swell/consolidation testing performed, the risk of potential heave from the silty to clayey sand and sandy clay encountered is considered low.

For the fat clay, our testing indicated a LL of about 60% and PI of about 37%. According to PDDM (Exhibit 7-2) this corresponds to a subexcavation depth of about 4 to 6 feet. A testable, undisturbed sample of the fat clay for swell/consolidation testing was not recovered. The fat clay; however, was encountered about 5 feet deep or deeper in all

111688-001 April 2025 borings except SW-06 where it was encountered at a depth of about 2 feet. Also, the fat clay was observed to have a relatively high moisture content (typically about 25% to 40%). Due to the depths at which the fat clay was typically encountered and its relatively high moisture content, the risk of potential heave from the in-place fat clay is considered low for most of the Project provided it is not allowed to dry during construction.

We recommend that the subgrade be scarified, moisture conditioned, and recompacted to the minimum depth of 6 inches in accordance with FP-14 (USDOT & FHWA, 2014).

7.6 Corrosion Testing

The soil encountered at the Project site can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, samples were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are summarized in Exhibit 7-3 and in Table B-1 in Appendix B.

Exhibit 7-3: Summary of Corrosion Test Results

Boring

Sample Depth (feet) Material Type pH

Resistivity (ohm-cm)

Sulfates

Chlorides

SW-01 0.0 to 2.0 Fill: clayey sand (SC, A-4) 6.7 2,470 0.01 0.021

SW-02 0.3 to 4.2 Fill: silty, clayey sand (SC-SM, A-2-4) 8.7 1,860 < 0.01 0.017

SW-04 0.8 to 2.0 Clayey sand (SC, A-2-6) 6.6 1,200 0.02 0.040

According to Roberge (2012), resistivity values between 1,000 to 3,000 ohm-cm indicate highly corrosive conditions. Based on Roberge (2012), the resistivity results indicate highly corrosive conditions.

The concentration of water-soluble sulfates measured between about 0.01% and 0.02% by weight. Based on classifications as defined by the American Concrete Institute (ACI) Building Code Requirements for Structural Concrete (ACI-318-19), these test results indicate a negligible degree of sulfate attach on concrete exposed to site soils (exposure class S0). We typically; however, recommend Class S2 sulfate resistance for all concrete structures, except prestressed concrete members, to protect against potential sulfate attack.

The test results and the above discussion are provided to assist the designer in the selection of Project materials, concrete type, or other features with respect to corrosion. As appropriate, the designer should consider protective measures, such as coatings, upsizing for section loss, or using alternative materials to reduce the corrosion potential.

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8 CONSTRUCTION AND MATERIAL SPECIFICATIONS

The applicability of the design parameters in Section 7 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 the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 U.S. (USDOT & FHWA, 2014). The following sections provide additional construction considerations for this Project.

8.1 Site Preparation

All surface and subsurface structures associated with current development of the site and other deleterious material should be removed. Any existing surficial topsoil and soil containing visible organics should be stripped and removed from all areas.

8.2 Earthwork

8.2.1 General

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

8.2.2 Subgrade Preparation and Fill Placement

Proper subgrade preparation is required for adequate pavement performance. The subgrade should be prepared in accordance with FP-14 Section 204. We recommend scarifying the upper 6-inches of subgrade (in accordance with FP-14 Section 204.06), compacting the scarified base course to FP-14 requirements, and then preforming a proof roll on the compacted subgrade in accordance with Section 7.2.3.

All subgrade material and fill should be compacted to a dense/firm and unyielding condition.

On-site subgrade and fill materials should be compacted to at least 95 percent maximum density, as determined by AASHTO T 180 or T 99, as presented in FP-14 Section 204. Fill should be placed in uniform, horizontal layers not exceeding 8 inches in loose thickness for heavy, self-propelled compactors, or 4 inches for hand-operated mechanical compactors.

The appropriate lift thickness will depend on the Contractor’s equipment as well as the moisture content and quality of the fill material.

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8.2.3 Proof Rolling and Soft Subgrade Treatment

We recommend proof-rolling and probing the subgrade to determine its suitability. The compacted surface should be proof-rolled with a fully-loaded, tandem-axle, 10-yard dump truck or equivalent. In areas that are identified as being loose, soft, or yielding during proof-rolling or probing, we recommend:

1. Overexcavating to a depth of 24 inches below the top of subgrade.

2. Installing a high strength geogrid (BX1200, TX5, or equivalent) at the base of the overexcavation.

3. Backfilling and moisture treating the 24 inches with either (a) ¾-inch minus crushed aggregate consisting of well graded sand with silt and gravel or (b) a CAB conforming to FP-14 (USDOT & FHWA, 2014) construction standards.

The amount of potential soft subgrade issues encountered during construction will be dependent on the soil type and moisture content of the subgrade during construction.

Seasonal conditions and construction means and methods will also play a role in the amount of soft subgrade issues encountered. More soft subgrade issues will likely be encountered during the wetter seasons. Also, 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.

Additionally, the subgrade should be protected from drying or wetting in excess of what is required to achieve the specified compaction requirements.

Based on our understanding of the Project and our assumptions, we recommend assuming 15% of the proposed area for roadway improvements will require subgrade stabilization with overexcavation, geogrid, and replacement with granular material (CAB). The actual area requiring subgrade stabilization should be expected to vary as it will depend on the contractor’s means and methods and seasonal/weather conditions before and during construction. The extents of treatment will likely be greater during the wet rather than the dry season and will depend on the means and methods used by the contractor.

Most of our boring logs indicate an increase in moisture with depth. We assume that the grade will be raised by the thickness of the proposed pavement section. If a cut were planned, more soft subgrade issues would have been anticipated. Minimizing cut will decrease the potential to expose soft subgrade soils.

8.2.4 Undocumented Fill

Undocumented fill up to 5½ feet deep was encountered in our borings. Although not observed in our explorations, it is possible that debris or other deleterious materials may be

111688-001 April 2025 present in this material. The contractor should be prepared to handle undocumented fill. If observed during construction, fill containing debris and deleterious material should be removed and replaced with an engineered fill.

Additionally, undocumented fill materials can cause poor subgrade performance.

Considering the proposed construction plans and the history of the roadway (Google Earth imagery indicates that 7th Street NE has been in place since at least 1997), in our opinion there is a relatively low risk of poor performance. However, if the Project team is not willing to accept this risk, all undocumented fill materials should be removed and replaced.

8.3 Paving Materials

Exhibit 8-1 summarizes our recommendations for pavement material selection using FP-14 (USDOT & FHWA, 2014). We assume a single HACP mix design will be used for the improvements. Based on the planned scope of the Project, we assume that the HACP material will meet FP-14 Section 403, which uses local department of transportation mix design.

Only a ½ inch nominal maximum aggregate size (NMAS) gradation with initial, design, and maximum gyratory numbers of 7, 75, and 115, respectively, is provided in the NDDOT Standard Specifications for Road and Bridge Construction (NDDOT, 2023b). Therefore, we assume that gradation and set of gyratory numbers will be used for construction of the

HACP.

We understand that NDDOT selects Superpave mix properties for pavements based on traffic loading. Exhibit 8-1 presents NDDOT’s selection guide for Superpave fine aggregate angularity (FAA) type by one-way daily ESALs.

Exhibit 8-1: Superpave FAA Type Selection Guide

Daily One-way ESALs Superpave FAA Type

<100 & Interstate shoulders FAA 42

100 – 300 FAA 43

> 300 & Roundabouts FAA 45

NOTE:

Reproduced from Hot Mix Asphalt (HMA) Selection Guide (NDDOT, 2021).

ESAL= equivalent single axle load, FAA = fine aggregate angularity

Based on NDDOT’s Superpave selection guide and the low traffic volumes anticipated, we consider an HACP mix corresponding to FAA 42 or higher (FAA 43 or 45) to be applicable

(NDDOT, 2021).

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To determine an appropriate HACP binder for the site, we used software developed by the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) Bind (2008). The LTPP Bind software indicated a performance grade (PG) of PG 58-34 for a 95% reliability, the anticipated traffic loading, and a “fast traffic speed”. Based on the NDDOT binder selection guide for one-way daily ESALs less than 100, a PG 58S-28 is considered applicable (see Exhibit 8-2). However, based on phone conversation with NDDOT Materials and Research in February 2024, we understand PG 58-34 to be a commonly used binder on NDDOT projects. We consider PG 58-34 binder to be appropriate for the Project. LTPP Bind output is provided in Appendix C.

Exhibit 8-2: Performance Graded (PG) Asphalt Binder Selection Guide with MSCR

Daily One-way ESALs PG Binder Grade

<100 & Interstate shoulders PG 58S-28

100 – 200 PG 58S-28 with < 20% RAP PG 58S-34 with ≥ 20% RAP

200 – 1000 PG 58H-34

> 1000 & Roundabouts PG 58V-34

NOTE:

Reproduced from Hot Mix Asphalt (HMA) Selection Guide (NDDOT, 2021).

MSCR = Multiple Stress Creep Recovery, ESAL= equivalent single axle load, FAA = fine aggregate angularity

We understand that NDDOT (2023b) allows HACP lift thicknesses from 1.5 to 3 inches. We recommend tack coats be placed between HACP lifts.

NDDOT (2023a) indicates that the aggregate base course (ABC) for pavements meet NDDOT (2023b) Aggregate Class 5 requirements. The gradation requirements for Class 5 appear to be generally consistent with the FP-14 base grading designation “D” listed in Section 703; however, the FP-14 designation “D” gradation requirements have a narrower range than NDDOT Class 5 (USDOT & FHWA, 2014). We assume that the CAB will meet FP-14 Section 301 and will have an R-value of 80 or higher.

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Exhibit 8-1: Recommended Materials for Pavements

Material FP-14 Specification Additional Requirements/Comments

HACP

Section 403

(NNDOT Section 430)

Aggregate Gradation: 1/2-inch NMAS (NDDOT) PG Binder: PG 58-34

Gyratory Design Number (N): 75 FAA 42 or higher (FAA 43 or FAA 45)

CAB

Section 301 and 703

(NDDOT Section 816) R-value: 80 minimum assumed

Gradation: NDDOT Class 5

Stabilization Geogrid Section 714 Tensar BX-1200 or equivalent product

NOTE:

Corresponding sections from the NDDOT Standard Specifications for Road and Bridge Construction are provided in parenthesis for reference. The NDDOT specifications may or may not be applicable to the project depending on the materials considered.

HACP = hot-mix asphalt concrete pavement; CAB = crushed aggregate base; PG = Performance Grade; NMAS = nominal maximum aggregate size, FAA = fine aggregate angularity

9 DOCUMENT REVIEW AND CONSTRUCITON

OBSERVATION

We recommend that we be retained to review the geotechnical portions of the plans and specifications to determine if they are consistent with our recommendations. In addition, because geotechnical design recommendations are developed from a limited number of explorations and tests, recommendations may need to be adjusted in the field. To this extent, we recommend that Shannon & Wilson be retained to monitor the geotechnical aspects of construction, particularly subgrade preparation, fill placement, and compaction.

This monitoring would allow us to determine that the work is accomplished in accordance with our recommendations.

10 CLOSURE

This report has been prepared for the exclusive use of HDR and the Central Federal Lands Highway Division for the purpose of providing pavement recommendations for the Hoffer Lake Access Road improvements. It should be made available to prospective contractors and/or the Contractor for information on factual data only, and not as a warranty of subsurface conditions.

This pavement design report should not be used without our approval if any of the following occurs:

Conditions change due to natural forces or human activity under, at, or adjacent to the site.

111688-001 April 2025

Assumptions stated in this report have changed.

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

If the site ownership or land use has changed.

More than 5 years have passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses, conclusions, 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 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 has prepared the attached document, "Important Information about Your Geotechnical Report", to assist you and others in understanding the use and limitations of our reports.

111688-001 April 2025

11 REFERENCES

American Concrete Institute (ACI), 2019, Building Code Requirements for Structural

Concrete and Commentary, Farmington Hills, Mich., ACI 318-19.

AASHTO, 1993, AASHTO Guide for Design of Pavement Structures: Washington, D.C., AASHTO, 2 v.

Bluemle, J.P., 1981, Geology of Sheridan County, North Dakota, North Dakota Geological Survey, Bulletin 75 - Part 1, 1:126,720.

Federal Highway Administration (FHWA), 1997, Design Pamphlet for the Determination of Design Subgrade in Support of the 1993 AASHTO Guide for the Design of Pavement Structures.

Federal Highway Administration (FHWA), 2008, LTPPBind 3.0/3.1; available:

https://infopave.fhwa.dot.gov/Page/Index/LTPP_BIND.

North Dakota Department of Transportation (NDDOT), 2021, Hot Mix Asphalt (HMA) Selection Guide, Version: October 22, 2021: Bismarck, North Dakota, Provided to Shannon & Wilson in e-mail attachement by NDDOT Materials & Research on February 28, 2024.

North Dakota Department of Transportation (NDDOT), 2023a, Construction and Planning Design Manual, Chapter III Roadway Design (revised date: 12/8/23); available:

https://www.dot.nd.gov/manuals/design/designmanual/Chapter%203.pdf.

North Dakota Department of Transportation (NDDOT), 2023b, Standard Specifications for Road and Bridge Construction: Bismarck, North Dakota.

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

U.S. Department of Transportation (USDOT) and Federal Highway Administration (FHWA), 2014, Federal Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14: USDOT and FHWA.

U.S. Department of Transportation (USDOT) and Federal Highway Administration (FHWA), 2018, Federal Lands Highway Project Development and Design Manual (PDDM): USDOT and FHWA.

https://infopave.fhwa.dot.gov/Page/Index/LTPP_BIND https://www.dot.nd.gov/manuals/design/designmanual/Chapter%203.pdf

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

MC Clusky Municipal

Airport

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State of North Dakota, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, EPA, NPS, USDA, Maxar

0 1 2

Miles

ND FLAP 7NE(1) Hoffer Lake Access Road McClusky, North Dakota

April 2025

VICINITY MAP

FIG. 1

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Project Location

Project Location

Hoffer Lake

Minot

Bismarck

Fargo

CANADA

April 2025

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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 Classification System ........................................................................................ A‐1

A.2.2 Standard Penetration Test (SPT) ............................................................................ A‐1

A.2.3 Shelby Tube Sampling ............................................................................................. A‐2

A.2.4 Bulk Sampling .......................................................................................................... A‐2

Figures Figure A‐1: Soil Classification and Log Key

Figures A‐2 through A‐8: Logs of Borings SW‐01 through SW‐07

Figures A‐9 through A‐15: Photographs of Boring Locations

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A.1 INTRODUCTION

Shannon & Wilson conducted a field exploration program on October 24, 2023 that consisted of drilling seven borings designated SW‐01 through SW‐07, at the locations shown on Figure 2. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The drilling was coordinated (including subcontractor coordination and utility locates) and observed by Shannon & Wilson. Individual boring logs are presented in Figures A‐2 through A‐8. The exploration logs represent our interpretation of the contents of the field log and results of select laboratory testing.

The borings were drilled by Materials Testing Services, LLC of Minot, North Dakota (under subcontract to Shannon & Wilson) using a CME 45‐C truck‐mounted drill rig. The borings were advanced with 4‐inch diameter, solid flight augers to depths of about 6.0 feet below the ground surface.

Borings were backfilled with cuttings. Upon completion of the borings, we obtained the locations of the borings using a handheld recreational GPS device. Therefore, the locations of the boring locations should be considered accurate to the degree implied by the methods used.

A.2.1 Soil Classification System

During drilling, 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 (USCS) is summarized in Figure A‐1.

A.2.2 Standard Penetration Test (SPT)

Disturbed samples were obtained 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 24 inches with a 140‐ pound hammer free‐falling a distance of 30 inches. An automatic hammer system was used

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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 N‐values are shown in 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 in Denver, Colorado.

A.2.3 Shelby Tube Sampling

Relatively undisturbed soil/rock samples were obtained using Shelby tube samplers in general accordance with ASTM D1587, Standard Practice for Thin‐Walled Tube

Geotechnical Sampling of Soils. The locations of these samples are shown on the individual boring logs. These samples were collected by using the hydraulic ram of the drill rig to push the thin‐walled tube sample into the soil/rock at the bottom of the borehole at the desired depth. The thin‐walled tube was connected to the drill rods via a rigid sampling head. After pushing, the drill rods were retracted, and the tube was detached from the sampling head. The Shelby tubes were then capped and transported to our office for laboratory testing.

A.2.4 Bulk Sampling

Bulk soil samples were obtained by collecting the drill cuttings from the upper 3.5 feet of borings SW‐02, SW‐04, and SW‐07 and approximately 3.5 to 5.5 feet in boring SW‐07. These samples were placed in sealed 5‐gallon buckets and transported to our laboratory for further analysis and testing.

McClusky, North Dakota

111688-001April 2025

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.

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

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

SS

8-

1_ U

PR

R

W P.

G

PJ

S W

N

EW

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/2 4/

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McClusky, North Dakota

April 2025

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) 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.

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

SS

8-

1_ U

PR

R

W P.

G

PJ

S W

N

EW

.G D

T

/2 4/

23 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)

111688-001

McClusky, North Dakota

April 2025

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 Diameter Elevation Feet Iron Oxide Gallons Horizontal Hollow Stem Auger Inside Diameter Inches Pounds Magnesium Oxide Millimeter Manganese Oxide Not Applicable or Not Available Nonplastic…