SD FW MADI 10(2) and 9000(1) PVMT Report.pdf

SUBMITTED TO:

HDR Engineering, Inc.

1670 Broadway, Ste. 3400 Denver, Colorado 80202

BY:

Shannon & Wilson 5900 W. 38th Avenue Wheat Ridge, CO 80212

(303) 825-3800 www.shannonwilson.com

PAVEMENT DESIGN REPORT

SD FTFW MADI 10(2) & 9000(1)

REHAB MADISON

LAKE COUNTY, SOUTH DAKOTA

November 2025 Shannon & Wilson No: 114282-001

SD FTFW MADI 10(2) & 9000(1) REHAB MADISON

Pavement Design Report

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CONTENTS

1 Introduction

2 Project and Site Description

3 Field ExploratIons and Laboratory testing

3.1 Subsurface Exploration

3.2 Geotechnical Laboratory Testing

3.3 Visual Pavement Assessment

4 Subsurface Conditions

4.1 Regional Geology

4.2 Existing Pavements

4.3 Pavement Subgrade Soils

4.4 Groundwater

4.5 Subsurface Variability

5 Pavement Design Recommendations

5.1 Traffic Loading

5.2 Subgrade Soils

5.3 Recommended Pavement Sections

5.4 Full Depth Reclamation (FDR)

6 Additional Considerations

6.1 Expansive Subgrade Potential

6.2 Frost Damage

6.3 Corrosive Soil

7 Construction Considerations

7.1 Site Preparation

7.2 Earthwork

7.2.1 General

7.2.2 Subgrade Preparation and Compaction

7.2.3 Soft Subgrade

7.3 Lime Treated Subgrade (LTS)

7.4 Paving Materials

8 Limitations

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9 References

Exhibits Exhibit 3-1: Visual Pavement Assessment Summary Exhibit 3-2: Access Road Typical Pavement Distress Exhibit 3-3: Parking Lot Typical Pavement Distress Exhibit 4-1: Existing Pavement Section Thickness Exhibit 5-1: Pavement Thickness Design Recommendations Exhibit 6-1: Corrosion Testing Results Exhibit 6-2: Corrosivity Ratings Based on Soil Resistivity Exhibit 6-3: Corrosivity Ratings Based on Water Soluble Sulfate Exposure Exhibit 6-1: Recommended Materials for Pavements

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

Appendices Appendix A: Subsurface Explorations Appendix B: Laboratoy Test Results Appendix C: Drilling Photographs Appendix D: Pavement Design Calculations Important Information About Your Geotechnical Report

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1 INTRODUCTION

This pavement design report summarizes the results of our subsurface exploration and laboratory testing program, and provides pavement design recommendations for the proposed pavement reconstruction of the access road and parking lot of the Madison Wetland Management District Visitor Center in Lake County, South Dakota (the Project).

Our services were conducted in general accordance with Task Order 014_1000100119900 of Master Agreement Number 1000100082214 with HDR Engineering, Inc. (HDR) dated May 20, 2025.

Our scope of services included:

Coordinating a subsurface exploration program, which included observing and logging three geotechnical borings (2 borings along the access road and 1 boring within the parking lot);

Performing geotechnical laboratory testing on selected soil samples retrieved from the borings;

Developing pavement thickness recommendations for reconstruction of the access road and parking lot;

Providing construction consideration for the above Project elements; and

Preparing this pavement design report.

Our scope of services did not include environmental assessments or evaluations regarding the presence or absence of wetlands, or hazardous or toxic substances in the soil, surface water, groundwater, or air, on or below or around this site, or for the evaluation or disposal of contaminated soils or groundwater should any be encountered. 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 at the Madison Wetland Management District (MWMD) Visitor Center, in Lake County, South Dakota, approximately 4 miles southeast of Madison, South Dakota (Figure 1). The Project consists of a single-lane access road that is approximately 0.2-miles long and 18-feet wide that leads from South Dakota Highway 19 to the approximately 7,000-square-foot parking lot for the Visitor Center.

The access road and parking lot are surfaced with asphalt concrete pavement (ACP) that was observed to have signs of distress (refer to Section 3.3). Based on information provided

114282-001 November 2025 by HDR, the proposed improvements are expected to consist of reconstruction of the access road and parking lot.

3 FIELD EXPLORATIONS AND LABORATORY TESTING

3.1 Subsurface Exploration

Shannon & Wilson conducted a subsurface exploration program on June 11, 2025, to explore subsurface conditions at the Project site. The subsurface exploration program consisted of drilling and sampling three borings, designated as SW-01 through SW-03, to depths of approximately 6 to 6.5 feet below ground surface (bgs); see Figure 2 for approximate boring locations. Appendix A presents a discussion of the drilling, sampling, and testing procedures used to complete the borings. Appendix A also presents individual exploration logs and an explanation of the symbols and terminology used.

3.2 Geotechnical Laboratory Testing

We completed geotechnical laboratory testing of selected samples retrieved from the borings to estimate index and engineering properties. The index tests included natural water content, grain size distribution, Atterberg limits, unit weight, and swell/collapse. The engineering property tests included Hveem Stabilometer (R-value), and corrosion.

Laboratory test methods and results are provided in Appendix B.

3.3 Visual Pavement Assessment

A Shannon & Wilson field representative conducted a visual pavement assessment of the existing ACP surfacing to characterize the general pavement conditions. The pavement assessment generally followed the terminology and descriptions provided in the Federal Highway Administration (FHWA) Distress Identification Manual (FHWA, 2014) and included recording typical crack patterns and level of severity of cracking based on typical crack length and aperture. A summary of our observations is provided in Exhibit 3-1, and photographs of typical distress are provided in Exhibits 3-2 and 3-3.

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Exhibit 3-1: Visual Pavement Assessment Summary

Location Observed Pavement Condition Description

Typical Distress Reference

Photographs

Access Road

Majority of cracks were previously sealed with bituminous crack sealant.

Low to moderate severity fatigue, block, and longitudinal cracking.

Moderate to high severity transverse cracking (more than half of cracks were either unsealed or the bituminous crack sealant needs replacement).

Exhibit 3-2

Parking Lot

Moderate to high severity transverse, longitudinal, and block cracking (more than half of cracks were either unsealed or the bituminous crack sealant needs replacement).

Exhibit 3-3

Exhibit 3-2: Access Road Typical Pavement Distress High Severity Transverse Cracking, Moderate Severity Longitudinal Cracking, and Low Severity Fatigue Cracking (Left); High Severity Transverse Cracking (Right).

Exhibit 3-3: Parking Lot Typical Pavement Distress Moderate to High Severity Transverse, Longitudinal, and Block Cracking.

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4 SUBSURFACE CONDITIONS

We based our understanding of the geology and subsurface conditions at the Project site on a review of regional geological maps, the results of our field explorations program, and laboratory testing on select samples retrieved from the borings.

4.1 Regional Geology

Based on a review of a geologic map of the Geologic Map of South Dakota (Martin et al., 2004), surficial soils are mapped as quaternary alluvium. The Quaternary Alluvium is described as clay to boulder-sized clasts with locally abundant organic material with a thickness of up to 75 feet (ft.). Additionally, on the outskirts of the Project site, surficial soils are mapped as till (stagnation moraine) of the Upper Wisconsin. The till is described as compact, silty, clay-rich matrix with sand to boulder-sized clasts of glacial origin with a composite thickness of all Upper Wisconsin till being up to 300 ft.

4.2 Existing Pavements

Existing ACP pavement thicknesses were measured from pavement cores collected at each boring location. Borings SW-01 and SW-02 encountered what appeared to be aggregate surfacing material similar to what was observed around the facilities north of the Project.

Similar aggregate surfacing material was not encountered below the asphalt in boring SW-

03. Exhibit 4-1 summarizes the observed pavement section thicknesses.

Exhibit 4-1: Existing Pavement Section Thickness

Boring

Asphalt(1)

Thickness (inches)

Aggregate Surfacing(2)

Thickness (inches)

SW-01 2.5 3.5

SW-02 3.25 8.75

SW-03 3.25 -

NOTE:

Asphalt thickness was measured for the pavement core.

Aggregate surfacing thickness (where encountered) was measured from the bore hole annulus.

4.3 Pavement Subgrade Soils

The subgrade soils encountered in the borings generally consisted of a layer of artificial fill consisting of medium stiff to stiff, silt with varying percentages of sand (American Association of State and Highway Transportation [AASHTO] soil classification A-5 and A-7-

6) and loose, silty sand (AASHTO A-4 soil), that extended to approximately 2 to 4 feet bgs.

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Below the fill layer, the borings encountered loose to medium dense, poorly graded sand (AASHTO A-2-4 soil).

4.4 Groundwater

Groundwater was not encountered in any of the borings during the subsurface exploration.

It should be noted that groundwater level fluctuations are possible and depend on many factors, including seasonal variations and local precipitation.

4.5 Subsurface Variability

The explorations were completed to evaluate subsurface conditions at the Project site. Our observations are specific to the locations and depths noted on the logs and may not be applicable to all areas of the site. Unanticipated subsurface conditions are commonly encountered, and no amount of exploration can precisely predict the characteristics, quality, or distribution of subsurface and site conditions. Potential variation includes, but is not limited to:

The conditions between and below explorations may be different.

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

Such unexpected conditions frequently require that additional expenditures be made to attain a properly constructed project. Therefore, some contingency fund is recommended to accommodate such potential extra costs. If conditions different from those described herein are encountered during construction, we should be retained to review our description of the subsurface conditions and reconsider our conclusions and recommendations.

5 PAVEMENT DESIGN 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 pavement reconstruction.

Our pavement design and results are based on the design procedures presented in the 1993 AASHTO Guide for the Design of Pavement Structures (AGDPS) (1993), with guidance from the U.S. Department of Transportation and Federal Highway Administration (FHWA) Federal Lands Highway Project Development and Design Manual (PDDM) (2008).

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5.1 Traffic Loading

Based on discussions with HDR, traffic data is not available for the Visitor Center. For pavement design purposes, we assumed an 18-kip equivalent single axle loading (ESAL) of 50,000 based on the minimum recommended ESAL in the PDDM (2008) for low volume roadways with less than 500 vehicles per day.

5.2 Subgrade Soils

The subgrade soils encountered in the subsurface explorations primarily consisted of sandy silt and silty sand overlying poorly graded sand. We performed a single R-value test on the subgrade material encountered in boring SW-02, which indicates an R-value of 17 for the sample tested (AASHTO A-2-4 soil). For the pavement analysis, we used an AASHTO (1993) correlation between R-value and resilient modulus to calculate a resilient modulus value of approximately 10,400 pounds per square inch (psi).

5.3 Recommended Pavement Sections

We considered paving alternatives consisting of full-depth ACP on native subgrade, composite ACP over crushed aggregate base (CAB), full-depth reclamation, and full-depth ACP over lime-treated subgrade (LTS). We did not consider an overlay due to the relatively thin existing pavement and existing transverse cracking, which is likely to cause reflective cracking. Due to the silty subgrade soils, which may be susceptible to pumping and instability (see Section 7.2.3), particularly if exposed to water during construction, we consider paving full depth ACP on the native subgrade to have a higher risk of constructability challenges (i.e., subgrade pumping during paving) than the other alternatives.

Refer to Exhibit 5-1 for the recommended pavement section alternatives. The pavement design calculations are provided in Appendix D. We recommend that all CAB be daylighted to avoid accumulation of water in the subgrade.

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Exhibit 5-1: Pavement Thickness Design Recommendations

Pavement Alternative

ACP

Thickness (inches)

CAB

Thickness (inches)

FDR

Thickness (inches)

LTS

Thickness (inches)

Full Depth ACP 4.5 - - -

ACP over CAB

3.5 4 - -

3 6 - -

ACP over FDR 3.5 - 4 -

ACP over FDR with Cement 3 - 4 -

ACP over LTS 3 - - 6 ACP = Asphalt Concrete Pavement, CAB = Crushed Aggregate Base, FDR = Full Depth Reclamation, LTS = Lime Treated Subgrade

5.4 Full Depth Reclamation (FDR)

FDR generally consists of in-place pulverization of the existing HMA pavement that becomes the base of a new HMA paving subgrade. The surface of the FDR can accommodate minor grading adjustments provided a minimum FDR thickness is maintained. A new HMA surface layer is then paved over the FDR prepared subgrade, typically resulting in an overall raise to the pavement grades, which may also require adjustments to the grade of the sidewalks adjacent to the parking lot.

Rehabilitation with FDR effectively provides a new pavement and eliminates the potential for reflective cracking from the existing pavement. As indicated in Exhibit 4-1, the existing pavement section does not include a CAB layer along the full length of the Project. At a minimum, we recommend placing 1 inch of CAB over the existing asphalt pavement in the parking lot and eastern portion of the access road, and performing a 4-inch-thick FDR.

Portland Cement and water may be added to the FDR prior to final grading and compacting to create a stabilized base layer. FDR with cement should meet the requirements provided in FP-24 Section 305. If the FDR with cement option is selected, a mix design should be completed evaluate the proportioning of the Project materials and to demonstrate the required compressive strength of the stabilized layer may be achieved.

FDR also requires a specialty contractor and equipment. Due to the relatively small amount of pavement included in the Project, full depth reconstruction may be more cost beneficial.

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6 ADDITIONAL CONSIDERATIONS

6.1 Expansive Subgrade Potential

Certain soil formations in South Dakota are susceptible to volume change by swelling and/or shrinking. This geological phenomenon has the potential to cause substantial damage to lightly loaded structures, such as pavements, when exposed to water. To evaluate the potential for swell at the site, we performed two swell/consolidation tests on soil samples encountered in our explorations. The swell tests results indicated nil to 0.1 percent swell, which is consistent with the low swell potential typically exhibited by the silty soils encountered in the borings. Also, soils that have been in place and covered with exiting pavement for a number of years typically have low swell susceptibility. This is due to the pavement inhibiting evapotranspiration of moisture in the subgrade and the subgrade moisture state being allowed to equilibrate.

Provided the existing access road and parking lot have been paved for several years and are not exhibiting swell-related damage, in our opinion, the risk of swell-related damage to the Project pavement is low.

6.2 Frost Damage

Frost susceptible soils can lead to pavement performance issues due to heaving or deformation from ice lenses in the underlying soil and pavement fatigue damage due to thaw-weakened subgrade of the springtime freeze-thaw cycle (FHWA, 2008). Frost susceptible soils typically include fine-grained soils such as silts and clays. In accordance with the PDDM, typical treatment for frost susceptible soils consists of assuring 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, we understand it is cost prohibitive to provide protection against frost heave on such projects. If this is not the case, we recommend partial removal and replacement (up to about 70% of the frost depth of 42 inches (City of Madison, 2025)) and we should be contacted to provided alternative pavement sections based on the import material. If frost mitigation is included, there may be some savings resulting from a reduced pavement section.

6.3 Corrosive Soil

The soil encountered at the Project site can be corrosive to steel and concrete in contact with the ground. To assist in estimating the corrosion potential in the Project area, selected samples were tested for pH, resistivity, water soluble sulfates, and chlorides to assess

114282-001 November 2025 corrosion potential at the Project site. Test results are presented in Exhibit 6-1 and Appendix B.

Exhibit 6-1: Corrosion Testing Results

Boring Depth (feet) pH

Resistivity (ohm-cm)

Sulfate Content

Chloride Content

SW-02 2.5 to 3.5 6.7 5,300 0.01 0.065

SW-03 0.3 to 1.3 - - <0.01 -

NOTES:

Water-soluble sulfate and chloride content values are shown as percent weight in dry soil.

ohm-cm = ohm-centimeter

The resistivity measured in the sample was 5,300 ohm-centimeters. Based on correlations developed by Roberge (2012) as shown in Exhibit 6-2, these values suggest a moderately corrosive subsurface environment for metal in contact with subsurface materials.

Exhibit 6-2: Corrosivity Ratings Based on Soil Resistivity

Soil Resistivity (ohm-cm) Corrosivity Rating

>20,000 Essentially Noncorrosive

10,000-20,000 Mildly Corrosive

5,000-10,000 Moderately Corrosive

3,000-5,000 Corrosive

1,000-3,000 Highly Corrosive

<1,000 Extremely Corrosive

The concentration of water-soluble sulfates measured in the samples was 0.01 and less than

0.01 by weight (100 parts per million and less). Based on classifications as defined by American Concrete Institute (ACI) ACI-318-21 (ACI, 2021) as shown in Exhibit 6-3, these results suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0).

Exhibit 6-3: Corrosivity Ratings Based on Water Soluble Sulfate Exposure

Water Soluble Sulfate in Soil (Percent by Weight)

Sulfate Severity (Class)

<0.10 Negligible (S0)

0.10-<0.20 Moderate (S1)

0.20-2.00 Severe (S2)

>2.00 Very Severe (S3)

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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 or using alternative materials to reduce the corrosion potential.

7 CONSTRUCTION CONSIDERATIONS

The applicability of the pavement design recommendations provided herein is contingent on good construction practices. Poor construction techniques may alter conditions from those on which our recommendations are based, resulting in reduced pavement performance and service life. Our analyses assumed that this Project is constructed according to FP-24 U.S. Customary Units (FHWA, 2024) construction standards. The following sections present additional construction and material considerations for this Project.

7.1 Site Preparation

All surface and subsurface structures associated with current development of the site, including pavement materials, should be removed. Any existing surficial topsoil and soil containing visible organics should be stripped and removed from all areas to be paved.

7.2 Earthwork

7.2.1 General

Earthwork, including placement of fill and subgrade preparation, should conform to the requirements provided in the FP-24 U.S. Customary Units, (FHWA, 2024) and the recommendations provided in the following sections.

7.2.2 Subgrade Preparation and Compaction

Proper subgrade preparation is required for adequate pavement performance. The subgrade should be prepared, moisture conditioned to at or above optimum moisture content, and compacted to at least 95% maximum density, as determined by AASHTO T180 or T99 in accordance with FP-24 Section 204.11.

The compacted surface should then be proof-rolled with a fully-loaded, tandem-axle, 10-yard dump truck or equivalent. All soft, wet, or yielding subgrade areas should be overexcavated, removed, and replaced as described in the following section.

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7.2.3 Soft Subgrade

As discussed above, the subgrade should be prepared in accordance with FP-24 Section 204.11, which includes the use of vibratory of compression-type rollers. The silty subgrade material is prone to pumping and yielding from construction activities when moisture conditioned to near optimum moisture content and may also be prone to pumping when compacted with vibratory equipment. The contractor will need to carefully control the movement of equipment around the site and minimize the passage of equipment over any over-excavated areas. Additionally, it may be preferable to limit the use of vibratory compaction if pumping occurs. Even with these precautions, compaction of the material will be difficult and extra working time may be needed. Placement and compaction testing should be monitored on a full-time basis to assist in this process.

Areas that are identified as being loose, soft, or yielding during proof rolling should be recompacted in place, removed and reconditioned, or overexcavated to depth of 2 feet and replaced with granular fill such as Select Borrow (FP-24 704.07), or Unclassified Borrow (FP- 24 704.06) with the additional requirement of a maximum particle size of 3 inches. If loose, soft, or yielding soils are encountered after over-excavating 2 feet, a geogrid (FP-24 Section 704.03) should be installed at the base of the excavation before backfilling with granular fill.

Lime treatment may also be considered to help stabilize soft subgrade soils.

7.3 Lime Treated Subgrade (LTS)

Based on subgrade conditions encountered in the borings, lime treatment is a suitable option for treating subgrades at the Project site. Lime is typically placed during construction, after the site is graded. The subgrade is then disced, lime added, mixed, and compacted prior to the lime setting up. A chemical reaction occurs between the lime, subgrade soil, and water resulting in a low plasticity, stiff layer.

Soils containing high sulfate concentrations can result in a deleterious reaction between the sulfate ions, soil, and water resulting in long-term heaving in the subgrade soils. Two samples from the subgrade soils were tested for water soluble sulfates and indicated a maximum sulfate content of 0.01%. Based on these test results, treatment for sulfate-rich soils does not appear to be necessary. However, if lime is used, the mix design should include additional sulfate testing to confirm this approach.

LTS requires a specialty contractor and equipment, and subgrade stabilization using methods described in section 7.2.3 may be more cost beneficial. Also, if the LTS option is selected, a mix design should be completed on the subgrade soils that will be treated to ensure that the materials are compatible with lime treatment.

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7.4 Paving Materials

The following exhibit summarizes our recommendations for pavement material selection using the FP-24 specifications. We anticipate that a single ACP mix design will be used for the pavements.

Exhibit 6-1: Recommended Materials for Pavements

Material FP-24 Specification Additional Requirements/Comments

CAB Section 302 Use Gradation C, D, or E

ACP Section 403 ½-inch or ¾-inch Nominal Maximum Aggregate Size (NMAS) PG Binder: PG 64-34 Gyratory Number (N): 75

NOTE:

ACP = Asphalt Concrete Pavement; CAB = Crushed Aggregate Base; PG = Performance Grade

To determine an appropriate ACP binder for the site, we used software developed by the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) Bind (2005). The LTPP Bind software indicated a performance grade (PG) of PG 64-34 for a 95% reliability for the ACP for the site and anticipated traffic loading. Based on binder availability according to the South Dakota Department of Transportation Standard Specifications for Roads and Bridges (2015), PG 64-34 is commonly used in South Dakota.

We recommend a gyratory number of 75 be used for the mix design. ACP lift thicknesses should be between 3 and 4 times the maximum aggregate thickness (e.g., a 3-inch ACP section may consist of a single lift of ¾-inch NMAS aggregate; a 4-inch ACP section should consist of 2 lifts with a ½-inch NMAS aggregate). A tack coat should be placed between subsequent lifts.

8 LIMITATIONS

This report was prepared for the exclusive use of HDR and Central Federal Lands Highway Division for the purpose of providing pavement design recommendations for the 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 analysis and recommendations may be affected.

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

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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 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 and included “Important Information About Your Geotechnical/Environmental Report,” to assist you and others in understanding the use and limitations of our reports.

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9 REFERENCES

American Association of State Highway and Transportation Officials (1993). AASHTO Guide for Design of Pavement Structures: Washington, D.C. (Vol. 2). AASHTO.

American Concrete Institute. (2021). Building code requirements for structural concrete and commentary (ACI 318-21) Farmington Hills, Michigan. American Concrete Institute.

City of Madison, South Dakota. (2025). Code of Ordinances, Supplement 3 Update 1, Chapter 10 - Buildings and Building Regulations.

https://library.municode.com/sd/madison/codes/code_of_ordinances?nodeId=1593

Federal Highway Administration. (2005). LTPPBind Version 3.1 Beta.

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

Federal Highway Administration. (2008). Federal Lands Highway project development and design manual (PDDM): U.S. Department of Transportation and Federal Highway Administration. http://flh.fhwa.dot.gov/resources/manuals/pddm/.

Federal Highway Administration. (2014). Distress Identification Manual for the Long-Term Pavement Performance Program (5th rev. ed., Publication No. FHWA-HRT-13-092), 142 p.

https://fhwa.dot.gov/publications/infrastructure/pavements/ltpp/13092/13092.pdf.

Federal Highway Administration. (2024). Federal standard specifications for construction of roads and bridges on Federal Highway projects (FP-24 English Units). U.S. Department of Transportation and Federal Highway Administration.

http://flh.fhwa.dot.gov/resources/pse/specs/.

Martin, J.E.; and others. (2004). Geologic map of South Dakota (General Map 10). South Dakota Geological Survey.

Roberge, P.R. (2012). Handbook of Corrosion Engineering (2nd ed.). McGraw-Hill, New York, New York.

South Dakota Department of Transportation. (2015). Standard Specifications for Roads and Bridges.

https://library.municode.com/sd/madison/codes/code_of_ordinances?nodeId=15931 https://library.municode.com/sd/madison/codes/code_of_ordinances?nodeId=15931 https://infopave.fhwa.dot.gov/Page/Index/LTPP_BIND http://flh.fhwa.dot.gov/resources/manuals/pddm/ http://flh.fhwa.dot.gov/resources/pse/specs/

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Brookings

Sioux Falls

South Dakota Game Fish and Parks, Esri, TomTom, Garmin, SafeGraph, FAO, METI/NASA, USGS, EPA, NPS, USFWS

0 10 20

Miles

VICINITY MAP

FIG. 1

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Project Location

Project Location

90 Sioux Falls

Pierre

Madison

Sioux Falls

November 2025

SD FTFW MADI 10(2) & 9000(1)

REHAB MADISON

Lake County, South Dakota

November 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 Modified California (MC) Test and Sampling ..................................................... A‐2

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

A.3 Pavement Cores ..................................................................................................................... A‐2

Figures Log Key

Boring Logs

Pavement Core Photographs

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A.1 INTRODUCTION

Shannon & Wilson’s field exploration program was conducted on June 11, 2025, and consisted of drilling and sampling three borings, designated SW‐01 through SW‐03, at the locations show on Figure 2. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The borings were coordinated (including subcontractor coordination, permitting, traffic control, and utility locates) and observed by a representative from Shannon & Wilson. The exploration boring logs represent our interpretation of the contents of the field logs and results of select laboratory testing.

The borings were drilled by Certified Testing Services of Sioux City, Iowa (under subcontract to Shannon & Wilson) using a Diedrich D50 truck mounted drill rig. The borings were advanced with 4‐inch outside diameter solid‐stem augers and sampled to depths of approximately 6 to 6.5 feet below existing grade. On completion of drilling, drill cuttings were spread on site, and the borings were backfilled with flow fill and patched with hot‐mix asphalt to match the existing pavement.

Boring locations were measured by Shannon & Wilson with a hand‐held recreational grade global positioning system (GPS) unit. The GPS coordinates are indicated on the individual boring logs and should be considered accurate to the degree implied by the method used.

A.2.1 Soil Classification System

During drilling, the Shannon & Wilson representative collected soil samples and prepared a field log of each boring. Soil classifications were 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 system is referred to as the Unified Soil Classification System and is summarized in the Log Key.

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, 1.375‐inch inside diameter split‐spoon sampler, a distance of 18 inches

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S 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 entire 18 inches, 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 Log Key). 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 the sample barrel is larger (2½‐inch O.D.) and lined with 2‐inch‐diameter brass tubing. The MC sampler is 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.

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. Representative samples were sealed in the brass liner tubes with plastic caps and transported to our laboratory for further testing.

A.2.4 Bulk Sampling

A bulk soil sample was obtained by collecting the drill cuttings from boring SW‐02.

Approximately 20 to 30 pounds of cuttings was placed in a plastic bag and transported to our laboratory for further evaluation and testing. The bulk sample is a composite sample sometimes spanning over several soil layers. For this reason, the USCS classification of the composite bulk samples is not included on the boring logs.

A.3 PAVEMENT CORES

A portable electric‐powered coring machine fitted with a 4‐inch‐diameter core barrel was used to take pavement cores of the existing pavement. The cores were brought to the

Shannon & Wilson laboratory where they were measured and photographed.

SHANNON & WILSON | 5900 WEST 38TH AVENUE | WHEAT RIDGE, COLORADO 80212 | 303-825-3800 | www.shannonwilson.com

Poorly Graded Gravel; Poorly Graded Gravel with Sand

Well-graded Gravel; Well-Graded Gravel with Sand

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

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Description

Term

LOG KEY

SOIL CLASSIFICATION

Organic

Inorganic

HIGHLY ORGANIC SOILS

Symbol / Graphic

Silty Sand; Silty Sand with Gravel

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

Poorly Graded Sand; Poorly Graded Sand with Gravel

Silty Gravel; Silty Gravel with Sand

Clayey Gravel; Clayey Gravel with Sand

<5 5 to 10 15 to 25 30 to 45

>50

Term

Well-graded Sand; Well-graded Sand with Gravel

Organic

Major Divisions

Gravel (< 5% fines3)

Silty or Clayey Gravel (> 12% fines3)

Sand (< 5% fines3)

Silty or Clayey Sand (> 12% fines3)

SILTS AND CLAYS

(liquid limit > 50)

Primarily organic matter, dark in color, and organic odor

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

Shannon & Wilson uses a soil identification system modified from the Unified Soil Classification System (USCS) as described on this Key.

Soil descriptions are based on visual-manual procedures (ASTM D2488) and available laboratory index test results (ASTM D2487).

SILTS AND CLAYS

(liquid limit < 50)

NOTE: For gravels and sands with 5 to 12% fines3, the following are added to the Group Name:

with Silt and/or Clay or Silty Clay.

Dual Symbols are used:

GW-GM, GP-GM, SW-SM, SP-SM

GW-GC, GP-GC, SW-SC, SP-SC

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

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

COARSE-GRAINED

SOILS

(> 50% of soil is retained on the No. 200 sieve3)

FINE-GRAINED

SOILS

(> 50% of soil passes the No. 200 sieve3)

Typical Identifications (USCS Group Names)2,4

Sum of the count of hammer blows to penetrate the second and third 6-inch increments in blows per foot (bpf).

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

Percent1

Crumbles or breaks with handling or slight finger pressure.

Crumbles or breaks with considerable finger pressure.

Will not crumble or break with finger pressure.

Description

GRAVELS

(> 50% of coarse fraction retained on the No. 4 sieve3)

Inorganic

Peat or other Highly Organic Soils (see ASTM D4427)

Clayey Sand; Clayey Sand with Gravel

Dry

Moist

Wet

Term

Absence of moisture, dusty, dry to the touch.

Damp but no visible water.

Visible free water, from below water table.

Term140-pound weight with a 30-inch free fall. Hammer types vary (e.g., automatic, rope and cathead). If available, the hammer type and energy ratio (E-ratio) is noted on the boring log.

Description Term

Nonplastic

Low Plasticity

Medium Plasticity

Slickensided

Lensed

Laminated

Interbedded

Homogeneous

Fissured

Description

Barrel I.D. / O.D. = 1.5 inches / 2 inches (liner not used) Barrel Length = 30 inches; Shoe I.D. = 1.375 inches

Blocky Cannot roll a 1/8-inch thread 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 in rolling 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 takes 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.

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

Breaks along definite planes or fractures with little resistance.

Same color and appearance throughout.

Alternating layers at least 1/4 inch thick of varying material or color.

Singular: bed

Alternating layers less than 1/4 inch thick of varying material or color.

Singular: lamination

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

Fracture planes appear polished or glossy, sometimes striated.

High Plasticity

Term

Sampler

N-Value (N)1

Term

Hammer Very Soft Soft Medium Stiff Stiff Very Stiff Hard

Very Loose Loose Medium Dense Dense Very Dense

N2 (bpf)

0 - 4 4 - 10 10 - 30 30 - 50 > 50

TV3 (tsf)

0 - 0.12

0.12 - 0.25

0.25 - 0.5

0.5 - 1 1 - 2 > 2

N2 (bpf)

0 - 2 2 - 4 4 - 8 8 - 15 15 - 30 > 30

PP3 (tsf)

0 - 0.25

0.25 - 0.5

0.5 - 1 1 - 2 2 - 4 > 4

Description

Trace Few Little Some Mostly

Weak

Moderate

Strong

Term

SANDS

(> 50% of coarse fraction passes the No. 4 sieve3)

Exhibit A: Unified Soil Classification System (USCS)1

Exhibit G: Percentages

Exhibit E: Soil Moisture Content1

EXHIBIT A NOTES:

1. Adapted, with permission, from USACE Tech Memo 3-357, ASTM D2487, and ASTM D2488.

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

3. No. 4 size = 4.75 millimeters (mm) = 0.187 inch; No. 200 sieve size = 0.075 mm = 0.003 inch. Particles smaller 0.075 mm are termed "fines".

4. Poorly graded indicates a narrow range or missing grain sizes. Well-graded indicates a full-range and even distribution of grain sizes.

5. If cobbles and/or boulders are observed, "with cobbles" or "with boulders" or "with cobbles and boulders" is added to the Group Name.

EXHIBIT E NOTE:

1. Adapted, with permission, from ASTM D2488 (Figure 2).

EXHIBIT G NOTE:

1. Percent estimated by weight for sand and gravel, and by volume for cobbles, organics, and other non-soil material (e.g., rubble, debris).

EXHIBIT D NOTE:

1. Adapted, with permission, from ASTM D2488.

Exhibit C: Soil Structure1 Exhibit D: Soil Plasticity1

EXHIBIT C NOTE:

1. Adapted, with permission, from ASTM D2488.

Exhibit B-3: Relative Density of Cohesionless Soils

Exhibit B-1: Standard Penetration Test (SPT)

EXHIBIT B NOTES:

1. N-values shown on boring logs are as recorded in the field and have not been corrected for hammer energy, overburden, or other factors. Where the hammer E-ratio is available, the N-value normalized to a ratio of 60% (N60) is listed.

2. Based on ASTM Standard D1586. Relative densities/consistencies noted on the boring logs are based on uncorrected N-values.

3. PP = pocket penetrometer; TV = torvane, tsf = tons per square foot. Correlations based on experience and multiple published references.

Exhibit B-2: Relative Consistency of Cohesive Soils

EXHIBIT F NOTE:

1. Adapted, with permission, from ASTM D2488.

Exhibit F: Soil Cementation1

SHANNON & WILSON | 5900 WEST 38TH AVENUE | WHEAT RIDGE, COLORADO 80212 | 303-825-3800 | www.shannonwilson.com

ATD

bpf dia, diam Elev.

ENV

ETR

FC

FeO ft or ' gal

GP

GWT

HSA

ID

in or " incl ksf lbs

LL

mm

N N60 NA, n/a

NE

NP

NR

NW

OC

OD

OW

pcf

PI

PID

PL

PMT

PP

ppm psi

PT

REC

REF

RQD

SC

SE

SPT

SW

TP

tsf

TV

UCS, qu

USCS

VST

VWP

WC

WOH

WOR

at time of drilling blows per foot diameter elevation environmental sample energy transfer ratio (hammer) fines content (< 0.075 mm) iron oxide foot or feet gallons geoprobe groundwater table hollow-stem auger inside diameter or identification inch inclinometer kips per square foot pounds liquid limit millimeter field (uncorrected) SPT N-value SPT N-value corrected for 60% ETR not applicable or not available northeast nonplastic no recovery northwest organic content outside diameter observation well pounds per cubic foot plasticity index photoionization detector plastic limit pressuremeter test pocket penetrometer reading parts per million pounds per square inch nonstandard penetration test N-value recovery refusal rock quality designation (ASTM D6032) sonic core southeast Standard Penetration Test (ASTM D1586) southwest test pit tons per square foot tor vane reading unconfined compressive strength Unified Soil Classification System vane shear test vibrating wire piezometer natural water content weight of hammer weight of rods

Bentonite-cement grout

Bentonite grout

Bentonite chips

Surface cement seal

Sand filter pack

Slough (hole caved)

Shannon & Wilson uses a rock classification system modified from the system recommended by the International Society for Rock Mechanics (ISRM).

Copyright limitations prevent us from reproducing summary tables from the ISRM system on this Key. General descriptions are provided in Exhibit M.

(continued)

Term

Strength

General Description

Weathering

Fabric

Ranges from extremely weak (qu = 36 to 135 psi) to extremely strong (qu > 36,250 psi), and is based on the ability to break the rock with a hammer or scrape the rock with a knife.

Ranges from fresh (no visible signs of weathering) to completely weathered, based on observed degree of discoloration, decomposition, and/or disintegration. When the rock material has completely converted to soil, it is termed a residual soil.

Describes the rock structure based on observed layering, tendency to break, and distribution of minerals (e.g., massive, bedded, foliated).

For discontinuities: Includes rough, smooth, and slickensided, and includes other descriptive terms (e.g., stepped, undular, irregular, planar).

For discontinuities: Ranges from extremely close (< 1 inch) to extremely wide (> 20 feet).

For discontinuities: Ranges from very low to very high.

Description of discontinuities (joints, fractures, bedding planes, etc.), observations of potential displacement, gouge, shear, etc.

Persistence

Roughness

Spacing

Term

REFERENCE: Brown, E. T., ed., 1981, Rock characterization, testing & monitoring: International Society of Rock Mechanics (ISRM) suggested methods:

Oxford, Pergamon Press, 211 p.

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LOG KEY

Sample Number Sample Type

Water Level Measured at Date in Well or VWP

Well/VWP ID No.

Water Level During Drilling

Measurement Date (M-D-YY)

Blank pipe or instrument casing

Perforated or slotted pipe

VWP and electric lead

Environmental Sample Taken

Split spoon (SS) (diameters vary)

Modified California (MC) sampler

Sonic core (SC) run (typically soil)

Other

REFERENCE: Loehr, J. E.; Lutenegger, A.; Rosenblad, B.; and Boeckmann, A., 2016, Geotechnical site characterization: U.S. Federal Highway Administration Report FHWA NHI-16-072, Geotechnical Engineering Circular no. 5, 1 v.

Rock Quality Designation (RQD) in %

Core Recovery (REC) in %

ROCK CLASSIFICATION

Graphic Description

Description

Irregular patches of different colors.

Soil disturbance or mixing by plants or animals.

Nonsorted sediment; sand and gravel in silt and/or clay matrix.

Material brought to surface by drilling action.

Material that caved from sides of borehole.

Disturbed texture, mix of strengths.

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 to thickness ratio > 3.

Width to thickness ratio < 3.

Term

Angular

Subangular

Subrounded

Rounded

Flat

Elongated

Term

Mottled

Bioturbated

Diamict

Cuttings

Slough

Sheared

Core run (typically rock)

Sheath (SH) (used for geoprobes)

Graphic Description

SYMBOLOGY AND GRAPHICS

Graphic Description Graphic Description

S-5

(SPT)

Description

Graphic Description Graphic Description

SOIL CLASSIFICATION

Gray bar indicates percent of sample length recovered.

Equation

SPT split spoon (2-inch OD)

Grab (GB) from cuttings or excavation

Tube (TB) (e.g., Shelby, piston)

ACRONYMS AND ABBREVIATIONS

Exhibit K: Hole Backfill and Instrument Graphics

Exhibit N: Rock Name Graphics

Exhibit O: Recovery and RQD Equations1

Length of Core in Pieces > 4 in Length of Core Run

100% x

100% x

Exhibit H: Particle Angularity and Shape1

EXHIBIT H NOTE:

1. Adapted, with permission, from ASTM D2488.

Length of Core Recovered Length of Core Run

No rock names defined for this Project

Exhibit I: Additional Descriptive Terms

SOIL CLASSIFICATION REFERENCES:

ASTM International, [current edition], Annual book of standards, v. 04.08, soil and rock (I): D420 - D5876, available: www.astm.org.

U.S. Army Corps of Engineers, 1953, The unified soil classification system: Vicksburg, Miss., Waterways

Experiment Station, Technical Memorandum 3-357, 2 v., March.

See Page 1 for Soil Classification Exhibits A through G

Exhibit M: General Rock Descriptive Terms - ISRM

Exhibit L: Other Log Symbols

Exhibit J: Sample and Run Graphics

0.2 0.5

2.0

6.5

S-1

(MC12)

S-2

(MC12)

S-3

(SPT)

6.5

PT = 3,4

(7 bpf)

PT = 8,9

(17 bpf)

N = 5,7,8 (15 bpf)

DRILLING INFORMATION

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Hole Size:

Solid Stem Auger

Certified Testing Services

Diedrich D-50

5 inch

EXPLORATION INFORMATION

6.5 feet

~1610 feet n/a

WGS [GCS1984]

~ 43.9755 degrees

~ -97.0740 degrees

Total Depth:

Top Elevation:

Vertical Datum:

Latitude:

Longitude:

Horizontal Datum:

FINAL

Logged by:

Review by:

Version:

ZAB

WJZ

= WC% = FC%

Uncorrected N-value, bpf Uncorrected, Penetration N-value, bpf

Liquid LimitPlastic Limit

NOTES:

- Refer to LOG KEY for explanation of symbols, codes, abbreviations, and definitions.

- Groundwater level, if indicated above, is for the date specified and may vary.

- Group symbol is based on visual-manual identification and selected lab testing.

- Report text contains limitations and information needed to contextually understand this log.

- Boring location was estimated using existing site features as well as a recreational grade GPS unit and should be considered approximate.

- Boring elevation was estimated using Google Earth and should be considered approximate.

Sample Number Sample Type

Symbols

(See separate LOG KEY for additional symbols, acronyms, and definitions)

Abbreviations

BASIC LEGEND

S-5

(SPT)

Standard Penetration Test (SPT) blows per 6-inch increment Penetration test (not SPT) blows per 6-inch increment Blows per foot for penetration test Natural water content (%) Fines content (% grains smaller than 0.075 mm) Plasticity index (Atterberg Limits)

N

PT

bpf

WC

FC

PI

Gray bar indicates percent of sample length recovered.

AWJ 1.75 inch

140 lbs/30 inches n/a

Rod Type/Dia.:

Hammer Wt. / Drop:

Hammer ETR:Hole Start Date:

Hole Finish Date:

June 11, 2025

June 11, 2025

BORING LOG

D ep th (f ee t)

D ep th (f ee t)

A pp ro x.

E le v.

fe et

Lab DataG ra ph ic

Field Data

Multiple Items Plotted (see bottom legend on Page 1)

500 100

Jo b#

: 1

2-

| T em pl at e Ve r:1

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SHANNON & WILSON | 5900 WEST 38TH AVENUE | WHEAT RIDGE, COLORADO 80212 | 303-825-3800 | www.shannonwilson.com

SD FTFW MADI 10(2) & 9000(1) REHAB MADISON

Lake County, South Dakota

WC=24%

FC=52%

LL/PI=51/9

WC=5%

WC=4%

SW-01

ASPHALT; 2.5 inches

AGGREGATE SURFACING; 3.5 inches

Medium stiff, dark brown to dark gray, SANDY ELASTIC SILT (MH); moist. [A-5] Fill

Medium dense, red-brown, POORLY GRADED SAND (SP); moist; few gravel; few silt. [A-2-4]

BOTTOM OF HOLE AT 6.5 FEET

Material Description and Other Observations

S am pl es

D ep th (f ee t)

0.2 0.5

2.0

6.5

0.3

1.0

4.0

6.0

S-1

(MC12)

B-1

(GB)

S-2

(MC12)

S-3

(MC12)

PT = 5,4

(9 bpf)

PT = 3,8

(11 bpf)

PT = 3,10

(13 bpf)

DRILLING INFORMATION

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Hole Size:

Solid Stem Auger

Certified Testing Services

Diedrich D-50

5 inch

EXPLORATION INFORMATION

6.0 feet