B08_Sol_-_Att_4_-_Geotechnical_Engineering_Report.pdf

Proposal Cover Page Report Cover PageTrail of Tears Overlook Rehabilitation – Fort Smith National Historic Site Geotechnical Engineering Report

January 13, 2025 | Terracon Project No. KB245035

Prepared for:

STRATA Architecture + Preservation 1701 Oak St. Ste 100 Kansas City, MO 64108

1003 Century Street Springdale, AR 72762

P (479) 621-0196 Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

January 13, 2025

STRATA Architecture + Preservation 1701 Oak St. Ste 100 Kansas City, MO 64108

Attn.: Angie Geist Gaebler P: (816) 474-0900 E: angie@strata-arch.com

Re: Geotechnical Engineering Report Trail of Tears Overlook Rehabilitation – Fort Smith National Historic Site 301 Parker Avenue Fort Smith, AR Terracon Project No. KB245035

Dear Ms. Gaebler:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PKB245035 dated June 5, 2024. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and pavements for the proposed project.

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

Sincerely, Terracon Certificate of Authorization No. 223, expires 12/31/2025

Aaron M. Baker, EI Field Engineer

Michael H. Homan, PE Office Manager / Senior Principal

Geotechnical Engineering Report Trail of Tears Overlook Rehabilitation – Fort Smith National Historic Site | Fort Smith, AR January 13, 2025 | Terracon Project No. KB245035

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Introduction Project Description Site Conditions Geotechnical Characterization Seismic Site Class Geotechnical Overview Earthwork

Site Preparation Subgrade Preparation Excavation Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Earthwork Construction Considerations Construction Observation and Testing

Shallow Foundations Design Parameters – Compressive Loads Foundation Construction Considerations

Pavements General Pavement Comments Pavement Design Parameters Pavement Section Thicknesses Pavement Drainage Pavement Maintenance

General Comments

Figures GeoModel

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Attachments

Exploration and Testing Procedures Site Location and Exploration Plans Exploration and Laboratory Results Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report shows a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

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January 13, 2025 | Terracon Project No. KB245035

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed scenic overlook to be located at the Fort Smith National Historic Site at 301 Parker Avenue in Fort Smith, AR. The purpose of these services was to provide information and Geotechnical Engineering recommendations related to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic Site Classification per International Building Code (IBC)

■ Site preparation and earthwork

■ Foundation design and construction

■ Concrete pavement sidewalks

The Geotechnical Engineering Scope of Services for this project included the advancement of test borings, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs in the Exploration Results section.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was started, and our final understanding of the project conditions is as follows:

Item Description

Information Provided

An email request for proposal was provided by Angie Gaebler on May 31, 2024. The request included conceptual drawings, a document outlining the Scope of Services requested and engineers notes from previous site-visits.

Project Description

The project includes the construction of a new interpretive area on the east side of the walkway, and the rehabilitation of the scenic overlook on the west side of the walkway.

Proposed Structure

Structures associated with the project include the construction of five concrete/stone columns and art panels.

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Item Description

Finished Floor Elevation

Finished elevation is expected to be at or near existing grades.

Maximum Loads We have conducted our analysis assuming that the structures will be lightly loaded.

Free-Standing Retaining Walls

It is our understanding that retaining walls are not planned for this project.

Pavements We understand that concrete pavement is planned for the trail which will experience pedestrian and light National Park Service (NPS) utility vehicle loading.

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel Information

The project is located at the Fort Smith National Historic Site at 301 Parker Avenue in Fort Smith, AR within the Fort Smith National Historic Site.

Latitude/Longitude (approximate): 35.3888839, -94.4330738 See Site Location

Existing Improvements

The site is currently improved as a pedestrian park with a concrete sidewalk trail.

Current Ground Cover

Short grass, trees, and concrete sidewalk.

Existing Topography

Based on the topographic profile provided by the client as well as online GIS software, it appears that the site slopes down ±29 feet east to west from the top of the embankment to the concrete sidewalk. It appears that a steep slope with an elevation change of ±14 feet is between the proposed scenic overlook and the river’s edge. The site appears relatively flat within the proposed interpretive outlook area.

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Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model Layer

Layer Name General Description

Lean Clay and Sand Mixtures

Lean clay with sand, sandy lean clay, clayey sand;

brown in color; medium stiff to hard; loose to medium dense

Weathered

Shale

Encountered at a depth of 6 feet below ground surface (bgs) in boring B-2, only; gray in color; very weak, weathered, rock

The borings were advanced using solid stem augers that allow for short term groundwater observations to be made while drilling. Groundwater seepage was not encountered within the maximum drilling depth at the time of our field exploration.

Groundwater conditions may be different at the time of construction. Mapping by the groundwater conditions may change because of seasonal variations in rainfall, runoff, and other conditions not apparent at the time of drilling. Long-term groundwater observation was outside the Scope of Services for this project.

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to identify the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC). Based on the soil properties observed at the site and as described on the exploration logs and results, our professional opinion is for that a Seismic Site Classification of C be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 20 feet. The site properties below the boring depth to 100 feet were estimated based on our experience

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Facilities | Environmental | Geotechnical | Materials 4 and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided that the recommendations provided in this report are implemented in the design and construction phases of this project.

The subsurface materials generally include clay and sand mixtures underlain by weathered shale bedrock (boring B-2). Groundwater was not encountered within the maximum depths of exploration during or at the completion of drilling.

Based on the conditions encountered and estimated load-settlement relationships, the proposed structures can be supported on conventional continuous or spread footings.

Grading for the proposed foundations should incorporate the limits of the foundations plus a lateral distance beyond the outside edge of footings, where space is available.

Some on-site soils are considered suitable to be used as engineered fill materials.

The near surface, low plasticity, lean clay with sand and sandy lean clay could become unstable with typical earthwork and construction traffic, especially after precipitation events. Effective drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

The Shallow Foundations section addresses support of the building directly bearing on native medium stiff to hard lean clay, loose to medium dense clayey sand, or engineered fill.

Our opinion of pavement section thickness design has been developed based on our understanding of the intended use, assumed traffic, and subgrade preparation recommended herein using methods contained in ACI 330 “Guide to Design and Construction of Concrete Parking Lots” and adjusted with consideration to local practice and Arkansas Department of Transportation (ArDOT) requirements. The Pavements section includes minimum pavement component thickness.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

sleach Highlight proposed structures can be supported on conventional continuous or spread footings.

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Earthwork

Earthwork is anticipated to include clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our Geotechnical Engineering evaluation for foundations and pavements.

Site Preparation

Before placing fill, existing vegetation, topsoil, and root mats should be removed.

Complete stripping of the topsoil should be performed in the proposed construction areas.

Mature trees are located within or near the footprint of some of the proposed construction, which will require removal at the onset of construction. Tree root systems can remove substantial moisture from surrounding soils. Where trees are removed, the full root ball and associated dry and desiccated soils should be removed. Soil materials which contain less than 5 percent organics can be reused as engineered fill provided the material is moisture conditioned and properly compacted.

Although no evidence of fill or underground facilities (septic tanks, cesspools, basements, and utilities) was observed during the exploration and site reconnaissance, these features could be encountered during construction. If unexpected fills or underground facilities are encountered, they should be removed, and the excavation thoroughly cleaned before backfill placement and construction.

Subgrade Preparation

We recommend that the soil within the footprint of the proposed structures be stripped and cleared of surface vegetation before placing fill. Structural fill placed beneath the entire footprint of the foundations should extend horizontally to a minimum distance of 3 feet beyond the outside edge of footings. Some on-site soils are considered suitable to be used as structural fill materials.

Subgrade soils beneath proposed pavements should be removed to a depth which allows for the full pavement profile to be placed up to the desired grade.

The subgrade should be proofrolled with an adequately loaded vehicle like a fully loaded tandem-axle dump truck. The proofrolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. These areas should either be removed or scarified and recompacted as per the recommendations in Earthwork. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

sleach Highlight the foundations should extend horizontally to a minimum distance of 3 feet beyond the outside edge of footings

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Exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 10 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. Compacted structural fill soils should then be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation or pavement construction.

Based upon the subsurface conditions identified from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

but, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Excavation

We anticipate that shallow excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The bottom of excavations should be thoroughly cleaned of loose soil and disturbed materials before backfill placement and construction.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill is material used below, or within 5 feet of structures or pavements.

General fill is material used to achieve grade outside of these areas.

Soil Type 1 USCS Classification

Acceptable Parameters

Imported Low Volume Change

Materials 2

CL, SC, GC

LL ≤ 45 & PI ≤ 20

All locations and elevations

On-Site Soils 2 CL, SC

LL ≤ 45 & PI ≤ 20

All locations and elevation

Granular 2,3 GW/GM Subbase beneath sidewalks and pavements

1. Structural and general fill should include approved materials free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

2. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation before use on this site.

3. ArDOT Class 7 aggregate base course or similar

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Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift Thickness

9 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 to 6 inches in loose thickness when hand-guided equipment (i.e., jumping jack or plate compactor) is used

Same as structural fill

Minimum Compaction

Requirements 1,2 95% of maximum dry density

Same as structural fill

Water Content

Range 1

Cohesive: -2% to +2% of optimum moisture content Granular: Workable moisture levels

As required to achieve minimum compaction requirements

1. Maximum density and optimum water content as identified by the standard Proctor test (ASTM D 698).

2. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least 70 percent relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or

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Facilities | Environmental | Geotechnical | Materials 8 other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

For low permeability subgrades, utility trenches are a common source of water infiltration and migration. Utility trenches penetrating beneath the structure should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the structure. The trench should provide an effective trench plug that extends at least 5 feet from the face of the structure exterior. The plug material should include cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

Grades must provide effective drainage away from the structures and pavements during and after construction and should be maintained throughout their life. Water next to the structures can result in soil movements greater than those discussed in this report.

Greater movements can result in unacceptable foundation movements.

Exposed ground should be sloped and maintained at a minimum 5 percent away from each structure for at least 10 feet beyond the edge of the structure. Locally, flatter grades may be necessary to transition American Disability Act (ADA) access requirements for flatwork. After construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades should also be periodically observed and adjusted, as necessary, as part of a maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and minimize surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structures are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content before construction of grade-supported improvements like sidewalks and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to minimize ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted before floor slab construction.

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As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendixes, and in accordance with any applicable local and state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; this responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our Scope of Services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects like ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure before any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be observed or instrumented for potential ground movements that could negatively affect adjoining property and structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer before placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for 2,500 square feet of compacted fill in the structure areas and 5,000 square feet in pavement areas. Where not specified by local ordinance, one density and water content test should be performed for 100 linear feet of compacted utility trench backfill and at least one test performed for nine vertical inches of compacted backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated by the Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

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Shallow Foundations

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description Maximum Net Allowable Bearing

Pressure 1, 2 1,500 psf

Required Bearing Stratum 3 GeoModel Layer 1, 2 (stiff lean clay or loose clayey sand), or tested and approved structural fill

Minimum Foundation Dimensions Isolated footings – 30 inches

Continuous footings – 16 inches Minimum Embedment Below

Finished Grade 4 24 inches

Estimated Total Settlement from Structural Loads 2 Less than about 1 inch

Estimated Differential Settlement 2, 5 About 2/3 of total settlement

1. The maximum net allowable bearing pressure is the pressure more than the minimum surrounding overburden pressure at the footing base elevation. Values assume that exterior grades are no steeper than 20 percent within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description. Additional geotechnical consultation will be necessary if higher loads are anticipated.

3. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

4. Embedment necessary to minimize the effects of frost and seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within five horizontal feet of the structure.

5. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of the Geotechnical Engineer. The base of foundation excavations should be free of water and loose soil, before placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to minimize wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

sleach Highlight Isolated footings – 30 inches Continuous footings – 16 inches sleach Highlight 24 inches

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Sensitive soils exposed at the surface of footing excavations may require surficial compaction with handheld dynamic compaction equipment before placing structural fill, steel, and concrete. Should surficial compaction not be adequate, construction of a working surface including either crushed stone or a lean concrete mud mat may be required before the placement of reinforcing steel and construction of foundations.

If unsuitable bearing soils are observed at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The lean concrete replacement zone is illustrated on the sketch below.

Overexcavation for structural fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with structural fill placed, as recommended in the Earthwork section.

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Pavements

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs noted in this section must be applied to the site which has been prepared as recommended in the Earthwork section.

Pavement Design Parameters

A modulus of subgrade reaction of 125 pci was used for the portland cement concrete (PCC) pavement thickness design. The value was empirically derived based upon our experience with the lean clay and sand mixture subgrade soils and our expectation of the quality of the subgrade as prescribed by the Site Preparation conditions as outlined in Earthwork. A modulus of rupture of 550 psi was used in design for the concrete (based on correlations with a minimum 28-day compressive strength of 4,000 psi).

Pavement Section Thicknesses

The following table provides our opinion of minimum thickness for pavement sections:

Layer Minimum Recommended Pavement Section Thickness (in.)

Portland Cement Concrete 1

(4000 psi) Aggregate Base 1 Total

Pedestrian and Light

Utility Vehicles

5 4 9

1. Arkansas State Highway and Transportation Department Standard Specifications for Highway Construction

Areas for parking heavy vehicles such as trash trucks, concentrated turn areas, and start/stop maneuvers could require thicker pavement sections on the order of 7 inches with 4 inches of aggregate base. Edge restraints (i.e., concrete curbs or aggregate shoulders) should be planned along curves and areas of maneuvering vehicles.

Although not required for structural support, a minimum 4-inch-thick base course layer is recommended to help reduce potential for slab curl, shrinkage cracking, and subgrade pumping through joints. Proper joint spacing will also be required to minimize excessive slab curling and shrinkage cracking. Joints should be sealed to minimize entry of foreign material and dowelled where necessary for load transfer. PCC pavement details for joint

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Facilities | Environmental | Geotechnical | Materials 13 spacing, joint reinforcement, and joint sealing should be prepared in accordance with ACI 330 and ACI 325.

Where practical, we recommend early-entry cutting of crack control joints in PCC pavements. Cutting of the concrete in its “green” state typically reduces the potential for micro-cracking of the pavements before the crack control joints being formed, compared to cutting the joints after the concrete has fully set. Micro-cracking of pavements may lead to crack formation in locations other than the sawed joints, and reduction of fatigue life of the pavement.

Openings in pavements, like decorative landscaped areas, are sources for water infiltration into surrounding pavement systems. Water can collect in the islands and migrate into the surrounding subgrade soils thereby degrading support of the pavement.

Islands with raised concrete curbs, irrigated foliage, and low permeability near surface soils are areas of concern. The civil design for the pavements with these conditions should include features to restrict or collect and discharge excess water from the islands.

Examples of features are edge drains connected to the stormwater collection system, longitudinal subdrains, or other suitable outlets and impermeable barriers minimizing lateral migration of water like a cutoff wall installed to a depth below the pavement structure.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section.

Pavement Maintenance

The pavement sections show minimum recommended thicknesses. Periodic upkeep should be anticipated. Preventive maintenance should be planned and provided for through an ongoing pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment. Pavement care includes both localized (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Additional engineering consultation is recommended to identify the type and extent of a cost-effective program.

Even with periodic maintenance, some movements and related cracking may still occur, and repairs may be required.

Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2 percent.

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■ Subgrade and pavement surfaces should have a minimum 2 percent slope to promote proper surface drainage.

■ Install pavement drainage systems surrounding areas anticipated for frequent wetting.

■ Install joint sealant and seal cracks immediately.

■ Seal landscaped areas in or adjacent to pavements to reduce moisture migration to subgrade soils.

■ Place compacted, low permeability backfill against the exterior side of curb and gutter.

■ Place curb, gutter and sidewalk directly on clay subgrade soils rather than on unbound granular base course materials.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of variations may not become evident until during or after construction. Terracon should be retained as the Geotechnical Engineer, where noted in this report, to provide observation and testing services during construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for contamination or pollution, other studies should be undertaken.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted Geotechnical Engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the information provided by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that

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Facilities | Environmental | Geotechnical | Materials 15 could significantly effect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others.

Construction and site development have the potential to affect adjacent properties.

Impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

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Facilities | Environmental | Geotechnical | Materials

Figures

Contents:

GeoModel

EL

EV

A

TI

O N

M

S L) fe et

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1

B-2

Legend

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

GeoModel

301 Parker Ave | Fort Smith, AR Terracon Project No. KB245035

Trail of Tears Overlook Rehabilitation

1003 Century St Springdale, AR

Topsoil Sandy Lean Clay

Clayey Sand Lean Clay with Sand

Weathered Shale

Model Layer Layer Name General Description

1 Brown in color; medium stiff to hard; loose to medium dense

2 Gray in color; very weak, weathered, rock

Lean Clay and Sand Mixtures

Weathered Shale

9.5

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Facilities | Environmental | Geotechnical | Materials

Attachments

January 13, 2025 | Terracon Project No. KB245035

Facilities | Environmental | Geotechnical | Materials

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

1 20 Top of eastern embankment

1 9.5 Proposed outlook area

Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) and referencing existing site features. Approximate ground surface elevations were obtained by interpolation from the topographic survey provided by Stantec, sheet No. V0.01, dated October 28, 2024. If elevations and a more precise boring layout are desired, we recommend borings be surveyed.

Subsurface Exploration Procedures: We advanced the borings with a track-mounted rotary drill rig using continuous flight augers (solid stem). Five samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, borings were backfilled with auger cuttings after their completion.

We also observed the boreholes while drilling and at the completion of drilling for the presence of groundwater. Groundwater was not observed at these times in the boreholes.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs show the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

January 13, 2025 | Terracon Project No. KB245035

Facilities | Environmental | Geotechnical | Materials

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following types of tests:

■ Moisture Content

■ Sieve Analysis

■ Atterberg Limits

The laboratory testing program often included examination of soil samples by an engineer. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System.

Geotechnical Engineering Report Addendum

January 13, 2025 | Terracon Project No. KB245035

Facilities | Environmental | Geotechnical | Materials

Site Location and Exploration Plans

Contents:

Site Location Plan Exploration Plan

Note: Attachments are one page unless noted above.

January 13, 2025 | Terracon Project No. KB245035

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Site Location

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

January 13, 2025 | Terracon Project No. KB245035

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Exploration Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

Exploration and Laboratory Results

Boring Logs (B-1 and B-2)

428.5

TOPSOIL

SANDY LEAN CLAY (CL), red, medium stiff to hard

CLAYEY SAND (SC), red and brown, loose to medium dense

Boring Terminated at 20 Feet

Boring Log No. B-1

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra ph ic

L og

17.2

14.6

10.0

10.0

6.6

9.8

18.7

29-14-15

25-12-13

0.5

10.0

20.0

2-2-3 N=5

4-5-8 N=13

10-15-16 N=31

18-23-25 N=48

2-8-7 N=15

4-8-4 N=12

2-4-5 N=9

301 Parker Ave | Fort Smith, AR Terracon Project No. KB245035 Springdale, AR

1003 Century St

Drill Rig

Hammer Type Automatic

Driller

EB

Logged by

JR

Boring Started 12-16-2024

Boring Completed 12-16-2024

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Solid Stem Augers

Notes

Water Level Observations Groundwater seepage was not encountered within the maximum drilling depth at the time of our field exploration.

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Trail of Tears Overlook Rehabilitation

Sa m pl e

Ty pe

Pe rc en t

Fi ne s

W at er C on te nt

D ry

U ni t W ei gh t (p cf

S tr ai n

C om pr es si ve

S tr en gt h (t sf

Te st

T yp e

Elevation: 429 (Ft.) +/-

Atterberg Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 35.3887° Longitude: -94.4326°

Depth (Ft.)

Strength Test

Fi el d Te st R es ul ts

406.5

402.5

TOPSOIL

LEAN CLAY WITH SAND (CL), brown, medium stiff

CLAYEY SAND (SC), brown, loose

WEATHERED SHALE, gray, very weak

Auger Refusal at 9.5 Feet

Boring Log No. B-2

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra ph ic

L og

30.8

17.6

20.2

19.4

8.5

25-16-9

30-14-16

0.5

2.0

6.0

9.5

1-2-2 N=4

2-3-3 N=6

2-3-4 N=7

5-18-50/4"

50/5"

301 Parker Ave | Fort Smith, AR Terracon Project No. KB245035 Springdale, AR

1003 Century St

Drill Rig

Hammer Type Automatic

Driller

EB

Logged by

JR

Boring Started 12-16-2024

Boring Completed 12-16-2024

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Solid Stem Augers

Notes

Water Level Observations Groundwater seepage was not encountered within the maximum drilling depth at the time of our field exploration.

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Trail of Tears Overlook Rehabilitation

Sa m pl e

Ty pe

Pe rc en t

Fi ne s

W at er C on te nt

D ry

U ni t W ei gh t (p cf

S tr ai n

C om pr es si ve

S tr en gt h (t sf

Te st

T yp e

Elevation: 408.5 (Ft.) +/-

Atterberg Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 35.3887° Longitude: -94.4330°

Depth (Ft.)

Strength Test

Fi el d Te st R es ul ts

Supporting Information

General Notes Unified Soil Classification System

Standard Penetration Test

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> 4.00

2.00 to 4.00

1.00 to 2.00

0.50 to 1.00

0.25 to 0.50 less than 0.25

Unconfined Compressive Strength Qu (tsf)

Trail of Tears Overlook Rehabilitation 301 Parker Ave | Fort Smith, AR Terracon Project No. KB245035

1003 Century St Springdale, AR

N

(HP)

(T)

(DCP)

UC

(PID)

(OVA)

Standard Penetration Test Resistance (Blows/Ft.)

Hand Penetrometer

Torvane

Dynamic Cone Penetrometer

Unconfined Compressive Strength

Photo-Ionization Detector

Organic Vapor Analyzer

Water Level After a Specified Period of Time

Water Level After a Specified Period of Time

Cave In Encountered

Water Level Field Tests

Water Initially Encountered

Sampling

Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations.

General Notes

Location And Elevation Notes

Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude and Longitude are approximate. See Exploration and Testing Procedures in the report for the methods used to locate the exploration points for this project. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory data exist to classify the soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this procedure is used. ASTM D2488 "Description and Identification of Soils (Visual-Manual Procedure)" is also used to classify the soils, particularly where insufficient laboratory data exist to classify the soils in accordance with ASTM D2487. In addition to USCS classification, coarse grained soils are classified on the basis of their in-place relative density, and fine-grained soils are classified on the basis of their consistency. See "Strength Terms" table below for details. The ASTM standards noted above are for reference to methodology in general. In some cases, variations to methods are applied as a result of local practice or professional judgment.

Exploration/field results and/or laboratory test data contained within this document are intended for application to the project as described in this document. Use of such exploration/field results and/or laboratory test data should not be used independently of this document.

Relevance of Exploration and Laboratory Test Results

Descriptive Soil Classification

> 30

15 - 30

8 - 15

4 - 8

2 - 4

Hard

> 50 Very Stiff

Stiff

Medium Stiff

Soft

Very Soft

30 - 50

10 - 29

4 - 9

0 - 3Very Loose

Loose

Medium Dense

Dense

Very Dense

Relative Density of Coarse-Grained Soils (More than 50% retained on No. 200 sieve.)

Density determined by Standard Penetration

Resistance

Consistency of Fine-Grained Soils (50% or more passing the No. 200 sieve.)

Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance

0 - 1

Relative Density Consistency Standard Penetration or

N-Value (Blows/Ft.)

Standard Penetration or N-Value

(B…