Country Club Road Geotechnical Report_2025111.pdf

Report Cover Page

Country Club Road Culvert Replacement Geotechnical Engineering Report

September 2, 2025 | Terracon Project No. ES255132

Prepared for:

Kimley-Horn and Associates Inc.

25 Bull Street, Ste. 400 Savannah, GA 31401

2201 Rowland Avenue Savannah, GA 31404

P (912) 629-4000 Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

September 2, 2025

Kimley-Horn and Associates Inc.

25 Bull Street, Ste. 400 Savannah, GA 31401

Attn: Mr. Drew Talley, EIT P: (912) 328-4805 E: drew.talley@kimley-horn.com

Re: Geotechnical Engineering Report Country Club Road Culvert Replacement Country Club Road Statesboro, GA Terracon Project No. ES255132

Dear Mr. Talley:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PES255132 dated May 23, 2025. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations 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

Nurudeen Abidoye, M.S. Guoming Lin, Ph.D., G.E., BC.GE Senior Staff Geotechnical Engineer Senior Consultant

Geotechnical Engineering Report Country Club Road Culvert Replacement | Statesboro, GA September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i Introduction Project Description Site Conditions Geotechnical Characterization

Subsurface Profile Groundwater Conditions Laboratory Testing

Geotechnical Overview Earthwork

Demolition Site Preparation Subgrade Preparation Fill Material Considerations Fill Placement and Compaction Requirements Earthwork Construction Considerations Construction Observation and Testing

Shallow Foundations Shallow Foundation Design Recommendations Foundation Construction Considerations

Lateral Earth Pressures Design Parameters

Seismic Site Class General Comments

Attachments

Exploration and Testing Procedures Photography Log 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 indicates 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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Report Summary

Topic 1 Overview Statement 2

Project Description

The project includes the replacement of the existing triple 42-inch reinforced concrete pipe (RCP) culvert crossing with a double-barrel 5’ W by 5’ H reinforced concrete box culvert (RCBC) system.

We assumed the maximum weight of the new culvert to be 2,010 lbs/linear foot for settlement estimation (based on ASTM C1577).

Geotechnical Characterization

■ The subsurface conditions are relatively consistent in the upper 13 feet between borings.

■ Approximately 6 inches of surface material (topsoil includes grass and roots), below ground surface (BGS).

■ Below the surface materials, the soils consist of loose to very dense silty/clayey sands in the upper 13 to 20 feet BGS, followed by 3 to 9 feet of medium stiff to stiff sandy clays. Below the clay layer, the soil consists of medium dense silty sands and stiff to very stiff sandy clays to the termination of the CPT sounding at 51 feet BGS. Detailed soil stratification is discussed in Geotechnical Characterization.

■ The groundwater depth at the time of our field exploration was measured at approximately 5 to 8 feet BGS. To evaluate the stabilized groundwater depths, two piezometers were installed. Please refer to the piezometer data for detailed groundwater depths.

Earthwork

Over-excavating the culvert bottom to remove loose and soft soils to a stable subgrade at a minimum of 2 feet below the culvert bottom should be anticipated. The required overexcavation depth should be evaluated at the time of construction. Following the overexcavation, a GDOT-approved non-woven geotextile fabric should be placed, and a minimum of 24 inches of #57 stone should be placed below culvert sections and wing wall(s). The fabric should also wrap around the sides to encapsulate the stone layer. The wing wall and box culvert backfill should be placed in accordance with the recommendations in the Earthwork section.

Shallow Foundations

■ After undercutting/backfilling and proper densification of the subgrade, the culvert and wing walls can be supported on shallow foundations.

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■ The new double box culvert system and wing wall(s) can be designed with an allowable bearing pressure of 2,000 psf.

■ Expected settlements: < 1-inch total, < 1-inch differential per box section after subgrade improvement.

■ Wing walls can be designed using the resistance values in the Shallow Foundations section of the report. Earth pressures acting are provided in the Lateral Earth Pressure section. Over-excavation of soft silts is expected below wall and culvert areas, once the culvert flow path is diverted for new construction. Clay soil should not be used as backfill.

■ The sandy soils at the site are susceptible to erosion. Anti-seepage collars or other measures should be used to prevent erosion of the soil along the sides of the wing walls and box culverts.

Seismic Recommendations

For seismic design purposes, the subject site is classified as Site Class D in accordance with the International Building Code (IBC) 2018 and ASCE 7-16 Section 11.4.2.

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

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Facilities | Environmental | Geotechnical | Materials

Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed new 5’ W by 5’ H culvert to be located along Country Club Road in Statesboro, GA. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Demolition considerations

■ Dewatering considerations

■ Foundation design and construction

■ Lateral earth pressure

The geotechnical engineering Scope of Services for this project included the advancement of 2 cone penetration test (CPT) sounding to depths ranging from approximately 47 to 51 feet below existing site grades (BGS, termination/refusal depths), 2 piezometer monitoring wells to depths ranging from 10 to 12 feet BGS, 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 and/or as separate graphs 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 initiated, and our final understanding of the project conditions is as follows:

Item Description

Information Provided

An email request for proposal was provided by Mr. Drew Talley on May 16, 2025. The request included a KMZ with the project boundary and a photograph of the existing culverts.

Additional information including the culvert dimensions was provided in an email on July 18, 2025.

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Item Description

Project Description

The project will include the replacement of the existing triple 42-inch reinforced concrete pipe (RCP) culvert crossing with a double-barrel of 5’ W by 5’ H reinforced concrete box culvert (RCBC) system.

Proposed Structure

New double-barrel 5’ W by 5’ H box culvert system.

Maximum Loads

Anticipated structural loads were not provided at the time of this report. Based on the dimensions provided and experience with similar projects we assumed the following,

■ A single 5’ W by 5’ H box culvert will have a maximum weight of 2,010 pounds per linear foot (based on ASTM C1577).

Grading/Slopes The finished grade elevation of the new culvert was not available at the time of this report.

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 Country Club Road in Statesboro, GA.

Latitude: 32.4141°, Longitude: -81.8492° See Site Location

Existing Improvements

An existing triple 42-inch reinforced concrete pipe (RCP) culvert crossing.

Current Ground Cover

Asphalt pavement and an earthen or grassed shoulder.

Existing Topography

The road is relatively level and slopes down on either side to the culvert.

We also collected photographs at the time of our field exploration program. Representative photos are provided in our Photography Log.

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Geotechnical Characterization

Subsurface Profile

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, geologic setting, and our understanding of the project. This characterization forms the basis of our geotechnical calculations and evaluation of the site preparation options. The following tables provide our geotechnical characterization.

Stratum

Approximate Depth to

Bottom of Stratum (feet)

Material Description Consistency/

Relative Density or Equivalent SPT N-Value

1 0.5 Surface Material: Silty

Sands (topsoil with grass)

NA

2 13 to 20 Silty/Clayey Sand loose to very dense 3 22 to 23 Sandy Clay Medium stiff to stiff 4 39 to 47 Silty Sand Medium dense

51, termination of CPT boring

Sandy Clay Stiff to very stiff

Conditions observed at each exploration location are indicated on the individual logs shown in Exploration Results in the attachment of this report. Stratification boundaries on the CPT boring logs represent the approximate location of changes in native soil types; in situ, the transition between materials may be gradual.

Groundwater Conditions

Both the hand auger and CPT soundings were observed while drilling and after completion for the presence and level of groundwater. Groundwater was encountered at the CPT Sounding locations at depths of 5 to 8 feet BGS. However, to confirm the groundwater depths after stabilization, two piezometers were installed near the CPT sounding locations, and readings were measured weekly for up to 3 weeks. The stabilized groundwater level measured was approximately 8 to 10 feet BGS (elevation +157 and +153 feet NAVD88).

The water levels can be found on boring logs and piezometer reading logs in Exploration Results attached to this report.

Groundwater conditions may change because of seasonal variations in rainfall, runoff, and other conditions not apparent at the time the borings were performed. The possibility of groundwater level fluctuations should be considered when developing the design and

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials construction plans for the project. The groundwater table should be checked prior to construction to assess its effect on site work and other construction activities.

Laboratory Testing

Laboratory testing procedures were performed on soil samples collected at various points around the project area. Bag samples were obtained from our exploration locations at depths ranging from 1 to 11 feet BGS and shipped to Terracon’s laboratory for the following testing procedures:

■ Moisture Content: Standard Test Methods for Laboratory Determination of Water Content of Soil and Rock by Mass (ASTM D2216)

■ Grain Size Analysis: Standard Test Method for Particle-Size Analysis of Soils

(ASTM D422)

■ Atterberg Limits: Standard Test Method for Liquid Limit, Plastic Limit, and Plasticity Index of Soils (ASTM D4318)

Our laboratory testing results are represented in individual graphs and tables in more detail in Exploration and Laboratory Results attached to this report.

Natural Moisture Content: The natural moisture contents of the samples ranged from

11.3 % to 15%. Based on our experience, we believe subgrade soils with moisture content of less than 20 percent are typically stable, as judged by proofrolling.

Fine Content: The soil samples have a percentage of fine passing the No.200 sieve between 7.7 % to 22.5 %.

Soil Plasticity: The soil samples tested have liquid limits of approximately 25. Soils with liquid limits (LL) greater than 50 are classified as high plasticity clays or elastic silts.

Geotechnical Overview

The subsurface soils in the vicinity of the existing triple 42-inch RCP culverts are consistent in the upper 13 feet BGS, consisting of medium dense to very dense sands. These conditions are adaptable to support the proposed box culverts on native soils without deep foundations or ground improvements. The generalized soil profile is presented in Geotechnical Characterization section.

Based on email communication, we understand the new box culvert will be approximately 5’ W by 5’ H. We have assumed a maximum weight of 2,010 lbs/linear foot for a single box culvert. We estimated a contact pressure of 715 psf, considering both the weight of the box culvert and fully loaded water. We have assumed the finished grade elevation of the culvert will be close to the elevation of the existing culvert. As such, the overburden

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials soils above the bottom of the culverts will be excavated and the weight of the removed soils should weigh more than the culvert. As such, the installation of the culvert should not cause an increase of the contact pressure to the underlying soils.

We performed settlement analyses at each sounding location using the soil parameters derived from the CPT soundings and assumed structural loads in the Project Description section. Based on the settlement analysis results, under the applied loads from the structural load, the total settlement is estimated to be one inch or less.

We recommend the subgrade be improved by targeted undercutting/backfilling and densification based on proofrolling during construction. After the removal of the existing culvert and once the culvert flow path is diverted for new culvert construction, the soft silts or very loose materials should be over-excavated a minimum of two feet to a stable subgrade. Required over-excavation depths should be evaluated at the time of construction.

After the subgrade has been over-excavated, a layer of non-woven geotextile fabric should be placed. New culvert sections and wing walls should bear on a minimum of 24 inches of #57 stone. The geotextile fabric should wrap around the sides of the stone layer to encapsulate it.

If the structural or load conditions are significantly different from those used in our evaluation and during construction, or if the subsurface conditions are significantly different from those presented in this report, Terracon should be retained to perform additional evaluation and revise the recommendations, as well as provide testing and inspection during construction.

A net allowable bearing capacity of 2,000 psf is recommended for shallow foundation design after achieving a stable subgrade. The allowable bearing capacity may be increased by 1/3 for transient wind load and seismic load conditions. Terracon should be retained to confirm and test the subgrade during construction to provide more specific recommendations on subgrade repair based on the conditions at the footing subgrade.

The recommendations contained in this report are based upon the results of field studies (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.

Earthwork

Earthwork is anticipated to include demolition, 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

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Facilities | Environmental | Geotechnical | Materials necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations.

Demolition

The proposed 5’ W by 5’ H culvert will be constructed within the footprint of the existing culvert, which will need to be demolished, as well as the wing walls and utilities. We recommend that the existing foundations and utilities be removed from within the proposed culvert footprint and at least 5 feet beyond the outer edge of the foundations.

Site Preparation

Site preparation should include the installation of a site drainage/dewatering system, stripping and grubbing, subgrade preparation, and evaluation of the subgrade. Please bear in mind, due to the uneven ground surface of the site, the volume of topsoil and organics may be significantly greater than the area times the topsoil/organics thickness indicated in the boring logs. Rutting of the subgrade can also cause the mixing of topsoil/organics with underlying soils, which will result in additional required topsoil/organics stripping.

Deeper undercuts will be required to remove unsuitable material.

Subgrade Preparation

We recommend that hand auger borings and dynamic cone penetration (DCP) testing be performed during construction to evaluate and confirm the subgrade conditions under the culvert sections and wing walls. It is anticipated that subgrade soil undercutting may be required during subgrade preparation.

If weak soils are encountered at the proposed subgrade level, we recommend subgrade improvement with undercut and backfill. The subgrade improvement should initially start with 1 foot of undercut. Additional undercut and backfill may be necessary to achieve a stable subgrade.

During site preparation, topsoil, organic matter, stumps, existing fill, or other unsuitable materials should not be left in the subgrade of structural areas. Culvert sections and wing walls should bear on a minimum of 24 inches of #57 stone. We recommend Terracon be retained to test the subgrade during construction so that Terracon can provide additional recommendations to prepare the subgrade based on the conditions uncovered during the subgrade preparation.

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Fill Material Considerations

Structural fill should be placed over a stable or stabilized subgrade. The properties of the fill will affect the performance of the culvert and roadways. The soils to be used as structural fill should be free of organics, roots, or other deleterious materials. Earthen materials used for structural fill should meet the following material property requirements:

Soil Type 1 USCS Classification

Acceptable Parameters (for Structural Fill)

Granular

GW, GP, GM, GC,

SW, SP, SM, SC

Less than 25% passing No. 200 sieve

1. Structural fill should consist of approved materials free of organic matter and debris. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

Based on the findings from our hand auger borings, the subject site consists of silty sands (SM), clayey sand (SC), poorly graded sand with silt (SP-SM) and sandy clay (CL) in the upper 12 feet BGS. The silty sands (SM) and poorly graded sand with silt (SP-SM) are generally considered suitable for structural fill, provided that the soils are free of roots, organics, or other foreign materials. Clayey sands (SC) may be considered marginally suitable, while the clays mixtures (CL) are deemed unsuitable for use as structural fill.

We define marginally suitable as the soils that may require extra effort to adjust the moisture before they can be compacted. The amount of effort required will be highly dependent on the season and the weather conditions during construction. We recommend Terracon be retained during construction to determine the suitability of the onsite soil as fill material.

Fill Placement and Compaction Requirements

Structural fill should meet the following compaction requirements.

Item Structural Fill

Maximum Lift Thickness

8 to 10 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

Minimum Compaction

Requirements 1

95% of max. below foundations and below the finished pavement subgrade

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Item Structural Fill

Water Content

Range 1 Granular: -3% to +3% of optimum

1. Maximum density and optimum water content as determined by the modified Proctor test (ASTM D 1557).

Some manipulation of the moisture content (such as wetting, drying) will be required during the filling operations to obtain the required degree of compaction. The manipulation of the moisture content is highly dependent on weather conditions and site drainage conditions. Therefore, the contractor should prepare both dry and wet fill materials to obtain the specified compaction during grading. A sufficient number of density tests should be performed to confirm the required compaction of the fill material.

Earthwork Construction Considerations

Shallow excavations for the proposed culvert 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. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over, or adjacent to, construction areas should be removed.

The water flow in the direction of the culvert should be diverted, and temporary dewatering should be implemented to facilitate construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or 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; such responsibility shall neither be implied nor inferred.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer. Monitoring should include documentation of adequate removal of vegetation and topsoil, probing and DCP testing, and mitigation of areas delineated by the probing and DCP testing that require mitigation.

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Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency provided by the project plan and specifications.

In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. If unanticipated conditions are encountered, 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.

Shallow Foundations

After the proper subgrade improvement as discussed in the Geotechnical Considerations section, the proposed development can be supported on a shallow, spread footing foundation system, provided that the proposed structures will not exceed the loads as provided in Project Description section and the structure meets criteria of the allowable settlement of 1 inch or greater.

Shallow Foundation Design Recommendations

Item Culvert/Wing wall

Maximum Net Allowable Bearing

Pressure 1, 2 2,000 psf

Minimum Foundation Dimensions 24 inches Estimated Total Settlement from

Structural Loads 2, 3 <1 inch

Estimated Differential Settlement 2 <1 inch between box sections

Ultimate Coefficient of Sliding

Friction 4 0.32

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. It assumes any unsuitable fill or soft soils, if encountered, will be replaced with compacted structural fill.

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

3. The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials thickness of the compacted fill, and the quality of the earthwork operations. Footings should be proportioned to reduce differential settlements. Proportioning on the basis of equal total settlement is recommended; however, proportioning to relative constant dead-load pressure will also reduce differential settlement between adjacent footings.

4. Sliding friction along the base of the footing will not develop where net uplift conditions exist.

Foundation excavations should be observed by Terracon. If the soil conditions encountered differ significantly from those presented in this report, Terracon should be contacted to provide additional evaluation and supplemental recommendations.

Foundation Construction Considerations

If cast-in-place concrete elements will be used in the new culvert, the bottom of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance.

Care should be taken to prevent wetting or drying of the bearing materials during construction. Extremely wet or dry material or any loose or disturbed material in the bottom of the footing excavations should be removed before the foundation concrete is placed. If the soils at the bearing level become excessively dry, disturbed, or saturated, the affected soil should be removed prior to placing concrete. A lean concrete mud-mat should be placed over the bearing soils if the excavations must remain open for an extended period of time.

Regarding the construction of footings, we generally anticipate material suitable for the recommended design bearing pressure will be present at the bottom of the footings.

However, there is a possibility that isolated zones of soft or loose native soils could be encountered below the footing bearing level, even though field density tests are expected to be performed during the fill placement operations. Therefore, it is important that Terracon be retained to observe, test, and evaluate the bearing soil prior to placing reinforcing steel and concrete to determine if additional footing excavation or other subgrade repair is needed for the design loads.

If unsuitable bearing soils are encountered 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. This is illustrated on the sketch below.

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As an alternative, the footings could also bear on properly compacted structural backfill extending down to the suitable soils. Over-excavation for structural fill placement below footings should be conducted as shown below. The over-excavation should be backfilled up to the footing base elevation, with structural fill placed, as recommended in the Earthwork section.

The over-excavation should be backfilled up to the footing base elevation with well-graded granular material placed in lifts of 6 inches or less in loose thickness and compacted to at least 95 percent of the material's maximum dry density as determined by the Modified Proctor test (ASTM D-1557). No. 57 stone is recommended in lieu of structural fill when the volume of excavation is relatively small, re-compaction of the fill is difficult, or the weather conditions or construction schedule becomes a controlling factor.

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Lateral Earth Pressures

Design Parameters

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to values indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction, and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The “at-rest” condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

Lateral Earth Pressure Design Parameters

Earth Pressure

Condition 1

Coefficient for Backfill Type 2

Surcharge Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

Active (Ka) Granular - 0.33 (0.33)S (40)H (80)H

At-Rest (Ko) Granular - 0.5 (0.5)S (55)H (90)H

1. For active earth pressure, the wall must rotate about the base, with top lateral movements of 0.002 H to 0.004 H, where H is the wall height. For passive earth pressure, wall must move horizontally to mobilize resistance. Fat clay or other expansive soils should not be used as backfill behind the wall.

2. Uniform, horizontal backfill, with a maximum unit weight of 120 pcf for granular soils.

3. Uniform surcharge, where S is the surcharge pressure.

4. Loading from heavy compaction equipment is not included.

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5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage for Below-Grade Walls below. “Submerged” conditions are recommended when drainage behind walls is not incorporated into the design.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 degrees from vertical for the active case.

Traffic or other loads on backfill behind walls may have a significant influence on the lateral earth pressure. Placing footings within wall backfill and in the zone of active soil influence on the wall should be avoided unless structural analyses indicate the wall can safely withstand the increased pressure.

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity type concrete walls.

Seismic Site Class

The seismic design requirements are based on Seismic Design Category. Based on the findings in the field exploration and our knowledge of the local geological formation in the project area, the site can be classified as Site Class D in accordance with ASCE 7-16. The seismic design parameters obtained based on ASCE 7-16 are summarized in the table below.

The design response spectrum curve, as presented in the Supporting Information attachment of this report, was developed based on the SDS and SD1 values.

Site Location (Latitude, Longitude)

Site Classification

Ss S1 Fa Fv SDS SD1

32.4141°, -81.8492°

D 0.238g 0.095g 1.6 2.4 0.254 0.152

■ In accordance with ASCE 7-16.

■ The ASCE 7-16 require a site soil profile determination extending a depth of 100 feet for seismic site classification. The current scope does not include 100-foot soil profile determination. Explorations for this project extended to a maximum depth of 51 feet BGS and this seismic site class definition was provided in consideration of the overall soil conditions as well as the general geology of the area.

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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 such 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 pertinent 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 such 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 provided information 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 could significantly affect 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. Such 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

Attachments

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

Exploration and Testing Procedures

Field Exploration

Number of Borings

Type of Exploration

Approximate Boring Depth

(feet) Location

Cone Penetration

Test (CPT) Sounding

50 Culvert Crossing Replacement Area.

2 Piezometer 12

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. Elevation readings displayed on the log were obtained in the field using survey grade Trimble R12 system (NAVD 88)

Subsurface Exploration Procedures: We pushed the CPT soundings with a track-mounted drill rig. CPT sounding is the technology in which an electronically instrumented cone penetrometer is hydraulically pushed through the soil while nearly continuous readings are recorded to a portable computer. The cone is equipped with electronic load cells to measure tip resistance and sleeve resistance and a pressure transducer to measure the generated ambient pore pressure. The face of the cone has an apex angle of 60° and an area of 10 cm2. Digital data representing the tip resistance, friction resistance, pore water pressure, and probe inclination angle are recorded about every 2 centimeters while advancing through the ground at a rate between 1½ and 2½ centimeters per second.

These measurements are correlated to various soil properties used for geotechnical design. No soil samples are gathered through this subsurface investigation technique.

CPT testing was conducted in general accordance with ASTM D5778 "Standard Test Method for Performing Electronic Friction Cone and Piezocone Penetration Testing of Soils." Upon completion, the CPT data collected was analyzed and processed by the project engineer.

Two (2) piezometers were installed near the CPT penetration locations to monitor groundwater levels. The groundwater levels obtained are indicated on the attached piezometer level logs, and the soils are classified in accordance with ASTM D2488.

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

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

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

■ ASTM D2216 Standard Test Methods for Laboratory Determination of Water Content of Soil and Rock Mass (Moisture)

■ ASTM D422 Standard Test Method for Particle-Size Analysis of Soils

■ ASTM D4318 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity

Index of Soils

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.

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

Photography Log

Existing surface condition near C1/PZ1

Eroded shoulder/slopes near the Culvert, north of C1/PZ1.

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

Photography Log

Existing culvert at Country Club Road. Picture taken from C2/PZ2

Existing surface condition near C2/PZ2

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

Site Location and Exploration Plans

Contents:

Site Location Exploration Plan

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

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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

September 2, 2025 | Terracon Project No. ES255132

Facilities | Environmental | Geotechnical | Materials

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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

Contents:

Subsurface Cross Section Profile CPT Sounding Logs Hand Auger Boring Logs Piezometer Level Logs Summary of Laboratory Results Atterberg Limits Grain Size Distribution

Subsurface Profile E le v a ti o n

F t.

N

A V

D

Facilities | Environmental | Geotechnical | Materials

Tip Resistance, qt (tsf)

0 100 200 300 400

C1 Material

Description Normalized CPT

Soil Behavior Type Tip Resistance, qt

(tsf) 0 100 200 300 400

C2 Material

Description Normalized CPT

Soil Behavior Type

Water Level Reading at time of drilling.

Water Level Reading after drilling.

Sampling (See General Notes)

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

Moisture Content

%w

C1

Borehole Lithology

Borehole Termination Type

Explanation

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PL

Notes Water Level Observations

Terracon Project No. ES255132

Country Club Road Culvert Replacement

Country Club Rd | Statesboro, GA

Savannah, GA

2201 Rowland Ave

CPT Soil Classification Graphic Color Code

7 Gravelly sand to dense sand 8 Very stiff sand to clayey sand 9 Very stiff fine grained

4 Silt mixtures - clayey silt to silty clay 5 Sand mixtures - silty sand to sandy silt 6 Sands - clean sand to silty sand

1 Sensitive, fine grained 2 Organic soils - clay 3 Clay - silty clay to clay

Depth (ft)

CPT Sounding ID C1

Elev.

(ft)

Tip Resistance, qt (tsf)

100 200 300 400

10 20 30 40

Facilities | Environmental | Geotechnical | Materials

Friction Ratio, Fr

0.8 1.6 2.4 3.2

Sleeve Friction, fs (tsf)

0.5 1.0 1.5 2.0

0.05 0.10 0.15 0.20 Material Description

Normalized CPT Soil Behavior Type

1 2 3 4 5 6 7 8

Pore Pressure, u2 (tsf)

0 1 2 3

Hydrostatic Pressure

CPT Terminated at 50.5 Feet

1 Sensitive, fine grained

Normalized Soil Behavior Type (Robertson 1990)

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.

Country Club Road Culvert Replacement

Country Club Rd | Statesboro, GA

Notes

Test Location: See Exploration Plan

Elevation Reference: Elevations measured in the field in NAVD 88

Elevation: 162.7 (ft)

CPT Equipment

Terracon Project No. ES255132

3 Clay - silty clay to clay

2 Organic soils - clay

CPT sensor calibration reports available upon request

Probe No. 5039 with net area ratio of .843

U2 pore pressure transducer location

Manufactured by Geoprobe Systems- Calibrated 9/26/2024

Tip and sleeve areas of 10 cm2 and 150 cm2

Ring friction reducer with O.D. of 2 in

Latitude: 32.4142° Longitude: -81.8491°

CPT Completed: 7/17/2025

10 ft measured water depth

(used in normalizations and correlations)

CPT Started: 7/17/2025

9 Very stiff fine grained

4 Silt mixtures - clayey silt to silty clay

8 Very stiff sand to clayey sand

7 Gravelly sand to dense sand

6 Sands - clean sand to silty sand

5 Sand mixtures - silty sand to sandy silt

Operator: AF/LP

CPT Rig: Geoprobe

2201 Rowland Ave

Savannah, GA

Water Level Observation

Depth (ft)

CPT Sounding ID C2

Elev.

(ft)

Tip Resistance, qt (tsf)

100 200 300 400

10 20 30 40

Facilities | Environmental | Geotechnical | Materials

Friction Ratio, Fr

0.8 1.6 2.4 3.2

Sleeve Friction, fs (tsf)

0.5 1.0 1.5 2.0

0.05 0.10 0.15 0.20 Material Description

Normalized CPT Soil Behavior Type

1 2 3 4 5 6 7 8

Pore Pressure, u2 (tsf)

0 1 2 3

Hydrostatic Pressure

Penetration Refusal at 47.2 Feet

1 Sensitive, fine grained

Normalized Soil Behavior Type (Robertson 1990)

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.

Country Club Road Culvert Replacement

Country Club Rd | Statesboro, GA

Notes

Test Location: See Exploration Plan

Elevation Reference: Elevations measured in the field in NAVD 88

Elevation: 160.6 (ft)

CPT Equipment

Terracon Project No. ES255132

3 Clay - silty clay to clay

2 Organic soils - clay

CPT sensor calibration reports available upon request

Probe No. 5039 with net area ratio of .843

U2 pore pressure transducer location

Manufactured by Geoprobe Systems- Calibrated 9/26/2024

Tip and sleeve areas of 10 cm2 and 150 cm2

Ring friction reducer with O.D. of 2 in

Latitude: 32.4139° Longitude: -81.8492°

CPT Completed: 7/17/2025

8 ft measured water depth

(used in normalizations and correlations)

CPT Started: 7/17/2025

9 Very stiff fine grained

4 Silt mixtures - clayey silt to silty clay

8 Very stiff sand to clayey sand

7 Gravelly sand to dense sand

6 Sands - clean sand to silty sand

5 Sand mixtures - silty sand to sandy silt

Operator: AF/LP

CPT Rig: Geoprobe

2201 Rowland Ave

Savannah, GA

Water Level Observation

162.2

157.7

153.4

TOPSOIL, with grass, brown

SILTY SAND (SM), fine to coarse grained, brown/orange fine to medium grained gray

CLAYEY SAND (SC), fine to medium grained, gray with organics (mulch, possible fabric debris) @ 108" BGS

Refusal due to wood debris at 9.3 Feet

Boring Log No. HA/PZ1

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

Elevation: 162.7 (Ft.)

G ra p h ic

L o g

14.3 25-14-11

0.5

5.0

9.3

22.5

Advancement Method Manual hand auger

Notes

Water Level Observations

Mottling encountered @ 0.5 ft BGS

Avg. Groundwater is 10'

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.

Elevation Reference: Elevations measured in the field in NAVD 88

Country Club Road Culvert Replacement

Country Club Rd | Statesboro, GA

Terracon Project No. ES255132 Savannah, GA

2201 Rowland Ave

Drill Rig Hand Auger

Driller

MM

Logged by

TV

Boring Started 07-03-2025

Boring Completed 07-03-2025

Abandonment Method Boring backfilled with auger cuttings upon completion.

S am pl e

T yp e

W at er C o n te n t

) Atterberg

Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 32.4142° Longitude: -81.8491°

Depth (Ft.)

Pe rc en t

Fi n es

159.8

154.9

152.6

151.1

150.3

148.6

CLAYEY SAND (SC), fine to coarse grained, dark brown/orange

SILTY SAND (SM), fine to coarse grained, dark brown/orange light brown/orange with trace pebbles, brown/orange fine to medium grained, gray light brown

CLAYEY SAND (SC), fine to medium grained, light brown/orange

SILTY SAND (SM), fine to coarse grained, brown/light gray

SANDY LEAN CLAY (CL), brown/orange/light brown

POORLY GRADED SAND WITH SILT (SP-SM), with clay, with pebbles, brown/orange

Boring Terminated at 12 Feet

Boring Log No. HA/PZ2

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

Elevation: 160.6 (Ft.)

G ra p h ic

L o g

11.3

15.0

NP

NP

0.8

5.7

8.0

9.5

10.3

12.0

16.5

7.7

Advancement Method Manual hand auger

Notes

Water Level Observations

Mottling encountered @ 5.7 ft BGS

Avg Groundwater is 8'

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

See Supporting Information…