Att E - Geotech report.pdf

REPORT COVER PAGE

Geotechnical Engineering Report

9355 APHIS College of Charleston Site Improvement Hollywood, South Carolina

June 2, 2021 Terracon Project No. EN215015

Prepared for:

Clark Nexsen, Inc.

Macon, GA

Prepared by:

Terracon Consultants, Inc.

North Charleston, SC

Terracon Consultants, Inc. 1450 F if th Street West North Charleston, South Carol ina 29405 P (843) 884 1234 F (843) 884 9234 terracon.com

REPORT COVER LET TER T O SIGN

June 2, 2021

Clark Nexsen, Inc.

440 Martin Luther King Jr Blvd.

Macon, GA 31201

Attn: Mr. Clint Hardie P: (478) 314-1241 E: chardie@clarknexsen.com

Re: Geotechnical Engineering Report 9355 APHIS College of Charleston Site Improvement 5297 Dixie Plantation Road Hollywood, South Carolina Terracon Project No. EN215015

Dear Mr. Hardie:

We have completed the Geotechnical Engineering services for the 9355 APHIS College of Charleston Site Improvement project located in Hollywood, South Carolina. This study was performed in general accordance with Terracon Proposal No. PEN215015 dated February 8, 2021. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, 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 Consultants, Inc.

Will J. Botts, P.E. Thomas C. Smoak, III, P.E.

Geotechnical Project Engineer Geotechnical Department Manager SC Registration No. 35805

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REPORT TOPICS

EXECUTIVE SUMMARY ................................................................................................. I

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

SEISMIC CONSIDERATIONS

LIQUEFACTION

EARTHWORK

SLAB ON GRADE

PAVEMENTS

GENERAL COMMENTS

Note: This report was originally delivered in a web-based format. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

■ DCP and HAB Logs

■ Infiltration Test Results

■ CPT Sounding Logs

SUPPORTING INFORMATION

■ General Notes

■ USCS Classification

Note: Refer to each individual Attachment for a listing of contents.

9355 APHIS College of Charleston Site Improvement ■ Hollywood, South Carolina June 2, 2021 ■ Terracon Project No. EN215015

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EXECUTIVE SUMMARY

Terracon has completed a geotechnical engineering report for the proposed 9355 APHIS College of Charleston Site Improvement project located at 5297 Dixie Plantation Road in Hollywood, South Carolina. Our geotechnical scope of work for this project included conducting geotechnical fieldwork, engineering analysis, and the development of this engineering report. This report provides recommendations for foundation options, seismic hazard, site preparation, and the other geotechnical related conditions that might affect the proposed construction. The following geotechnical considerations were identified during this phase of the investigation:

§ Based on the presence of potentially liquefiable soils, the 2018 International Building Code (IBC) seismic site classification for this site is F. However, there is an exemption in Section 20.3.1 of ASCE 7-16 which states that for structure(s) with a fundamental period equal to or less than 0.5 seconds, seismic site coefficients Fa and Fv can be determined from Tables 11.4-1 and 11.4-2 using Site Class D determined in accordance with Section 20.3. The structural engineer should verify that the site class exemption provided by the code is available for the proposed structures.

§ Due to the high seismicity in areas surrounding Charleston, South Carolina, we performed a liquefaction potential analysis to evaluate the stability of the soils. Our analysis indicates that the soils at this site are susceptible to liquefaction and post-earthquake settlement may range from 1 to 2 inches. In our experience, this amount of seismic induced settlement can typically be accommodated by the structural design without needing ground improvement mitigation.

§ Given our understanding of the project, assumed loads and fill heights, and assuming proper site preparation, the proposed canopy structure may be supported on typical shallow foundations sized for an allowable bearing pressure of 1,500 pounds per square foot. Total settlement is expected to be 1 inch or less with differential settlement of half of the total settlement.

§ The proposed slab-on-grade can be supported by the in-situ soils or properly compacted Control Fill if proper site preparation is performed as described in this report.

§ There are soft compressible clays located within the soil profile at this site. If structural loads exceed 15 kips for columns or fill heights exceed 1 ½ feet, Terracon should be notified to update our recommendations.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein.

The General Comments section provides an understanding of the report limitations.

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INTRODUC TION

Geotechnical Engineering Report 9355 APHIS College of Charleston Site Improvement

5297 Dixie Plantation Road Hollywood, South Carolina

Terracon Project No. EN215015 June 2, 2021

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed 9355 APHIS College of Charleston Site Improvement project located at 5297 Dixie Plantation Road in Hollywood, South Carolina. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Foundation design and construction

■ Groundwater conditions ■ Slab design and construction

■ Site preparation and earthwork ■ Seismic site classification per IBC

■ Pavement design and construction

The geotechnical engineering scope of work for this project included the advancement of in-situ tests consisting of three Cone Penetration Test (CPT) soundings to depths ranging from approximately 33 to 43 feet below existing site grades. Adjacent to each in situ sounding, a Hand Auger Boring was advanced to a depth of 4 feet. In addition, ten Dynamic Cone Penetrometer (DCPs) and an infiltration test were performed in the proposed drive and parking areas.

Maps showing the site and sounding test locations are presented in the Site Location and Exploration Plan sections, respectively, and logs of the soundings/borings are included in the Exploration Results section in the appendix of this GeoReport.

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 College of Charleston 1000 Acre Plantation North Research Station at 5297 Dixie Plantation Road in Hollywood, South Carolina.

■ Latitude: 32.74361 °

■ Longitude: -80.18194 °

See Site Location in the report Appendix.

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Item Description

Current Ground Cover The project site is mostly wooded and partially developed with an existing gravel parking/drives and railroad bed.

Existing Topography Based on visual observations the project site is relatively flat lying with some areas of undulation.

PROJECT DESCRIPTION

Our final understanding of the project conditions is as follows:

Item Description

Information Provided Project information, aerials, and preliminary plans were provided via email by Clint Hardie at Clark Nexsen, Inc.

Project Description

Based on our review of the project information provided, we understand the site will be developed with a new gravel parking area with paved ADA areas, security fencing and gates, two office trailers, a concrete slab and canopy for loading/unloading and an improved gravel roadway in the existing railroad bed.

Building Construction We assume the canopy will be light framed construction with a concrete slab on grade. Canopy foundations are expected to be founded on shallow spread footings.

Maximum Loads

The following loads were assumed based on our experience with structures of similar size and use:

■ Canopy Footings: up to 15 kips (Axial)

■ Slab: 150 pounds per square foot (psf)

Please let Terracon know when loads become available, so we can verify our analysis. If structural loads exceed these values, Terracon should be notified to update our recommendations.

Grading/Slopes

Grading plans were not provided. We assume that proposed grades will remain relatively consistent with existing grades and that minimal fill (1 ½ feet or less) will be required to develop final grade. If fill heights exceed these values, Terracon should be notified to update our recommendations, as excessive static settlement may occur.

Pavements

We understand paved and gravel driveway and parking will be constructed on the site. We assume both rigid (concrete), flexible (asphalt) and gravel pavement sections will be considered.

Traffic loads were not provided. Please confirm the following anticipated pavement loading:

■ Light Duty Pavements: 50,000 ESAL’s

■ The pavement design period is 20 years.

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GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

We have developed a general characterization of the subsurface soil and groundwater conditions based upon our review of the site-specific soils data and our understanding of the geologic setting and planned construction. The following table provides our geotechnical characterization.

The geotechnical characterization forms the basis of our geotechnical calculations and evaluation of site preparation, foundation options and pavement options. As noted in General Comments, the characterization is based upon widely spaced exploration points across the site, and variations are possible.

Description Approximate

Depth to Bottom of Stratum

Material Encountered1

Surface2 3 to 14 inches Topsoil3

9 to 14 inches Crushed Asphalt and Aggregate3

Stratum 1 6 feet Loose to medium dense silty and clayey sand with interbedded clay and silt layers

Stratum 2 9 feet Soft to medium stiff clays and silts

Stratum 3 10 feet Medium dense to dense sands

Stratum 4 27 feet Medium stiff to stiff silts and clays

Stratum 5 36 feet Dense to very dense sands

Stratum 6 43 feet4 Stiff clayey silt to sandy silt (Cooper Marl Formation5)

1. Material descriptions are based on visual classification from HAB samples and correlations with in situ data.

2. Topsoil was encountered in all HABs, except for DCP-2 DCP-3 and DCP-9 where we encountered crushed asphalt, aggregate, sand, and wood.

3. The thickness of these materials is variable as described in Site Preparation.

4. Termination depth of deepest sounding.

5. The Cooper Marl Formation (CMF) consists of a uniform calcareous clayey to sandy silt approximately 100 to 200 feet thick in the greater Charleston area. This soil stratum is a typical bearing layer for deep foundations in the Charleston area.

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

Groundwater Conditions

At the time of our exploration, groundwater was estimated at depths generally ranging from approximately 3 to 5 ½ feet below the existing ground surface. The ground water depths were determined by measuring the water table depth in the voids left by in situ testing and by estimating

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Test Depth to Groundwater within Voids left from

Testing

Estimated Depth to Groundwater based on CPT

Pore Pressure Data2

Depth to Groundwater in Adjacent Hand

Auger Boring

DCP-1 Not Encountered NA1 NA1

DCP-2 Not Encountered NA1 NA1

DCP-3 Not Encountered NA1 NA1

DCP-4 4.0 ft. NA1 NA1

DCP-5 3.3 ft. NA1 NA1

DCP-6 3.8 ft. NA1 NA1

DCP-7 3.2 ft. NA1 NA1

DCP-8 3.8 ft. NA1 NA1

DCP-9 3.5 ft. NA1 NA1

DCP-10 3.2 ft. NA1 NA1

CPT-12 4.7 ft. 4.0 ft. 3.7 ft.

CPT-13 3.9 ft. 4.0 ft. 3.5 ft.

CPT-14 5.4 ft. 5.0 ft. 3.7 ft.

1. NA- Not Applicable.

2. Pore pressure data is only available for CPT’s.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. The groundwater surface should be checked prior to construction to assess its effect on site work and other construction activities.

There is a possibility of a perched groundwater table due to the presence of clayey soils just below the ground surface at this site. To prevent subgrade softening a site drainage plan should be implemented to reduce the occurrence of a perched groundwater.

Groundwater levels were measured using the following criteria:

■ Physical observation within hand auger boring (HAB) testing depth.

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■ Where not physically encountered in HABs, groundwater levels are measured using a groundwater probe within the voids left by cone penetration (CPT) tests.

■ Where hole collapse does not allow for measurement within CPT voids, groundwater levels are estimated using the hydrostatic line (height of water below the ground surface) on the CPT porewater pressure (U) graph shown on the CPT logs.

■ Unless otherwise specified on the logs or in the report, all groundwater measurements are collected during or immediately after drilling.

Infiltration Testing Results

One Double Ring Infiltration test (DR-11) was performed in the proposed parking area at a depth of 12 inches below existing grade to determine the infiltration rate of the soil. The infiltration rate was determined to be 0.06 inches per hour.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine 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 7-16.

Based on the results of our site characterization program, we conclude that Site Class F is appropriate for the subject site due to the presence of liquefiable soils. Note that the scope of services did not include site profile determination to a depth of 100 feet. Shear wave velocity measurements collected extended to a maximum depth of about 43 feet. Based on our experience in the area, the site classification is based on the assumption that the soils encountered at the sounding termination depth (the Cooper Marl Formation), continue to a depth of 100 feet.

Seismic Evaluation

According to the International Building Code 2018 edition (2018 IBC), the design earthquake has a 50-year exposure period with a 2% probability of exceedance (i.e. a 2500-year design earthquake) with a Moment Magnitude (Mw) of 7.3. The seismic evaluation of the site identified potentially liquefiable soils. According to the 2018 IBC and ASCE 7-16, this potential for liquefaction classifies the site as Site Class F.

Section 11.4.8 of ASCE 7-16 states that a Site Response Analysis (SRA) shall be performed for structures on Site Class F sites unless exempted in accordance with Section 20.3.1 of ASCE 7-16.

The exemption in Section 20.3.1 states that for structure(s) with a fundamental period equal to or less than 0.5 seconds, seismic site coefficients Fa and Fv can be determined from Tables 11.4-1 and 11.4-2 using the Site Class as determined in accordance with Section 20.3.

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The structural engineer should verify the fundamental period of the structure(s). If the proposed structures meet the requirements of the exception, then the following seismic design parameters can be used for the site:

Code Used Site Classification

2018 International Building Code (IBC)1 F2

Seismic Design Parameter Value4

Fa 1.000

Fv 1.796

FPGA 1.100

SDS 1.097 g

SD1 0.603 g

PGAM

3 1.200 g

1. In general accordance with the 2018 International Building Code and ASCE 7-16 Table 20.3-1.

2. Based upon the presence of liquefiable soils.

3. Determined using Site Class D in Tables 11.4-1 and 11.4-2 of ASCE 7-16. This assumes the building meets the fundamental period exception outlined in section 20.3.1 of ASCE 7-16. Otherwise a Site-Specific Seismic Response Analysis may be required. Use of Site Class D is based on a weighted average shear wave velocity collected at nearby sites for the upper 100 feet of the soil profile.

4. Based on procedures outlined in ASCE 7-16 for geotechnical hazards.

If the proposed structure’s fundamental period does not qualify for the exception outlined in Section 20.3 of ASCE 7-16 a Site-Specific Response Analysis will be required by the International Building Code (IBC) since there are liquefiable soils present on site. Terracon can provide this analysis for an additional fee, upon request.

LIQUEFACTION

Due to the high seismicity of the Coastal Plain of South Carolina, we performed a liquefaction potential analysis to evaluate the stability of the soils. Ground shaking at the foundation of structures and liquefaction of the soil under the foundation are the principal seismic hazards identified for the design of earthquake-resistant structures. Liquefaction occurs when a rapid buildup in water pressure, caused by the ground motion, pushes sand particles apart, resulting in a loss of strength and later densification as the water pressure dissipates. This loss of strength can cause bearing capacity failure while the densification can cause excessive settlement.

While the amount of settlement is dependent on the magnitude and distance from a seismic event, and geologic age of the soil deposit, we estimate that seismic settlements from the design

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EARTHWORK

Earthwork is anticipated to include clearing and grubbing, excavations, and 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, slabs, and pavements.

Site Drainage

A main consideration for earthwork activities is the presence of clayey soils within the subsurface profile. These soils are moisture sensitive and exposure to water and construction traffic can lead to softening and rutting of the upper materials, which may subsequently require drying, reworking, and /or replacement. This will be especially critical at cut areas within the site. A construction drainage plan should be implemented to reduce impacts from surface water.

Site Preparation

The initial step in site preparation is to strip the proposed construction area of organic material, topsoil, debris, uncontrolled fill, and other deleterious material from within the footprint of the proposed buildings. Stripping should extend a minimum of 10 feet outside the construction area footprint, unless limited by project boundaries or existing structures. We expect stripping depths to be approximately 3 to 14 inches. Please bear in mind that the volume of topsoil and organics may be significantly greater than the area multiplied by the topsoil/organics thickness indicated in the boring logs. Rutting of the subgrade can also cause mixing of topsoil/organics with underlying soils, which will result in additional required topsoil/organics stripping. Deeper undercut may be needed in some localized areas to remove tree stumps or other unsuitable materials. Voids remaining from the clearing/stripping operation should be backfilled with properly compacted Controlled Fill.

After stripping and subgrade repair is completed, the exposed subgrade should be proofrolled with a loaded tandem axle dump truck or other similar approved construction equipment. A geotechnical engineer or representative should monitor proofrolling operations. Areas that pump or rut excessively should be undercut and reworked or replaced with Controlled Fill. Fill placement may commence after the subgrade stability has been verified by the geotechnical engineer.

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The subgrade soils for this site are considered marginal and depending on moisture conditions, moisture conditioning and/or undercutting may be required. If widespread instability is observed at the time of construction, chemical treatment using Quicklime or Portland cement may be considered. Chemical treatment is discussed further in subsequent sections.

Fill Material Types

The grading contractor should provide samples of proposed fill soils prior to placement. Controlled Fill should meet the following soil property requirements:

Controlled Fill Type1 USCS Classification Acceptable Location for Placement

Imported Fill 2 SP, SP-SM, SP-SW, SW, SM (Passing #200<12%) All locations.

Onsite Soils SP, SP-SM, SM, SC-SM (Passing #200<25%) All locations.

1. Controlled Fill should consist of approved materials that are free of organic matter and other deleterious debris.

2. It may be necessary to install an undrain system to mitigate ponding of water within the imported granular fill material.

Fill Compaction Requirements

Controlled Fill should meet the following compaction requirements:

ITEM DESCRIPTION

Fill Lift Thickness

10 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 inches or less in loose thickness when hand-guided equipment such as a jumping jack or plate compactor is used

Compaction Requirements1

Controlled Fill - 95% of the material’s maximum modified Proctor dry density

(ASTM D1557).

Graded Aggregate Base Course (GABC) - 95% of the material’s maximum modified Proctor dry density (ASTM D1557).

Moisture Content – Controlled Fill or Onsite Soils2

Fill materials should be placed near the optimal moisture content (typically between ±3 percent) as determined by laboratory testing. Actual range of acceptable moisture contents will be highly dependent on the type of soil used.

Soils with a higher fine-grained component typically have a tighter range of acceptable moisture contents as compared with coarse grained soils.

1. Fill should be tested for moisture content and compaction during placement. If the results of the in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved.

2. Specifically, moisture levels should be maintained low enough to allow for satisfactory compaction to be achieved without the Controlled Fill material pumping when proofrolled.

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Earthwork Construction Considerations

It is anticipated that shallow excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Upon completion of filling/cutting and grading, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs.

Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

Surface water should not be allowed to pond on the site and soak into the soil during construction.

Construction staging should provide drainage of surface water and precipitation away from the building areas. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils.

Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage.

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. This monitoring should include documentation of adequate removal of vegetation and top soil, proof-rolling and mitigation of areas delineated by the proof-roll to require mitigation.

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 of at least one test for every 2,500 square feet of compacted fill in the building areas and 5,000 square feet in pavement areas. One density and water content test for every 50 linear feet of compacted utility trench backfill.

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

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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

Given the provided loads and fill heights, and if the site has been prepared in accordance with the requirements noted in Earthwork, the design parameters in the following table are applicable for shallow foundations.

Please note that there are soft compressible clays located within the soil profile at this site. If structural loads exceed 15 kips for columns or fill heights exceed 1 ½ feet, Terracon should be notified to update our recommendations.

Design Parameters

Description Canopy

Allowable bearing pressure1 1,500 psf

Minimum dimensions 24 inches

Minimum embedment below finished grade 12 inches

Estimated total static settlement2 1 inch or less

Estimated differential static settlement2 < ½ inch between columns

1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. This assumes that any unsuitable fill, debris or soft soils, if encountered, will be undercut and replaced with Controlled Fill.

2. The settlement estimates are based on loading the building pads to a maximum load of 15 kips for columns, and the above allowable bearing pressure. The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth and dimensions of the footings, the thickness of compacted fill, and the quality of the earthwork operations. These settlement magnitudes assume the foundation subgrade will be repaired as recommended in this report. The settlement calculations were based on maximum footing sizes of 3 ft by 3 ft for canopy footings.

The allowable foundation bearing pressures apply to dead loads plus design live load conditions.

The design bearing pressure may be increased by one-third when considering total loads that include wind or seismic conditions.

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Uplift resistance can be developed from the weight of the footings, the effective weight of any overlying soil, and the weight of the supported structure itself. The effective unit weight of the soil can be assumed to be 110 pcf above the highest possible groundwater level and 48 pcf below.

Soil uplift resistance may be calculated as the weight of the soil prism defined by a diagonal line extending from the perimeter of the foundation to the ground surface at an angle q equal to 20 degrees from the vertical. Under moment and/or shear loading, the effective size of the uplift soil prism may be reduced. An appropriate safety factor should be applied.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction of the Geotechnical Engineer. Localized undercutting of the footings may be required in isolated areas.

The footings should be evaluated at the time of construction by a representative of the geotechnical engineer to determine the extent of undercut.

The base of all foundation excavations should be free of water and loose soil, 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.

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.

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.

Maximum Allowable Bearing Pressure

MP

Wc

H

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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 #57 stone or Controlled Fill placed, as recommended in the Earthwork section.

SLAB ON GRADE

The proposed slab can be supported by the in-situ soils or properly compacted Control Fill if prepared as described in Earthwork. Concrete slabs constructed on grade can be designed using the modulus of subgrade reaction presented in the following table.

ITEM DESCRIPTION

Modulus of subgrade reaction1 150 pounds per square inch per inch (psi/in) for point loading conditions

1. Modulus of subgrade reaction value is for a 30-inch plate and should be adjusted for appropriate size.

If a conventional slab and shallow foundation are used the structural engineer should design the slab to limit differential movements between the slab and building/machine foundations to reduce the possibility of floor slab cracking. Where appropriate, saw-cut control joints and expansion

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(ASTM D1557).

The use of a vapor retarder should be considered beneath concrete slabs on grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 and ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder/barrier.

Floor Slab Construction Considerations

On most project sites, the site grading is generally accomplished early in the construction phase.

However, as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab subgrade may not be suitable for placement of subbase and concrete and corrective action may be required.

We recommend the area underlying the floor slab be rough graded and then proofrolled with a tandem axle dump truck prior to final grading and observed by geotechnical engineer or their agent.

Areas where unsuitable conditions are located should be repaired by removing and replacing the affected material with properly compacted fill. All floor slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the subbase and concrete. Any trenches should be backfilled with Controlled Fill as described in the Earthwork section in this report.

PAVEMENTS

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.

Subgrade Preparation

Pavement subgrades should be carefully evaluated as the time for pavement construction approaches. The moisture content and density of the subgrade should be evaluated and the subgrade proofrolled immediately prior to commencement of base course placement. Yielding or soft areas should be undercut or should be moisture conditioned and recompacted prior to base course placement as outlined in the Earthwork Section of this report. The base course should be proofrolled immediately prior to commencement of pavement placement. Soft or yielding areas should be moisture conditioned and recompacted as outlined in the Compaction Requirements Section of this report prior to pavement placement.

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If a significant precipitation event occurs after the evaluation or if the surface becomes disturbed, the subgrade should be reviewed by qualified personnel immediately prior to paving. The subgrade should be in its finished form at the time of the final review.

Design Considerations

Based on the anticipated use of the development and assumed traffic information, we have provided minimum pavement thickness for “light-duty” traffic areas for a design life of 20 years.

The thickness of pavements subjected to heavy truck traffic should be determined using expected traffic volumes, vehicle types, and vehicle loads and should be in accordance with local, city, or county ordinances.

“Light-duty” pavement is used in parking/drive areas subjected solely to light passenger car and light truck traffic. We have estimated traffic loading conditions of “light-duty” pavement to be 50,000 Equivalent Single Axle Loads (ESALs) for a design life of 20 years. Based on the amount of fill required to achieve subgrade elevations and our experience with similar soils we have assumed a CBR value of 10, and this should be verified once site grading plans and fill material source is identified.

We have not included construction traffic loads in our pavement design. If the pavement is subject to heaver traffic loading than the assumed aforementioned ESALs, the thickness of pavements should be determined using expected traffic volumes, vehicle types, and vehicle loads and should be in accordance with local, city or county ordinances. Pavement thickness can be determined using AASHTO, Asphalt Institute and/or other methods if specific wheel loads, axle configurations, frequencies, and desired pavement life are provided. Terracon can provide thickness recommendations for pavements subjected to loads other than personal vehicle and occasional delivery and trash removal truck traffic if this information is provided.

A concrete slab is recommended for any areas where dumpsters are to be located in order to provide a more durable wearing surface. If utilized, the pad should be large enough to encompass both the dumpster and refuse truck. Additionally, the use of concrete should be considered in areas where high turning stresses are expected, such as entrance and exit aprons, or where forklift traffic is expected.

June 2, 2021 ■ Terracon Project No. EN215015

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Recommended Pavement Sections

Alternative AC1 Surface Course (in.)

(SCDOT Type C)

Portland Cement

Concrete 2 (in.)

Graded Aggregate Base

Course (in.)

(SCDOT GABC)

Total Thickness (in.)

Gravel -- -- 8.0 8.0

Asphalt Concrete 2.0 -- 6.0 8.0

Portland Cement Concrete -- 5.0 4.0 9.0

1. AC = Asphalt Concrete

2. 4,000 psi at 28 days, 4-inch maximum slump and 5 to 7% air entrained, 6-sack minimum mix. PCC pavements are recommended for trash container pads and in any other areas subjected to heavy wheel loads and/or turning traffic.

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 drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase.

Pavement Maintenance

The pavement sections provided in this report represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore, preventive maintenance should be planned and provided for through an on-going pavement management program.

Maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment. Maintenance consists of both localized maintenance (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Preventive maintenance is usually the first priority when implementing a pavement maintenance program.

Additional engineering observation is recommended to determine 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.

June 2, 2021 ■ Terracon Project No. EN215015

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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. Natural 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 or collaboration through this system 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 impact 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. 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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ATTACHMENTS

June 2, 2021 ■ Terracon Project No. EN215015

Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 1 of 1

EXPLORATION AND TESTING PROCEDURES

Field Exploration

The field exploration program consisted of the following:

Type of Test Test Location Number of Tests Test Depth 1

Cone Penetration Test (CPT) Soundings

Proposed Canopy, Slab and Trailer Areas 3 40 feet

Hand Auger Boring with Dynamic Cone Penetrometer (DCP)

Existing Railway Bed / Proposed Gravel Roadway 5 4 feet

Hand Auger Boring with Dynamic Cone Penetrometer (DCP)

Proposed Slab and Gravel Parking Area 5 4 feet

Double Ring Infiltration Test Proposed Gravel Parking Area 1 1 foot

1. Below ground surface.

Boring Layout and Elevations: We used handheld GPS equipment to locate borings with an estimated horizontal accuracy of +/-20 feet. Ground surface elevations were not determined.

Subsurface Exploration Procedures: The soundings were performed with the appropriate ASTM Standards. The in-situ tests were advanced with a Pagani TG73-200 rig. The field exploration included observations for groundwater, which occurred during the exploration program after or as the soundings/auger borings are being advanced. No provisions have been made to collect water level data other than the observations made during the advancement of the soundings/auger borings. The field data was reviewed and processed by the geotechnical engineer to create the final in situ sounding and hand auger boring logs.

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SITE LOCATION AND EXPLORATION PLANS

Contents:

Site Location Plan Exploration Plans

SITE LOCATION

9355 APHIS College of Charleston Site Improvement ■ Hollywood, SC June 2, 2021 ■ Terracon Project No. EN215015

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT

INTENDED FOR CONSTRUCTION PURPOSES

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY

QUADRANGLES INCLUDE: RAVENEL, SC (1/1/1971) and WADMALAW ISLAND, SC

(1/1/1971).

SITE

EXPLORATION PLAN 1

AERIAL PHOTOGRAPHY PROVIDED BY

MICROSOFT BING MAPS

EXPLORATION PLAN 2

AERIAL PHOTOGRAPHY PROVIDED BY

MICROSOFT BING MAPS

EXPLORATION RESULTS

Contents:

Hand Auger Boring Logs Infiltration Test Results CPT Sounding Logs

5 - 3 - 4

2 - 2 - 4

13 - 15+

6 - 8 - 9

TOPSOIL, dark brown to brown, dry

SILTY SAND (SM), fine to medium grained, light brown to brown, moist

Boring Terminated at 4 Feet

1.0

4.0

Hammer Type: NAStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

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LI

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IF

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P A

R A

T E

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IG

IN

A

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T . G

E O

S M

A R

T L

O G

-N O

W E

LL

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N

A

P H

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C

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.G P

J T

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A T

A T

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P

LA

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.G D

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/1

/2

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S E

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S

D E

P T

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F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

LOCATION See Exploration Plan

Latitude: 32.7449° Longitude: -80.1771°

G R

A P

H

IC

L O

G

DEPTH

Advancement Method:

Manual Hand Auger and DCP

Abandonment Method:

Boring backfilled with soil cuttings upon completion.

Notes:

Project No.: EN215015

Drill Rig: NA

BORING LOG NO. DCP-1

Clark Nexsen IncCLIENT:

Macon, GA

Driller: R. Frazier

Boring Completed: 05-04-2021

PROJECT: 9355 APHIS College of Charleston Site Improvement

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.

5297 Dixie Plantation Road Hollywood, SC

SITE:

Boring Started: 05-04-2021

1450 Fifth St W North Charleston, SC

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y P

E

D C

P

Groundwater not encountered

9 - 15+

15 - 15+

6 - 13 - 15+

10 - 13 - 8

FILL - SILTY SAND WITH CRUSHED ASPHALT AND AGGREGATE (SM), fine to coarse grained, dark brown to brown, dry

SILTY SAND (SM), fine to medium grained, brown to gray, moist

Boring Terminated at 4 Feet

1.2

4.0

Hammer Type: NAStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

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IN

G

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T E

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IG

IN

A

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E P

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T . G

E O

S M

A R

T L

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-N O

W E

LL

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N

A

P H

IS

C

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LL

E G

.G P

J T

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A T

A T

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P

LA

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/1

/2

W A

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E V

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S E

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A T

IO

N

S

D E

P T

H

F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

LOCATION See Exploration Plan

Latitude: 32.7444° Longitude: -80.1787°

G R

A P

H

IC

L O

G

DEPTH

Advancement Method:

Manual Hand Auger and DCP

Abandonment Method:

Boring backfilled with soil cuttings upon completion.

Notes:

Project No.: EN215015

Drill Rig: NA

BORING LOG NO. DCP-2

Clark Nexsen IncCLIENT:

Macon, GA

Driller: R. Frazier

Boring Completed: 05-04-2021

PROJECT: 9355 APHIS College of Charleston Site Improvement

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.

5297 Dixie Plantation Road Hollywood, SC

SITE:

Boring Started: 05-04-2021

1450 Fifth St W North Charleston, SC

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y P

E

D C

6 - 15+

8 - 15+

11 - 13 - 12

14 - 15+

FILL - SILTY SAND WITH CRUSHED ASPHALT AND AGGREGATE (SM), fine to coarse grained, dark brown to brown, dry

SILTY SAND (SM), fine to medium grained, brown to light brown, moist

Boring Terminated at 4 Feet

0.8

4.0

Hammer Type: NAStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

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IF

S E

P A

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T E

D F

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IG

IN

A

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O R

T . G

E O

S M

A R

T L

O G

-N O

W E

LL

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N

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P H

IS

C

O

LL

E G

.G P

J T

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C O

N _D

A T

A T

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P

LA

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T

/2

/2

W A

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R L

E V

E L

O B

S E

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A T

IO

N

S

D E

P T

H

F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

LOCATION See Exploration Plan

Latitude: 32.7439° Longitude: -80.1802°

G R

A P

H

IC

L O

G

DEPTH

Advancement Method:

Manual Hand Auger and DCP

Abandonment Method:

Boring backfilled with soil cuttings upon completion.

Notes:

Project No.: EN215015

Drill Rig: NA

BORING LOG NO. DCP-3

Clark Nexsen IncCLIENT:

Macon, GA

Driller: R. Frazier

Boring Completed: 05-04-2021

PROJECT: 9355 APHIS College of Charleston Site Improvement

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.

5297 Dixie Plantation Road Hollywood, SC

SITE:

Boring Started: 05-04-2021

1450 Fifth St W North Charleston, SC

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y P

E

D C

4 - 4 -7

2 - 5 - 5

11 - 11 - 9

6 - 8 - 6

TOPSOIL, tan, dry, Topsoil 4 inches w/ grass+roots

SILTY SAND (SM), tan, dry

SANDY LEAN CLAY (CL), tan with red, moist

SANDY LEAN CLAY (CL), tan and gray, moist

SILTY SAND (SM), red and gray, moist

Boring Terminated at 4 Feet

0.3

1.0

2.0

3.0

4.0

Hammer Type: NAStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

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A

LI

D

IF

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P A

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T E

D F

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IG

IN

A

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O R

T . G

E O

S M

A R

T L

O G

-N O

W E

LL

E

N

A

P H

IS

C

O

LL

E G

.G P

J T

E R

R A

C O

N _D

A T

A T

E M

P

LA

T E

.G D

T

/1

/2

W A

T E

R L

E V

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O B

S E

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A T

IO

N

S

D E

P T

H

F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

LOCATION See Exploration Plan

Latitude: 32.7435° Longitude: -80.1818°

G R

A P

H

IC

L O

G

DEPTH

Advancement Method:

Manual Hand Auger and DCP

Abandonment Method:

Boring backfilled with soil cuttings upon completion.

Notes:

Project No.: EN215015

Drill Rig: NA

BORING LOG NO. DCP-4

Clark Nexsen IncCLIENT:

Macon, GA

Driller: R. Frazier

Boring Completed: 05-03-2021

PROJECT: 9355 APHIS…