Exhibit B - ECS Preliminary Geotech Report - Edwards Wood Property Alcolu.pdf

ECS Southeast, LLP

Report of Preliminary Geotechnical Exploration and Engineering Analysis Services Edwards Woods Property

US HWY-301

Manning, Clarendon County, South Carolina 29102

ECS Project Number 34:4578

July 21, 2023

Edwards Woods Property July 21, 2023 ECS Project Number 34:4578 Page ii

July 21, 2023 Ms. Susan MacRae Alliance Consulting Engineers, Inc.

PO Box 8147 Columbia, South Carolina 29202

Reference: Report of Preliminary Geotechnical Exploration and Engineering Analysis Services Edwards Woods Property

US HWY-301

Manning, Clarendon County, South Carolina 29102

ECS Project Number 34:4578

Dear Ms. MacRae:

ECS Southeast, LLP (ECS) has completed the preliminary subsurface exploration and geotechnical engineering analyses for the above-referenced project. Our services were performed in general accordance with our Proposal No. 34:5476-GP, dated June 5, 2023. This report presents our understanding of the geotechnical aspects of the project along with the results of the exploration and engineering analyses conducted and our recommendations for design and construction of geotechnical related items.

It has been our pleasure to be of service to you during the conceptual phase of this project. We would appreciate the opportunity to remain involved during the continuation of the design phase, and to provide our services during construction phase operations as well to verify the assumptions of subsurface conditions made for this report. Should you have questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, ECS Southeast, LLP

Ashton Guest, E.I.T.

Geotechnical Staff Project Manager

Winslow Goins, P.E.

Principal Engineer

Jarred Wadford, P.E.

Senior Project Manager

ECS Project Number 34:4578 Page iii

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 PROJECT LOCATION

2.2 CURRENT SITE CONDITIONS

2.3 PROPOSED CONSTRUCTION

3.0 FIELD EXPLORATION AND LABORATORY TESTING

3.1.1 Cone Penetration Testing (CPT) Soundings

3.1.2 Hand Auger Borings

3.2 LABORATORY TESTING

3.3 REGIONAL/SITE GEOLOGY

3.4 SUBSURFACE CHARACTERIZATION

3.5 GROUNDWATER OBSERVATIONS

4.0 DESIGN RECOMMENDATIONS

4.1 GENERAL

4.2 SEISMIC DESIGN CONSIDERATIONS

4.2.1 Liquefaction

4.2.2 Seismic Site Classification

4.2.3 Ground Motion Parameters

4.3 PRELIMINARY SHALLOW FOUNDATION RECOMMENDATIONS

4.4 PRELIMINARY SLABS-ON-GRADE

4.5 SITE DRAINAGE

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 SUBGRADE PREPARATION

5.1.1 Stripping and Grubbing

5.1.2 Risk Associated with Undocumented Fill

5.1.3 Site Temporary Dewatering

5.2 EARTHWORK OPERATIONS

5.2.1 Plastic Soils

5.2.2 Structural Fill

5.2.3 On-Site Borrow Suitability

5.2.4 Fill Placement Considerations

5.3 FOUNDATION AND SLAB OBSERVATIONS

6.0 CLOSING

ECS Project Number 34:4578 Page iv

APPENDICES

APPENDIX A – Drawings & Reports

• Site Location Diagram

• Test Location Diagram

APPENDIX B – Field Operations

• Reference Notes for Cone Penetration Test (CPT) Soundings

• Subsurface Exploration Procedure: Cone Penetration Testing (CPT) ASTM D 5778

• CPT Logs (C-01 to C-05)

• Reference Notes for Boring Logs

• Subsurface Exploration Procedure: Hand Auger Boring ASTM D1452

• Hand Auger Logs (C-01 to C-05)

APPENDIX C – Laboratory Testing

• Laboratory Testing Summary

APPENDIX D – Miscellaneous

• Important Information about your Geotechnical Report

ECS Project Number 34:4578 Page 1

EXECUTIVE SUMMARY

ECS Southeast, LLP (ECS) has completed the preliminary subsurface exploration for the feasibility for a development located off US HWY-301 in Manning, South Carolina. This Executive Summary is intended as a very brief overview of the primary geotechnical conditions that are expected to affect design and construction. Information gleaned from this executive summary should not be utilized in lieu of reading the geotechnical report. Our findings, conclusions, and recommendations are summarized below.

SUBSURFACE CONDITIONS:

• Coastal Sedimentary Deposits: Observed below surface materials to the maximum depth explored of approximately 50 feet below the current site grades.

• Groundwater: Observed during the field exploration at depths ranging from approximately

3.3 to 10.5 feet below the current ground surface in the CPT soundings.

GEOTECHNICAL CONCERNS:

• Organic-laden topsoil was encountered at depths ranging between approximately 1.5 to 5 inches at our test locations.

• Soft near surface material was encountered to a depth of approximately 2.5 feet below existing site grades. Some localized undercutting should be expected in order to achieve proper bearing capacity.

• Plastic soils (SC, CL) were encountered within hand auger boring C-4 in the upper 4 feet. A separation layer of Structural Fill at least 12 inches thick should be placed between these materials and the bottom of aggregate base course in pavement areas and the bottom of footings and slabs.

• Hand auger boring C-05 encountered refusal at 0.5 feet below grade on possible debris.

DESIGN & CONSTRUCTION RECOMMENDATIONS:

• Seismic Design: Site Class “D.”

• Shallow Foundations: 2,000 psf allowable bearing capacity with recommended undercut.

• Slabs-on-Grade: Modulus of Subgrade Reaction, k=150 pci

This summary should not be considered apart from the entire text of the report with the qualifications and considerations mentioned herein. Details of our conclusions and recommendations are discussed in the report text.

ECS Project Number 34:4578 Page 2

1.0 INTRODUCTION

The purpose of this study was to provide preliminary geotechnical information for the design of the proposed development located off US HWY-301 in Manning, South Carolina.

Our services were provided in accordance with our Proposal No. 34:5476-GP, dated June 5, 2023, as authorized by Susan MacRae and includes the Terms and Conditions of Service outlined with our proposal.

This report contains the procedures and results of our subsurface exploration and laboratory testing programs, review of existing site conditions, engineering analyses, and recommendations for the design and construction for geotechnical aspects of the project.

The report includes the following items.

• Description of subsurface exploration program and test location plan.

• Description of tests performed, results of tests, and data collected.

• CPT sounding and Hand Auger boring logs and soil classification in accordance with

Unified Soil Classification System.

• Laboratory testing results

• Pertinent geological data and general description of area soils.

• Preliminary Site class determination per 2021 International Building Code (IBC 2021).

• Preliminary shallow foundation recommendations.

• Preliminary impact of potential soil liquefaction on design and construction.

• Constructability considerations including compaction requirements, dewatering and identifying undesirable subgrade material present such as old fill, refuse, rubble, existing foundations, organic material, etc. which are recommended for removal.

• Preliminary recommendations on subgrade modulus for design of at-grade slabs.

ECS Project Number 34:4578 Page 3

2.0 PROJECT INFORMATION

2.1 PROJECT LOCATION

The project site is located off US HWY-301 in Manning, South Carolina as shown below and on Figure 1 in Appendix A. This site consists of three parcels further identified as Clarendon County GIS TMS No. 185-00-02-017-00 (12.8 acres), 185-00-03-027-00 (6.37 acres), and a portion of 185-00-02-017- 00.

2.2 CURRENT SITE CONDITIONS

At the time of our site visit, the northern portion of the site was undeveloped and sparsely wooded.

The southern portion of the site contained multiple structures with surrounding gravel parking. Site specific topographic information was not available at the time of this report; however, from observations made during our site visit, the site appeared to be relatively flat with the exception of several ditches that bisect the site.

2.3 PROPOSED CONSTRUCTION

Based on the provided information, we understand that the proposed development consists of a fleet maintenance/public works facility and an animal control facility. The following table further explains our understanding of the planned development and design assumptions made for the purposes of this report. These are based on the correspondence with Alliance Consulting Engineers, Inc and provided documents.

ECS Project Number 34:4578 Page 4

DESIGN ASSUMPTIONS

SUBJECT DESIGN INFORMATION / ASSUMPTIONS

Structures Public works and Animal Control Facility Column Loads 50 Kips maximum (assumed) Wall loads 3 kips per linear feet (klf) (assumed) Finished Floor Elevation Up to 2 feet above existing grade (assumed)

3.0 FIELD EXPLORATION AND LABORATORY TESTING

The field exploration was planned with the objective of characterizing the project site in general geotechnical and geological terms and to evaluate subsequent field data to assist in the determination of recommendations for design of geotechnical related items.

Test locations were identified in the field by ECS personnel using hand-held GPS equipment and are shown on the Boring Location Diagram in Appendix A. Prior to performing the field exploration, we contacted SC PUPS to check the test locations for potential underground utilities.

3.1.1 Cone Penetration Testing (CPT) Soundings

Five (5) CPT soundings, designated C-01 to C-05, were performed at widely spaced locations across the site. The cone penetration test soundings were performed in general conformance with ASTM D5778 by our subcontractor with a track-mounted rig. The CPT sounding logs and an explanation of our exploration procedures are presented in Appendix B. CPT soundings C-01, C-04, and C-05 encountered refusal at various depths.

3.1.2 Hand Auger Borings

Five (5) hand auger borings, designated C-01 to C-05, were performed adjacent to the CPT sounding locations during our field exploration. The hand auger borings were conducted in general conformance with ASTM D6951. The hand auger logs, and an explanation of our exploration procedures are presented in Appendix B. Hand auger boring C-05 encountered refusal at approximately 6 inches below surface grade.

3.2 LABORATORY TESTING

The soil samples collected from the field exploration program were reexamined in our North Charleston office for soil classification and representative samples were selected for laboratory testing. The laboratory testing program was designed to evaluate the index properties of the soil at the site. Samples were evaluated to measure moisture content, Atterberg limits, and percent finer than the 200 sieve, where appropriate.

ECS Project Number 34:4578 Page 5

Each sample was visually classified on the basis of texture and plasticity in accordance with ASTM D2488 Standard Practice for Description and Identification of Soils (Visual-Manual Procedures) and including USCS classification symbols and ASTM D2487 Standard Practice for Classification for Engineering Purposes (Unified Soil Classification System (USCS)). After classification, the samples were grouped in the major zones noted on the hand auger boring logs in Appendix B. The group symbols for each soil type are indicated in parentheses along with the soil descriptions. The stratification lines between strata on the logs are approximate; in situ, the transitions may be gradual.

3.3 REGIONAL/SITE GEOLOGY

Based on the current development of the site, the natural geology of the site has been modified.

The site is located in the Bear Bluff Formation of the Coastal Plain Physiographic Province of South Carolina. The Coastal Plain is composed of seven terraces, each representing a former level of the Atlantic Ocean. Soils in this area generally consist of sedimentary materials transported from other areas by the ocean or rivers. These deposits vary in thickness from a thin veneer along the western edge of the region to more than 10,000 feet near the coast. The sedimentary deposits of the Coastal Plain rest upon consolidated rocks similar to those underlying the adjacent Piedmont Physiographic Province. In general, shallow unconfined groundwater movement within the overlying soils is largely controlled by topographic gradients. Recharge occurs primarily by infiltration along higher elevations and typically discharges into streams or other surface water bodies. The elevation of the shallow water table is transient and can vary greatly with seasonal fluctuations in precipitation.

3.4 SUBSURFACE CHARACTERIZATION

The subsurface conditions encountered were generally consistent with published geological mapping. The following sections provide generalized characterizations of the soil strata encountered during our subsurface exploration. For subsurface information at a specific location, refer to the CPT and hand auger boring logs presented in Appendix B.

GENERAL SUBSURFACE STRATIGRAPHY

Approximate Depth Range

(ft) Stratum Description

Estimated Ranges of CPT

N-values

0 to 0.42 N/A

Approximately 2 to 5 inches of organic-laden topsoil was observed at our test locations. Deeper organic-laden materials may be present at unexplored or low-lying areas of the site.

Hand auger boring C-05 encountered gravel-laden probable fill to an approximate depth of 6 inches.

N/A

0.42 to 20 I Very Loose to very dense SAND with various amounts of silt and clay (SP, SM, SC), moist to saturated. C-03, C-04, and C-05 encountered CLAY layers between approximately 4 to 20 feet.

5 to 40

20 to 50 II Medium dense to very dense SAND with varying amounts of clay and silt, (SP, SC, SM), interbedded layers of cemented material, saturated

12 to 50+

3.5 GROUNDWATER OBSERVATIONS

Groundwater depths were measured in our CPT soundings as noted on the logs in Appendix B. The groundwater depths measured at the time of our field investigation ranged from approximately 3.3

ECS Project Number 34:4578 Page 6 to 10.4 feet below ground surface in the CPT soundings. Groundwater was not observed in the hand auger borings.

Due to the presence of low permeability near surface soils, temporary “perched” water may develop at the site. Variations in the long-term water table may occur as a result of changes in precipitation, evaporation, surface water runoff, construction activities, and other factors.

4.0 DESIGN RECOMMENDATIONS

4.1 GENERAL

The primary purpose of this geotechnical exploration was to help identify and evaluate the general subsurface conditions relative to the proposed construction. Our recommendations have been developed on the basis of the previously described project information and subsurface conditions identified during this study.

4.2 SEISMIC DESIGN CONSIDERATIONS

4.2.1 Liquefaction

When saturated soil with little to no cohesion liquefies during a major earthquake, it experiences a temporary loss of shear strength as a result of a transient rise in excess pore water pressure generated by strong ground motion. Flow failure, lateral spreading, differential settlement, loss of bearing, ground fissures, and sand boils are evidence of excess pore pressure generation and liquefaction.

We completed a liquefaction analysis in accordance with the 2021 International Building Code (IBC) design earthquake 1. Layers of loose to medium dense saturated sand and silty sand were encountered below the groundwater table to a depth of approximately 38 feet below the existing ground surface. ECS has compared the cyclic stress in these saturated soils to the cyclic resistance to estimate a Factor of Safety Against Liquefaction (FSAL). 2 On the basis of the results of our analyses, we conclude several of these layers have the potential to liquefy during the design seismic event.

Although the FSAL represents the liquefaction resistance of a soil stratum at a specific depth in a soil profile and are used in determining liquefaction-induced settlements, it does not quantify the severity of liquefaction-induced settlements or potential infrastructure damage for a site. Iwasaki et al. (1978) proposed the liquefaction potential index (LPI), which expresses liquefaction potential over an entire soil profile by integrating the product of the liquefaction potential of liquefiable soil layers and a weighting factor with respect to depth to the center of each liquefiable layer.

LPI is an empirical tool used to assess site liquefaction hazards and potential for liquefaction-related damage that ranges from 0 to 100. An LPI less than 5 indicates no anticipation of surface

1 The IBC design earthquake has a 2% probability of exceedance in 50 years. Our liquefaction analysis was based on an earthquake with a magnitude of 7.3 and ground surface acceleration of 0.392 g.

2 Analysis completed following the procedures presented in the 1996 NCEER and the 1998 NCEER/NSF workshops on the Evaluation of Liquefaction Resistance of Soils (Youd and Idriss 2001). To estimate volumetric strain and associated liquefaction-induced settlement, we used the procedures developed by Zhang et al. (2002) and a depth weighting factor proposed by Cetin (2009).

ECS Project Number 34:4578 Page 7 manifestations and low to moderate liquefaction-induced damages, LPIs ranging from 5 to 15 indicates surface manifestations and a high degree of liquefaction-induced damages are possible, and an LPI greater than 15 indicates probable surface manifestations with severe liquefaction-induced damages and that foundation damage is likely.

The LPI estimated for this site is less than 5, which indicates a low risk of surface manifestations, and a low degree of liquefaction-induced damages are possible during and immediately following the design seismic event. When soils susceptible to liquefaction are located within approximately 10 feet of the surface, ground surface disruptions (i.e., sand boils) are possible. Such disruptions beneath at-grade structures would result in bearing capacity failure. Since potentially liquefiable sands are not located in the upper 10 feet at this site, there is a low risk of ground surface disruption.

Our analysis indicates that at-grade structures such as parking, slabs and shallow foundations could potentially settle on the order of up to 1 inch during and immediately following the design seismic event. Differential settlement associated with liquefaction-induced settlement is expected to be approximately 50 to 100 percent of the overall anticipated liquefaction settlement. This settlement would result from volumetric compression of the liquefiable sand layers which occurs as seismically-induced excess soil pore water pressures dissipate.

4.2.2 Seismic Site Classification

Section 1613 of the IBC 2021 and Section 20.3 of ASCE 7-16 classifies sites with the potential for liquefaction as Seismic Site Class F. However, Section 20.3 of ASCE 7-16 also allows the design spectral response accelerations for a site to be evaluated without regard to liquefaction provided structures have a fundamental period of less than or equal to 0.5 seconds and the risks of liquefaction are considered in design. Based on our past experience, the proposed building types should meet this criterion; however, this must be confirmed by the structural engineer.

Based on the results of the CPT soundings and our knowledge of local geologic conditions, it is our interpretation the site may be considered a Seismic Site Classification “D,” in accordance with the

IBC 2021.

The Site Class definition should not be confused with the Seismic Design Category designation, which the structural engineer typically assesses.

4.2.3 Ground Motion Parameters

In addition to the seismic site classification noted above, ECS has provided the design spectral response acceleration parameters following the IBC 2021 and ASCE 7-16 methodology. The Mapped Responses were estimated from the free Seismic Design Map Tool available from https://hazards.atcouncil.org. The design responses for the short (0.2 second, SDS) and long period (1-second, SD1) are noted in bold at the far right end of the following table.

https://hazards.atcouncil.org/

ECS Project Number 34:4578 Page 8

GROUND MOTION PARAMETERS – SITE CLASS D (IBC 2021/ASCE 7-16 METHOD)

Period (sec)

Mapped Spectral Response

Accelerations (g)

Values of Site Coefficient for

Site Class (unitless)

Maximum Spectral Response Acceleration Adjusted for Site Class

(g)

Design Spectral Response Acceleration

(g)

Reference Figures 1613.3.1

(1) & (2)

Tables 1613.3.3

(1) & (2)

Eqs. 16-37 & 16-38

Eqs. 16-39 & 16-40

0.2 SS 0.516 Fa 1.387 SMS=FaSs 0.716 SDS=2/3 SMS 0.477

1.0 S1 0.166 Fv 2.269 SM1=FvS1 0.376 SD1=2/3 SM1 0.250

4.3 PRELIMINARY SHALLOW FOUNDATION RECOMMENDATIONS

Undercutting: Below the surficial material, sounding C-03 encountered very loose Silty SAND (SM) during our field exploration to a depth of approximately 2.5 feet below the current site grades. We recommend these materials be undercut and replaced with suitable material as detailed in the following section in order to support the structure.

Assuming that the fill heights and building loads are no greater than those assumed, liquefaction risk is accepted or mitigated, and subgrade preparation and earthwork operations are completed in strict accordance with the recommendations of this report, the proposed structures can be supported by conventional shallow foundations: individual column footings and continuous wall footings. We recommend the design of the foundations utilize the following parameters:

SHALLOW FOUNDATION DESIGN

Design Parameter Column Footing Wall Footing

Net Allowable Bearing Pressure1 2,000 psf 2,000 psf Acceptable Bearing Soil Material Structural Fill or Approved

Native Soils Structural Fill or Approved

Native Soils Minimum Width for Shear Failure 30 inches 18 inches

Minimum Footing Embedment Depth (Below finished floor elevation)

12 inches 12 inches

Estimated Total Static Settlement2 1 inch 1 inch Estimated Differential Settlement3 ½ inch between columns ½ inch over 30 feet

1. Net allowable bearing pressure is the applied pressure in excess of the surrounding overburden soils above the base of the foundation.

2. The settlement of a structure is a function of the compressibility of the bearing materials, bearing pressure, actual structural loads, fill depths, and the bearing elevation of footings with respect to the final ground surface elevation.

3. Based on maximum column/wall loads and variability in subsurface data. Differential settlement can be re-evaluated once the foundation plans are more complete.

ECS Project Number 34:4578 Page 9

Estimates of settlement for foundations bearing on Structural Fill or non-structural fills are strongly dependent on the quality of fill placed. Factors which may affect the quality of fill include maximum loose lift thickness of the fills placed and the amount of compactive effort placed on each lift. The final footing elevation should be evaluated by ECS personnel to document that the bearing soils are capable of supporting the recommended net allowable bearing pressure and are suitable for foundation construction. These evaluations should include visual observations, hand rod probing, and dynamic cone penetrometer (ASTM STP 399) testing, or other methods deemed appropriate by the geotechnical engineer at the time of construction, in each column footing excavation and at intervals not greater than 25 feet in continuous footing excavations.

Areas of Potential Undercut: Soft or unsuitable soils observed at the footing bearing elevations should be undercut and removed. Undercutting or backfilling should be performed under the observation of ECS personnel. Undercut areas should be backfilled up to the original design bottom of footing elevation with one of the following:

• Lean concrete (f’c ≥ 1,000 psi at 28 days).

• AASHTO size No. 57 stone; up to 2 feet in thickness.

• Structural Fill in accordance with the recommendations of this report (with additional compaction testing and soil bearing evaluation).

4.4 PRELIMINARY SLABS-ON-GRADE

Provided subgrades and Structural Fills are prepared in accordance with the recommendations of this report, the proposed floor slabs can be constructed as ground supported slabs (Slabs-On- Grade). During initial site grading there will likely be areas of soft or yielding soils that should be removed and replaced with Structural Fill placed in accordance with the recommendations included in this report. Adjusting the moisture content of Structural Fills during earthwork operations, including the use of disking or appropriate drying equipment, may be necessary. The following graphic depicts our ground supported slab recommendations:

1. Drainage Layer Thickness: 4 inches

2. Drainage Layer Material: GRAVEL (GP, GW), SAND (SP, SW)

3. Subgrade compacted to a minimum of 95% maximum dry density per ASTM D1557

Subgrade Modulus: Provided the placement of structural fill and granular drainage layer per the recommendations discussed herein, the slab may be designed assuming a modulus of subgrade reaction, k1 of 150 pci (lbs/cu. inch).

Slab Isolation: Ground-supported slabs should be isolated from the foundations and foundation-supported elements of the structure so that differential movement between the foundations and slab do not induce excessive shear and bending stresses in the floor slab. Where the structural

Concrete Slab Vapor Barrier

Granular Capillary Break/Drainage Layer

Compacted Subgrade

ECS Project Number 34:4578 Page 10 configuration prevents the use of a free-floating slab, the slab should be designed by the structural engineer of record with suitable reinforcement and load transfer devices to avoid overstressing of the slab.

Design Considerations: We also recommend that slabs-on-grade be underlain by a minimum of 4 inches of suitable material as shown in the figure above to help provide a firm working surface for equipment and avoid the risk of capillary rise of subsurface moisture from adversely affecting the slab. If open graded aggregate is not available or is cost prohibitive, sand with less than 5 percent fines can be used provided the placement and compaction of the sand complies with the above recommendations.

A vapor barrier should be installed on top of the subgrade in areas to receive moisture-sensitive floor coverings to help reduce dampness on the surface of the floor slab. A vapor barrier is generally understood to consist of a minimum 10-mil thickness, overlapping sheets of plastic without sealing the overlap between the individual sheets. If a minimum of one foot of Structural Fill with less than 5 percent fines is placed prior to slab placement an open graded aggregate is not required under the slabs, provided that a 10 mil or thicker vapor barrier is provided.

We recommend that the perm rating of the vapor barrier be adequate to protect the rating of the floor coverings (0.01 perms or less for moisture sensitive floor coverings) and have adequate puncture resistance according to the expected foot traffic and equipment and materials placed on the barrier. If the vapor barrier is punctured or unsealed during construction, the perm rating will likely be greatly decreased, and vapor intrusion may occur through the slab after construction.

Punctures can be caused by concrete finishing, placement of reinforcement, or by equipment and foot traffic. Openings may be caused by unsealed edges at the floor wall interface or laps.

4.5 SITE DRAINAGE

Positive drainage should be provided around the perimeter of the structures to minimize the potential for moisture infiltration into the foundation and slab subgrade soils. We recommend that landscaped areas adjacent to the structures and pavements be sloped away from the construction and maintain a fall of at least 6 inches for the first 10 feet outward from the structure. Roof drains should discharge at least 5 feet from building perimeters or directly into below grade storm water piping. The parking lots, sidewalks, and any other paved areas should also be sloped to divert surface water away from the proposed buildings. Site drainage is the responsibility of the project civil engineer.

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 SUBGRADE PREPARATION

Based on the site currently being currently developed, we emphasize the importance of comprehensive subgrade evaluations prior to structural fill placement and/or other construction activities. These evaluations may include proofrolling the subgrade soils, performing hand auger borings, and excavation of test pits. The mentioned evaluations would help in identifying areas of soft, loose, or otherwise unsuitable materials, which would require remedial activities.

ECS Project Number 34:4578 Page 11

5.1.1 Stripping and Grubbing

The subgrade preparation should consist of stripping vegetation, rootmat, topsoil, and other soft or unsuitable materials from the 10-foot expanded building pad and 5-foot expanded pavement limits and to 5 feet beyond the toe of structural fills.

Existing organic-laden soil was observed in the borings to a depth of approximately 5 inches. Deeper topsoil, organics, or otherwise unsuitable materials may be present at unexplored areas of the site.

Based on our local experience, root balls and stumps may extend about 2 to 3 feet below existing grade in wooded areas and will likely require additional localized stripping depth to remove the organics. ECS should observe and document that unsuitable surficial materials have been removed and subgrades are firm and unyielding with adequate bearing capacity prior to the placement of structural fill or footing construction.

5.1.2 Risk Associated with Undocumented Fill

Based on the previous development of the site, we expect there is an increased potential for portions of the site to have been modified in the past by grading activities resulting in the placement of undocumented fill materials. If existing fill soils containing under-compacted soils or pockets of organics or debris are encountered during construction and are not removed, then localized excessive differential settlements could occur in response to new structural loads and the on-going process of volume change which may still occur in the fill. If such non-uniform settlements occur, then moderate structural distress could result. As such, if existing undocumented fill soils are encountered during construction, they should be further evaluated by proofrolling and Dynamic Cone Penetrometer (DCP) testing as discussed below.

5.1.3 Site Temporary Dewatering

The contractor shall make their own assessment of temporary dewatering needs based upon the limited subsurface groundwater information presented in this report. Soil sampling is not continuous, and thus soil and groundwater conditions may vary between sampling intervals. If the contractor believes additional subsurface information is needed to assess dewatering needs, they should obtain such information at their own expense. ECS makes no warranties or guarantees regarding the adequacy of the provided information to evaluate dewatering requirements; such recommendations are beyond our scope of services.

Dewatering systems are a critical component of many construction projects. Dewatering systems must be selected, designed, and maintained by a qualified and experienced (specialty or other) contractor familiar with the geotechnical and other aspects of the project. The failure to properly design and maintain a dewatering system for a given project can result in delayed construction, unnecessary foundation subgrade undercuts, detrimental phenomena such as ‘running sand’ conditions, internal erosion (i.e., ‘piping’), the migration of ‘fines’ down-gradient towards the dewatering system, localized settlement of nearby infrastructure, foundations, slabs-on-grade and pavements, etc. Water discharged from any site dewatering system shall be discharged in accordance with local, state and federal requirements.

ECS Project Number 34:4578 Page 12

5.2 EARTHWORK OPERATIONS

5.2.1 Plastic Soils

Plastic soils were encountered within hand auger boring C-04 in the upper 4 feet below existing grade. Plastic soils are those soil materials classified as Lean CLAY Clayey SAND (CL, SC). These soil types are challenging to reuse as fill due to their plasticity and moisture content. Where plastic soils are encountered at design subgrade elevations, a 12-inch or more separation of structural fill as described in this report should be provided between plastic soils and the bottom of base course and the bottom of foundations and slabs.

5.2.2 Structural Fill

Prior to placement of structural fill, representative bulk samples (about 50 pounds) of on-site and off-site borrow should be submitted to ECS for laboratory testing, which may include Atterberg limits, natural moisture content, grain-size distribution, and moisture-density relationships for compaction. Import materials should be tested prior to being hauled to the site to establish if they meet project specifications.

Satisfactory Structural Fill Materials: Materials satisfactory for use as structural fill should consist of inorganic soils classified as SM, SC, SW, SP, GW, GP, GM, and GC, or a combination of these group symbols, per ASTM D2487. The structural fill materials should be free of organic matter, debris, and should contain particle sizes less than 1 ½ inches in the largest dimension. Open graded materials, such as gravels (GP), which contain void space in their mass should not be used in structural fills unless properly encapsulated with geotextile filter fabric. Suitable structural fill material should consist of inorganic soils with the following engineering properties and compaction requirements.

STRUCTURAL FILL INDEX PROPERTIES

Subject Property

Atterberg Limits LL < 35, PI<10

Max. Particle Size 1 ½ inches

Fines Content (% passing the #200 sieve) Max. 25 %

Max. organic content 5% by dry weight

STRUCTURAL FILL COMPACTION REQUIREMENTS

Subject Requirement

Compaction Standard Modified Proctor, ASTM D1557

Required Compaction 95% of Max. Dry Density

Moisture Content -3 to +3 % points of the soil’s optimum value

Loose Thickness 8 inches prior to compaction

Unsatisfactory Materials: Materials that should not be used as structural fill include topsoil, organic materials (OH, OL), and low to high plasticity CLAYS and SILTS (CL, ML, CH, MH). Such materials removed during grading operations should be removed from the site and legally disposed.

ECS Project Number 34:4578 Page 13

Fill Placement Considerations: Fill materials should not be placed on excessively wet soils. Borrow fill materials should not be excessively wet at the time of placement. Excessively wet soils or aggregates should be scarified, aerated, and moisture conditioned. At the end of each workday, fill areas should be graded to facilitate drainage of precipitation and the surface should be sealed by use of a smooth-drum roller to limit infiltration of surface water.

Proper drainage should be maintained during the earthwork phases of construction to avoid the ponding of water which tends to degrade subgrade soils. Alternatively, if these soils cannot be stabilized by conventional methods as previously discussed, additional modifications to the subgrade soils such as cement stabilization may be utilized to adjust the moisture content. If cement is utilized to adjust moisture contents and/or for stabilization, regular Type I/II cement can be used. The contractor should be required to minimize dusting or implement dust mitigation measures, as required.

We recommend that the grading contractor have equipment on site during earthwork for both drying and wetting fill soils. We do not anticipate significant problems in adjusting moisture within the fill during dry weather, but moisture adjustments may be difficult during winter months or extended periods of rain. The adjustment of moisture content of higher plasticity soils is difficult when these soils become wet. Further, such soils are easily degraded by construction traffic when the moisture content is elevated.

5.2.3 On-Site Borrow Suitability

Approximately 2 to 5 inches of topsoil was observed during our field exploration. Below the topsoil, material identified as Silty SAND, Clayey SAND, and Lean CLAY (SM, SC, CL) were observed to the maximum depth explored in the hand auger borings of approximately 4 feet below the current site grades.

In our experience, the on-site upper Silty SAND (SM) is generally considered suitable for use as structural fill. Laboratory results on the upper silty SAND material indicate natural moisture content ranging between approximately 7 to 9 percent and fines content ranging between approximately 21 and 27 percent, where tested. The grading contractor should anticipate additional efforts including disking and drying as the material is placed to facilitate compaction and reduce the risk of pumping conditions during placement.

In our experience the on-site Clayey SAND (SC) is generally considered suitable for use as structural fill; however, of marginal quality. Laboratory results on the upper Clayey SAND indicate natural moisture content of approximately 14 percent and a fines content of approximately 32 percent, where tested. The grading contractor should anticipate additional efforts including disking and drying as the material is placed to facilitate compaction and reduce the risk of pumping conditions during placement.

Low to High plasticity Clay (CL, CH) materials, if encountered, should not be used as Engineering Fill.

5.2.4 Fill Placement Considerations

Fill materials should not be placed on excessively wet soils. Borrow fill materials should not be excessively wet at the time of placement. Excessively wet soils or aggregates should be scarified, aerated, and moisture conditioned. At the end of each workday, fill areas should be graded to facilitate drainage of any precipitation and the surface should be sealed by use of a smooth-drum roller to limit infiltration of surface water.

ECS Project Number 34:4578 Page 14

Proper drainage should be maintained during the earthwork phases of construction to prevent ponding of water which tends to degrade subgrade soils. Alternatively, if these soils cannot be stabilized by conventional methods as previously discussed, additional modifications to the subgrade soils such as cement stabilization may be utilized to adjust the moisture content. If cement is utilized to control moisture contents and/or for stabilization, regular Type I/II cement can be used. The contractor should be required to minimize dusting or implement dust control measures, as required.

We recommend that the grading contractor have equipment on site during earthwork for both drying and wetting fill soils. We do not anticipate significant problems in controlling moisture within the fill during dry weather, but moisture control may be difficult during winter months or extended periods of rain. The control of moisture content of higher plasticity soils is difficult when these soils become wet. Further, such soils are easily degraded by construction traffic when the moisture content is elevated.

5.3 FOUNDATION AND SLAB OBSERVATIONS

Protection of Foundation Excavations: Exposure to the environment may weaken the soils at the footing bearing level if the foundation excavations remain open for too long a time. Therefore, foundation concrete should be placed the same day that excavations are made. If the bearing soils are softened by surface water intrusion or exposure, the softened soils must be removed from the foundation excavation bottom immediately prior to placement of concrete. If the excavation must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, a 1 to 3-inch thick “mud mat” of “lean” concrete should be placed on the bearing soils before the placement of reinforcing steel.

Footing Subgrade Observations: It is important to have ECS observe the foundation subgrade immediately prior to placing foundation concrete to document the bearing soils are what were anticipated and that undercutting, if performed, has been done in accordance with ECS recommendations.

Slab Subgrade Verification: Prior to placement of a drainage layer, the subgrade should be prepared in accordance with the recommendations found in Section 5.1.2 Proofrolling.

ECS Project Number 34:4578 Page 15

6.0 CLOSING

ECS has prepared this report to guide the geotechnical-related design and construction aspects of the project. We performed these services in accordance with the standard of care expected of professionals in the industry performing similar services on projects of like size and complexity at this time in the region. No other representation expressed or implied, and no warranty or guarantee is included or intended in this report.

The description of the proposed project and design assumptions made by ECS are based on information provided by Alliance Consulting Engineers, LLC If any of this information is inaccurate, either due to our interpretation of the documents provided or site or design changes that may occur later, ECS should be contacted immediately in order that we can review the report in light of the changes and provide additional or alternate recommendations as may be required to reflect the proposed construction.

We recommend that ECS be retained to review the project’s plans and specifications pertaining to our work so that we may ascertain consistency of those plans/specifications with the intent of the geotechnical report.

Field observations, monitoring, and quality assurance testing during earthwork and foundation installation are an extension of and integral to the geotechnical design recommendation. We recommend that the Owner retain these quality assurance services and that ECS be allowed to continue our involvement throughout these critical phases of construction to provide general consultation as issues arise. ECS is not responsible for the conclusions, opinions, or recommendations of others based on the data in this report.

APPENDIX A – Drawings & Reports

Site Location Diagram

Test Location Diagram

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

SITE LOCATION DIAGRAM

EDWARDS WOOD PROPERTY

US HIGHWAY 301 @ JUNE BURN ROAD, ALCOLU, SC

ALLIANCE CONSULTING ENGINEERS, INC

0 3,0001,500 Feet

6/29/2023

ENGINEER

SCALE

34:4578

PROJECT NO.

FIGURE

DATE

NF

AS NOTED

C-01

C-02

C-03

C-04

C-05

6/29/2023

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

ENGINEER

SCALE

34:4578

PROJECT NO.

FIGURE

DATE

NF

Legend Approximate CPT/HA Location

TEST LOCATION DIAGRAM

EDWARDS WOOD PROPERTY

US HIGHWAY 301 @ JUNE BURN ROAD, ALCOLU, SOUTH CAROLINA

ALLIANCE CONSULTING ENGINEERS, INC

0 600300 Feet

AS NOTED

APPENDIX B – Field Operations

Reference Notes for Cone Penetration Test (CPT) Soundings

Subsurface Exploration Procedure: Cone Penetration Testing (CPT) ASTM D 5778

CPT Logs (C-01 to C-05)

Reference Notes for Boring Logs

Subsurface Exploration Procedure: Hand Auger Boring ASTM D1452

Hand Auger Logs (C-01 to C-05)

REFERENCE NOTES FOR CONE PENETRATION

TEST (CPT) SOUNDINGS

In the CPT sounding procedure (ASTM-D-5778), an electronically instrumented cone penetrometer is hydraulically advanced through soil to measure point resistance (qc), pore water pressure (u2), and sleeve friction (fs). These values are recorded continuously as the cone is pushed to the desired depth. CPT data is corrected for depth and used to estimate soil classifications and intrinsic soil parameters such as angle of internal friction, preconsolidation pressure, and undrained shear strength. The graphs below represent one of the accepted methods of CPT soil behavior classification (Robertson, 1990).

1. Sensitive, Fine Grained 6. Clean Sands to Silty Sands

2. Organic Soils-Peats 7. Gravelly Sand to Sand

3. Clays; Clay to Silty Clay 8. Very Stiff Sand to Clayey Sand

4. Clayey Silt to Silty Clay 9. Very Stiff Fine Grained

5. Silty Sand to Sandy Silt

The following table presents a correlation of corrected cone tip resistance (qc) to soil consistency or relative density:

SAND SILT/CLAY

Corrected Cone Tip Resistance (qc) (tsf)

Relative Density Corrected Cone Tip Resistance (qc) (tsf)

Relative Density

<20 Very Loose <5 Very Soft

20-40 Loose 5-10 Soft

40-120 Medium Dense 10-15 Firm

15-30 Stiff

120-200 Dense 30-45 Very Stiff

>200 Very Dense 45-60 Hard

>60 Very Hard

Pore Pressure Ratio, Bq

C o n e R e s is ta n c e Q t

C o n e R e s is ta n c e Q t

Friction Ratio, Fr (%)

SUBSURFACE EXPLORATION PROCEDURE:

CONE PENETRATION TESTING (CPT)

ASTM D 5778

In the CPT sounding procedure, an electronically instrumented cone penetrometer is hydraulically advanced through soil to measure point resistance (qc), pore water pressure (U2), and sleeve friction (fs). These values are recorded continuously as the cone is pushed to the desired depth. CPT data is corrected for depth and used to estimate soil classifications and intrinsic soil parameters such as angle of internal friction, pre-consolidation pressure, and undrained shear strength.

CPT Procedure:

Involves the direct push of an electronically instrumented cone penetrometer* through the soil

Values are recorded continuously

CPT data is corrected and correlated to soil parameters

*CPT Cone Size May Vary

Project: Edwards Wood Property - Alcolu

5935 Rivers Avenue, Suite 105A North Charleston, SC 29406 ECS Project #: 34:4578

Total depth: 39.56 ft, Date: 6/27/2023

CPT: C-1

Location: Manning, SC

Cone resistance qt

Tip resistance (tsf) 4002000

D ep th ft

3 8

Cone resistance qt Sleeve friction

Friction (tsf)

D ep th ft

3 9

Sleeve friction Pore pressure u

Pressure (psi) 150100500

D ep th ft

3 8

Pore pressure u SPT N60

N60 (blows/ft) 50403020100

D ep th ft

3 9

SPT N60 Norm. Soil Behaviour Type

SBTn (Robertson, 1990) 181614121086420

D ep th ft

3 8

Norm. Soil Behaviour Type

Clay

Sand & silty sand

Sand

Sand & silty sand Sand Sand & silty sand

Sand Sand & silty sand Sand Sand & silty sand Sand & silty sand Silty sand & sandy silt

Very dense/stiff soil Clay & silty clay

Very dense/stiff soil

Sand & silty sand Silty sand & sandy silt Silty sand & sandy silt

Sand & silty sand Silty sand & sandy silt Silty sand & sandy silt Sand & silty sand

Sand & silty sand

Sand & silty sand Silty sand & sandy silt

Sand & silty sand

Sand Sand & silty sand Clay & silty clay Silty sand & sandy silt Silty sand & sandy silt

Sand & silty sand

Sand

CPeT-IT v.3.7.1.12 - CPTU data presentation & interpretation software - Report created on: 7/11/2023, 10:48:20 AM 1 Project file:

5935 Rivers Avenue, Suite 105A North Charleston, SC 29406 ECS Project #: 34:4578

Total depth: 50.00 ft, Date: 6/27/2023

CPT: C-2

Location: Manning, SC

Cone resistance qt

Tip resistance (tsf) 3002001000

D ep th ft

5 0

Cone resistance qt Sleeve friction

Friction (tsf)

D ep th ft

4 8

Sleeve friction Pore pressure u

Pressure (psi) 2001000

D ep th ft

5 0

Pore pressure u SPT N60

N60 (blows/ft) 50403020100

D ep th ft

4 8

SPT N60 Norm. Soil Behaviour Type

SBTn (Robertson, 1990) 181614121086420

D ep th ft

5 0

Norm. Soil Behaviour Type

Sand & silty sand

Sand & silty sand

Silty sand & sandy silt

Sand & silty sand Sand Sand & silty sand

Sand

Sand & silty sand

Silty sand & sandy silt Silty sand & sandy silt Very dense/stiff soil Silty sand & sandy silt

Silty sand & sandy silt Clay & silty clay

Sand & silty sand

Sand Sand & silty sand Sand Sand & silty sand Silty sand & sandy silt Sand Clay & silty clay Sand Silty sand & sandy silt Silty sand & sandy silt Clay & silty clay Sand & silty sand Silty sand & sandy silt Clay & silty clay Sand & silty sand Silty sand & sandy silt Clay & silty clay Silty sand & sandy silt Clay & silty clay Sand & silty sand Sand & silty sand Sand & silty sand

CPeT-IT v.3.7.1.12 - CPTU data presentation & interpretation software - Report created on: 7/11/2023, 10:48:20 AM 2

5935 Rivers Avenue, Suite 105A North Charleston, SC 29406 ECS Project #: 34:4578

Total depth: 50.02 ft, Date: 6/27/2023

CPT: C-3

Location: Manning, SC

Cone resistance qt

Tip resistance (tsf) 4002000

D ep th ft

5 0

Cone resistance qt Sleeve friction

Friction (tsf)

D ep th ft

4 8

Sleeve friction Pore pressure u

Pressure (psi) 2001000

D ep th ft

5 0

Pore pressure u SPT N60

N60 (blows/ft) 50403020100

D ep th ft

4 8

SPT N60 Norm. Soil Behaviour Type

SBTn (Robertson, 1990) 181614121086420

D ep th ft

5 0

Norm. Soil Behaviour Type

Silty sand & sandy silt Sand & silty sand Sand & silty sand Silty sand & sandy silt Silty sand & sandy silt Silty sand & sandy silt Sand & silty sand

Clay & silty clay

Silty sand & sandy silt

Clay & silty clay

Very dense/stiff soil Very dense/stiff soil Silty sand & sandy silt Very dense/stiff soil Silty sand & sandy silt Very dense/stiff soil Sand & silty sand Sand Sand

Sand Sand & silty sand Sand & silty sand Clay & silty clay

Silty sand & sandy silt

Clay & silty clay Sand & silty sand Clay & silty clay Silty sand & sandy silt Clay & silty clay Sand & silty sand Silty sand & sandy silt Sand & silty sand

Silty sand & sandy silt Clay & silty clay

Clay & silty clay Clay & silty clay

CPeT-IT v.3.7.1.12 - CPTU data presentation & interpretation software - Report created on: 7/11/2023, 10:48:21 AM 3

5935 Rivers Avenue, Suite 105A North Charleston, SC 29406 ECS Project #: 34:4578

Total depth: 27.49 ft, Date: 6/27/2023

CPT: C-4

Location: Manning, SC

Cone resistance qt

Tip resistance (tsf) 4002000

D ep th ft

2 7

Cone resistance qt Sleeve friction

Friction (tsf)

D ep th ft

2 7

Sleeve friction Pore pressure u

Pressure (psi) 2001000

D ep th ft

2 7

Pore pressure u SPT N60

N60 (blows/ft) 50403020100

D ep th ft

2 7

SPT N60 Norm. Soil Behaviour Type

SBTn (Robertson, 1990) 181614121086420

D ep th ft

2 7

Norm. Soil Behaviour Type

Very dense/stiff soil

Sand & silty sand

Silty sand & sandy silt Clay & silty clay

Clay & silty clay

Silty sand & sandy silt Clay & silty clay

Sand & silty sand

Silty sand & sandy silt

Clay Clay & silty clay Clay Clay & silty clay Very dense/stiff soil Clay & silty clay Silty sand & sandy silt

Silty sand & sandy silt

Silty sand & sandy silt Silty sand & sandy silt Silty sand & sandy silt

Silty sand & sandy silt Very dense/stiff soil

Sand & silty sand Sand Silty sand & sandy silt Very dense/stiff soil Silty sand & sandy silt

Silty sand & sandy silt Very dense/stiff soil Sand & silty sand Clay & silty clay Silty sand & sandy silt Clay & silty clay Silty sand & sandy silt Clay & silty clay Silty sand & sandy silt Sand & silty sand

CPeT-IT v.3.7.1.12 - CPTU data presentation & interpretation software - Report created on: 7/11/2023,…