GEO TECH_Wampee Convenience Center.pdf

Report Cover Page

SWA Convenience Center, Hwy 90 - Wampee Geotechnical Engineering Report

August 31, 2023 | Terracon Project No. ER235015

Prepared for:

Thomas & Hutton Engineering Co.

611 Burroughs and Chapin Blvd.

Myrtle Beach, South Carolina 29577 flecknoe11882 Reviewed

Geotechnical Engineering Report SWA Convenience Center, Hwy 90 - Wampee | Horry County, South Carolina August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials i

Report Cover Letter to Sign

August 31, 2023

Thomas & Hutton Engineering Co 611 Burroughs and Chapin Blvd.

Myrtle Beach, South Carolina 29577

Attn: Mr. John Richards, PE E: Richards.j@thomasandhutton.com

Re: Geotechnical Engineering Report SWA Convenience Center, Hwy 90 - Wampee Horry County, South Carolina Terracon Project No. ER235015

Dear Mr. Richards:

We have completed our scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PER235015 dated February 27, 2023. This report describes our understanding of the project, presents the findings of the site subsurface exploration, and provides geotechnically related recommendations for borrow source suitability and pavement design.

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

Dylan Tanner Wendy H. Parsons, PE Field Engineer Senior Engineer

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Table of Contents

Introduction Project Description Site Conditions Site Characterization

Subsurface Profile Laboratory Testing Groundwater Conditions On-Site Borrow Suitability

Geotechnical Overview Earthwork

Site Preparation Subgrade Preparation Fill Material Types Fill Compaction Requirements Construction Observation and Testing

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

General Comments

Attachments

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

Refer to each individual Attachment for a listing of contents.

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Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed pavement and pond to be located on the new SWA Convenience Center in Horry County, South Carolina. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Site preparation and earthwork

■ On-site borrow suitability

■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of a total of seven (7) Hand Auger Borings (HABs). Dynamic Cone Penetrometer (DCP) testing was conducted within each of these hand auger borings. The hand augers were advanced to a depth of approximately 4 to 8 feet below the existing ground surface.

Although all the hand auger borings were proposed to be advanced to depths of 7 to 8 feet, HAB-01 was terminated early due to hole collapse. Data for both roadway and ponds was obtained at these locations. Our field procedures are described in Exploration and Testing Procedures.

Drawings showing the site and testing locations are shown on the Site Location and Exploration Plans, respectively.

Project Description

Our understanding of the project conditions is as follows:

Item Description

Information Provided

The following information was provided via e-mail by Thomas & Hutton:

■ Recombination survey dated 10/26/2022 prepared by Diamond

Shores Surveying, LLC, Project RFP from Horry County dated February 10, 2023 and USACE AJD letter dated 11/6/2022 all received on February 21, 2023

■ Site Plan prepared by Thomas & Hutton dated and received on July 27, 2023

■ Paving, Grading and Drainage Plans prepared by Thomas & Hutton dated August 7, 2023 and provided on August 14, 2023

■ Truck traffic counts provided on August 10, 2023

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Project Description

We understand that the ±13.34 acre site will be developed with a new HCSWA Convenience Center. The scope of this exploration is limited to determining the suitability of the proposed ±0.5 acre pond excavation for re-use as fill during proposed development as well as providing pavement recommendations for approximately 3½ acres of proposed paved area.

Grading/Slopes

Based on the grading plan provided, finished grades within the proposed pavement areas range from 31 to 33 feet. Final roadway elevations will result in up to 2 to 3 feet of fill at the north side of the site and transition to minimal cut at the south side of the site.

Pavements

We understand the site will be used as a solid waste recycling facility and will predominantly experience passenger vehicle and garbage truck traffic.

Heavy duty flexible (asphalt) and rigid (concrete) pavement sections have been considered. Traffic estimates were provided by Horry County’s Andy Markunas for a similar facility in email correspondence on August 10, 2023.

The following traffic information was used in our pavement calculations:

■ Garbage Trucks (2021): 2,100 one-way trips per year

■ This number is projected to grow to 3,500 trips per year in 20 years

In addition to the garbage truck data provided we have assumed the following for other vehicle types:

■ Automobiles: 500 one-way trips per day

■ Pick-up trucks: 500 one-way trips per day

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration.

Item Description

Parcel Information

The site is located off US Highway 90 in Longs, Horry County, SC. The approximate location of the property is Latitude 33.856693°, Longitude -78.741363°. For additional information, see Site Location

Existing Improvements

The site is currently undeveloped.

Current Ground Cover

The site is predominantly covered in dense vegetation. The northernmost end of the site adjacent to Hwy 90 is the exception to this, where it is clear of vegetation.

Existing Topography

Based on the proposed grading plan, the existing topographic lines shown on the plan range from 27 to 33 ft within the area to be paved.

The existing ditch that runs along a portion of the western side of the property has a bottom elevation of about 27 ft and is approximately 2 to 3 feet in depth.

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Site Characterization

Subsurface Profile

The table below provides a general characterization of the subsurface conditions based upon our review of the field data at test locations HAB-02 to HAB-07 and our knowledge of geologic conditions in the site area.

Description Approximate Depth to

Bottom of Stratum Material Encountered1

Stratum 1 12 inches Poorly graded sand with root mat at the ground surface

Stratum 2 4 ½ to 7 ½ feet Clayey sand to sandy lean clay

Stratum 3 8 feet Poorly graded sand with varying fines content

1. Material descriptions are based on visual classification from HAB samples.

The table below provides a characterization of the subsurface conditions encountered at test location HAB-01. This boring was offset due to hole cave at a depth of 4 feet below existing ground surface. Both the original and the offset were terminated at approximately 4 feet due to hole collapse. Based on aerial photographs, this area was cleared of vegetation between April 2021 and October 2022.

Description Approximate Depth to

Bottom of Stratum Material Encountered1

Stratum 1 2 feet Possible Fill: Poorly graded sand with silt, sparse grasses at the surface

Stratum 2 3 feet Clayey sands with few finger roots

Stratum 2 4 feet Silt with some organics

1. Material descriptions are based on visual classification from HAB samples.

Conditions observed at each exploration point are indicated on the individual logs which can be found in the Exploration Results section.

Laboratory Testing

The project engineer reviewed the collected field data and assigned laboratory tests to better understand the engineering properties of the sandy soils encountered within the borings advanced within the proposed pond area. The laboratory testing consisted of the following:

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■ 4 Percent Passing the No. 200 Sieve Test (ASTM D1140)

■ 4 Natural Moisture Content Test (ASTM D2216)

The results of the laboratory testing are shown on the boring logs in Exploration Results.

Sample Location

Depth Moisture Content (%) Passing No. 200 Sieve

HAB-02 5 – 5 ½ feet 18.2 11.5

HAB-02 7 ½ - 8 feet 16.4 4.1

HAB-03 6 – 6 ½ feet 16.5 8.3

HAB-03 7 ½ - 8 feet 18.0 5.8

Groundwater Conditions

At the time of our exploration, groundwater was observed at depths ranging from 3 to 7 feet below the existing ground surface. The water levels as observed during the field exploration are summarized in a table and on the individual boring logs, in Exploration Results.

Groundwater level fluctuations will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time exploration was performed.

Therefore, groundwater levels during construction or 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.

Fine-grained soils located near the existing ground surface are relatively impermeable and will impede percolation of rainfall into the site. Therefore, shallow “perched” groundwater conditions should be expected during wet months of the year, especially right after heavy rainfall. During periods of heavy precipitation, water will tend to move laterally across the site and collect in low-lying areas before it slowly descends into the groundwater table.

On-Site Borrow Suitability

Two HABs (HAB-02 and HAB-03) were performed within the footprint of the proposed pond area to a depth of 8 feet below the existing ground surface. Selected soil samples were tested in the laboratory in accordance with ASTM D1140 Standard Test Methods for Amount of Material in Soils Finer than No. 200 (75-µm) Sieve and ASTM D2216 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass. The laboratory test results for index properties are presented on the individual logs in attached to this report and in the table above in the Laboratory Testing section.

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Sandy clays/clayey sands were encountered within these borings to depths of approximately 4 ½ to 6 feet below the existing ground surface. These soils would not be considered suitable for use as borrow material.

Upper clays were underlain by relatively clean sands to boring termination depths of 8 feet. When tested in our laboratory, these soils were found to have fines contents ranging from approximately 4 to 12 percent. These sands would be considered suitable for use as structural fill. However, these soils will likely require some degree of mechanical manipulation/drying prior to use as fill material, especially where they are encountered beneath the water table. Soils excavated from beneath the water table can be expected to be wet and at a moisture content significantly higher than optimum. Time for drying should be allowed for during the construction process for soils containing elevated moisture contents at the time of excavation. Drying time will be largely weather dependent and will increase with lift thickness.

Please refer to the hand auger logs in the Attachments section of this report for thickness and depths of each soil type.

It should be noted that soil conditions may vary across this site and can vary between test locations. Terracon has reported our findings at each test location advanced in efforts to determine the extent of suitable fill material at this site. However, we cannot make assumptions regarding soils outside of what is observed at our test locations.

Geotechnical Overview

The site is suitable for the proposed construction assuming the recommendations in this report are followed, specifically the Earthwork section.

Our review of grading plans provided indicates final roadway elevations will result in up to 2 to 3 feet of fill at the north side of the site and transition to minimal cut at the south side of the site.

Near surface soils across the majority of the site predominantly consist of clayey sand and sandy clays. The primary geotechnical concern during earthwork operations will be maintaining the stability of the exposed subgrades upon which structural fill or the paving materials themselves are to be placed. These clayey soils will deteriorate rapidly when exposed to a combination of construction traffic and excess rainfall. Subgrade stabilization, in the form of undercutting and replacement of soft soils with structural fill, should be expected.

A portion of the site directly adjacent to Hwy 90 appears to have been filled in the past.

In this area of the site, at test location HAB-01, we encountered 2 feet of sand underlain by soft clayey sand and organic laden silt to a depth of 4 feet where we encountered hole collapse due to the presence of groundwater. This surficial sand thickness in combination

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Facilities | Environmental | Geotechnical | Materials 8 with fill planned for this area of the site is probably thick enough to “bridge” these soft soils. However, where a proofroll shows that this is not the case, undercut and replacement of the in-situ soils may be required. Although not encountered in our test locations, there is potential for the presence of buried deleterious debris and uncontrolled fill in this area of the site due to previous earthwork activities. Proofrolling will aid in identifying any debris and uncontrolled fill. If encountered during construction, it should be removed and replaced with structural fill.

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

Earthwork

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

Site Preparation

Positive site drainage should be established prior to the start of earthwork activities. This is especially important due to the presence of near surface clayey soils encountered across the site. These soils are moisture sensitive and exposure to water and construction traffic can lead to softening and rutting of the upper material. Therefore, we recommend that a site drainage plan be established and implemented prior to large scale clearing/stripping activities. This can include directing runoff water to existing drainage features and drainage ditches and/or swales across the project site as needed. These measures will allow for perched water to be directed away from construction areas limiting the softening of near surface soils.

With positive drainage established, the proposed limits of construction should be stripped of trees, organic material, topsoil, root balls, and other deleterious material from within the proposed roadway areas. Stripping should extend a minimum of 5 feet outside the construction area footprint. We anticipate stripping depths to average 6 inches across the site to remove the organics. Please bear in mind, due to the uneven ground surface of the site, the volume of topsoil and organics may be significantly greater than the area times the topsoil/organics thickness indicated in the boring logs. Rutting of the subgrade can also cause 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. Voids remaining from the clearing/stripping operation should be backfilled with properly compacted Structural Fill. Any material that will be removed in

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Subgrade Preparation

After clearing and site stripping, the subgrade should be evaluated by the Geotechnical Engineer. This evaluation might need to include proofrolling with a fully loaded tandem-axle dump truck or similar construction equipment. Areas excessively deflecting under the proofroll should either be removed or moisture-conditioned and recompacted.

Near surface soils at the site predominantly consisted of clayey soils (CL/SC). While stable in a dry condition, these clayey soils will deteriorate rapidly when exposed to excess moisture. Due to this moisture sensitivity, it is our opinion that subgrade stabilization will be required across much of the pavement areas, and some isolated areas beneath the building slab, especially within the vicinity of the existing ditches. The degree of subgrade stabilization necessary will depend greatly upon climatic conditions and can be evaluated at the time of construction.

Stabilization efforts can consist of undercutting to a stable material and backfilling with structural fill. Undercutting to depths of 18 to 24 inches will probably be sufficient. At a minimum, undercut depths should allow for 18 inches of structural fill between existing subgrade soils and the Graded Aggregate Base Course (GABC). Any structural fill already required to elevate the pavement areas to finished subgrade elevation can be included in this 18-inches, provided the condition of the existing subgrade is inspected and approved by the geotechnical engineer prior to fill placement. The extent of the undercutting will be dependent on moisture conditions at the time of construction including weather conditions, the effectiveness of site drainage in place at the time earthwork is in progress, as well as final roadway grading plans.

Undercutting may be deeper in isolated areas depending on soil conditions and in the vicinity of existing ditches. Undercutting should extend a minimum of 1 foot outside of pavement areas. Undercut soils should be replaced with structural fill as outlined below.

Undercut soils could be utilized as non-structural fill in landscaped and grassed areas.

As stated above, the layer of sand and planned fill material thickness above the organic laden silt in the northern portion of the site is likely sufficient to “bridge” the soft underlying silt. We recommend a proofroll of this area be conducted and anticipate that areas where this proof roll does not pass that undercut and replacement of these soils will need to take place. The extent of required undercutting will be dependent on moisture conditions at the time of construction, effectiveness of site drainage improvements and the thickness of this sand layer in different areas. Also, to help lessen the need for site undercutting, site drainage must be effective and construction equipment should not traffic wet or newly exposed subgrades; the latter of which should be backfilled immediately with new structural fill dozed out onto the cut subsurface from “high ground”.

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If near surface soils are exposed to rubber-tired traffic during wet periods, they may lose their strength leading to rutting and increased undercutting depths. The ability to maintain competent bearing soils will affect pavement design and overall performance. Placement of base course materials as soon as possible in pavement areas would provide protection for the subgrade as other construction takes place. Clearing techniques that minimize soil subgrade disturbance should be employed.

Soil conditions indicate underdrains will be required to adequately drain the roadway subgrades within the area of undercutting. The undercut subgrade should be graded to match final grading plans prior to placement of Structural Fill to promote drainage to low areas where the underdrains will be located. After underdrain placement, Structural Fill can be placed as required. In short, underdrain placement can proceed along with the overexcavation and replacement process. The configuration of underdrains would be dependent upon the project grading and drainage plans which can be reviewed to finalize underdrain placement. The underdrain plan should be coordinated with the site civil design engineer. Terracon can provide additional design criteria and input for underdrains as required.

Fill Material Types

Fill required to achieve design grade should be classified as Structural Fill. Structural fill is material used below, or within 10 feet, of pavements or constructed slopes. Earthen materials used for Structural Fill should meet the following material property requirements:

Soil Type 1 USCS Classification

Acceptable Parameters (for Structural Fill)

Structural, Imported Fill

SP, SP-SM, SP-SW,

SW

Non-plastic Less than 12% passing No. 200 sieve

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Fill Compaction Requirements

Item Description

Fill Lift Thickness

When heavy, self-propelled compaction equipment is used, fill lifts shall have a maximum of 8 inches in loose thickness.

When hand-guided equipment (i.e., jumping jack or plate compactor) is used, fill lifts shall have a maximum of 2 to 4 inches in loose thickness.

Compaction Requirements1

The pavement base course should be compacted to 100% of the material’s maximum Modified Proctor dry density (ASTM D1557).

Other structural areas and the upper 18 inches of the pavement subgrade should be compacted to 95% of the material’s maximum Modified Proctor dry density (ASTM D1557).

Moisture Content – Structural Fill or Onsite Soils2

Within the range of ±2% of optimum moisture content value as determined by the Modified Proctor test.

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 Structural Fill material pumping when proofrolled.

Construction Observation and Testing

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

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer 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 5,000 square feet in pavement areas. Where not specified by local ordinance, one density and water content test should be performed for every 100 linear feet of compacted utility trench backfill and a minimum of one test performed for every 12 vertical inches of compacted backfill.

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

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Pavements

General Pavement Comments

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

Pavement Design Parameters

A California Bearing Ratio (CBR) of 8 was used for the subgrade for the asphaltic concrete (AC) pavement designs. A modulus of subgrade reaction of 175 pci was used for the portland cement concrete (PCC) pavement designs. This value is based on the implementation of site preparation as outlined in the Earthwork section of this report. A modulus of rupture of 550 psi was used in design for the concrete (based on correlations with a minimum 28-day compressive strength of 4,000 psi).

Pavement Section Thicknesses

We have not included construction traffic loads in our pavement design. If the pavement is subject to heaver traffic loading than the assumed provided garbage truck counts, 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 sections were evaluated using the American Association of State Highway and Transportation Official’s (AASHTO) “Structural Number” (SN) system. For pavement design, the AASHTO system converts an estimated Average Daily Traffic (ADT) or Vehicles per Day (VPD) to an Equivalent 18-kip Single Axle Loads (ESAL’s) placed on the pavement during its design life.

We understand a design life of 20 years was assumed to develop the total traffic used in thickness design. However, as typical for pavement, it should be noted that some maintenance repairs are typical after a period of 7 to 10 years.

As previously mentioned, a portion of the site directly adjacent to Hwy 90 appears to have been filled in the past. In this area of the site, at test location HAB-01, we encountered 2 feet of sand underlain by soft clayey sand and organic laden silt to a depth of 4 feet.

Settlement may be concern in this area due to the combination of soft in-situ soils and planned fill heights of 2 to 3 feet. Flexible pavement may perform better in this area of the site.

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For new flexible pavements, the minimum SN required by the traffic loading and the subgrade soil strength is calculated from the subgrade strength data, assumed traffic volumes, assumed traffic growth rate, and design life. The following table provides our opinion of minimum thickness for AC sections:

Layer Thickness (inches)1

AC Surface 2.0

AC Intermediate 2.0

Aggregate Base 8.0

Total Thickness 12.0

1. All materials should meet the current South Carolina Department of Transportation (SCDOT) Standard Specifications for Highway and Bridge Construction.

■ Asphaltic Surface - SCDOT Type B

■ Asphaltic Intermediate - SCDOT Type B Binder

■ Graded Aggregate Base Course as specified in Section 305

The following table provides our estimated minimum thickness of PCC pavements. In general, concrete pavement performs better in areas with frequent turning and heavy wheel loads.

Portland Cement Concrete (PCC) Design

Layer

Thickness (inches)

Heavy Duty (Truck and Drive Areas, Loading Areas, and Trash Container Pad) 1

PCC 2 7.0

Aggregate Base 6.0

Total Thickness 13.0

1. See Project Description for more specifics regarding traffic assumptions.

2. All materials should meet the South Carolina Department of Transportation (SCDOT)

Standard Specifications for Highway and Bridge Construction.

■ Concrete Pavement - SCDOT Portland Cement Concrete Type C

Areas for parking of heavy vehicles, concentrated turn areas, and start/stop maneuvers could require thicker pavement sections. Edge restraints (i.e., concrete curbs or aggregate shoulders) should be planned along curves and areas of maneuvering vehicles.

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Although not required for structural support, a minimum 4-inch thick base course layer is recommended to help reduce potential for slab curl, shrinkage cracking, and subgrade pumping through joints. Proper joint spacing will also be required to prevent excessive slab curling and shrinkage cracking. Joints should be sealed to prevent entry of foreign material and doweled where necessary for load transfer. PCC pavement details for joint spacing, joint reinforcement, and joint sealing should be prepared in accordance with ACI 330 and ACI 325.

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

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

Islands with raised concrete curbs, and area with irrigated foliage and low permeability near-surface soils are particularly of concern. The civil design for the pavements with these conditions should include features to restrict or collect and discharge excess water from the islands. Examples of features are edge drains connected to the stormwater collection system, longitudinal subdrains, or other suitable outlets and impermeable barriers preventing lateral migration of water such as a cutoff wall installed to a depth below the pavement.

Construction methods and materials used in the development of the new pavement areas should meet the minimum requirements as directed by SCDOT Standard Specifications for Highway Construction, 2007 edition.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase.

Consideration should be given to installing a pavement subdrain system to control subgrade moisture, improve stability, and improve long-term pavement performance.

We recommend pavement subgrades be crowned at least 2% to promote the flow of water towards the subdrains, and to reduce the potential for ponding of water on the subgrade.

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The subdrains should be hydraulically connected to the free-draining granular base layer.

Subdrains should be sloped to provide positive gravity drainage to reliable discharge points such as the stormwater detention basin. Periodic maintenance of subdrains is required for long-term proper performance.

Pavement Maintenance

The pavement sections represent minimum recommended thicknesses and, as such, periodic upkeep should be anticipated. 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. Pavement care consists of both localized (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Additional engineering consultation 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.

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

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

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

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

■ Install joint sealant and seal cracks immediately.

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

General Comments

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

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

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Facilities | Environmental | Geotechnical | Materials 16 and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

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

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

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly effect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others. Construction and site development have the potential to affect adjacent properties. Such impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

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Attachments

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Exploration and Testing Procedures

Field Exploration

Type of Test Number of

Tests

Approximate Boring Depth

(feet) Location

Hand Auger Borings (HAB) with Dynamic Cone

Penetrometer (DCP) Testing 7 4 to 8

Proposed Pavement and Pond

Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) and referencing existing site features. If elevations and a more precise boring layout are desired, we recommend locations be surveyed.

Subsurface Exploration Procedures: All exploration is compliant with ASTM D3740, “Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction”.

All Hand Auger Borings and Dynamic Cone Penetration tests were conducted in general accordance with:

■ ASTM D1452, “Standard Practice for Soil Exploration and Sampling by Auger Borings”

■ ASTM D6951, “Standard Test Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications”

We also observed the testing locations for the presence of groundwater while drilling. Our observations of the groundwater table are between 3 and 7 feet. Groundwater water levels are summarized in the table below and are also available on the attached boring logs.

Test Location Groundwater Level (feet)

HAB-01 3

HAB-02 5

HAB-03 6

HAB-04 6 ½

HAB-05 7

HAB-06 6 ½

HAB-07 7

Additional sampling information was recorded on the field logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and/or classification

August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials by a Geotechnical Engineer. Our exploration team prepared field logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on visual-manual classification.

Laboratory Testing

Immediately following field exploration, the samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer.

Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System. The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following methods:

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

■ ASTM D1140, “Standard Test Methods for Determining the Amount of Material Finer than 75-μm (No. 200) Sieve in Soils by Washing”

The following ASTM methods were utilized for classification of soil:

■ ASTM D2487, “Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)”

■ ASTM D2488, “Standard Practice for Description and Identification of Soils (Visual-Manual Procedures)”

A summary of laboratory testing can be found in Exploration Results and is summarized on individual hand auger boring (HAB) logs.

August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials

Site Location and Exploration Plans

Contents:

Site Location Plan Exploration Plan Exploration Plan with Project Overlay

Note: All attachments are one page unless noted above.

August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials

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Site Location

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

SITE

August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials

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Exploration Plan

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

August 31, 2023 | Terracon Project No. ER235015

Facilities | Environmental | Geotechnical | Materials

Note to Preparer: This is a large table with outside borders. Just click inside the table above this text box, then paste your GIS Toolbox image.

When paragraph markers are turned on you may notice a line of hidden text above and outside the table – please leave that alone. Limit editing to inside the table.

Exploration Plan with Project Overlay

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

Exploration Results

Contents:

HAB Logs (HAB-01 through HAB-07)

POSSIBLE FILL - POORLY GRADED SAND WITH SILT (SP-SM), root mat at surface, brown

CLAYEY SAND (SC), dark gray, with few finger roots

SILT (ML), some organics, dark brown

Boring Terminated Due to Hole Collapse at 4 Feet

Boring Log No. HAB-01

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra ph ic

L og

2.0

3.0

4.0

8-9-10

3-2-2

2-2-2

4-3-1

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC Terracon Project No. ER235015

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.

Notes

Offset once with the same refusal result

Water Level Observations

Sa m pl e

Ty pe

Fi ne s C on te nt

M oi st ur e C on te nt

See Exploration PlanLocation:

Depth (Ft.)

Fi el d Te st R es ul ts

POORLY GRADED SAND WITH SILT (SP-SM), roots at surface, brown

SANDY LEAN CLAY (CL), grey and yellow

CLAYEY SAND (SC), grey

SANDY LEAN CLAY (CL), grey and yellow

POORLY GRADED SAND WITH SILT (SP-SM), grey

POORLY GRADED SAND (SP), grey

Boring Terminated at 8 Feet

Boring Log No. HAB-02

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

11.5

4.1

18.2

16.4

1.0

2.5

3.5

4.5

7.0

8.0

7-6-8

6-6-10

15+

15+

6-5-7

5-5-7

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC

Terracon Project No. ER235015

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.

Notes

Water Level Observations

S am pl e

T yp e

Fi n es

C o n te n t

M o is tu re

C o n te n t

See Exploration PlanLocation:

Depth (Ft.)

Fi el d T es t

R es u lt s

POORLY GRADED SAND WITH SILT (SP-SM), root mat at surface, brown

SANDY LEAN CLAY (CL), red and orange

CLAYEY SAND (SC), orange and grey

POORLY GRADED SAND WITH CLAY (SP-SC), orange

Boring Terminated at 8 Feet

Boring Log No. HAB-03

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra ph ic

L og

8.3

5.8

16.5

18.0

1.0

4.0

6.0

8.0

10-12-15+

12-15+

15+

15+

15+

13-19-10

7-7-5

7-5-7

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC Terracon Project No. ER235015

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.

Notes

Water Level Observations

Sa m pl e

Ty pe

Fi ne s C on te nt

M oi st ur e C on te nt

See Exploration PlanLocation:

Depth (Ft.)

Fi el d Te st R es ul ts

POORLY GRADED SAND WITH SILT (SP-SM), root mat at surface, tan

SANDY LEAN CLAY (CL), red and orange

CLAYEY SAND (SC), red and orange

POORLY GRADED SAND WITH SILT (SP-SM), grey

Boring Terminated at 8 Feet

Boring Log No. HAB-04

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

1.0

4.5

6.0

8.0

7-10-11

8-15+

15+

15+

15+

9-11-10

8-10-10

12-15+

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC

Terracon Project No. ER235015

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.

Notes

Water Level Observations

S am pl e

T yp e

Fi n es

C o n te n t

M o is tu re

C o n te n t

See Exploration PlanLocation:

Depth (Ft.)

Fi el d T es t

R es u

POORLY GRADED SAND (SP-SM), root mat at surface, grey

SANDY LEAN CLAY (CL), red and grey grey

POORLY GRADED SAND WITH SILT (SP-SM), grey

Boring Terminated at 8 Feet

Boring Log No. HAB-05

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

1.5

7.5

8.0

7-12-12

7-12-13

8-10-9

8-11-12

8-12-13

7-9-12

8-10-11

6-7-9

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC

Terracon Project No. ER235015

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.

Notes

Water Level Observations

S am pl e

T yp e

Fi n es

C o n te n t

M o is tu re

C o n te n t

See Exploration PlanLocation:

Depth (Ft.)

Fi el d T es t

R es u

POORLY GRADED SAND WITH SILT (SP-SM), grey

Boring Terminated at 8 Feet

Boring Log No. HAB-06

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

1.0

6.5

8.0

12-15+

15+

15+

12-15+

13-15+

15+

7-11-11

10-12-15+

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC

Terracon Project No. ER235015

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.

Notes

Water Level Observations

S am pl e

T yp e

Fi n es

C o n te n t

M o is tu re

C o n te n t

See Exploration PlanLocation:

Depth (Ft.)

Fi el d T es t

R es u grey and yellow

CLAYEY SAND (SC), grey

POORLY GRADED SAND WITH SILT (SP-SM), grey

Boring Terminated at 8 Feet

Boring Log No. HAB-07

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

1.0

7.0

7.5

8.0

6-8-8

7-8-10

10-10-12

12-12-11

8-11-15+

13-15+

10-10-12

7-7-15+

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method Manual Hand Auger Boring

Driller

WT

Logged by

KF

Boring Started 08-03-2023

Boring Completed 08-03-2023

1246 Howard Ave

Drill Rig

SWA Convenience Center, Hwy 90 - Wampee

Myrtle Beach, SC

SC Hwy 90 | Longs, SC

Terracon Project No. ER235015

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.

Notes

Water Level Observations

S am pl e

T yp e

Fi n es

C o n te n t

M o is tu re

C o n te n t

See Exploration PlanLocation:

Depth (Ft.)

Fi el d T es t

R es u

Supporting Information

Contents:

General Notes Unified Soil Classification System

Dynamic Cone Penetrometer

Facilities | Environmental | Geotechnical | Materials

1246 Howard Ave

Antioch Church Addition

2080 Hwy 129 | Galivants Ferry, SC

Myrtle Beach, SC

Terracon Project No. ER235060

N

(HP)

(T)

(DCP)

UC

(PID)

(OVA)

Standard Penetration Test Resistance…