Bailey_Tract_Geotechnical_Exploration_Rev._1.pdf

Report Cover Page

Bailey Tract in Bluffton Geotechnical Engineering Report Rev.1

December 21, 2023 | Terracon Project No. HG225058

Prepared for:

Kimley-Horn

25 Bull Street, Suite 400

Savannah, GA 31401

379 Browns Cove Road, Suite C

Ridgeland, SC 29936

P (843) 258 7070

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

December 21, 2023

Kimley-Horn

100 Bull Street, Suite 200

Savannah, GA 31401

Attn: Laura Ballock, PLA

P: 912-328-4447

E: Laura.ballock@kimley-horn.com

Re: Geotechnical Engineering Report

Bailey Tract in Bluffton

72 Ulmer Road

Bluffton, South Carolina

Terracon Project No. HG225058

Dear Ms. Ballock:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PHG225058 dated

May 9, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

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

Sincerely, Terracon

Kyle Nicholson, E.I.T. Guoming Lin, Ph.D., P.E., D.GE

Staff Geotechnical Engineer Senior Consultant

Geotechnical Engineering Report

Bailey Tract in Bluffton | Bluffton, South Carolina

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i

Introduction

Project Description

Site Conditions

Geotechnical Characterization

Groundwater Conditions

Geotechnical Overview

Geotechnical Considerations

Earthwork

Shallow Foundations

Floor Slabs

Deep Foundations

Pavements

General Comments

Facilities | Environmental | Geotechnical | Materials ii

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

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

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic Overview Statement

Project

Description

The project is for the park development in Bailey Memorial Park in Bluffton, South Carolina. The park consists of a parking lot, raised boardwalk through wetlands, earthen trail, and a wildlife blind.

Geotechnical

Characterization

▪ The soil profile consists of mainly sandy soils to the termination of our exploration at 5 feet below ground surface (BGS).

▪ Groundwater was encountered between 2 feet below the ground surface (BGS) during this investigation.

Earthwork

Recommendations

▪ Install a site drainage system.

▪ Strip/grub topsoil when encountered (Note: rutting of subgrade can cause mixing of topsoil with underlying soils, which may require additional topsoil stripping).

▪ Level, densify, and proofroll subgrade during subgrade preparation. If any soft/weak areas are detected during proofroll testing, repair subgrade by undercut and backfill.

The amount of undercut is based on the weather conditions during construction and the final grade elevation.

▪ The upper soils are silty sands to sands with silt. Minimal undercutting is anticipated for these soils. Loose surface soils will require additional in-place compaction.

Earthen Path

▪ Strip/grub topsoil when encountered (Note: rutting of subgrade can cause mixing of topsoil with underlying soils, which may require additional topsoil stripping).

▪ Raise path with compacted structural fill or an aggregate base above ground surface elevation for proper drainage.

Both surfaces are expected to be susceptible to erosion and routine maintenance should be expected. Of the two materials, aggregate base will be more resistant to erosion than conventional structural fill.

Facilities | Environmental | Geotechnical | Materials ii

Foundation

Recommendations

Shallow foundations are recommended for the wildlife blind after subgrade densification.

Allowable bearing pressure = 2,000 psf

Deep Foundations

The proposed boardwalk can be supported on the designed 8-inch timber piles. We recommend 20-25 foot piles be driven 12-15 feet below ground surface into the dense sand layer from 5 to 20 feet

BGS.

Pavements

We have evaluated three pavement sections based on the assumed traffic loading: light duty pavement for parking

(cars/light trucks), and heavy-duty pavement for trash trucks.

With subgrade prepared as noted in Earthwork

Permeable Asphalt:

▪ 4” asphalt open graded friction course over 12” graded aggregate base (GAB) in Light Duty areas

▪ 6” asphalt open graded friction course over 18” graded aggregate base (GAB) in Heavy Duty areas

NOTE: Bottom of GAB course should be a minimum of 24 inches above groundwater level.

Asphalt Concrete (AC):

▪ 2” AC over 4” GAB in Light Duty areas

▪ 3.5” AC over 8” GAB in Heavy Duty areas

Concrete (Portland Cement Concrete, PCC):

▪ 5” PCC over 4” of GAB in Light Duty areas

▪ 7” PCC over 4” of GAB in Heavy Duty areas

NOTE: For pavements areas subject to repetitive concentrated loads such as the truck entry/exit driveways and parking areas, we recommend a heavy-duty section and rigid pavements.

General

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

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

Facilities | Environmental | Geotechnical | Materials iii

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

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed park development to be located at 72

Ulmer Road in Bluffton, South Carolina. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Boring logs with field and laboratory data

■ Stratification based on visual soil classification

■ Groundwater levels observed during and after the completion of drilling

■ Site Location and Exploration Plans

■ Subsurface exploration procedures

■ Description of subsurface conditions

■ Subgrade preparation/earthwork recommendations

■ Recommended pavement options and design parameters

■ Recommended foundation options and engineering design parameters

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

Drawings showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and/or as separate graphs in the Exploration Results section.

Project Description

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

◼ Since the original scope was performed, a change order for two CPT soundings in the boardwalk area. A third CPT was conducted in the field due to concerns with poor soil profiles.

Item Description

Information

Provided

An email request for a proposal was provided by Ms. Laura Ballock on 4/7/23. The request included a conceptual plan of the planned development.

Project

Description

The project is for the park development in Bailey Memorial Park in Bluffton, South Carolina.

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Proposed

Structure

According to the conceptual site plan, the development will include:

▪ Entrance sign and gate

▪ Parking lot with pervious pavement

▪ Raised boardwalk – Approximately 800 feet long

▪ Earthen trail – Approximately 3,750 feet long

▪ Wildlife blind

Building

Construction

The raised boardwalk is to be constructed of timber with either concrete or timber pile supports.

Maximum Loads

(assumed)

The following loads are assumed:

▪ Maximum building slab load: 150 psf

▪ 2 feet of fill material: 240 psf

▪ Maximum wall loads: 3 klf

The client provided the following loads for the boardwalk:

Max pier load: 20 kips

Pavements

(assumed)

We recommend flexible (asphalt)/ rigid (concrete) pavement sections will be considered for this site. Pervious concrete pavement was also evaluated for this project.

Anticipated traffic is as follows:

▪ Autos/light trucks: 50 vehicles per day

▪ Delivery/trash trucks/buses: 5 vehicles per week

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

Facilities | Environmental | Geotechnical | Materials 3

Site Conditions

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

Item Description

Parcel

Information

The project is located at Bailey Memorial Park, 72 Ulmer Road in

Bluffton, South Carolina.

Latitude: 32.2310°, Longitude: -80.8416°

See Site Location

Existing

Improvements Undeveloped

Current Ground

Cover Heavily wooded

Existing

Topography

Not provided but observed to be relatively level with low-lying areas.

Geotechnical Characterization

We have developed a general characterization of the subsurface soil and groundwater conditions based upon our review of the data and our understanding of the geologic setting and planned construction. In general, the soils are relatively consistent throughout the project area.

The geotechnical characterization forms the basis of our geotechnical calculations and evaluation of site preparation, foundation options and pavement options.

Due to standing water in the area of the test location, hand auger 6 (HA6) was omitted.

Facilities | Environmental | Geotechnical | Materials 4

Soil Stratum – Earthen Trail and Parking Area

Stratum

Approximate

Depth to Bottom of

Stratum (feet)

Material

Description Consistency / Density

1 1 Topsoil Loose

2 5 Sands with silt Loose to medium dense

Soil Stratum – Boardwalk Area

Stratum

Approximate

Depth to Bottom of

Stratum (feet)

Material

Description Consistency / Density

1 1 Topsoil Loose

2 2 Silty clays Soft to medium stiff

3 20 Sands Dense to very dense

Termination of boring, 45.2 Clays Soft to medium stiff

Groundwater Conditions

The hand auger borings were observed while augering and after completion for the presence and level of groundwater. Groundwater was encountered between 2 and 5 feet below ground surface during or after the completion of the hand auger borings and completion of CPT soundings. Surface water was present at the location of HA6. See the table below for the observed ground water depths at each test location.

Facilities | Environmental | Geotechnical | Materials 5

Test Location

Boring Termination

Depth

(ft)

Approximate Depth to

Groundwater

(ft)

HA1 3.8, Cave in 3

HA2 5 5

HA3 5 Not Encountered

HA4 5 Not Encountered

HA5 5 3

HA7 2.5, Cave in 2

HA8 4.6, Cave in 3.5

HA9 5 4

HA10 5 4

IR1 5 4

C1 31.3 2.3

C2 45.2 2

C3 7.3 (refused) 0.7

Mottling, an indicator of high seasonal ground water levels, was not encountered during the completion of the hand auger borings.

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

Geotechnical Overview

The following evaluation and recommendations are based upon our understanding of the proposed construction and the results from our field exploration. If the above-described project conditions are incorrect or changed after this report, or subsurface conditions encountered during construction are significantly different from those reported, Terracon should be notified so we can re-evaluate our recommendations and make appropriate revisions.

Facilities | Environmental | Geotechnical | Materials 6

Geotechnical Considerations

The subsurface conditions at this site are suitable for the proposed construction. It is important to note that loose sand material was observed between approximately ground surface and 2 feet BGS. This material is suitable as subgrade for foundations and slabs after improvement efforts. The generalized soil profile is presented in the Geotechnical

Characterization section.

The column, slab, and wall load and the site grading plan were not available at the time of this report. Based on our experience with similar buildings in this area, the proposed wildlife blind structures are expected to have a typical column load of slab load of 150 psf, and a wall load of 3 kips per linear foot. The client provided pier loads of up to 20 kips for the proposed boardwalk.

If heavier structural loads are required than those discussed above, Terracon should be retained to perform the additional evaluation.

We performed the settlement analyses at the sounding locations using the soil parameters derived from the SPT N60 values correlated from DCP testing and the structural loads discussed above and CPT data. Based on the results of our settlement analyses, the settlement for the restroom structure was estimated to be less than 1 inch for the assumed slab load of 150 psf, the assumed wall load of 2 kips/ft, and an assumed fill height of two feet.

We do not anticipate significant undercutting and backfilling will be required under the footings to achieve a stable subgrade. However, Terracon should be retained to field check the subgrade soil with a hand auger boring and DCP tests during construction to verify.

The results of the hand auger boring and DCP tests will determine if an additional undercut is needed. The extent and the depth of any undercut should be based on the subsurface conditions encountered during the subgrade preparation. The contractor should prepare for undercuts and backfill with structural fill or No. 57 stone if needed.

A net allowable bearing capacity of 2,000 pounds per square foot (psf) is recommended for shallow foundation design after achieving a stable subgrade. The allowable bearing capacity may be increased by 1/3 for transient wind load and seismic load conditions.

Terracon should be retained to confirm and test the subgrade during construction to provide more specific recommendations on subgrade repair based on the conditions at the footing subgrade.

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

Facilities | Environmental | Geotechnical | Materials 7

Earthwork

The site work conditions will be largely dependent on the weather conditions and the contractor’s means and methods in controlling surface drainage and protecting the subgrade. Site preparation should include installation of a site drainage system, topsoil stripping and grubbing, subgrade preparation, densification, and proofrolling. Rutting of the subgrade can also cause mixing of topsoil/organics with underlying soils which will result in additional required topsoil/organics stripping. Undercutting is not anticipated in building and paving areas.

Site Drainage

The site has a shallow groundwater table. An effective drainage system should be installed prior to site preparation and grading activities to intercept surface water and improve overall shallow drainage. If water is encountered during foundation or utility installation, localized sumps and pumps should be sufficient to lower water levels for construction.

The site should be graded to shed water and avoid ponding over the subgrade.

Densification and Proofrolling

Prior to fill placement on the subgrade, the proposed building and pavement areas should be densified with a heavy-duty static roller to achieve a uniform subgrade. The subgrade underneath the building and the pavement should be thoroughly proofrolled after the completion of densification. Proofrolling will help detect any isolated soft or loose areas that "pump", deflect or rut excessively, and densify the near-surface soils for floor slab support.

A loaded tandem axle dump truck, capable of transferring a load in excess of 20 tons, should be utilized for this operation. Proofrolling should be performed under the

Geotechnical Engineer’s observation. Areas where pumping, excessive deflection or rutting is observed after successive passes of the proofrolling equipment should be undercut, backfilled and then properly compacted. It is anticipated that some amount of subgrade undercutting may be required under the footings during subgrade preparation.

If the subgrade area is too confined to perform a proofroll, the subgrade should be evaluated by the geotechnical engineer and probed to identify any soft/unsuitable areas.

Facilities | Environmental | Geotechnical | Materials 8

Fill Material Types

Fill required to achieve design grade should be classified as structural fill. During our field exploration, the project site included fill material placed over proposed building and pavement areas. Earthen materials used for structural should meet the following material property requirements:

Based on the findings from our hand auger and CPT borings, the subject site consists mostly of sands in Stratum 2. The sands (SP/SW) are generally considered suitable for structural fill, provided that the soils are free of roots, organics, or other foreign materials.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill

Maximum Lift

Thickness

8 to 10 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

4 to 6 inches in loose thickness when hand-guided equipment

(i.e., jumping jack or plate compactor) is used

Minimum Compaction

Requirements

95% of max. below foundations and finished pavement subgrade

Water Content Range Granular: -2% to +2% of optimum

1. Maximum density and optimum water content as determined by the modified Proctor test

(ASTM D 1557).

We recommend Terracon be retained during construction to determine the suitability of the on-site soil as fill material.

Soil Type1 USCS Classification Acceptable Parameters

(For Structural Fill)

Granular

GW, GP, GM, GC,

SW, SP, SM, SC

Less than 25% Passing No. 200 sieve

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

Facilities | Environmental | Geotechnical | Materials 9

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical

Engineer. Monitoring should include documentation of adequate removal of vegetation and topsoil, proofrolling, and mitigation of areas delineated by the proofroll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, until approved by the Geotechnical Engineer prior to placement of additional lifts. One density and water content test should be performed for every 100 linear feet of compacted utility trench backfill.

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

Geotechnical Engineer should prescribe mitigation options.

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

Shallow Foundations

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

Design Parameters

Description Column Wall

Net allowable soil bearing pressure

2,000 psf 2,000 psf

Minimum dimensions 24 inches 18 inches

Minimum embedment below finished grade 18 inches 18 inches

Estimated total settlement 2 < 1 inch < 1 inch

Estimated differential settlement

<1 inch between columns <1/2 inch over 40 feet

Ultimate coefficient of sliding friction

0.32

Facilities | Environmental | Geotechnical | Materials 10

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

2. The foundation settlement will depend upon the variations in the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of compacted fill, and the quality of the earthwork operations. Footings should be proportioned to reduce differential settlements. Proportioning on the basis of equal total settlement is recommended; however, proportioning to relative constant dead-load pressure will also reduce differential settlement between adjacent footings.

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

Foundation Construction Considerations

The bottom of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance.

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

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

Therefore, it is important that Terracon be retained to observe, test, and evaluate the bearing soil prior to placing reinforcing steel and concrete to determine if additional footing excavation or other subgrade repair is needed for the design loads.

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

Facilities | Environmental | Geotechnical | Materials 11

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

Earthwork section.

The over-excavation should be backfilled up to the footing base elevation with well-graded granular material placed in lifts of 6 inches or less in loose thickness and compacted to at least 95 percent of the material's maximum dry density as determined by the Modified

Proctor test (ASTM D-1557). No. 57 stone is recommended in lieu of structural fill when the volume of excavation is relatively small, re-compaction of the fill is difficult, or the weather conditions or construction schedule becomes a controlling factor.

Facilities | Environmental | Geotechnical | Materials 12

Floor Slabs

Floor Slab Design Parameters

Item Description

Floor slab support Compacted structural fill/inspected and tested natural ground

Modulus of subgrade reaction

120 pounds per square inch per in (psi/in) for point loading conditions

Base course/capillary break

4 inches of free-draining granular material. The on-site soils may be suitable subjected to field verification during construction.

Vapor barrier Project Specific

Structural considerations Floor slabs should be structurally separated from columns and walls to allow relative movements

1. As the existing ground may have been filled or previously disturbed, we recommend the subgrade be inspected and tested with proofrolling after the topsoil is stripped as outlined in

Earthwork section of this report.

2. The floor slab design should include a base course comprised of free draining, compacted, granular material, at least 4 inches thick. The granular subbase may be graded aggregate base (GAB) or sands containing less than 5 percent fines (material passing the #200 sieve).

GAB subbase can also help improve workability of the subgrade especially during rain periods.

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

4. Floor slabs should be structurally independent of any footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates that any differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks that occur beyond the length of the structural dowels. The structural engineer should account for this potential differential settlement through use of sufficient control joints, appropriate reinforcing, or other means.

Floor Slab Construction Considerations

Prior to construction of grade supported slabs, varying levels of remediation may be required to reestablish stable subgrades within slab areas due to construction traffic, rainfall, disturbance, desiccation, etc. As a minimum, the following measures are recommended:

Facilities | Environmental | Geotechnical | Materials 13

■ The interior trench backfill placed beneath slabs should be compacted in accordance with recommendations outlined in Earthwork section of this report.

■ All floor slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the stone base and concrete.

■ All floor slab subgrade areas should be proofrolled prior to placement of the stone base and concrete.

Deep Foundations

Timber Piles

8-inch timber piles were selected by the client for this proposed boardwalk project. Based on the soil profile at the location of the boardwalk, we recommend a minimum pile length to reach a tip elevations of 15 feet below the existing grade due to a very soft layer of clays and silts between 0 to 2 feet and again at 20 to 45 feet BGS.

Due to the density of the sand layer from 5 to 9 feet BGS, pile installation to greater depths with traditional driving or vibratory methods without damaging the pile may be difficult. Pre-drilling is recommended to achieve pile embedment depths of 10 feet or more. Alternatively, piles may be driven to refusal at shallower depths (<10 feet bgs), which would provide sufficient axial compression capacity, but shallow embedment depths will have reduced lateral stability and uplift capacity.

Analyzed pile axial capacities for the timber piles are listed in the table below. Based on the pile configuration and soil parameters from the subsurface exploration, we calculated the allowable axial compression and the tension capacities using the LCPC method and based on our experience with pile capacities in this area.

Timber piles should be Southern Yellow Pine and CCA pressure treated in accordance with the requirements of AWPA C3. We recommend at least two indicator piles be driven within the proposed boardwalk areas. The results of the indicator pile driving can be used to evaluate driving resistance, develop appropriate driving equipment, and determine production pile length. The indicator piles should be driven at a design pile location and is expected to be part of the final pile layout.

We recommend that 8-inch tip diameter 20-foot-long indicator piles be used. Production piles should not be ordered until their length has been determined by driving the indicator piles. Installation of the indicator piles should be observed by the Geotechnical

Engineer.

December 22, 2023 | Terracon Project No. HG225058

Facilities | Environmental | Geotechnical | Materials 14

Recommended Allowable Axial Capacities for timber piles

Pile Tip Depth BGS (feet)

8-inch Tip Timber Piles

Allowable Compression Capacities (kips)

-12 27

-15 36

Allowable Tension Capacities (kips)

-12 9

-15 12

Analysis Parameters

1. Tension capacities do not include dead weight of pile.

2. Factor of safety for end bearing is 3.

3. Factor of safety for skin friction is 2.

Timber Pile Lateral Capacities

The behavior of the vertical piles under lateral loads was analyzed using the computer program LPILE v.2019. The LPILE program employs the p-y method based on the user-specified soil and pile properties. The deflections, rotations, and bending moments in a pile were calculated by solving the beam bending equation using finite difference numerical analysis.

The allowable lateral pile capacities will be a function of the allowable lateral deflection at the pile top. The pile head deflections will be largely determined by the type of connections between pile head and pile cap. The actual connection may fall somewhere between a fixed head and free head conditions.

The following LPile analyses were performed based on the pile top at the existing ground elevation. The calculated lateral responses of timber piles are profiled in the Supporting

Information of this report. Based on the profiles, the maximum bending moments and shear forces occur in the upper 15 feet for timber piles. The following tables summarize the lateral capacities of piles based on the limiting lateral pile head deflection of 1.0 inch.

Recommended Lateral Capacities (kips) for 8-Inch Timber Piles

Lateral Deflection (inch)

8-Foot

Embedment

12-Foot

Embedment

15-Foot

Embedment

Free Head Connection 1.8 1.9 2.0

Fixed Head Connection 4.6 4.7 4.8

1. Non-yielding elastic pile section

2. 0.5-inch allowable lateral deflection

3. One-half of the lateral load that procedures a gross lateral movement of 0.5 inch was used as lateral capacities.

4. Embedment depth is depth below ground surface.

Note: No reduction of lateral pile capacity was considered for the group effect.

Facilities | Environmental | Geotechnical | Materials 15

Timber Pile Construction Considerations

We recommend dynamic driving criteria required for the recommended design capacity be developed once the rated energy of the hammer is known. The driving resistance may be determined by either the modified Engineering News Record Formula or by a wave equation driving analysis performed by the Geotechnical Engineer.

Driving should be terminated immediately if refusal (15 blows per 3 inches unless revised by the Geotechnical Engineer based on the driving system and soil conditions) is reached to minimize risk of damaging the piles.

The installation of a pile foundation system should be in accordance with the local and state building code requirements and standard industry practice. In addition, pile installation should be monitored by the Geotechnical Engineer’s representative.

In general, the representative should:

■ Prepare driving criteria.

■ Be present continuously during driving.

■ Record the dimensions of each pile, location, and report obvious defects.

■ Count and record the blows for each foot of driving, and the final 6 inches.

■ Record energy rating of the hammer and adjust where appropriate for chamber pressure, such as in the case of a diesel hammer.

■ Have knowledge of soil conditions at the site and the minimum required penetration of each pile.

■ Be cognizant of intended support mechanisms of piles on which to base acceptance or rejection, the need to pre-drill, or evaluating the presence of obstructions.

■ Have authority to suspend driving when unanticipated difficulties or conditions are encountered and notify the Structural Engineer and the Geotechnical Engineer for

Pavements

General Pavement Comments

We understand the proposed development will include paved drives and parking areas at the entrance to the park. This section presents thickness recommendations for asphalt concrete, Portland cement concrete pavements, permeable asphalt pavement, and general considerations for the pavement construction. Pavement thickness design is dependent upon:

Facilities | Environmental | Geotechnical | Materials 16

Traffic volumes, loads, traffic pattern, and desired service life of the pavement; subgrade conditions including soil strength and drainage characteristics; paving material characteristics; climatic conditions of the region.

Based on our experience with similar projects, we have assumed the proposed asphalt and concrete pavement sections will experience the following traffic loading for the pavement design of 20 years.

Autos/light trucks: 50 vehicles per day

Light delivery and trash collection trucks: 5 trucks per week

If heavier /higher volume traffic loading is expected, we should be provided with the information and allowed to review these pavement sections. As typical for pavement, maintenance repairs are typically required after a period of 7 to 10 years to keep the pavement in acceptable condition.

The following tables provide options for AC (“asphalt”) and PCC (“concrete”) sections. In general, concrete pavement performs better in areas with heavier loads and frequent turning. We have designated two pavement sections based on the traffic loading: light duty pavement for customer parking (cars/light trucks), and heavy-duty pavement for delivery and trash collection trucks. Please refer to the following tables for our pavement design recommendations for each section. Concrete pavements are also more commonly used for truck parking.

Facilities | Environmental | Geotechnical | Materials 17

Asphalt Pavement Design Recommendations

Material

Minimum Section Thickness (inches)

Light Duty Section Heavy Duty Section

Passenger Vehicle Only

(e.g., Auto Parking) Light Delivery and Bus Traffic Areas

Asphalt Surface Course

2 1.5

Asphalt Intermediate

Course

0 2

Aggregate Base Course

4 8

Total Pavement Section 6 11.5

Structural fill improved subgrade

24 24

1. Asphalt concrete and base course materials should conform to the following SCDOT material specifications.

2. Section 305 for Graded Aggregate

Section 401 for Hot Mix Asphalt Concrete Mixture. The select fill should be relatively clean sands with percent fines less than 25%. The fill material should be compacted to a minimum of

95% of the soil’s Modified Proctor maximum dry density (ASTM D-1557).

3. If SP or SP-SM or SM soils exist at the proposed subgrade elevation extending to a depth at least

24 inches below the proposed subgrade level, the in-situ soils can replace the select fill and the subgrade should be improved using densification as discussed in Earthwork section.

Notes:

Proper surface and subgrade drainage system should be installed to avoid saturation of subgrade soils underneath the asphalt pavements. The site drainage should be designed to maintain the groundwater at least 2 feet below the top of the subgrade.

Some subgrade soil undercutting and backfilling with suitable structural fill will be required if unstable subgrade soils are encountered during subgrade preparation. The use of geogrid

(Tensar BX1100 or equivalent) may be necessary to help reduce the depth of undercut to achieve stability if the unstable subgrade soils extend to greater depths. The need for geogrid and/or the need for undercutting and backfilling should be determined in the field during subgrade preparation.

For pavement support, the subgrade conditions can often be the overriding factor in pavement performance. The subgrade conditions will depend on the in-situ soils at the subgrade level, characteristics of fill material for the subgrade, as well as site preparation procedures.

The upper five feet of the site consisted of silty sands and sands with silt. The silty sands and sands with silt have good drainage characteristics and are deemed suitable for the pavement subgrade support. If encountered, clayey sands/sandy clays should not be used for the subgrade support due to poor drainage and moisture sensitivity

Facilities | Environmental | Geotechnical | Materials 18 during construction. During construction, where clayey sands or sandy clays are encountered at the subgrade level, the upper two (2) feet of the subgrade should be replaced with sands with less than 25 percent fines. Based on the onsite in-situ soils and typical available imported fills, a California Bearing Ratio (CBR) value of 8 has been estimated.

Concrete Pavement Design Recommendations

Material

Minimum Section Thickness (inches)

Light Duty

Section Heavy Duty Section

Passenger Vehicle

Only (e.g., Auto

Parking)

Passenger Vehicles and Buses (e.g., Entrance/Truck Access Driveways, and

Dumpster)

Concrete 5 7

Graded Aggregate Base

4 4

Structural fill

Improved Subgrade

24 24

1. The concrete should be air entrained and have a minimum compressive strength of 4,000 psi after 28 days of lab curing per ASTM C-31.

2. Graded aggregate base should conform to the SCDOT material specification Section 501.

3. The structural fill should be sands with percent fines less than 25%. The fill material should be compacted to a minimum of 95% of the soil’s Modified Proctor maximum dry density

(ASTM D-1557).

4. If SP or SP-SM or SM soils exist at the proposed subgrade elevation extending to a depth at least 24 inches below the proposed subgrade level, the in-situ soils can replace the select fill and the subgrade should be improved using densification as discussed in Earthwork.

Notes:

▪ Concrete joints should be properly sealed to avoid ingress of surface water into the subgrade soils. Proper surface and subgrade drainage system should be installed to avoid saturation of subgrade soils underneath the concrete pavements. The site drainage should be designed to maintain the groundwater at least 2 feet below the top of the subgrade.

▪ In areas of concentrated truck turning in the Heavy-duty pavement, the pavement should be designed to resist lateral sliding from the truck turning force. Additional measures such as tied edge panels and keyways along the curbs may be considered to add the lateral resistance against sliding.

▪ Some subgrade soil undercutting and backfilling with suitable structural fill will be required if unstable subgrade soils are encountered during subgrade preparation. The use of geogrid

(Tensar BX1100 or equivalent) may be necessary to help reduce the depth of undercut to achieve stability if the unstable subgrade soils extend to greater depths. The need for geogrid and/or the need for undercutting and backfilling should be determined in the field during subgrade preparation.

Facilities | Environmental | Geotechnical | Materials 19

Permeable Concrete Pavement Design Recommendations

Road

Alignment

20-year design period1,2,3

Pervious Concrete Friction

Course

(inches)

Open Graded Stone Course

(inches)

1 6 12

2 6 12

1. Asphalt concrete and base course materials should conform to the following SCDOT material specifications.

▪ Section 305 for Graded Aggregate

▪ Section 409 for Open Graded Friction Course. Do not use RAP, slag, or marine limestone in the course. Use a polymer modified binder of grade PG76-22 and hydrated lime in all OGFC mixtures. Per NAPA specification, a 15 to 20% air void content is recommended for the OPFC section.

2. For the open graded stone course, a void content of 40% is recommended to allow enough water storage capacity. A separation layer consisting of geotextile fabric should be placed between the aggregate base layer and the subgrade to prevent migration of fine material from the subgrade to the stone layer. The existing graded aggregate base layer encountered along road alignment 1 may be reused provided that the crushed stone is clean and free of soil particles.

3. The select fill should be relatively clean sands with percent fines less than 15%. The fill material should be compacted to a minimum of 95% of the soil’s Modified Proctor maximum dry density

(ASTM D-1557) for the lower lift and 100% for the surface 1 foot.

4. If SP or SP-SM or SM soils exist at the proposed subgrade elevation extending to a depth at least 24 inches below the proposed subgrade level, the in-situ soils can replace the select fill and the subgrade should be improved using densification as discussed in Subgrade Preparation and

Drainage section.

Notes:

▪ Proper surface and subgrade drainage systems should be installed to avoid saturation of subgrade soils underneath the asphalt pavements. The site drainage should be designed to maintain the groundwater at least 2 feet below the bottom of the graded aggregate base course.

Some subgrade soil undercutting and backfilling with suitable structural fill will be required if unstable subgrade soils are encountered during subgrade preparation. The use of geogrid (Tensar

BX1100 or equivalent) may be necessary to help reduce the depth of undercut to achieve stability if the unstable subgrade soils extend to greater depths. The need for geogrid and/or the need for undercutting and backfilling should be determined in the field during subgrade preparation.

The above rigid, flexible, and permeable pavement sections represent the minimum design thicknesses and, as such, periodic maintenance should be anticipated. Prior to the placement of the subbase (compacted structural fill), the pavement areas should be thoroughly proofrolled.

Facilities | Environmental | Geotechnical | Materials 20

Pavement Construction Considerations

Pavement subgrades prepared early in the project should be carefully evaluated as the time for pavement construction approaches. We recommend the pavement areas be rough graded and then thoroughly proofrolled with a loaded tandem-axle dump truck. Particular attention should be paid to high traffic areas that were rutted and disturbed and to the areas where backfilled trenches are located.

Areas where unsuitable conditions are located should be repaired by removing and replacing the materials with properly compacted fill. After proofrolling and repairing subgrade deficiencies, the entire subgrade should be scarified to a depth of 12 inches, and uniformly compacted to at least 95% of the materials’ Modified Proctor maximum dry density.

Pavement and Subgrade Drainage

Poor subgrade drainage is the most common cause of pavement failure. Pavement should be sloped to provide rapid drainage of surface water. Water should not be allowed to pond on or adjacent to the pavement which would saturate the subgrade soils and weaken the subgrade support.

Based on our hand auger boring logs, the groundwater depth was not observed. We recommend the site drainage be designed to maintain the groundwater at least two (2) feet below the top of the subgrade. Pavement subgrade drainage should be installed surrounding the areas anticipated for frequent wetting or having poor natural drainage, such as landscaped islands, along curbs and gutters and around drainage structures.

Pavement Maintenance

The performance of pavements will require regular maintenance. One key consideration of such maintenance is to minimize infiltration of water into the pavement base and subgrade. Preventive maintenance should include crack and joint sealing and patching as well as overall surface sealing and overlay. Additional engineering observation and evaluation is recommended prior to any major maintenance.

General Comments

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

Natural variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of such variations may not

Facilities | Environmental | Geotechnical | Materials 21 become evident until during or after construction. Terracon should be retained as the

Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

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

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

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly impact excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site Safety, and cost estimating including, excavation support, and dewatering requirements/design are the responsibility of others. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

Attachments

Exploration and Testing Procedures

Field Exploration

Number of

Borings Type of Exploration

Maximum Boring

Depth (feet) Location

5 Hand Auger (HA) Boring 5 Earthen trail

Hand Auger with Dynamic

Cone Penetrometer Boring

(HA-DCP)

Boardwalk, wildlife blind, parking area

1 Infiltration Test (IR) Boring 1 Parking area

3 CPT Sounding 45.2 Boardwalk area

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

Subsurface Exploration Procedures: We pushed the CPT soundings with a track-mounted drill rig. CPT sounding is the technology in which an electronically instrumented cone penetrometer is hydraulically pushed through the soil while nearly continuous readings are recorded to a portable computer. The cone is equipped with electronic load cells to measure tip resistance and sleeve resistance and a pressure transducer to measure the generated ambient pore pressure. The face of the cone has an apex angle of 60° and an area of 15 cm2. Digital data representing the tip resistance, friction resistance, pore water pressure, and probe inclination angle are recorded about every 2 centimeters while advancing through the ground at a rate between 1½ and 2½ centimeters per second.

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

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

Hand auger borings were conducted in general accordance with ASTM D 1452, Standard

Practice for Soil Investigation and Sampling by Auger Borings. In this test, hand auger borings are drilled by rotating and advancing a bucket auger to the desired depths while periodically removing the auger…