10 Final Geotechnical Report - January 2023.pdf

Report Cover Page

VAMC Fayetteville – New Mechanical Enclosure Geotechnical Engineering Report

January 4, 2023 | Terracon Project No. 70215256

Prepared for:

Charlotte Engineers, LLP 5838 Monroe Road Charlotte, North Carolina

Geotechnical Engineering Report VAMC Fayetteville – New Mechanical Enclosure | Fayetteville, North Carolina January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i Introduction Project Description Site Conditions Geotechnical Characterization Seismic Site Class Geotechnical Overview Earthwork Shallow Foundations Floor Slabs Lateral Earth Pressures General Comments

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.

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Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic 1 Overview Statement 2

Project Description

2,000 square foot new Mechanical Enclosure adjacent existing building.

Estimated maximum loads: columns 50 kips, wall loads 3 kips/ft, slabs 150 psf

Geotechnical Characterization

As the site is immediately adjacent to an existing building, and project test boring A-1 encountered approximately 3 feet of existing silty/clayey sand fill, it is anticipated that approximately 3 feet of existing silty/clayey sand fill may also be present within the footprint of the new Mechanical Enclosure Structure.

Native soils immediately underlying existing fill consist of clayey/silty sand Coastal Plain soils.

Earthwork Remove existing fill to its full depth and backfill to planned foundation or slab subgrade with engineered fill.

Shallow Foundations

Shallow foundations are recommended for building support Allowable bearing pressure = 3,000 psf Expected settlements: < 1-inch total, < 1/2-inch differential

General Comments

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

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

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

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Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed new Mechanical Enclosure to be located north end of the northeast corner of the main VA Building located at 2300 Ramsey Street in Fayetteville, North Carolina. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Demolition considerations

■ Foundation design and construction

■ Floor slab design and construction

■ Lateral earth pressure

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.

Item Description

Information Provided Information on the planned structure was provided in an email to Terracon on October 6, 2021.

Project Description We understand a single-story mechanical enclosure structure, with plan dimensions of approximately 40 feet by 50 feet, is planned for the site.

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Item Description

Proposed Structure/Construction

The mechanical enclosure structure will likely consist of steel or masonry framing with a concrete or gravel floor. Structure height is just less than 12 feet with no provisions for additional levels. An intake tower, at the northeast corner of the structure, will be approximately 30 feet high.

Finished Floor Elevation FFE is expected to be within 2 feet of existing grade.

Maximum Loads (assumed)

Columns: 50 kips Walls: 3 kips per foot Floor Slab: 150 psf

Grading/Slopes A Grading Plan has not been provided. We have assumed that cuts and fills will not exceed 2 feet. Final slope angles of 3H:1V or flatter are expected.

Below-Grade Structures None Assumed

Free-Standing Retaining Walls

None Assumed

Pavements None Assumed

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

Site Conditions

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

Item Description

Parcel Information

The project is located at the existing VA Medical Center located at 2300 Ramsey Street in Fayetteville, North Carolina.

Approximate Latitude and Longitude: 35.0889°, -78.8763° See Site Map

Existing Improvements

The project site is located in a utility/landscaped area immediately adjacent the north side of the main building. Existing mechanical equipment currently occupies, and temporary fencing surrounds, the site of the new structure. Adjacent areas include a picnic shelter and a gazebo, as well as a small historical land feature.

Current Ground Cover

The project area is currently unpaved and contains existing mechanical equipment. Scattered landscaped areas are located near the project site.

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Item Description

Existing Topography

The project area slopes downward away from the existing building at a slight grade. The existing ground surface is approximately el 190 feet.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model Layer

Layer Name General Description

1 Existing Fill Silty/Clayey Sand, red brown to dark brown

Coastal Plain

Deposits Silty/Clayey Sand, interbedded with layers of Silt/Clay or poorly sorted Sand

Groundwater seepage was not encountered within the maximum drilling depth at the time of our field exploration. Groundwater conditions may be different at the time of construction. Groundwater conditions may change because of seasonal variations in rainfall, runoff, and other conditions not apparent at the time of drilling. Long-term groundwater monitoring was outside the scope of services for this project.

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC). Based on the soil properties observed at the site and as described on the exploration logs and results, our professional opinion is for that a Seismic Site Classification of D be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 30 feet. The site

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Facilities | Environmental | Geotechnical | Materials 4 properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided that the recommendations contained within this report are implemented in the design and construction phases of this project.

As the site is immediately adjacent to the existing main VA building, and project test boring A-1 encountered approximately 3 feet of existing silty/clayey sand fill, it is anticipated that approximately 1 to 3 feet of existing silty/clayey sand fill may be present within the footprint of the new Mechanical Enclosure Structure. Native soils immediately underlying existing fill consist of clayey/silty sand Coastal Plain soils.

Effective site drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

We recommend that all existing fill be removed in its entirety within the footprint of the new mechanical enclosure structure. After excavation of existing fill, engineered fill can be placed to planned foundation or slab subgrade. Shallow wall or column foundations bearing on structural fill or native soils can be designed with an allowable contact pressure of 3,000 pounds per square feet.

The recommendations contained in this report are based upon the results of field and laboratory 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 demolition, stripping, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as

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Facilities | Environmental | Geotechnical | Materials 5 necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Demolition

The proposed mechanical enclosure will be constructed adjacent the existing main VA building, where existing mechanical equipment, exterior sidewalks and utilities are present. These exterior features will need to be properly decommissioned and demolished. We recommend existing sidewalks, slabs, and utilities to be removed from within the proposed enclosure footprint and at least 5 feet beyond the outer edge of foundations.

Site Preparation

Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.

Complete stripping of the topsoil should be performed in the proposed enclosure area.

Subgrade Preparation

We recommend that all existing fill be removed in its entirety within the footprint of the new mechanical enclosure structure. After excavation of existing fill, engineered fill can be placed to planned foundation or slab subgrade. Structural fill placed should extend horizontally a minimum distance of 5 feet beyond the outside edge of footings. On-site soils may be reused as structural fill materials provided they meet project specifications.

The subgrade should be proofrolled with an adequately loaded vehicle such as a half-loaded tandem-axle dump truck. The proofrolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Excessively wet or dry material should either be removed or moisture conditioned and recompacted. Compacted structural fill soils should then be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation or slab construction.

Existing Fill

As noted in Geotechnical Characterization, test boring A-1 encountered previously placed fill to a depth of about 3.0 feet. Due to the enclosure site’s close proximity to the existing main building, existing fill may be present to similar depths. We have no records to indicate the degree of control, and consequently, the fill is considered unreliable for support of foundation loads. We recommend that all existing fill be

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Facilities | Environmental | Geotechnical | Materials 6 removed from within the enclosure structure footprint, plus at least 5 feet outside the footprint.

is discussed in this report. However, even with the recommended construction procedures, inherent risk exists for the owner that compressible fill or unsuitable material, within or buried by the fill will, not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by following the recommendations contained in this report.

If the owner elects to support appurtenant minor structures on or above existing fill soils to reduce initial construction costs in exchange for increased potential longer-term distress, the following protocol should be followed. After the planned grading has been completed, the area should be undercut 3 feet within the minor structure area and 5 feet beyond the lateral limits of the minor structure area. Following this overexcavation, the entire area should be proofrolled with heavy, rubber tire construction equipment, to aid in delineating areas of soft or otherwise unsuitable soil. Once unsuitable materials have been remediated, and the subgrade has passed the proofroll test, backfill to finished subgrade elevation can begin. The existing undocumented fill that was removed can be evaluated for reuse as structural fill.

Excavation

We anticipate that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The bottom of excavations should be thoroughly cleaned of loose soils and disturbed materials prior to backfill placement and/or construction.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill is material used below, or within 10 feet of structures, pavements or constructed slopes. General fill is material used to achieve grade outside of these areas.

Fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Soil Type 1 USCS Classification

Acceptable Parameters (for Structural Fill)

Low Plasticity Cohesive

CL, CL-ML

ML

Liquid Limit less than 50 Plasticity index less than 30

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Soil Type 1 USCS Classification

Acceptable Parameters (for Structural Fill)

Granular

GW, GP, GM, GC,

SW, SP, SM, SC

Less than 50% passing No. 200 sieve

1. Structural and general 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.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift Thickness

8 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

Same as structural fill

Minimum Compaction Requirements

98% of the material’s standard Proctor maximum dry density (ASTM D698) within 1 foot of foundation or slab subgrade, otherwise 95% of the material’s standard Proctor maximum dry density (ASTM D698).

92% of the material’s standard Proctor maximum dry density (ASTM D698)

Water Content Range

-2% to +3% of optimum

As required to achieve min.

compaction requirements

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

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On-site materials may be considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances and approved by the geotechnical engineer.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors.

Grading and Drainage

All grades must provide effective drainage away from the new structure during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the structure.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

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As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

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 2,500 square feet of compacted fill in the building areas and 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 areas of foundation excavations, the bearing subgrade should be evaluated by the Geotechnical Engineer. If unanticipated conditions are observed, 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

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Facilities | Environmental | Geotechnical | Materials 10 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 design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description Maximum Net Allowable Bearing

Pressure 1, 2 3,000 psf - foundations bearing upon approved structural fill or undisturbed soils

Required Bearing Stratum 3 Undisturbed native soils or structural fill extending to undisturbed native soils.

Minimum Foundation Dimensions Per IBC 1809.7

Ultimate Passive Resistance4

(equivalent fluid pressures) 330 pcf

Sliding Resistance 5 0.4

Minimum Embedment below

Finished Grade 6 12 inches

Estimated Total Settlement from

Structural Loads 2 Less than about 1 inch

Estimated Differential Settlement 2, 7 About 1/2 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Values assume that exterior grades are no steeper than 5% within 10 feet of structure.

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

3. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face. Assumes no hydrostatic pressure.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Frictional resistance for granular materials is dependent on the bearing pressure which may vary due to load combinations. For fine-grained materials, lateral resistance using cohesion should not exceed ½ the dead load.

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Item Description

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

7. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Design Parameters – Overturning and Uplift Loads

Shallow foundations subjected to overturning loads should be proportioned such that the resultant eccentricity is maintained in the center-third of the foundation (e.g., e < b/6, where b is the foundation width). This requirement is intended to keep the entire foundation area in compression during the extreme lateral/overturning load event.

Foundation oversizing may be required to satisfy this condition.

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils with consideration to the IBC basic load combinations.

Construction Adjacent to Existing Building

Differential settlement between the enclosure structure and the existing building is expected to approach the magnitude of the total settlement of the addition. Expansion joints should be provided between the existing building and the proposed addition to accommodate differential movements between the two structures. Underground piping between the two structures should be designed with flexible couplings and utility knockouts in foundation walls should be oversized so minor deflections in alignment do not result in breakage or distress. Care should be taken during excavation adjacent to existing foundations to avoid disturbing existing foundation bearing soils.

New footings should bear at or near the bearing elevation of immediately adjacent existing foundations. Depending upon their locations and current loads on the existing

Item Description

Soil Moist Unit Weight 100 pcf

Soil Effective Unit Weight1 40 pcf

Soil weight included in uplift resistance

Soil included within the prism extending up from the top perimeter of the footing at an angle of 20 degrees from vertical to ground surface

1. Effective (or buoyant) unit weight should be used for soil above the foundation level and below a water level. The high groundwater level should be used in uplift design as applicable.

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Facilities | Environmental | Geotechnical | Materials 12 footings, footings for the new addition could cause settlement of adjacent walls. To reduce this concern and risk, clear distances at least equal to the new footing widths should be maintained between the addition’s footings and footings supporting the existing building.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable bearing soils are observed 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. The lean concrete replacement zone is illustrated on the sketch below.

Overexcavation for structural fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with approved soils placed, as recommended in the Earthwork section.

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Floor Slabs

Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

Floor Slab Design Parameters

Item Description

Floor Slab Support1

Use 4 inches base course material meeting material specifications of NCDOT ABC Subgrade compacted to recommendations in Earthwork

Estimated Modulus of Subgrade Reaction 2

150 pounds per square inch per inch (psi/in) for point loads

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

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, when the project includes humidity-controlled areas, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials 14 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.

Saw-cut contraction joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations, refer to the ACI Design Manual.

Joints or cracks should be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

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

Settlement of floor slabs supported on existing fill materials cannot be accurately predicted but could be larger than normal and result in some cracking. Mitigation measures, as noted in Existing Fill within Earthwork, are critical to the performance of floor slabs. In addition to the mitigation measures, the floor slab can be stiffened by adding steel reinforcement, grade beams, and/or post-tensioned elements.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed, and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should observe the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

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Lateral Earth Pressures

Design Parameters

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

Lateral Earth Pressure Design Parameters

Earth Pressure

Condition 1

Coefficient for Backfill Type 2

Surcharge Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

Active (Ka) Granular - 0.31

Fine Grained - 0.41 (0.31)S (0.41)S

(40)H (50)H

(80)H (85)H

At-Rest (Ko) Granular - 0.47

Fine Grained - 0.58 (0.47)S (0.58)S

(55)H (70)H

(90)H (95)H

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

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

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

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Lateral Earth Pressure Design Parameters

Earth Pressure

Condition 1

Coefficient for Backfill Type 2

Surcharge Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

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

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

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

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity type concrete walls. These recommendations are not applicable to the design of modular block - geogrid reinforced backfill walls (also termed MSE walls). Recommendations covering these types of wall systems are beyond the scope of services for this assignment. However, we would be pleased to develop a proposal for evaluation and design of such wall systems upon request.

General Comments

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

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

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner

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Facilities | Environmental | Geotechnical | Materials 17 is concerned about the potential for such contamination or pollution, other studies should be undertaken.

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

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly affect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others.

Construction and site development have the potential to affect adjacent properties. Such impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Attachments

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

1 30 feet Between A and B wings, west side of Main VA Building

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.

Subsurface Exploration Procedures: We advanced the boring with a track-mounted, ATV-mounted rotary drill rig using hollow stem augers. Five samples were obtained in the upper 10 feet of each boring, and at intervals of 5 feet thereafter. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, all borings were backfilled with auger cuttings after their completion.

We observed the boreholes while drilling and at the completion of drilling for the presence of groundwater. Groundwater was not observed at these times in the boreholes.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Laboratory Testing

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

■ Moisture Content

■ -200 Washed Sieve

■ Atterberg Limits

The laboratory testing program often included examination of soil samples by an engineer. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System.

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Site Map and Exploration Plan

Contents:

Site Map Exploration Plan

Note: All attachments are one page unless noted above.

Copyright:© 2013 National Geographic Society, i-cubed

0 2,000 4,000 Feet

File Path:

Date:

Project No.

Scale:

MW

MW

AAN

PM:

Drawn By:

Checked By:

Approved By: 2401 Brentwood Road, Suite 107 Raleigh, NC 27604

Phone: (919) 873-2211 Fax: (919) 873-9555

P70205256 Site Map VAMC Fayetteville Mechanical Enclosure Structure

2300 Ramsey Street Fayetteville, North Carolina

1 in = 2,000 ft

10/18/2021

SITE

@A

@A

New Mechanical Enclosure

A-1

Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community

0 75 150 FeetLegend

@A test boring

File Path:

Date:

Project No.

Scale:

MW

MW

AAN

PM:

Drawn By:

Checked By:

Approved By: 2401 Brentwood Road, Suite 107 Raleigh, NC 27604

Phone: (919) 873-2211 Fax: (919) 873-9555

70215256 Exploration Plan VAMC New Mechanical Enclosure

2300 Ramsey Street Fayetteville, North Carolina

1 in = 75 ft

10/27/2022

Main Building

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Exploration and Laboratory Results

Contents:

Boring Log (A-1) Atterberg Limits

TOPSOIL

FILL - SILTY SAND (SM), fine to coarse grained, medium brown to dark brown, moist, loose to medium dense, occasional red brown zones

SILTY SAND (SM), fine to medium grained, tan, very moist, soft to stiff CLAYEY SAND (SC), fine to coarse grained, red brown, moist, medium dense

SILTY SAND (SM), fine to coarse grained, brown, very moist, medium dense

LEAN CLAY (CL), fine grained, gray and rust brown, very moist, soft to stiff

Boring Terminated at 30 Feet

Boring Log No. A-1

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

M o d el

L ay er

8.9

13.2

12.8

13.7

14.1

16.2

12.9

37.3

30.6

NP

24-13-11

NP

43-24-19

0.3

3.0 3.5

17.5

22.5

30.0

7-6-5-4 N=11

2-2-3-3 N=5

4-5-5-4 N=10

7-8-9-10 N=17

6-7-7-8 N=14

3-5-6 N=11

9-6-5 N=11

1-2-2 N=4

6-6-6 N=12

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

No free water observed Water Level Observations cave at 9.3'

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method

HSA

Hammer Type Automatic

Driller Turnage

Logged by

Boring Started 10-14-2022

Boring Completed 10-14-2022

2401 Brentwood Rd Ste 107

Drill Rig Diedrich D50

VAMC Fayetteville Mechanical Enclosure - Main Bldg

Raleigh, NC

2300 Ramsey Street | Fayetteville, NC

Terracon Project No. 70215256

S am pl e

T yp e

Pe rc en t

Fi n es

W at er C o n te n t

D ry

U n it

W ei g h t

(p cf

S tr ai n

C om p re ss iv e S tr e n g th

(t sf

T es t T y p e

LL-PL-PI

Atterberg LimitsLocation:

Latitude: 35.0887° Longitude: -78.8767°

See Exploration Plan

Depth (Ft.)

Strength Test

Fi el d T es t

R es u lt s

0 10 20 30 40 50 60 70 80 90 100 110

"A " L ine

ASTM D4318

CH

o r

OH

CL

or

OL

ML or OL

MH or OH

NP

NP

20.2

28.9

13.9

92.8

SM

SC

SM

CL

NP

NP

NP

NP

20.2

28.9

13.9

92.8

SM

SC

SM

CL

NP

NP

NP

NP

SILTY SAND

CLAYEY SAND

SILTY SAND

LEAN CLAY

Atterberg Limit Results

CL - ML

"U " L in e

Liquid Limit

LL PL PI Fines USCS DescriptionFines

Pl a st ic it y

In d ex

Facilities | Environmental | Geotechnical | MaterialsLaboratory tests are not valid if separated from original report.

0 - 2

4 - 6

18.5 - 20

28.5 - 30

A-1

A-1

A-1

A-1

Boring ID Depth (Ft)

VAMC Fayetteville Mechanical Enclosure - Main Bldg

2300 Ramsey Street | Fayetteville, NC

Terracon Project No. 70215256

Raleigh, NC

2401 Brentwood Rd Ste 107

January 4, 2023 | Terracon Project No. 70215256

Facilities | Environmental | Geotechnical | Materials

Supporting Information

Contents:

General Notes Unified Soil Classification System

Note: All attachments are one page unless noted above.

Unconfined Compressive Strength Qu, (psf)

500 to 1,000

2,000 to 4,000

4,000 to 8,000

1,000 to 2,000 less than 500

> 8,000

Non-plastic Low Medium High

DESCRIPTION OF SYMBOLS AND ABBREVIATIONS

S

A M

P L

IN

G

W A

T E

R L

E V

E L

F

IE

L D

T E

S T

S

GENERAL NOTES

Over 12 in. (300 mm) 12 in. to 3 in. (300mm to 75mm) 3 in. to #4 sieve (75mm to 4.75 mm) #4 to #200 sieve (4.75mm to 0.075mm Passing #200 sieve (0.075mm)

Particle Size

< 5 5 - 12 > 12

Percent of Dry Weight

Descriptive Term(s) of other constituents

RELATIVE PROPORTIONS OF FINES

1 - 10 11 - 30

> 30

Plasticity Index

Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

LOCATION AND ELEVATION NOTES

Percent of Dry Weight

Major Component of Sample

Trace With Modifier

RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY

Trace With Modifier

DESCRIPTIVE SOIL CLASSIFICATION

Boulders Cobbles Gravel Sand Silt or Clay

Descriptive Term(s) of other constituents

N

(HP)

(T)

(DCP)

(PID)

(OVA)

< 15 15 - 29 > 30

Term

PLASTICITY DESCRIPTION

Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated.

Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations.

Water Level After a Specified Period of Time

Water Level After a Specified Period of Time

Water Initially Encountered

Split Spoon

Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

Standard Penetration Test Resistance (Blows/Ft.)

Hand Penetrometer

Torvane

Dynamic Cone Penetrometer

Photo-Ionization Detector

Organic Vapor Analyzer

S T

R E

N G

T H

T E

R M

S Standard…