Geotech Report_Fayetteville Bldg 4 Renovation.pdf

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Geotechnical Engineering Report Building No. 4 Renovation – VA Fayetteville

Fayetteville, North Carolina December 11, 2020

Terracon Project No. 70205072

Prepared for:

FFE, Inc.

Springdale, Ohio

Prepared by:

Terracon Consultants, Inc.

Raleigh, North Carolina

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REPORT TOPICS

REPORT TOPICS

REPORT SUMMARY ....................................................................................................... I

INTRODUCTION

SITE CONDITIONS

EXPLORATION AND TESTING PROCEDURES

GEOTECHNICAL CHARACTERIZATION

PROJECT DESCRIPTION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

HELICAL PIERS

SEISMIC CONSIDERATIONS

FLOOR SLABS

LATERAL EARTH PRESSURES

GENERAL COMMENTS

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section.

ATTACHMENTS

SITE MAP AND EXPLORATION PLAN

EXPLORATION RESULTS (Boring Logs and Laboratory Data) SUPPORTING INFORMATION (General Notes and Unified Soil Classification System)

Building No. 4 Renovation – VA Fayetteville ■ Fayetteville, North Carolina December 11, 2020 ■ Terracon Project No. 70205072

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REPORT SUMMARY

Topic 1 Overview Statement 2

Project Description

We understand that Building No. 4 renovation will include a 20- by 40-foot, two-story building addition (with elevator) at the south side of the existing building. The building addition exterior may consist of brick masonry. The building addition lowest floor level is to be ground supported and match the main floor level of the existing building. New ramps or sidewalks may also be constructed adjacent the existing building and new addition.

Geotechnical Characterization

Subsurface conditions generally consist of very loose to medium dense sands.

Within the upper 5 feet of the soil profile, sands are in a very loose to loose condition. Groundwater was not measurable at the time of drilling, however, very moist soil conditions, as noted in test boring samples, are present within 10 feet of the ground surface. Perched groundwater may also be present as well within 10 feet of the ground surface.

Earthwork & Foundations

Due to the loose nature of the upper 5 feet of the existing soil profile, possible presence of existing basement backfill, and proposed masonry exterior, we recommend building addition foundations to be supported on a 2- to 5-foot minimum thickness of structural fill. A 2-foot minimum thickness of structural fill combined with small-scale extended foundations, such as helical piers, can further reduce potential settlement of the proposed addition.

Overexcavation options:

2’ OX: Overexcavate to a minimum depth of 2 feet below planned foundation subgrade within the building addition footprint, and place structural fill up to planned foundation subgrade. Foundations bearing on a minimum 2 feet of properly prepared structural can be designed with an allowable bearing pressure of 1,500 psf (expected settlements: < 1 inch total, < ½ inch differential). We also recommend overexcavation of existing soils to a minimum 2 feet below planned subgrade for interior/exterior slabs, and exterior stairways, ramps, and sidewalks.

5’ OX: Overexcavate to a minimum depth of 5 feet below planned foundation subgrade within the building addition footprint, and place structural fill up to planned subgrade. Foundations bearing on a minimum 5 feet of properly prepared structural can be designed with an allowable bearing pressure of 3,000 psf (expected settlements: < 1 inch total, < ½ inch differential).

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Overexcavated subgrade found to contain deleterious materials, existing fill, or excessively wet, loose or soft zones should be removed and repaired as recommended by the geotechnical engineer. Overexcavated subgrade and structural fill should be densified with non-vibratory compaction equipment before placement of structural fill. Overexcavated soil can be reused as structural fill provided the material complies with earthwork specifications.

Materials proposed to be used for engineered fill should be tested and approved by the geotechnical engineer.

Helical Pier option:

As an option to further reduce potential settlement, building addition foundations can be supported on helical piers extending to depths of 15 to 30 feet to provide working capacities of 10 to 25 kips per pier (expected settlements: < ½ inch total, < ¼ inch differential). Helical pier capacities are highly dependent on contractor supplies, equipment and experience;

therefore, the selected helical pier contractor should provide working capacities corresponding with specific helical pier configuration and total depth. If helical piers are utilized, we recommend a 2-foot minimum thickness of structural fill to support the interior slab-on-grade.

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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INTRODUCTION

Geotechnical Engineering Report Building No. 4 Renovation – VA Fayetteville

2300 Ramsey Street Fayetteville, North Carolina

Terracon Project No. 70205072 December 11, 2020

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed Building No. 4 renovation at the VA Fayetteville facility at 2300 Ramsey Street in Fayetteville, North Carolina. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Floor slab design and construction

■ Groundwater conditions ■ Seismic site classification per IBC

■ Site preparation and earthwork ■ Lateral earth pressures

■ Foundation design and construction

The geotechnical engineering scope of services for this project included the advancement of five test borings to depths ranging from 20 to 35 feet below existing site grade.

Maps showing the site and boring locations are shown in the Site Map and Exploration Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the boring logs and in the Exploration Results section of this report.

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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 Building No. 4 in the VA Facility Complex at 2300 Ramsey Street in Fayetteville, North Carolina. The project site encompasses approximately one-half acre.

Latitude: 35.0896º, Longitude: -78.8757º (See Site Map)

Existing Improvements & Ground Cover

The project site consists of the existing two-story Building No. 4 (contains basement) with surrounding grass turf, landscaping, and sidewalks.

Existing Topography Relatively flat around building.

EXPLORATION AND TESTING PROCEDURES

Field Exploration

As requested, our field exploration work included the drilling and sampling of exploratory soil borings consistent with the following schedule.

Number of Borings Boring Depth (ft) 1 Planned Location 2

2 30 and 35 Building Addition Area

3 20 Existing Building Perimeter

1. Below existing ground surface

2. See Exploration Plan

Boring Layout: A Terracon representative used handheld GPS equipment to locate borings with an estimated horizontal accuracy of +/-3 feet.

Subsurface Exploration Procedures: We advanced soil test borings with an ATV-mounted drill rig using continuous hollow-stem flight augers. Four samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. Soil sampling was performed using split-barrel sampling procedures. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon is 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

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Our exploration team prepared field boring logs as part of standard drilling operations including sampling depths, penetration distances, and other relevant sampling information. Field logs include visual classifications of materials encountered during drilling, and our interpretation of subsurface conditions between samples. Final boring logs, prepared from field logs, represent the geotechnical engineer's interpretation, and include modifications based on observations and laboratory tests.

Property Disturbance: We backfilled borings with auger cuttings after drilling. Our services did not include repair of the site beyond backfilling our boreholes. Because backfill material often settles below the surface after a period, we recommend boreholes be checked periodically and backfilled, if necessary.

Laboratory Testing

The project engineer reviewed field data and assigned various laboratory tests to better understand the engineering properties of various soil strata. Testing included visual classification, moisture content, Atterberg Limits and washed sieve analyses. Procedural standards noted below are for reference to methodology in general. In some cases, local practices and professional judgement require method variations. Standards noted below include reference to other related standards. Such references are not necessarily applicable to describe the specific test performed.

■ ASTM D2488 Description and Identification of Soils (Visual-Manual Procedure)

■ ASTM D2216 Standard Test Methods for Laboratory Determination of Water (Moisture)

Content of Soil and Rock by Mass

■ ASTM D4318 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of

Soils

■ ASTM D1140 Standard Test Methods for Amount of Material in Soils Finer than No. 200

Sieve

Our laboratory testing program included examination of soil samples by an engineer. Based on the material’s texture and plasticity, we describe and classify soil samples in accordance with the Unified Soil Classification System (USCS).

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GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

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

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

Stratum Approximate Depth to Bottom of Stratum (feet) Material Description Consistency/Density

1 2 to 5 Silty Sand Very Loose to Loose 2 12.5 Clayey Sand Very Loose to Loose

3 24 to 27 Poorly Graded Sand with Silt or Silty Clayey Sand

Very Loose to Loose

4 28 to 30+ Fat Clay Soft to Medium Stiff

Although not encountered in test borings, existing fill may be present in utility trench fill or basement backfill. Conditions encountered at each boring location are indicated on the individual boring logs shown in the Exploration Results section and are attached to this report.

Stratification boundaries on the boring logs represent the approximate location of changes in native soil types; in situ, the transition between materials may be gradual.

Groundwater Conditions

Free ground water was not observed during time of drilling. However, very moist to wet zones within the soil profile were observed in soil samples and are noted on the boring logs in Exploration Results. Perched ground water may be present within the upper 10 feet of the soil profile.

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. Perched water is common in the area.

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PROJECT DESCRIPTION

Our understanding of the project conditions is as follows:

Item Description Information Provided Option 4 Floor Plan. dated November 5, 2020 by Leo A. Daly.

Project Description We understand that Building No. 4 renovation will include a 20- by 40-foot, two-story building addition (with elevator) at the south side of the existing building. New ramps or sidewalks may also be constructed adjacent the existing building and new addition.

Proposed Structure Two-story, building addition with brick masonry exterior.

Building Construction Conventional wood/steel/masonry framing supported on shallow foundations with slab-on-grade floor at the ground level.

Finished Floor Elevation The building addition lowest floor level is to be ground supported and match the main floor level of the existing building.

Maximum Loads (assumed)

■ Column Loads: 50 kips

■ Walls Loads: 3 - 6 klf

■ Floor slab Load: 100 psf

Grading/Slopes Proposed grading is assumed to be minimal, with assumed cut and fill of less than 2 feet.

Below Grade Structures None anticipated.

Free-Standing Retaining Walls None anticipated.

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GEOTECHNICAL OVERVIEW

Due to the loose nature of the upper 5 feet of the existing soil profile, possible presence of existing basement backfill or utility trench backfill, and proposed masonry exterior, we recommend building addition foundations to be supported on a 2- to 5-foot minimum thickness of structural fill. A 2-foot minimum thickness of structural fill combined with small-scale extended foundations, such as helical piers, is a foundation design option that can further reduce settlement potential.

Overexcavation options:

2’ OX: Overexcavate to a minimum depth of 2 feet below planned foundation subgrade within the building addition footprint, and place structural fill up to planned foundation subgrade.

Foundations bearing on a minimum 2 feet of properly prepared structural can be designed with an allowable bearing pressure of 1,500 psf (expected settlements: < 1 inch total, < ½ inch differential). We also recommend overexcavation of existing soils to a minimum 2 feet below planned subgrade for interior/exterior slabs, and exterior stairways, ramps, and sidewalks.

5’ OX: Overexcavate to a minimum depth of 5 feet below planned foundation subgrade within the building addition footprint, and place structural fill up to planned subgrade. Foundations bearing on a minimum 5 feet of properly prepared structural can be designed with an allowable bearing pressure of 3,000 psf (expected settlements: < 1 inch total, < ½ inch differential).

Overexcavated subgrade found to contain deleterious materials, existing undocumented fill, or excessively wet, loose or soft zones should be removed and repaired as recommended by the geotechnical engineer. Overexcavated subgrade and structural fill should be densified with non-vibratory compaction equipment before placement of structural fill. Overexcavated soil can be reused as structural fill provided the material complies with earthwork specifications. Materials proposed to be used for engineered fill should be tested and approved by the geotechnical engineer.

Helical Pier option:

To further reduce potential settlement, building addition foundations can be supported on helical piers extending to depths of 15 to 30 feet to provide working capacities of 10 to 25 kips per pier (expected settlements: < ½ inch total, < ¼ inch differential). Helical pier capacities are highly dependent on contractor supplies, equipment and experience; therefore, the selected helical pier contractor should provide working capacities of helical piers corresponding with specific helical pier configuration and total depth. If helical piers are utilized, we recommend a 2-foot minimum thickness of structural fill to support the interior slab-on-grade.

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We recommend that a full construction joint between the existing building and the building addition is incorporated in the structural design. Settlement of the building addition frame can occur after its construction. We recommend that structural or utility connections be designed to tolerate, or be readily adjusted for, potential differential settlement that may occur between the new building addition and the existing building.

Due to the presence of loose sandy soils within the vicinity of the existing building, we recommend use of non-vibratory compaction equipment, and a 6-inch maximum loose lift thickness of soil material used in placement of structural fill.

We recommend that the interior floor slab be supported on a 2-foot minimum thickness of structural fill. The Floor Slabs section addresses subgrade support of concrete slab-on-grade.

Design parameters and construction considerations have been provided. Specific attention should be given to ensure proper subgrade preparation and positive drainage away from the existing structure and aggregate base beneath the floor slab.

Support of floor slabs and footings on or above existing fill materials, which may be present in utility trench backfill or basement wall backfill, is discussed in this report. However, even with the recommended construction procedures, there is an inherent risk to 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. To take advantage of the cost benefit of not removing the entire amount of undocumented fill, the owner must be willing to accept the risk associated with building over the undocumented fills following the recommended reworking of the material. The General Comments section provides an understanding of the report limitations.

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EARTHWORK

Earthwork for this project will generally include clearing, stripping, demolition of existing utilities and sitework, grubbing, (over)excavation and structural fill placement. The following sections provide recommendations for use in the preparation of specifications for earthwork.

Recommendations include critical quality criteria as necessary to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Site Preparation

Existing utilities to be abandoned should be removed or filled with grout. Utilities that are to remain should be accurately located horizontally and vertically to minimize conflict with new construction.

Existing site work, vegetation, root mat and topsoil should be completely removed from proposed construction areas.

Following removal of demolition debris, existing vegetation and topsoil, the existing subgrade should be overexcavated a minimum of 2 feet below planned subgrade within the building addition footprint, and beneath exterior slabs, stairways, ramps and sidewalks. Overexcavated subgrade found to contain deleterious materials or excessively loose or soft zones should be removed and repaired as recommended by the geotechnical engineer. Geotextiles may be required.

Overexcavated subgrade should be densified with non-vibratory compaction equipment before placement of structural fill. Overexcavated soil can be reused as structural fill provided the material complies with earthwork specifications. Materials proposed to be used for engineered fill should be tested and approved by the geotechnical engineer. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

Fill Material Types

Fill required to achieve design grade should meet the following material property requirements:

Fill Material USCS Classification Acceptable Location for Placement Imported or Onsite Low- to

Moderate-Plasticity Soil

CL, ML, SC, SM, SP, SP-

SM, SC-SM

All locations and elevations except as backfill behind any retaining walls Sand / Gravel with less than

10% fines 2 GW/GP, SW/SP NCDOT ABC – suitable beneath pavement sections and floor slabs

1. Controlled, compacted fill should consist of approved materials that are free of organic matter and debris. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

2. Soil with less than 10% fines (silt and clay) should not be used as general fill to raise site grades to prevent perched water conditions where water infiltrating the surface zone can be trapped over the underlying less-permeable soil zone.

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Fill Compaction Requirements

Structural and general fill should meet the following compaction requirements. Due to the loose nature of shallow sands within vicinity of the existing building, we recommend the use of non-vibratory compaction equipment to densify structural fill.

Description

Fill Lift Thickness 6-inches or less in loose thickness (4-inch lifts when hand-operated equipment is used).

Compaction Requirements 1

Structural fill should be compacted to a minimum of 95% of the material’s standard Proctor maximum dry density (ASTM D698).

General fill should be compacted to a minimum of 90% of the material’s standard Proctor maximum dry density (ASTM D698).

Moisture Content Within the range of -2% to +2% of optimum moisture content as determined by the standard Proctor test at the time of placement and compaction.

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

Utility Trench Backfill

Utility trenches are a common source of water infiltration and migration. Utility trenches penetrating the building perimeter should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the building 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 building.

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Exposed ground should be sloped and maintained at a minimum 5 percent 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, 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

Due to the presence of loose sandy soils within the vicinity of the existing building, we recommend use of non-vibratory compaction equipment.

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 floor slabs. 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.

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.

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, overexcavation, proof-rolling and mitigation of areas delineated by the proof-roll to require mitigation. Each lift of compacted fill should be tested, evaluated, and reworked as necessary until approved by the Geotechnical Engineer prior to placement of additional lifts.

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In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. In the event that 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 design parameters are applicable for shallow foundations.

We recommend that a full construction joint between the existing building and the building addition is incorporated in the structural design. Settlement of the building addition frame can occur after its construction. We recommend that design of any structural or utility connections tolerate and be readily adjusted for potential differential settlement that may occur between the new building addition and the existing building.

Design Parameters – Compressive Loads

Description Column Wall

Net allowable soil bearing pressure 1 1,500 psf (2’OX) 3,000 psf (5’OX)

1,500 psf (2’OX) 3,000 psf (5’OX)

Minimum dimensions 30 inches 18 inches

Minimum embedment 12 inches 12 inches Estimated total settlement 2 < 1 inch < 1 inch

Estimated differential settlement 2 1/2-inch between columns 1/2-inch over 40 feet

Equivalent fluid pressure 3 288 pcf

Ultimate coefficient of sliding friction 0.35

1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Assumes any unsuitable fill or soft soils, if encountered, will be undercut and replaced with engineered fill. Disturbance of wet soils may require the need for a granular stabilization layer for an appropriate working surface. Terracon should be consulted if this issue becomes apparent.

2. The foundation settlement will depend upon the variations within the soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of compacted fill, and the quality of the earthwork operations. The above settlement estimates assume the maximum footing size is 8 feet for column footings, 4.5 feet for wall footings, and relatively uniform loading.

3. Sides of footing excavations must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid. If the loaded side is sloped or benched and then backfilled, the allowable passive pressure will be significantly reduced. Passive resistance in the upper 12 inches of the soil profile should be neglected.

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A representative of the geotechnical engineer should be retained at this time to carefully evaluate the foundation excavations through a combination of hand auger borings, dynamic cone penetrometer (DCP) testing, and probing. The materials within a depth of at least 2 feet below overexcavated grade should be evaluated. Soft, loose, or otherwise unsuitable materials, if encountered, should be further over-excavated and replaced with compacted engineered fill.

Design Parameters - Uplift Loads

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils. As illustrated on the subsequent figure, the effective weight of the soil prism defined by diagonal planes extending up from the top of the perimeter of the foundation to the ground surface at an angle, q, of 20 degrees from the vertical can be included in uplift resistance.

The maximum allowable uplift capacity should be taken as a sum of the effective weight of soil plus the dead weight of the foundation, divided by an appropriate factor of safety. A maximum total unit weight of 100 pcf should be used for the backfill. This unit weight should be reduced to 40 pcf for portions of the backfill or natural soils below the groundwater elevation.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction 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

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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.

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 approved fill material placed, as recommended in the Earthwork section.

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HELICAL PIERS

As a foundation design alternative to reduce potential settlements to less than ½ inch, building addition foundations can be supported on helical piers extending to depths of 15 to 30 feet with working capacities of 10 to 30 kips per pier. Helical pier capacities are highly dependent on contractor supplies, equipment and experience; therefore, the selected helical pier contractor should provide working capacities of helical piers corresponding with specific helical pier configuration and total depth. If helical piers are utilized, we recommend a 2-foot minimum thickness of structural fill to support the interior slab-on-grade.

Field monitoring of the helical pier installation should be considered as an extension of the design process. Helical pier installation techniques must be observed, weighed against load test data, and evaluated to determine the acceptance of each pier. Understanding of the subsurface conditions and helical pier design requirements are necessary to make the routine engineering judgments required during installation. Foundation recommendations that include helical piers should be considered valid only if the geotechnical engineer monitors pier installation.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine the Seismic Design Category for a structure.

The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7-10.

Seismic Design Parameters

Description Value 2015 International Building Code Site Classification

D 2

Site Latitude 35.0895

Site Longitude -78.8757

SDS Spectral Acceleration for a Short Period 3 0.163g

SD1 Spectral Acceleration for a 1-Second Period 3 0.114g

1. Seismic site classification in accordance with 2015 International Building Code, which refers to ASCE 7-10.

2. The 2015 International Building Code (IBC) uses a site profile extending to a depth of 100 feet for seismic site classification. Borings at this site were extended to a maximum depth of 35 feet. The site 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.

3. These values were obtained using online seismic design maps and tools provided by the USGS (http://earthquake.usgs.gov/hazards/designmaps/).

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FLOOR SLABS

Design parameters for floor slabs assume the requirements for Earthwork have been followed. We recommend interior floor slabs to be supported on a minimum 2-foot thickness of structural fill.

Specific attention should be given to positive drainage away from existing structures.

Floor Slab Design Parameters

Item Description

Floor slab support 1 Aggregate base (see below) underlain by subgrade prepared according to Earthwork.

Modulus of subgrade reaction 2 150 pounds per square inch per in (psi/in) Aggregate base course 4 inches of NCDOT ABC

1. Floor slabs should be structurally independent of building 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, 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.

Saw-cut control 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 water-proof, 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.

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Floor Slab Construction Considerations

Finished subgrade within and for at least 5 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 approve 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.

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. 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).

December 11, 2020 ■ Terracon Project No. 70205072

Responsive ■ Resourceful ■ Reliable

Lateral Earth Pressure Design Parameters

Earth Pressure Condition 1

Coefficient for Backfill Type2

Surcharge Pressure 3, 4, 5 p1 (psf)

Effective Fluid Pressures (psf) 2, 4, 5

Unsaturated Submerged

Active (Ka) Granular - 0.33 Lean Clay - 0.40

(0.33)S (0.40)S

(40)H (48)H

(80)H (85)H

At-Rest (Ko) Granular - 0.46 Lean Clay - 0.56

(0.46)S (0.56)S

(55)H (67)H

(90)H (95)H

Passive (Kp) Granular - 3.0 Lean Clay - 2.4

(300)H (288)H

(250)H (205)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.

2. Uniform, horizontal backfill, compacted to at least 95 percent of the ASTM D 698 maximum dry density, rendering a maximum unit weight of 120 pcf.

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

5. No safety factor is included in these values.

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 and 60 degrees from vertical for the active and passive cases, respectively.

Construction Considerations

Construction scheduling often involves grading and paving by separate contractors and can involve a time lapse between the end of grading operations and the commencement of paving.

Disturbance, desiccation or wetting of subgrade soils between grading and paving can result in deterioration of the previously completed subgrade. A non-uniform subgrade can result in poor pavement performance and local failures relatively soon after pavements are constructed. We recommend the moisture content and density of the subgrade be evaluated within two days prior to commencing paving operations. Scarification and recompaction may also be required.

Areas not in compliance with the required ranges of moisture or density should be moisture conditioned and recompacted. If significant precipitation occurs after the evaluation or if the surface becomes disturbed, the subgrade condition should be reviewed by Terracon personnel immediately prior to paving.

ATTACHMENTS

December 11, 2020 ■ Terracon Project No. 70205072

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GENERAL COMMENTS

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration. Natural variations will occur between exploration point locations or due to the modifying effects of construction or weather.

The nature and extent of such variations may not become evident until during or after construction.

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

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

Our services and any correspondence or collaboration through this system are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client.

Reliance upon the services and any work product is limited to our client, and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

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

Site safety, and cost estimating including, excavation support, and dewatering requirements/design are the responsibility of others. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

ATTACHMENTS

SITE LOCATION AND EXPLORATION PLANS

SITE MAP AND EXPLORATION PLAN

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

70205072 Site Map Building No. 4 VA Fayetteville

2300 Ramsey Street Fayetteville, North Carolina

1 in = 2,000 ft

12/10/2020

SITE

@A

@A

@A

@A

@A

B-5

B-4

B-3

B-2

B-1

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

0 20 40 Feet

Legend @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

70205072 Exploration Plan Building No. 4 VA Fayetteville

2300 Ramsey Street Fayetteville, North Carolina

1 in = 40 ft

12/10/2020

From Leo A. Daly Option 4 Floor Plan, dated 11-5-20.

Proposed Addition

EXPLORATION RESULTS

EXPLORATION RESULTS

4-3-2 N=5

1-1-1 N=2

1-1-2 N=3

4-4-5 N=9

4-5-3 N=8

3-3-4 N=7

TOPSOIL, 5 inches SILTY SAND (SM), fine to medium grained, brown gray, moist, very loose to loose

CLAYEY SAND (SC), fine to coarse grained, rust brown, very moist, very loose to loose

POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), fine to coarse grained, tan brown, moist, loose

Boring Terminated at 20 Feet

0.4

5.0

12.5

20.0

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

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ATTERBERG

LIMITS

LL-PL-PI

LOCATION See Exploration Plan

Latitude: 35.0897° Longitude: -78.8755°

G R

A P

H

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L O

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DEPTH

Advancement Method:

HSA

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

Notes:

Project No.: 70205072

Drill Rig: Acker Renegade

BORING LOG NO. B-1

FFE, Inc.CLIENT:

Cincinnati, OH

Driller: Duggins

Boring Completed: 11-30-2020

PROJECT: Building 4 Renovation

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.

2300 Ramsey Street Fayetteville, NC

SITE:

Boring Started: 11-30-2020

2401 Brentwood Rd Ste 107 Raleigh, NCcave at 11'cave at 11'

WATER LEVEL OBSERVATIONS

No free water observed

S A

M P

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T

Y P

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3-2-1 N=3

1-1-2 N=3

1-2-3 N=5

1-2-4 N=6

2-2-2 N=4

1-2-2 N=4

3-4-3 N=7

3-4-5 N=9

3-4-7 N=11

11.4

19.1

17.0

36-17-19

TOPSOIL, 3 inches SILTY SAND (SM), fine to medium grained, brown gray, moist, very loose to loose

CLAYEY SAND (SC), fine to coarse grained, rust brown, very moist to wet, very loose to loose

POORLY GRADED SAND WITH SILT (SP-SM), fine to coarse grained, brown, moist, loose

FAT CLAY WITH SAND (CH), fine grained, tan and brown, moist to very moist, medium stiff, laminated

POORLY GRADED SAND WITH SILT (SP-SM), fine to coarse grained, brown, moist, loose to medium dense, occasional clay seams

Boring Terminated at 35 Feet

0.2

2.0

12.5

24.0

28.0

35.0

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

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ATTERBERG

LIMITS

LL-PL-PI

LOCATION See Exploration Plan

Latitude: 35.0896° Longitude: -78.8755°

G R

A P

H

IC

L O

G

DEPTH

Advancement Method:

HSA

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

Notes:

Project No.: 70205072

Drill Rig: Acker Renegade

BORING LOG NO. B-2

FFE, Inc.CLIENT:

Cincinnati, OH

Driller: Duggins

Boring Completed: 11-30-2020

PROJECT: Building 4 Renovation

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.

2300 Ramsey Street Fayetteville, NC

SITE:

Boring Started: 11-30-2020

2401 Brentwood Rd Ste 107 Raleigh, NCcave at 15.9'cave at 15.9'

WATER LEVEL OBSERVATIONS

No free water observed

S A

M P

LE

T

Y

1-1-1 N=2

1-1-1 N=2

1-2-3 N=5

3-3-4 N=7

1-2-2 N=4

2-3-4 N=7

1-1-1 N=2

0-0-2 N=2 96

10.5

15.2

17.4

17.8

45.4 57-29-28

TOPSOIL, 3 inches SILTY SAND (SM), fine to medium grained, gray, moist, very loose

CLAYEY SAND (SC), fine to coarse grained, rust brown, very moist, very loose to loose

POORLY GRADED SAND WITH SILT (SP-SM), fine to coarse grained, brown, moist, very loose to loose

FAT CLAY WITH SAND (CH), fine grained, brown to dark gray, very moist, soft, laminated

Boring Terminated at 30 Feet

0.2

2.5

12.5

27.0

30.0

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

T H

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