Atch 9 - Geotechnical Report_MUHJ 19-4055 Repair Dormitory Facility 130.pdf

Facilities | Environmental | Geotechnical | Materials

Report Cover Page

Repair Dorm, Facility

Geotechnical Engineering Report

Hampton, Virginia

December 20, 2024 | Terracon Project No. K4245039

Prepared for:

Dills Architects, P.C.

1432 N. Great Neck Road, Suite

Virginia Beach, VA 23454

701 Alexander Lee Parkway

Williamsburg, VA 23185

P (757) 564-6452

Terracon.com

Report Cover Letter to Sign

December 20, 2024

Dills Architects, P.C.

1432 N. Great Neck Road, Suite 204

Virginia Beach, VA 23454

Attn: Anna Campbell

P: (757) 496-4926

E: acampbell@dillsarchitects.com

Re: Geotechnical Engineering Report

Repair Dorm, Facility 130

Joint Base Langley-Eustis (JBLE)

Hampton, Virginia

Terracon Project No. K4245039

Dear Ms. Campbell:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PK4245039 dated

April 25, 2024. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

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

Sincerely, Terracon

Collin Gerald Bruce R. Spiro, P.E.

Staff Geologist Senior Engineering Consultant

Virginia Lic. No. 015791

James R. Wheeler, P.G.

Principal https://na3.documents.adobe.com/verifier?tx=CBJCHBCAABAATGIWW-63Mu4biOowpFt2xfdp5vuyNUQu https://na3.documents.adobe.com/verifier?tx=CBJCHBCAABAATGIWW-63Mu4biOowpFt2xfdp5vuyNUQu

Geotechnical Engineering Report

Repair Dorm, Facility 130 | Hampton, Virginia x

Facilities | Environmental | Geotechnical | Materials i

Table of Contents Introduction Project Description Site Conditions Geotechnical Characterization

Field Exploration Field and Laboratory Testing Soil Classification and Index Testing

Geologic Setting Seismic Site Class Geotechnical Overview Earthwork

Site Preparation Subgrade Preparation Existing Fill Excavation Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Earthwork Construction Considerations Construction Observation and Testing

Shallow Foundations – Lightly Loaded Structures Design Parameters – Compressive Loads Foundation Construction Considerations

Specialty Foundations – Brick Piers Helical Piers

Floor Slabs Floor Slab Design Parameters Floor Slab Construction Considerations

General Comments

Figures GeoModel

Facilities | Environmental | Geotechnical | Materials ii

Attachments

Exploration and Testing Procedures

Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

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

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/ http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed Repair Dorm, 633 CES, Facility 130 project be located at Joint Base Langley-Eustis (JBLE) in Hampton, Virginia. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification estimation

■ Earthwork recommendations including site/subgrade preparation

■ Recommended foundation options and engineering design parameters

■ Estimation of foundation settlements

■ Floor slab design and construction

The geotechnical engineering Scope of Services for this project included the advancement of test borings, laboratory testing, engineering analyses, 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 as separate graphs in the Exploration and Laboratory Results attachment.

Project Description

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

Item Description

Information

Provided

An email request for proposal was provided by Anna Campbell on April 10, 2024. The request included a Statement of Work

(SOW) and a design change log. In addition, we consulted with the Structural Engineer, Peyton Mulé with NRW Engineering, and followed his direction for scope of work and quantity of borings.

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Project

Description

The project consists of renovations to an existing dormitory structure at Joint Base Langley-Eustis (JBLE) in Hampton, Virginia. Additions included within this project’s scope include a utility building, brick screen wall, and a cooling tower platform.

Existing Structure The existing dormitory structure is three (3) stories.

Building

Construction

As part of the renovations, new foundations will be constructed around the perimeter of the existing structure to support new brick piers that will be installed in front of the existing column faces which will possibly carry additional loading from a new roof. As part of the new construction, shallow foundations will be utilized to support a one-story utility building consisting of trusses on CMU, a solidly grouted, brick screen wall and a post supported steel frame cooling tower platform.

Maximum Loads

Anticipated structural loads were provided by Peyton Mulé with

NRW Engineering, P.C.

■ Columns/Piers: 21 kips

■ Utility Building: 1.0 klf

■ Brick Screen Wall: 1.0 klf

■ Cooling Tower Platform: 28 kips

Grading/Slopes

Grades directly adjacent to the existing building and within the vicinity of the new foundations are expected to essentially remain unchanged.

Building Code 2018 IBC

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 JBLE in Hampton, Virginia.

37.072412° N, -76.367286° W (See Exhibit D)

See Site Location

Facilities | Environmental | Geotechnical | Materials 3

Item Description

Existing

Improvements

Existing 3-story structure and associated infrastructure (utilities, landscaping, pavements, etc.). It is our understanding that this existing structure is supported on a deep foundation system

(piles).

Current Ground

Cover

Sidewalks and grass cover mainly directly around perimeter of the existing structure.

Existing

Topography

As indicated by the Hampton Online GIS Viewer, the site is relatively flat with elevations ranging from 7 to 8 feet in elevation (WGS84).

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 and Laboratory 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 SURFICIAL Topsoil or Asphalt underlain by Aggregate Base

2 FILL

SAND (SC, SM) and CLAY (CL), both containing varying amounts of Gravel, Sand, Clayey Sand, and/or fibrous organic material

FINE-

GRAINED

SOILS

CLAY (CL, CH) and SILT (ML) with varying amounts of sand, marine shell fragments, and/or fibrous organic material, with isolated deposits of SAND (SM, SC)

4 SAND

SAND (SM), contains marine shell fragments, "Yorktown Formation”

Facilities | Environmental | Geotechnical | Materials 4

The presence of groundwater at the boring locations was examined during drilling as observed through the relative wetness of the recovered soil samples during the drilling operations. During drilling operations, fluid (clay-water slurry) is introduced into the borehole generally impairing the ability to accurately determine groundwater levels.

Groundwater was determined to be encountered at depths of 6 to 7 feet below existing grades, corresponding to elevations 1 to 2 ft (WGS84). The boreholes were backfilled upon completion for safety considerations.

Groundwater conditions will vary with environmental variations, tidal fluctuations, and seasonal conditions, such as the frequency and magnitude of rainfall patterns and man-made influences, such as existing swales, drainage ponds, underdrains and areas of covered soil (paved parking lots, sidewalks, etc.). In the project’s area, seasonal groundwater fluctuations are common. We recommend that the contractor determine the actual groundwater levels at the time of the construction to determine groundwater impact on the construction procedures, if necessary.

Field Exploration

In order to explore the general subsurface soil types and to aid in developing associated foundation design parameters, the following exploration program was performed:

◼ Four (4) 50-foot deep Standard Penetration Test (SPT) borings (designated as B-1 through B-4), drilled around the perimeter of the existing three-story structure.

◼ Two (2) 15-foot deep SPT borings (designated as D-1 and U-1), drilled within the vicinity of where the utility building, screen wall, and cooling tower platform will be located.

◼ Review of historical site data.

The SPT borings were performed with the use of rotary wash “mud” drilling procedures in general accordance with ASTM D 1586. The tests were performed continuously from the existing ground surface to a depth up to 12-feet, and at 5-foot intervals thereafter starting at a depth of 13-feet. The soil samples were obtained with a standard 1.4” I.D., 2” O.D., 30” long split-spoon sampler. The sampler was driven with blows of a 140 lb.

hammer falling 30 inches, using an automatic hammer. The number of blows required to drive the sampler each 6-inch increment of penetration was recorded and is shown on the boring logs. The sum of the second and third penetration increments is termed the

SPT N-value (uncorrected for automatic hammer). A representative portion of each disturbed split-spoon sample was collected with each SPT, placed in a glass jar, sealed, labeled, and returned to our laboratory for review. All boreholes were backfilled upon completion with the drilling spoils and surface capped with cold-mix asphalt, as appropriate.

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The boring locations were established by Terracon and were approved by the Client prior to mobilization. The boring locations were staked in the field by a representative of

Terracon with a handheld GPS device and by corroborating the location with easily identifiable landmarks. The approximate boring locations are shown in the Figures attachment of this report.

Field and Laboratory Testing

Soil testing provided by Terracon was performed in accordance with American Society for Testing and Materials (ASTM) standards. All soils and materials tests were performed in our AASHTO re:source and US Army Corps of Engineers certified Williamsburg, Virginia laboratory.

Soil Classification and Index Testing

Representative portions of all soil samples collected during drilling operations were labeled, preserved and transferred to our laboratory in accordance with ASTM D4220 for classification and analysis. Soil descriptions on the boring logs are provided using visual-manual methods in general accordance with ASTM D2488 using the Unified Soil

Classification System (USCS).

Soil samples that were selected for index testing were classified in general accordance with ASTM D2487. It should be noted that some variation can be expected between samples classified using the visual-manual procedure (ASTM D2488) and the USCS

(ASTM D2487). A summary of the soil classification system is provided in the

Supporting Information attachment of this report.

Representative split-spoon soil samples were selected and subjected to natural moisture, #200 sieve wash, and Atterberg Limits testing in order to corroborate the visual classification. These test results, along with the soil test boring logs are presented in the

Exploration and Laboratory Results attachment of this report. A generalized subsurface soil profile is provided in the Figures attachment of this report.

Geologic Setting

The project site is located within the Atlantic Coastal Plain physiographic province.

Bedrock of the Late Mesozoic age is present at depths of greater than 2,000 ft, and is overlain by Lower and Upper Cretaceous, Tertiary, Pleistocene and Recent Sediments.

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Across the outer Coastal Plain, the Pliocene age Yorktown Formation of the Tertiary

Period is widespread, occurring from Maryland to North Carolina. Its age is estimated between 4.8 million and 2.8 million years and is estimated to have been deposited during three transgressive episodes. The depositional environment was shallow marine in nature, consisting of inner shelf, barrier-island, estuarine and lagoonal patterns. The

Yorktown Formation is a glauconitic, fossiliferous, Silty to Clayey greenish-gray fine

Sand. This material has been pre-consolidated by an increased effective overburden pressure generated due to a drop in the sea level at the end of the Tertiary Period, and by previously overlying sediments, which eroded away as the sea level subsequently lowered.

As sea levels rose during the Pleistocene Epoch of the Quaternary Period, areas within the project limits were filled and overlain by soils of the Tabb Formation; Lynnhaven

Member, which is composed of fluvial and estuarine deposits. The geologic stratigraphy encountered in our subsurface explorations generally consisted of marine deposited

Sands and Clays of this formation.

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 50 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.

Geotechnical Overview

The subsurface materials below the surficial material and undocumented Fill generally consisted of CLAY (CL, CH) and SILT (ML) underlain by loose to medium dense Sand to a depth of 50 feet. The groundwater was estimated to occur at depths ranging from about

6 to 7 feet below site grades at the boring locations at the time of drilling, corresponding to elevations of 1 to 2 feet (WGS84).

Facilities | Environmental | Geotechnical | Materials 7

Shallow foundations are not recommended to be placed on existing undocumented Fill.

Accordingly, undercutting and replacement by Structural Fill is recommended. Shallow foundations can be placed on firm natural soil. The proposed structure’s walls and columns can thereby be supported on shallow foundations.

Support of floor slabs on or above existing fill materials is discussed in this report.

However, even with the recommended construction procedures, an inherent risk remains 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. 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 of increased differential performance which can result in increased cracking and abrupt differential settlement. Should this risk be acceptable, floor slabs can be supported above the fill.

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

Comments section provides an understanding of the report limitations.

Earthwork

Earthwork is anticipated to include clearing and grubbing, excavations, 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 necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

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 building areas.

Where fill is placed on existing slopes steeper than 5H:1V, benches should be cut into the existing slopes prior to fill placement. The benches should have a minimum vertical face height of 1 foot and a maximum vertical face height of 3 feet and should be cut wide enough to accommodate the compaction equipment. This benching will help provide a positive bond between the fill and natural soils and reduce the possibility of failure along the fill/natural soil interface.

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Evidence of underground facilities was observed during the exploration and site reconnaissance. If underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

Subgrade Preparation

The subgrade should be proofrolled with an adequately loaded vehicle such as a fully 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. Such areas should either be removed or modified by treating/applying/mixing. Excessively wet or dry material should either be removed, or moisture conditioned and recompacted.

All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 10 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. 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 construction.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Existing Fill

As noted in Geotechnical Characterization, the soil borings encountered previously placed fill to depths extending up to 6 feet below existing site grades at the boring locations. We have no records to indicate the degree of control, and consequently, the fill is considered unreliable for support of foundation loads. We recommend full removal of existing Fill below foundation footprints and its replacement by Structural fill, VDOT

#57 stone or flowable concrete as detailed in Foundation Construction

Considerations.

Facilities | Environmental | Geotechnical | Materials 9

Support of floor slabs on or above existing undocumented fill soils 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 construct the floor slabs on the existing undocumented fill 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 entire area should be proofrolled with heavy, rubber tire construction equipment, to aid in delineating areas of soft or otherwise unsuitable soil. Areas of soft or otherwise unsuitable material should be undercut and replaced with either new structural fill or suitable, existing on-site materials.

In addition to the proofroll, several 3 to 6-foot deep test pits should be excavated within the proposed construction areas. The test pits are considered necessary to determine the thickness and composition of the undocumented fill materials. The test pits should be performed under the observation of the Geotechnical Engineer or representative who will evaluate the composition of the recovered soils. In addition to the test pits, several compaction tests should be performed on the undocumented fill material within the proposed building areas to further substantiate the suitability of the existing undocumented fill material. It is possible that some subgrade improvements will be required to provide suitable soils for building slab support. The undocumented fill material may remain in place under slabs if approved by the Geotechnical Engineer (to be determined following the completion of the test pits and compaction testing).

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.

Existing, on-site materials are not considered suitable for re-use as structural fill but may be used as general fill in green areas.

Facilities | Environmental | Geotechnical | Materials 10

Imported Fill Materials: Imported 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)

Granular

GW, GP, GM, GC,

SW, SP, SM

Less than 20% passing No. 200 sieve

Liquid Limit less than 20

Plasticity Index less than 6

1. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site. Additional geotechnical consultation should be provided prior to use of uniformly graded gravel on the site.

Fill Placement and Compaction Requirements

Structural fill should meet the following compaction requirements.

Item Structural 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

Minimum

Compaction

Requirements 1

98% of max. below foundations and within 1 foot of finished pavement subgrade

95% of max. above foundations, below floor slabs, and more than 1 foot below finished pavement subgrade

Water Content

Range 1 -2% to +2% of optimum

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

(ASTM D698).

Facilities | Environmental | Geotechnical | Materials 11

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.

On-site materials are 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.

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. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

For low permeability subgrades, utility trenches are a common source of water infiltration and migration. Utility trenches penetrating beneath the building 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% 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.

Groundwater was encountered at depths ranging from about 6 to 7 feet below existing grades during our exploration services. Groundwater as well as standing surface water and perched water could affect over-excavation efforts. Managing ground, surface and perched water may be necessary to achieve the recommended depth of over-excavation depending on water conditions at the time of 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.

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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.

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 provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

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Shallow Foundations – Lightly Loaded Structures

If the site has been prepared in accordance with the requirements mentioned above, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description

Maximum Net Allowable Bearing

Pressure 1, 2

1,500 psf - foundations bearing upon structural fill or undisturbed native soils

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

Minimum Embedment below

Finished Grade 4 24 inches

Estimated Total Settlement from

Structural Loads 2 Less than about 1 inch

Estimated Differential Settlement 2, 5 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.

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 over-excavated and replaced per the recommendations presented in Earthwork.

4. 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.

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

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.

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Sensitive soils exposed at the surface of footing excavations may require surficial compaction with hand-held dynamic compaction equipment prior to placing structural fill, steel, and/or concrete. Should surficial compaction not be adequate, construction of a working surface consisting of either crushed stone, or a lean concrete mud mat may be required prior to the placement of reinforcing steel and construction of foundations.

If unsuitable bearing soils or uncontrolled Fill are observed at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils and remove all existing Fill material, and the footings could bear directly on these soi ls at the lower level or have the footing base elevation re-established with approved backfill as illustrated on the sketch below.

The over-excavation should be backfilled up to the footing base elevation with Structural

Fill, washed crushed stone (VDOT No. 57) wrapped in a geotextile fabric (Mirafi 140N or equivalent) or flowable concrete.

Specialty Foundations – Brick Piers

Helical Piers

In order to eliminate the potential risk of differential settlement between the loads of the new brick piers and the columns of the existing structure, it is recommended that the structural loads of the piers be supported by helical piles.

We have conducted preliminary evaluations for Helical Anchor capacity as it would apply to the subsurface conditions noted at this site. Due to the relative slenderness of a typical Helical Anchor shaft, column buckling may be of concern. Therefore, a Round

Shaft section was analyzed. Buckling stability may also be achieved by grout-column modification of typical Square Shaft anchors if desired.

Facilities | Environmental | Geotechnical | Materials 16

For preliminary design considerations, it is anticipated that a two to three-helix, round-shaft Anchor, installed to a depth of approximately 30 feet below existing grade, should be able to achieve an allowable compression capacity of approximately 20 kips. It is recommended that a minimum safety factor of 2.5 in compression and 3 in tension should be incorporated in the pile design. It should be emphasized, however, that Helical

Anchor design is proprietary to the specific manufacturer, and that final design of such foundations should be carried out by the selected manufacturer’s professional representative.

We recommend the installation of at least four (4) test piles and performing a static load test at two of these locations selected by the Geotechnical Engineer to confirm the design helical anchor depth and capacity. The static load tests should be performed no sooner than 7 days after pile installation. The load test(s) should be performed in accordance with ASTM D 1143 - Quick Test Method for Piles Under Static Axial

Compressive Load and should also run uplift and lateral tests if these types of loads are to be applied. The static load tests should be performed under the observation of the

Geotechnical Engineer or his representative who should record the dial gage readings.

The records of the pile load tests should be reviewed by the Geotechnical Engineer and the Structural Engineer to verify the pile design criteria. The production piles should be installed using the same equipment and methods as for the test piles.

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.

Existing fill materials and materials described as undocumented fill were observed at the site to depths up to 6 feet below existing grade. As previously described, any existing fill present beneath floor slabs should be tested and further evaluated by the Geotechnical

Engineer.

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.

Depending upon the finished floor elevation, unsuitable, weak, loose and/or soft soils may be observed at the floor slab subgrade level. These soils should be replaced with structural fill for adequate floor slab support.

Facilities | Environmental | Geotechnical | Materials 17

Floor Slab Design Parameters

Item Description

Floor Slab

Support

■ Directly supported by at least a 4-inch layer of relatively clean, compacted, poorly graded sand (SP) or gravel

(GP) with less than 5% passing the No. 200 Sieve

(0.074 mm). The purpose of the 4-inch layer is to act as a capillary barrier and equalize moisture conditions beneath the slab.

OR

■ Directly supported by a 6 to 8-inch layer of well-compacted aggregate base stone (VDOT 21A or 21B

Gradation)

Subgrade compacted to recommendations in Earthwork

Estimated Modulus of Subgrade

Reaction

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

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, 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, 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.

Facilities | Environmental | Geotechnical | Materials 18

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.

In case the final grading results in significant fill heights beneath the floor slabs, internal fill compression and subsurface settlement from fill loads could induce cracking in the slab-on-grade members. While this settlement cannot be estimated at the time of this writing without knowing the actual fill height, mitigation measures include proper earthwork and a hold period before slab construction. In addition, 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.

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 is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Facilities | Environmental | Geotechnical | Materials 19

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

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

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

Attachments

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

4 50 Perimeter of Existing

Building

2 15

Utility Building, Screen

Wall, and Cooling Tower

Platform Areas

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. Approximate ground surface elevations were obtained by interpolation from the City of Hampton GIS Viewer (WGS84). If elevations and a more precise boring layout are desired, we recommend borings be surveyed.

Subsurface Exploration Procedures: The SPT borings were performed with a track-mounted, rotary drill rig using rotary wash “mud” drilling procedures. The tests were performed continuously from the existing ground surface to a depth of 12-feet, and at 5-foot intervals thereafter starting at a depth of 13-feet. The soil samples were obtained with a standard 1.4” I.D., 2” O.D., 30” long split-spoon sampler. The sampler was driven with blows of a 140 lb. hammer falling 30 inches, using an automatic hammer. The number of blows required to drive the sampler each 6-inch increment of penetration was recorded and is shown on the boring logs. The sum of the second and third penetration increments is termed the SPT N-value (uncorrected for automatic hammer). A representative portion of each disturbed split-spoon sample was collected with each SPT, placed in a glass jar, sealed, labeled, and returned to our laboratory for review. All boreholes were backfilled upon completion with the drilling spoils and surface capped with cold-mix asphalt, as appropriate.

We also observed the boreholes while drilling and at the completion of drilling for the presence of groundwater. The groundwater levels are shown on the attached boring logs.

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 Geologist. The final boring logs represent the Geologist's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

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

■ Atterberg Limits

■ #200 Sieve

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.

Figures

Contents:

GeoModel

-45

-40

-35

-30

-25

-20

-15

-10

-5

E L E

V A

T

IO

N

M S

L

(f e e t)

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1 B-2 B-3 B-4 D-1

U-1

Legend

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

GeoModel

37 W. Cedar Avenue | Hampton, VA

Terracon Project No. K4245039

Repair Dorm, Facility 130

701 Alexander Lee Pkwy

Williamsburg, VA

First Water Observation

Groundwater levels are temporal. The levels shown are representative of the date and time of our exploration. Significant changes are possible over time.

Water levels shown are as measured during and/or after drilling. In some cases, boring advancement methods mask the presence/absence of groundwater. See individual logs for details.

Topsoil Silty Sand

Clayey Sand Sandy Lean Clay

Lean Clay with Sand Sandy Silt

Asphalt Aggregate Base Course

Fat Clay

Model Layer Layer Name General Description

1 Topsoil or Asphalt underlain by Aggregate Base

CLAY (CL, CH) and SILT (ML) with varying amounts of sand, marine shell fragments, and/or fibrous organic material, with isolated deposits of SAND (SM, SC)

4 SAND (SM), contains marine shell…