AC_RTA_Geotech_Horiz_2017-07-12.pdf

REPORT OF

SUBSURFACE

EXPLORATION

AND

GEOTECHNICAL

ENGINEERING

SERVICES

Aviation Complex Horizontal Component

Newport News, Virginia

G E T Project No: WM15-164G

May 16, 2016

PREPARED FOR:

ADMINISTERED BY:

1592-E Penniman Road Williamsburg, VA 23185 Phone: (757) 564-6452 www.getsolutionsinc.com

1592 Penniman Road, Suite E Williamsburg, Virginia 23185 Phone: (757)-564-6452 Fax: (757)-564-6453 info@getsolutionsinc.com

May 16, 2016

TO: HNTB Corporation

2900 South Quincy Street, Suite 600 Arlington, VA 22206

Attn: Mr. Brian Pieplow

RE: Report of Subsurface Exploration and Geotechnical Engineering Services

Aviation Complex – Horizontal Component Newport News, Virginia G E T Project No. WM15-164G

Dear Mr. Pieplow:

In compliance with your instructions, we have completed our Subsurface Exploration and Geotechnical Engineering Services for the above referenced project. The results of this study, together with our recommendations, are presented in this report.

Often, because of design and construction details that occur on a project, questions arise concerning subsurface conditions. G E T Solutions, Inc. would be pleased to continue its role as Geotechnical Engineer during the project implementation.

We appreciate the opportunity to work with you on this project. We trust that the information contained herein meets your immediate need, and should you have any questions or if we could be of further assistance, please do not hesitate to contact us.

Respectfully Submitted, G E T Solutions, Inc.

James R. Wheeler Project Geologist

Bruce R. Spiro, P.E.

Principal Engineer Virginia Reg. # 015791

Copies: (1) Client

TABLE OF CONTENTS

Report of Subsurface Exploration and Geotechnical Engineering Services

EXECUTIVE SUMMARY ............................................................................................................... i

1.0 PROJECT INFORMATION

1.1 Project Authorization

1.2 Project Location and Description

1.3 Purpose and Scope of Services

2.0 FIELD AND LABORATORY PROCEDURES

2.1 Field Exploration

2.2 Laboratory Testing

3.0 SITE AND SUBSURFACE CONDITIONS

3.1 Site Geology

3.2 Subsurface Soil Conditions

3.3 Groundwater Discussion

4.0 EVALUATIONS AND RECOMMENDATIONS

4.1 Clearing and Grading

4.2 Subgrade Preparation

4.3 Structural Fill and Placement

4.4 Suitability of On-site Soils

4.5 Deep Foundation Recommendations

4.5.1 Axial Compression Capacity Recommendations - Driven Concrete Piles .. 13

4.5.2 Lateral Capacity Analysis - Driven Concrete Piles

4.5.3 Pile Group Settlement

4.5.4 Test Pile Program

4.5.5 Dynamic Testing

4.5.6 Production Pile/Acceptance Criteria

4.5.7 Allowable Driving Stresses

4.5.8 Hammer Types and Energies

4.5.9 Adjacent Structures

4.5.10 Approach Abutments

4.6 Below-Grade Construction

4.7 MSE Wall Stability Analyses

4.8 On-site Shrink/Swell Properties

4.9 Seismic Evaluation

4.10 Liquefaction Potential

4.11 Soil Permeability

5.0 CONSTRUCTION CONSIDERATIONS

5.1 Anticipated Excavation Characteristics

5.2 Excavation Stability

5.3 Dewatering

5.4 Site Utility Installation

5.5 Structure Protection and Monitoring

5.6 Construction Monitoring and Inspections

5.7 Excavations

6.0 REPORT LIMITATIONS

TABLE OF CONTENTS

Report of Subsurface Exploration and Geotechnical Engineering Services

APPENDIX I TEST BORING LOCATION PLANS

APPENDIX II SUMMARY OF SOIL CLASSIFICATION

APPENDIX III SUMMARY OF LABORATORY CLASSIFICATION RESULTS

APPENDIX IV SOIL TEST BORING LOGS

APPENDIX V GENERALIZED SOIL PROFILES

APPENDIX VI TRIAXIAL COMPRESSION TEST RESULTS

APPENDIX VII CBR TEST RESULTS

APPENDIX VIII CALCULATIONS

APPENDIX IX LATERAL PILE ANALYSIS PARAMETER SUMMARY

APPENDIX X LIQUEFACTION ANALYSES

APPENDIX XI INFILTRATION TEST RESULTS

APPENDIX XII MSE WALL GLOBAL STABILITY ANALYSES

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 i

EXECUTIVE SUMMARY

The Project site is located on a 75 Acre parcel generally opposite the south side of an existing Runway. This site is currently being used for training operations. The new construction at this site will consist of building a new Aviation Training Facility to include various structures and ancillary buildings, pavements and Taxiways. Additional analyses were performed as part of the Aviation Complex – Vertical design package. The results of these explorations, along with associated laboratory analyses and design evaluations, were presented previously under separate cover.

One Hundred Ninteen (119) 1 to 120-foot deep Standard Penetration Test (SPT) borings, Hand Augers and Test Pits were obtained within the vicinity of the proposed new site features, including Taxiway Bridge (17 Borings; Bxx), Stormwater Management Features (10 Borings;

SWMxx), Access Roadway (25 Test Pits; RDxx / 22 Hand Augers; HAxx), Taxiway (20 Borings;

TXxx) and Site Grading Features (25 Borings; RWxx).

The natural subsurface soils were generally arranged in a 2- to 3-layer configuration as described in the Tables below:

Subsurface Soil Conditions – General Site Borings

AVERAGE

DEPTH (ft)

STRATUM DESCRIPTION

RANGES OF

SPT(1) N-VALUES

to

0.2 - 0.7 Surficial 2 to 8 inches of Topsoil –

0.2 – 0.7 to

2 - 6 I

Red, orange, brown and tan, Sandy CLAY (CL) with varying amounts of Silt, and trace fibrous organics

3 – 18

2 - 6 to

II

Brown and gray SAND (SP-SM, SM, SC) with varying amounts of Silt and Clay

3 – 21

Notes: (1) SPT = Standard Penetration Test, N-Values in Blows-per-foot (Uncorrected for Automatic Hammer or Overburden)

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 ii

Subsurface Soil Conditions – Taxiway Bridge Borings

DEPTH (ft)

STRATUM DESCRIPTION

RANGES OF

SPT(1) N-VALUES

to

2 - 10 I Marsh Deposits (Muck, Organic CLAY) WOH

2 - 10 to

50 - 60

II

Brown and gray SAND (SP-SM, SM, SC) with varying amounts of Silt and Clay.

Isolated deposits of Soft, Gray, Silty and Sandy CLAY (CL, CH) noted at borings B-6A and B-12A between depths of 28- 32ft and 38-46ft, respectively.

to

III

Gray and Brown SAND (SM, SC) with varying amounts of Silt, Clay, Gravel, and marine shell fragments; Gray Sandy CLAY (CL) with varying amounts of Silt, and marine shell fragments

“Yorktown Formation”

3 – 26

Notes: (1) SPT = Standard Penetration Test, N-Values in Blows-per-foot (Uncorrected for Automatic Hammer or Overburden)

The initial groundwater-level was measured to occur at depths ranging from about 5 to 8 feet below existing grades at the more elevated boring locations and at or near the ground surface at the Taxiway Bridge crossing borings, corresponding to elevations of 0 to 3 feet NAVD88.

The following evaluations and recommendations were developed based on our field exploration and laboratory-testing program:

We recommend that the principal structures of the proposed Taxiway Bridge structure be supported on a deep foundation system comprised of square, pre-cast, pre-stressed concrete (SPPC) piles. Pile design characteristics are provided in Section 4.5 of the report. The Client is providing lateral capacity analyses for these deep foundation elements as part of an integrated evaluation of foundation and structure utilizing FB MultiPier™ evaluation procedures.

The shallow subsurface natural CLAY (CL) soils encountered at the boring locations do not appear to meet the criteria recommended in this report for reuse as structural fill; however, these soils may be used as fill in green areas. Shallow subsurface natural SAND (SP-SM, SM) soils were also encountered on site and appear to meet the recommended criteria for reuse as structural fill given that they are within the recommended moisture constraints.

The project’s budget should include an allowance for subgrade improvements in the form of undercut and backfill, use of geotextile fabric and/or geogrid, or lime stabilization.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 iii

Based on the laboratory classification results, the shallow subsurface soils encountered within the upper 10 feet at the boring locations are not considered to be expansive in accordance with 1803.5.3 of the 2012 International Building Code.

The subsurface granular soils recovered within the upper 100 feet at the project site are expected to have adequate resistance against liquefaction during a magnitude 6.5 earthquake or smaller.

Based on our experience in the vicinity of the project site and the composition of the soils recovered within the upper 100 feet at the boring locations, the site characteristics are indicative of a Site Class “D” in accordance with Table 20.3-1 of ASCE 7-10 as referenced by the 2012 International Building Code (IBC) and Table 3.10.3.1-1 of the AASHTO LRFD Bridge Design Specifications (7th ed.).

This summary briefly discusses some of the major topics mentioned in the attached report.

Accordingly, this report should be read in its entirety to thoroughly evaluate the contents.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

1.0 PROJECT INFORMATION

1.1 Project Authorization

G E T Solutions, Inc. has completed our subsurface exploration and geotechnical engineering services for the proposed Aviation Complex – Horizontal Component project located in Newport News, Virginia. The geotechnical engineering services were conducted in general accordance with the scope presented in G E T Proposal No. USACOE-VB15-371G. Authorization to proceed with our services was received from the client in the form of an executed Master Agreement and Task Order dated July 26, 2015.

1.2 Project Location and Description

The Project site is located on a 75 Acre parcel generally opposite the south side of an existing Runway. This site is currently being used for training operations. The site boundaries are limited by the wetland delineations that are identified in the 2012 Environmental Assessment documents published by HNTB. A Site Vicinity Map and General Location Plan are not included in this reporting per request of the Client.

The proposed main Hangar area is predominantly an open, grassy field currently in use as a training area. Surface elevations range around +6 to +8 MSL in this area. Moderately dense woods surround the project location, and a marshy area comprising the upper reaches of a drainage feature lies to the north of the site, between the proposed Hangar site and the existing Runway. A taxiway bridge crossing of this marsh is planned as a feature of the project development, and is reported along with other Horizontal elements of the project herein.

Existing Ground Surface Elevations in the vicinity of this crossing are approximately 0 MSL.

Deep foundation support is anticipated for the new Taxiway Bridge structure. The taxiway pavement is to be designed by the Client; specific field and laboratory data relevant to this design are presented within this report. Access roadways and Stormwater Management features are also included in the site development design to be provided by the Client, and specific field and laboratory data relevant to these designs are also presented herein.

If any of the noted information is incorrect or has changed, please inform G E T Solutions, Inc. so that we may amend the recommendations presented in this report, if appropriate.

1.3 Purpose and Scope of Services

The purpose of this study was to obtain information on the general subsurface conditions at the proposed project site. The subsurface conditions encountered were then evaluated with respect to the available project characteristics. In this regard, engineering assessments for the following items were formulated:

1. General assessment of the soils revealed by the borings performed at the proposed development and review of available geotechnical data.

2. General location and description of potentially deleterious material encountered in the borings that may interfere with construction progress or structure performance, including existing fills or surficial/subsurface organics.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

3. Evaluation of the on-site soils for re-use as structural fill.

4. Feasibility of utilizing a deep foundation system for support of the proposed Taxiway Bridge structure. Design parameters required for the foundation system, including pile type and length, design parameters, testing, and installation criteria.

5. Collection of field Subsurface data for Access Roadways and Stormwater Management features, and presentation of evaluated field and laboratory testing results for design by others.

6. Assessment of the shallow subsurface soils’ expansive properties in accordance with the 2012 International Building Code.

7. Assessment of the soils’ resistance against liquefaction.

8. Seismic site class determination in accordance with the 2012 International

Building Code and AASHTO LRFD Bridge Design Specifications.

The scope of services did not include an environmental assessment for determining the presence or absence of wetlands or hazardous or toxic material in the soil, bedrock, surface water, groundwater or air, on or below or around this site.

2.0 FIELD AND LABORATORY PROCEDURES

2.1 Field Exploration

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

One Hundred Ninteen (119) 1 to 120-foot deep Standard Penetration Test (SPT) borings, Hand Augers and Test Pits were obtained within the vicinity of the proposed new site features, including Taxiway Bridge (17 Borings; Bxx), Stormwater Management Features (10 Borings; SWMxx), Access Roadway (25 Test Pits; RDxx / 22 Hand Augers; HAxx), Taxiway (20 Borings; TXxx) and Site Grading Features (25 Borings; RWxx).

Additional SPT borings were performed as part of the Aviation Complex – Vertical design package. The results of these explorations, along with associated laboratory analyses and design evaluations, were presented under separate cover.

Standard Penetration Tests were performed in the field in general accordance with ASTM D 1586. The tests were performed continuously from the existing ground surface to depths of 12 feet, and at 5-foot intervals thereafter. 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 and overburden pressure). A representative portion of each

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 disturbed split-spoon sample was collected with each SPT, placed in a glass jar, sealed, labeled, and returned to our laboratory for review.

The SPT boring locations were established and staked in the field by a representative of G E T Solutions, Inc. using a hand-held Global Positioning System (GPS) device and corroborated with easily identifiable landmarks. These locations were first approved by the client.

Subsequently, the SPT boring locations were surveyed by the client, who provided the following coordinate location and elevations indicated in Table I below:

Table I - Schedule of SPT Boring Coordinates and Elevations

Boring Location Northing Easting Elevation

Taxiway Bridge Structure Borings

B1 3577014.68 12034306.43 3.8 B2 3576979.83 12034356.89 3.4 B3 3576977.20 12034237.10 0.9 B3A 3576919.90 12034303.10 0.3 B4A 3576890.00 12034251.90 0.7

B5A 3576869.90 12034180.10 0.4 B6A 3576815.50 12034182.20 0.9 B7A 3576817.50 12034114.70 0.0 B8A 3576736.22 12034161.05 ‐0.8 B9A 3576709.92 12034042.23 0.0 B10A 3576682.44 12034119.60 ‐0.8 B11A 3576691.63 12034019.74 ‐0.6 B12A 3576625.93 12034073.87 ‐0.3

B19 3576618.31 12033988.49 3.3 B20 3576588.66 12034017.36 3.1 B21 3576591.36 12033966.31 4.1 B22 3576556.16 12034010.03 3.5

Stormwater Management Borings

SWM1 3576994.76 12032333.68 3.9

SWM2 3576843.02 12032764.20 9.5

SWM3 3577306.52 12032340.05 5.4

SWM4 3576829.54 12033049.41 9.1

SWM5 3577000.78 12032929.24 5.9

SWM6 3576917.62 12033289.67 5.4

SWM7 3576586.54 12032913.40 9.2

SWM8 3576336.94 12033240.00 8.7

SWM9 3576034.80 12033626.64 7.9

SWM10 3575879.40 12033816.49 7.0

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Table I (cont’d.) - Schedule of SPT Boring Coordinates and Elevations

Boring Location Northing Easting Elevation

Access Roadway Test Pits

RD1 3579834.87 12030686.27 6.2

RD2 3579731.92 12030764.20 6.6

RD3 3579588.41 12030909.52 7.1

RD4 3579429.90 12031113.03 7.4

RD5 3579299.17 12031129.42 6.3

RD6 3579130.73 12031016.52 4.8

RD7 3578963.80 12030888.99 4.5

RD8 3578848.68 12030719.01 4.1

RD9 3578722.41 12030570.35 2.7

RD10 3578526.52 12030643.27 3.0

RD11 3578326.17 12030695.79 3.2

RD12 3578133.52 12030783.11 4.4

RD13 3577994.36 12030930.02 4.1

RD14 3577856.69 12031079.95 4.4

RD15 3577697.93 12031257.50 4.9

RD16 3577556.45 12031430.15 4.9

RD17 3577469.35 12031537.44 5.4

RD18 3577326.01 12031704.84 5.9

RD19 3577152.27 12031927.21 6.4

RD20 3577049.05 12032056.77 6.6

RD21 3576998.45 12032173.35 6.7

RD22 3576965.31 12032495.16 5.1

RD23 3576879.31 12032615.67 8.6

RD24 3576930.83 12032781.91 5.8

RD25 3576509.23 12034844.35 8.0

Taxiway Borings

TX1 3577088.25 12034372.67 8.9

TX2 3577022.82 12034324.51 3.8

TX3 3576784.03 12033358.64 6.3

TX4 3576702.02 12033467.03 6.5

TX5 3576605.17 12033574.75 6.9

TX6 3576537.02 12033694.62 5.7

TX7 3576435.32 12033802.85 5.9

TX8 3576371.46 12033905.14 5.2

TX9 3576679.95 12033272.23 8.0

TX10 3576582.64 12033390.07 7.8

TX11 3576503.07 12033493.29 7.9

TX12 3576418.34 12033602.76 8.5

TX13 3576344.14 12033704.78 8.4

TX14 3576247.90 12033813.89 8.1

TX15 3576921.75 12033057.29 6.0

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Boring Location Northing Easting Elevation

Taxiway Borings (cont’d.)

TX16 3576789.18 12032954.91 9.8

TX17 3576919.79 12032856.80 7.7

TX18 3576807.03 12032745.25 10.3

TX19 3576872.11 12033217.63 6.2

TX20 3576529.30 12033939.79 4.7

Site Grading Feature Borings

RW1 3576891.74 12033413.72 5.8

RW2 3576801.59 12033481.98 5.8

RW3 3576777.62 12033575.99 5.4

RW4 3576698.87 12033622.02 5.1

RW5 3576682.25 12033723.34 5.3

RW6 3576564.49 12033800.63 4.7

RW7 3576564.45 12033881.90 5.0

RW8 3576500.31 12034012.60 4.7

RW9 3576442.36 12033931.97 4.8

RW10 3576326.88 12033971.21 5.3

RW11 3576260.05 12034002.77 5.2

RW12 3576197.85 12033961.37 5.4

RW13 3575967.91 12033767.34 7.6

RW14 3575990.31 12033652.84 7.2

RW15 3576090.80 12033562.38 7.6

RW16 3576111.52 12033509.67 7.8

RW17 3576191.71 12033440.09 8.1

RW18 3576246.43 12033355.25 8.1

RW19 3576274.69 12033272.34 8.5

RW20 3576328.75 12033195.83 8.5

RW21 3576407.61 12033129.58 9.1

RW22 3576468.95 12033041.60 8.5

RW23 3576546.07 12032969.88 8.9

RW24 3576596.98 12032885.11 8.3

RW25 3576658.73 12032830.47 9.5

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Boring Location Northing Easting Elevation

Access Roadway Hand Auger Borings

HA1 3579784.75 12030717.84 0.0

HA2 3579673.41 12030820.71 0.0

HA3 3579511.84 12031010.09 0.0

HA4 3579364.89 12031132.25 0.0

HA5 3579198.91 12031065.72 0.0

HA6 3579057.42 12030965.13 0.0

HA7 3578897.38 12030813.55 6.2

HA8 3578797.95 12030620.00 0.0

HA9 3578618.90 12030609.14 0.0

HA10 3578419.18 12030672.07 0.0

HA11 3578238.76 12030721.14 0.0

HA12 3578069.88 12030851.14 0.0

HA13 3577934.53 12031002.28 0.0

HA14 3577754.70 12031194.89 4.9

HA15 3577636.34 12031331.93 4.6

HA16 3577500.19 12031499.10 5.2

HA17 3577366.63 12031658.76 6.0

HA18 3577270.62 12031777.38 5.7

HA19 3577121.95 12031960.97 6.4

HA20 3577014.69 12032120.40 6.3

HA21 3576941.91 12032297.86 6.5

HA22 3576870.62 12032470.19 8.9

NOTE: Coordinate Locations and Elevations provided by Client

The SPT boring locations are shown on the attached “Boring Location Plans” (Appendix I), which were developed based on site plans provided by the client.

Two (2) relatively undisturbed, 3-inch diameter, thin-walled Shelby tube samples were collected from the boring locations at depths identified in Table II. The Shelby tube samples were obtained by hydraulically pressing a 3-inch outside diameter Shelby tube into the targeted soils using the drill rig. The tubes were sealed in general accordance with ASTM standards and returned to G E T Solutions, Inc.’s Virginia Beach laboratory for extraction, classification and Unconsolidated-Undrained Triaxial Shear testing (per ASTM D 2850).

Table II - Schedule of Shelby Tubes

Boring Location Depth Shelby Tube Extracted

B-3A 33-35 feet below grades B-3A 38-40 feet below grades

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

2.2 Laboratory Testing

Representative portions of all soil samples collected during drilling were sealed in glass jars or plastic bags, labeled and transferred to our laboratory for classification and analysis. A Project Geologist performed the soil classification in general accordance with ASTM Specifications D 2487 and D 2488. A summary of the soil classification system is provided in Appendix II.

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 are summarized in the table presented in Appendix III and in the soil test boring logs presented in Appendix IV. The general subsurface soil profiles are presented in Appendix V.

Two (2), Unconsolidated-Undrained Triaxial Shear tests were performed at our Virginia Beach laboratory in general accordance with ASTM D 2850 on the specimens extracted from the Shelby tube samples obtained at the locations indicated in Table II above.

The U-U test results are presented in Table III below. The comprehensive test results are provided in Appendix VI.

Table III – Unconsolidated Undrained Triaxial Test Results

Boring No.

Depth (ft)

Water Content (avg)

Dry Unit

Weight (avg) (pcf)

Cohesion

(psf)

Strain at Failure (avg)

B-3A 33-35 39 77 562 6

B-3A 38-40 36 78 537 5

Eight (8) bulk soil samples, designated as CBR-1 through CBR-8, were collected from the proposed airfield taxiway and access pavement construction areas at the locations shown on the attached location plan. The bulk subgrade soil samples were collected from depths ranging from 0.5 to 3 feet below existing site grades. The bulk soil samples were returned to our laboratory and subjected to CBR testing in accordance with ASTM standards.

The selected representative bulk subgrade soil samples were subjected to natural moisture content, -#200 sieve, Atterberg Limits, Standard Proctor and CBR testing in accordance with ASTM standards. A summary of the CBR test results is presented on the following page in Table IV. In addition, this summary as well as the CBR curves and the moisture density relationship curves (Proctor Curves) are presented in Appendix VII.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Table IV – CBR Test Results

3.0 SITE AND SUBSURFACE CONDITIONS

3.1 Site Geology

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.

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 as 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 preconsolidated 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.

Sample Number CBR-1 CBR-2 CBR-3 CBR-4 CBR-5 CBR-6 CBR-7 CBR-8

Sample Depth (ft.) 0.5-1 0.5-2 0.5-2 0.5-1.5 0.5-1.5 0.5-2 0.5-1 0.5-2

Unified Soil Classification Symbol

SM SM CL SM SM SM SM CL

Natural Moisture Content

20 11 14 14 11 9 14 16

Atterberg Limits

LL/PL/PI

Non

Plastic Non

Plastic 23/15/8

Non Plastic

Non Plastic

Non Plastic

Non Plastic

27/18/9

% Passing #200 Sieve 47 40 52 46 32 32 44 70

Maximum Dry Density, pcf 111.3 115.1 114.4 115.7 117.8 119.3 113.6 107.0

Optimum Moisture % 13.9 12.3 13.2 12.4 12.1 11.5 13.4 17.1

Soaked CBR Value 18.8 15.1 8.8 18.3 14.9 18.4 15.5 8.5

Resiliency Factor 2.5 2.5 2.5 2.5 3.0 3.0 2.5 2.0

Swell % 0.5 0.3 0.1 0.2 0.1 0.1 0.2 0.6

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

As sea levels rose during the Pleistocene Epoch of the Quaternary Period, areas were filled and overlain by soils of the Lynnhaven, Poquoson, Windsor and Shirley members of the Tabb Formation. The Tabb Formation is composed of fluvial and estuarine sand, clay, organic soil and peat. In localized areas, Recent Holocene sediments, primarily marsh or swamp, colluvium, and alluvium, overlies the Tabb Formation.

Based on our review of existing geologic and soil boring data, the geologic stratigraphy encountered in our subsurface explorations generally consisted of marine deposited Sands, Silts and Clays of the Windsor and Shirley Members of the Tabb Formation overlain by Recent sediments and man-placed Fill deposits. The Yorktown Formation underlies the project site, and extends to significant depth.

3.2 Subsurface Soil Conditions

A summary of our SPT soil test borings is presented below in Tables V-a and V-b.

Table V-a Subsurface Soil Conditions – General Site Borings

DEPTH (ft)

STRATUM DESCRIPTION

RANGES OF

SPT(1) N-VALUES

to

0.2 - 0.7 Surficial 2 to 8 inches of Topsoil –

0.2 – 0.7 to

2 - 6 I

Red, orange, brown and tan, Sandy CLAY (CL) with varying amounts of Silt, and trace fibrous organics

3 – 18

2 - 6 to

II

Brown and gray SAND (SP-SM, SM, SC) with varying amounts of Silt and Clay

Notes: (1) SPT = Standard Penetration Test, N-Values in Blows-per-foot (Uncorrected for Automatic Hammer or Overburden)

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Table V-b Subsurface Soil Conditions – Taxiway Bridge Borings

AVERAGE

DEPTH (ft)

STRATUM DESCRIPTION

RANGES OF

SPT(1) N-VALUES

to

2 - 10 I Marsh Deposits (Muck, Organic CLAY) WOH

2 - 10 to

II

Brown and gray SAND (SP-SM, SM, SC) with varying amounts of Silt and Clay.

Isolated deposits of Soft, Gray, Silty and Sandy CLAY (CL, CH) noted at borings B-6A and B-12A between depths of 28- 32ft and 38-46ft, respectively.

to

III

Gray and Brown SAND (SM, SC) with varying amounts of Silt, Clay, Gravel, and marine shell fragments; Gray Sandy CLAY (CL) with varying amounts of Silt, and marine shell fragments

“Yorktown Formation”

3 – 26

Notes: (1) SPT = Standard Penetration Test, N-Values in Blows-per-foot (Uncorrected for Automatic Hammer or Overburden)

The subsurface descriptions are of a generalized nature provided to highlight the major soil strata encountered. The records of the subsurface exploration are included in Appendix IV (Boring Log Sheets) and in Appendix V (Generalized Soil Profiles) which should be reviewed for specific information as to the individual borings. The stratifications shown on the records of the subsurface exploration represent the conditions only at the actual boring locations. Variations may occur and should be expected between boring locations. The stratifications represent the approximate boundary between subsurface materials and the transition may be gradual.

It is noted that the topsoil designation references the presence of surficial organic laden soil, and does not represent any particular quality specification. It is recommended this material be tested for approval prior to use.

3.3 Groundwater Discussion

The initial groundwater-level was recorded at the boring locations and as observed through the wetness of the recovered soil samples during the drilling operations. The initial groundwater-level was measured to occur at depths ranging from about 5 to 8 feet below existing grades at the more elevated boring locations and at or near the ground surface at the Taxiway Bridge crossing borings, corresponding to elevations of 0 to 3 feet NAVD88. The boreholes were backfilled upon completion for safety considerations.

As subsurface soils begin to dry moisture moves upwards through the soil profile by means of capillary action. Based on the subsurface soil composition, these initial groundwater-level readings (based on the relative wetness of the soils) could be in part attributed to the capillary action of the soils.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Groundwater conditions will vary with environmental variations, particularly tidal fluctuations, and seasonal conditions, such as the frequency and magnitude of rainfall patterns, as well as man-made influences, such as existing swales, drainage ponds, underdrains and areas of covered soil (paved parking lots, sidewalks, etc.). Seasonal groundwater fluctuations of 2 feet are common in the project’s area; however, greater fluctuations have been documented. We recommend that the contractor determine the actual groundwater levels at the time of the construction to determine groundwater impact on the construction procedures.

4.0 EVALUATIONS AND RECOMMENDATIONS

Our recommendations are based on the previously discussed project information, our interpretation of the soil test borings, and our observations during our site reconnaissance. If the proposed construction should vary from what was described, we request the opportunity to review our recommendations and make any necessary changes.

Based on the anticipated structural loads in combination with the subsurface soil conditions, it is our recommendation that the Taxiway Bridge structure be supported by means of driven concrete piles. Deep foundation recommendations for this structure are provided in Section 4.5 of this report.

4.1 Clearing and Grading

The proposed construction areas should be cleared by means of removing the topsoil and any other unsuitable materials. It is estimated that a cut of up to 8 to 10 inches in depth will be required to remove the topsoil. This cut is expected to extend deeper in isolated areas or tree removal areas in order to remove deeper deposits of organic soils, or unsuitable soils, which become evident during the clearing. It is recommended that the clearing operations extend laterally at least 5 feet beyond the perimeter of the proposed construction area. The excavations associated with the site clearing should be backfilled with compacted structural fill as described in Section 4.3 of this report.

To reduce the potential for subgrade improvements (undercutting due to saturated soils in conjunction with heavy construction traffic), it is recommended that the grading operations be performed during the drier months of the year (historically April through November). This should minimize these potential problems, although they may not be eliminated. If grading is attempted during the winter months, undercutting of wet soils should be anticipated. However, during the drier months of the year, wet soils could be dried by disking or implementing other drying procedures to achieve moisture contents necessary to achieve adequate degrees of compaction.

The site should be graded to enhance surface water runoff to reduce the ponding of water.

Ponding of water often results in softening of the near-surface soils. In the event of heavy rainfall within areas to receive fill, we recommend that the grading operations cease until the site has had a chance to dry.

Any undercut and backfill should be performed under the observation of a representative of G E T Solutions, Inc. who will evaluate the composition of the recovered soils.

Recommendations concerning the subgrade improvements (as necessary) will be provided in the field following the testing procedures.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

4.2 Subgrade Preparation

Following the clearing operation, the exposed subgrade soils should be densified with a large static drum roller. After the subgrade soils have been densified, they should be evaluated by G E T Solutions, Inc. for stability. Accordingly, the subgrade soils should be proofrolled to check for pockets of loose material hidden beneath a crust of better soil. Several passes should be made by a large rubber-tired roller or loaded dump truck over the construction areas. The number of passes will be determined in the field by the Geotechnical Engineer depending on the soils conditions. Any pumping or unstable areas observed during proofrolling (beyond the initial cut) should be undercut and/or stabilized at the direction of the Geotechnical Engineer.

4.3 Structural Fill and Placement

Following the approval of the natural subgrade soils by the Geotechnical Engineer, the placement of the fill required to establish the design grades may begin. Any material to be used for structural fill should be evaluated and tested by G E T Solutions, Inc. prior to placement to determine if they are suitable for the intended use. Suitable structural fill material should consist of sand or gravel containing less than 25% by weight of fines (SP, SM, SW, GP, GW), having a liquid limit less than 20 and plastic limit less than 6, and should be free of rubble, organics, clay, debris and other unsuitable material.

All structural fill should be compacted to a dry density of at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557). In general, the compaction should be accomplished by placing the fill in maximum 10-inch loose lifts and mechanically compacting each lift to at least the specified minimum dry density. A representative of G E T Solutions, Inc.

should perform field density tests on each lift as necessary to assure that adequate compaction is achieved.

Backfill material in utility trenches within the construction areas should consist of structural fill (as previously above), and should be compacted to at least 95 percent of ASTM D 1557. This fill should be placed in 4 to 6 inch loose lifts when hand compaction equipment is used.

Care should be used when operating the compactors near existing structures to avoid transmission of the vibrations that could cause settlement damage or disturb occupants. In this regard, it is recommended that the vibratory roller remain at least 25 feet away from existing structures; these areas should be compacted with small, hand-operated compaction equipment.

4.4 Suitability of On-site Soils

Based on the laboratory testing program, the shallow subsurface natural CLAY (CL) soils encountered at the boring locations do not appear to meet the criteria recommended in this report for reuse as structural fill; however, these materials may be used as fill in green areas.

Shallow subsurface natural SAND (SP-SM, SM) soils were also encountered at the boring locations within depths that may be excavated during site activities. These appear to meet the criteria recommended in this report for reuse as select fill; however significant moisture manipulation is expected as these soils are located near or below the groundwater table. This manipulation will likely require stockpiling of wet soils and/or placing the material in thin layers.

The goal of these methods is to dry the soils to within +/- 2% of their optimum moisture at the time of compaction which could prove time consuming and cost prohibitive.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

Again, it is important that during excavation, the deposits of natural CLAY (CL) soils and deleterious organic materials are segregated from the suitable granular soils (SAND containing less than 25% by weight of fines).

Further classification testing (natural moisture content, gradation analysis, and Proctor testing) should be performed in the field during construction to evaluate the suitability of excavated soils for reuse as structural fill. That said, any uncontrolled FILL materials should not be expected to be suitable for reuse and the project’s budget should include an allowance for imported structural fill.

4.5 Deep Foundation Recommendations

We recommend that the Taxiway Bridge structure and any other heavily loaded structures be supported by means of a deep foundation system comprised of Square, Pre-stressed, Precast, Concrete (SPPC) piles. Design discussions for 16”, 20” and 24” sections are discussed below.

The following sections describe the pile resistance analyses and provide our recommendations for factored static axial compressive, tensile, and lateral pile resistance, pile testing program, and pile construction criteria. In addition, we have provided estimates of potential settlement.

4.5.1 Axial Compression Capacity Recommendations - Driven Concrete Piles

We conducted pile capacity analyses using static formulas with coefficients recommended by Geoffrey Myerhoff and George Sowers. The analyses include the contributions of shaft friction and end bearing to the pile resistance. The piles are expected to derive the majority of their resistance from the deeper Stratum III soils (Yorktown Formation) at the depths presented in Table V.

The soil materials typically exhibit time-dependent strength characteristics; consequently shaft friction and end bearing support tend to increase from initial installation through a process termed “soil setup”. Essentially, the dynamics of driving piles will cause excess pore pressures to develop, thereby decreasing driving resistance during initial pile installation. The pile capacities developed during driving are usually much lower than the design values. Once driving is complete, the excess pore pressures will dissipate with time (and soil setup occurs) and the nominal resistance of the pile will increase. Based upon our experience with similar projects in the area, 5 to 7 days is usually required for the full pore pressures to dissipation and soil setup to occur.

For the reasons previously described, it is not recommended to confirm pile resistance with a simple driving criterion such as number of hammer blows per foot of advanced pile. Instead, driving criteria will likely consist of a target tip elevation and/or certain embedded length in a bearing material with specified driving resistance. The specified driving resistance should be based on a Wave Equation Analysis of the contractor’s selected hammer.

Table VI provides our recommended pile type and embedment depths for the structures’ foundations. The Factored Resistance shown is based on a Resistance Factor of 0.65 applied to Nominal calculated pile resistance. It is recommended that the test program rely on dynamic testing. The capacity of a group of piles spaced at least 3 pile diameters apart, center to center, can be taken as the sum of the individual resistances with no further reduction factor. If closer pile spacing is anticipated, the Geotechnical Engineer should be contacted to evaluate the efficiency of the specific pile group. The final order lengths and tip elevations will be adjusted

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 based on the results of the test piles and load test programs. Calculations for the pile resistances presented below are provided in Appendix VII. No accommodation has been made for Negative Skin Friction effects. Should site grades be modified significantly from those assumptions made in this study, we should be consulted to re-evaluate resistances for these possible effects.

Table VI – Pile Design Recommendations

Pile Type &

Dimensions

Pile Tip

Embedment

Elevation(1) (ft)

Factored Resistance in Compression (tons)

Factored Resistance in Tension (tons)

Pre-Augering

Depth (ft)

16” SPPC -75 to -80 150 70

15 20” SPPC -70 to -75 150 80

24” SPPC -70 to -75 200 100

Notes: (1) Based on ground surface elevation data = 0 msl as provided by Client.

Pile locations should be pre-augered to depths of 15 feet below grade prior to driving in order to assist pile alignment and initial driving. This is also beneficial to help in minimizing the effects of vibrations from the driving effort and to reduce the potential for pile breakage. Following the pre-augering, the piles should be installed and advanced by driving with an impact hammer to their design tip embedment depths. The soils within the vicinity of the pile may densify during driving.

This densification will increase with each successive pile; thus possibly signaling that pile driving “capacity” is encountered before the piles reach their design tip elevations. The Geotechnical Engineer should be retained to review driving records and field reports to determine whether the pile can adequately support the design loads. To reduce the likelihood of this phenomenon, the piles should be installed starting from the center of the pile cap outwards. If the pile driving hammer is not properly matched to the pile type, size, and subsurface conditions, it may reach practical refusal before the pile reaches the design tip embedment depth, or the required resistance.

4.5.2 Lateral Capacity Analysis - Driven Concrete Piles

The Client is providing lateral capacity analyses for the deep foundation elements as part of an integrated evaluation of foundation and structure utilizing FB MultiPier™ evaluation procedures Our summarization of Soil Data Parameters for the Client’s use in this evaluation is provided in Appendix VIII of this report.

4.5.3 Pile Group Settlement

Based on the results of load tests performed on piles driven in similar soils conditions, it is anticipated that the total butt settlements (including elastic shortening) will not exceed about ½-inch, which is the settlement necessary to mobilize the soil/pile capacity in combination with the pile group settlements due to the stress increase in the underlying soils.

4.5.4 Test Pile Program

We recommend that a test pile program utilizing dynamic methods be implemented for the purpose of assisting in the development of final embedment depths, confirming the design capacities of the piles, and confirming the contractor’s equipment and installation methods are

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 acceptable. The test program shall involve test or “indicator” piles to provide an indication of various driving or installation conditions. We recommend twenty-two (22) indicator piles. It is important to note the relationship between the required testing and our design assumptions. The Geotechnical Engineer shall monitor the driving of these test piles. The geotechnical engineer will require all of the test piles to be re-struck following a waiting period of at least 7 days to check for pile/soil setup.

The test pile locations shall be selected by the geotechnical engineer. The piles shall be driven using the drive system submitted by the contractor and approved by the Geotechnical Engineer.

Test pile lengths shall be 10 feet longer that the estimated design length to ensure that the required capacity is developed, and to allow for refinement of estimated capacities. The indicator piles installed during the Test Pile Program, which satisfy the Geotechnical Engineer’s requirements for proper installation, may also be used as permanent project piles.

4.5.5 Dynamic Testing

Dynamic testing was developed as a method of improving upon the reliability of the wave equation and other dynamic predictions by actually measuring the acceleration and strain of a pile during driving. This technique was developed in the mid-1960s and has been continuously refined. The use of dynamic pile testing has permitted the possibility of checking the driving stresses in the pile and the hammer performance during pile driving. It is also possible to estimate the static capacity of the pile based upon the strain and acceleration measurements taken during pile driving.

The test pile installation should be monitored by the Geotechnical Engineer using the PDA, an electronic device that records driving stresses and pile/soil interactions, among other things.

The PDA results will confirm that the pile driving system (hammer type/energy, cushion type/ thickness, etc.) can successfully install the piles without over stressing them in compression or tension. In addition to performing PDA testing during the initial drive, it is essential that the test pile re-strikes also be monitored with the PDA.

No sooner than 7 days after installation, all of the test piles should be re-struck while being monitored with the PDA. This test establishes the “static capacity” of the pile. The initial hammer blow during re-strike activities is critical to the quality of dynamic data with respect to capacity interpretation. The contractor should make every effort to insure an initial high-energy blow of the hammer. After several blows during re-strike activities, pore pressures increase, soil setup diminishes, and ultimately pile capacities (as recorded by the PDA) decrease. Loss of estimated static capacity following repeated hammer blows is the reason the initial blows are critical.

The dynamic data recorded by the PDA during re-strike testing should be further refined by using CAPWAP® analysis. CAPWAP® analysis, not the initial assessment of capacity determined by the PDA, should be the basis of static pile capacity estimates. Interpretation of CAPWAP® data, in the context of the soils subsurface conditions and previous static pile capacity estimates, should allow the Geotechnical Engineer to estimate ultimate pile capacities and recommend appropriate production pile lengths.

Our previous experience with PDA indicates that a significant cost savings may be realized if PDA is properly utilized to monitor the installation of test piles, confirm pile capacity in production installations, and monitor potentially damaging stresses during driving. The use of PDA permits the confirmation of allowable compression and uplift capacities and pile integrity on

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016 several piles for a cost similar to or less than that of a single full-scale static load test. We recommend the owner retain the services of the Geotechnical Engineer to perform the dynamic testing, not the installation contractor, to avoid possible conflicts of interest.

4.5.6 Production Pile/Acceptance Criteria

Utilizing the driving records for the tested piles and the results of the dynamic analysis of the driving conditions (WEAP), the pile capacity versus driving resistance (BPF) may be more accurately estimated; and depending on the results of these analyses a static load test or some adjustment to the design capacity or depth may be necessary. The piles should be installed to the embedment depths identified or as refined by the Geotechnical Engineer following the pile test program. These piles should be driven to the dynamic driving resistance as determined in the field by the Geotechnical Engineer, or to practical refusal, whichever comes first.

Based on our experience with pile installation, it is essential that driving be terminated immediately if refusal is reached to prevent damage to the piles. The pile-driving hammer should be properly matched to the pile to provide sufficient energy to install the pile without damaging it.

The installation of all deep foundation systems should be in accordance with the local Building Code requirements. In addition, a qualified Geotechnical Engineer or representative should monitor the installation of all piles. General pile installation guidelines are provided below.

1. The piles should be evaluated and designed for the axial stresses by the project structural engineer. All of the piles in a foundation element should be of the same type and of equal load carrying capacity.

2. The pile-driving hammer should be capable of driving the pile to at least 3 times the design load without over-stressing the pile in tension or compression. At all times, the hammer should be operated at the chamber pressure, speed, etc. as recommended by the manufacturer.

3. Pile driving should be as continuous an operation as possible and should proceed without stopping over the last 3 feet of penetration. During pile installation, the contractor should exercise caution as not to over stress the piles.

Piles shall not be driven beyond practical refusal.

4. The contractor should exercise caution in pile driving so that the effects of heave are minimized. Careful monitoring by the contractor for possible heave during driving should be exercised. All piles that heave ¼ inch or more should be re-driven unless otherwise instructed by the Geotechnical Engineer.

5. Piles should be installed under continuous monitoring by a qualified Senior

Engineering Technician or Geotechnical Engineer in order to make field judgments of pile penetration and construction and to check for satisfactory foundation support conditions. Driven piles should be monitored for penetration resistance, blow counts, during pile driving and hammer action.

Report of Subsurface Exploration & Geotechnical Engineering Services May 16, 2016

4.5.7 Allowable Driving Stresses

Guidelines from the Prestressed Concrete Institute (PCI), American Society of Civil Engineers (ASCE), and the American Association of State Highway Transportation Officials (AASHTO) indicate that maximum compressive stresses, imposed on driven precast concrete piles during installation, should be less than the following equation: 0.85 x f’c (concrete compressive strength, psi) - fpe (effective pre-stressing after losses from relaxation). The three groups differ on the maximum tensile stresses. PCI recommends 6 x (f‘c)

0.5 + fpe; AASHTO and ASCE recommend 3 x (f‘c)

0.5 + fpe. We recommend using the consensus value for the maximum compressive stress, and the ASCE/AASHTO recommended value for the maximum tensile stress.

4.5.8 Hammer Types and Energies

In comparing hammers of equal energy, the…