P222_1737012_Geotech Report.pdf

REPORT OF

SUBSURFACE

EXPLORATION

AND

GEOTECHNICAL

ENGINEERING

SERVICES

P-222 MQ-25 Aircraft Laydown Facilities Naval Station Norfolk

Norfolk, Virginia

G E T Project No. K3225220

April 11, 2024

PREPARED FOR:

5465 Greenwich Road · Virginia Beach, VA 23462 Phone: (757)-518-1703

5465 Greenwich Road • Virginia Beach, Virginia 23462 • Phone: (757) 518-1703 • Fax: (757) 518-1704

April 11, 2024

TO: Clark Nexsen, Inc.

4525 Main Street, Suite 1400 Virginia Beach, Virginia 23462

Attn: Mr. Peter Allen, PE, SE, LEED AP BD+C

RE: Report of Subsurface Exploration and Geotechnical Engineering Services

P-222 MQ-25 Aircraft Laydown Facilities Contract: N40085-19-D-9041 Naval Station Norfolk, Norfolk, Virginia G E T Project No. K3225220

Dear Mr. Allen:

In compliance with your instructions, we have completed our geotechnical and environmental investigative consulting services for the above referenced project. The results of the subsurface investigation and laboratory testing services, 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., A Terracon Company (G E T) 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., A Terracon Company

Grey Weber, EIT Senior Staff Engineer

Chris M. Caton, PE, PG, PMP Senior Geotechnical Engineer Virginia Registration No. 046947

Copies: (1) Client

TABLE OF CONTENTS

Report of Subsurface Exploration and Geotechnical Engineering Services P-222 MQ-25 Aircraft Laydown Facilities Contract: N40085-19-D-9041

1.0 PROJECT INFORMATION

1.1 Project Authorization

1.2 Project Datum

1.3 Project Characteristics

1.3.1 Parking Garage

1.3.2 LP-48 Annex/Additions

1.3.3 Wash Rack

1.3.4 Alpha Taxiway

1.3.5 Ground-Based Sense-and-Avoid Tower

1.4 Purpose and Scope of Services

2.0 FIELD INVESTIGATION

2.1 CPTu and SCPTu Soundings

2.2 SPT Borings and Sampling

2.3 Temporary Groundwater Monitoring Wells

2.4 Soil Sampling

2.4.1 PID Readings

2.4.2 Soil Characterization Composites

2.5 Groundwater Sampling

2.6 IDW Drums

3.0 LABORATORY TESTING

3.1 Soil Property Testing

3.1.1 Split-Spoon Soil Samples

3.1.2 Shelby Tube Soil Samples

3.1.3 California Bearing Ratio Soil Samples

3.2 Analytical Testing and Results

3.2.1 Soil Characterization

3.2.2 Groundwater

3.2.3 IDW Drums

3.2.4 Summary of Findings and Conclusions

3.2.5 Recommendations

4.0 SUBSURFACE CONDITIONS

4.1 Site Geology

4.2 Observed Pavement Conditions

4.3 Observed Subsurface Soil Conditions

4.3.1 Parking Garage SPT Borings

4.3.2 LP-48 Annex/Additions SPT Borings

4.3.3 Alpha Taxiway and Wash Rack SPT Borings

4.3.4 GBSAA SPT Boring

4.4 Groundwater Information

5.0 EVALUATIONS AND RECOMMENDATIONS

5.1 Clearing and Grading

5.2 Subgrade Preparation

5.3 Structural Fill and Placement

5.4 Suitability of On-Site Soils

TABLE OF CONTENTS

Report of Subsurface Exploration and Geotechnical Engineering Services

Contract: N40085-19-D-9041

5.5 Deep Foundations – Parking Garage and LP-48 Annex/Additions

5.5.1 Axial Compressive Capacity Recommendations

5.5.2 Negative Skin Friction

5.5.3 Pile Lateral Capacity Analysis

5.5.4 Test Pile Program (Driven Concrete Piles)

5.5.5 Dynamic Testing

5.5.6 Establishing Pile Driving Criteria

5.5.7 Allowable Driving Stresses

5.5.8 Hammer Type and Energies

5.5.9 Driven Production Pile Installation Monitoring

5.5.10 Vibration Considerations and Adjacent Structures

5.5.11 Micropiles – LP-48 Elevator and Additions

5.6 Shallow Foundations – GBSAA Tower

5.7 Ground Floor Slab – LP-48 Annex and Additions

5.8 Settlements

5.9 Pavement Design Recommendations – Parking Garage, Wash Rack, Alpha Taxiway, and

GBSAA

5.10 Seismic Site Classification

5.11 Liquefaction Potential

5.12 Historical Subsurface Information

6.0 CONSTRUCTION CONSIDERATIONS

6.1 Excavation Stability

6.2 Dewatering

6.3 Site Utility Installation

7.0 REPORT LIMITATIONS

APPENDICES

Appendix 1 – Site Vicinity and Historical Maps Appendix 2 – Exploration Location Plans Appendix 3 – Subsurface Utility Photographs Appendix 4 – CPTu/SCPTu Sounding Results Appendix 5 – CBR Excavation Photographs Appendix 6 – Summary of Soil Classification System Appendix 7 – Classification/Index Testing Results Appendix 8 – Boring Logs Appendix 9 – Generalized Soil Profiles Appendix 10 – Shelby Tube Samples – Testing Results Appendix 11 – CBR Testing Results Appendix 12 – Soil Analytical Testing Results Appendix 13 – Groundwater Analytical Testing Results Appendix 14 – Core Logs Appendix 15 – Calculations Appendix 16 – Historical Geotechnical Information

Report of Subsurface Exploration and Geotechnical Engineering Services April 11, 2024

Contract: N40085-19-D-9041

1.0 PROJECT INFORMATION

1.1 Project Authorization

G E T has completed our subsurface exploration, environmental investigative, and geotechnical engineering services for the P-222 MQ-25 Aircraft Laydown Facilities project located at Naval Station Norfolk (NSN) in Norfolk, Virginia. The services were conducted in general accordance with the scope presented in G E T Proposal No. PK3221119 dated May 25, 2022. Authorization to proceed with our Preliminary Design Authority (PDA) services was received from the Client in the form of a Task Order dated July 13, 2022. Authorization to proceed with our Final Design Authority (FDA) services was received from the Client in the form of a Task Order dated August 22, 2023.

1.2 Project Datum

All locations associated with this subsurface investigation performed by G E T and its Subcontractor were staked in the field using the World Geodetic System 1984 (WGS84). The obtained WGS84 test location coordinates were then converted to State Plane northing and easting US Survey feet. Additionally, all surface elevations provided refer to the North American Vertical Datum (NAVD 88).

1.3 Project Characteristics

The project will consist of the construction of a laydown facility for MQ-25 aircraft and is divided into five

(5) sites as described in the following sections. Based on our understanding of the information provided, portions of the project site were formerly occupied by Mason Creek and Boush Creek (formerly known as Bush Creek) and were reclaimed between 1907 and 1948 to the current configuration. Portions of the current airfield were constructed on these areas of reclaimed/man-made land. Between 1948 and present day, site development has consisted of various hangars, support buildings, concrete airfield apron pavements, and asphalt taxiways/runways. A site vicinity map and historical maps (circa 1902 and 1978) are provided in Appendix 1.

1.3.1 Parking Garage

The parking garage site is within the existing concrete and asphalt paved parking lot north of the LP-34 hangar and south of Bellinger Boulevard. The parking garage site is adjacent to known CERCLA Land Use Controls (LUC) area(s). The proposed construction consists of a four-story parking garage (approximate plan footprint of 60,000 square feet) for roughly 663 personal owned vehicles (POVs). Square footage estimates are based on draft design documents dated July 25, 2022, which were provided by the Client at the onset of the project. Anticipated structural load requirements were based on the Geotechnical Basis of Design dated June 17, 2022. Design grades for the proposed structures and improvements are anticipated to coincide with current grades, so fills are expected to be less than 1 foot above existing grades. A topographic survey for the parking garage site was unavailable at the time of this reporting. The referenced elevations within the parking garage site were estimated from available United State Geological Survey (USGS) historical topographic resources and are expected to range between 7 feet and 10 feet.

Contract: N40085-19-D-9041

1.3.2 LP-48 Annex/Additions

The LP-48 annex and additions site includes the existing LP-48 hangar, the surrounding concrete apron, and a portion of the concrete and asphalt paved parking lot to the north. The existing LP-48 hangar was constructed in 2004 and consists of a pile-supported structure with a ground floor slab supported on grade. The existing LP-48 hangar and proposed annex and additions sites are adjacent to known CERCLA LUC area(s). The proposed construction consists of a detached two-story annex located north of the existing LP-48 hangar (approximate plan footprint of 24,000 square feet), a new elevator inside the existing LP-48 hangar, and two single-story additions to the existing LP-48 hangar (approximate combined plan footprint of 3,800 square feet). Square footage estimates are based on a revised site plan exhibit (not dated) provided by the Client (without graphic scale) at the onset of the FDA services. This plan indicates that the proposed plan footprints of the LP-48 annex as well as the two one-story additions have decreased relative to information obtained during the PDA services. Additionally, the revised site plan indicates that the LP-48 annex finished floor elevation (FFE) is proposed at 11.0 feet whereas previously this was not known. Accordingly, fills for the LP-48 annex would vary across the building pad but are expected to be a maximum of 2.5 feet above existing grades. Design finished floor elevations for the proposed LP-48 addition structures and improvements are anticipated to coincide with the finished floor of the existing hangar structure, so the cuts and fills are expected to be less than 1 foot. Anticipated structural load requirements were based on the Geotechnical Basis of Design dated June 17, 2022. A topographic survey was provided by the Client for the LP-48 annex and additions sites, and elevations generally range between 8.5 feet and 10 feet at and within the vicinity of the explored locations.

1.3.3 Wash Rack

The wash rack site is within a portion of the airfield’s existing concrete apron located south of the LP-21 hangar and currently serves as a wash rack. The wash rack area was previously occupied by a hangar (demolished in 2004), with most of its deep foundation structure (pile caps and piles) likely still in place beneath the existing concrete pavement. The wash rack site is adjacent to known CERCLA LUC area(s).

The proposed construction consists of a possible reduction to its existing footprint and additional reconfiguration. Full-depth repair of the concrete slab may be required, though final project characteristics were uncertain at the time of this reporting. Design grades for the proposed improvements are anticipated to coincide with current grades, so fills are expected to be less than 1 foot above existing grades. A topographic survey was provided by the Client for the wash rack site. The elevation is approximately 10 feet at the explored location, and surrounding surface elevations generally range between 9.5 feet and 10.5 feet within the vicinity of the explored location.

1.3.4 Alpha Taxiway

The Alpha Taxiway site includes the existing western section of the asphalt paved Alpha Taxiway just south of the wash rack and southern extent of the airfield’s concrete apron. Portions of the existing taxiway are failing or in near-failing condition due to weather, wear and tear, and poor drainage. The proposed construction consists of various asphalt surface repairs to the existing western section of Alpha Taxiway and its shoulders. Based on our understanding, new pavements improvements will be limited to mill and overlay. Design grades for the proposed improvements are anticipated to coincide with current grades. A topographic survey was provided by the Client for the Alpha Taxiway site, and elevations generally range between 10 feet and 12 feet at and within the vicinity of the explored locations.

Contract: N40085-19-D-9041

1.3.5 Ground-Based Sense-and-Avoid Tower

The ground-based sense-and-avoid tower (GBSAA) site includes the existing grass area slightly southeast of the Naval Station Norfolk Air Mobility Command (AMC) Passenger Terminal building. The proposed construction consists of a new asphalt drive, a concrete pad for an equipment shelter, and a 100-foot tall, four-legged steel structure roughly 15 feet by 15 feet in plan footprint. At the time of this report, the Client provided a maximum tower load of 300 kips (75 kips per tower leg). Based on a preliminary grading plan (not dated) and information provided by the Client, the tower pad footprint and configuration has not been determined (pad size approximated from shelter footprint shown on plan), the pad will not be heavily loaded, it is anticipated to have an FFE of 11.0 feet, and the pad will likely be supported on turn-down edges. Fills for the GBSAA tower pad are expected to be a maximum of 4 feet above existing grades.

A topographic survey was provided by the Client for the GBSAA site, and elevations within the grass areas generally range between 6.9 feet and 7.3 feet. The surface elevation of the existing concrete apron north of the grass area is approximately 7.9 feet.

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

1.4 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 included, but were not limited to, the following:

▪ General assessment of the soils revealed by the borings performed at the site and in regard to available historical information.

▪ Soil analytical testing for disposal characterization as well as corrosion/aggressiveness potential.

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

▪ Volatile organic compound (VOC) measurements of the subsurface materials. VOC measurements of the work zone ambient air within LUC areas.

▪ Determination of pertinent information regarding the groundwater conditions at the site, including chemical analysis.

▪ Soil subgrade preparation, including stripping, grading, fill placement criteria, and compaction.

▪ Feasibility of supporting the ground floor slabs of the LP-48 annex and additions on grade.

▪ Feasibility of supporting the GBSAA tower and associated pad on shallow foundations.

Contract: N40085-19-D-9041

▪ Feasibility of utilizing a deep foundation system for supporting the LP-48 annex, additions, and parking garage.

▪ Pavement recommendations for the parking garage, wash rack, and GBSAA tower drive; and mill and overlay recommendation for the Alpha Taxiway based on project information, field data, and our experience with similar soil conditions.

▪ Seismic evaluation in regard to site classification and liquefaction potential.

2.0 FIELD INVESTIGATION

In accordance with the project’s Statement of A-E Services (SAES) dated April 2021, a subsurface investigation was performed within the areas previously discussed in Section 1.3. All aspects of the field exploration program were scheduled and coordinated with the Client, NAVFAC Mid-Atlantic, and Naval Station Norfolk Air Operations (AIR OPS) and submitted for approval via a Work Plan dated September 19, 2022. The field exploration program for the FDA services was submitted for approval via a Work Plan dated December 4, 2023.

The following exploration program was performed to collect the requested project data and to aid in developing associated design parameters and recommendations.

▪ Fifteen (15) 65- to 100-foot Standard Penetration Test (SPT) borings, designated as S-1 through S-15, were drilled within or adjacent to the proposed footprints of the parking garage and the LP-48 annex and additions.

▪ Three (3) 93- to 100-foot soundings comprised of Cone Penetration Tests (CPTu) and Seismic Cone Penetration Tests (SCPTu), designated as CPT-01, SCPT-01, and SCPT-02, were advanced within or adjacent to the proposed footprints of the parking garage and the LP-48 annex and additions.

▪ Ten (10) 12-foot SPT borings, designated as T-1 through T-10, were drilled within the wash rack and Alpha Taxiway.

▪ One (1) 100-foot SPT boring, designated as B-1, was drilled near the proposed footprint of the GBSAA tower.

The exploratory locations were established by G E T through coordination with the Client and were subsequently approved by NAVFAC Mid-Atlantic. The boring locations were staked in the field by a representative of G E T with the use of a hand-held Global Positioning System (GPS) device while corroborating with easily identifiable landmarks. The locations were delineated with their respective name using white paint and red-taped wooden stakes where applicable. The approximate boring locations are shown on the Exploration Location Plans provided in Appendix 2.

Prior to advancement, utility clearance was obtained at each location through VA811, on-site assistance with AIR OPS, and using a third-party private subsurface utility locator. All existing subsurface utilities were marked within a 25-foot radius of each proposed field exploration location and photo-documented.

The private utility locator competency letters and subsurface utility photographs are provided in Appendix 3.

Contract: N40085-19-D-9041

2.1 CPTu and SCPTu Soundings

The CPTu and SCPTu soundings were performed in accordance with ASTM D5778 and ASTM D7400 using a 25-ton truck rig. The sounding depths and location coordinates (Latitude/Longitude and Northing/ Easting) are provided in Table 1. The presentation of site investigation results (CPTu/SCPTu soundings) is provided in Appendix 4.

Table 1. CPT Sounding Locations

Sounding

ID

Structure Sounding

Depth1 (ft)

Approximate Location

Latitude2 Longitude2 Northing3 Easting3

CPT-01 Parking Garage 100.4 36.94310 -76.29064 3510397.145 12128525.364

SCPT-01 Parking Garage 100.9 36.94361 -76.29069 3510582.436 12128506.411

SCPT-02

LP-48

Annex/Additions

92.8 36.94302 -76.29442 3510342.198 12127421.672

1. Depth below existing grade.

2. WGS 84 Lat/Long. Coordinates were taken with a handheld GPS and should be considered approximate.

3. State Plane northing and easting US Survey feet.

2.2 SPT Borings and Sampling

The SPT borings for the PDA services were performed using a CME-45 truck-mounted drill rig. The SPT boring for the FDA services was performed using a CME-55 track-mounted drill rig. The boring depths and location coordinates (Latitude/Longitude and Northing/ Easting) are provided in Table 2.

The SPT borings were performed with the use of rotary wash “mud” drilling procedures in general accordance with ASTM D1586. The soil samples were obtained with a standard 1.4-inch I.D., 2-inch O.D., 30-inch-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). Pocket penetrometer unconfined compressive strength testing was performed on the split-spoon cohesive soil samples. Each soil interval was screened in the field for organic vapors using a MiniRae 3000 photo-ionization detector (PID). Additionally, for locations adjacent to designated LUC, the ambient air was screened. This data is presented on the boring logs and notable detections are summarized in Section 2.4.1.

Contract: N40085-19-D-9041

Table 2. SPT Boring Locations

SPT

Boring ID

Structure/ Infrastructure

Boring Depth1

(ft)

Approximate Location

Latitude2 Longitude2 Northing3 Easting3

S-1 Parking Garage 100 36.94314 -76.29106 3510410.752 12128401.861

S-2 Parking Garage 80 36.94339 -76.29108 3510500.659 12128394.261

S-3 Parking Garage 80 36.94358 -76.29104 3510571.787 12128403.091

S-4 Parking Garage 80 36.94326 -76.29084 3510455.718 12128463.628

S-5 Parking Garage 80 36.94342 -76.29044 3510517.100 12128578.550

S-6 Parking Garage 80 36.94360 -76.29005 3510586.773 12128693.218

S-7 Parking Garage 100 36.94332 -76.29013 3510481.227 12128669.644

S-8 Parking Garage 80 36.94311 -76.29011 3510405.002 12128677.421

S-9 LP-48 Addition 80 36.94261 -76.29488 3510190.077 12127290.699

S-10 LP-48 Annex 80 36.94303 -76.29491 3510343.518 12127275.538

S-11 LP-48 Annex 80 36.94318 -76.29465 3510399.168 12127352.054

S-12 LP-48 Annex 65 36.94338 -76.29459 3510472.271 12127368.090

S-13 LP-48 Annex 80 36.94319 -76.29410 3510409.185 12127512.655

S-14 LP-48 Annex 80 36.94303 -76.29410 3510349.094 12127514.177

S-15 LP-48 Addition 80 36.94271 -76.29403 3510234.314 12127538.023

T-1 Alpha Taxiway 12 36.93686 -76.30023 3508061.457 12125773.836

T-2 Alpha Taxiway 12 36.93792 -76.30034 3508448.607 12125732.568

T-3 Alpha Taxiway 12 36.93843 -76.29842 3508645.015 12126291.943

T-4 Alpha Taxiway 12 36.93844 -76.29754 3508657.428 12126547.684

T-5 Alpha Taxiway 12 36.93851 -76.29622 3508690.367 12126933.768

T-6 Alpha Taxiway 12 36.93850 -76.29477 3508695.390 12127357.776

T-7 Alpha Taxiway 12 36.93869 -76.29338 3508773.325 12127761.342

T-8 Alpha Taxiway 12 36.93861 -76.29248 3508750.623 12128025.533

T-9 Alpha Taxiway 12 36.93864 -76.29074 3508773.515 12128533.872

T-10 Wash Rack 12 36.94086 -76.29597 3509545.871 12126985.151

B-1 GBSAA Tower 100 36.93047 -76.28728 3505823.697 12129613.321

1. Depth below existing grade.

2. WGS 84 Lat/Long. Coordinates were taken with a handheld GPS and should be considered approximate.

3. State Plane northing and easting US Survey feet.

Six (6) Shelby Tube soil samples were obtained from the cohesive soils in general accordance with ASTM D1587. The undisturbed samples were obtained by hydraulically pressing a 3-inch outside diameter Shelby Tube into the soils. The tubes were sealed to prevent moisture loss and returned to the laboratory in accordance with ASTM D4220 for extraction, photographing, classification, and strength testing. The Shelby Tube locations and collection depths are provided in Table 3.

Contract: N40085-19-D-9041

Table 3. Shelby Tube Locations

SPT Boring ID Structure Sample ID Collection Depth3

(ft)

S-4 Parking Garage

ST-1 21 – 23

ST-22 40 – 42

S-5 Parking Garage

ST-3 26 – 28

ST-4 56 – 58

S-14A1 LP-48 Annex/Additions

ST-52 35 – 37

ST-62 58 – 60

1. Pilot hole adjacent to boring S-14.

2. Recovered sample not tested.

3. Depth below existing grade.

All boreholes were backfilled with a NAVFAC approved grout mixture using the tremie method in accordance with the industry standard of care. The surplus boring soil cuttings, decontamination water, purged groundwater, and slurry (Investigation Derived Waste – IDW) were containerized within DOT-approved 55-gallon, chemical resistant drums, and were properly labeled and temporarily stored at a pre-selected staging area. Appropriate locations were patched with an approved rapid-setting repair material.

Four (4) bulk samples were collected in grass areas adjacent to selected borings and returned to our laboratory for California Bearing Ratio (CBR) testing in general accordance with ASTM D1883. The hand-dug holes were backfilled with the shoveled material and adequately compacted by hand-tampering. The bulk sample locations and collection depths are provided in Table 4. CBR excavation photographs are provided in Appendix 5.

Table 4. CBR Bulk Sample Locations

SPT Boring ID Infrastructure Sample ID Collection Depth1

(ft)

T-1 Alpha Taxiway CBR-1 0 – 1.672

T-4 Alpha Taxiway CBR-2 0 – 4

T-5 Alpha Taxiway CBR-3 0 – 4

T-7 Alpha Taxiway CBR-4 0 – 4

1. Depth below existing grade.

2. Concrete slab encountered approximately 20 inches below existing grade.

Contract: N40085-19-D-9041

2.3 Temporary Groundwater Monitoring Wells

Six (6) temporary piezometers were installed throughout the site to obtain stabilized groundwater readings and to obtain environmental samples at the groundwater interface. The piezometers were installed using hollow stem auger drilling methods and were constructed of 2-inch PVC pipe with a 5-foot riser and a 15-foot slotted section at the bottom end. The well screen interval was set at an appropriate depth to capture the soil/groundwater interface. The borehole annulus was backfilled with filter sand (silica sand with 10-20 mesh size) to 1 foot above the well screen and sealed with bentonite pellets to the ground surface. The piezometer depths and location coordinates (Latitude/Longitude and Northing/Easting) are provided in Table 5.

Table 5. Piezometer Locations

Well

Structure/ Infrastructure

Well Depth1

(ft)

Approximate Location

Latitude2 Longitude2 Northing3 Easting3

W-1 Parking Garage 20 36.94306 -76.29112 3510381.464 12128382.870

W-2

LP-48

Annex/Additions 20 36.94310 -76.29427 3510372.702 12127462.500

W-3 Wash Rack 20 36.94139 -76.29591 3509740.888 12126999.780

W-4 Alpha Taxiway 20 36.93813 -76.29853 3508537.633 12126262.020

W-5 Alpha Taxiway 20 36.93838 -76.29692 3508637.398 12126729.940

W-6 Alpha Taxiway 20 36.93837 -76.29408 3508654.364 12127559.125

1. Depth below existing grade.

2. WGS 84 Lat/Long. Coordinates were taken with a handheld GPS and should be considered approximate.

3. State Plane northing and easting US Survey feet.

2.4 Soil Sampling

2.4.1 PID Readings

As previously mentioned, each soil interval was screened in the field for organic vapors using a MiniRae 3000 PID. Locations and depth intervals of readings that exceeded 100 parts per million (ppm) are provided in Table 6.

Table 6. PID Readings

SPT Boring ID Structure/

Infrastructure PID Reading

(ppm) Interval Depth1

(ft)

S-14 LP-48 Annex/Additions 359.2 6 – 8

S-14 LP-48 Annex/Additions 300.9 8 – 10

S-14 LP-48 Annex/Additions 398.7 10 – 12

S-15 LP-48 Annex/Additions 291.7 6 – 8

T-3 Alpha Taxiway 505.6 4 – 6

Contract: N40085-19-D-9041

2.4.2 Soil Characterization Composites

To explore corrosion potential and to determine disposal requirements for the soils expected to be disturbed during construction, fifteen (15) composite soil samples were collected during the subsurface investigation from boreholes adjacent to the respective SPT boring. Soil samples were collected via split-spoon samplers with non-disposable sampling equipment decontaminated by a Liquinox® wash and a potable water rinse prior to soil boring advancement and between borings. The composite samples were placed in clean, laboratory supplied containers, packed in ice, and shipped to the contracted laboratory under chain-of-custody for analysis. The composite sample locations and collection depths are provided in Table 7.

Table 7. Composite Soil Sample Locations

SPT Boring / Sample ID Collection Depth1

(ft) SPT Boring / Sample ID

Collection Depth1 (ft)

S-1 0 – 4 S-14 0 – 4

S-4 0 – 4 S-15 0 – 4

S-5 0 – 4 T-2 0 – 4

S-6 0 – 4 T-4 0 – 4

S-10 0 – 4 T-5 0 – 4

S-12 0 – 4 T-7 0 – 4

S-13 0 – 4 T-9 0 – 4

B-1 0 – 4

1. Depth below existing grade.

2.5 Groundwater Sampling

Six (6) groundwater grab samples were collected at the groundwater interface at each of the piezometer locations. The temporary monitoring wells were developed using a peristaltic pump and disposable tubing to remove groundwater for a minimum of three well volumes or until the turbidity was decreased significantly and water ran clear. Low flow purging and sampling techniques (i.e., <250 milliliters per minute) were used for the wells to collect a representative sample, reduce turbidity, and minimize purge water volume. Each groundwater sample was collected after stabilization of field parameters (e.g., pH and specific conductance) and reduction of turbidity to below approximately 10 nephelometric turbidity units. The groundwater samples were placed in clean, laboratory supplied containers, packed in ice, and shipped to the contracted laboratory under chain-of-custody for analytical testing. The groundwater sample locations and approximate collection depth ranges are provided in Table 8.

Contract: N40085-19-D-9041

Table 8. Groundwater Sample Locations

Well / Sample ID Collection Depth1,2

(ft) Well / Sample ID

Collection Depth1,2 (ft)

W-1 2 – 6 W-4 4 – 8

W-2 2 – 6 W-5 3 – 7

W-3 4 – 8 W-6 3 – 7

1. Depth below existing grade.

2. Collection depth range corresponds to screen placement, which is within approximately 1 to 2 feet of the soil and groundwater interface.

2.6 IDW Drums

Drilling spoils and liquids that could not be returned to the boreholes were placed in 55-gallon drums and stored in a designated staging area until sampling and analysis of the drums was performed and reviewed by the preferred disposal facility. A representative composite sample was collected for every five (5) IDW drums. As such, for the PDA services, a total of three (3) composite samples (2 solid matrix samples and 1 wastewater matrix sample) were collected from the fourteen (14) 55-gallow IDW drums (10 solids and 4 wastewater) staged at the project site. For the FDA services, a total of two (2) composite samples (1 solid matrix and 1 wastewater matrix sample) were collected from the two (2) 55-gallon IDW drums stored at the pre-determined staging area. The composite samples were placed in clean, laboratory supplied containers, packed in ice, and shipped to the contracted laboratory under chain-of-custody for analytical testing.

3.0 LABORATORY TESTING

Soil testing was performed in accordance with current American Society for Testing and Materials (ASTM) or American Association of State Highway and Transportation Officials (AASHTO) standards. All soil tests were performed in an AASHTO re:source certified laboratory.

3.1 Soil Property 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 Appendix 6.

Contract: N40085-19-D-9041

3.1.1 Split-Spoon Soil Samples

Representative split-spoon soil samples were selected and subjected to various laboratory classification tests, which included moisture content (ASTM D2216), No. 200 sieve wash (ASTM D1140), and Atterberg Limits (ASTM D4318) testing and analysis to corroborate the visual classifications. A summary of these classification test results is provided in Appendix 7, with the individual results presented on the SPT boring logs provided in Appendix 8. Generalized subsurface soil profiles are provided in Appendix 9.

3.1.2 Shelby Tube Soil Samples

Three (3) of the Shelby Tube soil samples were subjected to various laboratory classification and strength tests, which included moisture content (ASTM D2216), No. 200 sieve wash (ASTM D1140), Atterberg Limits (ASTM D4318), one-dimensional consolidation (ASTM D2435), unconsolidated undrained (UU) triaxial compression (ASTM D2850), and consolidated undrained (CU) triaxial compression (ASTM D4767).

Summaries of the strength testing results are provided in Table 9 and Table 10. The comprehensive test reports are provided in Appendix 10.

Table 9. Consolidation Testing Summary

1. Depth below existing grade.

2. Values obtained from reconstructed consolidation curve.

Table 10. Triaxial Testing Summary

2. Shear strength soil parameters determined utilizing peak deviator stress failure criterion.

SPT

Boring / Sample

ID

Collection

Depth1 (ft)

Overburden Pressure, P’o

(tsf)

Preconsolidation Pressure, P’c

(tsf)

Overconsolidation Ratio, OCR2

Compression Index, Cc

Recompression Index, Cr

S-4 /

ST-1

21 – 23 0.90 1.13 1.3 0.87 0.11

S-5 /

ST-3

26 – 28 1.00 1.20 1.2 0.63 0.10

SPT Boring / Sample ID

Collection

Depth1 (ft)

Overburden Pressure, P’o

(tsf)

Test Type

Total Stress Shear Strength Parameters2

Effective Stress Shear Strength Parameters2

Cohesion, c (psf)

Angle of Internal

Friction, φ (deg)

Cohesion, c’ (psf)

Angle of Internal

Friction, φ’ (deg)

S-4 / ST-1 21 – 23 0.90 UU 591 – – –

S-5 / ST-3 26 – 28 1.00 UU 801 – – –

S-5 / ST-4 56 – 58 1.70 CU 373 11.5 300 18.8

Contract: N40085-19-D-9041

3.1.3 California Bearing Ratio Soil Samples

CBR testing was performed in accordance with the project’s SAES dated April 2021 (soaked CBR, one-point method, 15-lb surcharge, with the sample compacted to 95% of the maximum dry density on the wet side of the optimum moisture content). The bulk soil samples were subjected to Standard Proctor testing in accordance with ASTM D698 and CBR testing in general accordance with ASTM D1883. The stress-strain curve was plotted for each specimen. If necessary, the stress-strain curve was corrected by adjusting the location of the origin for concave shaped curves. Subsequently, the CBR values were selected at 0.1-inch penetration using the corrected load values. In addition, the soils samples were subjected to various laboratory classification tests, which included moisture content (ASTM D2216), No. 200 sieve wash (ASTM D1140), and Atterberg Limits (ASTM D4318). A summary of the CBR test results is presented in Table 11.

The comprehensive test reports are provided in Appendix 11.

Table 11. CBR Testing Summary

SPT Boring / Sample ID

Collection Depth1

(ft)

Soil Type2

Natural Moisture, wN

Passing No.

Sieve

Max.

Dry

Density (pcf)

Optimum Moisture

CBR

Value

Swell

T-1 / CBR-1 0 – 1.673

SILTY, CLAYEY

SAND

10.1 33.4 115.6 12.9 6.4 0

T-4 / CBR-2 0 – 4 CLAYEY SAND 10.2 33.2 124.8 9.3 6.2 0

T-5 / CBR-3 0 – 4 CLAYEY SAND 12.0 37.0 122.6 10.0 6.0 0.1

T-7 / CBR-4 0 – 4 CLAYEY SAND 10.0 22.5 124.9 10.2 6.9 0

1. Depth below existing grade.

2. Soils are Uncontrolled Fill.

3. Concrete slab encountered approximately 20 inches below existing grade.

3.2 Analytical Testing and Results

3.2.1 Soil Characterization

To explore corrosion potential and to determine disposal requirements for the construction excavation spoils, fifteen (15) composite soil samples were collected from boreholes adjacent to their respective boring location during the subsurface investigation at a predetermined depth interval of 0 to 4 feet below existing grades. The sample nomenclature denotes the boring location of the sample. “T” samples were collected from the airfield (wash rack and Alpha Taxiway), “S” samples were collected from the proposed parking garage and LP-48 annex and additions areas, and the “B” sample was collected from the proposed GBSAA tower site.

Contract: N40085-19-D-9041

The fifteen (15) composite samples were collected adjacent to boring locations T-2, T-4, T-5, T-7, T-9, S- 1, S-4, S-5, S-6, S-10, S-12, S-13, S-14, S-15, and B-1. The samples were placed into laboratory supplied containers, packed on ice, and shipped to Enthalpy Analytical (Enthalpy) in Richmond, Virginia. Each of the composite soil samples were analyzed for the following:

▪ Target Analyte List (TAL) metals via United States Environmental Protection Agency (EPA) methods 6000/7000

▪ Target Compound List (TCL) VOCs via EPA method 8260

▪ TCL semi-volatile organic compounds (SVOCs) via EPA method 8270

▪ Pesticides via EPA method 8081

▪ Polychlorinated biphenyls (PCBs) via EPA method 8082

▪ Herbicides via EPA method 8151

▪ Total petroleum hydrocarbons diesel range organics (TPH-DRO) and gasoline range organics (TPH- GRO) via EPA method 8015.

▪ pH via EPA method 9045

▪ Reactivity, ignitability, and corrosivity parameters via EPA methods 9012, 9215, 1010, and 7.2

▪ Soluble sulfate via USEPA method 300.0 R2.1

▪ Sulfide via EPA method 9215

▪ Chloride via EPA method 9056

▪ Electrical resistivity (method varies)

▪ Redox potential (method varies)

▪ Perfluoroalkyl and polyfluoroalkyl substances (PFAS) via EPA draft method 1633

Only PFAS-free equipment and supplies were used during field activities. Non-dedicated sampling equipment was decontaminated using a Liquinox®/water wash followed by a distilled water rinse prior to use and between borings. IDW and rinsate were containerized on-site in 55-gallon DOT-approved drums.

Soil data was compared to the EPA Regional Screening Levels (RSLs) (updated November 2022) and the Virginia Department of Environmental Quality (VADEQ) Voluntary Remediation Program (VRP) risk-based screening levels for commercial and industrial sites/Tier III (updated August 2022). Results of the soil sample analytical testing program are as follows:

▪ Four (4) TCL VOCs were detected at concentrations above their respective laboratory detection limit for those constituents in soil samples. Acetone, isopropylbenzene, methyl cyclohexane, and methylene chloride. When compared with the commercial and industrial sites/Tier III screening levels, methyl cyclohexane did not have a published value, and the other constituents were well below their respective limits. Furthermore, acetone and methylene chloride are known to be common laboratory contaminants.

▪ TCL SVOCs were not detected in exceedance of published commercial and industrial sites/Tier III screening levels set by VADEQ nor were any constituent detected above their respective laboratory detection limit.

Contract: N40085-19-D-9041

▪ Pesticides were not detected above the laboratory detection limits for each respective constituent.

▪ PCBs were not detected above the laboratory detection limits for each respective constituent.

▪ Herbicides were not detected above the laboratory detection limits for each respective constituent.

▪ Throughout the fifteen collected soil samples, eighteen (18) of the twenty-three (23) TAL metals were detected above their respective laboratory detection limits, including aluminum, arsenic, barium, calcium, cobalt, chromium, copper, iron, mercury, potassium, magnesium, manganese, silver, sodium, nickel, lead, vanadium, and zinc. None of the detected sample concentrations exceed their respective published concentration limits for commercial and industrial sites/Tier III screening levels. Calcium, chromium, potassium, magnesium, and sodium do not have published Tier III concentrations.

▪ TPH-DRO was detected in samples collected from S-14 and S-15 and ranged in concentration between 23.0 mg/kg and 85.7 mg/kg. TPH-GRO was detected in samples T-4, S-13, S-14, and S-15 at concentrations ranging from 0.12 mg/kg to 2.41 mg/kg. These concentrations did not exceed state regulatory guidance levels (100 mg/kg in soil) typically referenced for underground storage tank closure. It should be noted that the Virginia clean fill regulations for TPH in soils is <50 mg/kg, which was exceeded in the sample collected from S-15 (85.7 mg/kg). Per Virginia regulations, soils exceeding this threshold may be reused on site as fill from the same excavation from where it was excavated or other areas on site that are as impacted or worse. Off-site disposal will require affected soils to be disposed of as petroleum-impacted soils.

▪ All soils produced detectable concentrations of PFAS; however, for those that the VADEQ/EPA have established current risk-based standards, none of the reported concentrations exceed applicable regulatory exposure thresholds.

▪ For the soil samples analyzed, all constituent concentrations are reportable to the VADEQ.

▪ Comparison of the results for each of these composite samples to the soil-test evaluation via AWWA C105/A21.5-10 10-point test standards, indicates the soil samples from the parking garage, LP-48 annex, and LP-48 additions sites are likely to be corrosive to ductile-iron pipe. Soil samples from the GBSAA site are not likely to be corrosive to ductile-iron pipe. In addition, detectable concentrations of sulfate were indicated in the composite soil samples taken at the LP-48 annex and additions sites as well as several locations from the taxiway; however, the concentrations appear negligible in regard to corrosiveness towards concrete structures.

Comprehensive soil analytical results and a summary table are provided in Appendix 12.

Contract: N40085-19-D-9041

3.2.2 Groundwater

Six (6) groundwater grab samples were collected at the groundwater interface at each of the piezometer locations. The samples were placed in clean, laboratory supplied containers, covered with ice, and shipped under chain-of-custody to Enthalpy Analytical in Richmond, Virginia for analysis of the following:

▪ TAL metals via EPA methods 6000/7000 series

▪ TCL VOCs via EPA method 8260

▪ TCL SVOCs via EPA method 8270

▪ TPH-DRO/GRO via EPA method 8015

▪ PFAS via EPA draft method 1633

Only PFAS-free equipment and supplies were used during field activities. Non-dedicated sampling equipment was decontaminated using a Liquinox®/water wash followed by a distilled water rinse prior to use and between borings. IDW and rinsate were containerized on-site in 55-gallon DOT-approved drums.

Groundwater data was compared to the VADEQ VRP‘s risk-based screening levels, which are based on drinking water standards and take into account vapor intrusion and direct dermal contact by construction worker risk pathways. Results of the groundwater sample analytical testing program are as follows:

▪ TCL VOCs were not detected above the laboratory detection limits for each respective constituent.

▪ TCL SVOCs were not detected above the laboratory detection limits for each respective constituent.

▪ Throughout the fourteen collected soil samples, sixteen (16) of the twenty-three (23) TAL metals were detected above their respective laboratory detection limits, including aluminum, arsenic, barium, calcium, cobalt, chromium, copper, iron, potassium, magnesium, manganese, sodium, lead, selenium, vanadium, and zinc. None of these metals have published concentration limits for commercial and industrial sites/Tier III screening levels in regard to vapor intrusion. None of the detected sample concentrations exceed their respective published concentration limits for commercial and industrial sites/Tier III screening levels in regard to direct contact. Calcium, chromium, lead, potassium, magnesium, sodium, and lead do not have published Tier III concentrations in regard to direct contact.

▪ TPH-DRO/GRO were not detected in any of the groundwater samples.

▪ All groundwater samples produced PFAS compounds in cumulative concentrations above the EPA health-based advisory limit of 70 ng/L.

▪ For the groundwater samples analyzed, all constituent concentrations are reportable to the

VADEQ.

Comprehensive groundwater analytical results are provided in Appendix 13.

Contract: N40085-19-D-9041

3.2.3 IDW Drums

For the PDA services, two (2) composite soil samples and one (1) wastewater sample were collected from three (3) of the fourteen (14) 55-gallon IDW drums staged at the project site. For the FDA services, one

(1) composite soil sample and one (1) wastewater sample were collected from the two (2) 55-gallon IDW drums stored at the pre-determined staging area. As previously discussed, a representative composite sample was collected for every five (5) IDW drums. The composite samples were placed in clean, laboratory supplied containers, covered with ice, and shipped under chain-of-custody to Enthalpy Analytical Richmond, Virginia for analysis of the following:

▪ Full Toxicity Characteristic Leaching Procedure (TCLP) metals, VOCs, SVOCs, Herbicides, Pesticides, and PCBs via EPA methods (varies)

▪ TPH-DRO/GRO via EPA method 8015

▪ Benzene, toluene, ethylbenzene, and xylene (BTEX) via EPA method 8021

▪ Paint filter via EPA method 9095

▪ Reactivity, ignitability, and corrosivity via EPA methods 9012, 9215, 1010, and 7.2

▪ PFAS via EPA draft method 1633

Following the PDA field investigation, Clearfield MMG, Inc. removed the fourteen (14) 55-gallon drums from the project site on March 24, 2023. Following the FDA field investigation, Clearfield MMG, Inc.

removed the two (2) 55-gallon drums from the staging site on March 11, 2024. The manifests and remediation certifications are included in Appendix 13.

3.2.4 Summary of Findings and Conclusions

The findings and conclusions of this investigation are as follows:

▪ PFAS was detected in soil samples however, for those that the VADEQ/EPA have established current risk-based standards, none of the reported concentrations exceed applicable regulatory exposure thresholds. PFAS was detected in all groundwater samples, with cumulative concentrations above the EPA health-based advisory limit of 70 ng/L.

▪ TPH was not detected in groundwater. TPH-DRO and/or TPH-GRO were detected in shallow soil samples collected from borings T-4, S-13, S14, and S-15. Detections were below the Virginia clean fill regulation of 50 mg/kg, with the exception of sample S-15 with a concentration of 85.7 mg/kg.

▪ TAL metals were detected in soil and groundwater samples; however, none were found to exceed their respective commercial and industrial sites/Tier III screening levels set by VADEQ.

▪ Four (4) TCL VOCs were detected in soils; however, two of the compounds appear to be commonly known laboratory contaminants (acetone and methylene chloride). Methyl cyclohexane does not have a published value for commercial and industrial sites/Tier III screening levels. In addition, the detections of isopropylbenzene are well below the commercial and industrial sites/Tier III screening levels.

▪ Detections of all other constituents in soil and groundwater were found to be less than published commercial and industrial sites/Tier III screening levels.

Contract: N40085-19-D-9041

3.2.5 Recommendations

Based on the results of this investigation, G E T recommends the following:

▪ Naval Station Norfolk should report the analytical results to the VADEQ Tidewater Regional Office for their regulatory opinion based on the concentrations of TPH and VOCs identified. It is our opinion that further assessment is not warranted for the site based on its history and projected use.

▪ The planned development will need to consider impacted soil in the vicinity of borings T-4, S-13, S-14, and S-15. Development of a soil management plan is recommended prior to site development activities. It is likely that soil in specified areas may require special handling and disposal, particularly in areas where petroleum impacted soils were detected. If TPH exceeds 50 mg/kg, the soil may be reused on site in an area of equal or greater impact, or it must be disposed as petroleum contaminated soil.

▪ Due to PFAS concentrations, a groundwater/surface water management plan will need to be prepared and implemented for dewatering activities. Groundwater/surface water containerization and treatment will be necessary prior to discharge.

▪ All soil produced detectable concentrations of PFAS compounds. Neither EPA nor VADEQ have established disposal criteria for PFAS in soils. The soils will need to be characterized prior to off-site disposal.

▪ If ductile-iron pipe design were to be implemented for the parking garage and LP-48 annex and additions sites, it is likely that these structures would be subjected to a corrosive environment. As such, depending on the characterization/utilization of the pipe, the appropriate encasement, coating, or cathodic protection should be considered.

4.0 SUBSURFACE CONDITIONS

4.1 Site Geology

The project site lies within a major physiographic province called the Atlantic Coastal Plain. Numerous transgressions and regressions of the Atlantic Ocean have deposited marine, lagoonal, and fluvial (stream lain) sediments. The regional geology is very complex and generally consists of interbedded layers of varying mixtures of sands, silts, and clays. Based on our review of existing geologic and soil boring data, the geologic stratigraphy encountered in our subsurface explorations generally consisted of Formations from the Pliocene Epoch, Pleistocene Epoch, and the Holocene Epoch.

The formation of the Pliocene Epoch encountered within the project limits consists of the Yorktown Formation (Ty). The Yorktown Formation is typically characterized by its blue-gray or green-gray color silty and clayey sand, abundance of marine shell fragments, and the distinct compact nature of the soil. The Yorktown Formation stratum, once encountered, generally extends to depths of several hundred feet below sea level. The Yorktown Formation commonly provides a suitable bearing stratum for deep foundation support.

Contract: N40085-19-D-9041

Formations of the Pleistocene Epoch encountered within the project limits consist of the Norfolk Formation (Qn) and the Sand Bridge Formation (Qsb). More recent publications indicate varying correlations between geological formations of the Upper Pleistocene Epoch. Specifically, the upper and lower members of the Norfolk Formation and the Sand Bridge Formation have been categorized as facies within the Lynnhaven Member (Qtl) and Sedgefield Member (Qts) of the Tabb Formation (Qt). Because of this confusion and for the purposes of this report, distinctions between the Norfolk Formation and Sand Bridge Formation will not be made and these formations will be characterized as part of the Tabb Formation.

The most recent geological depositions at the project site are of the Holocene Epoch and consist of soils referred to as Alluvium (Qal). Alluvium is typically comprised of sand, silt, and clay with deposits of organic-laden soils of varying thicknesses. Typically, this formation increases in thickness in the vicinity of pre-existing water features (deep waterways, tributaries, etc.). It is common to encounter organic-laden soils, organic silt, organic clay, and peat at lower depths. Fill (Qf) is also present and consists of unsorted, mixed, or undifferentiated material such as sand or gravel used for fill placement.

Based on a review of historical geologic maps, notably Geology of the Norfolk North Quadrangle, Virginia (Barker and Bjorken), it is believed that a majority of the proposed parking garage site is located within reclaimed land from…