Amendment 0006 - P226 F35 MCAS Cherry Point Geotech Report.pdf

Contract No. N40085-22-D-0043 Task Order No. N4008522F5233 Modification No. P00001 eProjects Work Order No. 1712284

FY24 MILCON Project P-226 F-35 Maintenance Facility & Marine Air Group Headquarters

MCAS Cherry Point, North Carolina

Final Geotechnical Engineering Report

February 10, 2023 rajul.teredesai

NC PE

Geotechnical Engineering Report

February 10, 2023

Prepared for: Naval Facilities Engineering Command (NAVFAC) Mid-Atlantic

Prepared by: AECOM

AECOM Project Number: 60685225

Quality information

Document name Ref Prepared for Prepared by Date Reviewed by

Preliminary Geotechnical Engineering Report

DRAFT NAVFAC Mid- Atlantic Marco Gravina, PE 10-07-2022 Victor Omelchenko, PE, DGE Rajul Teredesai, PE, PMP,DGE

Revision history

Revision Revision date Details Name Position

FINAL 01-30-2023

Mod-1 subsurface investigation and draft report NAVFAC review comments have been incorporated

Ariana White, PE Geotechnical Engineer

REVISED FINAL 02-10-2023

Stamped and sealed geotechnical engineering report

Ariana White, PE Geotechnical Engineer

This document has been prepared by AECOM Limited for the sole use of our client (the “Client”) and in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM Limited and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM Limited.

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1 INTRODUCTION AND SCOPE OF WORK ..................................................................... 1-1

2 EXISTING SITE CONDITIONS AND PROPOSED CONSTRUCTION ........................... 2-1

2.1 Existing Site Conditions ........................................................................................................... 2-1

2.1.1 MALS-14 Engine Maintenance Shop ........................................................................ 2-1

2.1.2 Marine Air Group (MAG-14) Headquarters Facility Site ........................................... 2-1

2.1.3 Building 3916 Aviation Armament Shop Addition ..................................................... 2-2

2.1.4 POV Parking Lot ........................................................................................................ 2-2

2.2 Proposed Construction ............................................................................................................ 2-2

2.2.1 MALS-14 Engine Maintenance Shop ........................................................................ 2-2

2.2.2 Marine Air Group (MAG-14) Headquarters Facility .................................................. 2-2

2.2.3 Building 3916 Aviation Armament Shop Addition ..................................................... 2-3

2.2.4 POV Parking Lot ........................................................................................................ 2-3

3 HISTORICAL IMAGE REVIEW ........................................................................................ 3-4

4 EXISTING GEOTECHNICAL INFORMATION ................................................................. 4-5

5 RECENT FIELD EXPLORATION ..................................................................................... 5-1

5.1 Site Geology ............................................................................................................................ 5-1

5.2 Subsurface Explorations ......................................................................................................... 5-1

5.3 Boring Stakeout and Subsurface Utility Clearance ................................................................ 5-1

5.4 Drilling Methodology and Sampling ........................................................................................ 5-2

5.5 Cone Penetration Tests with Pore Pressure Measurements ................................................. 5-3

5.7 Investigative Derived Waste .................................................................................................... 5-4

6 SUBSURFACE EXPLORATION RESULTS .................................................................... 6-1

6.1 Subsurface Conditions ............................................................................................................ 6-1

6.2 Groundwater ............................................................................................................................ 6-2

6.3 Soil Engineering Property Test Results .................................................................................. 6-3

6.4 In-Situ Infiltration Testing ......................................................................................................... 6-4

6.5 Corrosion Testing .................................................................................................................... 6-5

6.6 Expected Variations in Subsurface Conditions ...................................................................... 6-5

7 GEOTECHNICAL ENGINEERING RECOMMENDATIONS............................................ 7-1

7.1 MAG-14 Headquarters Facility Building ................................................................................. 7-1

7.2 Building 3916 Aviation Armament Shop Addition ................................................................... 7-2

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7.3 MALS-14 Engine Maintenance Shop ..................................................................................... 7-2

7.4 Lateral Pile Analysis ................................................................................................................ 7-5

7.5 Floor Slab Subgrade Recommendations ............................................................................... 7-6

7.6 Seismic Design Criteria ........................................................................................................... 7-7

7.7 Liquefaction Potential .............................................................................................................. 7-7

7.8 Restrained Walls ..................................................................................................................... 7-7

7.9 Pavement Areas ...................................................................................................................... 7-7

7.9.1 MAG-14 Headquarters Facility POV Parking Lot ..................................................... 7-7

7.9.2 Building 3916 Aviation Armament Shop Additional Pavements .............................. 7-8

7.9.3 POV Parking Lot ........................................................................................................ 7-8

7.10 Temporary Slopes ................................................................................................................... 7-9

7.11 Pipe and Utility Bedding .......................................................................................................... 7-9

8 CONSTRUCTION CONSIDERATIONS ........................................................................... 8-1

8.1 Footing Subgrades .................................................................................................................. 8-1

8.2 Fill Subgrade Preparation ....................................................................................................... 8-1

8.3 Fill Placement and Compaction .............................................................................................. 8-1

8.4 Displacement Auger Cast Piles .............................................................................................. 8-2

8.5 Driven Piles .............................................................................................................................. 8-3

8.6 Dewatering Effluent Handling.................................................................................................. 8-3

8.7 Other Design and Construction Considerations ..................................................................... 8-4

8.8 Construction Monitoring .......................................................................................................... 8-4

9 LIMITATIONS .................................................................................................................... 9-1

List of Figures and Appendices

Figure 1- Site Vicinity Plan (1 sheet)

Figure 2 – Historical Orthophotos (1 sheet)

Figures 3, 4, 5 & 6 – Soil Boring, CPT, and Hand Auger Location Plan (4 sheets)

Figure 7 – Restrained Wall Lateral Earth Pressures (1 sheet)

Figure 8 – Over Excavation and Backfill Beneath Footings (1 sheet)

Appendix A- Soil Boring Logs (28 sheets), USCS Soil Identification Sheet (2 sheets)

Appendix B – CPT Logs and Correlation Graphs (14 sheets)

Appendix C – Utility Clearance Letter and Photographs (14 sheets)

Appendix D - Investigative Derived Waste Environmental Test Results (82 sheets)

Appendix E – Soil Profiles (4 sheets)

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Appendix F – Soil Engineering Property Test Results (67 sheets)

Appendix G –Corrosivity Test Results (3 sheets)

Appendix H – Geotechnical Calculations and Analysis (127 sheets)

Appendix I – Infiltration Test Results (2 sheets)

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1 INTRODUCTION AND SCOPE OF WORK

Task Order N4008522F5233 scope of work was provided in the “P226 NAVFAC SAES Geotech & Hazmat for DD1391” RFP on February 23, 2022. The scope includes providing a preliminary geotechnical site characterization and engineering report, and hazardous materials survey and report, to support validation of the Region/FEC Team Final DD1391 and construction cost estimate being developed under separate contract. The report herein only includes the geotechnical site characterization and engineering report. The hazardous materials report has been submitted as a separate report.

Naval Facilities Engineering Command-Mid Atlantic (NAVFAC-MIDLANT) plans to build a F-35 Engine Maintenance Shop, a Marine Air Group Headquarters facility, and an addition to Building 3916 (Aviation Armament Shop) within the grounds of the Marine Corps Air Station (MCAS) Cherry Point, North Carolina. These structures will be designed and constructed as part of the F- 35 MILCON project in support of the Marine Corps Aviation Plan, Operational Training, and Maintenance Requirements, Planned Development Schedules and overall flexibility of Aviation Assets and Facilities. AECOM’s scope of work for the subject project included drilling eight soil borings, three hand-augers, performing six cone penetration soundings with pore pressure measurements (CPTu), performing limited soil laboratory testing, review of the existing Geotechnical Engineering Reports for projects in the vicinity of the proposed project sites and preparation of this report. The scope includes preparation of a geotechnical engineering report based on the geotechnical data collected during our subsurface investigation with the following information:

A. A site vicinity map based on a USGS 7.5-minute quadrangle topographic map.

B. Description of regional geology.

C. A soil exploration location plan.

D. Discussion of current site conditions.

E. Soil boring logs, and CPTu sounding logs.

F. Graphic and written subsurface profiles with SPT N-values, CPTu tip resistance, groundwater data and other pertinent geotechnical data obtained during exploration and testing, as appropriate.

G. A summary of prior subsurface investigations performed near the site based on the data provided in the SAES.

H. Results of geotechnical soil laboratory testing, delineation of data and statistical evaluation.

I. Shallow and deep foundation recommendations for support of the proposed structures.

J. Recommendations for floor slab preparation.

K. Seismic site class in accordance with the current version of ASCE 7 and IBC based on the shear wave velocity data collected with seismic testing in CPTu soundings.

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L. Recommendations for handling of groundwater in the design.

M. Lateral earth pressures and backfill recommendations for design of below grade walls.

N. Recommendations for earthwork requirements, including re-use of site soils for structural fill.

O. Recommended pavement sections for the light duty bituminous pavement based on the lower bound estimated design CBR value for the material encountered during the subsurface investigation.

P. Recommendations for excavated soil management and disposal requirements.

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2 EXISTING SITE CONDITIONS AND PROPOSED CONSTRUCTION

2.1 Existing Site Conditions

The site for the Marine Air Group (MAG-14) Headquarters Facility and the MALS-14 Engine Maintenance Shop Site are located within the grounds of the MCAS, Cherry Point, North Carolina.

A site Vicinity Map is included as Figure 1.

2.1.1 MALS-14 Engine Maintenance Shop

The site for the MALS-14 Engine Maintenance Shop is located west of the intersection of F Street and 7th Street within the Cherry Point Base and west-southwest of the existing airfield. A single-story building (Building 3992) presently occupies part of the site. Based on existing drawings provided by the government, it is known that Building 3992 is founded on shallow foundations. Paved driveways and parking areas are also present at the north end of the site. The existing elevations around the site vary between approximately EL 21 feet and EL 23 feet. Several underground utility lines are known to be present at the site.

The existing Van Pad located adjacent to existing Building 3992 consists of a concrete area supporting an electrical distributing system. The existing Van Pad concrete was observed to be between about 5 inches and 8.5 inches thick.

The above information was obtained from our site visit during our field investigation and information provided to us by the government in the RFP dated February 23, 2022, and the RFP Mod-1 dated August 22, 2022.

Based on the RFP dated February 23, 2022, AECOM understands that the proposed sites fall within or adjacent to the boundaries of state and federal land control (LUC) areas that prohibit without regulatory consent, the insertion of objects into the groundwater table or the withdrawal of groundwater without expressed regulatory approval. We understand that contaminants of concern are present within the boundaries of the existing Building 1669 are adjacent to the boundaries of existing Building 3992. Contaminants of concern at the project sites include but are not limited to volatile organic compounds, metals, and petroleum hydrocarbons. No additional information regarding the location, depth or concentration of contaminants was provided to us.

2.1.2 Marine Air Group (MAG-14) Headquarters Facility Site

The proposed MAG-14 Headquarters Facility site is located at the north-west corner of the intersection of A Street and Wright Road. The site is presently occupied by a single-story building, Building No.1669, with several loading areas around the building sides. The building is believed to have been constructed in the early 1950s. The existing building is supported on timber piles designed for a capacity of about 15 tons with an embedment depth between about 32 and 45 feet. Paved asphalt areas surround the existing building. There is an existing and presumably abandoned railroad track running parallel along the southern side of the building. The tracks end at the north end of the existing building. The existing grades around the building were observed to be generally flat with grades varying between EL 23 feet and EL 24 feet. Several underground utility lines are known to be present at the site.

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2.1.3 Building 3916 Aviation Armament Shop Addition

The site for the proposed Aviation Armament Shop Addition is located next to the existing Building 3916. This structure is located off of 7th Ave, south of the Roosevelt Boulevard and 7th Avenue intersection within the Cherry Point Base, northwest of the existing airfield. Building 3916 is a single-story building founded on shallow foundations per the project information provided by the government. The building is surrounded by paved driveways and a parking area to the west of Building 3916 and two driveways connecting to 7th Avenue. The existing ground elevations vary between approximately EL 23 feet and EL 25 feet. Several underground utility lines and an above ground LPG tank are known to be present at the site.

2.1.4 POV Parking Lot

The site location for the proposed POV Parking Lot is located between 5th Avenue and 6th Avenue, northwest of G Street within the Cherry Point Base. This is west-northwest of the existing airfield.

The southern half of the site was formerly occupied by a building that has since been demolished.

The existing ground elevations vary between approximately EL 20 feet to EL 25 feet. An underground storm drain crosses the site and several other underground utilities, such as electric lines and storm lines, run under the southwest portion of the site.

2.2 Proposed Construction

2.2.1 MALS-14 Engine Maintenance Shop

It is our understanding that NAVFAC Mid-Atlantic intends to construct a MALS-14 Maintenance Engine Shop for the F-35B/C Lightning II aircraft Level 1 Maintenance, including crew and equipment space, air frames, administrative space, and Special Access Program Facility (SAPF).

The building will consist of a high-bay and partial 2-story structure covering a footprint of approximately 54,466 SF (241 feet by 226 feet). The construction is anticipated to include steel frame and roof trusses, reinforced concrete masonry unit walls with brick veneer, pre-finished standing seam insulated roof system, and concrete slab-on-grade first floor. It is understood that the government intends to support the building on a deep foundation system. The maximum compressive column loads will be 400 kips and maximum floor live load will be 300 psf. It is anticipated that the site grades will increase 2 feet or less above existing grades. A portion of the new building will be constructed over the current Building 3992 footprint. The facility does not include any vehicular pavement. Proposed grades were not available at the time of this writing.

2.2.2 Marine Air Group (MAG-14) Headquarters Facility

The proposed construction also includes construction of a MAG-14 Headquarters facility which will include administrative space and a Night Imaging and Threat Evaluation (NITE) lab. The new building will consist of a single-story structure covering a footprint of approximately 25,787 SF (253 feet by 107 feet). The new construction is anticipated to include steel frame and roof trusses, reinforced concrete masonry unit walls with brick veneer, pre-finished standing seam insulated roof system, and concrete slab-on-grade first floor. The maximum column and wall loads are anticipated to be 100 kips and 4 kips per linear foot, respectively. A maximum floor live load will be about 150 psf. It is understood that the surface grade increases will be 2 feet or less above

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existing grades. The facility will include an approximate 54-space asphalt parking lot for personally owned vehicles (POVs). The new building and parking lot will be constructed over the current footprint of Building 1669, which is supported on timber pile foundations. Personally owned vehicles (POVs) pavement will consist of a light duty flexible pavement and medium/heavy duty asphalt drives. The traffic loads are not available at this time and will likely not be available for another month. The pavement was tentatively being designed as a permeable pavement.

However, based on recent information by the government via email the new POV pavement areas will be constructed with standard asphalt.

2.2.3 Building 3916 Aviation Armament Shop Addition

An addition to Building 3916 Aviation Armament Shop is proposed to be built to the northwest of the existing building. The proposed building will consist of a single-story addition of approximately 4,665 SF. The construction is anticipated to include steel frame and roof trusses, reinforced concrete masonry unit walls with brick veneer, pre-finished standing seam insulated roof system, and concrete floor. It is understood that the government intends to support the building on a shallow foundation system, similar to the existing Building 3916. The maximum wall loads will be 4 kips per linear foot and maximum floor live loads will be 150 psf. Site grades are anticipated to increase up to 2 feet above existing grades to match the existing building. The facility will also include new asphalt paved driveways and nine parking stalls for POVs.

2.2.4 POV Parking Lot

The proposed POV Parking Lot will consist of a flexible pavement surface parking area to support approximately 280 POVs. The parking area is tentatively being designed as a permeable pavement with below-grade storage of storm water to meet low impact development (LID) requirements.

Based on the Mod-1 RFP and government provided information, the project no longer includes requirements to evaluate airfield pavements.

The above information was obtained from information provided to us by the government in the RFP dated February 23, 2022, and the RFP Mod-1 dated August 22, 2022, and from information provided by the government geotechnical manager.

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3 HISTORICAL IMAGE REVIEW

We have reviewed historical aerial photographs on Google Earth dating as far back to 1985 and available Havelock, NC USGS topographic maps. Based on our review, it was not obvious that the site conditions have changed significantly in comparison to the existing current conditions. There were not sufficient details in the 1985 Google Earth photographs and some USGS maps to make accurate comparisons between past and current conditions. It is noted that existing Building 3992 (site for the proposed MALS-14 Maintenance Engine Shop) was built on a portion of the former airfield running east-west (See Figure 1). A drawing illustrating some of the historical orthophotos is included as Figure 2.

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4 EXISTING GEOTECHNICAL INFORMATION

We have reviewed and considered in our analysis the geotechnical information provided by the government. The following historic documents were provided to us in the Request for Proposal (RFP) dated February 23, 2022:

1. Report of Preliminary Geotechnical Site Characterization for P-199 Aircraft Maintenance Hanger and Paraloft, prepared by GER Inc., dated August 18, 2017

2. Geotechnical Engineering Report for P-199 Aircraft Maintenance Hanger and Paraloft, prepared by Catlin Engineers and Scientists, dated June 18, 2020

3. Preliminary Report of Subsurface Exploration and Geotechnical Engineering Services, P- 228 ATC Tower and Air Operations Facility, prepared by GET Solutions, Inc., dated May 8, 2019

4. Geotechnical Site Characterization Report, P-197 F-35 Aircraft Maintenance Hanger and Parking Facility, prepared by HDR, Inc., dated December 6, 2019

AECOM considers that the data presented in the existing documents is fairly consistent with the findings from our recent subsurface investigation.

AECOM has assumed that the GER borings and CPTs were performed in accordance with ASTM criteria and that they are complete and accurate. It should be noted that AECOM assumes no responsibility for the accuracy or completeness of data obtained from the previous soil borings drilled at the site, as we were not present during the field investigation.

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5 RECENT FIELD EXPLORATION

5.1 Site Geology

All project sites are located within the North Carolina Atlantic Coastal Plain physiographic province.

The Coastal Plain providence is characterized by an eastward thickening wedge of marine, estuarine, and fluvial sediments that were deposited in a series of marine transgressive-regressive cycles, or high and low stands of sea level, during the Holocene to Miocene epochs of the late Cenozoic era.

The upper geologic units at the sites consist of unconsolidated Holocene and Upper Pleistocene age deposits of undivided members. Older underlying units include consolidated Tertiary deposits of the Yorktown and Duplin Formations, undivided, described as fossiliferous clay and shelly sand deposits. Bedrock is believed to be at more than 1000 feet below sea level.

Some human-placed uncontrolled fill was observed in the soil borings. The uncontrolled fill soils are believed to be associated with the previous development of the proposed sites.

5.2 Subsurface Explorations

AECOM conducted a subsurface investigation program to investigate the subsoil conditions within the proposed sites within the Cherry Point Base, North Carolina. A total of 14 soil borings, labeled SB-1 through SB-11 and P-1, P-2 and P-3 and a total of six CPTu’s were performed as part of the subsurface investigation. Two of the four proposed sites, MALS-14 Engine Maintenance Shop and MAG-14 Headquarters Facility, fall within or adjacent to the boundaries of the land use control (LUC) area that prohibit without regulatory consent, the insertion of objects into the groundwater table or the withdrawal of groundwater without expressed regulatory approval. Therefore, a field investigation work plan was prepared and approved by the Environmental Affairs Department (EAD) prior to staring the field investigation. The two proposed sites falling outside of the LUC boundaries are the Aviation Armament Shop Building 3916 Addition and the POV Parking Lot. The soil boring and CPTu locations are illustrated on the Soil Boring and CPTu Location Plans included as Figures 3,4, 5, and 6. The soil boring and CPTu logs are included in Appendix A and B.

5.3 Boring Stakeout and Subsurface Utility Clearance

The boring and CPTu locations were field located by AECOM and GER based on existing features at the site prior to drilling the borings to clear the staked boring locations. “North Carolina 811” was contacted by our drilling subcontractor, Fishburne Drilling, Inc., to mark the existing underground utilities around staked boring locations. Additionally, the boring and CPTu locations were cleared by Southeastern Location Services, LLC using non-destructive methods such as Ground Penetrating Radar (GPR), pipe locators, metal detectors, etc. The soil boring and CPTu locations were cleared within a 25-foot radius. A letter from Southeastern Location services, LLC for each round of drilling and photo logs of the cleared locations are included in Appendix C.

The as-drilled coordinates were obtained using a Trimble Geo7000 GPS. The government sites survey was not available at the time of this writing. Therefore, the soil boring, CPTu, and CBR bulk sample elevations were obtained from the Light Detection and Ranging (LiDAR) data sets. The

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approximate coordinates and ground surface elevations at the soil boring and CPTu locations are shown on the boring logs included in Appendix A and the approximate soil boring, CPTu, and CBR bulk sample locations are illustrated on the Soil Boring and CPT Location Plans included as Figures 3, 4, 5 and 6. The soil boring, CPTu, and CBR bulk sample elevations and coordinates are also summarized in the table below.

Table 1: Soil Boring and CPTu Summary

Point ID Northing* Easting*

NAVD88

(LiDAR)*** Lat** Long**

CPTu-1 428838.79 2630431.03 23.19 34.9099608 -76.8969765

CPTu-2 428982.43 2630587.31 21.00 34.9103463 -76.8964452

CPTu-3 428788.03 2630632.31 21.91 34.9098042 -76.896309

CPTu-4 425567.31 2632104.50 23.72 34.9008761 -76.8916275

CPTu-5 425292.12 2632088.51 23.94 34.900121 -76.8917003

CPTu-6 425245.92 2631836.95 23.77 34.9000088 -76.8925424

P-1 428548.34 2630406.34 24.52 34.9091644 -76.8970794

P-2 428593.69 2630591.31 22.88 34.9092782 -76.8964593

P-3 428521.41 2630173.36 23.72 34.9091039 -76.8978582

SB-1 428691.63 2630582.65 22.97 34.9095477 -76.8964813

SB-2 428910.78 2630506.48 21.86 34.9101542 -76.8967198

SB-3 428894.70 2630670.92 21.15 34.9101005 -76.8961726

SB-4 425460.63 2632236.50 23.69 34.9005753 -76.8911949

SB-5 425413.00 2631971.63 24.12 34.9004599 -76.8920815

SB-6 425153.50 2631938.57 23.80 34.899749 -76.8922101

SB-7 431080.35 2629151.48 24.34 34.9161931 -76.9010856

SB-8 431143.37 2629211.06 24.34 34.9163628 -76.9008824

SB-9 428122.47 2629908.41 22.99 34.9090503 -76.8987436

SB-10 428296.47 2629825.16 22.60 34.9085063 -76.8990353

SB-11 428122.47 2629748.59 22.10 34.9080327 -76.8993029

CBR-1 430971.25 2629045.12 24.57 34.9158996 -76.901448

CBR-2 425454.56 2632248.18 24.70 34.9005579 -76.8911564

* NAD83, North Carolina State Plane (US Survey Feet) ** Lat/Longs WGS84 *** Elevations North American Vertical Datum of 1988 (NAVD88)

5.4 Drilling Methodology and Sampling

Fishburne Drilling, Inc. of Chesapeake, Virginia drilled the first round of soil test borings, SB-1 through SB-6 and P-1, P-2, and P-3 between August 24th, 2022, and August 30th, 2022. Fishburne Drilling, Inc. drilled the second round of soil test borings, SB-7 and SB-8, on December 19, 2022.

Fishburne Drilling, Inc, conducted the drilling of the soil borings as licensed well drillers in the State of North Carolina (NCWC 4366-A & NCWC 4174-B).

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Soil test borings, SB-9, SB-10, and SB-11 were hand augered by GeoEnvironmental Resources (GER). A licensed Professional Geologist logged the hand auger borings and estimated the Seasonal High-Water Table (SHWT) by observing soil coloration and redoximorphic features.

The borings performed by Fishburne Drilling, Inc. were drilled with a truck mounted CME-45 using 3 inch diameter drill casing and mud drilling methods to advance the borings. Representative soil samples were obtained using a two-inch outside diameter split-barrel spoon sampler in general accordance with ASTM D1586 standards. Standard penetration tests (SPTs) were performed by driving the split-spoon sampler into the soil a distance of 24 inches over four six-inch intervals, by means of a 140-pound hammer falling 30 inches. The number of hammer blows required to drive the sampler through the second and third six-inch intervals (i.e., the N-values) for each sample are indicated on the soil test boring logs included in Appendix A. Soil samples were obtained continuously in the upper 12 feet and every five feet below the upper 12 feet. The N-values provide an indication of the in-place density (granular materials) and consistency (cohesive materials) of the soils. The borings were backfilled with cement/bentonite grout upon completion in accordance with the approved Geotechnical Investigation Work Plan.

After recovery, the soil samples were removed from the sampler and visually classified by a senior geologist from our AECOM office. Representative portions of the soil samples were sealed in glass jars and retained for further review. The visual classifications were based on texture and plasticity, in accordance with the Unified Soil Classification System (USCS). A brief description of the USCS is also included in Appendix A.

5.5 Cone Penetration Tests with Pore Pressure Measurements

Six CPTu soundings (CPTu-1 through CPTu-6) were performed by In-Situ Soil Testing, Inc. within the proposed building footprints in general accordance with ASTM D5778 20, “Standard Test Method for Electronic Friction and Piezocone Testing of Soils”. The CPTu were planned to be extended to a depth of 100 ft; however, refusal was encountered at depths between about 64.6 feet and 71.1 feet below the ground surface. The CPTu recorded tip resistance, side friction, and pore pressure. Shear wave velocity data was recorded at 3 feet depth intervals in two of the CPTu’s, (seismic CPTu), CPTu-2 and CPTu-5. The CPTu data logs are included in Appendix B.

Graphical correlations with SPT N-values, CPTu tip resistance, Friction ratio percentage and percent Passing #200 are also included in Appendix B. Additionally, the CPTu are plotted in the soil profiles for each site included in Appendix E. The CPTu locations are illustrated in the Soil Boring and CPTu Location Plan included as Figures 3 and 4.

5.6 Photoionization Detector (PID) Screening

All soil samples recovered from the borings were screened for volatile organic compounds (VOCs) using a photoionization detector (PID). The PID readings obtained in the field from the samples recovered varied from less than one part per million (ppm) to 3.7 ppm. The PID readings are included in the soil boring logs in Appendix A.

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5.7 Investigative Derived Waste

All investigative derived waste (IDW) from the soil borings was handled in accordance with the approved Geotechnical Investigation Work Plan. The IDW was stored in 13 US Department of Transportation (USDOT) approved drums. The drums were sealed, labeled, and stored at a selected location approved by the Environmental Affairs Department (EAD) point of contact. Two composite samples of the soil spoils were obtained from the drums for environmental testing. The environmental test results are included in Appendix D. The drums have since been removed off-site by our subcontractors and disposed based on the environmental laboratory test results.

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6 SUBSURFACE EXPLORATION RESULTS

6.1 Subsurface Conditions

The subsurface materials encountered in the soil borings are described below for the purposes of our discussions in this report. It should be noted that these descriptions do not imply the continuity of the materials encountered in the borings. The descriptions of the materials have been established to characterize similar subsurface conditions based on material gradations and parent geology. The subsurface materials encountered in the soil borings, along with the range of Standard Penetration Test (SPT) N-Values are described below.

Up to approximately 3 inches of organic surficial soil, 2 inches of asphalt and 8.5 inches of concrete were encountered at the soil boring locations. These depths should not be considered a stripping depth since the organic surficial soil, asphalt and concrete may be thicker at other areas of the site. The soil profiles for each proposed site including the CPTu data are included in appendix E.

Stratum A: Uncontrolled Fill

All the soil borings, except boring P-3, indicated the presence of uncontrolled fill soils below the organic surficial soil, concrete and asphalt. The uncontrolled fill extended to depths of between about 1.5 feet and 4.7 feet below the existing ground surface or between about EL +18.1 feet and EL +22.5 feet. Test N-values for the uncontrolled fill soils vary between 4 blows per foot (bpf) to 44 bpf for granular fill soils and 6 bpf to 7 bpf for fine-grained fill soils.

CPTu corrected tip resistance for the existing soils varies approximately between 10 tons per square foot (tsf) and 60 tsf. The effective friction angle of the cohesionless soils is between 320 to 400. The friction angle was estimated using the Robertson method.

Stratum B: (Coastal Plain- Alluvial Cohesionless Soils)

Below the uncontrolled fill soils and the concrete, sandy natural soils were encountered in all borings, to depths between about 33 feet and 48 feet below existing grades or between about El -25.0 feet and EL -8.9. The sandy natural soils consisted of very loose to very dense Silty Sand (SM), Clayey Sand (SC), Poorly-graded Sand (SP), and Poorly-graded Sand with Silt (SP-SM).

The N-values ranged from 2 bpf to 58 bpf. Soil borings P-1, P-2, P-3, SB-7, SB-8, SB-9, SB-10, and SB-11 terminated in this Stratum.

CPTu corrected tip resistance for the existing soils varies approximately between 20 tsf and 300 tsf. The effective friction angle of the cohesionless soils is estimated between 320 to 440. The friction angle was estimated using the Robertson method.

Stratum C: (Coastal Plain – Alluvial Cohesive Soils)

Below the Stratum B soils cohesive soils were encountered in soil borings SB-1 through SB-6 to depths between about 49 feet and 58 feet below existing grades or between about El -36.1 feet and EL -27.9. These soils consisted of very soft to soft Sandy Lean Clay (CL), Lean Clay with Sand (CL), Sandy Fat Clay (CH), Fat Clay (CH), and Elastic Silt (MH) and very loose to loose Clayey Sand (SC). The N-values ranged from 1 bpf to 4 bpf. Stratum C soils are referred in this

AECOM 6-2

report as the confining layer. The confining layer is a formation consisting of clayey soils that hydraulically separates two aquifers.

CPTu corrected tip resistance for these soils varies approximately between 20 tsf and 80 tsf. Peak undrained shear strength (su) of Stratum C is estimated to range from about 1,500 to 3,000 psf based on CPT resistance (Nkt=16). It is noted that these soils have a high sand content.

Therefore, the undrained shear strengths were observed to be higher than normal.

Stratum D: (Coastal Plain- Yorktown Formation)

Below the Stratum C soils, natural soils of the Yorktown Formation were encountered in all borings to the maximum depths investigated by borings SB-1 thought SB-6 or between about El -58.1 and EL -55.9. The sandy soils consisted of loose to very dense Silty Sand (SM, Silty Sand with Gravel (SM), Poorly-Graded Sand with Silt (SP-SM), Clayey Sand (SC) and Clayey Sand with Gravel (SC). The N-values ranged from 7 bpf to 92 bpf.

CPTu corrected tip resistance for the existing soils varies approximately between 50 tsf and greater than 300 tsf. The effective friction angle of the cohesionless soils is estimated between 320 to 420. The friction angle was estimated using the Robertson method.

6.2 Groundwater

Groundwater obtained from the soil borings and CPTu’s are summarized below. The groundwater measurements were obtained in the borings during drilling. All borings were grouted upon completion in accordance with the Geotechnical Investigation Work Plan. The groundwater observations are also included in the soil boring logs included in Appendix A.

AECOM 6-3

Table 2: Groundwater Observations Summary Soil Boring and CPT Number

Approximate Groundwater Depth (feet)*

Approximate Groundwater

Elevation (feet)

Proposed Site Location

SB-1 6 16.9

MALS-14 Engine Maintenance Shop

SB-2 6 15.8

SB-3 10 11.2

CPTu-1 10 13.2 CPTu-2 9 12 CPTu-3 8 13.9

P-1 6 16.8 Van Pad P-2 8 16.5

P-3 6 17.7

SB-4 8 15.7

MAG-14

Headquarters

Facility

SB-5 6 18.1

SB-6 6 17.8

CPTu-4 6.5 17.2 CPTu-5 6 17.9 CPTu-6 6.5 17.3

SB-7 13.0 11.3 Aviation Armament Shop Addition SB-8 18.0 6.3

SB-9 10, 8.0** 15.0

POV Parking Lot SB-10 Dry, 8.0** 14.6

SB-11 Dry, 8.0** 14.1 *Groundwater level measured during drilling

**Seasonal High-Water Table estimated from hand augers

Mud drilling methods were used to perform the soil borings and drilling fluid was introduced during the drilling process. Therefore, ground water measurements were not obtained upon completion of the borings. Seasonal perched water conditions may be encountered at a depth of approximately 2 to 3 feet during construction due to the presence of fine-grained soils interbedded with free-draining sandy soils. It is possible that stabilized groundwater levels are higher than those obtained from the soil borings. Seasonal high water table levels are anticipated to be approximately 5 to 8 feet below existing grades. It should be noted that fluctuations in groundwater levels may occur as a result of seasonal variations in rainfall, proximity of the site to large bodies of water, sea level tides, evaporation, construction activity, surface runoff, and other site-specific factors.

6.3 Soil Engineering Property Test Results

Select split-spoon soil samples were tested to determine the physical and engineering properties of the on-site soils. The soil laboratory tests were conducted by our AECOM soil laboratory in general accordance with applicable ASTM criteria for the soil samples from the first round of drilling. The testing included moisture content determinations (ASTM D2216), Atterberg Limits tests (ASTM D4318), mechanical gradation analyses (ASTM D6913), sieve analyses tests with hydrometer (ASTM D422) and incremental load 1-D consolidation tests (ASTM D2435). The second-round of soil laboratory tests were performed by JayKay Testing in general accordance

AECOM 6-4

with ASTM criteria. The testing included moisture content determinations (ASTM D2216), Atterberg Limits tests (ASTM D4318), mechanical gradation analyses (ASTM D6913), CBR tests ASTM D1833), and Modified Proctor tests (ASTM D1557). The AECOM soil laboratory and JayKay Testing certifications and the soil laboratory test results are included in Appendix F.

Additionally, some of the test results such as moisture content results are incorporated in the soil boring logs in Appendix A. The CBR test results are summarized in the table below:

Table 3: CBR Laboratory Test Results

6.4 In-Situ Infiltration Testing

GeoEnvironmental Resources (GER) conducted three constant head infiltration tests using an Amoozemeter at the proposed site for the POV Parking Lot. Borings SB-9, SB-10, and SB-11 were hand augered by GER to 10 feet below the ground surface (bgs). Infiltration test results are summarized in the below table and included in Appendix I. Water did not infiltrate at SB-11.

Therefore no results are presented at this location. SB-11 is located at the southwestern portion of the site, where a former building was demolished. Uncontrolled fill was observed to 4 feet bgs. Therefore this infiltration test was attempted at a deeper depth in natural soil.

Table 4: Constant Head Infiltration Rates at the POV Parking Lot Site(1)

Boring

ID

Test Depth

(ft bgs)

Infiltration Rate (in/hr)

USCS

Classification

USDA

Classification

SB-9 3.25 0.02

Clayey Sand

(SC) Sandy Loam

SB-10 6 9.38

Silty Sand

(SM) Loamy Sand

SB-11 5 NA

Sandy Lean

Clay (CL) Clay Loam

(1) An appropriate factor of safety must be applied to any infiltration test result and the presence of underlying confining layers must be addressed in the design of any stormwater management system.

Site Location Sample ID Sample Depth (feet)

Sample Description

CBR at 0.1 inch penetration

CBR at 0.2 inch penetration

As‐Molded Compaction

Bldg 3916 CBR‐1 1 ‐ 3' SM 29.8 35.7 94.7

MAG‐14

Headquarters

CBR‐2 1 ‐ 3' SM 39.9 46.1 95.2

POV Parking Lot

SB‐9/CBR‐3 1 ‐ 3' SC‐SM 38.0 46.7 96.6

SB‐10/CBR‐4 1 ‐ 3' CL 2.7* 2.9* 96.3

SB‐11/CBR‐5 1 ‐ 3' SC‐SM 11.1 12.7 94.1

*Uncorrected CBR values

AECOM 6-5

6.5 Corrosion Testing

The geochemical properties of the soils at the project site need to be considered in the final design of the facilities of the project, including, sewers, structures, and foundations. Two composite soil samples obtained from borings SB-2 and SB-5 were tested to determine the corrosion potential of the soils within the project area. The samples were obtained from approximately zero to 10 feet below the ground surface. All the tests were performed in accordance with AASTHO except the oxidation reduction potential which was performed in accordance with the ASTM standard. The soil laboratory test results for the corrosivity testing are included in Appendix G and are summarized in the table below.

Table 5: Corrosivity Test Results Summary

Boring Number

Proposed Site pH Chloride

(ppm) Sulfate (ppm)

Minimum Resistivity (ohm-cm)

Oxidation- Reduction Potential

(mV)

SB-2

MALS-14 Engine

Maintenance Shop Site

8.0 24 182 2,460 4.7

SB-5

MAG-14

Headquarter Site

8.0 14 97 1,960 4.7

Based on the American Concrete Institute (ACI 318), soils with water-soluble sulfate content less than 150 parts per million (ppm) are categorized as having an exposure class of S0 (negligible sulfate severity), and there is no concern of injurious sulfate attack on concrete at this level of soil sulfate concentration. Soils with water-soluble sulfate content between 150 parts per million (ppm) and 1,500 ppm are categorized as having an exposure class of S1, where injurious sulfate attack on concrete at this level of soil sulfate concentration is a concern. Final selection of the cement grade and approval of the concrete mix should be performed by the project structural engineer.

6.6 Expected Variations in Subsurface Conditions

Interpretation of general subsurface soil conditions presented herein is based on the soil and groundwater conditions obtained from the soil borings drilled at the sites. The subsurface conditions may vary between exploration locations. If conditions are found to be different from those observed in the recent borings, recommendations contained in this report should be re-evaluated by AECOM and confirmed in writing. Since the groundwater levels are expected to fluctuate with rainfall, season, temperature, proximity of the site to the coast, tidal changes, climate, construction in the area, etc., groundwater conditions at the time of construction may be different from those found during the time of the recent exploration.

AECOM 7-1

7 GEOTECHNICAL ENGINEERING RECOMMENDATIONS

The geotechnical engineering analysis was based on the existing soil boring data, CPTu data, soil laboratory testing, and the project information included in section 2 of this report. The geotechnical calculations and analyses packages are included in Appendix H of this report.

7.1 MAG-14 Headquarters Facility Building

It is understood that up to about two feet of new compacted fill will be required to reach the proposed lowest floor elevation. The lowest floor elevation has not been established at the time of this writing.

Soil borings SB-4, SB-5 and SB-6 drilled in the vicinity of the proposed building footprint, indicate the presence of up to 2.3 feet of uncontrolled fill underlain by sandy natural soils of Stratum B. The Uncontrolled Fill of Stratum A generally consists of sandy soils. AECOM is not aware of and has not been provided with any records of compaction quality control during placement of the uncontrolled fill soils. Therefore, we have considered that this material was placed in an uncontrolled manner. Supporting the new foundations on the Stratum A soils is not recommended as larger than normal building settlements may occur.

It is our opinion that the proposed MAG-14 Headquarters Facility building can be supported on spread footings founded on the natural soils of Stratum B or new compacted structural fill. All uncontrolled fill of Stratum A should be completely removed directly under the proposed footings.

Footing undercut excavations must be widened by 0.5 feet on each side of the planned footing location for each foot of undercut depth below the planned footing bearing elevation as shown in Figure 8. The undercut soils should be replaced with compacted imported structural fill material. In-lieu of backfilling the undercut excavations with new compacted fill, the footing undercut excavations may also be brought back to planned grades with crushed stone such as American Association of State Highway and Transportation Officials (AASHTO) No. 57 stone. Compacted fill recommendations are included in Section 8.1 of this report.

Spread footings and continuous wall footings founded on new compacted structural fill or natural soils of Stratum B may be designed using a net allowable soil bearing pressure of up to 2,500 pounds per square foot (psf). We estimate that the immediate and long-term settlement of footings will not exceed approximately 1 inch. Differential settlement between adjacent foundation elements should not exceed approximately half this amount. Continuous wall footings should have a minimum width of 18 inches and isolated column footings should have a minimum width of 36 inches. The minimum widths are recommended to provide a margin of safety against a local or punching shear failure of the foundation soils. Footings should bear at a minimum depth of 18 inches below the finished grades for frost protection. The bases of all foundation excavations must be free of water and loose soil prior to the placement of concrete. A maximum allowable slope of 1.5H:1V shall be maintained between the bottom edges of adjacent footings or underground utility trenches.

The MAG-14 Headquarters Facility building will be constructed within the footprint of existing Building 1669 which is founded on timber piles. It is our opinion that the existing piles can be left in-place. If the new footings conflict with the existing timber pile locations, the piles should be cut off a minimum one foot below the proposed bottom of footings.

AECOM 7-2

7.2 Building 3916 Aviation Armament Shop Addition

It is understood that up to about two feet of new compacted fill will be required to reach the proposed lowest floor elevation. The lowest floor elevation has not been established at the time of this writing.

Soil borings SB-7 and SB-8 drilled in the vicinity of the proposed building footprint, indicate the presence of up to 4 feet of uncontrolled fill underlain by sandy natural soils of Stratum B. The Uncontrolled Fill of Stratum A generally consists of sandy soils. AECOM is not aware of and has not been provided with any records of compaction quality control during placement of the uncontrolled fill soils. Therefore, we have considered that this material was placed in an uncontrolled manner. Supporting the new foundations on the Stratum A soils is not recommended as larger than normal building settlements may occur.

The Armament Shop Addition building will be constructed adjacent to the Building 3916 Aviation Armament Shop which is supported on a shallow foundation system. It is our opinion that the proposed addition can be supported on spread footings founded on the natural soils of Stratum B or new compacted structural fill. All uncontrolled fill of Stratum A should be completely removed directly under the proposed footings. Footing undercut excavations must be widened by 0.5 feet on each side of the planned footing location for each foot of undercut depth below the planned footing bearing elevation as shown in Figure 8. The undercut soils should be replaced with compacted imported structural fill material. In-lieu of backfilling the undercut excavations with new compacted fill, the footing undercut excavations may also be brought back to planned grades with crushed stone such as American Association of State Highway and Transportation Officials (AASHTO) No.

57 stone. Compacted fill recommendations are included in Section 8.1 of this report.

Spread footings and continuous wall footings founded on new compacted structural fill or natural soils of Stratum B may be designed using a net allowable soil bearing pressure of up to 2,500 pounds per square foot (psf).