7394134 SpecAsOne - Vol 2 Appendix A.pdf

VOLUME 2of 2

APPENDIX A

Geotechnical Engineering Report

DEPARTMENT OF THE NAVY

NAVAL FACILITIES ENGINEERING SYSTEMS COMMAND, MID-ATLANTIC

MARINE CORPS AIR STATION, CHERRY POINT, NORTH CAROLINA

P-253 CONSTRUCT LIBRARY

AT THE

MARINE CORPS AIR STATION

CHERRY POINT, NORTH CAROLINA

STATION PROJECT NO: 7394134

DESIGNED BY:

MBF ARCHITECTS, PA

317-C POLLOCK STREET

NEW BERN, NORTH CAROLINA 28560

LEAD & ASBESTOS TESTING: ECS CAROLINAS, LLP

CIVIL: AVOLIS ENGINEERING, P.A.

STRUCTURAL: KAYDOS-DANIELS ENGINEERS, PLLC

INTERIOR DESIGN: WITHIN INTERIOR DESIGN

FIRE PROTECTION: JENSEN HUGHES

MECHANICAL/PLUMBING/ELECTRICAL: J P HARVET ENGINEERS

AUDIO/VISUAL: THORBURN ASSOCIATES, INC

LANDSCAPING: STANTEC CONSULTING SERVICES

SPECIFICATION PREPARED BY:

DARDEN J. EURE, III, MBF ARCHITECTS

20 MAY 2024

This page is intentionally left blank.

Report Cover Page

Construct Library – MCAS Cherry Point Geotechnical Engineering Report

March 15, 2024 | Terracon Project No. K6235057

Prepared for:

MBF Architects, P.A.

317-C Pollock Street New Bern, North Carolina 25860

2108 Capital Drive Wilmington, NC 28405

P (910) 478-9915 North Carolina Registered, F-0869

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

March 15, 2024

MBF Architects, P.A.

317-C Pollock Street New Bern, North Carolina 25860

Attn: Mr. Bill Faulkenberry P: (252) 637-6373 E: faulkenberry@mbfarchitects.com

Re: Geotechnical Engineering Report Construct Library – MCAS Cherry Point Franklin Road and Woodside Drive Havelock, North Carolina Terracon Project No. K6235057

Dear Mr. Faulkenberry:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PK3235100 dated April 7, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the proposed project.

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

Sincerely, Terracon

Michael P. Delaney, PE Justin L. DeNicola, PE Chris M. Caton, PE, PG, PMP Senior Staff Engineer Registered, NC 056487

Office Manager Registered, NC 046129

Senior Engineer Registered, NC 038365 hris M. Catoooon, PE, PG, PMP

Geotechnical Engineering Report Construct Library – MCAS Cherry Point | Havelock, North Carolina March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary ................................................................................................ i Introduction Project Description Site Conditions Geotechnical Characterization Geologic Setting Laboratory Chemical Analysis Seismic Site Class Liquefaction Geotechnical Overview Earthwork Shallow Foundations Floor Slabs Pavements Frost Considerations General Comments

Figures GeoModel Soil Profiles

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans Photography Log Exploration and Laboratory Results Supporting Information

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

Refer to each individual Attachment for a listing of contents.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic 1 Overview Statement 2

Project Description

Plans for the project include the construction of a new single-story library spanning approximately 18,000 square feet with associated paved parking and drives and stormwater management pond.

Geotechnical Characterization

The exploration encountered SAND (SM, SC, SP) extending to depths of 30 feet beneath existing site grade (bgs).

Groundwater was observed between depths of 7 feet and 11 feet bgs, corresponding to elevations between 12 feet and 17 feet

(NAVD 88).

Earthwork

The majority of the near-surface sands may be densified in place.

Near-surface Clayey SANDS (SC), such as those encountered at location S-01, S-02 and S-03, could become unstable with typical construction traffic and require undercut and replacement depending on moisture conditions at that time.

Based on the provided information, approximately 3 feet to 6 feet of structural fill will be required to develop final grade. The weight of the fill material is anticipated to induce roughly 1 inch to 3.5 inches of settlement on the underlying soils. Fill materials should be placed up to the proposed Finished Floor Elevation (FFE), and a 90-day waiting period should be implemented between fill placement and foundation construction. The wait period could be reduced based on the results of Settlement Monitoring.

Shallow Foundations

With subgrade prepared as noted in Earthwork.

Allowable bearing pressure = 2,500 psf Expected settlements: < 1-inch total, < ½-inch differential

Pavements

With subgrade prepared as noted in Earthwork:

■ 2” Asphalt over 8” Aggregate Base Course (ABC) (Light-

Duty)

■ 2” Surface + 3” Intermediate over 8” ABC (Heavy-duty)

■ 6” reinforced Concrete over 6” ABC (Heavy-duty)

Further details provided in the Pavements section of this report.

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed library to be located on the southwest corner of Franklin Road and Woodside Drive within Marine Core Air Station Cherry Point in Havelock, North Carolina. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification

■ Site preparation and earthwork

■ Demolition considerations

■ Foundation design and construction

■ Floor slab design and construction

■ Pavement design and construction

■ Stormwater pond considerations

The geotechnical engineering Scope of Services for this project included the advancement of Standard Penetration Test (SPT) borings, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown in the Site Location and Exploration Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and as separate graphs in the Exploration and Laboratory Results section.

Project Description

Our final understanding of the project conditions is as follows:

Item Description

Information Provided

Information for the project was provided via email from Mr. Bill Faulkenberry on April 4, 2023.

Project Description

Plans for the project include the construction of a new single-story library spanning approximately 18,000 square feet with associated paved parking/drives, sidewalks, landscaped areas, and a stormwater management pond.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Building Construction

Based on information provided by the structural engineer we understand the building will consist of metal stud framing clad with brick veneer and is proposed to bear on shallow foundations with a concrete slab-on-grade.

Finished Floor Elevation

26.75 feet (NAVD 88)

Maximum Loads

The following structural loading information was provided by Kaydos-Daniels Engineers, PLLC:

■ Columns: Up to 80 kips

■ Walls: Up to 3 kips per linear foot (klf)

■ Slabs: Up to 150 psf

Grading/Slopes Based on the provided information, 3 feet to 6 feet of structural fill will be required to develop final grade, excluding remedial grading requirements.

Pavements

Based on the provided plans, approximately 18,000 square feet of paved area is proposed, consisting of an asphalt parking lot with 36 spaces and a drive lane running along the south side of the building. The site plan indicates that portions of the drive lane will be concrete, as well as the associated dumpster pad enclosure. We anticipate that the parking lot will primarily be subject to traffic loading from passenger vehicles, while the main drives may experience additional traffic from semi-trucks and emergency vehicles.

Assumed traffic loading information and our derivation of pavement section thickness, is summarized in the Pavements section of this report, as well as the PCASE Pavement Design Report within Supporting Information.

Stormwater Management

Based on the provided plans, a stormwater management feature spanning approximately 7,650 square feet is proposed south of the proposed building. A depth of up to 7 feet is anticipated for the pond, assuming 1-foot contours on the provided plans.

Other Structures No below-grade structures or free-standing retaining walls are indicated on the provided plans or the project SAES.

Building Code 2018 North Carolina State Building Code (based on 2015 International Building Code)

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading information, as modifications to our recommendations may be necessary.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 3

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel Information

The site is located southwest of the corner of Franklin Road and Woodside Drive within MCAS Cherry Point in Havelock, North Carolina.

Approximate coordinates: 34.8993°N, 76.9071°W See Site Location

Existing Improvements

The project site currently consists of an unoccupied parcel within MCAS Cherry Point. Overhead and underground utilities, as well as a concrete sidewalk, are present on the site.

Current Ground Cover

The ground surface is mostly grass-covered with sporadic old growth trees. The soil borings were performed in grassed areas.

Existing Topography

Based on the provided topographic site plan, the site ranges in elevation from approximately 19 feet to 23.5 feet (NAVD 88).

Elevations within the proposed building footprint range from 21 feet to 23.5 feet (NAVD 88).

We also collected photographs at the time of our field exploration program.

Representative photos are provided in our Photography Log.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration and Laboratory Results attachment and the GeoModel can be found in the Figures attachment of this report.

Soil Profile

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 4

Model Layer

Layer Name General Description

N/A Surficial Materials

3 inches to 5 inches surficial, organic-laden material

1 SAND

SAND with varying amounts of Silt (SP, SM); loose to medium dense

Clayey

SAND

SAND with varying amounts of Clay (SC); very loose to medium dense

Groundwater Conditions

The initial groundwater level was estimated at the SPT boring locations as observed through the relative wetness of the recovered soil samples during the drilling operations.

The initial groundwater level was estimated to occur at depths of approximately 7 feet to 11 feet below existing grades at the boring locations, corresponding to elevations of approximately 12 feet to 17 feet (NAVD 88). Drilling fluids (water) are introduced into the boreholes during the drilling operations, impairing the ability to accurately determine the groundwater levels. Groundwater conditions may be different at the time of construction.

It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, tidal events, and other factors not evident at the time the boring was performed. In addition, perched water can develop within higher permeability soils overlying less permeable soils. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the boring logs.

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

The estimated seasonal high water table (ESHWT) can fluctuate from year to year depending on many factors that include, but are not limited to, natural drainage, tidal patterns, man-made drainage, surrounding development, and frequency and magnitude of rainfall patterns. Historically, the ESHWT is expected to occur within the “wetter” months of the year, typically November through April. However, periods of high groundwater tables are expected to occur at other times of the year (usually associated

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 5 with major weather events). A few criteria of ESHWT include hydric soil indicators (color patterns and shades), variation in density of the soils within the presumed fluctuation zone, and current and historical monitoring well data. Of the three listed, analyzing data obtained from current and historical groundwater monitoring programs tends to be the most reliable indicator of the ESHWT. Soil coloring (redoximorphic features, mottling, etc.) is the result of saturation cycles over numerous years. Hydric indicators and relying on density variations can lead to false readings as development and added drainage features continue to alter the fluctuation zones.

Based on current and historical groundwater monitoring data within the vicinity of the project site, a review of publications referencing groundwater behavior in the local area, and an observation of the surrounding topography in conjunction with the current performance of existing drainage features, we have estimated the seasonal high groundwater table (ESHWT) depth at the site to range from 3 feet to 5 feet below existing grades, corresponding to elevations of approximately 17 feet to 21 feet (NAVD 88).

Field Exploration

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

Four (4) 30-foot deep SPT borings (designated as S-01 through S-04) were drilled for the proposed library.

o Composite samples were taken from depths of 1 foot to 4 feet at locations S-02 and S-04 for corrosivity testing.

Two (2) 10-foot deep SPT borings (designated as P-01 and P-02) were drilled for proposed pavements.

o One (1) composite bulk soil sample, blended over a depth of 1 foot to 3 feet bgs, was collected from each location for laboratory classification index, proctor, and CBR testing.

One (1) 15-foot deep SPT boring (designated as BMP-01) was drilled for the proposed stormwater management feature.

o A temporary 15-foot deep piezometer was installed at this location, and stabilized groundwater levels were recorded.

All excess spoils and decontamination fluids were containerized in a 55-gallon drum and profiled for contaminant disposal. One (1) aqueous sample and one (1) composite sample were collected from the 55-gallon Investigative Derived Waste (IDW) drum for analytical testing.

The SPT borings were performed with the use of rotary wash “mud” drilling procedures in general accordance with ASTM D 1586. The tests were performed continuously from

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 6 the existing ground surface to a depth of 10-feet at the pavement boring locations, and to a depth of 12-feet, and at 5-foot intervals thereafter starting at a depth of 13.5-feet at the structural boring locations. The soil samples were obtained with a standard 1.4” I.D., 2” O.D., 30” long split-spoon sampler. The sampler was driven with blows of a 140

lb. hammer falling 30 inches, using an automatic hammer. The number of blows required to drive the sampler each 6-inch increment of penetration was recorded and is shown on the boring logs. The sum of the second and third penetration increments is termed the SPT N-value (uncorrected for automatic hammer). A representative portion of each disturbed split-spoon sample was collected with each SPT, placed in a glass jar, sealed, labeled, and returned to our laboratory for review.

The soil boring and sampling operations were monitored and logged on-site on a full-time basis by an appropriately trained geotechnical representative. All boreholes that penetrated the groundwater table were backfilled upon completion with a cement-bentonite grout mix.

A temporary groundwater monitoring well was installed adjacent to boring location BMP- 01 to a depth of approximately 15 feet below existing grade for the purpose of obtaining delayed groundwater level readings following the completion of initial drilling. The monitoring well was constructed of 2-inch diameter, Schedule 40 PVC materials. A 5-foot section of 0.010-inch slotted screen was placed in the borehole with casing threaded to the top. An appropriate graded sand pack (10/20 mesh Silica Sand) was placed around the screen and extended 1 to 2 feet above the top of the screen. Bentonite seal was then placed above the sand pack up to the ground surface and hydrated with potable water.

The exploration locations were established in conjunction with the Client. The exploration locations were staked in the field by a Terracon representative with a handheld GPS device and by corroborating the location with easily identifiable landmarks.

The approximate boring locations are shown in the attachment of this report.

Field and Laboratory Testing

Soil testing was performed in accordance with American Society for Testing and Materials (ASTM) standards. All soils and materials tests were performed in our AASHTO re:source certified Wilmington, North Carolina laboratory.

Soil Classification and Index Testing

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

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 7 manual methods in general accordance with ASTM D2488 using the Unified Soil Classification System (USCS).

Soil samples that were selected for index testing were classified in general accordance with ASTM D2487. It should be noted that some variation can be expected between samples classified using the visual-manual procedure (ASTM D2488) and the USCS (ASTM D2487). A summary of the soil classification system is provided in the Supporting Information attachment of this report.

Representative split-spoon soil samples were selected and subjected to natural moisture, #200 sieve wash, and Atterberg Limits testing in order to corroborate the visual classification. These test results, along with the soil test boring logs, are presented in the Exploration and Laboratory Results attachment of this report. Generalized subsurface soil profiles are provided in the Figures attachment of this report.

Bulk Soil Sample CBR Testing

CBR testing was performed in accordance with the project’s SAES (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 sample was 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 the specimen. If necessary, the stress-strain curve was corrected by adjusting the location of the origin for concave shaped curves. Subsequently, the CBR value was selected at 0.1-inch penetration using the corrected load value. In addition, the bulk soil sample was subjected to Atterberg Limits, natural moisture content, and grain size distribution testing in general accordance with ASTM standards. These test results are presented in the Exploration and Laboratory Results attachment of this report.

Geologic Setting

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

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

Across the outer Coastal Plain, the Pliocene age Yorktown Formation of the Tertiary Period is widespread, occurring from Maryland to North Carolina. Its age is estimated between 4.8 million and 2.8 million years and is estimated to have been deposited during three transgressive episodes. The depositional environment was shallow marine in nature, consisting of inner shelf, barrier-island, estuarine and lagoonal patterns. The Yorktown Formation is a glauconitic, fossiliferous, Silty to Clayey greenish-gray fine Sand. This material has been pre-consolidated by an increased effective overburden pressure generated due to a drop in the sea level at the end of the Tertiary Period, and

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 8 by previously overlying sediments, which eroded away as the sea level subsequently lowered.

As sea levels rose during the Pleistocene Epoch of the Quaternary Period, areas within the project limits were filled and overlain by soils of the Yorktown Formation and Duplin Formation, Undivided (Tertiary), which is composed of fluvial and estuarine deposits.

The geologic stratigraphy encountered in our subsurface explorations generally consisted of marine deposited Sands and Clays of this formation.

Laboratory Chemical Analysis

Corrosivity

Two (2) composite soil samples were created from soils collected at depths of 1 foot to 4 feet below the existing ground surface from boring locations S-02 and S-04. The table below lists the results of laboratory soluble sulfate, sulfide, chloride, electrical resistivity, oxidation-reduction potential, pH testing, moisture, and total salts. The values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction.

Corrosivity Results Location Units S-02 S-04 Depth Feet (bgs) 1.0’ – 4.0’ 1.0’ – 4.0’ Moisture Content1 % 19.3 (1) 15.5 (1) pH 2 Standard Units 4.71 (0) 5.85 (0)

Oxidation/Reduction Potential 3 mV +564 (0) +551 (0)

Resistivity 4 ohms-cm 40,000 (0) 38,000 (0)

Sulfide 5 mg/Kg Nil (0) Nil (0)

Chloride 6 mg/Kg 13 (2) 11 (2)

Sulfate 7 mg/Kg 31 22

Total Salts 8 mg/kg 78 95

1. ASTM D 2216

2. ASTM G 51

3. ASTM G 200

4. ASTM G 57

5. AWWA 4500-S D

6. APHA 4500-Cl E

7. ASTM D516-07

8. AWWA 2520 B

9. (x) = Points Assigned per the DIPRA and AWWA C-105 Standard 10-Point Evaluation. 10 points or greater indicates that soil is corrosive to ductile-iron pipe in accordance with American Water Works Association standards.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 9

Results of soluble sulfate testing can be classified in accordance with ACI 318 – Building Code Requirements for Structural Concrete. Numerous sources are available to characterize corrosion potential to buried metals using the parameters above. Based on the above-indicated sulfate concentrations and the exposure classes and categories indicated on table 4.2.1 of the ACI 318-11, the on-site soils may be considered non-corrosive to concrete.

ANSI/AWWA is commonly used for ductile iron, while threshold values for evaluating the effect on steel can be specific to the buried feature (e.g., piling, culverts, welded wire reinforcement, etc.) or agency for which the work is performed. Imported fill materials may have significantly different properties than the site materials noted above and should be evaluated if expected to be in contact with metals used for construction.

Consultation with a NACE certified corrosion professional is recommended for buried metals on the site. 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 selected locations appear to be non-corrosive to ductile-iron pipe.

Analyte Testing

Drilling spoils and fluids generated during subsurface exploration were containerized in a 55-gallon drum. One (1) composite sample and one (1) liquid sample were collected.

These samples were analyzed for a combination of the following:

Full Toxicity Characteristic Leaching Procedure (TCLP) including metals, volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), herbicides, pesticides, and polychlorinated biphenyls (PCBs) via EPA methods (varies)

Total Petroleum Hydrocarbons (TPH) – Diesel Range Organics (DRO) and Gasoline Range Organics (GRO) via EPA method 8015C

Reactivity, ignitability, and corrosivity via EPA methods (varies)

PFAS via EPA draft method 1633

Additionally, each soil interval was screened in the field for organic vapors using a MiniRae 3000 photoionization detector; no organic vapors were detected during the field exploration.

The following table provides a summary of the analyte compounds that were identified during laboratory analysis of the samples taken from the site. Analytes that were not identified are not included in the table.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 10

Summary of Detected Analytes

Source (Matrix)

TCLP

Metals (mg/L)

Total Cyanide (mg/L)

TPH

(mg/L or mg/kg)

BTEX PFAS

Compound Concentration

(μg/L) Compound

Concentration (μg/L)

IDW

Drum (Solid)

Barium 0.090J

ND

GRO 9.81

-- ND -- ND

DRO 5.09J

IDW

Drum

(Liquid)

ND 0.0040J

GRO 0.0507J Toluene 0.96J PFHxA 0.0060J

PFOA 0.0052J

DRO 0.395 Xylene 1.2J PFHxS 0.0092J

PFOS 0.0074J

1. ND = Analyte(s) Not Detected Above Lab. Method Detection Limit

2. mg/Kg = milligrams/Kilogram or parts per million

3. mg/L = milligrams per liter or parts per million

4. μg/L = micrograms per liter or parts per billion

5. J = Results greater than the method detection limit but less than the limit of quantitation

6. Detection Limits = See Analytical Sheets in Exploration and Laboratory

Results

Investigative Derived Waste (IDW) was determined to be non-hazardous from a disposal perspective. A waste manifest must be signed by the Generator (Cherry Point EAD representative). Per Cherry Point EAD guidance, the liquid IDW requires solidification and landfilling as non-hazardous waste. The samples were determined not to exhibit corrosive, ignitable, and/or reactive waste characteristics. The samples produced PFAS compounds that did not cumulatively exceed 70 nanograms per Liter (ng/L) or parts per trillion (ppt).

It is important to note that the contractor is responsible for the characterization of all generated waste during construction prior to disposal to ensure compliance with Federal and North Carolina Solid Waste Management Regulations. The results of the TCLP analysis did not identify chemicals of concern at concentrations considered to be hazardous waste, nor do they exceed the applicable regulatory standards from an exposure perspective. However, due to the TPH detections in the soil, surplus soils generated during construction w require disposal as petroleum impacted and can be disposed of at a RCRA Subtitle D Landfill. If dewatering will occur, the water should be tested and disposed of appropriately based on the groundwater concentrations and applicable PFAS regulations at the time of dewatering.

The analytical results for the aqueous and composite samples are provided at the end of the Exploration and Laboratory Results attachment of this report.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 11

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7-16 and the International Building Code (IBC). Based on the soil properties observed at the site and as described on the exploration logs and results, as well as our extensive experience in the vicinity of the project site, it is our professional opinion that a Seismic Site Classification of D be considered for the project. Due to site-specific constraints on boring depth, subsurface explorations at this site were extended to a maximum depth of 30 feet.

The ASCE 7 Hazard Tool in reference to ASCE 7-16, utilizing a Risk Category II and a Site Class D, in conjunction with the USGS hazard tool, identified the mean Peak Ground Acceleration adjusted for Site Class (PGAM) to equal 0.05958g (unit represents gravitational acceleration). Determination of seismic design parameters for the site is summarized in Supporting Information. Pertinent design parameters are indicated in the table below:

Item Value United States Seismic Zone 1

Maximum Considered Earthquake (MCER) Ground Motion for 0.2 Second Period, SS

0.096

MCER Ground Motion for 1.0 Second Period, S1 0.048

Site Amplification Factor (0.2 Second Period), Fa 1.6

Site Amplification Factor (1.0 Second Period), FV 2.4

Site-Modified Spectral Acceleration Value, SMS 0.153

Site-Modified Spectral Acceleration Value, SM1 0.115

Design Spectral Response Acceleration (0.2 Second Period), SDS

0.102

Design Spectral Response Acceleration (1.0 Second Period), SD1

0.077

Liquefaction

Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction primarily occurs in saturated clean Sands and Silty Sands having low relative densities, while soils containing at least 15% Clay with a liquid limit greater than 35% are typically not susceptible to

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 12 liquefaction. Based on this criterion, the subsurface cohesionless soils at this project site exhibit the characteristics necessary for liquefaction.

The site’s liquefaction potential was analyzed in accordance with various calculation methods including Boulanger & Idriss (2014) utilizing SPT blow counts. The maximum liquefaction settlement at the site is estimated to be less than 1 inch. Based on the earthquake probability and the liquefaction analysis, liquefaction is unlikely to occur under the design event and thus, special construction considerations to account for soil liquefaction do not appear necessary at this project site, and the following potential consequences are not applicable:

Total and differential settlement

Lateral soil movement

Lateral soil loads on foundations

Reduction in foundation soil-bearing capacity and lateral soil reaction

The liquefaction assessment is provided in the Supporting Information attachment of this report.

Geotechnical Overview The exploration encountered very loose to medium dense SAND (SP, SM, SC) extending to depths of 30 feet bgs. Groundwater was observed at depths ranging from 7 feet to 11 feet bgs, corresponding to elevations of approximately 12 to 17 feet (NAVD 88). The predominant soils within the project site are mapped by the Soil Survey of Craven County, North Carolina. The soils encountered in the exploration appear to be consistent with these soil series. A map of these soil series is presented in the Supporting Information section of this report.

Based on the provided information, approximately 3 feet to 6 feet of structural fill will be required to develop final grade at the site. The planned grading is estimated to induce 1 inch to 3.5 inches of settlement on the underlying soils. The anticipated settlement will be elastic in nature (immediate settlement) as the subsurface soils generally consisted of granular materials (Sand). To comply with the project’s specifications, a 90-day waiting period should be implemented between fill placement and foundation construction to mitigate the potential for excessive foundation settlement. Prior to the waiting period, fill materials should be placed up to the proposed Finished Floor Elevation (FFE) to reduce differential floor slab movements to less than 1/500. The recommendations provided in the Settlement Monitoring section of this report should be implemented in areas of the site to receive 3 or more feet of structural fill. The waiting period could be reduced based on the results of settlement monitoring.

Remediation of the existing subgrade, as discussed in Earthwork, should be performed prior to the placement of structural fill in building and pavement footprints. Near-surface

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 13

Clayey SAND (SC) materials, such as those encountered at locations S-01, S-02, and S- 03, could become unstable with typical construction traffic and require undercut and replacement depending on moisture conditions at the site at that time. Grading for the proposed structure should incorporate the limits of the foundations plus a lateral distance of 5 feet beyond the outside edge of footings, where space is available.

Based on the laboratory classification results, the uncontrolled fill and other shallow subsurface SAND soils encountered at the boring locations have limited potential for expansion in accordance with International Building Code 1803.5.3. As such, subsurface soil improvements do not appear necessary for shrink-swell considerations.

Our opinion of pavement section thickness design has been developed based on our understanding of the intended use, assumed traffic, and subgrade preparation recommended herein. The Pavements section includes our recommended parameters for subgrade support and our recommended minimum pavement section thicknesses.

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

Earthwork

Earthwork is anticipated to include demolition, clearing and grubbing, excavations, and structural fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Demolition

Site preparation should begin with the demolition of the existing sidewalks and debris removal. As part of the demolition, buried utilities and/or concrete foundations should also be removed. Existing utilities that are to be abandoned should be removed or filled with grout. The excavations resulting from foundation and utility removal should be properly backfilled with compacted structural fill as described in the following subsections. Utilities that are to remain in service should be accurately located horizontally and vertically to minimize conflict with new foundation construction.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 14

Site Preparation

Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.

Based on the results of our exploration, topsoil thickness measurements ranged from approximately 3 to 5 inches. Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

Although no evidence of existing fill soils or underground facilities (such as septic tanks, cesspools, basements, and utilities) was observed during the exploration and site reconnaissance, such features could be encountered during construction. If unexpected existing fill soils or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

Subgrade Preparation

After stripping and removing topsoil and once any areas of cut have been excavated to proposed subgrade elevation, the exposed subgrade soils in the building and pavement footprints should be densified in place using a medium weight vibratory roller. The purpose of the vibratory rolling is to densify the exposed subgrade soils for floor slab and pavement support and to potentially improve the foundation bearing soils. The roller should make at least six passes across the site, with the second set of three passes perpendicular to the first set of three passes with intermittent vibration activated. If water is brought to the surface by the vibratory rolling, the operation should be discontinued until the water subsides. Vibratory rolling should be completed during dry weather. Static rolling and additional repairs should be anticipated for areas too wet for vibratory rolling.

After the vibratory rolling, pore pressures should be allowed to dissipate for a minimum of 16 hours. After the waiting period, proofrolling should be performed on the exposed subgrade soils in areas to receive fill or at the subgrade elevation with a loaded, tandem-axle dump truck (15 to 20 ton total vehicle weight) or similar rubber-tired construction equipment. Proofrolling is recommended as a means of detecting areas of soft or unstable subgrade soils. The proofrolling should be performed during a period of dry weather to avoid degrading an otherwise suitable subgrade. The proofrolling operations should be observed by a representative of the geotechnical engineer.

Subgrade soils that exhibit excessive rutting or deflection during proofrolling should be repaired as directed by the field representative. Typical repairs include overexcavation followed by replacement with either properly compacted fill or by a subgrade stabilization fabric in conjunction with a sand fill or crushed stone.

If subgrade soils are unsuitable, they will require removal and replacement; however, if they are unstable due to excessive moisture, the most economical solution for remediation may be to scarify, dry and recompact the material. This remediation is most effective during the typically hotter months of the year (May to October). If

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 15 construction is performed during the cooler period of the year, the timeline for scarifying, drying, and recompacting typically increases considerably and may lead to alternative remediation solutions. These solutions can include overexcavation of some or all of the unstable material to be backfilled with either approved structural fill or geotextile and ABC Stone. Potential undercutting can be reduced if the site preparation work is performed during a period of dry weather and if construction traffic is kept to a minimum on prepared subgrades. We recommend that the contractor submit a unit rate cost for undercutting as part of the bidding process.

All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 10 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. Compacted structural fill soils should then be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation or pavement construction.

Fill Material Types

Earthen materials used for structural fill should meet the following material property requirements:

Soil Type1 USCS Classification Acceptable Location for

Placement

Imported Soil

GW, GP, GM, GC, SW,

SP, SP-SM

All locations and elevations

On-Site Soils

SC2, SM, SP

(LL<50 or PI<20) All locations and elevations

1. Structural fill should consist of approved materials free of organic matter and debris.

Frozen materials should not be used, and fill should not be placed on frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

2. Reuse of Clayey SAND (SC) materials could lead to delays in construction depending on moisture conditions at the site at that time.

Fine-grained soils such as clays and silts should not be reused as structural fill due to their moisture sensitivity when compared to the sandier soils available. Silty and Poorly Graded SAND (SM, SP) materials excavated from the proposed stormwater management feature may be evaluated for reuse as structural fill.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 16

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements. General fill includes fill materials used to achieve design grade in landscaped (non-structural) areas.

Item Structural Fill General Fill

Maximum Lift Thickness

8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used

Same as structural fill

Minimum Compaction

Requirements 1,2,3 98% of maximum 92% of max.

Water Content

Range 1, 3 Within 3 percentage points of optimum moisture content

As required to achieve min.

compaction requirements

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

2. It is not necessary to achieve 95% compaction on the existing ground prior to placing fill or beginning construction. However, the subgrade should be evaluated by the Geotechnical Engineer prior to placing fill or beginning construction.

3. Maximum density and optimum water content as determined by the standard Proctor test (ASTM D 698).

4. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least 70% relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility being supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 17

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the material requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. Earthwork operations should be performed during the warmer, drier periods of the year (May through October) to avoid problems associated with a wet subgrade.

Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided.

The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the

March 15, 2024 | Terracon Project No. K6235057

Facilities | Environmental | Geotechnical | Materials 18 affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

Groundwater encountered in deeper excavations should be pumped out from sumps or well points if applicable. Pumping water, as required, should continue until excavations are completely backfilled.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts.