Attachment 03 Croatan Ranger District Geotechnical.pdf

ECS Southeast, LLP Geotechnical Engineering Report

Croatan Ranger Station

New Bern, Craven County, North Carolina

ECS Project No. 22:31399

February 23, 2022

February 23, 2022 Mr. Sam Karahalis USDA Forest Service 141 E Fisher Ave.

New Bern, NC 28560

ECS Project No. 22:31399

Reference: Geotechnical Engineering Report Croatan Ranger Station New Bern, Craven County, North Carolina

Dear Mr. Karahalis:

ECS Southeast, LLP (ECS) has finished the subsurface exploration and geotechnical engineering analyses for the above-referenced project. Our services were performed in general accordance with our agreed to scope of work. This report presents our understanding of the geotechnical aspects of the project along with the results of the field exploration and our design and construction recommendations.

It has been our pleasure to be of service to the USDA Forest Service during the design phase of this project. We would appreciate the opportunity to remain involved during the continuation of the design phase, and we would like to provide our services during construction phase operations as well to verify subsurface conditions assumed for this report. Should you have questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, ECS Southeast, LLP

Mike Delaney, E.I. Winslow Goins, PE Project Manager Principal Engineer MDelaney@ecslimited.com WGoins@ecslimited.com

Croatan Ranger Station February 23, 2022 ECS Project No. 22:31399 Page i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 Project Location/Current Site Use/Past Site Use

2.2 Proposed Construction

3.0 FIELD EXPLORATION testing

3.1 Subsurface Characterization

3.2 Groundwater Observations

4.0 DESIGN RECOMMENDATIONS

4.1 Deep Foundations ................................................................... Error! Bookmark not defined.

4.2 Pavements

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 Subgrade Preparation

5.1.1 Stripping and Grubbing

5.1.2 Proofrolling

5.1.3 Site Temporary Dewatering

5.2 Earthwork Operations

5.2.1 Structural Fill

5.3 Utility Installations

6.0 CLOSING

APPENDICES

Appendix A – Drawings & Reports Site Location Diagram Exploration Location Diagram

Appendix B – Field Operations

Reference Notes for CPT Soundings Cone Penetration Test Sounding Logs (S-1 and S-2) Reference Notes for Boring Logs Hand Auger Logs (K-1 through K-3) Kessler DCP Test Results (K-1 throughK-3)

Appendix C – Supplemental Report Documents

GBA Document

ECS Project No. 22:31399 Page 1

EXECUTIVE SUMMARY

The following summarizes the main findings of the exploration, particularly those that may have a cost impact on the planned development. Further, our principal foundation recommendations are summarized. Information gleaned from the executive summary should not be utilized in lieu of reading the geotechnical report.

The geotechnical exploration performed for the site included two (2) electronic cone penetration test (CPT) soundings drilled to termination depths ranging from approximately 35 to 45 feet.

Three (3) Kessler dynamic cone penetrometer (DCP) tests with hand auger borings were performed in the proposed pavements.

The proposed structure can be supported on a deep foundation system consisting of 8-inch round tip timber piles embedded to depths of 36 feet beneath existing grades for an axial capacity of 18 kips. Alternative embedment depths and their respective capacities are listed in section 4.1 of this report.

Groundwater was encountered in the soundings and borings at depths ranging from approximately 3.25 to 3.67 feet below existing grade. Groundwater was not encountered in hand auger borings K-1 and K-3 at the depths explored.

Due to the near-surface soft CLAY (CL) encountered in the hand auger borings, ECS recommends undercutting to depths of 2 feet beneath existing grades and backfilling with approved structural fill prior to the construction of pavements and placement of fill.

Please note this Executive Summary is an important part of this report and should be considered a “summary” only. The subsequent sections of this report constitute our findings, conclusions, and recommendations in their entirety.

ECS Project No. 22:31399 Page 2

1.0 INTRODUCTION

The purpose of this study was to provide geotechnical information for the design of foundations for the proposed new ranger station off of East Fisher Avenue in New Bern, North Carolina. The recommendations developed for this report are based on project information supplied by Mr. Sam Karahalis of the USDA Forest Service.

Our services were provided in accordance with our Proposal Nos. 22:25942.Rev1 and 22:25959 dated February 7, 2022, as authorized by authorized by Mr. Sam Karahalis on February 10, 2022, which includes our Terms and Conditions of Service.

This report contains the procedures and results of our subsurface exploration programs, review of existing site conditions, engineering analyses, and recommendations for the design and construction of the project.

The report includes the following items.

A brief review and description of our field test procedures and the results of testing conducted;

A review of surface topographical features and site conditions;

A review of subsurface soil stratigraphy with pertinent available physical properties;

Deep foundation recommendations including embedment depths, axial and uplift capacities;

Site development recommendations;

Pavement design recommendations;

Suitability of soils for use as fill material;

Discussion of groundwater impact;

Compaction recommendations;

Site vicinity map;

Exploration location plan;

Hand auger boring logs with Kessler DCP test results; and CPT sounding logs.

ECS Project No. 22:31399 Page 3

2.0 PROJECT INFORMATION

2.1 PROJECT LOCATION/CURRENT SITE USE/PAST SITE USE

The proposed site is located off of E Fisher Avenue in New Bern, Craven County, North Carolina. The site is bounded on the west by the National Forest Work Center, on the south by E Fisher Avenue, and on the north and east by wooded land and the Neuse River. Figure 2.1.1 below shows an image of where the site is located.

Figure 2.1.1 Site Location

At the time of our exploration, the site had been cleared. Based on our site visit and approximate elevations from Google Earth, the site is relatively level with typical elevations on site ranging from approximately 26 to 27 feet.

2.2 PROPOSED CONSTRUCTION

The following information explains our understanding and assumptions of the planned development including proposed buildings and related infrastructure. Additional information including anticipated structural loading and grading information was not available at the time of this report.

SUBJECT DESIGN INFORMATION / ASSUMPTIONS

Usage Ranger Station Column Loads Up to 50 kips Wall Loads Up to 3 kips per linear foot (klf)

ECS understands the project consists of construction of a new approximately 6,000 square-foot ranger station with associated paved parking and drives.

ECS Project No. 22:31399 Page 4

3.0 FIELD EXPLORATION TESTING

Our exploration procedures are explained in greater detail in Appendix B including the Reference Notes for Cone Penetration Soundings. Our scope of work included performing two (2) CPT soundings and three

(3) hand auger borings with Kessler DCP tests. Our approximate CPT soundings and hand auger boring locations are shown on the Exploration Location Diagram in Appendix A.

3.1 SUBSURFACE CHARACTERIZATION

The subsurface conditions encountered were generally consistent with published geological mapping.

The following sections provide generalized characterizations of the soil. Please refer to the CPT sounding logs and hand auger boring logs in Appendix B.

The site is located in the Coastal Plain Physiographic Province of North Carolina. The Coastal Plain is composed of seven terraces, each representing a former level of the Atlantic Ocean. Soils in this area generally consist of sedimentary materials transported from other areas by the ocean or rivers. These deposits vary in thickness from a thin veneer along the western edge of the region to more than 10,000 feet near the coast. The sedimentary deposits of the Coastal Plain rest upon consolidated rocks similar to those underlying the Piedmont and Mountain Physiographic Provinces. In general, shallow unconfined groundwater movement within the overlying soils is largely controlled by topographic gradients.

Recharge occurs primarily by infiltration along higher elevations and typically discharges into streams or other surface water bodies. The elevation of the shallow water table is transient and can vary greatly with seasonal fluctuations in precipitation.

Table 3.1.1 Subsurface Stratigraphy

Approximate Depth Range

Stratum Description Ranges of N*-Values(1) blows per foot (bpf)

0 to (0.67-0.75) N/A Topsoil was encountered on-site with an observed thickness of approximately 8 to 9 inches. Deeper topsoil or organic laden soils are most likely present in wet, poorly drained areas and potentially unexplored areas of the site.

N/A

(0.67-0.75) to 23.0 I Very Soft to Firm, Sandy Lean, Silty, and Fat CLAY (CL, CL- ML, CH); Moist to saturated

1 to 5

23.0 to 30.0 II Loose to Dense, Silty and Clean SAND (SM, SP); Saturated 9 to 45

30.0 to 43.0 III Medium Dense, Silty SAND (SM) and Firm to Stiff, Sandy SILT (ML); Saturated

10 to 25

43.0 to 44.5 IV Very Dense, Silty and Clean SAND (SM, SP); Saturated 25 to 50

Notes: (1) Equivalent Corrected Standard Penetration Test Resistances

3.2 GROUNDWATER OBSERVATIONS

Water levels were measured in our CPT soundings are shown in Appendix B. Groundwater depths measured at the time of drilling ranged from 3.25 to 3.67 feet below the ground surface. Groundwater was not encountered in hand auger borings K-1 and K-3 at the depths explored. Variations in the long-term water table may occur as a result of changes in precipitation, evaporation, surface water runoff, construction activities, and other factors.

ECS Project No. 22:31399 Page 5

4.0 DESIGN RECOMMENDATIONS

4.1 DEEP FOUNDATIONS

The proposed construction can be supported on a deep foundation system consisting of driven timber piles. The following table shows the allowable pile capacity for 8-inch tip round timber piles with 12-inch butts. The embedment depth listed is in reference to the existing grade at the time the sounding was performed.

Table 4.1.1: 8-Inch Tip Round Timber Piles (Tapered) Embedment Depth

(Feet) Axial Capacity

(kips) Uplift (kips)

25 10 1.8

28 12 2.5

34 17 3.8

36 18 4.3

In our opinion, piles installed to depths shallower than recommended depths, would not provide long-term stability of the proposed structure. Piles embedded at depths between the recommended depths will not support axial loads. Pile capacity analyses were performed assuming a free head condition and the provided compression and tension capacities are based on a factor of safety of 2.0 and 3.0, respectively. It is recommended that minimum spacing of the piles be equal to 36 inches (center to center).

We recommend that the pile driving hammer used to install each timber pile have a rated energy blow of 9,000 foot-pounds or higher. Driving criteria and bearing elevations should be established prior to driving piles. Based on the subsurface conditions, we recommend that the piles installed be limited to a pre-auger depth of approximately 10 feet below existing grades.

It is suggested that several over length piles be driven prior to the start of production pile driving, to establish the driving criteria, pile lengths to be ordered and to determine if auger “pilot” holes are justified. Production piles should not be ordered until the pile lengths can be determined. Two over length piles are recommended for the structure.

The over length piles could be driven in production pile locations. Pile installation operations and load tests, if necessary, should be monitored by a senior soil technician working under the supervision of a Licensed Engineer. ECS would be pleased to develop driving criteria for the project once the method of installation and the contractor has been selected.

ECS Project No. 22:31399 Page 6

4.2 PAVEMENTS

Subgrade Characteristics: Based on the results of our hand auger borings, it appears that the pavement subgrades will consist mainly of Approved Structural Fill. Due to the near-surface soft CLAY (CL) encountered in the hand auger borings, ECS recommends undercutting to depths of 2 feet beneath existing grades and backfilling with approved structural fill prior to the construction of pavements and placement of fill.

California Bearing Ratio (CBR) values were obtained from the Kessler DCP tests performed on site adjacent to the hand auger borings. For preliminary design purposes, provided subgrade preparation recommendations and in-place densification recommendations are followed, we recommend assuming a preliminary CBR value of 10.

We were not provided traffic loading information, so we have assumed loadings typical of this type of project. Our recommended pavement sections are based on up to 25,000 ESALs over a 20 year design life for light duty and up to 75,000 ESALs over a 20 year design life for heavy duty.

The preliminary pavement sections below are guidelines that may or may not comply with local jurisdictional minimums.

PROPOSED PAVEMENT SECTIONS

FLEXIBLE PAVEMENT RIGID PAVEMENT

MATERIAL Heavy Duty Light Duty Heavy Duty Light Duty

Portland Cement Concrete (f’c = 4000 psi) - - 6.5 in. 5 in.

Asphalt Surface Course 3 in 2 in - - Aggregate Base Course (ABC) 8 in 6 in 4 in. -

In general, heavy duty sections are areas that will be subjected to trucks, buses, or other similar vehicles including main drive lanes of the development. Light duty sections are appropriate for vehicular traffic and parking areas.

Large, front loading trash dumpsters frequently impose concentrated front wheel loads on pavements during loading. This type of loading typically results in rutting of asphalt pavement and ultimately pavement failures. For preliminary design purposes, we recommend that the pavement in trash pickup areas consist of a 6.5-inch thick, 4,000 psi, reinforced concrete slab overlying 4 inches of ABC stone. When traffic loading becomes available ECS or the Civil Engineer can design the pavements.

Prior to subbase placement and paving, CBR testing of the subgrade soils (both natural and fill soils) should be performed to determine the soil engineering properties for final pavement design. The soil subgrade should be smooth-rolled and proofrolled prior to ABC placement. Areas that pump, rut, or are otherwise unstable should be re-compacted or undercut and replaced. The ABC should conform to the gradation, liquid limit, plasticity index, resistance to abrasion, and soundness per Section 1005 of the 2012 NCDOT Standard Specifications for Roads and Structures.

ECS Project No. 22:31399 Page 7

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 SUBGRADE PREPARATION

5.1.1 Stripping and Grubbing

The subgrade preparation should consist of stripping vegetation, rootmat, topsoil, and soft or loose materials from the 10-foot expanded building and 5-foot expanded pavement limits. Borings performed in undisturbed areas of the site encountered approximately 8 to 9 inches of topsoil. Deeper topsoil or organic laden soils may be present in wet, poorly drained areas of the site. ECS should be retained to verify that the topsoil and unsuitable surficial materials have been removed prior to the placement of structural fill or construction of structures.

5.1.2 Proofrolling

Prior to fill placement or other construction on subgrades, the subgrades should be evaluated by an ECS field technician. The exposed subgrade should be proofrolled with construction equipment having a minimum axle load of 10 tons [e.g. tandem-axle dump truck loaded to capacity]. Proofrolling should be traversed in two perpendicular directions with overlapping passes of the vehicle under the observation of an ECS technician. This procedure is intended to assist in identifying localized yielding materials.

Where proofrolling identifies areas that are unsteady or “pumping” subgrade those areas should be repaired prior to the placement of subsequent Structural Fill or other construction materials. Methods of stabilization include undercutting and moisture conditioning. The situation should be discussed with ECS to determine the appropriate procedure. Test pits may be excavated to explore the shallow subsurface materials to help in determining the cause of the observed unsteady materials, and to assist in the evaluation of appropriate remedial actions to stabilize the subgrade. Due to the near-surface soft CLAY (CL) encountered in the hand auger borings, ECS recommends undercutting to depths of 2 feet beneath existing grades and backfilling with approved structural fill prior to the construction of pavements and placement of fill.

5.1.3 Site Temporary Dewatering

Perched Groundwater: After periods of precipitation, surface water can be characterized as being broadly perched above less permeable materials. In low-lying areas, the presence of perched water is more pronounced after rain events. Once the site is graded to drain and storm features are installed, ECS anticipates the perched conditions will become less pronounced after rain events.

Temporary Dewatering: Temporary dewatering operations can be handled by the use of conventional submersible pumps directly in the excavation or temporary trenches to direct the flow of water and to remove water from the excavation. If temporary sump pits are used, we recommend they be established at an elevation 3 to 5 feet below the bottom of the excavation subgrade or bottom of footing. A perforated 55-gallon drum or other temporary structure could be used to house the pump. We recommend continuous dewatering of the excavations using pumps during construction.

ECS Project No. 22:31399 Page 8

5.2 EARTHWORK OPERATIONS

5.2.1 Structural Fill

Prior to placement of Structural Fill, bulk samples (about 50 pounds) of on-site and/or off-site borrow should be submitted to ECS for laboratory testing, which typically include Atterberg limits, natural moisture content, grain-size distribution, and moisture-density relationships (i.e., Proctors) for compaction. Import materials should be tested prior to being hauled to the site to determine if they meet project specifications. Alternatively, Proctor data from other accredited laboratories can be submitted if the test results are within the last 90 days.

Structural Fill Materials: Materials selected for use as structural fill should consist of inorganic soils with the following engineering properties and compaction requirements.

STRUCTURAL FILL INDEX PROPERTIES

Subject Property

Building and Pavement Areas LL < 40, PI<10

Max. Particle Size 3 inches

Fines Content Max. 20 %

Max. organic content 5% by dry weight

STRUCTURAL FILL COMPACTION REQUIREMENTS

Subject Requirement

Compaction Standard Standard Proctor, ASTM D698

Required Compaction 98% of Max. Dry Density

Maximum Dry Density >100 pcf

Moisture Content -2 to +2 % points of the soil’s optimum value Loose Thickness 8 inches prior to compaction

On-Site Borrow Suitable: No significant natural deposits of possible fill material are present on the site.

Fill Placement: Fill materials should not be placed on frozen soils, on frost-heaved soils, and/or on excessively wet soils. Borrow fill materials should not contain frozen materials at the time of placement, and frozen or frost-heaved soils should be removed prior to placement of structural fill or other fill soils and aggregates. Excessively wet soils or aggregates should be scarified, aerated, and moisture conditioned.

5.3 UTILITY INSTALLATIONS

Utility Subgrades: The soils encountered in our exploration are not expected to be generally adequate for support of utility pipes. The pipe subgrades should be observed and probed for stability by ECS. Loose or unsteady materials encountered should be removed and replaced with compacted Structural Fill, or pipe stone bedding material.

ECS Project No. 22:31399 Page 9

Utility Backfilling: The granular bedding material (AASHTO #57 stone) should be 4 inches thick, but not less than that specified by the civil engineer’s project drawings and specifications. We recommend that the bedding materials be placed up to the springline of the pipe. Fill placed for support of the utilities, as well as backfill over the utilities, should meets the requirements for structural fill and fill placement.

Excavation Safety: Excavations and slopes should be constructed and maintained in accordance with OSHA excavation safety standards. The contractor is solely responsible for designing, constructing, and maintaining steady temporary excavations and slopes. The contractor’s responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. The slope height, slope inclination, or excavation depth, including utility trench excavation depth, should not exceed those specified in local, state, and federal safety regulations. ECS is providing this information solely as a service to our client. ECS is not assuming responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred.

ECS Project No. 22:31399 Page 10

6.0 CLOSING

ECS has prepared this report to guide the geotechnical-related design and construction aspects of the project. We performed these services in accordance with the standard of care expected of professionals in the industry performing similar services on projects of like size and complexity at this time in the region.

No other representation, expressed or implied, and no warranty or guarantee is included or intended in this report.

The description of the proposed project is based on information provided to ECS by Mr. Sam Karahalis of the USDA Forest Service. If this information is untrue or changes, either because of our interpretation of the documents provided or site or design changes that may occur later, ECS should be contacted so we can review our recommendations and provide additional or alternate recommendations that reflect the proposed construction.

We recommend that ECS review the project plans and specifications so we can confirm that those plans/specifications are in accordance with the recommendations of this geotechnical report.

Field observations and quality assurance testing during earthwork and foundation installation are an extension of, and integral to, the geotechnical design. We recommend that ECS be retained to apply our expertise throughout the geotechnical phases of construction, and to provide consultation and recommendation should issues arise.

ECS is not responsible for the conclusions, opinions, or recommendations of others based on the data in this report.

APPENDIX A – Diagrams & Reports

Site Location Diagram Exploration Location Diagram

2/18/2022

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

ENGINEER

SCALE

22:31399

PROJECT NO.

SHEET

DATE

WEG

US DEPARTMENT OF AGRICULTURE - CROATAN RANGER DISTRICT

CROATAN RANGER STATION - DRILLING

EAST FISHER AVE, NEW BERN, NORTH CAROLINA

SITE LOCATION DIAGRAM

0 200100 Feet

AS NOTED

2/18/2022

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

ENGINEER

SCALE

22:31399

PROJECT NO.

SHEET

DATE

WEG

Legend

Approximate Kessler DCP Test Locations

Approximate CPT Sounding Locations

US DEPARTMENT OF AGRICULTURE - CROATAN RANGER DISTRICT

CROATAN RANGER STATION - DRILLING

EAST FISHER AVE, NEW BERN, NORTH CAROLINA

BORING LOCATION DIAGRAM

0 200100 Feet

AS NOTED

APPENDIX B – Field Operations

Reference Notes for CPT Sounding Logs Cone Penetration Test Sounding Logs (S-1 and S-2) Reference Notes for Boring Logs Hand Auger Boring Logs (K-1 through K-3) Kessler DCP Test Results (K-1 through K-3)

APPENDIX C – Supplemental Report Documents

GBA Document