2-_GEOTECHNICAL_REPORT_SEALED.pdf

REPORT OF GEOTECHNICAL SERVICES

C-17 TYPE III HYDRANT REFUELING SYSTEM AND RAMP EXPANSION

145TH AIRLIFT WING

CHARLOTTE, NORTH CAROLINA

SUMMIT PROJECT NO. 4282.500

Prepared For:

Mr. Clinton D. Gallagher, PE Burns & McDonnell Aviation and Federal Division

9400 Ward Parkway Kansas City, MO 64114

Email: cgallagher@burnsmcd.com

Prepared By:

SUMMIT Engineering, Laboratory & Testing, P.C. (SUMMIT) 3575 Centre Circle Drive

Fort Mill, South Carolina 29715

July 21, 2017 i

July 21, 2017

Mr. Clinton D. Gallagher, PE Burns & McDonnell Aviation and Federal Division 9400 Ward Parkway Kansas City, MO 64114 Email: cgallagher@burnsmcd.com

Subject: Report of Geotechnical Services C-17 Type III Hydrant Refueling System and Ramp Expansion 145th Airlift Wing Charlotte, North Carolina SUMMIT Project No. 4282.500

Dear Mr. Gallagher:

SUMMIT Engineering, Laboratory & Testing, P.C. (SUMMIT) has completed the geotechnical services for the C-17 Type III Hydrant Refueling System and Ramp Expansion Project for the 145th Air Wing North Carolina Air National Guard (NCANG) located at Douglas/Charlotte International Airport (IAP) in Charlotte, North Carolina. These geotechnical services were performed in general accordance with our Proposal No. P-2016-660-G dated July 20, 2016 and the provided Geotechnical Scope of Services dated July 12, 2016. This report contains a brief description of the project information provided to us, general site and subsurface conditions revealed during our geotechnical subsurface exploration and our general recommendations regarding foundation design and construction.

SUMMIT appreciates the opportunity to be of service to you on this project. If you have any questions concerning the information presented herein or if we can be of further assistance, please feel free to call us at (704) 504-1717.

Sincerely yours, SUMMIT Engineering, Laboratory & Testing, P.C.

Kerry C. Cooper, P.E. Robert L. Price, P.E.

Senior Geotechnical Engineer Senior Geotechnical Engineer rprice Typewritten Text 7/25/2017

Report of Geotechnical Services SUMMIT Project No. 4282.500 C-17 Type III Hydrant Refueling System and Ramp Expansion July 21, 2017 145th Airlift Wing Charlotte, North Carolina ii

TABLE OF CONTENTS

SECTION ......................................................................................................................... PAGE

1.0 INTRODUCTION

1.1 Site and Project Description

1.2 Purpose of Subsurface Exploration

2.0 EXPLORATION PROCEDURES

2.1 Field

2.2 Laboratory Services

3.0 AREA GEOLOGY AND SUBSURFACE CONDITIONS

3.1 Physiography and Area Geology

3.2 Generalized Subsurface Stratigraphy

3.2.1 Surface/Topsoil

3.2.2 Existing Fill Soils

3.2.3 Residual Soils

3.2.4 Partially Weathered Rock and Auger Refusal

3.3 Water Level Measurements

4.0 PRELIMINARY EVALUATIONS AND RECOMMENDATIONS

4.1 General

4.2 Shallow Foundation Recommendations

4.3 Tank Foundation Locations with Over 10 Feet of Fill

4.4 Retaining Wall Recommendations

4.5 Seismic Site Class

4.5 Low to Moderate Plasticity and Moisture Sensitive Soils (Elastic Silts, MH)

4.6 Moderate to High Plasticity and Moisture Sensitive Soils (Fat Clays, CH)

4.7 Wet Weather Conditions

4.8 Floor Slabs

4.9 Pavement

4.10 Concrete

4.11 Cut and Fill Slopes

5.0 CONSTRUCTION CONSIDERATIONS

5.1 Abandoned Utilities/Structures

5.2 Site Preparation

5.3 Difficult Excavation

5.4 Temporary Excavation Stability

5.5 Structural Fill

5.6 Suitability of Excavated Soils

5.7 Engineering Services During Construction

6.0 RELIANCE AND QUALIFICATIONS OF REPORT

iii

APPENDICES

1. Figures – Figure 1: Site Vicinity Map Figure 2: Boring Location Plan

2. Subsurface Diagram

3. Boring Logs

4. Laboratory Test Results 4-A Classification Tests – Soil Test Boring Split Spoon Samples and Bulk Sample at B-5 4-B Modified Proctor and CBR – Bulk Sample at B-5 4-C Triaxial U-U Shear Test Report and Classification – Undisturbed Shelby Tube at B-8 4-D Chemical Analysis – Bulk Sample at B-2

5. ReMi Test Result - Submitted December 18, 2014 - Report of Preliminary Subsurface

Exploration for Proposed Improvements to Buildings 5 and 5

1.0 INTRODUCTION

1.1 Site and Project Description

The C-17 Type III Hydrant Refueling System/Ramp Expansion Project is located at the

Douglas/Charlotte International Airport (IAP) 145th Air Wing North Carolina National Guard

(NCANG). Please refer to the “Site Vicinity Map,” Figure No. 1 included in the Figures Section for the approximate location of the site. The site of the refueling system/ramp expansion is located north of existing hangar (Building 51) and between the existing ramp facilities and the two existing 2,500-bbl storage tanks.

The client (Burns & McDonnell Engineering Company) provided SUMMIT a “Geotechnical

Scope of Services” that included a Figure 1.1 Site Plan with Preliminary Geotechnical Boring

Layout, dated (July 12, 2016) that indicated the proposed configurations of the proposed construction. Based on our review of the provided Geotechnical Scope and the Type A2 Design

Submittal Plans dated December 5, 2016, we understand the proposed project is planned to include the following.

• Expansion of the existing ramp facilities, approximately 126,000 SF, to provide maneuver room and clearance between parked and refueling aircraft.

• Construction of a Type III Hydrant Refueling system to include new hydrant fueling pits located in the existing ramp facilities.

• Construction of a new pump station. The new pump station will occupy approximately

1,500SF.

• Construction of a 4,000-bbl aboveground storage tank to be added adjacent to the two existing 2,500-bbl storage tanks.

• Construction of new storm drainage system, retaining walls and ramp lighting. All utilities affected by this projects scope shall be relocated.

At the time of this report preparation, SUMMIT has been provided with the Type A2 Design

Submittal Layout that includes structural details indicating foundation bearing elevations, and finished floor elevations for the proposed structures. Provided plans indicate the proposed structures will be supported on a shallow foundation system consisting of spread, strip, and/or combined footings.

The new 4,000-BBL Tank indicates the tank will have an overall height of 29 feet and a diameter of 40 feet. We have assumed loads for the tank will be approximately 1,650 kips when the tank is full. We understand the proposed tank will likely be supported on either a concrete ring wall or concrete mat type foundation. Proposed grading plans provided indicate the site of the tank will include a 6-foot high dike wall constructed for secondary containment with an approximately 6 to 14-foot high segmental block retaining wall. New gabion retaining walls with approximate heights of 3 to 12-foot high are proposed to extend from the existing gabion retaining wall located adjacent to the fuel facility.

The new Type III Pump Shelter will be located between the two existing 2,500-bbl fuel storage tanks and the existing hangar building. We understand the pump shelter will be approximately

1,500 square foot metal skinned and CMU masonry block structure. We have assumed wall loads will be on the order of 1 to 3 kips per foot and column loads on the order of 50 to 100 kips.

Also, a final grading plan was not available at the time of this report and we have assumed that maximum cut/fill depths will be on the order of 1 foot to a maximum of 10 feet along the north side of the dike area.

1.2 Purpose of Subsurface Exploration

The purpose of this subsurface exploration was to obtain general geotechnical information regarding the subsurface conditions and to provide general recommendations regarding the geotechnical aspects of site preparation and foundation design. This report contains the following items:

• General subsurface conditions,

• Boring logs and an approximate “Boring Location Plan”,

• Suitable foundation types,

• Recommended maximum allowable bearing pressures for design of shallow foundations..

• Anticipated excavation difficulties during site grading and/or utility installation,

• Remedial measures to correct unsatisfactory soil conditions during site development, as needed,

• Drainage requirements around structures, under floor slabs and basements, as needed,

• Construction considerations,

• Soil values for the design of earthen retaining walls.

• Existing pavement thicknesses at cored locations, CBR Values, and Modulus of Subgrade

Reaction Values.

• Seismic Site Classification based on Refraction Microtremor (REMI) testing previously preformed for Building 51 (Geotechnical Report – December 18, 2014).

• Chemical Analysis for Soil Corrosivity

2.0 EXPLORATION PROCEDURES

2.1 Field

SUMMIT visited the site on December 7-8, 2016 to perform a subsurface exploration. The subsurface exploration consisted of eight (8) soil test borings (identified as B-1 through B-8) and two (2) pavement cores (identified as C-1 and C-2) at the approximate locations shown on the

“Boring Location Plan” (Figure 2) included in Appendix 1. The client (Burns & McDonnell) provided SUMMIT a plan that indicated the soil boring and pavement core locations. The borings were located by professionals from our office using the provided plans, recreation-grade handheld GPS, existing topography, and aerial maps as reference. Since the boring locations were not surveyed, the location of the borings should be considered approximate. Elevations provided on the “Boring Logs” were interpolated from the topographic information included on the A2 Concept Grading Plans dated December 5, 2016.

The mechanical soil test borings were performed using an ATV-mounted CME 550X drill rig and extended to depths of approximately 10 to 35 feet below the existing ground surface.

Hollow-stem, continuous flight auger drilling techniques were used to advance the borings into the ground. Standard Penetration Tests (SPT) were performed within the mechanical borings at designated intervals in general accordance with ASTM D 1586. When properly evaluated, the

SPT results can be used as an index for estimating soil strength and relative density.

The existing concrete ramp at locations C-1 and C-2 and the asphalt at locations B-4 and B-6 was cored with a four (4) inch nominal diameter diamond core-barrel drill to measure the existing pavement thicknesses. Upon completion of concrete coring the pavement was patched with fast curing non-shrink grout. Measured thicknesses of the pavement cores and stone base are included on the attached Boring Logs in Appendix 3 of this report.

In conjunction with the penetration testing, representative soil samples were obtained from each test location and returned to our laboratory for visual classification and potential laboratory testing. Water level measurements were attempted at the termination of drilling. The results of these tests are presented on the individual boring logs provided in Appendix 2 at the respective test depth.

2.2 Laboratory Services

The collected soil samples were transported to SUMMIT’s office to be visually examined and classified by a qualified geotechnical professional in general accordance with the Unified Soil

Classification System (USCS) and ASTM D 2488. The results of the visual classification are depicted on the Boring Logs provided in Appendix 3. Additional laboratory testing, to aid in the classification of soils and to better evaluate their engineering properties were performed on selected representative soil samples. Laboratory testing performed included five (5) Atterberg

Limit tests (ASTM D 4318), five (5) grain sizes with percent finer #200 sieve wash (ASTM D

422), four (4) percent moisture content tests (ASTM D 2216), and one (1) unconsolidated undrained triaxial compression test (ASTM D2435).

One (1) bulk sample of potential pavement subgrade soils was collected at boring location B-5 for additional laboratory testing which included one (1) Modified Proctor test (ASTM D 1557), one (1) California Bearing Ratio test (ASTM D 1883), one (1) Atterberg Limit test (ASTM D

4318), one (1) grain size with percent finer #200 sieve wash (ASTM D422) and one (1) percent moisture content test (ASTM D 2216). The Modified Proctor test was utilized to determine the maximum dry density and optimum moisture content of the soils.

One (1) bulk sample was collected at boring location B-2 for additional laboratory testing which included a chemical analysis consisting of pH, Soluble Sulfates, Chloride Ion, Electrical

Resistivity, Redox Potential, and Sulfides.

Laboratory test results are included in the Appendix 4 of this report and summarized in the following table. All laboratory test results are also included on the boring logs at the specific sample depth tested.

Summary of Laboratory Test Results

Sample ID

Atterberg Limits Sieve Analysis Modified

Compaction CBR3 Classification

LL1 PL1 PI1 %<40 %<200 MDD2

(pcf)

OMC2

(%) USCS4

B-2 (6'-7.5') 46 24 22 83.6 63.5 - - - CL

B-2 (13.5'-15') 33 18 15 77.9 54.5 - - - CL

B-4 (23.5'-25') 47 35 12 82.4 60.4 - - - ML

B-6 (3.5'-5') 59 31 28 90.1 74.0 - - - CH

B-5 (Bulk 1-5’) 60 30 30 84.1 67.9 115.3 15.5 3.4 CH

B-8 (Undisturbed 3-5) 39 30 9 69.4 46.3 - - - SM

Notes:

1.) LL = Liquid Limit; PL = Plastic Limit; PI = Plasticity Index; NV = Not Viscous; NP = Non-Plastic 2.) MDD = Maximum Dry Density; OMC = Optimum Moisture Content 3.) CBR = California Bearing Ratio 4.) USCS = Unified Soil Classification System

Summary of Triaxial Shear Test Results

Shelby Tube Data Parameter Total Stress

BORING B-8

3 ft. to 5 ft.

C, ksf 0.48 ϕ, degrees 35.9

Tan ϕ 0.73

Summary of Corrosion Series Chemical Analysis Results

Sample ID Parameter Test Results pH in Distilled

Water 7.4 pH in Calcium

Chloride 7.0

Soluble Sulfates 388 mg/kg BORING B-2 Chloride Ion <100 mg/kg

5 ft. to 10 ft. Electrical Resistivity 3,099 ohm-cm

Electrical Conductivity 3.23E-04 (ohm-cm)-1

Redox Potential 76 mV Sulfides ND

3.0 AREA GEOLOGY AND SUBSURFACE CONDITIONS

3.1 Physiography and Area Geology

The subject property is located in Charlotte, Mecklenburg County, North Carolina, which is located in the south central Piedmont Physiographic Province. The Piedmont Province generally consists of well rounded hills and ridges which are dissected by a well developed system of draws and streams. The Piedmont Province is predominantly underlain by metamorphic rock

(formed by heat, pressure and/or chemical action) and igneous rock (formed directly from molten material) which were initially formed during the Precambrian and Paleozoic eras. The volcanic and sedimentary rocks deposited in the Piedmont Province during the Precambrian era were the host of the metamorphism and were generally changed to gneiss and schist. The more recent

Paleozoic era had periods of igneous emplacement, with episodes of regional metamorphism resulting in the majority of the rock types seen today.

The topography and relief of the Piedmont Province has developed from differential weathering of the igneous and metamorphic rock. Ridges have been developed on the more easily weathered and erodible rock. Because of the continued chemical and physical weathering, the rocks in the

Piedmont Province are now generally covered with a mantle of soil that has weathered in place from the parent bedrock. These soils have variable thicknesses and are referred to as residuum or residual soils. The residuum is typically fine-grained and has higher clay contents near the surface because of the advanced weathering. Similarly, the residual soils typically become more coarse-grained with increasing depth because of decreased weathering. As the weathering decreases, residual soils generally retain the overall appearance, texture, gradation and foliations of the parent rock.

3.2 Generalized Subsurface Stratigraphy

General subsurface conditions observed during our geotechnical exploration are described herein.

For more detailed soil descriptions and stratifications at a particular field test location, the respective “Boring Logs”, provided in Appendix 3 should be reviewed. The horizontal stratification lines designating the interface between various strata represent approximate boundaries. Transitions between different strata in the field may be gradual in both the horizontal and vertical directions. Therefore, subsurface stratigraphy between test locations may vary.

3.2.1 Surface/Topsoil

Topsoil (surface soils with organic matter) was encountered in all borings except B-4 and

B-6 where asphalt pavement was encountered. The topsoil was encountered at the existing ground surface and extended down to approximately 3 to 12 inches. Even though the topsoil was encountered 3 to 12 inches thick at the ground surface of the locations, the surface material thicknesses can vary dramatically in short distances and between the test locations.

Surficial Organic Soil is typically a dark-colored soil material containing roots, fibrous matter, and/or other organic components, and is generally unsuitable for engineering purposes. SUMMIT has not performed any laboratory testing to determine the organic content or other horticultural properties of the observed surficial organic soils. Therefore, the phrase “surficial organic soil” is not intended to indicate suitability for landscaping and/or other purposes. The surficial organic soil depths provided in this report and on the individual “Boring Logs” are based on observations of field personnel and should be considered approximate. Please note that the transition from surficial organic soils to underlying materials may be gradual, and therefore the observation and measurement of the surficial organic soil depth is subjective. Actual surficial organic soil depths should be expected to vary and generally increases with the amount of vegetation present over the site.

Asphalt pavement was encountered at boring locations B-4 and B-6. The following Table summarizes the asphalt pavement and concrete ramp thicknesses encountered at locations

C-1 and C-2.

Summary of Pavement Thicknesses

Location Pavement Thickness Stone Base Thickness

B-4 Asphalt-6 Inches 12 Inches B-6 Asphalt - 3 Inches 3 Inches C-1 Concrete - 17 Inches 18 Inches C-2 Concrete - 15 Inches 12 Inches

3.2.2 Existing Fill Soils

Existing fill soils were encountered beneath the topsoil or pavement layer in Borings B-1 through B-6 to approximate depths ranging from 1.5 to 5.5 feet below the existing ground surface, respectively. The following table summarizes the location and approximate depth of fill material encountered in the boring. When sampled, the existing fill soils generally consisted of firm fat clays (CH), soft to very stiff elastic silts (MH), soft to firm sandy silts (ML), and loose silty sands (SM). The Standard Penetration Resistances (N-values) in the existing fill soils ranged from 4 to 9 blows per foot (bpf).

The following table summarizes the location and approximate depth of fill material encountered in the boring.

SUMMARY OF EXISTING FILL SOIL

LOCATION AND APPROXIMATE DEPTH

Boring No.

Existing Fill

Approx.

Depths (Feet)1

Boring No.

Existing Fill

Approx.

(Feet)1

Existing Fill

Approx.

Depths (Feet)1

B-1 1.5 B-2 1.5 B-3 3

B-4 3 B-5 1.5 B-6 5.5

1Approximate Depth from existing ground surface

3.2.3 Residual Soils

Residual (undisturbed) soils were encountered below the surface materials, and existing fill soils in all of the borings and extended to either the maximum termination depth or partially weathered rock (PWR) or auger refusal. The residual soils generally consisted of firm to stiff fat clays (CH), soft to firm lean clays (CL), soft to very hard elastic silts

(MH), firm to very stiff sandy silts (ML), loose clayey sands (SC), and medium dense to very dense silty sands (SM). The Standard Penetration Resistances (N-values) in the residuum ranged from 3 to 94 blows per foot (bpf).

Special considerations concerning moderate plasticity elastic silts (MH) and fat clays

(CH) are warranted. Elastic silts (MH) were encountered in five (5) of the borings to approximate depths ranging from 3 to 12 feet below the existing ground surface. Fat

Clays (CH) were encountered in two (2) of the borings to approximate depths of 5.5 feet below the existing ground surface. These soils are moisture sensitive soils and can undergo significant changes in volume, or shrink/swell, during moisture changes within the soils. Please refer to sections 4.5 and 4.6 of this report for more information.

The following table summarizes the location and approximate depths that elastic silt

(MH) and fat clays (CH) soils were encountered in our borings.

SUMMARY TABLE OF ELASTIC SILT AND FAT CLAY SOILS

LOCATIONS AND DEPTHS

Boring No.

Elastic Silts

Approx.

Depths (Feet)

Fat Clays

Approx.

(Feet)

Elastic Silts

Approx.

Depths (Feet)

Fat Clays

Approx.

Depths (Feet*

B-1 3 --- B-2 1.5-5.5;

and 8-12 ---

B-5 --- 0.25-5.5 B-6 1.5-3 3-5.5

B-7 1.5-3 --- B-8 8-10 ---

1Approximate Depth from existing ground surface NE – Not Encountered

3.2.4 Partially Weathered Rock and Auger Refusal

Partially weathered rock (PWR) material was encountered in four (4) of the borings at approximate depths ranging from 3 to 17 feet below the existing ground surface during this subsurface exploration. in Borings B-1, B-3, B-6, and B-7. The Partially weathered rock is defined as soil-like material exhibiting N-values in excess of 100 bpf.

Auger refusal was encountered in four (4) of the borings at approximate depths ranging from 20 to 26 feet below the existing ground surface during this subsurface exploration.

in Borings B-1, B-2, B-3, B-6. Auger refusal is defined as material that could not be penetrated with the drill rig equipment used on the project. Auger refusal material may consist of large boulders, rock ledges, lenses, seams or the top of parent bedrock. Core drilling techniques would be required to evaluate the character and continuity of the refusal material. However, rock coring was beyond the scope of this study and not performed.

The following table summarizes the location and approximate depths that partially weathered rock (PWR) and auger refusal conditions were encountered in our borings.

SUMMARY TABLE OF PARTIALLY WEATHERED ROCK

AND AUGER REFUSAL CONDITION LOCATIONS AND DEPTHS

Boring No.

Approx.

Depth of PWR (Feet)1

Approx.

Depth of

Auger Refusal (Feet) 1

Boring No.

Approx.

Depth of

PWR

(Feet) 1

Approx.

Depth of

Auger Refusal (Feet) 1

B-1 8 26 B-2 --- 23

B-3 12 20 B-6 17 20

B-7 3 --- --- --- ---

1Approximate Depth from existing ground surface NE – Not Encountered

3.3 Water Level Measurements

Groundwater, at the time of drilling, was encountered in borings B-2, B-4, and B-6 at an approximate depths of 23, 35, and 18.5 feet below the existing ground surface, respectively.

Also, moist soil conditions were encountered in the soils collected that may be an indicator of groundwater conditions. Measurements of the borehole cave in depths were performed and indicated on the provided borings logs.

Water levels tend to fluctuate with seasonal and climatic variations, as well as with some types of construction operations. Therefore, water may be encountered during construction at depths not indicated during this exploration.

4.0 PRELIMINARY EVALUATIONS AND RECOMMENDATIONS

4.1 General

Our evaluation and recommendations are based on the project information outlined previously and on the data obtained from the field testing program. If the structural loading, geometry, or proposed building locations are changed or significantly differ from those outlined, or if conditions are encountered during construction that differ from those encountered by the borings, SUMMIT requests the opportunity to review our recommendations based on the new information and make the necessary changes.

Final grading plan information with proposed foundation bearing elevations was not available for our review at the time of this report however based on the Type A2 Design Submittal the tank ringwall foundations are 2 feet wide and extend 3.5 feet below finished grade. The Type A2

Design Submittal indicates the Pump House Foundation consist of eight isolated 5.5 to 6.5 foot square column footings with dimensions ranging between 5.5 and 6.5 feet Finish grade elevations of proposed improvements in conjunction with the proposed foundation bearing elevation can have a significant effect on design and construction considerations. SUMMIT should be provided the opportunity to review the project grading plans prior to their finalization with respect to the recommendations contained in this report.

4.2 Shallow Foundation Recommendations

Based on the results of the soil test borings performed at the test locations and assumptions regarding site grading and structural design, the proposed structures can be adequately supported on shallow foundations bearing on the residual soils encountered in the borings or newly compacted fill soils provided site preparation and compacted fill recommendation procedures outlined in this report are implemented concerning poorly compacted surficial fill soils with N-values less than 7 bpf may. An allowable net bearing pressure of up to 3,000 pounds per square foot (psf) (Factor of Safety=3) can be used for design of the foundations bearing on undisturbed residual soils, or on structural fill compacted to at least 95 percent of its Modified Proctor maximum dry density. Please refer to sections 5.0 of this report for more information. With regards to short-term loading due to wind and seismic events, it is permitted to increase the allowable bearing pressures by 30 percent.

Provided the procedures and recommendations outline in this report are implemented and using the assumed loads, we have estimated a total settlement of less than 1 inch for footing design pressures of 3,000 psf. Differential settlement estimated based on the in-situ soil conditions are anticipated to be less than 0.5 inches between adjoining footings and along individual wall footings. Our total and differential settlements calculations were based on using maximum net bearing pressures of 3,000 psf with assumed foundation bearing elevations eighteen (18) inches below existing grade.

To avoid punching type bearing capacity failure, we recommend wall foundation widths of 18 inches or more and isolated spread (column) footings should be a minimum of 36 inches.

Exterior foundations and foundations in unheated areas should be designed to bear at least 12 inches below finished grade for frost protection. To reduce the effects of seasonal moisture variations in the soils, for frost protection and for bearing capacity, it is recommended that all foundations be embedded at least 12 inches below the lowest adjacent grade.

All footing excavations and undercutting remediation operations should be inspected by the geotechnical engineer or his/her designed representative to confirm that suitable soils are present at and below the proposed bearing elevation and that the backfill operations are completed with the recommendations of this report. If evaluation with dynamic cone penetrometer (DCP) testing encounters lower penetration resistances or other unsuitable materials in the footing excavations, they should be corrected per the recommendations of the project geotechnical engineer.

4.3 Tank Foundation Locations with Over 10 Feet of Fill

Based on emails dated July 12, 2017 we understand the tank will be supported on a ringwall foundation with a maximum bearing capacity of 1,400 psf dead load with increases of 2,300 psf during extreme load events. We also understand the tank foundations has settlement tolerances of lease than ¼ inch total settlement and 1/8 inch for differential settlement, and therefore has recommended monitoring the fill prior to tank foundation construction. Settlement monitoring points should be embedded at the proposed tank foundation locations and monitored regularly by a licensed surveyor Once the magnitude and rate of settlement has reached a state of equilibrium or are within acceptable level then tank foundation construction can begin. Based on previous experience and soil types we anticipate the time required to reduce settlement will be on the order of 30 to 45 days.

4.4 Retaining Wall Recommendations

Design Parameters for backfill properties (i.e., friction angle, earth pressure coefficients) should use the values in the table below. These parameters are based on suitable soils with a minimum moist unit weight of 120 pcf. A Geotechnical Engineer should be retained to test the actual soils used for construction to verify these design assumptions. To reduce long term creep or deflections to the wall system, desirable wall backfill soils should be used. These include non-plastic, granular soils (sands and gravels). However, these soils may not be available on site.

Table 1 – Lateral Earth Pressures for Retaining Walls

Backfill Material Condition Earth Pressure

Coefficients Equivalent Fluid Pressure*(pcf)

Free Draining Granular Soils

(φ = 33o, γ = 135 pcf)

At-rest (Ko) 0.46 61

Active (Ka) 0.29 40

Passive (Kp) 3.39 458

On-site Soils Used as Fill

(φ = 24 o, γ = 95 pcf)

At-rest (Ko) 0.59 56

Active (Ka) 0.42 40

Passive (Kp) 2.37 225

Undisturbed Residual Soils

(φ = 28 o, γ = 118 pcf)

At-rest (Ko) 0.53 63

Active (Ka) 0.36 43

Passive (Kp) 2.77 327 *Equivalent fluid pressures are for conditions where hydrostatic pressure buildup does not occur behind the wall.

**Allowable bearing pressures and sliding friction coefficients for shallow footings are provided in Section 4.2.

On-site residual soils classified as elastic silts (MH) and/or fat clays (CH) shall not be used for wall backfill or in the retained zone as shown in Table 1610.1 of the 2015 IBC. If on-site soils are used as backfill within the reinforced zone, the wall designer should address the need for wall drainage and the possibility of long-term, time-dependent movement or creep in their design. All structural fill soils should be placed in thin (not greater than 8 to 12 inches) loose lifts and compacted to a minimum of 95 percent of the soil's Modifed Proctor maximum dry density

(ASTM D 1557) at near optimum moisture content (±2%).

Resistance to sliding will be developed by friction along the base of the footings and passive earth pressure acting on the vertical face of the footing and a key installed in the base of the footings, if required. We recommend an ultimate coefficient of base friction of 0.4 be used along the bottom of the footing. The available passive earth resistance on the vertical face of the footing and a key constructed in the base of the footing may be calculated using an allowable passive earth pressure of 150 psf per foot of depth below a depth of 2 feet from adjacent grade.

At the time of report preparation, we were not provided retaining wall plans or specifications.

Therefore, we request the opportunity to review the wall plans and specifications once they are finalized. Also, we recommend an external stability analysis (including global stability) of the proposed wall(s) be conducted once the site layout and wall geometry is complete.

4.5 Seismic Site Class

SUMMIT has evaluated the Site Class for this site according to International Building Code

(IBC), Section 1615, Earthquake Loads – Site Ground Motion (2015) using Soil Shear Wave

Velocity. The approximate location of the ReMi Profile run previously performed for Building

51 and submitted in our Geotechnical Report dated December 18, 2014 is indicated on the Figure included in Appendix 5 of this report. We recommend that this project should be designed using a Seismic Site Class of “C” (Very Dense Soil and Soft Rock) having a shear wave velocity of

1,237 ft/sec as defined in Table 1615.1.1 of the IBC. The results of the ReMi test can be found in

Appendix 5 – ReMi Test Results. The following is the mapped acceleration parameters as provided by USGS Earthquake Hazards Program

(http://earthquake.usgs.gov/designmaps/us/application.php) using the following coordinates.

http://earthquake.usgs.gov/designmaps/us/application.php)

Latitude: 35.2175°N Longitude: 80.9297°W

Ss = 0.240 g S1 = 0.103 g

Fa = 1.200 Fv = 1.697

SMS = 0.288 g SM1 = 0.175 g

SDS = 0.192 g SD1 = 0.117 g

Seismic Site Class = C

4.5 Low to Moderate Plasticity and Moisture Sensitive Soils (Elastic Silts, MH)

Based on our boring results, low to moderate plasticity and moisture sensitive (elastic silts) soils were encountered in five (5) of the borings performed during this exploration. The locations and depths are summarized in the table provided in section 3.2.3 of the report. These materials, in their present state, are suitable for direct support of the foundation elements. However, these fined grained soils are susceptible to moisture intrusion and can become soft when exposed to weather and/or water infiltration. Consequently, some undercutting and/or reworking (drying) of the near-surface soils may be required depending upon the site management practices and weather conditions present during construction.

Should these materials be left in-place, special consideration should be given to providing positive drainage away from the structure and discharging roof drains a minimum of 5 feet from the foundations to reduce infiltration of surface water to the subgrade materials.

Note: Since Low to Moderate Plasticity and Moisture Sensitive Soils can become remolded (i.e., softened) under the weight of repeated construction traffic and changes in moisture conditions, these soils should be evaluated and closely monitored by a geotechnical engineer or his representatives prior and/or during construction and fill placement. Additional testing and inspections of moisture sensitive soils may be warranted such as laboratory testing, field density

(compaction) testing, hand auger borings with dynamic cone penetrometer (DCP) testing and/or test pit excavations.

4.6 Moderate to High Plasticity and Moisture Sensitive Soils (Fat Clays, CH)

Moderate to High Plasticity and Moisture Sensitive (fat clays) soils were encountered in two (2) of the borings to approximate depths of 5.5 feet below the existing ground surface. The locations and depths are summarized in the table provided in section 3.2.3 of the report. Moderate to high plasticity soils can undergo significant changes in volume, or shrink/swell, during moisture changes within the soils. These soils typically provide poor subgrade support for pavements and foundations.

The high plasticity (fat clays) materials encountered are typically not suitable for building or pavement subgrade support. Depending on final subgrade elevations, we recommend the high plasticity soils be undercut from beneath foundations and pavements to provide adequate separation. Recommended separation is a minimum of three (3) feet beneath foundations, and one and one-half (1.5) feet of separation on pavement areas. Instead of undercutting, the footings can be extended through the high plasticity (fat clays) soils and bear on suitable soils. The slab should be designed separately as described below.

The presence of the high plasticity material can adversely affect the performance of the foundation and pavement systems. Our geotechnical site development options are as follows:

1. The high plasticity materials should be undercut from all structural and pavement areas.

The undercut subgrades should be evaluated by a staff professional upon completion of undercut operations. Once the evaluation is completed and the subgrade appears suitable, structural fill should be placed to subgrade elevation.

2. Three (3) feet of separation should be provided between the high plasticity materials and foundations and one and one-half (1.5) feet of separation on pavement areas. The separation material should consist of suitable structural fill materials

3. Lime stabilization techniques could be utilized in order to lower the plasticity of the referenced soils in-place and minimize any undercut. These techniques should extend to a depth of at least 3 feet below structural subgrades in building areas and at least 1.5 feet on pavement areas. It should be noted that the success of lime stabilization techniques is highly dependent upon the means and methods utilized by the contractor.

4. If the expansive soils are not undercut from beneath the structures or adequate separation is not provided, the building foundations could be designed to either penetrate the expansive soils or should be designed to resist the differential volume and prevent structural damage. Slab-on-grades should be designed as structural slabs for the expansive soils in accordance with WRI/CRSI Design of Slab-on-Ground Foundations or

PTI Design and Construction of Post-Tensioned Slabs-on-Ground.

It should be noted that the high plasticity soils removed from cut areas or undercut excavations will not be suitable for use as structural fill. However, medium to high plasticity soils encountered during general site grading can be blended and/or mixed with lower plasticity soils and used as structural fill. We recommend that mixed soils be used below the top five (5) feet at deeper fill locations and adequate drainage be provided away from structural and pavement areas.

4.7 Wet Weather Conditions

As previously mentioned, the fine-grained subgrade materials encountered in our borings can be sensitive to moisture variations. Therefore, foundation excavations should remain opened for a minimum amount of time, particularly during inclement weather. Soils exposed to moisture variations may become highly disturbed and undercutting may be required prior to placing foundations on these materials. If excavations must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, we recommend that a 2-to 4-inch-thick

“mud-mat” of lean (2000 psi) concrete be placed on the bearing soils before placement of foundation concrete or reinforcing steel.

4.8 Floor Slabs

Slab-on-grade floor systems may be supported on residual soils, or newly compacted fill, provided the site preparation and fill placement procedures outlined in this report are implemented. Based on the field testing performed, a modulus of subgrade reaction of 150 pci is recommended for design of grade-supported slabs used in pavements or typical floor slab applications. Depending upon the amount of cuts and/or fills, unsuitable soils such as poorly compacted existing fill soils, with N-values less than 7 bpf may require remediation as described in Section 5.2. We recommend floor slabs be isolated from other structural components to allow independent movement of the slab and the building foundation elements.

Immediately prior to constructing a floor slab, the areas should be proofrolled to detect any softened, loosened or disturbed areas that may have been exposed to wet weather or construction traffic. Areas that are found to be disturbed or indicate pumping action during the proofrolling should be undercut and replaced with adequately compacted structural fill. This proofrolling should be observed by the staff professional or a senior soils technician under his/her direction.

Proofrolling procedures are outlined in the “Site Preparation” section of this report.

We recommend that special care be given to providing adequate drainage away from the building areas to reduce infiltration of surface water to the base course and subgrade materials. If these materials are allowed to become saturated during the life of the slab section, a strength reduction of the materials may result causing a reduced life of the section.

4.9 Pavement

The pavement sections can be adequately supported on the non-high plasticity residual soils, or newly compacted fill, provided the site preparation and fill placement procedures outlined in this report are implemented. Based on the field testing performed, a modulus of subgrade reaction of

150 pci is recommended for design of grade-supported slabs used in pavements or typical floor slab applications. Immediately prior to constructing the pavement section, we recommend that the areas be proofrolled to detect any softened, loosened or disturbed areas that may have been exposed to wet weather or construction traffic. Areas that are found to be disturbed or indicate instability during the proofrolling should be undercut and replaced with adequately compacted structural fill or repaired as recommended by the Geotechnical Engineer. This proofrolling should be observed by the staff professional or a senior soils technician under his/her direction.

Proofrolling procedures are outlined in the “Site Preparation” section of this report.

Due to prevalence of near surface moderate to high plasticity elastic silts and fat clays, remediation of pavement subgrade soils may be recommended (as determined by the

Geotechnical Engineer during construction) including undercutting and replacement with additional NCDOT ABC stone. Alternatively, lime stabilization of pavement subgrade may be a more economical option and SUMMIT can provide lime stabilization mix design services if requested. This may be more pronounced depending on the time of the year and seasonal conditions at the time of pavement construction. We recommend contingency for some remediation efforts for the subgrade soils be considered during the planning stage.

4.10 Concrete

We recommend the use of Type II cement for construction of concrete structures at this site. Due to potential uncertainties, as to the use of reclaimed irrigation water, or topsoil that may contain higher sulfate contents, pozzolan or admixtures designed to increase sulfate resistance may be considered.

Laboratory chemical tests were not performed to evaluate the sulfate content of the site soils for this project. We assumed that the soluble sulfate content at the project site is less than 0.2 percent by weight. If desired, laboratory chemical testing can be performed to estimate the sulfate content of the onsite soils.

Concrete should have a water-cement ratio of no more than 0.50 by weight for normal weight aggregate concrete. The Structural Engineer should ultimately select the concrete design strength and the water-cement ratio based on the project specific loading conditions. Higher strength concrete may be selected for increased durability and resistance to slab curling and shrinkage cracking.

In order to reduce the potential for shrinkage cracks in the concrete during curing, we recommend that for slabs-on-grade, the concrete be placed with a slump in accordance with

Table 5.2.1 of Section 302.1R of “Guidelines for Floor and Slab Construction”. If a higher slump is needed for screening and leveling, we recommend a super plasticizer be used to achieve the higher slump without changing the recommended water to cement ratio. The slump should be checked periodically at the site prior to concrete placement. We also recommend that crack control joints be provided in slabs in accordance with the recommendations of the Structural

Engineer to reduce the potential for distress due to minor soil movement and concrete shrinkage.

We further recommend that concrete cover over reinforcing steel for slabs-on-grade and foundations are in accordance with IBC 1907.7.1. The Structural Engineer should be consulted for additional concrete specifications.

4.11 Cut and Fill Slopes

Permanent project slopes should be designed with geometry of 3 horizontal to 1 vertical or flatter. The tops and bases of all slopes should be located 10 feet or more from structural limits and 5 feet or more from parking limits. Fill slopes should be properly compacted according to the recommendations provided in this report. In addition, fill slopes should be overbuilt and cut to finished grade during construction to achieve proper compaction on the slope face. All slopes should be seeded and maintained after construction and adhere to local municipal standards, if applicable.

5.0 CONSTRUCTION CONSIDERATIONS

5.1 Abandoned Utilities/Structures

We recommend that any existing utility lines and foundations be removed from within proposed building, tank and pavement areas. The utility backfill and foundation material should be removed and the subgrade in the excavations should be evaluated by a geotechnical professional prior to fill placement. The subgrade evaluation should consist of visual observations, probing with a steel rod and/or performing hand auger borings with Dynamic Cone Penetrometer tests to evaluate their suitability of receiving structural fill. Once the excavations are evaluated and approved, they should be backfilled with adequately compacted structural fill. Excavation backfill under proposed new foundations should consist of properly compacted structural fill, crushed stone, flowable fill or lean concrete as approved by the Geotechnical Engineer.

5.2 Site Preparation

Based on the results of our borings, and dependent on final grades, we anticipate that some undercutting and/or foundation extension through unsuitable soils such as poorly compacted existing fill soils with N-values less than 7 bpf may be required prior to building construction and/or fill placement. If these soils are encountered during the grading activities, the extent of the undercut required should be determined in the field by a Geotechnical Engineer and/or an experienced staff professional. Additional testing such as test pit excavations and/or hand auger borings may be required in order to further evaluate these soil conditions.

Topsoil, organic laden soils, construction debris and other organic materials should be stripped/removed from the proposed construction limits. Stripping and clearing should extend 10 feet or more beyond the planned construction limits. Upon completion of the stripping operations, we recommend areas planned for support of foundations, floor slabs, parking areas and structural fill be proofrolled with a loaded dump truck or similar pneumatic tired vehicle

(minimum loaded weight of 20 tons) under the observations of a staff professional. After excavation of the site has been completed, the exposed subgrade in cut areas should also be proofrolled. The proofrolling procedures should consist of four complete passes of the exposed areas, with two of the passes being in a direction perpendicular to the proceeding ones. Any areas which deflect, rut or pump excessively during proofrolling or fail to “tighten up” after successive passes should be undercut to suitable soils and replaced with compacted fill.

The extent of any undercut required should be determined in the field by an experienced staff professional or engineer while monitoring construction activity. After the proofrolling operation has been completed and approved, final site grading should proceed immediately. If construction progresses during wet weather, the proofrolling operation should be repeated after any inclement weather event with at least one pass in each direction immediately prior to placing fill material or aggregate base course stone. If unstable conditions are experienced during this operation, then undercutting or reworking of the unstable soils may be required.

5.3 Difficult Excavation

Based on the results of our soil test borings, it appears that the majority of general excavation for footings and utilities will be possible with conventional excavating techniques. We anticipate that the residual soils can be excavated using pans, scrapers, backhoes, and front end loaders.

Depending on the location, excavations deeper than approximately 5 to 8 feet may require specialized equipment and procedures.

Partially weathered rock (PWR) was encountered in four (4) of the borings and auger refusal conditions were encountered in four (4) of the borings performed during this subsurface exploration. Even though Partially Weathered Rock (PWR) material was encountered in Borings

B-1, B-3, B-6 and B-7 and Auger Refusal conditions encountered in Borings B-1, B-2, B-3, and

B-6, the depth and thickness of partially weathered rock, boulders, and rock lenses or seams can vary dramatically in short distances and between the boring locations; therefore, soft/hard weathered rock, boulders or bedrock may be encountered during construction at locations or depths, between the boring locations, not encountered during this exploration. Our experience in this geologic region is that materials with SPT “N”-values less than 60 bpf (“N”-value of 50 blows for 4 to 6 inches of sampler penetration) can generally be excavated with heavy-duty equipment such as a Caterpillar D-8 with a single-shank ripper. The actual rippability of these in-place materials is however dependent on many factors such as the operator’s skill level, the techniques used during grading, degrees of weathering, rock hardness, rock structure (i.e., foliations or bedding), jointing and fracture spacing and necessary size or width of excavation.

Blasting and/or removal with impact hammers are typically required for materials with SPT “N”-values greater than 100 blows per 0.5 feet (“N”-value of 50 blows for 0 to 2 inches of sampler penetration). Materials with SPT “N”-values greater than 60 bpf and less than 100 blows per 0.5 feet (“N”-value of 50 blows for 3 inches of sampler penetration) are considered marginally excavatable.

Care should be exercised during excavations for footings on rock to reduce disturbance to the foundation elevation. The bottom of each footing should be approximately level. When blasting is utilized for foundation excavation in rock, charges should be held above design grades. Actual grades for setting charges should be selected by the contractor and he should be responsible for any damage caused by the blasting. All loose rock should be carefully cleaned from the bottom of the excavation prior to pouring concrete. Footing excavations in which the rock subgrade has been loosened due to blasting should be deepened to an acceptable bearing elevation.

It is our opinion that a clear and appropriate definition of rock be included in the project specifications to reduce the potential for misunderstandings. A sample definition of rock for excavation specifications is provided below:

Rock is defined as any material that cannot be dislodged by a Caterpillar D-8 tractor, or equivalent, equipped with a hydraulically operated power ripper (or by a Cat 325 hydraulic backhoe, or equivalent) without the use of drilling…