B3 Project Manual - 03202023 (Rev 1).pdf

PROJECT MANUAL

GROUND BASE PV ARRAY

B-3 FINAL DESIGN

134TH AIR REFUELING WING

McGHEE TYSON AIR NATIONAL GUARD

BASE TENNESSEE

W9133L-16-D-0009

PROJECT No. PSXE172003

APRIL 29, 2022

AECOM

300 SOUTH GRAND AVENUE

LOS ANGELES, CALIFORNIA 90071

T 213-593-8100 F 213-593-8178

Ground Base PV Array, 134th Air Refueling Wing, 123 Briscoe Drive, McGhee Tyson ANG Base, Tennessee Contract No. W9133L-16-D-0009

AECOM No. 60604357

B-3 Final Design

Section TOC Table of Contents

Project No. PSXE172003

GROUND BASE PV ARRAY

April 29, 2022

TABLE OF CONTENTS

DIVISION 00 - PROCUREMENT AND CONTRACTING REQUIREMENTS

SECTION 00 0107 - SEALS PAGE

SECTION 00 3132 - GEOTECHNICAL DATA

Attachment

SECTION 00 4323 - ALTERNATES FORM

DIVISION 01 - GENERAL REQUIREMENTS

SECTION 01 1000 - SUMMARY

SECTION 01 2300 - ALTERNATES

SECTION 01 2500 - SUBSTITUTION PROCEDURES

SECTION 01 2600 - CONTRACT MODIFICATION PROCEDURES

SECTION 01 3100 - PROJECT MANAGEMENT AND COORDINATION

SECTION 01 3200 - CONSTRUCTION PROGRESS DOCUMENTATION

SECTION 01 3300 - SUBMITTAL PROCEDURES

Attachment

SECTION 01 4000 - QUALITY REQUIREMENTS

SECTION 01 4200 - REFERENCES

SECTION 01 5000 - TEMPORARY FACILITIES AND CONTROLS

SECTION 01 5723 - TEMPORARY STORM WATER POLLUTION CONTROL

SECTION 01 6000 - PRODUCT REQUIREMENTS

SECTION 01 7300 - EXECUTION

SECTION 01 7419 - CONSTRUCTION WASTE MANAGEMENT AND DISPOSAL

Attachments

SECTION 01 7700 - CLOSEOUT PROCEDURES

SECTION 01 7823 - OPERATION AND MAINTENANCE DATA

SECTION 01 7839 - PROJECT RECORD DOCUMENTS

SECTION 01 7900 - DEMONSTRATION AND TRAINING

SECTION 01 9113 - GENERAL COMMISSIONING REQUIREMENTS

DIVISION 02 - EXISTING CONDITIONS

NOT APPLICABLE

DIVISION 03 - CONCRETE

SECTION 03 2000 - CONCRETE REINFORCEMENT

SECTION 03 3000 - CAST-IN-PLACE CONCRETE

DIVISION 04 - MASONRY

NOT APPLICABLE

DIVISION 05 - METALS

SECTION 05 5000 - METAL FABRICATIONS

DIVISIONS 06 - 25

NOT APPLICABLE

DIVISION 26 – ELECTRICAL

SECTION 26 0513 - MEDIUM-VOLTAGE CABLES

SECTION 26 0519 - LOW-VOLTAGE ELECTRICAL POWER CONDUCTORS AND CABLES

SECTION 26 0523 - CONTROL-VOLTAGE ELECTRICAL POWER CABLES

123 Briscoe Drive, McGhee Tyson ANG Base, Tennessee

Contract No. W9133L-16-D-0009

AECOM No. 60604357

B-3 Final Design

Section TOC Table of Contents

Project No. PSXE172003

GROUND BASE PV ARRAY

April 29, 2022

SECTION 26 0526 - GROUNDING AND BONDING FOR ELECTRICAL SYSTEMS

SECTION 26 0529 - HANGERS AND SUPPORTS FOR ELECTRICAL SYSTEMS

SECTION 26 0533 - RACEWAYS AND BOXES FOR ELECTRICAL SYSTEMS

SECTION 26 0543 - UNDERGROUND DUCTS AND RACEWAYS FOR ELECTRICAL

SECTION 26 0553 - IDENTIFICATION FOR ELECTRICAL SYSTEMS

SECTION 26 0913 - ELECTRICAL POWER MONITORING AND CONTROL

SECTION 26 1219 - PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS

SECTION 26 1326 - MEDIUM-VOLTAGE, METAL-CLAD SWITCHGEAR

SECTION 26 2213 - LOW-VOLTAGE DISTRIBUTION TRANSFORMERS

SECTION 26 2413 - SWITCHBOARDS

SECTION 26 2416 - PANELBOARDS

SECTION 26 3100 - PHOTOVOLTAIC COLLECTORS

SECTION 26 3353 - STATIC UNINTERRUPTIBLE POWER SUPPLY

SECTION 26 4313 - SURGE PROTECTION FOR LOW-VOLTAGE ELECTRICAL POWER CIRCUITS

DIVISION 27 – COMMUNICATIONS

SECTION 27 0528 - PATHWAYS FOR COMMUNICATIONS SYSTEMS

SECTION 27 0553 - IDENTIFICATION FOR COMMUNICATIONS SYSTEMS

DIVISION 28 - ELECTRONIC SAFETY AND SECURITY

NOT APPLICABLE

DIVISION 31 - EARTHWORK

SECTION 31 1000 - SITE CLEARING

SECTION 31 2000 - EARTH MOVING

DIVISION 32 - EXTERIOR IMPROVEMENTS

SECTION 32 1216 - ASPHALT PAVING

SECTION 32 9200 - TURF AND GRASSES

DIVISIONS 33 - 48

NOT APPLICABLE

END OF TABLE OF CONTENTS

Ground Base PV Array, 134th Air Refueling Wing 123 Briscoe Drive, McGhee Tyson ANG Base, Tennessee

Contract No. W9133L-16-D-0009

AECOM No. 60604357

B-3 Final Design

Section 00 0107

SEALS PAGE

Project No. PSXE172003

GROUND BASE PV ARRAY

April 29, 2022

DOCUMENT 00 0107

SEALS PAGE

PART 1 - GENERAL

1.01 DESIGN PROFESSIONALS OF RECORD

A. Structural Engineer

B. Electrical Engineer

C. Civil Engineer

D.

END OF DOCUMENT

AECOM No. 60604357

B-3 Final Design

Section 00 3132

GEOTECHNICAL DATA

Project No. PSXE172003

GROUND BASE PV ARRAY

April 29, 2022

DOCUMENT 00 3132

GEOTECHNICAL DATA

PART 1 - GENERAL

1.01 GEOTECHNICAL DATA

A. This Document with its referenced attachments is part of the Procurement and Contracting Requirements for Project. They provide Government's information for Bidders' convenience and are intended to supplement rather than serve in lieu of Bidders' own investigations. They are made available for Bidders' convenience and information. This Document and its attachments are not part of the Contract Documents.

B. Because subsurface conditions indicated by the soil borings are a sampling in relation to the entire construction area, and for other reasons, the Government, the Architect, the Architect's consultants, and the firm reporting the subsurface conditions do not warranty the conditions below the depths of the borings or that the strata logged from the borings are necessarily typical of the entire site. Any party using the information described in the soil borings and geotechnical report shall accept full responsibility for its use.

C. A geotechnical investigation report for Project, prepared by GEOServices, LLC., dated November 3, 2020, is available for viewing as appended to this Document.

1. The opinions expressed in this report are those of a geotechnical engineer and represent interpretations of subsoil conditions, tests, and results of analyses conducted by a geotechnical engineer. Government is not responsible for interpretations or conclusions drawn from the data.

2. Any party using information described in the geotechnical report shall make additional test borings and conduct other exploratory operations that may be required to determine the character of subsurface materials that may be encountered.

END OF DOCUMENT

Attachment

GEOServices, LLC | 2561 Willow Point Way, Knoxville, TN, 37931 | Phone (865) 539-8242 Fax (865) 539-8252 | www.geoservicesllc.com

November 3, 2020

AECOM Technical Services, Inc.

9400 Amberglen Boulevard Austin, Texas 78729

ATTENTION: Mr. Mike Russell, AIA, LEED AP Mike.Russell@aecom.com

Subject: REPORT OF GEOTECHNICAL EXPLORATION

Ground Based PV Arrays – PSXE172003 McGhee Tyson Airport Alcoa, Tennessee 37701 GEOServices Project No. 21-20640

Dear Mr. Russell:

We are submitting the results of the geotechnical exploration performed for the subject project. The geotechnical exploration was performed, in accordance with our Proposal Number 11-19288, dated April 29, 2019 and as authorized by issuance of Purchase Order #126857 dated July 22, 2020. The following report presents our findings and recommendations for the proposed project. Should you have any questions regarding this report, or if we can be of any further assistance, please contact us at your convenience.

Sincerely, GEOServices, LLC

T. Brian Williamson, P.E. Stephen R. Martin, P.E.

Geotechnical Department Manager Geotechnical Project Manager

TN 118,861

mailto:Mike.Russell@aecom.com

Submitted by:

GEOServices, LLC 2561 Willow Point Way Knoxville, TN 37931

Phone (865) 539-8242 Fax (865) 539-8252

REPORT OF

GEOTECHNICAL EXPLORATION

Ground Based PV Array – PSXE172003

McGhee Tyson Airport Alcoa, Tennessee 37701

GEOServices Project No. 21-20640

Submitted to:

AECOM Technical Services, Inc.

9400 Amberglen Boulevard

Austin, Texas 78729

TABLE OF CONTENTS

Contents Page

1.0 INTRODUCTION

1.1 PURPOSE

1.2 PROJECT INFORMATION AND SITE DESCRIPTION

1.3 SCOPE OF STUDY

2.0 EXPLORATION AND TESTING PROGRAMS

2.1 FIELD EXPLORATION

2.2 LABORATORY TEST PROGRAM

3.0 SUBSURFACE CONDITIONS

3.1 GEOLOGIC CONDITIONS

3.2 SOIL STRATIGRAPHY

3.2.1 Soil Test Borings

3.2.2 Observation Pits

3.2.3 Groundwater

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 SITE ASSESSMENT

4.1.1 Existing Fill Materials

4.1.2 Very Soft to Firm & High Plasticity Clays

4.2 SITE PREPARATION RECOMMENDATIONS

4.2.1 Subgrade

4.2.2 Structural Soil Fill

4.2.3 Dense Graded Aggregate

4.3 DRIVEN PILE FOUNDATION DESIGN PARAMETERS

4.4 SHALLOW FOUNDATIONS AND CONCRETE SLABS-ON-GRADE

4.4.1 Shallow Foundations

4.4.2 Slabs-on-Grade

4.5 SEISMIC DESIGN CRITERIA

5.0 CONSTRUCTION CONSIDERATIONS

5.1 FOUNDATION CONSTRUCTION

5.2 EXCAVATIONS

5.3 HIGH PLASTICITY SOIL CONSIDERATIONS

5.4 MOISTURE SENSITIVE SOILS

5.5 DRAINAGE AND SURFACE WATER CONCERNS

5.6 SINKHOLE RISK REDUCTION AND CORRECTIVE ACTIONS

6.0 LIMITATIONS

APPENDICES

APPENDIX A – Figures, General Notes, Observation Pit Logs, and Soil Test Boring Records APPENDIX B – Laboratory Test Results

Report of Geotechnical Exploration GEOServices Project No. 21-20640 Ground Based PV Array – PSXE172003 – Alcoa, TN November 3, 2020

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1.0 INTRODUCTION

1.1 PURPOSE

The purpose of our geotechnical exploration was to explore the subsurface conditions for the proposed two PV Arrays to be located within McGhee Tyson Airport in Alcoa, Tennessee and provide geotechnical recommendations for site preparation and grading and for design and construction of the foundation system.

1.2 PROJECT INFORMATION AND SITE DESCRIPTION

Initial project information was provided via phone conversation and email correspondence with Mr. Mike

Russell of AECOM Technical Services on April 23, 2019. Based on the provided information, we understand construction will consist of two new PV Arrays. At this time, based on anticipated wind, uplift loads of up to 30 psf will be exerted on the panels. The panels will withstand the uplift loads by driven piles that will be driven a maximum depth of 16 feet below exiting ground surface.

In addition, some lightly-loaded ancillary structures will be constructed across the site and be supported using a system of conventional shallow foundations and slabs-on-grade. While we have not been provided structural loading information for these structures, we anticipate maximum column and continuous wall loads of less than 20 kips and 2 kips per linear foot, respectively.

Existing surface elevations reportedly range from approximately 1000 to 930 feet Mean Sea Level (MSL), sloping downwards from north to south. Although we have not been provided with grading information at this time, we have assumed that earthwork cuts and fills of less than 10 feet will be required to facilitate the proposed construction.

The proposed site is immediately bordered by Briscoe Drive to the west, construction of new pavement areas and a hangar to the north and east, and undeveloped land to the south. Based on our review of historical aerial imagery (Google Earth), the site appears to have been mass graded with adjacent construction sometime around 2002 and again around 2010. In addition, some areas may have been regraded during the ongoing adjacent construction. At the time of our field activities, the majority of the site was grass covered.

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1.3 SCOPE OF STUDY

This geotechnical exploration involved a site reconnaissance, field drilling, observation pit excavations, laboratory testing, and engineering analysis. The following sections of this report present discussions of the field exploration, site conditions, and conclusions and recommendations. Following the text of this report, Appendix A presents figures and test boring records.

The scope of our geotechnical engineering services did not include an environmental assessment for determining the presence or absence of wetlands, or hazardous or toxic materials in the soil, bedrock, surface water, groundwater, or air, on, or below, or around this site. Statements in this report or on the boring logs regarding odors, colors, and unusual or suspicious items or conditions are strictly for informational purposes.

2.0 EXPLORATION AND TESTING PROGRAMS

2.1 FIELD EXPLORATION

The site subsurface conditions were explored by drilling eight (8) soil test borings across the proposed site. The borings were located in the field by GEOServices personnel using the provided site plan. The borings were drilled between September 21 and 22, 2020 and advanced using 3¼-inch hollow stem augers and a GeoProbe track mounted drill rig.

Upon completion of our drilling activities, several areas were further explored by excavating observation pits. The excavation was performed on October 2, 2020 by our subcontractor using a backhoe with a 24-inch-wide tooth bucket. The excavations were observed by a member of our staff to document the materials encountered. The approximate locations of the soil test borings and observation pits are shown on Figure 2 of Appendix A of this report. The depths in this report reference the ground surface that existed at the time of this exploration. Detailed logs for soil test borings and observation pits can also be found in Appendix A.

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Within each boring, Standard Penetration Testing (SPT) and split-spoon sampling were performed on 2½-foot intervals in the upper 10 feet and on 5-foot centers thereafter. SPT and split-spoon sampling were performed in accordance with ASTM D 1586. In split-spoon sampling, a standard 2-inch O.D. split-spoon sampler is driven into the bottom of the boring with a 140-pound hammer falling a distance of 30 inches.

The number of blows required to advance the sampler the last 12 inches of the standard 18 inches of total penetration (or second and third 6-inch increments when sampling 24 inches) is recorded as the SPT resistance (N-value). These N-values are indicated on the boring logs at the test depth and provide an indication of the consistency or relative density of the soil.

2.2 LABORATORY TEST PROGRAM

After completion of the field drilling and sampling phase of this project, the soil samples were returned to our laboratory where they were visually-manually classified in general accordance with the Unified Soil

Classification System (USCS – ASTM D 2487) by a GEOServices geotechnical professional. Select samples were then tested for moisture content (ASTM D 2216) and Atterberg limits (ASTM D 4318). The laboratory test results are discussed in the following sections of this report and presented in Appendix B.

3.0 SUBSURFACE CONDITIONS

3.1 GEOLOGIC CONDITIONS

The project site, as most of east Tennessee, lies in the Appalachian Valley and Ridge Physiographic Province.

The Province is characterized by elongated, northeasterly-trending ridges formed on highly resistant sandstones and shales. Between ridges, broad valleys and rolling hills are formed primarily on less resistant limestones, dolomites and shales.

Published geologic information indicates that the site is underlain by the Chepultepec Dolomite formation of the Knox Group. This formation is primarily a light-colored dolomite with beds of sandstone along which the characteristic of weathering of predominantly dolomite units is greatly accelerated. These formations are known to exhibit dropouts and collapse activity. Residuum from the Chepultepec often contains a light-colored chert.

Report of Geotechnical Exploration GEOServices Project No. 21-20640

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The boundary between soil and rock is not sharply defined in this geologic setting and there often is a transitional zone, termed "weathered rock" overlying competent bedrock. Weathering is facilitated by fractures, joints, and the presence of less resistant rock types. Consequently, the profile of the weathered rock and hard rock is quite irregular and erratic, even over short horizontal distances. Also, it is not unusual to find lenses and boulders of hard rock and/or zones of weathered rock within the soil mantle well above the general bedrock level.

Since the bedrock underlying this site contains carbonate rock (i.e. dolomite), it is susceptible to the hazards of irregular weathering, cave and cavern conditions, and overburden sinkholes. Carbonate rock, while appearing very hard and resistant, is soluble in slightly acidic water. This characteristic, plus differential weathering of the bedrock mass is responsible for these hazards. Of these hazards, the occurrence of sinkholes is potentially the most damaging to overlying soil-supported structures. Sinkholes occur primarily due to differential weathering of the bedrock mass and flushing of overburden soil into the cavities within the bedrock. This loss of solids creates a cavity, or dome, within the overburden. Growth of the cavity over time, or excavation over the dome, can create a condition in which rapid subsidence, or collapse, of the roof of the dome occurs.

A rigorous effort to assess the potential for sinkhole development at this site was beyond our scope of service.

During our review of the United States Geological Survey (USGS – Louisville Quadrangle, TN), multiple closed depressions were noted within a 1-mile radius of the proposed site. Figure 1 in Appendix A shows a section of the USGS topographic map in the site vicinity. Surficial indications of solution activity were not observed during our site reconnaissance; however, the site has been previously mass graded which may have obscured any surficial indicators.

It is our opinion that the risk of sinkhole development at this site is no greater than at other sites located within similar geologic settings which have been developed successfully. However, the owner must be willing to accept the low to moderate risk of sinkhole development at this site. The risk of sinkhole development can be reduced by following the recommendations provided in the Sinkhole Corrective Actions (Section 5.6) section of this report.

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3.2 SOIL STRATIGRAPHY

The following subsurface description is of a generalized nature to highlight the subsurface stratification features and material characteristics at the observation pit and soil boring locations. The logs included in

Appendix A of this report should be reviewed for specific information at each location. Information on actual subsurface conditions exists only at the specific locations and is relevant only to the time that this exploration was performed. Variations may occur and should be expected at the site.

3.2.1 Soil Test Borings

Surficial & Fill Materials

In general, each boring encountered approximately 1 to 2 inches of surficial topsoil. We anticipate the actual depth may vary significantly across the site and between our widely spaced borings. As such, we recommend the contractor evaluate the surficial material depth for bidding purposes.

Beneath the surficial materials, each location encountered apparent fill materials consisting of gray, orangish brown, brown, tan, to reddish brown low plasticity (lean) and high plasticity (fat) clayey soils with varying amounts of organics, sand, gravel, and asphalt fragments. In addition, some plastic fragments were noted in boring B-7 at a depth of approximately 17 feet below existing grade. An apparent chemical odor and construction debris was also noted in the sample obtained from boring B-5 at a depth of approximately 5 ½ below existing grade.

The fill materials extended to depths of approximately 3 to 20 feet below existing grade. We note the depth of fill in borings B-5 and B-7 through B-9 may be greater as the boring was terminated within the fill.

Residuum

Underlying the fill materials in six locations (B-1 through B-4, B-6, and B-10), apparent residual materials were encountered and extended to boring termination depths. The residual materials generally consisted of tan, reddish brown, to orangish brown low plasticity (lean) and high plasticity (fat) clayey soils with varying amounts of chert fragments, sand, and manganese.

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The SPT N-values within the fill and residual soils generally ranged from 6 to 30 bpf, indicating firm to very stiff consistencies in the fine-grained materials. The exceptions were the initial samples in borings B-2 and

B-7 which had SPT N-values of 3 and 4 bpf, respectively, indicating soft consistencies. In addition, SPT N-values greater than 20 bpf were likely influenced by denser material, such as asphalt, gravel, or chert fragments.

Laboratory testing of selected samples of the fill and residual soils indicated in-situ moisture content values ranging from 15 to 47 percent which varied with depth. Atterberg limits testing was performed on select samples from borings B-2, B-7, and B-10 at depths ranging from approximately 3 ½ to 7 ½ feet below existing grade. The testing of the select samples indicated liquid limits ranging between 52 and 64 with plasticity indices between 30 and 46. According to the United Soils Classification System, the soils were classified as Fat Clay – CH, based on the plasticity testing alone.

Auger Refusal

Auger refusal was not encountered at our boring locations prior to reaching the predetermined termination depths of approximately 20 feet below existing grade. Auger refusal is a designation applied to any material that cannot be readily penetrated by the drill auger and is normally indicative of a very hard or very dense material, such as large boulders or the upper surface of bedrock. The following table indicates the approximate surficial materials thickness along with the fill and boring termination depths relative to the ground surface elevation.

Table 1 –Boring Summary Information

Boring Approximate Surficial Material Thicknesses

(inches)

Approximate Depth of Fill

(feet)

Approximate Boring Termination Depth

(feet)

B-1 1” Topsoil 3 20

B-2 1” Topsoil 8 20

B-3 1” Topsoil 5 ½ 20

B-4 1” Topsoil 3 20

B-5 1” Topsoil 20 20

B-6 2” Topsoil 12 20

B-7 1” Topsoil 20 20

B-8 1” Topsoil 20 20

B-9 1” Topsoil 20 20

B-10 2” Topsoil 8 20

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3.2.2 Observation Pits

Surficial & Fill Materials

Upon completion of our soil test borings, fifteen (15) observation pits were completed across the site to further evaluate the existing fill materials. Initially, the majority of the locations encountered surficial materials consisting 4 inches of topsoil.

Beneath the surficial materials, apparent fill materials were encountered at each location generally consisting of brown to reddish brown high plasticity (fat) clayey soils with varying amounts of asphalt, concrete, and rock fragments. Construction debris was encountered in observation pits OP-2, OP-3, OP-

9, OP-10, and OP-11. These materials generally extended to termination or refusal depths.

Observation Pit Refusal/Termination

Excavation refusal was encountered in four locations (OP-3 and OP-9 through OP-11) at depths of approximately 2 to 4 feet below existing grade. It should be noted these locations encountered fill materials that extended to refusal depths. Therefore, it is possible that refusal was upon denser fill materials, such as rock or concrete fragments. The remaining eleven observation pits were extended to a depth of approximately 8 feet below existing grade without encountering refusal materials. Refusal is a designation applied to materials that cannot be penetrated by typical excavation equipment. The following table indicates the approximate surficial materials thickness along with the fill and refusal depth relatively to the existing surface elevation.

Table 2 – Observation Pit Summary Information

Observation Pit # Approximate Surficial Material Thicknesses

(inches)

Approximate Depth of Fill

(feet)

Approximate Observation Pit Termination Depth

(feet)

OP-1 4” Topsoil 8 8

OP-2 4” Topsoil 8 8

OP-3 4” Topsoil 3 3* (R)

OP-4 4” Topsoil 8 8

OP-5 4” Topsoil 8 8

OP-6 4” Topsoil 8 8

OP-7 4” Topsoil 8 8

OP-8 4” Topsoil 8 8

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Observation Pit # Approximate Surficial Material Thicknesses

(inches)

Approximate Depth of Fill

(feet)

Approximate Observation Pit Termination Depth

(feet)

OP-9 4” Topsoil 2 2* (R)

OP-10 4” Topsoil 2 2* (R)

OP-11 4” Topsoil 4 4* (R)

OP-12 4” Topsoil 8 8

OP-13 4” Topsoil 8 8

OP-14 4” Topsoil 8 8

OP-15 4” Topsoil 8 8

NOTES: *(R) – Refusal materials encountered

3.2.3 Groundwater

Groundwater was encountered in one location (B-7) at a depth of approximately 19 ½ feet below existing grades. The remaining locations did not encounter apparent groundwater during or upon completion of the drilling activities. We note that stabilized water levels can sometimes be difficult to obtain as the encountered soils are known to be relatively impermeable. In addition, each boring was backfilled upon completion in consideration of safety so delayed water levels were not recorded.

It is possible for groundwater to exist within the depths explored during other times of the year depending upon climatic and rainfall conditions. Additionally, discontinuous zones of perched water may exist within the overburden materials. The high plasticity clays encountered will likely perch groundwater following heavy or prolonged periods of precipitation. The groundwater information presented in this report is the information that was collected at the time of our field activities.

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4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 SITE ASSESSMENT

Based on the results of our geotechnical exploration, it is our opinion that the site is generally adaptable for the proposed construction. These challenges include the existing fill materials, very soft to firm materials and some high plasticity (fat) clays which were encountered across the site.

4.1.1 Existing Fill Materials

During our exploration, apparent fill materials were encountered in the majority of the borings and observation pits generally consisting of soft to very stiff clays with varying amounts of organics, sand, and gravel. In addition, some asphalt and concrete fragments were noted in several borings and observation pits located in the central and eastern portions of the site. The fill materials extended to depths of approximately 3 to 20 feet below existing grade. We note the depth of fill in borings B-5 and B-7 through

B-9 and in our observation pits may be greater as they were terminated within the fill.

There is an inherent risk of excessive total or differential settlement of foundations and other features constructed on undocumented fill materials. At a minimum, we recommend that debris laden fill, deleterious materials, or very soft to soft materials encountered during grading or construction and/or between our borings, be completely undercut and disposed off-site. A budget contingency for additional undercutting and replacement of unsuitable materials that may be encountered during construction should be included. It is possible that deeper zones or pockets of fill materials may be encountered between our widely spaced borings. We note the presence of the concrete fragments within the fill could also present some difficulty during the installation of driven piles.

4.1.2 Very Soft to Firm & High Plasticity Clays

The majority of our borings encountered soft to firm materials at depths ranging from the existing surface to approximately 15 feet below existing. Therefore, we anticipate some remediation of foundation subgrade will be required where these materials are encountered. We recommend performing close construction observations during earthwork and foundation excavations activities to observe the consistency and suitability to support the proposed construction. Any areas observed to be unsuitable for use as foundation or subgrade support should be remediated accordingly. Generally, remediation of these

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10 | P a g e types of soils consists of undercutting and replacing a minimum of 2 feet below foundation bearing elevation and slab subgrade with properly compacted structural soil fill or compacted dense graded aggregate. The depth of undercutting should be determined at the time of construction.

While the majority of the residual soils were classified as lean clays, we note some of the fill materials along with residual soils in five locations (B-3 and B-14) were classified as high plasticity (fat) clays at depths ranging from the existing surface to 20 feet below existing grade. Therefore, we anticipate these materials will be encountered during construction activities. Typically, these materials are marginally suitable for foundation or slab support and may impede site grading activities as they are susceptible to moisture changes. We have provided recommendations pertaining to the fat clayey soils in this report.

The use of soil cement modification within the building area will help to reduce the concerns associated with high plasticity soils within proposed building areas.

We strongly encourage the client to confer with the design team and a contractor with regard to the recommendations contained in this report, in an effort to assess potential costs and schedule. Additional onsite testing during construction can further classify the fill materials suitability for reuse as structural soil fill.

4.2 SITE PREPARATION RECOMMENDATIONS

4.2.1 Subgrade

Site stripping within the proposed construction areas (building and pavement) should include the removal of, utilities, topsoil, unsuitable fill, rock fragments greater than 6 inches, and gravel. While construction debris was limited to some gravel and construction debris were noted in boring B-5 and observation pits

OP-2, OP-3, OP-9, OP-10 and OP-11, the previous development may have additional buried pockets of these materials in unexplored locations across the site which should be completely undercut and removed. The stripping operations should extend a minimum 10 feet beyond building footprints. These areas should be observed by a geotechnical engineer upon grading to confirm the recommendations in this report are followed.

After the completion of stripping operations and excavation to reach the planned subgrade elevation, we recommend that the subgrade be proofrolled with a fully-loaded, tandem-axle dump truck or other

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11 | P a g e pneumatic-tired construction equipment of similar weight. The geotechnical engineer or his representative should observe proofrolling. Areas judged to perform unsatisfactorily (e.g., pumping and/or rutting) by the engineer should be undercut and replaced with structural soil fill or remediated at the geotechnical engineer's recommendation. Areas to receive structural soil fill should also be proofrolled prior to the placement of new fill. Proofrolling operations should extend a minimum distance of 10 feet beyond the building perimeter.

4.2.2 Structural Soil Fill

Material considered suitable for use as structural fill should be clean soil free of organics and other deleterious material, containing no rock fragments greater than 6 inches in dimension. Preferably, structural soil fill material should have a standard Proctor maximum dry density of 90 pounds per cubic foot (pcf), or greater, and a PI value of 35 percent, or less. The material to be used as structural fill should be tested by the geotechnical engineer to confirm that it meets the project requirements before being placed.

Structural fill should be placed in loose, horizontal lifts not exceeding 8 inches in thickness. Each lift should be compacted to at least 98 percent of the soil’s maximum dry density per the standard Proctor method (ASTM

D 698) and within the range of minus (-) 2 percent to plus (+) 3 percent of the optimum moisture content.

Each lift should be tested by geotechnical personnel to confirm that the contractors’ method is capable of achieving the project requirements before placing subsequent lifts. Areas which have become soft or frozen should be removed before additional structural fill is placed.

4.2.3 Dense Graded Aggregate

Dense graded aggregate (DGA) fill may be required as backfill in undercut excavations and in utility trench excavations. The DGA used for this section should be Type A and Grading D or E in accordance with Section

903.05 of the Tennessee Department of Transportation (TDOT) specifications. The DGA fill should be placed in loose, horizontal lifts not exceeding 8 inches in loose thickness. Each lift should be compacted to at least 98 percent of maximum dry density per the standard Proctor method (ASTM D 698). Each lift should be compacted, tested by geotechnical personnel and approved before placing subsequent lifts.

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4.3 DRIVEN PILE FOUNDATION DESIGN PARAMETERS

A driven pile system is recommended for the support of the solar panels. Based on the soil conditions encountered, driving conditions along portions of the site are anticipated to be difficult and may encounter refusal prior to reaching design depths for uplift and lateral pile resistance. Driving difficulties will generally depend on the degree of calcareous induration and gravel content that is encountered at the installation location. In cases were shallow pile driving refusal is encountered, pre-drilling of pile holes, backfilling with concrete, then insertion of steel piles may be needed to meet design depths.

Table 3 – Design Values for Pile Foundations

Depth Range (ft)

Effective

Unit

Weight

(pcf)

Cohesion (psf) Friction Angle

Φ(Degrees)

Soil Strain

Ratio E50

Subgrade Modulus

Parameter k (pci)

0-1 Neglect

1-10.5 115 300 24 0.02 200

10.5 – 20 125 500 24 0.01 500

In general, lateral resistance of piles is non-linear and depends on several parameters, including depth, pile diameter and soil strength. The site-specific soil strength parameters presented in the tables above are recommended for the analysis of laterally loaded pile foundations.

An allowable end bearing capacity of 5,000 pounds per square foot at 7 feet below the existing ground surface is recommended. In addition, a skin friction of 300 pounds per square foot may be used for design of piles, neglecting the top one foot of pile. The safe upward capacity of the piles can be considered as being 80 percent of the safe downward skin friction capacity.

4.4 SHALLOW FOUNDATIONS AND CONCRETE SLABS-ON-GRADE

4.4.1 Shallow Foundations

At the time of this report detailed information regarding size and location of structures has not been provided.

However. Based on the data retrieved, we anticipate small ancillary shallow foundations may be required for the support of lightly loaded equipment cabinets. We recommend that if soft or unstable soils are

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We recommend that continuous foundations be a minimum of 18 inches wide and isolated spread footings be a minimum of 24 inches wide to reduce the possibility of a localized punching shear failure. Exterior foundations should be designed to bear at least 18 inches below finished exterior grade to develop the design bearing pressure and to protect against frost heave.

A geotechnical representative should be retained to perform foundation subgrade tests to confirm that the recommendations provided in this report are consistent with the site conditions encountered. Some undercutting of lower consistency fill soils where encountered in foundation excavations should be anticipated. A dynamic cone penetrometer (DCP) is commonly utilized to provide information that is compared to the data obtained in the geotechnical report. Where unacceptable materials are encountered, the material should be excavated to stiff, suitable soils or remediated at the geotechnical engineer's direction.

Based on the known subsurface conditions, geology, and past experience, we estimate foundations supported on recommended structural soil fill or other approved soils should experience maximum total and differential settlements of 1 inch and ½ inch, respectively. The settlement information provided was with maximum column and continuous foundation loads on the order of 20 kips and 2 kips per linear foot (kpf), respectively, and an allowable bearing pressure of 2,000 psf. Additionally, this information assumes that the site is prepared in accordance with our recommendations provided in this report. If these parameters are determined to be incorrect, we should be notified to reevaluate the settlements for the building.

4.4.2 Slabs-on-Grade

Following the recommended site preparation activities, it is our opinion that the floor slab can be grade supported on structural soil fill materials or suitable residual soils. Observing proofrolling of the subgrade, as discussed earlier in this report, should be accomplished to identify soft or unstable soils which should be removed from the floor slab area prior to fill placement and/or floor slab construction. Based on our exploration, the client should anticipate and budget for some remediation of the existing materials.

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We recommend that a minimum 4-inch thick granular mat be placed beneath the floor slab to enhance drainage and provide a capillary break. The subgrade should be proofrolled and approved prior to the placement of the crushed stone. Based on the conditions encountered on this site, we recommend that the floor slabs be designed using a subgrade modulus of 100 pounds per cubic inch (pci). This modulus is appropriate for small diameter loads (i.e. a 1ft x 1ft plate) and should be adjusted for wider loads.

4.5 SEISMIC DESIGN CRITERIA

In accordance with the International Building Code (IBC), 2018, we are providing the following seismic design information. After evaluating the SPT N-value data from the soil test borings and considering the changes to the site and foundation types, it was determined that the subsurface conditions at the site most closely matched the description for “Seismic Site Class D” or “Stiff Soil Profile”. Table 4 provides the spectral response accelerations for both short and 1-second periods, which may be used for design.

Table 4 – Seismic Design Parameters

The short and 1-second period values indicate the structure should be assigned a Seismic Design Category

“D” using the published information. The provided values are based on the results of our field exploration and the assumption that the structure will be designed utilizing a Risk Category I, II or III. If these assumptions are incorrect, we should be contacted to reevaluate the seismic design information.

For structures assigned a Seismic Design Category D, Sections 1803.5.12 of the 2018 IBC requires the determination of seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet of backfill height. If walls of more than 6 feet are included in the project design, GEOServices should be retained to develop the seismic lateral earth pressures.

In accordance with IBC 2018 sections 1803.5.11 and 1803.5.12, we have provided a discussion on the following geologic and seismic hazards: slope instability, liquefaction, total/differential settlement, and surface displacement due to faulting or seismically induced lateral spread or lateral flow.

Structure Ss S1 SDS SD1 g g g g

Ground Based PV Arrays – PSXE172003 0.877 0.159 0.672 0.241

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Liquefaction occurs when soil, primarily saturated cohesionless soils, undergo a loss in strength due to monotonic, transient, or repeated disturbance that commonly occurs during a seismic event (Kramer

1996). This loss of strength occurs due to increased pore water pressures caused by an undrained condition. The increase in pore water pressure decreases the effective stress in the soil, thus reducing the soils ability to support any applied loads. For liquefaction to occur, there must be an increase in pore pressure meaning the soil must be saturated and be able to behave in an undrained condition. According to the NHI 2011 Reference Manual on LRFD Seismic Analysis and Design of Transportation Geotechnical

Features and Structural Foundations, if any of the following criteria are satisfied then a significant liquefaction hazard does not exist:

• The geologic materials underlying the site are either bedrock or have very low liquefaction susceptibility according to the relative susceptibility ratings shown in the Estimated Susceptibility of Sedimentary Deposits to Liquefaction During Strong Ground Motion table presented by Youd and Perkins in 1978.

• The soils below the groundwater table at the site are one of the following:

o Clayey soils which have a clay content greater than 15%, liquid limit greater than 35%, or natural water content less than 90% of the liquid limit.

o Sand with a minimum corrected SPT (N1)60 value of 30 blows/foot.

o The water table is deeper than 50 feet below the ground surface or proposed finished grade at the site.

We note that the borings encountered plastic soils having clay contents likely above 15 percent.

Additionally, based on experience in this geologic region and immediate vicinity of the site, it is our opinion that a liquefaction hazard does not exist for the subject development. As such, we do not expect significant additional total and differential settlement, lateral soil movement, reduction in bearing capacity or lateral soil reaction, permanent increase in soil lateral pressure, or flotation of buried structures in accordance with Sections 1803.5.11 and 1803.5.12 of the 2018 IBC.

We also noted mapped faults on the geologic maps we reviewed for this project vicinity of the site.

However, the known faults within the East Tennessee valley are generally ancient, with no known active faults reaching the surface. Therefore, it is our opinion that surface displacement due to faulting or

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5.0 CONSTRUCTION CONSIDERATIONS

5.1 FOUNDATION CONSTRUCTION

Foundation excavations should be opened, the subgrade evaluated, remedial work performed (if required), and concrete placed in an expeditious manner. Exposure to weather often reduces foundation support capabilities, thus necessitating remedial measures prior to concrete placement. It is also important that proper surface drainage be maintained both during construction (especially in terms of maintaining dry footing trenches) and after construction. Soil backfill for footings should be placed in accordance with the recommendations for structural fill presented herein.

5.2 EXCAVATIONS

Auger refusal was not encountered prior to reaching the predetermined termination depth of 20 feet below existing grade at our boring locations. While we do note some shallow refusal materials were encountered in several of our observation pit locations and boring B-5, we anticipate this was on denser fill materials and not indicative of the underlying bedrock. Auger refusal conditions generally correspond to materials which require difficult excavation methods such as ripping, chipping (by track-mounted hydraulic hammers) or blasting for removal. However, excavation equipment varies, and field refusal conditions may vary. Generally, the weathering process is erratic and variations in the rock profile can occur in small lateral distances.

Based on existing grades and understanding of the project, we do not anticipate that the difficult excavation techniques will be necessary during most grading activities and foundation excavations.

However, as previously mentioned, the geology is known to be erratic and some weathered rock and/or rock ledges requiring difficult excavation techniques may be encountered in isolated areas. Where the proposed foundation extends below where weathered rock/refusal was encountered in the boring, excavation difficulty should be anticipated.

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Excavations should be sloped or shored in accordance with local, state, and federal regulations, including

OSHA (29 CFR Part 1926) excavation trench safety standards. The contractor is usually solely responsible for site safety. This information is provided only as a service, and under no circumstances should GEOServices be assumed responsible for construction site safety.

5.3 HIGH PLASTICITY SOIL CONSIDERATIONS

Based on our experience in the East Tennessee area, soils with plasticity indices (PI) less than 30 percent have a slight potential for volume changes with changes in moisture content, and soils with a PI greater than 50 percent are highly susceptible to volume changes. Between these values, we consider the soils to be moderately susceptible to volume changes. Based on our limited laboratory testing, we anticipate the majority of the onsite soils have a slight to moderate potential for volume change.

Plastic soils have the potential to shrink or swell with significant changes in moisture content. Unlike other areas of the country where high plasticity soils cause considerable foundation problems, East Tennessee does not typically endure long periods of severe drought or wet weather. However, in recent years drought conditions have been sufficient to cause soil shrinkage and related structural distress of buildings and floor slabs at sites underlain by high plasticity soils.

At sites that have high plasticity soils, certain precautions should be considered to minimize or eliminate the potential for volume changes. The most effective way to eliminate the potential for volume changes is to remove highly plastic soils and replace them with compacted fill of non-expansive material. Testing and recommendations for the required depth of removal can be provided, if needed. If removal of the highly plastic soils is not desirable, then measures should be taken to protect the soils from excessive amounts of wetting or drying. In addition, modification of the soils by lime or cement treatment can be utilized to reduce the soil plasticity.

Several construction considerations may reduce the potential for volume changes in the subgrade soils.

Foundations should be excavated, checked, and concreted in the same day to prevent excessive wetting or drying of the foundation soils. The floor subgrade should be protected from excessive drying and

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Installing moisture barriers around the perimeter of the slab will help limit the moisture variation of the soil and reduce the potential for shrinking or swelling. In addition, roof drains should discharge water away from the building area and foundations. Heat sources should be isolated from foundation soils to minimize drying of the foundation soils. Trees and large shrubs can draw large amounts of moisture from the soil during dry weather and should be kept well away from the building to prevent excessive drying of the foundation soils. Watering of lawns or landscaped areas should be performed to maintain moisture levels during dry weather.

Structural details to make the building flexible should be considered to accommodate potential volume changes in the subgrade. Floor slabs should be liberally jointed to control cracking, and the floor slab should not be structurally connected to the walls. Walls should incorporate sufficient expansion/contraction joints to allow for differential movement.

5.4 MOISTURE SENSITIVE SOILS

The plastic fine-grained soils encountered at this site will be sensitive to disturbances caused by construction traffic and changes in moisture content. During wet weather periods, increases in the moisture content of the soil can cause significant reduction in the soil strength and support capabilities. Construction traffic patterns should be varied to prevent the degradation of previously stable subgrade. In addition, the soils at this site which become wet may be slow to dry and thus significantly retard the progress of grading and compaction activities. We caution if site grading is performed during the wet weather season; increases in the undercut volumes should be expected.

Further for site fills, methods such as discing and allowing the material to dry will be required to meet the required compaction recommendations. It will, therefore, be advantageous to perform earthwork and foundation construction activities during dry weather. However, November through March is typically the difficult grading period due to the limited drying conditions which exist.

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5.5 DRAINAGE AND SURFACE WATER CONCERNS

To reduce the potential for additional undercut and construction induced sinkholes, water should not be allowed to collect in the foundation excavations, on floor slab areas, or on prepared subgrades of the construction area either during or after construction. Undercut or excavated areas should be sloped toward one corner to facilitate removal of collected rainwater, subsurface water, or surface runoff. Positive site surface drainage should be provided to reduce infiltration of surface water around the perimeter of the building and beneath the floor slab. The grades should be sloped away from the building and surface drainage should be collected and discharged such that water is not permitted to infiltrate the backfill and floor slab areas of the building.

Significant construction dewatering is not anticipated for site grading based on our limited understanding of the proposed grading. However, seasonal fluctuations and runoff from adjacent properties may occur once construction begins.