11_-_B720_Geotechnical_Report.pdf

GEOServices, LLC; 2561 Willow Point Way; Knoxville, Tennessee 37931; Phone: (865) 539-8242; Fax: (865) 539-8252

April 17, 2018

C2RL Engineers, Inc.

240 West Bessemer Street Alcoa, Tennessee 37701

ATTENTION: Ms. Becky Bowe, P.E.

bbowe@c2rl.com

Subject: REPORT OF GEOTECHNICAL EXPLORATION

Security Services – Building B720 Expansion 118th TNANG Nashville, Tennessee GEOServices Project No. 21-18219

Dear Ms. Bowe:

We are submitting the results of the geotechnical exploration performed for the subject project. The geotechnical exploration was performed, as authorized by you, in accordance with our Proposal No.

11-18118, dated March 7, 2018. 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. Matthew B. Haston, P.E.

Project Manager Senior Geotechnical Engineer

TN 118,861

TBW/MBH: tbw

REPORT OF

GEOTECHNICAL

EXPLORATION

Security Services –

Building B720 Expansion

118th TNANG

Nashville, Tennessee

GEOSERVICES, LLC

PROJECT NO. 21-18219

Submitted to:

C2RL Engineers, Inc.

240 West Bessemer Street Alcoa, Tennessee 37701 ATTENTION: Ms. Becky Bowe, P.E.

Submitted by:

GEOServices, LLC 2561 Willow Point Way Knoxville, Tennessee 37931

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

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

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 SITE ASSESSMENT

4.2 SITE PREPARATION RECOMMENDATIONS

4.2.1 Subgrade

4.2.2 Structural Soil Fill

4.2.3 Dense Graded Aggregate

4.3 FOUNDATION RECOMMENDATIONS

4.3.1 Shallow Foundations

4.3.2 Slabs-on-Grade

4.3.3 Settlement

4.4 SEISMIC DESIGN CRITERIA

4.5 PAVEMENT DESIGN RECOMMENDATIONS

4.5.1 Flexible Pavement Design

4.5.2 Rigid Pavement Design

4.5.3 General

4.6 LATERAL EARTH PRESSURES

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 and Test Boring Records APPENDIX B – Soil Laboratory Data

Report of Geotechnical Exploration GEOServices Project No. 21-18219 B720 Security Forces / Nashville, Tennessee April 17, 2018

1.0 INTRODUCTION

1.1 PURPOSE

The purpose of our geotechnical exploration was to explore the subsurface conditions and provide general recommendations for site preparation/grading and for design and construction of the foundation system, including allowable bearing pressure. Additionally, recommendations for light- and heavy-duty pavements are included.

1.2 PROJECT INFORMATION AND SITE DESCRIPTION

The project site is located on the existing campus of Nashville International Airport in Nashville, Tennessee. More specifically, the project site is located at Building B720 of the 118th Wing of the

Security Forces complex. Project information was provided by Ms. Becky Bowe via emails and communication which included a proposed site plan indicating the proposed construction area. It is our understanding that the proposed project is to consist of the renovation of Building B720 which will include the construction of a new 1,800 square-foot addition. We understand the building addition will be constructed as a steel-framed structure with a masonry façade and be a single-story structure bearing on a conventional system of shallow foundations and concrete slab-on-grade. Foundation loading information was also not provided at the time of this proposal.

However, we have assumed maximum column and continuous foundation loads on the order of

100 kips and 2 to 4 kips per linear foot, respectively.

Topographic information was not available as the project is still in the design phase. However, a review of available USGS topographic data revealed the project site is generally level and asphalt covered with a minimum topographic relief. Therefore, we anticipate that maximum earthwork cuts and fills of less than about 5 feet will be required in the area of the building pad to reach planned subgrade elevation for the proposed construction.

1.3 SCOPE OF STUDY

This geotechnical exploration involved a site reconnaissance, field drilling, laboratory testing, and engineering analysis. The following sections of this report present discussions of the field

Report of Geotechnical Exploration GEOServices Project No. 21-18219 exploration, site conditions, and conclusions and recommendations. Following the text of this report, Appendix A presents figures and test boring records and Appendix B presents a summary of laboratory test results.

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. Any 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 existing subsurface conditions were explored with four (4) soil test borings drilled within the general area of proposed building location. The boring locations were staked in the field by

GEOServices personnel. The borings were located by using the provided site plan and measuring distances from existing landmarks. Drilling was performed on April 6, 2018 by our subcontractor.

The borings were advanced using 2.25-inch inside diameter hollow stem augers (HSA) with a

Geoprobe® track mounted drill rig. The approximate locations of the test borings performed on site are referenced in Figure 2 of Appendix A of this report. Detailed logs for soil test borings can also be found in Appendix A.

Within each boring, standard penetration testing (SPT) and split-spoon sampling were performed at 2-1/2-foot intervals in the upper 10 feet and at 5-foot intervals thereafter. The borings extended to auger refusal. Rock coring was beyond the scope of our services. The drilling was performed in accordance with ASTM D6151 (hollow stem auger drilling). 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

Report of Geotechnical Exploration GEOServices Project No. 21-18219 to advance the sampler the last 12 inches of the standard 18 inches of total penetration is recorded as the Standard Penetration Resistance (N-value). These N-values are indicated on the boring logs at the testing depth, and provide an indication of consistency of cohesive materials.

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 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 natural moisture content (ASTM D 2216) and

Atterberg limits (ASTM D 4318). The laboratory test results are further discussed in the following sections of this report and a summary is provided in Appendix B.

3.0 SUBSURFACE CONDITIONS

3.1 GEOLOGIC CONDITIONS

The project site lies within the Central Basin Physiographic Province of Middle Tennessee. This province is a nearly elliptical area enclosed by the Highland Rim Physiographic Province. The

Central Basin is characterized by gently rolling to hilly terrain interspersed with level areas and meandering, low-gradient streams. This region is primarily composed of Ordovician-era limestone and dolomite overlying Precambrian-era igneous rock.

Published geologic information indicates that the site is underlain by bedrock of the Nashville

Group. In the area of this site the Nashville Group is composed of the Bigby-Cannon Limestone and Hermitage Formations. These formations generally consist of thin-bedded argillaceous and nodular limestone with minor amounts of shale and phosphatic calcarenite. These formations typically weather to produce a thin, sandy residual soil. Silica in the form of chert is resistant to weathering and scattered in various quantities throughout the residuum.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

Since the bedrock underlying this site contains carbonate rock (i.e. limestone/dolomite), the site is susceptible to the typical carbonate 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 the 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 and flushing or raveling of overburden soils into the cavities in the bedrock. The loss of solids creates a cavity or dome in the overburden. Growth of the dome over time or excavation over the dome can create a condition in which rapid, local subsidence or collapse of the roof of the dome occurs.

A certain degree of risk with respect to sinkhole formation and subsidence should be considered at any site located within geologic areas underlain by potentially soluble rock units. While a rigorous effort to assess the sinkhole potential at this site was beyond the scope of services, we did not observe obvious surficial signs of sinkhole activity at this site. Additionally, no closed depressions, which are indicative of past sinkhole activity, were observed on the United States

Geological Survey (USGS – Antioch Quadrangle, TN) topographic map within the near vicinity

(2,000 feet) of this site.

Based on this information, 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 a moderate risk of sinkhole development at this site. The risk of sinkhole development can be reduced by following the recommendations provided in the Sinkhole Risk Reduction and Corrective Actions (Section 5.6) section of this report.

3.2 SOIL STRATIGRAPHY

The following subsurface description is of a generalized nature to highlight the subsurface stratification features and material characteristics at the boring locations. The boring logs included in Appendix A of this report should be reviewed for specific information at each boring location.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

Information on actual subsurface conditions exists only at the specific boring locations and is relevant only to the time that this exploration was performed. Variations may occur and should be expected at the site.

Surficial

Each soil test boring drilled encountered a surficial topsoil layer that was approximately 3 to 7 inches in thickness.

Fill Soils

Beneath the existing surficial layer, existing fill soil was encountered in each soil test boring to depths ranging from approximately 3 to 5.5 feet beneath the existing ground surface. Fill is generally classified as soils that have been transported and placed by man. The existing fill soils generally consisted of brown, reddish brown and grey lean clay with varying amounts of rock fragments, and trace organics. Additionally, boring B-4 refused in what appeared to be existing fill material which contained brick and concrete fragments. An offset boring (B-4A) was performed adjacent to B-4 that extended below the fill. The SPT N-values used to evaluate the consistency of the fill soil encountered ranged from 2 to 14 blows per foot (bpf) indicating a relative soil consistency of very soft to very stiff. However, the very soft soils were isolated to one boring (B-1) at a depth of approximately 4 feet below existing ground surface. Additionally, the

N-values indicating “very stiff” soils were likely elevated due to rock fragments within the samples. Therefore, the existing fill was generally observed to be of firm to stiff consistency.

The in-situ moisture content of selected samples of fill material ranged from 16.7 to 22.2 percent and were observed to be moist during visual classification. Atterberg limits testing resulted in a liquid limit (LL) of 26 percent and plasticity index of 10 percent. The fill soils testing classifies as lean clay (CL) in accordance with the USCS.

Residual Soil

Beneath the existing fill soil, residual soil was encountered to depths of termination (i.e., 13.7 to

16.1 feet below existing ground surface). Residual soils are formed from the in place weathering of the underlying parent bedrock. The residual soils generally consisted of light brown and brown

Report of Geotechnical Exploration GEOServices Project No. 21-18219 fat clay (CH) and lean clay (CL) with varying amounts of chert fragments overlying sandy silt

(ML) with sandstone. The SPT N-values used to evaluate the consistency of the residual soil ranged from 7 bpf to50 blows with 1 inch of penetration, indicating a relative soil consistency ranging from firm to very hard. However, the very hard consistency soils were encountered near auger refusal materials. Therefore, the residual soil encountered was generally firm to very stiff in consistency.

The natural moisture content of selected samples of residual material ranged from 22.3 to 38.1 percent. It is also noted that the samples were typically determined to be moist when visually classified. Atterberg limits testing resulted in a liquid limit (LL) of 37 percent and plasticity index of 18 percent. The residual soils testing classifies as lean clay (CL) in accordance with the USCS.

Auger Refusal

Auger refusal materials were encountered in each boring performed at depths ranging from 2.9 to

16.1 feet below existing ground surface. Auger refusal is a designation of materials that cannot be penetrated by soil drilling tooling. As previously mentioned, rock coring was beyond the scope of our services. Therefore, the nature and continuity of the refusal material was not determined.

However, based on the results of field exploration and our experience in the geologic setting, we anticipate the refusal materials encountered (except those in B-4) likely correlate with top of continuous bedrock. As mentioned previously, boring B-4 refused on concrete at a depth of 2.9 feet.

Ground Water

Ground water was not encountered in the borings drilled on the site at time of drilling. Subsurface water levels may fluctuate due to seasonal changes in precipitation amounts. Additionally, areas of perched water may exist in the overburden and/or near the contact with bedrock.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 SITE ASSESSMENT

The results of the subsurface exploration indicate that the site is generally overlain by fill and residual soils. The existing fill material is generally firm, or better, in consistency. The residual soil encountered is generally stiff, or better, in consistency. Based on the results of our geotechnical exploration, it is our opinion that the site is generally adaptable for the proposed construction.

However, the firm existing soils will not provide adequate foundation support for the proposed structure. Furthermore, isolated areas of concrete/brick debris may be encountered in foundation excavations. Therefore, it will be necessary to overexcavate the foundations to stiff, or better, residual soils. We recommend performing close construction observations during earthwork and foundation excavations activities to observe the consistency of the existing soil and evaluate its suitability to support the proposed construction. Areas observed to be unsuitable for use as foundation or subgrade support should be remediated accordingly. Remediation of these materials will likely consist of undercutting and replacing with compacted fill soil or dense graded aggregate.

4.2 SITE PREPARATION RECOMMENDATIONS

4.2.1 Subgrade

Initially, vegetation, and deleterious materials (if encountered), as well as existing utilities, loose rock fragments greater than 6 inches, and other debris must be removed from the areas proposed for construction and the resulting excavations backfilled with compacted fill as described below.

Demolition should include the complete removal of all above and below grade structures. Stripping operations should extend a minimum of 5 feet beyond the limits of proposed pavement areas and

10 feet beyond building limits. These areas should be observed by a geotechnical engineer upon grading to ensure the recommendations in this report are followed.

After completion of stripping operations and excavation to reach planned the subgrade elevation, we recommend that the subgrade be proofrolled with a fully-loaded, single-axle dump truck or other pneumatic-tired construction equipment of similar weight. The geotechnical engineer or his

Report of Geotechnical Exploration GEOServices Project No. 21-18219 representative should observe proofrolling. Areas judged to perform unsatisfactorily (e.g., excessive 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 fill. Proofrolling operations shall be extended a minimum distance of 10 feet beyond the building perimeter and 5 feet beyond pavement areas.

4.2.2 Structural Soil Fill

Material considered suitable for use as structural fill should be clean soil free of organics, trash, 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 pcf, or greater, and a plasticity index (PI) of 35 percent or less. 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 contractor’s 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, to reach finished floor elevation. The

DGA used for this section should be Type A and Grading 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.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

4.3 FOUNDATION RECOMMENDATIONS

4.3.1 Shallow Foundations

Foundations for the proposed construction are anticipated to bear in stiff residual soils and/or properly compacted structural fill placed to backfill undercut excavations. The recommended allowable soil bearing capacity for design of the foundations is 2,500 psf or less. 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 footings should be designed to bear at least 18 inches below finished exterior grade 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 soft soils which may be found between boring locations during 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.

4.3.2 Slabs-on-Grade

For slab-on-grade construction, the site should be prepared as previously described. We recommend that the subgrade be topped with a minimum 4-inch layer of crushed stone to act as a capillary moisture block. 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.

4.3.3 Settlement

Based on the results of this geotechnical exploration and assuming that the site is prepared in accordance with this report, we anticipate total settlements of less than 1 inch and differential settlements of less than ¾ inch. The settlement information provided was with a maximum column

Report of Geotechnical Exploration GEOServices Project No. 21-18219 and continuous foundation load of 100 kips and 3 kips per linear foot as well as an allowable bearing pressure of 2,500 psf.

4.4 SEISMIC DESIGN CRITERIA

International Building Code, 2012

In accordance with the International Building Code, 2012/2015, we are providing the following seismic design information. After evaluating the SPT N-value data from the soil test borings, it was determined that the site subsurface conditions most closely matched the description for

“Seismic Site Class C”. Table 1 provides the spectral response accelerations for both short and 1-second periods, which may be used for design.

Table 1: Seismic Design Parameters

Structure Ss S1 SDS SD1 g g g g Proposed B720 Addition 0.286 0.140 0.229 0.155

4.5 PAVEMENT DESIGN RECOMMENDATIONS

4.5.1 Flexible Pavement Design

AASHTO flexible pavement design methods have been utilized for pavement recommendations. Our recommendations are based on the assumptions that the subgrade has been properly prepared as described previously. Based on our experience with similar developments, we recommend the following light and heavy-duty flexible pavement sections:

Table 2: Flexible Pavement Recommendations

Pavement Materials Light-Duty (in) Heavy-Duty (in)

Bituminous Asphalt Surface Mix 1.5 1.5

Bituminous Asphalt Base Mix 2.0 3.0

Compacted Crushed Aggregate Base 6.0 8.0

Report of Geotechnical Exploration GEOServices Project No. 21-18219

We recommend a base stone equivalent to a Type A and Grading D in accordance with Section 903.05 of the TDOT specifications. The bituminous asphalt pavement should be Grading "E" as per Section

411 for the surface mix and Grading “BM/BM2” as per section 307 for the binder mix. Compaction requirements for the crushed aggregate base and the bituminous asphalt pavement should generally follow TDOT specifications.

4.5.2 Rigid Pavement Design

AASHTO rigid pavement design methods have been utilized for pavement recommendations. In areas of trash dumpster pads or areas where large trucks will be parked on the pavement, we recommend the use of a concrete paving section. Our recommendations are based on the assumptions that the subgrade has been properly prepared. Based on our experience with similar developments, we recommend the following rigid pavement section:

Table 3: Rigid Pavement Recommendations Pavement Materials Light-Duty (in) Heavy-Duty (in)

4,000 psi Type I Concrete 6.0 7.0

Compacted Crushed Aggregate Base 4.0 6.0

Concrete should be reinforced with welded wire fabric or reinforcing bars to assist in controlling cracking from drying shrinkage and thermal changes. Sawed or formed control joints should be included for each 225 square feet of area or less (15 feet by 15 feet). Saw cuts should not cut through the welded wire fabric or reinforcing steel and dowels should be utilized at formed and/or cold joints.

4.5.3 General

Our recommendations are based upon the assumption that the subgrade has been properly prepared as described previously and that off-site soil borrows to be used to backfill to the final subgrade meets the requirements provided in this report.

All paved areas should be constructed with positive drainage to direct water off-site and to minimize surface water seeping into the pavement subgrade. The subgrade should have a minimum slope of 1

Report of Geotechnical Exploration GEOServices Project No. 21-18219 percent. In down grade areas, the basestone should extend through the slope to allow water entering the basestone a path to exit. For rigid pavements, water-tight seals should also be provided at formed construction and expansion joints.

4.6 LATERAL EARTH PRESSURES

We are currently unaware of below grade walls associated with the project. However, with the possibility, we are providing equivalent fluid pressures for three backfill conditions for cantilever-type walls. These are 1) active earth pressure for granular backfill (clean sand or gravel), 2) at-rest earth pressure for granular backfill, and 3) at-rest earth pressure for fine-grained (clay) backfill.

The equivalent fluid pressures provided have assumed a level backfill and a wall with a vertical face.

Condition 1 - The active earth pressure for granular backfill will result in an equivalent fluid pressure of 30 pounds per cubic foot (pcf). If the granular backfill is to develop active earth pressure conditions, walls must be flexible and/or free to rotate or translate at the top approximately one inch laterally for every 20 feet of wall height.

Condition 2 - The at-rest earth pressure for granular backfill will result in an equivalent fluid pressure of 47 pcf. For retaining walls that will not rotate or translate, such as building walls or other walls rigidly connected to structures, at-rest conditions will develop.

Condition 3 - Walls backfilled with fine-grained material (silt or clay) should be designed using the at-rest earth pressure whether restrained at the top, or not. Fine-grained soils typically creep over time which produces additional lateral stresses to the wall. The equivalent fluid pressure for this case is 70 pcf

Forces from surcharge loading including sloping backfill should be added to the equivalent fluid pressures. The walls should be properly drained to remove water or hydrostatic pressure should be added to the design pressure. Also, the backfill for the walls should be placed in accordance with the structural fill recommendations described hereinafter.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

For rigid, cast-in-place concrete walls, an ultimate friction factor of 0.35 between foundation concrete and the bearing soils may be used when evaluating friction. Also, an ultimate passive earth pressure resistance of well-compacted soil fill can be approximated by a uniformly acting resistance of 1000 psf. However, to limit deformation when relying on passive strength, we recommend using a minimum safety factor of 3.0 applied to the ultimate passive resistance value.

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

As previously mentioned, auger refusal materials was encountered in each of the borings performed at depths ranging from 2.9 to 16.1 feet. However, the shallow refusal was caused by concrete debris in the fill and auger refusal was generally between 13 and 16 feet. Auger refusal conditions generally correspond to materials which require difficult excavation techniques for removal. Typically, soils penetrated by augers can be removed with conventional earthmoving equipment. 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, particularly in this type of geology. Based on subsurface conditions encountered difficult excavation techniques will likely not be required across the site. However, as mentioned, pinnacles of bedrock (if encountered) will require special removal equipment (pneumatic splitters, hydraulic hammer, etc.) for excavation. Hard debris within the fill, such as concrete, may also cause some excavation difficulty.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

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 Middle 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.

Highly 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, Middle 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, floor slabs and pavements 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

Report of Geotechnical Exploration GEOServices Project No. 21-18219 excessive drying and wetting by covering the subgrade prior to slab construction. The site should be graded in order to drain surface water away from the building both during and after construction.

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 moderately 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 volume required due to the marginal fills 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 that exist.

Report of Geotechnical Exploration GEOServices Project No. 21-18219

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.

5.6 SINKHOLE RISK REDUCTION AND CORRECTIVE ACTIONS

Based on our experience, corrective actions can also be performed to reduce the potential for sinkhole development at this site. These corrective actions would decrease but not eliminate the potential for sinkhole development. Much can be accomplished to decrease the potential of future sinkhole activity by proper grade selection and positive site drainage.

In general, the portions of a site that are excavated to achieve the desired grades will have a higher risk of sinkhole development than the areas that are filled, because of the exposure of relic fractures in the soil to rainfall and runoff. On the other hand, those portions of a site that receive a modest amount of fill (or that have been filled in the past) will have a decreased risk of sinkhole development caused by rainfall or runoff because the placement of a cohesive soil fill over these areas effectively caps the area with a relatively impervious “blanket” of remolded soil. Therefore, the recommendations that follow incorporate a modest remedial treatment program designed to make the surface of the soil in excavated areas less permeable.

Although it is our opinion that the risk of ground subsidence associated with sinkhole formation cannot be eliminated, we have found that several measures are useful in site design and development to reduce this potential risk. These measures include:

Report of Geotechnical Exploration GEOServices Project No. 21-18219

Maintaining positive site drainage to route surface waters well away from structural areas both during construction and for the life of the structure.

The scarification and re-compaction of the upper 6 to 10 inches of soil in earthwork cut areas.

Verifying that subsurface piping beneath structures is carefully constructed and pressure tested prior to its placement in service.

The use of pavement or lined ditches, particularly in cut areas, to collect and transport surface water to areas away from structures.

Considerations when building within a sinkhole prone area are to provide positive surface drainage away from proposed building or parking areas both during and after construction. Backfill in utility trenches or other excavations should consist of compacted, well-graded material such as dense graded aggregate or compacted on site soils. The use of an open graded stone such as No. 57 stone is not recommended unless the stone backfill is provided an exit path and not allowed to pond. If sinkhole conditions are observed, the type of corrective action is most appropriately determined by GEOServices on a case-by-case basis.

6.0 LIMITATIONS

This report has been prepared in accordance with generally accepted geotechnical engineering practice for specific application to this project. This report is for our geotechnical work only, and no environmental assessment efforts have been performed. The conclusions and recommendations contained in this report are based upon applicable standards of our practice in this geographic area at the time this report was prepared. No other warranty, express or implied, is made.

The analyses and recommendations submitted herein are based, in part, upon the data obtained from the exploration. The nature and extent of variations between the borings will not become evident until construction. We recommend that GEOServices be retained to observe the project construction in the field. GEOServices cannot accept responsibility for conditions which deviate from those described in this report if not retained to perform construction observation and testing. If variations appear evident, then we will re-evaluate the recommendations of this report. In the event that any changes in the nature, design, or location of the structures are planned, the conclusions and recommendations

Report of Geotechnical Exploration GEOServices Project No. 21-18219 contained in this report will not be considered valid unless the changes are reviewed and conclusions modified or verified in writing. Also, if the scope of the project should change significantly from that described herein, these recommendations may need to be re-evaluated.

APPENDIX A

Figures and Test Boring Records

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DRILLING CO

DRILLER

BORING NO. / LOCATION LOGGED BY

DATE FT.

REFUSAL: Yes DEPTH 14.9 FT. ELEV. FT. COMPLETION: DEPTH Dry FT.

SAMPLED 14.9 FT. 4.5 M ELEV. FT.

TOP OF ROCK DEPTH FT. ELEV. FT.

BEGAN CORING DEPTH FT. ELEV. FT. AFTER 24 HRS. DEPTH N/A FT.

FOOTAGE CORED (LF) FT. ELEV. FT.

BOTTOM OF HOLE DEPTH 14.9 FT. ELEV. FT.

BORING ADVANCED BY: X.

FIELD LABORATORY

SAMPLE RESULTS RESULTS

FT. ELEV. TYPE N-Value Qp LL PI %M

SS 16.8

SS 22.2

SS 23.2

SS 25.1

22.8

AUGER REFUSAL AT 14.9 FEET

Lean CLAY (CL) with trace organics and trace rock fragments - brown; firm to soft; moist; (FILL)

Lean CLAY (CL) with trace chert fragments -brown, light brown, and reddish brown; stiff;

moist; (RESIDUUM)

Sandy SILT (ML) with trace sandstone - dark brown and brown; hard; moist; (RESIDUUM)

Security Forces B720 Expansion LOG OF BORING B-1 Nashville, Tennessee SHEET 1 OF

April 6, 2018 SURFACE ELEV. WATER LEVEL DATA (IF APPLICABLE)

GEOServices Project No.: 21-18219 Tri-State Drilling, LLC

Clifton Wombles

B-1 Scott Williams

-2.5

FROMDEPTH TO OR STRATUM DESCRIPTION

FT. FT. RUN NO.

Topsoil (7 inches)

4-5-8 N=13

POWER AUGERING WASHBORING

STRATUM SAMPLE DEPTH SAMPLE

5.0 -5.0

2.5

12.5 -12.5

7.5 -7.5

10.0 -10.0

8.5 10.0 4

9-2-50/2"

N=50/2"SS514.713.5

20.0 -20.0

REMARKS:

15.0

17.5 -17.5

-15.0

6.0 7.5 3

3-4-3 N=7

2-1-1 N=2

1.0 2.5 1

3.5 5.0 2

5-6-5 N=11

DRILLER

BORING NO. / LOCATION LOGGED BY

DATE FT.

REFUSAL: Yes DEPTH 16.1 FT. ELEV. FT. COMPLETION: DEPTH Dry FT.

SAMPLED 16.1 FT. 4.9 M ELEV. FT.

TOP OF ROCK DEPTH FT. ELEV. FT.

BEGAN CORING DEPTH FT. ELEV. FT. AFTER 24 HRS. DEPTH N/A FT.

FOOTAGE CORED (LF) FT. ELEV. FT.

BOTTOM OF HOLE DEPTH 16.1 FT. ELEV. FT.

BORING ADVANCED BY: X.

FIELD LABORATORY

SAMPLE RESULTS RESULTS

FT. ELEV. TYPE N-Value Qp LL PI %M

SS 26 10 17.5

SS 26.8

SS 22.3

SS 24.7

SS 31.2

Lean CLAY (CL) - brown; firm; moist;

(RESIDUUM)

Lean CLAY (CL) with trace small chert fragments - brown and light brown; very stiff to firm; moist to very moist; (RESIDUUM)

3-3-4 N=7515.013.5

AUGER REFUSAL AT 16.1 FEET

6-8-8 N=16

7-8-9 N=176.0 7.5 3

20.0 -20.0

REMARKS:

17.5 -17.5

15.0 -15.0

12.5 -12.5

10.0 -10.0

8.5 10.0 4

7.5 -7.5

3-3-4 N=73.5 5.0 2

5.0 -5.0

2.5 -2.5

Topsoil (3 inches)

5-6-8 N=141.0 2.5 1

Lean CLAY (CL) - brown and dark gray; stiff;

moist; (FILL)

DEPTH FROM TO OR STRATUM DESCRIPTION

FT. FT. RUN NO.

POWER AUGERING WASHBORING

STRATUM SAMPLE DEPTH SAMPLE

GEOServices Project No.: 21-18219 Tri-State Drilling, LLC

Clifton Wombles

B-2 Scott Williams

Security Forces B720 Expansion LOG OF BORING B-2 Nashville, Tennessee SHEET 1 OF

April 6, 2018 SURFACE ELEV. WATER LEVEL DATA (IF APPLICABLE)

DRILLER

BORING NO. / LOCATION LOGGED BY

DATE FT.

REFUSAL: Yes DEPTH 13.7 FT. ELEV. FT. COMPLETION: DEPTH 12.0 FT.

SAMPLED 13.7 FT. 4.2 M ELEV. FT.

TOP OF ROCK DEPTH FT. ELEV. FT.

BEGAN CORING DEPTH FT. ELEV. FT. AFTER 24 HRS. DEPTH N/A FT.

FOOTAGE CORED (LF) FT. ELEV. FT.

BOTTOM OF HOLE DEPTH 13.7 FT. ELEV. FT.

BORING ADVANCED BY: X.

FIELD LABORATORY

SAMPLE RESULTS RESULTS

FT. ELEV. TYPE N-Value Qp LL PI %M

SS 16.7

SS 37 18 25.4

SS 27.7

SS 38.1

SS N=50/1" 28.5

Lean CLAY (CL) - brown and light brown; firm;

moist; (RESIDUUM)

Fat CLAY (CH) with trace small chert fragments -brown and light brown with trace black mottling;

stiff; moist; (RESIDUUM)

Lean CLAY (CL) with siltstone - dark brown and brown; hard; moist; (RESIDUUM)

513.613.5 AUGER REFUSAL AT 13.7 FEET

5-5-7 N=12

4-6-6 N=126.0 7.5 3

20.0 -20.0

REMARKS:

17.5 -17.5

-15.0

12.5 -12.5

15.0

10.0 -10.0

8.5 10.0 4

7.5 -7.5

1-2-4 N=63.5 5.0 2

5.0 -5.0

2.5 -2.5

Topsoil (5 inches)

4-4-5 N=91.0 2.5 1

Lean CLAY (CL) with gravel and trace organics -dark brown and reddish brown; stiff; moist;

(FILL)

DEPTH FROM TO OR STRATUM DESCRIPTION

FT. FT. RUN NO.

POWER AUGERING WASHBORING

STRATUM SAMPLE DEPTH SAMPLE

GEOServices Project No.: 21-18219 Tri-State Drilling, LLC

Clifton Wombles

B-3 Scott Williams

Security Forces B720 Expansion LOG OF BORING B-3

DRILLER

BORING NO. / LOCATION LOGGED BY

DATE FT.

REFUSAL: Yes DEPTH 2.9 FT. ELEV. FT. COMPLETION: DEPTH Dry FT.

SAMPLED 2.9 FT. 0.9 M ELEV. FT.

TOP OF ROCK DEPTH FT. ELEV. FT.

BEGAN CORING DEPTH FT. ELEV. FT. AFTER 24 HRS. DEPTH N/A FT.

FOOTAGE CORED (LF) FT. ELEV. FT.

BOTTOM OF HOLE DEPTH 2.9 FT. ELEV. FT.

BORING ADVANCED BY: X.

FIELD LABORATORY

SAMPLE RESULTS RESULTS

FT. ELEV. TYPE N-Value Qp LL PI %M

SS N=50/4"

AUGER REFUSAL AT 2.9 FEET DUE TO

CONCRETE FRAGMENTS

Lean CLAY (CL) with brick debris and concrete debris - brown; hard; moist; (FILL)

20.0 -20.0

REMARKS:

17.5 -17.5

15.0 -15.0

12.5 -12.5

7.5 -7.5

10.0 -10.0

5.0 -5.0

2.5 -2.5

Topsoil (6 inches)

1.0 1.3 1

DEPTH FROM TO OR STRATUM DESCRIPTION

FT. FT. RUN NO.

POWER AUGERING WASHBORING

STRATUM SAMPLE DEPTH SAMPLE

GEOServices Project No.: 21-18219 Tri-State Drilling, LLC

Clifton Wombles

B-4 Scott Williams

Security Forces B720 Expansion LOG OF BORING B-4

DRILLER

BORING NO. / LOCATION LOGGED BY

DATE FT.

REFUSAL: Yes DEPTH 15.1 FT. ELEV. FT. COMPLETION: DEPTH 14.0 FT.

SAMPLED 15.1 FT. 4.6 M ELEV. FT.

TOP OF ROCK DEPTH FT. ELEV. FT.

BEGAN CORING DEPTH FT. ELEV. FT. AFTER 24 HRS. DEPTH N/A FT.

FOOTAGE CORED (LF) FT. ELEV. FT.

BOTTOM OF HOLE DEPTH 15.1 FT. ELEV. FT.

BORING ADVANCED BY: X.

FIELD LABORATORY

SAMPLE RESULTS RESULTS

FT. ELEV. TYPE N-Value Qp LL PI %M

SS 26.4

SS 26.8

SS 31.9

SS 23.4

Lean CLAY (CL) - brown; firm; moist;

(RESIDUUM)

Fat CLAY (CH) with trace chert fragments -brown, light brown, and gray; very stiff; moist;

(RESIDUUM)

Sandy SILT (ML) with sandstone - dark brown and brown; hard; very moist; (RESIDUUM)

2-5-50/4" N=50/4"514.813.5

9-13-14 N=27

5-8-9 N=176.0 7.5 3

2-3-4 N=73.5 5.0

20.0 -20.0

REMARKS: Boring B-4A was offset approximately 10 feet west of boring B-4 location due to shallow refusal encountered at boring B-4.

17.5 -17.5

AUGER REFUSAL AT 15.1 FEET15.0 -15.0

12.5 -12.5

10.0 -10.0

8.5 10.0 4

7.5 -7.5

5.0 -5.0

2.5 -2.5

Topsoil (6 inches)

Lean CLAY (CL) - brown; moist; (FILL) (Based on B-4, sample #1 and auger tailings)

DEPTH FROM TO OR STRATUM DESCRIPTION

FT. FT. RUN NO.

POWER AUGERING WASHBORING

STRATUM SAMPLE DEPTH SAMPLE

GEOServices Project No.: 21-18219 Tri-State Drilling, LLC

Clifton Wombles

B-4A Scott Williams

Security Forces B720 Expansion LOG OF BORING B-4A

APPENDIX B

Soil Laboratory Data

Natural Boring Sample Depth Moisture Soil

Number Number (feet) Content LL PL PI Type 1 1.0 - 2.5 16.8% 2 3.5 - 5.0 22.2% 3 6.0 - 7.5 23.2% 4 8.5 - 10.0 25.1% 5 13.5 - 14.7 22.8%

1 1.0 - 2.5 17.5% 26 16 10 CL

2 3.5 - 5.0 26.8% 3 6.0 - 7.5 22.3% 4 8.5 - 10.0 24.7% 5 13.5 - 15.0 31.2%

1 1.0 - 2.5 16.7%

2 3.5 - 5.0 25.4% 37 19 18 CL

3 6.0 - 7.5 27.7% 4 8.5 - 10.0 38.1% 5 13.5 - 13.6 28.5%

2 3.5 - 5.0 26.4% 3 6.0 - 7.5 26.8% 4 8.5 - 10.0 31.9% 5 13.5 - 14.8 23.4%

SOIL DATA SUMMARY

Security Forces B720 Expansion - Nashville, Tennessee

GEOServices Project No. 21-18219

B-1

B-4A

B-3

B-2

April 11, 2018

Atterberg Limits