564-19-101 - Geotech Report.pdf

Veterans Health Care System of the Ozarks

Engineering Services

Construct New Water Storage Facility

Project Number 564-19-101

Geotechnical Investigation

August 31, 2021

Prepared for

Veterans Health Care System of the Ozarks

Engineering Services

Planning, Design, & Construction

Prepared by

Hodges Engineering

231 Shoreline Drive

Mountain Home, AR 72653

Mr. John Brock

VHSO Project Engineer

Engineering SVS P & D

1100 North College Avenue

Fayetteville, AR 72703

Subject: Geotechnical Report for New Water Storage Facility, North of Building 9, Project

Number 564-19-101

Dear Mr. Brock:

Hodges Engineering has completed the Tab A Field Investigation and subsequent geotechnical evaluation for Project Number 564-19-101, New Water Storage Facility, North of Building 9 at the Veteran’s Health Care System of the Ozarks (VHSO) facility in Fayetteville, Arkansas.

The purpose of this evaluation was to investigate the general subsurface conditions in the vicinity of the proposed water storage facility, the information from this report is intended to help determine the geotechnical setting for the immediate area. Our recommendations are based on exploratory drilling, visual inspection, samples taken from borings, laboratory analysis, available geological information, physical security guidance and engineering evaluation.

We thank you for the opportunity to provide consulting services for the Veteran’s Health Care

System of the Ozarks. If you have any questions or comments, please feel free to contact us.

Sincerely, James C. Hodges, PE Kevin Hodges, PE

Principal Project Director

TABLE OF CONTENTS

1.0 EXECUTIVE SUMMARY

2.0 INTRODUCTION

3.0 SITE DESCRIPTION

4.0 GEOTECHNICAL INVESTIGATION

5.0 LABORATORY ANAYLSIS

6.0 SITE CHARACTERIZATION

7.0 NEW WATER TANK LOCATION AND FOUNDATION CONSIDERATIONS

8.0 RECOMMENDATIONS

1.0 EXECUTIVE SUMMARY

Hodges Engineering conducted a Geotechnical Investigation to evaluate the subsurface conditions in the vicinity of the new water storage facility at the VHSO campus in Fayetteville, Arkansas as part of the Tab A Field Investigation for Project Number 564-19-101, Construct

New Water Storage Facility. This report presents the results of the investigation. The VHSO is planning to construct a 600,000-gallon water storage tank with redundant pumping and backup generator facilities at the site.

Our recommendations are based on exploratory drilling, visual inspection, samples taken from borings, laboratory analysis, available geological information, physical security guidance, and engineering evaluation.

1. The proposed new water tank location will be in the existing storage area location, north of Building 9, as shown in Figures 1 and 11.

2. Construct a deep foundation system consisting of drilled cast in place concrete piers to support a shallow foundation for the proposed water tank based on less time and lower costs associated with this type of construction. The depth of the proposed piers for the new water tank will be +/- 10-½ to 15-½ feet BGS. The drilled piers may be sized using a net allowable bearing pressure of 20,000 pounds per square foot (PSF) in the Stratum 2 rock.

3. If visual observation of drilling for the new piers reveals subsurface conditions other than the expected Stratum 2, the conditions must be evaluated to ensure they provide the required bearing capacity.

4. Construction of the foundation system shall follow the recommendations as outlined in

Appendix 1.

5. Construction Quality Assurance (CQA) for the new water tower should also include services such as periodic engineering inspections, soil testing, verification of foundation dimensions (including pier depths and widths), structural steel rebar inspections, and concrete testing.

2.0 INTRODUCTION

The Project physical address of the VHSO is 1100 North College Avenue, Fayetteville, AR and the subject area for the geotechnical investigation is located near the northeast corner of the

VHSO campus, North of Building 9, as shown in Figure 1. The Geotechnical Investigation consisted of 5 borings. B-1 with a planned depth of +/- 50 feet BGS and B-2, B-3, B-4, and B-5 with a planned depth of +/- 20 feet or auger refusal. The surveyed boring locations are shown in

Figure 2. B-1 was located near the center of the proposed water storage structure, B-2 and B-3 near the perimeter of the water storage structure and B-4 and B-4 outside of the structure. The boring locations were field adjusted to avoid storage containers and fencing in the laydown yard for construction on Building 9.

Figure 1. Vicinity Map

Figure 2. Boring Locations

3.0 SITE DESCRIPTION

The Project was mapped using the U.S. Department of Agriculture (USDA) Natural Resources

Conservation Services (NRCS) Web Soil Survey to develop a general understanding of the site, as shown in Figure 3. The map units delineated in the soil survey area represent the soils for the area in the survey. The map unit descriptions from the USDA NRCS report can be used to determine the composition and properties of a soil unit. The Project is located in the Fayetteville

Fine Sandy Loam Complex (FaC2). FaC2 typical soil profile is fine sandy loam to sandy clay loam, as shown in Figure 4. The terrain in the subject area is sloping with good drainage.

Figure 3. USDA NRCS Soils Map

Figure 4. USDA NRCS Soils Description

Based on maps and literature published by the United States Geological Survey and the Arkansas

Geological Survey, the project area is underlain by the Bloyd and Hale Formations that dates to the Morrowan Series of the early Pennsylvanian Age. The Bloyd Formation is also referred to as

Bloyd Shale. The Hale Formation has two named members, the Prairie Grove (upper) and the

Cane Hill (lower).

The lower part of the Bloyd Formation consists of interbedded very thin to thin ripple-bedded micaceous siltstones and sandstones that are fine to medium-grained interbedded with black clay to silty shales. Throughout the lower portion is black fissile clay to silty shales and thin sandstones interbedded with thin to thick-bedded fossiliferous carbonate to sandy carbonate layers. Thin pebble conglomerates are present within the interbedded shales and sandstones. The carbonate zones vary from red to gray on fresh and weathered surfaces and can be mottled. The quartz grains are medium-grained and sub-angular to sub-rounded. The contact between the lower part of the Bloyd Formation and the Prairie Grove is placed below a shaley layer conformable with the underlying massive calcareous sand of the Prairie Grove Member of the Hale Formation. The Cane Hill Member of the Hale Formation is primarily a sandstone and shale interval.

A 7.5 Minute Geologic Worksheet from the Arkansas Geological Survey is shown in Figure 5 and delineates the general location of the VHSO (circled in red). Also in Figure 5, above the

“Pch” symbol, which is the Cane Hill Member, there is an arrow pointing above and to the left, indicating a lower contour from the “Pbpg” symbol which is the Bloyd Shale and Prairie Grove

Members. The Cane Hill Member rests with pronounced unconformity upon older strata with a reported thickness of the Hale Formation ranging from a few feet to more than 300 feet. A

Stratigraphic Chart from the USGS National Geologic Map Database shows the location of this

Series in relation to the Ozark Region in Figure 6.

Figure 5. 7.5 Minute Geologic Worksheet from Arkansas Geologic Survey, General Vicinity of the VHSO

Figure 6. Stratigraphic Chart, USGS National Geologic Map Database

Seismic conditions at the VHSO site are rated as Low per the U.S. Department of Veterans Affairs

Seismic Zone Map dated November 1, 2016, as shown in Figure 7. The Memorandum for Record provided by Force Protect to the Design Team for this project describes that Fayetteville is located in a low-risk area for earthquakes with the ISGS database showing a 0.32% chance of a major earthquake within 50 kilometers of Fayetteville within the next 50 years. Multiple minor earthquakes tend to occur near Little Rock to the southeast and neighboring Oklahoma to the west.

The largest earthquake within 30 miles of Fayetteville was a 2.7 magnitude in 2010. The VA has requested that the seismic design for the new water storage facility to be designed using “Moderate

Hazard” criteria in lieu of “Low Hazard”.

Figure 7. U.S. Department of Veterans Affairs Seismic Zone Map

4.0 GEOTECHNICAL INVESTIGATION

Subsurface exploration was conducted on Augst 10, 2021. The Geotechnical Investigation consisted of 5 borings. B-1 with a planned depth of +/- 50 feet below ground surface (BGS) and

B-2, B-3, B-4, and B-5 with a planned depth of +/- 20 feet or auger refusal. B-1 was complete near the center of the proposed Tank and was completed to a depth of +/- 40 feet. Hodges

Engineering consulted with Caldwell Tank Engineering during the coring of B-1 and the depth completed after auger refusal (depth at which coring began) was more than acceptable. Borings

2 and 3 were placed along the perimeter of the proposed water Tank approximately 180 degrees apart which was adjusted due to containers and equipment in the laydown yard. The borings were completed utilizing a truck-mounted CME 75B drill rig and a Track Mounted Geoprobe equipped with an automatic hammer, as shown in Photo 1 and Photo 2. The drill rigs utilized a

4-inch diameter solid stem auger to advance the boreholes. Soil samples were obtained at predetermined depths using a two-inch diameter split spoon sampler. The split-spoon sampler was driven by free falling blows from a 140-pound automatic hammer dropping 30 inches.

Photo 1. Truck-Mounted CME 75B Drill Rig Photo 2. Track Mounted Geoprobe

During sampling for the Standard Penetration Test (SPT), the drillers mark 18 inches in 6-inch increments on the drill rig. The number of blows required to drive the sampler each 6-inch increment was recorded. The initial 6 inches is considered a seating section of the Test because of loose or disturbed material in the bore hole. The number of blows required to drive the final

12 inches is referred to as the N-Value and is recorded on the boring log in the blows-per-foot column. The N-Value corresponds to In-Situ Strengths for the associated soils, a table with the correlation between N-Values and relative density is shown in Figure 8. Final drilled depths (or completion depths) are reported as the depths achieved by the split-spoon sampler. The material obtained from the split spoon sampling was used for visual soil classification and then bagged for laboratory testing.

Figure 8. Standard Penetration Test Key

5.0 LABORATORY ANAYLSIS

Laboratory tests were performed on soil samples obtained from the borings. The laboratory tests were intended to determine the engineering properties of the project soil strata. The laboratory tests were conducted in accordance with the American Society for Testing and Materials (ASTM)

Test Methods. Testing performed on the samples include:

• Natural Moisture Content – ASTM D2216-10, Method A

The natural moisture content is the ratio of the weight of the water in a soil sample in relation to the weight of the solid particles. For many materials, the water content is one of the most significant index properties used in establishing a correlation between soil behavior and its index properties.

• Classification of Soils for Engineering Purposes (USCS) – ASTM D2487

This standard classifies soils from any geographic location into categories representing the results of prescribed laboratory tests to determine the particle-size characteristics, the liquid limit, and the plasticity index. The assigning of a group name and symbol(s) along with the descriptive information required in ASTM D2488 can be used to describe a soil to aid in the evaluation of its significant properties for engineering use.

• Description and Identification of Soils (Visual- Manual Procedure) – ASTM D2488

Soils are visually examined, and descriptions are provided on selected samples. The samples are tested in accordance with the test method to determine the soil classification.

• Atterberg Limits – ASTM D4318, Method A

Atterberg Limits help determine the soil’s plasticity characteristics. The Liquid Limit (LL) and Plastic Limit (PL) of a soil are first determined by test procedures. The Plasticity Index

(PI) is determined by subtracting the PL from the LL, PI = LL-PL. The PI is an indicator of a soil’s potential for volume change. A soil’s potential for volume change typically increases with higher PI.

• Gradation Analysis – ASTM D6913, Method A

Soils consist of particles with various shapes and sizes. This test method is used to separate particles into size ranges and to determine quantitatively the mass of particles in each range.

These data are combined to determine the particles size distribution (gradation). The gradation of soils is used for classification in accordance with ASTM D2487.

• Compressive Strength of Rock Cores – ASTM D7012, Method C

This standard of test is used for determining the unconfined compressive strength of core samples.

The natural soil moisture content was determined for the selected soil samples to provide a moisture profile for the project borings. Atterberg Limits tests were performed on selected samples to aid in the soil classification and to help evaluate the potential for volume change characteristics.

Gradation analyses were performed on selected soil samples to aid in soil classification.

Descriptions, laboratory results, classifications and boring data are presented in Attachment 1, Geotechnical Engineering Report.

6.0 SITE CHARACTERIZATION

Surface Conditions: The surface of the subject area is primarily limestone gravel. B-1 was located in concrete pavement directly west of the subject area.

Existing Fill Material: Existing fill material was found in all the borings at varying depths. The fill material varied in composition which included: lean clay with sand; sandy lean clay; clayey gravel; clayey sand; and gravelly sand with varying amounts of chert, shale, sandstone, and limestone. Based on the material found which included pieces of concrete and some organics, it was evident that the area was used for fill. No records of prior compaction or moisture content exists. The fill material varied in thickness from +/- 2-½ feet to 13-½ feet. Based on SPT N-

Values of 4 to 30 blows per foot corresponds to loose to densely packed soil, per Figure 8.

Low strength soils [N-values less than 7 beats per foot (BPF) or less] were encountered in depths from 2 to 13-½ feet BGS. Any unstable subgrade materials need to be removed and replaced full depth with suitable select fill material as outlined in Table 4 of Appendix 1. The select fill material will need to be placed in 8-inch lifts and compacted to 95% Standard Proctor, +/- 2% of optimum moisture content up to 5 feet outside of the perimeter of the proposed storage tank.

It should be noted that the fill materials are susceptible to further strength loss with increases in moisture contact and repetitive construction traffic. Wet conditions during rain events can also contribute to strength loss. Potential over excavation due to wet soil conditions could require an additional removal of material up to 2 feet in depth.

Stratum 1: The in-situ overburden soils were found to vary from Clays to Sands ranging in depths from +/- 8-½ feet to 13-½ feet.

Fine grained soils of lean and fat clays had varying amounts of sand. The coarse-grained soils had sand as well as gravel, clay, and silt. Shale seams were also encountered. N-Values range from 2 to 29 which corresponds to very loose to compact, per Figure 8.

Low strength soils (N-values less than 7 BPF or less) were also encountered in depths from 2 to

13-½ feet BGS. Any unstable subgrade materials need to be removed and replaced full depth with suitable select fill material as outlined in Table 4 of Appendix 1. The select fill material would need to be placed in 8-inch lifts and compacted to 95% standard proctor, +/- 2% of optimum moisture content up to 5 feet outside of the perimeter of the proposed storage tank.

Similar to the Existing Fill Material, Stratum 1 soils are susceptible to further strength loss with increases in moisture contact and repetitive construction traffic. Wet conditions during rain events can also contribute to strength loss. Potential over excavation due to wet soil conditions could require an additional removal of material up to 2 feet in depth.

Stratum 2: The basal rock encountered included a thin layer of sandstone cap overlaying thin interbedded seams of shale and limestone below Stratum 1 (+/- 8-½ feet to 13-½ feet) and extended to auger refusal or completion of target bore hole depth.

Coring of Stratum 2 was conducted in B-1 from +/- 21-½ feet to 40 feet using a NQ-sized double barrel with a diamond drill bit. Representative Core samples are shown in Photo 3 which show the interbedded shale and limestone layers. A select core sample taken from +/- 28-½ to 29 feet was used for ASTM D7012, Method C, to determine the unconfined compressive strength which was determined to be 1,346 pounds per square inch (PSI).

Groundwater was only encountered in B-5 from 9-1/2 feet to 14 feet BGS and assumed to be perched water above Stratum II.

All borings were backfilled after auger refusal or completion.

Photo 3. Core Samples

7.0 NEW WATER TANK LOCATION AND FOUNDATION CONSIDERATIONS

The new water storage tank location is planned on the proposed project site, as shown in Figure

9. The new water tank will be in the center of the site enclosed by anti-ram fencing within a 50-foot standoff distance, as required by force protection standards. The location of the new water storage tank is suitable with the given site constraints, although impacts to existing facilities and infrastructure on the site will need to be mitigated.

There are two foundation system alternatives that should be considered for the new water tank:

(1) a shallow foundation system; and,

(2) a drilled pier foundation.

The first alternative would be a shallow foundation system would require the existing fill layer and the low-strength materials in Stratum 1 be removed up to 13-½ feet in depth and up to 5 feet outside of the proposed tank perimeter. In addition, OSHA required sloping would add to the volume of cut and fill. This option would require more volume removal and then more properly constructed and compacted lifts to bring the area up to design grade which may correlate to additional time and cost. The additional time also potentially exposes the site to rain events and corresponding soil strength loss, which would require over excavation and replacement with approved select fill placed in lifts at the proper density and moisture content.

The second alternative would be a deep foundation system which would consist of drilled cast in place concrete piers supporting a shallow foundation system. The drilled piers would be drilled and socketed into the Stratum 2 layer. The drilled shafts will be range from +/- 10-½ to 15-½ feet BGS. Drilled pier foundation design parameters and recommendations are discussed in

Appendix 1 beginning on Page 14.

Figure 9. Stand-off & Anti-ram 50-Foot Radius from New Water Tower

8.0 RECOMMENDATIONS

The following recommendations are based on exploratory drilling, visual inspection, samples taken from borings, laboratory analysis, available geological information, physical security guidance, and engineering evaluation:

1. The new water tank location should be placed in the existing storage area location, north of Building 9, as shown in Figure 1 and Figure 9.

2. Construct a deep foundation system consisting of drilled cast in place concrete piers to support a shallow foundation for the proposed water tank based on less time and lower costs associated with this type of construction. The depth of the proposed piers for the new water tank will be +/- 10-½ to 15-½ feet BGS. The drilled piers may be sized using a net allowable bearing pressure of 20,000 PSF in the Stratum 2 rock.

3. If visual observation of drilling for the new piers reveals subsurface conditions other than the expected Stratum 2, the conditions must be evaluated to ensure they provide the required bearing capacity.

4. Construction of the foundation system shall follow the recommendations as outlined in

Appendix 1.

5. Construction Quality Assurance (CQA) for the new water tower should also include services such as periodic engineering inspections, soil testing, verification of foundation dimensions (including pier depths and widths), structural steel rebar inspections, and concrete testing.

This geotechnical report was prepared for the VHSO for the purpose of evaluating the suitability of a new water tower at the proposed site. We have also researched and reported literature obtained from the Arkansas Geologic Survey, the USGS National Geologic Map Database pertaining to this area, and a separate Geotechnical Report from a project site adjacent to the proposed new water storage tank site.

Attachment 1

Geotechnical Engineering Report

Geotechnical Engineering Report

Planned 600,000 Gallon Water Storage Tank Veteran's Health System of the Ozarks

1100 North College Avenue

Fayetteville, Arkansas

GTS Project No. 21-1-5-120

August 24, 2021

Geotechnical Engineering | Construction Materials Testing | Environmental Due Diligence

Hodges Engineering

Prepared For:

231 Shoreline Drive

Mountain Home, Arkansas 72653 www.gtsconsulting.net

Planned 600,000-Gallon Water Storage Tank Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

TABLE OF CONTENTS

EXECUTIVE SUMMARY

PROJECT DESCRIPTION and INFORMATION

Project Site Planned Development Planned Site Grading Scope of Services

SUMMARY of SUBSURFACE FINDINGS

Site Geology Surface Subsurface Conditions

Existing Fill Stratum I – Clays and Sands Stratum II – Basal Rock Auger Refusal/Hard Drilling Conditions

Water Measurements

GEOTECHNICAL ENGINEERING ANALYSIS

Geotechnical Considerations Existing Fill Foundation Type Discussion

Drilled Pier Foundation Design Recommendations Drilled Pier Foundation Construction Recommendations Slab-On-Grade Design IBC Site Classification

MASS GRADING RECOMMENDATIONS

Stripping of Surface Materials and Organics Evaluation of Existing Fill General Mass Grading Re-Use of On-Site Soils as Fill Utility Trench Backfill Grading and Drainage

GEOTECHNICAL REPORT REQUIREMENTS and SPECIFICATIONS

SUBSURFACE EXPLORATION and PROCEDURES

LABORATORY TESTING and PROCEDURES

GEOTECHNICAL REPORT LIMITATIONS

ENVIRONMENTAL EXCLUSION

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

LIST of TABLES

Table 1: Depths to Hard Drilling Conditions and Auger Refusal Material

Table 2: Drilled Pier Foundation Design Parameters

Table 3: Drilled Pier Foundation Design Parameters

Table 4: Fill Placement and Compaction Recommendations

Table 5: Soil Fill Material Requirements

Table 6: Laboratory Test Method Designations

LIST OF APPENDICES

A

Boring Location Diagram

Boring Logs

B

Laboratory Classification Test Reports

C

Rock Core Photographs

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

EXECUTIVE SUMMARY

This report uses the terms “existing grade” and “finished subgrade”. Existing grade is used in this report to describe the site elevations at the time of our field drilling and sampling. Finished subgrade is used in this report to describe the Civil Engineer-designed top-of-soil elevations at the site at completion of grading.

The information presented in this report is based on an electronic mail (email) message received from Kevin Hodges, P.E. with Hodges Engineering on June 25, 2021. Briefly, we understand that the planned water storage tank will have a diameter of 56 feet and a volume of approximately 600,000 gallons. The type of foundation and the height of the tank are currently unknown. It is our understanding that the foundation type will be selected once the subsurface conditions have been investigated. Finally, we understand that tank and foundation designs will be performed in accordance with AWWA D100-11.

It should be noted that GTS, Inc. (GTS) has experience drilling elsewhere on this larger property. The site is at the intersection of several Geologic units, and karst features have been encountered previously at nearby project sites.

Based on the soil and rock types and in-place shear strengths encountered at the borings performed by GTS as well as our understanding regarding the planned site grading, summary geotechnical engineering considerations for designing and constructing the planned water tank are provided below. The below information should not be used separately from the more comprehensive discussion provided in the body of this report.

Subsurface Conditions

At the time of the field exploration, gravel and concrete pavement covered the planned tank footprint and its surrounds. Existing fill materials were present beneath the site surface at each of our exploration locations. The existing fill was highly variable in terms of both composition and consistency and extended to depths of about 2 ½ to 13 ½ feet below existing grades.

Underlying the fill materials, a presumed native stratum of interbedded fine-grained and coarse-grained soils was generally present and extended to depths of about 8 ½ to 13 ½ feet below existing grades. The fine-grained soils included both lean and fat clays with varying amounts of sand. The coarse-grained soils included sands with varying amounts of gravel, clay and silt. In addition, thin seams of shale were also encountered intermittently within the native soils.

Finally, the basal stratum at this site consisted of a relatively thin sandstone cap underlain by shale with interbedded limestone seams and layers which extended to the terminal depths of our explorations. Hard drilling conditions were encountered within the upper portions of the rock stratum at each boring location. More specifically, hard drilling conditions first occurred as

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence shallow as about 8 ½ to 13 ½ feet below existing grades, upon encountering the sandstone cap, at each of our exploration locations.

Groundwater was observed while drilling and after drilling at depth of about 9 ½ and 14 feet below existing grade at Boring B-5, respectively. No free water was observed while drilling or immediately after drilling completion at any other boring location.

Geotechnical Design Considerations

A shallow foundation system could potentially be an option for supporting the planned tank if the existing fill materials as well as the low-strength materials (discussed herein) are removed and replaced with new fill. To be clear, this would require excavations as deep as about 13 ½ feet within the planned tank footprint. As discussed during a phone conversation between Mr.

Kevin Hodges, P.E. with Hodges Engineering and Mr. Travis Willis, P.E. with GTS on August

17, 2021, this option would likely take longer to complete, be less cost-effective, and be more intrusive than installing deep foundations.

As such, we recommend the planned tank be supported on a deep foundation system bearing in the underlying, hard (i.e. competent) basal bedrock layer. The drilled piers should be designed to bear a minimum depth of 2 feet into the underlying bedrock. Based on the results of the sample borings, minimum drilled pier depths of about 10 ½ to 15 ½ feet below existing grade are anticipated to be required. The drilled piers may be sized using a net allowable bearing pressure of 20,000 pounds per square foot (psf) for the recommended shale/limestone.

It is unclear at this time if a concrete slab-on-grade will be constructed as part of the planned tank development. It should be noted that marginal strength soils were encountered within both the existing fill soils and presumed native soils. As such, we recommend new floor slabs-on-grade should be supported on a minimum of 1 foot of newly placed and compacted, select fill material. This is assuming that the owner is willing to accept the risks associated with supporting the new floor slab atop the existing fill materials and above low-strength soils as detailed herein.

The subsurface conditions at this project are consistent with a Site Class C per the

International Building Code (IBC), 2012 Edition.

Other Considerations

The on-site, existing fill and native soils are moisture-sensitive and prone to strength loss with increases in moisture content and when exposed to repetitive construction traffic. We expect that ground improvement will be required, particularly if wet conditions develop during construction.

All fill materials should be free of debris and deleterious materials. All on-site soils and imported soils should be tested and approved before use for fill material.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

PROJECT DESCRIPTION and INFORMATION

Project Site

The project site is located at an existing Veteran's Health System of the Ozarks facility with a real property address of 1100 North College Avenue, Fayetteville, Arkansas. The general boundary of the project site is shown in yellow in Figure 1, below.

Figure 1 - General Boundary of the Project Site

Based on our observations during the field exploration, the planned tank footprint will be located in an existing, relatively level, staging area where several steel conex containers have been placed.

Several lightly loaded storage/garage structures are also present adjacent to the planned tank footprint.

It is our experience that properties with existing structures have a higher potential for encountering unknown conditions during mass grading and construction. These conditions include backfilled basements, trash pits (buried debris), concrete foundations as well as underground utilities associated with the previous site development.

East Memorial Drive

North College Avenue

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

Planned Development

The information presented in this report is based on an electronic mail (email) message received from Kevin Hodges, P.E. with Hodges Engineering on June 25, 2021, which included the project information detailed below as well as a request for proposal (RFP):

Hodges Engineering requested a minimum of five (5) boring locations: one boring to a depth of 50 feet at the center of the planned tank footprint and four borings to a depth of

20 feet along the perimeter of the planned tank (180 degrees apart on the base circle diameter).

An undated and untitled excerpt of a site plan showing the proposed tank location

(56-foot diameter). The existing site improvements, existing grades, and the approximate locations of the proposed borings were also detailed in this document.

An undated document titled “Soil Investigation Report Requirements” presumably provided by the tank’s manufacturer (Caldwell Tank). This document summarizes the appropriate factors of safety for different foundation loading conditions as well as the settlement tolerances of the tank. However, the document states that a foundation system has yet to be selected.

Based on the email conversation and “Soil Investigation Report Requirements” document referenced above, we understand the following.

The planned water storage tank will have a diameter of 56 feet and a volume of approximately 600,000 gallons. The type of foundation and the height of the tank are currently unknown.

Tank and foundation designs will be performed in accordance with AWWA D100-11.

It should be noted that GTS has experience drilling elsewhere on this larger property. The site is at the intersection of several Geologic units, and karst features have been encountered at the nearby project sites.

Planned Site Grading

Currently, the final floor elevation of the tank is unknown. Based on the existing grades at our boring locations, obtained from the site plan referenced above, we have assumed that about 3 feet of cut and fill will be needed to achieve design grades.

If our assumption of site grading is incorrect or if the grading plans change, please contact us to allow the recommendations in this report to be reviewed and, if necessary, revised.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

Scope of Services

Our scope of services included evaluating the subsurface conditions at five (5) boring locations, identified as Borings B-1 through B-5. Boring B-1 was performed at the center of the proposed tank footprint and advanced to a depth of about 40 feet. The remaining borings performed in and around the planned tank footprint (Borings B-2 through B-5) were advanced to a planned depth of about 20 feet or auger refusal, whichever occurred first. Our scope of services is concluded with the issuance of this Geotechnical Engineering Services Report.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

SUMMARY of SUBSURFACE FINDINGS

Site Geology

According to the available geologic maps, the project site appears to be underlain by the geologic unit mapped as the Cane Hill Member of the Hale Formation1. The following is a brief description of this formation:

The Cane Hill Member of the Hale Formation consists of 60% fine-grained silty sandstone interbedded with 40%-siltstone, basal conglomerate.

Based on the results of our borings, it appears that the sandstone associated with the Cane Hill

Member of the Hale Formation is underlain by the Fayetteville Shale and Batesville Sandstone at depth. This unit is mapped slightly to the north of the planned tank footprint. The following is a brief description of this formation:

The Fayetteville Shale: (including the Wedington Sandstone member) is characterized as black shale with interbedded sandstone and minor limestone. It is approximately 200 feet thick in the project area. The Batesville Sandstone: (including the Hindsville Limestone

Member) is characterized as sandstone with some interbedded shale and limestone. It is also approximately 200 feet thick in the project area.

Surface

The surface of the boring locations was covered by a crushed gravel surfacing at every location except for Boring B-5, which was covered by concrete paving. The gravel was measured to be approximately 3 to 6 inches thick, where encountered, and the concrete pavement was approximately 8 inches thick. No gravel base materials were observed underneath the concrete slab at Boring B-5.

Surface conditions at each exploration location has been outlined at the top of each boring log attached to this report.

Subsurface Conditions

Existing Fill

Existing fill materials were present beneath the surface gravels and concrete pavement at each of our exploration locations. The existing fill was highly variable in terms of both composition and consistency. Lean clay with sand, sandy lean clay, clayey gravel, clayey sand, and gravelly sand were all encountered along with an inconsistent amount of chert, shale, sandstone, and limestone

1 Hanbest, L.G., 1953, Morrow group and lower Atoka Formation of Arkansas: Bulletin of the American Association of Petroleum Geologists, vol.37, no.8, pp.1935-1953

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence pieces. The soils were primarily identified as fill due to the irregular discoloration of the material, the presence of man-made materials (concrete chips) as well as the presence of a minor amount of buried organics. The fill extended to depths of about 2 ½ to 13 ½ feet below the existing ground surface.

The existing fill material had low to moderate, yet generally moderate, shear strength during drilling and sampling. Standard penetration test (SPT) N-values of 4 to 30 blows per foot (bpf) of penetration were recorded within the existing fill.

Stratum I – Clays and Sands

A presumed native stratum of interbedded fine-grained and coarse-grained soils was present beneath the existing fill soils, except for Boring B-4. The fine-grained soils included both lean and fat clays with varying amounts of sand. The coarse-grained soils included sands with varying amounts of gravel, clay, and silt. In addition, thin seams of shale (about 4 inches in thickness) were also encountered intermittently within the native soils. Overall, the presumed native soils extended to approximate depths of about 8 ½ to 13 ½ feet below existing grades.

As noted above, the Stratum I soils had variable shear strength during drilling and sampling ranging from very low to moderate, but were generally moderate. N-values ranged from 2 to 29 bpf of penetration for these soils.

Stratum II – Basal Rock

The basal rock units at this site consisted of a relative thin seam of sandstone (sandstone cap) underlain by thin interbedded seams (less than 1-inch thick) of shale and limestone. The basal stratum was first encountered at depths of about 8 ½ to 13 ½ feet below existing grades and extended to the terminal depths between about 9 ¼ and 40 feet at each of our exploration locations. Auger refusal was achieved at each location except for Boring B-2.

Auger refusal materials were continuously sampled from about 21 ½ feet to 40 feet at Boring B-1 with an NQ-sized, double-barrel, wireline coring assembly and a diamond-impregnated drill bit.

The auger refusal materials predominantly consisted of a relatively thin layer of sandstone underlain by interbedded shale and limestone seams (each generally less than 1 inch in total thickness). The rock cores had recoveries ranging from 22 to 100 percent. The Rock Quality

Designation (RQD) of the rock cores ranged from 0 to 100 percent.

Laboratory compressive strength tests were performed on a single, intact rock core specimen obtained from Boring B-1 from about 28 ½ to 29 feet. Results of the compressive strength test on the selected rock core sample was 1,346 psi.

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Auger Refusal/Hard Drilling Conditions

Hard drilling conditions were encountered in the upper portions of the basal rock (Stratum II) at each boring location. More specifically, hard drilling conditions first occurred as shallow as about

8 ½ to 13 ½ feet below existing grades, upon encountering the sandstone cap, at each of our exploration locations.

Auger refusal was achieved within the basal rock stratum at depths of about 9 ½ and 21 ½ feet below existing grades at each boring location except for Boring B-2, which was advanced to its planned terminal depth of 20 feet.

For the purposes of clarity, the depths to hard drilling conditions and the depths to auger refusal at the performed boring locations are summarized in Table 1 below.

Table 1: Depths to Hard Drilling Conditions and Auger Refusal Material

Boring Number

Depths to Hard Drilling Conditions (feet below existing grade)

Depths to Auger Refusal Material (feet below existing grade)

B-1 13 ½ 21 ½

B-2 13 ½ N/A

B-3 8 ½ 9 ½

B-4 13 ½ 14 ¼

B-5 13 ½ 17 ½

Water Measurements

Water observations were made by the drill crew during drilling and immediately after completion of drilling. Groundwater was observed while drilling and after drilling at depth of about 9 ½ and 14 feet below existing grade at Boring B-5, only. No free water was observed while drilling or immediately after drilling completion at any other boring location. This is likely indicative of a shallow, perched water table present above the underlying basal bedrock (Stratum II).

Cave-in depths noted on the boring logs represent a loss of soil shear strength in the sides of the borings. This may be associated with the presence of perched water and the cave-in depths may correlate to the surface of the perched water. Cave-in depths of about 9 to 14 ½ feet were observed when the borings were checked for groundwater at completion of drilling, where observed.

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The depths to water are intended as isolated measurements of groundwater levels at the time of drilling. The installation and periodic measurement of monitoring wells would be required to establish seasonal piezometric surfaces below this project site.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

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GEOTECHNICAL ENGINEERING ANALYSIS

Geotechnical Considerations

Existing Fill

As stated previously, existing fill materials were encountered immediately below the surface gravel and pavement at all five (5) boring locations. Existing fill material extended to depths of about 2 ½ to 13 ½ feet below existing grades.

GTS has no information regarding the placement and compaction history of the existing fill.

Compressible fill and/or deleterious and unsuitable materials might be buried within or by the existing fill. There is a potential risk of unpredictable settlement and performance by supporting foundations and floor slabs-on-grade above the existing fill. This risk cannot be eliminated unless the existing fill is removed and replaced full-depth with new fill.

Concrete slabs-on-grade span weak zones much more effectively than concentrated foundation loading. Also, clients/owners typically have a higher tolerance for cracks developing in concrete slabs compared to foundations. At this time, it is unclear if a slab-on-grade will be incorporated in the design of the tank. However, based on the results of our sample borings and our understanding of site grading, the existing fill material appears suitable for supporting typical tank slab loading, provided the subgrade soils are stable at the time of mass grading and construction and also provided the fill is generally free of deleterious material. However, the client/owner should understand that some premature surface distress and increased maintenance may occur in the slab-on-grade sections supported above the existing fill. Again, this risk cannot be eliminated without completely removing and replacing the existing fill with new fill, but the risk can be reduced if partially left in-place by performing thorough testing and evaluation of the existing fill as recommended in this report.

Provided the recommendations in this report are followed, the risk associated with constructing the tank slab-on-grade (if used) over the existing fill should be low.

Low-Strength Soils

Localized, intermittent low shear strength soils (N-values of 7 bpf or less) were encountered within both the existing fill material and native soils at depths ranging from 2 to 13 ½ feet below existing grades at each boring location except for Boring B-5. Based on the recommendations provided herein, these low-strength soils are not anticipated to affect the planned foundation. However, some isolated areas of remediation (i.e. ground improvement) may be needed beneath any planned floor slabs. Any unstable subgrade materials should be removed and replaced full depth with new select fill as recommended in this report.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

Geotechnical Engineering Construction Materials Testing Environmental Due Diligence

Moisture-Sensitive Soils

The existing fill materials and native soils encountered within the borings are susceptible to further strength loss with increases in moisture content and/or when exposed to repetitive construction traffic. Ground improvement will likely be required if these soils are exposed during wet periods of the year and when wet site conditions develop. Depending on the conditions at the time of construction, isolated overexcavation depths of 2 feet could be required if the existing fill/native materials become wet and are exposed to repetitive construction traffic.

Foundation Type Discussion

A shallow foundation system could potentially be an option for supporting the planned tank if the existing fills as well as the existing low-strength materials were removed and replaced with new fill. To be clear, this would require excavations as deep as 13 ½ feet within the planned tank footprint. As discussed during a conversation between Mr. Kevin Hodges, P.E. with Hodges

Engineering and Mr. Travis Willis, P.E. with GTS on August 17, 2021, this option would likely take longer to complete, be less cost-effective, and be more intrusive than installing deep foundations.

As such, we recommend the planned tank be supported on a deep foundation system bearing in the underlying, hard (i.e. competent) basal bedrock layer (Stratum II).

Drilled Pier Foundation Design Recommendations

As stated above, the planned tank structure can be supported on a deep foundation system. We recommend that the deep foundation system consist of cast-in-place, straight-shaft, concrete drilled piers. The drilled piers should be designed to bear a minimum of 2 feet or one pier diameter

(whichever is greater) into the hard, bedrock layer (Stratum II). Drilled piers should extend through any thin seams of shale present within the overlying soils (Stratum I). The piers may be designed using the geotechnical parameters shown in Table 2 on the following page.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

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Table 2: Drilled Pier Foundation Design Parameters

Depth Below Existing Ground Surface

Soil/Rock Description

LPile Soil Type

Effective Unit

Weight

Friction

Angle

Cohesion Allowable

Skin

Friction

Horizontal

Modulus of Soil

Reaction

Strain at 50% of Ultimate

Compression

Net Allowable

End Bearing Pressure

’ φ c Kf 50 qall

(ft.) (pcf) (psf) (psf) (pci) (psf)

0 to 3 Existing Fill and Native

Soils NA 110 The top 3 feet of soils should be ignored in design

3 to top of Bedrock

(8 ½ to 13 ½)

Existing Fill and Native

Soils

Stiff Clay without

Free Water

(Reese)

120 0° 2,000 500E 600 0.007 NRA

8 ½ to 13 ½ (Varies)

Hard, Sandstone, Interbedded

Shale/ Limestone Bedrock

Weak Rock

88 0° 350B 2,000 20,000C 0.0005 20,000D

A NR = Not recommended

B Uniaxial Compressive Strength (psi)

C Mass modulus of weak rock (psi)

D The drilled piers should be embedded a minimum distance of 2 feet into the recommended bedrock.

E Due to strain compatibility, skin friction in soils should only be used to resist uplift force, not axial compression loads.

The design soil and rock parameters shown in Table 2 were calculated using a factor of safety of approximately 3 for end bearing and 2 for side friction. For the purposes of this report, we consider hard, competent bedrock to have Standard Penetration Test N-value of 50 blows for no more than 6 inches of penetration.

The depths to top of apparent bedrock generally correspond with the depths of hard drilling conditions, summarized in Table 1 of this report.

We recommend a minimum shaft diameter of 24 inches. Drilled piers should have a minimum

(center-to-center) spacing of 3 pier diameters. The minimum spacing should be maintained to prevent the pile group compression load capacity from being significantly less than the summation of individual pile capacities. Closer spacing may require a reduction in axial load capacity.

A reduction in the lateral resistance of the shadowed shaft in a foundation designed with a shaft group (the lead shaft is not affected) should be considered when the shaft spacing in the direction of loading is less than 6 shaft diameters. Group action can be evaluated by reducing the lateral resistance of the shadowed shafts in the direction of loading as a function of the shaft spacing as follows in Table 3 on the following page.

Veteran’s Health System of the Ozarks Fayetteville, Arkansas GTS Project No. 21-1-5-120

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Table 3: Drilled Pier Foundation Design Parameters

Pier Spacing (center-to-center, diameters)

3D 4D 5D ≥6D

Lead Row 0.7 0.85 1.0 1.0

2nd Row 0.5 0.65 0.85 1.0

3rd Row and higher 0.35 0.5 0.7 1.0

Total long-term and differential settlement of drilled pier foundations, designed and constructed as recommended in this report, are estimated to be less than ½ inch (total and differential between isolated piers).

Drilled Pier Foundation Construction Recommendations

All drilled pier excavations should be evaluated for suitable bearing material by GTS, Inc. prior to placement of reinforcing bar and concrete. Additionally, the drilled pier excavations should be cleaned of loose soil/rock, debris and water prior to reinforcing bar and concrete placement.

Some groundwater may be encountered during construction and will need to be removed from the drilled shaft. If water cannot be successfully removed from the drilled shaft, the concrete should be placed using a tremie pipe and standard underwater placement techniques.

Drilled piers should have a minimum length to diameter ratio (L:D) of 3:1. Drilled shaft lengths of about 10 ½ to 15 ½ feet below existing grade (or more) are anticipated to be required to satisfy the recommended minimum rock penetration.

The concrete used in the foundations should have a slump of 5 to 7 inches to reduce the likelihood of honeycombing within the foundation and to provide a positive pressure against the…