FCI Freezer Storage Area Geotechnical Report No. G 5575-216 - ETTL 3-11-21.pdf

ETTL Engineers & Consultants Inc.

GEOTECHNICAL MATERIALS ENVIRONMENTAL DRILLING LANDFILLS

Main Office 1717 East Erwin Street Tyler, Texas 75702 Phone: 903-595-4421 Fax: 903-595-6613

Longview, TX

Arlington, TX

Austin, TX

Texarkana, AR 903-758-0402 817-962-0048 512-519-9312 870-772-0013

W W W . E T T L I N C . C O M

March 11, 2021

Jeff Hensley

FCI Texarkana

4001 Leopard Drive

Texarkana, Texas 755701

Re: Freezers Storage Area

FCI/FPC - Texarkana, Texas

Geotechnical Investigation

ETTL Job No. G 5201-19

Dear Mr. Hensley:

Submitted herein is the report summarizing the results of a geotechnical investigation conducted at the site of the above-referenced project.

If you have any questions concerning this report, or if we can be of further assistance during construction, please contact us. We are available to perform any construction materials testing and inspection services that you may require. Thank you for the opportunity to be of service.

Sincerely, ETTL Engineers & Consultants Inc.

Texas Registered Engineering Firm #F3208

Cameron Bradbury Owen B. Sanderson, P.E.

Project Manager Senior Engineer

March 11, 2021 Distribution (PDF): Jeff Hensley

Geotechnical Investigation

Freezer Storage Area FCI/FPC - Texarkana, Texas

Submitted to

FCI Texarkana

Texarkana, Texas

Prepared by

ETTL Engineers & Consultants Inc.

Tyler, Texas

March 2021

ETTL Engineers & Consultants Inc. Freezer Storage Area- Texarkana, TX

Geotechnical Investigation ETTL Job No. G 5575-216

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 PROJECT DESCRIPTION

3.0 SITE DESCRIPTION

4.0 FIELD OPERATIONS

5.0 LABORATORY TESTING

5.1 One Dimensional Pressure Swell

5.2 Unconsolidated/Undrained Triaxial Compression

6.0 FOUNDATION SOIL STRATIGRAPHY AND PROPERTIES

6.1 Regional Geology

6.2 Site Stratigraphy & Properties

6.3 Expansive Soil Behavior

6.4 Seismic Site Classification

7.0 GROUNDWATER OBSERVATIONS

8.0 FOUNDATION and SLAb DESIGN RECOMMENDATIONS

8.1 INDUSTRIAL SLABS

8.1.1 MODULUS OF SUBGRADE REACTION

8.2 Shallow Spread Footings

8.2.1 BEARING CAPACITY

8.2.2 PREDICTED SETTLEMENT

9.0 EXCAVATION & SITE WORK

9.1 Site Preparation

9.2 Subgrade Preparation to Reduce PVR to 1-inch (If Required for Design)

9.3 Slabs on Native Subgrade

9.4 Select Fill Placement

9.5 Site Design

10.0 PAVEMENT RECOMMENDATIONS

10.1 Rigid Pavement

10.2 Pavement Subgrade Preparation

11.0 LIMITATIONS

APPENDIX A

Plate I: Plan of Borings

Log of Borings with Laboratory Test Data

Key to Soil Classification & Symbols

APPENDIX B

Lab Testing Summary Sheet

One Dimensional Swell Report Sheet

Unconsolidated-Undrained Triaxial Report Sheet

APPENDIX C

Seismic Design Parameters

1.0 INTRODUCTION

This study was performed at the request and authorization to proceed granted by Jeff Hensley, with

FCI/RPC Texarkana, TX in accordance with our proposal dated January 20, 2021. Field operations were conducted on February 9, 2021.

The purpose of this investigation was to define and evaluate the general subsurface conditions at the proposed freezer storage area located northeast of the existing FCI facility in Texarkana, Texas.

Specifically, the study was planned to determine the following:

Subsurface stratigraphy within the limits of exploratory borings;

Classification and strength of the foundation soils;

Appropriate foundation types and bearing capacities for heavy concentrated loads to be used in the design;

Pavement for repeated delivery vehicle wheel loads; and, Construction-related issues that may be anticipated by the investigation.

This investigation was carried out in three phases: 1) field exploration, sampling, and testing; 2) laboratory testing; and 3) engineering evaluation of data and reporting. The details of which are set forth in the following sections.

A variety of tests were performed on selected soil samples to provide the data used to form the basis for the conclusions and recommendations of this study. The conclusions and recommendations that follow are based on limited information regarding site grading. The client staked the boring locations on the ground based on ETTL recommendations from a site plan provided by the client. ETTL did not confirm by a survey that the locations indicated on the Plan of

Borings. This information should be verified prior to design. Should any portion of it prove incorrect, this firm should be notified in order to assess the need for revisions to this report.

2.0 PROJECT DESCRIPTION

This project consists of constructing a 100’ x100’ concrete storage area to support multiple walk-in freezers with an approximate footprint of 58’11” L X 14’10” W X 11’6.25” H and a total weight of

25,000lbs. Preliminary grading plans were not provided, the recommendation herein assumes that the final grade will be at to near the existing grade.

3.0 SITE DESCRIPTION

The project site is a relatively flat and open grass-surfaced area, with an asphalt road running South to North on the Northwestern side of the proposed site. There is currently a dirt access road running through the north portion of the proposed site.

4.0 FIELD OPERATIONS

Subsurface conditions were defined by three (3) sample core borings drilled to depths of 10 feet or

20 feet. The field boring logs were prepared as drilling and sampling progressed. The final boring logs are also included in Appendix A. Descriptive terms and symbols used on the logs are in accordance with the Unified Soil Classification System (ASTM D 2487). A reference key is provided on the final page of this report.

A track-mounted drill rig was used for this project. Dry flight auger drilling procedures were used to advance the borings until caving conditions made it necessary to switch to rotary wash procedures

(if applicable). Soils were sampled utilizing a 1 3/8-inch I.D. by 24-inch long split-spoon sampler driven into the bottom of the borehole in accordance with ASTM D 1586 procedures. In conjunction with this sampling technique, the Standard Penetration Test was conducted by recording the N-value, which is the number of blows required by a 140-pound weight falling 30 inches to drive a split-spoon sampler 1 foot into the ground. For very dense strata, the number of blows is limited to a maximum of 50 blows within a 6-inch increment. Where possible, the sampler is "seated" six inches before the N-value is determined. The N-value obtained from the Standard Penetration Test provides an approximate measure of the relative density that correlates with the shear strength of the soil. The disturbed samples were removed from the sampler, logged, packaged, and transported to the laboratory for further identification and classification.

Soils were also sampled utilizing a 3-inch O.D. by 24-inch long thick-walled Shelby Tube sampler.

Using the drilling rig's hydraulic pressure, the sampler was pushed smoothly into the bottom of the borehole. The consistency of these samples was measured in the field by a calibrated pocket penetrometer. These values, recorded in tons per square foot, are shown on the boring logs. Such samples were extruded in the field, logged, sealed to maintain in situ conditions, and packaged for transport to the laboratory.

All boreholes were backfilled with cuttings after collecting final groundwater readings. Samples obtained during our field studies and not consumed by laboratory testing procedures will be retained in our Tyler office free of charge for 60 days. To arrange storage beyond this point in time, please contact the Tyler office.

5.0 LABORATORY TESTING

Upon return to the laboratory, a geotechnical engineer visually examined all samples and several specimens were selected for representative identification of the substrata. By determining the

Atterberg liquid and plastic limits (ASTM D 4318) and the percentage of fines passing the No. 200 sieve (ASTM D 1140), field classification of the various strata was verified. Also conducted were natural moisture content tests (ASTM D 2216). These results are presented in the individual log of boring provided in APPENDIX A.

5.1 One Dimensional Pressure Swell

Pressure-swell testing (ASTM D 4546 Methods A & B (mod)) was performed on intact, relatively undisturbed specimens. In some cases, the moisture content of a specimen is initially dried to assess the swell potential of soils that may be drier than the sample obtained. These tests are conducted by adding moisture to a specimen and observing the amount of pressure necessary to restrain swelling. The restraining pressure is removed and the specimen is allowed to swell.

5.2 Unconsolidated/Undrained Triaxial Compression

The strength characteristics of the cohesive substrata were evaluated by conducting

Unconsolidated-Undrained Triaxial compression tests (ASTM D 2850) on selected undisturbed field samples obtained with the Shelby tube sampler. The specimens were confined at in situ pressure and axially loaded until failure occurred. The shear strength (or cohesion) is equal to one-half of the peak compressive stress. Moisture content (ASTM D 2216) and dry density (ASTM D 7263) are determined as part of this test.

Laboratory tests were conducted on samples recovered from the borings to evaluate physical and engineering properties of the different materials encountered. The number and type of tests performed for this study are listed in the table below. Summaries of the results are presented on the individual log of boring in APPENDIX A. Details of the tests are also included in APPENDIX B.

Table 5.0 – Soil Laboratory Testing Procedures

Laboratory Test Test Method Number of Tests

Dry Sieve Analysis (% Passing No. 4) ASTM D 6913 6

Dry Sieve Analysis (% Passing No. 40) ASTM D 6913 6

Washed Sieve Analysis (% Passing No.

200)

ASTM D 1140 6

Atterberg Limits (Liquid & Plastic Limits) ASTM D 4318 5

Moisture Content by Dry Weight ASTM D 2216 6

One Dimensional Pressure Swell ASTM D 4546 1

U.U. Triaxial Compression ASTM D 2850 2

The above laboratory tests were performed in general accordance with applicable ASTM, U.S.

Army Corps of Engineers procedures, and/or generally accepted practice. It should be noted that reference to ASTM or other standard procedures does not imply that all cross-referenced procedures in ASTM or other standards have been used, or that all ASTM or other procedures used have been followed exactly. Only those ASTM or other standard procedures and/or portions of procedures, which, in the professional judgment of the geotechnical engineer of record for this report, are applicable, appropriate, and necessary for this particular project, have been used or followed.

6.0 FOUNDATION SOIL STRATIGRAPHY AND PROPERTIES

6.1 Regional Geology

According to the Bureau of Economic Geology at the University of Texas at Austin, Geologic Atlas of Texas, Texarkana Sheet, the proposed site is located in the Wilcox Group undivided (Ewi).

The characteristic lithology of this group in this area is mostly silty and sandy clay which is very thinly bedded to massive and locally cross-bedded. In part carbonaceous, calcareous siltstone and ironstone concretions are common. The soils are typically various shades of gray. There are local beds of clay, lignite, silt, and quartz sand which weather to various shades of gray, brown, yellow, and red. The thickness of the group in this area is about 700 feet.

For more information, please refer to the National Geologic Map Database and the Geologic Atlas of Texas. https://txpub.usgs.gov/txgeology/

6.2 Site Stratigraphy & Properties

The soil profile generally consists of very soft to very stiff lean clay (CL) and fat clay (CH) with varying amounts of sand. The soil profile contains a 5 feet thick layer of medium dense silt (ML) typically located between 8 and 13 feet below existing grade.

The classifications are based on weathering, depositional environment, mineralogy, color change, lithology, and structure. Detailed on the boring logs in Appendix A are the specific types and depths of the various soil strata encountered. The logs show defined boundaries between various soil types, but in reality, the transition between types is generally gradual.

6.3 Expansive Soil Behavior

Expansive soils can be any of the following soil types: Clayey Sand (SC), Lean Clay (CL), or Fat

Clay (CH), which exhibit the ability to change volume (shrink or swell) with the addition or subtraction of moisture. Expansive soils such as are found at various depths throughout the soil profile swell when they absorb moisture and shrink as they dry. Structures placed on these soils move up and down with such volume changes of the soil. When expansive soils are covered by an impermeable surface such as a structure or pavement, seasonal moisture fluctuation at the interior of the covered area tends to be reduced or eliminated due to the lack of exposure to natural wetting and drying conditions (i.e., wind, rain, sun, vegetative, etc.). At the perimeter of the structure, however, infiltration into the foundation soils from surface drainage could lead to local swelling of the clays (if they were dry at the start of construction) resulting in tilt or distortion of the foundation.

Where areas immediately adjacent to the structure are paved both the risk of swelling due to excess moisture absorption and shrinkage due to moisture loss are reduced significantly.

At the time of exploration, the moisture content of the surficial 10’ active zone of expansive clay soils encountered was moist based on a comparison with the plastic limit moisture. The potential for swelling based on conditions at the time of drilling is considered to be moderate. The potential for shrinkage is predicted to be high. As the moisture content of the soil changes from what it was in our samples, the potential for swelling and shrinkage will change accordingly. For example, the expansive soils will exhibit a much higher swell potential if they were to dry prior to construction.

6.3.1 VERTICAL HEAVE PREDICTIONS

The assessment of the impact of expansive soils given below is predicated on soil moisture change that is a result of normal climatological fluctuation only. Factors such as poor drainage and consequent ponding water, plumbing leakage, excavation details (e.g. permeable backfill in trenches or beneath structures), and vegetation (trees and shrubs) can result in moisture changes

(and consequent swelling or shrinkage) outside the ranges predicted herein. The predicted heave is also the predicted differential movement that could be experienced by a slab and/or foundation placed on native grade existing grade.

6.3.1.1 Potential Vertical Rise (PVR)

One method for quantifying the potential for subgrade movement at any given location is to calculate the Potential Vertical Rise (PVR) (Tex 124 E Modified). This calculation takes into account the inter-relationship between depth, Plasticity Index (PI), and fluctuations in soil moisture.

The maximum potential vertical rise, PVR, due to normal climatological fluctuations in soil moisture content, is predicted to 2-inches at existing grade. These calculations are based on assumed dry conditions and an estimated seasonal moisture fluctuation zone of approximately 10 feet.

6.3.1.2 USACE Potential Vertical Heave (PVH)

Another method for predicting the potential of vertical heave (PVH) of the subgrade soils is the

USACE Hand (manual) Method as described in FOUNDATIONS IN EXPANSIVE SOILS (TM 5-818-

7, 1983) section 5-4 (See also, EVALUATION OF LEVEL OF RISK FOR STRUCTURAL

MOVEMENT USING EXPANSION POTENTIAL, Nelson & Chao, Geo-Frontiers 2001 © ASCE

2011). This method is a prediction of vertical heave based on test results determined from a consolidometer free swell test. These calculations are based on moisture conditions at the time of sampling and an estimated moisture fluctuation zone of approximately 10 feet. Based on laboratory testing of the specimens initially dried below in-situ moisture, the predicted PVH is on the order of

3.3 inches at the existing grade.

6.4 Seismic Site Classification

ASCE 7-10 Standard requires a shear strength soil profile determination extending a depth of 100 feet for seismic site classification. The current scope does not include the required 100-foot soil profile. The current boring is a maximum of 20 feet below existing grade and the seismic site class definition assumes that the encountered material extends to a depth of 100 feet.

The seismic site class definition is Class D “Stiff Soil” and the Risk Category is II. California’s

Office of Statewide Health Planning and Development (OSHPD) provides an online tool that calculates the seismic design values based on the overall project and site information listed above.

A print out of this report is provided in APPENDIX C. ETTL does not warrant the accuracy of this report and it is presented to the client for information purposes only.

For more information in regards to the program please visit:

https://seismicmaps.org/

7.0 GROUNDWATER OBSERVATIONS

Groundwater was present during drilling operations for all borings. Once drilling activities were completed, water was observed in the open boreholes between 3 feet and 10 feet. The phreatic surface is predicted to be at some depth below 7 feet and confined by the less permeable clays above. Once the groundwater is encountered below 7 feet it can rise to a depth of 3 feet below the existing grade.

Data regarding the groundwater level was obtained by observations in open boreholes. At best this provides only an approximation of the phreatic surface at the time of drilling. The phreatic surface that should be considered for the design of this project may vary significantly from that which was observed in the borings due to the following factors:

The characteristics of the soil profile may have prevented the water level in the boring from rising to the phreatic level during the period of observation

A given boring may not intercept groundwater bearing zones (i.e. the groundwater is perched or travels in seams or fissures that are not continuous over the entire site)

Groundwater may only be perched in pockets above local aquacludes, but the distribution of borings is not generally adequate to confirm this with a high level of certainty

Groundwater level varies seasonally and with rainfall

Rotary wash drilling methods introduce fluid into the boring that often makes it impossible to distinguish between groundwater and drilling fluid

If the designer believes that the level of groundwater could significantly impact the project, then

ETTL should be contacted to develop a plan for piezometer installation and monitoring to more accurately assess the groundwater levels at the site.

8.0 FOUNDATION AND SLAB DESIGN RECOMMENDATIONS

The design of the storage area may be designed as a pavement to accommodate the effect of repeated wheel loads, or as an industrial slab to support the concentrated loads of the container feet. In which case the subgrade modulus would control the slab thickness.

8.1 INDUSTRIAL SLABS

8.1.1 MODULUS OF SUBGRADE REACTION

Design of Slabs on Ground, ACI 360R provides a methodology for thickness design of floors subjected to concentrated wheel and post loads as well as area rack loads. That procedure requires a characterization of the subgrade support in the form of the modulus of subgrade reaction

(MSR), k. This value represents the pressure applied to the subgrade surface on a 30” diameter plate that results in a deflection of 1” and is in units of psi/in (or PCI). Actual plate load testing of the finished subgrade to determine an appropriate value is not generally practical, so predictions are made based on published correlations of the modulus with soil properties (ACI 330R). Based on those correlations, the MSR is predicted to be 50 PCI at the top of the native soft clay subgrade and

100 PCI if the slab is founded on a minimum of 12 inches of compacted select fill. This value assumes that the anticipated select fill is densified to a minimum of 98% of the standard proctor

(ASTM D698) density. The use of a crushed stone base material in combination with select fill can be used to increase the modulus. Eight to twelve inches of crushed stone over a minimum of 12 inches of select fill can be considered to increase the modulus to 150 and 185 PCI respectively.

8.2 Shallow Spread Footings

8.2.1 BEARING CAPACITY

Shallow footings can either be monolithic with the slab or isolated from it. These footings should be designed to bear in undisturbed native subgrade or properly compacted select fill at a minimum depth of 2 feet below the finished subgrade or adjacent exterior grade (whichever is deeper).

Isolated footings should have a minimum width of 2 feet and strip footings should be at least 12 inches wide. Footings should be proportioned for allowable gross bearing pressures of 2,500 psf for individual (isolated) footings and 2,000 for continuous (strip) footings. These allowable pressures incorporate a safety factor relative to shear failure of the soil of at least 3 and may be increased up to 33% for intermittent loads such as wind.

8.2.2 PREDICTED SETTLEMENT

The predicted immediate settlement due to dead plus sustained live load pressure (assumed to be

2,000 psf) for footing widths less than 6 feet is less than 1.0 inch (total) and 0.5 inch (differential).

Detailed testing for the prediction of long-term settlement due to load for these footings is beyond the scope of this investigation, but the magnitude of settlement is not anticipated to be significantly more than the immediate settlement.

9.0 EXCAVATION & SITE WORK

To validate the design assumptions given above regarding allowable foundation loads, and, to provide a serviceable foundation system (within the limitations stated above), the subgrade of the structure must be properly prepared. The following procedures are recommended as a minimum.

9.1 Site Preparation

Strip to remove all topsoil, gravel, and other deleterious materials from the subgrade to a minimum of 1 foot below the existing grade.

9.2 Subgrade Preparation to Reduce PVR to 1-inch (If Required for Design) Over excavated a minimum of 4 feet below existing grade and replace with compacted select fill.

The over-excavation should extend a minimum of 3 feet beyond the edge of the footing. After the excavation is complete and prior to the placement of fill, scarify the exposed subgrade to a depth of

12 inches, adjust the moisture content to, and maintain it within a range of optimum to optimum

+4% and recompact to a minimum density of 98% of the maximum density defined by ASTM D 698

(Standard Proctor). Maintain specified moisture content until the subgrade is covered with fill or slab.

Over excavation and replacement of a portion of the expansive clay with more permeable select fill to reduce the potential movement can, in some instances, create a “bathtub” (reservoir) beneath the structure that has the potential to collect surface drainage (or water from other sources such as plumbing leaks) at its base. Water that collects on the native clay at the base of the undercut will soak into the deeper, expansive clays over time thus increasing the risk of excessive deep-seated heave. Based on the soil profile below the fill and the elevated groundwater the likelihood of deep-seated heave occurring is low. The site should be designed to allow surface water to rapidly drain away from the structure, see Section 9.4.

9.3 Slabs on Native Subgrade

If the slab is to be placed directly on the native subgrade, which will be subject to vertical movement as described in Section 6.3, as a minimum perform a proof roll with a fully loaded dump truck. Any areas the prove to be unstable should be cut out and replaced with compacted select fill. Following the proof roll, scarify the exposed subgrade to a depth of 12 inches, adjust the moisture content to, and maintain it within a range of optimum to optimum +4% and recompact to a minimum density of

98% of the maximum density defined by ASTM D 698 (Standard Proctor). Place select fill toe finish grade as needed.

9.4 Select Fill Placement

Select fill shall consist of homogeneous soils (i.e. not sand with clay lumps) free of organic matter and rocks larger than 3 inches in diameter. Select fill should possess an Atterberg PI between 8 and 18, with a liquid limit of 40 or less and with a percentage passing the No. 200 sieve of 70% or less. If the material has a percentage passing the No. 200 sieve less than 35% (excluding gravel retained on the No. 4 sieve) the upper limit of PI can be increased to 25, but first must be approved by the Geotechnical Engineer of record. Additional testing may be required. Atterberg limits testing of the fill at a rate of 1 test per every 500 cubic yards of fill placed or as visual changes are observed. The material should be placed in the following manner:

Prepare the subgrade in accordance with the recommendations discussed above. Sites, which slope more than about 15% should be benched with 5' wide benches prior to placing the fill.

Place subsequent lifts of select fill in thin, loose layers not exceeding nine inches in thickness to the desired rough grade and compact to a minimum of 98% of the maximum density defined by ASTM D 698. Maintain moisture within a range of optimum to optimum

+4%.

Conduct in-place field density tests at a rate of one test per 3,000 square feet for every lift with a minimum of 2 tests per lift.

Prevent the excessive loss of moisture during construction.

For select fill placed above the existing ground line, extend the lateral limits of the fill at least

5 feet beyond the perimeter of the construction area, transitioning back to the existing ground line on a 3:1(horizontal/vertical) slope.

9.5 Site Design

The following recommendations are derived from years of experience with structures founded on expansive soils and are considered essential to satisfactory performance:

The ground surface around the structure should be sloped away from it on all sides so that water will drain away from the structure. A minimum slope of 5% is recommended immediately adjacent to the structure. Drainage swales should have a minimum longitudinal slope of 2%. Water should not be allowed to pond near the structure.

To help limit surface water infiltration beneath the structure, backfill in the area 3 feet wide adjacent to the structure should be soil with an Atterberg Pi greater than 25 and compacted to a minimum density of 95% of ASTM D 698 (Standard Proctor) at a moisture content of optimum or greater. This zone should be from 1 to 2 feet thick. This backfill is not necessary where pavement abuts the structure and the joint is sealed. A vertical moisture barrier sealed to the side of the foundation and extending to a depth of about 5’ will provide added protection against moisture fluctuation beneath the structure footprint.

Backfill for utility line ditches should be carefully controlled and should consist of relatively impermeable material (See (1) above or select fill), especially in the area beneath and immediately outside of the structure. Granular fill (or loose backfill) that is often used to embed utility lines can become a conduit to feed free water under the structure resulting in heave, and, so, should not be used. Old utility lines should be removed from beneath the structure. Fill in new or old utility trenches should be placed to the same specifications as select fill. The top 6 inches under paving should be compacted to a density equal to that specified for the pavement subgrade.

Utility connections to the structure should be flexible to allow for anticipated soil movements

(see predictions elsewhere in this report) that will be different than the anticipated movement of the structure to which they are connected. In this case, the settlement due to load and heave/shrinkage predicted above represents the amount of potential differential movement. Drain lines should be placed so that potential movements beneath the building do not affect the functionality of the line.

10.0 PAVEMENT RECOMMENDATIONS

The following are general recommendations for the design of minimal pavement structures and are provided herein for your information. We anticipate that the civil engineer of record will produce a set of final design details and specifications. If requested, ETTL can review the pavement design drawings and specifications for compliance with our recommendations herein. NOTE: Minimal designs as included herein may not be adequate for significant heavy truck and/or forklift traffic. For such traffic, a specific design based on a numerical characterization of the traffic and detailed testing of the finished subgrade soils is recommended and was beyond the scope of this investigation.

These recommendations are based on surface soil characteristics inferred from the borings drilled for the Freezer Storage Area. An inspection of the pavement subgrade after it is cut to finished grade should be made to determine the applicability of these recommendations. Concrete rigid pavement sections are presented. A summary of proposed designs is provided in Tables 10.0, below.

10.1 Rigid Pavement

The performance of concrete pavement is dependent on many factors including weight and frequency of traffic, subgrade conditions, concrete quality (which itself is dependent on a host of factors), joint type and layout, jointing procedures, and numerous construction practices. A detailed discussion of all of these items is beyond the scope of this report. The designer is referred to the

American Concrete Institute Publication No. ACI 330R, Guide for Design and Construction of

Concrete Parking Lots, for more details. By way of general guidance, the following recommendations are offered:

The minimum concrete moment of rupture (MOR) = 500 psi at 28 days (approximately 3,600 psi) placed with a maximum slump of 4 inches. The mix should contain 4.5% - 6% entrained air for durability. The maximum aggerate size should be no greater than 1/3 the thickness of the slab. Allow a minimum of 7 days (warm weather, longer in cold weather) curing time before permitting light traffic on the pavement.

The Recommended minimum pavement thickness for light duty is 5.5 inches for an estimated CBR (Compacted to 98% ASTM D 698) of the prepared subgrade equal to 2 and a traffic category A (Average Daily Truck Traffic (ADTT=1)). All edges of pavement should be thickened to 7 inches (transitioning back to 5.5 inches over a minimum distance of 4 feet), see ACI 330R, Table 3.3. Replacing a proportion of the native subgrade with compacted select fill as noted in Section 10.2 increases the estimated CBR to a 10 and allows the minimum pavement thickness to be reduce by 0.5 inch.

The recommendations for medium-duty concrete paving (traffic category B (ADTT=25)) are the same as for light-duty except that 6.5 inches of portland cement concrete should be the minimum pavement section and the edges should be thickened to 8 inches.

The recommendations for heavy-duty concrete paving (traffic category C (ADTT=100)) are the same as for light-duty except that 7.5 inches of portland cement concrete should be the minimum pavement section and the edges should be thickened to 9 inches.

ACI 330R, Table 3.3 – Traffic Categories

Truck Type Parking Areas and

Interior Lanes

Entrances and

Exterior Lanes

Cars (light Vehicles) Category A Category B

Busses and Panel Trucks Category B Category C

Single Units (bobtailed trucks) Category B Category C

Multiple Units (tractor-trailer units with one or more trailers Category C Category D

Sand cushions should not be used as a construction expedient, instead of proper subgrade preparation. Granular aggregate subbases are not normally used for concrete parking lots. If a subbase is specified for some special reason, it should be placed on the prepared subgrade, compacted, and trimmed to the elevation called for in project plans.

For information regarding the amount and type of reinforcement (if any), load transfer across the joints (Dowels), joint spacing, saw cutting, curing, and placement of the concrete, the reader is referred to ACI 330R, specifically Section 3.7 & 3.8.

Table 10.1 - Pavement Options

Type Concrete Thickness

(inches)

Subgrade

Preparation

Light Duty Concrete 5.5 Notes 1 to 5

Medium Duty Concrete 6.5 Notes 1 to 5

Heavy Duty Concrete 7.5 Notes 1 to 5

Notes:

1) Cut out and remove all topsoil and organics. Cut to grade if required.

2) Under subgrade and replace with select fill as required by others, see Section 10.2

3) A visual inspection and proof roll of the exposed subgrade shall be made to determine areas to be undercut and replaced with select fill.

4) Recompact the subgrade to a minimum density of 98% of ASTM D698 (Standard Proctor).

5) The stability of the finished subgrade should be verified by proof rolling in accordance with

TxDOT.

6) Traffic volumes and pavement designs are based on 20 years.

10.2 Pavement Subgrade Preparation

If required by design, prepare the pavement subgrade as discussed in Section 9.2 to reduce PVR or Section 8.1.1 to increase subgrade modulus. If the subgrade is prepared per one of these sections the minimum pavement thickness listed in Table 10.2 can be reduced by 0.5 inch.

As a minimum, strip the native subgrade to remove topsoil and other deleterious materials. Cut to the proposed subgrade elevation as required. After cutting to grade and/or prior to placing fill, the stability of the finished subgrade should be verified by proof rolling in accordance with TxDOT Item

216 (with the exception of roller size – use fully loaded dump truck). Unstable areas will need to be cut out and reworked. The final subgrade should be scarified to a depth of 8 inches, adjust the moisture content to within a range of optimum to optimum +4%, and recompact to a minimum of

98% of the density as defined by ASTM D 698 (Standard Proctor). Positive surface drainage should be maintained during all phases of construction (especially in low areas) to help keep pavement subgrade in a dry and stable condition.

11.0 LIMITATIONS

Geotechnical design work is characterized by the presence of a calculated risk that soil and groundwater conditions may not have been fully revealed by the exploratory borings. This risk derives from the practical necessity of basing interpretations and design conclusions on a limited sampling of the subsoil stratigraphy at the project site. The number of borings and spacing is chosen in such a manner as to decrease the possibility of undiscovered anomalies while considering the nature of loading, size, and cost of the project. The recommendations given in this report are based upon the conditions that existed at the boring locations at the time they were drilled. The term "existing groundline" or "existing subgrade" refers to the ground elevations and soil conditions at the time of our field operations.

It is conceivable that soil conditions throughout the site may vary from those observed in the exploratory borings. If such discontinuities do exist, they may not become evident until construction begins or possibly much later. Consequently, careful observations by the geotechnical engineer must be made of the construction as it progresses to help detect significant and obvious deviations of actual conditions throughout the project area from those inferred from the exploratory borings.

Should any conditions at variance with those noted in this report be encountered during construction, this office should be notified immediately so that further investigations and supplemental recommendations can be made.

Construction plans and specifications should be submitted to ETTL for review prior to issuance for construction to help verify that the recommendations of this report have been correctly understood and implemented.

This company is not responsible for the conclusions, opinions, or recommendations made by others based on the contents of this report. The recommendations made in this report are applicable only to the proposed scope of work as defined in SECTION 2.0 PROJECT DESCRIPTION and may not be used for any other work without the express written consent of ETTL Engineers. The purpose of this study is only as stated elsewhere herein and is not intended to comply with the requirements of

30 TAC 330 Subchapter T regarding testing to determine the presence of a landfill. Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices.

No warranties are either expressed or implied.

Geotechnical-Engineering Report Important Information about This

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

While you cannot eliminate all such risks, you can manage them. The following information is provided to help.

The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer.

Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.

The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations.

Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.

Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client.

Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical-engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project.

Do not rely on this report if your geotechnical engineer prepared it:

• for a different client;

• for a different project or purpose;

• for a different site (that may or may not include all or a portion of the original site); or

• before important events occurred at the site or adjacent to it;

e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations.

Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems.

Read this Report in Full Costly problems have occurred because those relying on a geotechnical-engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full.

You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys.

Typical changes that could erode the reliability of this report include those that affect:

• the site’s size or shape;

• the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria;

• the composition of the design team; or

• project ownership.

As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.

Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed.

This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation.

This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical-engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to:

• confer with other design-team members;

• help develop specifications;

• review pertinent elements of other design professionals’ plans and specifications; and

• be available whenever geotechnical-engineering guidance is needed.

You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.

Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect.

Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes.

To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions.

Your geotechnical engineer should respond fully and frankly.

Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance.

Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies.

Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team.

Geotechnical engineers are not building-envelope or mold specialists.

Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind.

Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation.

Telephone: 301/565-2733 e-mail: info@geoprofessional.org www.geoprofessional.org

APPENDIX A

LEAN CLAY WITH SAND(CL) very soft; brown with reddish brown and light gray; saturated; with organics

FAT CLAY WITH SAND(CH) very soft;

brown with reddish brown and light gray; saturated; with organics

--medium stiff; reddish brown and light gray; slightly moist; mottled

SILT(ML) medium dense; reddish brown; very moist

FAT CLAY(CH) stiff; reddish brown with dark gray and light gray; slightly moist;

partially mottled

SANDY FAT CLAY(CH) stiff; reddish brown with dark gray and light gray;

slightly moist; partially mottled

Bottom of Boring @ 20'

1.38 5.82

E w i

0107 110 17

79 4.9

CL

CH

ML

CH

CH

P=0.5

P=0.5

P=1.75

P=2.25

P=3.0

P=2.25

LL

D E

P T

H ft)

Notes:

N -…