GEO-TECHNICAL REPORT.pdf

ECS Southwest, LLP Geotechnical Engineering Report VA Medical Center Improvements

1901 Veterans Memorial Drive Temple, Texas

ECS Project Number 17:6180

March 30, 2023

March 30, 2023

Ms. Jessica Soto H2B, Inc.

1225 North Loop West, Suite 800 Houston, Texas 77008

ECS Project No. 17:6180

Reference: Geotechnical Engineering Report

VA Medical Center Improvements 1901 Veterans Memorial Drive Temple, Texas

Dear Ms. Soto:

ECS Southwest, LLP (ECS) has completed the subsurface exploration, laboratory testing, and geotechnical engineering analyses for the referenced project. Our services were performed in general accordance with our agreed to scope of work. This report presents our understanding of the geotechnical aspects of the project along with the results of the field exploration and laboratory testing conducted, and our design and construction recommendations.

It has been our pleasure to be of service to H2B, Inc. during the design phase of this project. We would appreciate the opportunity to remain involved during the continuation of the design phase, and we would like to provide our services during construction phase operations as well to verify the subsurface conditions considered for this report. Should you have any questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, ECS Southwest, LLP

Connor Roman, P.E. Richard E. Webb, P.E.

Department Manager Geotechnical Principal croman@ecslimited.com rewebb@ecslimited.com

Delaney Diamond, E.I.T.

Geotechnical Staff Project Manager ddiamond@ecslimited.com

Electronic seal approved by Connor Roman, P.E. on March 30, 2023 mailto:rbennett1@ecslimited.com mailto:rewebb@ecslimited.com mailto:ddiamond@ecslimited.com

VA Medical Center Improvements, Temple, Texas March 30, 2023 ECS Project No. 17:6180 Page i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 Project Location/Current Site Use/Past Site Use

2.2 Proposed Construction

3.0 FIELD EXPLORATION AND LABORATORY TESTING

3.1 Subsurface Characterization

3.2 Groundwater Observations

3.3 Laboratory Testing

4.0 DESIGN RECOMMENDATIONS

4.1 Potential Vertical Rise

4.2 Deep Foundations

4.2.1 Straight-Shaft Drilled Pier Foundations

4.2.2 Pier Foundation Lateral Resistance

4.2.3 Drilled Pier Group Effects Considerations

4.3 Pavement Sections (Private parking & Drives)

4.3.1 Pavement Materials

4.3.2 Rigid Pavement Considerations

4.3.3 Pavement Drainage, Subdrainage, and Trenching

4.4 Retaining Walls

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 Subgrade Preparation

5.1.1 Removals, Stripping and Grubbing

5.1.2 Proof Rolling

5.1.3 Site Temporary Dewatering

5.2 Earthwork Operations

5.2.1 Weathered Rock and Rock

5.3 Material Specifications

5.3.1 General Fill

5.3.2 Select Fill

5.4 Foundation and Slab Observations

5.5 Utility Installations

6.0 CLOSING

ECS Project No. 17:6180 Page ii

APPENDICES

Appendix A – Figures

• Site Location Diagram

• Boring Location Diagram

• Site Geologic Diagram

• Generalized Subsurface Soil Profiles

Appendix B – Field Operations

• Subsurface Exploration Procedure

• Boring Logs B-01 to B-20

• Reference Notes for Boring Logs

Appendix C – Laboratory Testing

• Laboratory Testing Summary

• Grain Size Distributions

ECS Project No. 17:6180 Page 1

EXECUTIVE SUMMARY

The following summarizes the main findings of the exploration, particularly those that may have a cost impact on the planned development. Further, our principal geotechnical recommendations are summarized. Information gleaned from the executive summary should not be utilized in lieu of reading the entire geotechnical report.

• The predominant geotechnical and geological constraints that need to be addressed at the site are the highly expansive soil conditions, the existing developed nature of the site, the existing fill soils, and the very hard limestone anticipated in excavations.

• We have estimated potential heave in the proposed improvement areas utilizing the

TxDOT PVR method (Tex-124-E). We estimate the existing PVR in the proposed improvement areas to range from about 1 inch to about 4½ inches.

• Fill soils were evaluated at several locations extending to depths up to about 6 feet below the existing grade. Undocumented fill can vary in composition, consistency, and relative density. Existing fill soils may remain in place provided the subgrade preparation requirements (including proofrolling) outlined in Section 5.0 of this report are met.

• Pavement design options for private parking and drives are provided in this report’s Section 4.2 “Pavement Sections – Private Roadways.”

• Earthwork, utility, and foundation contractors should be prepared with heavy-duty rock excavation equipment and tooling to make proposed cuts into the Stratum III Limestone materials.

• Drilled shaft contractors should be prepared with high-torque drill rigs and rock tooling to excavate the Stratum III bedrock and provisions to handle the potential for groundwater in excavations.

• Straight-shaft drilled pier foundations can be utilized to support the proposed light poles.

Please refer to Section 4.2 “Deep Foundations” for geotechnical design parameters and other recommendations for design.

• It is recommended that ECS conduct a geotechnical review of the project plans (prior to issuance for construction) to check to see that ECS’ geotechnical recommendations have been properly interpreted and implemented.

• To prevent misinterpretation of our recommendations, ECS should be retained to perform quality control testing and documentation during construction of the earthwork and foundations for the project.

ECS Project No. 17:6180 Page 2

1.0 INTRODUCTION

The purpose of this study was to provide geotechnical information for the design of light pole foundations, pavements and appurtenances. Geotechnical recommendations for associated retaining walls are also included in this report.

Our scope of services was described and was performed in general accordance with ECS Proposal No. 17-8006 dated February 8, 2023. This study was authorized on February 8, 2023, by Ms. Jessica Soto of H2B, Inc. via signature of the referenced proposal acceptance page.

The report includes the following items.

• A brief review and description of our field and laboratory test procedures and the results of testing conducted.

• A review of surface topographical features and site conditions.

• A review of area and site geologic conditions.

• A review of subsurface soil stratigraphy with pertinent available physical properties.

• A final copy of our soil test boring logs.

• Recommendations for site preparation, grading, and drainage.

• Recommendations for foundation design and construction.

• Recommendations for retaining wall design and construction.

• Recommendations for pavement design and construction.

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

ECS did not provide any service to investigate or detect the presence of moisture, mold or other biological contaminants in or around any structure, or any service that was designed or intended to prevent or lower the risk of the occurrence of the amplification of the same. Mold is ubiquitous to the environment with mold amplification occurring when building materials are impacted by moisture.

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2.0 PROJECT INFORMATION

2.1 PROJECT LOCATION/CURRENT SITE USE/PAST SITE USE

The project site is located at 1901 Veterans Memorial Drive in Temple, Texas. The location is depicted in the figure below and on the Site Location Diagram in Appendix A.

Site Location

The site is developed with the Veterans Affair Medical Center campus which includes medical buildings, offices, private roadways, paved and gravel parking lots, and associated appurtenances.

There are also some maintained grassed areas and mature trees throughout the site.

Based on a review of historical aerial imagery dating back to 1964, the site appears to have undergone several periods of redevelopment, including conversions of building areas into paved parking lots, and development of grassed areas into building and/or paved and unpaved parking areas. Around 1964, the site was developed with medical buildings in the central and north portions of the site, with paved and/or gravel areas, and grassed areas on the south side of the site. By 1974, several portions of the existing Teague Tower (Building 163) were developed in the southwest of the site. By 1981, the CTVHS Business Office (Building 171) was developed in the northwestern portion of the site.

Notable periods of development appear to have occurred between around 1981 and 2004. Many of the previous buildings existing back to 1964 were demolished. Areas in the center, northeast and southeast were developed with the Teague Hospital Building (Building 204), the State Veterans Home, and Domiciliary Building (Building 202), respectively. Additional pavements were constructed during this period, including many of the current parking lots and drive lanes. After 2004, several buildings and parking areas were constructed in the center of the site. Between

Site Location

ECS Project No. 17:6180 Page 4 around 2012 and 2018, a large building in the southern portion of the site was demolished and this area, as well as a grassed area to the northwest, were converted into paved parking lots. Between 2019 and 2021, several buildings and parking areas north of Building 204 were demolished.

2.2 PROPOSED CONSTRUCTION

According to information provided by the Client, it is understood that the proposed development will include improvements to the existing parking areas, drive lanes, and private streets within the VA Medical Center complex, the addition of light poles, and associated appurtenances. Proposed grading and finished elevations were not provided at the time of this report.

If ECS’ understanding of the project is not correct, especially if the structural loads are different, please contact ECS so that we may review these changes and revise our recommendations as appropriate.

ECS Project No. 17:6180 Page 5

3.0 FIELD EXPLORATION AND LABORATORY TESTING

Our subsurface findings and procedures are included in Appendix B. Our scope of work included drilling 20 borings at the site. Five borings were advanced to depths of about 25 feet each, one boring was advanced to a depth of about 20 feet, and 14 borings were advanced to depths of about 5 feet each using a truck-mounted drill rig.

Our borings were located with a handheld GPS unit, and their approximate locations are shown on the Boring Location Diagram in Appendix A. The approximate ground surface elevations shown on the boring logs were selected based on a review of Google Earth terrain elevation data. The precision of this elevation data should be considered approximate.

3.1 SUBSURFACE CHARACTERIZATION

The Geologic Atlas of Texas – Waco Sheet indicates the site is underlain by the Ozan Formation (Ko), which generally consists of highly expansive clays and claystone. The Austin Chalk (Kau), which generally consists of chalk, limestone, marly limestone, and marl, is mapped just west of the site.

Based on the soil and rock encountered in our borings, the site is likely predominately underlain by the Austin Chalk. The approximate location of the site on the Site Geologic Diagram is provided in Appendix A.

The following table provides generalized characterizations of the soil strata encountered during our subsurface exploration. For specific information refer to the boring logs in Appendix B.

STRATUM

APPROXIMATE

RANGE OF

DEPTH (FEET)

MATERIAL DESCRIPTION PI(1)

RANGE

PI(1)

AVERAGE

I (2) (0.25 – 1)

(2 – 6)

FILL:

(CL) LEAN CLAY WITH SAND, SANDY LEAN CLAY

WITH GRAVEL, LEAN CLAY, (SC) CLAYEY SAND,

CLAYEY SAND WITH GRAVEL; (CH) SANDY FAT

CLAY, FAT CLAY WITH SAND, (GC) CLAYEY GRAVEL

WITH SAND; firm to very stiff, loose to medium dense; light brown, gray, dark brown

25 - 29 27

II (3)

(0 – 6)

(3.5 – 25)

(CH) FAT CLAY, FAT CLAY WITH SAND, (CL) LEAN

CLAY; light brown to gray, dark brown;

firm to very hard 23 - 56 43

III

(3.5 – 23.5)

LIMESTONE; Very Hard; Tan, Gray

Notes: (1) Plasticity Index

(2) Not encountered in boring B-06 & B-07

(3) Not encountered in boring B-12

A graphical presentation of the subsurface conditions is shown on the Generalized Subsurface Soil Profile included in Appendix A.

ECS Project No. 17:6180 Page 6

3.2 GROUNDWATER OBSERVATIONS

Groundwater level observations were made in the borings during drilling operations. In air rotary and solid-stem auger drilling operations, water is not introduced into the borehole and the groundwater position can often be determined by observing water flowing into the excavation.

Furthermore, visual observation of soil samples retrieved can often be used in evaluating the groundwater conditions. Groundwater was encountered during drilling in boring B-02 at a depth of 17 feet. Groundwater was not encountered in the remaining boreholes at the site. Upon completion of field operations, the boreholes were backfilled with soil cuttings generated during our field operations and/or bentonite hole plug and topped with asphalt cold patch or low-shrink grout, where applicable.

Water levels in open excavations may require several hours to several days to stabilize depending on the permeability of the soils and that groundwater levels at the site may be subject to seasonal conditions, recent rainfall, drought, or temperature effects. Clays and intact limestone are generally not conducive to the presence of groundwater; however, gravels, sands and silts, and open fractures and solution features; where present, can store and transmit “perched” groundwater flow or seepage.

The groundwater conditions at this site are expected to be significantly influenced by surface water runoff and rainfall and should therefore be evaluated just prior to construction. Specifically, rainfall that enters the site, either directly from overland flow or adjacent properties, begins to percolate through surficial soils and within granular seams and fissures. This groundwater flow continues downhill with the water table occasionally surfacing to form wet springs and intermittent streams.

In low-lying areas and areas adjacent to existing creeks or ponds, shallow groundwater tables can be present continuously.

3.3 LABORATORY TESTING

The laboratory testing was performed by ECS on selected samples obtained during our field exploration operations. Classification and index property tests were performed on representative soil samples obtained from the test borings to aid in classifying soils and to quantify and correlate engineering properties. The soil samples were tested for moisture content (ASTM D2216), Atterberg limits (ASTM D4318), and gradation (percent passing No. 200 sieve – (ASTM D1140).

A geotechnical engineer visually classified each soil sample from the test borings based on texture and plasticity in general accordance with ASTM D2487 (Unified Soil Classification System (USCS)) and ASTM D2488 (Description and Identification of Soils-Visual/Manual Procedures). After classification, the samples were grouped in the major zones noted on the boring logs in Appendix B.

The group symbols for each soil type are indicated in parentheses along with the soil descriptions.

The stratification lines between strata on the logs are approximate; in situ, the transitions may be gradual.

ECS Project No. 17:6180 Page 7

4.0 DESIGN RECOMMENDATIONS

The following recommendations have been developed according to the previously described project characteristics and subsurface conditions. If there are any changes to the project characteristics or if different subsurface conditions are encountered during construction, ECS should be consulted so that the recommendations of this report can be reviewed.

4.1 POTENTIAL VERTICAL RISE

Structural damage and/or cosmetic/operational distress can be caused by volume changes in clay soils. The expansive clays found at this site are capable of swelling and shrinking in volume dependent on potentially changing soil water conditions during or after construction. Clays can shrink when they lose water and swell (increase in volume) when they gain water. The potential of expansive clays to shrink and swell is related to; amongst other things, the Plasticity Index (PI). Clays with a higher PI generally have a greater potential for soil volume changes due to moisture content variations.

We have estimated potential heave for this site utilizing the TxDOT PVR method (Tex-124-E). The Tex-124-E method provides an estimate of potential vertical rise (PVR) using the liquid limits, plasticity indices, grain-sizes, and existing water contents for soils. The PVR is estimated in the seasonally active zone, which can be up to about 12 feet in the site vicinity, or shallower where limestone bedrock is present.

Estimated PVR values are based upon anticipated typical changes in soil moisture content from a dry to wet condition; however, soil movements in the field depend on the actual changes in moisture content. Thus, actual soil movements could be less than that calculated if little soil moisture variations occur, or the actual movement could exceed the estimated values if actual soil moisture content changes are greater than anticipated. These conditions are often the result of excessive droughts, flooding, “perched” groundwater infiltration, poor surface-drainage, excessive irrigation adjacent to pavements, and/or leaking irrigation lines or utilities.

We estimate the existing PVR in the proposed improvement areas to range from about 1 inch to about 4½ inches.

4.2 DEEP FOUNDATIONS

Straight-shaft drilled pier foundations can be utilized to support the light posts.

4.2.1 Straight-Shaft Drilled Pier Foundations

For a soil bearing condition, piers at least 10 feet in length can be designed using an allowable end bearing capacity of 6,000 psf and an allowable skin friction value of 350 psf. Skin friction should be neglected within the upper 5 feet of the pier shaft. Piers at least 10 feet in length and embedded at least 3 feet into Stratum III Limestone can be designed using an allowable end bearing capacity of 25,000 psf and an allowable skin friction value of 2,500 psf for the portion of the pier socketed into limestone. The allowable skin friction can be applied in compression and uplift as required.

ECS Project No. 17:6180 Page 8

Piers should be designed to resist tension loading as a result of the upper clay soils expanding due to variations in the moisture content if the light poles are sensitive to potential vertical movements described in Section 4.1 of this report. The uplift force acting on the piers is a function of the soil shear strength, soil-pier adhesion factor, pier circumference and the length of the pier subject to swelling soils. Based on the above listed criteria, the following equation can be used to estimate the uplift force acting on the piers due to expansive soils. Reinforcing steel and pier lengths should be designed to accommodate these forces.

Uf = 60·d

Where: Uf = uplift force acting on pier due to expansive soils (kips) d = diameter of pier shaft (feet)

The uplift forces created on the straight-shaft piers due to the expansive soils plus live loading conditions can be resisted by the dead load on the pier, the weight of the pier, and the allowable skin friction values listed above below a depth of 12 feet for soil, or for the socketed length of the pier into Stratum III limestone.

The post-construction total and differential settlement (over a 40-foot distance) for properly constructed piers is anticipated to be up to approximately 1 inch and ½ inch, respectively.

4.2.2 Pier Foundation Lateral Resistance

Resistance to lateral loads and the expected pier behavior under the applied loading conditions will depend not only on the subsurface conditions, but also on loading conditions, the pier size, and the engineering properties of the pier. We recommend the designer use a performance-based design methodology using non-linear soil support springs (“p-y curves”) to model the soil behavior. Several computer programs are commercially available for this purpose; we recommend LPILE (Ensoft, Inc.)

since the software is relatively current and actively supported.

The graphical relationship between the soil resistance (p) and pile deflection (y) is commonly referred to as a “p-y curve”. Along the depth of the shaft, soil resistance (p) is expressed as a non-linear function of lateral shaft deflection (y). Various researchers developed “p-y” criteria for different kinds of soils. The “p-y” curves can be automatically generated by LPILE. Recommended design soil properties needed for generating “p-y” curves are provided in the table below.

ECS Project No. 17:6180 Page 9

Depth (feet) LPILE Description

Effective Unit Weight

(pcf)

CU

(PSF) ε50

E (psi)

UCS,

qu

(psi) RQD krm

0-23 Stiff Clay w/o Free Water 110 1,500 0.008

23-25 Weak Rock 145 0.5 x 106 800 50% 0.0005

Notes: Depth – In reference to existing grade at the time of our subsurface exploration.

Cu – Undrained Cohesive Strength (psf) ε50 – Strain corresponding to one-half the principal stress E – Initial Mass Modulus for Weak Rock (psi) UCS, qu – Uniaxial Compressive Strength (psi) RQD – Rock Quality Designation krm – Strain Factor

The parameters presented in the above table are ultimate values. Laterally loaded foundations are typically designed according to a “limit state” and a factor of safety should be introduced into the analysis. The limit state criteria used for design should be selected by the project structural engineer.

4.2.3 Drilled Pier Group Effects Considerations

Piers should be spaced at least 3 shaft diameters, center-to-center apart, where the largest diameter of the piers in question is used. If piers will be placed within 3 diameters of each other, the skin friction acting on both piers will be affected. We recommend the values shown in the following table be used to reduce the available skin friction on closely spaced piers for design purposes. Groupings of more than 4 piers should be specifically reviewed by the geotechnical engineer for interaction and capacity analysis, and the reductions listed below are not valid.

CENTER-TO-CENTER PIER

SPACING/PIER DIAMETER

ALLOWABLE SKIN FRICTION

REDUCTION FACTOR

3.0 1.00

2.5 0.90

2.0 0.75

1.5 0.66

1.0 0.50 Note: If necessary, intermediate values may be interpolated linearly.

L-Pile analyses evaluate single piles. Pile groups have an efficiency less than one when subjected to a lateral load, due to pile-soil-pile interaction in a group. For this reason, the use of p-multipliers

(pm) in the L-Pile program is suggested. The AASHTO LRFD Bridge Design Specifications, 6th Edition (2013) and the FHWA Drilled Shaft Manual (2010) provide additional design guidance on this subject.

ECS Project No. 17:6180 Page 10

4.3 PAVEMENT SECTIONS (PRIVATE PARKING & DRIVES)

ECS has prepared the following recommendations for the design and construction of both flexible and rigid pavement systems for use on the subject project. The “AASHTO Guide for Design of Pavement Structures” published by the American Association of State Highway and Transportation Officials was used to develop the pavement thickness recommendations in this report. This method of design considers pavement performance, traffic, roadbed soil, pavement materials, environment, drainage and reliability. Each of these items is incorporated into the design methodology.

We have based our analysis on the following ESAL information and pavement-related subgrade design parameters, which are considered to be typical for the area. A CBR (California Bearing Ratio) value of 2 percent was selected for design purposes. The CBR value was estimated based on ECS’ knowledge and experience with similar soils and projects in this area.

Reliability 70

Initial Serviceability Index, Flexible Pavements

4.2

Initial Serviceability Index, Rigid Pavements

4.5

Terminal Serviceability Index, All Pavements

2.0

Standard Deviation, Flexible Pavements

0.45

Standard Deviation, Rigid Pavements

0.35

Based on the design parameters listed above, we developed recommendations for “light-duty,” “moderate-duty” and “heavy-duty” pavement sections. “Light-duty” pavements are intended for general parking areas with passenger vehicles only and have an approximate capacity of 20,000 ESAL. “Moderate-duty” pavements are intended for areas subject to channelized traffic and fire lanes and have an approximate capacity of 100,000 ESAL. “Heavy-duty” pavements are intended for areas subject to heavier vehicles with extensive turning, starting, and stopping, such as pavement aprons associated with trash enclosures, and have an approximate capacity of 250,000 ESAL. If the owner or other members of the design team feel that the ESAL values used for design are not appropriate, ECS should be notified in writing, so new information can be reviewed, and if necessary, the pavement recommendations revised accordingly.

The minimum recommended thickness for both hot mixed asphalt concrete (HMAC) and reinforced Portland cement concrete (PCC) pavement sections are presented in the tables below for the described “light”, “moderate” and “heavy” traffic conditions.

ECS Project No. 17:6180 Page 11

RECOMMENDED PAVEMENT SECTION OPTIONS (WITHOUT LIME TREATMENT)

Component

Light-Duty 20,000 ESALs

Moderate-Duty 100,000 ESALs

Heavy-Duty 250,000 ESALs

Rigid Asphalt Rigid Asphalt Rigid Asphalt Portland Cement Reinforced Concrete (PCC) 5.0 in -- 6.0 in -- 7.0 in --

Hot Mixed Asphalt Concrete (HMAC) -- 2.0 in -- 3.0 in -- -- Crushed Limestone Base (CLB) -- 10.0 in -- 12.0 in -- --

RECOMMENDED PAVEMENT SECTION OPTIONS (WITH LIME TREATMENT)

Component

Light-Duty 20,000 ESALs

Moderate-Duty 100,000 ESALs

Heavy-Duty 250,000 ESALs

Rigid Asphalt Rigid Asphalt Rigid Asphalt Portland Cement Reinforced Concrete (PCC) 5.0 in -- 5.5 in -- 6.5 in --

Hot Mixed Asphalt Concrete (HMAC) -- 2.0 in -- 2.5 in -- -- Crushed Limestone Base (CLB) -- 7.0 in -- 10.0 in -- -- Lime-Treated Subgrade 6.0 in 6.0 in 6.0 in 6.0 in 6.0 in --

The pavement sections described above are for general-purpose usage for the anticipated subgrade conditions and were designed using the AASHTO Pavement and Analysis System. An aggressive maintenance program to keep joints and cracks sealed to prevent moisture infiltration will help extend the pavement life.

We recommend that rigid pavement sections be used in heavy truck traffic areas. The concrete pavement should extend throughout the areas that require extensive turning and maneuvering of the delivery vehicles, etc. Waste dumpster pads, loading areas and other heavily loaded pavement areas that are not designed to accommodate these conditions often experience localized pavement failures, particularly if flexible pavement sections are used.

4.3.1 Pavement Materials

Recommendations regarding material requirements for the various pavement sections are summarized below:

Portland Cement Concrete - Concrete used for paving should have a minimum compressive strength of 3,500 psi at 28-days. The air content at the point of placement should range from 2 to 4 percent. The concrete pavements should be reinforced and jointed per current ACI recommendations.

Hot Mix Asphalt Concrete (HMAC) Surface Course - The asphalt concrete surface course should be plant mixed, hot laid Type D (Fine Graded Surface) or Type C (Coarse Graded Surface Course) meeting the specifications requirements of TxDOT Item 340 and specific

ECS Project No. 17:6180 Page 12 criteria for the job mix formula. The mix should be compacted to between 92 and 97 percent of the maximum theoretical density as determined by Tex-227-F.

Crushed Limestone Base Course - Crushed limestone base should be placed in maximum 6-inch compacted lifts. The base materials should be compacted to at least 98 percent of the maximum dry density as determined by TxDOT Tex-113-E. Flexible base materials should be moisture conditioned to between -2 and +3 percentage points of the optimum moisture content during compaction. Flexible base materials should meet the requirements specified in 2014 TxDOT Standard Specification Item 247, Type A, Grade 1-2.

Lime-Treated Subgrade – Lime-treated subgrade should be prepared in accordance with 2014 TxDOT Standard Specifications Item No. 260. We anticipate that approximately 5 to 7 percent hydrated lime will be required to treat the clayey soils at the site. However, laboratory testing will be required to determine the actual percent lime required. The lime treated subgrade should be compacted to at least 95 percent of the maximum dry density as determined by the TxDOT moisture-density relationship (Tex-113-E).

4.3.2 Rigid Pavement Considerations

Joints are typically placed in rigid pavements to control cracking, to facilitate construction, and to isolate a section of pavement from a structure or an adjacent pavement section. Joints used to control cracking are typically known as contraction or control joints as they are intended to control cracking that arises out of the shrinkage of concrete as it cures. Construction joints are used to provide clean breaks between pavement sections that result from the construction process.

Isolation joints (or expansion joints) are used to separate the pavement from other structures or pavements and typically include the use of compressible materials in the joint as opposed to contraction or construction joints. Contraction joints should be spaced no greater than 15 feet between the nearest parallel joints with joint depths of at least ¼ of the slab thickness. Contraction and construction joints should be no wider than ⅛ inch whereas isolation joints may be up to 1 inch wide.

Steel reinforcement is commonly used where subgrade conditions are not likely to provide uniform support to the concrete pavement. Generally, sites with expansive soils present are often unable to provide such support to rigid pavement sections. Therefore, reinforcing steel can be used to span between construction and isolation (expansion) joints and should consist of at-minimum No. 3 bars spaced 18 inches on-center, each way. The rebar should be Grade 60 steel.

As with steel reinforcement, in situations where the subgrade may not provide uniform support to the pavement, dowels are commonly used to transfer loads across joints. Smooth dowels can be used for this purpose and should be utilized as recommended in the following table.

ECS Project No. 17:6180 Page 13

DOWEL DESIGN INFORMATION

Slab Thickness, In.

Dowel Diameter, In.

Min. Dowel Embedment Each Side, In.

Min. Dowel Length, In.

Dowel Spacing On-Centers, In

5.0 ⅝ 5 10 12

5.5 to 6.0 ¾ 6 12 12

6.5 to 7.0 ⅞ 7 16 12

The joint and reinforcing design of a rigid pavement system is largely a function of geometry for the pavement area. The proper length of concrete panels (defined as the distance between discontinuous pavement sections, e.g., between construction or isolation joints, or a combination of the two) and the location of contraction, construction, and isolation (expansion) joints are not included as a function of the above concrete pavement guidelines. Rather, these features should be determined based on the geometry and construction sequencing of the pavement. Actual joint spacing should be based on actual pavement areas and final panel lengths so that joints are evenly spaced. Joints should be designed to form approximately square panels where geometrically feasible.

The values provided herein are guidelines and the recommendations selected by the project civil engineer and guidelines not provided or mentioned herein should not exceed the American Concrete Institute (ACI) 330R recommendations.

4.3.3 Pavement Drainage, Subdrainage, and Trenching

Longitudinal cracks and apparent distress due to expansive clays may appear in the pavement after construction and the introduction of landscape irrigation. These cracks and distress are not pavement failures with respect to traffic support, although they may be aesthetically undesirable.

In addition, without regular maintenance, the cracks can allow additional moisture intrusion and rapid degradation of the pavement section. The pavement sections are primarily designed to support the traffic and will not resist the forces generated by swelling soils.

Positive drainage should be provided on and around pavement areas to avoid ponding of water.

Irrigation of lawn and landscaped areas adjacent to the pavements should be moderate, with no excessive wetting or drying of soils. If landscaped islands are provided, they should be designed to restrict excess water from migrating to the pavement subgrade by using self-contained beds, raised planter boxes, vertical moisture barriers, and/or edge drains. Curbs should extend through the base course and at least 4 inches into the underlying subgrade. Good perimeter surface drainage guiding surface water away from the pavement area is also recommended.

4.4 RETAINING WALLS

The magnitude of the lateral earth pressures on retaining walls is dependent upon the in-situ material behind the wall; and if displaced, the type of material used to backfill the “critical zone” behind the wall. The magnitude of the earth pressure is also dependent upon whether the critical zone is allowed to drain water freely. The critical zone can be considered as the area behind the

ECS Project No. 17:6180 Page 14 structure within a boundary created by a 45-degree angle extending from the outside edge of the foundation heel upward to the ground surface.

The lateral earth pressures for drained, level soil backfill are expressed in terms of pounds per cubic foot (psf/ft) “equivalent fluid” weight applied in a triangular distribution pattern as listed below. If the walls are free to deflect or rotate slightly at the top, they may be designed using “active” lateral earth pressures. If the walls are laterally restrained at the top, “at-rest” lateral earth pressures should be used for the retaining wall design. Where multiple material types are used within the critical zone, the higher values below should be used. The equivalent fluid weights shown in the table do not include safety factors and do not account for surcharges. Lateral loads from uniform surcharges on the wall backfill can be calculated by multiplying the vertical surcharge by the below earth pressure coefficients and should be considered as rectangular loads acting on the full wall height. An increase of 1 pcf and 1.5 pcf should be added to the active and at-rest earth pressures;

respectively, for each degree of inclination of backfill.

For the design of site retaining walls, we recommend the following tabulated soil parameters.

RETAINING WALL BACKFILL IN THE CRITICAL SOIL ZONE

Soil Parameter Estimated Value

Soil Classification Undisturbed or

Compacted Native Soil

Select Fill

ASTM C33

Size #56, #57 or #467 Stone

Compacted Manufactured

Sand (< 8% Fines)

Retained Soil Moist Unit Weight (γ) 120 pcf 120 pcf 110 pcf 120 pcf

Angle of Internal Friction (φ) 24° 28° 30° 30° Coefficient of Active Earth

Pressure (Ka)

0.42 0.36 0.33 0.33

Coefficient of At-Rest Earth Pressure (Ko) 0.59 0.53 0.50 0.50

Active Equivalent Fluid Pressure 51 (psf/ft) 43 (psf/ft) 37 (psf/ft) 40 (psf/ft)

At-Rest Earth Equivalent Fluid Pressure 71 (psf/ft) 64 (psf/ft) 55 (psf/ft) 60 (psf/ft)

ECS Project No. 17:6180 Page 15

RETAINING WALL FOUNDATIONS

Parameter Estimated Value

Allowable Bearing Pressure on at least 2 feet of compacted fill 2,500 psf

Minimum Wall Embedment Below Grade 12 inches

Ultimate Sliding Friction Coefficient [Concrete on Soil] (μ) 0.45

Ultimate Passive Equivalent Fluid Pressure (Neglect in upper 18 inches) 280 (psf/ft)

It is critical that the soils used for backfill of the retaining walls meet the soil parameters recommended above. If the soils available do not meet those parameters, then ECS should be contacted to provide revised values and to confirm that only appropriate soils will be used for wall backfill.

Care should be used to avoid the operation of heavy equipment to compact the wall backfill since it may overload and damage the wall. In addition, such loads are not typically considered in the design of site retaining walls and are not provided for in our recommendations.

Wall Drainage: Retaining walls should be provided with a wall and foundation drainage system to relieve hydrostatic pressures which may develop behind the walls. This system can consist of weepholes through the wall and/or a 4-inch perforated, closed joint drain line located along the backside of the walls above the top of the footing. The drain line should be surrounded by a minimum of 6 inches of AASHTO #57 Stone wrapped with an approved non-woven geotextile, such as Mirafi 140N, Mirafi 160N or equivalent. Wall drains can consist of a 12-inch-wide zone of free draining gravel, such as AASHTO #57 Stone, employed directly behind the wall to within 2 feet of the ground surface and separated from the soils beyond with a non-woven geotextile.

Alternatively, the wall drain can consist of a geocomposite drainage board material such as MiraDRAIN 2000 or reviewed equivalent. The wall drain should be hydraulically connected to the foundation drain. The drainboard should extend from the base of the wall to within two feet of the ground surface and should be installed in accordance with manufacturer specifications. A subdrain collector pipe surrounded with at least 5 cubic feet per foot size #57 stone (wrapped in a geotextile) should be installed at the base of the drainboard; or alternatively, an engineered system can be selected with adequate capacity for direct connectivity to a closed pipe system. The groundwater should be conducted to an appropriate discharge or sump pump facility.

ECS Project No. 17:6180 Page 16

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 SUBGRADE PREPARATION

In a dry and undisturbed state, the soils at the site are expected to provide good subgrade support for fill placement and construction operations. However, when wet, this soil will degrade quickly with disturbance from contractor operations. Therefore, good site drainage should be maintained during earthwork operations, which would help maintain the integrity of the soil. We recommend that an attempt be made to enhance the natural drainage without interrupting its pattern.

The soils at the site are moisture and disturbance-sensitive and contain fines that are considered moderately erodible. Therefore, the contractor should carefully plan their operation to reduce exposure of the subgrade to weather and construction equipment traffic and provide and maintain good site drainage during earthwork operations to help maintain the integrity of the surficial soils.

Erosion and sedimentation should be controlled per sound engineering practice and current jurisdictional requirements.

In preparing the site for construction, loose or soft existing soils, vegetation, organic soil, existing pavements, foundations or utilities, or other deleterious materials should be removed from proposed structural and paving areas, and areas receiving new fill. Undocumented fill can vary in composition, consistency, and relative density. Existing fill soils may remain in place provided the preceding criteria is met, and a stable proof roll is achieved per Section 5.1.2.

After stripping and required cuts have been completed, the subgrade soils should be scarified, moisture conditioned and compacted to at least 95 percent of the maximum dry density as determined by TxDOT Tex-114-E to a depth of at least 8 inches. The soils should be moisture conditioned to between optimum and +4 percentage points of the optimum moisture content just prior to compaction.

5.1.1 Removals, Stripping and Grubbing

The subgrade preparation should consist of stripping deleterious materials (as discussed above) 5 feet beyond pavement limits and the toe of fills. ECS should be called on to check that topsoil and deleterious surficial materials have been removed before the placement of fill or construction of structures.

Appropriate diligence should be exercised to properly backfill removed below-grade structures.

Abandoned subsurface utilities and permeable backfills should be removed and/or grouted a sufficient distance from the proposed pavements to prevent the conduit of water beneath the proposed pavements.

5.1.2 Proof Rolling

After stripping and removing deleterious surface materials, cutting to the proposed grade, and before compacting the subgrade or placing of structural fill, the exposed subgrade should be reviewed by the Geotechnical Engineer or authorized representative. The exposed subgrade should be proof rolled with previously approved construction equipment having a minimum axle load of

ECS Project No. 17:6180 Page 17

25 tons (e.g., fully loaded tandem-axle dump truck). The areas subject to proof rolling should be traversed by the equipment in two perpendiculars (orthogonal) directions with overlapping passes of the vehicle under the observation of the Geotechnical Engineer or authorized representative.

This procedure is intended to assist in identifying localized yielding materials. If yielding or “pumping” subgrade is identified by the proof rolling, those areas should be marked for repair before the compacting the subgrade or placing fills or other construction materials. Methods of repair of yielding subgrade, such as undercutting, moisture conditioning, geogrid or lime/cement treatment, should be discussed with the Geotechnical Engineer to determine the appropriate procedure about the existing conditions causing the yielding.

If the area is deemed too small for a piece of equipment to traverse, the excavated area should be probed by the Geotechnical Engineer or authorized representative.

5.1.3 Site Temporary Dewatering

The contractor should make their own assessment of temporary dewatering needs based upon the limited subsurface groundwater information presented in this report. Soil sampling is not continuous, and thus soil and groundwater conditions may vary between sampling intervals (typically 5 feet). If the contractor believes additional subsurface information is needed to assess dewatering needs, they should obtain such information at their own expense. ECS makes no warranties or guarantees regarding the adequacy of the provided information to determine dewatering requirements; such recommendations are beyond our scope of services.

Dewatering systems are a critical component of many construction projects. Dewatering systems should be selected, designed, and maintained by a qualified and experienced (specialty or other) contractor familiar with the succinct geotechnical and other aspects of the project. The failure to properly design and maintain a dewatering system for a given project can result in delayed construction, unnecessary foundation subgrade undercuts, detrimental phenomena such as “running sand” conditions, internal erosion (i.e., “piping”), the migration of “fines” down-gradient towards the dewatering system, localized settlement of nearby infrastructure, foundations, slabs-on-grade and pavements, etc. Water discharged from site dewatering system should be discharged in accordance with local, state and federal requirements.

Strategies for Addressing Perched Groundwater: The typical primary strategy for addressing perched groundwater seeping into excavations is pumping from trenches (or French drains) and sump pits with sump pumps. A typical sump pump drain (found in a sump pit or along a French drain) is depicted on the following page. The inlet of the sump pump is placed at the bottom of the corrugated pipe and the discharge end of the sump is directed to an appropriate stormwater drain.

ECS Project No. 17:6180 Page 18

Sump Pit/Pump Diagram

A typical French drain consists of an 18-to-24-inch-wide bed of AASHTO #57 (or similar open graded aggregate) aggregate wrapped in a medium duty, non-woven geotextile such as Mirafi 140N or 160N and (often) containing a 4 to 6-inch diameter, Schedule 40 PVC perforated or slotted pipe.

Actual dimensions should be as determined necessary by ECS during construction. After the installation has been completed, the geotextile should be wrapped over the top of the aggregate and pipe followed by placement of backfill. The top of the drain should be positioned at least 18 inches beneath the design subgrade elevations.

Pumping wells or a vacuum system could also be used to address perched groundwater. These techniques often are only effective during the initial depletion of the perched water quantity and may quickly be ineffective at addressing accumulation of water from rain, lake level, etc.

5.2 EARTHWORK OPERATIONS

After stripping and grubbing, undercutting/removals, subgrade preparation (including proof rolling) and evaluation has been completed, fill placement may begin. Fills in pavement and landscape areas can consist of materials meeting the requirements of the General Fill section below.

Soil moisture levels should be preserved (by various methods that can include covering with plastic, watering, etc.) until new fill, pavements, or slabs are placed. Fill soils should be placed in 8 inches loose lifts for mass grading operations and 4 inches for trench excavations where walk-behind or “jumping jack” compaction equipment is used.

Upon completion of the filling operations, care should be taken to maintain the soil moisture content before the construction of pavements. If the soil becomes desiccated, the affected material should be removed and replaced, or these materials should be scarified, moisture conditioned, and re-compacted.

Utility cuts should not be left open for extended periods and should be properly backfilled.

Backfilling should be accomplished with properly compacted on-site soils, rather than granular materials. If granular materials are used, a utility trench cut-off at the pavement line is

ECS Project No. 17:6180 Page 19 recommended to help prevent water from migrating through the utility trench backfill to beneath the proposed pavements.

Field density and moisture tests should be performed on each lift as necessary to check that adequate compaction is achieved. As a guide, one test per 10,000 square feet per lift is recommended for paving areas (two tests minimum per lift). Utility trench backfill should be tested at a rate of one test per lift per every 150 linear feet of the trench (two tests minimum per lift).

Certain jurisdictional requirements may require testing in addition to that noted previously.

Therefore, these specifications should be reviewed, and more stringent specifications should be followed.

5.2.1 Weathered Rock and Rock

Shallow limestone was encountered at the site during our subsurface exploration, and rock excavation techniques may be necessary for this project. For purposes of contract terms, we recommend that “rock” be defined as follows: “Rock shall be defined as those natural materials which cannot be excavated in an open excavation with a Caterpillar Model No. D-8, heavy-duty track-type tractor, weighted at not less than 285 hp (flywheel power) and equipped with a single-shank hydraulic ripper, capable of exerting not less than 45,000 lbs. breakout force, or equivalent machinery. For footings, utility trenches and pits, rock shall be defined as those materials that cannot be excavated with a Caterpillar Model No. 215D LC track-type hydraulic excavator, equipped with a 42-inch wide short-tip radius rock bucket, rated at not less than 120 hp flywheel power with bucket-curling force of not less than 25,000 lbs. and stick-crowd force of not less than 18,000 lbs.”

Depending on the excavation methods, the marlstone and limestone at this site may excavate in relatively large, blocky and platy pieces, which are difficult to compact for long-term performance.

Excavated Stratum III limestone may be appropriate for fill within the paving limits. Excavated limestone from the site used as earthwork fill should have a well-graded grain size distribution with rock and soil particles ranging from clay or silt size particles to a maximum size of 4 inches in diameter. Particles larger than this should be decomposed by mechanical compaction equipment to achieve the desired grain size distribution.

Once appropriately broken down, this material may then be placed and compacted to at least 95% of the maximum dry density at -1 to +3 percent above the optimum moisture content as obtained using the Tex-114-E proctor method.

5.3 MATERIAL SPECIFICATIONS

5.3.1 General Fill

General fill should consist of on-site or imported soils, provided they meet the requirements described below. General fill materials should be free of organics, construction debris, deleterious materials, and should be free of rocks larger than 4 inches in greatest dimension. Proposed general fill should be evaluated and tested by ECS prior to placement in the field.

ECS recommends that general fill be placed in horizontal loose lifts of not more than 8 inches in thickness. Lift thickness should be decreased when using light compaction equipment. General fill

ECS Project No. 17:6180 Page 20 should be compacted to at least 95% of the maximum dry density at moisture contents within the range of optimum to +4 percentage points of the optimum moisture content (Tex-114-E).

5.3.2 Select Fill

Select fill materials should be free of organics, construction debris, deleterious materials, and should be free of rocks larger than 4 inches in greatest dimension. Select fill should have a Plasticity Index of between 5 and 20. Select fill should be evaluated and tested by ECS prior to placement in the field.

ECS recommends that select fill be placed in horizontal loose lifts of not more than 8 inches in thickness. Select fill should be compacted to at least 95% of the maximum dry density at moisture contents within the range of -1 to +3…