RONE GEO-TECHNICAL REPORT.pdf

GEOTECHNICAL ENGINEERING REPORT

RED BIRD EXECUTIVE ANTENNA TOWER

5303 CHALLENGER DRIVE

DALLAS, TEXAS

Prepared For:

FAA

6500 South MacArthur

RRF Building – 185 Oklahoma City, Oklahoma 73169

Attn: Mr. Greg Brooks

March 2019

PROJECT NO. 19-23356

www.roneengineers.com

GEOTECHNICAL ENGINEERING

ENVIRONMENTAL CONSULTING

CONSTRUCTION MATERIAL TESTING

DALLAS | FORT WORTH | AUSTIN | HOUSTON

8908 AMBASSADOR ROW | DALLAS, TEXAS 75247 | TEL: 214.630.9745

March 13, 2019

Mr. Greg Brooks

FAA

6500 South MacArthur

RRF Building – 185

Oklahoma City, Oklahoma 73169

Re: Geotechnical Engineering Report

Red Bird Executive Antenna Tower

5303 Challenger Drive

Dallas, Texas

Rone Report No. 19-23356

Dear Mr. Brooks:

Rone Engineering Services, Ltd. (Rone) is pleased to submit the Final Geotechnical

Engineering Report for the above referenced project. The geotechnical engineering services performed for this study were carried out in general accordance with Rone Proposal No.

P-26447-18, dated February 8, 2019.

This report presents engineering analyses and recommendations for site grading and foundations with respect to known project and site characteristics. Detailed results of our field exploration and laboratory testing are provided in the appendix of the report.

We appreciate the opportunity to be of service to you on this project and look forward to providing additional Geotechnical Engineering and Construction Materials Testing services as the project progresses through the final design and construction phases. Please contact us if you have any questions or if we can be of further assistance.

Respectfully Submitted, Eric M. Hollabaugh, P.E. Mark D. Gray, P.E.

Geotechnical Engineer Partner

Texas Engineering Firm License No. F-1572

03.1 3.20

Page

1 INTRODUCTION

2 PURPOSES AND SCOPE OF STUDY

3 FIELD OPERATIONS AND LABORATORY TESTING

4 GENERAL SITE CONDITIONS

4.1 Site Geology

4.2 Subsurface Soil Conditions

4.3 Groundwater

5 ANALYSIS AND RECOMMENDATIONS

5.1 Seismic Site Class

5.2 Potential Vertical Rise

5.3 Excavation Safety Considerations

5.4 Foundation Recommendations

5.4.1 Straight Sided Drilled Shafts

5.4.2 Lateral Design Considerations for Drilled Shafts

5.4.3 Design and Construction Considerations for Drilled Shafts

5.4.4 Spread Footing Design Recommendations

6 SITE PREPARATION AND FILL PLACEMENT

6.1 General

6.2 Site Preparation

6.3 Select Fill

6.4 Density Tests

6.5 Site Grading

6.6 Utility Backfill

6.7 Exterior Flatwork

6.8 Surface Drainage

6.9 Landscaping

6.10 Construction Observations

7 STUDY CLOSURE

8 COPYRIGHT 2019 RONE ENGINEERING SERVICES, LTD

APPENDIX A

Plate

VICINITY MAP ........................................................................................................................................... A.1

GEOLOGY MAP ........................................................................................................................................ A.2

BORING LOCATION DIAGRAM ................................................................................................................ A.3

LOG OF BORING ...................................................................................................................................... A.4

KEY TO CLASSIFICATIONS AND SYMBOLS .......................................................................................... A.5

UNIFIED SOIL CLASSIFICATION SYSTEM ............................................................................................. A.6

APPENDIX B

FIELD OPERATIONS ................................................................................................................................ B.1

LABORATORY TESTING .......................................................................................................................... B.2

APPENDIX C

IMPORTANT INFORMATION ABOUT THIS GEOTECHNICAL ENGINEERING REPORT .....................C.1

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GEOTECHNICAL ENGINEERING REPORT

1 INTRODUCTION

A brief description of the proposed project and project site is included in the table below:

Table 1: Project Information

Item Description

Location The project will be located at 5303 Challenger Drive in Dallas, Texas.

Project Description The project will consist of the construction of a new self-supported lattice antenna tower approximately 40 feet tall.

Site Conditions The site generally consists of an existing fenced communication equipment compound with a crushed stone surface.

A site vicinity map and geology map are attached as Plates A.1 and A.2, respectively. The general location and orientation of the site are shown on the Boring Location Diagram, Plate

A.3, in Appendix A of this study.

2 PURPOSES AND SCOPE OF STUDY

The principal purposes of this study are to evaluate the general subsurface conditions at the proposed site and to develop geotechnical recommendations for the design and construction of foundations and pavements. To accomplish its intended purposes, the study was conducted in the following phases:

• One boring was drilled and sampled to evaluate the subsurface conditions at the boring location and to obtain soil and rock samples.

• Laboratory tests were conducted on selected samples recovered from the boring to estimate the pertinent engineering characteristics of the foundation soils and rock.

• Engineering analyses were performed using field and laboratory data, to develop foundation and pavement design recommendations.

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3 FIELD OPERATIONS AND LABORATORY TESTING

The boring was located in the field by the client. This location was not surveyed. The provided location is accurate only to the extent implied by the technique used in its determination.

Subsurface conditions were evaluated by completing a total of one boring to a depth of approximately 20 feet near the proposed tower center. The approximate boring location is shown on Plate A.3, Boring Location Diagram. Sample depth, description of soils, and classification (based on the Unified Soil Classification System) are presented on the Log of

Boring, Plate A.4. Keys to terms and symbols used on the log are shown on Plates A.5 and

A.6.

Laboratory tests were performed on selected samples recovered from the boring to confirm visual classification and determine the pertinent engineering properties of the soils encountered.

Classification test results are presented on the Log of Boring. Descriptions of the procedures used in the field and laboratory phases of this study are presented in Appendix B of this report.

4 GENERAL SITE CONDITIONS

4.1 Site Geology

Based on the subsurface conditions encountered in the boring and the Geologic Atlas of Texas, Dallas Sheet (published by the Bureau of Economic Geology), the site appears to be located within the Austin Chalk Formation (mapped as Kau). The USGS Mineral Resources On-Line

Spatial Data reference contains the following description of this geologic formation:

The Austin Chalk Formation in north Texas is predominantly a light gray massively bedded chalk with some interbeds and partings of calcareous clay. The middle part is mostly thin-bedded marl with interbeds of massive chalk, hard lime mudstone, and some soft chalk. It typically weathers white, and marine fossils are scarce in this formation. The chalk is mostly microgranular calcite. Locally, thin bentonitic beds can occur in the lower part.

Please note that the geologic mapping was originally performed using aerial photography.

Local variations and anomalies do occur.

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Descriptions of the various strata encountered in the boring and their approximate depths and thickness are shown on the log of boring. A brief description of the stratigraphy indicated by the log of boring is given below.

4.2 Subsurface Soil Conditions

The various strata and their approximate depths and thickness are shown on the Log of Boring.

The stratification boundaries shown on the Log of Boring represent the approximate locations of changes in types of soil and rock; in-situ, the transition between material types may be gradual and indistinct. A brief summary of the stratigraphy indicated by the boring is given below.

Materials described as weathered limestone may, in fact, have been taken from zones of competent limestone, marl, or even dolomite.

The boring generally encountered tan weathered limestone from the ground surface to a depth of approximately 2 feet below existing grades. Underlying the weathered limestone, the boring encountered gray limestone to the boring termination depth of approximately 20 feet.

4.3 Groundwater

The boring was advanced using flight augers to observe the potential for water seepage during and after drilling. Free water was not observed in the boring during drilling or immediately upon completion. The scope of work did not include long-term observations of ground water or perched water conditions. In addition, it is difficult to accurately predict the magnitude of subsurface water fluctuations that might occur following periods of drought or rainfall.

Groundwater can be encountered above any of the less permeable soil or rock at this site, creating a temporary perched water condition, particularly during wet periods of the year.

Groundwater levels should be expected to fluctuate throughout the year with variations in precipitation, runoff, the water levels in nearby surface water features, and other factors not evident at the time of the field services.

These observations have been made during the course of the field exploration, as indicated on the Log of Boring. A groundwater study has not been performed. Long-term observations would be necessary to more accurately evaluate the groundwater levels and fluctuations. If these services are desired, Rone would be pleased to provide groundwater level monitoring as an additional scope of services.

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5 ANALYSIS AND RECOMMENDATIONS

5.1 Seismic Site Class

The site class for seismic design is based on several factors that include soil profile (soil or rock), shear wave velocity, density, relative hardness, and strength, averaged over a depth of

100 feet. The boring for this project did not extend to a depth of 100 feet; we have assumed the soil and rock conditions below the termination depth of the boring to be similar to those encountered at the termination depth of the boring. Based on Section 1613.3.2 of the 2015

International Building Code and Table 20.3-1 of ASCE 7-10, we recommend using Site Class B

(Rock) for seismic design.

5.2 Potential Vertical Rise

Based on the subsurface conditions encountered in the boring, we anticipate negligible potential vertical rise (PVR) at this site.

5.3 Excavation Safety Considerations

Please note that in accordance with Texas State Law, the design and maintenance of excavation safety systems is the sole responsibility of the contractor. Please reference

Occupational Safety and Health Administration (OSHA) Standards 29 CFR – 1926 Subpart P, Appendix A and B, for guidance in the design of such systems.

5.4 Foundation Recommendations

Based on the subsurface conditions encountered in the boring and the anticipated loading conditions, the proposed tower may be supported on straight sided drilled shafts bearing in suitable gray limestone. As an alternative, the proposed tower may also be supported on shallow spread footings bearing in suitable gray limestone. Foundation design recommendations are provided below.

5.4.1 Straight Sided Drilled Shafts

A straight-sided drilled shaft foundation system can be utilized to support the proposed tower.

The shafts should bear in suitable gray limestone at least 12 feet below the proposed final grade. The design of the drilled shafts may be based on the following recommendations.

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Table 2: Drilled Shaft Recommendations

Bearing Stratum Unweathered gray limestone

Approximate depth to Bearing Stratum (feet) 2

Minimum Penetration into the Bearing Stratum (feet) 1 8

Minimum Shaft Length (feet) 10

Allowable Bearing Capacity (psf) 2 30,000

Allowable Skin Friction (psf) 3 4,500

1. Or one shaft diameter, whichever is larger.

2. At or below the minimum penetration into the bearing stratum

3. For portions of the shaft below the minimum penetration

Foundation settlements for drilled shafts constructed as described above are estimated to be on the order of ½-inch.

The shafts should contain sufficient full length reinforcing steel to resist uplift forces. The uplift forces can be resisted by the dead load on the shafts plus the allowable skin friction resistance in the portion of the shaft below the minimum penetration depth, or below the bottom of the casing (if needed), whichever is deeper.

For constructability, we recommend a minimum shaft diameter of 18 inches. Adjacent shafts should have a minimum center-to-center spacing of 3 shaft diameters (based on the larger shaft). Reduced shaft spacing could result in reduced shaft capacity for both uplift forces and gravity forces. Rone should be contacted to review reduced shaft spacing on a case-by-case basis.

5.4.2 Lateral Design Considerations for Drilled Shafts

Lateral load analysis should be performed for drilled shafts subjected to horizontal loads. Drilled shafts will provide lateral load capacity from the passive soil resistance developed on the side of the shafts. The lateral load analysis can be performed using computer programs such as L-

PILE. The upper 5 feet of soils should be neglected for lateral support. The following input data can be used for the L-PILE analysis.

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Table 3: L-PILE Input Parameters for P-Y Curves

Material Description Qu (psi) K-rm E(psi) Unit Weight

(pcf)

Gray Limestone 700 0.0003 105,000 140

For lateral loads, Rone recommends using the reduction factors (p-multipliers) presented in

“Drilled Shafts: Construction Procedures and Design Methods” published by the Federal

Highway Administration (FHWA). The reduction factors depend on their relative position within the group. Only two positions (front and back row) are identified, as research has shown that all shafts or piles in or behind the second row of in-line groups behaved similarly.

Table 4: Lateral Load Group Reduction Factors

Pile Spacing (Diameter) Reduction Factors

Front Row Back Row (s)

3D 0.90 0.50

4D 0.95 0.65

5D 1.00 0.80

It should be noted that factors of safety are not generally applied to the lateral load analysis.

Instead, performance criteria, or a “limit state” is usually considered.

5.4.3 Design and Construction Considerations for Drilled Shafts

The geotechnical engineer or senior project manager should be onsite at the beginning of drilled shaft operations to initiate observation and testing procedures, and confirm the intent of the geotechnical recommendations contained in this report. The construction of all drilled shafts should be observed by experienced geotechnical personnel to document conformance with project documents and confirm the following:

• shafts are plumb and within the acceptable tolerance

• groundwater seepage, when encountered, is correctly handled

• sides of shaft are not sloughing or caving

• minimum penetration into the competent bearing strata or below the bottom of the casing (if needed), whichever is deeper, is achieved

• bearing surface is clean

• proper mix design and concrete slump

• proper removal of casing

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Groundwater seepage was not encountered in the boring at the time of our field exploration.

The risk of encountering groundwater seepage is increased during or after periods of precipitation. We do not anticipate the need for temporary casings during shaft excavation, but the need for casings should be determined during construction based on the conditions encountered during the shaft excavations. Reinforcing steel cages and concrete should be placed in the shafts immediately after the excavation has been completed, dewatered, cleaned and observed. Complete installation of individual shafts should be accomplished within 8 hours of the excavation. Prolonged air exposure or inundation of the bearing surface could deteriorate the bearing material.

If casing is used, a full head of concrete should be maintained within the casing during removal.

In no case should water be allowed to infiltrate the concrete of the shaft. Vibratory casing removal is recommended, and is required for friction shafts. Complete installation of a shaft should be accomplished at least 48 hours before beginning another excavation located within four shaft diameters, center-to-center. If groundwater is encountered, a sump may be excavated immediately adjacent to each shaft to collect water displaced during concrete placement.

Concrete should have a slump of 8 to 10 inches and the concrete mix design should allow for sufficient working time. The concrete should not be allowed to strike the casing sidewall or steel reinforcement during placement. Submersible pumps may be required to control seepage; the concrete must be placed using a tremie if groundwater cannot be kept at a depth of 1 inch or less during placement. Rone should be contacted for further evaluation and recommendations if excessive groundwater seepage or caving occurs.

5.4.4 Spread Footing Design Recommendations

Shallow spread footing foundations can also be used to support the proposed tower. A net allowable bearing pressure of 8,000 pounds per square foot may be used for design of all spread footings bearing in approved gray limestone at least 3 feet below final grades. If suitable gray limestone is present for only a portion of an individual footing, we recommend that the excavation be extended deeper to bear entirely on suitable gray limestone. Over-excavation is not necessary where the entire footing bears entirely within gray limestone at the design bearing elevation. The allowable bearing pressure contains a safety factor of at least 3 against shear failure of the foundation bearing soils. Individual spread footings should be at least 30 inches

Project No. 19-23356 Red Bird Executive Antenna Tower P A G E | 8 wide, and strip footings should be at least 18 inches wide. The footings can also be constructed as shallow drilled shafts at least 24 inches in diameter bearing in suitable gray limestone at least

5 feet below final grades. The bottom of footing excavations should be free of any loose or soft material prior to the placement of the concrete.

Excavations for foundations should be filled with concrete as soon as possible, and no later than the end of the workday, to reduce deterioration of the bearing surface. Prolonged drying or inundation of the bearing surface will negatively affect strength and compressibility characteristics. If delays occur, the excavation should be deepened as necessary and cleaned, in order to provide a fresh bearing surface. If more than 24 hours of exposure of the bearing surface is anticipated, a lean concrete “mud slab” should be used to protect the bearing surface.

If a mud slab is used, the foundation excavation should initially be over-excavated by approximately 4 inches and a lean concrete mud slab approximately 4 inches thick should be placed in the bottom of the excavation immediately following exposure of the bearing surface.

The mud slab will protect the bearing surface, maintain more uniform moisture in the subgrade, facilitate dewatering of excavations if required, and provide a working surface for the placement of formwork and reinforcing steel.

We anticipate that long-term total and differential movement of shallow footings bearing on suitable gray limestone due to applied loads will be ½ inch or less, provided footings are designed and constructed as recommended above.

6 SITE PREPARATION AND FILL PLACEMENT

The following recommendations for site preparation and fill placement may contain elements that do not appear to apply to the presently known conditions at the project site. These items have been included based on our experience that unforeseen obstacles can be encountered, and progress can be delayed while written guidance is prepared. While we cannot cover every possible circumstance, we have attempted to address the most frequently occurring issues in this report section.

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6.1 General

Standard construction practices of providing good surface water drainage should be used. All grading should provide adequate drainage away from the paving, and should prevent water from collecting near the edges of pavements and structures. Also, ditches or swales should be provided to carry the run-off water both during and after construction.

Backfill for utility lines or along the perimeter beams should consist of site-excavated soil. If the backfill is too dense or too dry, it will swell and a mound will form along the trench line. If the backfill is too loose or too wet, it will settle and a depression will form along the trench line.

Backfill should be compacted as recommended in the “Site Preparation and Fill Placement” section of this report.

All excavations should be sloped, shored, or shielded in accordance with OSHA requirements.

6.2 Site Preparation

Preparation of the site for any future construction should include the removal and proper disposal of any obstructions that would hinder construction. These obstructions include all abandoned structures, foundations, debris, water wells, septic tanks, and loose material. It is the intent of these recommendations to provide for the removal and disposal of all obstructions not specifically provided for elsewhere by the plans and specifications.

Any abandoned utility lines should be removed and disposed of properly. All abandoned utilities that are not removed represent a risk to future performance; if the lines are abandoned in place, they must be fully grouted and capped so that the pipes do not provide a ready conduit for water.

All concrete, trees, stumps, brush, abandoned structures, roots, vegetation, rubbish and any other undesirable matter should be removed and disposed of properly. It is the intent of these recommendations to provide a loose surface with no features that would tend to prevent uniform compaction by the equipment to be used.

All areas to be filled should be disced or bladed until uniform and free from large clods. Soils should be brought to the proper moisture content and compacted as indicated in the Fill

Placement Criteria table below.

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Table 5: Fill Placement Criteria

Item Description Plasticity

Requirement

Compaction

Standard

Density

Requirement

Moisture

Requirement

On-site soils General grading None ASTM D698

95% to 100% of maximum dry density

Optimum moisture to

4% above optimum moisture

Imported general fill General grading

Liquid Limit less than

ASTM D698

95% to 100% of maximum dry density

Optimum moisture to

4% above optimum moisture

Select fill (soils) Structural fill 5≤ PI ≤ 15; LL ≤ 35 ASTM D698

95% to 100% of maximum dry density

Minus 2% to Plus 2% of optimum moisture

Select fill (crushed rock or concrete) Structural fill

Per TxDOT Item 247, Type A, C, or D Grade

1-2 or 3

ASTM D1557

95% to 100% of maximum dry density

Minus 2% to Plus 2% of optimum moisture

Select fill (crushed rock from Austin

Chalk Formation)

Structural fill 5≤ PI ≤ 15; LL ≤ 35 ASTM D698

95% to 100% of maximum dry density

From -1% to +3% of optimum moisture

Select fill (crushed rock or concrete)

Structural fill – fill body cap (over soil fill body)

Per TxDOT Item 247, Type A, C, or D Grade

1-2 or 3

ASTM D698

95% to 100% of maximum dry density

Minus 2% to Plus 2% of optimum moisture

Deep fill

Clay fill 10 feet or more below final grades

Liquid Limit less than

ASTM D698

97% to 100% of maximum dry density

Optimum moisture to

3% above optimum moisture

Deep utility line backfill

Clay utility backfill

10 feet or more below final grades

Liquid Limit less than

ASTM D698

98% to 100% of maximum dry density

Minus 2% to Plus 2% of optimum moisture

6.3 Select Fill

Select fill should consist of a clean, natural soil meeting the criteria recommended above. The fill should have a moisture content within the specified range, be placed in loose lifts less than 9 inches thick, and compacted as indicated. Lime-treated, on-site soils may also be used as select fill, provided the PI of the treated material meets the specifications for select fill. The quantity of lime needed to achieve the PI requirement for select fill is not known. The actual percentage of lime should be determined once soils have been stockpiled and sampled.

Crushed limestone or concrete can also be used as select fill, provided it meets the criteria listed in the Fill Placement Criteria table. The material should have a moisture content within the specified range, be placed in loose lifts less than 9 inches thick, and compacted as indicated in the table.

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The fill material should be placed in level, uniform layers that have a compacted moisture content and density conforming to the recommendations in this report. Each layer should be thoroughly mixed during spreading to provide uniformity within the layer. The loose lift thickness should not exceed 9 inches.

6.4 Density Tests

Field density tests should be made by the geotechnical engineer or his representative. Density tests should be taken in each layer of the compacted material below the disturbed surface. If the materials fail to meet the specified moisture and/or density, the course should be reworked as necessary to obtain the specified criteria.

Proper moisture content and compaction must be maintained until placement of the overlying lift, or construction of overlying flatwork. Failure to maintain the moisture content and compaction could result in excessive soil movement that can have a detrimental effect on structures supported on or above the fill. The contractor should provide some means to control the moisture content and compaction (such as water hoses, water trucks, etc.). Maintaining subgrade moisture and compaction is always critical, but will require extra effort during warm, windy, and/or sunny conditions. Density and moisture testing is recommended to provide some indication that adequate earthwork is being performed; however, the quality of the fill is the sole responsibility of the contractor. Satisfactory testing is not a guarantee of the quality of the contractor’s earthwork operations.

6.5 Site Grading

Site grading operations should be performed in accordance with the recommendations provided in this report. Grading plans and construction operations should strive to achieve positive drainage around all sides of the proposed structures. Inadequate drainage around structures supported on-grade will likely cause excessive vertical movement to occur.

6.6 Utility Backfill

If granular material is used for embedment in utility trenches, we recommend placing a clay plug, as a replacement for the granular embedment, at the location where the city line is located, at locations where the utility enters structures or passes beneath the pavement, and at other connections. The intent is to prevent free moisture from passing through the granular embedment and entering the soil beneath structures and pavement.

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On-site clayey soils should be used as backfill. These materials should be placed in maximum

6-inch lifts and properly compacted to between 95 and 100 percent of the maximum dry density, as determined by Standard Moisture Density Relation test (ASTM D 698), and at a moisture content of at least two percent (min +2%) above the soil’s optimum moisture content. In instances where utility lines are more than 10 feet deep, the backfill below 10 feet should be compacted at 98 to 100 percent of the maximum dry density, as determined by Standard

Moisture Density Relation test (ASTM D698), and at a moisture content of within two percent (-2 to +2%) of the soil’s optimum moisture content.

It is typical for fills over 10 feet in depth to experience settlement. On an average, fills over 10 feet will experience between 1 and 2 percent settlement. This should be considered when designing utility lines beneath pavements, flatwork or any structure.

6.7 Exterior Flatwork

Concrete flatwork should be steel reinforced to reduce the formation and size of the cracks.

Flatwork should also include frequent and regularly spaced expansion/control joints and dowels to limit vertical offsets between neighboring flatwork slabs and reduce formation of trip hazards.

Structure entrances should either be part of the structure or designed to tolerate vertical movement without inhibiting access. The moisture content of the subgrade must be maintained up to the time of concrete placement. If subgrade soils are allowed to dry below the optimum moisture content, the moisture of the soils should be increased to raise the surface soil moisture content. These recommendations are intended to limit possible distress to exterior flatwork, but will not prevent movement and/or vertical offsets between slabs.

6.8 Surface Drainage

Proper drainage is critical to the performance and condition of the foundation and flatwork.

Surface drainage should direct water away from structures and pavement. If water is collect next to or below the foundation or flatwork, then undesired soil movements can occur, and these movements can exceed estimates contained in this report. The slopes should direct water away from the structure, and must be maintained to prevent water ponding adjacent to all site improvements. The location of gutter downspouts, and other features, should be designed such that these items will not create moisture concentrations at or beneath the structure or flatwork.

Downspouts should discharge well away from the structure, and should not be allowed to erode surface soil.

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Moisture related issues can be positively addressed by constructing continuous exterior flatwork that extends to the foundation line. The joints created at the interface of the flatwork and building line must be sealed with a flexible joint sealer to prevent the infiltration of water. Open cracks that may develop in the flatwork should also be sealed. The joint and any cracks that develop must be maintained and resealed, in a timely manner and should be part of a periodic inspection and maintenance program.

6.9 Landscaping

We do not recommend the use of landscaping against and around the exterior of the foundations, as landscaped areas can adversely affect subgrade moisture. Landscaped areas can create both saturated and desiccated conditions that cause localized/differential movements and the formation of cracks. If used, landscaping should be kept as far away from the foundation as possible and positive drainage must be maintained. Landscaping element (such as edging) must not prohibit or slow the drainage of water. When feasible, irrigation lines and heads should not be placed in close proximity to the foundation to prevent the collection of water near the foundation or flatwork, particularly in the event of leaking lines or sprinkler heads.

Trees should not be placed in proximity to the structure or movement sensitive flatwork, as trees are known to cause localized soil shrinkage due to desiccation of the soil by the root system.

This would result in localized differential settlement. The desiccation zone varies by tree, but trees should generally set back 1½ to 2 times the mature tree height, and in no cases should the drip-line of the mature tree extend over or within 15 feet of rooflines.

6.10 Construction Observations

In any geotechnical study, the design recommendations are based on a limited amount of information about the subsurface conditions. In the analysis, the geotechnical engineer must assume the subsurface conditions at the site are similar to the conditions encountered in the borings; however, during construction, anomalies in the subsurface conditions are often revealed. The potential for the presence of varied geologic formations and significantly different support conditions at this site, which could result in changes in our design recommendations, increases the risk of damaging soil movements at this site. Therefore, it is recommended that

Rone Engineering Services, Ltd. be retained to observe earthwork and foundation construction, and perform materials evaluation and testing during the construction phase of the project. This enables the geotechnical engineer to stay abreast of the project and to be readily available to

Project No. 19-23356 Red Bird Executive Antenna Tower P A G E | 14 evaluate unanticipated conditions, to conduct additional tests if required and, when necessary, to recommend alternative solutions to unanticipated conditions. Until these construction phase services are performed by the project geotechnical engineer, the recommendations contained in this report on such items as final foundation bearing elevations, final depth of undercut of expansive soils for non-expansive earth fill pads, and other such subsurface-related recommendations should be considered preliminary.

It is proposed that construction phase observation and materials testing commence by the project geotechnical engineer at the outset of the project. Experience has shown that the most suitable method for procuring these services is for the owner to contract directly with the project geotechnical engineer. This results in clear, direct lines of communication among the owner, the owner's design engineers, and the geotechnical engineer.

7 STUDY CLOSURE

The analyses, conclusions, and recommendations contained in this report are based on site conditions as they existed at the time of the field exploration and further on the assumption that the exploratory boring is representative of the subsurface conditions throughout the site; that is, the subsurface conditions everywhere are not significantly different from those disclosed by the boring at the time it was completed. If during construction, different subsurface conditions from those encountered in our boring are observed, or appear to be present in excavations, we must be advised promptly so that we can review these conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of this report and the start of the work at the site, if conditions have changed due either to natural causes or to construction operations at or adjacent to the site, or if structure locations, structural loads, or finished grades are changed, we urge that we be promptly informed and retained to review our study to determine the applicability of the conclusions and recommendations, considering the changed conditions and/or time lapse.

Further, it is urged that Rone Engineering Services, Ltd. be retained to review those portions of the plans and specifications for this particular project that pertain to earthwork and foundations as a means to determine whether the plans and specifications are consistent with the

Project No. 19-23356 Red Bird Executive Antenna Tower P A G E | 15 recommendations contained in this report. In addition, we are available to observe construction, particularly the compaction of structural fill, or backfill and the construction of foundations as recommended in the report, and such other field observations as might be necessary.

This study has been completed for the exclusive use of the client and their designated agents for specific application to design of this project. We have used that degree of care and skill ordinarily exercised under similar conditions by reputable members of our profession practicing in the same or similar locality. No warranty, expressed or implied, is made or intended.

8 COPYRIGHT 2019 RONE ENGINEERING SERVICES, LTD.

This document, including all text and graphics, are copyrighted materials that are the property of

Rone Engineering Services, Ltd. except as otherwise noted. This document may not be used, in whole or in part, without the express written permission of Rone Engineering Services, Ltd.

APPENDIX A

APPROVED BY:

REVISED BY:

DRAWN BY:

FILE NAME:

PROJECT NO:

DATE:

DATE:

DATE:

CM

REVISED BY: DATE:

EH

19-23356

1923356.DWG

3-5-2019

3-5-2019

PLATE A.1

VICINITY MAP

RED BIRD EXECUTIVE ANTENNA TOWER

5303 CHALLENGER DRIVE

DALLAS, TEXAS

SCALE: NTS

ENGINEERING

SITE

PLATE A.2

GEOLOGY MAP

RED BIRD EXECUTIVE ANTENNA TOWER

5303 CHALLENGER DRIVE

DALLAS, TEXAS

SCALE: NTS

APPROVED BY:

REVISED BY:

DRAWN BY:

FILE NAME:

PROJECT NO:

DATE:

DATE:

DATE:

CM

REVISED BY: DATE:

EH

19-23356

1923356.DWG

3-5-2019

3-5-2019

SITE

B1

B

O

U

L

D

E

R

D

R

SCALE: NTS

APPROVED BY:

REVISED BY:

DRAWN BY:

FILE NAME:

PROJECT NO:

DATE:

DATE:

DATE:

CM

REVISED BY: DATE:

EH

19-23356

1923356.DWG

3-5-2019

3-5-2019

PLATE A.3

BORING LOCATION DIAGRAM

RED BIRD EXECUTIVE ANTENNA TOWER

5303 CHALLENGER DRIVE

DALLAS, TEXAS

4.5+

50/¼" 50/¼"

50/¼" 50/¼"

50/¼" 50/¼"

50/¼" 50/¼"

50/¾" 50/¼"

WEATHERED LIMESTONE - tan

LIMESTONE - gray

Boring Terminated at Approximately 20 Feet

Stratum Description

While Drilling

At Boring Completion

End of Day

Not Observed

Not Observed

Not Measured

Boring Location

S w el l

S am p le

T yp e

E le va ti o n ft

M o is tu re C o n te n t

D ep th , f t.

S ym b o l

U n co n fi n ed C o m p re ss io n p sf

Material boundaries are approximate; in situ, transitions may be gradual.

32.67662° N

96.87120° W

Driller: Total Depth - Donny Drilling Method: Continuous Flight Augers Plate A.4T hi s bo rin g lo g sh ou ld n ot b e co ns id er ed v al id if s ep ar at ed fr om th e re m ai nd er o f t he g eo te ch ni ca l r ep or t.

A tt er b er g

L im it s

LL-PL-PI

Latitude

Longitude

Project No.

19-23356

D ry

U n it W ei g h t, p cf

P en et ro m et er R ea d in g ts f

W at er L ev el

O b se rv at io n s

P as si n g N o

S ie ve

Water Level Observations (feet) Date

S P

T o r T

C P

2-26-19

Log

B-1 Red Bird Executive Antenna Tower 5303 Challenger Drive

Dallas, Texas

APPENDIX B

B.1

F I EL D EX P LOR AT I O N

Subsurface conditions for this project were defined by one sample boring located as shown on the Boring Location Diagram, Plate A.3. The boring was completed at a location identified in the field by the client. The boring was advanced between sample intervals using continuous flight auger drilling procedures. The results of the boring are shown graphically on the Log of Boring.

Sample depth, description, and soil classification based on the Unified Soil Classification System are shown on the Log of Boring. Keys to the symbols and terms used on the Log of Boring are presented in Appendix A.

Relatively undisturbed samples of cohesive soils were obtained with Shelby tube samplers in general accordance with ASTM D1587. The Shelby tube sampler consists of a thin-walled steel tube with a sharp cutting edge connected to a head equipped with a ball valve threaded for rod connection. The tube is hydraulically pushed into the undisturbed soils by the drill rig. The soil specimens were extruded from the tube in the field, logged, tested for consistency with a hand penetrometer, sealed to reduce moisture loss, and packaged for transport to our laboratory.

To evaluate the bedrock materials, a modified version of the Texas Cone Penetration test was performed at selected locations. Texas Department of Transportation (TxDOT) Test Method Tex-

132-E specifies driving a 3-inch diameter cone with a 170-pound hammer freely falling 24 inches.

This results in 340 foot-pounds of energy for each blow. This method was modified by utilizing a

140-pound hammer freely falling 30 inches. This results in 350 foot-pounds of energy for each hammer blow. In relatively soft materials, the penetrometer cone is driven 1 foot and the number of blows required for each 6-inch penetration is tabulated at respective test depths as blows-per-

6-inches on the Log of Boring. In hard materials (rock and rock-like), the penetrometer cone is driven with the resulting penetrations, in inches, recorded for the first and second 50 blows, a total of 100 blows.

Groundwater observations during and after completion of the boring are shown on the Log of

Boring. Upon completion of the boring, the borehole was backfilled from the top and plugged at the surface.

B.2

L AB O R AT O R Y T ES TI NG

General

Laboratory tests were performed on selected samples retrieved from the boring to evaluate the engineering characteristics of the subsurface materials encountered, and to provide data for developing engineering design parameters. The subsurface materials recovered during the field exploration were described by an engineering geologist or senior staff member in the field and/or the laboratory and were later refined based on results of the laboratory tests performed.

Testing was performed in general accordance with the following American Society for Testing and

Materials (ASTM) standards, as applicable.

Test Name ASTM Standard Number

Moisture Content D2216

Classification Tests

To determine soil characteristics and to aid in classifying the soils, index property and classification testing was performed on selected samples of the soils. Visual classification of soils was verified by natural moisture content determinations. All recovered soil samples were classified and described, in part, using the Unified Soil Classification System (USCS).

APPENDIX C

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, clients can benefit from a lowered exposure to the subsurface problems 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 below, contact your GBA-member geotechnical engineer.

Active involvement in the Geoprofessional Business Association exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Geotechnical-Engineering Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs 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. Those who rely on a geotechnical-engineering report prepared for a different client can be seriously misled. No one except authorized client representatives should rely on this geotechnical-engineering report without first conferring with the geotechnical engineer who prepared it. And no one

– not even you – should apply this report for any purpose or project except the one originally contemplated.

Read this Report in Full Costly problems have occurred because those relying on a geotechnical engineering report did not read it in its entirety. Do not rely on an executive summary. Do not read selected elements only. Read this report in full.

You Need to Inform Your Geotechnical Engineer about Change Your geotechnical engineer considered unique, project-specific factors when designing the study behind this report and developing the confirmation-dependent recommendations the report conveys. A few typical factors include:

• the client’s goals, objectives, budget, schedule, and risk-management preferences;

• the general nature of the structure involved, its size, configuration, and performance criteria;

• the structure’s location and orientation on the site; and

• other planned or existing site improvements, such as retaining walls, access roads, parking lots, and underground utilities.

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

• the site’s size or shape;

• the function of the proposed structure, as when it’s changed from a parking garage to an office building, or from a light-industrial plant to a refrigerated warehouse;

• the elevation, configuration, location, orientation, or weight of the proposed structure;

• the composition of the design team; or

• project ownership.

As a general rule, always inform your geotechnical engineer of project 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.

This Report May Not Be Reliable Do not rely on this report if your geotechnical engineer prepared it:

• for a different client;

• for a different project;

• 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, that it could be unwise to rely on a geotechnical-engineering report whose reliability may have been 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 your geotechnical engineer has not indicated an “apply-by” date on the report, ask what it should be, and, in general, if you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying it. A minor amount of additional testing or analysis – if any is required at all – could prevent major problems.

Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface through various sampling and testing procedures.

Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing were performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgment 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 from project start to project finish, so the individual can provide informed guidance quickly, whenever needed.

C.1

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 judgment and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions revealed 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 full-time 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 on hand quickly 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 observation.

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 informational 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, but they may rely on the factual data relative to the specific times, locations, and depths/elevations referenced. 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…