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Geotechnical Engineering Report

CEP Switchgear (Phase I) Underground Utility Exploratory Pit

UTHSCSA Main Campus

San Antonio, Texas

Prepared for:

S&GE, LLC

San Antonio, Texas

Prepared by:

Drash Consultants, LLC

San Antonio, Texas

February 15, 2015

Drash Project No. 116G1011.00

TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY ........................................................................................................... i

INTRODUCTION ...................................................................................................................... 1

Authorization ................................................................................................................. 1

Purpose and Scope of Services .................................................................................... 1

PROJECT INFORMATION ....................................................................................................... 1

SITE AND SUBSURFACE CONDITIONS ................................................................................ 2

Site Conditions .............................................................................................................. 2

Subsurface Conditions .................................................................................................. 2

Subsurface Stratigraphy ............................................................................................................ 2 Subsurface Water ...................................................................................................................... 2

GEOTECHNICAL RECOMMENDATIONS AND GUIDELINES ................................................ 3

Lateral Earth Pressures ................................................................................................ 3

Construction Sequence of Secant Pile Wall .............................................................................. 4

Drilled Piers .................................................................................................................. 5

Slope Stability ............................................................................................................... 8

OSHA Trench Safety Guidelines ................................................................................... 9

Slab Foundations ........................................................................................................ 10

Seismic Design Considerations ................................................................................... 11

Corrosion Considerations ............................................................................................ 11

INTERPRETATION OF REPORT ........................................................................................... 11

CONSTRUCTION MONITORING AND TESTING .................................................................. 12

LIMITATIONS OF REPORT ................................................................................................... 12

EXHIBITS

Exhibit 1 Project Location Map

Exhibit 2 Bore Location Plan

Exhibit 3 Log of Boring

APPENDIX – FIELD AND LABORATORY

Exploratory Drilling Program

Laboratory Testing Program

Notes Regarding Soil and Rock


CEP Switchgear (Phase I)

Underground Utility Exploratory Pit

i

EXECUTIVE SUMMARY

This geotechnical engineering report has been prepared for the design and construction of the

CEP Switchgear (Phase I) Underground Utility Exploratory Pit at the existing UTHSCSA Main

Campus (Project). The project is located at 7703 Floyd Curl Drive in San Antonio, Texas.

Based on the information provided to us for this study and from data developed as part of our

engineering service, the site is suitable for the planned improvements. A general summary of our

findings, conclusions, and recommendations with regard to the geotechnical engineering aspects

of the Project are provided below:

Subsurface conditions generally consist of fat clay and lean clay soils.

A secant pile wall may be used as an earth retention system for the exploratory

pit.

After excavating to 15 feet to observe and locate any existing underground

utilities in the area, the pit will be backfilled with 7 to 9 feet of material (flowable

fill) to install the proposed duct bank, manhole and utility vault.

Several of the piers on the east and west sides of the exploratory pit will need to

be “chipped out” to accommodate the installation of the duct bank.

The slab for the proposed underground duct bank (cast-in-place or pre-cast) can

be designed for a net bearing pressure of 4,000 psf on the flowable fill.

This summary is provided for convenience only. For those individuals and entities that may

need more details or technical information from this report for their use, it must be read in its

entirety to have an understanding of the information and recommendations provided for the

Project.




1

GEOTECHNICAL ENGINEERING REPORT

CEP SWITCHGEAR (PHASE I) UNDERGROUND UTILITY EXPLORATORY PIT

UTHSCSA MAIN CAMPUS

SAN ANTONIO, TEXAS

INTRODUCTION

This geotechnical engineering report has been prepared for the design and construction of the

CEP Switchgear (Phase I) Underground Utility Exploratory Pit at the existing UTHSCSA Main

Campus (Project). The project is located at 7703 Floyd Curl Drive in San Antonio, Texas.

Based on the information provided to us by the client, we understand that the Underground

Utility Exploratory Pit will be approximately 30 feet by 26 feet in plan dimension. The utility pit is

to identify existing utilities in the area of a proposed electrical utility vault, a duct bank with a

manhole and a future switchgear station with a vault. The utility vault and the duct bank with a

manhole are expected to be approximately 6 to 8 feet deep. The vault below the switchgear

station will be about 15 feet deep. The utility pit will be partially filled-in to support the duct bank

and manhole. Several of the piers on the east and west side will need to be “chipped out” to

accommodate the installation of the duct bank.

Authorization

This Project was authorized by Mr. Edward L. Sherfey, Jr. with S&GE, LLC, by acceptance of

our Agreement for Services, No. PG1151234.00, dated December 30, 2015.

Purpose and Scope of Services

The purposes of this engineering service were to evaluate the general subsurface conditions

(soil, rock, subsurface water) within the Project limits by drilling an exploratory boring, conduct

tests on samples recovered during drilling of the exploratory boring, analyze and evaluate the

test data, perform engineering analyses using the data analyzed and evaluated from the field

and laboratory programs to develop geotechnical engineering recommendations and guidelines

with respect to:

Site conditions as applicable Earthwork as applicable

Subsurface stratigraphy Secant pile wall recommendations

Subsurface water conditions

PROJECT INFORMATION

The following information was provided to us by the Client, design professionals working on the

Project, or was collected by our firm:

Project Location The project is located at 7703 Floyd Curl Drive in San Antonio, Texas. The

general vicinity of the Project is illustrated on Exhibit 1, the Project Location Map.




2

Project

The Project will involve design and construction of an underground utility

exploratory pit. The exploratory pit will be partially filled-in to install a duct bank

with a manhole and a utility vault. West of the exploratory pit a switchgear station

with a vault will be constructed.

Current Site Conditions The Project site is currently a vacant area within the existing UTHSC – San

Antonio facility.

Current Topography Based on our visual observations, the site appeared relatively flat and gently

slopes down to the west.

Proposed Topography

Based on the information provided to us, we understand that the utility vault

and the duct bank with a manhole are expected to be approximately 6 to 8 feet

deep. The vault below the switchgear station will be about 15 feet deep. If

this information changes, Drash should be contacted to re-evaluate

these recommendations.

SITE AND SUBSURFACE CONDITIONS

Site Conditions

The site, as noted previously, is currently a vacant area within the existing UTHSC – San Antonio

facility. Based on visual observations, there were no noticeable or obvious surface conditions

within the site that would affect the geotechnical engineering aspects of this Project.

Subsurface Conditions

Subsurface conditions within the Project limits were evaluated by drilling an exploratory boring at

the location shown on Exhibit 2, the Bore Location Plan. Information retrieved from the exploratory

boring is summarized herein.

Subsurface Stratigraphy

Subsurface stratigraphy, based on the exploratory boring, can be generalized as follows:

Layer

Identification

Approximate Depth

To and Thickness Of

Layer (feet)

Description of Layer

Layer 1 0 to 8½ SANDY FAT CLAY (CH); dark brown, tan and olive; medium stiff

to very stiff; with roots in the upper 1 foot.

Layer 2 8½ to 50 LEAN CLAY (CL); tan and olive, gray; very stiff to hard; partially

cemented below 18½ feet.

The log of boring, presenting more specific information about the subsurface stratigraphy

encountered at the exploratory boring location, is provided in the Exhibits section of this report.

Subsurface Water

Subsurface water was not encountered during or upon completion of our drilling activities. The

exploratory boring was backfilled with spoils generated during drilling operations.

Subsurface water is generally encountered as a ‘true’ or permanent water source or as a

‘perched’ or temporary water source. Permanent subsurface water is generally present year

round, which may or may not be influenced by seasonal and climatic changes. Temporary

subsurface water generally develops as a result of seasonal and climatic conditions.




3

Subsurface water levels should be re-checked prior to the planned construction activities.

GEOTECHNICAL RECOMMENDATIONS AND GUIDELINES

Based on the information provided to us by the Client and Project Team, our exploratory boring

drilled at the site, results of laboratory tests performed on samples recovered during the

subsurface exploration program, and our engineering analyses, the following statements can be

made regarding the Project site:

The site is suitable for the planned construction.

The subsurface stratigraphy exhibits a moderate potential for volume changes

(expansion and contraction) with fluctuations in its moisture content.

A secant pile wall may be used as an earth retention system for the exploratory

pit excavation.

The secant pile wall being considered must be designed to reduce the possibility of soil failure

when subjected to lateral earth pressure. The secant pile wall must also be designed so the

vertical, horizontal or rotational loads are within allowable limits of the soil and within design and

operational limits.

The following geotechnical recommendations and guidelines have been prepared based on the

data collected or developed during this Project, our experience with similar projects, and our

knowledge of sites with similar surface and subsurface conditions.

Lateral Earth Pressures

We understand that secant pile walls are being considered as the retention system for the

exploratory pit excavation. Active earth pressures should be used for the design of secant pile

walls since the top of the walls will not be restrained from horizontal movement. Presented

below are active earth pressure coefficients and equivalent fluid pressures for the existing soils

that may be used to design the secant pile wall at this site.

LATERAL EARTH PRESSURE DESIGN CRITERIA

LATERAL EARTH

COEFFICIENT

EQUIVALENT FLUID

DENSITY (pcf)

SURCHARGE

PRESSURE, p1

(psf)

EARTH PRESSURE,

p2

(psf)

Active (ka)

On-Site Soil - 0.53 64 (0.53)S (64) H.D

D: spacing between secondary (reinforced) secant piles.




4

A passive equivalent fluid density of 150 pcf may be used for the embedded portion of the

secant pile wall. The passive pressure should be neglected in the upper 12 inches below the

bottom of the excavation.

Applicable conditions to the above table include:

Uniform surcharge, S, should be included where applicable.

For on-site soil, use a maximum total unit weight of 120 pcf.

The earth pressure criteria presented in the table do not include:

o Hydrostatic conditions developing behind the retaining wall.

o Surcharge loading from compaction equipment and floor slabs.

o A factor of safety.

Construction Sequence of Secant Pile Wall

Pertinent details of secant pile wall construction are presented below:

All existing above-grade and below-grade structures that interfere with the secant

pile installation will be relocated or removed.

Install secant piles beginning with the Primary Piles (“non-reinforced piles).

Install the Primary Piles and Secondary Piles (“reinforced piles”) as presented in

the typical installation sequence.

Complete the secant pile wall as follows:

o Power-wash all the soil off the exposed face of the secant pile wall.




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o Install the applicable water-proofing material at all applicable joints.

o Concurrent with the water-proofing activity, construct the drainage channel

along the bottom of the secant pile wall.

Typical construction sequence of secant pile walls is presented below:

Drilled Piers

Drilled piers will be used to construct the secant pile wall for this Project. The drilled piers must

be straight-sided piers. The drilled piers should not bear deeper than 45 feet below the

existing ground surface without contacting our office.

Design Considerations. Reinforced and unreinforced drilled piers will be installed for the

proposed secant pile wall. There will not be much in the way of compressive axial loads or uplift

loads on the drilled piers in the secant pile wall. The drilled piers will primarily need to be

designed for lateral loading. However, the clay soils will apply axial tension loads on the drilled

piers due to shrinking and swelling of the near surface clay soils.

A number of methods, including hand solutions and computer programs, are available for

calculating the lateral behavior of drilled piers. The majority of these methods rely on “key” soil

parameters such as soil elastic properties (E and k), strain at 50 percent of the principal stress

difference (50), undrained shear strength (c), angle of internal friction (), and load-deflection (p-

y) criteria. The p-y criteria, which are commonly used to model soil reaction, were developed

from instrumented load tests and are generally considered to provide the best model of soil

behavior under short-term lateral loading. It should be noted that the p-y criteria is not only a

function of the soil properties but also the diameter of the structure foundation.




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The majority of p-y curve models use a form of parabola to describe the initial portion of a p-y

curve; at small deflections the slope of these p-y curves approaches infinity. This is an

important consideration, since most laterally loaded pile analysis programs use p-y curves to

develop equivalent soil springs in their computations. These soil springs are defined as the soil

reaction, p, divided by the soil deflection, y, or the secant modulus of the p-y curve.

Factors of safety are not generally applied to the lateral load analysis. A performance criteria,

or “limit state”, is usually considered. The analysis is generally conducted using the working

loads and the limit state values. A limit state value of 1 inch of groundline deflection should be

used for design of the secant pile wall.

The choice of the final design embedment depth is also evaluated by determining the critical

depth of the foundation. The critical depth is actually a depth range and can be defined as that

range in depth at which a small decrease in the pier embedment depth will result in a large

increase in the groundline deflection of the pier. The analysis is conducted by incrementally

decreasing the embedment depth and plotting the resultant groundline deflection versus

embedment depth. The embedment depth is then chosen below the critical depth range. In

some cases, groundline deflections significantly less than one (1) inch are needed to satisfy the

critical depth issue.

Criteria for the LPILE series program are contained in Table 1 below. It should be noted that

the initial elastic moduli for soil is referred to as soil modulus (k) in the Table and in the LPILE

program. The parameters provided on these tables can be used for lateral design of concrete

piers with or without reinforcing steel.

TABLE 1

Soil

Layer

LPILE Depth to Soil

Layer

LPILE

Soil Effective Undrained Internal

LPILE

Soil

Soil Type &

Number

Top Bottom Modulus Unit

Weight

(pcf)

Shear

Strength

(psf)

Friction

Angle

(degrees)

Strain

Factor

ε50 (feet) (feet)

k

(pci)

1 Stiff Clay without

Free Water (3) 0 2 351 110 600 0 0.014


Free Water (3) 2 8 622 120 2,000 0 0.007


Free Water (3) 8 18 815 120 3,000 0 0.006


Free Water (3) 18 38 1395 125 6,000 0 0.004


Free Water (3) 38 50 1782 125 8,000 0 0.003

Construction Considerations. The pier foundation excavations should be augered and

constructed in a continuous manner. Steel and concrete should be placed in the excavations

immediately following drilling and evaluation for proper bearing stratum, embedment, and

cleanliness. Under no circumstances should the excavations remain open overnight.




7

As stated previously, no subsurface water was encountered during or immediately after drilling

of the exploratory boring. For the initial piers in the secant pile wall, the foundation contractor

should be prepared to use casing to control sloughing of the excavation sidewalls and to reduce

the influx of water (should any water be encountered) into the excavation. The casing method is

discussed in the following paragraphs:

Casing Method - Casing will provide stability of the excavation walls and will

reduce water influx; however, casing may not completely eliminate potential

subsurface water influx potential. In order for the casing to be effective, a “water

tight” seal must be achieved between the casing and surrounding soils. The

drilling subcontractor should determine the type of casing, casing depths and

casing installation procedures. Water that accumulates in excess of six (6)

inches in the bottom of the pier excavation should be pumped out prior to steel

and concrete placement. If the water is not pumped out, a closed-end tremie

should be used to place the concrete completely to the bottom of the pier

excavation in a controlled manner to effectively displace the water during

concrete placement. If water is not a factor, concrete should be placed with a

short tremie so the concrete is directed to the bottom of the pier excavation. The

concrete should not be allowed to ricochet off the walls of the pier excavation nor

off the reinforcing steel.

If dry augering after casing installation is not successful or to the satisfaction of

the design engineer, the pier excavation should be flooded with fresh water to

offset the differential water pressure caused by the unbalanced water levels

inside and outside of the casing. When the pier excavation depth is achieved

and the bearing area has been cleaned, steel and concrete should then be

placed immediately in the excavation. The concrete should be tremied

completely to the bottom of the excavation with a closed-end tremie.

Removal of casing should be performed with extreme care and under proper

supervision to minimize mixing of the surrounding soil and water with the fresh

concrete. Rapid withdrawal of casing or the auger may develop suction that

could cause the soil to intrude into the excavation. An insufficient head of

concrete in the casing during its withdrawal could also allow the soils to intrude

into the wet concrete. Both of these conditions may induce "necking", a section

of reduced diameter, in the pier.

In addition to the lateral loads acting on the drilled piers due to the retained soil, the drilled piers

will also be subjected to axial tension loads due to swelling of the near surface clay soils and

possibly due to other induced structural loading conditions. To compute the axial tension force

due to the swelling soils along straight-sided piers, the following equation may be used.

Qu = 37 ● d

Where: Qu = Uplift force due to expansive soil conditions in kips (k)

d = Diameter of pier in feet (ft)




8

This calculated force can be used to compute the longitudinal reinforcing steel required in the

pier to resist the uplift force induced by the swelling clays.

All aspects of concrete design and placement should comply with the most recent version of

American Concrete Institute (ACI) 318 Building Code Requirements for Structural Concrete, ACI

336.1, the section titled Standard Specification for the Construction of Drilled Piers, ACI 336.3,

the section titled Suggested Design and Construction Procedures for Pier Foundations, ACI

305.1 Hot-Weather Concreting and ACI 306.1 Cold-Weather Concreting. Concrete should be

designed to achieve the specified 28-day strength when placed at an 8-inch slump with a 1

inch tolerance. Adding water to a mix that has been designed for a lower slump does not meet

the intent of this recommendation. If a high range water reducer is used to achieve this slump,

the span of slump retention for the specific admixture under consideration should be thoroughly

investigated. Compatibility with other concrete admixtures should also be considered. A

technical representative of the admixture supplier should be consulted on these matters.

Successful installation of drilled piers is a coordinated effort involving the general contractor,

design consultants, subcontractors and suppliers. Each must be properly equipped and

prepared to provide their services in a timely fashion. Several key items are:

Proper drilling rig with proper equipment (including casing, augers, and teeth);

Reinforcing steel cages tied to meet project specifications;

Proper scheduling and ordering of concrete for the piers; and

Monitoring of the installation by design professionals.

Foundation construction should be carefully monitored to assure compliance of construction

activities with the appropriate specifications. Particular attention to the referenced publication is

warranted for foundation installation. A number of items for foundation installation include those

listed below.

Foundation locations Concrete properties and placement

Vertical alignment Proper casing seal for subsurface water control

Competent bearing Casing removal

Steel placement

Slope Stability

The soil outside of the exploratory pit will be excavated and sloped back to install the duct bank

and utility vault. The length of duct bank and utility vault outside of the exploratory pit will need

to be sloped back at (3H:1V) for excavations open longer than 24 hours or trench shields should

be used.

We understand that the excavation of the underground sections may require sloping back the

sides of the trench excavations. Analysis for slope stability and slope performance evaluation

were not part of this study. However, general information regarding slope stability is presented

in the following paragraphs.




9

Slopes will be created or constructed at this site with cuts into the existing subsurface soils

(natural slopes) and by constructing fill pads or embankments for the construction. The stability

of a created or constructed slope is dependent on several criteria and include:

The height of the slope;

The material comprising the slope;

The slope angle; and

Erosion considerations.

We anticipate that on-site soils may be excavated and sloped back to install the duct bank and

utility vault. For cut slopes, in the on-site soils, a permanent slope of four (4) horizontal to one

(1) vertical (4H:1V) can be used. On a temporary basis, OSHA will allow slopes up to 1H:1V for

excavation less than 20 feet deep.

Steeper slopes might be considered if the face of the slope is protected from erosion and/or if

the fill section is reinforced with soil reinforcement such as geogrid. Any surcharge loads should

not be placed within 10 feet of the crest of any fill or natural slope at this site.

Further protection of the sloped section may be provided with the use of concrete terrace drains

or other interceptor drains designed to protect the slope from surface water. Maintenance of the

slope should be done on an “as needed basis”.

OSHA Trench Safety Guidelines

Occupational Safety and Health Administration (OSHA) Safety and Health Standards (29 CFR

Part 1926 Revised, 1997) require that all trenches in excess of five (5) feet deep be shored or

appropriately sloped unless the trench sidewalls are comprised of "solid" rock. Clayey soil was

encountered at this site within the depths explored.

Our recommendations are intended for use in conjunction with OSHA safety regulations and not

as a replacement of those regulations. Based on the laboratory results, we feel that soils

encountered at the boring locations would be considered as Type B soils according to OSHA

soil classification guidelines.

As stated previously, OSHA requires all soil trenches in excess of five (5) feet be shored or

appropriately sloped. Currently available and practiced methods for achieving slope and/or

trench wall stability includes sloping, benching, combinations of sloping and benching, and

installation of shoring systems (hydraulic, timber, etc.). Trench shields may also be considered

for use. However, these shields only provide protection to workers; they are not a means for

providing slope or trench wall stability.

OSHA addresses construction slopes in large excavations that are less than 20 feet deep. The

table shown below is a reproduction of the OSHA Table B-1:

OSHA TABLE B-1 MAXIMUM ALLOWABLE SLOPES

Soil or Rock Type Maximum Allowable Slopes (H:V)1 for Excavations Less Than 20 Feet Deep3

Stable Rock VERTICAL(90º)




10

OSHA TABLE B-1 MAXIMUM ALLOWABLE SLOPES

Soil or Rock Type Maximum Allowable Slopes (H:V)1 for Excavations Less Than 20 Feet Deep3

Type A ¾:1 (53º)

Type B 1:1 (45º)

Type C 1 ½:1 (34º)

1. Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from

the horizontal. Angles have been rounded off.

2. A short-term maximum allowable slope of ½H: 1V (63°) is allowed in excavations in Type A soil that are 12

feet or less in depth. Short-term maximum allowable slopes for excavations greater than 12 feet in depth

shall be ¾H: 1V (53°).

3. Sloping or benching for excavations greater than 20 feet shall be designed by a registered professional

engineer.

The OSHA regulations define short-term as a period of 24 hours or less.

Slab Foundations

We understand that a pre-cast concrete duct bank or utility vault will be placed approximately 6

to 8 feet deep from the ground surface. The subsoils at approximately 6 to 8 feet depth yield a

Potential Vertical Rise (PVR) of about 1½ inches in their current state. The actual movement

could be greater if inadequate drainage or other sources of water are allowed to infiltrate

beneath the structure after construction. Recommendations for this foundation type are

presented below.

In order for the duct bank, manhole or utility vault to only be 6 to 8 feet below the existing

ground surface in the area of the exploratory pit, the pit excavation will need to be filled-in with 7

to 9 feet of flowable fill. The flowable fill should have a minimum compressive strength of 100

psi and a maximum compressive strength of 150 psi. Washed or crushed gravel should not be

used to fill the excavation, because the clay bottom and secant pile wall will cause water to be

trapped in the gravel, creating a “bathtub” situation. Due to the size of the excavation, moisture

conditioning and compacting lean clay fill in the excavation would be difficult to install safely and

properly.

The bedding for the duct bank, manhole and utility vault outside of the exploratory pit should be

excavated 12 inches below the proposed bearing elevation and backfilled with flowable fill to

provide a uniform bearing surface along the length of the duct bank, manhole and utility vault.

This will also prevent creating a channel for water to collect in and travel under the electrical

structures.

Several of the piers in the secant pile wall will need to be “chipped out” on the east and west

sides of the exploratory pit to accommodate the duct bank, manhole and utility vault. The walls

should be removed at least 6 inches below the proposed bearing elevations of the new

structures to place flowable fill across the wall threshold.

The precast concrete duct bank, manhole or utility vault may be designed for a net bearing

pressure of 4,000 psf on the flowable fill.




11

Seismic Design Considerations

Presented below are the seismic design criteria for the project site and immediate area.

Description Value

2015 IBC Site Classification1 C2

Site Latitude 29.50652°

Site Longitude -98.57713°

Maximum Considered Earthquake 0.2 second Design Spectral Response Acceleration (SDS) 0.061

Maximum Considered Earthquake 1.0 second Design Spectral Response Acceleration (SD1) 0.033

1 As per the requirements of Section 1613.3.2 in the 2015 IBC, the site class definition was determined

using Table 20.3-1 of Chapter 20 of American Society of Civil Engineers (ASCE) 7. The Spectral

Acceleration values were determined using publicly available information provided on the United States

Geological Survey (USGS) website.

2 Note: Chapter 20 of ASCE 7 requires a site soil profile determination extending to a depth of 100 feet for

seismic site classification. The current scope does not include the required 100-foot soil profile

determination. The boring extended to a maximum depth of 50 feet, and this seismic site class definition

considers that hard soil continues below the maximum depth of the subsurface exploration. Additional

exploration to deeper depths would be required to confirm the conditions below the current depth of

exploration.

Corrosion Considerations

Laboratory tests were conducted on a soil sample recovered from the boring to assess the

corrosivity risk of the soils at the site. The soil sample was submitted to an analytical lab for

determination of the sulfate content. The result of the laboratory test is provided below.

Summary of Laboratory Sulfate Tests

Boring No. Sample

Depth (ft) Sulfate (ppm)

B-1 6½ to 8 136

According to the 2015 IBC, concrete that is exposed to sulfate-containing solutions should be

designed in accordance with ACI 318. The sulfate test result indicates that the sulfate exposure

level is low. Therefore, Type I or Type II cement may be used at this site.

INTERPRETATION OF REPORT

Drash understands that its geotechnical engineering report is used by the Client and various

individuals and firms involved with the design and construction of the Project. Drash should be

invited to attend Project meetings (in person or teleconferencing) or be contacted in writing to

address applicable issues relating to the geotechnical engineering aspects of the Project. Drash

should also be retained to review the final construction plans and specifications to evaluate if the

information and recommendations in our geotechnical engineering report has been properly

interpreted and implemented in the design and specifications.




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CONSTRUCTION MONITORING AND TESTING

The performance of the foundation system for the proposed structure will be highly dependent

upon the quality of construction. As the Geotechnical Engineer of Record for this Project, Drash

should be retained to provide construction observation and materials testing services during the

Project, particularly the construction activities relating to foundations, generator pad,

pavements, excavation and site grading.

LIMITATIONS OF REPORT

This geotechnical engineering report is based upon the information provided to us by the Client

and various other individuals and entities associated with the Project, exploratory boring drilled

within the Project limits, laboratory testing of randomly selected soil or rock samples recovered

during drilling of the exploratory boring, and our engineering analyses and evaluation. The

Client and readers of this geotechnical engineering report, should realize that subsurface

variations and anomalies can and will exist across the site and between the exploratory boring.

The Client and readers should realize that site conditions will change due to the modifying

effects of seasonal and climatic conditions.

The nature and extent of such site or subsurface variations may not become evident until

construction commences or is in progress. If site and subsurface anomalies or variations exist

or develop, Drash should be contacted immediately so that the situation can be evaluated and

addressed with applicable recommendations. The contractor and applicable subcontractors

should familiarize themselves with this report prior to the start of their construction activities,

contact Drash for any interpretation or clarification of the report, retain the services of their own

consultants to interpret this report, or perform additional geotechnical testing prior to bidding and

construction.

Unless stated otherwise in this report or in the contract documents between Drash and Client,

our scope of services for this Project did not include, either specifically or by implication, any

environmental or biological assessment of the site or buildings, or any identification or

prevention of pollutants, hazardous materials or conditions at the site or within buildings. If the

Client is concerned about the potential for such contamination or pollution, Drash should be

contacted to provide a scope of services to address the environmental concerns. Also,

permitting, site safety, excavation support, and dewatering requirements are the responsibility of

others.

This geotechnical engineering report has been prepared for the exclusive use of our Client for

specific application to this Project. This geotechnical engineering report has been prepared in

accordance with generally accepted geotechnical engineering practices. No warranties,

express or implied, are intended or made.

Should the nature, design, or location of the Project, as outlined in this geotechnical engineering

report, be modified, geotechnical engineering recommendations and guidelines provided in this

document will not be considered valid unless Drash reviews the changes and either verifies or

modifies the applicable Project changes in writing.

EXHIBITS

EXHIBITDrawn By:

Checked By:

Reviewed By:

Project Mngr:

Date:

Scale:

Project No. PROJECT LOCATION MAP

NOT TO SCALE

02-02-2016

116G1011.00KS

SR

1045 Central Parkway North, Suite 103 ▪ San Antonio, Texas 78232Office: 210.340.5004 ▪ Facsimile: 210.340.5009

1

N

SR

GKCEP SWITCHGEAR (PHASE 1): UNDERGROUND UTILITY EXPLORATORY PIT

UTHSCSA MAIN CAMPUSSAN ANTONIO, TEXAS

TBPE Firm Registration F-13654

PROJECT SITE

B-1

EXHIBITDrawn By:

Checked By:

Reviewed By:

Project Mngr:

Date:

Scale:

Project No. BORE LOCATION PLAN

NOT TO SCALE

02-2-2016

116G1011.00SR

KSGK

SR1045 Central Parkway North, Suite 103 ▪ San Antonio, Texas 78232

Office: 210.340.5004 ▪ Facsimile: 210.340.5009TBPE Firm Registration F-13654

CEP SWITCHGEAR (PHASE 1): UNDERGROUND UTILITY EXPLORATORY PITUTHSCSA MAIN CAMPUS

SAN ANTONIO, TEXAS2

N

MERTON MINTER

SYMBOLS:Exploratory Boring Location

54

49

35

N=5

N=13

N=16

N=18

N=22

N=26

N=ref/5"

N=ref/4"

N=75

N=50/5"

N=ref/5"

N=ref/5"

N=ref/4"

15

15

14

14

18

9

8

14

13

16

11

11

10

19

17

15

35

32

20

Layer 1SANDY FAT CLAY (CH); dark brown to tan and olive;

medium stiff to very stiff; with roots in the upper 1 foot

Layer 2LEAN CLAY (CL); tan and olive; very stiff to hard

- partially cemented below 18½ feet

- becomes gray below 43½ feet

Boring Terminated at 50 feet.

64

88

5

10

15

20

25

30

35

40

45

50

DRILLING METHOD(S):

PISA

MP

LES

PROJECT NO.BORING NO.

DATESURFACE ELEVATION

REMARKS

N: B

LOW

S/F

TP

: TO

NS

/SQ

FT

T: T

ON

S/S

Q F

TP

ER

CE

NT

RE

CO

VE

RY

/R

OC

K Q

UA

LIT

Y D

ES

IGN

AT

ION

The boring was backfilled with cuttings after completion of drilling activities.

116G

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.00

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epor

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CO

NF

ININ

G P

RE

SS

UR

E

(PO

UN

DS

/SQ

IN)

DESCRIPTION OF STRATUMMO

IST

UR

E C

ON

TE

NT

(%

)

CEP Switchgear (Phase I): Underground Utility Exploratory PitSan Antonio, Texas 116G1011.00

B-11/20/2016

Existing Grade

SO

IL S

YM

BO

L

LOG OF BORING

LABORATORY DATAFIELD DATA

DR

Y D

EN

SIT

Y

(PO

UN

DS

/CU

FT

)

S&GE, LLCSan Antonio, Texas

CLIENT:

PL

3

EXHIBIT

FA

ILU

RE

ST

RA

IN (

%)

MIN

US

NO

. 200

SIE

VE

(%

)

LIQ

UID

LIM

IT

PLA

ST

IC L

IMIT

PLA

ST

ICIT

Y IN

DE

X

PROJECT:

LLDE

PT

H (

FT

)

Dry augered from 0 to 50 feet.

Subsurface water was not encountered during or upon completion of our drillingactivities.

PAGE 1 OF 1

ATTERBERGLIMITS (%)

CO

MP

RE

SS

IVE

ST

RE

NG

TH

(TO

NS

/SQ

FT

)

SUBSURFACE WATER INFORMATION:

APPENDIX – FIELD AND LABORATORY

EXPLORATORY DRILLING PROGRAM

LABORATORY TESTING PROGRAM

NOTES REGARDING SOIL AND ROCK

EXPLORATORY DRILLING PROGRAM

A truck-mounted, drilling rig was used to drill the exploratory boring and to recover soil/rock samples during

the drilling. Soil samples were obtained by pushing thin wall tube samplers (“Shelby tube”) or with a split-

barrel (“split-spoon”) sampler while performing the Standard Penetration Test (“SPT”). Rock samples were

obtained by performing the SPT or coring.

When a soil sample was recovered using a Shelby tube sampler, a pocket penetrometer test (“PPT”) or

hand torvane (“TV”) was conducted and recorded on the applicable exploratory field log of boring (“field

log”). When a soil/rock sample was recovered using a split-barrel sampler, the SPT N-value was recorded

on the applicable field log. The SPT procedure consists of driving the split-barrel into the subsurface

stratum with a 140-pound hammer falling a distance of 30 inches. The number of blows (“N”) required to

advance the split-spoon sampler the last 12 inches during a normal 18-inch penetration is the SPT

resistance value or N-value. These N-values are indicated on each applicable field log at the depths of

occurrence. The samples were sealed and transported to the laboratory for testing and classification.

Our field representative prepared the field logs as part of the drilling operations. The field logs included

visual classifications of the materials encountered during drilling, our field representative interpretation of

the subsurface conditions between samples, and recording the results of various tests (N-values, PPT, and

TV) performed during drilling and sampling. Each field log included with this report represents our technical

interpretation of the field log and includes modifications based on visual observations and testing of the

samples in the laboratory.

The scope of services for our geotechnical engineering services does not include addressing any

environmental issues pertinent to the site.

LABORATORY TESTING PROGRAM

Samples retrieved during the field exploration were taken to the laboratory for further observation by one

of our technical representatives, and they were classified in accordance with the Unified Soil

Classification System (USCS). At that time, the field descriptions were confirmed or modified as

necessary and an applicable laboratory testing program was formulated to determine the physical (index)

and engineering properties of the soil/rock.

Laboratory tests were conducted on selected soil samples and the test results are presented in this

appendix. The laboratory test results were used for the geotechnical engineering analyses, and the

development of foundation and earthwork recommendations. Laboratory tests were performed in general

accordance with the applicable ASTM or other accepted standards. The following tests were conducted:

Moisture Content

Atterberg Limits

Amount of Material In-Soil Finer than the No 200 Mesh (75-µm) Sieve

Sample Disposal

All samples were returned to our laboratory. Unless stated otherwise in this report or the Project contract,

the samples not tested in the laboratory will be stored for a period of 30 days subsequent to submittal of

this report and will be discarded after this period, unless other arrangements are made prior to the

disposal period.

NOTES REGARDING SOIL AND ROCK

GEOTECHNICAL SAMPLING SYMBOLS:

SS: Split Barrel (Split Spoon) ST: Thin-Walled Tube (Shelby tube)

AG: Auger Sample, Grab Sample, or Bulk Sample

RC: Rock Coring Sample

WATER LEVEL MEASUREMENT SYMBOLS:

Water Level Encountered While Drilling and Sampling.

▼ Water Level Measurement After Initial Water Level Encountered During Drilling and Sampling.

DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Soil Classification System (ASTM D2487).

Coarse Grained Soils have more than 50 percent of their dry weight retained on a No. 200 sieve. The primary descriptors of these soils are: boulders, cobbles, gravel, or sand. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density. Fine Grained Soils have less than 50 percent of their dry weight retained on a No. 200 sieve. These soils are principally described as clays if they are plastic (have binding/molding characteristics), and silts if they are slightly plastic or non-plastic. Fine-grained soils are defined on the basis of their consistency.

CONSISTENCY OF FINE-GRAINED SOILS RELATIVE DENSITY OF COARSE-GRAINED SOILS

Undrained

Shear

cu, psf

Standard Penetration Test (SPT) N-value

Blows Per Foot Consistency

Standard Penetration Test (SPT) N-Value

Blows Per Foot Relative Density

< 250 < 2 Very Soft 0 – 3 Very Loose

250 – 500 2 - 3 Soft 4 – 9 Loose

500 – 1,000 4 - 6 Medium Stiff 10 – 29 Medium Dense

1,000 – 2,000 7 - 12 Stiff 30 – 49 Dense

2,000 – 4,000 13 - 26 Very Stiff 50+ Very Dense

4,000+ 26+ Hard

RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY

Descriptive Terms Percent of Dry Weight Major Constituent of

Soil Sample Particle Size Trace < 15 Boulders Over 12 in. (300mm)

With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm)

Modifier > 30 Gravel 3 in. to No. 4 sieve (75mm to 4.75 mm)

Sand

Silt or Clay

No. 4 to No. 200 sieve (4.75mm to 0.075mm)

Passing No. 200 Sieve (0.075mm)

RELATIVE PROPORTIONS OF CLAYS AND SILTS PLASTICITY DESCRIPTION

Descriptive Terms Percent of Dry Weight Term Plasticity Index (PI)

Trace < 5 Non-plastic 0

With 5 – 12 Low 1 - 10

Modifier > 12 Medium 11 - 30

High 30+

CLASSIFICATION OF ROCK WITH RESPECT TO STRENGTH

Very Low Strength 18 – 72 ksf Low Strength 72 – 288 ksf Medium Strength 288 – 1,152 ksf High Strength 1,152 – 4,608 ksf Very High Strength 4,608 – 18,432 ksf

RQD DESCRIPTION OF ROCK QUALITY

0 – 25 Very Poor 25 – 50 Poor 50 – 75 Fair 75 – 90 Good 90 - 100 Excellent

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