FUGRO CONSULTANTS, INC.

GEOTECHNICAL STUDY

HIDDEN VALLEY SPORTS PARK RESTROOM FACILITY

MABEL JONES DRIVE

CANYON LAKE, TEXAS

COMAL COUNTY Canyon Lake, Texas

Project No. 04.36101159

GEOTECHNICAL STUDY

HIDDEN VALLEY SPORTS PARK RESTROOM FACILITY

MABEL JONES DRIVE

CANYON LAKE, TEXAS

Prepared for:

COMAL COUNTY ENGINEER’S OFFICE

Comal County, Texas

Submitted by:

FUGRO CONSULTANTS, INC. October 2010

Project No. 04.36101159

CONTENTS PAGE

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

PURPOSE AND SCOPE ............................................................................................................1

SUBSURFACE INVESTIGATION................................................................................................ 1

LABORATORY INVESTIGATION................................................................................................ 2

GENERALIZED SITE AND SUBSURFACE CONDITIONS ...................................................... 3

Site Description ................................................................................................................. 3

Site Geology...................................................................................................................... 3

Stratigraphy and Engineering Properties .......................................................................... 3

Groundwater ..................................................................................................................... 3

STRUCTURAL DETAILS............................................................................................................. 4

FOUNDATION EVALUATION...................................................................................................... 4

FOUNDATION RECOMMENDATIONS ....................................................................................... 4

Preparation of the Building Pad ........................................................................................ 5

Grid Beam Stiffened Slab-on-Ground ............................................................................... 5

PTI Parameters .................................................................................................................6

BRAB Parameters............................................................................................................. 6

Seismicity .......................................................................................................................... 7

CONSTRUCTION CONSIDERATIONS....................................................................................... 7

Groundwater Control ......................................................................................................... 7

Site Drainage .................................................................................................................... 7

Trench Excavations........................................................................................................... 8

Continuing Service ............................................................................................................ 8

CONDITIONS ............................................................................................................................... 8

ILLUSTRATIONS PLATES

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

BORING PLAN ............................................................................................................................. 2

BORING LOG ............................................................................................................................... 3

KEY TO TERMS AND SYMBOLS USED ON BORING LOG ............................................... 4

Project No. 04.36101159

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INTRODUCTION

Comal County is adding a new Restroom Facility at the Hidden Valley Sports Park located at

the corner of South Access Road and Mabel Jones Drive in Canyon Lake, Texas. Slab on

grade foundation recommendations have been requested for the project. It is assumed the new

structure will be constructed at or near existing grade at the time of our boring. The

approximate site location is shown on the vicinity map, Plate 1.

Ms. Ramona Womack, Purchasing Director, with Comal County, authorized the study with the

signed acceptance of our proposal on September 29, 2010. This study was performed in

general accordance with the scope of work outlined in our proposal (Fugro’s Proposal

No. 04.36101159) dated September 21, 2010.

PURPOSE AND SCOPE

The purpose of the study was to 1) obtain subsurface information to identify geotechnical

conditions at the boring location, and 2) provide geotechnical recommendations for design and

construction of the proposed structure foundations.

This was accomplished through a three phase study including 1) a field investigation for

determining general subsurface conditions at the boring location and obtaining representative

samples for classification and testing, 2) a laboratory testing program to aid in soil classification

and to establish engineering properties of the strata encountered, and 3) analyses of field and

laboratory data to develop geotechnical design and construction recommendations.

Field sampling, laboratory testing, soil classifications and strata descriptions were in general

accordance with methods, procedures, and practices set forth by the American Society for

Testing and Materials, Annual Book of ASTM Standards, current edition, where applicable.

SUBSURFACE INVESTIGATION

The subsurface exploration program consisted of one boring, designated as Boring B-1, drilled

to a depth of 15 ft. The boring was drilled within the footprint of the proposed Restroom Facility.

The approximate location of the boring is illustrated on Plate 2, boring plan.

The boring was drilled with a truck-mounted rig using the following equipment: 1) continuous

flight augers for advancing the holes dry and recovering disturbed samples (ASTM D 1452);

2) push tubes for obtaining undisturbed samples of cohesive strata (ASTM D 1587); and 3) split-

barrel samplers and drive weight assembly for obtaining representative samples and measuring

the penetration resistance (N-values) of non-cohesive soil strata (ASTM D 1586). Samples

Project No. 04.36101159

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were generally obtained at about 2-ft intervals to a depth of about 10 ft and at 5-ft intervals

thereafter to the boring completion depths. After recovery, each sample was removed from the

sampler and visually classified by our field technician. Representative portions of each sample

were then packaged, sealed, and transported to Fugro's San Antonio laboratory for testing.

During drilling and sampling, a record of field observations was maintained in the form of a field

log describing the visual identification of the subsurface materials encountered, and other

pertinent field data. This log was later edited to incorporate information obtained from

laboratory evaluation and testing. The final boring log for Boring B-1 is presented on Plate 3. A

key to terms and symbols used on the boring log is presented on Plate 4.

To aid in field classification, the compressive strength of cohesive samples was estimated using

a pocket penetrometer, and the penetration resistance of the SPT sampler was recorded. The

pocket penetrometer values, in tons per square foot (tsf), and the SPT N-values, in blows per

foot (bpf), are shown on the log. The compressive strength estimates in tons per square foot

(tsf) obtained with the hand penetrometer are equivalent to the undrained shear strength of the

soil in kips per square foot (ksf).

The boring was advanced without the use of drilling fluids. At the completion of the field

exploration, the borehole was sounded for groundwater using a weighted measuring tape and

then backfilled with the soil cuttings. Any depth to water measurements are recorded on the

boring log.

LABORATORY INVESTIGATION

The laboratory testing program was directed toward identification and classification of the

foundation soils. To aid in soil classification, Atterberg limits (ASTM D4318), and the

percentage of material passing selected U.S. Standard sieves (ASTM D 422) were performed

on selected soil samples. Water content measurements were performed on selected samples.

The results of the laboratory classification tests are presented on the boring log on Plate 3.

SOIL DESCRIPTIONS AND CLASSIFICATIONS

Descriptions of strata made in the field at the time the boring was drilled were modified in

accordance with results of laboratory tests and visual evaluation in the laboratory. All recovered

soil samples were evaluated, classified and described in accordance with ASTM D 2487 and

ASTM D 2488. Classifications of the soils and finalized descriptions of soil strata are shown on

the attached boring log.

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GENERALIZED SITE AND SUBSURFACE CONDITIONS

Site Description

The Hidden Valley Sports Park is located on Mabel Jones Drive, in Canyon Lake, Texas as

shown on the Vicinity Map, Plate 1. The park is located below Canyon Lake Dam and is

bounded by the South Access Road to the south and the Guadalupe River to the north. The

Restroom Facility site is located between the baseball and softball fields, southeast of the

Recreation Center. Based on field observations, the Restroom Facility location is relatively

level and vegetated with grasses.

Site Geology

A review of available geologic information indicates that the project site is underlain by Fluviatile

Terrace Deposits (Qt)1. The fluviatile soils are river and stream deposits and consist primarily of

clays containing various amounts of silt, sand, and gravel.

Stratigraphy and Engineering Properties

Subsurface conditions were explored at the site by one boring. The subsurface conditions

consisted of tan low plasticity ‘lean’ clay (CL) with variable amounts of sand. The tested lean

clay samples had measured liquid limits of 27 and 37, plasticity index values of 9 and 22, and

77 and 89 percent of silt and clay-sized particles passing the No. 200 Sieve. The clays would

typically be expected to have a low to medium shrink/swell potential due to the plasticity of the

material. The clay is considered firm to very stiff based on correlations with SPT N-values

ranging from 6 to 17 bpf.

Groundwater

The boring was advanced without the use of drilling fluids. During the drilling and sampling

operations, the boring was observed for signs of groundwater. No groundwater was

encountered. However, it should be noted the presence and amount of groundwater may

change seasonally, and after development, in response to precipitation, landscape irrigation,

and changes in surface drainage patterns.

1 The University of Texas at Austin Bureau of Economic Geology, (1983), “Geologic Atlas of Texas, San Antonio

Sheet”.

Project No. 04.36101159

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STRUCTURAL DETAILS

Comal County is planning the design and construction of a Restroom Facility at the Hidden

Valley Sports Park. Design plans were not available at the time of this study; however, we

understand the Restroom Facility will be lightly loaded. We also understand a slab on grade is

the proposed foundation system for the structure. The final finished floor elevation (FFE) and

existing topographic information have not been provided. Therefore, the recommendations

contained herein are based on the assumption that the structure will be constructed at or near

existing grade at the time the boring was drilled. The design of flatwork or other associated

facilities are not included in the scope of this study.

FOUNDATION EVALUATION

Estimates of soil swell at the site were evaluated using the Texas Department of Transportation

(TxDOT) Potential Vertical Rise2 (PVR) test method, TEX-124-E3. Past experience indicates

actual heave may be more than calculated by this method. The PVR procedure derives

potential swell from a historic PI versus swell curve. Therefore, the estimated vertical

movement values calculated using the PVR method might be different from actual measured

movements that occur at the project site.

Based on the heave estimates and our experience, approximately 1¼ inches of potential vertical

movement can be anticipated for the site soils. About 6 inches of removal would be required to

reduce the calculated PVR value to 1 inch, a value typically used as a maximum by structural

engineers for stand alone structures.

FOUNDATION RECOMMENDATIONS

Detailed design recommendations are presented in this section. Design recommendations for

Preparation of the Building Pad, Grid-Beam Stiffened Slab-on-Ground, PTI and BRAB

Parameters, and Seismicity are presented in this section. The proposed structure may be

supported on a grid beam stiffened slab on ground.

2 McDowell, C., (1956), “Interrelationship of Load, Volume Change, and Layer Thickness of Soil to the Behavior of

Engineering Structures,” Proceedings, Highways Research Board. 3 The State of Texas, Texas Department of Transportation, Materials and Test Division, Manual of Testing

Procedures, Volume 1, Test Method TEX-124-E, Rev. January 1, 1978.

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Preparation of the Building Pad

1. Within the building footprint and 3 ft outside the footprint, remove and dispose of

6 inches of the near-surface soils and any deleterious materials which may be

present. The final building pad (comprised of concrete slab and inert fill) should be a

minimum of 1-ft thick.

2. Scarify at least 6 inches of the cut soil subgrade, and recompact to at least

95 percent of the maximum dry density determined using Texas Department of

Transportation (TxDOT) Test Method TEX-114-E. Maintain water contents from 0 to

+4 percent of the optimum moisture content.

3. Bring the building pad to grade with Flexible Base Type A or C; Grade 3 or better as

specified by TxDOT, Standard Specifications for Construction of Highways, Streets

and Bridges, Item 247, current edition. Alternative select fill material meeting the

intent of this specification may be submitted to the Geotechnical Engineer for review,

prior to mobilizing or stockpiling the material on site.

4. Compact the flexible base material to at least 98 percent of the maximum dry density

as determined using TxDOT Test Method TEX-113-E. Hold water contents to

2 percent of the optimum moisture content, and maintain compacted lift

thicknesses to 6 inches or less.

5. Keep trees and any other vegetation capable of withdrawing moisture from the soil at

a distance from the slabs equal to at least three-quarters of their ultimate height.

Grid Beam Stiffened Slab-on-Ground

The Structural Engineer should design the grid-beam stiffened slab-on-grade including: the slab

thickness and reinforcement, and stiffening beam depth, spacing and reinforcement, based on

the following soil parameters.

1. Beams should be founded at least 18 inches below the final ground surface and widths

should be sized for an allowable bearing pressure of 2,000 psf in the select fill, but

beam widths should be no less than 12 inches.

2. Ensure that any concentrated loads are centered at the intersections of beams.

Beneath concentrated loads, beam intersections should be widened and sized for an

allowable bearing pressure of 2,500 psf in the select fill.

3. If needed, the floor slab should be designed using a modulus of subgrade reaction of

100 pci. This relatively low value was selected to accommodate support conditions

including the free-draining, capillary moisture barrier/drainage layer.

Project No. 04.36101159

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4. During the excavation for the grade beams, any loose soils should be removed from

the bottom and sides of the grade beams. The excavation bottoms should be

observed by a geotechnical engineer or his representative prior to the placement of

concrete.

PTI Parameters

The following PTI parameters have been developed as part of this study for the proposed site.

The parameters are based upon the recommended removal. The conditions were evaluated

using the two-dimensional moisture flow analysis computer program, VOLFLO v1.5. The

VOLFLO program generates the PTI support parameters (em and ym) in accordance with the

updated methods outlined in PTI’s “Design of Post-Tensioned Slabs-on-Ground, 3rd Edition

(2004).” 4

PTI Differential

Movement (ym)

(inches)

Edge Moisture

Variation Distance (em)

(feet)

Removal/

Replacement

(feet)

Estimated

PVR

(inches) Center Lift Edge Lift Center Lift Edge Lift

½

1 1.0 1.4 9.0 4.6

The PTI differential soil movement (ym) estimates are based on the computer software VOLFLO

v1.5. Our analysis assumes the soil moisture conditions are controlled by climate alone, which

results in the maximum soil swelling and shrinking. The center lift condition represents an initial

wet suction profile and a final dry profile. The edge lift condition was computed using an initial

dry profile and final wet suction profile.

The soil volume changes can be mitigated by providing and maintaining favorable site

conditions related to drainage, vegetation, and irrigation. Furthermore, the soil movement

estimates are considered invalid when soil moisture conditions are influenced by non-climatic

factors such as vegetation, slope, drainage, irrigation, downspouts, leaking water lines, etc.

BRAB Parameters

Soil design parameters have been developed based on the Building Research Advisory Board

(BRAB) method. BRAB parameters were obtained from the Board’s Report No. 33 to the

Federal Housing Administration entitled “Criteria for Selection and Design of Residential Slabs-

on-Ground” (1968). According to the manual, the slab could be classified as one of four types,

Type I through Type IV, based on the conditions encountered at the site. The type of slab

4 Design of Post-Tensioned Slabs-on-Ground, 3rd Edition, Post-Tensioning Institute, Phoenix, 2004, Chapter 3.

Project No. 04.36101159

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depends on two fundamental factors, the soil type and the climate. Fugro recommends a

Type III, grid beam stiffened slab-on-ground foundation, be used at this site. Using the BRAB

report and U.S. Weather Bureau data presented in the BRAB report, the factors on the following

page were estimated to describe the soil and climate at this site. We have developed the

parameters based on the current conditions at the site.

½-ft Removal/Replacement

Effective Plasticity Index 18

Climate Rating, Cw 17

Soil-Climate Support Index, C 0.03

Allowable Soil Bearing Pressure 3,000 psf

Seismicity

The International Building Code (IBC)5 provides guidelines for the maximum considered

earthquake spectral response accelerations for “short” periods (SSM) and at 1-second period

(SM1), adjusted for site class effects. The following parameters have been developed from the

IBC guidelines, taking into consideration the site-specific location and conditions.

Parameter Value/Designation

Acceleration, SMS, 0.2 sec spectral response 0.25 g

Acceleration, SM1, 1 sec spectral response 0.11 g

Site Class E

CONSTRUCTION CONSIDERATIONS

Groundwater Control

Groundwater seepage is not anticipated for shallow excavations during construction of the

proposed building. However, localized groundwater levels may rise during times of wet

seasonal conditions. If groundwater seepage does occur in construction excavations, this

seepage can, more likely than not, be pumped from the excavation.

Site Drainage

The optimum performance of any foundation system is dependent on positive site drainage.

Since expansive soil conditions occur in this site, it is essential to the future performance of the

foundation system that positive drainage of all water away from the building foundation be 5 “International Building Code”, (2009), International Code Council, Inc., Falls Church, Virginia, Section 1615,

“Earthquake Loads – Site Ground Motion”.

Project No. 04.36101159

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included in the design of this project. This positive drainage should be carefully maintained

throughout the life of the building. The contractor should provide for positive drainage of the site

during construction.

Trench Excavations

All OSHA trench safety guidelines should be strictly followed during excavation operations. The

design of construction slopes and temporary support systems is the sole responsibility of the

contractor.

Continuing Service

Two additional elements of geotechnical engineering service are important to the successful

completion of this project.

1. Consultation with design professionals during the design phases. This is important

to ensure that the intentions of our recommendations are properly incorporated in the

design, and that any changes in the design concept properly consider geotechnical

aspects.

2. Observation and monitoring during construction. A representative of the

geotechnical engineer of record should observe the foundation installation to

determine that subsurface conditions are compatible with those used in the analysis

and design.

CONDITIONS

The professional services that form the basis for this report has been performed using that

degree of care and skill ordinarily exercised, under similar circumstances, by reputable

geotechnical engineers practicing in the same locality. No warranty, express or implied, is

made as to the professional advice set forth. Fugro Consultants, Inc.’s scope of work does not

include the investigation, detection, or design related to the presence of any biological

pollutants. The term ‘biological pollutants’ includes, but is not limited to, mold, fungi, spores,

bacteria, and viruses, and the byproducts of any such biological organisms.

Our interpretations of subsurface conditions are based on data obtained at the soil boring

location only. Subsurface variations may exist at areas not explored by the soil boring.

Statements in this report as to subsurface variation over given areas are intended only as

estimations from the data obtained at the specific boring location. In addition, the condition of

the soils may change subsequent to our field exploration. Significant variations in subsurface

conditions or changed soil conditions may require changes to our conclusions and

Project No. 04.36101159

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recommendations. Observations during construction are recommended to check for variations

in subsurface conditions and possible changed conditions.

The results, conclusions, and recommendations contained in this report are directed at, and

intended to be utilized within the scope of work contained in this report. This report is not

intended to be used for any other purposes. Fugro Consultants, Inc. makes no claim or

representation concerning any activity or condition falling outside the specified purposes to

which this report is directed, said purposes being specifically limited to the scope of work as

defined in said agreement. Inquiries as to said scope of work or concerning any activity or

condition not specifically contained therein should be directed to Fugro Consultants, Inc. for a

determination and, if necessary, further investigation.

This report was prepared for the sole and exclusive use by the client, as an instrument of

service. This report shall remain the property of Fugro Consultants, Inc. No third party may use

or rely upon the information provided in this report without our express written consent. We

assume no responsibility for the unauthorized use of this report by other parties and for

purposes beyond the stated project objectives and scope limitations.

-- ... -

Project No. 04.36101159

I L L U S T R A T I O N S

Project No. 04.36101159

PLATE 1

VICINITY MAP

Hidden Valley Sports Park Restroom Facility Mabel Jones Drive

Canyon Lake, Texas

Project No. 04.36101159

PLATE 2

BORING PLAN Hidden Valley Sports Park Restroom Facility

Mabel Jones Drive Canyon Lake, Texas

22

9

100

100

15

19

769.015.0

37

27

LEAN CLAY WITH SAND (CL), tan, firm to very stiff

Notes:1) Coordinates obtained with a handheld GPS unit.2) Elevation shown was estimated using Google® Earth.

77

89

N = 12

N = 6

N = 7

N = 17

N = 9

N = 9

PLATE 3

Mabel Jones DriveCanyon Lake, Texas

LOG OF BORING NO. B-1Hidden Valley Sports Park Restroom Facility

SAM

PLES

PROJECT NO. 04.36101159

WATER LEVEL / SEEPAGE: DryUPON COMPLETION: Dry

COMPLETION DEPTH: 15.0

Fugro Consultants, Inc.

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DATE DRILLED: 10-5-10

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SURF. ELEVATION: 784.0 ft

LATITUDE: 29°51'54.12" N

LONGITUDE: 98°11'11.1" W

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Note: Information on each boring log is a compilation of subsurface conditions and soil and rock classificaitons obtained from the field as well as from laboratory testing of samples. Strata have been interpreted by commonly accepted procedures. The stratum lines on the logs may be transitional and approximate in nature. Water level measurements refer only to those observed at the times and places indicated, and may vary with time, geologic condition or construction activity.References: (1) Peck, Hanson and Thornburn, (1974), Foundation Engineering. (2)TxDOT, (1999), Tex-142-E, Laboratory Classification of Soils for Engineering Purposes. (3)ASTM International, ASTM D 2488 Standard Practice for Description and Identification of Soils. PLATE

Sampler Types

TERMS AND SYMBOLS USED ON BORING LOGS FOR SOIL

Thin-walled TubeStandard Penetration Test (SPT)

Texas Cone Penetration Test (TCP)

Auger Sample Bag Sample

Material Types

LEAN CLAy (CL) SANDy LEAN CLAy (CL) FAT CLAy (CH) SANDy FAT

CLAy (CH)

WELL-gRADED gRAvEL (gW)

POORLy-gRADED gRAvEL (gP)

SILTy gRAvEL (gM)

CLAyEy gRAvEL (gC)

WELL-gRADED SAND (SW)

POORLy-gRADED SAND (SP) SILTy SAND (SM) CLAyEy

SAND (SC)

FILL (F) ASPHALT (A) CONCRETE (C) AggREgATE BASE (AB)

ConsistencyStrength of Fine Grained Soils

Consistency SPT(#blows/ft)(1) UCS(TSF)(1) PP(FugroDFW)Very Soft < 2 < 0.25 0.4Soft 2 - 4 0.25 - 0.5 0.5 - 0.8Medium Stiff 4 - 8 0.5 - 1.0 0.9 - 1.6Stiff 8 - 15 1.0 - 2.0 1.7 - 3.3Very Stiff 15 - 30 2.0 - 4.0 > 3.4Hard > 30 > 4.0

Density of Coarse Grained SoilsApparentDensity SPT(#blows/ft) TCP(#blows/ft)(2)

Very Loose 0 - 4 < 8Loose 4 - 10 8 - 20Medium Dense 10 - 30 20 - 60Dense 30 - 50 60 - 100Very Dense > 50 > 100

Moisture Moisture Content adapted from (3)

Dry No water evident in sampleMoist Sample feels dampVery Moist Water visible on sampleWet Sample bears free water

Structure(3)

Criteria for Describing StructureDescription CriteriaStratified Alternating layers of varying material or color

with layers at least 6 mm thick; note thicknessLaminated Alternating layers of varying material or color with

the layers less than 6 mm thick; note thicknessFissured Breaks along definite planes of fracture

with little resistance to fracturingSlickensided Fracture planes appear polished or

glossy, sometimes striatedBlocky Cohesive soil that can be broken down into small

angular lumps which resist further breakdownLensed Inclusion of small pockets of different soils,

such as small lenses of sand scattered through a mass of clay; note thickness

Homogeneous Same color and appearance throughout

Grain Size(3)

Boulders CobblesGravel

Coarse FineSand

Coarse Medium FineSilt Clay

U.S. Standard Sieve12” 3” 3/4” 4 10 40 200

300 75 19 4.75 2.00 0.425 0.075 0.002

Particle Grain Size in Milimeters

Secondary Components Criteria for Describing Structure adapted from (3)

Trace < 5% of sampleFew 5% to 10% of sampleLittle 10% to 25% of sampleSome 25% to 50% of sample

Size Modifiers for InclusionsPocket Inclusion of different material that is smaller

than the diameter of the sampleFragment Pieces of a whole item - often used with shell and woodNodule A concretion, a small, more or less rounded body that is

usually harder than the surrounding soil (as in carbonate nodule) and was formed in the soil by a weathering process

Streak A line or mark of contrasting color or texture. The mark or line should be paper thin, and it should be natural - not a smear caused by extruding or trimming the sample