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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
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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.
PLA
STIC
ITY
IND
EX (P
I), %
PASS
ING
NO
.4
SIEV
E, %
DATE DRILLED: 10-5-10
WA
TER
CO
NTE
NT,
%
LAYERELEV./DEPTH
LIQ
UID
LIM
IT, %
DEP
TH, F
T
5
10
15
STRATUM DESCRIPTION
PASS
ING
NO
.20
0 SI
EVE,
%
CO
MPR
ESSI
VEST
REN
GTH
, TSF
CO
NFI
NIN
GPR
ESSU
RE,
PSI
POC
KET
PEN
Blo
ws/
ft.R
EC./R
QD
, %
SYM
BO
L
UN
IT D
RY
WEI
GH
T, P
CF
SURF. ELEVATION: 784.0 ft
LATITUDE: 29°51'54.12" N
LONGITUDE: 98°11'11.1" W
FUG
RO
STD
UC
S &
UU
(NO
PL)
04.
3610
1159
.GP
J F
UG
RO
DA
TA T
EM
PLA
TE 0
4261
0.G
DT
10/
15/1
0
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