United States
Environmental Protection
Agency
Off Ic* of Emergency and
Remedial Response
Vasnington, DC 20460
Publication 9360,4-10
PB92-963408
November 1991
Removal Program '««'
Representative Sampling
Guidance
REPRODUCED BY
U.S. DEPARTMENT OF COMMERCE
NATIONAL TECHNICAL
INFORMATION SERVICE-
SPRINGFIELD, VA 22161
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1. AGENCY USE ONLY (le**t Otoi*/ 2. REPORT DATE J. REPORT TYPE AND DATES COVERED
November 1991 Publication
4. TITLE AND SUBTITLE
Removal Program Representative Sampling Guidance
Volume 1 — Soil 9360.4-10
f. AUTHOR(S)
USEPA/OERR
?. PERFORMING ORGANIZATION NAME(S) AND ADORESS(ES)
Environmental Protection Agency
Office of Solid Waste and Emergency Response
401 M Street SW
Washington, DC 20460
9. SPONSORING /MONITORING AGENCY NAME(SJ AND ADDRESS(ES)
Environmental Protection Agency
Office of Emergency and Remedial Response
401 M Street SW
Washington, DC 20460
S. FUNDING NUMBERS
t. PERFORMING ORGANIZATION
REPORT NUMBER
10. SPONSORING /MONITORING
AGENCY REPORT NUMBER
11. SUPPLEMENTARY NOTES
PB92-963408 Removals
12l. DISTRIBUTION 'AVAILABILITY STATEMENT
12b. DISTRIBUTION CODE
13. ABSTRACT (MiximumlQQwardi)
This is the first volume in a series of guidance documents that assist
Removal Program Qn-Scene Coordinators and other field staff in obtaining
representative samples at removal sites. The objective of representative
sampling is to ensure that a sample or a group of samples accurately
characterizes site conditions. This document specifically addresses
representative sampling for soil.
14. SUBJECT TERMS
IS. NUMBER OF PAGES
48
16. PRICE CODE
17. SECURITY CLASSIFICATION ti, SECURITY CLASSIFICATION If, SECURITY CLASSIFICATION1 20. LIMITATION OF ABSTRACT
OF REPORT 'OF THIS PAGE OF ABSTRACT
NSM
S;a.-aard :Qrm 298 (*tv 2-89}
»'«
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OSWER Directive 9360.4-10
November 1991
REMOVAL PROGRAM
REPRESENTATIVE SAMPLING GUIDANCE
VOLUME 1: SOIL
Interim Final
Environmental Response Branch
Emergency Response Division
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC 2)460
Prepared by.
The U.S, EPA Committee on Representative Sampling for the Removal Program
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Notice
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved
for publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
The policies and procedures established in this document are intended solely for the guidance of government
personnel, for use in the Superfund Removal Program. They are not intended, and cannot be relied upon, to
create any rights, substantive or procedural, enforceable by any party in litigation with the United States. The
Agency reserves the right to act at variance with these policies and procedures and to change them at any time
without public notice.
For more information on Soil Sampling and Surface Geophysics procedures, refer to the Compendium ofERT
Soil Sampling and Surface Geophysics Procedures, OSWER directive 9360.4-02, EPA/540/P-91/006. Topics
covered in this compendium include Sampling Equipment Decontamination, Soil Sampling, Soil Gas Sampling,
and General Surface Geophysics. The compendium describes procedures for collecting representative soil
samples and provides a quick means of waste site evaluation. It also addresses the general procedures used to
acquire surface geophysical data.
Questions, comments, and recommendations are welcomed regarding the Removal Program Representative
Sampling Guidance, Volume 1 — Soil. Send remarks to:
Mr. Wiffiam A. Coakky
Removal Program QA Coordinator
U.S. EPA - ERT
Raritan Depot - Building 18, MS-101
2890 Woodbridge Avenue
Edison, NJ 08837-3679
For additional copies of the Removal Program Representative Sampling Guidance, Volume 1 - Soil, please
contact:
Superfund Document Center
U.S. EPA - Headquarters
401 M Street, SW
OS-240
Washington, DC 20406
E-mail: OERR/PUBS
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Acknowledgments
This document was prepared by the U.S. EPA Committee on Representative Sampling for the Removal Program,
under the direction of Mr. William A. Coakley, the Removal Program QA Coordinator of the Environmental
Response Team, Emergency Response Division. Additional support was provided by the following EPA
Workgroup and under U.S. EPA contract # 68-WO-0036 and U.S. EPA contract # 68-03-3482.
EPA Headquarters
Office of Emergency and Remedial Response
Office of Research and Development
Region 1
Region 4
Region 8
National Enforcement Investigation Center
EMSL, Las Vegas, NV
EPA Regional
EPA Laboratories
Harry Allen
Royal Nadeau
George Prince
John Warren
Alex Sherrin
William Bokey
Jan Rogers
Denise Link
Peter Stevenson
Chuck Ramsey
Delbert Earth
Ken Brown
Evan England
George Flatman
Ann Pitchford
Llew Williams
ui
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Table of Contents
Notice ii
Acknowledgments iii
List of Tables viii
List of Figures ix
1.0 INTRODUCTION
1.1 Objective and Scope 1
1.2 Removal Program Sampling Objectives 1
13 Representative Sampling 1
1.4 Example Site 2
2.0 SAMPLING DESIGN
2.1 Introduction 3
22 Historical Data Review 3
23 Site Reconnaissance 3
2.4 Migration Pathways and Receptors 4
2.4,1 Migration Pathways and Transport Mechanisms 4
2,4.2 Receptors 4
2 J Removal Program Sampling Objectives 4
2.6 Data Quality Objectives 5
2.7 Field Analytical Screening and Geophysical Techniques 5
2M Parameters for Analysis 6
2.9 Representative Sampling Approaches 6
2.9.1 Judgmental Sampling 6
2.9.2 Random Sampling 6
2.9.3 Stratified Random Sampling 6
2.9.4 Systematic Grid Sampling 8
2.9.5 Systematic Random Sampling 8
2.9.6 Search Sampling 8
2.9.7 Transect Sampling 9
2.10 Sampling Locations 11
2.11 Example Site 11
2.11.1 Background Information 11
2.11.2 Historical Data Review and Site Reconnaissance 12
2.11.3 Identification of Migration Pathways, Transport Mechanisms and Receptors 14
2.11.4 Sampling Objectives 14
2.11.5 Selection of Sampling Approaches 14
2.11.6 Field Analytical Screening, Geophysical Techniques, and Sampling Locations 15
2.11.7 Parameters for Analysis 17
Preceding page blank
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Table of Contents (continued)
Page
3.0 EQUIPMENT
3.1 Introduction 21
32 Held Analytical Screening Equipment 21
33 Geophysical Equipment 21
3.4 Selecting Sampling Equipment 21
3.5 Example Site 24
3 J.I Selection of Sampling Equipment 24
3.5,2 Selection of Held Analytical Screening Equipment 24
3J3 Selection of Geophysical Equipment 24
4.0 FIELD SAMPLE COLLECTION AND PREPARATION
4.1 Introduction 27
4.2 Sample Collection 27
4.2.1 Sample Number 27
4.2.2 Sample Volume 27
43 Removing Extraneous Material 27
4,4 Sieving Samples 28
43 Homogenizing Samples 28
4.6 Splitting Samples 28
4.7 Compositing Samples 29
4.8 Rnal Preparation 30
4.9 Example Site 30
5£ QUALITY ASSURANCE/QUALITY CONTROL EVALUATION
5.1 Introduction 31
5.2 QA/QC Objectives 31
53 Sources of Error 31
53.1 Sampling Design 31
53.2 Sampling Methodology 32
533 Sample Heterogeneity 32
53.4 Analytical Procedures 32
5.4 QA/QC Samples 32
5.4.1 Held Replicates 33
5.42 Collocated Samples 33
5.43 Background Samples 33
5.4.4 Rinsate Blanks 33
5.4J Performance Evaluation Samples 33
5.4.6 Matrix Spike Samples 33
5.4.7 Held Blanks 34
5.4A Trip Blanks 34
5 J Evaluation of Analytical Error 34
5.6 Correlation Between Held Screening Results and Confirmation Results 34
5.7 Example Site 35
VI
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Table of Contents (continued)
figs
6.0 DATA PRESENTATION AND ANALYSIS
6.1 Introduction 37
62 Data Posting 37
63 Geologic Graphics 37
6.4 Contour Mapping 37
65 Statistical Graphics 37
6.6 Geostatistics 39
6.7 Recommended Data Interpretation Methods 39
6.8 Utilization of Data 39
6.9 Example Site 40
References 45
Vll
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Ust of Tables
Table Page
1 Probability of Missing an Elliptical Hot Spot 10
2 Representative Sampling Approach Comparison 12
3 Portable Held Analytical Screening Equipment 22
4 Geophysical Equipment 23
5 Soil Sampling Equipment 25
viii
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Ust of Figures
Figure Page
1 Random Sampling 7
2 Stratified Random Sampling 1
3 Systematic Grid Sampling 7
4 Systematic Random Sampling 8
5 Search Sampling 9
6 Transect Sampling 11
7 Site Sketch and Phase 1 Soil Sampling Locations, ABC Plating Site 13
8 Phase 2 Soil Sampling and XRF Screening Locations, ABC Plating Site 16
9 Phase 2 Sampling Grid Cell Diagram 17
10 GPR Surrey Results, ABC Plating Site 18
11 EM-31 Survey Results, ABC Plating Ske 19
12 Phase 2 Sampling Grid Cell Diagram (Grid Sizes > 100 x 100 ft.) 28
13 Quartering to Homogenize and Split Samples 29
14 Sampling Error due to Sampling Design 32
15 Computer-Generated Contour Map, ABC Plating Site (4000 mg/kg Hot Spot) 38
16 Computer-Generated Contour Map, ABC Plating Site (1400 mg/kg Hot Spot) 38
17 Histogram of Surface Chromium Concentrations, ABC Plating Site 41
18 Phase 2 Surface Data Posting for Chromium, ABC Plating Site 42
19 Phase 2 Subsurface Data Posting for Chromium, ABC Plating Site 43
20 Contour Map of Surface Chromium Data (ppm), ABC Plating Site 44
21 Contour Map of Subsurface Chromium Data (ppm), ABC Plating Site 44
IX
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1.0 INTRODUCTION
1.1 OBJECTIVE AND SCOPE
This is the first volume in a series of guidance
documents that assist Removal Program Da-Scene
Coordinators (OSCs) and other field staff in
obtaining representative samples at removal sites.
The objective of representative sampling is to
ensure that a sample or a group of samples
Accurately characterizes site conditions. This
document specifically addresses representative
sampling for soil. The following chapters are
designed to assist field personnel in representative
sampling within the objectives and scope of the
Removal Program. This includes: assessing
available information; selecting an appropriate
sampling approach; selecting and utilizing
geophysical, field analytical screening, and sampling
equipment; utilizing proper sample preparation
techniques; incorporating suitable types and
numbers of QA/QC samples; and interpreting and
presenting the analytical and geophysical data.
As the Superfund program has developed, the
Removal Program has expanded its emphasis
beyond emergency response and short-term
cleanups. Longer, more complex removal actions
must meet a variety of sampling objectives,
including identifying threat, delineating sources and
extent of contamination, and confirming the
achievement of clean-up standards. Many important
and potentially costly decisions are based on the
sampling data, making it very important that OSCs
and field personnel understand how accurately the
sampling data characterize the actual site conditions.
In keeping with this strategy, this document
emphasizes field analytical screening and
geophysical techniques as cost effective approaches
to characterize the site and to select sampling
locations.
1.2 REMOVAL PROGRAM
SAMPLING OBJECTIVES
Although field conditions and removal activities can
vary greatly from site to site, the primary Removal
Program soil sampling objectives include obtaining
data to:
1. Establish threat to public health or welfare or
to the environment;
2. Locate and identify potential sources of
contamination;
3. Define the extent of contamination;
4. Determine treatment and disposal options; and
5. Document the attainment of clean-up goals.
These objectives are discussed in detail in section
2.5.
1.3 REPRESENTATIVE SAMPLING
Representative soil sampling ensures that a sample
or group of samples accurately reflects the
concentration of the contaminant(s) of concern at a
given time and location. Analytical results from
representative samples reflect the variation in
pollutant presence and concentration throughout a
site.
This document concentrates on the variables that
are introduced in the field — namely, those that
relate to the site-specific conditions, the sampling
design approach, and the techniques for collection
and preparation of samples. The following variables
affect the representativeness of samples and
subsequent measurements:
* Geological variability ~ Regional and local
variability in the mineralogy of rocks and soils,
the buffering capacity of soils, lithologic
permeability, and in the sorptive capacity of the
vadose zone.
* Contaminant concentration variability —
Variations in the contaminant concentrations
throughout the site.
* Collection and preparation variability —
Deviations in analytical results attributable to
bias introduced during sample collection,
preparation, and transportation (for analysis).
* Analytical variability — Deviations in analytical
results attributable to the manner in which the
sample was stored, prepared, and analyzed by
the on-site or off-site laboratory. Although
analytical variability cannot be corrected
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through representative sampling, it can falsely
lead to the conclusion that error is due to
sample collection and handling procedures.
1.4 EXAMPLE SITE
An example site, presented at
the end of each chapter,
illustrates the development of a
representative soil sampling
plan that meets Removal
Program objectives.
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2.0 SAMPLING DESIGN
2,1 INTRODUCTION
The following procedures are recommended for
developing a sound sampling design. Many steps
can be performed simultaneously, and the sequence
is not rigid.
* Review existing historical site information;
* Perform a site reconnaissance;
* Evaluate potential migration pathways and
receptors;
* Determine the sampling objectives;
* Establish the data quality objectives;
* Utilize field screening techniques;
* Select parameters for which to be analyzed;
* Select an appropriate sampling approach; and
* Determine the locations to be sampled.
Real-time field analytical screening techniques can
be used throughout the removal action. The results
can be used to modify the site sampling plan as the
extent of contamination becomes known.
2.2 HISTORICAL DATA REVIEW
Unless the site is considered a classic emergency,
every effort should be made to first thoroughly
review relevant site information. An historical data
review examines past and present site operations
and disposal practices, providing an overview of
known and potential site contamination and other
site hazards. Sources of information include
federal, state and local officials and files (e.g., site
inspection reports and legal actions), deed or title
records, current and former facility employees,
potentially responsible parties, local residents, and
faculty records or fifes. For any previous sampling
efforts, obtain information regarding sample
locations (on maps, if possible), matrices, methods
of collection and analysis, and relevant contaminant
concentrations. Assess the reliability and usefulness
of existing analytical data. Even data which are not
substantiated by documentation or QA/QC controls
may still be useful.
Collect information that describes any specific
chemical processes used on site, as well as
descriptions of raw materials used, products and
wastes, and waste storage and disposal practices.
Whenever possible, obtain site maps, facility
blueprints, and historical aerial photographs,
detailing past and present storage, process, and
waste disposal locations. The local Agricultural
Extension Agent, a Soil Conservation Service (SCS)
representative, has information on soil types and
drainage patterns. County property and tax records,
and United States Geological Survey (USGS)
topographic maps are also useful sources of site and
regional information.
2.3 SITE RECONNAISSANCE
A site reconnaissance, conducted either prior to or
in conjunction with sampling, is invaluable to assess
site conditions, to evaluate areas of potential
contamination, to evaluate potential hazards
associated with sampling, and to develop a sampling
plan. During the reconnaissance, fill data gaps left
from the historical review by:
* Interviewing local residents, and present or past
employees about site-related activities;
* Researching facility files or records (where
records are made accessible by
owner/operator);
* Performing a site entry, utilizing appropriate
personal protective equipment and
instrumentation. Observe and photo-document
the site; note site access routes; map process
and waste disposal areas such as landfills,
lagoons, and effluent pipes; inventory site
wastes; and map potential transport routes such
as ponds, streams, and irrigation ditches. Note
topographic and structural features, dead
animals and dead or stressed vegetation,
potential safety hazards, and visible label
information from drums, tanks, or other
containers found on the she.
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2.4 MIGRATION PATHWAYS AND
RECEPTORS
The historical review and site visit are the initial
steps in defining the source areas of contamination
which could pose a threat to human health and the
environment. This section addresses how to
delineate the spread of contamination away from
the source areas. Included are pollutant migration
pathways and the routes by which persons or the
environment may be exposed to the on-site
chemical wastes.
2.4.1 Migration Pathways and
Transport Mechanisms
Migration pathways are routes by which
contaminants have moved or may be moved away
from a contamination source. Pollutant migration
pathways may include man-made pathways, surface
drainage, vadose zone transport, and wind
dispersion. Human activity (such as foot or
vehicular traffic) also transports contaminants away
from a source area. These five transport
mechanisms are described below.
* Man-made pathways — A site located in an
urban setting has the following man-made
pathways which can aid contaminant migration:
storm and sanitary sewers, drainage culverts,
sumps and sedimentation basins, French drain
systems, and underground utility lines.
* Surface drainage -- Contaminants can be
adsorbed onto sediments, suspended
independently in the water column, or dissolved
in surface water runoff and be rapidly carried
into drainage ditches, streams, rivers, ponds,
lakes, and wetlands. Consider prior surface
drainage routes; historical aerial photographs
can be invaluable for delineation of past surface
drainage patterns. An historical aerial
photograph search can be requested through
the EPA Regional Remote Sensing
Coordinator.
* Vadose zone transport — Vadose zone transport
is the vertical or horizontal movement of water
and of soluble and insoluble contaminants
within the unsaturated zone of the soil profile.
Contaminants from a surface source or a
leaking underground storage tank can percolate
through the vadose zone and be adsorbed onto
subsurface soil or reach groundwater.
Wind dispersion — Contaminants deposited
over or adsorbed onto soil may migrate from a
waste site as airborne participates. Depending
on the particle-size distribution and associated
settling fates, these participates may be
deposited downwind or remain suspended,
resulting in contamination of surface soils
and/or exposure of nearby populations.
Human and animal activity - Foot and
vehicular traffic of facility workers, response
personnel, and trespassers can move
contaminants away from a source. Animal
burrowing, grazing, and migration can also
contribute to contaminant migration.
2.4.2 Receptors
Once the migration pathways have been determined,
identify all receptors (i.e., potentially affected
human and environmental populations) along these
pathways. Human receptors include on-site and
nearby residents and workers. Note the
attractiveness and accessibility of site wastes
(including contaminated soil) to children and other
nearby residents. Environmental receptors include
Federal- or state-designated endangered or
threatened species, habitats for these species,
wetlands, and other Federal- and state-designated
wilderness, critical, and natural areas.
2.5 REMOVAL PROGRAM
SAMPLING OBJECTIVES
Collect samples if any of the following Removal
Program sampling objectives in the scope of the
project are not fulfilled by existing data.
1. Establishing Threat to Public Health or
Welfare or to the Environment — The
Comprehensive Environmental Response,
Compensation and Liability Act of 1980
(CERCLA) and the National Contingency Plan
(NCP) establish the funding mechanism and
authority which allow the OSC to activate a
Federal removal action. The OSC must
establish (often with sampling) that the site
poses a threat to public health or welfare or to
the environment.
2. Locating and Identifying Potential Sources of
Contamination — Sample to identify the
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locations and sources of contamination. Use
the results to formulate removal priorities,
containment and clcan-up strategics, and cost
projections.
3. Defining the Extent of Contamination — Where
appropriate, sample to assess horizontal and
vertical extent of contaminant concentrations.
Use the results to determine the site boundaries
(i.e., extent of contamination), define clean
areas, estimate volume of contaminated soil,
establish a clearly defined removal approach,
and assess removal costs and timeframe.
4. Determining Treatment and Disposal Options
- Sample to characterize soil for in situ or
other on-site treatment, or excavation and off-
site treatment or disposal
5. Documenting the Attainment of Clean-up Goals
— During or following a site cleanup, sample to
determine whether the removal goals or clean-
up standards were achieved, and to delineate
areas requiring further treatment or excavation
when appropriate.
2.6 DATA QUALITY OBJECTIVES
Data quality objectives (DQOs) state the level of
uncertainty that is acceptable from data collection
activities. DQOs also define the data quality
necessary to make a certain decision. Consider the
following when establishing DQOs for a particular
project:
• Deeision(s) to be made or question(s) to be
answered;
* Why environmental data are needed and how
the results will be used;
* Tune and resource constraints on data
collection;
* Descriptions of the environmental data to be
collected;
• Applicable model or data interpretation method
used to arrive at a conclusion;
* Detection limits for anah/tes of concern; and
* Sampling and analytical error.
In addition to these considerations, the quality
assurance components of precision, accuracy (bias),
completeness, representativeness, and comparability
should also be considered. Quality assurance
components are defined as follows:
* Precision — measurement of variability in the
data collection process.
* Accuracy (bias) — measurement of bias in the
analytical process. The term "bias" throughout
this document refers to the QA/QC accuracy
component.
* Completeness - percentage of sampling
measurements which are judged to be valid.
* Representativeness -- degree to which sample
data accurately and precisely represent the
characteristics of the site contaminants and
their concentrations.
* Comparability ~ evaluation of the similarity of
conditions (e.g., sample depth, sample
homogeneity) under which separate sets of data
are produced,
Quality assurance/quality control (QA/QC)
objectives are discussed further in chapter 5.
2.7 FIELD ANALYTICAL
SCREENING AND
GEOPHYSICAL TECHNIQUES
There are two primary types of analytical data
which can be generated during a removal action:
laboratory analytical data and field analytical
screening data. Reid analytical screening
techniques (e.g., using a photoionization detector
(FID), portable X-ray fluorescence (XRF) unit, and
hazard categorization kits) provide real-time or
direct reading capabilities. These screening
methods can narrow the possible groups or classes
of chemicals for laboratory analysis and are effective
and economical for gathering large amounts of site
data. Once an area is identified using field
screening techniques, a subset of samples can be
sent for laboratory analysis to substantiate the
screening results. Under a limited sampling budget,
field analytical screening (with laboratory
confirmation) will generally result in more analytical
data from a site than will sampling for off-site
laboratory analysis alone. To minimize the
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potential for false negatives (not detecting cm-site
contamination), use only those field analytical
screening methods which provide detection limits
below applicable action levels. It should be noted,
that some field analytical screening methods which
do not achieve detection limits below site action
levels can still detect grossly contaminated areas,
and can be useful for some sampling events.
Geophysical techniques may also be utilized during
a removal action to help depict locations of any
potential buried drums or tanks, buried waste, and
disturbed areas. Geophysical techniques include
ground penetrating radar (GPR), magnetometry,
electromagnetic conductivity (EM) and resistivity
surveys.
2.8 PARAMETERS FOR ANALYSIS
If the historical data review yields little information
about the types of waste on site, use applicable field
screening methods to narrow the parameters for
analysis by ruling out the presence of high
concentrations of certain contaminants. If the
screening results are inconclusive, send a subset of
samples from the areas of concern for a full
chemical characterization by an off-site laboratory.
It is advised that samples from known or suspected
source areas be sent to the laboratory for a full
chemical characterization so that all contaminants of
concern can be identified (even at low detection
levels), and future sampling and analysis can then
focus on those substances.
Away from source areas, select a limited number of
indicator parameters (e.g., lead, PAHs) for analysis
based on the suspected contaminants of concern.
This will result in significant cost savings over a full
chemical characterization of each sample. Utilize
EPA-approved methodologies and sample
preparation, where possible, for all requested off-
site laboratory analyses.
2.9 REPRESENTATIVE SAMPLING
APPROACHES
Selecting sampling locations for field screening or
laboratory analysis entails choosing the most
appropriate sampling approach. Representative
sampling approaches include judgmental, random,
stratified random, systematic grid, systematic
random, search, and transect sampling. A
representative sampling plan may combine two or
more of these approaches. Each approach is
defined below.
2.9.1 Judgmental Sampling
Judgmental sampling is the subjective selection of
sampling locations at a site, based on historical
information, visual inspection, and on best
professional judgment of the sampling team. Use
judgmental sampling to identify the contaminants
present at areas having the highest concentrations
(i.e., worst-case conditions). Judgmental sampling
has no randomization associated with the sampling
strategy, precluding any statistical interpretation of
the sampling results.
2.9.2 Random Sampling
Random sampling is the arbitrary collection of
samples within defined boundaries of the area of
concern. Choose random sample locations using a
random selection procedure (e.g., using a random
number table). Refer to VS. EPA, 1984a, for a
random number table. The arbitrary selection of
sampling points requires each sampling point to be
selected independent of the location of all other
points, and results in all locations within the area of
concern having an equal chance of being selected.
Randomization is necessary in order to make
probability or confidence statements about the
sampling results. The key to interpreting these
probability statements is the assumption that the
site is homogeneous with respect to the parameters
being monitored. The higher the degree of
heterogeneity, the less the random sampling
approach will adequately characterize true
conditions at the site. Because hazardous waste
sites are very rarely homogeneous, other statistical
sampling approaches (discussed below) provide ways
to subdivide the site into more homogeneous areas.
These sampling approaches may be more
appropriate for removal activities than random
sampling. Refer to U.S. EPA, February 1989, pages
5-3 to 5-5 for guidelines on selecting sample
coordinates for random sampling. Figure 1
illustrates a random sampling approach.
2.9.3 Stratified Random Sampling
Stratified random sampling often relies on historical
information and prior analytical results (or field
screening data) to divide the sampling area into
smaller areas called strata. Each strata is more
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Figure 1: Random Sampling
**
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25 50 75 100 125 150 175 200 225
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Figure 2: Stratified Random Sampling
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Figure 3: Systematic Grid Sampling
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50-
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I I I I I I T I I
25 50 75 100 125 150 175 200 225
FEET
**
After U.S. EPA, February, 1989
LEGEND
SAMPLE AREA BOUNDARY
SELECTED SAMPLE LOCATION
SAMPLE LOCATION
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homogeneous than the site is as a whole. Strata can
be defined based on various factors, including:
sampling depth, contaminant concentration levels,
and contaminant source areas. Place sample
locations within each of these strata using random
selection procedures. Stratified random sampling
imparts some control upon the sampling scheme but
still allows for random sampling within each
stratum. Different sampling approaches may also
be selected to address the different strata at the
site. Stratified random sampling is a useful and
flexible design for estimating the pollutant
concentration within each depth interval or area of
concern. Figure 2 illustrates a stratified random
sampling approach where strata are defined based
on depth. In this example, soil coring devices are
used to collect samples from given depths at
randomly selected locations within the strata.
2.9.4 Systematic Grid Sampling
Systematic grid sampling involves subdividing the
area of concern by using a square or triangular grid
and collecting samples from the nodes (intersections
of the grid lines). Select the origin and direction
for placement of the grid using an initial random
point. From that point, construct a coordinate axis
and grid over the whole site. The distance between
sampling locations in the systematic grid is
determined by the size of the area to be sampled
and the number of samples to be collected.
Systematic grid sampling is often used to delineate
the extent of contamination and to define
contaminant concentration gradients. Refer to U.S.
EPA February 1989, pages 5-5 to 5-12, for
guidelines on selection of sample coordinates for
systematic grid sampling. Figure 3 illustrates a
systematic grid sampling approach.
2.9.5 Systematic Random Sampling
Systematic random sampling is a useful and flexible
design for estimating the average pollutant
concentration within grid cells. Subdivide the area
of concern using a square or triangular grid (as
described in section 2.9.4) then collect samples from
within each cell using random selection procedures.
Systematic random sampling allows for the isolation
of cells that may require additional sampling and
analysis. Figure 4 illustrates a systematic random
sampling approach.
2.9.6 Search Sampling
Search sampling utilizes either a systematic grid or
systematic random sampling approach to search for
areas where contaminants exceed applicable clean-
up standards (hot spots). The number of samples
and the grid spacing are determined on the basis of
the acceptable level of error (i.e., the chance of
missing a hot spot). Search sampling requires that
assumptions be made about the size, shape, and
depth of the hot spots. As illustrated in figure 5,
the smaller and/or narrower the hot spots are, the
Figure 4: Systematic Random Sampling
25 50 75 100 12i 150 175 200 225
FCET
After; U.S. EPA, February, 1989
LEGEND
SAMPLE AREA BOUNDARY
SELECTED SAMPLE LOCATION
-------
smaller the grid spacing must be in order to locate
them. Also, the smaller the acceptable error of
missing hot spots is, the smaller the grid spacing
most be. This, in effect, means collecting more
samples.
Once grid spacing has been selected, the probability
of locating a hot spot can be determined. Using a
systematic grid approach, table 1 lists approximate
probabilities of missing an elliptical hot spot based
on the grid method chosen as well as the
dimensions of the hot spot. The lengths of the long
and short axes (L and S) are represented as a
percentage of the grid spacing chosen. The
triangular grid method consistently shows lower
probabilities of missing a hot spot in comparison to
the block grid method. Table 1 can be used in two
ways. If the acceptable probability of missing a hot
spot is known, then the size of the hot spot which
can be located at that probability level can be
determined. Conversely, if the approximate size of
the hot spot is known, the probability of locating it
can be determined. For example, suppose the block
grid method is chosen with a grid spacing of 25 feet.
The OSC is willing to accept a 10% chance of
missing an elliptical hot spot. Using table 1, there
would be a 90% probability of locating an elliptical
hot spot with L equal to 90% of the grid spacing
chosen and S equal to 40% of the grid spacing
chosen. Therefore the smallest elliptical hot spot
which can be located would have a long axis L =
0.90 x 25ft. = 22.5 ft. and a short axis S = 0.40 x
25ft. = 10 ft.
Similarly, if the approximate size of the hot spot
being searched for is known, then the probability of
missing that hot spot can be determined. For
example, if a triangular grid method was chosen
with a 25 foot grid spacing and the approximate
shape of the hot spot is known, and L is
approximately 15 feet or 60% of the grid spacing,
and S is approximately 10 feet or 40% of the grid
spacing, then there is approximately a 15% chance
of missing a hot spot of this size and shape.
2.9.7 Transect Sampling
Transect sampling involves establishing one or more
transect lines across the surface of a site. Collect
samples at regular intervals along the transect lines
at the surface and/or at one or more given depths.
The length of the transect Hue and the number of
samples to be collected determine the spacing
between sampling points along the transect.
Multiple transect lines may be parallel or non-
parallel to one another. If the lines are parallel, the
sampling objective is similar to systematic grid
sampling. A primary benefit of transect sampling
over systematic grid sampling is the ease of
establishing and relocating individual transect lines
versus an entire grid. Transect sampling is often
used to delineate the extent of contamination and to
define contaminant concentration gradients. It is
also used, to a lesser extent, in compositing
sampling schemes. For example, a transect
sampling approach might be used to characterize a
Figure 5: Search Sampling
100-
75-
I50-
25-
i
25
I I I I I i I I
50 75 100 lit 150 175 200 225
PtSrT
After: U.S. EPA, February, 1989
LEGEND
'""^ SAMPLE AREA BOUNDARY
B SELECTED SAMPLE LOCATION
'"A"? HOT SPOT
-------
Table 1: Probability of Missing an Elliptical Hot Spot
LENGTH OF SHORT AXIS AS A PERCENTAGE OF GRID SPACING
C5
z
i
CO
Q
DC
CD
LLJ
I
LLI
o
cr
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
10%
0.97,
0.95
20%
0.95.
0.88.
0.92
0.85
30%
0.92.
0.66
40%
0.88,
0.41
50%
0.85,
0.08
C/3
60%
0.80,
0.06^
0.03
0.0
70%
0.77.
0.01
0.03
0.0
80%
0.75
0.50
0.32,
0.0
0.0
0.0
90%
0.72.
0.51
0.30.
0.10
0.03,
0.0
0.0
0.0
0.0
0.72
0.45
0.21
0.06
0.0
0.0
0.0
0.0
0.0
100%
0.70,
0.0
From tables in: Gilbert, 1987
L = length of long axis
S = length of short axis
BLOCK GRID
TRIANGULAR GRID
-------
linear feature such as a drainage ditch. A transect
line is run down the center of the ditch, along its
full length. Sample aliquots are collected at regular
intervals along the transect line and are then
composited. Figure 6 illustrates transect sampling.
Table 2 summarizes the various representative
sampling approaches and ranks the approaches from
most to least suitable, based on the sampling
objective. Table 2 is intended to provide general
guidelines, but it cannot cover all site-specific
conditions encountered in the Removal Program.
2.10 SAMPLING LOCATIONS
Once a sampling approach has been selected, the
next step is to select sampling locations. For
statistical (non-judgmental) sampling, careful
placement of each sampling point is important to
achieve representativeness.
Factors such as the difficulty in collecting a sample
at a given point, the presence of vegetation, or
discoloration of the soil could bias a statistical
sampling plan.
Sampling points may be located with a variety of
methods. A relatively simple method for locating
random points consists of using either a compass
and a measuring tape, or pacing, to locate sampling
points with respect to a permanent landmark, such
as a survey marker. Then plot sampling coordinates
on a map and mark the actual sampling points for
future reference. Where the sampling design
demands a greater degree of precision, locate each
sample point by means of a survey. After field
sample collection, mark each sample point with a
permanent «;ake so that the survey team can
identify all the locations.
2.11 EXAMPLE SITE
2.11.1 Background
Information
The ABC Plating Site is located
in Carroll County, Pennsylvania,
approximately L5 miles north of the town of
Jonesville (figure 7). The site covers approximately
4 acres, and operated as an electroplating facility
from 1947 to 1982. During its years of operation,
the company plated automobile and airplane parts
with chromium, nickel, and copper. Cyanide
solutions were used in the plating process. ABC
Plating deposited electroplating wastes into two
shallow surface settling lagoons in the northwest
sector of the site. The county environmental health
department was attempting to enforce cleanup by
the site owner, when, in early 1982, a fire on site
destroyed most of the process building. The owner
then abandoned the facility and could not be located
by enforcement and legal authorities. The county
contacted EPA for an assessment of the site for a
possible removal action.
100-
75-
UJ -ni
lit 50~
U.
25-
Rgure 6; Transect Sampling
25
I I
50 7S 1
ItS 160 175 200 225
i
FEET
After: U.S. EPA, February, 1989
LEGEND
SAMPLE AREA BOUNDARY
SELECTED SAMPLE LOCATION
11
-------
Table 2: Representative Sampling Approach Comparison
SAMPLING APPROACH
SAMPLING OBJECTIVE
ESTABLISH
THREAT
IDENTIFY
SOURCES
DELINEATE EXTENT
OF CONTAMINATION
EVALUATE
TREATMENT
AND DISPOSAL
OPTIONS
CONFIRM
CLEANUP
a!
t;
LU
1
1
1
4
3
4
§
1
4
4
3
3
1°
O
UJ
U- .5
i- p
co £
3
?
3
1
3
O
H
UJ
11
2°
?a
1b
?
!b
O
S
10 S
w z
3
a
1
y
t
s
CO
3
?
1
4
1
H
«
i
2
3
1
2
..d
1 - PREFERRED APPROACH
2 - ACCEPTABLE APPROACH
3 - MODERATELY ACCEPTABLE APPROACH
4 ~ LEAST ACCEPTABLE APPROACH
a -- SHOULD BE USED WITH FIELD ANALYTICAL SCREENING
b - PREFERRED ONLY WHERE KNOWN TRENDS ARE PRESENT
c -MWwsfcmml^mw^s^^x^
-------
Figure 7: Site Sketch and Phase 1 Soil Sampling Locations
ABC Plating Site
\
—j
HOUSE
TRAILER
.' .'FENCE
SCALE IN FEET
100 50 0
100
LEGEND
DAMAGED
BUILDING
AREA
f| SAMPLING LOCATIONS
SURFACE FLOW
SHE BOUNDARY
13
-------
the ground) were leaking and bulging, due to the
fire. TAT noted many areas of stained soil, which
indicated container leakage, poor waste handling
practices, and possible illegal dumping of wastes.
2,11.3 Identification of Migration
Pathways, Transport
Mechanisms and Receptors
During the site entry, the OSC and TAT noted that
several areas were devoid of vegetation, threatening
wind erosion which could transport heavy metal-
and cyanide-contaminated soil participates off site.
These particulates could be deposited on residential
property downwind or be inhaled by nearby
residents.
Erosion gullies located on site indicated soil erosion
and fluvial transport due to storms. Surface
drainage sloped towards the northwest. TAT
observed stressed and discolored vegetation
immediately off site, along the surface drainage
route. Surface drainage of heavy metals and
cyanide was a direct contact hazard to local
residents. Further downgradient, runoff enters an
intermittent tributary of Little Creek. Little Creek
in turn feeds Barker Reservoir, the primary water
supply for the City of Jonesville and neighboring
communities, which are located 2.5 miles
downgradient of the site. The site entry team
observed that the site was not secure and there
were signs of trespass (confirming a neighbor's
claim that children play at the facility). These
activities could lead to direct contact with cyanide
and heavy metal contaminants, in addition to the
potential for chemical burns from direct contact
with strong adds and bases.
2.11,4 Sampling Objectives
The OSC selected three specific sampling objectives,
as follows:
* Phase 1 — Determine whether a threat to public
health, welfare, and the environment exists.
Identify sources of contamination to support an
immediate CERCLA-funded activation for
containment of contaminants and security
fencing.
* Phase 2 - Define the extent of contamination
at the site and adjacent residential properties.
Estimate the volume of contaminated soil and
the associated removal costs.
* Phase 3 — After excavation (or treatment),
document the attainment of clean-up goals.
Assess that cleanup was completed to the
selected level.
2.11.5 Selection of Sampling
Approaches
The OSC selected a judgmental sampling approach
for Phase 1. Judgmental sampling supports the
Action Memorandum process by best defining on
site contaminants in the worst-case scenario in
order to evaluate the threat to human health,
welfare, and the environment. Threat is typically
established using a relatively small number of
samples (less than 20) collected from source areas,
or suspected contaminated areas based on the
historical data review and site reconnaissance. For
this site, containerized wastes were screened to
categorize the contents and to establish a worst-
case waste volume, while soil samples were
collected to demonstrate whether a release had
already occurred.
For Phase 2, a stratified systematic grid design was
selected to define the extent of contamination. The
grid can accommodate field analytical screening and
geophysical surveys and allow for contaminated soil
excavation on a cell-by-cell basis. Based on search
sampling conducted at similar sites, the hot spots
being searched for were assumed to be elliptical in
shape and 45 feet by 20 feet in size. Under these
assumptions, a block grid, with a 50 foot grid
spacing, was selected. This grid size ensured a no
more than 10% probability of missing a hot spot
(see table 1). The grid was extended to adjacent
residential properties when contaminated soil was
identified at grid points near the boundary of the
site.
Phase 3 utilized a systematic grid sampling approach
to confirm the attainment of clean-up goals.
Following cleanup, field analytical screening was
conducted on excavated soil areas using a
transportable X-ray fluorescence (XRF) unit
mounted in a trailer (mobile laboratory instrument).
Based on the results, each area was documented as
clean, or was excavated to additional depth, as
necessary.
14
-------
2.11.6 Field Analytical Screening,
Geophysical Techniques,
and Sampling Locations
During Phase 1 operations, containerized wastes
were screened using hazard categorization
techniques to identify the presence of acids, bases,
oxidizers, and flammable substances. Following this
procedure, photoionization detector (FID) and
flame ionization detector (FID) instruments, a
radiation meter, and a cyanide monitor were used
to detect the presence of volatile organic
compounds, radioactive substances, and cyanide,
respectively, in the containerized wastes. Phase 1
screening indicated the presence of strong adds and
bases and the absence of volatile organic
compounds. TAT collected a total of 12 surface soil
samples (0-3 inches) during this phase and sent
them to a laboratory for analysis. The soil sampling
locations included stained soil areas, erosion
channels and soil adjacent to leaking containers.
Background samples were not collected during
Phase 1 because they were unnecessary for
activating funding. Phase 1 sampling locations are
shown in figure 7. Based on Phase 1 analytical
results, consultation with a Regional EPA
lexicologist and with the Agency for Toxic
Substances and Disease Registry (ATSDR), an
action level of 100 ppm for chromium was selected
for cleanup.
During Phase 2 sampling activities, the OSC used a
transportable XRF unit installed in an on-site trailer
to screen samples for total chromium in order to
limit the number of samples to be sent for off-site
laboratory analysis. The transportable XRF (rather
than a portable unit) was selected for field analytical
screening to accommodate the 100 ppm action level
for chromium. Sampling was performed at all grid
nodes at the surface (0-4 inches) and subsurface
(36-40 inches) (figure 8). The 36-40 inch depth was
selected based on information obtained from county
reports and local interviews which indicated the
lagoon wastes were approximately 3 feet below
ground surface. The samples were homogenized
and sieved (discussed in chapter 4), then screened
for chromium using the XRF. The surface and
subsurface samples from areas downgradient of the
original facility (21 grid nodes) and three upgradient
(background) locations were sent for off-site
laboratory analysis following XRF screening. The
analytical results from these samples allowed for
site-specific calibration of the XRF unit. Once grid
nodes with a contamination level greater than the
selected action level were located, composite
samples were collected from each adjoining cell.
Surface aliquots were collected and then
composited, sieved, thoroughly homogenized, and
screened using the XRF to pinpoint contaminated
cells. Additionally, four subsurface aliquots were
collected at the same locations as the surface
aliquots. They were also composited, sieved,
thoroughly homogenized, and screened using the
XRF. Figure 9 illustrates a Phase 2 sampling grid
cell diagram r Based on the XRF data, each
adjoining cell was either identified as dean (below
action level), or designated for excavation (at or
above action level).
For Phase 3 sampling, cleanup was confirmed by
collecting and compositing four aliquots from the
surface of each grid cell excavated during Phase 2.
The surface composites were then screened (as in
Phase 2), using the transportable XRF. Ten
percent of the screened samples were also sent to
an off-site laboratory for confirmatory sampling.
Based on the Phase 3 screening and sampling
results, each cell was documented as dean, or,
excavated to additional depth, as necessary.
During Phase 2, the OSC conducted ground
penetrating radar (GPR) and electromagnetic
conductivity (EM) geophysical surveys to help
delineate the buried trench and lagoon areas along
with any other waste burial areas. The GPR survey
was run along the north-south grid axis across the
suspected locations of the trench and lagoons.
Several structural discontinuities, defining possible
disturbed areas, were detected. One anomaly
corresponded with the suspected location and
orientation of the feeder trench. Several
discontinuities were identified in the suspected
lagoon areas; however, the data did not conclusively
pinpoint precise locations. This could be due to a
disturbance of that area during the backfilling
process by the PRP. The GPR survey is illustrated
in figure 10.
For the comprehensive EM survey, the original 50
foot grid spacing was decreased to 25 feet along the
north-south grid axis. The EM survey was run
along the north-south axes and readings were
obtained at the established grid nodes. The EM
survey was utilized throughout the site to detect the
presence of buried metal objects (e.g., buried pipe
leading to the lagoons), and potential subsurface
contaminant plumes. The EM survey identified
several high conductivity anomalies: the suspected
feeder trench location, part of the lagoon area, and
15
-------
Figure 8: Phase 2 Soil Sampling and XRF Screening Locations
ABC Plating Site
Y9
rs
rr
s
o
8 w
ft
I
x Y4
V7
*»
Y1
.--_GAtE (EAST-VEST GRID COORDINATES)
DAMAGED
BUILDING
AREA
I l
.' /PENCE
SCALE IN FEET
100 50 0
100
LEGEND
XRF SCREENING LOCATION
A DOWNGRADJENT
^ SAMPLING LOCATION
^ BACKGROUND
"^ SAMPUNG LOCATION
SFTE BOUNDARY
16
-------
Figure 9: Phase 2 Sampling Grid
Cell Diagram*
GRID NODE
COMPOSITE ALIQUOTS
a small area west of die process building (figure
11), which could have been an illegal waste dumping
area. Several areas of interference were
encountered due to the presence of large metal
objects at the surface (a dumpster, surface vats and
a junk car).
2.11.7 Parameters for Analysis
During Phase 1 sampling activities, full priority
pollutant metals and total cyanide analyses were
conducted on all samples. Since Phase 1 samples
were collected from the areas of highest suspected
contaminant concentration (i.e., sources and
drainage pathways), Phase 2 samples were run for
total chromium and cyanide, the only analytes
detected during the Phase 1 analyses. During Phase
3, the samples sent to the laboratory for screening
confirmation were analyzed for total chromium and
cyanide. Throughout the removal, it was not
possible to screen soils on site for cyanide, therefore
the OSC requested laboratory cyanide analysis on
the 10% confirmatory samples.
CHROMIUM ABOVE ACTION LEVEL
Surface samples should be taken over a
minimum area of one square foot Sampling
areas for depth sampling are limited by the
diameter of the sampling equipment (e.g.,
auger, split spoon, or coring devices).
17
-------
Figure 10: GPR Survey Results
ABC Plating Site
DAMAGED
BUILDING
AREA
SCALE IN FEET
100 50 0
100
LEGEND
I STRUCTURAL
DISCONTINUITY (GPR)
SrTE BOUNDARY
18
-------
Figure 11: EM-31 Survey Results
ABC Plating Site
:-SUSPEGTEB-•••:••••:••••
LAGOONS : : : :
SUSPECTED :
TRENCH-:--:-!
DAMAGED
BUILDING
AREA
SCALE IN FEET
100 50
100
LEGEND
EM-31 > i
MILLIMHOS / MEIER
SITE BOUNDARY
19
-------
20
-------
3.0 EQUIPMENT
3.1 INTRODUCTION
Sample collection requires an understanding of the
capabilities of the sampling equipment, since using
inappropriate equipment may result in biased
samples. This chapter provides information for
selecting field sampling and screening equipment.
3.2 FIELD ANALYTICAL
SCREENING EQUIPMENT
Field analytical screening methods provide on-site
measurements of contaminants of concern, limiting
the number of samples which need to be sent to an
off-site laboratory for time-consuming and often
costly analysis. Field screening techniques can also
evaluate soil samples for indications that soil
contamination exists (e.g., X-ray fluorescence
(XRF) for target metals or soil gas survey for
identification of buried wastes or other subsurface
contamination). All field screening equipment and
methods described in this section are portable (the
equipment is hand-held, and generally no external
power is necessary). Examples are photoioni/ation
detectors (PID), flame ionization detectors (FID),
and some XRF devices.
Field screening generally provides analytical data of
suitable quality for site characterization, monitoring
during removal activities, and on-site health and
safety decisions. The methods presented here can
provide rapid, cost-effective, real-time data;
however, results are often not compound-specific
and not quantitative.
When selecting one field screening method over
another, consider relative cost, sample analysis time,
potential interferences or instrument limitations,
detection limit, QA/QC requirements, level of
training required for operation, equipment
availability, and data bias. Also consider which
elements, compounds, or classes of compounds the
field screening instrument is designed to analyze.
As discussed in section 2.7, the screening method
selected should be sensitive enough to minimize the
potential for false negatives. When collecting
samples for on-site analysis (e.g., XRF), evaluate
the detection limits and bias of the screening
method by sending a minimum of 10% of the
samples to an off-site laboratory for confirmation.
Table 3 summarizes the advantages and
disadvantages of selected portable field screening
equipment.
3.3 GEOPHYSICAL EQUIPMENT
Geophysical techniques can be used in conjunction
with field analytical screening to help delineate
areas of subsurface contamination, including buried
drums and tanks. Geophysical data can be obtained
relatively rapidly, often without disturbing the site.
Geophysical techniques suitable for removal
activities include: ground penetrating radar (GFR),
magnetometry, electromagnetic conductivity (EM)
and resistivity. Specific advantages and
disadvantages associated with geophysical equipment
are summarized in table 4. See also EPA ERT
Standard Operating Procedure (SOP) #2159,
General Surface Geophysics (U.S, EPA, January
1991).
3.4 SELECTING SAMPLING
EQUIPMENT
The mechanical method by which a sampling tool
collects the sample may impact representativeness.
For example, if the sampling objective is to
determine the concentrations of contaminants at
each soil horizon interface, using a hand auger
would be inappropriate: the augering technique
would disrupt and mix soil horizons, making the
precise horizon interface difficult to determine.
Depth of sampling is another factor to consider in
the proper selection of sampling equipment. A
trowel, for example, is suitable for unconsolidated
surface soils, but may be a poor choice for sampling
at 12 inches, due to changes in soil consistency with
depth.
All sampling devices should be of sufficient quality
not to contribute contamination to samples (e.g.,
painted surfaces which could chip off into the
sample). In addition, the sampling equipment
should be either easily decontaminated, or cost-
effective if considered to be expendable. Consider
ease of use when selecting sampling equipment.
Complicated sampling procedures usually require
increased training and introduce a greater likelihood
21
-------
Table 3: Portable Reid Analytical Screening Equipment
Equipment
X-ray fluorescence
(portable)
Flame ionization
detector (FID)
Photoionization
detector (PID)
Field test kits
Radiation detector
Application to
Sampling Design
Detects heavy metals
in soils.
Semi-quantitatively
detects VOCs in soils.
Detects total concentration
of VOCs and some non-
volatile organics and
inorganics in soils.
Detects specific elements,
compounds, or compound
classes in soils.
Detects the presence of selected
forms of radiation in soils or
other waste materials.
Advantages and Disadvantages
Rapid sample analysis; may be used in situ;
requires trained operator; potential matrix
interferences; may be used with a generic or site-
specific calibration model; detection limit may
exceed action level; detects to ppm level; detection
limit should be calculated on a site-specific basis.
Immediate results; can be used in GC mode to
identify specific organic compounds; detects VOCs
only; detects to ppm level.
Immediate results; easy to use; non-compound
specific; results affected by high ambient humidity
and electrical sources such as radios; does not
respond to methane; detects to ppm level.
Rapid results; easy to use; low cost; limited number
of kit types available; kits may be customized to
user needs; semi-quantitative; interferences by other
analytes is common; colorimetric interpretation is
needed; detection level dependent upon type of kit
used; can be prone to error.
Easy to use; low cost; probes for one or a
combination of alpha, beta or gamma forms of
radiation; unit and detection limits vary greatly;
detailed site surveys are time intensive and require
experienced personnel to interpret results.
Sources:
U.S, EPA, September 1988a; U.S. EPA, December 1987; U.S. EPA, 1987,
22
-------
Table 4: Geophysical Equipment
Equipment
Ground penetrating
radar (GPE)
Magnetometer
Electromagnetic
conductivity
meter (EM)
Wadi
Application to
Detects reflection anomalies caused
by lithology changes or buried
objects; varying depths of investi-
gation, 15 to 30 feet, are possible.
Detects presence and area! extent
of ferromagnetic material in
subsurface soils, including buried
metal containers. Single 55-gallon
drums can be identified at depths
up to 10 feet and large masses of
drums up to 30 feet or more.
Detects electrical conductivity
changes in subsurface geologic lith-
ology, pore fluids, and buried
objects. Depth of investigation
varies from 9 feet to 180 feet
depending on instrument used, coil
spacing, and coil configuration.
Detects electrical conductivity
changes in surface and sub-surface
materials utilizing existing very low
frequency (VLF) radio waves.
Advantages fl"d Disadvantages
Capable of high resolution; generates
continuous measurement profile; can survey
large area quickly, site specific: best results are
achieved in dry, sandy soils; clay-rich and water
saturated soils produce poor reflections and
limit depth of penetration; data interpretation
requires a trained geophysicist.
Quick and easy to operate; good initial survey
instrument; readings are often affected by
nearby man-made steel structures (including
above-pound fences, buildings, and vehicles);
data interpretation may require geophysicist.
Rapid data collection; can delineate inorganic
and large-scale organic contamination in sub-
surface fluids; sensitive to man-made structures
(including buried cables, above-ground steel
structures and electrical power lines); survey
planning and data interpretation may require
geophysicist.
Utilizes existing long-distance communication
VLF radio waves (10-30 Khz range): no need to
induce electrical field; directional problems can
be overcome with portable transmitters.
Resistivity meter
Detects electrical resistivity var-
iations in subsurface materials (e.g.,
lithology, pore fluids, buried pipe-
lines and drums). Vertical resol-
ution to depths of 100 feet are
possible.
Detects lateral and vertical variations;
instrument requires direct ground contact,
making it relatively labor intensive; sensitive to
outside interference; data interpretation requires
a trained geophysicist.
Sources : Benson, et. al. 1988; NJDEP, 1988.
23
-------
of procedural errors. Standard operating
procedures help to avoid such errors. Sample
volume is another selection concern. Specific
advantages and disadvantages of soil sampling
equipment are given in table 5. Refer also to EPA
ERT SOP #2012, Soil Sampling (in U.S. EPA,
January 1991) for guidance on using various types of
soil sampling equipment.
3.5 EXAMPLE SITE
3.5.1 Selection of
Sampling
Equipment
Dedicated plastic scoops were
used for Phase 1 soil sampling. For Phase 2, the
OSC used bucket augers for both surface and
subsurface soil sampling because of their ease of
use, good vertical depth range, and uniform surface
sampling volume. Standard operating procedures
were followed to promote proper sample collection,
handling, and decontamination. From the bucket
auger, each sample was placed into a dedicated
plastic pan and mixed using a dedicated plastic
scoop. Samples were further prepared for XRF
screening and laboratory analysis (section 4.8).
3.5.2 Selection of Field Analytical
Screening Equipment
Phase 1 sampling identified the sources and types of
on-site contaminants in order to establish a threat.
Hazard categorization techniques, organic vapor
detecting instruments, and radiation and cyanide
monitors were utilized to tentatively identify
containerized liquid wastcstrcams in order to select
initial judgmental soil sampling locations. During
Phase 2 sampling, a portable XRF unit was used to
determine the extent of contamination and to
identify additional hot spots. Samples to be sent for
laboratory analysis were then placed into sampling
jars (as discussed in section 4.8). Samples collected
from upgradient grid nodes for XRF screening only
were stored on site for later treatment/disposal.
For Phase 3, the XRF was used to confirm whether
contaminated areas identified during Phase 2 were
sufficiently excavated.
3.5.3 Selection of Geophysical
Equipment
The GPR instrument delineated buried trench and
lagoon boundaries. The EM meter detected
subsurface conductivity changes due to buried metal
containers and contaminants. The EM-31 (a
shallower-surveying instrument than the EM-34)
was selected because expected contaminant depth
was less than 10 feet and because of the
instrument's maneuverability and ease of use.
24
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Table 5: Soil Sampling Equipment
Equipment
Trier
Scoop or trowel
Annlicabilitv
Soft surface soil
Soft surface soil
Tulip bulb planter Soft soil, 0-6 in.
Soil coring device
Soft soil, 0-24 in.
Thin-wall tube sampler Soft soil, 0-10 ft
Split spoon sampler Soil, 0 in.-bedrock
Shelby tube sampler Soft soil, 0 in.-bedrock
Bucket auger
Hand-operated
power auger
Soft soil, 3 in,-10 ft
Soil, 6 in.-l5 ft
Advantages and Disadvantages
Inexpensive; easy to use and decontaminate; difficult to use
in stony, dry, or sandy soil.
Inexpensive; easy to use and decontaminate; trowels with
painted surfaces should be avoided.
Easy to use and decontaminate; uniform diameter and
sample volume; preserves soil core (suitable for VGA and
undisturbed sample collection); limited depth capability; not
useful for hard soils.
Relatively easy to use; preserves soil core (suitable for VOA
and undisturbed sample collection); limited depth capability;
can be difficult to decontaminate.
Easy to use; preserves soil core (suitable for VOA and
undisturbed sample collection); may be used in conjunction
with bucket auger; acetate sleeve may be used to help
maintain integrity of VOA samples; easy to decontaminate;
can be difficult to remove cores from sampler.
Excellent depth range; preserves soil core (suitable for VOA
and undisturbed sample collection); acetate sleeve may be
used to help maintain integrity of VOA samples; useful for
hard soils; often used in conjunction with drill rig for
obtaining deep cores.
Excellent depth range; preserves soil core (suitable for VOA
and undisturbed sample collection); tube may be used to
ship sample to lab undisturbed; may be used in conjunction
with drill rig for obtaining deep cores and for permeability
testing; not durable in rocky soils.
Easy to use; good depth range; uniform diameter and sample
volume; acetate sleeve may be used to help maintain
integrity of VOA samples; may disrupt and mix soil horizons
greater than 6 inches in thickness.
Good depth range; generally used in conjunction with bucket
auger for sample collection; destroys soil core (unsuitable for
VOA and undisturbed sample collection); requires 2 or more
equipment operators; can be difficult to decontaminate;
requires gasoline-powered engine (potential for cross-
contamination).
Sources:
NJDEP, 1988; U.S. EPA, January 1991.
25
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4.0 FIELD SAMPLE COLLECTION AND PREPARATION
4.1 INTRODUCTION
In addition to sampling equipment, field sample
collection includes sample quantity and sample
volume. Field sample preparation refers to all
aspects of sample handling after collection, until the
sample is received by the laboratory. Sample
preparation for soils may include, but is not limited
to:
removing extraneous material;
sieving samples;
homogenizing samples;
spitting samples;
compositing samples; and
final preparation.
Sample preparation depends on the sampling
objectives and analyses to be performed. Proper
sample preparation and handling help to maintain
sample integrity. Improper handling can result in a
sample becoming unsuitable for the type of analysis
required. For example, homogenizing, sieving, and
compositing samples all result in a loss of volatile
constituents and are therefore inappropriate when
volatile contaminants are the concern.
4.2 SAMPLE COLLECTION
How a sample is collected can affect its
representativeness. The greater the number of
samples collected from a site and the larger the
volume of each sample, the more representative the
analytical results will be. However, sampling
activities are often limited by sampling budgets and
project schedules. The following sections provide
guidelines on appropriate sample numbers and
volumes.
4.2.1 SAMPLE NUMBER
The number of samples needed will vary according
to the particular sampling approach that is being
used. For example, in grid sampling, one sample is
generally collected at each grid node, regardless of
grid size. As discussed in section 2.11.6, once
contaminated grid node samples are located,
adjoining grid cells can be sampled more thoroughly
to define areas of contamination. Four aliquots
from each grid cell, situated equidistant from the
sides of each cell and each other (as illustrated in
figure 9), are recommended for grid cells measuring
up to 100 x 100 feet. One additional aliquot may be
collected from the center of each cell, making a
total of five aliquots per cell For grid sizes greater
than 100 feet x 100 feet, nine aliquots, situated
equidistant from the sides of each cell and each
other (as illustrated in figure 12), are recommended.
Depending on budget and other considerations, grid
cell aliquots can be analyzed as separate samples or
composited into one or more samples per cell.
4.2.2 Sample Volume
Both sample depth and area are considerations in
determining appropriate sample volume.
Depending on the analytes being investigated,
samples are collected at the surface (0-3 in.),
extended surface (0-6 in.), and/or at one-foot depth
intervals. Non-water soluble contaminants such as
dioxin and PCBs are often encountered within the
first six inches of soil. Water-soluble contaminants
such as metals, acids, ketones, and alcohols will be
encountered at deeper depths in most soils except
clays. Contaminants in solution, such as PCPs in
diesel fuel and pesticides in solvents, can penetrate
to great depths (e.g., down to bedrock), depending
on soil type.
For surface samples, collect soil over a surface area
of one square foot per sample. A square cardboard
template measuring 12 in. x 12 in., or a round
template with a 12 in. diameter can be used to mark
sampling areas. For subsurface samples, one of
several coring devices may be used (see table 5).
Using a coring device results in a smaller diameter
sampling area than a surface template, and
therefore somewhat lessens the representativeness
of the sample.
4.3 REMOVING EXTRANEOUS
MATERIAL
Identify and discard materials in a field sample
which are not relevant or vital for characterizing the
sample or the site, since their presence may
introduce an error in the sampling or analytical
procedures. Examples of extraneous material in soil
samples include pieces of glass, twigs or leaves.
However, not all non-soil material is extraneous.
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Rgure 12: Phase 2 Sampling Grid Cell
Diagram (Grid Sizes > 100
x 100 ft.)
GRID NODE
COMPOSITE ALIQUOTS
For example, when sampling at a junkyard, lead-
contaminated battery casing pieces should not be
removed from a sample if the casing composes
more than 10% of the sample composition. For a
sample to be representative, it must also incorporate
the lead from the casing. Collect samples of any
material thought to be a potential source of
contamination for a laboratory extraction procedure.
Discuss any special analytical requirements for
extraneous materials with project management,
geologists, and chemists and notify the laboratory of
any special sample handling requirements.
4.4 SIEVING SAMPLES
Sieving is the process of physically sorting a sample
to obtain uniform particle sizes, using sieve screens
of predetermined size. For example, the sampler
may wish to sieve a certain number of samples to
determine if particle size is related to contaminant
distribution. In the Removal Program, sieving is
generally only conducted when preparing soil
samples for XRF screening. For this purpose, a 20-
mesh screen size is recommended.
Be aware of the intent of the sampling episode,
when deciding whether to sieve a sample prior to
analysis. Prior to sieving, samples may need to be
oven-dried. Discarding non-soil or non-sieved
materials, as well as the sieving process itself, can
result in physical and chemical losses. Sieving is not
recommended where volatile compounds are of
concern. Analyze the discarded materials, or a
fraction thereof, to determine their contribution to
the contamination of the site being investigated.
4.5 HOMOGENIZING SAMPLES
Homogenization is the mixing or blending of a soil
sample in an attempt to provide uniform
distribution of contaminants. (Do not homogenize
samples for volatile compound analysis). Ideally,
proper homogenization ensures that portions of the
containerized samples are equal or identical in
composition and are representative of the total soil
sample collected. Incomplete homogenization will
increase sampling error. All samples to be
composited or split should be homogenized after all
aliquots have been combined. Manually
homogenize samples using a stainless steel spoon or
scoop and a stainless steel bucket, or use a
disposable scoop and pan. Quarter and split the
sample as illustrated in figure 12, repeating each
step a minimum of 5 times until the sample is
visually homogenized. Samples can also be
homogenized using a mechanically-operated stirring
device as depicted in ASTM standard D422-63.
4.6 SPLITTING SAMPLES
Splitting samples after collection and field
preparation into two or more equivalent parts is
performed when two or more portions of the same
sample need to be analyzed separately. Split
samples are most often collected in enforcement
actions to compare sample results obtained by EPA
with those obtained by the potentially responsible
party (PRP). Split samples also provide a measure
of the sample variability, and a measure of the
analytical and extraction errors. Before splitting,
follow homogenization techniques outlined above.
Fill two sample collection jars simultaneously with
alternate spoonfuls (or scoopfuls) of homogenized
sample. To simultaneously homogenize and split a
sample, quarter (as illustrated in figure 13) or
mechanically split the sample using a riffle sample
splitter. The latter two techniques are described in
detail in ASTM Standard C702-87.
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Figure 13: Quartering to Homogenize and Split Samples
Stepl:
* Cone Sample on Hard Clean Surface
* Mix by Forming New Cone
Stepl:
• Quarter After Flattening Cone
Step 3:
Divide Sample
into Quarters
Step 4:
* Remix Opposite Quarters
* Reform Cone
* Repeat a Minimum of 5 Times
After: ASTM Standard C702-87
4.7 COMPOSITING SAMPLES
Compositing is the process of physically combining
and homogenizing several individual soil aliquots.
Compositing samples provides an average
concentration of contaminants over a certain
number of sampling points, which reduces both the
number of required lab analyses and the sample
variability. Compositing can be a useful technique,
but must always be implemented with caution.
Compositing is not recommended where volatile
compounds are of concern.
Specify the method of selecting the aliquots that are
composited and the compositing factor in the
sampling plan. The compositing factor is the
number of aliquots to be composited into one
sample (e.&, 3 to 1; 10 to 1). Determine this factor
by evaluating detection limits for parameters of
interest and comparing them with the selected
action level for that parameter. Compositing also
requires that each discrete aliquot be the same in
terms of volume or weight, and that the aliquots be
thoroughly homogenized. Since compositing dilutes
high concentration aliquots, the applicable detection
limits should be reduced accordingly. If the
composite value is to be compared to a selected
action level, then the action level must be divided by
the number of aliquots that make up the composite
in order to determine the appropriate detection
limit (e.g., if the action level for a particular
substance is 50 ppb, an action level of 10 ppb
should be used when analyzing a 5-aliquot
composite). The detection level need not be
reduced if the composite area is assumed to be
homogeneous in concentration (for example, stack
emission plume deposits of particulate
contamination across an area, or roadside spraying
of waste oils).
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4.8 FINAL PREPARATION
Select sample containers on the basis of
compatibility with the material being sampled,
ttsistance to breakage, and volume. For soil
sampling, use wide-mouth glass containers with
Teflon-lined fids. Appropriate sample volumes and
containers will vary according to the parameter
being analyzed. Keep low and medium
concentration soil samples to be analyzed for
organic constituents at 4°C. Actual sample volumes,
appropriate containers, and holding times are
specified in the QA/QC Guidance far Removal
Activities (U.S. EPA, April 1990), in 40 CFR 136,
and in the Compendium of ERT Soil Sampling and
Surface Geophysics (U.S. EPA, January 1991).
Package all samples in compliance with Department
of Transportation (DOT) or International Air
Transport Association (IATA) requirements.
It is sometimes possible to ship samples to the
laboratory directly in the sampling equipment For
example, the ends of a Shelby tube can be sealed
with caps, taped, and sent to the laboratory for
analysis. To help maintain the integrity of VOA
samples, collect soil cores using acetate sleeves and
send the sleeves to the laboratory. To ensure the
integrity of the sample after delivery to the
laboratory, make laboratory sample preparation
procedures part of all laboratory bid contracts.
4.9 EXAMPLE SITE
After placing each sample in a
dedicated pan and mixing (as
discussed in section 3.5.1), plant
matter, stones, and broken glass
were removed. Soil samples
were oven-dried (at 104° C) and sieved using a 20-
mesh screen in preparation for XRF analysis.
Samples were then homogenized and split using the
quartering technique. Opposite quarters were
remixed and quartering was repeated five times to
ensure thorough hotnogenization, A portion of
each sample was placed into XRF analysis cops for
screening. The remainder of each sample was
placed into 8-ounce, wide-mouth glass jars with
Teflon-lined lids and sent to a laboratory for
inorganic analysis. The samples were packaged in
compliance with IATA requirements. Chain-of-
custody paperwork was prepared for the samples.
Laboratory paperwork was completed as
appropriate and the samples were shipped to the
predesignated laboratories for analysis.
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5.0 QUALITY ASSURANCE/QUALITY CONTROL EVALUATION
5.1 INTRODUCTION
The goal of representative sampling is to collect
samples which yield analytical results that accurately
depict site conditions during a given time frame.
The goal of quality assurance/quality control
(QA/QC) is to identify and implement correct
methodologies which limit the introduction of error
into the sampling and analytical procedures,
ultimately affecting the analytical data.
QA/QC samples evaluate the degree of site
variation, whether samples were cross-contaminated
during sampling and sample handling procedures, or
if a discrepancy in sample results is due to
laboratory handling and analysis procedures.
The QA/QC sample results are used to assess the
quality of the analytical results of waste and
environmental samples collected from a site.
5.2 QA/QC OBJECTIVES
Three QA/QC objectives (QA1, QA2, and QA3)
have been defined by die Removal Program, based
on the EPA QA requirements for precision,
accuracy (bias), representativeness, completeness,
comparability, and detection level. The QA1
objective applies when a large amount of data are
needed quickly and relatively inexpensively, or when
preliminary screening data, which do not need to be
anatyte or concentration specific, are useful. QA1
requirements are used with data from field
analytical screening methods, for a quick,
preliminary assessment of site contamination.
Examples of QA1 activities include; determining
physical and/or chemical properties of samples;
assessing preliminary on-site health and safety;
determining the extent and degree of contamination;
assessing waste compatibility; and characterizing
hazardous wastes.
QA2 verifies analytical results. The QA2 objective
intends to provide a certain level of confidence for
a select portion (10% or more) of the preliminary
data. This objective allows the OSC to use field
screening methods to quickly focus on specific
pollutants and concentration levels, while at the
same time requiring laboratory verification and
quality assurance for at least 10% of the samples,
QA2 verification methods are analyte specific
Examples of QA2 activities include; defining the
extent and degree of contamination; verifying site
cleanup; and verifying screening objectives
obtainable with QA1, such as pollutant
identification.
QA3 assesses the analytical error of the
concentration level, as well as the identity of the
analyte(s) of interest QA3 data provide the highest
degree of qualitative and quantitative accuracy and
confidence of all QA objectives by using rigorous
methods of laboratory analysis and quality
assurance. Examples of QA3 activities include:
selecting treatment and disposal options; evaluating
health risk or environmental impact; verifying
cleanup; and identifying pollutant source. The QA3
objective should be used only when determination
of analytical precision in a certain concentration
range is crucial for decision-making.
5.3 SOURCES OF ERROR
Identifying and quantifying the error or variation hi
sampling and laboratory analysis can be difficult.
However, it is important to limit their effect(s) on
the data. Four potential sources of error are:
* sampling design;
* sampling methodology;
* sample heterogeneity; and
* analytical procedures.
5.3.1 Sampling Design
Site variation includes the variation both in the
types and in the concentration levels of
contaminants throughout a site. Representative
sampling should accurately identify and define this
variation. However, error can be introduced by the
selection of a sampling design which "misses* site
variation. For example, a sampling grid with
relatively large distances between sampling points or
a biased sampling approach (i.e., judgmental
sampling) may allow significant contaminant trends
to go unidentified, as illustrated in figure 14.
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Figure 14; Sampling Error Due
to Sampling Design
LEGEND
X SAMPLING POINTS
CONTAMINATED SOIL
SOURCE OF CONTAMINATION
5.3.2 Sampling Methodology
Error can be introduced by the sampling
methodology and sample handling procedures, as in
cross-contamination from inappropriate use of
sample collection equipment, unclean sample
containers, improper sampling equipment
decontamination and shipment procedures, and
other factors. Standardized procedures for
collecting, handlin and shipping samples allow for
easier identification of the source(s) of error, and
can limit error associated with sampling
methodology. The use of standard operating
procedures ensures that all sampling tasks for a
given matrix and analyte win be performed in the
same manner, regardless of the individual sampling
team, date, or location of sampling activity. Trip
blanks, field blanks, replicate samples, and rinsate
blanks are used to identify error due to sampling
methodology and sample handling procedures.
5.3.3 Sample Heterogeneity
Sample heterogeneity is a potential source of error.
Unlike water, soil is rarely a homogeneous medium
and it exhibits variable properties with lateral
distance and with depth. This heterogeneity may
also be present in the sample container unless die
sample was homogenized in the field or in the
laboratory. The laboratory uses only a small aliquot
of the sample for analysis; if the sample is not
properly homogenized, the analysis may not be truly
representative of the sample and of the
corresponding site. Thoroughly homogenizing
samples, therefore, can limit error associated with
sample heterogeneity.
5.3.4 Analytical Procedures
Error which may originate in analytical procedures
includes cross-contamination, inefficient extraction,
and inappropriate methodology. Matrix spike
samples, replicate samples, performance evaluation
samples, and associated quality assurance evaluation
of recovery, precision, and bias, can be used to
distinguish analytical error from error introduced
during sampling activities.
5.4 QA/QC SAMPLES
This section briefly describes the types and uses of
QA/QC samples that are collected in the field, or
prepared for or by the laboratory. QA/QC samples
are analyzed in addition to field samples and
provide information on the variability and usability
of environmental sample results. They assist in
identifying the origin of analytical discrepancies to
help determine how the analytical results should be
used. They are used mostly to validate analytical
results. Field replicate, collocated, background, and
rinsate blank samples are the most commonly
collected field QA/QC samples. Performance
evaluation, matrix spike, and matrix spike duplicate
samples, either prepared for or by the laboratory,
provide additional measures of control for the data
generated. QA/QC results may suggest the need
for modifying sample collection, preparation,
handling, or analytical procedures if the resultant
data do not meet site-specific quality assurance
objectives. Refer to data validation procedures in
U.S. EPA, April 1990, for guidelines on utilizing
QA/QC analytical results. The following
paragraphs briefly describe each type of QA/QC
sample.
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5.4.1 Field Replicates
Field replicates are field samples obtained from one
location, homogenized, divided into separate
containers and treated as separate samples
throughout the remaining sample handling and
analytical processes. These samples are used to
assess error associated with sample heterogeneity,
sample methodology and analytical procedures. Use
field replicates when determining total error for
critical samples with contamination concentrations
near the action level For statistical analysis to be
valid in such a case, a minimum of eight replicate
samples would be required.
5.4.2 Collocated Samples
Collocated samples are collected adjacent to the
routine field sample to determine local variability of
the soil and contamination at the site. Typically,
collocated samples are collected about one-half to
three feet away from the selected sample location.
Analytical results from collocated samples can be
used to assess site variation, but only in the
immediate sampling area. Due to the non-
homogeneous nature of soil at sites, collocated
samples should not be used to assess variability
across a site and are not recommended for assessing
error. Determine the applicability of collocated
samples on a site-by-site basis. Collecting many
samples (more than SO samples/acre), is sufficient
to demonstrate site variation.
5.4.3 Background Samples
Background samples are collected upgradient of the
area(s) of contamination (either on or off site)
where there is little or no chance of migration of
the contaminants of concern. Background samples
determine the natural composition of the soil
(especially important in areas with high
concentrations of nanirally-occurring metals) and
are considered "dean" samples. They provide a
basis for comparison of contaminant concentration
levels with samples collected on site. At least one
background soil sample should be collected;
however, more are warranted when site-specific
factors such as natural variability of local soil,
multiple on-site contaminant source areas, and
presence of off-site facilities potentially contributing
to soil contamination east. Background samples
may be collected for all QA objectives, in order to
evaluate potential error
associated with sampling design, sampling
methodology, and analytical procedures.
5.4.4 Rlnsate Blanks
Rinsate blanks are samples obtained by running
analyte-free water over decontaminated sampling
equipment to test for residual contamination. The
blank is placed in sample containers for handling,
shipment, and analysis identical to the samples
collected that day. A rinsate blank is used to assess
cross-contamination brought about by improper
decontamination procedures. Where dedicated
sampling equipment is not utilized, collect one
rinsate blank, per type of sampling device, per day
to meet QA2 and OA3 objectives.
5,4.5 Performance Evaluation
Samples
Performance evaluation (PE) samples evaluate the
overall bias of the analytical laboratory and detect
any error in the analytical method used. These
samples are usually prepared by a third party, using
a quantity of analyte(s) which is known to the
preparer but unknown to the laboratory, and always
undergo certification analysis. The analyte(s) used
to prepare the PE sample is the same as the
anaryte(s) of concern. Laboratory procedural error
is evaluated by the percentage of analyte identified
in the PE sample (percent recovery). Even though
they are not available for all analytes, PE samples
are required to achieve QA3 objectives. Where PE
samples are unavailable for an analyte of interest,
QA2 is the highest QA standard achievable,
5.4.6 Matrix Spike Samples
Matrix spike and matrix spike duplicate samples
(MS/MSDs) are environmental samples that are
spiked in the laboratory with a known concentration
of a target analyte(s) to verify percent recoveries.
MS/MSDs are primarily used to check sample
matrix interferences. They can also be used to
monitor laboratory performance. However, a
dataset of at least three or more results is necessary
to distinguish between laboratory performance and
matrix interference.
MS/MSDs can also monitor method performance.
Again, a dataset is helpful to assess whether a
method is performing properly. Generally,
33
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interference and poor method performance go
together.
MS/MSDs can also evaluate error due to laboratory
bias and precision (when four or more pairs are
analyzed). Analyze one MS/MSD pair to assess
bias for every 20 soil samples. Use the average
percent recovery for the pair. To assess precision,
analyze at least 8 matrix spike replicates from the
same sample, determine the standard deviation and
the coefficient of variation. See pages 9 - 10 of the
QA/QC Guidance for Removal Activities (U.S, EPA,
April 1990) for procedures on calculating analytical
error. MS/MSDs are optional for QA2 and
required to meet QA3 objectives as one of several
methods to determine analytical error.
5.4.7 Reid Blanks
Reid blanks are samples prepared in the field using
certified dean sand or soil and are then submitted
to the laboratory for analysis. A field blank is used
to evaluate contamination error associated with
sampling methodology and laboratory procedures.
If available, submit field blanks at a rate of one per
day.
5.4.8 Trip Blanks
Trip blanks are samples prepared prior to going
into the field. Trip blanks consist of certified clean
sand or soil and are handled, transported, and
analyzed in the same manner as the other volatile
organic samples acquired that day. Trip blanks are
used to evaluate error associated with sampling
methodology and analytical procedures by
determining if any contamination was introduced
into samples during sampling, sample handling and
shipment, and/or during laboratory handling and
analysis. If available, utilize trip blanks to meet
QA2 and QA3 objectives for volatile organic
analyses only.
5.5 EVALUATION OF ANALYTICAL
ERROR
The percentage and types of QA/QC samples
needed to help identify the error and confidence in
the data is based on the sampling objectives and the
corresponding QA/QC objectives. The acceptable
level of error is determined by the intended use of
the data and the sampling objectives, including such
factors as: the degree of threat to public health,
welfare, or the environment; selected action levels;
litigation concerns; and budgetary constraints.
The use of replicate samples is one method to
evaluate error. To evaluate the total error of
samples with contaminant concentrations near the
selected action level, prepare and analyze a
minimum of eight replicates of the same sample.
Analytical data from replicate samples can also be
used for a quick check on errors associated with
sample heterogeneity, sample methodology and
analytical procedures. Differing analytical results
from two or more replicate samples could indicate
improper sample preparation (e.g., incomplete
homogenization), or that contamination was
introduced during sample collection, preparation,
handling, shipment, or analysis.
It may be desirable to try to quantify confidence;
however, quantification or analytical data correction
is not always possible. A 95% confidence level (i.e.,
5% acceptable error) should be adequate for most
Removal Program sampling activities. Experience
will provide the best determination of whether to
use a higher (e.g., 99%) or lower (e.g., 90%) level
of confidence. It must be recognized that the use of
confidence levels is based on the assumption that a
sample is homogeneous. See also section 6.8 for
information on total error.
5.6 CORRELATION BETWEEN
FIELD SCREENING RESULTS
AND CONFIRMATION RESULTS
One cost-effective approach for delineating the
extent of site contamination is to correlate
inexpensive field screening data and other field
measurements (e.g., XRF, soil-gas measurements)
with laboratory results. The relationship between
the two methods can then be described by a
regression analysis and used to predict laboratory
results based on field screening measurements. In
this manner, cost-effective field screening results
may be used in addition to, or in lieu of, off-site
laboratory sample analysis.
Statistical regression involves developing a model
(equation) that relates two or more variables at an
acceptable level of correlation. When field
screening techniques, such as XRF, are used along
with laboratory methods (e-g., atomic absorption
(AA)), a regression equation can be used to predict
a laboratory value based on the results of the
34
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screening device. The model can also be used to
place confidence limits around predictions.
Additional discussion of correlation and regression
can be found in most introductory statistics
textbooks. A simple regression equation (e.g.,
linear) can be developed on many calculators or
computer databases; however, a statistician should
be consulted to check the accuracy of more complex
models.
Evaluation of the accuracy of a model in part relies
on statistical correlation. Statistical correlation
involves computing an index called the correlation
coefficient (r) that indicates the degree and nature
of the relationship between two or more sets of
values. The correlation coefficient ranges from
-1.0 (a perfect inverse or negative relationship),
through 0 (no relationship), to +1.0 (a perfect
direct, or positive, relationship). The square of the
correlation coefficient, called the coefficient of
determination, or simply R2, is an estimate of the
proportion of variance in one variable (the
dependent variable) that can be accounted for by
the independent variables. The R2 value that is
acceptable depends on the sampling objectives and
intended data uses. As a rule of thumb, statistical
relationships should have an R2 value of at least 0.6
to determine a reliable model; however, for health
or risk assessment purposes, the acceptable Ra value
may be made more stringent (e.g., 0.8). Analytical
calibration regressions have an R2 value of 0.98 or
better.
Once a reliable regression equation has been
derived, the field screening data can be used to
predict laboratory results. These predicted values
can then be located on a base map and contoured
(mapping methods are described in chapter 6).
These maps can be examined to evaluate the
estimated extent of contamination and the adequacy
of the sampling program.
5.7 EXAMPLE SITE
The field screening of
containerized liquid wastes
performed during Phase 1
utilized the QA1 objective. The
purpose of this screening was to
quickly obtain data indicating general chemical
class. The screening did not need to be analyte or
concentration specific nor was confirmation of the
results needed. The Phase 1 sampling was
performed according to the QA2 objective. The
analyses were analyte and concentration specific.
Confirmational analysis was run on 10% of the
samples in order to verify screening results.
Recoveries of matrix spike and matrix spike
duplicate samples indicated no matrix interferences.
Dedicated equipment was used during Phase 1
sampling, making rinsate blanks unnecessary. Phase
2 field screening (XRF) was performed according to
the QA2 objective. During Phase 2, samples were
collected at 30% of the nodes screened with the
XRF. These samples were sent for laboratory AA
analysis. A correlation was established by plotting
the Phase 2 AA and XRF data. This allowed the
XRF data from the other 70% of the nodes to be
used to evaluate the chromium levels across the site.
For Phase 2 and 3 sampling, 10% of the data were
confirmed by running replicate analyses to obtain an
estimate of precision. The results indicated good
correlation. Matrix spikes and matrix spike
duplicate samples indicated no matrix interferences.
During Phase 2, the OSC opted to include
performance evaluation (PE) samples for metals to
evaluate the overall laboratory bias (although not
required for QA2 data quality). The laboratory
achieved 92% recovery, which was within the
acceptable control limits.
During Phases 2 and 3, a rinsate blank was
collected each day. Following the decontamination
of the bucket augers, anal vte-free water was poured
over the augers and the rinsate was placed into 1-
liter polyethylene bottles and preserved. The
rinsate blanks were analyzed for total metals and
cyanide to determine the effectiveness of the
decontamination procedures and the potential for
cross-contamination. All rinsate blank samples
were "clean", indicating sufficient decontamination
procedures.
The correlation analysis run on Phase 2 laboratory
(AA) data and corresponding XRF values resulted
in r values of 0.97 for both surface and subsurface
data, which indicated a strong relationship between
the AA and XRF data. Following the correlation
analyses, regression analyses were run and equations
to predict laboratory values based on the XRF data
were developed. The resulting equation for the
surface data was: AA = 0.87 (XRF) + 10.16. The
resulting regression equation for the subsurface data
was: AA » 0.94 (XRF) + 0.30.
35
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36
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6.0 DATA PRESENTATION AND ANALYSIS
6.1 INTRODUCTION
Data presentation and analysis techniques are
performed with analytical, geophysical, or field
screening results. Hie techniques discussed below
can be used to compare analytical values, to
evaluate numerical distribution of data, to
determine and illustrate the location of hot spots
and the extent of contamination across a site, and to
assess the need for removal of contaminated soil
with concentrations at or near the action level. The
appropriate methods to present and analyze sample
data depend on the sampling objectives, the number
of samples collected, the sampling approaches used,
and a variety of other considerations.
6.2 DATA POSTING
Data posting involves placement of sample values
on a site basemap. Data posting is useful for
displaying the spatial distribution of sample values
to visually depict extent of contamination and to
locate hot spots. Data posting requires each sample
to have a specific location (e.g., X and Y
coordinates). Ideally, the sample coordinates would
be surveyed values to facilitate placement on a
scaled map.
between sample points. Contour lines can be drawn
manually or be generated by computer using
contouring software. Although the software makes
the contouring process easier, computer programs
have a limitation: they may interpolate between all
data points, attempting to fit a contour interval to
the full range of data values. This can result in a
contour map that does not accurately represent
general site contaminant trends. Typical removal
sites have low concentration/non-detect areas and
hot spots. Computer contouring programs may
represent these features as in figure 15 which
illustrates a site that has a 4000 mg/kg hot spot.
Because there is a large difference in concentration
between the hot spot and the surrounding area, the
computer contouring program used a contour
interval that eliminated most of the subtle site
features and general trends. However, if that same
hot spot concentration value is posted at a reduced
value, then the contouring program can select a
more appropriate contour interval to better
illustrate the general site trends. Figure 16 depicts
the same site as in figure 15 but the hot spot
concentration value has been arbitrarily posted at
1400 mg/kg. The map was recontoured and the
contouring program selected a contour interval that
resulted in a map which enhanced the subtle detail
and general site contaminant trends.
6.3 GEOLOGIC GRAPHICS
Geologic graphics include cross-sections and fence
diagrams, which are two- and three-dimensional
depictions, respectively, of soils and strata to a given
depth beneath the site. These types of graphics are
useful for posting subsurface analytical data as well
as for interpreting subsurface geology and
contaminant migration.
6.4 CONTOUR MAPPING
Contour maps are useful for depicting contaminant
concentration values throughout a site. Contour
mapping requires an accurate, to-scale basemap of
the site. After data posting sample values on the
basemap, insert contour fines (or isopleths) at a
specified contour interval, interpolating values
6.5 STATISTICAL GRAPHICS
The distribution or spread of the data set is
important in determining which statistical
techniques to use. Common statistical analyses such
as the t-test relies on normally distributed data.
The histogram is a statistical bar graph which
displays the distribution of a data set. A normally
distributed data set takes the shape of a bell curve,
with the mean and median dose together about
halfway between the maximum and minimum
values. A probability plot depicts cumulative
percent against the concentration of the
contaminant of concern. A normally distributed
data set, when plotted as a probability plot, would
appear as a straight line. Use a histogram or
probability plot to see trends and anomalies in the
data prior to conducting more rigorous forms of
statistical analysis.
37
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Figure 15: Computer Generated Contour Map (4000 mg/kg Hot Spot)
ABC Plating Site
EAST-WEST COORDINATES
Total Chromium Concentration
Units = mo/kg
Contour Interval - 100 mg/kg
Includes 4000 mg/kg Hot Spot
Rgure 16: Computer Generated Contour Map (1400 mg/kg Hot Spot)
ABC Plating Site
Total Chromium Concentration
Units = mg/kg
Contour Interval = 100 mg/kg
Includes 1400 mg/kg Hot Spot*
EAST-UEST COORDINATES
1400 mg/kg hot spot is substituted for
4000 mg/kg hot spot (see section 6.4
~ Contour Mapping)
38
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6.6 GEOSTATISTICS
6.8 UTILIZATION OF DATA
Geostatistical methods are useful for data analysis
and presentation. The characteristic feature of
geostatistics is the use of variograms to quantify and
model the spatial relationship between values at
different sampling locations and for interpolating
(e.g., kriging) estimated values across a site. The
geostatistical analysis can be broken down into two
phases. First, a model is developed that describes
the spatial relationship between sample locations on
the basis of a plot of spatial variance versus the
distance between pairs of samples. This plot is
called a variogram. Second, the spatial relationship
modeled by the variogram is used to compute a
weighted-average interpolation of the data. The
result of geostatistical mapping by data interpolation
is a contour map that represents estimates of values
across a site, and maps depicting potential error in
the estimates. The error maps are useful for
deciding if additional samples are needed and for
calculating best or worst-case scenarios for site
cleanup. More information on geostatistics can be
found in U.S. EPA, September 1988b and U.S.
EPA, 1990. Geo-EAS and GEOPACK,
geostatistical environmental assessment software
packages developed by U.S. EPA, can greatly assist
with geostatistical analysis methods.
6.7 RECOMMENDED DATA
INTERPRETATION METHODS
The data interpretation method chosen depends on
project-specific considerations, such as the number
of sampling locations and their associated range in
values. A site depicting extremely low data values
(e.g., non-detects) with significantly higher values
(e.g., 5,000 ppm) from neighboring hot spots, with
little or no concentration gradient in-between, does
not lend itself to contouring and geostatistics,
specifically the development of variograms.
However, data posting would be useful at such a
site to illustrate hot spot and dean areas.
Conversely, geostatistics and contour mapping, as
well as data posting, can be applied to site data with
a wide distribution of values (i.e., depicting a "bell
shaped" curve) with beneficial results.
When conducting search sampling to determine the
locations of hot spots (as discussed in section 2.9),
analyze the dau> using one of the methods discussed
in this chapter. For each node that is determined to
be close to or above the action level, the following
procedure is recommended.
Investigate all neighboring grid cells to determine
which areas must be excavated and/or treated.
From each grid cell, take a composite sample
consisting of four or more aliquots, using the
procedure described in section 2.11.6. Grid cells
with contaminant concentrations significantly above
the action level (e.g., 20%) should be marked for
removal. Grid cells with contaminant
concentrations significantly less than the action level
should be designated as dean. For grid cells with
contaminant concentrations dose to the action level,
it is recommended that additional sampling be done
within that grid cell to determine whether it is truly
a hot spot, or whether the analytical result is due to
sampling and/or analytical procedural error. If
additional sampling is to be performed, one of the
following methods should be considered:
* Collect a minimum of four grab samples within
the grid cell in question. Use these samples to
develop a 95% confidence interval around the
mean concentration. If the action level falls
within or below this confidence interval, then
consider removal/treatment of the soil within
that grid cell. More information on confidence
intervals and standard deviation can be found
in Gilbert, 1987.
* Collect additional composite samples from the
grid cells in question using the technique
discussed in section 2.11.6. From these
additional samples, determine the need for
removal/treatment.
These two practical approaches help to determine
the total error associated with collecting a sample
from a non-homogeneous site. Total error includes
design error, sampling error, non-homogeneous
sampling error, and analytical error.
If additional sampling is being considered, weigh the
cost-effectiveness of collecting the additional
samples versus removing the soil from the areas in
question. This decision must be made on a site-by-
site basis.
39
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After removal/treatment of the contaminated soil,
re-investigate the grid cells to verify cleanup below
the action level. Each grid cell that had soil
removed must either be composite sampled again,
or have multiple grab samples collected with a 95%
confidence interval set up again. Again, this
decision must be made on a site-by-site basis. The
methodology should be repeated until all grid cells
are determined to have soil concentrations below
the action level
6.9 EXAMPLE SITE
The Phase 2 XRF/atomic
absorption (AA) data were
examined to determine the
appropriate data interpretation
method to use. A histogram
was generated to illustrate the distribution of the
data as depicted in figure 17. The histogram
showed an uneven distribution of the data with most
values less than X (approximately 4 on the LN
scale of the histogram). Also, the presence of a
single data point of 4000 (8 on the LN scale) was
shown on the histogram. The data were initially
posted as illustrated in figures 18 and 19. Data
posting was performed manually to give the OSC a
quick depiction of the general site contamination
trends. A contour mapping program was used to
generate contours based on the posted data. Figure
15 illustrates the results of contouring with the 4000
mg/kg hot spot included. This contour map
exaggerated the hot spot while eliminating the
subtle site features and contaminant trends. Figure
16 depicts the same site data with the hot spot
arbitrarily reduced to 1400 mg/kg. The resulting
contour map enhanced more of the subtle site
features and trends while reducing the effects of the
hot spot.
AA concentrations predicted by the regression
equations were kriged and contoured using Geo-
EAS (figures 20 and 21). Both the kriged contours
and the data posting showed the same general site
contaminant trends. However, data posting gave a
more representative depiction of actual levels of
contamination and the OSC used data posting for
decision-making.
For each node with chromium concentrations dose
to or above die 100 ppm action level, the adjacent
grid cells were further investigated. Composite
samples consisting of four aliquots of soil were
taken from within each grid cell in question and
analyzed. If the soil concentration level was
significantly below 100 ppm of chromium, the cell
was designated as clean. Each cell that had a soil
concentration level well above the action level was
marked for treatment/removal. Any cells having
soil concentrations dose to the action level were
sampled further using the compositing method to
better quantify the actual contaminant
concentration. Since the surrounding area is
residential, on-site landfilling was not considered a
viable treatment option. To expedite
treatment/disposal, all excavated soil from
contaminated cells was stockpiled on site until
treatment/disposal could be accomplished under a
fixed-price contract. The stockpile, placed in the
area of the most highly contaminated grid cells
(where the lagoons were located), was covered until
treatment/disposal could be arranged. Cleanup was
verified with composite sampling in the excavated
cells. Results of the composite sampling were
compared with the action level to verify cleanup.
All action levels were met. The excavation pits
were filled with stone and clean soil, covered with
lopsoil, graded and seeded.
40
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Figure 17: Histogram of Surface Chromium Concentrations
ABC Plating Site
Histogram
Data rilei Jo>j»supf ,
-------
Figure 18: Phase 2 Surface Data Posting for Chromium
ABC Plating Site
re
is
»
rr
.--BATE CAST-WEST GRID COORDINATES)
11
.* .'FEMCE
SCALE IN FEET
100 50 0
100
LEGEND
DAMAGED
BUILDING
AREA
< 100 ppm
100 - 500 ppm
> 500 ppm
---SITE BOUNDARY
42
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Figure 19: Phase 2 Subsurface Data Posting for Chromium
ABC Plating Site
Y9
n
Tf
a
n
§
x Y4
i*
.•"-«• G*TE (EAST-VEST C3HD CDDRD1NATCS>
I I
SCALE IN FEET
100 50
100
LEGEND
DAMAGED
BUILDING
AREA
< 100 ppm
100 - 500 ppm
> 500 ppm
StTE BOUNDARY
43
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Rgure 20: Contour Map of Surface Chromium Data (ppm)
ABC Plating Site
400.
350.
300.
250.
WO,
ISO.
100.
50.0
£0.0'
JO.O-
100. 150. 200. 25O. 300. 390.
Eost-WMt Grid Coortlnotw
Figure 21: Contour Map of Subsurface Chromium Data (ppm)
ABC Plating Site
400.
I
250.
200.
1SO.
100.
50.0
100. iso. 200. zso. ae&
Emrt-W«nrt Grid Coordinate
3SO.
44
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