OSWER Directive 9360.4-16
EPA xxx/x-xx/xxx
PBxx-xxxxxx
December 1995
SUPERFUND PROGRAM
REPRESENTATIVE SAMPLING GUIDANCE
VOLUME 5: WATER AND SEDIMENT
PART I -- Surface Water and Sediment
Interim Final
Environmental Response Team
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC 20460
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Notice
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved
for publication.
The policies and procedures established in this document are intended solely for the guidance of government
personnel for use in the Superfund 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 water sampling procedures, refer to the U. S. EPA Compendium ofERT Surface Water and
Sediment Sampling Procedures, OSWER Directive 9360.4-03. Topics covered in the compendium include sampling
equipment decontamination, surface water and sediment sampling procedures, sampling equipment, and quality
assurance/quality control (QA/QC) methods.
Please note that the procedures in this document should be used only by individuals properly trained and certified
under a 40-hour hazardous waste site training course that meets the requirements set forth in 29 CFR 1910.120(e)(3).
This document should not be used to replace or supersede any information obtained in a 40-hour hazardous waste site
training course.
Questions, comments, and recommendations are welcomed regarding the Superfund Program Representative
Sampling Guidance, Volume 5 Water and Sediment, Part I - Surface Water and Sediment. Send remarks to:
Mr. William A. Coakley
Chairman, Representative Sampling Committee
U.S. EPA-ERT
Rantan Depot - Building 18, MS-101
2890 Woodbridge Avenue
Edison, NJ 08837-3679
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Disclaimer
This document has been reviewed under 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 following trade name is mentioned in this document:
Teflonฎ is a registered trademark of E.I. DuPont de Nemours and Company of Wilmington, Delaware.
in
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Contents
Notice ii
Disclaimer iii
List of Figures vii
List of Tables vii
1.0 INTRODUCTION 1
1.1 Objective and Scope 1
1.2 Characteristics of Surface Water and Sediment 1
1.2.1 Surface Water 1
1.2.2 Sediment 3
1.3 Representative Sampling 4
1.4 Conceptual Site Model 4
1.5 Representative Sampling Objectives 6
1.5.1 Determine Hazard and Identify Contaminant 6
1.5.2 Establish Imminent or Substantial Threat 6
1.5.3 Determine Long-Term Threat 6
1.5.4 Develop Containment and Control Strategies 6
1.5.5 Identify Available Treatment/Disposal Options 6
1.5.6 Verify Treatment Goals or Clean-up Levels 7
1.6 Example Site 7
2.0 SURFACE WATER AND SEDIMENT SAMPLING DESIGN 8
2.1 Introduction 8
2.2 Sampling Plan 8
2.2.1 Historical Data Review 9
2.2.2 Site Reconnaissance 9
2.2.3 Physiographic and Other Factors 9
2.3 Migration Pathways and Receptors 10
2.4 Surface Water and Sediment Sample Types 11
2.4.1 Grab Sample 11
2.4.2 Composite Sample 11
2.5 Surface Water and Sediment Characteristics 12
2.6 Sampling Considerations 12
2.7 Quality Assurance Considerations 12
2.8 Data Quality Objectives 13
2.9 Analytical Screening 13
2.10 Analytical Parameters 13
2.11 Representative Sampling Approaches 14
2.11.1 Judgmental Sampling 14
2.11.2 Random Sampling 14
2.11.3 Systematic Grid Sampling 15
2.11.4 Systematic Random Sampling 17
2.11.5 Transect Sampling 17
2.11.6 Stratified Sampling 18
2.11.7 Three Dimensional (3D) 18
2.12 Sampling Locations and Numbers 18
IV
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2.13 Example Site 19
2.13.1 Background 19
2.13.2 Historical Data Review and Site Reconnaissance 19
2.13.3 Identification of Migration Pathways, Transport Mechanisms, and Receptors 21
2.13.4 Sampling Objectives 21
2.13.5 Selection of Sampling Approaches 21
2.13.6 Analytical Screening, Geophysical Techniques, and Sampling Locations 22
2.13.7 Parameters for Analysis 23
3.0 FIELD ANALYTICAL SCREENING AND SAMPLING EQUIPMENT 24
3.1 Introduction 24
3.2 Field Analytical Screening Equipment 24
3.3 Surface Water and Sediment Sampling Equipment and Selection 24
3.4 Example Site 25
3.4.1 Selection of Analytical Screening Equipment 25
3.4.2 Selection of Geophysical Equipment 26
3.4.3 Selection of Sampling Equipment 26
4.0 FIELD SAMPLE COLLECTION AND PREPARATION 33
4.1 Introduction 33
4.2 Sample Volume and Number 33
4.3 Surface Water Sample Collection 33
4.3.1 Rivers, Streams, and Creeks 35
4.3.2 Lakes, Ponds, and Impoundments 35
4.3.3 Estuaries 36
4.3.4 Wetlands 36
4.4 Sediment Sample Collection 37
4.5 Sample Preparation 38
4.5.1 Removing Extraneous Materials 38
4.5.2 Homogenizing 38
4.5.3 Splitting 38
4.5.4 Compositing 38
4.5.5 Final Preparation 39
4.6 Example Site 39
4.6.1 Sampling 39
4.6.2 Sample Preparation 40
5.0 QUALITY ASSURANCE/QUALITY CONTROL 41
5.1 Introduction 41
5.2 Data Categories 41
5.3 Sources of Error 41
5.3.1 Sampling Design 41
5.3.2 Sampling Methodology 42
5.3.3 Sample Heterogeneity 42
5.3.4 Analytical Procedures 42
5.4 QA/QC Samples 42
5.4.1 Field Replicate Samples 42
5.4.2 Collocated Samples 43
5.4.3 Background Samples 43
5.4.4 Rinsate Blank Samples 43
5.4.5 Field Blank Samples 43
5.4.6 Trip Blank Samples 43
5.4.7 Performance Evaluation/Laboratory Control Samples 43
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5.4.8 Matrix Spike/Matrix Spike Duplicate Samples 44
5.4.9 Laboratory Duplicate Samples 44
5.5 Evaluation of Analytical Error 44
5.6 Correlation Between Field Screening Results and Definitive Laboratory Results 44
5.7 Example Site 45
5.7.1 Data Categories 45
5.7.2 Sources of Error 45
5.7.3 Field QA/QC Samples 45
5.7.4 Laboratory QA/QC 46
6.0 DATA PRESENTATION AND ANALYSIS 47
6.1 Introduction 47
6.2 Data Posting 47
6.3 Cross-Section/Fence Diagrams 47
6.4 Contour Mapping 47
6.5 Statistical Graphics 47
6.6 Recommended Data Interpretation Methods 48
6.7 Example Site 48
Appendix A EXAMPLE OF FLOW DIAGRAM FOR CONCEPTUAL SITE MODEL 49
References 52
VI
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List of Figures
1 Conceptual Site Model for Water Sampling 5
2 Random Sampling 16
3 Systematic Grid Sampling 16
4 Systematic Random Sampling 17
5 Transect Sampling 18
6 ABC Plating Site 20
A-l Migration Routes of a Gas Contaminant 49
A-2 Migration Routes of a Liquid Contaminant 50
A-3 Migration Routes of a Solid Cotaminant 51
List of Tables
1 Surface Water and Sediment Field Analytical Screening Equipment 27
2 Surface Water Sampling Equipment 29
3 Sediment Sampling Equipment 31
4 Surface Water and Sediment Sample Method Location 34
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1.0 INTRODUCTION
1.1 OBJECTIVE AND SCOPE
This is Part I of the fifth volume in a series of
guidance documents that assist Superfund Program
Site Managers, On-Scene Coordinators (OSCs),
Remedial Project Managers (RPMs), and other field
staff in obtaining representative samples at Superfund
sites. In the Superfund Program, surface water or
sediment sampling can be conducted during:
emergency responses, site assessments, and removal
or early action activities. The representative sampling
principles discussed in this document are applicable
throughout the Superfund Program. This guidance
document presents basic and general principles for
sampling approaches, methods, and equipment.
Surface water or sediment sampling specifically for
remedial investigations and at remediation sites is not
discussed directly in this guidance. However, general
sampling decisions discussed in this document could
be applicable to more detailed surface water or
sediment sampling instances such as those performed
for remedial investigations. More samples may be
collected or more specific analytical parameters may
be established for remedial investigations, but the
sampling objectives and methods remain similar to
those in this guidance.
The objective of representative sampling is to ensure
that a sample or a group of samples accurately
characterizes site conditions. The selected sample
must possess the same qualities or properties as the
location and source under investigation. In order to
conduct representative sampling, proper sampling
techniques and sample handling must be used to
maintain the integrity of the sample (preserving the
original form and chemical composition). The
following chapters will help field personnel to assess
available information, select an appropriate sampling
approach, select and utilize field analytical screening
methods and sampling equipment, incorporate suitable
types and numbers of quality assurance/quality control
(QA/QC) samples, and interpret and present site
analytical data.
As the Superfund Program has developed, the
emphasis has shifted beyond addressing emergency
response and short-term cleanups. Each planned
response action must consider a variety of sampling
objectives, including identifying threat, determining
the need for long-term action, delineating sources of
contamination, and confirming the achievement of
clean-up standards. Because many important and
potentially costly decisions are based on the sampling
data, Site Managers and other field personnel must
characterize site conditions accurately. Inappropriate
sample collection procedures can seriously bias the
representativeness of a sample as well as its analytical
results. This document emphasizes the use of cost-
effective field analytical screening techniques in
characterizing sites and aiding in the selection of
sampling locations.
1.2 CHARACTERISTICS OF
SURFACE WATER AND
SEDIMENT
1.2.1 Surface Water
Surface waters are water bodies that rest or flow over
land, with a surface that is open to the atmosphere.
Surface water sampling consists of the collection of
representative samples from streams, lakes, rivers,
ponds, creeks, lagoons, estuaries, and surface
impoundments. It includes samples collected from the
depth of the water as well as the surface. Water
sampling typically involves sampling low to medium-
hazard wastes rather than the more concentrated high-
hazard wastes found in drums or storage facilities.
(For high-hazard waste sampling, see U.S. EPA
Superfund Program Representative Sampling
Guidance, Volume 4 Waste, OSWER Directive
9360.4-14, 1995.) Surface water sampling requires
recognition of special properties and precautions. The
following aspects of surface water should be
considered in developing a representative sampling
design:
Stratification - Stratification in a water body
can be thermally or chemically induced.
The temperature profile is often the
controlling force in the circulation of a water
body. The warm, less dense surface water
(epilimnion) and the deeper cold water mass
(hypolimnion) become stratified and create
a thermocline region where the temperature
changes rapidly with depth. The position of
the thermocline varies in surface water
bodies, but is typically less than 30 meters
below the surface. Chemically-induced
stratification generally results when two
levels of a water body are separated by a
steep salinity gradient. Still water bodies,
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such as lakes or reservoirs, have a much
greater tendency to stratify than rivers or
streams.
The epilimnion is exposed to the
atmosphere, whereas the hypolimnion is a
"confined" stratum which is vented only
during seasonal overturn. These two zones
may thus have very different concentrations
of contaminants if: 1) the point of discharge
is to one zone only; 2) the contaminants are
volatile (thus vented in the epilimnion but
possibly not in the hypolimnion); or 3) the
surface stratum is influenced by short-term
flushing due to inflow or outflow of shallow
streams.
Current - A current is a large portion of
water moving in a certain direction.
Currents can disturb mixing zones and
reduce the chances of obtaining a
representative sample. For example, a
strong current may carry and distribute
contamination over a larger area or move
contaminated sediments further downstream,
complicating source identification.
Storm events - Storms may turn over strata
in a water body and reduce the
representativeness of the sample. Increased
precipitation or runoff may increase or
decrease representative concentrations of
contaminants. For example, a large storm
will dilute the concentration of contaminants
present in a water body, possibly below
detection levels. A water body which
receives surface runoff may show a higher
concentration of contaminants from the
ensuing runoff than are representative of the
water body under "normal" conditions.
Precipitation may affect a field screening
instrument's operation and accuracy through
water or humidity interference during field
use. This interference may affect screening
for sample locations or put samplers at risk
for health and safety concerns.
Time of year - Temperate water bodies
(usually lakes) experience two periods of
overturn annually. As air temperature cools
in the fall, the epilimnion becomes cooler
and eventually isothermal conditions exist in
the lake. Overturning and total mixing
occurs. Similar overturning occurs again in
the spring. The chemical composition of
lakes and ponds can vary considerably
depending on the season. Variations can
occur during periods of increased water
movement due to temperature variations,
vegetation decay, freezing and thawing, as
well as turnovers and inversions.
The time of year also influences rainy and
dry periods. For most areas of the United
States, precipitation is greater in the late fall
through spring with an accompanying
increase in volume and flow in surface water
bodies. In the spring, flowing water bodies
may swell from upland headwaters receiving
melting snow. By summer, water bodies
may reduce in volume and velocity due to
drying or drought conditions. Some water
bodies, such as in intermittent streams, may
actually be dry during certain times of the
year.
Circulation - Lakes shallower than 5 meters
are subject to mixing by wind action. Large-
scale water motion in lakes may be either
wind driven or the result of density
gradients. Sediment distribution may be
dominated by either or both types of water
motion. If a water body lacks stratification,
the entire lake may be circulated or mixed
by wind-generated motion.
Velocity - The speed at which a surface
water body flows can affect the selection of
sampling locations, times, equipment, and
techniques. Varying flow rates across or
within the cross-section of the water body
can lead to non-homogeneous mixing of
contaminants, producing different phases,
increasing the difficulty of collecting a
representative sample.
Turbidity - Surface water may contain
suspended particles of fine sediments or
solid contaminants. These particles may
have a higher concentration of contaminants
adhering to their surface area than is
dissolved in the aqueous portion of the
sample. Turbidity will vary due to mixing
and settling in the water body.
Salinity - The natural salt concentration, or
salinity, of a water body may vary with its
proximity to the ocean and seasonal
gradients/stratification. An estuary is
generally categorized as one of three types,
depending upon fresh water inflow and
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mixing properties: mixed estuary, salt
wedge estuary, or oceanic estuary. Tidal
phases of the water body must also be
considered when sampling in saline waters.
Salt concentration in the surface water may
alter concentrations of contaminants due to
chemical reaction/transformation. See
Section 4.3.3 for additional details regarding
estuaries.
1.2.2 Sediment
The characteristics of sediment are dependent on
biological, chemical, and physical phenomena.
Sediments consist of particles derived from rocks or
biological materials that are either transported by
flowing water bodies (e.g., rivers, streams) or situated
beneath a static aqueous layer (e.g., lakes, ponds,
impoundments). They include solids and sludges,
suspended or settled in the water. Sediment types are
classified by particle size, mineralogy, source
materials, and other potential variables. Analysis of
sediment can determine whether concentrations of
specific contaminants exceed established threshold
action levels or pose a risk to public health or the
environment. Media-specific variables that can affect
sediment sampling include:
Particle size (grain size) - Particle size can
affect sampling results because many
pollutants adhere to particle surfaces and
therefore occur in highest concentrations in
small-grained material, where total surface
area is greater, than in large-grained
material.
Terrigenous sediments - Sediments may
consist of material eroded from a land
surface, transported and deposited in the
water body. The origin of the sediment may
influence the selection of analytical methods
to determine soil physical characteristics and
the presence of chemical contaminants.
Terrigenous sediments may exhibit a
historical release not associated with the
water body. For example, chemical
reactions from sediments which originated in
mining areas may result in changes in iron,
sulfate, and pH concentrations in the surface
water.
Chemical constituents - Chemical
constituents associated with sediments may
reflect an integration of chemical and
biological processes. Sediments may reflect
the historical input with respect to time,
application of chemicals, and land use.
Bottom sediments, especially fine-grained
particles, may act as a reservoir for adsorbed
heavy metals and trace organic
contaminants. Organic materials and metals
are more concentrated and readily found in
sediment than in water and can be detected
in sediment analysis if they have not
degraded. Ion exchange properties of certain
clays may affect concentrations of soluble
inorganic ions by removing them from
solution. The clay-based sediments may
remain suspended in water and thereby not
provide a representative sediment sample.
The clay or other suspended sediments may
serve to transport contaminants that have
adhered to the solid particles, to other
locations in the water body.
Depositional/erosional areas - Sediment
accumulation depends on depth of water,
water flow rate, and bottom configuration as
well as temperature, rainfall, and latitude.
Surface water velocity and flow
characteristics can directly affect the
distribution of substrate particle size and
organic content. Contaminants are more
likely to be concentrated in sediments
typified by fine particle size and high
organic content. This type of sediment is
most likely to be collected from depositional
zones. In contrast, coarse sediments with
low organic content, found in erosional
zones, do not typically concentrate
pollutants. Identify depositional and
erosional zones and plan the sampling
design accordingly.
Anaerobic/aerobic conditions - Deep
sediments subject to no disturbance or
mixing may exhibit anaerobic conditions, or
lack of oxygen. The
transformation/degradation of historical
deposits of contaminants will be affected by
either anaerobic or aerobic processes
depending on the substrate conditions.
Knowledge of whether anaerobic or aerobic
conditions exist in the substrate at a specific
sampling location will help to identify
transformation products of suspected
contaminants. Detection of these
transformation products can be used to
delineate the spread of contamination.
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1.3 REPRESENTATIVE SAMPLING
1.4 CONCEPTUAL SITE MODEL
Representative surface water and sediment 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.
In addition to the variables introduced due to the
characteristics of the sample media (as is discussed in
Section 1.2), this document concentrates on those that
are introduced in the field. These latter variables
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 their
method of collection:
Media variability - The physical and
chemical characteristics of surface water and
sediments, such as stratification, flow rate,
particle size, and deposition. (Section 1.2
provides additional specifics of media
variability.)
Contaminant concentration variability -
Variations in the contaminant concentrations
throughout the site and/or the variables
affecting the release of site contaminants
into surface water bodies away from the site.
Collection and preparation variability - Bias
introduced during sample collection,
preparation, and transportation (for analysis)
can cause deviations in analytical results.
Analytical variability - The manner in which
the sample was stored, prepared, and
analyzed by the on-site or off-site laboratory
can affect the analytical results. Analytical
variability can falsely lead to the conclusion
that error is due to sample collection and
handling procedures, although it cannot be
corrected through representative sampling.
A conceptual site model is a useful tool for selecting
sampling locations. It helps ensure that sources,
migration pathways, and receptors throughout the site
are considered before sampling locations are chosen.
The conceptual model assists the Site Manager in
evaluating the interaction of different site features.
Risk assessors use conceptual models to help plan for
risk assessment activities. A conceptual model may
be created as a site map (see Figure 1) or it may be
developed as a flow diagram which describes potential
migration of contaminants to site receptors (see
Appendix A).
A conceptual site model follows contaminants from
their sources through migration pathways (e.g., air,
surface water) to the assessment endpoints. Consider
the following when creating a conceptual site model:
The state(s) of each contaminant and its
potential mobility
Site topographic features
Meteorological conditions (e.g., wind
direction/speed, average precipitation,
temperature, humidity)
Human/wildlife activities on or near the site
The conceptual site model in Figure 1 is an example
created for this document. The model assists in
identifying the following site characteristics:
Potential Sources: Site (waste pile, lagoon);
drum dump; sewage plant outfall;
agricultural activities.
Potential Migration Pathway (Surface
Water): Runoff from the waste pile, lagoon,
drum dump, or agricultural activities; outfall
from the lagoon or sewage plant.
Potential Migration Routes: Ingestion or
direct contact with water in the river, lake,
or aquifer (e.g., ingestion of drinking water,
direct contact with water at the public
beach).
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Potential Receptors of Concern'.
Human Population
(Residents/Workers/Trespassers):
Ingestion or direct contact with
contaminated water in the river,
lake, or aquifer (e.g., swimming,
drinking).
Biota: Endangered/threatened
species or human food chain
organisms suspected of ingesting or
being in direct contact with
contaminated water.
Preliminary site information may provide the
identification of the contaminant(s) of concern and the
level(s) of the contamination. Develop a sampling
plan based upon the receptors of concern and the
suspected sources and pathways. The model may
assist in the selection of on-site and off-site sampling
locations.
1.5 REPRESENTATIVE SAMPLING
OBJECTIVES
Representative sampling applies to all phases of a
Superfund response action. The following are
representative sampling objectives for surface water
and sediment:
Determine if the contaminant is hazardous
by identifying its composition and
characteristics.
Determine if there is an imminent or
substantial threat to public health or welfare
or to the environment.
Determine the need for long-term action.
Develop containment and control strategies.
Evaluate appropriate disposal/treatment
options.
Verify treatment goals or clean-up levels.
1.5.1 Determine Hazard and Identify
Contaminant
One of the first objectives during a response action at
a site is to determine the presence, identity, and
potential threat of any hazardous materials. Field
screening techniques can be used (discussed in
Chapter 3) for rapid detection of contaminants. Upon
confirming the presence of hazardous materials,
sample and/or continue screening to identify their
compositions and determine their concentrations.
1.5.2 Establish Imminent or
Substantial Threat
Establishing threat to the public or the environment is
a primary objective during a response action. The
data obtained from characterizing the contaminants
will help the Site Manager to determine whether an
imminent or substantial threat exists and whether a
response action is necessary. The type and degree of
threat determines the rate at which a response action
is taken.
1.5.3 Determine Long-Term Threat
Site conditions may establish a long-term threat that
is not imminent or substantial. Characterization of the
contaminants can assist the Site Manager to determine
the need for long-term remediation and response.
Samples should be collected in a manner that enables
their use to support evaluating the site under the
Hazard Ranking System.
1.5.4 Develop Containment and
Control Strategies
Once the chemical constituents and threat have been
determined, many strategies for surface water and
sediment containment and control are available.
Analytical data indicating the presence of chemical
hazards are not in themselves sufficient to select a
containment or control strategy. Site reconnaissance
and historical site research provide information on site
conditions and the physical state of the contaminant
sources; containment and control strategies are largely
determined by this information. For example, harbor
booms, sorbent booms, sorbent pad strings, and filter
fences can prevent spread of contamination in a
surface water body.
1.5.5 Identify Available Treatment/
Disposal Options
The contaminants should be identified, quantified, and
compared to selected action levels. Where regulatory
action levels do not exist, site-specific clean-up levels
are determined by the Region (often in consultation
with the Agency for Toxic Substances and Disease
Registry [ATSDR]) or by State identification of
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Applicable or Relevant and Appropriate Requirements
(ARARs). If action levels are exceeded, a series of
chemical and physical tests may be required to
evaluate possible treatment and/or disposal options.
1.5.6 Verify Treatment Goals or
Clean-up Levels
After treatment or disposal, representative sampling
results should either confirm that the response action
has met the site-specific treatment goals or clean-up
levels, or indicate whether further treatment or
response is necessary.
Sampling to verify cleanup requires careful
coordination with demobilization activities. After
treatment of a water body, verification sampling can
begin by using field screening and on-site analysis.
Lab confirmation of the screening performed can help
ensure accuracy of subsequent screening to meet data
quality objectives, as is discussed in Section 5.2.
Sediment sampling can be conducted in phases before,
during, and after cleanup. While verification
sampling on a previously treated area is being
conducted, treatment on other areas can begin.
1.6 EXAMPLE SITE
An example site, presented at the end of each chapter,
illustrates the development of a representative surface
water and sediment sampling plan that meets
Superfund Program objectives for early actions or
emergency responses.
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2.0 SURFACE WATER AND SEDIMENT SAMPLING DESIGN
2.1 INTRODUCTION
There is no universal sampling method to fully
characterize surface water and sediment contaminants
because site characteristics and sampling situations
vary widely. The sampling methods and equipment
must be suited to the specific sampling situation. A
properly developed surface water/sediment sampling
design defines the sampling purpose, protects site
worker health and safety, effectively utilizes
resources, and minimizes errors. The sampling design
will vary according to the type and characteristics of
the water body (e.g., river, estuary) being sampled, as
well as the characteristics of the site. When
developing a sampling design, consider:
Prior actions at the site (e.g., prior sampling
practices, compliance inspections)
Properties and characteristics of the
suspected contaminants
Site waste sources (e.g., impoundments,
waste piles, buried drums)
Topographic, geologic, hydrologic, and
meteorologic conditions of the site
Flora, fauna, and human populations in the
area
Surface water and sediment samples can vary greatly
in composition, therefore making it difficult to obtain
truly representative samples. Variation is due to both
the location within the body of water being sampled
and the time of collection. The change in composition
of flowing waters such as streams or rivers is subject
to the variance in flow and depth. Real-time field
analytical screening techniques can be helpful
throughout the response action. The results can be
used to modify the site sampling plan as the extent of
contamination becomes known. Emergency response
sampling may require the use of a generic but media-
specific sampling plan.
2.2 SAMPLING PLAN
The purpose of sampling is to obtain a small but
representative portion of the medium of interest.
Planning to ensure proper sample collection is
essential. Many site-specific factors are important in
the development of a good sampling plan, including:
data use and quality assurance objectives, sampling
objectives, sampling equipment and sampling
methodology, sampling design, standard operating
procedures (SOPs), field analytical screening,
analytical method selection, decontamination, sample
handling and shipment, and data validation. Each of
these components should be addressed in one
document, a site-specific sampling plan, to be used
throughout the investigation. A sampling plan should
be referred to throughout the field activities, along
with the site-specific quality assurance/quality control
plan, and the health and safety plan.
The U.S. EPA Quality Assurance Sampling Plan for
Environmental Response software (QASPER), is a
database that was designed to assist with the
development of sampling plans for response actions.
QASPER is menu driven software that prompts the
user to input background information and to select
prescribed parameters in order to develop a site-
specific sampling plan. It also gives the user access
to any previously developed site-specific sampling
plans.
The following procedures are recommended for
developing a thorough surface water/sediment
sampling plan. Many steps can be performed
simultaneously, and the sequence is flexible.
Review the history of the site and adjoining
areas, including regulatory and reported spill
history; note current and former locations of
buildings, tanks, and process, storage, and
disposal areas.
Perform a site reconnaissance; categorize
physical/chemical properties and hazardous
characteristics of materials involved.
Identify topographic, geologic, and
hydrologic characteristics of the site,
including surface water, ground-water, and
soil characteristics, as well as potential
migration pathways and receptors.
Determine geographic and demographic
information, including population size and
its proximity to the site (e.g., public health
threats, source of drinking water); identify
threatened environments (e.g., potentially
contaminated wetlands or other sensitive
ecosystems).
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Select sampling strategies considering field
analytical screening and statistical
applications when appropriate.
Determine data quality and quality assurance
objectives for field analytical screening,
sampling, and analysis; as the extent of
contamination becomes quantified, the
sampling plan can be modified to better
achieve sampling objectives throughout the
response action.
It is recognized that many of these steps (described in
detail below) may not be applicable during an
emergency response because of the lack of advance
notice. Emergency response sampling nevertheless
requires good documentation of sampling events.
2.2.1 Historical Data Review
The first step in developing a sampling plan is a
review of historical site data, examining past and
present site operations and disposal practices to
provide clues on possible contaminants and waste
sources. Available sources of information include:
federal, state and local agencies and officials; federal,
state, and local agency files (e.g., site inspection
reports and legal actions); deed or title records;
current and former facility employees; potentially
responsible parties (PRPs); local residents; and
facility records or files. Where possible, data
regarding adjoining properties should also be
reviewed.
A review of previous sampling information should
include sampling locations, matrices, methods of
collection and analysis, and relevant contaminant
concentrations. The reliability and usefulness of
existing analytical data should be assessed, including
data which are not substantiated by documentation or
QA/QC controls, but which may still illustrate general
site trends.
Information that describes specific chemical
processes, raw materials used, products and wastes,
and waste storage and disposal practices should also
be collected. Information on materials handled at a
site may provide guidance in the selection of
analytical parameters. Review any available site
maps, facility blueprints, and historical aerial
photographs detailing past and present storage,
process, and waste disposal locations. Areas on a site
where particular processes occurred are good choices
as sampling locations. U.S. Geological Survey
(USGS) topographic maps should be reviewed to
identify possible contamination overland flow or
migration routes to surface water bodies. County
property and tax records are also useful sources of
information about the site and its surroundings.
2.2.2 Site Reconnaissance
A site reconnaissance can be conducted at an earlier
date or on the same day immediately prior to sampling
activities. It allows field personnel to assess site
conditions, evaluate areas of potential contamination,
evaluate potential hazards associated with sampling,
and finalize a sampling plan. Site reconnaissance
activities include: observing and photographing the
site; noting site access routes and potential evacuation
routes; noting potential safety hazards; recording label
information from drums, tanks, or other containers;
mapping effluent pipes or other point source
discharges; mapping potential contaminant migration
routes such as streams and irrigation ditches; noting
the condition of animals and/or vegetation; and noting
topographic and structural features (e.g., bridges or
piers). Field personnel should use appropriate
personal protective equipment when engaged in any
site activities. A site reconnaissance for a surface
water body should focus on collecting as much
information as possible on the physical and chemical
parameters of the water body. National Oceanic
Atmospheric Administration (NOAA) tide tables and
USGS freshwater surface water flow records are
useful in determining the water body type. Common
measurement tools and means for a surface water
body reconnaissance include: boat, recording
fathometer, salinometer, and conductivity and
dissolved oxygen meters.
2.2.3 Physiographic and Other
Factors
Other procedures, such as determining data quality
and QA/QC objectives, utilizing field analytical
screening techniques, identifying topographic,
geologic, and hydrologic characteristics, and
determining geographic and demographic information
are important steps in an overall sampling plan. The
remainder of this chapter includes a brief discussion
of many of these procedures. Field analytical
screening techniques and equipment are discussed in
greater detail in Chapter 3; QA objectives are
discussed in Chapter 5. For additional guidelines on
preparing a sampling plan, please refer to the U.S.
EPA Superfund Program Representative Sampling
Guidance, Volume 1 Soil, OSWER Directive
9360.4-10.
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2.3 MIGRATION PATHWAYS AND
RECEPTORS
The historical data review and site reconnaissance are
the initial steps in defining the source areas of
contamination which could pose a threat to human
health and the environment. Source areas could
include waste impoundments, landfills, spills,
contaminated soil, drums, tanks and other containers,
and other waste management areas. Often these
source areas are not directly located in or even
adjacent to the surface water body. The contaminants
are transported or migrate to the surface water or
sediments. 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.
The fate of a contaminant is dictated by the source,
the characteristics of the contaminant, and by the
physical environment into which it is released. By
defining the contaminants and the physical
environment, the fate of contaminants can be
predicted and the migration pathway can be identified.
Knowing the migration pathway ensures that samples
are collected in the most appropriate location(s).
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/topography, vadose zone transport, and wind
dispersion. Human activity (such as foot or vehicular
traffic) and animal activity also transport
contaminants away from a source area. These five
transport mechanisms are described below.
Man-made pathways - A site located in an
urban/suburban setting has the following
man-made pathways which can aid
contaminant migration to surface water
bodies: storm and sanitary sewers, drainage
culverts, sumps and sedimentation basins,
French drain systems, and underground
utility lines. A facility might utilize effluent
pipes or point source discharges.
Surface drainage/topography - Contaminants
can be adsorbed onto sediments, suspended
independently in the water column, or
dissolved in surface water runoff. The
runoff, following natural topography, can be
rapidly carried into drainage ditches,
streams, rivers, ponds, lakes, and wetlands.
Historical aerial photographs can be
invaluable for delineation of past surface
drainage patterns. A search of historical
aerial photographs can be requested through
the U.S. EPA Regional Remote Sensing
Coordinator. The U.S. Soil Conservation
Service and local county planning offices are
also excellent sources of historical aerial
photographs.
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
ground water. Contaminants might migrate
to surface water through a ground-water
discharge area.
Wind dispersion - Contaminants deposited
over or adsorbed onto soil may migrate from
a waste site as airborne particulates.
Depending on the particle-size distribution
and associated settling rates, these
particulates may be deposited downwind or
remain suspended, resulting in
contamination of surface soils, surface
waters, and/or exposure to 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.
Once the migration pathways have been determined,
identify all possible receptors (i.e., potentially affected
human and environmental receptors) along these
pathways. Human receptors include on-site and
nearby residents, workers, and school children. Note
the attractiveness and accessibility of site wastes to
children and other nearby residents. Environmental
receptors include edible aquatic species, federal- or
state-designated endangered or threatened species,
habitats for these species, wetlands, and other federal -
or state-designated wilderness, critical, and natural
areas.
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2.4 SURFACE WATER AND
SEDIMENT SAMPLE TYPES
Sampling procedures should be designed to be
consistent with sampling objectives. The type of
sample collected may depend on suspected
contaminant types and characteristics; projected extent
of water contamination; type of water body to be
sampled (e.g., stream, impoundment); target analytes;
and health and safety requirements. The following
section describes and gives examples of the two types
of surface water and sediment samples.
2.4.1 Grab Sample
A grab sample is a discrete aliquot from one specific
sampling location at a specific point in time, and may
be considered representative of homogenous
conditions over a period of time and/or geographical
area. When obtaining grab samples from a water body
having stratified layers, sample each phase or stratum
separately; the separate aliquots are representative of
their respective stratum. When sampling stratified
sources, determine as many properties as possible for
the contaminants through historical data and site
reconnaissance prior to sampling. Grab samples can
be collected for both surface water and sediments, and
are generally the preferred method for screening
investigations. However, because the release of a
contaminant in a surface water body is subject to
variance over time and distance, a grab sample may
not be a representative sample.
For many sampling situations grab sampling
techniques are preferred over composite sampling.
Grab sampling minimizes the amount of time and
expense required for multiple samples; minimizes
sampling personnel's exposure to potential hazardous
substances; reduces risks associated with compositing
unknowns; and eliminates physical and chemical
changes that might occur due to compositing. Grab
sampling also documents contamination at a specific
point or location which can be easily identified and
also re-located in later investigations for possible
remedial or enforcement purposes.
2.4.2 Composite Sample
A composite sample is a non-discrete sample
composed of two or more aliquots (of equal volume)
collected at various sampling points or times. It can
represent portions collected at various locations,
various times, or a combination of both location and
time variables. Composite samples are made by
combining grab samples collected at defined intervals.
There are four types of composite samples: areal,
vertical, flow proportional, and time. The areal
composite is composed of individual aliquots
collected over a defined area. It is made up of
aliquots (of equal volume) from grab samples
collected in an identical manner (e.g., sediment
aliquots collected along a streambed). A variation of
this approach is the equal-width-increment (EWI)
technique, in which equally-spaced vertical samples
are collected across a stream with the sampling device
passing through the water column at the same velocity
at each location. This technique ensures that water
and suspended particles are collected equally across
the water body. Another variation is the equal-
discharge-increment (EDI) technique, which positions
the sampling locations across the stream based on
incremental discharges rather than width (i.e.,
locations in deeper or higher velocity areas of the
stream's cross-section are spaced more closely). This
technique measures total discharge of contaminants in
poorly mixed water bodies, but it requires knowledge
of the cross-sectional stream flow distribution. Both
techniques, however, are very time-consuming and
expensive to employ. (Both techniques, as well as
other depth integration approaches, are discussed in
detail in ASTM standards, such as Standard D4411, in
the 1989 Annual Book of ASTM Standards - Volumes
11.01 and 11.02, Water and Environmental
Technology.)
A vertical, also referred to as a zonal, composite is
composed of individual aliquots collected at different
depths but along the same vertical line. Like an areal
composite, it is made up of aliquots collected in an
identical manner. A flow proportional composite is
a sample collected proportional to the flow rate during
the compositing period by either a time-
varying/constant volume or time-constant/varying
volume method. A time composite, or chronological
sampling, is composed of a varying number of
discrete aliquots collected at equal time intervals
during the compositing period. Both flow
proportional and time composite samples are most
appropriate for sampling flowing water bodies.
By design, composite samples reflect an "average"
concentration within the composite area, flow, or
interval. Compositing is appropriate when
determining the general characteristics or the
representativeness of certain sources for treatment or
disposal. Samples collected along the length of the
watercourse or at different times may reflect differing
inputs or dilutions. It should be noted that
compositing can mask problems by diluting isolated
concentrations of some contaminants to below
11
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detection levels. When compositing samples from a
water body, note that resulting concentrations are
representative of the water body's average
concentration, but not of discrete areas within the
water body. Compositing is not recommended where
volatile compounds are a concern.
When compositing either surface water or sediment
samples, specify in the sampling plan the method of
selecting the aliquots that are composited and the
compositing factor. The compositing factor is the
number of aliquots to be composited into one sample
(e.g., 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 requires that each discrete aliquot be the
same in terms of volume or weight and that they be
thoroughly homogenized. Because 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.
The detection level need not be reduced if the
composite area is assumed to be homogenous in
concentration. Generally the number of samples to be
taken for a composite depends upon the width, depth,
discharge, and suspended sediments of the water
body. The greater number of individual aliquots, the
more likely the composite sample is truly
representative of the overall characteristics of the
water body.
2.5 SURFACE WATER
AND SEDIMENT
CHARACTERISTICS
The physical and chemical characteristics of the
surface water and sediments, including stratification,
current/flow rate, salinity, particle size,
depositional/erosional areas, and degradation
conditions, among other factors, influence the number
and types of samples collected. These characteristics
may also assist in determining sampling approaches
and analytical parameters. Many of the characteristics
of surface water and sediments are defined in
Section 1.2.
2.6 SAMPLING CONSIDERATIONS
Factors to consider when designing a sampling plan
include: hydrology, topography, water quality data,
and water quality measurements such as pH,
conductivity, temperature, dissolved oxygen, and
salinity. Hydrology and morphometrics (e.g.,
measurements of volume, depth) of the surface water
should be determined prior to sampling. Before
sampling, identify the presence of phases or layers in
impoundments and lakes, flow patterns in streams,
and/or appropriate sample locations and depths.
Water quality data should be collected in
impoundments and non-flowing (static) water bodies
to determine if stratification is present. Measurements
of dissolved oxygen, pH, temperature, conductivity,
and oxidation-reduction potential can indicate if strata
exist which would affect analytical results.
Measurements should be collected at one-meter
intervals from the substrate to the surface using an
appropriate instrument (e.g., Hydrolab or equivalent).
Knowing these variables assists in selecting locations
and depths and interpreting analytical data.
2.7 QUALITY ASSURANCE
CONSIDERATIONS
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 measurement
Completeness - Percentage of sampling
measurements which are judged to be valid
Representativeness - Degree to which
sample data accurately and precisely
represent the characteristics and
concentrations of the site contaminants
Comparability - Evaluation of the similarity
of conditions (e.g., sample depth, sample
homogeneity) under which separate sets of
data are produced
12
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To ensure that the analytical samples are
representative of site conditions, quality assurance
measures must be associated with each sampling and
analysis event. The sampling plan must specify these
QA measures, which include, but are not limited to,
sample collection, laboratory standard operating
procedures (SOPs), sample container preparation,
equipment decontamination, field blanks, replicate
samples, performance evaluation samples, sample
preservation and handling, and chain-of-custody
requirements (see Chapter 5, Quality
Assurance/Quality Control).
2.8 DATA QUALITY OBJECTIVES
Data quality objectives (DQOs) state the level of
uncertainty that is acceptable for data collection
activities and define the data quality necessary to
make certain decisions. When establishing DQOs for
a particular project, consider:
Decision(s) to be made or question(s) to be
answered by the data
Why analytical data are needed and how the
results will be used
Time and resource constraints on data
collection
Descriptions of the analytical data to be
collected
Applicable model or data interpretation
method used to arrive at a conclusion
Detection limits for analytes of concern
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. These components are
defined in Section 2.7 and are discussed in further
detail in Chapter 5, Quality Assurance/Quality
Control.
2.9 ANALYTICAL SCREENING
There are two primary types of analytical data that can
be generated during a response action: field analytical
screening data and laboratory analytical data. Field
analytical screening instruments and techniques
provide real-time or direct (or colorimetric) reading
capabilities. They include: flame ionization detectors
(FIDs), photoionization detectors (PIDs), colorimetric
tubes, portable X-ray fluorescence (XRF) units,
portable gas chromatography (GC) units,
immunoassay tests, and hazard categorization (hazcat)
kits. These screening methods can assist with the
selection of sample locations and depths or samples to
be sent for laboratory analysis by narrowing the
possible groups or classes of chemicals. They are
effective and economical for gathering large amounts
of site data. Once an area has been characterized
using field screening techniques, a subset of samples
can be sent for laboratory analysis to substantiate the
screening results.
Under a limited sampling budget, analytical screening
(with laboratory confirmation) will generally result in
more analytical data from a site than will sampling for
rigorous laboratory analysis alone. To minimize the
potential for false negatives (not detecting
contamination), use only those field analytical
screening methods which provide detection limits
below applicable action levels. If these methods are
not available, field analytical screening can still be
useful for detecting grossly contaminated areas, as
well as for health and safety determination. Field
analytical screening techniques to support surface
water and sediment sampling are discussed in greater
detail in Chapter 3.
Geophysical techniques (e.g., ground penetrating radar
[GPR], magnetometry, electromagnetic conductivity
[EM]) may be utilized during a response action to
locate potential buried or disturbed waste source
areas. These techniques are generally not used
directly with representative surface water and
sediment sampling. Please refer to U.S. EPA
Superfund Program Representative Sampling
Guidance, Volume 1 Soil, OSWER Directive
9360.4-10, for a discussion of geophysical techniques.
2.10 ANALYTICAL PARAMETERS
Designing a representative surface water and sediment
sampling plan includes selecting analytical parameters
and methods. Use data collected during the historical
data review (e.g., past site operations and processes,
materials stored on site, effluent discharges) to select
appropriate analytical parameters and methods. If the
historical data reveal little information about the
possible types of contaminants on site, use applicable
field analytical 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. These
analyses can identify all contaminants of concern
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(even at low detection levels). Methods often used
for characterization include gas chromatography/mass
spectrometry (GC/MS) for tentatively identified
compounds (TICs) in the volatile and semivolatile
organic fractions, infrared spectroscopy (IR) for
organic compounds, and inductively coupled plasma
(ICP) for inorganic substances.
After characterization, future sampling and analysis
efforts can focus on substances identified above the
action level. This will result in significant cost
savings over a full chemical characterization of each
sample. Utilize U.S. EPA-approved methodologies
and sample preparation, where possible, for all
requested off-site laboratory analyses. Knowledge of
the analytical methodology and requirements is
helpful when selecting sampling devices. Refer to the
American Public Health Association Standard
Methods for the Examination of Water and
Wastewater, Seventeenth Edition, 1989, for detailed
descriptions of analytical procedures/methodologies.
2.11 REPRESENTATIVE SAMPLING
APPROACHES
Representative sampling approaches include
judgmental, random, systematic grid, systematic
random, transect, stratified, and three-dimensional
(3D) sampling. The random and systematic random
approaches are not very practicable for sampling
water systems. When these two approaches are used,
however, they are more appropriate to sediment
samples than to surface water. The remaining
approaches may be applied to both surface water and
sediment sampling plans. Selection of a
representative sampling approach must also consider
the practicability of reaching sediments and obtaining
a sample from a specific location, particularly difficult
in surface waters. A representative sampling plan
may use one or a combination of the approaches, each
of which is described below.
2.11.1 Judgmental Sampling
Judgmental sampling is the biased selection of
sampling locations based on historical information,
visual inspection, and professional judgment.
Judgmental sample collection is most appropriate
when knowledge of the contaminant or its origin is
available or when sampling non-static systems, such
as flowing bodies of water. Judgmental sampling
includes no randomization in the sampling strategy,
precluding statistical interpretation of the sampling
results. Criteria for selecting the sampling location
depend on the sampling objectives and best
professional judgment. Judgmental sampling does not
necessitate sampling from the middle of the water
body, but may consider factors such as source
locations, tributaries, or depositional areas for more
representative samples. Judgmental sampling also
enables the investigator to select sampling locations
with the fewest physical barriers impeding sample
collection (e.g., docks, piers, stumps, dry stream
beds). For surface water and sediment sampling for
site assessments, emergency responses, and some
early actions, judgmental sampling is often utilized.
Judgmental sampling allows no statistical analysis of
error or bias. It is not always representative of site
conditions, and tends to document "worst-case"
scenarios. Judgmental sampling meets the objective
to qualify hazardous substances on site, but not to
quantify them. The judgmental approach is best used
as a screening investigation to be followed with a
statistical approach when determining extent of
contamination or action alternatives. Judgmental
approaches should be incorporated into sampling
designs for remedial investigations and large-scale
early and long-term response actions.
2.11.2 Random Sampling
Random sampling, also referred to as simple random
sampling, is the arbitrary collection of samples having
like contaminants within defined boundaries of the
area of concern (see Figure 2). Obtaining a
representative sample depends on random chance
probabilities. Random sampling is useful when there
are many sampling locations available and no criteria
for selecting one location over another. Choose
random sampling locations using a random selection
procedure (e.g., a random number table). (Refer to
Ford and Turina, July 1984, for an example of a
random number table.) The arbitrary selection of
sampling points ensures that each sampling point is
selected independently from all other points, so that
all locations within the area of concern have an equal
chance of being sampled. Randomization is necessary
in order to make probability or confidence statements
about the sampling results. The key to interpreting
these statements is the assumption that the site or
water body is homogeneous with respect to the
parameters being sampled. The higher the degree of
heterogeneity, the less the random sampling approach
will adequately characterize true conditions. Random
sampling is useful for sites with little background
information available or for sites where obvious
contaminated areas do not exist or are not evident.
Random sampling is not recommended in flowing
14
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water bodies and is only practicable for sediment bed
sampling in non-flowing (static) water bodies.
2.11.3 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) (see Figure 3). 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 area of concern. Generally, the
more samples collected (and the smaller the grid
spacing), the more reproducible and representative the
results. Shorter distances between sampling locations
improve representativeness. Systematic grid sampling
can be used to characterize non-flowing (static) water
bodies and their sediment beds.
15
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Figure 2: Random Sampling
200-
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50-
r STATIC WATER
i BODY BOUNDARY
-\ h
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0 50 100 150 200 250 300 350 400
FEET
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Figure 3: Systematic Grid Sampling
200-
150-
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0
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50 100
KEY
X SELECTED SAMPLE LOCATION
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150 200 250 300 350 400
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16
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2.11.4 Systematic Random Sampling
Systematic random sampling is a flexible design for
estimating the average pollutant concentration within
grid cells (see Figure 4). Subdivide the area of
concern using a square or triangular grid (as
mentioned above) then collect samples from within
each grid cell using random selection procedures.
Systematic random sampling allows for the isolation
of cells that may require additional sampling and
analysis. Like systematic grid sampling, systematic
random sampling can be used to characterize sediment
in an impoundment or non-flowing (static) water
body; it is not recommended or practicable for surface
water in any system.
Figure 4: Systematic Random Sampling
200-
150-
ti
ffi 100-
50-
/X
X
V X
'
X
X
X
^d
X
X
X
X
X
X
X
X
X
X
X
X
/*v^
/ ^
/ STATIC WATER
I BODY BOUNDARY
X \
X ^y
50 100 150 200 250 300 350 400
FEET
KEY
X SELECTED SAMPLE LOCATION
2.11.5 Transect Sampling
Transect sampling involves establishing one or more
transect lines across a surface (see Figure 5). 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 line and the number of samples
to be collected determine the spacing between
sampling points along the transect. Transect sampling
can best be accomplished when surface water bodies
are small in size and the sampling locations within the
transect grid boundaries are easily accessible. This is
not the most desirable method in large lakes and
ponds, or inaccessible areas where surface water
samples can be obtained only by boat. Multiple
transect lines may be parallel or non-parallel to one
another, or may intersect. If the lines are parallel, the
sampling objective is similar to systematic grid
sampling. The primary benefit of transect sampling is
the ease of establishing and relocating individual
transect lines. Transect sampling is applicable to
characterizing water flow and contaminant
characteristics and contaminant depositional
characteristics in sediments, such as distinguishing
erosional versus depositional zones.
17
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Figure 5: Transect Sampling
20-
35
40
KEY
X SELECTED SAMPLE LOCATION
2.11.6 Stratified Sampling
Stratified sampling involves dividing the area to be
sampled into mutually exclusive strata or areas where
different sampling strategies may be employed in each
stratum. Strata are chosen either based on areas
where separate clean-up decisions need to be made or
where variable strata contamination constituents or
levels are expected. Where access is not a problem,
stratified sampling is more appropriate for collecting
representative sediment samples than surface water
samples. Prior knowledge of stratification is required
in order for this method to be most effective.
2.11.7 Three Dimensional (3D)
Three-dimensional (3D) sampling is similar to
systematic sampling. First, the water body is divided
along three axes (x, y, z), as opposed to the two
horizontal axes in grid sampling. Then, a systematic
approach (random or grid) is used to select sampling
locations across the surface and at depth. Three-
dimensional sampling is useful in static water bodies
which exhibit distinct strata with depth but for which
few data are available on contaminants and/or
contaminant locations.
2.12 SAMPLING LOCATIONS AND
NUMBERS
Selection of a surface water or sediment sampling
location is based on many factors, including sampling
objectives, surface water use, point source discharges,
nonpoint source discharges, mixing zones, tributaries,
changes in stream characteristics, stream depth,
turbulence, presence of structures (e.g., dams, weirs),
and accessibility to the sampling location. Tidal
movement must also be considered when selecting
sampling locations in tidal zones. Seasonal salinity
ranges should be considered in estuaries.
The sampling objective can determine which
characteristics of the surface water body warrant more
attention. For example, when investigating a water
body that serves as a source of water supply, factors
such as accessibility, flow, and velocity are not as
critical as they would be when determining
contaminant impact on wetlands or sediments. This
is because water supply intakes draw water from
across the water body, also drawing in contaminants,
while contaminants settle into wetlands by natural
flow or mixing. When multiple sampling locations
need to be investigated to determine pollution patterns
or to obtain data for mathematical modeling purposes,
several related factors may need to be considered.
(See A Practical Guide to Water Quality Studies of
18
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Streams, F.W. Kittrells, for additional guidelines on
extensive or complicated sampling designs.)
The sampling objective will also influence the number
of samples collected. When determining the
presence/absence of a contaminant, few samples are
required. More samples are needed if the objective is
to identify the characteristic concentrations of a
contaminant or the extent of contamination.
Judgmental and statistical sampling techniques can be
used together to thoroughly address an area. Some
samples may be obtained from locations considered
potentially affected areas by a judgmental approach
(e.g., sediments downstream of a discharge outfall
pipe). For areas less likely to be affected or with little
available historic information, a random or grid
approach may be used to adequately assess the entire
water body or site.
To determine whether a water body has been affected
by site contaminants, two sample sets are generally
required: one surface water and sediment sample each
from the point (or slightly downstream) where on-site
contaminants are suspected to have entered the water
body (also referred to as the probable point of entry
[PPE]), and another surface water and sediment
sample set from an upstream, unaffected background
location. If multiple sources or contaminants from
other sites upstream of the PPE are suspected in the
water body, additional sample locations will be
needed downstream of those alternate sources,
upstream of the PPE.
Where the sampling objective is to delineate the
extent of sediment contamination for response action
alternatives, a greater number of samples and
sampling locations will be required. In this situation,
a systematic approach will be needed (e.g., transect or
systematic grid) to accurately "map" the
contamination. The exact number of samples required
will be determined by the analytical parameters and
the size of the line or grid and their intersects.
2.13 EXAMPLE SITE
2.13.1 Background
The ABC Plating Site is located in northeastern
Pennsylvania approximately 1.5 miles north of the
town of Jonesville. Figure 6 provides a layout sketch
of the site and surrounding area. The site covers
approximately 4 acres and was operated as a multi-
purpose specialty 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 unlined shallow surface
settling lagoons in the northwest portion of the site.
Surface drainage from this area then entered a nearby
stream.
Pennsylvania Department of Environmental Resources
(PADER) personnel cited the owner/operator for the
operation of an unpermitted treatment system and
ordered the owner to submit a remediation plan for
state approval. Before PADER could follow up on the
order, the lagoons were partially backfilled with the
wastes in place. The process building was later
destroyed by a fire of suspicious origin. The owner
abandoned the facility and could not be located by
enforcement and legal authorities. Several vats,
drums, and containers were left unsecured and
exposed to the elements. The state contacted EPA for
an assessment of the site for a possible federally
funded response action; an EPA On-Scene
Coordinator (OSC) was assigned to the task.
2.13.2 Historical Data Review and
Site Reconnaissance
The EPA OSC reviewed the PADER site file. In 1974
the owner was cited for violating the Clean Streams
Act and for storing and treating industrial waste
without a permit. The owner was ordered to file a site
closure plan and to remediate the settling lagoons.
The owner, however, continued operations and was
then ordered to begin remediation in 90 days or be
issued a cease and desist order. Soon after, a follow-
up inspection revealed that the lagoons had been
backfilled without removing the waste.
The OSC and a sampling contractor (Team) arrived on
site to interview local and county officials, fire
department officers, neighboring residents (including
a former facility employee), and PADER
representatives regarding site operating practices and
other site details. The former employee sketched
facility process features on a map copied from state
files. The features included two settling lagoons and
a feeder trench which transported plating wastes from
the process building to the lagoons. The OSC
obtained copies of aerial photographs of the site area
from the local district office of the U.S. Soil
Conservation Service. The state provided the OSC
with copies of all historical site and violation reports.
These sources indicated the possible presence and
locations of chromium, copper, and nickel plating
process areas.
19
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Figure 6: ABC Plating Site
A
-\
r
A A >
o o ^
T"^ f
TREELINE
SUSPECTED
LAGOONS
SUSPECTED
TRENCH
HOUSE
TRAILER
SCALE IN FEET
100
50
100
LEGEND
DAMAGED
BUILDING
AREA
SURFACE FLOW
SITE BOUNDARY
20
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The Team mobilized to the site with all the equipment
needed to perform multi-media sampling. The OSC
and Team made a site entry, utilizing appropriate
personal protective equipment and instrumentation, to
survey the general site conditions. They observed 12
vats, likely containing plating solutions, on a concrete
pad where the original facility process building once
stood. Measurements of pH ranged from 1 to 11.
Fifty drums and numerous smaller containers (some
on the concrete pad, others sitting directly on the
ground) were leaking and bulging, because of the fire.
Some rooms of the process building could not be
entered due to unsafe structural conditions caused by
the fire. The Team noted many areas of stained soil,
which indicated container leakage, poor waste
handling practices, and possible illegal dumping of
wastes.
2.13.3 Identification of Migration
Pathways, Transport
Mechanisms, and Receptors
During the site entry, the OSC and Team noted that
several areas were devoid of vegetation, threatening
wind erosion which could transport heavy metal- and
cyanide-contaminated soil particulates off site. These
particulates could be deposited on residential property
downwind or be inhaled by nearby residents.
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 acids and bases as might be found in
leaking or unsecured drums or containers.
After interviewing residents, it was established that
the homes located to the south and nearest to the site
rely upon private wells for their primary drinking
water supply. Ground water is also utilized by several
small community systems which have wells located
within 2 miles of the site. The on-site settling lagoons
were unlined and therefore posed a threat to ground
water, as did precipitation percolating through
contaminated soils. Contamination might have
entered shallow or deeper aquifers and potentially
migrated to off-site drinking water wells.
Erosion gullies located on site indicated soil erosion
and water transport due to storms. Surface drainage
sloped toward the west and northwest, including a
distinct drainage path topographically downgradient of
the former lagoon area. The Team observed stressed
and discolored vegetation along the surface water
drainage path. Surface runoff of heavy metals and
cyanide was a direct contact hazard to local residents.
Surface water systems were also potentially affected.
Further downgradient, site runoff and the drainage
path entered an intermittent tributary of Little Creek.
The naturally eroded tributary flows west/southwest
into a heavily wooded area off-site prior to its
convergence with Little Creek. Little Creek in turn
feeds Barker Reservoir, located southwest of the site.
This reservoir is the primary water supply for the City
of Jonesville and neighboring communities, which are
located 2.5 miles downgradient of the site. Shallow
ground-water discharges into the creek and reservoir
at several locations, serving as another possible
contaminant migration route.
2.13.4 Sampling Objectives
The OSC initiated a removal assessment with a
specific sampling objective, 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 (site stabilization
strategies) to reduce direct contact concerns
on site.
Once CERCLA funding was obtained and the site was
stabilized:
Phase 2 - Define the extent of contamination
at the site and adjacent areas. Estimate the
costs for early action options and review any
potential long-term remediation objectives.
Phase 3 - After early actions are completed,
document the attainment of goals. Assess
that the response action was completed to
the selected level and is suitable for long-
term goals.
2.13.5 Selection of Sampling
Approaches
The OSC, Team, and PADER reviewed all available
information to formulate a sampling plan. The OSC
selected a judgmental sampling approach for Phase 1.
Judgmental sampling supports the immediate action
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
21
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is typically established using a relatively small
number of samples (fewer 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 bias-selected soil, ground-water,
surface water, and sediment 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 in
soils. The grid could accommodate analytical
screening and geophysical surveys. A block grid
with 50-foot grid spacing was selected. This grid size
ensured a 10 percent or less probability of missing a
"hot spot." The grid was extended to adjacent
residential properties when contaminated soil was
identified at grid points near the boundary of the site.
Based on the results of soil sampling, a judgmental
approach was used to locate sample locations along
the drainage path. A judgmental approach was also
used for the intermittent tributary and Little Creek.
Based on the results of soil sampling and geophysical
surveys, a judgmental approach was used to select
locations for installation of monitoring wells; at "hot
spots"; along the perimeter of the suspected plume
established from analytical results and geophysical
survey plots; and at background ("clean") locations.
Subsurface soil and ground-water samples were
collected from each of the 15 monitoring well
locations for laboratory confirmatory analysis to
establish the presence and, if applicable, the degree of
contamination at depth.
A judgmental approach was selected for Phase 2
sampling in the surface water migration route. During
Phase 1, samples were collected of soils along the
drainage path and of surface water and sediments in
the intermittent tributary. For purposes of EPA target
and listing criteria, surface water at this site was
considered to begin at Little Creek, the perennially
flowing stream. Phase 1 samples exhibited limited
site-related contamination along the drainage path.
Because of Little Creek's distance from the site and
the tributary traversing through the wooded area,
detection of contamination in the surface water body
had to be determined first. For this reason, during
Phase 2 biased locations were selected for sampling in
Little Creek, the intermittent tributary, and along the
drainage path topographically downgradient of the
former lagoons, to establish contaminant migration.
A surface water and sediment sample set was
collected along Little Creek upstream of the tributary
PPE to determine background conditions.
2.13.6 Analytical Screening,
Geophysical Techniques,
and Sampling Locations
During Phase 1, containerized wastes were screened
using hazard categorization techniques to identify the
presence of acids, bases, oxidizers, and flammable
substances. Following this procedure, photoionization
detector (PID) 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 acids and
bases and the absence of volatile organic compounds.
The Team collected a total of 12 surface soil samples
(0-3 inches), 3 ground-water samples, one surface
water sample, and one sediment sample 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 immediate action response funding.
Ground-water samples were collected from three
nearby residential wells. The surface water and
sediment samples were collected from the observed
PPE at the confluence of the unnamed intermittent
tributary and the on-site surface water drainage
pathway. Based on Phase 1 analytical results,
chromium was selected as the target compound for
determination of extent of contamination in all
media/pathways.
During Phase 2 sampling activities, the OSC used a
transportable X-ray fluorescence (XRF) unit installed
in an on-site trailer to screen soil and sediment
samples for total chromium in order to limit the
number of samples to be sent for laboratory analysis.
Soil sampling was performed at all grid nodes at the
surface (0-4 inches) and subsurface (36-40 inches).
The 36-40 inch depth was selected based on
information obtained from state reports and local
interviews, which indicated that lagoon wastes were
approximately 3 feet below ground surface. Twenty-
four surface and subsurface samples were sent for
laboratory confirmation 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 a selected target action level were located,
composite samples were collected from each
adjoining grid cell. Based on the XRF data, each
adjoining cell was either identified as "clean" (below
22
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action level) or designated for response consideration
(at or above action level).
Also during Phase 2, the OSC oversaw the
performance of ground penetrating radar (GPR) and
electromagnetic conductivity (EM) geophysical
surveys to help delineate the buried trench and lagoon
areas, any conductive ground-water plume, and any
other waste burial areas. The GPR survey was
conducted over the original grid and run along the
north-south grid axis across the suspected locations of
the trench and lagoons. 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.
Using the data obtained during soil sampling and the
geophysical surveys, a ground-water investigation
plan for Phase 2 was prepared. Monitoring wells were
located in areas shown to be heavily contaminated
during soil sampling; along the outer perimeter of a
contaminant plume based on soil XRF results and the
geophysical surveys; and apparent upgradient
locations for background conditions comparison.
Fifteen wells were located at grid nodes established
using the above data. Upon monitoring well
installation and sampling, a hydraulic (pump) test was
completed of the bedrock monitoring wells to gather
information about aquifer characteristics, which help
assess the ability of contaminants to migrate through
ground water.
Three soil grid samples collected along the bank of the
surface water drainage path, topographically
downgradient of the former lagoon area, exhibited
chromium contamination ranging from 772 to 2,060
mg/kg. The samples were from random locations
according to the layout of the sampling grid. This
chromium contamination suggests that a contaminant
plume may have traveled topographically
downgradient from the lagoons along the drainage
path. (Contamination was not detected at depth in
these samples.) Based on these results, it was decided
that the surface water migration route should be
further evaluated.
The tributary PPE sample set collected during Phase
1 did not exhibit any contamination at the time of
sampling. However, the Team observed that the
drainage path and tributary became very level and
shallow prior to, and in, the heavily wooded area.
Contaminants may settle out in this area due to its
level terrain and many flow obstructions. Any
contaminants here would be transported downstream
only during heavy flow or storm events. It was
decided to collect additional surface water and
sediment sample sets along the drainage path and
tributary using a judgmental approach during Phase 2
activities. If the site were to continue under
Superfund remedial site evaluation for consideration
of the surface water migration route, contamination
must have been detected or suspected in the
perennially flowing stream, Little Creek. A surface
water and sediment sample set at the PPE for the
tributary to Little Creek was collected to establish
whether the contamination had migrated to the surface
water body. The sediment sample would establish
historical contamination, while the surface water
aliquot would indicate current contamination
migration. (Phase 2 sampling activities were
scheduled to occur while the intermittent tributary was
flowing.) A background sample set was collected in
Little Creek by obtaining surface water and sediments
upstream of the tributary confluence (PPE).
Phase 3 activities are discussed in Section 6.7.
2.13.7 Parameters for Analysis
During Phase 1 sampling activities, full priority
pollutant metals and total cyanide analyses were
conducted on all soil, ground-water, surface water,
and sediment samples sent to the laboratory. These
parameters were initially selected based on research of
plating chemistry (plating facilities generally use
either an acid bath or basic cyanide bath to achieve the
desired coating on their metal products). Since Phase
1 samples were collected from the areas of highest
suspected contaminant concentration (i.e., sources and
drainage pathways), Phase 2 samples (all media types)
were analyzed for total chromium, hexavalent
chromium (in water only), and cyanide, the only
analytes detected consistently during the Phase 1
analyses. During Phase 3, the samples sent to the
laboratory for definitive analysis were analyzed for
total chromium and cyanide.
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3.0 FIELD ANALYTICAL SCREENING AND SAMPLING EQUIPMENT
3.1 INTRODUCTION
Sample collection requires an understanding of the
capabilities of the sampling equipment, since using
inappropriate equipment may result in biased or
nonrepresentative samples. The limitations, uses,
construction, and ease of use of the equipment or
techniques must be understood prior to designing a
sampling plan.
Section 3.2 provides an overview of the most
commonly utilized field analytical screening
equipment and techniques that are applicable to
surface water and sediment sampling. Section 3.3
provides information for selecting sampling
equipment. The example site synopsis continues at
the end of the chapter.
3.2 FIELD ANALYTICAL
SCREENING EQUIPMENT
Field analytical screening techniques and equipment
may provide valuable information for developing
sampling strategies. Field analytical screening can
determine chemical classes of contaminants and in
some cases can identify particular substances of
concern. Real-time or direct-reading capabilities
narrow the possible groups or classes of substances,
which aids in selecting the appropriate laboratory
analytical method. These screening techniques are
useful and economical when gathering large amounts
of site data. The screening techniques can also be
utilized to select sample locations, as well as samples
to be sent for off-site laboratory analysis or
confirmation. The analytical screening methods
provide on-site measurements of contaminants of
concern, limiting the number of samples which need
to be sent for off-site analysis. All screening
equipment and methods described in this section are
portable (the equipment is hand-held and generally no
external power source is necessary). Screening
techniques for surface water and sediment sample
analysis are discussed in Table 1; the methods are
presented in a general order of those most utilized and
applied shown first. Field analytical screening
methods are most often used to identify waste or
contaminant source areas and may not be required
during all surface water and sediment sampling
events.
Field screening generally provides analytical data of
suitable quality for site characterization, monitoring
response activities, and health and safety decisions.
Its application with surface water and sediment
sampling may be more limited than with other sample
media. For investigations of water bodies, these
methods may assist with sample selection for
laboratory analysis or for a preliminary determination
of the extent of contamination in sediments or of a
contaminant plume in a static water body. Screening
methods can provide rapid, cost-effective, real-time
data; however, results are often not compound-
specific and not quantitative.
When selecting one screening method over another,
consider relative cost, sample analysis time, potential
interferences or instrument limitations, applicability to
the sample medium, detection limit, QA/QC
requirements, level of training required for operation,
equipment availability and durability, and data bias.
Also consider which elements, compounds, or classes
of compounds the screening instrument is designed to
analyze. As discussed in Section 2.9, the screening
method selected should be sensitive enough to
minimize the potential for false negatives. When
collecting samples for screening analysis (e.g.,
portable gas chromatograph), evaluate the detection
limits and bias of the screening method by sending a
minimum of 10 percent of the samples for laboratory
confirmation. For additional information on specific
field screening analytical techniques and equipment,
please refer to the U.S. EPA Compendium of ERT
Waste Sampling Procedures, OSWER Directive
9360.4-07 or Superfund Program Representative
Sampling Guidance, Volume 4 - Waste, OSWER
Directive 9360.4-14.
3.3 SURFACE WATER AND
SEDIMENT SAMPLING
EQUIPMENT AND
SELECTION
Sample collection requires an understanding of the
capabilities of the sampling equipment, since the use
of inappropriate equipment may result in
nonrepresentative samples. Select approved sampling
equipment based on the sample type and medium,
matrix, physical location of the sample point,
sampling objectives, and other site-specific
conditions. Site-specific conditions may dictate that
24
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only one method or type of equipment will work.
Also consider the equipment design. For example, a
device which aerates a sample during collection might
release volatile organic compounds and thus not yield
a sample representative of actual conditions.
Also consider the compatibility of the contaminants
being sampled with the composition of the sampling
device. All sampling devices should be of good
quality. They should be made of material that will not
affect the outcome of analytical results; they must not
contaminate the sample being collected and must be
able to be cleaned easily in order to reduce the risk for
cross-contamination. Use of a device constructed of
undesirable material may compromise sample quality
by having components of its material leach into the
sample or adsorb constituents of the sample. If a
sampling device cannot be easily decontaminated,
consider the cost-effectiveness of expendable
equipment. Standard construction materials typically
include Teflonฎ, polyvinyl chloride (PVC), glass,
stainless steel, and steel. Selection is commonly
determined by considering the substance to be
sampled and the cost of sampling.
Select, when possible, equipment that is easy to
operate, in order to decrease training requirements and
when wearing cumbersome personal protective
equipment. Complicated sampling procedures usually
require increased training and introduce a greater
likelihood of procedural errors; SOPs help to avoid
such errors. Follow SOPs for the proper use and
decontamination of all sampling equipment. The U.S.
EPA Compendium of ERT Surface Water and
Sediment Sampling Procedures, OSWER Directive
9360.4-03, provides SOPs for some standard surface
water and sediment sampling equipment and methods.
This section provides appropriate uses, advantages,
and disadvantages of select examples of surface water
and sediment sampling equipment. Representative
sampling requires that appropriate sampling
equipment be chosen for each sampling objective and
location. The surface water sample collected may
represent all phases or a specific stratum present in the
water, as required by the sampling objective.
Construction material, design and operation,
decontamination procedures, and the procedures for
proper use are factors to consider when selecting
equipment. The following characteristics of surface
water can affect the representativeness of a sample:
density, analyte solubility, temperature, and currents.
A sampling device should have a capacity of at least
500 milliliters, if possible, to reduce the number of
times the liquid must be disturbed and to reduce
sediment agitation.
When selecting sediment sampling equipment,
consider the width, depth, flow, and the bed
characteristics of the area to be sampled. Sediment
may be sampled in both flowing and standing water.
Samples may be recovered using a variety of methods
and equipment, depending on the depth of the aqueous
layer, the portion of the sediment profile required
(surface vs. subsurface), the type of sample required
(disturbed vs. undisturbed) and the sediment type.
Sediment is collected from beneath an aqueous layer
either directly using a hand-held device, or indirectly
using a remotely-activated device. Selection of a
sampling device is most often contingent upon the
depth of water at the sampling location as well as the
physical characteristics of the medium to be sampled.
Take care to minimize disturbance and sample
washing as the sample is retrieved through the
aqueous layer. It is important to get a representative
sample of all horizons present in the sediments.
Maintain sample integrity by preserving the sample's
physical form and thus its chemical composition.
Tables 2 and 3 provide examples of commonly used
surface water and sediment sampling equipment,
respectively, but the list is not exhaustive. The
advantages and disadvantages listed represent only
highlights of the equipment use. Additional details on
surface water and sediment sampling equipment and
procedures are provided in the U.S. EPA
Compendium of ERT Surface Water and Sediment
Sampling Procedures, OSWER Directive 9360.4-03.
3.4 EXAMPLE SITE
3.4.1 Selection of 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 wastestreams in order to select
initial judgmental sampling locations. During Phase 2
sampling, a portable XRF unit was used to determine
the extent of soil contamination and to identify
additional "hot spots." Soil samples to be sent for
laboratory analysis were placed into sampling jars.
An organic vapor detecting instrument (PID)
continued to be utilized throughout all field activities
for health and safety monitoring during Phases 1
through 3.
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The portable XRF was used during soil screening,
monitoring well installation, and sediment sampling.
Ground-water and surface water samples were
screened in the field for pH, conductivity, and
temperature using a three-in-one monitoring
instrument. The instrument probe was placed into a
clean glass jar containing an aliquot of the water
sample. The instrument was decontaminated prior to
and after each sample screening.
3.4.2 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-31D, a
shallower-survey ing 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.
3.4.3 Selection of Sampling
Equipment
Disposable plastic scoops were used for Phase 1 soil
and sediment sampling. Phase 1 ground-water and
surface water samples were collected directly into
sample containers. For Phase 2, soils were collected
from the near surface (0-4 inches) and at depth.
Stainless steel trowels were used to collect shallow
samples. Subsurface samples were collected by
advancing boreholes using a hand-operated power
auger to just above the sampling zone and then using
a stainless steel split spoon to retrieve the soil. The
split spoon was advanced with a manual hammer
attachment.
Monitoring wells were installed using a dual-tube, air
percussion drill rig. Borehole soil samples were
retrieved using 2-foot stainless steel split spoon
samplers. Soil from the split spoons was transferred
to sample containers using disposable plastic scoops.
Ground water was sampled in Phase 2 from the
monitoring wells installed on site. The ground-water
samples were obtained using dedicated bottom-fill
Teflonฎ bailers. The bailer was attached to nylon
rope, which was selected because less material would
be adsorbed onto the nylon and brought out of the
well. Residential ground-water samples were
collected directly into the sample containers from the
kitchen sink tap. Water level and depth measurements
were obtained from monitoring wells using
decontaminated electronic measuring equipment.
As in Phase 1, Phase 2 sediment samples were
collected using dedicated disposable plastic scoops.
Surface water samples were collected directly into the
sample containers. The shallow depth and narrow
breadth of the intermittent tributary and Little Creek
did not require any specialized equipment or remote
sampling devices.
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TABLE 1: SURFACE WATER AND SEDIMENT FIELD ANALYTICAL SCREENING EQUIPMENT
Instrument
Use(s)
Advantage(s)
Disadvantage(s)
Direct -
Reading/
Real - Time
Instruments
Portable monitoring instruments used to
measure or identify specific parameters
under field conditions including: pH,
specific conductivity, temperature, salinity,
and dissolved oxygen
1 Portable and easy to operate and
maintain in the field
1 Qualitative identification
1 May be used with probes placed
directly into the sample medium
May return a reading with a high degree
of error
Field Test Kits
and
Colorimetric
Indicator Tubes
Used for detecting specific compounds,
elements, or compound classes in surface
water and sediment
Rapid results
Easy to use
Kits may be customized to user needs
Limited number of kit types available
Interference by other analytes is
common
Subjective interpretation is needed
Can be prone to error
May have limited shelf life
Colorimetric tubes may be used for
ambient air only
Photoionization
Detector (PID)
Detects and measures total concentration of
volatile organic compounds (VOCs) and
some non-volatile organic and inorganic
contaminants in ambient air or container
headspace; used to evaluate existing
conditions, identify potential sample
locations, or identify extent of
contamination
1 Immediate results
1 Easy to operate and maintain
1 Detects to parts per million (ppm) level
for headspace analysis
Limited use to quantify specific
substances
Does not detect methane
Readings can be affected by high winds,
humidity, condensation, dust, power
lines, and portable radios
Probe should not be placed directly into
sample medium
Flame
lonization
Detector (FID)
Detects and measures the level of total
organic compounds (including methane) in
ambient air or container headspace; used to
evaluate existing conditions, identify
potential sample locations, or identify
extent of contamination
1 Immediate results
1 Detects to ppm level for headspace
analysis
1 Rugged
1 Available with a GC mode to detect
specific VOCs
Does not respond to inorganic
substances
Does not recognize and may be
damaged by acids
Requires training and experience
Requires a hydrogen fuel source
Probe should not be placed directly into
samnle medium
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TABLE 1: SURFACE WATER AND SEDIMENT FIELD ANALYTICAL SCREENING EQUIPMENT (Cont'd)
Instrument
Use(s)
Advantage(s)
Disadvantage(s)
Hazard
Categorization
(hazcat)
Performed as an initial screen for hazardous
substances to provide identification of the
classes/types of substances in the individual
surface water or sediment sample
Rapid categorization of unknown
liquids
Good for screening and determining
contaminant compatibility
Not analyte-specific, yields only basic
information (e.g., base vs. acid,
chlorinated vs. non-chlorinated
substance)
Requires numerous chemical reagents
Requires interpretation of results
Portable Gas
Chromatograph
(GC)
Used to measure occurrence and
concentration of VOCs and some semi-
VOCs
1 Can screen "hot spots"
1 Determines potential interferences
1 Conducts headspace analysis
1 Semi-quantitation of VOCs and semi-
VOCs
Highly temperature sensitive
Requires set-up time, many standards,
and extensive training
Radiation
Detector
Detects the presence of selected forms of
radionucliides in sediments
1 Easy to use
1 Probes for one or combination of
alpha, beta, or gamma emitters
Units and detection limits vary greatly
Time intensive for detailed surveys
Experienced personnel required to
interpret results
Portable X-ray
Fluorescence
(XRF)
Used to detect heavy metals in sediments
1 Rapid sample analysis
1 Detects to ppm level (detection limit
should be calculated on a site-specific
basis)
Requires trained operator
Sediment must be dried
Potential matrix interferences
Detection limit may exceed action level
Radioactive source
Cannot be used for surface water
samnles
28
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TABLE 2: SURFACE WATER SAMPLING EQUIPMENT
Sampler
Uses
Advantages
Disadvantages
Laboratory-
cleaned
Sample
Container
(Direct
Method)
Used to collect samples from surface and
shallow depths of surface water bodies
' Quick and easy to use
' No decontamination required
' Disposable
' Reduces risk of cross-contamination from sampling equipment
' Reduces the loss of volatile fraction during transfer to a sample
container
' Preferred if there is an oily layer on the sample surface; the
layer will not stick to a sampling device and thus miss being
transferred to the sample container
Cannot be used for other water bodies, such as waste
impoundments, where contact with concentrated
contaminants is a concern
Labelling can be difficult
May not be possible when containers are pre-preserved
Scoop,
Ladle,
Beaker
(Transfer
Devices)
Stainless steel, Teflonฎ, or other inert
composition material devices to transfer
the sample directly into a sample
container at a near shore location
' Easy to use and decontaminate
' Allows collection without a loss of preservative in the sample
container
Difficult to maneuver sample especially if placing into VOA
vials
Avoid equipment with painted or chrome-plated surfaces
May aerate sample releasing VOCs, or some contaminants
may adhere to the surface of the transfer device
Weighted
Bottle
Sampler
Used to collect samples in a water body
or impoundment at predetermined depth
' Easy to decontaminate
' Simple to operate
' Sampler remains unopened until at desired sampling depth
Cannot be used to collect liquids that are incompatible with
the weight sinker, line or actual collection bottle
Sample container may not fit into sampler, thus requiring
additional equipment
Sample container exposed to matrix
Pond Used for near shore sampling where
Sampler cross-sectional sampling is not
appropriate and for sampling from outfall
pipe or along a disposal pond, lagoon, or
pit bank where direct access is limited
' Easy to fabricate using a telescoping tube; not usually
commercially available
' Can sample at depths or distances up to 3.5 meters (can sample
areas difficult to reach with extension)
Difficult to obtain representative samples in stratified water
bodies
Sample container may not fit into sampler, thus requiring
additional equipment
Peristaltic Used to extend the reach of sampling
Pump effort by allowing the operator to reach
into the water body, sample at depth, or
sweep the width of narrow streams
through the use of Teflonฎ or other
tubing
Very versatile
Easy to carry and operate; fast
With medical-grade silicone, it is suitable to sample almost
any parameter including most organic contaminants
Sample large bodies of water
Capable of lifting water from depths in excess of 6 meters
Depth limited to 7.5 meters/25 feet
Cannot be used if volatile compounds are to be analyzed
Lift ability decreases with higher density fluids, increased
wear on silicone pump tubing, and increases with altitude
Oil and grease contaminants may adhere to tubing and thus
decrease concentration in sample
Must often change tubing between locations to decrease
cross-contamination; must always have extra tubing on hand
At high flow, must weight tubing in stream
29
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TABLE 2: SURFACE WATER SAMPLING EQUIPMENT (Cont'd)
Sampler
Bailer
Kemmerer
Bottle/Van
Dorn
Sampler
Bacon
Bomb
Sampler
Wheaton
Dip Sampler
Depth-
Integrating
Samplers
PACS Grab
Sampler
Uses
Used for collecting samples in deep
bodies of water where cross-sectional
sampling is not appropriate
Used when access is from a boat or
structure such as a bridge or pier, and
where discrete samples at specific depths
are required
Used to collect samples from discrete
depths within a water body; generally
used when access is from a boat or
structure
Useful for sampling liquids in shallow
areas or from areas where direct access is
limited; also useful when sampling from
an outfall pipe
Used to collect water and suspended
sediment samples; used with the EWI
and EDI composite sampling techniques
Used to collect water samples from
impoundments, or ponds with restricted
work areas
Advantages
Easy to use
No power source needed
Bailers can be dedicated to sample locations
Disposable equipment available
Can be constructed of a varietv of materials
Can take discrete samples at specific depths
Can sample at great depths
Kemmerer Bottle lowers vertically; Van Dorn Sampler lowers
horizontally, which is more appropriate for estuary sampling
Remains unopened until the sampling depth
Can collect a discrete sample at desired depth/stratum
Widely used and available
Long handle allows access from a discrete location
Sample container is not opened until specified sampling depth
Sampler can be closed after sample is collected ensuring
integrity
Easy to operate
Allows for collection of representative samples of suspended
materials
Samples proportionate to the velocity of the water body
Allows discrete samples to be collected at depth
Disadvantages
Transfer of sample may cause aeration, thus not appropriate
for VOCs
Inappropriate for strong currents or where a discrete sample
at a specific depth is required
Sampling tube is exposed to material while traveling down to
sampling depth
Transfer of sample into sample container may be difficult
May need extra weight
Often constructed of materials incompatible with sample
Difficult to decontaminate
Difficult to transfer sample to sample container
Tends to aerate sample thereby losing volatile organic
constituents
Depth of sampling is limited by length of extension poles
Exterior of sample container may come in contact with
sample
Sample container may not fit into sampler
Requires experienced operator
Depth of sampling is limited by length of extension pole
Difficult to decontaminate
Note: Standard operating procedures and example figures of some of the equipment is available in the U.S. EP Compendium ofERT Surface Water and Sediment Sampling Procerfwre^OSWER
Directive 9360.4-03.
Abbreviations
EWI = equal-width-increment
EDI = equal-discharge-increment
30
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TABLE 3: SEDIMENT SAMPLING EQUIPMENT
Sampler
Scoops,
Trowels,
Dippers,
Shovels
(Direct Method)
Vertical-pipe,
Core Sampler
Ponar/Ekman/
Peterson
Thin-Wall Tube
Auger
Veihmeyer
Sampler
Uses
Used for surface sediments where
water depth is shallow (limited to
near surface)
Used to collect samples of most
sediments to depths of 75 cm (30 in.)
Ponar dredge is used to sample most
types of sediments
Ekman dredge is used where bottom
material is unusually soft, such as
organic s u ges
Peterson dredge is used when
bottom is rocky, in deep water or in a
Used to collect consolidated
sediments at surface and at depth
Used for sampling most types of soil
and sediments, except very wet or
stony sediments
Advantages
Quick and easy to use
Easy to decontaminate
Available in a variety of materials
Appropriate for consolidated sediments
Disposability reduces the risk for cross-
contamination
Laboratory scoop is less subject to
corrosion or chemical reactions than
commercially available garden or
household tools (less risk for sample
contamination)
Easy to use
Can collect undisturbed sample
(minimum loss of fine fraction) that
can profile any stratification as a result
of changes in deposition
Provides historical record of deposition
Ponar is easily operated by one person;
light weight
be operated without a winch or crane
Appropriate for most sediment types
rom si s o granu ar ma ena s
Ekman can obtain samples of bottom
fauna
Peterson can be used in rocky
substrates and high velocity water
Easily operated by one person
Easy to use
Preserves core sample
Can achieve substantial depths with
appropriate length of tubing
Various driveheads available for
different sediment types
Disadvantages
Disturbs the water/sediment interface and may alter sample integrity; fine fraction is lost
Not efficient in mud or other soft substrates
Difficult to release secured undisturbed samples to readily permit subsurface sampling
Difficult to maneuver sample especially if placing into VOA vials
Limited by depth of aqueous layer
Avoid equipment with painted or chrome-plated surfaces (common with garden trowels)
When used in impoundments, penetration depths could exceed that of substrate and
damage the liner material
A relatively small surface area and sample size result in the need for repetitive sampling
to obtain an adequate amount for analysis
Dredges are normally used from a boat, bridge or pier due to the weight of the
equipment which may require a boom for lowering or raising
Not capable of collecting undisturbed sample and may cause agitation currents that may
temporarily resuspend some settled solids
Ekman is not suitable for sand rock and hard bottoms ve elation covered bottoms
and streams with high velocities
Should not be used from a bridge more than a few feet high because spring mechanism
Not capable of collecting an undisturbed sample and may cause agitation currents that
may temporarily resuspend some settled solids
Peterson can displace and miss light materials if allowed to drop freely
Limited by the depth of the aqueous layer
May be difficult to remove core sample from auger
Possible washout during retrieval
Very difficult to clean
Parts needed for sampler are not appropriate for certain analyses
Not appropriate in rocky substrate
31
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TABLE 3: SEDIMENT SAMPLING EQUIPMENT (Cont'd)
Sampler
PACS Grab
Sampler/Sludge
Getter
Sampling Trier
Soil Coring
Device/ Silver
Bullet Sampler
Sludge Judge
Hand Corer
Gravity Corer
Bucket and
Pesthole
Augers
Uses
Used for collecting grab samples
from ponds and impoundments at
depth
Used to collect sediments up to 40
inches depth from water surface
Used when a core sample is required
Used to collect a core of sediments
or water and sediments
Used for sediments in water that is
very shallow (a few inches)
Collects core samples from most
sediments; can be used in water
deeper than 5 feet
Used for direct method samples
Advantages
Allows discrete samples to be collected
at depth
Can be used in heavy sediments or
sludges, or moderately viscous
materials
Preferred for moist or sticky samples
Contains a collection tube which holds
core relatively intact
Bit of silver bullet sampler is
replaceable
Easy to use
Core allows delineation of settled state
of sediments or physical state of water
body
Easy to use
Preserves sequential layer of deposit
(useful for historical information)
Appropriate for trace organic
compounds or metals analyses
May have a check valve on top to
prevent wash-out during retrieval
Collects undisturbed samples
Can collect to a depth of 75 cm (30 in.)
within the sediment substrate
Preserves sequential layer of deposit
(useful for historical information)
Has a check valve to prevent washout
during retrieval
Direct sample recovery
Fast and easy to use
Provides a large volume sample
Disadvantages
Not useful in very viscous materials
Depth of sampling is limited by length of extension pole
Heavy, possibly requiring more than one person to operate
Difficult to use in stony or sandy substrates
May be difficult to remove sample from sampling device
Difficult to use in rocky or tightly packed substrates
Depth restrictions
Use is limited due to possible reactivity of construction material
Difficult to decontaminate
Not useful in thick sediments
Can be disruptive to water/sediment interface
May cause disruption to sample integrity
Delivers small sample size requiring repetitive sampling
May damage liners in impoundments if penetration is too deep
Not suitable for obtaining coarse-grained samples
Disturbs sediment horizons
May cause disruption to sample integrity
Pesthole augers that are designed to cut through fibrous, rooted swampy areas have
limited sample collection utility
Note: Standard operating procedures and figures of many of these equipment types are available in the U.S. EP'Compendium ofERT Surface Water and Sediment Sampling Procerfwre^OSWER
Directive 9360.4-03.
32
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4.0 FIELD SAMPLE COLLECTION AND PREPARATION
4.1 INTRODUCTION
When sampling a water body, the following critical
factors must be considered to ensure that the sample
is representative: points of sampling, frequency of
sampling, and maintenance of integrity of sample
prior to analysis. During a response action, proper
field sample collection and preparation methods are as
important as proper sampling equipment selection.
Sample collection refers to the physical removal of
water or sediments from a water body for the purposes
of either screening or laboratory analysis, and includes
sample quantity and sample volume. Field sample
preparation refers to all aspects of sample handling
from collection to the time the sample is received by
the laboratory. This chapter provides information on
sample collection and preparation for various sample
types and sources.
The collection of samples from water bodies presents
unique challenges. Some samples involve merely
collection by a direct method in shallow waters.
Often however, site-specific conditions may dictate
the use of special equipment to access the sample
location, increased health and safety concerns, and
proper timing to consider tidal fluctuations and/or
flow rates.
4.2 SAM RLE VOLUME AND
NUMBER
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 should be. However, sampling
activities are often limited by sampling budgets and
project schedules.
Sampling objectives and analytical methods are
considerations in determining appropriate sample
volume and number. The volume of a sample should
be sufficient to perform all required laboratory
analyses with an additional amount remaining to
provide for analysis of QA/QC samples (including
duplicate analyses). The volume of water samples can
vary depending on the requirements of the laboratory
and the analytical method(s). The minimum volume
collected should be three to four times the amount
required for the analysis. Typically, no more than 8
liters are required for each water sample. The amount
of sediment required for analysis can also vary but
will not usually exceed 16 ounces. Always consult
the analytical laboratory during sampling design to
determine the adequate volume required for each
matrix and location. Sometimes site conditions may
limit the available sample volume; creek waters may
be shallow during a dry season or the sediments may
consist of a rocky substrate. Review the site
conditions when selecting laboratory analyses. Where
sample volume may be limited, it may be necessary to
reduce the number of analyses to those most critical to
the investigation and its objectives.
The number of sample locations will depend upon
site-specific requirements and must satisfy the
investigation objectives. A few selected locations
may be enough to identify the existence of
contamination, or multiple location, systematic
sampling may be required to delineate the full extent
of contamination. Both strategies may be used during
different phases of a site investigation. The physical
characteristics of the water body might also dictate
sample numbers. A complicated, well-developed
system of tributaries, changes in flow, and sediment
deposition will necessitate additional sample locations
to ensure that samples are representative of site
contaminant migration conditions. The number of
samples may vary according to the particular sampling
approach used at the site. Chapter 2 provides
additional information on sampling approaches and
sample locations and numbers.
4.3 SURFACE WATER SAMPLE
COLLECTION
Sampling situations vary widely and therefore no
universal sampling procedure can be recommended.
Sampling considerations and guidelines, however, do
apply to every case. Prior to sample collection,
review the characteristics of the water body. When
sampling surface waters and sediments, always collect
the water samples before sediment samples to avoid
disturbing sediments into the water and biasing the
water sample. Avoid surface scum. Sampling should
proceed from downstream to upstream locations to
minimize disturbance. Determine tidal influences and
flow rates, which can affect sample collection.
33
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Surface water samples are generally collected as grab
samples because of the natural mixing effect of
flowing waters. However, compositing samples may
assist in the attempt to document intermittent or
sporadic contaminant discharges. This is particularly
of concern with effluent releases which are highest
during certain times of the day. Representative
sampling would seek to obtain an average
concentration from release and no release conditions.
Section 2.4.2 describes composite samples and
compositing approaches. Surface water compositing
is generally completed using the surface water
collection equipment described in Chapter 3. A
programmable composite sampler is available for time
compositing. This electronic pumping tool collects an
aliquot of the sample water from a stationary location
over designated time intervals (e.g., 30 or 60 minutes)
for a certain study period (e.g., 24 hours). This
equipment allows the collection of an "averaged,"
uniform, representative sample, but will not
distinguish a particular interval when contaminant
levels are high or low. The criteria for selection of the
"automatic sampler" are the same as for other
sampling equipment, including compatibility, sample
integrity, etc. (Automatic sampling equipment is
generally not used at EPA CERCLA sites prior to
remedial investigations and is therefore not discussed
in greater detail in this document; please refer to U.S.
EPA, 1986 and Krajca, 1989 for further discussion of
these devices.)
Fresh water environments are commonly separated
into three groups: flowing waters, such as rivers,
streams, and creeks; static water bodies, such as lakes,
ponds, and impoundments; and estuaries. These
waterways differ in characteristics, therefore sample
collection must be adapted to each. A discussion of
special considerations for sampling in wetlands is also
included in this section. This section provides general
information on sampling several types of water
bodies. Table 4 compares advantages and
disadvantages of sample method locations. For
specific sampling information, refer to the U.S. EPA
Compendium of ERT Surface Water and Sediment
Sampling Procedures, OSWER Directive 9360.4-03.
TABLE 4: SURFACE WATER AND SEDIMENT SAMPLE METHOD LOCATION
Location
Water Body Type
Advantages
Disadvantages
Bridge, Pier
Rivers, streams, large ponds or
impoundments
Provide ready access;
allow sampling at any
point across water body
Little disturbance
Structure can alter water
flow and influence
sediment deposition and
scouring
Not always in ideal
location
Wading,
Shore
Lakes, ponds, slow-moving
rivers and streams
Ease of collecting
sediment samples
Disturbs bottom
deposits; introduces
particulate and sediments
into water
Samplers must carry
large amounts of
equipment
Boat
Slow-moving, deep water, and
estuaries
Appropriate for
locations where no other
means are available
Safety concerns
Difficult to
decontaminate
Requires a means of
launching and
transporting boat
May affect flow of
water
Depending on depth,
may disturb sediments
34
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4.3.1 Rivers, Streams, and Creeks
This group of water bodies includes outfalls and
drainage features (e.g., ditches and culverts), as well
as rivers, streams, and creeks. Methods for sampling
flowing water bodies vary from the simplest direct
methods to more sophisticated multipoint sampling
techniques. The size of the stream or river and its
amount of turbulence can affect the number and type
of sampling locations. In small streams (less than 20
feet wide) it is possible to select a location with well-
mixed water for grab sampling. A grab sample
collected at mid-depth in moving water at the main
flow line would represent the entire cross-section.
(The main flow line is not necessarily the center of the
stream; observe flow patterns across the surface to
identify this area.) Slightly larger streams or rivers
would require multiple samples at locations across the
channel width. At the minimum, one vertical
composite (consisting of grab locations from just
below surface, mid-depth, and just above the bottom)
collected at the main flow line would be necessary.
Identifying sampling locations that are well mixed
vertically or ones that are horizontally stratified is
useful prior to sampling. When sampling rivers,
streams, or creeks, locate the area that exhibits the
greatest degree of cross-sectional homogeneity. Since
mixing is primarily attributed to turbulence and water
velocity, selecting a site immediately downstream of
a mixing zone will ensure good vertical mixing. In
the absence of mixing zones, the selection of a site
without any immediate point sources, such as
tributaries and industrial and municipal effluent, is
preferred for the collection of representative water
samples.
For fast flowing rivers and streams, it may be difficult
to collect a mid-channel sample at a specific location;
health and safety concerns must dictate where to
collect the sample. For low flowing streams, health
and safety concerns are reduced, but obtaining a
specific representative location may be difficult. For
low flow or intermittent streams, either locate an area
where a pool has been created or, in the most extreme
situations, use a cleaned trowel to create a pool in the
sediments for water to accumulate.
When sampling a point source, two samples from
channel mid-depth are typically drawn: one upstream
and one adjacent to, or slightly downstream of, the
site PPE or the point of discharge. Additional
samples may be required if multiple discharges or
additional tributaries are present. Structural features
such as dams, weirs, and bridges can cause changes in
the physical characteristics of a stream or river by
creating shallow pools. When water travel times are
long through these areas, sampling locations should be
established in them. Some stream structures allow
overflow that significantly re-aerates oxygen-deficient
water. This requires locations to be close (both
upstream and downstream) to the structures in order to
measure the rapid and artificial increase in dissolved
oxygen (DO), which may cause the sample to be non-
representative. Also collect a sample at a location
well away from the aeration effect of the obstacle.
4.3.2 Lakes, Ponds, and
Impoundments
The number of samples collected in these three types
of water bodies will vary according to the size and
shape of the water body. Stratification from
temperature differences is often present in these
bodies and is more prevalent than in rivers or streams.
Different layers can be detected visually as well as by
compiling a temperature profile. In ponds and small
impoundments, a single vertical composite at the
deepest point would be adequate to characterize the
water body. (The deepest point of a naturally formed
pond is generally near the center (although this may
need to be determined), and near the dam in an
impoundment.) Measure DO, pH, and temperature in
each aliquot of the vertical composite. Fewer mixing
zones require more samples to be collected. One way
to obtain representative samples is to divide the area
into a grid and then perform systematic grid sampling
at each node. If stratified, collect a sample from each
stratum at each node location (three-dimensional or
stratified sampling). Transect sampling may also
apply.
Lakes and larger impoundments require several
vertical aliquots to be collected which can then be
composited. Sampling locations may be determined
by a transect or grid. Separate composites of
epilimnetic and hypolimnetic zones may be collected
if desired; however, a composite should consist of
several vertical aliquots collected at various depths.
Irregularly shaped lakes may require additional
separate composite samples to be collected. Lakes
where discharges, tributaries, land use characteristics,
and other such factors may affect mixing, water
quality and/or the accuracy of representative water
body sampling may also require additional composite
samples. Compositing is discussed further in
Section 2.4.2.
Surface impoundments (such as wastewater lagoons)
which contain concentrated wastes are addressed in
U.S. EPA Superfund Program Representative
-------
Sampling Guidance, Volume 4 - Waste, OSWER
Directive 9360.4-14. Precautions and concerns exist
when dealing with waste impoundments which are not
addressed in general surface water and sediment
sampling.
4.3.3 Estuaries
Estuaries are areas where inland fresh water (both
surface water and ground water) mixes with oceanic
saline water. Estuaries are generally categorized as
mixed, salt wedge, or oceanic, dependent upon inflow
and mixing properties. Determining estuary category
is critical to establishing sample locations. Estuaries
may be classified as critical areas, wetlands, or
fisheries, and therefore also present special target
considerations.
Mixed estuaries are characterized by homogenous
salinity in the water column and a gradual increase in
salinity toward the sea. This type of estuary is
typically shallow and well mixed. Locating specific
sampling points, particularly in the vertical water
column, is not critical due to this mixing. Location
with respect to the open sea is more important in
mixed estuaries.
Salt wedge estuaries are characterized by a significant
vertical increase in salinity and stratified fresh-water
flow along the surface. Density differential between
fresh and saline waters overrides any vertical mixing;
a salt wedge tapering inland moves horizontally with
the tide. Contamination entering from upstream may
be missed if sampling into the salt wedge.
Oceanic estuaries exhibit salinity levels near to full-
strength ocean waters. Seasonally, fresh-water inflow
is low compared to the fresh-saline water mixing
occurring near, or at, the shoreline.
Sampling in estuary zones is typically performed on
successive slack tides. Estuary studies can be
complex and are usually performed in two phases,
during both wet and dry periods. Estuary dynamics
can be affected by fresh-water inflow sources and
therefore cannot be studied in a single season.
Samples are generally collected at mid-depth in areas
where the depth is less than 10 feet, unless the salinity
profile indicates the presence of salinity stratification.
In those cases, samples are collected from each
stratum. Measurements of dissolved oxygen and
temperature should accompany the sampling. In
estuaries where the depth is greater than 10 feet, water
samples may be collected at the one-foot depth, mid-
depth, and one foot from the bottom.
True salt-water bodies (e.g., oceans, salt lakes) are
rarely sampled at Superfund sites. Salt-water bodies
would be sampled according to the fresh water and
estuary guidance above. Review stratification,
flow/turbulence, and other site factors prior to
developing the sampling plan. As with fresh water
bodies, sampling in estuaries can demonstrate current
and historical contamination through surface water
and sediment samples, respectively. Be certain to
evaluate the effect of the salt concentration on the
contaminants of concern and their analytical methods
in order to accurately document a contaminant plume
or establish connection to a source or site. Also
consider the salt concentration and its compatibility
with sampling equipment. For estuarine sampling, the
Van Dorn horizontal sampler is often utilized.
4.3.4 Wetlands
Wetlands are considered a sensitive environment and
generally include swamps, marshes, bogs and similar
areas. Wetlands can be natural or man-made.
Wetlands can include fresh and estuarine water
systems and are commonly contiguous to open waters
(e.g., rivers, lakes, bays). As defined in 40 CFR Part
230.3, as part of Superfund's Hazard Ranking System
(HRS), wetlands are those "areas that are inundated or
saturated by surface or ground water at a frequency
and duration sufficient to support, and that under
normal conditions do support, a prevalence of
vegetation typically adapted for life in saturated soil
conditions." Wetlands are also identified using other
definitions, including a classification system of the
U.S. Fish and Wildlife Service (USFWS) and the
1989 Federal Manual for Identifying and Delineating
Jurisdictional Wetlands, as is used by the U.S. Army
Corps of Engineers.
National Wetlands Inventory maps use the USFWS
classifications. These maps serve as an excellent
starting point for identifying wetlands at a site, but
should not be used as the sole source of identification.
(A detailed comparison of the relationship between
the HRS and the USFWS definitions of wetlands is
addressed in the U.S. EPA Hazard Ranking System
Guidance Manual, OSWER Directive 9345.1-07,
Section A.2.) Where possible, an attempt should be
made to field verify and document (e.g., logbook,
photograph) the wetlands location and area.
In some instances, historical data may document the
presence of wetlands which no longer exist during the
site reconnaissance. Attempt to determine whether
the wetlands were eliminated or filled, particularly if
the alteration was due to site activity. Dredged or
36
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filled former wetlands may affect sampling design,
methods, and results due to the potential effects from
non-native soils, confined or void subsurface spaces,
or buried organic layers and on-site contaminants.
Special care should be taken when sampling wetlands
to collect surface water and sediment samples free of
vegetation and other organic matter or detritus. As
with other surface water and sediment samples,
consider curves and bends, slow versus fast flow, and
depositional areas when selecting locations. Due to
the slow movement of water through the vegetated
wetlands, contaminants may tend to collect in
wetlands sediments. Wetlands may also serve as a
valuable source to document historical contaminant
releases. For some purposes (e.g., HRS
documentation), an aqueous sample is preferred or
required to document contamination within wetlands,
therefore surface water samples should be collected
where possible for all response action considerations.
As with other water bodies, wetlands can demonstrate
historical contamination through sediment samples,
current contamination through surface water samples,
and concern for future contamination if the wetlands
can be documented to be the receiving body for a
contaminant drainage pathway or surface water route,
although not currently exhibiting any site-related
contamination. The probable point of entry for a
tributary or drainage path into a surface water body
may be located within adjoining wetlands. As a
sensitive environment, wetlands present special threat
and target considerations beyond those of other water
body systems.
Depending on the type of wetlands and the season,
wetlands may contain fresh or salt water, and
saturated or dry sediments. Follow the protocols and
procedures discussed throughout this guidance
document for sampling each medium, respectively,
depending on the site-specific characteristics of the
wetlands. Wetlands, if periodically dry, should be
sampled during a wet period, if possible, to establish
the wetlands sample as a sediment versus a surface
soil. For complex sites with extensive surface water,
sediment and wetlands concerns, a wetlands expert
should be consulted for identification, delineation and
sampling.
4.4 SEDIMENT SAM RLE
COLLECTION
and are subject to variations in texture, bulk
composition, water content, and pollutant content.
Therefore, large numbers of samples may be required
to characterize a small area. Many sediment samples
along the cross-section of a river or stream need to be
collected in order to accurately characterize the
deposits. Generally, samples are collected at quarter
points along the cross-section of the water body.
Aliquots can usually be combined into a single
composite sample except for those of unlike
composition. For small streams, one single sediment
sample can be collected at the main flow line of the
water body. In most cases, a sediment sample is
collected at the same location(s) as a surface water
sample.
Sediments in low flowing waters are largely the
products of erosion and may contain a variety of
organic matter. Sediment samples from ponds, lakes,
and reservoirs should be collected approximately in
the deepest point of the water body. This is especially
applicable to reservoirs formed by impoundments of
rivers or streams. Coarser grain sediments are found
near the headwaters of the reservoir, while bed
sediments are composed of fine-grained materials
which may have an increased concentration of
contaminants. Sediment sampling locations can be
influenced by the shape, flow pattern, depth
distribution, and circulation of the water body.
Sediment samples from ponds and lakes can be
collected from each node of the grid or transect set up
for sampling surface water. For streams or rivers,
collect a sediment sample in at least two locations:
one upstream and one adjacent to, or slightly
downstream of, the site PPE or at point of discharge.
Consider depositional versus erosional areas against
the objectives for sampling; contaminants tend to
concentrate in the fine-grained sediments in
depositional zones.
Take care to minimize disturbance and sample
washing as the sediment is retrieved through the water
column. Fine fractions lost during sample collection
can result in a non-representative sample. Any liquid
collected when sampling can be considered
representative of sediment conditions. Wet sediments
which are to be analyzed while still wet should be
collected in rigid containers, not collected or stored in
bags.
As with water sampling, determine tidal influence and
its possible effect on sediment sample collection.
Sediments are typically heterogenous in composition
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4.5 SAMPLE PREPARATION
4.5.2 Homogenizing
Sample preparation depends on the sampling
objectives and analyses to be performed. Proper
sample preparation and handling maintain sample
integrity. Improper handling can render samples
unsuitable for analysis. For example, homogenizing
and compositing samples result in a loss of volatile
constituents and are thus inappropriate methods when
volatile contaminants are of concern. The effective
use of SOPs can ensure that the same methods are
used for all samples and by all samplers. Where
possible, the same person should sample all of one
matrix per water body to ensure similar methodology
in collection. Sample preparation for water and
sediments may include, but is not limited to:
Removing extraneous materials
Homogenizing
Splitting
Compositing
Final preparation
4.5.1 Removing
Materials
Extraneous
During sample collection, identify and discard
materials from the sample which are not relevant or
vital for characterizing the site. Avoid the collection
of floating or suspended debris (e.g., leaves, paper
trash, etc.) in the surface water flow or column. For
sediments, avoid collecting decaying or other organic
material, such as twigs, leaves, roots, and insects.
Avoid trash and other unrelated materials. Remove
the materials with the cleaned sampling tool, not with
your hand or other instrument which might cross-
contaminate the sample. The presence of extraneous
materials may introduce an error into the sampling or
analytical procedures.
Not all external materials are extraneous, however.
For example, some contaminants may be adsorbed
onto inert materials, such as fly ash or other industrial
by-products or waste, which settle onto the bottom
sediments. Collect samples of any material thought to
be a potential source of contamination. Discuss any
special analytical requirements for extraneous
materials with the project team (e.g., project
management, geologist, chemist), and notify the
laboratory of any special sample handling
requirements or method changes.
Homogenizing is the mixing or blending of a grab or
composite sample to distribute contaminants
uniformly within the sample. Ideally, proper
homogenizing ensures that all portions of the sample
are equal or identical in composition and are
representative of the total sample collected.
Incomplete homogenizing thus introduces sampling
error. All samples to be composited or split should be
homogenized after all aliquots have been combined.
Homogenizing generally does not apply to water
samples; unless stratified, surface water is assumed to
be homogenous due to natural mixing. If phases
occur, treat each stratum as a unique homogenous
medium and sample each separately. The mixing of
sediments may release some contaminants into the
water phase of the sediment sample. If homogenizing
is required, manually mix the sediment sample using
a spoon or scoop and a tray or bucket constructed of
inert or compatible materials (stainless steel is
preferred). Samples can also be homogenized using
a mechanically operated stirring device as depicted in
ASTM Standard D422-63. Do not homogenize
samples for volatile compound analysis.
4.5.3 Splitting
After collection, samples are split into two or more
equivalent parts 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. Split samples also provide measures of sample
variability and analytical error (field replicates).
Homogenize the samples before splitting, when
collecting only non-VOC sediment samples. For each
parameter, split water samples by alternately filling
sample collection jars for the sample and its split from
the same sampling device. For sediment, alternate
spoonfuls of homogenized sample between collection
jars. Surface water and sediment samples for VOC
analysis should not be homogenized; instead, collect
two uniform samples concurrently from the same
location (collocated samples).
4.5.4 Compositing
Compositing is the process of physically combining
and homogenizing (if applicable) several individual
aliquots of the sample. The field preparation
technique of compositing of samples requires that
each discrete aliquot be equal, and that the aliquots be
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thoroughly homogenized. Compositing samples
provides an "average" concentration of contaminants
over a certain number of sampling points, which
reduces both the number of required laboratory
analyses and the sample variability. Compositing can
be a useful technique but must always be implemented
with caution. Compositing is not recommended where
volatile organic compounds are of concern.
Compositing may dilute an isolated contaminant to
below detection limits, thus masking a possible
problem. Additional information on compositing for
surface water and sediment sampling is provided in
Sections 2.4.2, Composite Sample, and 4.3, Surface
Water Sample Collection.
4.5.5 Final Preparation
Obtain sample containers from a vendor that certifies
their decontamination/cleanliness. Consider their
compatibility with the material being sampled,
resistance to breakage, volume, container color,
storage and transport, and decontamination procedures
(see U.S. EPA Compendium of ERT Surface Water
and Sediment Sampling Procedures OSWER
Directive 9360.4-03). Additional information on
containers and cleaning procedures is available in
U.S. EPA's Specifications and Guidance for
Obtaining Contaminant-Free Sample Containers,
OSWER Directive 9240.0-05. Volume and containers
will vary according to the parameter(s) to be analyzed.
Glass is appropriate for most sampling because it is
chemically inert to most substances, although some
metals may adhere to the sides of glass containers.
Glass is not recommended for samples containing
strong alkali solutions and hydrofluoric acid.
Polyethylene plastic bottles are suitable for metals,
cyanide, and sulfide in water, but are not
recommended for organic analyses since plasticizers
may leach into the sample. Amber glass bottles help
preserve sample integrity for extractable organic
constituents in water which may degrade in light, such
as hydrocarbons, pesticides, and petroleum residues.
Sample containers must be tightly capped in order to
prevent oxidation from the air and/or the loss of
volatile components. Most sample aliquots for VOC
analysis are stored in 40-milliliter glass Teflonฎ
septum vials, which allow for easy syringe removal of
the sample for analysis, without the loss of headspace
gases. VOC sample containers must be completely
filled to the top with no air pockets. Improper
decontamination of sampling equipment may result in
cross-contamination of samples.
Keep low and medium concentration surface water
and sediment samples to be analyzed for organic
constituents at not more than 4E C by using ice or
"blue ice" when shipping. This cooling is to retard the
transformation of contaminants through
biodegradation or reaction while awaiting laboratory
analysis. If required, add any preservatives to specific
samples before shipping. The analytical laboratory
will recommend or provide any chemical
preservatives prior to sampling. Follow the
laboratory's instructions for quantity and timing of
preservative addition; many laboratories will provide
the sample containers already chemically preserved.
Refer to the laboratory, as well as 40 CFR 136, and
the U.S. EPA Compendium of ERT Surface Water
and Sediment Sampling Procedures, OSWER
Directive 9360.4-03, for actual sample volumes,
appropriate containers, and holding times. Label all
sample containers in accordance with the analytical
laboratory or Regional procedures and place them into
reclosable plastic bags prior to packaging for
shipment. Package all samples in compliance with
current U.S. Department of Transportation (DOT) or
International Air Transport Association (IATA)
requirements. Be certain the sample container meets
these requirements, and check the shipping/packing
instructions about preservatives.
Packaging should be performed by someone trained in
current DOT shipping procedures. Be certain all
containers are packaged to prevent breakage or
leakage. For all samples, be certain to maintain
secure chain-of-custody from collection to shipment
to the analytical laboratory.
4.6 EXAMPLE SITE
4.6.1 Sampling
During Phase 1, soil samples were collected as grab
samples from shallow surface locations. The sample
locations were cleared of surface debris, then the
samples were retrieved with disposable scoops and
placed directly into sample containers. During Phase
2, soil samples were collected using trowels and split
spoon samplers. The shallow soil samples were
collected in the same manner as the Phase 1 soil
samples. The subsurface soil samples were retrieved
from the split spoon sampler using a disposable plastic
scoop which transferred the soil into a stainless steel
bowl. Several scoopfuls were collected along the
length of the split spoon sampler and composited in
the bowl. The composite sample was then transferred
directly into the sample container using a disposable
plastic scoop.
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Phase 1 and Phase 2 residential well ground-water
samples were collected directly from the taps of
homes, which used private wells near the site. Fifteen
monitoring wells were installed at the site with 4-inch
Schedule 40 PVC casing and 0.010 slot screen in
lengths appropriate to each well. Shallow wells were
drilled to approximately 40 feet below ground surface,
and bedrock contact wells were drilled to
approximately 55 to 60 feet. Continuous split spoon
sampling was completed at each well location from 4
feet to well completion depth. Upon completion, all
monitoring wells were developed using a
decontaminated submersible pump and flexible PVC
hose.
After development, the 15 on-site monitoring wells
were sampled for analysis of ground water. Each
monitoring well was purged to obtain a representative
sample. Wells with sufficient yield were purged three
well volumes. Low-yielding wells were purged once
to dryness.
Each monitoring well was sampled after purging and
recovery. Ground-water samples were collected using
dedicated disposable Teflonฎ bailers. Each bailer
was attached to a clean nylon rope and introduced into
the well. After well sampling, a hydraulic (pump) test
was performed to determine aquifer characteristics for
mathematical modeling of potential contaminant
plume migration. To generate accurate gradient and
well location maps, the fifteen newly installed
monitoring wells were surveyed for vertical location
using feet above mean sea level (MSL) units.
Surface water and sediment samples were also
collected as grab samples during Phase 1 and Phase 2.
Sampling activities occurred when the intermittent
tributary was flowing in order to obtain water
samples. Because of the shallow depth and narrow
breadth of the tributary and Little Creek, samples
could be obtained by reaching into the near center in
the main flow line of the water body from the stream
bank. The sampler stood downstream of the desired
sampling location and created as little disturbance of
the streambank and water body as possible. This
caution reduced the potential for cross-contamination
of the sample locations.
Sampling proceeded from the most downstream
location in Little Creek, to upstream, and the surface
water aliquot was sampled prior to sediment
collection at each location to reduce entraining
suspended material into the water samples. Cleaned
and labeled surface water sample containers were
placed directly into the flow of the water body for
sample collection. The sediment samples were
collected (using dedicated disposable plastic scoops)
from the substrate directly beneath the location where
the water sample was retrieved. The sample material
was then transferred immediately into a clean, labeled
sample container.
All non-disposable equipment, including drill rig and
equipment, stainless steel bailers, submersible pumps,
water level indicators, and depth sounders, were
decontaminated between sampling at each location
and prior to the first sampling event each day.
4.6.2 Sample Preparation
All sample containers were supplied by the contracted
analytical laboratory. Chemical preservation was also
provided by the laboratory through pre-preserved
bottleware. Sample containers for surface water
samples consisted of:
1-liter polyethylene bottles for total
chromium, pre-preserved with reagent-grade
nitric acid to result in, after sample addition,
a pH of less than 2
1-liter polyethylene bottles for hexavalent
chromium
1-liter polyethylene bottles for cyanide, pre-
preserved with sodium hydroxide
Sample containers for sediments consisted of 8-ounce
glass jars with Teflonฎ caps for all parameters.
All samples were preserved to 4E C by placing them
in coolers packed with "blue ice" immediately after
collection and during shipment. (The laboratory was
responsible for cooling and refrigeration of samples
upon arrival.)
The samples were packaged in compliance with IATA
requirements for environmental samples. 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. Holding times for total
chromium and cyanide are less than six months, but
hexavalent chromium has a holding time of less than
24 hours. This was coordinated in advance with the
analytical laboratory and required daily ground
delivery of samples to the laboratory.
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5.0 QUALITY ASSURANCE/QUALITY CONTROL
5.1 INTRODUCTION
The goal of representative sampling is to obtain
analytical results that accurately depict site conditions
during a defined time interval. The goal of quality
assurance/quality control (QA/QC) is to implement
correct methodologies which limit the introduction of
error into the sampling and analytical procedures, and
ultimately into the analytical data.
QA/QC samples evaluate three types of information:
1) the magnitude of site variation; 2) whether samples
were cross-contaminated during sampling and sample
handling procedures; and 3) whether a discrepancy in
sample results is a result of laboratory handling and
analysis procedures. The QA/QC sample results are
used to assess the quality of analytical results of
environmental samples collected from a site.
5.2 DATA CATEGORIES
EPA has established data quality objectives (DQOs)
which ensure that the precision, accuracy,
representativeness, and quality of environmental data
are appropriate for their intended application.
Superfund DQO guidance defines two broad
categories of analytical data: screening and
definitive.
Screening data are generated by rapid, less precise
methods of analysis with less rigorous sample
preparation than definitive data. Sample preparation
steps may be restricted to simple procedures such as
dilution with a solvent, rather than elaborate
extraction/digestion and cleanup. At least 10 percent
of the screening data are confirmed using analytical
methods and QA/QC procedures and criteria
associated with definitive data. Screening data
without associated confirmation data are not
considered to be data of known quality. To be
acceptable, screening data must include the following:
chain-of-custody, initial and continuing calibration,
analyte identification, and analyte quantification.
Streamlined QC requirements are the defining
characteristic of screening data.
Definitive data are generated using rigorous analytical
methods (e.g., approved EPA reference methods).
These data are analyte-specific, with confirmation of
analyte identity and concentration. Methods produce
tangible raw data (e.g., chromatograms, spectra,
digital values) in the form of paper printouts or
computer-generated electronic files. Data may be
generated at the site or at an off-site location, as long
as the QA/QC requirements are satisfied. For the data
to be definitive, either analytical or total measurement
error must be determined. QC measures for definitive
data contain all of the elements associated with
screening data, but also may include trip, method, and
rinsate blanks; matrix spikes; performance evaluation
samples; and replicate analyses for error
determination.
For further information on these QA/QC objectives,
please refer to U.S. EPA's Data Quality Objectives
Process for Superfund, 1993, pp. 42-44.
5.3 SOURCES OF ERROR
Identifying and quantifying the error or variation in
sampling and laboratory analysis can be difficult.
However, it is important to limit their effect(s) on the
data. The four most common potential sources of data
error in surface water and sediment sampling are:
Sampling design
Sampling methodology
Sample heterogeneity
Analytical procedures
Refer to U.S. EPA's Data Quality Objective Process
for Superfund, for further discussion on error.
5.3.1 Sampling Design
Site variation includes the variation both in the types
and in the concentration levels of contaminants
throughout a water body. Representative sampling
should accurately identify and define this variation.
However, error can be introduced by the selection of
a sampling design which "misses" this 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. Surface water might have multiple
strata; failure to account for differences in
composition of multiple phases can introduce
sampling error. The sampling design must account for
all phases and strata which might contain hazardous
substances.
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The sampling design should utilize approved SOPs
and previously approved sampling designs to ensure
uniformity and comparability between samples. The
actual sample collection process should be determined
prior to sampling. All samples should be collected
using a uniform surface area and/or depth to ensure
data comparability. Sampling equipment must be
standardized for similar sampling situations.
The sampling design should fulfill sampling and data
quality objectives. Data quality objectives should be
built into the sampling design, including all necessary
QA/QC samples.
5.3.2 Sampling Methodology
Sampling methodology and sample handling
procedures have possible sources of error, including:
cross-contamination from inappropriate use of sample
collection equipment, unclean sample containers,
improper sampling equipment decontamination, and
improper shipment procedures. Standardized
procedures for collecting, handling, and shipping
samples identify potential source(s) of error and help
minimize them. Use SOPs to ensure that all given
sampling techniques are performed in the same
manner, regardless of the sampling team, date, or
location of sampling activity. Use field blanks,
replicate samples, trip blanks, and rinsate blanks
(discussed in Section 5.4) to identify errors due to
improper sampling methodology and sample handling
procedures.
Site screening methods might employ hazard
categorization kits or "cookbook" procedures requiring
interpretations based on chemical reactions which
produce a color change. The degree of subjectivity
inherent in interpretation, and the complexity of some
of the procedures, introduce a significant source of
potential error.
5.3.3 Sample Heterogeneity
Sample heterogeneity is a potential source of error in
sediment sampling. Unlike water, sediment is rarely
a homogeneous medium. Sediments exhibit variations
with lateral distance and depth. This heterogeneity
may also be present in the sample container unless the
sample was homogenized in the field or in the
laboratory. The laboratory uses only a small aliquot
of the sample for analysis; poor reproducibility from
heterogenous samples is a common error. If the
sample is not properly homogenized, the analysis may
not be truly representative of the sample and of the
corresponding site. Thorough homogenization of
samples limits the error associated with sample
heterogeneity. (Note: Do not homogenize when
analyzing for VOCs.)
5.3.4 Analytical Procedures
Analytical procedures may introduce errors from
laboratory cross-contamination, inefficient extraction,
and inappropriate methodology. Matrix spike,
laboratory duplicate, performance evaluation, and
laboratory control samples help to distinguish
analytical error from sampling error.
5.4 QA/QC SAMPLES
QA/QC samples are collected at the site or prepared
for or by the laboratory. Analysis of QA/QC samples
provides information on the variability and usability of
sampling data, indicates possible field sampling or
laboratory error, and provides a basis for future
validation and usability of the analytical data. The
most common field QA/QC samples are field
replicate, collocated, background, and rinsate, field,
and trip blank samples. The most common laboratory
QA/QC samples are performance evaluation (PE),
matrix spike (MS), and matrix spike duplicate (MSD)
samples. 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.
The following sections briefly describe the types of
QA/QC samples appropriate for surface water and
sediment sampling.
5.4.1 Field Replicate Samples
Field replicates, also referred to as field duplicates and
split samples, are field samples obtained from one
sampling point, homogenized (where appropriate),
divided into separate containers, and treated as
separate samples throughout the remaining sample
handling and analytical processes. (Splitting samples
for surface water and sediments is discussed in
Section 4.5.3.) Use replicate samples to assess error
associated with sample heterogeneity, sample
methodology, and analytical procedures. Field
replicates can also be used when determining total
error for critical samples with contamination
concentrations near the action level. In such a case, a
minimum of eight replicate samples is recommended
for valid statistical analysis. Field replicates may be
sent to two or more laboratories or to the same
laboratory as unique samples. For total error
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determination, samples should be analyzed by the
same laboratory. Generally, one field replicate per 20
samples per day is recommended.
5.4.2 Collocated Samples
Collocated samples are collected adjacent to the
routine field sample to determine local variability of
the sample location and contamination at the site.
Typically, collocated samples for sediments are
collected side by side, but no more than 3 feet away
from the selected sample location. Collocated
samples for surface water are collected from the same
location and depth. Collocated samples are collected
and analyzed as discrete samples; they are not
composited. Analytical results from collocated
samples can be used to assess site variation, but only
in the immediate sampling area. Because of the non-
homogeneous nature of sediment at sites, collocated
samples should not be used to assess variability across
a site and are not recommended for assessing error.
Collecting many samples can demonstrate variation in
sediments in a water body. Determine the
applicability of collocated samples on a site-by-site
basis.
5.4.3 Background Samples
Defining background conditions may be difficult
because of natural variability and the physical
characteristics of the site, but it is important in order
to quantify true changes in contaminant concentrations
due to a source or site. Defining background
conditions is critical for avoiding false positives and
for enforcement purposes in naming responsible
parties. Background samples are collected upstream
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 surface water
and sediments and are considered "clean" samples.
They provide a basis for comparison of contaminant
concentration levels with samples collected on site.
Collect at least one background surface water and one
background sediment sample. Additional samples are
often warranted by site-specific factors such as natural
variability of local sediments, multiple sources, and
discharges from off-site facilities. Tidal influences
must be considered when selecting a background
location. Background samples may also be collected
to evaluate potential error associated with sampling
design, sampling methodology, and analytical
procedures.
5.4.4 Rinsate Blank Samples
A rinsate blank, also referred to as an equipment
blank, is used to assess cross-contamination from
improper equipment decontamination procedures.
Rinsate blanks are samples obtained by running
analyte-free water over decontaminated sampling
equipment. Any residual contamination should appear
in the rinsate sample data. Analyze the rinsate blank
for the same analytical parameters as the field samples
collected that day. Handle and ship the rinsate like a
routine field sample. Where dedicated sampling
equipment is not utilized, collect one rinsate blank per
type of sampling device per day.
5.4.5 Field Blank Samples
Field blanks are samples prepared in the field using
certified clean water (HPLC-grade water [carbon-free]
for organic analyses and deionized or distilled water
for inorganic analyses) or sand, which are submitted
to the laboratory for analysis. A field blank is used to
evaluate contamination or error associated with
sampling methodology, preservation,
handling/shipping, and laboratory procedures.
Handle, ship, and analyze a field blank like a routine
field sample. Submit one field blank per day.
5.4.6 Trip Blank Samples
Trip blanks are samples prepared prior to going into
the field. They consist of certified clean water
(HPLC-grade) or sand and are not opened until they
reach the laboratory. Utilize trip blanks for volatile
organic analyses only. Handle, transport, and analyze
trip blanks in the same manner as the other volatile
organic samples collected that day. A trip blank
should be included with each shipment or two-day
sampling event. Trip blanks are used to evaluate error
associated with shipping and handling, and analytical
procedures.
5.4.7 Performance Evaluation/
Laboratory Control Samples
A performance evaluation (PE) sample evaluates the
overall error contributed by the analytical laboratory
and detects any bias in the analytical method being
used. PE samples contain known quantities of target
analytes manufactured under strict quality control.
They are usually prepared by a third party under an
EPA certification program. The samples are usually
submitted "blind" to analytical laboratories (the
sampling team knows the contents of the samples, but
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the laboratory does not). Laboratory analytical error
may be evaluated by the percent recoveries and
correct identification of the components in the PE
sample. Note: Even though they are not available for
all analytes, analysis ofPE samples is recommended
in order to obtain definitive data.
A blind PE sample may be included in a set of split
samples provided to the PRP. The PE sample will
indicate PRP laboratory accuracy, which may be
critical during enforcement litigation.
A laboratory control sample (LCS) also contains
known quantities of target analytes in certified clean
water. In this case, the laboratory knows the contents
of the sample (the LCS is usually prepared by the
laboratory). PE and LCS samples are not affected by
waste matrix interference, and thus can provide a clear
measure of laboratory error.
5.4.8 Matrix Spike/Matrix Spike
Duplicate Samples
Matrix spike and matrix spike duplicate samples
(MS/MSDs) are field samples that are spiked in the
laboratory with a known concentration of a target
analyte(s) in order to determine percent recoveries in
sample extraction. The percent recovery from
MS/MSDs indicates the degree to which matrix
interferences will affect the identification of a
substance. MS/MSDs can also be used to monitor
laboratory performance. When four or more pairs of
MS/MSDs are analyzed, the data obtained may be
used to evaluate error due to laboratory bias and
precision. Analyze one MS/MSD pair to assess bias
for every 20 samples of each matrix, and use the
average percent recovery for the pair. To assess
precision, analyze at least eight matrix spike replicates
from the same sample, and determine the standard
deviation and the coefficient of variation. MS/MSDs
are recommended for screening data and are required
as one of several methods for determining analytical
error for definitive data. Since the MS/MSDs are
spiked field samples, provide sufficient volume for
three separate analyses (i.e., triple volume).
5.4.9 Laboratory Duplicate Samples
A laboratory duplicate is a sample that undergoes
preparation and analysis twice. The laboratory takes
two aliquots of one sample and analyzes them as
separate samples. Comparison of data from the two
analyses provides a measure of analytical
reproducibility within a sample set. Discrepancies in
duplicate analyses may indicate poor homogenization
in the field or other sample preparation error, either in
the field or in the laboratory.
5.5 EVALUATION OF
ANALYTICAL ERROR
The acceptable level of error in sampling data is
determined by the intended use of the data and the
sampling objectives, including: the degree of threat to
public health, welfare, or the environment; selected
action levels; litigation concerns; and budgetary
constraints.
Error may be determined with replicate samples. 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 also
serve as a quick check on errors associated with
sample heterogeneity, sample methodology, and
analytical procedures. Different analytical results
from two or more replicate samples could indicate
improper sample preparation (e.g., incomplete
homogenization), or improper sample handling,
shipment, or analysis.
Although a quantified confidence level may be
desirable, it may not always be possible. A 95%
confidence level (5% acceptable error) should be
adequate for most Superfund activities. Note that the
use of confidence levels is based on the assumption
that a sample is homogeneous.
5.6 CORRELATION BETWEEN
FIELD SCREENING RESULTS
AND DEFINITIVE
LABORATORY RESULTS
One cost-effective approach for delineating the extent
of site contamination is to correlate inexpensive field
screening data and other field measurements with
definitive laboratory results. The relationship between
the two methods can then be described by a regression
analysis. The resulting equation can be used to
predict laboratory results based on field screening
measurements. In this manner, cost-effective field
screening results may be used in conjunction with off-
site laboratory analysis.
Statistical regression involves developing an equation
that relates two or more variables at an acceptable
level of correlation. In this case, the two variables are
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field screening results and definitive laboratory
results. The regression equation can be used to
predict a laboratory value based on the results of the
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 linear regression equation can be developed
on many calculators or computer databases. Consult
a statistician to check the accuracy of more complex
models.
Evaluation of the accuracy of a model relies in part on
statistical correlation, which 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 the dependent
variable. The value of an acceptable coefficient of
variation 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
assessment purposes, the acceptable R2 value may be
more stringent (e.g., 0.8). Analytical calibration
regressions have an R2 value of 0.98 or greater.
Field screening data can be used to predict laboratory
results if there is an acceptable correlation between
them. The predicted values can be located on a base
map and contoured. These maps can be examined to
evaluate the estimated extent of contamination and the
adequacy of the sampling program.
5.7 EXAMPLE SITE
5.7.1 Data Categories
Screening data which generate non-definitive,
unconfirmed results were used to select analytical
parameters and samples to be sent for off-site
laboratory confirmation analysis. Samples were sent
to the analytical laboratory under protocols which
provided definitive data. The rigorous laboratory
analyses provided definitive identification and
quantitation of contaminants.
5.7.2 Sources of Error
All direct reading instruments were maintained and
calibrated in accordance with their instruction
manuals. Many of these instruments are class-specific
(e.g., volatile organic vapors) with relative response
rates that are dependent on the calibration gas
selected. Instrument response to ambient vapor
concentrations may differ by an order of magnitude
from response to calibration standards. If compounds
of interest are known, site-specific standards may be
prepared.
The number and location of initial field samples were
based on observation and professional judgment (as
outlined in Section 2.13.5). Field standard operating
procedures, documented in the site sampling plan,
established consistent screening and sampling
procedures among all sampling personnel, reducing
the chances for variability and error during sampling.
Site briefings were conducted prior to all sampling
and screening events to review the use of proper
screening and sampling techniques.
Other steps taken to limit error included proper
sample preparation, adherence to sample holding
times, and the use of proper IATA shipment
procedures. All off-site laboratory sample analyses
were performed using EPA standard methods and
protocols.
5.7.3 Field QA/QC Samples
Field QA/QC samples were collected during surface
water and sediment sampling at the ABC Plating site.
One each of field duplicates were collected for surface
water and sediment, respectively, plus duplicates for
other media. Rinsate blanks were collected from
ground-water and soil sampling equipment after
decontamination by pouring deionized water through
the respective piece of equipment and then into a
sample container. The field duplicates and blanks
were preserved and prepared as "regular" field
samples. A trip blank for VOC analysis and a
performance evaluation (PE) sample for metals were
sent to the laboratory. (The PE sample is not affected
by matrix interferences.) The trip blank was provided
by the laboratory (pre-filled and preserved) and sent
with the sample containers prior to sample collection.
One trip blank per day was submitted to the
laboratory. Additional volume was collected and
provided to the laboratory for matrix spike/matrix
spike duplicate analyses for one per ten sample
locations for each medium.
45
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5.7.4 Laboratory QA/QC
Instructions on matrices, target compounds, and
QA/QC criteria of particular interest were provided to
the laboratory to help ensure that analytical results
met the required objectives. The laboratory analyzed
for metals using the methods of inductively coupled
plasma (ICP) spectrometry and atomic absorption
(AA). Two methods were conducted for hexavalent
chromium: Method 7196, a colorimetric method, and
Method 2185, a chelation method. These two
methods were utilized in an attempt to better quantify
hexavalent results. The presence of cyanide was
confirmed in the laboratory using total and amenable
cyanide analyses (colorimetric manual Method 9010).
46
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6.0 DATA PRESENTATION AND ANALYSIS
6.1 INTRODUCTION
6.4 CONTOUR MAPPING
Data presentation and analysis techniques are
performed with analytical or field screening results.
The techniques discussed below can be used to
compare analytical values, to evaluate numerical
distribution of data, and to reveal the location of "hot
spots" and the extent of contamination at a site. The
appropriate methods to present and analyze sample
data depend on the sampling objectives, the number of
samples collected, the sampling approaches used, and
other considerations.
6.2 DATA POSTING
Data posting involves the placement of sample values
on a site base map or cross-section. Data posting is
useful for displaying the distribution of sample values,
visually depicting the location of contaminants with
associated assessment data. Data posting requires
each sample to have a specific location (e.g., x, y, and
sometimes z coordinates). Ideally, the sample
coordinates are surveyed values or marked sampling
locations facilitating placement on a scaled map. Data
posting is useful for depicting concentration values for
both surface water and sediments.
Contour maps can depict contaminant concentration
values in surface waters and sediments throughout the
water body. This method may be useful for sediment,
but is not typically used for surface water. Contour
mapping requires an accurate, to-scale base map of the
site. After data posting sample values on the base
map, insert contour lines (or isopleths) at a specified
contour interval, interpolating values between sample
points. Contour lines can be drawn manually or can
be generated by computer using contouring software.
Although the software makes the contouring process
easier, computer programs have a limitation: as they
interpolate between data points, they attempt to
"smooth" the values by fitting contour intervals to the
full range of data values. This can result in a contour
map that does not accurately represent general site
contaminant trends. Typical Superfund sites have low
concentration/non-detect areas and "hot spots." If
there is a big difference in concentration between the
"hot spot" and the surrounding area, the computer
contouring program, using a contour interval that
attempts to smooth the "hot spots," may eliminate
most of the subtle site features and general trends.
Contour mapping is generally best used with non-
flowing, static water bodies, or over large areas.
6.3 CROSS-SECTION/FENCE
DIAGRAMS
Cross-section diagrams (two-dimensional) and fence
diagrams (three-dimensional) depict layers or phases
of contaminants in the surface waters or sediments of
rivers, lakes, and impoundments. Two-dimensional
cross-sections may be used to illustrate vertical
profiles of contaminants in surface water and
sediment. Three-dimensional fence diagrams are
often used to interpolate data between sampling
locations, particularly where contaminants do not
form horizontal layers. Both cross-sections and fence
diagrams can provide useful visual interpretations of
contaminant concentrations and migration.
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, rely 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 close
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, appears as a
straight line. A histogram or probability plot can be
used to see trends and anomalies in the data from a
contaminant source prior to conducting more rigorous
forms of statistical analysis. As with contour
mapping, statistical data interpretation applications are
typically used for sediment analysis.
47
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6.6 RECOMMENDED DATA
INTERPRETATION METHODS
The data interpretation methods chosen depend on
project-specific considerations, such as the number of
sampling locations and their associated range in
values. Data which are dissimilar in composition
should not be compared using statistical interpretation
methods. Data posting, screening, and sampling data
sheets, and cross-section/fence diagrams may be
appropriate. A site showing extremely low data
values (non-detects), with significantly higher values
(e.g., 5,000 ppm) from neighboring hot spots and little
or no concentration gradient in between, does not lend
itself to contour mapping. Data posting would be
useful at such a site to illustrate hot spots and clean
areas.
6.7 EXAMPLE SITE
A water table contour map was generated with the
water level data for the shallow overburden
monitoring wells. This indicated a westward flow
direction, which generally coincides with the surface
topography.
All surface water and sediment samples were
analyzed for total chromium and cyanide. Cyanide
and chromium were not found above the 50 ppm
detection limit in any of the surface water or sediment
samples. Chromium was detected in soil and ground-
water samples at the site.
The rate of chromium contaminant migration in
ground water and the potential long-term impact to
nearby residential wells was estimated using a
mathematical model which included worst case
assumptions and evaluated attenuation of
contaminants through soil and ground water. The
OSC concluded that the potential for residential well
contamination was minimal and therefore, the
potential for contamination of surface water through
the discharge of ground water was also considered
minimal. Removal of soil, the source of
contamination, was recommended. This decision met
the Phase 2 objective of establishing early action
options and consideration of long-term remediation
requirements for ground water.
All containers of wastes were removed from the site.
Soil treatment/disposal was completed using the
existing grid design. Cells were sampled and
designated as clean or excavated. Excavated material
was stockpiled while treatment/disposal options were
evaluated. Excavated cells were filled with stone and
clean soil. Composite sampling in each cell verified
cleanup, using an action level of 100 mg/kg chromium
in the soil composite. (The clean-up level was
established based on the earlier mathematical model
and soil attenuation calculations.) The soil response
served as an early action to meet the Phase 3 objective
originally established for the site.
48
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APPENDIX A -- Example of Flow Diagram For Conceptual Site Model
Figure A-1
Migration Routes of a Gas Contaminant
from Origin to Receptor
Gas
Pathway
from
origin
> Air
condc
solldl
Change of
contaminant
state In
pathway
insatlon
> Liquid
* *
t. ^^orป
> OaS
^> Solid
Flcatlon
Final
pathway
to receptor
> SO
> sw
> SO
> AT
^ /A -I
> sw
p-> SO
I > sw
Receptor
Human
G,D
G,D
I,D
I,D
G,D
G,D
G,D
Ecological Threat
Terrestrial
G,D
G,D
I,D
I,D
I,D
G,D
G,D
Aquatic
N/A
G,D
N/A
N/A
G,D
N/A
G,D
* May be a transformation product
** Includes vapors
Receptor Key
D - Dermal Contact
] - Inhalation
G - Ingestlon
N/A = Not Applicable
Pathway Key
Al -Air
SO - Soil
SW - Surface Water
(Including sediments)
GW - Ground Water
49
-------
Figure A-2
Migration Routes of a Liquid Contaminant
from Origin to Receptor
Change of
Original state Pathway contaminant
of contaminant from state In
of concern* origin pathway
Liquid
* May be a t
** Includes v
> Liquid
-t SW > ftfl<5**
solidification SฐllCl
k Of"l k 1 i n 1 1 n H
' OU * L-LUU-LU
leachate,
Infiltration
> AT t fine**
A\J. P Vjdo
ransformation product
apors
Final
pathway
to receptor
> SW
h AT
* Al
k CIA/
" oW
^ SW
> so
>> SW
> GW
^ SO
^ AI
* SW
Receptor
Human
G,D
I,D
G,D
G3D
Ecological Threat
Terrestrial
G,D
I,D
G,D
G,D
Aquatic
G,D
N/A
G,A
G,D
G,D
G,D
G,D
G,D
G,D
N/A
N/A
G,D
N/A
G,D
I,D
G,D
G,D
I,D
G,D
N/A
N/A
G,D
Receptor Key
D - Dermal Contact
I - Inhalation
G - Ingestlon
N/A - Not Applicable
Pathway Key
AI - Air
SO - Soil
SW - Surface Water
(Including sediments)
GW - Ground Water
50
-------
Figure A-3
Migration Routes of a Solid Contaminant
from Origin to Receptor
Original state
of contaminant
of concern*
Solid
AI
partlculates/
dust
Solid
sw
^ Solid
-> Liquid
SO
Gas
**
Solid
Liquid
* May be a transformation product
** Includes vapors
AI
SW
so
sw
sw
Receptor Key
D - Dermal Contact
I - Inhalation
G - Ingestlon
N/A - Not Applicable
Pathway Key
AI . Air
SO - Soil
SW - Surface Water
(Including sediments)
GW - Ground Water
Receptor
Human
I,D
G,D
G,D
Ecological Threat
Terrestrial
I,D
G,D
G,D
Aquatic
N/A
G,D
N/A
G,D
G,D
G,D
G,D
G,D
G,D
so
AI
SW
SO
SO
sw
G3D
I,D
G,D
G,D
G,D
G,D
G,D
G,D
I,D
G,D
G,D
G,D
N/A
G,D
N/A
N/A
G,D
N/A
N/A
N/A
G,D
51
-------
References
American Public Health Association. 1989. Standard Methods for the Examination of Water and Wastewater.
Seventeenth Edition. Washington, DC.
American Society for Testing and Materials (ASTM). 1989. 1989 Annual Book ofASTM Standards - Volumes
11.01 and 11.02, Water and Environmental Technology. American Society for Testing and Materials,
Philadelphia, Pennsylvania.
Ford, Patrick I, and Paul J. Turina. July 1984. Characterization of Hazardous Waste Sites A Methods Manual.
Volume I -- Site Investigations. EPA/600/S4-84/075. U.S. Environmental Protection Agency.
Environmental Monitoring Systems Laboratory. Las Vegas, Nevada.
Kittrells, F.W. 1969. A Practical Guide to Water Quality Studies of Streams. U.S. Federal Water Pollution Control
Administration. Washington, DC.
Krajca, Jaromil M. 1989. Water Sampling. Ellis Horwood Ltd., Chichester, England
National Research Council. 1990. Managing Troubled Waters - The Role of Marine Environmental Monitoring.
Committee on a Systems Assessment of Marine Environmental Monitoring. National Academy Press,
Washington, DC.
New Jersey Department of Environmental Protection, Hazardous Waste Programs. February 1988. Field Sampling
Procedures Manual.
Pavoni, Joseph L. 1977. Handbook of'Water Quality Management Planning. Van Rostrand Reinhold Co., New
York, New York.
Tchobanoglous, George, and Edward D. Schroeder. 1985. Water Quality - Characteristics, Modeling, Modification.
Addison-Wesley Publishing Co., Reading, Massachusetts.
U.S. Environmental Protection Agency. January 1995. Quality Assurance Sampling Plan for Environmental
Response (QASPER), User's Guide. (Based on Office of Solid Waste and Emergency Response
Directive 9360.4-01.)
U.S. Environmental Protection Agency. 1995a. Superfund Program Representative Sampling Guidance, Volume
1 Soil. Office of Solid Waste and Emergency Response Directive 9360.4-10.
U.S. Environmental Protection Agency. 1995b. Superfund Program Representative Sampling Guidance, Volume
4 Waste. Office of Solid Waste and Emergency Response Directive 9360.4-14.
U.S. Environmental Protection Agency. September 1993. Data Quality Objectives Process for Superfund. Office
of Emergency and Remedial Response Directive 9355.9-01.
U.S. Environmental Protection Agency. November 1992. Hazard Ranking System Guidance Manual. Office of
Solid Waste and Emergency Response Directive 9345.1-07
U.S. Environmental Protection Agency. September 1992. Guidance for Performing Site Inspections Under
CERCLA. Office of Solid Waste and Emergency Response Directive 9345.1-05.
U.S. Environmental Protection Agency. 1992. Specifications and Guidance for Obtaining Contaminant-Free
Sample Containers. Office of Solid Waste and Emergency Response Directive 9240.0-05.
52
-------
U.S. Environmental Protection Agency. January 1991. Compendium of ERT Surface Water and Sediment Sampling
Procedures. Office of Solid Waste and Emergency Response Directive 9360.4-03.
U.S. Environmental Protection Agency. 1990. Samplers Guide to the Contract Laboratory Program. Office of
Solid Waste and Emergency Response Directive 9240.0-06.
U.S. Environmental Protection Agency. 1986. Manual-Sampling for Hazardous Materials, Parti.
U.S. Environmental Protection Agency, Region 3 Remedial Engineering Management. 1986. REM III Program
Guidelines. Ebasco Services, Incorporated, Langhorne, Pennsylvania.
U.S. Environmental Protection Agency. 1983. Characterization of Hazardous Waste Sites - A Methods Manual.
Volume II Available Sampling Methods. EPA/600/4-83/040. Environmental Monitoring Systems
Laboratory, Las Vegas, Nevada.
53
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OSWER Directive 9360.4-16
EPA xxx/x-xx/xxx
PBxx-xxxxxx
December 1995
SUPERFUND PROGRAM
REPRESENTATIVE SAMPLING GUIDANCE
VOLUME 5: WATER AND SEDIMENT
PART II-- Ground Water
Interim Final
Environmental Response Team
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC 20460
-------
Notice
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved
for publication.
The policies and procedures established in this document are intended solely for the guidance of government
personnel for use in the Superfund 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 Ground-Water Sampling procedures, refer to the U.S. EPA Compendium ofERT Ground-
Water Sampling Procedures, OSWER Directive 9360.4-06. Topics covered in this compendium include: sampling
equipment decontamination; ground-water monitoring well installation, development, and sampling; soil gas
sampling; water level measurement; controlled pump testing; slug testing.
Please note that the procedures in this document should be used only by individuals properly trained and certified
under a 40-hour hazardous waste site training course that meets the requirements set forth in 29 CFR 1910.120(e)(3).
This document should not be used to replace or supersede any information obtained in a 40-hour hazardous waste site
training course.
Questions, comments, and recommendations are welcomed regarding the Superfund Program Representative
Sampling Guidance, Volume 5 Water and Sediment, Part II Ground Water. Send remarks to:
Mr. William A. Coakley
Chairman, Representative Sampling Committee
U.S. EPA-ERT
Rantan Depot - Building 18, MS-101
2890 Woodbridge Avenue
Edison, NJ 08837-3679
-------
Disclaimer
This document has been reviewed under 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 following trade names are mentioned in this document:
Teflonฎ is a registered trademark of E.I. DuPont de Nemours and Company of Wilmington, Delaware
Geoprobeฎ is a registered trademark of Geoprobe, Inc. of Salina, Kansas
Gilianฎ is a registered trademark of Gilian Instrument Corporation of Wayne, New Jersey
in
-------
Contents
Notice ii
Disclaimer iii
List of Figures vii
List of Tables vii
1.0 INTRODUCTION 1
1.1 OBJECTIVE AND SCOPE 1
1.2 UNIQUE CHARACTERISTICS OF GROUND WATER 1
1.3 REPRESENTATIVE SAMPLING 2
1.4 REPRESENTATIVE SAMPLING OBJECTIVES 2
1.4.1 Identify Contamination and Determine Hazard 2
1.4.2 Establish Imminent or Substantial Threat 2
1.4.3 Determine Long-Term Threat 3
1.4.4 Develop Containment and Control Strategies 3
1.4.5 Evaluate Treatment Options 3
1.5 CONCEPTUAL SITE MODEL 3
1.6 OVERVIEW OF GROUND-WATER MONITORING WELL INSTALLATION AND
GROUND-WATER MODELING 5
1.6.1 Ground-Water Monitoring Well Installation 5
1.6.2 Ground-Water Modeling 6
1.7 EXAMPLE SITE 6
2.0 GROUND-WATER SAMPLING DESIGN 7
2.1 INTRODUCTION 7
2.1.1 Pre-Sampling Plan Investigation 7
2.1.2 Types of Information Provided by Ground-Water Sampling Assessment 8
2.1.3 Site Reconnaissance 9
2.2 PARAMETERS OF CONCERN, DATA QUALITY OBJECTIVES, AND QUALITY
ASSURANCE MEASURES 10
2.2.1 Parameters of Concern 10
2.2.2 Data Quality Objectives 10
2.2.3 Quality Assurance Measures 11
2.3 REPRESENTATIVE GROUND-WATER SAMPLING APPROACHES
AND SAMPLE TYPES 11
2.3.1 Judgmental Sampling 11
2.3.2 Random, Systematic Grid, and Systematic Random Sampling 12
2.3.3 Grab versus Composite Sample Types 12
2.4 SAMPLING PLAN 12
2.5 EXAMPLE SITE 13
2.5.1 Background 13
2.5.2 Site History and Reconnaissance 15
2.5.3 Identification of Parameters of Concern 15
2.5.4 Sampling Objectives 16
2.5.5 Selection of Sampling Approaches 16
2.5.6 Sampling Plan 16
IV
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3.0 FIELD ANALYTICAL SCREENING, SAMPLING EQUIPMENT, AND GEOPHYSICAL
TECHNIQUES 18
3.1 FIELD ANALYTICAL SCREENING 18
3.1.1 Flame lonization Detector 18
3.1.2 Photoionization Detector 18
3.1.3 Gas Chromatograph 19
3.1.4 Geoprobe 19
3.1.5 Soil Gas Technique 19
3.1.6 Field Parameter Instruments 19
3.1.7 X-Ray Fluorescence 19
3.2 GROUND-WATER SAMPLING EQUIPMENT 20
3.2.1 Bailer 20
3.2.2 Hydraulic Probe 20
3.2.3 Air-Lift Pump 20
3.2.4 Bladder Pump 20
3.2.5 Rotary Pump 21
3.2.6 Peristaltic Pump 21
3.2.7 Packer Pump 21
3.2.8 Syringe Sampler 21
3.2.9 Ground-Water Sampling Equipment Selection Factors 21
3.3 GEOPHYSICAL METHODS 22
3.3.1 Surface Geophysics 22
..
Borehole Geophysics ................................................ 23
3.3.3 Geophysical Techniques for Ground- Water Investigations .................... 25
3.4 EXAMPLE SITE [[[ 26
3.4.1 Selection of Field Analytical Screening Techniques ......................... 26
3.4.2 Selection of Sampling Equipment ...................................... 26
3.4.3 Selection of Geophysical Methods ...................................... 26
4.0 GROUND-WATER SAMPLE COLLECTION AND PREPARATION ....................... 31
4.1 INTRODUCTION [[[ 31
4.2 STATIC WATER LEVEL [[[ 31
4.3 WELL PURGING [[[ 31
4.3.1 Stabilization Purging Techniques ....................................... 32
4.3.2 Wells that Purge Dry ................................................ 32
4.4 GROUND-WATER SAMPLE COLLECTION ................................... 32
4.5 GROUND-WATER SAMPLE PREPARATION .................................. 33
4.5.1 Filtering [[[ 34
4.5.2 Homogenizing/Aliquotting ............................................ 34
4.5.3 Splitting [[[ 34
4.5.4 Final Preparation [[[ 34
4.6 EXAMPLE SITE [[[ 34
4.6. 1 Sample Collection .................................................. 34
4.6.2 Sample Preparation ................................................. 37
5.0 QUALITY ASSURANCE/QUALITY CONTROL (QA/QC) ............................... 38
5. 1 INTRODUCTION [[[ 38
-------
5.4 QA/QC SAMPLES 39
5.4.1 Field Replicate Samples 39
5.4.2 Background Samples 39
5.4.3 Rinsate Blank Samples 40
5.4.4 Field Blank Samples 40
5.4.5 Trip Blank Samples 40
5.4.6 Performance Evaluation/Laboratory Control Samples 40
5.4.7 Matrix Spike/Matrix Spike Duplicate Samples 40
5.4.8 Laboratory Duplicate Samples 41
5.5 EVALUATION OF ANALYTICAL ERROR 41
5.6 CORRELATION BETWEEN FIELD SCREENING RESULTS AND DEFINITIVE
LABORATORY RESULTS 41
5.7 EXAMPLE SITE 42
5.7.1 Data Categories 42
5.7.2 Sources of Error 42
5.7.3 Field QA/QC Samples 42
5.7.4 Laboratory QA/QC 42
6.0 DATA PRESENTATION AND ANALYSIS 43
6.1 INTRODUCTION 43
6.2 DATA POSTING 43
6.3 CROSS-SECTION/FENCE DIAGRAMS 43
6.4 CONTOUR MAPPING 43
6.5 WELL LOCATION MAP 43
6.6 STATISTICAL GRAPHICS 43
6.7 RECOMMENDED DATA INTERPRETATION METHODS 44
6.8 EXAMPLE SITE 44
Appendix A EXAMPLE OF FLOW DIAGRAM FOR CONCEPTUAL SITE MODEL 45
References 48
VI
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List of Figures
1 Conceptual Site Model 4
2 Site Sketch: ABC Plating Site 14
3 Soil Boring/Monitoring Well Completion Log 36
A-l Migration Routes of a Gas Contaminant 45
A-2 Migration Routes of a Liquid Contaminant 46
A-3 Migration Routes of a Solid Contaminant 47
List of Tables
1 Applicability of Surface Geophysical Techniques to Ground-Water Investigations 27
2 Advantages and Disadvantages of Surface Geophysical Techniques to Ground-Water Investigations . 28
3 Applicability of Borehole Geophysical Techniques to Ground-Water Investigations 29
4 Advantages and Disadvantages of Borehole Geophysical Techniques to Ground-Water Investigations 30
vn
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1.0 INTRODUCTION
1.1 OBJECTIVE AND SCOPE
This is Part II of the fifth volume in a series of
guidance documents that assist Superfund Program
Site Managers, On-Scene Coordinators (OSCs),
Remedial Project Managers (RPMs), and other field
staff in obtaining representative samples at Superfund
sites. The objective of representative sampling is to
ensure that a sample or a group of samples accurately
characterizes site conditions.
Most hazardous waste site investigations utilize some
form of a ground-water sampling or monitoring
program to fully characterize the nature and extent of
contamination. Because site conditions may differ,
experienced hydrogeologists and geochemists should
be consulted to establish the most suitable types of
sampling and monitoring for each site.
The purpose of this document is to address
representative ground-water sampling. Ground-water
modeling and monitoring well installation are briefly
introduced but are not addressed in detail in this
document. References on these topics are provided in
Section 1.6
The representative ground-water sampling principles
discussed in this document are applicable throughout
the Superfund Program. The following chapters will
help field personnel to assess available information,
select an appropriate sampling approach and design,
select and utilize field analytical/geophysical
screening methods and sampling equipment,
incorporate suitable types and numbers of quality
assurance/quality control (QA/QC) samples, and
interpret and present the site analytical data.
As the Superfund Program has developed, the
emphasis of the response action has expanded beyond
addressing emergency response and short-term
cleanups. Each planned response action must
consider a variety of sampling objectives, including
identifying threat, delineating sources of
contamination, and confirming the achievement of
clean-up standards. Because many important and
potentially costly decisions are based on the sampling
data, Site Managers and other field personnel must
characterize site conditions accurately. To that end,
this document emphasizes the use of cost-effective
field analytical and geophysical screening techniques
to characterize the site and aid in the selection of
sampling locations.
1.2 UNIQUE CHARACTERISTICS
OF GROUND WATER
The following are media-specific variables of ground
water that should be considered when performing
representative ground-water sampling:
Homogeneity - Ground water, as a medium, is
usually homogeneous, especially when compared
to other media such as soil, air, or waste.
Seasonal and Localized Variation in Flow -
Seasonal and localized variations in ground-water
flow should be considered when developing a
ground-water assessment program. Seasonal
variations are generally controlled by weather.
Surface streams gain or lose water to the
subsurface when flood or drought conditions are
present. Localized variations in flow are caused
by nearby, outside influences, as when a
production well creates a cone of depression in
the water table.
Inaccessibility for Investigation - Ground water
is often inaccessible to standard grab sampling
techniques. Because ground water is subsurface,
wells must often be drilled and completed for
sampling if no existing wells are available.
Sampling ground water is generally more
complicated, labor-intensive, time-consuming,
and expensive than sampling other media.
Natural Background Composition - Knowledge of
the natural background composition is necessary
in order to determine the effects of a site on the
ground water. Background or control monitoring
wells are necessary to determine ambient
composition.
Water Treatment - Ground-water samples are
often extracted from existing residential or
commercial wells that have been treated with
softeners or have been filtered or altered in other
ways. Sampling (times, parameters, methods,
preservatives, etc.) may have to be altered in
order to compensate for or avoid treatment
variables.
Reproducibility of Sampling Results - Ground
water is a flowing water body below the earth's
surface. Physical and chemical characteristics
may vary over time and space because of the
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factors listed above (e.g., seasonal variation).
Contaminants tend to flow through ground water
in a plume or plug of varying concentration;
contamination sources may discharge in pulses or
as a continuous flow; and contaminants may react
with ground water to chemically transform over
time. Because of this flowing nature,
contaminant or natural constituent concentrations
can vary. This variation could affect duplicating
sample results over an extended time period.
Contaminants will most often continue to be
detected in ground water, but sample
concentration ranges may be altered, either by an
increase or a decrease, or contaminant by-
products may be detected.
1.3 REPRESENTATIVE SAMPLING
Representative ground-water 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.
In addition to the variables introduced due to the
characteristics of the sample media (as discussed in
Section 1.2), this document concentrates on those that
are introduced in the field. These latter variables
relate to 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:
Media variability - The physical and chemical
characteristics of ground water.
Contaminant concentration variability
Variations in the contaminant concentrations
throughout the site and/or variables affecting the
release of site contaminants into ground water on
or away from 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 through
representative sampling, it can lead to the false
conclusion that error is due to sample collection
and handling procedures.
1.4 REPRESENTATIVE SAMPLING
OBJECTIVES
Representative sampling objectives for ground water
include the following:
Identify the presence of contamination, including
source, composition, and characteristics.
Determine if it is hazardous.
Establish the existence of an imminent or
substantial threat to public health or welfare or to
the environment.
Establish the existence of potential threat
requiring long-term actions.
Develop containment and control strategies.
Evaluate treatment options.
Note: Clean-up goals are generally established for
ground water and are not considered a sampling
objective.
1.4.1 Identify Contamination and
Determine Hazard
One of the first objectives during a response action at
a site is to determine the presence, identity, and
potential threat of any hazardous materials. Field
screening techniques can be used for rapid detection
of contaminants. Upon confirming the presence of
hazardous materials, sample and/or continue screening
to identify their compositions and determine their
concentrations.
1.4.2 Establish Imminent or
Substantial Threat
Establishing threat to the public or environment is a
primary objective during any response action. The
data obtained from characterizing the contaminants
will help the Site Manager to determine whether an
imminent or substantial threat exists and whether a
response action is necessary. The type and degree of
threat determines the rate at which a response action
is taken.
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1.4.3 Determine Long-Term Threat
Site conditions may support a long-term threat that is
not imminent or substantial. Characterization of the
contaminants can assist the Site Manager to determine
the need for long-term remediation and response.
Samples should be collected in a manner that enables
their use for evaluating the site under the Hazard
Ranking System.
1.4.4 Develop Containment and
Control Strategies
Once the chemical constituents and threat have been
determined, many strategies for ground-water
containment and control are available. Analytical data
indicating the presence of chemical hazards are not in
themselves sufficient to select a containment or
control strategy. Site reconnaissance and historical
site research provide information on site conditions
and the physical state of the contaminant sources;
containment and control strategies are largely
determined by this information. For example,
trenching and pump and treat systems can prevent
spread of contamination in an aquifer.
1.4.5 Evaluate Treatment Options
The contaminants should be identified, quantified, and
compared to action levels (e.g., maximum
contaminant levels (MCLs) for drinking water).
Where regulatory action levels do not exist, site-
specific clean-up levels are determined by the Region
(often in consultation with the Agency for Toxic
Substances and Disease Registry (ATSDR)) or by
State identification of Applicable or Relevant and
Appropriate Requirements (ARARs). If action levels
are exceeded, a series of chemical and physical tests
may be required to evaluate possible treatment
options.
1.5 CONCEPTUAL SITE MODEL
A conceptual site model is a useful tool for selecting
sampling locations. It helps ensure that sources,
migration pathways, and receptors throughout the site
have been considered before sampling locations are
chosen. The conceptual model assists the Site
Manager in evaluating the interaction of different site
features. Risk assessors use conceptual models to
help plan for risk assessment activities. Frequently, a
conceptual model is created as a site map (see Figure
1) or it may be developed as a flow diagram which
describes potential migration of contaminants to site
receptors (See Appendix A).
A conceptual site model follows contaminants from
their sources, through migration pathways (e.g., air,
ground water), and eventually to the assessment
endpoints. Consider the following when creating a
conceptual site model:
The state(s) of each contaminant and its potential
mobility
Site topographic features
Meteorological conditions (e.g., wind
direction/speed, average precipitation,
temperature, humidity)
Human/wildlife activities on or near the site
The conceptual site model in Figure 1 is an example
created for this document. The model assists in
identifying the following site characteristics:
Potential Sources: Site (waste pile, lagoon);
drum dump; agricultural activities.
Potential Migration Pathway (Ground Water):
Leachate from the waste pile, lagoon, drum
dump, or agricultural activities.
Potential Migration Routes: Ingestion or direct
contact with water from the aquifer (e.g.,
ingestion of drinking water, direct contact when
showering).
Potential Receptors of Concern:
Human Population (Residents/Workers):
Ingestion or direct contact with contaminated
water from the aquifer.
Preliminary site information may provide the
identification of the contaminant(s) of concern and the
level(s) of the contamination. Develop a sampling
plan based upon the receptors of concern and the
suspected sources and pathways. The model may
assist in the selection of on-site and off-site sampling
locations.
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1.6 OVERVIEW OF GROUND-
WATER MONITORING WELL
INSTALLATION AND
GROUND-WATER MODELING
Ground-water monitoring well installation and
ground-water modeling are complex issues which fall
outside the scope of this document. Many standard
operating procedures (SOPs) covering ground-water
monitoring well installation techniques have been
published. Monitoring well installation and ground-
water modeling are briefly introduced here with
several specific items for consideration. Refer to
existing SOPs and other reference documents for more
in-depth study.
1.6.1 Ground-Water Monitoring Well
Installation
For most Superfund response actions where ground-
water sampling is performed, existing ground-water
production wells (commercial or residential) are used,
if available, to obtain samples. Chemical data
obtained from this type of well depict the general
quality of water that is being delivered to the user
community. Ground water is usually a composite of
multiple aquifer strata which may mask the presence
of narrow or small contaminant plumes from a single
stratum. For this reason, production wells are not
suitable for detailed source, case-preparation, or
research types of monitoring. Such detailed
monitoring efforts require wells designed to determine
the geologic and hydrologic quality at specific
locations and depths. The following items must be
considered for ground-water sampling from
monitoring wells:
Drilling method
Monitoring well components
Monitoring well location
Well diameter
Well depth
Well screen location
Refer to the U.S. EPA A Compendium of Superfund
Field Operations Methods, OSWER
Directive 9355.0-14; Compendium of ERT
Ground-water Sampling Procedures, OSWER
Directive 9360.4-06; RCRA Ground-Water
Monitoring Technical Enforcement Guidance
Document, OSWER Directive 9950.1; and RCRA
Ground-Water Monitoring: Draft Technical
Guidance, EPA/530-R-93-001, for specific details on
monitoring well installation. The latter two
documents should be referenced for information on
locating, installing, and developing monitoring wells.
Locating Monitoring Wells
Often, one well is sited near the center of the
contaminant plume just downgradient from the
contamination source. Another well is installed
downgradient of the contaminant source, outside the
limits of the plume. For background data, one well
may be placed outside of the contaminant plume,
upgradient of the contaminant source. Additional
wells may be installed to track the amount of
contaminant dispersion taking place.
Determining the depth to sample is critical for
successful ground-water monitoring. Sampling depth
depends on the contaminant density, the aquifer
characteristics, and the slope of the water table or
potentiometric surface. The number of wells
necessary to monitor ground water varies depending
on many factors. For example, if an impoundment
contamination source is higher than the surrounding
landscape, leachate may flow locally in all four
downgradient directions. In this case, at least four
wells are needed to monitor plume movement, plus a
background well may be desired in an unaffected area.
In addition, some wells may be installed at more than
one depth in a contaminant plume to verify vertical
flow or spread of contamination at different depths.
See Driscoll, 1986, pp. 715-16 for more information
on locating monitoring wells.
Well Casing and Well Screen
Select a well casing material based on water quality,
well depth, cost, borehole diameter, drilling
procedure, and Federal, state, and local regulations.
Types of casing materials include: steel, poly vinyl
chloride (PVC), fiberglass, and Teflonฎ. Common
well casing diameters range from 2 inches to 12
inches or greater, and depend on well type, well size,
well depth, and subsurface geology. Often a series of
progressively smaller-diameter well casings are used
from the ground surface to the well depth.
A well screen is a filtering device which permits
water to enter the well from the saturated aquifer
while preventing sediment from entering the well. A
well screen has slots or perforations and attaches to
the well casing. It can be constructed of metal,
plastic, or other material. Important criteria for
selecting a well screen include: a large percentage of
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open area, nonclogging slots, resistance to corrosion,
and a sufficient column and collapse strength.
SeeDriscoll, 1986, pp. 413-431, and Fetter, 1993, pp.
339-344 for more information regarding well casing.
See Driscoll, 1986, pp. 395-405, and Fetter, 1993, pp.
345-346 for more information regarding well screens.
See U.S. EPA, November 1992, pp. 6-16 - 6-38 for
advantages and disadvantages of selecting well casing
and screen materials.
1.6.2 Ground-Water Modeling
Ground-water models, like conceptual site models,
can be useful when selecting sampling approaches,
objectives, and locations. Ground-water models
developed for Superfund sites attempt to provide an
estimation of how the actual ground-water system
functions.
There are many types of ground-water models
available (e.g., physical, analog, mathematical). The
International Ground-Water Modeling Center
(IGWMC) has developed a ground-water model
definition which emphasizes the importance of
describing a ground-water system mathematically.
The IGWMC defines a ground-water model as " a non-
unique, simplified, mathematical description of an
existing ground-water system, coded in a
programming language, together with a quantification
of the ground-water system the code simulates in the
form of boundary conditions, system parameters, and
system stresses."
A ground-water model may be useful throughout site
investigation activities because it can be adjusted as
conditions in the actual ground-water system become
better defined. The data which are generated by the
model can be used to refine sampling approaches and
locations as necessary. Typically, a ground-water
modeling report will include data (results), along with
a discussion of activities such as model calibration
and conceptual model development. A suggested
format for a ground-water modeling report can be
found in U.S. EPA Ground-Water Issue:
Fundamentals of Ground-Water Modeling
(EPA/540/S-92/005).
1.7 EXAMPLE SITE
An example site, presented at the end of each chapter,
illustrates the development of a representative ground-
water sampling plan that meets Superfund Program
objectives for early actions or emergency responses.
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2.0 GROUND-WATER SAMPLING DESIGN
2.1 INTRODUCTION
The purpose of ground-water sampling is to provide
technical information relative to the nature and
condition of subsurface water resources at a specific
time and place. Designs to monitor the status of
ground water range from the studies of naturally
occurring geochemical constituents to the detection or
assessment of contamination within a ground-water
system.
Ground-water sampling objectives include identifying
threats, delineating sources and extent of
contamination, determining treatment and disposal
options, and confirming the attainment of targeted
clean-up levels. Representative sampling designs are
developed to most accurately characterize the
hydrogeologic system and its interaction with the
environment. Sampling protocols must integrate
detailed sampling methodology, techniques and
practices to ensure valid assessment. Sampling
methodology and practice may be the most common
source of assessment error. Consequently, sampling
methodology and practice collectively demand careful
preparation, execution, and evaluation to accurately
characterize the hydrogeologic system or its
subsystems. (For additional information see: U.S.
EPA Ground Water, Volume II: Methodology,
EPA/625/6-90/016b; and Palmer, Christopher M,
Principles of Contaminant Hydrogeology.)
There are many methods and types of equipment
useful for site characterization and sample collection.
Selection of these factors is a critical component of a
site-specific sampling design.
A properly developed ground-water sampling design
defines the sampling purpose, protects site worker
health and safety, effectively utilizes resources, and
minimizes errors. The sampling design will vary
according to the characteristics of the site. When
developing a sampling design, consider:
Prior actions at the site (e.g., sampling events,
compliance inspections)
Regional ground-water properties and
characteristics
Potential on-site waste sources (e.g.,
impoundments, waste piles, drums)
Topographic, geologic, hydrologic, and
meteorologic conditions of the site
Flora, fauna, and human populations in the area
2.1.1 Pre-Sampling Plan
Investigation
The pre-sampling plan investigation provides the
planner with information critical to the development
of a sound ground-water sampling design. Integration
of all pertinent facts regarding the site history, the
population(s) affected, and concentrations of
substances on a site must be reviewed. After all of the
pertinent information has been processed and
incorporated into a thorough site pre-evaluation, the
sampling plan can be developed. Considerations for
sampling plan modification should be reviewed as
necessary in light of the complex nature of ground-
water resource dynamics.
Site History
Review of the site's history helps assess the natural
and man-made impacts on a site. Geographic,
geologic, tax, and fire insurance maps can indicate the
status of the site. These maps can usually be found at
local and collegiate libraries or municipal and county
tax offices. Aerial photographs are helpful in
reviewing operational use of the site. Archival aerial
photographs may show changes in operation and site
condition over time. This information can be
correlated with information from potentially
responsible parties.
Hydrogeologic information is critical to developing a
sampling plan. A ground-water system is site
specific, depending upon local geology, land and
subsurface use, precipitation and water use, proximity
to water bodies, and hydrogeologic parameters
affecting contaminant transport. Hydrologic and
hydrogeologic information can be found in libraries or
requested from the U.S. Geological Survey (USGS),
Water Resources Division, or state geological
agencies and their water branches. Inspection
histories can be used to determine prior health status
of the site in view of possible trends. Local, state, and
federal agencies dealing with health or environmental
inspection can provide such historical information
about a site.
Affected Populations
Human population statistics for the selected area can
establish the number of people threatened by the
contaminant exposure. Include populations affected
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by projected migration of contaminants within the
ground-water system. Knowing the interaction of the
contaminant within a ground-water system and the
potential regional populations exposed to the
contaminant will focus the sampling plan to the source
and possible pathways of the contaminant. Wildlife
populations in the area must be studied as well.
Wildlife in ponds, lakes, streams, rivers, and bays is
often affected by contaminants transported by ground
water discharging into surface water. Information
regarding regional wildlife populations and
susceptibility to hazardous substances can be obtained
from federal and state wildlife and conservation
agencies.
Detection Levels versus Maximum
Contaminant Levels
Sampling plan development must also address the
concentration level of the contaminant within the
ground-water system in relation to the maximum
contaminant levels (MCLs) allowed within a public
water system. Refer to the Federal Register for the
levels requiring enforceable action. Knowledge of the
chemical contaminant interaction within the ground-
water system can add insight into the fate of the
contaminant (soluble or insoluble in water; less or
more dense than water; the nature of reactivity with
sediment or geology of the subsurface). Correlate the
concentration level versus the location of these
concentrations. A sequence of order can then be
applied to the locations. Ideally, a pattern may
develop that can be related to the ground-water system
and its dynamics. In the case of a single location,
investigate potential sources in the surrounding area
either by working backwards from an identified
contaminant spot to a potential source, or from a
potential source to an identified contaminant spot.
Also consider source-to-current-location pathways and
projected pathways when developing a sampling plan.
2.1.2 Types of Information
Provided by Ground-Water
Sampling Assessment
There are several types of information that a ground-
water sampling assessment provides. These include
but are not limited to: measure of ground-water
quality, contaminant concentrations compared to
action levels, selection of the appropriate response
action, and determination of ground-water flow and
contaminant plume movement.
Measure of Ground-Water Quality
Ground-water sampling assessments provide
information concerning measure of ground-water
quality of a site or region. Water quality is classified
according to many categories and its intended use.
Drinking water is especially subject to guidelines. A
sampling assessment of ground water can determine
whether the quality of the water has been maintained,
upgraded, or allowed to degrade. The natural and
artificially induced characteristics of ground water
from a specific site or region can be established by
ground-water sampling assessments specifically, the
chemical, biological, and physical characteristics of
the ground water.
Contaminant Concentrations Compared
to Action Levels
Ground-water sampling assessments provide a single
contamination level for a particular sampling location,
or a set of contamination levels for several sampling
locations within a site. Comparison to action levels in
ARARs determines the basis for further action. Thus,
sampling can evaluate potential hazards and represent
a condition of ground-water character requiring
enforceable action procedures.
Selection of Appropriate Response
Action
The level of contaminant concentration as determined
through sampling assessments is a critical factor in
selecting a site response action. Depending upon the
degree or level of contaminant concentration,
contaminant frequency, or number of locations
established as contaminated, and the site's potential
threat to human health or the environment, a rapid or
extensive clean-up program can be formulated, as well
as temporary or short-term responses (e.g., provision
of bottled water).
A sampling assessment may not always indicate
contamination of the site. Careful examination of
sampling protocol must consider the range of
explanations. A miscalculation of suspected source
sites; gross procedure error in sampling, laboratory
analysis, or documentation; or error at many other
points in sampling protocol could be the source of
assessment error. These errors are addressed more
extensively in Chapter 5.
If quality assurance/quality control (QA/QC)
procedures have been followed for ground-water
sampling assessment, then it is possible that sources
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of contamination may originate from above ground
systems (e.g., lead entering tap water in the proximity
of the facility). In any case, a sampling assessment at
the least can characterize the natural ground-water
conditions, which can be used as a control or
comparison.
Determination of Ground- Water Flow and
Contaminant Plume Movement
Knowing the direction of ground-water flow is
important when evaluating a contaminated aquifer.
When contamination enters the ground at a higher
head (gradient) than exists at nearby shallow wells,
these wells may become contaminated. Ground water
flows from higher head to lower head. The direction
of water movement may be determined using water-
elevation data from a minimum of three wells. See
Driscoll, 1986, pp. 79-85 and Freeze and Cherry,
1979, pp. 168-236 for more information regarding
ground-water flow.
Ground-water tracers, such as dye or salt may be used
to track ground-water flow velocities and contaminant
plume movement. A tracer is placed in one well and
the time of its arrival in a second well downgradient
from the first well is noted. The dilution of the tracer
detected in the second well can indicate the
contaminant dilution rate and help determine the
contaminant source concentration as well as the width,
depth, and spreading velocity of the plume. Tracers
also may be used to help determine aquifer porosity,
hydraulic conductivity, and dispersivity.
The tracer selected must be detectable in extremely
low concentrations and must not react chemically or
physically with the ground-water or aquifer
composition. See Driscoll, 1986, pp. 84-85 for more
information regarding ground-water tracers.
2.1.3 Site Reconnaissance
A site reconnaissance can be conducted at an earlier
date or immediately prior to sampling activities. It
allows field personnel to assess actual, current site
conditions, evaluate areas of potential contamination,
evaluate potential hazards associated with sampling,
and finalize a sampling plan. Site reconnaissance
activities for a ground-water assessment include:
observing and photographing the site; noting site
access and potential evacuation routes; noting
potential safety hazards; inventorying and recording
label information from drums, tanks, or other
containers; mapping process and waste disposal areas
such as landfills, impoundments, and effluent pipes;
mapping potential contaminant migration routes such
as drainage, streams, and irrigation ditches; noting the
condition of animals and/or vegetation; noting
topographic and/or structural features; noting and
mapping existing ground-water monitoring or other
types of wells for potential sampling; and siting
potential locations for new monitoring wells if
necessary. Field personnel should use appropriate
personal protective equipment when engaged in any
on-site activities. Consider the following site-specific
factors while performing a site reconnaissance:
Sampling Objectives - Sampling is conducted
typically to comply with regulations for the
detection or assessment of suspected
contamination within the subsurface. The
information gathered aids in the identification of
known and unknown substances present within
the site and the level and extent of contamination
of the environment. The information is used to
document the condition of the ground-water
system as an initial assessment, a record of
development, or as evidence of remediation
efficiency and compliance.
Sample Collection and Toxicity - The samples
collected are intended to document the absence or
measure the presence of contaminants. The
measure of acute or chronic toxicity is evaluated
by assessing the site's extent of contamination,
the time period in relation to the extent, and
health hazards associated with the contaminant
exposure time frame.
Statistical Concerns - A site visit will familiarize
the sampling planner with the environment to be
sampled. Conspicuous indicators of potential
contamination sources or contamination effects
may suggest use of a judgmental or bias sampling
design. A geostatistical sampling method can be
cost-effective and time-efficient when compared
to strictly random or random-stratified
procedures. When using less random methods,
the choice of sampling locations should be
documented and justified. Employ random
sampling in addition to bias sampling and include
background or control samples for a thorough
representation of the ground-water character.
(See Section 2.3 for a discussion of sampling
approaches.) (For additional information see
Keith, Lawrence H., Principles of Environmental
Sampling.)
Timing of the Response - Consider seasonal
variation when evaluating a site. Predictions of
bad weather can influence technique and design.
The urgency of the action weighed against
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seasonal constraints may dictate the options
available within the targeted budget.
Site-Specific Factors Affecting Ground-Water
Flow Many factors of a site control the path or
direction of ground-water flow. A combination of
geologic survey information with the site
reconnaissance can better familiarize the planner
with the dynamics of the hydrogeologic system.
The local geology of a site can determine the
direction and rate of ground-water movement by
means of its orientation and composition (e.g.,
horizontal, tilted or vertical structures, and
confining clay versus unconfining sand and
gravel). The degree of development of a site and
its local topography can affect the ground-water
flow (e.g., parking lot runoff disproportionally
delivers water quantities to the subsurface and
greater slopes afford less infiltration of water to
the subsurface). The extent and type of
vegetation can affect the amount of rainfall that
actually recharges an aquifer system. Dense
vegetation and high evapo-transpiration from
vegetation allows very little water to descend to
the subsurface. Seasonal variations can cause
reversal of ground-water flow direction. This is
usually associated with water bodies such as
streams, rivers, ponds, and lakes. Water may
flow to or from streams depending upon its
surface elevation in relation to adjacent water
table surfaces. During flood conditions, water
usually flows from rivers toward the surrounding
subsurface. During drought, water moves toward
the lower level of the stream surface from higher
ground-water surfaces. (Consult U.S. EPA
Handbook, Ground Water, EPA/625/6-87/016,
Chapter 4: Basic Hydrogeology.)
Analytical Parameters - The site reconnaissance
can help develop the list of analytical parameters.
For example, a reconnaissance may indicate the
presence of battery casings. Lead would then be
a substance of concern. The site may contain
constraints that may or may not allow a variety of
tests to be performed. The cost-effectiveness of
testing within the site's constraints can lead to
limited options available to properly analyze the
ground-water system. Testing methods may vary
within one site (e.g., monitoring well sampling,
hydroprobe extraction, etc.) in order to evaluate
multiple criteria vital to the site assessment.
Degradation for Transformation') Products - Sites
may contain degradation (or transformation)
products, or by-products, of the contaminant that
are detectable and potentially as hazardous as the
contaminant itself. Sampling for the product can
lead to clues of the source substance location and
its reactive status within the subsurface.
Sampling Order - The sampling plan should
address a specific order of sampling locations
(and depths at a single location) to be developed.
In order to use equipment efficiently, the plan
should attempt to sample from "clean" to "dirty"
locations, reducing the potential for contaminants
to affect relatively less contaminated locations.
Typically, the background or "clean" location of
a site is hydrologically upgradient from the
suspected contaminant "hot spot." Depending
upon the nature of the contaminant (e.g., a
"sinker" or "floater"), the sampling at different
depths within a column of water in a monitoring
well should also follow a sequence.
2.2 PARAMETERS OF CONCERN,
DATA QUALITY OBJECTIVES,
AND QUALITY ASSURANCE
MEASURES
2.2.1 Parameters of Concern
Drinking water populations, contaminants, and
migration pathways are additional parameters that
should be considered when developing a sampling
plan. Often, ground-water contamination goes
undetected because it is not directly visible. Drinking
water odor or taste complaints by residents close to
the site are usually the initial indication of ground-
water contamination and potential health hazards.
The sampling data should accurately delineate the
extent of ground-water contamination, determine the
impact on drinking water populations, and indicate
potential migration pathways to such populations. It
is important to design the sampling plan to determine
where contaminants are most highly concentrated, and
to locate areas of decreasing detectable concentrations
and those not yet contaminated.
2.2.2 Data Quality Objectives
Data quality objectives (DQOs) state the level of
uncertainty that is acceptable for data collection
activities and define the certainty of the data necessary
to make decisions. The overall goal of DQOs for a
representative ground-water sampling plan are to
acquire thorough and accurate information about
subsurface water conditions at a site. DQOs are
unique and site specific and should address the
10
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contaminant's interaction with the immediate site
environment. When establishing DQOs for a
particular project, consider:
Decision(s) to be made or question(s) to be
answered
Why analytical data are needed and how the
results will be used
Time and resource constraints on data collection
Descriptions of the analytical data to be collected
Applicable model or data interpretation method
used to arrive at a conclusion
Detection limits for analytes of concern
Sampling and analytical error
2.2.3 Quality Assurance Measures
To ensure that analytical samples are representative of
site conditions, quality assurance measures must be
associated with each sampling and analysis event.
The sampling plan must specify QA measures, which
include, but are not limited to, sample collection,
laboratory SOPs, sample container preparation,
equipment decontamination, field blanks, replicate
samples, performance evaluation samples, sample
preservation and handling, and chain-of-custody
requirements. 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 (QA/QC) accuracy
measurement
Completeness - Percentage of sampling
measurements which are judged to be valid
Representativeness - Degree to which sample
data accurately and precisely represent the
characteristics and concentrations of the
source/site contaminants
Comparability - Evaluation of the similarity of
conditions (e.g., sample depth, sample
homogeneity) under which separate sets of data
are produced
Refer to Chapter 5, Quality Assurance/Quality Control
(QA/QC), for more detailed ground-water QA/QC
information.
2.3 REPRESENTATIVE GROUND-
WATER SAMPLING
APPROACHES AND SAMPLE
TYPES
Judgmental sampling is the primary representative
sampling approach used for ground water. Other
representative sampling approaches for ground water
such as random, systematic grid, and systematic
random sampling are described below. For
information on the other types of sampling
approaches, refer to U.S. EPA, Superfund Program
Representative Sampling Guidance, Volume 1 Soil,
OSWER Directive 9360.4-10.
2.3.1 Judgmental Sampling
Judgmental sampling is the biased selection of
sampling locations at a site, based on historical
information, visual inspection, sampling objectives,
and professional judgment. A judgmental approach is
best used when knowledge of the suspected
contaminant(s) or its origins is available. Judgmental
sampling includes no randomization in the sampling
strategy, precluding statistical interpretation of the
sampling results. Criteria for selecting sampling
locations are dependent on the particular site and level
of contamination expected.
Once a contaminant has been detected in the ground
water, the source and extent must be identified. To do
this, an understanding of the contaminant
characteristics and the local geologic and
hydrogeologic conditions is needed. Characteristics
of the contaminant and any daughter (degradation)
products must be known in order to understand how
the material may be transported (both vertically and
laterally) from the contamination source. Knowledge
of the local hydrogeology is needed in order to
identify areas or zones that would facilitate
contaminant migration, such as water bodies and
gravelly or sandy soils. The permeability of the
underlying rock type should be analyzed, as well as its
depth, which will help to narrow the potential
sampling area. For example, if the underlying
bedrock strikes northeast to southwest, then sampling
of an aquifer should also be in this direction, unless
cross-contamination between aquifers has already
been identified.
When appropriate (based on sampling objectives,
availability, sampling parameters, and budget), sample
available local residential or commercial wells
following a relatively systematic pattern based on the
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geology of the area. In the example given in the
paragraph above, wells would be sampled along a line
northeast to southwest. If the number of wells
available is not sufficient to adequately identify the
extent of contamination, then additional monitoring
wells could be installed.
During a ground-water assessment, the selection of
locations for monitoring well installation is done with
a judgmental approach. This is generally because
monitoring wells are complex, expensive, and time-
consuming to install. In order to best determine the
nature of a suspected contaminant plume, monitoring
wells need to be placed in areas most likely to
intercept the plume. Using a random, systematic grid
or a systematic random approach would likely result
in too many wells that miss the contaminant plume.
Even placement of background or control monitoring
wells favors a judgmental approach. Locations are
selected based on the site reconnaissance and the
planner's knowledge of the suspected contaminants,
site geology, and hydrology.
2.3.2 Random, Systematic Grid, and
Systematic Random Sampling
Random, systematic grid, and systematic random
sampling are generally not used for ground-water
sampling because sampling points are pre-determined
from either existing wells or monitoring wells which
are placed by judgment. However, these approaches
may be useful for soil gas testing to assist in the siting
of new monitoring wells. They can also be useful for
conducting Geoprobeฎ sampling, if necessary. For
additional information on these sampling approaches,
refer to U.S. EPA, Superfund Program
Representative Sampling Guidance, Volume 1 Soil,
OSWER Directive 9360.4-10.
2.3.3 Grab versus
Sample Types
Composite
Grab samples are essentially the only type of samples
collected for ground water. Unlike surface water,
ground water is not composited. Each ground-water
sample is representative of a discrete location and
horizon in the subsurface.
Site Location - The location of the site will often
influence the size of the sampling area and
whether sampling should be conducted on or off
site or a combination of both.
Local Geology and Hydrology - Local geology
and hydrology can determine whether off-site
sampling is necessary and defines ground-water
sampling boundaries and locations. For example,
if an aquifer is very deep or there is a confining
layer between the ground surface and the aquifer,
then sampling within a small area may be all that
is necessary in order to determine the extent of
contamination within that aquifer.
Topography - Topography will control the
direction of surface runoff and may give clues to
subsurface conditions. For example, wells in
valleys may not be of the same aquifer as wells
on a hill.
Analytical Parameters - If contaminants are
initially unknown, then a broad spectrum of
analytical parameters is usually collected. As
more information about the site becomes
available (through screening or laboratory
analysis), the number of parameters can be
streamlined or altered in order to more effectively
characterize the site. If the contaminant is
known, then concentrate on sampling for it and
its degradation products.
Sampling Budget - Budget constraints inevitably
affect operations. A combination of screening
and analytical techniques minimizes expenses
while still providing an acceptable level of
quality for the sampling data.
Physiochemical Nature of Suspected
Contamination When designing the sampling
plan, take into account the physical and chemical
nature of the suspected contaminants, then design
the sampling plan to facilitate efficient detection
of the contaminants through sampling
methodology, equipment, and analyses. For
example, the water density or solubility of a
contaminant may provide an indication of the
contaminant's physical location within the water
column.
2.4 SAMPLING PLAN
To develop a successful and practical representative
ground-water sampling plan, the following site-
specific information is required:
Water has a specific gravity of one. Some
chemical compounds, such as many complex
petrochemicals, have a specific gravity of greater
than one, and are therefore more dense than
water. These substances tend to sink and include
chlorinated solvents, wood preservatives, other
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coal tar wastes, and pesticides. These compounds
are referred to as dense nonaqueous phase
liquids (DNAPLs), or "sinkers". On the other
hand, a specific gravity of less than one will
allow a contaminant to float on or near the water
table, and includes many fuel oil products and
byproducts (e.g., gasoline, benzene, toluene, ethyl
benzene, xylene (BTEX), and other straight chain
hydrocarbons). These compounds are referred to
as light nonaqueous phase liquids (LNAPLs), or
"floaters". Nonaqueous phase liquids (NAPLs)
tend to exist as separate layers in the water
column. A substance with a specific gravity
value near to or equal to one will generally
dissolve in the water column (e.g., acetone,
phenols, and creosote). Because of the potential
stratification in the water column due to NAPL
substances, sampling location with respect to the
suspected contaminant location within the well
should always be considered.
LNAPLs commonly occupy the capillary fringe
zone above the water table. In a confined aquifer,
these compounds are found along the upper
surface of the permeable unit and also within the
overlying confining layer.
DNAPLs cause additional representative
sampling concerns. These compounds move
downward under the influence of gravity until
reaching a less permeable formation where they
may either accumulate, move downslope along
the bedrock, or penetrate fractures. Special
precautions should be taken during drilling at
sites suspected of DNAPL contamination; ensure
that the drilling does not induce the spread of
free-phase DNAPL contaminants. Monitoring
well installation should be suspended when a
DNAPL or low permeability lithogic unit is
encountered. Fine-grained aquitards (e.g., silt or
clay) should be assumed to permit downward
DNAPL migration. For guidance on sites with
potential DNAPL contamination, see U.S. EPA
Estimating the Potential for Occurrence of
DNAPL at Superfund Sites, OSWER Directive
9355.4-07.
Additional elements which should be addressed in a
representative ground-water sampling plan include:
Sample Number - The number of samples
collected depends on the number of sample
locations. Normally one sample is taken at each
location, except for QA/QC requirements (e.g.,
replicates, and matrix spike/matrix spike
duplicates). If there are multiple, discreet
aquifers at the site, then samples of each may be
necessary. Splitting samples also requires an
increase in the number of samples.
Sample Volume - The sample volume is
dependent on the analytical parameters. It is also
dependent on whether the contaminant is known
or unknown. A greater volume is generally
needed when the contaminant is unknown
because a larger suite of parameters is usually
selected.
Sample Location - Sample location is generally
dictated by the availability of existing
monitoring, residential, or commercial wells.
New monitoring wells are located by judgmental
methods.
Sample Depth - Sampling depth is typically the
bottom or screened zone of a well. However,
there may be times when certain stratigraphic
horizons within the water column may need to be
discreetly sampled (e.g., capturing "floaters" or
"sinkers"). (Procedures for addressing stratified
samples are discussed in Section 4.4.)
Sample Order - Sampling order is from the least
contaminated to the most contaminated wells or
areas (if known).
2.5 EXAMPLE SITE
2.5.1 Background
The ABC Plating Site is located in northeastern
Pennsylvania approximately 1.5 miles north of the
town of Jonesville. Figure 2 provides a layout sketch
of the site and surrounding area. The site covers
approximately four acres and operated as a multi-
purpose specialty 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 unlined shallow surface
settling lagoons in the northwest portion of the site.
Pennsylvania Department of Environmental Resources
(PADER) personnel cited the owner/operator for the
operation of an unpermitted treatment system and
ordered the owner to submit a remediation plan for
state approval. Before PADER could follow up on the
order, the lagoons were partially backfilled with the
wastes in place. The process building was later
destroyed by a fire of suspicious origin. The owner
abandoned the facility and could not be located by
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Figure 2: Site Sketch
ABC Plating Site
A
TREELINE
A
A
A
SUSPECTED
- LAGOONS
SUSPECTED
TRENCH
HOUSE
TRAILER
SCALE IN FEET
100 50
I
100
LEGEND
DAMAGED
BUILDING
AREA
- SURFACE FLOW
--- SITE BOUNDARY
14
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enforcement and legal authorities. Several vats,
drums, and containers were left unsecured and
exposed to the elements. The state contacted EPA for
an assessment of the site for a possible federally
funded response action; an EPA On-Scene
Coordinator (OSC) was assigned to the task.
2.5.2 Site History and
Reconnaissance
The EPA OSC reviewed the PADER site file. In 1974
the owner was cited for violating the Clean Streams
Act and for storing and treating industrial waste
without a permit. The owner was ordered to file a site
closure plan and to remediate the settling lagoons.
The owner, however, continued operations and was
then ordered to begin remediation in 90 days or be
issued a cease and desist order. Soon after, a follow -
The OSC obtained copies of aerial photographs of the
site area from the local district office up inspection
revealed that the lagoons had been backfilled without
removing the waste.
The OSC and a sampling contractor (Team) arrived on
site to interview local and county officials, fire
department officers, neighboring residents (including
a former facility employee), and PADER
representatives regarding site operating practices and
other site details. The former employee sketched
facility process features on a map copied from state
files. The features included two settling lagoons and
a feeder trench which transported plating wastes from
the process building to the lagoons. The OSC
obtained copies of aerial photographs of the site area
from the local district office of the U.S. Soil
Conservation Service. The state provided the OSC
with copies of all historical site and violation reports.
These sources indicated the possible presence and
locations of chromium, copper, and zinc plating
process areas.
The Team mobilized to the site with all the equipment
needed to perform multi-media sampling. The OSC
and Team made a site entry, utilizing appropriate
personal protective equipment and instrumentation, to
survey the general site conditions. They observed 12
vats, likely containing plating solutions, on a concrete
pad where the original facility process building once
stood. Measurements of pH ranged from 1 to 11.
Fifty drums and numerous smaller containers (some
on the concrete pad, others sitting directly on the
ground) were leaking and bulging because of the fire.
Some rooms of the process building could not be
entered due to unsafe structural conditions caused by
the fire. The Team noted many areas of stained soil,
which indicated container leakage, poor waste
handling practices, and possible illegal dumping of
wastes.
2.5.3 Identification of Parameters of
Concern
During the site entry, the OSC and Team noted that
several areas were devoid of vegetation, threatening
wind erosion which could transport heavy metal- and
cyanide-contaminated soil particulates off site. These
particulates could be deposited on residential property
downwind or be inhaled by nearby residents.
Erosion gullies located on site indicated surface soil
erosion and stormwater transport. Surface drainage
gradient was toward the west and northwest. The
Team observed stressed, discolored, and necrotic
vegetation immediately off site along the surface
drainage route. Surface drainage of heavy metals and
cyanide was a direct contact hazard to local residents.
Surface water systems were also potentially affected.
Further downgradient, site runoff entered an
intermittent tributary of Little Creek, which in turn
feeds Barker Reservoir. This reservoir is 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 acids and bases as might be found in
leaking or unsecured drums or containers.
After interviewing residents, it was established that
the homes located to the south and nearest to the site
rely upon private wells for their primary drinking
water supply. Ground water is also utilized by several
small community production systems which have
wells located within 2 miles of the site. The on-site
settling lagoons were unlined and therefore posed a
threat to ground water, as did precipitation percolating
through contaminated soils. Contamination might
have entered shallow or deeper aquifers and
potentially migrated to off-site drinking water wells.
During Phase 1 sampling activities, full priority
pollutant metals and total cyanide analyses were
conducted on all soil and ground-water samples sent
to the laboratory. These parameters were initially
selected based on a study of plating chemistry:
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plating facilities generally use either an acid or basic
cyanide bath to achieve the desired coating on their
metal products. Since Phase 1 samples were collected
from the areas of highest suspected contaminant
concentration (i.e., sources and drainage pathways),
Phase 2 samples (all media types) were analyzed for
total chromium, hexavalent chromium (in water only),
and cyanide, the only analytes detected consistently
during the Phase 1 analyses. During Phase 3, the
samples sent to the laboratory for definitive analysis
were analyzed for total chromium and cyanide.
2.5.4 Sampling Objectives
The OSC initiated an assessment with a specific
sampling objective, 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
(site stabilization strategies) to reduce direct
contact concerns on site. Sample the nearby
drinking water wells for immediate human health
concerns.
Once CERCLA funding was obtained and the site was
stabilized:
Phase 2 Define the extent of contamination at
the site and adjacent residential properties.
Estimate the costs for early action options and
review any potential long-term remediation
objectives. For example, install and sample soil
borings and monitoring wells on site to evaluate
potential impact on subsurface soils and ground
water.
Phase 3 After early actions are completed,
document the attainment of goals. Assess that the
response action was completed to the selected
level and is suitable for long-term goals.
2.5.5 Selection of Sampling
Approaches
The OSC, Team, and PADER reviewed all available
information to formulate a sampling plan. The OSC
selected a judgmental sampling approach for Phase 1.
Judgmental sampling supports the immediate action
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 (fewer 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,
and nearby residential drinking water wells were
sampled for immediate human health concerns.
For Phase 2, a stratified systematic grid design was
selected to define the extent of contamination in soils.
The grid could accommodate analytical screening and
geophysical surveys. Based on search sampling
conducted at sites similar to ABC Plating, a block grid
with a 50-foot grid spacing was selected. This grid
size ensured a 10 percent or less probability of
missing a "hot spot" of 45 feet by 20 feet. The grid
was extended to adjacent residential properties when
contaminated soil was identified at grid points near
the boundary of the site.
Based on the results of soil sampling and geophysical
surveys, a judgmental approach was used to select
locations for installation of 15 monitoring wells: at
"hot spots"; along the perimeter of the suspected
plume established from analytical results and
geophysical survey plots; and at background ("clean")
locations. Subsurface soil and ground- water samples
were collected from each of the 15 monitoring well
locations for laboratory analysis to establish the
presence and, if applicable, the degree of
contamination at depth.
2.5.6 Sampling Plan
During Phase 1, containerized wastes were evaluated
using field analytical screening techniques. Phase 1
wastes-screening indicated the presence of strong
acids and bases and the absence of volatile organic
compounds. The Team collected a total of 12 surface
soil samples (0-3 inches) and 3 ground-water samples
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 immediate action response
funding. Ground-water samples were collected from
three nearby residential wells. Based on Phase 1
analytical results, chromium was selected as the target
compound for determination of extent of
contamination in soil and ground water.
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During Phase 2 sampling activities, the OSC used a
transportable X-ray fluorescence (XRF) unit installed
in an on-site trailer to screen soil samples for total
chromium in order to limit the number of samples to
be sent for laboratory analysis. Soil sampling was
performed at all grid nodes at the surface (0-4 inches)
and subsurface (36-40 inches). The 36-40 inch depth
was selected based on information obtained from state
reports and local interviews, which indicated that
lagoon wastes were approximately 3 feet below
ground surface. Once grid nodes with a
contamination level greater than a selected target
action level were located, composite samples were
collected from each adjoining grid cell. Based on the
XRF data, each adjoining grid cell was either
identified as "clean" (below action level) or
designated for response consideration (at or above
action level).
Also during Phase 2, the OSC oversaw the
performance of ground penetrating radar (GPR) and
electromagnetic conductivity (EM) geophysical
surveys to help delineate the buried trench and lagoon
areas, any conductive ground-water plume, and any
other waste burial areas. The GPR and
comprehensive EM surveys were conducted over the
original grid. Several structural discontinuities,
defining possible disturbed areas, were detected. One
GPR anomaly corresponded with the suspected
location and orientation of the feeder trench. The EM
survey identified several high conductivity anomalies:
the suspected feeder trench location, part of the lagoon
area, and a small area west of the process building,
which may have been an illegal waste dumping area.
(Field analytical screening and geophysical techniques
are further discussed in Chapter 3.)
Using the data obtained during soil sampling and the
geophysical surveys, a ground-water assessment plan
for Phase 2 was prepared. The Team collected depth
soundings and water level measurements of the nearby
residential wells to assess aquifer usage and location
(depth). With these data and the analytical results
from Phase 1, a work plan for monitoring well
installation and testing on site was developed. The
plan consisted of:
Installation of overburden, bedrock contact and
bedrock (open borehole) monitoring wells in
order to evaluate the shallow water table and
aquifer conditions
Analysis of subsurface soils retrieved during
borehole/well drilling in order to evaluate the
extent of contamination in overlying soils
Collection of depth soundings and water level
measurements of the newly installed monitoring
wells to map aquifer and water table gradients
Collection of ground-water samples from each
monitoring well
Performance of hydraulic tests in order to
evaluate aquifer characteristics
The monitoring wells were located in areas shown,
during soil sampling, to be heavily contaminated;
along the outer perimeter of a contaminant plume
based on soil XRF results and the geophysical
surveys; and an apparent upgradient location for
background conditions comparison. Fifteen wells
were located at grid nodes corresponding to the above
results. (Section 4.6.1 provides details on the
performance of well installation (drilling), testing and
surveying, and ground-water sampling procedures.)
Upon monitoring well installation and sampling, a
hydraulic (pumping) test was completed of the
bedrock monitoring wells to gather information about
aquifer characteristics. These data characterize
contaminant transport through the ground-water
aquifer. The hydraulic test provided transmissibility,
hydraulic conductivity, and storativity values.
Utilizing these values with ground-water level data,
the estimated vertical and horizontal ground-water
gradient and velocity could be calculated. All
monitoring wells installed were surveyed for elevation
above mean sea level, needed to determine accurate
depth to ground water (piezometric surface) and
relative gradients.
Phase 3 activities are discussed in Section 6.8.
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3.0 FIELD ANALYTICAL SCREENING, SAMPLING EQUIPMENT,
AND GEOPHYSICAL TECHNIQUES
3.1 FIELD ANALYTICAL
SCREENING
Field analytical screening techniques can provide
valuable information in ground-water sampling. Field
analytical screening for ground water is used primarily
as a tool for siting monitoring wells and for on-site
health and safety assessment during well drilling
activities. When used correctly, screening techniques
can help to limit the number of "non-detect"
monitoring wells installed. Some of the commonly
used screening methods for ground-water assessment
are presented in this chapter in the general order that
they would initially be used at a site, although site-
specific conditions may mandate a different sequence.
For more information on ground-water field screening
devices, refer to the U.S. EPA Compendium ofERT
Field Analytical Procedures, OSWER Directive
9360.4-04, and Compendium of ERT Ground-Water
Sampling Procedures, OSWER Directive 9360.4-06.
Refer to Standard Operating Safety Guides for each
instrument, and the U.S. Department of Health and
Human Services Occupational Safety and Health
Guidance Manual for Hazardous Waste Site
Activities (NIOSH Pub. 85-115) for site entry
information.
3.1.1 Flame lonization Detector
The flame ionization detector (FID) detects and
measures the level of total organic compounds
(including methane) in the ambient air in proximity to
a well or in a container headspace. The FID uses the
principle of hydrogen flame ionization for detection
and measurement. It is especially effective as an
ethane/methane detector when used with an activated
charcoal filter because most organic vapors are
absorbed as the sample passes through the filter,
leaving only ethane and methane to be measured.
The FID operates in one of two modes: the survey
mode, or the gas chromatography (GC) mode. In the
survey mode, the FID provides an approximate total
concentration of all detectable organic vapors and
gases measured relative to the calibration gas (usually
methane). The GC mode identifies and measures
specific components, some with detection limits as
low as a few parts per million (ppm), using known
standards analyzed concurrently in the field. Since the
GC mode requires standards to identify classes of
compounds, it is necessary to have an idea of which
compounds might be present on site before sampling.
Advantages of the FID are that it is portable,
relatively rugged, and provides real-time results.
During a ground-water assessment, the FID is used in
the survey mode for monitoring the borehole during
drilling and in the survey or GC mode for health and
safety screening.
The FID does not respond to inorganic substances. It
has positive or negative response factors for each
compound depending on the selected calibration gas
standard. Ambient air temperatures of less than 40
degrees Fahrenheit will cause slower responses;
relative humidity of greater than 95 percent can cause
inaccurate and unstable responses. Interpretation of
readings (especially in the GC mode) requires training
and experience with the instrument.
3.1.2 Photoionization Detector
Another portable air monitoring instrument frequently
used for field screening during ground-water
assessments is the photoionization detector (PID).
Like the FID, the PID provides data for real-time total
organic vapor measurements, identifying potential
sample locations and extent of contamination, and
supporting health and safety decisions. The PID is
useful in performing soil gas screening, health and
safety monitoring during well drilling activities, and
headspace screening analysis. The PID works on the
principle of photoionization. Unlike the FID, the PID
can be used to detect gross organic and some
inorganic vapors, depending on the substance's
ionization potential (IP) and the selected probe energy.
It is portable and relatively easy to operate and
maintain in the field.
The PID detects total concentrations and is not
generally used to quantify specific substances. PIDs
cannot detect methane; however, methane is an
ultraviolet (UV) light absorber, and false negative
instrument readings may register in methane-rich
environments. The PID cannot detect substances with
IPs greater than that of the UV light source.
(Interchangeable UV lamps are available.) Readings
can be affected by high wind speeds, humidity,
condensation, dust, power lines, and portable radios.
Dust particles and water droplets (humidity) in the
sample may collect on the light source and absorb or
18
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deflect UV energy, causing erratic responses in PIDs
not equipped with dust and moisture filters.
3.1.3 Gas Chromatograph
Although many FIDs are equipped with a GC mode,
an independent, portable GC (gas chromatograph) can
also be used on site to provide a chromatographic
profile of the occurrence and intensity of unknown
volatile organic compounds (VOCs) in ground water.
The GC is useful as a soil gas screening tool to
determine "hot spots" or plumes, potential
interferences, and semi-quantitation of VOCs and
semi-volatile organic compounds (semi-VOCs) in
ground-water samples. For example, when installing
a monitoring well, the GC might be used to screen
water samples during drilling in order to indicate
when a target contaminated aquifer zone is
encountered.
Compounds with high response factors, such as
benzene and toluene, produce large response peaks at
low concentrations, and can mask the presence of
compounds with lower response factors. However,
recent improvements in GCs, such as pre-concentrator
devices for lower concentrations, pre-column
detection with back-flush capability for rapid
analytical time, and the multi-detector (PID, FID, and
electron capture detector (BCD)), all enable better
compound detection. The GC is highly temperature-
sensitive. It requires set-up time, many standards, and
operation by trained personnel.
3.1.4 Hydraulic Probe
The hydraulic probe (Geoprobeฎ is one brand) is a
truck-mounted device used to collect screening
ground-water, soil, and soil gas samples at relatively
shallow depths. The probe is mounted on the back of
a small truck or van and is operated hydraulically
using the vehicle's engine. Small diameter hardened
steel probes are driven to depths of up to 40 feet or
more, depending on soil conditions. Soil gas samples
can then be collected using a vacuum pump. Soil or
water samples can also be collected using a small-
diameter shelby tube or slotted well point and foot
valve pump.
The hydraulic probe can be used in ground-water
investigations to assess vertical and horizontal extent
of contamination. Shallow samples can be collected
relatively quickly and easily. It is useful in a ground-
water assessment to assist in siting monitoring wells
and to install shallow wells if necessary. It can also
collect undisturbed ground-water samples without
installing wells. The hydraulic probe is only effective
in unconsolidated geologic materials, however. In
general, probing is possible under conditions
amenable to hollow stem auger drilling.
3.1.5 Soil Gas Technique
Soil gas testing is a quick method of site evaluation.
For ground-water assessments, soil gas testing is used
to track contaminant plumes and determine
appropriate locations for installing monitoring wells.
For this technique, a thin stainless steel probe is
inserted into a hole made in the soil with a special
slam bar. The hole is sealed around the probe and a
sampling pump is attached. Samples are then
collected in Tedlar bags, sorbent cartridges, or
SUMMA canisters. The samples are analyzed using
an FID, PID, or GC. A disadvantage of the soil gas
technique is that its ability to detect contaminants
diminishes the further it is from the source (as
contaminant concentration diminishes).
3.1.6 Field Parameter Instruments
Field parameters measured during ground-water
sampling include pH, specific conductivity,
temperature, salinity, and dissolved oxygen. Specific
conductivity, pH, and temperature are often used as
standard indicators of water quality. Instruments that
measure these three indicators are used during ground-
water assessments to determine if a well has been
purged sufficiently (stabilized) prior to sampling (see
Section 4.3).
3.1.7 X-Ray Fluorescence
Field analytical screening using X-ray fluorescence
(XRF) is a cost-effective and time-saving method to
detect and classify lead and other heavy metals in a
sample. XRF screening provides immediate semi-
quantitative results. The principle behind XRF is the
detection and measurement of the X-rays released
from an atom when it is excited by the absorption of
source X-rays. The energy released (fluorescent X-
rays) are characteristic of the atoms present.
Results of XRF analysis help determine the presence
of metals and are often used to assess the extent of
soil contamination at a site. For ground-water
assessment, XRF may be used on subsurface soil
samples collected during drilling or with surface soils
when selecting locations for monitoring well
installation. XRF use requires a trained operator and
may require numerous site-specific calibration
samples.
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3.2 GROUND-WATER SAMPLING
EQUIPMENT
Conducting representative ground-water sampling
requires an understanding of the capabilities of the
equipment used for sampling, since the use of
inappropriate equipment may result in biased samples.
Select appropriate sampling equipment based on the
sampling objectives, the analytical parameters, the
type of well being sampled (e.g., monitoring well or
drinking water well), and other site-specific
conditions. Follow SOPs for the proper use and
decontamination of sampling equipment. This section
presents various types of ground-water sampling
equipment and information to assist in selecting
appropriate materials.
The ground-water sampling devices discussed below
are covered in greater detail in many SOPs and
references on the various types of available ground-
water sampling devices. Refer to U.S. EPA A
Compendium of Superfund Field Operations
Methods, OSWER Directive 9355.0-14, and
Compendium of ERT Ground-Water Sampling
Procedures, OSWER Directive 9360.4-06, for details
on the equipment listed. Also refer to Driscoll,
Fletcher G., Ground-Water and Wells, 2nd ed., and
the 1985 "Proceedings of the Fifth National
Symposium and Exposition on Aquifer Restoration
and Ground-Water Monitoring," for additional
comparisons of the various types of sampling
equipment.
3.2.1 Bailer
A bailer is a simple purging device for collecting
samples from monitoring wells. It usually consists of
a rigid length of tube with a ball check-valve at the
bottom. A line is used to mechanically lower the
bailer into the well to retrieve a volume of water.
Because bailers are portable and inexpensive, they can
be dedicated to monitoring wells at a site, thus
avoiding the need to use a bailer for sampling more
than one well (and avoiding cross-contamination).
Bailers are available in a variety of sizes and
construction materials (e.g., polyvinyl chloride (PVC),
Teflonฎ, and stainless steel).
Bailers are best suited for purging shallow or narrow
diameter monitoring wells. Deeper, larger diameter,
and water supply wells generally require mechanical
pumps to evacuate a large volume of water.
For VOC analysis, a positive-displacement volatile
sampling bailer is most effective. Bottom-fill bailers,
which are more commonly used, are suitable provided
that care is taken to preserve volatile constituents. Fill
sample containers directly from the bailer, filling
samples for VOC analysis first.
3.2.2 Hydraulic Probe
The hydraulic probe can be used to collect shallow
(generally 40 feet or less) ground-water samples using
a mill-slotted well point or retractable screen drive
point. After the well point is driven to the desired
depth, the probe rod is connected to a vacuum pump
for purging. (Since ground water is sampled in situ
and is not exposed to the atmosphere, extensive
purging is not required.)
Water samples are collected using dedicated
polypropylene tubing fitted with a small diameter
foot-valve pump. Samples are collected in 40-ml vials
or other containers for laboratory analysis. See
Section 3.1.4 for more information on the hydraulic
probe.
3.2.3 Air-Lift Pump
An air-lift pump operates by releasing compressed air
via an air line lowered into the well. The air mixes
with the water in the well to reduce the specific
gravity of the water column and lift the water to the
surface.
Air-lift pumping is used in well development and for
preliminary testing. For sampling, air-lift pumping is
less efficient than other pumping methods which
follow; it may be selected for use when aeration is
needed to remove gas or corrosive water which can be
destructive to a well pump. Because an air-lift pump
aerates the water, it is not applicable for VOC sample
collection.
3.2.4 Bladder Pump
A bladder pump consists of a stainless steel or
Teflonฎ housing that encloses a Teflonฎ bladder.
The bladder pump is operated using a compressed gas
source (bottled gas or an air compressor). Water
enters the bladder through a lower check valve;
compressed gas moves the water through an upper
check valve and into a discharge line. The upper
check valve prevents back flow into the bladder.
The bladder pump can be used to purge and sample to
a depth of approximately 100 feet. It is recommended
for VOC sampling because it causes minimal
alteration of sample integrity as compared with other
20
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ground-water sample methods. The bladder pump
requires a power supply and a compressed gas supply
or air compressor. The pump is somewhat difficult to
decontaminate and should thus be dedicated to a well
(or dedicated tubing should be used).
3.2.5 Rotary Pump
A rotary pump is a positive displacement pump which
discharges the same volume of water regardless of the
water pressure. The rate of discharge is the same at
both low and high pressure, but the input power varies
in direct proportion to the pressure. The rotary pump
consists of a housing with inlet and outlet ports and
rotating gears or vanes. As water is discharged from
the pump, a replacement supply of equal volume is
taken in.
Rotary pumps are useful for well purging and general
sample collection at shallow to deep sampling depths.
Because of water agitation, they may not be suitable
for sampling VOCs, and they are difficult to
decontaminate between sampling stations.
3.2.6 Peristaltic Pump
A peristaltic pump is a suction lift pump consisting of
a rotor with ball-bearing rollers. Dedicated Teflonฎ
tubing is threaded around the rotor. Additional
lengths of dedicated Teflonฎ tubing are attached to
both ends of the rotor tubing: one end is inserted into
the well; the other end is a discharge tube. The
sample makes contact with the tubing only, not with
the pump. The tubing should be equipped with a foot
valve to avoid having aerated water from the tubing
fall back into the well.
A peristaltic pump is suitable for sampling small
diameter wells (e.g., 2 inches). Cross-contamination
is not of concern because dedicated tubing is used and
the sample does not come into contact with the pump
or other equipment. The peristaltic pump has a depth
limitation of 25 feet and its use can result in a
potential loss of the volatile fraction due to sample
aeration.
3.2.7 Packer Pump
A packer pump is used to isolate portions of a well or
water column for sampling. The pump consists of two
expandable parts that isolate a sampling unit between
them. The parts deflate for vertical movement within
the well and inflate when the desired sampling depth
is reached. The packers are constructed of rubber and
can be used with various types of pumps.
An advantage of the packer pump is it allows the
isolation of a portion of the water column in order to
sample at a discrete depth. Disadvantages relate to
the rubber construction of the packers which may
deteriorate over time allowing cross contamination.
The rubber also poses potential contaminant
compatibility concerns. A packer pump should not be
used if the contaminants are unknown, or where well
casing or contaminant characteristics interfere or
interact with the pump construction materials.
3.2.8 Syringe Sampler
Syringe samplers are a relatively new and less
commonly available sampling device. Syringe
samplers were developed by research groups to obtain
ground water samples over a period of time. The
device consists of a syringe (15 to 1500 ml in volume)
which is lowered into the well to the desired sampling
depth. The syringe plunger is then pulled open by a
remote method, either mechanical or pneumatic,
allowing the syringe to fill.
The remote operation allows the collection of a
sample at a discrete depth. In addition, the interior of
the sampler (i.e., the syringe) is not exposed to the
water column. Disadvantages to this device include
the small volume of sample that can be collected, it
cannot be adapted for evacuation/purging uses, and it
is not readily commercially available.
3.2.9 Ground-Water Sampling
Equipment Selection Factors
The following factors should be considered when
selecting ground-water sampling equipment.
Composition - Select the composition of the
sampling equipment based on the sampling
parameters and objectives. For example, use
samplers made of Teflonฎ, glass, or stainless
steel instead of PVC when sampling for VOCs.
Consider well composition when selecting
sampling equipment. For example, select a
stainless steel bailer when bailing a well with
stainless steel casing to avoid the introduction of
organic constituents. When sampling a PVC-
cased well, PVC, stainless steel, or Teflonฎ
bailers may be used.
Physical Constraints - Physical constraints of the
monitoring well location, power availability, and
topography are factors that affect selection of
ground-water sampling equipment. For example,
a small diameter or particularly deep well may
21
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require the use of different purging and sampling
equipment than that used for other wells at the
site. Site accessibility may hinder the use of
large or vehicle-mounted equipment.
Sample Analysis - Equipment should be chosen
based on its impact on the samples. For example,
sampling equipment selected for collecting VOCs
should agitate the water as little as possible. This
is not as critical for metals or other non-volatile
analyses.
Ease of Use - Generally, the more complicated
the sampling equipment is, the greater the chance
for some form of failure in the field. Utilize the
simplest effective sampling devices available.
Adequate training in equipment safely and use is
critical to personnel safety as well as to sample
representativeness. Consider ease of
decontamination when using non-dedicated
equipment.
3.3 GEOPHYSICAL METHODS
Geophysical methods can be useful in conjunction
with screening and sampling activities to help
delineate subsurface features and boundaries,
contaminant plumes, and bedrock types. Geophysical
data can be obtained relatively rapidly, often without
disturbing the site. The data are helpful in selecting
well locations and screen depths. The following
sections discuss surface and borehole geophysics and
preferable geophysical techniques for ground-water
investigations.
3.3.1 Surface Geophysics
The following surface geophysical techniques may be
useful in ground-water investigations. As implied by
the name, these techniques are performed above
ground. For more detailed information on each of
these techniques (with the exception of gravimetric
surveys), see ERT SOP #2159 and Driscoll, 1986.
For more information on gravimetric surveys, see
Driscoll, 1986.
Ground Penetrating Radar (GPR) - Uses a high
frequency transmitter that emits radar pulses into
the subsurface. These waves are scattered at
points of change in the dielectric permittivity of
the subsurface material and are reflected back to
an antenna. (Dielectric permittivity is a function
of bulk density, clay content, and water content of
the subsurface.) The returning energy wave is
then plotted as a function of time on an analog
plot. Interpretation of the analog plot identifies
anomalies, clay layers, and water content in the
substrate.
GPR works best in dry, sandy soil above the
water table, and at depths between 1 and 10
meters (although the full instrument depth range
is less than one meter to tens of meters). When
properly interpreted, GPR data can indicate
changes in soil horizons, fractures, and other
geological features, water-insoluble
contaminants, man-made buried objects, and
hydrologic features such as water table depth.
Uneven ground surfaces or cultural noise affect
GPR results.
Electromagnetic Conductivity (END - Relies on
the detection of induced electrical current flow
through geologic strata. This method measures
bulk conductivity (inverse of resistivity) of
subsurface materials below the transmitter and
receiver. EM is commonly used in the detection
of ground-water pollution, as well as to locate
pipes, utility lines, cables, trenches, buried steel
drums, and other buried waste.
EM has limited applications in areas of cultural
noise, including above-ground power lines and
metal fences, and lateral geologic variations
which might be misinterpreted as contaminant
plumes.
Electrical Resistivity - Used to map subsurface
structures through differences in their resistance
to electrical current. Material resistivities are
measured as functions of porosity, permeability,
water solution, and concentrations of dissolved
solids in pore fluids. Bulk resistivity is measured
in the subsurface by measuring electrical currents
injected through electrodes placed in the soil.
Electrical resistivity surveys are limited by
electrical noise, such as occur in industrial areas.
Resistivity surveys should ideally be conducted
in areas removed from pipelines and grounded
metallic structures such as metal fences and
railroad tracks. This requirement precludes use
of electrical resistivity surveys on many sites.
Resistivity can often be used off site to map area
stratigraphy. Resistivity surveys are labor
intensive, requiring ground setup and removal of
electrodes for each station measurement. Use
extreme care during rain or wet ground
conditions.
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Seismic Investigations - Conducted by two
methods: refractive and reflective. In the
refractive method, the travel time of acoustic
waves is measured as they move through and are
refracted along an interface of the subsurface.
The reflective method measures travel time of
acoustic waves as they are reflected off an
interface. Seismic refraction is typically used
when bedrock is within 500 feet of the ground
surface.
Seismic refraction is useful for mapping discrete
stratigraphic layers and therefore can help in
selecting monitoring well locations and depths.
A seismic refraction survey can provide
subsurface stratigraphic and structural data in
areas between existing wells or boreholes.
Seismic reflection is used less often in ground-
water investigations, but is more commonly used
for deeper and larger-scale stratigraphic mapping
(e.g., petroleum exploration).
Magnetic Investigations - Rely on local variations
in the earth's magnetic field to detect ferrous or
magnetic objects. By mapping variations in the
concentrations of the local magnetic fields,
detection of buried objects such as drums or tanks
may be accomplished. Magnetic surveys are
limited by cultural noise such as power lines,
utilities, and metal structures.
Gravimetric Surveys - Measure small localized
differences in the earth's gravity field caused by
subsurface density variations, which may be
produced by changes in rock type (porosity and
grain type), saturation, fault zones, and varying
thickness of unconsolidated sediments overlying
bedrock. This method is useful in identifying
buried valleys, particularly in glaciated areas.
Gravimetric surveys use a portable gravity meter
which can survey a large area relatively quickly.
The accuracy of the readings is dependent upon
the accuracy of the elevation determination of
each station. (Most altimeters are accurate only
to plus or minus 2 ft (0.6 m), so gravity stations
should be surveyed.) A gravimetric survey can
provide a quick preliminary screening of an area.
Other geophysical methods or test drilling can
then be used to help identify stratigraphy and
aquifer characteristics.
Table 1 illustrates the applicability of various surface
geophysical techniques to ground-water
investigations. Table 2 lists some advantages and
disadvantages of surface geophysical techniques to
ground-water investigations.
3.3.2 Borehole Geophysics
The following borehole geophysical techniques may
be useful in ground-water investigations. Borehole
geophysics may be used alone or to supplement
surface geophysical techniques. Site terrain is an
important factor when conducting borehole
geophysical surveys. Much of the equipment is
mounted or housed inside a truck but can be carried to
well locations if necessary. Some borehole logs can
be run in a cased as well as open hole.
Often several of the following tests are run at the
same time for comparative purposes. Borehole
geophysical logs can be interpreted to determine the
lithology, geometry, resistivity, formation factor, bulk
density, porosity, permeability, moisture content, and
specific yield of water-bearing formations as well as
the chemical and physical characteristics of ground
water. The operating principles of the various
borehole geophysical techniques are similar. A sonde
(a cylindrical tool containing one or more sensors) is
lowered to the bottom of the borehole, activated, and
slowly withdrawn. Signals or measurements at
various depths are recorded at the surface.
Instruments vary from hand-held portable gear to
truck-mounted, power-driven equipment. For more
detailed information on each of these techniques, see
Driscoll, 1986.
Resistance Logs - Electric logs measuring the
apparent resistivity of the rock and fluid
surrounding a well. They are good indicators of
subsurface stratigraphy and water quality.
Electric current is measured as it flows from
electrodes in the probe to other electrodes in the
probe or on the ground surface.
Resistance logs have a small radius of
investigation and are very sensitive to
conductivity of borehole fluid and changes in
borehole diameter. Increases in formation
resistivity produce corresponding increases in
resistance measurements on the log. Deflections
on the log are interpreted as changes in lithology.
Because of its excellent response to lithology
changes, the resistance log is very useful for
geological correlation. Formation fluids are
perhaps the most important variable in
interpreting resistance logs. For example, dry
sands and clays have high resistivities, but their
resistivities decrease with water saturation.
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Dissolved minerals also affect resistivity. (Fresh
water is a poor conductor whereas salt water is a
good conductor; water in saturated clays contains
dissolved minerals from the clay, which results in
high conductivities.)
A limitation of resistance logs is that they can be
run only in uncased boreholes that are filled with
drilling fluid and water. Resistance logging is
therefore most appropriately conducted before
monitoring well completion.
Spontaneous Potential CSP) Logs - Used in
conjunction with resistivity logs to show the
naturally occurring electric potentials of the
chemical and physical changes at contacts
between differing types of geologic materials.
The electric current is measured between an
electrode placed in an uncased borehole and one
placed at the surface.
SP response is due to small voltage differences
caused by chemical and physical contacts
between the borehole fluid and the surrounding
formation. Voltage differences appear at
lithology changes or bed boundaries and their
response is used to quantitatively determine bed
thickness or formation fluid resistivity.
Qualitative interpretation of the data can be used
to identify permeable beds.
Buried cables, pipelines, magnetic storms, and the
flow of ground water can all cause anomalous
readings. Caution must be exercised when using
SP data in a quantitative fashion. Mathematical
formulas are structured for oil well logging and
incorporate assumptions which may not apply to
fresh water wells. As with resistance logs, SP
logs can be run only in uncased, liquid-filled
boreholes.
Gamma Logs - Measure the naturally occurring
gamma radiation emitted from the decay of
radioisotopes normally found in the substrate.
Elements that emit natural gamma radiation are
potassium-40 and daughter products of the
uranium and thorium decay series. Changes in
radiation levels are commonly associated with
differences in substrate composition.
Gamma logs can be run in open or cased
boreholes filled with water or air. The sensing
device can be part of the same sonde that
conducts SP and resistance logs. Gamma rays or
photons are measured and plotted as counts per
minute. This method is useful in identifying clay
layers or other naturally radioactive geologic
units.
Gamma logging is used to identify the lithology
of detrital sediments, where the finer-grained
units have higher gamma intensity. (Fine-grained
materials also tend to have lower permeability
and effective porosity, important for evaluating
aquifer zones.) A limitation with gamma and
other nuclear logs is that they are affected by
changes in borehole diameter and borehole media
(e.g., air, water, or mud). Gamma logs record the
sum of the radiation emitted from the formation
and do not distinguish between radioactive
elements. For use in stratigraphic correlation
however, specific element identification is not
critical. Interpretation of gamma logs is difficult
where sandstone and other strata contain volcanic
rock fragments with radioactive minerals (e.g.,
rhyolite). Interpretation is also difficult in
sandstone containing a large proportion of
feldspar (which contains radioactive potassium-
40).
Gamma-Gamma Logs - Similar to gamma logs
except that a radioactive gamma source is
attached to the gamma sonde and the gamma
particles reflected back from the geologic
formation are measured. Gamma-gamma logs
measure the differing bulk densities of geologic
materials. They can be used to identify lithology
and also to calculate porosity when fluid and
grain density are known.
Neutron Logs - Also utilize a radiation source in
the sonde. The neutron source is a europium-
activated, lithium iodide crystal enriched in
lithium-6. The neutron logging tool bombards
the formation with neutrons and measures the
returning radiation. Neutrons, when ejected from
a nucleus, have great penetrating power and may
travel through several feet of subsurface
formation. All free neutrons are eventually
captured by the nuclei of some element. Neutron
logs respond primarily to hydrogen density. The
high energy neutrons from the source are slowed
by collision with hydrogen ions in the formation.
This response to hydrogen ion content is then
cross-calibrated to porosities for water-saturated
rocks. Neutron logs respond to the hydrogen
content in the borehole and surrounding
formation and indicate the porosity of the various
geologic units in the survey. Neutron logs can be
run in cased or open holes which are dry or filled
with fluid.
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Neutron logs are typically used to determine
moisture content above the water table and total
porosity below the water table. Neutron logs are
effective for identifying perched water tables.
Neutron log information can also be used to
determine lithology and conduct stratigraphic
correlation of aquifers and associated formations
as well as to help determine the effective porosity
and specific yield of unconfined aquifers.
Acoustic CSonic') Logs - Measure the travel time
and attenuation of an acoustic signal created by
an electromechanical source in the borehole. A
transmitter in the borehole converts the electrical
energy to acoustic (sound) energy which travels
through the formation as an acoustic pulse to one
or more receivers. The acoustic energy is then
converted back to electrical energy, which is
measured at the surface. The acoustic wave
velocity is affected by the type of material
through which it passes (rock or sediment is more
conductive than is pore fluid), hence it is useful in
determining porosity.
Acoustic logs can help determine fracture patterns
within semiconsolidated and consolidated
bedrock such as sandstone, conglomerate, and
igneous rocks. Knowledge of fracture patterns in
an aquifer is helpful in estimating ground-water
flow, and thereby estimating the rate of plume
movement. Acoustic logs can be used to locate
the static water level and to detect perched water
tables.
Temperature Logs - Used to measure the thermal
gradient of the borehole fluid. The sonde
measures changes in temperature of the fluid
surrounding it, and the log records resistivity as a
function of temperature. Borehole fluid
temperature is influenced by fluid movement in
the borehole and adjacent strata. In general, the
temperature gradient is greater in low
permeability rocks than in high permeability
rocks, likely due to ground-water flow.
Temperature logs provide information regarding
ground-water movement and water table
elevation. Temperature logs are useful for
detecting seasonal recharge and subsurface
infiltration of irrigation and industrial wastewater
runoff, and quantitative interpretation of
resistivity logs.
Temperature logs are designed to be operated
from the top to the bottom of the borehole, in
order to channel water past the sensor. Repeat
temperature logs should be delayed until the
borehole fluid has had time to reach thermal
equilibrium.
Table 3 illustrates the applicability of various borehole
geophysical techniques to ground-water
investigations. Table 4 lists some advantages and
disadvantages of borehole geophysical techniques to
ground-water investigations.
3.3.3 Geophysical Techniques for
Ground-Water Investigations
The following situations illustrate uses for
geophysical techniques in ground-water assessment.
To define the location, extent, and the movement
of a contaminant plume, several geophysical
techniques may be utilized, including EM,
electrical resistivity, and possibly GPR.
Resistivity and spontaneous potential (SP) logs
could also be utilized as borehole geophysical
methods.
To locate faults and fracture systems, seismic
refraction and reflection and EM are the preferred
methods, but GPR, electrical resistivity and
acoustic logs could also be used.
The mapping of grain size distribution in
unconsolidated sediments is not possible with
any geophysical technique. It is possible,
however, to identify different soil types of
different grain sizes (e.g., sand, silt, and clay).
Seismic reflection and refraction, GPR, and
gravimetric surveys may be used to identify
differing formations. Several borehole
geophysical techniques could also be utilized in
this type of analysis, including gamma, gamma-
gamma, neutron porosity, resistivity, and SP logs.
Definition of lithologic boundaries may be
accomplished with seismic reflection and
refraction and with GPR techniques. When using
borehole geophysics, resistivity, SP, and acoustic
logs are useful.
For mapping water tables, GPR and electrical
resistivity are preferred but seismic refraction and
reflection and gravimetric surveys may also be
used. If using borehole geophysics, direct
measurement or temperature logs would be the
method of choice. Resistivity and SP logs could
also be used.
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To define the bedrock topography, seismic
refraction and reflection, GPR and gravimetric
surveys may be used.
For delineating stratigraphic layers or subsurface
features, such as buried stream channels and
lenses, seismic refraction and reflection, electrical
resistivity, gravimetric surveys, and possibly GPR
could be used.
collected directly from the residential taps into sample
containers. For Phase 2, soils were collected from the
near surface (0-4 inches) and at depth. Stainless steel
trowels were used to retrieve shallow soil samples.
Subsurface samples were collected by advancing
boreholes using a hand-operated power auger to just
above the sampling zone and then using a stainless
steel split spoon to retrieve the soil. The split spoon
was advanced with a manual hammer attachment.
3.4 EXAMPLE SITE
3.4.1 Selection of Field Analytical
Screening Techniques
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 (FID and PID), and radiation
and cyanide monitors were utilized to tentatively
identify containerized liquid wastestreams in order to
select initial judgmental soil sampling locations.
During Phase 2 sampling, a portable XRF unit was
used to determine the extent of soil contamination and
to identify additional "hot spots." A FID and PID
continued to be utilized throughout all field activities
for health and safety monitoring during Phases 1
through 3.
The portable XRF for soil screening was also used
during monitoring well installation. Continuous split
spoon samples were collected during advancement of
the boreholes. Each spoon was sampled and screened
in the field using the XRF unit. Selected samples (one
per borehole location) were submitted to the
laboratory for confirmation analysis. One off-site
sample was selected by the field geologist based on
field observations and professional judgment.
Ground-water samples were screened in the field for
pH, specific conductivity, and temperature using a
three-in-one monitoring instrument. The instrument
probe was placed into a clean glass jar containing an
aliquot of the ground-water sample. The instrument
was decontaminated prior to and after each sample
screening.
3.4.2 Selection of Sampling
Equipment
Dedicated plastic scoops were used for Phase 1 soil
sampling. Phase 1 ground-water samples were
Monitoring wells were installed using a dual-tube, air
percussion drill rig. Borehole soil samples were
retrieved using 2-foot stainless steel split spoon
samplers. Soil from the split spoons was transferred
to sample containers using disposable plastic scoops.
Monitoring well installation is described further in
Section 4.6.1.
Ground water was sampled in Phase 2 from the
monitoring wells installed on site. First, monitoring
wells were purged using a 1.5 gallon per minute (gpm)
submersible rotary pump with flexible PVC outflow
hose and safety cable. The pump and hose were
decontaminated between well locations by pumping
deionized water through the system. A similar pump
and hose system was used to perform the hydraulic
(pumping) test. The pumps are operated by a gas-
powered generator placed near the well location.
The ground-water samples were obtained using
dedicated bottom-fill Teflonฎ bailers. The bailer was
attached to nylon rope, which was selected because
less material would be adsorbed onto the nylon and
brought out of the well. Residential ground-water
samples were collected directly into the sample
containers from the kitchen sink tap. Water level and
depth measurements were obtained from monitoring
wells using decontaminated electronic measuring
equipment.
3.4.3 Selection of Geophysical
Methods
The GPR instrument delineated buried trench and
lagoon boundaries. The EM meter detected
subsurface conductivity changes, thereby identifying
buried metal containers and contaminants. The EM-
3 ID, a shallower-surveying instrument than the EM-
34, was selected because of the instrument's
maneuverability and ease of use, and because the
expected contaminant depth was less than 10 feet.
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Table 1: Applicability of Surface Geophysical Techniques to Ground-Water Investigations
Contaminant
Plume Delineation
Faults/Fracture
Detection
Lithologic
Boundary
Delineation
Bedrock
Topography
Delineation
Stratigraphic
Mapping
Water Table
Mapping
Soil Type of
Unconsolidated
Sediments
Metallic Detection
Non-Metallic
Detection
Seepage Detection
Buried Structure
Detection
Seismic
Reflection
P
P
P
P
A
P
Seismic
Refraction
P
P
P
A
P
Electromagnetic
Conductivity
P
P
P
A
Magnetic
Investigations
p
A
Ground
Penetrating
Radar
A
A
A
A
A
P
P
P
P
A
Electrical
Resistivity
P
A
P
P
A
P
A
A
A
P
A
P
P - Preferred Method A - Applicable Method (in most cases)
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Table 2: Advantages and Disadvantages of Surface Geophysical Techniques to Ground-Water Investigations
Advantages
Seismic Reflection
1 Ability to discern discrete layers
1 Less offset space is required than for
refraction
Velocities 10-20% of true velocities
Data collection and interpretation are
more labor intensive and complex than
for refraction
Depth data not as precise as refraction
Signal enhancement needed to identify
reflected waves
Seismic Refraction
1 Relatively precise depth can be
determined
1 Provide subsurface data between
boreholes
1 Ability to map water table and top of
bedrock
Data collection can be labor intensive
Large geophone line lengths needed
Electromagnetic
Conductivity
1 Lightweight, portable equipment
1 Continuous or quick scan survey
1 Rapid data collection
Interference from cultural noise and
surface metal objects
Limited use where geology varies
laterally
Magnetic
Investigations
1 Can survey large area quickly and cost
effectively
1 Little site preparation needed
Interference from cultural noise, and
large metal objects
Unable to differentiate between steel
anomalies
Ground Penetrating
Radar
Can survey large area quickly
Continuous real-time data display
Quick data processing
Interference from cultural noise,
uneven terrain, and vegetation
Clay content and shallow water table
inhibit radar penetration
Gravimetric Surveys
1 Can survey large area quickly
1 Little site preparation
Accurate elevations require surveying
Should be used only as preliminary
screening tool
Electrical
Resistivity
Quantitative modeling can estimate
depth, thickness, and resistivity of
subsurface layers
Interference from cultural noise,
surface metal objects, and industry
A minimum of two to three crew
members is required
Surveys are labor intensive
28
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Table 3: Applicability of Borehole Geophysical Techniques to Ground-Water Investigations
Contaminant
Plume Delineation
Faults/Fracture
Detection
Lithologic Boundary
Delineation
Bedrock
Topography
Delineation
Stratigraphic
Mapping
Water Table
Mapping
Soil Type of
Unconsolidated
Sediments
Resistance
Logs
P
P
P
P
A
P
Spontaneous
Potential
Logs
P
P
P
P
A
P
Gamma
Logs
P
P
P
P
P
Gamma-
Gamma
Logs
P
P
P
P
Neutron
Logs
A
A
P
P
P
Temperature
Logs
P
P
P
A
P
P
A
P - Preferred Method A - Applicable Method (in most cases)
29
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Table 4: Advantages and Disadvantages of Borehole Geophysical Techniques to Ground-Water Investigations
Advantages
Resistance Logs
Indicates lithologic changes
Indicates amount and type of subsurface
fluid (water quality)
Can only be run in uncased borehole
Difficult to interpret lithology when
using drilling fluid with clay additives
Spontaneous
Potential Logs
Can be run in conjunction with resistance
log
Indicates lithologic changes and
permeable beds
Can only be run in uncased borehole
Interpretation for water well often
more difficult than for oil well
Gamma Logs
1 Easy to operate
1 Can be run in open or cased borehole
1 Qualitative guide for stratigraphic
correlation and permeability
Affected by changes in borehole
diameter and borehole media
Feldspar and volcanic rock fragments
make interpretation difficult
Gamma-Gamma
Logs
Can identify lithology and calculate
porosity when fluid and grain density are
known
Porosity readings of low density
materials can be erroneously high
Neutron Logs
Can determine total porosity in saturated
zone
Can determine moisture content in
unsaturated zones
Can be run in open or cased borehole
Radioactive source requires special
handling by trained personnel
Logging can be somewhat complex
Acoustic Logs
1 Useful for determining relative porosity
1 Indicates fracture patterns in aquifer
1 Can indicate static water level and
perched water tables
Clays may distort readings
Temperature Logs
1 Can indirectly measure permeability
1 Provides information regarding
ground-water movement and water table
elevation
Delay repeat logs until borehole fluid
reaches thermal equilibrium
30
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4.0 GROUND-WATER SAMPLE COLLECTION AND PREPARATION
4.1 INTRODUCTION
During a response action, proper field sample
collection and preparation is as important as proper
sampling equipment selection. Sample collection
refers to the physical removal of an aliquot of ground
water from its source (i.e., aquifer) for the purpose of
either screening or laboratory analysis. Ground-water
sample collection procedures should be selected so
that the resultant sample is representative of the
aquifer or particular water zone being sampled. Field
sample preparation refers to all aspects of sample
handling from collection to the time the sample is
received by the laboratory. This chapter provides
information on sample collection and preparation for
ground water.
The representativeness of a ground-water sample is
greatly influenced by the sampling device used and
the manner in which the sample is collected. Proper
training and use of SOPs will limit variables and
enhance sample representativeness. Selection of
ground-water sampling devices such as bailers and
pumps should be site-specific and dependent on well
diameter, yield, lift capacity, and the analytes being
sampled. Excessive aeration should be minimized to
preserve volatile constituents. Where possible, the
bailer or pump used should be compatible with the
analyte(s) of concern.
4.2 STATIC WATER LEVEL
Prior to sampling, the static water level elevation in
each well should be measured. All measurements
should be completed prior to the sampling event so
that static water levels will not be affected. The water
level measurements are necessary to establish well
purging volumes. These measurements can also be
used to construct water table or potentiometric surface
maps and hence determine local ground-water flow
gradient. Measure the depth to standing water and the
total depth of the well to calculate volume of stagnant
water in the well for purging. See ERT SOP #2151
for detail on collecting static water level
measurements.
4.3 WELL PURGING
There is little or no vertical mixing of water in a
nonpumping well, therefore stratification occurs. The
well water in the screened section mixes with the
ground water due to normal flow patterns, but the well
water above the screened section will remain isolated
and become stagnant. The stagnant water may contain
foreign material inadvertently or deliberately
introduced from the surface, resulting in
unrepresentative data. Adequate well purging prior to
sample withdrawal will safeguard against collecting
nonrepresentative stagnant water samples.
Well purging techniques are specific to the following
well types.
Residential. Commercial, and Public Supply
Wells - Sample residential, commercial, and
public supply wells as near to the wellhead as
possible and at a point before treatment, such as
filtering and water softening units, whenever
possible. Open the tap to a moderate flow and
purge for approximately 15 minutes. If this is not
possible, a 5-minute purge is considered a
minimum. As an alternative to a minimum
volume, purging can be conducted until the field
parameters pH, temperature, and specific
conductivity have stabilized (see Section 4.3.1).
Monitoring Wells - To obtain a representative
sample from a monitoring well, it is necessary to
evacuate the standing water in the well casing
prior to sampling. The minimum recommended
amount that should be purged from a monitoring
well is one casing volume, but three to five
casing volumes of standing water should be
evacuated where possible in order to obtain a
ground-water sample representative of the
aquifer. In a high yield aquifer where there is no
standing water above the screened section of the
well casing, purging three volumes is not as
critical as in lower yield aquifers. (The faster
recharge rate limits the amount of time that the
water has to interact with the atmosphere and
casing materials.) If the well is purged dry, it
should be considered sufficiently purged for
sampling (refer to Section 4.3.2 for additional
information).
31
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The amount of purging a well receives prior to sample
collection depends on the intent of the sampling as
well as the hydrogeologic conditions. When the
sampling objective is to assess overall water resource
quality, long pumping periods may be required to
obtain a sample that is representative of a large
volume of the aquifer. The pumped volume is
determined prior to sampling, or the well is pumped
until the stabilization of parameters such as
temperature, specific conductivity, and pH has
occurred.
Monitoring to define a contaminant plume requires a
representative sample of a small volume of the
aquifer. These circumstances require that the well be
pumped enough to remove the stagnant water but not
enough to induce flow from other areas. Generally,
three well volumes are considered effective.
Otherwise, the appropriate volume to be removed
prior to sampling can be calculated, based on aquifer
parameters and well dimensions.
Well purging devices include bailers, submersible
pumps (rotary-type), non-gas contact bladder pumps,
suction pumps, and hand pumps. See ERT SOP
#2007 for specific guidelines on purging wells prior to
sampling and for more detail on each purging device.
4.3.1 Stabilization Purging
Technique
The stabilization technique is an alternative to volume
purging. This method requires that several field
parameters be continuously monitored during purging.
When these parameters stabilize, begin sampling. The
parameters used for this method are pH, temperature,
and specific conductivity. Stabilization of these
parameters indicates that the standing water in the
monitoring well has been removed and that a
representative sample of the aquifer water may now
be collected. This method of purging is useful in
situations where it is not feasible to evacuate three
casing volumes from the well prior to sampling (e.g.,
large casing diameter, extremely deep, and active
supply wells). See ERT SOP #2007 for specific
volume and stabilization purging techniques.
4.3.2 Wells that Purge Dry
A well that is purged dry should be evacuated and
allowed to recover prior to sample withdrawal. If the
recovery rate is fairly rapid and time allows,
evacuation of more than one volume of water is
desirable. If the recovery rate is slow, the first
recharge can be considered suitable for sample
collection.
4.4 GROUND-WATER SAMPLE
COLLECTION
In order to maintain sample representativeness,
dedicated samplers should be used for each well
whenever possible. When not possible, the sampler
should be decontaminated after each sample collection
and sufficient QA/QC blank samples should be
collected to assess potential cross-contamination.
After well purging is complete, collect and
containerize samples in the order of most volatile to
least volatile, such as:
Volatile organic analytes (VOAs)
Purgeable organic carbon (POC)
Purgeable organic halogens (POX)
Total organic halogens (TOX)
Total organic carbon (TOC)
Extractable organic compounds
Total metals
Dissolved metals
Phenols
Cyanide
Sulfate and chloride
Turbidity
Nitrate and ammonia
Radionucliides
See ERT SOP #2007 for specific detail on filling
sample containers, with special considerations for
VOA sampling.
If the contaminants in the water column are stratified
(e.g., DNAPLs, LNAPLs), be certain to use an
appropriate sampling device. Modify, where possible,
standard sampling procedures to collect the sample
from the suspected depth for the contaminant layer. It
may be necessary to lower the bailer used for sample
collection to a particular depth in the well, or to use a
point-source bailer or other discrete-depth sampling
device.
After a monitoring well is initially constructed, it
should be developed and purged to remove invaded
water. The well should sit idle for at least two weeks
to allow the water level to fully stabilize and the
suspected stratified layers to settle out. Measurement
of the thickness of a floating (LNAPL) layer may be
accomplished in several ways. An indicator gel, chalk
or paste may be applied to an incremented steel tape.
32
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The indicator changes color in the presence of water
or the immiscible layer, depending on the specific use
of the indicator compound. For example, water-level
indicator gel is used to determine the depth to the
water surface. A weighted float is then used to
determine the depth to the top of the LNAPL layer.
The difference between these two readings is the
thickness of the floating layer.
An electronic monitoring device called an interface
probe is also available for the LNAPL layer
measurement. This device, like an electric water-level
sounder, is lowered into the well along an electronic
wire/line. When the probe contacts the surface (the
LNAPL layer) a sound is generated. As the sampler
continues to lower the probe, a different electronic
sound is emitted when the water surface, or water/oil
interface, is reached. The line of the device is
incremented, like a water-level sounder, so the layer
thickness can be determined. Standard electric water-
level sounding devices, however, will not work
properly for these measurements. The interface probe
is a specialized instrument which is commonly
available and used at fuel oil/ground-water
contamination sites.
A sample of a floating layer may be obtained using a
bottom-fill bailer. Care should be taken to lower the
bailer just through the floating layer, but not
significantly down into the underlying ground water.
(A clear bailer is preferable for this activity.)
For sampling sinking layers, a discrete-depth-capable
sampling device, such as a packer pump or syringe
sampler, is best suited. When these specialized
devices are not available, depending on the sampling
parameters, standard devices may be used. For
example, samples at the bottom of the screen or at
some intermediate location may also be obtained with
a standard bailer and a second well casing. In order to
avoid mixing the waters, a separate casing is
temporarily lowered inside the permanent well casing.
The temporary casing is equipped with an easily
removed cap on the bottom so that no fluid enters the
casing until it has reached the desired sampling depth.
The cap is then freed from the bottom of the inner
casing, allowing water to enter to be sampled by a
bailer. At significant depths below the nonaqueous
layer, several bailers full of water may need to be
withdrawn and discarded before the sample is
obtained from a fresh formation sample.
When a temporary casing and all other specialized
equipment is unavailable, a standard bailer alone may
be used. Collect a water sample from the well and
transfer it to the sample container. Allow the sample
to settle in the sample container into the separate
stratified layers. The analytical laboratory may then
decant, as appropriate, to obtain a sample of the
desired layer. More commonly, the parameters of
concern in the stratified layers are simply included in
the laboratory analysis of the sample as a whole
without the need to separate into unique layers. In
this last example, care must be taken to allow the
bailer to reach the desired depth in the water column
to insure collecting any dense layers at the bottom of
the well. (See Section 2.4 for additional discussion on
sampling concerns and the physiochemical nature of
contaminants.)
4.5 GROUND-WATER SAMPLE
PREPARATION
This section addresses appropriate ground-water
sample preparation and handling techniques. Proper
sample preparation and handling maintain sample
integrity. Improper handling can render samples
nonrepresentative and unsuitable for analysis.
The analyses for which a sample is being collected
determines the type of bottles, preservatives, holding
times, and filtering requirements. Samples should be
collected directly into appropriate containers that have
been cleaned to EPA or other required standards.
Check to see that a Teflonฎ liner is present in the
sample bottle cap, if required.
Samples should be labeled, logged, and handled
correctly, including appropriate chain-of-custody
documentation. Place samples in coolers to be
maintained at 4EC. Ship samples to arrive at the
designated analytical laboratory well before their
holding times are expired. It is preferable that
samples be shipped or delivered daily to the analytical
laboratory in order to maximize the time available for
the laboratory to do the analysis.
Certain conditions may require special handling
techniques. For example, treatment of a sample for
VOAs with sodium thiosulfate preservative is required
if there is residual chlorine in the water (e.g., a public
water supply) that could cause free radical
chlorination and change the identity of the original
contaminants. (The preservative should not be used if
there is no chlorine in the water.) All such special
requirements must be determined prior to conducting
fieldwork.
Sample preparation for ground water may include, but
is not limited to:
33
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Filtering
Homogenizing/Aliquotting
Splitting
Final Preparation
4.5.1 Filtering
Samples may require filtering, such as for total metals
analysis. Samples collected for organic analyses
should not be filtered. Two types of filters may be
used, which must be decontaminated prior to use. A
barrel filter works with a bicycle pump, which builds
up positive pressure in the chamber containing the
sample and then forces it through the filter into a
container placed underneath. A vacuum filter has two
chambers; the upper chamber contains the sample, and
a filter divides the chambers. Using a hand pump or
a Gilianฎ-type pressure pump, a vacuum is created in
the upper chamber and the sample is filtered into the
lower chamber. Preservation of the sample, if
necessary, should be done after filtering.
See ERT SOP #2007, Section 2.7.5, for more detail on
filtering ground-water samples.
4.5.2 Homogenizing/Aliquotting
Homogenizing, or aliquotting, is the mixing or
blending of a grab sample to distribute contaminants
uniformly. Ideally, proper homogenizing ensures that
all portions of the sample are equal or identical in
composition and are representative of the total sample
collected. Incomplete homogenizing can introduce
sampling error. Homogenizing disturbs the ground-
water sample, so it is not appropriate for VOC
sampling.
Homogenizing is done during only one sampling event
per well location, and only after the VOC sample
portions have first been filled. It may be utilized for
wells with extremely low yield and potentially
insufficient sample volume to fill all sample
containers provided by the laboratory. In some low
yielding wells, the percentage of suspended material
in a bailer-full of sample will increase as sampling
proceeds. Homogenizing ensures that at least a
minimum volume is aliquotted per analytical
parameter, and the percentage of suspended material
is equitably divided among all containers (excluding
VOCs).
4.5.3 Splitting
Split samples are created when the samples have to be
separated into two or more equivalent parts and
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. Split samples also
provide measures of sample variability and analytical
error. Fill two sample collection jars simultaneously,
alternating the sample stream or bailer full of sample
between them.
4.5.4 Final Preparation
Final preparation includes preserving, packaging, and
shipping samples.
Sample preservation is used to retard chemical
breakdown of the sample. Preservation of ground-
water samples includes controlling pH with chemical
preservatives, refrigerating samples, and protecting
samples from light.
Select sample containers on the basis of compatibility
with the material being sampled, resistance to
breakage, and capacity. Appropriate sample volumes
and containers will vary according to the parameters
being analyzed. Actual sample volumes, appropriate
containers, and holding times are specified in the
U.S. EPA Compendium of ERT Ground-Water
Sampling Procedures, OSWER Directive 9360.4-06.
Package all samples in compliance with current
International Air Transport Association (IATA) or
U.S. Department of Transportation (DOT)
requirements, as applicable. Packaging should be
performed by someone trained in current DOT
shipping procedures.
See ERT SOP #2007, Section 2.3 for more detail on
ground-water sample preparation.
4.6 EXAMPLE SITE
4.6.1 Sample Collection
During Phase 1 and Phase 2, surface soil samples
were collected from shallow locations. The samples
were collected as grab samples. The sample locations
were cleared of surface debris, then samples were
retrieved with disposable plastic scoops and placed
directly into sample containers. During Phase 2,
subsurface soil samples were collected at the soil
boring/well installation locations, using stainless steel
split spoon samplers. The split spoon samples were
collected using a hand-held power auger to advance
the hole. A 2-foot stainless steel split spoon sampler
with hammer attachment was then pushed into the
34
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hole. The soil sample was retrieved from the split
spoon sampler using a disposable plastic scoop to
transfer the soil into a stainless steel bowl. Several
scoopfuls were collected along the length of the split
spoon sampler and composited in the bowl. The
composite sample was then transferred directly into
the sample container using the disposable plastic
scoop.
Phase 1 and Phase 2 residential well ground-water
samples were collected directly from the kitchen taps
of homes using private wells near to the site. The
configuration of the residential system was noted in
the logbook prior to sampling. If present, water
softeners were taken off line. Any screen or filter was
first removed from the tap, which was allowed to run
for a minimum of five minutes prior to sampling. The
samples were collected directly into the sample
containers.
Fifteen monitoring wells were installed at the site at
locations described in Section 2.5.6. The wells were
drilled with a dual-tube, air percussion rig. Each
boring was completed to a 9.5-inch diameter. After
completion of the boring, 4-inch Schedule 40 PVC
casing and 0.010 slot screen were installed in lengths
appropriate to each well. Shallow wells were drilled
to approximately 40 feet below grade surface (BGS)
and bedrock contact wells were drilled to
approximately 55 to 60 feet BGS. Continuous split
spoon sampling was performed at each well location
from 4 feet BGS to well completion depth. The
boreholes were grouted from the bottom to the top of
the lower confining layer, then 10 feet of screen were
set above the grouted portion. PVC casing was set
above the screen to above the ground surface. Casing
was extended to accommodate a 2-foot stick-up above
grade, and then capped. A 6-inch diameter metal
outer casing with locking cover was installed over the
well casing stick-up and secured 2 feet BGS in
concrete. A concrete spill pad was then constructed
around each well outer casing to prevent re-infiltration
at the well point. Upon completion, all monitoring
wells were developed by purging using a
decontaminated rotary pump and flexible PVC
disposable hose.
A Team geologist supervising the monitoring well
installation logged each borehole soil lithology from
the retrieved split spoon samplers collected during
drilling of the boreholes. The geologist scanned each
sampler with a PID immediately upon opening (into
halves) for health and safety monitoring. All logging
was accomplished utilizing the Unified Soils
Classification System standard method. Figure 3
provides an example of a soil boring and monitoring
well completion log.
Soil samples were then collected in wide-mouth clear
glass jars by transferring a portion of each lithologic
unit in the split spoon with a disposable plastic scoop
and compositing the sample in the jar. At the
completion of each borehole, each sample was
screened in the field using the XRF unit. Select
samples (one per borehole location) were forwarded to
the laboratory for confirmation analysis. Split spoon
samplers were decontaminated after each use.
Upon completion and development, the 15 on-site
monitoring wells were sampled for ground-water
analysis. The well caps were brushed and cleaned off
prior to opening. Immediately upon removing the
well cap, a PID was operated over the opening to
determine VOC levels, if any, in the breathing zone.
The VOC monitoring was performed to establish if a
higher level of respiratory protection was required.
Depth to water level measurements were then taken of
each well to the nearest 0.01 ft. The total depth of the
well was obtained with a depth sounder. The volume
of water in the well was then calculated using the
formula below. For a four-inch well, well volume
would equal 0.632 gallon/ft.:
Well volume = B x (radius of well)2 x height
of water column x 7.48 gallon/ft3
(conversion factor for ft3 to gallons)
Each monitoring well was purged prior to obtaining a
representative sample. Wells with sufficient yield
were purged three well volumes. Low-yielding wells
were purged once to dryness. (Most wells on site are
low-yielding.) Purging was completed using a 1.5
gpm decontaminated submersible (rotary-type) pump
with flexible PVC outflow hose and safety cable. The
pump was slowly lowered to a point approximately 3
feet above the bottom of the well. With the known
flow rate, length of pumping required was calculated.
Purge water was pumped into 55-gallon steel drums.
(The drums were staged and later disposed of properly
based on the results of analysis of their contents.)
Low-yielding overburden wells were purged with a
decontaminated stainless steel bottom-fill bailer and
polypropylene rope until dry. All wells were allowed
to recover overnightbefore sample collection, or until
sufficient water was present to complete a sample set.
Each monitoring well was sampled after purging and
recovery. Ground-water samples were collected using
dedicated disposable Teflonฎ bailers. Each bailer
was attached to a clean polypropylene rope and intro-
-------
Figure 3: Soil Boring/Monitoring Well Completion Log
JZ
*-ซ
Q.
(D
Q
-
-
-
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-
15
20
-
-
an
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35
Ww
40
T^W
-
45
-
-
en
OU
55
Symbol
Stratigraphy
SP/
SM
SM
SP
SC
SP
SM
SM/
SC
SC
Sample Description
Tan. vf. Sd. w. 10% Sit.
As above w. 30% Sit.
Tan. vf. Sd. coarsening
to med. Sd. at 25'
Tan. vf. Sd. w. 10% Gry.
lumpy Cly.
Iron oxide staining
Tan. F-med. Sd.
As above w. 2% Sit. & Cly.
Tan. vf. Sd. & Sit. w. lumps of
Gry. Cly. w. Iron oxide staining
Brn. vf. Sd. & Sit. w. lumps of
Gry. Cly. w. Iron oxide staining
Cly. 30%
Completion Data
Protective steel casing
with locking cap
Portland
Cement
+ 5%
Bentonite
Grout
41 Diam.
PVP
r V \j
Casing
# 2/16
f\ i
Sand
Bottom
^\ -^
Cap ^
/
/
/
/
/
-^ ,
/
/
/
/
/
/
1
\
\
\
\
\
^
\
\
v
v
\\
\
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a
"B-
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g 51
Borehole
Bentonite
Slurry
Lonestar
# 2/12
Sand
0.010
slot
screen
TD56ft
36
-------
duced into the well. The bailer was lowered slowly to
the approximate mid-point of the well. Once the
sample was collected, care was taken not to agitate the
water while pouring directly into the appropriate
sample containers. An additional ground-water
aliquot was placed into a large wide-mouth glass jar
in order to obtain conductivity, temperature, and pH
measurements. These measurements were recorded in
the field logbook.
After well sampling, a hydraulic (pumping) test was
performed to determine aquifer characteristics for
mathematical modeling of potential contaminant
plume migration. The hydraulic test was conducted
using one well as a pumping well with three
observation wells. The pumping well was purged at
a rate of 22 gpm for 30 hours. All wells (observation
and pumping) were monitored during pumping and for
4 hours after pumping ceased. Drawdown data from
the wells were used to calculate the characteristics of
the aquifer.
To generate accurate gradient and well location maps,
the 15 newly installed monitoring wells were surveyed
for vertical location using feet above mean sea level
(MSL) units. Vertical elevations were taken at a mark
on the top of the inner casing of each monitoring well,
to establish a permanent location for all future water
level measurements and elevations. A permanent
benchmark was located near to the site by the survey
team to determine all the well elevations. Elevations
were then measured against the benchmark and
mapped in MSL units.
All non-disposable equipment, including drill rig and
equipment, stainless steel bailers, pumps, water level
indicators, and depth sounders, were decontaminated
between each location and prior to the first sampling
event each day.
4.6.2 Sample Preparation
All sample containers were supplied by the contracted
analytical laboratory. Chemical preservation was also
provided by the laboratory through pre-preserved
bottleware. Sample containers for ground-water
samples consisted of:
1-liter polyethylene bottles for total chromium,
pre-preserved with reagent-grade nitric acid
lowering the pH to less than 2 after addition of
the sample
1-liter polyethylene bottles for hexavalent
chromium
1-liter polyethylene bottles for cyanide, pre-
preserved with sodium hydroxide
Sample containers for soils consisted of 8-ounce glass
jars with Teflonฎ caps for all parameters.
All samples were preserved to 4E C by placing them
in coolers packed with "blue ice" immediately after
collection and during shipment. (The laboratory was
responsible for cooling and refrigeration of samples
upon arrival.)
The samples were packaged in compliance with IATA
requirements for environmental samples. 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. Holding times for total
chromium and cyanide are less than six months, but
hexavalent chromium has a holding time of less than
24 hours. This was coordinated in advance with the
analytical laboratory and required daily ground
delivery of samples to the laboratory.
Because many of the ground-water samples from the
on-site wells were extremely turbid, the non-volatile
portions of samples were filtered in the laboratory
prior to analysis. Filtering was accomplished using a
barrel filtering device with a minimum pore size of
0.45 microns. Samples for chromium analysis were
split and filtered so that dissolved and particulate
chromium could be differentiated. Dissolved
chromium is of concern because of its ability to be
transported in ground water.
37
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5.0 QUALITY ASSURANCE/QUALITY CONTROL (QA/QC)
5.1 INTRODUCTION
The goal of representative sampling is to obtain
analytical results that accurately depict site conditions
during a defined time interval. The goal of quality
assurance/quality control (QA/QC) is to implement
correct methodologies which limit the introduction of
error into the sampling and analytical procedures, and
ultimately into the analytical data.
QA/QC samples evaluate three types of information:
1) the magnitude of site variation; 2) whether samples
were cross-contaminated during sampling and sample
handling procedures; and 3) whether a discrepancy in
sample results is a result of laboratory handling and
analysis procedures.
5.2 DATA CATEGORIES
EPA has established data quality objectives (DQOs)
which ensure that the precision, accuracy,
representativeness, and quality of environmental data
are appropriate for their intended application.
Superfund DQO guidance defines two broad
categories of analytical data: screening and
definitive.
Screening data are generated by rapid, less precise
methods of analysis with less rigorous sample
preparation than definitive data. Sample preparation
steps may be restricted to simple procedures such as
dilution with a solvent, rather than elaborate
extraction/digestion and cleanup. At least 10 percent
of the screening data are confirmed using the
analytical methods and QA/QC procedures and
criteria associated with definitive data. Screening
data without associated confirmation data are not
considered to be data of known quality. To be
acceptable, screening data must include the following:
chain-of-custody, initial and continuing calibration,
analyte identification, and analyte quantification.
Streamlined QC requirements are the defining
characteristic of screening data.
Definitive data are generated using rigorous analytical
methods (e.g., approved EPA reference methods).
These data are analyte-specific, with confirmation of
analyte identity and concentration. Methods produce
tangible raw data (e.g., chromatograms, spectra,
digital values) in the form of paper printouts or
computer-generated electronic files. Data may be
generated at the site or at an off-site location, as long
as the QA/QC requirements are satisfied. For the data
to be definitive, either analytical or total measurement
error must be determined. QC measures for definitive
data contain all of the elements associated with
screening data, but also may include trip, method, and
rinsate blanks; matrix spikes; performance evaluation
samples; and replicate analyses for error
determination.
For further information on these QA/QC objectives,
please refer to U.S. EPA Data Quality Objectives
Process for Superfund, pp. 42-44.
5.3 SOURCES OF ERROR
There are many potential sources of data error in
ground-water sampling. The following is a list of
some of the more common potential sources of error:
Sampling design
Sampling methodology
Analytical procedures
Seasonal variations
See U.S. EPA Data Quality Objectives Process for
Superfund, pp. 29-36, for more information on error.
5.3.1 Sampling Design
The sampling design should utilize approved SOPs
and previously approved sampling designs to ensure
uniformity and comparability between samples. The
actual sample collection process should be determined
prior to sampling. Sampling equipment and
techniques must be standardized for like sampling
situations.
The sampling design should fulfill sampling and data
quality objectives. The quality assurance objectives
selected should be built into the sampling design,
including all necessary QA/QC samples.
Sampling design errors for ground water include: well
selection, well location, well construction and
development, background sample location, and
equipment (material and type).
38
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5.3.2 Sampling Methodology
Sampling methodology and sample handling
procedures have possible sources of error, including:
cross-contamination from inappropriate use of sample
collection equipment; unclean sample containers;
improper sampling equipment decontamination; and
improper shipment procedures. Procedures for
collecting, handling, and shipping samples should be
standardized to allow easier identification of any
source(s) of error, and to minimize the potential for
error. Use approved SOPs to ensure that all given
sampling techniques are performed in the same
manner, regardless of the sampling team, date, or
location of sampling activity. Use field blanks,
replicate samples, trip blanks, and rinsate blanks
(discussed in Section 5.4) to identify errors due to
improper sampling methodology and sample handling
procedures. An example of a sampling methodology
error for ground water is inappropriate purging.
5.3.3 Analytical Procedures
Analytical procedures may introduce errors from
laboratory cross-contamination, inefficient extraction,
and inappropriate methodology. Matrix spike,
laboratory duplicate, performance evaluation, and
laboratory control samples help to distinguish
analytical error from sampling error.
5.3.4 Seasonal Variations
Seasonal variations are not controllable but must be
taken into consideration as a source of error during
ground-water assessments. Changes in flow direction
or volume can redistribute contaminants throughout a
site, making assessment difficult. Plan sampling
events in order to minimize the effects of seasonal
variations, if possible.
5.4 QA/QC SAMPLES
QA/QC samples are collected at the site or prepared
for or by the laboratory. Analysis of the QA/QC
samples provides information on the variability and
usability of sampling data, indicates possible field
sampling or laboratory error, and provides a basis for
future validation and usability of the analytical data.
The most common field QA/QC samples are field
replicate, background, and rinsate, field, and trip blank
samples. The most common laboratory QA/QC
samples are performance evaluation (PE), matrix
spike (MS), matrix spike duplicate (MSD), and
laboratory duplicate samples. 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.
Ground water is typically characterized by low or
trace concentrations of contaminants, making
precision and accuracy more important than for
samples with higher concentrations (e.g., waste).
Frequent field blanks are thus appropriate in ground-
water sampling.
The following sections briefly describe the most
common types of QA/QC samples appropriate for
ground-water sampling.
5.4.1 Field Replicate Samples
Field replicates, also referred to as field duplicates and
split samples, are field samples obtained from one
sampling point, homogenized (where appropriate),
divided into separate containers, and treated as
separate samples throughout the remaining sample
handling and analytical processes. Use replicate
samples to assess error associated with sample
methodology and analytical procedures. Field
replicates can also be used when determining total
error for critical samples with contamination
concentrations near the action level. In such a case, a
minimum of eight replicate samples is recommended
for valid statistical analysis. Field replicates may be
sent to two or more laboratories or to the same
laboratory as unique samples. For total error
determination, samples should be analyzed by the
same laboratory. Generally, one field replicate per 20
samples per day is recommended.
5.4.2 Background Samples
Defining background conditions may be difficult
because of natural variability and the physical
characteristics of the site, but it is important in order
to quantify true changes in contaminant concentrations
due to a source or site. Defining background
conditions is critical for avoiding false positives and
for enforcement purposes in naming responsible
parties. Background sampling is often required in
ground-water sampling to verify plume direction,
ambient conditions, and attribution of sources. A
properly collected background sample serves as the
baseline for the measure of contamination throughout
the site. Ground-water background sample locations
should be chosen carefully, usually upgradient from
the suspected source of contamination where there is
little or no chance of migration of contaminants of
39
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concern. Collect at least one background sample for
comparison, although additional samples are often
warranted by site-specific factors such as natural
variability of local geology and multiple sources.
Background samples may be collected to evaluate
potential error associated with sampling design,
sampling methodology, and analytical procedures.
Refer to U.S. EPA "Establishing Background Levels"
fact sheet, OSWER Directive 9285.7-19FS, for
detailed discussion on the proper selection and
considerations of a background sample location.
5.4.3 Rinsate Blank Samples
A rinsate blank, also referred to as an equipment
blank, is used to assess cross-contamination from
improper equipment decontamination procedures.
Rinsate blanks are samples obtained by running
analyte-free water over decontaminated sampling
equipment. Any residual contamination should appear
in the rinsate sample data. Analyze the rinsate blank
for the same analytical parameters as the field samples
collected that day. Handle and ship the rinsate like a
routine field sample. Where dedicated sampling
equipment is not utilized, collect one rinsate blank per
type of sampling device per day.
5.4.4 Field Blank Samples
Field blanks are samples prepared in the field using
certified clean water (HPLC-grade water (carbon-free)
for organic analyses and deionized or distilled water
for inorganic analyses) which are then submitted to
the laboratory for analysis. A field blank is used to
evaluate contamination or error associated with
sampling methodology, preservation,
handling/shipping, and laboratory procedures.
Handle, ship, and analyze a field blank like a routine
field sample. Submit one field blank per day.
5.4.5 Trip Blank Samples
Trip blanks are samples prepared prior to going into
the field. They consist of certified clean water
(HPLC-grade) and are not opened until they reach the
laboratory. Utilize trip blanks for volatile organic
analyses only. Handle, transport, and analyze trip
blanks in the same manner as the other volatile
organic samples collected that day. Trip blanks are
used to evaluate error associated with shipping and
handling and analytical procedures. A trip blank
should be included with each shipment.
5.4.6 Performance Evaluation/
Laboratory Control Samples
A performance evaluation (PE) sample evaluates the
overall error contributed by the analytical laboratory
and detects any bias in the analytical method being
used. PE samples contain known quantities of target
analytes manufactured under strict quality control.
They are usually prepared by a third party under an
EPA certification program. The samples are usually
submitted "blind" to analytical laboratories (the
sampling team knows the contents of the samples, but
the laboratory does not). Laboratory analytical error
may be evaluated by the percent recoveries and
correct identification of the components in the PE
sample. Note: Even though they are not available for
all analytes, analyses of PE samples are
recommended in order to obtain definitive data.
A blind PE sample may be included in a set of split
samples provided to the potentially responsible party
(PRP). The PE sample will indicate PRP laboratory
accuracy, which may be critical during enforcement
litigation.
A laboratory control sample (LCS) also contains
known quantities of target analytes in certified clean
water. In this case, the laboratory knows the contents
of the sample (the LCS is usually prepared by the
laboratory). PE and LCS samples are not affected by
matrix interference, and thus can provide a clear
measure of laboratory error.
5.4.7 Matrix Spike/Matrix Spike
Duplicate Samples
Matrix spike and matrix spike duplicate samples
(MS/MSDs) are field samples that are spiked in the
laboratory with a known concentration of a target
analyte(s) in order to determine percent recoveries in
sample extraction. The percent recovery from
MS/MSDs indicates the degree to which matrix
interferences will affect the identification of a
substance. MS/MSDs can also be used to monitor
laboratory performance. When four or more pairs of
MS/MSDs are analyzed, the data obtained may be
used to evaluate error due to laboratory bias and
precision. Analyze one MS/MSD pair to assess bias
for every 20 samples, and use the average percent
recovery for the pair. To assess precision, analyze at
least eight matrix spike replicates from the same
sample, and determine the standard deviation and the
coefficient of variation. MS/MSDs are recommended
for screening data and are required as one of several
methods for determining analytical error for definitive
40
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data. Since the MS/MSDs are spiked field samples,
provide sufficient volume for three separate analyses
(triple volume). When selecting a well for spiked
samples, choose a well capable of providing steady
volume.
5.4.8 Laboratory Duplicate Samples
A laboratory duplicate is a sample that undergoes
preparation and analysis twice. The laboratory takes
two aliquots of one sample and analyses them as
separate samples. Comparison of data from the two
analyses provides a measure of analytical
reproducibility within a sample set. Discrepancies in
duplicate analyses may indicate poor homogenization
in the field or other sample preparation error, either in
the field or in the laboratory.
5.5 EVALUATION OF
ANALYTICAL ERROR
The acceptable level of error in sampling data is
determined by the intended use of the data and the
sampling objectives, including the degree of threat to
public health, welfare, or the environment; response
action levels; litigation concerns; and budgetary
constraints.
Error may be determined with replicate samples. To
evaluate the total error of samples with contaminant
concentrations near the response action level, prepare
and analyze a minimum of eight replicates of the same
sample. Analytical data from replicate samples also
serve as a quick check on errors associated with
sample heterogeneity, sampling methodology, and
analytical procedures. Different analytical results
from two or more replicate samples could indicate
improper sample preparation, or improper sample
handling, shipment, or analysis.
Although a quantified confidence level may be
desirable, it may not always be possible. A 95%
confidence level (5 percent acceptable error) should be
adequate for most Superfund activities. Note that the
use of confidence levels is based on the assumption
that a sample is homogeneous.
5.6 CORRELATION BETWEEN
FIELD SCREENING RESULTS
AND DEFINITIVE
LABORATORY RESULTS
One cost-effective approach for delineating the extent
of site contamination is to correlate inexpensive field
screening data and other field measurements with
definitive laboratory results. The relationship between
the two methods can then be described by a regression
analysis. The resulting equation can be used to
predict laboratory results based on field screening
measurements. In this manner, cost-effective field
screening results may be used in conjunction with off-
site laboratory analysis.
Statistical regression involves developing an equation
that relates two or more variables at an acceptable
level of correlation. In this case, the two variables are
field screening results and definitive laboratory
results. The regression equation can be used to
predict a laboratory value based on the results of the
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 linear regression equation can be developed
on many calculators or computer databases. Consult
a statistician to check the accuracy of more complex
models.
Evaluation of the accuracy of a model relies in part on
statistical correlation, which 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, 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 the dependent variable. The
value of an acceptable coefficient of variation 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 assessment purposes, the
acceptable R2 value may be more stringent (e.g., 0.8).
Analytical calibration regressions have an R2 value of
0.98 or greater.
41
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Field screening data can be used to predict laboratory
results if there is an acceptable correlation between
them. The predicted values can be located on a base
map and contoured. These maps can be examined to
evaluate the estimated extent of contamination and the
adequacy of the sampling program.
5.7 EXAMPLE SITE
5.7.1 Data Categories
Screening data which generate non-definitive,
unconfirmed results were used to select analytical
parameters and samples to be sent for laboratory
confirmation analysis. Samples were sent to the
analytical laboratory under protocols which provided
definitive data. The rigorous laboratory analyses
provided definitive identification and quantitation of
contaminants.
5.7.2 Sources of Error
All direct reading instruments were maintained and
calibrated in accordance with their instruction
manuals. Many of these instruments are class-specific
(e.g., volatile organic vapors) with relative response
rates that are dependent on the calibration gas
selected. Instrument response to ambient vapor
concentrations may differ by an order of magnitude
from response to calibration standards. If compounds
of interest are known, site-specific standards may be
prepared.
The number and location of initial field samples were
based on observation and professional judgment (as
outlined in Section 2.5.5). Field standard operating
procedures, documented in the site sampling plan,
established consistent screening and sampling
procedures among all sampling personnel, reducing
the chances for variability and error during sampling.
Site briefings were conducted prior to all sampling
and screening events to review the use of proper
screening and sampling techniques.
Other steps taken to limit error included proper
sample preparation, adherence to sample holding
times, and the use of proper IATA shipment
procedures. All off-site laboratory sample analyses
were performed using approved EPA standard
methods and protocols.
5.7.3 Field QA/QC Samples
Field QA/QC samples were collected during soil and
ground-water sampling at the ABC Plating site. Two
field replicate samples were collected for subsurface
soils; two wells (one overburden and one bedrock)
were selected for replicate collection and analysis of
ground water. Rinsate blanks were collected from
split spoon samplers, a bailer, and the submersible
rotary pump after decontamination by pouring
deionized water through the respective piece of
equipment and then into a sample container. The field
replicates and blanks were preserved and prepared as
"regular" field samples. A trip blank for VOC
analysis and a performance evaluation (PE) sample for
metals were sent to the laboratory. (The PE sample is
not affected by matrix interferences.) The trip blank
was provided by the laboratory (pre-filled and
preserved) and sent with the sample containers prior
to sample collection. One trip blank per day was
submitted to the laboratory. Additional volume was
collected and provided to the laboratory for matrix
spike/matrix spike duplicate analyses for one per 20
sample locations for each medium.
5.7.4 Laboratory QA/QC
Instructions on matrices, target compounds, and
QA/QC criteria of particular interest were provided to
the laboratory to help ensure that analytical results
met the required quality assurance objectives. The
laboratory analyzed for metals using the methods of
inductively coupled plasma (ICP) spectrometry and
atomic absorption (AA). Two SW-846 methods were
employed for hexavalent chromium analysis: Method
7196, a colorimetric method, and Method 2185, a
chelation method. These two methods were utilized
in an attempt to better quantify hexavalent results.
The presence of cyanide was confirmed in the
laboratory using total and amenable cyanide analyses
(colorimetric manual Method 9010).
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6.0 DA TA PRESENTA TION AND ANAL YSIS
6.1 INTRODUCTION
Data presentation and analysis techniques are
performed with analytical, field screening, or
geophysical results. The techniques discussed below
can be used to compare analytical values, to evaluate
numerical distribution of data, and to reveal the
location of "hot spots," contaminant plumes, and the
extent of contamination at a site. The appropriate
methods to present and analyze sample data depend on
the sampling objectives, the number of samples
collected, the sampling approaches used, and other
considerations.
6.2 DATA POSTING
Data posting involves placement of sample values on
a site base map or cross-section. Data posting is
useful for displaying the distribution of sample values,
visually depicting the location of contamination with
associated assessment data. Data posting requires
each sample to have a specific location (e.g., x, y, and
sometimes z coordinates). Ideally, the sample
coordinates are surveyed values facilitating placement
on a scaled map. Data posting is useful for depicting
concentration values of ground-water and plume
migration.
6.3 CROSS-SECTION/FENCE
DIAGRAMS
Cross-section diagrams (two-dimensional) and fence
diagrams (three-dimensional) depict subsurface
features such as stratigraphic boundaries, aquifers,
plumes, impermeable layers, etc. Two-dimensional
cross-sections may be used to illustrate vertical
profiles of ground-water concentrations on a site.
Both cross-sections and fence diagrams can provide
useful visual interpretations of contaminant
concentrations and migration.
6.4 CONTOUR MAPPING
Contour maps are useful for depicting ground-water
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 lines (or isopleths) at
a specified contour interval, interpolating values
between sample points. Contour lines can be drawn
manually or can be generated by computer using
contouring software. Although the software makes
the contouring process easier, computer programs
have a limitation: as they interpolate between data
points, they attempt to " smooth" the values by fitting
contour intervals to the full range of data values. This
can result in a contour map that does not accurately
represent general site contaminant trends. If there is
a big difference in concentration between a "hot spot"
and the surrounding area, the computer contouring
program, using a contour interval that attempts to
smooth the "hot spots," may eliminate most of the
subtle site features and general trends.
6.5 WELL LOCATION MAP
A well location map should be prepared using
surveyed data for all features at the site. This map
serves as a basemap onto which other data may be
plotted (e.g., data posting, contaminant plume
contours, water elevation contours). The map is
drawn to scale and incorporates all wells located,
installed, and sampled, including residential and
monitoring wells. The surveyed coordinates for each
monitoring well location could also be posted onto the
map (in feet above mean sea level (msl)) to illustrate
topography and surface gradient.
6.6 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, rely 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 close
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, appears as a
straight line. A histogram or probability plot can be
used to see trends and anomalies in the data from a
ground-water site prior to conducting more rigorous
forms of statistical analysis.
43
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6.7 RECOMMENDED DATA
INTERPRETATION METHODS
The data interpretation methods chosen depend on
project-specific considerations, such as the number of
sampling locations and their associated range in
values. Data which are dissimilar in composition
should not be compared using statistical interpretation
methods. Data posting, screening, and sampling data
sheets, and cross-section/fence diagrams may be
appropriate. A site feature showing extremely low
data values (e.g., non-detects), with significantly
higher values (e.g., 5,000 ppm) from neighboring "hot
spots" and little or no concentration gradient in
between, does not lend itself to contouring software.
6.8 EXAMPLE SITE
A water table contour map was generated with the
water level data for the shallow overburden
monitoring wells. This indicated a westward flow
direction, which generally coincides with the surface
topography. The deep bedrock wells lie nearly on a
straight line, and therefore a confident determination
of flow direction was not possible. A westward
component of flow direction is evident in the data,
however. The bedrock contact wells provided
inconsistent water level data, most likely due to the
presence of discontinuous perched water zones at the
well locations.
All ground-water samples were analyzed for total
chromium and cyanide. Cyanide was not found in any
of the samples above the 50 (ig/1 detection limit.
Using a detection limit of 50 (ig/1 for chromium, three
filtered samples were found to be contaminated at two
locations (3OB, and 6OB/6AW). Five of the
unfiltered ground-water samples (Wells 2SA, SOB,
4SA, 6OB, and 6AW) exceeded the detection limit.
These data were posted on a site/well location map to
illustrate well proximities, as well as a map indicating
the contours of contamination.
The rate of chromium contaminant migration in
ground water and the potential long-term impact to
nearby residential wells were estimated using a
mathematical model which included worst case
assumptions and evaluated attenuation of
contaminants through soil and ground water. The
OSC concluded that the potential for residential well
contamination was minimal. Removal of soil, the
source of contamination, was recommended. This
decision met the Phase 2 objective of establishing
early action options and consideration of long-term
remediation requirements for ground water.
All containers of wastes were removed from the site.
Soil treatment/disposal was completed using the
existing grid design. Cells were sampled and
designated as clean or excavated. Excavated material
was stockpiled while treatment/disposal options were
evaluated. Excavated cells were filled with stone and
clean soil. Composite sampling in each cell verified
cleanup, using an action level of 100 mg/kg chromium
in the soil composite. (The clean-up level was
established based on the earlier mathematical model
and soil attenuation calculations.) The soil response
served as an early action to meet the Phase 3 objective
originally established for the site.
44
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APPENDIX A -- Example of Flow Diagram For Conceptual Site Model
Figure A-1
Migration Routes of a Gas Contaminant
from Origin to Receptor
Change of
Original state Pathway contaminant
of contaminant from state In
of concern" origin pathway
conch
RpQ > A:r
V-^CIO r Mil
solldl
insatlon
> Liquid
_ **
> Solid
Mcatlon
Final
pathway
to receptor
> SO
^ sw
> so
> AT
> ^V J.
> sw
^ so
^ sw
Receptor
Human
G,D
G,D
I,D
I,D
G,D
G,D
G,D
Ecological Threat
Terrestrial
G,D
G,D
I,D
I,D
I,D
G,D
G,D
Aquatic
N/A
G,D
N/A
N/A
G,D
N/A
G,D
* May be a transformation product
** Includes vapors
Receptor Key
D - Dermal Contact
] - Inhalation
G Ingestlon
N/A - Not Applicable
Pathway Key
Al -Air
SO - Soil
SW = Surface Water
(Including sediments)
GW - Ground Water
45
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Figure A-2
Migration Routes of a Liquid Contaminant
from Origin to Receptor
Original state
of contaminant
of concern*
Liquid
sw
* Liquid
-> Gas**
SO
solidification
leachate,
Infiltration
AI
* May be a transformation product
** Includes vapors
Solid
Liquid
Gas
**
-> so
-> sw
-> GW
-> SO
-> AI
+ sw
Receptor Key
D Dermal Contact
I - Inhalation
G Ingestlon
N/A - Not Applicable
Receptor
Human
G,D
I,D
G,D
G,D
Ecological Threat
Terrestrial
G,D
I,D
G,D
G,D
Aquatic
G,D
N/A
G,A
G,D
G,D
G,D
G,D
G,D
G,D
N/A
N/A
G,D
N/A
G,D
I,D
G,D
G,D
I,D
G,D
N/A
N/A
G,D
Pathway Key
AI - Air
SO - Soil
SW - Surface Water
(Including sediments)
GW - Ground Water
46
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Figure A-3
Migration Routes of a Solid Contaminant
from Origin to Receptor
Original state
of contaminant
of concern*
Solid
AI
partlculates/
dust
Solid
sw
^ Solid
-> Liquid
SO
Gas
**
Solid
Liquid
* May be a transformation product
** Includes vapors
AI
SW
so
sw
sw
Receptor Key
D - Dermal Contact
I - Inhalation
G - Ingestlon
N/A - Not Applicable
Pathway Key
AI . Air
SO - Soil
SW - Surface Water
(Including sediments)
GW - Ground Water
Receptor
Human
I,D
G,D
G,D
Ecological Threat
Terrestrial
I,D
G,D
G,D
Aquatic
N/A
G,D
N/A
G,D
G,D
G,D
G,D
G,D
G,D
so
AI
SW
SO
SO
sw
G3D
I,D
G,D
G,D
G,D
G,D
G,D
G,D
I,D
G,D
G,D
G,D
N/A
G,D
N/A
N/A
G,D
N/A
N/A
N/A
G,D
47
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References
Aller, Bennett, Hackett, et al. 1989. Handbook of Suggested Practices for the Design ad
Installation of Ground-Water Monitoring Wells National Water Well Association, Dublin,
Ohio.
Code of Federal Regulations (CFR), Title 40 -Protection of Environment. Part 136 - Guidelines
Establishing Test Procedures for the Analysis of Pollutants.
Custodio, Gurgui, Ferreira. 1987. Ground-Water Flow and Quality Modelling D. Reidel
Publishing Company, Dordrecht, Holland.
Driscoll, Fletcher G. 1986. Ground Water and Wells(2nd edition).
Fetter, C.W., Jr. 1980. Applied Hydrogeology. Charles E. Merrill Publishing Company,
Columbus, Ohio.
Garrett, Peter. 1988. How to Sample Ground Water and Soils National Water Well
Association, Dublin, Ohio.
Keith, Lawrence, H. 1988. Principles of Environmental Sampling
New Jersey Department of Environmental Protection. February 1988. Field Sampling
Procedures Manual
Palmer, Christopher, M. 1992. Principles of Contaminant Hydrogeology
Proceedings of the Fifth National Symposium and Exposition on Aquifer Restoration and
Ground-Water Monitoring. 1985.
U.S. Department of Health and Human Services. 1985. Occupational Safety and Healh
Guidance Manual for Hazardous Waste Site ActivitiesNIOSH Pub. 85-115.
U.S. Environmental Protection Agency. 1995a. "Establishing Background Levels." Office of
Solid Waste and Emergency Response Directive 9285.7-19FS.
U.S. Environmental Protection Agency. 1995b. SuperfundProgram Representative Sampling
Guidance, Volume 1 Soil. Office of Solid Waste and Emergency Response Directive
9360.4-10.
U.S. Environmental Protection Agency. 1995c. Superfund Program Representative Sampling
Guidance, Volume 4 Waste. Office of Solid Waste and Emergency Response Directive
9360.4-14.
48
-------
U.S. Environmental Protection Agency. September 1993. Data Quality Objectives Process for
Superfund. Office of Solid Waste and Emergency Response Directive 9355.9-01.
U.S. Environmental Protection Agency. 1993. Project Summary- Compilation of Ground-Water
Models. Office of Research and Development. EPA/600/SR-93/118.
U.S. Environmental Protection Agency. November 1992. RCRA Ground-Water Monitoring:
Draft Technical Guidance EPA/530-R-93-001.
U.S. Environmental Protection Agency. September 1992. Guidance for Performing Sit
Inspections Under CERCLA Office of Solid Waste and Emergency Response Directive
9345.1-05
U.S. Environmental Protection Agency. February 1992. Estimating the Potential for Occurrence
of DNAPL at Superfund Sites Office of Solid Waste and Emergency Response Directive
9355.4-07.
U.S. Environmental Protection Agency. January 1992. Statistical Training Course for Ground-
Water Monitoring Data Analysis EPA/530-R-93-003.
U.S. Environmental Protection Agency. 1992. Ground-Water Issue- Fundamentals of Ground-
Water Modeling. Office of Research and Development and Office of Solid Waste and
Emergency Response. EPA/540/S-92/005.
U.S. Environmental Protection Agency. January 1991a. Compendium of ERT Field Analytical
Procedures. Office of Solid Waste and Emergency Response Directive 9360.4-04.
U.S. Environmental Protection Agency. January 1991b. Compendium of ERT Ground-Water
Sampling Procedures Office of Solid Waste and Emergency Response Directive 9360.4-06.
U.S. Environmental Protection Agency. January 1991c. Compendium of ERTSurface Water and
Sediment Sampling Procedures. Office of Solid Waste and Emergency Response Directive
9360.4-03.
U.S. Environmental Protection Agency. 1990. Ground Water, Volume II: Methodology
EP A/625/6-90/016b.
U.S. Environmental Protection Agency. April 1989. Statistical Analysis of Ground-Wate
Monitoring Data at RCRA Facilities, Interim Final Guidance Office of Solid Waste and
Emergency Response.
U.S. Environmental Protection Agency. September 1988. Field Screening Methods Catalog
User's Guide. Office of Solid Waste and Emergency Response. EPA/540/2-88/005.
U.S. Environmental Protection Agency. December 1987. A Compendium of Superfund Fiei.
Operations Methods Office of Solid Waste and Emergency Response Directive 9355.0-14.
49
-------
U.S. Environmental Protection Agency. 1987. Handbook, Ground Water. EPA/625/6-87/016.
U.S. Environmental Protection Agency. September 1986. RCRA Ground-Water Monitoriig
Technical Enforcement Guidance Documen(TEGD). Office of Solid Waste and Emergency
Response Directive 9950.1.
U.S. Geological Survey. 1991. Concepts and Modeling in Ground-Water Hydrology - A Self-
Paced Training Course Open File Report 90-707.
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