P/EPA
United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(5103)
OSWER Directive #9029.00
EPA 500-B-94-003
July 1994
Assessment Framework For
Ground-Water Model Applications
OSWER Information Management
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\
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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OFFICE OF
SOLID WASTE AND EMERGENCY
RESPONSE
MEMORANDUM
SUBJECT:
FROM:
TO:
Assessment Framework for Ground-Water- Model
Applications - Directive No/ 9029.00
Elliott P. Laws
Assistant Administ
tor
OSWER Office Directors
Regional Waste Management Division Directors
This memorandum establishes the guidance, "Assessment
Framework for Ground-Water- Model.Applications", as an OSWER
Directive 9029.00.
The Framework provides guidance for planning and evaluating
ground-water 'flow and advective transport model applications.
The set of .criteria helps guide current or future modeling by
assessing modeling activities, thought processes, and
documentation needs. It is intended for EPA technical support
staff and remedial project managers, as well as program managers
and contractors who support EPA's waste management program.
Purpose of the Guidance ' '
The purpose of this guidance is to promote the appropriate
use of .ground-water models in EPA's waste management programs.
More specifically, the objectives of the "Assessment Framework
for Ground-Water Model Applications" are to: . '
Support the use of ground-water models as tools for aiding
decision-making under conditions of uncertainty;
Guide current or future modeling;
Assess., modeling activities and thought processes; and
Identify 'model application documentation needs.
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
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Background
OSWER management has been addressing the issue of the
increasing use of environmental regulatory models first by
reviewing modeling use and support in the waste management
program. In 1992, OSWER produced the: Ground-Water Modeling-
Compendium to increase the awareness of ground-water models which
are available and supported by EPA. The Compendium contained the
first version of the "Assessment Framework for Ground-Water Model
Applications", which was developed by a group of experts from
within and outside of EPA and reviewed by a cross-Agency ad hoc
group of scientists.
The Science Advisory Board (SAB) then reviewed the Framework
and suggested that it be distributed apart from the Compendium.
The SAB's comments are reflected in the attached version.
The 1994 edition of the Ground-Water Modeling Compendium,
c6ntaining additional model information and cost guidelines, will
soon be available for distribution from the National Center for
Environmental Publications and Information (NCEPI), 500-B-94-003.
In addition, in 1992, -OSWER and the Office of Research and
Development, requested the Deputy Administrator to establish a
temporary Agency Task Force on Environmental Regulatory Modeling
.(ATFERM) to address modeling issues across the Agency. ATFERM
'has produced a report which it presented to the Science Policy
Council in July. The Deputy Administrator has distributed the
"Guidance for External Peer Review of Environmental Regulatory
Modeling" which was developed by ATFERM and is^in their report.
In addition, the Science Policy Council agreed to the
establishment of a permanent, Agencywide group to provide a focus
for modeling issues and information.
*
In summary, OSWER and Regional managers should encourage the
use of the Framework to ensure that sound and defensible models
are being chosen, that these models are being applied in a
reasonable manner, and that management's decision objectives are
incorporated into the modeling objectives for each application.
Attachment - Assessment Framework for Ground-Water Model
Applications - OSWER Directive 9029.00
(EPA500-G-94-004)
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Assessment Framework
OSWER Directive #9029.00
Introduction
Assessment Framework for Ground-Water Model Applications
Introduction
The Assessment Framework addresses the use and review of primarily
ground-water flow and advective transport model applications. The criteria in this
Assessment Framework focus upon the activities and thought processes that should
be part of a model application and the subsequent documentation of that activity or
process. The Assessment Framework is a "living document" which may be
expanded as additional information is collected, analyzed, and organized.
The intended primary users of this framework are U.S. Environmental
Protection Agency (EPA) technical support staff and remedial project managers. The
secondary users of the framework are Office of Solid Waste and Emergency
Response (OSWER) and Regional management, EPA contractors, and other
consultants. However, this Assessment Framework is not a substitute for modeling
education and experience. The framework should not be used to promote modeling
by inexperienced people, nor should it be relied upon to supplant experienced
professional judgment or measurement.
The objectives of the Assessment Framework are to:
O Support the use of ground-water models as tools for aiding decision-making
under conditions of uncertainty;
O Guide current or future modeling;
n Assess modeling activities and thought processes; and
D Identify model application documentation needs.
Modeling is often used for prediction and/or evaluation of alternative
remedial schemes. While prediction is often the endpoint of the modeling process,
the value of modeling is not limited to this goal. The modeling process can
enhance one's understanding of the natural system, help in the refinement of a
conceptual model, facilitate hypothesis testing, help check consistency of data sets,
help identify critical processes, and aid in the planning of site characterization.
Modeling is not a linear process but instead is an iterative evolutionary
approach to the refinement of our understanding of a natural system.
The framework contains a series of assessment criteria, grouped into eight
categories:
O Modeling Application Objectives
O Project Management
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Assessment Framework
OSWER Directive #9029.00
Introduction
O Conceptual Model Development
O Model (code) Selection
O Model Setup and Input Estimation
O Simulation of Scenarios
O Post Simulation Analysis
O Overall Effectiveness.
Figure 1 clarifies how the criteria in the Assessment Framework apply to the
ground-water modeling process. The figure also indicates key points in the
modeling process where prior decisions or assumptions should be reviewed and
adjusted if necessary. These review steps are emphasized because modeling is
naturally an iterative process and is analogous to the scientific method of
formulating a hypothesis and testing it. If the hypothesis, or for example,
conceptual model, is shown at a later stage in the modeling process to be incorrect or
incomplete, another hypothesis needs to be formulated and the modeling process
started again. To optimize or streamline this process, a model should be prepared at
the beginning of a project (for example, during site characterization) so that it can be
refined and used during the entire length of a project (for example, for feasibility
studies, remedial design, remedial action, and eventually for site closure). Because
Figure 1 is generic and may not apply to all sites, professional advice and experience
should be utilized in the application of models.
A user with the appropriate training and experience may apply these criteria
at various stages in the modeling process. For example, when modeling is initially
proposed the user may apply the "Modeling Application Objectives" and "Project
Management" criteria to help determine the applicability of the modeling to the
specific situation. During the early application of the model a user may apply the
"Conceptual Model Development," "Model (code) Selection," and "Model Setup
and Input Estimation" criteria to help guide the modeling process. Upon
completion of the model application the user may apply the "Simulation of
Scenario," "Post Simulation Analysis," and "Overall Effectiveness" criteria to help
assess the results of the modeling and to guide future efforts.
OSWER and Regional managers may encourage the use of the criteria to
ensure that sound and defensible models are being chosen and that these models are
being applied in a reasonable manner. The manager may also encourage the use of
the criteria to ensure that management decision objectives are incorporated into the
modeling objectives.
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Assessment Framework
Introduction
ESTABLISH MODELING OBJECTIVES
- Establish decision objectives
- Determine the necessity of ground-water modeling
- Determine the level of model complexity
ESTABLISH PROJECT MANAGEMENT PLAN
COLLECT, ORGANIZE, AND INTERPRET AVAILABLE
DATA
PREPARE A CONCEPTUAL MODEL
SELECT A SUITABLE MATHEMATICAL CODE
SET UP THE MODEL AND PERFORM INPUT
ESTIMATION
COMPARE WITH FIELD
DATA
Ifc.
CALIBRATE THE MODEL*
^
r
NO
HISTORY MATCHING
NOTES:
* Includes calibration
sensitivity analysis
** Includes predictive
sensitivity analysis
EVALUATE THE OVERALL EFFECTIVENESS
NO
ARE THE MODELING
OBJECTIVES MET?
YES
ARE CALIBRATION
TARGETS MET?
SIMULATE THE SCENARIOS
PERFORM POST-SIMULATION ANALYSIS
( COMPLETE )
FIGURE 1 - Diagram of the groundrwater modeling process.
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Assessment Framework
OSWER Directive #9029.00
Introduction
These criteria will generally apply to most modeling applications, however,
in certain, instances some of the criteria may not be applicable or some of the criteria
may be applicable at different stages in the modeling process. In other instances,
some criteria may have to be modified or expanded.
Documentation of the modeling process is crucial for assuring the
defensibility of the modeling application. Consequently, some of the following
criteria are preceded with an asterisk (*) indicating that the analysis, process, or data
referred to in the question should be documented. Some users may find it useful to
reference additional information when applying the criteria. Therefore, some of the
criteria are followed by endnotes which provide further explanation and reference
additional sources of information. The criteria also contain numerous technical
terms that may require additional explanation. These terms are italicized
throughout the document. A glossary that follows the criteria contains the
definitions for these terms in the context of the criteria.
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OSWER Directive #9029,00
Assessment Criteria
Assessment Criteria
Modeling Application Objectives
1 ^Management's decision objectives should be clearly specified up front,
considering applicable regulatory and .policy issues.
2 The role and need for a modeling study in the pursuit of management's
decision objectives should be established.
3 * Management's decision objectives should be translated into modeling
objectives up front.
4 Modeling objectives should be based upon existing information about the
physical characteristics of the site (e.g., hydrogeologic system) and the source,
location> and nature of the contamination.
5 *A11 assumptions incorporated within the modeling objectives should be
reviewed with respect to reality and their potential impacts on
management's decision objectives.
6 The purpose of the model application (e.g., data organization,
understanding the system, planning. additional field characterization,
prediction, or evaluation of remediation alternatives) should be defined
during the development of the modeling objectives.
7 The purpose of the model application should be reviewed during the course
of the project and, if necessary, modified.
8 Potential solutions to be evaluated (e.g., containment and/or remediation
solutions) should be identified prior to the initiation of the modeling.
9 The level of model complexity and, in turn, the type of model required
(e.g., numerical model, analytical model, or graphical techniques) should be
determined during the definition of the modeling objectives.
See Endnote 1.
10 This level of model complexity should be reviewed as a better
understanding of the site/problem/data is developed.
11 *Management, in consultation with a professional ground-water scientist,
should specify the time period (e.g., 1 year, 10 years, or hundreds of years) for
which model predictions are intended.
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OSWER Directive #9029.00
Assessment Criteria
12 Calibration targets (e.g., multiple criteria such as heads and ground-water
discharge) for the model application should be specified up front.
13 If, during the modeling process, it is determined that the original calibration
targets cannot be met, the modeling objectives should be reviewed.
14 *An analysis should be performed of the incremental costs associated with
expanding these study objectives (e.g., expanding the size of the study area,
the number of remedial technologies modeled, or the calibration targets of
the model) and the consequent incremental improvement in supporting
management's decision objectives.
15 Management's decision objectives should be reaffirmed throughout the
modeling process.
16 The modeling objectives should be reviewed, after the development of the
conceptual model and prior to the initiation of the modeling, to ensure that
they support management's decision objectives.
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Assessment Criteria
Project Management
17 *A financial budget appropriate to the modeling objectives, level of analysis,
available data, and available resources should be established at the inception
of the project.
18 The individuals who are actually managing or performing the modeling
should participate in the development of the financial budget.
19 The project organization should .be designed to facilitate the interative
nature of the modeling process.
20 The individuals who are actually performing the modeling, managing the
modeling effort, or performing the peer review should have the ground-
water modeling experience required for the project. Specifically, for their
role on the project, each should have the appropriate level of:
' Formal training in mathematics, physics, chemistry, soil science,
fluid -mechanics, geology, hydrogeology, and modeling
Work experience in modeling physical systems, preferably with
the type of model being used on the project
Field experience characterizing site hydrogeology
Modeling project management experience.
See Endnote 2.
21 These individuals should be organized as a cohesive modeling team with
well defined roles, responsibilities, and level of participation.
22 The organization of the team should be appropriate for the application.
23 A documentation procedure should be established up front to assure that
an independent reviewer can duplicate the modeling results or perform a
postapplication assessment using the documentation.
24 The documentation should include a discussion of the following:
General setting of the site
Physical systems of interest
Management's decision objectives
Role of modeling study
Potential solutions to be evaluated
Modeling objectives and timeframe for model predictions
Level of model complexity
Calibration targets
Quality assurance and peer review process
Composition of the modeling team ; ,
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Assessment Criteria
Data -sources, quality, and completeness
Conceptual model
Hydro stratigraphy
Ground-water flow system
Hydrologic boundaries
Hydraulic properties
Water sources and sinks
Contaminant identity, source, loading, and areal extent
Contaminant transport and transformation processes
Background chemical quality
Boundary conditions
Selection of the computer code
Description of the code and documentation
Reliability
Usability
Transportability
Performance
Access to source code
Limitation
Related Applications
Ground-water model construction'
Code modifications
Geologic representation
Flow representation
Data averaging procedures
Input estimation procedures
Model grid . .
Hydraulic parameters
Chemical parameters
Boundary conditions
Water budget
Simplifying assumptions
Uncertainty analysis , , '
Calibration and calibration sensitivity analysis
Predictive simulations
Scenarios
Implementation of the scenarios
Discussion of the results of each run
Predictive sensitivity analysis
Postprocessing
Modeling study scope, conceptual model, and model code
assumptions with respect to reality and their impacts on the
modeling results
Results related to management's information needs as formulated
in the decision objectives
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OSWER Directive #9029.00
Assessment Criteria
Executive summary (in terms of the decision objectives)
References
Input and output files.
See Endnote 3.
\
25 An independent quality assurance (QA) process not involving staff
assigned to any aspect of the project should be established at the beginning
of the project,
See Endnote 4.
26 *This QA process should include ongoing peer review of the:
Modeling objectives development
Conceptual model development
Model code selection
Model setup and calibration
Simulation of scenarios
Postsimulation analysis.
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Assessment Criteria
Conceptual Model Development
27 An initial conceptual model of both the local and regional hydrogeological
system should be developed prior to any computer modeling.
28 The conceptual model should be based upon a quantification of field data
as well as other qualitative data that includes information on the nature
and variability of the:
Aquifer system (distribution and configuration of aquifer and
confining formations)
Hydrologic boundaries
Hydraulic and chemical properties of formations
Piezometric head and hydraulic gradient (i.e., magnitude and
direction of flow within each model layer)
Fluid properties
Contaminant sources and properties
Fluid sources and sinks.
See Endnote 5.
29 The quantity, quality, and completeness of the data should be analyzed
with regard to their impact on the overall success of the model application.
30 *I£ there are data gaps, the tradeoff should be analyzed between the cost of
acquiring additional data and the consequent improvement in meeting
management's decision objectives.
31 If there are data gaps (e.g., missing water level or hydraulic conductivity
information), any additional field work and other attempts to fill in these
gaps should be documented.
32 The data sources should be documented.
33 *Any and all potential interactions with other physical systems (e.g., surface
water systems or agricultural systems) should be evaluated prior to the
beginning of the modeling by means of a water budget, a chemical mass
balance, or other analytical techniques.
34 The manner in which existing and future engineering (e.g., wells or slurry
walls) must be represented in a numerical or analytical model should be
explicitly incorporated into the conceptual model.
35 A mass balance of the contaminant should be developed as part of the
conceptual model. .
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Assessment Criteria
36 *The conceptual model should include a dear statement of the location,
type, and state of boundary conditions; justification of their formulation;
and source(s) of information used to develop the boundary conditions.
37 *A11 assumptions incorporated within the conceptual model should be
reviewed with respect to reality and their potential impacts on the modeling
objectives.
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Assessment Criteria
Model (code) Selection
38 "The selected model (code), as distinguished from the model application,
should be described with regard to its flow, contaminant transport and
transformation processes, mathematics, hydrogeologic system
representation, boundary conditions, and input parameters.
39 The reliability of the model (code) should be assessed including a review
of:
Peer reviews of the model's theory (e.g., a formal review process
by an individual or organization acknowledged for their expertise
in ground-water modeling or the publication of the theory in a
peer-reviewed journal)
Peer reviews of the model's code (e.g., a formal review process by
an individual or organization acknowledged for their expertise in
assessing ground-water computer models)
Verification studies (e.g., evaluation of the model results against
laboratory tests, analytical solutions, or other well accepted
models)
Relevant field tests (i.e., the application and evaluation of the'
model to site-specific conditions for which extensive data sets are
available)
The model's (code) acceptability in the user community as
evidenced by the quantity and type of use.
See Endnote 6.
40 The usability of the model (code) should be assessed including the
availability of:
The model binary code
The model source code
Pre- and postprocessors
Existing data resources
Standardized data formats
Complete user instruction manuals
Sample problems
Necessary hardware
Transportability across platforms
User support
Key assumptions.
41 The tradeoff should be analyzed between model (code) performance (e.g.,
accuracy and processing speed) and the human and computer resources
required to perform the modeling.
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Assessment Criteria
42 If the ground-water model results will be used to form expert opinions, all
parties should have access to the foundation of those opinions, including
the source code and an executable image of the version used, if present. In
addition, the ground-water model code should meet the following criteria:
Publication and peer review of the model's conceptual and
mathematical framework, including the model's underlying
assumptions
Full model documentation
Publication and peer review of model code testing.
See Endnote 7.
43 The assumptions in the model (code) should be analyzed with regard to
their impact upon the modeling objectives and site-specific conditions.
44 *Any and all discrepancies between the modeling requirements (i.e., as
indicated by management's decision objectives, conceptual model, and
available data) and the capabilities of the selected model should be identified
and justified. For example, the implications of the selected code supporting
1-, 2- or 3-dimensional modeling; providing steady versus unsteady state
modeling; or requiring simplifications of the conceptual model should be
discussed.
45 *If the modeling objectives are modified due to such discrepancies", those
modifications should be documented.
46 *If the model source code is modified, the following tests should be
performed and the testing methodology and results should be justified:
Reliability testing (See Criterion #38)
Usability evaluation (See Criterion #39)
Performance testing.
See Endnote 8. ^
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Assessment Criteria
Model Setup and Input Estimation
47 *When the dimensional aspects of the geology at the site are simplified in
the model representation (e.g., representing a multilayer aquifer with a
single layer), the impact of this simplification on the modeling results
should be evaluated.
48 *When data averaging procedures are used to represent the site conditions
in the model, the impact of the averaging upon the modeling results should
be evaluated.
See Endnote 9.
49 *When flow representations in the model are assumptions or
simplifications of site conditions (e.g., only horizontal flow is considered,
thus ignoring the impact of vertical flow components), the impact of these
assumptions and simplifications on the modeling results should be
evaluated.
50 For numerical models, generally acceptable rules of grid design and time
step selection should be applied to meet the modeling objectives.
See Endnotes 10 and 19.
51 *When a numerical model is used, the mapping of the location of the
boundary conditions and other geometric details (e.g., wells, slurry walls,
and contaminant sources) on the grid should be evaluated. For example:
The manner in which the boundaries are represented in the grid
should ensure the fineness of the grid, the accuracy of the
geometry, and the accuracy of the boundary conditions.
For finite element grids, internal and external boundaries should
coincide with element boundaries.
See Endnotes 11 and 12.
52 *If arbitrary or artificial boundaries are used, justification for their use
should be given and evidence presented to demonstrate that their use does
not adversely impact the model results within the area of interest.
53 *When an. analytical model Is used, the following boundary conditions
should be evaluated:
Where infinite boundaries are used, the engineering feature being
modeled should not impact actual physical boundaries at the site
during the timeframe of interest.
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Assessment Criteria
Where image wells are used, general rules of imaging should be
followed.
See Endnote 13.
54 The data sources, the data collection procedures, and the data uncertainty
for the model input data should be evaluated and documented in the
project report or file.
55 *A11 model inputs should be defined as to whether they are measurements,
interpretations, or assumptions including:
The constitutive coefficients and parameters (i.e., parameters that
are not generally observable but must be inferred from
observations of other variables; for example, the distribution of
transmissivity and specific storage)
The forcing terms (e.g., sources and sinks of water and dissolved
contaminants)
The Boundary conditions
The initial conditions.
56 The input estimation process whereby data are converted into model
inputs (e.g., spatial and temporal interpolation, extrapolation or Kriging, or
averaging) should be described. This description should include a map or
table containing the spatial location and the associated values of data used to
perform the interpolation.
See Endnote 12.
57 The uncertainty associated with the input estimation process should be
specified, explained, and documented.
58 The model should be calibrated.
59 *If the model is not calibrated, the rationale for not calibrating the model
should be explained.
See Endnote 14.
60 The criteria (i.e., calibration targets) used in the termination of the
calibration process should be justified with regard to the modeling
objectives.
See Endnote 12.
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Assessment Criteria
61 *The calibration should be performed in a generally acceptable manner.
Specifically:
A calibration sensitivity analysis should be performed to
determine the key parameters and boundary conditions to be
investigated during calibration.
The calibration should include an evaluation of spatial residuals
between simulated and measured values. If transient data are
available, an evaluation of spatial residuals at selected time steps
should also be performed.
The calibration should be performed in the context of the physical
features (e.g., residuals should be analyzed with respect to the
pattern of ground-water contours including mounds, depressions,
or indications of surface water discharge or recharge).
See Endnote 15.
62 A water budget for the natural aquifer system based upon measurements
and/or estimates should be developed and used to create a mass balance for
the model.
63 *If a water budget is not developed, the reasoning for not developing a
water budget should be explained.
64 *If actual measurements of components of the water budget are available,
they should'be used to calibrate the model.
65 *A11 changes in initial model parameter values due to calibration should be
justified as to their reasonableness.
66 *Any discrepancies between the calibrated model parameters and the
parameter ranges estimated in the conceptual model should be justified.
67 *If the conceptual model is modified as a result of the model calibration, all
changes in the conceptual model should be justified.
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Assessment Criteria
Simulation of Scenarios
68 *For each modeling scenario, the model inputs and the location of features
in the model grid should be justified. For example:
For finite element models, if a pumping well was not located at a
node, the allocation of well discharges among neighboring nodes
should be justified.
If a slurry wall is a remedial alternative, the representation in the
model of the wall's geometric and hydraulic properties should be
justified.
If cleanup times are calculated, all assumptions about the location,
quantity, and state of the contaminants should be justified.
When a remedial action, such as extraction wells, affects the flow,
such effects should be determined, including the extent of the
capture zone.
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Assessment Criteria
Postsimulation Analysis
69 The success of the model application in simulating the site scenarios
should be assessed.
70 This assessment should include an analysis of:
Whether the modeling simulations were realistic
Whether the simulations accurately reflected the scenarios
Whether the hydrogeologic system was accurately simulated
Which aspects of the conceptual model were successfully
modeled.
71 The sensitivity of the model results to uncertainties in site-specific
parameters (predictive sensitivity analysis} and the level of error in the
model calibration (calibration sensitivity analysis) should be examined and
quantified. For example, the modeling scenarios should be simulated for
the range of possible values of the more sensitive hydrogeologic parameters.
Moreover, the range of error in the model calibration should be considered
when drawing conclusions about the model results.
See Endnote 16.
72 The modeling results should be consistent with available data.
73 *The postprocessing, including the use of interpolation and smoothing,
should be analyzed and documented to ensure that it accurately represents
the modeling results.
74 The postprocessing results should be analyzed to ensure that they support
the modeling objectives.
75 The final presentation should effectively and accurately communicate the
modeling results.
76 When feasible, a postaudit of the model should be carried out or planned
for the future.
See Endnote 17. . .
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Assessment Criteria
Overall Effectiveness
77
*Any difficulties encountered in the model application should be ,,0
documented.
78 The model application should provide the information being sought by
management for decision making.
See Endnote 18.
79 The model application results should be acceptable to-all relevant parties.
80 The model application should support a timely and effective regulatory
decision process.
81 Those aspects of the modeling effort that in hindsight might have been
done differently should be documented. ;'c:
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Endnotes
Endnotes ,
A complete list of references follows the Glossary of Technical Terms.
1. Some of the factors which might influence the level of model complexity and,
in turn, the selection of a particular type (e.g., numerical model,, analytical
model, or graphical techniques) of model include:
The importance of the decisions which will be influenced by the
model results
The sensitivity of these decisions to the range of possible or likely
outcomes of the modeling
The availability of time and resources for the modeling application
The complexity of site characteristics.
See Anderson and Woessner 1992a, and other standard modeling references.
2.' gee USOTA 1982 and van der Heijde and Park 1986.
3. For more information on documentation see ASTM and CADHS.
4. QA should assure that:
The project is staffed with qualified people
There is appropriate documentation of the modeling process
Peer review of the modeling process and project deliverables is
performed.
It should be noted that there is no way to assure that a specific model of a
physical system can ever be completely verified. Thus, the QA process helps to
build confidence in a model application, but following the QA process does not
guarantee accurate predictions. See Konikow and Bredehoeft 1992.
5. For more information on data requirements for conceptual model
development, see ASTM; CADHS, page 4; NCR 1990, pages 221-230; and
Anderson and Woessner 1992a.
6. Sources of information on model codes include USEPA 1992; Bond and Hwang
1989; the International Ground Water Modeling Center (IGWMC) data base; the
Integrated Model Evaluation System (IMES); and numerous ground-water
modeling texts.
7. The Special Master in the case of United States of America, et al.vs. Hooker
Chemicals & Plastics Corporation, et al.(Love Canal) ruled on November 30,
1989 that if models are to be relied upon to form expert opinions in litigation,
all relevant parties will be permitted access to the foundation of those opinions,
including the source code. At the same time, the Special Master granted a
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Endnotes
Protective Order so that the code could not be used by the opposing side for any
purpose other than the trial. (See United States of America, et al. vs. Hooker
Chemicals & Plastics Corporation, et al. (Love Canal) on November 30,1989.)
For further information on the use of ground-water models in litigation, see
Kezsbom and Goldman 1991. For more information on model code
documentation, see van der Heijde and Elnawawy 1992.
8. For more information on the testing of model codes, see van der Heijde and
Elnawawy 1992, Section 3.
9. Contaminant transport is affected by "nonaverage" conditions, with
contaminant plumes following preferential flow paths. See Anderson and
Woessner 1992a, page 326; and Fetter 1988, page 395.
10. For example, the grid should be fine enough in the area of interest to produce
accurate results and nodes should coincide with physical features, remediation
wells, and contamination sources as much as possible. Grid orientation, grid
expansion factors, and aspect ratios should also meet general modeling
standards. For more information, refer to Anderson and Woessner 1992a; and
van der Heijde, El-Kadi, and Williams 1988, pages 45-48.
11. For information on properly locating and representing boundary conditions,
see Franke, Reilly, and Bennett 1984; and Anderson and Woessner 1992a.
12. For information on model setup, input estimation, and criteria for the
termination of the calibration process, see Anderson and Woessner 1992a.
13. For more information on imaging, see Freeze and Cherry 1979, page 330.
14. The model should be calibrated, especially if it is used for predictive purposes.
For interpretive or generic models, calibration is encouraged but not required
(Anderson and Woessner 1992a). Analytical models should also be calibrated,
if possible (e.g., in the case of flow, to transient data; or in the case of transport,
to plume data).
15. For more information on the calibration of ground-water models, see
Anderson and Woessner 1992a; van der Heijde, El-Kadi, and Williams 1988;
ASTM, Subpart 6.5; and CADHS, Section 3.3.2.4.
16. When a physical system is subject to new stresses (as during the application of a
remedial strategy), errors in the conceptual model which had little impact
during the calibration phase may become dominant sources of error for the
prediction phase. Because a specific model of a physical system can never be
completely "verified," it becomes important to identify uncertainties in model
input parameters and conceptual assumptions and to explore the implications
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OSWER Directive #9029.00
Endnotes
of these uncertainties on model predictions. For a more complete discussion,
see Konikow and Bredehoeft 1992, pages 75-83.
17. For more information on post audits, see Anderson and Woessner 1992b.
18. For more information on decision making under conditions of uncertainty, see
Freeze, Massmann, Smith, Sperling, and James 1990, pages 738-766.
19. For information on how time-step size can affect the numerical accuracy of a
model, see Huyakorn and Finder 1983, pages 206 and 392; van der Heijde, El-
Kadi, and Williams 1988, pages 45-48; and Anderson and Woessner 1992a.
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OSWER Directive #9029.00
Glossary of Technical Terms
Glossary of Technical Terms
This glossary provides definitions for some of the technical terms used in Section
2.0, Assessment Framework, of the Compendium of Modeling Information. Words
appearing in italics are defined elsewhere in the glossary. Numbers in parentheses
following each definition correspond to the reference source for the definition. A
complete list of references follows the glossary.
Analytical model - mathematical expression used to study the behavior of
physical processes such as ground-water ,flow and contaminant transport.
This type of model is generally more economical and simpler than a
numerical model, but it requires many simplifying assumptions regarding
the geologic setting and hydrologic conditions. In comparison with a
numerical model, however, an analytical model provides a solution of the
governing partial differential equation at any location and/or time instead
of approximate solutions at discreet locations and moments in time. (15, 22)
Boundary conditions - mathematical expressions specifying the dependent
. variable (head) or the derivative of the dependent variable (flux) along the
boundaries of the problem domain. To solve the ground-water flow
equation specification of boundary conditions, along with the initial
conditions, is required. .Ideally, the boundary of the model should
correspond with a physical boundary of the ground-water flow system, such
as an impermeable body of rock or a large body of surface water. Many
model applications, however, require the use of nonphysical boundaries,
such as ground-water divides and areas of aquifer underflow. The effect of
. nonphysical boundaries on the modeling results must be tested. (4) -
: Calibration - a procedure for finding a set of parameters, boundary
conditions,, and stresses that produces simulated heads and fluxes that
match field-measured values within an acceptable range of error. (4)
Calibration sensitivity analysis - a procedure to establish the effect of
uncertainty .on the calibrated model. The calibrated model is influenced by
uncertainty owing to the inability to define the exact spacial (and temporal)
distribution of parameter values in the problem domain. There is also
uncertainty over the definition of boundary conditions and stresses. (4)
Calibration target - a preestablished range of allowable error between heads
and fluxes and field measured values. (4)
Capture zone - steady state: the region surrounding the well that contributes
flow to the well and which extends up gradient to the ground-water divide
of the drainage basin; .travel time related: the region surrounding a well that
contributes flow to the well within a specified period of time. (22)
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Glossary of Technical Terms
Conceptual model - an interpretation or working description of the
characteristics and dynamics of a physical system. The purpose of building a
conceptual model is to simplify the field problem and organize the field data
so the system can be analyzed more readily. (4,15)
Confining bed - a geologic unit with low values of hydraulic conductivity
which allows some movement of water through it, but at rates of flow
lower than those of adjacent aquifers. A confining bed can transmit
significant quantities of water when viewed over a large area and long time
periods, but its permeability is not sufficient to justify production wells
being placed in it. It may serve as a storage unit, but it does not yield water
readily. (1,19,20,23)
Constitutive coefficients and parameters - type of model input that is not
directly observable but must be inferred from observations of other model
variables; for example, the distribution of transmissivity, specific storage,
porosity, recharge, and evapotraspiration. These are difficult to estimate
because they vary spatially and may vary temporally as well. (21)
Containment - action(s) undertaken, such as' constructing slurry trenches,
installing diversionary booms, earth moving, plugging damaged tank cars,
and using chemical retardants. These actions focus on controlling the
source of a discharge" or release and minimizing the spread of the hazardous
substance or its effects. (28)
Contaminant source, loading, and areal extent - the physical location of the
source contaminating the aquifer, the rate at which the contaminant is
entering the ground-water system, and the surface area of the contaminant
source, respectively. In order to model fate and transport of a contaminant,
the characteristics of the contaminant source must be known or assumed.
(3)
Contaminant transformation - chemical changes, reactions, and biological
transformations that change the chemical properties of the contaminant. (3)
Contaminant transport - flow and dispersion of contaminants dissolved in
ground-water in the subsurface environment. (21)
Evapotranspiration - a combined term for water lost as vapor from a soil or
open water surfaces, such as lakes and streams (evaporation) and water lost
through the intervention of plants, mainly via the stomata (transpiration).
Term is used because, in practice, it is difficult to distinguish water vapor
from these two sources in water balance and atmospheric studies. Also
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OSWER Directive S90E9.00
Glossary of Technical Terms
known as fly-off, total evaporation, and water loss. Losses from
evapotranspiration can occur at the water table. (1,3)
Field characterization - a review of historical, on- and off site, as well as
surface and subsurface data, and the, collection of new,data to meet project
objectives. When possible, aerial photographs/ contaminant source
investigations, soil and aquifer sampling, and the delineation of aquifer
head and contaminant concentrations should be reviewed. Field
characterization is a necessary prerequisite to the development of a
conceptual model. (3)
Finite difference model - a type of numerical model that uses a
mathematical technique called finite difference to obtain an approximate
solution to the partial differential ground-water flow and transport
equations. Aquifer heterogeneity is handled by dividing the aquifer into
homogeneous rectangular blocks. An algebraic equation is written for each
block, leading to a set of equations which can be input into a matrix and
solved numerically. This type of model has difficulty incorporating
irregular and uneven boundaries. (3,11,15,16)
Finite element model - a type of numerical model that uses the finite
element technique to obtain an approximate solution to the partial
differential ground-water flow and transport equations. To handle aquifer
heterogeneity the aquifer can be divided into irregular, homogeneous
elements, usually triangles. This type of model can incorporate irregular
and curved boundaries, sloping soil, and rock layers more easily than a
finite difference model for some problem types. This technique, like finite
difference, leads to a set of simultaneous algebraic equations which is input
into a matrix and solved numerically. (3,11,15,16)
Fluid potential - mechanical energy per unit weight of fluid at any given
point in space and time with regard to an arbitrary state and datum. (11, 24)
* f
Forcing terms - type of model input included in most ground-water models
to account for sources and sinks of water or dissolved contaminants. They
may be measured directly (e.g:, where and when contaminants are
introduced into the subsurface environment), inferred from measurements
of more accessible variables, or they may be postulated (e.g., effect of
^proposed cleanup strategy). (21) , .
Ground-water divides - ridges in the water table or potentiometric surface
from which ground-water moves away in both directions (14); a hydraulic
boundary at the crest or valley bottom of a ground-water flow system across
which there is no flow. (11) : .
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OSWER Directive #9029.00
Glossary of Technical Terms
Ground-water flow system - a rather vague designation pertaining to a
ground-water reservoir that is more or less separate from neighboring
ground-water reservoirs. Ground-water reservoirs can be separated from
one another by geologic or hydrologic boundaries. In some ground-water
modeling studies, artificial or arbitrary boundaries may be applied. Water
moves or "flows" through the ground-water reservoir through openings in
sediment and rock. (10)
Hydraulic conductivity - the ability of a rock, sediment, or soil to permit
water to flow through it. The scientific definition is the volume of water
that will move in unit time under a unit hydraulic gradient through a unit
area measured at right angles to the direction of flow. (22)
Hydraulic properties - those properties of a rock, sediment, or soil that
govern the entrance of and the capacity to yield and transmit water (e.g.,
porosity, effective porosity, specific yield, and hydraulic conductivity). (3,33)
Hydrologic boundaries - boundary conditions which relate to the flow of
water in an aquifer system. (3)
Hydrostratigraphy - a sequence of geologic units delimited on the basis of
hydraulic properties. (10)
Kriging - an interpolation procedure for estimating regional distributions of
ground-water model inputs from scattered observations. (21)
Management's decision objectives - the information needs required to
identify courses of action necessary for reaching environmental and
regulatory goals.
Model grid - a system of connected nodal points superimposed over the
aquifer to spatially discretize the aquifer into cells (finite difference method)
or elements (finite element method) for the purpose of mathematically
modeling the aquifer. (31, 33)
Model representation - a conceptual, mathematical, or physical depiction of
a field or laboratory system. A conceptual model describes the present
condition of the system. To make predictions of future behavior: it is
necessary to develop a dynamic model, such as physical scale models, analog
models, or mathematical models. Laboratory sand tanks simulate ground-
water flow directly. The flow of ground-water can be implied by using an
electrical analog model. Mathematical models, including analytical, finite
difference, and finite element models are more widely used because they are
easier to develop and manipulate. (4,10)
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OSWER Directive #9029.00
Glossary of Technical Terms
Modeling objectives - the information that the modeling application is
expected to provide, so that management can evaluate potential courses of
action. (4) ,
Numerical model - a mathematical model that allows the user to let the
controlling parameters vary in space and time, enabling detailed
replications of the complex geologic and hydrologic conditions existing in
the field. Numerical models require fewer restrictive assumptions and are
potentially more realistic and adaptable than analytical models, but provide
only approximate solutions at discreet locations and moments in time for
the governing differential equations. (3, 16, 21)
Peer review - a process by which a panel or individual is charged to review
and compare the results of modeling efforts and to assess the importance
and nature of any differences which are present. The review may examine,
for example, the scientific validity of the model, the mathematical code,
hydrogeological/chemical/biological conceptualization, adequacy of data,
and the application of the model to a specific site. (3, 21)
Performance testing - determining for the range of expected uses, the
efficiency of the model in terms of the accuracy obtained versus the human
and computer resources required by comparing model results with
predetermined benchmarks. (30)
Porosity - total volume of void space divided by the total volume of porous
material. The term;"effective porosity" is related. It is the total volume of
interconnected void space divided by the total volume of porous material.
Effective porosity is used to compute average linear ground-water velocity.
(3,10)
Postaudit - comparison of model predictions to the actual outcome
measured in the field. Used to determine the success of a model application
as well as the acceptability of the model itself. (21)
Potentiometric surface - a surface that represents the level to which water
will rise in tightly cased wells. The water table is a particular potentiometric
surface for an unconfined aquifer. (10)
Predictive sensitivity analysis - a procedure to quantify the effect of
uncertainty in parameter values on the prediction. Ranges and estimated
future stresses are simulated to examine the impact on the model's
prediction. (4)
Reliability - the probability that a model will satisfactorily perform its
intended function under given circumstances. It is the amount of credence
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OSWER Directive #9029.00
Glossary of Technical Terms
placed in a result. Measures of reliability include peer review of model
theory and code; evaluation of the model results against laboratory tests,
analytic solutions, or other well accepted modes; field testing; and user
acceptability. (23,30)
Remediation - long-term action that stops or substantially reduces and
prevents future migration of a release or threat of hazardous substances that
are a serious but not an immediate threat to public health, welfare, or the
environment. (25)
Residuals - the differences between field measurements at calibration points
and simulated values. (13)
Sources and sinks - gain or loss of water or contaminants from the system.
In a ground-water flow system typical examples are pumping or injection
wells. (3,21)
Specific yield - quantity of water that a unit volume of aquifer, after being
saturated, will yield by gravity (expressed as a ratio or percentage of the
volume of the aquifer). (23)
Surface water bodies - all bodies of water on the surface of the earth. (23)
Transmissivity - the rate at which ground-water of a prevailing density and
viscosity is transmitted through a unit width of an aquifer or confining bed
under a unit hydraulic gradient/ It is a function of the properties of the
liquid, porous media, and the thickness of the porous media. Often
expressed as the product of the hydraulic conductivity and the full saturated
thickness of the aquifer. (1, 22)
Uncertainty analysis - process to identify uncertainties in model input
parameters and conceptual assumptions, and the implications of these on
the uncertainty in model predictions, including potential impacts on the
decisions which will be made based on these predictions. (26)
Verification study - consists of the verification of governing equations
through laboratory or field tests, the verification of model code through
comparison with other models or analytical solutions, and the verification
of the model through tests independent of the model calibration data. (4, 7,
30)
Water budget - the sources and outflow of water to the system, which may
include ground-water recharge from precipitation, overland flow, recharge
from and discharge to surface water bodies, springflow, evaportranspiration,
or pumping. (4)
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OSWER Directive #9029.00
Sources
Sources
Definitions and endnotes are directly drawn from and based upon the following
sources:
1. Allaby, Ailsa and Michael. 1990. The Concise Oxford Dictionary of Earth
Sciences. Oxford: Oxford University Press.
2. ' American Society of Testing and Materials (ASTM). (No date.) "Guide for
Application of a Ground-Water Flow Model to a Site-Specific Problem." Draft
ASTM Standard Section D-18.21.10.
3. Anderson, Mary P. 1992. Based wholly or in part on written comments
provided on the initial draft version of the glossary.
4. Anderson, Mary P., and William W. Woessner. 1992a. Applied Groundwater
Modeling - Simulation of Flow and Advective Transport. New York:
Academic Press, Inc.
5. Anderson, Mary P., and William W. Woessner. 1992b. "The Role of the
Postaudit in Model Validation." Advances In Water Resources.
6. California Department of Health Services (CADHS). (No date.) "Standards for
Mathematical Modeling of Ground Water Flow and Contaminant Transport at
Hazardous Waste Sites." Chapter 4, Volume 2 of Scientific and Technical
Standards for Hazardous Waste Sites-Draft.
7. Belgin, Milovan S. 1987. Testing, Verification, and Validation of Two-
Dimensional Solute Transport Models. Golden, Colorado: International
Ground Water Modeling Center, Colorado School of Mines.
8. Bond, P., and S. Hwang. 1989. "Selection Criteria for Mathematical Models
Used in Exposure Assessments: Ground Water Models." Office of Health and
Environmental Assessment (OHEA1 Manual. EPA/600/2-89/028. U.S.
Environmental Protection Agency.
9. Franke, O.L., T.E. Reilly, and G.D. Bennett. 1984. Definition of Boundary and
Initial Conditions in the Analysis of Saturated Ground-Water Flow Systems -
An Introduction. Open-File Report 84-458. Reston, Virginia: U.S. Geological
Survey.
10. Fetter, C.W. 1988. Applied Hydrogeology - 2nd Edition. Columbus: Merrill
Publishing Company.
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Sources
11. Freeze, R. Allen, and John A. Cherry. 1979. Groundwater. Englewood, New
Jersey: Prentice-Hall.
12. Freeze, Allen, Joel Massman, Leslie Smith, Tony Sperling, and Bruce James.
1990. "Hydrogeological Decision Analysis." Ground Water 28(5).
13. Golden Software, Inc. September 1990. Surfer Version 4 Reference Manual.
Golden, Colorado.
14. Huyakorn, P.S., and G.F. Finder. 1983. Computation Methods in Subsurface
Flow. New York: Academic Press.
15. Istok, Jonathan. 1989. Groundwater Modeling by the Finite Element Method.
Washington, D.C.: American Geophysical Union.
16 Javandel, Iraj, Christine Doughty, and Chin-Fu Tsang. 1984. Ground Water
Transport: Handbook of Mathematical Models. Washington, D.C.: American
Geophysical Union.
17. Kezsbom, A., and A.V. Goldman. 1991. "The boundaries of groundwater
modeling under the law; Standards for excluding speculative expert
testimony." Tort and Insurance Law Tournal. Vol. XXVII, No.l.
18. Konikow, Leonard F., and John D. Bredehoeft. 1992. "Ground-water Models
Cannot Be Validated." Advances in Water Resources 15.
19. Kruseman, G.P., and N.A. de Ridder. 1990. Analysis and Evaluation of
Pumping Test Data. The Netherlands: International Institute for Land
Reclamation and Improvement.
20. Lohman, S.W. 1972. Definitions of Selected Ground-Water Terms - Revisions
and Conceptual Refinements. Geological Survey Water-Supply Paper 1988.
Washington, D.C.: U.S. Government Printing Office.
21. National Research Council (NRC) Committee on Ground-Water Modeling
Assessment. 1990. Ground Water Models. Scientific and Regulatory
Applications. Washington, D.C.: National Academy Press.
22. The Ohio State University, Department of Geological Sciences. 1991. Capzone
Users Manual. Columbus, Ohio.
23. Parker, Sybil P. 1989. McGraw-Hill Dictionary of Scientific and Technical
Terms. Fourth Edition. New York: McGraw-Hill Book Company.
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Sources
24. Subsurface-Water Glossary Working Group, Ground Water Subcommittee,
Interagency Advisory Committee on Water Data. 1989. Subsurface-Water and
Solute Transport Federal Glossary of Selected Terms.
25. U.S. Environmental Protection Agency (USEPA) Office of Public Affairs. 1988.
Glossary of Environmental Terms and Acronym List. Washington, D.C.
26. U.S. Environmental Protection Agency (USEPA) Science Advisory Board. 1993.
Review of the Assessment Framework for Ground-water Model Applications.
Washington, D.C.
27. U.S. Environmental Protection Agency (USEPA). 1992. Ground-Water
Modeling Compendium - Draft. Washington, D.C.
28. U.S. Environmental Protection Agency (USEPA). 1981. Technical Assistance
Team (TAT) Contract Users Manual. Washington, D.C.
29. U.S. Office of Technology Assessment (USOTA). 1982. Use of Models for
Water Resources of the United States. Washington, D.C.: U.S. Government
' Printing Office.
30. van der Heijde, Paul, KM., and O.A. Elnawawy. 1992. Quality Assurance and
Quality Control in the Development and Application of Groundwater Models.
EPA/600/R-93/011. U.S. Environmental Protection Agency Office of Research
and Development.
31. van der Heijde, Paul, K.M., Aly I. El-Kadi, and Stan A. Williams, 1988. :
Groundwater Modeling: An Overview and Status Report. EPA/600/2-89/028.
U.S. Environmental Protection Agency.
32. van der Heijde, Paul K.M., and Richard A. Park. 1986. Ground-water Modeling
Policy Study Group Report. Report for the U.S. EPA Office of Research and
Development. Golden, Colorado: International Ground Water Modeling
Center, Colorado School of Mines.
33. Wang, Herbert P., and Mary P. Anderson. 1982. Introduction to Groundwater
Modeling. Finite Difference and Element Methods. San Francisco, California:
W.H. Freeman and Company.
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OSWER Directive #9029.00
EPA Publications Related
To Ground-Water Modeling
EPA Publications Related to Ground-Water Modeling
CONTAMINANT FATE AND TRANSPORT
USEPA. Grove, D.B., and J. Rubin. 1976. Transport and Reaction of Contaminants
in Ground Water Systems, Proceedings of the National Conference on Disposal
of Residues on Land. Office of Research and Development, pages 174-178.
USEPA. 1989. Determining Soil Response Action Levels Based on Potential
Contaminant Migration to Ground Water: A Compendium of Examples.
EPA/540/2-89/057.
USEPA. 1989. Laboratory Investigations of Residual Liquid Organics from Spills,
Leaks, and Disposal of Hazardous Wastes in Groundwater. EPA/600/6-90/004.
USEPA. Schmelling, Stephen, et al. 1989. Contaminant Transport in Fractured
Media: Models for Decision Makers: Superfund Ground Water Issue. Ada,
Oklahoma.
USEPA. 1990. Subsurface Contamination Reference Guide. EPA/540/2-90/011.
USEPA. 1990. Groundwater, Volume I: Ground Water and Contamination.
EPA/625/6-90/016a.
DNAPLs
USEPA. 1992. OSWER Directive No. 9355.4-07. Estimating the Potential for
Occurrence of DNAPL at Superfund Sites.
USEPA. 1992. OSWER Directive No. 9283.1-06. Considerations in Ground Water
Expediation at Superfund Sites and RCRA Facilities Update.
USEPA. (No date.) Dense Nonaqueous Phase Liquids - A Workshop Summary.
GROUND-WATER ISSUE PAPERS
USEPA. Puls, R.W., and M.J. Barcelona. 1989. Ground Water Sampling for Metals
Analysis. EPA/540/4-89/001.
USEPA. Lewis, T.Y., R.L. Crockett, R. L. Siegrist, and K. Zarrab. 1991. Soil Sampling
and Analysis for Volatile Organic Compounds. EPA/450/4-91/001.
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EPA Publications Related
to Ground-Water Modeling
USEPA. Breckenridge, R.P., J.R. Williams, and J.F. Keck. 1991. Characterizing Soils
for Hazardous Waste Site Assessments. EPA/540/4-91/003.
USEPA. Schmelling, S.G., and R.R. Ross. 1989. Contaminant Transport in
Fractured Media: Models for Decision Makers. EPA/540/4-89/004.
USEPA. Ruling, S.G. 1989. Facilitated Transport. EPA/540/4-89/003.
USEPA. Piwoni, M.D., and J.W. Keeley. 1990. Basic Concepts of Contaminant
Sorption at Hazardous Waste Sites. EPA/540/4-90/053.
USEPA. Huling, S.G., and J.W. Weaver. 1991. Dense Nonaqueous Phase Liquids.
EPA/540/4-91/002.
USEPA. Keely, J.F. 1989. Performance Evaluations of Pump-and Treat
Remediations. EPA/540/4-89/005.
USEPA. Sims, J.L., J.M. Suflita, and H.H. Russell. 1991. Reductive Dehalogenation
of Organic Contaminants in Soils and Ground Water. EPA/540/4-90/054.
USEPA. Russell, H.H., J.E. Matthews, and G.W. Sewell. 1992. TCE Removal from
Contaminated Soil and Ground Water. EPA/540/S-92/002.
USEPA. Palmer, C.D., and W. Fish. 1992. Chemical Enhancements to Pump-and-
Treat Remediation. EPA/540/S-92/001.
USEPA. Sims, J.L., J.M. Suflita, and H.H. Russell. 1992. In-Situ Bioremediation of
Contaminated Ground Water. EPA/540/S-92/003.
USEPA. 1990. Colloidal-Facilitated Transport of Inorganic Contaminants in Ground
Water: Part 1, Sampling. EPA/600/M-90/023,
USEPA. Puls, R.W., R.M. Powell, D.A. Clark, and C.J. Paul. 1991. Facilitated
Transport of Inorganic Contaminants in Ground Water: Part 2, Colloidal
Transport. EPA/600/M-91/040.
GROUND-WATER MONITORING AND WELL DESIGN
USEPA. Denit, Jeffrey. 1990. Appropriate Materials for Well Casing and Screens in
RCRA Ground Water Monitoring Networks.
USEPA. Aller; L., T.W. Bennett, G. Hackett, J.E. Denne, and R.J. Petty. 1990.
Handbook of Suggested Practices for the Design and Installation of Ground
Water Monitoring Wells. EPA/600/4-89/034.
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EPA Publications Related
To Ground-Water Modeling
USEPA. 1992. Chapter Eleven of SW-846, Ground Water Monitoring. Office of
Solid Wastes, Washington, DC. Pre-Publication.
HYDROGEOLOGY
USEPA. 1985. Issue Papers in Support of Groundwater Classification Guidelines.
EPA/440/6-85/001.
USEPA. 1986. Criteria for Identifying Areas of Vulnerable Hydrogeology Under
RCRA. Appendix D: Development of Vulnerability Criteria Based on Risk
Assessments. Office of Solid Waste and Emergency Response, Washington,
DC.
USEPA. 1990. A New Approach and Methodologies for Characterizing the
Hydrogeologic Properties of Aquifers. EPA/600/2-90/002.
USEPA. Molz, F.J., G. Oktay, and J.G. Melville. 1990. Measurement of Hydraulic
Conductivity Distributions: A Manual of Practice. Auburn University.
USEPA. 1990. Ground Water, Volume II: Methodology. EPA/625/6-90/016b.
MODELING
USEPA. Pettyjohn, W.A., D.C. Kent, T.A. Prickett, and H.E. LeGrand. (No date.)
Methods for the Prediction of Leachate Plume Migration and Mixing. Office of
Research Laboratory, Cincinnati.
USEPA. Bond, F., and S. Hwang. 1988. Selection Criteria for Mathematical Models
Used in Exposure Assessments: Ground Water Models. EPA/600/2-89/028.
USEPA. 1988. OSWER Directive No. 9355.0-08. Modeling Remedial Actions at
Uncontrolled Hazardous Waste Sites.
USEPA. Bear, J., M. Geljin, and R. Ross. 1992. Fundamentals of Ground Water
Modeling for Decision Makers. EPA/540/S-92/005.
USEPA. van der Heijde, Paul K.M., Aly I. El-Kadi, and Stan A. Williams. 1988.
Groundwater Modeling: An Overview and Status Report. EPA/600/2-89/028.
USEPA. van der Heijde, Paul K.M., and O.A. Elnawawy. 1992. Quality Assurance
and Quality Control in the Development and Application of Groundwater
Models. EPA/600/R-93/011. Office of Research and Development.
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EPA Publications Related
to Ground-Water Modeling
RCRA
USEPA. 1984. OSWER Directive No. 9504.01-84. Enforcing Groundwater
Monitoring Requirements in RCRA Part B Permit Applications.
USEPA. 1984. OSWER Directive No. 9481.06-84. Clarification of the Definition of
Aquifer in 40 CFR 260.10.
USEPA. 1984. OSWER Directive No. 9481.02-84. ACL Demonstrations, Risk Levels,
and Subsurface Environment.
USEPA. 1985. OSWER Directive No. 9481.02-85. Ground Water Monitoring Above
the Uppermost Aquifer.
USEPA. 1985. OSWER Directive No. 9481.05-85. Indicator Parameters at Sanitary
Landfills.
USEPA. 1985. OSWER Directive No. 9931.1. RCRA Ground "Water Monitoring -
Compliance Order Guidance.
USEPA. 1985. OSWER Directive No. 9476.02-85. RCRA Policies on Ground Water
Quality at Closure. ' .
USEPA. 1985. OSWER Directive No. 99050.0. Transmittal of the RCRA Ground ,
Water Enforcement Strategy.
USEPA. 1986. OSWER Directive No. 9950.2. Final RCRA Comprehensive Ground
Water Monitoring Evaluation (CME) and Guidance.
USEPA. 1986. Leachate Plume Management. EPA/540/2-85/004.
USEPA. 1987. OSWER Directive No. 9950.1. RCRA Ground Water Monitoring
Technical Enforcement Document.
USEPA. 1987. OSWER Directive No. 9481.00-10. Implementation Strategy for
Alternate Concentration Levels.
USEPA. 1988. OSWER Directive No. 9476.00-10. Ground Water Monitoring at
Clean Closing Surface Impoundment and Waste Pile Units.
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Assessment Framework
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EPA Publications Related
To Ground-Water Modeling
USEPA. 1988. ,O§WER Directive No. 9950.3. Operation and Maintenance
Inspection Guide (RCRA) Ground Water Monitoring Systems.
RISK ASSESSMENT
USEPA. Bond, F., and S. Hwang. 1988. Selection Criteria for Mathematical
Models Used in Exposure Assessments: Ground Water Models. EPA/600/8-
88/075.
USEPA. 1988. Superfund Exposure Assessment Manual. EPA/540/1-88/001.
USEPA. 1989. Risk Assessment Guidance for Superfund, Vol. I: Human Health
Evaluation Manual. EPA/540/1-89/002.
USEPA. 1989. Risk Assessment Guidance for Superfund, Vol. II: Environmental
Evaluation Manual. EPA/540/1-89/001.
SAMPLING AND DATA ANALYSIS
Bauer, K.M., W.D. Glauz, and J.D. Flora. 1984. Methodologies in Determining
Trends in Water Quality Data.
USEPA. 1986. NTIS No. PG-86-137-304. Practical Guide for Ground Water
Sampling. .
USEPA. 1987. OSWER Directive No. 9355.0-14. A Compendium of Superfund Field
Operation Methods, Volumes 1 and 2.
USEPA. 1988. Field Screening Methods Catalog: User's Guide. EPA/540/2-88/005.
USEPA. 1989. Data Quality Objectives for Remedial Response Activities:
Development Process. EPA/540/G-87/003.
USEPA. 1991. OSWER Directive No. 9355.4-04FS. A Guide: Methods for
Evaluating the Attainment of Clean-Up Standards for Soils and Solid Media.
USEPA. 1991. OSWER Directive No. 9360.4-06. Compendium of ERT Ground
Water Sampling Procedures.
REMEDIAL INVESTIGATION/FEASIBILITY STUDY
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EPA Publications Belated
to Ground-Water Modeling
USEPA. 1988. Guidance on Conducting Remediation Investigation and Feasibility
Studies (RI/FS) Under CERCLA. EPA/540/G-89/004.
USEPA. 1988. OSWER Directive No. 9283.1-02. Guidance on Remedial Action for
Contaminated Ground Water at Superfund Sites.
USEPA. 1989. OSWER Directive No. 9355.4-03. Considerations in Ground Water
Remediation at Superfund Sites.
USEPA. 1989. Example Scenario: RI/FS Activities at a Site with Contaminated Soil
and Ground Water. EPA/540/G-87/004.
USEPA. 1989. OSWER Directive No. 9835.8. Model Statement of Work for a
Remedial Investigation and Feasibility Study Conducted by a Potentially
Responsible Party.
USEPA. 1991. Conducting Remedial Investigation/Feasibility Studies for CERCLA
. Municipal Landfill Sites. Office of Emergency Remedial Response,
Washington, DC.
USEPA. 1991. OSWER Directive No. 9835.3-2a. Model Administrative Order on
Consent for Remedial Investigation/Feasibility Study.
USEPA. 1992. Site Characterization for Subsurface Remediation. EPA/625/4-
91/026.
REMEDIAL DESIGN/REMEDIAL ACTION
USEPA. 1986. OSWER Directive 9355.0-4A. Superfund Remedial Design and
Remedial Action Guidance.
USEPA. 1988. OSWER Directive No. 9355.0-08. Modeling Remedial Actions at
Uncontrolled Hazardous Waste Sites.
USEPA. 1988. OSWER Directive No. 9283.1-02. Guidance on Remedial Action for
Contaminated Ground Water at Superfund Sites.
USEPA. 1989. OSWER Directive No. 9355.4-03. Considerations in Ground Water
Remediation at Superfund Sites.
USEPA. 1990. OSWER Directive No. 9355.0-27FS. A Guide to Selecting Superfund
Remedial Actions:
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Assessment Framework
OSWER Directive #9029.00
EPA Publications Related
To Ground-Water Modeling
USEPA. 1990. Guidance on Expediting Remedial Design and Remedial Action.
EPA/540/G-90/006.
USEPA. 1990. Guidance on EPA Oversight of Remedial Designs and Remedial
Actions Performed by Potentially Responsible Parties. Interim Final.
EPA/540/G-90/001.
USEPA. Ross, R. (No date.) General Methods for Remedial Operations
Performance Evaluations.
USEPA. 1990. OSWER Directive No. 9355.4-01FS. Guide on Remedial Actions at
Superfund Sites with PCB Contamination.
USEPA. 1990. OSWER Directive No. 9833.0-2b. Model Unilateral Order for
Remedial Design and Remedial Action.
USEPA. 1991. OSWER Directive No. 9835.17. Model CERCLA RD/RA Consent
Decree.
RECORD OF DECISION
USEPA. 1990. OSWER Directive No. 9283.1-03. Suggested ROD Language for
Various Ground Water Remediation Options.
USEPA. 1991. OSWER Directive No. 9355.3-02FS-3. Guide to Developing
Superfund No Action, Interim Action, and Contingency Remedy RODs.
USEPA. 1991. OSWER Directive No. 9355.7-02. Structure and Components of Five
Year Reviews.
CLEANUP STANDARDS
USEPA. 1990. OSWER Directive No. 9234.2-11FS. ARARs Q's and A's: State
Ground Water Antidegradation Issues.
USEPA. 1990. OSWER Directive No. 9234.2-09FS. ARARs Q's and A's: Compliance
with Federal Water Quality Criteria.
USEPA. 1990. OSWER Directive No. 9234.2-06FS. CERCLA Compliance with Other
Laws Manual: CERCLA Compliance with the Clean Water Act (CWA) and the
Safe Drinking Water Act (SDWA).
USEPA. 1991. OSWER Directive No. 9355.4-04FS. A Guide: Methods for
Evaluating the Attainment of Cleanup Standards for Soil and Solid Media.
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EPA Publications Related
to Ground-Water Modeling
PUMP AND TREAT REMEDIATION
USEPA. 1989. Evaluation of Ground Water Extraction Remedies, Volume I:
Summary Report. EPA/540/2-89/054a.
USEPA. 1989. Evaluation of Ground Water Extraction Remedies, Volume II: Case
Studies 1-19. EPA/540/2-89/054b.
USEPA. 1989. Evaluation of Ground Water Extraction Remedies, Volume III:
General Site Data, Data Base Reports. EPA/540/289/054c.
USEPA. 1989. OSWER Directive No. 9355.0-28. Control of Air Emissions from
Super fund Air Strippers at Superfund Ground Water Sites.
USEPA. Mercer, J.W., D.C. Skipp, and D. Giffin. 1990. Basics of Pump and Treat
Ground Water Remediation Technology. EPA/600/8-90/003.
USEPA. Saunders, G.L. 1990. Comparisons of Air Stripper Simulations and Field
' Performance Data. EPA/450/1-90/002.
USEPA. 1989. Forum on Innovative Hazardous Waste Treatment Technologies:
Domestic and International. EPA/540/2-89/056.
USEPA. 1990.. OSWER Directive No. 9355.0-27FS. A Guide to Selecting Superfund
Remedial Actions.
IN SITU REMEDIATION
Middleton, A.C., and D.H. Killer. 1990. In Situ Aeration of Ground Water: A
Technology Overview.
USEPA. 1990. OSWER Directive No. 9355.0-27FS. A Guide to Selecting Superfund
Remedial Actions.
USEPA. 1990. Emerging Technologies: Bio-Recovery Systems Removal and
Recovery of Metal Ions from Ground Water. EPA/540/5-90/005a.
USEPA. 1989. Forum on Innovative Hazardous Waste Treatment Technologies:
Domestic and International. EPA/540/2-89/056.
LANDFILLS AND LAND DISPOSAL
USEPA. Kirkham, R.R., et al. 1986. Estimating Leachate Production from Closed
Hazardous Waste Landfills. Project Summary. Cincinnati, Ohio.
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EPA Publications Related
To Ground-Water Modeling
USEPA. Mullen, H., and S.I. Taub. 1976. Tracing Leachate from Landfills, A
Conceptual Approach, Proceedings of the National Conference on Disposal of
Residues on Land. Environmental Quality Symposium, Inc. pages 121-126.
USEPA. 1990. OSWER Directive No. 9481.00-11. Status of Contaminated Ground
Water and Limitations on Disposal and Reuse.
Federal Register, Part H, 40 CFR Parts 257 and 258, Wednesday, October 9,1991. Solid
Waste Disposal Facility Criteria: Final Rule.
USEPA. 1989. NTIS No. PB91-921332/CCE. Applicability of Land Disposal
Restrictions to RCRA and CERCLA Ground Water Treatment Reinjection,
Superfund Management.
USEPA. 1991. Conducting Remedial Investigation/Feasibility Studies for CERCLA
. Municipal Landfill Sites. Office of Emergency Remedial Response,
Washington, D.C.
MISCELLANEOUS GROUND-WATER PUBLICATIONS
USEPA. 1986. Background Document Groundwater Screening Procedure. Office of
Solid Waste.
USEPA. 1990. Continuous Release - Emergency Response Notification System and
Priority Assessment Model: Model Documentation, Office of Emergency and
Remedial Response, Washington, D.C.
USEPA. 1991. Protecting the Nation's Ground Water: EPA's Strategy for the 1990s;
The Final Report of the EPA Ground Water Quality Task Force. Office of the
Administrator, Washington, D.C.
USEPA. 1990. ORD Ground Water Research Plan: Strategy for 1991 and Beyond.
EPA/9-90/042.
DRINKING WATER SUPPLY
USEPA. 1988. Guidance on Providing Alternate Water Supplies. EPA/540/G-
87/006.
CATALOGS
USEPA. 1992. Catalog of Superfund Program Publications. EPA/540/8-91/014.
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Assessment Framework
OSWER Directive #9029.00
EPA Publications Related
to Ground-Water Modeling
To obtain these documents, contact the EPA Regional Libraries, the EPA Regional
Records Center, or the Center for Environmental Research Information (513-569-
7562).
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