United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(5103)
EPA 500-B-94-004
July 1994
Ground-Water Modeling
Compendium -Second Edition
Model Fact Sheets, Descriptions, Applications
and Cost Guidelines
OSWER Information Management
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Purpose of This Compendium
The use of this Compendium by technical staff and remedial project
managers is intended to help promote the appropriate use of
models thus effecting sound and defensible modeling in the
Agency.
The second edition of the Ground-Water Modeling Compendium
increases the reader's awareness by describing eight widely-used
ground-water models.
It provides summary descriptions of six model applications which
illustrate the complexities of the use of models in the Agency's waste
management program.
The new section, Cost Guidelines For Ground-Water Model
Applications, provides general guidelines and hints for improving
cost estimation and cost review of ground-water model applications.
Who May Benefit From This Compendium
This Compendium is intended for use by:
Technical Support Staff
Remedial Project Managers
This Compendium may also help:
OSWER and Regional Management
EPA Contractors
Other Consultants
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Table of Contents
Section 1.0 - Introduction
Background 1_1
Objective and Intended Use 1-1
Organization and Structure 1-2
Future Plans 1_3
Acknowledgements 1-3
Section 2.0 - Cost Guidelines For Ground-Water Model
Applications
Introduction 2-1
Cost Control of Ground-Water Model Applications 2-4
Overall Cost of Ground-Water Modeling Applications 2-12
Cost Elements of a Project Management Plan for a Ground-Water
Modeling Application 2-20
Summary 2-28
Appendix A 2-29
Section 3.O - Model Applications
Introduction 3_1
Summary Description #1 3.3
Summary Description #2 3-H
Summary Description #3 3-25
Summary Description #4 3.39
Summary Description #5 3.53
Summary Description #6 3-71
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Table of Contents
(Continued)
Sect/on 4.0 Modal Descriptions
Introduction 4-1
Model Fact Sheets 4-5
Detailed Model Descriptions 4a
MOC 4a-l
MODFLOW 4b-l
PLASM 4c-l
RANDOM WALK 4d-l
AT123D 4e-l
MT3D 4f-l
MODPATH 4g-l
WHPA 4h-l
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1.0
Introduction
Background
During the past few years, Office of Solid Waste and Emergency Response
(OSWER) conducted a pilot project on ground-water modeling with the primary
objective of providing useful information on existing modeling practices and
models to EPA staff, contractors, and the regulated community.
The first Ground-Water Modeling Compendium was prepared as part of the
Models Management Initiative conducted by EPA's Office of Solid Waste and
Emergency Response (OSWER). OSWER's Resource Management and Information
Staff (RMIS) directed this effort in order to promote improved usage of
environmental models ~ initially focusing on waste management programs, and in
the future, supporting Agency-wide efforts.
The second edition of the Compendium has been produced for the same
purpose; it provides additional information about models and model applications
and includes a new section on the cost of ground-water model applications.
The first edition (October 1992) of the Ground-Water Modeling Compendium
contained the "Assessment Framework for Ground-Water Model Applications". It
provides a framework for planning and evaluating ground-water model
applications. In 1993, the Science Advisory Board (SAB) was asked to review the
Framework in terms of its scientific correctness and its usefulness in improving the
use of models. The SAB commented that the "Framework represents a significant
advance in OSWER's approach to the management and use of mathematical
models" and provided some suggestions for its refinement. The Framework was
edited to reflect the SAB's comments and is being distributed separately from the
Compendium, as suggested by the SAB. For information about the revised
Framework, contact OSWER's Resource Management and Information
Staff/Information Management Staff.
Objective and Intended Use
OSWER recognizes that ground-water models are being used in a variety of
ways and under different circumstances and constraints. Models can be used to
guide arid complement field investigations, thereby improving the understanding
of the consequences of site-specific hydrogeologic conditions. However, models
should riot be used in lieu of field investigations and care must be taken to ensure
that models are not misused.
Page 1-1
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Section 1: Introduction
The intention of this Compendium is to:
G promote the appropriate use of models by increasing users' awareness
about the strengths, weaknesses and inherent uncertainties associated
with ground-water models and modeling in general; and
G support model users and decision-makers by providing a convenient
source of information on how certain models have been applied in the
context of waste management programs, the characteristics of eight specific
ground-water models, and guidelines on the cost of ground-water
modeling applications.
The contents of the Compendium have been reviewed extensively by
ground-water modeling experts both within and external to EPA. OSWER
recommends this document as a reference source for promoting sound and
defensible modeling methods and approaches. This document does not, however,
constitute official EPA guidance, nor should it be construed as an endorsement of
specific models.
Organization and Structure
The Compendium is organized into four distinct sections designed to meet the
needs of various audiences, including project/site managers, technical reviewers,
and model users. The four sections of the Compendium are:
G 1.0, this section, is the Introduction describing the Compendium's purpose
and organization.
G 2.0, Cost Guidelines For Ground-Water Model Applications, provides
guidelines for estimating and managing costs for comprehensive
numerical ground-water model applications for waste management
projects. Historical modeling cost information, derived from private
sector firms only, is provided to help plan for resources needed for
different elements of a modeling application project and to provide some
guidance for estimating overall modeling costs.
G 3.0, Model Applications, provides summary descriptions of six model
applications, some of which were developed to test the original
assessment framework. Each description contains the decision objective,
regulatory context, site characteristics (e.g., geology, ground-water
contamination), modeling activities and results, interesting features of the
application, and the names of EPA staff to contact for more details. This
section is intended to help readers understand the variety of modeling
applications.
Pago 1-2
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Section 1: Introduction
01 4.0, Model Descriptions, provides both brief and detailed descriptions for
the eight selected models. The brief descriptions are contained on a series
of Fact Sheets, which provide important characteristics of the model and
sources of additional information. The detailed model information
contained in the latter part of the section includes names of the
developers, names and addresses of the custodian, technical features, and
solution methods. This information has been extracted from a database of
ground-water models developed and maintained by the International
Ground Water Modeling Center (IGWMC).
Future Plans
OSWER, with the Office of Research and Development (ORD), requested that the
Deputy Administrator establish a temporary Agency Task for Environmental
Regulatory Modeling (AFTERM) to address Agency-wide modeling issues. The Task
Force has produced a final report which requests a permanent Agency-wide focus for
the coordination of information and support concerning modeling. Thus, further
editions of any ground-water modeling compendium would come under the
direction of this Agency-wide modeling group.
Acknowledgements
The OSWER Pilot Project has benefited since its inception from input by a team
of ground-water modeling experts that included Dr. Mary Anderson, University of
Wisconsin, Dr. Paul van der Heijde, International Ground Water Modeling Center,
and Dr. Luanne Vanderpool, EPA Region V. These individuals were instrumental
in developing the Assessment Framework in the first edition of the Compendium,
and their insights led to many improvements in the other sections. In addition,
staff and managers from the Robert S. Kerr Environmental Research Laboratory,
especially David Burden and Joseph Williams, have provided expert review and
guidance.
The original Ad hoc committee, representing model users in the EPA Regional
offices, in OSWER, and other program offices served as a review group and
provided suggestions for the Compendium. Its members include:
Office of Solid Waste and Emergency Response
David Bartenfelder Subijoy Dutta
Randall Breeden Loren Henning
Dorothy Canter Tony Jover
Matthew Charskey Zubair Saleem
Lynn Deering Richard Steimle
Page 1-3
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Sect/on 1: Introduction
Richard Willey
Allison Barry
Fred Luckey
Nancy Cichowicz
Mike Arnett
Shawn Ghose
Mary Bitney
Darcy Campbell
Richard Freitas
Glenn Bruck
Region I
Region II
Region III
Region IV
Region VI
Region VII
Region VIII
Region IX
Region X
Christos Tsiamis
Michael Hebert
Office of Research and Development
Bob Ambrose Will LaVeille
David Burden Ron Wilhelm
Carl Enfield Darwin Wright
Amy Mills
Robert Dyer
Joe Tikvart
Office of Air and Radiation
Kung-Wei Yeh
Office of Water
Marilyn Ginsberg
Page 1-4
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Section 1: Introduction
Office of Information Resources Management
DwightClay
Page 1-5
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Section Is Introduction
(THIS PAGE INTENTIONALLY LEFT BLANK)
Pago 1-6
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Section 2; Cost Guidelines for Ground-Water Model Applications
2.0
Cost Guidelines for Ground-Water Model Applications
2.1 Introduction
This section provides guidance for estimating and managing costs for
numerical ground-water modeling for projects related to the Comprehensive
Environmental Response Compensation and Liability Act (CERCLA)/Superfund
Amendment and Reauthorization Act (SARA) and the Resource Conservation and
Recovery Act (RCRA). Historical modeling cost information is provided to help
managers evaluate the reasonableness of estimated costs. Information on the costs
of different elements, or phases, of a modeling project is provided to help managers
plan for and allocate resources among those elements. In addition, factors which
impact the cost of numerical modeling projects are discussed.
The information in this section is derived from the experiences of hazardous
waste investigation and remediation project managers and ground-water modelers.
The information is also the result of the collection and analysis of historical cost
data from more than fifteen experienced ground-water modelers employed by three
environmental restoration firms; thus the data represent project results of private
sector firms only.
Thirty-four numerical ground-water model applications were documented
using a data collection questionnaire. The majority of these comprehensive
numerical ground-water model applications was developed to gain an
understanding of the site. A small number of applications was developed for other
purposes such as limited design, permitting, and litigation.
It should be noted that, although the cost guidelines and data are based on facts,
the following considerations or caveats are important.
G Modeling costs within federal agencies may differ from private sector
modeling projects. Likewise, companies regulated by EPA may have in-
house modeling staff and thus have lower costs.
G In 1994, the cost of numerical modeling is generally lower than ten years
before because of the availability of personal computer versions of the
code, decrease in the cost of workstations, reduction in the cost of
simulations and presentation of results, and more sophisticated and
experienced users.
Page 2-1
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Section 2: Cost Guidelines for Ground-Water Model Applications
O The cost data range from 1984 to 1994 and have not been adjusted to 1994
dollar values.
O For a given project, it may be appropriate to analyze the benefit/cost ratios
of a modeling project versus data collection and investigation, with
respect to the resulting uncertainty factors.
G For a given modeling project, the use of an analytical model may be more
appropriate and less costly than the use of a numerical model.
Effective and Ineffective Usage of Ground-Water Modeling
Properly managed, ground-water models may provide significant cost savings
for site investigation and remediation projects. Some project managers responding
to the data collection questionnaire had positive things to say about ground-water
modeling:
O "By having a comprehensive ground-water model application, over $5
million in data collection costs were saved."
O "The use of the model application saved the agency and the PRP millions
of dollars by gaining public acceptance of EPA's program."
O "During the litigation process, the model application helped keep the
experts focused on the pertinent issues so that, ultimately, settlement was
achieved expeditiously."
O "The model application showed the maximum possible extent of the
plume and maximum contaminant concentration, helping to reduce any
undue concerns or ^ alarm' about the site and to minimize site cleanup
costs."
All too often, however, managers can expend a great deal of money developing
expensive models which never provide useful information. Other managers
responding to the questionnaire shared with us some of their frustrations about the
use of ground-water models:
O "Modeling was not considered until late in the project, after a great deal of
data had been collected. The model application development process
identified many gaps in the data, but no funding was available for
additional data collection. So the confidence level of the model was
Page 2-2
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Section 2s Cost Guidelines for Ground-Water Model Applications
eroded to the point where the model was deemed unusable by site
regulators."
O "The model application was originally developed for a feasibility study.
Later, the same model was applied for PRP enforcement. The approximate
nature of the particle tracking component of the model approach allowed
one PRP to "escape1 the enforcement process."
O "A complex model application was developed and calibrated on the basis
of incorrect survey data. This led to invalidation of the modeling results
and a costly re-development of the model application."
The Cost Guidelines for Ground-Water Model Applications have been
developed to help increase the number of positive ground-water modeling
outcomes.
Organization of This Section
Sub-section 2.2, Cost Control of Ground-Water Model Applications, presents
five guidelines that when followed will improve the management of ground-water
modeling application costs. Sub-section 2.3, Overall Cost of Ground-Water Model
Applications, presents information and graphs on numerical ground-water model
application costs based upon historic cost data. This information may help
managers plan for and assess the reasonableness of proposed modeling cost
estimates. Sub-section 2.4 provides information on the cost of different components
of a modeling application project and when and why the cost of a component might
lie outside the typical range of costs. Two examples of the ground-water modeling
cost data questionnaires used to solicit the historic cost data are provided in an
appendix. Completed questionnaires for the thirty-four model applications are
available from the Resource Management and Information Staff in the Office of
Solid Waste and Emergency Response. Names of the sites and parties have been
removed to protect confidentiality.
Page 2-3
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Section 2: Cost Guidelines for Ground-Water Model Applications
2.2 Cost Control of Ground-Water Model Applications
Cost control of ground-water model applications is essential to ensure that the
benefits of modeling justify modeling costs. The five guidelines presented in Table
2.2-1 arid described below will assist in controlling model application costs. These
guidelines reflect years of experience by senior ground-water modelers and project
managers. The guidelines should help to ensure:
G The efficient use of both ground-water modeling and overall project
resources
O The consideration of modeling costs when changes in the modeling
objectives or data requirements are proposed.
GUIDELINE #1: INTEGRATE GROUND-WATER MODELS INTO THE OVERALL
INVESTIGATION AND REMEDIATION PROCESS
Too often, ground-water modeling is performed as an afterthought, rather than
being integrated into the project at its inception. Ground-water modeling's purpose
is to provide an improved understanding of the site flow and transport processes
and to help predict the future consequences of past or proposed actions. When
ground-water modeling is integrated into the overall investigation and remediation
process, it can help to minimize investigation and remediation costs and to ensure
that the best remediation alternative is selected. Modeling may also correctly
indicate the need for additional investigation.
Bringing ground-water modelers into a project during the initial planning
phase will help to ensure that ground-water modeling is integrated into the overall
process. The modeler can assist in comprehensively organizing the available data
and can help in the determination of new field data collection needs. Conducting
the project in this integrated manner enables investigators to minimize the cost of
collecting the data needed to support any necessary modeling.
The integrated approach also helps to ensure that the type and timing of the
modeling will meet management's decision objective (see Guideline #3 below). For
example, the use of a less sophisticated model during the remedial investigation
phase of a project may help determine the potential off-site impact of the
contamination. The use of a more sophisticated model during the remediation
design phase of a project may help to ensure more effective and less costly site
remediation. An example, a paraphrase of an actual project, which demonstrates
the cost of failing to integrate ground-water models into the overall project
planning is provided below.
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Section 2s Cost Guidelines for Ground-Water Model Applications
Table 2.2-1
Five Guidelines for Cost Control of Ground-Water Modeling
#1 Integrate Ground-Water Models into the Overall
Investigation and Remediation Process
#2 Plan for the Iterative Nature of Ground-Water Model
Applications
#3 Match the Modeling Objectives to Management's
Decision Objectives
#4 Use Modeling to Guide and Optimize Data Collection
#5 Perform a Cost Review at Major Decision Points in the
Model Process
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Section 2: Cost Guidelines for Ground-Water Model Applications
Example #1: On a site in the Northeast, a major water supply wellfield was shut
down because of volatile organic compounds (VOCs). Underlying the site were a
sand and gravel aquifer and a thin layer of the fractured bedrock. The general
presumption was that the wells were being contaminated by a plume in the sand
and gravel aquifer. Instead of investigating this assumption through the use of a
relatively simple ground-water model early in the investigative process, an
extensive design of a large pump-and-treat system for the sand and gravel aquifer
was initiated. A third-party review uncovered inconsistencies in the ground-water
data being used for the design. The project managers then decided to use a model to
verify the location of the plume. The results of the modeling demonstrated that the
plume lay in the fractured bedrock, and thus, initial design efforts were wasted at
some cost to the project. These costs could have been avoided if there had been a
careful integration of modeling throughout the overall investigation and
remediation process.
GUIDELINE #2: PLAN FOR THE ITERATIVE NATURE OF GROUND-WATER
MODEL APPLICATIONS
Ground-water modeling is usually most effective when performed as a series of
phases, with iterations between the phases, as shown in Figure 2.2-1. Flexibility
must be incorporated into the initial project plan. The second phase in Figure 2.2-1
is the development of an initial conceptual model, with subsequent phases leading
to the development of an improved conceptual model and, if necessary, the
application of a computer model. The result of each phase may be a decision that
the results of a prior phase of the modeling process must be amended. Such results
are common because modeling is a deductive reasoning process that focuses upon
verifying assumptions about hydrogeologic conditions and flow and transport
systems. The disproof of an assumption will often require the review of prior
assumptions and a fundamental change in the characterization of the ground-water
system. This iterative process continues until the characterization of the ground-
water system and its response to past or proposed actions is sufficiently accurate and
detailed to support management's decision objectives.
Approaching modeling this way helps to eliminate unnecessarily complex
modeling and best reflects the practical aspects of the modeling process. An example
which demonstrates the benefit of planning for the iterative nature of ground-water
model applications is provided below.
Example #2: On a large? project, failure to plan for the iterative nature of ground-
water modeling caused serious difficulties for one of the interested parties. This
party chose to begin a large and complex modeling effort at the onset of the RI/FS,
when there was a limited understanding of the site. After the installation of
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Th
Plan Project
p
Conceptual
Model >
1
Existing I
Data 1
U^^1
Set Up &
Calibrate
Models
Collect
Additional
FiflH
Data
Simulate Scenarios
Present Results &
Determine Effectiveness
Figure 2.2-1
ie Ground-Water Modeling Process
Set Groundwater |^
Analysis Objectives "
1
V
^ Conceptual Model |
^^T^/Mr, r^T^N^ N° fc/ C-J ^\
^^^Y
v K
Model 1
4
Set Up & Calibrate I
Flow Model 1
Yes .x^-x. No
Set Up & Calibrate I
B Transport Model |
Do Post-Simulation Analysis 1
Assess Overall 1
Modeling Effectiveness 1
( End J
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Section 2: Cost Guidelines for Ground-Water Model Applications
numerous wells and many rounds of data collection, the party reviewed the
modeling effort and realized that the entire effort was based upon a fundamental
misunderstanding of the site hydrogeology. Consequently, much of their prior data
collection and modeling efforts were wasted.
By contrast, at this same site, another interested party utilized an iterative
modeling approach in which the party began with a relatively simple model of the
site. The results of this model were compared with newly acquired field data and
adjustments in the modeling were made. With these adjustments, this party was
able to rapidly identify the fundamental components of the ground-water system
and to focus the remedial alternatives analysis. By planning for the iterative nature
of ground-water modeling, this party was able to significantly reduce both modeling
and project costs as compared to the first interested party.
GUIDELINE #3: MATCH THE MODELING OBJECTIVES TO MANAGEMENT'S
DECISION OBJECTIVES
Often, modeling is initiated without a clear understanding of management's
decision objectives. When this is the case, the results of the modeling, regardless of
the technical quality of the modeling, will often fail to support management's
decision objectives. This is the" most common modeling pitfall and the cause of
most modeling "horror stories." For example, a typical management decision
objective is to identify all potentially responsible parties (PRPs). A modeling
objective that matches this decision objective would be to assist in the identification
of the spatial location, timing and/or quantities of source based upon the
contaminant ground-water plume and the underlying site hydrogeology.
Modeling, used as a tool, may support many different objectives. For example,
a modeling project may identify the best locations for monitoring and pumping
wells. It may produce estimates of concentrations at receptors. It may test
alternative cleanup scenarios. Or it may support several different objectives
concurrently. Because modeling is a often multi-purpose exercise, defining the
particular set of objectives in each case is critical to the ultimate success of the effort.
Modeling is most successful when its objectives are tied to management's
decision objectives. The link between these two should be clearly defined in the
project plan. It should also be reflected in the project controls. A strong link, set at
the beginning and built into the project controls will keep modeling focused on the
right objectives. It aids in the shaping of all future aspects of the process, from
developing the initial conceptual model to presenting the findings and conclusions.
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Section 2: Cost Guidelines for Ground-Water Model Applications
Management must accept the responsibility for clearly communicating their
decision objectives. The modeling team must accept the responsibility for
translating management's objectives into modeling objectives. Regular review of
the compatibility between the modeling objectives and management's decision
objectives is the most important component of the modeling quality assurance
program. Management's decision objectives and the role that modeling is to play in
meeting their objectives must be clearly defined at the onset of the project and must
be reviewed regularly. An example of what can happen when this guideline is not
followed is described below.
Example #3: In this case, a municipal well was contaminated by nearby VOC spills.
Three of the regulatory decision objectives were: 1) to quantify the nature and the
extent of the contamination, 2) to identify potential remedial technologies, and 3) to
identify the PRPs. However, because the regulators were confident that they could
easily identify the PRPs, they did not explain to the modeling team that they would
need to use the model results to support the PRP identification. The modeling team
therefore focused upon supporting the first two decision objectives and
consequently developed a relatively simple ground-water model application. This
application was well suited to these two decision objectives and was implemented at
very little cost.
Difficulties, however, were encountered when the regulators tried to utilize the
modeling application to support their enforcement recovery against the PRPs.
Because the application had not been designed to support this use, the assumptions,
level of detail, and documentation of the application could not withstand legal
challenges. The regulatory agencies were thus unable to recover costs from several
of the PRPs. The modeling team noted that if they had been advised that the
application was to be used to support enforcement recovery, they would have
insisted on enough resources to enable them to develop a much more sophisticated
modeling application. They were confident that the results of the more
sophisticated application would have mirrored the results of the simpler
application, but the more sophisticated application would have better withstood the
legal challenges.
GUIDELINE #4: USE MODELING TO GUIDE AND OPTIMIZE DATA COLLECTION
Site ground-water data collection efforts are often inefficient and costly because
critical data needs are not identified early in the project planning process. While
iterative data collection plans are often very appropriate, incorporating ground-
water modeling expertise at the conceptualization of the project can significantly
improve the efficiency and completeness of each round of data collection. For
example, a preliminary conceptual model of the site can help to identify the type,
location, and frequency of data required to characterize the site's ground-water
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Section 2: Cost Guidelines for Ground-Water Model Applications
system. As additional data are collected, the assumptions of the conceptual model
can be reviewed, adjustments made, and additional data needs for numerical
modeling identified and incorporated into the regular site data collection activities.
By using the modeling activities to optimize this data collection process, it is more
probable that the "right" data will be collected from the beginning and the
subsequent field data collection stages can be more focused. This process typically
results in better cost control. Figure 2.2-1 illustrates the phasing of data collection
efforts. An example of the benefit of using modeling to guide and optimize data
collection is presented below.
Example #4: At a site involving an active landfill, a nearby water supply well was
contaminated with VOCs. The landfill was the only apparent source, but was
situated downgradient of the well. One hypothesis to explain the upgradient
presence of VOCs was that landfill gas migration could have caused the VOCs to
move from the landfill into the capture zone of the water supply well. To verify
this hypothesis subsurface vapor and ground-water sampling data were required. A
ground-water model was used to identify the most appropriate locations for
collection of these data. The use of the model significantly reduced the number of
wells needed to collect data. Thus, significant cost savings were achieved by using
the model to guide and optimize data collection for verification of the landfill gas
hypothesis.
GUIDELINE #5: PERFORM A COST REVIEW AT MAJOR DECISION POINTS IN
THE MODEL PROCESS
The iterative nature of ground-water modeling often requires frequent
adjustments to the modeling process. These adjustments can result in changes to
the cost of the modeling project. These cost changes must be regularly reviewed to
ensure that the benefits of the modeling results continue to justify the incurred and
projected costs and that the costs remain within the project budget.
Cost reviews should be performed at the completion of the conceptual model,
at the completion of the flow model, at the completion of the transport model, and
whenever another iteration of the modeling process is proposed. The cost reviews
are performed in conjunction with regular technical reviews of the project (see
Assessment Framework for Ground-Water Modeling, OSWER Draft Directive,
April 1994). For example, if calibration targets cannot be met during the preparation
of a flow model, the conceptual model may have to be revised, and therefore,
additional data may need to be collected. At this point, the cost of collecting the
additional data, revising the conceptual model, and recalibrating the model should
be reviewed to determine whether the benefit of the modeling results justifies the
additional costs.
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Sect/on 2: Cost Guidelines for Ground-Water Model Applications
Example 5 illustrates what can happen when this guideline is not followed.
Example #5: Near a large federal facility, ground-water modeling was proposed to
support both the screening of remediation alternatives and the conceptual design of
the selected alternative. Supporting the conceptual design required a more
sophisticated model application than was needed to support the screening of the
remedial alternatives. During the formulation of the initial conceptual model, it
was discovered that the existing field data did not meet the data requirements of a
sophisticated ground-water model. Without first performing a cost review, an
extensive data collection effort was initiated. The costs of the data collection effort
were significant and, at the completion of the additional data collection, there were
insufficient funds remaining to proceed with a sophisticated model application.
Consequently, attempts to use modeling to support the conceptual design of the
selected alternative were abandoned and a simpler model application was
developed to assist only in the screening of remedial alternatives. The simpler
model application, however, could have been developed without the additional
data collection. Thus a large part of the cost of the data collection effort was wasted.
If a cost review had been performed as part of the conceptual model development,
the impact of the data collection costs on the overall project budget and the
modeling objectives could have been identified prior to initiating the additional
data collection and adjustments could have been made.
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Section 2: Cost Guidelines for Ground-Water Model Applications
2.3 Overall Cost of Ground-Water Modeling Applications
The purpose of this sub-section is to provide information that can be used to
evaluate the reasonableness of the overall cost of numerical ground-water modeling
applications. This information is based on historical ground-water modeling costs
for hazardous waste investigation and remediation projects.
Engineering and modeling cost data were collected for numerical saturated
flow and contaminant transport model applications at CERCLA and RCRA facilities.
The modeling cost data were compared to the total engineering costs.
Engineering costs include data collection, modeling, and drilling supervision
costs. They do not include analytical laboratory or drilling costs.
The modeling costs include project planning, preparing a conceptual model,
setting up and calibrating a flow model, setting up and calibrating a transport model,
simulating scenarios, and presenting results and determining the overall
effectiveness of the modeling project. The modeling costs do not include data
collection costs.
The cost data were collected through questionnaires and follow-up telephone
conversations with over 15 experienced ground-water modelers and project
managers at three environmental restoration firms. Sufficient data to meet the
analysis objectives were obtained for 34 projects. For a number of the projects, it was
impossible to obtain precise cost breakdowns. In such cases, estimates were used
only if provided by individuals with first-hand knowledge of the model
applications.
NOTE: Cost data are not all expressed in 1994 dollars. Table 2.3-1 shows that costs
are associated with projects ranging in time from 1984 to 1994.
BASIC CONCLUSIONS
G The historical cost information shows that ground-water modeling costs
increase as the total engineering costs increase (See Figure 2.3-1).
G The percent of modeling costs to engineering costs decreases as the
engineering costs increase (see Figure 2.3-2).
For example, the modeling costs of smaller projects tend to be
approximately 20 percent of the engineering costs, while the modeling
costs of very large projects ($10 million and over) tend to be approximately
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Section 2: Cost Guidelines for Ground-Water Model Applications
Table 2.3-1
Ground-Water Modeling Historical Costs
NUMBER
1
2
3
4
5
6
7
3
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
TYPE
I
Y
Z
d
I
O
I
P
I
Z
Z
I
L
Z
I
I
Z
I
O
X
I
I
Z
D
I
Z
I
D
D
D
Z
I
D
d
PHASE
RFI
OTHER
RI/FS/RD
RD
RI/FS
RI/FS
RI/FS
OTHER
RI/FS
RI/FS/RD
RI/FS/RD
RI/FS
OTHER
RI/FS/RD
RI/FS
RI/FS
RI/FS/RD
RI/FS
RI/FS
RI/FS
RI/FS
RI/FS
RI/FS/RD
RD
Rl
RI/FS/RD
RI/FS
RD
RD
RD
RI/FS/RD
RFI
RD
RD
MODEL $
$42,000
$80,000
$700,000
$23,400
$30,000
$521,000
$160,000
$112,800
$100,000
$120,000
$117,600
$100,000
$150,000
$100,000
$40,000
$50,000
$92,300
$70,000
$175,000
$124,600
$75,000
$60,000
$696,000
$85,000
$50,000
$534,000
$278,500
$60,000
$37,700
$80,000
$70,000
$400,000
$120,000
$60.000
$
$1,000,000
$1,400,000
$20,000,000
$883,600
$656,800
$5,250,000
$1,455,300
$460,000
$838,000
$875,000
$958,000
$1,500,000
$350,000
$1,000,000
$1,400,000
$637,000
$1,075,000
$220,000
$667,200
$1,173,700
$400,000
$288,000
$11,000,000
$2,000,000
$400,000
$5,149,500
$1,149,500
$1,000,000
$400,000
$1,500,000
$1,000,000
$8,000,000
$680,000
$3.000.000
/ENG $
4.2%
5.7%
3.5%
2.6%
4.6%
9.9%
1 1 .0%
24.5%
1 1 .9%
13.7%
12.3%
6.7%
42.9%
10.0%
2.9%
7.8%
8.6%
31.8%
26.2%
10.6%
18.8%
20.8%
6.3%
4.3%
12.5%
10.4%
24.2%
6.0%
9.4%
5.3%
7.0%
5.0%
17.6%
2.0%
PERIOD
92
92
93-94
87-present
87
87-present
87-89
86-87
86-88
87-94
91-94
92
90-92
86-88
89-90
85-86
86-88
90-93
NK
84-87
85-86
85-86
89-94
NK
NK
93-94
84-94
90-91
93-94
88-90
88-90
89-92
NK
LEGEND
D = Design
d = Limited Design
I = Site Investigation (typically RI/FS)
L = Litigation
O = Oversight
= Permitting
= Site Investigation & Litigation
= Permitting & Design
= Investigation & Design (typically part of RI/FS/RD)
P
X
Y
Z
NK= Not Known
Page 2-13
-------
$800,000
$700,000
$600,000
$500,000
g $400,000
<
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$300,000
$100,000
$0
$100,000
$1,000,000 $10,000,000
TOTAL ENGINEERING COSTS
Legend: O
D = Design (RD) P
d = Limited Design X
I = Site Investigation (Typically RI/FS) Y
L = Litigation Z
Oversight
Permitting
Site Investigation & Litigation (I/L)
Permitting & Design (P/D)
Investigation & Design (Typically RI/FS & RD)
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-------
Section 2: Cost Guidelines for Ground-Water Model Applications
5 percent of the engineering costs. The distribution of case studies when
modeling costs are expressed as a percent of engineering costs, versus total
engineering costs is depicted in Figure 2.3-2.
Looking at this figure it is reasonable to assume a decreasing trend in the
ratio of modeling costs to total engineering costs. Total engineering costs
may increase dramatically as a project moves from site investigation to
remedial design and remedial action. The incremental costs of updating a
site investigation ground-water model, however, to support remedial
design or action activities are relatively low. Thus the modeling costs as a
percentage of the engineering costs can be expected to decrease.
O The historical costs data also show that, regardless of the project size, there
was a start-up or basic cost of $40,000 to $60,000 to use a numerical ground-
water model. This start-up cost can be seen in Figure 2.3-1, where very
little of the data lies below $40,000 and much of the data on even the
smallest projects lies above $50,000. In 1994 dollars, however, it is safe to
conclude that start-up costs range from $50,000 to $75,000. However, it
should be noted that basic costs may be less depending on such factors as
availability of in-house modeling staff and user-friendly, highly functional
software.
O The data suggest that total engineering costs may be used to reasonably
estimate modeling costs.
O There are factors that may cause modeling costs to exceed the normal cost
ratios. These factors include very complex geology, modeling transient
situations, or modeling multiple contaminants. These factors are
summarized in Figure 2.4-2 in Sub-section 2.4.
DISCUSSION OF GROUND-WATER MODELING COSTS
To better explore the variance in the cost data, the case studies listed in Table 2.3-1
were segregated into nine modeling types, based on the purpose of the modeling. A
description of each type, the number of case studies under each type, and the ranges
in modeling costs and engineering costs are discussed below. Engineering costs
include data collection arid drilling supervision costs. They do not include
analytical laboratory or drilling costs. The modeling costs do not include data
collection costs. The cost data are also plotted by type in Figure 2.3-1.
O Site Investigation (I): This type of model is used for Remedial Investiga-
tions/Feasibility Studies (RI/FS) and RCRA projects. This model
application is used to: (1) support site characterization, (2) evaluate
Page 2-15
-------
Section 2s Cost Guidelines for Ground-Water Model Applications
Figure 2.3-2
Percent of Ground-Water Modeling Costs to Engineering Costs
Versus Engineering Costs
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2-f 6
-------
Sect/on 2s Cost Guidelines for Ground-Water Model Application*
different remediation alternatives, and (3) develop a conceptual design of
the selected alternative. Thirteen of the 34 case studies are of this type. In
general, the ground-water modeling costs ranged from $30,000 to $278,500
and the total engineering costs ranged from $220,000 to $1.5 million. Case
Study No. 32 was the one exception to these general ranges; this was a
large RI/FS project with ground-water modeling application costs of
$400,000, and total engineering costs of $8 million (see Figure 2.3-1). The
ratio of the modeling costs to the engineering costs range from 2.9 percent
to 31.8 percent, with half of the model applications having ratios that lie
between 5 percent and 19 percent (see Figure 2.3-3).
O Design (D): This type of model application is used for Remedial Design
Action (RD) projects. Five of the 34 case studies are of this application
type. Ground-water modeling costs ranged from $37,700 to $120,000, while
engineering costs ranged from $400,000 to $2 million. The ratio of the
modeling costs to the engineering costs range from 4.3 percent to 17.6
percent, with half of the model applications having ratios that lie between
5.3 percent and 9 percent (see Figure 2.3-3).
O Investigation and Design (Z): This type of model is a combination of the
Investigation and Design and Implementation models. The Investigation
and Design model is generally initiated at the beginning of a site
characterization and refined and updated as a project proceeds through
various phases. Typically, the model is used for the detailed design (RD)
of a remediation system, and to support the RA. Eight of the 34 case
studies are of this type. The ground-water modeling costs ranged from
$70,000 to $700,000, while engineering costs ranged from $875,000 to $20
million. The ratio of the modeling costs to the engineering costs ranged
from 3.5 percent to 13.7 percent, with half of the model applications
having ratios that lay between 7 percent and 12 percent (see Figure 2.3-3).
O Limited Design Analysis (d): This type of model is used to support limited
design objectives such as the design of a ground-water capture/well-point
system. Generally, this type of modeling only requires the use of a flow
model, and the conceptual model may be relatively simple. The ratio of
modeling costs to engineering costs is generally very low as compared to
other types. Two of the 34 case studies are this type. The ground-water
modeling costs ranged from $23,400 to $60,000, while engineering costs
ranged from $883,600 to $3 million. The ratio of the modeling costs to the
engineering costs ranged from 2.0 percent to 2.6 percent.
Page 2-17
-------
Section 2; Cost Guidelines for Ground-Water Model Applications
Figure 2.3-3
Variation In The Ratio Of Ground-Water Modeling Cost To Engineering
Costs By Model Type
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Page 2-18
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
a Permitting of Facilities (P): This type of model is used to support the
permitting of landfill facilities and is very similar to the Investigation (I)
type described above. However, the P-type model typically involves less
feasibility study work and more preliminary design efforts. Only one of
the 34 case studies fell within this type. The total ground-water modeling
costs were $112,800, while engineering costs for this case were $460,000 for
a ratio of 24.5 percent.
O Oversight (O): This type of model is used to support technical oversight.
Modeling is used to evaluate or verify the results of another model
application. In the two case studies presented here, the ratios of modeling
costs to engineering costs are 9.9 percent and 26.2 percent, with actual
ground-water modeling costs of $521,000 and $175,000 respectively.
O Litigation (L): This type of model is used to support litigation or
enforcement actions. In general, the ratio of modeling costs to
engineering costs is high because the modeling results may be subject to
legal challenge. In the single case study, the ground-water modeling cost
was $150,000, with a total engineering cost of $350,000, with a ratio of 42.9
percent.
Page 2-19
-------
Sect/on 2; Cost Guidelines for Ground-Water Model Applications
2A Cost Elements of a Project Management Plan for a Ground-Water
Modeling Application
A typical ground-water modeling project may be divided into cost elements for
planning and allocating resources. Described below are those cost elements and
general ranges of the ratio of the costs of the elements compared with the
engineering cost. The cost elements correspond to the activities described in the
Assessment Framework for Ground-Water Model Applications (OSWER Draft
Directive, April 1994).
In addition, a base case ground-water modeling application is described and the
factors which impact the costs are identified.
The following findings and conclusions are the result of analyzing
questionnaires completed by modeling application project managers. Two
completed questionnaires are in Appendix A. Completed questionnaires for the
thirty-four model applications are available from the Resource Management and
Information Staff in the Office of Solid Waste and Emergency Response. Names of
the sites and parties have been removed to protect confidentiality.
COST DATA COLLECTION METHODOLOGY
Most ground-water modeling applications may be divided into six cost
elements. Each of these cost elements accounts for a percentage of the total cost of a
given modeling effort. Figure 2.4-1 shows the range of estimated percentages of total
cost for each of the six cost elements, based on responses to the modeling study
questionnaires.
Cost Element 1 - Project Planning
The first cost element is probably the most important part of a modeling
project; however, in many cases it is de-emphasized. In these cases, not enough
time is spent on an initial review of the available data and finalizing the modeling
objectives with project management. As a result of this poor planning, additional
costs may be incurred at a later date. As shown on Figure 2.2-1 in Sub-section 2.2,
time needs to be spent up-front to develop and incorporate the modeling objectives
into a work plan. A start-up meeting should be held with project management at
this stage. Flexibility should be built into the work plan to anticipate the iterative
nature of a ground-water modeling project.
Despite the importance of Cost Element 1, the historical cost data generally
encompasses only about 3 to 5 percent of a modeling budget (see Figure 2.4-1), a
small investment that can yield important benefits when made wisely. However,
Page 2-20
-------
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LEGEND:
3 4
Cost Elements
1 = Project Planning
2 = Prepare a Conceptual Model
3 = Set Up and Calibrate a Flow Model
4 = Set Up and Calibrate a Transport Model
5 = Simulate Scenarios
6 = Present Results and Determine Overall Effectiveness
Key:
outlier
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Section 2: Cost Guidelines for Ground-Water Model Applications
on more complex projects, especially those with lower total modeling budgets, this
element can consume up to 20 percent of the budget.
Cost Element 2 - Prepare a Conceptual Model
The second cost element involves development of a sound conceptual model
to provide a foundation upon which to build a flow and transport model. Existing
site and regional data are organized into an initial conceptual model which forms
the basis for deciding whether or not to develop a numerical model for a particular
site. If the decision is made to move forward, data gaps should be identified and
used to help guide the preparation of a field data collection plan for the site. (Cost of
data collection is not included as part of model costs.) Additional data are
condensed, organized, and used to prepare a working conceptual model.
Although the statistically determined middle range to prepare a conceptual
model is somewhat small (10 to 20 percent, as shown in Figure 2.4-1), there is large
range of deviation: values of up to 30 percent were common and one extreme case
had a value of 98 percent. In that particular case, the only objective was to provide
an understanding of the hydrogeologic conditions for site characterization.
Cost Element 3 - Set Up arid Calibrate a Flow Model
The third cost element includes activities such as selecting a suitable
mathematical model, building a grid, estimating input, selecting suitable calibration
targets, and calibrating the? model. Figure 2.2-1 shows that if the original calibration
targets cannot be met, it may be necessary to collect additional data, update the
working conceptual model, and re-calibrate the flow model.
Although a flow model can be set up rather easily due to the sophisticated
modeling software now available, calibration of a flow model is still a costly and
time-consuming step. Cost Element 3 is generally the costliest portion of modeling
efforts, because the calibrated flow model is essential for both the "understanding"
aspects of the modeling project and for being able to simulate and predict future
conditions. As shown in Figure 2.4-1, calibration costs typically consume 20 to 35 of
the modeling budget, and may be as high as 58 percent of the total modeling cost.
Cost Element 4 - Set Up and Calibrate a Transport Model
The fourth cost element includes the selection of representative indicator
compounds, input estimation, adjustment to the model grid and layering, selection
of suitable transport model calibration targets, and calibration.
Page 2~22
-------
Section 2: Cost Guidelines for ground-Water Model Applications
Although it is a recommended step, calibration of the transport model is not
incorporated in some modeling projects. This is either because the available
calibration data are too limited or due to the scope of the modeling project. When
calibration targets are used, often it becomes apparent that the working conceptual
model needs to be updated, and more data may need to be collected (as shown on
Figure 2.2-1).
Figure 2.4-1 shows that Cost Element 4 typically requires 10 to 25 percent of the
total budget, with possible costs ranging up to 40 percent. Note that, once the
calibration is completed, it is likely that over 60 percent of the budget, and perhaps
more than 75 percent, will have been expended.
Cost Element 5 - Simulate Scenarios
The fifth cost element includes the selection of the scenarios to be modeled,
modeling the scenarios, making predictions, and summarizing the results for oral
presentations. Cost Element 5 usually consumes 15 to 28 percent of the modeling
budget, with costs rarely exceeding 30 percent (see Figure 2.4-1).
Cost Element 6 - Present Results and Determine Overall Effectiveness
The sixth cost element includes the preparation of a modeling report, meeting
with client to discuss the report, and evaluation of how the modeling results
satisfied management's objectives.
Follow-up work may be required, such as providing negotiation support,
performing a post audit of the model results based on any new data collected, or
ongoing usage of the model for predictions or fine-tuning the remediation system.
If these follow-up costs can be anticipated, they should be included as a part of this
cost element within the ground-water modeling plan. Otherwise, they should be set
up under a separate budget.
Figure 2.4-1 shows that Cost Element 6 typically requires 10 to 15 percent of the
total budget, with possible costs ranging up to 20 percent.
TYPICAL COSTING APPROACH
When estimating costs for modeling, the professionals in charge of the
modeling have stated that they typically work from a "base case." The "base case"
method utilizes the simplest possible situation, in terms of the hydrogeologic and
contaminant source/transport factors. Then, the modelers add or subtract costs (and
corresponding scope elements) to handle the additional complexities that go beyond
the "base case."
Page 2-23
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
The modeling base case has the following characteristics:
G Single-layer aquifer
G Unconsolidated sediments (i.e., not fractured bedrock)
G RI/FS-type investigation, with some testing of alternative remediation
plans
G Single contaminant plume from a single source
G Conservative contaminant
G No resource-significant peer review or technical oversight, and no
litigation-level modeling.
The table below provides the range of percentages for each of the base case cost
components based on analysis of the 34 completed questionnaires.
Table 2.4-1
Range of Costs in Percent of Base Cost, by Element
Element
Number
1
2
3
4
5
6
Element Name
Project Planning
Prepare Conceptual Model
Set Up & Calibrate Flow Model
Set Up & Calibrate Transport Model
Simulate Scenarios
Present Results & Determine Overall
Effectiveness
Range
3 - 5%
10 - 20%
20 - 35%
10 - 25%
15 - 28%
10 - 15%
Page 2-24
-------
Section 2s Cost guidelines tor Ground-Water Model Applications
Once the base case is established, then factors that may increase or diminish the
costs of a modeling exercise in relation to the base case are identified. These factors
are described below and summarized in Figure 2.4-2. Figure 2.4-2 represents the
results of analyses of data from the subset of questionnaires which contained
information on the percentage of model cost element to model application cost (Part
III of the questionnaires in the Appendix). Further analyses of the questionnaires
resulted in the classification of those model applications according to the factors
which impact the cost of the base case. The determination of the cost impact,
whether an increase or a decrease, was straightforward. The relative amount of
increase or decrease (small, medium, large), as displayed, is not strictly quantitative.
The analyses were performed by an experienced ground-water modeler.
Flow Model Only: If only a flow model is prepared, generally the cost of the
modeling project will be less than the base case, since the base case includes
transport modeling.
Large Model Area: A large model area can significantly impact the cost of preparing
a conceptual model, since additional data need to be organized. In addition, the cost
of the flow model setup may be more than the base case since a larger grid is
required. Also, computational costs may be higher due the higher number of input
arrays.
Large Number of Nodes: Even though the model may cover a small area, it can still
have a larger number of nodes depending upon the specific problem and modeling
objectives. More nodes add to the overall cost, particularly in the model setup and
computational phases. (Some models have a local grid refining capability which
reduces the overall number of nodes.)
Geology: Geologic conditions may greatly impact the ground-water modeling
application costs. Multi-layer or three-dimensional models are more difficult to set
up and more data are required. This also applies for sites which have complex
geology. At many sites, the geology may vary greatly over both horizontal and
vertical distances. Contaminants will be transported more quickly in zones of
higher hydraulic conductivity; therefore, clear delineation of these zones is
important.
Flow Model: The type of flow model affects cost. In general, uncalibrated modeling
is not appropriate. However, if, in exceptional cases, an uncalibrated model is used
that is not based on actual site data, the ground-water modeling costs may be slightly
less than the base case. If transient calibration of the model is performed, there will
a higher cost, especially in the flow-model-calibration step (Cost Element No. 3).
Page 2-25
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
Figure 2.4-2
Factors Which Impact Cost Of Base Case
COST ELEMENTS
345
Overall
Costs
Flow Model Only
Large Model Area
Large Number of Nodes
Multi-Layer
Complex Geology
Uncalibrated
Transient Calibration o
Transient Scenarios o
M^
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tr
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Particle Tracking
Only
Uncalibrated
Multiple Sources
Multiple
Contaminants
Base Case Definition: Calibrated Flow and Calibrated Transport Modeling; Single Uyer Aquifer; unconsolidated-
RI/FS investigation and alternatives Identification only; no litigation or oversight or peer review-
single plume, single source; single contaminant, conservative.
Page 2-26
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
When transient scenarios are performed, this will lead to a higher cost in the
simulation-of-scenarios step (Cost Element No. 5).
Transport Model: Likewise, the type of transport model also affects cost. For limited
modeling objectives, simple particle tracking to identify contaminant pathways or to
outline capture zones of extraction systems can be used, resulting in a slightly lower
modeling cost. This is also the case if the transport model is uncalibrated. Modeling
of multiple sources or multiple contaminants can lead to a significantly higher cost,
especially in the transport-model step (Cost Element No. 4) and in the simulation-
of-scenarios step (Cost Element No. 5).
In addition, although not represented in Figure 2.4-2, the purpose for which a
model application is developed impacts its cost. Model applications used for
enforcement purposes may have a significantly higher cost. Model applications
used for projects which require the applications to be externally peer reviewed may
have a higher cost.
Page 2-27
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
2.5 Summary
The execution of a properly calibrated numerical model may support a greater
understanding of site conditions, lead to the selection of the best remediation
alternative, and in the long run, decrease total costs by contributing to a more
effective remediation design. Such proper use of a model may also help EPA in cost
recovery efforts by enabling investigators to properly identify PRPs.
To support cost management of ground-water modeling applications, five
guidelines for cost control have been described. The guidelines are:
G Integrate ground-water models into the overall investigation and
remediation process.
G Plan for the iterative nature of ground-water model applications.
G Match the modeling objectives to management's decision objectives.
O Use modeling to guide and optimize data collection.
O Perform a cost review at major decision points in the model process.
To support the estimation of costs of numerical ground-water model
applications, the historical data presented in Table 2.3-1 may be referenced. There
usually is a relatively constant start-up cost and the ratio of modeling costs to total
engineering costs decreases as the engineering costs increase. The purpose of a
model application, of course, directly affects the cost. It should also be noted that the
cost of numerical modeling is generally lower than ten years ago due to the
availability of personal computer versions of the code, the decrease in the cost of
modeling software, and the increased capability of software to present modeling
results.
To support estimation of the various elements or phases of a numerical
ground-water model application, general ranges of percents of those elements are
provided. In addition, a "base case" model is described and the cost impact of factors
such as geology and large model area is provided.
Trie intention of this Section on Cost Guidelines for Ground-Water Model
Application is to promote not only the appropriate use of models within the
Agency's waste management programs, but also to provide references and
suggestions for better management of the costs of numerical ground-water
modeling.
Page 2-2B
-------
Section 2: Cost Guidelines for Ground-Water Model Applications
APPENDIX A
TWO EXAMPLES OF COMPLETED
GROUND-WATER MODELING COST DATA
QUESTIONNAIRES
Page 2-29
-------
Section 2; Cost Guidelines for Ground-Water Model Applications
GROUND-WATER MODELING COST DATA
PROJECT I - CASE STUDY 30 IN TABLE 2.3-1
I. TOTAL ENGINEERING COST
A. Total Cost of Project for All Phases of a Site (in which the model
application was used). $1.5 million
B. Total Cost of Project by Phase. N/A
II. MODEL APPLICATION COST
A. Total Cost of the Model Application (for all phases in which the model
was used). $80,000
B. Total Cost of the Model Application by Phase. N/A
III. PERCENTAGE OF MODEL COST ELEMENT TO MODEL APPLICATION
COST
A. Cost Element No. 1: Establish Modeling Objectives and Prepare a
Project Management Plan. 5%
B. Cost Element No. 2: Collect Existing Data and Set Up a Conceptual
Model. 15%
C. Cost Element No. 3: Select, Set Up, and Calibrate a Flow Model. 45%
D. Cost Element No. 4: Select, Set Up, and Calibrate a Transport Model.
No transport model was used for this project.
E. Cost Element No. 5: Simulate Scenarios. 25%
F. Cost Element No. 6: Present Results and Determine Overall
Effectiveness. 10%
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Section 2: Cost Guidelines for Ground-Water Model Applications
IV. ADDITIONAL DATA
A. Type of Project and Purpose of the Model Application.
The project supported (1) the collection of site characterization
information and (2) the design and construction of a groundwater
extraction/hydraulic barrier system for the remediation of groundwater
at a site located at a harbor. Involvement by the modeling contractor
began in December 1988 and continued through May 1990. Following
the development of a preliminary ground-water flow model for the
site, the modeling results guided the collection of additional
hydrogeologic data. The additional information led to the refinement
of the flow model calibration. Predictive scenarios simulated with the
model evaluated the effectiveness of remedial design alternatives
involving combinations of ground-water extraction wells, drains and
hydraulic barriers.
B. Brief Description of Groundwater Contamination Problem at the Site.
The contaminant of concern at the site was hexavalent chromium.
C. Major Geologic Conditions at the Site Affecting the Model Application
Cost.
The model simulated groundwater flow in a multiaquifer system
consisting of unconsolidated sediment and bedrock material.
Discretization of these geologic materials required six model layers.
The flow model was calibrated in two steps. Following a preliminary
calibration of the model using available data, the model guided the
collection of additional hydraulic conductivity and water-level data in
the field. The results from the field testing provided new information
for the refinement of the model calibration.
D. Type of Model Used on the Project.
The U.S. Geological Survey (USGS) three-dimensional modular flow
model (MODFLOW) was used for the flow modeling. Particle-tracking
simulations were performed with MODPATH, also developed by the
USGS, for the purpose of evaluating groundwater flow directions.
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Section 2; Cost Qu/de//ne* for ground-Water Model Applications
E. Start Dates arid Completion Dates of Both the Model Application and
the Project.
The modeling began in December 1988 and continued through May
1990.
F. Benefits of the Model Application - Economic/Environmental
The modeling results provided the client with a quantitative decision-
making tool that evaluated the effectiveness of various remedial
alternatives costing millions of dollars. The model predicted that a
suitable hydraulic barrier system placed around the perimeter of the
site would require very low pumping rates to maintain a specified
inward hydraulic gradient across the barrier. The pumping rate
significantly affected long-term treatment costs for the system.
G. Technical Information about the Model.
1. Modeled Area (in square miles). 0.18 square miles
2. Number of Nodes and Layers. 3456 nodes and 6 layers
3. Flow Model.
a. Calibrated - yes/no? Yes
b. Steady-state and/or transient calibration? Steady-state
c. Steady-state and/or transient scenarios? Steady-state
4. Transport Model. N/A
H. Other Miscellaneous Information
1. Area of the Country (e.g., midwestern, northeastern, etc.).
Mid-Atlantic
2. Shortcomings and Limitations of the Model Application.
None. The modeling met the objectives of the study.
3. Peer Review.
The EPA reviewed the model application.
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Sect/on 2: Cost Guidelines for Ground-Water Model Applications
4. Tandem Model.
No tandem modeling of the site was performed. That is,
the PRP did not conduct an independent modeling
exercise concurrently ("in tandem") with EPA's modeling
as a means of checking the agency's conclusions.
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Section 2s Cost Guidelines for Ground-Water Model Applications
GROUNDWATER MODELING COST DATA
PROJECT II - CASE STUDY 28 IN TABLE 2.3-1
I. TOTAL ENGINEERING COST
A. Total Cost of Project for All Phases of a Site (in which the model
application was used). $1 million
B. Total Cost of Project by Phase. N/A
II. MODEL APPLICATION COST
A. Total Cost of the Model Application (for all phases in which the model
was used). $60,000
B. Total Cost of the Model Application by Phase. N/A
III. PERCENTAGE OF MODEL COST ELEMENT TO MODEL APPLICATION
COST
A. Cost Element No. 1: Establish Modeling Objectives and Prepare a
Project Management Plan. Modeling objectives and management plan
developed during scoping.
B. Cost Element No. 2: Collect Existing Data and Set Up a Conceptual
Model. 10%
C. Cost Element No. 3: Select, Set Up, and Calibrate a Flow Model. 25%
D. Cost Element No. 4: Select, Set Up, and Calibrate a Transport Model.
15%
E. Cost Element No. 5: Simulate Scenarios. 25%
F. Cost Element No. 6: Present Results and Determine Overall
Effectiveness. 25%
IV. ADDITIONAL DATA
A. Type of Project and Purpose of the Model Application.
The project was performed to assess the performance of an asphalt cap
to control leaching through stabilized contaminated material.
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Section 2: Cost Guidelines for Ground-Water Model Applications
B. Brief Description of Groundwater Contamination Problem at the Site.
Groundwater contaminated with PAHs, PCBs, lead and benzene.
C. Major Geologic Conditions at the Site Affecting the Model Application
Cost.
Site has surficial aquifer controlled by local waterbodies. Some contact
with underlying regional aquifer.
D. Type of Model Used on the Project.
The Corps model, HELP, was used to estimate infiltration rates through
the asphalt cap. The USGS groundwater flow model, MODFLOW, was
used to develop steady-state flows in the aquifer systems underlying
the site. The USGS model, MOC, was used to simulate contaminant
transport and to estimate solute diffusion at the site boundary.
E. Start Dates and Completion Dates of Both the Model Application and
the Project.
12/90 to 4/91.
F. Benefits of the Model Application - Economic/Environmental
The model study demonstrated that a properly designed cap would
contain the underlying contaminated material within the site
boundaries. The study was used to help establish cap performance
criteria.
G. Technical Information about the Model.
1. Modeled Area (in square miles). 0.4 square miles
2. Number of Nodes and Layers. 700 nodes and 3 layers
3. Flow Model
a. Calibrated - yes/no? Yes
b. Steady-state and/or transient calibration? Steady-state
c. Steady-state and/or transient scenarios? Steady-state
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Section 2s Cost Guidelines for Ground-Water Model Applications
4. Transport Model.
a. Practice Tracking or Advection/Dispersion Model? MOC
b. Fate Model? None
c. Calibrated Transport - yes/no? Yes
H. Other Miscellaneous Information
1. Area of the Country (e.g., midwestern, northeastern, etc.).
Northwest
2. Shortcomings and Limitations of the Model Application.
Poor linkage between flow and transport models.
3. Peer Review.
Internal by client.
4. Tandem Model.
None. The PRP did not conduct an independent
modeling exercise concurrently ("in tandem") with EPA's
modeling as a means of checking the agency's
conclusions.
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9octlon 3: iiodol Appllcmtlont Introduction
3.0
Model Applications
Introduction
This section provides summary descriptions of the model applications,
some of which were developed to test the original Assessment Framework.
These descriptions are presented to help the reader understand the variety of
model applications that the Framework was tested against. These
descriptions are not intended to be examples of the application of the
Framework but simply summaries of the test cases. Each description
discusses the:
O Decision objective;
O Regulatory context;
O Site characteristics (e.g., geology, ground-water contamination);
O Modeling activities and results;
O Interesting features of the application; and
O Names of EPA staff to contact for more details about the test case.
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Sect/oil 3; Model Applications Introduction
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3.1 - Summary Description #1
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Section 3: Model Applications Summary Description #1
3.1
Model Applications
Summary Description #1
Decision Objective:
This RCRA site was modeled to determine if the effects of a hydraulic barrier
and hydraulic head maintenance system would meet hydraulic gradient
performance standards set forth in a Consent Decree. This was an enforcement lead
site where contractors for the responsible party performed the modeling. The
Region reviewed the modeling effort and results to ensure that the site was
modeled as accurately as possible and that the model results indicated that the
proposed corrective action would meet the Consent Decree performance standards.
Background:
The site is located in an area of industrial, commercial and warehousing
operations on a peninsula in Baltimore Harbor. A significant portion of the
perimeter of the site abuts the harbor. Chromium ore was processed at the site from
1845 to 1985. This was a waste intensive operation that generated large quantities of
process residuals containing soluble chromium. Historically, these process residuals
were used as fill material at the plant site and in other areas around Baltimore
Harbor. (See Figure 3.1-1.)
The contamination of soil and ground water with elevated levels of chromium
creates the potential for human and environmental exposure. The risk of such
exposure, although small, will potentially exist as long as the site remains
uncontrolled. To minimize this risk of exposure, a combination of a low
permeability cap, a hydraulic barrier and ground-water extraction wells was
proposed as a containment strategy.
Remedial investigation and subsequent ground-water modeling of this site
began in October 1985, with further site investigations occurring through 1989 as
potential remedial actions were evaluated and the ground-water model was refined.
The ground-water modeling that is the focus of this case study began with the
refinement of the prior model to increase modeling accuracy. This work was
performed in 1989 and 1990.
Geologic Summary:
The site is located within the Coastal Plain Physiographic Province, an area that
is characterized by an unconsolidated sediment wedge that thickens toward the
Atlantic coast. In the vicinity of the site, coastal plain sediments are on the order of
70 ft thick. This site is underlain by artificial fills, recent organic silty clay deposited
in the harbor, Pleistocene sediments, lower Cretaceous sediments and bedrock.
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Section 3: Model Applications Summary Description #1
The deepest geologic unit investigated consists of gneiss bedrock which is
composed of three distinct strata. The lowest stratum is weathered rock composed
of fine to medium grained gneiss that is often broken and fractured. Overlaying this
lowest stratum is a second stratum with an average thickness of eighteen feet. This
stratum consists of fine to coarse sand within a white clay-silt matrix that includes a
high feldspar content and a fine to coarse sand containing trace to some silt with a
high biotite content. The upper bedrock stratum consists of clayey fine to coarse
sand and has an average thickness of ten feet.
Overlaying the bedrock are Lower Cretaceous sediments which vary in
thickness from 12 to 40 feet. These sediments range from a silty white sand to white
sand and gravel to a white clayey silt. Blanketing the Lower Cretaceous sediments
are Pleistocene deposits composed of silty clay, sand, gravel and cobbles which range
from 5 to 15 feet in thickness. Above the Pleistocene deposits black organic silty
clays and silty fine sand are found along the bulkhead margins of the site. The
organic silty clays have an average thickness of 20 feet and the silty fine sand varies
between 5 and 10 feet in thickness.
The fill materials, which created the level surface on which the site facilities
were built, consist of silty sands, micaceous sandy silts and poorly to well graded
sands as well as construction debris, bricks and wood fragments. The fill material
occurs at every location across the site and can be as much as 30 feet thick.
Ground-Water Contamination Summary:
The chromium contamination at the site was found to be present in two
ground-water yielding layers, one shallow, a water table aquifer, and one deep, a
regional aquifer system. The shallow ground water, which lies principally above the
low permeability silts near the site perimeter, flows radially off the site through the
bulkheads to the north, west and south. The shallow ground-water contamination,
which occurs chiefly near major source areas was found to have chromium levels
from 0.01 mg/L to 14,500 mg/L.
Deep ground-water contamination within the Cretaceous sands was also
highest near the source areas. Regionally, flow in the deep ground water originates
from the northwest of the site and flows towards the southeast. Locally, the deep
ground water flows radially away from the central portion of the site, with localized
small upward and downward flow gradients between the deep and shallow ground
water.
Modeling Summary:
The U. S. Geological Survey's three dimensional flow code, MODFLOW, was
used to model this site in a steady state. Six model layers, each of which was
constructed with variable thicknesses and bottom elevations, were used to simulate
the flow of ground water under the site. A 24 row by 24 column finite-difference
grid was constructed. (See Figure 3.1-2.) Grid cell dimensions varied between 75 and
Page 3-4
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Section 3: Model Applications Summary Description #1
150 feet with the smallest cells located directly over the study site. Boundary
conditions modeled included the flow directions and gradients of the water table
and regional aquifer systems, leakage from the harbor and precipitation recharge.
Horizontal hydraulic conductivity was determined for each layer by averaging
hydraulic conductivities from field tests. Vertical hydraulic conductivities were
initially assumed to equal the horizontal hydraulic conductivities and were adjusted
during calibration of the model.
During the calibration of the model, water levels in the observation wells were
used as targets and compared to simulated water levels. The hydraulic parameters
were adjusted to provide the best possible match between measured and calculated
heads at the calibration targets. Residual analysis was used to measure the
effectiveness of the calibration. The residual sum of squares was equal to 32.6 ft2 and
the residual mean was 0.0053 ft.
Additional field testing was performed to refine the calibration of the model.
Aquifer tests were used to improve hydraulic conductivity estimates. Additional
piezometers were also installed to better understand hydraulic gradients. The
model was then recalibrated with these new data.
Three hydraulic barrier scenarios were evaluated through model simulations.
All scenarios assumed site closure with the emplacement of a low-permeability cap
over the entire site. The first scenario simulated a "deep soil mixing" wall that
extended one foot into the uppermost stratum of the bedrock, a clayey fine to coarse
sand. This scenario was modeled in combination with ground-water extraction
wells and with perimeter trench drains placed at different depths.
The second scenario simulated a shallow slurry wall that extended two feet into
the clayey silt stratum of the Lower Cretaceous sediments. This scenario was
modeled in combination with alternative configurations of ground-water extraction
wells and with perimeter trench drains placed at different depths.
The third scenario simulated only ground-water extraction wells on the site.
Modeling Results Summary:
Model simulations of the first scenario indicated that the use of a deep
hydraulic barrier without pumping or trench drains would not meet the head
difference performance standards of the Consent Decree. However, the use of 12
extraction wells pumping a total of 2100 gal/day in combination with the wall
would meet these performance standards. The model simulations also indicated
that perimeter drains in combination with the deep hydraulic barrier would meet
the performance standards. When drains were placed at -0.5 ft msl. and 0.0 ft msl.
the model simulations indicated that 13,500 gal/day and 3,500 gal/day of ground-
water extraction would occur respectively.
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Section 3; Model Applications Summary Description #1
Model simulations of the second scenario indicated that the shallow hydraulic
barrier without pumping or drains would not meet the head difference performance
standards of the Consent Decree. Moreover, the modeling indicated that the use of
the shallow hydraulic barrier instead of the deep hydraulic barrier would require
significantly increased ground-water extraction. If twelve extraction wells were used
a total pumpage of 27,500 gal/day would be needed. If only eight wells were used,
the pumpage requirements would increase to 28,000 gal/day. If perimeter trench
drains were used in lieu of wells the ground-water extraction rate would vary
between 17,440 arid 13,500 gal/day depending on the elevation of the drains.
Model simulations of the third scenario indicated that the head difference
performance standards of the Consent Decree could be met by pumping alone with
no hydraulic barrier. The total pumpage, however, required to meet the
performance standard would be 92,580 gal/day distributed over twelve extraction
wells.
In summary, model simulations indicated that the Consent Decree hydraulic
head difference performance standards could be met by each of the three modeling
scenarios. The first scenario, a deep wall and pumping resulted in minimum
extraction rates. Pumping wells alone were able to meet the performance standards;
however, in the absence of a hydraulic barrier, the amount of pumpage necessary to
maintain the performance standards was more than an order of magnitude greater
than that of the first scenario.
Strengths And Interesting Fpatiires Of This Application:
In this case study, an existing model of a site was refined and recalibrated. The
refinement of the model reflected the need for increased simulation accuracy as the
regulatory process moved from site characterization, to technology screening, to the
design of a specific containment technology and management strategy.
This modeling application was used to predict the performance of alternative
corrective actions and the impact of those alternatives upon the hydrogeologic
system. It should be noted that the quantity and quality of site field data in this case
study are atypical of most sites. These data allowed the development of a model
with considerable hydrogeologic specificity.
This application provided the information necessary to justify the need for
both a slurry wall and ground-water pumping inside the wall. Originally the
responsible party had proposed just a slurry wall with no pumping. This study
demonstrated the problems with such an approach and the effectiveness of
combining the slurry wall with pumping. For example, this study dramatized that
required pumping rates varied by over an order of magnitude with and without the
slurry wall. Moreover, this study helped to determine the design capacity of a water
treatment system by determining the volume of ground-water extraction for each
scenario.
Pmgm 3-6
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Section 3: Model Applications Summary Description #i
This study demonstrated that the hydrogeologic system would be modified by
the proposed corrective action and provided a mechanism for predicting these
impacts. The Region noted that they will monitor the effectiveness of the selected
corrective action and if necessary the corrective action and/or the model application
will be modified as additional information is gained. This type of review, often
called a post audit, is strongly encouraged by ground-water modeling experts.
The calibration report provides an example of the use of residual analysis to
evaluate the model calibration.
Areas that should be covered in model calibration documentation include:
1. Explicitly establishing and documenting a reasonable range of
parameter values to be used in the calibration of the model;
2. Documenting the model residuals and the residual analysis;
3. Documenting the sensitivity of the model to variations in model
parameters;
4. Documenting the impact of grid spacing and time step on the
numerical accuracy of the model;
5. Documenting the criteria being used to terminate the calibration
process; and
6. Documenting the evaluation of the spatial and temporal distribution
of residuals.
Contacts:
For further information about this ground-water study please contact:
Joel Hennessy Region 3 Tel. # (215) 597-7584
Nancy Cichowicz Region 3 Tel. # (215) 597-8118
Modeling Documents:
Please contact the above people for specific modeling documents.
Page 3-7
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Section 3: Model Applications
Summary Description #1
Figure 3.1-1
Site Location
Page 3-8
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Section 3: Model Applications
Summary Description #1
Figure 3.1-2
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Page 3-9
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Section 3s Modal
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3.2 - Summary Description #2
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Section 3: Model Applications Summary Description #2
3.2
Model Applications
Summary Description #2
Decision Objective:
The United States Army's (Army) Aberdeen Proving Ground O-Field site was
modeled in the early phases of a site investigation to assist in screening corrective
actions for the site. Specifically, the objective of the modeling was to:
1. Provide a framework for the characterization of contaminant releases
and plumes;
2. Determine if contamination was migrating to other aquifers or
surrounding surface water bodies; and
3. Predict the probable hydrologic and chemical effects of relevant
remedial actions.
This modeling was performed as a requirement of a RCRA permit that EPA
issued to the U.S. Department of Army. In turn, the U.S. Army Environmental
Management Office of the Aberdeen Proving Ground contracted with the U. S.
Geological Survey (USGS) to conduct the modeling that is the focus of this case
study. The EPA Region reviewed the modeling results to ensure that the site was
modeled as accurately as possible and that the above decision objectives were met.
Background:
O-Field site is a 259 acre area located within the 79,000 acre Aberdeen Proving
Ground Army installation and is surrounded by Army testing ranges. O-Field lies
on a neck that extends into the Chesapeake Bay and is directly bordered on the west
by the Gunpowder River and on the north and east by a tributary of the Gunpowder
River, Watson Creek. (See Figures 3.2-1 and 3.2-2.) Watson Creek, which is better
described as a pond, discharges into the Gunpowder River through a man-made
culvert that restricts tidal flushing and therefore causes high organic loading in the
creek. To the south of O--Field lie other Army testing ranges. The site topography is
relatively flat with the highest elevation being about 19 feet above sea level.
O-Field includes two sub areas, Old O-Field and New O-Field. Old O-Field was
periodically used from the late 1930's into the 1950's for the disposal of munitions
and chemical-warfare agents. Disposal at New O-Field began in 1950 and continued
for an unspecified period. Disposal materials at New O-Field included ordnance,
contaminated material, laboratory quantities of chemical-warfare agents and dead
animals. The primary activity in later years at New O-Field was the destruction of
material by burning.
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At both New and Old O-Field, containerized and uncontainerized material was
disposed m unlined and uncovered trenches, pits and directly on the ground
Beginning in 1949, sporadic cleanup efforts were initiated with the goal of destroying
some of the explosives. Periodically during the cleanup operations explosions
ruptured container casings and directly exposed contaminants. Today, most of the
pits and trenches have been covered with soil.
In 1976, the Army recommended an assessment of the Aberdeen Proving
Ground to determine the potential for off-post migration of chemical contaminants.
Observation wells installed at O-Field in 1978 showed the presence of arsenic and
chlorinated organic solvents in the ground water. Analysis of surface water and soil
samples indicated that the ground water was transporting arsenic into Watson
Creek. A limited resampling of ground and surface water in 1984 confirmed these
findings.
An observation well network was developed in 1985 when eleven existing
wells were supplemented with 21 additional wells installed at eight locations All
well drilling was performed using a remote control drill, bombproof shelters and
other extraordinary safety and security procedures due to the possibility of
encountering buried ordnance or chemical-warfare agents. An additional five wells
were installed in 1987 when quarterly sampling indicated the possibility that
contaminants might be present beyond the area covered by the original observation
well network.
Geologic Summary;
O-Field is located on unconsolidated sand, clay and silt of the Atlantic Coastal
Plain Beneath the Coastal Plain sediments lies a basement complex of Precambrian
to Paleozoic crystalline rocks and Mesozoic rift-basin sedimentary rocks The depth
to the pre-Cretaceous basement rocks at O-Field is approximately 650 feet.
The site hydrogeology was investigated to only a 200 hundred foot depth
because of the difficulties associated with remote drilling operations and the
improbability that contamination had extended to this depth. Four aquifers were
discovered but only the upper three were investigated. These three consisted of a
water table aquifer and two confined aquifers with the lowest confined aquifer
occurring at a depth of 70 to 90 feet. (See Figure 3.2-3.)
The uppermost soils at O-Field are silt to silty lean clay and below this layer lies
a low permeability, tan to grey sand with some silt. Lenses of gray clay underlie the
sand followed by silty sand where the water table begins. Extensive excavation and
explosions have probably destroyed much of the natural strata of the site to a depth
of 10 to 12 feet. r
The water table aquifer lies 9 to 15 feet below ground surface with an average
saturated thickness of ten feet that varies seasonally by as much as three feet This
aquifer is present across the site and is composed of brown to reddish-brown quartz
Page 3-12
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Section 3: Model Applications Summary Description #2
sand interbedded with discontinuous silt and clay layers. The sand is medium
grained in the central areas of the site and becomes finer to the east and north and
coarser to the northeast. The water table aquifer is underlain by a confining layer
composed of highly plastic black to gray or greenish gray clay. The depth of this
confining layer is 11 to 30 feet below ground surface and ranges in thickness from 0.5
to 5 feet. The presence of contamination below this layer indicates that the
confining layer is either leaky or discontinuous.
The upper confined aquifer is below this confining layer. This aquifer lies 20 to
30 feet below the ground surface with a thickness that varies from 13 feet in the east
and south to less than a foot as it nears the Gunpowder River to the west. The
aquifer probably remains confined beneath the Watson Creek shoreline but loses its
confining bed beneath the deeper parts of the creek. This aquifer is composed of
dark grey to brown, medium to coarse-grained sand interbedded with gravel and
discontinuous clay lenses. This aquifer is underlain by a confining layer composed
of dense, black to dark grey clay. The depth of this confining layer is 20 to 39 feet
below ground surface and ranges in thickness from 43 to 60 feet. The extent,
thickness and low permeability of this confining bed are probably adequate to
prevent contaminant migration or significant water movement from the upper
confined aquifer to the lower confined aquifer.
The lower confined aquifer lies approximately 80 feet below ground surface and
is 10 to 20 feet thick. There is little information on the extent and lithology of this
aquifer. Downhole gamma, spontaneous-potential and resistance logs as well auger
behavior during drilling suggests that it is composed of a highly permeable, gravel
like material.
Ground-Water Hydrology Summary:
Water flow in the aquifers underlying this site is complex due to the surface-
water interactions and lagging tidal cycles in Watson Creek. Ground water in the
water-table and upper confined aquifer generally flows from south to
north/northeast towards Watson Creek. A ground-water divide that lies to the west
of Old O-Field causes a portion of the ground water to bypass Old O-Field and flow
into the Gunpowder River. (See Figure 3.2-4.) A gross estimate of the ground-water
flow rate is 50 feet/year.
The water-table aquifer derives most of its recharge from vertical infiltration of
precipitation. Additional recharge occurs by lateral movement of ground water as
discussed above and periodically by Watson Creek, which overflows its banks
during periods of high tides. Discharge is primarily to Watson Creek and the
Gunpowder River.
Recharge to the upper confined aquifer is by downward leakage from the
overlying water-table aquifer. Discharge is by slow upward leakage through the
confining bed to the water table aquifer in down gradient areas and by leakage to
surface water bodies where the confining bed has eroded.
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Section 3; Model Applications Summary Description #2
The hydraulic gradient indicates that the ground water in the lower confined
aquifer flows toward the west-northwest, possibly discharging into the Gunpowder
River. The heads in this aquifer are typically higher than those in the upper
confined aquifer. Thus, in the unlikely event that there are pathways for downward
contaminant migration between the upper and lower confined aquifers, the
hydraulic gradient would oppose all such flow except for the density driven
migration of free product.
Ground-Water And Surfarp Water Contamination Summary:
The ground water in both the water table and the upper confined aquifer at O-
Field contains inorganic and organic contaminants. Inorganic contaminants
include arsenic, iron, manganese, zinc, boron, antimony, cadmium and chloride.
For example, arsenic concentrations range from 1.96 parts per million (ppm) in the
water-table aquifer to 0.0016 ppm in the upper confined aquifer. Dominant organic
contaminants are chlorinated aliphatic hydrocarbons, aromatic hydrocarbons and
chemical-warfare degradation products which contain sulfur and phosphorus.
Concentrations of thiodiglycol, a degradation product, ranged from 1000 ppm to 5
ppm in the water-table aquifer. In general the highest contaminant concentrations
are measured in the water-table aquifer, although higher concentrations of boron
and 1,1,2,2-tetrachloroethane are present in the upper confined aquifer than in the
water-table aquifer. The arsenic and cadmium concentrations found exceed EPA
drinking water maximum contaminant levels. The concentrations of chloride,
iron, manganese and zinc exceed 1987 EPA secondary maximum contaminant'
levels.
The distribution of individual dissolved contaminants varies areally in the
water table and upper confined aquifer. For example, the concentrations of arsenic
and organic contaminants are highest along the northeastern side of Old O-Field.
However, iron is present as two distinct plumes, one along the eastern side and one
along the northeastern side of Old O-Field. The areal distribution of contaminants
at New O-Field could not be evaluated because of the limited number of wells at the
site.
Although low concentrations of organic contaminants have been detected in
water samples from the lower confined aquifer, hydraulic gradients and the
lithology and thickness of the overlying bed make it unlikely that O-Field
operations have contaminated the lower confined aquifer.
A surface water quality study in 1985 of Watson and nearby creeks found
unusually high organic loading in Watson Creek and dissolved inorganic
constituents that exceed EPA chronic toxicity levels for freshwater and saltwater
aquatic life. The lateral migration of ground-water contaminants into Watson
Creek is thought to be partially responsible for the surface water contamination.
Ultimately, this surface water contamination may migrate into the Gunpowder
River.
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Section 3: Model Applications Summaj
Modeling Summary;
The U. S. Geological Survey's (USGS) three dimensional flow code,
MODFLOW, was used to model this site in a quasi three dimensional, steady state
mode. Two model layers were used, one layer simulating the water-table aquifer
and the second layer simulating the underlying confining layer and the upper
confined aquifer. The lower boundary of the second layer coincides with the top of a
fifty foot thick layer of dense clay below the upper confined aquifer. The low
permeability and continuity of the clay was thought to justify its use as a no-flow
boundary for this model application and thus eliminated the need to model the
lower confined aquifer. The model was found to be relatively insensitive to this
assumption as discussed below.
A 66-row by 61-column finite-difference grid was constructed and aligned with
the principal direction of flow. The grid extends to the south and considerably
beyond O-Field to coincide with surface water bodies that could be modeled under
steady state conditions as constant head boundaries. Grid cell dimensions varied
between 20 and 2375 feet with the smallest cells located directly over the areas of
interest. Changes in cell size were limited to no more than 1.5 times the size of
adjacent cells.
Boundary conditions modeled included surface water bodies, no-flow regions,
drains, and leakage between the layers. Vertical hydraulic conductivities were based
upon typical values for similar soil types, limited field data and model calibration.
The water-table aquifer was bounded at most locations by constant head boundaries
which represented the shoreline of surface water bodies. At the two areas where the
water-table aquifer extended beyond the modeled area the ground-water flow was
parallel to the model boundaries and thus these areas were modeled as no-flow
boundaries.
The lateral boundaries of the upper confined aquifer were specified as no-flow
boundaries. However, a relatively high vertical hydraulic conductivity was
specified for those portions of the overlying confining layer that lay beneath surface
water bodies and thus these areas of the modeled layer responded almost as if they
had been established as constant head boundaries. Consequently, as the modeled
portion of the upper confined aquifer is almost entirely surrounded by surface water
bodies this layer was effectively modeled with constant head boundaries with one
exception. That exception was determined to be far enough from O-Field that the
no-flow boundary had negligible effects on simulations within O-Field.
Preliminary calibration of the steady-state model was achieved by setting
average annual recharge constant and adjusting model coefficients, primarily the
horizontal hydraulic conductivity of the water-table aquifer and the transmissivity
of the upper confined aquifer. These coefficients were adjusted within a range of
reasonable values based upon field measurements. The calibration was considered
acceptable if the simulated and observed average annual heads agreed within 0.5
feet. The model was then recalibrated against observed head data for a period of
Page 3-15
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Summary Description #2
elevated ground-water levels. During this second calibration the horizontal
hydraulic conductivity and transmissivity values obtained from the first calibration
were held constant and recharge was uniformly increased until the predicted heads
acceptably matched the observed heads Horizontal hydraulic conductivity and
transmissivity were then adjusted slightly to improve the match. These new values
were then used to once again calibrate the model against the average annual
observed heads. This process was repeated until the model met the calibration
criteria under both hydrologic scenarios.
Because of uncertainties about the actual recharge and hydraulic conductivities
at O-Field, several alternative solutions to the steady state model were then
generated by varying both recharge and hydraulic conductivity. Based upon
recharge estimates and field measurements of horizontal hydraulic conductivity,
the recharge was varied between 9 and 16 inches per year and the hydraulic
conductivity was uniformly adjusted by the same percentage. The resulting head
configurations still closely matched the observed heads. These alternative
hydrogeologic system representations were used to model the system responses to
the remedial alternatives evaluated also. Thus, the impact of hydrogeologic
uncertainty upon the results of the remedial alternatives modeled could be
quantified.
A sensitivity analysis of the calibrated flow model was performed for a range of
recharge, hydraulic conductivity and transmissivity values. This analysis indicated
that heads in the water-table aquifer were relatively insensitive to variations in the
vertical hydraulic conductivity of the confining layer or transmissivity of the
confined aquifer. Heads in the confined aquifer were somewhat more sensitive to
these variations. The sensitivity analysis also indicated that simulated heads in
both aquifers were very sensitive to changes in the horizontal hydraulic
conductivity and recharge of the water-table aquifer.
The assumption that the lower confined aquifer did not need to be modeled
was also examined during the sensitivity analysis. Simulations of a modified
version of the model that included the lower confined aquifer as a third layer
demonstrated that significant head variations in the lower confined aquifer had a
minimal impact on the head in the upper two aquifers. This confirmed that
simulation of the ground-water system as a two layer system was adequate for the
purposes of this modeling effort.
Five remedial actions and a sixth no-action scenario were evaluated. These
remedial actions were evaluated on the basis of their ability to lower ground-water
levels within the disposal areas and to limit lateral or vertical movement of water
through the disposal areas. The remedial actions evaluated included: installation of
an impermeable cap; installation of subsurface barriers; installation of a ground-
water drain; ground-water pumping to control water levels; ground-water pumping
to recover contaminants; and no action. All remedial actions were also simulated
Page 3-16
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Section 3: Model Applications Summary Description #2
with the alternative model configurations described above to quantify the impact of
hydrogeologic uncertainty upon each remedial alternative's predicted effectiveness.
The impermeable cap remedial alternative was simulated by establishing areas
of no ground-water recharge. The subsurface hydraulic barriers were simulated by
reducing horizontal hydraulic conductances in the model cells representing the
barriers. These conductances were calculated to represent a 5 foot thick barrier with
a horizontal hydraulic conductivity of 0.001 feet per day and accounted for the fact
that the barriers did not comprise the entire cell. The ground-water drain was
simulated by lowering the surface elevation of an existing natural drain to 1.5 feet
above sea level during the period of record.
Ground-water pumping to control water levels was simulated with the
addition of three pumping wells upgradient from Old O-Field and two wells
upgradient from New O-Field. Each of these wells were simulated at pumping rates
of 2,900, 5,800,10,000 and 21,600 gallons per day (gal/d) but Old O-Field and New Old
Field wells were simulated separately. The pumping was simulated with and
without impermeable covers. Similarly, ground-water pumping to recover
contaminants (pump-and-treat) was simulated with the addition of two wells
adjacent to the southeastern side of Old O-Field and two wells adjacent to the
northeastern side of New O-Field. Again, each of these wells was pumped at rates of
2,900, 5,800,10,000 and 21,600 gal/d; Old O-Field and New O-Field wells were
simulated separately; and the pumping was simulated with and without
impermeable covers on the respective disposal areas.
Modeling Results Summary:
The simulations indicated that covering Old O-Field with an impermeable cap
would lower water levels beneath the site by less than 1 foot. An impermeable cap
over New O-Field would be even less effective and reduce water levels by only 0.3
feet. Ground-water velocities appear to be sufficient to compensate for the loss of
recharge water intercepted by the caps. However, the reduction of precipitation
infiltration into the unsaturated zone at the fill could decrease the amount of
contaminant leaching.
Subsurface hydraulic barriers upgradient from Old O-Field resulted in water
level declines below Old O-Field of about 1 foot but produced increases in water
levels at New O-Field. Thus while potentially reducing contaminant leaching at
Old O-Field the barriers may also increase leaching at New O-Field. Complete
encapsulation of Old O-Field with hydraulic barriers and an impermeable cap was
also simulated and was shown to provide short term aquifer protection. However,
the concentrations of some contaminants would likely increase in solution and
should the encapsulating walls fail at some future point, the concentrations of some
contaminants in the ground water would then increase.
The simulation of subsurface barriers at the New Old-Field reduced water
levels at the disposal trenches by 2.5 feet but increased water levels by 2 feet on the
Page 3-17
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upgradient side. These reductions increased to 3.5 to 4.5 feet with the addition of an
impermeable cap.
The simulation of deepening an existing natural drain lowered water levels in
the water table aquifer beneath both Old and New O-Field. In turn, a ground-water
divide developed between the drain and Old O-Field and contaminant movement
rrom Old O-Field towards the drain probably would not occur. However during
periods of low ground-water levels or high surface water levels, brackish'surf ace
water would enter the drain and recharge parts of the water-table aquifer with
brackish surface water.
Pumping to manage water levels at Old O-Field indicated that the water-table
aquifer would be drawn down by 0.7 to 1.0 feet when the wells were pumped at 5800
gal/d per well. When an impermeable cap was added the drawdown increased by
0.5 feet. However, some simulations within the range of hydrogeologic uncertainty
demonstrated that a pumping rate of 5800 gal/d per well or more could induce
contaminants to migrate to previously uncontaminated areas.
Pumping rates of 10,000 and 21,600 gal/d per well were required at New O-Field
to reduce ground-water levels by 1.0 and 2.3 to 3.5 feet respectively. However both
rates would produce hydraulic gradient reversals extending to the disposal trenches
and thus induce the movement of contaminants toward the wells.
The simulations predicted that pump-and-treat at a rate of 2900 gal/d per well
in combination with an impermeable cap would intercept the bulk of ground-water
contamination at Old O-Field in the spring, summer and fall. This rate would have
to be increased to 5800 gal/d in the winter when ground-water levels are higher
However, this higher rate could induce the movement of water from Watson Creek
into the aquifer if it is maintained throughout the year. Pump-and-treat at New O-
Field resulted in drawdowns of 1.1 to 1.8 feet for pumpage of 5800 gal/d and 2 2 to 3 5
feet for pumpage of 10,000 gal/d. As little is known about the extent of
contamination under New O-Field, no conclusions could be drawn as to whether
this would intercept the bulk of the contamination. New O-Field simulations at
these rates did not show inducement of infiltration of creek water but the proximity
of the hydraulic grade reversal to the creek implies that infiltration would probably
be induced if a 5800 gal/d per well pumping rate was maintained during dry
summer months.
If no remedial actions are taken at O-Field, the simulations indicated that
mobilization and transport of organic and inorganic contaminants will continue
primarily because the seasonal and recharge induced water levels rise above the base
of the buried contamination. The ground water contaminants, in turn will
continue to discharge to Watson Creek. If the contaminants in the creek attain
sufficient concentrations, then the depletion mechanisms in the creek may be
inadequate to prevent contaminant migration from the creek into the Gunpowder
River. r
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Section 3: Model Applications Summary Description #2
Strengths And Interesting Features Of This Study:
In this case study, a model was applied in the early phases of a site investigation
to assist in characterizing the contaminant releases and plumes, the future
migration of contaminants and to explore and screen potential remedial
alternatives. Because of the hazards associated with sampling at this site, only
limited hydrogeologic data was available when the modeling began. Perturbations
in the ground-water system caused by tidal induced changes in the elevations of the
surrounding surface water bodies further complicated the modeling. Nevertheless,
data acquired after this modeling was completed confirmed the general flow field
and the surface water and ground-water interactions predicted by the model.
A major effort was made to ensure that the model application would accurately
predict the system response during both the average and the extreme hydrogeologic
conditions found at the site. Specifically, the model was calibrated against two
different sets of observed conditions; one representing average annual head
observations, the other representing a period of time when significantly higher than
average heads were observed. The calibration continued until the model
application accurately predicted system response under both sets of conditions.
This modeling effort quantified the impact of the hydrogeologic uncertainty
upon the results of the simulations. Alternative solutions to the steady state model
application were developed by increasing and decreasing recharge and horizontal
hydraulic conductivity within ranges defined by field measurements and
professional judgement. These alternative solutions closely matched the observed
heads, and therefore, were judged to bound the set of reasonable representations of
the ground-water system. In turn, these alternative representations of the system
were used to bracket the range of system responses to the remedial alternatives
evaluated.
An analysis of the sensitivity of the calibrated model application to changes in
hydrogeologic parameters was also performed. As a part of this analysis the
sensitivity of the model predictions to modeling the site as a two layer system was
investigated. The sensitivity analysis indicated that the two-layer representation
was sufficient for the purposes of the study.
The model application provided the EPA Region with the framework for
selecting the most appropriate remedial alternative. It provided guidance in
determining the goals and objectives of the remediation effort. Based upon the
results of the modeling described in this case study, ground-water extraction was
selected as the preferred remedial action. The model application was subsequently
used to evaluate alternative extraction systems.
Contacts:
For further information about this ground-water study please contact:
Page 3-19
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Section 3: Model Applications
Steven Hirsh
Nancy Cichowicz
Cindy Powels
Region 3
Region 3
Aberdeen
Proving Ground
Summary Description #2
Tel.# (215)597-0549
Tel.tf (215)597-8118
Tel. # (410) 671-4429
Modeling Dnrnmpntc-
Please contact the above people for specific modeling documents.
-------
Section 3s Model Applications
Summary Doscrlotlon
Figure 3.2-1
Site Location
PENNSYLVANIA
39°25
76°15'
\Edgewood
/ / PROVING AGROUND
Base from U.S. Geological Survey. 1:100.000
0123 KILOMETERS
Page 3-21
-------
39 20' «S
39 20' 30" -
3*'20' IS
Figure 3.2-2
Detailed Site Location
EXPLANATION
OF1
9 Observation-well samping site and identification
number n O-Field.
OM7
e Observation-we! cluster site and identification
number in O-Field.
Abandoned supply wef in H-FieM
Topographic contour. Interval is 6 feel. Datum
« sea level
WATSON
CREEK
0 100 «00 (00 ICO *(
\ttfff Y
0 «0 HO KO 2*0 M«i«rf
Page 3-22
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Section 3: Model Applications
Summary Description #2
Figure 3.2-3
Sample Hydrogeologic Sections
S"« OFe
(Allllud* U ».7
Sll« On 7 Sll« OF21 SIU OF20
(Altitude ! 0.2 F««|) (Altltud* l> «.2 (AltltuU* ! S.«
F««t)
o ?0 «y
o 10 ?o MCTtns
Lower conlin«d aquifer
HYDROGEOLOGIC SECTION A-A'
Vertical E«agg«ranon x 4
B
FEET
30
B'
5II« OFtS Old O-Fl«ld Sit* OF« Sit* OF 12
(Altltud* ! 15 7 F««t) (AltlttMt* ! t.7 F*«t) (Altltud* to
HYDROGEOLOGIC SECTION B-B
, Vertical Ex«09«rat«on X 10
Page 3-23
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Section 3: Model Application*
Summary Description #2
Figure 3.2-4
Site Water-Table Contours
TS'H
WATSOH
CHECK
TOPCXaRATMC OONTOUB«ho«M mud* of tand
Co*«ourlntorMl It S iMt Ottum b
Page 3-24
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3.3 - Summary Description #3
-------
-------
Section 3: Model Applications
3.3
Model Applications
Summary Description #3
Decision Objective:
This fund-lead site was modeled during the Remedial Design (RD) to ensure an
appropriate design while minimizing design costs. Specifically, additional
information on the ground-water flow and contaminant fate and transport was
required to design a ground-water extraction and collection system that had been
specified in the Record of Decision (ROD). The EPA contractor proposed additional
field investigations including an extensive drilling program to obtain the needed
design information. EPA suggested that much of the required information could be
obtained through the use of ground-water modeling, thus significantly reducing
design costs. The contractor agreed to the modeling effort and specific modeling
objectives were established. These objectives were to:
1. Delineate the maximum possible extent of the contaminant plume in
January 1993, when the pump and treat system is scheduled to begin
operation;
2. Estimate the mass of contamination per unit volume of the aquifer;
3. Conceptualize extraction well alignment designs; and
4. Evaluate the design alternatives.
An EPA contractor working under an Alternative Remediation Contracting
System contract did the modeling that is the subject of this case study. The EPA
project manager reviewed the modeling work.
Background:
This is a six acre site located in a 250 home residential area with homes within
100 feet of the site. (See Figure 3.3-1.) Other land use in the area includes some
commercial development along a state highway southeast of the site and
agricultural activities southeast of the same highway. The site is an inactive
manufacturing facility and is currently used for minor non-production activities
primarily warehousing. Located on the site are process, office and warehouse
buildings. (See Figure 3.3-2.) A tank farm and a laboratory have been removed
from the site. The site topography is relatively flat but exhibits occasional low rises
and gentle depressions. The average annual precipitation is approximately 35
inches and the mean monthly temperatures range from 26° F to 72° F.
This site was used to manufacture and repackage non-lubricating automotive
fluids from the early 1960s to 1978. During the facility's operation, a number of
releases and a major fire contributed to the site contamination. Undocumented
Page 3-25
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Section 3:
releases of chlorinated hydrocarbons into the vadose zone occurred south of the
process buildings. Documented releases of diethyl ether occurred in 1972 when an
underground pipeline was ruptured during excavation. Chlorinated organics,
benzene and other solvents were released during a two day fire in 1978. During this
fire numerous tanks and drums ruptured and their contents were spread onto
unpaved areas by the water used to fight the fire. The unsaturated zone soil was
thought to be the primary remaining source of contamination at the site.
History of Investigation
The owner of the site installed six on-site monitoring wells in 1972.
Contaminant levels detected in these wells and nearby residential wells indicated
that the contamination was moving off-site. Consequently, under an agreement
with the state agency responsible for environmental protection, the owner began
supplying bottled water to homes with contaminated wells in 1973. After the 1978
fire, the owner began removing underground tanks. Then in 1980, 15 more
monitoring wells were installed at 9 locations. In 1982, the state agency initiated
legal actions against the site owner to force site remediation. The following year the
owner began operating a ground-water treatment system.
The site was placed on the National Priorities list (NPL) in 1984 and at that time
EPA assumed the lead enforcement role. In 1985, the owner agreed to fund a
remedial investigation and feasibility study (RI/FS) under an Administrative Order
of Consent. The completion of that study was funded by EPA when the owner filed
for bankruptcy in 1986. The state, in 1986, extended a public water supply to the
residents in the area near the site. In 1988, the ground-water treatment system was
closed down by the site owner due to financial problems.
In 1988, the Record of Decision (ROD) was issued. The ROD specified soil and
ground-water remediation including a contaminated soil flushing system, a ground-
water extraction arid collection system and a ground-water treatment (air stripping)
and discharge system. The ROD further specified that the aquifer within the 1.5
parts per billion contaminant concentration isopleth would have to be restored to
drinking water standards.
Geologic Summary:
This site is located in an area dominated by glacial sediments deposited in a
northeast-southwest trending belt. The two major types of deposits are glacial
outwash with post glacial alluvium and ice-contact outwash deposits. Both types of
deposits contain fine sand to coarse gravel with occasional large cobbles and are very
poorly sorted. Sixteen borings made in the vicinity of this site indicate that the
glacial sediments extend to an average depth of 117 feet below the surface.
Underlying the site are clay, silty sand, sand and gravel facies which laterally
intergrade with one another and result in laterally discontinuous layers.
Page 3-26
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*nH Sc°i 3t 6 She C°nSist °f a 5 to 10 foot uP?er laygr of toe sand
and a lower 115 to 125 foot sand layer. (See Figures 3.3-3 and 3 3-4.) Underlying the
lower sand layer is a 20 to 25 foot clay layer and then a layer composed of sands and
gravel with occasional minor clay lenses. One boring on the eastern boundary of the
site indicated the presence of a five foot silty clay layer just below the upper fine
sand layer. This silty clay layer was presumed to be a very small localized lense as
no other borings showed evidence of this layer. A large clay lense, however, begins
jus east of the site 50 feet below the ground surface. This lense extends ove; 3000
feet to the west and rises to thirty feet below the surface. It reaches a maximum
thickness of 20 feet. Several small gravel beds where detected also in the lower parts
of the lower sand layer. F
Ground-Water Hydrology Summary:
The site hydrogeology is composed of three distinct hydrogeoloeic units The
uppermost unit is an unconfined aquifer that is encountered at approximately 30
feet below the ground surface with a saturated thickness of 70 to 90 feet in the site
area and increasing to a thickness of 135 feet just over a mile and a half to the west
This aquifer corresponds to the lower sand layer discussed previously. The second'
hydrologic unit, a confining layer of sandy clay that varies between 7 and 22 feet in
thickness near the site but thins to a two foot thickness a mile to the west, lies below
the aquifer. The third hydrogeologic unit, a confined aquifer, whose confined head
is approximately one and one half feet lower than the head of the upper aquifer lies
below this confining layer. This lower aquifer corresponds to the layer of sands and
gravel with occasional minor clay lenses discussed above. The thickness of this
confined aquifer is unknown as none of the borings reached bedrock.
The upper unconfined aquifer is no longer used as a drinking water supply in
the immediate site area because of contamination. Two miles to the west of the site
are three municipal wells which produce more than a million gallons per day from
this aquifer. The cone of depression caused by the operation of these wells may
eventually enhance the off-site movement of contaminated ground-water towards
the west. The direction of flow in this aquifer is generally west-southwest with a
velocity of approximately 0.5 feet per day. Both pump and slug test data were used
to estimate the hydraulic properties of this aquifer. The pump test data indicated an
average aquifer hydraulic conductivity and transmissivity of 0.0775 cm/sec and
148,000 gpd/ft, respectively, assuming an average aquifer thickness of 90 feet The
nfUn8n!f«SQ / mdiCa4tendonnnaVerage ****** hydraulic conductivity and transmissivity
of 0.0489 cm/sec, and 98,000 gpd/ft, respectively. y
The lower confined aquifer was not extensively studied for the purposes of
remediating this site because of: (1) the presence of the confining layer above the
aquifer, (2) prior sampling which indicated no presence of contamination in the
lower aquifer and (3) the relatively small difference in head between the two
aauifprs
aquifers.
Page 3-27
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Section 3s Model Applications Summary Description #3
Ground-Water Contamination Summary:
Eighteen contaminants were found at the site, with ten being selected as
indicator compounds. These included 1,1-DCE, 1,1-DCA, 1,1,1-TCA and Benzene.
The Remedial Investigation (RI) identified the unsaturated zone underlying two
areas of the site as the major sources of contamination. The RI also speculated that
there was potentially one other on-site source and several additional off-site sources
of contamination based upon the location and discontinuity of the contaminant
plume. This plume begins; beneath the site and extends west-southwest beyond the
site property boundaries. The plume may not be continuous within its boundaries
and the thickness of the plume diminishes as it extends off-site. The contaminated
zone reaches the bottom of the upper aquifer at the site and at a minimum extends
1500 feet downgradient.
The on-site ground-water contamination was being partially contained by two
purge wells that operated from 1983 to the spring of 1988. These wells had a
combined pumping rate of 200 gallons per minute which resulted in a maximum
drawdown of about one foot. When these wells were operating they apparently
contained the plume within the western and northern site boundaries. Since they
ceased operation, significant additional contaminant migration has occurred.
Modeling Summary:
Analytic and analytic/numeric models and graphical techniques were used to
investigate the site and to evaluate the effectiveness of ground-water extraction
alternatives. This approach was chosen after a review of project objectives, the
limited quantity and poor quality of the available field data, the modeling budget
and project time constraints.
The modeling was divided into three phases. The objective of the Phase One
modeling was to determine the maximum extent of contamination in the upper
aquifer. An analytical function driven variation of the fate and transport model
Random Walk and the analytic transport model PLUME were used in this phase.
The objective of the Phase Two modeling was to conceptualize remedial design
alternatives. Graphical Javandel type curve analysis procedures were used to
determine the minimum number of pumping wells, discharge rates and recovery
well locations under different pumping scenarios. Then time related zones of
capture for each alternative were determined using the the U.S. EPA Wellhead
Protection Area Model (WHPA). Finally, the aquifer drawdown resulting from each
alternative was simulated using the analytic ground-water flow model WELFLO.
The objective of the Phase Three modeling was to evaluate the most promising
remedial design alternatives. Again, Random Walk was used in this phase to: (1)
estimate the discharge rates, average concentration and mass of contaminants in the
extraction well discharge; (2) evaluate and compare the remedial alternatives and (3)
identify areas of uncertainty in design features. This case study will focus on the use
of the Random Walk model in phases one and three.
Page 3-28
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Plications Summary Description #3
The analytical function driven variation of the Random Walk model was
oTTbaS6d °n the advice °f an outside consultant, to verify the results of the
PLUME model. Random Walk was suggested because of the modeling objectives
data limitations and the outside consultant's detailed familiarity with the model'
This version of the Random Walk model utilizes an analytic function based upon
the Theis equation to generate the flow field. The numeric Random Walk model is
applied to simulate the fate and transport of the contaminants.
The simplifying assumptions associated with the analytic flow component of
the Random Walk model required that the aquifer be treated as homogeneous
isotropic and infinite in areal extent. Thus, no site-specific boundary conditions or
spatial variability in aquifer characteristics could be modeled. Moreover
unidirectional, steady state ground-water flow had to be assumed. The modeling
team established a uniform hydraulic conductivity, saturated thickness
transmissivity, hydraulic gradient and aquifer porosity for the modeled area based
upon information obtained from the RI report and field data.
For the Phase One modeling, three contaminants were originally selected- the
most toxic (1,1-DCE), the most mobile (1,1-DCA) and the most pervasive (1 1 1-TCA)
However, initial modeling efforts indicated that insufficient soil and ground-water
data were available to develop or calibrate contaminant transport models for 1,1-
DCE or 1,1-DCA. As 1,1,1-TCA had migrated and persisted farther downgradient
than the other contaminants the modeling team felt that focusing solely on 1,1,1-
TCA was valid and appropriately conservative.
The site conceptual model developed by the modeling team hypothesized that
the downgradient plume developed primarily through the dissolution of 1 1 1-TCA
retained in aquifer pores at residual saturation. This was in contrast to prior studies
of the site which suggested that the major contaminant source lay in the
unsaturated zone and was percolating into the saturated zone. Initially, the
modeling team had accepted this latter hypothesis and developed a batch flushing
model to simulate the migration of the contaminant into the saturated zone
However, when the results of the batch flushing model were compared with
observed phenomena, there were major discrepancies. For example, only 2 to 4
percent of the contamination in the aquifer could be accounted for under this
hypothesis.
After a careful review and some initial skepticism about the validity of the
batch flushing model results, the modeling team hypothesized that the source term
lay in the saturated zone. They searched peer reviewed ground-water literature for
examples of similar conceptual models and found three. Then, additional site
sampling including a soil gas survey was initiated. The results of this sampling
indicated very limited soil contamination, thus further supporting the new
hypothesis that the source term lay in the saturated zone.
The particle tracking component of the Random Walk model was then used to
model the 1,1,1-TCA dissolution from the 1,1,1-TCA mass stored at residual
Page 3-29
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Section 3: Model Applications Summary Description #3
saturation in the saturated zone. This included the rate of loading of 1,1,1-TCA
from the unsaturated zone? by percolation to the ground water, minus the mass
removal of 1,1,1-TCA from the ground-water system, during the historic operation
of the purge wells described previously. This approach resulted in a source term
that varied as a function of time and dropped to zero during the historical operation
of the purge wells. The longitudinal and transverse dispersivities, background
concentrations, and organic carbon partition coefficients utilized in the model were
based upon field data and established EPA methods. All ground-water
contamination was assumed to exist in the dissolved phase; and, consequently,
dense, nonaqueous phase liquid migration was not simulated. Biodegradation and
volatilization was also ignored.
The calibration of the Random Walk model was restricted to the contaminant
fate arid transport component. This version of Random Walk assumes a
unidirectional flow field which can not be directly calibrated against observed
piezometric heads. Field data from the RI report was used to establish the flow field
parameters. Calibration of the contaminant transport model was achieved by
adjusting the flow direction, flow velocity and dispersivity until predicted
concentration values matched observed concentrations. These modifications were
within reasonable parameter ranges and in the case of the flow direction were based
upon additional field data The source release term was held constant during the
calibration process.
The calibration of the model presented a number of challenges. First, the data
used to calibrate the model was obtained from prior studies conducted by the site
owner's contractors. A review of that data indicated numerous data quality
problems including transcription errors, false positive and false negative
indications, conflicting sampling dates and surface maps of conflicting scales.
Second, data from nested monitoring wells indicated the presence of a vertical
contaminant concentration gradient. However, the direction and magnitude of this
gradient varied inconsistently from one monitoring location to another.
The modeling team established a two-tier calibration target after analyzing
these constraints and the primary model objective, which was to predict the extent
of the contaminant plume at the beginning of operation of the extraction system.
For those wells where the field data indicated no contamination, the model would
have to indicate no contamination. For those wells where field data indicated
contamination, the model concentrations would have to be within one half an
order of magnitude of the measured values at that location. Furthermore, at nested
monitoring wells, the average of the measured values would be used for model
calibration. The model was then calibrated against three different sampling events
spanning an 8 year period utilizing field data from up to 19 wells.
Recognizing the limitations of the calibration data and in turn the calibration
process, the contractor initiated a new round of sampling at 23 monitoring wells
under stringent quality assurance procedures. This data was not available until the
calibration of the model had been completed. The modeling team, however, was
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Section 3: Model Applications Summary Description #3
able to use this data to verify the model calibration. The success of this verification
surprised the modeling team. With only one exception the model accurately
simulated all wells where no contamination was detected. At those wells where
field data indicated evidence of contamination, the residuals between the simulated
and observed values were much closer than the one half order of magnitude
calibration target used. Moreover, at the downgradient monitoring well that lay
directly on the center line of the plume, the measured and simulated concentration
value varied by only one part per billion.
Modeling Results Summary:
The Phase One modeling results indicated that the 1,1,1-TCA plume will have
migrated 625 meters downgradient and 225 meters laterally by 1993. This migration
has occurred in spite of the operation of two purge wells from 1983 to 1988. The
modeling team was careful to note that they were more confident of the delineation
of the plume boundary than the predicted concentrations within the plume because
of model and data limitations.
Based upon these results, 15 extraction well alternatives were developed in
Phase Two using Javandel type curve analysis, the GPTRAC module of the U.S. EPA
Well Head Protection Area Model (WHPA), and the analytic model WELFLO. This
analysis indicated that under ideal conditions only one extraction well discharging
at 100 gallons per minute would be required. However, recognizing the limitations
associated with the Phase One modeling and the models used in this second phase,
two additional alternatives utilizing three and five wells respectively were chosen
for further consideration in the Phase Three modeling. The location of the capture
zone of one alternative is shown in Figure 3.3-5.
The efficiency, flexibility and the mass of contaminants in the extraction well
discharges for these three alternative were then evaluated in Phase Three using the
Random Walk model. The efficiency of each alternative was defined as a function
of the pumping rate, the volume of water requiring treatment and the time required
to restore the ground water to clean-up goals. While the pumping rates for the
three alternatives were found to be very similar, the five well alternative was found
to meet the cleanup goals in one quarter the time of the other two alternatives. The
five well alternative, moreover, would significantly reduce the volume of water
requiring treatment.
The flexibility of each alternative was defined as the ability of the alternative to
operate efficiently when the actual aquifer response to the pumping varied
significantly from the response predicted by the modeling. In particular, the
modeling team was concerned about the possibility of unmodeled heterogeneity in
aquifer properties and the distribution of contaminant concentrations within the
plume. The five well alternative was again found to be the preferred alternative
because it allowed the operation of each of the five extraction wells to be tailored to
the specific characteristics of that part of the plume and aquifer within which the
well was located.
Page 3-31
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Section 3: Model
EPA has awarded a contract for the construction of the five well ground-water
extraction system developed as part of this modeling effort. This system is expected
to be in place in early 1993. A ground-water monitoring program has been proposed
which will allow the monitoring of the remediation progress and the ongoing
validation of this ground-water modeling application.
Strengths And Tntprpsting Futures Of This Study:
In this case study, a model was utilized as part of the remedial design process
The modeling was initiated at the suggestion of EPA in order to reduce the
magnitude and cost associated with additional site sampling. The model chosen
represented a compromise between the level of detail and accuracy desired by the
designers, the available data and the modeling budget. In fact, during the
development of the modeling objectives, the modeling team attempted to use both
a simple analytic and a finite difference contaminant transport model before
abandoning the former for its lack of specificity, and the latter because of the limited
site data available.
O'ne of the more interesting aspects of this case is that both EPA and the
contractor agreed that the modeling reduced the design costs by $450,000 Part of this
cost reduction was due to the use of the model to delineate the plume boundary in
lieu of locating the boundary by means of an extensive drilling program The other
part of the cost reduction occurred as a result of the modeling process which led to
the identification of an error in the source characterization.
Previously it had been hypothesized that the source lay in the unsaturated
^' '^sequently, soil Bushing had been specified as a remedial action in the
ROD. While trying to develop the source term for the model, the modeling team
began to question this hypothesis. Based upon the results of a batch flushing model
a search of peer-reviewed literature for similar cases, and additional field sampling '
the modeling team determined that the source term most probably lay in the
saturated zone. Thus, the need for the design and implementation of the soil
flushing system specified in the ROD was eliminated. This resulted in considerable
design cost savings and will result in considerable additional construction and
operational cost savings.
Another interesting aspect of this modeling was that the Phase One modeling
was actually performed twice using two different models. First the site was modeled
using PLUME. Then at the suggestion of an outside consultant the site was
remodeled using Random Walk. There was a high degree of correlation between
the model results. However, such correlation is not necessarily evidence that a site
was modeled properly. Rather it demonstrates that for this same conceptual model
these two models produce very similar results.
Both EPA and the contractor noted that this case is another example of how the
use of modeling early in the remedial investigation process could have improved
the entire remediation effort. Specifically, it was noted that a very simple analytic
Page 3-32
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Section 3; Model Applications Summary Description #3
model could have improved the sampling plan and monitoring well locations in
prior site studies. This in turn would have increased the possibility that a more
accurate numerical model could have been used during the design process, possibly
resulting in a more efficient design.
Contacts:
For further information about this ground-water study please contact:
Bob Whippo Region 5 Tel. # (312) 886-4759
Modeling Documents:
Please contact the above person for specific modeling documents.
Page 3-33
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Section 3: Model Application*
Summary Description #3
Figure 3.3-1
Site and Contaminant Plume Location
Pmgm 3-34
-------
Section 3: Model Applications
Summary Description #3
Figure 3.3-2
Detailed Site Location and Monitoring Wells
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Page 3-35
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Section 3: Model Application*
Summary Description #3
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Page 3-36
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Section 3: Model Applications
Summary Description #3
Figure 3.3-4
Location of Sample Hydrogeologic Section
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Page 3-37
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Section 3: Model Application*
Summary Description #3
Figure 3.3-5
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-------
3.4 - Summary Description #4
-------
-------
Section 3: Model Applications Summary Description #4
3.4
Model Applications
Summary Description #4
Decision Objective:
This enforcement lead site was modeled by EPA during the remedial design
(RD) to ensure an appropriate RD and remedial action (RA). Specifically,
information on the ground-water flow and contaminant fate and transport was
required to support RD and RA negotiations. As this was an enforcement lead site,
the objective of EPA in conducting this modeling was to gather sufficient
information to be able to review the responsible party's characterization of the
nature and extent of contamination at the site and the remedial design.
The modeling was deemed necessary because it was recognized in the Record of
Decision (ROD) that the design objectives and remedial action specified in the ROD
were based upon incomplete knowledge of both the sources and the actual extent of
the contamination and the contaminant plume. Consequently, EPA determined
that a limited modeling effort would assist in better understanding the site and the
effectiveness of the proposed pump and treat remedial design. In support of these
decision objectives the following four modeling objectives were established:
1. Identify potential off-site contaminant migration;
2. Examine the proposed pump and treat extraction well alignment;
3. Improve (if necessary) the extraction well alignment design; and
4. Determine the time required to clean the site.
The modeling that is the subject of this case study was performed by an EPA
contractor under a Technical Enforcement Support at Hazardous Waste Sites
contract. The modeling work was reviewed by both the EPA project manager and an
EPA hydrogeologist.
Background:
This site is comprised of 18 acres located in an industrial corridor adjacent to an
interstate in a major western metropolitan area. The site abuts a major railroad line
and is surrounded by other small industries. (See Figure 3.4-1.) Located on the site
are abandoned and active tank farms and a filled and abandoned sump. There is
also a capped evaporation pond, the contents of which are unknown. The site
topography is generally flat and low lying with a vacant swampy area to the south.
The nearest residential area is within a quarter mile of the site and the total
population within a one mile radius of the site is less than 5000.
Page 3-39
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'Operations at the site began in 1957 and included the production of herbicides
and pesticides; the production of sodium hypochlorite; refilling and distributing
chlorine and ammonia cylinders; and the packaging and distribution of acids,
caustics and organic solvents. Information related to the historical operations at the
site indicates that the uncontrolled release of contaminates may have begun in the
very first year of operation and may have continued through 1989. These releases
are believed to have been the result of both disposal practices and spills.
Examples of disposal practises that led to releases include: the use of unlined
settlement and evaporation ponds for process wastewater discharge; the discharge of
industrial and process waste materials to an on-site septic tank and drain field; and
the dumping of wastewater, pesticide and herbicide tank wash water on the ground
Examples of spills included a 4000 to 8000 gallon spill of muriatic acid that occurred
during the unloading of a rail tanker and a hydrochloric acid spill due to a tank
rupture. Sources of contamination include the former evaporation pond which was
filled with earthen materials and capped with concrete in 1980, a process drain
system and sump, settlement ponds (location unknown), a leach field, dioxin
removal wastes and contaminated soil.
History of Investigation
Beginning in 1980, the site was operated as a RCRA Interim Status Hazardous
Waste Storage Facility. Between 1983 and 1989, the owner/operator of the site was
cited for several violations by a state agency responsible for RCRA enforcement. In
1984, that agency advised the owner/operator of an alleged release from the property
to the environment and then initiated a Preliminary Assessment and a follow-up
Site Investigation. Additional field investigations were conducted by the state
agency between 1985 and 1987.
In 1986, CERCLA enforcement activities were initiated. This led to an
emergency action by EPA later that year to remove drums, cylinders and
contaminated material from the site. In 1987, EPA proposed that the site be placed
upon the National Priorities List. In 1988, the owner/operator agreed to undertake a
Remedial Investigation/Feasibility Study (RI/FS) which was completed in March
1990. In 1989, the owner/operator notified the relevant agencies of its intent to close
its RCRA Part A Interim Status Storage Facility. In 1990, additional site sampling
was initiated under EPA's "Make Sites Safe" initiative. This sampling found
evidence of high levels of dioxin on that part of the site where contaminated
materials had been removed as part of EPA's 1986 emergency action. Consequently,
actions to stabilize the contaminants on the site pending remediation were initiated.
In March 1991, the Record of Decision (ROD) was issued. In the ROD, EPA with
the concurrence of the state, specified soil and ground-water remediation measures
at the site but reserved the right to further modify the ground-water remedy because
the ground-water contamination had not been fully characterized. The ground-
water remedy specified consisted of a pump and treat system utilizing approximately
ten wells to capture and treat the contaminant plume. These wells were proposed to
Pago 3-40
-------
Section 3; Model Applications Summary Description #
be located along the northern and western boundaries of the site and to be operated
at an extraction rate of two gallons per minute.
Geologic Summary:
This site is located in a valley that was part of a Pleistocene great basin lake.
The surficial geology of the valley is the result of successive expansions and
contractions of that great basin lake and glacial surges and retreats. The valley
consists of alluvial deposits which overlie and merge with deep, unconsolidated
lacustrine sediments. The alluvial deposits typically consist of silt and sand in the
first several feet and mostly fine pebble gravel to a depth of 5 feet or more. These
deposits are of a deltaic type and are associated with the development of the valley
drainage network. The underlying lacustrine deposits consist of clay, silt, sand and
gravel facies that laterally intergrade with one another and result in laterally
discontinuous layers.
The uppermost soils at the site consist of a 2 to 6 foot layer of mixed fill
material and a 2 to 5 foot layer of clay to silty clay material beneath the fill material.
Underlying the clay material is a sand to clayey to silty sand layer that extends to a
depth of 15 to 18 feet and below this point a clayey layer begins. Two borings to
depths of 27 and 50 feet indicated that this clayey layer extends to at least a depth of
50 feet and exhibits interfingering (clay, silt and sand) characteristic of the general
geology of the valley. A fluvial paleochannel consisting of fine to coarse grained
sand appears to meander across the center of most of the site. The top of this
channel lies 7 to 9 feet below the surface of the site and the channel is approximatelv
61 <">/"« 1 L 1 J
to 8 feet deep.
Ground-Water Hydrology Summary:
There is some disagreement regarding the ground-water hydrology. Prior
studies by the responsible party's consultants indicated that the site hydrogeology is
consistent with the regional hydrogeology and is composed of three distinct
hydrogeologic units. These studies indicated that the uppermost unit is a shallow
unconfined aquifer that begins 3 to 5 feet beneath the site and extends to a depth of
15 to 18 feet. This aquifer corresponds to the sand to clayey to silty sand layer
discussed in the above paragraph. Below this shallow aquifer lies the second
hydrogeologic unit, a relatively impermeable confining layer which acts as a single
confining bed that ranges from approximately 40 to 100 feet in thickness. This unit
corresponds to the clayey layer described in the above paragraph. Below this
confining unit lies a confined aquifer that consists of Quaternary deposits of clay,
silt, sand and gravel. The maximum thickness of this aquifer is greater than 1000
feet.
The state agency responsible for environmental enforcement disagrees with the
concept that there are two completely distinct aquifers underneath the site. They
take the position that the second hydrologic unit is not truly impermeable as there
are interfingerings of sand and silt in the clay layer. Consequently, they believe that
Page 3-41
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Sect/on 3: Model Applications Summary Description #4
there is communication between the upper and lower hydrologic unit and all three
units should be considered as one aquifer with shallow and deep portions. The
modeling team did not feel it was necessary to resolve this discrepancy in the
conceptual model given EPA's decision objectives and the fact that the modeling
focused solely on the upper 13.5 feet of the shallow aquifer.
The shallow unconfmed aquifer is not used as a drinking water supply because
of its poor quality (e.g. high total dissolved solids, sulfide and chloride) and the low
yields to wells. The direction of flow in this aquifer is generally to the west-
northwest, which is consistent with the regional flow direction. In the late summer
there are several localized deviations in the flow pattern as several ground-water
mounds build and dissipate. The transmissivity of this aquifer is estimated to be 77
ft^ per day. The recharge to this aquifer is primarily from upward flow through the
confining layer from the underlying confined aquifer and infiltration from
irrigation, precipitation and a nearby drainage ditch. This drainage ditch which runs
adjacent to the site is hydraulically connected to the shallow unconfined aquifer. In
the spring this ditch appears to recharge the aquifer while during the summer that
portion of the aquifer underlying the site appears to contribute 1.1 to 1.4 gallons per
minute to the flow in the ditch.
The deep confined aquifer is a primary source of drinking water for the
surrounding metropolitan area. Pumping tests from other studies indicate that the
transmissivity of this aquifer ranges from 4000 to 10,000 ft^. This aquifer was not
extensively studied for the purposes of managing this site because of the presence of
a thick confining layer above the aquifer and the upward movement of water from
this aquifer to the shallow aquifer.
Ground-Water Contamination Summary:
A wide variety of contaminants was found at the site including VOCs, SVOCs,
Pesticides, Herbicides, Dioxins and Furans. The major sources of contamination on
the site include a process drain system, a former evaporation pond, a yard drain
system and a septic system. The primary contaminants of concern in the ground
water are the indicator chemicals TCE, PCE, PCP and 2,4-D. Ground-water samples
from monitoring wells indicated that these contaminants exceed maximum
contaminant levels (MCLS) as established under the Safe Drinking Water Act by up
to three orders of magnitude. These contaminants are widely dispersed horizontally
and vertically in the shallow aquifer underlying the site. (See Figure 3.4-1.)
However, ground-water samples from monitoring wells below the shallow aquifer
do not indicate that the contamination has extended into the confining layer
separating the shallow aquifer from the deep confining aquifer.
At the time the ROD was issued, the extent and origin of the contaminated
water found on the northern portion of the site had not been fully characterized.
The ROD anticipated that further investigations and subsequent ground-water
Page 3-42
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Sect/on 3: Model Applications Summary Description #4
remediation decisions would have to be made prior to the initiation of remedial
actions.
Modeling Summary:
A series of analytic and analytic/numeric models were used to investigate the
site. An analytic modeling approach was chosen as a function of EPA's decision
objectives and resource constraints. As this was an enforcement lead site, EPA's
responsibility was to review the responsible party's remediation plan and activities
to ensure they met regulatory and legal requirements. Thus, EPA's objective in
conducting this modeling was not to develop a definitive remedial design but to
gather sufficient information to be able to review the responsible party's
characterization of the site and the RD.
New information, received since the issuance of the ROD, suggested the need
for the RD/RA to address ground-water contamination not previously thought to be
connected with the site. Evidence suggested that the plume in the shallow aquifer
may have migrated off-site. EPA desired to explore this possibility and to examine
its impact upon the proposed remedial design. As these were review and not design
objectives, these decision objectives were not considered sufficient to warrant the
costs associated with a full fledged numerical modeling effort at this stage in the
remediation process. Moreover, EPA and their contractor believed that current data
on the site was not sufficient to support a numerical model. Consequently, an
analytic modeling approach was chosen.
The modeling was divided into two phases. The objective of the phase one
modeling was to determine the maximum extent of chloride and TCE
contamination in the shallow aquifer. An analytical function-driven variation of
the fate and transport model Random Walk was used in this phase. The objective
of the phase two modeling was to examine the effectiveness of proposed and
alternative extraction well designs. Two models were used in this phase. The
analytic flow model THWELLS was used to determine well field drawdown. Then
the capture zones for the ground-water remedial alternatives were estimated using
the particle tracking module of the U.S. EPA Wellhead Protection Area (WHPA)
model called GPTRAC. This case study will focus on phase one of the modeling
which is the use of the Random Walk model to delineate the contaminate plume
and potential sources.
The analytical function-driven variation of the Random Walk model was
chosen for the phase one modeling because of its relative simplicity, prior contractor
experience and prior contractor verification of the model through a comparison of
its results with that of another well-respected model. This version of the Random
Walk model utilizes an analytic function based upon the Theis equation to generate
the flow field. Then the numeric Random Walk model is applied to simulate the
fate and transport of the contaminants.
Page 3-43
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Section 3; Model Applications Summary Description #4
The simplifying assumptions associated with the analytic flow component of
the Random Walk model required that the aquifer be treated as homogeneous,
isotropic and infinite in a real extent. Thus, no site specific boundary conditions or
spatial variability in aquifer characteristics could be modeled. Moreover,
unidirectional, steady state ground-water flow had to be assumed. The modeling
team established a uniform hydraulic conductivity, saturated thickness,
transrnissivity, hydraulic gradient and aquifer porosity for the modeled area based
upon information obtained from the RI report and the ROD. They assumed that
there was no precipitation recharge to the aquifer.
Chloride was chosen as one of the two contaminants to be modeled because it is
mobile and non-retarded. Thus, its plume would represent the outermost limits of
the plumes of the other contaminants of interest. Moreover, since chloride is a
conservative substance, it was hypothesized that the successful replication in the
model of the existing chloride plume would be evidence that the simplifying
assumptions of the analytic flow model did not unduly compromise the model
results given EPA's decision objectives. TCE was selected as the other contaminant
to be modeled because it is relatively toxic and ubiquitous to the site.
The particle tracking component of the Random Walk model was used to
model the chloride releases as slugs that began in 1982 at four potential sources. The
TCE releases were modeled as continuous releases that began in 1957 at eight
potential sources. The location of the sources and the timing of the releases were
inferred from soil and ground-water chemistry, information in the RI and the ROD
and model calibration. The longitudinal and transverse dispersivities, background
concentrations and organic carbon partition coefficients were based upon field data
and established EPA methods. All ground-water contamination was assumed to
exist in the dissolved phase and consequently dense, nonaqueous phase liquid
migration was not simulated. Biodegradation and volatilization were also ignored.
The calibration of the Random Walk model was restricted to the contaminant
fate and transport component. This version of Random Walk assumes a
unidirectional flow field which can not be directly calibrated against observed
piezometric heads. Field data from the RI report was used to establish the flow field
parameters. Moreover, as was noted above, it was thought that the successful
calibration of the chloride plume would serve as an indication of the
appropriateness of the assumed flow field. Calibration of the contaminant transport
model was achieved by adjusting the number, location and release terms of the
sources until simulated concentrations matched field observations for twelve on-
site monitoring wells. The calibration process was terminated when:
The mean model error and standard deviation of errors were less than 10
percent of the largest observed field concentration;
» The regression analyses of field data versus model results yielded a
correlation coefficient squared (r^) value greater than 0.90, (an r^ value of
Page 3-44
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Section 3s Model Applications Summary Description #4
1.0 indicates perfect correlation between the field data and the model data);
and
* The shapes of the simulated plumes approximated the shapes of the
plumes observed in the field.
The calibration of the contaminant transport model required that the grid
nodes in the model be close to the physical location of the monitoring wells on the
site. Considerable effort was made to do this, but in order to determine the predicted
contamination concentrations at the monitoring wells, linear interpolation routines
ultimately had to be developed In retrospect, the modeling team realized that by
varying the location of the origin of the model grid, the grid nodes could have been
located precisely over the? monitoring well locations thus eliminating the need to
interpolate the contaminate concentrations and possibly improving the calibration.
It was noted, however, by the modeling team that the shifting of the grid would
become very time consuming with a large number of wells.
Difficulties were encountered calibrating the model. These difficulties caused
the modeling team to explore the possibility of the existence of undocumented on
and off-site sources. In an iterative fashion, sources were added to the model until
all calibration targets were met, the simulated plumes approximated the field
observable plumes and r^ values of 0.92 and 0.99 were obtained for the chloride and
TCE models respectively. (See Figures 3.4-2 and 3.4-3.) The reasonableness of the
location of these hypothetical contaminate sources was examined using site
information and aerial photographs of the site taken in the 1960's and 1980's.
Interestingly, these photographs had not been available to the modeling team
during the calibration process, yet wherever a hypothetical source had been
introduced into the model in order to effect a better calibration, the aerial
photographs provided confirming evidence of the existence of a potential source at
that location.
Because of budget limitations a sensitivity analysis was not performed to
determine the potential variations in the results as a function of changes in key
parameters or the removal of hypothetical sources. In retrospect, the modeling
team felt additional resources should have been requested to perform a sensitivity
analysis.
Modeling Results Summary:
The phase one modeling results indicated that the ground-water
contamination moved much further off-site than was estimated in the ROD.
Moreover, the model simulations suggested the possibility of off-site sources of
chloride and TCE contamination. (See Figure 3.4-4.) Specifically, the model
indicated that the plume had migrated almost 450 feet north and a 150 feet west of
the site and covered a surface area over 1/3 larger than the contaminant plume
defined in the ROD.
Page 3-45
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Section 3; Model Applications Summary Description #4
Four potential chloride sources and eight potential TCE sources were identified.
One of the chloride sources and three of the TCE sources were located off-site. None
of these potential off-site sources had been identified in the ROD. Consequently,
EPA's concerns about the completeness of the field characterization were supported
by the modeling results.
The phase one results were then used to evaluate the proposed and alternative
pump and treat extraction well designs. This evaluation (not part of this case study)
determined that the proposed design of the pump and treat extraction wells would
not fully capture the contaminant plume because the plume had migrated so far off-
site. Moreover, it was determined that the proposed pumping rate would de-water
the aquifer.
Based upon the information developed in this modeling effort, EPA directed
the Responsible Party to initiate further site characterization including a search for
additional off-site sources. The Agency also requested that the design of the
extraction wells be reviewed. However, the Agency and the modeling team were
careful to not assign certitude to the model results. As was stated in the modeling
report, the simplifications associated with the use of analytic models and the limited
field data available required that the results of this modeling effort be used with
great care. Thus the Agency limited the use of the model results to:
1. Estimate the maximum downgradient and lateral extent of ground-water
contamination;
2, Focus future field activities;
3. Provide insight into the location of additional potential sources; and
4. Provide preliminary ideas regarding the conceptual design of pump and
treat alternatives.
Strengths And Interesting Fpatures Of This Study:
In this case study, a model was applied late in the remedial process to review
the completeness and accuracy of the site characterization and remedial design
specified in the ROD. The decision and modeling objectives of this model
application were carefully limited so as not to exceed the limitations of the model
and available data.
Perhaps the most striking aspect of this case was that the entire modeling effort
required only 180 hours. This was possible because the decision objectives of the
modeling effort were limited in such a way that relatively simple models and
simplifying assumptions could be used. Nonetheless, the information gained from
the modeling could be used to guide field characterization activities and to raise
significant concerns about the characterization of the site and the design of the
proposed extraction wells. The ultimate consequences may be a considerable cost
savings through the implementation of a more appropriate remedial design.
Page 3-46
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Section 3: Model Applications Summary Description #4
Another interesting aspect of this study was the use of the model to identify the
location of previously undocumented potential sources of contamination and the
post modeling corroboration through the use of aerial photographs. This is an
example of the power of relatively simple models when they are carefully used as
preliminary investigation tools.
In retrospect, the Region noted that it might have been useful to conduct this
type of modeling during the RI/FS phase of the cleanup. The Region also noted that
additional modeling might be required later, once the additional site
characterization activities are completed. The Region suspected that should
additional modeling be performed, the level of certainty they would then require
would necessitate the use of a more sophisticated model and significantly more data.
Contacts:
For further information about this ground-water study please contact:
Bert Garcia Region 8 Tel. # (303) 293-1537
Modeling Documents:
Please contact the above person for specific modeling documents.
Page 3-47
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Section 3: Model Applications
Summary Description #4
Figure 3.4-1
Chloride Concentrations
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3-48
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Section 3: Model Applications
Figure 3.4-3
Model Calibration - Chloride
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Page 3-50
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EXPLANATION
EXISTING MONiromNC WELL
PROPOSED EXTRACTION WEU.
GROUND WATER CONTAMINANT PLUUE OEFINEO
m THE RECORD OF DECISION (US EPA. IM1)
SIMULATED PLUUE 80UNOAMY
T~0 lOCATION Of POSSIBLE SLURRY WALL
(WI01M MOT TO SCALE)
1CM.I f .
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Section 3s Model Applications Summary Description #4
(THIS PAGE INTENTIONALLY LEFT BLANK.)
Page 3-52
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3.5 - Summary Description #5
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Section 3: Model Applications Summary Description #5
3.5
Model Applications
Summary Description #5
Abstract:
Purpose of Model Application: To support the 30% Remedial Design1 of a
ground-water extraction and treatment system.
Type of Site: Former Hazardous Waste Landfill located next to a populated
residential area.
Models Used: WHPA(GPTRAC module); THWELLS.
Type of Models: Analytical.
Result of Study: The model demonstrated that six wells installed at the site
with a combined capacity of 150 to 800 gallons per minute would meet the remedial
design requirements. The range of flow rates is due to uncertainty in site
parameters. Once the wells are installed, they will be tested to determine the actual
design flow rates.
Decision Objectives:
The U.S. Environmental Protection Agency (EPA) Region tasked an
environmental contractor to perform a Remedial Design (RD) of a former
hazardous waste landfill facility based on the EPA's recommended alternative, as
outlined in the Record of Decision (ROD) for this site. During this process, two
decision objectives were established: (1) To prevent migration of ground-water
contamination off-site; and (2) To ensure that the waste material did not become
saturated with ground-water. To meet these objectives, it was decided to design a
ground-water extraction and treatment system at the site. A ground-water model
was developed and utilized to support the 30% RD of this system.
Strengths and Interesting Features of the Model Application:
This is the first case study that demonstrates the utilization of the model
Assessment Framework2 with a model application. The contractor who performed
the modeling was involved in the development of some of the model applications
described in case studies in the Ground-Water Modeling Compendium (EPA 500-B-
92-006, October 1992). During the development of those case studies, the contractor
became aware of the Assessment Framework which he then applied to this model
application.
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Section 3; Model Applications Summary Description #5
The contractor decided to use an observational approach3 to the design. This
involved using a simple analytical model, rather than a numerical model, to
perform preliminary design. Predictive sensitivity analysis4 was performed to assess
the uncertainty in the design of extraction wells, as well as the range of possible flow
rates. The actual design flow rates will be determined by testing the wells after their
installation. Use of analytical models effected cost savings and rapid development
of the modeling results.
This study demonstrated the importance of organizing all the site data in a
comprehensive manner as part of the development of a conceptual model. For
example, a QA check of the water level data showed that the datum upon which
water level measurements were based had changed since the time the monitoring
wells were originally installed. Thus, water level data had to be adjusted for this
changed datum. Another example is that by preparing hydrogeologic cross-sections,
the contractor was able to determine that the water table was not in contact with the
landfill waste material but was within two feet at its eastern end. Thus, an
extraction system for dewatering purposes was only needed on the eastern side of
the landfill.
The results of the model application demonstrated that a total of six extraction
wells with flow rates ranging from 25 to 133 gallons per minute per well (or 150 to
800 gpm combined flow) would meet the objectives of containing (and capturing)
the contaminant plume and provide contingency on the eastern side of the landfill
for dewatering to maintain water levels below the waste material (in the case of
water level rise).
Site Background Information:
The site is an inactive landfill occupying 30 acres in a Midwestern rural
residential area. Prior to 1966, the site was a sand and gravel pit. In September 1966,
the site began operating as a landfill and accepted an assortment of municipal,
commercial, and industrial wastes. The State estimated that 780,000 tons of solid
wastes and solvents had been disposed at the site. In addition, it was reported that
up to 1,000,000 gallons of chemical and liquid wastes were directly deposited at the
landfill from 55-gallon drums or from tanker trucks. The composition of these
wastes included latex, oil, solvents, and industrial chemicals. Large amounts of
flyash had also been accepted. Operations continued at the site until May 1980 when
local authorities ordered closure of the landfill. The area was subsequently covered
with clean soil and seeded. A base map of the site is included on Figure 3.5-1.
A fence that completely enclosed the site was installed to prevent nearby
residents from accessing the landfill. The contaminated ground-water migrating
off-site posed the largest threat to nearby residences and the environment. Based on
accounts of waste disposal and the ground-water mounding under the landfill,
landftlled wastes were probably acting as a continuing source of contamination.
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Section 3s Model Applications Summary Description #5
History of the Site Investigation:
A number of years after closure, the site was proposed for the National
Priorities List (NPL) as a result of community concern. The EPA Region ordered a
remedial investigation/feasibility study (RI/FS) and began field work consisting of
collecting and analyzing surface and subsurface soils, sediments, soil gas, and
ground-water samples.
During this RI, it was found that the most extensive body of contaminated
materials consisted of the wastes and waste-soil mixtures in the landfilled portions
of the site; and residential and monitoring well samples collected on and near the
site indicated that the sand and gravel aquifer beneath and west of the site was
contaminated.
Interim remedial measures were taken at the site, including installation of a
methane venting system (MVS) after explosive levels of methane were found along
the landfill boundaries and at nearby residences. The system consisted of 12 gas
extraction wells along the northern, southern, and western boundaries of the
landfill.
After sampling 67 residential and commercial wells, the EPA Region found
ground-water contaminated with volatile organic compounds (VOCs) in 10 private
wells up to 1,000 feet west of the site. Three of these wells contained elevated levels
of vinyl chloride. Air-strippirijg units were installed to remove vinyl chloride and
other VOCs. The private wells were shut down and an alternate water supply was
provided to approximately 100 residences downgradient (west) of the site. At the
conclusion of the FS, the EPA specified a remedial action for the site in a ROD.
Geologic Setting:
The site is within an area that was affected by Pleistocene-age glaciation. It is
marked by a distinct hummocky topography and rolling terrain. Elevations range
from 1,100 to 1,200 feet above mean sea level.
Regional glacial features identified in the area include irregularly shaped knolls
and hills (kames) of gravel, undrained depressions (kettles), level-to-sloping
outwash plains, end moraines, and ground moraines. Glacial deposits in the area
generally consist of interbedded sand and gravel with lesser amounts of silt and clay.
The deposits range between 50 and 210 feet in thickness and serve as an important
aquifer for residential water supplies.
Figure 3.5-2 illustrates the site geology in a north-south cross-section across
the landfill. Glacial deposits overlie Pennsylvanian-age consolidated sedimentary
bedrock. The glacial deposits include: (1) an upper unit (which is generally
unsaturated), (2) a. lower unit (the zone modeled), and (3) a glacial till overlying
bedrock. Both the upper and lower units are subdivided into fine-grained and
coarse-grained portions.
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Sect/on 3: Model Applications Summary Description #5
The unconsolidated glacial deposits are separated from bedrock by an
unconformity which also defines the configuration of the bedrock surface at the site.
The bedrock is about 400 feet thick and consists of 250 feet of interbedded sandstone,
limestone, siltstone, shale, and coal underlain by 150 feet of sandstone and
conglomerate rock formations. The bedrock is also an important source of water for
about half of the residential wells in the area. These wells are primarily installed in
the sandstone member.
Hydrogeology:
The climate is typical of the upper midwestern United States. The average
annual temperature is 49.5° Fahrenheit (F). The coldest month is January with an
average temperature of 25.1° F and the warmest month is July with an average 71.6°
F. The average annual precipitation is 35.9 inches with most of the rainfall
occurring in the spring arid summer months.
Figure 3.5-1 shows the location of the site in relation to the regional ground-
water flow system. Water in the regional system flows primarily from east to west,
discharging to a ditch to the west and south of the site. A major discharge area west
of the site is shown on the map as an area of ponded water and marshy ground.
Generalized elevations of the regional ground-water system are also shown.
Regional flow in the bedrock appears to "mirror" flow in the overlying glacial
aquifer system.
The RI identified a localized flow system surrounding the site. This area is a
zone of recharge. A ground-water high or "mound" resulting from a buildup of
precipitation exists under the landfill and contributes to the formation of leachate.
The water in the local system flows primarily westward and downward, except for a
small area of discharge to a ditch just east of the site. The dynamics of flow in the
local system are more complex than that of the regional system, i.e., this system has
both horizontal and vertical flow. The local system merges into the regional flow
system at a depth of 10 feet and does not exist more than 200 feet away from the
landfill.
One of the major concerns of the EPA Region was the level of the water table
below the landfill and whether the landfill intersected this water table. By drawing
cross-sections and plotting the water levels, the modeling team was able to
determine that the water table is currently within two feet of the bottom of the waste
material. A temporal analysis of water level data indicates that the probability for
rising water levels is low; however, the RD allows for this contingency.
For purposes of this model application, the main zone of interest was the
regional flow system. Figure 3.5-3 shows a potentiometric surface map for this zone.
The average hydraulic gradient of the regional flow was moderate and was about
equal to 0.001 feet/foot. The range in hydraulic conductivities as determined from
slug tests was 1 foot per day to 200 feet per day. The lower values were for glacial till,
and the higher values were obtained in the sand and gravel glacial aquifer.
Page 3-56
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Section 3; Model Applications Summar Descrition #
Ground-Water Contamination:
According to the RI, ground-water contamination at the site was confined to
shallow portions of the upper sand and gravel aquifer. Samples from residential
and monitoring wells showed minor-to-significant ground-water contamination by
VOCs, semivolatile organic compounds (SVOCs), and metals. Benzene and 1,2-
dichloroethane were the compounds of greatest concern found in monitoring well
samples. Drinking water standards for barium were exceeded in two residential
wells; three downgradient residential wells contained vinyl chloride in excess of
maximum contaminant levels (MCLs); and nickel exceeded ambient water quality
criteria (AWQC) levels in eight downgradient residential wells. Contaminants
found in excess of MCLs and AWQCs were vinyl chloride, benzene, 1,2-
dichloroethane, barium, nickel, and lead.
Figure 3.5-4 shows the extent of the dissolved organics and metals plume at the
site at the time of the RI.
Modeling Summary:
Project Management
A draft work plan for RD was submitted to the EPA by the environmental
contractor. An important component of this plan was to perform the modeling to
design the ground- water extraction system at the site.
The ground-water modeling project team was composed of:
1. A contractor project manager who wrote the work plan and was
familiar with the project decision objectives.
2. A modeler who was located in a different office than the project
manager.
3. A technical person with modeling experience who performed the peer
review of the model application.
The first step was to translate the decision objectives to modeling objectives.
This was done by the project manager and the modeler (upon acceptance of the
work plan by the EPA Region). The modeling objectives were developed as follows:
1. The extraction system should be designed to capture all of the
contaminant plume 200 feet north and south of the site.
2. The extraction wells should be located to capture the organics plume
rather than the dissolved metals plume.
3. The water levels in the aquifer should be maintained below the landfill
by dewatering if necessary.
4. The level of analysis required should be based on the requirements of
30% RD.
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Section 3: Model Applications Summary Description #5
5. Due to the wide range of conditions at the site, the preliminary design
should be based on a worst-case scenario developed by performing a
predictive sensitivity analysis.
Assumptions Due to the Project Scope:
After development of the modeling objectives, the project team assessed how
to best achieve the overall project objectives within budgetary and time constraints.
Based on that assessment, the project team decided that the best approach to the
project would involve: (1) preparation of a conceptual model that was as simple as
possible but that would incorporate the features important for 30% design, and (2)
utilization of an analytical model to perform the analysis. By using an analytical
model, the objectives could be achieved in a cost-effective manner within a short
time frame.
Due to the fact a simple model was selected and that the available data was
limited, the project team expected that there would be a certain amount of
uncertainty in the model results. Therefore, it was decided to use an observational
approach. This would involve quantifying the uncertainty using predictive
sensitivity analysis and installing extraction wells at the site with flow capacities
within this range of uncertainty. The actual flow rates would be determined by well
testing.
Model Development Plan:
To achieve the modeling objectives, the model development plan was
developed internally by the design contractor to include the following steps:
1. Collect and review available data on the site.
2. Organize the data prior to development of a conceptual model, if
needed.
3. Prepare a conceptual model of the site; outline assumptions of this
conceptual model.
4. Select a model code to represent the conceptual model and to meet the
modeling objectives; outline assumptions of the model code.
5. Perform model setup and input estimation.
6. Perform predictive sensitivity analysis to identify the worst-case
scenario.
7. Run the model and evaluate the results.
Data Review:
The modeling team reviewed the available data and the historical work
performed at the site. The team determined that the data collected through previous
field investigations had not been organized into a comprehensive conceptual
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Section 3: Model Applications Summary Description #5
understanding of the site. Therefore, more work was required under the data
organization task than originally anticipated.
Data Organization:
To organize the data properly prior to development of the conceptual model,
the modeling team performed the following tasks:
1. Tabulated the available well data; divided wells into shallow,
intermediate,, and deep aquifer zones.
2. Prepared hydrogeologic cross-sections showing the site geology,
thickness, and elevation of the landfill material, and location of the
water table. (Figure 3.5-2 shows one of these new cross-sections.)
3. Prepared new potentiometric surface maps for the shallow and
intermediate aquifer zones. (Figure 3.5-3 shows the new potentiometric
surface map for the intermediate zone.)
4. Evaluated the existing data on hydraulic conductivity, hydraulic
gradient and direction, aquifer thickness, and porosity. Determined
baseline ("average") values and range of uncertainty. (See section on
Model Setup and Input Estimation for the reported values.)
The modeler performed a Quality Assurance (QA) check on this data and
discovered that the datum on which water level measurements were based had
changed since the time that the monitoring wells were originally installed. A
correction was applied to the water level data to account for this change.
Preparation of the Conceptual Model:
In order to meet the modeling objectives, a simple conceptual model (shown
on Figure 3.5-5) was developed. This conceptual model incorporated the following
components:
1. A single-layer, unconfined aquifer system of constant thickness and
uniform properties.
2. A uniform flow gradient to represent regional flow.
3. Arbitrary boundaries at an infinite distance away from the site.
Assumptions of the Conceptual Model:
Additional assumptions of the conceptual model were as follows:
1. The local or shallow flow system underlying the landfill, although it
contained vertical flow components, was not considered to
significantly impact the extraction system. (See Assumptions Due to
the Project Scope.)
Page 3-59
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Section 3: Model Applications Summary Description #5
2. The bedrock underlying the site, although it contained flow, would not
impact the extraction system design. (See Assumptions Due to the
Project Scope.)
3. The model results within the area of interest at the site (e.g., marshy
land to the west) would not be impacted if regional hydrologic features
(shown on Figure 3.5-2) were not incorporated.
4. The aquifer system, as a whole, could be represented by "average"
properties.
5. There were no significant stresses caused by pumping other than the
prop>osed extraction system.
6. The impact of installation of a multi-layer cap would not be considered.
Model Code Selection:
Based on the modeling objectives, the GPTRAC module of the EPA's Wellhead
Protection Area (WHPA) model was selected to perform the capture zone analysis.
In addition, the International Ground-Water Modeling Center (IGWMC) THWELLS
model was selected to perform drawdown analysis for dewatering at the site.
The reasons for selecting these models are listed below:
1. Based on the modeling objectives, the modeling team decided that
analytical models, rather than numerical models, could meet the
objectives of 30% design. This decision would allow the model to be
constructed quickly and cost-effectively.
2. The WHPA model was selected due to its analytical nature and because
it could perform the required capture zone analysis.
3. The THWELLS model was selected because it could calculate the
drawdown produced by extraction wells proposed for dewatering.
4. Other factors in the selection of these models were that the modeler
had experience with these model codes and, therefore, did not require
training to use them; and the codes had been developed and were
supported by nationally recognized institutions.
Assumptions Due to thp MnHpl TnHp-
The selection of these codes imposed a number of additional constraints on the
representation of the conceptual model in the analytical model. These constraints
required that the representation of the conceptual model be limited to:
1. A single-layer aquifer (2-D);
2. An unconfined, homogeneous, isotropic, infinite acting aquifer;
3. Horizontal, steady-state flow;
4. Uniform flow gradient;
Page 3-6O
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Section 3: Model Applications Summary Description #5
5. Input of "average" aquifer properties; and
6. Fully penetrating extraction wells.
The main impact of these assumptions is two-fold: (1) the real variability
(heterogeneity) of the geologic deposits could not be represented, and (2) the actual
flow dynamics at the site had to be simplified. The project team recognized these
limitations of the model. In order to address the uncertainty due to these
assumptions, predictive sensitivity analysis was performed. (See section on
Scenario Representation)
Model Setup and Input Estimation:
The analytical module of WHPA requires input of "average" values. Given
below are the baseline average values entered and the range (from minimum to
maximum) in which the values were changed during predictive sensitivity analysis.
The minimum and maximum values were based on site data and professional
judgment.
Input Parameter
Hydraulic Conductivity (ft /day)
Hydraulic Gradient (ft/ft)
Gradient Direction (degrees)
Saturated Thickness (ft)
Effective Porosity
Pumping Rate (gpm)
Baseline Avg.
46.3
0.001
167.
100.
0.3
75.
Minimum
23.1
0.0005
142.
50.
0.225
38.
Maximum
92.6
0.0015
192.
150.
0.375
800.
Model Calibration:
As discussed above, the WHPA requires input of "average" parameters and it
runs in steady-state. Therefore, the WHPA model cannot be calibrated. To increase
confidence in the model results, predictive sensitivity analysis was performed. (See
Scenario Representation,)
Scenario Representation:
The first step in modeling the scenarios was to determine the minimum
number and the optimum location of wells to meet the modeling objectives. The
project manager relayed to the modeler that a maximum of 10 extraction wells could
be used. Based on preliminary modeling runs with the baseline input parameters,
the modeler was able to determine that three wells located just west of the landfill
would meet the first decision objective of containing the organics plume.
After closely examining the water level data interpretation and making a
comparison with the base? of the landfill site (see section on Hydrogeology), the
modeler was able to determine that only the eastern section of the landfill was close
to the water table. By using this knowledge in combination with additional
preliminary modeling runs, the modeler was able to determine that only three wells
Page 3-61
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Section 3: Model Applications Summary Description #5
located in the eastern section of the landfill would be required to meet the objective
of maintaining water levels below the bottom of the waste material by dewatering.
The next step, based on the modeling objectives, was to determine the worst-
case scenario by performing predictive sensitivity analysis. The width of the capture
zone was calculated for the possible range of each input parameter (given in the
section on Model Setup and Input Estimation) by running the model. The value of
the parameter which gave the worst-case scenario (i.e., smallest capture zone) was
identified as:
Input Parameter
Hydraulic Conductivity (ft /day)
Hydraulic Gradient (ft/ft)
Gradient Direction (degrees)
Saturated Thickness (ft)
Effective Porosity
Worst Case
92.6
0.0015
192.
150.
0.375
Modeling Results Summary:
Under the worst-case scenario, the flow rates of the extraction wells had to be
increased from 150 to 800 gpm to capture the entire plume. Figure 3.5-6 shows the
location of the extraction wells and the capture zones as determined by the GPTRAC
module of WHPA. By using the worst-case scenario, a factor of safety was built into
the design.
Upon completion of capture zone analysis, input data used for the worst-case
scenario were input into the THWELLS model to determine the amount of
drawdown generated by the six extraction wells. Figure 3.5-7 shows that a
drawdown of 5.6 feet is maintained across the site by pumping at a rate of 800 gpm.
These results are considered conservative because they are based on the worst-case
scenario combination of input parameters.
Overall Effectiveness:
The model results were used in the context of an observational design
approach to expedite clean-up of this Superfund site. The model demonstrated that
six extraction wells were needed, indicated where they should be located, and
provided a range of potential flow rates. Based on these results, extraction wells will
be installed at the site and a pump test will be performed to determine the actual
design flow rates needed.
The EPA Region considered this approach and the model results to be a timely
and cost-effective means of meeting the regulatory requirements.
Contacts for Further Information:
For further information about this ground-water study, please contact:
Pmg* 3-62
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Section 3; Model Applications Summary Description #5
Linda Kern EPA Region V Telephone: (312) 886-7341
Dr. Luanne Vanderpool EPA Region V Telephone: (312) 353-9296
Relevant Modeling Documents:
Please contact the people listed in the previous section for specific modeling
documents related to this case study.
End Notes:
1. 30% Remedial Design represents the first part of the detailed design
process after approval of the conceptual design for the site.
2. See the Assessment Framework in the Ground-Water Modeling
Compendium (EPA 500-B-92-006, October 1992).
3. The observational approach (originally developed for soil mechanics)
addresses the uncertainty associated with limited site data and the immediate need
for a remediation system by utilizing simple models to develop a design that will
remain effective over the range of possible hydrogeologic conditions that may be
found at the site. A remediation system is then installed quickly and its
performance is regularly monitored and adjusted as necessary.
4. Predictive sensitivity analysis is 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.
Page 3-63
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Section 3: Model Applications
Summary Description
Figure 3.5-1
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Page 3-64
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Section 3; Model Applications
Summary Description #5
Figure 3.5-2
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Page 3-65
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Section 3: Model Applications
Summary Description #5
Figure 3.5-3
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Page 3-66
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Section 3: Model Applications
Summary Description
Figure 3.5-4
Dissolved Organics and Metals Plume
Limit of fcteUI*
Contamination
Umlt of Organic Contamination
(Including T1C»)
PRESENT EXTENT OF GROUNDWATEH
CONTAMINATION
Seal* ApproumM. f . HOT
Page 3-67
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Section 3; Model Applications
Summary Description #5
Figure 3.5-5
Simple Conceptual Model
UNIFORM FLGW HYDRAULIC
GRADIENT DF MAGNITUDE
AND DIRECTION
CAPTURE ZONE DF
EXTRACTION WELL AS
DETERMINED BY WHPA/GPTRAC
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CONCEPTUAL MODEL FOR THIS CASE STUDY
Page 3-68
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Section 3s Model Applications
Summary Description #5
Figure 3.5-6
Location of Extraction Wells
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Page 3-69
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Section 3: Model Application*
Summary Description #5
Figure 3.5-7
Drawdown Across the Site at 800 gpm
? /\ -'Obr/!/'
Page 3-70
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3.6 - Summary Description #6
-------
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Section 3: Model Applications Summary Description #6
3.6
Model Applications
Summary Description #6
Abstract:
Purpose of Model Application: To perform a detailed analysis of alternatives
for ground-water and soil remediation in conjunction with a Feasibility Study (FS).
Type of Site: Former Processing Center for waste industrial chemicals. The soil
underlying the site is contaminated with organic compounds with concentrations
up to 150,000 micrograms/kilogram (ug/kg). A dissolved ground-water plume has
been identified that extends as much as 1,500 feet from the site and lies 35 feet below
the ground surface.
Models Used: MODFLOW; MOC
Types of Models: Numerical; Finite-Difference.
Result of Study: Results provided by the ground-water models led to the
recommendations made in the FS, thereby supporting the U. S. Environmental
Protection Agency's (EPA) timely decision regarding the best way to remediate the
site. Based on these results and recommendations, the EPA installed a multi-media
cap and a plume stabilization well at the site. Installation of this well prevented the
off-site migration of contamination, except for only one of the most mobile
contaminants.
Decision Objectives:
The EPA Region tasked an environmental contractor to perform the FS to
determine site remediation alternatives at a former processing center for waste
industrial chemicals. The project decision objectives, developed to support the FS,
were: (1) To determine the potential effectiveness of each alternative; (2) To define
the potential range of clean-up times for each remediation option identified in the
FS; and (3) To develop a better understanding of the flow dynamics at the site.
Ground-water model applications were developed to support these decision
objectives.
Strengths and Interesting Features of the Model Application:
The site hydrogeology was complex and the site was highly contaminated with
organic compounds; therefore, numerical models were selected to perform a
detailed analysis of extraction schemes in support of the FS. The selected modeling
approach combined two numerical models: MODFLOW (to model groundwater
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flow) and MOC (to model contaminant transport). This approach was considered
innovative at the time because there was no software available that could perform
transport modeling in conjunction with MODFLOW. (Note that MODPATH and
MT3D became available later.)
The flow model was set up using MODFLOW as a two-layer system
representing the shallow and deep aquifer systems at the site. The semi-confining
layer was represented as a quasi-three-dimensional (quasi-3D) layer through input of
vertical conductance. Boundary conditions were set up using a combination of
physical hydrologic boundaries and artificial boundaries.
An embedded model application1 was set up using MOC and shallow aquifer
zone heads generated by MODFLOW. The two-dimensional (2D) MOC model was
used because flow in the shallow aquifer is considered primarily horizontal. The
heads from the calibrated MODFLOW model were used to set up constant head
boundaries on the outside of the MOC grid.
Another interesting feature of this model application was the choice of
indicator compounds for the transport simulations. Generally, it is common
practice to select the most volatile and the more mobile compounds. Instead, two
indicator compounds were chosen to represent the range of behavior of the
contaminants of concern. The highly mobile compounds were represented by 1,2-
dichloroethane and the less mobile compounds by tetrachloroethene. By selecting
representative indicator compounds, the modelers were able to determine that an
optimal system designed to remediate the more mobile contaminants would not be
simultaneously effective in remediation of the less mobile contaminants. As a
result, additional extraction wells would be required in the center of the less mobile
plume, in order to remediate the less mobile contaminants. The model application
demonstrated the importance of modeling the less mobile compounds (as well as
highly mobile and volatile compounds).
Five extraction scenarios were evaluated in support of the FS study and an
additional one was evaluated for negotiations support for the Record of Decision
(ROD). The ground-water model showed the importance of installing a multi-
media cap and a plume stabilization well at the site. Both remedial actions were
implemented by the EPA. This provided an opportunity to evaluate the modeling
results for accuracy and efficiency. The multi-media cap virtually reduced the
amount of rainfall to zero; and the extraction well (for plume stabilization)
contained most of the contaminants, except the highly mobile ones. Therefore, the
importance of selecting the most representative indicator compound was
demonstrated.
Site Background Information:
The site is located southwest of a large town near a Midwestern metropolitan
area. From 1970 until early 1980, the site was operated as a processing center for
waste industrial chemicals. The chemical processing activities included reclamation
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and recycling, destruction by incineration, production of chemical fuels, and storage
of chemicals. When these activities were halted by state and federal regulatory
agencies in 1980, the site contained approximately 50,000 drums and 98 bulk-storage
tanks filled with various chemicals. Many tanks and drums had deteriorated and
leaked, thus contaminating the soil and ground-water.
The site comprises about 12 acres of relatively flat terrain surrounded by
farmland. Within one mile north of the site is a community of about 100 homes,
some of which have private wells used for lawn irrigation, but potable water is
supplied to these homes by the municipal water system. East of the site is a
municipal airport and industrial park; a water supply system drawing from five
production wells is located less than one mile from the site. The airport facilities
were built in the early 1940s as a military training base and flight school. The base
was turned over to the nearby town after World War II for use as a municipal
airport and industrial park. There is very little information regarding activities in
the base area from the late 1940s through the 1960s. However, it is known that the
base area was leased to a chemical company which had contracts with the military
services for the testing of rocket propellants.
History of the Site Investigation:
Prior to cessation of chemical processing activities at the site, the State declared
the site a serious health and fire hazard. The State filed suit against the site operator
for improper handling and disposal of hazardous wastes. Local residents
complained of a variety of physical ailments and property damage caused by
emissions from the incinerator. Crop damage was alleged to have occurred, and
cattle in nearby fields became sick and died. The State filed a contempt of court
petition against the site owner because violations of the conditions of the order.
The site was closed and placed in a state court-appointed receivership in early 1980.
Soon after closure, the site became an immediate threat to public health and
the environment during heavy rainstorms due to potentially explosive chemical
reactions in the deteriorating drums on-site. Local residents detected vapors rising
from the site, and the immediate area was evacuated. Stormwater ran through the
site into a ditch that emptied into a tributary of a navigable river. The EPA Region
Emergency Response Team arrived on-site and immediately implemented
containment operations to stop the migration of waste chemicals via surface-water
run-off. Several chemicals defined as Section 311 hazardous substances, in 40 CFR
116, had been found in the ditch. The response team also found approximately
50,000 55-gallon drums and 98 large tanks. A few months later, the response team
completed its action at the site. The immediate action concluded with the relocation
of an estimated 45,000 drums to staging areas on the site. The action did temporarily
stop surface run-off. Subsequently, ground-water and soil studies were conducted at
the site.
A surface clean-up was begun during which all wastes were removed from the
site for disposal. Then, a Superfund Remedial Investigation (RI) commenced at the
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site to evaluate the extent and severity of the soil and ground-water contamination
remaining after the surface clean-up. The RI report was completed, at which time
the FS was begun to evaluate the soil and groundwater remediation alternatives. A
major component of the FS was the use of numerical modeling to predict the
impact of alternative extraction well, containment barrier, and soil clean-up options
on the contaminant migration.
Geologic Setting:
The site is within an area of relatively flat terrain surrounded by farmland.
Elevations range from 565 to 575 feet above mean sea level. The site is located on a
gently sloping plain which drains toward the east fork of a navigable river, which
was a glacial floodway during the Pleistocene age. The river is 6,000 feet northwest
of the site. The land surface slopes gradually at a gradient of less than 10 feet per
mile. Figure 3.6-1 is a base map of the site, including surface geology.
The sediments in the area are predominantly glacial-fluvial in origin. They are
unconsolidated deposits of sand and gravel, silt and clay, and fine sand. In the site
area, the sediments are 75 to 80 feet thick and overlie bedrock of Mississippian age.
Three geologic facies have been identified at the site: (1) sand dune/outwash
facies (shallow aquifer), (2) lacustrine facies (confining layer), and (3) outwash facies
(deep aquifer). These facies are represented as separate physical layers in the
conceptual model and as two layers separated by a quasi-3D layer in the numerical
flow model. The geometry of these deposits has been defined through the
preparation of a series of structure contour maps and isopach maps of the site. The
top of the sand dune facies is ground surface.
The sand dune/outwash facies, which comprise the shallow aquifer system, are
composed of a series of wind-deposited layers of fine sand with some silt; the lower
part of the sand is fairly clean, medium-to-coarse grained sand, with some gravel
present. The facies vary in thickness from 18 feet at the southern end of the site to
as much as 50 feet thick north of the site. Figure 3.6-2 is a structure contour map of
the base of the sand dune/outwash facies and the top of the lacustrine facies
(confining layer).
The lacustrine facies, which comprises the confining layer, consists of lake
deposits that formed in shallow water or marsh that once existed at the site. The
deposits consist of interbedded fine sand, silt, clay, and thin carboneous and peat
layers. The confining layer is up to 50 feet thick at the southern end of the site and
thins to as little as 20 feet thick at the north. Figure 3.6-3 is an isopach map of the
lacustrine facies.
The outwash facies comprising the deep aquifer system is composed of coarse
sand and gravel. It is thickest at the east end of the site where it is 22 feet thick, and it
thins to as little as 1.3 feet northwest of the site. Based on the structure contour map
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Section 3: Model Applications Summary Description #6
of the top of the outwash facies (Figure 3.6-4), an area exhibiting a subsurface hill-
like feature exists at the southeastern corner of the site.
It is believed that this is a geological feature known as a glacial kame, a hill of
sand or gravel. Figure 3.6-5 shows an isopach map for the outwash facies.
The bedrock is a reel shale formation of Mississippian age which is considered
an aquiclude. The bedrock surface slopes gently to the southeast.
Hydrogeology:
The average annual temperature at the site is 75° Fahrenheit (F). The coldest
month is January with an average temperature of 30.4° F and the warmest month is
July with an average temperature of 75.8° F. The average annual precipitation is 41.3
inches, and the mean monthly precipitation is 3.44 inches, with most of the rainfall
occurring in the spring and early summer months.
The regional flow dynamics at the site are fairly complex. Surface run-off
drains to the east fork of a river, approximately 1.5 miles to the northwest. The site
is within an area with a significant amount of excess water available for recharge.
The average annual run-off is 14.4 inches per year, and most of the water seeps into
the ground. The shallow aquifer system comes into contact with a ditch north of the
site, which contains water throughout the year. Water in the shallow system
continues to flow to the northwest where it discharges into the major river system.
Water in the deep system, however, flows primarily to the south.
Figure 3.6-6 shows the potentiometric surface map of the shallow aquifer
system. The shallow system is unconfined, with depth to water being 4 to 6 feet
from the ground surface. Ground-water flow is to the north-northwest. The
horizontal hydraulic gradient varies from 0.00240 to 0.0039 feet/feet.
Figure 3.6-7 shows the potentiometric surface map of the deep aquifer system.
The deep system is primarily confined throughout the site by the lacustrine facies.
Ground-water flow is primarily to the south and is impacted by five water supply
wells located to the east of the site at the municipal airport. The average horizontal
hydraulic gradient is 0.0035.
Vertical flow through the confining layer is primarily downward. Calculated
hydraulic gradients across the confining layer are within the range of 0.05 to 0.56
feet/feet. The lower range is at the northern end of the site, where the two
potentiometric surfaces appear close to one another. The higher gradients are to the
southern end of the site.
The estimated hydraulic properties of both the shallow and deep aquifers are
based primarily on slug test data; however, one pumping test was performed in the
deep aquifer. The shallow aquifer has an estimated hydraulic conductivity of 28 to
79 feet per day. The hydraulic conductivity's of the deep aquifer ranges from 3 to 482
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Section 3: Model Applications Summary Description #6
feet per day based on slug test data alone. A more representative value as obtained
from the pumping test was 153 feet per day. Based upon these estimates, the
horizontal velocity of the shallow aquifer was estimated to range from 103 to 289
feet per year while that of the deep aquifer ranges from 188 to 637 feet per year.
Ground-Water Contamination:
At the time of the El report, it was concluded that the shallow aquifer system
was contaminated with organic compounds. Contamination was found both in the
soil and in the ground-water. Figure 3.6-8 shows the distribution of the ground-
water plume. Concentrations as high as 370,000 micrograms per liter (|Xg/L) of total
hazardous organic compounds were found in the ground-water underlying the site.
The plume reached as far as 1,100 feet downgradient of the site.
Figure 3.6-9 shows the distribution of contamination on a northwest-southeast
cross-section. It is clear from this cross-section that the plume follows the flow of
ground-water in the shallow system to the northwest. A small area of
contamination in the deep aquifer system was also identified.
Modeling Summary:
Project Management
To support the objectives of the RI/FS study, a ground-water model was
prepared. The ground-water modeling team was composed of:
1. A contractor project manager.
2. A modeler.
3. An expert hydrogeologist.
4. An expert in contaminant transport.
5. Two technical personnel who performed Quality Assurance (QA) peer
review.
The first step in the process was to formulate the modeling objectives based on
the management decision objectives. Given below is a list of modeling objectives
developed for this study:
1. Develop a conceptual flow model of the site that incorporates all of the
hydrogeologic features which may have a significant impact on
ground-water flow.
2. Extend the conceptual model as necessary to ensure that the
effectiveness of remediation alternatives could be evaluated.
3. Identify suitable indicator compounds for plume contaminants
modeling.
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Section 3: Model Applications Summary Description #6
4. Examine and evaluate alternative extraction schemes, in terms of
plume containment, aquifer restoration, and clean-up times.
Assumptions Due to the Project Scope:
After development of the modeling objectives, the project team assessed how
best to achieve the overall project objectives. The team recognized that the
sophistication of the required modeling might exceed the capabilities of existing
models. Consequently, the team decided to utilize only the public domain models
that had source code available. Thus, the code could be modified if required.
Moreover, to reduce modeling costs and increase the accessibility of the modeling
application, it was decided to choose a model that could be run on a microcomputer.
Model Development Plan:
To achieve the modeling objectives, a model development plan was
implemented based on the following steps:
1. Perform data review and data organization tasks in conjunction with
the RI study.
2. Develop a conceptual model for ground-water flow.
3. Select a suitable model code based on the representational needs of the
conceptual model and the code's ability to model the proposed
remediation alternatives.
4. Perform model setup and input estimation of the ground-water flow
model; including setup of a suitable finite-difference grid.
5. Calibrate the; flow model.
6. Determine the best way to represent the contaminant plume and
residual sources at the site within the limitations of the selected code.
7. Determine the best way to model various extraction schemes in
support of the FS remediation alternatives.
8. Run the model, evaluate the results, and make recommendations to
the EPA about the most optimal and cost-effective remediation
alternatives.
Data Review:
The data review was performed as part of the RI study. The RI study area was
designated as that area within a 2,000-foot radius of the site (covering 14 acres). The
well inventory area was much larger, however, covering a 6,000-foot radius. Thus,
residential wells located outside of the study area northwest of the site and five large
capacity water supply wells located at the municipal airport to the east lay within the
study area. Moreover, there were 46 monitoring wells at the site, including 16 wells
drilled during the RI study.
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Section 3; Model Applications Summary Description #6
In addition, 28 soil samples from the shallow aquifer were subjected to physical
property tests, and gamma logs were run in 18 monitoring wells. Water levels were
measured in the monitoring wells on a monthly basis.
Data Organization:
After the data were collected and reviewed, the following data organization
tasks were performed (in support of ground-water modeling):
1. Preparation of four geologic cross-sections.
2. Preparation of structure contour maps for the confining layer, deep
aquifer zone, and bedrock (Figures 3.6-2 and 3.6-4). Isopach maps were
also prepared (Figures 3.6-3 and 3.6-5).
3. Preparation of potentiometric surface maps for the shallow and deep
aquifer zones (Figures 3.6-6 and 3.6-7).
4. Plotting of ground-water contaminant concentrations on map and
cross-section (Figures 3.6-8 and 3.6-9).
In addition, all of the data collected was presented in tables in the RI.
Preparation of the Conceptual Model:
A detailed conceptual model was developed (shown on Figure 3.6-10) in order
to meet the study objectives. The conceptual model incorporated the following
components:
1. A multi-layer aquifer system representing the shallow aquifer,
confining layer, and deep aquifer systems. The actual elevations
(shown on Figures 3.6-3, -4, and -5) were input into the model.
2. Incorporation of the non-uniform flow fields in both the shallow and
deep aquifers. The shallow aquifer is unconfined and the deep is semi-
confined.
3. Incorporation of both physical hydrologic boundaries and artificial
boundaries. (See discussion of boundary conditions below.)
An important component of the conceptual model was the setup of boundary
conditions:
1. Shallow aquifer: A constant head boundary along the ditch north of
the site was established with no-flow boundaries to the east, west, and
south. The constant head boundary at the ditch was a real physical
boundary; as was the no-flow boundary to the south based on
identification of a ground-water divide. The east and west no-flow
boundaries were based on flow patterns in the shallow aquifer.
2. Deep aquifer: A constant head along all boundaries, except the west
edge, was established. The west edge was treated as a no-flow
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Section 3s Model Applications Summary Description #6
boundary. The north, south, and west boundaries were based on
inferred flow patterns in the deep aquifer. The east constant head
boundary was located at the center of a well field located near a
municipal airport. The heads along this boundary were calculated
using the Jacob equation assuming an "average" flow from the
municipal water supply wells.
Assumptions of the Conceptual Model:
Additional assumptions of the conceptual model were that:
1. A quasi-3D model was adequate to represent the flow patterns in the
multi-layer aquifer system. In a quasi-3D model, it is assumed that
flow in the confining layer is vertical; whereas, flow in the shallow and
deep systems is primarily horizontal.
2. The bedrock underlying the site was a no-flow boundary.
3. A small east-west creek north of the site was believed to have an
insignificant impact on ground-water flow and was ignored in the
model.
4. The primary recharge to the aquifer was from infiltrating rainwater
and seepage from run-off.
5. The aquifer was in a dynamic steady-state condition. (Although heads
vary in the aquifer throughout the year, the hydraulic gradients are
always the same).
Model Code Selection:
Based on the modeling objectives and the conceptual model developed, two
numerical model codes were selected. Both were developed by the United States
Geological Survey (USGS); both are numerical models; and both use a mathematical
technique called finite-difference to simulate ground-water flow and contaminant
transport.
MODFLOW was selected to model ground-water flow because it is capable of
modeling multi-layer aquifers, handling the varying properties within each layer,
and handling confined, unconfined, and leaky aquifers. Another reason for the
MODFLOW selection was that it is a widely accepted and tested model.
MOC was selected to model contaminant transport. By itself, MOC is limited to
single-layer aquifers and has high computational requirements. However, by
relying on MODFLOW to generate an accurate flow field, a smaller embedded model
grid could be used by MOC and the simulation could be limited to the shallow
aquifer system (which is where the bulk of the ground-water contamination exists).
A modified version of the code was used. This version, modified by J.V. Tracy,
included the effects of adsorption and decay.
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Assumptions Due to the Model Code:
The selection of these codes imposed a number of additional constraints on the
representation of the conceptual model in the analytical model. These constraints
required that the representation of the conceptual model be limited to:
1. A multi-layer; quasi-3D aquifer system.
2. An unconfined aquifer type for the shallow aquifer; confined for the
lower.
Model Setup and Input Estimation:
The first step was to set up the finite-difference grids to be used in the model
simulations. Figure 3.6-11 shows the contaminant transport grid embedded in the
flow model grid.
The flow grid covers an area of approximately 9,100 by 7,600 feet and has 40
columns and 42 rows. Near the center of the grid, the cell dimensions are 100 by 100
feet. The cell size is gradually expanded toward the edges of the grid to a maximum
dimension of 850 feet.
Interpretations of the site data are shown on Figures 3.6-2, -3, -5, and -6. These
figures were utilized to set up the geometry within each layer in MODFLOW. The
potentiometric surface for the shallow aquifer is shown on Figure 3.6-6. Figure 3.6-2
was used to input the bottom elevation of the shallow aquifer. The shallow aquifer
is represented by Model Leiyer 1. The confining layer was represented as a quasi-3D
layer with a vertical conductance, which is the vertical conductivity of 1.67 x 10-3
feet/day divided by thickness of the confining bed at each grid point (shown on
Figure 3.6-3). The bottom layer was represented by a transmissivity (the hydraulic
conductivity times the thickness of the deep aquifer, shown on Figure 3.6-5).
The input arrays to the model as described above were constructed with the aid
of a geostatistics technique called kriging to provide a smooth spatial distribution.
The shallow aquifer was given a hydraulic conductivity of 57 feet/day and the lower
aquifer a value of 153 feet/ day. The conductivity of the upper aquifer was adjusted
during the calibration process (along with the distributed recharge to the aquifer).
To determine the specified head at the eastern boundary of Model Layer 2
required application of the 1942 Jacob solution for steady-flow to wells in a leaky
confined aquifer. Input into the Jacob solution included a uniform gradient of 2.5
feet per 1,000 feet sloping downward to the south, and constant thicknesses of 20 feet
for the deep aquifer and 40 feet for the confining layer.
An embedded model grid was set up for contaminant transport as shown on
Figure 3.6-11. The transport grid contained 24 rows by 28 columns and each cell was
125 feet by 167 feet in areal size. A smaller transport grid (not shown) was also set up
for some of the simulations;. This grid was 28 rows by 28 columns and each cell was
75 by 75 feet in areal size.
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Section 3; Model Applications Summary Description #6
Model Calibration:
The flow model was calibrated in Model Layer 1 (representing the shallow
aquifer) to the head data presented on Figure 3.6-6. The best match was obtained by
using a uniform distributed recharge of 7 inches per year and the following
hydraulic conductivities (K) in Model Layer 1:
1. K = 57 feet/day in rows 1-25.
2. K = 10 feet/day in rows 26-32.
3. K = 20 feet/day in rows 33-42.
The conductivity of 57 feet per day prevails over most of the region of interest
and is within the range of values determined by slug tests. Only a visual
comparison of simulated contours with Figure 3.6-6 was performed (no mean error
was calculated).
Model Layer 2, which represented the deep aquifer, was not calibrated because
there were very limited data to calibrate against.
The calibrated heads for Model Layer 1 were used to establish boundary
conditions for the contaminant transport model. A computer program was written
by the modeler to transfer the head values from the flow model (using MODFLOW)
to the transport model (using MOC). This step was required because the two grids
were different. Constant heads were placed around the boundaries of the transport
grid. The same parameter values used in the calibrated flow model were used in the
transport model. The contaminant transport model was not calibrated because a
historical record of plume movement was not available.
Plume/Source Representation:
The first step in representing the contaminant plume observed at the site and
its associated sources was to identify representative indicator compounds. Field
investigations had detected more than 100 different organic compounds in the soil
and ground-water. Simulating solute transport for each compound would have
been impractical. Instead, two indicator compounds were chosen to represent the
range of behavior of the contaminants of concern. The highly mobile compounds
were represented by 1,2-dichloroethane and the less mobile compounds by
tetrachloroethene. Based on the data collected, the highly mobile compounds had
leached rapidly out of the soil into the ground-water. For the less mobile
compounds, the leaching process was still ongoing. The two types of compounds
were handled in the model in the following way:
1. For the highly mobile compounds, it was assumed that no source
remained, but that a residual plume existed in the ground-water. This
was handled by inputting the residual concentrations measured in
December 1984 into the model. Note: The assumption that no source
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Section 3s Model Applications Summary Description #6
remained was not entirely accurate, but was a simplification made by
the modeling team to meet the modeling objectives.
2. For the less mobile compounds, it was assumed that a residual source
remained in the unsaturated zone, as well as a dissolved plume in the
ground-water. For the dissolved plume, the residual concentrations
measured in December 1984 were input into the model. The residual
source in the unsaturated zone was handled in a unique way as
discussed below:
The MOC code did not have the capability to represent a residual source
concentration from the unsaturated zone; therefore, it was modified by the modeler
to perform this function. The MOC code can model a continuous source of solution
by specifying a recharge concentration on a cell-by-cell basis. However, it does not
allow for a decrease in concentrations over time. The modeler modified the MOC
code to recalculate the recharge concentrations for each time increment in the
simulation. Thus, the residual source in the unsaturated zone could be
incorporated into the model application. (Note: This modification was tested by the
modeler.) The input array of plume concentrations was determined by preparing an
interpretation of measured depth-averaged solute concentration for the two
indicator compounds and by combining modeling judgment with kriging.
The transport parameters input into the model were:
Parameter Value
Effective porosity 0.25
Longitudinal dispersivity 30.
Transverse dispersivity 10.
Retardation Factors
1,2-dichloroethane 2.0
Tetrachloroethene 9.2
The parameters were based mostly on representative values reported in the
technical literature. None of these parameters were measured in the field.
Scenario Representation:
Seven groundwater extraction, injection, and treatment alternatives, including
a no action alternative, were considered. To optimize ground-water extraction, five
ground-water extraction schemes were examined for each alternative.
1) Extraction wells only.
2) Extraction wells preceded by an interim plume stabilization well.
3) Extraction wells in combination with injection wells.
4) Extraction wells combined with partial containment within a slurry
wall around the site.
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Section 3s Model Applications Summary Description #6
5) Three off-site extraction wells to contain the plume.
The following assumptions were made:
1. Each well was assumed to be fully penetrating.
2. Whichever scenario was selected, it was anticipated that the final
remedy would not be implemented for up to five years. Therefore,
predictions had to be made regarding future locations of existing
plumes.
3. At the same time that the extraction wells were to be installed and
turned on, a multi-media cap would be installed over the landfill site.
This cap affected the schemes in two ways: (1) the cap eliminated
recharge over the 12 acres of the site, which in turn modified the
steady-state ground-water flow patterns in the shallow aquifer; and (2)
the cap eliminated the leaching source into the solute transport model.
4. The pumping rates for the extraction wells were limited to produce
drawdown less than 2/3 of saturated thickness, because it was not
considered practical to drawdown each well to its maximum level.
All extraction schemes had to be optimized prior to comparative analysis.
Optimization involved making numerous simulations with MODFLOW and
looking at the number, location of wells, and combination of pumping rates that
would result in the quickest removal of contaminated ground-water.
Figure 3.6-12 shows the predicted location of the 1,2-dichloroethane plume after
five years of simulation; and Figure 3.6-13 shows the predicted location of the
tetrachloroethene plume. Also shown on both figures is the well configuration for
Scheme 1 and associated capture zones.
Model Results Summary:
The well configuration for Scheme 1 is shown on Figures 3.6-12 and 3.6-13. The
three on-site wells would be installed in five years and would be located within the
tetrachloroethene plume but somewhat downgradient of its center. These three
wells would reverse the natural flow gradients in a region north of the site but
would be unable to create flow reversal as far north as the tip of the 1,2-
dichloroethane plume. Trie northernmost part of this plume would be captured by
the off-site well. The flow rate for the off-site well was limited so it would not
reduce the effectiveness of the three on-site wells. The solute transport simulations
were run until the maximum simulated concentrations in the aquifer were less
than the 10-6 excess cancer risk concentration. For 1,2-dichloroethane, restoration of
the aquifer would require 20 years; and for tetrachloroethene, the restoration was
projected at 35 years.
Scheme 2 considered the installation (in two-and-one-half years) of a single off-
site well as an interim plume stabilization measure. Another two-and-one-half
years later, three on-site wells would be installed along with the multi-media cap,
Page 3-83
-------
Section 3: Model Applications Summary Description #6
bringing the total extraction system up to four wells (similar to Scheme 1). It was
expected that early commencement of off-site extraction would have a significant
beneficial effect on the configuration of the contaminant plume by the time the full
system began operation. Figure 3.6-14 shows the location of all wells and the
predicted 1,2-dichloroethane plume after the five years of simulation.
Because the plume stabilization well would capture contaminants before they
traveled far off-site, the off-site well could be moved closer to the site. Also, due to
the beneficial effect of the plume stabilization well, the 1,2-dichloroethane plume is
considerably smaller than for Scheme 1 (Figure 3.6-12) and is, therefore, easier to
clean-up with the four wells of Scheme 2. Moreover, even when the flow rates of
the center well were reduced, the simulations showed that 1,2-dichloroethane was
cleaned up significantly faster than in Scheme 1. However, the scheme had little
effect on clean-up) times of tetrachloroethene, probably due to its low mobility.
In order to determine if the clean-up time of tetrachloroethene could be
improved, an injection well was modeled in the center of the tetrachloroethene
plume in Scheme 3 as shown on Figure 3.6-15.
In Schemes 1 and 2, well interference between the three on-site wells caused
low hydraulic gradients in the area of the highest contaminant concentrations.
Installing an injection well in the middle of the plume would eliminate this area of
stagnation (or low gradient) and increase the hydraulic gradient toward the
extraction wells. A special model grid of 75-foot square cells was required in this
scheme to handle the highly diverging and converging flows caused by the addition
of an ejection well. Scheme 3 significantly reduced the clean-up times for
tetrachloroethene; however, this scheme did not work as well for removing 1,2-
dichloroethane as did Schemes 1 and 2.
Scheme 4 looked at the installation of a slurry wall around the most
contaminated part of the aquifer as shown on Figure 3.6-16.
Inside the slurry wall, a single well would be installed to maintain upward flow
through the confining layer and to prevent contamination of the deep aquifer.
Outside the slurry wall, aquifer restoration would be accomplished by a system of
five extraction wells. Ground-water flow and contaminant transport simulations
were conducted only for that part of the aquifer outside of the slurry wall. The
slurry wall acted as a barrier to flow, thereby tending to cause zones of low hydraulic
gradient in the aquifer. This increased the clean-up times for 1,2-dichloroethane.
Furthermore, the costs of the slurry wall option were higher than the costs of the
other extraction schemes. Because of these factors, Scheme 4 was not considered a
reasonable option.
During the public comment period after the FS, Scheme 5 was proposed and
consisted entirely of off-site wells. The configuration of this system is shown on
Figure 3.6-17.
Page 3-84
-------
Section 3: Model Application* Summary Description #6
The objectives of this system were different than the other four schemes. More
emphasis was placed on controlling plume migration and on ease of construction,
and less on rapid aquifer restoration. Consequently, the pumping rates were not
optimized to produce the highest gradients or to minimize the extent of stagnation
regions, but were optimized to maintain an effective capture zone. The well capture
zones, indicated by Figure 3.6-17, show that this system would not be able to control
the entire 1,2-dichloroethane plume predicted.
In addition to the extraction scenarios, two other scenarios using the ground-
water model were reviewed during the FS study. The first involved removing
contaminated soils from the site. Simulations showed that installation of a multi-
media cap was more effective than soil removal. The second scenario was soil
remediation with in-situ washing. In this option, installation of the site cap would
be postponed for six years while spray irrigation would be used to increase
contaminant leaching from the soil. The model showed that soil washing would
cause an increase in aquifer remediation time; therefore, it was not further
considered.
Overall Effectiveness:
The EPA was satisfied with the modeling results and was able to make
decisions about an effective remedial action needed at the site. Based on the
ground-water model results and the recommendations made in the FS, the EPA
installed a multi-media cap (Figure 3.6-14). The cap is considered to be an effective
solution, preventing further leaching of contaminants through the unsaturated
zone. The FS recommended installation of at least one plume stabilization well
similar to that shown on Scheme 2 (Figure 3.6-14). Additional investigations after
the decision documents required the EPA to modify this scheme. These
investigations showed 1,4-dioxane traveled faster and further than did 1,2-
dichloroethane. Therefore, the EPA decided to install two plume stabilization wells
to prevent further migration of 1,4-dioxane. One of these wells was located 300 feet
from the source, and the other 1,000 feet from the source.
Contacts for Further Information:
For further information about this ground-water study, please contact:
Jeff Gore EPA Region V Tel.tf (312) 886-6552
Dr. Luanne Vanderpool EPA Region V Tel.# (312) 353-9296
Relevant Modeling Documents
Please contact the people listed in the previous section for specific modeling
documents related to this case study.
Page 3-85
-------
Section 3: Model Applications Summary Description #B
End Notes:
1. An embedded model application is a subset of a larger model application;
thus, the embedded model application considers only a part of the area modeled in
the larger model application.
Page 3-06
-------
Sect/on 3: Model Applications
Summary Description #6
Figure 3.6-1
Base Map of Site
Page 3-87
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-2
Structure Contour Map of Base
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LEVATIOK OF SURFACE OF
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ALL ILIVATION0ARE IN
FEET ABOVE MEAN SEA LEVEL
563
CONFINING LAYER STRUCTURE CONTOUR MAP
Page 3-80
-------
Section 3: Model Applications
Summary Description
Figure 3.6-3
Isopach Map of Lacustrine Facies
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CONFINING LAYER ISOPACH MAP
Page 3-89
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-4
Structure Contour Map of Top of Outwash Facies
\ .507
496 ':-^->V ='--.-. --
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OWOUNDIUMFACE ELEVATION
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ALL BLCVATIOfM ARE IN
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60S
DEEP AQUIFER STRUCTURE CONTOUR MAP
Page 3-90
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-5
Isopach Map of Outwash Facies
sc/u.1 m KIT
U1OEND
OBOUNDSURFACE ELEVATION
WOT ELEVATION
ENCH MARK
AQUIPEN THICKNESS
IN f BET
ALL ELEVATIONS ARE IN
FEET AIOVE MEAN SEA LEVEL
.13
.,., r § \
: ^V-^0 / -.-
DEEP AQUIFER ISOPACH MAP
Page 3-91
-------
Section 3: Model Applications
Summary Descriotlon #6
Figure 3.6-6
Potentiometric Surface Map of Shallow Aquifer System
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574.0
SHALLOW AQUIFER POTENTIOMETRIC SURFACE
WEEK OF DECEMBER 3,1964
Pmgm 3-92
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-7
Potentiometric Surface Map of Deep Aquifer System
663.0
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- *;n.-- «ROUND«U*FAC« ELEVATION
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DEEP AQUIFER POTENTIOMETRIC SURFACE
WEEK OF DECEMBER 3,1984
Page 3-93
-------
Figure 3.6-8
Distribution of Ground-Water Plume
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SHALLOW AQUIFER - AUGUST 1984
-------
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206 B
206 C
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Page 3-96
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-11
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Page 3-97
-------
Section 3: Model Applications
Summary Description
Figure 3.6-12
Predicted Location of 1,2-dichloroethane Plume
UPPCftACMFEH
Ptedicled t. 2-OcMDioelliane Plume in
19B9 and WeU Conliguraiiofi toi Scheme 1
Page 3-98
-------
Section 3: Model Application*
Summary
Ifi
Figure 3.6-13
Predicted Location of Tetrachloroethene Plume
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UPFtH AOUIfER
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Page 3-99
-------
Section 3: Model Application*
Summary Description #6
Figure 3.6-14
Location of All Wells and Predicted 1,2-dichloroethane Plume
Watt Conflgumtontor Scliama 2. and
1,2-Otttororthafw Pljme In
Altai Ptuma SlaMHialkin
Page 3-f 00
-------
Section 3s Model Applications
Summary Description
Figure 3.6-15
Hypothetical Placement of an Injection Well for Scheme 3
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3-f Of
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-16
Slurry Wall Installation for Scheme 4
-f
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Page 3-f O2
-------
Section 3: Model Applications
Summary Description #6
Figure 3.6-17
Configuration of Off-Site Wells for Scheme 5
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Page 3-103
-------
Section 3: Model Applications Summary Description
(THIS PAGE INTENTIONALLY LEFT BLANK.)
Page 3-104
-------
Section 4: Modal Descriptions Introduction
4.0
Model Descriptions
Introduction
This section provides summary and detailed descriptions for eight ground-
water models that were selected as the initial set of models to be considered as part
of this pilot project. The eight models are:
O MOC
O MODFLOW
a PLASM
O RANDOM WALK
O AT123D
a MT3D
a MODPATH
a WHPA Modules
GPTRAC
MWCAP
RESSQC
MONTEC
While these models are generally well known and have been used often in
EPA programs, the inclusion of them in the Compendium does not represent an
endorsement of them by OSWER for any specific purpose. In the future, OSWER
may develop guidelines for application of models under certain conditions or for
specified types of analyses, and add other models to the Compendium. At this time,
the descriptions are provided as general reference information only.
Fact Sheets
The beginning of this section contains a two-sided Fact Sheet for each of the
models and their modules. These were developed based on comments received
from EPA Regional office staff, who identified a need to have quick access to some
Page 4-1
-------
Sect/on 4: Model Description* Introduction
overview of the models' characteristics, scope, and applicability, as well as the name
of a contact for technical support and more information.
Model Descriptions
The latter part of this section contains more detailed information on the same
set of eight models. This information was extracted from a computerized database
maintained by the International Ground Water Modeling Center (IGWMC) in
Golden, Colorado. The? information has been re-formatted, and in some cases, sub-
sections have been re-numbered and re-ordered, but the information itself has been
modified only slightly. IGWMC's database contains information on many more
ground-water models. Using data that comes directly from the IGWMC database
will maintain the integrity of the information, if for example, OSWER wishes to
expand this portion of the Compendium in the future by taking larger extracts from
the IGWMC database.
Modeling Data Requirements
There is often confusion about how modeling data requirements are
determined and the relationship between data requirements and the model (code).
It is important to understand that the determination of a modeling application's
general data requirements should precede the selection of a model. Furthermore,
the determination of the type, quantity, and accuracy of the data required for the '
modeling application can be complex because it is dependent upon:
1. Management's reasons for performing the modeling and the subsequent
accuracy and level of detail required of the modeling results. For example,
a preliminary screening of alternative remedial technologies conducted as'
part of a remedial investigation and feasibility study can usually be
modeled with less detail than a remedial design being modeled as part of
the remedial design phase.
2. The physical processes and the characteristics of the site being modeled.
For example, chemical fate and transport processes often require
considerably more types of data than flow processes. Moreover, the
quantity and the accuracy required of the data are often a function of the
types of chemicals being modeled or the level of heterogeneity of the site.
3. The engineering objectives of the modeling. For example, the types and
quantity of data required to determine the effectiveness of a deep hydraulic
barrier design are often different from the data required to analyze a
network of ground-water extraction wells.
Once the data requirements have been determined, a model can be selected
which will support these data requirements and provide management with the
Page 4-2 -^^___^________.
-------
Section 4: Model Descriptions Introduction
information they need to make informed decisions. Thus, the decision objectives,
process and site characteristics, and engineering objectives are the factors which
primarily determine a model application's data requirements and, in turn, govern
the selection of a particular model.
To determine if a model will support an application's data requirements, the
reader is referred to the model descriptions that follow and the model
documentation that is usually available from the model's authors or the
International Ground Water Modeling Center.
Page 4-3
-------
Section 4s Model Descrlptlont Introduction
(THIS PAGE INTENTIONALLY LEFT BLANK.)
Page 4-4
-------
Model Type: Solute Transport
MOC
Summary Updated May 1994
(USGS-2D-TRANSPORT, KONBRED)
Version 3.0
Release Date: 11/89
MOC is a ground-water flow and mass transport model. It provides capabilities for two dimensional simulation of
non-conservative solute transport in heterogeneous, anisotropic aquifers. It computes changes in time in the spatial
concentration distribution caused by convective transport, hydrodynamic dispersions, mixing or dilution from
recharge, and chemical reactions. The chemical reactions include first-order sorption irreversible rate reaction (e.g.
radioactive decay), equilibrium-controlled sorption with linear, Freundlich or Langmuir isotherms, and monovalent
and/or divalent ion-exchange reactions. MOC solves the finite difference approximation of the ground-water flow
equation using iterative ADI and SIP. It uses the method of characteristics followed by an explicit procedure to solve
the transport equation. MOC uses a subgrid of the flow grid for simulation of containment transport.
Note: A version of MOC called MCKI Dense simulates two dimensional density dependent flow and transport in a
crossectional plane. The specific characteristics of MOC Dense are not incorporated in this summary.
Scope
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MOC
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware Prime
Platforms: DEC VAX
IBM PC/XT/AT
IBM 80386/486
Apple Macintosh
Preprocessors: PREMOC
MODELCAD
Postprocessors: POSTMOC
MOCGRAF
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
PH
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Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401, USA
(303) 273-3103
U.S. Geological Survey
WRD WGS - Mail Stop 433
National Center
Reston, Virginia 22092
Scientific Software Group
P.O. Box 23041
Washington D.C. 20026-3041
(703) 620-9214
Geraghty & Miller, Inc.
Modeling Group
1895 Preston Drive, Suite 301
Reston, Virginia 22091
(703) 476-0335
Page 4-6
-------
Model Type: Saturated Flow
MODFLOW
Version 3.2
Release Date: 10/89
Summary Updated: May 1994
MODFLOW is a modular, block-centered finite difference model for the simulation of two dimensional and quasi-
or fully-three-dimensional, transient ground-water flow in anisotropic, heterogeneous, layered aquifer systems. It
calculates piezometric head distributions, flow rates and water balances. The model includes modules of flow
towards wells, through riverbeds, and into drains. Other modules handle evapotranspiration and recharge. Various
textual and graphic pre-and postprocessors are available.
Note: Several particle tracking programs including ModPath utilize Modflow output to simulate contaminant
transport. The specific characteristics of these particle tracking programs are not incorporated in this summary.
Scope
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MODFLOW
Definitions
Boundary Conditions;
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware
Platforms:
DEC VAX 11/780
IBM PC/XT/AT
PRIME 750
IBM 80386/486
Apple Macintosh
Intel 80386/80486
Preprocessors: PREMOD
MODELCAD
Postprocessors: POSTMOD
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
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Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401, USA
(303) 273-3103
U.S. Geological Survey
WRD WGS - Mail Stop 433
National Center
Reston, Virginia 22092
Scientific Publications Co.
P.O. Box 23041
Washington D.C. 20026-3041
(703) 620-9214
Geraghty & Miller, Inc.
Modeling Group
1895 Preston Drive, Suite 301
Reston, Virginia 22091
(703) 476-0335
Pag* 4-8
-------
Model Type: Saturated Flow
Summary Updated: May 1994
PLASM
Version - Illinois State Water Survey
Release Date: 1985
PLASM (Prickett Lonnquist Aquifer Simulation Model) is a finite difference model for simulation of transient,
two-dimensional or quasi-three-dimensional flow in a single or multi-layered, heterogeneous, anistropic aquifer
system. The original model of 1971 consisted of a series of separate programs for various combinations of
simulation options. Later versions combined most of the options in a single code, including variable pumping
rates, leaky confined aquifer conditions, induced infiltration from a shallow aquifer or a stream, storage coefficient
conversion between confined and waterable conditions, and evapotranspiration as a function of depth to
watertable. The model uses the iterative alternating implicit method (IADI) to solve the matrix equation.
Scope
Remedial Design Feature
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Contaminant Source Type
Solid Waste
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Technical Characteristics
Model!
Processes
Flow
System
Aquifer
Type
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Fate&
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Page 4-9
-------
PLASM
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware DEC VAX
Platforms: IBM PC/XT/AT
IBM 360, 370
Preprocessors: PREPLASM
MODELCAD
Postprocessors: None
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
I
Q
8
OH
CU
1
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1
Reliability
§
J3
8
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Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401, USA
(303) 273-3103
Thomas A. Prickett
6 G.H. Baker Drive, Urbana IL 61801
(217) 384-0615
Illinois State Water Survey
P.O. Box 232
Urbana, Illinois 61801
Ann Koch
2921 Greenway Drive
Ellicott City, Maryland 21043
(301) 461-6869
Geraghty & Miller, Inc., Modeling Group
1895 Preston Drive, Suite 301
Reston, Virginia 22091
(703) 476-0335
Page 4-1O
-------
Model Type: Solute Transport
Summary Updated: May 1994
RANDOM WALK
Version - Illinois State Water Survey
Release Date: 7/81
RANDOM WALK/TRANS is a numerical model to simulate two-dimensional steady or transient flow and
transport problems in heterogeneous aquifers under water table and/or confined or leaky confined conditions.
The flow is solved using a finite difference approach and the iterative alternating direction implicit method. The
advective transport is solved with a particle-in-cell method, while the dispersion is analyzed with the random
walk method.
Note: A number of other versions of Random Walk including analytical function driven versions are available.
The specific characteristics of these other versions including output capababilities vary considerably.
Scope
Remedial Design Feature
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Model
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Page 4-11
-------
RANDOM WALK
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified alone the boundary
(Dirichlet Condition) J
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware Cyber 175
Platforms: VAX 11/780
IBM PC/XT/AT
Preprocessors: PREWALK
MODELCAD
Postprocessors: POSTWALK
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
§
43
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Reliability
§
43
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-------
Model Type: Mass Transport
AT123D
Version 1.1
Release Date: 5/92
Summary Updated: May 1994
AT123D is a generalized analytical transient, one- two-, and/or three-dimensional computer code developed
for estimating the transport of chemicals in an isotropic, homogeneous, confined aquifer system with uniform
flow. The model handles various source configurations (including point source, line source, and areal source) and
release characteristics. The transport mechanisms include advection, longitudinal as well as horizontal and
vertical transverse hydro-dynamic dispersion, diffusion, linear adsorption, and first-order decay/degeneration
and chemical losses to the atmosphere. The model calculates concentration distribution in space and time using
Green's function.
Scope
Remedial Design Feature
8
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too
N/A
N/A
N/A
N/A
N/A
N/A
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Technical Characteristics
Model
Processes
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System
Aquifer
Type
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(Saturated)
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Page 4-13
-------
AT123D
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC/XT/AT
Platforms: Other platforms with
Fortran compiler
Preprocessors: Part of some
model package
Postprocessors: Part of some
model package
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
o
Q
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Availability
Usability
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ex
C/i
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OH
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Reliability
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Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401
USA
G.T. Yeh
Pennsylvania State University
Department of Civil Engineering
225 Sackett Building
University Park, PA 16802
Pago 4-14
-------
Model Type: Mass Transport
MT3D
Summary Updated: 10/29/93
Version 1.8
Release Date: October 1992
MT3D is a tiiree-dimensional contaminant transport model using a hybrid method of characteristics Two
numencal techniques are provided for the solution of the advective-dispersive reactive solute transport equation:
the method of characteristics (MOC) and the modified method of characteristics (MMOC). The MMOC method
overcomes many of the traditional problems with MOC, especially in 3D simulations, by directly tracking nodal
points backwards in time and by using interpolation techniques. MT3D selectively uses the MOC or the MMOC
technique dependent on the problem at hand. The transport model is so structured that it can be used in
conjunction with any block-centered finite difference flow model such as the USGS MODFLOW model
Remedial Design Feature
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Scope
Solid Waste
Disposal
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Model
Processes
Technical Characteristics
Flow
System
Aquifer
Type
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(Saturated)
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Processes
Fate&
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B
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Page 4-f 5
-------
MT3D
Definitions
Boundary Conditions;
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC or
Platforms: compatible
Preprocessors: Part of model
package
Postprocessors: Part of model
package
Detailed information on this model, sources of distribution, and postprocessors and preprocessors
is available in section ? of the Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 332-8800
Availability
Usability
§
43
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OH
O,
C/3
fr
£
fl
1
Reliability
I
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Distributed By:
Center for Subsurface Modeling Support
R. S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: 405/332-8800
Page 4-16
-------
Model Type: Particle Tracking
MODPATH
Version 1.2
Release Date: 1990
Summary Updated: May 1994
MODPATH is a postprocessing package to compute three-dimensional pathlines based on the output from
^o FS%e AS^ ^ °?tamed Wlth *f USGS MODFLOW ground-water flow model. The package consists of
two FORTRAN 77 computer programs: 1) MODPATH, which calculates pathlines, and 2) MODPATH-PLOT which
8SE2£ ^8KT *°?*k MODPATH uses asemi-analytical particle backing scheme, based on the assumption
£n ,t tn , MSSSKS * locity component vanes linearly within a grid ceU in its own coordinate direction. Data is
input to MODPATH through a combination of files and interactive dialogue. The MODPATH-PLOT program
KS^eMGKSr ^ *" "* ^ ^ °ISSPLA graphiCS r°UtineS ^T3^' and one *"* uses ^ Graphical
Scope
Remedial Design Feature
1 Capping, Grinding &
Reveeetation
O
Groundwater Pumping
Wastewater Injection
C)
Interceptor Trenches
Impermeable Barriers
bo
5
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i
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§
43
1
| Excavation
Contaminant Source Type
Solid Waste
Disposal
Uncontrolled Dumps
N/A
Sard. & Secured Landfills
N/A
Deep Subsurface Burial
N/A
Leachate
N/A
Liquid Waste Disposal
Wastewater Impound.
N/A 1
Deep Subsurface Injection
4/A 1
Land Spraying
SI/A
Discharge To Surf. Water
Ind. Sewage Disposal
N/A N/A
Leakage
Surface Storage Facilities J
N/A
Subsurface Storage Faci. |
N/A
Subsurface Transport Sys.
Subsurface Disposal Faci.
N/A N/A
-------
MODPATH
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware Prime
Platforms: IBM PC/386/486
Preprocessors:
(Techsoft, Inc.)
Model CAD
(Geraghty & Miller)
Postprocessors: None
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
&
1
PH
§
Tl
«J
-
I
PH
fr
I
I
Reliability
I
S
I
D
ss
w
I
£
I
2
C/5
Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401, USA
Scientific Software Group
P.O. Box 23041
Washington, D.C. 20026-3041
Tel. (703) 620-9214
Geraghty & Miller, Inc.
Modeling Group
10700 Park Ridge Blvd., Suite 600
Reston, VA 22091
Tel. (703) 758-1200
Page 4-18
-------
Model Type: Ground-water
Row
WHPA - GPTRAC
Version 2.2
Release Date: 9/93
Summary Updated: May 1994
WHPA-GPTRAC is the WHPA module used to delineate time-related capture zones for pumping wells in
homogeneous aquifers with steady & uniform ambient ground-water flow (semi-analytical option) and also
o±nf ^ffT1*, * n Ca?*?e Z°neS ab°Ut P0**"* welk for steady ground-water flow fields (numerical
option). Effects of well interference are accounted for. WHPA is an integrated program of analytical and semi-
analyncal solutions for the ground-water flow equation coupled with pathline £ acSig. It isTeSSed to assS?
£S± * Wlt\ delmea,ti0^ °f Wef:ea-. .25 u
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/
Surface Spills
N/A
Key
Likely
Possibly
Not Likely
O
Not
Applicable
N/A
Parameter
Representation
m
Homogeneou
/
«
Heterogeneou
/
_y
/
Anisotropic
/
Key
Model
M
Pre or Post
Processor
P
Both
B
Neither
X
Page 4-19
-------
WHPA - GPTRAC
Definitions
Boundary Conditions;
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC/AT
Platforms:
Preprocessors: Menu Driven
Postprocessors: Display Results
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
o
Q
§
PH
Availability
Usability
c
o
.a
8
Q
c
o
a
a,
PH
1
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§
43
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Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401
USA
Center for Subsurface Modeling Support
R. S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: (405) 436-8500
Page 4-2O
-------
Model Type: Ground-water
Row
WHPA - MWCAP
Version 2.1
Release Date: 4/92
Summary Updated: May 1994
WHPA-MWCAP is the WHPA module used to delineate steady-state, time-related or hybrid capture zones for
pumping wells in homogenous aquifers with steady and uniform ambient ground-water flow. If multiple wells
are examined, the effects of well interference are ignored. WHPA is an integrated program of analytical and semi-
analytical solutions for the ground-water flow equation coupled with pathline tracking. It is designed to assist
technical staff with delineation of wellhead protection areas. Developed for the U.S. EPA's Office of Groundwater
Protection, the package includes modules for capture zone delineation in a homogeneous aquifer with 2-
dimensional steady-state flow with options for multiple pumping/injection wells and barrier or stream boundary
conditions.
Scope
Remedial Design Feature
oo
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.
N/A
00
I
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8
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1
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N/A
N/A
§
PQ
8
1
1
CD
£«
N/A
N/A
Contaminant Source Type
Liquid Waste Disposal
I
I
N/A
N/A
1
N/A
N/A
N/A
Leakage
CD
N/A
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N/A
en
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Key
Likely
Possibly
Not Likely
O
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Applicable
N/A
Technical Characteristics
Model
Processes
Flow
System
Aquifer
Type
Flow
Characteristics
(Saturated)
Transport
Processes
Fatefe
Transfer
Processes
Flow
Solution
Technique
Parameter
Representation
I
E
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Conditions
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Boundary
Conditions
Flow
Output
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Output
Output
Format
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P
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B
Neither
X
Page 4-21
-------
WHPA - MWCAP
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC/AT
Platforms:
Preprocessors: Menu Driven
Postprocessors: Display Results
Dot Matrix
Laser Printers
Pen Plotters
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
o
Q
§
OH
c
O
I
1
i
IH
I*
PH
/
I
Reliability
g
ft
8
o»
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(Q
u
Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401
USA
Center for Subsurface Modeling Support
R. S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: (405) 436-8500
Pago 4-22
-------
Model Type: Ground-water
Flow
WHPA - RESSQC
Version 2.1
Release Date: 4/92
Summary Updated: May 1994
SESSSr^^^^
r\f A extent with steady and uniform ambient ground-water flow. Well interference effects arp arrrmnteri
for. WHPA is an integrated program of analytical anlsemi-analytical solutions^^oun^waterflo^
==rffl
±S^^S±2SS :£0?>'I?*' * 2-dimensional stead^tatrf^wlS^for11168
Scope
Remedial Design Feature
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Page 4-23
-------
WHPA-RESSQC
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminant mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC/AT
Platforms:
Preprocessors: Menu Driven
Postprocessors: Display Results
Dot Matrix
Laser Printers
Pen Plotters
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405)436-8606
Availability
Usability
&
I
c/i
/ /
Pmge4-24
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Reliability
1
I
Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401
USA
Center for Subsurface Modeling Support
R. S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: (405) 436-8500
-------
Model Type: Ground-water
Flow
WHPA - MONTEC
Version 2.1
Release Date: 4/92
Summary Updated: May 1994
WHPA-MONTEC is the WHPA module for Monte Carlo analysis of uncertainty and a particle-tracking
SSF^£?!^^ models/Ucl? as MODFLOW an'd PLASM, usinga^ twcnlEne^Sigular
id. WHPA is an integrated program of analytical and semi-analytical solutions for the ground-water flow
equation coupled with pathline tracking. It is designed to assist technical staff with delineation oTwStad
protection areas. Developed for tihe U.S. EPA's Office of Groundwater Protection, the package include? Modules
6 01"6 dehnea aquifer with 2-dimensional steady-state flow^ith optio^or
multiple pumping/injection wells
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Page 4-25
-------
WHPA-MONTEC
Definitions
Boundary Conditions:
Specified Value - Values of head, concentration or temperature are specified along the boundary.
(Dirichlet Condition)
Specified Flux - Flow rate of water, contaminent mass or energy is specified along the boundary.
(Neumann Condition)
Value Dependent Flux - A specified flux is given for a specified value. (Cauchy Condition)
Hardware IBM PC/AT
Platforms:
Preprocessors: Menu Driven
Postprocessors: Display Results
Dot Matrix
Laser Printers
Pen Plotters
Detailed information on this model, sources of distribution, and postprocessors and preprocessors is
available in the Ground-Water Modeling Compendium.
Technical
Assistance:
Dr. David S. Burden, Director
Center for Subsurface Modeling Support (CSMoS)
Robert S. Kerr Environmental Research Laboratory (RSKERL)
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
(405) 436-8606
Availability
Usability
C/3
I
Page 4-26
I
05
£
I
1
E
Reliability
ss
w
1
u
Distributed By:
International Ground Water Modeling Center
Colorado School of Mines
Golden, CO 80401
USA
Center for Subsurface Modeling Support
R. S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: (405) 436-8500
-------
Model Description For
MOC
(USGS-2D- TRANSPOR T/KONBRED)
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
MOC
Table of Contents
PAGE
i. Model Identification......... ...... ...... ........ ........... ......... - ...... ...
1.1. Model Name(s) [[[ 4s-
1.2. Date of First Release [[[ 4a-!
1.3. Current Version [[[ 4a-l
1.4. Current Release Date [[[ 4a'l
1.5. Author [[[ 4a-!
2. Model Information....................-^'-"-' ..... ................................ 4a-1
2.1. Model Category [[[ 4a-!
2.2. Model Developed For [[[ 4a~l
2.3. Units of Measurement Used [[[ 4a-l
2.4. Abstract [[[ ....... 4a-1
2.5. Data Input Requirements [[[ 4a"2
2.6. Versions Exist For The Following Computer Systems .................... 4a-2
2.7. System Requirements [[[ 4a~2
2.8. Graphics Requirements [[[ 4a~2
2.9. Program Information [[[ 4a~2
3. General Model Capabilities ....... . ...... .............. ......... ........ ....... 4a-3
3.1. Parameter Discretization [[[ 4a~3
3.2. Coupling [[[ 4a~3
3.3. Spatial Orientation [[[ 4a~3
3.4. Types of Possible Updates [[[ 4a~3
3.5. Geostatistics and Stochastic Approach ................................................ 4a-3
3.6. Comments [[[ 4a'3
4. Flow Characteristics .. ........... ............. ........... ........................ 4a-3
4.1. Flow System Characterization [[[ ........ 4a~3
-------
PAGE
7. Documentation and Support.................................................. 4a-7
7.1. Documentation Includes [[[ 4a-7
7.2. Support Needs [[[ ........... 4a-7
7.3. Level of Support [[[ 4a-7
8. Availability [[[ 4a-8
8.1. Terms [[[ 4a_8
8.2. Form [[[ 4a-8
9. Pre and Post Processors[[[^... 4a-8
9.1. Data Preprocessing [[[ ......... 4a-8
-------
MOC
1. Model Identification
1.1. Model Name(s)
USGS-2D-TRANSPORT
MOC
KONBRED
1.2. Date of First Release
11/76
1.3. Current Version
3.0
1.4. Current Release Date
11/89
1.5. Author
1. Konikow, L.F.
2. Bredehoeft, J.D.
2. Model Information
2.1. Model Category
ground-water flow
mass transport
2.2. Model Developed For
general use (e.g. in field applications)
2.3. Units of Measurement Used
SI system
metric units
US customary units
any consistent system
2.4. Abstract
MOC is a two-dimensional model for the simulation of non-conservative
solute transport in heterogeneous, anisotropic aquifers. It computes changes
in time in the spatial concentration distribution caused by convective
transport, hydrodynamic dispersion, mixing or dilution from recharge, and
chemical reactions. The chemical reactions include first-order irreversible
rate reaction (e.g. radioactive decay), equilibrium-controlled sorption with
linear, Freiundlich or Langmuir isotherms, and monovalent and/or divalent
ion-exchange reactions. MOC solves the finite difference approximation of
' Pmge 4a-1
-------
Section 4: Model Descriptions Model Description for HOC
the ground-water flow equation using iterative ADI and SIP. It uses the
method of characteristics followed by an explicit procedure to solve the
transport equation.
2.5. Data Input Requirements:
Data input requirements are provided in the model documentation and are
discussed in the introduction to Section 4.0 of the Compendium.
2.6. Versions Exist For The Following Computer Systems
minicomputer
workstations
mainframe
microcomputer
Make/Model
Prime
- DEC VAX
-IBM PC/XT/AT
- operating system
MS DOS
- IBM 80386/486
- operating system
MS DOS
OS/2
Unix
Apple Macintosh
2.7. System Requirements
core memory (FLAM) for execution (bytes)
-- 640Kb (standard IBM PC version)
mass storage (disk space in bytes)
at least 2Mb for data files
numeric/math coprocessor
(for micro computers)
compiler required
(for mainframe)
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
- Fortran 77
number of program statements (total)
- 2000
Page 4a-2
-------
Section 4; Model Descriptions Model Description for HOC
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Coupling
none
3.3. Spatial Orientation
saturated flow
2D-horizontal
2D-vertical
3.4. Types of Possible Updates
parameter values
boundary conditions
3.5. Oostatistics and Stochastic Approach
none
3.6. Comments
This model has restart capability
4. Flow Characteristics
4.1. Flow System Characterization
Saturated Zone
System
single aquifer
Aquifer Type(s)
confined
- semi-confined (leaky-confined)
Medium
porous media
Parameter Representation
homogeneous
heterogeneous
isotropic
- anisotropic
Flow Characteristics (Saturated Zone)
laminar flow
- linear (Darcian flow)
" Page 4a-3
-------
Section 4: Model Descriptions Model Description for MOC
steady-state
transient
Flow Processes Included
areal recharge
induced recharge (from river)
Changing aquiJfer conditions
in space
variable thickness
Well Characteristics
-- none
Unsaturated Zone
none
4.2. Fluid Conditions
Single Fluid Flow
water
Flow of Multiple Fluids
none
Fluid Properties
constant in time/space
4.3. Boundary Conditions
First Type - Dirichlet
head/pressure
Second type - Neumann (Prescribed Flux)
injection/production wells
no flow boundary
areal boundary flux
-- ground-water recharge
Third Type - Cauchy
head/pressure-dependent flux
4.4. Solution Methods for Flow
General Method
Numerical
Page 4a-4
-------
Section 4: Model Descriptions Model Description for MOC
Spatial Approximation
finite difference method
block-centered
Time-Stepping Scheme
Crank-Nicholson
Matrix-Solving Technique
- SIP
iterative ADIP
4.5. Grid Design
Cell/Element Characteristic
constant cell size
-- variable cell size
Possible Cell Shapes
2D-square
2D-rectangular
Maximum Number of Nodes
- 2000
4.6. Flow Output Characteristics
Simulation Results
Head/Pressure/Potential
- ASCII file (areal values)
- ASCII file (hydrograph)
Water Budget Components
- ASCII file (global total area)
5. Mass Transport Characteristics
5.1. Water Quality Constituents
any component(s)
single component
total dissolved solids (TDS)
inorganics
organics
radionuclides
5.2. Processes Included
(Conservative) Transport
advection
dispersion (Jsotropic; anisotropic)
diffusion
^^~"" Page 4a-5
-------
Section 4: Model Descriptions Model Description for MOC
Phase Transfers
Solid <-> Liquid
- sorption equilibrium isotherm
linear
- Langmuir
- Freundlich
Fate
first-order radioactive decay (single mother/daughter decay)
-- first-order chemical decay
first-order microbial decay
5.3. Boundary Conditions
First Type - Dirichlet
Chemical processes embedded in transport equation
concentration
Second Type - Neumann (Prescribed Solute Flux)
areal boundaries
injection wells
point sources
line sources
areal sources
5.4. Solution Methods for Transport
General Method
numerical
uncoupled flow and transport equation
Spatial Approximation
finite difference method
block-centered
particle-tracking
Time-Stepping Scheme
fully explicit
Matrix-solving Technique
~ method of characteristics
5.5. Output Characteristics for Transport
Simulation Results
Concentration in Aquifer/Soil
- ASCII file (areal values)
- ASCII file (time series)
Page 4a-6
-------
Section 4: Model Descriptions
Model Description for MOC
Mass Balance Components
- ASCII file (global total area)
6. Evaluation
6.1. Verification / Validation
verification (analytic solutions)
laboratory data sets
field datasets (validation)
synthetic datasets
code intercomparison
6.2. Internal Code Documentation (Comment Statements)
incidental
6.3. Peer (Independent) Review
concepts
theory (math)
coding
accuracy
7. Documentation and Support
7.1. Documentation Includes
model theory
user's instructions
example problems
code listing
7.2. Support Needs
Can be used without support
Support is available
from author
from third parties
7.3. Level of Support
limited
support agreement available
Page 4a-7
-------
Section 4: Model Descriptions Model Description for MOC
8. Availability
8.1. Terms
available
public domain
proprietary
8.2. Form
source code only (tape/disk)
source and compiled code
compiled code only
9. Pro and Post Processors
9.1. Data Preprocessing
name: PREMOC
separate (optional) program
generic (can be used for various models)
textual data entry/editing
name: MODELCAD
- separate (optional) program
generic (can be used for various models)
textual data entry/editing
graphic data entry/modification (e.g manual grid design, arrays)
data reformatting (e.g. for GIS)
~ error-checking
help screens
9.2. Data Postprocessing
name: POSTMOC
separate (optional) program
reformatting (e.g. to standard formats)
10. Institution of Model Development
10.1. Name
U.S. Geological Survey
10.2. Address
National Center
Reston, Virginia
10.3. Type of Institution
federal/national government
Page 4a-8
-------
Section 4: Model Descriptions Model Description for MOC
11. Remarks
The MOC package distributed by the International Ground Water Modeling Center
includes a preprocessor (PREMOC) to prepare input files, a postprocessor
(POSTMOC) to reformat parts of the output file to allow the import the results in
graphic display programs, and two versions of the MOC simulation program,
MOCADI and MOCSIP. MOCADI and MOCSIP are identical apart from the methods
used to solve the finite difference flow equations. The IGWMC distributes both
IBM-PC and mainframe versions.
Contact the International Ground Water Modeling Center for latest information:
IGWMC USA: Inst. for Ground-Water Res. and Educ,
Colorado School of Mines,
Golden, CO 80401, USA.
IGWMC Europe: TNO Institute of Applied Geoscience,
P.O. Box 6012, 2600JA Delft,
The Netherlands.
IBM-PC, Macintosh and mainframe versions of the MOC code are also available
from:
Scientific Software Group
P.O. Box 23041
Washington, D.C. 20026-3041
(703) 620-9214
MOCGRAF is a program developed by TECSOFT, Inc. to provide graphics capability
to MOC. It uses the output from MOC to contour heads and concentrations and to
plot velocity vectors. It supports a variety of graphic screen formats, printers and
plotters. MOCGRAF requires TECSOFTs TRANSLATE program. MOCGRAF is
available from Scientific Software Group
MACMOC is the implementation of the USGS Method of Characteristics
Solute Transport Model (MOC) for the Apple Macintosh. The data input
editor, simulation code and output postprocessor are integrated in a single
application. Graphic output includes head and concentration contouring,
and velocity vector plotting. It requires a Macintosh Plus with System 6.02
and Finder 6.1 or higher arid at least 2Mb RAM. MACMOC is available
from the Scientific Software Group.
Page 4a-9
-------
Section 4: Model Descriptions Model Description for MOC
Notes on computer program updates have been published by the USGS, Reston,
Virginia, on the following dates:
1. May 16,1979 7. Jul. 26,1985 13. Oct. 20,1986
2. Mar. 26,1980 8. Jul. 31,1985 14. Mar. 2,1987
3. Dec. 4,1980 9. Aug. 2,1985 15. Mar. 5,1987
4. Aug. 26,1981 10. Aug. 8,1985 16. Jan. 29,1988
5. Oct. 12,1983 11. Aug. 12,1985 17. Nov. 21,1988
6. Jun. 10,1985 12. Jul. 2,1986 18. Jul. 20,1989
A modification of this model to track representative water of tracer particles initially
loaded along specific lines has been developed by Garabedian and Konikow (1983):
TRACK (see IGWMC key # 0741).
The code has been modified by Hutchinson to allow head-dependent flux as a
boundary condition:
Hutchinson, C.B. et al. 1981. Hydrogeology of Well-field Areas near Tampa,
Florida. USGS Open-File Report 81-630.
A modification to allow linear and non-linear sorption isotherms and first-order
decay was introduced in 1982:
Tracy, J.V. 1982. Users Guide and Documentation for Adsorption and Decay
Modifications of the USGS Solute Transport Model. NUREG/CR-2502, Div.
of Waste Management, Off. of Nuclear Material Safety and Safeguard, U.S.
Nuclear Regulatory Comm., Washington, D.C.
MODELCAD is a graphical oriented, model-independent preprocessor to prepare
and edit input files for two- and three-dimensional ground-water models, including
aquifer properties, boundary conditions, and grid dimensions. The program
prepares input files for MODFLOW, MOC, PLASM and RANDOM WALK, among
others. File formatting routines for other models are available upon request.
Contact:
Geraghty & Miller Modeling Group
1895 Preston White Drive
Suite 301, Reston, VA 22091
(703) 476-0335
Page 4a-10
-------
Section 4: Model Descriptions Model Description for MOC
Strecker,E.W., VV-S. Chu, and D. P. Lettenmaier. 1985. Evaluation of Data
Requirements for Ground water Contaminant Transport Modeling. Water
Resources Series, Techn. Rept. 94, Univ. of Washington, Seattle, Wash.
In this study a parameter identification algorithm was used together with the USGS-
MOC code and applied to two synthetic aquifers, evaluating the effects of data
availability and uncertainty on ground-water contaminant transport prediction.
The parameter identification algorithm is based on constrained least-squares
minimization.
Also:
Strecker, E.W., and W-s. Chu. 1986. Parameter Identification of a Ground-Water
Contaminant Transport Model. Ground Water, Vol. 24(1), pp. 56-62.
A modified version of the 1978 version of the USGS MOC model has been presented
by Kent et Al. (1983; see references). Modifications include water-table option for
flow and non-linear sorption. The same authors developed a menu-driven,
preprocessor for their version of MOC. For more information contact Dr. Douglas C.
Kent, School of Geol., Oklahoma State University, Stillwater, Oklahoma.
A stochastics-based analysis of the performance of the MOC model in remedial
action simulations is discussed in:
El-Kadi, A.I. 1988. Applying the USGS Mass-Transport Model (MOC) to
Remedial Actions by Recovery Wells. Ground Water, Vol. 26(3), pp. 281-288.
An IBM PC/386 extended memory version of this model is also available from:
Geraghty & Miller, Inc.
Modeling Group
1895 Preston Drive, Suite 301
Reston, VA 22091
tel.: 703/476-0335
fax: 703/476-6372
Page 4a-f 1
-------
Section 4: Model Descriptions Model Description for MOC
12. References
Finder, G.F. and H.H. Cooper. 1970. A Numerical Technique for Calculating the
Transient Position of the Saltwater Front. Water Resources Research, Vol.
6(3), pp. 875-882.
Bredehoeft, J.D., and G.F. Finder. 1973. Mass Transport in Flowing
Groundwater. Water Resources Research, Vol. 9(1), pp. 194-210.
Konikow, L.F., and J.D. Bredehoeft. 1974. Modeling Flow and Chemical Quality
Changes in an Irrigated Stream-Aquifer System. Water Resources Research,
Vol. 10(3), pp. 546-562.
Konikow, L.F., and J.D. Bredehoeft. 1978. Computer Model of Two-Dimensional
Transport and Dispersion in Ground Water. USGS Techniques of Water
Resources Investigations, Book 7, Chapter 2, U.S. Geological Survey, Reston,
Virginia.
Kent, D.C., J. Alexander, L. LeMaster, and J. Wagner. 1983. Interactive
Preprocessor Program for the U.S.G.S. Konikow Solute Transport Model.
Oklahoma State University, School of Geology, Stillwater, Oklahoma.
Kent, D.C., M.M. Hoque, L. LeMaster, and J. Wagner. 1983. Modifications to the
U.S.G.S. Solute Transport Model. School of Geology, Oklahoma State
University, Stillwater, Oklahoma.
Goode, D.J., arid L.F. Konikow. 1989. Modification of a Method-of-Characteristics
Solute Transport Model to Incorporate Decay and Equilibrium-Controlled
Sorption or Ion Exchange. USGS Water Resources Investigations Report 89-
4030, U.S. Geological Survey, Reston, Virginia.
Page 4a-12
-------
Section 4s Model Descriptions Model Description for MOC
13. Users
Spinazola, J.M., J.B. Gillespie, and R.J. Hart. Ground-Water Flow and Solute
Transport in the Equus Beds Area, South Central Kansas, 1940-79. Water-
Resources Investig. Kept. 85-4336, Lawrence, Kansas.
The transport model was used to study the movement of chloride in the past
and under the various proposed pumping development schemes. The
sources of the chloride is oilfield brine moving towards the wellfields and the
Arkansas river.
Robertson, J.B. 1974. Digital Modeling of Radioactive and Chemical Waste
Transport in the Snake River Plain Aquifer at the National Reactor Testing
Station, Idaho. USGS Open-File Report IDO-22054. U.S. Geological Survey,
Boise, Idaho.
Konikow, L.F. 1977. Modeling Chloride Movement in the Alluvial Aquifer at
the Rocky Mountain Arsenal, Colorado. USGS Water Supply Paper 2044, U.S.
Geological Survey, Denver, Colorado.
Sohrabi, T. 1980. Digital Transport Model Study of Potential Nitrate
Contamination from Sceptic Tank Systems near Edmond, Oklahoma. Rept.
80-38, National Center for Ground Water Research, University of Oklahoma,
Norman, Okla.
Sophocleous, M.A. 1984. Groundwater Flow Parameter Estimation and Quality
Modeling of the Equus Beds Aquifer in Kansas, USA. Journ. of Hydrology,
Vol. 69, pp. 197-222.
In an accompanying Technical Completion Report of the Kansas Water
Resources Research Institute at the University of Kansas, Lawrence,
Sohocleous et al. compares the MOC code with Finder's ISOQUAD-4 code and
Grove's finite difference solute transport code.
Freeberg, K.M. 1985. Ground Water Contaminant Modeling Applied to Plume
Delineation and Aquifer Restoration at an Industrial Site. M.Sc. Thesis, Dept.
of Env. Sciences and Eng., Rice Univ., Houston, Texas.
Groschen, G.E. 1985. Simulated Effects of Projected Pumping on the Availability
of Fresh Water in the Evangeline Aquifer in an Area Southwest of Corpus
Christi, Texas. USGS Water Resources Investigations Report 85-4182, Austin,
Texas.
Chapelle, F.H. 1986. A Solute Transport Simulation of Brackish Water Intrusion
near Baltimore, Maryland. Ground Water, Vol. 24(3), pp 304-311.
The model was used to estimate the future movement of the brackish-water
plume in the coarse sands and gravels of the Patuxent Formation based on
Page 4a-13
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Section 4; Model Descriptions Model Description for MOC
alternative strategies of aquifer use. (see also Maryland Geological Survey
Report of Investig. 43 (1986)).
Davis, A.D. 1986. Deterministic Modeling of Dispersion in Heterogeneous
Permeable Media. Ground Water, Vol. 24(5), pp. 609-615.
Perez, R. 1986. Potential for Updip Movement of Saline Water in the Edwards
Aquifer, San Antonio, Texas. USGS Water Resources Investigations Report
86-4032, U.S. Geological Survey, Austin, Texas.
Bond, L.D., and J.D. Bredehoeft. 1987. Origins of Seawater Intrusion in a Coastal
Aquifer-A Case Study of the Pajaro Valley, California. Journ. of Hydrology,
Vol. 92, pp,363-388.
Mixon, P.O., A.S. Damle, R.S. Truesdale, and C.C. Allen. 1987. Effect of
Capillarity and Soil Structure on Flow in Low permability Saturated Soils at
Disposal Facilities. EPA/600/2-87/029, Hazardous Waste Eng. Research Lab.,
U.S. Environmental Protection Agency, Cincinnati, Ohio.
Patterson, C-V. 1987. Risk Analysis of Annular Disposal of Oil and Gas Well
Brines. M.Sc. Thesis, Dept. of Systems Eng., Case Western Reserve
University, Cleveland, Ohio.
Al-Layla, R., H. Yazicigil, and R. de Jong. 1988. Numerical Modeling of Solute
Transport Patterns in the Damman Aquifer. Water Resources Bulletin, Vol.
24(1), pp. 77-85.
Used to predict the extent of the saline intrusion in this carbonate rock aquifer
in the Kingdom of Saudi Arabia and studying the effects of changes in the
hydrologic regime on TDS concentration. The model was modified to
include the effects of salt gradients resulting from vertical leakage into the
host aquifer.
Satkin, R.L., and P.b. Bedient. 1988. Effectiveness of Various Aquifer Restoration
Schemes under Variable Hydrogeologic Conditions. Ground Water, Vol.
26(4), pp. 488-498.
Yager, R.M. and M.P. Bergeron. 1988. Nitrogen Transport in a Shallow Outwash
Aquifer at Olean, Cattaraugus County, New York. Water-Resources
Investigations Report 87-4043, U.S. Geological Survey, Ithaca, New York.
Page 4a-14
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Model Description For
MODFLOW
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
MODFLOW
Table of Contents
PAGE
1. Model Identification 4b-f
1.1. Model Name(s) 4b-l
1.2. Date of First Release 4b-l
1.3. Current Version # 4b-l
1.4. Current Release Date 4b-l
1.5. Authors 4b-l
2. Model Information 4b-f
2.1. Model Category 4b-l
2.2. Model Developed For 4b-l
2.3. Units of Measurement Used 4b-l
2.4. Abstract 4b-l
2.5. Data Input Requirements 4b-2
2.6. Versions Exist for the Following Computer Systems 4b-2
2.7. System Requirements 4b-2
2.8. Graphics Requirements 4b-2
2.9. Program Information 4b-2
3. General Model Capabilities................................................ 4b-3
3.1. Parameter Discretization 4b-3
3.2. Coupling 4b-3
3.3. Spatial Orientation 4b-3
3.4. Types of Possible Updates 4b-3
3.5. Geostatistics and Stochastic Approach 4b-3
3.6. Comments 4b-3
4. Flow Characteristics[[[ 4b-3
4.1. Flow System Characterization 4b-3
4.2. Fluid Conditions 4b-4
4.3. Boundary Conditions 4b-4
4.4. Solution Methods for Flow 4b-5
4.5. Grid Design 4b-5
4.6. Flow Output Characteristics 4b-5
5. Evaluation.................................................................. 4b-6
5.1. Verification/Validation 4b-6
5.2. Internal Code Documentation (Comment Statements) 4b-6
5.3. Peer (Independent) Review 4b-6
6. Documentation and Support............................................. 4b-6
6.1. Documentation Includes 4b-6
-------
PAGE
7. Availapilify[[[M..
7.1. Terms 4b-7
7.2. Form 4b-7
8. Pre and Post Processors[[[ 4b-7
8.1. Data Preprocessing 4b-7
8.2. Data Postprocessing 4b-7
9. Institution of Model Development.................................... 4b-8
9.1 Name 4b-8
9.2. Address 4b-8
9.3. Type of Institution 4b-8
10, Remarks[[[ 4b-8
-------
MODFLOW
1. Model Identification
1.1. Model Name(s)
MODFLOW
1.2. Date of First Release
6/83
1.3. Current Version #
3.2
1.4. Current Release Date
10/89
1.5. Authors
1. McDonald, M.G.
2. Harbaugh, A.W.
2. Model Information
2.1. Model Category
ground-water flow
2.2. Model Developed For
general use (e.g. in field applications)
research (e.g. hypothesis/theory testing)
demonstration/education
2.3. Units of Measurement Used
SI system
metric units
any consistent system
2.4. Abstract
MODFLOW is a modular, block-centered finite difference model for the
simulation of two-dimensional and quasi- or fully-three-dimensional,
transient ground-water flow in anisotropic, heterogeneous, layered
aquifer systems. It calculates piezometric head distributions, flow rates
and water balances. The model includes modules for flow towards
wells, through riverbeds, and into drains. Other modules handle
evapotranspiration and recharge. Various textual and graphic pre- and
postprocessors are available.
Page 4b-1
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Section 4: Model Descriptions Model Description for MODFLOW
2.5. Data Input Requirements:
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
supercomputer
minicomputer
workstations
mainframe
microcomputer
Make/Model
- IBM-PC/XT/AT
- operating system
DOS 2.1 or later
- DEC VAX 11/780
- PRIME 750
Macintosh
- Intel 80386/80486 based computers
2.7. System Requirements
core memory (FLAM) for execution (bytes)
- 640Kb (standard IBM PC version)
mass storage (disk space in bytes)
~ at least 2Mb for data files
numeric/math coprocessor
(for micro computers)
compiler require
(for mainframe)
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
- Fortran 77
number of program statements (total)
- 5000 lines
size of runtime (compiled) version (bytes)
- 580Kb (IBM-PC version)
Page 4b-2
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Section 4: Model Descriptions Model Description for MODFLOW
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Coupling
N.A.
3.3. Spatial Orientation
saturated flow
2D-horizontal
2 D-vertical
3D-layered (quasi 3D)
3.4. Types of Possible Updates
parameter values
boundary conditions
3.5. Geostatistics and Stochastic Approach
optional
3.6. Comments
This model has restart capability.
4. Flow Characteristics
4.1. Flow System Characterization
Saturated Zone
System:
- single aquifer
- single aquifer/aquitard system
~ multiple aquifer/aquitard systems
Aquifer Type(s)
- confined
- semi-confined (leaky-confined)
- uncorifined (phreatic)
Medium:
- porous media
Parameter Representation
homogeneous
heterogeneous
Page 4b-3
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Section 4: Model Descriptions Model Description for MODFLOW
isotropic
anisotropic
Flow Characteristics (Saturated Zone)
laminar flow
linear (Dardan flow)
steady-state
transient
Flow Processes Included
areal recharge
induced recharge (from river)
-- evapotranspiration
Changing Aquifer Conditions
in space
- variable thickness
- confined/unconfined
- pitching aquitard
in time
- desaturation(saturated/unsat.)
confined/unconfined
resaturation of dry cells
Well Characteristics
partial penetration
4.2. Fluid Conditions
Single Fluid Flow
water
Flow of Multiple Fluids
- N.A.
Fluid Properties
constant in time/space
4.3. Boundary Conditions
First Type - Dirichlet
head/pressure
Second Type - Neumann (Prescribed Flux)
injection/production wells
no flow boundary
areal boundary flux
ground-water recharge
Page 4b-4
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Section 4: Model Descriptions Model Description for MODFLOW
seepage face
springs
induced infiltration
Third Type - Cauchy
- head/pressure-dependent flux
- free surface (steady-state; movable)
4.4. Solution Methods for Flow
General Method
- Numerical
Spatial Approximation
finite difference method
block-centered
Time-Stepping Scheme
- fully implicit
Matrix-Solving Technique
Iterative
-- SIP
- LSOR
4.5. Grid Design
Cell/Element Characteristic
constant cell size
variable cell size
3D-hexahedral
Possible Cell Shapes
~ 2D-square
2D-rectangular
~ 3D-cubic
Maximum Number of Nodes
- 9999
4.6. Flow Output Characteristics
Simulation Results
- Head/Pressure/Potential
- binary file (areal values)
- ASCII file (areal values)
- binary file (hydrograph)
- ASCII file (hydrograph)
Page 4b-5
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Section 4: Model Description* Modal Description for MODFLOW
Fluxes/Velocities
- binary file (areal values)
- ASCII file (areal values)
- binary file (temporal values)
- ASCII file (temporal values)
Water Budget Components
- ASCII file (cell-by-cell values)
- ASCII file (global total area)
5. Evaluation
5.1. Verification/Validation
verification (analytical solutions)
synthetic datasets
code intercomparison
5.2. Internal Code Documentation (Comment Statements)
sufficient
5.3. Peer (Independent) Review
concepts
theory (math)
coding
accuracy
documentation
usability
6. Documentation and Support
6.1. Documentation Includes
model theory
user's instructions
example problems
code listing
program structure and development
verification/validation
6.2. Support Needs
Can be used without support
Support is available
from author
from third parties
Page 4b-6
-------
6.3. Level of Support
limited
support agreement available
7. Availability
7.1. Terms
available
public domain
proprietary
7.2. Form
source code only (tape/disk)
source and compiled code
compiled code only
paper listing of source code
0. Pre and Post Processors
8.1. Data Preprocessing
name: MODELCAD
- separate (optional) program
- graphic data entry/modification (e.g manual grid design,
arrays)
- (semi-) automatic grid generation
- data reformatting (e.g. for CIS)
- error-checking
help screens
name: PREMOD
-- part of model package (dedicated)
- textual data entry/editing
8.2. Data Postprocessing
name: POSTMOD
- part of model package (dedicated)
- textual data display on screen/printer
~ reformatting (e.g. to standard formats)
Pmgo 4b-7
-------
Section 4: Model Descriptions Model Description for MODFLOW
9. Institution of Model Development
9.1 Name
U.S. Geological Survey
9.2. Address
Ground Water Branch
WRD WGS - Mail Stop 433
National Center
Reston, Virginia 22092
9.3. Type of Institution
federal/national government
10. Remarks
The code is available from the U.S.G.S. on tape ($40). Contact Arlen
Harbaugh (see contact address). The documentation (paper copy $69.95,
microfiche $3.50) is available from:
U.S. Geological Survey
Open-File Service Section
Branch of Distribution
Box 25425, Federal Center
Denver, CO 80225
Various MODFLOW implementations for IBM-PC and main frame systems
are also available from the International Ground Water Modeling Center (see
also MARS # 3983, 3984, 3985, and 3986), including MODFLOW PC for IBM
PC/XT/AT (640K), and MODFLOW PC/EXT for extended memory Intel
80386/80486 based computers (2Meg,4Meg) which includes a preconditioned
conjugate gradient solver and a stream-flow routing package.
IGWMC USA: Inst. for Ground-Water Res. and Educ.,
Colorado School of Mines,
Golden, CO 80401, USA.
IGWMC Europe: TNO Institute of Applied Geoscience,
P.O. Box 6012, 2600JA Delft,
The Netherlands.
Page 45-8
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Section 4: Model Descriptions
Wagner, Heindel and Noyes Inc. has implemented MODFLOW on a Hewlett-
Packard microcomputer (series 200). Contact Jeffrey E. Noyes, Geologist:
Wagner, Heindel and Noyes, Inc.
285 North St.
Burlington, Vermont 05401
phone: (802) 658-0820.
Various implementations of MODFLOW are available from:
Scientific Publications Co.
P.O. Box 23041
Washington, DC 20026-3041
phone: 703/620-9214
fax: 703/620-6793.
Versions included:
MODFLOW/PC for IBM PC/XT/AT (640K)
MODFLOW/EM for extended memory Intel 80386/80486 based
computers (2Meg,4Meg) which includes a preconditioned conjugate
gradient solver and a stream-flow routing package.
MOCGRAF is a program developed by TECSOFT, Inc. to provide graphics
capability to MODFLOW. The menu-driven MODGRAF program uses the
output from MODFLOW to automatically contour heads and drawdowns
from each layer, stress period and time step and superpose velocity vectors on
the head contour plots. The program requires TECSOFT's TRANSLATE
program. A special 80386/486 version is available. Contact:
Scientific Software Group
P.O. Box 23041
Washington, D.C. 20026-3041
phone 703/620-9214.
1^°?^TH: a Partide-trackmg program developed by the USGS for use with
the MODFLOW model. MODPATH calculates the path a particle would take
in a steady-state three-dimensional flow field in a given amount of time It
operates as a post-processor for MODFLOW using heads, cell-by-cell flow
terms and porosity to move each particle through the flow field. The
program handles both forward and backward particle tracking (See also
IGWMC Key 3984). 6' V
Page 4b-9
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Sect/on 4; Model Descriptions Model Description for MODFLOW
MODPATH-PLOT: a graphic: display program for use with MODPATH-PC. It
uses the Graphical Kernal System (GKS) to produce graphical output on a
wide range of commonly used printers and plotters. MODPATH-PLOT comes
with MODPATH.
MACMODFLOW: this is the Macintosh implementation of the MODFLOW
model. It supports the standard Macintosh user-interface. The simulation
code is integrated with the input data editor and the graphic post-processor.
Extensive data-checking is employed and simulation stops are trapped with
control returning to the program. Graphic functions include contouring of
heads, drawdowns, hydraulic conductivity, transmissivity, and plots of the
finite difference grid. This version of MODFLOW is available from Scientific
Software Group.
PATH3D is a general particle tracking program for calculating ground-water
paths and travel times. The program uses the head solution of the USGS
modular finite difference model MODFLOW. The program is available from:
S.S. Papadopulos and Assoc, Inc
12250 Rockville Pike
Suite 290
Rockville , Maryland 20852
MODELCAD is a graphical oriented, model-independent pre- processor to
prepare and edit input files for two- and three-dimensional ground-water
models, including aquifer properties, boundary conditions, and grid
dimensions. The program prepares input files for MODFLOW, MOC, PLASM
and RANDOM WALK, among others. File formatting routines for other
models are available upon request. Contact:
Geraghty & Miller Modeling Group
1895 Preston White Drive
Suite 301
Reston, VA 22091
Phone: (703) 476-0335.
A related program contains a preconditioned conjugate gradient method for
the solution of the finite difference approximating equations generated by
MODFLOW (Kuiper 1987; see references). Five preconditioning types may be
chosen: three different types of incomplete Choleski, point Jacobi or block
Jacobi. Either a head change or residual error criteria may be used as an
indication of solution accuracy and interation termination. A later version of
this solver is included in the extended memory PC version from IGWMC,
Scientific Software and Geraghty & Miller Modeling Group.
Page 4b-10
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Section 4: Model Descriptions Model Description for MODFLOW
A computer program to summarize the data input and output from
MODFLOW is described by Scott (1990; see references). This program, the
Modular Model Statistical Processor, provides capabilities to easily read data
input to and output from MODFLOW, calculate descriptive statistics, generate
histograms, perform logical tests using relational operators, calculate data
arrays using arithmic operators, and calculate flow vectors for use in a
graphical display program. The program is written in Fortran 77 and tested on
a Prime 1/model 9955-11.
A computer program for simulating aquifer-system compaction resulting
from ground-water storage changes in compressible beds has been published
by Leake and Prudic (1988; see references). This program can be incorporated
in MODFLOW as the INTERBED-STORAGE-PACKAGE. (see also MARS
3985).
STR1 is a computer program written for use in MODFLOW to account for the
amount of flow in streams and to simulate stream-aquifer interaction. The
program is known as the Streamflow Routing Package (Prudic 1989; see
references.) (see also MARS 3896).
PCG2 (Hill 1990; see references) is a numerical code to be used with the USGS
MODFLOW model. It uses the preconditioned conjugate-gradient method to
solve the equations produced by the MODFLOW model. Both linear and
nonlinear flow conditions may be simulated. PCG2 includes two
preconditioning options: modified Cholesky preconditioning and polynomial
preconditioning. Convergence of the solver is determined using both head-
change and residual criteria. Non linear problems are solved using Picard
iterations. This solver is included in various extended memory PC versions.
An IBM PC/386 extended memory version of this model is also available
from:
Geraghty & Miller, Inc.
Modeling Group
1895 Preston Drive
Suite 301
Reston, VA 22091
tel.: 703/476-0335
fax: 703/476-6372
Page 4b-11
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Sect/on 4: Model Descriptions Model Description for MODFLOW
11. References
McDonald, M.G. and A.W. Harbaugh. 1983. A Modular Three-
Dimensional Finite-Difference Ground Water Model. Open-File Report
83-875, U.S. Geological Survey, Reston, Virginia.
Kuiper, L.K. 1987. Computer Program for Solving Ground-Water Flow
Equations by the Preconditioned Conjugate Gradient Method. Water-
Resources Investigations Report 87-4091, U.S. Geological Survey,
Austin, Texas.
Leake, S.A., and D.E. Prudic. 1988. Documentation of a Computer Program
to Simulate Aquifer-System Compaction using the Modular Finite-
Difference Ground-Water Flow Model. Open-File Report 88-482, U.S.
Geological Survey, Tuscon, Arizona.
McDonald, M.G., and A.W. Harbaugh. 1988. A Modular Three-
Dimensional Finite-Difference Ground-Water Flow Model. Book 6,
Modeling Techniques, Chapter Al, U.S. Geological Survey, Reston,
Virginia.
Prudic, D.E. 1989. Documentation of a Computer Program to Simulate
Stream-Aquifer Relations using a Modular, Finite-Difference, Ground-
Water Flow Model. Open-File Report 88-729, U.S. Geological Survey,
Carson City, Nevada.
Hill, M.C. 1990. Preconditioned Conjugate Gradient 2 (PCG2), A Computer
Program for Solving Ground-Water Flow Equations. Water Resources
Investigations Report 90-4048, U.S. Geological Survey, Denver,
Colorado.
Scott, J.C. 1990. A Statistical Processor for Analyzing Simulations Made
Using the Modular Finite-Difference Ground-Water Flow Model.
Water-Resources Investigations Report 89-4159, U.S. Geological
Survey, Oklahoma City, Oklahoma.
Page 45-Y 2
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Section 4: Model Descriptions Model Description for MODFLOW
12. Users
Brahana, J.V., and T.O Mesko. Hydrogeology and Preliminary Assessment
of Regional Flow in the Upper Cretaceous and Adjacent Aquifers in the
Northern Mississippi Embayment. Water-Resources Investig. Rept. 87-
4000, U.S. Geolog. Survey, Nashville, Tennessee.
McDonald, M.G., 1984. Development of a Multi-Aquifer Well Option for a
Modular Ground Water Flow Model. In: Proceedings Practical
Applications of Ground Water Models, Columbus, Ohio, August 15-17,
1984, pp. 786- 796. National Water Well Association, Dublin, Ohio.
Bailey, Z.C., 1985. Hydrologic Effects of Ground and Surface Water
Withdrawals in the Howe Area, LaGrange County, Indiana. Water
Resources Investig. Report 85-4163, U.S. Geological Survey,
Indianapolis, Indiana.
Grannemann, N.G. and F.R. Twenter, 1985. Geohydrology and Ground
Water Flow at Verona Well Fields, Battle Creek, Michigan. Water
Resources Investig. Report 85-4056, U.S. Geological Survey, East
Lansing, Michigan.
Kuniansky, E.L., 1985. Complex Depositional Environment at Baton
Rouge, Louisiana, Requires Innovative Model Layering. In:
Proceedings Practical Applications of Ground Water Models,
Columbus, Ohio, pp. 122-143. National Water Well Association
Dublin, Ohio.
Lindgren, H.A., 1985. Hydrologic Effects of Ground and Surface Water
Withdrawals in the Milford Area, Elkart and Kosciusko Counties,
Indiana. Water Resources Investig. Report 85-4166, U.S. Geological
Survey, Indianapolis, Indiana.
Spinazola, J.M., J.B. Gillespie and RJ. Hart, 1985. Ground Water Flow and
Solute Transport in the Equus Beds Area, South-Central Kansas, 1940-
79. Water Resources Investig. Report 85-4336, U.S. Geological Survey,
Lawrence, Kansas.
Trudeau, D.A. and A. Buono, 1985. Projected Effects of Proposed Increased
Pumpage on Water Levels and Salinity in the Sparta Aquifer Near
West Monroe, Louisiana. Technical Report No. 39, Louisiana Dept. of
Transportation and Development, Baton Rouge, Louisiana.
Weatherington - Rice, J.P., 1985. A Three-Dimensional Ground Water
Modeling Study for Development of the New Well Field at London
Correctional Institute in Madison County, Ohio. In: Proceedings
Practical Applications of Ground Water Models, Columbus Ohio pp
197-211. Nat. Water Well Association, Dublin, Ohio
Page 4b-13
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Section 4: Model Descriptions Model Description for MODFLOW
Yager, R.M. 1985. Simulation of Ground Water Flow Near the Nuclear
Fuel Reprocessing Facility at the Western New York Nuclear Service
Center, Cattaraugus County, New York. Water Resources Investig.
Report 85-4308, U.S. Geological Survey, Albany, New York.
Delin, G.N. 1986. Hydrogeology of Confined-Drift Aquifers near the
Pomme De Terre and Chippewa Rivers, Western Minnesota. Water
Resources Investig. Report 86-4098, U.S. Geological Survey,
Minneapolis, Minnesota.
Maridle, RJ. and A.L. Kontis, 1986. Directions and Rates of Ground Water
Movement in the Vicinity of Kesterson Reservoir, San Joaquin Valley,
California. Water Resources Investig. Report 86-4196, U.S. Geological
Survey, Sacramento, California.
Martin, P. and C. Berenbrock, 1986. Ground Water Monito ring at Santa
Barbara, California: Phase 3- Development of a Three-Dimensional
Digital Ground Water Flow Model for Storage Unit I of the Santa
Barbara Ground- Water Basin. Water-Resources Investig. Report 86-
4103, U.S. Geological Survey, Sacramento, California.
Tucci, P., 1986. Ground Water Flow in Melton Valley, Oak Ridge
Reservation, Roane County, Tennessee - Preliminary Model Analysis.
Water Resources Investig. Report 85-4221, U.S. Geological Survey,
Nashville, Tenn.
Zitta, V.L. and T.K. Pang, 1986. Application of a Groundwater Model to
Critical Areas in Northeast Mississippi. Department of Civil
Engineering, Water Resources Research Institute, Mississippi State
University, Mississippi State, Mississippi.
Bergeron, M.P. 1987. Effect of Reduced Industrial Pumpage on the
Migration of Dissolved Nitrogen in an Outwash Aquifer at Clean,
Cattaraugus County, New York. Water-Resources Investig. Report 85-
4082, U.S. Geological Survey, Ithaca, New York.
Kernodle, J.M. R.S. Miller and W.B. Scott. 1987. Three- Dimensional
Model Simulation of Transient Ground Water Flow in the
Albuquerque-Belen Basin, New Mexico. Water Resources Investig.
Report 86-4194, U.S. Geological Survey, Albuquerque, New Mexico.
Kidd, R.E., and W.S. Mooty. 1987. Simulation of the Flow System in the
Shallow Aquifer, Dauphin Island, Alabama. In: E.J. Edwards (ed.),
Proceed. 17th Mississippi Water Resources Conference, Jackson,
Mississippi, March 25-26,1987, pp. 99-107. Water Resources Research
Inst., Mississippi State Univ., Mississippi State, Mississippi.
Pmg* 4b-14
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Section 4; Model Descriptions Model Description for MODFLOW
Kyllonen, D.P., and K.D. Peter. 1987. Geohydrology and Water Quality of
the Inyan Kara, Minnelusa, and Madison Aquifers of the Northern
Black-Hills, South Dakota and Wyoming, and Bear Lodge Mountains,
Wyoming. Water-Resources Investigations Report 86-4158, U.S.
Geological Survey, Rapid City, South Dakota.
Phillips, S.W. 1987. Hydrogeology, Degradation of Ground- Water Quality,
and Simulation of Infiltration from the Delaware River into the
Potomac Aquifers, Northern Delaware. Water-Resources Investig.
Rept. 87-4185, U.S. Geol. Survey, Towson, Maryland.
Pool, D.R. 1987. Hydrogeology of McMullen Valley, West- Central
Arizona. Water-Investigations Report 87-4140, U.S. Geological Survey,
Tuscon, Arizona.
Risser, D.W. 1987. Possible Changes in Ground-Water Flow to the Pecos
River Caused by Santa Rosa Lake, Guadalupe County, New Mexico.
Water-Resources Investigations Report 85-4291, U.S. Geological
Survey, Albuquerque, New Mexico.
Weiss, E. 1987. Ground-Water Flow in the Navajo Sandstone in Parts of
Emery, Grand, Carbon, Wayne, Garfield, and Kane Counties, Southeast
Utah. Water-Resources Investigations Report 86-4012, U.S. Geological
Survey, Denver, Colorado.
Zitta, V.L., and T-K. Pang. 1987. Application of a Layered Groundwater
Model to Critical Areas in Northeast Mississippi. In: E.J. Hawkins (ed.),
Proceedings 17th Mississippi Water Resources Conference, Jackson,
Mississippi, March 25-26, 1987, pp, 89-94. Water Resources Research
Inst., Mississippi State Univ., Mississippi State, Mississippi.
Aucott, W.R. 1988. The Predevelopment Ground-Water Flow System and
Hydrologic Characteristics of the Coastal Plain Aquifers of South
Carolina. Water-Resources Investigations Report 86-4347, U.S.
Geological Survey, Columbia, South Carolina.
Bailey, Z.C. 1988. Preliminary Evaluation of Ground- Water Flow in Bear
Creek Valley, The Oak Ridge Reservation, Tennessee. Water-
Resources Investigations Report 88-4010, U.S. Geological Survey,
Nashville, Tennessee.
Brown, J.G., and J.H. Eychaner. 1988. Simulation of Five Ground-Water
Withdrawal Projections for the Black Mesa Area, Navajo and Hopi
Indian Reservations, Arizona. Water-Resources Investigations Report
88-4000, U.G. Geological Survey, Tuscon, Arizona.
Page 4b-15
-------
Section 4: Model Descriptions Model Description for MODFLOW
Buckles, D.R., arid K.R. Watts. 1988. Geohydrology, Water Quality, and
Preliminary Simulations of Ground-Water Flow of the Alluvial
Aquifer in the Upper Black Squirrel Creek Basin, El Paso County,
Colorado. Water-Resources Investigations Report 88-4017, U.S.
Geological Survey, Denver, Colorado.
Danskin, W.R. 1988. Preliminary Evaluation of the Hydrogeologic System
in Owens Valley, California. Water- Resources Investigations Report
88-4003, U.S. Geological Survey, Sacramento, California.
Davies-Smith, A.,, E.L. Bolke, and C.A. Collins. 1988. Geohydrology and
Digital Simulation of the Ground- Water Flow System in the Umatilla
Plateau and Horse Heaven Hills Area, Oregon and Washington.
Water- Resources Investigations Report 87-4268, U.S. Geological
Survey, Portland, Oregon.
Emmons, P.J. 1988. A Digital Simulation of the Glacial- Aquifer System in
Sanborn and Parts of Beadle, Miner, Hanson, Davison, and Jerauld
Counties, South Dakota. Water-Resources Investigations Report 87-
4082, U.S. Geological Survey, Huron, South Dakota.
Fenemor, A.D. 1988. A Three-Dimensional Model for Management of the
Waimea Plains Aquifers, Nelson. Publication 18, Hydrology Centre,
Dept. of Scientific and Industrial Research, Christchurch, New Zealand.
Fretwell, J.D. 1988. Water Resources and Effects of Ground-Water
Development in Pasco County, Florida. Water-Resources
Investigations Report 87-4188, U.S. Geological Survey, Tallahassee,
Florida.
Hamilton,F.A., arid J.D. Larson. 1988. Hydrogeology and Analysis of the
Ground-Water Flow System in the Coastal Plain of Southeastern
Virginia. Water- Resources Investigations Report 87-4240, U.S.
Geological Survey, Richmond, Virginia.
Hansen, D.S. 1988. Appraisal of the Water Resources of the Big Sioux
Aquifer, Moody County, South Dakota. Water-Resources
Investigations Report 87-4057, U.S. Geological Survey, Huron, South
Dakota.
Johnson, M.J., CJ. Londquist, J. Laudon, and H.T. Mitten. 1988.
Geohydrology and Mathematical Simulation of the Pajaro Valley
Aquifer System, Santa Cruz and Monterey Counties, California.
Water-Resources Investigations Report 87-4281, U.S. Geological
Survey, Sacramento, California.
Page 4b-16
-------
Section 4: Model Descriptions Model Description for MODFLOW
Laczniak, R.J., and A.A. Meng III. 1988. Ground-Water Resources of the
York-James Peninsula of Virginia. Water-Resources Investig. Rept. 88-
4059, U.S. Geol. Survey, Richmond, Virginia.
McAda, D.P., and M. Wasiolek. 1988. Simulation of the Regional
Geohydrology of the Tesque Aquifer System near Santa Fe, New
Mexico. Water-Resources Investigations Report 87-4056, U.S.
Geological Survey, Albuquerque, New Mexico.
Morgan, D.S. 1988. Geohydrology and Numerical Model Analysis of
Ground-Water Flow in the Goose Lake Basin, Oregon and California.
Water-Resources Investigations Report 87-4058, U.S. Geological
Survey, Portland, Oregon.
Yates, E.B. andJ.H. Wiese. 1988. Hydrogeology and Water Resources of
the Los Osos Valley Ground-Water Basin, San Luis Obispo County,
California. Water-Resources Investigations Report 88-4081, U.S.
Geological Survey, Sacramento, California.
Ackerman, D.J. 1989. Hydrology of the Mississippi River Valley Alluvial
Aquifer, South-Central United States ~A Preliminary Assessment of
the Regional Flow System. Water-Resources Investig. Rept. 88-4028,
U.S. Geol. Survey, Little Rock, Arkansas.
Coen III, A.W. 1989. Ground-Water Resources of Williams County, Ohio,
1984-86. Water-Resources Investigations Report 89-4020, U.S.
Geological Survey, Columbus, Ohio.
Duwelius, R.F., and T.K. Greeman. 1989. Geohydrology, Simulation of
Ground-Water Flow, and Ground-Water Quality at Two Landfills,
Marion County, Indiana. Water-Resources Investigations Report 89-
4100, U.S. Geological Survey, Indianapolis, Indiana.
Freckleton, J.R. 1989. Geohydrology of the Foothill Ground-water Basin
near Santa Barbara, California. Water-Resources Investig. Report 89-
4017, U.S. Geological Survey, Sacramento, California.
Imes, J.L. 1989. Analysis of the Effect of Pumping on Ground-Water Flow
in the Springfiled Plateau and Ozark Aquifers near Springfield,
Missouri. Water-Resources Investigations Report 89-4079, U.S.
Geological Survey, Rolla, Missouri.
A model of 42 by 42 mile area was calibrated under predevelopment
and transient pumping conditions. The model then was used to
quantify hydraulic properties of the aquifer and confining unit and the
hydro logic budget.
Page 4b-17
-------
Section 4s Model Descriptions Model Description for MODFLOW
Lima, V. de, and J.C Olimpio. 1989. Hydrogeology and Simulation of
Ground-Water Flow at Superfund-Site Wells G and H, Woburn,
Massachusetts. Water-Resources Investigations Report 89-4059,
U.S.Geological Survey, Boston, Massachusetts.
(The calibrated three-dimensional ground-water flow model of the
stratified drift area was designed as a tool for predicting the steady-state
and transient effects of pumpage in the vicinity of public supply wells.)
Martin, Jr., A., and C.D. Whiteman, Jr. 1989. Geohydrology and Regional
Ground-Water Flow of the Coastal Lowlands Aquifer System in Parts
of Louisiana, Mississippi, Alabama, and Florida-A Preliminary
Analysis. Water-Resources Investigations Report 88-4100, U.S.
Geological Survey, Baton Rouge, Louisiana.
Summer, D.M., B.E. Wasson, and S.J. Kalkhoff. 1989. Geohydrology and
Simulated Effects of Withdrawals on the Miocene Aquifer System in
the Mississippi Gulf Coast. Water-Resources Investig. Rept. 87-4172,
U.S. Geological Survey, Jackson, Mississippi.
Watson, L.R., R.J. Shedlock, K.J. Banaszak, L.D. Arihood, and P.K. Doss.
1989. Preliminary Analysis of the Shallow Ground-Water System in
the Vicinity of the Grand Calumet River/Indiana Harbor Canal, North-
western Indiana. Open-File Report 88-492, U.S. Geological Survey,
Indianapolis, Indiana.
Yobbi, D.K. 1989. Simulation of Steady-State Ground Water and Spring
Flow in the Upper Floridan Aquifer of Coastal Citrus and Hernando
Counties, Florida. Water-Resources Investig. Rept., U.S. Geol. Survey,
Tallahassee, Florida.
Young, H.W., and G.D. Newton. 1989. Hydrology of the Oakley Fan Area,
South Central Idaho. Water- Resources Investigations Rept. 88-4065,
U.S. Geolog. Survey, Boise, Idaho.
Bair, E.S., R.A. Sheets, and S.M. Eberts. 1990. Particle-Tracking Analysis of
Flow Paths and Traveltimes from Hypothetical Spill Sites within the
Capture Area of a Wellfield. Ground Water, Vol. 28 (6), pp. 884-892.
Velocity fields computed from simulated flows from a steadystate,
three-dimensional numerical model of a glacial drift/carbonate-
bedrock aquifer system were used in conjunction with a particle
tracking program to delineate traveltimes related capture areas of a
municipal wellfield and compute flow paths from a hypothetical spill
site.
Page 4b-18
-------
Model Description For
PLASM
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
PLASM
Table of Contents
PAGE
f. Model Identification. .. ..... 4. f
1.1. Model Name(s) """"""" '""""""
1.2. Date of First Release .3.ZZZZZ"."'.'.'.'.'.'.'.'.!!!! 4c-l
1.3. Current Release Date 4(>1
1.4. Authors 4 -
2. Model Information
2.1. Model Category
2.2. Model Developed For !.!!.^.."...... 4c-l
2.3. Units of Measurement Used 4r i
2.4. Abstract .'".'.'.'.'.'.'.'.'.'.".'.'.'.".'.'.'.'.'.'.'.'.'.'.'.'.'.".' 4c-l
2.5. Data Input Requirements 4c-2
2.6. Versions Exist for the Following Computer Systems.........I'I.4c-2
2.7. System Requirements 4c_2
2.8. Graphics Requirements 4C_2
2.9. Program Information .'.'.'.'.'.'.'.'.'.'.'.'.' 4c-2
3. General Model Capabilities 4c,2
3.1. Parameter Discretization "'"'"'"'"'"... 4c-2
3.2. Spatial Orientation 4c_2
3.3. Types of Possible Updates .'.'.'.'.'.'.'.'.'.'.'.*.'.'.'.'.'.'.'.'.'.'.'.'4c-2
3.4. Geostatistics and Stochastic Approach ."....4c-3
3.5. Comments 40
4. Flow Characteristics.. 4c-3
4.1. Flow System Characterization """".""."".""""". 4c-3
4.2. Fluid Conditions 4c-4
4.3. Boundary Conditions .3*Z'.'.'.'.'.'.'.'.'.'.'.'.'."'4c-4
4.4. Solution Methods for Flow
4.5. Grid Design
4.6. Flow
5. Evaluation
4.6. Flow Output Characteristics .............................................. "!".'".'.' ..... 4c-5
4C-5
.
5.1. Verification/Validation ....................
5.2. Internal Code Documentation (Comment Statements) ............ 4c-5
5.3. Peer (Independent) Review [[[ ......'*.4c-5
6. Documentation and Support
.
6.1. Documentation Includes ........................................... ..""" 4c-6
-------
PAGE
7. Availability. .. 4c-6
7.1. Terms 4c-6
7.2. Form 4c-6
8. Pre and Post Processors[[[ 4c-7
8.1. Data Preprocessing 4c-7
9. Institution of Model Development.................................... 4c-7
9.1. Name 4c-7
9.2. Address 4c-7
9.3. Type of Institution 4c-7
-------
PLASM
1. Model Identification
1.1. Model Namp(s)
PLASM
1.2. Date of First
1971
1.3. Current Rp1pa«?P
1985
1.4. Authors
1. Prickett, T.A.
2. Lonnquist, C.G.
2. Model Information
2.1. Model Category
ground-water flow
2.2. Model Developed Fnr
general use (e.g. in field applications)
research (e.g. hypothesis/theory testing)
demonstration/education
2.3. Units of Measnrpmpnt Used
SI system
metric units
US customary units
any consistent system
2.4. Abstract
PLASM (Prickett Lonnquist Aquifer Simulation Model) is a finite
difference model for simulation of transient, two-dimensional or
quasi-three-dimensional flow in a single or multi-layered,
heterogeneous, anisotropic aquifer system. The original model of 1971
consisted of a series of separate programs for various combinations of
simulation options. Later versions combined most of the options in a
single code, including variable pumping rates, leaky confined aquifer
conditions, induced infiltration from a shallow aquifer or a stream,
storage coefficient conversion between confined and watertable
conditions, and evapotranspiration as a function of depth to water
table. The model uses the iterative alternating implicit method (IADI)
to solve the matrix equation.
.
Page 4c-1
-------
Section 4: Model Descriptions Model Description for PLASM
2.5. Data Input Requirements:
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
minicomputer
workstations
mainframe
microcomputer
make/model
- IBM 360,370
- DEC VAX
- IBM PC/XT/AT
2.7. System Requirements
core memory (RAM) for execution (bytes)
- 640K (for IBM PC version)
mass storage (disk space in bytes)
- 1M
numeric/math coprocessor
(for micro computers)
compiler required
(for mainframe)
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
Fortran IV
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Spatial Orientation
saturated flow
2D-horizontal
3D-laye:red
3.3. Types of Possible Updates
parameter values
boundary conditions
Page 4c-2
-------
S«cf/oii4; Model Description*
3.4. Geostatistics and Stochastic
none
3.5. Comments
This model has restart capability.
4. Flow Characteristics
4.1. Flow System Character! gaftnn
Saturated Zone
System
single aquifer
- single aquifer/aquitard system
- multiple aquifer/aquitard systems
Aquifer Type(s)
confined
- semi-confined (leaky-confined)
- unconfined (phreatic)
Medium
- porous media
Parameter representation
homogeneous
heterogeneous
~ isotropic
aniso tropic
Flow characteristics (saturated zone)
laminar flow
-- linear (Darcian flow)
- steady-state
transient
Flow processes included
areal recharge
- induced recharge (from river)
- evapotranspiration
Pag* 4c-3
-------
Section 4: Model Descriptions Model Demcriptlon for PLASM
Changing aquifer conditions
in space
- variable thickness
- confined / unconf ined
in time
- confined/unconf ined
Well characteristics
none
4.2. Fluid Conditions
Single Fluid Flow
water
Flow of Multiple Fluids
- N.A.
Fluid Properties
constant in time/space
4.3. Boundary Conditions
First Type - Dirichlet
head/pressure
Second Type - Neumann (Prescribed Flux)
- injection/production wells
no flow boundary
areal boundary flux
ground-water recharge
induced infiltration
Third Type - Cauchy
head/pressure-dependent flux
4.4. Solution Methods for Flow
General Method
Numerical
Spatial Approximation
finite difference method
node-centered
Time-Stepping Scheme
fully implicit
Pmg* 4c-4
-------
Section 4: Model Descriptions Model Description for PLASM
Matrix-Solving Technique
Iterative
iterative ADIP
Direct
Gauss elimination
4.5. Grid Design
Cell/Element Characteristic
constant cell size
variable cell size
Possible Cell Shapes
2D-square
2D-rectangular
Maximum Number of Nodes
- 5000
4.6. Flow Output Characteristics
Simulation Results
- head/pressure/potential
- ASCII file (areal values)
- ASCII file (hydrograph)
water budget components
- ASCII file (cell-by-cell values)
- ASCII file (global total area)
5. Evaluation
5.1. Verification/Validation
verification (analytical solutions)
field datasets (validation)
synthetic datasets
code intercomparison
5.2. Internal Code Documentation (Comment Statements)
incidental
5.3. Peer (Independent) Review
concepts
theory (math)
coding
accuracy
documentation
Page 4c-5
-------
Section 4: Model Descriptions
Model Description for PLASM
usability
efficiency
6. Documentation and Support
6.1. Documentation Tnrhidps
model theory
user's instructions
example problems
code listing
program structure and development
verification/validation
6.2. Support Needs
Can be used without support
Support is available
~ from author
from third parties
6.3. Level of Support
limited
7. Availability
7.1.
available
public domain
proprietary
restricted public domain
purchase
license
7.2.
source code only (tape/disk)
source and compiled code
compiled code only
paper listing of source code
(depends on version)
Page 4c-6
-------
Section 4: Model Descriptions Model Description for PLASM
8. Pre and Post Processors
8.1. Data Preprocessing
name: PREPLASM
- part of model package (e.g. under a shell; dedicated)
- textual data entry/editing
error-checking
name: MODELCAD
separate (optional) program
- graphic data entry/modification (e.g manual grid design, -
arrays)
- (semi-) automatic grid generation
- data reformatting (e.g. for GIS)
error-checking
help screens
9. Institution of Model Development
9.1. Name
Illinois State Water Survey
9.2. Address
P.O. Box 232
Urbana, Illinois 61801
9-3. Type of Institution
state/provincial government
10. Remarks
A modified version of PLASM to analyze hydrologic impacts of mining is
documented in in a report of the U.S. Office of Surface Mining (1981; see user
references).
An extended and updated single aquifer version of PLASM for the IBM-PC is
available from:
T.A. Prickett
6 G.H. Baker Drive
Urbana, IL 61801
phone: 217/384-0615.
Page 4c-7
-------
Section 4: Model Descriptions Model Description for PLASM
This version is the same as published in Bulletin 55, except for the multi-
layered option and the confined/unconfined storage conversion.
The IGWMC distributes a mainframe version of PLASM running on the
DEC/VAX 11 series. The Center distributes also an IBM-PC version. This
latter version comes as a program package including separate codes for
confined (CONPLASM) and watertable (UNCPLASM) conditions and a
textual preprocessor for input data preparation (PREPLASM). Contact:
IGWMC USA: International Ground Water Modeling
Center,
Colorado School of Mines, Golden, Colorado,
USA, or
TNO Inst. of Applied Geoscience, P.O. Box
6012, 2600JA
Delft, The Netherlands.
IGWMC Europe: TNO Institute of Applied Geoscience,
P.O. Box 6012, 2600JA Delft,
The Netherlands.
For earlier microcomputer versions of PLASM see IGWMC Key # 6010 and
6011 (MARS historic data base).
MODELCAD is a graphical oriented, model-independent pre-processor to
prepare and edit input files for two- and three-dimensional ground-water
models, including aquifer properties, boundary conditions, and grid
dimensions. The program prepares input files for MODFLOW, MOC, PLASM
and RANDOM WALK, among others. File formatting routines for other
models are available upon request. Contact:
Geraghty & Miller Modeling Group
1895 Preston White Drive
Suite 301
Reston, VA 22091
Phone: (703) 476-0335.
The IBM-PC version of this program is also available from:
National Water Well Association
Ground Water Bookstore
P.O. Box 182039
Dept. 017
Columbus, Ohio 43218
Tel. (614) 761-1711
Page 4c-8
-------
Section 4s Model Descriptions Model Description for PLASM
The version available from the National Water Well Association runs on
IBM PC or compatible and has been prepared by Koch and Associates and
includes interactive data preparation. The code is directly available from
Koch and Associates. Contact:
Ann Koch
2921 Greenway Drive
Ellicot City, Maryland 21043
tel. 301/461-6869.
Page 4c-9
-------
Section 4: Model Descriptions Model Description for PLASM
11. References
Prickett, T.A. and C.G. Lonnquist. 1971. Selected Digital Computer
Techniques for Groundwater Resource Evaluation. Bulletin 55.
Illinois State Water Survey, Urbana, 111.
Texa.s Water Development Board, Systems Engineering Division. 1974.
GWSIM - Groundwater Simulation Program, Program Documentation
and User's Manual. Texas Dept. of Water Resourc., Austin, Texas.
Prickett, T.A. and C.G. Lonnquist. 1976. Methods de Ordenador para
Evaluacion de Recursos Hidraulicos Subterraneas. Boletin 41.
(Spanish version of Bulletin 55, ISWS). Ministerio de Obras Publicas,
Direccion General de Obras Hidraulicos, Madrid, Spain.
Texas Dept. of Water Resources. 1979. Program Description of GWSIM.
In: Mathematical Simulation Capabilities in Water Resources Systems
Analysis, Eng. and Environm. Systems Section, Report LP-16, revised
November 1979.
Institute Geologico Y Minero de Espana. 1981. Modelos Multicapa -
Tomo II: Listados de Programas, Ministreio de Industria Y Energia,
Madrid, Spain.
Institute Geologico Y Minero de Espana. 1981. Modelos Multicapa -
Tomo I: Manuales de Utilizacion. Ministerio de Industria Y Energia,
Madrid, Spain.
Institute Geologico Y Minero de Espana. 1982. Modelos Monocapa en
Regimen Transitorio - Tomo II: Listados de Ordenador. Ministerio de
Industria Y Energia, Madrid, Spain.
Institute Geologico Y Minero de Espana. 1982. Modelos Monocapa en
Regimen Transitorio -- Tomo I: Manuales de Utilizacion. Dirrecion de
Aguas Subterraneas y Geotecnia, Ministerio de Industria y Energia,
Madrid, Spain.
Page 4c-10
-------
Section 4; Model Descriptions Model Description for PLASM
12. Users
T.R. Knowles developed two models based on PLASM for the Texas Dept.
of Water Resources, Austin, Texas. See models GWSIM (IGWMC key
# 0681) and GWSIM II (IGWMC key # 0680).
Beltran, J.M.A., L.L. Garcia, and M.R.L. Madurga. 1973. Estudio de la
Explotacion de los Aquiferos del Llano de Palma de Mallorca Mediante
un Modelo Digital Simplificado. Boletin 38, Dirrecion General de
Obras Hidraulicas, Ministerio de Obras Publicas, Madrid, Spain.
Karanjac, J., M. Altunkaynak, and G. Ovul. 1976. Mathematical model of
Elazig-Uluova Plain, Republic of Turkey. Ministry of Energy and
Natural Resources. Geotechnical Services and Groundwater Division,
Ankara, Turkey.
Naymik, T.G. 1979. The Application of Digital Model for Evaluating the
Bedrock Water Resources of the Maumee River Basin, Northwestern
Ohio. Lawrence Livermore Laboratory. University of California.
Livermore, California.
U.S. Department of the Interior. 1981. Office of Surface Mining -
Reclamation and Enforcement. Ground Water Model Handbook (H-
D3004-021-81-1062D). Office of Surface Mining. Western Technical
Service Center. Denver, Colorado.
Yazicigil, H. and L.V.A. Sendlein. 1981. Management of Ground Water
Contaminated by Aromatic Hydrocarbons in the Aquifer Supplying
Ames, Iowa. Groundwater, Vol. 19(6), pp. 648-665.
Grosser, P.W. 1984. Application of Ground Water Models to the
Identification of Contaminant Sources. In: Proceed. Conf. on Practical
Applications of Ground Water Models, Columbus, Ohio, pp. 452-461
Nat. Water Well Assoc., Dublin, Ohio.
Khaleel, R. and D.M. Peterson. 1984. A Quasi Three- Dimensional
Ground Water Flow Model for the Mesilla Bolson, New Mexico. In:
Proceed. Conf. on Practical Applications of Ground Water Models,
Columbus, Ohio, pp. 52-67. Nat. Water Well Assoc., Dublin, Ohio!
Martin, P.L. 1984. The Use of a Numerical Model in Predicting the
Effectiveness of a Dewatering System. In: Proceed. Conf. on Practical
Applications of Ground Water Models, Columbus, Ohio, pp. 759-777.
Nat. Water Well Assoc., Dublin, Ohio.
Osiensky, J.L., G.V. Winter, and R.E. Williams. 1984. Monitoring and
Mathematical Modeling of Contaminated Ground Water Plumes in
Fluvial Environments. Ground Water, Vol. 22(3), pp. 298-306.
Page 4c-11
-------
Section 4: Model Descriptions Model Description for PLASM
Potter, S.T. and WJ. Gburek. 1984. Seepage Face Simulation Using the
Illinois State Water Survey Ground Water Model. In: Proceed. Conf.
on Practical Applications of Ground Water Models, Columbus, Ohio,
pp. 674-700. Nat. Water Well Assoc., Dublin, Ohio.
Ritchey, J.D. 1984. Method for Including the Effects of River Stage and
Precipitation on Ground Water Levels in an Aquifer Model. In:
Proceed. Practical Applications of Ground Water Models, Columbus,
Ohio, pp. 649-673. Nat. Water Well Assoc., Dublin, Ohio.
Sevi, E.A., T.M. Cosgrave, and F.L. Fox. 1984. Sequential Horizontal and
Vertical Cross-Sectional Modeling of a Small Site. In: Proceed. Conf. on
Practical Applications of Ground Water Models, Columbus, Ohio pp
621-633. Nat. Water Well Assoc., Dublin, Ohio.
Sing;h, R., S.K. Sondhi, J. Singh, and R. Kumar. 1984. A Ground Water
Model for Simulating the Rise of Water Table under Irrigated
Conditions. Journ. of Hydrol., Vol. 71, pp. 165-179.
Kalinski, R.J. 1985. Investigation and Computer Simulation of Stream-
Aquifer Relationship at Elm Creek, Nebraska. In: Proceed. Practical
Applications of Ground Water Models, Columbus, Ohio, pp. 146-161.
Nat. Water Well Assoc., Dublin, Ohio.
Song, S. and A.O. Akan. 1985. Ground Water Management by Linear
Programming with Sample Applications to the Eastern Shore of
Virginia Aquifer. In: Proceed. Conf. on Practical Applications of
Ground Water Models, Columbus, Ohio, pp. 90-107. Nat. Water Well
Assoc., Dublin, Ohio.
Contractor, D.N., S.M.A. El-Didy, and A.S. Ansary. 1986. Numerical
Modeling of Groundwater Flow and Water Quality at Underground
Coal Gasification Sites. DOE/ LC/11053-2151. Office of Fossil Energy,
U.S. Dept. of Energy, Laramie, Wyoming, (pp.7-50).
Page 4c-12
-------
Model Description For
RANDOM WALK
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
RANDOM WALK
Table of Contents
PAGE
i . Model Identification .............. ....... .................................. 4d-1
1.1. Model Name(s) ........................................... !""""""""""""""" 4d-1
1.2. Date of first release [[[ ' ' ............. 4^
1.3. Current Release date ................................................ I'.'.'."'.!!!!!!!!".'.' ...... 4d-l
1.4. Authors [[[ ................... 4d-1
2. Model Information ...................
4d-1
2.1. Model Category """~4d-i
2.2. Model Developed For 4d_i
2.3. Units of Measurement Used 4d-l
2.4. Abstract 4d-l
2.5. Data Input Requirements 4d_2
2.6. Versions Exist for the Following Computer Systems....... 7. l".4d-2
2.7. System Requirements 4d_2
2.8. Graphics Requirements 4d-2
2.9. Program Information 4d-2
3. General Model Capabilities............. .44.2
3.1. Parameter Discretization """'"''"'"'" 4d-2
3.2. Coupling 4 ,_2
3.3. Spatial Orientation 4d_2
3.4. Geostatistics and Stochastic Approach ...........'.......4d-3
4. Flow Characteristics. 4d-3
4.1. Flow System Characterization """"'""'"""""'" 4d-3
4.2. Fluid Conditions 4d_4
4.3. Boundary Conditions ZZ'"" 4d-4
4.4. Solution Methods for Flow Z'Z'.'Z 4d-4
4.5. Grid Design ZZZZZZZ 4d-5
4.6. Flow Output Characteristics .'."Z....4d-5
5. Mass Transport Characteristics ..... 4d.s
5.1. Water Quality Constituents """""""" 4d-5
5.2. Processes Included 4d-5
5.3. Boundary Conditions
5.4. Solution Methods for ..............-
5.5. Output Characteristics for Transport .......................... ...................4d-6
5.4. Solution Methods for Transport .......................... '.Z'.'.'.'.'.'.'.'.!'..".'.".*'4d-6
6. Evaluation
.
6.1. Verification/Validation ................. "'"'"'"'""" 4d-7
-------
PAGE
7. Documentation and Support 4d-7
7.1. Documentation Includes 4d-7
7.2. Support Needs 4d-7
7.3. Level of Support 4d-7
8. Availability. 4d-7
8.1. Terms 4d-7
8.2. Form 4d-8
9. Pre and Post Processors[[[ 4d-8
9.1. Data Preprocessing 4d-8
9.2. Data Postprocessing 4d-8
1O. Institution of Model Development....................................4d-8
10.1. Name 4d-8
10.2. Address 4d-8
10.3. Type of Institution 4d-9
11. Remarks 4d-9
-------
RANDOM WALK
1. Model Identification
1.1. Model Namp(s)
RANDOM WALK
1.2. Date of first rplpas?
7/81
1.3. Current Rplpase date
7/81
1.4. Authors
Prickett, T.A.
Naymik, T.G.
Lonnquist, C.G.
2. Model Information
2.1. Model Category
ground-water flow
mass transport
2.2. Model Developed Fnr
general use (e.g. in field applications)
research (e.g. hypothesis/theory testing)
demonstration/education
2.3. Units of Mpa«uirpmpnt Used
metric units
US customary units
any consistent system
2.4. Abstract
RANDOM WALK/TRANS is a numerical model to simulate two-
dimensional steady or transient flow and transport problems in
heterogeneous aquifers under water table and/or confined or leaky
confined conditions. The flow is solved using a finite difference
approach and the iterative alternating direction implicit method
The advective transport is solved with a particle-in-a-cell method
while the dispersion is analyzed with the random walk method
Page 4d-1
-------
Section 4: Model Descriptions Model Description for Random Walk
2.5. Data Input Requirements
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
minicomputer
workstations
mainframe
microcomputer
make/model
- Cyber 175
- VAX 11/780
- IBM PC/XT/AT or compatible
2.7. System Requirements
core memory (RAM) for execution (bytes)
- 640K (for IBM PC version)
mass storage (disk space in bytes)
at least 2Mb for data files
numeric:/math coprocessor
(for micro computers)
compiler required
(for mainframe)
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
Fortran IV
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Coupling
none
3.3. Spatial Orientation
saturated flow
2D-horizontal
Page 4d-2
-------
Section 4: Model Descriptions Model Description for Random Walk
3.4. Geostatistics and Stochastic Approach
random walk
4. Flow Characteristics
4.1. Flow System Characterization
Saturated Zone
System
single aquifer
single aquifer/aquitard system
Aquifer Type(s)
confined
semi-confined (leaky-confined)
unconfined (phreatic)
Medium
porous media
Parameter representation
homogeneous
heterogeneous
-- isotropic
anisotropic
Flow characteristics (saturated zone)
laminar flow
linear (Darcian flow)
~ steady-state
transient
Flow processes included
area! recharge
induced recharge (from river)
evapotranspiration
Changing aquifer conditions
in space
variable thickness
- confined/unconfined
in time
- confined/unconfined
Page 4d-3
-------
Section 4: Model Descriptions Model Description for Random Walk
Well characteristics
none
4.2. Fluid Conditions
Single Fluid Flow
water
Flow of Multiple Fluids
- N.A.
Fluid Properties
constant in time/space
4.3. Boundary Conditions
First Type - Dirichlet
head / pressure
Second Type - Neumann (Prescribed Flux)
injection/production wells
no flow boundary
areal boundary flux
ground-water recharge
springs
induced infiltration
Third Type - Cauchy
head/pressure-dependent flux
4.4. Solution Methods for Flow
General Method
Numerical
Spatial Approximation
finite difference method
- node-centered
Time-Stepping Scheme
fully implicit
Matrix-Solving Technique
Iterative
iterative ADIP
Direct
Gauss elimination
Page 4d-4
-------
Section 4: Model Descriptions Model Description for Random Walk
4.5. Grid Design
Cell/Element Characteristic
constant cell size
variable cell size
Possible Cell Shapes
2D-square
2D-rectangular
Maximum Number of Nodes
- 5000
4.6. Flow Output Characteristics
Simulation Results
-- head/pressure/potential
- ASCII file (areal values)
- ASCII file (hydrograph)
fluxes/velocities
- ASCII file (areal values)
water budget components
- ASCII file (cell-by-cell values)
- ASCII file (global total area)
5. Mass Transport Characteristics
5.1. Water Quality Constituents
any component(s)
single component
total dissolved solids (IDS)
inorganics
organics
radionuclides
5.2. Processes Included
(Conservative) Transport
advection
dispersion
isotropic
anisotropic
diffusion
Page 4d-5
-------
Section 4: Model Descriptions Model Description for Random Walk
Phase Transfers
- equilibrium
isotherm
Fate
first-order radioactive decay (single mother/daughter decay)
first-order chemical decay
5.3. Boundary Conditions
First Type - Dirichlet
Chemical processes embedded in transport equation
concentration
Second Type - Neumann (Prescribed Solute Flux)
areal boundaries
injection wells
point sources
line sources
areal sources
5.4. Solution Methods for Transport
General Method
numerical
uncoupled flow and transport equation
Spatial Approximation
finite difference method
- node-centered
particle-tracking
Time-Stepping Scheme
fully implicit
Matrix-Solving Technique
-- Random Walk
direct
Gauss elimination
5.5. Output Characteristics for Transport
Simulation Results
concentration in aquifer/soil
- ASCII file (areal values)
- ASCII file (time series)
concentration in well
ASCII file (time series)
Page 4d-6 ~~""~"~""~~"~~"~~
-------
Section 4s Model Descriptions Model Description for Random Walk
velocities (from given heads)
- ASCII file (areal values)
mass balance components
- ASCII file (cell-by-cell values)
- ASCII file (global total area)
6. Evaluation
6.1. Verification / Validation
verification (analytic solutions)
code intercomparison
6.2. Internal Code Documentation (Comment Statements')
incidental
6.3. Peer (Independent) Review
concepts
theory (math)
7. Documentation and Support
7.1. Documentation Includes
model theory
user's instructions
example problems
program structure and development
code listing
verification/validation
7.2. Support Needs
Can be used without support
Support is available
from author
from third parties
7.3. Level of Support
limited
8. Availability
8.1. Terms
available
public domain
Page 4d-7
-------
Section 4; Model Descriptions Model Description for Random Walk
proprietary
purchase
8.2. Form
source code only (tape/disk)
source and compiled code
compiled code only
paper listing of source code
9. Pro and Post Processors
9.1. Data Preprocessing
name: PREWALK (IGWMC)
separate (optional) program
textual data entry/editing
data reformatting
error-checking
name: MODELCAD
separate (optional) program
generic (can be used for various models)
- textual data entry/editing
- graphic data entry/modification (e.g manual grid design,
arrays)
- data reformatting (e.g. for GIS)
error-checking
help screens
9.2. Data Postprocessing
name: POSTWALK (IGWMC)
separate (optional) program
textual data display on screen/printer
- reformatting (e.g. to standard formats)
1O. Institution of Model Development
10.1. Name
Illinois State Water Survey
10.2. Address
P.O. Box 5050
Sta.A
Urbana, IL 61820
Page 4d-8
-------
Section 4: Model Descriptions Model Description for Random Walk
10.3. Type of Institution
state/provincial government
11. Remarks
Various microcomputer versions are available among others from the
International Ground Water Modeling Center:
IGWMC USA: Inst. for Ground-Water Res. and Educ.,
Colorado School of Mines,
Golden, CO 80401, USA.
IGWMC Europe: TNO Institute of Applied Geoscience,
P.O. Box 6012
2600JA Delft
The Netherlands.
Code is available from:
Bob Sinclair
Director of Computer Service
Illinois State Water Survey
Box 5050
Station A
Champaign., IL 61820
telephone (217) 333-4952
at cost of magnetic tape, copying and postage.
Code is also available from:
Thomas A. Prickett
6 G.H. Baker Drive
Urbana, IL 61801
Phone 217/384-0615
A modified version of PLASM and RANDOM WALK to analyze hydrologic
impacts of mining is documented in U.S. Office of Surface Mining (1981; see
user references). Program codes are available through Boeing Computer
Network.
MODELCAD is a graphical oriented, model-independent pre-processor to
prepare and edit input files for two- and three-dimensional ground-water
models, including aquifer properties, boundary conditions, and grid
dimensions. The program prepares input files for MODFLOW, MOC, PLASM
and RANDOM WALK, among others. File formatting routines for other
models are available upon request. Contact:
Page 4d-9
-------
Section 4: Model Descriptions Model Description for Random Walk
Geraghty & Miller Modeling Group
1895 Preston White Drive
Suite 301, Reston, VA 22091
(703) 476-0335
Page 4d-10
-------
Section 4; Model Descriptions Model Description for Random Walk
12. References
Prickett, T.A. and C.G. Lonnquist. 1971. Selected Digital Computer
Techniques for Groundwater Resource Evaluation. Bulletin 55, Illinois
State Water Survey, Champaign, Illinois.
Naymik, T.G. and MJ. Barcelona. 1981. Characterization of a
Contaminant Plume in Groundwater, Meredesia, Illinois. Ground
Water, Vol. 19(5), pp. 517-526.
Prickett, T.A., T.G. Naymik and C.G. Lonnquist. 1981. A Random-Walk
Solute Transport Model for Selected Groundwater Quality Evaluations.
Bulletin 65, Illinois State Water Survey, Champaign, Illinois.
Naymik, T.G. and M.E. Sievers. 1983. Groundwater Tracer Experiment (II)
at Sand Ridge State Forest. Illinois State Water Survey Division,
Illinois Dept. of Energy and Natural Resources, Report 334, Champaign,
Illinois, pp. 1-105.
Page 4d-11
-------
Section 4; Model Descriptions Model Description for Random Walk
13. Users
U.S. Office of Surface Mining. 1981. Groundwater Model Handbook.
Rept. H-D3004-021-81-1062D, U.S. Dept. of Interior, Western Technical
Service Center, Denver, Colorado.
Royce, B., M. Garrell, A. Kahn and E. Kaplan. 1983. A Methodology for
Modeling the Migration of Eor Chemicals in Fresh Water Aquifers.
Prepared for Bartlesville Energy Technology Center, Order No. DE-
AP19-82BC99996, U.S. Dept. of Energy, West Virginia.
Johnson, R. and S.A. Dendrou. 1984. Evaluation of the Potential Water
Supply Impacts Posed by the Transgulf Pipeline, Broward County,
Florida. In: Proceed. Practical Applications of Ground Water Models,
Columbus, Ohio, August 15-17, 1984, pp. 584-601. Nat. Water Well
Assoc., Dublin, Ohio.
Wright, S.J. 1984. Modeling Contaminant Migration Under the Influence
of a Series of Pumping Wells. In: Proceed. Practical Applications of
Ground Water Models, Columbus, Ohio, August 15-17, 1984, pp. 462-
477. Nat. Water Well Assoc., Dublin, Ohio.
Herweijer, J.C., G.A. Van Luijn and C.AJ. Appelo. 1985. Calibration of a
Mass Transport Model Using Environmental Tritium. Journ. of
Hydrology, Vol. , pp.
Nayrnik, T.G. and M.E. Sievers. 1985. Characterization of Dyetracer
Plumes: In Situ Field Experiments. Ground Water, Vol. 223(6), pp. 746-
752.
American Petroleum Institute. 1986. Cost Model for Selected
Technologies for Removal of Gasoline Components from
Groundwater. API Publication No. 4422, American Petroleum
Institute, Washington D.C.
Anderson, M.P. and C.J. Bowser. 1986. The Role of Groundwater in
Delaying Lake Acidification. Water Resources Research, Vol. 22(7), pp.
1101-1108.
Taylor, M.D., M.K. Leslie, and R.C. Johnson. 1989. Groundwater Modeling
Key to Isolating Contamination. Water and Waste Water
International, February 1989.
Page 4d-12
-------
Model Description For
AT123D
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
AT123D
Table of Contents
PAGE
1, Model Identification[[[ 4e-1
1.1. Model Name 4e-l
1.2. Date of First Release 4e-l
1.3. Current Version 4e-l
1.4. Current Release date 4e-l
1.5. Authors 4e-l
2. Model Information[[[ 4e-1
2.1. Model Category 4e-l
2.2. Model Developed For 4e-l
2.3. Units of Measurement Used 4e-l
2.4. Abstract 4e-l
2.5. Data Input Requirements 4e-2
2.6. Versions Exist for the Following Computer Systems 4e-2
2.7. System Requirements 4e-2
2.8. Graphics Requirements. 4e-2
2.9. Program Information 4e-2
3. General Model Capabilities................................................ 4e-2
3.1. Parameter Discretization 4e-2
3.2. Coupling 4e-2
3.3. Spatial Orientation 4e-2
4. Mass Transport Characteristics....................................... 4e-3
4.1. Water Quality Constituents 4e-3
4.2. Processes Included 4e-3
4.3. Boundary Conditions 4e-3
4.4. Solution Methods for Transport 4e-4
4.5. Output Characteristics for Transport 4e-4
5. Evaluation[[[ttt.4e'4
5.1. Verification/Validation 4e-4
5.2. Internal Code Documentation (Comment Statements) 4e-4
-------
PAGE
............................ ....................................
tm A VaffflOfffTJf...........
7.1. Terms [[[ 4e-5
7.2. Form [[[ 4e-5
8. Pro and Post Processors [[[ 4e-5
8.1. Data Preprocessing [[[ 4e-5
8.2. Capabilities (Preprocessing) [[[ 4e-5
8.3. Data Postprocessing [[[ 4e-5
8.4. Capabilities (Postprocessing) [[[ 4e-5
9. Institution of Model Development..... ............................... 4e-5
-------
AT123D
1. Model Identification
1.1. Model Name
AT123D
1.2. Date of First Release
1979
1.3. Current Version
1.1
1.4. Current Release date
5/92
1.5. Authors
1. Yeh,G.T.
2. etal.
2. Model Information
2.1. Model Category
mass transport
2.2. Model Developed For
general use
demonstration/education
2.3. Units of Measurement Used
metric units
any consistent system
2.4. Abstract
AT123D is a generalized analytical transient, one- two-, and/or three-
dimensional computer code developed for estimating the transport of
chemicals in an isotropic, homogeneous, confined aquifer system with
uniform flow. The model handles various source configurations
(including point source, line source, and areal source) and release
characteristics. The transport mechanisms include advection,
longitudinal as well as horizontal and vertical transverse hydro-
dynamic dispersion, diffusion, linear adsorption, and first-order
Page 4e-1
-------
Section 4: Model Descriptions Model Description for AT123D
decay/degeneration and chemical losses to the atmosphere. The model
calculates concentration distribution in space and time using Green's
function.
2.5. Data Input Requirements
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
minicomputer
mainframe
microcomputer
make/model
- VAX 11/780'
-- IBM PC/XT/AT
2.7. System Requirements
compiler required (e.g., for mainframe)
language
-- FORTRAN
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
- FORTRAN IV
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Coupling
N.A.
3.3. Spatial Orientation
saturated flow
ID-horizontal
ID-vertical
2D-horizontal
2D vertical
3D-fully
Page 4o-2
-------
Sect/on 4: Model Descriptions Model Do9criptlon for AT123D
4. Mass Transport Characteristics
4.1. Water Quality Constituents
any component(s)
single component
total dissolved solids (IDS)
inorganics
organics
radionuclides
4.2. Processes Included
(Conservative) Transport
advection
-iso tropic
-anisotropic
- longitudinal dispersion
-- transverse dispersion
diffusion
Phase Transfers
- solid <-> liquid
- sorption
- equilibrium isotherm
- linear
Fate
first-order radioactive decay
single mother/daughter decay
first-order chemical decay
- first-order microbial decay
4.3. Boundary Conditions
First type - Dirichlet
Chemical processes embedded in transport equation
concentration
Second type - Neumann (Prescribed Solute Flux)
areal boundaries
injection wells
point sources
~ line sources
Page 4e-3
-------
Sect/on 4: Model Descriptions Model Description for AT123D
4.4. Solution Methods for Transport
General Method
areal sources
uncoupled flow and transport equation
Analytical
single solution
superposition
4.5. Output Characteristics for Transport
Simulation Results
concentration in aquifer/soil
- ASCII file (areal values)
5. Evaluation
5.1. Verification/Validation
verification (analytical solutions)
5.2. Internal Code Documentation (Comment Statements)
incidental
5.3. Peer (Independent) Review
concepts
theory (math)
coding
documentation
6. Documentation and Support
6.1. Documentation Includes
model theory
user's instructions
example problems
program structure and development
code listing
verification/validation
6.2. Support Needs
Can be used without support
Support is available
from third party
Page 4e-4
-------
Sect/on 4: Model Descriptions Model Description for AT123D
6.3. Level of Support
limited
7. Availability
7.1. Terms
available
public domain
7.2. Form
source code only (tape/disk)
source and compiled code
paper listing of source code
8. Pro and Post Processors
8.1. Data Preprocessing
data preprocessing available
part of model package (e.g. under a shell; dedicated)
8.2. Capabilities (Preprocessing)
textual data entry/editing
error-checking
8.3. Data Postprocessing
data postprocessing (output manipulation)
part of model package (e.g. under a shell; dedicated)
8.4. Capabilities (Postprocessing)
textual data display on screen/printer
reformatting (e.g. to standard formats)
9. Institution of Model Development
9.1. Name
Oak Ridge National Laboratory
9.2. Address
Environmental Sciences Division
Oak Ridge, Tennessee 37830
9.3. Type of Institution
research institute
Page 4e-5
-------
Section 4: Model Descriptions Model Description for AT123D
10. Remarks
This model is available from the International Ground Water Modeling
Center:
IGWMC USA: Institute for Ground-Water Research and Education
Colorado School of Mines
Golden, CO 80401
USA
IGWMC Europe : TNO Institute of Applied Geoscience
P.O. Box 6012, 2600 JA Delft
The Netherlands
Page 4e-6
-------
Section 4: Model Descriptions Model Description for AT123D
11. References
Yeh, G.T. 1981. AT123D: Analytical Transient One-, Two-, and Three-
Dimensional Simulation of Waste Transport in the Aquifer System.
ORNL-5602, Oak Ridge National Lab., Oak Ridge, Tennessee.
Thomas, S.D., B. Ross, and J.W. Mercer. 1982. A Summary of Repository
Siting Models. NUREG/CR-2782, U.S. Nuclear Regulatory
Commission, Washington, D.C.
Page 4e-7
-------
Section 4: Model Descriptions Model Description for AT123D
(THIS PAGE INTENTIONALLY LEFT BLANK)
Pmge 4e-8
-------
Model Description For
MT3D
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
MT3D
Table of Contents
PAGE
1. Model Identification[[[4M
1.1. Model Name 4f-l
1.2. Date of First Release 4f-l
1.3. Current Version 4f-l
1.4. Current Release Date 4f-l
1.5. Authors 4f-l
2. Model Information[[[4f-1
2.1. Model Category 4f-l
2.2. Model Developed For 4f-l
2.3. Units of Measurement Used 4f-l
2.4. Abstract 4f-l
2.5. Data Input Requirements 4f-2
2.6. Versions Exist for the Following Computer Systems 4f-2
2.7. System Requirements 4f-2
2.8. Graphics Requirements 4f-2
2.9. Program Information 4f-2
3. General Model Capabilities.................................................4f-2
3.1. Parameter Discretization 4f-2
3.2. Spatial Orientation 4f-2
4. Mass Transport Characteristics........................................4f-3
4.1. Water Quality Constituents 4f-3
4.2. Processes Included 4f-3
4.3. Boundary Conditions 4f-3
4.4. Solution Methods for Transport 4f-3
4.5 Output Characteristics for Transport 4f-4
5. Evaluation.....,.........................................^............................41-4
5.1. Verification/Validation 4f-4
5.2. Internal Code Documentation (Comment Statements) 4f-4
6. Documentation and Support.............................................. 4f-4
6.1. Documentation Includes 4f-4
6.2. Support Needs 4f-4
6.3. Level of Support 4f-5
-------
8. Pro and Post Processors[[[ 4f-5
8.1. Data Postprocessing 4f-5
8.2. Capabilities (Postprocessing) 4f-5
9. Institution of Model Development.....................................4f-5
9.1. Name 4f_5
9.2 Address 4f_5
9.3 Type of Institution 4f_5
fO. Remarks 4f-6
-------
MT3D
1. Model Identification
1.1. Model Name
MT3D (Modular Transport in 3 Dimensions
1.2. Date of First Release
1990
1.3. Current Version
1.5
1.4. Current Release Date
3/92
1.5. Authors
1. Zheng, C.
2. Model Information
2.1. Model Category
mass transport
2.2. Model Developed For
research (e.g. hypothesis/theory testing)
general use (e.g. in field applications)
2.3. Units of Measurement Used
metric units
2.4. Abstract
MT3D is a three-dimensional contaminant transport model using a
hybrid method of characteristics. Two numerical techniques are
provided for the solution of the advective-dispersive reactive solute
transport equation: the method of characteristics (MOC) and the
modified method of characteristics (MMOC). The MMOC method
overcomes many of the traditional problems with MOC, especially in
3D simulations, by directly tracking nodal points backwards in time and
by using interpolation techniques. MT3D selectively uses the MOC or
the MMOC technique dependent on the problem at hand. The
transport model is so structured that it can be used in conjunction with
any block-centered finite difference flow model such as the USGS
MODFLOW model.
Page 41-1
-------
Section 4: Model Descriptions Model Description tor MT3D
2.5. Data Input Requirements
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
minicomputer
mainframe-microcomputer
make/model
IBM PC or compatible
operating system
- DOS 2.0 or higher
2.7. System Requirements
core memory (FLAM) for execution (bytes)
3.5Mb extended memory
mass storage (disk space in bytes)
- 3Mb
numeric/math coprocessor (for microcomputers)
compiler required (e.g. for mainframe)
language
- FORTRAN 77
2.8. Graphics Requirements
none
2.9. Program Information
programming language/level
- FORTRAN 77
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Spatial Orientation
saturated flow
3D-fully
3D-layered
Page 41-2
-------
Section 4s Model Descriptions Model Description for MT3D
4. Mass Transport Characteristics
4.1. Water Quality Constituents
any component(s)
single component
total dissolved solids (IDS)
inorganics
organics
radionuclides
4.2. Processes Included
(Conservative) Transport
advection
longitudinal dispersion
transverse dispersion
diffusion
Phase Transfers
solid <-> liquid
sorption
- equilibrium isotherm
linear
Langmuir
- Freundlich
Fate
first-order radioactive decay
single mother/daughter decay
first-order chemical decay
- first-order microbial decay
4.3. Boundary Conditions
First Type - Dirichlet
- chemical processes embedded in transport equation
concentration
Second Type - Neumann (Prescribed Solute Flux)
areal boundaries
injection wells
point sources
line sources
4.4. Solution Methods for Transport
General Method
areal sources
uncoupled flow and transport equation
Page 41-3
-------
Section 4: Model Descriptions Model Description for MT3D
Time-Stepping Scheme
fully implicit
Spatial Approximation
Matrix-Solving Technique
numerical
~ particle-tracking
method of characteristics
4.5. Output Characteristics for Transport
Simulation Results
concentration in aquifer/soil
- ASCII file (areal values)
- ASCII file (time series)
concentration in well
- ASCII file (time series)
mass balance components
- ASCII file (global total area)
5. Evaluation
5.1. Verification / Validation
verification (analytical solutions)
5.2. Internal Code Documentation (Comment Statements)
incidental
6. Documentation and Support
6.1. Documentation Includes
model theory
user's instructions
example problems
program structure and development
verification/validation
6.2. Support Needs
Support is available
from author
from third party
Page 41-4
-------
Section 4s Model Descriptions Model Demcrlotlon tor MT3D
6.3. Level of Support
full
7. Availability
7.1. Terms
available
public domain
proprietary
7.2. Form
source code only (tape/disk)
source and compiled code
8. Pre and Post Processors
8.1. Data Postprocessing
data postprocessing (output manipulation)
part of model package (e.g. under a shell; dedicated)
8.2. Capabilities (Postprocessing')
textual data display on screen/printer
reformatting (e.g. to standard formats)
9. Institution of Model Development
9.1. Name
S.S. Papadopulos & Assoc., Inc.
9.2 Address
12250 Rockville Pike
Rockville, Maryland
9.3 Type of Institution
consultant
Page 41-5
-------
Section 4: Model Descriptions Model Description for MT3D
10. Remarks
The MT3D code is distributed together with a version of the USGS flow
model MODFLOW, including the PCG2 solver. The code has been developed
with support of the U.S. Environmental Protection Agency and is available
from:
Center for Subsurface Modeling Support
R.S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
Phone: 405/332-8800
Page 41-6
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Section 4: Model Descriptions Model Description for MT3D
11. References
Zheng, C. 1990. MT3D, A Modular Three-Dimensional Transport Model
for Simulation of Advection, Dispersion and Chemical Reactions of
Contaminants in Groundwater Systems. Report prepared by S.S.
Papadopulos & Associates, Inc., Rockville, Maryland, for EPA/RSKERL,
Ada, Oklahoma.
Page 41-7
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Section 4; Model Descriptions Model Description for MT3D
(THIS PAGE INTENTIONALLY LEFT BLANK)
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Model Description For
MODPATM
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MODPATM
Table of Contents
££££
1. Model Identification ...... . ......... ...... ---------- .......... -------- . 4g-f
1.1. Model Name [[[ 4g-l
1.2. Date of First Release [[[ 4g-l
1.3. Current Release Date [[[ 4g-l
1.4. Authors [[[ 4g-l
2. Model Information.... [[[ 4g-1
2.1. Model Category [[[ 4g-l
2.2. Model Developed For [[[ 4g-l
2.3. Units of Measurement Used [[[ 4g-l
2.4. Abstract [[[ 4g-l
2.5. Data Input Requirements [[[ 4g-2
2.6. Versions Exist for the Following Computer Systems ................ 4g-2
2.7. System Requirements... [[[ 4g-2
2.8. Graphics Requirements [[[ 4g-2
2.9. Program Information [[[ 4g-2
3. General Model Capabilities................................................ 4g-2
3.1. Parameter Discretization [[[ 4g-2
3.2. Spatial Orientation [[[ 4g-3
4. Flow Characteristics[[[ 4g-3
4.1. Flow System Characterization [[[ 4g-3
4.2. Fluid Conditions [[[ 4g-3
4.3. Boundary Conditions [[[ 4g-3
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PAGE
8. Pro and Post Processors[[[ 4g-6
8.1. Data Preprocessing '. 4g-6
8.2. Capabilities (Preprocessing) 4g-6
8.3. Data Postprocessing 4g-6
8.4. Capabilities (Postprocessing) 4g-6
9. Institution of Model Development.................................... 4g-6
9.1. Name 4g-6
9.2. Address 4g-6
9.3. Type of Institution 4g-6
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MODPATH
1. Model Identification
1-1- Model Name
MODPATH
1.2. Date of First Release
1988
1.3. Current Release Date
1988
1.4. Authors
1. Pollock, D.W.
2. Model Information
2.1. Model Category
particle tracking
2.2. Model Developed For
general use (e.g. in field applications)
2.3. Units of Measurement Used
metric units
US customary units
any consistent system
2.4. Abstract
MODPATH is a postprocessing package to compute three-dimensional
pathlines based on the output from steady-state simulations obtained
with the USGS MODFLOW ground-water flow model. The package
consists of two FORTRAN 77 computer programs: 1) MODPATH,
which calculates pathlines, and 2) MODPATH-PLOT, which presents
results graphically. MODPATH uses a semi-analytical particle tracking
scheme, based on the assumption that each directional velocity
component varies linearly within a grid cell in its own coordinate
direction. Data is input to MODPATH through a combination of files
and interactive dialogue. The MODPATH-PLOT program comes in
two versions, one for use with the DISSPLA graphics routines library,
and one that uses the Graphical Kernel System (GKS).
Page 4g-1
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Section 4: Model Descriptions Model Description for MODPATH
2.5. Data Input Requirements
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
minicomputer
workstations
mainframe
microcomputer
make/model
Prime
-- IBM PC/386
2.7. System Requirements
core memory (RAM) for execution (bytes)
- 640K
mass storage (disk space in bytes)
- 3M
numeric/math coprocessor (for micro computers)
compiler required (e.g. for mainframe)
language
- FORTRAN 77
resident software
- DISSPLA or GKS routines
2.8. Graphics Requirements
type/mode/convention
various
resident graphics drivers
- DISSPLA or GKS
plotter make/model
various
2.9. Program Information
programming language/level
- FORTRAN 77
3. General Model Capabilities
3.1. Parameter Discretization
distributed
Page 4g-2
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Section 4s Model Descriptions
Model Description for MODPATH
3.2. Spatial Orientation
saturated flow
ID-horizontal
ID-vertical
2D-horizontal
2D-vertical
3D-fully
3D-layered
4. Flow Characteristics
4.1. Flow System Characterization
Saturated zone
System
single aquifer
single aquifer/aquitard system
multiple aquifer/aquitard systems
Aquifer Type(s)
confined
semi-confined (leaky-confined)
unconfined (phreatic)
Medium
porous media
Parameter Representation
homogeneous
heterogeneous
isotropic
anisotropic
Flow Characteristics (Saturated Zone)
laminar flow
linear (Darcian flow)
steady-state
4.2. Fluid Conditions
Single fluid flow
water
4.3. Boundary Conditions
First type - Dirichlet
Second type - Neumann (Prescribed Flux)
Third type - Cauchy
Page 4g-3
-------
Section 4s Model Descriptions Model Description for MODPATH
4.4. Solution Methods for Flow
General Method
semi-analytical
approximate analytical solution
4.5. Grid Design
Cell/Element Characteristic
constant cell size
variable cell size
Possible Cell Shapes
2D-square
2D-rectangular
- 3D-cubic
Maximum Number of Nodes
- 5000
-3D-hexahedral
4.6. Output Characteristics
Simulation Results
streamlines/pathlines
- binary file (spatial values)
- ASCII file (spatial values)
- screen display (spatial values)
- paper copy (spatial values)
- graphics (spatial values)
traveltimes
- binary file (areal values)
- ASCII file (areal values)
- screen display (areal values)
- paper copy (areal values)
- graphics (areal values)
isochrones
- binary file (areal values)
- ASCII file (areal values)
- screen display (areal values)
- paper copy (areal values)
- graphics (areal values)
Pmge 40-4
-------
Sect/on 4s Model Description* Model Do9criptlon for MODPATH
5. Evaluation
5.1. Internal Code Documentation (Comment Statements)
incidental
5.2. Peer (Independent) Review
concepts
theory (math)
documentation
6. Documentation and Support
6.1. Documentation Includes
model theory
user's instructions
example problems
program structure and development
code listing
6.2. Support Needs
Can be used without support
Support is available
from author
from third party
6.3. Level of Support
limited
7. Avaiiability
7.1. Terms
available
public domain
7.2. Form
source code only (tape/disk)
source and compiled code
compiled code only
paper listing of source code
Pmgo 4g-5
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Section 4; Model Descriptions Model Description for MODPATH
8. Pre and Post Processors
8.1. Data Preprocessing
data preprocessing available
include in simulation model (dedicated)
8.2. Capabilities (Preprocessing')
textual data entry/editing
8.3. Data Postprocessing
data postprocessing (output manipulation)
include in simulation model (dedicated)
8.4. Capabilities ('Postprocessing)
textual data display on screen/printer
graphic display spatial data
graphic plotting
9. Institution of Model Development
9.1. Name
Water Resources Division, U.S. Geological Survey
9.2. Address
411 National Center
Reston, VA 22092
9.3. Type of Institution
federal/national government
10. Remarks
MODPATH: a particle-tracking program developed by the USGS for use with
the MODFLOW model. MODPATH calculates the path a particle would take
in a steady-state three-dimensional flow field in a given amount of time. It
operates as a postprocessor for MODFLOW using heads, cell-by-cell flow
terms, and porosity to move each particle through the flow field. The
program handles both forward and backward particle tracking. (See also
IGWMC Key 3984.)
MODPATH-PLOT: a graphic display program for use with MODPATH-PC. It
uses the Graphical Kernal System (GKS) to produce graphical output on a
wide range of commonly used printers and plotters. MODPATH-PLOT comes
with MODPATH.
Pmgo 40-6
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Sect/on 4; Model Descriptions Model Description for MODPATH
This model is available from the International Ground Water Modeling
Center:
IGWMC USA Institute for Ground-Water Research and Education
Colorado School of Mines
Golden, CO 80401
USA
IGWMC Europe TNO Institute of Applied Geoscience
P.O. Box 6012,2600 JA Delft
The Netherlands
This model is also available from:
Scientific Software Group
P.O. Box 23041
Washington, D.C. 20026-3041
Tel. 703/620-9214
An IBM PC/386 extended-memory version of this model is also available
from:
Geraghty & Miller, Inc.
Modeling Group
10700 Park Ridge Blvd., Suite 600
Reston, VA 22091
Tel. 703/758-1200
Fax 703/758-1204
MPATHIN is a textual input processor for MODPATH, prepared by TECSOFT,
Inc., and available from Scientific Software Group, Washington, D.C.
Page 40-7
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Section 4: Model Descriptions Model Description for MODPATH
11. References
Pollock, D.W. 1989. Documentation of Computer Programs to Compute
and Display Pathlines Using Results from the U.S. Geological Survey
Modular Three-Dirnensional Finite-Difference Ground-Water Flow
Model. Open-File Report 89-381, U.S. Geological Survey, Reston,
Virginia.
Pollock, D.W. 1990. A Graphical Kernel System (GKS) Version of
Computer Program MODPATH-PLOT for Displaying Path Lines
Generated from the U.S. Geological Survey Three-Dimensional
Ground-Water Flow Model. Open-File Report 89-622, U.S. Geological
Survey, Reston, Virginia.
Pollock, D.W. 1988. Semianalytical Computation of Path Lines for Finite-
Difference Models. Ground Water, Vol. 26(6), pp. 743-750.
Page 4g-8
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Model Description For
WHPA
SOURCE:
INTERNATIONAL GROUND WATER
MODELING CENTER
(IGWMC)
-------
-------
WHPA
Table of Contents
1. Model Identification. ...........................4fi-f
1.1. Model Name 4h-l
1.2. Date of First Release 4h-l
1.3. Current Version 4h-l
1.4. Current Release Date 4h-l
1.5. Authors 4h-l
2. Model Information[[[ 4h-f
2.1. Model Category 4h-l
2.2. Model Developed For 4h-l
2.3. Units of Measurement Used 4h-l
2.4 Abstract 4h-l
2.5. Data Input Requirements 4h-2
2.6. Versions Exist for the Following Computer Systems 4h-2
2.7. System Requirements 4h-2
2.8. Graphics 4h-2
2.9. Program Information 4h-3
3. General Model Capabilities................................................4h-3
3.1. Parameter Discretization 4h-3
3.2. Coupling 4h-3
3.3. Spatial Orientation 4h-3
3.4. Types of Possible Updates 4h-3
3.5. Geostatistics and Stochastic Approach 4h-3
3.6 Comments 4h-3
4« Flow Character/sites[[[4n-3
4.1. Flow System Characterization 4h-3
4.2. Fluid Conditions 4h-4
4.3. Boundary Conditions 4h-4
4.4. Solution Methods for Flow 4h-4
4.5. Grid Design 4h-4
4.6. Flow Output Characteristic 4h-4
5» Evaluation[[[4/1-5
5.1. Verification/Validation 4h-5
-------
EAGE
7.
7.1. Terms... [[[ 4h-6
7.2. Form [[[ 4h-6
8. Pre and Post Processing[[[4|i-6
8.1. Data Preprocessing [[[ 4h-6
8.2. Capabilities (Preprocessing) [[[ 4h-6
8.3. Data Postprocessing [[[ 4h-6
8.4. Capabilities (Postprocessing) [[[ 4h-6
9. Institution of Model Development ................................. ...4h-6
-------
WHPA
1. Model Identification
1.1. Model Name
WHPA (Well Head Protection Area delineation model)
1.2. Date of First Release
2/90
1.3. Current Version
2.1
1.4. Current Release Date
04/92
1.5. Authors
1. Blandford, T.N.
2. Huyakorn, P.S.
2. Model Information
2.1. Model Category
ground-water flow
2.2. Model Developed For
general use (e.g. in field applications)
2.3. Units of Measurement Used
metric units
US customary units
any consistent system
2.4 Abstract
WHPA is an integrated program of analytical and semi-analytical
solutions for the ground-water flow equation coupled with pathline
tracking. It is designed to assist technical staff with delineation of
wellhead protection areas. Developed for the U.S. EPA's Office of
Groundwater Protection, the package includes modules for capture
zone delineation in a homogeneous aquifer with 2-dimensional
steady-state flow with options for multiple pumping/injection wells
and barrier or stream boundary conditions. Also included are modules
for Monte Carlo analysis of uncertainty and a particle-tracking
Page 4h-1
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Section 4: Model Description* Model Detcrtptlon lor WHPA
postprocessor for numerical flow models such as MODFLOW and
PLASM, using a two-dimensional rectangular grid.
WHPA-GPTRAC is the WHPA module used to delineate time-related
capture zones for pumping wells in homogeneous aquifers with steady
& uniform ambient ground-water flow (semi-analytical option) and
also delineates time-related capture zones about pumping wells for
steady ground-water flow fields (numerical option).
WHPA-MWCAP is the WHPA module used to delineate steady-state,
time-related or hybrid capture zones for pumping wells in
homogenous aquifers with steady and uniform ambient ground-water
flow. If multiple wells are examined, the effects of well interference are
ignored.
WHPA-RESSQC is the WHPA module used to delineate time-related
capture zones around pumping wells, or contaminant fronts around
injection wells, for multiple pumping and injection wells in
homogeneous aquifers of infinite areal extent with steady and uniform
ambient ground-water flow. Well interference effects are accounted
for.
WHPA-MONTEC is the WHPA module for Monte Carlo analysis of
uncertainty and a particle-tracking postprocessor for numerical flow
models such as MODFLOW and PLASM, using a two-dimensional
rectangular grid.
2.5. Data Input Requirements
Data input requirements are provided in the model documentation
and are discussed in the introduction to Section 4.0 of the
Compendium.
2.6. Versions Exist for the Following Computer Systems
microcomputer
make/model
- IBM PC/AT
operating system
- DOS 2.0 or higher
2.7. System Requirements
core memory (RAM) for execution (bytes)
- 640K
2.8. Graphics
type/mode/convention
- CGA
Page 4h-2
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Section 4: Model Descriptions Model Description for WHPA
2.9. Program Information
programming language/level
- FORTRAN 77
3. General Model Capabilities
3.1. Parameter Discretization
distributed
3.2. Coupling
N.A.
3.3. Spatial Orientation
saturated flow
2D-horizontal
3.4. Types of Possible Updates
parameter values
boundary conditions
3.5. Geostatistics and Stochastic Approach
Monte Carlo simulation
3.6 Comments
This model has restart capability.
4. Flow Characteristics
4.1. Flow System Characterization
Saturated Zone
System
single aquifer
Aquifer Type(s) Present
confined
semi-confined (leaky-confined)
unconfined (phreatic)
Medium
porous media
Page 4h-3
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Section 4s Model Descriptlonf Model Description for WHPA
Parameter Representation
homogeneous
heterogeneous
isotropic
anisotropic
Flow Characteristics (Saturated Zone)
laminar flow
linear (Darcian flow)
steady-state
4.2. Fluid Conditions
Single Fluid Flow
water
4.3. Boundary Conditions
First type - Dirichlet
head/pressure
Second type - Neumann (Prescribed Flux)
injection/production wells
no flow boundary
areal boundary flux
groundwater recharge
4.4. Solution Methods for Flow
General Method
analytical
- single solution
- superposition
semi-analytical
- continuous in time, discrete in space
- approximate analytical solution
4.5. Grid Design
maximum number of nodes
- 0
4.6. Flow Output Characteristics
Simulation Results
head/pressure/potential
- AS>CII file (areal values)
- screen display (areal values)
graphics (areal values)
Page 4h-4
-------
Section 4: Model Descriptions Model Description for WHPA
head differential/drawdown
- ASCII file (areal values)
- screen display (areal values)
- graphics (areal values)
streamlines/pathlines
- screen display (spatial values)
- graphics (spatial values)
traveltimes
- ASCII file (areal values)
- screen display (areal values)
isochrones
- screen display (areal values)
- graphics (areal values)
5. Evaluation
5.1. Verification /Validation
verification (analytical solutions)
5.2. Peer (Independent) Review
concepts - theory (math)
documentation
usability
6. Documenlaffon and Support
6.1. Documentation Includes
model theory
user's instructions
example problems
verification/validation
6.2. Support Needs
Can be used without support
Support is available
from author
6.3. Level of Support
full
Page 4h-5
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Section 4s Model Descriptions Model Description for WHPA
7. Availability
7.1. Terms
available
public domain
7.2. Form
compiled code only
8. Pre and Post Processing
8.1. Data Preprocessing
data preprocessing available
include in simulation model (dedicated)
8.2. Capabilities (Preprocessing)
textual data entry/editing
error-checking
help screens
8.3. Data Postprocessing
data postprocessing (output manipulation)
include in simulation model (dedicated)
8.4. Capabilities (Postprocessing)
textual data display on screen/printer
graphic display spatial data
9. Institution of Model Development
9.1. Name
Hydrogeologic, Inc.
9.2. Address
Herndon, Virginia
9.3. Type of Institution
consultant
Page 4h-6
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Section 4; Model Descriptions Model Description for WHPA
10. Remarks
This model is available from the International Ground Water Modeling
Center:
IGWMC USA Institute for Ground-Water Research and Education
Colorado School of Mines
Golden, CO 80401
USA
IGWMC Europe TNO Institute of Applied Geoscience
P.O. Box 6012, 2600 JA Delft
The Netherlands
Pmge 4fi-7
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Section 4: Model Descriptions Model Description for WHPA
11, References
Blandford, T.N., and P.S. Huyakorn. 1991. WHPA; A Modular Semi-
Analytical Model for the Delineation of Wellhead Protection Areas,
Version 2.0. U.S. Environmental Protection Agency, Office of Ground-
Water Protection, Washington, D.C.
Page 4ft-0
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Section 4: Model Descriptions Model Description for WHPA
12. Users
Kilborn, K., H.S. Rifai, and P.B. Bedient. 1992. Connecting Groundwater
Models and GIS. Geo Info Systems, Vol 2, No. 2, pp. 26-31. Discussing
the linkage of WHPA with System 9 GIS of Computervision running
on a SUN workstation. The linkage is illustrated for a project for the
city of Houston, Texas. Based on: The Integration of Groundwater
Models and Geographic Information Systems (GIS), Technical Papers
1991, ACSM-ASPRS Annual Convention, Volume 2, pp. 150-159.
Page 4fi-9
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Sect/on 4: Modal Descriptions Model Description for WHPA
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