UNITED STATISINVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
December 29, 1993
EPA-SAB-EEC-LTR-94-005
Administrator Carol M. Browner "'SCIENCEADVISORY BCWD"
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Re: Ground-Water Monitoring Network Research
Dear Ms. Browner:
The Office of Solid Waste (OSW) requested that the Science Advisory Board's
Environmental Engineering Committee (EEC) review the Ground-Water Monitoring
Network Design Research Program of the Environmental Monitoring Systems
Laboratory is Las Vegas (EMSL-LV). The EEC's Ground-Water Monitoring and
Network Design Review Subcommittee (GWMNDRS) conducted its review of a June
1993 draft of the subject research plan at a site visit at EMSL-LV on July 29-30, 1993.
OSW would like to use the results of this research to develop quantitative
standards for the design of ground-water monitoring well networks. The Subcommittee
found that the goal of developing tools for implementing quantitative data quality
objectives (QDQOs) for RCRA ground-water monitoring network system design and
performance is achievable and has practical merit for RCRA as well as for the
Superfund monitoring programs. Although the scientific quality of the work reviewed is
very high, the projects as structured appear to fall short for meeting the stated specific
needs for delivering readily useable methods in the near future. Additional planning is
needed to improve guidance for new network design and to provide tools for
evaluating existing networks and modifying them as needed.
The enclosure with this letter provides elaboration of the following answers to
the charge and the Subcommittee's resulting recommendations.
Specific Response to Charge:
1, "(A) Do the quantitative methods employed in the program assist in designing
monitoring networks? (B) What advantages do they have over current network
design methods, such as best professional judgement? (C) Are the methods too
complex for the user community?"
At the program level, there have been several advances in research that could
augment professional judgement in designing monitoring networks for detection
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monitoring (Illinois project) and compliance monitoring (Stanford project), but not
rtmediation monitoring. However, these advances in quantitative methods are not
now available in a readily usable form.
2. "(A) Are the underlying assumptions of the models valid? (B) Do the model
assumptions make sense considering the physical systems being modeled?"
Each of the models make basic assumptions regarding site characteristics
which provide a reasonable starting point for the development of quantitative methods
for monitoring network design. However, they may not be appropriate at many
facilities. The models have been developed by making assumptions not only
regarding the physical system, but also the regulatory and institutional characteristics
of the RCRA program. This includes an implicit assumption that an acceptable
probability-of-failure can be identified.
No single model can be broadly applicable to all types of sites. Test
applications of the methodology should be made in conjunction with hydrogeologists
familiar with particular sites (i.e., those who are now exercising their professional
judgement in designing monitoring network) and, if possible, using their models
(conceptual, or if available, numerical) to represent the site,
3. "(A) Are the data requirements for the models realistic? (B) How does the
model address data reliability.variance, and sample sizes? (C) What improvements
could be made to address these concerns?"
All of EMSL's proposed methods presumably will add information to the process
in terms of correlations among data, physical constraints, or possible answers via the
ground-water flow equation. Therefore, better decisions should be possible by using
these techniques, especially in combination with existing data bases. However, large
amounts of data are required by each technique.
With regard to the second question, none of the projects directly address data
reliability as a source of uncertainty in monitoring well network design (although the
geostatistical program developed at Stanford does allow the uncertainty of a measured
value to be considered).
The Subcommittee's answer to the third part of this question, is to develop
means for incorporating expert judgement into the tools that EMSL is developing.
4. "How can the research be used to enhance implementation of the RCRA
ground-water monitoring program?"
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At the program level, information in the literature and obtained from this
research could be incorporated into technical guidance documents, along with active
technology transfer and training of EPA staff who are the intended users.
Recommendations
The Subcommittee's chief recommendations are that the Agency; (1) sponsor a
comprehensive literature review on the research topic, (2) undertake a "fourth project"
that attempts to implement the methods and tools developed in the first three projects
at actual RCRA sites, and (3) critically review the problems associated with current
approaches to network design.
The Subcommittee thanks you for giving it the opportunity to review this
program and looks forward to a written response to its recommendations above.
Sincerely,
Dr, Ishwar P. Murarka, Chair Mr Richard A. Conway, Chair
Ground-Water Monitoring Network Environmental Engineering
Design Research Subcommittee Committee
Environmental Engineering Committee Science Advisory Board
Dr, Genevieve M. Matanoski, Chair
Executive Committee
Science Advisory Board
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Enclosure 1
Elaboration of the
Environmental Engineering Committee's Review
of ORD's
draft Monitoring Network Design Research Plan
supplemented by related documents
at a site visit at EMSL-LV on July 29-30, 1993
QSW would like to use the results of the research to develop quantitative
standards for the design of ground-water monitoring well networks. The Subcommittee
found that the goal of developing tools for implementing quantitative data quality
objectives (QDQOs) for RCRA ground-water monitoring network system design and
performance is achievable and has practical merit for RCRA as well as for the Superfund
monitoring programs. Second, although the scientific quality of the work reviewed is very
high, the projects as structured appear to fall short for meeting the stated specific needs
for delivering readily useabie methods in the near future. Finally, additional planning is
needed to improve guidance for new network design and to provide tools for evaluating
existing networks and modifying them as needed.
The Ground-Water Monitoring Network Design Research Program funded the
following three projects:
1. "OMNe Geostatistical Software for Monitoring" at Stanford
University's Civil Engineering Department,
2. "Quantitative Methods for the Design of Groundwater Quality
Monitoring Networks" at the University of Illinois at Urbana-
Champaign's Department of Civil Engineering, and
3. "Site Characterization for Heterogeneous Porous Media: The
Use of Scale Information Via the Wavelet Transform" at the
University of Nevada, Reno's Desert Research Institute
The Subcommittee considered both the scientific quality of the individual research
projects and their contribution to the EPA's objective of developing tools for implementing
QDQOs in RCRA detection monitoring, and related ground-water quality protection
activities.
The Subcommittee recommends that the Ground-Water Monitoring Network Design
research plan be enhanced to set clearer and more focused goals tied to ORD's ground-
water issue research plan. Clear, concise uses for results from the projects should be
identified.
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Specific Response to Charge:
1. "(A) Do the quantitative methods employed in the program assist in designing
monitoring networks? (8) What advantages do they have over current network design
methods, such as best professional Judgement? (C) Are the methods too complex for
the user community?"
At the program level, there have been several advances in research, which could
augment professional judgement in designing monitoring networks for detection
monitoring (Illinois project) and compliance monitoring (Stanford project), but not
remediation monitoring. However, these advances in quantitative methods are not now
available in a readily usable form.
The Subcommittee also addressed this question at the project level. The Stanford
project on geostatlsticat methods involves a very productive effort to combine the most
advanced suite of spatial statistical tools in a user-friendly computer environment. In the
context of the overall effort to develop tools for network design for detection monitoring,
these software tools have specific value in characterizing the statistical properties of the
spatial field of hydraulic conductivity. However, as currently presented to the
Subcommittee, these tools have a more appropriate application to characterizing
contaminant concentration distributions, once contamination has occurred,
Although no table was presented that compared the OMNe software from Stanford
with other specific current geostatistieal tools (such as GEQEAS, a code developed by
QRD/EMSL-LV), such a comparison would be useful. The OMNe software package is
suited for users with hydrogeologicai or modeling experience. To enhance statistical
confidence, it is anticipated that large amounts of site-specific data will be needed.
The Principal Investigator, Peter Kltandis, describes three-dimensional OMNe code
as, "a toolbox or software package that is currently being developed for the geostatistical
analysis of hydrogeologic and environmental data used as input in the design of
monitoring networks." OMNe, which runs on the UNIX system, can use one-, two, or
three-dimensional data.
EMSL-LV developed a two-dimensional code, GEOEAS, for the analysis of soil
contamination problems such as mapping the plume of lead in soil around a smelter.
GEOEAS, in contrast to the Ada laboratory's GEOPACK does ordinary, rather than
disjunctive kriging. The latter is better suited to the sparse data typically available for
ground-water environments.
Post-implementation audits at existing sites might also be performed.
The University of Illinois effort on detection monitoring design could strengthen
professional judgement The project on optimization of well placement is, as basic
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research, well-conceived and implemented The implementation of advanced optimization
techniques and the consideration of performance trade-offs has yielded a number of new
and important insights. Although the methods are not conceptually complex, a user
friendly product is not yet available. Furthermore, the linkage between the Illinois models
and OMNe is not obvious in that OMNe focuses on defining existing plumes and Illinois
focuses on detection monitoring.
The Desert Research Institute (DRI) project took a basic research approach to the
same problem as the Stanford project.
The DRI project on wavelets is at the leading edge of research and considers
many of the newest and most advanced methods for stochastic characterization of the
subsurface. Advances in this area could be important to the long-term evolution of
ground-water science, and the eventual benefits may be realized in a broad range of
ground-water programs. The research team demonstrates a solid capability and
performance in this area. However, as a very advanced tool, the methodology will not
likely be used by regions or facility operators for characterization of their RCRA sites for
many years as yet. Another aspect of the DRI project is that it is not dear how this
approach will incorporate field data and subjective estimates of uncertainty and variability.
2. "(A) Are the underlying assumptions of the models valid? (B) Do the model
assumptions make sense considering the physical system being modeled?"
(A) Each of the models make basic assumptions regarding site characteristics.
These assumptions include homogenous and isotropic porous media, steady flow, and
miscible transport. Such assumptions provide a reasonable starting point for the
development of quantitative methods for monitoring network design. However, they may
not be appropriate at many facilities. The presence of fractured media and non-aqueous
phase liquids (NAPLs) are two examples of real-world conditions that are not included in
the current models.
The models focus on uncertainty and variability in transport parameters, such as
hydraulic conductivity. Uncertainties in subsurface geometry such as buried channels and
discontinuous confining units are not addressed in the current work. Effects of
uncertainties in boundary conditions may also be important but are not included in the
current work. The models have been developed by making assumptions not only
regarding the physical system, but also the regulatory and institutional characteristics of
the RCRA program. This includes an implicit assumption that an acceptable probability-
of-failure can be identified.
(8) No single model can be broadly applicable to all types of sites. Test
applications of the methodology should be made in conjunction with hydrogeologists
familiar with particular sites (i.e., those who are now exercising their professional
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judgement in designing monitoring network) and, if possible, using their models
(conceptual, or if available, numerical) to represent the site.
The current research projects define monitoring in terms of ground-water wells.
Other technologies such as surface geophysics and soil gas analysis should also be
considered.
The Subcommittee also addressed these questions at the project level.
For the Stanford work, the validity of assumptions will depend on site-specific
application and the tools developed are not suitable for sites with geologic discontinuities
(such as clay lenses, buried channels). The DRI's work did not seem to show that natural
media exhibit the characteristics assumed in its model.
For the work performed at Illinois, the validity of assumptions likewise depends on
site-specific conditions. Unfortunately, the fate and transport part of the model is too
simple to be realistic for all but a few field situations.
Although the Illinois work is a good starting point, many sources of uncertainty
were hot considered (e.g. boundary conditions, chemical transformations) and there is a
need to consider other types of monitoring methods (e.g. soil vapor, geophysical). The
idealized aquifer representation used by the model may not be sufficiently representative
of individual sites to allow direct application for network design.
The ground-water model used to demonstrate the methodology was fairly simple
in order to illustrate the optimization approach. Future use of this approach should
incorporate a more realistic and complex ground-water flow and transport model. Some
of the limitations of this model are addressed in the OKI's proposal for future research.
Proposed recommendations for improvement include:
i. The use of variable or uncertain boundary conditions and recharge. This
would allow the model to address the common issue of proper placement of
background wells when the ground-water flow direction is radial, seasonally
variable, or uncertain.
ii. Addition of adsorption and degradation processes.
iii. Use of conditioning when there are measured values of hydraulic conductivity.
iv. The need to develop methodologies and approaches for incorporating
subjective information into the network design process.
Work currently being conducted at DRI is theoretical and field complexities have
not been incorporated into the model to date. Therefore an evaluation at this time is
premature.
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3. "(A) Are the data requirements for the models realistic? (B) How does the model
address data reliability, variance, and sample sizes? (C) What improvements could be
made to address these concerns?"
AH of EMSL's proposed methods presumably will add information to the process
in terms of correlations among data (Stanford and DRI), physical constraints, or possible
answers via the ground-water flow equation (U of Illinois), Therefore, better decisions
should be possible by using these techniques, especially in combination with existing data
bases. However, when the question is asked, "how much data are required in terms of
computer code input?11, it appears that large amounts of data are required by each
technique. To fulfill such data-needs in practice, the field people who currently design
networks use a large amount of subjective judgement. Therefore, the answer to the third
part of this question, and the resolution of this problem, is not to choose one technique
over another on the basis of large or small data requirements, but to combine the two
techniques into one approach by developing means for incorporating expert judgement
into the tools that EMSL is developing.
With regard to the second question, none of the projects directly address data
reliability as a source of uncertainty in monitoring well network design (although the
geostatistical program developed at Stanford does allow the uncertainty of a measured
value to be considered).
4. "How can the research be used to enhance implementation of the RCRA ground-
water monitoring program?"
At the program level, information in the literature and obtained from research could
be incorporated into technical guidance documents, along with active technology transfer
and training of EPA staff who are the intended users.
If consistency can be developed between the modeled and the true environments
(both physical and regulatory), then the research can provide an additional tool to aid in
network design. The quantitative methods might be used to demonstrate alternatives to
some default-level monitoring requirement.
Monitoring network design should be linked with site characterization activities and
with liner and facility design activities. Trade-offs exist among these three activities in
that more monitoring may be warranted at sites with less site characterization data or at
sites with less conservative engineering designs.
5. "What other technical expertise or resources within EPA, other federal agencies,
national laboratories, and academic institutions could be utilized to better serve the
clients' needs?"
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This is an issue at the program level. Increased interaction within the EMSL-LV
and with other relevant projects outside of the lab should be encouraged. For example,
performance assessment associated with the high-level radioactive waste isolation
program has focused on stochastic methods that EMSL-LV should consider.
EPA should, at a minimum, conduct a workshop to further such interaction. Such
a workshop should include ground- water scientists and engineers conducting research
on site and monitoring network design, as well as groups responsible for establishing
existing and planned monitoring networks at particular facilities. This would encourage
a better match between new conceptual approaches and the realities of actual site
problems.
Specific Recommendations
1 < The Subcommittee recommends that a more comprehensive literature review be
conducted and documented to define the state of the practice for monitoring network
design. Such a review should determine the current state-oRhe-art and technology needs
for the RCRA ground-water monitoring research program, and also serve as the basis for
a RCRA program guidance document that could be periodically updated to include future
research findings. Such a basic literature review should include case studies for which
these methods have been used, and will, thus, provide helpful guidance for project
managers at hazardous waste sites. A good beginning for such a review can be found
in the thesis of Philip D. Meyer, "The Optimal Design of Ground-Water Quality Monitoring
Networks Under Conditions of Uncertainty (section 1.1 A Brief Review of Some Previous
Work)," University of Illinois Urbana-Champagne (19S2). Statistical methods can be
summarized using documents such as Methods for Evaluating the Attainment of Cleanup
Standards-Volume 2: Ground Water (EPA, 1992).
2. In view of the above findings presented in the Summary above, the Subcommittee
recommends that the projects within the EMSL-LV program be better coordinated to
achieve the specified goals.
Further, the Subcommittee recommends that any model or tool developed under
the plan utilize similar assumptions so modeling components or subsets are easily
combined together. Such improved coordination between projects should result in the
generation of products which are timely, readily usable and easily combined while filling
current technology gaps. Coordination will require additional support, perhaps in the form
of a fourth project specifically designed to develop tools to facilitate the implementation
of QDQOs for RCRA ground-water detection monitoring.
Such a "fourth project" should use the methods and tools developed in the three
existing projects and attempt to implement them at actual RCRA sites, in cooperation with
site hydrogeologists and in conjunction with existing ground-water models for those sites.
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This project might begin by considering only the simpler sources of variability and
uncertainty at a site, such as the location of a release.
The professional judgement of the site hydrogeologist can be used to identify a
smali number of alternative conceptual models for the aquifer (e.g., with vs. without
possible high permeability zones) that could be assigned initial probabilities for their
occurrence. Best estimate hydraulic conductivity fields could then be assigned to, or
simulated for, each conceptual model. The probability simulation would then consider
only the use of the selected alternative conceptual models and the random location of the
release. Such an approach would facilitate the dissemination of probabilistic modeling
experience. It could even provide a basis for an interim methodology for implementing
probabilistic QDQOs, until methods and experience with stochastic simulation of hydraulic
conductivity fields become more readily accessible.
3. The Subcommittee recommends that EPA undertake a review of the problems
associated with current approaches to network design.
This should provide the program with a clearer specific direction for the
development of new techniques. The Subcommittee remained unclear as to whether the
program research was initiated because: (1) current monitoring-well networks are failing,
(2) there is no way to quantitatively assess the performance of existing networks, or (3)
to provide a more efficient (in terms of cost and time) approach to network design.
4. The Subcommittee recommends that appropriate resources be allocated to implement
the research plan once it is well defined and focused and, for limited resources, the
research plan should be implemented in phases. That is, funding should match
expectations.
5. The Subcommittee recommends that EPA develop a consistent approach to
evaluating improvements to the methods for describing the spatial variability of hydraulic
conductivity-both relative to other methods and relative to "reality." For example, if the
program continues to use "synthetic" realities to check the accuracy of the new
techniques, then the Subcommittee suggests that all methods be tested on the same
artificial hydraulic conductivity fields data. In addition, the Subcommittee suggests that
the program develop a means of comparing the fields generated by these techniques with
data from real sites. Such standardization of comparison methods should provide
potential users not only a clearer distinction among the techniques but also assurance
that they are potentially applicable to their sites.
6, The Subcommittee recommends that the role of temporal variations in monitoring
data be considered for inclusion in the current work.
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7, The Subcommittee recommends that continued support from EPA's Office of
Research and Development (ORD) shift focus to meet the needs for Superfund and
RCRA compliance or enforcement monitoring,
8. The Subcommittee recommends that the specific technical comments made in the
response to the charge be considered in any program revisions.
8
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Enclosure 2
U.S. ENVIRONMENTAL PROTECTION AGENCY
Science Advisory Board
Environmental Engineering Committee
Ground-Water Monitoring Design Review Subcommittee
Members and Consultants
Chair
Dr. Ishwar P, Murarka, Manager, Waste, Land and Water Programs
Electric Powtr Research Institute, Palo Alto, California
Members
Dr. Linda M, Abriola, Associate Professor
University of Michigan, Dept of Civil & Environmental Engineering
Ann Arbor, Michigan
Or, George F. Carpenter, Michigan Dept of Natural Resources
Environmental Response Division, Lansing, Michigan
Mr, Paul A, Davis, Department Manager, SANDIA National Laboratory
Albuquerque, New Mexico
Dr. James Johnson Jr..Professor and Chairman
Department of Civil Engineering, Howard University
Washington, District of Columbia
Dr. Joel W. Massmann, Professor, Department of Civil Engineering
University of Washington, Seattle, Washington
Dr, James W. Mercer, President
GeoTrans, Inc., Sterling, Virginia
Dr* Mitchell J. Small, Professor
Department of Civil Engineering, Carnegie-Mellon University
Pittsburgh, Pennsylvania
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Enclosure 3
U.S. ENVIRONMENTAL PROTECTION AGENCY
Science Advisory Board
FY93 Environmental Engineering Committee
Chairman
Mr. Richard A. Conway, Senior Corporate Fellow
Union Carbide Corporation, So, Charleston, West Virginia
Members
Dr. Linda M. Abriola, Associate Professor
University of Michigan, Dept of Civil and Environmental Engineering
Ann Arbor, Michigan
Dr. George F. Carpenter, Michigan Dept. of Natural Resources
Environmental Response Division, Lansing, Michigan
Dr. James H, Johnson, Jr., Professor and Chairman
Department of Civil Engineering, Howard University
Washington, District of Columbia
Dr. Wayne M. Kachei, Martin Marietta Corporation
Oak Ridge, Tennessee
Dr. Ishwar P. Murarka, Manager-Waste, Land and Water Programs
Environmental Division, Electric Power Research Institute
Palo Alto, California
Dr. Frederick G. Portland, Weidlein Chair of Environmental Engineering
Department of Civil Engineering, University of Pittsburgh
Pittsburgh, Pennsylvania
Dr, Robert B. Pojasek, Corporate Vice President-Environmental Programs
GEI Consultants, Inc., Winchester, Massachusetts
Dr. Wm. Randall Seeker, Senior Vice President
Energy & Environmental Research Corp., Irvine, California
Dr. Walter M. Shaub, President, CORRE, Inc., Reston, Virginia 22090
Dr. C, Herbert Ward, Director & Professor, Energy and Environmental
Systems Institute, Rice University, Houston, Texas
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