EPA/600/R-03/048
AUGUST 2002
PRELIMINARY ANALYSIS OF
ALTERNATIVES FOR THE LONG TERM
MANAGEMENT OF EXCESS MERCURY
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Project Officer: Paul Randall
Contract # GS-10F-0076J
-------
NOTICE
The U.S. Environmental Protection Agency through its Office of Research and Development
funded and managed the research described here under Contract number GS-10F-0076J. It has
been subjected to the Agency's peer and administrative review and has been approved for
publication as an EPA document. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
-------
FOREWORD
The U.S. Environmental Protection Agency (EPA) is charged by Congress with
protecting the Nation's land, air, and water resources. Under a mandate of national environmental
laws, the Agency strives to formulate and implement actions leading to a compatible balance
between human activities and the ability of natural systems to support and nurture life. To meet
this mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center
for investigation of technological and management approaches for preventing and reducing risks
from pollution that threaten human health and the environment. The focus of the Laboratory's
research program is on methods and their cost-effectiveness for prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites, sediments and ground water; prevention and control
of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and
private sector partners to foster technologies that reduce the cost of compliance and to anticipate
emerging problems. NRMRL's research provides solutions to environmental problems by:
developing and promoting technologies that protect and improve the environment; advancing
scientific and engineering information to support regulatory and policy decisions; and providing
the technical support and information transfer to ensure implementation of environmental
regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term
research plan. It is published and made available by EPA's Office of Research and Development
to assist the user community and to link researchers with their clients.
Hugh W. McKinnon, Director
National Risk Management Research Laboratory
in
-------
TABLE OF CONTENTS
LIST OF TABLES v
LIST OF FIGURES v
ACRONYMS AND SYMBOLS vi
EXECUTIVE SUMMARY S-l
S.I Background S-l
S.2 Approach S-l
S.3 Sources of Information S-l
S.4 Limitation of Scope S-2
S.5 Goals, Criteria and Intensities S-4
S.7 Conclusions and Recommendations S-6
1.0 INTRODUCTION 1-1
1.1 Background 1-1
1.2 Approach 1-2
1.3 Defining the Boundaries of the Problem 1-3
1.3.1 Mercury Use and Disposition Cycle 1-3
1.3.2 Limitation of Scope 1-5
1.4 Sources of Information 1-6
2.0 CHOICE OF CRITERIA AND INTENSITIES 2-1
2.1 The Goal 2-1
2.2 First-Level Criteria 2-1
2.3 Benefits 2-1
2.3.1 Benefit Criterion 1 - Compliance with Current Laws and Regulations 2-1
2.3.2 Benefit Criterion 2 - Implementation Considerations 2-2
2.3.3 Benefit Criterion 3 - Maturity of the Technology 2-2
2.3.4 Benefit Criterion 4 - Risks 2-2
2.3.5 Benefit Criterion 5 - Environmental Performance 2-3
2.3.6 Benefit Criterion 6 - Public Perception 2-4
2.3.7 Pairwise Comparison of the Criteria 2-5
2.4 Costs 2-5
2.4.1 Cost Criterion 1 - Implementation Costs 2-5
2.4.2 Cost Criterion 2 - Operating Costs 2-6
2.5 Summary of Criteria and Intensities 2-6
3.0 DISCUSSION AND EVALUATION OF OPTIONS 3-1
3.1 Storage Information 3-1
3.1.1 Storage in a Standard RCRA-Permitted Storage Building 3-1
3.1.2 Storage in aHardened RCRA-Permitted Storage Building 3-2
3.1.3 Storage in a Mined Cavity 3-2
3.1.4 Storage Options Not Considered 3-3
3.1.5 Summary of Storage Options versus Evaluation Criteria 3-3
3.2 Treatment Information 3-5
3.2.1 ADA / Permafix Treatment 3-7
3.2.2 BNL Sulfur Polymer Solidification 3-7
3.2.3 IT/NFS DeHgฎ Process 3-8
3.2.4 Selenide Process 3-9
IV
-------
3.2.5 Treatment Technologies Not Considered 3-10
3.2.6 Summary of Treatment Options versus Evaluation Criteria 3-11
3.3 Disposal Information 3-14
3.3.1 Disposal in a Mined Cavity 3-14
3.3.2 Disposal in a RCRA-permitted Landfill 3-15
3.3.3 Disposal in a RCRA-permitted Monofill 3-16
3.3.4 Disposal in an Earth-Mounded Concrete Bunker 3-16
3.3.5 Other Disposal Options not Evaluated 3-17
3.3.6 Summary of Disposal Options versus Evaluation Criteria 3-17
3.4 Evaluation of Options 3-19
4.0 RESULTS 4-1
4.1 Initial Results 4-1
4.2 Sensitivity Analysis 4-3
4.2.1 Sensitivity Analyses for Non-Cost Criteria 4-3
4.2.2 Sensitivity Analyses for Cost Criteria 4-6
4.3 Discussion of Uncertainty 4-6
5.0 CONCLUSIONS AND RECOMMENDATIONS 5-1
6.0 BIBLIOGRAPHY 6-1
Appendix A - The Analytical Process and the Expert Choice Mercury Retirement Model
Appendix B - Screening of Technologies
Appendix C - Environmental Performance Data
Appendix D - Evaluation of Treatment and Disposal Alternatives
Appendix E - Disposition of Comments
LIST OF TABLES
Table S-l Summary of Results for 11 Evaluated Alternatives S-8
Table S-2 Sensitivity Analysis ofNon-Cost Criteria S-9
Table 2-1 Ranking of Non-Cost Criteria after Pairwise Comparisons 2-5
Table 2-2 Criteria Used for Evaluating Options 2-7
Table 3-1 Evaluation for Three Storage Options 3-4
Table 3-3 Evaluation for Treatment Options 3-12
Table 3-4 Evaluation for Four Disposal Options 3-18
Table 3 -5 Summary of Criteria Values Assigned to Each Evaluated Alternative 3-21
Table 3-6 Continuation of Summary of Criteria Values Assigned to Each
Evaluated Alternative 3-22
Table 4-1 Summary of Results for 11 Evaluated Alternatives 4-2
Table 4-2 Sensitivity Analysis of Non-Cost Criteria 4-5
Table 4-3 Sensitivity Analysis of Cost Criteria to Results for
9 Evaluated Alternatives 4-7
Table 4-4 Uncertainty Analysis for Mercury Management Alternatives 4-9
LIST OF FIGURES
Figure 1-1 Simplified Schematic of the Mercury use and Disposal Cycle....
..1-2
-------
ACRONYMS AND SYMBOLS
AHP Analytical Hierarchy Process
BNL Brookhaven National Laboratory
CBD Commerce Business Daily
DLA Defense Logistics Agency
DNSC Defense National Stockpile Center
DoD Department of Defense
DOE Department of Energy
DOT Department of Transportation
EPA Environmental Protection Agency
ETC Environmental Technology Council
FAA Federal Aircraft Administration
g grams
GSA General Services Administration
Ib pounds
LDR Land Disposal Restrictions
LS Liquid to Solid Ratio
mEq milli-equivalents
mV milli-volts
MMEIS Mercury Management Environmental Impact Statement
NEI Nuclear Energy Institute
ORD Office of Research and Development
OSW Office of Solid Waste
PBT Persistent, Bio-accumulative, and Toxic
RCRA Resource Conservation and Recovery Act
S/A Sulfide/Amalgamation
SAIC Science Applications International Corporation
SEK Swedish Kroner
SPSS Sulfur Polymer Solidification/Stabilization Process
TCLP Toxicity Characteristic Leaching Procedure
TLV Threshold Limit Value
USAGE US Army Corps of Engineers
UTS Universal Treatment Standard
VA Veterans Administration
WIPP Waste Isolation Pilot Plant
VI
-------
PRELIMINARY ANALYSIS OF ALTERNATIVES FOR THE LONG
TERM MANAGEMENT OF EXCESS MERCURY
EXECUTIVE SUMMARY
This report is intended to describe the use of a systematic method for comparing options for the
retirement of excess mercury. The results are presented in Section S.6 of this summary with
conclusions and recommendations in Section S.7. Sections S.I through S.5 discuss the
background, approach and assumptions.
S.I Background
Over the past decade, the Environmental Protection Agency (EPA) has promoted the use of
alternatives to mercury because it is a persistent, bio-accumulative, and toxic (PBT) chemical.
The Agency's long-term goal for mercury is the elimination of mercury released to the air, water,
and land from anthropogenic sources. The use of mercury in products and processes has
decreased. The Department of Defense (DoD) and the Department of Energy (DOE) have excess
mercury stockpiles that are no longer needed. Mercury cell chlor-alkali plants, although still the
largest worldwide users of mercury, are discontinuing the use of mercury in favor of alternative
technologies. In EPA, the Office of Solid Waste (OSW), working with the Office of Research
and Development (ORD) and DOE, is evaluating technologies to permanently stabilize and
dispose of wastes containing mercury. Furthermore, OSW is considering revisions to the Land
Disposal Restrictions (LDRs) for mercury. Therefore, there is a need to consider possible
retirement options for excess mercury.
S.2 Approach
The approach chosen for the present work is the Analytical Hierarchy Process (AHP) as
embodied in the Expert Choice software1. AHP was developed at the Wharton School of Business
by Dr. Thomas Saaty and continues to be a highly regarded and widely used decision-making
tool. The AHP engages decision-makers in breaking down a decision into smaller parts,
proceeding from the goal to criteria to sub-criteria down to the alternative courses of action.
Decision-makers then make simple pairwise comparison judgments throughout the hierarchy to
arrive at overall priorities for the alternatives. The decision problem may involve social, political,
technical, and economic factors. The AHP helps people cope with the intuitive, the rational and
the irrational, and with risk and uncertainty in complex situations. It can be used to: a) predict
likely outcomes; b) plan projected and desired futures; c) facilitate group decision making; d)
exercise control over changes in the decision making system; e) allocate resources; f) select
alternatives; and g) perform cost/benefit comparisons.
S.3 Sources of Information
The principal sources of information that were consulted to obtain data for this study are as
follows.
Canadian Study: SENES Consultants (SENES, The Development of Retirement and Long Term
Storage Options of Mercury, prepared for Environment Canada, 2001) has produced a draft report
1 Information on the Expert Choice software can be found at www.expertchoice.com. Most of the material about
Expert Choice in this Executive Summary and in Section 1.2 of the main report is abstracted from that Web site.
S-l
-------
for Environment Canada on the development of retirement and long-term storage options for
mercury. The report provides comprehensive identification of the range of technologies that are
potentially available for mercury storage or retirement, together with a wealth of references.
Mercury Management Environmental Impact Statement: The Defense Logistics Agency (DLA) is
currently preparing a Mercury Management Environmental Impact Statement (MMEIS). In
2001, DLA published Commercial Sector Provision of Elemental Mercury Processing Services -
Request for Expressions of Interest in the Commerce Business Daily (CBD). This announcement
solicited expressions of interest in providing technologies for the permanent retirement of 4,890
tons of elemental mercury from the national stockpile. Five expressions of interest were received
and, to the extent that this information is non-proprietary, it has been used in the present work. In
addition, the MMEIS project has assembled a long list of references on mercury treatment.2
Mercury Workshop: EPA has prepared the proceedings of the mercury workshop that was held in
March 2000 in Baltimore, Maryland. This workshop covered: a) the state of the science of
treatment options for mercury waste; and b) the state of the science of disposal options for
mercury waste, such as landfill disposal, sub-seabed emplacement, stabilization, and surface and
deep geological repositories for mercury waste storage.
Other US EPA and US DOE Activities: For several years, both EPA and DOE have been
evaluating the performance and feasibility of mercury treatment technologies. DOE has
published various Innovative Technology Summary Reports that evaluate the treatment
technologies applicable to mercury containing mixed wastes (i.e., wastes that are both hazardous
and radioactive). The reports include environmental performance testing, cost information, and
other operations information. In addition, EPA has conducted performance testing of mercury-
containing wastes processed by various treatment technologies. Performance testing in these
studies has involved both comprehensive analytical testing and standard Toxicity Characteristic
Leaching Procedure (TCLP) tests.
S.4 Limitation of Scope
The resources available for this project required that the scope be limited to manageable
proportions. To this end, certain ground rules and simplifications were developed:
Industry-specific technologies are excluded on the grounds that they can only manage a
small fraction of the total mercury problem and in any case should be regarded as an
integral part of that specific industry's waste management practices
The study focuses on options for retirement of surplus bulk elemental mercury on the
grounds that: a) this alone is a large enough project to consume the available funding; b)
that it anyway addresses a large fraction of the problem; and c) that it will provide an
adequate demonstration of the decision-making technique that can readily be expanded in
the future. Thus, for example, the treatment of wastewater streams is excluded.
The chemical treatment options are limited and are chosen to be representative of major
classes of treatment options, such as metal amalgams, sulfides, or selenides. The choice
is to some extent driven by available information. If the decision analysis favors any one
class of options, then in principal it will be possible later to focus on individual
Note that, in its MMEIS, the DLA is expected to analyze only three alternatives in detail: 1) consolidation and
storage at one or more of the current mercury storage sites or other suitable locations, 2) sale of the mercury
inventory, and 3) no action, maintaining storage at four existing sites. (Lynch 2002)
S-2
-------
technologies within that class and perform a further decision analysis to choose between
individual technologies.
Only technologies that can in principal treat contaminated media as well as elemental
mercury are considered. This compensates to some extent for the decision to focus on
elemental mercury.
Retorting is excluded as merely being a well-established prior step for producing
elemental mercury, some of which may end up in the pool of surplus mercury
Deep-sea disposal is excluded because obtaining the necessary modifications to
international laws and treaties is regarded as too onerous a task
Storage in pipelines is excluded because the project team could not find information
about this option.
As a result of the above-described ground rules and simplifications, two types of treatment
technologies were evaluated: sulfide/amalgamation (S/A) techniques and the mercury selenide
treatment process. The S/A techniques were represented by: a) DeHgฎ amalgamation; b) the
Sulfur Polymer Solidification/Stabilization (SPSS) process; and c) the Permafix sulfide process.
These were grouped as a single class because they have very similar characteristics when
compared against the criteria defined by the team (comprised of SAIC staff) and modeled in
Expert Choice. Therefore, only these two general types of treatment technologies were evaluated.
These were combined with four disposal options: a) disposal in a RCRA-permitted landfill; b)
disposal in a RCRA-permitted monofill; c) disposal in an engineered belowground structure; and
d) disposal in a mined cavity. In addition, there are three storage options for elemental mercury:
a) storage in an aboveground RCRA- permitted facility; b) storage in a hardened RCRA-
permitted structure; and c) storage in a mined cavity. Altogether, eleven options were chosen for
examination with the decision-making tool:
Storage of bulk elemental mercury in a standard RCRA-permitted storage building
Storage of bulk elemental mercury in a hardened RCRA-permitted storage structure
Storage of bulk elemental mercury in a mined cavity
Stabilization/amalgamation followed by disposal in a RCRA- permitted landfill
Stabilization/amalgamation followed by disposal in a RCRA- permitted monofill
Stabilization/amalgamation followed by disposal in an earth-mounded concrete bunker
Stabilization/amalgamation followed by disposal in a mined cavity
Selenide treatment followed by disposal in a RCRA- permitted landfill
Selenide treatment followed by disposal in a RCRA- permitted monofill
Selenide treatment followed by disposal in an earth-mounded concrete bunker
Selenide treatment followed by disposal in a mined cavity
Several of the more critical assumptions made in compiling these options include the following:
(1) The project team considered storage to be temporary. As a result, costs were considered
as those associated with storage itself (e.g., initial costs and operating costs), as well as
projected costs for subsequent treatment and disposal when storage is terminated. As is
demonstrated in the sensitivity analyses in Table S-l and Section 4.0, this is an
assumption that has an important effect on the ranking of the storage options.
(2) Storage, treatment, or disposal of the mercury was assumed to require RCRA-permitting.
There is uncertainty as to whether local and federal environmental authorities would
require such permitting for all management steps; this is a conservative assumption. This
is further discussed in Section 3.1.1 of this report.
(3) No distinction is made between individual stabilization and amalgamation technologies.
As a result, the model is intended to identify the relative preference of this management
S-3
-------
technique to other options rather than assessing the performance of individual treatment
technologies.
S.5 Goals, Criteria and Intensities
Expert Choice requires the definition of a goal, criteria, and intensities. The goal in this case is
simple, namely to "Select the best alternatives for mercury retirement." The team3 developed two
first-level criteria, benefits and costs. Initially, equal weights were assigned to them. This is a
simple example of the pairwise comparison that is performed at every level in the hierarchy of
criteria developed as input to Expert Choice.
Under costs, two-second level criteria were developed, implementation costs and operating costs.
For each retirement option, the team then asked, whether the implementing costs would be low,
medium, or high, and whether the operating costs would be low, medium, or high. These
assignments of low, medium, or high are examples of intensities. Section 3 of the report explains
in detail how the costs associated with each retirement option were determined, although this is
an area in which there is considerable uncertainty.
Six second-level criteria were developed under the heading of benefits. Some of the second-level
benefits were further split into third-level criteria. Intensities were then assigned to each of the
lowest-level criteria. The six second-level criteria and associated sub-criteria are listed below.
The figures in parentheses give the weights assigned to each of the criteria and sub-criteria using
the process of pairwise comparison which is at the core of AHP (see Appendix A of the main
report). Thus, it can be seen that, of the six second-level criteria, the analysts judged that
environmental performance (0.336) and risks (0.312) are the most important. At the second level,
the weights add to one. At each sub-criterion level, the weights are determined independently
and also add to one.
Compliance with Current Laws and Regulations (0.045)
Implementation Considerations (0.154)
Volume of waste (0.143)
Engineering requirements (0.857)
Maturity of the Technology (0.047)
State of maturity of the treatment technology (0.500)
Expected reliability of the treatment technology (0.500)
Risks (0.312)
- Public risk ((0.157)
- Worker risk (0.594)
Susceptibility to terrorism/sabotage (0.249)
Environmental Performance (0.336)
Discharges during treatment (0.064)
Degree of performance testing of the treatment technology (0.122)
Stability of conditions in the long term (0.544)
- Ability to monitor (0.271)
Public Perception (0.107)
As noted above, intensities were then assigned to each of these criteria and sub-criteria. For
example, three intensities were assigned to the sub-criterion "State of maturity of the treatment
The team consisted of five analysts from SAIC. Their names and qualifications are described at the beginning of
Section 2.0.
S-4
-------
technology": a) experience with full-scale operation; b) pilot treatment technology with full-scale
operation of disposal option; and c) pilot treatment technology with untested disposal.
Brainstorming about the relative importance of each pair of these three intensities ("pairwise
comparison") leads to the following relative ranking of the importance of these intensities: 0.731,
0.188, and 0.081 respectively. These are numerical weights that factor into the final AHP
calculations. Details on the development of intensities for all criteria and sub-criteria are given in
Chapter 2 of the main report. The assignment of individual retirement options to intensities is
provided in Chapter 3. Pairwise comparison judgments made for intensities, criteria, and sub-
criteria are provided in Appendix A.
S.6 Results
Table S-l summarizes the results of the base-case analysis together with variations on the results
assuming that only benefits (non-costs) or only costs are important. The ranking from the base-
case analysis appears in the second column ("overall") and shows that the landfill options are
preferred independent of the treatment technology. The storage options rank next, followed by
the treatment technologies combined with monofills, bunkers, or mined cavities.
The reasons why the landfill options are preferred become apparent when costs are considered.
The third column of results shows the rankings if only cost is taken into account. The landfill
options are cheapest and this clearly outweighs the relatively unfavorable rankings that result
from a focus on the benefits. However, if the costs are not an important factor, then the three
storage options occupy the first three places in the "non-costs only" ranking.
The last column of Table S-l shows unfavorable rankings for the operating costs of the storage
options. This arises for two reasons: a) if storage continues for a long period, even relatively
small per annum costs will add up; and b) storage is not a means for permanent retirement of bulk
elemental mercury and the analysts assumed that, sooner or later, a treatment and disposal
technology will be adopted, which adds to the cost. This is enough to drive the storage options
out of first place in the base-case rankings. However, the analysis would support continued
storage for a short period (up to a few decades) followed by a permanent retirement option. This
would allow time for the treatment technologies to mature.
Table S-2 displays a sensitivity study for non-cost criteria only.4 These sensitivity studies show
that, if cost is not a concern, then storage in a hardened, RCRA-permitted structure performs
favorably against all the criteria. By contrast, the landfill options do not perform as well, with
public perception and environmental performance being among the criteria for which these
options receive relatively low rankings.
The standard storage option ranks least favorably of all against risks (public, worker, and
susceptibility to terrorism). Although the analysts consider that none of the options has a high
risk, the fact that the standard storage option would have large quantities of elemental mercury in
a non-hardened, aboveground structure suggested to the team that the risks are somewhat higher
than those for other options.
4 The sensitivity studies were performed by adjusting weights so that the individual criterion receives 90% of the
weighting, while the rest receive only 10% altogether while maintaining the relative weightings from the base case.
The exceptions are columns 2 and 3 of the results in Table S-l where only benefits or only costs were considered,
respectively.
S-5
-------
The options that include selenium treatment also rank less favorably with respect to risk because
they were assigned a higher worker risk than were the other retirement options due to the
relatively high temperature of operation and the presence of an additional toxic substance
(selenium). They also (unsurprisingly) perform relatively unfavorably with respect to
technological maturity.
The last row of Table S-2 shows the ratio between the scores for the alternatives that are ranked
highest and lowest. Table S-2 shows that, if high importance is assigned to them, compliance
with laws and regulations (ratio 7.1), implementation considerations (ratio 6.8) and the maturity
of the technology (ratio 5.0) are the most significant discriminators between the retirement
options. By contrast, the ratio for sensitivity to risks is only 1.6. This is because the analysts
concluded that none of the retirement options has a high risk and that any variations are between
low and very low risk.
Finally, a limited number of analyses were performed to address uncertainties in the assignment
of the retirement options to each intensity. These analyses are discussed in Section 4.3 of the
main report. Examples include increasing implementation costs for storage in a mine from
medium to high, decreasing operating costs for storage of elemental mercury in a hardened,
RCRA-permitted structure from high to low, and looking forward to when selenide treatment
followed by storage in a mined cavity can be considered as a fully mature technology. Altogether
twelve such analyses were performed by changing just one intensity assignment from the base
case. These analyses showed expected trends, with scores and rankings improving if a more
favorable assignment was made and decreasing if a less favorable assignment was made. In no
case did the score increase or decrease by more than 40% and in most cases the change was less
than 10%. These analyses are only uncertainty analyses in a very limited sense because (due to
funding limitations) only one parameter at a time could be varied. A future study could
potentially perform a true uncertainty analysis using Monte Carlo techniques.
S.7 Conclusions and Recommendations
A limited scope decision-analysis has been performed to compare options for the retirement of
surplus mercury. The analysis has demonstrated that such a study can provide useful insights for
decision-makers. Future work could include:
1. Involve additional experts or stakeholders in the process of assigning weights to the various
criteria. The individuals involved in producing the current report were exclusively from
SAIC. They are listed at the beginning of Section 2.0. This would ensure that a wider range
of expertise and interests is incorporated into the analysis. For example, working groups
within EPA, involving a cross-section of EPA offices, would provide additional perspectives.
Other examples would involve the inclusion of other Federal agencies, States,
nongovernmental organizations, foreign governments, industry, and academia. Such
participation could be performed in stages. As discussed above, differences in the importance
of the criteria relative to one another can change the results.
2. The alternatives considered in this report were limited to elemental mercury. Additional
alternatives could be considered for mercury-containing wastes.
3. Additional Expert Choice analyses could be conducted in which certain alternatives are
optimized. For example, within the general alternative of stabilization/ amalgamation
treatment followed by landfill disposal are potential sub-alternatives addressing individual
treatment technologies or landfill locations.
4. Revisit the available information periodically to determine if changes in criteria, or changes
in intensities, are required. For example, some candidate criteria were not considered
because insufficient information was available. One example is volatilization of mercury
S-6
-------
during long-term management. Very little data are available at this time to adequately
address this as a possible criterion.
5. Consider performing a formal uncertainty analysis utilizing Monte-Carlo-based techniques.
S-7
-------
Table S-l Summary of Results for 11 Evaluated Alternatives
Alternative
Stabilization/amalgamation followed by disposal
in a RCRA- permitted landfill
Selenide treatment followed by disposal in a
RCRA- permitted landfill
Storage of elemental mercury in a standard
RCRA-permitted storage building
Stabilization/amalgamation followed by disposal
in a RCRA- permitted monofill
Storage of elemental mercury in a hardened
RCRA-permitted storage structure
Selenide treatment followed by disposal in a
RCRA- permitted monofill
Storage in a mine
Stabilization/amalgamation followed by disposal
in an earth-mounded concrete bunker
Stabilization/amalgamation followed by disposal
in a mined cavity
Selenide treatment followed by disposal in an
earth-mounded concrete bunker
Selenide treatment followed by disposal in a
mined cavity
Number of alternatives evaluated
Total
Average score (total divided by number of
alternatives, either 9 or 11)
Ranking (as fraction of l,000a)
Overall
Score
137
123
110
103
95
94
81
70
63
62
61
11
1,000
91
Rank
1
2
3
4
5
6
7
8
9
10
11
Non-Costs
Only
Score
99
66
152
92
173
74
140
108
97
c
c
9
1,000
111
Rank
5
9
2
7
1
8
3
4
6
c
c
Costs Onlyb
Score
217
217
126
135
44
135
44
42
42
c
c
9
1,000
111
Rank
1
1
5
3
6
3
6
8
8
c
c
Shading indicates the highest ranking alternative.
a Scores normalized to total 1,000.
b Costs for storage options include both the storage costs as well as end-of-storage costs for subsequent treatment and
disposal.
c These options were evaluated for the overall goal but were not evaluated at the lower levels of cost and non-cost
items separately, due to the low score from the overall evaluation.
S-8
-------
Table S-2 Sensitivity Analysis of Non-Cost Criteria"
Alternative
Storage of elemental mercury in a hardened
RCRA-permitted structure
Storage of elemental mercury in a standard
RCRA-permitted building
Storage in a mine
Stabilization/amalgamation followed by
disposal in an earth-mounded concrete
bunker
Stabilization/amalgamation followed by
disposal in a RCRA- permitted landfill
Stabilization/amalgamation followed by
disposal in a mined cavity
Stabilization/amalgamation followed by
disposal in a RCRA- permitted monofill
Selenide treatment followed by disposal in a
RCRA- permitted monofill
Selenide treatment followed by disposal in a
RCRA- permitted landfill
Total
Range: highest to lowest alternative
Ranking (as fraction of l,000b; average score 111)
Non-Cost
Baseline
Score
173
152
140
108
99
97
92
74
66
1,000
Rank
1
2
o
5
4
5
6
7
8
9
2.6 times
Sensitivity:
Env Perf
Score
176
173
145
94
71
110
92
81
58
1,000
Rank
1
2
o
J
5
8
4
6
7
9
3.0 times
Sensitivity:
Risks
Score
142
87
101
132
131
95
130
92
91
1,000
Rank
1
9
5
2
o
6
6
4
7
8
1.6 times
Sensitivity:
Implement
Score
172
259
168
57
146
38
55
53
52
1,000
Rank
2
1
o
J
5
4
9
6
7
8
6.8 times
Sensitivity:
Public
Score
197
52
193
190
46
189
46
44
43
1,000
Rank
1
5
2
3
6
4
6
8
9
4.6 times
Sensitivity:
Maturity
Score
226
224
223
52
67
51
66
46
45
1,000
Rank
1
2
o
5
6
4
7
5
8
9
5.0 times
Sensitivity:
Compliance
Score
263
261
78
74
73
37
73
71
70
1,000
Rank
1
2
o
5
4
5
9
5
7
8
7.1 times
Shading indicates the two, three, or four highest-ranking alternatives. Cut-off is determined by where a large drop in the score occurs.
In the sensitivity analysis for each criterion, the importance of the criterion is set at 90 percent. The five other criteria comprise the remaining ten percent, proportional to their original
contributions.
a Two options were not evaluated for the sensitivity analysis: selenide treatment followed by disposal in a mined cavity, and selenide treatment followed by disposal in an earth-mounded
concrete bunker. This is because of the low score from the overall evaluation and because the version of Expert Choice used for this analysis only allowed the use of nine alternatives for the
sensitivity analysis.
b Scores normalized to total 1,000.
S-9
-------
PRELIMINARY ANALYSIS OF ALTERNATIVES FOR THE LONG
TERM MANAGEMENT OF EXCESS MERCURY
1.0 INTRODUCTION
This report is intended to describe the use of a systematic method for comparing options for the
retirement of excess mercury. The method chosen is the Analytical Hierarchy Procedure (AHP)
as embodied in the Expert Choice software.
In this introduction, Section 1.1 provides background on why such a procedure is potentially
helpful in the decision-making process. Section 1.2 describes the approach and summarizes the
AHP. AHP and Expert Choice are described in more detail in Appendix A. Section 1.3 describes
how the scope of the present work was limited to manageable proportions by judicious choice of
retirement options for which there is reasonable information and which are representative of a
wide range of technologies. Section 1.4 describes sources of information used for the work.
Section 2.0 describes the choice of a goal, criteria, and intensities for the Expert Choice software.
These terms are defined in Appendix A. The criteria and intensities are the foundation of the
model for mercury retirement.
Section 3.0 contains discussion and evaluation of the retirement options. The purpose of the
section is to assign each technology to an intensity under each criterion. These assignments
constitute the basic activity from which numerical scores emerge for each option.
Section 4.1 presents the numerical results of the Expert Choice analysis. The meaning of these
results and their potential usefulness as an aid to decision making are discussed in Section 4.2 by
presenting the results of some sensitivity studies. Section 4.3 contains a discussion of
uncertainty.
Section 5 contains suggestions for future work. As noted above, Appendix A describes the AHP
and Expert Choice. Appendix B reviews an earlier study from Environment Canada. This was a
comprehensive review of many potential mercury treatment and retirement options. In the
Appendix, those options are reviewed one-by-one and reasons are given why they were or were
not chosen for the AHP analysis. Appendix C summarizes available environmental performance
data for the treatment technologies identified in the present work. Appendix D details of the
values assigned to each intensity for each of the retirement options other than those simply
involving storage of bulk elemental mercury. Finally, Appendix E addresses the disposition of
comments that were received on an earlier draft report.
1.1 Background
Over the past decade, the Environmental Protection Agency (EPA) has promoted the use of
alternatives to mercury because it is a persistent, bio-accumulative, and toxic (PBT) chemical.
The Agency's long-term goal for mercury is the elimination of mercury released to the air, water,
and land from anthropogenic sources. The use of mercury in products and processes has
decreased. The Department of Defense (DoD) and the Department of Energy (DOE) have excess
mercury stockpiles that are no longer needed. Mercury cell chlor-alkali plants, although still the
largest worldwide users of mercury, are discontinuing the use of mercury in favor of alternative
technologies. Therefore, there is a need to consider possible retirement options for excess
mercury.
1-1
-------
In the USEPA, the Office of Solid Waste(OSW), working with the Office of Research and
Development (ORD) and DOE, is evaluating technologies to permanently stabilize and dispose of
wastes containing mercury. Furthermore, OSW is considering revisions to the Land Disposal
restrictions (LDRs) for mercury. These revisions will address the Hg Stockpile and retirement
issue. However, the regulatory system currently strongly supports all recycling initiatives and the
concept of retirement is in its infancy as far as conceptualization is concerned. Indeed, EPA has
yet to define exactly what is meant by the "retirement" of mercury.
As noted above, the Agency has focused its efforts on the reduction of current uses of mercury
and future releases of mercury to the environment. The agency has focused on recycling
(retorting) for mercury-containing hazardous wastes and has only performed preliminary
investigations of other management options. Analysis has not been performed at the level of
detail necessary to make decisions on retirement options and, in any case, data is not presently
available on many of the commercially available technologies. However, despite the
unavailability of information, there is a need to examine potential scenarios for the long-term
management of mercury.
1.2 Approach
The approach chosen for the present work is the Analytical Hierarchy Process (AHP) as
embodied in the Expert Choice software. AHP was developed at the Wharton School of Business
by Dr. Thomas Saaty and continues to be a highly regarded and widely used decision-making
tool. The AHP engages decision-makers in breaking down a decision into smaller parts,
proceeding from the goal to criteria to sub-criteria down to the alternative courses of action.
Decision-makers then make simple pairwise comparison judgments throughout the hierarchy to
arrive at overall priorities for the alternatives. The decision problem may involve social, political,
technical, and economic factors. The AHP helps people cope with the intuitive, the rational and
the irrational, and with risk and uncertainty in complex situations. It can be used to; a) predict
likely outcomes; b) plan projected and desired futures; c) facilitate group decision making; d)
exercise control over changes in the decision making system; e) allocate resources; f) select
alternatives; and g) do cost/benefit comparisons.
The Expert Choice software package incorporates the principles of AHP in an intuitive,
graphically based and structured manner that is valuable for conceptual and analytical thinkers,
novices and subject matter experts. Because the criteria are presented in a hierarchical structure,
decision-makers are able drill down to their level of expertise, and apply judgments to the criteria
deemed important to their objectives. At the end of the process, decision-makers are fully
cognizant of how and why the decision was made, with results that are meaningful and
actionable.
In summary, Expert Choice was chosen for the present work for the following reasons:
It is based on the well-established and widely-used Analytical Hierarchy Process
It allows the user to incorporate both data and qualitative judgements
It can be used even in the presence of uncertainties, because it allows users to make
subjective judgments
Once the basic model for a particular decision has been set up, it is easy to perform
sensitivity studies
The model can readily be adjusted as better data become available, or if more alternatives
need to be added
1-2
-------
Appendix A contains information on the AHP and on how the inputs to the Expert Choice
software were specifically developed for the comparison of mercury retirement options.
1.3 Defining the Boundaries of the Problem
This section describes the overall mercury use and disposition cycle, and then summarizes what
was done to limit the scope to manageable proportions for the purposes of the present work.
1.3.1 Mercury Use and Disposition Cycle
Figure 1-1 is a simplified summary of the total mercury use and disposal cycle.
Industrial Applications
There are numerous industrial uses of mercury. These include: a) flowing mercury electrodes in
the chlor-alkali industry (still the largest worldwide use of mercury); b) thermometers; c)
fluorescent lights and fixtures; d) switching devices and relays; e) environmental manometers;
and f) etc. Many of these uses are being phased out, so there is a growing surplus of mercury.
Sources of Elemental Mercury for Industrial Applications
In principal, stockpiled mercury is a source for use in industrial applications, although because
many uses of mercury are being phased out, stockpiles are in practice growing rather than
shrinking. Fresh mercury can be obtained from mining, although there is no longer mining of
mercury in the USA or Canada. Some mercury is obtained by recycling techniques such as
retorting. Other mercury may be imported. Finally, mercury may be recovered from waste
streams and/or from contaminated media.
Surplus Elemental Mercury
As noted above, mercury is being phased out of many industrial applications so that, increasingly,
there is mercury that is surplus to requirements. The principal focus of the present work is to
consider options for disposal of this surplus.
Storage of Elemental Mercury
Currently, considerable amounts of surplus elemental mercury are stored. For example, in the
USA the Defense Logistics Agency has nearly 5,000 MT stored in warehouses. One option is to
continue to store it, in which case there are a number of possibilities: three representative ones are
shown on Figure 1-1.
Store it in aboveground, RCRA-permitted facilities, such as warehouses.
Store it in a RCRA-permitted hardened structure.
Store it underground in a mined cavity.
Treatment of Elemental Mercury
There exist a number of processes for the chemical treatment of mercury, the purpose being to
produce mercury in a form that is suitable for long-term, unsupervised disposition. Figure 1-1
lists four of these, the DeHg Amalgamation Process, the Sulfur Polymer
1-3
-------
Sources of Mercury
Elemental
Hg Stockpile
Elemental
Hg Mining
Elemental
Hg Recycled
Elemental
Hg Imports
Elemental
Hg - Recovered
From Waste Streams
Elemental
Hg - Recovered from
Contaminated Media
Industrial
Applications
Storage-/
v
/
Treatment - Hg - Contaminated
Media and Wastes
DeHg Amalgamation
SPSS Process
Permafix Sulfide Process
Selenide Process
etc.
Storage and
Disposal Options
///7
Aboy^^ground/RCRA
P^rmitted^cility/
Portion of cycle selected to limit scope to manageable proportions
Figure 1-1 Simplified Schematic of the Mercury use and Disposal Cycle
-------
Stabilization/Solidification Process, the Permafix Process and the mercury selenide process. The
fact that these processes are mentioned here does not mean that they are favored: they should be
regarded as representative of various processes such as forming a metal amalgam, producing a
sulfide, or producing a selenide.
Treatment of Waste Streams and Contaminated Media
Waste streams and contaminated media can be directly treated (bypassing the mercury recovery
step) to produce wastes that are suitable for disposition. Some processes that can treat elemental
mercury are also able to treat wastes and contaminated media. It was decided early on that, to
limit the scope of the present study to manageable proportions, technologies examined would be
limited to those that can potentially treat all of elemental mercury, waste streams, and
contaminated media.
Disposition of Treated Mercury
Figure 1-1 displays four representative options for disposing of treated mercury. One is by
sending the waste to an independently operated, RCRA-permitted landfill. Another would be
disposition to a customized, RCRA-permitted monofill. Third, there is disposal in an earth-
mounded concrete bunker. Finally, there is an option that overlaps with the storage of elemental
mercury, namely disposal in a mined cavity.
1.3.2 Limitation of Scope
It would be an enormous task to consider all of the treatment and disposal options that are
implicit in Figure 1-1. The resources available for the present work necessitated a limitation of
the scope to manageable proportions. Brainstorming among the project team led to the following
decisions:
Industry-specific technologies are excluded on the grounds that they can only manage a
small fraction of the total mercury problem and in any case should be regarded as an
integral part of that specific industry's waste management practices
The study focuses on options for retirement of surplus bulk elemental mercury on the
grounds that: a) this alone is a large enough project to consume the resources that are
available for the present work; b) that it anyway addresses a large fraction of the
problem; and c) that it will provide an adequate demonstration of the decision-making
technique that can readily be expanded in the future. Thus, for example, the treatment of
wastewater streams is excluded.
The chemical treatment options are limited in number and are chosen to be representative
of major classes of treatment options, such as metal amalgams, sulfides, or selenides.
The choice is to some extent be driven by available information. If the decision tool
favors any one class of options, then in principal it will be possible later to focus on
individual technologies within that class and perform a further decision analysis to
choose between individual technologies.
Only technologies that can in principal treat contaminated media as well as elemental
mercury are considered. This compensates to some extent for the decision to focus on
elemental mercury.
Retorting is excluded as merely being a well-established prior step for producing
elemental mercury, some of which may end up in the pool of surplus mercury
Deep-sea disposal is excluded because obtaining the necessary modifications to
international laws and treaties is regarded as too onerous a task
1-5
-------
Storage in pipelines is excluded because the project team could not find information
about it.
As a result of the above-described brainstorming, four treatment technologies were chosen:
DeHgฎ amalgamation
SPSS process
Permafix sulfide process
Selenide process
In practice, three of the treatment options have very similar characteristics when compared
against the Expert Choice evaluation criteria (see Section 3.2.6 for further discussion). These are
the DeHgฎ amalgamation process, the SPSS process, and the Permafix sulfide process. They are
grouped together into one class titled Sulfide/Amalgamation (S/A). Thus, two treatment options
remain, S/A and Selenide. These were combined with the four disposal options shown on Figure
1-1: disposal in a RCRA-permitted landfill; disposal in a RCRA-permitted monofill; disposal in
an engineered belowground structure; and disposal in a mined cavity. In addition, there are the
three storage options discussed above: storage in an aboveground RCRA- permitted facility;
storage in a hardened RCRA-permitted structure; and storage in a mined cavity. Altogether,
eleven options were chosen for examination with the decision-making tool (note that SAIC's
proposal stated that only ten options would be considered because of the limited funding
available):
Storage of elemental mercury in a standard RCRA-permitted storage building
Storage of elemental mercury in a hardened RCRA-permitted storage structure
Storage of elemental mercury in a mined cavity
Stabilization/amalgamation followed by disposal in a RCRA- permitted landfill
Stabilization/amalgamation followed by disposal in a RCRA- permitted monofill
Stabilization/amalgamation followed by disposal in an earth-mounded concrete bunker
Stabilization/amalgamation followed by disposal in a mined cavity
Selenide treatment followed by disposal in a RCRA- permitted landfill
Selenide treatment followed by disposal in a RCRA- permitted monofill
Selenide treatment followed by disposal in an earth-mounded concrete bunker
Selenide treatment followed by disposal in a mined cavity
1.4 Sources of Information
In preparing this report, information was obtained from a variety of government sources and the
general literature. All of the information used is publicly available; no proprietary information or
data was used in preparing the report. All information is cited throughout the report with full
citations presented in the bibliography. While there were many data sources used for this report,
some of the principal sources of information that were consulted to obtain data for this study are
as follows:
Canadian Study: SENES Consultants (SENES, 2001) has produced a draft report for
Environment Canada on the development of retirement and long-term storage options for
mercury. SENES evaluated 67 technologies using the Kepner-Tregoe ranking technique and
reviewed a further 9 technologies but did not rank them because there was insufficient
information. This report provides comprehensive identification regarding the range of
technologies that are potentially available for mercury storage or retirement, together with a
wealth of references.
1-6
-------
Mercury Management Environmental Impact Statement: The Defense Logistics Agency (DLA)
is currently preparing a Mercury Management Environmental Impact Statement (MMEIS).
Information used in developing the EIS has been used in this report (e.g., DNSC 2002a). In
particular, DLA published the following announcement in the Commerce Business Daily (CBD)
on May 24, 2001: Commercial Sector Provision of Elemental Mercury Processing Services -
Request for Expressions of Interest, to solicit expressions of interest in providing treatment
technologies for the permanent retirement of 4,890 tons of elemental mercury from the national
stockpile. Expressions of interest were received from five companies (or teams of companies).
To the extent that this information is non-proprietary, it has been used in the present work. In
fact, these expressions of interest generally constitute the best available sources of information
and drove the choice of technologies. SAIC is currently supporting the Defense Logistics
Agency (DLA) and DNSC in preparing the Mercury Management Environmental Impact
Statement (MMEIS).
2000 Mercury Workshop: EPA has prepared the proceedings of the mercury workshop that was
held in March 2000, in Baltimore, Maryland covering the following issues:
State of the science of treatment options for mercury waste
State of the science of disposal options for mercury waste such as landfill disposal, sub-
seabed emplacement, stabilization, surface and deep geological repositories for mercury
waste storage.
A summary of the workshop is available in the proceedings (US EPA 2001). Additional
information from individual presentations held at the workshop was used throughout this report
as well.
US EPA and US DOE Activities: Both EPA and DOE have been evaluating the performance and
feasibility of mercury treatment technologies for several years. DOE has published various
Innovative Technology Summary Reports that evaluate the treatment technologies applicable to
mercury containing mixed wastes (i.e., wastes that are both hazardous and radioactive). The
reports include environmental performance testing, cost information, and other operations
information.
In addition, EPA has conducted performance testing of mercury-containing wastes processed by
various treatment technologies. Performance testing in these studies has involved both
comprehensive analytical testing and standard Toxicity Characteristics Leaching Procedure
(TCLP) tests.
1-7
-------
2.0 CHOICE OF CRITERIA AND INTENSITIES
Use of the Expert Choice computer model requires that a goal and criteria be chosen and that
intensities be assigned to each criterion. The meaning of these terms will become clear in the
following discussion. The criteria are then compared pairwise to obtain relative weightings, as
described in Appendix A Some criteria are further reduced to sub-criteria, which are pairwise
compared among themselves to obtain their relative weightings. Finally, intensities are assigned
to each criterion or sub-criterion, and those intensities are themselves compared pairwise to
obtain relative weightings. Development of the model, criteria, and intensities were performed by
SAIC based on the review of resources identified in Section 1 and their knowledge and
experience of mercury retirement, disposal, and life cycle issues.
SAIC staff primarily involved in this development included:
John DiMarzio, with experience in mercury retirement issues and decision methodologies
based on work with the Department of Defense. He is managing DLA's MMEIS project.
John Vierow, P.E., with experience in mercury life cycle issues at various EPA offices
and knowledge of EPA-sponsored treatment technology assessments;
Geoff Kaiser, Ph.D., with experience in safety, risk assessment; and mercury issues
through participation in MMEIS work.
Linda Brown and Larry Deschaine, P.E., with experience in applying Expert Choice
software to various alternative assessment problems. In addition, Larry Deschaine is
experienced in the use of a variety of decision making tools to solve environmental
problems.
2.1 The Goal
The goal is simply stated: "Select the best alternatives for mercury retirement." Having this goal
helps the project team keep focused.
2.2 First-Level Criteria
The team developed two first-level criteria, benefits and costs. Initially, equal weights were
assigned to them. Section 4.2 provides sensitivity analyses that show how weighting entirely in
favor of costs or of benefits changes the rankings of the retirement options.
2.3 Benefits
Six second-level criteria were developed under the heading of benefits. These are described
below. Some of the second-level benefits were further split into third-level criteria. Intensities
were then assigned to each of the lowest-level criteria.
2.3.1 Benefit Criterion 1 - Compliance with Current Laws and Regulations
Clearly, a technology is more desirable if it is already compliant with existing laws and
regulations. The team identified three intensities: a) already compliant; b) non-compliant with
Land Disposal restrictions ( LDRs) ; and c) atypical permit required. Item a) is self-explanatory.
Standard storage in an existing or hardened structure would rate this intensity. The case that
would require an atypical permit would be one of a type that has not been granted before, such as
storage in a mined cavity. The merely non-compliant case is one in which some work has to be
2-1
-------
done to change regulations, but there is reason to believe that the cognizant agency would be
supportive, such as for disposal in a landfill or a monofill.
2.3.2 Benefit Criterion 2 - Implementation Considerations
This criterion is directed at the storage or disposal option and contains two sub-criteria; a)
whether there is a large increase in the volume of the waste; and b) whether new construction is
necessary.
Sub-criterion 2A- Volume of Waste
The volume of waste influences the costs of disposal and possibly the necessity for new
construction. Three intensity levels were used: a) zero or minimal increase; b) increase up to ten
times, and c) increase greater than ten times. Clearly, there is zero increase for all three storage
options. From the information available to the team, it appears that all treatment technologies
generate a factor often or more increase in the volume of the waste
Sub-criterion 2B - Engineering Requirements
Three self-explanatory intensities have been chosen: a) no new construction required or at most
minor modifications; b) new construction; c) construction of a mined cavity.
2.3.3 Benefit Criterion 3 - Maturity of the Technology
This criterion attempts to assess whether it is expected to be easy to implement a technology that
will operate reliably at full scale. There are two sub-criteria, the state of maturity of the
technology, and how reliably it operates.
Sub-criterion 3A- State of Maturity of the Technology
The confidence with which a technology can be accepted clearly depends on how much
experience there has been with its operation. Three intensities were chosen: a) experience with
full-scale operation; b) pilot treatment with full-scale disposal; and c) pilot treatment with
untested disposal. Thus, the team considered that all three storage options (including the mined
cavity) have had experience with full-scale operation. All of the treatment technologies are
considered to be at the pilot plant stage, and disposal of treated mercury wastes into a bunker or a
mined cavity is considered to be untested.
Sub-criterion 3B - Expected Reliability of the Treatment Technology
Here reliability is assigned three intensities: a) no treatment; b) simple; and c) complex. Thus, the
three storage options are assigned to the no treatment intensity. The S/A options are considered
to be simple and therefore likely to be reliable. The selenium technology is somewhat more
complex and, as a general rule, the more complex the technology, the less reliable it is apt to be.
2.3.4 Benefit Criterion 4 - Risks
This criterion addresses risks and is divided into three sub-criteria: public risk; worker risk; and
terrorism/sabotage.
2-2
-------
Sub-Criterion 4A - Public Risk
This sub-criterion is intended to assess whether there are any potential catastrophic accident
scenarios that can affect the public or the environment. The team did not consider that any of the
technologies poses a high risk to the public. For storage in a standard building, there is a large
quantity of elemental mercury that would cause large consequences if released to the
environment. However, the team considered that the frequency of such an accident would be
very low, so that the overall risk is low. All of the other retirement options were assessed as
having a very low public risk, either because there are no large quantities of elemental mercury
or because the elemental mercury would be in a hardened or underground structure. Thus, two
intensities have been chosen: a) very low; and b) low.
Sub-Criterion 4B - Worker Risk
As for public risk, the team identified only two intensities, very low and low. Worker risk can
never be totally eliminated, because someone could always fall off a ladder or be subject to some
other common industrial accident. It was considered that all retirement options pose very low
risk to the workers, except for storage in a mine and the selenium technology. One would expect
that workers regularly accessing a mine would be more at risk than those accessing an
aboveground structure. The selenium technology does involve the presence of some hazardous
materials and high temperatures. Therefore, these retirement options were considered to have a
low risk, rather than a very low risk.
Sub-Criterion 4C - Susceptibility to Terrorism/Sabotage
It seems necessary to include consideration of terrorism or sabotage in the wake of the events of
September 11, 2001. The goal here is to assess how attractive a target each retirement option
would be to a terrorist or saboteur, and to assign each option to one of two intensities: a) very
low; and b) low. The goal of an international terrorist is to create maximum impact, by causing
spectacular damage to a highly prestigious target, by causing a very large number of casualties
and/or by strongly affecting the national economy or the national security. The goal of a saboteur
motivated by local grievances may be revenge or to cause local embarrassment. Pertinent
considerations here therefore whether there is potential for someone to engineer a catastrophic
accident, whether this is easy, and whether it is worth wasting a precious resource (such as a
hijacked plane) on this target rather than others where the effect might be more spectacular. The
team considered that none of the retirement options would qualify as particularly attractive to a
terrorist or saboteur. Therefore, all of the options were assigned to the very low intensity with the
exception of the aboveground storage in a standard building, where it might be somewhat less
difficult to engineer a serious accident.
2.3.5 Benefit Criterion 5 - Environmental Performance
There are several aspects of environmental performance, so the team deemed it necessary to
develop four sub-criteria: a) discharges during treatment; b) degree of performance testing; c)
stability of conditions in the long term; and d) ability to monitor conditions during storage or
disposal.
Sub-Criterion 5A - Discharges during Treatment
Issues that need to be considered under this criterion include atmospheric discharges, liquid
discharges, and solid waste streams. Appropriate intensities are a) no impact; and b) minimal.
20
-3
-------
The "no impact" intensity was introduced for the storage options, where there is no treatment
step; the "minimal" intensity was introduced for the treatment technologies. The team considered
that, while there would be some discharges during operations, there was no reason to believe that
any of the technologies would lead to discharges that would not be compliant with discharge
permits.
Sub-Criterion SB - Degree of Performance Testing
This refers to the tests that have been carried out on the treatment technologies to demonstrate
that the product of the technology meets requirements for leachability, etc. The three intensities
are: a) adequate; b) moderate and c) low. The "adequate" intensity was introduced for the storage
options. The "moderate" intensity apples to all of the S/A options, while the selenium options
remain the least tested and were assigned to the "low" intensity.
Sub-Criterion 5C - Stability of Conditions in the Long Term
This sub-criterion applies to the storage or disposal options. It is expected that the selected
technology will meet EPA standards for such criteria as leachability, and that any containers will
meet certain requirements with respect to corrosion. However, those criteria are not valid in all
environments. Therefore, it is necessary to be confident that the long-term storage or disposal
conditions can be controlled so that the disposed materials remain in their repository. The
intensities chosen here are: a) very good; b) good; c) fair; and d) poor. Thus, one would
anticipate that conditions in a carefully engineered mined cavity would be expected to remain
stable over long periods, so that the appropriate intensity would be "very good." For a monofill
or a bunker, conditions are likely to remain good. In a landfill, where many materials in addition
to the mercury waste may be disposed of, conditions may be no more than fair. Finally, storage
options are characterized as poor simply because they are not intended to be long-tern options.
Sub-Criterion 5D - Ability to Monitor
The ability to monitor is one of the key factors in ensuring good performance after storage or
disposal. The team identified four intensities; a) easy and correctable; b) easy to monitor but not
necessarily easy to correct; and c) difficult to monitor. Thus, all of the storage options are
characterized as easy and correctable because they are designed to be monitored and, if
conditions deteriorate, the storage containers can easily be moved. Disposal in a mine would be
difficult to monitor because the intention would be to dispose of the materials and seal the mine.
Other options would be easy to monitor but not necessarily easy to correct.
2.3.6 Benefit Criterion 6 - Public Perception
Clearly, any mercury retirement project will not fly if the public is strongly against it. It was
decided that there are two distinct possibilities: a) public perception is positive to neutral, in
which case there is no problem; b) public perception is negative, but a campaign that combines
elements of public relations, marketing and the distribution of information might be sufficient to
overcome it. Initially, a third intensity was considered, namely that public perception is intensely
negative, so that there is a strong likelihood that the retirement project will never be accepted.
However, the team did not identify any retirement options that could potentially attract such
strong public opposition.
These two possibilities are the intensities that were assigned to the public perception criterion.
The team then brainstormed pairwise the relative desirability of each of these intensities, as
2-4
-------
described in Appendix A. In this particular case, there is only one pair and it was decided that a
positive to neutral perception is strongly preferable to a negative perception, within a scale that
allows the team to choose between equally preferable, moderately preferably, strongly preferable,
very strongly preferable, and extremely preferable. In Expert Choice, these correspond to
multipliers on a numerical scale from 1 to 9, with strongly preferable corresponding to 5 times
more preferable. This is provided as an example of pairwise comparison of intensities. Detailed
discussion of all pairwise comparisons of intensities is provided in Appendix A.
The allocation of intensities to each of the retirement options is discussed in detail in Section 3.
As an example, in this specific case, the team decided that all options that provided for bulk
elemental mercury or treated mercury to be stored or disposed of in hardened structures or in a
mine would be regarded favorably by the public. The other options that allow for storage in a
regular warehouse or disposal into a landfill or monofill could potentially attract some negative
public attention.
2.3.7 Pairwise Comparison of the Criteria
It is necessary to pairwise compare the six second-level criteria under the overall benefit criterion.
The numerical weightings generated in this way can then be manipulated in expert choice to rank
the criteria in terms of importance, as shown in the table below.
Table 2-1 Ranking of Non-Cost Criteria after Pairwise Comparisons
Criterion
Environmental Performance
Risks
Implementation Considerations
Public Perception
Maturity of the Technology
Compliance with Current Laws and Regulations
Relative Numerical Ranking
Index from Expert Choice
0.336
0.312
0.154
0.107
0.047
0.045
This ranking emerged from the team's brainstorming of pairwise comparisons between each of
these criteria. In other words, the team brainstormed each of the 15 pairs that can be extracted
from the first column of Table 2-1 and in each case determined whether the two criteria in the
pair were equally important, or whether one was extremely, very strongly, strongly, or
moderately more important than the other. Table 2-1 then provides a "sanity check" - does it
seem reasonable? Of course, the answer is subjective, as are the pairwise comparisons
themselves. However, the team reviewed Table 2-1 carefully and decided that the ranking looks
reasonable.
2.4 Costs
Costs were divided into two components - the cost of implementation and operating costs. These
were assigned equal importance.
2.4.1 Cost Criterion 1 - Implementation Costs
Different implementation costs are associated with storage, treatment, and disposal. For storage
and disposal, implementation costs are those associated with site development, construction,
permitting, etc., which take place before any material is introduced to the unit. For treatment,
implementation costs in this report are generally limited to capital expenditures. Other costs such
2-5
-------
as for research and development are not included because they are difficult to project, or because
all of the alternatives considered have already been developed and used to some extent.
The intensities applied to this criterion are identified as either low, medium, or high. While no
hard-and-fast dollar delineations are provided with these intensities, approximate costs are as
follows: (1) low (includes the use of existing facilities or expenditures under about $5 million);
(2) medium (includes the construction of new facilities projected to require expenditures between
$5 million and $50 million), and (3) high (includes the construction of new facilities projected to
require expenditures above $50 million).
2.4.2 Cost Criterion 2 - Operating Costs
Operating costs refer to expenditures which maintain the management option. In the case of
mercury retirement, the metal is assumed to be removed from commerce on an annual basis and
require subsequent management. This is different from a case where a 'one-time' quantity of
waste requires management. In this context, operating costs associated with storage include the
costs to maintain the storage structure, staff costs, monitoring, etc. Operating costs associated
with treatment include the cost to treat the waste; in commercial waste management these are
typically cited on a 'per ton' basis. Finally, operating costs associated with disposal include
similar components as with storage.
One additional costs component is assessed for storage options that is not assessed for treatment
and disposal options. Once stored, the material is assumed to require some type of further
management (i.e., it will not be stored forever). Consequently, the costs for this future
management alternative are added into the other existing operating cost components. While the
ultimate alternative, and the associated costs, are unknown, the costs are expected to be similar to
those reflected in the alternatives evaluated here.
The intensities applied to this criterion are also qualitatively identified as low, medium, or high.
In general, operating costs for disposal are assumed to be lowest for landfills and higher for more
complex disposal (where additional operating mechanisms may be required). Operating costs for
storage are assumed to be highest due to the additional, end-of-life costs identified above.
Therefore, these intensities were applied to operating costs more as a rank order than as
representing specific dollar amounts.
2.5 Summary of Criteria and Intensities
Table 2-2 summarizes the criteria and intensities in a convenient form.
2-6
-------
Table 2-2 Criteria Used for Evaluating Options
Criterion
Benefit - Public
perception
Benefit - Compliance
with current laws and
regulations
Benefit - Environmental
performance: discharges
during treatment
Benefit - Environmental
performance: degree of
performance testing
Benefit - Environmental
performance: stability of
conditions in the long
term
Benefit - Environmental
performance: ability to
monitor
Benefit - Risks: public
risk
Benefits - Risks: worker
risk
Benefit - Risks:
susceptibility to
terrorism/sabotage
Benefit - Maturity of the
technology: state of
maturity of the
technology
Benefit - Maturity of the
technology: expected
reliability of operation
Benefit - Implementation
considerations: volume of
waste
Benefit - Implementation
considerations:
engineering requirements
Costs of Implementation
Operating Costs
Intent of Criterion
To assess the degree to which the
public might be for or against the
technology.
To assess whether new regulations
and/or laws will be required.
To assess the acceptability of
atmospheric or liquid discharges, or
solid waste streams during treatment.
To assess to what extent the product
of the treatment technology meets the
requirements for storage or disposal
(e.g. teachability)
To assess to what extent conditions in
the long term storage or disposal
repository can be controlled so that the
results of performance tests remain
valid (e.g. teachability)
To assess whether conditions in the
long term disposal or storage
repository can be easily monitored
To assess whether the retirement
option poses a risk to the public as a
result of accidents.
To assess whether a retirement option
poses a risk to workers.
To assess the attractiveness of a
retirement option to a terrorist or
saboteur.
To assess how much experience there
has been with the retirement option.
To assess whether the treatment
technology is likely to operate reliably
and deliver reliable quality in the
product.
To assess whether the technology
causes large increases in the volume
of waste for storage or disposal.
To assess whether construction of the
storage or disposal option is required.
To assess the cost of developing the
retirement option to the point at which
it is ready to accept mercury or
mercury waste
To assess costs after the retirement
option begins operation
How Option is Evaluated Against
Criterion
a) public reaction positive to
neutral; or b) public reaction
negative.
a) already compliant; b) non-
compliant with LDRs; or c) atypical
permit required.
a) no impact; or b) minimal.
a) adequate; b) moderate; or c) low.
a) very good; b) good; c) fair; or d)
poor.
a) easy and correctable; b) easy to
monitor but not necessarily easy to
correct; c) difficult to monitor.
a) very low; or b) low.
a) very low; or b) low.
a) very low; or b) low.
a) experience with full-scale
operation; b) pilot treatment with
experience of full-scale disposal; or
c) pilot treatment with untested
disposal.
a) no treatment; b) simple; or c)
complex.
a) zero or minimal increase in
volume; b) an increase in volume
by less than a factor often; or c) an
increase in volume by greater than a
factor of 10.
a) no new construction needed or
minor modifications; b) new above-
ground construction needed; c)
construction of a mined cavity
needed.
a) low; b) medium; c) high.
a) low; b) medium; c) high.
2-7
-------
3.0 DISCUSSION AND EVALUATION OF OPTIONS
3.1 Storage Information
Storage allows for certain flexibility in management. As depicted in the options below, storage
has the following characteristics:
Temporary management. While the materials being stored can certainly be left in one
place for many years, storage should offer a means of moving the mercury to another
location.
Ease of monitoring. There should be a means for the materials to be monitored for
releases, such as air emissions or leaks, which could affect public health and worker
safety. In a related sense, there should also be a mechanism to stop or remediate any
releases, if found.
Based on these criteria, three storage options have been identified for evaluation: storage in a
standard RCRA-permitted storage building, storage in a hardened RCRA-permitted storage
building, and storage in an underground mine.
3.1.1 Storage in a Standard RCRA-Permitted Storage Building
Hazardous waste or hazardous materials are commonly stored throughout the U.S. using a variety
of methods. DNSC uses warehouses for the storage of mercury. At one site, the mercury is
contained in 76 Ib steel flasks within wooden pallets. At three of the sites, the steel flasks are
overpacked within steel drums on wooden pallets. The warehouses are covered (as a building)
and have a sealed concrete floor. Access restrictions are provided by fencing and 24-hour
security personnel. (DNSC 2002a)
The DNSC sites are storing mercury that is considered an industrial commodity and therefore are
not RCRA-permitted for hazardous waste storage. RCRA-permitted hazardous waste storage is
required any time hazardous waste is stored for more than three months and entails detailed
requirements, higher costs, greater regulatory oversight, etc. While certain mercury-containing
wastes (e.g., dental amalgam) are hazardous wastes, there is uncertainty as to whether elemental
mercury would be similarly designated by the regulatory authorities, if stored at other sites. One
example of elemental mercury storage is the national stockpile. DLA considers its mercury to be
a commodity rather than a RCRA hazardous waste. (Lynch 2002) Another example is elemental
mercury from the now closed HoltraChem (Maine) site in which 80 tons of mercury stored at the
facility is considered a hazardous waste by the State. (Young 2001) Therefore, the regulatory
status is expected to depend on the source of mercury, State laws and regulations, and other
factors.
For this evaluated alternative, it is conservatively assumed that elemental mercury storage would
require a hazardous waste storage permit. Information from several sites in Utah was obtained to
identify typical requirements. Security measures at facilities with RCRA-permitted storage are
similar to those at the DNSC sites. DOT-acceptable containers are required, with visual
inspection for integrity every year. Enclosed buildings with concrete floors, with sumps for spill
control and ventilation systems, are used for storage. (Utah 2002)
Costs for the storage of 1,500 tons of elemental mercury at a single hypothetical commercial site
have been estimated by SAIC as $3.8 million of initial costs and $200,000 of annual costs, if a
new structure is required. (SAIC 2002) Alternatively existing sites could be used. The DNSC
3-1
-------
has also estimated the present annual costs associated with the storage of the 4,890 ton stockpile
at its four sites at $750,000 per year (DNSC 2002b). In descending order of magnitude, cost
components included: (1) rent, (2) labor, (3) security, (4) other expenses of utilities,
groundskeeping, etc. These estimates have uncertainty because the cost components may not
necessarily be applicable to a commercial site, and because they are preliminary and not based on
in-depth accounting.
An additional source of cost estimates for storage is from options being considered for 82 tons of
elemental mercury located at the now-closed HoltraChem chemical facility in Maine. The long-
term storage costs for this quantity at an existing commercial facility were estimated to be
$120,000 to $180,000 per year. The capital cost of construction of a storage structure on facility
property was estimated to be $100,000 to $750,000 with no operating costs provided. A small
sample of area residents favored the idea of sending the material offsite rather than storing it at
the plant, even though the costs were identified as higher. (Gagnon 2001)
3.1.2 Storage in a Hardened RCRA-Permitted Storage Building
Concrete bunkers have been constructed and used for the storage of radioactive or nuclear
materials. They have not been used in the U.S. for the storage of hazardous materials or
hazardous wastes. Nevertheless, a similarly-designed structure can be used for the storage of
mercury. One such structure was constructed in Russia in 1999. The storage bunker has double
concrete walls with sand between the two concrete layers. It is 450 feet long and 240 feet wide.
It is used for the storage of nuclear material from dismantled weapons. (Rizley 2000) More
specific information regarding the construction is not available.
Another example of this design is associated with the storage of spent fuel at nuclear power
plants. Approximately twelve U.S. nuclear power plants include areas for dry storage of nuclear
waste. These areas are designed to temporarily hold the material until it can be moved and
transported to a permanent disposal site, once a site is selected and constructed. The radioactive
material is placed inside large containers comprised of steel, concrete, and/or lead with total
thickness of 18 inches or more. The containers are stored outside on a concrete pad or are stored
within a concrete vault. Costs for construction and storage of the containers were identified as an
initial cost of $10 to $20 million, plus $500,000 to $1,000,000 per container. For this analysis it
is assumed that a container can hold a year's supply of spent fuel. In 1998, 6,200 spent
assemblies were generated from 104 generating units, or about 60 assemblies per unit on average.
(DOE 2001) A single container can hold between 7 and 56 fuel rods, each 12-feet long, in an
inert gas. (NEI 2001) However, these costs are in all likelihood very much higher than would be
the case for similar storage of mercury because there would not be the need to design against
radioactive exposures.
Because these design and storage costs are reflective of radioactive waste storage, both the
upfront and continuing costs are expected to overestimate the costs of elemental mercury because
the measures designed to protect against radioactivity would be unnecessary to protect against the
migration of mercury.
3.1.3 Storage in a Mined Cavity
For purposes of this analysis, storage in a mined cavity is assumed to differ from disposal in a
mined cavity. Like other storage options, the mercury is assumed to be stored in movable
containers which can be monitored, moved, and if necessary repackaged over the lifetime of the
mine. This differs from disposal, where it is expected to be difficult or impossible to move the
3-2
-------
mercury once placed in the mine. Further, for storage, it is assumed that an existing underground
cavity can be used for holding the mercury. While some additional construction modifications
may be needed, this eliminates high additional costs of drilling, detailed site characterization, etc.
The costs and complexities associated with mine cavity storage are likely to vary greatly
depending on the suitability of currently available underground cavities. Underground cavities
for hard rock minerals, coal, and other commodities exist in the U.S. It is assumed that such
facilities can be used with minimal upgrades.
No examples of temporary storage in a mined cavity were identified for mercury or any other
waste types. In contrast, permanent deep underground disposal has been suggested and used for
various wastes. Nevertheless, the use of a mined cavity for the temporary storage of mercury will
be retained as an option in this analysis.
3.1.4 Storage Options Not Considered
Storage in an Earth-Mounded Concrete Bunker
This technology is used worldwide as a method of disposing low-level and mid-level nuclear
waste. As depicted in the examples identified during this review, this is a permanent disposal
technology rather than a temporary or long-term storage solution (See Section 3.3.4). Therefore,
this alternative is eliminated as a storage option and will be retained as a disposal option.
3.1.5 Summary of Storage Options versus Evaluation Criteria
Table 3-1 summarizes the available information regarding the above three options for storage,
based on the available information. These results will be subsequently used in the evaluation
process. Table 3-1 uses the specific information above for individual alternatives in conjunction
with other information that is available for storage alternatives in general. Specifically, the
information summarized in Table 3-1 is based on the following for each evaluated criterion:
Compliance with current laws and regulations. The aboveground storage of elemental mercury
can be accomplished in the current regulatory framework, even if it is assumed that the storage of
untreated elemental mercury will require hazardous waste permitting. This is because land
disposal is not involved. In the case of mine storage, it is unclear whether this method would
require any deviations from the procedures applicable to above-ground storage; although the
mercury is not placed or disposed on the land, there is very little precedent to assess if land
disposal restrictions requirements for hazardous wastes would be applicable. In a conservative
case, it is assumed that there will be some additional difficulties with mine storage that would not
be the case with above ground storage which would require some modifications to current
regulations to allow such storage: that is, an atypical permit would be required.
Implementation Considerations. All storage options have a similar attribute in that there is no
volume increase with the mercury (because there is no treatment). Additionally, it is assumed
that aboveground storage could occur at an existing hazardous waste storage facility (because it is
relatively common), while the other two options would require construction of new structures
and/or auxiliary facilities.
Maturity of the technology. Aboveground storage is a very common and mature procedure for
many hazardous materials, including elemental mercury. While the other options are not as
3-3
-------
common for storage, it is assumed that similar features of aboveground storage are applicable to
all.
Table 3-1 Evaluation for Three Storage Options
Criteria
Compliance with current laws
and regulations
Implementation
considerations: volume of
waste
Implementation
considerations: engineering
requirements
Maturity of the technology:
state of maturity of the
technology
Maturity of the technology:
expected reliability of
treatment
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental performance:
discharges during treatment
Environmental performance:
degree of performance testing
Environmental performance:
stability of conditions in the
long term
Environmental performance:
ability to monitor
Public perception
Costs: implementation
Costs: operating
Standard RCRA-
Permitted Storage
Building
Already compliant
Zero increase in
volume
Existing facilities can
be used
Experience with full-
scale operation
No treatment
Very low
Low (while unlikely,
large quantities of
mercury are present at
one time and could be
released)
Low (while unlikely,
large quantities of
mercury are present at
one time and could be
released)
No impact (no
treatment)
Adequate
Poor
Easy (monitoring)
Somewhat negative
Low (about $4 million,
or zero if existing
facilities are used)
High
Hardened RCRA-
Permitted Storage
Structure
Already compliant
Zero increase in
volume
Construction of new
facilities is required
Experience with full-
scale operation
(extrapolated from the
warehouse case)
No treatment
Very low
Very low (although
large quantities of
mercury are present at
one time, the mercury
is less easily accessible
than the warehouse
case)
Very low (although
large quantities of
mercury are present at
one time, the mercury
is less easily accessible
than the warehouse
case)
No impact (no
treatment)
Adequate (extrapolated
from the warehouse
case)
Poor
Easy (monitoring)
Positive to neutral
(probably)
Medium (up to $10 to
$20 million)
High
Underground Mine
Cavity
Atypical permit
required.
Zero increase in
volume
Construction of new
facilities is required
Experience with full-
scale operation
(extrapolated from the
warehouse case)
No treatment
Low
Very low (although
large quantities of
mercury are present at
one time, the mercury
is less easily accessible
than the warehouse
case)
Very low (although
large quantities of
mercury are present at
one time, the mercury
is less easily accessible
than the warehouse
case)
No impact (no
treatment)
Adequate (extrapolated
from the warehouse
case)
Poor
Easy (monitoring)
Positive to neutral
Medium (expected to
be similar to hardened
storage case)
High
3-4
-------
Worker risks. Potential risks to workers from routine handling or accidental release are expected
to be very low for the aboveground options. Potential risks for mine storage may be slightly
higher due to the increased hazards posed from belowground work (i.e., unrelated to mercury).
Public Risks and Risk Susceptibility to Terrorism or Sabotage. The most significant potential
risks are due to the presence of large quantities of mercury at a site. In above ground storage, a
fire or explosion, while extremely unlikely, could result in a widespread distribution of the toxic
element. A principal advantage of the other options is the ability to prevent, control, or contain
such an unlikely occurrence.
Environmental performance. The results of the DNSC's experience with aboveground storage of
elemental mercury indicate that mercury can be effectively monitored and safely managed with
little or no release to the environment. These results have been extrapolated to the other storage
options. One drawback of storage that is reflected in Table 3-1 is that while storage is expected
to be effective for the short term (e.g., 10 to 100 years) with active monitoring and maintenance,
its performance for the long term (hundreds or thousands of years) if simply left in place is
unknown. In this case it is assumed to be poor because elemental mercury may be released from
the containers if left unattended.
Public perception. Public perception to any alternative is likely different at the local level (e.g.,
city or county) than at the national level. In almost any action involving mercury, a negative
local perception is likely in the same way that most citizens would oppose a landfill close to their
homes. At the national level, a different perception may result. Reaction can be neutral or even
positive for an action identified as a suitable and defensible alternative for mercury management.
This is assumed to be the case for the hardened storage and mine storage, which are designed to
mitigate some of the potential risks posed by a more simple aboveground storage. Of course,
forecasting the potential public perception of any alternative is uncertain.
Costs of Implementation. As identified above, the cost of construction of a standard storage unit
is estimated to be up to $4 million. Alternatively, an existing commercial site could be used
which would require no additional costs. Such is the case for the DLA mercury stockpile in
which existing warehouses or munition bunkers could be used. (DLA 2002) Standard storage is
expected to have the lowest initial cost for any of the storage alternatives. In contrast, the
estimated initial cost of $10 to $20 million for concrete-hardened storage, while expected to be
overstated since it is based on radioactive containment, is nonetheless higher than for standard
storage. There are no cost estimates for mine storage but it is assumed that costs are similar to
those estimated for hardened storage.
Operating Costs. As identified above, the costs for operating the 4,890 ton mercury stockpile by
DLA are estimated to be about $750,000 per year, and costs for storing 80 tons of mercury at a
commercial facility are estimated to be $120,000 to $180,000 per year. Costs for other storage
options are assumed to be similar. A key additional component considered in this analysis is
eventual disposal costs. While it is possible to continue the practice of storage for the short term,
sooner or later treatment and disposal will be required and additional costs for such management
will result. Therefore, operating costs include both the costs of maintaining storage integrity and
the additional costs of eventual implementation of a long-term retirement option.
3.2 Treatment Information
Treatment reduces the mobility of mercury in the environment to the air (i.e., from volatilization)
and groundwater (i.e., from leaching). Mercury is typically treated through chemical and/or
3-5
-------
physical methods through the addition of additives to convert the mercury into a less mobile
form, such as mercury compounds or amalgams. In addition, physical methods such as
stabilization reduce the exposure of mercury to environmental media such as leachant within a
landfill.
Four treatment options have been identified for evaluation. These are: a) ADA / Permafix
treatment; b) BNL sulfur polymer solidification; c) IT/NFS DeHgฎ process; and d) the selenide
process. More detailed information is presented below to the extent information is publicly
available.
The environmental performance of the treatment technologies has been evaluated by EPA and
DOE, in addition to data collected by the vendors themselves. In the past several years EPA and
DOE have evaluated various treatment technologies for wastes containing a wide range of
mercury, from 'low mercury' solid wastes of less than 260 mg/kg to elemental mercury. The
tests and programs conducted by EPA and DOE are summarized in Table 3-2. In some cases, the
vendor names were not provided in the reports. To retain consistency, the vendor names in such
cases are not included here. More detailed results from the studies are provided in Appendix C.
Mercury mobility is influenced by many factors, and only some of the factors have been
evaluated in the tests summarized in Table 3-2. Factors affecting the mobility of mercury, or any
other metal, include the following:
Liquid/solid ratio of test or in disposal environment.
Redox potential (which influences whether the conditions are more likely to oxidize or to
reduce mercury)
Co-contaminants such as other ionic species.
pH
Particle size
Exposure duration.
Table 3-2 Summary of Available Environmental Performance Data
Reference
Sanchez (2001). Evaluated
mercury-contaminated soil, ~
4,500 ppm
DOE (1999a and 1999b).
Elemental mercury
DOE (1999c, 1999d, 1999e).
Mercury -contaminated waste,
<260 ppm)
USEPA (2002a). Evaluated
mercury waste, ~ 5,000 ppm
USEPA (2002b). Evaluated
elemental mercury
Participating Vendors/ Wastes
Evaluated
ATG
BNL
Unnamed vendor
NFS
ADA
NFS
GTS Duratek
ATG
Four vendors
Three vendors. In addition, there
was limited testing of simulated
mercury selenide
Major Tests Conducted
Evaluate mercury leaching with
respect to pH and liquid-to-solid
ratio
TCLP
TCLP
Evaluate mercury leaching with
respect to pH
Evaluate mercury leaching with
respect to pH
Cost information is provided in this section of the report for the treatment of 1,500 tons of
elemental mercury. This is done to provide a constant basis of comparison between the different
data. The estimate of 1,500 tons was selected as representative of approximately a ten-year
supply at current use rates. Based on estimates from Bethlehem Apparatus Company (2000), a
company specializing in recycling mercury and mercury bearing wastes, the United States
3-6
-------
produces between 2,000 to 4,000 76-lb. flasks, or 152,000 to 304,000 pounds, of mercury per
year from recovery operations. Therefore, this is an upper bound on the rate of increase of
surplus mercury.
3.2.1 ADA / Permafix Treatment
Perma-Fix Environmental Services and ADA Technologies Inc. have submitted an expression of
interest for treatment of the U.S. DoD mercury stockpile. Perma-Fix operates waste treatment
facilities for a variety of materials, while ADA Technologies have developed technology specific
to mercury treatment. ADA's technology converts mercury to mercuric sulfide, and is capable of
treating elemental mercury or mercury in waste material.
Raw materials for the ADA process include a sulfur-based reagent. The treated material can be a
granular material or a monolithic material. Permafix proposed to treat 880 flasks of mercury per
week (66,800 Ib) and generate 150 55-gallon drums. This represents a volume increase of 14
times. The vendor estimates it would take three years to process the 4,890 tons of mercury
stockpile.
The ADA amalgamation process, a batch process, consists of combining liquid mercury with a
proprietary sulfur mixture in a pug mill; in one application a 60-liter capacity pug mill was used
for treatment of an elemental mercury waste. Treatment of the liquid mercury was conducted by
adding powdered sulfur to the pug mill, while a preweighed amount of mercury was poured into
the mill. As the mill continued to mix and the reaction took place, additional chemicals were
added. While the processing of mercury in the pug mill was performed without the addition of
heat, the reaction of mercury with sulfur is exothermic at room temperature, and the mixture
increases in temperature during processing. Reaction products include water vapor. Off-gas is
passed through a HEPA filter and then passed through a sulfur-impregnated carbon filter.
Mercury vapor concentrations above the pug mill were below the Threshold Limit Value (TLV)
of 50 mg/m3. All operators wore respirators fitted with cartridges designed to remove mercury
vapor. (DOE 1999b).
Costs for this treatment process were estimated by DOE as $300 per kg, exclusive of disposal
costs, when treating more than 1,500 kg of elemental mercury. (DOE 1999a) It is not known if
such costs are representative of treatment on a much larger scale. For example, using this unit
cost estimate, costs for the treatment of 1,500 tons of elemental mercury would equate to more
than $400 million for treatment alone.
3.2.2 BNL Sulfur Polymer Solidification
The sulfur polymer solidification/ stabilization process (SPSS) is a batch process. In this process,
elemental mercury is combined with an excess of powdered sulfur polymer cement and sulfide
additives and heated to 40ฐC to 70ฐC for several hours. This converts mercury to the mercuric
sulfide form. Additional sulfur polymer cement is added and heated to 135ฐC. The molten
mixture is poured into a mold to cool and solidify. (Fuhrmann 2002) The system is currently
operated at pilot scale, using a one cubic foot conical mixer. The process has been demonstrated
for both elemental mercury and for mercury-containing soil. (Kalb, 2001) The vendor has
projected it can scale up by a factor of 350 for treatment of the DLA stockpile of 4,890 tons and
complete treatment in 60 days. Currently, BNL is attempting to license the technology for
different applications to be installed at customer sites. BNL estimates that commercial scale
implementation would take one year or less. (BNL Response, 2001)
3-7
-------
Volume and weight changes for the treatment of elemental mercury are estimated from several
case studies. In one test, a total of 140 Ib was treated using the process. (Kalb, 2001) Each batch
of mercury, about 25 pounds, generated about 4 gallons of molten product, which solidified in a
container. This represents a volume increase from about 0.22 gallons (assuming pure elemental
mercury) to 4 gallons, or 18 times. In another study, a volume increase of 15 times was
identified. (USEPA, 2002b) The treated waste had a waste loading of 33 percent (i.e., 100
pounds of treated waste contained 33 pounds mercury). Mass balance measurements show an
estimated 0.3 percent mercury is released from the process vessel and captured in the air control
system.
Additives used include the sulfur polymer cement and sulfide additives. Sulfur polymer cement
consists of 95 weight percent elemental sulfur and 5 percent organic binders. Sulfide additives
which have been examined include sodium sulfide monohydrate and triisobutyl phosphine
sulfide.
During operation, 1 to 2 personnel are expected to operate the equipment, exclusive of additional
workers for waste handling, etc. Typical protective equipment is expected to be required (e.g.,
gloves and lab coat).
Costs for treatment of the 4,890 metric ton mercury stockpile were estimated by BNL to be
approximately $2.4 million for materials, additives, and process unit capital. This represents
$250,000 in capital costs for a single 350-cubic foot treatment vessel, $2 million for additives,
and $150,000 for other materials. Costs for other components (e.g., treatment facility, disposal)
were not included. Based on this information, the costs for the treatment of 1,500 tons of
elemental mercury would equate to less than $1 million for treatment alone.
3.2.3 IT/NFS DeHgฎ Process
This is a batch metal amalgamation process conducted at ambient temperature. The final product
is monolithic. The first step is an amalgamation process using proprietary powdered reagents. In
a second step, the waste is stabilized using liquid reagents. The process generates hydrogen gas
as a byproduct, which is vented following control equipment. The quantity of hydrogen gas
produced was not identified, and the chemical reactions are proprietary. However, conservatively
assuming that hydrogen is generated from mercury treatment at a stoichiometric ratio of 4 to 1
(hydrogen to mercury), the batch treatment of 75 kg of mercury (the quantity to be used at
production scale) would generate about 600 standard cubic feet of hydrogen gas. (IT/NFS 2001)
This is not expected to represent a significant additional hazard to personnel or the process in
general.
The process has been used to treat 50 cubic meters of mixed radioactive hazardous waste
containing mercury at the NFS site in Erwin TN. For larger scale treatment, construction of a
new additional site would be required. (IT/NFS 2001)
Releases of mercury from the process are estimated at 0.05 percent. Ambient air measurements
have been taken during processing and have been less than regulatory and nongovernmental
standards. (IT/NFS 2001)
The processing of mercury-containing wastes can generate a waste liquid. Following
stabilization, the material is a presscake. Any filtrate from this processing is recycled to the
reactor for further treatment, or is discharged. (DOE 1999a) For elemental mercury treatment
using small quantities of mercury (about 10 kg of treated material per batch), the treated product
3-8
-------
is reported to consist of moist amalgam in polyethylene bottles with no free liquid. No discussion
is available concerning whether the treatment of elemental mercury by itself would be expected to
generate a wastewater stream.
As with the ADA process discussed above, costs for the DeHgฎ treatment process were
estimated by DOE at $300 per kg, exclusive of disposal costs, when treating more than 1,500 kg
of elemental mercury. (DOE 1999a) It is unknown if such costs are representative of treatment
on a much larger scale. For example, using this unit cost estimate, costs for the treatment of
1,500 tons of elemental mercury would equate to more than $400 million for treatment alone.
3.2.4 Selenide Process
Bjasta Atervinning, a Swedish firm, uses a full-scale commercial process for the treatment of
mercury in fluorescent lights. Unlike the previously described treatment processes, this is a
continuous process. In this process, the lamps are crushed and melted in a 1400ฐC electric
furnace. The molten glass is tapped and selenium is added to the hot gas to form mercury
selenide in a vapor phase reaction. The mercury selenide, a less mobile compound than elemental
mercury, is condensed by refrigeration. (Bjasta 2002)
The quantity of mercury demonstrated to have been treated by this process is relatively small.
The process has been used for fluorescent lamps. In the U.S., an estimated 17 tons of mercury in
lamps was disposed of in 1999 (NEMA 2000), which is a good indication of the upper bound of
mercury that can be managed by this treatment method. The process has also been patented for
treatment of batteries, which in Sweden (the company's base) are expected to contain no more
than about 3 tons of mercury.5 In treating wastes such as batteries, a rotary kiln is used to provide
agitation of the material; selenium is added to the furnace under inert conditions and other
components of the process are similar to those used for lamps. In a lab scale test using a feed rate
of 100 grams of batteries per hour, 0.9 percent of the mercury remained in the solid residue and 3
percent in the vapor phase was not precipitated as mercury selenide. This unreacted quantity was
captured in a downstream filter, which would potentially require further processing for adequate
treatment. (Lindgren 1996)
The process has not been applied to elemental mercury, although lamps do contain elemental
mercury. The quantities of mercury in batteries and lamps, as identified above, are much less
than the quantities of elemental mercury available in commerce. This is another limitation to
applying the process to relatively large quantities of elemental mercury.
The company claims that less than 20 grams of mercury escapes for every million kg of lamps
processed. (Bjasta 2002) This corresponds to a release rate of 0.03 percent.6 Reagent-grade
mercury selenide (i.e., not produced from a treatment step) was part of the EPA elemental
mercury treatment study that evaluated the mobility of mercury subject to a treatment method that
generates such a product. EPA data are available for the constant leaching test at two pHs, 7 and
10, and two simulated environmental conditions, with and without chloride in the leaching
solution. (USEPA 2002b)
Lindgren (1996) identifies that the mercury composition of batteries can vary widely, from less than one percent to
35 percent. About 11 tons of batteries are generated in Sweden each year as of the mid-1990's (Lindgren 1996).
Using the annual battery generation rate and the mercury composition data gives an upper bound estimate of about
three to four tons.
Data from Phillips Lighting (Phillips 2002) indicates that about 26,000 four-foot lamps weigh 5,000 kg. The lighting
and electrical trade association, NEMA, estimates that the average mercury composition of a four-foot lamp is 12 mg
in 1999, the latest year available (NEMA 2000). Thus, one million kg of lamps contain about 60 kg of mercury.
3-9
-------
No cost estimates are available for this process.
3.2.5 Treatment Technologies Not Considered
ATG
The ATG process has been demonstrated for mercury-containing wastes (DOE, 1999c; USEPA,
2002a), but not for elemental mercury itself. ATG demonstrated its process at full-scale for the
treatment of a process waste stream with a total mercury content less than 260 mg/kg. The full-
scale demonstration was a batch set-up capable of treating 165-kg of waste at one time, although
it was demonstrated at 33-kg batches. The process used raw materials that included a
dithiocarbamate formulation, phosphate and polymeric reagents, magnesium oxide, calcium
carbonate, sodium metasulfite, sodium hydrosulfide, and activated carbon. The volume of the
treated waste was reported to be 16 percent greater than that of the untreated waste. The treated
waste was in the form of a damp paste. Additional wastes generated include PPE, containers, etc.
Costs of treatment were estimated as $1.73/kg waste. This includes both capital costs ($30,000)
and operating costs ($95/hr). (DOE 1999c)
GTS/Duratek
The GTS/Duratek process has been demonstrated for mercury-containing wastes (DOE, 1999d),
but not for elemental mercury itself. In this process, water and cement are added to sludge, and
then blended with sodium metasilicate, a stabilization agent. The process was demonstrated at
pilot scale in treating four 55-gallon drums containing approximately 570 kg of waste sludge.
The materials are mixed in the 5 5-gallon drum using a vertical mixer, and then allowed to harden
(cure).
Phosphate Ceramics
This is a stabilization technique, which has been demonstrated at bench scale for mercury-
containing waste. It is an ambient temperature process that combines chemical stabilization of
mercury within a ceramic encapsulation. Raw materials include magnesium oxide and potassium
phosphate, as well as a sulfur compound such as sodium sulfide or potassium sulfide. The treated
waste forms a dense ceramic. The process has been demonstrated on wastes containing up to 0.5
percent mercury. (Wagh, 2000)
Mercury Recovery
Several U.S. facilities currently recover elemental mercury from mercury-containing wastes for
subsequent reuse. While this is a treatment method, it does not, by itself, serve to reduce the
mobility of elemental mercury. Information on mercury recovery facilities, nevertheless, is
useful for projecting the characteristics of other treatment methods, which are not as widespread.
Bethlehem Apparatus, a mercury recovery facility, has operated commercial scale mercury
recovery facilities in the Bethlehem Pennsylvania area for many years. The facilities are also
permitted for mercury waste storage with additional permitting for limited treatment prior to
recovery. Presently, they principally conduct recovery from mercury wastes and while changes
to existing equipment would be necessary for conducting more extensive treatment operations,
many capital expenditures (e.g., containment, ventilation) are already in place. The facility uses
30 workers in the production area for various activities. (Bethlehem 2001)
3-10
-------
3.2.6 Summary of Treatment Options versus Evaluation Criteria
Table 3-3 summarizes the available information regarding the above four options for treatment.
These will be subsequently used in the evaluation process. In Table 3-3, three of the treatment
processes (the ADA / Permafix treatment, BNL sulfur polymer solidification, and IT/NFS
DeHgฎ process) are grouped together and termed 'stabilization/ amalgamation.' This is done for
several reasons: (1) they have very similar characteristics when compared against the evaluation
criteria, (2) environmental performance data in available reports do not always identify the
vendors associated with the data, although information is available regarding the general process
type, and (3) differentiating between individual treatment processes is anticipated to be a required
decision only after it is decided that treatment is an appropriate decision. Note that, in Table 3-3,
the selenide process is evaluated separately due to significant differences between this process
and the other three technologies.
Table 3-3 summarizes the available information regarding the above four treatment options,
based on the available information. These results are subsequently used in the evaluation process.
Table 3-3 uses the specific information above for individual alternatives in conjunction with more
general information that is available for treatment alternatives in general. Specifically, the
information summarized in Table 3-3 is based on the following for each evaluated criterion:
Compliance with current laws and regulations. Each of the treatment options would likely
require hazardous waste permitting, which can be accomplished in the current regulatory
framework with no special difficulties anticipated. The subsequent disposal of the treated waste
would be prohibited based on current regulations, as discussed in a subsequent section of this
report.
Implementation Considerations. Data and calculations for the ADA and BNL processes show
that the treatment process results in a volume increase of at least 14 times. Data for the other two
processes are not available. Due to the lack of data, it is assumed that the volume increase for all
treatment options is approximately the same. In addition, each of the three stabilization/
amalgamation processes use simple 'off-the shelf equipment while the selenide process may
require additional construction considerations.
Maturity of the technology. In all cases the treatment technologies have been demonstrated for
elemental mercury or related wastes. However, the projected scale of retirement options is much
larger than the more limited capability already demonstrated.
Worker risks. Potential risks to workers from routine handling or accidental release are expected
to be very low for the stabilization/ amalgamation options because of the simple, ambient
temperature characteristics. Potential risks may be slightly higher for the selenide process due to
the additional components of heat and selenium (atoxic metal).
Public Risks and Risk Susceptibility to Terrorism or Sabotage. Risks are anticipated to be very
low because small quantities of mercury are anticipated to be present at the treatment site at any
one time.
3-11
-------
Table 3-3 Evaluation for Treatment Options
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume of
waste
Implementation
considerations: engineering
requirements
Maturity of the technology:
state of maturity of the
technology
Maturity of the technology:
expected reliability of
treatment operation
Risks: worker risk
Risks: public risk
Amalgamation/Stabilization Options
ADA / Permafix
Treatment
Would require
permitting through
existing regulatory
structure
Volume increase of 14x
Simple components
Not commercial scale
Simple components
and batch processing
Very low
Very low because large
quantities of mercury
will not be present
BNL Sulfur Polymer
Solidification
Would require
permitting through
existing regulatory
structure
Volume increase of 18x
Simple components
Not commercial scale
Simple components
and batch processing
Very low
Very low because large
quantities of mercury
will not be present
IT/NFS DeHgฎ
Process
Would require
permitting through
existing regulatory
structure
Volume increase not
known
Simple components
Not commercial scale
Simple components
and batch processing
Very low
Very low because large
quantities of mercury
will not be present
Overall for 3
Stabilization/
Amalgamation
Options
Would require
permitting through
existing regulatory
structure
Volume increase about
15x
Simple components
Not commercial scale
Simple components
and batch processing
Very low
Very low because large
quantities of mercury
will not be present
Selenide Process
Would require
permitting through
existing regulatory
structure
Volume increase not
known, assumed
similar to others
More capital
requirements and
relatively complex
Commercial scale for
mercury wastes but not
for elemental mercury.
Quantities of wastes
treated are likely much
less than quantities of
elemental mercury.
Relatively complex and
continuous processing
Higher than other
alternatives due to high
temperatures and
additional toxic
chemical
Very low because large
quantities of mercury
will not be present
3-12
-------
Table 3-3 Evaluation for Treatment Options (Continued)
Criteria
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Amalgamation/Stabilization Options
ADA / Permafix
Treatment
Very low because large
quantities of mercury
will not be present
Minimal discharges
expected
Moderate: TCLP and
additional testing
performed
Not applicable
Not applicable
Neutral
BNL Sulfur Polymer
Solidification
Very low because large
quantities of mercury
will not be present
Minimal discharges
expected
Moderate: TCLP and
additional testing
performed
Not applicable
Not applicable
Neutral
IT/NFS DeHgฎ
Process
Very low because large
quantities of mercury
will not be present
Minimal discharges
expected
Moderate: TCLP and
additional testing
performed
Not applicable
Not applicable
Neutral
Overall for 3
Stabilization/
Amalgamation
Options
Very low because large
quantities of mercury
will not be present
Minimal discharges
expected
Moderate: TCLP and
additional testing
performed
Not applicable
Not applicable
Neutral
Selenide Process
Very low because large
quantities of mercury
will not be present
Minimal discharges
expected
Low: limited testing
performed by EPA
Not applicable
Not applicable
Neutral
Extremely variable estimates
Mainly operating costs from the initial treatment
-------
Environmental performance. Discharges of mercury potentially occur during treatment. Based
on the above information, the estimated releases for each treatment process are 0.3 percent for the
BNL process, 0.05 percent for the DeHgฎ process, 0.03 percent for the selenide process, and no
data for the ADA process. In each case, the mercury may continue to be collected in filters, etc.
prior to discharge to the atmosphere.
Based on Table 3-2, there is a moderate amount of data regarding the mobility of mercury in
treated wastes for the stabilization/ amalgamation technologies. Fewer data were identified for
the selenide process.
Public perception. The principal 'driver' of public perception of a treatment and disposal train
likely results from the disposal method used, rather than specific concerns regarding the
treatment. Therefore, the public perception of disposal options is used for this analysis.
Costs. The identified costs for these treatment options vary widely. In one case (BNL), the cost
of treatment of 1,500 tons of elemental mercury is estimated as less than $1 million. Using DOE
data for two other cases (ADA and NFS) results in estimates exceeding $400 million. No cost
data are available for the selenide process. This wide range in costs represent a significant
uncertainty.
3.3 Disposal Information
Disposal provides a permanent method of managing mercury. Unlike storage, elemental mercury
once disposed of is very difficult, or impossible, to move again. While it is certainly possible to
remediate a site if the disposal site is causing environmental concerns, this is clearly not an
intended outcome.
Four disposal options have been identified for evaluation: disposal in a mined cavity, disposal in a
RCRA-permitted landfill, disposal in a RCRA-permitted monofill and disposal in an earth-
mounded concrete bunker.
3.3.1 Disposal in a Mined Cavity
There are several examples of deep underground storage for the long-term disposal of wastes.
The Swedish EPA decided in December 1997 to dispose of waste mercury in deep rock mine
sites. This involves treating the waste and then storing it 200 to 400 meters below the surface at
one or more locations. The rock would serve as a buffer to emissions and would provide stability
in disposal. Reasons given by the Swedish EPA for selecting this alternative include the
following: (1) leaching is estimated at less than 10 grams of mercury per year; and (2) the method
provides protection against unforeseen occurrences such as inadvertent human entry or breach of
containment. Barriers noted by the Swedish EPA to implementation include the following: (1)
changes in regulations would be required along with a timeline for when the new regulations
would be effective; and (2) it could take 5 to 10 years until the proposal becomes effective due to
reasons such as selecting a site, technical site analysis, and permit procedure. Wastes with one
percent or more mercury would be priority candidates for storage. The Swedish EPA also
investigated other options including surface storage and shallow storage in rock (Sweden, 1997)
Sweden has not actually selected any site(s) for a disposal location. One potential location for
such a disposal site is Stripa Mine, an existing hard rock mine located about 180 km west of
Stockholm. This site has only been identified as a candidate, and has not been selected by any
government agency for waste disposal. (Stripa 1999).
3-14
-------
In the U.S., deep underground storage/disposal is an option for radioactive materials. The
Carlsbad, New Mexico Waste Isolation Pilot Plant (WIPP) is an up-and-running site. This site
has been characterized by long periods of study and development: the WIPP began operation in
1999 following a 20+ year period of study, public input, and regulatory changes and compliance.
Disposal at the WIPP occurs in a salt formation 2,000 feet below the surface. (WIPP 2002) In
this facility, drummed waste is placed in larger macroencapsulation containers consisting of
polyurethane foam and a relatively thin steel exterior. Congress requires that WIPP be used
solely for noncommercial U.S. defense related transuranic waste. Therefore, WIPP itself is
unlikely to be used as a disposal site for mercury (because authorization from Congress would be
required). However, this could serve as an example for the design of a future disposal site for
mercury.
The Swedish EPA provides data with which to estimate the costs for this alternative. A storage
capacity of 13,000 cubic meters is required for Sweden's needs. No upfront costs are provided
(such costs may be integrated with the ongoing disposal costs). For every kilogram of mercury,
the estimated disposal cost is SEK 240 to 650 (about $10 to $30/lb). The Swedish EPA estimates
that, in 50 years, the country will generate 1,100 metric tons of mercury and estimates the total
cost as about SEK 260 million ($25 million, or $10 per pound and in the lower range of the
previously cited estimate). These costs do not include costs for treatment which are estimated to
be an additional SEK 10 to 80/kg ($0.43 to $3.50/lb). Applying these costs to a hypothetical
1,500 ton quantity of mercury results in costs ranging from $30 million to 90 million for disposal.
An additional example of mine disposal is available for arsenic-containing mining wastes. At the
Giant mine in Yellowknife Canada, 265,000 tons of dust from ore roasting was placed in
underground storage chambers from the early 1950s to the 1990s. Most of these chambers were
specially constructed for storage of the dust, which was stored without treatment or other
containment, in areas intended to be dry. (Thompson 2001) This example can be applied to the
disposal of treated mercury; it is less applicable to mercury storage because it is assumed that
mercury would be contained prior to storage. Options for future management of this material are
being considered; leaving the dust 'as is' is expected to require pumping and treating of
underground water to prevent flooding of the chambers, and inclusion of barriers such as grouting
or reestablishing the permafrost. (Thompson 2001) Cost of an option to reestablish permafrost is
estimated to be $50 million. (O'Reilly 2000) This example shows that additional, and
unanticipated, complexities from mine disposal of mercury may be encountered, which would
affect costs, environmental impact, and implementation considerations.
3.3.2 Disposal in a RCRA-permitted Landfill
Landfills are a common management method for many types of hazardous wastes, with several
commercial hazardous waste landfills currently in operation. Landfills typically dispose of
hazardous wastes treated to remove organics and immobilize metals; such immobilization
methods typically involve stabilization with alkaline agents. Presently, the disposal of hazardous
waste containing more than 260 mg/kg mercury is prohibited, even if treated. Requirements for
landfills vary with the year that they were constructed, but current regulations require design
criteria such as double synthetic liners, leachate collection, and ground water monitoring.
Costs for commercial landfill disposal vary according to the waste complexity, quantity, and
disposal site. However, industry averages are compiled by Environmental Technology Council, a
trade association representing the disposal industry. The industry average costs for 2001 without
treatment ranged from $66 per ton (for bulk soil) to $220 per ton (for drummed waste). Industry
3-15
-------
average costs with treatment ranged from $130 per ton (for bulk soil) to $400 per ton (for
drummed waste). Costs do not include transportation. (ETC 2001) Applying these costs to a
hypothetical 1,500 ton quantity of mercury results in an overall range of $100,000 for bulk solids
(without treatment) to $600,000 for drummed waste with treatment.
3.3.3 Disposal in a RCRA-permitted Monofill
Monofills are constructed to hold only one type of waste or wastes with very similar
characteristics. For example, a company may construct a landfill to dispose of large quantities of
waste generated from onsite processes rather than sending the waste to a commercial facility.
Design requirements are required to follow those for any other hazardous waste landfill (if the
monofill is used for hazardous waste). A monofill provides certain environmental advantages
over conventional, commercial co-disposal. First, the disposal conditions may be more closely
controlled to minimize incompatibility with treated mercury. Second, monitoring and risk
reduction may be more focused towards mercury.
As identified above, land disposal of elemental mercury is prohibited under current U.S.
regulations and therefore this alternative is only applicable with a regulatory change. A monofill
for mercury disposal would be relatively small. For example, a hypothetical 1,500 tons of
mercury (a ten year supply as discussed above) corresponds to 130 cubic yards. Even assuming a
significant volume increase during treatment and the use of a single disposal location, this would
require relatively little space. In contrast, a typical landfill cell at one commercial landfill facility
is 500,000 cubic yards. (Utah 2002)
A monofill would require construction of a new unit or cell. Construction costs are not available.
Ongoing disposal costs would likely be comparable to the costs identified above for commercial
landfills.
3.3.4 Disposal in an Earth-Mounded Concrete Bunker
Earth-mounded concrete bunker technology is used in France as means for disposing of low-level
and mid-level nuclear waste. This technique has been used since 1969. The newest site is the
Centre de 1'Aube. At this site, drummed waste is taken to aboveground, concrete vaults with one-
foot think concrete and underground drainage. The structure is protected with a removable
(temporary) roof; when filled, a three-foot thick roof is poured and overlain with earth to form a
mound. In addition, within the vault the containers are covered in grout. As depicted in this
example, this is a permanent disposal technology rather than a temporary or long-term storage
solution. Materials managed in this manner would be very difficult or impossible to remove at a
later time.
Development costs for the site are estimated at $240 million and disposal costs are estimated at
$1,600 per cubic meter (1997 prices). (USAGE 1997) A hypothetical 1,500 tons of mercury
(corresponding to 130 cubic yards untreated) may result in about 1,300 to 2,600 cubic yards of
treated material (a volume increase often to twenty times), and therefore cost $1.6 to $3.2 million
for disposal in addition to the initial capital costs. Costs for radioactive waste disposal (as cited
here) are expected to be higher than costs for mercury disposal because of the additional
protection required for radioactive wastes. Nevertheless, the capital costs for this alternative are
expected to be higher than the costs for landfilling or monofilling.
3-16
-------
3.3.5 Other Disposal Options not Evaluated
Sub-Seabed Emplacement
Sub-seabed emplacement was originally developed as a disposal alternative for nuclear waste. In
this plan, solidified and packaged waste is buried in containers tens of meters below the ocean
floor. The multiple layers of the waste container, in addition to the ocean sediments and the
ocean water, would serve to delay migration of any contaminants. Research and models
developed in the 1970s and 1980s for nuclear waste could be applied to mercury. However, such
research specific to mercury has not resumed and therefore this represents a very preliminary
option. (Gomez, 2000) Sub-seabed emplacement is not considered further as an option because
(1) it is very preliminary with a correspondingly small amount of available information, and (2)
significant, onerous changes in international treaties will be required.
3.3.6 Summary of Disposal Options versus Evaluation Criteria
Table 3-4 summarizes the available information regarding the above four disposal options, based
on the available information. These results are subsequently used in the evaluation process.
Table 3-4 uses the specific information above for individual alternatives in conjunction with more
general information that is available for disposal alternatives in general. Specifically, the
information summarized in Table 3-4 is based on the following for each evaluated criterion.
Compliance with current laws and regulations. The land disposal of mercury-containing waste
(above 260 mg/kg) is prohibited under current regulations. Any of the disposal alternatives
would require changes in EPA regulations. Additional difficulties may be encountered for the
mine disposal option because local permitting authorities would have less experience with this
alternative and a longer approval process may occur.
Implementation Considerations. The complexities of the above land disposal alternatives cover a
wide range. Existing commercial landfills can be used with little or no modifications, as one
alternative. A monofill or bunker would require new construction. Finally, a mined cavity (in
hard rock or in material such as salt) would likely be more complex than any of the other options.
Maturity of the technology. Landfills (both co-disposal units and monofills) are very common for
hazardous and industrial wastes. In contrast, bunker and mine alternatives are present as only
isolated examples.
Worker risks. Potential risks to workers from routine handling or accidental release are expected
to be very low for all of the alternatives, although additional potential hazards are present in any
alternative where underground activity is required.
Public Risks and Susceptibility to Terrorism or Sabotage. Risks are anticipated to be very low
for all alternatives because the mercury is present in the ground and cannot be widely dispersed.
3-17
-------
Table 3-4 Evaluation for Four Disposal O]
Criteria
Compliance with current laws
and regulations
Implementation considerations:
volume of waste
Implementation considerations:
engineering requirements
Maturity of the technology: state
of maturity of the technology
Maturity of the technology:
expected reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental performance:
discharges during treatment
Environmental performance:
degree of performance testing
Environmental performance:
stability of conditions in the long
term
Environmental performance:
ability to monitor
Public perception
Costs: implementation
Costs: operating
RCRA Permitted Landfill
Non-compliant with LDRs
Not applicable (affected by
treatment, not disposal)
An existing commercial landfill
can be used
Very mature in U.S.
Not applicable
Very low
Very low (because no bulk
elemental mercury)
Very low (because no bulk
elemental mercury)
Not applicable
Not applicable
Fair
Easy
Negative
Low (existing unit can be used)
Low
RCRA Permitted Monofill
Non-compliant with LDRs
Not applicable (affected by
treatment, not disposal)
New in-ground construction
is required
Very mature in U.S.
Not applicable
Very low
Very low (because no bulk
elemental mercury)
Very low (because no bulk
elemental mercury)
Not applicable
Not applicable
Good
Easy
Negative
Medium (requires new
construction)
Low
ptions
Earth-Mounded
Concrete Bunker
Non-compliant with LDRs
Not applicable (affected by
treatment, not disposal)
New in-ground
construction is required
Technology has been
applied but not widely used
Not applicable
Very low
Very low (because no bulk
elemental mercury)
Very low (because no bulk
elemental mercury)
Not applicable
Not applicable
Good
Easy
Positive to neutral
High (costs are likely
higher than monofill)
Medium
Mined Cavity
Non-compliant with LDRs
and unusual permitting
may be required
Not applicable (affected by
treatment, not disposal)
Construction would be
more complex than other
alternatives
Technology has been
applied but not widely used
Not applicable
Low
Very low (because
underground and no bulk
elemental mercury)
Very low (because
underground and no bulk
elemental mercury)
Not applicable
Not applicable
Very good
Difficult
Positive to neutral
High (costs are likely
higher than monofill)
Medium
3-18
-------
Environmental performance. A significant difference among the alternatives involves the
projected stability of the disposal site over the long term. Of course, this performance can only
be imperfectly projected or modeled. Deep underground or mine storage is expected to offer the
greatest stability of conditions, and the presence deep underground offers additional protection
from other environmental media to help mitigate any release (although the Yellowknife example
presents some uncertainty). The monofill alternative, because it is only used for one type of
waste, can be designed to encourage conditions promoting the stability of mercury (e.g.,
conditions involving pH, oxygen availability). The bunker alternative provides a means of
limiting rainfall and providing additional containment, in addition to the potential advantages of
the monofill. Finally, conditions in the commercial landfill alternative are subject to the
properties of the co-disposed, non-mercury wastes and represent the least stable conditions.
The alternatives also differ in the ability to monitor releases, if any. Deep underground disposal
is expected to be the most difficult to monitor. The other alternatives, representing shallow
disposal, are easier to monitor using conventional technologies. In these alternatives, however, if
releases are identified it is very difficult to change or adjust the disposal conditions to prevent
such occurrences in the future.
Public perception. As stated previously, it is extremely difficult to forecast the potential public
perception of any alternative. Reaction can be neutral or even positive for an action identified as
a suitable and defensible alternative for mercury management. This is assumed to be the case for
the bunker and mine disposal alternatives, which are designed to mitigate some of the potential
risks posed by conventional landfill disposal.
Costs. As discussed above, each of these alternatives have different cost components. These are
summarized as follows:
Commercial landfill: no upfront costs, estimated disposal costs of $100,000 to $600,000
for 1,500 tons of mercury.
Monofill: upfront costs are unknown, estimated disposal costs similar to those for
commercial landfill.
Bunker: upfront costs are unknown with $240 million the only available estimate, for
radioactive waste. Estimated disposal costs are $1.6 million to $3.2 million for 1,500 tons
of mercury.
Mine: upfront costs are unknown and may be included in the unit disposal costs.
Disposal costs for 1,500 tons of mercury are estimated to range from $30 million to $90
million.
Each of the alternatives would require ongoing costs such as testing, monitoring, and operational
costs.
3.4 Evaluation of Options
In this section, the various options are evaluated against the intensities associates with each
criterion or sub-criterion. For storage, it is assumed that no pretreatment occurs and any post
storage management (e.g., disposal) will not be planned until much later in the future. This
results in three storage options: storage in a standard building, storage in a hardened building, and
storage in a mine. This differs from the evaluation for treatment and disposal, in which each
treatment option is evaluated with each disposal option. Specifically, the two treatment options
and the four disposal options result in a total of eight (four multiplied by two) alternatives. As
identified above, the two treatment options are as follows:
3-19
-------
One of the following three stabilization/amalgamation technologies:
- DeHg amalgamation
- SPSS process
- Permafix sulfide process
Selenide process
Altogether, 11 options for treatment, storage, and disposal were evaluated. These options are
identified as follows:
Storage of elemental mercury in a standard RCRA-permitted storage building
Storage of elemental mercury in a hardened RCRA-permitted storage structure
Storage of elemental mercury in a mine
Stabilization/amalgamation followed by disposal in a RCRA- permitted landfill
Stabilization/amalgamation followed by disposal in a RCRA- permitted monofill
Stabilization/amalgamation followed by disposal in an earth-mounded concrete bunker
Stabilization/amalgamation followed by disposal in a mined cavity
Selenide treatment followed by disposal in a RCRA- permitted landfill
Selenide treatment followed by disposal in a RCRA- permitted monofill
Selenide treatment followed by disposal in an earth-mounded concrete bunker
Selenide treatment followed by disposal in a mined cavity
The evaluation of each of the 11 alternatives against the various criteria, which is input to Expert
Choice, is summarized in Tables 3-5 and 3-6. Table 3-5 includes half of the criteria for all of the
options, and Table 3-6 includes the remaining criteria (all information could not be included in a
single table). This table was generated using the data previously presented in Tables 3-1,3-3, and
3-4. For example, data for the storage options are identical in Table 3-1 and Tables 3-5/3-6. For
the treatment and disposal alternatives, information was integrated between Table 3-3 (for
treatment) and Table 3-4 (for disposal). In most cases this integration was straightforward;
Appendix D provides more detailed tables for each of the eight treatment and disposal
alternatives to better show how this was conducted.
3-20
-------
Table 3-5 Summary of Criteria Values Assigned to Each Evaluated Alternative
Alternative
Standard storage
Hardened storage
Mine storage
S/A + landfill
S/A + monofill
S/A + bunker
S/A + mine
Se + landfill
Se + monofill
Se + bunker
Se + mine
Compliance with
current laws and
regulations
Compliant
Compliant
Non-compliant w/LDRs
Non-compliant w/LDRs
Non-compliant w/LDRs
Non-compliant w/LDRs
Atypical permit required
Non-compliant w/LDRs
Non-compliant w/LDRs
Non-compliant w/LDRs
Atypical permit required
Implementation considerations
Volume
change of
waste
Zero or minimal
Zero or minimal
Zero or minimal
Increase > lOx
Increase > lOx
Increase > lOx
Increase > lOx
Increase > lOx
Increase > lOx
Increase > lOx
Increase > lOx
Engineering
requirements
Existing facilities
New facilities
New facilities
Existing facilities
New facilities
New facilities
Mine cavity
construction req'd
New facilities
New facilities
New facilities
Mine cavity
construction req'd
Maturity of the technology
State of maturity of the
technology
Full-scale operation
Full-scale operation
Full-scale operation
Pilot trt/ full-scale disposal
Pilot trt/ full-scale disposal
Pilot trt/ untested disposal
Pilot trt/ untested disposal
Pilot trt/ full-scale disposal
Pilot trt/ full-scale disposal
Pilot trt/ untested disposal
Pilot trt/ untested disposal
Expected
reliability of
treatment step
No treatment
No treatment
No treatment
Simple
Simple
Simple
Simple
Complex
Complex
Complex
Complex
3-21
-------
Table 3-6 Continuation of Summary of Criteria Values Assigned to Each Evaluated Alternative
Alternative
Standard storage
Hardened storage
Mine storage
S/A + landfill
S/A + monofill
S/A + bunker
S/A + mine
Se + landfill
Se + monofill
Se + bunker
Se + mine
Risks
Worker
Risk
Very low
Very low
Low
Very low
Very low
Very low
Low
Low
Low
Low
Low
Public
Risk
Low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Suscepti-
bility to
Terrorism/
Sabotage
Low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Very low
Environmental Performance
Discharges
During
Treatment
No impact
No impact
No impact
Minimal
Minimal
Minimal
Minimal
Minimal
Minimal
Minimal
Minimal
Degree of
Treatment
Performance
Testing
Adequate
Adequate
Adequate
Moderate
Moderate
Moderate
Moderate
Low
Low
Low
Low
Stability of
Conditions
in the Long
Term
Poor
Poor
Poor
Fair
Good
Good
Very good
Fair
Good
Good
Very good
Ability to Monitor
Easy and correctible
Easy and correctible
Easy and correctible
Easy
Easy
Easy
Difficult
Easy
Easy
Easy
Difficult
Public perception
Negative
Positive to neutral
Positive to neutral
Negative
Negative
Positive to neutral
Positive to neutral
Negative
Negative
Positive to neutral
Positive to neutral
Cost
Imple-
mentation
Low
Medium
Medium
Low
Medium
High
High
Low
Medium
High
High
Oper-
ating
High
High
High
Low
Low
Medium
Medium
Low
Low
Medium
Medium
3-22
-------
4.0 RESULTS
This section presents base-case results (Section 4.1), a sensitivity analysis (Section 4.2), and a
discussion of uncertainty (Section 4.3).
4.1 Initial Results
The 11 options identified in the previous section of this report were evaluated using the Expert
Choice software. The data from Tables 3-5 and 3-6 are used as inputs to the model. The model
outputs provide results based on comparisons to the criteria and to the other alternatives. While
the input to the model is somewhat narrative (based on Tables 3-5 and 3-6), the output provides a
single numerical result for each alternative.
To interpret the results, it is important to note that no alternative will achieve a 'perfect score,'
however defined. This is because the options are evaluated partially against each other, so that
the total score will always equal unity no matter how many options are evaluated. In addition, as
the number of options increases or decreases, the score of each option will change to maintain the
same sum of scores of all options (i.e., unity). In this manner, the results are best interpreted as
scores relative to each other, rather than the absolute value of an option's score.
Table 4-1 presents the Expert Choice results for each of the eleven alternatives discussed in the
previous section of this report. Three columns of results are presented. The first result represents
the overall score when considering all criteria. The second result represents only those criteria
comprising the six non-cost items (i.e., compliance with current laws and regulations,
implementation considerations, maturity of the technology, risks, environmental performance,
and public perception). The third result represents only the cost criteria. As described in Section
3, cost criteria and non-cost criteria each comprise 50 percent of the overall goal. The results
from the model were multiplied by 1,000 for convenience to provide a score as a whole number,
rather than as a decimal.
The three columns show the strong effect that cost criteria can have upon the results. For
example, each of the two options involving treatment followed by commercial landfilling are
clearly the lowest cost alternatives, based on these results, and contribute heavily towards a high
overall score even though the results for the non-cost criteria are not as high. Similarly, the
option of storage in a hardened building provides the best result when only non-cost criteria are
considered. Because of its relatively low result for cost criteria, its overall result is only slightly
better than average. Of course, putting more or less emphasis on cost factors would change the
results.
Table 4-1 shows that the general order of the option scores are as follows when considering both
cost and non-cost criteria: treatment and commercial landfill disposal options, storage options,
treatment and monofill disposal options, treatment and concrete bunker disposal options, and
treatment and mine disposal options. When cost criteria are not considered, the general order
changes to the following: storage options, concrete bunker disposal options, commercial landfill
disposal options, mine disposal options, and monofill disposal options. Section 4.2 helps explain
how contributions from individual criteria influence the results.
4-1
-------
Table 4-1 Summary of Results for 11 Evaluated Alternatives
Alternative
Stabilization/amalgamation followed by disposal
in a RCRA- permitted landfill
Selenide treatment followed by disposal in a
RCRA- permitted landfill
Storage of elemental mercury in a standard
RCRA-permitted storage building
Stabilization/amalgamation followed by disposal
in a RCRA- permitted monofill
Storage of elemental mercury in a hardened
RCRA-permitted storage structure
Selenide treatment followed by disposal in a
RCRA- permitted monofill
Storage in a mine
Stabilization/amalgamation followed by disposal
in an earth-mounded concrete bunker
Stabilization/amalgamation followed by disposal
in a mined cavity
Selenide treatment followed by disposal in an
earth-mounded concrete bunker
Selenide treatment followed by disposal in a
mined cavity
Number of alternatives evaluated
Total
Average score (total divided by number of
alternatives, either 9 or 11)
Ranking (as fraction of 1,000)
Overall
Score
137
123
110
103
95
94
81
70
63
62
61
11
1,000
91
Rank
1
2
3
4
5
6
7
8
9
10
11
Non-Costs
Only
Score
99
66
152
92
173
74
140
108
97
a
a
9
1,000
111
Rank
5
9
2
7
1
8
3
4
6
a
a
Costs Only
Score
217
217
126
135
44
135
44
42
42
a
a
9
1,000
111
Rank
1
1
5
3
6
3
6
8
8
a
a
Shading indicates the highest-ranking alternative.
a These options were evaluated for the overall goal but were not evaluated at the lower levels of cost and non-cost
items separately, due to the low score from the overall evaluation.
Because storage options rank high in this analysis, storage appears to be a viable option for the
long-term management of mercury. Storage is generally only a temporary solution, however,
because the ultimate disposition of mercury would not be achieved. Nevertheless, during the time
that decisions take place regarding more permanent solutions, storage can be a good alternative
while longer-term mercury disposition solutions are formatted.
Another important consideration is the relative difference between the results for each alternative.
Given that each alternative will result in a different numerical score, it must be determined if the
magnitude of these differences are large enough to be significant, or whether the results indicate
that the numerical results are similar. In general, small differences between one option and
another indicate that no discernible difference exists between the two. A determination of what is
'small' can be addressed in several ways. One is through examination of the sensitivity analysis,
as identified in Section 4.2. A second is by conducting an uncertainty analysis, as described in
Section 4.3.
Another method is by assessing the range in potential results. By evaluating two extreme,
hypothetical options where one option receives the highest intensities for each criteria and the
second option receives the lowest intensities for each criteria, such a range can be determined.
When this is conducted using the data for weightings and intensities presented in Appendix A, the
4-2
-------
range between an option which scores the 'highest' for all criteria and that which scores the
'lowest' for all criteria is a factor of 7.2 (i.e., the result for one option is 7.2 times greater than the
other). This overall, hypothetical range should be kept in mind when interpreting results of these
analyses. For the results in Table 4-1, the difference between the highest option and the lowest
option results in a difference of a factor of 2.2, when considering the results for the overall
analysis in the first column. This indicates that, even when comparing the highest-ranking
alternative to the lowest ranking alternative in Table 4-1, the difference between the two is not
extreme.
4.2 Sensitivity Analysis
Sensitivity analyses were conducted within Expert Choice. These analyses served two functions:
(1) to provide insight into how the overall scores were generated, and (2) to identify how greater
emphasis on different criteria would influence the results. In the baseline analysis, each
alternative was evaluated according to the following non-cost and cost criteria. The percentages
in parentheses represent the value of each criterion in developing the overall score:
Non-cost criteria (50% of total)
Environmental performance (3 3.1 % of non-cost criteria)
Potential for accidents or risks to public safety (31.1% of non-cost criteria)
Implementation considerations (13.8% of non-cost criteria)
Public perception (11.4% of non-cost criteria)
Maturity of technology (6.1 % of non-cost criteria)
Compliance with current laws and regulations (4.5% of non-cost criteria)
Cost criteria (5 0 % of total)
Implementation cost (50% of cost criteria)
Operating cost (50% of cost criteria)
The results from Table 4-1 show how the different alternatives are affected by changes in the
importance of cost criteria. The sensitivity analyses similarly identify how changes in the
importance of different criteria affect the results, although at a more detailed level. For example,
in the initial results presented in Table 4-1, environmental performance criteria contributed to
33.1% of all non-cost criteria. A sensitivity analysis is a type of 'what-if?' analysis where the
contribution of this criterion is made extremely important, contributing 90% (+/- 1%) of all non-
cost criteria, with the remaining five criteria contributing a combined importance of only 10%.
A similar type of analysis is conducted for all six non-cost criteria, and the two cost criteria,
analyzing the results as each criterion is alternately made the most important.
4.2.1 Sensitivity Analyses for Non-Cost Criteria
The sensitivity analysis results are summarized in Table 4-2 for non-cost criteria. Note that Table
4-2 does not consider cost criteria at all to belter understand the effects of non-cost objectives.
The first column of results in Table 4-2, labeled 'baseline,' corresponds to the results in Table 4-1
when cost criteria are not considered. In this column, the importance of each of the six criteria is
equal to the above percentages (e.g., environmental performance is 33.1%). The next columns
list the sensitivity results for each of the six non-cost criteria. For example, for the environmental
performance sensitivity analysis, the contribution of this criterion to the importance of all non-
cost criteria was moved from 33.1% (i.e., the 'baseline' reflected in the first results column) to
90% (+/- 1%). The importance of each of the other five criteria was reduced proportionally so
that the contributions from all six criteria add to 100 percent.
4-3
-------
Some of the data in Table 4-2 are highlighted to emphasize results. The top two, three, or four
ranking alternatives are highlighted (i.e., to account for the highest scoring alternatives, taking
into account small or large differences in scores).
Some of the significant findings from the sensitivity analysis are as follows:
Identifying the importance of criteria: the last row of Table 4-2 shows the ratio between
the highest scoring alternative and the lowest scoring alternative. The higher the ratio,
the more sensitive the criterion. For example, the ratio between the highest and lowest
score from the catastrophic risks criterion is 1.6. This is due, in part, to the fact that each
of the alternatives were assigned similar or identical values for this criterion. In contrast,
compliance with the current regulatory climate resulted in the highest differences
between the highest and lowest ranked alternative, a factor of 7.1. This indicates that this
criterion can significantly impact results, if a high importance is placed on this criterion
for evaluating the objective.
Isolating how alternatives perform against individual criteria: this analysis demonstrates
how an alternative performs when overriding, but not absolute, importance is placed on
one criteria. Other criteria continue to influence the result. Nevertheless, the results are
useful to show potential flaws in particular alternatives (e.g., ranks of 8s and 9s) as well
as bright spots (e.g., ranks of Is and 2s). Further discussion is provided below for
individual criteria.
Alternatives impacted by environmental performance criterion: the alternatives scoring
the highest in this portion of the sensitivity analysis are the storage alternatives. Of the
disposal options, the highest-ranking alternative is stabilization/ amalgamation treatment
with mine disposal. As detailed in Section 2 of this report, environmental performance
includes a number of sub-criteria including testing adequacy and disposal conditions, and
therefore is not limited to performance in leaching tests.
Alternatives impacted by catastrophic risk criterion: this portion of the sensitivity
analysis demonstrates one drawback of standard aboveground storage, which is ranked
last in this portion of the sensitivity analysis. However, as noted above, the ratio between
the highest and lowest scores from catastrophic risks is only 1.6, so this should not be
regarded as a severe disadvantage of the standard storage option.
Alternatives impacted by implementation issues: a wide range between the highest
ranking alternative and the lowest ranking alternative (a factor of 6.8) shows this criterion
can significantly affect results for some alternatives. Disposal in a mined cavity is ranked
last in this portion of the sensitivity analysis, while an 'easy to implement' option, storage
in a standard building, ranks first.
Alternatives impacted by public perception: vaues for this criteria have the greatest
uncertainty, but the wide range in results suggests that it can impact results. Therefore,
attempts to better gauge public perception issues would improve the selection of an
appropriate alternative.
Alternatives impacted by technology maturity: the results of this portion of the analysis
are similar to the results for implementation issues.
Alternatives impacted by current regulatory compliance: as expected, the only two
alternatives that could be implemented without change to federal laws or regulations
score the highest in this portion of the sensitivity analysis.
The sensitivity analysis demonstrates that if greater (or less) emphasis is placed on one particular
criterion, then the results of the overall analysis will change. The general trend of the results in
response to these changes can be predicted from Table 4-2.
4-4
-------
Table 4-2 Sensitivity Analysis of Non-Cost Criteria"
Alternative
Storage of elemental mercury in a hardened
RCRA-permitted structure
Storage of elemental mercury in a standard
RCRA-permitted building
Storage in a mine
Stabilization/amalgamation followed by
disposal in an earth-mounded concrete
bunker
Stabilization/amalgamation followed by
disposal in a RCRA- permitted landfill
Stabilization/amalgamation followed by
disposal in a mined cavity
Stabilization/amalgamation followed by
disposal in a RCRA- permitted monofill
Selenide treatment followed by disposal in a
RCRA- permitted monofill
Selenide treatment followed by disposal in a
RCRA- permitted landfill
Total
Range: highest to lowest alternative
Ranking (as fraction of l,000b; average score 111)
Non-Cost
Baseline
Score
173
152
140
108
99
97
92
74
66
1,000
Rank
1
2
3
4
5
6
7
8
9
2.6 times
Sensitivity:
Env Perf
Score
176
173
145
94
71
110
92
81
58
1,000
Rank
1
2
3
5
8
4
6
7
9
3.0 times
Sensitivity:
Risks
Score
142
87
101
132
131
95
130
92
91
1,000
Rank
1
9
5
2
3
6
4
7
8
1.6 times
Sensitivity:
Implement
Score
172
259
168
57
146
38
55
53
52
1,000
Rank
2
1
3
5
4
9
6
7
8
6.8 times
Sensitivity:
Public
Score
197
52
193
190
46
189
46
44
43
1,000
Rank
1
5
2
o
6
6
4
6
8
9
4.6 times
Sensitivity:
Maturity
Score
226
224
223
52
67
51
66
46
45
1,000
Rank
1
2
3
6
4
7
5
8
9
5.0 times
Sensitivity:
Compliance
Score
263
261
78
74
73
37
73
71
70
1,000
Rank
1
2
3
4
5
9
5
7
8
7.1 times
Shading indicates the two, three, or four highest-ranking alternatives. Cut-off determined by where there is a big drop in the score.
In the sensitivity analysis for each criterion, the importance of the criterion is set at 90 percent. The five other criteria comprise the remaining ten percent, proportional to their original
contributions.
a Two options were not evaluated for the sensitivity analysis: selenide treatment followed by disposal in a mined cavity, and selenide treatment followed by disposal in an earth-mounded
concrete bunker. This is because of the low score from the overall evaluation and the version of Expert Choice used for this analysis only allowed the use of nine alternatives for the
sensitivity analysis.
b Scores normalized to total 1,000.
4-5
-------
4.2.2 Sensitivity Analyses for Cost Criteria
The sensitivity analysis results are summarized in Table 4-3 for cost criteria. Note that Table 4-3
only includes two criteria as identified in Section 2 of this report. The format of Table 4-3 is very
similar to that for Table 4-2. The first column of results in Table 4-3, labeled 'baseline,'
corresponds to the results in Table 4-1 when only cost criteria are considered. In this column, the
importance of each criterion is equal (i.e., both implementation and operating costs contribute
equally to the total 'cost scores. The next columns list the sensitivity of the results of each of
these two cost criteria. For example, for the implementation cost sensitivity analysis, the
contribution of this criterion to the importance of both non-cost criteria was moved from 50%
(i.e., the 'baseline' reflected in the first results column) to 90% (+/- 1%). The importance of the
other criterion was reduced proportionally (to 10%), so that the contributions from both criteria
add to 100 percent.
Some of the data in Table 4-3 are highlighted to emphasize results. The top two, three, or four
ranking alternatives are highlighted (i.e., to account for the highest scoring alternatives, taking
into account small or large differences in scores).
Some of the significant findings from the sensitivity analysis are as follows:
Identifying the importance of criteria: The last row of the Table 4-3 shows the ratio
between the highest scoring alternative and the lowest scoring alternative. The higher the
ratio, the more sensitive the criterion. The ratio is relatively high for each of the two
criteria indicating that each can significantly affect results for the overall objective.
Differences between implementation costs and operating costs: In the 'baseline' results
presented in Table 4-1, equal weight was given for each of implementation and operating
costs. Table 4-3 helps demonstrate how results for alternatives would be impacted if one
or the other criterion was given more importance. In most cases, alternatives which score
high in the implementation cost sensitivity analysis also score well in the operating cost
sensitivity analysis. However, for some cases there appear to be greater differences. For
example, the sensitivity analysis for implementation costs for standard aboveground
storage results in a high score for this alternative. The sensitivity analysis for operating
cost gives a low score for this alternative. Therefore, placing a different level of
importance on these two criteria would result in significant differences in results.
The sensitivity analysis demonstrates that if greater (or less) emphasis is placed on one particular
criterion, then the results of the overall analysis will change. The general trend of the results in
response to these changes can be predicted from Table 4-3.
4.3 Discussion of Uncertainty
Uncertainty identifies the extent to which variation in the information and data influences
appropriate conclusions. An uncertainty analysis is conducted to assess confidence in the results.
In this section of the report, uncertainty is incorporated into the analysis by using (1) ranges of
available information and data, and (2) 'what-if analyses for cases in which the true range is
unknown or not well defined. For example, a different calculation, or assessment, is generated
for values associated with the extreme of a range.
4-6
-------
Table 4-3 Sensitivity Analysis of Cost Criteria to Results for 9 Evaluated Alternatives"
Alternative
Stabilization/amalgamation followed
by disposal in a RCRA- permitted
landfill
Selenide treatment followed by
disposal in a RCRA- permitted
landfill
Stabilization/amalgamation followed
by disposal in a RCRA- permitted
monofill
Selenide treatment followed by
disposal in a RCRA- permitted
monofill
Storage of elemental mercury in a
standard RCRA-permitted storage
building
Storage of elemental mercury in a
hardened RCRA-permitted storage
structure
Storage in a mine
Stabilization/amalgamation followed
by disposal in an earth-mounded
concrete bunker
Stabilization/amalgamation followed
by disposal in a mined cavity
Total
Range: highest to lowest alternative
Ranking (as fraction of 1,000; average score 111)
Cost Baseline
Score
217
217
135
135
126
44
44
42
42
1,000
Rank
1
1
3
3
5
6
6
8
8
5.2 times
Sensitivity:
Implementation Cost
Score
227
227
79
79
209
61
61
28
28
1,000
Rank
1
1
4
4
3
6
6
8
8
8.1 times
Sensitivity:
Operating Costs
Score
207
207
190
190
43
27
27
55
55
1,000
Rank
1
1
3
o
6
7
8
8
5
5
7.7 times
Shading indicates the two, three, or four highest-ranking alternatives.
a Two options were not evaluated for the sensitivity analysis: selenide treatment followed by disposal in a mined cavity,
and selenide treatment followed by disposal in an earth-mounded concrete bunker. This is because of the low score
from the overall evaluation and the version of Expert Choice used for this analysis only allowed the use of nine
alternatives for the sensitivity analysis.
Section 3 of this report identifies the values used in the analysis. It also discusses the certainty, or
confidence, associated with some of the data. Rather than identify all the areas of uncertainty and
attempt to address each of them for every alternative, this section of the analysis will identify the
sources of uncertainty identified in Section 3 that are expected to impact the results and
demonstrate their effect for selected alternatives. These areas of uncertainty include the
following:
Environmental performance - long term stability: it is difficult or impossible to predict
future conditions impacting environmental releases in a disposal environment. Therefore,
this represents an obvious area of uncertainty.
Public perception: again, it is difficult to assess what local and national attitudes will be
towards any of the alternatives.
Cost data: the publicly available cost data for treatment alternatives showed an extremely
wide range. In addition, the operating costs for storage options include projected costs
for future treatment and disposal. Future management practices and their costs, as well as
whether additional management would be needed, are also uncertain. Finally,
4-7
-------
implementation cost estimates for mine storage could potentially vary between those
estimated for more typical storage (i.e., generally low costs) to those for mine disposal
(i.e., generally high costs).
Technology maturity of treatment and storage alternatives. Each of the treatment
alternatives has been demonstrated for limited quantities of mercury or mercury-
containing wastes. There is uncertainty as to whether treatment of additional quantities
would raise any unforeseen difficulties. Some of the storage alternatives may present
similar uncertainties.
Waste volume increase: No data were available for the increase in waste volume during
the treatment of elemental mercury in the selenide process.
The analysis described in this section takes into account the uncertainty of the above parameters
for some of the evaluated alternatives. A series of different analyses were conducted using
Expert Choice, for several of the selected alternatives to better identify the impact that uncertainty
has on the results. These analyses and results are described in Table 4-4. Each row of the table
represents an instance where data are changed for just one of the alternatives. Table 4-4 presents
results when compared against both cost and non-cost objectives. As shown, a total of 12
different uncertainty analyses were conducted.
The 12 sets of uncertainty analysis results in Table 4-4 show how the overall ranking of each
alternative is affected as the intensities of individual criteria are changed. These uncertainty
analyses show that results change most significantly in the case of costs, which may cover the
wide range of available information. The uncertainty analysis can be used to identify important
parameters in which further research may be required. That is, particular attention could be
placed on uncertain data, which significantly affect the results.
In general, Table 4-4 shows that changes in a single criterion produce relatively small effects in
the overall rankings, except in certain cases involving costs. For example, if the operating costs
for storage in a hardened structure were changed from high to low, the overall rank of the
alternative is greatly improved. This change in the intensity of the criterion would correspond to
a case where only the maintenance costs of storage are considered, rather than any subsequent
long-term disposal costs following storage.
A true uncertainty analysis should take into account potential simultaneous variations in all of the
values that are input to the Expert Choice calculation. This can in principle be done by using
Monte-Carlo-based techniques. However, the limited funding available meant that this was not
feasible in the course of the present work.
-------
Table 4-4 Uncertainty Analysis for Mercury Management Alternatives
Ref.
No.
0
1
2
o
J
4
5
6
7
8
9
10
11
12
Alternative
All
Storage in a mine
Stabilization/ amalgamation followed
by disposal in a RCRA- permitted
monofill
Storage of elemental mercury in a
standard RCRA-permitted building
Storage of elemental mercury in a
hardened RCRA-permitted building
Storage in a mine
Selenide treatment followed by
disposal in an earth mounded concrete
bunker
Stabilization/ amalgamation followed
by disposal in a RCRA- permitted
landfill
Stabilization/ amalgamation followed
by disposal in a RCRA- permitted
landfill
Storage of elemental mercury in a
hardened RCRA-permitted structure
Selenide treatment followed by
disposal in a mined cavity
Storage of elemental mercury in a
hardened RCRA-permitted building
Selenide treatment followed by
disposal in a RCRA- permitted landfill
Criteria
Change in Intensity for Uncertainty
Analysis
Baseline
Change
Baseline for comparison: Same results as Table 4-1
Stability of disposal
conditions
Stability of disposal
conditions
Public perception
Public perception
Implementation costs
Implementation costs
Operating Costs
Operating Costs
Operating Costs
State of Technology
Maturity
State of Technology
Maturity
Volume of waste
increase
Poor
Good
Negative
Positive to neutral
Medium
High
Low
Low
High
Pilot treatment/
untested disposal
Full scale operation
Increase greater
than 10 times
Very good
Poor
Positive to neutral
Negative
High
Medium
High
Medium
Low
Full scale operation
Pilot treatment/
untested disposal
Increase up to 10
times
Initial Result
(Table 4-1)
Score
81
103
110
95
81
62
137
137
95
61
95
123
Rank
7
4
o
J
5
7
10
1
1
5
11
5
2
Uncertainty
Analysis Result
Score
87
100
117
88
74
69
101
110
130
63
93
124
Rank
7
4
3
6
7
9
4
3
2
9
6
2
4-9
-------
5.0 CONCLUSIONS AND RECOMMENDATIONS
A limited scope decision-analysis has been performed to compare options for the retirement of
surplus mercury. The analysis has demonstrated that such a study can provide useful insights for
decision-makers. Future work could include:
1. Involve additional experts in the process of assigning weights to the various criteria. The
individuals involved in producing the current report were exclusively from SAIC. They are
listed at the beginning of Section 2.0. This would ensure that a wide range of expertise is
incorporated into the analysis. For example, working groups within EPA, involving a cross-
section of EPA offices, would provide additional perspectives. Other examples would
involve the inclusion of other Federal agencies, States, nongovernmental organizations,
foreign governments, industry, and academia. Such participation could be performed in
stages. As shown in the sensitivity analysis in Section 4.2 of this report, differences in the
importance of the criteria relative to one another can strongly affect the results.
2. The alternatives considered in this report were limited to elemental mercury. Additional
alternatives could be considered for mercury-containing wastes.
3. Additional Expert Choice analyses could be conducted in which certain alternatives are
optimized. For example, within the general alternative of stabilization/ amalgamation
treatment followed by landfill disposal are sub-alternatives addressing individual treatment
technologies or landfill locations. Such optimization, however, is unlikely to be necessary
until a general alternative is selected or more detailed criteria are established to assess the
more detailed alternatives.
4. Revisit the available information periodically to determine if changes in criteria, or changes
in intensities, are required. For example, some candidate criteria were not considered
because insufficient information was available. One example is volatilization of mercury
during long-term management. Very little data are available at this time to adequately
address this as a possible criterion.
5. Consider performing a formal uncertainty analysis utilizing Monte-Carlo-based techniques.
5-1
-------
6.0 BIBLIOGRAPHY
Bethlehem 2000. Bethlehem Apparatus Company Incorporated. 2000. The Mercury
Marketplace: Sources, Demand, Price and the Impacts of Environmental Regulations. Presented
at the Workshop on Mercury in Products, Processes, Waste and the Environment: Eliminating,
Reducing and Managing Risks from Non-Combustion Sources. Baltimore, Maryland. Sponsored
by U.S. EPA. March 22-23, 2000.
Bethlehem 2001. Bethlehem Apparatus Company, Inc., Expression of Interest (for Mercury
Processing), Hellertown, PA. July 6, 2001.
Bjasta2002. BjastaAtervinning company information, http://www.guru.se/bjasta/main.htm
BNL Response, 2001. Brookhaven National Laboratory. Response to Defense Logistics Agency
Request for Expression of Interest. July 2001.
DNSC 2002a. Defense National Stockpile Center. Mercury Management Environmental Impact
Statement Information Website, http://mercuryeis.com/.
DNSC 2002b. Defense National Stockpile Center. Spreadsheet from "No Action Alternative"
data. Prepared by Dennis Lynch, Defense Logistics Agency. January 30, 2002.
DOE 1999a. U.S. Department of Energy. Mercury Contamination -Amalgamate (Contract with
NFS and ADA) Demonstration of DeHgSM Process. Mixed Waste Focus Area. Innovative
Technology Summary Report, DOE/EM-0471. Prepared for Office of Environmental
Management, Office of Science and Technology, September 1999.
http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999b. U.S. Department of Energy. Mercury Contamination - Amalgamate (Contract with
NFS and ADA) Stabilize Elemental Mercury Wastes. Mixed Waste Focus Area. Innovative
Technology Summary Report, DOE/EM-0472. Prepared for Office of Environmental
Management, Office of Science and Technology, September 1999.
http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999c. U.S. Department of Energy. Demonstration of ATG Process for Stabilizing
Mercury (<260 ppm) Contaminated Mixed Waste. Mixed Waste Focus Area. Innovative
Technology Summary Report, DOE/EM-0479. Prepared for Office of Environmental
Management, Office of Science and Technology, September 1999.
http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999d. U.S. Department of Energy. Demonstration of GTS Duratek Process for Stabilizing
Mercury (<260 ppm) Contaminated Mixed Waste. Mixed Waste Focus Area. Innovative
Technology Summary Report, DOE/EM-0487. Prepared for Office of Environmental
Management, Office of Science and Technology, September 1999.
http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999e. U.S. Department of Energy. Demonstration of NFS DeHg Process for Stabilizing
Mercury (<260 ppm) Contaminated Mixed Waste. Mixed Waste Focus Area. Innovative
Technology Summary Report, DOE/EM-0468. Prepared for Office of Environmental
6-1
-------
Management, Office of Science and Technology, September 1999.
http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 2001. U.S. Department of Energy, Energy Information Administration. U.S. Nuclear
Reactors, http://www.eia.doe.gov/cneaf/nuclear/page/nuc_reactors/reactsum.html.
ETC 2001. Environmental Technology Council. Incinerator and Landfill Cost Data. May 2001.
www.etc.org.
Fuhrmann, 2002. Fuhrmann, M., Melamed, D., Kalb, P., Adams, J., and Milian, L. W. Sulfur
Polymer Solidification/ Stabilization of Elemental Mercury Waste. Waste Management Journal.
In press c. 2002.
Gagnon 2001. Gagnon, D. Residents Want Mercury Moved; Orrington Forum Attendees
Divided on Options for Removal, Disposal. Bangor Daily News. December 7, 2001.
Gomez, 2000. Gomez, L.S. Emplacement of Mercury Wastes in the Sediments of the Deep-
Ocean? (author affiliation: Sandia National Laboratories). Presented at the Workshop on
Mercury in Products, Processes, Waste and the Environment: Eliminating, Reducing and
Managing Risks from Non-Combustion Sources. Baltimore, Maryland. Sponsored by U.S. EPA.
March 22-23, 2000.
IT/NFS, 2001, Expression of Interest for Processing Services of Elemental Mercury Using
DeHgฎfor the Defense National Stockpile Center, Knoxville, TN. September 13, 2001.
Kalb, 2001. Kalb, P.O., Adams, J.W., and Milian, L.W. Sulfur Polymer Stabilization/
Solidification (SPSS) of Treatment of Mixed-Waste Mercury Recovered from Environmental
Restoration Activities at BNL. Report for U.S. Department of Energy, BNL-52614. January
2001.
Lindgren 1996. Lindgren, Per-Olov, Paulsson, Karin, and Svedberg, Anna (Bolinden Mineral
AB). Method for Dealing with Mercury-Containing Waste. U.S. Patent No. 5,567,223. October
22, 1996.
Lynch 2002. Letter from D. Lynch, Defense Logistics Agency (Department of Defense), to P.
Randall, U.S. Environmental Protection Agency. June 10, 2002.
NEI 2001. Nuclear Energy Institute. Safe Interim On-site Storage of Used Nuclear Fuel.
http://www.nei.org.
NEMA 2000. Environmental Impact Analysis: Spent Mercury-Containing Lamps. January 2000.
www.nema.org.
O'Reilly 2000. O'Reilly, K. The Giant Mine in Yellowknife, Northwest Territories, Canada.
April 15, 2000. Canadian Artie Resources Committee.
Permafix 2001. Proposal by Permafixfor Provision of Elemental Mercury Processing Services.
July 6, 2001. Business sensitive information removed.
Philips 2002. Philips Lighting. Frequently Asked Questions About the Universal Waste Rule.
http: //www .lighting .philips. com/nam/feature/alto/u_waste. shtml.
6-2
-------
Rizley 2000. Nuke Weapons Bunker Built in Siberia. Engineer Update. U.S. Army Corps of
Engineers. Volume 24, no. 5. May 2000.
SAIC 2002. Preliminary Cost Estimate for Long Term Mercury Storage. Prepared for U.S. EPA
Office of Solid Waste through a subcontract with IEC. March 8, 2002.
Sanchez 2001. Sanchez, F., Kosson, D.S., Mattus, C.H., and Morris, M.I. Use of a New
Leaching Test Framework for Evaluating Alternative Treatment Processes for Mercury
Contaminated Mixed Waste (Hazardous and Radioactive). Vanderbilt University, Department of
Civil and Environmental Engineering. December 14, 2001.
http://www.cee.vanderbilt.edu/cee/researchjrojects.html.
SENES 2001. SENES Consultants Ltd. The Development of Retirement and Long Term Storage
Options of Mercury. Draft Final Report Prepared for National Office of Pollution Prevention,
Environment Canada. June 2001.
Stripa 1999. Stripa Mine Service AB. January 1999. http://www.stripa.se/index_en.html.
Sweden 1997. Swedish Environmental Protection Agency. Terminal Storage of Mercury: An
Important Step on the Road to a Sustainable Society. Report summary. 1997.
Thompson 2001. Thompson, N., Spencer, P., and Green, P. Management of Arsenic Trioxide
Bearing Dust at Giant Mine, Yellowknife, Northwest Territory. Department of Indian Affairs and
Northern Development. USGS Workshop on Arsenic in the Environment, February 21-22, 2001,
Denver CO.
USAGE 1997. U.S. Army Corps of Engineers. Guidance for Low-Level Radioactive Waste
(LLRW) and Mixed Waste (MW) Treatment and Handling. EM 1110-1-4002. June 1997.
USEPA 2001. U.S. Environmental Protection Agency. Proceedings and Summary Report.
Workshop on Mercury in Products, Processes, Waste and the Environment: Eliminating,
Reducing and Managing Risks from Non-Combustion Sources. March 22-23, 2000. Baltimore.
EPA/625/R-00/014. June 2001.
USEPA 2002a. U.S. Environmental Protection Agency. Technical Background Document:
Mercury Wastes. Evaluation of Treatment of Mercury Surrogate Waste. Final Report. February
8, 2002.
USEPA 2002b. U.S. Environmental Protection Agency. Technical Background Document:
Mercury Wastes. Evaluation of Treatment of Bulk Elemental Mercury. Final Report. February
8, 2002.
Utah 2002. Utah Department of Environmental Quality, Division of Solid and Hazardous
Wastes. Information on Commercial and Federal Facilities.
http://www.deq.state.ut.us/EQSHW/cffs-1 .htm.
Wagh, 2000. Wagh, A.S., Singh, D., and Jeong, S.Y. Mercury Stabilization in Chemically
Bonded Phosphate Ceramics, (author affiliation: Argonne National Laboratory). Presented at the
Workshop on Mercury in Products, Processes, Waste and the Environment: Eliminating,
6-3
-------
Reducing and Managing Risks from Non-Combustion Sources. Baltimore, Maryland. Sponsored
by U.S. EPA. March 22-23, 2000.
WIPP 2002. U.S. Department of Energy, Waste Isolation Pilot Plant.
http://www.wipp.carlsbad.nm.us/.
Young 2001. Young, S. DEP Decides Not to Reclassify HoltraChem Mercury. Bangor Daily
News. February 16,2001.
6-4
-------
APPENDIX A
THE ANALYTICAL PROCESS AND THE EXPERT CHOICE MERCURY
RETIREMENT MODEL
THE ANALYTIC HIERARCHY PROCESS
The analytic hierarchy process (AHP), developed at the Wharton School of Business by Thomas
Saaty, allows decision makers to model a complex problem in a hierarchical structure showing
the relationships of the goal, objectives (criteria), sub-objectives, and alternatives as show in
Figure A-l. Uncertainties and other influencing factors can also be included.
Goal
Objective
Sub-
Objective
Alternative
Figure A-l Decision Hierarchy
AHP allows for the application of data, experience, insight, and intuition in a logical and
thorough way. AHP enables decision-makers to derive ratio scale priorities or weights as
opposed to arbitrarily assigning them. In doing so, AHP not only supports decision-makers by
enabling them to structure complexity and exercise judgment, but also allows them to incorporate
both objective and subjective considerations in the decision process. AHP is a compensatory
decision methodology because alternatives that are deficient with respect to one or more
objectives can compensate by their performance with respect to other objectives. AHP is
composed of several previously existing, but unassociated concepts and techniques such as
hierarchical structuring of complexity, pairwise comparisons, redundant judgments, and the
Eigenvector method for deriving weights, and consistency considerations. Although each of
these concepts and techniques were useful in and of themselves, Saaty's synergistic combination
of the concepts and techniques along with some new developments produced a process whose
power is indeed far more than the sum of its parts (Formar and Selly, Undated).
One of the major benefits of AHP is that the theory does not demand perfect consistency. AHP
allows inconsistency, but provides a measure of the inconsistency in each set of judgments. This
inconsistency measure is an important by-product of the process of deriving priorities based on
pairwise comparisons. Being consistent is often thought of as a prerequisite to clear thinking.
However, the real world is hardly ever perfectly consistent. Another reason for inconsistency is
lack of information about the factors being compared. An inconsistency ratio of about 10% or
less is usually considered acceptable. With the model developed for mercury retirement options,
consistency ratios of 0-6% were achieved.
A-l
-------
AHP is built on a solid yet simple theoretical foundation based on three basic principles:
decomposition, comparative judgments, and hierarchic composition or synthesis of priorities.
The decomposition principle is applied to structure a complex problem into a hierarchy of
clusters, sub-clusters, and so on. The principle of comparative judgments is applied to construct
pairwise comparisons of all combinations of elements in a cluster with respect to the parent of the
cluster. These pairwise comparisons are used to derive "local" priorities of the elements in a
cluster with respect to their parent. The principle of hierarchic composition of synthesis is
applied to multiply the local priorities of elements in a cluster by the "global" priority of the
parent element, producing global priorities for the lowest level elements (the alternatives)
(Saaty, 1980).
All theories are based on axioms. The simpler and fewer the axioms, the more general and
applicable is the theory. Originally, AHP was based on three relatively simple axioms. The first
axiom, the reciprocal axiom, requires that if Pc (EA ,EB) is a paired comparison of elements A
and B with respect to their parent, element C, representing how many times more element A
possesses a property than does element B, then Pc (EB, EA ) = 1 / Pc (EA, EB ) . For example, if
A is 5 times larger than B, then B is one fifth as large as A.
The second, or homogeneity axiom, states that the elements being compared should not differ by
too much, else there will tend to be larger errors in judgment. When constructing a hierarchy of
objectives, one should attempt to arrange elements in a cluster so that they do not differ by more
than an order of magnitude. (The AHP verbal scale ranges from 1 to 9, or about an order of
magnitude. The numerical and graphical modes of Expert Choice accommodate almost two
orders of magnitude, allowing a relaxation of this axiom. Judgments beyond an order of
magnitude generally result in a decrease in accuracy and increase in inconsistency).
The third axiom states that those judgments about, or the priorities of, the elements in a hierarchy
do not depend on lower level elements. This axiom is required for the principle of hierarchic
composition to apply. While the first two axioms are always consonant with real work
applications, this axiom requires careful examination, as it is not uncommon for it to be violated.
A fourth axiom, introduced later by Saaty, says that individuals who have reasons for their beliefs
should make sure that their ideas are adequately represented for the outcome to match these
expectations. While this axiom might sound a bit vague, it is very important because the
generality of AHP makes it possible to apply AHP in a variety of ways and adherence to this
axiom ensures the application AHP in appropriate ways.
Most mathematicians will agree that the simplest of two or more competing theories is preferable.
As discussed above, the axioms behind AHP are simple. This simplicity and the ratio scale
measures that AHP produces make it a powerful decision theory.
MATHEMATICS OF AHP
The following example of the decision making process behind buying a new car illustrates AHP
and the associated mathematics used to derive weights and priorities (TASC, Undated). An
approximation to the Eignevector method suitable for hand calculations is used. While this
approximation is reasonable when the judgements are consistent, it may not be so for inconsistent
judgements and is therefore not recommended unless a computer and software are available.
A-2
-------
The first three steps are to:
State the Goal:
Select a New Car
Define the Criteria (or Objectives)
Style (i.e., want a good looking car)
Reliability (i.e., want a reliable car)
Fuel Economy (i.e., want a fuel efficient car)
Identify the Alternatives:
Civic Coupe
Saturn Coupe
Ford Escort
Mazda Miata
This information is then arranged in a hierarchical tree as follows:
CRIT
c
ERIA
Style
Civic
Saturn
Escort
Miata
Select a
New Car
Reliability
Civic
^^ IrU
Saturn
Escort
Miata
Fuel Economy
Civic
Saturn
Escort
Miata
ALTERNATIVES
To determine the relative importance or ranking of the criteria or objectives by making
judgements using the established scale below:
1 Equal 3 Moderate 5 Strong 7 Very Strong 9 Extreme
Thus, one possible outcome of a brainstorming sessions would be that:
1. Reliability is 2 times as important as style
2. Style is 3 times as important as fuel economy
A-3
-------
3. Reliability is 4 times as important as fuel economy
This can be expressed as a matrix
Style Reliability Fuel Economy
Style
Reliability
Fuel Economy
1/1
2/1
1/3
1/2
1/1
1/4
3/1
4/1
1/1
To get a ranking of priorities from a pair wise matrix, Eigenvectors are used. The Eigenvector
solution was demonstrated mathematically as the best approach by Dr. Saaty. To solve for the
Eigenvector:
1. In successive calculations, square the matrix.
2. The row sums are then calculated and normalized
3. Stop when the difference between these sums in two consecutive calculations is
smaller than a prescribed value
First convert the fractions to decimals so that standard matrix algebra can be used:
Style Reliability Fuel Economy
Style
Reliability
Fuel Economy
1.0000
2.0000
3.0000
0.5000
1.0000
0.2500
3.0000
4.0000
1.0000
Step 1. Square the matrix, using standard rules of matrix
times
1.0000
2.0000
3.0000
0.5000
1.0000
0.2500
3.0000
4.0000
1.0000
1.0000 0.5000 3.0000
2.0000 1.0000 4.0000
3.0000 0.2500 1.0000
so that, for example, (1.0000 * 1.0000) + (0.50000 * 2.0000) + (3.0000* 0.3333) = 3.0000 gives
the first entry in the squared matrix, which is as follows:
3.0000
5.3332
1.1666
1.7500
3.0000
0.6667
8.0000
14.0000
3.0000
Step 2. Compute the first Eigenvector
First, sum the rows,
3.0000
5.3332
1.1666
+ 1.7500 -
+ 3.0000 -
+ 0.6667 -
f- 8.0000
f- 14.0000
f- 3.0000
12.7500
= 22.3332
4.8333
Next sum the row totals (i.e., 12.7500 + 22.3332, + 4.8333 = 39.9165), and then normalize by
dividing the row sum by the row totals.
A-4
-------
12.7500/39.9165 = 0.3194
22.3332/39.9165 = 0.5595
4.8333/39.9165 = 0.1211
1.0000
The result is our Eigenvector:
0.3194
0.5595
0.1211
This process must be iterated until the Eigenvector solution does not change from the previous
iteration. Therefore, continuing the example, again we square our resulting matrix from the first
iteration (step 1).
3.0000
5.3332
1.1666
1.7500 + 8.0000
3.0000 + 14.0000
0.6667 + 3.0000
which results in
27.6653
48.3311
10.5547
+ 15.8330
+ 27.6662
+ 6.0414
+ 72.4984
+ 126.6642
+ 27.6653
Next compute the Eigenvector (step 2):
27.6653
48.3311
10.5547
+ 15.8330
+ 27.6662
+ 6.0414
+ 72.4984
+ 126.6642
+ 27.6653
= 115.9967
= 202.6615
= 44.2612
0.3196
0.5584
0.1220
362.9196
1.0000
Finally, compute the difference between the previously computed Eigenvector and this one:
0.3194
0.5595
0.1211
0.3196
0.5584
0.1220
-0.0002
0.0011
-0.0009
This process should be continued until there is no difference to four decimal places. Although it
is helpful to understand the mathematics behind the decision theory, it is not necessary to know
how to do the calculations as Expert Choice, does all the calculations automatically.
The computed Eigenvector provides us the relative ranking of our criteria or objectives. Using
the second computed Eigenvector as an example,
Style
Reliability
Fuel Economy
0.3196
0.5584
0.1220
The second most important criterion
The most important criterion
The least important criterion
A-5
-------
Going back to our hierarchical tree, our weights would be shown as follows:
CRI1
c
ERIA
|
Style
.3196
Civic
Saturn
Escort
Miata
Select a New
Car (1.0)
Reliability
.5584
/^^-"^ VJVJ
1
Fuel Economy
.1220
Civic
Saturn
Escort
Miata
Civic
Saturn
Escort
Miata
GOAL
ALTERNATIVES
Next, the same type of pairwise comparisons would be performed for each of the alternatives.
For example, in terms of style, pairwise comparisons determines the preferences of each
alternative over another:
Civic
Saturn
Escort
Miata
Civic
1/1
4/1
1/4
6/1
Saturn
1/4
1/1
1/4
4/1
Escort
4/1
4/1
1/1
5/1
Miata
1/6
1/4
1/5
1/1
Following the above steps, the Eigenvector would be computed to determine the relative ranking
of alternatives, namely:
Civic
Saturn
Escort
Miata
.1160
.2470
.0600
.5770
The Eigenvector and ranking of alternatives for reliability would be accomplished the same way.
Since AHP can combine both qualitative and quantitative information, fuel economy information
in miles per gallon for each alternative would be obtained and normalized to allow it to be used
with the other rankings as shown below.
A-6
-------
Civic
Saturn
Escort
Miata
34
27
24
28
34/113
27/113
24/113
28/113
.3010
.2390
.2120
.2480
113
1.0000
The populated hierarchical tree with all the weights is shown on the following page. To derive
the solution, matrix algebra is used one more time to multiply the alternative weights by the
criteria weights.
Style
Civic
Saturn
Escort
Miata
.1160
.2470
.0600
.5770
Reliability Fuel Econojny
.3790 .3010
.2900 .2390
.0740 .2120
.2570
.2480
_Criterion_
.3196
.5584
.1220
Style
Reliability
Fuel Economy
Civic
Saturn
Escort
Miata
.3060
.2720
.0940
.3280
CRITERIA
Select a New
Car (1.0)
Style
.3196
GOAL
Reliability
.5584
Civic .1160
Saturn .2470
Escort .0600
Miata .5770
Fuel Economy
.1220
Civic .3790
Saturn .2900
Escort .0740
Miata .2570
Civic .3010
Saturn .2390
Escort .2120
Miata .2480
ALTERNATIVES
The end results show that the Miata is the best choice for the stated criteria based on the highest
ranking of .3280. Of course costs were not included. Although costs could have been included,
in many complex decisions, costs should be set aside until the benefits of the alternatives are
evaluated. Discussing costs together with benefits can sometimes bring forth many political and
emotional responses. There are several ways to handle benefits and costs to include:
1. Graphing benefits and costs of each alternative and chose the alternative with the lowest
cost and highest benefit.
A-7
-------
2. Benefit to cost ratios
3. Linear programming
4. Separate benefit and cost hierarchical trees and then combine the results
Using the benefits to cost ratios for the simple car example, the Civic would then become the best
choice.
Normalized Benefit to
Cost Costs Cost Ratios
1. Miata $18,000 .3333 .3280/.3333 = .9840
2. Civic $12,000 .2222 .3060/.2222 = 1.332
3. Saturn $15,000 .2778 .2720/.2778 = .9791
4. Escort $9,000 .1667 .09407.1667 = .5639
$54,000 1.000
EXPERT CHOICE
Expert Choice was developed in 1983 and as of 1995, was being used by major Fortune 100
companies such as IBM, Ford, General Electric and Rockwell; numerous government agencies to
include the FAA, VA, GSA, the U.S. Navy, and the U.S. Air Force; and in 57 countries
throughout the world. The list of commercial and government users and sponsors continues to
grow today as AHP gains wider understanding and acceptance. Expert Choice automates the
analytic hierarchy process and calculates all of the mathematical computations detailed in the
earlier section. It provides an easy to use graphical interface for structuring the decision problem
as a hierarchy and deriving ratio scales measures through pairwise relative comparisons.
The pairwise comparison process can be performed in Expert Choice using words, numbers, or
graphical bars, and typically incorporates redundancy, which results in a reduction of
measurement error as well as producing a measure of consistency of the comparison judgments.
Humans are much more capable of making relative rather than absolute judgments. The use of
redundancy permits accurate priorities to be derived from verbal judgments even though the
words themselves are not very accurate. Therefore, words can be used to compare qualitative
factors and derive ratio scale priorities that can be combined with quantitative factors. In
addition, Expert Choice allows the conduct of sensitivity analysis. Sensitivity analysis allows the
investigation of the effect on the optimal solution or ranking if the objectives or criteria take on
other possible values or weights. Usually there are some parameters that can be assigned any
reasonable value without affecting the optimality of the solution. However, there may also be
parameters with likely values that would yield a new optimal solution. Therefore, the basic
objective of sensitivity analysis is to identify these particularly sensitive parameters so that
special care can then be taken in estimating them more closely and in selecting a solution which
performs well for most of their likely values.
The steps in applying AHP and Expert Choice to a decision problem include:
Step 1: Problem identification and research
la) Problem identification
Ib) Identify objectives and alternatives. A list of the pros and cons of each alternative is
often helpful in identifying the objectives
A-8
-------
Ic) Research the alternatives
Step 2: Eliminate infeasible alternatives
2a) Determine the "musts"
2b) Eliminate alternatives that do not meet the "musts"
Step 3: Structure a decision model in the form of a hierarchy to include goal, objectives (and
sub objectives), and alternatives. Add other relevant factors (such as scenarios) as required.
Step 4: Evaluate the factors in the model by making pairwise relative comparisons
4a) Use as much factual data as is available, but interpret the data as it relates to to
satisfying the objectives (i.e., do not assume a linear utility curve without thinking
about whether it is a reasonable assumption)
4b) Use knowledge, experience, and intuition for these qualitative aspects of the problem
or when no hard data is available
Step 5: Synthesize to identify the "best" alternative. Once judgments are entered for each
part of the model, the information is synthesized to achieve an overall preference. The
synthesis ranks the alternatives in relation to the goal.
Step 6: Examine and verify decision, iterate as required.
6a) Examine the solution and perform sensitivity analyses. If the solution is sensitive to
factors in the model for which accurate data are not available, consider spending the
resources to collect the necessary data and iterate back to step 4.
6b) Check the decision against intuition. If they do not agree, ask why intuition suggests
that a different alternative is best. See if the reason is already in the model. If not,
revise the model (and or judgements). Iterate as required. In general both model and
intuition may change as more information about the problem becomes available.
Step 7: Document the decision for justification and control.
MERCURY RETIREMENT MODEL
The model was developed using the Expert Choice software following the steps identified above
and using the expertise of SAIC engineers and analysts. The hierarchical model is comprised of a
goal, several levels of objectives (or criteria), and rating intensities or scales for the alternatives
that were identified. Two modes are available within Expert Choice for prioritizing alternatives:
relative measurement and absolute measurement. When a model is created based on relative
measurement, the priorities of the objectives, sub-objectives and alternatives are computed by
comparing the elements to each other. If there is a large number of alternatives (from 10 to
thousands), which is the case with this specific mercury refinement problem, the pairwise
comparison process can become overwhelming.
In contrast, absolute measurement gauges elements against an established scale, thereby reducing
the volume of comparisons. In Expert Choice, absolute measurement is performed in a Ratings
spreadsheet that is incorporated into the software. The objectives and sub-objectives are pairwise
compared against one another, but the alternatives are compared against a pre-established scale.
A-9
-------
While some scales such as cost (e.g. dollars) and measurement (e.g., tons, milligrams, etc.) are
well established and widely recognized, other scales can be customized for the particular model.
The scale of intensities for each objective appears as a group of nodes under that objective. The
intensities are prioritized through the usual pairwise comparison process. Alternatives do not
appear within the main structure of the tree, but instead are maintained in the Ratings spreadsheet.
Each alternative is then rated against the established scale of intensities defined for each criterion.
The scores for each alternative are weighted according to the priorities derived from the pairwise
comparison process and then summed to determine the overall score. When alternatives are rated
in this way, the alternatives are not compared against each other, but against the standard scales
that have been derived for each criterion.
Model Structure
Figure A-2 below depicts the tree structure for the preliminary model. The goal as shown on the
top of the screen is to "Select the best alternatives for mercury retirement".
i 2000 C:\PROGRAM FILES\EC2000\MERCURYB.AHP
File Edit Assessmenl Synthesize Sensitive-Graphs View Go lools Help
-I J1 *J ^Redraw ง> A
Goal: Select the best alternatives for mercury retirement
PC
- Benefits (L: .500)
| Compliance with current laws and regulations (L: .045)
- D Implementation considerations (L: .154)
: Volume of waste (L: .143)
G Engineering requirements (L: .857)
| i Maturity of the techology (L: .047)
; State of maturity of the technology (L: .500)
: Expected reliability of treatment (L: .500)
j 4 Risks (L: .312)
Worker risk (L: .157)
H Public risk (L: .594)
: Susceptibility to terrorism/sabotage (L: .249)
| g Environmental performance (L: .336)
: Discharges during treatment (L: .064)
; Degree of treatment performance testing (L: .122)
; Stability of conditions in the long-term (L: .544)
H Ability to monitor (L: .271)
Public perception (L: .107)
B BCost (L: .500)
I Implementation (L: .500)
H Operating (L: .500)
Figure A-2 Decision Model Tree Structure
The top level criteria are Benefits and Cost. The associated objectives obviously are to
maximize the benefits and to minimize the costs. Equal weightings were assigned to each of
these top level objectives. Each of these objectives include one level or more sub-objectives as
seen in Figure A-2. Six sub-objectives were defined for the covering Benefits objective, four of
which was further broken down into additional sub-objectives. Two objectives were defined for
the covering Cost objective. These are detailed below:
A-10
-------
Benefits
Cost
Compliance with current laws and regulations (maximize)
Implementation considerations
Volume of waste (minimize)
Engineering requirements (minimize)
Maturity of the technology
State of the maturity of the technology (maximize)
Expected reliability of treatment (maximize)
Risks (minimize)
Risks to worker (minimize)
Risks to public (minimize)
Susceptibility to terrorist attack or sabotage (minimize)
Environmental performance
Discharges during treatment (minimize)
Degree of treatment performance testing (maximize)
Stability of conditions in the long term (maximize)
Ability to monitor (maximize)
Public perception (maximize positive reaction)
Implementation costs (minimize)
Operating costs (minimize)
The derived priorities for the Benefits sub-objectives from the pairwise comparison by the team's
scientists can be seen in Figure A-3. Equal priorities were given to the two Cost sub-objectives.
_l
F,le
Derived Priorities with respect to Benefits < GOAL
INCONSISTENCY RATIO = O.OG
An Inconsistency Ratio of .1 or more may warrant some investigation.
Comply .045 ^^H
Imp Cons -154
.047
.312
.336
Figure A-3 Derived Benefits Sub-objectives Priorities
A-ll
-------
The resulting priorities shown are normalized and indicate that the environmental performance
and the potential for catastrophic accidents are the most significant criteria when evaluating
options for retirement of mercury.
The rating intensity scales defined for each objective/criterion are shown in Table A-l.
Table A-l. Rating Intensities Scale
Covering Objective
Cost
Benefits
Benefits:
Implementation
Considerations
Benefits: Maturity of
the technology
Benefits: Risk
Benefits:
Environmental
Performance
Criteria
Implementation cost
Operating cost
Compliance with current
laws and regulations
Public perception
Volume of waste
Engineering requirements
State of the maturity of
the technology
Expected reliability of
treatment
Worker risk
Public risk
Susceptibility to terrorist
attack or sabotage
Discharges during
treatment
Degree of treatment
performance testing
Stability of conditions in
the long term
Ability to monitor
Rating Scale Parameters
Low(0.717)a
Medium (0.205)
High (0.078)
Low (0.717)
Medium (0.205)
High (0.078)
Compliant (0.731)
Non-complaint with LDRs (0.188)
Atypical permit required (0.081)
Positive to neutral (0.833)
Negative (0.1 67)
Zero or minimal (0.731)
Increase up to 10 times (0.188)
Increase greater than 10 times (0.081)
Existing or minor modifications (0.73 1)
New facilities (0.1 8 8)
Construction of a mined cavity (0.081)
Full-scale operation (0.731)
Pilot treatment/full-scale disposal (0.188)
Pilot treatment/untested disposal (0.081)
No treatment (0.7 17)
Simple (0.205)
Complex (0.078)
Very Low (0.800)
Low (0.200)
Very Low (0.800)
Low (0.200)
Very Low (0.800)
Low (0.200)
No impact (0.833)
Minimal (0.1 67)
Adequate (0.705)
Moderate (0.2 11)
Low (0.084)
Very good (0.554)
Good (0.289)
Fair (0.1 06)
Poor (0.051)
Easy and correctable (0.649)
Easy (0.279)
Difficult (0.072)
A-12
-------
a The figures in parentheses are the relative weights given to each intensity.
The corresponding weights determined from comparison of the intensities are shown in
Figures A-4 through A-27.
file
Derived Priorities with respect to Implemnt < Cost < GOAL
INCONSISTENCY RATIO = 0.02
An Inconsistency Ratio of .1 or more may warrant some investigation.
.717
Figure A-4 Derived Priorities for Implementation Costs and
Operating Costs with Respect to Cost
GOAL: Select the best alternatives lor mercury retirement
ฃ.116 yptions inconsistency j^si
]f Verbal J M/itrix ( (Questionnaire f Graphic
With respect to Implemnt < Cost < GOAL
Low: Low
is 4.0 times (MODERATELY to STRONGLY) more PREFERABLE than
Medium: Medium
(Best Fit!
Low
Medium
Medium
* 4.0
High
8.0
3.0
Equal
Moderate
Calculate Abandon invert
Strong
V. Strong 8" Extreme
E_nter
P Product r Structure T Link Elem
Figure A-5 Pairwise Judgements of Implementation Cost Rating
Scale Parameters
A-13
-------
The pairwise judgements for the Operating cost rating scale parameters were identical to that of
the implementation costs.
File
Derived Priorities with respect to Comply < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
Comliant .731 ^^^^^^^^^^^^^^^^^^^^^^^^^^H
Non-Comp .188
Atypical .081
Figure A-6 Derived Priorities for Compliance with Current Laws
and Regulations with Respect to Benefits
GOAL; Select the best alternatives for mercury i
File Options
\p\.--\
f Verbal j M_atrix j Questionnaire f Graphic
With respect to Comply < Benefits < GOAL
Comliant: Compliant
is 5.0 times (STRONGLY) more PREFERABLE than
Non-Comp: Non-compliant w/LDRs
Equal 2- Moderate 4'
Calculate Abandon Invert
Strong B* V. Strong 8* Extreme
r Product P Structure P Link Elem
Figure A-7 Pairwise Judgements of Compliance with Current
Laws and Regulations Rating Scale Parameters
A-14
-------
File
Derived Priorities with respect to Public < Benefits < GOAL
INCONSISTENCY RATIO = 0.0
An Inconsistency Ratio of .1 or more may warrant some investigation.
Positive -833
Negative 167
Figure A-8 Derived Priorities for Public Perception with Respect
to Benefits
GOAL: Select the best alternatives for mercury retirement
File Options I nconsistency
In] I
r
iminary
Verbal
Matrix f Questionnaire ] Graphic
With respect to Public < Benefits < GOAL
Positive: Positive to neutral
is 5.0 times (STRONGLY) more PREFERABLE than
Negative: Negative
IBest Fill
Positive
Negative
* 5.0
Equal
Modeiate
Strong
V. Strong 8" Extreme
Calculate Abandon Invert
Enter
T Product T Structure T Link Elem
Figure A-9 Pairwise Judgements of Public Perception Rating
Scale Parameters
A-15
-------
-1J
Derived Priorities with respect to Volume < Imp Cons < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
.731
Figure A-10 Derived Priorities for Volume of Waste with Respect
to Implementation Considerations
GOAL: Select
lives far mercury retirement
I inconsistency
Preliminary ( Verbal | Matrix \ Questionnaire | Graphic
With respect to Volume < Imp Cons < Benefits < GOAL
Zero: Zero or minimal
is 5.0 times (STRONGLY) more PREFERABLE than
Up to 10: Increase up to 10 times
IBest Fill
Zen
Up to 10
Up to 10
5.0
7.0
3.0
Equal 2* Moderate 1*
Strong IV V. Strong 8" Extreme
Calculate Abandon Invert
Enter
T Product P Structure P Link Elem
Figure A-ll Pairwise Judgements of Volume of Waste Rating
Scale Parameters
A-16
-------
Derived Priorities with respect to Eng Req < Imp Cons < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
.731
Exist
New 188
Construe -081
Figure A-12 Derived Priorities for Engineering Requirements with
Respect to Implementation Considerations
llerndlives loi mercury retirement
...JD.1 J
File Qptions Inconsisjen
Verbal J Matrix ( Questionnaire ] Graphic
With respect to Eng Req < Imp Cons < Benefits < GOAL
Exist: Existing or minor mods
is 5.0 times (STRONGLY) more PREFERABLE than
New: New facilities
V. Strong 8' Extreme
Figure A-13 Pairwise Judgements of Engineering Requirements
Rating Scale Parameters
A-17
-------
Derived Priorities with respect to State < Mature < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
Full-sea .731 ^^^^^^^^^^^^^^^^^^^^^^^^^B
FSDisp 188
Untested .001
Exit
Figure A-14 Derived Priorities for State of Maturity of the
Technology with Respect to Maturity of the Technology
GOAL: Select the best alternatives for mercury retirement
. . If Verbal ]
Matri
Questionnaire | Graphic
With respect to State < Mature < Benefits < GOAL
Full-sea: Full-scale operation
is 5.0 times (STRONGLY) more PREFERABLE than
FS Disp: Pilot Treatment/Full-scale disposal
[Best Fill
Full-sea
FS Disp
FS Disp
5.0
Untested
7.0
3.0
Equal 2* Moderate 4'
Strong 6* V. Strong 8* Extreme
r Product r Structure T Link Elem
Figure A-15 Pairwise Judgements of State of Maturity of the
Technology Rating Scale Parameters
A-18
-------
Derived Priorities with respect to Reliab < Mature < Benefits < GOAL
INCONSISTENCY RATIO = 0.02
An Inconsistency Ratio of .1 or more may warrant some investigation.
No treat .717 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^B
Simple .205
Complex .070
Exit
Figure A-16 Derived Priorities for Expected Reliability of
Treatment with Respect to Maturity of the Technology
GOAL: Select the best alternatives for mercurv retiiemenl
onststency [
Y Verbal
Matrix Y Questionnaire f Graphic
With respect to Rehab < Mature < Benefits < GOAL
No treat: No treatment
is 4.D times (MODERATELY to STRONGLY) more PREFERABLE than
Simple: Simple
No treat
Simple
Simple
4.0
Equal 2- Moderate 4'
Strong 6' V. Strong 8* Extreme
Calculate Abandon Invert
Enter
T Product T Structure T Link Elem
Figure A-17 Pairwise Judgements of Expected Reliability of
Treatment Rating Scale Parameters
A-19
-------
Derived Priorities with respect to Worker < Risks < Benefits < GOAL
INCONSISTENCY RATIO = 0.0
An Inconsistency Ratio of .1 or more may warrant some investigation
Very Low .000
Low .ZOO
Figure A-18 Derived Priorities for Worker Risk with Respect
to Risks
GOAL: Select the best alternatives far mercury retirement
|D| I
Preliminary ( Verbal | Matrix \ Questionnaire | Graphic
With respect to Worker < Risks < Benefits < GOAL
Very Low:
is 1.0 times (MODERATELY to STRONGLY) mote PREFERABLE than
Low: Low
IBest Fill
Very Low
* 4.0
Equal 2' Moderate
Calculate Abandon Invert
Strong IV V. Strong 8" Extreme
Enter
T Product P Structure P Link Elem
Figure A-19 Pairwise Judgements of Worker Risk Rating
Scale Parameters
The derived priorities and pairwise judgements for the public risk and susceptibility to terrorist
attack or sabotage criteria were identical to that of the worker risk shown in the above two
figures.
A-20
-------
Derived Priorities with respect to Discharg < Env Pert < Benefits < GOAL
INCONSISTENCY RATIO = 0.0
An Inconsistency Ratio of .1 or more may warrant some investigation.
No Impac .033
Minimal -167
Exit
Figure A-20 Derived Priorities for Discharges During Treatment
with Respect to Environmental Performance
GOAL: Select the best alternatives for mercury retirement
Pieliminaiy T Verbal
Matrix
Questionnaire f Graphic
With respect to Discharg < Env Pelt < Benefits < GOAL
No Impac: No impact
is 5.0 times [STRONGLY) mote PREFERABLE than
Minimal: Minimal
Strong 6" V. Strong 8* Extreme
F Product P Structure r Link El
Figure A-21 Pairwise Judgements of Discharges During
Treatment Rating Scale Parameters
A-21
-------
Derived Priorities with respect to Degree < Env Pert < Benefits < GOAL
INCONSISTENCY RATIO = 0.03
An Inconsistency Ratio of .1 or more may warrant some investigation.
Adeguate .705
Moderate 211
Low .004
Exit
Figure A-22 Derived Priorities for Degree of Treatment
Performance Testing to Environmental Performance
GOAL: Select the best alternatives lor mercurv retirement
onststency [
Y Verbal
Matrix Y Questionnaire f Graphic
With respect to Degree < Env Perl < Benefits < GOAL
Adequate: Adequate
is 4.D times (MODERATELY to STRONGLY) more PREFERABLE than
Moderate: Moderate
IBest_EilL_
Adequate
Moderate
Moderate
* 4.0
Low
7.0
3.0
Equal
Strong
E* V. Strong 8' Extreme
Calculate Abandon Invert
Enter
T Product T Structure T Link Elem
Figure A-23 Pairwise Judgements of Degree of Treatment
Performance Testing Rating Scale Parameters
A-22
-------
Derived Priorities with respect to Stable < Env Pert < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
Very Goo 551 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^|
Good .289
Fair .106
Poor .051
Exit
Figure A-24 Derived Priorities for Stability of Conditions in the
Long Term to Environmental Performance
GOAL: Select the best alternatives for mercury retirement
. . . | Verbal j H_ainx j Questionnaire j Graphic
With respect to Stable < Env Pert < Benefits < GOAL
Very Goo: Very Good
is 3.0 times (MODERATELY) more PREFERABLE than
Good: Good
Good
3.0
Fail I Poor
5.0
4.0
7.0
G.O
3.0
Equal 2* Moderate 4'
Strong 6* V. Strong 8* Extreme
r Product r Structure T Link Elem
Figure A-25 Pairwise Judgements of Stability of Conditions in the
Long Term Rating Scale Parameters
A-23
-------
Derived Priorities with respect to Monitor < Env Pert < Benefits < GOAL
INCONSISTENCY RATIO = 0.06
An Inconsistency Ratio of .1 or more may warrant some investigation.
E and C .649 ^^^^^^^^^^^^^^^^^^^^^^^^^B
Easy .279
Difficul .072
Exit
Figure A-26 Derived Priorities for Ability to Monitor to
Environmental Performance
GOAL: Select the best alternatives foi mercury retirement
Verbal
Matrix
Questionnaire f Graphic
With respect to Monitor < Env Perf < Benefits < GOAL
E and C: Easy and Collectable
is 3.0 times (MODERATELY) mote PREFERABLE than
Easy: Easy
Strong 6" V. Strong 8* Extreme
F Product P Structure r Link El
Figure A-27 Pairwise Judgements of Ability to Monitor Rating
Scale Parameters
The derived priorities of the objectives with respect to the goal and of the rating intensities with
respect to the sub-objectives or criteria were then fed into the ratings worksheet. A rating for
each criterion for each alternative is then made. Figures A-28 and A-29 below display the
completed ratings worksheet.
A-24
-------
\MERCURY\MERCURY - [Rate / Cost]
msiimH]
Lomlianl 1 ]N on-Comp 1 Atypical
1 (1.000) 1 2 (.258) || 3 (.111)
Alternatives
1 (Standard Storage
2 Hardened Storage
3 Mine Storage
4 S /A H- Landfill
5 S /A + Monofill
6 S/A + Bunker
7 S/A + Mine
8 Se* Landfill
9 I Set Monofill
10 Set Bunker
11 ISe + Mine
PRIORITY
0.110
0.095
0.081
0.137
0.103
0.070
O.OG3
0.123
0.094
O.OG2
O.OG1
Benefits-
Comply
.0224
~omliant
~omliant
J on-Comp
J on-Comp
J on-Comp
ion-Cong
Atypical
J on-Comp
J on-Comp
J on-Comp
Atypical
Imp Cons-
Volume
.0384
Zero
Zero
Zero
>10
>10
>10
>10
>10
>10
>10
>10
Eng Req
.0384
Exist
New
New
Exist
New
New
Construe
New
New
New
Construe
Mature -
State
.0117
Futl-sca
Full-sea
Full-sea
FS Disp
FS Disp
Untested
Untested
FS Disp
FS Disp
Untested
Untested
Reliab
.0117
No treat
No treat
No treat
Simple
Simple
Simple
Simple
Complex
Complex
Complex
Complex
Woiker
.0520
Very Low
Very Low
Low
Very Low
Very Low
Very Low
Low
Low
Low
Low
Low
<| 1 >
-
-r
r
LฐCal I11:16PM I
Figure A-28 Completed Ratings Worksheet (First Page)
1
2
3
4
5
6
7
8
9
10
11
1,2
<
Alternatives
Standard Storage
Hardened Storage
Mine Storage
S/A + Landfill
S/A + Monofill
S/A + Bunker
S/A ! Mine
Se + Landfill
Se + Monofill
Se + Bunker
Se i Mine
Terror
.0520
Low
Veiy Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Discharg
.0420
No Impac
No Impac
No Impac
Minim 1
Minim 1
Minim 1
Minim 1
Minim 1
Minim 1
Minim 1
Minim 1
Degree
.0420
Adequa e
Adequa e
Adequa e
Modera e
Modera e
Modera e
Modera e
Low
Low
Low
Low
Stable
.0420
Poor
Poor
Poor
Fail
Good
Good
Very Goo
Fair
Good
Good
Very Goo
Monitor
.0420
E andC
E andC
Easy
Easy
Easy
Easy
Difficul
Easy
Easy
Easy
Difficul
.053G
Negative
Positive
Positive
Negative
Negative
Positive
Positive
Negative
Negative
Positive
Positive
.2500
Low
Medium
Medium
Low
Medium
High
High
Low
Medium
High
High
.2500
High
High
High
Low
Low
Medium
Medium
Low
Low
Medium
Medium
Ready
Local |12:06PM |
Figure A-29 Completed Ratings Worksheet (Second Page)
A-25
-------
The overall totals can be seen on the first page of the ratings worksheet which provides the
priority of alternatives. The top nine alternatives were then extracted back to the pairwise
comparison model so that sensitivity analysis on the objectives and criteria could be conducted to
see how well the alternatives performed with respect to each of the objectives as well as how
sensitive the alternatives are to changes in the importance of the objectives.
A-26
-------
REFERENCES
Forman, Ernest, and Selly, Mary Ann. Undated. Decision By Objectives, www.expertchoice.com.
Saaty, Thomas L. 1980. The Analytic Hierarchy Process. New York: McGraw-Hill.
The Analytic Sciences Corporation (TASC). Undated. An Illustrated Guide to the Analytic
Hierarchy Process.
A-27
-------
APPENDIX B
SCREENING OF TECHNOLOGIES
This section is intended to briefly review the long-term retirement solutions that were identified
in the Canadian Study (SENES, 2001) and explain why some were selected for further analysis.
The analysis is presented in Tabular form after the list of references.
REFERENCES FOR APPENDIX B
DOE, 1999a. U.S. Department of Energy, Mixed Waste Focus Area. Innovative Technology
Summary Report, Mercury Contamination - Amalgamate Mercury (contract with NFS and ADA)
Demonstration of DeHgSMProcess, [online] OST Reference 1675. Erwin, Tn.: U.S.
Department of Energy, September, [cited 22 February 2001]. Available at:
http://OST.em. doe.gov.itsrtmwfa.html.
DOE, 1999b: U.S. Department of Energy, Mixed Waste Focus Area. Innovative Technology
Summary Report, Demonstration ofNSF DeHg Process for Stabilizing Mercury (<260 ppm)
Contaminated Mixed Waste, [online] OSR Reference 2229. Erwin, Tn.: U.S. Department of
Energy, September, [cited 22 February 2001]. Available at:
http://OST.em.doe.gov/itsrtmwfa.html.
Envirolight, 1999. EnviroLight and Disposal, Inc. General Description - EnviroLight &
Disposal, Inc. Florida, EnviroLight Disposal, Inc.
EPA, 1993a. U.S. Environmental Protection Agency (EPA). "Recovery of Mercury D-009 and
U-151 Waste from Soil." InMercury and Arsenic Wastes. New York: William Andrew
Publishing.
EPA, 1993b. U.S. Environmental Protection Agency. "The Recovery of Mercury from Mineral
Extraction Residues." In Mercury and Arsenic Wastes. New York: William Andrew Publishing.
EPA, 1993c. U.S. Environmental Protection Agency. "Biological and Physico-Chemical
Remediation of Mercury-Contaminated Waste." In Mercury and Arsenic Wastes. New York:
William Andrew Publishing.
EPA, 1993d. U.S. Environmental Protection Agency. "Development of Bacterial Strains for the
Remediation of Mercurial Wastes." In Mercury and Arsenic Wastes. New York: William
Andrew Publishing.
EPA, 1998a. U.S. EPA Office of Solid Waste, Waste Treatment Branch. Analysis of Alternatives
to Incineration for Mercury Wastes Containing Organics - EPA ID # F-1999-MTSP-S0003
[online]. Washington, D.C. : EPA Office of Solid Waste, June, [cited 22 February 2001].
Available at: http://www.epa.gov/epaoswer/hazwaste/ldr/mercury/index.htm.
EPA, 1998b. U.S. EPA Office of Solid Waste, Waste Treatment Branch. Technologies for
Immobilizing High Mercury Subcategory Wastes - EPA ID# F-1999-MTSP - S0004 [online].
Washington, D.C.: EPA Office of Solid Waste, July, [cited 22 February 2001]. Available at:
http://www.epa.gov/epaoswer/hazwaste/ldr/mercury/index.htm.
EPA, 1998c. U.S. EPA Office of Solid Waste, Waste Treatment Branch. Waste Specific
Evaluation ofRMERC Treatment Standard - EPA ID # F-1999- MTSP - S0002 [online].
B-l
-------
Washington, D.C.: EPA Office of Solid Waste, July, [cited 22 February 2001]. Available at:
http://www.epa.gov/epaoswer/hazwaste/ldr/mercury/index.htm.
Freeman, 1989. Freeman, Harry M. Section 10.6 in the Standard Handbook of 'Hazardous Waste
Treatment and Disposal. U.S. EPA Hazardous Waste Engineering Research Laboratory.
Hall, undated. Hall, D.W. and Holbein, B.E. Technology for the Treatment of Mercury and
Associated Wastes from Lighting Apparatus. Quebec: Tallon Metal Technologies Inc.
IGT, 2000. Institute of Gas Technology & ENDESCO Services Inc. DesPlaines, IL. [cited 22
February 2001] Available at: http://www.igt.org.
Kalb, undated. Kalb, P.D., Melamed, D., Fuhrmann, M., Adams, J.W., Sapanara, M., and
DeTello, C. [undated] Sulfur Polymer Stabilization/Solidification of Elemental Mercury Mixed
Waste, [online]. [Upton, NY]: [Brookhaven National Laboratory]. [cited 22 February 2001].
Available at: http://www.dne.bnl.gov/~kalb/hgpaper.htm.
Nordic Council of Ministers. 1999. Treatment and Disposal of Mercury Waste - Strategic
Elements proposed by a Nordic Expert Group. Copenhagen: Nordic Council of Ministers.
Philips, 1995. Philips Services Corporation. Thermal Desorption - Fluidized Bed Technology.
Philips Services Corporation.
SENES, 2001. SENES Consultants Limited, The Development of Retirement and Long Term
Storage Options of Mercury. Prepared for the National Office of Pollution Prevention,
Environment Canada.
Sobral, 2000. Sobral, L.G.S., Santos, R.L.C., and Barbosa, L.A.D. "Electrolytic Treatment of
Mercury Loaded Activated Carbon from a Gas Cleaning System." The Science of the Total
Environment 261:195-201.
Spence, Roger D. 1997. Mercury Amalgamation Solidification/Stabilization (MASS). Oak Ridge,
TN.: Oak Ridge National Laboratory, March, [cited 22 February 2001]. Available at:
http://www.ornl.gov/divisions/ctd/Eng Dev/capabilities/tmg 1 .htm.
Wagh, 2001. Wagh, Arun S., Singh, Dileep, and Jeong, Seung-Young. "Chemically Bonded
Phosphate Ceramics for Stabilization and Solidification of Mixed Waste." Chapter 6.3 in
Hazardous and Radioactive Waste Treatment Technologies Handbook. CRC Press LLC.
Wescott, Undated. Wescott, James. Mercury Treatment for Small Site Generators. Argonne
National Laboratory.
B-2
-------
Process Name and
References
Brief Description
Included in Current Study?
Retorting
References:
EPA, 1998b
SENES, 2001
Retorting is a high temperature, vacuum assisted batch
process and is used for recovery of elemental mercury
from Hg containing waste. Waste is placed into a bell
type retort in drums or trays on a stationary base. The
top bell unit is lowered, fastened and sealed. The
vacuum is drawn to approximately 0.03 atmospheres.
Electrical radiant heaters inside the retort raise the
temperatures to about 675ฐ C, vaporizing the mercury.
Downstream water-cooled condensers condense the
mercury saturated air stream. Mercury is collected in
a reservoir for transfer to a continuous triple
distillation process for further purification.
No. A mercury recovery
technique. Regarded as a well-
established prior step for
producing elemental mercury,
some of which ends up in the
pool of surplus mercury. See
Section 1.3.2
Thermal Desorption
Fluidized Bed
References:
Philips, 1995
SENES, 2001
This technology is particularly useful on soil
containing contaminants, such as mercury.
Contaminated soil is screened and crushed so that the
material sent into the fluidized bed unit is uniform in
size. The soil is heated up to 1200ฐ F, by re-
circulation of the exhaust gas that has already been
treated and reheated through a radiant tube air pre-
heater. The mercury-containing vapors are first
filtered in a baghouse, cooled and condensed.
No. A mercury recovery
technique. Not suitable for
treating bulk elemental
mercury, see Section 1.3.2
Liquid Waste
Incineration
Reference:
SENES, 2001, citing
Hennin, P. 2001
Conversation with
Safety-Kleen Employee,
March 2001
The mercury-bearing waste acceptance criterion is <
10 ppm. Liquid wastes are injected into the primary
or secondary chambers of a stationary incinerator,
depending on their heat content.
No. Not suitable for treatment
of bulk elemental mercury.
See Section 1.3.2
Rotary Kiln
Incineration
References:
EPA, 1998a
SENES, 2001
Non-wastewaters are fed into a furnace (thermal
processor) equipped with a two-stage afterburner.
The gas leaving the furnace is cooled through a two-
stage scrubbing and cooling system using a
combination of water and sodium hydroxide solution.
A final stage of scrubbing and cooling in a venturi and
separator is used. The gases exiting this final stage of
cooling are passed through sulfur impregnated carbon
to remove residual mercury before being exhausted to
the atmosphere. Metallic mercury is recovered from
each stage of the scrubbing/cooling process.
No. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2
Amalgamation Using
Metals
References:
EPA, 1998b
SENES, 2001
This is a well-established technology for elemental
mercury. It has low air emissions of elemental
mercury vapor. Other metals (Cu, Ni, Sn, Zn, Au,
Ag) form an amalgam with mercury. It can also treat
wastewater containing dissolved mercury salts. To
further improve on amalgamation and stabilization,
encapsulation of amalgamated mercury waste is
possible and will limit the volatilization and leaching
of mercury.
Yes. This is a class of
treatment technologies that is
represented in the present
study by the ITS/NFS DeHgฎ
process. See Section 3.2.3.
B-3
-------
Process Name and
References
Brief Description
Included in Current Study?
Ion Exchange
References:
EPA, 1998a
SENES, 2001
Ion exchange applications are useful to remove Hg
from aqueous streams at low concentrations (1-10
ppb Hg). A synthetic resin or mineral is suspended in
a solution where suspended Hg ions are exchanged
onto the resin or mineral (packed column).
Organomercury compounds do not ionize, thus are
unsuitable for this technology.
No. Wastewater treatment
technologies excluded. See
Section 1.3.2
Amalgamation: ADA
Technologies Process
References:
EPA, 1998c
SENES, 2001
The ADA process stabilizes radioactively
contaminated elemental mercury with a proprietary
powdered sulfur mixture in a commercially available
pug mill to produce a stable mercury sulfide product.
The process operates at ambient temperature and
pressure without addition of heat - reaction is
exothermic at room temperature. Air in the mixing
area is exhausted through a HEPA filter plus sulfur-
impregnated carbon filter.
Yes. See Section 3.2.1.
Chemical Precipitation
References:
EPA, 1998a
SENES, 2001
This process involves precipitating mercuric sulfide
(HgS) from wastewaters containing HgCl2 generated
during prior oxidation and/or chemical leaching steps.
Reagents used in precipitation include Na2S and FeS.
No. Wastewater treatment
technologies excluded. See
Section 1.3.2
Amalgamation: Hg
Absorbv
References:
Wescott, undated
SENES,2001
Applicable to mixed wastes streams such as elemental
mercury contaminated with radioactive materials.
Amalgamation of the elemental mercury with Hg
Absorbu, a manufactured product, produces a mercury
amalgam meeting the TCLP of < 0.025 mg/1 leaching
criteria. Hg Absorbu contains granular zinc and citric
acid, and it is wetted and mixed with mercury at a 3:1
ratio by volume until no free visible mercury is
visible.
Not explicitly, but belongs to
the class of treatment
technologies that is
represented in the present
study by the ITS/NFS DeHgฎ
process. See Section 3.2.3.
Chemical Oxidation
References:
EPA, 1998a
SENES, 2001
This technology is primarily used to treat aqueous
waste (Chemical Oxygen Demand (COD) <5000
mg/1), but may be applied to solids (slurry). It
chemically oxidizes organomercury compounds and
converts Hgฐ to HgCl2 or HgO, which can be
separated from waste matrix and further treated.
Various oxidizing and proprietary agents are utilized
(NaOCl, O3, C12, H2O2).
No. Does not treat bulk
elemental mercury. See
Section 1.3.2
Chemical
Leaching/Acid
Leaching
References:
EPA, 1998a
SENES, 2001
This process is employed for mercury separation when
mercury is present in an inorganic or organic media
and when mercury in waste is at the percent level.
Acid leaching (strong acids - H2SO4, HC1, HNO3) is
most commonly used to remove Hg from inorganic
media. The leaching solution generates ionic soluble
form of mercury that is filtered off for further
treatment (precipitation, ion exchange, carbon
adsorption). However, nitric acid is used for organic
media leaching and it achieves both conversion of Hg
to a soluble form and destruction of the organic
content. It is referred to as oxidative acid leaching.
No. Does not treat bulk
elemental mercury. See
Section 1.3.2.
B-4
-------
Process Name and
References
Brief Description
Included in Current Study?
Stabilization (TMT)
References:
EPA, 1998b
SENES, 2001
Involves precipitating mercuric sulfide (HgS) from
scrubber wastewaters in off-gas treatment systems
with trimercapto-s-triazine (TMT). Its insolubility in
water is similar to that of mercuric sulfide, and it is a
relatively stable final waste form. Polyelectrolytes
coagulants/filters aids may be used to optimize Hg
immobilization. The solids precipitate is removed by
settling using circular clarifier and filtration for final
polishing.
No. Wastewater treatment
technologies excluded. See
Section 1.3.2.
Leaching-Oxidation-
Precipitation
References:
EPA, 1998a
SENES, 2001
Depending on the form of mercury bearing waste
(elemental, organomercury), a higher degree of waste
matrix digestion must be achieved than either leaching
or precipitation alone.
This three-step process train (individual steps
described before), has been demonstrated as an
alternative to incineration, but cannot destroy dioxins,
furans, orPCB.
No. Not intended for the
treatment of bulk elemental
mercury. See Section 1.3.2.
Amalgamation:
DeHgSM Process
References:
DOE, 1999a,b
SENES, 2001
DeHg process is a two-step process capable of
converting mercury-containing mixed waste of
various matrices and chemical species to non-
hazardous final waste forms. Waste pretreatment
would consist of sorting, shredding and slurrying (if
necessary) to create a homogeneous mixture. In the
1st step, wastes are treated using classical
amalgamation to stabilize elemental mercury
contained in the waste. The 2nd step is a chemical
stabilization process using a proprietary reagent to
break mercury complexes and allow for removal of
the mercury from the waste slurry as a stable
precipitant. The DeHg process operates at ambient
temperature and pressure.
Yes. See Section 3.2.3.
ATG Stabilization
References:
DOE, 1999a
SENES, 2001
The Allied Technology Group (ATG) process uses a
dithiocarbamate formulation and small amount of
proprietary liquid to produce a stabilized waste that
satisfies the UTS treatment limits for mercury
(0.025mg/l). It has been tested on ion-exchange waste
material (mixed waste < 260 ppm Hg). The process
equipment consists of a pug mill and mortar mixer and
air treatment system. Presence of water < 10% is
tolerable for the process. Higher water concentrations
hinder the reaction process. Volume increases are
small at 16% of the untreated waste volume. This
process is most effective on Hg and Cr contaminants
and is only moderately effective for Ba and Cd.
No. Not intended for the
treatment of bulk elemental
mercury. See Section 3.2.2.
Stabilization:
Sachtleben-Lurgi
Process
References:
EPA, 1998b
SENES, 2001
Stabilization SLP involves precipitating mercuric
sulfide (HgS) from acidic scrubber wastewaters with
H2S gas. Scrubbing off-gas from smelting of metal
ores generates the wastewater.
No. Wastewater treatment
technologies excluded.
Industry-specific. See Section
1.3.2
B-5
-------
Process Name and
References
Brief Description
Included in Current Study?
Encapsulation: Sulfur
Polymer Stabilization/
Solidification
References:
Kalb, undated
SENES, 2001
Sulfur Polymer Cement (SPC) consist of 95% S
reacted with 5% of organic modifier to enhance
mechanical integrity and long-term durability. A two-
stage process converts elemental Hg to HgS by
reaction with SPC in its 1st stage. Equal masses of Hg
and SPC are mixed in a reaction vessel previously
blanketed with nitrogen, thus preventing HgO
formation. Vessel is heated to 40ฐ C to accelerate the
sulfide formation. Once the Hg is chemically
stabilized, more SPC is added in a 2nd stage, and the
mixture heated to 130ฐ C until a homogeneous molten
mixture is formed. It is then poured into a suitable
mold where it cools to form a monolithic solid waste
form.
Yes. See Section 3.2.2.
Encapsulation: Sodium
Sulfide Nonahydrate in
Sulfur Polymer Cement
References: EPA, 1998b
SENES, 2001
Sulfur Polymer Cement (SPC) consist of 95% S
reacted with 5% of organic modifier to enhance
mechanical integrity and long-term durability. A one-
stage process converts HgO to HgS by reaction with
SPC and sodium sulfide nonahydrate. Sodium sulfide
nonahydrate added at 7% w/w to the SPC mixture
enhances the conversion reaction. The recommended
mixing temperature range is 127-138ฐ C. SPC-
stabilized waste achieves good unconfmed
compressive strength, it contains no water and is
resistant to acids and salts for years. It is less resistant
to strong alkali (> 10%), strong oxidizers (hot chromic
acid, sodium chlorate-hypochlorite), hot solvents, and
some metal slimes like copper.
Yes. Similar to BNL Sulfur
Polymer Stabilization
Solidification (SPSS) Process.
See Section 3.2.2.
Sequestration of
Mercury as a Stable
Solid
References:
Institute of Gas
Technology Endesco
Services, Inc. 2000.
Mercury-containing soils and sediments can be treated
by thermal desorption followed by sequestration. The
thermal desorption process will cause the mercury to
be removed from the soil. A condensation step will
condense it into liquid. The liquid is then converted
into a hard, unreactive, nonporous, monolithic solid
form by using an inexpensive metal (amalgamation)
for permanent disposal or recovered for later use by
simple distillation. The metal used to amalgam Hg is
treated by a reactive fluid so that Hg will coat, wet,
and adhere to the metal. This is followed by vigorous
mixing with a greater mass of Hg to expel the reactive
fluid, remove porosity, and form a metallic slurry.
The resulting amalgam (Hg at 50-80 % by weight)
hardens in 1-2 days.
Yes. The thermal desorption
phase is a mercury recovery
process. The subsequent
amalgamation step is
represented by the ITS/NFS
DeHgฎ process. See Section
3.2.3.
Mercury Stabilization
in Chemically Bonded
Phosphate Ceramics:
References:
Wagh, 2001
SENES, 2001
This is a room temperature setting process based on an
acid base reaction between, MgO, KH2PO4 solution
and solid or liquid waste streams. It forms a dense
ceramic of high strength and low open porosity within
2 hours.
No. Only demonstrated on
wastes containing up to 0.5%
mercury. See Section 3.2.5.
B-6
-------
Process Name and
References
Brief Description
Included in Current Study?
Stabilization:
Simultaneous
Precipitation and Froth
Flotation
References:
EPA, 1998b
SENES, 2001
Heavy metal precipitated as sulfides has very fine
particles, and is hard to dewater to separate from the
reaction solution. This process involves precipitating
mercuric sulfide (HgS) from wastewaters with H2S
gas in a continuously operated froth flotation column.
No. Wastewater treatment
technologies excluded. See
Section 1.3.2
Electro-oxidation
References:
Sobral, 2000
SENES, 2001
Recycling of mercury and activated carbon can be
accomplished by electro-oxidizing mercury in a
reaction system where the loaded carbon is the anode
during the electrolysis of brine.
No. Industry-specific process.
See Section 1.3.2.
Adsorption
References:
EPA, 1998c
SENES, 2001
Inorganic mercury present in aqueous wastes can be
effectively removed with carbon (granular or powder)
at target pH ranges.
No. Aqueous wastes not
considered in this study. See
Section 1.3.2.
Stabilization of
Mercury in an Inert
Matrix
References:
EPA, 1998b
SENES, 2001
Portland cements, cement kiln dust and fly ash are
pozzolanic materials having hydraulic cementitious
properties when mixed with free lime. Other
materials include volcanic rocks, blast furnace slag
and silica fume. Substantial reduction in mercury
teachability is easily accomplished in most
stabilization processes (waste with < 260 ppm total
Hg). Difficult may arise when treating wastes with
higher Hg concentration, elemental Hg and
organomercury compounds.
No. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
GTS Duratek
Stabilization
References:
DOE, 1999b
SENES, 2001
This process utilises a Portland cement-based grout
process for stabilization of sludges and laboratory
residues.
No. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2
Mercury Sublimation
References:
Envirolight, 1999
SENES, 2001
This technology is applicable to treatment of lighting
fixtures. Crushing of lamps releases Hg vapors
through a furnace operating a ~ 1400ฐ C under
negative pressure. The Hg gas exiting the furnace
reacts with selenium in a smaller chamber (selenium
sublimes at 800ฐ C) and forms a mercury selenide.
Yes. A selenide technology.
See Section 1.3.2. See Section
3.2.4.
GZA/HM Process
References:
EPA, 1993a
SENES, 2001
The GZA/HM technology utilizes the high specific
gravity of mercury and adapts basic mining techniques
into a process capable of recovering 99.8% of
elemental mercury from soil matrixes.
No. A mercury recovery
technique. See Section 1.3.2.
B-7
-------
Process Name and
References
Brief Description
Included in Current Study?
Remerc Process
References:
EPA, 1998a
SENES, 2001
It is a two-step leach procedure. The first leach stage
is conducted at a slightly acidic pH and uses sodium
hypochlorite to extract the mercury. A vertical wash
tower (thickener) washes the leach product. The
overflow solution from this tower is transferred to the
cementation step. The thickened leach residue from
the tower contains about SOOppm of mercury and
continues on to the second leach stage. The second
leach step is identical to the first, except it is
conducted at a more acidic pH.
No. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
Tallon Process
References:
Hall, undated
SENES, 2001
This technology is applicable to the treatment of
lighting fixtures. It uses a series of wet process steps:
crushing, milling, segregation together with a
hydrometallurgical step to yield a recyclable glass by-
product.
No. Industry-specific. See
Section 1.3.2.
Xtaltite Synthetic
Mineral
Immobilization of
Mercury Xtaltite
Synthetic Mineral
Immobilization of
Mercury
References:
EPA, 1998b
SENES, 2001
This technology was developed for stabilization of
high-level radioactive waste. It incorporates heavy
metals (Hg, As, Cd, Pb) into an apatite type of mineral
crystal structure.
No. Not proven for bulk
elemental mercury.
Conventional Mines
References:
Freeman, 1989.
Nordic Council of
Ministers, 1999.
SENES, 2001
Suitable repositories may be found in salt, potash,
gypsum, limestone and underground granite mines.
The main criteria for these mines to be used are, be
dry, remain geologically stable and not cave in or
close due to plastic flow of the mineral for a long
time. Mines can range in depth down to 3000 ft.
Stability and access problems would make deeper
mines undesirable for hazardous waste storage or
disposal. Pretreated waste containing mercury is
placed in a stable semi-soluble form in containers. It
could also be used as a long-term underground
warehouse, if retrievability for recycling were desired.
Yes. Mined cavity taken as
representative. See Section
3.3.1.
Solution Mine
References:
Freeman, 1989
SENES, 2001
Salt deposit occurs either as bedded deposits or as
dome deposits. Stability considerations dictate that
the depth for a solution-mined cavern for hazardous
waste storage not exceed 3,000 ft.
Yes. Mined cavity taken as
representative. See Section
3.3.1.
B-8
-------
Process Name and
References
Brief Description
Included in Current Study?
Secure Landfill
Reference:
SENES, 2001, citing
Hennin, P., 2001,
Conversation with
Safety-Kleen Employee,
March.
Hazardous wastes not meeting the slump test criteria
are pretreated by solidification. The solidified wastes
are initially deposited below grade in an excavated
cell. Landfilling then proceeds above grade forming a
mound that causes drainage of water precipitation
from the landfill surface. Hazardous wastes are
placed in the cell in a manner such that only
compatible wastes are disposed of together. This can
be accomplished by placing the waste either in
separate areas or in individual control cells.
Yes. See Section 3.3.2.
Stabilization/
Solidification/
Landfill: Stablex
Process
Reference:
SENES, 2001, citing
Stablex. [n.d.] [online]
Blainville, Quebec.
Available at:
http://www.envirobiz.co
m/homepages/stx/stx-
ser2.htm
This is a silicate-type process whereby any soluble
ions that are left [after chemical pretreatment] are
bound with the silicates and the insoluble ions are
trapped in a silicate lattice or matrix that is formed
during the solidification process. Final hydration, or
solidification, takes between 6 and 72 hours. The final
Stablex material is placed in the landfill cells as a
slurry so that it forms a continuous monolith within
the cell. The compressive strength of the material is
high, and the hydraulic conductivity is low within the
cell.
Yes, to the extent that the
landfill options selected for
this study are representative of
all landfill options. See
Section 3.3.2.
Mercury
Amalgamation
Solidification/Stabilizat
ion (MASS)
References:
Spence, 1997
SENES, 2001
Unique features of these technologies are: stabilises
either elemental or soluble mercury compounds,
minimises the mercury vapor pressure inside the waste
form, controls the oxygen potential inside the waste
form to prevent oxidation of the amalgamating agents,
solidifies mercury, other RCRA metals, and
radionuclides inside a cementitious waste form.
No. Not enough information
available.
Hydrometallurgical:
Selective Precipitation
of Mercury Sulfide
References:
EPA, 1993b
SENES, 2001
Selective precipitation of mercury sulfide with
thioacetamide to yield sulfide from a copper-mercury
solution obtained by sulfuric acid leaching.
Thioacetamide and thiourea will precipitate mercury
sulfide from a sulfate solution at a pH ~ 2 so that it
can be removed by filtration before significant copper
is also precipitated.
No. Not enough information
available. Wastewater
treatment technology. See
Section 1.3.2.
Hydrometallurgical:
Selective Leaching of
Sulfide Concentrates
References:
EPA, 1993b
SENES, 2001
Selective leaching of sulfide concentrates with an
acidic chlorobromide leach and a hypochlorite-
bromine oxidant has been effective in a complex
sulfide concentrate. The mercury is recovered as Hg+1
sulfide precipitate
No. Not enough information
available.
B-9
-------
Process Name and
References
Brief Description
Included in Current Study?
Hydrometallurgical:
Leaching of Mercury-
Sulfur Residue
References:
EPA, 1993b
SENES, 2001
The wash liquor from acid scrubbers operating on
sulfide concentrate roasters is treated is treated to
remove the dissolved mercury by cementation with
aluminum metal pellets. It produces a solid residue,
which is primarily elemental mercury.
No. Not enough information
available. Wastewater
treatment technology. See
Section 1.3.2.
Hydrometallurgical:
Recovery of Mercury
and Selenium from
Roaster Gas
References:
EPA, 1993b
SENES, 2001
A sulfatization process is used to remove mercury
from roaster gases. After dust removal from the
mercury bearing off-gases, they are contacted with a
recirculating 90% sulfuric acid in a sulfatizing tower
and then in a weak acid scrubber to remove HC1 and
HgCl2 gases. The product from the sulfatizing unit
contains selenium (if present in concentrate) that upon
washing leaves a complex mercury-selenium
precipitate. A controlled potential sulfite-chloride
leach procedure then recovers mercury as a precipitate
(Hg2 SO3) and elemental selenium.
No. Not enough information
available. Off-gas treatment
system not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
Hydrometallurgical:
Ethylene Leaching
References:
EPA, 1993b
SENES, 2001
Ethylene gas is the reagent used to form a strong
complex with Hg+2. The process is operated at a gas
pressure of 4 atmospheres, and after the leach
procedure, releasing the pressure can precipitate HgO.
No. Not enough information
available. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
Mercury Reducing
Bacteria - Completely
Mixed Bioreactor
References:
EPA, 1993c
SENES, 2001
Biological detoxification using mercury-resistant
bacteria in a completely mixed, aerobic biological
treatment process has been shown to have a capability
for long-term removal of mercury from polluted water
or soil slurry.
No. Not enough information
available. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
Mercury Reducing
Bacteria - Fixed Bed
Bioreactor
References:
EPA, 1993d
SENES, 2001
Process development of bioreactors utilizing Hg
reducing bacteria has shown that reduced Hg can be
retained within a fixed bed bioreactor. This offers the
possibility of reclaiming Hg+2 removed from the waste
in a concentrated, less toxic and potentially reusable
form. This bacterial reduction system might be
utilized also for on-site remedial projects, since
volatilized Hg is less toxic and bioavailable.
No. Not enough information
available. Not suitable for the
treatment of bulk elemental
mercury. See Section 1.3.2.
B-10
-------
APPENDIX C
ENVIRONMENTAL PERFORMANCE DATA
Available environmental performance data are presented in this appendix for the treatment
technologies identified in this report. In the past several years EPA and DOE have evaluated
various treatment technologies for wastes containing a wide range of mercury, from 'low
mercury' solid wastes of less than 260 mg/kg to elemental mercury. The tests and programs
conducted are summarized in Table C-1. Detailed information concerning each program is
presented in Tables C-2 to C-6.
Table C-l Summary of Available Environmental Performance Data
Reference
Sanchez (2001). Evaluated
mercury -contaminated soil,
~ 4,500 ppm
USEPA (2002a). Evaluated
mercury waste, ~ 5,000 ppm
USEPA (2002b). Evaluated
elemental mercury
USDOE (1999a and 1999b).
Elemental mercury
USDOE (1999c, 1999d, 1999e).
Mercury -contaminated waste,
<260 ppm)
Participating Vendors/
Wastes Evaluated
ATG
BNL
Unnamed vendor
Four vendors
Three vendors. In addition, there
was limited testing of simulated
mercury selenide
NFS
ADA
NFS
GTS Duratek
ATG
Major Tests Conducted
Evaluate mercury leaching with
respect to pH and liquid-to-solid
ratio
Evaluate mercury leaching with
respect to pH
Evaluate mercury leaching with
respect to pH
TCLP
TCLP
C-l
-------
Table C-2 Summary of Treatment Performance Data for Mercury Contaminated Soil from Sanchez (2001)
Property
Concentration reduction from
treatment
Acid and base neutralization
capacity
pH of treated waste
Mercury solubility as a
function of pH
Description and Purpose of Test
The total concentration of the untreated
material is always greater than the total
concentration of the treated material.
Sanchez cautions that it is unknown to what
extent this reduction is due to dilution by the
treatment process, volatilization, or sample
heterogeneity
Measures the buffering capacity. A high
buffering capacity provides greater stability
from external changes in disposal conditions
Identifies equilibrium pH of material.
Identifies mercury solubility in various pH
conditions over the range of 2 to 13 at a
Liquid to Solid (LS) ratio of 10. The pH
conditions were adjusted using nitric acid
and potassium hydroxide.
Result for ATG
66% reduction in
concentration, from
untreated to treated
Increased from 1 mEq
acid/gram (for
untreated soil) to 10
mEq acid/gram (for
treated soil).
pH = 12.7 (treated);
pH = 7.8 (untreated)
The mercury
solubility was its
lowest at pH 12.7 (at
levels below UTS of
0.025 mg/L). From
pH 2 to 10, the
solubility was
consistently greater
than UTS. In disposal
conditions, Sanchez
theorizes that the
alkaline matrix will
result in uptake of
carbon dioxide, and
subsequently lower
the pH of the matrix
to 8-9 (where mercury
solubility is higher).
Result for
Unnamed Vendor
30% reduction in
concentration, from
untreated to treated
Increased from 1 mEq
acid/gram (for
untreated soil) to 6
mEq acid/gram (for
treated soil).
pH = 10.2 (treated);
pH = 6.8 (untreated)
The mercury
solubility was its
lowest at pH 10.2 (at
levels below UTS of
0.025 mg/L). From
pH 4 to 8, the
solubility was
consistently greater
than UTS. In disposal
conditions, Sanchez
theorizes that the
alkaline matrix will
result in uptake of
carbon dioxide, and
subsequently lower
the pH of the matrix
to levels where
mercury solubility is
higher.
Result for BNL
SPSS
70% reduction in
concentration, from
untreated to treated
Very little difference
between untreated
and treated soil (both
about 1 mEq
acid/gram).
pH = 9.7 (treated); pH
= 6.6 (untreated)
The mercury
solubility was its
lowest at pH less than
2 (at levels below
UTS of 0.025 mg/L).
From pH 2 to 13, the
solubility was
somewhat constant
but consistently
greater than UTS
C-2
-------
Table C-2 Summary of Treatment Performance Data for Mercury Contaminated Soil from Sanchez (2001) (Continued)
Property
pH and solubility vs. LS ratio
Mercury availability
Mass transfer rate
Description and Purpose of Test
The pH and mercury solubility was
monitored at five different LS ratios from
0.5 to 10. (In comparison, the TCLP uses an
LS of 20.) Lower LS ratios (ratio of liquid
to solid quantities) provide an
approximation of pore water concentrations.
Mercury was extracted at two different pH
values (4 and 8) at a high LS ratio (100) to
avoid solubility limitations. Availability
defines the fraction of total mercury present
that might be released over an infinite time
period under extreme environmental
conditions.
Mercury was extracted with deionized water
following leaching times ranging from 2
hours to 8 days, generating 7 different
samples. Unlike most leaching tests
involving 'shaker flasks,' this test was
conducted where only the surface of
compacted waste was exposed to the
leachant and no mixing occurred. The
purpose of this test is to assess the release
rate of mercury from compacted granular
matrices under mass transfer-controlled
release conditions.
Result for ATG
For the treated waste,
the pH was relatively
constant at 12.7 for all
LS variations. The
solubility ranged from
0.001 mg/L (at highest
LS ratio) to 5 mg/L (at
lowest LS ratio)
Therefore, the UTS
limit of 0.025 mg/L
was exceeded for the
lower LS ratios
Mercury availability
at pH 8 was 10% of
the total, while
availability at pH 4
was 26% of the total.
The availability of
untreated waste at pH
8 was 0.2%,
indicating that
treatment increases
availability.
The final pH of the
leachant from the
treated waste was 10.8
to 12.0, which is
consistent with prior
pH tests. The
cumulative release of
mercury was 0.03%,
and similar to the
release of the
untreated mercury.
The diffusivity was
1.3xlO-16m2/s.
Result for
Unnamed Vendor
For the treated waste,
the pH was relatively
constant at 10 for all
LS variations. The
solubility was less
than the UTS limit of
0.025 mg/L at all LS
ratios, with
concentration
increasing with lower
LS ratios.
Mercury availability
at pH 4 and 8 was
each 2.5% of the total.
The availability of
untreated waste at pH
4 and 8 was each
0.003%, indicating
that treatment
increases availability.
The final pH of the
leachant from the
treated waste was 7.9
to 9.4, which is
slightly lower than in
prior pH tests. The
cumulative release of
mercury was
0.0002%, and much
less than the release
of the untreated
mercury. The
diffusivity was
1.0xlO-20m2/s.
Result for BNL
SPSS
For the treated waste,
the pH slightly
increased from 9.7 to
10.2 as LS decreased.
The solubility was
greater than the UTS
limit of 0.025 mg/L at
all LS ratios, with
concentration
decreasing with lower
LS ratios.
Mercury availability
at pH 4 and 8 was
2.7% and 0.9%,
respectively, of the
total. The availability
of untreated waste at
pH 4 and 8 was each
0.003%, indicating
that treatment
increases availability.
The final pH of the
leachant from the
treated waste was 6.3
to 8.9, which is
slightly lower than in
prior pH tests. The
cumulative release of
mercury was 0.015%,
and much less than
the release of the
untreated mercury.
The diffusivity was
2.5xlQ-17 m2/s.
C-3
-------
Table C-2 Summary of Treatment Performance Data for Mercury Contaminated Soil from Sanchez (2001) (Continued)
Property
100-year release estimates
Description and Purpose of Test
Based on prior measurements, the estimated
quantity of mercury released over 100 years
was estimated. Calculations are made at
several different disposal pH conditions and
two different rate-limiting step assumptions.
These assumptions are either that the water
percolates through the material (and
therefore equilibrium concentrations limit
the rate of release) or that the water flows
around the material (and therefore mass
transfer within the solid matrix limits the
rate of release).
Result for ATG
Several different
estimates of release
rate were obtained.
At the equilibrium pH
of the material (12.7),
between 0.001 and
1.8% would be
released. Much
higher percentages (up
to 30%) would be
released at conditions
of pH 5 (e.g., due to
acidification during
disposal). With a
diffusion-controlled
assumption, 0.4
percent of the material
is released.
Result for
Unnamed Vendor
Several different
estimates of release
rate were obtained.
At the equilibrium pH
of the material (10.2),
less than 0.009%
would be released.
Much higher
percentages (up to
8%) would be
released at conditions
of pH 5 (e.g., due to
acidification during
disposal). With a
diffusion-controlled
assumption, 0.004
percent of the
material is released.
Result for BNL
SPSS
Several different
estimates of release
rate were obtained.
At the equilibrium pH
of the material (9.7),
0.5% would be
released. Similar
percentages (0.4%)
would be released at
conditions of pH 5
(e.g., due to
acidification during
disposal). With a
diffusion-controlled
assumption, 0.2
percent of the
material is released.
The Sanchez (2001) study used two different mercury-contaminated soils, each containing about 4,500 mg/kg mercury in addition to containing radionuclide components.
Three treatment processes were used: the BNT amalgamation and encapsulation process, a Portland cement stabilization/solidification process by ATG, and a third vendor
whose name was withheld from the study results at their request. Each vendor only evaluated one soil type.
C-4
-------
Table C-3 Summary of Treatment Performance Data for Mercury Surrogate Waste from USEPA (2002a)
Property
Waste loading
Volume increase
Air loss
Cation exchange capacity
pH of treated waste
Redox
Mercury solubility as a
function of pH
Percent leached as a
function of pH
Description and
Purpose of Test
Correlates to the quantity of
additives; a 100% waste loading
indicates no dilution)
Vendor-reported, approximate
increase in volume between
untreated and treated form.
Vendor-reported loss to air during
treatment
Determines extractable quantities of
certain alkali and alkaline earth
metals; higher capacities indicate a
higher potential to hold other
cations such as toxic metals.
Identifies equilibrium pH of
material.
Measures oxidation-reduction
potential. An oxidizing (aerobic)
environment is represented by a
positive value
Identifies mercury mobility in
various pH conditions over the
range of 2 to 12 at an LS ratio of 20
(the same LS as used for TCLP).
The pH conditions were adjusted
using nitric acid and sodium
hydroxide.
Uses above data for calculations of
percentage leached during the test
Result for
Vendor A
30%
36% increase
Estimated 0.3%
0.9 to 2.0 mEq/g
treated; 1.7 mEq/g
untreated
-7.0 treated; 1.9
untreated
-30 to -60 mV
treated; +520 mV
untreated
The mercury
solubility was
consistently below
UTS (0.025 mg/L)
from pH 2 to 10.
The concentration
rose significantly at
pH12.
The treated waste
leached from 0.001
to 0.1 3% between pH
2 and 10; leaching
increased to 3.5% at
pH12.
Result for
Vendor B
72%
No data
No data
1.6 to 3.0 mEq/g
treated; 1.5 mEq/g
untreated
-6.2 treated; -1.4
untreated
60 to 120 mV
treated; +550 mV
untreated
The mercury
solubility was
consistently above
UTS (0.025 mg/L)
from pH 2 to 10, with
higher concentration
at lower pH. The
concentration
dropped below UTS
atpH12.
The treated waste
leached less than
0.02% at pH 12. It
leached a maximum
of 13% mercury at
lower pH.
Result for
Vendor C
45%
No data
Estimated
0.05%
0.5 to 5.2
mEq/g treated;
1.7 to 2.0
mEq/g
untreated
-8.9 treated; 1.8
untreated
-100 to +210
mV treated;
+580 mV
untreated
The mercury
solubility was
highest at pH of
2. The
concentration
was at or below
UTS at pH 8 to
12.
The treated
waste leached
less than 0.06%
at pH 4 and
above, and up to
6%atpH2.
Result for Vendor
D
25%
25% increase
No data
2.3 to 2.5 mEq/g
treated; 1.3 mEq/g
untreated
-9.7 treated; -1.6
untreated
-20 to -90 mV
treated; +580 mV
untreated
The mercury
solubility was
highest at pH of 4.
The concentration
was at or above
UTS at other pH
values, with a low
atpH12.
The treated waste
leached between
0.02% and 4%
mercury
The USEPA (2002a) study
treat' waste. The mercury
used a surrogate waste comprised of five different compound and elemental forms of mercury, and other additives, to simulate a 'difficult to
content was 5,000 ppm. Four treatment processes were used.
C-5
-------
Table C-4 Summary of Treatment Performance Data for Elemental Mercury from USEPA (2002b)
Property
Waste loading
Volume increase
Loss to Air
Cation exchange capacity
pH of treated waste
Redox
Mercury solubility as a
function of pH
Percent leached as a
function of pH
Description and
Purpose of Test
Correlates to the quantity of additives; a
100% waste loading indicates no
dilution)
Vendor-reported, approximate increase
in volume between untreated and treated
form.
Vendor-reported loss to air during
treatment
Determines extractable quantities of
certain alkali and alkaline earth metals;
higher capacities indicate a higher
potential to hold other cations such as
toxic metals.
Identifies equilibrium pH of material.
Measures oxidation-reduction potential.
An oxidizing (aerobic) environment is
represented by a positive value
Identifies mercury mobility in various
pH conditions over the range of 2 to 12
at an LS ratio of 20 (the same LS as used
for TCLP). The pH conditions were
adjusted using nitric acid and sodium
hydroxide. The chloride addition (for
one treated waste only) simulates co-
disposal conditions.
Uses above data for calculations of
percentage leached during the test
Result for
Vendor A
33%
1500% increase
Estimated 0.3%
0.4 to 0.8 mEq/g
treated
11.0 treated
-460 mV treated
The mercury
solubility was
below UTS (0.025
mg/L) at pH 2 and
pHll. The
concentration was
highest at pH 12,
and in the pH range
6 to 8.
The treated waste
leached a maximum
of 1.0% (pH 12)
and a minimum of
0.00003 (pH 2).
Result for
Vendor B
44-55%
No data
No data
0.4 to 0.5 mEq/g
treated
6. 9 to 8.1 treated
-10 to -80 mV
treated
The mercury
solubility was
consistently below
UTS (0.025 mg/L)
from pH 2 to 10,
with concentration
increasing with
increasing pH.
The treated waste
leached less than
0.0007% at pH 12,
the maximum rate.
Result for
Vendor C
20%
No data
None expected
1.4 to 2.1 mEq/g
treated
-10 treated
-650 to -850 mV
treated
The mercury
solubility was
highest at pH of 2.
The concentration
was between the
TCLP (0.2 mg/L)
and the UTS from
pH 6 to 12.
The treated waste
leached less than
0.004% between pH
6 and 12, and up to
0.4% at pH 2.
Result for HgSe
Reagent-grade
mercury selenide
was leached at
pH 7 and 10 with
and without
chloride to
simulate co-
disposal.
Leaching was
lower at pH 7
and with no
added chloride.
The treated waste
leached less than
0.00006%
without added
chloride and up
to 0.0003% with
chloride.
The USEPA (2002b) study used lab-scale batch sizes of elemental mercury (less than one kg). Three treatment processes were used.
C-6
-------
Table C-5 Other DOE Elemental Mercury Studies
Property
Waste loading
TCLP from two waste sources
Vapor measurements during
treatment step
Description or
Purpose of test
Correlates to the
quantity of additives; a
100% waste loading
indicates no dilution)
TCLP - current EPA
standard, although the
regulation does not
apply to elemental
mercury.
Quantifies air releases
of mercury from the
process
Results: NFS DeHg
Process (DOE 1999a)
20 to 25%
The results from 14
'two step' treatment
batches (amalgamation
plus stabilization)
showed results ranging
from 0.02 to 0. 12 mg/L,
with four results below
UTS. A 'one step'
treatment
(amalgamation only)
produced much higher
results, ranging from
0.05 to 7.5 mg/L.
No information
Results: ADA Process
(DOE 1999b)
50 to 60%
Not detected (<0.1
mg/L) TCLP in five
batches; additional
testing of composites
showed results of 0.035
to 0.048 mg/L (which is
between UTS and TC
limits)
Less than OSHA limit
of 50 ug/m3 in five
batches
The waste was radioactively-contaminated mercury from DOE sites.
C-7
-------
Table C-6 Other DOE Mercury Waste Studies
Reference and Vendor
DOE 1999e; NFS DeHg
Process
DOE 1999d; GTS Duratek
Process
DOE 1999c;ATG Process
Waste Type
Ion-exchange resin (<260
ppm mercury)
Sludge (<260 ppm
mercury)
Ion-exchange resin (<260
ppm mercury)
TCLP Results
0.0 11 to 0.025 mg/L,
treated, based on two
samples
0.001 to 0.031 mg/L,
treated, based on two
batches
5 of 7 different additive
formulations resulted in
treatment to below UTS.
The overall range was
0.006 to 0.11 mg/L TCLP
Weight or
Volume Increase
No information
No information
15% weight and 24%
volume, using formulation
giving lowest TCLP
measurements
C-8
-------
REFERENCES FOR APPENDIX C
DOE 1999a. U.S. Department of Energy. Mercury Contamination -Amalgamate (contract with NFS and
ADA) Demonstration of DeHgSM Process. Mixed Waste Focus Area, Innovative Technology Summary
Report, DOE/EM-0471, prepared for Office of Environmental Management, Office of Science and
Technology, September 1999. http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999b. U.S. Department of Energy. Mercury Contamination - Amalgamate (contract with NFS
and ADA) Stabilize Elemental Mercury Wastes. Mixed Waste Focus Area, Innovative Technology
Summary Report, DOE/EM-0472, prepared for Office of Environmental Management, Office of Science
and Technology, September 1999. http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999c. U.S. Department of Energy. Demonstration ofATG Process for Stabilizing Mercury (<260
ppm) Contaminated Mixed Waste. Mixed Waste Focus Area, Innovative Technology Summary Report,
DOE/EM-0479, prepared for Office of Environmental Management, Office of Science and Technology,
September 1999. http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999d. U.S. Department of Energy. Demonstration of GTS Duratek Process for Stabilizing
Mercury (< 260 ppm) Contaminated Mixed Waste. Mixed Waste Focus Area, Innovative Technology
Summary Report, DOE/EM-0487, prepared for Office of Environmental Management, Office of Science
and Technology, September 1999. http://apps.em.doe.gov/ost/itsrtmwfa.html.
DOE 1999e. U.S. Department of Energy. Demonstration of NFS DeHg Process for Stabilizing Mercury
(<260 ppm) Contaminated Mixed Waste. Mixed Waste Focus Area, Innovative Technology Summary
Report, DOE/EM-0468, prepared for Office of Environmental Management, Office of Science and
Technology, September 1999. http://apps.em.doe.gov/ost/itsrtmwfa.html.
Sanchez 2001. Sanchez, F., Kosson, D.S., Mattus, C.H., and Morris, M.I. Use of a New Leaching Test
Framework for Evaluating Alternative Treatment Processes for Mercury Contaminated Mixed Waste
(Hazardous and Radioactive). Vanderbilt University, Department of Civil and Environmental
Engineering. December 14,2001. http://www.cee.vanderbilt.edu/cee/researchjrojects.html.
USEPA 2002a. U.S. Environmental Protection Agency. Technical Background Document: Mercury
Wastes. Evaluation of Treatment of Mercury Surrogate Waste. Final Report. February 8, 2002.
USEPA 2002b. U.S. Environmental Protection Agency. Technical Background Document: Mercury
Wastes. Evaluation of Treatment of Bulk Elemental Mercury. Final Report. February 8, 2002.
C-9
-------
APPENDIX D
EVALUATION OF TREATMENT AND DISPOSAL ALTERNATIVES
This appendix details the derivation of the values of the intensities assigned to each criterion for
each of the eight alternatives involving treatment and disposal. This is conducted using
individual information on treatment and disposal presented in the main section of this report. In
most cases this integration was straightforward. Tables D-l to D-8 in this appendix provide more
detailed explanations for each alternative individually. Each table identifies the assigned value
for the treatment disposal sequence based on information on the items separately. Explanations
are included in these tables where needed. In several cases, information about a treatment step
differs from the information about a disposal step. In such cases, information about the step
likely to be the 'bottleneck' was used for the entire treatment/ disposal sequence. For example,
the first criterion is compliance with current laws and regulations. In most cases, it is expected
that the treatment process is relatively easy to conduct in the current regulatory framework and
the disposal step is currently prohibited. Therefore, the composite value for the sequence as a
whole is assigned the more stringent value associated with the disposal step.
The alternatives identified in this appendix are as follows:
Stabilization/amalgamation followed by disposal in a RCRA- permitted landfill
(Table D-l)
Stabilization/amalgamation followed by disposal in a RCRA- permitted monofill
(Table D-2)
Stabilization/amalgamation followed by disposal in an earth-mounded concrete bunker
(Table D-3)
Stabilization/amalgamation followed by disposal in a mined cavity (Table D-4)
Selenide treatment followed by disposal in a RCRA- permitted landfill (Table D-5)
Selenide treatment followed by disposal in a RCRA- permitted monofill (Table D-6)
Selenide treatment followed by disposal in an earth-mounded concrete bunker
(Table D-7)
Selenide treatment followed by disposal in a mined cavity (Table D-8)
D-l
-------
Table D-l Evaluation for Treatment Disposal Option: Stabilization/Amalgamation
Followed by Disposal in a RCRA-Permitted Landfill
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume of
waste
Implementation
considerations: engineering
requirements
Maturity of the technology:
state of maturity of the
technology
Maturity of the technology:
expected reliability of
treatment operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental performance:
discharges during treatment
Environmental performance:
degree of performance
testing
Environmental performance:
stability of conditions in the
long term
Environmental performance:
ability to monitor
Public perception
Implementation costs
Operating costs
Amalgamation/ Stabilization
Treatment
Would require permitting
through existing regulatory
structure
Volume increase about 1 5x
Simple components
Not commercial scale
Simple components and batch
processing
Very low
Very low because large
quantities of mercury will not
be present
Very low because large
quantities of mercury will not
be present
Minimal discharges expected
Moderate: TCLP and
additional testing performed
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
RCRA-Permitted
Landfill
Non-compliant with
LDRs
Not applicable (affected
by treatment, not
disposal)
An existing commercial
landfill can be used
Very mature in U.S.
Not applicable
Very low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Fan-
Easy
Negative
Low (existing unit can
be used)
Low
Overall Sequence
Non-compliant with LDRs
(assigned the more
restrictive value for the
disposal step)
Volume increase above
lOx
Existing facilities can be
used (it is assumed that the
treatment sequence can be
quickly integrated into
existing landfill treatment
operations)
Pilot treatment/
full-scale disposal
Simple
Very low
Very low (very low risks
for both treatment and
disposal)
Very low (very low risks
for both treatment and
disposal)
Minimal
Moderate
Fair
Easy
Negative (the disposal step
is permanent while
treatment is temporary)
Low (additive between
treatment and disposal;
even with unknowns still
expected to be a lower cost
alternative)
Low (additive between
treatment and disposal;
even with unknowns still
expected to be a lower cost
alternative)
D-2
-------
Table D-2 Evaluation for Treatment Disposal Option: Stabilization/Amalgamation
Followed by Disposal in a RCRA-Permitted Monofill
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume
of waste
Implementation
considerations:
engineering requirements
Maturity of the
technology: state of
maturity of the
technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long
term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Amalgamation/
Stabilization Treatment
Would require permitting
through existing regulatory
structure
Volume increase about 1 5x
Simple components
Not commercial scale
Simple components and
batch processing
Very low
Very low because large
quantities of mercury will
not be present
very low because large
quantities of mercury will
not be present
Minimal discharges expected
Moderate: TCLP and
additional testing performed
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
RCRA-Permitted
Monofill
Non-compliant with
LDRs
Not applicable
(affected by
treatment, not
disposal)
New in-ground
construction is
required
Very mature in U.S.
Not applicable
Very low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Good
Easy
Negative
Medium (requires
new construction)
Low
Overall Sequence
Non-compliant with LDRs
(assigned the more restrictive
value for the disposal step)
Volume increase above lOx
A new facility must be
constructed (monofill
construction would require more
complex effort than treatment
sequence)
Pilot treatment/ full-scale
disposal
Simple
Very low
Very low (very low risks for
both treatment and disposal)
Very low (very low risks for
both treatment and disposal)
Minimal
Moderate
Good
Easy
Negative (the disposal step is
permanent while treatment is
temporary)
Medium (additive between
treatment and disposal)
Low (additive between treatment
and disposal)
D-3
-------
Table D-3 Evaluation for Treatment Disposal Option: Stabilization/Amalgamation
Followed by Disposal in an Earth-Mounded Concrete Bunker
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume of
waste
Implementation
considerations:
engineering requirements
Maturity of the
technology: state of
maturity of the technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long
term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Amalgamation/
Stabilization Treatment
Would require permitting
through existing regulatory
structure
Volume increase about 15x
Simple components
Not commercial scale
Simple components and batch
processing
Very low
Very low because large
quantities of mercury will not
be present
Very low because large
quantities of mercury will not
be present
Minimal discharges expected
Moderate: TCLP and
additional testing performed
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
Earth-Mounded
Concrete Bunker
Non-compliant with
LDRs
Not applicable
(affected by treatment,
not disposal)
New in-ground
construction is
required
Technology has been
applied but not widely
used
Not applicable
Very low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Good
Easy
Positive to neutral
High (costs are likely
higher than monofill)
Medium
Overall Sequence
Non-compliant with LDRs
(assigned the more restrictive
value for the disposal step)
Volume increase above lOx
A new facility must be
constructed (bunker construction
would require more complex
effort than treatment sequence)
Pilot treatment/ untested disposal
Simple
Very low
Very low (very low risks for both
treatment and disposal)
Very low (very low risks for both
treatment and disposal)
Minimal
Moderate
Good
Easy
Positive to neutral
High (additive between treatment
and disposal)
Medium (additive between
treatment and disposal)
D-4
-------
Table D-4 Evaluation for Treatment Disposal Option: Stabilization/Amalgamation
Followed by Disposal in a Mined Cavity
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume
of waste
Implementation
considerations:
engineering requirements
Maturity of the
technology: state of
maturity of the
technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long
term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Amalgamation/
Stabilization Treatment
Would require permitting
through existing regulatory
structure
Volume increase about 15x
Simple components
Not commercial scale
Simple components and
batch processing
Very low
Very low because large
quantities of mercury will
not be present
Very low because large
quantities of mercury will
not be present
Minimal discharges expected
Moderate: TCLP and
additional testing performed
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
Mined Cavity
Non-compliant with
LDRs and unusual
permitting may be
required
Not applicable
(affected by
treatment, not
disposal)
Construction would
be more complex
than other
alternatives
Technology has been
applied but not
widely used
Not applicable
Low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Very good
Difficult
Positive to neutral
High(costs are likely
higher than monofill)
Medium
Overall Sequence
Atypical permit required (assigned
the more restrictive value for the
disposal step)
Volume increase above lOx
A mine cavity construction is
required (mine construction would
require more complex effort than
treatment sequence)
Pilot treatment/ untested disposal
Simple
Low (assigned the more restrictive
value from the disposal step)
Very low (very low risks for both
treatment and disposal)
Very low (very low risks for both
treatment and disposal)
Minimal
Moderate
Very good
Difficult
Positive to neutral
High (additive between treatment
and disposal)
Medium (additive between
treatment and disposal)
D-5
-------
Table D-5 Evaluation for Treatment Disposal Option: Selenide Process Followed by
Disposal in a RCRA-Permitted Landfill
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume of
waste
Implementation
considerations:
engineering requirements
Maturity of the
technology: state of
maturity of the technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Selenide Process
Would require permitting
through existing regulatory
structure
Volume increase not known,
assumed similar to others
More capital requirements
and relatively complex
Commercial scale for
mercury wastes but not for
elemental mercury.
Quantities of wastes treated
are likely much less than
quantities of elemental
mercury.
Relatively complex and
continuous processing
Higher than other
alternatives due to high
temperatures and additional
toxic chemical
Very low because large
quantities of mercury will
not be present
Very low because large
quantities of mercury will
not be present
Minimal discharges expected
Low: limited testing
performed by EPA
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
RCRA-
Permitted
Landfill
Non-compliant
with LDRs
Not applicable
(affected by
treatment, not
disposal)
An existing
commercial
landfill can be
used
Very mature in
U.S.
Not applicable
Very low
Very low
(because
underground)
Very low
(because
underground)
Not applicable
Not applicable
Fair
Easy
Negative
Low (existing
unit can be
used)
Low
Overall Sequence
Non-compliant with LDRs
(assigned the more restrictive value
for the disposal step)
Volume increase above lOx
New facilities are needed (it is
assumed that the treatment
sequence is more of a limiting
factor here than for S/A)
Pilot treatment/ full-scale disposal
Complex
Low (assigned the more restrictive
value from the treatment step)
Very low (very low risks for both
treatment and disposal)
Very low (very low risks for both
treatment and disposal)
Minimal
Low
Fair
Easy
Negative (the disposal step is
permanent while treatment is
temporary)
Low (additive between treatment
and disposal; even with unknowns
still expected to be a lower cost
alternative)
Low (additive between treatment
and disposal; even with unknowns
still expected to be a lower cost
alternative)
D-6
-------
Table D-6 Evaluation for Treatment Disposal Option: Selenide Process Followed by
Disposal in a RCRA-Permitted Monofill
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume of
waste
Implementation
considerations:
engineering requirements
Maturity of the
technology: state of
maturity of the technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability of
conditions in the long term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Selenide Process
Would require permitting
through existing regulatory
structure
Volume increase not known,
assumed similar to others
More capital requirements
and relatively complex
Commercial scale for
mercury wastes but not for
elemental mercury.
Quantities of wastes treated
are likely much less than
quantities of elemental
mercury.
Relatively complex and
continuous processing
Higher than other
alternatives due to high
temperatures and additional
toxic chemical
Very low because large
quantities of mercury will
not be present
Very low because large
quantities of mercury will
not be present
Minimal discharges
expected
Low: limited testing
performed by EPA
Not applicable
Not applicable
Neutral
Extremely variable
estimates
Costs will be from the initial
treatment
RCRA-
Permitted
Monofill
Non-compliant
with LDRs
Not applicable
(affected by
treatment, not
disposal)
New in-ground
construction is
required
Very mature in
U.S.
Not applicable
Very low
Very low
(because
underground)
Very low
(because
underground)
Not applicable
Not applicable
Good
Easy
Negative
Medium
(requires new
construction)
Low
Overall Sequence
Non-compliant with LDRs
(assigned the more restrictive
value for the disposal step)
Volume increase above lOx
New facilities are needed (for
both treatment and disposal)
Pilot treatment/ full-scale disposal
Complex
Low (assigned the more
restrictive value from the
treatment step)
Very low (very low risks for both
treatment and disposal)
Very low (very low risks for both
treatment and disposal)
Minimal
Low
Good
Easy
Negative (the disposal step is
permanent while treatment is
temporary)
Medium (additive between
treatment and disposal)
Low (additive between treatment
and disposal; even with unknowns
still expected to be a lower cost
alternative)
D-7
-------
Table D-7 Evaluation for Treatment Disposal Option: Selenide Process Followed by
Disposal in an Earth-Mounded Concrete Bunker
Criteria
Compliance with current
laws and regulations
Implementation
considerations: volume
of waste
Implementation
considerations:
engineering
requirements
Maturity of the
technology: state of
maturity of the
technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance: discharges
during treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability
of conditions in the long
term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Selenide Process
Would require permitting through
existing regulatory structure
Volume increase not known,
assumed similar to others
More capital requirements and
relatively complex
Commercial scale for mercury
wastes but not for elemental
mercury. Quantities of wastes
treated are likely much less than
quantities of elemental mercury.
Relatively complex and
continuous processing
Higher than other alternatives due
to high temperatures and
additional toxic chemical
Very low because large quantities
of mercury will not be present
Very low because large quantities
of mercury will not be present
Minimal discharges expected
Low: limited testing performed by
EPA
Not applicable
Not applicable
Neutral
Extremely variable estimates
Costs will be from the initial
treatment
Earth-Mounded
Concrete Bunker
Non-compliant with
LDRs
Not applicable
(affected by treatment,
not disposal)
New in-ground
construction is
required
Technology has been
applied but not widely
used
Not applicable
Very low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Good
Easy
Positive to neutral
High (costs are likely
higher than monofill)
Medium
Overall Sequence
Non-compliant with LDRs
(assigned the more
restrictive value for the
disposal step)
Volume increase above
lOx
New facilities are needed
(for both treatment and
disposal)
Pilot treatment/ untested
disposal
Complex
Low (assigned the more
restrictive value from the
treatment step)
Very low (very low risks
for both treatment and
disposal)
Very low (very low risks
for both treatment and
disposal)
Minimal
Low
Good
Easy
Positive to neutral
High (additive between
treatment and disposal)
Medium (additive between
treatment and disposal)
D-8
-------
Table D-8 Evaluation for Treatment Disposal Option: Selenide Process Followed by
Disposal in a Mined Cavity
Criteria
Compliance with
current laws and
regulations
Implementation
considerations: volume
of waste
Implementation
considerations:
engineering
requirements
Maturity of the
technology: state of
maturity of the
technology
Maturity of the
technology: expected
reliability of treatment
operation
Risks: worker risk
Risks: public risk
Risks: susceptibility to
terrorism/sabotage
Environmental
performance:
discharges during
treatment
Environmental
performance: degree of
performance testing
Environmental
performance: stability
of conditions in the
long term
Environmental
performance: ability to
monitor
Public perception
Implementation costs
Operating costs
Selenide Process
Would require permitting
through existing regulatory
structure
Volume increase not
known, assumed similar to
others
More capital requirements
and relatively complex
Commercial scale for
mercury wastes but not for
elemental mercury.
Quantities of wastes treated
are likely much less than
quantities of elemental
mercury.
Relatively complex and
continuous processing
Higher than other
alternatives due to high
temperatures and additional
toxic chemical
Very low because large
quantities of mercury will
not be present
Very low because large
quantities of mercury will
not be present
Minimal discharges
expected
Low: limited testing
performed by EPA
Not applicable
Not applicable
Neutral
Extremely variable
estimates
Costs will be from the
initial treatment
Mined Cavity
Non-compliant with
LDRs and unusual
permitting may be
required
Not applicable (affected
by treatment, not
disposal)
Construction would be
more complex than other
alternatives
Technology has been
applied but not widely
used
Not applicable
Low
Very low (because
underground)
Very low (because
underground)
Not applicable
Not applicable
Very good
Difficult
Positive to neutral
High (costs are likely
higher than monofill)
Medium
Overall Sequence
Atypical permit required
(assigned the more restrictive
value for the disposal step)
Volume increase above lOx
A mine cavity construction is
required (mine construction
would require more complex
effort than treatment sequence)
Pilot treatment/ untested
disposal
Complex
Low (both treatment and
disposal steps have slightly
greater risks than other
alternatives)
Very low (very low risks for
both treatment and disposal)
Very low (very low risks for
both treatment and disposal)
Minimal
Low
Very good
Difficult
Positive to neutral
High (additive between
treatment and disposal)
Medium (additive between
treatment and disposal)
D-9
-------
APPENDIX E
DISPOSITION OF COMMENTS
The current report was first issued as a draft document on April 22, 2002. A presentation based
on the April 2002 version of this report was made during the Northeast Waste Management
Official's Association (NEWMOA) conference, Breaking the Mercury Cycle, held in Boston MA
on May 1 to 3, 2002. Comments on the report were solicited and comments were subsequently
received from the Defense Logistics Agency (DLA), EPA's Office of Solid Waste (OSW), EPA's
Office of Research and Development's (ORD's) Quality Assurance Review office, and from Paul
Randall of EPA ORD, who was EPA's Technical Lead Person (TLP) for the present work. The
disposition of these comments is addressed below.
COMMENTS FROM PAUL RANDALL, ORD
Mr. Randall sent the following comments. Rather than changing the report, the answers to his
questions are provided in a question and answer format.
Comments
"How can this information, this model, this software be used by the USEPA? What is required for
a technical person at the USEPA to perform other analysis? Is this software costly or is it
freeware? How many hours is required to learn this software? As you know, USEPA's Office of
Solid Waste is the office that will most likely implement any suggestion. Is this mercury
retirement model too complex to be implemented? Big picture questions: What overall impact can
this study have? Mercury retirement model: How can this be implemented by others (state
agencies, international)?
"Under conclusions and recommendations, what is required to implement these
recommendations? For example, it says, ' additional expert choice analyses could be conducted
in which certain alternatives are optimized. ' Can a technical person in the USEPA do this, or
does SAIC only have this expertise? How can the available information be revisited? How many
hours would it take to re-input the information and arrive at an answer? How long did it take to
arrive at a basic model for decision making? Is this mercury retirement model practical?
"How does the software take into consideration the varying effectiveness of each treatment
technology? Please be specific. How are the intensities calculated to incorporate the
effectiveness and leaching characteristics of each technology? It appears 3 of the technologies
were lumped into a stabilization/amalgamation category. "
DISCUSSION OF THESE POINTS IN A QUESTION AND ANSWER FORMAT IS
PRESENTED BELOW.
RESPONSES
1) How can this information, this model, this software be used by the USEPA?
SAIC is providing the complete report and the input files to the EPA to use however they desire
in the future. This includes this project and all derivative work that can be developed from the
ideas contained in the project. EPA owns the product. Examples of how EPA can use these
materials include: using the framework of the model with input from inter-Agency staff in
E-l
-------
revising the criteria weighting; and using the results in conjunction with other Agency data to
further develop mercury retirement policy options.
2) What is required for a technical person at the USEPA to perform other analysis?
At a minimum, a technical person from EPA needs only the software, this report, and input files
(whose essential elements are reproduced in this report). The software is relatively easy to learn,
and the screen shots in this report can be used in guiding the analyst in learning. In addition, the
web site www.expertchoice.com has many references, books, tutorials, example solutions, slide
shows, etc. to download for free or purchase. Many books and dissertations have been written on
the AHP algorithm, which is the engine of Expert Choice, and there are about 20,000 active users
use it. One of the software developers, Dr. Forman, also teaches Expert Choice locally in the
Washington B.C. area at George Washington University. In addition, some EPA staff may
already be trained in its use or be familiar with the product and EPA may want to determine if
this is the case.
3) Is this software costly or is it freeware?
The pricing depends on the single or team version, and number of licenses purchased. There is
also a 15 day free trial demo. For a single user, the price is estimated to be in the range of $1,000.
Such a user could replicate the analyses performed in this report and conduct similar evaluations.
4) How many hours is required to learn this software? As you know, USEPA's Office of Solid
Waste is the office that will most likely implement any suggestion. Is this mercury retirement
model too complex to be implemented?
SAIC built the model with the intent that EPA, not SAIC would be actually using it in the future.
EPA should find it easy to implement. As analytical models go, this one is not particularly
complex. The software can be learned in two or three days.
5) Big picture questions: What overall impact can this study have? Mercury retirement model:
How can this be implemented by others (state agencies, international)?
The model is intended to be shared at will by the EPA in any manner. The model may be most
suitable to be used centrally with results shared with a wider audience. As more experts get
involved with wider expertise, the model can be tweaked as desired. In addition, when ideas are
suggested that do not affect the outcomes significantly, they can be documented as considered but
not included. This will help keep the model manageable when expanded to a larger audience.
The results of the model can be used in development of EPA policy and recommendations to
others such as states or the international community.
6) Under conclusions and recommendations, what is required to implement these
recommendations? For example, it says, " additional expert choice analyses could be conducted
in which certain alternatives are optimized. " Can a technical person in the USEPA do this, or
does SAIC only have this expertise? How can the available information be revisited?
First, it should be emphasized that any additional Expert Choice analysis would require the
development of data, criteria, and intensities as described in the report. As noted above, we
believe that technical persons within EPA can implement this process with a manageable amount
of training. The expertise is not unique to SAIC. There are several ways in which the available
information could be revisited, of varying levels of complexity.
E-2
-------
One approach would be to take the database that has already been developed and change it - for
example, by adding extra criteria, or more alternatives, or by changing the intensities. This could
be done in a day or two through a brain-storming session.
A second method would involve developing a second Expert Choice model "from the ground up"
which would be appropriate for certain alternatives such as choosing between specific storage
options or specific stabilization treatment and disposal alternatives. This would require
identifying alternatives and criteria and formulating a new model; any person familiar with
Expert Choice and the alternatives would have the necessary expertise to do this.
Another method is to develop a separate algorithm (i.e., something other than Expert Choice).
One example is an algorithm that was developed for the DOE's National Energy Technology
Laboratory (NETL)1, known as an "Optimization Tool Kit." The Tool-kit integrates proven
program and project optimization and risk assessment approaches with advanced applications in
the area of optimization under uncertainty and integrated program management. It runs in the
Microsoft Windowsฎ environment using the Microsoft Projectฎ and Excelฎ platforms. These
standard tools are augmented with Monte Carlo simulation software and optimization algorithms.
The result is a powerful tool-kit that is easy to use, easy to explain, and provides a lot of
documentation. It has more capabilities than does Expert Choice because, for example, it can be
used for uncertainty analyses.
As noted above, this Tool-kit was developed for the US government. As such, it is also free to
the EPA but would require modification for this particular application. It was developed by Larry
Deschaine (SAIC) for a specific purpose (future energy production project selection), and would
need to be customized to be usable to the Mercury retirement project (e.g., different decision
variables and goals), which may best be conducted by SAIC. The tool would then be turned over
to EPA to use, however desired, in conjunction with appropriate and effective EPA training. The
DOE NETL paper provides a general description of the tool; a copy is attached. There already is
a training manual on the tool, which would be tailored for EPA as well.
The level of effort required by SAIC to develop such a tool depends on what answers are needed
and types of uncertainties. The conversion of the tool to the mercury project would take about 3-4
weeks, and additional runs and training would be on top of that. Tailoring the manual for the
EPA would take about a week extra, which would involve modifying existing templates, etc.
Additional time may be needed for training or integrating additional features requested by users.
Further discussion of this tool is presented below.
7) How many hours would it take to re-input the information and arrive at an answer?
All of the information used in the model is available from this report and from the input files. It
is a fairly straightforward exercise to duplicate the results presented in this report. Of course, the
time needed to conduct modifications to the existing model is dependent on the types of changes
proposed, but a great deal can be accomplished in a day or two of brain-storming.
1 Deschaine, L.; Rawls, P.; Manfredo, L.; Patel, J. "The DOE NETL Program and Project Source Selection, Risk
Quantifier, Management Support, and Optimization Tool-Kit." Published at the Society for Computer Simulation's
Advanced Technology Simulation Conference, Seattle WA, April 2001. A copy of this paper is attached.
E-3
-------
8) How long did it take to arrive at a basic model for decision making?
Two sessions were conducted. In an initial session, two days were spent brainstorming to
develop an initial set of criteria, weighting factors, and intensities. A period of a few weeks was
spent researching and applying the available information to this initial framework. Towards the
end of the project, an additional two-day session was spent to review the framework and discuss
what changes to make to better use the available information. These sessions involved three
members of SAIC's staff with experience in mercury retirement and risk assessment issues and
one member of SAIC's staff with in-depth knowledge of the software.
9) Is this mercury retirement model practical?
The results of the model are practical: i.e., they result in recommendations that can be
implemented. For example, one outcome of the study was the conclusion that it supports
continuing to store elemental mercury for a few decades until the treatment technologies are more
mature. This seems to be an eminently practical recommendation. Using and making
refinements to the model is also practical (i.e., relatively easy), as described above..
10) How does the software take into consideration the varying effectiveness of each treatment
technology? Please be specific.
The applied model used environmental performance as one criterion in assessing alternatives.
This criterion was comprised of sub criteria consisting of (1) discharges during treatment; (2)
degree of performance testing of the treatment technology; (3) stability of conditions in the long
term; and (4) ability to monitor long term conditions. Therefore, the model did not explicitly take
into account the varying effectiveness of each treatment technology. One reason is because
EPA's OSW is conducting an ongoing review of this information and preliminary results or
conclusions of this review were not available prior to the presentation of initial findings at the
Boston conference. Secondly, deciding amongst different vendors is a specific application, or
optimization, of an alternative. In place of these differences, other criteria relating to the
technologies were used.
Effectiveness can be integrated into the model using the existing Expert Choice analysis or the
above-mentioned algorithm tool for optimization. The difference between the Expert Choice
analysis and the NETL algorithms are that the EC gives the average value of the team vote (i.e.,
single point averages), while the NETL algorithms provide the distribution of the uncertainty in
the expert's knowledge and opinions. Given the data gaps and lack of clear conclusions
involving treatment efficiency, such an algorithm may be the more appropriate tool. However,
the EC software is much easier to use, whereas the NETL algorithms are more complex because
they include stochastic simulation (MonteCarlo / Latin Hypercube) and machine learning (genetic
algorithms) for decision optimization under uncertainty. For the DOE application, they have
been integrated with Excel and other commercial off-the shelf software to make it a little easier to
apply and read results.
11) How are the intensities calculated to incorporate the effectiveness and leaching
characteristics of each technology? It appears 3 of the technologies were lumped into a
stabilization/amalgamation category.
The leaching effectiveness of individual technologies was not assessed in this report. The three
vendors discussed were placed into a single category for a number of reasons. First, not all data
are publicly available or publicly attributable to a specific vendor. In other words, the results of a
E-4
-------
study cannot be traced back to a specific vendor without compromising prior agreements or
decisions to 'blind' the data. Second, the data are being evaluated by the Office of Solid Waste
(OSW) including the use of an external peer review process. It was felt that there is much to be
gained to allow this review to continue and to not duplicate this particular assessment effort given
the complexities that OSW is experiencing in assessing these data. Finally, without OSW
concurrence, we did not want to take the position in this report of favoring one vendor over
another.
Sections Changed to Address Paul Randall's Comments
Only one change was made: the end of Section S.4 was amended to clarify that evaluation of
individual treatment technologies was not conducted as part of the methodology.
COMMENTS FROM OSW
OSW provided the following comments:
Comments
"Overall, I think the report is good and will help inform some of the discussions that will be
occurring in the Quiksilver Caucus (QC)/EPA workgroups (and will be especially useful to some
of the newcomers to the subgroups). Having said this, my main comment focuses on the
conclusions and recommendations from page S-6.
"Rather than spend more money on further analyses (e.g., by adding additional experts, by
optimizing certain alternatives in the Expert Choice Software, by performing a formal uncertainty
analysis utilizing Monte-Carlo based techniques), it might make more sense to turn the process of
selecting the best alternatives for mercury retirement over to the QC/EPA group. I don't know
who besides SAIC was involved in drafting your report (maybe you could add a list somewhere in
the report so everyone knows), but I'm assuming we will have a more diverse group (i.e., not only
EPA HQs, but also States, Regions, DOD, DOE, USGS, and State organizations) available as
part of the QC/EPA group.
"Here are a couple of other comments:
"- By making the storage option really expensive (i.e., by assuming that in addition to storing,
eventually you would have to treat and dispose), the result is that storage doesn 't look that great
(at least not when you consider costs). You say as much on p. S-5. This is a critical assumption
that greatly colors the result of the analysis, and it is buried in the report. We think this should
be moved closer to the front.
"- The disposal options should consider additional environmental risks & costs (mine water and
landfill leachate collection and treatment for starters). Yellowknife is the prime example of use of
a mined shaft gone wrong. The water ate the concrete plugs and arsenic tailings ran out. "
Sections Changed to Address OSW Comments
Recommendation Item # 1 in the Conclusions and Recommendations (Section S.7 and Section
5.0) was amended so as to clarify that, so far, the development of criteria and intensities was
carried out by SAIC staff and that involving a more diverse group could lead to the development
of further insights.
E-5
-------
The opening Paragraph in Section 2 was amended, clarifying that SAIC developed the model,
criteria, etc., and who was involved. An additional, shorter explanation was added to Section S.4
of the Executive Summary. ORD had a similar comment (see below).
A footnote to Table S-l was added and additional discussion provided in Section S.4, to better
explain the assumptions about how costs were considered for storage options
The Yellowknife 'case study' for mine disposal was added to Section 3.3.1 and its application to
the environmental performance criteria is summarized in Section 3.3.6. The bibliography in
Section 6 was adjusted accordingly.
No changes to the model are necessary as a result of the OSW comments.
COMMENTS FROM DLA
DLA provided the following comments.
Comments
"... assuming that peer review supports the EPA studies, the MMEIS will only analyze three
alternatives in detail. These alternatives are: 1) consolidation and storage at one or more of the
current mercury storage sites or other suitable locations, 2) sale of the mercury inventory, and 3)
no action, maintaining storage at the four existing sites. The description of the DNSC MMEIS on
page S-2 should be changed to reflect this revision.
"Two of the draft SAIC report's assumptions differ significantly from those in the DNSC MMEIS.
Most important, the DNSC mercury is considered a commodity rather than a RCRA waste.
Second, the draft SAIC report assumes that containment bunkers will be constructed if mercury is
stored. Should one of the MMEIS storage alternatives be selected, DNSC could use existing
warehouses or munition bunkers. Use of existing facilities might more than offset the monitoring
and maintenance cost penalty of storage postulated on page 3-5 of the SAIC report. "
Sections Changed to Address DLA Comments
The discussion of the MMEIS on page S-2 was revised as suggested. The DLA letter was added
to the bibliography in Section 6.
Additional discussion regarding the 'RCRA waste' assumption was added to Section S.4 and
Section 3.1.1. An additional example was extracted from the literature and the bibliography
revised accordingly. Basically, SAIC made a conservative assumption that RCRA permits will
be required for the storage of bulk elemental mercury.
The discussion in Section 3.1.5 was changed to better show that the use of existing facilities could
result in lower costs.
An additional 'case study' of mercury storage was identified in the literature and added to Section
3.1.1 and the bibliography revised accordingly
No changes to the model are necessary as a result of the DLA comments.
E-6
-------
ORD QA REVIEW
Comments in the ORD QA review that require changes are as follows:
Comments
"Volume of Waste. Section 2.3.2, Sub-criterion 2A, page 2-1, and Table 2-2, page 2-7. Both the
text and the table list two intensity levels for volume of waste. However, Table A-l (Appendix A,
page A-13) lists three levels. This inconsistency should be resolved.
"Section S.5, page S-4, first full paragraph. The numerical rankings presented for the sub-
criterion "State of maturity of the treatment technology " (0.717, 0.205, and 0.078) are not
consistent with Table A-l, page A-l 3 (0.731, 0.188, 0.081).
"Section 2.3.7, page 2-5, last sentence of section. "Table 1" should be corrected to "Table 2-1. "
"Table 3-3, page 3-12. Under the criterion "Risks: susceptibility to terrorism/sabotage, "
columns 2 and 3 say "Low " risks rather than "Very low " risks, as in columns 3 and 4. This
appears to be a typo because there is no mention in the text as to why these treatment options
would have different risk levels.
"Section 3.4, page 3-19. Bullets 2, 3, and 4 should be indented further to distinguish between the
stabilization/amalgamation technologies and the selenide process. The paragraph above talks
about "two treatment options, " but the bullets appear to show five treatment options.
"Appendix A, Table A-l, page A-l 3. In the operating cost row, it appears that the value for
"High " should be corrected to 0.078. In the volume of waste row, it appears that the value for
"Increase greater than 10 times" should be corrected to 0.081.
"Appendix B, pages B-4 and B-5. Under "Chemical Leaching/Acid Leaching " and "Leaching-
Oxidation-Precipitation, " there are references to "EPA, 1999a. " However, this item is not
included in the Appendix B list of references.
"Defining "the team. " Section S.4, page S-3, first paragraph. The Expert Choice software
appears to have been used by a team of people for this application; however, "the team " is not
defined. It would be useful to describe the membership of this team. "
Sections Changed to Address ORD QA Review Comments
The number of intensity levels associated with the volume of waste (in Section 2.3.2 and Table 2-
2) was changed to be made consistent with the number of intensity levels in Appendix A (3).
The rankings for technology maturity criteria in Section S.5 were changed to be made consistent
with Appendix A, as suggested.
The referencing of Table 2-1 was changed as suggested.
The intensity listed in Table 3-3 for susceptibility to terrorist attack for two of the treatment
methods was changed as suggested. The change is consistent with the intensity used in the model
as identified in Table 3-6.
E-7
-------
The formatting of Section 3.4 was changed as suggested.
The intensities for operating cost and volume of waste in Table A-l were changed to be made
consistent with Figure A-4 and Figure A-10, respectively, as suggested.
Referencing of Appendix B was corrected and confirmed to be consistent with the 2001 Canadian
Study.
Clarification of the composition of "the team" that developed the model, etc., was made to
Section S.4 and the opening paragraph of Section 2. OSW had a similar comment (see above).
No changes to the model are necessary as a result of the ORD QA comments.
DOE-NETL TOOL-KIT
If you are reading this report as a .pdf file or as a paper document in a 3-ring binder, the paper
referenced in Footnote #1 included in this Appendix. If you are reading a Word document, the
paper is available separately as a .pdf file.
------- |