SVV947
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V
LAND DISPOSAL OF HAZARDOUS WASTE
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Summary of Panel Discussions
This document (SW-947) is a summary
of panel discussions sponsored by EPA on issues
related to land disposal of hazardous waste
US. Environmental Pr^t.:?' ^
Region V, Library
230 South Dearoorn Street
Chicago, Illinois 60604
U.S. ENVIRONMENTAL PROTECTION AC2NCY
May 18-22, 1981
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'.^j-.n/ironrnentaj footection A—_•
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This summary was prepared by Mitre Corp. under contract no. 68-01-6092;
it is reproduced as received from the contractor. Opinions expressed in
this document are those of the panel members and do not necessarily reflect
the views of EPA; nor does the mention of commercial products constitute
endorsement by the U.S. Government. . - "
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INTRODUCTION
This document is a summary of a series of panel discussions
held in the Washington, B.C. area by the Environmental Protection
Agency (EPA) during the week of May 18-22, 1981. The panel discussions
were held to provide a cross-section of experts' views on the technical
issues related to land disposal of hazardous wastes. The discussions
are being used by EPA as a source of information for formulating final
permitting standards for hazardous waste land disposal facilities.
However, the discussions focused on generic technical issues rather
than on proposed or potential regulatory provisions.
Four major topics were addressed during the five days the
discussions were held:
May 18 and 19: Leachate generation (quantity and quality);
attenuation in liners and the unsaturated
zone; and management approaches to control
leachate quantity and quality.
May 20: Predicting leachate plume migration in ground
water - modeling and monitoring.
May 21: Gas generation and migration; rates of
emissions; control practices; and dispersion
modeling.
May 22: Health effects resulting from exposure to
hazardous wastes disposal on or in the land.
Each discussion topic featured a different set of panelists
chosen through recommendations by industry trade associations, the
Association of State and Territorial Solid Waste Management Officials,
environmental groups, and upon EPA's knowledge of experts in the field.
Each panel was moderated by a cognizant EPA staff member. An agenda
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for each session was provided in advance that contained a detailed
list of questions and" discussion topics to be addressed by the panelists.
Copies of the agenda were distributed to the audience.
Since the regulated community, state regulatory agencies, environ-
mental groups, and the general public were likely to be interested in
the discussions, various members of these groups were invited to
attend the sessions. Members of the audience were provided the
opportunity in each session to ask questions of the panelists.
The moderator and panelists for each session are listed immediately
preceding the session's summary. To assist the reader in identifying
and locating particular topics and to provide a precis for each
session, a listing of specific technical issues and major points
raised is contained at the beginning of each day's summary. The agenda
for each session is contained in Appendix A. Appendix B contains a
listing of the attendees for each of the five days.
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TABLE OF CONTENTS
Paste
Introduction i
First Day, Leachate Generation and Attenuation
Introduction to the First Day 1-1
The Panel for the First Day 1-3
Technical Issues of the First Day 1-4
Summary of the First Day 1-5
1. Precipitation as a Source of Leaching Fluids 1-5
2. Use of Top Liners to Control Infiltration 1-7
3. Groundwater Infiltration 1-9
4. Liquids Produced by or Associated with Wastes 1-11
5. Predicting the Permeability of Clay Liners 1-14
6. Use of Synthetic Liners 1-17
7. Leachate Collection Systems 1-13
Second Day, Leachate Generation and Attenuation
Introduction to the Second Day 2-1
The Panel for the Second Day 2-3
Technical Issues of the Second Day 2-4
Summary of the Second Day 2-5
1. Prediction of Leachate Quality from a
Single Waste Stream 2-5
2. Prediction of Leachate Quality from Complex
or Mixed Wastes 2-8
3. Waste Segregation and Separation 2-9
4. Use of Solidification, Stabilization, and
Encapsulation Techniques 2-11
5. Degradation of Organic Constituents in
the Landfill 2-14
6. Attenuation of Waste Constituents Prior to
Discharge 2-16
Third Day, Predicting Leachate Plume Migration in
Groundwater
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Page
Introduction to the Third Day 3-1
The Panel for the Third Day 3-3
Technical Issues of the Third Day 3-4
Summary of the Third Day 3-5
1. Direction and Velocity of Groundwater Flow 3-5
2. Phase Separation and Movement of Immiscible
Fluids 3-8
3. Dispersion of Waste Constituents 3-10
4. Degradation of Waste Constituents 3-13
5. Sorption of Constituents 3-15
6. Supply of Trained Professionals to Make and
Evaluate Predictions 3-18
Fourth Day, Gas Generation and Migration
Introduction to the Fourth Day 4-1
The Panel for the Fourth Day 4-3
Technical Issues of the Fourth Day 4-4
Summary of the Fourth Day 4-5
1. Models for Prediction of Constituents and
Atmospheric Emissions from Land Disposal
Facilities 4-5
2. Appearance of Gas in Leachate or Subsurface
Soils 4-9
3. Prediction of the Migration of Landfills 4-10
4. Management Controls for Gas Migration 4-13
5. Monitoring of Ambient Emissions from
Surface Impoundments 4-19
Fifth Day, Health Effects Resulting From Hazardous
Waste Exposures
Introduction to the Fifth Day 5-1
The Panel for the Fifth Day ' 5-2
Technical Issues of the Fifth Day 5-3
Summary of the Fifth Day 5-5
1. Methodologies and Techniques for predicting
Carcinogenic Effects 5-5
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Page
2. Use of Human Risk Numbers for Permitting
Decisions 5-9
3. Sources of Additional Data"for the Permit
Writer 5-12
4. Toxic Effects to Humans 5-14
Appendix A, Agenda
Appendix B,. List of Attendees
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First Day
Monday, May 18, 1981
Leachate Generation and Attenuation
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INTRODUCTION TO THE FIRST
-S
The purpose of this session was for the panel to examine the
chief factors that are relevant to predicting the quantity, the
time of first release, and the quality of leachate that is discharged
from land disposal facilities into the ground. In discussing these
general topics, the panelists were requested to identify, whenever
possible, the relative degrees of confidence and uncertainty in
making predictions, and to identify situations in which such pre-
dictions are subject to particularly high or low degrees of
confidence. The first day focused specifically on topics related
to leachate quantity and duration of the containment period.
The panel first focused its attention on the sources of liquids
that produce the leachate. These sources included precipitation,
groundwater, and liquids associated with the wastes. The emphasis
was on the ability to predict leachate generation and the associated
facility performance.
With respect to precipitation the key questions were related to
the characteristics of the rainfall distribution throughout the year
and the evapotranspiration rates as they influence predictions of the
amount of leachate generated. In this context, the attendant
questions regarding the use of top liners to prevent infiltration
were discussed from the standpoints of effectiveness, expected"life, and
various penetration modes such as roots, erosion, or cracks.
The discussion of groundwater infiltration attempted to answer
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questions regarding prevention techniques such as clay or synthetic
liners. For cases where, the water table intersects the facility, the
efficiency of passive systems such as trenches and active systems such
as pumps were discussed.
For landfills, the significance of the quantities of liquids
in buried wastes or liquids produced by the wastes was assessed in
relation to the total amount of liquids entering the land disposal
facility. In this regard, the reliability and cost of pretreatment
techniques were estimated.
Following the discussion of the mechanisms for leachate generation,
an examination was conducted of control techniques and the ability to
predict their effectiveness. These predictions depend both upon the
availability of data and the accuracy of the model applied to the data.
Therefore,- there was a discussion of the type and amount of data
needed, the cost of obtaining the data, and the degree of confidence
in the models'.
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THE PANEL FOR THE FIRST DAY
Moderator
Jack Lehman
Acting Director
Land Disposal Division
U.S. Environmental Protection Agency
Washington, D.C.
Panel Members
Dirk Brunner
U.S. Environmental Protection Agency
Municipal Environmental Research Lab.
26 West St. Clair
Cincinnati, Ohio 45268
Benjamin C. Garrett
Battelle Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
Robert A. Griffin
Illinois State Geological Survey
615 East Peabody Street
Champaign, Illinois 61820
Robert Ham
Dept. of Civil and Environmental
Engineering
University of Wisconsin
3232 Engineering Building
Madison, Wisconsin 53706
Amir Metry
Roy F. Weston
West Chester,
Pennsvlvania 19380
Charles A. Moore
Geotechnics, Inc.
912 Bryden Road
Columbus, Ohio 43205
Philip A. Palmer, Jr.
E.I. duPont de Nemours
Engineering Department
Wilmington, Delaware 19898
(L13 W28)
Robert Stadelmeyer
Cecos International
P.O. Box 619
Niagara Falls, New York 14302
Peter Vardy
Chemical Waste Management
900 Jorie Boulevard
Oak Brook, Illinois 60521
Jim Williams
Division of Geology and Land
Survey
P.O. Box 1638
Jefferson City, Missouri 65102
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TECHNICAL .ISSUES OF THE FIRST DAY
o Precipitation as Sources of Liquids
- Major source of liquids for leachate
- Manageable problem during open periods
- Easily controlled after closure
- Intensity of rainfall more a factor than amount
o Use of Top Liners to Control Infiltration
- Standard practice for chemical landfills
- Characteristics of effective ,top liners
- Pros and cons of synthetic materials
o Groundwater Infiltration
- Very site-specific
- No problem if above groundwater table
- May need pumping
- Designs for control
o Liquids Produced by or Associated With Wastes
- Minor contributor to•leachate generation
- Introducing liquids can assist in decomposition
- Controversy regarding liquids in drums
o Predicting the Permeability of Clay Liners
- Mass flew through the liner easier to predict than
time of first discharge
- Capillary action not well understood
- Influences of leachate constituents on permeability
o Use of Synthetic Liners
- Highest risk during installation
- Uncertainty regarding liner life
o Leachate Collection Systems
- Pros and cons of need
- Problems with (broken pipes, plugging)
- Cost estimates
- Best serve as monitoring for breakthroughs
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SUMMARY OF THE FIRST DAY
1. Precipitation as .a Source of Leachating Fluids
Rainfall was regarded by the panel as a problem during the open
periods of landfill cells before the cover is in place. However,
this problem was seen by several landfill operators on the panel
as manageable by using diversion structures for water control, of
if possible by planning the timing of cell openings and closings
so that a cell would be closed by the time the wet period would
arrive. The panel agreed that the use of top caps or liners would
easily control the amount of rainfall infiltrating into the landfill
after closure when such layers are well designed and maintained.
There was general agreement that meterological data are very
site specific, and consequently the prediction of precipitation rates
depends on a region's specific rainfall patterns. Based on data
obtained by one panelist for Illinois, the prediction of precipitation
for a 10-year cycle would be plus or minus 40 percent, on a 30-year
cycle would be plus or minus 15 to 20 percent, and on a 100-year cycle
would be plus or minus 2 to 3 percent of the average annual mean.
In other words, the prediction accuracy for rainfall increases with
the length of the time period over which the prediction is made.
The panel also felt that the variation for evapotranspiration
rates would generally be greater than that for precipitation since
evapotranspiration is a derived quantity based upon calculation
rather than actual data. In that respect, they "believed that the
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accuracy of prediction would tend to be greater for precipitation
rates.
The intensity of rainfall rather than the amount of rainfall
was agreed to be more important with respect to water infiltration
into the landfill. Measurements taken in Illinois during April
suggest that periods of rain characterized by a slow drizzle can
produce up to 70 percent infiltration, whereas a heavy thunderstorm
type of rain produces only 30 percent infiltration. One panelist
pointed out that standard infiltration rates are noc applicable to
chemical landfills because materials within the landfill would have
lower infiltration rates than natural soils primarily due to the
effects of construction. Several members of the panel suggested
that from the standpoint of leachate generation, EPA should be
thinking more in terms of" seasonally long wet periods or dry periods
rather than short-term daily storm events, and that longer periods
of rainfall measurements would provide more accurate predictions
of potential leachate generation than shorter periods.
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2. Use of Top Liners to Control Infiltration
,f
Most of the members of the panel believed that use of some sort
of top cap is fairly standard industrial practice for chemical land
disposal sites to control infiltration, although the configuration
of such caps may vary from location to location. One panelist, who
constructs and operates chemical landfills, indicated that he routinely
designs landfills with top liners to provide what he believed to be
additional insurance and to drastically reduce the requirement for
post-closure cash reserves for leachate management. This is done at
a cost of about 1 to 1.5 million dollars for a site covering approx-
imately 100 acres.
Several panelists recommended the use of a multi-layer cap system
rather than a single layer of clay material for infiltration control.
Such multi-layer systems would also allow more reliable predicting
of hydraulic head for infiltration calculations. Some panel members
suggested that the design of the top liner was basically a function
of the overall design goal of the landfill site and facility.
Consequently, they argued that it is very difficult to make general
pronouncements about top liners and their ability to prevent infil-
tration.
While there was not unanimous agreement in all cases, most
panelists agreed that if top liners are to function effectively
they should have the following characteristics:
o At a minimum be below the depth of frosty penetration to
prevent cracking
o Be graded perhaps between 4 to 7 percent slope to insure runoff,
yet minimize erosion.
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o Be protected from erosion and differential subsidence.
There was also support among the panel for using synthetic
materials over a clay top liner to prevent dehydration cracking of
the underlying layer. However, several members pointed out that such
synthetic materials are largely untried and there is little research
experience to make definite conclusions about the longevity of these
materials. Most panelists believed, however, that poor quality control
during the placement of such synthetic liners was perhaps the greatest
single factor leading to failures. Several members suggested that
third-party inspections by reputable engineering firms could serve to
help prevent such failures.
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3. Groundwater Infiltration
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Groundwater infiltration into chemical landfills was judged by
the panel to be a very site-specific phenomenon which they felt was
primarily dependent on the hydrogeology of the particular landfill.
Overall, there was consensus that it is much better practice to build
landfills which are above the groundwater table, if at all possible,
than to engineer chemical landfills which intersect the groundwater
table. The potential for groundwater infiltration was generally
agreed to be nil for landfills built above the groundwater table.
In such cases, infiltration from rainfall is far more significant
than groundwater infiltration in the generation of leachate. On
the other hand, building a landfill below the level of the groundwater
table was felt by the panel to increase the potential volume of liquids
that could come into contact with the waste, creating leachate.
Several participants argued that there might be a distinct
advantage, however, to building a facility which intersects the
piezometric surface or the groundwater table. They argued that if a
leak occured in the liner, fluids would flow into the facility rather
than out of the facility due to the inward gradient. One member
of the panel argued that this leakage might require perpetual
pumping, raising the issue of long-term maintenance of the pumps.
Several participants indicated that it is possible to design
groundwater infiltration of underdrain systems that are essentially
natural in their operation. That is, they do no.£ depend on mechanical
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pumping systems, but rather on intercepting or diverting the ground-
water flow on the upstream side of the facility and letting it drain
out of the lower part of the facility by gravity.
The panelists also discussed the relative merits of having an
individual groundwater control system at each trench of the landfill as
opposed to an overall control system that helps to intercept ground-
water flow over the entire facility. Several panelists suggested
different techniques to solve this problem. Some participants argued
that it was physically difficult to line each trench of the landfill
to prevent groundwater infiltration and that intercepting this water
at the perimeter of the area might be more economic and more achievable.
Others suggested that it is possible to construct grout curtains or
diversion trenchs on the upgradient side of the trench to reduce ground-
water flow. One participant argued that since such systems are more
accessible to maintenance and observation than underdrain systems he
would have more confidence in them than tile systems which could
become plugged up over the long term.
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4. Liquids Produced by or Associated with Wastes
The panelists generally agreed that the relative importance of
liquids in buried wastes or liquids produced by wastes, as opposed to
other sources of liquids that, flow through the landfill, is site
specific. Climate is a significant factor in this relationship. For
example, in an area of high rainfall where a site is designed to allow
some infiltration, the amount of liquids that might be contained in
the waste or the amount of liquids being produced during the decompo-
sition process would be insignificant. On the other hand, however,
the amount of liquids that may be within the waste would be more
significant in landfills situated in areas with lower rainfall. Another
panelist suggested that although water in the waste would not be
expected to generate significant quantities of leachate, wastes with
high water contents (e.g., wet sludges) might saturate the landfill
contents faster than would otherwise occur with drier wastes. Conse-
quently, leachate might be generated during the first few years of
operations rather than after four or five years, though the total
quantities would not be appreciably different. In other words, it
will cause the field capacity of the waste to be reached at an earlier
date. However, most of the participants concurred that the liquids
produced by wastes in the landfills contribute a very small amount
of moisture relative to the generation of leachate, and furthermore,
the water that is produced leaves primarily as a vapor.
Another question that the panel addressed was whether there were
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situations where it was environmentally preferable not to prevent or
minimize the entry of liquids into landfills. Overall, the panel
agreed that the answer to this question was generally dependent on the
design objectives for the landfill. One participant suggested that
there may be some benefits of introducing water or nutrients into the
landfill to achieve a slow controlled rate of decomposition. Other
panelists indicated that while they believed such chemical reactions
could provide for waste attenuation in chemical landfills, it might
be better to achieve it through pretreataient processes prior to place-
ment in the fill.
The panel also briefly discussed the merits of burying liquids
in drums in the landfill. Current EPA regulations prohibit liquids
in drums primarily because it is felt by the agency that drums will
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eventually corrode and open up causing leakage, and that excessive
subsidence would result from such activity. There was lively discussion
among panel members on this question. Several panel members repre-
senting the chemical landfill industry argued against this prohibition
because they believed that landfills could be designed adequately to
prevent subsidence caused by collapsing or corroding drums. Furthermore,
they argued that the capital costs involved and personal hazards to
operators to remove liquids from those drums far outweight the two
arguments against drum disposal in chemical landfills. Several
participants argued for a middle position of allowing at least some
liquids in drums in landfills. Generally, there was a consensus among
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the panel that the answer to this argument is clearly a judgement
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call based, on the relative tradeoffs with long-term environmental
protection on the one hand and the ease of handling and protection of
workers on the other.
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5. Predicting the Permeability of Clay Liners
The members of the panel generally agreed that reasonably
accurate prediction of the clay liner permeability can be made,
leading to an estimate of the mass flow through the liner to within
1/2 to 1 order of magnitude. However, the panelists were less
optimistic about making predictions of the first arrival or time of
first discharge of Liquid, which are commonly calculated as functions
of the effective porosity. One participant indicated that errors
in estimating effective porosity can be between one and two orders
of magnitude. Several panelists commented that the concept of effective
porosity is an irrational or misleading concept in this context,
since clay liners within a landfill would probably r.ever exhibit
simple saturated flow subject to the Darcy flow equations.
Another panel member indicated that capillary action would have
a significant impact on the velocity of the first drop through the
clay liners. That is, the pressure differential resulting from
capillary forces in fine grained soils could overwhelm the low
permeability of the material, causing much faster migration than
would be expected based on the unsaturated permeability alone. However,
there was strong support among the panelists against the use of
capillary action in determining the velocity of liquid flow through
a liner since the concept is not well understood and validated at this
time. In summary then, there was a general consensus that evaluation
of a landfill liner system would be based on the mass flow- rate through
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the liner rather than on the arrival time of the first drop of leachate.
The panel next "discussed the issue of whether leachate constituents
could affect the permeability of liners through various mechanisms.
It was believed to be unlikely that leachate constituents would
lead to plugging liner pores, or in other words, decreasing the
permeability of liners in chemical landfills. Most believed soil
plugging should be considered a bonus if it does occur. As was
pointed out by several participants, much of the evidence for this
phenomenon has been collected from municipal or sanitary landfill
sites and limited laboratory testing. One participant indicated that
his studies in Illinois suggested that there was a significant decrease
in clay liner permeability (between a factor of 2 and 10) using sani-
tary landfill leachate. His previous work on landfill sites had
indicated that plugging of a calcium-saturated bentonite liner is
likely with leachate high in sodium because of cation exchange.
Conversely, a highly-ionic strength waste placed on a highly-dispersed,
sodium-saturated, montmorillonite liner caused cracking, also due to
cation exchange. Based on this evidence this panelist argued that
there is probably no simple quantitative answer to the question of
increases or decreases in the permeability of clay liners, primarily
because the enormous range of chemicals that might appear at an
industrial site. When soil plugging does occur, it 'generally causes
no more (often much less) than 1 to 2 orders of magnitude decreases
in saturated permeability, and it is occasionally reversible. When
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liner/waste interaction leads to increases in permeability the result
is generally catastrophic failure. Several participants pointed out
that there are methods of testing certain types of liner materials
against certain types of waste leachate, but that these are rarely
done at this point in time. The panel agreed that more research on
these quantitative techniques needs to be done.
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6. Use of Synthetic Liners
Most of the discussion on synthetic liners focused on the issue
of the risks involved in a synthetic liner tearing or degrading by
chemical reactions. There was general agreement among the panelists
that the period of highest risk for synthetic liners occurs during or
immediately after installation, and that once these liners are in
place, the prospects were good for "moderate" long-term survival.
Most panelists agreed, however, that due to the lack of aging data on
typical commercial membranes, it was currently impossible to predict
with confidence the very long-term physical survival or integrity of
synthetic liners. Several panelists representing the chemical land-
fill industry argued that this uncertainty about the long-term
survivability of synthetic liners should not stop the design and
construction of chemical landfills. They felt there are usually
risks for other similar installations such as industrial plants,
sewage treatment plants, etc., and that these risks are normal and
acceptable. It was suggested that full-time, third-party inspection
of the entire installation process by a qualified observer would be
a means of insuring proper placement.
It was also suggested that it is highly unlikely that failure of
a synthetic liner in a landfill would result in sudden releases of
large volumes of liquid, although the public tends to focus on such
so-called catastrophic events. On the other hand, catastrophic
failures would be a more likely occurrence with surface impoundments.
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7. Leachate Collectiou Systems
There was a range of opinion regarding the need for or emphasis
on leachate collection systems in chemical landfills. In the case of
landfills designed for minimal infiltration, one participant felt
that the leachate flow coming out of the bottom of a landfill would
be minimal after closure. In his opinion, therefore, a leachate
collection system would more or less act in that case as a leachate
monitoring system, and that heavy flows would only occur when the
landfill had open faces during waste emplacement. This viewpoint
was seconded by several other members who indicated that at several
research sites they were aware of there were generally only small
amounts of leachata to collect. However, it was pointed out that
experience with well-designed and operated landfills is limited to
the relatively recent past, and that long term leachate
generation in these facilities is still largely a matter of conjecture.
One member indicated that as a matter of basic policy he no longer
regularly designs a landfill without a leachate collection system
since he believed that the cost of that installation is the cheapest
insurance one could buy. His organization firmly believes that such
systems are well worth the investment during construction since
chemical landfill sites, in their experience, do not reach field
capacity until 10 to 13 years after they are started.- Consequently,
many operators can be lulled into a false sense of security saying
they have a dry site, when in reality their sites have not-yet reached
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field capacity. It was his view that, in those circumstances, he
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would much rather have a leachate collection system at that point.
The discussion that followed focused on the operating experience
of several panelists with leachate collection systems. One operator
indicated that one of his major problems with these systems was broken
riser pipes which were probably caused during the initial landfill
construction period. Once this initial period was over his main
problem was usually plugging of this .system due to settlement and
sediment collection in the pipes. He indicated that his usual design
goal was for 80 to 90 percent leachate removal over a period of about
30 years. He indicated that his costs for such a system typically
ranged between 7 and 9 dollars per lineal foot, including the cost
for riser sumps.
Another operator revealed that his firm constructs leachate
collection systems for each of the individual subcells with their
chemical landfill sites. To maintain a suitable hydraulic conductivity
to prevent clogging in the draining medium, they construct systems
to act as graded filters. That is, fine-grained materials in the
upper portion of the collection medium traps the sediment portions
carried by infiltrating leachates, allowing the fluids to flow out
through the coarser media in the bottom of the collection system.
Based on their experience so far, the bulk of the leachate that is
collected has been during the initial operational period, and by using
the graded type of collection system they estimated that they could
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dewater a facility within about 2 to 3 years after closure.
Treatment and offsite disposal of leachate from such collection
systems was seen by several of the panelists as a typical practice.
One industrial operator indicated that his capital costs for waste-
water treatment, involving the physical, chemical, and biological
treatments, have run batween 1.7 and 2 million dollars, with
operating costs about 4 to 7 cants per gallon. Another panel member
indicated that off.site disposal of leachate could generally cost from
about 20 to 50 cents per gallon, and deep well recharge from about
1.5 to 2 million dollars per well, including the surface facility
and the wells.
Alternatives to leachata collection systems were not in general
regarded by the panel as reliable for indicating the breakthrough of
liquids out of a facility. Several participants,related their rather
disappointing experiences with such early-warning systems as suction
lysimeters and earth resistivity equipment. Many of the comments were
directed at their limitations under common landfill conditions. This
led one landfill operator to add that such equipment might currently
provide results which were academically interesting, but generally a
waste of money for most operators. The panel generally concluded that
much more research needs to be done in perfecting these techniques.
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Second Day
Tuesday, May 19, 1981
Leachate Generation and Attenuation
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INTRODUCTION TO THE SECOND DAI
_f
The second session of this panel discussion explored a number of
technical issues related to leachate management which were largely
left undiscussed by the panel during the previous day. The focus of
this day's discussion was on predicting the quality or composition of
leachate that may be produced and migrate from a facility. The
discussions first focused on leachate produced in a monofill, a site
where waste is from a single generating source. Next, complex fills
with wastes from numerous generators and with a variety of compositions
were discussed. Topics of discussion included the influence of the
waste on leachate composition, the characteristics of the leaching
medium, and commonly utilized techniques to control leachate quality,
such as waste separation, pretreatment, in situ treatment, solidifi-
cation, stabilization, encapsulation, and attenuation mechanisms.
These topics were selected to obtain insight into the confidence level
of predicting leachate quality, situations which increase or decrease
the predictability of leachate quality, and data needed to achieve a
particular level of confidence.
Examining particular land disposal facilities or proposed
facilities to predict their ability to achieve a stated goal (i.e.,
controlling leachate quantity, containment time, or leachate quality)
involves some uncertainty. To narrow the uncertainty the relative
degrees of confidence in predictions must be defined. This requires
knowledge of data needs and availability of individual facilities
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as well as those that relate to the industry. The second session
examined the state of the art of predicting leachata quality and
migration to establish the degree of confidence used when analyzing
leachate management for facilities.
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THE PANEL FOR THE SECOND DAY
,y
Moderator
Kenneth Schuster
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, D.C.
Panel Members
Dirk Brunner
U.S. Environmetal Protection Agency
Municipal Environmental Research Lab,
26 West St. Clair
Cincinnati, Ohio 45268
Benjamin C. Garrett
Battelle Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
Robert A. Griffin
Illinois State Geological Survey
615 East Peabody Street
Champaign, Illinois 61820
Robert Ham
Department of Civil and
Environmental Engineering
University of Wisconsin
3232 Engineering Building
Madison, Wisconsin 53706
Charles A'" Moore
Geotechnics, Inc.
912 Bryden Road
Columbus, Ohio 43205
Philip A. Palmer, Jr.
E.I. duPont de Nemours
Engineering Department
Wilmington, Delaware 19898
Amir Metry
Roy F. Weston
West Chester, Pennsulvania 19380
Peter Skinner
New York State Law Department
Justice Building
The Capitol
Albany, New York 12224
Robert Stadelmeyer
Cecos International
P.O. Box 619
Niagara Falls, New York 14302
Peter Vardy
Chemical Waste Management
900 Jorie Boulevard
Oak Brook, Illinois 60521
Jim Williams
Division of Geology and Land
Survey
P.O. Box 1638
Jefferson City, Missouri 65102
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TECHNICAL ISSUES OF THE SECOND DAY
o Prediction of Leachate Quality from a. Single Waste
- pH value of leachate medium
- Knowledge of waste characteristics
- State of equilibrium between waste and leaching medium
- Ratio of leaching medium to waste
- Properties of soil or clay covers
o Prediction of Leachate Quality from Complex or Mixed Wastes
- Significance of prediction
o Waste Segregation and Separation
- Initial stage of research
- Aid to management
- Example criteria
o Use of Solidification, Stabilization, and Encapsulation
Techniques
- Purpose of techniques
- Need for regulation
- Control specifications to increase solidification
- Confidence level in tests for leachate on solidified
or stabilized waste
o Degradation of Organic Constituents in the Leachate
- Data availability for chemical landfills
- Predictability for sanitary landfills
o Attenuation of Waste Constituents Prior to Discharge
- Information needed for predicting attenuation methods
- Simple systems
- Complex systems
- Landfill design
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SUMMARY OF THE SECOND DAY
1. Prediction of Leachate Quality from a Single Waste Stream
With reference to the predictability of leachate quality, the
panel first addressed the situation of a landfill receiving a single
stream of waste from generators. The discussion primarily focused on
the degree to which the following factors could be used to confidently
predict leachate quality'based on laboratory testing:
o Leaching medium
o Waste characteristics
o Duration of waste contact with leaching medium
o Properties of soil or clay used as cover or intermittent
cover
o Ratio of leaching medium to the waste
*
The panelists felt that the leaching medium is an important
factor in predicting leachate quality when simulating a monofill
situation. Unbuffered distilled water is the leaching medium of
choice, although other mediums can be justified on a site-specific
basis. Most members felt that it is realistic co use something close
to rainwater (e.g., distilled water or groundwater in the vicinity
of the landfill) as the leaching medium since rain or groundwater is the major
source of leachate in a landfill. They discussed the importance of
the pH level of the test fluid in accurately modelling the composition
of the expected leachate. Leachate mediums which are buffered or
assigned a pK level could cause leaching of materials which might not
occur in the natural situation. In fact, by assigning a pti level the
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leachate results are being predetermined to some extent since various
materials will be released only at specific pH levels. One panelist
was opposed to the use of an acidic leaching medium since he felt
that it would not allow an investigator to do a bioassay test at the
same time. One panelist indicated that his laboratory's batch tests
for leachate composition using distilled water often predicted
concentrations within a factor of two, and nearly always within a half
order of magnitude of his actual field test for a particular leachate
component.
The panel generally concluded that the characteristics of the
particular waste are also important factors in confidently predicting
the leachate quality. That is, the more that is known about how the
waste material is generated and its daily variation, the greater the
confidence in the prediction of the leachate quality. Several of the
panelists suggested that a simple analysis of the waste is not adequate
to predict leachate concentrations. They felt that an elemental
analysis is also necessary in order to provide the exact form of
the individual waste component and its particular solubility products.
Most members believed duration of waste contact to be a relatively
unimportant factor overall in comparison to the waste characteristics
themselves., The panel, as a whole, believed that in most normal
hazardous disposal environments hydraulic conductivities and rates of
leachate movement are very slow. Thus, leaching tests that simulate
equilibrium conditions were felt to be more representative .than very
s*-
fast leaching tests.
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With reference to the volume ratio of the leachate to the waste,
the panel was undecided whether this factor was critical in predicting
leachate quality. One member suggested that it is very difficult, in
his opinion, to predict leachate quality in the landfill on the basis
of the ratio of the leaching medium to the waste in a test sample.
Similarly, the panel did not reach a concensus regarding the usefulness
of physical properties of the soil or clay cover materials in
predicting leachate quality. One member believed, however, that the
physical properties of various clay soils could affect the movement
of leachate and overall leachate quality.
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2. Prediction of Leachate Quality from Complex or Mixed Wastes
The panel next focused its attention on the state-of-the-art
in predicting leachate quality from a mixed stream of chemical wastes.
In comparison to the rather simple case of a single waste stream,
prediction of leachate quality from mixed waste landfills was judged
to be a much more complicated situation. Many members of the panel
felt that due to synergistic, antagonistic, and buffering
interactions between the different types of wastes and the difficulties
in obtaining representative samples, the common types of batch and short-
term laboratory tests would not be effective for prediction. Several
members indicated that such impacts are not well understood today,
making the prediction of leachate quality highly speculative. Because
of the tremendous swings in the daily waste stream, they questioned
the need for quantitative leachate prediction exercises for complex,
mixed waste systems.
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3. Waste Segregation and Separation
Segregation or separation of hazardous chemical wastes to prevent
undesirable reactions within a landfill was discussed as a possible
means of minimizing adverse reactions between wastes which could affect
leachate quality. There were a number of participants on the panel who
believed that the state of the art did not provide procedures for
operators to efficiently segregate incompatable waste materials in a
practical manner. Other panel members from the chemical landfill
industry disagreed with this philosophy suggesting instead that there
has been a significant amount of evaluation and effort already done by
individual operators in this area, although this work is still in the
very early stages of research. Based on results from existing landfills,
these panelists believed that operators could generally segregate their
wastes in various ways such as separating different types of waste
materials which could generate harmful gases or release excessive
amounts of energy upon contact with each other.
•
One panel member from New York described his firm's approach to
waste segregation on several chemical landfills located in the north-
eastern part of the United States, he indicated that they practice
subcell segregation on the following types of wastes:
o Heavy metals
o "Pseudometallic" wastes such as arsenic, atimony, and
selenium
o Toxic organics
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o Low flash point materials
o General organic or low toxicity organic materials
These individual segregations are-chosen for purposes of applying
specific covers to each different subcells. They believed that this
will aid in the management of the waste materials, either by reducing
the mobility of the individual components that are present through
attenuation mechanisms, or by the detoxification of individual materials
through acidic or basic hydrolysis reactions within the individual subcells
of the facility.
Another panelist indicated that his firm also segregated its
wastes within chemical landfills based upon on waste compatibility,
potential exposures to employees, and other health and safety consid-
erations. He indicated that his firm currently segregates toxic
organics, acids, and PCBs, although the mobility of these wastes
are taken into account at this time in a very general, nonquantitative
way.
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4. Use of Solidification, Stabilization, and Encapsulation Techniques
These techniques'were generally seen by the panel as standard
practices used by the chemical landfill industry to reduce the leaching
potential and physical mobility of wastes prior to landfilling. Most
members agreed that wastes which are in a solid or chemically stabilized
form can reduce significantly the potential infiltration of rain
water into a landfill environment, and also reduce the potential
amount of leachate constituents that could leave a landfill. One
panel member went so far- as to suggest that there should be a regulatory
effort on the part of the EPA to encourage the use of these pretreatment
processes. Without this kind of regulatory effort, he felt that
most chemical wastes would be pretreated using the least expensive,
but not necessarily the most environmentally acceptable approach.
Most panelists agreed that the bulk of the pretreatment processing
of wastes currently occurs at the generating site, although some
pretreatment using these solidification processes takes place at
land disposal operations.
One operator revealed that most of the waste pretreatment his firm
employs is solidification of liquid waste materials and the modifi-
cation of sludge materials to a more solid form. Their primary objective
is to decrease the mobility of the waste material. He indicated that
wastes accepted by his firm must meet specific control specifications
regarding their volatility, mobility, solubility, and liquid content:
o Maximum volatility and physical mobility for each waste are
specified based on generic standards set by the firm
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o Liquid mobility is specified based upon load bearing strength
o Physical mobility is specified based upon the requirement
for containerization of very low density materials which could
readily be transported by wind activity
o Limits of solubility for inorganics are defined as follows :
limits of solubility for heavy metals
- absolute limits for pseudometal components
- maximum limits for acid sensitive substances
o Maximum allowable level of total fluids in barrels is set
at 15 percent of total container space, including air space.
If the wastes can be converted to a solid form meeting these specifi-
cations they are accepted by his firm for disposal. Otherwise, his
firm requires that the waste undergo additional pretreatment, by either
the generator or by some other agency, to be placed into the form that
is appropriate for disposal.
The panel did not offer a clear cut opinion on the type of test
that might be used for leachate on a solidified or stabilized waste.
There was some disagreement over whether or no.t such techniques are
sufficiently well-established to confidently predict the leachate
constituents in the long run. One panel member, for example, suggested
that grinding, crushing, or the use of acids to destroy the consoli-
dated or stabilized waste monolith could negate or reverse the benefit
of waste stabilization. Offering a solution to this potential dilemma,
another panelist indicated that there are two processes used for
stabilizing chemical wastes, one for organic materials, and another
for inorganic materials. By stabilizing organic materials a relatively
impermeable mass can be produced which minimizes ,£he amount of leaching
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that can occur, although the process does not tie up the individual
.f
chemical constituents. Consequently, it was his opinion, that as far
as leaching tests are concerned grinding or crushing would not be an
appropriate technique to determine if the stabilized organic waste
has potential leaching properties. He suggested that the character-
istics of the monolith should be considered when predicting potential
leachability using specific leachate tests. On the other hand, he
suggested that such destructive grinding or crushing techniques would
not have much of an effect on chemically stabilized inorganic wastes
which are chemically bound up in the crystalline structure of the soil
or other material. In such cases, he believed that a leaching test
would be as successful as that employed on nonstabilized wastes.
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5. Degradation of Organic Constituents in the Landfill
The panel, as a whole, questioned whether biodegradation of
organic materials takes place in chemical landfills. While most
members agreed that biodegradation is known to occur in sanitary or
municipal landfills, they felt that there are not very much definitive
data currently available with respect to the degree of the biotreatment
that takes place in a chemical landfill. In general, biodegradation
was regarded by the panel as fairly predictable in sanitary landfills
because of the large data base already collected. One of the panelists
suggested that there are firms that purposely mix organic wastes with
soil in their chemical landfills to take advantage of what they believe
is biodegradation. He indicated that these firms report that the con-
stituents which accumulate in their leachate collection system are not
the same as those contained in the wastes. By and large, they believe
that degradation does take place. However, this panelist indicated
that there is not a lot of data to support their claims of biodegradation.
One member observed that the entire question of whether biodegra-
dation can be predicted for chemical landfills is virtually impossible
to answer at this time. He indicated that one of the things that makes
it so difficult is that the degradation pathways can be highly
variable depending on the conditions within the landfill during the
different seasons of the year, i.e., different rainfall or temperature
f
regimes. In his opinion, he felt that these many factors could affect
biodegradation differently making predictions extremely difficult at
JU~
this time.
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Another panelist, while agreeing that biodegradation cannot be
_y
counted on by landfill operators at this particular time, indicated
that chemical degradation can take place within the landfill because
operators have the ability to control the internal chemical environ-
ment of their facilities. He suggested that operators could use
different management techniques to create in situ mechanisms such as
alkaline hydrolysis within the landfill which can result in chemical
degradation. This view was criticized by another panelist who questioned
whether there was sufficient documentation or evidence to prove that
chemical degradation actually occurs and offers a measurable degree
of public protection. He maintained that he had not seen sufficient
evidence to substantiate such claims.
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6. Attenuation of Waste Constituents Prior to Discharge
The panel attempted to specifically answer the question, "is
it possible to predict the type of attenuation mechanisms which will
take place in a landfill to assure adequate protection of public
health?" Most of the panel members agreed that in order to make
these predictions, operators would need to know the following infor-
mation at the very minimum:
o An accurate description of the chemical constituents that
will be released from a given waste
o The chemical composition and homogeniety of the earth
materials that comprise the liner
The panel felt that the more information available about a waste and
the soil/material combination in the landfill, the more accurately
attenuation that will occur could be predicted.
Several members indicated that much is currently known about
attenuation mechanisms for certain simple systems of wastes in a
landfill. For example, metals and many toxic organics such as PC3s
are known to be very strongly absorbed and attenuated in soils,
particularly in those sails rich in organic matter. They believed
that for such systems fairly quantitative decisions with respect to
the overall attenuation of the waste within the landfill could be
made. On the other hand, most panel members judged that, for complex
situations where multiple waste streams are being landfilled at the
same site, this type of quantification becomes more and more subject
to uncertainty and requires more in the way of qualitative or worst-
case judgments.
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Given this uncertainty of predictions, most members of the panel
_j»
did not favor the use of "leaking" landfill designs in which it is
assumed that the waste components would be attenuated, either in the
natural clay liner or through use of dispersion and dilution mechanisms
prior to discharging into the local groundwater system. Instead most
members felt that chemical landfill operators should concentrate more
on designs to maximize containment of leachate rather than relying on
attenuation mechanisms which are highly variable and sometimes
extremely unpredictable with complex waste mixes.
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Third Day
Wednesday, May 20, 1981
Predicting Leachate Plume
Migration in Groundwater—
Modeling and Monitoring
-------
INTRODUCTION TO THE THIRD DAY
The topic of the third session was "Predicting Leachate Plume
Migration in Groundwater, Modeling and Monitoring". The panel con-
sidered the predictability of the fate and transport of. leachate and
its constituents in groundwater. Specifically, how precise can the
concentrations of waste constituents at any one location and time be
predicted? In attempting to answer such questions the panel assumed
that the location, mass rate, and concentrations of contaminants entering
the groundwater are known with some degree of confidence or uncertainty.
These assumptions were made to avoid repeating any of the discussion
from Monday and Tuesday on predicting leachate quality and quantity in
a landfill. As a result, the discussion considered only the potential
error in predicting plume migration which would result from varying
degrees of certainty in leachate.
The discussion focus on technical issues relating to plume
migration and the availability of professionals working in this area.
One issue discussed was the type and amount of data required to pre-
dict plume migration of waste constituents to make quantitative
predictions and worse case predictions. The panel examined the cost
and time involved in generating such data. Also examined were the
use of these different types of predictions. The panel tried to
determine if precise knowledge of the leachate is needed in all cases
or if a worse case prediction can be used to assure acceptability of
a facility. Another issue discussed was the degree of expertise
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required to produce data and evaluate predictions on the fate of
leachate. The discussion specifically considered the current
supply of people with such expertise and the training and employment
opportunities available to them.
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THE PANEL FOR THE THIRD DAY
Moderator
Barry Stoll, Chief of Disposal Branch
Land Disposal Division
U.S. Environmental Protection Agency
Washington, D.C.
Panel Members
Patrick Domenico
Department of Geology
University of Illinois
245 Natural History Building
1301 West Green Street
Urbana, Illinois 61801
Richard Eldredge
Eldredge Engineering Association
2625 Butterfield Road
Oak Brook, Illinois 60521
Carl Enfield
U.S. Environmental Protection Agency
Robert S. Kerr Environmental
Research Laboratory
P.O. Box 1198
Ada, Oklahoma 74820
James J. Geraghty
Geraghty & Miller
844 West Street
Annapolis, Maryland 21401
Leonard Konikow
U.S. Geological Survey
431 National Center
Reston, Virginia 22092
John Moore
Illinois Environmental Protection
Agency
2200 Churchill Road
Springfield, Illinois 62705
Paul Roberts
Civil Engineering Department
Stanford University
Stanford, California 94305
Paul H. Roux
Stauffer Chemical Company
Nyala Farms Road
Westport, Connecticut 06880
Eric Wood
Director, Water Resources Program
Civil Engineering Department
Princeton University
Princeton, New Jersey 08544
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TECHNICAL ISSUES OF THE THIRD DAY
o Direction and Velocity of Groundwater Flow
- Accuracy.of physical measurement vs calculation
- Flow prediction difficult in complex systems
- Imposed limitations of time and money
o Phase Separation and Movement of Immiscible Fluids
- Extreme difficulty in modeling multi-phase flows
- Petroleum Industry's experience
- Predicting phase separation of organic compounds
o Dispersion of Waste Constituents
- Importance of diffusion and dilution
- Estimating dispersion coefficients
o Degradation of Waste Constituents
- Accuracy of biological degradation predictions
- Significance of chemical hydrolysis and precipitation
o Sorption of Constituents
- Relationship between chemicals in solution and
the soil matrix
- Reversing the sorption process
- Determining the sorption capacity
o Supply of Trained Professionals to Make and Evaluate
Predictions
- Benefits from public sector vs. private sector
- Shortage of qualified educators
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SUMMARY OF THE THIRD DAY
1. Direction and Velocity of Groundvater Flow
The panel addressed the issues associated with predicting the
direction and velocity of groundwater flow prior to contamination of
the groundwater by leachate. At the outset of the discussion, one
of the panelists indicated that the direction of groundwater flow can
be determined by actual physical measurement while groundwater
velocity estimates are calculations. Observations of water levels
from a minimum of three wells are necessary to determine the slope
of the groundwater table or piezometric surface. The direction of
the groundwater flow is that of the maximum downward slope along that
surface. On the other hand, estimates of groundwatar velocity are
calculations which require the measurement of other parameters, such
as porosity and permeability.
Notwithstanding this apparent lack of precision, he felt that
there is a higher degree of confidence in the measurement of ground-
water direction and calculation of groundwater velocity than in most
other hydrologic calculations and measurements made in the field.
Another panelist generally agreed with this viewpoint, adding that
the solution of numerical groundwater flow equations has become
almost routine. He felt that many models used to numerically
simulate groundwater flow are very well documented and straightforward
in their use. He also believed that they can now be applied by people
not familiar with the internal working of these models.
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Some of the ocher members of the panel were not as optimistic.
They argued that there are many conditions for which the direction
and velocity of groundwater flow are extremely difficult to predict
with confidence. One panelist, for example, felt that watershed
groundwater flow models often do not accurately match the ground-
water flow system actually existing in many landfills because geo-
logical materials often vary significantly over as short a distance
as a few meters. He argued that a few measurements of flow direction
taken from wells hundreds of meters apart may not represent actual
conditions existing at a smaller geologic scale, such as a landfill.
Thus, models using these larger scale measurements may miss important
local groundwater flows. Another panelist pointed out that data
from only three wells are usually grossly inadequate to accurately
*
predict groundwater direction. He felt that information was necessary
from different aquifer depths to develop precise 3-dimensional models
for measuring groundwater direction. He felt that additional data
concerning groundwater recharge and discharge were also clearly
necessary for predicting both grswndwater direction and velocity,
since the input and output relationships of groundwater
would also probably keep changing due to future man-made events.
Most panelists believed that given enough time and money for
geologic drilling and testing it would be possible to model, and
predict with a high degree of certainty, the groundwater direction
and velocity in all geologic systems. However, in real world
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situations limits are placed on time and money. Most panelists,
,t
therefore, conceded that there will probably never be enough data
to make precise predictions of groundwater direction and flow for
all geologic conditions. They also agreed that it is easier to
predict groundwater flow in simple alluvial materials where the
primary intergranular permeability and porosity is responsible for
driving the flow, than in regions where flow occurs in solution cracks
or fracture system (i.e., limestone and other karst terrain; fractured
igneous and metamorphic rocks; and in highly layered materials such as
shales and siltstones).
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2. Phase Separation and Movement of Immiscible Fluids
There was a lively discussion among the panelists over whether
or not the movement and phase separation or organic constituents in
groundwater can be predicted with confidence. One of the panelists
indicated that this field research has shown that most organics
usually remain in a single phase with water, and thus flow along
with the water in a single plume. At low concentrations, even
organics which generally are immiscible with water will be entrained
in the plume. However, as the concentration of these immiscible
organic constituents increase relative to the groundwater, he has
seen a two phase or multiphase plume flow develop. Those organics
which are heavier than the water were shewn to migrate to the bottom
of the landfill in response to hydrodynamic forces. Subsequent
movement is constrained by the surface characteristics of the liner.
In some cases,the heavier phase may collect in holes or depressions
in the surface of the liner, remaining there indefinitely. Therefore,
he concluded that modeling such multiphase flows is extremely
difficult.
Another of the panelists agreed that modeling these phases of
immiscible fluids is complicated, but felt that the panel should
not imply that it is a totally intractable problem. He
indicated that the petroleum industry has been dealing with this
type of research problem on a routine basis involving the secondary
recovery of crude oil for some time. They have extensive .-laboratory
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experience in this area, and have conducted complex modeling of these
_,•
processes. In contrast, he felt that the groundwater industry has
not yet developed the requisite experience necessary to analyze and
predict with confidence the direction and movement of these immiscible
fluids.
With reference to phase separation, one of the panelists
suggested a method that could be used to predict the likelihood of
different organic compounds to separate into phases. He felt that
there is enough evidence suggesting that compounds with low solubil-
ity will tend to form separate phases, if they are present in large
enough amounts. Thus, if the solubilities of the particular compounds
were known,as well as the relative rate of their introduction and
the salt and mineral content of the groundwater, estimates within a
factor of two could be made for phase separation of the compounds.
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3. Dispersion of Waste Constituents
Dispersion of a plume was discussed in relation to both
molecular diffusion and dilution. For purposes of this discussion,
dispersion was considered to be the family of mechanisms by which
a plume spreads out as it moves down gradient, decreasing the con-
centrations of contaminants, but increasing the area affected by
the plume. Its two principle components are molecular diffusion,
the scattering of individual molecules due to thermally induced
random motions; and dilution, the decrease in concentration of con-
taminants due to mixing with uncontaminated groundwater.
The mechanism of molecular or ionic diffusion was regarded by
several members of the panel to be well understood, but in general,
orders of magnitude less important than other convective properties
in determining plume migration. One panelist suggested that trans-
verse dispersion (lateral or vertical spreading) of a contaminant
plume is essentially similar in nature to that of diffusion. He
believed that by making this assumption it is possible to calculate
the diffusion coefficient of a contaminant plume by taking the square
root of its transverse dispersion coefficient and multiplying this
by the length of time for the dispersion to occur. The panelist
suggested, however, that these diffusion coefficients in porous media
are usually quite small, commonly in the range ^of 10~ square
centimeters per second. Several other panelists suggested that there
may be groundwater situations (e.g., archaic water with almost no
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movement) where diffusion will be more important. They believed
./•
that under such conditions diffusion may still be small, but more
important relative to the dilution mechanism.
In contrast to the diffusion mechanism, the panel generally
agreed that dilution is a much, more important factor in groundwater
systems. Several panelists felt that the dilution coefficient
depends primarily upon the fluid velocity and the physical charac-
teristics of the porous geological medium. While the dependence of
the dispersion coefficient was generally agreed to be approximately
proportional to the fluid velocity, its dependence on the physical
characteristics of the aquifer are currently not well understood,
and thus hard to predict. One panelist stated that field measure-
ments of this parameter can vary over about three orders of magnitude,
and are generally many orders of magnitude higher than what is found
in the laboratory. He believed that estimates of dilution in the
field, based on laboratory results, would greatly underestimate the
parameter.
Several panelists argued that the lack of field measurement for
.dispersion coefficients does not mean that reasonable dispersion
coefficients could not be developed for solute transport models. One
panelist suggested that although it is not possible to predict the
dispersion coefficient exactly in all circumstances, an estimate of
its range can be made to yield a worse or best case. Another
panelist indicated that the U.S. Geological Suryey has developed a
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solute transport model for the Rocky Mountain Arsenal using a
sensitivity analysis to achieve a reasonable estimate for the
dispersion coefficient based on the observed 30-year record of
contamination. He believed that field measures of dispersion
coefficients for the Arsenal would not have yielded useful informa-
tion since recharge was found to be a more important factor in
diluting the concentration of contaminants than other dispersion
mechanisms.
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4. Degradation of Waste Constituents
. ,•
Biological and chemical degradation processes were discussed by
the panel as possible mechanisms for the decay of waste constituents
found in leachate plumes from chemical landfills. The panel members
focused on the accuracy to which these processes can be predicted.
In general, the panel concluded that while biological degrada-
tion is understood as it takes place in the soil, recent studies have
shown that current techniques used to predict biological degradation
of plumes in soil are inadequate.since certain unexpected micro-
organisms have been identified in the groundwater. Several of the
panelists felt that most of the current research in this area is
being primarily directed to determine if biological degradation takes
place, rather than how fast. They believed that there are too many
unknown variables in biological degradation to make quantitative
predictions. For example, a slight change in the chemical structure
of different compounds has been shown to cause an order of magnitude
difference in the rate of biological degradation. Further, the
composition of wastes going into a landfill can change dramatically
with time, causing interruptions in the food supply for a particular
organism, or even introducing toxic chemicals which would kill
organisms which promote degradation. They, therefore, concluded that
it is difficult to accurately predict the rate of biological
degradation.
It is generally believed that the chemical hydrolysis and
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precipitation processes are more significant in attenuating leachate
concentration and easier to predict than biological degradation.
Research has shown these processes to be pH dependent. If the p'H
of the waste constituents is known, then estimates of the effects
of these processes could be made.
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5. Sorption of Constituents
The attenuation "'of waste constituents by the sorption mechanism
was discussed by the panelists, primarily focusing their efforts on
the degree of confidence to which sorption can be predicted. Sorption
is a mechanism that works to retard the apparent movement of chemical
constituents by establishing-an equilibrium condition between the
chemical in solution and the chemical absorbed by the soil matrix.
Most panelists believed that there is a definite relationship between
the chemical in solution and the soil matrix that can be related to
several factors:
o The type of clays that are in the soil matrix
o The soil particle sizes comprising the soil matrix
o The organic carbon present in the organic matter in
the soil matrix
For example, certain types of clays adsorb some chemicals much more
readily than others; and porous mediums with finely divided clay and
silts will allow fluids immediate access to adsorption sites when
compared to a fractured medium where the porosity is more hetero-
geneous and absorption may not take place in voids. Most members
thought, however, that the organic matter was the site of most of
the chemical sorption. They believed that as long as there was
adequate uptake sorption capacity of this organic phase, it would
remove some portion of the leachate constituents from solution,
according to the equilibrium established between soil and solution.
Eventually, however, this capacity is exhausted and further sorption
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will not occur. Several members suggested that the sorption follows
an S-shaped curve oxrer time. .At the outset there is a gradual
increase in adsorption which tails off as adsorption capacity of
the organic phase is approached.
Several panelists also believed that this sorption process
which takes place in the organic phase of the soil matrix is
reversible over time. One member reported on his observations made
during a university ground-water recharge project. He indicated that
sorption was shown to be reversible when the input concentration of
the aqueous phase decreased causing it to desorb from the soil matrix.
He argued that this desorption mechanism may be particularly impor-
tant, sine a to clean up an aquifer after contamination would requira
removal not only of what is in the water, but also a large component
of the soil matrix. He felt this would be an enormous undertaking.
There were several members of the panel who believed that there
is enough expertise available for determining the sorption capacity
of a soil matrix. One member indicated that sorption capacity is
usually determined by hydrologists in terms of a distribution or
partitioning coefficient (K^). That is, sorption is calculated in
terms of the partitioning between the aqueous chemical phase and the
sorbing organic phase. He indicated that university laboratories can
*
estimate distribution coefficients for about $150 per ion per sample.
Once determined, he indicated that he often used £4 in the following
equation to predict the velocity of movement of a contaminant relative
x"
.»•
to the velocity of the groundwater:
3-16
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„ , . Velocity of groundwater
Contaminant velocity • £ r£
1 + — Kd
U
where Pb - dry density of the material
U » porosity
£b_ » 1-5 for most materials
v
For example, if the Kd of a particular ion is 100 and the velocity
of the groundwater is 100 feet per year, solution of the equation
would indicate that the velocity of the contaminant is less than a
foot per year, suggesting that the contaminant is of little or no
consequence in a human time frame. Several members pointed out that
they also have used this transport equation with fair success. They
believe, however, that its greatest drawback is the current lack of
t
experience in measuring distribution coefficients for most compounds.
They also believed that it is difficult to obtain representative core
samples of the geological media in place for calculation of K^. One
member suggested that the overall cost o.f these representative core
samples may also be as much as ten times the cost of running the K^
test in the laboratory. They argued that additional work is needed in
this area to establish reasonable correlations between different soils
and chemicals to obtain K^ coefficients without having to run laboratory
tests for each chemical in each soil matrix in a landfill.
3-17
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6. Supply of Trained Professionals to Make and Evaluate Predictions
The shortage of trained professionals to help make and evaluate
predictions of groundwater transport (e.g., hydrogeologists, soil
scientists, engineering geologists, etc.) was seen by the group as
a serious impediment to the development of an effective regulatory
program in this area. Several panelists believed that the demand for
trained experts in this particular area was beginning to outstrip
the supply of these individuals being produced by the universities.
They believed that this trend was detrimental to the state and
Federal agencies assigned to regulate the chemical landfill industry
because many of these agencies may not be able to attract enough
talented people to cope with their difficult regulatory mission. It
was believed that many of these individuals would be attracted
instead to private industry where they would probably receive better
pay and benefits than in the public sector.
One of the panelists who is an educator indicated that a similar
trend exists in the universities. He believed that since many
students with bachelor or master degrees are receiving $25,000 to
$30,000 offers from private industry, there is often very little
incentive for them to stay on and obtain advanced graduate training.
In addition, he believed that many faculty members are now finding
it more financially attractive to leave the university and secure
employment with private industry as well. The overall result of
these two trends, in his opinion, is a shortage of qualified people
3-18
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to go back into the universities to teach other students. Some
./
panel members suggested that setting up a national training program
might help deal with this particular problem, although it might take
5 to 10 years before any individuals would be adequately trained and
be ready for employment.
3-19
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Fourth Day
May 21, 1981
•
Gas Generation and Migration
-------
-------
INTRODUCTION TO THE FOURTH DAY
./•
This session was concerned with several issues related to the
movement of gases and vapors in and out of land disposal facilities.
Both impoundments and landfills were discussed. The panel attempted
to examine how confidently a permit writer could predict the genera-
tion of gases, their movement within the landfill, and their eventual
release to points of human and environmental exposure. This involved
first identifying what the state of the art for predicting gas
migration is. To make this determination the panel discussed the
predictive tools and control options available to management. The
discussion on predictive tools focused on models in use and currently
being developed. Physical, chemical, or manipulative methods were
examined as control options. As the panel discussed the state of the
art they tried to identify the amount and cost of data needed for
prediction, and the availability of the expertise required to produce
and evaluate data and predictions. The panel also made suggestions
on areas that need further development.
4-1
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THE PANEL FOR THE FOURTH DAY
,/*
Moderator;
Kenneth Shuster
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, D.C.
Panelists:
David Bauer
IT Corporation
336 West Anahein Street
Wilmington, CA 90744
Paul Harrison
Engineering Science
125 West Huntington Drive
Arcadia, California 91006
Charles Johnson
National Solid Waste Management
Association
1120 Connecticut Avenue, N.W.
Washington, D.C. 20036
Charles A. Moore
Geo t echnics, Inc.
912 Bryden Road
Columbus, Ohio 43205
Mike Roulier
U.S. Environmental Protection Agency
Municipal Environmental Research
Laboratory
26 West St. Clair
Cincinnati, Ohio 45268
Jerry Schroy
Monsanto Company
800 North Lindbergh Boulevard
St. Louis, Missouri 63166
Tom Shen
New York State Department of
Environmental Conservation
Room 138
50 Wolf Road
Albany, New York 12233
Louis J. Thibodeaux
Department of Chemical Engineering
University of Arkansas
Fayetteville, Arkansas 72701
4-3
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TECHNICAL ISSUES OF THE FOURTH DAY
o Models for Prediction of Constituents and Atmospheric
Emissions from Land Disposal Facilities
- Model development in its infancy
- Limitations on model use
- Identification of data needs for improvements
o Appearance of Gas in Leachate or Subcell Soils
- Several simplistic models for sanitary landfills
- Lack of data on chemical or co-disposal sites
o Prediction of the Migration of Gases within Landfills
- Capabilities, shortcomings, and potential uses of
a model for gas migration in the unsaturated zone
o Management Controls for Gas Migration
- Wind barrier placement
- Surfactants effectiveness
- Venting/Collection systems application to pressure
and diffusion problems
- Active venting systems disadvantages
- Use of subsurface injection plowing in Petroleum
Industry
- Overall disposal cost reduction from pretreatment
and segregation
o Monitoring Ambient Emissions from Surface Impoundments
- Lack of universal sampling and analysis standards
- Lower emission rates found at properly managed
facilities
- Measuring emissions at night or day
- Measuring over an impoundment vs downwind
- Insignificant monitoring results on gases selected
based on incoming liquid wastes
4-4
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SUMMARY OF THE FOURTH DAY
1. Models for Prediction of Constituents and Atmospheric Emissions
From Land Disposal Facilities
There was a lively discussion among the panelists regarding the
usefulness of state of the art models to make predictions regarding
both constituents likely to be present in land disposal facilities
and the release of such constituents to the atmosphere. Several of
the panelists contended that existing models, for example those
listed in Appendix F of the February 5th proposed regulations in the
Federal Register, contained too many erroneous simplifying assumptions
that did not account for necessary interactions (e.g., chemical
interactions) occuring in landfills.
The panelists indicated that except for certain simple cases,
the present models are still in their infancy. The models identify
the major factors of concern but need to be improved if they are
to be used for accurately predicting constituents. A major obstacle
to Improving the models is the sparce data base available. Several
of the panelists indicated that models for emissions from surface
impoundments are farther along than similar modeling efforts for
other land treatment facilities and can provide reasonable correlations
(within an order of magnitude) between predictions and monitoring for
simple cases. One panelist indicated that currently developed sur-
face impoundment models which are based on the general laws of
thermodynamics, can help predict, for example, the atmospheric
emissions of methanol and acetone wastes within'10 to 20 percent
of field and laboratory measurements. However, most members agreed
4-5
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chat emissions from more complex waste groupings in landfills, especially
those from existing landfills and co-disposal landfills, continue to
be extremely difficult to predict. They felt that the modeling of
such situations is handicapped both by a lack of data and lack of
understanding of important factors such as biodegradation and mass
transport mechanisms operating within these complex landfill
environments.
A number of the panelists argued that the results from existing
theoretical models for these complex landfill situations can provide
EPA with at least worst-case predictions until these mechanisms are
more fully understood and quantified. Other panelists indicated
that there is little confidence in such predictions. Further, these
panelists cautioned that there is a problem in looking at any model
for a single number. They indicated that there is no single numb.er,
only a statistical relation which should be considered for regulation.
One panelist went so far as to state that he would not endorse the
•use of existing models for writing EPA regulations, nor for making
any decisions on locating landfills. He also argued that these
models should not be considered representative of the state of the
art in modeling atmospheric emissions from landfills since such few
researchers in the nation are now utilizing them. In his opinion,
such models would more correctly be classified as developmental
rather than being termed state-of-the-art technology. He
revealed that his firm, a large chemical manufacturer uses, these
4-6
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atmospheric dispersion models only as "engineering tools" in making
judgments, e.g., selecting which equipment to use and whether to use
top caps to reduce emissions. He and several other panelists felt
that these models were most useful for pointing out generic emission
trends, but not for providing specific numbers for engineering and
regulatory purposes.
Several panelists focused their remarks on the type and amount
of data that are required to improve existing theoretical models
for the prediction of atmospheric emissions from impoundments. It
was generally agreed that the data in current literature on
atmospheric emissions from landfills and surface impoundments are
relatively sparce and that additional data are necessary from
detailed monitoring programs. Some of the panelists suggested that
EPA begin a pilot study to monitor the emissions from, say, five
representative landfill locations across the nation. These panel
members indicated that it would be desirable to collect better infor-
mation than exists on the following variables:
o Solubilities (Henry's Law Constants)
o Vapor equilbrium data (vapor pressures)
o Heat capacities
o Densities
o Diffusion coefficients
o Biological kinetics
o Wind velocity and duration
4-7
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o Air densities
° Solar insolation
They indicated that much of this kind of data is either unavailable
or erroneous in the current literature. The cost of obtaining some
of the data, however, may be quite high. One panelist, for example,
indicated that it cost his firm over $50,000 to gather data on just
the biokinetic factors for the compound acrylonitrile. He indicated
that other types of data would be considerably cheaper to obtain.
4-8
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2. Appearance of Gas in Leachate or Subsurface Soils
The panelists discussed the question regarding the types of
waste constituents that are most likely to produce gases in leachate
or subsurface soils of chemical landfills. Several panelists
indicated that cellulose or other organic materials in sanitary
municipal landfills commonly generates biogas, primarily methane and
C02. They indicated that several simplistic models have been devel-
oped to help predict the generation rate of such gases. However,
the panelists generally concluded that there are insufficient data
available on chemical or co-disposal sites to accurately determine
the types of constituents that would appear as gases. Some panelists
believed that additional data are necessary from existing sites,
particularly those practicing co-disposal of hazardous and municipal
wastes since their gas generation is typically the hardest to accurately
predict. Several other panelists believed, however, that existing
data were sufficient to show that chemical landfill sites generally
have less gas production than municipal landfills. Overall, most
of the panel agreed that there is limited experience in predicting
the generation of different gases from landfills.
4-9
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3. Prediction of Migration Within Landfills
This discussion focused on the degree of confidence with which
state of the art models can help predict the migration of gases in
the unsaturated and saturated zones. They indicated that most current
models deal only with municipal landfills. There are some first
order kinetic models available, but most assume a homogeneous fill
which is rarely applicable to actual practice. These models are
designed primarily for methane and carbon monoxide.
One panelist presented a detailed overview of a model which he
has recently developed to predict migration of gases in the partially
unsaturated zone. He indicated that his model can handle the combined
diffusional and convective pressure transport of multi-component
gases under partial and total pressure gradients. While temperature
is considered as a parameter in the model, transport under a thermal
gradient is not considered, nor is the transport of heat itself.
His model can, however, handle any number of chemical reactions,
provided that the kinetics of the reactions are known. The model
can also handle the combined flow of gases either in the presence
or absence of control mechanisms.
He defined his model as being "predictive" and he believed the
model eliminated the necessity of conducting laboratory tests to
predict the transport of gases. His model only requires that the
properties of the gas and soil be specified and does not require
calibration data or laboratory flow rates. He believed that this
4-10
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was a. particular advantage to this model because it has the potential
capability of being "easily extended to other types of constituents.
He indicated that the current cost of running the model was generally
around $1,000 per computer run. A field verification study of his
model is now underway in which methane transport will be empirically
determined,
This panelist indicated that his model has several important
shortcomings or limitations. For example, his non-linear model
handles a fair degree of heterogenicity, but was not specifically
developed to simulate the type of cell structure that exists in a
landfill. His model also deals only with gaseous transport within
the soil. He indicated that the greatest weakness is that venting
at the surface is taken into consideration using simplified surface
evaporation based on partial and total pressure differential equations,
He felt that researchers may need to couple his model with
atmospheric transport equations so as to account for the interface
conditions between the soil and the air instead of only the boundary .
conditions. The panelist also indicated that if his model is used
to predict the migration of gases other than the "light gases" (e.g.,
methane) for which it was designed, laboratory confirmation may be
necessary to verify the basic equations of gas transport. Lastly,
the model does not account for the transport of gases through frac-
tures in the landfill top cap or cover.
Overall, most of the group generally agreed that the "model
4-11
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was a good start toward helping predict the movement or migration
of gases within a landfill. Several participants were concerned
that this model, as presently constituted,does not model gaseous
flow in the unsaturated zone, nor is it applicable to gases other
than methane. Under questioning from the panel, the model developer
indicated that his model does take into account the solution of
gas in groundwater, particularly C02, by predicting the groundwater
qualities as a function of time and position as the groundwater
becomes altered by the C02 going into it. With reference to the
later question, the panelist was uncertain whether his model
could be used to predict the gaseous migration of organic compounds
other than methane. He suggested that the diffusion constants for
methane in his model might provide the upper.limit on the rate of
gaseous diffusion in a landfill because no other hydrocarbon is
expected to diffuse any faster than methane.
4-12
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4. Management Controls for Gas Migration
There are several different management techniques that have been
utilized by hazardous waste facility operators to help control
the migration of gases. The panel briefly discussed the following
different control techniques, focusing primarily on their applicability
in mitigating the effects of gas migration:
o Barriers
o 'Surfactants
o Venting/Collection Systems
o Liners
o Injection Plowing
o Pretreatment and Segregation (source control)
Wind barriers such as trees, crops, and snow fences placed
perpendicular to the direction of the wind can deflect the wind stream,
potentially affecting the impacts of wind (e.g., gas volatilization)
blowing across an impoundment. One panelist suggested, however,
that without the proper design, a wind barrier might protect one
side of a large impoundment while the middle or other side could
actually receive more ventilation and turbulence than they would
otherwise. This panelist also suggested that a thick non-volatile
material placed on top of an impoundment could also serve as a wind
barrier. He indicated that this layer would reduce the increased
volatilization of gases due to wind. However, in high wind conditions
such an artificial layer could be blown around the impoundment. In
4-13
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addition, several panelists argued that these barriers, by reducing
the wind's action, can reduce the oxygen transfer available for
aerobic biological activity in impoundments. Nevertheless, a few
panelists believed that such barriers could be used effectively
with holding ponds. One panelist indicated that agitation or aeration
systems seem to have less emissions. However, one panelists noted
that the effect of an aerator will depend on whether degradation is
controlled by the gas phase or the liquid phase. Another panelists
indicated that if the material does not biodegrade then air stripping
predominates and would be increased by aeration.
Surfactants were judged by most members of the panel as not
being highly effective in reducing gas emissions from surface
impoundments. One panelist indicated that surfactants should not
be utilized in impoundments with activated sludge systems. He felt
that these materials would probably be degraded by the microorganisms
and thus, the surfactant would not serve a useful purpose other
than as an expensive food for the microbes in the impoundment. He
also indicated that some detergents could destroy the microorganisms.
Several other panelists suggested that some pulp and paper wastes
may act as natural surfactants, but they may otherwise increase the
gaseous emissions from the landfill. Another panelist suggested
that flocculants may be more effective than surfactants because they
f
can bind materials in an impoundment, thereby minimizing the partial
pressure and total surface area. His experience indicated that the
4-14
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hydrocarbon emission rate in impoundments was commonly reduced by
_/•
the addition of flocculating agents.
Venting or collection systems are also used by landfill operators
to control atmospheric emissions and the build-up of gases. One
panelist suggested that in order for an operator to determine if gas
venting systems will operate efficiently, he should first determine
whether the gas migration is primarily a pressure or diffusion
problem. He indicated that if the predominant mechanism is pressure
flow then the operator should probably choose a passive venting system
which will remove the pressure gradient. On the other hand, if the
primary gas transport process is diffusion, he suggested that a
passive venting system would probably not be effective and may in-
crease the problem. He stated that in cases where gas diffusion
exists a landfill operator should construct a gas impervious barrier
that would reach to another gas impervious layer such as the ground-
water table. Failing to do this, the gas will eventually escape
from the landfill.
Active venting systems, which incorporate a flaring or incinerating
process, have been suggested by some as a means to reduce the
quantities of captured gas in a landfill. Most panelists believed,
however, that such processes should not be used in a landfill situation
primarily because the hazardous gases being flared off may not be
totally incinerated during flaring and could pose an environmental
hazard. One panelist suggested that instead of^incinerating materials
4-15
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such as PCBs and benzenes, refrigeration should be considered as a
possible commercial means for reducing these emissions. He argued
that it was probably far less expensive to lower the temperature of
such gases than to heat them to temperatures as high as 2,000°!.
Synthetic liners or impermeable caps have also been prominantly
mentioned as tools to control the migration of gases from landfills.
Most members of the panel generally concluded that during the course
of normal operations such materials might exhibit differential
cracking due to environmental conditions and that clay covers would
require active maintenance. One panelist argued that if the gas migration
within a landfill is a diffusion flow mechanism the probability that the
gas within the landfill would escape from any one hole or crack in
the liner is remote. One the other hand, if the gas migration is a
pressure flow phenomenon, then he felt that a good deal of the gas
would move to the tear or crack in the liner and exit the landfill.
Some panelists suggested that landfill operators can construct a
hybrid type of control system that would have both a liner and a
granualar trench. One panelist hypothesized that the granular trench
would insure that the gas pressure would be relieved with the liner
membrane serving to slow down the diffusional flow even if it had an
occasional hole or tear. Another participant cautioned the panel
that most synthetic liner products are not totally impermeable to
gas diffusional flow, since membranes are used industrially to
separate gases.
4-16
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The panel also briefly discussed the effectiveness of subsurface
injection plowing to deduce gas volatility in land treatment opera-
tions. Several panelists indicated that this technique has been
used by the petroleum industry to reduce the potential emissions of
sludge from refinery tank bottoms. Typically, the materials are
plowed into the top eight to ten inches of the soil, resulting in
significant emissions for the first few days. One panelist indicated
that the industry is currently experimenting with subsurface injection
plowing which involves lowering the plow slice to below ten inches and
then injecting the sludge material at the bottom of the plow slice
allowing the soil to fall back on top. This technique has been shown to
reduce the gas emission rate and prevent the destruction of aerobic life
at the soil surface. However, it is necessary to replow two to four
weeks later and this action can cause a burst of emissions. Another
panelist said that now subsurface injection is being done by vacuum
trucks and re-aeration is done without turning the soil. Several panel-
ists noted, however, that injection plowing is a new technique and
there are very little data concerning its effectiveness.
Pretreatment, or segregation of wastes (source control) has also
been suggested as another management technique to reduce 'gas
volatilization. One panelist indicated that his disposal firm
routinely pretreats its wastes to remove any volatile organics before
these materials are placed within the impoundment. He indicated that
4-17
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they have internal rules for heating and stripping (e.g., distillation,
air and stream stripping) volatile materials as well as separating
wastes into categories. His fira believes that if pretreatment is
not done correctly, the final treatment takes longer and increases
the overall disposal costs.
4-18
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5. Monitoring of Ambient Emissions From Surface Impoundments
Most of the panelists in earlier discussions generally agreed
that techniques for predictive modeling of emissions from surface
impoundments are more advanced than similar modeling efforts for land-
t
fills and land treatment facilities, but that they still need improve-
ments if they are to be used as a predictive tool. One of their
conclusions was that the development appropriate emission factors to
characterize existing or new surface impoundments is handicapped by
the lack of an adequate data base. The panel discussed several methods
that they felt could be used to help measure the atmospheric emissions
from surface impoundments, focusing on the various problems and
factors that may influence monitoring efforts.
The discussion that followed generally indicated that there
is no universally accepted method to collect samples, let
alone to analyze samples of hazardous emissions that are found
over impoundments. Furthermore, analytical procedures are not well
defined for measuring concentrations that are found. There
appears to be a variety of techniques currently utilized by dif-
ferent researchers around the nation, each technique with its
own particular advantages and disadvantages. The panelists also
indicated that monitoring only gives trends not absolutes. At
the outset of the discussion, several panelists pointed out that if
the wastes placed into an impoundment are pretreated, the level of
atmospheric emissions coming off the facility may be extremely low,
4-19
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probably below the level of detectability for most air sampling
devices. These lower thresholds nay be detectable using more expen-
sive devices. However, thresholds at this low of a level may not
be a threat to human health and safety. Most of the panelists
agreed, however, that if impoundments are not properly managed, their
emission rates may be very high. Thus, current monitoring techniques
may be successful la measuring their emissions. A number of panelists
reviewed their currant experiences in monitoring emissions in impound-
ments. Most indicated that meterological conditions (e.g., wind
speed) greatly affected the monitoring. Emission rates are likely
to be highest when wind speeds are high; however, due to the diluting
effect of the wind, the concentrations cannot be measured. On the
other hand, when wind speeds are low, emission rates may be lowest
*
but have the highest concentrations.
One panelist discussed a technique that he used to monitor air
emissions, primarily methanol, from impoundments for the pulp and
paper industry. From samples of the wastewdter going into the
impoundment it was known that methanol was readily available and
would be emitted. His research team sampled at six heights over
each point over several day's time at one impoundment (e.g., upwind and
downwind of the basin). They found that the best time for
detection (of a readable sample) was in the middle of the night
when the wind was very calm, rather than sampling the air
in the middle of the day when the wind speed is much higher. Although
4-20
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the emission rates may be higher in the afternoon than at night, the
methanol being emitted from the impoundment could not be detected
because of the wind's diluting effect.
Another panelist indicated that he has attempted to run a
material balance just in the air boundary layer above a large waste
lagoon (roughly 80 to 100 acres) and has found it extremely difficult.
His technique involved attempting to plot the plume coming off the
impoundment by sampling air emissions at the shoreline at different
lateral points, measuring the flux through an imaginary wall at dif-
ferent heights along the plume, and determining average concentrations
over long periods of time. The need to average over long periods of
time was emphasized. He also indicated that when the contaminant
concentrations are very close to the background concentration, his
flux equations are very difficult to solve. In such instances, his
results are usually poor. He believes that if the particular para-
meter cannot be measured over the impoundment, the chances of measur-
ing the parameter downwind is quite small.
Another panelist indicated that his firm, a large chemical manu-
facturer, has developed a scenario in which they can monitor specific
parameters to help estimate air emissions at the property line for
an impoundment. They monitor the solution of waste liquids coming
into their impoundments and analyze their results using a gas chroma-
tograph. These results tell them what constituents to monitor for in
the air over the particular site. Their monitoring technique involved
4-21
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stringing a cable with sensors across the impoundment and at the
property line. He indicated their research so far has indicated
insignificant concentrations of organic emissions. However, another
panelist indicated that he did not believe that there was a direct
correlation between what is in the impoundment and what is in the air.
In summary, most of the panel generally agreed that atmospheric
monitoring of emissions from impoundments is not a very well developed
field. The techniques described by the various panelists are largely
experimental and require specialized training, particularly in
meterology. Additional work on improved monitoring techniques was
a major suggestion by most panelists.
4-22
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Fifth Day
May 22, 1981
Health Effects Resulting From
Hazardous Waste Exposures
-------
INTRODUCTION TO THE FIFTH DAY
./•
The final session of the conference addressed the topic of
Health Effects Resulting from Hazardous Waste Exposures. Panelists
in the previous days discussions had addressed the phenomenon of
fluid flow from land disposal facilities and the means that exist to
quantify and control that flow. For sake of discussion, the panelists
in this session assumed that the concentrations of hazardous constit-
uents present in individual land disposal facilities are known.
They discussed the various types of risks that may be presented to
human health and the available means to estimate the magnitude of
those risks. The focus of the discussion was on how a permit writer
proceeds to evaluate the potential health effects posed by an exist-
ing or proposed land disposal facility. The panel attempted to
identify existing regulatory standards and criteria which could be
used as guidance. If no such standards or criteria exist they
considered other feasible approaches. Where possible the panel was
asked to identify degrees of confidence and suggest areas or
techniques for development which would increase the accurate predic-
tion of health effects to humans from the disposal of hazardous
wastes.
5-1
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THE PANEL FOR THE FIFTH DAY
Moderator
Robert Taylor
U.S. Environmental Protection Agency
Washington, D.C.
Panel Members
Larry Claxton
U.S. Environmental Protection Agency
Research Triangle Park
North Carolina 27711
Robert B. Gumming
Biology Division
Oak Ridge National Laboratory
P.O. Box Y
Oak Ridge, Tennessee 37830
Joseph Fiksel
Risk Management Unit
Arthur D. Little, Inc.
Acorn Park
Cambridge, Massachusetts 02174
Ralph Fruedenthal
Stauffer Environmental Health Center
400 Farmington Avenue
Faraington, Connecticut 06032
Joseph Highland
Chairman, Toxic Chemicals Program
Environmental Defense Fund
1525 18th Street, N.W.
Washington, D.C. 20036
Robert McGaughy
Cancer Assessment Group
U.S. Environmental Protection Agency
Washington, D.C. 20460
Riva Rubenstein
National Solid Wastes Management
Association
1120 Connecticut Avenue, N.W.
Washington, D.C. 20036
David Smith
IT Corporation
336 West Anaheim Street
Wilmington, California 90744
5-2
-------
TECHNICAL ISSUES OF THE FIFTH DAY
_,>
o Methodologies and Techniques for Predicting Carcinogenic
Effects
- Results from in vitro useful in identifying carcinogenic
substances of concern
- Results from animal bioassay fairly predictive in
evaluating carcinogenic potential
- Results from bioassay test establishing health criteria
in legal system
- Epidemiclogical results useful when cancer risk factor
is very large and unequivocal
o Use of Human Risk Numbers for Permitting Decisions
- Use of ranges rather than numbers causes concern
- Inadequate assessment techniques create difficulties
in establishing permit standards
- Assumptions behind standards must be understood before
used
o Sources of Additional Data for the Permit Writer
- EPA is the largest producer of related data
- Considerations for reforming EPA's protocol on
unpublished data
o Toxic Effects to Humans
- Dose level methodology provides "legal safety"
measures not scientific measures
- Safety levels should apply to the human population, not a
standard man
5-3
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SUMMARY OF THE FIFTH DAY
1. Methodologies and'Techniques for Predicting Carcinogenic Effects
The panelists discussed two types of tests that are currently
available for evaluating, the carcinogenic effects of chemicals. The
first is the in vitro (e.g., Ames test) which uses cell systems and
cultures to predict transformations from normal cells to malignant
cells. The panel believed that such short-term tests can be most
useful as a screening tool in identifying carcinogenic substances
of concern. Several panelists indicated that the in vitro test
can give quick and inexpensive qualitative (not conclusive) predictions,
but is not useful for making extrapolations to human risk. One
panelist even suggested that the use of human cell cultures in a
short-term in vitro test may not be a better predictor of human risk
than the use of animal cells since there is evidence that results of
all in vitro tests are much more similar to each other than to
in vivo tests. They noted that there is a major difference in
findings on human cells and predicting results on humans. Several
panelists felt that these short-term tests often do not consider -~
the effects of important mechanisms such as the biological rates of
absorption of carcinogens. One panelist revealed that his research
has indicated that often the chemicals which are the most carcinogenic
have shown the weakest response in these short-term cell tests and
thus doubted- their usefulness for predicting in the qualitative sense.
The second type of test that is currently available for
5-5
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evaluating the carcinogenic effects of chemicals is. the animal
bioassay. An in vivo animal bioassay takes about two years and
costs about $0.5 million. The panelists indicated that about one
thousand in vitro tests could be done for each animal bioassay. Most
of the panelists generally agreed that if these long-term tests
show carcinogenic results with at least two species of animals, the
results obtained are believed to be fairly effective, especially
with the NCI (National Cancer Institute) bioassay, in predicting the
carcinogenic potential of the particular compound under study. One
panelist also indicated that when these bioassay tests are repeated
using the same route of carcinogenic exposure, the results are
usually reproduceable within a factor of 10, and often within a
factor of 2 or 3. Using different routes of exposure, there is a
wider range of difference. Yet, while most panelists believed that
such tests are fairly predictable of cancer risks, extrapolation to
the human situation was felt to be uncertain and subject to consider-
able variability. The greatest uncertainty was felt to be in
extrapolating from large doses used in tests to the effects of small
doses. One panelist indicated that the an-final bioassay is the
best test available for assessing the carcinogenic potential, but
he does not agree it is necessarily a predictor of human carcinogen-
ic ity.
Several of the panelists indicated that animal bioassay
tests have already been built into the legal system. In order to
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determine legal safety in terms of carcinogenic chemicals, the results
of the bioassays have generally been utilized in existing formulas
to calculate a legal standard of human risk. These panelists argued
that such a technique does not really predict the risk to human health,
but rests totally on a legal determination of safety and does not
necessarily relate to the actual impact on human health measured in
terms of the number of hospital admissions, morbidity, etc. Most of
the panel felt that while such formulas are good for determining legal
risk these formulas are based on simplifying assumptions and uncertainties.
They believed that the public is often not aware of these assumptions
and thus, takes the unit risk numbers of cancer in the human population
predicted by such formulas at face value. While such numbers are
useful, most panelists believed that this type of risk assessment is
semi-quantitative at best and is only an estimate. Yet, most panelists
believed this is about the best that can be done given current
state-of-the-art conditions in risk assessment of carcinogens.
A number of panelists suggested that the accumulation of epidemio-
logical experience with carcinogens is the only reliable indicator
of how well the current techniques have predicted human risk. Most
panelists felt, however, that epidemiological techniques may be
effective only when the cancer risk factor is very large and
unequivocal (e.g., cigarette smoking). Where the risk factor is
low or where there are a multiplicity of factors involved, most
panelists believed that epidemiology is only marginally useful
5-7
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in estimating human risk. In addition, it was believed that the
accumulation of epidemiological data to support predictions would
be slow and difficult for chemicals of interest to EPA.
5-8
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2. Use of Human Risk Numbers for Permitting Decisions
_y
One of EPA's current concerns is whether risk assessments can be
useful in making permitting decisions in the area of land disposal of
hazardous wastes. The panel specifically focused on this topic
addressing the issue of whether these techniques can provide useful
data on human risks with respect to either authorizing a new site, or
denying continued operation of an existing activity.
The panelists indicated that risk assessment is only applicable
to chronic effects. They noted that no one has ever done risk
assessments for acute effects and that the distribution on sensitivity
of human populations to acute effects is not known.
The panelists agreed that risk assessment is semi-quantitative
at best. One panelist postulated that risk assessment may be going
too far too fast and expressed doubt in the existing numbers. Another
panelist indicated that there is considerable value in developing
quantitative risk assessments even if there are large error ranges,
providing the inaccuracies are understood. Major sources of error
result from assumptions that data on one species are transferable to
other species and from extrapolation of results from high doses to
low doses. This panelist indicated that relative risk assessments
are done based on the number generated. Another panelist disagreed
stating that the magnitude of the large error precludes relative risk
assessment.
With regard to applying risk criteria to permitting of sites,
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most members of the panel argued that while scientists can predict
impacts to ground-water quality as a result of land disposal activities,
current risk assessment techniques are inadequate in determining if
a particular level of contaminants is acceptable with regard to human
health. They indicated that the risk pathway for land disposal of solid
wastes is very poorly understood at present. The problem is in
determining the transport of contaminants and in quantifying exposure,
especially for new sites. Several panelists noted that predicting
exposure patterns from land disposal sites is currently impossible.
The panelists stated that there was also a need to develop reliable
exposure data. These panelists believed that the protection of human
health would probably best be achieved through source related standards
(e.g., landfill standard) which are more concerned with minimizing
the releases rather than with attempting to evaluate what an acceptable
level would be upon human and biological health. However, several
panelists were somewhat more optimistic in using risk numbers for
existing sites since the exposure patterns were felt to already exist.
*
Several of the panelists felt there was, nevertheless, a need by the
land disposal industry for EPA to set specific standards for new and
existing land disposal sites. They argued that these limits could
be reset if the limits were found at a later date not to be acceptable.
Another panelist argued that while it is not possible to extrap-
t
olate precisely, EPA's water quality criteria for toxic pollutants
(45 FR 79318) were directly applicable for evaluating risk-of chemical
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toxicity to human health. He felt that this document represents the
_t
most consistent framework so far for analyzing the level of human risk
in landfill situations. He argued that hazardous waste permit writers
could select an acceptable risk level from the numbers provided in
this document for both new and existing sites. Another indicated
that existing numbers should not be used without first looking at the
exposure assumptions behind the criteria.
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3. Sources of Additional Data for the Permit Writer
The panelists discussed additional sources of data available to
EPA permit writers dealing with human risk factors associated with
land disposal of hazardous wastes. Most panelists indicated that the
major source of data outside of EPA is other agencies of the Federal
government. There are a number of Federal agencies such as NIOSH that
internally produce toxicological data. The NIOSH Registry of Toxic
Effects of Chemical Substances may be an important source of infor-
mation on the toxic effects to humans. Several of the national
laboratories also produce similar data in their biological programs.
One panelist suggested that much of the government agency and
national laboratory data ultimately appears in print and is usually
carefully produced. The panel indicated that other sources of data
are industries, hospitals and contract laboratories. Some of this
data may be difficult to obtain or proprietory in nature, but could
be released in support of a particular government permit. Several
panelists indicated that some data produced from contract laboratories
and other businesses producing data for a fee are of variable quality
and reproducability.
The panel next turned to the question of whether data that are
currently unpublished should be accepted in permitting hazardous
waste management facilities. Several panelists indicated that there
is a protocol in EPA Water Quality Criteria Document stating that
only published data (e.g., published journal articles7
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company reports to EPA) can be accepted so as to provide for public
./•
rebuttal. -Overall, the panel thought that it vas not a good policy to
limit data use to only published data. Several members of the panel
believed that peer reviews accompanying regularly published data is
commonly not adequate for discerning the quality of data. Additionally,
they believed that much of the data which gets into the published
literature after getting through the peer review process may not be
in a form that is usable to EPA. Several other panelists disagreed
arguing instead that peer review has value since it filters out the
worst sets of data and research designs. However, most of the panel
agreed that whenever published data are used in a permit application
they must be independently evaluated regarding the overall research
design and statistical validity. They also recommended that primary
data sources be used rather than secondarv sources.
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4. Toxic Effects Co Humans
The panelists next discussed the methodologies and techniques
used for predicting acute and chronic effects resulting from exposures
to toxic compounds. The moderator indicated that EPA, in developing
water quality criteria, used several toxic effect levels: NOEL (no-
observed-effect-level) , LOEL (lowest-observed-effect-level), LOAEL
(lowest-observed-adverse-effect-level), and FEL (frank-effect-level).
The panel was asked whether this methodology or any other had
particular merits in determining toxic effects in man.
Several panelists indicated that a common practice is to reduce
the LOEL available from a good number of comparable studies by a
factor of 100 in order to determine an acceptable daily dose rate
for that compound for a normal, 70 kilogram (150 pounds), adult male.
They noted that when additional information is known about the
interaction of the compound and humans (e.g., metabolism of a particular
substance) the LOEL may need to be reduced by a factor of 1,000 rather
than by 100. A number of panelists indicated that the daily dose
level that is calculated by this technique is a very crude safety
level for acute toxic effects. Although this technique was felt to
have very little theory behind it, some panelists believed that the
technique has provided dose measures that allow fairly good protection
against acute*toxic effects in man (e.g., people do not die ingesting
these concentrations). Several panelists cautioned, however, that
the daily dose rates produced by this technique do not necessarily
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provide protection to humans against a chronic effect or from synergistic
-/•
effects of multiple compounds. However, panelists noted that while
these measures do not offer absolute safety, they do provide a measure
of "legal safety" which regulators can potentially monitor and enforce.
A number of panelists noted that results from animal studies
suggest that different safety factors would be appropriate for
different substances and that they expect human populations would have
a much larger variability and sensitivity to toxic chemicals than any
animal population. They indicated that there are certain substances
for which the acute levels or the incidence of acute effects in
animals increases as the dosage of the toxic compound gradually in-
creases . They indicated that for certain compounds a relatively flat
increase can be observed whereas with other substances a very sudden
threshold is observed at which detoxification mechanisms no longer
work and the LDso (dose causing death in 50 percent of test animals)
is reached fairly rapidly. They felt, therefore, that it would be
an exercise in futility to try to create a dose rate for a standard
human since there are numerous subpopulations of humans that are
uniquely sensitive to a given dose of a toxic chemical. Overall,
most of the panel generally agreed that while there are usually
sensitive people to certain chemicals, the general approach still
*
should be to determine a legal margin of safety for the human pop-
ulation as a whole.
The panelists also indicated that determination of synergistic
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or antagonistic effects, morbidity, phytotoxic effects, and bioaccum-
ulation need to be carried out on a compound-by-compound basis. Results
from one compound cannot be extrapolated to another compound.
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Appendix A
Agenda
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AGENDA
May 18 and 19, 1981
I. Leachate Generation (Quantity and Quality); Attenuation in
Liners and the Unsaturated Zone; and Management Approaches to
Control 'Leachare Quantity and Quality
In this session, we will examine the chief factors which are
relevant to controlling the quantity, the time of first release,
and the quality of leachate which is discharged from land disposal
facilities into the ground. {On Wednesday, the fate and transport
in ground water of leached constituents which have been discharged
will be discussed.)
The questions listed below are intended to direct the panelists'
attention to several major issues.
First, we will attempt to establish leve'ls of confidence in
predicting the performance of facilities. No matter what one's
goal is (i.e., controlling leachate quantity, containment time,
or leachate quality), it will be necessary to examine particular
land disposal facilities or proposed facilities and predict
whether they will achieve the stated goal. Any such prediction
involves some uncertainty. We wish to identify the relative
degrees of confidence and uncertainty in making predictions and,
if possible, to identify situations in which such predictions
are subject to particularly high or low degrees of confidence.
Some factors affect facility performance more than ethers.
In particular, given any mathematical model for predicting leachate
generation, the range of variability or error in predicting
particular inputs to the model (e.g., the pe'rmeability of a
natural clay liner or the infiltration rate of liquids) may
be either compressed or expanded in the output (e.g., the
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concentration of 'a particular constituent exiting the facility
or the time when leachate first exits the facility). The questions
below attempt to identify the factors that are most critical in
predicting leachate generation, and of those factors, the subset
of factors for which errors in prediction result in significant ' "
errors in predicting the facility's performance. Furthermore,
we will try to identify how confidently these important factors
can be estimated or predicted.
Since such estimates or predictions depend to a large part
en data, we will discuss the type and amount of data needed to
achieve particular levels of confidence, the cost of obtaining
the data, the degree of expertise required to generate or collect
the data, and the current availabiity of such expertise. Since
the estimates also depend on the accuracy of the model or equation
applied to the data, we will also discuss the confidence with
which models which use simplified assumptions or complex models
(which may or may not have been field tested) can be used. Finally,
for each discussion, we will consider the capacity of regulatory
agencies to evaluate these estimates and predictions.
Second, we will identify and discuss the major waste management
techniques that can help achieve any identified goal. Furthermore,
we will examine whether any of them help narrow the range of
uncertainty in making predictions.
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A. Leachate Quantity and Duration of Co.ntainment Period
1. Sources of Liquids
a. Net Precipitation Rates; With what degree of
confidence can one predict precipitation and evapotranspiration
rates? What range of error is likely to be introduced by major
/
storm events or periods of unusually large cumulative precipitation?
Given the longevity of land disposal facilities, what is the effect,
for example of preventing run-on from a 25-year, 24-hour storm
but not from a 100-year, 24-hour storm? To what extent will this
introduce error into predictions of leachate quantity? (Consider
both wet and arid climates.) To what extent can any design or
management techniques minimize the- range of error? How can
appropriate worst-case assumptions be developed to provide
confidence in predicting maximum possible leachate quantities?
b. Use of Top Liners to Prevent Infiltration of
Precipitation.
With what degree of confidence can infiltration of rainwater
(or of inadvertent run-on) be prevented or minimized by the use
of synthetic liners and clay liners as caps after closing the
facility or by the use of intermediate liners during the facility's
operating life?
i. What is the maximum period of time during which
a synthetic liner or cap may be expected to function effectively?
Is it technically feasible to replace synthetic top liners when
necessary over long periods of time? Are appropriate laboratory
or field tests methods available to predict a svnthetic liner's life
s~ **
with confidence?
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ii. With respect to a clay liner or cap/ how likely
is it that any of the events listed below may occur? In each
i
case, how much uncertainty could the occurrence of such an event
introduce into a prediction of the amount of liquids entering
( •
the facility? In discussing the likelihood of such events,
i
consider the available management techniques for decreasing the
likelihood, and the feasibility and cost of those techniques.
Consider the ability to address these events over varying periods
of time (e.g., 30, 100 or 500 years).
(1) Channels in the liner or cap caused by root penetration
(2) Channels in the liner or cap caused by burrowing animal3,
(3) Channels in the liner or cap caused by fingering
resulting from nonuniformity of material
(4)" Erosion of the liner or cap
• i
(5) Cracks in the line*r or cap caused by the consolidation
of underlying waste and earth materials and
resulting differential settlement
(6) Cracks in the liner or cap caused by decreases in
moisture content or by reactions of infiltrating <
liquid with the liner's earth materials
(7) Cracks in the liner or cap caused by freeze-thaw cycles
c. Groundwater Infiltration • '
To what extent can water infiltration into the facility ,
through the sides and bottom be prevented?
i. If synthetic liners are used on the sides of '
the facility, is replacement of failed liners a technically
feasible option? If clay liners are used on the sides of the
facility, how confident can we be that the liners' relative
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impermeability will not be impaired? In particular, what manage-
ment techniques may be used to minimize the problems listed in
Questions (b)(ii)(3)-(7) above?
ii. Where the natural water table is high enough
to intersect at least part of the facility, what means could be
used to artifically lower the water table and prevent water from
infiltrating through the aides or bottom of the facility? Could
these means effectively keep infiltration out in the long term
after closure? Consider both passive systems (e.g., trenches)
and active systems (e.g., pumps).
d. Liauids in or Produced bv Wastes (Applies only to
landfills)
i. How significant are the quantities of liquids
in buried wastes (including liquids in drums) or liquids produced
by wastes (by decomposition of organic wastes) in relation to
'the total amount of liquids entering the land disposal facility?
ii. In cases where such liquids could be significant,
what pretreatment techniques (e.g., dewatering of sludges or
biologically degrading the organic wastes prior to disposal) are
available to minimize this problem? How reliable are these
techniques and what are their costs?
e. In what situations, if any, would it be environmentally
preferable not to prevent or minimize the entry of liquids into a
landfill or a closed surface impoundment?
2. Mass Rate of Discharge and Time of First Discharge of
Liquids
Whenever clay liners are discussed below, consider the unsaturated
soil as well.
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a. Permeability of Clay Liners
i. What level of confidence can we achieve in
predicting the overall permeability (and thus mass rate and time
of first discharge) of intermediate and bottom liners in light
of variations in the materials used for liners (e.g., variation
in type or amount of clay, existence of lenses in in-situ liners ,
and in leachate composition)? How much data must be obtained on
such variations (particularly in the case of natural in-place
bottom liners or unsaturated zones relied upon to control leachate i
migration) to achieve a particular degree of confidence? What
is the cost of developing such data? What expertise and equipment
is required, and to what extent are they currently available? <
•
How likely is it that collecting many samples to develop data
would impair containment by creating channels?
ii. To what extent can leachate decrease the " '
permeability of liners? Can any leachate constituents reduce
permeability by precipitating and plugging pores? In what situations
can this be predicted, and with what confidence? Consider different
types of liner material.
iii. To what extent can leachate constituents
i
increase liner permeability by sorbing to clay surfaces and
changing interlayer spacings; dissolving constituents of clay ' ,
minerals; shrinking clay liners by displacing pore water; and
(
affecting the surface' tension of pore water? How confidently can
such effects be predicted? To what extent does the level of
confidence depend on precise knowledge of leachate quality (discussed
<
in section B of this session)? What impact does error in predicting
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changes in permeability have on the range of error in predicting
either containment time or the rate of discharge after containment?
_y
Are any liners or natural soils relatively immune from attack by
leachate or by certain types of leachate as the result of structural
properties (e.g./ types of crystal formation) which resist expansion
and contraction?
b. Permeability of synthetic Liners. During its useful
life (see Question A(l) (b.) (i)), what level of risk is there that
a synthetic liner will tear or be degraded by chemical reactions?
In such event, how likely is it that a surge of leachate will be
able to exit the facility?
c. Capillary Forces; How signficant is correct estimation
of clay liners' capillary forces to predicting the initial contain-
ment period of the liner system? How dependent is this estimation
on knowledge of moisture content? How much data is needed to
estimate moisture content? What is the effect of leachate with
a specific gravity or surface tension differing from water?
d. Leachate Collection System
i. What are the practical limits on the effectiveness
of leachate collection systems? Consider the use of different types
of liner materials.
ii. In the long term, what is the likelihood
that the effectiveness of a leachate collection system will be
impaired? Consider, for example, plugging of the drainage media,
or increased permeability of the liner under the drain (as discussed
in question (a)(ii)(2) above).
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iii. In the long term, what maintenance will be
necessary to operate the leachate collection system? Consider both
active (pumps) and passive (gravity) systems.
iv. Given that the rate of ieachate discharge is
very sensitive to errors or variability between the design and actuai
*
performance of leachate collection systems (e.g., if a system
that is designed to remove 99% of any liquids passing through
actually removes only 90%, the actual leachate quantity discharged
will be 10 times the predicted quantity), how well can such
error or variability be controlled? Is it reasonable to assume
a very high (e.g. 99%) theoretical efficiency in predicting the
discharge rate of leachate? Is it reasonable to build in a safety
factor in designing the system?
v. What are the costs of installing and operating
and maintaining leachate collection systems over long periods?
vi. What are feasible techniques for managing
collected leachate, both during facility operation and after
facility closure?
e. What methods other than leachate collection systems
are currently available as early warning systems for breakthrough
of liquids out of a facility? How reliable are these methods,
»
particularly over long periods of time?
3. Quality of Leachate Discharged From a Facility
1. Production of Leachate from Single Wastes
Assuming for purposes of simplicity that only a single
type of waste is placed in the facility, how,, well can we predict
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the constituents that will be leached from the waste and the
concentrations at which they will be released?
a. How critical are each of the following factors in
-»•
confidently predicting the leachate quality?
(i) Leaching medium
(1) Proton and electron environment (pH,
redox potential, ionic strength and buffering capacity)
(2) Presence of solubilizing agents
(ii) Waste characteristics
(1) Metals
(2) Other salts
(3) Polar organics (acids/ bases or- neutrals)
(4) Neutral, non-polar organics
(iii) Duration of contact of waste with leaching medium
(iv) Properties of soil or clay used as cover
or intermittent cover
(1) Particle size
(2) Organic content
(3) Clay content
(v) Ratio of leaching medium to the waste (Does a large
amount of liquids 'infiltration into the facility result in dilution
of the leachate and thus a lowering of constituent concentrations?)
b. For those properties identified in paragraph (a) as
most significant, with what degree of confidence must they be known
in order to confidently predict leachate quality? (Answer separately
for inorganics, semi-volatile organics and volatile organics.)
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(i) Is it possible to predict leachate quality by
separately determining or estimating each of the factors and then
computing the leachate quality by the use of equations or models?
If so, how much information is needed on these factors? What
laboratory or field tests are appropriate for such predictions?
What are the associated costs? How much time and expertise is
needed to run the tests and make the predictions? Is a sufficiently
large pool of expertise presently available?
(ii) Is it preferable or absolutely necessary to
use leaching tests which use representative combined samples of
the waste and soil, rather than to rely on separate analyses of
each factor as in paragraph (i) above?
(2) How well can such tests simulate leaching
in the field? To what extent have such tests been verified in
the field so far? How well can one design a decision tree to select
an appropriate test method for specific cases, to obviate the need
to separately study each situation? Can one design a scheme
whereby leachate quality for certain types of wastes are easily
predicted generically and more specific testing is required for
certain others?
(3) Is the use of water as a leaching fluid
to simulate leaching appropriate? (Consider organic and inorganic
wastes separately.) §hould a mild acid be used instead?
(4) What is the cost of developing adequate
data under this approach and how much expertise is required?
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2. Prediction of leachate from complex or mixed wastes.
Does the state of the art enable the composition of leached
complex or mixed wastes to be predicted?
- a. How does one choose an appropriate leaching
medium to simulate various water/waste interactions? To what
extent does error in choosing an appropriate leaching medium
result in error in predicting leachate quality?
b. To confidently predict leachate, must one
know in advance precisely what wastes will be accepted by the
facility, how much of each will be accepted, and where they will
be placed? .Must laboratory tests be run for this combination o-f
wastes or on particular wastes only? To the extent that one
fails to run such tests, what error results in the prediction of
leachate quality? If one does run these tests, what are the
associated costs,and are enough qualified people available to run
and interpret these tests?
c. Can a worst-case estimate of leachate generation be
confidently assessed by considering the solubilities of the most
prevalent constituents in the waste?
3. Separation and Pretreatment of Wastes
In situations where it is difficult or impossible to
confidently predict leachate quality, what options are available
for separating or pretreating wastes in order to maximize leachate
«#•
quality or at least make it easier to predict?
a. Waste separation
(i) Other than separating each waste into separate
cells or impoundments, are there groupings of wastes which would
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siaplify analyses of leachate quality (e.g., separate wastes into
metals, polar organics, nonpolar organics)?
(ii) To what extent do impurities (e.g., metal
catalyst in organic wastes) reduce the utility of waste separation?
k* Solidification, Stabilization, Encapsulation. To
what extent can these techniques be used to reduce the leaching
of constituents?
(i) In what ways should leachate tests for
solidified or stabilized wastes differ from those discussed above
for wastes in general? Are these tests easier or more difficult
to perform in any respects? Do they provide the tester greater
or lesser confidence in their results? What confidence can we have
in the long-term properties of current stabilization processes?
(ii) For metal wastes, what types of techniques
provide long-term reduction in leaching of constituents? How
are these techniques limited by (1) exposure to freeze-thaw
conditions; (2) presence of organic contaminants; (3) exposure
to wet-dry conditions; (4) physical stresses; and (5) various
factors leading to reversibility of reactions (e.g., pH changes)?
(iii) For organic wastes, are any stabilization
techniques sufficiently well established to allow confident
prediction of low levels of leachate constituents in the long
run?
4. Degradation of Organic Constituents in the Leachate
How well can we predict whether, and how rapidly, particular
/-
constituents in the leachate will be decomposed by biodegradation,
hydrolysis, chemical reactions or other means?
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a. How well must one simulate field conditions in
performing laboratory tests (e.g. availability of oxygen, sunlight,
water, appropriate aerobic or anaerobic microbes)? Have field
.*•
studies been conducted which confirm prior predictions of sorption
of constituents of hazardous waste leachates?
b. What is the cost of performing the appropriate tests,
what is the degree of expertise needed to perform the tests, and
how much time would the testing require?
c. How well can one predict the resulting decomposition
by-products and the relative amounts of each one? How likely is
it that these by-products will be as or more mobile or toxic as
the parent compounds?
d. To what extent can a bottom liner serve as a
biotreatment layer or filter to reduce the concentrations of
organic constituents in the leachate? To what degree does it
depend on permeability'of the liner? How'is a prediction affected
by errors in estimating these factors? (See Question A(2)(a)
and (b)).
3. Attenuation of Constituents Prior to Discharge From
Facility
a. (i) If clay bottom liners are used, how reliably
can we predict the degree to which constituents will be attenuated
by sorption? How confident can we be in predictions of sorption?
What are the major factors producing uncertainty, and to what
extent can they be overcome by collecting enough data? Have
field studies been conducted which confirmed prior predictions of
adsorotion of constituents of hazardous waste' leachates?
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(ii) How significant is the risk that sorption will
be reversed over time (e.g., due to pH changes in the facility}?
b. Are any chemical or physical mechanisms other than
sorption significant enough and definable enough to be evaluated
in predicting attentuation of constituents? In such cases, how •,
«
significant is the risk that the reactions will reverse over time?
c. Is confidence in predictions of attenuation in the
unsaturated zone less than in the case of clay liners? How much
less? For example, what effect would increased oxygen and other gas
content have?
6. Summary
Combining your responses to Question 1-5, with what degree
of confidence can we predict leachate quality? In what situations
are such predictions more easily made? In what situations are
they impossible to make with any confidence? Is there an adequate
supply of trained professionals to make these predictions and evaluate
them?
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May 20, 1981
II. Predicting Leachate Plume Migration in Groundwater Modeling
and Monitoring
,s
This discussion will address the issue of how well one can *
predict the fate and transport of the leachate and its constituents
» in the ground water. Specifically, how precisely can the concen-
trations of constituents at any loction and time be predicted?
Assume that the location/ mass rate and concentrations entering
into the ground water are known with some degree of confidence or
uncertainty, as discussed in Question I in the Monday and Tuesday
sessions. Among other things, the questions below will examine the
sensitivity to, or potential error in predicting plume migration which
results from, varying degrees of uncertainty in .the preceding pre-
diction of the leachate quantity and quality entering the ground water.
In considering methods for predicting leachate plume migration,
we will consider the type and amount of data required, the cost
of generating such data, and the degree of expertise required to
produce and evaluate the data and predictions.
1. Ground-water flow; With what degree of confidence can we
predict the direction and velocity of ground-water flow prior to
contamination of the ground water by leachate?
a. Are there certain types of geological systems (e.g.,
fractured strata or strata which may easily be dissolved) for
which predictions of the direction of ground-water flow are too
speculative to be made with any confidence? How well can we identify
such systems prior to site-operation? Where are such systems
j-
predominantly located?
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b. Are there certain types of geological systems for which
predictions of the direction of ground-water flow can be made
with a high degree of confidence? How well can we identify such
systems prior to site operation? Where are such systems predominantly
located?
c. How good is the current stare of the art for estimating
ground-water velocity?
d. How is any prediction affected by the nearby presence
of wells which are used for withdrawal or recharge of ground water
by use of pumps or other means? How good is the state of the art
for calculating how far the leachate plume must be from such wells
to remain relatively unaffected by the use or cessation of use
of these wells?
2. General Movement of Constituents in Ground Water.
If one ignores all attenuation, how well can one predict the
transport of leachate constituents?
a. Separation of Phases Based on Specific Gravities
(i) Heavy organics. If a leachate plume contains
organic constituents which are heavier than water, will those
constituents form a separate plume which does not move with the
ground water? If so, how well can we predict the direction and
rate of flow of this plume? Which type of organic constituents
are most likely to form separate plume? With what precision
must one know the leachate quality to determine the likelihood
that such a separate plume will form?
(ii) Light organics. Answer £or light organics
j-
the same cuestions as raised in Question(i) above.
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-17-
(iii) Is the answer to Questions (i) and (ii)
dependent on the salt or mineral content of the ground water? To
what degree?
b. Molecular Diffusion. How well can we predict the
• degree to which the leachate plume will expand and concentrations
;- of constituents will decrease by virtue of molecular diffusion?
(i) To what extent, if any, does this effect
depend on the initial concentrations in the plume? Does the rate
of diffusion differ for different constituents? To what degree?
(ii) To what extent does this effect depend on
ground-water velocity?
c. Dilution in Ground Water. How well can we predict the
degree to which constituent concentrations will be decreased by virtue
of dilution in the ground water? (Disregard the effect of separate
plumes discussed in Question (a) above.) How dependent is the
dilution effect on ground-water velocity and geological stratification?
3. Degradation of Constituents. To what extent can the
following mechanisms be expected to cause the decay of constituents
in the unsaturated zone? For what types of constituents, if any,
is such decay likely to be signficant? If not significant, can
any fate equation or model ignore the degradation effect? If
signficant, how well can the effect be predicted, and how sensitive
is any fate/transport prediction to error in predicting the
degradation effect?
a. Biological degradation - both aerobic and
/-
anaerobic processes
b. Degradation by hydrolysis
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-18-
c. Reaction with other constituents in the leachate
plume, groundwater, or geologic environment
4. Sorption of constituents. With what degree of confidence
can the attenuation of constituents by sorption be predicted?
a. How dependent is sorotion capacity and rate uoon
i '
factors such as soil particle size, organic content, porosity
*
and cation exchange capacity? How much data concerning these
factors is needed to characterize the geology and confidently
predict sortion capacity and rate? Does sufficient expertise
and equipment exist to make the required analyses?
b. To what degree is sorption enhanced by a low ground-water
velocity?
c. How dependent is the sorption rate for a particular
constituent upon the concentrations and sorption rates of the
constituent or other constituents in the leachate plume? Is it
likely that constituents would compete for sorption sites, or
are enough sites available for all leached constituents within a
short distance from the facility?
d. What is the role of humic and fulvic acids in
attenuating (by coraplexation) or accelerating (by decreasing soil
sorptive potential) the migration of organics and inorganics?
How well can this role be predicted in any particular situation?
e^ What other factors, if any, are highly significant
f
r
in predicting sorption rates?
f. How likely is it that sorption will be reversed
over time? What factors are significant in promoting such reversal?
In cases of potential reversal, how well can one predict the
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-19-
extent to which constituent concentrations will be altered by
the sorption and subsequent desorption?
./
5. Attenuation or Retardation by Means other than
Sorption.
Are any mechanisms other than sorption signficant enough
and predictable enough to be evaluated in predicting attenuation
of constituents? How reversible are these mechansims?
6. Simplified approaches.
Where knowledge of the leachate quality entering the ground water
is highly uncertain, what simplified approaches can be used to
characterize plume migration?
(i) Can particular constituents known to be
prominent constituents in the leachate be selected for analysis
as representative of all constituents? (For example, select one
or two metals, organic acids, organic bases, neutral polar organics
and neutral non-polar organics.) What factors would one apply to
determine representativeness? Chemical structure? Mobility?
Toxicity? Concentration in the leachate?
(ii) Rather than select representatives constituents,
could "worst-case" (i.e., highly mobile) constituents be selected
to determine the maximum mobility of all constituents? Going one
step further, is it reasonable, in light of data and modeling
difficulties, not to consider attenuation and degradation and
only consider dispersion?
7. Summary
Is prediction of the concentration of constituents at various
locations in the ground water possible and, if so, with what
degree of accuracy? Is the answer dependent on a detailed knowledge'
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-20-
of leachate quality? Can qualitative predictions suffice for
some situations? Can worst-case analyses be used to assure
acceptability of faculties? Is there an adequate supply of trained
professionals to make these predictions and to evaluate them? If
not/ how much time is needed to develop the supply through education*
and training?
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May 21, 1981
III. Gas Generation and Migration; Rates of Emissions; Control
Practices; and Dispersion Modeling
v This session is Divided into several topics related to the
movement of gases and vapors in and out of land disposal facilities.
As in the previous sessions on leachate and ground-water migration,
we will examine how confidently a permit writer could, given the
current state of the art/ predict the generation, movement and
release of constituents to points of human and environmental
exposure. This examination will include monitoring techniques,
predictive techniques, the type, amount and cost of data needed
for predictions, and the availability of the expertise required to
produce and evaluate data and predictions.
The discussion is divided into several subtopics. First is a
discussion of gas generation and migration within and out of
landfills and of the available techniques to control these factors.
Second is the volatilization of constituents from leachate into
i
buildings. Third is emission rates of volatile organic compounds
from surface impoundments into the atmosphere. - Fourth is dispersion
modeling of emitted compounds.
A. Gas Generation and Migration
1. With what degree of confidence can one predict the
constituents that will be generated as gases and the concentrations
at which they will occur in landfills? Can conservative estimates
of maximum or minimum concentrations be developed?
a. Have models been developed to predict the generation
^-
of gases? What type and amount of data is generally required to
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be input into these models? What assumptions are generally made
in applying these models?
(i) Have any of these models been used to predict (
the generation of gases other than methane, carbon dioxide and
hydrogen? Have any been used to predict specific organic compounds?, ,
(ii) To what extent have any of the existing
models been subject to field verification? For what compounds have
they been field-tested? How well do the predicted and measured values
i
correlate?
b. Which types of constituents are most likely to
appear as gases in the leachate or subsurface soils? Can a screening
i
mechanism (e.g./ waste analysis) be used to determine whether
significant production of gases may occur?
c. How does codisposal of wastes affect one's ability
i
to predict the constituents that will be generated in gaseous form?
d. How likely is it that substantial amounts of gas
would be generated in a landfill that does not accept municipal waste
(e.g., food and paper wastes) or liquids? What are the zypes of
wastes or compounds most likely to generate gases in such a landfill?
2. With what degree of confidence can the migration of gases
j
within and out of a land disposal facility be predicted? At what cos.t''
a. How well can one predict the paths in which gases
*•
will travel? Which of these paths are most or least significant?
Consider the following:
(i) Gases moving with leachate in the. subsurface soil
or unsaturated zone
(ii) Gases dissolved in ground water
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(iii) Gases moving with, but not dissolved in,
water
_/•
(iv) Gases migrating independently of water movement
b. How significant is diffusion in predicting gas
movement? How well can this factor be determined?
c. How significant is pressure gradient in the soil in
predicting gas migration?
(i) What are the major factors governing pressure
gradient? Hew are these factors likely to vary over the life of the
facility?
(ii) Does pressure gradient affect soluble and non-
soluble constituents to the same degree?
d. Have any models been developed to predict the direction
and rate of flow of gases in land disposal facilities? Which of
these have been field-tested? With what results?
3. What type and amount of data is needed to accurately
characterize gas migration at an existing site? What is the
range of sampling error in measuring emissions at any particular
point?
4. How significant a factor is degradation of gases by chemical
reaction, biodegradation, photolysis (if near or at the ground surface)
or other means? Can any of these means of degradation be ignored
without signficantly impairing predictions of ga-s concentrations
ultimately released from the ground surface?
5. How significant is sorption in attenuating concentrations
s~
of gases in the soil and in the unsaturatec and saturated zones?
How confidently can one predict the extent to which particular
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-24-
gaseous constituents will be sorbed or subsequently cesorbed?
What are the major factors in making such a prediction?
6. With what confidence can one predict the average or maximum
rate at which gases will migrate through synthetic membranes,
compacted clay liners,or relatively permeable soil? What are the
most significant factors in making such predictions?
7. Are closed surface impoundments in which sludges or liquids
have been left in place capable of generating significant quantities
of gas?
8. For how many years after closure can gas generation and
migration remain a potential problem at a facility? Would it be
reasonable to allow buildings to be built on or near the closed
site after a certain specified number of years have passed? Can
this number be determined in advance, or must it be solely determined
subsequently through gas monitoring?
3. Controls for Generated Gas
What means are available to control the migration of gas from
landfills? What are the most probable failures of these means?
1. Liners. To what extent can relatively impermeable caps
and side liners reduce the rate of migration of gas from landfills?
2. Collection/Venting Systems. To what' extent can vents
be used to control emissions or build-up of gases?
a. Can vents interfere with liner systems that are designed
to minimize the. infiltrations of liquids into the facility and
the discharge of leachate from the facility? If so," what are the
.*•-
available tradeoffs between designing for leachate and gas control?
b. Discuss the following options for handling collected
gases and their costs.
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(i) Emission to the air
(ii) Burning
(iii) Sorption
(iv) others
c. How effective are vents absent pumping? Does this depend
on gas characteristics?
d. For how many years after closure of a landfill would
such a system need to be operated before nearly all potential
gases have been removed from the landfill? Do models exist to
confidently address this question at a particular site? What degree
of maintenance would be required during operation of the system?
(Consider both systems with pumping and those without pumping.)
3* Barriers How effective are barriers in preventing
passage of gas to particular locations of concern? For how long
a period of time can they be relied upon to remain effective?
Consider different types of geology.
4. Reclamation. Can gases be economically recovered for
use as an energy source from a landfill that contains only chemical
wastes or that contains a mixture of sanitary and chemical wastes?
C. Emissions from Surface Impoundments
1. Eow significant are surface impoundments as sources of
emissions? What is the range of daily or annual emissions (measured
by total organic carbon, for example), considering different
sizes of impoundments and variations in climatic temperatures?
s~
2. What is the range of sampling error in measuring TOC at
a particular site? What is the error in measuring specific organic
compounds?
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t
-26-
3. In attempting to develop appropriate emission factors
to characterize existing surface impoundments, what are appropriate <
methods for sampling? What is the cost of each sampling method?
-,
Are the necessary equipment and skilled technicians currently available
a. At what locations (both vertical and horizontal) _. '
should sampling be conducted?
b. How does the size of the impoundment affect the answer
to this question? '
c. How many samples are needed? Does the answer depend
upon meterological conditions?
4. For new surface impoundments, what confidence can one
have in predictions of emission rates of various constituents
from the impoundment?
- (
a. How critical are each of the following factors?
(i) Solubility, Henry's law constant, and other
physical properties of the volatile constituent
<
(ii) Temperature
(iii) Wind
(iv) Solar mixing
i
(v) Peed ratios and methods :>-
(vi) Properties of the waste as a whole
(vii) Aeration of impounded wastes
b. Have models been developed for emission rate predictions?
Have they been field-tested? How well do the predicted and actual
measured results correlate? ,'~ (
c. Can a worst-case assumption or model be used to
predict with a high degree of confidence that emission rates for '
various constituents will not exceed specified maxima? i
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5. Can emission rates for particular compounds in existing
or new impoundments be estimated by performing mass balances for
./•
the compounds by analyzing the liquid and solid waste streams?
For example, could one analyze the influent, effluent and sludge
at an activated sludge facility, including analysis for potential
daughter compounds of the compounds of interest?
6. What management techniques are currently available to
control the rate of emissions? Consider both pre-treatment (e.g.,
stripping prior to placing in impoundment) and in-place methods.
a. What are the costs of these methods?
b. To what extent, if any, do these methods interfere
with the purpose of impoundments? For example, are any of them
incompatible with impoundments used for aerobic decomposition?
7. Are there certain types of impounded wates which clearly
result in very little air emissions and do not require any emissions
analysis?
D. Dispersion Modeling
1. How well can one predict average annual concentrations of
constituents.in the vicinity of a land disposal facility, assuming
that emission rates from the facility are known?
a. If one considers a land disposal facility as a point
source, do adequate models exist to predict the facility's impact upon
ambient concentrations ox total volatile organic compounds? What are
the major difficulties with such models? In what types of situations
have they been used successfully, and with what degree of accuracy?
/"
How much data is needed, and at what cost, to apply these models?
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b. Answer, for specific volatile organic compounds (e.g.,
specific solvents), the same questions as raised in the preceding
question.
c. Must different models be used for aerosols, gases
and particles?
d. Can concentrations near a facility of several or more
acres be predicted by the use of a model which has been designed for
point sources? Hew much more reliable does such a model become as
one increases distance from the facility?
2. Can short-term concentrations (e.g., daily or weekly) of
either total VOC or specific organic compounds be predicted if
necessary to assess acute effects? What degree of error is
introduced by such factors as wind and temperature variations?
Hew much data, and at what cost, must be collected to account for
these -factors?
3. Can a screening model be used to confidently predict
maximum annual or short-term concentrations?
4. How significant is the problem of toxic by-products that-
are created by photochemicals? Can the by-products affect
local concentrations at significant levels or only broader ambient
concentrations at low levels? What is the state of the art for
considering photoconversion?
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May 22, 1981
IV. Health Effects Resulting from Exposures to Hazardous Wastes
Disposed on or in the Land
In the previous-panel discussions, we have examined techniques
for controlling and predicting the migration of waste constituents,
including their .reaction products and decomposition by-products,
out of a land disposal facility into the ground water, surface
water, subsurface soil and air. In this session, we assume that
the concentrations of constituents in various media, at various times,
and at various locations are known. We will examine the various
types of risks that may be presented to human health and the
available means to estimate the magnitude of those risks.
The central question in this discussion is: How may a typical
permit writer proceed to evaluate the potential health effects
posed by an existing or proposed land disposal facility? We
•
will briefly review basic methodology for assessing effects.
We will also try to identify existing regulatory standards and
suggestive criteria which may be used as guidance, consider
feasible approaches where no such standards or criteria exist,
and identify the range of uncertainty and the means of compensating
for that uncertainty.
A. Toxic Effects (Acute and Chronic) to Humans-
1. What are the most reliable and readily usable methodologies
and techniques for predicting acute effects that may result
from human exposures to toxic compounds? With what degree of
confidence can these methodologies and techniques be- used?
,*-
a.(i) What are the appropriate techniques for using
animal toxicity data to determine, in animals, a. NOEL (no-observed-
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effecu-level), NCAEL (no-observed-adverse-effect-level), LOEL (lowest-
observed-effeet-level), LOAEL (lowest-observed-adverse-effect-levei ;
and PEL (frank-effect-level)? How does one distinguish between <
an "effect" and an "adverse effect"?
(ii) What are the most reliable published sources
for determining these levels (e.g., NIOSH Registry of Toxic __ (
Effects of Chemical Substances; Sax, Dangerous Properties of Industrie
Materials) and how reliable is the information they contain for use
in either setting regulatory standards or judging the acceptability (
of particular facilities?
b.(i) What are the appropriate techniques for using animal
toxicity data to determine, in animals, an LDjQ (dose causing
lethality in 50% of test animals), or LC5Q (concentration causing
lethality in 50% of test animals)?
(
(ii) What are the most reliable published sources for
determining these levels (e.g. NIOSH Registry; Sax) and how
reliable is the information that they contain?
<
c.(i) Can NOELs, NOAELs, LOELs, LOAELs, and FELs be used
to determine the risk of mortality to humans from exposure to a
particular level? Is it possible to define risk in such terms as
i
"10-5 risk of lethal effect from inhaling concentration continuously;*?
(1) If so, how is such a risk determined? What published
* •"
sources, if any, provide this sort of estimated risk?
(2) If not, is it possible to predict risk at all or is one
forced to assure safety by seeking to limit permissible levels
to, e.g., below the NOAEL?
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(ii) Can LD5Q or LCjQ be used to determine the risk of
mortality to humans from exposure to a particular level? Consider
_s
the same issues as in the previous question.
(iii) Can any animal toxicity data or other means be
used to predict the risk of morbidity to humans from exposure to
a particular level? Do any means exist to quantify these risks?
Consider the same issues as in question (i).
(iv) Does human epidemiological data exist on morbidity
due to various compounds?
d. What are appropriate techniques to account for the
bioaccumulation potential of a compound in assessing chronic
toxicity effects? Can bioconcentration factors for fish be
extrapolated to humans?
e. What are appropriate means to account for uncertainty in
extrapolating animal daca to man? Should uncertainty factors be
*
used? If so, how large should they be?
f. How can the more sensitive segments of the population
(e.g., infants, old people, people with certain types of health
problems or high background exposures) be protected?
g. To what extent can data developed for one exposure route
(e.g., inhalation) be used to predict effects caused by exposure
through a different route (e.g., ingestion)? What type and amount
of comparative uptake data is required?
h. How significant are synergistic or antagonistic effects?
Does the present state of the art enable any reasonable estimate
s~
of these effects? Where a waste or leachate from a waste is
available, can an animal study be performed on the waste or
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Isachats to give an overall picture of the toxicity?
2. Can threshhold limit values (TLVs) published by the ,
American Conference of Governmental and Industrial Hygienists
(ACGIH), National Institute for Occupational Safety and Health
h
(NICSH) or Occupational Safety and Health Administration (OSHA) <
be used to predict human health effects or select safe levels?
a. How are TLVs determined?
b. Can simple equations be used to transform TLVs (based on i
work-week exposure) to potential full-time exposures?
c. Since TLVs are designed to protect healthy, working
people, how can they be adjusted to protect sensitive populations (
exposed to waste-site emissions?
d. Can TLVs be used only to protect against inhalation -
induced effects? How much information would be required concerning " {
absorption efficiency and metabolic pathways before one could
use TLVs to predict, e.g., ingestion - induced effects?
3. Can EPA's water quality criteria for toxic pollutants
(a summary of which was published on November 23, 1980, in 45 FR 79318]
be used to evaluate risks of toxicity or to establish safe levels
i
with respect to ground water? What calculations or manipulations . .
would be needed to adjust the criteria (which are set for surface
water quality and assume a certain level of fish consumption by • '"
i
people) for use as ground-water criteria? How much information
is needed to correctly make these adjustments?
4. Do any other criteria or standards^-exist that may be
useable by permit writers in protecting against risks of toxicity
from hazardous waste land disposal facilities?
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5. Is it technically possible to develop EPA criteria or
standards to protect .against risks of toxicity from hazardous
waste land disposal facilities? What approach should be used?
How long would such an effort take for each compound studied?
Would any assumptions need to be made about background concentra-
tions?
6. If no standards or usable quantitative criteria are
available to the permit writer, what approach may be used to
evaluate risk?
a. If a permit applicant were required to conduct studies,
what types of -studies would be appropriate? How much quality
control would be required? How long would such -studies take, and
what would they cost?
b. Is there any way to use a qualitative approach, other
than totally subjective judgment by the permit writer, to determine
whether a site is acceptable or unacceptable without quantifying
the effects of toxicity from all compounds or preventing all
exposures?
B. Carcinogenic Effects
1. What are the most reliable and readily available
methodologies and techniques for predicting carcinogenic effects
that may result from human exposures to, compounds? With what
degree of confidence can these techniques be applied?
a. To what extent can short-term (including mutagenicity)
studies be relied upon to identify carcinogens? To what extent
can they be used to quantify the carcinogenic risks from particular
carcinocens?
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b. What is the range of uncertainty in quantitatively
predicting risk of human cancer based upon animal studies?
i
Consider the following sources of uncertainty:
(i) Estimating the carcinogenic potential at high doses
(ii) Extrapolating high doses to low doses.
i
(a) Which models (linear one-hit; linear multistage;"
threshold) are most consistent with the available data?
(b) Which models are the most conservative in terms
i
of protecting human health? Which are the least conservative?
(c) What is the potential variability among the
various non-threshold models in predicting effects at low doses?
(iii) Extrapolation of animal studies to humans, in
light of different metabolic pathways. Can this be confidently
done if several varieties of animal species are used? (
c. Can evidence of carcinogenic risk through one route of
exposure b'e issued to predict the risk through a different exposure
route? (
d. What are the appropriate techniques for resolving
uncertainty? (Consider, e.g., statistical confidence intervals
and safety factors) i
2. What regulatory standards, criteria or guidances have
•
been published in a form that may be used by a permit writer to
assess the potential carcinogenic effects of exposure to waste <
constituents from a hazardous waste land disposal facility? (Consider
the effect of non-he^alth criteria used in part to help develop some
j~
of these standards.) *
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a. Consider, e.g., the following:
(i) Surface water quality criteria for toxic
pollutants under the Clean Water Act
(ii) Drinking Water Standards (NIPDWS) under the
Safe Drinking Water Act
(iii) National emissions standards for hazardous
air pollutants under the Clean Air Act
(iv) Criteria and regulations by the Occupational
Safety and Health Administration
(v) Criteria and regulations by the Consumer
Product Safety Commission
(vi) Criteria and regulations by the Food and
Drug Administration
b. For what routes of exposure are these standards and
criteria usable?
c. To what extent do the sources listed in Question (a)
conflict? What assumptions or differences in techniques lead to
the conflicts?
d. When any of the above standards or criteria are not
directly usable, can they be readily modified by changing certain
assumptions (e.g., routes and times of exposure) and recalculating
the values for purposes of assessing risks from hazardous waste
land disposal facilities?
3. Where published standards or criteria are unavailable for
a particular compound believed to be significant at a waste disposal
site, how readily can appropriate risk values be selected based on
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-36-
the techniques discussed in Question 1? How much time is needed?
What is a typical cost?
4. Can synergistic or antagonistic effects of different corapourv;
in a waste be accounted for? Can experiments on a whole waste (or
v
leachate or emissions) be performed to assess its toxicity?
5. Can the risks-presented by carcinogens to identified
sensitive portions of the population be separately estimated or
compensated for?
C. Reproductive Effects
1. With what confidence can mutagenic effects be predicted?
How do -mutagenic risks from particular compounds compare to the
carcinogenic risks?
2. What types of effects are most likely to occur as the
result of mutagencity, based on present studies?
3. What potential is there for a particular population's
long-term (e.g., several generations) exposure to mutagenic
compounds to develop adverse effects? To what extent will the
effects multiply over time?
4. Can teratogenic effects be predicted with any confidence?
What types of effects are most likely?
D. Exposures to Waste Constituents
1. How can future exposures to waste constituents placed in . .-
the ground today be predicted?
a. Based upon past trends, is it reasonable to assume
that populations in any particular areas wi^.1 not decrease
s~
substantially?
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b. Based upon past trends, is it reasonable to assume
that any ground-water or surface-water resource currently used
./•
for drinking or other purposes at least the same extent in the
future, unless it is depleted?
c. Where future land-use water-use projections are
difficult to make, do techniques for predicting maximum exposures
to waste constituents exist?
-------
Appendix B
List of Attendees
-------
-------
NOTE
,f
Since there was no pre-registration for this seminar, the list of
attendees is based solely upon the information contained in the daily
sign-up sheets that were available at the registration desk. In
many cases, individuals who attended more than one session,only
signed up for the first session they attended. Consequently, the
list of attendees as presented here is not complete for each day.
Moreover, in some cases the handwriting on the sign-up sheet was
illegible, abbreviations were used for the affiliation, and the addresses
were incomplete. No attempt was made to overcome these limitations and
the listing that follows reflects exclusively the information on the
sign-up sheets.
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May 18, 1981
Name
Kant Anderson
Tom Aspitarte
Jim Bachmaier
Ralph Basinski
Donna Berry
Susan Broom
Paul Cassidy
Len Caarca
Rob Clemens
Irish Cooper
Arthur Day
Paul R. dePercin
Gary Dietrich
Hike Duo-kin
Richard W. Eldredge
Mark Evans
Mike Flynn
David Friedman
Kevin Garrahan
Benjamin C. Garrect
Allen G«swein
Mark. Greenwood
Bob Griffin
Ed Hall
Bob Ham
Rick Holberger
Kay Holub
Dick Janowiecki
Charles Johnson
John Keller
Gregory Kev
Todd KissBell
Barry Kerb
Affiliation
EPA
Crown Zeller Bach
EPA/OSW
J & L Steel
U.S. EPA
U.S. EPA
EPA/OSW
GM Legal Staff
EPA, OHWE
U.S. EPA
U.S. EPA
U.S. EPA
U.S. EPA
U.S. EPA
Eldredge Bag. Asso.
U.S. EPA
EPA/OSW
EPA/OSW
EPA/OSW
Battelle Columbus
Laboratories
U.S. EPA
U.S. EPA
II. State
Geological Survey
UCC
University Vis.
MUSE Corp.
SPA/Eaforcement
Monsanto
HSWMA
NR2C
Exp. Assess Gp. EPA
EPA/OSW
U.S. EPA
Address
401 M St., S.W. Washington, D.C. WH-564
CA MAS, Washington, D.C.
401 M St., S.W. Washington, D.C. WH-564
900 Agnev Rd., Pittsburgh, PA 15227
401 M St., S.W. Washington, D.C. KM-220
401 M St., S.W. Washington, D.C. HH-564
401 M St., S.W. Washington, D.C. WH-564
3044 W Grand Blvd., Detroit, MI 43202
401 N St., S.W. Washington, D.C. EN-340
Room 222
401 M St., S.W. Washington, D.C.
lERL-Ci, Cincinnati, OH 45268
401 M St., S.W. Washington, D.C.
2625 Butterfield Rd., Oak Brook, ?
401 M St., S.W. Washington, D.C. WH-654
401 M St., S.W. Washington, D.C. WH-564
401 M St., S.W. Washington, D.C. WH-565
401 M St., S.W. Washington, D.C. WH-564
Columbus, OH 43201
401 M St., S.W. Washington, D.C. WE-564
401 M St., S.W. Washington, D.C.
615 E. Peabody, Champaign, It 61820
South Charleston, WV
3232 Engineering Bldg. Madison, WI 53705
1820 Dolley Madison Blvd., McLean, VA
1515 Nicholas, Dayton, OH
1120 Connecticut Ave., N.W. Wash., D.C.
1725 I St., H.W. Washington, D.C.
RD-689, EPA Hqs. Washington, D.C. 20460
401 M St., S.W. Washington, D.C. WH-565
1120 Connecticut Ave., K.W. Room 222
-------
Name Affiliation Address
Joseph Thornton U.S. Ecology 9200 Shelbyville Sd., Louisville, SET 40222
Jim Tripp EDF 444 Park Ave., S. New Tork, NT 10018
Peter Vardy Waste Mgmt. Inc. 900 Jorie Blvd., Oak Brook, IL 60515
Dov Weitsian EPA/OGC 401 M St., S.W. Washington, D.C. 20460
Jim Williams Missouri Dept. P.O. Box 250, Rolla, MO
Kat'l. Resources
-------
Name
Affiliation
Address
David Lennett
Michelle Love
Bruce Lundy
Don McClenahan
Richard A. Meserve
Amir Mecry
Michael Miller
Hugh Mullen
Sam Napolicon
Les Otte
Philip A. Palmer
Dale E. Papajcik
Suellen Pirages
iCen Poet
Pacer Querrero
Jacqueline M. Rama
Chris Rhyne
Cliff Rothenstein
Mike Roulier
Reva Rubenscein
Eldon Rucker
Tim Savior
John Segna
Edward R. Shuater
Ken Shuster
Barbara Simeo«
J.W. Spear Sc.
Anthony A. Sptoda
Robert A. Stadalmarer
3.3. Taylor
William E. Thacker
EDF
Wald, Harkrader
& Ross
0.S. EPA
CTM, Inc.
Covington & Burling
Weacoa
3FI
rues
a.s. EPA
(J.S. EPA
DuPont
Republic Steel
Congressional Off.
Tech. Asst.
?H3
EPA/OSW
ASTSWMO
EPA/OSW
EPA/OSW
tJSEPA—Cincinnati
SHWBD/MEBL
HSWMA
Amarican
Petroleum Inst.
Hammermill Paper Co.
EPA/OURS
CZCOS International
EPA/OSW
ASTSWHO
SEXTON
TOS Corp.
CECOS lat'l Inc.
EPA
NCASI
1525 13th St., N.W.
1300 19th St., S.W.
401 S St., S.W. Washington, D.C. EN-340
900 Josie Blvd., Oak Brook, IL
388 16th St., N.W. Washington, D.C.
Roy F. Weston, Westchester, PA 19380
P.O. Box 3151, Houston, TX
Horsham, ?A
401 M St., S.W. Washington, D.C.
401 M St., S.W. Washington, D.C. '..11-364
Eng. Dept L1378 - Wilmington RI 19898
1000 Prospect Ave., Cleveland, OH
Washington, D.C. 20510
2828 Pennsylvania Ave., Washington, D.C.
401 M St., S.W. Washington, D.C. WH-562
444 S. Capitol St., S.W. Washington, D.C.
401 M St., S.W. Washington, D.C.
401 M St., S.W. Washington, D.C. WH-562
26 W. St. Clair St. Cinncinatti, OH 45263
1120 Connecticut Ave., NW Washington,D.C.
2101 L St. Washington, D.C.
PO 1440, Erie, PA 16533
P.O. Box 619, Niagara Falls, -TT 14302
401 M SC., S.W. Washington, D.C. WH-564
444 ti. Capitol St., Washington, D.C.
1814 S. Wolf Rd., Hillside, U. 60162
600 Grant St., Pittsburgh, PA 15230
P.O. Box 619, Niagara Falls, NT 14302
201 I St., S.W. Washington, D.C. "520"'
Western Michigan University
Kalamazoo, MI 49008
-------
ame
Affiliation
Address
David Lennett
Bruce Lundy
Don McClenahan
Richard A. Meserve
Amir Metry
Michael Miller
Norman Mines
Hugh Mullen
Sam Xapoliton
Las Octe
Philip A. Palmer
Dale E. Papajcik
Jon Perry
Suellen Pirages
Pecer Querrero
Marc Rogoff
Mike Roulier
Paul R.OUX
Reva Rubens cein
Tim Saylor
E.R. Shuster
Ken Shuscer
Peter Skinner
J.W. Spear
Anthony A. Spinola
Scan Spracker
Richard Spri&ce
R.A. SCadelman
Barry Scoll
Robert B. Taylor
EOF
U.S. EPA/OHWE
CWM, Inc.
Covlnton & Burling
Roy ?. West on
BFI
MITRE
I0CS
U.S. EPA
U.S. EPA/OSW
E.I. DuPont
Republic Steel
U.S. EPA/OSW
OTA-Congress
U.S. EPA/OSW
MITSE
EPA/MERL Cincinnati
CMA (Stauffer)
NSWMA
Haamermill Paper CO.
CECOS
U.S. EPA/OSQ
NTS. Att. General
SEXTON
U.S. Steel Corp.
Wald, Ear trader &
Ross
Tracor, lac.
CECOS, Inc'l.
U.S. EPA/OSW
U.S. EPA
1525 18th St., N.W. Washington, D.C.
Etf-335 Washington, D.C. 20460
Oak Brook, IL
888 16th St., N.W. Washington, D.C.
West Chester, PA 19380
Houston, TX
1S20 Dolley Madison Blvd., McLean, 7A
Horsham, PA
401 M St., S.W. Washington, D.C.
WH-564 Washington, D.C. 20A60
Engr. Dept. L1378, Wilmington, DE 19898
25 W. Prospect Ave., Cleveland, OH 44115
Washington, D.C. 20460
Washington, D.C. 20510
WH-562 Washington, D.C.
1820 Dolley Madison Blvd. , McLean, VA
Cincinnati, OH 45268
Westport, CT.
1120 Connecticut Ave., Washington, D.C.
P.O. Box 1440, Erie, PA. 16533
Niagara Falls, JTT 14302
401 M St., S.W. Washington, D.C.
Justice Bldg. The Capitol, Albany, ST 12196
1815 S. Wolf Rd., Hillside, IL 60162
600 Grant St., Pittsburgh, PA 15230
Washington, D.C.
1601 Research Blvd., Rockville, MD 20850
Hiagara Falls, NT. 14107
Washington, D.C. 20460
EN-335 Washington, D.C. 20460
-------
May 19, 1981
Name
Tom Aspicarte
Salph Basinski
Donna Berry
Dave Slounc
Susan Bromai
Paul Gassidy
Leonard F. Charla
Rob Clemans
Steve Cordle
Arthur Day
Paul defercin
R.W. Eldredge
David M. Erickson
Mark L. Evaas
David Friedman
Allen Geswein
Mark Greenwood
M.E. Hall
3ob Ham
Douglas G. Hayman
Rick Holberger
Say Holmes
Bruce Hunter
Seong T. Hwang
Andrew Jackson
Dick Janowiecki
John Keller
Gregory Sew
Todd
Carol
Affiliation
Crown Zellerbach
JiL Sceel
EPA
EPA (OWE&P)
EOA/OSW
EPA/OWS
SSI Legal Staff
U.S. EPA/OHWE
EPA/ORD/OEPER
EPA/OSV
U.S. EPA IESL
EEA, Inc.
EPA/OPE
U.S. EPA- Land
Disposal Div.
U.S. EPA/OSW
U.S. EPA/OSW
0.3. EPA
Union Carbide Corp.
University of WI.
Fuller, Henry,
Hedge & Snyder
MITBE
EE.CO
ERGO
U.S. EPA
a.S EPA/OHWE
Monsanto
SRDC
EPA/OKD/Zxp.
Asacaa. Gp
EPA/OSW/HIWD
MITRE
Address
Camas, VA2M.
900 Agnew Eld., Pittsburgh, PA 15227
Washington, D.C.
EN-336 Washington, D.C. 20406
WH-564
401 M St., S.W. Washington, D.C.
3044 W. Grand Blvd., Detroit Ml. 43202
EN-335 Washington, D.C.
401 M St., S.W. Washington, D.C.
401 M St., S.W. Washington, O.C.
Cincinnati, OH. 45263
Oak. Brook, IL
401 M St., S.W. Washington, D.C.
Washington, D.C_.
Washington, D.C. 20460
Washington, D.C. 20460
401 M St., S.W. Washington, D.C.
P.O. Box 8361, S. Charleston, W 25177
Madison, WI
P.O. Box 2038, Toledo, OH 43603
1820 Dolley Madison Blvd., McLean, VA
Boston
Boston
Washington, D.C.
401 H St., S.W. Washington, O.C.
1515 Nicholas, Dayton, OH 45407
1725 I St., N.W. Washington, D.C.
SD-639 Washington, D.C.
WS-565 Washington, D.C. 20460
1820 Dolley Madison Blvd., McLean, 7A
-------
May 20, 1981
flame
Jim Bachmaier
Frank Barber
Ralph Basinski
Donna Berry
Mary Bishop
Susan Bronm
Paul Caasidy
Leonard F. Charla
Bob Clemens
Steve Cordle
Arthur Day
Paul dePercis
George Dixon
Patrick. Domenico
Richard Eldredge
Carl Enfield
Mark Evans
Janes J. Geraghty
Claire Goal man
Douglas G. Haynan
J.W. Hirry
Rick Holberger
Dick Janowiecki
John Keller
Gregory Kev
Leonard Konikov
Barry Sorb
John D. Koutsanders
Affiliation
U.S. EPA/OSW
U.S. EPA/OE/OHBE/
REU
J&L Steel
U.S. EPA
API (lnc'1. Paper)
U.S. EPA/OSW
U.S. EPA/OSW
GM Legal Staff
U.S. EPA/OHWE
U.S. EPA/ORD
U.S. EPA/OSW
U.S. EPA/IESL
U.S. EPA
Univ. of Illinois
EEA
U.S. EPA, RSKEBL
U.S. EPA/OSW/LDD
Geragfaty & Miller,
Inc.
EPA/OE/OWEP/DHSEB
Fuller, Henry,
Hodge & Snydar
U.S. EPA
MURE
Monsanto
NRDC
EPA/ORD/Exp.
Assess. Gp.
uses
EPA/OPE
EPA/ORD
Address
401 M St., S.W. Washington, D.C.
ES-338
900 Agnev Rd., Pittsburgh, ?A 15227
401 M St., S.W. Washington, D.C.
77 West 45th St.
OH-564
401 M St., S.W. Washington, D.C.
3044 W Grand Blvd., Detroit, MI 48202
EN-335 401 M St., S.W., Washington, D.C.
RD-682
401 M St., S.W. Washington, D.C.
Cincinnati, OH 45268
401 M St., S.W. Washington, D.C.
Urbana, XL
2625 Batterdiald Rd., Oak Brook, XL
P.O. Box 1198, Ada, OK 74820
401 M St., S.W. Washington, D.C.
Annapolis, MD
EN-338
P.O. Box 2088, Toledo, OH 43603
401 M St., S.W. Washington, D.C.
1820 Dolley Madison Blvd., McLean, VA
1515 Nicholas Rd., Dayton, OH 45407
1725 I St., N.W. Washington, D.C.
Has. RD-689, Washington, D.C.
431 Nat'l. Center, Rescon, 7A 22092
Ba 222
RD-680
-------
Name
William E. Thacker
Joe Thornton
Peter Vardy
Bumell W. Vincent
Dov Wei nan
Linda Wilbur
Jim Williams
Affiliation
HCASI
U.S. Ecology
Waste ttgmt. Inc.
U.S. EPA
O.S. EPA/OGC
a.s. EPA/OWRS
Missouri Geological
4 Land Survey
Address
Western Mich. Univ.,
Kalamazoo, MI. 49008
9200 Shelbyvllle Rd., Louisville, KY 40222
900 Joria Blvd., Oak 3rook, IL . 60521
Washington, D.C.
401 M St., S.W. Washington, D.C.
Washington, D.C.
P.O. Box 250, Rolla, MO 65401
-------
Name Affiliation Address
Dov Weitman EPA/OGC Washington, D.C.
Linda Wilbur U.S. EPA Washington, D.C.
James H. Williams Missouri Div. Geol. P.O. Box 250, Rolle MO 65401
& Land Survey
Eric Wood Princeton Dept. Civil Eng'g., Princeton
University, Princeton, NJ 08544
3..L. Wormell U.S. EPA. 401 M St., S.W. Washington, D.C.
-------
Maae
Affiliation
Address
Carol Kuhlman
David Lennett
Bruce Lundry
Don McClenahan
3.. A. Meserve
Michael Miller
Hugh Mullen
Sam Mapolitan
Dale E. Papajcki
Suellen Pirages
XaryAnn Pocock
Paul S. Price
Peter Querrero
Paul Roberts
Marc Jogoff
Paul Xoux
Reva Rubenstein
Mark Segal
Thomas T. 5hen . ,
Edward R. Shuster
Ken Shuster
P. Skinner
J.W. Spear
Anthony A. Spinola
Scoec 0. Springer
Barry Scoll
Robert 3. Taylor
William Thacker
Joe Thornton
Surnell W. Vincent
MITRE
EOF
EPA/OHWE
Chem. Waste Mamt
Covinton & Bulny
BFI
rocs
EPA/OPE
Republic Steel
Material Prog. Cong.
Off Tech. Assess.
OPE
EPA/OPTS
EPA/OSW
Stanford b'niv.
MITSE
Stauffer
HSWtA
U.S. EPA
NT State DEC
CECOS
OSW/EPA
NTS Att. &en.
SECTON
U.S. Steel
EPA/OSW/LDD
EPA/OSW
O.S. EPA
NCASI
U.S. Ecology
OSW
1820 Dolley Madison Blvd., McLean, 7A
1525 18th St., N.W. Washington, D.C.
EN-335 Washington, D.C.
Oak Brook, H.
388 16th St., S.W. Washington, D.C.
P.O. Box 3151, Houston, TX 77001
115 Girraltar Rd., Horsham, PA 19044
401 M St., 5.W. Washington, D.C.
25 W. Prospect Ave., Cleveland, OH 44115
Washington, D.C.
2828 Pennsylvanie Ave. ,
401 M St., S.W. Washington, D.C.
WH-562
Dept. of Civil Eng'g., Tarsian Sng'g.
Center, Stanford Univ. Stanford, GA 94305
1820 Dolley Madison Blvd., McLean, VA
Westport, CT. 06881
1120 Connecticut Ave. Washington, D.C.
401 M St., Washington, D.C.
50 Wolf Sd., Albany, Mt
Niagara Falls, M7
401 M St., S.W. Washington, D.C.
Justice Bldg., Albany, NT 12224
1815 S. Wolf M., Hillside, IL
600 Grant St., Pittsburgh, PA 15230
wa-564
WH-564 Washington, D.C.
201 I St., S.W. #520, Washington, D.C.
Western Mich. Univ., Kalanazoo, MI 49008
9200 Shelbyvill* 5d., Louisville, KT
401 M St., S.W. Washington, D.C.
-------
Name
Kent Anderson
Alfred Angiola
Jim Bachmaier
Ellen Barrett
Donna Berry
Mary Bishop
Dave Blount
Susan Broom
Sue Suggum
Kathleen M. Burke-
?aul Cassidy
Larry Claxton
Steve Cordle
Arthur Day
Charles Delos
Paul dePercin
George Dixon
Michael Dworkin
Aon Fisher
Richard C. Fortan
Ralph Freudenthal
Lisa Friedman
&evin Garrahan
Al Geswe a
Iris Goodman
Peter Guerrero
John Harris
Stuart Haus
Toue Hewitt
Joe Highland
Affiliation
WAPORA
EPA/OSW
EPA/OTS
EPA
laternat'l. Paper
EPA
0.S. EPA
W*ld, Harkroderi
Boss
EPA
EPA/OSW
EPA
EPA/OHD
EPA
EPA/OWRS
EPA/IEHL
EPA
EPA/oec/wasw
EPA
Hoere SC Transp. &
Commerce
Stauffer Chan Co.
EPA/OGC
EPA/OSM
OTA
EPA
EPA/AD-tqDB
MTISE
EPA
EOF
211 E 43, N.T., N.Y. 10017
401 M St., S.W. Washington, D.C. WH-564
ET 329 (TS 798)
401 M St'., S.K. Washington, D.C. PM-220
72 W 45th St., N.Y., H.T.
401 M St., S.W. Washington, 3.C. EN-336
401 M St., S.W. Washington, D.C. WH-564
1300 19th St., S.W.
Washington, D.C.
401 M St., S.W. Washington, D.C. WH-564
MD-68, HEEL, RIP, N.C. 27711
401 M St., S.W. Washington, D.C. KD-682
Washington, D.C.
401 M St., S.W. Washington, D.C. WH-553
Cincinnati, Ohio 45268
401 M St., S.W. Washington, D.C.
401 M St., S.W. Washington, D.C. PM-220
225-1467
400 Farmington Ave., Farmington, CT 06032
Hdqtrs. 426-4497
401 M St., S.W. Washington, D.C. WH-564
401 M St., S.W. Washington, D.C. WH-562
401 M St., S.W. Washington, D.C.
TS-278, Room 926, CM #2
Westgate Research Park, McLean, VA
E537C
Washington, D.C. 833-1484
-------
May 21, 1981
Ngge
Alfred Angiola
Jim Bachmaier
David 3auer
Donna Serry
Mary Bishop
Sue 3uggum
Arthur Day
?aul de Fercia
Michael Dworicia
Paul 3.. Harrison
Stuart Bans
Douglas G. Eaynes
Dick Janowiacici
Gregory Kew
David Lennett
3.. A. Meserve
Xoraan H. Mines
Las Otte
Java Rubease*in
Jerry M. Schroy
£.&. Shuster
Sea Shuster
David a. Smith
Robert 8. Taylor
William E. Thacicar
T.J. Thibodeaux
Don Ucicnaa
Unda Wllber
Affiliation
Address
211 £. 43rd Street, Sew Toric, M7
WAP08A, Inc.
EPA
IT Corporation 336 W. Aubern Street, Wilmington, CA
EPA Washington, D.C.
International Paper 77 W. 45th Street, Mew Torie, Tf
Vald, Saritrodar
SLoss
EPA
U.S. EPA, ISHL
Engineering Science
fflTBE
"Ilia, Henry,
Hodge i Sayden
Monsanto
SPA/ ORB
EDF
Covlngton & Burling
MIT2E
a.s. EPA/OSW
Monsanto Co.
CSCOS
EPA/PSW
IT Carp.
SPA
XCASI
University of
Arkansas
EPA
EPA
1300 19th Street, JI.W. , Washington, 3.C.
Cincinnati, OH 45253
125 ». Huntington Dr., Arcadia, CA 91006
1320 Dolley Madison Blvd., McLean, TA
P.O. 3ox 2088
1215 Nicholas Soad , Daycaa, OH -3407
SPA Hqs. Rd-639, Washington, D.C. 20460
Toledo, OH 43603
388 16th Street, M.W., Washington, D.C.
1320 Dolley Madison Blvd., XcLaan, 7A
WH56A, Washington, D.C. 20460
300 S. Lindbergh Blvd., St. Louis, MO 53166
Xiagara Falls, JtT
401 H Street, S.W. , Washington, D.C. 20460
336 S. Ananiem Street, Wilmington, CA 90744
201 Street, S.W. , #523, Washington, D.C.
Western Michigan University , KaXaaazoo, MI
49008
Department of Chemical Engineering
Washington
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
-------
Name
Affiliacion
Addraas
Seong Hwong
Dick Janowiecki
Cace Jenkins
Laurel 0. Kasaoka
Tom Kally
Gregory Kew
Kathy Kohl
Mike Koaakowski
Carol Kuhlaan
J. Lehman
David Lannett
Bruce Lundy
Horaian H. Mines
Bruce Mintz
Chuck Morgan
Ronald E. Ney, Jr.
Sam "lapolitano
tarry 0' Bryan
Donald ft. Olson
Chec Opacsky
Laa Otte
Suallen Pirages
Chris Rhyne
Marc J. SogofS
leva Rubensteia
Hark S«gul
E.H.. Shuster
San Shuscer
David a. Smith
Dick S prince
Barry Stoll
Bada Talboc
Robert 3. Taylor
Buroall Vincent
Don V«itman
EPA
Monsa&to
2PA/OSW
E?A/OSW
EPA/PED
E2A/OSD
EPA
EPA
MIT22
EDF
SPA
MITSE
EPA
OHWE/OE
EPA
EPA
OTS
EPA
EPA/HStD
EPA/OSQ
Materials Program
Cong. Off. Tech,
Assessment
M1TBE
HSSMA
EPA/OTS
CZCOS
EPA/OSW
IT Corporation
T5ACOR
E5A/OSW
EPA/ORE/OHR
EPA
/
EPA
1515 Nicholas M., Dayton, OH 45407
401 M St., S.W. Washington, D.C. WH-565
401 M St., S.W. Washington, D.C. KH-56A
407 W 755-0306
SPAHqs., 3D-6fi9, Washington, D.C.
Washington, D.C.
Hdqtrs. EN-335
Westgata Research ?ark, McLean, 7A
1525 13th St., S.W.
401 M St., S.W. Washington, D.C. 21-335
W«stgate Research Park, McLean, 7A
401 M St., S.W. Washington, D.C. WS-547
Hdqcrs. 426-6374
Washington , D.C.
Hdqtrs.
E613B 755-2110
OWE? ES-338
E714 755-1500
401 M St., S.W. Washington, D.C. WH-564
Washington, D.C. 20510
Westgace Research Park, McLaan, 7A
1120 Conn. Ava. , N.W. Washington, D.C.
755-4360
Niagara Falls, H.T.
401 M St., S.W. Washington, D.C.
336 W. Anaheim St., Wilmington, CA 90744
1601 Research Blvd., Sockviile, MD
Washington, D.C. 20510
401 M St., S.W. Washington, Q.C. SD-633
201 I St., S.W. Washington, D C. "520"
OGC
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