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4
Potential Impacts from Placement of Coal
Combustion Residues in Coal Mines
T his chapter evaluates the potential human health and environmental im-
pacts posed by the placement of CCRs in mines. As discussed in previous
chapters, the concentrations of sulfate and metallic compounds in CCRs
are often elevated relative to the parent coal and/or surrounding deposits (see
Chapter 2). Once in contact with water, these constituents can leach from CCRs
and subsequently become mobilized in both ground- and surface water (see Chap-
ter 3). However, the composition of this leachate varies widely based on parent
coal composition, the combustion and waste-handling technologies utilized by a
particular power plant, and the geochemical environment in which the CCRs are
placed. This chapter examines known cases of damage that have occurred from
disposing of CCRs in a variety of environmental settings to understand what
conditions pose the greatest risk to human health and the environment. The
review of these cases assists the assessment of the potential impacts of CCR
placement in coal mines.
The incidents presented in this chapter are from published accounts in the
peer-reviewed scientific literature and/or are damage cases reviewed and recog-
nized by the U.S. Environmental Protection Agency (EPA). In the late 1990s and
revised in 2005 (USEPA, 2005a), the EPA reviewed monitoring data and identi-
fied damage cases, defined as sites where contaminants exceeded drinking water
or other health-based standards, usually from wells or in surface waters
downgradient of CCR management sites. The EPA considered the evidence of
proven and potential environmental impacts along with factors that may have
contributed to these impacts, including the interaction of CCRs with water. It did
not independently investigate most damage cases, but relied primarily on infor-
81
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82 MANAGING COAL COMBUSTION RESIDUES IN MINES
mation contained in state files. The EPA also acknowledged in the Regulatory
Determination of May 22, 2000 (40 CFR Part 261) that it did not use a statistical
sampling method and reviewed possible damage cases in only a subset of states.
The EPA noted that given the volume of CCRs generated nationwide and the
number of facilities that lack sufficient environmental monitoring and controls,
especially groundwater monitoring, other cases of proven and/or potential envi-
ronmental impacts are likely to exist.
For the 2000 regulatory determination, EPA cited 11 proven damage cases
(i.e., that met its "tests of proof"), all of which involved landfills (including some
CCR monofills) or surface impoundments. Since then, the number of damage
cases recognized by EPA has nearly doubled; as of 2005, EPA had recognized 24
proven damage cases involving CCR landfills and surface impoundments, and
one CCR minefill is now under investigation as a potential damage case (USEPA,
2005b; Table 4.1). According to the EPA, a damage case is proven if it satisfies
one or more so-called tests of proof, which include (1) scientific investigation,
such as formal investigations and technical tests that demonstrate significant
impacts on human health or the environment; (2) administrative ruling, such as an
enforcement action; (3) court decisions, which include official court rulings and
out-of-court settlements; and (4) sufficient evidence that the damages could be
attributable to CCR wastes (USEPA, 1999a).
During the course of the EPA's 2000 regulatory determination, public com-
ments contained information on 59 additional potential damage cases. Similarly,
this National Resource Council (NRC) committee received public testimony on
numerous sites where it was alleged that CCR placement in coal mines has been
implicated in the degradation of ground- or surface-water quality. In most of
these cases, industry disputed the claims of environmental impacts made by
public citizens, and in several cases, clear discrepancies in data, or in the interpre-
tation of data, existed among stakeholders (EarthTech, Inc., 2000; Richardson,
2004; Kyshakevych and Prellwitz, 2005; Zimmerman, 2005). Because these pur-
ported environmental impacts have not withstood the scrutiny of review by the
scientific and/or regulatory communities, they are not explicitly discussed in this
report. However, as discussed in Chapter 1, these local controversies were noted
by the committee during its deliberations and helped it to identify research needs
and formulate recommendations.
ENVIRONMENTAL IMPACTS
Currently, there are very few data available to indicate directly that place-
ment of CCRs in abandoned or active coal mines is either safe or detrimental. In
2000 the EPA noted, "For minefilling, although we have considerable concern
about certain current practices (e.g., placement directly into groundwater) we
have not yet identified a case where placement of coal wastes can be determined
to have actually caused increased damage to groundwater" (65 FR 32214). In its
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POTENTIAL IMPACTS FROM PLACEMENT 83
TABLE 4.1 Environmental Protection Agency Proven Damage Cases
Facility Type State
Vitale Fly Ash Pit Landfill MA
Salem Acres Landfill MA
Don Frame Trucking Landfill NY
PEPCO Faulkner Off-site Disposal Facility Landfill MD
VEPCO/Virginia Power Possum Point Surface impoundment VA
VEPCO/Virginia Power Chisman Creek Landfill VA
Chestnut Ridge Y-12 Steam Plant Operable Unit 2 Surface impoundment TN
Georgia Power Bowen Surface impoundment GA
South Carolina E&G Canadys Plant Landfill SC
Savannah River Project Surface impoundment SC
Belews Lake Surface impoundment NC
Hyco Lake (CP&L Roxboro) Surface impoundment NC
Lansing Board Power & Light North Lansing Landfill Landfill MI
Dairyland Power Old E.J. Stoneman Ash Pond-Cassville Surface impoundment WI
Site
WEPCO Highway 59 Landfill Landfill WI
Alliant Nelson Dewey Landfill WI
WEPCO Cedar Sauk Landfill Landfill WI
WEPCO Port Washington Landfill WI
Yard 520, Pines Landfill IN
Martin Creek Reservoir Surface impoundment TX
Brandy Branch Reservoir Surface impoundment TX
Welsh Reservoir Surface impoundment TX
Basin Electric WJ Neal Station Surface Impoundment Surface impoundment ND
(BESI)
Cooperative Power Association-United Power Coal Creek Landfill ND
SOURCE: USEPA, 2005b.
1999 report to Congress, EPA found the assessment of impacts from CCR
minefilling exceedingly difficult due to several factors, including insufficient
data and inadequacy of groundwater models. EPA stated, "With its existing data
the Agency is unable to determine if elevated contaminants in groundwater are
due to minefill practices, or rather are associated with pre-existing problems or
conditions," such as those of nearby mining operations (USEPA, 1999a).
A variety of studies have shown environmental impacts attributable to CCR
placement in non-coal mines (e.g., sand and gravel), and the EPA (65 FR 32214)
has identified numerous cases of water contamination related to CCR landfills
and surface impoundments that, in some cases, have caused environmental im-
pacts. Such cases are instructive because unlike the data currently available for
minefilling sites, these impacts can be clearly related to CCRs. Although landfills
and surface impoundments represent disposal conditions that may differ substan-
tially from mine settings, they are useful for understanding the specific condi-
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84 MANAGING COAL COMBUSTION RESIDUES IN MINES
tions under which CCRs threaten human health and ecosystems. Because mine
environments differ substantially across the United States, insights drawn from
CCR landfills and surface impoundments are ultimately useful for selecting the
least hazardous mining environments for CCR placement.
Landfills
Of the disposal options currently available for CCRs, landfills represent the
most analogous disposal method to surface minefills (see Sidebar 1.2). When
CCRs are managed in landfills with up-to-date liners and caps, reactivity with
water can be minimized. Thus, understanding the situations in which CCR land-
fills fail can be useful for inferring the types of mine environments that may be
least preferable for CCR placement. The EPA currently recognizes a variety of
potential and proven ecological damage cases attributable to landfilling CCRs.
Several of these and others are highlighted below. It should be noted here that the
landfills discussed in relation to damage cases are typically not the well-designed
structures with covers, compaction, and other characteristics discussed in the
definition of landfills provided in Chapter 1, but rather are less engineered loca-
tions used to store wastes.
Although no landfill damage cases quantified adverse effects to fauna, sev-
eral cases document adverse effects on plant communities and others document
contamination of surface waters at concentrations sufficient to harm inverte-
brates, fish, and wildlife. For example, from 1969 to 1979, CCRs were placed in
the Cedar Saulk Ash Landfill, an abandoned sand and gravel mine in Wisconsin.
In 1980, vegetation in a wetland downstream from the landfill began to show
symptoms of stress (e.g., leaf discoloration, defoliation) and plant die-offs were
subsequently observed (see Plate 1). The impacts on plants resulted in a shift
from a community dominated by woody species to a marsh community domi-
nated by grasses, sedges, and rushes. Tissue analyses revealed that boron leach-
ing from the landfill was the cause of toxicity to plant populations and the ob-
served shift in community composition (Wisconsin Electric Power Company,
1982, 1988). State officials reacted promptly to this situation by increasing moni-
toring efforts to identify the problem and taking mitigation measures (e.g., in-
stalling groundwater extraction wells and covering the site with a geomembrane
cap; USEPA, 2001a).
Factors Contributing to Adverse Consequences from
CCR Disposal at Landfills
A review of CCR landfill damage cases (Table 4.1) reveals one commonality
among the incidents: when CCRs react with water and the resulting leachate is
not contained, adverse consequences can result. Importantly, reactions with water
appear to be exacerbated by at least one of four factors. The first two factors
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POTENTIAL IMPACTS FROM PLACEMENT 85
SIDEBAR 4.1
Faulkner Landfill, Maryland
The Faulkner CCR landfill site associated with the PEPCO Morgantown gener-
ating station in Maryland is a recognized damage case by the EPA. This site differs
from other CCR damage cases in that fly ash, bottom ash, and pyrites were co-
managed there. In the early 1990s, it became clear that the contaminants migrat-
ing into the groundwater eventually reached surface waters, injuring vegetation
and leaving orange coatings from iron oxide precipitates in a nearby wetland and
stream. Pyrite oxidation at the site appears to have also resulted in low pH, a
situation analogous to many mine sites where pyrites are exposed. A shallow
groundwater table combined with the absence of liners appears to be a major
driver for environmental impacts at the site, but the EPA also concluded that the
low-pH conditions created by pyrite oxidation may have enhanced the mobility of
trace elements. Given the geochemical conditions of many coal mine sites, this
conclusion is particularly pertinent to issues surrounding minefilling of CCRs. In
response to the impacts occurring at Faulkner, the State of Maryland required
capping and installation of protective liners to prevent leaching of additional dis-
posal units at the site. In addition, further disposal of pyrites was separated from
CCR disposal in an effort to avoid interactions between these materials and subse-
quent pH-enhanced mobility.
SOURCE: SAIC, 2000.
relate to the permeability of the strata underlying the CCRs and the depth of the
water table. CCR placement in sand and gravel mines has resulted in environ-
mental impacts at CCR landfills in several localities including Wisconsin, Vir-
ginia, and Massachusetts. The EPA concluded that at each of these sites the
permeable nature of the underlying substrate allowed CCR constituents to leach
into ground- and surface waters. Shallow water tables aggravate the problem by
enhancing the interaction of water with the CCRs and increasing the likelihood of
leachate reaching the water table. For example, the EPA concluded that the
shallow water table at the Faulkner Landfill in Maryland was at least partly
responsible for the contamination of groundwater that eventually resurfaced and
impacted nearby wetland and stream communities (Sidebar 4.1; SAIC, 2000).
The third characteristic that appears to increase the likelihood of environ-
mental impacts from CCR placement in landfills relates to improper cover. In at
least one site, the Vitale Brothers Fly Ash Pit in Massachusetts, CCRs were left
uncovered, resulting in erosion and off-site migration of CCRs into a nearby
swamp and stream, the latter of which was a tributary to a local source of drinking
water. Surface waters were contaminated with iron and manganese, and ground-
water quality was compromised with high concentrations of arsenic, selenium,
aluminum, iron, and manganese. Other sites, such as the Cedar Saulk Ash Land-
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86 MANAGING COAL COMBUSTION RESIDUES IN MINES
SIDEBAR 4.2
Chisman Creek Disposal Site, Virginia
In one of the most severe landfill damage cases, approximately 500,000 tons of
fly ash were placed in a series of abandoned sand and gravel mines between 1957
and 1974 in York County, Virginia. By 1980, groundwater contamination was clearly
evident. Excessive concentrations of vanadium, nickel, selenium, and sulfates were
found in groundwater near the 27-acre disposal area. Water in adjacent residential
wells actually turned green, and subsequent testing revealed they were contaminat-
ed with selenium and sulfate at levels in excess of maximum contaminant levels
(MCLs). Ecological systems were also threatened at the site; on-site ponds and
creeks were contaminated with the aforementioned pollutants, as well as beryllium,
arsenic, chromium, copper, and molybdenum. There was also considerable concern
about contamination of the downstream Chisman Creek Estuary.
As a result of the proven contamination at the Chisman Creek disposal site, a
variety of regulatory and remedial responses ensued. In 1983, the site was listed
on the EPA's National Priority List under the Comprehensive Environmental Re-
sponse, Compensation, and Liability Act, commonly known as Superfund. This
Superfund site subsequently underwent aggressive cleanup that included sup-
plying city water in substitution for the 55 residential wells that were eliminated,
capping the CCR-containing pits, installing a leachate collection system, divert-
ing surface-water runoff, and rerouting a nearby stream. In addition, extensive
post-closure monitoring was established and continues today.
SOURCE: USEPA, 2001a.
fill (discussed above), covered CCRs but used insufficient quantities of post-
placement cover material. In both cases, the EPA and state officials concluded
that proper cover could have reduced the magnitude of impacts observed at the
site (USEPA, 2001a).
The final characteristic that is commonly cited by the EPA as contributing to
environmental impacts is the proximity of a CCR placement site to drinking
water supplies and/or aquatic habitats. In some cases, streams and wetlands occur
within the disposal site's boundaries, increasing the risk of environmental im-
pacts. For example, at the Chisman Creek site (Sidebar 4.2), a stream actually
passed so close to the waste site that the channel had to be redirected during the
remediation process. The site was also in close proximity to residential wells,
increasing the potential for human exposure (USEPA, 2001a).
Surface Impoundments
Disposal of CCRs in aquatic surface impoundments or settling basins has
been the most conspicuous mechanism by which surface environments have been
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POTENTIAL IMPACTS FROM PLACEMENT 87
contaminated by CCRs, resulting in degradation at a variety of sites in the United
States (Rowe et al., 2002). For example, the environmental impacts caused by
CCRs at Belew's Lake, North Carolina (Sidebar 4.3), was so severe that it be-
came one of the primary drivers behind the EPA's 1987 regulatory determination
for selenium in surface waters (USEPA, 1987). Unlike landfills and minefills, the
use of surface impoundments requires that CCRs be slurried with water and the
wastes remain ponded on the land surface until the system is dewatered and
dredged or covered. Therefore, opportunities for flora and fauna to interact di-
rectly with CCRs or CCR-contaminated waters are much more likely than at
minefills and landfills. There is a large body of peer-reviewed scientific literature
highlighting the impacts of CCR surface impoundments (Rowe et al., 2002), and
in most cases these impacts are clearly attributable to elemental constituents of
CCRs. However, in several cases other physicochemical characteristics of CCRs
give rise to changes in pH, conductivity, and physical smothering due to siltation
and can play important roles in the toxic potential of the effluent (e.g., Birge,
1978; Cherry et al., 1979a). Because of the known risks associated with surface
impoundments, CCR disposal in this manner is being phased out. According to
the Department of Energy Energy Information Administration, 25 percent of
CCRs produced in 1996 were placed in surface impoundments compared to only
SIDEBAR 4.3
Belews Lake, North Carolina
The Belews Lake story is the most widely recognized and cited damage case
associated with CCR disposal and offers an example of the adverse environmental
consequences that can occur when CCRs leach trace elements into surficial sys-
tems. In 1974, Duke Power began discharging surface water from fly ash settling
basins into Belews Lake, a large reservoir that provided cooling water for a coal-
fired power plant. Within a year, fish population declines were documented, and by
1978, 16 of 20 fish species had been eliminated completely from the reservoir.
Ultimately, three additional species were rendered sterile, leaving only one spe-
cies of fish in the reservoir. Intensive studies revealed that selenium, a highly mo-
bile and reproductively toxic element associated with CCRs, was the source of the
problem. Subsequent studies revealed that female fish accumulated high concen-
trations of selenium in their tissues and then transferred selenium to their offspring,
resulting in grotesque developmental abnormalities and high mortality rates. In
1985 after 10 years of thorough study, Duke Power ceased discharge of CCRs into
the settling impoundments. Subsequent monitoring efforts have revealed slow re-
covery of the system. By 1996, selenium levels and adverse effects on fish repro-
duction had decreased but were still higher than normal background levels.
SOURCE: Lemly, 1985, 1996.
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88 MANAGING COAL COMBUSTION RESIDUES IN MINES
19 percent in 2003 (USDOE, EIA, 1996, 2003b) As a result, increasing quantities
of CCRs may be placed in landfills or used as minefill.
Although surface impoundment environments are conspicuously different
from subsurface disposal in landfills and mines, they provide useful insight into
the severity of effects that can emerge when organisms come in contact with
CCRs or CCR-contaminated waters. Thus, they help to emphasize the importance
of proper placement of CCRs so that surface impacts do not occur. The following
section highlights the range of environmental effects that have been observed in
systems impacted by CCR surface impoundments, ranging from individual-level
responses (e.g., reductions in reproduction and survival) to population- and com-
munity-level effects (e.g., local extinctions of species).
Bioaccumulation and CCR as a Stressor
As a consequence of CCR disposal in surface impoundments, contaminants
have been found to accumulate in the tissues of organisms utilizing the impound-
ments or downstream habitats. Contaminants originating in CCRs enter food
chains by a variety of mechanisms. These mechanisms include direct uptake by
plants, epithelial accumulation by organisms in contact with the sediments and/or
porewater (e.g., benthic invertebrates), and direct sediment ingestion by grazing
(e.g., amphibian tadpoles) or dabbling wildlife (e.g., waterfowl). Uptake of some
contaminants can be high, exceeding the concentrations known to be toxic to
many organisms. For example, benthic invertebrates collected from streams and
wetlands downstream from CCR surface impoundments have concentrations of
arsenic, cadmium, and selenium that can exceed the concentrations in uncontami-
nated sites by orders of magnitude (Cherry et al., 1979a; Brieger et al., 1992;
Rowe, 1998; Lohner and Reash, 1999; Reash et al., 1999; Hopkins et al., 2004).
Of the contaminants associated with CCRs, selenium has received the greatest
attention in surface impoundment systems because of its high mobility, propen-
sity to bioaccumulate in food webs, and reproductive toxicity. However, in some
CCR-impacted systems, other constituents (e.g., arsenic, boron) may be impor-
tant and should always be considered in the risk assessment process.
Accumulation of metals and metalloids in animal tissues is important because it
can have a variety of adverse health consequences in organisms. For example, studies
on fish inhabiting reservoirs contaminated with effluent from surface impoundments
reveal high tissue levels of selenium associated with liver and kidney necrosis, in-
flammation of heart tissue, disruption of respiratory tissue, and abnormal female
reproductive tissue (Sorensen et al., 1982a,b, 1983a,b; Garrett and Inman, 1984).
More recent studies have demonstrated that predators that feed on fish from CCR
disposal sites are also at risk of tissue damage. For example, water snakes experimen-
tally fed fish collected from a CCR disposal site accumulated high concentrations of
arsenic, cadmium, selenium, strontium, and vanadium in their tissues (Hopkins et al.,
2002) and exhibited necrosis of the liver (Rania et al., 2003). In addition to tissue
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POTENTIAL IMPACTS FROM PLACEMENT 89
abnormalities, bioaccumulation of CCR constituents can lead to various symptoms
indicative of physiological stress including blood, enzymatic, hormonal, and meta-
bolic abnormalities (Farris et al. 1988; Hopkins et al., 1998, 1999; Rowe, 1998; Rowe
et al., 1998, 2002; Lohner et al., 2001).
Impacts on Growth, Survival, and Reproduction
Taken together, the diverse physiological disruptions described above may
contribute to the changes in growth, survival, and reproductive success that have
been observed in organisms exposed to CCRs. Early developmental stages of fish
and amphibians appear particularly sensitive to CCRs and CCR effluent (Lemly,
1996; Rowe et al., 2001; Snodgrass et al., 2004, 2005), with some species exhib-
iting 100 percent mortality after exposure in the laboratory (Birge, 1978) and the
field (Rowe et al., 2001). However, some amphibian species exhibit high survival
even after full larval period exposure (Snodgrass et al., 2004) but display reduced
growth and abnormal development (Snodgrass et al., 2004). Similarly, juvenile
benthic fish exposed to CCRs exhibit reductions in growth even when ample
uncontaminated food is provided (Hopkins et al., 2000). When predatory fish are
fed smaller fish from CCR disposal sites, predatory fish exhibit reductions in
food consumption, growth, and body condition (Coughlan and Velte, 1989).
Most importantly, reproductive failure has repeatedly been observed in or-
ganisms exposed to CCRs or CCR effluent (Lemly, 1996; Sidebar 4.3). Decades
of study of fish populations in North Carolina and Texas suggest that selenium
from CCRs is readily accumulated in reproductive tissues and subsequently trans-
ferred to offspring (Lemly, 1985, 1996, 1997). Maternal transfer is not isolated to
fish, but has been documented in a wide variety of wildlife exposed to CCRs
including birds, turtles, alligators, and amphibians (King et al., 1994; Nagle et al.,
2001; Bryan et al., 2003; Roe et al., 2004; Hopkins et al., 2005). For example,
research has demonstrated that high concentrations of selenium and strontium
can be maternally transferred in frogs, and these same frogs experienced a 19
percent reduction in reproductive success compared to individuals from uncon-
taminated sites (Hopkins et al., 2005). Reduced hatching success has also been
observed in bird eggs collected from nests at one CCR disposal reservoir, sug-
gesting that effects on wildlife reproduction may not be restricted to aquatic
habitats (USDOI, 1988).
Population and Community Effects
From an ecological perspective, the greatest concerns regarding CCRs are not
the effects on individual organisms as described above, but the impacts of CCR on
the integrity of populations and communities. Changes in zooplankton and benthic
invertebrate community composition have been observed in waters receiving CCR
effluent from surface impoundments (Spencer et al., 1983; Bamber, 1984; Specht
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90 MANAGING COAL COMBUSTION RESIDUES IN MINES
et al., 1984; Walia and Mehra, 1998), as well as in experimental settings (Hopkins
et al., 2004). Similarly, the diversity and density of macroinvertebrates have been
adversely affected in streams receiving surface impoundment effluent (Cairns et
al., 1970; Cherry et al., 1979a,b; Forbes and Magnuson, 1980; Magnuson et al.,
1980; Forbes et al., 1981). Such changes in invertebrate composition can have
widespread environmental implications, including changes in nutrient and energy
cycling and effects on predatory organisms that depend on invertebrates as a food
source (Hopkins et al., 2004).
Applicability of Landfills and Surface Impoundments to
Coal Mine Settings
As noted above nearly all of the damage cases cited and discussed in this
chapter reflect CCR disposal in sites other than coal mines. Because the
committee's statement of task (see Chapter 1) specifically addressed the disposal
of CCRs in coal mines, it is important to note the committee's view on the
applicability of landfill and surface impoundments impacts to coal mine settings.
Many of the damage cases discussed in this chapter involve older legacy
sites that were developed under less rigorous regulations than now exist. Many
were either slurry impoundments that drained to nearby surface waters or aban-
doned aggregate quarries that, by their very nature, were in highly permeable
geologic environments. In contrast, coal mines are generally, but not always,
located in less permeable rock formations, more remote areas, and further from
surface-water courses. Furthermore, while current regulations covering coal mine
placement of CCRs may require strengthening, as will be discussed in later
chapters, they are generally more demanding than those that were applicable
when the damage case sites were permitted. For example, landfills developed
before the implementation of RCRA were not subjected to requirements for
covers, compaction, liners, and other characteristics discussed in the definition of
RCRA-compliant landfills provided in Chapter 1.
In spite of these dissimilarities, however, the damage cases do illustrate the
types of adverse ecological impacts that may arise from CCR disposal that is not
properly managed. The damage cases illustrate many of the same processes that
are at work in coal mine sites, but on an accelerated time scale due to more
permeable hydrogeologic conditions at many of the damage case sites. Thus, the
committee, while aware of the limitations of using data from non-coal mine
settings, concluded that the damage cases contained important and relevant infor-
mation. The following section details some of the lessons that can be discerned
from non-mine settings.
Lessons Learned Relevant to CCR Placement in Mines
Taken together, available landfill and surface impoundment case studies
clearly indicate that environmental impacts can emerge when CCRs react with
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POTENTIAL IMPACTS FROM PLACEMENT 91
water and constituents are mobilized in significant concentrations and volume.
Surface impoundments represent an extreme example of such an interaction,
because the CCRs are slurried directly with water for disposal purposes and the
impoundments themselves often serve as suboptimal wildlife habitat or dis-
charge directly into streams. In contrast, CCR landfills offer a more analogous
situation to surface minefilling. Impacts can occur in landfilling situations when
water flow through CCRs results in leachate that is not adequately contained
within the landfill or attenuated in the surrounding subsurface environment.
Reactivity with water and off-site migration of soluble constituents can be
enhanced in landfills with permeable substrata, shallow water tables, insuffi-
cient post-fill cover, and/or close proximity to drinking water supplies or aquatic
habitats. With current liner, placement, and leachate collection technologies,
landfills can be designed to minimize contact with water and/or minimize the
rate of water flow through the material, thereby reducing contaminant trans-
port. In its 2000 regulatory determination, the EPA stated that minefilling can
contaminate groundwater when not sufficiently isolated or when the wastes and
sites are not matched properly based on geochemical characterization. Thus,
for minefilling to be a safe and effective disposal option, proper site selection,
site and waste characterization, and placement technologies are of utmost im-
portance to avoid adverse interactions between water and CCRs (see Chapters 6
and 7). Pre-placement characterization and careful site management are also
important considering that the placement of CCR in mines is effectively irre-
versible, because the removal of CCRs from a mine is not likely to be a practi-
cal remediation solution.
Environmental impacts can be reduced at CCR minefilling sites by prevent-
ing off-site migration of CCR constituents into surficial systems. The two pri-
mary mechanisms by which such migration of CCR constituents can occur are
transport via groundwater flow into interconnected surface waters and improper
cover of the CCRs. Each of these mechanisms is discussed briefly in an effort to
identify high-risk situations for CCR placement in mine settings.
Surface waters are most likely to be impacted by CCR placement in mines
when connected groundwater sources are contaminated. The CCR landfills at
Chisman Creek, Virginia, and Faulkner, Maryland (described above), provide
good examples of proven EPA damage cases that emerged from this process. In
both cases, unlined landfills were situated in areas with shallow water tables,
resulting in contaminated leachate that was transported into nearby wetlands and
streams. Some mining areas have similarly shallow water tables, making these
sites potentially higher-risk locations for CCR placement. Likewise, mine set-
tings that are in close proximity to streams are higher-risk settings for CCR
placement than areas more isolated from surficial waters. The Chisman Creek
landfill had additional risks of groundwater contamination because of the highly
permeable substrate characteristic of abandoned sand and gravel mines. To the
extent that similar highly permeable substrates exist at some coal mine sites (e.g.,
overburden, spoils, fractured shales; see Chapter 3), a similar potential may exist
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94 MANAGING COAL COMBUSTION RESIDUES IN MINES
SIDEBAR 4.5
Contaminant Concentration Limits Needed to Protect
Human and Environmental Health
Drinking water standards for the protection of human health are established by
the MCL, the highest level of a contaminant that is allowed in drinking water. The
MCL is set as close as technologically and economically feasible to the level at
which there is no known or expected risk to human health. In contrast, thresholds
for the protection of environmental health are set through EPA water quality crite-
ria, including the freshwater chronic water quality criteria. The freshwater chronic
water quality criteria represent the highest pollutant concentrations to which fresh-
water aquatic organisms can be exposed for an extended period of time without
deleterious effects. A partial summary of relevant CCR constituents with estab-
lished MCLs and freshwater chronic water quality criteria is presented in Table 4.2.
Beyond EPA, many states have established even lower levels of mercury to pro-
tect aquatic life, such as Nevada's freshwater chronic water quality criteria of 0.012
µg/L (NEC, 1991).
In general, water quality criteria designed to protect aquatic life are often lower
than drinking water standards in part because aquatic biota spend their entire life
in the water and, hence, are constantly exposed, whereas drinking water consti-
tutes only a portion, sometimes a small portion, of the exposure of humans. Other
reasons for differences between aquatic life and human health criteria include the
physiological sensitivity of some species and the exposure of early life stages of
aquatic organisms.
TABLE 4.2 A Comparison of EPA Freshwater
Chronic Water Quality Criteria with Drinking Water
MCLs for Select Constituents Relevant to CCRs
Drinking Water EPA Freshwater
Constituent MCL (ug/L) Criteria (µg/L)
Cadmium 05.0 0.25
Mercury 02.0 0.77
Selenium 50.0 5.0a
a
USEPA is currently replacing its water quality criterion for selenium with
a tissue-based criterion (Fed register EPA-822-D-04-001, Draft Aquatic
Life Criteria for Selenium-2004).
SOURCE: USEPA, 2002b.
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POTENTIAL IMPACTS FROM PLACEMENT 95
HUMAN HEALTH
Coal combustion residues contain a wide variety of constituents that are
potentially of concern for human health. The primary concern for human health
noted by EPA from the placement of CCRs in landfills, surface impoundments,
or minefills is the contamination of actual or potential sources of drinking water,
particularly groundwater, by metals that may be leached from the material (65 FR
32214; USEPA, 1999a). Surface waters that may be used as drinking water are
also of concern. This section first examines what is known about the potential
impacts of CCR leachate on drinking water sources and the characteristics of the
contaminants of concern. Although information is limited, the section provides a
qualitative assessment of the potential health risks to the public from exposure to
CCR-derived contaminants in the water supply. The section then describes the
tools available to further evaluate the potential for adverse human health effects
due to CCR placement in active or abandoned coal mines.
This section is not intended to provide a comprehensive examination of
potential health risks attributable to CCRs. Such an examination is beyond the
information available and the committee's task. CCRs, like many industrial efflu-
ents, represent a complex mixture of contaminants. Although the vast majority of
established exposure and health effects standards are for single compounds, these
contaminants can have complex interactions (e.g., antagonism, synergism) in the
environment. Also outside the scope of this report is a treatment of the health risk
associated with fugitive dusts that can be created in the transfer of CCRs or by
other handling procedures. Airborne particulate matter, such as fugitive dust,
poses a potential health risk through inhalation exposure. A full evaluation of
human health risk due to CCRs would consider cumulative risk, meaning the
combined risk to human health posed by exposure to multiple agents or exposure
through multiple pathways.
Current State of Knowledge
The only CCR coal minefill currently being considered as a potential damage
case by the EPA is the Center Mine in North Dakota. At this site there are at least
eight years of monitoring data that reveal probable groundwater contamination.
Although maximum contaminant levels (MCLs) have been exceeded for chro-
mium, iron, manganese, pH, sulfates, total dissolved solids (TDS), selenium,
cadmium, lead, and aluminum at the site, the origin of these contaminants is a
source of uncertainty. Conditions at the site were also degraded due to mining
activities, making it challenging to distinguish between leachate from mined
materials and from CCRs. A review of monitoring data by Beaver et al. (1987)
concluded that leachate was migrating from the CCR disposal areas. However, no
municipal or private wells have been identified as being threatened by this con-
tamination (USEPA, 1988).
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96 MANAGING COAL COMBUSTION RESIDUES IN MINES
A variety of CCR landfills have degraded groundwater and raised human
health concerns. As discussed in the previous section, the committee considers
landfills to represent the most analogous disposal method to surface minefills.
The landfills in Wisconsin, Massachusetts, Maryland, and Virginia, discussed
above in environmental damage cases, also exceeded drinking water MCLs in
groundwater. In the case of the Chisman Creek disposal site, remedial actions
included the closure of residential wells to reduce the risk of human exposure
(USEPA, 2001a). An additional damage case not discussed above is the North
Lansing CCR landfill that posed risks to drinking water wells for Lansing, Michi-
gan. The placement of CCRs results in contamination of groundwater with lithium
in a shallow aquifer below the landfill. Although initial reviews of the site sug-
gested the presence of other known or potential sources of groundwater contami-
nation, further data collection and analysis resulted in EPA recognition of the site
as a damage case linked to CCR disposal. The landfill is located in an unlined
former gravel quarry. The permeable nature of the disposal site's substrate,
coupled with CCR coming into contact with a rising water table, appears to have
accelerated the contamination. However, no contamination was observed to have
migrated to wells used for drinking water (SAIC, 2003).
The EPA's review of CCR characterization and leach test data, as well as
monitoring data and evaluations of potential damage cases, points to several
contaminants of concern. In particular, EPA identified potential risks from ar-
senic and cadmium. The concern for arsenic in part stems from EPA's recent
decision to lower the National Primary Drinking Water Standard MCL for this
contaminant (66 FR 6976; NRC, 2001; USEPA, 2001b). Also, in the EPA's
review of monitoring data and damage cases, various drinking water standards
were identified not to have been met, usually from wells on-site, downgradient
off-site, or from nearby surface waters impacted by surface impoundments or
landfills containing CCR. While MCLs were exceeded in cases that were not in
public drinking water wells, and hence not violations, the EPA considered them
examples of its concern. The EPA noted that arsenic, selenium, and fluoride
exceeded MCLs; sulfate, iron, chloride, manganese, and TDS exceeded second-
ary MCLs; and lead and boron levels exceeded state standards (65 FR 32214).
As indicated previously, quantitative estimates of human health risks are not
made in this report due to inadequacies in available information. Table 4.3 offers
a brief description of some examples of chemical contaminants of concern in
CCRs that can be transported in groundwater and that are regulated under the
Safe Drinking Water Act. This table provides a basis to develop a qualitative
perspective of potential health risks that might be associated with CCRs.
Another area of concern for potential adverse health effects is the impact of
CCR on surface-water quality. For example, a recent peer-reviewed study indi-
cates that changes in microbial communities in CCR-impacted streams may have
human health implications. Stepanauskas et al. (2005) demonstrated that micro-
bial communities from three CCR effluent discharge sources were more resistant
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POTENTIAL IMPACTS FROM PLACEMENT 97
to metal exposure than upstream microbial communities, suggesting that the
community composition had changed due to the selective pressures imposed by
contaminants in CCRs. These metal-resistant communities were also more resis-
tant to antibiotics, a finding that could have broad public health consequences
(Stepanauskas et al., 2005).
Tools for Evaluating Health Effects
This section examines the tools available to further evaluate the potential for
adverse human health effects from exposure to contaminated water supplies such
as could occur from improperly managed CCR disposal. The two primary tools or
analytical techniques for health risk evaluations are environmental epidemiology
and risk assessment, both of which have been the subject of NRC reports (e.g.,
NRC, 1991, 1994).
Epidemiological Studies
Epidemiological studies are concerned with patterns of disease in human
populations and the factors that influence these patterns. The most important
challenge for epidemiologists is finding explanations of why a specific exposure
is associated with a particular disease or condition. In general, scientists view
well-conducted epidemiologic studies as the most valuable information from
which to draw inference about human health risks. Compared to other techniques
used in risk evaluation, epidemiology is well suited to situations in which expo-
sure to risk agents is high (e.g., cigarette smoke), adverse health effects are
clearly defined (e.g., a form or forms of cancer), and where exposure to the
potential risk is known. Epidemiology is well suited to situations in which the
link between the risk factor and the outcome is known, where the factor can be
measured directly in the bodies of the affected population or inferred, and where
high levels of the risk agent are present in the environment (e.g., soil, water).
Epidemiological studies used to assess risks have important limitations that
constrain their usefulness associated with contamination of water supplies. These
limitations arise not from epidemiology per se but rather from the nature of the
analysis to which epidemiological data are applied. For example, one limitation
of environmental epidemiological studies is that they can be conducted only for
hazards to which people already have been exposed. They generally are not
useful for predicting the effects of exposure to environmental toxicants, such as
exposure to contaminated drinking water. Another limitation of epidemiological
studies is that they have poor sensitivity and are generally unable to detect small
increases in risk unless very large populations are studied. At low exposure
levels, which are likely to be the case with CCR-derived contaminants, adverse
effects will be difficult to detect. Still another limitation of epidemiological stud-
ies is that they fail to account for the effects of multiple sources of exposure. If
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98
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exposure
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neurological tissues and dental fluorosis
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99
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100 MANAGING COAL COMBUSTION RESIDUES IN MINES
the CCR-exposed population is also exposed to contaminants from numerous
other sources, epidemiological analysis may not show an association even if one
is actually present.
Risk Assessment
Earlier NRC reports contain lengthy discussions of risks and approaches to
its analysis, including Understanding Risk: Informing Decisions in a Democratic
Society (NRC, 1996b). The EPA guidance on the conduct of human health and
ecological risk assessments is described in USEPA (1998b, 1999a, 2001b). The
EPA (USEPA, 2004d) provides an examination of current risk assessment prin-
ciples and practices at the agency. NRC (1996b) sets forth an elaborate descrip-
tion of risk characterization, which it defines as a "synthesis and summary of
information about a hazard that addresses the needs and interests of decision
makers and of interested and affected parties. It is a prelude to decision making
and depends on an iterative, analytic-deliberative process." Risk assessment in-
volves (1) hazard identification, (2) dose-response assessment, (3) exposure as-
sessment, and (4) risk characterization (NRC, 1983). Given the large number and
range of factors that cannot be quantified, the risks associated with CCR place-
ment in mines are not easily quantifiable. However, monitoring data at CCR
placement sites may provide information on the types of contaminants to which
the public could be exposed.
Additionally, prior studies have developed relationships between dose and
response for these contaminants that could help in the risk assessment process.
Improving the understanding of exposure is one area that would allow better risk
characterization from CCR placement.
Exposure Pathway
Exposure is a key element in the chain of events that leads from release of
contaminants into the environment to a concentration of those contaminants in
one or more environmental media (e.g., air, water, soil); to actual human expo-
sure (internal or delivered dose of a toxicant); and ultimately, to environmentally
induced disease. In other words, without exposure to the contaminant there is no
risk. Different individuals or subpopulations will be exposed to different amounts
of contaminants. For risk evaluation to be credible there must be measurements,
or sound assumptions, made about the four basic characteristics that describe
exposure: (1) route--inhalation, ingestion, or dermal absorption; (2) magnitude--
the pollutant concentration; (3) duration--the length of exposure; and (4) fre-
quency--how often exposure occurs. These estimates must also take into account
that populations exposed to contaminants will have variable intakes of water,
depending on age, gender, and health status. Evaluations of risk that do not
account for variation in water consumption may result in underestimating the
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POTENTIAL IMPACTS FROM PLACEMENT 101
upper bounds of health risk attributable to contact with mixtures of contaminants
in water supplies.
Additionally, as discussed in Chapter 3, physical and chemical processes
will also impact exposure. Of relevance is the fact that contamination and expo-
sure by the water route can be modified by transport and transformation of the
mixture. Some elements (e.g., selenium, cadmium, mercury) form complexes,
whose bioavailability is dependent on their thermodynamic and kinetic stability.
Dilution and degradation can attenuate mixtures of chemicals, while processes
that concentrate the chemicals can magnify the risk. The actual fate of mixtures,
and hence the level of exposure, depends on the contaminants' physical and
chemical properties combined with the characteristics of the environment to which
it is released. The influence of these variables creates additional uncertainties in
predicting exposures.
Despite their importance for assessing human health risks, human exposure
data are not collected in a systematic or comprehensive manner for CCRs. Only
limited information is available; therefore, understanding historical trends, esti-
mating current levels, and predicting future directions for CCR exposures to
population and population subgroups is difficult. In general, exposure assess-
ment, critical to the evaluation of potential adverse health effects, is one of the
most difficult problems facing environmental health scientists and public health
and other regulatory officials. Without data and an understanding of these vari-
ables as they relate to exposure to CCRs, it is difficult to assess with any degree
of accuracy the health risks from CCR-derived contaminants at any given loca-
tion in the environment, including potential drinking water sources. Thus, as part
of a recommended research program looking at potential adverse environmental
and human health impacts from CCR placement, studies should assess the poten-
tial for human exposure to contaminated drinking water that might occur due to
CCR placement.
SUMMARY
The committee's review of literature and damage cases recognized by EPA
supports EPA's previously stated concerns about proper management of CCRs.
The two most common CCR disposal options, surface impoundments and land-
fills, have been utilized for decades and provide valuable insights into the types
of problems that can emerge when CCRs or their soluble constituents are not
contained within the waste management unit. In some landfill settings, ground-
water has been degraded to the point that drinking water standards were exceeded
off-site. In other landfills and surface impoundments, contamination of surface
waters has resulted in considerable environmental impacts; in the most extreme
cases, multiple species have experienced local extinctions. The waste manage-
ment in these impoundments and landfills often involved older, unlined units, and
most landfill impacts involved CCR placement in sand and gravel mines that are
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102 MANAGING COAL COMBUSTION RESIDUES IN MINES
characterized by permeable substrata. In contrast, some contamination of lotic
systems (streams, rivers) may not pose as obvious a risk because of the continual
dilution and off-site migration of mobile CCR contaminants. However, total
contaminant loading to these lotic systems may possibly affect downstream sites
after protracted periods.
To minimize the risk of adverse impacts from disposal of CCR in mine sites,
a variety of steps should be taken. The most effective strategy for avoiding
contamination is proper hydrogeological characterization of the site prior to place-
ment and employment of placement technologies that reduce the probability of
reaction of CCRs with groundwater (see Chapter 6 and 7). Sites with shallow
water tables, highly porous or permeable substrata, or close proximity to surface
waters (e.g., streams, wetlands) likely constitute higher-risk CCR placement en-
vironments and may require additional characterization before CCR placement
can be justified. In many cases, complete isolation from water will not be pos-
sible, but a variety of steps can be taken to reduce the reactivity of CCRs with
water and the off-site transport of soluble constituents. In some cases, this can be
achieved with proper compaction of base and/or surface cover layers, reducing
the water contact with, and water flux through, the CCRs. In all cases, proper
cover should be placed over CCRs to prevent erosion, as well as root penetration
by plants and subsequent upward mobilization of CCR constituents.
Of the three methods currently available for disposal of CCRs (surface im-
poundments, landfilling, and minefilling), comparatively little is known about the
potential for minefilling to degrade the quality of groundwater and/or surface
waters particularly over longer time periods. Additionally, there are insufficient
data on the contamination of water supplies by placement of CCRs in coal mines,
making human risk assessments difficult. The committee was presented with
numerous testimonies in which public citizens, industry, and state regulatory
agencies disagreed about the degradation of water quality attributable to CCR
placement in mines. The committee noted that involvement by state regulators,
particularly in monitoring and early detection of potential problems, followed by
the collection of additional data and appropriate mitigation, such as the proactive
measures observed in Wisconsin, could be adequate to resolve these discrepan-
cies. However, in other cases, oversight and study by independent scientists
could provide much-needed answers to these emerging disputes. In assessing
potential adverse health and environmental risks from CCR placement in coal
mines, the committee was faced with a lack of peer-reviewed research reports and
data with specific reference to CCRs in coal mines. The EPA has not identified
any cases in which water quality standards that had not been met could be attrib-
uted directly to CCR mine placement. However, data limitations suggest that the
absence of EPA damage cases should not be taken as conclusive evidence of no
effects on human health and ecosystems. The committee concluded that the pres-
ence of high levels of some contaminants in CCR leachates may create human
health and ecological concerns at or near some mine sites over the long term.
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POTENTIAL IMPACTS FROM PLACEMENT 103
Peer-reviewed research relating to CCR impacts on aquatic biota from landfills
and impoundments provides evidence of impacts, indicating that independent
studies of water quality and environmental impacts of CCR minefilling are
needed.
Given the increasing quantities of CCRs likely to be placed in mines, the
potentially toxic constituents of CCRs, the conditions in some mine sites that
may favor leaching of these constituents, and the inadequacies in our understand-
ing of potential environmental and human health impacts of CCR placement in
mines, the committee concluded that additional research is needed. The com-
mittee recommends additional research to provide information on the po-
tential ecological and human health effects of placing CCRs in coal mines. In
particular, clarification of the fate and transport of contaminants from CCRs is
needed. It should include studies to determine the effects (or lack thereof) on
biological communities over protracted time scales in mine placement sites where
nearby streams or wetlands are likely connected to groundwater. Studies should
also assess whether there is the potential for human exposure to drinking water
impacts from CCR placement.
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Representative terms from entire chapter:
ccr placement
