include: natural water table, probable maximum precipitation, surface
water, systemic toxicants and upstream toe. New definitions are
discussed in the technical section of the rule for which they apply.
The majority of the regulatory definitions contained in the proposed
rule have been retained in the final rule, as proposed or with minor
clarifying changes. These definitions are codified in Sec.  257.53 and
include the following: acre foot, active life, aquifer, area capacity
curves, areas susceptible to mass movement, coal combustion residuals
(CCR), displacement, facility, factor of safety, fault, freeboard,
groundwater, hazard potential classification, high hazard potential
surface impoundment, significant hazard potential surface impoundment,
low hazard potential surface impoundment, holocene, hydraulic
conductivity, karst terrain, lithified earth material, maximum
horizontal acceleration in lithified earth material, new CCR landfill,
new CCR surface impoundment, operator, owner, poor foundation
conditions, recognized and generally accepted good engineering
practices, representative sample, run-off, run-on, sand and gravel pit
or quarry, seismic impact zone, state, structural components, unstable
area, uppermost aquifer, and waste boundary.
    Several definitions received a significant number of comments and
upon further evaluation by EPA have been modified to better explain
their meaning or intent. This includes the definitions for the
following terms: CCR landfill or landfill, CCR surface impoundment or
impoundment, existing CCR landfill and existing CCR surface
impoundment. These comments, along with the revisions made in response
are discussed in more detail below. In addition, EPA has revised a
number of definitions, or added new definitions, to be consistent with
revisions made in the corresponding technical requirements. These are
discussed in the various sections of the preamble that address the
specific technical requirement. For example, as discussed in Unit V of
this document, EPA has revised the definition of ``independent
registered professional engineer or hydrologist'' to ``qualified
professional engineer'' to address the concerns raised in comments.
1. Definition of CCR Landfill
    EPA proposed to define a CCR landfill as a disposal facility or
part of a facility where CCR is placed in or on land and which is not a
land treatment facility, a surface impoundment, an underground
injection well, a salt dome formation, a salt bed formation, an
underground mine, a cave, or a corrective action management unit. For
purposes of this subpart, landfills also include piles, sand and gravel
pits, quarries, and/or large scale fill operations. Sites that are
excavated so that more coal ash can be used as fill are also considered
CCR landfills. (See 75 FR 35239.) The Agency received a significant
number of comments on the proposed definition. These comments focused
almost exclusively on the inclusion of ``large-scale fill operations''
and ``piles'' within the definition of CCR landfill. Regarding large-
scale fills, commenters argued that one of the fundamental problems
with the proposed definition was that it assumed all CCR placed in
large scale fill operations constituted ``disposal'' of CCR (and that
these operations therefore constitute CCR landfills) rather than
beneficial use. Commenters further argued that CCR is often used in
engineered fills, such as road base and road embankments and that these
legitimate beneficial use operations should not be subject to the CCR
landfill regulations.
    Commenters also argued that ``piles'' should be omitted from the
definition of a CCR landfill for a variety of reasons. Several
commenters argued that including the word ``pile'' was overly broad and
insufficiently prescriptive and would inappropriately capture on-going
or short-term CCR management activities that did not constitute
disposal, such as storage for beneficial use. These commenters also
raised concern that including ``piles'' in the definition of CCR
landfill without further clarification or specificity, i.e., when used
as part of a beneficial use operation, would negatively affect
beneficial use activities. Other commenters raised concern that the
term ``piles'' was too vague, and suggested that whether piles were
treated as CCR landfills should be determined by the size of the piles,
or the intent for which such piles exist. These commenters suggested
the Agency should exclude small piles of CCR that are staged and/or
consolidated prior to transport or placement for disposal. These
commenters argued that subjecting all CCR piles to all of the landfill
requirements was ``illogical and inappropriate.''
    Certain commenters argued that piles should not be regulated under
this rule because they do not present a significant risk to the
environment, as evidenced by a lack of damage cases. Alternately, other
commenters suggested that if EPA were to regulate piles, the Agency
should consider a regulatory strategy other than regulation as a CCR
landfill. One alternative regulatory strategy suggested was to include
an option establishing a limit (e.g., 180 days) on the amount of time
that the CCR could be allowed to be maintained in a pile without
regulation as a CCR landfill. Another option suggested was to develop a
set of reasonable design and operating standards consistent with the
uses and risks posed by piles. Such design standards could include the
requirement for a low permeability underlayment or base such as
asphalt, concrete or a high density polyethylene (HDPE) liner.
Operating standards could include such provisions as labeling, and the
requirement to remove at least 90 percent of the contents every 90
days, with a full cleanout annually.
    EPA believes the suggested option to establish a time limit would
be difficult to oversee and verify. States and citizens would have no
way to determine when CCR is placed in a pile and when the CCR was
subsequently removed. Therefore, EPA is rejecting this suggested
option. The suggested option to develop appropriate design and
operating standards is essentially the approach EPA has adopted, as
discussed in more detail below. However, the final design and operating
standards differ according to the management practices, and include
measures to control fugitive dust, and for certain practices, require
the installation of a composite liner and leachate collection system.
    EPA discussed its final approach to large-scale fill operations in
Unit V of this document; the definition of a CCR landfill has been
revised to be consistent with the approach described in that section.
As explained at length, EPA has adopted a final approach that
distinguishes between beneficial use and the ``disposal'' of CCR.
Activities that meet the definition of beneficial use are not subject
to these regulations. Activities that do not meet all of the criteria
in the definition of a beneficial use--and in particular, such
activities that involve the placement of unencapsulated CCR on the
land--are considered disposal and are subject to the requirements of
this final rule. Consistent with this approach the final definition of
a CCR landfill has been revised to clarify that it includes ``the

use of CCR that does not meet the definition of a beneficial use of
CCR.'' Waste piles, including those used to temporarily store or manage
CCR on-site prior to disposal in a CCR landfill or subsequent
beneficial use, have been retained within the definition of a CCR
landfill. In making this determination the Agency was strongly
influenced by the similarities in the potential risks posed by both
waste piles and CCR landfills to human health, groundwater resources,
or the air if improperly managed. Both CCR piles and CCR landfills are
subject to external factors such as rain and wind, which can adversely
affect human health and the environment. For example, uncontrolled run-
on and run-off can result in ponding of water in and around the unit
resulting in increased leachate which has the potential to affect
groundwater. Similarly, absent dust control measures, such as the
conditioning of CCR, both CCR landfills and CCR piles have the
potential to generate significant amount of fugitive dust. Indeed, CCR
piles are generally more susceptible to the creation of fugitive dusts.
And contrary to the commenters' contention about the absence of damage
cases, the single most frequent issue presented during the public
hearings was the allegation by individual citizens of damage caused by
fugitive dusts from neighboring CCR facilities. Moreover, the same
pollution control measures, such as liners, leachate collection
systems, and groundwater monitoring, will address the potential adverse
effects from both of these units. As such, the Agency sees no reason to
treat piles and landfills differently.
    EPA also disagrees that the inclusion of CCR piles would capture
on-going or short-term CCR management activities that do not constitute
disposal. Irrespective of whether the facility is using the pile as
``temporary storage'' or ultimately intends to direct the CCR to
beneficial use, by placing the CCR on the land with no containment or
other method of preventing environmental exposures, the facility is
engaging in an activity that clearly falls within the statutory
definition of disposal. See 42 U.S.C. 6903(3)(``placing of solid waste
. . . on any land, so that such solid waste . . . or any constituent
thereof may enter the environment.'') Moreover, even where the facility
intends the pile to be ``temporary,'' some amount of CCR inevitably
remains in place. And if this was not the case, under section
1008(a)(3), EPA is authorized to establish criteria governing all
aspects of solid waste management--which explicitly is defined to
include ``storage'' as well as all of the other activities identified
by the commenters--to ensure the protection of human health and the
environment. See 42 U.S.C. 6903(28).
    Nevertheless, EPA agrees that not every activity that involves the
management of CCR must occur in a unit that meets all of the technical
requirements of a CCR landfill (e.g., groundwater monitoring). The key
concern EPA is seeking to address with the inclusion of piles is the
uncontrolled exposure from the extended, repeated, or indefinite
placement of large amounts of unconsolidated CCR directly on the land.
To the extent those exposures are controlled, whether through the use
of tanks or some other kind of containment measures, the practice is
neither considered to be a ``pile'' nor disposal in a landfill.
    To clarify this, and in response to the concern that the term
``piles'' was too vague, EPA has adopted a definition of the term ``CCR
pile'' to identify those ``piles'' that are subject to the disposal
requirements in this regulation. The final regulation specifies that a
CCR pile means any non-containerized accumulation of solid, non-flowing
CCR that is placed on the land. This definition mirrors the existing
definition of ``waste pile or pile'' from the part 257 regulations,
(i.e., the regulations that currently apply to CCR facilities), as well
as the definition in part 260. The use of the phrase ``non-
containerized'' is not intended to require that all activities occur
within tanks or containment structures, but merely that specific
measures have been adopted to control exposures to human health and the
environment. This could include placement of the CCR on an impervious
base such as asphalt, concrete, or a geomembrane; leachate and run-off
collection; and walls or wind barriers. CCR managed in such a fashion
would not be CCR piles and, therefore, not CCR landfills subject to
this regulation. To further clarify how this relates to EPA's overall
approach to beneficial use it is important to distinguish between CCR
that is actually being used beneficially and CCR that may someday be
used beneficially. CCR that is currently being used beneficially--for
example, fly ash that has been transferred to a cement manufacturer and
that is stored off-site in a ``temporary pile,'' and that complies with
all of the criteria in the definition to be considered a beneficial use
including the fourth criterion relating to the placement of large
quantities of unconsolidated CCR on the land--would not be subject to
the regulations applicable to CCR disposal. Accordingly, the final
regulation specifies that practices that meet the definition of
beneficial use of CCR are not subject to the `disposal'' requirements
of the rule.
    By contrast, CCR located on-site that may someday be used
beneficially but is not yet beneficially used remains subject to the
disposal rule. Given that landfills and surface impoundments can be
periodically dredged to provide material for beneficial use, any other
approach would be impracticable, and would exclude from regulation many
of the greatest sources of risk. An example of a ``pile'' that is not
yet beneficially used is unconsolidated CCR placed on the land, that
have been designated by the CCR facility to be transferred to another
location for subsequent beneficial use (e.g., use as road bed) in the
near future.
    Several commenters also suggested that the definition of a CCR
landfill should explicitly exclude the use of CCR at surface coal
mining and reclamation operations, to reflect the Agency's intention
not to cover such activities. The Agency agrees and has revised the
definition to explicitly provide that the term CCR landfill does not
include the use of CCR at coal mining and reclamation operations.
    Consequently, the Agency is finalizing a definition of ``CCR
landfill or landfill'' that can be found in Sec.  257.73. On a related
matter, the definition of CCR landfill or landfill contains the terms
``sand and gravel pits or quarries.'' EPA proposed a ``sand and gravel
pit and/or quarry'' to mean an excavation for the commercial extraction
of aggregate for use in construction projects. The Agency received
comments on the definition of sand and gravel pit and/or quarry
suggesting that the term ``commercial extraction'' was too narrow.
Specifically commenters were concerned it would exclude non-commercial
extraction, such as gravel pits operated by municipalities, and exclude
metallic mineral mines, nonmetallic mining for other than sand and
gravel, and coal mines. EPA agrees that the use of the term
``commercial extraction'' renders the proposed definition too narrow,
as there is no basis for distinguishing between commercial and non-
commercial extraction, either because of the risks these activities
pose, or any other consideration relevant to this rulemaking. EPA is,
therefore, revising ``sand and gravel pit and/or quarry'' to mean an
excavation for the extraction of aggregate, minerals, or metals. The
term sand and gravel pit and/or quarry does not include subsurface or
surface coal mines.

2. Definition of CCR Surface Impoundment
    EPA proposed to define a CCR surface impoundment to mean a facility
or part of a facility which is a natural topographic depression, man-
made excavation, or diked area formed primarily of earthen materials
(although it may be lined with man-made materials) which is designed to
hold an accumulation of CCR containing free liquids, and which is not
an injection well. Examples of CCR surface impoundments are holding,
storage, settling, and aeration pits, ponds and lagoons. CCR surface
impoundments are used to receive CCR that have been sluiced (flushed or
mixed with water to facilitate movement), or wastes from wet air
pollution control devices, often in addition to other solid wastes.
    The Agency received many comments on the proposed definition of CCR
surface impoundment. The majority of commenters argued that the
definition was overly broad and would inappropriately capture surface
impoundments that are not designed to hold an accumulation of CCR.
Commenters were concerned that the proposed definition could be
interpreted to include downstream secondary and tertiary surface
impoundments, such as polishing, cooling, wastewater and holding ponds
that receive only de minimis amounts of CCR. Commenters reasoned that
these types of units in no practical or technical sense could be
described as units ``used to receive CCR that has been sluiced.''
    Other commenters raised concern that the definition did not
differentiate between temporary and permanent surface impoundments.
Commenters stated that many facilities rely on short-term processing
and storage before moving CCR off-site for beneficial use or permanent
disposal and that these units should not be required to comply with all
of the technical criteria required for more permanent disposal
impoundments.
    Upon further evaluation of the comments, the Agency has amended the
definition of CCR surface impoundment to clarify the types of units
that are covered by the rule. After reviewing the comments, EPA
reviewed the risk assessment and the damage cases to determine the
characteristics of the surface impoundments that are the source of the
risks the rule seeks to address. Specifically, these are units that
contain a large amount of CCR managed with water, under a hydraulic
head that promotes the rapid leaching of contaminants. These risks do
not differ materially according to the management activity (i.e.,
whether it was ``treatment,'' ``storage'' or ``disposal'') that
occurred in the unit, or whether the facility someday intended to
divert the CCR to beneficial use. However, EPA agrees with commenters
that units containing only truly ``de minimis'' levels of CCR are
unlikely to present the significant risks this rule is intended to
address.
    EPA has therefore revised the definition to provide that a CCR
surface impoundment as defined in this rule must meet three criteria:
(1) The unit is a natural topographic depression, man-made excavation
or diked area; (2) the unit is designed to hold an accumulation of CCR
and liquid; and (3) the unit treats, stores or disposes of CCR. These
criteria correspond to the units that are the source of the significant
risks covered by this rule, and are consistent with the proposed rule.
EPA agrees with commenters that relying solely on the criterion from
the proposed rule that the unit be designed to accumulate CCR could
inadvertently capture units that present significantly lower risks,
such as process water or cooling water ponds, because, although they
will accumulate any trace amounts of CCR that are present, they will
not contain the significant quantities that give rise to the risks
modeled in EPA's assessment. By contrast, units that are designed to
hold an accumulation of CCR and in which treatment, storage, or
disposal occurs will contain substantial amounts of CCR and
consequently are a potentially significant source of contaminants.
However, EPA disagrees that impoundments used for ``short-term
processing and storage'' should not be required to comply with all of
the technical criteria applicable to CCR surface impoundments. By
``short-term,'' the commenters mean that some portion of the CCR is
removed from the unit; however, in EPA's experience these units are
never completely dredged free of CCR. But however much is present at
any given time, over the lifetime of these ``temporary'' units, large
quantities of CCR impounded with water under a hydraulic head will be
managed for extended periods of time. This gives rise to the conditions
that both promote the leaching of contaminants from the CCR and are
responsible for the static and dynamic loadings that create the
potential for structural instability. These units therefore pose the
same risks of releases due to structural instability and of leachate
contaminating ground or surface water as the units in which CCR are
``permanently'' disposed.
    The final definition makes extremely clear the impoundments that
are covered by the rule, so an owner or operator will be able to easily
discern whether a particular unit is a CCR surface impoundment. CCR
surface impoundments do not include units generally referred to as
cooling water ponds, process water ponds, wastewater treatment ponds,
storm water holding ponds, or aeration ponds. These units are not
designed to hold an accumulation of CCR, and in fact, do not generally
contain significant amounts of CCR. Treatment, storage, or disposal of
accumulated CCR also does not occur in these units. Conversely, a
constructed primary settling pond that receives sluiced CCR directly
from the electric utility would meet the definition of a CCR surface
impoundment because it meets all three criteria of the definition: It
is a man-made excavation and it is designed to hold an accumulation of
CCR (i.e., directly sluiced CCR). It also engages in the treatment of
CCR through its settling operation. The CCR may be subsequently dredged
for disposal or beneficial use elsewhere, or it may be permanently
disposed within the unit. Similarly, secondary or tertiary impoundments
that receive wet CCR or liquid with significant amounts of CCR from a
preceding impoundment (i.e., from a primary impoundment in the case of
a secondary impoundment, or from a secondary impoundment in the case of
a tertiary impoundment), even if they are ultimately dredged for land
disposal elsewhere are also considered CCR surface impoundments and are
covered by the rule. To illustrate further, consider a diked area in
which wet CCR is accumulated for future transport to a CCR landfill or
beneficial use. The unit is accumulating CCR, while allowing for the
evaporation or removal of liquid (no free liquids) to facilitate
transport to a CCR landfill or for beneficial use. In this instance,
the unit again meets all three definition criteria, it is a diked area
(i.e., there is an embankment), it is accumulating CCR for ultimate
disposal or beneficial use; and it is removing any free liquids, (i.e.,
treatment). As such, this unit would meet the definition of CCR surface
impoundment. In all of these examples significant quantities of CCR are
impounded with water under a hydraulic head that will be managed for
extended periods of time. This gives rise to the conditions that both
promote the leaching of contaminants from the CCR and are responsible
for the static and dynamic loadings that create the potential for
structural instability. These units therefore all pose the same risks
of

releases due to structural instability and of leachate contaminating
ground or surface water.
3. Definition of Existing CCR Landfill
    EPA proposed to define an existing CCR landfill to mean a CCR
landfill which was in operation on, or for which construction commenced
prior to the effective date of the final rule. The proposed definition
specified that a CCR landfill has commenced construction if the owner
or operator has obtained the federal, state, and local approvals or
permits necessary to begin physical construction; and either: (1) A
continuous on-site, physical construction program has begun; or (2) the
owner or operator has entered into contractual obligations--which
cannot be cancelled or modified without substantial loss--for physical
construction of the CCR landfill to be completed within a reasonable
time.
    In response to the proposed definition, the Agency received several
comments arguing that the use of the phrase ``was in operation on, or
for which construction commenced prior to'' would lead to confusion.
Commenters contended that most units defined as CCR landfills at some
point in time ``were in operation'' and had ``commenced construction''
prior to the effective date of the regulation. Commenters claimed that
this definition would unnecessarily capture thousands of closed
structural fill projects, including residential properties, commercial
properties used by small businesses, and many recreational facilities.
Furthermore, commenters doubted that EPA intended for the rule to cover
all of these units and urged the Agency to clarify that closed units
are excluded from the definition of existing CCR landfill.
    Other commenters argued that the proposed definition of existing
CCR landfill should be modified to include lateral expansions of
operation units where such an expansion is within the site footprint of
an area already approved and permitted by the state for the landfill.
Commenters contended that while the proposed definition included
undeveloped areas within the footprint of an approved permitted site,
it also required that the construction be initiated at the site or that
some type of binding contractual obligation be present. Commenters
contended that the existence of a contractual obligation unfairly
subjects undeveloped, yet approved permitted areas to design and
operating standards for new CCR landfills based merely on the existence
of a contract to commence construction. Commenters argued that such a
distinction was arbitrary and capricious and provided no practical
benefit. Other commenters questioned the usefulness of requiring a
contractual obligation at all. As written, the commenters argued, that
the definition was vague, unenforceable, and thus, not protective of
human health and the environment. Commenters reasoned that there was no
definitive or generally accepted meaning for the term ``substantial
loss'' or the term ``reasonable time'' and an owner or operator,
sensing that these proposed rules may be passed, could sign a contract
now with minimum predetermined cancellation or modification penalties
and a contract term of say five years or even longer to avoid the new
unit requirements, i.e., a composite liner.
    The commenters are correct that EPA did not intend to cover
inactive landfills under this rule. The Agency agrees that, as drafted,
the proposed definition could cause confusion. EPA therefore deleted
the phrase ``was in operation on the effective date of the rule'' and
has substituted the phrase ``that receives CCR both before and after
[the effective date of the rule].'' EPA also agrees that the phrase
``commenced construction prior to the effective date of the rule''
could similarly cause confusion. Therefore, the Agency has made a
similar revision, by adding the phrase ``and receives CCR on or after
[the effective date of the rule]'' after the phrase ``for which
construction commenced prior to [the effective date of the rule].''
These revisions will clarify which units are covered by the technical
requirement of the rule and alleviate any confusion. EPA is also making
conforming modifications to the definition of existing CCR surface
impoundment.
    EPA disagrees that lateral expansions should be considered to be
``existing'' based solely on the fact that such an expansion is within
the site footprint of an area already approved and permitted by the
state. EPA has frequently distinguished between the types of
requirements applicable to new and existing units, reasoning that in
many instances, risk mitigation measures would be adequate such that
existing units need not wholly retrofit to meet the new ``state of the
art.'' For new units, however, the balance is generally struck in favor
of requiring a greater degree of risk prevention, rather than relying
solely on risk mitigation measures. In determining whether a unit is
``new'' or ``existing,'' EPA has historically considered that the
equities lie in favor of considering a unit to be ``existing'' when
there has been an irretrievable commitment of resources on the part of
the facility. That has not occurred merely because permits have been
obtained. While admittedly resources have been committed, at this stage
modifications to the design and construction of the unit are still
feasible. Specifically, the critical differences between the
requirements applicable to new and existing CCR landfills are the type
of liner that must be installed and the location restrictions that
apply. Compliance with these requirements can be addressed through
modifications to the design and construction of the unit, and are
therefore readily feasible until construction has begun.
    EPA agrees with those commenters who were concerned that the
phrase, ``the owner or operator has entered into contractual
obligations--which cannot be cancelled or modified without substantial
loss--for physical construction of the CCR landfill to be completed
within a reasonable time,'' is vague and potentially subject to abuse.
While this phrase has been included in other EPA regulations, those
regulations operate within a regulatory program overseen by a
regulatory authority. No similar guarantee exists under these
regulations. EPA could not discover a definitive or generally accepted
meaning for the terms ``substantial loss'' or ``reasonable time,'' or
develop sufficiently objective and determinate criteria for these
concepts. Consequently, the Agency has decided to remove this provision
from the definition of existing CCR landfill. EPA is retaining the two
most important elements of the definition that will effectively
determine whether the facility has irretrievably committed resources
such that it would not reasonable to require compliance with all of the
requirements applicable to new units. Accordingly, a unit will be
considered to be existing if, first, the owner or operator has obtained
the federal, state, and local approvals or permits necessary to begin
physical construction; and second, that a continuous on-site, physical
construction program has begun (i.e., groundbreaking has occurred).
Therefore, EPA is finalizing the definition of existing CCR landfill
that can be found in Sec.  257.53.
4. Definition of Existing CCR Surface Impoundment
    EPA proposed to define an existing CCR surface impoundment to mean
a surface impoundment which was in operation on, or for which
construction commenced prior to the effective date of the final rule.
The proposal also specified that a CCR surface impoundment has
commenced

construction if the owner or operator has obtained the federal, state,
and local approvals or permits necessary to begin physical
construction; and either: (1) A continuous on-site, physical
construction program has begun; or (2) the owner or operator has
entered into contractual obligations--which cannot be cancelled or
modified without substantial loss--for physical construction of the CCR
landfill to be completed within a reasonable time.
    EPA received many of the same comments on the definition of an
existing CCR surface impoundment that were received on an existing CCR
landfill. This included comments requesting clarification that the term
did not include impoundments that had ceased receiving CCR before the
effective date of the rule. Commenters also suggested that EPA modify
the definition to include the phrase that the surface impoundment ``was
in operation and had not yet ceased receiving CCR prior to the
effective date of the rule'' to make clear that the definition did not
encompass units that are no longer receiving CCR on the effective date
of the rule, even though the unit may not have completed final closure
prior to the rule's effective date. Commenters reasoned that units no
longer receiving CCR on the effective date of the rule are not ``in
operation'' and therefore should not be subject to the standards
applicable to active units. Commenters also requested that EPA clarify
that the definition of ``existing CCR surface impoundment'' include
units that were in operation on the effective date of the rule and that
periodically dredged out during the operating life of the impoundment.
Commenters contended that while this may seem self-evident, EPA needed
to clarify that these impoundments would not be characterized as ``new
CCR surface impoundments.''
    The Agency is generally conforming the definition of an existing
CCR surface impoundment to the revised definition of an existing CCR
landfill. Although inactive CCR surface impoundments are covered by the
final rule (unlike inactive CCR landfills), EPA decided it would
provide greater clarity to establish a section specific to inactive CCR
surface impoundments rather than merely including such units within the
definition of an existing CCR surface impoundment. As discussed in
greater detail in Unit VI.A of this document, under Sec.  257.100, any
CCR surface impoundment that continues to impound CCR and water after
the effective date of the rule, must either (1) breach, dewater, and
place a cover on the unit within three years or (2) must comply with
all of the requirements applicable to existing CCR surface
impoundments. Without the need to account for inactive CCR surface
impoundments within the definition, the definitions of ``existing''
landfills and surface impoundments should be the same.
    Thus, the Agency has removed the term ``in operation'' from the
definition and has instead focused on when the surface impoundment
received or will receive CCR. EPA has also deleted the provision that
would have allowed a unit to be considered to be ``existing'' based on
the existence of a contract. Accordingly, for purposes of this rule, a
CCR surface impoundment will be considered to be ``existing'' if the
unit received CCR both before and after the effective date of the rule.
For example, if a CCR surface impoundment received CCR prior to the
effective date and was in the process of dredging on the effective date
with the intent of receiving additional CCR after the effective date,
the unit would still be considered to be an ``existing'' rather than a
new unit. Conversely, if a unit received CCR prior to the effective
date and was no longer receiving CCR, this unit would be considered
``inactive,'' and would only be subject to the technical criteria
applicable to ``existing'' CCR surface impoundments if they had not
completed closure within three years. Similarly, if a CCR surface
impoundment had commenced construction prior to the effective date with
the intention of receiving CCR on or after the effective date of the
rule, the unit would be considered an ``existing'' unit only if the
physical construction program had begun (e.g., groundbreaking had
occurred) with the appropriate federal, state and local approvals or
permits in place. But if prior to the effective date of the rule, the
permits had been obtained but the physical construction of the unit had
not begun (e.g., groundbreaking had not occurred), the unit would be
considered ``new'' and would be subject to all the applicable technical
criteria for new CCR surface impoundments. Therefore, the Agency is
finalizing the definition of existing CCR surface impoundment that can
be found in Sec.  257.53.

C. Location Restrictions and Individual Location Requirements

    In the proposed rule, EPA stated that any RCRA subtitle D
regulation would need to ensure that CCR landfills, CCR surface
impoundments and all lateral expansions were appropriately sited to
ensure that no reasonable probability of adverse effects on health or
the environment from the disposal of CCR would occur. Under the
subtitle D option, EPA proposed location restrictions for CCR units
which included requirements relating to the placement of CCR in five
general locations: (1) Above the natural water table; (2) wetlands; (3)
fault areas; (4) seismic impact zones; and (5) unstable areas. The
proposed requirements relied in large measure, on the record EPA
developed to support the 40 CFR part 258 requirements for MSWLFs and on
EPA's Guide for Industrial Waste Management (EPA530-R-03-001, February
2003). EPA also chose to add one additional location restriction that
would ban the placement of CCR units within two feet of the upper limit
of the natural water table. This proposed requirement was originally
included in the proposed rule, Standards for the Management of Cement
Kiln Dust (64 FR 45631, August 20, 1999) because of the potential
damage to groundwater caused by the management of cement kiln dust at
sites located below the natural water table. While the proposed cement
kiln dust rule has not yet been finalized, EPA extended this reasoning
to CCR by applying the same location restriction to CCR units. The
proposed applicability of these location requirements varied depending
on whether the unit was an existing or new CCR landfill, an existing or
new CCR surface impoundment, or a lateral expansion of such units. For
example, for existing CCR landfills, the Agency proposed that only the
location requirement for unstable areas would apply. By contrast, the
proposed rule applied all of the location restrictions to new CCR
landfills and all CCR surface impoundments, both existing and new--an
approach consistent with RCRA subtitle C and Congressional distinctions
between the risks presented by landfills and surface impoundments. (See
75 FR 35198-35199.) This meant that owners or operators would need to
close existing CCR surface impoundments located less than two feet
above the natural water table, or for existing CCR units in sensitive
but not prohibited locations, make a technical demonstration that the
unit met the requirements of a performance standard that serves as the
alternative to the location restriction, retrofit the unit so that it
could meet the performance standard, or close. For those CCR units that
need to close (i.e., owners or operators that could not make the
necessary technical demonstrations), EPA proposed that the unit must
close within five years of the effective date of the rule. If closure
could not occur within the five year timeframe, the

Agency proposed allowing for a case-by-case extension for up to two
more years if the facility demonstrated that there was no alternative
disposal capacity and no immediate threat to health or the environment.
    EPA proposed not to impose all of the location requirements on
existing CCR landfills based on the conclusion that CCR landfills pose
less risk and are structurally less vulnerable than existing CCR
surface impoundments. EPA also raised concern that a significant number
of these CCR landfills could be located in areas subject to these
requirements, (particularly wetlands), which could cause disposal
capacity shortfalls in certain regions of the U.S., if existing CCR
landfills in these locations were required to close. Disposal capacity
shortfalls can pose significant environmental and public health
concerns based on the potential for significant disruption of solid
waste management state-wide from the closure of these units. EPA
concluded that these risks would be greater than the potential risks
from allowing existing CCR landfills to remain in these locations,
given that these units would be subject to all of the design and
operating requirements of the rule. To ensure the accuracy of its
preliminary conclusions, the Agency requested commenters to provide any
available information regarding the number of existing CCR landfills
located in these sensitive areas. The Agency also sought information
regarding the extent to which CCR landfill capacity would be affected
by applying all of the location restrictions to existing CCR landfills,
the extent to which facilities could comply with the proposed
performance standards, and the costs that would be incurred to retrofit
existing CCR landfills to meet these standards.
    The Agency received numerous comments in response to the Agency's
request for additional information regarding the extent to which
landfill capacity would be affected by applying all the proposed
subtitle D location restrictions to existing CCR landfills. Commenters
generally agreed with the Agency that applying the other location
restrictions to existing CCR landfills would cause a significant
decrease in disposal capacity across the country, although they did not
provide any data or information which would support this concern.
Commenters noted, however, that if existing CCR landfills located in
these areas were to close, it would greatly complicate operations at
many utilities. Affected facilities would need to find additional
disposal capacity, which would require utilities to procure new real
estate on which to site a new CCR landfill (which may be a significant
distance from a power plant), obtain a new disposal permit for the CCR
landfill (which can take an extended period of time), and potentially
transport significant volumes of CCR great distances to newly-permitted
facilities. Commenters argued that there was simply no environmental
basis for causing this level of disruption to utility CCR disposal
practices.
    EPA received no data or information in response to the Agency's
request for the costs associated with retrofitting a CCR surface
impoundment or CCR landfill to meet the demonstrations for existing
units. Similarly, the Agency received little to no information in
response to EPA's request for additional information on the location of
these facilities. Some commenters acknowledged that specific states
were located in some of these restricted areas but did not provide
specific information on specific units.
    Overwhelmingly, the issue receiving the most comment was EPA's
intention to subject existing CCR surface impoundments to all of the
new location criteria. Commenters contended that subjecting existing
units to all of the location criteria was a radical departure from the
location restriction provisions of the existing MSWLF rules on which
the subtitle D option is based (i.e., existing MSWLFs are only subject
to the floodplains and unstable areas restrictions) without any
justification for regulating CCR surface impoundments more stringently
than existing CCR landfills. Commenters argued that EPA must
demonstrate that there are increased risks posed by each CCR surface
impoundments based on its location; otherwise, they claimed, there was
no justification for EPA to subject CCR surface impoundments to more
stringent location restrictions. Some commenters suggested that a more
reasonable approach would be to limit the restrictions for existing CCR
surface impoundments to unstable areas, consistent with the approach
proposed for existing CCR landfills. Finally, commenters raised concern
about the inconsistency between the preamble language and the
corresponding regulatory text. Specifically, the preamble stated EPA's
intention to apply all of the location criteria to all CCR surface
impoundments (existing and new) while the proposed regulatory language
applied all location criteria only to new CCR surface impoundments and
lateral expansions.
1. Applicability of the Location Criteria to Existing CCR Surface
Impoundments
    EPA acknowledges the discrepancies between the preamble language
and the regulatory text regarding the proposed regulatory language for
the location restrictions as it applies to existing CCR surface
impoundments. In the proposed rule, the regulatory language should have
included, ``all surface impoundments'' as opposed to only ``new surface
impoundments.''
    EPA disagrees that in order to justify national minimum standards
applicable to existing CCR surface impoundments, the Agency must
demonstrate an adverse impact to human health and the environment from
each individual unit, based on the specific risks posed at each
location. As an initial matter, it is well established that an agency
may regulate a class of similarly situated entities through rulemaking,
rather than on the basis of an individualized assessment of every
entity that will be subject to the rule. And indeed, Congress
specifically directed EPA to proceed by rulemaking to establish minimum
national standards under RCRA sections 1008(a) and 4004(a). Moreover,
section 4004(a) does not require a demonstration of actual impacts,
merely that these units present an unacceptable risk of harm. Thus, it
is sufficient for EPA to establish a factual record demonstrating that
the specific location restrictions in the final rule are necessary for
CCR units (landfills and surface impoundments), as a class, to ensure
that there will be no reasonable probability of adverse effects on
health or the environment. As discussed in greater detail in the next
section and in Unit X of the preamble, the factual record supports the
need for all of the location standards for existing CCR surface
impoundments imposed by this rule.
    The Agency also rejects the suggestion that EPA establish the same
location restrictions for both existing CCR landfills and CCR surface
impoundments. As laid out in the proposal and elsewhere in this final
rule in greater detail, the risks associated with CCR surface
impoundments are substantially higher than the risks associated with
CCR landfills, by approximately an order of magnitude. Surface
impoundments are utilized by 45 percent of coal-fired power plants and
in 2000 accounted for disposal of one-third of all CCR generated.\46\
Unlike landfills, CCR surface impoundments

contain slurried residuals that remain in contact with ponded waters
until closure. In a statewide investigation of impacts to groundwater
quality from CCR disposal sites, the Wisconsin Department of Natural
Resources reported that closed sites which originally contained sluiced
coal-combustion residuals displayed extremely elevated mean arsenic
levels (as high as 364 [micro]g/l).\47\ The highest contaminant
concentrations in the study were associated with sluiced CCR residuals.
In addition, releases of toxic contaminants to surface water and
groundwater from mostly unlined CCR surface impoundments and ponds are
a relevant factor in 34 of 40 cases of proven damage to the environment
(as well as in several cases of ``potential'' damage to the
environment) from mismanagement of CCR.\48\ In many of these cases,
effluent discharges from the surface impoundments caused significant
ecological damage to aquatic life in nearby streams and wetlands. In
one case, in 2002, the structural stability of a CCR surface
impoundment was directly compromised by sinkhole development, leading
to the release of 2.25 million gallons of CCR slurry. In another, an
unusually weak foundation of ash and silt beneath a CCR surface
impoundment (i.e., man-made unstable ground) was identified as one of
several likely factors contributing to the dike failure that in 2008
resulted in the largest CCR spill in United States history.
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    \46\ Rowe, C.L., Hopkins, W.A., Congdon, J.D., 2002.
Ecotoxicological Implications of Aquatic Disposal of Coal Combustion
Residues in the United States: A Review. Environmental Monitoring
and Assessment, Vol. 80, pp. 207-276.
    \47\ Zillmer, M. and Fauble, P., 2004. Groundwater Impacts from
Coal Combustion Ash Disposal Sites in Wisconsin. Waste & Materials
Management, Wisconsin Department of Natural Resources, PUB-WA 1174
2004.
    \48\ Cases of damage attributable to disposal of coal combustion
residuals are summarized in the appendix to the preamble of the
proposed rule, 75 FR 35230-35239, June 21, 2010, and can be found in
the RCRA Docket.
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    Unlike RCRA subtitle C, subtitle D does not explicitly authorize
EPA to establish different standards for existing and new units, and
Congress specifically intended subtitle D to address the risks from
existing, abandoned ``open dumps.'' In the proposed rule preamble, EPA
explained the rationale for applying these provisions to existing CCR
surface impoundments, and the commenters have submitted nothing to
rebut that rationale. Thus, EPA maintains its determination that
application of the location standards to existing CCR surface
impoundments is necessary to achieve the standard in section 4004(a).
Absent these location restrictions, the risk of impacts to human health
and the environment from releases from CCR units, including from the
rapid and catastrophic destruction of CCR surface impoundments, sited
in these sensitive areas would exceed acceptable levels. Given that the
risks associated with CCR surface impoundments are substantially higher
than the risks posed by CCR landfills, this is the appropriate
regulatory course for existing CCR surface impoundments.
    In this rule, EPA is finalizing location restrictions that will
ensure that CCR units are appropriately sited, that the structure of
the CCR unit will not be adversely impacted by conditions at the site,
and that overall there will be ``no reasonable probability of harm to
human health or the environment'' due to the location of the CCR unit.
EPA is finalizing different sets of location restrictions depending on
whether the unit is a CCR landfill or CCR surface impoundment and
whether it is an existing or new unit. Lateral expansions fall within
the definitions of new units and are treated accordingly. These
standards provide minimum national siting and performance criteria for
all CCR units. The location restrictions under Sec.  257.60 through
Sec.  257.64 include: (1) Placement above the uppermost aquifer; (2)
wetlands; (3) fault areas; (4) seismic impact zones; and (5) unstable
areas. Each of these locations is generally recognized as having the
potential to impact the structure of any disposal unit negatively and
as such, increase the risks to human health or the environment through
structural failures or leaching of contaminants into the groundwater.
Under the final rule and as proposed, new CCR landfills, existing and
new CCR surface impoundments, and all lateral expansions will be
required to comply with all of the location restrictions. Existing CCR
landfills however, will be subject to only two of the location
restrictions--floodplains, and unstable areas. As noted in the proposed
rule, and restated here, existing landfills and surface impoundments
are already subject to the location standards in subpart A of 40 CFR
part 257 for floodplains, endangered species and surface waters. The
final rule does not change this requirement, and so facilities should
already be in compliance. The Agency is finalizing, as proposed, the
unstable area location restriction for existing CCR landfills because
the record clearly shows that failure of CCR units in these areas
(e.g., due to instabilities in Karst terrains) have and in all
likelihood would continue, in the absence of the restrictions in the
final rule, to result in damage caused by the release of CCR
constituents, affecting both groundwater and surface waters. As the
Agency stated in the proposed rule, the impacts resulting from the
failure of CCR units from location instability are of far more concern
than any disposal capacity concerns resulting from the closure of
existing CCR units in unstable areas.
    Conversely, and also consistent with the proposed rule, EPA is not
applying the following location restrictions to existing CCR landfills:
The requirement to construct a unit with a base located no less than
1.52 meters (five feet) above the upper limit of the uppermost aquifer,
as well as the siting restrictions applicable to wetlands, fault areas,
and seismic impact areas. Existing CCR landfills pose lower risks and
are structurally less vulnerable than existing CCR surface
impoundments. In addition, disposal capacity shortfalls, which could
result if existing CCR landfills in these locations were required to
close, raise greater environmental and public health concerns than the
potential failure of the CCR landfills in these locales.
2. Placement Above the Uppermost Aquifer
    Under Sec.  257.60(a) EPA is requiring new CCR landfills, existing
and new CCR surface impoundments and all lateral expansions to be
constructed with a base that is located no less than 1.52 meters (five
feet) above the uppermost aquifer, or to demonstrate that there will
not be an intermittent, recurring, or sustained hydraulic connection
between any portion of the base of the CCR unit and the uppermost
aquifer due to normal fluctuations in groundwater elevations (including
groundwater elevations during the wet season). Existing surface
impoundments that fail to achieve this standard must close. New CCR
landfills, new CCR surface impoundments and all lateral expansions of
existing and new CCR landfills and CCR surface impoundments cannot be
constructed unless they meet one of these two standards. In response to
comment, the Agency has modified the criteria in two ways. First, EPA
has replaced ``a base that is located a minimum of two feet above the
upper limit of the natural water table'' with ``a base no less than
1.52 meters (five feet) above the uppermost aquifer.'' EPA received
comment explaining that fluctuations in groundwater levels in many
geological settings can exceed ten feet over the course of the year,
and alleging that the proposed two foot minimum buffer between the base
of the unit and the top of the water table would therefore be
insufficiently protective. The

commenter recommended that the minimum vertical separation be at least
three to five feet from the base of the liner components. After
additional research, EPA is finalizing a minimum buffer of five feet
instead of two feet. EPA's research confirmed the commenter's claims.
In addition, EPA determined that several states consider five feet
between the base of the surface impoundment and the top of the
uppermost aquifer to be the minimum distance that is protective of
human health and the environment. These are California, Michigan,
Nebraska, New York, West Virginia, and Wisconsin. The Agency has
concluded from geographic and climatic spacing of these states that the
hydrogeologic conditions within them encompass the range of conditions
found in the United States. Therefore, EPA is finalizing a minimum
buffer of five feet instead of two feet.
    EPA is also clarifying the definition of the natural water table.
As some commenters noted, there are many factors (hydrologic and
geologic settings, nearby pumping, etc.) that influence the location of
the groundwater table making it difficult to determine the ``natural''
level. In addition, as noted, local site-specific hydrogeologic
conditions within the aquifer may cause the natural groundwater table
to exceed five feet and vary as much as ten feet. To account for the
possibility of such large seasonal fluctuations, EPA is revising the
definition of ``uppermost aquifer'' to specify that the measurement of
the upper limit of the aquifer must be made at a point nearest to the
natural ground surface to which the aquifer rises during the wet
season. This definition of ``uppermost aquifer'' will encompass large
seasonal variations, and is a more appropriate parameter than
``seasonal high groundwater table'' as suggested by several commenters
and the proposed ``natural water table'' because it is more clearly
defined.
    In Sec.  257.60(a) the term uppermost aquifer has the same
definition as under the general provisions of Sec.  257.40: The
geologic formation nearest the natural ground surface that is an
aquifer, as well as lower aquifers that are hydraulically
interconnected with this aquifer within the facility's property
boundary. This definition includes a shallow, deep, perched, confined
or unconfined aquifer, provided it yields usable water. Although EPA
originally proposed that all CCR surface impoundments be located ``. .
. . above the upper limit of the natural water table'', the Agency is
amending this requirement and replacing ``water table'' with
``uppermost aquifer'' to make it consistent with the way natural
underground water sources are described elsewhere in the rule. EPA made
a second revision to the criteria that were originally proposed. As an
alternative to requiring that the CCR units described in this section
be constructed with a base that is located no less than five feet above
the uppermost aquifer, owners and operators may instead demonstrate
that there will not be an intermittent, recurring, or sustained
hydraulic connection between any portion of the base of the CCR unit
and the uppermost aquifer due to normal fluctuations in groundwater
elevations (including groundwater elevations during the wet season).
    This alternative standard was developed in response to concerns
from commenters that a single depth to the aquifer failed to account
for the wide variations in the level of water table fluctuations in
different regions of the country. For example, arid regions of the
country, such as Arizona, under normal conditions generally do not
experience the same degree of fluctuations in groundwater elevations as
more temperate regions, such as Minnesota. Accordingly, EPA developed
an alternative performance standard focused on the conditions
identified in the damage cases and the risk assessment that this
location criterion was designed to prevent: Specifically, where the
groundwater elevation is high enough to intersect the base of the waste
management unit. In such situations, this hydraulic connection can
enhance the transport of contaminants of concern from the CCR unit into
groundwater. By requiring owners and operators to ensure that these
conditions do not occur, the alternative standard to allow owners and
operators to account for situations where there are relatively small
variations in groundwater levels and a buffer of five feet is not
necessary. This will also ensure that a CCR unit need not address
situations where an infrequent, unexpected event (e.g., hurricane)
could cause a brief, temporary condition where the uppermost aquifer
rises to less than the prescribed five feet but which would not in and
of itself constitute a long-term threat to the aquifer. However, where
normal fluctuations in groundwater elevation (including, but not
limited to, seasonal or temporal variations, groundwater withdrawal,
mounding effects,\49\ etc.) will result in the failure of the unit to
meet the performance standard (i.e., no intermittent, recurring, or
sustained hydraulic connection between the base of the CCR unit and the
uppermost aquifer), the unit must close.
---------------------------------------------------------------------------

    \49\ A phenomenon usually created by the recharge of groundwater
from a manmade structure, such as a surface impoundment, into a
permeable geologic material, resulting in outward and upward
expansion of the free water table. Mounding can alter groundwater
flow rates and direction; however, the effects are usually localized
and may be temporary, depending upon the frequency and duration of
the surface recharge events.
---------------------------------------------------------------------------

    In some recent damage cases, placement of large volumes of CCR into
highly permeable strata in the disposal area promoted CCR-water
interactions. For example, from 1995 to 2006 in Anne Arundel County,
Maryland 4.6 million tons of CCR were placed directly in two sand and
gravel quarries without a geomembrane liner or leachate collection
system. Rainwater infiltration into exposed CCR coupled with
groundwater-CCR interactions and the transmissivity characteristics of
local strata contributed to rapid migration of heavy metals, including
antimony, arsenic, cadmium, nickel, and thallium to residential
drinking water wells located near the mine pits and significant
deterioration of water quality as a result of placement of CCR.
Similarly, from 1980 to 1997 in Lansing, Michigan, around 0.5 million
tons of coal ash was dumped for disposal into a gravel pit with an
elevated water table. A remedial investigation has established that
groundwater mounding has immersed the CCR into the upper aquifer
resulting in on-site exceedances of groundwater quality protection
standards for sulfate, manganese, lead, selenium, lithium, and boron.
Placement of CCR into un-engineered, unlined units in permeable strata
has plainly led to adverse impacts to groundwater. The phrase ``normal
fluctuations'' has been used to clarify that EPA does not intend for
the facility to account for extraordinary or highly aberrant conditions
(e.g., one-in-a million or ``freak'' events). Normal fluctuation can
include those resulting from natural as well as anthropogenic sources.
Natural sources that could affect groundwater levels include, but are
not limited to precipitation, run-off, and high river levels.
Anthropogenic sources that could affect groundwater levels include
groundwater withdrawal, pumping, well(s) abandonment, and groundwater
mounding. In satisfying this location restriction, it may be necessary
for a professional engineer to model these effects before he can make
the necessary certifications.\50\ EPA also

notes that this modeling may include the same considerations already
evaluated under some state programs.\51\ EPA expects that owners and
operators will have sufficient information to determine whether their
CCR unit meets either performance standard. Most, if not all, of this
information would be information a facility would typically have as
part of normal operations (e.g., the depth of the CCR unit itself), or
that will be developed as part of implementing other rule requirements.
For example, through the groundwater monitoring system required under
Sec. Sec.  257.90-257.98, the facility can obtain water level
measurements in a sufficient number of locations (e.g., monitoring
wells, piezometers) to use in determining whether they satisfy either
performance standard. Similarly, under Sec.  257.91 a thorough
characterization of the geology and hydrogeology of the site must be
conducted. Finally, EPA notes that available technology and guidance
are available for using existing groundwater monitoring wells, like
those required under this final rule, to measure groundwater
levels.\52\
---------------------------------------------------------------------------

    \50\ For example, evaluations can be done to estimate
groundwater mounding such as pubs.usgs.gov/sir/2010/5102/,
www.groundwatersoftware.com/calculator_9_hantush_mounding.htm, and
www.ndwrcdp.org/documents/wu-ht-02-45/wuht0245_electronic.pdf.
    \51\ See, e.g., dnr.wi.gov/topic/stormwater/standards/gw_mounding.html.
    \52\ See, e.g., U.S. EPA (Environmental Protection Agency).
2013. Groundwater Level and Well Depth Measurement. SESDPROC-105-R2.
Region 4. Athens, GA. Available online at: www.epa.gov/region4/sesd/fbqstp/Groundwater-Level-Measurement.pdf.
---------------------------------------------------------------------------

3. Wetlands
    In Sec.  257.61 of this rule, EPA is finalizing the regulatory text
essentially as proposed. Specifically, EPA is adopting a prohibition on
locating all CCR surface impoundments and new CCR landfills, as well as
lateral expansions of existing CCR units, in wetlands as defined in 40
CFR 232.2, absent specific demonstrations made by the owner or operator
that ensure the CCR unit will not degrade sensitive wetland ecosystems.
These provisions place the burden of proof for these demonstrations
directly on the owner or operator (the discharger). The owner or
operator must make the results of these demonstrations available in the
facility record. Failure to make any of the demonstrations will bar
siting of the CCR unit in a wetland.
    In 2003, disposal of CCR in natural or man-made aquatic basins
accounted for nearly one-third of all CCR land disposal. Historically,
aquatic disposal of CCR has been attractive economically to facilities
because of its lower overall cost relative to dry management and the
ease of handling of residuals. During aquatic disposal, CCR is commonly
piped as a slurried mixture to surface impoundments designed to retain
the solids in contact with water for the life of the unit. Particulate
solids from the waste stream gravitationally settle while clarified
waters ultimately discharge into nearby streams and wetlands.
    The term `wetlands' refers to those areas inundated or saturated by
surface or groundwater at a frequency and over a duration sufficient to
support a prevalence of vegetation typically adapted for life in
saturated soil conditions. Wetlands include marshes, swamps, bogs and
similar areas that are commonly located between open water and dry
land. Under the CWA, wetlands are considered 'special aquatic sites'
deserving of special protection because of their ecologic significance.
Wetlands are very important, fragile ecosystems that must be protected,
and EPA has long identified wetlands protection as a high priority.
    Undisturbed, natural wetlands provide many benefits to society by
improving water quality, providing essential breeding, rearing, and
feeding grounds for fish and wildlife, reducing shoreline erosion, and
absorbing flooding waters and pollution. Wetlands are also commercial
source areas of products for human use such as timber, fish, and
shellfish. Recreational hunters harvest wetland-dependent waterfowl.
Wetland environments, however, may be adversely impacted by releases of
wastes from co-located industrial facilities. Wetland ecosystems can be
degraded by accidental discharges that can change the habitat value for
fish and wildlife by obstructing surface water circulation patterns,
altering substrate elevation, dewatering, or permanent flooding.
    In support of the provisions finalized in this rule, EPA is citing
several damage cases, including 30 cases of ``proven'' damage to the
environment that involve aquatic disposal of CCR, 14 of which involve
impacts to wetlands from release of CCR. For example, at the Hyco
Reservoir in Roxboro, North Carolina from 1966 to 1990 the lake
received contaminated effluent from coal ash disposal basins that were
authorized by National Pollutant Discharge Elimination System (NPDES)
permits under the CWA. High levels of the trace element selenium
bioaccumulated in aquatic food chains (phytoplankton), poisoning
invertebrates and fish in the lake, particularly species of sport fish
(bluegill, largemouth bass), causing reproductive failure and severe
declines in fish populations in the late 1970's and early 1980's.
Consequently, from 1988-2001 the North Carolina Department of Health
and Human Services (NCDHHS) issued a consumption restriction advisory
for selenium contamination in fish from the reservoir. In 1990, a dry
ash handling system was implemented resulting in lower selenium
discharge and reduced mean selenium concentration in reservoir waters.
As of 2005, concentrations of selenium in fish tissues remained above a
toxic threshold even with reduced influx of selenium, due to migration
of the element from contaminated sediments to benthic food chains. The
total monetized value of damage can be divided among ecologic factors
(e.g., major impacts on fish), recreational factors (e.g., fishing
trips not taken), depreciated real estate values, aesthetic factors,
and human health damages (e.g., losses due to stress and anxiety from
knowing ecosystem is poisoned) and is estimated at $877 million.\53\
---------------------------------------------------------------------------

    \53\ Lemly, A.D. 2010. Op.cit.
---------------------------------------------------------------------------

    Although this consideration is not relevant for purposes of
establishing the minimum national criteria under RCRA sections 1008(a)
and 4004(a), the rulemaking record demonstrates that the monetary cost
of environmental damage from releases of CCR at surface impoundments
could be considerable. A report on the environmental damage caused by
releases of CCR at 22 sites estimates the total cost of poisoned fish
and wildlife at the surface impoundment sites at $2.32 billion. At
twelve of these sites the releases were legally permitted under the
CWA. Five of the 22 cases were caused by structural failures, two
resulted from an unpermitted discharge, and one was from a
landfill.\54\ Effluent contaminated with coal combustion residues is
directly linked with high loadings of toxic metals in the discharge
areas of aquatic basins, where some metals (primarily arsenic, cadmium,
chromium, copper, lead, and selenium) have accumulated in aquatic food
chains.\55\ In a research overview (literature synthesis) on the
environmental effects of disposal of CCR, Rowe et al. (2002) listed
adverse biological responses, including histopathological, behavioral,
and physiological (reproductive, energetic, and endocrinological)
effects, that have been observed in some vertebrates and invertebrates
following exposure to and bioaccumulation of CCR-related contaminants.
---------------------------------------------------------------------------

    \54\ Lemly, A.D.2010. Op. cit.
    \55\ Rowe, C.L. et. al. 2002. Op. cit.
---------------------------------------------------------------------------

    Under the criteria finalized in this rule, in order to locate a CCR
unit or

lateral expansion in a wetland, the owner or operator must: (1)
Successfully rebut the presumption that an alternative site (i.e., one
that does not involve a wetland) is reasonably available for the CCR
unit or lateral expansion; (2) show that the construction or operation
of the unit will not cause or contribute to violations of any
applicable state water quality standard, violate any applicable toxic
effluent standard or prohibition, jeopardize the continued existence of
endangered or threatened species or critical habitats, or violate any
requirement for protection of a marine sanctuary; (3) show that the CCR
unit or lateral expansion will not cause or contribute to significant
degradation of wetlands; and (4) demonstrate that steps have been taken
to attempt to achieve no net loss of wetlands.
    In addition to these requirements, other federal laws may be
applicable in siting a CCR unit in a wetland. These include: Sections
401, 402, and 404 of the CWA; the Rivers and Harbors Act of 1989; the
National Environmental Policy Act; the Migratory Bird Conservation Act;
the Fish and Wildlife Coordination Act; the Coastal Zone Management
Act; the Wild and Scenic Rivers Act; and the National Historic
Preservation Act. In addition, the use of a wetlands location for a CCR
unit may require a permit from the U.S. Army Corps of Engineers. To the
extent these are applicable, compliance with these RCRA criteria does
not alleviate the need to comply with these other federal requirements,
and the owner or operator of the facility remains responsible for
ensuring compliance with all applicable federal and state requirements.
    The rule adopts a regulatory presumption that a less damaging
alternative to locating a disposal unit in a wetland exists, unless the
owner or operator can demonstrate otherwise. Thus, when proposing to
locate a new facility or lateral expansion in a wetland, owners and
operators must be able to demonstrate that alternative sites are not
available and that the impact to wetlands is unavoidable. If this
presumption is not clearly rebutted, then the CCR unit may not be sited
in a wetland location. Such an analysis necessarily includes a review
of reasonable alternatives to locating or laterally expanding CCR units
in wetlands. As part of the evaluation of reasonable (that is,
available and feasible) alternatives the owner or operator must show,
and a qualified professional engineer must verify, that operation or
construction of the CCR unit will not: (1) Violate any applicable state
water quality standards; (2) cause or contribute to the violation of
any applicable toxic effluent standard or prohibition; (3) cause or
contribute to violation of any requirement for the protection of a
marine sanctuary; and jeopardize the continued existence of endangered
or threatened species or critical habitats.
    When evaluating the impacts of a CCR unit on a wetland, the owner
or operator must ensure that the unit cannot cause or contribute to
significant wetland degradation. Therefore, the owner or operator and
the qualified professional engineer must: (1) Verify the integrity of
the CCR unit, and its ability to protect ecological resources by
addressing the erosion, stability, and migration potential of native
wetland soils, and dredged and fill materials used to support the unit;
(2) verify that the design and operation of the CCR unit minimizes
impacts on fish, wildlife, and other aquatic resources and their
habitat(s) from any release of coal combustion residuals; (3) evaluate
the effects of catastrophic release of CCR to the wetland and the
resulting impacts on the environment; and (4) verify that ecological
resources in the wetland are sufficiently protected, including
consideration of the volume and chemistry of the CCR managed in the
unit; and any additional factors, as necessary.
    When a wetland functions properly, it provides water quality
protection, fish and wildlife habitat, natural floodwater storage, and
reduction in the erosive potential of surface water. A degraded wetland
is less able to effectively perform these functions. For this reason,
wetland degradation is as big a problem as outright wetland loss,
though often more difficult to identify and quantify. Any change in
hydrology can significantly alter the soil chemistry and plant and
animal communities. The common hydrologic alterations that can lead to
significant degradation in wetland areas include: (1) Deposition of
fill material, including CCR; (2) drainage for development; (3)
dredging and stream channelization for development; (4) diking and
damming to form ponds or impoundments; (5) diversion of CCR-bearing
waters or other flows to or from wetlands; (6) addition of impervious
surfaces in the watershed, thereby increasing water and CCR-bearing
run-off into wetlands. These activities can mobilize CCR-bearing
sediment; and once the sediment is discharged into the environment,
toxic metals in CCR can become available to organisms within the
wetland. Consequently, while the mere presence of one or more of these
activities does not necessarily demonstrate that the CCR unit causes or
contributes to significant degradation, the fact that they may do so
means these activities need to be carefully evaluated.
    In determining what constitutes ``significant'' degradation, it is
important to understand that although wetlands are capable of absorbing
pollutants from the surface water, there is a limit to their capacity
to do so. For the purposes of this rule, the primary pollutants of
concern are CCR-bearing sediment and toxic metals. Although the risk
assessment did not assess the exposure and hazard to wetlands, these
can originate from uncontrolled run-off from the facility, fugitive
dust from uncovered CCR landfills and piles, and uncontrolled discharge
from CCR units (landfills, waste piles, surface impoundments). A clear
example of biologically significant degradation in wetlands is when
these toxic metals accumulate in benthic and aquatic food chains as a
result of uncontrolled runoff. Another is obrution (smothering) of
benthic organisms from discharge(s) of CCR to surface water, thereby
jeopardizing the continued existence of organisms or critical habitats
within the wetland. EPA notes that there are other requirements
established under this rule that can also be relevant in this context,
as they have the potential to reduce the likelihood that facility
operations will cause or contribute to significant wetland degradation.
EPA anticipates that as the facility begins to implement all of the
requirements under this rule, the facility will consider how
modifications to facility operations to address one requirement can
affect compliance with other requirements.
    After consideration of these factors, if an existing CCR unit
cannot meet all of the requirements in paragraphs (1)-(3) (i.e., if it
causes or contributes to significant degradation, or if no reasonable
alternative to locating a new CCR unit in wetlands is available), the
facility can comply with the location criterion by compensatory steps
that must be taken to achieve no net loss of wetlands (as defined by
acreage and function). Owners or operators must first take measures to
avoid impacts to wetlands. If potential impacts cannot be avoided, all
reasonable steps are to be taken to minimize such impacts to the extent
feasible. Appropriate measures (for example, engineered containment
systems to control discharge of leachate or surface water run-off to
wetlands) will likely be site-specific and should be incorporated into
the design and operation of the CCR unit. Any remaining unavoidable
impacts must be offset, or compensated for through all appropriate and
feasible compensatory mitigation actions. This compensatory

mitigation may take the form of restoration (re-establishment or
rehabilitation of a wetland), establishment (creation of a man-made
wetland where one did not previously exist), enhancement (improving one
or more wetland functions), and preservation (permanent protection of
important wetlands through implementation of appropriate legal and
physical mechanisms). The functions and values of a wetland will vary
based on any number of site specific characteristics, including
location, wetland type, hydrology, degradation, and whether it is
natural or constructed to treat waste. Strictly limited to the
application of the wetlands location requirements under this rule, any
assessment of the nature and extent of mitigation required under the
CCR rule shall consider these kinds of characteristics, including
wetlands designed for the treatment of CCR. The Agency recognizes that
the function and value of a particular man-made wetland constructed to
perform a wastewater treatment function may present a unique situation
that may affect both the determination of whether the wetland is
significantly degraded, and the nature and extent of any required
compensatory mitigation. This discussion refers only to the wetlands-
related requirements of this rule and does not affect any requirements
or obligations under the Federal Water Pollution Control Act (33 U.S.C.
1251, et seq.) and its implementing regulations.
    Although EPA is not finalizing an outright ban on siting of
existing or new CCR units in wetlands, the Agency continues to believe
that discharges to wetlands of pollutants that can be reasonably
avoided should be avoided. Therefore, the amount and quality of
compensatory mitigation may not substitute for avoiding and minimizing
impacts. For purposes of this rule, EPA assumes CCR units that are
designed to avoid discharge of CCR into wetlands have less adverse
impact to the aquatic environment than CCR units that ultimately
discharge such residuals in wetlands.
4. Fault Areas
    In Sec.  257.62 of this rule, EPA is banning the location of new
CCR landfills, existing and new CCR surface impoundments, and all new
lateral expansions within 60 meters (200 feet) of a fault that has had
displacement in Holocene time, unless the owner or operator
demonstrates that an alternative setback distance of less than 60
meters (200 feet) will prevent damage to the structural integrity of
the unit. For existing surface impoundments, the demonstration is
required only if the unit is located closer than 60 meters (200 feet)
to an active Holocene fault. If a demonstration cannot be made, the
existing surface impoundment must close. These requirements have been
adopted with only minor changes from the proposal, and will minimize
the risks associated with CCR units located in fault areas.
    Stresses produced during earthquake motion can cause serious damage
to landfill integrity via seismically induced ground failure and
associated rupture of liner systems and subsequent damage to leachate
collection systems. Or if the unit is unlined, seismic motion could
disrupt landfill caps and foundation soils that impede migration of
percolating water. Potential damage to CCR units resulting from
structures located across a fault include surface breakage, cracks and
fissures between fill and confining slopes, slope failure via
landslides, liquefaction-induced lateral spreading and settlement of
the pile, disruption of surface water and drainage control systems, and
rupture of leachate collection systems. In impoundments, for example,
interior dike failure and leakage, and rupture of multilayer liner
systems would also be of concern. Failure of the leachate collection
system may prevent removal of generated leachate, allowing it to pond
on the liner. If the liner system is ruptured, this may create a
pathway for leachate to migrate into and contaminate the uppermost
aquifer. In addition to the potential damage to leachate collection and
liner systems, the integrity of the landfill slopes could also be
impaired by fault rupture, potentially exposing coal combustion
residuals to surface run-off.
    The best protection is to avoid locating new CCR landfills and all
CCR surface impoundments across faults and fault zones subject to
displacement. For new units or lateral expansions there is no need to
construct units in these areas. For existing surface impoundments, the
Agency has been unable to find any way to retrofit or engineer the unit
to be protective. A setback distance of 60 meters (200 feet) from the
outermost damage zone of a Holocene fault will provide an adequate
margin of safety to protect the facility from displacements due to
surface faulting and any associated damage because 60 meters typically
covers the zone of deformation where the ground may be bent or warped
as a consequence of fault movement. By including this as a siting
requirement for new units the risk of rupture of the unit, including
any liner and leachate collection systems, due to surface faulting will
be minimized.
    Observations of engineered landfill response during earthquake
motion come primarily from California where field data have been
reported from MSWLFs (including some meeting the current part 258
standards) affected by strong shaking from six major nearby
earthquakes. In these large magnitude events (M >= 6.7), bedrock peak
horizontal ground accelerations, an index of the intensity of
earthquake motion, endured by the landfills were in excess of 0.3g.
Engineered dry MSWLFs in California are reported to have performed well
after strong earthquake motion (no documented incidence of an
earthquake-induced release of contaminants harmful to human health or
to the environment). Minor cracking of cover soils and breaking of
vertical wells and headers were among the most common types of damage
reported at MSWLFs subject to strong ground shaking. In the 1994
Northridge earthquake, only one landfill compliant with RCRA Part 258
standards experienced tears in a liner (a geomembrane liquid barrier):
One tear 23 meters in length. However, there is little data on seismic
stability and performance from industrial solid waste landfills with
geosynthetic liners or units with water-saturated CCR waste. The
Agency, therefore, remains concerned over the potential instability of
engineered disposal units, and particularly CCR surface impoundments,
under seismic loadings. Accordingly, EPA is prohibiting new CCR
landfills, CCR surface impoundments, and any new extensions from sites
located within an active fault zone, unless the owner or operator makes
a demonstration, certified by a qualified professional engineer, that
an alternative setback distance of less than 60 meters will prevent
damage to the structural integrity of the unit.
    EPA is clarifying its definition of fault to incorporate updated
technical information.\56\ Although a fault can be thought of as a
simple planar surface across which there has been measurable
displacement of one side relative to the other, field-based
observations show fault architecture to often be complex. In the
geologic literature faults developed in the upper crust are
characterized as zones of brittle deformation composed of linked fault
segments, with each segment composed of one or more subparallel,
curved, or anastomosing fault cores nested within

a damage zone. Some fault zones may contain broad deformational
features such as pressure ridges and sags rather than clearly defined
fault scarps or shear zones.\57\ Fault cores are regions of high strain
slip that have accommodated most of the displacement and are marked by
mylonites, cataclastites, and gouge, whereas the damage zone is
characterized by low strain structures mechanically related to the
growth of the fault zone such as small faults, fractures, veins and
folds. To avoid displacement that would damage unit integrity, it is
best to restrict new CCR landfills and surface impoundments, and all
new extensions, to locations no less than 60 meters from the outermost
damage zone created by an active fault. Fault zones can range from one
meter to several kilometers in width.
---------------------------------------------------------------------------

    \56\ Sibson, R.H. 2003. Thickness of the Seismic Slip Zone.
Bulletin of the Seismological Society of America, Vol. 93, No. 3,
pp. 1169-1178.
    \57\ Bryant, W.A. and Hart, E.W., 2007. Fault-Rupture Zones in
California. Special Publication 42 (Interim Revision), California
Division of Mines and Geology, Sacramento, California.
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    For purposes of this section, a fault is considered active if it
has moved during Holocene time. Holocene time is defined as the
geological epoch which began at the end of the Pleistocene, at 11,700
years BP (before present), and continues to the present. In the field,
evidence for Holocene activity may be hard to obtain. Therefore, the
Agency cautions that faults which show no evidence for Holocene
activity may not necessarily be inactive.
    To investigate active faults, EPA expects owners and operators of
CCR units to follow standard engineering and geologic practices.
Technical considerations include: (1) A geologic reconnaissance of the
site to determine the location of active faults. Such a reconnaissance
would include utilizing the seismic analysis maps and tools (Quaternary
fault maps, earthquake probability maps) of the United States
Geological Survey (USGS) Earthquake Hazards Program (http://earthquake.usgs.gov/hazards/apps/); and (2) a site fault
characterization within 1000 meters of a site to determine whether it
is within 60 meters of an active fault. Such characterizations would
include subsurface exploration, including drilling or trenching, to
locate any fault zones and evidence of faulting, trenching
perpendicular to any faults or lineaments found within 60 meters of the
site, and determination of the age of any displacements. Based on this
information, the qualified professional engineer would prepare a report
that delineates the location of any active (Holocene) fault, including
any damage zones, and the associated 60 meter setback. To take
advantage of an alternative setback distance of less than 60 meters,
the owner or operator must make a demonstration, certified by a
qualified professional engineer, that the CCR landfill, surface
impoundment, or lateral expansion has a foundation or base capable of
providing support for the structure, and capable of withstanding
hydraulic pressure gradients to prevent failure due to settlement,
compression, or uplift, and all effects of ground motions resulting
from at least the maximum surface acceleration expected from a probable
earthquake.
5. Seismic Impact Zones
    In Sec.  257.63, EPA is adopting the provisions applicable to
seismic impact zones, as proposed. The rule prohibits new CCR
landfills, existing and new CCR surface impoundments and all lateral
extensions from being located in seismic impact zones unless the owner
or operator makes a demonstration, certified by a qualified
professional engineer, that all containment structures, including
liners, leachate collection systems, and surface water control systems,
are designed to resist the maximum horizontal acceleration in lithified
earth material from a probable earthquake. A Seismic impact zone means
an area having a 2% or greater probability that the maximum expected
horizontal acceleration, expressed as a percentage of the earth's
gravitational pull (g), will exceed 0.10 g in 50 years. Seismic zones,
which represent areas of the United States with the greatest seismic
risk, are mapped by the U.S. Geological Survey and readily available
for all the U.S. (http://earthquake.usgs.gov/hazards/apps/).
    Maximum Horizontal Acceleration in lithified earth material means
the maximum expected horizontal acceleration at the ground surface as
depicted on a seismic hazard map, with a 98% or greater probability
that the acceleration will not be exceeded in 50 years, or the maximum
expected horizontal acceleration based on a site-specific seismic risk
assessment. This requirement translates to a 10% probability of
exceeding the maximum horizontal acceleration in 250 years.
    For units located in seismic impact zones, as part of any
demonstration, owners and operators should include: (1) A determination
of the expected peak ground acceleration from a maximum strength
earthquake that could occur in the area; (2) a determination of the
site-specific seismic hazards such as soil settlement; and (3) a
facility design that is capable of withstanding the peak ground
acceleration. Seismic designs broadly should include a response
analysis to quantify the demands of earthquake motion on facility
structures (i.e., landfills, surface impoundments, liners, covers,
leachate collection systems, surface water handling systems),
liquefaction analyses of both waste and foundation soils to evaluate
stability under seismic loading, and a slope stability and deformation
analyses. Design modifications to accommodate seismic risks should
include use of conservative design factors, use of ductile materials,
built-in redundancy for critical system components, and other measures
capable of mitigating the potential for seismic upset.\58\
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    \58\ The seismic location standard requires a demonstration that
a CCR disposal unit can withstand the stresses imposed by peak
ground acceleration during earthquake motion. The seismic factor of
safety is a unitless measure of strength calculated for fill
material assuming earthquake conditions. It is the ratio of material
shear strength relative to the magnitude of shear forces acting on
the material. For a CCR disposal unit, the seismic location
demonstration could be composed of numerous factor of safety
calculations showing that the structural components of the unit have
factors of safety greater than or equal to 1.00.
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    Following trends in earthquake engineering, seismic design criteria
for new CCR landfills, new CCR surface impoundment and all lateral
expansions should be based on a ``withstand without discharge''
standard.\59\ EPA interprets the performance standard in this criterion
(``designed to resist the maximum horizontal acceleration in lithified
earth material from a probable earthquake'') to require any new CCR
unit located in a seismic impact zone to be designed to withstand
seismic motion from a credible earthquake without damage to the
foundation or to the structures that control leachate, surface
drainage, or erosion. In other words, the CCR unit must be able to
withstand an expected earthquake without discharging waste or
contaminants. The owner or operator must make a demonstration,
certified by a qualified professional engineer, that the CCR unit has a
foundation or base capable of providing support for the structure, and
capable of withstanding hydraulic pressure gradients to prevent failure
due to settlement, compression, or uplift and all effects of ground
motions resulting from at least the maximum surface acceleration
expected from a probable earthquake. In practice, the Agency recognizes
that the CCR unit may sustain some limited damage during an earthquake,
but ultimately, the CCR unit design must remain

capable of preventing harmful release of CCR, leachate, and
contaminants both during and after the seismic event.
---------------------------------------------------------------------------

    \59\ Kavazanjian, E., 1999. Seismic Design of Solid Waste
Containment Facilities. Proceedings of the Eight Canadian Conference
on Earthquake Engineering Vancouver, BC, pp. 51-89.
---------------------------------------------------------------------------

6. Unstable Areas
    EPA laid out its rationale for these requirements in the proposal
at 75 FR 35201. No significant comments were received on either this
rationale or the specific regulatory provisions. Consequently, EPA is
adopting the regulatory text as proposed. Specifically, under Sec.
257.64(a) new and existing CCR landfills, new and existing CCR surface
impoundments and all lateral expansions are prohibited from sites
classified as unstable areas unless the owner or operator makes a
demonstration, certified by a qualified professional engineer, that
engineering measures have been incorporated into the CCR unit's design
to ensure that the structural components will not be disrupted. EPA
considers a structural component to include any component used in the
construction and operation of CCR landfill or CCR surface impoundment
that is necessary to ensure the integrity of the unit and to ensure
that the contents will not be released to the environment, including
liners, leachate collection system, embankments, spillways, outlets,
final covers, inflow design flood controls systems. Liners and leachate
collection systems require a firm, secure foundation to maintain their
integrity, and may be disrupted as a result of uneven settlement
induced by hydrocompaction. Similarly, sudden differential movement
resulting from CCR placement and the consequent exceedance of the
weight-bearing strength of subsurface materials in unstable areas can
destroy liners and damage the unit's structural integrity, resulting in
catastrophic release of CCR. It is essential for the owner or operator
of any CCR unit to extensively evaluate the adequacy of the subsurface
foundation support for the structural components of the unit.
Therefore, the Agency is making this demonstration mandatory for all
CCR units; existing CCR units for which a demonstration cannot be made
must be closed.
    EPA has adopted the following definitions without material change
from the proposal: Unstable area means a location that is susceptible
to natural or human-induced events or forces capable of impairing the
integrity of some or all of the structural components responsible for
preventing releases from a CCR unit. Natural unstable areas include
those areas that have poor soils for foundations, areas susceptible to
mass movements, and karst terrains. Structural components mean liners,
leachate collection systems, final covers, run-on/run-off systems, and
any other component used in the construction and operation of a CCR
unit. Poor foundation conditions means those areas where features exist
which may result in inadequate foundation support for the structural
components of a CCR unit. Areas susceptible to mass movement means
those areas of influence (i.e., areas characterized as having an active
or substantial possibility of mass movement) where the movement of
earth material at, beneath, or adjacent to the CCR unit, because of
natural or man-induced events, results in the downslope transport of
soil and rock material by means of gravitational influence. Areas of
mass movement include, but are not limited to, landslides, avalanches,
debris slides and flows, solifluction, block sliding, and rock fall.
Karst terrain means an area where karst topography, with its
characteristic erosional surface and subterranean features, is
developed as the result of dissolution of limestone, dolomite, or other
soluble rock. Characteristic physiographic features present in karst
terrains include, but are not limited to, dolines (sinkholes), vertical
shafts, sinking streams, caves, seeps, large springs, and blind
valleys.
    The owner or operator must consider at a minimum, the following
factors when determining whether an area is unstable: (1) On-site or
local soil conditions that may result in significant differential
settling; (2) on-site or local geologic or geomorphologic features; and
(3) on-site or local human-made features or events (both surface and
subsurface). To evaluate subsurface conditions for purposes of Sec.
257.64(c)(3), EPA considers it essential that the owner or operator
conduct a geotechnical site investigation, certified by a qualified
professional engineer, to identify any potential thick layers of soil
that are soft and compressible (e.g., loess, unconsolidated clays,
wetland soils), which could cause a significant amount of post-
construction differential settlement of foundation soils, adjacent
embankments, and slopes unless improved. In addition, it is essential
that the investigation identify on-site or local soil conditions that
are conducive to downslope movement of soil, rock, and/or debris (alone
or mixed with water) under the influence of gravity. Local topography,
surface and subsurface soils, surface slope angles, surface drainage
and run-off patterns, seepage patterns, rock mass orientations, joint
patterns, fissures, and any other landscape factors that could
influence downslope movement should be identified. Anthropogenic
activities that could induce instability include mining, cut and fill
activities during construction, excessive drawdown of groundwater,
which may cause excessive settlement or bearing capacity failure of
foundation soils, and use of an old landfill as the foundation for a
new landfill without verification of complete settlement of the
underlying wastes.
    In designing a new CCR unit located in an unstable area, recognized
and generally accepted good engineering practices dictate that a
stability assessment should be conducted to prevent a destabilizing
event from damaging the structural integrity of the component systems.
For CCR units this involves three components: (1) An evaluation of
subsurface conditions, (2) an analysis of slope stability, and (3) an
examination of related design needs. In addition to explaining site
constraints, identifying any soft soils, and recommending any
appropriate ground improvement techniques, the assessment report should
include a description of: The site, site geology; and investigative
methodology; the results from all site investigations including
subsurface exploration, field and laboratory tests, and test results;
the subsurface profile, recommended foundation types, depths, and
bearing capacities; the water content, grain-size distribution, shear
strength, plasticity, and liquefaction potential of foundation soils
and subsoils; and other foundation consolidation and settlement issues
relevant to site development.
    In addition to assessing the ability of soils and rocks to serve as
a foundation, it is essential that the report also include a stability
assessment of excavated sideslopes, aboveground embankments or dikes,
and retaining structures. The slope stability analyses are performed as
part of an evaluation of the design configuration under all potential
hydraulic and loading conditions, including conditions that may exist
during construction of a lateral or vertical expansion. As part of any
demonstration, owners and operators should make an assessment,
certified by a qualified professional engineer, that finalized site
embankments and slopes are able to maintain a stable condition. In
addition to evaluating the potential for post-construction differential
settlement, the stability assessment should also consider seepage-
induced saturation and softening of soils, particularly at CCR surface
impoundments and CCR landfill sites that manage effluent.
    Engineering considerations for CCR landfills and lateral expansions
located in unstable areas are expected to be

similar to those for MSWLFs, which can be found in EPA's 1993 Technical
Manual on Solid Waste Disposal Facility Criteria (EPA530-R-93-017). For
surface impoundments the relevant design criteria are found in the
Agency's 1991 Technical Resource Document on Design, Construction and
Operation of Hazardous and Non-Hazardous Waste Surface Impoundments
(EPA/530/SW-91/054). Any stability assessment should consider the
following: (1) The adequacy of the subsurface exploration program; (2)
the liquefaction potential of the embankment, slopes and foundation
soils; (3) the expected behavior of the embankment slopes, and
foundation soils when they are subjected to seismic activity; (4) the
potential for seepage-induced failure; and (5) the potential for
differential settlement.
    For facilities in areas of karst, to support the demonstration
required under the regulations, the owner or operator would need to
evaluate the subsurface conditions to ensure that the unit is located
away from the influence of potential sinkholes. For areas where the
solution-weathered limestone is close to the surface (e.g., Florida)
recognized and generally accepted good engineering practices dictate
that there must be no conduits beneath the CCR unit that allow piping
of groundwater into the karst aquifer, or shallow caves that could
cause sudden collapse of the unit foundation. Where unconsolidated
sediments cover underlying limestone, piping is commonly marked by
paleosinks where sands and clays from the overburden have filled
solution cavities in the underlying limestone.\60\ Local hydraulic
gradients in paleosinks typically point downward. EPA generally expects
the potential for sinkhole development to be minimal at locations in
karst areas where there are no paleosinks, or historical record of
sinkhole development, and where there are no local hydraulic gradients
that point downward.
---------------------------------------------------------------------------

    \60\ For examples, see Garlanger, J.E., Foundation Design in
Florida Karst. Online presentation by Ardaman & Associates. http://www.ardaman.com/foundation_design.htm.
---------------------------------------------------------------------------

    In making a demonstration, it is important for owners and operators
of CCR landfills and surface impoundments in karst areas to adequately
characterize subsurface conditions. Karst hydrogeology is complex,
since contaminant flows can occur along paths and networks that are
discreet and tortuous, and groundwater monitoring wells must be capable
of detecting any contaminants released from the CCR unit into the karst
aquifer. Therefore, the owner or operator will need to ensure, with
verification by a qualified professional engineer, that monitoring
wells installed in accordance with Sec.  257.91 will intercept these
pathways. Verification will usually necessitate the use of tracers to
track groundwater flow towards offsite seeps or springs from the
uppermost aquifer beneath the facility.
    Any engineered solution employed to mitigate weak ground strength
in karst areas must be able to prevent the kind of foundation collapse
and settlement that could lead to sudden release to the environment of
CCR with its toxic constituents and associated leachate. Solution
cavities present at the site should be filled with grout or other
suitable stiff material to avoid further crumbling and erosion. Where
necessary, CCR unit foundations could be reinforced with engineered
ground supports such as concrete footings that bridge voids. Larger
caverns could be filled with concrete to underpin the CCR unit
foundation by transferring load to the cavern floor. However, such
engineered solutions are complex and costly, and the best protection is
not to site CCR landfills and surface impoundments in karst areas.
Nevertheless, this rule does not ban the location of CCR landfills,
surface impoundments, or lateral extensions in karst areas.
7. Closure of Existing CCR Landfills and Existing CCR Surface
Impoundments
    The final provisions of Sec.  257.60 require owners or operators of
an existing CCR surface impoundment to demonstrate that the unit meets
the minimum requirements for placement above the uppermost aquifer
(i.e., constructed with a base located no less than 1.52 meters (five
feet) above the upper limit of the uppermost aquifer) no later than 42
months after the date of publication of this rule in the Federal
Register.
    Owners and operators of existing CCR surface impoundments subject
to Sec. Sec.  257.61-257.64 of this rule and existing CCR landfills
subject to Sec.  257.64, must complete demonstrations by the date
corresponding to 42 months from publication of this rule. The Agency is
setting the compliance deadline at 42 months to allow owners and
operators time to complete the requisite studies (e.g., to adequately
characterize seasonal variations in the elevation of the top of the
uppermost aquifer) and to complete any engineering measures necessary
to allow the CCR unit to meet the performance standards. If closure is
warranted, it must be initiated no later than 48 months from
publication of this rule. Closure and post-closure care must be done in
accordance with Sec. Sec.  257.100-103; which allow certain regulatory
flexibilities provided specific conditions are met.

D. Design Criteria--Liner Design

    EPA proposed that existing CCR landfills without a composite liner
could continue to operate and receive CCR without violating the open
dumping prohibition. Conversely, EPA proposed that existing CCR surface
impoundments would be required to retrofit with a composite liner
system, as defined in the proposed rule, within five years of the
effective date of the rule or to close. EPA also proposed that all new
CCR units must be constructed with a composite liner and leachate
collection and removal system.
    In the proposal, EPA defined a composite liner to mean a liner
system consisting of two components; the upper component consisting of
a minimum 30-mil flexible membrane liner (FML), and the lower component
consisting of at least a two-foot layer of compacted soil with a
hydraulic conductivity of no more than 1 x 10-7 cm/sec.\61\
FML components consisting of high density polyethylene (HDPE) were
required to be at least 60-mil thick; and the FML component was
required to be installed in direct and uniform contact with the
compacted soil component.
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    \61\ The definition of hydraulic conductivity is being
promulgated as proposed, and will mean the rate at which water can
move through a permeable medium (i.e., the coefficient of
permeability).
---------------------------------------------------------------------------

    EPA solicited comment on a number of issues, including: (1) Whether
EPA should allow facilities to use an alternative design for new CCR
units; (2) whether clay liners designed to meet a 1 x 10-7
cm/sec hydraulic conductivity might perform differently in practice
than modeled in the risk assessment, including a request for specific
data on the hydraulic conductivity of clay liners associated with CCR
units; and (3) whether the effectiveness of such additives as
organosilanes, would allow the use of these additives in lieu of
composite liners. (See 75 FR 35203 and 35222.) \62\ With respect to the
last two issues, the Agency received little comment. However, in
response to the use of alternative liner designs in lieu of a composite
liner (as defined in the rule), significant comment was received.
Commenters advocated for a number of alternative composite liner
designs, with a majority recommending that a

geosynthetic clay liner (GCL) be allowed as an alternative to the lower
component of the composite liner. Other commenters stated that GCLs
alone should be allowed as an alternative to the proposed composite
liner. Still others argued that alternative liner designs, such as an
FML/FML \63\ provided a level of performance similar to the proposed
composite liner system and should be allowed. Conversely, there were
also comments opposing the use of any alternative liners, claiming that
alternatives have not been proven to be effective.
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    \62\ The terms compacted soil and compacted clay are used
interchangeably, i.e., when referring to a compacted soil liner this
is the same as referring to a compacted clay liner (CCL).
    \63\ Current terminology favors the use of geomembrane liner or
GM when referring to flexible membrane liners or FMLs. Hereafter in
the preamble, except when referring to specific comments or the
proposed rule, and in the final rule, the Agency will use the term
geomembrane liner or GM in place of flexible membrane liner or FML.
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    EPA also received significant comment on the actual design of the
composite liner system proposed by the Agency as it pertained to CCR
surface impoundments (see 75 FR 35202-35203).\64\ Commenters argued
that the proposed requirement for a leachate collection and removal
system in a CCR surface impoundment was illogical since it would have
to be constructed between the lower component (two feet of compacted
soil) and upper component (flexible membrane liner) and the proposed
rule specifically states that the flexible membrane liner component
must be installed in direct and uniform contact with the compacted soil
component. Commenters reasoned that the inclusion of a leachate
collection and removal system between the upper and lower components
precluded direct and uniform contact between the two components and
that placing a leachate collection and removal system between the lower
and upper components of a composite liner would compromise the
integrity of the composite liner. With regard to this last point, the
Agency has reviewed the requirements for a proposed composite liner
system as it would pertain to CCR surface impoundments and agrees that
the leachate collection and removal system requirements proposed for
CCR surface impoundments would be counterproductive; EPA proposed this
requirement in error. The integrity of the composite liner system is
indeed dependent upon the direct and uniform contact of the upper GM
component with the lower soil component. The proposed requirement for
CCR surface impoundments to construct a leachate collection system
between the FML and soil components would prevent the direct and
uniform contact of the upper and lower components and, therefore,
compromise the integrity of the composite liner. For this reason, EPA
is not requiring a leachate collection and removal system for new
surface impoundments or any lateral expansion of a CCR surface
impoundment.
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    \64\ See proposed Sec.  257.71 which states that an existing CCR
surface impoundment shall be constructed with a composite liner and
a leachate collection system between the upper and lower components
of the composite liner; where a composite liner means a system
consisting of two components; the upper component consisting of a
minimum 30-mil flexible membrane liner (FML) and a lower component
consisting of at least a two-foot layer of compacted soil with a
hydraulic conductivity of no more than 1 x 10-7 cm/sec.
The FML component would be required to be installed in direct and
uniform contact with the compacted soil component (see 75 FR 35243).
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    While EPA agrees with those commenters arguing that new CCR units
should only be installed with a composite liner system of some kind,
the Agency has concluded that not all alternative designs for a
composite liner system should necessarily be rejected as insufficiently
protective. Many commenters provided strong and compelling evidence
that the specific composite liner system described in the proposed rule
was not always feasible or necessary to protect groundwater resources
and that alternate composite liner designs could be equally protective,
and may be a necessity in many areas of the country where soil with the
appropriate hydraulic conductivity may not be available (e.g.,
Alaska).\65\
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    \65\ See for example comments from the states of Alaska (EPA-HQ-
RCRA-2009-0640-06409); Florida (EPA-HQ-RCRA-2009-0640-06846); and
North Carolina (EPA-HQ-RCRA-2009-0640-09282) available at
www.regulations.gov.
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    In re-evaluating the proposed requirement for a composite liner
system, EPA was influenced by a number of factors.\66\ First, the data
provided by commenters showing the performance of a GM/GCL design.
Second, EPA's own studies showing that a GM/GCL liner can be
constructed to achieve hydraulic efficiencies in the range of 99 to
99.9% which meets or exceeds the hydraulic performance of a GM/
compacted clay liner (CCL) design.\67\ In addition, these high
efficiencies demonstrate that the GCL component of a GM/GCL composite
liner is at least as effective in impeding leakage through holes in the
GM component of the composite liner system as a CCL with a hydraulic
conductivity no more than 1 x 10-7 cm/sec.\68\ In fact, EPA
has developed guidance for the selection and installation of various
types of liners including a GM/GCL.\69\ And third, EPA was influenced
by the many comments arguing that a ``one-size-fits all'' approach to
liner design stifles design innovation and regulatory flexibility in
addressing site specific factors such as geologic or climatic
conditions. These commenters reasoned that if EPA established some type
of performance standard for composite liners, it would mitigate the
negative impacts of a ``one-size fits all'' regulatory framework.
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    \66\ Geomembranes (GMs), which are flexible membrane liners
(FMLs), are thin materials manufactured from polymers and reinforced
with woven fabric or fibers which are used as hydraulic barriers.
Resins used to manufacture geomembrane liners typically include high
density polyethylene (HDPE), linear low density polyethylene
(LLDPE), low density linear polyethlene (LDLPE), very low density
polyethylene (VLDPE) and polyvinyl chloride (PVC). Geomembranes
manufactured using HDPE are the least flexible of the geomembranes.
    \67\ USEPA, ``Assessment and Recommendations for Improving the
Performance of Waste Containment Systems,'' EPA 600/R-02/029,
December 2002. http://nepis.epa.gov/Adobe/PDF/P1001O83.pdf.
    \68\ USEPA, ``Assessment and Recommendations for Improving the
Performance of Waste Containment Systems,'' EPA 600/R-02/029,
December 2002.
    \69\ USEPA, ``Guide for Industrial Waste Management,'' Chapter 7
(http://www.epa.gov/osw/nonhaz/industrial/guide/pdf/chap7b.pdf).
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1. Development of Composite Liner Design Criteria
    In this final rule EPA is requiring all new CCR units to be
designed and constructed with a composite liner as specified in Sec.
257.70. EPA is also providing the owner or operator with an option to
install an alternative composite liner provided it meets the required
performance standard and it is certified by a qualified professional
engineer. EPA has concluded, consistent with many of the comments
received and its own analysis, that an alternative composite liner for
new CCR units is warranted if it can be shown to be equivalent to the
performance of a composite liner and affords the same protections to
groundwater resources as a composite liner. The Agency is promulgating
this alternative option to provide flexibility in designing and
constructing a protective composite liner system that addresses site
specific conditions and situations. The Agency acknowledges that it was
overly prescriptive by requiring one particular type of liner rather
than relying on a performance standard to define the lower component of
the composite liner. The overwhelming amount of data supporting the
effectiveness of a GC/GCL liner has convinced the Agency that the final
rule should allow for some flexibility in composite liner designs. As
such, the Agency is allowing new CCR units to be designed and
constructed

with an alternative composite liner, as described below, provided the
lower component of the composite liner meets a specified performance
standard that ensures it functions in a manner equivalent to the
composite liner system defined in the rule.
    Composite liner systems installed in either a CCR landfill or CCR
surface impoundment provide an effective hydraulic barrier by combining
the complementary properties of the two different liner components. The
geomembrane provides a highly impermeable layer that can maximize
leachate collection and removal in a CCR landfill or minimize
infiltration of leachate in a CCR surface impoundment, while the soil
component (e.g., CCL) serves as a backup in the event of any leakage/
infiltration from the geomembrane occurs. Data indicate that
alternatives to the lower component of the composite liner system
(e.g., GCLs) are available and can perform at a level equivalent to a
compacted soil liner, based on a comparison of their flow rates with
two feet of compacted soil with a hydraulic conductivity of no more
than 1 x 10-7 cm/sec.
2. Liner Designs That Would Not Meet the Requirements of a Composite
Liner or Alternative Liner
    Contrary to the arguments made by several commenters, EPA has
concluded that a composite liner consisting of two 30-mil GMs (GM/GM)
will not provide an equivalent degree of protection as a composite
liner consisting of a GM and two feet of compacted soil, or an
alternative composite liner such as a GM/GCL. While GMs have the
advantages of extremely low rates of water permeation, the
disadvantages of a composite liner consisting of two GMs include
leakage through occasional GM imperfections and punctures, potential
for slippage along the interface between the GMs, and GM embrittlement
over time. Furthermore, a critical component of a composite liner is
the compacted soil or GCL component beneath the GM layer that will
impede the flow of liquid that may leak through a hole or defect in the
GM. This added protection cannot be achieved using two GMs for the
composite liner. Additionally, the potential exists for liquid
transport through the GMs through holes caused by punctures, tears,
flawed seams, etc. If a puncture occurs, the puncture could compromise
both GMs and create a conduit for liquid flow to underlying permeable
soil. Moreover, a liner system consisting of two GMs in contact with
each other poses the risk of creating a slip plane that may compromise
the stability of the disposal unit (although EPA acknowledges that
using textured GMs would reduce or eliminate this particular risk).
These data are documented in EPA research.\70\
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    \70\ ``Assessment and Recommendations for Improving the
Performance of Waste Containment Systems.''
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    Consistent with the previous determination, EPA has also determined
that the double liner system set forth in Florida regulations (see
Florida Rules 62-701.400(3)(c), F.A.C) also does not meet the level of
performance achieved by EPA's composite liner system or the alternative
liner system. While this double liner system provides the advantage of
a leak detection system between the two GMLs, the lower composite
liner, consisting of a 60-mil HDPE over six inches of soil with a
saturated hydraulic conductivity of less than or equal to 1 x
10-5 cm/sec, is not equivalent to a GM over two feet of
compacted soil with a hydraulic conductivity of less than or equal to 1
x 10-7 cm/sec. To be hydraulically equivalent, soil with a
hydraulic conductivity of 1 x 10-5 cm/sec would need to be
on the order of 100 times thicker than soil with a hydraulic
conductivity of less than or equal to 1 x 10-7 cm/sec.
Similarly, a lower composite liner consisting of a 60-mil HDPE over a
GCL with a hydraulic conductivity not greater than 1 x 10-7
cm/sec would require a GCL thickness of 24 inches to be equivalent to a
GM over two feet of compacted soil with a hydraulic conductivity of
less than or equal to 1 x 10-7 cm/sec.
    EPA has also examined the performance of GCLs approved for use as
alternatives to composite liners in MSWLFs.\71\ The EPA report titled
``Assessment and Recommendations for Improving the Performance of Waste
Containment Systems,'' \72\ concluded that if a CCL or GCL is used
alone, liquid migration can occur over the entire area of the liner
that is subject to a hydraulic head. The report also concluded that in
a composite liner, leakage will only occur at the location of the
geomembrane penetration (e.g., hole, tear), and will be much slower
than flow through an orifice due to the hydraulic impedance provided by
the CCL or GCL alone. The report also evaluated, among other
characteristics, the hydraulic efficiencies of a GM/GCL composite liner
system for 28 cells at seven landfills. Liner hydraulic efficiencies
were reported between 97% and 100%. However, potential stability
problems were reported with GCLs constructed on slopes greater than 10
H:1 V (5.7[deg]), and GCLs may not be appropriate for the disposal of
liquid wastes or sludges. The Agency is also concerned that GCLs, being
much thinner than the two feet of compacted soil required for composite
liners, may allow for the flow of liquids through the GCL at a faster
rate than through two feet of compacted soil. Taking all of this
information into account, the Agency remains unconvinced that a GCL
alone is a viable alternative to a composite liner.
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    \71\ ``Geosynthetic Clay Liners Used in Municipal Solid Waste
Landfills,'' http://www.epa.gov/wastes/nonhaz/municipal/landfill/geosyn.pdf; ``Geosynthetic Clay Liners in Waste Containment,''
http://www.epa.gov/superfund/remedytech/tsp/download/2001_meet/prez/carson.pdf; and ``Assessment and Recommendations for Improving the
Performance of Waste Containment Systems,'' http://nepis.epa.gov/Adobe/PDF/P1001O83.pdf.
    \72\ ``Assessment and Recommendations for Improving the
Performance of Waste Containment Systems.''
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3. Design Requirements
a. Existing CCR Landfills
    As proposed, the final rule allows existing CCR landfills as
defined in Sec.  257.54, to continue to operate without retrofitting
with a composite liner and leachate collection and removal system. As
previously discussed, given the volume of the material currently
managed in CCR landfills, the potential for disruption in CCR disposal
capacity if existing CCR landfills were required to retrofit would be
significant. Significant disruptions in the state-wide solid waste
management (and possibly power generation) are associated with
significant risks to public health and the environment in their own
right. EPA has concluded that these risks are greater than the risks
associated with allowing unlined CCR landfills to continue to operate.
Further, existing CCR landfills will be required to comply with the
extensive groundwater monitoring and corrective action requirements,
among others, to ensure that any groundwater releases from the CCR unit
are identified and promptly remediated, which will significantly
mitigate the risks from these existing units. By themselves, the risk
assessment results and the risk migration from the other regulatory
requirements in this rule would not support a decision to allow these
CCR units to continue to operate on a national basis. But when the
risks associated with the level of disruption EPA estimates to be
possible from requiring existing CCR landfills to retrofit are also
included, the totality of the evidence supports a determination that
allowing these units to continue operating meets the section 4004(a)
standard.

b. Existing CCR Surface Impoundments
    In a departure from the proposed rule and after considerable
evaluation and analysis, the Agency is finalizing a provision to allow
all existing CCR surface impoundments to remain in operation provided
certain conditions are met.\73\ Owners or operators of existing CCR
surface impoundments are required, within one year of the effective
date of the rule, to document, certified by a qualified professional
engineer, whether the unit is constructed with any one of the three
liner types: (1) A liner consisting of a minimum of two feet of
compacted soil with a hydraulic conductivity of no more than 1 x
10-7 cm/sec; (2) a composite liner that meets the
requirements of Sec.  257.70(b); or (3) an alternative liner that meets
the requirements of Sec.  257.70(c). In some instances, owners or
operators may have information readily available to determine if an
existing CCR surface impoundment is constructed with one of the three
liner types listed above. On the other hand, this information may not
be readily available and may require an owner or operator to conduct an
engineering evaluation to determine if the unit was constructed with
any of the three liner type. Factors such as the availability of
engineering personnel and weather may impede the engineering
evaluation. Therefore, EPA believes that 12 months from the effective
date, or 18 months from publication of the rule, is a reasonable amount
of time to make the determination of whether the existing CCR surface
impoundment was constructed with one of the three liner types described
above. Existing surface impoundments with liners that meet the criteria