site conditions. Discussion of the site conditions and the specific
comments received is provided in the following Units of this preamble.
a. Number and Location of Samples
    EPA did not provide specific discussion in the proposal about the
required number, depth, or spacing of samples for analysis of hydraulic
conductivity for the second line of evidence. Instead, EPA stated in
the first line of evidence that samples must be located around the
perimeter of the surface impoundment at a spatial resolution sufficient
to ensure that any regions of substantially higher conductivity have
been identified. EPA had intended for the variability of the
hydrogeology identified in the first line of evidence to inform the
number and location of samples analyzed for the second line of
evidence.
    Based on comments received, EPA believes that commenters generally
assumed EPA had proposed that the location of samples for hydraulic
conductivity must coincide with samples collected for the first line of
evidence. As such, EPA considers all general comments requesting that
the frequency of data collection be based on the variability of the
site geology to be equally relevant here.
    EPA did not envision that samples collected to characterize
hydraulic conductivity would exactly match the number or location of
those collected for the first line of evidence. For example, as
discussed in Unit III.C.1.b of this preamble, this rule also allows for
use of non-intrusive methods to support the first line of evidence.
Because non-intrusive methods do not advance equipment into the soil,
they do not allow for simultaneous collection of subsurface soil
samples. The combination of methods used to characterize site
hydrogeology may identify regions of subsurface variability some
distance away from the point of measurement. Therefore, facilities
should instead use the information available on subsurface variability
from the first line of evidence to inform the number and location of
samples for the second line of evidence.
    Therefore, for clarity and consistency with the first line of
evidence, EPA is finalizing a requirement at Sec.
257.71(d)(1)(ii)(B)(1) that facilities are required to document where
samples were collected around the surface impoundment and how the
number, depth, and spacing of these samples (1) are supported by the
data collected for the first line of evidence and (2) are sufficient to
capture the variability of hydraulic conductivity for the soil-based
liner components and/or naturally occurring soil.
b. Permeant Liquid
    EPA discussed in the proposal that tests used to estimate hydraulic
conductivity need to use a permeant liquid that reflects the
composition of the infiltrating surface impoundment porewater. The
method must account for the chemistry of CCR porewater that can have
both extreme pH and high salinity. Extreme pH may dissolve key
components of the soil structure, while high salinity may result in
interlayer shrinkage of clays, both of which can result in higher
hydraulic conductivity. Use of a non-representative liquid (e.g.,
deionized water) as the permeant liquid or pre-hydrating the clay may
actually decrease the conductivity of clay through swelling and result
in a lower measured conductivity than would actually occur in the
field.
    EPA received no adverse comments on this topic. One commenter
raised concern that exposure to CCR leachate can adversely affect the
integrity of a liner, though this commenter made no reference to the
preamble discussion. Instead, the commenter cited to multiple studies
purported to show that CCR leachate can adversely affect geosynthetic
clay liners and that pre-hydrating samples with deionized water may
underestimate long-term conductivity.
    As discussed in the proposal and above, EPA agrees that the effects
of leachate chemistry on long-term soil conductivity are potentially
significant. Therefore, EPA is finalizing a requirement at Sec.
257.71(d)(1)(ii)(B) that the liquid used to pre-hydrate the clay and
measure long-term hydraulic conductivity must reflect the pH and major
ion composition of the impoundment porewater.
c. Thixotropic Effects
    EPA raised concern in the proposal that preparation of samples
intended to reflect compacted soil liners for testing may result in the
soil becoming temporarily less permeable as a result of

thixotropic behavior. EPA previously raised the potential for the
structure of thixotropic materials, such as certain clays, to become
temporarily more dispersed when agitated, which might limit flow
through interstitial pores and make it more difficult for water to
infiltrate.\24\ EPA was concerned that the material will gradually
become more permeable as it is allowed to rest and return to its
original state. Therefore, EPA stated in the proposal that compacted
samples should be allowed to rest for sufficient periods prior to
testing to reflect the long-term behavior of the soil in the field.
---------------------------------------------------------------------------

    \24\ U.S. EPA. 1986. ``Design, Construction, and Evaluation of
Clay Liners For Waste Management Facilities.'' EPA/530-SW-86-007-F.
Prepared for the Office of Solid Waste and Emergency Response.
Washington, DC.
---------------------------------------------------------------------------

    EPA received no comments that expressed support for this
requirement. One commenter questioned whether thixotropy is a relevant
consideration and if a ``rest period'' is actually needed to provide a
realistic measurement of hydraulic conductivity. This commenter pointed
to multiple studies that found minimization of void spaces in the soil
macrostructure was a key control on hydraulic conductivity. Based on
this literature, the commenter concluded that the microscale structure
described with terms such as ``dispersed'' or ``flocculated'' is not a
major concern.
    The literature provided by the commenter indicates that effects
from thixotropy are not a major concern in the measurement of hydraulic
conductivity. EPA acknowledges that this topic is not raised in more
recent literature discussed as part of this rulemaking. Similarly, none
of the standardized tests for hydraulic conductivity reviewed by EPA
specifies a need for an extended rest period. In addition, studies
conducted more recently by EPA and others have obtained good agreement
between measurements in the lab and field for many compacted, low-
conductivity soils without a rest period. Finally, this requirement has
the potential to add a considerable amount of time to an already time-
intensive analysis. For all these reasons, EPA concludes that the
available evidence does not support finalization of this provision.
d. Natural Soil Structure
    EPA discussed in the proposal that preparation for samples intended
to reflect the naturally-occurring soils beneath the surface
impoundment for testing may result in the soil becoming permanently
less permeable by disturbing the natural structure of the soil and
eliminating voids and other features that may act as conduits for
infiltration in the field. Failure to preserve the structural integrity
of such samples could result in a lower measured conductivity than
would actually occur in the field because it results in greater
compaction or consolidation than exists in the field. EPA pointed out
that standardized methods have been developed to obtain undisturbed
soil samples.
    EPA received no comments relevant to this topic. Therefore, EPA is
finalizing a requirement at Sec.  257.71(d)(1)(ii)(B)(3) that
facilities must ensure that samples intended to represent the hydraulic
conductivity of naturally-occurring soils (i.e., not mechanically
compacted) are handled in a manner that will ensure the macrostructure
of the soil is not physically disturbed during collection, transport,
or analysis (e.g., initial saturation). Facilities must provide
documentation of the measures taken to ensure the integrity of the
samples relied upon.
e. Test Termination Criteria
    EPA discussed that the termination point of a test must be
established at a point that ensures the long-term behavior of the liner
is accurately reflected. Some tests for hydraulic conductivity stop
after the inflow and outflow rates equilibrate or after a specified
volume of water has passed through the soil. However, these metrics may
not be sufficient to identify the reactions that can occur between the
soil and liquid (e.g., exchange of adsorbed cations). Some metrics that
more directly address the chemistry of the soil-leachate interactions
include equilibration of electrical conductivity and pH. Failure to run
the test on a timeframe relevant to the chemical reactions of interest
may result in a lower measured conductivity than would actually occur
in the field.
    One facility stated that the proposed hydraulic conductivity
testing is difficult, time-consuming, and not commonly conducted. The
facility asserted that the information obtained from such tests would
not significantly inform a determination of whether the impoundment is
protective. Another commenter suggested two methods as most appropriate
for use in the demonstration: ASTM D6766 (Standard Test Method for
Evaluation of Hydraulic Properties of Geosynthetic Clay Liners
Permeated with Potentially Incompatible Liquids) and ASTM D7100
(Standard Test Method for Hydraulic Conductivity Compatibility Testing
of Soils with Aqueous Solutions). This commenter noted that both
methods include termination criteria based on chemical equilibrium.
    EPA acknowledges that it can take considerable time for hydraulic
conductivity tests to meet termination criteria, and that criteria
based on chemical equilibrium may require more time than those based on
other metrics. However, the Agency disagrees that these tests provide
no useful information. By allowing the chemistry of the system to reach
equilibrium, it ensures that the long-term effects of leachate
chemistry on the soil are adequately characterized. High ionic strength
liquids have been shown to increase the long-term hydraulic
conductivity of some soil materials by orders of magnitude compared to
deionized water. The fact that these types of tests have been uncommon
does not negate their importance.
    EPA agrees that the two methods referenced by the second commenter
are more appropriate for use in the demonstration than ASTM D5084,
which EPA provided as an example in the preamble. However, the two
methods referenced by the commenter identify somewhat different
termination criteria based on solution chemistry. While one method
identifies only equilibrium for electrical conductivity, the other
further identifies pH, concentrations of unspecified solutes, and/or
the dielectric constant. Electrical conductivity and pH provide a means
to identify changes in the dominant solution chemistry. In addition,
both can be tested for rapidly and easily. That is why EPA believes
they serve as practical indicators for the hydraulic conductivity
tests. While other criteria, such as specific solute concentrations,
can provide further information on how the leachate interacts with the
soil (e.g., which ions are substituted on the soil surface), EPA has
not seen evidence that these additional parameters will identify
significant changes in the solution chemistry that electrical
conductivity and pH would not.
    Therefore, EPA is finalizing a requirement at Sec.
257.71(d)(1)(ii)(B)(4) that any test for hydraulic conductivity relied
upon must include, in addition to other relevant termination criteria
specified by the method, criteria that equilibrium has been achieved
within acceptable tolerance limits between the inflow and outflow for
both electrical conductivity and pH.
3. Additional Lines of Evidence
    EPA solicited comment on whether there are any additional lines of
evidence that should be included as part of the demonstration. Various
industry groups, individual facilities,

environmental groups, and states all proposed additional factors to be
considered. These factors included whether a unit had individual liner
components that met the standard of the CCR regulations, previous
certification of performance from states or professional engineers, and
the impact of closure on releases. These are discussed in more detail
in the following Units of this preamble.
a. Presence of Geomembrane Liner
    One commenter requested that EPA waive the demonstration
requirement for units that have at least a 60-mil geomembrane liner,
but do not meet the remaining requirements to be considered a lined
unit. This and another commenter indicated that a successful initial
application combined with decades of operation without any indication
the unit has adversely affected groundwater should be sufficient
evidence that the liner is protective.
    EPA emphasizes that the intent of a demonstration is to
characterize the potential for future groundwater exceedances. It can
take years or even decades for leachate released from an impoundment to
reach downgradient wells. Thus, the fact that a unit has not yet
triggered corrective action does not mean it is not possible at some
point in the future. This is why groundwater monitoring is required at
all units. Furthermore, as part of the demonstration, facilities are
required to test the hydraulic conductivity of the soil component of
the composite liner to demonstrate its long-term performance when
exposed to leachate. If the soil liner beneath a geomembrane liner is
found to be ineffective, then imperfections in the geomembrane liner
may lead to unimpeded flow of leachate into the subsurface. Based on
this, EPA concludes that information on the subsurface soil component
is a necessary line of evidence for all impoundments. Therefore, both
an initial application and final demonstration must be submitted as
part of an alternate liner demonstration for any impoundment.
b. Previous Certification
    Multiple commenters requested that EPA give deference to a previous
certification by a professional engineer or prior approval by a state
regulatory authority when determining whether to approve a
demonstration. Some commenters noted that their states require quality-
assurance/quality-control (QA/QC) plans for liner construction and
maintenance be included in the permit and that their surface
impoundment liner was inspected and certified by a licensed
professional engineer with appropriate expertise. One commenter
asserted that this helps establish a presumption that a surface
impoundment liner is adequately protective. However, none of the
commenters elaborated on how the Agency should assign weight to such
findings as part of the larger review.
    EPA agrees that documentation about the quality of liner
construction is necessary to prove that the surface impoundment has
been well constructed and so has the potential to be protective. That
is why information on construction quality must be provided upfront in
the application step. However, the fact that a unit meets an
unspecified design standard does not guarantee that particular standard
will be protective in the long term. A purpose of the demonstration
step is to document that the design of an alternate liner will remain
protective in the long-term when exposed to CCR leachate. EPA cannot
outright substitute a prior approval by either a qualified professional
engineer (PE) or state agency for the comprehensive alternate liner
demonstration required by this rule. State requirements can vary in
both scope and specificity and EPA does not have a reliable record of
what was considered as part of these reviews or how it aligns with the
requirements of this rule. To the extent that previous findings by a PE
or state authority details how a unit achieves the requirements of this
rule, EPA will consider the rationale provided as part of the larger
demonstration. However, this rationale does not substitute for
providing any of the data or other underlying documentation required by
this rule. Therefore, EPA made no changes to the rule in response to
these comments.
c. Consideration of Unit Closure
    One state recommended that the existence of plans to dewater the
surface impoundment and install an impermeable cap be included as an
additional line of evidence in the demonstration. The commenter noted
such actions could alter the hydrogeologic model and/or reduce
groundwater impacts. However, the commenter did not elaborate on how
the Agency should weigh such information as part of the larger review.
    The intent of the determination is to document the potential
environmental impacts associated with continued operation of the unit.
Although the installation of an impermeable cap would reduce
infiltration, such actions would not be feasible during operation and
are already required of all surface impoundments as part of closure.
Therefore, it is not clear how this could be incorporated as a line of
evidence. Therefore, EPA concludes that is not a relevant line of
evidence and made no changes to the regulations in response to this
comment.
4. Incorporation of Lines of Evidence Into Demonstration
    EPA proposed that the data collected for the two lines of evidence,
characterization of site hydrogeology and potential for infiltration,
must be incorporated into the final demonstration. Each one provides
different, site-specific data necessary to understand the potential for
continued operation of the unit to adversely affect groundwater in the
future. Consideration of future effects will necessitate some amount of
fate and transport modeling. EPA acknowledged that the type of model
used will depend on the complexity of the site. Regardless of the
modeling approach used, all of the data incorporated into the
calculations must be documented and justified.
    EPA received some general comments related to the incorporation of
the lines of evidence into the demonstration. One commenter stated that
groundwater and contaminant flow models should be developed by drawing
on the data used for the conceptual site models and run using various
scenarios to ensure adequate consideration of a range of operating and
site conditions. A second commenter stated that the magnitude of
releases from surface impoundments is determined by a myriad of
variables and reducing these systems to only one (i.e., hydraulic
conductivity) fails to capture this complexity, increasing the chance
of mischaracterizing the probability of groundwater contamination.
    EPA agrees with the first commenter that it is critical that
facilities document how any data relied upon adequately reflect the
range of variability in operational and environmental conditions at and
around the surface impoundment to ensure that high-end risks are not
underestimated. EPA disagrees with the second commenter that the
required lines of evidence are not adequate to identify this
variability and the potential for adverse effects to groundwater.
Although the effective hydraulic conductivity of the engineered liner
and/or naturally occurring soil is one of the most important
parameters, this does not mean other parameters are not also important
or accounted for in the demonstration. EPA previously identified a list
of highly sensitive

model parameters in the 2014 Risk Assessment. Data for some of these
parameters are already available through the existing groundwater
monitoring program (i.e., depth to groundwater, hydraulic gradient).
Data for others will be collected for the two lines of evidence
required by this rulemaking (i.e., infiltration rate, hydraulic
conductivity). EPA did not propose to require the remaining parameters
to be collected on a site-specific basis (i.e., leachate concentration,
sorption coefficients) because a national-scale record of these
parameters already exists for the constituents modeled in the 2014 Risk
Assessment. To avoid the need for entirely new, site-specific risk
assessments that evaluate impacts to both groundwater and surface
water, facilities will need to consider the same high-end leachate
concentrations that the clay-lined units were found unable to contain
in order to demonstrate that the alternate liner performs materially
better. Therefore, EPA is requiring that the owner or operator draw
from the existing risk record to characterize leachate chemistry and
behavior in the demonstration. Use of these data will help mitigate any
uncertainties about the representativeness of the sampled ash or how
conditions might change in the future. Altogether, this will ensure
confidence that GWPS will not be exceeded.
    EPA is finalizing a requirement at Sec.  257.71(d)(1)(ii)(C) that
facilities must incorporate the site-specific data collected for the
two lines of evidence, characterization of site hydrogeology and
potential for infiltration, into a mathematical model used to calculate
the potential groundwater concentrations that may result in
downgradient wells as a result of the impoundment. EPA is amending the
proposed regulatory text to incorporate greater specificity based on
the discussion in the preamble to the proposed rule. Accordingly, the
final regulation specifies that facilities must also, where available,
incorporate the national-scale data on constituent concentrations and
behavior provided by the existing risk record. Where an existing record
is not available, the owner or operator must justify how the data used
are adequate to reflect high-end concentrations and behavior at the
site. The regulation also specifies that application of the model must
account for the full range of current and potential future conditions
at and around the site to ensure that high-end groundwater
concentrations have been effectively characterized. All of the data and
assumptions incorporated into the model must be documented and
justified.
a. Specific Models Used
    EPA discussed in the proposal that the model used may vary based on
the complexity of a particular site. More complex sites may merit the
use of a probabilistic fate and transport model similar to that used in
the 2014 Risk Assessment. If a site is less complex (e.g., homogenous,
low-conductivity soil), then more deterministic calculations may be
sufficient to demonstrate that no adverse effects will occur.
Regardless of the approach used, all of the data incorporated into the
calculations must be documented and justified.
    One commenter expressed concerns that the EPA Composite Model for
Leachate Migration with Transformation Products (EPACMTP) is not able
to fully represent the complexities of site conditions and so should
not be allowed as the basis for decisions about future unit
performance. EPACMTP was previously used by the Agency in the 2014 Risk
Assessment and later by EPRI in a white paper submitted to EPA to show
that some unlined surface impoundments can also be protective. This
commenter raised two specific concerns about EPACMTP. First, that the
model treats the subsurface environment as homogenous and so is not
able to reflect variable hydraulic conductivity in any individual model
run. Second, that the model cannot account for constituent mass sinks
beyond the unit, such as discharge of groundwater to water bodies.
    The Agency agrees that there can be instances where EPACMTP is not
the model best suited to represent the complexities of a particular
site. EPA discussed one such example in a memorandum included in the
docket for the proposed rule.\25\ Based on these considerations, EPA
did not propose to require use of EPACMTP or any other specific model
in a demonstration. However, this does not mean that use of EPACMTP is
never appropriate. EPA was cognizant of the limitations of the model
when preparing the 2014 Risk Assessment and took steps to ensure that
risks were neither underestimated nor overestimated. To address
heterogeneity in the subsurface, EPA conducted a probabilistic analysis
that varied the hydraulic conductivity based on the range of soil types
identified around a facility. To address losses to nearby water bodies,
EPA applied a post-processing module to subtract out the intercepted
mass. This shows that how a model is applied can be just as important
as the model design. Appropriate use of a model will help reduce
uncertainties to a degree that allows decisions to be made with the
necessary level of confidence.
---------------------------------------------------------------------------

    \25\ U.S. EPA. 2020. ``Review of Analyses in EPRI White Paper:
Model Evaluation of Relative Performance of Alternative Liners.''
Prepared by the Office of Land and Emergency Management. February.
---------------------------------------------------------------------------

    To ensure that a model is applied appropriately, it is critical to
understand all the assumptions built into that model. All models
include some degree of simplification compared to the real world so
that calculations are both feasible and manageable. More simplistic
models may provide less precise results, but that does not mean these
results are inadequate. Whether a model is appropriate is more often
determined by how it is applied to support decision-making. The goal of
modeling in the demonstration step is to provide confidence that peak
groundwater concentrations that may result from releases throughout the
active life of the impoundment will not exceed GWPS at the waste
boundary. In this context, simplifying assumptions that will tend to
overestimate the magnitude of contaminant release and transport can
actually provide greater confidence in the conclusions of the
demonstration.
    Therefore, based on the comments received, EPA is finalizing an
additional requirement at Sec.  257.71(d)(1)(ii)(C)(1) that the models
relied upon must be well-established and validated, with background
documentation that can be made available for public review. Proprietary
models that operate in a black box will not be considered appropriate
for use in a demonstration.
b. Use of Groundwater Protection Standards
    EPA discussed in the proposal that as part of the demonstration,
the owner or operator must demonstrate that the surface impoundment has
not and will not result in groundwater concentrations above relevant
GWPS at the waste boundary (health-based or background, whichever is
higher). EPA stated that this is the standard used to trigger
corrective action for lined surface impoundments and it is considered
equally appropriate in this context.
    Several commenters raised concerns about the use of GWPS as the
basis to determine that an impoundment is protective. One commenter
alleged that facilities were allowed to set their own GWPS. Another
commenter stated that EPA had not provided justification why the
standard used to determine that lined surface impoundments must
initiate corrective action is equally

appropriate to use in the approval of alternate liners.
    EPA believes that use of GWPS is appropriate and protective. GWPS
are set as either specific regulatory standards identified in the CCR
regulations or background groundwater concentrations, whichever is
higher. Facilities are not granted discretion to establish alternate
values. These standards are deemed to be protective and used in a
number of regulatory programs within the Agency. EPA also considers
them to be sufficient to demonstrate if the long-term performance of an
alternate lined CCR impoundment can be protective because these
standards align with those previously used to determine that composite-
lined units are protective.
    The 2014 Risk Assessment evaluated the risks associated with
releases from CCR surface impoundments. As discussed previously, the
only risks identified for clay-lined units in this risk assessment were
the result of human ingestion of lithium in groundwater up to a mile
away from the waste boundary. Lithium is one of the most mobile CCR
constituents. If the engineered liner and/or naturally occurring soil
of the alternate liner has an effective hydraulic conductivity
sufficient to eliminate the risks associated with high-end lithium
concentrations previously considered in the 2014 Risk Assessment, then
there is confidence that the alternate liner will also prevent risks to
both groundwater or surface water from the remaining constituents.
Requiring the impoundment to meet the health-based GWPS for lithium at
the waste boundary, where concentrations are highest, will only further
limit the potential magnitude of releases from the alternate liner.
    Therefore, EPA is adopting a revised provision in the final rule
that will better align the ALD requirements with the existing risk
record and with the statutory standard in RCRA Sec.  4004(a). EPA is
finalizing an additional requirement at Sec.  257.71(d)(1)(ii)(C)(2)
that facilities must demonstrate that there is no reasonable
probability that the peak groundwater concentrations that may result
from releases that occur over the active life of the unit will exceed
GWPS at the waste boundary.
c. Consideration of Background Groundwater Concentrations
    EPA did not explicitly discuss consideration of existing background
groundwater concentrations in the proposal but noted that it is a key
factor when establishing GWPS at a particular site. It follows that
background is also a factor when determining if these standards have
been exceeded. Naturally occurring background concentrations are
typically much lower than promulgated GWPS, but have been found to
exceed these standards in some places. Even when contributions from the
impoundment are small, the addition of these releases to high existing
background concentration may still trigger corrective action. Because a
characterization of background is available on a site-specific basis
and an ALD is required to show that the peak groundwater concentration
that may result from releases over the active life of the impoundment
will not exceed GWPS, existing background concentrations are a relevant
consideration for all constituents. Consideration of existing
background concentrations will only further limit the potential
magnitude of any releases from the alternate liner.
    EPA is finalizing a new provision at Sec.  257.71(d)(1)(ii)(C)(3)
that documentation of the model outputs must include the peak
groundwater concentrations modeled for all Appendix IV constituents
attributed to the impoundment both in isolation and in addition to
background. This will provide an understanding of both the increase in
concentration attributed to releases from the surface impoundment and
the overall likelihood for an exceedance of GWPS.
d. Risk From Other Constituents
    Some commenters stated that units with ALDs should be forced to
close after an SSI over background of any Appendix III constituent.
Under this approach, any increase in concentrations distinguishable
from background would trigger closure, regardless of the magnitude.
Commenters expressed concern that reliance on Appendix IV constituents
would not adequately protect against risks from the release of Appendix
III constituents, such as boron and sulfate.
    EPA disagrees with these commenters. As discussed previously, EPA
distinguishes between the situation prior to the time EPA has
determined that the unit meets the requirements of the ALD and after
EPA has determined that the unit meets the requirements. In the former
case EPA must assume that the unit does not have the low hydraulic
conductivity necessary to ensure the GWPS will never be exceeded; as a
consequence, EPA is requiring the unit to remain in detection
monitoring throughout the application process. By contrast, the record
is very different with respect to a unit that has been approved for an
ALD. In this case the site characteristics can support the additional
time needed to determine the appropriate actions to address all the
potential risks at that particular site. In addition, the Appendix III
list is not intended to identify risk. These constituents and water
quality parameters are intended to indicate that the overall
groundwater chemistry has shifted, which may be the result of a release
from the unit. Some additional constituents that were evaluated in the
risk assessment, such as boron and fluoride, were selected because the
higher mobility in the subsurface makes them ideal early indicators.
EPA did not identify any risks for these constituents from clay-lined
units. Therefore, a unit with an ALD that has been found to perform
better than the modeled clay-lined units will also pose no concern for
these constituents. Sulfate was not modeled in the risk assessment
because EPA did not identify any health benchmarks derived in a manner
consistent with the OLEM hierarchy for human health toxicity values or
relevant ecological benchmarks. Nor did EPA receive any comments on the
risk assessment identifying relevant benchmarks that the Agency had
omitted. The review of the literature conducted in support of the
advisory level identified some potential for laxative effects from
elevated sulfate levels, though these effects were not observed for
longer-term exposures as individuals appeared to adapt over time. EPA
concluded that available data did not permit a full dose-response
assessment for sulfate in water and ultimately set an advisory level
lower than associated with short-term effects reported by any
individual study.\26\ The World Health Organization subsequently
reached a similar conclusion, stating that ``the existing data do not
identify a level of sulfate in drinking-water that is likely to cause
adverse human health effects.\27\'' Some organizations have chosen to
compare this advisory level to monitoring well data reported by
facilities to estimate risk.\28\ Even if this were an appropriate use
of this advisory level, the report shows that sulfate levels above the
advisory level occur concurrently with exceedances of GWPS and do not

outpace the magnitude of these exceedances. This is expected because
several Appendix IV constituents can be associated with sulfate in the
ash. There is no indication that the hypothetical risks from sulfate
raised by the commenter would not be addressed by the requirements of
this rule. Therefore, EPA maintains use of Appendix IV constituents as
the basis for the alternate liner demonstration. However, as discussed
in Unit IV.D.5.b of this preamble, detection of an SSI of Appendix III
constituents will trigger additional measures designed to ensure that
levels of Appendix IV constituents are never detected at SSLs. As
discussed in Unit IV.D.5.b of this preamble, detection of an SSI of
Appendix III parameters will trigger additional measures designed to
ensure that an SSL of Appendix IV constituents do not occur.
---------------------------------------------------------------------------

    \26\ U.S. EPA. 2003. ``Drinking Water Advisory: Consumer
Acceptability Advice and Health Effects Analysis on Sulfate.'' EPA
822-R-03-007. Office of Water. February.
    \27\ World Health Organization. 2004. ``Sulfate in Drinking-
Water: Background Document for the Development of WHO Guidelines for
Drinking-Water Quality.'' WHO/SDE/WSH/03.04/114.
    \28\ Environmental Integrity Project. 2019. ``Coal's Poisonous
Legacy: Groundwater Contaminated by Coal Ash Across the U.S.''
---------------------------------------------------------------------------

D. Procedures for Approval and Denial of Alternate Liner Demonstration

    As mentioned previously, EPA proposed a two-step process first
requiring the submittal of an application, and then, if the application
is approved a demonstration. EPA also proposed regulations to govern
the procedures for the review of and public comment on those documents.
These elements of the proposal are discussed below.
1. Application Process
a. Deadline of Application Submission
    EPA proposed at Sec.  257.71(d)(2)(i) that the initial applications
were due no later than thirty days after the effective date of the
final rule. Industry commenters requested additional time to prepare
and submit the application, as well as the ability to provide follow-up
information beyond the deadline if EPA finds some aspect of the
documentation to be inadequate. Commenters worried generally that a
fixed deadline of 30 days would provide little time to prepare an
application, and in particular that any time spent waiting for input
from EPA would further limit the time remaining to make any necessary
updates. Commenters stated that given the significance of this step,
EPA must provide facilities with adequate time to assemble this
critical preliminary information, which may require the assistance of
third-party engineering firms. They further stated that facilities
should not be rushed to prepare this information, which, if determined
to be insufficient, will disqualify a facility from being able to seek
an alternate liner demonstration and subject the unit to closure. EPA
received comments requesting the ability to meet with EPA before
submitting their application. Additionally, industry commenters were
also concerned about the initial application deadline as it related to
the proposed deadline of August 31, 2020 to cease receipt of waste, as
well as the deadlines for submission of requests to obtain alternative
compliance deadlines in 84 FR 65941 (December 2, 2019) (``Part A
Proposed Rule'').
    EPA agrees with commenters that the proposed thirty-day deadline
and the proposed date to cease receipt of waste could have made
implementation difficult. In response to the comments, EPA is extending
the timeframe available for facilities to submit the initial
application. EPA believes that submittal by November 30, 2020, is
appropriate for facilities to prepare and submit the application. This
is the same date by which facilities will be required to submit
requests for extensions pursuant to Sec.  257.103(f), and in the
interest of simplifying the regulations it makes sense to coordinate
the dates. This will provide sufficient time for facilities to become
familiar with requirements of this rule and collect the information
needed for the initial application. It is worth noting in this respect
that EPA is not requiring the generation of new data or additional
sampling to support the initial application. The additional time will
also provide the Agency the ability to engage in a limited amount of
discussion with a facility before the application submission deadline.
Such discussions would need to occur before the deadline for final
submission of the application. In regard to the deadline to cease
receipt of waste, the Part A final rule established a deadline of April
11, 2021, for those units that are closing pursuant to Sec.
257.101(a)(1) or Sec.  257.101(b)(1)(i). This alleviates the concern
that an owner or operator would not have sufficient time to submit an
application before the deadline to cease receipt of waste.
    EPA also received comments in support of allowing the Participating
State Director (i.e. the State Director of a State with an approved CCR
State Permit Program in accordance with RCRA section 4005(d)) to review
and approve alternate liner demonstrations. The commenters said states
often have resources and expertise to evaluate applications and the
associated technical documents necessary in order to approve alternate
liner demonstrations. The Agency agrees that a Participating State
Director should have the ability to review and approve an ALD, and
therefore finalized provisions in Sec.  257.71(d) to allow that to
occur.
    Therefore, EPA is finalizing at Sec.  257.71(d)(2)(i) that the
owner or operator of the CCR surface impoundment must submit the
application to EPA or the Participating State Director by November 30,
2020. This date is consistent with the date in the Part A final rule to
submit an alternative closure demonstration.
b. Application Review
    EPA proposed at Sec.  257.71(d)(2)(ii) that EPA or the
Participating State Director will evaluate the application and may
request additional information as necessary to complete its review. If
the application was complete it would toll the facility's deadline to
cease receipt of waste for that surface impoundment until issuance of a
final decision on the surface impoundment's eligibility. However, EPA
proposed that incomplete submissions would not toll the deadline. EPA
proposed that within sixty days of receiving the application, EPA or
the Participating State Director would notify the owner or operator of
its determination on the eligibility of their surface impoundment, and
finally, that the facility must post the determination to its publicly
accessible CCR internet site. EPA stated in the proposed rule that if
the Agency or Participating State Director determines the application
is lacking necessary information or specificity, the facility may have
an opportunity to resubmit with the required information, provided it
was submitted before the deadline for all initial applications (i.e.,
30 days after the effective date of the final rule). However, no
resubmissions could be accepted after this deadline.
    Many industry commenters requested clarification as to what
information is required to constitute a complete application. Other
commenters requested that EPA provide a separate certification process
through PE certification, development of a checklist, or other means
that could be used to confirm an application is ``complete'' before
submittal. Commenters stated that a ``complete'' application consists
of all the information necessary to trigger tolling of the facility's
deadline to cease receipt of waste into that unit until a final
decision on the unit's eligibility is issued. Commenters contrasted
this with a ``sufficient'' application, which would allow a facility to
proceed to the demonstration step. Because of the relatively short
timeline provided to submit an application in the proposal, these
commenters worried there would not be an opportunity to resubmit an

application found to be incomplete and the facility would not be
allowed to toll the deadline. One commenter said that EPA should
provide owners/operators with additional time beyond the original
deadlines to make their resubmittals because an insufficient
application submittal does not mean the liner itself is insufficient,
which is the ultimate point for the alternate liner demonstrations.
    EPA is adopting procedures that largely mirror those adopted for
requests submitted pursuant to Sec.  257.103(f). Upon receiving the
application, EPA will evaluate the application to determine whether it
is complete. EPA may request additional, clarifying information to
complete its review and/or discuss the application with the facility.
Consistent with the proposed rule, submissions that EPA determines to
be incomplete will be rejected without further process, at which point
any tolling of the facility's deadline will end. (EPA anticipates that
the question of tolling for incomplete submissions should not generally
arise, as the agency anticipates making these determinations before
April 11, 2021). No commenter disagreed that this was appropriate.
Incomplete submissions include both the situation in which the
submission does not include all of the required material, and the
situation in which EPA is unable to determine from the submission
whether the facility or the unit meets the criteria for the
application. EPA does not agree with the commenter that it would be
appropriate to grant additional time to allow a facility to cure an
incomplete application; the new deadline of November 30, 2020, provides
more than a sufficient amount of time for the facility to submit a
complete application. As discussed above, if an application was deemed
incomplete, the owner or operator could attempt to cure the
deficiencies and resubmit the application provided that it can do so
before the November 30, 2020 deadline. If the application is deemed
incomplete, the owner or operator may seek an alternative closure
deadline pursuant to Sec.  257.103(f)(1) or (f)(2). For more
information on this please see Unit III.D.3.
    EPA agrees that the timeframes are ambitious but continues to
believe that they can be met. As discussed in more detail below, the
Agency has limited the issues to be resolved during this process, and,
as requested by commenters, has amended the proposed regulation to
specify in detail the information needed for a submission to be
considered complete. Consequently, EPA anticipates it will be able to
make most decisions without further requests for information. Once the
owner or operator submits the application to EPA for approval, the
owner or operator must place a copy into the facility's operating
record and on its publicly accessible CCR internet site. EPA will also
post who has submitted an application on EPA's website.
    One commenter expressed concern that utilities' alternate liner
applications would not be posted publicly prior to a proposed approval,
and the beginning of the thirty-day comment period on the alternate
liner demonstration would likely be the first time the vast majority of
the public would have the opportunity to review many of the highly
complex, technical documents that would form the basis of EPA's
decision. In response to the comment about not providing an opportunity
for public comment on the application and to be consistent with the
process established in the Part A final rule, EPA is finalizing a
requirement at Sec.  257.71(d)(2)(iii)(C) to provide for public comment
on the application by granting a twenty day public comment period.
After reviewing the submission, EPA will either post a determination
that the submission is incomplete on EPA's website or a proposed
decision to grant or to deny the request in the docket on
www.regulations.gov for public notice and comment. EPA will also post
the application on its website. EPA will allow for a 20-day public
comment period. EPA will evaluate the comments received and amend its
final decision as warranted. EPA will post all decisions on its
website, in the relevant docket and notify the facility. EPA will make
best efforts to complete the application review within sixty days of
receiving the complete application.
    Some commenters raised the argument that because part 257 is self-
implementing and because certain regulatory provisions might be viewed
as ambiguous, there could be differences in opinion on what constitutes
compliance. These commenters felt that differences in interpretation
should be discussed during EPA's review process and corrected as
warranted as part of a facility's completion of its demonstration.
    EPA is establishing an expedited process to resolve requests for
continued operation under Sec.  257.71(d); in order to meet these time
frames EPA has limited the issues to be resolved in this proceeding.
One of the primary issues to be resolved will be whether the facility
is in compliance with the regulations. Although EPA does not agree that
the regulations are ambiguous, EPA may be able to engage in a limited
amount of discussion with a facility before the submission deadline. In
addition, as explained previously, documentation that a facility
remains in compliance with the requirements of part 257 subpart D
provides critical support for a decision to allow continued operation
of the unlined surface impoundment. This means that EPA must be able to
affirmatively conclude that the facility meets this criterion prior to
authorizing any continued operation of the unlined surface impoundment.
As a consequence, any opportunity to correct the demonstration is
limited to the period before the deadline for submission.
    Finally, note that any determinations made in evaluating the
compliance aspects of submitted applications will be made solely for
the purpose of determining whether to grant an initial application. In
making these determinations the Agency generally expects to consider
and rely on the information in a submission, information contained in
submitted comments to a proposed decision, and any other information
the Agency has at the time of the determination. These determinations
may not be applicable or relevant in any other context. Should the
facility's compliance status be considered outside of this context in
the future, the Agency may reach a contrary conclusion based, for
example, on new information or information that was not considered as
part of this process.
    EPA is revising the regulatory text (now found at Sec.
257.71(d)(2)(iii)) for the application review to more clearly reflect
the circumstances under which a facility's deadline to cease receipt of
waste will be tolled. Consistent with the recently promulgated
regulations in Sec.  257.103, the regulations provide that the deadline
to cease receipt of waste will be tolled by the submission of an
application until EPA determines the application is incomplete or the
application is denied. As previously discussed, because EPA anticipates
making determinations on the initial application before the April 11,
2021 deadline, issues of tolling should not arise for incomplete or
denied applications. If EPA approves an application, the deadline to
cease receipt of waste will continue to be tolled until EPA determines
the demonstration is incomplete or issues the final disposition on the
merits of the demonstration. The language in this section will still
state that within sixty days of receiving a complete application, EPA
or the Participating State Director will notify the owner or operator
of its determination on the

eligibility of their surface impoundment. This section will also
require that the facility must also post EPA's determination to its
publicly accessible CCR internet site. Finally, this section states
that the application will be available for public comment on EPA's
docket for 20 days. EPA will evaluate comments as part of the review.
EPA or the Participating State Director will post the decision on the
application on their website and will add it to the docket.
c. Application Denial
    EPA proposed at Sec.  257.71(d)(2)(vi) that if EPA or the
Participating State Director determines that the unit is not eligible
for an ALD, the owner or operator must cease receipt of waste and
initiate closure within six months of the denial or by the deadline in
Sec.  257.101(a), whichever is later. If a facility needed to obtain
alternative capacity, they could do so in accordance with the
procedures in Sec.  257.103.
    Commenters requested clarification on how the timing of a denial
would work with the deadlines applicable to units closing under Sec.
257.101(a) and 257.101(b)(1)(i). EPA is revising its proposal to better
account for coordination with the recently promulgated final deadlines
and procedures associated with these surface impoundments. As
previously discussed, EPA intends to issue a final decision within
sixty days of submission of a complete application. Therefore, if the
application was received on November 30, 2020, EPA would make best
efforts to issue the denial by February 1, 2021 which is two months
before the April 11, 2021 deadline by which these units are required to
cease receipt of waste. Under the newly promulgated regulations the
surface impoundment must either cease receipt of waste no later than
April 11, 2021 or the owner or operator may apply for an alternative
closure deadline in accordance with Sec.  257.103(f)(1) or (f)(2).
Under the procedures associated with Sec.  257.103(f) facilities will
have four months to submit an application. EPA is therefore granting
facilities that need to submit an application to continue to operate
the unit pursuant to Sec.  257.103 four months from the date of denial
to submit their application. All other facilities must cease receipt of
waste--either by the April 11, 2021 deadline (assuming EPA has issued
its decision prior to the deadline) or by the revised deadline which
will be included in the denial. This revised deadline will account for
the amount of time EPA has taken to issue its decision. EPA has no
basis to universally authorize the surface impoundment to continue
operating for an additional six months in these circumstances. Those
units that can close by the deadline must do so (e.g. because they have
alternative capacity on site) or the facility must be treated the same
as any other facility seeking an extension pursuant to Sec.
257.103(f). Further discussion of the relationship of the timing of an
application denial and the alternative closure standards is found in
Unit III.D.3 below.
    Therefore, EPA is revising Sec.  257.71(d)(2)(vi) to remove the
provision requiring the facility to initiate closure ``within six
months of the denial.''
d. Multi-Unit Liner Demonstration
    The 2015 CCR Rule allowed monitoring networks for CCR units to be
designed with consideration of multi-unit systems (i.e., multiple
surface impoundments at one site) that share groundwater monitoring
systems and other technical features. EPA made no reference to multi-
unit systems in the proposed rule. Multiple commenters requested
clarification on how ALD requirements would apply to these multi-unit
systems. Specifically, commenters inquired whether facilities with
multiple units can submit a single application and demonstration that
covers all the units, or if documentation for each individual unit must
be submitted separately.
    Given that decisions about the design and implementation of these
groundwater monitoring programs and such sites were made based on
consideration of multiple units, EPA considers it to be reasonable that
the ALD documentation could also include multiple units to reduce
redundancy and ensure that each individual unit is discussed in the
full context of the larger system. Further, given that these units are
located in close proximity, the data generated for one is likely to be
equally applicable to multiple units in the demonstration. For example,
grouping data from wells around adjacent units will provide a more
comprehensive picture of groundwater depth and flow around the wider
facility. Therefore, EPA is amending the rule to make clear that a
single application and demonstration may be submitted for multi-unit
systems.
2. Demonstration Process
a. Deadline of Demonstration Submission
    EPA proposed at Sec.  257.71(d)(2)(i) that the facility would have
one year from the date the application was due (i.e., 13 months from
the effective date of the final rule) to submit their alternate liner
demonstration if EPA approved their application. The proposal also
stated that if the owner or operator cannot meet this deadline due to
analytical limitations related to the measurement of hydraulic
conductivity, the owner or operator must submit a request for an
extension no later than 90 days prior to the deadline for submission of
the demonstration, that includes a summary of the data collected to
date that show the progress towards relevant test termination criteria
for all samples responsible for the delay, along with an alternate
timeline for completion that has been certified by the laboratory.
    One commenter stated that one year would not provide the amount of
time needed to perform the robust analyses needed to provide greater
certainty that the unit would pose no reasonable probability of adverse
effects to human health or the environment. The commenter also stated
that some of that one year would be spent waiting for a determination
from EPA that the unit is eligible for an ALD. The commenter stated
that this gave the facility only 10 months to prepare the ALD if they
waited until their application was approved, and that would not be
sufficient if they needed to install additional groundwater monitoring
wells, validate fate and transport models, develop three-dimensional
visualization to support conceptual site models, or establish
background water quality to evaluate the potential effects for
seasonality in the groundwater quality observations.
    EPA does not agree with the commenter. First, a facility should not
wait for application approval to start their demonstration work.
Second, EPA is not requiring a facility to install additional
monitoring wells or further characterize background water quality to
support the demonstration. Facilities were required to have installed
an appropriate number of monitoring wells and to adequately
characterize background water quality to evaluate the potential effects
for seasonality years ago under part 257. EPA is not granting
additional time as part of this process for facilities to come into
compliance with existing requirements. Finally, while three-dimensional
visualization may be useful for EPA's review, it is not a requirement.
Therefore, the Agency is not revising the amount of time given to
develop the demonstration package.
    EPA is finalizing Sec.  257.71(d)(2)(i) to require facilities to
have one year from the date the application was due to submit their
alternate liner demonstration. Therefore,

demonstrations are due no later than November 30, 2021. Once the owner
or operator submits the demonstration to EPA for approval, the owner or
operator must place a copy into the facility's operating record and on
its publicly accessible CCR internet site.
    As mentioned above, EPA also proposed to allow extensions on the
demonstration submittal deadline in the limited circumstance that it is
not feasible for the lab to fully analyze the field samples by the
demonstration deadline. EPA proposed that the request must be submitted
no later than 90 days prior to the demonstration deadline. The proposal
further stated that EPA or a Participating State Director would
evaluate the information provided in the request and determine whether
the duration of the requested extension is acceptable. EPA did not
receive any comments that indicated the type of delay considered in the
preamble was unreasonable or entirely avoidable. Some facilities
requested additional information on the maximum duration of an
extension, what information the facility should provide as part of the
request, and whether extensions could be provided for any other
reasons.
(i) Extension Due to Analytical Limitations for Chemical Equilibrium
    EPA discussed in the proposal that extensions would be allowed on
the condition that analytical limitations prevent the necessary data
from being collected by the demonstration deadline. EPA specifically
pointed to the fact that tests for hydraulic conductivity may take
upwards of 300 days to complete for extremely low conductivity soils.
It is important that these tests be allowed to run to completion
because long-term changes to soil structure, such as flocculation of
clay particles, can substantially alter the conductivity of the soil.
    One commenter raised concerns that hydraulic conductivity tests for
low permeability soils may take longer than the timeframe allotted for
the demonstration but made no reference to the deadline extension
discussed in the preamble. Another commenter requested clarification on
the duration of an extension and what information should be provided as
part of the request.
    As acknowledged in the proposal, EPA understands that the test
methods for hydraulic conductivity may take a considerable amount of
time. EPA continues to believe it is critical that these tests are
allowed to run to completion to ensure that effects of leachate
chemistry on the liner integrity are identified. Therefore, EPA will
allow a one-time extension on the deadline for submittal of the
demonstration for analytical limitations associated with completing the
hydraulic conductivity test. The duration of the extension will be
determined solely by the time projected by the lab to achieve
termination criteria for chemical equilibrium. These metrics will
progress along either a linear or asymptotic curve as the composition
of the effluent approaches that of the influent. Thus, it is
reasonable, based on these curves and the rate of flow for the lab to
estimate how long it will take to approach and maintain conditions for
test termination for the necessary duration. EPA expects facilities
that receive this extension will use this additional time to prepare
all other necessary documentation so that, once the data is available,
it will be a relatively straightforward task to run the model and
document the results. Once the owner or operator receives the data,
they will have 45 days beyond the timeframe certified by the laboratory
for the facility to submit the completed demonstration.
    In response to comments, EPA is finalizing amendments to clarify
that, as part of the extension request, facilities must provide (1) a
brief timeline of fieldwork to confirm that samples were collected
expeditiously, (2) a chain of custody documenting when samples were
sent to the laboratory, (3) written certification from the lab
identifying how long it is projected for the necessary termination
criteria to be met, and (4) documentation of the progression towards
all termination metrics to date.
(ii) Other Analytical Limitations
    One commenter requested clarification on what other types of
analytical limitations EPA would be considered eligible for extension.
However, the commenter did not provide a specific example of another
type of analytical limitation that might warrant a similar extension.
    It is possible that chemical interactions between the soil and
leachate may cause the measured hydraulic conductivity to shift
abruptly and substantially due to resulting changes in the soil
structure. This shift may be substantial enough that it will take
longer for the hydraulic conductivity to stabilize than it will for the
chemistry of the system to reach equilibrium. This scenario may occur
regardless of whether an extension has been provided to allow system
chemistry to reach equilibrium. Yet, unlike chemical equilibrium
between the influent and effluent, there is no predefined endpoint for
hydraulic conductivity. As a result, there are no reasonable means to
predict how much longer it will take for this parameter to fully
stabilize. However, it is expected that the bulk of any changes to soil
structure and hydraulic conductivity will have occurred by the time
that the chemistry of the system has achieved equilibrium. This is
because the primary driver of these changes, the exchange of ions
between the soil and the leachate, is mostly complete. For this reason,
EPA believes that the magnitude of any changes to hydraulic
conductivity recorded by the time chemical equilibrium has been
established can provide a reasonable upper bound on any future changes.
Thus, rather than provide an unspecifiable amount of additional time to
allow the hydraulic conductivity to fully stabilize, EPA concludes it
is preferable in this case that the owner or operator complete the
demonstration within the existing deadline with the available data. Use
of appropriate bounds of uncertainty based on the magnitude of changes
to hydraulic conductivity measured to date can ensure that long-term
contaminant transport is not underestimated.
    Therefore, EPA is finalizing amendments to the proposal to clarify
that, if the measured hydraulic conductivity has not stabilized to
within acceptable tolerance limits by the time the termination criteria
for solution chemistry are met, the owner or operator must submit a
preliminary demonstration within the existing deadline (with or without
the one-time extension for analytical limitations). In this preliminary
demonstration, the owner or operator must justify how the bounds of
uncertainty applied to the available measurements of hydraulic
conductivity ensure that the final value is not underestimated. The
preliminary demonstration will be subject to all of the same process,
notification and posting requirements of a final demonstration. EPA
will review the preliminary demonstration to determine if it is
complete and will propose to deny or to tentatively approve the
demonstration. Once the final laboratory results are available, the
owner or operator must submit a final demonstration that incorporates
the finalized hydraulic conductivity data to confirm that the model
results in the preliminary demonstration are accurate. Until the time
that EPA takes final action on this final demonstration, the surface
impoundment must stay in detection monitoring to remain eligible for an
ALD. If EPA tentatively approved the preliminary demonstration, EPA
will then take action on the newly

submitted final demonstration using the same procedures that apply to
the initial determination. The public will have an opportunity to
comment only on the new information presented in the complete final
demonstration or in EPA's proposed decision on the revised
demonstration.
(iii) Extension Request Deadline
    EPA proposed that facilities must submit a request for an extension
no later than 90 days before the deadline for submission of the
demonstration. One commenter requested additional time to submit the
request, stating that unforeseen issues might arise late in the
demonstration process that necessitate an extension. The commenter did
not elaborate on the types of delays that may occur so late in the
process. In order to complete the demonstration on time, EPA expects
facilities to collect the necessary field data expeditiously and long
before the extension request deadline. The facility should be aware of
and be able to plan for any complications associated with sample
collection. Once data have been collected from the field and analyzed,
the remaining modeling and documentation can be completed in the office
where the risk of unavoidable delay is minimal. Indeed, much of the
necessary documentation can be compiled concurrently with sample
collection and analysis. EPA is maintaining the submission deadline for
extension requests that the owner or operator of the CCR surface
impoundment must submit the extension request no later than September
1, 2021. The owner or operator must also post this extension request on
their publicly accessible CCR internet site.
b. Demonstration Review
    EPA proposed at Sec.  257.71(d)(2)(iii) that EPA or the
Participating State Director will evaluate the demonstration package
and may request additional information as necessary to complete its
review. Submission of a complete demonstration package will continue to
toll the facility's deadline to cease receipt of waste into that unit
until issuance of a final decision under Sec.  257.71(d)(2)(v).
Incomplete submissions will cease tolling the facility's deadline. EPA
also proposed at Sec.  257.71(d)(2)(iv) that EPA or the Participating
State Director will propose a decision on the demonstration and post
that decision on EPA or Participating State Director's website for a
30-day public comment period. Finally, EPA proposed at Sec.
257.71(d)(2)(v) that after consideration of the comments, EPA or the
Participating State Director will make a final decision within four
months of receiving the complete alternate liner demonstration and that
if no substantive comments were received the decision would become
automatically effective 5 days from the close of the comment. The
facility must also post EPA's determination on its ALD to its publicly
accessible CCR internet site.
    Commenters pointed out that there appeared to be an unintended gap
in tolling. The proposed regulatory text indicated that the deadline to
cease receipt of waste would not be tolled during the period between
approval of the initial application and the time the alternate liner
demonstration package was submitted. That was not the Agency's intent.
EPA intended that the deadline would be tolled during the entire time
between an approved application and the final determination on the ALD.
Accordingly, the regulatory text has been amended to make this clear.
    EPA also received comments that the 30-day public comment period
was too short to allow for sufficient opportunity for members of the
public to review and comment on such highly complex, technical
documents. EPA acknowledges that the public comment period is short but
disagrees that it is too short to be meaningful. EPA is requiring
facilities to post all submissions on their publicly accessible CCR
internet site at the same time they submit them to EPA. The public can
start their review at the same time as EPA and begin to gather
information and prepare their comments. For similar reasons, EPA also
disagrees that a 30-day comment period violates either the
Administrative Procedures Act (APA) or RCRA 7004(b). This process is
not a rulemaking, but an informal adjudication. Such adjudications do
not typically include an opportunity for public comment and therefore
the provision of a 30-day comment period meets the mandate in RCRA
Sec.  7004(b) to promote public participation. Moreover, the APA
imposes neither a requirement to provide an opportunity for public
comment nor any minimum time for a comment period for such procedures.
Finally, EPA notes that the same commenters requesting longer comment
periods have also raised concern that the process grants facilities too
much additional time to continue operating. EPA is also interested in
not granting undue amounts of additional time for facilities to
continue operating and is expediting all aspects of this process,
including the comment period. After reviewing the submission, EPA will
post a proposed decision to grant or to deny the demonstration in the
docket on www.regulations.gov for public notice and comment. EPA will
also post the demonstration on its website.
    One commenter stated that the regulations do not give the reviewing
agency a deadline for approving or disapproving a submitted
demonstration, so that such a demonstration can remain pending
indefinitely. The Agency disagrees with that comment and is finalizing
as proposed Sec.  257.71(d)(2)(v) which states that EPA will evaluate
the comments received and amend its decision as warranted within four
months. EPA will post all final decisions on EPA's website and in the
appropriate docket. The facility must post, along with a copy of its
demonstration, the Agency's final decision on the facility's publicly
accessible CCR internet site.
    Finally, EPA is not finalizing the automatic five-day effective
date for demonstrations with no substantive comments since this
approach would be too difficult to implement.
c. Demonstration Denial
    EPA proposed at Sec.  257.71(d)(2)(vi) that if EPA or the
Participating State Director determines that the unit's alternate liner
does not meet the standard for approval, the owner or operator must
cease receipt of waste and initiate closure within six months of the
denial. If a facility needs to obtain alternative capacity, they may do
so in accordance with the procedures in Sec.  257.103.
    Commenters were primarily concerned about the ability to pursue a
capacity extension under Sec.  257.103 if their ALD was denied.
    If an ALD is denied and the facility lacks capacity, the owner or
operator may apply for one of the site-specific alternative deadlines
Sec.  257.103(f)(1) or (f)(2) as described below. As discussed in that
section the time frames for applying for those alternatives will be
governed by Sec.  257.103(f) rather than the six months contemplated by
the proposal. By contrast, if the owner or operator chooses to not
apply for Sec.  257.103(f)(1) or (f)(2), for example, if they already
have alternative capacity to manage their waste on site, then the
surface impoundment must cease receipt of waste and initiate closure by
the date specified in EPA's decision (which will be the date EPA
determines that such actions are technically feasible).

3. Relationship to Sec.  257.103(f)(1) and (f)(2) Alternative Closure
Requirements
    In the proposal, EPA stated that should a facility pursuing an ALD
not have alternative capacity, the owner or operator must continue to
actively pursue avenues of obtaining alternative capacity during the
time they are pursuing the ALD. Commenters were concerned that this
would put the owner or operator in the position of devoting resources
to two parallel paths to seek an extension under both Sec.  257.71(d)
and under either Sec.  257.103(f)(1) or (f)(2). The Agency understands
that the facility will be required to expend resources on two parallel
tracks, but continues to believe that owners or operators that are
pursuing an ALD who lack alternative capacity in which to manage their
wastes must actively work to attain that capacity during the ALD
process. As discussed in more detail below, facilities will not be able
to obtain more than the maximum time allowed under Sec.  257.103(f); in
order to meet these deadlines, facilities will need to be pursuing
alternative capacity well before EPA would render a decision on their
ALD. To do otherwise would create incentives for facilities to apply
for an ALD as a means of obtaining additional time under Sec.
257.103(f)(1) or (f)(2). Any owners or operators that are preparing to
submit an ALD and whose facilities lack alternative capacity should
therefore also be preparing to submit a demonstration of lack of
capacity under either Sec.  257.103(f)(1) or (f)(2) in the event their
application is denied.
    The current deadline for all facilities who lack capacity and wish
to apply for the Sec.  257.103(f)(1) or (f)(2) alternative closure
requirements is November 30, 2020. That provides the owner or operator
approximately 4 months from the signature date of the Part A final rule
to submit the demonstration. Accordingly, if an application is rejected
or an ALD is denied the owner or operator will be given four months to
apply for either Sec.  257.103(f)(1) or (f)(2). The facility's deadline
to cease receipt of waste will be tolled during these four months to
allow the owner or operator to develop the Sec.  257.103(f)(1) or
(f)(2) demonstration. Thereafter, consistent with the procedures
adopted in Sec.  257.103, the deadline to cease receipt of waste will
continue to be tolled until the Agency determines whether the
submission is incomplete or reaches a final decision. As stated
earlier, the Part A final rule requires owners and operators to submit
demonstrations under the alternative closure provisions of Sec.
257.103(f)(1) or (f)(2) by November 30, 2020. To accommodate facilities
whose application or alternative liner demonstration under Sec.
257.71(d) is denied and who intend to submit a demonstration under the
alternative closure provisions, the Agency is revising Sec.
257.103(f)(3)(i)(A) and (C) to allow such demonstrations to be
submitted after the deadline of November 30, 2020. Specifically, EPA is
revising Sec.  257.103(f)(3)(i)(A) and (C) by adding the clause
``Except as provided by Sec.  257.71(d)(2)(iii)(E) and (viii),'' to
each paragraph.
    A facility may not be granted more time than the maximum that is
provided in Sec.  257.103(f)(1) or (f)(2), even if the owner or
operator is applying for the alternate closure requirements after they
are denied an ALD. Specifically, a unit that qualifies for alternate
closure dates under Sec.  257.103(f)(1) would still be required to
cease receipt of waste no later than October 15, 2023. An eligible
unlined surface impoundment granted a capacity extension must cease
receiving CCR and/or non-CCR wastestreams no later than October 15,
2024. In order to continue to operate until October 15, 2024, the owner
or operator must demonstrate that the unit meets the definition of an
eligible unlined CCR surface impoundment. Units applying for an ALD
that ultimately are granted alternate closure dates under Sec.
257.103(f)(2) would need to cease operation of their coal fired boiler
and complete closure of the surface impoundment no later than October
17, 2023 if they are 40 acres or smaller and by October 17, 2028 if
they are larger than 40 acres.
4. Recertification
    EPA discussed in the proposal that the approved demonstration will
be effective for the remaining active life of the unit since the
demonstration must show that the engineered liner and/or naturally
occurring soil is sufficient to prevent adverse effects from the
surface impoundment.
    Several facilities and industry groups affirmed that a one-time
demonstration is appropriate. Several other commenters argued that
units should be required to periodically recertify the results of the
ALD. One of these commenters cited to several studies to argue that
onsite hydrogeologic conditions can shift suddenly and affect the
performance of the liner. These commenters pointed to shifting land use
and climate change as phenomena that could impact liner performance.
The land uses envisioned by the commenter include increased agriculture
or urban development. However, the commenters provided no direct
explanation how these changes were expected to impact liner
performance.
    A study cited by this commenter noted that the climate change would
primarily impact surface water, but that there could also be impacts to
the quantity and quality of groundwater.\29\ The most likely way in
which this could impact liner performance would be a decrease in the
depth to groundwater. However, the long-term trends considered by these
and other studies are often projected out many decades into the future
and are variable across the country. Portions of the country are
projected to see a decrease in precipitation, while others are
projected to see an increase through more intense storms, which may or
may not translate to increased groundwater recharge. Similarly, the
land uses cited would only further deplete groundwater through
increased extraction for agriculture or increased runoff from more
impervious surfaces. Regardless, the 2014 Risk Assessment found that
variations in the water table height did not substantially shift high-
end risks, particularly for the most mobile constituents. Therefore,
there is no indication that shifts in the groundwater table would alter
the conclusion whether continued operation of a surface impoundment in
the near term is protective. In addition, depth to groundwater is a
parameter that is routinely measured during all phases of groundwater
monitoring and so it will be apparent without recertification if
groundwater levels are rising. Changes to the background quality of
groundwater that has no direct contact with the unit would have no
effect on whether the unit remains protective. As a result, it is not
apparent from the comments provided what would be further achieved by
requiring facilities to periodically recertify the characterization of
local hydrogeology. Therefore, EPA made no amendments to the
requirements of the rule in response to this comment.
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    \29\ Green, T.R., M. Taniguchi, H. Kooi, J.J. Gurdak, D.M.
Allen, K.M. Hiscock, H. Treidel, and A. Aureli. 2011. ``Beneath the
Surface of Global Change: Impacts of Climate Change on
Groundwater.'' Journal of Hydrology. 405:532-560.
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5. Loss of Authorization
    EPA proposed at Sec.  257.71(d)(2)(vii)(A) that authorization of an
ALD could be rescinded at any time if the facility fails to maintain
the performance standard or any other requirement of this rule. To
identify the potential for a future exceedance of GWPS, the Agency
proposed that facilities that trigger assessment monitoring would need
to

conduct intra-well analyses on each downgradient well to identify any
trends of increasing concentrations and this information would be
included as part of subsequent groundwater monitoring reports. The
proposal further stated that if there is evidence that the unit may
exceed GWPS before source control measures were put in place (e.g.,
dewatering, impermeable cap, clean closure), then the alternative liner
authorization would be reconsidered.
    EPA also proposed at Sec.  257.71(d)(2)(vii)(B) that the onus would
remain on the facility at all times to demonstrate that the unit meets
the conditions for authorization of the ALD. The proposal further
stated that EPA or the Participating State Director could, without
further notice or process, deny or revoke the owner or operator's
authorization if these conditions for qualification were no longer
being met.
    EPA received a number of comments on the proposed loss of
authorization provisions. Some industry groups and facilities requested
confirmation that an option is available to demonstrate whether
increased groundwater concentrations are attributed to a source
unrelated to the unit before authorization would be revoked. One
facility claimed that it was inappropriate to rely on groundwater
monitoring at all to determine compliance. Several environmental groups
stated that use of GWPS to determine ongoing compliance is not
protective, while several industry groups commented that use of trend
analysis was not a reliable way to determine compliance.
a. Use of Groundwater Monitoring To Determine Ongoing Compliance
    The proposed rule stated at Sec.  257.71(d)(2)(vii)(A) that if at
any time assessment monitoring pursuant to Sec.  257.95 is triggered
for the unit, the facility must conduct intra-well analyses on each
well as part of subsequent groundwater monitoring reports to identify
any trends of increasing concentrations. The proposal further explained
that if trend analysis predicts there will be an exceedance of GWPS for
any constituent, EPA or the Participating State Director would
reconsider the authorization and may revoke it if source control
measures could not be put in place while the unit continues to operate.
    In response to that provision, one commenter stated it was
inappropriate to rely on groundwater monitoring to determine whether a
unit continued to meet the standards of the ALD because groundwater
monitoring does not provide direct information about whether the
conditions of the liner or site soils have changed. Instead, this
commenter argued the rule should allow for an examination of changes to
the liner itself, or changes in the site soils, hydrology or other site
conditions evaluated in the demonstration.
    EPA disagrees that groundwater monitoring is an inappropriate
method by which to establish whether a unit remains in compliance with
this rule. Groundwater monitoring provides direct evidence of the
impoundment's impact on groundwater quality. Whether these impacts are
a result of a material change to the liner is immaterial to the fact
that those impacts have occurred. In addition, the commenter provided
no indication of what types of examinations were envisioned, how these
examinations would be triggered, how these examinations could be used
to prove a unit remains protective, and how this all would proceed
faster than groundwater monitoring. To address all of these issues, EPA
proposed the use of trend analysis to identify the potential for harm
before it would occur so that it can be addressed. Therefore, EPA
maintains the requirement to base continued authorization of an ALD on
the results of groundwater monitoring.
b. Trend Analysis
    EPA proposed at Sec.  257.71(d)(2)(vii)(A) that units with an
approved ALD that have entered into assessment monitoring (i.e., SSI of
Appendix III) must conduct additional intra-well analysis to identify
any increasing trends of Appendix IV constituents in groundwater. A
positive trend can show that contaminant levels have gotten worse
compared to earlier measurements from the same well. Understanding the
nature of the trend, including the rate of increase per unit of time,
allows estimation of how rapidly concentration levels are increasing.
If the identified trendline is steep enough to result in an exceedance
of GWPS within the timeframe required to complete closure of the unit,
the facility would have to begin implementation of source control
measures at that time.
    The final rule adopts a provision that largely tracks the proposal.
The final rule requires that if a unit with an approved ALD enters into
assessment monitoring, the facility must, in addition to their regular
groundwater monitoring, conduct additional intra-well analysis to
identify any statistically significant trend of increasing
concentrations of appendix IV constituents in groundwater. If the
identified trendline is steep enough that it would result in an
exceedance of a GWPS at any point during the active life of the unit,
the facility must close the unit.\30\ This final provision represents a
change only for those units that have a geosynthetic liner; the
proposal specified that units with only natural soil liners would be
required to close at this point, as the agency was aware of no other
effective option for source control. The Agency is expanding this
requirement to units with geosynthetic liners in response to comments
stating that the Agency lacked data to demonstrate that these liners
can be effectively repaired.
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    \30\ The comparison of a projected concentration to groundwater
standards is not a statistical test of significance because, without
measurements of future groundwater concentrations, it is predicated
on the assumption that the current trend will persist unchanged.
Nevertheless, the fact that the impoundment has entered into
assessment monitoring, there is a statistically significant trend of
increasing concentration, and the current magnitude of that trend
has the potential to result in a future exceedance of GWPS is
considered sufficient evidence that a release has occurred and there
is a reasonable probability that continued operation of the
impoundment could adversely affect groundwater.
---------------------------------------------------------------------------

    Trend analysis will require collection of multiple samples to
define whether and to what extent concentrations are changing over
time. As discussed in the following Unit, EPA is requiring that the
necessary samples be collected over the course of the following year;
however, there is minimal risk that an impoundment able to obtain an
ALD and that has no prior history of releases might trigger corrective
action so soon after entering into assessment monitoring. As discussed
previously, an SSI of Appendix III constituents is not an indication
that adverse effects have occurred or will occur. An SSI only shows
that there has been some increase in Appendix III constituents
discernable from background, regardless of the magnitude. Multiple
constituents on Appendix III were included on this list for their
mobility in the environment and so provide the best early indicators
that a release has occurred. As a result, at the time that an SSI is
first identified, it is possible that there will not have been any
associated increase in most Appendix IV constituents. This will be
confirmed by the first sample collected within the initial 90-day
window in accordance with the existing requirements in Sec.  257.95(b).
Any further increase in concentrations of Appendix IV constituents is
expected to be gradual based on the documented low conductivity of the
engineered liner and/or naturally occuring soil provided in the ALD.
The fact that many of these alternately lined units will have operated
for decades without ever leaving detection monitoring provides
additional evidence that any releases

identified in the future are indeed slow moving or small in magnitude.
It is possible for an impoundment to remain in assessment monitoring
for the remainder of its operational life without ever exceeding GWPS.
As demonstrated for composite-lined units in the 2014 Risk Assessment,
releases can occur from even the most well-designed units and these
units can remain protective for the duration of their active life.
    EPA received a number of specific comments on the application of
trend analysis. These comments and the revisions made to the proposed
rule in response are discussed in the following Units of preamble.
(i) Identification of Trends
    Commenters claimed that use of trend analysis is inconsistent and
inferior to the statistical methods already required and do not meet
the performance standards of Sec.  257.93(g). Commenters stated that
the proposal provided no guidance on how to identify trends and that
the criteria used by EPA to determine that units were noncompliant
would be subjective.
    Trend analysis serves a distinct purpose from the other statistical
methods. Methods detailed in Sec.  257.93(f) for use in assessment
monitoring are intended to identify whether groundwater concentrations
have exceeded GWPS, while trend analysis, as used in this context, is
intended to identify whether GWPS could be exceeded in the future.
Trend analysis does not substitute for monitoring data and statistical
evaluations already required by the rule. Trend tests are robust
statistical methods and have previously been applied by the Agency both
to provide evidence of plume migration and the need to expand the
monitoring well network. EPA has previously developed guidance and
tools to aid in applying trend analysis.\31\ \32\ Statistical
identification of a positive trend involves testing the estimated slope
coefficient from the regression trend line. Identification of a pattern
of increase within the sampling record provides a reliable method to
determine that concentrations have risen more than expected by chance
alone. Once the trend is calculated, confidence limits around the trend
line should be calculated to account for variability within the
dataset. The upper 95th percentile confidence limit on the trend line
must be used to ensure potential increases have not been
underestimated. Use of the upper percentile is considered appropriate
here because the goal is to prevent the impoundment entering into
corrective action in the future. Waiting for the corresponding lower
confidence limit to exceed GWPS to take action would provide greater
certainty that an exceedance will occur by a certain time, but it would
also make it far more likely that an exceedance could occur before
then.
---------------------------------------------------------------------------

    \31\ U.S. EPA. 2009. ``Statistical Analysis of Groundwater
Monitoring Data at RCRA Facilities Unified Guidance.'' EPA 530-R-09-
007. Prepared by the Office of Solid Waste and Emergency Response.
Washington, DC. March.
    \32\ U.S. EPA. 2018. ``Groundwater Statistics Tool User's
Guide.'' Prepared by the Office of Solid Waste and Emergency
Response. Washington, DC. September.
---------------------------------------------------------------------------

    The final rule also includes a minimum sampling frequency to ensure
that the number of samples collected is consistent with the data
requirements in Sec.  257.93(e). Four independent samples is generally
considered the minimum number necessary to conduct meaningful
statistical analysis on a trend. The first of these samples must be
collected within 90 days of triggering assessment monitoring in
accordance with Sec.  257.95(b). The remaining three must be collected
on a quarterly basis within a year of triggering assessment monitoring.
After establishing this baseline from the initial sampling events, the
subsequent monitoring frequency will be established in accordance with
Sec.  257.95(d). The trend analysis must be updated after each sampling
event.
    There will always be some degree of uncertainty associated with
extrapolation of measured data into the future, with uncertainty
increasing the further the trend is projected into the future. There is
potential that reliance on trends can overestimate the potential of
future exceedances. For example, it is possible that linearly
increasing concentrations may eventually plateau at some level below
GWPS. However, asymptotic conditions occur gradually and during that
time concentrations continue to increase, albeit at a slower rate.
Therefore, a decline in the slope of the trend does not itself ensure
that GWPS will not eventually be exceeded. Additionally, there is no
way to guarantee based on existing monitoring data that any plateau in
current concentrations will be sustained in perpetuity. The timeframe
required for trendline projection is commensurate with the uncertainty
associated with closure, which is directly related to the size and
complexity of the unit. Although full closure may take the full time
projected, the initial steps of ceasing placement of new ash and
dewatering the unit will have the greatest relative impact on releases
by eliminating the primary mechanisms driving infiltration to the
subsurface.
    Therefore, EPA is adopting a provision at Sec.
257.71(d)(2)(vii)(A) to ensure that the number of samples available
will provide sufficient information to support decisions. Except as
provided for in Sec.  257.95(c), the owner or operator must collect a
minimum of four independent samples from each well (background and
downgradient) within one year of triggering assessment monitoring and
analyze each sample for all Appendix IV constituents.\33\ After the
initial sampling period, monitoring may revert to the previously
established frequency.
---------------------------------------------------------------------------

    \33\ U.S. EPA. 2018. ``Groundwater Statistics Tool User's
Guide.'' Prepared by the Office of Solid Waste and Emergency
Response. Washington, DC. September.
---------------------------------------------------------------------------

    EPA is also finalizing a requirement at Sec.
257.71(d)(2)(vii)(A)(1) to clarify that the owner or operator of the
CCR unit must apply an appropriate statistical test to identify trends
within the monitoring data. For normal distributions of data, linear
regression will be used to identify the presence and magnitude of any
trends. For non-normal distributions of data, the Mann-Kendall test
will be used to identify the presence of a trend and the Theil-Sen
trend line will be used to determine the associated magnitude. The test
used shall comply, as appropriate, with the performance standards in
Sec.  257.93(g). If a trend is identified, the facility will use the
upper 95th percentile confidence limit on the trend line to determine
if GWPS could be exceeded in the future. The facility will project this
trend line into the future for a duration set to the maximum number of
years allowed for closure of the surface impoundment pursuant to Sec.
257.102.
    The owner or operator must submit to EPA a report of the results of
each sampling event, as well as the initial trend analysis and they
must include all data relied upon by the facility to support the
analysis. The reports and the final trend analysis must be posted to
the facility's publicly accessible CCR internet site and submitted to
EPA within 14 days of completion. EPA will publish a proposed decision
on the trend analysis on www.regulations.gov for a 30-day comment
period. After consideration of the comments, EPA will issue its
decision. If the trend analysis shows the potential for a future
exceedance of a groundwater protection standard the CCR surface
impoundment must cease receipt of waste pursuant to the withdrawal
notice. Furthermore, if at any time the unit exceeds any GWPS, the
authorization will be withdrawn.

(ii) Alternative Source Demonstrations Under Sec.  257.94(e)
    Under an approved alternative liner demonstration, EPA proposed
that if groundwater monitoring detects a statistically significant
increase of any Appendix III constituent, the facility would need to
complete an alternative source demonstration pursuant to Sec.
257.94(e) or initiate assessment monitoring pursuant to Sec.  257.95.
85 FR 12462 (March 3, 2020). In response to the proposal, commenters
noted that the proposed regulatory text did not include a specific
provision allowing for alternative source demonstrations to be made
under Sec.  257.94(e) prior to proceeding to assessment monitoring.
These commenters requested the final rule include such regulatory text.
These commenters further requested that the final rule allow facilities
the opportunity to complete an alternative source demonstration when an
Appendix IV constituent is detected at statistically significant levels
above a GWPS pursuant to Sec.  257.95(g) prior to initiating corrective
action activities.
    The current regulations provide facilities the opportunity under
each phase of the groundwater monitoring program to demonstrate that a
source other than the CCR unit caused the increase in groundwater
concentrations for a constituent or that the increase resulted from an
error in sampling, analysis, statistical evaluation, or natural
variation in groundwater quality. Sec. Sec.  257.94(e) and 257.95(g).
The final rule does not eliminate the opportunity for an owner or
operator to make an alternative source demonstration for an Appendix
III constituent pursuant to Sec.  257.94(e), but the Agency has amended
it slightly for units with an ALD. Similar to the provision at
257.95(g), the unit with an ALD may pursue an alternate source
demonstration simultaneously while conducting the trend analysis. Given
that it will take close to a year to complete a trend analysis, EPA
considers that waiting an additional 90 days to commence the trend
analysis is not warranted in this circumstance. As a consequence, the
Agency agrees with commenters that the rule should include a specific
provision allowing for alternative source demonstrations to be made
under Sec.  257.94(e). This regulatory text is codified in Sec.
257.71(d)(2)(ix)(A)(1) in the final rule.
    EPA disagrees with commenters that the rule should allow for
alternative source demonstrations in the assessment monitoring program
under Sec.  257.95(g) when an Appendix IV constituent is detected at a
statistically significant level. First, because the purpose of the
requirement to close based on the trend analysis is to ensure that no
Appendix IV constituent is detected at a statistically significant
level, the provision at Sec.  257.95(g) should never be triggered while
the unit is operating under an alternative liner demonstration. Nor is
it likely that an alternative source of contamination will be present
that had not been discovered previously as a consequence of the
detection of a statistically significant increase of one or more
Appendix III constituents. Finally, while the Agency does agree that
the risk of drawing incorrect conclusions about unit performance based
on the presence of an error is equally applicable to the trend analysis
conducted during assessment monitoring, EPA believes it is more
appropriate for the facility to address such errors in the trends
analysis sampling results report required under Sec.
257.71(d)(2)(ix)(B). Therefore, the final rule does not allow owners
and operators to make use of the alternative source demonstration
provisions under Sec.  257.95(g) while operating under the alternative
liner demonstration provisions.
    If an owner or operator pursuing an alternative liner demonstration
makes a successful alternative source demonstration for an Appendix III
constituent pursuant to Sec.  257.94(e), the final rule requires the
owner or operator to submit the alternative source demonstration to EPA
for review and approval. The Agency is requiring review and approval of
alternative source demonstrations because a successful demonstration
under Sec.  257.94(e) allows a CCR unit to continue with the detection
monitoring program instead of progressing to an assessment monitoring
program. EPA is finalizing this requirement at Sec.
257.71(d)(2)(ix)(A)(4).
    The owner or operator must post the alternative source
demonstration to the facility's publicly accessible CCR internet site
and submit it to EPA for review and approval within 14 days of
completing the demonstration. EPA will publish a proposed decision on
the alternative source demonstration on www.regulations.gov for a 20-
day comment period. After consideration of the comments, EPA will issue
its decision. If the alternative source demonstration is approved by
EPA, the owner operator may return to detection monitoring under Sec.
257.94 and cease conducting the trend analysis. If the alternative
source demonstration is denied by EPA, the owner or operator must
either complete the trend analysis or cease receipt of waste and
initiate closure of the unit, as well as initiating an assessment
monitoring program as provided by Sec.  257.94(e). See Sec.
257.71(d)(2)(ix)(A)(5).
(iii) Source Control
    In the proposed rule EPA explained that if there was evidence that
the groundwater concentrations may exceed the groundwater protection
standard for any Appendix IV constituent within the operational life of
the CCR unit, EPA or the Participating State Director would reevaluate
the authorization and may revoke it if source control measures could
not be put in place while the unit continues to operate. 85 FR 12462,
12477 (March 3, 2019). EPA further explained that for units without a
geomembrane liner the only source control that would be effective was
the unit to cease receipt of waste and initiate closure.
    Several commenters stated that the proposed rule contemplates
repair of clay-lined impoundments as part of source control. These
commenters further explained that the available record does not support
the conclusion that a clay-lined surface impoundment can be repaired
successfully. These commenters also raised the concern that proposal
procedures were deficient in that facilities were not required to
provide evidence of liner repairability in order to continue to
operate. Commenters also stated that the proposed source control
provisions would cause harmful delays in closure of unlined
impoundments by providing additional time for a facility to continue
operating while attempting to put source controls in place after
detection of a groundwater protection standard exceedance. EPA received
no comments that contradicted the agency's conclusion that closure is
the only method of source control that would be effective for units
with a natural soil-based liner.
    After reviewing the record again, EPA agrees that the agency failed
to identify any data to demonstrate that the source of a leak from an
impoundment that receives an ALD can be identified and repaired.
Therefore, the final rule treats units with a geomembrane the same as
impoundments that rely on only a natural soil-based liner and requires
them to close upon a determination that a GWPS will be exceeded during
the active life of the unit.

IV. Corrections to Sec. Sec.  257.102 and 257.103

A. Correction to the Alternative Final Cover System Requirements

    EPA proposed to revise the alternative final cover system
requirements under Sec.  257.102(d)(3)(ii) to correct a typographical
error (85 FR 12468, March 3, 2020). In the introductory text to Sec.
257.102(d)(3)(ii), the regulations provide that the ``owner or operator
may select an alternative final cover system design, provided the
alternative final cover system is designed and constructed to meet the
criteria in paragraphs (f)(3)(ii)(A) through (D) . . .'' EPA explained
in the proposal that the reference to paragraphs (f)(3)(ii)(A) through
(D) is an incorrect cross-reference approval and that the correct
cross-reference should be to the criteria in paragraphs (d)(3)(ii)(A)
through (C). The Agency received no comments in response to this
proposed change. In this action, EPA is finalizing the proposal to
revise the introductory text of Sec.  257.102(d)(3)(ii).

B. Revisions to the Alternative Closure Requirements

    EPA recently promulgated amendments to the alternative closure
requirements under Sec.  257.103 that provide closure options in
situations where an owner or operator is closing a CCR unit but has no
alternative disposal capacity or is permanently closing the coal-fired
boiler in the foreseeable future (85 FR 53516, August 28, 2020)(``Part
A final rule''). Since publication of the Part A final rule, the Agency
has identified a typographical error in the regulatory text. This error
is being corrected in this final rule and are described below.
1. Correction to Sec.  257.103(f)(1)(vi)
    Section 257.103(f)(1)(vi) establishes maximum time frames that
wastes may be managed in a CCR surface impoundment while operating
pursuant to the alternative closure provisions under Sec.
257.103(f)(1). The regulatory text under Sec.  257.103(f)(1)(vi)
provides that ``All CCR surface impoundments covered by this section
must cease receiving waste by the deadlines specified . . .'' (emphasis
added). As discussed in the Part A final rule, the maximum time frames
provided for in Sec.  257.103(f)(1)(vi) only apply to impoundments
operating under Sec.  257.103(f)(1); however, the use of the term
``section'' in this regulatory text could be interpreted incorrectly to
apply also to other provisions under Sec.  257.103, such as the
alternative closure provisions under Sec.  257.103(f)(2). Therefore,
EPA is replacing the word ``section'' in the introductory text of Sec.
257.103(f)(1)(vi) with ``paragraph (f)(1)'' to reflect the intent of
the provision.

V. Rationale for 30-Day Effective Date

    The effective date of this rule is 30 days after publication in the
Federal Register. With some exceptions (see 5 U.S.C. 553(a),(d)), the
Administrative Procedure Act (APA) provides that publication of a
substantive rule shall be made not less than 30 days before its
effective date and that this provision applies in the absence of a
specific statutory provision establishing an effective date. See 5
U.S.C. 553(d) and 559. EPA has determined there is no specific
provision of RCRA addressing the effective date of regulations that
would apply here, and thus the APA's 30-day effective date applies.
    EPA has previously interpreted section 4004(c) of RCRA to generally
establish a six-month effective date for rules issued under subtitle D.
See 80 FR 37988, 37990 (July 2, 2015). After further consideration, EPA
interprets section 4004(c) to establish an effective date solely for
the regulations that were required to be promulgated under subsection
(a). Section 4004(c) is silent as to subsequent revisions to those
regulations; EPA therefore believes section 4004(c) is ambiguous.
    Section 4004(c) states that the prohibition in subsection (b) shall
take effect six months after promulgation of regulations under
subsection (a). Subsection (a), in turn provides that ``[n]ot later
than one year after October 21, 1976 . . . [EPA] shall promulgate
regulations containing criteria for determining which facilities shall
be classified as sanitary landfills and which shall be classified as
open dumps within the meaning of this chapter.'' As noted, section
4004(c) is silent as to revisions to those regulations.
    In response to Congress's mandate in section 4004(a), EPA
promulgated regulations on September 13, 1979. 44 FR 53438. EPA
interprets section 4004(c) to establish an effective date applicable
only to that action, and not to future regulations the Agency might
issue under this section. In the absence of a specific statutory
provision establishing an effective date for this rule, APA section
553(d) applies.
    EPA considers that its interpretation is reasonable because there
is no indication in RCRA or its legislative history that Congress
intended for the agency to have less discretion under RCRA subtitle D
than it would have under the APA to establish a suitable effective date
for subsequent rules issued under section 4004(c). Consistent with
EPA's interpretation of the express language of section 4004, EPA
interprets statements in the legislative history, explaining that
section 4004(c) provides that the effective date is to be 6 months
after the date of promulgation of regulations, as referring to the
initial set of regulations required by Congress to be promulgated not
later than 1 year after October 21, 1976. These statements do not
mandate a 6 month effective date for every regulatory action that EPA
takes under this section. This rule contains specific, targeted
revisions to the 2015 rule and the legislative history regarding
section 4004 speaks only to these initial 1976 mandated regulations.
    This reading allows the Agency to establish an effective date
appropriate for the nature of the regulation promulgated, which is what
EPA believes Congress intended. EPA further considers that the minimum
30-day effective date under the APA is reasonable in this circumstance
where none of the provisions being finalized require an extended period
of time for regulated entities to comply.

VI. Effect of This Final Rule on States With Approved CCR Programs

    This final rule has impacts on states with an approved program. As
of this final rule, EPA has granted approvals to the states of Oklahoma
and Georgia.
    Oklahoma and Georgia were each granted approval for Sec.  257.71,
and their regulations continue to operate without change in lieu of the
federal program. In essence this means that the revisions promulgated
in this rule making will not take effect in either of these states
until such time as Oklahoma or Georgia revises the program to adopt
them.
    EPA has determined that this rule is not more stringent than the
current regulations in 40 CFR Subpart D. As a consequence, neither
state is required to adopt these provisions in order to maintain
program approval. See, RCRA section 4005(d)(1)(D)(i)(II).
    The process for approving Oklahoma or Georgia's modifications is
the same as for the initial program approval: EPA will propose to
approve or deny the program modification and hold a public hearing
during the comment period. EPA will then issue the final program
determination within 180 days of determining that the state's
submission is complete.

VII. The Projected Economic Impacts of This Action

A. Introduction

    EPA estimated the costs and benefits of this action in a Regulatory
Impact

Analysis (RIA) which is available in the docket for this action. The
RIA estimates that the net annualized impact of this proposed
regulatory action over a 100-year period of analysis will be annual
cost savings of approximately $ 4.0 million to $ 8.0 million when
discounting at 7% and approximately $ 2.2 million to $ 4.5 million when
discounting at 3%. This action is not considered an economically
significant action under Executive Order 12866.

B. Affected Universe

    The rule potentially affects coal fired electric utility plants
(assigned to the utility sector North American Industry Classification
System (NAICS) code 221112) that dispose of their waste onsite in
surface impoundments. The universe consists of approximately 523
surface impoundments at 229 facilities.

C. Costs, Cost Savings, and Benefits of the Final Rule

    The Alternative Liner Demonstration finalized in this rule results
in paperwork costs associated with submitting an application for
demonstration and, if approved, the required demonstration. Provision
One also results in cost savings associated with delays in closure of
units (i.e., time value of money savings). Overall, the RIA estimates
that the time value of money cost savings will be greater than the
paperwork costs, making this a net cost savings rule of approximately
$4.0 million to $8.0 million per year when discounting at 7% and
approximately $2.2. million to $4.5 million per year when discounting
at 3%.
    The rule is not anticipated to result in impacts to benefits. A
qualitative discussion of benefits is available in Chapter 3 of the
RIA, which can be found in the docket for this rulemaking.

VIII. Executive Orders

    Additional information about these statutes and Executive Orders
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    This is a significant regulatory action that was submitted to the
Office of Management and Budget (OMB) for review because it raises
novel legal or policy issues. Any changes made in response to OMB
recommendations have been documented in the docket. EPA prepared an
analysis of the potential costs and benefits associated with this
action. This analysis is available in the docket and is summarized in
Unit VII of this preamble.

B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs

    This action is considered an Executive Order 13771 deregulatory
action. Details on the estimated cost savings of this final rule can be
found in EPA's analysis of the potential costs and benefits associated
with this action.

C. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have
been submitted for approval to the Office of Management and Budget
(OMB) under the PRA. The Information Collection Request (ICR) document
that the EPA prepared has been assigned EPA ICR number 2609.02. You can
find a copy of the ICR in the docket for this rule, and it is briefly
summarized here.
    The information to be collected as a part of this rule includes
demonstrations that must be made to EPA by owners and operators of
units that seek to obtain an alternate liner demonstration under Sec.
257.71(d). These demonstrations will show that the unit in question
meets the necessary criteria to receive the extension.
    Respondents/affected entities: Coal-fired electric utility plants
that will be affected by the rule.
    Respondent's obligation to respond: The recordkeeping,
notification, and posting are mandatory as part of the minimum national
criteria being promulgated under Sections 1008, 4004, and 4005(a) of
RCRA.
    Estimated number of respondents: 7.
    Frequency of response: The frequency of response varies.
    Total estimated burden: EPA estimates the total annual burden to
respondents to be an increase in burden of approximately 2,179 hours
from the currently approved burden. Burden is defined at 5 CFR
1320.3(b).
    Total estimated cost: $900,000 (per year), includes $0 annualized
capital costs and $785,000 annualized operation & maintenance costs.
    An agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for the
EPA's regulations in 40 CFR are listed in 40 CFR part 9.

D. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. In
making this determination, the impact of concern is any significant
adverse economic impact on small entities. An agency may certify that a
rule will not have a significant economic impact on a substantial
number of small entities if the rule relieves regulatory burden, has no
net burden or otherwise has a positive economic effect on the small
entities subject to the rule. This action is expected to result in net
cost savings of approximately $4.0 million to $8.0 million per year
when discounting at 7% and $2.2 million to $4.5 million per year when
discounting at 3%. These cost savings will accrue to all regulated
entities. We have therefore concluded that this action will relieve
regulatory burden for all directly regulated small entities.

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate of $100 million
or more as described in UMRA, 2 U.S.C. 1531-1538, and does not
significantly or uniquely affect small governments. This action imposes
no enforceable duty on any state, local or tribal governments or the
private sector.

F. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states, or on the distribution of power
and responsibilities among the various levels of government.

G. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This action does not have tribal implications as specified in
Executive Order 13175. This action does not impose substantial direct
compliance costs or otherwise have a substantial direct effect on one
or more Indian tribes, to the best of EPA's knowledge. Neither will it
have substantial direct effects on the relationship between the federal
government and Indian tribes, or on the distribution of power and
responsibilities between the Federal government and Indian tribes.
Thus, Executive Order 13175 does not apply to this action.

H. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    This action is not subject to Executive Order 13045 because it is
not economically significant as defined in Executive Order 12866, and
because the EPA does not believe the environmental health risks or
safety risks addressed by

this action present a disproportionate risk to children. This action's
health and risk assessments are contained in the document titled
``Human and Ecological Risk Assessment of Coal Combustion Residuals,''
which is available in the docket for the final rule as docket item EPA-
HQ-RCRA-2009-0640-11993.
    As ordered by E.O. 13045 Section 1-101(a), for the ``Final Rule:
Hazardous and Solid Waste Management System; Disposal of Coal
Combustion Residuals from Electric Utilities'' published April 17, 2015
(80 FR 21302), EPA identified and assessed environmental health risks
and safety risks that may disproportionately affect children in the
revised risk assessment. The results of the screening assessment found
that risks fell below the criteria when wetting and run-on/runoff
controls required by the rule are considered. Under the full
probabilistic analysis, composite liners required by the rule for new
waste management units showed the ability to reduce the 90th percentile
child cancer and non-cancer risks for the groundwater to drinking water
pathway to well below EPA's criteria. Additionally, the groundwater
monitoring and corrective action required by the rule reduced risks
from current waste management units. This action does not adversely
affect these requirements and EPA believes that this rule will be
protective of children's health.

I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use

    This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution or use of energy. For the 2015 CCR rule, EPA analyzed the
potential impact on electricity prices relative to the ``in excess of
one percent'' threshold. Using the Integrated Planning Model (IPM), EPA
concluded that the 2015 CCR Rule may increase the weighted average
nationwide wholesale price of electricity between 0.18 percent and 0.19
percent in the years 2020 and 2030, respectively. As the final rule
represents a cost savings rule relative to the 2015 CCR rule, this
analysis concludes that any potential impact on wholesale electricity
prices will be lower than the potential impact estimated of the 2015
CCR rule; therefore, this final rule is not expected to meet the
criteria of a ``significant adverse effect'' on the electricity markets
as defined by Executive Order 13211.

J. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

K. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    The EPA believes that this action does not have disproportionately
high and adverse human health or environmental effects on minority
populations, low-income populations and/or indigenous peoples, as
specified in Executive Order 12898 (59 FR 7629, February 16, 1994). The
documentation for this decision is contained in EPA's Regulatory Impact
Analysis (RIA) for the CCR rule which is available in the docket for
the 2015 CCR final rule as docket item EPA-HQ-RCRA-2009-0640-12034.
    The EPA's risk assessment did not separately evaluate either
minority or low-income populations. However, to evaluate the
demographic characteristics of communities that may be affected by the
CCR rule, the RIA compares the demographic characteristics of
populations surrounding coal-fired electric utility plants with broader
population data for two geographic areas: (1) One-mile radius from CCR
management units (i.e., landfills and impoundments) likely to be
affected by groundwater releases from both landfills and impoundments;
and (2) watershed catchment areas downstream of surface impoundments
that receive surface water run-off and releases from CCR impoundments
and are at risk of being contaminated from CCR impoundment discharges
(e.g., unintentional overflows, structural failures, and intentional
periodic discharges).
    For the population as a whole 24.8 percent belong to a minority
group and 11.3 percent falls below the Federal Poverty Level. For the
population living within one mile of plants with surface impoundments
16.1 percent belong to a minority group and 13.2 percent live below the
Federal Poverty Level. These minority and low-income populations are
not disproportionately high compared to the general population. The
percentage of minority residents of the entire population living within
the catchment areas downstream of surface impoundments is
disproportionately high relative to the general population i.e., 28.7
percent, versus 24.8 percent for the national population. Also, the
percentage of the population within the catchment areas of surface
impoundments that is below the Federal Poverty Level is
disproportionately high compared with the general population, i.e.,
18.6 percent versus 11.3 percent nationally.
    Comparing the population percentages of minority and low income
residents within one mile of landfills to those percentages in the
general population, EPA found that minority and low-income residents
make up a smaller percentage of the populations near landfills than
they do in the general population, i.e., minorities comprised 16.6
percent of the population near landfills versus 24.8 percent nationwide
and low-income residents comprised 8.6 percent of the population near
landfills versus 11.3 percent nationwide. In summary, although
populations within the catchment areas of plants with surface
impoundments appear to have disproportionately high percentages of
minority and low-income residents relative to the nationwide average,
populations surrounding plants with landfills do not. Because landfills
are less likely than impoundments to experience surface water run-off
and releases, catchment areas were not considered for landfills.
    The CCR rule is risk-reducing with reductions in risk occurring
largely within the surface water catchment zones around, and
groundwater beneath, coal-fired electric utility plants. Since the CCR
rule is risk-reducing and this action does not add to risks, this
action will not result in new disproportionate risks to minority or
low-income populations.

L. Congressional Review Act (CRA)

    This action is subject to the CRA, and EPA will submit a rule
report to each House of the Congress and to the Comptroller General of
the United States. This action is not a ``major rule'' as defined by 5
U.S.C. 804(2).

List of Subjects in 40 CFR Part 257

    Environmental protection, Beneficial use, Coal combustion products,
Coal combustion residuals, Coal combustion waste, Disposal, Hazardous
waste, Landfill, Surface impoundment.

Andrew Wheeler,
Administrator.

    For the reasons set out in the preamble, EPA amends 40 CFR part 257
as follows:

PART 257--CRITERIA FOR CLASSIFICATION OF SOLID WASTE DISPOSAL
FACILITIES AND PRACTICES

0
1. The authority citation for part 257 continues to read as follows:

    Authority: 42 U.S.C. 6907(a)(3), 6912(a)(1), 6944, 6945(a) and
(d); 33 U.S.C. 1345(d) and (e).

0
2. Amend Sec.  257.71 by adding paragraph (d) to read as follows:

Sec.  257.71  Liner design criteria for existing CCR surface
impoundments.

* * * * *
    (d) Alternate Liner Demonstration. An owner or operator of a CCR
surface impoundment constructed without a composite liner or alternate
composite liner, as defined in Sec.  257.70(b) or (c), may submit an
Alternate Liner Demonstration to the Administrator or the Participating
State Director to demonstrate that based on the construction of the
unit and surrounding site conditions, that there is no reasonable
probability that continued operation of the surface impoundment will
result in adverse effects to human health or the environment. The
application and demonstration must be submitted to the Administrator or
the Participating State Director no later than the relevant deadline in
paragraph (d)(2) of this section. The Administrator or the
Participating State Director will act on the submissions in accordance
with the procedures in paragraph (d)(2) of this section.
    (1) Application and alternative liner demonstration submission
requirements. To obtain approval under this paragraph (d), the owner or
operator of the CCR surface impoundment must submit all of the
following:
    (i) Application. The owner or operator of the CCR surface
impoundment must submit a letter to the Administrator or the
Participating State Director, announcing their intention to submit a
demonstration under paragraph (d)(1)(ii) of this section. The
application must include the location of the facility and identify the
specific CCR surface impoundment for which the demonstration will be
made. The letter must include all of the following:
    (A) A certification signed by the owner or operator that the CCR
unit is in full compliance with this subpart except for Sec.